JP2010228393A - Inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium, especially a cast coated paper for inkjet recording wherein recesses on a glossy surface caused by metal spur rollers arranged at an outlet of a conveying part in an inkjet printer is inconspicuous. <P>SOLUTION: The inkjet recording medium includes at least one ink receiving layer containing a pigment and a water-based binder and a glossy layer on at least one surface of a support having gas permeability, an image sharpness of the glossy layer measured according to JIS-K 7105 is 65% or more, and a microhardness of the ink receiving layer adjacent to the glossy layer obtained by the following equation 1 is 5-15. The equation 1: DH=α×P/D<SP>2</SP>, wherein P: load (2 mN), D: push-in depth to a sample by an indenter (μm), α: constant corresponding to indenter shape (α=3.8584 for a triangular pyramid indenter (a ridge line angle of 115 degrees) used in this application). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ink jet recording medium, and more particularly to a cast coated paper for ink jet recording in which a concave surface of a glossy surface is not noticeable by a metal spur roll installed at a transport unit outlet of an ink jet printer.

  In general, the ink jet recording method uses a variety of mechanisms to eject ink droplets and deposit them on the recording paper to form dots and perform recording. However, compared with the dot impact type recording method, noise is generated. In addition, there is an advantage that full color is easy and high-speed printing is possible. On the other hand, inks used for ink jet recording are usually water-based inks using direct dyes, acid dyes, etc., and thus have a drawback of poor drying properties. In addition, a printer using pigment ink has excellent storage stability such as weather resistance, but has a disadvantage that the image quality is extremely inferior when there is a crack on the surface of the ink receiving layer.

  Recently, with the widespread use of high-resolution digital video and digital cameras, there are more opportunities to handle high-definition images than ever, and there are more opportunities to output these hard copies with an inkjet printer. Along with this, the required characteristics of the recording medium have been diversified, and in particular, there has been a growing demand for a recording medium having glossiness similar to that of a silver salt photograph.

  As such a glossy recording medium, a method of producing by a cast coating method has already been proposed (Patent Document 1, Patent Document 2, Patent Document 3, etc.). In each of these production methods, an ink receiving layer composed of a pigment mainly composed of synthetic silica and a binder is pressure-bonded to a heated mirror-finished drum surface while it is in an undried wet state. The mirror surface is copied and dried at the same time to obtain a high-gloss cast-coated paper, but the glossiness of the outermost layer is low and the glossiness equivalent to that of a silver salt photograph is not obtained. In addition, glossy paper using plate-like alumina has been proposed for the purpose of enhancing glossiness (Patent Document 4). However, such glossy paper has a drawback that the appearance of the glossy surface is conspicuous due to the concavity of the glossy surface due to the metal spur roll installed at the exit of the conveyance section of the ink jet printer.

JP-A-62-95285 JP-A-63-264391 Japanese Patent Laid-Open No. 2-27487 JP 2006-88663 PR

  The present invention relates to an ink jet recording medium, and in particular, to provide a cast coated paper for ink jet recording in which a concave surface of a glossy surface is not conspicuous by a metal spur roll installed at an exit of a conveyance section of an ink jet printer.

  The present inventors blended a specific binder in the second ink receiving layer adjacent to the outermost layer, and after treating the outermost surface of the ink receiving layer with a liquid having an action of solidifying the aqueous binder, the ink absorbing layer In a wet state, it is pressed against a heated mirror drum through a press roll and dried, so that it has a glossiness similar to that of a silver salt photograph and is made of a metal installed at the outlet of the inkjet printer. It has been found that a cast coated paper for ink jet recording can be obtained in which a glossy surface is not conspicuous by a spur roll.

  Therefore, the above object has been achieved by the following invention.

The present invention
(1) An inkjet recording medium in which at least one ink-receiving layer and a glossy layer are provided on at least one surface of a gas-permeable support, and the image clarity measured according to JIS-K 7105 of the glossy layer is 65. %, And the ink receiving layer adjacent to the glossy layer has a microhardness (DH) determined from the following (Equation 1) in the range of 5 to 15.
DH = α × P / D ² (Formula 1)
P ... Load (2mN)
D: Depth of indenter into sample (μm)
α: Constant depending on indenter shape (α = 3.8584 for triangular pyramid indenter (ridge angle 115 °) used in this application)
(2) The ink jet recording layer according to (1), wherein the ink receiving layer adjacent to the glossy layer contains a pigment and an aqueous binder, and the aqueous binder contains a polymer having a glass transition temperature of 70 ° C. or higher. Medium.
(3) The ink receiving layer adjacent to the glossy layer contains a pigment and an aqueous binder, and the aqueous binder contains polyvinyl alcohol and an ethylene / vinyl acetate copolymer as described in (1) and (2). Inkjet recording medium.
(4) The ink receiving layer adjacent to the glossy layer contains a pigment and an aqueous binder, and the aqueous binder has a saponification degree of 98 to 99% and a polymerization degree of 1700 to 2400. The inkjet recording medium in any one of (1)-(3) containing this.
(5) The gloss layer contains an aqueous binder, and after the treatment liquid having the action of coagulating the aqueous binder is applied, the gloss layer is wet on the heated mirror surface while the gloss layer is in a wet state. The inkjet recording medium according to any one of (1) to (4), wherein gloss is imparted to the glossy layer by pressure-bonding and drying.

  According to the present invention, there is provided an inkjet recording medium that has glossiness similar to that of a silver salt photograph, but has an inconspicuous dent on a glossy surface due to a metal spur roll installed at a transport unit outlet of the inkjet printer. Obtainable.

  Hereinafter, embodiments of the inkjet recording medium of the present invention will be described. In the ink jet recording medium of the present invention, at least one ink receiving layer and a gloss layer are provided on at least one surface of a gas-permeable support.

