JPH1081064A - Ink-jet recording paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide ink-jet recording paper which contains fine solid particles dispersed in a hydrophilic binder, has high ink absorption power, keeps the fragility of a membrane even when stored in an atmosphere of low humidity, and is capable of high quality ink-jet recording. SOLUTION: In ink-jet recording paper, at least one ink absorption layer containing fine solid particles and polyvinyl alcohol is provided on a support, and in at least one ink absorption layer, the weight ratio of the particles to polyvinyl alcohol is 2-200. A layer containing the particles contains polyvinyl alcohol of at most 1000 average molecular weight and polyvinyl alcohol of at least 2000 average molecular weight.

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 having improved ink absorbability.

[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. .

[0003] The ink jet recording paper used in this ink jet recording system has a high density of print dots, a bright and vivid color tone, and the ink absorbs quickly so that even when the print dots overlap, the ink flows out. It is required that the print dots do not spread or bleed, that the diffusion of the print dots in the horizontal direction is not unnecessarily large, and that the periphery is smooth and not blurred.

[0004] In particular, when the ink absorption speed is low, when ink droplets of two or more colors are recorded in an overlapping manner, the droplets may cause a repelling phenomenon on the ink jet recording paper to become uneven or different. It is necessary that the ink jet recording paper has a high ink absorbency because the colors are easily blurred in the boundary area of the colors and the image quality is easily deteriorated.

[0005] To solve these problems, a great many techniques have been proposed.

For example, an ink jet recording sheet described in JP-A-52-53012 in which a coating for surface processing is wetted on a low-size base paper is disclosed in JP-A-55-5830.
Ink-jet recording paper provided with an ink-absorbing coating layer on the surface of a support described in JP-A-56-157, containing a non-colloidal silica powder as a pigment in a wearable layer described in JP-A-56-157 Ink jet recording paper, JP 57
-1077878, an ink jet recording paper using an inorganic pigment and an organic pigment in combination;
No. 0287, an ink jet recording sheet having two pore distribution peaks,
No. 782, an inkjet recording paper comprising two upper and lower porous layers, JP-A-59-68292,
Ink jet recording paper having irregular cracks described in JP-A-59-123696 and JP-A-60-18383;
JP-A-148092 and JP-A-62-149475, etc., have an ink-jet recording sheet having a fine powder layer, JP-A-63-252779, JP-A-1-1080.
No. 83, 2-136279, 3-65376 and 3-27976, and ink-jet recording paper containing pigments having specific physical properties and fine-particle silica, JP-A-57-14091. 60-21
No. 9083, No. 60-210984, No. 61-207
No. 97, 61-188183, JP-A-5-2783
No. 24, No. 6-92011, No. 6-183134,
Ink jet recording paper containing fine particle silica such as colloidal silica described in JP-A-7-137431 and JP-A-7-276789, and JP-A-2-2766.
No. 71, JP-A-3-67684, JP-A-3-2150
No. 82, No. 3-251488, No. 4-67986,
Many ink jet recording papers containing alumina hydrate fine particles described in JP-A-4-263983 and JP-A-5-16517 are known.

Above all, when the ink receiving layer is a layer having a large number of voids for absorbing and retaining the ink (hereinafter, referred to as a void layer), the ink absorbing property is good, the bleeding at the boundary is small, and high quality is obtained. Images can be recorded.

In addition, since the volume of the void may change during storage, particularly under high temperature and high humidity, it is preferable that the void layer contains solid fine particles that do not change the void.

In the case where voids are formed by containing solid fine particles in the void layer, it is necessary to contain a hydrophilic binder in order to form a stable film. However, if the amount of the hydrophilic binder added to the solid fine particles is too large, the solid fine particles themselves or the voids formed between the solid fine particles may be closed, or the hydrophilic binder itself may swell at the initial stage of ink absorption when ink is absorbed. There are problems such as a decrease in ink absorbency by closing the gap layer, and the amount of use is limited.

According to the study of the present inventors, it has been found that the ratio of the amount of the hydrophilic binder to the solid fine particles needs to be approximately 2-200 times by weight.

The layer containing such a high proportion of solid fine particles, however, has the drawback that the film is inferior in fragility, and particularly when stored under low humidity, the surface of the ink absorbing layer has a fine cracking state. Occur. When ink-jet recording is performed on such an ink-jet recording sheet, the ink spreads along the cracked line, and the image quality is significantly reduced.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a high ink absorbing property containing solid fine particles dispersed in a hydrophilic binder. Another object of the present invention is to provide an ink jet recording sheet capable of performing high-quality ink jet recording without reducing the brittleness of a film even when stored under low humidity.

[0013]

The above object of the present invention is attained by the following constitutions.

1. At least one ink-absorbing layer containing solid fine particles and polyvinyl alcohol is provided on a support, and at least one of the ink-absorbing layers has a weight ratio of solid fine particles of 2 to 2 with respect to the total amount of polyvinyl alcohol.
An inkjet recording sheet containing 200 times, wherein the layer containing the solid fine particles contains polyvinyl alcohol having an average degree of polymerization of 1000 or less and polyvinyl alcohol having an average degree of polymerization of 2000 or more.

