U.S. patent application number 10/969784 was filed with the patent office on 2005-06-30 for recording paper.
This patent application is currently assigned to SEIKO EPSON CORPORATION. Invention is credited to Onishi, Hiroyuki, Shibatani, Masaya.
Application Number | 20050139338 10/969784 |
Document ID | / |
Family ID | 34641789 |
Filed Date | 2005-06-30 |
United States Patent
Application |
20050139338 |
Kind Code |
A1 |
Shibatani, Masaya ; et
al. |
June 30, 2005 |
Recording paper
Abstract
The invention relates to a recording paper comprising a sheet
core layer mainly comprising a recycled pulp, and having multiplied
on both sides of said sheet core layer, at least one sheet surface
layer mainly comprising a bleached chemical pulp.
Inventors: |
Shibatani, Masaya; (Nagano,
JP) ; Onishi, Hiroyuki; (Nagano, JP) |
Correspondence
Address: |
LADAS & PARRY
26 WEST 61ST STREET
NEW YORK
NY
10023
US
|
Assignee: |
SEIKO EPSON CORPORATION
|
Family ID: |
34641789 |
Appl. No.: |
10/969784 |
Filed: |
October 20, 2004 |
Current U.S.
Class: |
162/125 ;
162/129; 162/135; 162/147; 162/158; 428/341 |
Current CPC
Class: |
B41M 5/5245 20130101;
D21H 19/36 20130101; D21H 27/30 20130101; B41M 5/5218 20130101;
Y10T 428/273 20150115; B41M 5/52 20130101 |
Class at
Publication: |
162/125 ;
162/129; 162/147; 162/158; 162/135; 428/341 |
International
Class: |
D21H 027/30; D21H
019/36 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 22, 2003 |
JP |
P.2003-362009 |
Claims
What is claimed is:
1. A recording paper comprising a sheet core layer mainly
comprising a recycled pulp, and having multiplied on both sides of
said sheet core layer, at least one sheet surface layer mainly
comprising a bleached chemical pulp.
2. The recording paper according to claim 1, wherein said at least
one sheet surface layer on either one of the both sides has a
thickness that gives a ratio of 0.4 to 4.0 relative to the
thickness of the sheet core layer.
3. The recording paper according to claim 1, wherein said bleached
chemical pulp in said sheet surface layer is one obtained by a
kraft digester process.
4. The recording paper according to claim 1, wherein said bleached
chemical pulp in said sheet surface layer has a whiteness of 85% or
higher.
5. The recording paper according to claim 4, wherein the whiteness
of said bleached chemical pulp is 90% or higher.
6. The recording paper according to claim 1, wherein at least one
of said sheet surface layers further comprises at least one of a
sizing agent and a paper strength-enhancer.
7. The recording paper according to claim 1, further having, on at
least one side thereof, a porous ink-receiving layer containing a
pigment.
8. The recording paper according to claim 7, wherein the pigment
contained in said porous ink-receiving layer comprises at least one
of gas-phase-process silica and an alumina compound.
9. The recording paper according to claim 8, wherein said
gas-phase-process silica has an average primary particle diameter
of 3 to 50 nm.
10. The recording paper according to claim 8, wherein said alumina
compound is alumina hydrate of a tabular shape having an average
aspect ratio of 3 to 8.
11. The recording paper according to claim 8, wherein said alumina
compound is .gamma.-form aluminum oxide ultrafine particles having
an average primary particle diameter of less than 80 nm.
12. The recording paper according to claim 7, wherein said porous
ink-receiving layer contains the pigment in an amount of 40 to 90%
by weight based on the total weight of solid matter therein.
13. The recording paper according to claim 7, wherein said porous
ink-receiving layer further comprises a binder in an amount of 2 to
50% by weight based on the weight of said pigment.
14. The recording paper according to claim 7, wherein said porous
ink-receiving layer further comprises a cationic substance.
15. The recording paper according to claim 14, wherein said
cationic substance is a polymer having a quaternary ammonium salt
group.
16. The recording paper according to claim 14, wherein said porous
ink-receiving layer contains said cationic substance in an amount
of 0.5 to 15% by weight based on the total weight of solid matter
therein.
17. The recording paper according to claim 7, wherein said porous
ink-receiving layer has a coating amount of 10 to 40 g/m.sup.2 in
terms of solid matter.
18. The recording paper according to claim 1, further having, on at
least one side thereof, an ink-receiving layer containing a
water-soluble resin as a main component.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a recording paper suitable
for various recording processes such as an ink-jet process. More
specifically, the invention relates to a global
environment-friendly recording paper using a recycled pulp.
BACKGROUND OF THE INVENTION
[0002] The methods for recording letters and images include various
printing processes such as an ink-jet process, an
electrophotographic process, and a melt-transfer process. As
recording papers, paper is mainly used from the viewpoints of
usability and cost.
