JPH115359A - Ink jet recording sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink jet recording sheet having excellent performance of scarcely lowering glossiness and bronzing at a printed paint with excellent ink receptivity, high transparency and glossiness. SOLUTION: In the ink jet recording sheet comprising an ink receptive layer containing 35 wt.% or more of water soluble polymer by dry weight, the layer contains at least one type of acid compound selected from weak acid and its salt having a dissociation constant of at least one proton of 2×10<-10> to 5×10<-2> , and compound for dissipating weak acid.

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 applicable to various ink jet printer systems.

[0002]

2. Description of the Related Art An ink jet recording apparatus (hereinafter, also referred to as an ink jet printer) has low noise, can perform high-speed printing, and can easily perform multicolor recording by using a plurality of ink nozzles. Therefore, in recent years, in particular, it has been rapidly spread in recent years as an image information output device for a computer.

Some ink jet printers developed for full-color printing can output high-quality images comparable to silver halide photographic color images. As a recording medium, a transparent film or glossy resin-coated paper is used.
It is expanding from characters and figures to color prints and design images that require image quality close to that of photographs.

[0004] By the way, for the ink for ink jet recording, an aqueous ink mainly composed of water and a water-soluble organic solvent is mainly used from the viewpoint of safety and recording characteristics, thereby preventing clogging of the ink and discharging. Improvements in characteristics and the like have been made. As a recording sheet, a recording sheet in which a porous ink absorbing layer is provided on a support called ordinary paper or ink jet recording paper has been used.

[0005] However, these recording sheets do not meet the recent demand for high image quality due to large ink bleeding and low glossiness. Furthermore, when a conventional porous ink absorbing layer is used on a transparent film or a glossy resin-coated paper support, transparency and gloss are lost because the porous ink absorbing layer has low light transmittance. There are drawbacks. In addition, since such a porous ink absorbing layer generally has a small ink absorption capacity, when a support that does not absorb ink, such as a transparent film or a glossy resin-coated paper support, is used, the ink overflows and the image quality is reduced. There was a problem of deterioration.

In order to solve these problems, it has been proposed to use, for example, a water-soluble polymer having high light transmittance and excellent water-ink receptivity as a binder in the receptor layer. For example, in Japanese Patent Application Laid-Open No.
The receiving layer formed from the gelatin aqueous solution of
Japanese Patent No. 64306 proposes a recording sheet obtained by first converting a coated gelatin into a gel state and then drying it by a cold drying method.

However, when these water-soluble polymers are used as a binder, the physical and chemical changes caused by the ink absorbed in the receptor layer affect the physical properties of the binder surface, and the print after printing is printed. The study by the present inventors has revealed that a problem that the gloss of the surface is lost due to a change in the storage environment occurs.
In addition, in some inks that are easily aggregated, not only the gloss of the print surface is easily lost, but also a glare called bronzing occurs, and this bronzing occurs when the pH of the film surface of the receiving layer is less than 7. It has also become clear that this is particularly likely to occur.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an ink jet recording sheet having excellent ink receptivity, high transparency and gloss. Secondly, it is an object of the present invention to provide an ink jet recording sheet in which gloss is not easily reduced or bronzing is less likely to occur in a printed print.

[0009]

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

(1) An ink-receiving layer containing 35% by weight or more of a water-soluble polymer on a dry basis on a support, wherein the ink-receiving layer has a dissociation constant of at least one proton of 2 × 10 ^-10. It contains at least one kind of an acid compound selected from a weak acid or a salt thereof having a content of 5 × 10 ⁻² or less and a compound capable of releasing a weak acid (hereinafter, also referred to as an acid compound of the present invention). Characteristic inkjet recording sheet.

(2) The ink jet recording sheet as described in (1) above, wherein the water-soluble polymer is at least one selected from gelatins, polyvinyl alcohols and polyvinylpyrrolidones.

(3) The ink jet recording sheet as described in (2) above, wherein the water-soluble polymer is gelatin.

(4) The gelatin has an isoelectric point of 5.5 to 5.5.
4. The ink jet recording sheet according to the item 3, wherein the value is in the range of 9.6.

(5) The ink jet recording sheet as described in any one of (1) to (4) above, wherein the pH of the film surface of the receptor layer is less than 7.

(6) The acid compound is added to the receiving layer in an amount of 0.0
1 to 5 characterized by containing not less than 01 mol / m ^2.
The inkjet recording sheet according to any one of the above.

(7) The ink jet recording sheet as described in any one of (1) to (6) above, wherein the acid compound has a molecular weight of 180 or less in terms of free acid.

Hereinafter, the present invention will be described in detail.