(Support)
As the support used in the present invention, any support can be used as long as it has air permeability. However, paper (coated paper, uncoated paper, etc.) is preferably used. As raw material pulp of the paper, chemical pulp (coniferous bleached or unbleached kraft pulp, hardwood bleached or unbleached kraft pulp, etc.), mechanical pulp (crushed wood pulp, thermomechanical pulp, chemisermomechanical pulp, etc.), deinked pulp Etc. can be used alone or in admixture at any ratio. The pH of the paper may be acidic, neutral or alkaline. In addition, when a filler is included in the paper, the opacity of the paper tends to be improved. Therefore, it is preferable to include a filler. Examples of the filler include hydrated silicic acid, white carbon, talc, kaolin, clay, calcium carbonate. Well-known fillers such as titanium oxide and synthetic resin fillers can be used.

(Ink receiving layer)
The ink receiving layer contains a pigment and an aqueous binder as main components.
1. Pigment The pigment contributes to the adsorption of the dye ink and the pigment ink colorant and the absorbability of the ink solvent, and has a function of serving as a carrier for other auxiliary agents. Examples of the inorganic fine particles used in the present invention include synthetic amorphous silica, colloidal silica, colloidal alumina, vapor phase silica, vapor phase method alumina, boehmite, pseudoboehmite, water synthesized by a wet method, a vapor phase method, and the like. Aluminum oxide, alumina, lithopone, zeolite, hydrous halloysite, magnesium carbonate, magnesium hydroxide, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, white carbon, light calcium carbonate, heavy calcium carbonate, kaolin, calcined kaolin, talc, Clay, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white and the like can be used. In addition, inorganic fine particles that have been modified such as cationization or silylation or whose shape has been changed can also be used. Further, one or more of the above inorganic fine particles can be used in combination. In particular, it is preferable to use synthetic amorphous silica from the viewpoint of improving transparency, strength, and color density of the printed portion.

  Synthetic amorphous silica can be roughly classified into wet method silica and gas phase method silica depending on the production method. Synthetic amorphous silica produced by a wet process (hereinafter referred to as “wet process silica” where appropriate) is inferior to gas-phase process silica in terms of pigment transparency, but is excellent in paint stability when used in combination with polyvinyl alcohol. Furthermore, compared with gas phase method silica having no internal voids, wet method silica has good dispersibility in the liquid and can increase the coating concentration. Therefore, when wet method silica is used as the pigment of the ink receiving layer, the pigment ratio in the ink receiving layer can be increased to increase the absorbability of the ink receiving layer, so that the ink absorbability can be improved and the coloring property of the dye ink can be improved. Can be improved.

  Further, as the wet method silica, there are “gel method silica” produced by a gel method and “precipitation method silica” produced by a precipitation method. As the pigment of the ink receiving layer, either gel method silica or precipitation method silica may be used alone or in combination.

2. Water-based binder The water-based binder is for maintaining the properties of the ink receiving layer as a coating film. Examples of the aqueous binder used in the present invention include polyvinyl alcohol such as polyvinyl alcohol (hereinafter referred to as “PVA” as appropriate), silyl-modified polyvinyl alcohol, and cation-modified polyvinyl alcohol, and modified products thereof, oxidized starch, acetylated, and the like. Starches such as starch and etherified starch and derivatives thereof, water-soluble polymer binders such as proteins such as casein, gelatin, and soy protein; cellulose derivatives such as polyvinylpyrrolidone, carboxymethylcellulose, and hydroxyethylcellulose; and styrene -Polymers such as butadiene copolymer (SB) latex, acrylonitrile-butadiene copolymer (NB) latex, acrylic latex, vinyl acetate latex, ethylene vinyl acetate latex, polyurethane, unsaturated polyester resin Wear agents and the like can be used.

  When an ethylene / vinyl acetate copolymer (hereinafter appropriately referred to as “EVA”) is used as a binder, the coating layer strength is increased and paper dust at the time of cutting is reduced. Further, since the contact angle of the ethylene / vinyl acetate copolymer itself with water is smaller than that of other synthetic resins (for example, styrene / butadiene copolymer (SBR)), the ink absorbability of the ink receiving layer is improved. In particular, when the following polyvinyl alcohol / ethylene / vinyl acetate graft copolymer is used, these effects increase.

  The ethylene / vinyl acetate copolymer is, for example, a dry emulsion obtained by copolymerizing ethylene and vinyl acetate in an aqueous system in which polyvinyl alcohol is present as an emulsifier. The polymerization initiator mainly acts on ethylene and vinyl acetate, but depending on the reaction conditions and the amount of polyvinyl alcohol as an emulsifier, the ethylene / vinyl acetate copolymer is branched from the polyvinyl alcohol chain, and grows polyvinyl alcohol / ethylene. -An emulsion of vinyl acetate graft copolymer may be formed. As the ethylene / vinyl acetate copolymer used in the present invention, it is preferable to use an emulsion in which a number of molecules obtained by grafting an ethylene / vinyl acetate copolymer onto polyvinyl alcohol is increased. Moreover, when the glass transition point (Tg) of the ethylene / vinyl acetate copolymer is 0 ° C. or less, the cutting edge at the time of cutting the cutter is improved, and the coating layer (glossy layer and ink receiving layer) is less likely to fall off. The generation of paper dust tends to be further reduced. This is presumably because the flexibility of the coating layer (glossy layer and ink receiving layer) is increased. On the other hand, when the particle size is 1 μm or less, the transparency of the under layer increases, and the printing color density tends to improve (particularly in the case of dye ink). The effect of improving the cut at the time of cutting described above is particularly great when a gloss layer is provided by a casting method described later.

