JPH11277891A - Ink jet recording paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the occurrence of creases and cracks of skin caused by printing with an increased ink absorption capacity by laminating an ink absorption layer consisting of an air layer containing minute grains on one surface of a water absorption carrier. SOLUTION: An ink absorption layer consisting of an air layer containing minute grains is laminated on one surface of a water absorption carrier, and then a non-water absorption resin layer having a thickness of 3-10 μm is laminated on the other surface for manufacturing an ink jet recording paper. As a concrete example, there is given a sheet or board comprising paper, synthetic paper, cloth, or the like, and paper is suitable because it has a fine water absorptiveness, and is inexpensive in cost. For such minute grains to be contained in the air layer, silica minute grains are suitable, and silica synthesized by a gaseous phase method is more suitable in terms of the capability of being blended at high density, recorded with vivid images, and the like. The minute grains of these silica are suitable to have an average diameter of 100 nm or lower.

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 from both the ink and device aspects.
It is rapidly spreading in various fields such as facsimile and computer terminals.

The details of the ink jet recording technique are described, for example, in the trend of the ink jet recording technique (edited by Koichi Nakamura, published on March 31, 1995, Japan Science Information Co., Ltd.).

The 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 and causes ink to flow or bleed even when the print dots overlap. It is required that the printing dots do not spread unnecessarily in the horizontal direction and that the periphery is smooth and not blurred.

[0005] In particular, in ink jet recording paper,
When the ink absorption speed is low, when ink droplets of two or more colors are printed in an overlapping manner, the droplets cause a repelling phenomenon on the recording paper and become uneven, or in a boundary region of a different color. It is necessary for recording paper to have high ink absorptivity because the colors are easily blurred and the image quality is apt to be greatly reduced.

[0006] To solve these problems, a great many techniques have been proposed.

[0007] For example, a recording paper described in JP-A-52-53012 in which a coating material for surface processing is wetted on a low-size base paper, a support surface described in JP-A-55-5830 is disclosed. Recording paper having an ink-absorbing coating layer thereon, recording paper containing non-colloidal silica powder as a pigment in a coating layer described in JP-A-56-157, JP-A-57-107878 Recording paper comprising a combination of an inorganic pigment and an organic pigment described in
JP-A-110287 discloses a recording sheet having two pore distribution peaks, JP-A-62-111782 discloses a recording sheet comprising two upper and lower porous layers, and JP-A-59-68292. Publication No. 59-1236
Recording paper having irregular cracks described in JP-A Nos. 96 and 60-18383, JP-A-61-1
JP-A-63-252779, recording paper having a fine powder layer described in JP-A-35786, JP-A-61-148092 and JP-A-62-149475,
JP-A-1-108083, JP-A-2-136279, JP-A-3-65376, JP-A-3-27976, and the like, a recording paper containing a pigment having specific physical properties or fine-particle silica, JP-A-57-1409
No. 1, No. 60-219083, No. 60-21
0984, 61-20797, 61-
188183, JP-A-5-278324,
JP-A-6-92011, JP-A-6-183134,
Recording papers containing fine particle silica such as colloidal silica described in JP-A-7-137431 and JP-A-7-276789, JP-A-2-276671, JP-A-3-67684, and JP-A-3-267684. No. 2,15082, JP-A-3-251488, JP-A-4-67998, JP-A-4-263983, and JP-A-5-16517. The technology is known.

[0008] Among these techniques, recording paper in which the ink receiving layer is a layer having many voids for absorbing and retaining ink has good ink absorbency, has low bleeding at the boundary, and has high quality images. Can be expected.

However, in the ink absorbing layer having the void structure, the ink absorption amount is smaller than the dry capacity of the original film. For example, in a film having a dry film thickness of 40 μm,
In the case where a film having a solid content of 22 μm as a uniform volume is formed, the amount of voids is determined by the inkjet recording paper 1
0.0001 × (40-22) (cm) × 10000 per m ²
(Cm ² ) = 18 ml, and depending on the recording method, there may be a case where the ink absorption capacity may be insufficient near the maximum ink amount. When the ink absorption capacity is insufficient, the ink overflows, and the image quality is greatly deteriorated.

In the ink absorbing layer having a void layer, the void volume may change during storage, particularly during storage under high temperature and high humidity, so that the void does not change in the void layer. It preferably contains fine particles. When a void is formed by containing fine particles in the void layer,
The incorporation of a hydrophilic binder can stabilize the film, but these ink-absorbing layers are harder than the ink-absorbing layer that receives ink due to the swelling property of the hydrophilic binder.