[0003] Hitherto, paper for use as the recording papers is desirably
one obtained using as a raw material a virgin pulp which is
produced from cut-down trees from tree plantation and natural
forest. However, in recent years, based on social demands for
environmental protection and garbage reduction, it is strongly
desired to promote use of recycled pulps using recycled waste paper
as the raw material, and thus recycled pulps have been utilized for
the recording papers.
[0004] As a recording paper using a recycled pulp, there is an
ink-jet recording paper comprising a white pigment layer on the
surface of a base paper, wherein a recycled pulp using recycled
waste paper as the raw material and/or a grind pulp is used in the
base paper in an amount of 10% by weight or more based on the
weight of the whole pulp of the base paper (see Patent Document 1).
Further, there is an ink-jet recording paper comprising a base
paper having provided thereon an ink-receiving coated layer
containing a porous pigment and a binder, wherein the base paper
contains a recycled pulp obtained from recycled waste paper and
contains at least one filler selected from zeolite, silica, and
calcined kaolin in an amount of 1 to 30% by weight based on the
weight of the whole pulp, and Stockigt sizing degree (JIS-P8122) of
the recording paper is 40 seconds or less (see Patent Document
2).
[0005] Patent Document 1: JP 10-278416 A
[0006] Patent Document 2: JP 2001-171223 A
[0007] As recycled waste paper for use as the raw material of
recycled pulps, old newspaper, old magazine, office waste paper,
and the like are used. Of these, since a mechanical pulp having a
large lignin content is blended in old newspaper and old magazine
in a high ratio, there is a problem that a recycled pulp using
these as raw materials is apt to induce so-called yellowing with
time, i.e., color change into yellow with the passage of time.
Therefore, as a recycled pulp to be used for a recording paper, one
would like to use recycled waste paper having a small lignin
content, such as office waste paper, and avoid a mechanical pulp as
far as possible. However, at present, it is difficult to completely
prevent contamination of a mechanical pulp under the present
situation of waste paper recycling. In the case that a recycled
pulp is used as the raw material for a recording paper, it is
important how to overcome the problem of yellowing with time.
Further, since a recycled pulp is subjected to extra processes such
as a deinking step and a bleaching step and hence keratinization of
the fibers tends to proceed, so that there are also problems of
weak mechanical strength and deterioration of texture when the pulp
is converted into sheets.
[0008] As above, a recycled pulp has defects such as easy yellowing
with time and insufficient mechanical strength when it is converted
into sheets. Therefore; paper produced by simply blending the
recycled pulp has a problem especially in storability, and hence is
unsuitable for important documents and as silver salt photograph
substitutes where a long-term storage is desired. In addition, even
when a coated layer such as a white-pigment layer or an
ink-receiving coated layer is provided on a base paper containing
the recycled pulp as in the above-mentioned ink-jet recording
paper, the storability of the base paper itself is not improved, so
that a satisfactory recording quality cannot be maintained for a
long period of time even though such a quality is maintained for a
while after image recording.
SUMMARY OF THE INVENTION
[0009] Accordingly, an object of the invention is to provide a
recording paper which satisfies social demands such as
environmental protection and garbage reduction by using a recycled
pulp and is capable of a long-term storage with hardly inducing
yellowing with time and degradation with time.
[0010] Other objects and effects of the invention will become
apparent from the following description.
[0011] The above-described objects of the invention have been
achieved by providing a recording paper comprising a sheet core
layer mainly comprising a recycled pulp, and having multiplied on
both sides of said sheet core layer, at least one sheet surface
layer mainly comprising a bleached chemical pulp.
[0012] Since the recording paper of the invention has a
constitution that the sheet core layer mainly comprising a recycled
pulp is sandwiched between the sheet surface layers mainly
comprising a bleached chemical pulp, the problems of yellowing with
time and degradation with time, which are concerns for a sheet core
layer, are solved in the recording paper as a whole, and thus the
recording paper can be used with security even in a recording
application where a long-term storage is desired. Namely, the
recording paper of the invention is a global environment-friendly
recording paper which achieves both of global environment
protection and storability, which had been difficult with
conventional recording papers using a recycled pulp.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The recording paper of the invention is described in detail
below.
[0014] The recording paper of the invention is a sheet-shape
product obtained by multiplying one or more sheet surface layers on
each of both sides of a sheet core layer.
[0015] The sheet core layer is a paper layer mainly comprising a
recycled pulp. In the invention, the recycled pulp means a
paper-making material obtained by subjecting recycled waste paper
to maceration. As the recycled waste paper, office waste paper, old
newspaper, old magazine, advertising leaflet, and the like can be
used. The recycled waste paper are not particularly limited but
preferred are waste paper mainly comprising a chemical pulp. The
larger content of a chemical pulp in the waste paper is more
preferable. Such waste paper is suitable as a material for the
recycled pulp according to the invention since it is resistant to
yellowing with time and degradation with time owing to high
cellulose purity, i.e., low lignin content. In general, most of
office paper mainly comprises a chemical pulp and hence office
waste paper, i.e., waste paper thereof can be suitably used in the
invention.
