JPH1178217A - Ink jet recording paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide ink jet recording paper of high image quality high in ink absorbability and glossiness, capable of obtaining a sharp image, generating no undulation in a printing part and capable of being produced in low cost. SOLUTION: Ink jet recording paper is obtained by providing a void layer having a dry film thickness of 5-20 μm and containing fine particles with an average particle size of 100 nm or less, a hydrophilic binder and a cationic polymer mordant on a water absorbable support with a thickness of 160 μm or more as an ink absorbing layer and the wt. ratio of the cationic mordant is 0.5 times or more that of the hydrophilic binder. This void layer pref. contains polyvinyl alcohol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink-jet recording sheet for recording using an aqueous ink, and more particularly to an ink-jet recording sheet which can be manufactured at low cost and has a high image quality and a photographic texture.

[0002]

2. Description of the Related Art Ink-jet recording is a method in which fine droplets of ink are caused to fly according to various operating principles and adhere to a recording sheet such as paper to record images and characters. It has advantages such as easy noise and multicoloring. With regard to nozzle clogging and maintenance, which has been a problem in the past, improvements have been made in both ink and equipment, and are now rapidly spreading in various fields such as various printers, facsimile machines, and computer terminals. .

The details are described, for example, in the trend of ink jet recording technology (Koichi Nakamura, edited by Nippon Kagaku Kogyo Co., Ltd., March 31, 1995).

The recording paper used in this ink jet recording method has a high density of print dots, a bright and vivid color tone, and the ink absorbs quickly so that even if the print dots overlap, the ink may flow out. It is generally required that the ink does not bleed, that the diffusion of print dots in the horizontal direction is not unnecessarily large, and that the periphery is smooth and not blurred.

Conventionally, various recording papers have been used as ink jet recording paper. For example, plain paper, various coated papers (art paper, coated paper, cast coated paper, etc.) in which a layer composed of a hydrophilic binder and an inorganic pigment is coated on a paper support, and further, these papers, transparent or opaque Recording paper in which an ink-absorbing layer is coated as a recording layer on various plastic film supports or various supports in which paper is coated on both sides with a plastic resin is used.

The ink absorbing layer is roughly classified into a so-called swellable ink absorbing layer mainly composed of a hydrophilic binder and a void type ink absorbing layer having a void layer in a recording layer.

The advantage of the swellable ink absorbing layer is that very high gloss and high maximum density can be obtained after the ink solvent (water and high boiling point organic solvent) is completely evaporated. The speed is slower than that of the gap type recording paper described later, and there is a problem that image quality is easily deteriorated due to occurrence of graininess due to occurrence of beading or the like in a high ink region, and furthermore, evaporation of an ink solvent, particularly a high boiling point organic solvent, is extremely slow. For this reason, there is a problem that the high-boiling organic solvent remains in the hydrophilic binder for a while after printing, and the hydrophilic binder is swelled and is left in a wet state for a long time.

[0008] Specifically, there are situations in which it is not possible to rub the printed surface strongly or overlap paper or the like for several hours, sometimes several days after printing.

On the other hand, the void-type ink-absorbing layer exhibits high ink-absorbing properties due to the presence of voids in the recording layer. For this reason, beading of the image in the high ink region is less likely to occur than in the swelling type, and the image quality is less deteriorated in the high density region.

Also, if the void-type ink-absorbing layer has a sufficient void volume with respect to the ink amount, at least the surface is apparently dry immediately after printing even if the organic solvent remains in the void structure. , And it is possible to touch the surface or overlap prints.

As this type of ink-absorbing layer, fine particles having a low refractive index (especially a refractive index of about 1.6 or less are preferable) and a small particle diameter are preferable because a layer having relatively high transparency is formed. Particularly preferably 200 nm or less) is preferably used. Among them, silica fine particles satisfying the above conditions efficiently form voids, and furthermore, relatively high gloss can be obtained,
It is particularly preferably used because an image having a high maximum density can be obtained.

[0012] As a prior art for using such inorganic fine particles having a small particle size in ink jet recording paper, for example, JP-A-57-14091 and JP-A-60-219083.
No. 60-219084, JP-A-2-274857
Nos. 4-93284, 5-51470, 7-1
No. 79029, No. 7-137431, No. 8-2580
Nos. 0, 8-67064 and 8-118790, colloidal silica described in JP-B-3-56552, JP-A-63-170074, JP-A-2-113986, and JP-A-2-113986. 187383, 7-
No. 276789, No. 8-34160, No. 8-1327
No. 28, and fine particle silica synthesized by a gas phase method described in JP-A-8-174992, for example, Japanese Patent Publication Nos. 3-24906, 3-24907, 6-9.
Nos. 8844, 7-2430, 121609, JP-A-60-245588, JP-A-2-43083,
2-198889, 2-263683, 8-
Nos. 112964, 8-197832 and 8-2
No. 58397 and the like, and hydrates thereof, for example, JP-A Nos. 57-120486, 57-129778, 58-55283, 61
-20792 and 63-57277, JP-A-4-24-2
No.50091, No.3-251487, No.4-2500
Nos. 91, 4-260092 and 7-40648
And fine particles of calcium carbonate described in No. 1 and the like.