When an ink-absorbing layer having such a void structure is provided on a non-water-absorbing support, a clear image with a high density can be obtained. It is necessary to make the dry film thickness of the ink absorbing layer sufficiently thick. In this case, the brittleness of the film (particularly, cracking under low humidity) is caused by the characteristics of the film. It is also disadvantageous in terms of cost.

On the other hand, when an ink-absorbing layer having a void structure is provided on a water-absorbing support, the support itself has a high absorption capacity and ink absorbability, which is preferable from the viewpoint of ink absorption. Therefore, the dry thickness of the ink absorbing layer can be reduced as compared with the case where the ink absorbing layer is provided on a non-water-absorbing support.

It is considered that such a recording sheet is suitable for high-quality image recording close to a photograph, which is a field of application of ink jet recording, which has been particularly noted in recent years.

However, when a recording sheet using a water-absorbing support is used, if the ink penetrates into the support during recording and then is dried, the support is likely to be wavy and wrinkled. As a result of the study of the present inventors, when the support becomes wavy and wrinkles occur on the recording paper provided with the ink absorbing layer having the void layer on the water-absorbing support, from the characteristics of the film of the ink absorbing layer,
It became clear that cracks occurred in the film and the quality of the recorded image was apt to deteriorate.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a first object of the present invention is to unnecessarily increase the thickness of an ink absorbing layer. An object of the present invention is to provide an ink jet recording paper which is free from wrinkles due to printing and has no cracks in a film without increasing the ink absorption capacity without any problem.

A second object of the present invention is to provide a low-cost, high-quality ink jet recording sheet.

[0017]

Means for Solving the Problems The above-mentioned problems are as follows: (1) A water-absorbing support having a void layer containing fine particles on one surface as an ink absorbing layer and a non-water absorbing layer having a thickness of 3 to 10 μm on the other surface. An ink jet recording paper comprising a conductive resin layer. (2) The ink jet recording sheet according to the above (1), wherein the non-water-absorbing resin layer is a polyolefin resin layer. (3) The ink jet recording paper according to the above (1) or (2), wherein the fine particles are fine particles having an average particle diameter of 100 nm or less. (4) The ink jet recording paper as described in any one of (1) to (3) above, wherein the void layer contains a cationic mordant. (5) The ink jet recording paper according to any one of (1) to (4), wherein the water-absorbing support is a water-absorbing support having a thickness of 100 μm or more. Achieved by

Hereinafter, the present invention will be described in detail.

In the present invention, as the water-absorbing support,
Any support can be used as long as it has the required water absorption.

For example, sheets and plates made of ordinary paper, synthetic paper, cloth, wood and the like can be mentioned. In particular, paper is most preferable because the base material itself has excellent water absorption and is also excellent in cost. Hereinafter, the paper support will be described.

As the paper support, chemical pulp such as LBKP and NBKP, 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. In addition, various fibrous substances such as synthetic pulp, synthetic fiber, and inorganic fiber can be used as a raw material as needed.

In the paper support, various conventionally known additives such as a sizing agent, a pigment, a paper strength enhancer, a fixing agent, a fluorescent whitening agent, a wet paper strength enhancer, a cationizing agent and the like may be added, if necessary. Agents can be added. As a sizing agent, higher fatty acids,
Alkyl ketene dimer etc., pigments include calcium carbonate, talc, titanium oxide, etc., paper strength enhancers include starch, polyacrylamide, polyvinyl alcohol, etc., and fixing agents include sulfate bands, cationic polymer electrolytes, etc. However, the present invention is not limited to this.

The paper support is prepared by mixing a fibrous substance such as the above-mentioned wood pulp with various additives and forming a fourdrinier paper machine, a round paper machine,
It can be manufactured by making paper with 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 calendar treatment can be performed at or after the papermaking.

In the present invention, an ink-absorbing layer is provided on one side of the water-absorbing support, and a non-water-absorbing resin layer (hereinafter sometimes referred to as the backside layer of the present invention) is provided on the other side. In order to increase the adhesive strength between the ink absorbing layer and the water absorbing support or the backing layer of the present invention, the corona is applied to the water absorbing support prior to the installation of the ink absorbing layer or the backing layer of the present invention. Discharge treatment, undercoat treatment, or the like can be performed.

