JP5439203B2 - Glossy paper for inkjet recording - Google Patents

Description

  The present invention relates to a glossy paper for ink-jet recording having a glossiness similar to that of a silver salt photograph, an extremely excellent scratch resistance of a glossy surface, and a small amount of paper dust at the time of cutting, and a high print quality.

The ink jet recording system is a system in which ink droplets are ejected and deposited on recording paper to form dots and recording is performed. In recent years, recording with high print quality has become possible due to technological advances in inkjet printers, inks, and recording media. As an element required for an inkjet recording medium,
(A) Fast ink absorption and drying (b) High printing density (c) No dot spread and whiskers. If ordinary plain paper has a certain size or more, it can be expected to have a certain level of printing quality with less blur. However, when a higher printing quality is required, a dedicated recording medium in which an ink receiving layer suitable for the ink of an ink jet printer is provided on various media on a medium is used. As these ink jet recording media, a paper or film as a support and a pigment coating layer mainly composed of a pigment and a binder or a resin coating layer not containing a pigment provided on the surface are often used. .

  Inkjet recording media are further classified into matte and glossy media from the surface state. The latter glossy medium is used when image quality closer to silver halide photography is required. Quality characteristics required for such a glossy medium include high glossiness, fast ink drying speed, high print density, and no ink overflow or bleeding. Furthermore, the ink jet recording medium is often subjected to paper small judgment processing before or after ink jet recording, and is required to have less paper dust at the time of cutting processing.

  Various methods have been proposed for producing glossy media in order to maintain the above-mentioned quality characteristics while maintaining ink absorbability and drying properties. There are a method of forming a layer and imparting gloss to the surface, and a method of forming an ink receiving layer on a photographic paper substrate.

  In general, the former is easier to control the ink absorptivity than the latter, but is inferior to the latter in terms of dot roundness, image reproducibility, and glossiness of a blank paper portion.

  When the ink-receiving layer is formed on the surface of the photographic paper base, since the polyethylene film layer is formed on the paper base as generally called RC paper (resin-coated paper), the film surface Is smooth, the surface of the ink receiving layer is also smooth, and a glossy surface is easily formed. However, the overall cost needs to be increased in order to increase ink absorbency, and the base material itself is more expensive than paper, so it is higher than the former glossy media produced by the cast coating method. It becomes. In addition, when it is discarded, there is a problem that it cannot be recycled because it is a composite material.

  Glossy paper for ink-jet recording by the cast coating method is advantageous for the above problems, but there are problems in terms of quality in terms of dot roundness, image reproducibility, and glossiness of the white paper portion, and these Various proposals have been made to solve the problem.

  As a proposal for solving the problems related to the glossiness of the surface and the ink absorbency, for example, by specifying the average roughness of the recording layer surface, the glossiness and the air permeability of the recording paper, the surface smoothness is high, An ink jet recording sheet that has excellent image quality and high ink absorption and absorption speed has been proposed (see, for example, Patent Document 1).

  In addition, an ink jet recording paper having excellent gloss and ink absorbency by defining the size and number of cracks on the surface of the recording layer has been proposed (see, for example, Patent Document 2).

  Furthermore, by defining the gloss layer thickness to be 0.02 to 4 μm, an ink jet recording material having excellent transparency and water resistance and a surface gloss as high as that of a silver salt photograph has been proposed (for example, patent document). 3).

  In recent years, as a recording sheet for an ink jet printer having a high ink absorption rate and a glossiness similar to that of a silver salt photograph, a paper coated with a mixture of alumina hydrate and a water-soluble binder has been proposed (for example, (See Patent Document 4).

  In addition to the problems related to surface glossiness and ink absorption, various proposals have been made for scratch resistance of glossy surfaces. For example, there is a proposal to improve the scratch resistance by defining the average degree of polymerization and the degree of saponification of polyvinyl alcohol used for the binder of the glossy layer (see, for example, Patent Document 5). There is also a proposal for improving scratch resistance by defining the smoothness and roughness of the surface of the ink receiving layer (see, for example, Patent Document 6).

  On the other hand, several methods have been disclosed as methods for preventing the generation of paper dust. For example, there is a proposal to suppress the generation of paper dust by increasing the adhesive content of the undercoat layer provided on the paper support (see, for example, Patent Document 7).