The recording paper having the above-mentioned void-type ink-absorbing layer on a support is particularly excellent in that high gloss, high porosity, and high maximum density can be obtained. When a recording paper is used, a recording paper having a high glossy surface can be obtained.

In particular, JP-A-8-174992 discloses a method of using silica particles having an average primary particle diameter of 10 nm or less and a water-soluble resin on an opaque support having a surface gloss of 70% or more.
An ink jet recording paper that achieves high gloss is described.

By the way, many attempts have been made in recent years to bring the image quality obtained by color ink jet recording closer to that of photographs.

Among them, the most important point in improving the image quality of dots is to make each dot indistinguishable by the naked eye. For this purpose, it is necessary to reduce the size of ink droplets, or in particular, to make dots in a highlight portion. The point is to use ink having a low dye concentration in combination in order to lower the reflection density of the image and make it difficult to identify dots.

For this reason, the amount of ink to be ejected tends to increase, and the image quality and the drying property have been lowered due to the shortage and overflow of the ink absorption capacity.
However, when the thickness of the void-type ink-absorbing layer is increased, cracks are likely to occur due to the properties of the film, or the coating speed is reduced due to the drying ability, thereby causing problems such as an increase in manufacturing cost. .

When plain paper, high-quality paper, or coated paper or cast-coated paper is used as recording paper, the ink penetrates into the support, so that some ink absorption capacities are satisfactory. There were drawbacks in that undulations caused by absorption and drying of the ink caused undulation, resulting in a significant decrease in print quality, a decrease in gloss, and a difficulty in obtaining a clear image due to difficulty in obtaining the highest density due to penetration of the dye into the support. .

The present invention relates to an ink jet recording sheet for recording using an aqueous ink, and more particularly to an ink jet recording sheet which can be manufactured at a low cost and can provide a high quality image with a photographic texture.

[0020]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and provides a recording sheet having a void layer as a recording layer on a support. An object of the present invention is to provide high-quality recording paper which can obtain an image, has no undulation in a printing portion, can be manufactured at low cost, and has high image quality.

[0021]

The above objects of the present invention have been attained by the following constitutions.

(1) On a water-absorbing support having a thickness of 160 μm or more, a dry film thickness of 5 to 20 μm and an average particle size of 1
It has a void layer containing fine particles of not more than 00 nm, a hydrophilic binder and a cationic polymer mordant as an ink absorbing layer, wherein the cationic mordant is 0.5 times or more in weight ratio to the hydrophilic binder. Inkjet recording paper.

(2) The ink jet recording sheet according to (1), wherein the fine particles are secondary aggregated particles of primary fine particles having an average particle diameter of 30 nm or less.

(3) The ink jet recording paper according to (2), wherein the fine particles are silica synthesized by a gas phase method.

(4) The ink jet recording paper as described in any one of (1) to (3), wherein the void layer contains polyvinyl alcohol.

(5) The ink jet recording paper according to (4), wherein the amount of the fine particles with respect to the polyvinyl alcohol is 3 to 8 by weight.

(6) The ink jet recording paper as described in (4) or (5), wherein the void layer is hardened with a hardener.

Hereinafter, the present invention will be described in detail.

In the present invention, as the water-absorbing support of the ink-jet recording paper, any material having a desired water-absorbing property can be used.

For example, there may be mentioned sheets and plates made of general paper, synthetic paper, cloth, wood and the like, and paper is most preferable because the base material itself is excellent in water absorption and cost. . Hereinafter, the paper support will be described.

As the paper support, chemical pulp such as LBKP, NBKP, etc., GP, CGP, RMP, TMP, CTM
Pulverized wood pulp, such as mechanical pulp such as P, CMP, and PGW, and waste paper pulp such as DIP, can be used. Various fibrous substances such as synthetic pulp, synthetic fiber, inorganic fiber and the like can also be used as a raw material as needed.

