U.S. patent application number 10/146047 was filed with the patent office on 2003-06-05 for laser-heat transfer recording method and image-receiving sheet.
This patent application is currently assigned to FUJI PHOTO FILM CO., LTD.. Invention is credited to Sasaki, Yoshiharu, Shimomura, Akihiro.
Application Number | 20030104308 10/146047 |
Document ID | / |
Family ID | 18993379 |
Filed Date | 2003-06-05 |
United States Patent
Application |
20030104308 |
Kind Code |
A1 |
Shimomura, Akihiro ; et
al. |
June 5, 2003 |
Laser-heat transfer recording method and image-receiving sheet
Abstract
A laser-heat transfer recording method comprising the
image-recording steps of feeding an image-receiving sheet and a
heat transfer sheet to an exposure-recording unit, fixing the
image-forming layer in the heat transfer sheet and the
image-receiving layer in the image-receiving sheet being superposed
vis-a-vis on a recording medium fixing member of the
exposure-recording unit; irradiating the heat transfer sheet with
laser beams corresponding to image data; and transferring the
irradiated are with laser beam of the image-forming layer onto the
image-receiving layer in the image-receiving sheet, wherein the
surfaces of the image-receiving sheet and/or the heat transfer
sheet are cleaned by being brought into contact with an adhesive
roll of a crown shape for removing foreign matters, the diameter of
the central part of which is larger than the diameters of both ends
in the axis direction of the roll body, provided at at least one of
the feeding part of the image-receiving sheet and the heat transfer
sheet of the exposure-recording unit, a carrying part and a
recording part, and the adhesive strength of the image-receiving
layer and the underlayer of the image-receiving layer in the
image-receiving sheet is from 20 to 100 mN/cm.
Inventors: |
Shimomura, Akihiro;
(Shizuoka, JP) ; Sasaki, Yoshiharu; (Shizuoka,
JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
WASHINGTON
DC
20037
US
|
Assignee: |
FUJI PHOTO FILM CO., LTD.
|
Family ID: |
18993379 |
Appl. No.: |
10/146047 |
Filed: |
May 16, 2002 |
Current U.S.
Class: |
430/200 ;
347/212; 430/201 |
Current CPC
Class: |
B41M 5/42 20130101; B41J
2/475 20130101; B41M 5/52 20130101 |
Class at
Publication: |
430/200 ;
430/201; 347/212 |
International
Class: |
G03F 007/34; G03F
007/38; G01D 015/10 |
Foreign Application Data
Date |
Code |
Application Number |
May 17, 2001 |
JP |
P.2001-147983 |
Claims
What is claimed is:
1. A laser-heat transfer recording method comprising the
image-recording steps of feeding an image-receiving sheet having an
image-receiving layer and a heat transfer sheet comprising a
support having provided thereon at least a light-to-heat converting
layer and an image-forming layer to an exposure-recording unit;
fixing the image-forming layer in the heat transfer sheet and the
image-receiving layer in the image-receiving sheet being superposed
vis-a-vis on a recording medium fixing member of the
exposure-recording unit; irradiating the heat transfer sheet with
laser beams corresponding to image data; and transferring the
irradiated area with laser beams of the image-forming layer onto
the image-receiving layer in the image-receiving sheet; wherein the
surface of the image-receiving sheet is cleaned by being brought
into contact with an adhesive roll of a crown shape for removing
foreign matters, the diameter of the central part of which is
larger than the diameters of both ends in the axis direction of the
roll body, provided at at least one of the feeding part of the
image-receiving sheet and the heat transfer sheet of the
exposure-recording unit, a carrying part and a recording part, and
the adhesive strength of the image-receiving layer and the
underlayer of the image-receiving layer in the image-receiving
sheet is from 20 to 100 mN/cm.
2. The laser-heat transfer recording method as claimed in claim 1,
wherein the static friction coefficient of the image-receiving
layer surface in the image-receiving sheet is 0.7 or less.
3. The laser-heat transfer recording method as claimed in claim 1,
wherein the surface roughness Rz of the image-receiving layer
surface in the image-receiving sheet is from 1 to 5 .mu.m.
4. The laser-heat transfer recording method as claimed in claim 1,
wherein pressing controlling members made of a harder material than
the material of the adhesive member are provided at both ends of
the adhesive roll.
5. The laser-heat transfer recording method as claimed in claim 1,
wherein the cleaning of the surface of the image-receiving sheet by
the adhesive roll comprises the steps of fixing the image-receiving
sheet on the recording medium-fixing member, cleaning the surface
from almost the central part of the relative moving direction of
the image-receiving sheet toward one end of the relative moving
direction by keeping the adhesive roll in contact with the surface;
and thereafter cleaning the surface from almost the central part of
the relative moving direction of the image-receiving sheet toward
another end of the relative moving direction by keeping the
adhesive roll in contact with the surface.
6. An image-receiving sheet for use in a laser-heat transfer
recording unit equipped with an adhesive roll of a crown shape for
removing foreign matters, the diameter of the central part of which
is larger than the diameters of both ends in the axis direction of
the roll body, at at least one of a feeding part of a recording
medium, a carrying part and a recording part, wherein the adhesive
strength of the image-receiving layer and the underlayer of the
image-receiving layer is from 20 to 100 mN/cm.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a multicolor image-forming
method for forming a full color image of high resolution by
irradiation with laser beams. In particular, the present invention
relates to a multicolor image-forming method which is useful in the
field of printing for forming a color proof (DDCP: direct digital
color proof) or a mask image from digital image signals by laser
recording.
BACKGROUND OF THE INVENTION
[0002] In the field of graphic arts, printing of a printing plate
is performed with a set of color separation films formed from a
color original by a lith film. In general, color proofs are formed
from color separation films before actual printing work for
checking an error in the color separation step and the necessity
for color correction. Color proofs are desired to realize high
resolution which makes it possible to surely reproduce a half tone
image and high performances such as high stability of processing.
Further, for obtaining color proofs closely approximating to an
actual printed matter, it is preferred to use materials which are
used in actual printing as the materials for making color proofs,
e.g., the actual printing paper as the base material and pigments
as the coloring materials. As the method for forming a color proof,
a dry method not using a developing solution is strongly
desired.
[0003] As the dry method for forming color proofs, a recording
system of directly forming color proofs from digital signals has
been developed with the spread of electronized system in
preprocessing of printing (pre-press field) in recent years. Such
electronized system aims at forming in particular high quality
color proofs, generally reproducing a dot image of 150 lines/inch
or higher. For recording a proof of high image quality from digital
signals, laser beams capable of modulation by digital signals and
capable of finely diaphragming recording lights are used as
recording heads. Therefore, the development of an image-forming
material having high recording sensitivity to laser beams and
exhibiting high resolution property capable of reproducing highly
accurate dots is required.
[0004] As the recording material for use in a transfer
image-forming method using laser beams, a heat fusion transfer
sheet comprising a support having thereon in the order of a
light-to-heat converting layer which absorbs laser beams and
generates heat, and an image-forming layer which contains a pigment
dispersed in components such as a heat fusion type wax and a binder
is known (JP-A-5-58045 (the term "JP-A" as used herein means an
"unexamined published Japanese patent application")). In an
image-forming method using such a recording material, the heat
generated at the area of a light-to-heat converting layer
irradiated with laser beams fuses an image-forming layer
corresponding to the irradiated area, and the fused layer is
transferred to an image-receiving sheet arranged on a transfer
sheet by lamination, thus a transferred image is formed on the
image-receiving sheet.
[0005] Further, a heat transfer sheet comprising a support having
provided thereon in the order of a light-to-heat converting layer
containing a light-to-heat converting material, an extremely thin
heat-peeling layer (from 0.03 to 0.3 .mu.m), and an image-forming
layer containing a coloring material is disclosed in JP-A-6-219052.
In the heat transfer sheet, the bonding strength between the
image-forming layer and the light-to-heat converting layer bonded
through the intervening heat-peeling layer is reduced by laser beam
irradiation, as a result, a highly accurate image is formed on an
image-receiving sheet arranged on the heat transfer sheet by
lamination. The image-forming method by the heat transfer sheet
utilizes so-called ablation, specifically the heat-peeling layer
partially decomposes at the area irradiated with laser beams and
vaporizes, thereby the bonding strength of the image-forming layer
and the light-to-heat converting layer at the irradiated area is
reduced and the image-forming layer at that area is transferred to
the image-receiving sheet laminated thereon.
[0006] These image-forming methods have advantages such that an
actual printing paper provided with an image-receiving layer (an
adhesion layer) can be used as the material of an image-receiving
sheet, a multicolor image can be easily obtained by transferring
images different in colors in sequence on the image-receiving
sheet, and highly accurate image can be easily obtained. Therefore,
these methods are useful for forming a color proof (DDCP: direct
digital color proof) or a highly accurate mask image.
[0007] For shortening the time required in laser recording when an
image is recorded with laser beams, laser beams comprising
multi-beams using a plurality of laser beams are used in recent
years. When recording is performed using a conventional heat
transfer sheet by laser beams of multi-beam, there are cases where
the image density of the transferred image formed on an
image-receiving sheet is insufficient. The reduction of image
density is particularly conspicuous in the case of laser recording
with high energy. As a result of the investigation by the present
inventors, it was found that the reduction of image density was
attributable to transfer unevenness caused by irradiation with high
energy laser beams.
[0008] Now, there are cases where foreign matters, e.g., dusts,
adhere to a recording medium-feeding part, a recording
medium-carrying part and printing part in a recording unit and the
surface of a recording medium in transportation due to static
electricity, and if printing is performed without removing these
foreign matters, the foreign matters present between an
image-receiving sheet and a heat transfer sheet cause a clear spot
and those present between a recording drum and an image-receiving
sheet or between a heat transfer sheet and a roller cause image
defect such as ring-like unevenness. Accordingly, to remove the
foreign matters adhered to the surfaces of the carrying route of a
recording medium and a recording part in a recording unit, an
adhesive rubber roller (a cleaning roller) is arranged to remove
the adhered substance periodically or according to necessity by
pressing the adhesive roller against the objective faces of foreign
matter removal, to thereby maintain good recording condition.
[0009] However, since ordinarily used adhesive rollers are of a
type of straight shape of constant roller diameter in the entire
width direction, the pressure at the central part of the width
direction of the roller weakens due to the deflection of the
roller, as a result the degree of adhesion of the roller with
recording media lowers and the performance of removing foreign
matters is reduced. Further, there is a case where the adhesive
force of adhesive rubber materials or adhesive substance used in
adhesive rollers lowers by natural aging, therefore, the
performance of rollers of removing foreign matters is deteriorated
in a couple of months after the production. Due to the reduction of
the performance of rubber rollers of removing foreign matters on a
printing medium, image defect is sometimes caused such that a
desired image is not printed on a recorded image.
[0010] On the other hand, there is another problem that by the
application of high pressure or by the use of an adhesive roller
made of strongly adhesive material, excessive adhesive force is
caused and accompanied by peeling of the surface layers such as an
image-receiving layer and a cushioning layer of an image-receiving
sheet in transportation, and the deviation of the position of an
image-receiving sheet fixed on a fixing part of a recording medium,
which lead to an image failure of the obtained image.
SUMMARY OF THE INVENTION
[0011] Accordingly, the present invention aims at solving the
problems of the prior art technique and to accomplish the following
objects. That is, the objects of the present invention are: 1) a
heat transfer sheet can provide excellent sharpness of dots and
stability by transfer of a membrane of coloring material, which is
not influenced by light sources of illumination as compared with
the pigment material and the printed matter, 2) an image-receiving
sheet can receive stably and surely the image-forming layer in a
heat transfer sheet by laser energy, 3) transfer to actual printing
paper can be effected corresponding to the range of from 64 to 157
g/m.sup.2 such as art paper (coat paper), mat paper and finely
coated paper, delicate texture can be imaged, and a high-key part
can be reproduced accurately, and 4) extremely stable transfer
releasability can be obtained. A further object of the present
invention is to provide a method for forming a multicolor image
capable of forming an image having good image quality and stable
transfer image density on an image-receiving sheet even when
recording is performed by multi-beam laser beams of high energy
under different temperature and humidity conditions.
[0012] In particular, the object of the present invention is to
provide a heat transfer recording method by laser irradiation
capable of forming a transfer image having good image quality free
of image defects due to foreign matters such as dusts.
[0013] A contract proof substituting proofs of an analog style
color proof becomes necessary in this film-less CTP
(computer-to-plate) age. For obtaining the approval of customers,
color reproduction which coincides with the printed matters and
analog style color proof is required, and the present inventors
have developed DDCP system capable of transfer to actual paper
without generating moire by using the same pigment materials as
used in the printing inks. That is, this object has been realized
by a large sized direct digital color proof (A2/B2) high in
approximation to a printed matter and capable of transfer to actual
paper and capable of using the same pigment materials as used in
the printing inks. The system of the present invention is a system
adopting laser membrane transfer, using pigment coloring materials
and capable of transferring to actual paper by performing actual
dot recording.
[0014] The above objects of the present invention have been
attained by the following means.
[0015] (1) A laser-heat transfer recording method comprising the
image-recording steps of feeding an image-receiving sheet having an
image-receiving layer and a heat transfer sheet comprising a
support having provided thereon at least a light-to-heat converting
layer and an image-forming layer to an exposure-recording unit;
fixing the image-forming layer in the heat transfer sheet and the
image-receiving layer in the image-receiving sheet being superposed
vis-a-vis on a recording medium fixing member of the
exposure-recording unit; irradiating the heat transfer sheet with
laser beams corresponding to image data; and transferring the
irradiated area with laser beams of the image-forming layer on the
image-receiving layer in the image-receiving sheet; wherein the
surface of the image-receiving sheet is cleaned by being brought
into contact with an adhesive roll of a crown shape for removing
foreign matters, the diameter of the central part of which is
larger than the diameters of both ends in the axis direction of the
roll body, provided at at least one of the feeding part of the
image-receiving sheet and the heat transfer sheet of the
exposure-recording unit, a carrying part and a recording part, and
the adhesive strength of the image-receiving layer and the
underlayer of the image-receiving layer in the image-receiving
sheet is from 20 to 100 mN/cm.
[0016] (2) The laser-heat transfer recording method as described in
the above item (1), wherein the static friction coefficient of the
image-receiving layer surface in the image-receiving sheet is 0.7
or less.
[0017] (3) The laser-heat transfer recording method as described in
the above item (1) or (2), wherein the surface roughness Rz of the
image-receiving layer surface in the image-receiving sheet is from
1 to 5 .mu.m.
[0018] (4) The laser-heat transfer recording method as described in
the above item (1), (2) or (3), wherein pressing controlling
members made of a harder material than the material of the adhesive
member are provided at both ends of the adhesive roll.
[0019] (5) The laser-heat transfer recording method as described in
the above item (1), (2), (3) or (4), wherein the cleaning of the
surface of the image-receiving sheet by the adhesive roll comprises
the steps of fixing the image-receiving sheet on the recording
medium-fixing member, cleaning the surface from almost the central
part of the relative moving direction of the image-receiving sheet
toward one end of the relative moving direction by keeping the
adhesive roll in contact with the surface; and thereafter cleaning
the surface from almost the central part of the relative moving
direction of the image-receiving sheet toward another end of the
relative moving direction by keeping the adhesive roll in contact
with the surface.
[0020] (6) An image-receiving sheet for use in a laser-heat
transfer recording unit equipped with an adhesive roll of a crown
shape for removing foreign matters, the diameter of the central
part of which is larger than the diameters of both ends in the axis
direction of the roll body, at at least one of a feeding part of a
recording medium, a carrying part and a recording part, wherein the
adhesive strength of the image-receiving layer and the underlayer
of the image-receiving layer is from 20 to 100 mN/cm.
BRIEF DESCRIPTION OF THE DRAWING
[0021] FIG. 1 is a drawing showing the outline of the scheme of
multicolor image-forming by membrane heat transfer by irradiation
with a laser.
[0022] FIG. 2 is a drawing showing an example of constitution of a
recording unit for laser-heat transfer.
[0023] FIG. 3 is a drawing showing the conceptual figure of an
adhesive roller, FIG. 3 (a) shows a figure of taper crown, and FIG.
3 (b) shows a figure of radial crown.
[0024] FIG. 4 is a drawing showing the results of the test of
degradation of foreign matter removal due to natural aging.
[0025] FIG. 5 is a drawing showing an adhesive roller before being
pressed against an objective face of foreign matter removal, FIG. 5
(a) is a cross-sectional view, and FIG. 5 (b) is a side view.
[0026] FIG. 6 is a drawing showing an adhesive roller after being
pressed against an objective face of foreign matter removal, FIG. 6
(a) is a cross-sectional view, and FIG. 6 (b) is a side view.
[0027] FIG. 7 is a drawing showing the relationship between a
recording medium and an adhesive roller mounted on a recording
drum.
[0028] FIG. 8 is a drawing showing the relationship between a
recording medium and an adhesive roller by developing the
circumferential plane of a recording drum.
[0029] FIG. 9 is a drawing showing the starting position of an
adhesive roller of coming into contact with a recording medium on
the circumferential plane of a recording drum.
[0030] FIG. 10 is a drawing showing the state that the cleaning
area of a recording medium in the circumferential direction of one
end and the cleaning area in the circumferential direction of
another end overlap.
DESCRIPTION OF REFERENCE NUMERALS
[0031] 1: Recording unit
[0032] 2: Recording head
[0033] 3: By-scan rail
[0034] 4: Recording drum
[0035] 5: Heat transfer sheet-loading unit
[0036] 6: Image-receiving sheet roll
[0037] 7: Carrier roller
[0038] 8: Squeeze roller
[0039] 9: Cutter
[0040] 10: Heat transfer sheet
[0041] 10K, 10C, 10M, 10Y: Heat transfer sheet rolls
[0042] 11: Recording media (image-receiving sheet, heat transfer
sheet)
[0043] 12: Support
[0044] 14: Light-to-heat converting layer
[0045] 16: Image-forming layer
[0046] 20: Image-receiving sheet
[0047] 22: Support for image-receiving sheet
[0048] 24: Image-receiving layer
[0049] 30: Laminate
[0050] 31: Discharge table
[0051] 32: Discard port
[0052] 33: Discharge port
[0053] 34: Air
[0054] 35: Discard box
[0055] 40: Adhesive roller
[0056] 41: Core part
[0057] 42: Adhesive member
[0058] 43: Pressing controlling member
[0059] 44: Cylinder (moving part)
[0060] 45: Piston rod (moving part)
DETAILED DESCRIPTION OF THE INVENTION
[0061] The present invention realizes a heat transfer image by
sharp dots and is effective and suitable for a system capable of
transferring an image to actual printing paper and recording of B2
size (515 mm.times.728 mm, B2 size is 543 mm.times.765 mm).
[0062] The heat transfer image obtained by this system is a dot
image corresponding to print line number of resolution of from
2,400 dpi to 2,540 dpi. Since individual dot obtained is very sharp
and almost free of blur and chip, dots of a wide range from
highlight to shadow can be clearly formed. As a result, it is
possible to output dots of high grade having the same resolution as
obtained by an image setter and a CTP setter, and dots and
gradation which are excellent in approximation to the printed
matter can be reproduced.
[0063] Since the heat transfer image obtained is sharp in dot
shape, dots corresponding to laser beams can be faithfully
reproduced and recording characteristics are hardly influenced by
the surrounding temperature and humidity, repeating reproducibility
stable in hue and density can be obtained under wide temperature
and humidity conditions.
[0064] The heat transfer image obtained by this system is formed
with coloring pigments used in printing inks and since excellent in
repeating reproducibility, highly accurate CMS (color management
system) can be realized.