2. The solid fine particles each have an average primary particle diameter of 7 to 80 nm, silica, calcium carbonate,
2. The ink jet recording paper according to the item 1, wherein the ink jet recording paper is solid fine particles selected from alumina, alumina hydrate, and magnesium silicate.

3. 2. The ink jet recording paper according to the item 1, wherein the solid fine particles are silica synthesized by a gas phase method having an average primary particle diameter of 7 to 30 nm.

4. The amount of polyvinyl alcohol having an average degree of polymerization of 1000 or less is 1 to 30% by weight based on the weight of polyvinyl alcohol having an average degree of polymerization of 2000 or more.
The inkjet recording paper according to any one of the above items 1 to 3, wherein

5. The support has at least one ink absorbing layer containing at least solid fine particles and polyvinyl alcohol as a hydrophilic binder, and the weight ratio of the solid fine particles to the hydrophilic binder of at least one layer of the ink absorbing layer is 2 to 200 times. Wherein the ink-absorbing layer contains oil droplets selected from a hydrophobic organic compound having a melting point of 40 ° C. or less or a polymer latex having a glass transition temperature of 40 ° C. or less by 5 to 50% by weight based on solid fine particles. Ink jet recording paper characterized by containing.

6. The oil droplets have an average particle size of 0.05 to 0.
6. The inkjet recording paper as described in 5 above, wherein the thickness is 5 μm.

[7] FIG. The solid fine particles each have an average primary particle diameter of 7 to 80 nm, silica, calcium carbonate,
7. The ink jet recording paper as described in 5 or 6 above, which is solid fine particles selected from alumina, alumina hydrate, and magnesium silicate.

8. 7. The ink jet recording paper as described in 5 or 6, wherein the solid fine particles are silica synthesized by a gas phase method with an average primary particle diameter of 7 to 30 nm.

Hereinafter, the present invention will be described in detail.

As the solid fine particles contained in the ink jet recording paper of the present invention, conventionally known solid fine particles can be used for the ink jet recording paper, but inorganic fine particles are preferable.

The inorganic fine particles used for this purpose include:
Known in inkjet, for example, light calcium carbonate,
Heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate,
Hydrotalcite, aluminum silicate, diatomaceous earth,
White inorganic pigments such as calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, and magnesium hydroxide can be used.

Such inorganic fine particles may be used in a state of being uniformly dispersed in a binder as primary particles, or may be added in a state of forming secondary aggregated particles and being dispersed in a binder. May be.

On the other hand, examples of the organic fine particles include polystyrene, polyacrylates, polymethacrylates, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, copolymers thereof, and urea resin. Or a melamine resin.

In the present invention, it is preferable to use inorganic solid fine particles from the viewpoint that a void layer having a relatively high void ratio can be obtained.
Among them, the solid fine particles are preferably solid fine particles selected from silica, calcium carbonate, alumina, alumina hydrate, and magnesium silicate in that high gloss and high image density are easily obtained.

As the silica fine particles preferably used in the ink jet recording paper of the present invention, various types of silica fine particles conventionally known in ink jet can be used.

For example, synthetic silica, colloidal silica synthesized by a wet or gas phase method, and porous silica in which primary particles are aggregated to form secondary particles can be used. As such examples, synthetic amorphous silicas described in, for example, JP-A-55-51583 and JP-A-56-148583, such as JP-A-60-2
Ultrafine silica particles synthesized by the gas phase method described in JP-A-04390, fluorine-containing synthetic amorphous silica described in JP-A-60-222282, JP-A-60-22
Synthetic amorphous silica surface-treated with a silane coupling agent described in JP-A Nos. 4580 and 62-178384, for example, JP-A Nos. 62-183382 and 6-178384.
Spherical silica described in JP-A-3-104878;
The Na ₂ O content described in 3-317381 is 0.
5% by weight or more of synthetic silica fine particles
No. 5677, synthetic silica fine particles having a specific surface area of 100 m ² / g or more, alumina surface-treated synthetic silica fine particles described in JP-A-62-286787, and Ca described in JP-A-1-259998. Silica fine particles surface-treated with a salt of Mg, Ba or the like, synthetic silica fine particles having an oil absorption of 180 ml / g or more,
Colloidal silica described in JP-A-14091, JP-A-60-219084, JP-A-6-92011, and 6
Cationic colloidal silica described in JP-A-297830 and JP-A-7-81214;
No. 8324 and No. 7-81214, colloidal silica linked or branched in a rosary and the like.

However, in order to obtain high gloss and high void volume, it is preferable to use ultrafine silica having an average particle diameter of 7 to 80 nm. The silica fine particles may be those whose surface is cationically modified, and further, Al,
It may be a material treated with Ca, Mg, Ba or the like.

Examples of the calcium carbonate preferably used in the ink jet recording paper of the present invention include, for example, JP-A Nos. 57-12486, 57-129778, and 58.
Light calcium carbonate having a specific specific surface area described in JP-A-55283 and JP-A-61-20792.
Needle-shaped calcium carbonate described in JP-A-57277 and JP-A-4-2,50091, calcium carbonate fine particles in which specific needle-shaped primary particles described in JP-A-3-251487 are aggregated to form secondary particles, JP-A-4-25009
Needle-column-like orthorhombic calcium carbonate having a specific oil absorption described in JP-A Nos. 1-4-260092 and spherical precipitated calcium carbonate described in JP-A-7-40648.