In the paper support, if necessary, a sizing agent,
Conventionally known various additives such as a pigment, a paper strength agent, a fixing agent, a fluorescent whitening agent, a wet paper strength agent, a cationizing agent and the like can be added. Higher fatty acids, alkyl ketene dimer, etc. as sizing agents, calcium carbonate, talc, titanium oxide, etc. as pigments, starch as paper strength agent,
Examples of the fixing agent include polyacrylamide and polyvinyl alcohol, and examples of the fixing agent include a sulfuric acid band and a cationic polymer electrolyte. However, the fixing agent is not limited thereto.

The paper support is prepared by mixing a fibrous substance such as wood pulp and various additives with a fourdrinier paper machine, a round paper machine,
It can be manufactured by various paper machines such as a twin wire paper machine. Further, if necessary, a size press treatment with starch, polyvinyl alcohol, or the like, various coating treatments, or a calendering treatment can be performed at or after the papermaking.

As a result of various studies, the thickness of the support is required to be 160 μm or more, and preferably 180 μm or more in order to obtain a photographic texture. If the thickness is less than 160 μm, the printed portion tends to be undulated, and the printing quality may be degraded.

The dry film thickness of the ink absorbing layer is generally determined by the porosity of the film and the required amount of porosity. In the ink jet recording paper of the present invention, it is necessary that the thickness be 5 μm or more and 20 μm or less. If it is smaller than 5 μm, the gloss and the maximum density may be reduced. If it is larger than 20 μm, the film shrinks at the time of drying after application of the void layer,
Cracking of the film is likely to occur, glossiness and flatness are degraded, and it is necessary to increase the coating amount to increase the dry film thickness, drying load increases, and productivity decreases There are drawbacks.

In the present invention, the support has at least one void layer containing a hydrophilic binder and inorganic fine particles as an ink absorbing layer.

As the above-mentioned inorganic fine particles, inorganic fine particles having a low refractive index and a small particle size are preferable. Examples thereof include silica, colloidal silica, calcium silicate, calcium carbonate, boehmite aluminum hydroxide and hydrates thereof. Preferably it is silica.

Silica fine particles are roughly classified into a gas phase method and a wet method according to the production method. Examples of the gas phase method fine silica include a method in which silicon halide is hydrolyzed at a high temperature in a gas phase method, and a method using silica sand and coke in an electric furnace. There is known a method of heating and reducing vaporization by an arc method and oxidizing it by air. In addition, the wet process silica is obtained by generating active silica by acid decomposition of a silicate and then polymerizing it appropriately to cause aggregation and precipitation.

In the present invention, among the silica fine powders,
In particular, the use of anhydrous silica synthesized by a gas phase method is preferable in that particularly high porosity and strong film strength can be obtained.

The average particle diameter of the inorganic fine particles must be 100 nm or less from the viewpoint of glossiness and ink absorption.
It is preferably 30 nm or less.

When the inorganic fine particles are fumed silica, the average particle size of the primary particles is 3 to 30 nm, especially 6 to 2 nm.
0 nm is most preferred. The fumed silica can be secondary aggregated in the coating solution to form larger particles. In this case, the average particle diameter of the secondary aggregated particles is preferably 30 to 100 nm.

In the above description, the average particle diameter of the inorganic fine particles is determined by observing the cross section or surface of the particles themselves or the void layer with an electron microscope, obtaining the particle diameter of 100 arbitrary particles, and calculating the simple average value (number average). Desired. Here, each particle size is represented by its diameter assuming a circle equal to its projected area.

In the recording paper of the present invention, the hydrophilic binder used in combination with the inorganic fine particles includes polyvinyl alcohol and its derivatives, polyalkylene oxide, polyvinylpyrrolidone, polyacrylamide, gelatin, hydroxyl ethyl cellulose,
Carboxymethylcellulose, pullulan, casein,
Dextran and the like can be used, but it is preferable to use a hydrophilic binder having a low swelling property and low solubility in water with a high boiling point organic solvent or water contained in the ink from the viewpoint of the film strength immediately after printing.

In the present invention, polyvinyl alcohol or a derivative thereof is particularly preferred.
As described above, polyvinyl alcohol having an average degree of polymerization of 2000 or more or a derivative thereof is most preferable. The saponification degree is preferably from 70 to 100%, particularly preferably from 80 to 100%.
Is most preferred.

The above-mentioned hydrophilic binders can be used in combination of two or more kinds, but even in this case, it is preferable that polyvinyl alcohol or its derivative is contained at least 50% by weight or more.

The above-mentioned polyvinyl alcohol derivatives include:
Cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol or nonion-modified polyvinyl alcohol can be used.

The cation-modified polyvinyl alcohol can be obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.