[0065] Further, the heat transfer image almost coincides with the
hues of Japan color and SWOP color, i.e., the hues of printed
matters, and the colors appear similarly to the printed matters
even when light sources of illumination are changed, such as a
fluorescent lamp, an incandescent lamp.
[0066] Since the heat transfer image is sharp in dot shape, the
fine line of a fine character can be reproduced sharply. Heat
generated by laser beams is not diffused in the surface direction
and conducted up to the transfer interface, and an image-forming
layer ruptures sharply at interface of heating area/non-heating
area. The thickness of the light-to-heat converting layer in the
heat transfer sheet is thinned and dynamic properties of the
image-forming layer are controlled for this purpose.
[0067] A light-to-heat converting layer is presumed from simulation
to reach about 700.degree. C. in a moment, and a thin layer is
liable to be deformed and ruptured at that high temperature. When
deformation and rupturing occur, a light-to-heat converting layer
is transferred to an image-receiving sheet together with a transfer
layer or a transferred image becomes uneven. On the other hand, a
high concentration of light-to-heat converting materials must be
present in a light-to-heat converting layer for obtaining a desired
temperature, which results in a problem of precipitation or
migration of the dyes to the adjacent layer.
[0068] Therefore, it is preferred to make a light-to-heat
converting layer as thin as about 0.5 .mu.m or less by selecting an
infrared absorbing dye excellent in light-to-heat converting
characteristics and a heat-resisting binder such as polyimide
compounds.
[0069] In general, when a light-to-heat converting layer is
deformed or an image-forming layer itself is deformed due to high
temperature, thickness unevenness is caused in an image-forming
layer transferred to an image-receiving layer corresponding to the
by-scanning pattern of laser beams, as a result the image becomes
uneven and apparent transfer density is reduced. The thinner the
thickness of an image-forming layer, the more conspicuous is this
tendency. On the other hand, when the thickness of an image-forming
layer is thick, dot sharpness is impaired and sensitivity
decreases.
[0070] To reconcile these reciprocal properties, it is preferred to
improve transfer unevenness by adding a low melting point material
to an image-forming layer, e.g., a wax. Transfer unevenness can be
improved by adding inorganic fine particles in place of a binder to
adjust the layer thickness of an image-forming layer properly so
that the image-forming layer ruptures sharply at the interface of
heating area/non-heating area while maintaining dot sharpness and
sensitivity.
[0071] In general, materials having a low melting point, such as a
wax, are liable to ooze to the surface of an image-forming layer or
to be crystallized and cause a problem in image quality and the
aging stability of a heat transfer sheet in some cases.
[0072] To cope with this problem, it is preferred to use a low
melting point material having no great difference from the polymer
of an image-forming layer in an SP value, by which the
compatibility with the polymer can be increased and the separation
of the low melting point material from the image-forming layer can
be prevented. It is also preferred to mix several kinds of low
melting point materials to prevent crystallization by eutectic
mixture. As a result, an image showing a sharp dot shape and free
of unevenness can be obtained.
[0073] Further, the dynamic properties and thermal physical
properties of the coated layers of a heat transfer sheet are
generally varied by absorbing moisture, thus the humidity
dependency of recording condition is caused.
[0074] For reducing the temperature and humidity dependency, it is
preferred that the dye/binder system of a light-to-heat converting
layer and the binder system of an image-forming layer are made
organic solvents. It is also preferred to use polyvinyl butyral as
the binder of an image-receiving layer and to introduce a
hydrophobitization technique of polymers for the purpose of
lowering water absorption properties of polymers. As the
hydrophobitization technique of polymers, the techniques of
reacting a hydroxyl group with a hydrophobic group, or crosslinking
two or more hydroxyl groups with a hardening agent as disclosed in
JP-A-8-238858can be exemplified.
[0075] About 500.degree. C. or more heat is also generally applied
to an image-forming layer by laser exposure imaging, and so some of
conventionally used pigments are heat-decomposed, but this problem
can be prevented by using highly heat resisting pigments in an
image-forming layer.
[0076] For preventing the variation of hue due to migration of an
infrared absorbing dye from a light-to-heat converting layer to an
image-forming layer by high heat at exposure, it is preferred to
design a light-to-heat converting layer by combination of an
infrared absorbing dye having high retentivity and a binder as
described above.
[0077] Shortage of energy occurs generally in high speed printing
and, in particular, time lag is caused in intervals of laser
by-scanning and gaps are generated. As described above, using a dye
of high concentration in a light-to-heat converting layer and
thinning of a light-to-heat converting layer and an image-forming
layer can improve the efficiency of generation and conduction of
heat. It is also preferred to add a low melting point material to
an image-forming layer for the purpose of slightly fluidizing the
image-forming layer at heating to thereby fill the gaps and
improving the adhesion with the image-receiving layer. Further, for
enhancing the adhesion of the image-receiving layer and the
image-forming layer and sufficiently strengthening a transferred
image, it is preferred to use the same polyvinyl butyral as used in
the image-forming layer as the binder in the image-receiving
layer.
[0078] It is preferred that an image-receiving sheet and a heat
transfer sheet are retained on a drum by vacuum adhesion. Since an
image is formed by the adhesion control of both sheets, image
transfer behavior is very sensitive to the clearance between the
image-receiving layer surface in an image-receiving sheet and the
image-forming layer surface in a transfer sheet, hence vacuum
adhesion is important. If the clearance between the materials is
widened with foreign matter, e.g., dust, as a cue, image defect and
image transfer unevenness come to occur.
[0079] For preventing such image defect and image transfer
unevenness, it is preferred to give uniform unevenness to a heat
transfer sheet to thereby improve the air passage, to obtain
uniform clearance.
[0080] For giving unevenness to a heat transfer sheet, a method of
post treatment such as embossing treatment and a method of the
addition of a matting agent to a coating layer are generally used,
but in view of the simplification of manufacturing process and
stabilization of materials with the lapse of time, the addition of
a matting agent is preferred. The particle size of a matting agent
must be larger than the coating layer thickness. When a matting
agent is added to an image-forming layer, there arises a problem of
coming out of the image of the part where the matting layer is
present, accordingly, it is preferred to add a matting agent having
an optimal particle size to a light-to-heat converting layer,
thereby the layer thickness of an image-forming layer itself
becomes almost uniform and an image free of defect can be obtained
on an image-receiving sheet.
[0081] For surely reproducing sharp dots as described above, a
recording unit is also required to be designed highly accurately.
The recording unit for use in laser-heat transfer in the present
invention is the same as those conventionally used in fundamental
constitution. The constitution is a so-called heat mode outer drum
recording system wherein recording is performed such that recording
head provided with a plurality of high power lasers irradiates
laser rays on a heat transfer sheet and an image-receiving sheet
fixed on a drum. Preferred embodiments are as follows.
[0082] Feeding of an image-receiving sheet and a heat transfer
sheet is performed by full automatic roll feeding. Fixing of an
image-receiving sheet and a heat transfer sheet on a recording drum
is performed by vacuum adsorption. Many vacuum adsorption holes are
formed on a recording drum, and a sheet is adsorbed by a drum by
reducing the pressure in a drum with a blower or a decompression
pump. Since a heat transfer sheet is further adsorbed over the
adsorbed image-receiving sheet, the size of the heat transfer sheet
is made larger than the size of the image-receiving sheet. The air
between the heat transfer sheet and the image-receiving sheet which
most affects recording performance is sucked from the area outside
of the image-receiving sheet where the heat transfer sheet is
alone.
[0083] In the apparatus in the present invention, a great number of
sheets of a large size, such as B2, are to be accumulated on a
discharge table. Therefore, a method of floating the film
discharged later by blasting air between two films is used in the
present invention.
[0084] An example of the constitution of the apparatus in the
present invention is shown in FIG. 2.
[0085] The sequence of the apparatus in the present invention as
above is described below.
[0086] 1) By-scan axis of recording head 2 of recording unit 1 is
reset by by-scan rail 3, main scan rotation axis of recording drum
4 and heat transfer sheet loading unit 5 are respectively reset at
origin.
[0087] 2) Image-receiving sheet roll 6 is unrolled by carrier
roller 7, and the tip of the image-receiving roll is fixed on
recording drum 4 by vacuum suction via suction holes provided on
the recording drum.
[0088] 3) Squeeze roller 8 comes down on recording drum 4 and
presses the image-receiving sheet, and when the prescribed amount
of the image-receiving sheet is conveyed by the rotation of the
drum, the sheet is stopped and cut by cutter 9 in a prescribed
length.
[0089] 4) Recording drum 4 further makes a round, thus the loading
of the image-receiving sheet finishes.
[0090] 5) In the next place, in the same sequence as the
image-receiving sheet, heat transfer sheet K of the first color,
black, is drawn out from heat transfer sheet roll 10K, cut and
loaded.
[0091] 6) Recording drum 4 begins high speed rotation, recording
head 2 on by-scan rail 3 begins to move and when reaches the
starting position of recording, recording laser is irradiated on
recording drum 4 by recording head 2 according to recording
signals. Irradiation finishes at finishing position of recording,
operation of by-scan rail and drum rotation finish. The recording
head on the by-scan rail is reset.
[0092] 7) Only heat transfer sheet K is peeled with the
image-receiving sheet remaining on the recording drum. For the
peeling, the tip of heat transfer sheet K is caught by the claw,
pulled out in the discharge direction, and discarded from discard
port 32 to discard box 35.
[0093] 8) The procedures of 5) to 7) are repeated for the remaining
three colors. Recording is performed in the order of black, cyan,
magenta and yellow. That is, heat transfer sheet C of the second
color, cyan, is drawn out from heat transfer sheet roll 10C, heat
transfer sheet M of the third color, magenta, from heat transfer
sheet roll 10M, and heat transfer sheet Y of the fourth color,
yellow, from heat transfer sheet roll 10Y in order. This is the
inverse of general printing order, since the order of the colors on
actual paper becomes inverse by the later process of transfer to
actual paper.
[0094] 9) After recording of four colors, the recorded
image-receiving sheet is finally discharged to discharge table 31.
The peeling method from the drum is the same as that of the heat
transfer sheet in above 7) , but since the image-receiving sheet is
not discarded unlike the heat transfer sheets, the image-receiving
sheet is returned to the discharge table by switch back when
conveyed to discard port 32. When the image-receiving sheet is
discharged to the discharge table, air 34 is blasted from under
discharge port 33 to make it possible to accumulate a plurality of
sheets.
[0095] For preventing image defects due to adhesion of foreign
matters such as dusts on the surfaces of the image-receiving sheet
and the heat transfer sheet, cleaning by bringing an adhesive roll
into contact with the surfaces is performed in the present
invention.
[0096] It is sufficient that an adhesive roll should be provided at
at least one of the feeding part of an image-receiving sheet and a
heat transfer sheet, a carrying part and a recording part. For
example, in the recording unit shown in FIG. 2, an adhesive roll
may be provided at any of carrier rollers 7.
[0097] The adhesive roll for use in the present invention is of a
crown shape having the difference in the diameter of the central
part in the width direction of the roll body and the diameters of
the positions near the ends.
[0098] The conceptual figure of an adhesive roller is shown in FIG.
3. FIG. 3 (a) shows a figure of taper crown having tapered planes
at the ends of the width direction, and FIG. 3 (b) shows a figure
of radial crown formed in a curve over the width, and both shapes
can be used in the present invention.
[0099] The adhesive roller in the present invention is formed by
covering a metal core bar having supporting parts at both ends with
a cylindrical rubber of a crown shape, and the specific dimensions
are, for example, as follows.
[0100] The length of the roller body in the axis direction (the
width of the rubber roller): 500 mm
[0101] The central diameter of the rubber roller: 40 mm
[0102] The end diameter of the rubber roller: 39 mm
[0103] The crown shape: taper crown
[0104] The supporting parts at both ends of the adhesive roller of
the above type are connected with driving mechanism such as air
piston, and a prescribed pressure (e.g., 98 N (10 kgf)) is applied
to each supporting part by the driving mechanism. When pressure is
applied to the recording medium (an image-receiving sheet and a
heat transfer sheet) to be cleaned, since the adhesive roller is a
crown shape, the pressure at central part in the width direction
does not reduce and the pressure is applied uniformly over all the
width direction. The adhesive roller is pressed against the
recording medium uniformly over all the width direction by a
prescribed thrust on plane due to this configuration, thereby the
foreign matters on the surface of the recording medium are removed
by the adhesion of the adhesive roller itself. When the adhesive
roller is in contact with only one part of a recording medium, the
trace of the roller is left on a part of the layer surface of the
recording medium, and recording sensitivity (density) changes and
leads to image failure by the presence of the trace of the roller,
but the pressure is distributed uniformly and the force does not
work locally by applying roller pressure uniformly in the width
direction of the roller, and generations of image failure and
something wrong, e.g., peeling of a film, can be prevented.
[0105] The adhesive roller of the above figure can also be used for
removing foreign matters adhered on, besides the surface of a
recording medium, the feeding part of a recording medium, a
carrying part and a recording part by being provided on an
appropriate place in a recording unit.
[0106] It is preferred to set the dimensions of the crown shape of
an adhesive roller as follows.
[0107] (A1) The difference in diameter between diameter D at the
central position in the width direction of a roller and diameter d
at the position near the end in the width direction is from 0.1 to
2 mm.
[0108] (A2) 1.002.ltoreq.D/d.ltoreq.1.11
[0109] For example, when diameter D at almost the central position
is 40 mm, the diameter at both ends should be set in the range of
from 36 to 39.9 mm.
[0110] (A3) 0.0001.ltoreq.(D-d)/L.ltoreq.0.005
[0111] For example, when diameter D at almost the central position
is 40 mm and the length of the roller L is 500 mm, the diameter at
both ends should be set in the range of from 37.5 to 39.9 mm.
[0112] By setting the dimensions in the above ranges, uniforming of
the pressure by the crown shape can be particularly heightened.
[0113] As adhesive materials which are used for adhesive rollers,
e.g., an ethylene-vinyl acetate copolymer, an ethylene-ethyl
acrylate copolymer, a polyolefin resin, a polybutadiene resin, a
styrene-butadiene copolymer (SBR), a
styrene-ethylene-butene-styrene copolymer (SEBS), an
acrylonitrile-butadiene copolymer (NBR), a polyisoprene resin (IR),
a styrene-isoprene copolymer (SIS), an acrylic ester copolymer, a
polyester resin, a polyurethane resin, an acrylate resin, a butyl
rubber, and a polynorbornene can be exemplified.
[0114] Rubber materials are preferred above all, and adhesive
rubbers containing TiO.sub.x (titanium oxide), and(or) hydrocarbon
compounds having functional groups, e.g., C--O or Si--O, and not
containing Ba (barium) can be preferably used. By containing these
materials, it becomes possible to maintain the property of removing
foreign matters adhered on a recording medium for a long period of
time. Specifically, these materials are commercially available from
Miyagawa Roller Co., Ltd., under the trade name of "Carboless
MIMOSA", and graded "LT" and "ST" (refer to Table 1) are preferably
used.
1 TABLE 1 Grade LT ST Adhesive Strength 27 62 (hPa) Hardness
(.degree.) 35 25 (JIS K 6253) Value of electric 4 .times. 10.sup.7
8 .times. 10.sup.7 resistance (.OMEGA.)
[0115] The adhesive strength, the hardness and the value of
electric resistance of "Carboless MIMOSA LT" (abbreviated to "LT"
in Table 1) and "Carboless MIMOSA ST" (abbreviated to "ST" in Table
1) are shown in Table 1. These adhesive rubbers also have a
property of capable of removing the static electricity generated in
a recording medium, since their electric resistance values are
small.
[0116] The results of the test of degradation of foreign matter
removal due to natural aging of four kinds of "Carboless MIMOSA
LT", "Carboless MIMOSA ST", other kinds of "Cleaner Green" and
"MIMOSA Under LT" are shown in FIG. 4. The graph in FIG. 4 shows
the results of counting the number of image defects due to foreign
matters when each roller is used after allowing to stand in the
state of not using for one month. The axis of abscissa shows the
number of months passed, and the axis of ordinate shows the number
of image defects due to foreign matters. From the comparison, the
number of image defects due to foreign matters of "Carboless MIMOSA
LT" and "Carboless MIMOSA ST" was less than 10 after 8 months have
passed, contrary to these, the number of image defects due to
foreign matters was more than 10 (the number of image defects was
15) in the case of "MIMOSA Under LT" after 1 month has passed, 36
after two months, 60 after three months, and the image defects were
almost 70 after eight months have passed. Further, in the case of
"Cleaner Green", image defects due to foreign matters were already
more than 20 after one month, 50 after 2 months, 67 after three
months, and exceeded 70 after eight months have passed. Thus, great
differences were brought about depending upon adhesive rubber
materials.
[0117] Table 2 below shows the results of analyses of the rubbers
materials and the comparison of comprehensive performances of
"Carboless MIMOSA LT", "Carboless MIMOSA ST", "Cleaner Green" and
"MIMOSA Under LT".
2TABLE 2 Degra- dation of Property Adhesive to Strength Name of
Main Remove due to Adhesive Example Adhesive Polymer Traveling
Foreign Natural Strength No. Rubber of Rubber Filler Plasticizer
Propertry Matters Aging (Hpa) Example 1 Carboless Isobutylene
SiO.sub.2 Paraffin .smallcircle. .smallcircle. .smallcircle. 62
MIMOSA series TiO.sub.2 Hydrocarbon- ST (polymer ZnO.sub.2 based
compound, mainly or hydrocarbon- comprising based compound
isobutylene- having function- based al groups such polymer) or as
C--O Isoprene and Si--O copolymer Example 2 Carboless SiO.sub.2
.smallcircle. .smallcircle. .smallcircle. 27 MIMOSA TiO LT
ZnO.sub.2 Comparative Cleaner SiO.sub.2 Paraffin x.sup.*1
.smallcircle. x 70 Example 1 Green BaSO.sub.2 ZnO.sub.2 Comparative
MIMOSA -- -- -- .smallcircle. x.sup.*2 x 8 Example 2 Under LT
.sup.*1Since the adhesive strength is too strong, the film of the
image-receiving layer was peeled off, or the recording medium
itself is sometimes turned up. .sup.*2Since the adhesive strength
is too weak, foreign matters cannot be removed sufficiently.
[0118] It can be understood that adhesive rubber materials such as
"Carboless MIMOSA LT" and "Carboless MIMOSA ST" containing
TiO.sub.x as a filler and a hydrocarbon compound having a
functional group, e.g., C--O or Si--O, as a plasticizer are
superior in traveling property and slow in the degradation of
adhesive strength due to natural aging, therefore, they are
preferably used as the roller in the embodiment of the present
invention. Contrary to this, adhesive rubbers containing Ba are
inferior in traveling property and the degradation of adhesive
strength due to natural aging. From these facts, it can be seen
that adhesive rubbers containing Ba are not suited for removing
foreign matters in a recording unit.
[0119] Accordingly, the component which constitutes the adhesive
rubber applicable to the adhesive roller for use in the present
invention is any of the following (B1) to (B5), i.e., the adhesive
rubber which:
[0120] (B1) contains TiO.sub.x,
[0121] (B2) contains TiO.sub.x, and does not contain Ba,
[0122] (B3) contains a hydrocarbon compound having a functional
group, e.g., C--O or Si--O,
[0123] (B4) contains TiO.sub.x and a hydrocarbon compound having a
functional group, e.g., C--O or Si--O,
[0124] (B5) contains TiO.sub.x and a hydrocarbon compound having a
functional group, e.g., C--O or Si--O, and does not contain Ba.
