JP4504239B2 - Inkjet recording sheet - Google Patents

Description

  The present invention relates to an ink jet recording sheet having image clarity comparable to silver salt photographic printing paper, high ink absorption and printing density, and high scratch resistance on the recording surface.

  The ink jet recording method is a method in which micro droplets of ink are ejected and adhered to a recording sheet such as paper by various operating principles to record images, characters, etc., but high speed, low noise, and multiple colors are achieved. It has features such as easy recording pattern flexibility and no need for development-fixing, and is rapidly spreading in various applications as a recording apparatus for various figures and color images including Chinese characters. In addition, an image formed by the multicolor ink jet method can obtain a recording that is inferior to that of multicolor printing by a plate making method or printing by a color photographic method. Furthermore, in applications that require a small number of copies, they are widely applied to the field of full-color image recording because they are cheaper than printing by photographic technology, and are diversifying.

  Diversification has also been developed for the appearance of inkjet recording materials. In addition to the conventional dull or low gloss appearance of plain paper and matte paper, similar to art paper, coated paper, cast coated paper, photographic paper, etc. Therefore, an appearance having a glossiness of 1 is required. This is because the inkjet recording can reproduce the image quality comparable to that of printing and photography, so that the appearance is desired to be similar.

  Therefore, as an ink jet recording material with improved surface gloss, a material in which an ink receiving layer made of a resin is provided on a base material has been proposed (for example, see Patent Document 1). However, the ink receiving layer made of these resins has the disadvantages that the surface gloss is obtained, but the absorption speed is slow and the absorption capacity is small, as compared with the ink receiving layer made of pigment fine particles such as silica.

  As an ink jet recording paper having a high ink absorption rate and an improved surface glossiness, an ink jet recording paper using an alumina hydrate (cationic alumina hydrate) in an ink receiving layer has been recently proposed (for example, Patent Document 2). However, although the ink receiving layer using alumina hydrate has a very high surface glossiness, the pore volume is small, so the ink absorption capacity per unit coating amount is small, and sufficient ink absorption capacity is obtained. For this purpose, there is a disadvantage that thick film coating is required.

  In addition, as a method for imparting surface gloss to ink jet recording paper, there is a method in which a calendar device such as a super calender or gloss calender is used and passed between rolls to which pressure or temperature is applied. However, when calendar treatment is performed under high linear pressure for the purpose of imparting surface gloss to the ink jet recording paper, voids in the coating layer are reduced, leading to deterioration in ink absorbability. For this reason, in the calendar process, conditions must be selected within a range that maintains the acceptable ink absorbency, and it is difficult to obtain high gloss.

  A cast processing method is known as a method for imparting surface gloss without using calendar processing. For example, a recording material (for example, refer to Patent Document 3) in which an ink receiving layer and a glossy expression layer are provided on a paper base material and the glossy expression layer is formed by a casting method. There are the following three methods as typical cast processing methods. That is, in a state where the coating liquid applied to the base material is not dried at all, a direct method in which it is pressed against a heated mirror roll (hereinafter referred to as a cast drum), the coating liquid applied to the base material is once dried. Alternatively, after being semi-dried, after being returned to the plastic state again by the rehumidifying liquid, the rewetting method in which the heated casting drum is pressed, the coating liquid applied to the substrate is treated with the coagulation liquid, This is a solidification method in which the gel is in a non-flowable gel state and is pressed against a heated cast drum. These casting methods are common in that a high gloss coating layer surface is obtained by copying a mirror-like drum surface.

  Among these casting methods, the solidification method does not dry and solidify the coating layer like the rewetting method, but presses and dries the mirror-finished surface in a plasticized solidified state, so the coating layer is a mirror-finished surface. It is possible to adhere uniformly to the surface. Moreover, even if the temperature of the mirror finished surface is increased, the coating layer is not destroyed. Furthermore, since a bulky and porous coating layer can be formed, it is suitable as a method for producing an ink jet recording sheet among the casting methods.