The ink jet recording sheet of the present invention comprises:
In the ink receiving layer, at least one kind of acid selected from a weak acid or a salt thereof and a compound capable of releasing a weak acid, wherein the dissociation constant of at least one proton is 2 × 10 ⁻¹⁰ or more and 5 × 10 ⁻² or less. Contains compounds. Such a weak acid may be an inorganic acid or an organic acid. When the weak acid is a polybasic acid, the dissociation constant of at least one proton may be within the above range. The weak acid is not necessarily a free acid, and may be a salt such as an alkali metal salt, an alkaline earth metal salt, or an ammonium salt. Further, a compound that can easily react and release a weak acid having a dissociation constant of at least one proton within the above range may be used.

Specific examples of the weak acid of the acid compound of the present invention include inorganic acids such as phosphoric acid, phosphorous acid, pyrophosphoric acid, orthosilicic acid, metasilicic acid, boric acid, carbonic acid, thiosulfuric acid and sulfurous acid. Salt, formic acid, acetic acid, propionic acid, n-
Butyric acid, isobutyric acid, trimethylacetic acid, valeric acid, diethylacetic acid, caproic acid, acrylic acid, vinylacetic acid, crotonic acid, isocrotonic acid, oxalic acid, malonic acid, mesaconic acid, methylmalonic acid, succinic acid, dimethylmalonic acid, ethyl Malonic acid, glutaric acid, pyrotartaric acid, adipic acid,
Pimelic acid, diethyl malonic acid, spearic acid, acetylenedicarboxylic acid, fumaric acid, maleic acid, glutaconic acid, itaconic acid, glycolic acid, lactic acid, tartaric acid, grape acid, glyoxylic acid, acetoacetic acid, malic acid, citric acid, ascorbic acid , Atrobic acid, aminobenzenesulfonic acid, benzoic acid, phthalic acid, hydroxybenzoic acid, dihydroxybenzoic acid, quinolinic acid, cinnamic acid, salicylic acid, phenylacetic acid, cyclopropanedicarboxylic acid, cyclobutanedicarboxylic acid, cyclopentanedicarboxylic acid,
Organic acids such as cyclohexanedicarboxylic acid and salts thereof are exemplified.

Examples of the acid compound of the present invention that can release a weak acid include acetic anhydride, borax and the like.

Among the acid compounds of the present invention, those having a molecular weight of 180 or less in terms of free acid are preferably used.

The acid compounds particularly preferably used in the present invention include inorganic acids such as phosphoric acid, phosphorous acid, pyrophosphoric acid, orthosilicic acid, metasilicic acid, boric acid, carbonic acid, thiosulfuric acid, sulfurous acid and salts thereof, and boric acid. Organic acids such as sand, formic acid, acetic acid, propionic acid, glycolic acid, lactic acid, tartaric acid, fumaric acid, malic acid, citric acid, adipic acid, phthalic acid, hydroxybenzoic acid and glutaric acid, and salts thereof.

When the acid compound of the present invention is contained in the receptor layer in an amount of 0.001 mol or more per square meter in terms of free acid, the effect of the present invention can be more effectively obtained. It is more effective when it contains less than 1 mole.

The ink jet recording sheet according to the present invention is characterized in that an ink receiving layer containing a water-soluble polymer in an amount of 35% by weight or more on a dry basis is provided on a support.

As the support used in the ink jet recording sheet of the present invention, either a transparent support or an opaque support can be used according to the purpose of use.

As the transparent support, any of those conventionally known can be used, for example, resin films such as polyester resin, cellulose acetate resin, acrylic resin, polycarbonate resin, polyvinyl chloride resin, polyimide resin, cellophane, and celluloid. There is. Among them, the rigidity of the support, polyester resin from the viewpoint of transparency,
Particularly, a polyethylene terephthalate film is preferable.
Such a transparent support preferably has a thickness of about 10 to 200 μm, more preferably 50 to 150 μm.
Of the degree.

As the opaque support, paper, resin-coated paper,
Conventionally known ones such as a pigment-containing opaque film and a foamed film can be used, but resin-coated paper and various films are preferable from the viewpoint of glossiness and smoothness. Resin-coated paper, especially polyolefin resin-coated paper or polyester-based film is more preferable from the feeling of touch and luxury.

The base paper constituting the polyolefin-coated paper preferably used in the present invention is not particularly limited, and generally used paper can be used. More preferably, for example, a smooth paper such as that used for a photographic support is used. Base paper is preferred. As the pulp constituting the base paper, natural pulp, recycled pulp, synthetic pulp or the like may be used alone or in combination of two or more. The base paper is blended with additives generally used in papermaking, such as a sizing agent, a paper strength enhancer, a filler, an antistatic agent, a fluorescent whitening agent, and a dye.