The thickness of the water-absorbing support of the present invention is 100 μm
It is preferable that there is the above. If the thickness is smaller than this, even if the back layer of the present invention is provided, the support itself absorbs the ink solvent, and by drying the ink solvent after recording, the support becomes wavy and wrinkles are formed in an image form, Cracks easily occur in the ink absorbing layer. Although there is no particular upper limit on the thickness of the water-absorbing support, it is generally about 500 μm from the viewpoint of handleability.

In the present invention, as the fine particles contained in the void layer, various known inorganic or organic solid fine particles used in conventional ink jet recording paper can be used. It is preferable to use silica fine particles in terms of being able to record an image and being able to be manufactured at low cost.

The method for producing silica fine particles is a dry method (gas phase method).
The dry method is a method based on gas-phase hydrolysis of silicon halide at high temperature (flame hydrolysis method).
Also known is a method (arc method) in which silica sand and coke are heated and reduced and vaporized by an arc in an electric furnace, and this is air-oxidized. In addition, as a wet method, a method is known in which active silica is generated by acid decomposition of a silicate, and is then appropriately polymerized to cause aggregation and precipitation.

In the present invention, among silica fine particles, silica synthesized by a gas phase method is most preferable.

The fine particles used in the ink jet recording paper of the present invention preferably have an average particle diameter of 100 nm or less.

When the average particle diameter of the fine particles exceeds 100 nm, the glossiness of the recording paper is reduced, the roundness of dots during ink jet recording is reduced, unnecessary dots are spread, or It is difficult to obtain a clear image because the maximum density is reduced due to irregular reflection on the surface.

The lower limit of the average particle diameter of the fine particles is not particularly limited, but is generally about 10 from the viewpoint of handleability and stability during production.
nm.

The fine particles may be used in a state of being uniformly dispersed as primary particles, or may be added in a state where the primary particles form secondary aggregated particles and dispersed. Good, but the latter is more preferred.

When the fine particles are used in the form of secondary aggregated particles, it is preferable to use primary particles having an average particle diameter of 30 nm or less from the viewpoint of gloss.

The lower limit of the average particle diameter of the primary particles is not particularly limited, but is preferably about 3 nm or more, particularly preferably 6 nm or more from the viewpoint of the production of the particles.

The average particle diameter of the fine particles is obtained 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 obtaining the simple average value (number average). Here, each particle size is represented by a diameter assuming a circle equal to the projected area.

The ink jet recording paper of the present invention has a void layer containing fine particles as an ink absorbing layer. In the case where fine particles are contained to form voids, the film is stabilized by adding a hydrophilic binder. Can be planned.

As the hydrophilic binder used, gelatin or a gelatin derivative, polyvinylpyrrolidone,
Pullulan, polyvinyl alcohol or derivatives thereof, polyethylene glycol, carboxymethyl cellulose,
Hydroxyethylcellulose, dextran, dextrin, polyacrylic acid and salts thereof, agar, κ-carrageenan, λ-carrageenan, ι-carrageenan, xanthen gum, locust bean gum, alginic acid, gum arabic, JP-A-7-195826 and JP-A-7-195826 -975
No. 7, polyalkylene oxide copolymerizable polymer, water-soluble polyvinyl butyral, or a homopolymer of a vinyl monomer having a carboxyl group or a sulfonic acid group described in JP-A No. 62-245260, or a homopolymer thereof. Examples include polymers such as copolymers of vinyl monomers and other monomers. These hydrophilic binders may be used alone or in combination of two or more.

Among them, polyvinyl alcohol or a derivative thereof is preferable because of its hygroscopicity of the film, stickiness under high humidity, and less bleeding of dye during ink jet recording.

The above-mentioned polyvinyl alcohol or a derivative thereof includes cationically modified, nonionic modified and anionic modified polyvinyl alcohol.

The average degree of polymerization of polyvinyl alcohol is preferably from 1,000 to 5,000 from the viewpoint of film forming properties, and particularly preferably the average degree of polymerization is 2,000 or more.

The degree of saponification of polyvinyl alcohol is 70
-100% is preferred, and 80-100% is particularly preferred.

