JP2006248007A - Inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium which is less costly and free from the generation of cockling after printing, and has excellent glossiness and ink absorption. <P>SOLUTION: This inkjet recording medium has a cast coating layer formed on one of the surfaces of a paper base material, a polymer layer formed on the cast coating layer and an ink absorbing layer with a void structure formed on the upper side of the polymer layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink jet recording medium (hereinafter also referred to as a recording medium or recording paper).

  Ink-jet recording is a method in which micro droplets of ink are ejected according to various operating principles and deposited on a recording sheet such as paper to record images and characters. In recent years, it has rapidly spread in various fields such as various printers, facsimiles, computer terminals, and the like.

As a recording medium used in this ink jet recording method, the density of the printed dots is high, the color tone is bright and vivid, and even when the printed dots overlap quickly, the ink does not run out or bleed. In addition, it is generally required that the horizontal spread of the printed dots is not larger than necessary, and the periphery is smooth and unblurred.
In addition, a remarkable improvement has been observed in recent years in terms of storability of printed images, and overall image quality and image storability are rapidly approaching those of silver salt photographs.

  In addition to these, glossiness and image clarity of the surface of the recording medium are also important factors in achieving so-called silver salt photography-like high image quality by ink jet recording. When the glossiness and image clarity are low, the sharpness of the image is lowered, and the three-dimensionality and the depth are often felt. For this reason, resin-coated supports used in silver salt photography are often used in inkjet glossy papers that improve photographic image quality. The resin coat support has high surface smoothness, high gloss and excellent image transferability, and has water resistance so that the coating liquid does not penetrate into the support when the ink absorbing layer is applied on the support. There is no reduction in smoothness, gloss and image clarity due to cockling of the support.

  However, such a high-quality resin-coated support may be limited in its use and is expensive, and thus the price of a photographic image-quality ink jet recording medium must be increased.

  On the other hand, instead of the resin coat support, an ink-absorbing layer is applied on a water-absorbent paper support, and then the casting process or calendar process is performed to increase the smoothness of the recording medium surface and to improve the gloss and image clarity. Inkjet recording paper is known (for example, described in Patent Documents 1 to 3). This is so-called ink-jet cast-coated paper, and can be provided at a lower cost than paper using a resin-coated support. However, since the ink absorption layer of the cast-treated ink absorption layer has high ink permeability (after removing “the substrate is paper”), the ink solvent passes through the ink absorption layer after printing and penetrates into the paper support. However, there is a problem that cockling occurs and the quality deteriorates.

In response to these issues, instead of resin-coated paper, we used cast-coated paper that has the same smoothness as resin-coated paper and relatively low ink absorbency as the base material, and formed an ink-absorbing layer on it. By doing so, it was found that an ink jet recording medium excellent in gloss and image clarity can be obtained. (For example, see Patent Documents 1 to 3)
However, in a dark image portion where the amount of ink emitted is large, there is a problem that the solvent in the ink passes through the cast coat layer and reaches the paper base material, causing cockling and reducing gloss and image clarity.

  Patent Document 4 discloses a cockling after printing by providing a layer made of an adhesive having a pigment and a glass transition point of 30 to 60 ° C. between a plain paper substrate and an ink receiving layer. A technique for improving the expression “kotsuki” is disclosed. This is to provide a resin layer with a high glass transition point, that is, a high rigidity, as an intermediate layer to increase the rigidity of the entire recording paper and suppress cockling. As a result, the cockling tends to occur, which is insufficient as an improvement means. Further, even when the above layer was formed as an intermediate layer on a plain paper substrate, the smoothness was insufficient, and the gloss and image clarity were not as good as those of resin-coated paper.

  Patent Document 5 discloses a structure in which an anchor layer made of a pigment having a self-adhesive property is provided between a support mainly composed of wood pulp and an ink receiving layer. The anchor layer transmits ink to the support. Because it has the function of making it, it has no effect on cockling after printing. Further, the smoothness was not sufficient only by forming the anchor layer on the paper base material, and the glossiness and image clarity equivalent to the resin-coated paper were not achieved.

  Patent Document 6 proposes an ink jet recording paper comprising a hardened hydrophilic binder layer and a gap layer thereon, but the ink absorption rate is slow because the hydrophilic binder is hardened. There was a problem.

  Patent Document 7 discloses a technique of a layer containing a water-soluble polymer between an ink receiving layer and a support, but it is a problem to supplement ink absorbency when a water-resistant support is used. In addition, since a water-resistant support is used, it costs as much as resin-coated paper, and one of the objects of the present invention, namely cost reduction, cannot be achieved. In the case of resin-coated paper, the wettability of the surface of the resin layer is poor, and therefore, when water-based coating is performed on the resin-coated paper, subbing coating or the like is necessary, which further complicates the process.