  Various proposals have been made in order to obtain an ink jet recording sheet excellent in surface gloss using a coagulation method. For example, a combination of a resin in the coating layer and a coagulant that can coagulate the resin (see, for example, Patent Document 4, Patent Document 5, and Patent Document 6), and examination of the coagulation liquid itself (see, for example, Patent Document 7) However, an ink jet recording sheet satisfying all of glossiness, ink absorption and surface strength has not been obtained yet.

  Although the surface gloss can be obtained as it is by the casting method, it is an index called image clarity as well as the surface gloss that determines the aesthetic element of the gloss. The image clarity is an index of how clear and undistorted the image is when an object is reflected on a glossy surface. Even with the same surface gloss, it can be said that a higher gloss level is perceived as there is no distortion, and the aesthetic element is higher. However, an evaluation that correlates with visual sensation cannot be made only by measuring the surface gloss level. In the prior art, an ink jet recording sheet satisfying image clarity has not been obtained.

  In addition, the ink jet recording sheet prepared by the cast processing method has a problem that the inorganic pigment used is very fine and easily scratched, and the surface of the coating layer is highly glossy so that the scratch is easily noticeable. Further, in order to obtain higher ink absorbability, it is necessary to reduce the content ratio of the binder amount to the inorganic pigment. However, by reducing this ratio, scratches are more likely to occur.

In recent years, a recording sheet having both sides suitable for inkjet recording, such as a postcard, has been required to have a photo-like texture, high gloss, and high printing quality on the surface. Ink jet recording sheets used for such postcard applications are more likely to be scratched by the printer because they are printed twice on the front and back, compared to ordinary recording sheets that are printed on one side. Also, as a problem specific to postcards, it is necessary to print a postal code frame on the address side with a printing machine such as an offset, and usually it is printed in a large format before cutting into postcards. For this reason, scratches also occur in the printing press, and in particular, scratches called needle marks that occur on the communication surface during printing alignment are problematic.
JP-A-4-282282 Japanese Patent Laid-Open No. 5-24335 Japanese Unexamined Patent Publication No. 7-117335 JP-A-9-59897 JP 2002-266282 A JP 2002-293004 A JP 2002-166645 A

  An object of the present invention is to provide an ink jet recording sheet having very high image clarity, high ink absorbability and print density, and having high scratch resistance on the glossy surface.

  As a result of intensive studies to solve this problem, the present inventors have reached the present invention. That is, after an ink receiving layer and a glossy expression layer are sequentially provided on a gas-permeable paper support, the glossy expression layer is solidified using a coagulation liquid, and is placed on a heated mirror roll while in a wet state. In the inkjet recording sheet finished by pressure contact and drying, in the glossy expression layer, pseudo-boehmite structure alumina hydrate and cation-treated colloidal silica as inorganic fine particles, and at least selected from polyvinyl alcohol and polyvinyl acetal as a binder Inkjet recording comprising an acrylic resin emulsion containing an alkyl acrylate ester and a dimethylaminoalkyl methacrylate methacrylate as constituent monomers, and containing a boron compound, casein, and a release agent in the coagulation liquid Achieved by sheet.

  The mass ratio of the pseudoboehmite-structured alumina hydrate contained in the glossy layer and the cationized colloidal silica is preferably in the range of 95: 5 to 30:70.

  The glass transition temperature of the acrylic resin emulsion contained in the glossy layer is preferably 30 ° C to 90 ° C.

  The ink jet recording sheet of the present invention has very high image clarity, high ink absorbability and print density, and has high scratch resistance on the glossy surface.

The ink jet recording sheet of the present invention will be described in detail below. The support used in the present invention is a gas-permeable support, and a known paper support can be appropriately selected and used. For example, chemical pulp such as LBKP and NBKP, mechanical pulp such as GP, PGW, RMP, TMP, CTMP, CMP, and CGP, wood pulp such as waste paper pulp such as DIP, and a conventionally known pigment as a main component, binder and Various types of equipment such as long net paper machine, circular net paper machine, twin wire paper machine, etc. are mixed using one or more additives such as sizing agent, fixing agent, yield improver, cationizing agent, paper strength enhancer, etc. And a base paper provided with a size press or an anchor coat layer of starch, polyvinyl alcohol or the like on the base paper. The basis weight of the support is usually 40 to 300 g / m ² , but is not particularly limited.