As the cation-modified polyvinyl alcohol, for example, as described in JP-A-61-10483, a primary to tertiary amino group or a quaternary ammonium group is added to the main chain or side chain of polyvinyl alcohol. And a polyvinyl alcohol contained therein, which 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,
Hydroxylethyltrimethylammonium chloride, trimethyl- (3-methacrylamidopropyl) ammonium chloride, N- (1,1-dimethyl-3-
Dimethylaminopropyl) acrylamide and the like.

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

As the anion-modified polyvinyl alcohol, for example, polyvinyl alcohol having an anionic group as described in JP-A-1-206088, JP-A-61-237681 and JP-A-63-30 can be used.
No. 7979, a copolymer of vinyl alcohol and a vinyl compound having a water-soluble group, and a modified polyvinyl alcohol having a water-soluble group as described in JP-A-7-285265. Can be

As the nonionic modified polyvinyl alcohol, for example, a polyvinyl alcohol derivative obtained by adding a polyalkylene oxide group to a part of vinyl alcohol as described in JP-A-7-9758, and JP-A-8-25795 And a block copolymer of a vinyl compound having a hydrophobic group and a vinyl alcohol.

In the void layer of the present invention, the weight ratio of the solid fine particles to the hydrophilic binder is generally 2 to 200 times, preferably 3 to 20 times.

When the ratio is less than 3 times, the ink absorbency decreases, and when it exceeds 20 times, the ink absorbing layer becomes brittle, and it becomes difficult to perform high-quality ink jet recording.

In the ink jet recording paper of the present invention, since the ink can be absorbed by the support together with the ink absorbing layer, the density tends to decrease due to the diffusion of the dye into the support. In order to improve the reduction in density and the water resistance and bleeding resistance of an image, it is preferable that a cationic mordant is contained in the ink absorbing layer of the inkjet recording paper of the invention.

The cationic mordants include primary to tertiary
A polymer mordant having a quaternary amino group and a quaternary ammonium base is preferably used, but a cationic non-polymer mordant can also be used.

As the polymer mordant, a polymer mordant having a quaternary ammonium salt group is preferable from the viewpoint of weather resistance and strong dyeing properties.

The preferred polymer mordant is a homopolymer of a monomer having a quaternary ammonium group, a copolymer with another monomer or a condensation polymer.

The polymer mordant may be a water-soluble polymer or water-dispersible latex particles.

As the non-polymer mordant, a compound having a quaternary ammonium base having a total of 12 or more, preferably 18 or more carbon atoms is used.

The amount of the polymer mordant and the non-polymer mordant used is 0.2 to 10 g, preferably 0.5 to 5 g per 1 m ² of recording paper.

When a hydrophilic binder is used in the ink absorbing layer of the ink jet recording paper of the present invention, it is preferable to add a hardener capable of crosslinking the hydrophilic binder. Examples of the 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 chromium alum, boric acid or a salt thereof, and borax.

When the hydrophilic binder is polyvinyl alcohol, an epoxy hardener having at least two epoxy groups in the molecule, boric acid or a salt thereof, and borax are particularly preferred. As boric acid, not only orthoboric acid but also metaboric acid, hypoboric acid, tetraboric acid, pentaboric acid and the like can be used.

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

In the present invention, the dry thickness of the ink absorbing layer is preferably 5 to 30 μm. If the thickness is less than 5 μm, the ink absorbency and gloss may be reduced.
If it exceeds m, cracking of the coating film may be caused.

The ink jet recording paper of the present invention can be provided with two or more ink absorbing layers, and at least one of them needs to be a void layer containing fine particles.

Various additives can be added to the ink absorbing layer of the present invention as needed.

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
Nos. 091 and 3-13376; various anionic, cationic or nonionic surfactants; JP-A-59-42993;
Nos. 2689, 62-280069 and 61
Various known additives such as fluorescent whitening agents, antifoaming agents, diluents such as diethylene glycol, preservatives, thickeners, antistatic agents, matting agents and the like described in JP-A-242871 and JP-A-4-219266. An agent can also be included.

The ink absorbing layer of the present invention comprises, for example,
The material for forming the ink absorbing layer is added to an appropriate solvent, for example, water, alcohol or various organic solvents to prepare a coating solution, the coating solution is applied to a water-absorbing support, and dried to form a void structure. Can be formed by forming an ink absorbing layer having

The method of applying the coating solution on the support can be appropriately selected from known methods.

When the ink absorbing layer is composed of two or more layers, two or more layers can be applied simultaneously. Further, all the hydrophilic binder-containing layers are preferably formed by a simultaneous coating method in which all the layers are formed by one coating.