  Patent Document 8 discloses a technique in which a non-porous layer mainly composed of a hydrophilic binder is provided between an absorbent support and an ink receiving layer, but the absorbent support is made to absorb ink. This is the intention of the invention, and there is a concern that cockling may occur in a high-density printing portion with a large amount of ink.

Therefore, a low-cost and high-quality image, that is, an ink jet recording medium having a high gloss as in the case of using a resin coat support, excellent ink absorbability, no cockling after printing, and good gloss The provision of
JP-A-62-95285 JP-A 63-265680 JP-A-5-59694 Japanese Patent Laid-Open No. 5-85035 Japanese Patent Laid-Open No. 8-300806 Japanese Patent Laid-Open No. 11-34481 JP 2001-1630 A JP 2002-67492 A

  An object of the present invention is to provide an inkjet recording medium that is low in cost, excellent in glossiness and ink absorption, and free from cockling after printing.

  The object of the present invention is achieved by the following configurations.

(Claim 1)
An ink jet recording medium comprising a cast coat layer on one side of a paper substrate, a polymer layer provided on the cast coat layer, and an ink absorbing layer having a void structure formed thereon. .

(Claim 2)
2. The ink jet recording medium according to claim 1, wherein the polymer layer absorbs the ink solvent and swells, and the degree of swelling is 5 to 40.

(Claim 3)
The inkjet recording medium according to claim 1 or 2, wherein the polymer layer has a thickness of 1 to 10 µm before swelling.

(Claim 4)
The inkjet recording medium according to claim 1, wherein the ink absorbing layer contains inorganic fine particles and an organic binder resin.

(Claim 5)
J. of the surface of the cast coat layer before forming the polymer layer. TAPPI paper pulp test method no. 51-87; The water absorption amount at a contact time of 10 seconds in the measurement according to the “liquid absorption test method for paper and paperboard” (Bristow method) is 15 ml / m ² or less. 2. An ink jet recording medium according to item 1.

(Claim 6)
And wherein before the formation of the polymer layer, the moisture permeability of the support in a state where one side of the paper substrate cast-coated layer is formed is ^{500g / m 2 · day~10000g / m} 2 · day The inkjet recording medium according to any one of claims 1 to 5.

  The ink jet recording medium according to the present invention is excellent in gloss and ink absorbency at low cost, and has an excellent effect without occurrence of cockling after printing.

  Details of the present invention will be described below.

  The raw material of the paper base that can be used in the present invention includes chemical pulp such as LBKP and NBKP, mechanical pulp such as GP, CGP, RMP, TMP, CTMP, CMP, and PGW, and waste wood pulp such as DIP. What uses pulp as the main raw material can be used. In addition, various fibrous materials such as synthetic pulp, synthetic fiber, and inorganic fiber can be appropriately used as raw materials as necessary.

  Various conventionally known additives such as a sizing agent, pigment, paper strength enhancer, fixing agent, fluorescent whitening agent, wet paper strength agent, and cationizing agent may be added to the paper base as necessary. it can. Higher fatty acids, alkyl ketene dimers, etc. as sizing agents, calcium carbonate, talc, titanium oxide, etc. as pigments, starch, polyacrylamide, polyvinyl alcohol, etc. as paper strength enhancing agents, sulfate bands, cationics as fixing agents However, the present invention is not limited to this.

  The paper substrate can be produced by mixing various fibrous materials such as wood pulp and various additives and using various paper machines such as a long net paper machine, a circular net paper machine, and a twin wire paper machine. Further, if necessary, a size press treatment with starch, polyvinyl alcohol, or the like, a various coating treatment, or a calendar treatment can be performed at the paper making stage or after paper making.

  In the present invention, the cast coat layer is applied by a method similar to a normal cast coat method. As a normal cast coating method, a direct method in which the coating layer is pressed against a mirror roll heated in a wet state and dried (also referred to as a wet method), and the coating layer is solidified with a coagulating liquid in a wet state and then heated. The solidification method (also called gelation method) that presses and dries the mirror-finished roll, and after the coating layer is dried, the wetting liquid is applied and the coating layer is wetted again. And re-wetting method (also referred to as a rewetting method).

  The cast coat layer of the present invention is mainly composed of fine particles and a binder.