  The blending amount of the ethylene / vinyl acetate copolymer in the ink receiving layer is not particularly limited, but is preferably 10 to 40 parts by mass, more preferably 15 to 30 parts by mass with respect to 100 parts by mass of the pigment. When the blending amount of the ethylene / vinyl acetate copolymer exceeds 40 parts by mass, the hydrophobicity of the binder becomes remarkable and the ink absorbability tends to be lowered.

  On the other hand, from the viewpoint of increasing the hardness of the ink receiving layer, the glass transition temperature (Tg) is preferably 70 ° C. or higher. When the glass transition temperature is lower than 70 ° C., the hardness of the ink receiving layer is difficult to increase, and the spur installed at the outlet of the ink jet printer is likely to penetrate the ink receiving layer, thereby suppressing the dent on the glossy surface. I can't.

  By using a polymer having a glass transition temperature (Tg) of 70 ° C. or higher as the aqueous binder, the transparency and the color density of the printed portion are improved. As such an aqueous binder, it is preferable to use polyvinyl alcohol. Particularly preferable polyvinyl alcohol is a completely saponified type having a polymerization degree of 1700 or more, and most preferably having a polymerization degree of 2000 to 2400.

  The degree of saponification of polyvinyl alcohol refers to the reaction of synthesizing polyvinyl alcohol by replacing the acetate groups of polyvinyl acetate with hydroxyl groups, and saponifying the percentage of hydroxyl groups relative to the total of acetate groups and hydroxyl groups in polyvinyl alcohol. It is called degree. The degree of saponification of polyvinyl alcohol affects the stability of the coating solution and the hardness of the coating layer. Usually, polyvinyl alcohol having a saponification degree of 86 to 89% is called partially saponified polyvinyl alcohol, and polyvinyl alcohol having a saponification degree of 98 to 99% is classified as fully saponified polyvinyl alcohol. Polyvinyl alcohol having a saponification degree of 90 to 96% is partially saponified polyvinyl alcohol, but is also called intermediate saponified polyvinyl alcohol because it is close to completely saponified polyvinyl alcohol. In the present application, it is most preferable to use completely saponified polyvinyl alcohol. When intermediate saponified or partially saponified polyvinyl alcohol is used, the hardness of the ink receiving layer is low. When a glossy layer is provided on such an ink receiving layer, it is not possible to suppress dents on the glossy surface due to a metal spur roll installed at the exit of the ink jet printer.

  When the degree of polymerization of the fully saponified polyvinyl alcohol is less than 1700, not only the hardness of the ink receiving layer is insufficient, but also the strength is low, which causes a lack of a coating layer at the time of cutting. For these reasons, the degree of polymerization of fully saponified PVA is preferably 1700-2400, and most preferably polyvinyl alcohol having a degree of polymerization of 2000-2400. The blending amount of such polyvinyl alcohol is preferably 5 to 15 parts by weight with respect to 100 parts by weight of the pigment of the ink receiving layer. When the blending amount of polyvinyl alcohol is less than 5 parts by weight, the strength of the ink receiving layer is insufficient and the hardness of the ink receiving layer is also insufficient. Therefore, when a glossy layer is applied using such an ink receiving layer However, the conspicuous dents on the glossy surface cannot be suppressed by the metal spur roll installed at the exit of the conveyance section of the ink jet printer. On the other hand, when the blending amount of polyvinyl alcohol in the ink receiving layer exceeds 15 parts by weight, the hardness of the ink receiving layer is increased, but the acceptability of the ink is inferior and the air permeability is significantly impaired. When a glossy layer is applied to the ink-receiving layer and pressure-dried on a drum having a mirror surface, the vapor escape is extremely inferior, so that a good glossy surface cannot be obtained and the operability is significantly lowered. In such an ink jet recording medium, fine unevenness occurs on the glossy surface, so that the image clarity is significantly lowered. Examples of polyvinyl alcohol that can be used in the present invention include PVA117 (manufactured by Kuraray Co., Ltd.), PVA120 (manufactured by Kuraray Co., Ltd.), PVA124 (manufactured by Kuraray Co., Ltd.), Gohsenol N-300 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), Examples include GOHSENOL NH-18 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and GOHSENOL NH-20 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.).

  By using a mixture of at least two of these water-based binders, it is possible to achieve both improved cutting suitability and suppression of dents on the glossy surface due to a metal spur installed at the outlet of the inkjet printer. . The blending ratio of the polyvinyl alcohol and the ethylene / vinyl acetate copolymer is preferably 1: 6 to 3: 4.

3. Sizing Agent The sizing agent is necessary from the viewpoint of adjusting the contact angle of the ink on the surface of the ink receiving layer and preventing image blurring. Common sizing agents include styrene / acrylate, higher fatty acid, styrene / maleic acid, polyacrylamide, petroleum sizing, and silicone sizing. Of these, a styrene / acrylate sizing agent is particularly preferable in terms of compatibility with other chemicals blended in the ink-receiving layer coating and bleeding of the printed matter of the printer.

  Examples of the styrene / acrylate sizing agent that can be used in the present invention include Polymeralon 1308 (manufactured by Arakawa Chemical Co., Ltd.), SE-2250 (manufactured by Seiko PMC), Hi-Coat B-120 / Harsize CP-800 (Harima). (Made by Kasei Co., Ltd.).

4). Ink fixing agent Ink fixing agent is used to hold ink in the ink receiving layer by combining with ink when an image is printed by a printer, and is cationic so as to easily hold an anionic ink. Ink fixing agents are often used. Examples of cationic ink fixing agents include diallyldimethylammonium chloride polymer, dicyandiamide / formaldehyde resin, dicyandiamide / alkylamine polymer, diethylenetriamine / dicyandiamide / ammonium chloride condensate, and (meth) acryloyloxyalkyltrialkylammonium chloride polymerization. Products, ethyleneimine polymer, diallylamine polymer, ammonia / epichlorohydrin / dimethylamine copolymer, polymethacrylic acid quaternary ammonium salt derivatives, and the like. Among these, diallyldimethylammonium chloride polymer (hereinafter, appropriately referred to as “poly-DADMAC”) is particularly preferable in terms of compatibility with other chemicals, color development and water resistance of printed matter. Examples of the poly-DADMAC that can be used in the present invention include T-DK129 (manufactured by Seiko PMC), Himax SC-100, SC-120, SL-100L, SC-600L, SC-607 (all of which are Hymo Corporation). PAS-H-5L, PAS-H-10L, PAS-J-41, PAS-J-81 (all manufactured by Nitto Boseki Co., Ltd.) and HP-189A (manufactured by Senka Co., Ltd.). it can.