Examples of the ethylenically unsaturated monomer having a cationic group include trimethyl- (2-acrylamido-2,2-dimethylethyl) ammonium chloride and trimethyl- (3-acrylamido-3,3-dimethylpropyl). Ammonium chloride, N-vinylimidazole, N-vinyl-2-methylimidazole, N
-(3-dimethylaminopropyl) methacrylamide,
Examples thereof include hydroxylethyltrimethylammonium chloride, trimethyl- (methacrylamidopropyl) ammonium chloride, and N- (1,1-dimethyl-3-dimethylaminopropyl) acrylamide.

The ratio of the cation-modified group-containing monomer in the cation-modified polyvinyl alcohol is 0.1 to 10 mol%, preferably 0.2 to 5 mol%, based on vinyl acetate.

The polymerization degree of the cation-modified polyvinyl alcohol is usually 500 to 4000, preferably 1000 to 40.
00 is preferred.

The saponification degree of the vinyl acetate group is usually 60
-100 mol%, preferably 70-99 mol%.

The anion-modified polyvinyl alcohol is, for example, a polyvinyl alcohol having an anionic group as described in JP-A-1-2060888, JP-A-61-237681, and JP-A-63-307979.
As described in JP-A-7-285265, copolymers of vinyl alcohol and a vinyl compound having a water-soluble group, and modified polyvinyl alcohol having a water-soluble group as described in JP-A-7-285265 are disclosed. No.

Nonionic modified polyvinyl alcohols include, for example, polyvinyl alcohol derivatives described in JP-A-7-9758, in which a polyalkylene oxide group is added to a part of vinyl alcohol, and JP-A-8-25795. And a block copolymer of a vinyl compound having a hydrophobic group and vinyl alcohol described in Japanese Patent Application Laid-Open Publication No. H11-157,086.

The ratio of the inorganic fine particles to the hydrophilic binder in the void layer of the recording paper of the present invention is preferably at least 3 times by weight in order to obtain a high void ratio and a high film strength. If the ratio is less than 3 times, the porosity decreases and it becomes difficult to obtain a sufficient ink absorption capacity, and after inkjet recording, the strength of the film decreases due to the high boiling organic solvent remaining in the hydrophilic binder. Cheap. A particularly preferred ratio of the inorganic fine particles to the hydrophilic binder is 6 or more.

On the other hand, in the process of shrinkage of the film during drying after the application of the void layer, minute cracks are locally formed in the film due to minute undulations and irregularities on the surface of the support due to too high rigidity of the film. The upper limit of the ratio of the inorganic fine particles to the hydrophilic binder in the ink jet recording paper of the present invention is preferably about 8 or less.

The hardening agent capable of crosslinking with the hydrophilic binder is added to the void layer of the recording paper of the present invention to improve the film forming property of the void layer, the water resistance of the film, and the film strength after printing. It is preferable in that it improves. Examples of such a hardener include an organic hardener containing an epoxy group, an ethyleneimino group, an active vinyl group, and the like, and an inorganic hardener such as chrome alum, boric acid, or borax.

In particular, when the hydrophilic binder is polyvinyl alcohol, an epoxy hardener having at least two epoxy groups in a molecule, boric acid or a salt thereof,
Borax is preferred. As boric acid, not only orthoboric acid but also metaboric acid and hypoboric acid can be used.

The hardener is added in an amount of 1 to 200 mg, preferably 2 to 100 m, per 1 g of the hydrophilic binder.
g.

It is necessary to add a cationic polymer mordant to the void layer of the recording paper of the present invention in order to improve the water resistance and bleeding resistance of the image. In addition, in the case of the present invention in which the support can absorb ink and the support has a large thickness in addition to the ink absorbing layer, it is also preferable from the viewpoint that the dye in the ink is mordanted to the ink absorbing layer.

As the cationic polymer mordant used in the present invention, a cationic polymer mordant having a primary to tertiary amino group and a quaternary ammonium group can be used. A cationic polymer mordant having a quaternary ammonium base is preferred because the deterioration is small and the mordant ability of the dye is sufficiently high.

Preferred cationic polymer mordants are obtained as a homopolymer of the above-mentioned monomer having a quaternary ammonium salt group, as a copolymer with other monomers or as a condensation polymer.

The following are specific examples of the monomer having a quaternary ammonium base which is preferably used.

[0063]

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[0064]

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Specific examples of monomers copolymerizable with the above monomers are shown below.