[0125] By the adhesive roller constituted of the adhesive material
consisting of the above component, foreign matters adhered to the
objective face of foreign matter removal can be removed and the
image defects of recorded images can be prevented for a long period
of time.
[0126] Vickers hardness Hv of the material having viscosity used in
the adhesive roller is preferably 50 kg/mm.sup.2 (=about 490 MPa)
or less in view of capable of sufficiently removing foreign matters
and suppressing image defect.
[0127] Vickers hardness is the hardness obtained by measurement
with applying static load to a pyramid indenter of diamond having
the angle between the opposite faces of 136.degree., and Vickers
hardness Hv can be obtained by the following equation:
Hardness Hv=1.854 P/d.sup.2 (kg/mm.sup.2)=about 18.1692 P/d.sup.2
(Mpa)
[0128] wherein P: load (kg), d: the length of diagonal line of the
square of depressed area (mm).
[0129] It is also preferred in the present invention that the
modulus of elasticity at 20.degree. C. of the material having
viscosity used in the adhesive roller is 200 kg/cm.sup.2 (=about
19.6 MPa) or less in view of capable of sufficiently removing
foreign matters and suppressing image defect similarly to the
above.
[0130] For preventing the adhesive roller from being excessively
pressed against the objective face of foreign matter removal, it is
preferred to provide pressing controlling members made of a harder
material than the material of the adhesive member at both ends of
the adhesive roller.
[0131] FIG. 5 is a drawing showing an adhesive roller before being
pressed against an objective face of foreign matter removal, FIG. 5
(a) is a cross-sectional view of the adhesive roller, and FIG. 5
(b) is a side view of the adhesive roller.
[0132] The adhesive roller shown in FIG. 5 (a) is constituted such
that the cylindrical core part 41 is formed with the axis of
rotation as center and adhesive member 42 is installed so as to
cover around core part 41.
[0133] At both ends of the axis of rotation direction of adhesive
roller 40 comprised of core part 41 and adhesive member 42, a pair
of pressing controlling members 43, 43, a pair of air cylinders 44,
44, and a pair of piston rods 45, 45 are arranged.
[0134] The adhesive roller is of a crown shape and has diameter d
at near the end part in the width direction of the roller, pressing
controlling members 43 has diameter d.sub.c, and the roller is
designed so that diameter d.sub.c of pressing controlling members
43 is slightly smaller than diameter d of near the end part in the
width direction of the roller. Accordingly, the value obtained by
[the radius of the roller (d/2)]-[the radius of the pressing
controlling members (d.sub.c/2)] is the deformed amount by
compression of adhesive member 42 when adhesive roller 40 is
pressed against the objective face of foreign matter removal.
[0135] When air is supplied to air cylinders 44, 44 from air
supplying source not shown in the Figure, piston rods 45, 45 are
extended and moving action begins so as to press adhesive roller 40
against the objective face of foreign matter removal. When moving
action begins, adhesive member 42 having a larger diameter than the
controlling disc is brought into contact with the objective face of
foreign matter removal in the first place, then adhesive member 42
is gradually deformed by compression with the extension of piston
rods 45, 45, and then pressing controlling members 43, 43 are
brought into contact with the objective face of foreign matter
removal, thereby deformation by compression of adhesive member 42
is controlled.
[0136] FIG. 6 is a drawing showing an adhesive roller after being
pressed against an objective face of foreign matter removal, FIG. 6
(a) is a cross-sectional view of the adhesive roller, and FIG. 6
(b) is a side view of the adhesive roller.
[0137] After the deformation by compression of adhesive member 42
is controlled by bringing pressing controlling members 43, 43 into
contact with objective face F of foreign matter removal, the
foreign matters on objective face F of foreign matter removal are
removed by adhesive member 42 deformed by compression. At this
time, the radius from the center of the rotation axis of adhesive
roller 40 to the outer surface of adhesive member 42
compression-deformed by the compression-deformed amount .alpha.
(d/2-.alpha.) and the radius of the controlling disc (d.sub.c/2)
become the same. After foreign matter-removing work of objective
face F of foreign matter removal by adhesive roller 40 finishes,
piston rods 45, 45 are contracted, adhesive roller 40 separates
from objective face F of foreign matter removal, and
compression-deformed adhesive member 42 expands and restores the
original radius.
[0138] For effecting good foreign matter removalby the adhesive
roller according to the present invention, the difference in the
outer diameter of an adhesive member d and the diameter of a
pressing controlling member dc is related as shown in Table 3
below.
3TABLE 3 In the case where the objective face of foreign matter
removal In the case where the is a rotary drum for objective face
of foreign recording or a matter removal is an recording medium
image-receiving sheet or a face-fixing member d - d.sub.c (mm) heat
transfer sheet (plate) 0 foreign matter removal was foreign matter
removal not good was not good 0.5 foreign matter removal was
foreign matter removal good was good 1 foreign matter removal was
foreign matter removal very good was very good 2 foreign matter
removal was foreign matter removal very good was very good 2.5 the
sheet was partially rotation resistance of turned up or the film
was the drum slightly peeled off increased or the plate deviated
from position 3 the sheet was turned up or rotation resistance of
the film was peeled off the drum increased or the plate came
off
[0139] As can be seen from Table 1, when d-d.sub.c is 0, i.e., the
outer diameter of an adhesive member and the diameter of a pressing
controlling member are the same, the adhesive member of the
adhesive roller cannot be deformed by compression, therefore,
adhesion-removal of foreign matters is hardly done on the objective
face of foreign matter removal, which results in foreign matter
removal failure. When transfer is performed on this condition,
image defects such as clear spots and ring-like unevenness occur
due to the presence of foreign matters.
[0140] On the other hand, when the diameter of a pressing
controlling member is smaller than the outer diameter of an
adhesive member by 0.5 to 2 mm, an excellent foreign
matter-removing effect can be obtained, since the adhesive member
is deformed by compression and closely adheres to the object of
foreign matter removal. If the diameter of a pressing controlling
member is smaller than the outer diameter of an adhesive member by
2.5 to 3 mm, the compression-deformed amount (adhesion amount) of
the adhesive member to the objective face of foreign matter removal
becomes too great to cause peeling off of the image-receiving layer
in an image-receiving sheet, partial peeling off of the
image-forming layer in a heat transfer sheet, and increase in
bending of the rotation axis of the adhesive roller. Further, in
the case where the objective face of foreign matter removal is a
recording medium face-fixing member (plate) for fixing the sheet
laid on a rotary drum for recording, the surface of a rotary drum
for recording, or the opposite roller, since the pressing force of
the adhesive member is too strong and the rotation resistance of
the drum increases, normal rotational motion is hindered.
[0141] In the next place, a preferred procedure of cleaning
recording media (an image-receiving sheet and a heat transfer
sheet) fixed on a recording medium-fixing member, e.g., a recording
drum, is described with reference to FIGS. 7 and 8.
[0142] FIG. 7 is a drawing showing the relationship between a
recording medium and an adhesive roller mounted on a recording
drum, and FIG. 8 is a drawing showing the relationship between a
recording medium and an adhesive roller by developing the
circumferential plane of a recording drum.
[0143] In the first place, as shown in FIG. 7 (a) and FIG. 8 (a),
adhesive roller 40 is brought into contact with recording medium 11
fixed on recording drum 4 at almost the central part in the
circumferential direction (the relative moving direction to
adhesive roller 40), and recording drum 4 is rotated by driving as
shown in FIG. 7 (b) and FIG. 8 (b) (in the clockwise direction as
an example here). Then, as shown in FIG. 7 (c) and FIG. 8 (c),
adhesive roller 40 is separated from the surface of recording
medium 11 almost vertically after adhesive roller 40 has passed one
end in the circumferential direction of recording medium 11. By the
above operation, cleaning of the region from the central part in
the circumferential direction where adhesive roller 40 is brought
into contact with recording medium 11 first to one end in the
circumferential direction is performed.
[0144] In the next place, as shown in FIG. 7 (d) and FIG. 8 (d),
adhesive roller 40 is again brought into contact with recording
medium 11 fixed on recording drum 4 at almost the central part in
the circumferential direction, and recording drum 4 is rotated by
driving in the reverse direction of the last time as shown in FIG.
7 (e) and FIG. 8 (e) (in the counterclockwise direction). Then, as
shown in FIG. 7 (f) and FIG. 8 (f), adhesive roller 40 is separated
from the surface of recording medium 11 almost vertically after
adhesive roller 40 has passed the other end in the circumferential
direction of recording medium 11. By the above operation, cleaning
of the region from the central part in the circumferential
direction where adhesive roller 40 is brought into contact with
recording medium 11 in the second place to the other end in the
circumferential direction is performed, thus the entire surface of
the recording medium is to be cleaned.
[0145] The position where adhesive roller 40 is brought into
contact with recording medium 11 is preferably set as follows.
[0146] The starting position of an adhesive roller of coming into
contact with a recording medium on the circumferential plane of a
recording drum is shown in FIG. 9. As shown in FIG. 9, when the
length of in the circumferential direction of recording medium 11
is taken as L, the central position of recording medium 11 in the
circumferential direction is the position of 0.5L from the end of
the circumferential direction of recording medium 11. The starting
position of an adhesive roller of coming into contact with a
recording medium on the circumferential plane of a recording drum
is preferably the range of .+-.25L in the circumferential direction
from the central position in the circumferential direction, i.e.,
the range of 50% of the circumferential length with the central
position in the circumferential direction as the center. By
beginning contacting within this range, a sufficient distance from
the end of the circumferential direction of recording medium 11 can
be kept, cleaning range per one time can be widened and effective
cleaning can be performed.
[0147] The state of the first cleaning area of recording medium 11
to one end in the circumferential direction overlapping the second
cleaning area to another end in the circumferential direction is
shown in FIG. 10. As is shown in FIG. 10, the entire surface of
recording medium 11 can be cleaned leaving no space by overlapping
the cleaning areas in both directions. It is preferred to set 45%
or less of the length in circumferential direction of a recording
medium as the overlapping amount, by which cleaning can be
performed by overlapping surely even if errors are generated in the
rotary position of a recording drum or in the fixing position of a
recording medium, further, useless cleaning can be prevented by
excess overlapping.
[0148] According to the above cleaning method of recording medium
11, recording medium 11 can be prevented from turning up from the
surface of recording drum 4, recording medium 11 can be prevented
from deviating from the position, film peeling off can be prevented
from occurring, and recording medium 11 can be prevented from
coming off recording drum 4. When an image-receiving sheet is
subjected to cleaning with adhesive roller 40, the foreign matters
adhered on the image-receiving layer of the image-receiving sheet
are removed, which prevents image blank spots from occurring, and
when a heat transfer sheet on an image-receiving sheet is subjected
to cleaning, the foreign matters on the support of the heat
transfer sheet are removed, which prevents laser beams irradiated
at recording from being interrupted, thus generation of image blank
spots can be inhibited.
[0149] The cleaning method of a recording medium has been described
taking a recording unit of a rotary drum type of recording by
fixing a recording medium on recording drum 4 as an example, but
the present invention is not limited thereto, for example, the
above cleaning method of a recording medium is also applicable to a
fixing type recording unit of performing recording by fixing a
recording medium taking recording drum 4 whose circumferential
plane is developed shown in FIG. 8 as a planar fixing platform, and
to a carrying type recording unit of performing recording while
carrying a recording medium with nip rollers. That is, recording
unit may be any constitution so long as the adhesive roller can be
moved relatively to a recording medium-fixing member such as a
recording drum or a planar fixing platform.
[0150] It is preferred that the absolute value of the difference
between the surface roughness Rz of the front face of the
image-forming layer in the heat transfer sheet and the surface
roughness Rz of the back face of the image-forming layer is 3.0 or
less, and the absolute value of the difference between the surface
roughness Rz of the front face of the image-receiving layer in the
image-receiving sheet and the surface roughness Rz of the back face
of the image-receiving layer is 3.0 or less. By such constitution
of the present invention, conjointly with the above cleaning means,
image defect can be prevented, jamming in carrying can be done away
with, and dot gain stability can be improved.
[0151] The surface roughness Rz in the present invention means ten
point average surface roughness corresponding to Rz of JIS B 0601
(maximum height). The surface roughness is obtained by inputting
and computing the distance between the average value of the
altitudes of from the highest peak to the fifth peak and the
average value of the depths of from the deepest valley to the fifth
valley with the average surface of the part obtained by removing by
the reference area from the curved surface of roughness as the
reference level. A feeler type three dimensional roughness meter
(Surfcom 570A-3DF, manufactured by Tokyo Seimitsu Co., Ltd.) is
used in measurement. The measurement is performed in machine
direction, the cutoff value is 0.08 mm, the measured area is 0.6
mm.times.0.4 mm, the feed pitch is 0.005 mm, and the speed of
measurement is 0.12 mm/sec.
[0152] For further improving the above effects, it is preferred
that the absolute value of the difference between the surface
roughness Rz of the front surface of the image-forming layer in the
heat transfer sheet and the surface roughness Rz of the back
surface of the image-forming layer is 1.0 or less.
[0153] Further, as another embodiment, it is preferred that the
surface roughness Rz of the front surface and the back surface of
the heat transfer sheet is from 2 to 30 .mu.m. By such constitution
conjointly with the above cleaning means, image defect can be
prevented, jamming in carrying can be done away with, and dot gain
stability can be improved.
[0154] It is also preferred that the glossiness of the
image-forming layer in the heat transfer sheet is from 80 to
99.
[0155] The glossiness largely depends upon the surface smoothness
of the image-forming layer and can affect the uniformity of the
layer thickness of the image-forming layer. When the glossiness is
higher, the image-forming layer becomes more uniform and more
preferred for highly accurate use, but when the smoothness is high,
the resistance at conveying becomes larger, thus they are in
relationship of trade off. When the glossiness is from 80 to 99,
both are compatible and well-balanced.
[0156] The scheme of multicolor image-forming by membrane heat
transfer using a laser is outlined with referring to FIG. 1.
[0157] Laminate 30 for image formation comprising image-receiving
sheet 20 laminated on the surface of image-forming layer 16
containing pigment black (K), cyan (C), magenta (M) or yellow (Y)
in heat transfer sheet 10 is prepared. Heat transfer sheet 10
comprises support 12, having provided thereon light-to-heat
converting layer 14 and further thereon image-forming layer 16, and
image-receiving sheet 20 comprises support 22 and having provided
thereon image-receiving layer 24, and image-receiving layer 24 is
laminated on the surface of image-forming layer 16 in heat transfer
sheet 10 in contact therewith (FIG. 1 (a)). When laser beams are
irradiated imagewise in time series from the side of support 12 in
heat transfer sheet 10 of laminate 30, the irradiated area with
laser beams of light-to-heat converting layer 14 in heat transfer
sheet 10 generates heat, thereby the adhesion with image-forming
layer 16 is reduced (FIG. 1 (b)). Thereafter, when image-receiving
sheet 20 and heat transfer sheet 10 are peeled off, the area
irradiated with laser beams 16' of image-forming layer 16 is
transferred to image-receiving layer 24 in image-receiving sheet 20
(FIG. 1 (c)).
[0158] In multicolor image formation, the laser beam for use in
irradiation preferably comprises multi-beams, particularly
preferably comprises multi-beams of two-dimensional array.
Multi-beams of two-dimensional array means that a plurality of
laser beams are used when recording by irradiation with laser beam
is performed, and the spot array of these laser beams comprises
two-dimensional array comprised of a plurality of rows along the
main scanning direction and a plurality of rows along the
by-scanning direction.
[0159] The time required in laser recording can be shortened by
using multi-beams of two-dimensional array.
[0160] Any laser beam can be used in recording with no limitation
so long as it is comprised of multi-beams, such as gas laser beams,
e.g., an argon ion laser beam, a helium neon laser beam, and a
helium cadmium laser beam, solid state laser beams, e.g., a YAG
laser beam, and direct laser beams, e.g., a semiconductor laser
beam, a dye laser beam and an excimer laser beam, can be used.
Alternatively, laser beams obtained by converting these laser beams
to half the wavelength through secondary harmonic generation
elements can also be used. In multicolor image formation,
semiconductor laser beams are preferably used taking the output
power and easiness of modulation into consideration. In multicolor
image formation, it is preferred that laser beam emission is
performed on conditions that the beam diameter of laser beam on the
light-to-heat converting layer is from 5 to 50 .mu.m (in particular
from 6 to 30 .mu.m), and scanning speed is preferably 1 m/second or
more (particularly preferably 3 m/second or more).
[0161] In addition, it is preferred in multicolor image formation
that the layer thickness of the image-forming layer in the black
heat transfer sheet is larger than the layer thickness of the
image-forming layer in each of yellow, magenta and cyan heat
transfer sheets, and is preferably from 0.5 to 0.7 .mu.m. By
adopting this constitution, the reduction of density due to
transfer unevenness by the irradiation of the black heat transfer
sheet with laser beams can be suppressed.
[0162] When the layer thickness of the image-forming layer in the
black heat transfer sheet is less than 0.5 .mu.m, image density is
reduced due to transfer unevenness by high energy recording, thus
it is difficult in some cases to obtain required image density as
the proof of printing. Since this tendency becomes more conspicuous
under high humidity conditions, density variation due to
surrounding conditions sometimes becomes too great. On the other
hand, when the layer thickness is more than 0.7 .mu.m, transfer
sensitivity is reduced at recording time by laser and impression of
small dots and fine lines is sometimes deteriorated. This tendency
becomes more conspicuous under low humidity conditions. Resolution
often lowers when the layer thickness of the image-forming layer is
not within the above range. The layer thickness of the
image-forming layer in the black heat transfer sheet is more
preferably from 0.55 to 0.65 .mu.m and particularly preferably 0.60
.mu.m.
[0163] Further, it is preferred that the layer thickness of the
image-forming layer in the above black heat transfer sheet is from
0.5 to 0.7 .mu.m, and the layer thickness of the image-forming
layer in each of the above yellow, magenta and cyan heat transfer
sheets is from 0.2 to less than 0.5 .mu.m.
[0164] When the layer thickness of each image-forming layer in
yellow, magenta and cyan heat transfer sheets is less than 0.2
.mu.m, image density is liable to lower due to transfer unevenness
when recording is performed by laser irradiation. On the other
hand, when the layer thickness is 0.5 .mu.m or more, the reduction
of transfer sensitivity and the deterioration of resolution are
sometimes caused. The layer thickness of each image-forming layer
in yellow, magenta and cyan heat transfer sheets is more preferably
from 0.3 to 0.45 .mu.m.
[0165] It is preferred for the image-forming layer in the black
heat transfer sheet to contain carbon black, and the carbon black
preferably comprises at least two carbon blacks having different
tinting strength from the viewpoint of capable of controlling
reflection density with maintaining P/B (pigment/binder) ratio in a
specific range.
[0166] The tinting strength of carbon black can be represented
variously, e.g., PVC blackness disclosed in JP-A-10-140033, can be
exemplified. PVC blackness is the evaluation of blackness, i.e.,
carbon black is added to PVC resin, dispersed by a twin roll mill
and made to a sheet, and the blackness of a sample is evaluated by
visual judgement, with taking the blackness of Carbon Black #40 and
#45 (manufactured by Mitsubishi Chemicals Co., Ltd.) as 1 point and
10 points respectively as the standard values. Two or more carbon
blacks having different PVC blacknesses can be used arbitrarily
according to purposes.
[0167] The specific producing method of a sample is described
below.
[0168] Producing Method of Sample
[0169] In a banbury mixer having a capacity of 250 ml, 40 mass %
(i.e., by weight %) of sample carbon black is compounded to LDPE
(low density polyethylene) resin and kneaded at 115.degree. C. for
4 minutes.