  Examples of the fine particles that can be used in the cast coat layer of the present invention include kaolin, talc, soft calcium carbonate, heavy calcium carbonate, magnesium carbonate, aluminum hydroxide, alumina, alumina hydrate, calcium carbonate, titanium dioxide, Barium sulfate, calcium sulfate, satin white, zinc sulfide, zinc oxide, zinc carbonate, magnesium hydroxide, zeolite, synthetic amorphous silica, colloidal silica, aluminum silicate, calcium silicate, magnesium silicate, diatomaceous earth, hydrohalo Examples include inorganic fillers such as sight and lithopone, and organic fillers such as plastic pigments.

  Examples of binders that can be used in the cast coat layer of the present invention include cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, starch derivatives such as oxidized starch, etherified starch, and phosphate esterified starch, polyvinyl alcohol and derivatives thereof, casein, Examples include gelatin, soybean protein, styrene-maleic acid resin and derivatives thereof, polyvinyl pyrrolidone, styrene-butadiene copolymer, acrylic copolymer, vinyl acetate copolymer and the like.

  Since the cast coat layer of the present invention is composed of fine particles and a binder, it has fine voids on the surface. As a result, the wettability with the liquid is improved, and the coating liquid can be applied directly on the cast coat layer. Resin coat has poor surface wettability. In particular, in the case of an aqueous coating solution, since it cannot be applied as it is, a treatment such as formation of an undercoat layer is essential.

In the present invention, before forming the polymer layer, the moisture permeability of the support in a state where one side of the paper substrate cast-coated layer is formed is at ^{500g / m 2 · day~10000g / m} 2 · day It is preferable.

If the moisture permeability is greater than 10,000 g / m ² · day, cockling may occur when the polymer layer is applied, because the support absorbs moisture in the coating solution.

On the other hand, in order to make the moisture permeability smaller than 500 g / m ² · day, it is necessary to remarkably improve the water resistance of the substrate, for example, by forming a water-insoluble resin layer like resin-coated paper. Becomes complicated and expensive.

The moisture permeability of the present invention is a value measured under the conditions of 40 ° C. and 90% RH in accordance with the method described in JIS-Z-0208, and the greater this value, the greater the amount of moisture permeation.
In the present invention, before forming the polymer layer, the cast coat layer surface in a state in which the cast coat layer is formed on one side of the paper substrate has a water absorption amount at a contact time of 10 seconds in the measurement method by the Bristow method. It is preferably 15 ml / m ² or less. The Bristow method referred to in the present invention is a method for measuring the liquid absorption behavior of paper and paperboard in a short time. TAPPI paper pulp test method no. 51-87 Paper or paperboard liquid absorbency test method (Bristow method). If the water absorption amount at a contact time of 10 seconds is more than 15 ml / m ^{2, the} base paper is likely to absorb water through the cast coat layer when the ink absorption layer is applied, and cockling tends to occur.
Since the moisture permeability is 500 g / m ² · day or more, water is absorbed even though the amount is small, so the amount of water absorption is not zero.

What is commonly known as ink-jet cast coated paper has increased ink absorbency, so the water absorption at a Bristow method contact time of 10 seconds is greater than 15 ml / m ² . Examples of cast coated paper having a water absorption of 15 ml / m ² or less at a Bristow method contact time of 10 seconds include cast coated paper for printing. For example, there are Oji Paper's mirror coat and Nippon Paper's Esprit coat.

  The polymer layer of the present invention has a function of swelling and absorbing ink.

Since the ink is absorbed by the polymer layer, water and solvent do not penetrate through the cast coat layer to the paper substrate, so that the glossiness due to cockling and cockling can be prevented from decreasing. The polymer layer absorbs the ink solvent. It swells and the degree of swelling needs to be 5-40.

  When the degree of swelling is less than 5 times, it is necessary to form a thick polymer layer in order to secure a sufficient ink absorption amount, and curling tends to occur. In addition, the ink absorption speed becomes slow, and mottle may occur in the printing portion. If the degree of swelling is greater than 40 times, there will be a difference in thickness in the direction perpendicular to the support between the portion that has been printed and the ink has been absorbed and swelled and the portion that has not been printed and has not swollen, and the contour of the image portion In some cases, the image may not be suitable for viewing due to cracking.

  The degree of swelling is determined as follows. That is, only the polymer layer of the non-absorbent support is applied and dried, and the mass is measured. Then, after immersing in pure water at 23 ° C. for 30 seconds, the surface water is wiped off, mass measurement is performed, and the rate of mass increase relative to its own weight before and after being immersed in water is defined as the degree of swelling.

  In addition, when the polymer layer is crosslinked, the ink absorption speed becomes slow, and when a high density image is printed at high speed, the ink overflows from the upper void layer and becomes mottled. preferable.