[0066]

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[0067]

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Specific examples of the cationic polymer mordant having a quaternary ammonium base which is preferably used are shown below. (Numbers indicate mole percentage of monomer)

[0069]

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[0070]

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[0071]

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The cationic mordant may be a water-soluble polymer mordant or latex particles synthesized by emulsion polymerization. In the present invention, a water-soluble polymer mordant is preferred.

Among the water-soluble cationic mordants, the cationic mordant having an average molecular weight of 50,000 or less has less aggregation with the inorganic fine particles, so that the cation site effectively contributes to the improvement of water resistance and moisture resistance. This is preferable because the property is hardly deteriorated.

The preferred average molecular weight is 30,000 or less. The lower limit of the average molecular weight is not particularly limited, but is about 2000 or more from the viewpoint of water resistance and moisture resistance.

Here, the average molecular weight means a number average molecular weight, and means a value in terms of polystyrene obtained by gel permeation chromatography.

In the present invention, the amount of the mordant used is 0.5 times or more in terms of weight ratio to the hydrophilic binder used in the ink absorbing layer. When it is less than 0.5 times, when the ink seeps from the ink absorbing layer to the absorbent support, the ability to mordant the dye is insufficient, so that the diffusion of the dye to the support is caused. For this reason, a desirable maximum density cannot be obtained particularly for a support having a large thickness.

In addition, from the viewpoint of water resistance, the ratio of the cationic polymer mordant to which the dye is distributed and the hydrophilic binder is important. Unless this ratio is 0.5 or more, sufficient water resistance cannot be obtained.

Further, when the ratio is less than 0.5 times, there is a problem that it is difficult to obtain a satisfactory gloss. The most preferred ratio of cationic mordant / hydrophilic binder is 0.6 to 2.0.

The upper limit of the amount of the mordant is not particularly limited, but is preferably 3 g / m ² or less from the viewpoint of securing the void volume and suppressing unnecessary curl.

Various additives can be contained in any layer on the ink receiving layer side of the ink jet recording paper of the present invention, if necessary.

For example, JP-A-57-74193,
UV absorbers described in JP-A-57-87988 and JP-A-62-261476, JP-A-57-74192, JP-A-57-87989, and JP-A-60-72785.
JP-A-61-146591, JP-A-1-95
No. 091 and No. 3-13376, various anionic, cationic or nonionic surfactants described in JP-A-59-42993, JP-A-59-52689, and JP-A-6-32376. 280069, 61-242871 and JP-A-4-21
No. 9266, a fluorescent whitening agent, sulfuric acid,
Known pH adjusters such as phosphoric acid, acetic acid, citric acid, sodium hydroxide, potassium hydroxide and potassium carbonate, defoamers, lubricants such as diethylene glycol, preservatives, thickeners, antistatic agents, matting agents, etc. Can be added.

When the recording paper of the present invention is used as an ink-jet recording paper, the void volume of the void layer in the ink absorbing layer is 5 to 15 m / m ² of the recording paper.
It is preferable to adjust the range to be l.

The void volume is a value obtained by subtracting the total amount of the solid content of the binder and various fillers in the void layer from the dry thickness of the void layer. For example, 6 g / m ^{2 of} inorganic fine particles (specific gravity 2.0) and a hydrophilic binder (specific gravity 1.0)
1 g / m ² , cationic polymer mordant (specific gravity 1.0)
When the void layer of 1 g / m ² has a dry film thickness of 10 μm, the void volume is determined to be 5 ml / m ^{2 according} to the following equation.

10- (6 ÷ 2.0)-(1 ÷ 1.0)-
(1 ÷ 1.0) = 5 The recording paper of the present invention may have two or more recording layers having the above-described void layer, and in this case, the hydrophilic property of the inorganic fine particles in the two or more void layers The ratio to binder may be different from each other.

Further, other than the above-mentioned gap layer, there is no gap,
It may have a layer swellable with respect to the ink.

Such a swelling layer may be provided below the gap layer (on the side closer to the support) or above the gap layer (on the side away from the support). Further, when there are two or more gap layers, May be provided between the void layers. A hydrophilic binder is usually used for such a swellable layer, and examples of the hydrophilic binder used here include the hydrophilic binder used for the above-mentioned void layer.

On the side of the recording paper of the present invention having the ink-absorbing layer and the side opposite to the support, there are various types of paper for preventing curling and further improving sticking and ink transfer when superimposed immediately after printing. It is preferable to provide different types of back layers.

Although the configuration of the back layer varies depending on the type and thickness of the support and the configuration and thickness of the ink absorbing layer, a hydrophilic binder or a hydrophobic binder is generally used. The thickness of the back layer is usually in the range of 0.1 to 10 μm.