[0170] Compounding Condition
4 LDPE resin 101.89 g Calcium stearate 1.39 g Irganox .RTM. 1010
0.87 g Sample carbon black 69.43 g
[0171] In the next place, dilution is performed in a twin roll mill
at 120.degree. C. so as to reach the concentration of carbon black
of 1 mass %.
[0172] Preparation Condition of Diluted Compound
5 LDPE resin 58.3 g Calcium stearate 0.2 g Resin compounded with 40
mass % of carbon black 1.5 g
[0173] The above-prepared product is made to a sheet having a slit
width of 0.3 mm, the sheet is cut to chips, and a film having a
thickness of 65.+-.3 .mu.m is formed on a hot plate at 240.degree.
C.
[0174] A multicolor image may be formed, as described above, by the
method of using the heat transfer sheet, and repeatedly superposing
many image layers (an image-forming layer on which an image is
formed) on the same image-receiving sheet, alternatively a
multicolor image may be formed by the method of forming images on a
plurality of image-receiving sheets once, and then transferring
these images to an actual paper (i.e., a printing paper).
[0175] With the latter case, for example, heat transfer sheets
having image-forming layers each containing a coloring material
mutually different in hue are prepared, and independently four
kinds (cyan, magenta, yellow, black) of laminates for image-forming
each comprising the above heat transfer sheet combined with an
image-receiving sheet are produced. Laser irradiation according to
digital signal on the basis of the image is performed to each
laminate through a color separation filter, subsequently the heat
transfer sheet and the image-receiving sheet are peeled off, to
thereby form independently a color-separated image of each color on
each image-receiving sheet. Thereafter, the thus-formed each
color-separated image is laminated in sequence on an actual
support, such as (actual) printing paper prepared separately, or on
a support approximates thereto, thus a multicolor image can be
formed.
[0176] Heat transfer recording which utilizes laser beam
irradiation is not particularly restricted with respect to pigments
and dyes at the time of transferring, and the change of state of an
image-forming layer, including a solid state, a softened state, a
liquid state and a gas state, preferably a solid state and a
softened state, so long as the heat transfer recording is capable
of converting laser beams to heat and transferring an image-forming
layer containing a pigment on an image-receiving sheet using the
above converted heat energy and forming an image on the
image-receiving sheet. Conventionally well-known fusion transfer,
ablation transfer and sublimation transfer also belong to the heat
transfer recording utilizing laser beam irradiation.
[0177] The above-described membrane transfer, fusion transfer and
ablation transfer are preferred in point of capable of forming an
image of a hue analogous to a printed matter.
[0178] Further, a heat laminator is generally used in the process
for transferring an image-receiving sheet printed with an image in
printing unit to a printing paper (referred to as "actual paper") .
An image-receiving sheet and an actual paper are superposed and
heat and pressure are applied, thereby the image-receiving sheet
and the actual paper are adhered, and then the image-receiving
sheet is peeled off the actual paper, as a result only the
image-receiving sheet having an image is left on the actual
paper.
[0179] By connection the above unit with a plate-making system, a
system capable of exhibiting the function as color proof is
constructed. As the system, it is necessary that a printed matter
having an image quality approximating as far as possible to the
printed matter outputted from certain plate-making data must be
outputted from the printing unit. Therefore, a software for
approximating dots and colors to a printed matter is necessary. The
specific example of connection is described below.
[0180] When the proof of a printed matter is obtained from a
plate-making system (e.g., Celebra.TM., manufactured by Fuji Photo
Film Co., Ltd.), the system connection is as follows. CTP (computer
to plate) system is connected with the plate-making system. The
final printed matter can be obtained by mounting the printing plate
outputted from this system on a printing machine. As a color proof,
the above recording unit is connected with the plate-making system,
and as proof drive software for approximating dots and colors to
the printed matter, PD system (registered trademark) is connected
with the plate-making system.
[0181] Contone data (continuous tone data) converted to raster data
by the plate-making system are converted to binary data for dots
and outputted to CTP system and finally subjected to printing. On
the other hand, the same contone data are also outputted to PD
system. PD system converts the received data according to four
dimensional (black, cyan, magenta and yellow) table so that the
colors coincide with the printed matter, and finally converts to
binary data for dots so that the dots coincide with the dots of the
printed matter and the data is outputted to the recording unit.
[0182] The four dimensional table is experimentally prepared in
advance and saved in the system. The experiment for the preparation
of the four dimensional table is as follows. The printed image of
important color data via CTP system and the outputted image of
important color data from the recording unit via PD system are
prepared, the measured color values of these images are compared
and the table is formed so that the difference becomes minimum.
[0183] A heat transfer sheet and an image-receiving sheet which are
preferably used in the recording unit of the above system are
described below.
[0184] Heat Transfer Sheet
[0185] A heat transfer sheet comprises a support having thereon at
least a light-to-heat converting layer and an image-receiving
layer, and, if necessary, other layers.
[0186] Support
[0187] The materials of the support of the heat transfer sheet are
not particularly restricted, and various supports can be used
according to purposes. The support preferably has stiffness, good
dimensional stability, and heat resistance capable of resisting the
heat at image formation. The preferred examples of the support
include synthetic resins, e.g., polyethylene terephthalate,
polyethylene-2,6-naphthalate, polycarbonate, polymethyl
methacrylate, polyethylene, polypropylene, polyvinyl chloride,
polyvinylidene chloride, polystyrene, a styrene-acrylonitrile
copolymer, polyamide (aromatic and aliphatic), polyimide,
polyamideimide, and polysulfone. Biaxially stretched polyethylene
terephthalate is preferred above all from the viewpoint of
mechanical strength and dimensional stability against heat. When
resins are used in the preparation of color proofs utilizing laser
recording, it is preferred to form the support of a heat transfer
sheet from transparent synthetic resins which transmit laser beams.
The thickness of the support is preferably from 25 to 130 .mu.m,
particularly preferably from 50 to 120 .mu.m. The central line
average surface roughness Ra of the support of the side on which an
image-forming layer is provided is preferably less than 0.1 .mu.m
(the value obtained by measurement using Surfcom, manufactured by
Tokyo Seiki Co., Ltd., according to JIS B0601). The Young's modulus
of the support in the machine direction is preferably from 200 to
1,200 kg/mm.sup.2 (=about 2 to 12 GPa), and the Young's modulus of
the support in the transverse direction is preferably from 250 to
1,600 kg/mm2 (=about 2.5 to 16 GPa). The F-5 value of the support
in the machine direction is preferably from 5 to 50 kg/mm.sup.2
(=about 49 to 490 MPa), and the F-5 value of the support in the
transverse direction is preferably from 3 to 30 kg/mm.sup.2 (=about
29.4 to 294 MPa), and the F-5 value of the support in the machine
direction is generally higher than the F-5 value of the support in
the transverse direction, but when it is necessary to make the
strength particularly in the transverse direction high, this rule
does not apply to the case. Further, the heat shrinkage rate at
100.degree. C. for 30 minutes of the support in the machine
direction and the transverse direction is preferably 3% or less,
more preferably 1.5% or less, the heat shrinkage rate at 80.degree.
C. for 30 minutes is preferably 1% or less, more preferably 0.5% or
less. The breaking strength is from 5 to 100 kg/mm.sup.2 (=about 49
to 980 MPa) in both directions, and the modulus of elasticity is
preferably from 100 to 2,000 kg/mm.sup.2 (=about 0.98 to 19.6
GPa).
[0188] The support of the heat transfer sheet may be subjected to
surface activation treatment and/or one or two or more undercoat
layers may be provided on the support for the purpose of improving
the adhesion with the light-to-heat converting layer which is
provided on the support. As the examples of the surface activation
treatments, glow discharge treatment and corona discharge treatment
can be exemplified. As the materials of the undercoat layer,
materials having high adhering property to both surfaces of the
support and the light-to-heat converting layer, low heat
conductivity, and excellent heat resisting property are preferably
used. As the materials of such an undercoat layer, styrene, a
styrene-butadiene copolymer and gelatin can be exemplified. The
thickness of the undercoat layer is generally from 0.01 to 2 .mu.m
as a whole. If necessary, various functional layers such as a
reflection-preventing layer and an antistatic layer may be provided
on the surface of the heat transfer sheet of the side opposite to
the side on which a light-to-heat converting layer is provided, or
the support may be subjected to various surface treatments.
[0189] Backing Layer
[0190] It is preferred to provide a backing layer on the surface of
the heat transfer sheet of the side opposite to the side on which a
light-to-heat converting layer is provided. The backing layer
preferably comprises the first backing layer contiguous to the
support and the second backing layer provided on the side of the
support opposite to the side on which the first backing layer is
provided. In the present invention, the mass A of the antistatic
agent contained in the first backing layer to the mass B of the
antistatic agent contained in the second backing layer, B/A, is
preferably less than 0.3. When B/A is 0.3 or higher, a sliding
property and powder dropout resistance of the backing layer are
liable to be deteriorated.
[0191] The layer thickness C of the first backing layer is
preferably from 0.01 to 1 .mu.m, more preferably from 0.01 to 0.2
.mu.m. The layer thickness D of the second backing layer is
preferably from 0.01 to 1 .mu.m, more preferably from 0.01 to 0.2
.mu.m. The ratio of the layer thickness of the first backing layer
to that of the second backing layer, C/D, is preferably from 1/2 to
5/1.
[0192] As the antistatic agents for use in the first and second
backing layers, a nonionic surfactant, e.g., polyoxyethylene
alkylamine, and glycerol fatty acidester; acationic surfactant,
e.g., a quaternary ammonium salt; an anionic surfactant, e.g.,
alkylphosphate; an ampholytic surfactant and electrically
conductive resin can be used.
[0193] Electrically conductive fine particles can also be used as
antistatic agents. The examples of such electrically conductive
fine particles include oxides, e.g., ZnO, TiO.sub.2, SnO.sub.2,
Al.sub.2O.sub.3, In.sub.2O.sub.3, MgO, BaO, CoO, CuO, Cu.sub.2O,
CaO, SrO, BaO.sub.2, PbO, PbO.sub.2, MnO.sub.3, MoO.sub.3,
SiO.sub.2, ZrO.sub.2, Ag.sub.2O, Y.sub.2O.sub.3, Bi.sub.2O.sub.3,
Ti.sub.2O.sub.3, Sb.sub.2O.sub.3, Sb.sub.2O.sub.5,
K.sub.2Ti.sub.6O.sub.13, NaCaP.sub.2O.sub.18 and MgB.sub.2O.sub.5;
sulfide, e.g., CuS and ZnS; carbide, e.g., SiC, TiC, ZrC, VC, NbC,
MoC and WC; nitride, e.g., Si.sub.3N.sub.4, TiN, ZrN, VN, NbN and
Cr.sub.2N; boride, e.g., TiB.sub.2, ZrB.sub.2, NbB.sub.2,
TaB.sub.2, CrB, MoB, WB and LaB.sub.5; silicide, e.g., TiSi.sub.2,
ZrSi.sub.2, NbSi.sub.2, TaSi.sub.2, CrSi.sub.2, MoSi.sub.2 and
WSi.sub.2; metal salts, e.g., BaCO.sub.3, CaCO.sub.3, SrCO.sub.3,
BaSO.sub.4and CaSO.sub.4; and composite, e.g., SiN.sub.4-SiC and
9Al.sub.2O.sub.3-2B.sub.2O.sub.3. These electrically conductive
fine particles may be used alone or in combination of two or more.
Of these fine particles, SnO.sub.2, ZnO, Al.sub.2O.sub.3,
TiO.sub.2, In.sub.2O.sub.3, MgO, BaO and MoO.sub.3 are preferred,
SnO.sub.2, ZnO, In.sub.2O.sub.3 and TiO.sub.2 are more preferred,
and SnO.sub.2 is particularly preferred.
[0194] When the heat transfer sheet in the present invention is
used in a laser-heat transfer system, the antistatic agent used in
the backing layer is preferably substantially transparent so that
laser beams can be transmitted.
[0195] When electrically conductive metallic oxides are used as the
antistatic agent, their particle size is preferably smaller to make
light scattering as small as possible, but the particle size should
be determined using the ratio of the refractive indices of the
particles and the binder as parameter, which can be obtained
according to the theory of Mie. The average particle size of the
electrically conductive metallic oxides is generally from 0.001 to
0.5 .mu.m, preferably from 0.003 to 0.2 .mu.m. The average particle
size used herein is the value of the particle size of not only the
primary particles of the electrically conductive metallic oxides
but the particle size of the particles having the hkl structure is
included.
[0196] Besides an antistatic agent, the first and second backing
layers may contain various additives, such as a surfactant, a
sliding agent and a matting agent, and a binder. The amount of the
antistatic agent contained in the first backing layer is preferably
from 10 to 1,000 mass parts (i.e., weight parts) per 100 mass parts
of the binder, more preferably from 200 to 800 mass parts. The
amount of the antistatic agent contained in the second backing
layer is preferably from 0 to 300 mass parts per 100 mass parts of
the binder, more preferably from 0 to 100 mass parts.
[0197] As the binders for use for forming the first and second
backing layers, homopolymers and copolymers of acrylic acid-based
monomers, e.g., acrylic acid, methacrylic acid, acrylic ester and
methacrylic ester, cellulose-based polymers, e.g., nitrocellulose,
methyl cellulose, ethyl cellulose and cellulose acetate,
vinyl-based polymers and copolymers of vinyl compounds, e.g.,
polyethylene, polypropylene, polystyrene, vinyl chloride-based
copolymer, vinyl chloride-vinyl acetate copolymer, polyvinyl
pyrrolidone, polyvinyl butyral and polyvinyl alcohol, condensed
polymers, e.g., polyester, polyurethane and polyamide, rubber-based
thermoplastic polymers, e.g., butadiene-styrenecopolymer, polymers
obtained by polymerization or crosslinking of photopolymerizable or
heat polymerizable compounds, e.g., epoxy compounds, and melamine
compounds can be exemplified.
[0198] Light-to-Heat Converting Layer
[0199] A light-to-heat converting layer may contain a light-to-heat
converting material, a binder, a matting agent and other additives,
if necessary.
[0200] A light-to-heat converting material is a material having a
function of converting irradiated light energy to heat energy. A
light-to-heat converting material is in general a dye (inclusive of
a pigment, hereinafter the same) capable of absorbing a laser beam.
When image-recording is performed by infrared laser, it is
preferred to use an infrared absorbing dye as the light-to-heat
converting material. As the examples of the dyes, black pigments,
e.g., carbon black, pigments of macrocyclic compounds having
absorption in the visible region to the near infrared region, e.g.,
phthalocyanine and naphthalocyanine, organic dyes which are used as
the laser-absorbing material in high density laser recording such
as photo-disc, e.g., a cyanine dye such as an indolenine dye, an
anthraquinone dye, an azulene dye and a phthalocyanine dye, and
organic metallic compound dyes, e.g., dithiol nickel complex, can
be exemplified. Of the above compounds, cyanine dyes are
particularly preferably used, since they show a high absorption
coefficient to the lights in the infrared region, and the thickness
of a light-to-heat converting layer can be thinned when used as the
light-to-heat converting material, as a result, the recording
sensitivity of a heat transfer sheet can be further improved.
[0201] As the light-to-heat converting material, particulate
metallic materials such as blackened silver and inorganic materials
can also be used besides dyes.
[0202] As the binder to be contained in the light-to-heat
converting layer, resins having at least the strength capable of
forming a layer on a support and preferably having high heat
conductivity are preferred. Heat resisting resins which are not
decomposed by heat generated from the light-to-heat converting
material at image recording are preferably used as the binder
resin, since the surface smoothness of the light-to-heat converting
layer can be maintained after irradiation even when light
irradiation is performed with high energy. Specifically, resins
having heat decomposition temperature (the temperature at which the
mass decreases by 5% in air current at temperature increasing
velocity of 10.degree. C./min by TGA method (thermal mass
spectrometry)) of 400.degree. C. or more are preferably used, more
preferably 500.degree. C. or more. Binders preferably have glass
transition temperature of from 200 to 400.degree. C., more
preferably from 250 to 350.degree. C. When the glass transition
temperature is lower than 200.degree. C., there is a case where fog
is generated on the image to be formed, while when it is higher
than 400.degree. C., the solubility of the resin is decreased,
followed by the reduction of the productivity in some cases.
[0203] Further, the heat resistance (e.g., heat deformation
temperature and heat decomposition temperature) of the binder in
the light-to-heat converting layer is preferably higher than the
heat resistance of the materials used in other layers provided on
the light-to-heat converting layer.
[0204] Specifically, acrylate resins, e.g., polymethyl
methacrylate, vinyl resins, e.g., polycarbonate, polystyrene, vinyl
chloride/vinyl acetate copolymer and polyvinyl alcohol, polyvinyl
butyral, polyester, polyvinyl chloride, polyamide, polyimide,
polyether imide, polysulfone, polyether sulfone, aramid,
polyurethane, epoxy resin and urea/melamine resin are exemplified
as the binder resins for use in the light-to-heat converting layer.
Of these resins, polyimide resin is preferred.
[0205] Polyimide resins represented by the following formulae (I)
to (VII) are soluble in an organic solvent and the productivity of
the heat transfer sheet is improved when they are used. Further,
these polymide resins are preferred in view of capable of improving
the stability of viscosity, long term storage stability and
moisture resistance of the coating solution for the light-to-heat
converting layer. 1
[0206] In formulae (I) and (II), Ar.sup.1 represents an aromatic
group represented by the following formula (1), (2) or (3), and n
represents an integer of from 10 to 100. 2
[0207] In formulae (III) and (IV), Ar.sup.2 represents an aromatic
group represented by the following formula (4), (5), (6) or (7),
and n represents an integer of from 10 to 100. 3
[0208] In formulae (V), (VI) and (VII), n and m each represents an
integer of from 10 to 100. In formula (VI), the ratio of n/m is
from 6/4 to 9/1.
[0209] As the criterion whether a resin is soluble in an organic
solvent or not, when 10 mass parts (i.e., weight parts) or more of
the resin is dissolved in 100 mass parts of N-methylpyrrolidone at
25.degree. C., the resin can be preferably used in the
light-to-heat converting layer, more preferably 100 mass parts is
dissolved in 100 mass parts of N-methylpyrrolidone.
[0210] As the matting agent contained in the light-to-heat
converting layer, inorganic and organic fine particles can be
exemplified. The examples of the inorganic fine particles include
metal salts, e.g., silica, titanium oxide, aluminum oxide, zinc
oxide, magnesium oxide, barium sulfate, magnesium sulfate, aluminum
hydroxide, magnesium hydroxide and boron nitride, kaolin, clay,
talc, zincflower, leadwhite, zeeklite, quartz, diatomaceous earth,
pearlite, bentonite, mica and synthetic mica. The examples of the
organic fine particles include resin particles, e.g., fluorine
resin particles, guanamine resin particles, acrylic resin
particles, styrene/acryl copolymer resin particles, silicone resin
particles, melamine resin particles and epoxy resin particles.
[0211] The matting agents generally have a particle size of from
0.3 to 30 .mu.m, preferably from0.5 to20 .mu.m, and the addition
amount is preferably from 0.1 to 100 mg/m.sup.2.
[0212] The light-to-heat converting layer may further contain a
surfactant, a thickener, and an antistatic agent, if necessary.