Further, a surface sizing agent, a surface paper strengthening agent, a fluorescent whitening agent, an antistatic agent, a dye, an anchoring agent and the like may be applied to the surface.

The thickness of the base paper is not particularly limited. However, it is preferable that the base paper has good surface smoothness, for example, by applying pressure by using a calender or the like during or after papermaking, and has a basis weight of 30%. ~250g / m ² is preferred.

As the resin of the resin-coated paper, a polyolefin resin or a resin curable by an electron beam can be used.
Examples of the polyolefin resin are low-density polyethylene, high-density polyethylene, polypropylene, polybutene, a homopolymer of an olefin such as polypentene or a copolymer of two or more olefins such as an ethylene-propylene copolymer and a mixture thereof, Those having various densities and melt viscosity indices (melt index) can be used alone or in combination.

In the resin of the resin-coated paper, white pigments such as titanium oxide, zinc oxide, talc and calcium carbonate; fatty acid amides such as stearamide and arachidic amide; zinc stearate; calcium stearate; Aluminum, fatty acid metal salts such as magnesium stearate, antioxidants such as Irganox 1010 and Irganox 1076, blue pigments and dyes such as cobalt blue, ultramarine blue, cecilian blue, and phthalocyanine blue, cobalt violet, fast violet, and manganese purple It is preferable to add various additives such as magenta pigments and dyes, fluorescent brighteners and ultraviolet absorbers in an appropriate combination.

The resin-coated paper, which is preferably used in the present invention, is manufactured by a so-called extrusion coating method in which, in the case of a polyolefin resin, a heat-melted resin is cast on a running base paper. Coated. In the case of a resin that is cured by an electron beam, the resin is applied by a commonly used coater such as a gravure coater or a blade coater, and then irradiated with an electron beam to cure and coat the resin. Further, before coating the resin on the base paper, the base paper is preferably subjected to an activation treatment such as a corona discharge treatment or a flame treatment. The surface (surface) of the support on which the ink receiving layer is applied has a glossy surface, a matte surface, and the like, depending on the application, and the glossy surface is used particularly advantageously. It is not necessary to coat the back surface with a resin, but it is preferable to coat the resin from the viewpoint of curling prevention. The back surface is usually a matte surface, and the front surface or both front and back surfaces can be subjected to an activation treatment such as a corona discharge treatment or a flame treatment as required. Although the thickness of the coating resin layer is not particularly limited, it is generally coated on the surface or both the front and back to a thickness of 5 to 50 μm.

In the ink jet recording sheet of the present invention, at least one water-soluble polymer is used. Examples of the water-soluble polymer that can be used in the present invention include polyvinyl formals such as polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), polyvinyl pyridinium halide, and various modified polyvinyl alcohols and derivatives thereof (Japanese Unexamined Patent Publication No. −145879
No. 60-220750, No. 61-143177
Nos. 61-235182 and 61-235183
Nos. 61-237681 and 61-26189), polyalkylene oxides, polyacrylamide, polydimethylacrylamide, polydimethylaminoacrylate, gelatin, starch, oxidized starch, dialdehyde starch, cationized starch, dextrin, casein,
Natural polymer materials such as pullulan, dextran, methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxypropylcellulose and derivatives thereof (JP-A-59-174382, JP-A-60-262885)
Nos., 61-143177 and 61-181679
Nos. 61-193879 and 61-287778), polyvinyl ether, polyglycerin and the like. Among these water-soluble polymers, gelatin, polyvinyl pyrrolidone (PVP), and polyvinyl alcohol (PVA) are preferably used.

In the ink jet recording sheet of the present invention, gelatin is particularly preferably used as a water-soluble polymer in order to enhance the effects of the present invention. As the gelatin, any gelatin can be used as long as it is made of animal collagen. There is no particular limitation on the type of gelatin, but lime-treated gelatin, acid-treated gelatin, and gelatin derivatives (for example, JP-B-38-4854, JP-B-39-39)
No.-5514, No.40-12237, No.42-263
No. 45, Japanese Patent Publication No. 2-1359, U.S. Pat.
No. 5,753, No. 2,594,293, No. 2,6
No. 14,928, No. 2,763,639, No. 3,
Nos. 118,766, 3,132,945, 3,186,846, 3,312,553, British Patents 861,414, 1,033,189, etc. Described gelatin derivatives) can be used alone or in combination thereof.