5). Other Components In addition to the above components, a known pigment or a known binder can be used in combination with the ink receiving layer as long as the effects of the present invention are not impaired. Other additives include ink fixing agents, pigment dispersants, thickeners, fluidity improvers, antifoaming agents, antifoaming agents, mold release agents, foaming agents, penetrating agents, colored dyes, colored pigments, fluorescent enhancers. A white agent, an ultraviolet absorber, an antioxidant, an antiseptic, an antibacterial agent, a water resistant agent, a wet paper strength enhancer, a dry paper strength enhancer, and the like can be appropriately blended in the ink receiving layer.

(Production method)
As a method of applying the ink receiving layer coating material on the support, known coatings such as blade coater, air knife coater, roll coater, brush coater, kiss coater, squeeze coater, curtain coater, die coater, bar coater, gravure coater, etc. What was suitably selected from the method of coating using a machine is mentioned.

5). Micro-hardness of ink receiving layer Micro-hardness (dynamic hardness) is created by applying a load such as Vickers hardness and Knoop hardness widely used for measuring the hardness of metal materials. The hardness is obtained from the diagonal length, and the microhardness used in the present application obtains the hardness depending on how much the indenter has entered the sample. An example of such a testing machine is a dynamic ultra-small hardness meter DUH-W201S manufactured by Shimadzu Corporation. The dynamic hardness (DH) obtained with such a testing machine can be obtained by the following equation.
Dynamic hardness (DH) calculation formula DH = α × P / D ² (Formula 1)
P: Load (2mN)
D: Depth of indenter into sample (μm)
α: Constant due to indenter shape (α = 3.88584 for triangular pyramid indenter (ridge angle 115 °) used in this application)

  It is essential that the micro hardness of the ink receiving layer measured in this way is in the range of 5-15. When the micro hardness of the ink receiving layer is less than 5, since the ink receiving layer is soft, the metal spur roll that has entered through the glossy layer can suppress the entrance of the spur on the surface of the ink receiving layer. Can not. Therefore, since a large dent is formed in the glossy layer, spur marks are conspicuous. On the other hand, when the micro hardness of the ink receiving layer exceeds 15, the spur entering through the glossy layer can be stopped near the surface of the ink receiving layer, but the ink absorbability of the ink receiving layer is extremely high. Inferior. When a glossy layer is provided on such an ink receiving layer, the aesthetic appearance of the image is remarkably impaired.

  In addition, when the gloss layer has a high microhardness, the dent due to the spur becomes inconspicuous, but when printing with an ink jet printer, the ink penetration becomes extremely slow, so that the ink dries slowly and the bleeding is large. Therefore, a beautiful image cannot be formed. The fine hardness of the gloss layer is preferably in the range of 1-5.

(Glossy layer)
The gloss layer is mainly composed of a pigment and an aqueous binder as in the ink receiving layer.
(Glossy layer pigment)
As the pigment for the glossy layer in the present invention, known pigments such as precipitated silica, gel silica, gas phase silica and colloidal silica can be used. In addition, other pigments such as α-type crystal alumina, θ-type crystal alumina, synthetic silica, kaolin, talc, calcium carbonate, carbon dioxide are used as long as they do not impair the ink absorbability, color developability and glossiness upon ink jet recording. Titanium, clay, zinc oxide or the like may be used in combination. The pigment used in the gloss layer of the present invention preferably contains colloidal silica, synthetic amorphous silica produced by a wet method, and synthetic amorphous silica produced by a gas phase method. These will be described.

1. Colloidal silica The secondary particle diameter of the colloidal silica used in the present invention is preferably 5 to 55 nm, more preferably 10 to 40 nm. When the secondary particle diameter is less than 5 nm, the ink coloring property is greatly lowered when printing is performed with an ink jet printer using pigment ink. When the secondary particle diameter exceeds 55 nm, the space between the particles increases and the ink absorbability of the glossy layer is improved, but the opacity increases, and therefore the color developability when ink jet recording with the dye ink is lowered.

  The ratio of the secondary particle diameter to the primary particle diameter of the colloidal silica (secondary particle diameter / primary particle diameter) is preferably 1.5 to 3.0. When the ratio is less than 1.5, the color developability of the pigment ink and the dye ink is remarkably lowered. The primary particle size and secondary particle size of colloidal silica can be measured by the BET method, dynamic light scattering method, or the like.

  By incorporating the colloidal silica having the secondary particle size and ratio described above into the gloss layer, the color developability of the pigment ink can be greatly improved. If the secondary particle diameter and the ratio are in the above ranges, two or more kinds of colloidal silicas having different secondary particle diameters and / or ratios can be used in combination.

  In addition, when the dispersion state of the colloidal silica in the present invention is observed with a microscope, a large number of spherical single colloidal silicas (secondary particles) that are continuous (aggregated) are observed. Such an agglomerated state is represented as a peanut shape for convenience. The colloidal silica in the present invention is a silica in which at least 5 spherical single colloidal silicas, usually 10 or more, are aggregated when the dispersion state is observed with a microscope (referred to as tufted or chain colloidal silica). Not included. However, the term “not included” as used herein does not mean that when the dispersion state is observed with a microscope, the above-described tufted or chain colloidal silica or single colloidal silica is not observed at all. Although colloidal silica may be observed, the said ratio which is a macroscopic physical property should just be 1.5-3.0. Here, the average value of the number of connected secondary particles of colloidal silica described above substantially corresponds to the above ratio.