  Polymers that swell and absorb ink include, for example, polyvinyl alcohol, gelatin, gelatin derivatives, graft polymers of gelatin and other polymers, proteins such as albumin and casein, hydroxyethyl cellulose, carboxymethyl cellulose, and cellulose sulfate. Single sugar derivatives such as cellulose derivatives, sodium alginate, cellulose sulfate, dextrin, dextran, dextran sulfate, poly-N-vinylpyrrolidone, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyvinylimidazole, polyvinylpyrazole, etc. Alternatively, various synthetic hydrophilic polymers such as copolymers can be used. As gelatin, in addition to lime-processed gelatin, acid-processed gelatin may be used in combination, and a hydrolyzate of gelatin and an enzyme-decomposed product of gelatin can also be used. These polymers may be used alone or in a plurality of types.

  The film thickness of the polymer layer is preferably 1 to 10 μm. If it is smaller than 1 μm, the effect of absorbing ink and suppressing cockling is insufficient, and if it is larger than 10 μm, curling is likely to occur and the edge may be soiled by contacting the head during printing.

  The ink absorbing layer of the present invention is a void type having a void structure. The void-type ink absorbing layer is excellent in ink absorption speed and has become mainstream in recent years.

  Examples of the void-type ink absorbing layer include those that form voids from inorganic fine particles and organic binder resin, those that form voids from phase separation of polymers, and those that form voids from organic fine particles and organic binder resin.

  In the present invention, those in which voids are formed from various inorganic fine particles having an average particle diameter of 100 nm or less and an organic binder resin are particularly preferred from the viewpoint of ink absorption speed.

  Examples of the inorganic fine particles used to form the voids in the ink absorption layer include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, zinc hydroxide, zinc sulfide, and zinc carbonate. Inorganic pigments such as hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, magnesium hydroxide Used.

  The average particle size of the inorganic fine particles is determined by observing the particles themselves or the particles appearing on the cross section or surface of the void-type ink absorbing layer with an electron microscope, obtaining the particle size of 100 arbitrary particles, and calculating the simple average value (number Average). Here, the particle diameter of each particle is expressed by a diameter assuming a circle equal to the projected area.

  From the viewpoint of high density image, clear image, low cost, etc., the inorganic fine particles should be solid fine particles selected from fine particle silica, colloidal silica and alumina or alumina hydrate synthesized by vapor phase method. Is preferred. Alumina or alumina hydrate may be crystalline or amorphous, and any shape such as irregular particles, spherical particles, and acicular particles can be used.

  At present, fine particle silica synthesized by such a vapor phase method includes various types of Aerosil manufactured by Nippon Aerosil Co., Ltd. and Leolo Seal of Tokuyama Co., Ltd.

  The particle size of the inorganic fine particles is not particularly limited, but is preferably 100 nm or less, and the most suitable particle size for forming the void layer varies depending on the compound. For example, in the case of the gas phase method silica, the average particle size of the primary particles of the inorganic fine particles is most preferably 4 to 20 nm.

  Examples of the organic binder resin that can be used in the void-type ink absorbing layer of the present invention include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide, polyurethane, dextran, dextrin, and color ginane (κ, ι, λ, etc.), agar, pullulan, water-soluble polyvinyl butyral, hydroxyethyl cellulose, carboxymethyl cellulose and the like. Two or more of these organic binder resins can be used in combination. An organic binder resin that is crosslinked or polymerized by ionizing radiation can also be used. Among these, polyvinyl alcohol is preferable from the viewpoint of compatibility with inorganic fine particles and film-forming properties.

The amount of inorganic fine particles used in the void-type ink absorbing layer of the present invention greatly depends on the required ink absorption capacity, the void ratio of the void layer, the type of inorganic pigment, and the type of organic binder resin. When only a void-type ink absorbing layer is used as the ink absorbing layer, 5 to 30 g is usually required per 1 m ^{2 of} recording paper in order to secure a necessary void capacity. However, in the present invention, since the polymer layer for preventing cockling swells and absorbs ink, the thickness of the void layer can be greatly reduced. Therefore, the amount of inorganic fine particles added can be greatly reduced. When the amount of inorganic fine particles added is small, the crack resistance of the coating film is improved, so that coating and drying can be performed at a higher speed.

  In the void-type ink absorbing layer of the present invention, the ratio (F / B) of the inorganic fine particles (F) to the organic binder resin (B) is preferably 3 to 20. When the mass ratio is 3 or more, the ink absorption layer has a good porosity, and a sufficient void volume is easily obtained. On the other hand, if this ratio is 20 or less, it is preferable that cracks are not likely to occur when the ink absorbing layer is applied as a thick film. The ratio F / B of the inorganic fine particles to the particularly preferable organic binder resin is 4-8.