In this case, it is preferable to use calcium carbonate fine particles having a particle size of about 7 to 80 nm, since high gloss and a high void amount can be obtained.

The magnesium silicate preferably used in the present invention may be any of irregular particles, spheres and plates, but is preferably a plate. The average particle diameter of the plate-shaped magnesium silicate is represented by a diameter when a plate-shaped average projected area is obtained and converted to a circle, and fine particles of 7 to 80 nm are preferable.

The alumina or alumina hydrate preferably used in the present invention may be crystalline or amorphous, and may have any shape such as irregular particles, spherical particles, and acicular particles. Can be used.

The average particle diameter of the above-mentioned various inorganic solid fine particles represents the diameter when the average projected area of the fine particles is measured with an electron microscope and converted into a circle.

The solid fine particles preferably used in the present invention preferably have an average primary particle diameter of 7 to 80 nm.

When the primary particle size is less than 7 nm, the handleability is difficult, and when the primary particle size is more than 80 nm, the decrease in gloss tends to be remarkable.

It is necessary for the ink jet recording paper of the present invention that the solid fine particle-containing layer contains a hydrophilic binder from the viewpoint of film formation.

As a hydrophilic binder generally used for ink jet recording paper, gelatin or a gelatin derivative, polyvinylpyrrolidone (preferably having an average molecular weight of about 200,000 or more), pullulan, polyvinyl alcohol or a derivative thereof (an average molecular weight of about 20,000 or more) is used. Preferred), polyethylene glycol (preferably having an average molecular weight of 100,000 or more), carboxymethylcellulose, hydroxyethylcellulose, dextran, dextrin,
Polyacrylic acid and salts thereof, agar, κ-carrageenan, λ-carrageenan, ι-carrageenan, xanthen gum, locust bean gum, alginic acid, gum arabic, pullulan, JP-A-7-195826 and 7-
No. 9557 polyalkylene oxide copolymerizable polymer, water-soluble polyvinyl butyral, or
Japanese Patent Application Laid-Open No. Sho 62-245260 discloses a vinyl monomer having a carboxyl group or a sulfonic acid group alone or a polymer such as a copolymer having a repetition of these vinyl monomers. It is necessary to contain at least an alcohol from the viewpoints of high ink absorbency and glossiness, suppression of curling, and prevention of stickiness under high humidity.

The polyvinyl alcohol referred to here includes not only polyvinyl alcohol such as partially saponified or completely saponified polyvinyl acetate but also cation-modified polyvinyl alcohol.

The degree of saponification of the polyvinyl acetate is 60 to 1
00%, preferably 70-99% is used in the present invention.

A preferred cation-modified polyvinyl alcohol is 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 proportion of the cation-modified group-containing monomer in the cation-modified polyvinyl alcohol is preferably from 0.1 to 10 mol%, more preferably from 0.2 to 10 mol%, based on vinyl acetate.
~ 5 mol%. The saponification degree of the cation-modified polyvinyl alcohol is preferably from 60 to 100%, more preferably from 70 to 99%.

In the ink jet recording paper of the present invention, the ratio of the solid fine particles forming the void layer to the hydrophilic binder needs to be 2 to 200 times by weight. When the ratio is less than twice, the void ratio formed is small, and various problems tend to occur due to the film thickness being too large to completely absorb the maximum ink amount. It swells and reduces the ink absorption rate of the void layer, thereby lowering the obtained image quality.

On the other hand, when it exceeds 200 times, even if various means described later are adopted, the brittleness of the film is greatly deteriorated and high-quality ink jet recording cannot be performed.

The preferred ratio is 2.5 to 100 times, and the particularly preferable ratio is 3 to 50 times.

When particularly preferable fumed silica is used as the solid fine particles, the preferable ratio is 3 to 20.
It is.

Since the void layer of the ink jet recording paper of the present invention contains a particularly high ratio of solid fine particles to the hydrophilic binder, the solid fine particle-containing layer is formed as described above in order to improve the film brittleness accompanying the solid fine particles. Contains polyvinyl alcohol having an average degree of polymerization of 1000 or less and polyvinyl alcohol having an average degree of polymerization of 2000 or more.
It is necessary that at least one of the two is contained.

In the above, it is preferable to use polyvinyl alcohol having a higher polymerization degree in order to form a stable film which is less likely to crack. From this viewpoint, it is preferable to use polyvinyl alcohol having an average polymerization degree of 2,000 or more alone. By using it, a good film can be obtained to some extent. Conversely, when only low-molecular-weight polyvinyl alcohol is used, cracks are likely to occur in the drying process after coating, especially in a film containing a large amount of solid fine particles.

However, when only polyvinyl alcohol having an average degree of polymerization of 2,000 or more is used, fine cracks in the film are not completely eliminated, and the film becomes brittle when stored at a high temperature after coating and drying. Is reduced,
In particular, cracks tend to occur in the film under low humidity conditions.

