U.S. patent application number 16/671270 was filed with the patent office on 2020-02-27 for thermal transfer sheet, coating liquid for colorant layer, method for manufacturing thermal transfer sheet, and image forming me.
This patent application is currently assigned to Dai Nippon Printing Co., Ltd.. The applicant listed for this patent is Dai Nippon Printing Co., Ltd.. Invention is credited to Hiroyuki HASEGAWA, Tomohiko IMODA, Yoshimasa KOBAYASHI, Kano SAKAMOTO, Hiroaki SEGAWA, Tomoko SUZUKI, Kazuya YOSHIDA.
Application Number | 20200062016 16/671270 |
Document ID | / |
Family ID | 54867439 |
Filed Date | 2020-02-27 |
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United States Patent
Application |
20200062016 |
Kind Code |
A1 |
YOSHIDA; Kazuya ; et
al. |
February 27, 2020 |
THERMAL TRANSFER SHEET, COATING LIQUID FOR COLORANT LAYER, METHOD
FOR MANUFACTURING THERMAL TRANSFER SHEET, AND IMAGE FORMING
METHOD
Abstract
A thermal transfer sheet which can prevent a kick and a
scumming, and can form a photographic tone color image of high
quality with a continuous tone image by sublimation transfer; a
coating liquid for colorant layer to be used for forming the
colorant layer of this thermal transfer sheet; a method for
manufacturing this thermal transfer sheet; and image forming method
employing this thermal transfer sheet. The problem is solved by a
thermal transfer sheet (1) in which at least a colorant layer (3)
is layered on a substrate sheet (2), wherein the colorant layer (3)
contains a predetermined solvent, a colorant (10x) dispersible in
the predetermined solvent, a dispersant, and a binder resin, and
the dispersant being one or more selected from the group consisting
of polyether-based dispersants, graft type polymer dispersants,
acryl-based block type polymer dispersants, urethane-based polymer
dispersants and azo-based dispersants.
Inventors: |
YOSHIDA; Kazuya; (Tokyo,
JP) ; SEGAWA; Hiroaki; (Tokyo, JP) ; IMODA;
Tomohiko; (Tokyo, JP) ; KOBAYASHI; Yoshimasa;
(Tokyo, JP) ; SUZUKI; Tomoko; (Tokyo, JP) ;
HASEGAWA; Hiroyuki; (Tokyo, JP) ; SAKAMOTO; Kano;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dai Nippon Printing Co., Ltd. |
Tokyo |
|
JP |
|
|
Assignee: |
Dai Nippon Printing Co.,
Ltd.
Tokyo
JP
|
Family ID: |
54867439 |
Appl. No.: |
16/671270 |
Filed: |
November 1, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15680411 |
Aug 18, 2017 |
10525757 |
|
|
16671270 |
|
|
|
|
14781221 |
Sep 29, 2015 |
9764580 |
|
|
PCT/JP2014/059321 |
Mar 28, 2014 |
|
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|
15680411 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08L 67/04 20130101;
C09B 25/00 20130101; C08K 5/3437 20130101; B41M 5/42 20130101; B41M
5/3856 20130101; B41M 5/39 20130101; C08L 71/02 20130101; C09B
67/009 20130101; C09B 67/0013 20130101; C09D 129/14 20130101; B41M
5/385 20130101; B41M 5/38228 20130101; B41M 2205/30 20130101; B41M
2205/38 20130101; C09D 151/00 20130101; B41M 2205/36 20130101; C09D
153/00 20130101; B41M 5/3858 20130101; B41M 5/395 20130101; B41M
2205/02 20130101; B41M 5/392 20130101; C08L 71/00 20130101 |
International
Class: |
B41M 5/395 20060101
B41M005/395; B41M 5/385 20060101 B41M005/385; C08K 5/3437 20060101
C08K005/3437; C09D 129/14 20060101 C09D129/14; C08L 71/02 20060101
C08L071/02; B41M 5/382 20060101 B41M005/382; B41M 5/392 20060101
B41M005/392; C09B 25/00 20060101 C09B025/00; C09B 67/08 20060101
C09B067/08; C09B 67/46 20060101 C09B067/46; C09D 151/00 20060101
C09D151/00; C09D 153/00 20060101 C09D153/00; C08L 67/04 20060101
C08L067/04; C08L 71/00 20060101 C08L071/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2013 |
JP |
2013-071897 |
Sep 5, 2013 |
JP |
2013-184375 |
Sep 30, 2013 |
JP |
2013-205833 |
Mar 28, 2014 |
JP |
2014-068207 |
Claims
1. A thermal transfer sheet comprising: a substrate, a first
colorant layer and a second colorant layer, layered in this order:
the first colorant layer containing a first residual solvent, a
sublimable dye soluble in the first residual solvent, and a first
binder resin; and the second colorant layer containing a second
residual solvent, a colorant dispersible in the second residual
solvent, and a second binder resin.
2. A method of manufacturing a thermal transfer sheet comprising: a
first colorant layer forming step of applying a coating liquid
containing a first solvent, a sublimable dye soluble in the first
solvent and a first binder resin, onto a surface of a substrate
sheet to form a first colorant layer; and a second colorant layer
forming step of applying a coating liquid containing a second
solvent, a colorant dispersible in the second solvent and a second
binder resin, onto the first colorant layer to form a second
colorant layer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional of U.S. application Ser.
No. 15/680,411, filed Aug. 18, 2017, the entirety of which is
incorporated herein by reference, which is a Divisional of U.S.
application Ser. No. 14/781,221, filed Sep. 29, 2015 (now U.S. Pat.
No. 9,764,580 Issued Sep. 19, 2017), which is a 371 National Phase
Application of PCT/JP2014/059321, filed Mar. 28, 2014, and claims
the benefit under 35 U.S.C. .sctn. 119 (a)-(d) of Japanese Patent
Application No. 2013-071897 filed on Mar. 29, 2013, Japanese Patent
Application No. 2013-184375 filed on Sep. 5, 2013, Japanese Patent
Application No. 2013-205833 filed on Sep. 30, 2013 and Japanese
Patent Application No. 2014-068207 filed on Mar. 28, 2014.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present invention relates to a thermal transfer sheet, a
coating liquid for colorant layer, a method for manufacturing
thermal transfer sheet and an image forming method.
2. Description of Related Art
[0003] Conventionally, thermal transfer method has been widely used
as a simple printing method. The melt-transfer method as one of the
thermal transfer method is an image forming method wherein a
thermal transfer sheet, which has a thermally fusible ink layer
comprising a colorant, such as a pigment, and a binder such as a
thermally fusible wax or resin, is superposed on a thermal transfer
image-receiving sheet such as a paper or a plastic film; then, an
energy in accordance with image information is applied from the
back side of the thermal transfer sheet by a heating means such as
a thermal head; and thereby the colorant is transferred onto the
thermal transfer image-receiving sheet together with the binder.
The image formed by the melt-transfer method is suitable for
recording binary images such as characters, since the image has
excellent sharpness and high concentration.
[0004] On the other hand, the sublimation transfer method as
another one of the thermal transfer method is another image forming
method wherein a thermal transfer sheet, which has a colorant layer
comprising a dye which is able to be transferred thermally by
sublimation, is superposed on a thermal transfer image-receiving
sheet in which a dye receiving layer is provided on a substrate,
then, an energy in accordance with image information is applied
from the back side of the thermal transfer sheet by a heating means
such as a thermal head; and thereby only the sublimable dye is
transferred onto the thermal transfer image-receiving sheet. With
respect to the sublimation transfer method, since the transferring
amount of dye can be controlled by the amount of energy applied, it
is possible to form a gray-scale image in which image density is
controlled. In addition, since the colorants used are dyes, the
image formed has transparency. Thus, when dyes of different colors
are superposed, the reproducibility of neutral tints becomes
excellent. Therefore, when using thermal transfer sheets of
different colors such as yellow, magenta, cyan, black or the like,
and transferring dye of each color on the thermal transfer
image-receiving sheet so as to superpose the dyes each other, it is
possible to form a photographic full-color image of high quality in
which reproducibility of neutral tints is excellent. Furthermore,
since the sublimation transfer method can express the full color
image as the original onto the thermal transfer image-receiving
sheet clearly, it is applied to a color image forming for a digital
camera, a video camera, a computer or the like. The image is one
that is high-quality comparable to silver halide photography.
[0005] In general, the thermal transfer sheet is stored and used in
wound state. When the colorant contained in the colorant layer is
present in a state of being localized to the surface of the
colorant layer by bleeding, etc., the sublimable dye tends to
migrate to the back face layer side of the thermal transfer sheet
(so-called "kick"). When the sublimable dye migrated to the back
layer side is again re-migrated to the colorant layer side
(so-called "back"), in particular, in the case that, in the thermal
transfer sheet in which a plural numbers of colorant layers which
are different in the hue from each other are provided so as to be
layered in parallel on the substrate sheet across the surface of
the substrate sheet, as being frame sequentially, the sublimable
dye migrated to the back layer side is again re-migrated to another
colorant layer which is different in the hue from the sublimable
dye, a decrease in color development property would be caused at
the time of image formation using the another colorant layer.
[0006] Under these circumstances, with respect to the thermal
transfer sheet capable of suppressing the occurrence of kick,
various studies have been made. For example, in Patent literature
2, a thermal transfer sheet which comprises a dye layer provided on
one surface of the substrate sheet, and a back face layer provided
on another surface of the substrate sheet, wherein the dye layer
contains an indoaniline based dye, a polyvinyl acetal resin A, and
a polyvinyl acetal resin B (represented by the formula (1) in
Patent literature 2), has been proposed. Further, in Patent
literature 3, a thermal transfer sheet which comprises a dye layer
provided on one surface of the substrate sheet film and containing
a resin and a dye, and a back face layer provided on another
surface of the substrate sheet and containing a lubricant and a
resin, wherein the dye layer contains a prescribed dye (the dye
represented by the formula (1) in Patent literature 3) in a
prescribed amount range, has been proposed. According to the
thermal transfer sheets proposed by Patent literatures 2 and 3, it
is stated that it is possible to prevent the migration of colorant
to the back layer side during the storage of the thermal transfer
sheet.
[0007] Further, in the thermal transfer sheet proposed in Patent
Literature 2, since the kind of the dye contained in the dye layer,
and the kind of the binder resin are limited to the prescribed
components, a problem such that the width of the material selection
becomes narrower is inherent.
PRIOR ART LITERATURE
Patent Literature
[0008] Patent literature 1: JP 2007-119762 A [0009] Patent
literature 2: JP 2009-286060 A [0010] Patent literature 3: JP
2010-83003 A
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0011] The present invention has been made in view of such
circumstances, and the present invention aims principally to
provide a thermal transfer sheet which can prevent a kick and a
scumming, and can form a photographic tone color image of high
quality with a continuous tone image by sublimation transfer, while
expanding the range of choices for colorants to be included in a
colorant layer; a coating liquid for colorant layer to be used for
forming the colorant layer of this thermal transfer sheet; a method
for manufacturing this thermal transfer sheet; and image forming
method employing this thermal transfer sheet.
Means for Solving the Problems
[0012] An aspect of the present invention for solving the
above-mentioned problems is thermal transfer sheet which comprises
a substrate and a colorant layer provided on one surface of the
substrate sheet, wherein the colorant layer contains a
predetermined solvent, a colorant dispersible in the predetermined
solvent, a dispersant and a binder resin, and wherein the
dispersant is one or more kinds of dispersants selected from the
group consisting of polyether-based dispersants, graft type polymer
dispersants, acryl-based block type polymer dispersants,
urethane-based polymer dispersants and azo-based dispersants.
[0013] Further, the colorant layer may contain a
quinophthalone-based colorant represented by the following formula
1 as a colorant dispersible in the predetermined solvent:
##STR00001##
[0014] Wherein, X represents a hydrogen atom or a halogen atom,
R.sup.1 represents a hydrogen atom, an alkyl group or derivative
thereof having 1 to 5 carbon atoms, an acyl group including an
alkyl group or a benzoic ring and having a total carbon number of 6
to 10.
[0015] In addition, the colorant layer may further contain a
colorant represented by the following formula 2 as a colorant
dispersible to the predetermined solvent:
##STR00002##
[0016] wherein, each of R.sup.1-R.sup.5 represents independently a
hydrogen atom, or a sulfonated derivative having at least one
sulfonic acid group (--SO.sub.3H) or sulfonamide group.
[0017] Another aspect of the present invention for solving the
above-mentioned problems is a coating liquid for colorant layer to
be used for forming a colorant layer of a thermal transfer sheet,
wherein the coating liquid for colorant layer contains a
predetermined solvent, a colorant dispersible in the predetermined
solvent, a dispersant and a binder resin; wherein the colorant
dispersible in the predetermined solvent is dispersed in a particle
size of not less than 50 nm and not more than 300 nm in the coating
liquid for colorant layer; and, wherein the dispersant is one or
more kinds of dispersants selected from the group consisting of
polyether-based dispersants, graft type polymer dispersants,
acryl-based block type polymer dispersants, urethane-based polymer
dispersants and azo-based dispersants.
[0018] In addition, the coating liquid for the colorant layer in
the above invention may further contain a quinophthalone-based
colorant represented by the above formula 1 as a colorant
dispersible to the predetermined solvent.
[0019] Still another aspect of the present invention for solving
the above-mentioned problems is a method of manufacturing a thermal
transfer sheet, which comprises a colorant layer forming step where
a coating liquid for colorant layer is applied onto a surface of a
substrate sheet to form a colorant layer; wherein the coating
liquid for colorant layer used in the colorant layer forming step
contains a predetermined solvent, a colorant dispersible in the
predetermined solvent, a dispersant and a binder resin; wherein the
dispersant is one or more kinds of dispersants selected from the
group consisting of polyether-based dispersants, graft type polymer
dispersants, acryl-based block type polymer dispersants,
urethane-based polymer dispersants and azo-based dispersants.
[0020] In addition, the coating liquid for colorant layer may
further contain a quinophthalone-based colorant represented by the
above formula 1 as a colorant dispersible to the predetermined
solvent.
[0021] Further, another aspect of the present invention for solving
the above-mentioned problems is an image forming method for forming
image on a thermal transfer image-receiving sheet by using a
thermal transfer sheet having a colorant layer on a surface of a
substrate sheet in combination with the thermal transfer
image-receiving sheet having a receiving layer on a surface of
another substrate sheet, wherein the colorant layer of the thermal
transfer sheet contains a predetermined solvent, a colorant
dispersible in the predetermined solvent, a dispersant and a binder
resin; and wherein the dispersant is one or more kinds of
dispersants selected from the group consisting of polyether-based
dispersants, graft type polymer dispersants, acryl-based block type
polymer dispersants, urethane-based polymer dispersants and
azo-based dispersants.
[0022] Also, the colorant layer may further contain a
quinophthalone-based colorant represented by the above formula 1 as
a colorant dispersible to the predetermined solvent.
[0023] Furthermore, another aspect of the present invention for
solving the above-mentioned problems is a thermal transfer sheet
which comprises a substrate and a colorant layer provided on one
surface of the substrate sheet, wherein the colorant layer contains
a predetermined solvent, a sublimable dye soluble in the
predetermined solvent, a colorant dispersible in the predetermined
solvent, and a binder resin.
[0024] Further, still another aspect of the present invention for
solving the above-mentioned problems is a thermal transfer sheet
which comprises a substrate and a colorant layer provided on one
surface of the substrate sheet, wherein the colorant layer
comprises a layered structure in which a first colorant layer and a
second colorant layer are layered in this order; wherein the first
colorant layer contains a first solvent, a sublimable dye soluble
in the first solvent, and a first binder resin; and wherein the
second colorant layer contains a second solvent, a colorant
dispersible in the second solvent, and a second binder resin.
[0025] Further another aspect of the present invention for solving
the above-mentioned problems is a method of manufacturing a thermal
transfer sheet, which comprises a colorant layer forming step where
a coating liquid for colorant layer is applied onto a surface of a
substrate sheet to form a colorant layer; wherein the coating
liquid for colorant layer contains a predetermined solvent, a
sublimable dye soluble in the predetermined solvent, a colorant
dispersible in the predetermined solvent, and a binder resin.
[0026] Further, the coating liquid for colorant layer may further
contain a dispersant.
[0027] Furthermore, another aspect of the present invention for
solving the above-mentioned problems is a method of manufacturing a
thermal transfer sheet, which comprises a first colorant layer
forming step where a coating liquid which contains a first solvent,
a sublimable dye soluble in the first solvent and a first binder
resin is applied onto a surface of a substrate sheet to form a
first colorant layer; and a second colorant layer forming step
where a coating liquid which contains a second solvent, a colorant
dispersible in the second solvent and a second binder resin is
applied onto the first colorant layer to form a second colorant
layer.
Effect of the Invention
[0028] According to the thermal transfer sheet of the present
invention, while expanding the range of choices for the colorant to
be included in the colorant layer, in other words, without
receiving any particular restrictions on the dye to be contained in
the colorant layer, it is possible to prevent the kick and the
scumming. Further, according to the coating liquid for colorant
layer of the present invention, it is possible to attain a high
colorant dispersibility, to improve coatability and thus, to form
the colorant layer of a thermal transfer sheet having the above
characteristics. Also, according to the manufacturing method of the
thermal transfer sheet of the present invention, it is possible to
manufacture a thermal transfer sheet which exhibits the above
effects. According to the image forming method of the present
invention, it is possible to form a high-quality photographic color
image with gradation image by the sublimation transfer.
[0029] According to an embodiment of the thermal transfer sheet of
the present invention, in addition to the above effects, it is
possible to enhance the durability such as light resistance of the
printed article, and possible to repress lowering of the printing
density at the highlight portion, and thus, it is possible to form
a high-quality photographic color image with gradation image by a
sublimation transfer. Also, according to the thermal transfer sheet
of the other embodiments, in addition to the above effects, it is
possible to forma high density image.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a schematic sectional view showing an example of
the thermal transfer sheet of the first embodiment.
[0031] FIG. 2 is a schematic sectional view showing an example of a
thermal transfer sheet of the first embodiment.
[0032] FIG. 3 is a schematic sectional view showing an example of
the intermediate transfer medium for comparison.
[0033] FIG. 4 is a schematic sectional view showing an example of a
thermal transfer sheet of the second embodiment.
[0034] FIG. 5 is a schematic sectional view showing an example of a
thermal transfer sheet of the third embodiment.
DETAILED DESCRIPTION OF THE INVENTION
Thermal Transfer Sheet of First Embodiment
[0035] As shown in FIG. 1, the thermal transfer sheet 1 of the
first embodiment according to the present invention may takes a
configuration in which a primer layer 4 and a colorant layer 3 are
provided in this order on one surface of a substrate 2, and a back
face layer 5 is provided on another surface of the substrate.
Incidentally, the primer layer 4, and the back layer 5 are optional
components of the thermal transfer sheet of the first embodiment.
Here, FIG. 1 is a schematic sectional view showing an example of a
thermal transfer sheet of the first embodiment.
[0036] Hereinafter, each layer constituting the thermal transfer
sheet 1 of the first embodiment will be described in detail.
(Substrate Sheet)
[0037] The substrate sheet 2 which constitutes the thermal transfer
sheet of the first embodiment is provided for the purpose of
supporting the colorant layer 3 as mentioned below, or the primer
layer 2 and/or the back face layer which may be optionally
provided, and it is possible to use any known material for the
substrate. Concretely, as the substrate 1, any known material may
be used as long as it has a known certain degree of heat resistance
and a known certain degree of strength, and, it is possible to
select one arbitrarily from materials known in the art. As such a
substrate, for instance, a resin film, such as polyethylene
terephthalate film, 1,4-polycyclohexylene dimethylene terephthalate
film, polyethylene naphthalate film, polyphenylene sulfide film,
polystyrene film, polypropylene film, polysulfone film, aramide
film, polycarbonate film, polyvinyl alcohol film, cellulose
derivatives such as cellophane and cellulose acetate, polyethylene
film, polyvinyl chloride film, nylon film, polyimide film, ionomer
film, etc.; and a paper such as condenser paper, paraffin paper,
synthetic paper, etc.; and a complex such as complex of paper or
nonwoven fabric and resin, etc., can be enumerated. Further,
although these materials may be used singly, it is also possible to
use a certain material as a layered film in which the material is
combined with one or more of other materials.