The surface of the back layer can be roughened in order to prevent sticking to other recording papers, improve writing properties, and improve transportability in an ink jet recording apparatus. Organic or inorganic fine particles having a particle size of 2 to 20 μm are preferably used for this purpose.

The recording paper of the present invention having the above configuration can be obtained, for example, by the following method. First, a coating solution is prepared by adding the material for forming the void layer to an appropriate solvent, for example, water, alcohol or various organic solvents,
This is applied to the water-absorbing support and dried to form a void layer.

The method of applying the above-mentioned void layer on a support can be appropriately selected from known methods. Examples of the coating method include a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method, and US Pat.
The extrusion coating method using a hopper described in Japanese Patent Application Publication No. 1,294 is preferably used.

For drying after coating, it is preferable to cool once to increase the viscosity of the coating solution or to gel it and then blow it with hot air to dry.

The temperature of the coating solution is usually 25 to 60 ° C.
0-50 ° C is preferred. Cooling is performed when the film surface temperature is 20
The temperature is preferably set to not more than 5 ° C, preferably 5 to 15 ° C, and the subsequent drying is preferably performed by blowing air at 20 to 60 ° C in order to obtain a uniform film surface.

The wet film thickness to be applied varies depending on the desired dry film thickness, but is generally 50 to 300 μm, preferably 7 to 300 μm.
The coating speed is generally 20 to 200 m / min, though it largely depends on the drying ability. Drying time is about 2
10 minutes.

The amount of solids applied on the ink recording surface side of the ink jet recording paper of the present invention is generally 5 to 40 g / m 2.
² is preferable, and 10 to 30 g / m ² is more preferable.

Next, the water-based ink when the recording paper of the present invention is used as an ink-jet recording paper will be described below.

The aqueous ink is a recording liquid usually composed of a water-soluble dye, a liquid medium, and other additives. As the water-soluble dye, a water-soluble dye such as a direct dye, an acid dye, a basic dye, a reactive dye, or a food dye known in the ink jet can be used, but a direct dye or an acid dye is preferable.

The solvent of the aqueous ink is mainly composed of water. However, in order to prevent the dye from being deposited when the ink liquid dries and to prevent clogging at the nozzle tip and the ink supply path, the boiling point is usually about 120 ° C. or higher. And a high-boiling organic solvent which is liquid at room temperature. High boiling organic solvents are required to have a vapor pressure much lower than that of water in order to prevent solid components such as dyes from being precipitated when water evaporates and to prevent generation of coarse precipitates. Must have high miscibility.

For such purposes, high-boiling organic solvents are usually often used. Specific examples thereof include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, glycerin, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, and triethylene glycol. Glycol monobutyl ether, glycerin monomethyl ether, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,
2,4-pentanetriol, 1,2,6-hexanetriol, thiodiglycol, triethanolamine,
Polyethylene glycol (average molecular weight of about 300 or less)
And the like. In addition to the above, dimethylformamide, N-methylpyrrolidone and the like can also be used.

Among these many high boiling organic solvents,
Preferred are polyhydric alcohols such as diethylene glycol, triethanolamine and glycerin, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monobutyl ether.

Other additives contained in the aqueous ink include, for example, a pH adjuster, a metal sequestering agent, a fungicide, a viscosity adjuster, a surface tension adjuster, a wetting agent, a surfactant, and a rust inhibitor. Is mentioned.

The aqueous ink liquid is 25 to 50 dy at 25 ° C. for the purpose of improving the wettability to the recording paper and stabilizing the discharge from the ink jet nozzle.
It preferably has a surface tension in the range of ne / cm, preferably 28-40 dyne / cm.

The viscosity of the aqueous ink is usually 2 to 8 cp at 25 ° C., preferably 2.5 to 5 cp.

The pH of the aqueous ink is usually in the range of 4 to 10.

It is preferable that the minimum ink droplet ejected from the ink nozzle has a capacity of 1 to 30 × 10 ⁻³ nl, since a minimum dot diameter of about 20 to 60 μm can be obtained on recording paper. A color print printed with such a dot diameter gives a high quality image. Preferably 2-20 ×
This is a case where a droplet having a volume of 10 ⁻³ nl is ejected as a minimum droplet.

In a method in which the aqueous ink is recorded with at least two types of inks, each of which has at least a density difference of at least twice for magenta and cyan, a low density ink is used in a highlight portion, so that dot identification is performed. However, the present invention can be applied to the case where such a recording method is adopted.

In the ink jet recording method, various known methods can be used as the recording method, and details thereof are described in, for example, the trend of the ink jet recording technology (edited by Koichi Nakamura, edited by Nihon Kagaku on March 31, 1995). Information Co., Ltd.).