The present inventors have found that this problem can be improved by using polyvinyl alcohol having a high average polymerization degree and polyvinyl alcohol having a low polymerization degree having an average polymerization degree of 1000 or less in combination. It has arrived.

Among polyvinyl alcohols having an average polymerization degree of 2000 or more, those having an average polymerization degree of 3000 or more are particularly preferable. The upper limit of the average degree of polymerization is not limited from the viewpoint of improving the brittleness of the film, but generally, the higher the degree of polymerization, the lower the solubility of polyvinyl alcohol and the more difficult it is to produce a liquid having a desired concentration. Is generally 5
000 or less, especially 4000 or less.

On the other hand, among the polyvinyl alcohols having an average degree of polymerization of 1000 or less, the average degree of polymerization is most preferably 500 or less, particularly preferably 400 or less.

The lower limit of the average degree of polymerization is not particularly limited, but is usually 200 or more.

The amount of polyvinyl alcohol having an average degree of polymerization of 1000 or less is preferably 1 to 30% by weight based on polyvinyl alcohol having an average degree of polymerization of 2000 or more. When the amount is less than 1%, the effect of the present invention is hardly substantially obtained. When the amount is more than 30%, the formability of a film after coating and drying tends to be deteriorated. Adhesion to the body is likely to be reduced. A particularly preferred range is 2 to 20%.

In the above, oil droplets contained in the ink absorbing layer are roughly classified into two types.

The first is a case where the oil droplet is an oil droplet having a hydrophobic organic compound having a melting point of 40 ° C. or less,
The second case is where the oil droplet is a polymer latex having a glass transition temperature of 40 ° C. or lower.

The oil droplets of the first type usually have a solubility in water at room temperature of 0.1% by weight or less, particularly preferably 0.1% by weight.
It is a hydrophobic organic compound having a melting point of not more than 01% by weight and a melting point of not more than 40 ° C.

Examples of such a hydrophobic organic compound include an organic compound known as a normal hydrophobic high-boiling organic solvent and a hydrophobic polymer having a melting point of 40 ° C. or less.

Examples of the hydrophobic organic compound include phthalic esters (eg, dibutyl phthalate, dioctyl phthalate, diisodecyl phthalate), phosphates (eg, tricresyl phosphate, trioctyl phosphate, etc.), fatty acid esters (Butyl stearate, bis (2-ethylhexyl) sebacate, ethylene glycol distearate, glycerol tributyrate, etc.), amides (N, N-diethyl lauryl amide, N, N-diethyl-2- (2, 5-di-
t-amylphenoxy) butanamide and the like, ethers (ethylene glycol dibutyl ether, decyl ether, dibenzyl ether and the like), silicone oil, liquid paraffin and the like.

Examples of the hydrophobic polymer having a melting point of 40 ° C. or less include poly (2-ethylhexyl methacrylate), polybutyl methacrylate, and copoly (butyl acrylate / hydroxylethyl methacrylate).
90/10), polyvinyl acetate, polyvinyl propionate, copoly (butyl acrylate / t-butyl acrylate / 2-ethylhexyl methacrylate / styrene: 60/20/10/10) and the like.

As the hydrophobic polymer, a polymer having an average molecular weight of about 5,000 to 100,000 is preferably used. In the case of a polymer exceeding 100,000, it becomes difficult to form oil droplets of fine particles by a method such as emulsification dispersion described later.

The above-mentioned hydrophobic organic compound is emulsified and dispersed in a hydrophilic binder by a high-speed homogenizer or a high-pressure homogenizer, preferably in the presence of a surfactant. At this time, it is preferable to emulsify and disperse in the presence of a low-boiling organic solvent such as ethyl acetate, propyl acetate, methyl ethyl ketone, acetone, N, N, dimethylformamide, etc., in order to form a finer oily substance.

At the time of this emulsification and dispersion, an organic compound having a melting point of more than 40 ° C. with another hydrophobic organic compound (for example, an ultraviolet absorber, a fluorescent whitening agent, an image stabilizer, etc.) can be used, but it is preferable. Is an organic compound that forms an oily substance.
The compound having a melting point of 40 ° C. or less is preferably 0% by weight or more.

On the other hand, the polymer latex having a second glass transition temperature of 40 ° C. or lower is a polymer latex polymerized by an emulsion polymerization method, and is, for example, a styrene-butadiene copolymer latex, a polyacrylate latex, or a polyacrylate latex. Methacrylate latex, vinyl acetate latex, ethylene-vinyl acetate latex and the like are preferably used.

Examples of the above polymer latex include styrene / butadiene latex (7/3), polyvinyl acetate latex, vinyl acetate / ethylene latex (9/1), and vinyl acetate / ethyl methacrylate latex (5 / 5), vinyl chloride / ethyl acrylate (3 /
2), ethyl acrylate / methyl acrylate / HEMA
(5/4/1), styrene / butyl acrylate / HEM
A (1/3), silicon latex, and the like. In the above, the weight ratio represents a molar ratio, and H
EMA stands for hydroxylethyl methacrylate.