[0038] Although there is no particular limitation on the thickness
of the substrate sheet 2, the thickness of the substrate is not
particularly limited, it is usually about 0.5 .mu.m-50 .mu.m, and
preferably, about 3 .mu.m-10 .mu.m. The substrate may undergo
adhesive treatment on its one or both surface, if necessary. By
applying the adhesive treatment, it is possible to improve
wettability and/or adhesiveness of a coating liquid for colorant
layer against the substrate sheet on the formation of the colorant
layer by coating the coating liquid for colorant layer to the
substrate sheet. As the adhesive treatment, it is possible to apply
any resin surface reforming technique known in the art, as-is, such
as corona discharge treatment, flame treatment, ozone treatment,
ultraviolet ray treatment, radiation treatment, roughening
treatment, chemical agent's treatment, plasma treatment,
low-temperature plasma treatment, primer treatment, grafting
treatment, etc., in order to give an ease-adhesive property. These
treatments may be applied singly or in combination of two or more
kinds of them. In addition, in the case that a plastic film is
manufactured via a stretching procedure, the primer treatment
mentioned above may be also carried out by coating a primer liquid
to an unstretched film and stretching the film thereafter.
(Primer Layer)
[0039] As an adhesive treatment of the substrate sheet, a primer
layer 4 may be provided on the substrate sheet. When the primer
layer is provided, it becomes possible to improve the adhesion
between the substrate sheet 2 and the colorant layer 3, and
thereby, to prevent the colorant layer 3 from being abnormally
transferred during the image formation procedure. Furthermore, by
using a material having low dye dyeability as a primer layer, it is
possible to improve the printing density as compared with that in
case of the absence of a primer layer. The primer layer 4 is an
optional component of the thermal transfer sheet of the first
embodiment, and, for example, it may be formed with any of the
following organic materials and inorganic materials. As the organic
materials, for instance, polyester based resins, polyacrylic acid
ester based resins, polyvinyl acetate based resins, polyurethane
based resins, styrene acrylate based resins, polyacrylamide based
resins, polyamide based resins, polyether based resins, polystyrene
based resins, polyethylene based resins, polypropylene based
resins, vinyl based resins such as polyvinyl chloride resins,
polyvinyl alcohol resins, polyvinyl pyrrolidone and modified forms
thereof, and polyvinyl acetal based resins such as polyvinyl
acetoacetal and polyvinyl butyral, and the like, may be
exemplified. As the inorganic materials, for instance, colloidal
inorganic pigment minute particles such as silica (colloidal
silica), alumina or alumina hydrate (alumina sol, colloidal
alumina, cationic aluminum oxide or hydrates thereof,
pseudo-boehmite, etc.), aluminum silicate, magnesium silicate,
magnesium carbonate, magnesium oxide, titanium oxide, and the like
may be exemplified. In addition, polymers having an inorganic main
chain formed from: organic titanates, such as tetrakis
(2-ethylhexyl) titanate, bis (ethyl-3-oxo-butanoate rate -0.sup.1,
0.sup.3) bis (2-propanolate) titanium, or isopropyl triisostearoyl
titanate; or titanium alkoxides, such as titanium
tetra-isopropoxide or titanium tetra-n-butoxide, may be used as the
material for the primer layer.
[0040] Further, by constituting the primer layer from the colloidal
inorganic pigment minute particles, it is possible to prevent
abnormal transfer of the colorant layer to the thermal transfer
image-receiving sheet during the image formation more effectively.
Further, during the image formation, it is possible to prevent the
colorant transition from the colorant layer to the primer layer.
This makes it possible to carry out the diffusion of the colorant
into the receiving layer side of the thermal transfer
image-receiving sheet effectively, and thus it is possible to form
a high printing density image. As the colloidal inorganic pigment
minute particles, colloidal silica, alumina sol are particularly
preferably used. With respect to the size of these colloidal
inorganic pigment minute particles, it is preferable to use them
with an average primary particle diameter of not more than 100 nm,
more desirably, not more than 50 nm.
[0041] By treating the surface of the substrate sheet 2, to which
the colorant layer 3 will be formed, with adhesive treatment, or by
providing a primer layer between the substrate sheet 2 and the
colorant layer 3, it becomes possible to improve the adhesion of
the substrate sheet 2 and the colorant layer 3, and to prevent the
colorant layer 3 from being abnormally transferred during the image
formation. Furthermore, by using a material having low dye
dyeability as the primer layer, it is possible to improve the
printing density as compared with that in case of the absence of a
primer layer.
[0042] The primer layer can be formed by preparing a coating liquid
for the primer layer where one or more materials selected from the
materials enumerated as above are dispersed or dissolved in an
appropriate solvent such as an organic solvent, coating thus
prepared coating liquid in accordance with a known coating
procedure such as the gravure printing method, the screen printing
method, the reverse roll coating printing method using a gravure
plate, or the like, and then drying the coated solution. Although
there is no particular limitation about the coating amount of the
coating liquid for the primer layer, but usually it may be about
0.02 g/m.sup.2-about 10 g/m.sup.2 in terms of solid content.
(Colorant Layer)
[0043] As shown in FIG. 1, on one surface of the substrate sheet 2,
the colorant layer 3 is provided either directly, or indirectly via
an optional primer layer and the like. The colorant layer 3 is an
essential component in the thermal transfer sheet of the first
embodiment, and the colorant layer 3 contains, a predetermined
solvent, the colorant dispersible in the predetermined solvent, a
dispersant, and a binder resin. Further, with respect to the
thermal transfer sheet of the first embodiment, it is characterized
in that the dispersant which is included in the colorant layer 3 is
one or more kinds of dispersants selected from the group consisting
of polyether-based dispersants, graft type polymer dispersants,
acryl-based block type polymer dispersants, urethane-based polymer
dispersants and azo-based dispersants.
[0044] According to the colorant layer 3 that satisfies the above
characteristics, in the thermal transfer sheet 1 of the first
embodiment, it is possible to prevent a kick and a scumming, while
expanding the range of choices for colorants to be included in the
colorant layer 3. Further, the printed article to be formed can
enjoy high durability, such as light resistance, and can prevent
the printing density at the highlight portion from lowering, and
further, can provide a high quality photographic color image with
gradation image by the sublimation transfer.
[0045] Hereinafter, advantages of the thermal transfer sheet 1 of
the first embodiment will be explained with exemplifying a thermal
transfer sheet 1X (See, FIG. 3) wherein a colorant layer 3C which
includes a binder resin, a solvent, and a sublimable dye 10y
dissolvable in the solvent, is formed on the substrate. Here, FIG.
3 is a partial schematic cross-sectional view of a thermal transfer
sheet schematically showing the state of sublimable dye 10y in the
colorant layer 3C.
[0046] Since the sublimable dye 10y dissolvable in the solvent may
usually have a low molecular weight and it is to be monomolecular,
as shown in FIG. 3, the sublimable dye 10y is present in a state of
being localized to the interfaces of the colorant layer 3C, wherein
the colorant layer 3C was formed by using a coating liquid where
the sublimable dye had been dissolved in a solvent. Thermal
transfer sheet is generally stored at a rolled-up state, and in
this rolled-up state, since the colorant layer 3C and the back face
layer are being directly in contact with each other. Thus, under
the state that the sublimable dye 10y is present so as to be
localized to the interfaces of the colorant layer 3C as shown in
FIG. 3, when the thermal transfer sheet is stored at the rolled-up
state or the like, there is a tendency that the sublimable dye 10y
are easily transferred to the back layer side of the substrate
sheet 2. That is, in the case that a colorant layer 3C is simply
provided on the substrate sheet 2 by using the coating liquid
wherein the sublimable dye 10 has been dissolved in a solvent, it
is impossible to suppress occurrences of the kick.
[0047] Meanwhile, when using a sublimable dye having a high
molecular weight, and thereby, even possible to reduce the
localization of the sublimable dye to the interfaces, it is
difficult to prevent the occurrences of kick and/or scumming unless
the affinity of between the high molecular weight sublimable dye
and the binder becomes sufficiently. In other words, with respect
to the sublimable dye, to have a high molecular weight is
preferable in viewpoint of preventing the localization of the
sublimable dye to the interfaces, whereas to have a high affinity
with the binder resin is preferable in view point of preventing the
occurrence of the kick and/or the scumming, but the sublimable dyes
which can satisfy both of the above mentioned conditions are
considerably restricted in their kinds, and thus, the range of
choices for raw materials is forced to narrow.
[0048] Therefore, the thermal transfer sheet 1 of the first
embodiment is characterized in that, as shown in FIG. 2, the
colorant layer 3 provided on one surface of the substrate sheet 2
contains a binder resin, a predetermined solvent, a colorant 10x,
and a "specific dispersant" described later, and the colorant 10x
is the one that is dispersible in the predetermined solvent. In
other words, it is characterized in that, a colorant layer 3 is
provided on one surface of the substrate sheet 2, the colorant
layer being formed by using a coating liquid for the colorant layer
containing the "specific dispersant", the binder resin, the
colorant 10x, and the predetermined solvent to which the colorant
10x is dispersible, and dispersing the colorant.
[0049] According to the colorant layer 3 containing the
predetermined solvent and the colorant 10x dispersible to the
predetermined solvent, as shown in FIG. 2, it is possible to allow
the colorant 10x to exist in a state of being dispersed in the
colorant layer 3. Thus, it becomes possible to prevent the
occurrences of the kick and/or the scumming that may occur due to
the localization of the sublimable dye to the interfaces. Further,
since the colorant layer 3 contains the "specific dispersant"
described later, in addition to the colorant 10x dispersible to the
predetermined solvent, it is possible to allow the colorant 10x
dispersible to the predetermined solvent to exist in a state of
being dispersed homogenously in the colorant layer, and thus, it
becomes possible to prevent more effectively the occurrences of the
kick and/or the scumming, in cooperation with the effects of the
above mentioned colorant 10x dispersible to the predetermined
solvent. Here, FIG. 2 is a schematic partial sectional view of the
thermal transfer sheet schematically showing the state of the
colorant 10x dispersible in a predetermined solvent which is
contained in the colorant layer 3. Further, it should be noted that
in FIG. 2, and FIGS. 3 to 5, the sublimable dye 10y and the
colorant 10x in the colorant layer are illustrated
exaggeratingly.
"Binder Resin"
[0050] The colorant layer 3 contains a binder resin. The binder
resin are the one that carries the colorant dispersible in the
predetermined solvent. As the binder resins, for example, cellulose
based resin such as methyl cellulose, ethyl cellulose, hydroxyethyl
cellulose, ethyl hydroxyethyl cellulose, hydroxypropyl cellulose,
cellulose acetate, cellulose butyrate, nitrocellulose, etc.; vinyl
based resin such as polyvinyl alcohol, polyvinyl acetate, polyvinyl
butyral, polyvinyl acetal, polyvinyl pyrrolidone, polyacrylamide,
etc.; acryl based resins such as poly (meth)acrylates, poly
(meth)acryl amide, etc.; polyurethane based resins; polyester based
resins; phenoxy resins; and the like may be enumerated. Among them,
cellulose based, vinyl based, acryl based, polyurethane based, and
polyester based resins, etc., are preferred from the viewpoint of
the heat resistance, the thermal transferability of the colorant
and the like. The binder resin may be used singly or in any mixture
of two or more of them.
[0051] As the binder resin, further, releasing graft copolymers may
also be mentioned. The releasing graft copolymer may be also added
as a releasing agent, in addition to the above mentioned binder
resin. Herein, the above mentioned releasing graft copolymer
donates the one wherein at least one releasing segment selected
from the group consisting of polysiloxane segments, carbon fluoride
segments, fluorinated hydrocarbon segments and long-chained alkyl
segments is graft-polymerized to a polymer main chain which
constitutes any of the above mentioned binder resins. As the
releasing graft polymer, in particular, the graft polymer which is
obtained by graft-polymerizing a polysiloxane segment to a main
chain consisting of polyvinyl acetal is preferable. Furthermore, as
a releasing agent for the purpose of improving releasing property,
a silicone oil, a phosphoric acid ester, a fatty acid ester or the
like may be added.
"Predetermined Solvent"
[0052] The colorant layer 3 contains a solvent which is capable of
dispersing the colorant 10x. The predetermined solvent contained in
the colorant layer 3 means a solvent capable of dispersing the
colorant 10x. In other words, it means a solvent incapable of
dissolving the colorant 10x. There is no particular limitation for
the predetermined solvent, and can be appropriately selected
depending on the relationship with the colorant 10x contained in
the colorant layer 3. As examples of the solvent, for instance,
organic solvent such as methyl ethyl ketone, toluene, xylene,
methyl isobutyl ketone, ethyl acetate, isopropyl alcohol, ethanol,
etc., and water may be enumerated. As the predetermined solvent, it
is possible to use a kind of solvent singly, or to use in any
mixture of two or more of them.
[0053] Here, it should be noted that, although the thermal transfer
sheet of the first embodiment has an essential condition that the
colorant layer 3 contains a predetermined solvent, the condition
does not intend to denote that the predetermined solvent capable of
dispersing the colorant 10x is positively and actively contained in
the colorant layer 3. But, the predetermined solvent contained in
the colorant layer 3 refers to a residual solvent contained in the
colorant layer 3. With respect to the identification of the
residual solvent contained in the colorant layer 3, it will be
described later.
"Colorant Dispersible in the Predetermined Solvent"
[0054] The colorant layer 3 contains a colorant 10x dispersible in
the predetermined solvent. The term "colorant" used herein is a
concept which also involves sublimable dyes, and pigments. There is
no particular limitation on the colorant 10x dispersible in the
predetermined solvent, and can be appropriately selected depending
on the type of the predetermined solvent. Concretely, as long as
the colorant 10x is dispersible to the predetermined solvent which
is contained in the colorant layer 3, it may be any colorant.
[0055] As the colorant 10x dispersible in the predetermined
solvent, any colorant can be appropriately selected from, for
example, the sublimable dyes mentioned below and/or the pigments
mentioned below, depending on the solvent contained in the colorant
layer 3. Concretely, a predetermined solvent is selected at first,
and then, a colorant may be selected from, for example, the
sublimable dyes mentioned below and/or the pigments mentioned
below, by a criterion whether it is dispersible to the
predetermined solvent or not.
[0056] As the sublimable dye, for instance, diarylmethane based
dyes; triarylmethane based dyes; thiazole based dyes; merocyanine
dyes; pyrazolone dyes; methine based dyes such as pyrazolone
methine and pyridone methine; indoaniline based dyes; indonaphthole
based dyes; azomethine dyes such as acetophenone azomethine dyes,
pyrazolo azomethine dyes, imidazol eazomethine dyes, imidazo
azomethine dyes, and pyridone azomethine dyes; xanthene based dyes;
oxazine based dyes; cyanostyrene based dyes such as dicyanostyrene
dyes and tricyanostyrene dyes; thiazine based dyes; azine based
dyes; acridine based dyes; benzeneazo based dyes; azo based dyes
such as, pyridoneazo dyes, thiopheneazo dyes, isothiazoleazo dyes,
pyrroleazo dyes, pyrazoleazo dyes, imidazoleazo dyes,
thiadiazoleazo dyes, triazoleazo dyes, and disazo dyes; spiropyran
based dyes; indolinospiropyran based dyes; fluoran based dyes;
rhodaminelactam based dyes; naphthoquinone based dyes;
anthraquinone based dyes; quinophthalone based dyes; aminopyrazole
based dyes; pyrazolotriazole based dye; styryl based dyes such as
dicyano styryl and tricyano styryl; etc., can be enumerated.
[0057] Concretely, for instance, C. I. (Color index) Disperse
Yellow 51, 3, 54, 79, 60, 23, 7, 141, 201, 231; C. I. Disperse Blue
24, 56, 14, 301, 334, 165, 19, 72, 87, 287, 154, 26, 354; C. I.
Disperse Red 135, 146, 59, 1, 73, 60, 167; C. I. Disperse Orange
149; C. I. Disperse Violet 4, 13, 26, 36, 56, 31; C. I. Solvent
Yellow 56, 14, 16, 29, 93; C. I. Solvent Blue 70, 35, 63, 36, 50,
49, 111, 105, 97, 11; C. I. Solvent Red 135, 81, 18, 25, 19, 23,
24, 143, 146, 182; C. I. Solvent Violet 13; C. I. Solvent Black 3;
C. I. Solvent Green 3; and the like may be enumerated. As the
sublimable dye, from the viewpoint of having alight resistance and
also a high intensity, the quinophthalone based dyes, anthraquinone
based dyes are preferable, and further, the quinophthalone based
dyes are particularly preferable.
[0058] As the quinophthalone based dyes (colorant), quinophthalone
based colorants represented by the following formula 1 are
preferred. By containing a quinophthalone based dye represented by
the formula 1 in the colorant layer 3, it becomes possible to
improve the light resistance and the sharpness of a printed article
that is formed using the thermal transfer sheet of the first
embodiment. With respect to the quinophthalone based colorant
represented by Formula 1, when both X and R.sup.1 are a hydrogen
atom, individually, it represents a Disperse Yellow 54. Also, when
X is Br, and R.sup.1 is hydrogen atom, it represents Disperse
Yellow 64. As quinophthalone-based colorants represented by the
following formula 1, Disperse Yellow 149, and further, the
quinophthalone dyes described in JP Hei 10-287818 A and the like
can be enumerated. The related content of this reference are
incorporated herein by reference.
##STR00003##
[0059] Wherein, X represents a hydrogen atom or a halogen atom,
R.sup.1 represents a hydrogen atom, an alkyl group or derivative
thereof having 1 to 5 carbon atoms, an acyl group including an
alkyl group or a benzoic ring and having a total carbon number of 6
to 10.
[0060] As the sublimable dye, it is also possible to use any
commercially available product as-is. For instance, as a yellow
dye, Holon brilliant yellow-S-6GL (manufactured by Sandoz, Disperse
Yellow 231), MACROLEX Yellow 6G (manufactured by Bayer, Disperse
Yellow 201); as a magenta dye, MS-Red-G (manufactured by Mitsui
Toatsu Chemicals, Inc., Disperse Red 60), Macrolex Red Violet R
(manufactured by Bayer, Disperse Violet 26); as a cyan dye, Kayaset
Blue 714 (manufactured by Nippon Kayaku Co., Ltd., Solvent Blue
63), Holon Brilliant Blue S-R (manufactured by Sandoz, Disperse
Blue 354), Waxoline Blue AP-FW (manufactured by ICI, Solvent Blue
36); etc., are exemplified.
[0061] As the sublimable dye dispersible in the predetermined
solvent, it is possible to use one kind of the sublimable dye
singly, or to use in any mixture of two or more of them. As a
dispersible colorant in a predetermined solvent, the sublimable
dye(s) may also be used in combination with pigment(s). It can also
be used in combination of two or more pigments. Here, the colorant
layer 3 has to contain at least one of the color material(s) 10x
dispersible in any solvent(s) which is contained in the colorant
layer 3, provided that none of the solvents included in the
colorant layer 3 can dissolve the dispersible colorant 10x. This is
because, even in the case that the colorant layer 3 contains a
predetermined solvent and a colorant 10x dispersible to the
predetermined solvent, if the colorant 10x can be dissolved by any
other solvent included in the colorant layer 3, the dispersible
colorant 10x would exist in its dissolved condition in the coating
liquid for the colorant layer as a consequence.
[0062] When pigment(s) is used as the colorant 10x dispersible in a
predetermined solvent, the pigment(s) may be suitably selected from
known organic or inorganic pigments. As the pigment, the one which
has a sufficient color density, and is not easily discolored or
faded by light, heat or the like, is preferable. As the color of
the pigments, it is possible to use various colors of the coloring
agents, without being limited to cyan, magenta, yellow and
black.
[0063] As examples of the pigment, azo based pigments,
phthalocyanine based pigments, quinacridone based pigments,
perylene-perinone based pigments, isoindolinone based pigments,
isoindoline based pigments, dioxazine based pigments,
quinophthalone based pigments, diketopyrrolopyrrole based pigments,
anthraquinone based pigments, thioindigo based pigments, metal
complex based pigments and the like may be enumerated. Among these
organic pigments, C. I. Pigment Yellow 138, C. I. Pigment Yellow
150, C. I. Pigment Green 7, C. I. Pigment Green 36, C. I. Pigment
Red 122 and C. I. Pigment Violet 19 are desirable from the
viewpoint of having high luminance.
[0064] Although the quinophthalone-based colorant represented by
the above formula 1 which mainly has a hue of yellow, it is
preferable to use a colorant (pigment) represented by the following
formula 2 to the colorant layer, in addition to the above mentioned
quinophthalone-based colorants represented by the above formula 1,
from the viewpoint of improving the dispersibility of the colorants
and the stability of the ink, and the viewpoint of preventing the
contamination due to the transfer of the colorants from the
colorant layer and the retransfer of this transferred
colorants.