In the ink jet recording sheet according to the present invention, particularly preferably used gelatin is gelatin whose isoelectric point is in the range of 5.5 to 9.6.
Such gelatin is generally different from lime-processed gelatin used in silver salt photography, and is obtained by subjecting collagen obtained from pig skin, cow skin, and bovine bone to a raw material and subjecting it to an acid treatment such as hydrochloric acid in the production process. See The Macromolecular Chemistry of Gelatin (Academic Press)
And so on. The isoelectric point of gelatin is measured with a pH meter, and is particularly preferably in the range of 8.0 to 9.5.

In the ink jet recording sheet according to the present invention, a water-soluble binder is contained in the receiving layer in an amount of 35% by weight or more on a dry weight basis in order to obtain a high quality and high gloss image. It is preferable to contain 50% by weight or more.

The receiving layer of the present invention preferably has a pH of less than 7 on the film surface of the receiving layer in order to further enhance the effects of the present invention. More preferably, it is 3 or more and 6 or less. The pH of the film surface of the receiving layer refers to the common logarithm of the reciprocal of the hydrogen ion molarity measured in a state in which a slight amount of pure water is dropped on the surface of the receiving layer and the receiving layer is swollen. A calomel electrode is used as a reference electrode with a glass electrode using an ordinary pH meter, and a flat composite single electrode is generally used for actual measurement.

In the present invention, in addition to a surfactant and a hardener, an inorganic pigment, a coloring dye, a coloring pigment, a fixing agent for an ink dye, an ultraviolet absorber, an antioxidant, a dispersant for a pigment, Antifoaming agent, leveling agent, preservative, optical brightener,
Various known additives such as a viscosity stabilizer and a pH adjuster can also be added.

In the present invention, for the purpose of improving the image quality, a surfactant is preferably added to the ink receiving layer as long as the ink absorbency is not impaired. As the surfactant used, cationic, nonionic and betaine surfactants are preferably used. Further, low-molecular-weight or high-molecular-weight ones or different types may be used in combination. A fluorine-based surfactant is most preferably used regardless of an anionic, cationic, nonionic or betaine surfactant.

The anionic or cationic fluorosurfactants which can be used in the present invention are described, for example, in US Pat. Nos. 2,559,751,
Nos. 567,011, 2,732,398, 2,7
64,602, 2,806,866, 2,80
9,998, 2,915,376, 2,91
5,528, 2,918,501, 2,93
No. 4,450, No. 2,937,098, No. 2,95
7,031, 3,472,894, 3,55
5,089, British Patent Nos. 1,143,927 and 1,130,822, JP-B-45-37304, JP-A-47-9613, JP-A-49-134614, and JP-A-5-134614.
No. 0-117705, No. 50-117727, No. 50
No. 121243, No. 52-41182, No. 51-1
No. 2392, Journal of the British Chemical Society (J. Chem. Soc.)
2789, p. 2789, 1957, p. 2574 and 2
640 pages, Journal of the American Chemical Society (J. Amer. Chem. S)
oc. 79, 2549 (1957), J. Japan Oil Chemist So
c. ) 12, 653, Journal of the Society of Organic Chemistry (J. Org. C).
hem. 30), p. 3524 (1965) and the like.

Certain of these fluorosurfactants are trade names Megafac F from Dainippon Ink and Chemicals, Inc., and Fluorad (trade name) from Minnesota Mining and Manufacturing Company. Fluorad) under the trade name of FC, Imperial Chemical Industry under the trade name of Monflor, E.I.Dupont Nemelas and Company under the trade name of Zonyls, and Farbeberke. Licovet V from Hoechst
Each is marketed under the trade name PF.

The total amount of the cationic fluorine-based surfactant and the anionic fluorine-based surfactant used is preferably from 0.1 to 1000 mg, preferably from 0.5 to 3 mg / m ^2.
00 mg, more preferably 1.0 to 150 mg.
When used together, two or more of them may be used in combination. In addition, a nonionic fluorine-based surfactant, a betaine-type fluorine-based surfactant, or a hydrocarbon-based surfactant may be used in combination.

The molar ratio of the anionic fluorinated surfactant to the cationic fluorinated surfactant which can be used in the present invention is preferably 1:10 to 10: 1, more preferably 3: 7 to 7: 1. : 3 is preferred.