  As a method of forming voids by polymer phase separation, (1) a solution in which a polymer is dissolved in a good solvent is applied on the ink absorption layer, and then the void is formed by overcoating the polymer poor solvent on the coating layer. Wet phase conversion method to be formed, (2) A polymer, a good solvent for this polymer, and a coating solution having a boiling point higher than that of this good solvent and containing a poor solvent for the polymer, and then evaporating the solvent to dry Thus, there is a dry phase conversion method in which microphase separation occurs to form voids.

  Examples of the polymer include olefin polymers, vinyl polymers, acrylic polymers, styrene polymers, polyesters, polyamides, polycarbonates, polyurethanes, polysulfones, polymers derived from epoxides, and cellulose derivatives.

  The organic fine particles used in the void-type ink absorbing layer comprising organic fine particles and a binder resin include polymethyl methacrylate, polyfunctional methacrylate polymer, polyamide, polystyrene, polyvinyl chloride, chloroprene rubber, nitrile rubber, and styrene-butadiene. For example, rubber.

  The binder resin may be the same as the void-type ink absorbing layer made of inorganic fine particles and organic binder resin.

When only a void-type ink absorbing layer is used as the ink absorbing layer, it is usually necessary to have a void volume of 15 ml / m ² or more per unit area of the coating film. In particular, when printing an image with high image quality and high density, a void volume of about 20 ml / m ² may be required.

However, in the present invention, since the polymer layer for preventing cockling swells and absorbs ink, the film thickness of the void layer can be greatly reduced, so that the void volume can be greatly reduced. From the viewpoint of ink absorption speed, the void volume is preferably 5 ml / m ² or more.

  The void volume as used herein refers to the volume of bubbles generated when a unit volume of the coating film is applied to water, the volume of water that the coating film can absorb, or the recording paper finally obtained. It is defined as the amount of liquid transfer when the contact time is 2 seconds as measured by the paper and paperboard liquid absorbency test method (Bristow method) specified in TAPPI 51-87.

In the ink absorption layer of the present invention, a cationic polymer can be used as a fixing agent for dye ink and a dispersion aid for inorganic fine particles. Examples of cationic polymers include polyethyleneimine, polyallylamine, polyvinylamine, dicyandiamide polyalkylene polyamine condensate, polyalkylene polyamine dicyandiamide ammonium salt condensate, dicyandiamide formalin condensate, epichlorohydrin-dialkylamine addition polymer, diallyldimethylammonium chloride polymerization , Diallyldimethylammonium chloride / SO ₂ copolymer, polyvinyl imidazole, vinyl pyrrolidone / vinyl imidazole copolymer, polyvinyl pyridine, polyamidine, chitosan, cationized starch, vinyl benzyl trimethyl ammonium chloride polymer, (2 methacryloyloxyethyl) ) Trimethylammonium chloride polymer, dimethylaminoethyl methacrylate Polymer, and the like. Examples include the cationic polymers described in Chemical Industry Times, August 15 and 25, 1998, and polymer dye fixing agents described in “Introduction to Polymer Drugs” issued by Sanyo Chemical Industries, Ltd.

  In addition to the above cationic polymer, nonionic or anionic ones such as polyacrylic acid can be used as the dispersant for the inorganic fine particles. In this case, the dye ink fixing agent can be applied by overcoating the cationic polymer or polyvalent metal salt after the ink absorbing layer is applied.

  Various additives other than those described above can be used in the ink absorption layer of the ink jet recording medium of the present invention and other layers provided as necessary. For example, organic latex fine particles such as polystyrene, polyacrylic acid esters, polymethacrylic acid esters, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or a copolymer thereof, urea resin, or melamine resin , Anionic, cationic, nonionic and amphoteric surfactants, UV absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, JP-A-57-74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091 and JP-A-3-13376, etc., JP-A-59-42993, 59- Nos. 52689, 62-280069, 61-242871, and JP-A-4-2192. Optical brighteners described in No. 6 etc., pH adjusters such as sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, antifoaming agents, preservatives, thickeners, antistatic Various known additives such as an agent and a matting agent can also be contained.

  The ink absorbing layer may be composed of two or more layers. In this case, the structures of the ink absorbing layers may be the same or different from each other.

  A known method can be used as a method of applying the polymer layer and the ink absorbing layer of the present invention. 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, an extrusion coating method using a hopper described in US Pat. No. 2,681,294, and a gravure. There are coating methods.

  The polymer layer and the ink absorbing layer formed on the upper side thereof are preferably coated by simultaneous multilayer coating from the viewpoint of productivity, but the ink absorbing layer may be coated after the polymer layer is coated and dried.