Japanese Patent Laid-Open No. 06-072017 JP-A-11-348416 JP 2004-338100 A Japanese Patent Laid-Open No. 06-055829 JP 2005-280012 A JP 2006-168046 A JP 2007-021751 A

  However, in the case of the technique described in Patent Document 2, if the number of cracks is too small, there is a problem that glossiness increases while ink absorbability decreases.

  The technique described in Patent Document 3 has a certain effect in improving the ink absorbency by reducing the coating amount of the glossy layer, but the surface scratch resistance is not always satisfactory.

  The glossy paper for ink-jet recording described in Patent Documents 1 to 4 has a characteristic that the glossiness is very excellent, but has a defect that the glossy surface is easily damaged because of the excellent glossiness. For example, when using for postcard applications, when printing standard items such as postal code frames and postage stamp frames on the address side, rubbing with the paper feed unit guide of a printing machine such as an offset printer and the paper discharge unit There is a drawback that the surface of the glossy layer is easily damaged by rubbing with the suction wheel. In addition, when the address is printed by the ink jet printer, there is a problem that the contact between the glossy surface and the paper feeding roller is easily damaged.

  Glossy paper for ink-jet recording is used after being processed to a predetermined size according to the application, such as postcards, but pigments with a large specific surface area such as silica and alumina, or binders such as polyvinyl alcohol are applied by multilayering. When the layer becomes thick, the strength of the coating layer decreases, and there is a problem that paper dust is likely to be generated. Moreover, when it hardens | cures by bridge | crosslinking a coating layer, since this coating layer becomes weak, it becomes easy to generate | occur | produce paper dust. The glossy paper for ink jet recording described in Patent Documents 1 to 4 does not solve this problem.

  In recent years, as described above, due to the problem of workability in the printing process such as address printing on the non-glossy surface and the post-processing process such as paper small judgment processing, the scratch resistance of the glossy surface and the amount of paper dust generated at the time of paper small judgment judgment. The current situation is that the demand for reduction is increasing. Therefore, it is easily guessed that the required level of quality required for glossy paper for ink-jet recording will gradually increase in the future.

  Thus, in order to improve the scratch resistance and the generation of paper dust, the techniques described in Patent Documents 5 to 7 have been proposed. From the results of research on the scratch resistance of glossy surfaces by the present inventors, Patent Document 5 Or, it came to a conclusion that the contents of each proposal in 6 are not sufficient to supplement the scratch resistance. Further, the technique described in Patent Document 7 has a problem in that the amount of paper powder that is absolutely dropped increases because the coating amount of all layers is high.

  In view of the prior art, the glossy paper for inkjet recording produced by the cast coating method has an image quality and a uniform glossiness exceeding those of an inkjet recording medium produced using a photographic paper substrate or a film substrate, and At present, there is no ink jet recording medium having very excellent workability.

  Accordingly, an object of the present invention is to provide a glossy paper for ink jet recording produced by a cast coating method, having a very good high gloss feeling similar to a silver salt photograph while having good ink absorbability, and having a glossy surface. It has excellent scratch resistance, has a small amount of paper dust at the time of paper small judgment, has an image quality equivalent to an inkjet recording medium produced using a photographic paper substrate or a film substrate, and a uniform glossiness, and It is to provide a recyclable ink jet recording medium.

The glossy paper for ink-jet recording according to the present invention is provided with one or more ink-receiving layers containing a pigment on at least one side of a substrate, and contains a pigment and a binder on the outermost layer of the ink-receiving layer. In the glossy paper for ink jet recording in which the gloss developing layer is provided by the cast coating method, the ink receiving layer contains only wet method silica and / or dry method silica as a pigment and aluminum hydroxide, and the ink. 70% by mass or more of the total pigment in the receiving layer is wet process silica and / or dry process silica, and the gloss developing layer is 80% by mass or more of the pigment is colloidal silica, and Polyvinyl alcohol is contained as the binder, and the coating amount of the glossy expression layer is ² to 11 g / m ² in terms of solid content. The ratio in terms of solid content expressed by (quantity) / (coating amount of the ink receiving layer) is more than 1.