##STR00004## [0065] wherein, each of R.sup.1-R.sup.5 represents
independently a hydrogen atom, an aryl group or derivative thereof
having 1 to 5 carbon atoms, or a sulfonated derivative having at
least one sulfonic acid group (--SO.sub.3H) or sulfonamide
group.
[0066] Among the colorants (pigments) represented by the above
formula 2, the ones wherein at least one of R.sup.1-R.sup.5 is the
sulfonated derivative having at least one sulfonic acid group
(--SO.sub.3H) or sulfonamide group are preferable. Furthermore, a
part of or all of the sulfonic acid group(s) may take a salt form
by salifying with amine, ammonium hydroxide, chloride, bromide,
etc., or a metal. A derivative of the colorant represented by
Formula 2 is represented by the following formula 3.
##STR00005##
[0067] It is preferable to use the sulfonated derivative
represented as above formula as the colorant, because it can brings
many advantages such as, to enhance the adhesiveness with the
substrate sheet of the thermal transfer sheet, to enhance the
dispersibility of the colorants in the colorant layer, etc. Here,
with respect to the sulfonated derivative, albeit at a hue of
yellow, since its hue is slightly changed as compared with the hue
of quinophthalone-based colorants represented by the above formula
1, it is preferable to use in a small proportion, that is, to add
at not more than 15% (by weight) of the total of colorants, from
the viewpoint of the color reproduction.
[0068] Further, the thermal transfer sheet 1 of the first
embodiment is characterized in that the colorant layer 3 contains a
dispersant, and the dispersant is one or more kinds of dispersants
selected from the group consisting of polyether-based dispersants,
graft type polymer dispersants, acryl-based block type polymer
dispersants, urethane-based polymer dispersants and azo-based
dispersants. Hereinafter, these dispersants may be referred to
collectively as "specific dispersants", occasionally.
[0069] As the polyether-based dispersants, for example, polyether
based carboxylic acids, polyether based phosphoric acids, polyether
based phenols, and the like can be enumerated. As commercially
available products of the polyether-based dispersants, for
instance, DISPARLON DA234, DISPARLON DA325, (trade names of
Kusumoto Chemicals, Co., Ltd.), Solsperse 20000 (The Lubrizol
Corporation), etc., may be enumerated.
[0070] The graft-type polymer dispersant denotes a polymer having a
structure wherein branch polymer segment(s) is grafted to a main
polymer segment which has a plural number of functional groups such
as basic groups, for instance, a polymer of which the main polymer
segment is polyallylamine and the branch polymer segment is
.epsilon.-caprolactone ring-opening polymerized polymer may be
enumerated. As the dispersant of the above graft-type polymer, for
instance, AjisperPB821, AjisperPB822, Ajisper PB823, Ajisper PB824,
Ajisper PB827, Ajisper PB880, and mention may be made of Ajisper
PB881 (manufactured by Ajinomoto Fine-Techno Co., Ltd.), etc., may
be enumerated. As the graft-type polymer dispersant, it is possible
to use one kind of the dispersants singly, or to use in any
combination of two or more of them.
[0071] As the acryl based block type polymer dispersant, those
which has, as the main chain structure, for example, methacryl
based resin or acryl based resin or the like, may be enumerated.
Especially, dispersants of methacrylic or acrylic block type
polymer including tertiary amino groups are preferred. The weight
average molecular weight (Mw) of the block type polymer dispersant
is preferably in the range of not less than 500 or not more than 20
000, more preferably, in the range of not less than 1,000 and not
more than 15,000, still more preferably, in the range of not less
than 3000 and not more than 12000. When using the acryl based block
type polymer dispersant having a weight average molecular weight
within the above preferred range, it is possible to achieve both
the wettability and dispersion stability to the colorant at the
initial stage of dispersion to disperse uniformly the colorant.
Incidentally, the weight average molecular weight (Mw) used herein
denotes a value measured by the gel permeation chromatography (GPC)
and calibrated with polystyrene standard. As the dispersant of the
methacrylic or acrylic block type polymer including tertiary amino
groups, for instance, Disperbyk-2000, Disperbyk-2001, BYK-LPN6919,
BYK-LPN21116, BYK-LPN21324 (manufactured by BYK Additives &
Instruments) may be enumerated. As the acryl based block type
polymer dispersant, it is possible to use one kind of the
dispersants singly, or to use in any combination of two or more of
them.
[0072] As the urethane based polymer dispersant, an urethane based
block-type polymer dispersant is preferable used. The weight
average molecular weight (Mw) of this block type polymer dispersant
is preferably in the range of not less than 4000 and not more than
300,000, more preferably not less than 5,000 and not more than
200,000, further preferably, in the range of not less than 6,000
and more than 100,000, and furthermore preferably, in the range of
not less than 10,000 and not more than 50,000. As the above
mentioned block type polymer dispersant, for example, "BYK-161,
BYK-162, BYK-163, BYK-164, BYK-167", manufactured by BYK Additives
& Instruments; "EFKA 4047, 4050, 4010, 4165", manufactured by
BASF; etc. may be enumerated. As the urethane based polymer
dispersant, it is possible to use one kind of the dispersants
singly, or to use in any combination of two or more of them.
[0073] As the azo-based dispersant, azo pigment derivatives may
preferably be used. As the azo pigment derivative, for instance,
Solsperse 22000 (manufactured by The Lubrizol Corporation) may be
enumerated. As the azo based dispersant, it is possible to use one
kind of the dispersants singly, or to use in any combination of two
or more of them.
[0074] Although there are many dispersants for dispersing the
colorant 10x dispersible to the predetermined solvent is present a
number, but in the present invention, since the colorant layer 3
contains the "specific dispersant", it is possible to keep the
dispersion stability of the colorant 10x dispersible to the
predetermined solvent at a high level. Incidentally, when the
colorant layer contains a dispersant other than the "specific
dispersant", its preventing ability for kick and scumming, light
resistance, printing quality of a printed article to be formed is
lowered, as compared to those obtained by the colorant layer 3
containing the "specific dispersant". As the "specific dispersant",
it is possible to use one kind of the dispersants singly, or to use
in any combination of two or more of them. The content of the
"specific dispersant" is usually in the range of not more than 100
parts by weight, preferably in the range of 0.5 to 100 parts by
weight, more preferably, 1 to 70 parts by weight, and particularly
preferably, 10 to 50 parts by weight, on the basis of 100 parts by
weight of the colorants. When the content of "a specific
dispersant" is more than 100 parts by weight, there is a
possibility that the sharpness may be impaired. On the other hand,
when the content of the "specific dispersants" is too small, there
is a possibility that the functions as the "specific dispersants"
cannot be sufficiently exhibited. Next, preferred combinations of
the colorant and the "specific dispersant" is the colorant layer
containing 3 will be described by taking some examples.
Incidentally, the colorants and the "specific dispersants"
contained in the colorant layer 3 are not limited to the following
combinations. As long as the condition that the colorant layer 3
contains a predetermined solvent, a colorant dispersible to the
predetermined solvent, a "specific dispersant", and a binder resin
is satisfied, it is possible to suppress the occurrence of the kick
and/or the scumming, and the lowering of print density in the
highlight portion in the thermal transfer sheet provided with the
colorant layer, and also possible to improve durability such as
light resistance of the printed article to be formed by the thermal
transfer sheet, and to obtain a high quality image.
[0075] The colorant layer 3 of a preferred example contains the
quinophthalone-based colorant represented by the above formula 1,
the colorant represented by the above formula 2, the acryl based
block type polymer dispersant, the predetermined solvent, and a
binder resin. In other words, the colorant layer 3 of this
preferred example is a colorant layer which is formed by using a
coating liquid for colorant layer which includes the
quinophthalone-based colorant represented by the above formula 1,
the colorant represented by the above formula 2, the acryl based
block type polymer dispersant, the predetermined solvent, and a
binder resin. According to the coating liquid for colorant layer
which includes the quinophthalone-based colorant represented by the
above formula 1, the colorant represented by the above formula 2,
the acryl based block type polymer dispersant, the predetermined
solvent and the binder resin, it is possible to disperse the
quinophthalone-based colorant represented by the above formula 1
with a small particle diameter, concretely, with a particle
diameter of not more than 200 nm, in the coating liquid for
colorant layer. Therefore, by constituting a thermal transfer sheet
comprising a colorant layer formed by using the coating liquid for
colorant layer as above mentioned, in addition to the above
effects, it becomes possible to form an image of high
concentration, and also possible to improve the adhesion between
the substrate sheet 2 and the colorant layer 3.
[0076] The colorant layer 3 of another preferred example contains
the quinophthalone-based colorant represented by the above formula
1, a predetermined solvent, the urethane based polymer dispersant,
the azo based dispersant, and a binder resin. In other words, the
colorant layer 3 of this preferred example is a colorant layer
which is formed by using a coating liquid for colorant layer which
includes the quinophthalone-based colorant represented by the above
formula 1, a predetermined solvent, the urethane based polymer
dispersant, the azo based dispersant, and a binder resin. In such
the coating liquid for colorant layer which includes the colorant
and the dispersants in the above mentioned combination, it is also
possible to disperse the quinophthalone-based colorant represented
by the above formula 1 with a particle diameter of not more than
200 nm, in the coating liquid for colorant layer, same as the
colorant layer of the above mentioned first example.
[0077] With respect to the blending ratio of the urethane based
dispersant and the azo-based dispersant, although there is no
particular limitation, it is preferable to be in the range of about
9:1 to about 1:9, in their weight ratio.
[0078] The colorant layer 3 of further another preferred example is
a colorant layer which is formed by using a coating liquid for
colorant layer which is prepared by a "specific preparation method
of the coating liquid for colorant layer". The "specific
preparation method of the coating liquid for colorant layer" is a
method where a dispersion containing the colorant in the
predetermined solvent is prepared by using the "specific
dispersant" under a condition of containing no or a very small
amount of the binder resin, and thereafter, a binder resin is added
to the obtained dispersion as post-addition in order to obtain the
coating liquid for colorant layer". According to the coating liquid
for colorant layer prepared by this preparation method, it is
possible to disperse the colorant with a small particle diameter in
a short time, as compared with the coating liquid for colorant
layer which is prepared by dispersing the colorant in the
predetermined solvent with using the "specific dispersant" under
the presence of the binder resin.
"Determination Method for Dispersibility of Colorant to
Predetermined Solvent"
[0079] By the following method, it is possible to determine whether
a colorant of interest to be contained in the colorant layer can be
dispersed in the predetermined solvent or not. To the predetermined
solvent, the colorant of interest is added so as to be an amount of
2 w/v %, then the colorant added solvent is heated for 1 hour at
50.degree. C. with stirring. Then, the resulting liquid is left
standing for 60 hours at 25.degree. C., and after the leaving, the
liquid is observed visually about the presence or absence of
precipitation of the colorant of interest. When precipitation of
the colorant of interest does not observed visually, the colorant
of interest can be determined to be a colorant soluble in a
predetermined solvent. On the other hand, when precipitation of the
colorant of interest is observed visually, the colorant of interest
can be determined to be a colorant insoluble to the predetermined
solvent, in other words, a colorant dispersible to the
predetermined solvent. With respect to the sublimable dye, it is
possible to determine the dispersibility in the same manner. With
respect to the colorant layer of the thermal transfer sheet of the
second embodiment described later, and the colorant layer of the
thermal transfer sheet of the third embodiment, it is also possible
to determine the dispersibility in the same manner.
"Determination Method for Colorant, Residual Solvent"
[0080] For instance, by the following method, it is possible to
determine whether a thermal transfer sheet of interest
(hereinafter, referred to as target thermal transfer sheet)
satisfies the matters specifying the thermal transfer sheet of the
first embodiment or not. First, the colorant layer of the target
thermal transfer sheet is analyzed in order to identify the
colorant component contained in the colorant layer. As the
identification method of the colorant components, any
conventionally known analytical method such as the nuclear magnetic
resonance spectroscopy, IR spectroscopy or the like is
applicable.
[0081] Then, the kind of the solvent remaining in the colorant
layer is determined. As the identification method of the kind of
the solvent, for example, the gas chromatography is applicable. In
the identification of the kind of the solvent by the gas
chromatography, for instance, a gas chromatography analyzer such as
Gas Chromatography GC14-A, manufactured by Shimadzu Corporation,
and the like can be utilized. Incidentally, in order to eliminate
the influence of the solvents which have been contained in the
substrate sheet, back face layer, and/or any arbitrary layers in
the target thermal transfer sheet, it is necessary to analyze to
the layer corresponding to the colorant layer of the target thermal
transfer sheet on the identification of the kind of the solvent.
Concretely, when the kind of the solvent remaining in the colorant
layer is determined by using the gas chromatography method, it is
important to take only a part of the layer corresponding to the
colorant layer of the target thermal transfer sheet and carry out
the analyze to the portion.
[0082] When at least one of the identified colorant components as
mentioned above is the colorant component dispersible in the
identified solvent as mentioned above, and the above "specific
dispersant" is contained as the dispersant, the target thermal
transfer sheet can be judged as being satisfying the matters
specifying the thermal transfer sheet of the first embodiment.
Using the "determination method for dispersibility of colorant to
predetermined solvent", it is possible to identify whether the
identified colorant component is soluble or dispersible in the
identified solvent.
[0083] The colorant layer 3 may contain other optional additives,
for instance, a releasing agent for improving releasability from
the receiving layer of the thermal transfer-image receiving sheet,
an antistatic agent, an organic or inorganic filler for controlling
the lubricity with the receiving layer, etc., in addition to the
essential components, i.e., the binder resin, the predetermined
solvent, the colorant dispersible to the predetermined solvent, and
one or more kinds of dispersants selected from the group consisting
of polyether-based dispersants, graft type polymer dispersants,
acryl-based block type polymer dispersants, urethane-based polymer
dispersants and azo-based dispersants.
[0084] As the release agent, for instance, silicone oils,
polyethylene waxes, amide waxes, Teflon (registered trademark),
surfactants such as fluorine based surfactants or phosphoric ester
based surfactants may be exemplified. Although there is no
particular limitation on the content of the release agent in the
colorant layer, it is preferable to be in the range of not less
than 0.1% by weight and not more than 10% by weight on the basis of
the total solid content of the binder resin contained in the
colorant layer. By incorporating the release agent in this range,
even when the receiving layer does not contain a release agent, it
is possible to sufficiently satisfy the releasing property between
the colorant layer 3 and the receiving layer.
[0085] There is no particular limitation on the method of forming
the colorant layer 3, and for instance, the colorant layer 3 can be
formed by preparing a coating liquid for the colorant layer where
the binder resin, the predetermined solvent, the colorant
dispersible to the solvent, and the "specific dispersant", and any
optionally added component(s) are used and the colorant is
dispersed in the predetermined solvent, coating thus prepared
coating liquid for colorant layer in accordance with a known
coating procedure such as the gravure printing method, the screen
printing method, the reverse roll coating printing method using a
gravure plate, or the like, and then drying the coated solution.
The coating amount of the coating liquid for colorant layer is not
particularly limited, but usually, it is in the range of about 0.2
g/m.sup.2-about 10 g/m.sup.2 in term of the solid content.
(Back Face Layer)
[0086] As shown in FIG. 1, in the thermal transfer sheet of the
first embodiment, a back face layer 5 may be provided on a backside
surface of the substrate 1, that is, the surface which is different
from another surface on which the colorant layer is provided, in
order to prevent adverse effects such as sticking or wrinkles due
to heat from the thermal head, to impart slipperiness to the
thermal transfer printer or the like, and enhance transportability
of the sheet therein. As the resin for forming the back face layer,
any conventionally known resin may be used, for instance,
thermoplastic resins such as polyester type resins, polyacrylic
ester type resins, polyvinyl acetate type resins, styrene acrylate
type resins, polyurethane type resins, polyolefin type resins such
as polyethylene type resins and polypropylene type resins,
polystyrene type resins, polyvinyl chloride type resins, polyether
type resins, polyamide type resins, polyimide type resins,
polyamide-imide type resins, polycarbonate type resins,
polyacrylamide type resins, polyvinyl chloride resins, polyvinyl
butyral resins, and polyvinyl acetal resins; and silicone-modified
forms of these thermoplastic resins may be enumerated. Concretely,
for example, polyvinyl butyral resins, polyvinyl acetoacetal
resins, polyester resins, vinyl chloride-vinyl acetate copolymers,
polyether resins, polybutadiene resins, styrene-butadiene
copolymers, acryl polyols, polyurethane acrylates, polyester
acrylates, polyether acrylates, epoxy acrylates, urethane or epoxy
prepolymers, nitrocellulose resins, cellulose nitrate resins,
cellulose acetopropionate resins, cellulose acetate butyrate
resins, cellulose acetate hydrodiene phthalate resins, cellulose
acetate resins, aromatic polyamide resins, polyimide resins,
polyamide-imide resins, polycarbonate resins, and chlorinated
polyolefin resins and the like may be enumerated.
[0087] As a slipping property-imparting agent to be added to the
back face layer comprising above mentioned resin or to be
overcoatedon the back face layer, for instance, phosphoric acid
esters, fatty acid esters, metallic soaps, waxes, silicone oils,
graphite powders, silicone based graft polymers, fluorine
containing graft polymers, acrylic silicone graft polymers,
silicone polymers such as acrylic siloxanes and aryl siloxanes may
be exemplified. However, it is preferable to be a layer which
comprises a polyol such as a polyalcohol polymer compound, and a
polyisocyanate compound and a phosphoric acid ester-based compound,
and further, it is more preferably to further add a filler.
Further, phosphate esters, fatty esters, metallic soaps, waxes,
etc. may be also preferably used.
[0088] As the metal soaps, for instance, multivalent metallic salts
of alkyl phosphoric esters, multivalent metal salts of fatty acids,
metallic salts of alkyl carboxylic acid may be enumerated. As the
metal soaps, the ones which are known in the art as additive for
plastics may be used. Among them, zinc stearate and/or zinc stearyl
are preferred.
[0089] As the phosphoric acid ester, for example, (1) phosphoric
diesters or monoesters of saturated or unsaturated higher alcohols
having a carbon number of 6 to 20, (2) phosphoric monoesters or
diesters of polyoxyalkylene alkyl ethers or polyoxyalkylene alkyl
allyl ethers, (3) phosphoric diesters or monoesters of alkylene
oxide adducts (average addition molar number: 1-8) of the above
mentioned saturated or unsaturated alcohols, (4) phosphoric
monoesters or diesters of alkyl phenols or alkyl naphthols which
have an alkyl group having a carbon number of 8-12, are enumerated.
As the saturated and unsaturated higher alcohols for the above (1)
and (3) compounds, for example, cetyl alcohol, stearyl alcohol,
oleyl alcohol, etc., are enumerated. As the alkyl phenol for the
above (3) compounds, for example, nonyl phenol, dodecyl phenol,
diphenyl phenol, etc., are enumerated.
[0090] There is no particular limitation about the method for
forming the back face layer. The back face layer 3 may be formed by
dissolving or dispersing the above exemplified resin, and
optionally, other ingredients such as lubricant into a suitable
solvent; coating thus prepared coating liquid onto the substrate 2
in accordance with a known coating procedure such as the gravure
printing method, the screen printing method, the reverse roll
coating method using a gravure plate, or the like; and then drying
the coated liquid. As the solvent to be used for preparing the
coating liquid, for instance, water, toluene, methyl ethyl ketone,
ethanol, isopropyl alcohol, cyclohexane, dimethyl formamide, ethyl
acetate, etc., can be enumerated. The coating amount of the coating
liquid for back face layer is not limited as long as the
anti-fusion property, the lubricity or the like is fulfilled, and
usually, it is in the range of about 0.1 g/m.sup.2-about 3
g/m.sup.2 in term of the solid content.
(Back Face Primer Layer)
[0091] Further, in the thermal transfer sheet of the first
embodiment, a back face primer layer (not shown) can also be
provided between the substrate sheet 2 and the back face layer 5.
The back face primer layer is a layer provided for improving the
adhesion between the substrate sheet 2 and the back surface layer
5, and it is an optional layer. As the back face primer layer, for
example, polyester resins, polyurethane resins, acrylic resins,
polycarbonate resins, polyamide resins, polyimide resins,
polyamideimide resins, vinyl chloride-vinyl acetate copolymers,
polyvinyl butyral resins, polyvinyl alcohol resins, polyvinyl
pyrrolidone resins and the like may be enumerated. It may also
contain a conductive material for imparting appropriate
conductivity. For example, sulfonated polyaniline, carbon
particles, silver particles, gold particles, and the like may be
enumerated.