[0213] The light-to-heat converting layer can be provided by
dissolving a light-to-heat converting material and a binder,
adding, if necessary, a matting agent and other components thereto
to thereby prepare a coating solution, and coating the coating
solution on a support and drying. As the organic solvents for
dissolving polyimide resins, e.g., n-hexane, cyclohexane, diglyme,
xylene, toluene, ethyl acetate, tetrahydrofuran, methyl ethyl
ketone, acetone, cyclohexanone, 1,4-dioxane, 1,3-dioxane, dimethyl
acetate, N-methyl-2-pyrrolidone, dimethyl sulfoxide,
dimethylformamide, dimethylacetamide, .gamma.-butyrolactone,
ethanol and methanol can be exemplified. Coating and drying can be
performed according to ordinary coating and drying methods. Drying
is generally performed at 300.degree. C. or less, preferably
200.degree. C. or less. When polyethylene terephthalate is used as
the support, the drying temperature is preferably from 80 to
150.degree. C.
[0214] If the amount of the binder in the light-to-heat converting
layer is not sufficient, the cohesive strength of the light-to-heat
converting layer lowers and the light-to-heat converting layer is
liable to be transferred together when an image formed is
transferred to an image-receiving sheet, which causes color
mixture. While when the amount of the polyimide resin is too much,
the layer thickness of the light-to-heat converting layer becomes
too large to achieve a definite absorptivity, thereby sensitivity
is liable to be decreased. The mass ratio (i.e., weight ratio) of
the solid content of the light-to-heat converting material to the
binder in the light-to-heat converting layer is preferably 1/20 to
2/1, particularly preferably 1/10 to 2/1.
[0215] As described above, when the layer thickness of the
light-to-heat converting layer is thinned, the sensitivity of the
heat transfer sheet is increased and so preferred. The layer
thickness of the light-to-heat converting layer is preferably from
0.03 to 1.0 .mu.m, more preferably from 0.05 to 0.5 .mu.m. Further,
when the light-to-heat converting layer has the optical density of
from 0.80 to 1.26 to the beam having wavelength of 808 nm, the
transfer sensitivity of the image-forming layer is improved, more
preferably the optical density is from 0.92 to 1.15 to the beam
having wavelength of 808 nm. When the optical density at wavelength
of 808 nm is less than 0.80, irradiated light cannot be
sufficiently converted to heat and sometimes transfer sensitivity
is reduced. Contrary to this, when it exceeds 1.26, the function of
the light-to-heat converting layer at recording is affected and
sometimes fog is generated.
[0216] Image-forming Layer
[0217] An image-forming layer contains at least a pigment which is
transferred to an image-receiving sheet and forms an image, in
addition, a binder for forming the layer and, if necessary, other
components.
[0218] Pigments are broadly classified to organic pigments and
inorganic pigments, and they have respectively characteristics such
that the former are particularly excellent in the transparency of
the film, and the latter are excellent in shielding property, thus
they may be used arbitrarily according to purposes. When the heat
transfer sheet is used for the proofs of printing colors, organic
pigments which are coincident with yellow, magenta, cyan and black
generally used in printing ink or near to them in tone are
preferably used. Further, metallic powder and fluorescent pigments
are also used in some cases. The examples of the pigments which are
preferably used include azo pigments, phthalocyanine pigments,
anthraquinone pigments, dioxazine pigments, quinacridone pigments,
isoindolinone pigments and nitro pigments. The pigments for use in
an image-forming layer are listed below by hues, but the present
invention is not limited thereto.
[0219] 1) Yellow Pigment
[0220] Pigment Yellow 12 (C.I. No. 21090)
[0221] Example:
[0222] Permanent Yellow DHG (manufactured by Clariant Japan, K.K.),
Lionol Yellow 1212B (manufactured by Toyo Ink Mfg. Co., Ltd.),
Irgalite Yellow LCT (manufactured by Ciba Specialty Chemicals),
Symuler Fast Yellow GTF 219 (manufactured by Dai-Nippon Ink &
Chemicals Inc.)
[0223] Pigment Yellow 13 (C.I. No. 21100)
[0224] Example:
[0225] Permanent Yellow GR (manufactured by Clariant Japan, K.K.),
Lionol Yellow 1313 (manufactured by Toyo Ink Mfg. Co., Ltd.)
[0226] Pigment Yellow 14 (C.I. No. 21095)
[0227] Example:
[0228] Permanent Yellow G (manufactured by Clariant Japan, K.K.),
Lionol Yellow 1401-G (manufactured by Toyo Ink Mfg. Co., Ltd.),
Seika Fast Yellow 2270 (manufactured by Dainichi Seika K.K.),
Symuler Fast Yellow 4400 (manufactured by Dai-Nippon Ink &
Chemicals Inc.)
[0229] Pigment Yellow 17 (C.I. No. 21105)
[0230] Example:
[0231] Permanent Yellow GG02 (manufactured by Clariant Japan,
K.K.), Symuler Fast Yellow 8GF (manufactured by Dai-Nippon Ink
& Chemicals Inc.)
[0232] Pigment Yellow 155
[0233] Example:
[0234] Graphtol Yellow 3GP (manufactured by Clariant Japan,
K.K.)
[0235] Pigment Yellow 180 (C.I. No. 21290)
[0236] Example:
[0237] Novoperm Yellow P-HG (manufactured by Clariant Japan,
K.K.),
[0238] PV Fast Yellow HG (manufactured by Clariant Japan, K.K.)
[0239] Pigment Yellow 139 (C.I. No. 56298)
[0240] Example:
[0241] Novoperm Yellow M2R 70 (manufactured by Clariant Japan,
K.K.)
[0242] 2) Magenta Pigment
[0243] Pigment Red 57:1 (C.I. No. 15850:1)
[0244] Example:
[0245] Graphtol Rubine L6B (manufactured by Clariant Japan, K.K.),
Lionol Red 6B-4290G (manufactured by Toyo Ink Mfg. Co., Ltd.),
Irgalite Rubine 4BL (manufactured by Ciba Specialty Chemicals),
Symuler Brilliant Carmine 6B-229 (manufactured by Dai-Nippon Ink
& Chemicals Inc.)
[0246] Pigment Red 122 (C.I. No. 73915)
[0247] Example:
[0248] Hosterperm Pink E (manufactured by Clariant Japan, K.K.),
Lionogen Magenta 5790 (manufactured by Toyo Ink Mfg. Co., Ltd.)
,Fastogen Super Magenta RH (manufactured by Dai-Nippon Ink &
Chemicals Inc.)
[0249] Pigment Red 53:1 (C.I. No. 15585:1)
[0250] Example:
[0251] Permanent Lake Red LCY (manufactured by Clariant Japan,
K.K.), Symuler Lake Red C conc (manufactured by Dai-Nippon Ink
& Chemicals Inc.)
[0252] Pigment Red 48:1 (C.I. No. 15865:1)
[0253] Example:
[0254] Lionol Red 2B-3300 (manufactured by Toyo Ink Mfg. Co.,
Ltd.), Symuler Red NRY (manufactured by Dai-Nippon Ink &
Chemicals Inc.)
[0255] Pigment Red 48:2 (C.I. No. 15865:2)
[0256] Example:
[0257] Permanent Red W2T (manufactured by Clariant Japan, K.K.),
Lionol Red LX235 (manufactured by Toyo Ink Mfg. Co., Ltd.), Symuler
Red 3012 (manufactured by Dai-Nippon Ink & Chemicals Inc.)
[0258] Pigment Red 48:3 (C.I. No. 15865:3)
[0259] Example:
[0260] Permanent Red 3RL (manufactured by Clariant Japan, K.K.),
Symuler Red 2BS (manufactured by Dai-Nippon Ink & Chemicals
Inc.)
[0261] Pigment Red 177 (C.I. No. 65300)
[0262] Example:
[0263] Cromophtal Red A2B (manufactured by Ciba Specialty
Chemicals)
[0264] 3) Cyan Pigment
[0265] Pigment Blue 15 (C.I. No. 74160)
[0266] Example:
[0267] Lionol Blue 7027 (manufactured by Toyo Ink Mfg. Co., Ltd.),
Fastogen Blue BB (manufactured by Dai-Nippon Ink & Chemicals
Inc.)
[0268] Pigment Blue 15:1 (C.I. No. 74160)
[0269] Example:
[0270] Hosterperm Blue A2R (manufactured by Clariant Japan, K.K.),
Fastogen Blue 5050 (manufactured by Dai-Nippon Ink & Chemicals
Inc.)
[0271] Pigment Blue 15:2 (C.I. No. 74160)
[0272] Example:
[0273] Hosterperm Blue AFL (manufactured by Clariant Japan, K.K.),
Irgalite Blue BSP (manufactured by Ciba Specialty Chemicals),
Fastogen Blue GP (manufactured by Dai-Nippon Ink & Chemicals
Inc.)
[0274] Pigment Blue 15:3 (C.I. No. 74160)
[0275] Example:
[0276] Hosterperm Blue B2G (manufactured by Clariant Japan, K.K.),
Lionol Blue FG7330 (manufactured by Toyo Ink Mfg. Co., Ltd.),
Cromophtal Blue 4GNP (manufactured by Ciba Specialty Chemicals),
Fastogen Blue FGF (manufactured by Dai-Nippon Ink & Chemicals
Inc.)
[0277] Pigment Blue 15:4 (C.I. No. 74160)
[0278] Example:
[0279] Hosterperm Blue BFL (manufactured by Clariant Japan, K.K.),
Cyanine Blue 700-1OFG (manufactured by Toyo Ink Mfg. Co., Ltd.),
Irgalite Blue GLNF (manufactured by Ciba Specialty Chemicals),
Fastogen Blue FGS (manufactured by Dai-Nippon Ink & Chemicals
Inc.)
[0280] Pigment Blue 15:6 (C.I. No. 74160)
[0281] Example:
[0282] Lionol Blue ES (manufactured by Toyo Ink Mfg. Co., Ltd.)
[0283] Pigment Blue 60 (C.I. No. 69800)
[0284] Example:
[0285] Hosterperm Blue RL01 (manufactured by Clariant Japan, K.K.),
Lionogen Blue 6501 (manufactured by Toyo Ink Mfg. Co., Ltd.)
[0286] 4) Black Pigment
[0287] Pigment Black 7 (carbon black C.I. No. 77266)
[0288] Example:
[0289] Mitsubishi Carbon Black MA100 (manufactured by Mitsubishi
Chemicals Co., Ltd.), Mitsubishi Carbon Black #5 (manufactured by
Mitsubishi Chemicals Co., Ltd.), Black Pearls 430 (manufactured by
Cabot Co.)
[0290] As the pigments which can be used in the present invention,
commercially available products can be arbitrarily selected by
referring to Ganryo Binran (Pigment Handbook), compiled by Nippon
Ganryo Gijutsu Kyokai, published by Seibundo-Shinko-Sha (1989), and
COLOUR INDEX, THE SOCIETY OF DYES & COLOURIST, Third Ed.
(1987).
[0291] The average particle size of the above pigments is
preferably from 0.03 to 1 .mu.m, more preferably from 0.05 to 0.5
.mu.m.
[0292] When the particle size is less than 0.03 .mu.m, the costs
for dispersion are increased and the dispersion solution cause
gelation, while when it is more than 1 .mu.m, since coarse
particles are contained in pigments, good adhesion of the
image-forming layer and the image-receiving layer can not be
obtained, further, the transparency of the image-forming layer is
inhibited.
[0293] As the binders for the image-forming layer, amorphous
organic high polymers having a softening point of from 40 to
150.degree. C. are preferably used. As the amorphous organic high
polymers, homopolymers and copolymers of styrene, derivatives
thereof, and substitution products thereof, e.g., butyral resin,
polyamide resin, polyethyleneimine resin, sulfonamide resin,
polyester polyol resin, petroleum resin, styrene, vinyltoluene,
.alpha.-methylstyrene, 2-methylstyrene, chlorostyrene, vinylbenzoic
acid, sodium vinylbenzenesulfonate, and aminostyrene, methacrylic
esters and methacrylic acid, e.g., methyl methacrylate, ethyl
methacrylate, butyl methacrylate, and hydroxyethyl methacrylate,
acrylic esters and acrylic acid, e.g., methyl acrylate, ethyl
acrylate, butyl acrylate, and .alpha.-ethylhexyl acrylate, dienes,
e.g., butadiene and isoprene, homopolymers of vinyl monomers or
copolymers of vinyl monomers with other monomers, e.g.,
acrylonitrile, vinyl ethers, maleic acid and maleic esters, maleic
anhydride, cinnamic acid, vinyl chloride and vinyl acetate can be
used. Two or more of these resins may be used as mixture.
[0294] It is preferred for the image-forming layer to contain a
pigment in an amount of from 30 to 70 mass % (i.e., weight %), more
preferably from 30 to 50 mass %. It is also preferred for the
image-forming layer to contain resins in an amount of from 30 to 70
mass %, more preferably from 40 to 70 mass %.
[0295] The image-forming layer can contain the following components
(1) to (3) as the above-described other components.
[0296] (1) Waxes
[0297] The examples of waxes include mineral waxes, natural waxes
and synthetic waxes. As the examples of the mineral waxes,
petroleum wax such as paraffin wax, microcrystalline wax, ester wax
and oxide wax, montan wax, ozokerite and ceresin can be
exemplified. Paraffin wax is preferred above all. The paraffin wax
is separated from petroleum, and various products are commercially
available according to melting points.
[0298] As the examples of the natural waxes, vegetable wax, e.g.,
carnauba wax, Japan wax, ouriculy wax and esparto wax, and animal
wax, e.g., beeswax, insect wax, shellac wax and spermaceti can be
exemplified.
[0299] The synthetic waxes are generally used as a lubricant and
generally comprises higher fatty acid compounds. As the examples of
the synthetic waxes, the following can be exemplified.
[0300] 1) Fatty Acid-based Wax
[0301] A straight chain saturated fatty acid represented by the
following formula:
CH.sub.3 (CH.sub.2).sub.nCOOH
[0302] In the formula, n represents an integer of from 6 to 28. As
the specific examples, stearic acid, behenic acid, palmitic acid,
12-hydroxystearic acid, and azelaic acid can be exemplified.
[0303] In addition, the metal salts of the above fatty acids (e.g.,
with K, Ca, Zn and Mg) can be exemplified.
[0304] 2) Fatty Acid Ester-based Wax
[0305] As the examples of the fatty acid esters, ethyl stearate,
lauryl stearate, ethyl behenate, hexyl behenate and behenyl
myristate can be exemplified.
[0306] 3) Fatty Acid Amide-based Wax
[0307] As the examples of the fatty acid amides, stearic acid amide
and lauric acid amide can be exemplified.
[0308] 4) Aliphatic Alcohol-based Wax
[0309] A straight chain saturated aliphatic alcohol represented by
the following formula:
CH.sub.3 (CH.sub.2).sub.nOH
[0310] In the formula, n represents an integer of from 6 to 28. As
the specific examples, stearyl alcohol can be exemplified.
[0311] Of the above synthetic waxes 1) to 4), higher fatty acid
amides such as stearic acid amide and lauric acid amide are
preferred. Further, these wax compounds can be used alone or in
arbitrary combination, as desired.
[0312] (2) Plasticizers
[0313] As the plasticizers, ester compounds are preferred, and
well-known plasticizers can be exemplified, such as phthalic
esters, e.g., dibutyl phthalate, di-n-octyl phthalate,
di(2-ethylhexyl) phthalate, dinonyl phthalate, dilauryl phthalate,
butyllauryl phthalate, and butylbenzyl phthalate, aliphatic dibasic
esters, e.g., di(2-ethylhexyl) adipate, and di(2-ethylhexyl)
sebacate, phosphoric triesters, e.g., tricresyl phosphate and
tri(2-ethylhexyl) phosphate, polyol polyesters, e.g., polyethylene
glycol ester, and epoxy compounds, e.g., epoxy fatty acid ester. Of
these compounds, esters of vinyl monomers, in particular, acrylic
esters and methacrylic esters are preferred in view of the
improvement of transfer sensitivity, the improvement of transfer
unevenness, and the big controlling effect of breaking
elongation.
[0314] As the acrylic or methacrylic ester compounds, polyethylene
glycol dimethacrylate, 1,2,4-butanetriol trimethacrylate,
trimethylolethane triacrylate, pentaerythritol acrylate,
pentaerythritol tetraacrylate, dipentaerythritol polyacrylate can
be exemplified.
[0315] The above plasticizers may be high polymers, and polyesters
are preferred above all, since the addition effect is large and
they hardly diffuse under storage conditions. As the polyesters,
e.g., sebacic acid polyester and adipic acid polyester are
exemplified.
[0316] The additives contained in the image-forming layer are not
limited these compounds. The plasticizers may be used alone or in
combination of two or more.
[0317] When the content of these additives in the image-forming
layer are too much, in some cases, the resolution of the
transferred image is deteriorated, the film strength of the
image-forming layer itself is reduced, or sometimes the unexposed
area is transferred to the image-receiving sheet due to the
reduction of the adhesion of the light-to-heat converting layer and
the image-forming layer. From the above viewpoint, the content of
the waxes is preferably from 0.1 to 30 mass % of the entire solid
content in the image-forming layer, more preferably from 1 to 20
mass %. The content of the plasticizers is preferably from 0.1 to
20 mass % of the entire solid content in the image-forming layer,
more preferably from 0.1 to 10 mass %.
[0318] (3) Others
[0319] In addition to the above components, the image-forming layer
may further contain a surfactant, inorganic or organic fine
particles (metallic powder and silica gel), oils (e.g., linseed oil
and mineral oil), a thickener and an antistatic agent. Except for
the case of obtaining a black image, energy necessary for transfer
can be reduced by containing the materials which absorb the
wavelengths of light sources for use in image recording. As the
materials which absorb the wavelengths of light sources, either
pigments or dyes may be used, but in the case of obtaining a color
image, it is preferred in view of color reproduction to use
infrared light sources such as a semiconductor laser in image
recording and use dyes having less absorption in the visible region
and large absorption in the wavelengths of light sources. As the
examples of infrared absorbing dyes, the compounds disclosed in
JP-A-3-103476 can be exemplified.
[0320] The image-forming layer can be provided by dissolving or
dispersing the pigment and the binder, to thereby prepare a coating
solution, coating the coating solution on the light-to-heat
converting layer (when the following heat-sensitive peeling layer
is provided on the light-to-heat converting layer, on the
heat-sensitive peeling layer) and drying. As the solvent for use in
the preparation of the coating solution, n-propyl alcohol, methyl
ethyl ketone, propylene glycol monomethyl ether (MFG), methanol and
water can be exemplified. Coating and drying can be performed
according to ordinary coating and drying methods.
[0321] A heat-sensitive peeling layer containing a heat-sensitive
material which generates gas by the action of the heat generated in
the light-to-heat converting layer or releases adhesive moisture to
thereby lower the adhesion strength between the light-to-heat
converting layer and the image-forming layer can be provided on the
light-to-heat converting layer in the heat transfer sheet. As such
heat-sensitive materials, compounds (polymers or low molecular
compounds) which themselves are decomposed by heat, or properties
of which are changed by heat, and generate gas, and compounds
(polymers or low molecular compounds) which are absorbing, or are
being adsorbed with, an equivalent amount of easily-vaporizing
gases, such as moisture, can be used. These compounds may be used
in combination.
[0322] As the examples of the polymers which themselves are
decomposed by heat, or properties of which are changed by heat, and
generate gas, self oxidizing polymers, e.g., nitrocellulose,
halogen-containing polymers, e.g., chlorinated polyolefin,
chlorinated rubber, poly-rubber chloride, polyvinyl chloride, and
polyvinylidene chloride, acryl-based polymers, e.g., polyisobutyl
methacrylate which is being adsorbed with volatile compound such as
moisture, cellulose esters, e.g., ethyl cellulose which is being
adsorbed with volatile compound such as moisture, and natural high
molecular compounds, e.g., gelatin which is being adsorbed with
volatile compound such as moisture can be exemplified. As the
examples of low molecular compounds which are decomposed by heat or
properties of which are changed by heat and generate gas, diazo
compounds and azide compounds which generate heat, decomposed and
generate gas can be exemplified.