The ink receiving layer in the invention preferably contains a pigment. For example, synthetic amorphous silica, light calcium carbonate, heavy calcium carbonate, kaolin, calcined kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth , Calcium silicate, magnesium silicate, colloidal silica, colloidal alumina, pseudoboehmite, aluminum hydroxide, alumina, lithopone, zeolite, hydrous halloysite, magnesium carbonate, magnesium hydroxide, white inorganic pigments, styrene plastic pigments, acrylic plastic pigments And organic pigments such as polyethylene, microcapsules, and melamine resins, and synthetic amorphous silica having a large pore volume is particularly preferable. Such synthetic amorphous silica is porous, amorphous fine particles in which a three-dimensional structure of SiO ₂ is formed by gelation of silicic acid, and has a pore diameter of about 1 to ₂₀₀ nm.

  As such synthetic amorphous silica, commercially available products can be suitably used. For example, Mizukacil P-526, Mizukacil P-801, Mizukacil NP-8, Mizukacil P-802, Mizukacil P-802Y, Mizukacil C -212, Mizukacil P-73, Mizukacil P-78A, Mizukacil P-78D, Mizukacil P-78F, Mizukacil P-87, Mizukacil P-705, Mizukacil P-707, Mizukacil P-707D, Mizukacil P-709, Mizukacil C -402, Mizukasil C-484 (Mizawa Chemical Co., Ltd.), Toxeal U, Toxeal UR, Toxeal GU, Toxeal AL-1, Toxeal GU-N, Toxeal N, Toxeal NR, Toxeal PR, Sorex, Fineseal E -50, fine seal T-32, INSEAL X-37, FINE SEAL X-37B, FINE SEAL X-60, FINE SEAL X-70, FINE SEAL RX-70, FINE SEAL A, FINE SEAL B (above, manufactured by Tokuyama), Carplex FPS-101, Carplex CS-7, Carplex 80, Carplex XR, Carplex 67 (above, manufactured by Shionogi & Co., Ltd.), Nipgel AY-420, Nipgel AY-601, Nipgel AY-603, Nipgel AZ-600, Nipgel BY-400 Nip gel BY-001, nip gel G-0123, nip gel G-0124, nip sill VN3, nip sill LP, nip sill ER, nip sill NA, nip sill E-200A (above, manufactured by Tosoh Silica), siricia 770, siricia 40, Cylicia 730, Cylicia 440, Cylicia 431, Cylicia 450, Cylicia 470, Cylicia 250, Cylicia 310, Cylicia 350, Cylicia 320 (manufactured by Fuji Silicia Chemical), Cyloid AL-1, Cyloid AL-1B, Cyloid CP4, Thyroid 72W, Thyroid ED3, Thyroid 74, Thyroid 74X6500, Thyroid 74X5500, Thyroid 74X4500, Thyroid 622, Thylojet P405, Thylojet P407, Thylojet P409, Thyrojet P412, Thyrojet P416, Thylojet P616 (above, made by Grace) Etc.

  The ink receiving layer preferably contains a binder. Examples of the binder include various derivatives such as polyvinyl alcohol or its silanol-modified product, carboxylated product, cationized product, acetoacetylated product, conjugated diene copolymer such as styrene-butadiene copolymer and methyl methacrylate-butadiene copolymer. Unitary latex, acrylic polymer latex such as polymer or copolymer of acrylic ester and methacrylic ester, vinyl polymer latex such as ethylene-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, or These include functional group-modified polymer latexes and polyurethane resin latexes based on functional group-containing monomers such as carboxy groups of these various polymers. Among these, silanol-modified polyvinyl alcohol, ethylene-vinyl acetate copolymer latex, and styrene-butadiene copolymer latex are preferred, and at least one of these can be selected and used.