[0016] Further, a recycled pulp is generally obtained though a
maceration step where waste paper is macerated with water to obtain
a pulp suspension, a rough selection/fine selection step where
foreign matter in the pulp suspension is separated, a deinking step
wherein printing ink is separated, and a bleaching step using ozone
or the like. In the invention, however, not only the recycled pulp
obtainable by these respective steps but also a recycled pulp
obtained without subjecting to the deinking treatment or bleaching
treatment or a recycled pulp obtained without subjecting to the
deinking treatment and bleaching treatment may be used.
[0017] The blending amount of the recycled pulp is preferably 50%
by weight or more based on the weight of the whole pulp in the
sheet core layer.
[0018] As other pulps capable of blending with the recycled pulp in
the sheet core layer, a mechanical pulp may be used, but preferred
is a bleached chemical pulp. As the bleached chemical pulp, those
for use in the sheet surface layer described below can be
employed.
[0019] As components other than pulps, if necessary, various
additives such as dispersion aid for a pulp slurry, a dry
paper-strength enhancer, a wet paper-strength enhancer, a filler, a
sizing agent, a fixing agent, a pH regulator, a dye, a colored
pigment, and a fluorescent whitening agent may be added to the
sheet core layer.
[0020] Examples of the dispersion aid include polyethylene oxide,
polyacrylamide, and Hibiscus manihot L. Examples of the
paper-strength enhancer include anionic paper-strength enhancers
such as vegetable gum, starch, and carboxy-modified polyvinyl
alcohol and cationic paper-strength enhancers such as cationized
starch, cationized polyacrylamide, and polyamidepolyamine
epichlorohydrin resins. Examples of the filler include clay,
kaolin, talc, heavy calcium carbonate, precipitated calcium
carbonate, barium sulfate, titanium oxide, aluminum hydroxide, and
magnesium hydroxide. Examples of the sizing agent include higher
fatty acid salts, rosin, rosin derivatives such as maleylated
rosin, dialkyl ketene dimers, alkenyl- or alkyl-succinic acid
salts, epoxydized fatty acid amides, and polysaccharide esters.
Examples of the fixing agent include polyvalent metal salts such as
aluminum sulfate and aluminum chloride, cationic polymers such as
cationized starch and polyamidepolyamine epichlorohydrin resins.
Examples of the pH regulator include hydrochloric acid, caustic
soda, and sodium carbonate.
[0021] On the other hand, the sheet surface layer to be multiplied
on each of both sides of the above sheet core layer is a paper
layer mainly comprising a bleached chemical pulp. In the invention,
the bleached chemical pulp means one obtained by bleaching, using
any of various bleaching agents such as chlorine-based chemicals,
hydrogen peroxide, enzymes and ozone, an unbleached virgin pulp
obtained by a digester process such as a kraft digester process, a
polysulfide digester process, or a sulfite digester process each
starting with broad-leaved wood or coniferous wood. Various methods
are known for the digesting treatment and bleaching treatment,
respectively but the treating methods are not particularly limited
in the invention.
[0022] As the raw material for the bleached chemical pulp, wood
fibers from coniferous tree and broad-leaved tree are generally
used but grass fibers from straw, esparto, bagasse and kenaf, bast
fibers from hemp, paper mulberry, clove-like bush and mitumata
(Edgeworthia papyrifera), and cotton can be also employed. A
mixture of two or more thereof may be also used. The pulp which
receives forest standard council from FSC (Forest Stewardship
Council) or PEFC (Pan European Forest Certification) meets global
environment protection that is a purpose of the invention and hence
is preferably used.
[0023] Preferred as the bleached chemical pulp is a bleached
chemical pulp obtained by a kraft digester process (kraft pulp).
The kraft pulp is excellent in not only productivity and mechanical
strength of sheets but also efficient utilization of resources due
to a high pulp yield from starting wood as compared with pulps
obtained by other digester processes, so that the kraft pulp
satisfies the purpose of the invention, i.e., global environment
protection. Examples of the kraft pulp include a coniferous tree
bleached kraft pulp (NBKP) and a broad-leaved tree bleached kraft
pulp (LBKP). More preferred is a kraft pulp subjected to a
bleaching method (so-called ECF bleaching) in which the bleaching
treatment after kraft digesting does not use elemental chlorine as
used in chlorine bleaching or hypochlorite bleaching, which
discharges organic chlorinated substances.
[0024] As the recording papers, those having a high degree of
whiteness are preferred. From such a point of view, the bleached
chemical pulp preferably has an ISO whiteness defined by JIS-P8148
of 85% or more, more preferably 90% or more. There is a correlation
between whiteness and degree of delignification of a pulp. In
general, the higher the degree of delignification is, the higher
the degree of whiteness is and the more excellent the stability of
whiteness is, so that the pulp is resistant to yellowing with time.