A crosslinking agent can be added for the purpose of improving water resistance. Preferred crosslinking agents include aldehyde compounds such as formaldehyde and glutaraldehyde, ketone compounds such as diacetyl and chloropentanedione, bis (2-chloroethylurea), 2-hydroxy-4,6-dichloro-1,3,5-triazine. ,
U.S. Pat. No. 3,288,775, compounds having a reactive halogen, divinyl sulfone, compounds having a reactive olefin as described in U.S. Pat. No. 3,635,718, U.S. Pat. N described in No. 316
-Methylol compounds, isocyanates as described in U.S. Pat. No. 3,103,437, U.S. Pat.
Nos. 280 and 2,983,611; aziridine compounds as described in US Pat. No. 3,100,704; carbodiimide-based compounds as described in US Pat. No. 3,100,704;
There are epoxy compounds as described in No. 537, halogen carboxaldehydes such as mucochloric acid, organic crosslinking agents such as dioxane derivatives such as dihydroxydioxane, etc., and these can be used alone or in combination of two or more. The amount of the crosslinking agent added is preferably from 0.01 to 10 g, more preferably from 0.1 to 5 g, per 100 g of the ink receiving layer.

Fine particles having an average particle diameter of 1 μm or less can be contained in the ink receiving layer of the recording sheet of the present invention.
The average particle diameter of the fine particles is preferably 0.2 μm or less, more preferably 0.02 μm, from the viewpoint of glossiness.
The range is as follows. The fine particles may be inorganic fine particles or organic fine particles. In the case of organic fine particles, the glass transition temperature or the film forming temperature is 50 ° C. or more and 300 ° C.
The following is preferred.

Examples of the inorganic fine particles include oxides (eg, silicon dioxide, titanium oxide, magnesium oxide, aluminum oxide, etc.) and alkaline earth metal salts (eg, sulfates and carbonates, specifically, barium sulfate). , Calcium carbonate, magnesium sulfate, etc.), silver halide grains which do not form an image (silver chloride, silver bromide, etc., and a small amount of iodine atom may be added as a halogen component) or glass.

In addition, West German Patent No. 2,529,321
Nos., British Patent Nos. 760,775 and 1,260,77
No. 2, U.S. Pat. Nos. 1,201,905 and 2,19
2,241, 3,053,662 and 3,06
2,649, 3,257,206, 3,32
2,555, 3,353,958, 3,37
No. 0,951, 3,411,907, 3,43
7,484, 3,523,022 and 3,61
5,554, 3,635,714, 3,76
9,020, 4,021,245, 4,02
No. 9,504 and the like can also be used.

Among them, silica-based fine particles or barium sulfate is most preferable in consideration of compatibility and handleability.

The organic fine particles include starch, cellulose ester (for example, cellulose acetate propionate), cellulose ether (for example, ethyl cellulose), and synthetic resin. Examples of synthetic resins are water-insoluble or poorly soluble synthetic polymers, such as alkyl (meth) acrylate, alkoxyalkyl (meth) acrylate, glycidyl (meth) acrylate, (meth) acrylamide, vinyl ester (for example, vinyl acetate),
Acrylonitrile, olefins (such as ethylene),
Styrene, benzoguanamine / formaldehyde condensate alone or in combination, or a combination thereof with acrylic acid, methacrylic acid, α, β-unsaturated dicarboxylic acid, hydroxyalkyl (meth) acrylate, sulfoalkyl (meth) acrylate, styrene sulfonic acid, etc. A polymer having a combination as a monomer component can be used.

Other epoxy resin, nylon, polycarbonate, phenol resin, polyvinyl carbazole,
Polyvinylidene chloride can also be used.

In addition to this, British Patent No. 1,055,713
Nos., U.S. Pat. Nos. 1,939,213 and 2,221,
873, 2,268,662, 2,322,0
Nos. 37, 2,376,005 and 2,391,18
No. 1, 2,701,245, 2,992,101
No. 3,079,257 and 3,262,782
No. 3,443,946, No. 3,516,832
Nos. 3,539,344 and 3,591,379
Nos. 3,754,924 and 3,767,448
And JP-A-49-106821 and 57-14835.
Organic matting agents described in Nos. 1 and 2 can be used.

Among them, polymethyl methacrylate, benzoguanamine / formaldehyde condensation polymer (benzoguanamine resin, specifically represented by the following structural formula, for example, trade name: eposter: Nippon Shokubai Chemical Industry Co., Ltd.
Manufacture: existing chemical substances 7-31, etc., polyolefins (for example, flow beads LE-1080, CL-208, trade names)
0, HE-5023: manufactured by Steelmaking Chemical Co., Ltd. or Commodity Chemipearl V-100: manufactured by Mitsui Petrochemical), polystyrene beads (manufactured by Moritex), nylon beads (manufactured by Moritex), AS resin beads (manufactured by Moritex), epoxy resin Beads (manufactured by Moritex Corporation) and polycarbonate resins (manufactured by Moritex Corporation) are preferred.