  The binder content in the ink-receiving layer is preferably from 5 to 70% by mass with respect to the pigment because good coating layer strength and ink absorbability can be obtained. More preferably, it is 10-60 mass%.

  Furthermore, in the ink receiving layer, as an additive, a dye fixing agent (various cationic resins), a pigment dispersant, a thickener, a fluidity improver, an antifoaming agent, an antifoaming agent, a release agent, a sizing agent, A penetrating agent, a coloring dye, a coloring pigment, a fluorescent brightening agent, an ultraviolet absorber, an antioxidant, an antiseptic, a baitproofing agent, a wet strength enhancer, a dry strength enhancer, and the like can be appropriately blended.

  In particular, from secondary amines, tertiary amines, and quaternary ammonium salts that form insoluble salts with sulfonic acid groups, carboxyl groups, amino groups, etc. in water-soluble direct dyes and water-soluble acid dyes, which are the dye components of water-based inks. When the cationic dye fixing agent is added, the color is improved because the dye is captured in the ink receiving layer. In addition, formation of an insoluble salt is preferable because destruction of a recorded image due to the dye or pigment in the ink flowing out of the ink receiving layer due to dripping or moisture absorption of water is suppressed.

When the coating amount of the ink receiving layer is 5 to 25 g / m ² , good ink absorbability and surface quality are obtained, which is preferable. More preferably, it is 5-20 g / m < ² >. In addition, the ink receiving layer can be applied by dividing a certain coating amount into several times.

  Various methods such as blade coater, roll coater, air knife coater, comma coater, bar coater, rod blade coater, curtain coater, short dwell coater, size press, etc. can be applied on-machine or off-machine. Can be used. Coating by a curtain coater is particularly preferred because a coating layer having a uniform thickness with no coating unevenness can be obtained.

  After application of the ink receiving layer, the back surface may be sprayed with humidified air or humidified steam to correct the curl, and further, calendar processing using a machine calendar, TG calendar, super calendar, soft calendar, etc. may be performed. .

  In the present invention, the gloss developing layer is subjected to a coagulation method. The coagulation method is a treatment method in which a glossy expression layer coated on an ink receiving layer is gelled by being treated with a coagulation liquid when it has fluidity. Pressed against the cast drum and dried.

  The glossy layer of the present invention contains at least quasi-boehmite structure alumina hydrate and cation-treated colloidal silica as inorganic fine particles. These inorganic fine particles have an extremely small average particle size and a high glossiness, and also improve the transparency of the glossy layer and increase the printing density. In addition, cation-treated colloidal silica has a cationic charge on the particle surface, so that the direct interaction of the dye component in the ink or the sulfone group, carboxyl group, amino group in the water-soluble acidic dye due to electrical interaction. Insoluble salts are formed and the dye component is fixed in the glossy layer to increase the print density.

  Further, when the luster-expressing layer contains alumina hydrate having a pseudo boehmite structure and cationized colloidal silica as a pigment in a mass ratio of 95: 5 to 30:70, high image clarity and printing density can be obtained. Obtained and preferred.

  The image clarity referred to in the present invention is a measure of how sharp and undistorted an image is projected when an object is reflected on a glossy surface, using an optical device defined in JIS H8686, The image definition (C) is obtained from the light intensity waveform obtained through the optical comb. There are various types of optical combs having a dark part bright part ratio of 1: 1 and a width of 0.125, 0.5, 1.0 and 2.0 mm. In the measurement, the optical comb is moved, the highest waveform (M) and the lowest waveform (m) on the recording paper are read, and the image definition is obtained as C = (M−m) / (M + m) × 100. The image clarity C is an index indicating that the image clarity is good when the value is large, and “blur” or “distortion” is present when the value is small. It has been found that if this “blurring” or “distortion” is small, the visual glossiness is improved even when the gloss value on the gloss meter is the same.