[0092] As described above, the thermal transfer sheet according to
the first embodiment of the present invention is fairly explained.
However, without deviating from the scope and the spirit of the
first embodiment of the present invention, the thermal transfer
sheet can takes various modified embodiments other than the ones as
disclosed above. For example, in the constitution shown in FIG. 1,
it is possible to provide the above-mentioned colorant layer 3 and
a transferable protective layer (not shown) are provided on the
same surface of the substrate sheet 2 as being frame sequentially
in order to manufacture an integral type thermal transfer sheet. In
addition, it is also possible to provide colorant layers having
each individual hue different from each other on the same surface
of the substrate sheet 2 as being frame sequentially. For instance,
it is possible to provide a yellow colorant layer, a magenta
colorant layer, and a cyan colorant layer on the substrate sheet 2
so as to the dye layers are layered in parallel on the substrate
sheet 2 across the surface of the substrate sheet, as being frame
sequentially. In this case, as long as at least one colorant layer
of these colorant layers provided as being frame sequentially is
the colorant layer 3 as above described, it can be embraced in the
first embodiment of the present invention.
Coating Liquid for Colorant Layer of the First Embodiment
[0093] Next, the coating liquid for colorant layer of the first
embodiment of the present invention will be described below. The
coating liquid for colorant layer of the first embodiment is the
coating liquid for forming the above explained colorant layer of
the thermal transfer sheet of the first embodiment, and is
characterized in that it contains a predetermined solvent, a
colorant dispersible to the predetermined solvent, a dispersant,
and a binder resin.
[0094] The coating liquid for colorant layer of the first
embodiment is further characterized in that the colorant
dispersible in the predetermined solvent is dispersed in a particle
size of not less than 50 nm and not more than 300 nm in the coating
liquid for colorant layer; and, the dispersant is the above
mentioned "specific dispersant(s)", i.e., one or more kinds of
dispersants selected from the group consisting of polyether-based
dispersants, graft type polymer dispersants, acryl-based block type
polymer dispersants, urethane-based polymer dispersants and
azo-based dispersants. With respect to the coating liquid for
colorant layer of the first embodiment, although the particle size
of the colorant dispersible to the predetermined solvent is defined
as above, the particle size of the colorant used herein denotes the
average dispersed particle diameter of the colorant in the coating
liquid for colorant layer in the first embodiment. Concretely, it
is a dispersed particle diameter of the colorant particles
dispersed in a dispersion medium of the coating liquid, and it is
determined by a laser light scattering particle size distribution
meter. With respect to the measurement of the particle diameter by
the laser light scattering particle size distribution meter, the
coating liquid to be measured is appropriately diluted to a
concentration that is capable of being measured by the laser light
scattering particle size distribution meter (for example, 1000-fold
dilution, etc.) with the same predetermined solvent as being
contained in the coating liquid, and then the particle diameter can
be determined by using the laser light scattering particle size
distribution analyzer (for example, Nanotrac particle size
distribution analyzer UPA-EX150, manufactured by Nikkiso Co. Ltd.)
in accordance with the dynamic light scattering method at
23.degree. C. The average dispersed particle diameter used herein
is a volume average particle size.
[0095] Further, with respect to the coating liquid for colorant
layer of the first embodiment, the "colorant in the coating liquid
for colorant layer are dispersed" denotes the condition that no
precipitation of the colorant particles is observed visually after
120 hours (5 days) standing of the coating liquid for colorant
layer at 20-25.degree. C. With respect to the coating liquid for
colorant layer of the first embodiment, it is defined that the
colorant dispersible to the predetermined solvent is dispersed in a
particle diameter of not less than 50 nm and not more than 300 nm
in the coating liquid for colorant layer. This is because, if the
particle diameter of the colorant dispersed is less than 50 nm,
there is a tendency that the colorant caused gelation due to an
interaction with the binder resin, and the coating liquid owns the
same properties as the state of the colorant is dissolved, and as a
result, background stain (stains at the non-printing portion is
caused) is likely to occur during printing. On the other hand, if
the particle diameter of the colorant dispersed is more than 300
nm, there is a tendency that the precipitation of the colorant is
easily caused by variation of the coating liquid for colorant layer
with time, and, also the transfer sensitivity becomes insufficient,
and the desired print density cannot be obtained.
[0096] In the coating liquid for colorant layer of the first
embodiment, it is preferable that the colorant dispersible in the
predetermined solvent is in the range of 50-300 parts by weight,
and more desirably, in the range of 85-250 parts by weight, on the
basis of 100 parts by weight of the binder resin. Furthermore, it
is preferable that the colorant dispersible in the predetermined
solvent is in the range of 0.5-20% by weight on the basis of the
total weight of the coating liquid for colorant layer of the first
embodiment. Furthermore, the total weight of the colorant
dispersible in the predetermined solvent, the binder resin and the
"specific dispersant(s)" to the total weight of the coating liquid
for colorant layer of the first embodiment, that is, the solid
content is preferably in the range of 2-40% by weight, and more
preferably in the range of 5-35% by weight. Incidentally, when the
coating liquid for the colorant layer of the first embodiment
contains two or more kinds of colorants dispersible in the
predetermined solvent, both the content and the solid content of
the above colorant represent the total amount of the individual
color materials.
[0097] It is preferable that as the colorant dispersible in the
predetermined solvent, a dye such as Disperse Yellow 54, and a
pigment represented by the Formula 3 are mixed and contained in the
coating liquid for colorant layer of the first embodiment, form the
view point that the ink becomes good, and the printed articles
becomes excellent in durability such as light resistance, and it
becomes possible to enhance the transfer sensitivity during
printing. The colorant layer of the thermal transfer sheet is a
layer containing a colorant for thermal transition by heating with
a thermal head or the like, by sublimation or the like, and thus,
it is preferable to mix the pigment to the above mentioned dye as
the main ingredient. In detail, when using the pigment, it is
preferable to mix the dye and the pigment in a range of
dye/pigment=7/3 to 9.5/0.5 (weight ratio).
[0098] The details for the predetermined solvent the colorant
dispersible in the predetermined solvent, the "specific
dispersant(s)", and the binder resin, which are essential
components of the coating liquid for colorant layer of the first
embodiment, are the same with those described above in the
explanation about the colorant layer of the thermal transfer sheet.
Further, as a preferred combination of the "specific dispersant(s)"
and the colorant dispersible to the predetermined solvent in the
coating liquid for colorant layer of the first embodiment, the
combinations described above in the explanation about the colorant
layer 3 of the thermal transfer sheet of the first embodiment can
be cited. In the coating liquid for colorant layer of the first
embodiment, it is possible to add optionally any of various
additives known in the art, if necessary, in addition to the
essential components. As the optional additives, for instance,
polyethylene wax, silane coupling agent, organic minute particles,
inorganic minute particles and the like may be enumerated.
"First Method for Preparation of Coating Liquid for Colorant
Layer"
[0099] The coating liquid for colorant layer of the first
embodiment can be prepared in accordance with a known preparation
method in the art using, for example, a paint shaker, a propeller
type stirrer, a dissolver, a homomixer, a ball mill, a bead mill, a
sand mill, a biaxial roll mill, a triaxial roll mill, an ultrasonic
dispersing machine, a kneader, a line mixer, a biaxial extruder or
the like. As one approach to preparing the coating liquid for
colorant layer of the first embodiment, in the case of using a bead
mill, or a ball mill, as for the beads, the balls to be used,
glass, ceramic, steel, zirconia and the like may be enumerated.
Among them, zirconia beads are especially desirable from the
viewpoint of hardness, wear resistance, specific gravity and
particle size. As the diameter of the beads, it is preferable to be
in the range of 0.05-2.0 mm, and particularly, it is preferable to
select the bead diameter depending on the initial particle diameter
of the colorant.
"Second Method for Preparation of Coating Liquid for Colorant Layer
of First Embodiment"
[0100] Further, as another method for preparing the coating liquid
for colorant layer of the first embodiment, there is a method
where, at a high shear rate, the colorant dispersible to the
predetermined solvent, the "specific dispersant(s)", and a lump of
the binder resin are kneaded, then the predetermined solvent is
added, and the colorant dispersible to the predetermined solvent is
dispersed in the added predetermined solvent with using a paint
shaker. For instance, an ink which underwent dispersing treatment
by using Ultra Visco Mill UVM-2, manufactured by AIMEX Co., Ltd.,
with zirconia beads (average diameter of 0.3 mm) at a rotation rate
of 1000 rpm for 10 hours, and a colorant dispersible to the
predetermined solvent, "specific dispersant(s)", a binder resin and
a solvent are kneaded by using a biaxial roll mil, manufactured by
Kansai Roll Co., Ltd., under the conditions of roll temperature of
20.degree. C., roll rotation rate for front roll of 20 rpm, and
roll rotation rate for rear roll of 24 rpm, and then the solvent is
further added to kneaded product, and they underwent dispersion
using a paint shaker, in order to prepare the coating liquid for
colorant layer of the first embodiment. With respect to both of the
coating liquids for colorant layer of the first embodiment which
were prepared in accordance with either one of the above two
methods, it has been confirmed that the particle size distribution
of the colorant in the coating liquid is in the range of 50 nm-300
nm in the diameter on the measurement in accordance with the above
mentioned measurement method of the particle size distribution.
"Method for Preparation of Coating Liquid for Specific Colorant
Layer (Third Method for Preparation of the Coating Liquid for
Colorant Layer of the First Embodiment)"
[0101] In the above two methods, in the presence of the binder
resin, by using the "specific dispersant(s)", the colorant
dispersible in the predetermined solvent is dispersed in the
predetermined solvent. However, depending on the type of the binder
resin contained in the coating liquid for colorant layer of the
first embodiment, the binder resin may interfere in the
dispersibility of the colorant owing to the "specific
dispersant(s)". Thus, in the "method for preparation of coating
liquid for specific colorant layer", in order to sufficiently
exhibit the dispersibility of the colorant owing to the "specific
dispersant(s)", under the condition that no binder resin or a
little amount of binder resin exists, a dispersion where the
colorant is dispersed in the predetermined solvent is prepared by
using the "specific dispersant(s)". Then, the binder resin, or a
liquid containing the binder resin is post-added to the above
mentioned dispersion, in order to prepare the coating liquid for
colorant layer which contains the predetermined solvent, the
colorant dispersible in the predetermined solvent, the "specific
dispersant(s)", and a binder resin. According to this preparation
method, it is possible to disperse the colorant into the
predetermined solvent, under the condition of being free from, or
receiving little extent of, the influence of the binder resin which
becomes a factor of interfering in the dispersibility of the
colorant owing to the "specific dispersant". Thus, as compared with
the above mentioned two methods, it is possible to allow the
colorant to exist with a smaller particle size in the finally
prepared coating liquid for colorant layer of the first embodiment.
This preparation method can be carried out by appropriately
selecting and using procedures in the above mentioned two methods,
except the points that the colorant undergoes dispersing under the
condition that the binder resin does not exist, or exists in a
small amount, and that the binder resin is post-added after the
colorant has been dispersed.
[0102] The coating liquid for colorant layer of the first
embodiment, in addition to the above essential components, may
contain any optional ingredient(s).
Method of Manufacturing Thermal Transfer Sheet of the First
Embodiment
[0103] Next, the method of manufacturing the thermal transfer sheet
of the first embodiment of the present invention will be explained.
The method of manufacturing the thermal transfer sheet of the first
embodiment is characterized in that it comprises a colorant layer
forming step where a coating liquid for colorant layer is applied
onto a surface of a substrate sheet to form a colorant layer;
wherein the coating liquid for colorant layer used in the colorant
layer forming step contains a predetermined solvent, a colorant
dispersible in the predetermined solvent, a dispersant and a binder
resin; wherein the colorant dispersible in the predetermined
solvent is dispersed in a particle size of not less than 50 nm and
not more than 300 nm in the coating liquid for colorant layer; and,
wherein the dispersant is one or more kinds of dispersants selected
from the group consisting of polyether-based dispersants, graft
type polymer dispersants, acryl-based block type polymer
dispersants, urethane-based polymer dispersants and azo-based
dispersants.
(Colorant Layer Forming Step)
[0104] As the coating liquid for colorant layer used in the
colorant layer forming step, the coating liquid for the colorant
layer of the first embodiment described above can be used as-is,
thus the detailed description thereof will be omitted here.
[0105] There is no particular limitation on the coating method of
the coating liquid for colorant layer, and for instance, it is
possible to select appropriately and use any known method such as
gravure coating, roll coating method, screen printing method,
reverse roll coating method using a gravure plate, etc. There is no
particular limitation on the coating amount of the coating liquid
for colorant layer, but usually, it is in the range of about 0.2
g/m.sup.2-about 10 g/m.sup.2 in terms of solid content.
[0106] The method of manufacturing a thermal transfer sheet of the
first embodiment may include optional step(s) other than the above
colorant layer forming step. For example, it may include a back
face layer forming step that forms the back face on another surface
of the substrate sheet, a step for forming a back face primer layer
between the substrate sheet and the back face layer.
Method of Manufacturing Thermal Transfer Sheet of the Second
Embodiment
[0107] Next, a method of manufacturing a thermal transfer sheet of
the second embodiment of the present invention will be explained,
while the superiority of the thermal transfer sheet which is
manufactured by the manufacturing method of the second embodiment
will be referred.
[0108] FIG. 4 is a schematic cross-sectional view of a thermal
transfer sheet which is manufactured by the manufacturing method of
the second embodiment. In the manufacturing method of the second
embodiment, a colorant layer 3 is formed on a substrate sheet 2 by
using a coating liquid for colorant layer which contains a
predetermined solvent, a sublimable dye soluble in the
predetermined solvent, a colorant dispersible in the predetermined
solvent, and a binder resin. In other words, the colorant layer 3
is formed by using a coating liquid which contains a binder resin,
and wherein a sublimable dye 10y is dissolved in the predetermined
solvent and a colorant 10x is dispersed in the predetermined
solvent.
[0109] Density of an image formed by thermal transfer recording
method is believed to be closely related to the thermal migration
of the sublimable dye contained in the colorant layer, and thus it
is important to improve the thermal migration of the sublimable dye
contained in the colorant layer in order to prepare the colorant
layer capable of forming a high density image. As a method for
improving the thermal migration of the sublimable dye, a method of
forming a colorant layer which uses a coating liquid where a
sublimable dye is dissolved in the solvent may be enumerated.
According to the colorant layer formed by this method, it is
possible to allow the sublimable dye to present at its molecular
level in the colorant layer, and thus it is possible to improve the
thermal migration of the sublimable dye in the colorant layer. On
the other hand, with respect to a colorant layer formed by using a
coating liquid prepared by dispersing the sublimable dye in a
solvent in place of the coating liquid obtained by dissolving the
sublimable dye in a solvent, since the sublimable dye presents in
its state of having a certain degree of particle diameter in the
colorant layer, the thermal migration of the sublimable dye is
forced to decrease, and it becomes difficult to perform
high-density image formation.
[0110] As described in the thermal transfer sheet of the first
embodiment, in the case of forming the colorant layer 3C by using
the coating liquid prepared by dissolving the sublimable dye 10y in
the predetermined solvent (see FIG. 3), it is impossible to prevent
the occurrence of the kick and the scumming.
[0111] Moreover, in order to prevent localization of the sublimable
dye to the interfaces, the localization being the cause of
occurrence of the kick and the scumming, it is preferable to form a
colorant layer by using a coating liquid wherein a colorant is
dispersed in a solvent. Therefore, in the method of manufacturing
the thermal transfer sheet of the first embodiment as mentioned
above, by forming the colorant layer with the coating liquid for
colorant layer which includes a predetermined solvent and a
colorant dispersible to the predetermined solvent, the occurrences
of the kick and the scumming are repressed. Furthermore, in the
method of manufacturing the thermal transfer sheet of the first
embodiment, by containing the "specific dispersant(s)" in the
coating liquid for colorant layer, it is plotted to improve the
light resistance, and to repress the lowering of the printing
density at the highlight portion, while repressing the occurrences
of the kick and the scumming.
[0112] Incidentally, in order to obtain a colorant layer which can
form a high density image, while repressing the occurrences of the
kick and the scumming, it is preferable to present the colorant at
its molecular level in the colorant layer. When the colorant layer
is formed by using the coating liquid for colorant layer where the
colorant is dispersed in the solvent, the colorant 10x comes to be
in a condition of showing a certain degree of the particle diameter
in the colorant layer 3. Thus, it is impossible to sufficiently
enhance the thermal migration of the colorant, and it is inferior
in the density to the colorant layer which is formed by using the
coating liquid where the sublimable dye 10y is dissolved in the
solvent (See FIG. 3).
[0113] Therefore, in order to obtain a thermal transfer sheet
capable of forming an image of a higher density, while preventing
the occurrences of the kick and the scumming, the method for
manufacturing the thermal transfer sheet of the second embodiment
is characterized in that it comprises a colorant layer forming step
where a coating liquid for colorant layer is applied onto a surface
of a substrate sheet to form a colorant layer; and the coating
liquid for colorant layer contains a predetermined solvent, a
sublimable dye soluble in the predetermined solvent, and a colorant
dispersible in the predetermined solvent. That is, the method is
characterized in that the colorant layer is formed by using the
coating liquid for colorant layer where the sublimable dye is
dissolved in the predetermined solvent and the colorant is
dispersed in the predetermined solvent. According to the
manufacturing method of the thermal transfer sheet of the second
embodiment having this feature, it is possible to manufacture a
thermal transfer sheet which is capable of forming a high density
image, while preventing the occurrences of the kick and the
scumming.
[0114] The detailed mechanisms for the aspect that the thermal
transfer sheet manufactured in accordance with the manufacturing
method of the second embodiment plays the above effects have been
not clarified well, but the localization of the sublimable dye to
the interfaces is repressed in the colorant layer 3 which is formed
in accordance with the manufacturing method of the second
embodiment. Thus, it can be assumed that the occurrences of the
kick and/or the scumming are repressed by that condition.
Specifically, it can be assumed that the colorant 10x dispersed in
the coating liquid for colorant layer plays a roll of repressing
the localization of the sublimable dye 10y to the interfaces of the
colorant layer 3, and thus the sublimable dye 10y can be present in
its dispersed state in the colorant layer 3 which is formed in
accordance with the manufacturing method of the second
embodiment.
[0115] As a reason why the colorant 10x dispersed in the coating
liquid for colorant layer plays a roll of repressing the
localization of the sublimable dye 10y dissolved in the coating
liquid for colorant to the interfaces of the colorant layer, the
affinity of the sublimable dye 10y with the colorant 10x can be
mentioned. According to the conventional method, when the colorant
layer is formed by using a sublimable dye 10y dissolved in a
coating liquid for colorant layer, the sublimable dye 10y comes to
be localized toward free boundary (interface) as shown in FIG. 3.
However, in the manufacturing method of the second embodiment,
since the colorant 10x is dispersed in the coating liquid for
colorant layer, it is inferred that it is possible to locate the
sublimable dye 10 around the particles of the colorant 10x that are
present in a dispersed state in the colorant layer 3 formed by the
manufacturing method of the second embodiment, owing to the
affinity of the colorant 10x with the sublimable dye 10y. Thus, as
shown in FIG. 4, in the colorant layer 3 which is formed in
accordance with the manufacturing method of the second embodiment,
it is believed that the localization of the sublimable dye 10y to
the interfaces is suppressed, and thus it becomes possible to allow
the sublimable dye 10y to present in its distributed state in the
colorant layer 3, and it becomes possible to prevent the
occurrences of the kick and/or the scumming.
[0116] Further, in the manufacturing method of the second
embodiment, since the colorant layer 3 is formed by using a coating
liquid for colorant layer where the sublimable dye is dissolved in
a solvent, it is possible to allow the sublimable dye to present at
its molecular level in the colorant layer 3. Thus, while preventing
the occurrences of the kick and/or the scumming, it is possible to
form a high density image.
[0117] Even not according to this hypothetical mechanisms, the
point that, when using the colorant layer which is formed by using
the coating liquid where the sublimable dye 10y is dissolved in the
predetermined solvent and the colorant 10x is dispersed in the
predetermined solvent, it becomes possible to form a high density
image, while repressing the occurrences of the kick and/or the
scumming, is revealed from the results of Examples and Comparative
Examples described later.
[0118] Hereinafter, each component used in the manufacturing method
of the second embodiment, and each component contained in the
coating liquid for colorant layer will be described.