Among them, the glass transition temperature is 50 ° C. or higher.
It is most preferable to use polyurethane fine particles having a temperature of 00 ° C. or lower.

The content of these fine particles is desirably from 1% by weight to less than 35% by weight, more preferably from 10% by weight to 30% by weight.

In the present invention, compounds that can be used together with the water-soluble polymer within a range that does not affect the performance include phenolic compounds, thiazoline compounds, triazine compounds, morpholine compounds, imidazole compounds, guanidine compounds, and benztriazole. And the like.

Specific compounds include orthophenylphenol and its salts (potassium and sodium), 2-
Octyl-4-isothiazoline, benzisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazoline-3
-One, 2-thiomethyl-4-ethylamino-6
(1,2-dimethylpropylamino) -s-triazine, hexahydro-1,3,5-tris (2-hydroxyethyl) -s-triazine, 4- (2-nitrobutyl) morpholine, 4- (3-nitrobutyl) Examples include, but are not limited to, morpholine, 2- (4-thiazolyl) benzimidazole, dodecylguanidine hydrochloride, and benztriazole.

The method for forming the ink receiving layer of the present invention includes a size press method, a roll coater method, a blade coater method, an air knife coater method, a gate roll coater method, a rod bar coater method, a curtain method, a slide hopper method, and an extrusion method. A commonly used coating method such as a lubrication method is used.

The drying method after coating is not particularly limited, but the cold drying method described on page 4 of JP-A-6-64306 is a preferable drying method for obtaining a high quality recording sheet.

In the present invention, the ink receiving layer may have a single-layer structure or a multi-layer structure. However, it is preferable that the ink-receiving layer is formed of a plurality of layers in order to separate functions such as ink absorbency and ink fixability. It is composed of more than layers. It is preferable that fine particles be present in the uppermost layer.

In the present invention, the coefficient of static friction on the surface opposite to the ink receiving layer (also referred to as the back surface) of the support is set to 0.6 or less, preferably 0.34 or less. To prevent abrasion and transfer to the surface, thereby dramatically improving the effects of the present invention. At this time, the back surface may be the support itself, or may have a back coat layer for controlling curling characteristics and static friction coefficient. The back coat layer is a layer formed on the opposite side (back side) from the side having the ink receiving layer,
It may have substantially the function of an ink receiving layer. The material used for the back coat layer is preferably the same material as that used for the ink receiving layer. Also,
It is preferable to add a physical property improver such as a commercially available hardener or matting agent to the back coat layer. Other additives such as pH adjusters, sequestering agents, antifungal agents, viscosity adjusters,
A surface tension adjuster, a wetting agent, a rust inhibitor, and the like can be applied.

Examples of ink solvents and dyes used in the ink jet printer preferably used in the present invention are shown below.

Examples of the dye (colorant) include direct dyes, acid dyes, basic dyes, reactive dyes, and water-soluble dyes such as food colorants.

As a solvent for the ink, water and various water-soluble organic solvents such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol,
Butyl alcohol, sec-butyl alcohol, ter
C 1-4 alkyl alcohols such as t-butyl alcohol and isobutyl alcohol; amides such as dimethylformamide and dimethylacetamide; ketones and 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;
Alkylene glycols having 2 to 6 alkylene groups such as propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol; glycerin, ethylene glycol methyl ether, diethylene glycol Lower alkyl ethers of polyhydric alcohols such as methyl (or ethyl) ether, triethylene glycol and monomethyl ether; pyrrolidinones such as 2H-pyrrolidinone; and pyrrolidones such as 1-methyl-2-pyrrolidone and 2-pyrrolidone. Can be Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol, lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether and triethylene glycol monoethyl ether, and pyrrolidones are preferable.

In the present invention, a mixed solvent of water and the above-mentioned organic solvent is preferably used as a solvent for the ink from the viewpoint of preventing clogging of the ink head nozzle. / 9 to 9/1, more preferably 4/6 to 9/1.

As other additives to the ink, for example, a pH adjuster, a metal sequestering agent, a fungicide, a viscosity adjuster,
Examples include surface tension adjusters, wetting agents, surfactants, and rust inhibitors.

The ink jet printer used in the present invention can exhibit any effect, but an on-demand piezo system, a thermal system, and an array system are particularly preferable.

At this time, in order to realize a high resolution, the ejection amount is preferably 5 to 40 pl (picoliter) per droplet, and the size of the ejection hole is preferably 3 μm to 60 μm. . Further, in order to increase the printing speed, it is preferable that the number of ejection holes is 10 or more and 40 or less per head. Further, in order to obtain the maximum density, the maximum ink ejection amount from the maximum density portion to the intermediate density portion is preferably 45 cc / m ² or more and 70 cc / m ² or less.