The degree of delignification of a pulp can be evaluated using
chlorine consumption defined by IS03260-1982 or a hypo value
defined by TAPPI T253. The larger these values are, the larger the
lignin content remaining in the pulp is. The degree of
delignification can be adjusted by suitably controlling the
treating conditions of digesting and bleaching in the pulp
production process.
[0025] The bleached chemical pulp is blended in the sheet surface
layer preferably in a large amount as far as possible from the
viewpoint of enhancing suitability for recording papers. It is
desired that the whole pulp in the sheet surface layer comprises
the bleached chemical pulp.
[0026] To the sheet surface layer, as components other than pulps,
various additives such as dispersion aid for a pulp slurry, a dry
paper-strength enhancer, a wet paper-strength enhancer, a filler, a
sizing agent, a fixing agent, a pH regulator, a dye, a colored
pigment, and a fluorescent whitening agent may be added, if
necessary. As these additives, those which can be used in the sheet
core layer can be employed.
[0027] The recording paper of the invention comprising the sheet
core layer and the sheet surface layer can be produced by carrying
out paper-making of the respective layers together using a cylinder
paper-making machine. The above-mentioned individual pulps are
usually beaten by a beating machine such as double disc refiner in
order to improve paper-making suitability and various properties of
paper, such as strength, smoothness and uniformity of texture. The
degree of beating is not particularly limited and may be selected
from the range of about 100 to 600 ml in terms of Canadian Standard
Freeness (CSF) according to the intended purposes.
[0028] With regard to the ratio in thickness of the sheet surface
layer (multiplied to either one surface of the sheet core layer) to
the sheet core layer, it is preferably in the range of 0.4 to 4.0.
When the thickness of the sheet surface layer is less than 0.5
relative to the thickness of the sheet core layer, the disadvantage
of the sheet core layer, i.e., storability (aptness to induce
yellowing with time and degradation with time) can be not
sufficiently compensated. When the relative thickness exceeds 4.0,
the blending rate of the recycled pulp decreases in the recording
paper as a whole and thus it is impossible to sufficiently
contribute environmental protection.
[0029] In this connection, the thickness of the sheet surface layer
on one side of the sheet core layer is usually made the same as the
thickness of the sheet surface layer on the other said of the sheet
core layer, but they may be different from each other. Further, it
is sufficient that at least one sheet surface layer is multiplied
on each of both sides of the sheet core layer. One side or both
sides of the sheet core layer may be covered with a sheet surface
layer having a multilayer structure containing two or more layers.
Further, the number of the sheet surface layer may be different
between one side and the other side of the sheet core layer.
[0030] The surface pH of the recording surface of the recording
paper of the invention is preferably 6.5 or higher. When the
surface pH of the recording paper is less than 6.5, there is a
possibility that an acid hydrolysis reaction proceeds with time to
invite decrease of mechanical strength and yellowing. The surface
pH herein is measured in accordance with Method A (a coating
method) of the surface pH test method of paper and paper board
defined by Japan Technical Association of the Pulp and Paper
Industry [J. TAPPI No. 6], and means surface pH (paper face-pH)
determined by adding dropwise an indicator for pH measurement to an
objective surface to be measured, spreading the indicator with
defatted cotton thinly and rapidly, and subsequently comparing the
hue of the objective surface to be measured with the hues described
in pH Standard Color-change Table at the time point when 10 seconds
have passed from the dropwise addition of the indicator for pH
measurement. Examples of methods for adjusting the surface pH of
the recording paper to be 6.5 or higher include a method of making
the sheet core layer and sheet surface layer (especially sheet
surface layer) by a so-called neutral paper-making process, a
method of applying an appropriate alkali agent onto the recording
paper, and the like.
[0031] Further, the recording paper of the invention preferably has
a good surface smoothness. Beck's smoothness measured in accordance
with JIS-P8119 is preferably 50 seconds or more, more preferably
100 seconds or more. The smoothness can be adjusted by compressing
the recording paper through applying pressure using a calendar or
the like during or after making the recording paper.
[0032] The recording paper of the invention can be suitably used
for various recording processes, such as an ink-jet recording
process, an offset printing process, a gravure printing process, a
sublimation-transfer process, melt-transfer process, and an
electrostatic toner-recording process, as well as handwriting. In
particular, the recording paper can be suitably used in recording
applications where a long-term storage is desired, e.g., printing
of important documents and as ink-jet photo papers which are
expected to give an output of photo-grade quality.
[0033] In general, the recording paper for ink-jet recording is
required to have a high ink absorbability with respect to an
aqueous ink is required. Therefore, as the recording paper for
ink-jet recording, an ink-receiving layer is preferably multiplied
on at least one side of the above recording paper. The
ink-receiving layer is described in detail below.
[0034] As one example of the ink-receiving layer applicable to the
invention, a porous ink-receiving layer containing a pigment as an
essential component may be mentioned. The ink-receiving layer has
numerous pores on the surface and thus is also called void-type one
or the like.