The average particle size of the various oil droplets is 0.05 to
It is preferably 0.5 μm. Oil droplet size is 0.
When it is not more than 05 μm, oil droplets are likely to be unstable, and the effect of improving fragility is likely to be reduced. If the size of the oil droplets exceeds 0.5 μm, the gloss tends to decrease.

It is necessary to use the oil droplets in an amount of 5 to 50% by weight based on the solid fine particles contained in the ink absorbing layer in order to obtain the effect of the present invention.

The ratio of oil droplets to solid fine particles is 5% by weight.
When the amount is less than 50%, the effect of improving the brittleness of the film is insufficient, and when the amount exceeds 50% by weight, the void ratio is reduced, so that the ink absorption capacity and the gloss are likely to be reduced.

A particularly preferred amount is from 10 to 40% by weight.

The ink jet recording paper of the present invention may have two or more ink absorbing layers containing solid fine particles and a hydrophilic binder. In this case, the kind or ratio of the hydrophilic binder and the solid fine particles used in the plurality of ink absorbing layers is arbitrarily selected, but at least one layer has a ratio of the solid fine particles to the hydrophilic binder of 2 to 200 times. In the case where there is a layer, it is necessary to use two types of polyvinyl alcohols having different average degrees of polymerization as in the present invention or to add the oil droplets of the present invention to the layer.

In order to maximize the effects of the present invention, the use of polyvinyl alcohol having different average polymerization degrees and the use of oil droplets are used in combination.

The ink jet recording paper of the present invention has at least one ink absorbing layer containing the above-mentioned solid fine particles and a hydrophilic binder, but may have a hydrophilic binder layer other than the solid fine particle-containing layer. . Such a hydrophilic binder layer may or may not have solid fine particles, but when it is not a void layer, preferably when provided on the side farther from the support than the solid fine particle-containing layer of the present invention. It is preferable that the dry film thickness is 2 μm or less, preferably 1.5 μm or less from the viewpoint of the ink absorption speed.

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, and JP-A-57-74192.
Nos. 57-87989, 60-72785, 61-146591, and JP-A-1-950.
No. 91, No. 3-13376, etc., antifading agents, various anionic, cationic or nonionic surfactants, JP-A-59-42993, JP-A-5-42993.
Nos. 9-52689 and 62-280069,
JP-A-61-242871 and JP-A-4-2192.
No. 66, a whitening agent, a pH adjusting agent such as sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, and potassium carbonate; a defoaming agent; a lubricant such as diethylene glycol; And various known additives such as a thickener, a hardener, an antistatic agent, and a matting agent.

As the hardener, an inorganic or organic hardener can be used. For example, chromium alum, formaldehyde, glyoxal, epoxy compound, vinylsulfone compound, acryloyl compound, s-triazine compound, N -Methylol compounds, carbodiimide compounds, ethyleneimino compounds and the like can be used.

The amount of solids applied on the ink recording surface side of the ink jet recording paper of the present invention is not particularly limited.
Generally, 10 to 40 g / m ² is preferable, and 20 to 30 g / m ^2.
Is more preferred. Note that, from the viewpoint of preventing curl after forming a recorded image, it is preferable to form the recording image as thin as possible.

In any of the constituent layers on the ink recording surface side of the present invention, a polycationic polymer electrolyte disclosed in JP-A-56-89992 and a JP-A-57-366 are used as a water-proofing agent for images.
No. 92, the basic latex polymer disclosed in
One or more kinds of polyallylamine described in JP-A-58788 and JP-A-62-174184, and alkali metal weak acid salts described in JP-A-61-47290 can be used.

As the support for use in the ink jet recording paper of the present invention, those conventionally known as ink jet recording papers can be appropriately used.

The transparent support is made of a material such as polyester resin, diacetate resin, triacesate resin, acrylic resin, polycarbonate resin, polyvinyl chloride resin, polyimide resin, cellophane, celluloid and the like. Examples thereof include a film, a plate, and a glass plate. Among them, those having a property of resisting radiant heat when used as OHP are preferable, and polyethylene terephthalate is particularly preferable. The thickness of such a transparent support is preferably about 10 to 200 μm.

Examples of the support used when it is not necessary to be transparent include, for example, sheets and plates made of general paper, synthetic paper, resin-coated paper, cloth, wood, metal, etc. Examples of the support include those obtained by making the support opaque by a known means. As an opaque support,
A resin-coated paper (so-called RC paper) having a polyolefin resin coating layer in which a white pigment or the like is added to at least one of the base paper, and a so-called white pet obtained by adding a white pigment to polyethylene terephthalate are preferable.

The effect of the present invention is particularly significant when the support is non-water-absorbing. Particularly, a transparent or opaque polyethylene terephthalate support or a support having base paper coated on both sides with a hydrophobic resin such as polyethylene are preferred. It is preferably used.

Prior to the application of the ink receiving layer, it is preferable to subject the support to a corona discharge treatment or a subbing treatment for the purpose of increasing the adhesive strength between the support and the ink receiving layer. Further, the ink jet recording paper of the present invention does not necessarily need to be colorless, and may be a colored recording sheet.