[0119] As a substrate sheet used in the manufacturing method of the
second embodiment, the substrate sheet as described in the above
explanation of the thermal transfer sheet of the first embodiment
can be used as-is, and thus, a detailed description thereof will be
omitted here.
(Coating Liquid for the Colorant Layer in the Manufacturing Method
of the Second Embodiment)
[0120] The coating liquid for colorant layer used in the
manufacturing method of the second embodiment (hereinafter, it is
referred to as "coating liquid for colorant layer of the second
embodiment") contains a binder resin, a predetermined solvent, a
sublimable dye dissolvable in the predetermined solvent, and a
colorant dispersible in the predetermined solvent. That is, in the
coating liquid for colorant layer of the second embodiment, the
sublimable dye 10y is present in its dissolved state, and the
colorant 10x is present in its dispersed state.
[0121] There is no particular limitation on the binder resin which
is included in the coating liquid for colorant layer of the second
embodiment, for example, it is possible to use the binder resins
described in the above explanation of the colorant layer of the
thermal transfer sheet of the first embodiment as-is, and thus, a
detailed description thereof will be omitted here.
[0122] The "predetermined solvent" contained in the coating liquid
for colorant layer of the second embodiment means a solvent which
is possible to dissolve the sublimable dye, and is possible to
disperse the colorant. There is no particular limitation for the
predetermined solvent, for example, it is possible to appropriately
select one from the solvents as described in the above explanation
of the colorant layer of the thermal transfer sheet of the first
embodiment, and use it. Thus, a detailed description thereof will
be omitted here.
[0123] The coating liquid for colorant layer of the second
embodiment may contain one kind of the solvent singly,
alternatively, it may contain two or more solvents. For example, it
is possible to use a solvent A capable of dissolving the sublimable
dye in combination with a solvent B capable of dispersible the
colorant. Here, the case of using the solvent A and the solvent B
is applicable with the proviso that the solvent A capable of
dissolving the sublimable dye cannot dissolve the colorant.
Incidentally, since the sublimable dye is to be dissolved by the
solvent A, the solvent B may be either capable of or incapable of
dissolving the sublimable dye as long as it satisfies the condition
that it can disperse the colorant. Further, the coating liquid for
colorant layer of the second embodiment may further contain
solvent(s) other than the solvent A and the solvent B, provided
that at least one colorant contained in the coating liquid for
colorant layer of the second embodiment is not dissolved in all of
the solvent contained in the coating liquid for colorant layer of
the second embodiment.
[0124] There is no particular limitation on the "sublimable dye
dissolvable in the predetermined solvent" which is contained in the
coating liquid for colorant layer of the second embodiment, and it
can be appropriately selected depending on the kind of the
predetermined solvent contained in the coating liquid for colorant
layer of the second embodiment. Concretely, as far as the
sublimable dye is dissolvable to a solvent contained in the coating
liquid for colorant layer of the second embodiment, any sublimable
dye is usable.
[0125] There is also no particular limitation on the "colorant
dispersible in the predetermined solvent" which is contained in the
coating liquid for colorant layer of the second embodiment, and it
can be appropriately selected depending on the kind of the above
mentioned predetermined solvent contained in the coating liquid for
colorant layer of the second embodiment. Concretely, as far as the
colorant is dispersible to a solvent contained in the coating
liquid for colorant layer of the second embodiment, any colorant is
usable. Incidentally, the "colorant dispersible to the
predetermined solvent" which is contained in the coating liquid for
colorant layer of the second embodiment denotes a colorant which is
impossible to be dissolved in the predetermined solvent, and there
is no particular limitation on the dispersibility of the colorant.
For instance, it is possible to improve the dispersibility of the
colorant by using the dispersant. That is, as far as the colorant
is dispersed in the coating liquid for colorant layer of the second
embodiment as a result, there is no limitation.
[0126] The sublimable dye soluble in the predetermined solvent and
the colorant dispersible in the predetermined solvent can be
appropriately selected depending on the solvent contained in the
coating liquid for colorant layer of the second embodiment.
Concretely, at first a predetermined solvent is selected, and then,
a sublimable dye soluble in the predetermined solvent and a
colorant dispersible in the predetermined solvent may be
selected.
[0127] As the sublimable dye and the colorant contained in the
coating liquid for colorant layer of the second embodiment, the
sublimable dyes and the colorants as described in the above
explanation for the colorant layer of the thermal transfer sheet of
the first embodiment can be used with an appropriate selection, and
thus, a detailed description thereof will be omitted here.
[0128] Here, since the quinophthalone dyes represented by the above
formula (1) possesses light resistance and a high brightness, they
are preferable as the sublimable dye dissolvable to the
predetermined solvent, or the sublimable dye dispersible to the
predetermined solvent.
[0129] Further, since the pigments represented by the above formula
(2) can show a high dispersibility in the coating liquid for
colorant layer of the second embodiment, and can increase the
stability of the coating liquid for colorant layer of the second
embodiment, and further it can also prevent the occurrences of the
kick and the scumming effectively, they are preferable as the
colorant dispersible to the predetermined solvent.
[0130] The coating liquid for colorant layer of the second
embodiment may contain, as the "sublimable dye dissolvable in the
predetermined solvent", a kind of the sublimable dye singly, or two
or more kind of the sublimable dyes in combination. Further, in the
case that the "colorant dispersible to the predetermined solvent"
is a sublimable dye, the coating liquid for colorant layer of the
second embodiment may contain, as the "sublimable dye dispersible
in the predetermined solvent", a kind of the sublimable dye singly,
or two or more kind of the sublimable dyes in combination. It is
also possible to contain, as the "colorant dispersible to the
predetermined solvent", sublimable dye(s) and pigment(s) in
combination. It is also possible to use two or more kinds of
pigments in combination. With respect to the pigment, it is
possible to use the pigments as described in the above explanation
for the colorant layer of the thermal transfer sheet of the first
embodiment with an appropriate selection, and thus, the detailed
description thereof will be omitted here.
[0131] Hereinafter, examples of the colorant(s) and the sublimable
dye(s) contained in the coating liquid for colorant layer of the
second embodiment will be explained with referring to concrete
solvents. The manufacturing method of the thermal transfer sheet of
the second embodiment is not limited to these combinations.
[0132] In the case that the predetermined solvent is a mixed
solvent of methyl ethyl ketone/toluene:
[0133] As the sublimable dye capable of dissolving in the mixed
solvent of methyl ethyl ketone/toluene, for example, Disperse
Yellow 201 or the like can be used. Further, as the colorant
dispersible in the mixed solvent of methyl ethyl ketone/toluene,
for instance, the pigments exemplified above, the sublimable dyes
exemplified above, for example, Disperse Yellow 54 or the like can
be used.
[0134] In the coating liquid for colorant layer, a dispersant for
improving the dispersibility of the colorant may be contained. As
the dispersant, for instance, graft-type polymer dispersion aids,
polyether-based dispersant aids, acryl based block type polymer
dispersant aids and the like may be enumerated. In addition, as the
dispersant, derivatives in which organic pigment was treated with a
sulfonated compound or the like may be enumerated. As the treating
method, in addition to rosin treatment, surface treatments such as
acidic group treatment, basic treatment, pigment derivative
treatment, and the like may be enumerated.
[0135] Further, the coating liquid for colorant layer may contain
other optional additives, for instance, a releasing agent for
improving releasability from the receiving layer of the thermal
transfer-image receiving sheet, an antistatic agent, an organic or
inorganic filler for controlling the lubricity with the receiving
layer, etc., in addition to the essential components, i.e., the
binder resin, the predetermined solvent, the sublimable dye
dissolvable in the predetermined solvent, and the colorant
dispersible to the predetermined solvent.
[0136] In a preferred method for manufacturing a thermal transfer
sheet of the second embodiment, the coating liquid for colorant
layer of the second embodiment contains the "specific
dispersant(s)" as described in the above explanation for the
coating liquid for colorant layer of the first embodiment, in
addition to the binder resin, the predetermined solvent, the
colorant 10x dispersible to the predetermined solvent and the
sublimable dye dissolvable in the predetermined solvent. According
to this manufacturing method of the thermal transfer sheet of this
preferred form, owing to the function of the "specific
dispersants", it is possible to further repress the occurrences of
the kick and the scumming, and further improve the density of the
image formed, in the thermal transfer sheet manufactured by the
manufacturing method of the second embodiment, and further, it is
also possible to further improve the light resistance, and suppress
the reduction of the print density in the highlight portion.
[0137] Although there is no particular limitation for the method of
forming the colorant layer 3, and for instance, the colorant layer
can be formed by preparing a coating liquid for colorant layer
where a binder resin, a solvent, a sublimable dye dissolvable in
the solvent, and a colorant dispersible to the solvent, and
optionally any additive(s) such as a dispersant, a releasing agent
or the like as necessary, are used, and the sublimable dye is
dissolved in the solvent and the colorant is dispersed in the
solvent, coating thus prepared coating liquid for colorant layer on
the substrate sheet in accordance with a known coating procedure
such as the gravure printing method, the screen printing method,
the reverse roll coating printing method using a gravure plate, or
the like, and then drying the coated solution. Although there is no
particular limitation about the coating amount of the coating
liquid for the colorant layer, it is preferable that it is in the
range of 0.2 g/m.sup.2-10 g/m.sup.2 in terms of solid content.
[0138] As described above, the manufacturing method of the second
embodiment is fairly explained as mainly describing about the
manufacturing method for providing the colorant layer 3 directly on
the substrate sheet 2. Similar to the method of manufacturing a
thermal transfer sheet of the first embodiment, however, the
manufacturing method of the second embodiment may include step(s)
of providing arbitrary layer(s), between the substrate sheet 2 and
the colorant layer 3, and/or on another surface side of the
substrate sheet 2, on which the colorant layer 3 does not
formed.
<Thermal Transfer Sheet of the Second Embodiment>
[0139] The thermal transfer sheet 1 of the second embodiment, as
shown in FIG. 1, takes a configuration in which the colorant layer
3 is provided on the substrate sheet 2. Here, w the thermal
transfer sheet 1 of the second embodiment is characterized in that,
as shown in FIG. 4, the colorant layer 3 includes a predetermined
solvent, a sublimable dye 10y, and a colorant 10x, and the
sublimable dye 10y is a sublimable dye that is soluble in the
predetermined solvent, and the colorant 10x is a colorant that is
dispersible in the predetermined solvent.
[0140] According to the thermal transfer sheet of the second
embodiment comprising the colorant layer 3 having the above
characteristics, for the reasons as described in the above
explanation for the manufacturing method of the second embodiment,
it is possible to prevent the occurrences of the kick and/or the
scumming, and to form a high density image.
[0141] Here, it should be noted that, although the thermal transfer
sheet of the second embodiment also has an essential condition that
the colorant layer 3 contains a predetermined solvent, the
condition does not intend to denote that the predetermined solvent
is positively and actively contained in the colorant layer 3. But,
the predetermined solvent contained in the colorant layer 3 refers
to a residual solvent contained in the colorant layer 3.
Concretely, when the solvent remaining in the colorant layer 3 is a
solvent which can dissolve the sublimable dye included in the
colorant layer and which can disperse the colorant included in the
colorant layer, it can be said that the thermal transfer sheet of
the second embodiment can exhibit the same functions and effects as
the thermal transfer sheet manufactured by the manufacturing method
of the second embodiment.
"Determination Method for Colorant, Residual Solvent"
[0142] For instance, by the following method, it is possible to
determine whether a thermal transfer sheet of interest
(hereinafter, referred to as target thermal transfer sheet)
satisfies the matters specifying the thermal transfer sheet of the
second embodiment or not. First, the colorant layer of the target
thermal transfer sheet is analyzed in order to identify the
colorant component contained in the colorant layer. As the
identification method of the colorant components, any
conventionally known analytical method such as the nuclear magnetic
resonance spectroscopy, IR spectroscopy or the like is
applicable.
[0143] In the above analysis of the colorant layer, when it is
determined that the colorant contained in the colorant layer is
only one kind, the target thermal transfer sheet can be judged as
not being satisfying the matters specifying the thermal transfer
sheet of the second embodiment. On the other hand, when it is
determined that the colorants contained in the colorant layer are
two or more kinds, the kind of the solvent remaining in the
colorant layer is further determined. As the identification method
of the kind of the solvent, for example, the gas chromatography is
applicable. In the identification of the kind of the solvent by the
gas chromatography, for instance, a gas chromatography analyzer
such as Gas Chromatography GC14-A, manufactured by Shimadzu
Corporation, and the like can be utilized. Incidentally, in order
to eliminate the influence of the solvents which have been
contained in the substrate sheet, a heat resisting sliding layer,
and/or any arbitrary layers in the target thermal transfer sheet,
it is necessary to analyze to the layer corresponding to the
colorant layer of the target thermal transfer sheet on the
identification of the kind of the solvent. Concretely, when the
kind of the solvent remaining in the colorant layer is determined
by using the gas chromatography method, it is important to take
only a part of the layer corresponding to the colorant layer of the
target thermal transfer sheet and carry out the analyze to the
portion.
[0144] When at least one of the identified colorant components as
mentioned above is the colorant component dissolvable in the
identified solvent as mentioned above, and at least one of the
identified colorant components as mentioned above is the colorant
component dispersible in the identified solvent as mentioned above,
the target thermal transfer sheet can be judged as being satisfying
the matters specifying the thermal transfer sheet of this
embodiment. Incidentally, in the case that two or more kinds of
solvents are identified in the colorant layer of the target thermal
transfer sheet, when at least one of the identified colorant
components is the colorant component dissolvable in at least one of
the identified solvents, and at least one of the identified
colorant components is the colorant component dissolvable to none
of the identified solvents, the target thermal transfer sheet can
be judged as being satisfying the matters specifying the thermal
transfer sheet of this embodiment. Further, by using the
"determination method for dispersibility of colorant to
predetermined solvent" as described in the above explanation for
the manufacturing method of the first embodiment, it is possible to
determine whether the identified colorant can be dissolved or can
be dispersed in the identified solvent.
[0145] Hereinafter, each component of the thermal transfer sheet of
the second embodiment will be described. Incidentally, the thermal
transfer sheet of the second embodiment is correlated with the
manufacturing method of the second embodiment, and thus, unless
otherwise specified, those described in the manufacturing method of
the second embodiment can be used as-is.
[0146] There is no particular limitation on the substrate sheet 2,
and it is possible to use any of the substrate sheets described in
the manufacturing method of the second embodiment by selecting
appropriately.
(Colorant Layer)
[0147] In the colorant layer 3, a binder resin, a sublimable dye, a
colorant and a predetermined solvent are included. With respect to
each individual component, it is possible to use any of the
corresponding components described in the manufacturing method of
the second embodiment by selecting appropriately. Herein, the
sublimable dye referred to in the thermal transfer sheet of the
second embodiment means a sublimable dye dissolvable in a
predetermined solvent, and the colorant means a colorant
dispersible in the predetermined solvent.
[0148] With respect to the containing ratio of the sublimable dye
and the colorant in the colorant layer, there is no particular
limitation, and the ratio can be determined appropriately depending
on the function(s) required to the colorant layer, for instance,
light resistance, density characteristics, etc.
[0149] In a preferred form, the colorant layer 3 further contains
the "specific dispersant(s)" as described in the above explanation
for the first embodiment. According to this colorant layer 3, it is
possible to repress the occurrences of the kick and the scumming,
and further improve the density of the image formed, and further,
it is also possible to further improve the light resistance, and
suppress the reduction of the print density in the highlight
portion, owing to the function of the "specific dispersant(s)".
[0150] The colorant layer 3 may also contain optional components
such as a releasing agent. For example, by containing a releasing
agent in the colorant layer 3, it is possible to improve the
releasing property between the colorant layer 3 and the receiving
layer at the time of image formation. In the case that measures for
releasing property is taken in the receiving layer side, it is not
always necessary to include the releasing agent in the colorant
layer 3.
[0151] As the releasing agent, it is possible to use the releasing
agents as described in the above explanation for the manufacturing
method of the first embodiment with an appropriate selection, and
thus, the detailed description thereof will be omitted here.
[0152] Further, a primer layer may be provided between the
substrate sheet 2 and the colorant layer 3. As the primer layer,
the primer layer as described in the above explanation for the
thermal transfer sheet of the first embodiment can be used as-is,
and thus, the detailed description thereof will be omitted
here.
(Back Face Layer)
[0153] Further, a back face layer may be provided on the other
surface of the substrate sheet 2. As the back face layer, the back
face layer as described in the above explanation for the thermal
transfer sheet of the first embodiment can be used as-is, and thus,
the detailed description thereof will be omitted here.
(Back Face Primer Layer)
[0154] Further, aback face primer layer may be provided between the
substrate sheet 2 and the back face layer 5. As the back face
primer layer, the back face primer layer as described in the above
explanation for the thermal transfer sheet of the first embodiment
can be used as-is, and thus, the detailed description thereof will
be omitted here.
<Method of Manufacturing a Thermal Transfer Sheet of Third
Embodiment>
[0155] Next, a thermal transfer sheet which is manufactured by a
method for manufacturing a thermal transfer sheet of the third
embodiment will be explained with reference to FIG. 5. FIG. 5 is a
schematic cross-sectional view of the thermal transfer sheet which
is manufactured by the method for manufacturing a thermal transfer
sheet of the third embodiment.
[0156] The method for manufacturing a thermal transfer sheet of the
third embodiment is characterized by comprising a first colorant
layer forming step where a coating liquid which contains a first
solvent and a sublimable dye soluble in the first solvent is
applied onto a surface of a substrate sheet to form the first
colorant layer; and a second colorant layer forming step where a
coating liquid which contains a second solvent and a colorant
dispersible in the second solvent is applied onto the first
colorant layer to form the second colorant layer.
[0157] In the third embodiment, on the substrate sheet, the first
colorant layer 3A is formed by coating a coating liquid which
contains a first solvent and a sublimable dye soluble in the first
solvent. As explained above, in the colorant layer formed by using
the coating liquid wherein the sublimable dye is dissolved, the
sublimable dye is present in a state of being localized to the
interfaces (See, FIG. 3), and is in a state of causing the kick
and/or the scumming with ease. In other words, in the case that a
thermal transfer sheet where only the first colorant layer 3A is
provided on the substrate sheet 2 is manufactured, it is impossible
to prevent the kick and/or the scumming, although it becomes
possible to form a high density image by using the thermal transfer
sheet.
[0158] Therefore, in the third embodiment, the occurrences of the
kick and/or the scumming for which the first colorant layer 3A
cannot compensate is prevented by forming another layer on the
first colorant layer 3A. Concretely, in the third embodiment, a
second colorant layer is formed on the first colorant layer by
coating a coating liquid which contains a second solvent and a
colorant dispersible in the second solvent onto the first colorant
layer 3A. Since the second colorant layer 3B provided in the third
embodiment is formed by using the coating liquid where the colorant
is dispersed, the colorant 10x in the second colorant layer 3B thus
formed (See FIG. 2) are uniformly dispersed, and it is possible to
prevent the occurrences of the kick and the scumming owing to the
presence of the second colorant layer 3B. That is, the second
colorant layer 3B is mainly serves just as a lid for closing the
sublimable dye 10y localized at the interfaces of the first
colorant layer 3A.
[0159] Moreover, since the first colorant layer 3A is formed
between the substrate sheet 2 and the second colorant layer 3B, by
using the coating liquid where the sublimable dye has been
dissolved, the sublimable dye can be present at its molecular in
the first colorant layer 3A. Thus, it is possible to enhance the
thermal migration of the sublimable dye contained in the first
colorant layer 3A, and also possible to foam a high density image.
Furthermore, since the second colorant layer 3B contains the
colorant 10x, owing to the synergistic effect of the sublimable dye
10y with the colorant 10x, it becomes possible to form a higher
density image.
[0160] Next, the coating liquid for forming the first colorant
layer 3A, and the coating liquid for forming the second colorant
layer 3B will be described. Hereinafter, the coating liquid for
forming the first colorant layer 3A is referred to as "first
coating liquid" and the coating liquid for forming the second
colorant layer 3B is referred to as "second coating liquid" for
these explanations.
(First Coating Liquid)
[0161] In the first coating liquid, a first binder resin, a first
solvent, and a sublimable dye dissolvable to the first solvent are
included. That is, the sublimable dye is present in a state of
being dissolved in the first coating liquid.
[0162] There is no particular limitation for the first binder resin
contained in the first coating liquid, and it can be appropriately
selected depending on the kind of the sublimable dye dissolvable in
a first solvent. For example, the binder resins contained in the
coating liquid for the colorant layer as described in the
manufacturing method of the first embodiment may be mentioned.