  The colloidal silica is preferably synthesized by sol-gel method using alkoxysilane as a raw material, and the secondary particle size (BET method particle size) and secondary particle size (dynamic light scattering method particle size) are controlled according to the synthesis conditions. Examples of colloidal silica that can be used in the present invention include trade name Quartron manufactured by Fuso Chemical Industries.

2. Synthetic Amorphous Silica Manufactured by Wet Method Synthetic amorphous silica can be roughly classified into wet method silica and gas phase method silica depending on the production method. Synthetic amorphous silica produced by a wet process (hereinafter referred to as “wet process silica” where appropriate) is inferior to gas-phase process silica in terms of pigment transparency, but is excellent in paint stability when used in combination with polyvinyl alcohol. Furthermore, compared with gas phase method silica having no internal voids, wet method silica has good dispersibility in the liquid and can increase the coating concentration. Therefore, when wet method silica is used as the pigment of the ink receiving layer, the pigment ratio in the glossy layer can be increased to increase the absorbability of the ink receiving layer, so that the ink absorbability can be improved and the color of the dye ink can be improved. It can be improved.

  Further, as the wet method silica, there are “gel method silica” produced by a gel method and “precipitation method silica” produced by a precipitation method. As the pigment for the glossy layer, either gel method silica or precipitation method silica may be used alone, or these may be used in combination, but the use of precipitation method silica is preferred because the ink absorbability is further improved.

From the viewpoint of obtaining a high gloss feeling, the preferred secondary particle size of the wet process silica is 4 to 6 μm. Moreover, it is preferable that a BET specific surface area is 150-500 m < ² > / g. As the specific surface area increases, the color developability tends to decrease.

3. Vapor Phase Silica Further, in the present invention, it is preferable that the glossy layer contains vapor phase silica. When the vapor phase method silica is contained in the glossy layer, the reason is not clear, but the ink of the glossy layer becomes better wetted, so that unevenness in solid printing tends to be improved.

  Vapor phase process silica is also called dry process silica or fumed silica, and is generally produced by flame hydrolysis. Vapor phase silica is specifically produced by gas phase hydrolysis of volatile silane compounds such as silicon tetrachloride in an oxyhydrogen flame. It can be obtained by changing conditions such as the silicon supply amount. Instead of silicon tetrachloride, silanes such as methyltrichlorosilane and trichlorosilane can be used alone or mixed with silicon tetrachloride. Vapor phase process silica is commercially available as Aerosil from Nippon Aerosil Co., Ltd., and is commercially available as Toyoyama Co., Ltd. as Leolosil QS type, and can be easily obtained.

The average secondary particle size of the vapor phase method silica is preferably 5 to 50 nm. Moreover, it is preferable for the specific surface area (by the BET method) to be 130 to 300 m ² / g because the transparency of the gloss layer is high and the stability when blended in the paint is good. When the specific surface area of vapor-phase process silica is smaller than 130 m ² / g, the opacity of the glossy layer may increase, and problems such as a decrease in print density when printing with an ink jet printer may occur. When the specific surface area of the vapor-phase process silica exceeds 300 m ² / g, the gloss layer becomes more transparent and the printing density is improved, but the viscosity stability of the paint tends to be inferior, and the coating property is lowered. There is.

(Glossy layer aqueous binder)
The gloss layer of the present invention contains at least one water-based binder (water-soluble and / or water-dispersible resin emulsion). It is particularly preferable to use partially and / or intermediately saponified polyvinyl alcohol. The addition amount of polyvinyl alcohol is preferably 3 to 30 parts by weight with respect to 100 parts by weight of the pigment. Furthermore, other aqueous binders can be blended within a range that does not impair the ink absorptivity, color developability and glossiness upon ink jet recording. For example, polyvinylpyrrolidone, urethane resin derived from urethane resin emulsion, starches such as oxidized starch and esterified starch, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, casein, gelatin, soybean protein, styrene-acrylic resin and derivatives thereof, styrene -A butadiene resin latex, an acrylic resin emulsion, a vinyl acetate resin emulsion, a vinyl chloride resin emulsion, a urea resin emulsion, an alkyd resin emulsion, and derivatives thereof are not particularly limited.

(Image clarity)
Next, the image definition of the glossy layer will be described. The image definition in the present invention follows the method defined in JIS-K 7105 (measurement of image definition by the reflection method), but the incident direction of the measurement light is made parallel to the paper making direction (MD direction, machine direction). Measured with a reflection angle of 60 degrees and an optical comb width of 2 mm. The image definition varies depending on the pigment and binder of the gloss layer, but in order to increase the image definition, a pigment having a small particle diameter is preferable. The colloidal silica is easy to obtain high image definition, but when used alone, the ink absorbability is poor when ink-jet printing is performed. Therefore, the colloidal silica is used in combination with the precipitated silica or gel silica. Is preferred. The silica particle diameter is preferably 4 to 6 μm (laser method type particle size measuring instrument), and it is easy to balance ink absorbency. As the binder, the above-mentioned polyvinyl alcohol is preferable. In order to obtain glossy paper having high image definition, it is preferable to use partially saponified or intermediate saponified PVA alone or in combination. For the purpose of obtaining a glossiness similar to that of a silver salt photograph, it is essential that the image definition is 65% or more, and it is more preferable that the image definition is 70% or more. When the image definition is less than 65%, the glossiness of appearance is low, and a clear image such as a silver salt photograph cannot be obtained, so that the image becomes slightly blurred.