As a method for applying the ink absorbing layer, a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method, and a hopper described in US Pat. No. 2,681,294 are used. The extrusion coating method is preferably used. In particular, a curtain coating method or a slide hopper coating method is preferred as the multilayer simultaneous coating method.

For drying after coating, it is preferable that the coating liquid is once cooled to increase the viscosity of the coating liquid or gelled, and then dried by blowing air.

The temperature of the coating solution is usually from 25 to 60 ° C., preferably from 30 to 50 ° C. The cooling is preferably performed so that the film surface temperature after coating is 20 ° C. or less, preferably 15 to 5 ° C., and the subsequent drying is performed by blowing air at 20 to 60 ° C. It is preferable from the point of obtaining.

The wet film thickness after coating varies depending on the desired dry film thickness, but is generally from 40 to 200 μm, preferably from 50 to 150 μm. The coating speed largely depends on the drying ability, but is generally 20 to 200 m / min.
The drying time is approximately 2 to 10 minutes.

In the ink jet recording paper of the present invention, a non-water-absorbing resin layer is provided on the side of the water-absorbing support opposite to the side on which the ink-absorbing layer is formed.

The term "non-water-absorbing" means that the layer does not substantially absorb water.
Refers to a resin layer of 1 g / m ² or less.

The non-water-absorbing resin layer is made of, for example, polyolefin resin, acetate resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyester resin, acrylic resin, polyurethane resin, polycarbonate resin, nylon, or the like. Such as a mixture of
It can be formed of a known hydrophobic resin.

Among these, polyolefin resins are preferable, and polyolefin resins include α-polymers such as low-density polyethylene, high-density polyethylene, and polypropylene.
A mixture of various polymers such as a homopolymer of an olefin and a mixture of a low-density polyethylene and a high-density polyethylene is exemplified.

The back surface layer of the present invention can be formed on a support using a method appropriately selected from various known formation methods. For example, the support is coated on the support by melt extrusion, a film prepared by a known film forming method (for example, a calendering method or a casting method) is bonded to the support by a known lamination method, and a back layer component is contained. It can be formed by applying a coating solution to be formed and forming a film.

The thickness of the back layer according to the present invention is 3 to 10 μm. When the thickness of the back layer of the present invention is less than 3 μm, the effect of suppressing the occurrence of image-like wrinkles caused by recording is reduced, and cracks in the ink absorbing layer are likely to occur. Also, 10μ
When the distance exceeds m, the recording paper is apt to curl.

The ink jet recording paper of the present invention may have two or more layers on the side where the back layer of the present invention is provided, and at least one of the layers is the back layer of the present invention. It is necessary to be.

Various additives can be added to the back layer according to the present invention, if necessary.

For example, white pigments such as rutile-type or anatase-type titanium oxide, calcium carbonate, barium carbonate, zinc oxide, and alumina, and those previously mentioned as additives for the ink absorbing layer can be added. .

Further, the back surface layer of the present invention can have a roughened surface for preventing sticking to other recording paper, improving writability, and further improving transportability in an ink jet recording apparatus.

Next, an aqueous recording liquid used for ink jet recording using the ink jet recording paper of the present invention will be described.

The aqueous recording liquid usually comprises a water-soluble dye, a liquid medium, and other additives. As the water-soluble dye, known direct dyes, acid dyes, basic dyes, reactive dyes or food dyes used in ink jet recording can be used, but direct dyes or acid dyes are preferred.

The solvent is mainly composed of water. However, in order to prevent the dye from being precipitated when the aqueous recording liquid is dried and clogging at the nozzle tip and the recording liquid supply path, the boiling point is usually used. A high boiling organic solvent that is liquid at room temperature above 120 ° C. is added. The high-boiling organic solvent must have a function of preventing solid components such as dyes from being precipitated when water evaporates and generating a coarse precipitate, and therefore have a vapor pressure far lower than that of water. Required to have. In addition, it is necessary to have high miscibility with water.

There are many high-boiling organic solvents used for such purposes. 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,
Alcohols such as 2,4-pentanetriol, 1,2,6-hexanetriol, 1,2-hexanediol, thiodiglycol, triethanolamine, and polyethylene glycol (average molecular weight of about 300 or less) are exemplified. In addition to the above, dimethylformamide, N-methylpyrrolidone and the like can also be used.