Ditto for the second binder resin which is contained in the second
coating liquid described below. Also, the first binder resin may be
the same with or may be different from the second binder resin.
"Sublimable Dye"
[0163] There is no particular limitation on the sublimable dye
which is dissolved in the first coating liquid, and it can be
appropriately selected depending on the kind of the first solvent
to be contained in the first coating liquid. For example, the
sublimable dyes as described in the above explanation for the
manufacturing method of the first embodiment may be mentioned. The
first coating liquid may contain two or more kinds of the
sublimable dyes.
"First Solvent"
[0164] As the first solvent, as long as it is capable of dissolving
the sublimable dye, it is not particularly limited, and it may be
appropriately selected from known solvents. The first coating
liquid may contain two or more solvents, provided that at least one
of the solvents is capable of dissolving at least one of the
sublimable dyes contained in the first coating liquid.
[0165] In the first coating liquid, colorant(s) dispersible to the
first solvent may be contained. That is, the first colorant layer
3A may have a same constitution as the colorant layer 3 (See FIG.
5) which is formed by the manufacturing method of the above
mentioned second embodiment. Further, in the first coating liquid,
any optional ingredient(s) may be contained, in addition to the
first binder resin, the first solvent, and the sublimable dye.
[0166] Although there is no particular limitation on the method of
forming the first colorant layer, and for instance, the first
colorant layer can be formed by preparing a first coating liquid
where a sublimable dye is dissolved in the solvent, coating thus
prepared first coating liquid on the substrate sheet in accordance
with a known coating procedure such as the gravure printing method,
the screen printing method, the reverse roll coating printing
method using a gravure plate, or the like, and then drying the
coated solution. Although there is no particular limitation about
the coating amount of the first coating liquid, it is preferable
that it is in the range of 0.1 g/m.sup.2-5 g/m.sup.2 in terms of
solid content.
(Second Coating Liquid)
[0167] In the second coating liquid, a second binder resin, a
second solvent, and a colorant dispersible to the second solvent
are included. That is, the colorant is present in a state of being
dispersed in the second coating liquid.
"Colorant"
[0168] There is no particular limitation on the colorant which is
dispersed in the second coating liquid, and it can be appropriately
selected depending on the kind of the second solvent to be
contained in the second coating liquid. The colorant may be
sublimable dye(s), or may be pigments, and it is possible to use
any of the colorants as described in the above explanation for the
manufacturing method of the first embodiment. The second coating
liquid may contain two or more kinds of colorants.
"Second Solvent"
[0169] As the second solvent, as long as it is capable of
dispersing the colorant as mentioned above, it is not particularly
limited, and it may be appropriately selected from known solvents.
The first coating liquid may contain two or more solvents, provided
that at least one of the colorants contained in the second coating
liquid can be dissolved in none of the solvents contained in the
first coating liquid.
[0170] In the second coating liquid, any optional ingredient(s) may
be contained, in addition to the second binder resin, the second
solvent, and the dispersible colorant. For example, the second
coating liquid may contain a dispersant for improving the
dispersibility of the colorant. As the dispersant, for example, it
is possible to use the dispersants as described in the thermal
transfer sheet of the first embodiment.
[0171] Further, in the second coating liquid, a sublimable dye
dissolvable in the second solvent to be contained in the second
coating liquid may contained. That is, the second colorant layer 3B
may have a same constitution as the colorant layer 3 (See FIG. 4)
which is formed by the manufacturing method of the above mentioned
second embodiment. According to this constitution, since the
sublimable dye(s) is dissolved in both of the first coating liquid
and the second coating liquid, it can be expected to form a higher
density image, by means of the synergistic effect of the first
colorant layer 3A and the second colorant layer 3B.
[0172] In the case that the second colorant layer 3B which is
formed using the second coating liquid is located at the outermost
surface of the thermal transfer sheet, it is preferable that a
releasing agent is contained in the second coating liquid. As the
releasing agent, the releasing agents as described in the
explanation of the colorant layer of the thermal transfer sheet of
the first embodiment may be used. Incidentally, in the case that
measures for improving the releasing property is taken in the
transfer receiving article side, for instance, the receiving layer
side of the thermal transfer image-receiving sheet, it is not
always necessary to include the releasing agent in the second
coating liquid.
[0173] As described above, the first solvent and the sublimable dye
dissolvable to the first solvent which are contained in the first
coating liquid, as well as the second solvent and the colorant
dispersible to the second solvent which are contained in the second
solvent, in accordance with the method of manufacturing the thermal
transfer sheet of the third embodiment are fairly explained. The
first solvent and the second solvent may be different from each
other, and the sublimable dye contained in the first coating liquid
and the colorant contained in the second coating liquid may be also
different from each other. Alternatively, the first solvent and the
second solvent may be the same with each other, and the sublimable
dye contained in the first coating liquid and the colorant
contained in the second coating liquid may be also different from
each other. In this case, at least one kind of the sublimable dyes
included in the first coating liquid should be dissolved in the
common solvent, and at least one kind of the colorants included in
the second coating liquid should be dispersed in the common
solvent
[0174] In further another instance, the first solvent and the
second solvent may be different from each other, and the sublimable
dye contained in the first coating liquid and the colorant
contained in the second coating liquid may be the same with each
other. In this case, the first solvent contained in the first
coating liquid should be able to dissolve the common colorant, and
the second solvent contained in the second coating liquid and being
different from the first solvent should be able to disperse the
common colorant.
[0175] In a preferred method for manufacturing a thermal transfer
sheet of the third embodiment, the second coating liquid further
contains the "specific dispersant(s)" as described in the above
explanation for the coating liquid for colorant layer of the first
embodiment, in addition to the binder resin, the predetermined
solvent, and the colorant 10x dispersible to the predetermined
solvent. According to the manufacturing method of the thermal
transfer sheet of this preferred form, it is possible to repress
the occurrences of the kick and the scumming in the thermal
transfer sheet obtained by the manufacturing method of the third
embodiment, and further improve the density of the image formed,
and further, it is also possible to further improve the light
resistance, and suppress the reduction of the print density in the
highlight portion, owing to the function of the "specific
dispersant(s)".
[0176] Although there is no particular limitation on the method of
forming the second colorant layer, and for instance, the second
colorant layer can be formed by preparing a second coating liquid
where a colorant is dispersed in the solvent, coating thus prepared
second coating liquid on the first colorant layer in accordance
with a known coating procedure such as the gravure printing method,
the screen printing method, the reverse roll coating printing
method using a gravure plate, or the like, and then drying the
coated solution. Although there is no particular limitation about
the coating amount of the second coating liquid, it is preferable
that it is in the range of 0.1 g/m.sup.2-5 g/m.sup.2 in terms of
solid content.
[0177] As described above, the manufacturing method of the third
embodiment is fairly explained as mainly describing about the
manufacturing method for providing the second colorant layer 3B
directly on the first colorant layer 3A. However, the manufacturing
method of the third embodiment may include step(s) of providing
arbitrary layer(s) between the first colorant layer 3A and the
second colorant layer 3B. Further, the manufacturing method of the
third embodiment may include step(s) of providing arbitrary
layer(s) between the substrate sheet 2 and the first colorant layer
3A. In addition, it may include step(s) of providing arbitrary
layer(s) on another surface side of the substrate sheet 2, on which
the first colorant layer 3A does not formed.
<Thermal Transfer Sheet of Third Embodiment>
[0178] The thermal transfer sheet 1 of the third embodiment is
characterized in that it comprises a substrate 2 and a colorant
layer 3 provided on one surface of the substrate sheet 3, as shown
in FIG. 5; wherein the colorant layer 3 comprises a layered
structure in which a first colorant layer 3A and a second colorant
layer 3B are layered in this order; wherein the first colorant
layer 3A contains a first solvent and a sublimable dye soluble in
the first solvent; and wherein the second colorant layer contains a
second solvent and a colorant dispersible in the second
solvent.
[0179] According to the thermal transfer sheet of the third
embodiment having the colorant layer 3 of the above features, since
the second colorant layer 3B is serves just as a lid for closing
the sublimable dye 10y localized at the interfaces of the first
colorant layer 3A, and by the same reasons with those explained in
the method for manufacturing the thermal transfer sheet of the
third embodiment, it is possible to prevent the occurrences of the
kick and the scumming, and to form a high density image.
[0180] Here, it should be noted that, although the thermal transfer
sheet of the third embodiment also has an essential condition that
the first colorant layer 3A contains a first solvent and the second
colorant layer 3B contains a second solvent, as is the case with
the thermal transfer sheet of the first embodiment or the second
embodiment, the conditions does not intend to denote that the first
and second solvents are positively and actively contained in the
first colorant layer 3A and the second colorant layer,
respectively. But, the first solvent contained in the first
colorant layer 3A refers to residual solvent contained in the first
colorant layer 3A, and the second solvent contained in the second
colorant layer 3B refers to residual solvent contained in the
second colorant layer 3B. Concretely, when the solvent remaining in
the first colorant layer 3A is a first solvent which can dissolve
the sublimable dye included in the first colorant layer and the
solvent remaining in the second colorant layer 3B is a second
solvent which can disperse the colorant included in the second
colorant layer, it can be said that the thermal transfer sheet of
the third embodiment can exhibit the same functions and effects as
the thermal transfer sheet manufactured by the manufacturing method
of the third embodiment.
[0181] As long as the dissolving and dispersing conditions for the
sublimable dye in the first colorant layer 3A and the colorant in
the second colorant layer 3B can satisfy the above mentioned
relation, as described in the manufacturing method of the third
embodiment, the first solvent remained in the first colorant layer
and the second solvent remained in the second colorant layer may be
the same with each other. In this case, the first colorant layer 3A
should contain at least one kind of the sublimable dye which is
soluble in the common solvent, and also, the second colorant layer
should contain at least one kind of the colorant which is
dispersible in the common solvent. Alternatively, the sublimable
dye contained in the first colorant layer 3A and the colorant
contained in the second colorant layer may be the same with each
other. In this case, a first solvent capable of dissolving the
common colorant should be remained in the first colorant layer 3A,
and a second solvent capable of dispersing the common colorant
should be remained in the second colorant layer 3B.
[0182] It is possible to determine whether a thermal transfer sheet
of interest satisfies the matters specifying the thermal transfer
sheet of the third embodiment or not, by investigating the
relations of the solvents and the colorants contained in the
individual layers. Concretely, when the colorant layer in the
target thermal transfer sheet does not have a layered structure,
the target thermal transfer sheet can be judged as not being
satisfying the matters specifying the thermal transfer sheet of the
third embodiment. On the other hand, when the colorant layer of the
target thermal transfer sheet can be determined as to have a
layered structure, solvent(s) and colorant(s) contained in the
colorant layer closer to the substrate sheet are identified. On
this identification, when the colorant component is the one which
can be dissolved in the identified solvent, the colorant layer can
be judged as being satisfying the construction of the first
colorant layer. Then, solvent(s) and colorant(s) contained in the
colorant layer farther from the substrate sheet are identified. On
this identification, when the colorant component is the one which
can be dispersed in the identified solvent, the colorant layer can
be judged as being satisfying the construction of the second
colorant layer. Further, when a layer of the same construction as
the first colorant layer and a layer of the same construction as
the second colorant layer are layered, the target heat transfer
sheet can be judged as being satisfying the matters specifying the
thermal transfer sheet of the third embodiment. As the
determination method for colorant and solvent, the methods as
described in the explanation for the first embodiment can be used
as-is. Further, by using the "determination method for
dispersibility of colorant to predetermined solvent" as described
in the above explanation for the manufacturing method of the first
embodiment, it is possible to determine whether the identified
colorant can be dissolved or can be dispersed in the identified
solvent.
[0183] Next, each component of the thermal transfer sheet of the
third embodiment will be described. Incidentally, the thermal
transfer sheet of the third embodiment is correlated with the
manufacturing method of the third embodiment, and thus, unless
otherwise specified, those described in the manufacturing method of
the third embodiment can be used as-is.
[0184] There is no particular limitation on the substrate sheet 2,
and it is possible to use any of the substrate sheets described in
the manufacturing method of the first embodiment by selecting
appropriately.
(First Colorant Layer)
[0185] In the first colorant layer 3A, a first binder resin, a
first solvent, and a sublimable dye dissolvable to the first
solvent are included. With respect to each individual component, it
is possible to use any of the corresponding components described in
the above explanation for the first coating liquid of the
manufacturing method of the third embodiment by selecting
appropriately.
[0186] The first colorant layer may contain a colorant dispersible
in the first solvent. The first colorant layer 3A may any optional
component(s) which are described in the above explanation for the
first coating liquid of the manufacturing method of the third
embodiment, in addition to the first binder resin, the first
solvent, the sublimable dye dissolvable to the first solvent.
[0187] With respect to the method for forming the first colorant
layer 3A, it is possible to use the method as described in the
manufacturing method of the third embodiment. Ditto for the second
coloring layer 3B.
(Second Colorant Layer)
[0188] In the second colorant layer 3B, a second binder resin, a
second solvent, and a colorant dispersible to the second solvent
are included. With respect to each individual component, it is
possible to use any of the corresponding components described in
the above explanation for the second coating liquid of the
manufacturing method of the third embodiment by selecting
appropriately.
[0189] The second colorant layer 3B may contain a colorant
dissolvable in the second solvent. The second colorant layer 3B may
any optional component(s) which are described in the above
explanation for the second coating liquid of the manufacturing
method of the third embodiment, in addition to the second binder
resin, the second solvent, the colorant dispersible to the first
solvent.
[0190] The second colorant layer of a preferred mode may further
contain the "specific dispersant(s)" as described in the above
explanation for the coating liquid for colorant layer of the first
embodiment. According to the thermal transfer sheet which having
this second colorant layer 3B, it is possible to repress the
occurrences of the kick and the scumming in the thermal transfer
sheet, and further improve the density of the image formed, and
further, it is also possible to further improve the light
resistance, and suppress the reduction of the print density in the
highlight portion, owing to the function of the "specific
dispersant(s)".
[0191] The thermal transfer sheet of the third embodiment, as is
the same with the thermal transfer sheet of the first embodiment,
may have a primer layer between the substrate sheet 2 and the first
colorant layer 3A, and may have aback face layer on another surface
of the substrate sheet 2. Further, a back face primer layer may be
provided between the substrate sheet 2 and the back face layer.
Image Forming Method
[0192] Next, the image forming method of an embodiment of the
present invention will be described.
[0193] The image forming method of the first embodiment is
characterized in that it is for forming image on a thermal transfer
image-receiving sheet by using a thermal transfer sheet having a
colorant layer on a surface of a substrate sheet in combination
with the thermal transfer image-receiving sheet having a receiving
layer on a surface of another substrate sheet; wherein the colorant
layer of the thermal transfer sheet contains a predetermined
solvent, a colorant dispersible in the predetermined solvent, a
dispersant and a binder resin; and wherein the dispersant is one or
more kinds of dispersants selected from the group consisting of
polyether-based dispersants, graft type polymer dispersants,
acryl-based block type polymer dispersants, urethane-based polymer
dispersants and azo-based dispersants. That is, it is characterized
by using the thermal transfer sheet of the first embodiment as the
thermal transfer sheet.
[0194] The image forming method of the second embodiment is
characterized by using the thermal transfer sheet of the second
embodiment as the thermal transfer sheet. The image forming method
of the third embodiment is characterized by using the thermal
transfer sheet of the third embodiment as the thermal transfer
sheet.
[0195] According to the image forming methods of the first
embodiment, the second embodiment, and the third embodiment, of the
present invention, it is possible to form a photographic tone color
image of high quality with a continuous tone image by sublimation
transfer.
(Thermal Transfer Image-Receiving Sheet)
[0196] The thermal transfer image-receiving sheet to be used in
combination with the above thermal transfer sheet has another
substrate sheet and a receiving layer provided on the another
substrate sheet as essential components. As the another substrate
sheet used herein, it is possible to use the same type with the
substrate sheet of the above mentioned thermal transfer sheet.
Alternatively, it is also possible to use a different type from the
substrate sheet of the above mentioned thermal transfer sheet. The
thermal transfer image-receiving sheet may be any one provided with
this constitution, without any limitation. It can be selected from
any conventionally known thermal transfer image-receiving sheets as
appropriate to be used it.
(Image Formation)
[0197] With respect to the image forming method of the present
invention, as long as the condition that the thermal transfer sheet
to be used for the image formation is one of the thermal transfer
sheet of the first embodiment, the thermal transfer sheet of the
second embodiment and the thermal transfer sheet of the third
embodiment as described above is satisfied, there are no particular
restrictions for other requirements. For example, the image can be
formed by superposing the colorant layer of the thermal transfer
sheet to the receiving layer of the thermal transfer
image-receiving sheet, then applying heat from the back side of the
thermal transfer sheet with by a heating means such as a thermal
head in order to transfer the colorant contained in the colorant
layer to the receiving layer side.
EXAMPLE
[0198] Next, the present invention will be described with referring
to Examples. Hereinafter, the expressions of "part(s)" and "%" are
based on "weight", unless otherwise especially mentioned.
Example 1
[0199] In accordance with the procedure described below, a coating
liquid for colorant layer and a thermal transfer sheet were
prepared.
(Preparation of Coating Liquid for Colorant Layer 1)
[0200] As the following composition, a coating liquid for colorant
layer 1 was prepared by adding a colorant, a dispersant, a binder
resin, a solvent and 250 parts by weight of zirconia beads having a
particle diameter of 2.0 mm into a glass bottle, sealing the glass
bottle, shaking the content with a paint shaker (manufactured by
Asada Iron Works Co., Ltd.) for 1 hour as a preliminary crushing,
then removing the above mentioned zirconia beads from the bottle
and adding 250 parts by weight of zirconia beads having a particle
diameter of 0.1 mm to the bottle, and dispersing the content with
the paint shaker similarly for 24 hour as a main crushing, in order
to prepare a coating liquid for colorant layer 1. Preparation of
the following coating liquids for colorant layer 2-7 and 10 were
carried out in the same manner an mentioned above.
[0201] The point whether the following each individual colorant to
be contained in the coating liquid for colorant layer can be solved
in a mixed solvent of toluene and methyl ethyl ketone or can be
dispersed in this mixed solvent was determined in advance by the
following method. Namely, the method was performed by using
toluene/methyl ethyl ketone=1/1 mixed solvent, adding the colorant
into the mixed solvent so as to obtain a colorant concentration of
2 w/v %, then, stirring for one hour with heating to 50.degree. C.
Then, the resultant solution was allowed to left standing for 60
hours at 25.degree. C., and after the standing, it was observed
visually whether the precipitation or deposition of the colorant is
caused or not. As a result of this observation, if no precipitation
or deposition of the colorant was observed, the colorant was
determined as the soluble colorant, whereas if precipitation or
deposition of the colorant was observed, the colorant was
determined as the dispersible colorant.
[0202] According to the above determination method, the "C. I.
Disperse Yellow 54" which was to be included in the coating liquids
for the colorant layers was determined to be a dispersible colorant
in the toluene/methyl ethyl ketone mixed solvent. The "sulfonated
derivative of C. I. Pigment Yellow 138" represented by the above
Formula 3, was determined to be a dispersible colorant (pigment) in
the toluene/methyl ethyl ketone mixed solvent, in addition to
having the function as a dispersant for improving the
dispersibility of the "C. I. Disperse Yellow 54". Further, the "C.
I. Disperse Yellow 201", and the colorants represented by the
following formulae 4 and 5 were determined to be soluble
colorants.
<Coating Liquid for Colorant Layer 1>
TABLE-US-00001 [0203] C.I. Disperse Yellow 54 (it is referred to as
"dye A") 4.75 parts Dispersant of poly allyl amine-based graft type
polymer 1.75 parts (Ajisper PB881, Mw: 40000-50000, manufactured by
Ajinomoto Fine-Techno Co., Ltd.) Polyvinyl acetal resin 2.05 parts
(KS-5, manufactured by Sekisui Chemical Co., Ltd.) Methyl ethyl
ketone 32.25 parts Toluene 32.25 parts
[0204] The chemical formula of dye A is shown below.
##STR00006##
(Preparation of Thermal Transfer Sheet)
[0205] As a substrate, polyethylene terephthalate (PET) film which
had 4.5 .mu.m in thickness was used. On this substrate, a coating
liquid for primer layer having the following composition was coated
so as to obtain a coating amount of solid content of 0.05 g/m.sup.2
in accordance with the wire bar coating method, and then the coated
liquid was dried to form a primer layer.