In producing the ink jet recording paper of the present invention, the method of applying each hydrophilic layer including the ink receiving layer on the 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 an extrusion coating method using a hopper described in US Pat. No. 2,681,294. It is preferably used.

The aqueous ink referred to in the present invention is a recording liquid comprising the following colorant, liquid medium, and other additives.
As the colorant, a water-soluble dye such as a direct dye, an acid dye, a basic dye, a reactive dye, or a food colorant known by inkjet can be used.

Examples of the solvent for the aqueous ink include water and various water-soluble organic solvents, for example, alcohols such as methyl alcohol, isopropyl alcohol, n-butyl alcohol, tert-butyl alcohol and isobutyl alcohol; dimethylformamide, dimethylacetamide and the like. Amides; ketones or ketone alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol, propylene glycol, butylene glycol, triethylene glycol; 1,2,6
Polyhydric alcohols such as hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol, glycerin and triethanolamine; polyhydric alcohols such as ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether and triethylene glycol monobutyl ether; And lower alkyl ethers.

Among these many water-soluble 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.

Examples of other water-based ink additives include a pH adjuster, a metal sequestering agent, a fungicide, a viscosity adjuster, and the like.
Examples include a surface tension adjuster, a wetting agent, a surfactant, and a rust inhibitor.

The water-based ink liquid is dried at 20 ° C.
The surface tension is preferably 5 to 60 dyne / cm, more preferably 30 to 50 dyne / cm.

[0092]

EXAMPLES The present invention will be described specifically with reference to examples, but embodiments of the present invention are not limited to these examples.

Example 1 The following coating was carried out on a photographic printing paper support in which both sides of a 160 g / m ² base paper were coated with polyethylene (containing 12% by weight of anatase type titanium oxide in the polyethylene layer on the ink absorbing layer side). Liquid-1 was applied so as to have a wet film thickness of 190 μm, and dried to prepare inkjet recording paper-1.

The coating was carried out by a slide hopper method. After the coating, the coating was cooled to about 10 ° C., dried with air at this temperature for 1 minute, and dried with air at 30 ° C. to 45 ° C. for 4 minutes.

Coating solution-1 Pure water (ion-exchanged water) 950 ml Ethanol 30 ml 50 ml Silica (vapor-phase method silica having an average primary particle diameter of 13 nm) 51 g Polyvinyl alcohol 8 g (average degree of polymerization = 3500, saponification degree = 88%) ) Surfactant (AS-1) 0.1 g AS-1: sodium triisopropylnaphthalenesulfonate Next, as shown in Table 1, the hydrophobic organic compound of the present invention was added to inkjet recording paper-1 for comparison. Inkjet recording papers-2 to 11 were prepared in the same manner as the inkjet recording paper-1 to which the organic compound was added. However, with the addition of the oil droplets, the total amount of the coating liquid was adjusted with pure water so as to be the same for each ink jet recording paper. Further, each of the above hydrophobic compounds was added by emulsification and dispersion in polyvinyl alcohol in the presence of AS-1 as a surfactant.

[0096]

[Table 1]

Each of the obtained ink-jet recording papers was evaluated for ink absorbency, film brittleness and glossiness by the following methods. The ink absorbency was measured by an inkjet printer MJ-90 manufactured by Seiko Epson Corporation.
0C was used.

(1) Ink absorptivity: The ink is uniformly ejected so that the maximum ink amount of each of yellow and cyan becomes 40%, and the recording is performed. The red reflection density of the solid portion is measured with a microdensitometer (aperture = 200 μmφ). The measurement was carried out at 20 points, and the standard deviation of the density variation was calculated, and the value was divided by the average reflection density.

When the ink absorbency is good, there is no unevenness in the image, and this value is small. However, when the ink absorbency is low, the ink droplets bead each other on the recording paper and become uneven. This value increases.

(2) Film brittleness: Each ink jet recording paper was stored for a day and night at 25 ° C. and a relative humidity of 20% in a cylindrical shape having a diameter of 60 mm so that the printing surface was on the outside. The condition was observed with a loupe.

◎: No cracks were observed even with a loupe. Adverse effects are observed. ×: Cracks are visually observed, and the effect on image quality is very large. (3) Glossiness The recording layer surface is a variable-angle gloss meter (V) manufactured by Nippon Denshoku Industries Co., Ltd.
GS-1001-DP), and measured the gloss at 75 degrees.

Table 2 shows the obtained results.

[0103]

[Table 2]

From the results shown in Table 2, it can be seen that the ink jet recording papers 3, 4, 7, and 8 of the present invention can greatly improve the brittleness of the film without lowering the ink absorbency, and that there is almost no decrease in gloss. I understand.

On the other hand, the ink jet recording papers-2 and 6 in which the added amount of oil droplets is equal to or less than the present invention have almost no crack improving effect, whereas the ink jet recording papers in which the added amount of oil droplets are equal to or more than the present invention. In the cases of Nos. 5 and 9, the ink absorption speed is reduced, and the gloss is also significantly reduced.

On the other hand, when a hydrophobic organic compound having a melting point exceeding 40 ° C. is used, there is no crack improving effect.