[0069]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 A resin composition comprising 70 parts of low-density polyethylene and 20 parts of high-density polyethylene was coated on a surface of a base paper having a basis weight of 110 g with 25 parts.
g / m ² , and a resin composition comprising 50 parts of low density polyethylene and 50 parts of high density polyethylene
Using a resin-coated paper coated with m ² (Taber stiffness according to JIS P-8125: 8.2 g · cm), a coating solution having the following composition (solid content concentration: 8% by weight) has a film thickness of about 10 after drying.
It was applied with a bar coater and dried so as to have a thickness of μm to obtain inkjet recording sheet samples 1 to 25 of Example 1.

<Ink receiving layer composition> Gelatin (KV-3000 manufactured by Konica Gelatin Co., Ltd.) 5 g / m ² · PVP-K90 (manufactured by BASF) 5 g / m ² · Compound described in Table 1 · Amount described in Table 1 In addition, in the case of the compound of the present invention, the addition amounts were four points of a, b, c, and d.

The ink jet recording sheet thus produced was printed using PM-700C manufactured by Seiko Epson Corporation.

The sample after printing was placed at 23 ° C. and 80% RH.
After storing for 48 hours, the glossiness (60 degrees) of the black print portion surface was measured using a gloss meter VG-1D (manufactured by Nippon Denshoku Industries Co., Ltd.), and the results are shown in Table 1. The value measured by the gloss meter and the evaluation of the glossiness visually correspond substantially as follows.

Gloss of 70 or more: has extremely good gloss Gloss of 60 to less than 70: has good gloss Gloss of 50 to less than 60: has almost good gloss Gloss of 40 to less than 50: practical Has an acceptable lower limit glossiness Glossiness less than 40: Not glossy and not practically acceptable

[0075]

[Table 1]

As is clear from Table 1, Sample 1 containing no compound of the present invention (Comparative Example), Sample 2-d containing a compound having an acid dissociation constant not less than the range of the present invention (Comparative Example), Sample 3-d (Comparative Example) containing a compound having a dissociation constant less than the range of the present invention had a gloss level that was not practically acceptable, but Samples 4 to 25 containing the compound of the present invention had It can be seen that the glossiness is at a practically acceptable level.

Example 2 Table 2 is described with reference to The Macromolecular Chemistry of Gelatin (Academic Press) and Recent Advances in Gelatin and Glue Research (Pergamon Press). Nine kinds of acid-treated gelatins having different isoelectric points were prepared. These water-soluble polymers of gelatin, polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA) were used in combination in Table 2 on the same support as in Example 1 so that the film thickness after drying was about 10 μm. Then, an ink receiving layer was applied using a bar coater in the same manner as in Example 1.

As shown in Table 2, in the ink receiving layer, a sample a not containing the compound of the present invention, acetic acid 0.0
1 mol of sample b and borax were added in an amount of 0.1% in terms of boric acid.
A sample c containing 01 mol was prepared. After drying, the prepared inkjet recording sheet samples 26 to 35 were subjected to PM-700 manufactured by Seiko Epson Corporation in the same manner as in Example 1.
After printing using C and storing at 23 ° C. and 80% RH for 48 hours, the glossiness was measured, and the results are summarized in Table 2.

[0079]

[Table 2]

As is clear from Table 2, the sample b of the present invention
And c have gloss levels that are practically acceptable.

Example 3 A resin composition comprising 70 parts of low-density polyethylene and 20 parts of high-density polyethylene was coated on a surface of a base paper having a basis weight of 140 g with 30 parts.
g / m ² , and a resin composition comprising 50 parts of low-density polyethylene and 50 parts of high-density polyethylene on the back surface at 30 g / m ^2.
Comparative ink-jet printing was performed in the same manner as in Example 1 except that a coating solution having the following composition was applied to the resin-coated paper coated with m ² using a slide hopper method so that the film thickness after drying was about 12 μm. A recording sheet sample 36 was prepared.

The first layer, the second layer,
A third layer and a fourth layer.