In the glossy paper for ink jet recording according to the present invention, under the following dynamic hardness test conditions, the gloss dynamic layer has a dynamic hardness of 5.0 or more and a dynamic hardness of 20 when unloaded by an ultra-micro hardness tester. Including forms that are greater than or equal to 0. As a result of examining the relationship between the degree of plastic deformation of the surface of the glossy layer and the scratch resistance, the present inventors have found that the glossy paper having the glossy layer having a smaller plastic deformation level has better scratch resistance.
(Dynamic hardness test conditions)
Indenter: Triangular pyramid diamond indenter (edge angle 115 degrees, indenter shape factor 3.8854)
Test load: 1.0mN
Load speed: 1.42 mN / sec

  In the glossy paper for ink jet recording according to the present invention, in accordance with JIS H 8686-2: 1999 “Image clarity test method of anodized film of aluminum and aluminum alloy—Part 2: Instrument measurement method”, optical comb width 2 mm incident reflection The image clarity of the glossy layer under the condition of an angle of 60 ° is preferably 50% or more. A glossy paper for ink jet recording having a more excellent gloss feeling can be obtained.

  In the glossy paper for ink jet recording according to the present invention, it is preferable that the cast coating method for forming the glossy layer is a coagulation method, and a boron compound is contained as a coagulant. A more uniform glossy surface quality can be obtained.

  In the glossy paper for ink-jet recording according to the present invention, the glossy layer preferably has a surface pH of 6.4 or less. A glossy paper for ink-jet recording with little white paper fading and discoloration can be obtained.

  Although the present invention is a glossy paper for ink-jet recording produced by the cast coating method, it balances a very good surface glossiness, ink absorption and excellent print quality, and scratch resistance on the surface of the glossy layer at a high level. In addition, it is possible to provide glossy paper for ink-jet recording with a small amount of paper dust at the time of cutting. In particular, because of the problem of workability in post-processing, the demand for reducing the scratch resistance and the amount of paper dust generated on the surface of the glossy layer is easily inferred from the fact that the level will be increased more and more. Significance is considered large. In addition, since the glossy paper for inkjet recording according to the present invention uses paper as a base material, the manufacturing cost is low compared to a photographic paper base material having a film layer, and can be recycled when discarded. It is also preferable from the viewpoint of effective use.

  Next, the present invention will be described in detail with reference to embodiments, but the present invention is not construed as being limited to these descriptions. As long as the effect of the present invention is exhibited, the embodiment may be variously modified.

The glossy paper for ink-jet recording according to this embodiment is provided with at least one ink receiving layer containing a pigment on at least one side of a substrate, and contains a pigment and a binder on the outermost layer of the ink receiving layer. In the glossy paper for ink jet recording in which the gloss developing layer is provided by a cast coating method, the ink receiving layer contains only wet method silica and / or dry method silica as a pigment and aluminum hydroxide, 70% by mass or more of the total pigment in the ink receiving layer is wet process silica and / or dry process silica, and the gloss developing layer has 80% by mass or more of the pigment is colloidal silica, and , Containing polyvinyl alcohol as the binder, and the coating amount of the glossy layer is ² to 11 g / m ² in terms of solid content (of the glossy layer) The ratio in terms of solid content expressed by (coating amount) / (coating amount of the ink receiving layer) exceeds 1.

  In order to predict the scratch resistance of the surface of the glossy layer, it is necessary to measure the microhardness of the surface. As a result of intensive studies, the present inventors have found that the size of a scratch generated by rubbing the glossy layer shows a correlation with microhardness.

  Furthermore, as a result of investigations on improvement of scratch resistance by the present inventors, it has been found that the scratch resistance of the coating layer surface is affected not only by the hardness of the outermost layer but also by the hardness of the lower layer. For example, when an impact is given to the gloss developing layer, even if it is a strong gloss developing layer, if the hardness of the lower ink receiving layer is insufficient, the ink receiving layer is compressed and broken. As a result, the glossy layer surface is also deformed. In particular, wet-type silica or dry-type silica is mainly used in the ink receiving layer, and these have a high ink absorption capacity due to their aggregate structure, while forming a high void structure. Therefore, in order to improve scratch resistance while realizing high ink absorption, it is necessary to increase the coating amount of a strong glossy layer and minimize the influence of the lower layer.

  The glossy paper for ink-jet recording according to this embodiment includes a mode in which the dynamic hardness at the time of loading of the glossy expression layer by the ultra-micro hardness meter is 5.0 or more and the dynamic hardness at the time of unloading is 20.0 or more. . More preferably, the dynamic hardness at loading is 10.0 or more and the dynamic hardness at unloading is 30.0 or more, and particularly preferably, the dynamic hardness at loading is 12.0 or more and the dynamic hardness at unloading is 35. 0.0 or more. A dynamic hardness of 30.0 or more at the time of unloading is preferable because the gloss-developing layer is more difficult to be plastically deformed.