<Coating Liquid for Primer Layer>
TABLE-US-00002 [0206] Alumina sol (average primary particle
diameter: 30 parts 10 .times. 100 nm (solid content: 10%) (Alumina
sol 200, manufactured by Nissan Chemical Industries Co., Ltd.)
Polyvinyl pyrrolidone resin 3 parts (K-90, manufactured by ISP)
Water 50 parts Isopropyl alcohol 17 parts
[0207] Subsequently, the above mentioned coating liquid for
colorant layer 1 was coated on the primer layer so as to obtain a
coating amount of solid content of 0.8 g/m.sup.2 in accordance with
the wire bar coating method, and then the coated liquid was dried
at 80.degree. C. for 2 minutes to form the colorant layer. Thus,
the thermal transfer sheet was prepared. Incidentally, on another
surface of this substrate, a coating liquid for back face layer 1
having the following composition was coated so as to obtain a
coating amount of solid content of 1.0 g/m.sup.2 and then the
coated liquid was dried to form a back face layer in advance.
<Coating Liquid for Back Face Layer 1>
TABLE-US-00003 [0208] Polyvinyl acetal resin 4.55 parts (S-LEC
BX-1, manufactured by Sekisui Chemical Co., Ltd.) Polyisocyanate
21.0 parts (BURNOCK D750-45, solid content: 45% by weight,
manufactured by DIC Corporation) Phosphate-based surfactant 3.0
parts (PLYSURF A-208N, manufactured by Dai-ichi Kogyo Seiyaku Co.,
Ltd.) Talc 0.7 part (MICRO ACE P-3, manufactured by Nippon Talc
Co., Ltd.) methyl ethyl ketone 100.0 parts toluene 100.0 parts
Example 2
[0209] A thermal transfer sheet of Example 2 was obtained by
carrying out the same procedure as in Example 1 except that a
coating liquid for colorant layer 2 wherein 1.7 parts of a
polyether type dispersant (Solsperse 20000, weight average
molecular weight: 1900, manufactured by The Lubrizol Corporation)
was used instead of 1.7 parts of the poly allyl amine-based graft
polymer dispersant in the composition of the coating liquid for
colorant layer 1 was used in place of the coating liquid for
colorant layer 1.
Example 3
[0210] A thermal transfer sheet of Example 3 was obtained by
carrying out the same procedure as in Example 1 except that a
coating liquid for colorant layer 3 wherein 2.83 parts (solid
content: 1.7 parts) of an acryl-based block type polymer dispersant
(BYK-LPN6919, weight average molecular weight: 9000, solid content:
60%, manufactured by BYK Additives & Instruments) was used
instead of 1.7 parts of the poly allyl amine-based graft polymer
dispersant in the composition of the coating liquid for colorant
layer 1 was used in place of the coating liquid for colorant layer
1.
Example 4
[0211] A thermal transfer sheet of Example 4 was obtained by
carrying out the same procedure as in Example 1 except that a
coating liquid for colorant layer 4 having the following
composition was used in place of the coating liquid for colorant
layer 1.
<Coating Liquid for Colorant Layer 4>
TABLE-US-00004 [0212] C.I. Disperse Yellow 54 (it is referred to as
"dye A") 4.75 parts Dispersant of acryl-based block type polymer
1.67 parts (BYK-LPN6919, weight average molecular weight: (solid
content 9000, solid content: 60%, manufactured by BYK 1.0 part)
Additives & Instruments) Polyether-based dispersant 0.7 part
(Solsperse 20000, weight average molecular weight: 1900,
manufactured by The Lubrizol Corporation) Polyvinyl acetal resin
2.05 parts (KS-5, manufactured by Sekisui Chemical Co., Ltd.)
Methyl ethyl ketone 32.25 parts Toluene 32.25 parts
[0213] The chemical formula of the dye A is that as mentioned
above.
Example 5
[0214] A thermal transfer sheet of Example 5 was obtained by
carrying out the same procedure as in Example 1 except that a
coating liquid for colorant layer 5 having the following
composition was used in place of the coating liquid for colorant
layer 1.
<Coating Liquid for Colorant Layer 5>
TABLE-US-00005 [0215] C.I. Disperse Yellow 54 (it is referred to as
"dye A") 4.275 parts Pigment represented by the above Formula 3
0.475 parts (sulfonated derivative of C.I. Pigment Yellow 138)
Dispersant of acryl-based block type polymer 2.83 parts
(BYK-LPN6919, weight average molecular weight: (solid content 1.7
parts) 9000, solid content: 60%, manufactured by BYK Additives
& Instruments) Polyvinyl acetal resin 2.05 parts (KS-5,
manufactured by Sekisui Chemical Co., Ltd.) Methyl ethyl ketone
32.25 parts Toluene 32.25 parts
[0216] The chemical formula of the dye A is that as mentioned
above.
Example 6
[0217] A thermal transfer sheet of Example 6 was obtained by
carrying out the same procedure as in Example 1 except that a
coating liquid for colorant layer 5 having the following
composition was used in place of the coating liquid for colorant
layer 1.
<Coating Liquid for Colorant Layer 6>
TABLE-US-00006 [0218] C.I. Disperse Yellow 54 (it is referred to as
"dye A") 9.00 parts Pigment represented by the above Formula 3 0.90
parts (sulfonated derivative of C.I. Pigment Yellow 138) Dispersant
of acryl-based block type polymer 4.08 parts (BYK-LPN6919, weight
average molecular weight: (solid content 9000, solid content: 60%,
manufactured by 2.45 parts) BYK Additives & Instruments)
Polyvinyl acetal resin 3.50 parts (KS-5, manufactured by Sekisui
Chemical Co., Ltd.) Methyl ethyl ketone 42.00 parts Toluene 42.00
parts
[0219] The chemical formula of the dye A is that as mentioned
above.
Example 7
[0220] A thermal transfer sheet of Example 7 was obtained by
carrying out the same procedure as in Example 1 except that a
coating liquid for colorant layer 7 wherein 4.25 parts (solid
content: 1.7 parts) of an acryl-based block type polymer dispersant
(BYK-LPN21116, weight average molecular weight: 8000, solid
content: 40%, manufactured by BYK Additives & Instruments) was
used instead of 2.83 parts (solid content: 1.7 parts) of an
acryl-based block type polymer dispersant (BYK-LPN6919, weight
average molecular weight: 9000, solid content: 60%, manufactured by
BYK Additives & Instruments) in the composition of the coating
liquid for colorant layer 5 was used in place of the coating liquid
for colorant layer 1.
Example 8
[0221] A thermal transfer sheet of Example 8 was obtained by
carrying out the same procedure as in Example 1 except that a
coating liquid for colorant layer 8 having the following
composition was used in place of the coating liquid for colorant
layer 1.
(Preparation of Coating Liquid for Colorant Layer 8)
[0222] As the following composition, a dispersion was prepared by
adding a colorant, a dispersant, a binder resin, a solvent and 250
parts by weight of zirconia beads having a particle diameter of 2.0
mm into a glass bottle, sealing the glass bottle, shaking the
content with a paint shaker (manufactured by Asada Iron Works Co.,
Ltd.) for 1 hour as a preliminary crushing, then removing the above
mentioned zirconia beads from the bottle and adding 250 parts by
weight of zirconia beads having a particle diameter of 0.1 mm to
the bottle, and dispersing the content with the paint shaker
similarly for 3 hour as a main crushing, in order to prepare the
dispersion. Then, 50 parts of a binder solution having the
following composition was added to 50 parts of thus prepared
dispersion, in order to prepare a coating liquid for colorant layer
8.
<Dispersion>
TABLE-US-00007 [0223] C.I. Disperse Yellow 54 ("dye A") 9.9 parts
Azo-based dispersant 0.7 part (Solsperse 22000, manufactured by The
Lubrizol Corporation) Dispersant of urethane-based polymer 13.33
parts (BYK-161, solid content: 30%, manufactured (solid content 4.0
parts) by BYK Additives & Instruments) Methyl ethyl ketone
32.25 parts Toluene 32.25 parts
[0224] The chemical formula of the dye A is that as mentioned
above.
<Binder Solution>
TABLE-US-00008 [0225] Polyvinyl acetal resin 4.68 parts (KS-5,
manufactured by Sekisui Chemical Co., Ltd.) Methyl ethyl ketone 50
parts Toluene 50 parts
Example 9
[0226] A thermal transfer sheet of Example 9 was obtained by
carrying out the same procedure as in Example 1 except that a
coating liquid for colorant layer 9 having the following
composition was used in place of the coating liquid for colorant
layer 1.
(Preparation of Coating Liquid for Colorant Layer 9)
[0227] The same procedure for the preparation of the coating liquid
for colorant layer 10 was carried out except that 10.53 parts
(solid content: 4.0 parts) of an urethane-based polymer dispersant
(BYK-162, solid content: 38%, manufactured by BYK Additives &
Instruments) was used instead of 13.33 parts (solid content: 4.0
parts) of the urethane-based polymer dispersant (BYK-161, solid
content: 30%, manufactured by BYK Additives & Instruments) in
the dispersion used for preparing the above mentioned coating
liquid for colorant layer 8, in order to prepare a coating liquid
for colorant layer 9.
Example 10
[0228] A thermal transfer sheet of Example 10 was obtained by
carrying out the same procedure as in Example 1 except that a
coating liquid for colorant layer 10 having the following
composition was used in place of the coating liquid for colorant
layer 1.
<Coating Liquid for Colorant Layer 10>
TABLE-US-00009 [0229] C.I. Disperse Yellow 201 2.0 parts C.I.
Disperse Yellow 54 ("Dye A") 4.0 parts Quinophthalone-based dye
represented by the following 2.0 parts formula 4 Pigment
represented by the above Formula 3 0.42 parts (sulfonated
derivative of C.I. Pigment Yellow 138) Dispersant of acryl-based
block type polymer 4.25 parts (BYK-LPN21116, weight average
molecular (solid content weight: 8000, solid content: 40%,
manufactured by 1.7 parts) BYK Additives & Instruments)
Polyvinyl acetal resin 2.50 parts (KS-5, manufactured by Sekisui
Chemical Co., Ltd.) Polyethylene wax (particle diameter: 5 .mu.m)
0.09 parts Toluene 33 parts Methyl ethyl ketone 33 parts
[0230] The chemical formula of the dye A is that as mentioned
above.
##STR00007##
Comparative Example 1
[0231] As the following composition, a coating liquid for colorant
layer A was prepared by adding a colorant, a dispersant, a binder
resin, a solvent and 250 parts by weight of zirconia beads having a
particle diameter of 2.0 mm into a glass bottle, sealing the glass
bottle, shaking the content with a paint shaker (manufactured by
Asada Iron Works Co., Ltd.) for 1 hour as a preliminary crushing,
then removing the above mentioned zirconia beads from the bottle
and adding 250 parts by weight of zirconia beads having a particle
diameter of 0.1 mm to the bottle, and dispersing the content with
the paint shaker similarly for 96 hour as a main crushing, in order
to prepare a coating liquid for colorant layer A. The thermal
transfer sheet of the Comparative example 1 was prepared by
carrying out the same procedure as in Example 1 except that the
coating liquid for colorant layer A prepared by the following
procedure was used instead of the coating liquid for colorant layer
1.
<Coating Liquid for Colorant Layer A>
TABLE-US-00010 [0232] C.I. Disperse Yellow 54 ("dye A") 4.75 parts
Polyvinyl acetal resin 3.75 parts (KS-5, manufactured by Sekisui
Chemical Co., Ltd.) Methyl ethyl ketone 32.25 parts Toluene 32.25
parts
[0233] The chemical formula of the dye A is that as mentioned
above.
Comparative Example 2
[0234] A thermal transfer sheet of Comparative example 2 was
obtained by carrying out the same procedure as in Example 1 except
that a coating liquid for colorant layer B having the following
composition was used in place of the coating liquid for colorant
layer 1. Incidentally, the coating liquid for colorant layer B was
the one which was prepared by dissolving a dye and a resin in a
solvent. Ditto for a coating liquid for colorant layer C.
<Coating Liquid for Colorant Layer B>
TABLE-US-00011 [0235] Quinophthalone-based dye represented by the
4.75 parts following formula 4 Polyvinyl acetal resin 3.75 parts
(KS-5, manufactured by Sekisui Chemical Co., Ltd.) Methyl ethyl
ketone 32.25 parts Toluene 32.25 parts
Comparative Example 3
[0236] A thermal transfer sheet of Comparative example 3 was
obtained by carrying out the same procedure as in Example 1 except
that a coating liquid for colorant layer C having the following
composition was used in place of the coating liquid for colorant
layer 1.
<Coating Liquid for Colorant Layer C>
TABLE-US-00012 [0237] C.I. Disperse Yellow 54 ("dye A") 4.75 parts
Polyvinyl acetal resin 3.75 parts (KS-5, manufactured by Sekisui
Chemical Co., Ltd.) Polyethylene wax (particle diameter: 5 .mu.m)
0.99 parts Methyl ethyl ketone 33 parts Toluene 33 parts
(Volume Average Particle Diameter of the Colorant)
[0238] With respect to the coating liquids for colorant layer 1-10,
and A-C, which were prepared in the above Examples and Comparative
examples for manufacturing thermal transfer sheet, the volume
average particle diameter (nm) of colorant in each individual
coating liquid which was dispersed in accordance with the above
mentioned colorant dispersing condition was determined by using the
particle size distribution measuring apparatus in accordance with
the laser diffraction scattering method as mentioned above. The
obtained results are shown in Table 1.
(State of Coating Liquid)
[0239] With respect to the coating liquids for colorant layer which
were prepared in the above Examples and Comparative examples for
manufacturing thermal transfer sheet, each coating liquid was
observed visually, at the initial time after preparing the coating
liquid in accordance with the above mentioned colorant dispersing
condition, and after being left for 120 hours at room temperature
from the initial time, about the presence or absence of precipitate
in the coating liquid. The evaluation was done according to the
following criteria.
1: There was no precipitate at all. 2: There was substantially no
precipitate. 3: There was a little precipitate. 4; There was a lot
of precipitate.
(Adhesiveness)
[0240] With respect to the thermal transfer sheets prepared as
above, the adhesiveness of the colorant layer to the substrate
sheet was examined by applying a cellophane tape to a surface of
the colorant layer, rubbing the applied cellophane tape with a
thumb by a to-and-fro motion so as to attach the cellophane tape to
the colorant layer, and peeling the cellophane tape off from the
colorant layer with an angle of 180.degree. by hand just after the
attaching. The evaluation was done by observing visually the state
of transition of the colorant layer onto the peeled-off cellophane
tape. Criteria for this evaluation are as follows.
1: The transition of the colorant layer onto the cellophane tape
was not observed at all. 2: Although the transition of the colorant
layer onto the cellophane tape was observed with a very little
extent, but no problem arises in a practical use. 3: Although the
transition of the colorant layer onto the cellophane tape was
observed with a little extent, but no problem arises in a practical
use. 4: The transition of the colorant layer onto the cellophane
tape was observed with a certain extent.
(Printing Aptitude)
[0241] Using a test printer, and combining the each individual
thermal transfer sheet as mentioned above with a thermal transfer
receiving sheet prepared in accordance with the following
condition, under the following printing condition 1, a yellow
gradation pattern was printed in order to examine the density
characteristics and the presence or absence of the abnormal
transfer. The evaluation of the density characteristics was done at
the highest concentration when applying a maximum energy and at a
concentration of the highlight portion when applying a 60% energy.
The measured concentrations are shown in Table 1. The evaluation of
the abnormal transfer was done in accordance with the following
criteria.
1: Abnormal transfer was not observed. 2: Although it was within a
level of no problem in the practical use, a little stronger
resisting level was observed on the peeling the thermal transfer
sheet off from the thermal transfer receiving sheet after printing.
3: Abnormal transfer was observed.
(Printing Condition 1)
[0242] Thermal head: F3598 (manufactured by Toshiba Hokuto
Electronics Co., Ltd.) [0243] Average resistance value of heating
element: 5176 (.OMEGA.) [0244] Printing density along the main
scanning direction: 300 dpi [0245] Printing density along the sub
scanning direction: 300 dpi [0246] Printing Power: 0.12 (W/dot)
[0247] 1-line period: 2 (msec.) [0248] Pulse duty: 85% [0249]
print-starting temperature: 35.5 (SC)
(Preparation of Thermal Transfer Image-Receiving Sheet)
[0250] On a porous film layer made of a porous polyethylene film
(Toyopearl-SS P4255, manufactured by Toyobo Co., Ltd., thickness:
35 .mu.m), a coating liquid for forming intermediate layer having
the following composition, and a coating liquid for forming
receiving layer having the following composition, were coated and
then dried in that order in accordance with the gravure reverse
coating method, in order to form an intermediate layer and a
receiving layer. On another side surface of the porous polyethylene
film which was opposite to the surface onto which the intermediate
layer and the receiving layer were formed, a coating liquid for
forming adhesive layer having the following composition was coated
and then dried in accordance with the gravure reverse roll coating
method, in order to form an adhesive layer. Then, this adhesive
layer side of the porous film was adhered to RC paper (155
g/m.sup.2, 151 .mu.m in thickness, manufactured by Mitsubishi Paper
Mills) so as to forma thermal transfer image-receiving sheet. With
respect to the coated amount of the above intermediate layer,
receiving layer, and adhesive layer were 1.5 g/m.sup.2, 5.0
g/m.sup.2, and 5.0 g/m.sup.2 in a dried state, respectively.
<Coating Liquid for Intermediate Layer>
TABLE-US-00013 [0251] Polyester resin 50 parts (Polyester WR-905,
manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.)
Titanium oxide 20 parts (TCA888, manufactured by Tochem Products)
Fluorescent whitening agent 1.2 parts (Uvitex BAC, manufactured by
Ciba Specialty Chemicals Inc.) Water/isopropyl alcohol = 1/1 28.8
parts
<Coating Liquid for Receiving Layer>
TABLE-US-00014 [0252] Vinyl chloride-vinyl acetate copolymer 60
parts (SOLBIN C, manufactured by Nissin Chemical Industry Co.,
Ltd.)) Epoxy-modified silicone 1.2 parts (X-22-3000T, manufactured
by Shin-Etsu Chemical Co., Ltd.) Metylstyl-modified silicone 0.6
parts (X-24-510, manufactured by Shin-Etsu Chemical Co., Ltd.)
Methyl ethyl ketone/toluene (mass ratio 1:1) 5 parts
<Coating Liquid for Adhesive Layer>
TABLE-US-00015 [0253] Urethane resin 30 parts (TAKELAC A-969V,
manufactured by Mitsui Takeda Chemical Inc.) Isocyanate 10 parts
(TAKENATE, manufactured by Mitsui Takeda Chemical Inc.) Ethyl
acetate 100 parts
(Evaluation of Light Resistance)
[0254] The colorant layer of each individual thermal transfer sheet
was opposed to the receiving layer surface of the thermal transfer
image-receiving sheet and superposed thereon, and then they were
subjected to printing by using the test printer from the backside
of the thermal transfer sheet under the above mentioned printing
condition 1 so as to form a yellow printing pattern having 18
steps' gradation patterns of from 0/255 to 255/255 (Max
concentration). Furthermore, by using the protective layer transfer
sheet prepared in the following condition, and under the following
printing conditions 2, the transferable protective layer was
transferred onto the yellow printing pattern in order to obtain a
final printed article.
(Preparation of Protective Layer Transfer Sheet)
[0255] As a substrate, polyethylene terephthalate (PET) film which
had 4.5 .mu.m in thickness was used. On a surface of this
substrate, a coating liquid for peeling layer having the following
composition was coated so as to obtain a coating amount of solid
content of 1.0 g/m.sup.2 in accordance with the wire bar coating
method, and then the coated liquid was dried on an oven at
110.degree. C. for 1 minute to form a peeling layer. Then, on the
peeling layer, the above mentioned coating liquid for primer layer
which was used in the above mentioned preparation of the thermal
transfer sheet was coated so as to obtain a coating amount of solid
content of 0.2 g/m.sup.2 in accordance with the wire bar coating
method, and then the coated liquid was dried on the oven at
110.degree. C. for 1 minute to form a primer layer. Next, on the
primer layer, a coating liquid for adhesive layer mentioned below
was coated so as to obtain a coating amount of solid content of 1.0
g/m.sup.2 in accordance with the wire bar coating method, and then
the coated liquid was dried on the oven at 110.degree. C. for 1
minute to form an adhesive layer. Incidentally, on another surface
of this substrate, the coating liquid for back face layer 1 which
had the above mentioned composition and which was used in the above
mentioned preparation of the thermal transfer sheet was coated so
as to obtain a coating amount of solid content of 1.0 g/m.sup.2 and
then the coated liquid was dried to form a back face layer in
advance. Ultimately, a protective layer transfer sheet wherein the
peeling layer, the primer layer and the adhesive layer which
constituted the transferable protective layer were layered in this
order on one surface of the substrate sheet, and the back face
layer was provided on the another surface of the substrate was
obtained.