  The binder used in the glossy layer contains at least one selected from polyvinyl alcohol and polyvinyl acetal having various saponification degrees. These binders effectively coagulate with a boron compound which is a coagulant in a coagulation liquid described later.

  Further, together with the binder, natural polymers such as casein, gelatin and soybean protein, starch derivatives such as etherified starch and phosphate esterified starch, carboxyl cellulose, hydroxyethyl cellulose and the like Natural polymers such as cellulose derivatives and their derivatives, and various derivatives such as silanol-modified products, carboxyl-modified products, and cation-modified products of polyvinyl alcohol having various saponification degrees, water-soluble properties such as polyethylene oxide, polyethylene glycol, polyacrylamide, and polyvinylpyrrolidone. Various water-soluble synthetic polymers such as polymers, melamine resins, urea resins, polyurea polyamide resins, and derivatives thereof such as carboxyl-modified products, amide-modified products, and cation-modified products, and styrene-butadiene systems, ethylene-vinyl acetate systems, Polyurethane etc. Synthetic polymer emulsion, latex and its carboxyl, amides, and modified derivatives and cationic modification products with various amine groups may be used in combination.

  The binder content in the glossy layer is preferably 1 to 40% by mass with respect to the dry total solid content, because good ink absorbability and coating layer strength can be obtained. More preferably, it is 3-30 mass%.

  The glossy layer contains an acrylic resin emulsion containing acrylic acid alkyl ester and methacrylic acid dimethylaminoalkyl ester as constituent monomers. The alkyl alkyl ester of the acrylic acid alkyl ester is preferably 1 to 4. Moreover, it is preferable that the alkyl carbon number of this dimethylamino alkyl methacrylate is 1-3. The acrylic resin emulsion may contain other monomers copolymerizable with these constituent monomers. The acrylic resin emulsion forms a film when the glossy layer that has been gelated by the coagulation method is pressed against a heated cast drum to dry, and exhibits higher glossiness and image clarity. The glass transition temperature of the acrylic resin emulsion is preferably lower than the surface temperature of the cast drum, and more preferably 30 ° C to 90 ° C.

  Furthermore, as the additive for the glossy layer, a cationic dye fixing agent, a pigment dispersant, a thickener, a fluidity improver, a viscosity stabilizer, a pH adjuster, a surfactant, an antifoaming agent, an antifoaming agent. , Mold release agent, foaming agent, penetrating agent, coloring dye, coloring pigment, white inorganic pigment, white organic pigment, fluorescent whitening agent, UV absorber, antioxidant, leveling agent, antiseptic, antibacterial agent, water resistance An agent or the like can be appropriately added within a range not impairing the object of the present invention.

  For the application of the glossy layer, for example, various devices such as various blade coaters, roll coaters, air knife coaters, bar coaters, rod blade coaters, comma coaters, lip coaters, curtain coaters, short dwell coaters, and size presses are used. Can do.

When the coating amount of the glossy layer is 5 to 30 g / m ² , high image clarity and ink absorbability are obtained, which is preferable. More preferably, it is 5-20 g / m < ² >.

  The coagulation liquid of the present invention contains a boron compound as a coagulant. Examples of boron compounds include orthoborate, diborate, metaborate, tetraborate (borax), pentaborate, and octaborate. This is preferable. The concentration of the boron compound in the treatment liquid can be adjusted as necessary, but the concentration of the boron compound in the liquid mainly composed of water is preferably in the range of 0.5 to 5% by mass in terms of anhydride. More preferably, it is 1 to 3% by mass.

  The coagulation liquid contains casein. When casein is contained in the coagulation liquid, it is unevenly distributed on the surface of the glossy expression layer that has been gelled during the coagulation treatment, so it effectively forms a film when pressed against the cast drum and dries, resulting in high surface strength. Expresses glossiness and image clarity.