  Here, dynamic hardness is a method of applying a force such as Vickers hardness and Knoop hardness widely used for measuring the hardness of metal materials to create a dent, and obtaining the hardness from the diagonal length of the dent. Rather, a method is employed in which the hardness is determined by how much the indenter has entered the sample. When the test force P (mN) and the penetration depth (indentation depth) D (μm) of the indenter into the sample are set, the dynamic hardness DH is obtained by the following equation (Equation 1).

(Expression 1) DH = α × P ÷ D ² (α: indenter shape factor)

  This dynamic hardness is the hardness obtained from the test force and indentation depth during the process of indenting the indenter. In the case of load, the strength characteristics of the sample include not only plastic deformation but also elastic deformation. It can be said. In the case of unloading, plastic deformation is shown, and there is a correlation with Vickers hardness, Knoop hardness, and the like. In this embodiment, the dynamic hardness is measured using an ultra-micro hardness meter (DUH-201, manufactured by Shimadzu Corporation), and the measurement condition is a triangular pyramid diamond indenter (inter-ridge angle 115 degrees, indenter). Using a shape factor of 3.8584), the test force was 1.0 mN and the load speed was 1.42 mN / sec. In the present embodiment, it is preferable that the test conditions are within a range of a test force of 0.2 to 10.0 mN. When the test force is less than 0.2 mN, the accuracy of the obtained value is low, and when it is greater than 10.0 mN, the load is overloaded as compared with the actual rubbing condition, and the difference in hardness value is difficult to distinguish. Here, the reason for setting the test force to 1.0 mN is that the difference in hardness is easily evaluated.

  In glossy paper for ink-jet recording, colloidal silica, wet-type silica, dry-type silica, alumina (α-type crystal alumina, θ-type crystal alumina, γ-type crystal alumina, etc.) And alumina hydrate (alumina sol, colloidal alumina, pseudoboehmite, etc.) are used. In the glossy paper for ink-jet recording according to the present embodiment, it is essential to use colloidal silica as a pigment contained in the glossy layer in order to achieve the improvement of scratch resistance which is the object of the present invention. Colloidal silica has a high binding force with the binder and can provide a structure with few voids. In this way, since a highly scratch-resistant surface can be formed during film formation, plastic deformation of the coating layer can be minimized.

  On the other hand, wet method silica, dry method silica, alumina (α type crystal alumina, θ type crystal alumina, γ type crystal alumina, etc.) or alumina hydrate (alumina sol, colloidal alumina, pseudo boehmite, etc.) It is a pigment commonly used in glossy paper for ink-jet recording due to its good ink absorption due to its high specific surface area, but because of its porosity, it is prone to plastic deformation and is extremely difficult to have high scratch resistance. It is.

  Based on the above research results, in view of the properties of the pigment, in the glossy paper for ink jet recording according to the present embodiment, the gloss developing layer contains colloidal silica as the main pigment. This makes it possible to obtain glossy paper for ink-jet recording that is truly excellent in scratch resistance. The colloidal silica is preferably used in a spherical or nearly spherical shape or a pearl necklace-like aggregate shape. From the viewpoint of scratch resistance and high glossiness, it is more preferable to use a spherical or nearly spherical shape. These can be used alone or in combination. Here, the pearl necklace-like colloidal silica refers to colloidal silica in which silica fine particles are connected in a ring shape like a pearl necklace. On the other hand, tufted colloidal silica in which silica fine particles are aggregated in a tuft or chain colloidal silica in which silica fine particles are elongated and connected may be inferior in terms of ink absorbability.

  The average particle diameter of primary particles of spherical colloidal silica and aggregated colloidal silica is preferably 10 to 300 nm, and more preferably 15 to 200 nm. If it is less than 10 nm, the surface of the coating film becomes brittle and the coefficient of friction becomes high, so that the scratch resistance may be inferior. On the other hand, when the particle diameter exceeds 300 nm, the film formability of the coating film is too good, and the ink absorbability of the pigment ink may be inferior. In addition, the size (length) of the aggregate-shaped colloidal silica is preferably 50 to 500 nm, and more preferably 80 to 400 nm. Here, the average particle diameter of the primary particles is an average particle diameter measured by the BET specific surface area measurement method, and the size (length) of the aggregate-shaped colloidal silica is a laser diffraction / scattering type particle size measuring device. This is the median diameter measured in.

  Colloidal silica includes an anionic one and a cationic one. In the present embodiment, any colloidal silica can be used, but anionic colloidal silica is more preferably used. The hardness of the gloss expressing layer surface is improved, and as a result, the scratch resistance can be further improved.