<Composition of Coating Solution for Fourth Layer for Ink-Receiving Layer> Gelatin (isoelectric point 8.0, manufactured by STS) 0.44 g / m ² · PVP-K90 (manufactured by BASF) 0.08 g / m ²・ Nonion-modified polyvinyl alcohol (OKS-9162 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 0.30 g / m ²・ Cationic polymer (Polyment NK-100M manufactured by Nippon Shokubai Co., Ltd.) 0.15 g / m ²・ Organic fine particle matting agent (Soken Chemical) 0.008 g / m ² · Surfactant (1) 0.002 g / m ² · Crosslinking agent (2) 0.02 g / m ²

[0084]

Embedded image

<Composition of Coating Solution for Third Layer for Ink Receiving Layer> Gelatin (isoelectric point 8.0, manufactured by STS) 2.50
g / m ² · PVP-K90 (manufactured by BASF) 1.00 g / m ² · PEG150,000 (Alcox R-150 manufactured by Meisei Chemical Co., Ltd.) 1.00 g / m ² <Composition of second layer coating solution for ink receiving layer>・ Gelatin (isoelectric point 8.0, manufactured by STS) 2.00 g / m ²・ PEG150,000 (Alcox R-150 manufactured by Meisei Chemical Co., 0.50 g / m ²・ Nonion-modified polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) OKS-9162) 1.25 g / m ² cationic polymer (Polyment NK-100M manufactured by Nippon Shokubai Co., Ltd.) 0.75 g / m ² <Composition of coating solution for first layer for ink receiving layer> Gelatin (isoelectric point 8. 0, manufactured by STS Inc.) 0.50 g / m ^2. Nonionic modified polyvinyl alcohol (OKS-9162 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 0.30 g / m
^2. Cationic polymer (Polyment NK-100M, manufactured by Nippon Shokubai Co., Ltd.) 0.20 g / m ² All coating solutions were adjusted with 5% KOH aqueous solution or 6% nitric acid aqueous solution to adjust the pH. The surface pH of the layer was obtained. The surface pH was measured using a composite integrated electrode and an Orion ionizer.

Next, an ink jet recording sheet sample 37 of the present invention was prepared in exactly the same manner as above except that 0.5 g / m ^{2 of} acetic acid was added to the coating solution for the third layer and the second layer for the ink receiving layer. And the third and second ink-receiving layer coating solutions of the present invention prepared in exactly the same manner except that borax (as an anhydrous salt) was used in an amount of 0.05 g / m ² each. An ink jet recording sheet sample 38 was prepared.

After drying, the prepared ink jet recording sheet samples 36 to 38 were printed using PM-700C manufactured by Seiko Epson Corporation in the same manner as in Example 1, and
After storing at 3 ° C. and 80% RH for 48 hours, the glossiness was measured, and the results are summarized in Table 3.

At the same time, bronzing was visually evaluated according to the following five grades and summarized in Table 4.

: No bronzing occurred at all ○: Bronzing occurred slightly in solid black portions 黒: Bronzing of a practically acceptable limit occurred in solid black portions ×: Practically unacceptable black solid portions Level bronzing occurs XX: Bronzing occurs over the entire black solid area

[0090]

[Table 3]

[0091]

[Table 4]

As is clear from Tables 3 and 4, Samples 37 and 38 of the present invention have both glossiness and bronzing at levels that are practically acceptable as compared with Comparative Sample 36. .

[0093]

The ink jet recording sheet of the present invention is excellent in ink receptivity, high in transparency and gloss, and has excellent performance in which the gloss after printing and the occurrence of bronzing hardly occur in the print after printing. .

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // B41J 2/01 B41J 3/04 101Y (72) Inventor Hiroyuki Uemura 1st Sakuramachi, Hino-shi, Tokyo Konica Corporation

Claims (7)

[Claims] 1. An ink receiving layer containing a water-soluble polymer in a dry weight of at least 35% by weight on a support, wherein the ink receiving layer has a dissociation constant of at least one proton of 2 or more.
A weak acid or a salt thereof, which is from × 10 ^{−10 to} 5 × 10 ⁻² ,
And an at least one acid compound selected from compounds capable of releasing a weak acid. 2. The method according to claim 1, wherein the water-soluble polymer is at least one selected from gelatins, polyvinyl alcohols, and polyvinylpyrrolidones.
3. The sheet for inkjet recording according to item 1. 3. The ink jet recording sheet according to claim 2, wherein the water-soluble polymer is gelatin. 4. An isoelectric point of said gelatin of 5.5 to 9.6.
The inkjet recording sheet according to claim 3, wherein 5. The ink jet recording sheet according to claim 1, wherein the pH of the film surface of the receptor layer is less than 7. 6. The method according to claim 6, wherein the acid compound is added in an amount of 0.001 to the receiving layer.
The inkjet recording sheet according to claim 1, wherein the content is at least mol / m ² . 7. The molecular weight of the acid compound is 1 in terms of free acid.
The inkjet recording sheet according to any one of claims 1 to 6, wherein the number is 80 or less.