  The content of casein in the coagulation liquid is preferably 0.05 to 0.5% by mass of the coagulation liquid because good surface strength, image clarity, and ink absorptivity are obtained. If the casein content is too low, the desired surface strength cannot be obtained sufficiently. If the casein content is too high, the ink absorbability and the print density are reduced, and the mold is released from the cast drum surface. Occasional problems such as worsening of sex will also occur.

  The coagulating liquid contains a release agent. Examples of the release agent include higher fatty acids or esters thereof, amides or metal salts, higher alcohols, liquid hydrocarbon oils, waxes such as shellac wax, carnauba wax, polyethylene wax, paraffin wax, Teflon (R), silicone, and the like. Is mentioned. Since these release agents are hydrophobic, a product dispersed with a hydrophilic dispersant is preferably used. The content of the releasing agent is preferably 0.02 to 0.05% by mass of the coagulating liquid. If the release agent content is too low, the desired releasability cannot be obtained sufficiently, and if the release agent content is too high, quality deterioration such as a decrease in ink absorbency and a decrease in print density occurs.

  In the coagulation liquid, as additives, for example, water retention agents, thickeners, antifoaming agents, preservatives, coloring agents, water resistance agents, wetting agents, plasticizers, fluorescent dyes, ultraviolet absorbers, antioxidants, etc. These known auxiliaries can be added as appropriate.

Examples of the present invention will be described below, but the present invention is not limited to these examples. In Examples and Comparative Examples, “parts” and “%” indicate parts by mass and mass% unless otherwise specified. In addition, the number of parts shown in the blend is the number of substantial components. Moreover, the particle diameter shown in an Example and a comparative example is an average particle diameter calculated | required by the dynamic light scattering method.
The cast coater was operated at the maximum speed at which no uneven gloss occurred.

A mixture of 50 parts of hardwood bleached kraft pulp (LBKP, whiteness 90%) and 50 parts of softwood bleached sulfite pulp (NBSP, whiteness 90%) was beaten to 350 ml with Canadian Standard Freeness to prepare a pulp slurry. Add 6 parts of talc as a filler, 0.5 part of alkyl ketene dimer as a sizing agent, 1.0 part of polyacrylamide and 2.0 parts of cationized starch as a dry paper strength enhancer, and dilute with water to make a 1% slurry. It was. This slurry was made with a long paper machine so as to have a basis weight of 150 g / m ² to prepare a support. On one surface of this support, coating liquid a as an ink receiving layer was applied and dried by an air knife coater so that the coating amount after drying was 10 g / m ² . On the ink receiving layer thus obtained, the coating liquid b of the glossy layer is applied using an air knife coater so that the coating amount after drying is 10 g / m ^2, and the coated surface has fluidity. After being treated with a coagulating liquid, the ink-jet recording sheet of the present invention was obtained by performing a casting process by a coagulation method in which it was pressed against a cast drum heated to 100 ° C. and dried.

<Ink-receiving layer coating solution a>
100 parts of synthetic amorphous silica (Syloid ED5; oil absorption 300 ml / 100 g, manufactured by Grace), 20 parts of silanol-modified polyvinyl alcohol (R-1130, manufactured by Kuraray), styrene-butadiene copolymer latex (Luckster DS226, Dainippon Ink & Chemicals Co., Ltd.) 10 parts and cationic dye fixing agent (Smileze Resin 1001, Sumitomo Chemical Co., Ltd.) 10 parts are mixed in water, uniformly dispersed and coated with an ink receiving layer having a solid content concentration of 18%. A working fluid a was prepared.

<Glossy layer coating liquid b>
60 parts of cationized colloidal silica (Snowtex ST-AK, manufactured by Nissan Chemical Industries, Ltd.), 40 parts of alumina hydrate with a pseudoboehmite structure and an average particle size of 50 nm, alkyl acrylate (alkyl 10 parts of an acrylic resin emulsion (glass transition temperature 55 ° C.) containing 4 carbon atoms and dimethylaminoalkyl methacrylate (2 carbon atoms of alkyl), 10 parts of polyvinyl alcohol (PVA117, manufactured by Kuraray Co., Ltd.), release agent (Nonionic oleic acid emulsion) 3 parts were mixed and uniformly dispersed to prepare a glossy layer coating liquid b having a solid content concentration of 20%.