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

Other additives to be added to the aqueous recording liquid include, for example, a pH adjuster, a metal sequestering agent, a fungicide,
Examples include viscosity modifiers, surface tension regulators, wetting agents, surfactants, and rust inhibitors.

The aqueous recording liquid is used at 25 ° C. to improve the wettability to the ink jet recording paper and to stabilize the discharge from the ink jet nozzle.
5 to 50 dyne / cm, preferably 28 to 40 dyn
It preferably has a surface tension in the range of e / cm.

The viscosity of the aqueous recording liquid is usually 25 ° C.
Is 2 to 10 Cp, preferably 2.5 to 8 Cp. The pH of the aqueous recording liquid is preferably from 3 to 9.

It is preferable that the minimum ink droplet ejected from the ink nozzle has a volume of 1 to 30 pL, since a dot diameter of about 20 to 60 μm can be obtained on the ink jet recording paper. A high-quality image can be obtained in a color print printed with such a dot diameter. More preferably, 2
This is the case where a droplet having a volume of ２０20 pL is ejected as a minimum droplet.

When ink jet recording is performed by a recording method using two types of aqueous recording liquids, each of which has a density twice or more different in magenta and cyan, since a low density ink is used in a highlight portion, the dot density is low. Although the identification becomes difficult, the present invention does not cause these disadvantages even when the ink jet recording method is used.

As the ink jet recording method, various conventionally known methods can be used. The details of the recording method are described, for example, in "Trends in Inkjet Recording Technology" (edited by Koichi Nakamura, published on March 31, 1995, Japan Science Information Co., Ltd.).

[0091]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

Example << Preparation of Recording Paper 1 (Invention) >> After a corona discharge treatment was applied to a water-absorbing paper support having a thickness of 180 μm, a low-density polyethylene resin was reduced to a thickness of 8 μm using a melt extruder. And melt extrusion coating to form the backside layer of the present invention. Thereafter, a coating solution 1 having the following structure is applied to the opposite side of the back surface layer of the present invention, and dried to obtain a dry film thickness of 20.
Recording paper 1 (invention) having a μm void layer was prepared.

The composition of the coating solution is the amount per liter of the coating solution.

[Coating Liquid 1] Fine Particle Silica Dispersion (1) 450 ml Cationic Polymer (1) 12 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 (Kuraray Co., Ltd.) PVA235) 12 g Boric acid 2.0 g Borax 1.0 g

Fine particle silica dispersion (1): 80 g of A200 manufactured by Nippon Aerosil Industrial Co., Ltd. (a fumed silica having an average primary particle diameter of 12 nm) was added to 400 ml of pure water, dispersed by an emulsifying and dispersing machine, and then dispersed. Is made to 450ml with pure water.

[0096]

Embedded image

<< Preparation of Recording Paper 2 (Present Invention) >> In preparation of recording paper 1, except that the thickness of the back layer of the present invention formed by melt extrusion coating was changed to 5 μm, the same as recording paper 1 was used. Recording paper 2 (the present invention) was prepared.

<< Preparation of Recording Paper 3 (Invention) >> Thickness 18
After performing a corona discharge treatment on a water-absorbing paper support of 0 μm,
A coating liquid containing a styrene-butadiene latex having a monomer amount ratio (weight%) of butadiene / styrene / acrylic acid = 58/40/2 was applied and dried to form a back layer of the present invention having a dry film thickness of 8 μm. . Thereafter, on the side opposite to the backside layer of the present invention, the coating liquid 1 used in preparing the recording paper 1 was applied and dried to prepare a recording paper 3 (the present invention) having a void layer having a dry film thickness of 20 μm.

<< Preparation of Recording Paper 4 (Invention) >> In preparation of recording paper 1, A200 (manufactured by Nippon Aerosil Co., Ltd.) used for fine particle silica dispersion (1) of coating liquid 1 was subjected to TT600 (average primary Recording paper 4 (invention) was prepared in the same manner as recording paper 1 except that fumed silica having a particle diameter of 40 nm (manufactured by Nippon Aerosil Co., Ltd.) was used.

<< Preparation of Recording Paper 5 (Invention) >> In preparation of recording paper 1, recording paper was used except that coating liquid 1 was omitted from coating liquid 1 instead of coating liquid 1. Recording paper 5 in the same manner as 1 (the present invention)
It was created.