[0323] Decomposition and property change by heat of the
heat-sensitive material as described above preferably occur at
280.degree. C. or less, particularly preferably 230.degree. C. or
less.
[0324] When low molecular compounds are used as the heat-sensitive
material of the heat-sensitive peeling layer, it is preferred to
combine the material with a binder. As the binder, the polymers
which themselves are decomposed by heat, or properties of which are
changed by heat, and generate gas can be used, but ordinary binders
which do not have such property can also be used. When the
heat-sensitive low molecular compound is used in combination with a
binder, the mass ratio (i.e., the weight ratio) of the former to
the latter is preferably from 0.02/1 to 3/1, more preferably from
0.05/1 to 2/1. It is preferred that the heat-sensitive peeling
layer cover the light-to-heat converting layer almost entirely and
the thickness of the heat-sensitive peeling layer is generally from
0.03 to 1 .mu.m, and preferably from 0.05 to 0.5 .mu.m.
[0325] When the constitution of the heat transfer sheet comprises a
support having provided thereon a light-to-heat converting layer, a
heat-sensitive peeling layer and an image-forming layer in this
order, the heat-sensitive peeling layer is decomposed by heat
conducted from the light-to-heat converting layer, or properties of
which are changed by heat, and generates gas. The heat-sensitive
peeling layer is partially lost or cohesive failure is caused in
the heat-sensitive peeling layer due to the decomposition or gas
generation, as a result the adhesion strength between the
light-to-heat converting layer and the image-forming layer is
lowered and, according to the behavior of the heat-sensitive
peeling layer, a part of the heat-sensitive peeling layer is
adhered on the image-forming layer and migrates to the surface of
the image finally formed with the image-forming layer and thereby
causes color mixing of the image. Therefore, it is preferred that
the heat-sensitive peeling layer is scarcely colored, i.e., the
heat-sensitive peeling layer shows high transmittance to visible
rays, so that color mixing does not appear visually on the image
formed, even if such transfer of the heat-sensitive peeling layer
occurs. Specifically, the absorptivity of the heat-sensitive
peeling layer to visible rays is 50% or less, preferably 10% or
less.
[0326] Further, instead of providing an independent heat-sensitive
peeling layer, the heat transfer sheet may take the constitution
such that the light-to-heat converting layer is formed by adding
the heat-sensitive material to the coating solution of the
light-to-heat converting layer, and the light-to-heat converting
layer doubles as the heat-sensitive peeling layer.
[0327] It is preferred that the coefficient of static friction of
the outermost layer of the heat transfer sheet of the side on which
the image-forming layer is provided is 0.35 or less, preferably
0.20 or less. When the coefficient of static friction of the
outermost layer is 0.35 or less, the contamination of the roll for
carrying the heat transfer sheet can be suppressed and the quality
of the image formed can be improved. The measurement of coefficient
of static friction is according to the method disclosed in
paragraph [0011] of JP-A-2001-47753.
[0328] It is preferred that the image-forming layer surface has
Smooster value at 23.degree. C., 55% RH of from 0.5 to 50 mmHg
(=about 0.0665 to 6.65 kPa), and Ra of from 0.05 to 0.4 .mu.m,
which can reduce a great number of micro voids by which the
image-receiving layer and the image-forming layer cannot be brought
into contact with each other at the contact area, which is
preferred in the point of transfer and image quality. The Ra value
can be measured by a surface roughness meter (Surfcom, manufactured
by Tokyo Seiki Co., Ltd.) according to JISB0601. It is preferred
that the surface hardness (defined in JIS K 5600-5-5) of the
image-forming layer is 10 g or more when measured with a sapphire
needle. When the image-forming layer is electrically charged
according to U.S. test standard 4046 and then grounded, the
electrification potential 1 second after grounding of the
image-forming layer is preferably from -100 to 100 V. It is
preferred that the surface resistance of the image-forming layer at
23.degree. C., 55% RH is 10.sup.9 .OMEGA. or less.
[0329] In the next place, the image-receiving sheet which can be
used in combination with the heat transfer sheet is described
below.
[0330] Image-Receiving Sheet
[0331] Layer Constitution
[0332] The constitution of the image-receiving sheet generally
comprises a support having provided thereon one or more
image-receiving layer(s) and, if necessary, any one or two or more
layer(s) of a cushioning layer, a peeling layer and an intermediate
layer is(are) provided between the support and the image-receiving
layer. It is preferred in view of conveyance to provide a backing
layer on the surface of the support opposite to the side on which
the image-receiving layer is provided.
[0333] Support
[0334] A plastic sheet, a metal sheet, a glass sheet, a
resin-coated paper, a paper, and ordinary sheet-like substrate
materials, e.g., various composites, are used as the support. As
the examples of plastic sheets, a polyethylene terephthalate sheet,
a polycarbonate sheet, a polyethylene sheet, a polyvinyl chloride
sheet, a polyvinylidene chloride sheet, a polystyrene sheet, a
styrene-acrylonitrile sheet, and a polyester sheet can be
exemplified. As the examples of papers, an actual printing paper
and a coated paper can be used.
[0335] It is preferred for the support to have minute voids in view
of capable of improving the image quality. Such supports can be
produced by mixing a thermoplastic resin and a filler comprising an
inorganic pigment and a high polymer incompatible with the above
thermoplastic resin to thereby prepare a mixed melt, extruding the
mixed melt by a melt extruder to prepare a monolayer or multilayer
film, and further monoaxially or biaxially stretching the film. In
this step, the void ratio is determined by the selection of the
resin and the filler, a mixing ratio and stretching condition.
[0336] As the thermoplastic resins, a polyolefin resin, such as
polypropylene, and a polyethylene terephthalate resin are
preferred, since they are excellent in crystallizability and
orientation property and voids can be formed easily. It is
preferred to use the polyolefin resin or the polyethylene
terephthalate resin as the main component and use a small amount of
other thermoplastic resin arbitrarily in combination. The inorganic
pigments for use as the filler preferably have an average particle
size of from 1 to 20 .mu.m, e.g., calcium carbonate, clay,
diatomaceous earth, titanium oxide, aluminum hydroxide and silica
can be used. As the incompatible resins for use as the filler, when
polypropylene is used as the thermoplastic resin, it is preferred
to combine polyethylene terephthalate as the filler. A support
having minute voids is disclosed in detail in JP-A-2001-105752.
[0337] The content of the filler, e.g., an inorganic pigment, in
the support is generally from 2 to 30% by volume or so.
[0338] The thickness of the support in the image-receiving sheet is
generally from 10 to 400 .mu.m, preferably from 25 to 200 .mu.m.
For enhancing the adhesion with the image-receiving layer (or the
cushioning layer) or with the image-forming layer in the heat
transfer sheet, the surface of the support in the image-receiving
sheet may be subjected to surface treatment, e.g., corona discharge
treatment and glow discharge treatment.
[0339] Image-receiving Layer
[0340] It is preferred to provide one or more image-receiving
layer(s) on the support in the image-receiving sheet for
transferring and fixing the image-forming layer on the
image-receiving sheet. The image-receiving layer is preferably a
layer formed with an organic polymer binder as the main component.
The binders are preferably thermoplastic resins, such as
homopolymers and copolymers of acryl-based monomers, e.g., acrylic
acid, methacrylic acid, acrylic acid ester, and methacrylic acid
ester, cellulose-based polymers, e.g., methyl cellulose, ethyl
cellulose and cellulose acetate, homomonomers and copolymers of
vinyl-based monomers, e.g., polystyrene, polyvinyl pyrrolidone,
polyvinyl butyral, polyvinyl alcohol and polyvinyl chloride,
condensed polymers, e.g., polyester and polyamide, and rubber-based
polymers, e.g., butadiene-styrene copolymer. The binder for use in
the image-receiving layer is preferably a polymer having a glass
transition temperature (Tg) of 90.degree. C. or lower for obtaining
appropriate adhesion with the image-forming layer. For that
purpose, it is possible to add a plasticizer to the image-receiving
layer. The binder polymer preferably has Tg of 30.degree. C. or
more for preventing blocking between sheets. As the binder polymer
of the image-receiving layer, the same or analogous monomer unit as
the monomer unit constituting the binder polymer of the
image-forming layer is preferably used from the point of improving
the adhesion with the image-forming layer at laser recording and
improving sensitivity and image strength.
[0341] It is preferred that the image-receiving layer surface has
Smooster value (i.e., Smooster smoothness: JAPAN TAPPI No. 5) at
23.degree. C., 55% RH of from 0.5 to 50 mmHg (=about 0.0665 to 6.65
kPa), which can reduce a great number of micro voids by which the
image-receiving layer and the image-forming layer cannot be brought
into contact with each other at the contact area, which is
preferred in the point of transfer and image quality. When the
image-receiving layer is electrically charged according to U.S.
test standard 4046 and then grounded, the electrification potential
1 second after grounding of the image-receiving layer is preferably
from -100 to 100 V. It is preferred that the surface resistance of
the image-receiving layer at 23.degree. C., 55% RH is 10.sup.9
.OMEGA. or less. It is preferred that the surface energy of the
surface of the image-receiving layer is from 23 to 35
mg/m.sup.2.
[0342] When the image once formed on the image-receiving layer is
re-transferred to the actual printing paper, it is also preferred
that at least one image-receiving layer is formed of a
photo-setting material. As the composition of such a photo-setting
material, combination comprising a) a photopolymerizable monomer
comprising at least one kind of a polyfunctional vinyl or
vinylidene compound which can form a photopolymer by addition
polymerization, b) an organic polymer, and c) a photopolymerization
initiator, and, if necessary, additives, e.g., a thermal
polymerization inhibitor can be exemplified. As the above
polyfunctional vinyl monomer, unsaturated ester of polyol, in
particular, an acrylic or methacrylic ester (ethylene glycol
diacrylate, pentaerythritol tetraacrylate) is used.
[0343] As the organic polymer, the polymers for use for forming the
image-receiving layer can be exemplified. As the
photopolymerization initiator, an ordinary photo-radical
polymerization initiator, e.g., benzophenone and Michler's ketone,
can be used in proportion of from 0.1 to 20 mass % in the
layer.
[0344] The thickness of the image-receiving layer is generally from
0.3to7 .mu.m, preferably from 0.7 to4 .mu.m. When the thickness of
the image-receiving layer is less than 0.3 .mu.m, the film strength
is insufficient at re-transferring to the actual printing paper and
the film breaks easily. While when the thickness of the
image-receiving layer is too thick, the glossiness of the image
after re-transferring to the actual printing paper increases, and
the approximation to the printed matter is reduced.
[0345] When the surface of the image-receiving sheet is subjected
to cleaning with an adhesive roller, for certainly removing foreign
matters without causing peeling of the image-receiving layer, the
adhesive strength of the image-receiving layer and the underlayer
of the image-receiving layer (a support, or a corresponding layer
when a cushioning layer or a peeling layer is provided) is from 20
to 100 mN/cm, preferably from 40 to 70 mN/cm, the static friction
coefficient of the image-receiving layer surface is 0.7 or less,
preferably 0.4 or less, and the surface roughness Rz of the
image-receiving layer surface is from 1 to 5 .mu.m, preferably from
2 to 4 .mu.m.
[0346] Other Layers
[0347] A cushioning layer may be provided between the support and
the image-receiving layer. When a cushioning layer is provided, it
is possible to increase the adhesion of the image-forming layer and
the image-receiving layer at heat transfer by laser and the image
quality can be improved. Further, even if foreign matters enter
between the heat transfer sheet and the image-receiving sheet
during recording, the voids between the image-receiving layer and
the image-forming layer are reduced by the deforming action of the
cushioning layer, as a result the size of image defect such as
clear spots can be made small. Further, when the image formed by
transfer is re-transferred to the actual printing paper, since the
surface of the image-receiving layer is deformed according to the
surface unevenness of the paper surface, the transferring property
of the image-receiving layer can be improved. Further, by reducing
the glossiness of the transferred image, the approximation to the
printed matter can be improved.
[0348] The cushioning layer is formed to be liable to be deformed
when stress is laid on the image-receiving layer, hence for
obtaining the above effect, the cushioning layer preferably
comprises materials having a low modulus of elasticity, materials
having elasticity of a rubber, or thermoplastic resins easily
softened by heat. The modulus of elasticity of the cushioning layer
at room temperature is preferably from 0.5 MPa to 1.0 GPa, more
preferably from 1 MPa to 0.5 GPa, and particularly preferably from
10 to 100 MPa. For burying foreign matters such as dust, the
penetration according to JIS K2530 (25.degree. C., 100 g, 5
seconds) is preferably 10 or more. The cushioning layer has a glass
transition temperature of 80.degree. C. or less, preferably
25.degree. C. or less, and a softening point of preferably from 50
to 200.degree. C. It is also preferred to add a plasticizer to the
binder for controlling these physical properties, e.g., Tg.
[0349] As the specific materials for use as the binder of the
cushioning layer, besides rubbers, e.g., urethane rubber, butadiene
rubber, nitrile rubber, acryl rubber and natural rubber,
polyethylene, polypropylene, polyester, styrene-butadiene
copolymer, ethylene-vinyl acetate copolymer, ethylene-acryl
copolymer, vinyl chloride-vinyl acetate copolymer, vinylidene
chloride resin, vinyl chloride resin containing a plasticizer,
polyamide resin and phenol resin can be exemplified.
[0350] The thickness of the cushioning layer varies according to
the resins used and other conditions, but is generally from 3 to
100 .mu.m, preferably from 10 to 52 .mu.m.
[0351] It is necessary that the image-receiving layer and the
cushioning layer are adhered to each other until the stage of laser
recording, but it is preferred that they are designed to be
peelable for transferring an image to the actual printing paper.
For easy peeling, it is also preferred to provide a peeling layer
having a thickness of from 0.1 to 2 .mu.m or so between the
cushioning layer and the image-receiving layer. When the thickness
of the peeling layer is too thick, the properties of the cushioning
layer are difficult to be exhibited, thus it is necessary to adjust
the thickness by the kind of the peeling layer.
[0352] The specific examples of the binders of the peeling layer
include thermo-setting resins having Tg of 65.degree. C. or more,
e.g., polyolefin, polyester, polyvinyl acetal, polyvinyl formal,
polyparabanic acid, methyl polymethacrylate, polycarbonate, ethyl
cellulose, nitrocellulose, methyl cellulose, carboxymethyl
cellulose, hydroxypropyl cellulose, polyvinyl alcohol, polyvinyl
chloride, urethane resin, fluorine resin, styrenes, e.g.,
polystyrene and acrylonitrile styrene, crosslinked products of
these resins, polyamide, polyimide, polyether imide, polysulfone,
polyether sulfone, aramid, and hardened products of these resins.
As the hardening agent, generally used hardening agents, e.g.,
isocyanate and melamine, can be used.
[0353] When the binders of the peeling layer are selected by taking
the above physical properties into consideration, polycarbonate,
acetal and ethyl cellulose are preferred in view of the storage
stability, and further, when acrylate resins are added to the
image-receiving layer, peelability (i.e., peeling property) at
re-transferring of the image after laser-heat transfer becomes good
and preferred.
[0354] Further, a layer whose adhesion with the image-receiving
layer extremely lowers by cooling can be used as the peeling layer.
Specifically, layers containing heat fusion compounds such as waxes
and binder, and thermoplastic resins as the main component can be
used as such a layer.
[0355] The examples of the heat fusion compounds are disclosed in
JP-A-63-193886. In particular, micro crystalline wax, paraffin wax,
and carnauba wax are preferably used. As the thermoplastic resins,
ethylene-based copolymers, e.g., ethylene-vinyl acetate resins and
cellulose-based resins are preferably used.
[0356] As the additives, higher fatty acid, higher alcohol, higher
fatty acid ester, amides, and higher amine can be added to the
peeling layer, according to necessity.
[0357] As another constitution of the peeling layer, there is a
layer which has peelability by causing cohesive failure due to
fusion or softening by heating. It is preferred to add a
supercooling substance to such a peeling layer.
[0358] As the supercooling substance, poly-.epsilon.-caprolactone,
polyoxyethylene, benzotriazole, tribenzylamine and vanillin can be
exemplified.
[0359] In another constitution of the peeling layer, a compound to
reduce the adhesion with the image-receiving layer is added to the
peeling layer. As such compounds, silicone-based resins, e.g.,
silicone oil; Teflon, fluorine-based resins, e.g.,
fluorine-containing acrylate resin; polysiloxane resins;
acetal-based resins, e.g., polyvinyl butyral, polyvinyl acetal and
polyvinyl formal; solid waxes, e.g., polyethylene wax and amide
wax; and fluorine-based and phosphoric ester-based surfactants can
be exemplified.
[0360] The peeling layer can be prepared by dissolving the above
materials in a solvent or dispersing the above materials in a latex
state, and coating the above solution or dispersion on the
cushioning layer by a blade coater, a roll coater, a bar coater, a
curtain coater, or gravure coater, or extrusion lamination by hot
melt. As another method, the solution or dispersion obtained by
dissolving the above materials in a solvent or dispersing the above
materials in a latex state is coated on a temporary base by the
above coating method, the temporary base is adhered with the
cushioning layer, and then the temporary base is peeled.
[0361] In the image-receiving sheet to be combined with the heat
transfer sheet, the image-receiving layer may double as the
cushioning layer, and in that case, the image-receiving sheet may
take the constitution such as support/cushioning image-receiving
layer, or support/undercoat layer/cushioning image-receiving layer.
In this case, it is also preferred that cushioning image-receiving
layer has peelability so that re-transferring to the actual
printing paper is possible. In this case, the image after being
re-transferred to the actual printing paper becomes a glossy
image.
[0362] The thickness of the cushioning image-receiving layer is
from 5 to 100 .mu.m, preferably from 10 to 40 .mu.m.
[0363] It is preferred to provide a backing layer on the side of
the support of the image-receiving sheet opposite to the side on
which the image-receiving layer is provided for improving the
traveling property of the image-receiving sheet. When a surfactant,
an antistatic agent, e.g., fine particles of tin oxide, and a
matting agent, e.g., silicon oxide and PMMA particles, are added to
the backing layer, the traveling property in the recording unit is
improved.
[0364] These additives can be added not only to the backing layer
but also to the image-receiving layer and other layers, if desired.
The kinds of the additives cannot be prescribed unconditionally
according to purposes, but a matting agent having an average
particle size of from 0.5 to 10 .mu.m can be added in concentration
of from 0.5 to 80% or so, and an antistatic agent can be added by
selecting arbitrarily from among various surfactants and
electrically conductive agents so that the surface resistance of
the layer at 23.degree. C., 50% RH becomes preferably 10.sup.12
.OMEGA. or less, more preferably 10.sup.9 .OMEGA. or less.
[0365] As the binder for use in the backing layer, widely used
polymers can be used, e.g., gelatin, polyvinyl alcohol, methyl
cellulose, nitrocellulose, acetyl cellulose, aromatic polyamide
resin, silicone resin, epoxy resin, alkyd resin, phenol resin,
melamine resin, fluorine resin, polyimide resin, urethane resin,
acryl resin, urethane-modified silicone resin, polyethylene resin,
polypropylene resin, polyester resin, Teflon resin, polyvinyl
butyral resin, vinyl chloride-based resin, polyvinyl acetate,
polycarbonate, organic boron compounds, aromatic esters,
polyurethane fluoride, and polyether sulfone can be used.