<Adjustment of coagulation liquid>
A coagulating liquid containing borax (anhydrous equivalent) in a solid content concentration of 2%, casein in a solid content concentration of 0.2%, and a release agent (anionic paraffin wax emulsion) in a solid content concentration of 0.03% was prepared. .

  An ink jet recording sheet of the present invention was obtained in the same manner as in Example 1 except that the casein content in the coagulation liquid was changed to a solid content concentration of 0.4%.

  An ink jet recording sheet of the present invention was obtained in the same manner as in Example 1, except that the casein content in the coagulation liquid was changed to a solid content concentration of 0.1%.

  In the glossy layer coating liquid b, 20 parts of cationized colloidal silica (Snowtex ST-AK, manufactured by Nissan Chemical Industries, Ltd.) and 80 parts of alumina hydrate with a pseudo boehmite structure and an average particle size of 50 nm were used. Except for the above, an ink jet recording sheet of the present invention was obtained in the same manner as in Example 1.

  In the glossy layer coating solution b, the same as in Example 1 except that an acrylic resin emulsion containing an acrylic acid alkyl ester and a methacrylic acid dimethylaminoalkyl ester as a constituent monomer has a glass transition temperature of 85 ° C. Thus, an ink jet recording sheet of the present invention was obtained.

  In the glossy layer coating liquid b, the same as in Example 1 except that an acrylic resin emulsion containing an alkyl acrylate ester and a dimethylaminoalkyl methacrylate methacrylate as a constituent monomer has a glass transition temperature of 40 ° C. Thus, an ink jet recording sheet of the present invention was obtained.

(Comparative Example 1)
In the glossy layer coating liquid b, the same procedure as in Example 1 was conducted except that an acrylic resin emulsion (glass transition temperature 55 ° C.) containing an alkyl acrylate ester and a dimethylaminoalkyl methacrylate methacrylate as a constituent monomer was not added. Thus, an ink jet recording sheet was obtained.

(Comparative Example 2)
An ink jet recording sheet was obtained in the same manner as in Example 1 except that the release agent (anionic paraffin wax emulsion) was not added to the coagulation liquid.

(Comparative Example 3)
An ink jet recording sheet was obtained in the same manner as in Example 1 except that casein and a release agent (anionic paraffin wax emulsion) were not added to the coagulation liquid.

(Comparative Example 4)
In the glossy layer coating liquid b, an acrylic resin emulsion containing an alkyl acrylate ester and a dimethylaminoalkyl methacrylate ester as constituent monomers, an acrylic resin emulsion containing no dimethylaminoalkyl methacrylate ester (glass transition temperature) as constituent monomers The inkjet recording sheet of the present invention was obtained in the same manner as in Example 1 except that the temperature was changed to 60 ° C.

(Comparative Example 5)
The coagulation liquid is borax (anhydrous equivalent) with a solid content concentration of 2%, casein with a solid content concentration of 0.2%, and non-spherical colloidal silica (Snowtex PS-M, manufactured by Nissan Chemical Industries, Ltd.) with a solid content concentration of 1. An ink jet recording sheet of the present invention was obtained in the same manner as in Comparative Example 1 except that the coagulating liquid was changed to a coagulating liquid containing 1%.

  As described above, the inkjet recording sheets prepared in Examples and Comparative Examples were evaluated by the following evaluation methods, and the results are shown in Table 1.

<Image clarity>
The image definition (C) defined by JIS H8686 was used. Using an image clarity measuring device (ICM-1DP manufactured by Suga Test Instruments Co., Ltd.), using an optical comb having a width of 2.0 mm, reading the maximum waveform (M) and the minimum waveform (m) at a reflection angle of 60 degrees, C = The image definition was determined as (M−m) / (M + m) × 100. When the image clarity of image clarity is 70% or more, the glossiness of appearance is high, indicating that it is excellent in aesthetic elements that look like printing paper.