<< Preparation of Recording Paper 6 (Invention) >> In preparation of recording paper 1, the same as recording paper 1 except that a water-absorbing paper support having a thickness of 80 μm was used instead of a water-absorbing paper support having a thickness of 180 μm. Thus, recording paper 6 (the present invention) was prepared.

<< Preparation of Recording Paper 7 (Comparison) >> Thickness 180
After performing a corona discharge treatment on a μm water-absorbent paper support, the coating liquid 1 used in preparing the recording paper 1 is applied and dried to prepare a recording paper 7 having a dry film thickness of 20 μm and a void layer (comparative). did.

<< Preparation of Recording Sheet 8 (Comparison) >> Recording Sheet 1
Recording paper 8 (comparative) was prepared in the same manner as recording paper 1 except that the thickness of the back layer of the present invention formed by melt extrusion coating was changed to 2 μm.

<< Preparation of Recording Paper 9 (Comparison) >> Recording Paper 1
Recording paper 9 (comparative) was prepared in the same manner as recording paper 1 except that the thickness of the back layer of the present invention formed by melt extrusion coating was changed to 15 μm.

When the cross sections of the void layers of the obtained samples 1 to 9 were observed with an electron microscope, the average particle size of the secondary aggregated particles was:
In each of Samples 1 to 3 and 5 to 9, 65 nm
And in sample 4, it was 150 nm.

Further, the obtained samples 1 to 9 were evaluated for maximum density, glossiness, wrinkles and swell after printing, cracks and curls after printing, as described below.

<< Evaluation of Maximum Density >> Solid printing of yellow, magenta, and cyan was performed using an inkjet printer MJ-5000C manufactured by Sae Epson Corporation, and the reflection density was measured with monochromatic light of blue, green, and red, respectively. .

<< Evaluation of Glossiness >> A 75-degree specular glossiness was measured with a variable angle photometer (VGS-101DP) manufactured by Nippon Denshoku Industries Co., Ltd.

<< Evaluation of Wrinkles and Waviness after Printing >> The sheet surface after printing was visually observed and judged according to the following evaluation criteria. [Evaluation Criteria] ；: Wrinkles and undulations are not recognized and the appearance is not impaired. ○: Wrinkles and undulations are small and do not impair the appearance. Greatly impairs aesthetics

<< Evaluation of Cracks after Printing >> The recording surface after printing was visually observed, and the number of cracks per 100 cm ² was counted.

<< Evaluation of Curl >> An A4 size sample was placed on 23
48 ° C in an environment of 20 ° C, 20% RH and 23 ° C, 80% RH.
After standing for a period of time, the curl heights at the four corners were measured, and the curl direction and the degree of curl were evaluated.

<Direction of curl> +: The ink absorbing layer was curled inward-; The back layer was curled inward <Degree of curl> ；: The average of curl heights at the four corners was less than 5 mm ；: Curl height at the four corners Average of 5 mm or more and less than 15 mm Δ; Average of curl height at four corners of 15 mm or more, 25 mm
Less than × Average of curl height at four corners is 25 mm or more. The results obtained are shown in Table 1.

[0113]

[Table 1]

As is clear from the results shown in Table 1, the ink jet recording paper (samples 1 to 6) of the present invention had good density and gloss, no wrinkles, undulations and cracks due to printing, and had curl characteristics. And a high-quality image can be obtained. On the other hand, the recording paper (samples 7 to 9) of the comparative inkjet recording paper has good density and gloss, but has wrinkles and undulations due to printing, and has poor curling characteristics.

[0115]

As described above, the ink jet recording paper of the present invention increases the ink absorption capacity without unnecessarily increasing the thickness of the ink absorption layer, and provides the maximum density, glossiness, wrinkles after printing,
Excellent over undulation, cracks after printing, and curling.

Claims (5)

[Claims] An ink-absorbing layer having a void layer containing fine particles on one surface of a water-absorbing support, and having a thickness of 3 to 10 on the other surface.
An ink jet recording paper having a non-water-absorbing resin layer of μm. 2. The ink jet recording paper according to claim 1, wherein the non-water-absorbing resin layer is a polyolefin resin layer. 3. The ink jet recording paper according to claim 1, wherein the fine particles have an average particle diameter of 100 nm or less. 4. The ink jet recording paper according to claim 1, wherein the void layer contains a cationic mordant. 5. The ink jet recording paper according to claim 1, wherein the water absorbing support is a water absorbing support having a thickness of 100 μm or more.