[0366] When crosslinkable water-soluble binder is used as the
binder of the backing layer for crosslinking, dropout prevention of
a matting agent and scratch resistance of the backing layer are
improved, further it is effective for blocking during storage.
[0367] The crosslinking means can be selected with no limitation
from heat, actinic rays and pressure, according to the
characteristics of the crosslinking agent to be used, and these may
be used alone or in combination. For providing an adhering property
to the support, an arbitrary adhesion layer may be provided on the
same side of the support on which the backing layer is
provided.
[0368] Organic or inorganic fine particles are preferably added to
the backing layer as the matting agent. As the organic matting
agent, polymethyl methacrylate (PMMA), polystyrene, polyethylene,
polypropylene, fine particles of other radical polymers, and
condensed polymers such as polyester and polycarbonate are
exemplified.
[0369] The backing layer is preferably provided in an amount of
about 0.5 to 5 g/m.sup.2. When the amount is less than 0.5
g/m.sup.2, coating property is unstable and a problem of dropout of
the matting agent is liable to occur. While when the coating amount
greatly exceeds 5 g/m.sup.2, the preferred particle size of the
matting agent becomes extremely large and embossing of the
image-receiving layer surface by the backing layer is caused during
storage, and in the heat transfer of a thin image-forming layer,
the dropout of the recorded image and unevenness are liable to
occur.
[0370] The number average particle size of the matting agent is
preferably larger than the layer thickness of the backing layer
containing a binder alone by 2.5 to 20 .mu.m. Of the matting
agents, particles having a particle size of 8 .mu.m or more are
necessary to be present in an amount of 5 mg/m.sup.2or more,
preferably from 6 to 600 mg/m.sup.2, by which the defect due to
foreign matters can be improved. Further, when a matting agent of
narrow particle size distribution is used, i.e., when a matting
agent having the value obtained by dividing the standard deviation
of the particle size distribution by the number average particle
size, .sigma./rn (the variation coefficient of particle size
distribution) of 0.3 or less is used, the defect which occurs when
particles having an extraordinary big particle size are used can be
improved, and further, the desired performance can be obtained with
the less addition amount. The variation coefficient is more
preferably 0.15 or less.
[0371] It is preferred to add an antistatic agent to the backing
layer for the purpose of preventing adhesion of foreign matters due
to the frictional electrification with a carrier roller. As the
antistatic agent, a cationic surfactant, an anionic surfactant, a
nonionic surfactant, a high molecular antistatic agent,
electrically conductive fine particles, in addition, the compounds
described in 11290 no Kagaku Shohin (Chemical Commercial Products
of 11290), pp. 875 and 876, Kagaku Kogyo Nippo-Sha can be widely
used.
[0372] As antistatic agents which can be used in the backing layer
in combination, of the above compounds, metallic oxide, e.g.,
carbon black, zinc oxide, titanium oxide and tin oxide, and
electrically conductive fine particles, e.g., organic
semiconductors, are preferably used. In particular, when
electrically conductive fine particles are used, the dissociation
of the antistatic agent from the backing layer can be prevented,
and stable antistatic effect can be obtained irrespective of the
surroundings.
[0373] It is also possible to add a mold-peeling agent, e.g.,
various activators, silicone oil, and fluorine resins, to the
backing layer for providing a coating property and a mold-peeling
property.
[0374] When the softening point of the cushioning layer and the
image-receiving layer measured by TMA (Thermomechanical Analysis)
is 70.degree. C. or lower, the backing layer is particularly
preferred.
[0375] TMA softening point is obtained by observing the phase of
the object with increasing the temperature of the object of
observation at constant rate and applying a constant load to the
object. In the present invention, the temperature at the time when
the phase of the object begins to change is defined as TMA
softening point. The softening point by TMA can be measured with an
apparatus such as Thermoflex (manufactured by Rigaku Denki-Sha
Co.).
[0376] The heat transfer sheet and the image-receiving sheet can be
used in image forming as the laminate by superposing the
image-forming layer in the heat transfer sheet and the
image-receiving layer in the image-receiving sheet.
[0377] The laminate of the heat transfer sheet and the
image-receiving sheet can be produced by various methods. For
example, the laminate can be easily obtained by superposing the
image-forming layer in the heat transfer sheet and the
image-receiving layer in the image-receiving sheet and passing
through a pressure and heating roller. The heating temperature in
this case is 160.degree. C. or less, preferably 130.degree. C. or
less.
[0378] The above-described vacuum adhesion method can also be
preferably used for obtaining the laminate. The vacuum adhesion
method is a method of winding the image-receiving sheet around the
drum provided with suction holes for vacuum sucking, and then
vacuum-adhering the heat transfer sheet of a little larger size
than the image-receiving sheet on the image-receiving sheet with
uniformly blasting air by a squeeze roller. As other method, a
method of mechanically sticking the image-receiving sheet on a
metal drum with pulling the image-receiving sheet, and further
mechanically sticking the heat transfer sheet thereon with pulling
in the same manner can also be used. Of these methods, the vacuum
adhesion method is especially preferred in the point of requiring
no temperature control and capable of effecting lamination rapidly
and uniformly.
EXAMPLE
[0379] The present invention will be described in detail with
reference to the examples below but the present invention is not
limited thereto at all. In the examples, "parts" means "parts by
mass (i.e., parts by weight)" unless otherwise indicated.
[0380] Preparation of Heat Transfer Sheet K (Black)
[0381] Formation of Backing Layer
[0382] Preparation of First Backing Layer Coating Solution
6 Water dispersion solution of acrylic 2 parts resin (Julymer
ET410, solid content: 20 mass %, manufactured by Nippon Junyaku
Co., Ltd.) Antistatic agent (water dispersion 7.0 parts of tin
oxide-antimony oxide, average particle size: 0.1 .mu.m, 17 mass %)
Polyoxyethylenephenyl ether 0.1 part Melamine compound 0.3 parts
(Sumitic Resin M-3, manufactured by Sumitomo Chemical Industry Co.,
Ltd.) Distilled water to make the total amount 100 parts
[0383] Formation of First Backing Layer
[0384] One surface (back surface) of a biaxially stretched
polyethylene terephthalate support (Ra of both surfaces was 0.01
.mu.m) having a thickness of 75 .mu.m was subjected to corona
discharge treatment. The first backing layer coating solution was
coated on the support in dry coating thickness of 0.03 .mu.m, and
the coated layer was dried at 180.degree. C. for 30 seconds,
thereby the first backing layer was prepared. The Young's modulus
of the support in the machine direction was 450 kg/mm.sup.2 (=about
4.4 GPa) , and the Young's modulus of the support in the transverse
direction was 500 kg/mm.sup.2 (=about 4.9 GPa). The F-5 value of
the support in the machine direction was 10 kg/mm.sup.2 (=about 98
MPa), and the F-5 value of the support in the transverse direction
was 13 kg/mm.sup.2 (=about 127.4 MPa), the heat shrinkage rate at
100.degree. C. for 30 minutes of the support in the machine
direction was 0.3%, and that in the transverse direction was 0.1%.
The breaking strength was 20 kg/mm.sup.2 (=about 196 MPa) in the
machine direction, and that in the transverse direction was 25
kg/mm.sup.2 (=about 245 MPa) in the transverse direction, and the
modulus of elasticity was 400 kg/mm.sup.2 (=about 3.9 GPa).
[0385] Preparation of Second Backing Layer Coating Solution
7 Polyolefin (Chemipearl S-120, 3.0 parts 27 mass %, manufactured
by Mitsui Petrochemical Industries, Ltd.) Antistatic agent (water
dispersion 2.0 parts of tin oxide-antimony oxide, average particle
size: 0.1 .mu.m, 17 mass %) Colloidal silica 2.0 parts (Snowtex C,
20 mass %, manufactured by Nissan Chemical Industries, Ltd.) Epoxy
compound (Denacol EX-614B, 0.3 parts manufactured by Nagase Kasei
Co., Ltd.) Distilled water to make the total amount 100 parts
[0386] Formation of Second Backing Layer
[0387] The second backing layer coating solution was coated on the
first backing layer in dry coating thickness of 0.03 .mu.m, and the
coated layer was dried at 170.degree. C. for 30 seconds, thereby
the second backing layer was prepared.
[0388] 1) Preparation of Light-to-Heat Converting Layer Coating
Solution
[0389] The following components were mixed with stirring by a
stirrer and the light-to-heat converting layer coating solution was
prepared.
[0390] Composition of Light-to-Heat Converting Layer Coating
Solution
8 Infrared absorbing dye (NK-2014, 7.6 parts manufactured by Nippon
Kanko Shikiso Co., Ltd., a cyanine dye having the following
composition) 4
[0391] In the formula, R represents CH.sub.3 and X.sup.- represents
ClO.sub.4.sup.-.
9 Polyimide resin represented by the 29.3 parts following formula
(Rikacoat SN-20F, manufactured by Shin Nihon Rika K.K., heat
decomposition temperature: 510.degree. C.) 5
[0392] In the formula, R.sub.1 represents SO.sub.2 and R.sub.2
represents the following formula:
10 6 or 7 Exxon naphtha 5.8 parts N-Methylpyrrolidone (NMP) 1,500
parts Methyl ethyl ketone 360 parts Surfactant (Megafac F-176PF,
0.5 parts manufactured by Dainippon Chemicals and Ink Co., Ltd.,
fluorine surfactant) Dispersion solution of matting agent 14.1
parts having the following composition Dispersion solution of
matting agent N-Methyl-2-pyrrolidone (NMP) 69 parts Methyl ethyl
ketone 20 parts Styrene-acrylate resin 3 parts (Joncryl 611,
manufactured by Johnson Polymer Co., Ltd.) SiO.sub.2 Particles 8
parts (Sea Hoster-KEP150, silica particles, manufactured by Nippon
Shokubai Co., Ltd.)
[0393] 2) Formation of Light-to-Heat Converting Layer on Support
Surface
[0394] The above light-to-heat converting layer coating solution
was coated with a wire bar coater on one surface of a polyethylene
terephthalate film (support) having a thickness of 75 .mu.m, and
the coated product was dried in an oven at 120.degree. C. for 2
minutes, thereby a light-to-heat converting layer was formed on the
support. The optical density OD of the obtained light-to-heat
converting layer at wavelength of 808 nm measured by
UV-spectrophotometer UV-240 (manufactured by Shimadzu Seisakusho
Co. Ltd.) was 1.03, and the layer thickness measured with a
scanning electron microscope was 0.3 .mu.m on average.
[0395] 3) Preparation of Black Image-Forming Layer Coating
Solution
[0396] Each of the following components was put in a kneading mill,
and pre-treatment was performed with adding a small amount of a
solvent and applying a shear force. The solvent was further added
to the dispersion so as to reach the following composition, and
dispersion was performed for two hours in a sand mill, thereby the
mother solution of a pigment dispersion was obtained.
[0397] Composition of Black Pigment Dispersion Mother Solution
11 Composition 1 Polyvinyl butyral 12.6 parts (Eslec B BL-SH,
manufactured by Sekisui Chemical Industries, Ltd.) Pigment Black 7
(carbon black, 4.5 parts C.I. No. 77266, Mitsubishi Carbon Black
#5, manufactured by Mitsubishi Chemicals Co. Ltd., PVC blackness:
1) Dispersing aid 0.8 parts (Solspers S-20000, manufactured by ICI
Co.) n-Propyl alcohol 79.4 parts Composition 2 Polyvinyl butyral
12.6 parts (Eslec B BL-SH, manufactured by Sekisui Chemical
Industries, Ltd.) Pigment Black 7 (carbon black, 10.5 parts C.I.
No. 77266, Mitsubishi Carbon Black MA100, manufactured by
Mitsubishi Chemicals Co., Ltd., PVC blackness: 10) Dispersing aid
0.8 parts (Solspers S-20000, manufactured by ICI Co.) n-Propyl
alcohol 79.4 parts
[0398] The following components were mixed by stirring with a
stirrer to prepare a black image-forming layer coating
solution.
[0399] Composition of Black Image-Forming Layer Coating
Solution
12 Above black pigment dispersion mother 185.7 parts solution
(composition 1/composition 2: 70/30 (parts)) Polyvinyl butyral 11.9
parts (Eslec B BL-SH, manufactured by Sekisui Chemical Industries,
Ltd.) Wax-based compound Stearic acid amide (Newtron 2, 1.7 parts
manufactured by Nippon Seika Co., Ltd.) Behenic acid amide (Diamid
BM, 1.7 parts (manufactured by Nippon Kasei Co., Ltd.) Lauric acid
amide (Diamid Y, 1.7 parts (manufactured by Nippon Kasei Co., Ltd.)
Palmitic acid amide (Diamid KP, 1.7 parts (manufactured by Nippon
Kasei Co., Ltd.) Erucic acid amide (Diamid L-200, 1.7 parts
(manufactured by Nippon Kasei Co., Ltd.) Oleic acid amide (Diamid
O-200, 1.7 parts (manufactured by Nippon Kasei Co., Ltd.) Rosin
(KE-311, manufactured by 11.4 parts Arakawa Kagaku Co., Ltd.
components: resin acid 80-97%, resin acid components: abietic acid:
30 to 40% neoabietic acid: 10 to 20% dihydroabietic acid: 14%
tetrahydroabietic acid: 14%) Surfactant (Megafac F-176PF, 2.1 parts
solid content: 20%, manufactured by Dai-Nippon Ink & Chemicals
Inc.) Inorganic pigment (MEK-ST, 7.1 parts 30% methyl ethyl ketone
solution, manufactured by Nissan Chemical Industries, Ltd.)
n-Propyl alcohol 1,050 parts Methyl ethyl ketone 295 parts
[0400] It was found that the particles in the thus-obtained black
image-forming layer coating solution had an average particle size
of 0.25 .mu.m, and the ratio of the particles having a particle
size of 1 .mu.m or more was 0.5% from the measurement by particle
size distribution measuring apparatus of laser scattering
system.
[0401] 4) Formation of Black Image-Forming Layer on Light-to-Heat
Converting Layer Surface
[0402] The above black image-forming layer coating solution was
coated on the light-to-heat converting layer with a wire bar coater
for 1 minute, and the coated product was dried in an oven at
100.degree. C. for 2 minutes, thus a black image-forming layer was
formed on the light-to-heat converting layer. By the above
procedure, a heat transfer sheet (hereinafter referred to as heat
transfer sheet K, similarly, a heat transfer sheet provided with a
yellow image-forming layer is referred to as heat transfer sheet Y,
a heat transfer sheet provided with a magenta image-forming layer
is referred to as heat transfer sheet M, and a heat transfer sheet
provided with a cyan image-forming layer is referred to as heat
transfer sheet C) comprising a support having provided thereon a
light-to-heat converting layer and a black image-forming layer in
this order from the support was prepared.
[0403] The optical density (OD) of the black image-forming layer in
the thus-obtained heat transfer sheet K was 0.91 measured by
Macbeth densitometer TD-904 (W filter), and the layer thickness of
the black image-forming layer was 0.60 .mu.m on average.
[0404] The obtained image-forming layer had the following physical
properties.
[0405] The surface hardness of the image-forming layer is
preferably 10 g or more when measured with a sapphire needle, and
specifically 200 g or more.
[0406] The Smooster value of the surface at 23.degree. C., 55% RH
is preferably from 0.5 to 50 mm Hg (=about 0.0665 to 6.65 kPa), and
specifically 9.3 mm Hg (=about 1.24 kPa).
[0407] The coefficient of static friction of the surface is
preferably 0.2 or less, and specifically 0.08.
[0408] Preparation of Heat Transfer Sheet Y
[0409] Heat transfer sheet Y was prepared in the same manner as in
the preparation of heat transfer sheet K, except that the yellow
image-forming layer coating solution having the composition shown
below was used in place of the black image-forming layer coating
solution. The layer thickness of the image-forming layer in the
obtained heat transfer sheet Y was 0.42 .mu.m.
[0410] Composition of Yellow Pigment Dispersion Mother Solution
[0411] Yellow Pigment Composition 1
13 Polyvinyl butyral 7.1 parts (Eslec B BL-SH, manufactured by
Sekisui Chemical Industries, Ltd.) Pigment Yellow (pigment yellow
180, 12.9 parts C.I. No. 21290) (Novoperm Yellow P-HG, manufactured
by Clariant Japan, K.K.) Dispersing aid 0.6 parts (Solspers
S-20000, manufactured by ICI Co.) n-Propyl alcohol 79.4 parts
[0412] Composition of Yellow Pigment Dispersion Mother Solution
[0413] Yellow Pigment Composition 2
14 Polyvinyl butyral 7.1 parts (Eslec B BL-SH, manufactured by
Sekisui Chemical Industries, Ltd.) Pigment Yellow 139 (carbon
black, 12.9 parts C.I. No. 56298) (Novoperm Yellow M2R 70,
manufactured by Clariant Japan, K.K.) Dispersing aid 0.6 parts
(Solspers S-20000, manufactured by ICI Co.) n-Propyl alcohol 79.4
parts
[0414] Composition of Yellow Image-Forming Layer Coating
Solution
15 Above yellow pigment dispersion mother 126 parts solution
(yellow pigment composition 1/ yellow pigment composition 2:95/5
(parts)) Polyvinyl butyral 4.6 parts (Eslec B BL-SH, manufactured
by Sekisui Chemical Industries, Ltd.) Wax-based compound Stearic
acid amide (Newtron 2, 0.7 parts manufactured by Nippon Seika Co.,
Ltd.) Behenic acid amide (Diamid BM, 0.7 parts (manufactured by
Nippon Kasei Co., Ltd.) Lauric acid amide (Diamid Y, 0.7 parts
(manufactured by Nippon Kasei Co., Ltd.) Palmitic acid amide
(Diamid KP, 0.7 parts (manufactured by Nippon Kasei Co., Ltd.)
Erucic acid amide (Diamid L-200, 0.7 parts (manufactured by Nippon
Kasei Co., Ltd.) Oleic acid amide (Diamid O-200, 0.7 parts
(manufactured by Nippon Kasei Co., Ltd.) Nonionic surfactant 0.4
parts (Chemistat 1100, manufactured by Sanyo Chemical Industries,
Co., Ltd.) Rosin (KE-311, manufactured by 2.4 parts Arakawa Kagaku
Co., Ltd.) components: resin acid 80-97%, resin acid components:
abietic acid: 30 to 40% neoabietic acid: 10 to 20% dihydroabietic
acid: 14% tetrahydroabietic acid: 14%) Surfactant (Megafac F-176PF,
0.8 parts solid content: 20%, manufactured by Dai-Nippon Ink &
Chemicals Inc.) n-Propyl alcohol 793 parts Methyl ethyl ketone 198
parts
[0415] The obtained image-forming layer had the following physical
properties.
[0416] The surface hardness of the image-forming layer is
preferably 10 g or more when measured with a sapphire needle, and
specifically 200 g or more.
[0417] The Smooster value of the surface at 23.degree. C., 55% RH
is preferably from 0.5 to 50 mm Hg (=about 0.0665 to 6.65 kPa), and
specifically 2.3 mm Hg (=about 0.31 kPa).
[0418] The coefficient of static friction of the surface is
preferably 0.2 or less, and specifically 0.1.
[0419] Preparation of Heat Transfer Sheet M
[0420] Heat transfer sheet M was prepared in the same manner as in
the preparation of heat transfer sheet K, except that the magenta
image-forming layer coating solution having the composition shown
below was used in place of the black image-forming layer coating
solution. The layer thickness of the image-forming layer in the
obtained heat transfer sheet M was 0.38 .mu.m.