Example 2 Ink jet recording papers 21 to 28 obtained by adding the polymer latex to the coating solution as shown in Table 3 were prepared in the same manner as the ink jet recording paper 1 in the ink jet recording paper of Example 1.

Evaluation was performed in the same manner as in Example 1, and the results shown in Table 4 were obtained.

[0109]

[Table 3]

[0110]

[Table 4]

From the results in Table 4, it can be seen that even when the polymer latex was used as the oil droplet, the glass transition temperature was 4
Inkjet recording paper 21, 22, 24, 25 containing 0 to 50 ° C. or less and containing 5 to 50% by weight based on silica.
Shows that cracks are improved without deteriorating ink absorbency or glossiness. When used in excess of 50% by weight, cracking is good but ink absorption and gloss are reduced.

When a polymer latex having a glass transition temperature exceeding 40 ° C. is used, cracking is not improved.

Example 3 A 100 g / m ² base paper coated with polyethylene on both sides of a photographic paper support (thickness: 140 μm, containing 7% by weight of anatase type titanium oxide in the polyethylene layer on the ink jet recording layer side; ink jet recording layer side) Has a layer containing 4.2 g / m ² of alkali-treated gelatin and a hardener as a back layer on the back side of the ink-jet recording surface. And dried to give a layer having voids on the support.

[Coating Liquid-1] Pure water 980 ml Vapor-phase fine-particle silica having an average particle diameter of 0.007 μm 48.0 g Polyvinyl alcohol having an average polymerization degree of 3500 10.8 g (PVA3500, saponification degree 94%) Surface activity 1.2 g of Agent-1 (AS-1) Next, on this coating layer, [Coating Solution-3] having the following composition was applied so as to have a wet film thickness of 8 [mu] m and dried to form an inkjet recording paper-31. Obtained.

[Coating liquid-2] Pure water Phenylcarbamoylated gelatin 800 ml (amino group blocking rate = 88%) 40 g polyvinylpyrrolidone (K-90) 25 g polyethylene oxide (average molecular weight = about 150,000) 12 g surfactant-2 (AS-2) 0.7 g Hardener-1 2.1 g AS-2: sulfosuccinic acid-dioctyl ester-sodium salt Hardener-1: 1,5-diglycidyl-3-hydroxypentane Next, inkjet recording paper- In 31, ink-jet recording papers -32 to 34 were produced in the same manner as for ink-jet recording paper-31, using [Coating liquid-2] to which an LP dispersion as shown in Table 5 was added.

The amount of pure water was adjusted so that the total amount of the coating solution was constant when the LP dispersion was added.

The LP dispersion used was an 8% by weight dispersion of liquid paraffin, and the droplet diameter was approximately 0.1%.
13 μm.

[0118]

[Table 5]

The obtained ink jet recording paper was evaluated in the same manner as in Example 1. Table 6 shows the results.

[0120]

[Table 6]

From the results shown in Table 6, when the uppermost swelling layer mainly composed of gelatin is provided, the ink absorptivity is reduced as a whole, but the gloss is improved.

Among them, the ink jet recording papers -32 and 33 of the present invention have a relatively small decrease in ink absorbency and glossiness, and furthermore, cracks are greatly improved.

On the other hand, ink jet recording paper-3 containing 100% by weight of liquid paraffin based on silica.
In No. 4, although the cracks were good, the ink absorbency and glossiness were greatly reduced.

Example 4 In Example 3, [Coating liquid-2] was replaced with the following [Coating liquid-2].
a), except that the DI shown in Table 7 was the same as in Example 3.
By adding a DP dispersion (containing 10% by weight of diisodecyl phthalate, the particle size of droplets is about 0.23 μm), inkjet recording papers 41 to 44 having the same configuration as the inkjet recording papers 31 to 34 were prepared and implemented. Evaluation was performed in the same manner as in Example 3. Table 8 shows the results.

[Coating Liquid-2a] Pure water 920 ml Fine particle calcium carbonate (average particle size = about 0.03 µm) 120 g 6.2 g of polyvinyl alcohol having an average degree of polymerization of 1700 (degree of saponification 90%) Surfactant-1 0g

[0126]

[Table 7]

[0127]

[Table 8]

From the results shown in Table 8, it can be seen that the same effects as in Example 3 can be obtained even when the fine particle calcium carbonate is used as the solid fine particles.

Example 5 8 g of polyvinyl alcohol (average degree of polymerization of 350) was used for the ink jet recording paper-1 prepared in Example 1.
As shown in Table 9, No. 0) was changed to a combination of polyvinyl alcohol having a high polymerization degree and polyvinyl alcohol having a low polymerization degree, and inkjet recording papers-51 to 61 were produced in the same manner as the inkjet recording paper-1. (In all cases, the amount of polyvinyl alcohol is the same.) In the table, the high polymerization degree PVA and the low polymerization degree PVA indicate the amounts of the high and low polymerization degree polyvinyl alcohols, respectively.