  In image recording using the ink jet recording medium of the present invention, a water-based ink composition, an oil-based ink composition, a solid (phase change) ink composition, or the like can be used.

  In the present invention, a recording method using water-based ink is preferable. The water-based ink as used in the present invention means a recording liquid comprising the following colorant, liquid medium, and other additives.

  When water-based ink is used, the subject of the present invention called cockling after printing occurs.

  As the colorant that can be used in the present invention, water-soluble dyes or water-dispersible pigments such as direct dyes, acid dyes, basic dyes, reactive dyes, food dyes, and the like known in ink jet can be used.

  Examples of the water-based ink solvent include water and various water-soluble organic solvents, for example, alcohols such as methyl alcohol, i-propyl alcohol, butyl alcohol, t-butyl alcohol, and i-butyl 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 Polyhydric alcohols such as 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol, glycerin, triethanolamine; Glycol methyl ether, diethylene glycol methyl (or ethyl) ether, lower alkyl ethers of polyhydric alcohols such as triethylene glycol monobutyl ether. Among these water-soluble 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 preferable.

  Examples of other water-based ink additives include pH adjusters, metal sequestering agents, antifungal agents, viscosity modifiers, surface tension adjusters, wetting agents, surfactants, and rust inhibitors.

  The aqueous ink liquid preferably has a surface tension of 250 to 600 μN, preferably 300 to 500 μN at 20 ° C. from the viewpoint of wettability with respect to the recording medium.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, the embodiment of this invention is not limited to these.

<Preparation of silica dispersion S-1>
The average particle size of primary particles uniformly dispersed in advance in 150 g of an aqueous 10% cationic polymer dispersant solution P-1 (containing 10% by mass of n-propanol and 2% by mass of ethanol) is about 7 nm. 435 g of a silica dispersion (pH 2.6, containing 0.5% by mass of ethanol) containing 23% by mass of a vapor phase silica (produced by Nippon Aerosil Co., Ltd .; Aerosil 300), 3.6 g of boric acid, and 0.6% of borax. 8 g was added with stirring at 3000 rpm at room temperature.

Subsequently, it disperse | distributed by the pressure of 3000 N / cm < ² > with the high pressure homogenizer by Sanwa Kogyo Co., Ltd., and the whole quantity was finished with pure water so that the silica content might be 18 mass%, and silica dispersion liquid S-1 was obtained. The obtained dispersion was filtered using a TCP-10 type filter manufactured by Advantex Toyo. It was 37 nm when the silica average secondary particle diameter was measured.

  The average secondary particle size is a value measured by diluting the dispersion 50 times and using a dynamic light scattering method particle size measuring device Zetasizer 1000HS (Malvern).

<Preparation of Ink Absorbing Layer Coating Liquid 1>
While stirring 500 g of the inorganic fine particle dispersion S-1 at 40 ° C., 205 g of an 8% aqueous solution of polyvinyl alcohol having a polymerization degree of 3500 (PVA235 manufactured by Kuraray Co., Ltd.) is gradually added, and finally the whole amount is finished to 1000 ml with pure water. Thus, an ink absorbing layer coating solution 1 was prepared.

<Preparation of Ink Absorbing Layer Coating Liquid 2>
Ink absorbing layer coating solution 2 was prepared by adding 45 g of cyclohexanol to 100 g of a methyl cellosolve 8% solution of cellulose acetate (acetylation degree 55, viscosity average polymerization degree 170).

<Preparation of polymer layer coating solution 1>
10% aqueous solution of acid-processed gelatin: 50 parts 10% aqueous solution of polyvinyl alcohol having a polymerization degree of 2400 (PVA224 manufactured by Kuraray):
17 parts 10% aqueous solution of polyethylene oxide having a molecular weight of 150,000: 33 parts The above was mixed while heating to 40 ° C to prepare a polymer layer coating solution 1.

<Preparation of polymer layer coating solution 2>
10% aqueous solution of acid-processed gelatin: 75 parts 10% aqueous solution of polyvinyl alcohol having a polymerization degree of 2400 (PVA224 made by Kuraray):
15 parts The above was mixed while heating to 40 ° C. to prepare a polymer layer coating solution 2.

<Preparation of polymer layer coating solution 3>
In 800 g of pure water, phenylcarbamoylated gelatin; 80 g, tetrakis (vinylsulfonylmethyl) methane; 5 g were dissolved and mixed at 40 ° C. to prepare a polymer layer coating solution 3.