(Other components of the gloss layer)
In addition to the pigment and water-based binder described above, the gloss layer includes, for example, a thickener, an antifoaming agent, an antifoaming agent, a pigment dispersant, a release agent, a foaming agent, a pH adjusting agent, a surface sizing agent, Colored dyes, colored pigments, fluorescent dyes, ultraviolet absorbers, antioxidants, light stabilizers, preservatives, water resistance agents, dye fixing agents, surfactants, wet paper strength enhancers, water retention agents, cationic polymers An electrolyte or the like can be appropriately added within a range not impairing the effects of the present invention.

(Glossy layer formation)
As a method of applying the gloss layer coating liquid on the ink receiving layer, a blade coater, an air knife coater, a roll coater, a brush coater, a kiss coater, a squeeze coater, a curtain coater, a die coater, a bar coater, a gravure coater, and the like are known. It can select from the method of coating using the coating machine of this, and can use it suitably.
Examples of the method for applying the treatment liquid include, but are not limited to, a roll, a spray, and a curtain method.

The coating amount of the gloss layer can be arbitrarily adjusted within a range that covers the surface of the ink receiving layer and sufficient gloss is obtained, but is preferably 5 to 30 g / m ² in terms of solid content. A more preferable range is 10 to 25 g / m ² . If the coating amount is less than 5 g / m ² , the surface of the ink receiving layer cannot be sufficiently covered, which causes uneven gloss. On the other hand, when it exceeds 30 g / m ² , the peelability from the mirror drum is lowered, and problems such as adhesion of the coating layer to the mirror drum occur.

  In the present invention, after applying a treatment liquid that solidifies the aqueous binder in the glossy layer, the wet glossy layer is pressed against a heated mirror-finished surface and dried to give gloss to the glossy layer. To do. The glossy layer when applying the treatment liquid may be in a wet state or in a dry state, but in the case of the former (in which the treatment liquid is applied while the glossy layer is in a wet state), it is mirror-finished. Since the surface can be easily copied and minute irregularities on the surface can be reduced, it is easy to obtain a glossiness equivalent to that of a silver salt photograph.

  As a method for imparting gloss to the gloss layer surface, a cast coating method using a cast coater is suitable from the viewpoint of production cost. The cast coating method is a method in which a coating liquid mainly composed of a pigment and a binder is coated on a support to provide a coating layer, and the coating layer is pressed onto a cast drum to give a gloss finish. The gloss coating layer becomes the gloss layer.

  The cast coating method includes (1) a wet casting method (direct method) in which a coating layer is pressure-bonded to a mirror-finished heating drum while the coating layer is wet, and (2) a wet coating method. Re-wetting method in which the coating layer is once dried or semi-dried and then swelled and plasticized with a re-wetting liquid, and the coating layer is pressure-bonded to a mirror-finished heating drum and dried. There are three types: gelled cast method (coagulation method) in which the coating layer is pressed onto a mirror-finished heating drum and dried. The principle of each method is the same in that the wet coating layer is pressed against the mirror-finished surface to give gloss to the coating layer surface.

  In the present invention, the gloss layer is glossed by forming the outermost gloss layer of the inkjet recording medium by a cast coating method. Preferably, a gelled cast coating method (coagulation method) is used in that it can provide a surface feel and gloss comparable to silver salt photographs.

(Coagulation liquid)
As the coagulation liquid, those having an action of coagulating the aqueous binder in the wet coating layer, for example, various kinds of calcium such as formic acid, acetic acid, citric acid, tartaric acid, lactic acid, hydrochloric acid, sulfuric acid, zinc, magnesium, etc. A salt solution is used. In particular, when polyvinyl alcohol is used as the aqueous binder, it is preferable to use a liquid containing boric acid and borate as the coagulating liquid. By mixing and using boric acid and borate, it becomes easy to make the coating layer hardness at the time of solidification moderate, and a glossiness can be imparted to the gloss layer. The method for applying the coagulating liquid is not particularly limited as long as it can be applied to the coating layer, and can be appropriately selected from known methods (for example, roll method, spray method, curtain method, etc.).

  Moreover, a release agent can be added to the gloss layer coating solution and / or the coagulation solution as required. The melting point of the release agent is preferably 90 to 150 ° C, and particularly preferably 95 to 120 ° C. In the above temperature range, since the melting point of the release agent is substantially equal to the temperature of the mirror finish surface, the ability as a release agent is maximized. The release agent is not particularly limited as long as it has the above characteristics, but it is preferable to use a polyethylene wax emulsion.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in full detail, this invention is not limited by this. Unless otherwise specified, “part” and “%” described below represent “part by weight” and “% by weight”, respectively.