[0421] Composition of Magenta Pigment Dispersion Mother
Solution
[0422] Magenta Pigment Composition 1
16 Polyvinyl butyral 12.6 parts (Denka Butyral #2000-L,
manufactured by Denki Kagaku Kogyo Co., Ltd., Vicut softening
point: 57.degree. C.) Pigment Red (pigment yellow 57:1, 15.0 parts
C.I. No. 15850:1) (Symuler Brilliant Carmine 6B-229, manufactured
by Dainippon Chemicals and Ink Co., Ltd.) Dispersing aid 0.6 parts
(Solspers S-20000, manufactured by ICI Co.) n-Propyl alcohol 80.4
parts
[0423] Composition of Magenta Pigment Dispersion Mother
Solution
[0424] Magenta Pigment Composition 2
17 Polyvinyl butyral 12.6 parts (Denka Butyral #2000-L,
manufactured by Denki Kagaku Kogyo Co., Ltd., Vicut softening
point: 57.degree. C.) Pigment Red 57:1 15.0 parts C.I. No. 15850)
(Lionol Red 6B-4290G, manufactured by Toyo Ink Mfg. Co., Ltd.)
Dispersing aid 0.6 parts (Solspers S-20000, manufactured by ICI
Co.) n-Propyl alcohol 79.4 parts
[0425] Composition of Magenta Image-Forming Layer Coating
Solution
18 Above magenta pigment dispersion mother 163 parts solution
(magenta pigment composition 1/ magenta pigment composition 2:95/5
(parts)) Polyvinyl butyral 4.0 parts (Denka Butyral #2000-L,
manufactured by Denki Kagaku Kogyo Co., Ltd., Vicut softening
point: 57.degree. C.) Wax-based compound Stearic acid amide
(Newtron 2, 1.0 part manufactured by Nippon Seika Co., Ltd.)
Behenic acid amide (Diamid BM, 1.0 part (manufactured by Nippon
Kasei Co., Ltd.) Lauric acid amide (Diamid Y, 1.0 part
(manufactured by Nippon Kasei Co., Ltd.) Palmitic acid amide
(Diamid KP, 1.0 part (manufactured by Nippon Kasei Co., Ltd.)
Erucic acid amide (Diamid L-200, 1.0 part (manufactured by Nippon
Kasei Co., Ltd.) Oleic acid amide (Diamid O-200, 1.0 part
(manufactured by Nippon Kasei Co., Ltd.) Nonionic surfactant 0.7
parts (Chemistat 1100, manufactured by Sanyo Chemical Industries,
Co., Ltd.) Rosin (KE-311, manufactured by 4.6 parts Arakawa Kagaku
Co., Ltd.) components: resin acid 80-97%, resin acid components:
abietic acid: 30 to 40% neoabietic acid: 10 to 20% dihydroabietic
acid: 14% tetrahydroabietic acid: 14%) Pentaerythritol
tetraacrylate 2.5 parts (NK ester A-TMMT, manufactured by
Shin-Nakamura Kagaku Co., Ltd.) Surfactant (Megafac F-176PF, 1.3
parts solid content: 20%, manufactured by Dai-Nippon Ink &
Chemicals Inc.) n-Propyl alcohol 848 parts Methyl ethyl ketone 246
parts
[0426] The obtained image-forming layer had the following physical
properties.
[0427] The surface hardness of the image-forming layer is
preferably 10 g or more when measured with a sapphire needle,
specifically 200 g or more.
[0428] The Smooster value of the surface at 23.degree. C., 55% RH
is preferably from 0.5 to 50 mm Hg (=about 0.0665 to 6.65 kPa), and
specifically 3.5 mm Hg (=about 0.47 kPa).
[0429] The coefficient of static friction of the surface is
preferably 0.2 or less, and specifically 0.08.
[0430] Preparation of Heat Transfer Sheet C
[0431] Heat transfer sheet C was prepared in the same manner as in
the preparation of heat transfer sheet K, except that the cyan
image-forming layer coating solution having the composition shown
below was used in place of the black image-forming layer coating
solution. The layer thickness of the image-forming layer in the
obtained heat transfer sheet C was 0.45 .mu.m.
[0432] Composition of Cyan Pigment Dispersion Mother Solution
[0433] Cyan Pigment Composition 1
19 Polyvinyl butyral 12.6 parts (Eslec B BL-SH, manufactured by
Sekisui Chemical Industries, Ltd.) Pigment Blue (pigment blue 54:7,
15.0 parts C.I. No. 74160) (Cyanine Blue 700-10FG, manufactured by
Toyo Ink Mfg. Co., Ltd.)) Dispersing aid 0.8 parts (PW-36,
manufactured by Kusumoto Kasei Co., Ltd.) n-Propyl alcohol 110
parts
[0434] Composition of Cyan Pigment Dispersion Mother Solution
[0435] Cyan Pigment Composition 2
20 Polyvinyl butyral 12.6 parts (Eslec B BL-SH, manufactured by
Sekisui Chemical Industries, Ltd.) Pigment Blue 15 15.0 parts (C.I.
No. 74160, Lionol Blue 7027, manufactured by Toyo Ink Mfg. Co.,
Ltd.) Dispersing aid 0.8 parts (PW-36, manufactured by Kusumoto
Kasei Co., Ltd.) n-Propyl alcohol 110 parts
[0436] Composition of Cyan Image-Forming Layer Coating Solution
21 Above cyan pigment dispersion mother 118 parts solution (cyan
pigment composition 1/ cyan pigment composition 2:90/10 (parts))
Polyvinyl butyral 5.2 parts (Eslec B BL-SH, manufactured by Sekisui
Chemical Industries, Ltd.) Inorganic pigment (MEK-ST) 1.3 parts
Wax-based compound Stearic acid amide (Newtron 2, 1.0 part
manufactured by Nippon Seika Co., Ltd.) Behenic acid amide (Diamid
BM, 1.0 part (manufactured by Nippon Kasei Co., Ltd.) Lauric acid
amide (Diamid Y, 1.0 part (manufactured by Nippon Kasei Co., Ltd.)
Palmitic acid amide (Diamid KP, 1.0 part (manufactured by Nippon
Kasei Co., Ltd.) Erucic acid amide (Diamid L-200, 1.0 part
(manufactured by Nippon Kasei Co., Ltd.) Oleic acid amide (Diamid
O-200, 1.0 part (manufactured by Nippon Kasei Co., Ltd.) Rosin
(KE-311, manufactured by 2.8 parts Arakawa Kagaku Co., Ltd.)
components: resin acid 80-97%, resin acid components: abietic acid:
30 to 40% neoabietic acid: 10 to 20% dihydroabietic acid: 14%
tetrahydroabietic acid: 14%) Pentaerythritol tetraacrylate 1.7
parts (NK ester A-TMMT, manufactured by Shin-Nakamura Kagaku Co.,
Ltd.) Surfactant (Megafac F-176PF, 1.7 parts solid content: 20%,
manufactured by Dai-Nippon Ink & Chemicals Inc.) n-Propyl
alcohol 890 parts Methyl ethyl ketone 247 parts
[0437] The obtained image-forming layer had the following physical
properties.
[0438] The surface hardness of the image-forming layer is
preferably 10 g or more when measured with a sapphire needle, and
specifically 200 g or more.
[0439] The Smooster value of the surface at 23.degree. C., 55% RH
is preferably from 0.5 to 50 mm Hg (=about 0.0665 to 6.65 kPa), and
specifically 7.0 mm Hg (=about 0.93 kPa).
[0440] The coefficient of static friction of the surface is
preferably 0.2 or less, and specifically 0.08.
[0441] Preparation of Image-Receiving Sheet
[0442] Image-Receiving Sheet A
[0443] The cushioning layer coating solution and the
image-receiving layer coating solution each having the following
composition were prepared.
[0444] 1) Cushioning Layer Coating Solution
22 Vinyl chloride-vinyl acetate copolymer 20 parts (main binder,
MPR-TSL, manufactured by Nisshin Kagaku Co., Ltd.) Plasticizer 10
parts (Paraplex G-40, manufactured by CP. HALL. COMPANY) Surfactant
(fluorine surfactant, 0.5 parts coating assistant, Megafac F-177,
manufactured by Dainippon Chemicals and Ink Co., Ltd.) Antistatic
agent (quaternary ammonium salt, 0.3 parts SAT-5 Supper (IC),
manufactured by Nippon Junyaku Co., Ltd.) Methyl ethyl ketone 60
parts Toluene 10 parts N,N-Dimethylformamide 3 parts
[0445] 2) Image-Receiving Layer Coating Solution
23 Polyvinyl butyral 8 parts (Eslec B BL-SH, manufactured by
Sekisui Chemical Industries, Ltd.) Antistatic agent 0.7 parts
Sanstat 2012A, manufactured by Sanyo Chemical Industries, Co.,
Ltd.) Surfactant (Megafac F-177, 0.1 parts manufactured by
Dainippon Chemicals and Ink Co., Ltd.) n-Propyl alcohol 20 parts
Methanol 20 parts 1-Methoxy-2-propanol 50 parts
[0446] The above-prepared cushioning layer coating solution was
coated on a white PET support (Lumiler # 130E58, manufactured by
Toray Industries Inc., thickness: 130 .mu.m) with a narrow-broad
coater and the coated layer was dried, and then the image-receiving
layer coating solution was coated and dried. The coating amounts
were controlled so that the layer thickness of the cushioning layer
after drying became about 20 .mu.m and the layer thickness of the
image-receiving layer after drying became about 2 .mu.m. The white
PET support was a void-containing plastic support of a laminate
(total thickness: 130 .mu.m, specific gravity: 0.8) comprising a
void-containing polyethylene terephthalate layer (thickness: 116
.mu.m, void ratio: 20%), and titanium oxide-containing polyethylene
terephthalate layers provided on both sides thereof (thickness: 7
.mu.m, titanium oxide content: 2%). The prepared material was wound
in a roll, stored at room temperature for one week, then used in
the image recording by laser beam as shown below.
[0447] The obtained image-receiving layer had the following
physical properties.
[0448] The Smooster value of the surface of the image-receiving
layer at 23.degree. C., 55% RH is preferably from 0.5 to 50 mm Hg
(=about 0.0665 to 6.65 kPa), and specifically 0.8 mm Hg (=about
0.11 kPa).
[0449] The coefficient of static friction of the surface of the
image-receiving layer is preferably 0.7 or less, and specifically
0.37.
[0450] Image-Receiving Sheet B
[0451] Image-receiving sheet B was prepared according to the same
formulation as in the preparation of image-receiving sheet A except
that 0.5 mass parts of polymethacrylate particles having a particle
size of 5 .mu.m (manufactured by Soken Kagaku Co., Ltd.) was added
to the image-receiving layer coating solution.
[0452] Image-Receiving Sheet C
[0453] Image-receiving sheet C was prepared according to the same
formulation as in the preparation of image-receiving sheet A except
that the equimolecular amount of citric acid polyester was added to
the cushioning layer coating solution in place of the plasticizer
Paraplex G-40 used in image-receiving sheet A.
[0454] Each of above-prepared image-receiving sheets A to C (56
cm.times.79 cm) was wound around the recording drum having a
diameter of 38 cm provided with vacuum suction holes having a
diameter of 1 mm (surface density of 1 hole in the area of 3
cm.times.8 cm) and vacuum sucked. Before forming a transfer image,
each image-receiving sheet was cleaned with an adhesive roller. The
adhesive rollers used and the physical properties of the
image-receiving sheets are shown in Table 4 below.
24 TABLE 4 Image-Receiving Sheet Adhesive Strengh of Image -
Adhesive Roller Receiving Pressing Image - Layer/ Static Control-
Receiv- Cushioning Friction Example Crown ling ing Layer Coeffi- Rz
No. Shape Member Sheet (mN/cm) cient (.mu.m) Example 1 Yes Present
A 50 0.35 0.40 Example 2 Yes Present B 55 0.22 3.5 Comparative Yes
Present C 10 0.36 0.42 Example 1 Example 3 Yes Absent A 50 0.35
0.40 Comparative No Present A 50 0.35 0.40 Example 2 Comparative No
Absent A 50 0.35 0.40 Example 3
[0455] In above Table 4, the adhesive rollers used in the case
corresponding to "Yes" in the column "Crown Shape" are those which
satisfy all the conditions of the above (A1) to (A3), specifically,
the rollers of a crown shape having the central diameter D of 40
mm, the diameter d of the end part of 9.9 mm, and the length of the
roller L of 500 mm. "No" in the column "Crown Shape" means that the
adhesive rollers of a straight type are used.
[0456] "Present" in the column "Pressing Controlling Member" means
that the pressing controlling member of d-d.sub.c=1 mm in Table 3
above is used.
[0457] The adhesive strength of image-receiving layer/cushioning
layer was measured according to the following method.
[0458] A sample of an image-receiving sheet (4.5 cm.times.16 cm)
was put on a stand and adhered with the image-receiving layer faced
the stand side with an adhesive tape (e.g., a polyester adhesive
tape No. 31B 75 high, manufactured by Nitto Denko Co., Ltd.). In
the next place, the cushioning layer was peeled off the
image-receiving layer by an adhesive tape using a force gauge
(e.g., FGX-2, manufactured by Nippon Densan Shinpo Co., Ltd.) at an
angle of 180.degree. to the image-receiving layer at peeling
velocity of 1,500 mm/min. The adhesive strength was obtained by
measuring the load (g) applied at this time and calculating in
terms of the unit length (cm).
[0459] A static friction coefficient was measured as follows.
[0460] A sample of an image-receiving sheet (5 cm.times.20 cm) was
put on a stand and adhered with the support faced the stand side
with an adhesive tape (e.g., a polyester adhesive tape No. 31B 75
high, manufactured by Nitto Denko Co., Ltd.). A stainless steel
terminal (35 mm.times.75 mm, curved surface of a radius of 2.5 mm,
200 g) having a smooth surface was put on the image-receiving
layer, and the stand was slanted slowly. The angle of inclination
of the stand of the time when the stainless steel terminal began to
slide was measured, and the static friction coefficient was
obtained as tan .theta..
[0461] Formation of Transferred Image
[0462] The above heat transfer sheet K (black) cut into a size of
61 cm.times.84 cm was superposed on the image-receiving sheet fixed
on the recording drum so as to deviate from the image-receiving
sheet uniformly, squeezed by a squeeze roller, and closely adhered
and laminated so that air was sucked by suction holes. The degree
of pressure reduction in the state of suction holes being covered
was -150 mm Hg per 1 atm (=about 81.13 kPa) . The drum was rotated
and semiconductor laser beams of the wavelength of 808 nm were
condensed from the outside on the surface of the laminate on the
drum so that the laser beams became a spot of a diameter of 7 .mu.m
on the surface of the light-to-heat converting layer, and laser
image recording (line image) was performed on the laminate by
moving the laser beam at a right angle (sub-scan) to the rotary
direction of the drum (main scanning direction). The condition of
laser irradiation was as follows. The laser beams used in the
example was multi-beam two dimensional array comprising five rows
along the main scanning direction and three rows along the sub-scan
direction forming a parallelogram.
[0463] Laser power: 110 mW
[0464] Drum rotation speed: 500 rpm
[0465] Sub-scan pitch: 6.35 .mu.m
[0466] Circumferential temperature and humidity conditions:
[0467] Three conditions of 18.degree. C. 30%, 23.degree. C. 50%,
26.degree. C. 65%
[0468] The diameter of exposure drum is preferably 360 mm or more,
and specifically 380 mm was used.
[0469] The size of the image was 515 mm.times.728 mm, and the
resolution was 2,600 dpi.
[0470] The laminate finished laser recording was detached from the
drum and heat transfer sheet K was peeled from the image-receiving
sheet manually. It was confirmed that only the irradiated area of
the image-forming layer in heat transfer sheet K had been
transferred from heat transfer sheet K to the image-receiving
sheet.
[0471] In the same manner as above, the image was transferred to
the image-receiving sheet from each of heat transfer sheet Y, heat
transfer sheet M and heat transfer sheet C.
[0472] Evaluation
[0473] 1) Image Defect due to Foreign Matters
[0474] The transferred image was visually observed and the number
of image defects due to foreign matters, e.g., clear spots, was
confirmed.
[0475] o: The number of image defect is 1 or less.
[0476] .DELTA.: The number of image defects is from 2 to 10.
[0477] x: The number of image defects is 11 or more.
[0478] 2) Peeling of Image-Receiving Layer
[0479] The surface of each image-receiving sheet was observed just
after cleaning with the adhesive roller, and evaluated by the
following criteria.
[0480] o: Peeling of the image-receiving layer was not
generated.
[0481] .DELTA.: A part of the image-receiving layer was peeled.
[0482] x: The image-receiving layer was peeled off all over the
surface.
[0483] The results of evaluation are shown in Table 5 below.
25 TABLE 5 Peeling of Image Defect due to Image-Receiving Example
No. Foreign Matters Layer Example 1 .largecircle. .smallcircle.
Example 2 .largecircle. .smallcircle. Comparative .largecircle. x
Example 1 Example 3 .DELTA. .DELTA. Comparative X X Example 2
Comparative X X Example 3
[0484] It can be seen from the results of evaluation that the
images obtained according to the present invention are less in
image defects due to foreign matters and the peeling of the
image-receiving layer when the surface of the image-receiving sheet
is subjected to cleaning by the adhesive roller is suppressed. It
is also understood that the crown shape of the adhesive roller for
cleaning and the pressing controlling members provided at both ends
of the roller are effective for preventing the generation of image
defects and peeling of the image-receiving layer.
[0485] Further, when images of four colors formed by transfer were
re-transferred to a printing paper to form a multicolor image, a
multicolor image having excellent image quality and stable transfer
density could be obtained even in the case of high energy laser
recording by multi-beam two dimensional array under different
temperature and humidity conditions.
[0486] In the stage of transfer to the actual paper, the heat
transfer unit having a dynamic friction coefficient against insert
platform of polyethylene terephthalate of from 0.1 to 0.7 and
traveling speed of from 15 to 50 mm/sec was used. The Vickers
hardness of the material of the heat roller of the heat transfer
unit is preferably from 10to 100. Specifically, the heat roller
having Vickers hardness of 70 was used.
[0487] Every image obtained under three different surroundings of
temperature humidity conditions was good.
EFFECT OF THE INVENTION
[0488] The present invention can provide a laser-heat transfer
method capable of producing an image free of image defects due to
the adhesion of foreign matters such as dusts on an image-receiving
sheet. The present invention can provide an adhesive roller for
cleaning capable of cleaning an image-receiving sheet without
peeling an image-receiving layer.
[0489] The present invention can provide contract a proof
corresponding to film-less CTP system and contract proof
substituting analog style color proofs. By this proof, color
reproduction which coincides with printed matters and analog style
color proofs for obtaining the approval of customers can be
realized. The present invention can provide DDCP system by using
the same pigment materials as used in the printing inks, effecting
transfer to actual paper and generating no moire. The present
invention can also provide a large sized high grade DDCP (A2/B2)
capable of transferring to actual paper, capable of using the same
pigment materials as used in the printing inks, and showing high
approximation to printed matters. The system of the present
invention is a system adopting laser membrane transfer, using
pigment coloring materials and capable of transferring to actual
paper by real dot recording. According to the multicolor
image-forming system according to the present invention, even when
laser recording by high energy using multi-beam two dimensional
array under different temperature humidity conditions is performed,
an image having good image quality and stable transfer density can
be formed on the image-receiving sheet.
[0490] The entitle disclosure of each and every foreign patent
application from which the benefit of foreign priority has been
claimed in the present application is incorporated herein by
reference, as if fully set forth herein.
[0491] While the invention has been described in detail and with
reference to specific examples thereof, it will be apparent to one
skilled in the art that various changes and modifications can be
made therein without departing from the spirit and scope
thereof.
* * * * *