<Preparation of recording medium 1>
A slide hopper is used on the cast coat layer of the cast coat paper for printing (mirror coat satin kanto, 209.3 g, made by Oji Paper Co., Ltd.) so that the wet film thickness is 90 μm. The recording medium 1 was prepared by sequentially drying in a wind whose temperature was changed stepwise from 20 ° C. to 65 ° C., and storing in a constant temperature bath at 40 ° C. and 80% RH for 12 hours.

<Preparation of recording medium 2>
On the cast coat layer of cast coat paper for printing (mirror coat satin kanto, 209.3 g Oji Paper), the polymer layer coating solution 1 has a wet film thickness of 30 μm, and the ink absorbing layer is coated thereon. The liquid 1 was applied simultaneously in two layers using a slide hopper so that the wet film thickness would be 90 μm, and dried sequentially with a wind whose temperature was changed stepwise from 20 ° C. to 65 ° C., followed by 40 ° C., 80 It was stored in a constant temperature bath of% RH for 12 hours to obtain a recording medium 2.

<Preparation of recording medium 3>
On the cast coat layer of the cast coat paper for printing (mirror coat satin kanto, 209.3 g, made by Oji Paper Co., Ltd.), the polymer layer coating solution 2 has a wet film thickness of 30 μm, and further the ink absorbing layer thereon. The coating solution 1 was applied simultaneously in two layers using a slide hopper so that the wet film thickness was 90 μm, and sequentially dried with a wind whose temperature was changed stepwise from 20 ° C. to 65 ° C., then 40 ° C., The recording medium 3 was obtained by storing in an 80% RH thermostatic bath for 12 hours.

<Preparation of recording medium 4>
On the cast coat layer of a cast coat paper for printing (mirror coat satin kanto, 209.3 g of rice tsubo, manufactured by Oji Paper Co., Ltd.), the polymer layer coating solution 3 has a wet film thickness of 30 μm, and the ink absorbing layer thereon. The coating solution 1 was applied simultaneously in two layers using a slide hopper so that the wet film thickness was 90 μm, and sequentially dried with a wind whose temperature was changed stepwise from 20 ° C. to 65 ° C., then 40 ° C., The recording medium 4 was obtained by storing for 12 hours in a constant temperature bath of 80% RH.

<Preparation of recording medium 5>
A recording medium 5 was produced in the same manner as the recording medium 2 except that the wet film thickness of the polymer coating solution 1 was changed to 5 μm.

<Preparation of recording medium 6>
A recording medium 6 was produced in the same manner as the recording medium 2 except that the wet film thickness of the polymer coating solution 1 was changed to 150 μm.

<Preparation of recording medium 7>
A recording medium 7 was produced in the same manner as the recording medium 2 except that the cast-coated paper for printing was changed to the cast-coated paper for ink jet (Photo Print Paper 2 manufactured by Seiko Epson Corporation).

<Preparation of recording medium 8>
On the cast coat layer of the cast coat paper for printing (mirror coat satin kanto, 209.3 g Oji paper), the above polymer layer coating solution 1 is used using a slide hopper so that the wet film thickness becomes 30 μm. It apply | coated and dried one by one with the wind which changed temperature in steps from 20 degreeC to 65 degreeC.

  Further, the ink absorbing layer coating liquid 3 is applied thereon so as to have a dry film thickness of 20 μm, dried in an atmosphere of 35 ° C. and 90% RH for 5 minutes, and then dried at 120 ° C. for 3 minutes. The recording medium 8 was produced by storing in a constant temperature bath at 40 ° C. and 80% RH for 12 hours. The resulting ink absorption layer had a porosity of 55%.

<Preparation of recording medium 9>
A recording medium 9 was produced in the same manner as the recording medium 2 except that the cast-coated paper for printing was changed to high-quality paper (Shiraoi, 157 tsubo, made by Nippon Daishowa Paperboard).

<< Inkjet image printing and evaluation >>
The following evaluation was performed on each of the obtained recording media.

<Evaluation of glossiness>
For glossiness, multiple factors such as surface reflection and image clarity are involved. In the present invention, a silver salt photograph gloss type was used as a comparison, and a relative evaluation was made visually.

1: Glossiness more than silver salt photography 2: Glossiness almost equivalent to silver salt photography 3: Slightly inferior to silver salt photography but sufficient glossiness 4: Inferior to silver salt photography, but glossy Feeling slightly felt 5: Glossiness is not felt at all <Measurement of liquid absorption>
Regarding the liquid absorptivity of the cast coat layer before applying the ink absorbing layer, J. Org. TAPPI paper pulp test method no. The Bristow method was used in accordance with the liquid absorbency test method for 51-87 paper or paperboard. The liquid absorbency in the present invention is represented by the amount of water transfer (ml / m ² ) at a contact time of 10 seconds in the measurement.