<Ink absorbability>
Using an ink jet recording apparatus (BJC420J, manufactured by Canon Inc.), a white line (non-printing portion) lattice pattern is created in a mixed color solid pattern composed of cyan ink and magenta ink, and the ink bleeding into the lattice is visually observed. And evaluated.
A: The lattice is completely clear.
○: Ink oozing is observed on only a part of the lattice.
(Triangle | delta): A grating | lattice becomes narrow and the bleeding of an ink is seen generally.
X: Lattice is absent due to ink bleeding.

<Print density>
Using the ink jet recording apparatus, a solid pattern was printed with black ink, and the optical reflection density of the printed portion was measured with a Macbeth RD-918 model.

<Surface strength>
On the opposite side of the glossy surface, address printing is performed at a speed of 8000 sheets per hour using a sheet-fed offset printing machine “Diamond” manufactured by Mitsubishi Heavy Industries, Ltd. Scratches called marks were visually evaluated.
A: Scratches do not occur on the glossy surface.
○: A thin scratch is seen on the glossy surface, but it is not noticeable.
Δ: Scratches are observed on the glossy surface.
X: Scratches deep enough to destroy the coating layer on the glossy surface.

<Operability>
The cast layer was evaluated by the releasability from the cast drum during the casting process.
○: The coating layer is released from the cast drum without any problem.
X: The coating layer sticks to the cast drum.

  From Table 1, after the ink receiving layer and the glossy expression layer were sequentially provided on the air-permeable paper supports of Examples 1 to 5, the glossy expression layer was coagulated with a coagulating liquid and was in a wet state. In addition, in an inkjet recording sheet that is pressed against a heated mirror roll and dried to finish, in the glossy layer, pseudo-boehmite structured alumina hydrate and cation-treated colloidal silica as inorganic fine particles, polyvinyl as a binder At least one selected from alcohol and polyvinyl acetal, containing acrylic resin emulsion containing alkyl acrylate ester and dimethylaminoalkyl methacrylate methacrylate as constituent monomers, containing boron compound, casein, mold release agent in the coagulation liquid The inkjet recording sheet is characterized by the same quality as photographic paper for silver salt photography. Has an image property and high ink absorption and print density, and surface strength are higher good.

  On the other hand, if Comparative Example 1, 4, and 5 do not contain an acrylic resin emulsion containing alkyl acrylate and dimethylaminoalkyl methacrylate as constituent monomers in the glossy layer, the image clarity is not sufficiently improved. Further, as in Comparative Examples 2 and 5, if the coagulating liquid does not contain a release agent, sticking to the drum occurs during the casting process, which is not preferable for operation. Further, as in Comparative Example 3, if casein is not contained in the coagulation liquid, sufficient coating layer strength cannot be obtained, and in addition, low image clarity is obtained, and satisfactory operation and quality are obtained in any case. I could not.

Claims (3)

  After sequentially providing an ink-receiving layer and a gloss developing layer on a gas-permeable paper support, the gloss developing layer is coagulated with a coagulating liquid, and pressed against a heated mirror roll while in a wet state. In the inkjet recording sheet to be dried and finished, in the glossy expression layer, at least one kind selected from alumina hydrate having a pseudo boehmite structure and cation-treated colloidal silica as inorganic fine particles, polyvinyl alcohol and polyvinyl acetal as a binder, An ink jet recording sheet comprising an acrylic resin emulsion containing an alkyl acrylate ester and a dimethylaminoalkyl methacrylate methacrylate as constituent monomers, and containing a boron compound, casein, and a release agent in the coagulation liquid.   2. The ink jet recording sheet according to claim 1, wherein the mass ratio of the pseudoboehmite-structured alumina hydrate and the cationized colloidal silica contained in the glossy layer is in the range of 95: 5 to 30:70.   The inkjet recording sheet according to claim 1 or 2, wherein the acrylic resin emulsion contained in the glossy layer has a glass transition temperature of 30C to 90C.