[0130]

[Table 9]

[0131]

[Table 10]

From the results shown in Table 10, the average degree of polymerization was 1000
Ink jet recording paper (51, 52, 53, 5) using the following low polymerization degree polyvinyl alcohol in combination with a high polymerization degree polyvinyl alcohol having an average polymerization degree of 2000 or more.
4, 55, 56, 58, 60, and 61) have improved fragility of the film before and after the heat treatment as compared with Sample-1 in which the film is not used together. And the ratio to the high polymerization degree is 2 to 2
It can be seen that 0% of the samples (52, 53, 55, 58, 60, 61) have particularly good fragility.

The ink jet recording papers (51-54, 60, 61) of the present invention in which the average degree of polymerization of the high polymerization degree polyvinyl alcohol is 3000 or more and the average degree of polymerization of the low polymerization degree polyvinyl alcohol is 400 or less are glossy. It can be seen that the properties are particularly excellent.

Example 6 10.8 g of polyvinyl alcohol (average degree of polymerization: 3500) used for the coating liquid-1 in the ink jet recording paper-31 prepared in Example 3 was subjected to a high polymerization degree as shown in Table 11. Ink jet recording papers -71 to 78 were produced in the same manner as in ink jet recording paper -31, except that the combination of polyvinyl alcohol and low polymerization degree polyvinyl alcohol was changed (the amount of polyvinyl alcohol was the same in all cases).

[0135]

[Table 11]

The obtained sample was evaluated in the same manner as in Example-5, and the results shown in Table 12 were obtained.

[0137]

[Table 12]

From the results in Table 12, it can be seen that even when a thin swelling layer mainly composed of gelatin is provided as the uppermost layer, the effect of improving brittleness and the high glossiness, which are the effects of the present invention, are obtained by the inkjet recording paper of the present invention. (71-75.77).

Example 7 In the ink jet recording paper-7 prepared in Example 1, 8 g of polyvinyl alcohol having an average degree of polymerization of 3500, 7.5 g of polyvinyl alcohol having an average degree of polymerization of 3500, and 0.5 g of polyvinyl alcohol having an average degree of polymerization of 3500 were used. Inkjet recording paper-80 was prepared in the same manner as inkjet recording paper-7, except that the polymerization degree was changed to the use of polyvinyl alcohol having a degree of polymerization of 300.
Was prepared. Evaluation was made in the same manner as in Example 1. As a result, the results were as follows: ink absorption: 0.04 brittleness: ◎ gloss: 66% From this, it is understood that the brittleness can be further improved by using the hot water droplet and the low polymerization degree polyvinyl alcohol and the high polymerization degree polyvinyl alcohol in combination.

[0140]

According to the present invention, as demonstrated in the examples,
Ink-jet recording paper has high ink absorbency containing solid fine particles dispersed in a hydrophilic binder, enabling high-quality ink-jet recording without reducing the brittleness of the film even when stored under low humidity. Has excellent effects.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location D21H 27/00 D21H 5/00 Z

Claims (8)

[Claims] 1. A support having at least one ink-absorbing layer containing solid fine particles and polyvinyl alcohol on a support, wherein at least one of the ink-absorbing layers has a weight ratio of the solid fine particles to the total amount of polyvinyl alcohol. 2 ~ 2
An ink jet recording sheet containing 00 times, wherein the layer containing the solid fine particles contains polyvinyl alcohol having an average degree of polymerization of 1000 or less and polyvinyl alcohol having an average degree of polymerization of 2000 or more. 2. The method according to claim 1, wherein the solid fine particles are selected from silica, calcium carbonate, alumina, alumina hydrate or magnesium silicate, each of which has an average primary particle diameter of 7 to 80 nm. The inkjet recording paper according to claim 1. 3. The ink jet recording paper according to claim 1, wherein the solid fine particles are silica synthesized by a gas phase method with an average primary particle diameter of 7 to 30 nm. 4. The amount of the polyvinyl alcohol having an average degree of polymerization of 1000 or less is 1 to 30% by weight based on the weight of polyvinyl alcohol having an average degree of polymerization of 2000 or more.
The inkjet recording paper according to any one of claims 1 to 3, wherein 5. A support having at least one ink absorbing layer containing at least solid fine particles and polyvinyl alcohol as a hydrophilic binder on a support, wherein the weight ratio of the solid fine particles to the hydrophilic binder in at least one layer of the ink absorbing layer. Is an ink jet recording paper having a ratio of 2 to 200 times, wherein the ink absorbing layer is formed by adding oil droplets selected from a hydrophobic organic compound having a melting point of 40 ° C. or less or a polymer latex having a glass transition temperature of 40 ° C. or less to solid fine particles 5
An ink-jet recording sheet, characterized in that it contains about 50% by weight. 6. An oil droplet having an average particle size of 0.05 to 0.5.
The inkjet recording paper according to claim 5, wherein the thickness of the inkjet recording paper is μm. 7. The solid fine particles, wherein each of the primary particles has an average particle diameter of 7 to 80 nm and is selected from silica, calcium carbonate, alumina, alumina hydrate or magnesium silicate. The inkjet recording paper according to claim 5. 8. The ink-jet recording sheet according to claim 5, wherein the solid fine particles are silica synthesized by a gas phase method, wherein primary particles have an average particle diameter of 7 to 30 nm.