<Cock ring>
The surface of the ink absorbing layer of each recording medium was observed with the naked eye and judged according to the following criteria. If it is more than Δ, there is no practical problem.

○: Waviness on the surface is not known and the aesthetic appearance is not impaired. ○ △: Although slight undulation is observed on the surface, the glossiness is not impaired.

Δ: Surface waviness is small and does not impair the appearance. ×: Waviness is greatly observed on the surface and the appearance is impaired. <Ink absorbability>
Using an inkjet printer PM-950C (manufactured by Seiko Epson Corporation), a solid green image was printed on recording media 1 to 9 in an environment of 23 ° C. and 55% RH. Each recording medium was printed using what was stored at 23 ° C. for one day.

  The solid image printing portion of each recording medium was visually observed, and beading resistance was evaluated according to the following criteria, which was used as a measure of ink absorbability. If it was 3 or more, it was judged to be a practically acceptable range.

No unevenness of the printed image is observed even at an observation distance of 1:30 cm. Some unevenness of the printed image is observed at an observation distance of 2:30 cm, but no unevenness of the printed image is observed at an observation distance of 45 cm. 3:45 cm At the observation distance of 1, the printed image is slightly uneven, but at the observation distance of 60 cm, the printed image is not uneven at all. 4: At the observation distance of 60 cm, the printed image is slightly uneven. At the observation distance of 60:60 cm. Unevenness of printed image is clearly recognized <Print stain>
Using an inkjet printer PM-950C (manufactured by Seiko Epson Corp.), 10 solid images of each of the recording media 1 to 9 are printed on the recording media 1 to 9, and stains due to contact between the recording media and the print head are observed. It was evaluated whether it occurred. When the curl of the recording medium is severe, the recording medium and the printer head come into contact with each other and the edge of the recording medium becomes dirty.

○: Not generated Δ: 1-2 of 10 sheets are generated but dirt is small and not conspicuous ×: 2 or more of 10 outstanding spots are generated <Evaluation of image outline cracking>
A solid green image was printed on recording media 1 to 9 using an inkjet printer PM-950C (manufactured by Seiko Epson Corporation). A solid image of each recording medium was visually observed from a distance of 30 cm, and it was confirmed whether a crack occurred at the boundary between the printed portion and the unprinted portion.

○: No cracking △: Slightly cracked but no problem for viewing ×: Large cracking occurred and not suitable for viewing <Measurement of moisture permeability>
In the preparation of each recording medium, the moisture permeability (g / m ² · day) was measured under the conditions of 40 ° C. and 90% RH according to the method described in JIS-Z-0208 for the sample before applying the ink absorbing layer. did.

<Measurement of swelling degree>
The polymer layer coating solution was applied onto a polyethylene terephthalate sheet subtracted with an aqueous latex so as to have a dry film thickness of 3 μm and dried. After the coated sample was made 10 cm × 10 cm in size, the mass was measured. Then, after being immersed in pure water at 23 ° C. for 30 seconds, the surface water was wiped off and the mass was measured. The mass of the dried coating film was obtained by subtracting the mass of the polyethylene terephthalate sheet used as the support. The degree of swelling was calculated from the following formula.

  (Mass after soaking-Mass before soaking) / Mass of dry paint film

  As is apparent from the results shown in the above table, it can be seen that the recording medium of the present invention is superior in gloss and cockling to the comparative example.

Claims (6)

An ink jet recording medium comprising a cast coat layer on one side of a paper substrate, a polymer layer provided on the cast coat layer, and an ink absorbing layer having a void structure formed thereon. . 2. The ink jet recording medium according to claim 1, wherein the polymer layer absorbs the ink solvent and swells, and the degree of swelling is 5 to 40. The inkjet recording medium according to claim 1 or 2, wherein the polymer layer has a thickness of 1 to 10 µm before swelling. The inkjet recording medium according to claim 1, wherein the ink absorbing layer contains inorganic fine particles and an organic binder resin. J. of the surface of the cast coat layer before forming the polymer layer. TAPPI paper pulp test method no. 51-87; The water absorption amount at a contact time of 10 seconds in the measurement according to the “liquid absorption test method for paper and paperboard” (Bristow method) is 15 ml / m ² or less. 2. An ink jet recording medium according to item 1. And wherein before the formation of the polymer layer, the moisture permeability of the support in a state where one side of the paper substrate cast-coated layer is formed is ^{500g / m 2 · day~10000g / m} 2 · day The inkjet recording medium according to any one of claims 1 to 5.