The recording paper of the present invention has been described above as a recording paper for ink jet recording. However, the recording paper of the present invention can be applied to a thermal transfer system (a recording material containing a heat-meltable ink) in addition to the ink jet recording. A so-called sublimation type thermal transfer system in which heating and melting are performed from the ink sheet support side for recording, and a sublimation type thermal transfer system in which heating and recording are performed in the same manner as the recording material fusion type thermal transfer system including a sublimation dye and a highly softening resin ) And electrophotographic recording paper.

[0109]

The present invention will be described below with reference to examples of the present invention.
The present invention is not limited to these examples.

<Recording Paper-1 (Comparative Example)> As a raw material pulp, LBK having a freeness (CSF) of 350 ml was used.
Using 100 parts by weight of P, 10 parts by weight of kaolin (Tsuchiya Kaolin) as a filler, and a reinforced rosin sizing agent (Colopearl CS, Seiko Chemical Co., Ltd.) as a sizing agent
0.15 parts by weight) and 1 part by weight of a sulfuric acid band were added thereto, followed by papermaking using a paper machine. The basis weight was 160 g / m ² , and the film thickness was 180 μm.
m of Support-1 was obtained.

Next, the following coating solution-1 was prepared and applied so that the wet film thickness became 80 μm. The drying conditions were such that the film temperature was rapidly cooled within 30 seconds so that the film temperature would be 15 ° C. or lower, and dried with air at 50 ° C. for 3 minutes to obtain recording paper-1 (Comparative Example). The dry film thickness of the void layer thus formed was 15 μm.

The composition of Coating Liquid-1 is described below (the amount of addition is shown per 1 L of coating liquid).

Coating liquid-1 The following fine particle silica dispersion (1) 450 ml The following cationic polymer (2) 4 g Ethanol 35 ml n-propanol 10 ml Ethyl acetate 5 ml Polyvinyl alcohol (PVA203 manufactured by Kuraray Co., Ltd.) 0.1 g Polyvinyl alcohol (Co., Ltd.) Kuraray PVA235) 12 g Boric acid 2.0 g Borax 1.0 g Fine particle silica dispersion (1): 80 g of Aerosil 200 (Nippon Aerosil Co., Ltd., average particle size 12 nm, vapor-phase silica) is put in 400 ml of pure water. After adding and dispersing with an emulsifying and dispersing machine for 20 minutes, the whole amount is finished to 450 ml with pure water.

[0114]

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<Recording paper-2 (invention)> Next, recording paper-2 (invention) was obtained in exactly the same manner as in recording paper-1, except that coating liquid-1 was changed to coating liquid-2. . The dry thickness of the void layer was 15 μm.

Coating liquid-2 The fine particle silica dispersion (1) 450 ml The cationic polymer (2) 8 g Ethanol 35 ml n-propanol 10 ml Ethyl acetate 5 ml Polyvinyl alcohol (PVA203 manufactured by Kuraray Co., Ltd.) 0.1 g Polyvinyl alcohol (Co., Ltd.) Kuraray PVA235) 12 g Boric acid 2.0 g Borax 1.0 g <Recording paper-3 (comparative example)> Recording paper-1 was recorded in exactly the same manner except that coating liquid-1 was changed to coating liquid-3. Paper-3 (comparative example) was obtained. The dry thickness of the void layer is 1
It was 7 μm.

Coating solution-3 The fine particle silica dispersion liquid (1) 450 ml The cationic polymer (2) 8 g Ethanol 35 ml n-propanol 10 ml Ethyl acetate 5 ml Polyvinyl alcohol (Kuraray PVA203) 0.1 g Polyvinyl alcohol (Kuraray PVA235) 24 g Boric acid 2.0 g Borax 1.0 g <Recording paper-4 (present invention)> Recording paper-1 was recorded in exactly the same manner except that coating liquid-1 was changed to coating liquid-4. Paper-4 (the present invention) was obtained. The dry thickness of the void layer is 1
It was 7 μm.

Coating Solution-4 The Fine Particle Silica Dispersion (1) 450 ml The Cationic Polymer (2) 16 g Ethanol 35 ml n-propanol 10 ml Ethyl acetate 5 ml Polyvinyl alcohol (Kuraray PVA203) 0.1 g Polyvinyl alcohol Kuraray PVA235) 24 g Boric acid 2.0 g Borax 1.0 g <Recording paper-5 (comparative example)> A support ² having a basis weight of 80 g / m ² and a thickness of 90 μm was prepared in the same manner as the support 1. Preparation was performed, and recording paper-5 (comparative example) was obtained in exactly the same manner except that support-1 of recording paper-2 was changed to support-2.