<Coating Liquid for Peeling Layer>
TABLE-US-00016 [0256] Polymethyl methacrylic acid (PMMA) 20 parts
(Dianal BR-87, manufactured by Mitsubishi Rayon Co., Ltd.) Toluene
40 parts Methyl ethyl ketone 40 parts
TABLE-US-00017 Polyester resin 23.5 parts (VYLON 220, manufactured
by Toyobo Co., Ltd.) UVA compound 6 parts (Tinuvin 900,
manufactured by Ciba Specialty Chemicals Co., Ltd.) Silica filler
25 parts (Sylysia 310P, manufactured by FUJI Silysia Chemical Ltd.)
Toluene 35 parts Methyl ethyl ketone 35 parts
(Printing Condition 2)
[0257] Thermal head: F3598 (manufactured by Toshiba Hokuto
Electronics Co., Ltd.) [0258] Average resistance value of heating
element: 5176 (.OMEGA.) [0259] Printing density along the main
scanning direction: 300 dpi [0260] Printing density along the sub
scanning direction: 300 dpi [0261] Printing Power: 0.096 (W/dot)
[0262] 1-line period: 2 (msec.) [0263] Pulse duty: 85% [0264]
print-starting temperature: 35.5 (.degree. C.)
[0265] The yellow printing pattern of the final printed article
obtained by the above procedure underwent light irradiation under
the following condition.
(Irradiation Conditions)
[0266] Irradiation tester: Ci35 manufactured by Atlas Corp. [0267]
Light source: xenon lamp [0268] Filter: inside=IR filter,
outside=soda lime glass [0269] Black panel temperature: 45.degree.
C. [0270] Irradiation intensity: 1.2 W/m.sup.2, measured at 420 nm
[0271] Irradiation energy: 700 kJ/m.sup.2, integrated value at 420
nm
[0272] The color difference of images before and after the
irradiation of the above irradiation condition was measured by a
spectrophotometer (SpectroLino, manufactured by Gretag Macbeth Co.,
Ltd.). The measurement results are shown in Table 1. With respect
to this measurement, the measurement was carried out for the places
where the OD of Ye (yellow printed portion) before irradiation was
at around 1.0.
Color difference
.DELTA.E*.sup.ab=((.DELTA.a*).sup.2+(.DELTA.b*).sup.2).sup.1/2
Please see, CIE 1976 La*b*color system (JIS 28729 (1980))
Aa*=a*(after irradiation)-a*(before irradiation)
Ab*=b*(after irradiation)-b*(before irradiation)
Incidentally, a* and b* are based on the CIE 1976 L* A* b* color
system, and the a* and b* represent perceptual brightness
indexes.
(Contamination to the Back Face Layer)
[0273] The contamination to the back layer was evaluated in order
to determine the storage stability of the thermal transfer sheet.
The prepared dye face was opposed to the surface of the back face
layer of the following substrate having the back face layer and
superposed thereon, and then they were stored for 98 hours under
loading of 40 kg/m.sup.2 at 40.degree. C., 90% RH, in order to
evaluate the migration of colorant to the back face layer. For this
evaluation of migration, the surfaces of the back face layers
before and after the storage were measured by the spectrophotometer
(SpectroLino, manufactured by Gretag Macbeth Co., Ltd.), and then,
the color difference (.DELTA.E*.sup.ab) was calculated in
accordance with the following equation. The obtained results are
shown in Table 1. Here, the above mentioned substrate having the
back face layer was the one which was obtained by coating the
coating liquid for back face layer 1 which had the above mentioned
composition and which was used in the above mentioned preparation
of the thermal transfer sheet, on a polyethylene terephthalate
(PET) film which had 4.5 .mu.m in thickness, so as to obtain a
coating amount of solid content of 1.0 g/m.sup.2 in accordance with
the wire bar coating method, and then drying the coating liquid so
as to form the back face layer.
Color difference
.DELTA.E*.sup.ab=((.DELTA.a*).sup.2+(.DELTA.b*).sup.2).sup.1/2
[0274] Please see, CIE 1976 La* b* color system (JIS 28729
(1980))
Aa*=a*(after storage)-a*(before storage)
Ab*=b*(after storage)-b*(before storage)
Incidentally, a* and b* are based on the CIE 1976 L* A* b* color
system, and the a* and b* represent perceptual brightness
indexes.
[0275] Here, the smaller the value of the .DELTA.E*.sup.ab becomes,
the less contamination arises. In other words, it indicates that
the degree of kick is less.
[0276] The respective results of the above evaluations are shown in
Table 1.
TABLE-US-00018 TABLE 1 Volume Density Density Light average
characteristics characteristics resistance particle State of
(Density at the (Density color diameter coating Abnormal maximum at
60% difference Contamination (nm) liquid Adhesiveness transfer
energy) energy) (.DELTA.E*.sup.ab) (.DELTA.E*.sup.ab) Example 1 258
2 1 1 2.32 0.5 8 0.8 Example 2 265.7 2 1 1 2.31 0.51 8 0.9 Example
3 249.3 2 1 1 2.33 0.51 8 0.8 Example 4 267.6 2 1 1 2.31 0.51 8 0.9
Example 5 193.1 2 1 1 2.34 0.53 8 0.8 Example 6 195.2 2 2 2 2.57
0.55 8 1.2 Example 7 182.5 2 1 1 2.35 0.52 8 0.8 Example 8 158.9 2
1 1 2.34 0.54 8 1.3 Example 9 161.4 2 1 1 2.33 0.54 8 1.5 Example
10 189.5 2 1 2 2.70 1.05 10 4 Comparative 494.4 4 3 3 2.27 0.39 9 1
Example 1 Comparative -- 1 1 1 2.18 0.99 8 10.9 Example 2
Comparative -- 1 3 2 2.48 1.13 14 12.2 Example 3
[0277] As shown above, with respect to the coating liquids for
colorant layer 1-10 which were used for preparing the thermal
transfer sheets of Examples 1 to 10, the volume average particle
diameters of all colorants were in the range of less than 270 nm
and the colorants were uniformly dispersed, and there was
substantially no precipitate, and thus they brought no problem in
practical use as the coating liquid. In addition, there was also no
problem in the adhesiveness. Furthermore, with respect to the
printed articles that were formed using the thermal transfer sheets
of Examples 1-10, no abnormal transfer was observed, and the
density was also excellent as indicating 2.3 at the maximum
density. Further, the light resistance was also good. Further, the
colorant contamination to the back face layer was also in low
level, thus the storage stability of the thermal transfer sheet was
good. In particular, with respect to the coating liquids for
colorant layer 7-10 which were used for preparing the thermal
transfer sheets of Examples 1 to 7, the volume average particle
diameters of colorants were miniaturized to 190 nm or less, and the
density at the 60% energy and the density at the maximum energy
were in relatively high level. In addition, with respect to the
thermal transfer sheets of Examples 7-10 which have the colorant
layer formed by using each individual coating liquids for colorant
layer 7-10, the colorant contamination to the back face layer was
also in low level, thus the storage stability of the thermal
transfer sheet was good.
[0278] In particular, with respect to the coating liquids for
colorant layer that were prepared in accordance with the above
mentioned "third procedure for preparation of the coating liquid
for colorant layer", that is, the coating liquids for colorant
layer 8 and 9, which were prepared by post-addition of a liquid
containing a binder resin, it was possible to miniaturize the
particle diameter with a short period's dispersion (3 hours'
dispersion for the coating liquids for colorant layer 8 and 9,
whereas, 24 hours' dispersion for the coating liquids for colorant
layer 1-7, and 10)
[0279] Further, with respect to the thermal transfer sheet of
Example 10 which was prepared by using the coating liquid for
colorant layer 10 which contained the colorant that was dispersible
in the solvent, and the other colorant that was soluble in the
solvent, it was possible to heighten the density at the 60% energy
and the density at the maximum density, and also to obtain a good
light resistance and a good storage stability.
[0280] In contrast, the printed article that was formed by using
the thermal transfer sheet of Comparative Example 1 suffered with
an inferior result in the highlight density and the abnormal
transfer observed. The coating liquid for colorant layer A which
was used for forming the thermal transfer sheet of Comparative
Example 1 had a volume average particle diameter of the colorant of
more than 300 nm, and tended to cause precipitation of the
colorant, and thus, owned problems in the practical use. Also, the
thermal transfer sheet of Comparative Example 1 possessed a low
adhesiveness, and thus, owned problems in the practical use. The
thermal transfer sheets of Comparative Examples 2 and 3 suffered
with inferior results in the colorant contamination to the back
face layer.
Example 11
[0281] As a substrate, polyethylene terephthalate film which
underwent easy-adhesive treatment in advance, and has 4.5 .mu.m in
thickness was used. On one surface of this substrate, a coating
liquid for back face layer 2 having the following composition was
coated so as to obtain a coating amount of solid content of 0.5
g/m.sup.2 and then the coated liquid was dried to form a back face
layer. Then, on another surface of the substrate, the coating
liquid for primer layer having the above mentioned composition was
coated so as to obtain a coating amount of solid content of 0.1
g/m.sup.2 and then the coated liquid was dried to form the primer
layer. Next, on the primer layer, a coating liquid for colorant
layer 11 which was prepared in accordance with the procedure
mentioned below was coated so as to obtain a coating amount of
solid content of 1.0 g/m.sup.2, and then the coated liquid was
dried to form an colorant layer. Ultimately, a thermal transfer
sheet of Example 11 was prepared.
<Coating Liquid for Back Face Layer 2>
TABLE-US-00019 [0282] Polyvinyl acetal resin 60.8 parts (S-LEC
BX-1, manufactured by Sekisui Chemical Co., Ltd.) Polyisocyanate
4.2 parts (BURNOCK D750, manufactured by DIC Corporation) Zinc
stearyl phosphate 10 parts (LBT-1830 purified, manufactured by
Sakai Chemical Industry Co., Ltd.) Zinc stearate 10 parts (SZ-PF,
manufactured by Sakai Chemical Industry Co., Ltd.) Talc 5 part
(MICRO ACE P-3, manufactured by Nippon Talc Co., Ltd.) Polyethylene
wax 10 parts (Polyethylene wax 3000, manufactured by Toyo ADL
Corporation) toluene 200 parts methyl ethyl ketone 100 parts
(Preparation of Coating Liquid for Colorant Layer 11)
[0283] A coating liquid for colorant layer 11 was prepared by
adding a colorant, a dispersant, a binder resin, a polyethylene
wax, and a solvent as the following composition of a coating liquid
for colorant layer 11, as well as 250 parts by weight of zirconia
beads having a particle diameter of 2.0 mm into a glass bottle,
sealing the glass bottle, shaking the content with a paint shaker
(manufactured by Asada Iron Works Co., Ltd.) for 1 hour as a
preliminary crushing, then removing the above mentioned zirconia
beads from the bottle and adding 250 parts by weight of zirconia
beads having a particle diameter of 0.1 mm to the bottle, and
dispersing the content with the paint shaker similarly for 24 hour
as a main crushing.
<Coating Liquid for Colorant Layer 11>
TABLE-US-00020 [0284] C.I. Disperse Yellow 201 2.3 parts C.I.
Disperse Yellow 54 2.3 parts Pigment represented by the above
Formula 3 0.42 parts (sulfonated derivative of C.I. Pigment Yellow
138) Dispersant of acryl-based block type polymer 4.25 parts
(BYK-LPN21116, weight average molecular (solid content weight:
8000, solid content: 40%, manufactured 1.7 parts) by BYK Additives
& Instruments) Polyvinyl acetal resin 2.05 parts (KS-5,
manufactured by Sekisui Chemical Co., Ltd.) Polyethylene wax
(particle diameter: 5 .mu.m) 0.09 part Toluene 33 parts Methyl
ethyl ketone 33 parts
Example 12
[0285] A thermal transfer sheet of Example 12 which was provided
with a colorant layer wherein a first colorant layer and a second
colorant layer were layered was obtained by carrying out the same
procedure as in Example 11 except that a coating liquid for
colorant layer 12 having the following composition was coated on
the substrate sheet so as to obtain a coating amount of solid
content of 0.5 g/m.sup.2 and then the coated liquid was dried to
form the first colorant layer, and then a coating liquid for
colorant layer 13 having the following composition was coated on
the first colorant layer so as to obtain a coating amount of solid
content of 0.5 g/m.sup.2 and then the coated liquid was dried to
form the second colorant layer, instead of using the coating liquid
for colorant layer 11 of Example 11. Incidentally, the coating
liquid for colorant layer 13 was prepared by a manufacturing
procedure similar to that for the above mentioned coating liquid
for colorant layer 11.
(Preparation of Coating Liquid for Colorant Layer 12)
[0286] A coating liquid for colorant layer 12 was prepared by
adding a colorant, a dispersant, a binder resin, a polyethylene
wax, and a solvent as the following composition of a coating liquid
for colorant layer 12 into a glass bottle, sealing the glass
bottle, heating the content at 50.degree. C. for 1 hour, and then
shaking the heated content with a paint shaker (manufactured by
Asada Iron Works Co., Ltd.) for 30 minutes.
<Coating Liquid for Colorant Layer 12>
TABLE-US-00021 [0287] C.I. Disperse Yellow 201 3.51 parts Polyvinyl
acetal resin 2.63 parts (KS-5, manufactured by Sekisui Chemical
Co., Ltd.) Polyethylene wax (particle diameter: 5 .mu.m) 0.06 part
Toluene 33 parts Methyl ethyl ketone 33 parts
<Coating Liquid for Colorant Layer 13>
TABLE-US-00022 [0288] C.I. Disperse Yellow 54 3.31 parts Pigment
represented by the above Formula 3 0.20 parts (sulfonated
derivative of C.I. Pigment Yellow 138) Dispersant of acryl-based
block type polymer 2.975 parts (BYK-LPN21116, weight average
molecular (solid content weight: 8000, solid content: 40%,
manufactured 1.19 parts) by BYK Additives & Instruments)
Polyvinyl acetal resin 1.44 parts (KS-5, manufactured by Sekisui
Chemical Co., Ltd.) Toluene 33 parts Methyl ethyl ketone 33
parts
Example 13
[0289] A thermal transfer sheet of Example 13 was obtained by
carrying out the same procedure as in Example 11 except that a
coating liquid for colorant layer 14 wherein a sublimable dye
represented by the following formula 5 (2.3 parts) was used instead
of the C. I. Disperse Yellow 201 (2.3 parts) in the coating liquid
for colorant layer 11 was used in place of the coating liquid for
colorant layer 11.
##STR00008##
Comparative Example 4
[0290] A thermal transfer sheet of Comparative example 4 was
obtained by carrying out the same procedure as in Example 11 except
that the coating liquid for colorant layer 12 having the above
mentioned composition was used in place of the coating liquid for
colorant layer 11, and the coating liquid for colorant layer 12 was
coated so as to obtain a coating amount of solid content of 1.0
g/m.sup.2 and then the coated liquid was dried.
Comparative Example 5
[0291] A thermal transfer sheet of Comparative example 5 was
obtained by carrying out the same procedure as in Example 11 except
that a coating liquid for colorant layer D wherein a sublimable dye
represented by the following formula 5 (3.51 parts) was used
instead of the C. I. Disperse Yellow 201 (3.51 parts) in the
coating liquid for colorant layer 12 was prepared and the coating
liquid for colorant layer D was coated so as to obtain a coating
amount of solid content of 1.0 g/m.sup.2 and then the coated liquid
was dried. Incidentally, the coating liquid for colorant layer D
was prepared by a manufacturing procedure similar to that for the
above mentioned coating liquid for colorant layer 12.
(Evaluation of Printing Density)
[0292] Using the same test printer that was used in the evaluation
of the printing aptitude, and combining each individual thermal
transfer sheet of Examples and Comparative Examples with the
thermal transfer image-receiving sheet prepared in the above
conditions, the gradation pattern was printed under the above
mentioned printing condition 1 to examine the density property. The
density property was measured at the highest density when applying
a maximum energy, the evaluation of print density was done in
accordance with the following criteria. The reflection density was
measured by the spectrometer (SpectroLino, manufactured by Gretag
Macbeth Co., Ltd.). The evaluation results are shown in Table
2.
"Evaluation Criteria"
[0293] .circleincircle.: Concentration was not less than 2.1.
.smallcircle.: Concentration was not less than 2.0 and less than
2.1. .DELTA.: Concentration was less than 2.0.
(Evaluation of Contamination)
[0294] The contamination to the back layer was evaluated in order
to determine the storage stability of the thermal transfer sheet.
The evaluation of contamination was carried out in the same method
as the above mentioned evaluation of the contamination to the back
surface layer of Examples 1-10 and Comparative Examples 1-3, and
the evaluation of contamination was done in accordance with the
following criteria. The evaluation results are shown in Table
2.
"Evaluation Criteria"
[0295] .smallcircle.: .DELTA.E*.sup.ab was less than 10. .DELTA.:
.DELTA.E*.sup.ab was not less than 10.
(Scumming Evaluation)
[0296] The scumming of the printed article was evaluated in order
to determine the storage stability of the thermal transfer sheet.
In order to evaluate the scumming, a group wherein each individual
thermal transfer sheet of Examples and Comparative examples had
been stored for 60 hours under a condition of 50.degree. C. and 80%
RH, and another group wherein each individual thermal transfer
sheet of Examples and Comparative examples had not been stored in
such a condition as above mentioned were prepared. Then, using
predetermined image-receiving paper, the printing was executed. The
white background portion of each individual printed article
obtained, to which no energy had been applied, underwent
measurement by using the spectrometer (SpectroLino, manufactured by
Gretag Macbeth Co., Ltd.), and the color difference
(.DELTA.E*.sup.ab) was determined by the following equation. Then,
the scumming was evaluated in accordance with the following
criteria. The evaluation results are also shown in Table 2.
Color difference
.DELTA.E*.sup.ab=((.DELTA.a*).sup.2+(.DELTA.b*).sup.2).sup.1/2
Please see, CIE 1976 La* b* color system (JIS 28729 (1980))
Aa*=a*(after storage)-a*(before storage)
Ab*=b*(after storage)-b*(before storage)
Incidentally, a* and b* are based on the CIE 1976 L* A* b* color
system, and the a* and b* represent perceptual brightness
indexes.
[0297] Here, the smaller the value of the .DELTA.E*.sup.ab becomes,
the less reduction under high temperature and high humidity
condition and the higher storing stability arise.
"Evaluation Criteria"
[0298] .circleincircle.: .DELTA.E*.sup.ab was less than 0.2.
.smallcircle.: .DELTA.E*.sup.ab was not less than 0.2 and less than
0.3. .DELTA.: .DELTA.E*.sup.ab was not less than 0.3.
TABLE-US-00023 TABLE 2 Printing Contamination Scrumming density
evaluation evaluation Example 11 .largecircle. .largecircle.
.largecircle. Example 12 .largecircle. .largecircle.
.circleincircle. Example 13 .circleincircle. .largecircle.
.largecircle. Comparative .largecircle. .DELTA. .DELTA. example 4
Comparative .circleincircle. .DELTA. .DELTA. example 5
[0299] As is apparent from Table 2, with respect to the printed
articles obtained by using the thermal transfer sheets of Examples
11 to 13, the concentration was good as indicating a value of not
less than 2.0 at the highest concentration. In addition, the
colorant contamination to the back face layer surface was in low
level and the scumming was also in low level, and thus the storage
stability of the thermal transfer sheet was good. In contrast, with
respect to the printed articles obtained by using the thermal
transfer sheets of Comparative Examples 4 and 5, although the
concentration was good enough, the colorant contamination to the
back face layer and the scumming increased, and thus the storage
stability of the thermal transfer sheet became worse.
EXPLANATION OF NUMERALS
[0300] 1 . . . thermal transfer sheet [0301] 2 . . . substrate
sheet [0302] 3 . . . colorant layer [0303] 4 . . . primer layer
[0304] 5 . . . back face layer [0305] 10y . . . sublimable dye
capable of being dissolved in the predetermined solvent [0306] 10x
. . . colorant capable of being dispersed in the predetermined
solvent [0307] 1X . . . thermal transfer sheet for comparison
* * * * *