[Example 1]
10 parts talc, 1.0 part aluminum sulfate, 0.1 part synthetic sizing agent, 0.1 part synthetic sizing agent and 0% yield improver in a pulp slurry consisting of 100 parts hardwood bleached kraft pulp (L-BKP) with 285 ml Canadian Standard Freeness (CSF) upon papermaking the support was added .02 parts in paper machine, by applying starch so that 2.5 g / m ² on one surface per solids on both surfaces, to obtain a base paper having a basis weight of 150 g / m ² . As an ink receiving layer, this base paper was coated with the following coating liquid A with a blade coater so that the coating amount was 15 g / m ² and dried by blowing at 140 ° C. to provide an ink receiving layer. Next, 13 g / m ^{2 of the following} coating liquid B was applied onto the surface coated with the coating liquid A with a roll coater, and the coating layer was coagulated with the following coagulating liquid C while the coating layer was in a wet state. Then, it was pressed against a mirror-finished surface heated through a press roll and dried, and the mirror surface was copied to give a glossy layer to obtain a 178 g / m ² ink jet recording medium.
-Coating liquid A: As a pigment, 100 parts of synthetic silica (Fine Seal X-60: trade name manufactured by Tokuyama Co., Ltd.), ethylene vinyl acetate copolymer emulsion (AM-3150: manufactured by Showa Polymer Co., Ltd.) Product name) 25 parts, 5 parts of polyvinyl alcohol (PVA117: product name manufactured by Kuraray Co., Ltd.) having a saponification degree of 99% and a polymerization degree of 1700, a cationic ink fixing agent (T-DK129: product name manufactured by Seiko PMC Co., Ltd.) ) 5 parts and 5 parts of a sizing agent (SE-2250: trade name manufactured by Seiko PMC Co., Ltd.) were mixed to prepare an aqueous coating solution having a concentration of 30%.
-Coating liquid B: Colloidal silica having an average secondary particle size of 30 nm and a secondary particle / primary particle size ratio of 2.2 (Quarton PL-3: trade name of Fuso Chemical Industries) as a pigment 60 parts of fumed silica having a specific surface area of 300m ² / g (Aerosil 300: Nippon Aerosil K.K.) and 10 parts of precipitated silica having a specific surface area of 270m ² / g (Fine seal X37: Co., Ltd. 15 parts of Tokuyama trade name), 15 parts of precipitated silica (Fine Seal E50: trade name of Tokuyama Co., Ltd.) having a specific surface area of 190 m ² / g, polyvinyl having a saponification degree of 95% and a polymerization degree of 1700 as a binder 6 parts of alcohol (PVA617: trade name, manufactured by Kuraray Co., Ltd.), polyvinyl alcohol having a saponification degree of 88% and a polymerization degree of 1700 (Kuraray 217: manufactured by Kuraray Co., Ltd.) (Commercial name) 6 parts, release agent (FL-48C: product name manufactured by Toho Chemical Co., Ltd.) 1 part, antifoaming agent (deformer 480: product name manufactured by San Nopco Co., Ltd.) 0.2 part A coating solution having a concentration of 22% was prepared.
Coagulating liquid C: Borax / boric acid compounding ratio is 1, the concentration is 2% in terms of Na ₂ B ₄ O ₇ and H ₃ BO ₃ , release agent (FL-48C: manufactured by Toho Chemical Industry Co., Ltd.) Product name) 0.2% was blended to adjust the coagulation liquid.

[Example 2]
An ink jet recording medium was obtained in the same manner as in Example 1, except that 10 parts of the polyvinyl alcohol in the coating liquid A was used.

[Example 3]
An ink jet recording medium was obtained in the same manner as in Example 1 except that 15 parts of the polyvinyl alcohol in the coating liquid A was used in Example 1.

[Example 4]
An ink jet recording medium was obtained in the same manner as in Example 1 except that the polyvinyl alcohol of the coating liquid A had a saponification degree of 99% and a polymerization degree of 2000, and was 10 parts.

[Example 5]
An ink jet recording medium was obtained in the same manner as in Example 1 except that the polyvinyl alcohol of the coating liquid A was changed to a saponification degree of 99% and a polymerization degree of 2400.

[Example 6]
In Example 5, an inkjet recording medium was obtained in the same manner as in Example 5 except that the polyvinyl alcohol of the coating liquid A was changed to 10 parts.

[Example 7]
In Example 5, an inkjet recording medium was obtained in the same manner as in Example 5 except that 15 parts of the polyvinyl alcohol of the coating liquid A was used.

[Example 8]
In Example 1, an inkjet recording medium was obtained in the same manner as in Example 1 except that polyvinyl alcohol of the coating liquid A was changed to 10 parts of urethane resin (Superflex 600: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) having a Tg of 70 ° C. It was.

[Example 9]
In Example 7, precipitation silica (Fine Seal X37: trade name manufactured by Tokuyama Co., Ltd.) of the coating liquid B was not distributed, and precipitation silica (Fine Seal E50: manufactured by Tokuyama Co., Ltd.) having a specific surface area of 190 m ² / g. The ink jet recording medium was obtained in the same manner as in Example 7 except that the product name was changed to 30 parts.

[Comparative Example 1]
Inkjet recording medium in the same manner as in Example 1 except that the polyvinyl alcohol of the coating liquid A was changed to polyvinyl alcohol having a saponification degree of 88% and a polymerization degree of 1700 (PVA217: trade name, manufactured by Kuraray Co., Ltd.). Got.

[Comparative Example 2]
Inkjet recording medium in the same manner as in Comparative Example 1, except that the polyvinyl alcohol of the coating liquid A was changed to polyvinyl alcohol having a saponification degree of 88% and a polymerization degree of 2400 (PVA224: trade name, manufactured by Kuraray Co., Ltd.). Got.

[Comparative Example 3]
In Example 1, the same procedure as in Example 1 was repeated except that polyvinyl alcohol in coating solution A was 99% saponified and 3 parts polyvinyl alcohol having a polymerization degree of 1700 (PVA117: Kuraray Co., Ltd.). An ink jet recording medium was obtained.

[Comparative Example 4]
Inkjet recording medium in the same manner as in Example 1 except that the polyvinyl alcohol of the coating liquid A was changed to polyvinyl alcohol having a saponification degree of 99% and a polymerization degree of 1100 (PVA110: trade name, manufactured by Kuraray Co., Ltd.). Got.

[Comparative Example 5]
In Example 1, the inkjet recording medium was obtained like Example 1 except the addition amount of the polyvinyl alcohol of the coating liquid A having been 20 parts.

[Comparative Example 6]
An ink jet recording medium was obtained in the same manner as in Example 1 except that the polyvinyl alcohol of the coating liquid A was not used in Example 1.

[Comparative Example 7]
In Example 1, the polyvinyl alcohol of the coating liquid A was polyvinyl alcohol having a saponification degree of 88% and a polymerization degree of 1700 (PVA217: trade name manufactured by Kuraray Co., Ltd.), and the saponification degree of the coating liquid B was 88% and the polymerization degree. 1700 polyvinyl alcohol (PVA217: trade name, manufactured by Kuraray Co., Ltd.) was not blended, except that the saponification degree was 99% and the polymerization degree 1700 polyvinyl alcohol (PVA117: product name, manufactured by Kuraray Co., Ltd.) was 12 parts. An ink jet recording medium was obtained in the same manner as in Example 1.