[0035] Examples of the pigment suitable as an ink-receiving layer
component include inorganic pigments such as precipitated calcium
carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate,
barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc
carbonate, satin white, aluminum silicate, diatomaceous earth,
calcium silicate, magnesium silicate, synthetic amorphous silica,
colloidal silica, colloidal alumina, pseudo boehmite, aluminum
hydroxide, alumina, lithopone, zeolite, hydrated halocite,
magnesium carbonate and magnesium hydroxide, and organic pigments
such as styrene-based plastic pigments, acrylic plastic pigments,
polyethylene, urea resins, and melamine resins. In the invention,
one of them may be used singly, or two or more thereof may be used
in combination.
[0036] Particularly, vapor-phase-process silica, alumina compounds
(alumina hydrate, aluminum oxide ultrafine particles) are
preferably used in the invention.
[0037] The vapor-phase-process silica for use in the invention is
preferably in the form of ultrafine particles having an average
primary particle diameter of 3 to 50 nm. Particularly preferred
average primary particle diameter is from 5 to 30 nm. The secondary
particle diameter formed by conjunction thereof is preferably from
10 to 200 nm, but the form thereof in the coated layer is not
certain and the size of secondary particles are not so important.
With regard to the amorphous silica fine particles synthesized by a
vapor phase process, examples of commercially available products
include Aerosil (Degussa AG).
[0038] The alumina hydrate for use in the invention can be
represented by the general formula Al.sub.2O.sub.3.nH.sub.2O.
Alumina hydrate is classified into gypsite, bialite, norstrandite,
boehmite, boehmite gel (pseudo boehmite), diaspore, amorphous one,
and the like according to difference in composition and crystal
form. Of these, the case that the value of n in the above formula
is 1 represents alumina hydrate having a boehmite structure, the
case that n is larger than 1 and less than 3 represents alumina
hydrate having a pseudo boehmite structure, and the case that n is
3 or more represents alumina hydrate having an amorphous structure.
In particular, preferable alumina hydrate in the invention is
alumina hydrate having a pseudo boehmite structure where n is
larger than 1 and less than 3. Further, the shape of alumina
hydrate may be any of tabular shape, fiber shape, needle shape,
spherical shape, rod shape, etc., and preferable shape in view of
ink absorbability is tabular shape. The tabular-shape alumina
hydrate has an average aspect ratio of 3 to 8, preferably an
average aspect ratio of 3 to 6. The aspect ratio is represented by
the ratio of "diameter" to "thickness" of a particle. The diameter
of the particle herein means a diameter of a circle having an area
equal to the projected area of the particle when the alumina
hydrate is observed under an electron microscope. When the aspect
ratio is smaller than the above range, the pore distribution in the
ink-receiving layer becomes narrow and ink absorbability decreases.
On the other hand, when the aspect ratio exceeds the above range,
it becomes difficult to produce an alumina hydrate of uniform
particles.
[0039] As the alumina hydrate, commercially available products can
also be suitably employed. Examples thereof include Cataloid AS-1,
Cataloid AS-2, Cataloid AS-3 (they are manufactured by Catalysts
& Chemicals Ind. Co., Ltd.), Alumina Sol 100, Alumina Sol 200,
Alumina Sol 520 (they are manufactured by Nissan Chemical
Industries, Ltd.), M-200 (it is manufactured by Mizusawa Industrial
Chemicals, Ltd.), and Alumi Sol 10, Alumi Sol 20, Alumi Sol 132,
Alumi Sol 132S, Alumi Sol SH5, Alumi Sol CSA55, Alumi Sol SV102,
Alumi Sol SB52 (they are manufactured by Kawaken Fine Chemicals
Co., Ltd.).
[0040] As the aluminum oxide ultrafine particles for use in the
invention, .gamma.-form aluminum oxide fine particles that are
.gamma.-form crystals are preferably employed.
Crystallographically, the .gamma.-form crystals are further
classified into .gamma.-group and .delta.-group. Fine particles
having a crystal form of .delta.-group are preferred. Further, the
.gamma.-form aluminum oxide fine particles preferably have an
average particle diameter of primary particles of less than 80 nm.
When secondary particles composed of primary particles having an
average particle diameter of 80 nm or more are used, brittleness
increases and defects on the coated film markedly tend to occur.
Examples of commercially available .gamma.-type aluminum oxide fine
particles include aluminum oxide C (manufactured by Japan Aerosil)
belonging to the 6-group, AKP-G015 (manufactured by Sumitomo
Chemical Co., Ltd.) belonging to the .gamma.-group, and the
like.
[0041] The content of the foregoing pigment is preferably in the
range of 40 to 90% by weight based on the total weight of solid
matter in the ink-receiving layer. When the content is less than
40% by weight, there is a possibility of decrease in ink
absorbability. When the content exceeds 90% by weight, there is a
possibility of decrease in coated film strength of the
ink-receiving layer.
[0042] Into the ink-receiving layer, as a binder for the pigment, a
polymer compound having an affinity to an ink can be incorporated.