<Recording Paper-6 (Comparative Example)> Recording Paper-2
In the same manner as above, the wet film thickness was set to 120 μm, and recording paper-6 (comparative example) was obtained. The dry thickness of the void layer was 23 μm.

<Recording Paper-7 (Comparative Example)> Recording Paper-2
The wet film thickness was set to 20 μm in the same manner as
7 (Comparative Example) was obtained. The dry thickness of the void layer was 4 μm.

<Recording Paper-8 (Comparative Example)> The recording paper-8 was completely the same as recording paper-2 except that the fine particle silica dispersion (1) used for the coating liquid-2 was changed to the following fine particle silica dispersion (2). Thus, recording paper-8 (comparative example) was obtained. The dry thickness of the void layer was 15 μm.

Fine Particle Silica Separation Liquid (2): 80 g of Aerosil 200 manufactured by Nippon Aerosil Co., Ltd. (average primary particle diameter: 12 nm, fumed silica) was added to 400 ml of pure water and dispersed for 3 minutes by an emulsifying and dispersing machine. To 450 ml with pure water.

<Recording Paper-9 (Invention)> Recording Paper-2 except that boric acid and borax were not added to the coating solution-2.
In the same manner as above, recording paper-9 (the present invention) was obtained. The dry thickness of the void layer was 15 μm.

Measurement Each section of the recording paper was observed with an electron microscope, and the secondary particle diameter was calculated from the obtained image by image analysis software. The measurement results are also shown in Table 1.

Evaluation The following items were evaluated for the obtained recording paper.

(1) Maximum Density Solid printing of yellow, magenta and cyan was performed using an inkjet printer MJ-5000C manufactured by Seiko Epson Corporation, and the reflection density was measured with blue, green and red monochromatic lights, respectively.

(2) Water Resistance The solid printed area was immersed in pure water for 24 hours, washed with water and dried, and the reflection density was measured with blue, green and red monochromatic lights, respectively.

(3) Initial ink absorbency TAPPI Paper Pulp Test Method No. 51-87
The liquid transfer amount (ml / m ² ) at a contact time of 0.5 seconds was measured by the method described in the liquid absorption test method for paper and paperboard (Bristow method). The ink used was C.I. I.
Acid Red 52 is a 2% aqueous solution.

(4) Glossiness A goniophotometer (VGS-101D) manufactured by Nippon Denshoku Industries Co., Ltd.
The specular gloss at 75 degrees was measured in P).

(5) Cracks The surface of the recording paper before printing was observed, and the degree of cracks was judged according to the following criteria. A and B do not matter in quality.

A: No crack is found.

B: Fine cracks can be observed with a magnifying glass, but there is no problem in aesthetic appearance with the naked eye.

C: Cracks can be seen with the naked eye.

D: Cracks visible to the naked eye are observed on the entire surface of the recording paper.

(6) Swell after Printing The swell was determined by visual observation of the surface of the recording paper after printing according to the following criteria. A and B do not matter in quality.

A: The swell is not recognized, and the appearance is not impaired.

B: The swell is small and does not impair the aesthetic appearance.

C: The undulation is large and the appearance is impaired.

Table 1 shows the evaluation results.

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[Table 1]

From the above results, it has become possible to provide an ink jet recording paper excellent in ink absorbency and water resistance without impairing the photographic appearance.

[0142]

According to the present invention, it is possible to provide an ink jet recording paper which has a high image quality and a photographic texture and is excellent in ink absorbency and water resistance.

Claims (6)

[Claims] 1. A dry film having a thickness of 5 to 20 μm and an average particle size of 100 μm on a water-absorbing support having a thickness of 160 μm or more.
having a void layer containing fine particles of not more than nm, a hydrophilic binder and a cationic polymer mordant as an ink absorbing layer, wherein the cationic mordant is at least 0.5 times in weight ratio to the hydrophilic binder. Inkjet recording paper. 2. The ink jet recording paper according to claim 1, wherein said fine particles are secondary aggregated particles of primary fine particles having an average particle diameter of 30 nm or less. 3. The ink jet recording paper according to claim 2, wherein the fine particles are silica synthesized by a gas phase method. 4. The ink jet recording paper according to claim 1, wherein the gap layer contains polyvinyl alcohol. 5. The ink jet recording sheet according to claim 4, wherein the amount of the fine particles with respect to the polyvinyl alcohol is 3 to 8 in weight ratio. 6. The ink jet recording paper according to claim 4, wherein the void layer is hardened with a hardener.