  The hardness of the ink receiving layer of the ink jet recording media obtained in Examples 1 to 9 and Comparative Examples 1 to 8, the image clarity of the glossy layer, the spur mark, and the ink jet recording test were performed by the following methods. The results are summarized in Table 1.

(1) Measurement of micro hardness of ink receiving layer Using a dynamic ultra micro hardness meter DUH-W201S manufactured by Shimadzu Corporation, the micro hardness of the ink receiving layer at a load of 2 mN of a triangular pyramid indenter (ridge angle 115 °) was measured. It calculated | required by following formula 1.
DH = α × P / D ² (Formula 1)
P: Load (2mN)
D: Depth of indenter into sample (μm)
α: Constant due to indenter shape (α = 3.88584 for triangular pyramid indenter (ridge angle 115 °) used in this application)

(2) Measurement of image definition The image definition on the surface of cast coated paper is measured with a image clarity measuring instrument (model number: ICM-1T, manufactured by Suga Test Instruments Co., Ltd.) according to JIS-K 7105, and glossiness is measured. evaluated. The measurement angle was 60 ° and the MD direction of the paper was measured. Evaluation was performed as follows according to the level of image sharpness obtained.
A: Very high gloss (image clarity of 80% or more)
○: High glossiness (image definition of 65% or more)
(Triangle | delta): It is the glossiness like cloudiness (image clarity 45-64%)
X: Low gloss or uneven coating (image clarity of less than 45%)

(3) Evaluation of spur mark A black solid was printed with an inkjet printer, and the spur mark was visually evaluated.
◎: Spur mark is hardly seen ○: Spur mark is slightly seen, but there is no problem in practical use △: Spur mark is seen and practically interesting level ×: Spur mark is seen tight

(3) Inkjet recording test

In the recording test, a predetermined pattern was recorded using an ink jet printer (iP-4500: trade name, manufactured by Canon Inc.) using a dye ink, and evaluated according to the following criteria.
Ink absorption (bleeding)
Bleeding was visually evaluated at the boundary between the solid mixed parts of red and green.
○: The color boundary is clearly separated △: The color boundary is slightly blurred x: The color boundary is heavily blurred

(4) Measurement of average particle diameter of silica The particle diameter was measured with a laser particle size measuring instrument (model number Mastersizer S type, manufactured by Malvern) to determine the average particle diameter.

(5) Particle size measurement of colloidal silica a) Measurement of primary particle size The specific surface area (nitrogen adsorption method) of the sample was measured, and the primary particle size was determined by calculation according to the following formula.
d = 6000 / (ρ × S)
(However, in the formula, d: primary particle diameter (nm), ρ: silica density (= 2.2 g / m ³ ), S: specific surface area S (m ² / g))
b) Measurement of secondary particle size
Measurement was performed using ZETASIZER 3000HSA manufactured by MALVERN INSTRUMENTS.

表１から明らかなように、実施例１から９の本発明のインクジェット記録用紙では、像鮮明度が高く且つ、インクジェットプリンターで印字した際に生ずる拍車痕が目立たない光沢紙を得られた。一方、インク受理層の硬度が低い比較例１〜４および６〜７は写像性と拍車痕のバランスが悪く、比較例５で、インク受理層が硬すぎた場合には、光沢感とインクジェット印字適性のバランスが劣り、像鮮明度と拍車痕のバランスの良好なものが得られなかった。

As is apparent from Table 1, with the ink jet recording papers of the present invention of Examples 1 to 9, glossy paper having high image definition and inconspicuous spur marks generated when printing with an ink jet printer was obtained. On the other hand, Comparative Examples 1-4 and 6-7, in which the hardness of the ink receiving layer is low, have a poor balance between image clarity and spur marks. In Comparative Example 5, when the ink receiving layer is too hard, glossiness and inkjet printing The balance of aptitude was inferior, and a good balance between image clarity and spur marks could not be obtained.

Claims (5)

An inkjet recording medium having at least one ink-receiving layer and a glossy layer provided on at least one side of a gas-permeable support, wherein the glossiness of the glossy layer measured according to JIS-K 7105 is 65% or more. An ink jet recording medium having a microhardness (DH) obtained from the following (Equation 1) of the ink receiving layer adjacent to the glossy layer in the range of 5 to 15.
DH = α × P / D ² (Formula 1)
P: Load (2mN)
D: Depth of indenter into sample (μm)
α: Constant due to indenter shape (α = 3.88584 for triangular pyramid indenter (ridge angle 115 °) used in this application) 2. The inkjet according to claim 1, wherein the ink receiving layer adjacent to the glossy layer contains a pigment and an aqueous binder, and the aqueous binder contains a polymer having a glass transition temperature of 70 ° C. or higher. recoding media. 3. The ink receiving layer adjacent to the glossy layer contains a pigment and an aqueous binder, and contains polyvinyl alcohol and an ethylene / vinyl acetate copolymer as the aqueous binder. Inkjet recording medium. The ink receiving layer adjacent to the glossy layer contains a pigment and an aqueous binder, and the aqueous binder contains polyvinyl alcohol having a saponification degree of 98 to 99% and a polymerization degree of 1700 to 2400. The inkjet recording medium according to any one of claims 1 to 3. The gloss layer contains an aqueous binder, and after applying a treatment liquid having a function of solidifying the aqueous binder, the gloss layer is pressed against a heated mirror surface while the gloss layer is in a wet state. The inkjet recording medium according to claim 1, wherein the glossy layer is given a gloss by drying.