Examples of such a polymer compound include polyvinyl alcohol,
silanol-modified polyvinyl alcohol, polyvinyl acetate, starch,
cellulose derivatives such as carboxymethyl cellulose, casein,
gelatin, latexes of conjugated diene copolymers such as
styrene-butadiene copolymers, latexes of vinyl copolymers such as
ethylene-vinyl acetate copolymers, latexes of acrylic copolymers
such as polymers of acrylic acid and methacrylic acid,
vinylpyrolidone/vinyl acetate copolymers, and acetal resins such as
polyvinylbutyral and polyvinylformal. One of them may be used
singly, or two or more thereof may be used in combination.
Particularly, use of polyvinyl alcohol is preferred. The content of
the polymer compound (binder) is preferably from 2 to 50% by weight
relative to the weight of the pigment. The content of the polymer
compound less than 2% by weight relative to the pigment weight may
invite insufficient strength of the coated film. To the contrary,
when the content exceeds 50% by weight, there is a possibility of
decrease in ink absorbability.
[0043] Into the ink-receiving layer, in addition to the pigment and
polymer compound (binder), a pigment dispersant, a thickening
agent, a flow improver, a viscosity stabilizer, a pH regulator, a
surfactant, a deforming agent, a form inhibitor, a releasing agent,
a foaming agent, a penetrant, a fluorescent whitening agent, a UV
absorber, an antioxidant, a leveling agent, an antiseptic, an
antifungal agent, a water-resisting agent, a wet paper-strength
enhancer, a dry paper strength enhancer, and the like can be
suitably incorporated.
[0044] Further, into the ink-receiving layer, for the purpose of
further enhancing color-developing property and water resistance of
recorded images, a cationic substance can be incorporated. Examples
of the cationic substance include low-molecular-weight compounds
such as primary to secondary amine compounds, primary to tertiary
amine salts, and quaternary ammonium salts, oligomers having a
primary to secondary amino group, a primary to tertiary amine salt
group, and a quaternary ammonium salt group, and polymers having
one of these groups, and specifically include cationic organic
substances such as diallyldimethylammonium chloride polymers,
epihalohydrin-secondary amine copolymers, diallyldimethylammonium
chloride-sulfur dioxide copolymers, diallyldimethylammonium
chloride-acrylamide copolymers, diallylmethylammonium salt
polymers, diallylamine hydrochloride salt-sulfur dioxide
copolymers, dimethylmethylamine hydrochloride salt copolymers,
polyallylamine, polyethyleneimine, polyethyleneimine quaternary
ammonium salt compounds, (meth)acrylamide alkylammonium salt
polymers, and ionenes containing a quaternary ammonium salt group.
In addition, multivalent metal ions such as Al.sup.3+, Ca.sup.2+,
and Mg.sup.2+ and cationic surfactants such as benzalkonium
chloride can be also used as the above cationic substances.
Preferred are polymers having a quaternary ammonium salt group.
[0045] The content of the cationic substance is preferably in the
range of 0.5 to 15% by weight based on the total weight of solid
matter in the ink-receiving layer. When the content of the cationic
substance is less than 0.5% by weight, an improving effect of
color-developing property and water resistance is poor. When the
content exceeds 15% by weight, there is a possibility that
deterioration in ink absorbability and too high glossiness
(so-called bronzing) induced by precipitation of an ink color
material occurs, which may contrarily deteriorate image
quality.
[0046] The ink-receiving layer can be multiplied on the sheet
surface layer using a known coating method. For example, the
ink-receiving layer can be formed by applying a coating liquid for
the ink-receiving layer containing the above respective components
on the sheet surface layer using one of various coating instruments
such as an air-knife coater, a curtain coater, a slid lip coater, a
die coater, a blade coater, a gate roll coater, a bar coater, a rod
coater, a roll coater, a bill blade coater, a short dowel blade
coater, and a size press, followed by drying. The constitution of
the ink-receiving layer may be a monolayer structure or may be a
multilayer structure having two or more layers.
[0047] The coating amount of the ink-receiving layer is not
particularly limited but is preferably from 10 to 40 g/m.sup.2,
more preferably from 20 to 30 g/m.sup.2 in terms of solid matter.
When the coating amount is less than 10 g/m.sup.2, the improving
effect of the ink-jet suitability is poor. When the amount exceeds
40 g/m.sup.2, there is a possibility of generation of powder
dropping and also the effect is saturated, so that the case is
inferior in economical efficiency. Incidentally, the thickness is
preferably from 10 to 40 .mu.m, more preferably from 20 to 30
.mu.m.
[0048] The so-called void-type ink-receiving layer as described
above can be adjusted to have any surface texture, e.g., delustered
tone (mat tone) where glossiness is subtly adjusted, semi-glossy
tone (luster tone), and highly glossy tone where glossiness is
excellent. As a method for enhancing gloss, a method for smoothing
the coated ink-receiving layer by calendering treatment may be
mentioned. Equipments for the calendering treatment at that time
include a gloss calender, a super calender, a soft calender, and
the like. In particular, heat calendering treatment where smoothing
is carried out under heating is preferably employed. Also, the
gloss of the coated ink-receiving layer can be enhanced by a
so-called casting method where the surface of the coated
ink-receiving layer is transcribed to a mirror plane of a metal, a
film, or the like.
[0049] Further, as another example of the ink-receiving layer
applicable to the invention, a so-called swelling ink-receiving
layer containing a water-soluble resin as a main component may be
mentioned. The water-soluble resins include polyvinyl alcohol,
polyvinyl pyrrolidone, acrylic resins, cellulose modified resins,
gelatin, and the like. One of these water-soluble resins may be
used singly, or two or more thereof may be used in combination.
Into the swelling ink-receiving layer, as components other than the
water-soluble resin, various agents usable for the aforementioned
void-type ink-receiving layer may be incorporated.
EXAMPLES
[0050] The present invention will be illustrated in greater detail
with reference to the following Examples, but the invention should
not be construed as being limited thereto.
Example 1
[0051] Preparation of Slurry for Sheet Core Layer
[0052] Used office paper made of a bleached chemical pulp was
subjected to deinking treatment to obtain a recycled pulp having
ISO whiteness of 80%. Then, a 1:1 mixture of the recycled pulp and
a bleached chemical pulp (LBKP, ISO whiteness of 90%) was beaten
until it reached a value of 300 ml as Canadian Standard Freeness,
whereby a pulp slurry was prepared. To the pulp slurry were added,
as a sizing agent, 0.5% by weight of an alkylketene dimer based on
the pulp weight and, as a paper strength-enhancer, 1.0% by weight
of polyacrylamide based on the pulp weight, 2.0% by weight of
cationized starch based on the pulp weight and 0.5% by weight of a
polyamide epichlorohydrin resin based on the pulp weight, followed
by dilution with water to form a 1% slurry.
[0053] Preparation of Slurry for Sheet Surface Layer
[0054] A 1:1 mixture of LBKP and NBKP (both having ISO whiteness of
90%) was beaten until it reached a value of 300 ml as Canadian
Standard Freeness, whereby a pulp slurry was prepared. To the pulp
slurry were added, as a sizing agent, 0.5% by weight of an
alkylketene dimer based on the pulp weight and, as a paper
strength-enhancer, 1.0% by weight of polyacrylamide based on the
pulp weight, 2.0% by weight of cationized starch based on the pulp
weight and 0.5% by weight of a polyamide epichlorohydrin resin
based on the pulp weight, followed by dilution with water to form a
1% slurry.
[0055] Using the slurry for a sheet core layer and the slurry for a
sheet surface layer, a recording paper (basis weight of 84
g/m.sup.2, waste paper blending rate of 20%) having a three-layer
structure, in which a sheet surface layer having a basis weight of
20 g/m.sup.2 is multiplied on each of both sides of a sheet core
layer having a basis weight of 44 g/m.sup.2, was made by a cylinder
paper-making machine. This paper was used as the sample of Example
1. The recording surface of the recording paper had a surface pH of
6.7.
Example 2
[0056] Composition of Coating Liquid 1 for Ink-Receiving Layer
[0057] An aqueous solution containing vapor-phase-process silica
and SHALLOL DC902P was dispersed by a high-pressure homogenizer,
and polyvinyl alcohol etc. were added thereto to prepare a coating
liquid 1 for an ink-receiving layer having the following
composition.
1 Vapor-phase-process silica 100 parts by (average primary particle
diameter of 7 nm, weight specific surface area by BET method of 300
m.sup.2/g) Polyvinyl alcohol 25 parts by (trade name: PVA 235,
manufactured by weight Kuraray Co., Ltd.) Methyldiallylammonium
chloride 3 parts by polycondensate weight (trade name: SHALLOL
DC902P, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Amphoteric
surfactant 0.3 parts by (trade name: SWAM AM-2150, Nihon weight
Surfactant Kogyo K. K.)
[0058] The above coating liquid 1 for an ink-receiving layer was
uniformly applied to one side of a recording paper having the same
constitution as the sample of Example 1 using a wire bar, and then
dried by a drier to form an ink-receiving layer having a thickness
of 40 .mu.m (coated amount of 25 g/cm.sup.2). A recording paper for
ink-jet recording thus manufactured is used as the sample of
Example 2. The recording surface of the recording paper had a
surface pH of 6.6.
Example 3
[0059] A recording paper for ink-jet recording was manufactured in
the same manner as in Example 2, except that a coating liquid 2 for
an ink-receiving layer having the below-shown composition was used
instead of the coating liquid 1 for an ink-receiving layer in
Example 2. The recording paper was used as the sample of Example 3.
The recording surface of the recording paper had a surface pH of
6.7.
2 Composition of coating liquid 2 for ink-receiving layer Silica
gel 100 parts by (trade name: Finesil X37B, manufactured weight by
Tokuyama Corp.) Polyvinyl alcohol 16 parts by (trade name: PVA 117,
manufactured by weight Kuraray Co., Ltd.) Cationic substance (ink
fixing agent) 5 parts by (trade name: Sumirase Resin 1001, weight
manufactured by Sumitomo Chemical Co., Ltd.) Ammonia water 0.1
parts by weight
Comparative Example 1
[0060] A recording paper having a waste paper-blending rate of 20%
(trade name: Hyperpirenu Tough, manufactured by Nippon Paper
Industries Co., Ltd., basis weight of 84.3 g/m.sup.2) is used as it
is as the sample of Comparative Example 1. The recording surface of
the recording paper had a surface pH of 6.5.
Comparative Example 2
[0061] A recording paper for ink-jet recording was manufactured in
the same manner as in Example 2, except that in the constitution of
Example 2 the above-mentioned Hyperpirenu Tough was used instead of
the recording paper having the same constitution as the sample of
Example 1. The recording paper thus prepared was used as the sample
of Comparative Example 2. The recording surface of the recording
paper had a surface pH of 4.2.
Comparative Example 3
[0062] A recording paper for ink-jet recording was manufactured in
the same manner as in Example 3, except that in the constitution of
Example 3 the above-mentioned Hyperpirenu Tough was used instead of
the recording paper having the same constitution as the sample of
Example 1. The recording paper thus prepared was used as the sample
of Comparative Example 3. The recording surface of the recording
paper had a surface pH of 5.5.
Test Example
[0063] On the above respective examples, bleeding, whiteness,
yellowing resistance, and heat degradation resistance were
evaluated according to the following methods. The evaluation
results thereof were shown in the following Table 1.
[0064] Method for Evaluation of Bleeding
[0065] Using an ink-jet printer (PM-4000PX, manufactured by Seiko
Epson Corp.), color patches of respective colors having OD (optical
density) of 1 were printed on the recording surface of each of the
above samples using aqueous pigment inks of four colors of cyan
(C), magenta (M), yellow (Y), and black (K). Then, the area where
the color patches of Y and C are adjoining (i.e., a portion where
decrease of image quality can be most easily recognized) was
visually observed immediately after printing. Cases where no color
mixing was observed were ranked as A, cases where color mixing was
slightly observed but was not problematic from a practical
standpoint were ranked as B, and cases where color mixing was
observed to such an extent that color boundary was unclear were
ranked as C.
[0066] Method for Evaluation of Whiteness
[0067] On the recording surface of each of the above samples, ISO
whiteness was measured in accordance with JIS-P8148. Samples having
a measured value of 90% or more were ranked as A (good for
recording papers), samples having a measured value of 85% or more
to less than 90% were ranked B (no problem from a practical
standpoint), and samples having a measured value of less than 85%
were ranked as C (impossible to use practically)
[0068] Method for Evaluation of Yellowing Resistance
[0069] Each of the above samples was left on standing in a
constant-temperature and constant-humidity chamber set at the
temperature of 80.degree. C. and the relative humidity of 50% RH
for 1 week. Then, .DELTA.E on the recording surface of each sample
between before and after standing was measured in accordance with
L*a*b* (CIE 1976) using a color-difference meter (Spectrolino,
manufactured by Gretag Macbeth). Samples having .DELTA.E of 4 or
less were ranked as A (good yellowing resistance), samples having
.DELTA.E in the range of more than 4 to less than 8 were ranked as
B (no problem from a practical standpoint), and samples having AE
of 8 or more were ranked as C (impossible to use practically).
[0070] Method for Evaluation of Heat Degradation Resistance
[0071] Each of the above samples was left on standing in a
constant-temperature and constant-humidity chamber set at the
temperature of 80.degree. C. and the relative humidity of 65% RH
for 2 weeks. Then, on each sample after standing, tear strength was
measured in accordance with Elmendorff JIS-P8116 and the ratio (%)
thereof to the tear strength of each sample before standing which
had been measured beforehand [(tear strength of sample after
standing/tear strength of sample before standing).times.100] was
determined. Samples having a value of 80% or more were ranked as A
(good heat degradation resistance), samples having a value in the
range of more than 50% to less than 80% were ranked as B (no
problem from a practical standpoint), and samples having a value of
50% or less were ranked as C (impossible to use practically).
3 TABLE 1 Ratio of thickness Core Heat layer:Surface Bleed- White-
Yellowing degradation layer ing ness resistance resistance Example
1 1:1 B A A A Example 2 1:1 A A A B Example 3 1:1 A A A A
Comparative -- B B C C Example 1 Comparative -- A A C C Example 2
Comparative -- A A C C Example 3
[0072] While the present invention has been described in detail and
with reference to specific embodiments 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.
[0073] The present application is based on Japanese patent
application 2003-362009 filed Oct. 22, 2003, the contents thereof
being herein incorporated by reference.
* * * * *