  In the present embodiment, in addition to colloidal silica as the pigment of the glossy layer, wet method silica, dry method silica, as long as the scratch resistance and ink absorbability, color developability, and glossiness when ink jet recording are performed are not impaired. Alumina or alumina hydrate may be used in combination. In addition, other pigments such as aluminum hydroxide, kaolin, talc, calcium carbonate, titanium dioxide, clay, and zinc oxide can be used in combination.

  The content of colloidal silica is 80% by mass or more in terms of dry mass in all pigments in the glossy layer. More preferably, it is 90 mass% or more, and particularly preferably 100 mass%. If it is less than 80% by mass, the scratch resistance is deteriorated or the ink absorbability is deteriorated when ink jet printing is performed.

  Polyvinyl alcohol is used as the binder contained in the glossy layer. By containing polyvinyl alcohol, the ink absorbability and color developability are excellent. Furthermore, as a result of intensive studies by the present inventors, it has been found that polyvinyl alcohol is the most effective resin for minimizing plastic deformation of the coating layer. In the present embodiment, polyvinyl alcohol includes a saponified product or a modified product thereof. The saponified product of polyvinyl alcohol is divided into partially saponified polyvinyl alcohol or fully saponified polyvinyl alcohol according to the degree of saponification. Examples of the modified polyvinyl alcohol include anion group-modified polyvinyl alcohol, cationic group-modified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, sulfone group-modified polyvinyl alcohol, and silanol group-modified polyvinyl alcohol. Among these, it is more preferable to use partially saponified polyvinyl alcohol or silanol group-modified polyvinyl alcohol. When a boron compound is used as a coagulant used in the cast coating process described later, the coagulation property is improved.

  In the present embodiment, a binder other than polyvinyl alcohol can be used in combination as long as the effects of the present invention are not impaired. Examples of binders that can be used in combination include polyvinyl acetal, oxidized starch, etherified starch, carboxymethyl cellulose, hydroxyethyl cellulose, casein, gelatin, soybean protein, polyethylene imide resin, polyvinyl pyrohydrin resin, polyacrylic acid or The copolymer, maleic anhydride copolymer, acrylamide resin, acrylate resin, polyamide resin, polyurethane resin, polyester resin, polyvinyl butyral resin, alkyd resin, epoxy resin, epichlorohydrin resin, Acrylic polymer latex such as urea resin, melamine resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, acrylic acid ester, methacrylic acid ester polymer or copolymer Examples thereof include vinyl polymer latexes such as ethylene-vinyl acetate copolymer, copolymer resins of colloidal silica and acrylic, and resins such as copolymer resin of colloidal silica and styrene-acrylic. it can.

  The addition amount of the binder is determined in consideration of the printability of the ink jet recording medium, the strength of the ink receiving layer, and the coating liquid property. Usually, it is added in the range of 1 to 60 parts by mass with respect to 100 parts by mass of the total pigment in the glossy layer. Preferably, it is added in the range of about 5 to 50 parts by mass. If it is less than 1 part by mass, the coating layer strength may decrease. If it exceeds 60 parts by mass, the ink absorbability may decrease.

  The content of polyvinyl alcohol is preferably 5% by mass or more in terms of dry mass in all binders in the glossy layer. More preferably, it is 10 mass% or more. If it is less than 5% by mass, the ink absorbability and color developability may be inferior. In addition, plastic deformation of the glossy layer may not be sufficiently suppressed.

  It is preferable to add a cationic polymer for fixing the ink for inkjet recording to the glossy layer. Furthermore, auxiliary agents such as mold release agents, dispersants, thickeners, preservatives, antifoaming agents, coloring dyes, coloring pigments, fluorescent whitening agents, water resistance agents, leveling agents, antioxidants, ultraviolet absorbers, etc. Can be appropriately selected and added.

The gloss developing layer is prepared by blending various components contained in the gloss developing layer, such as the pigment and binder, and applying a coating solution for the gloss developing layer adjusted to an appropriate solid content concentration by a cast coating method. . The coating method of the coating liquid for the glossy layer is not limited in this embodiment, and a known coating machine such as an air knife, roll coater, reverse roll coater, bar coater, comma coater, blade coater may be used. it can. The coating amount is ² to 11 g / m ^{2 in} terms of solid content. More preferably 3 to 10 g / ^{m 2,} particularly preferably 5~8g / ^{m 2.} When the coating amount exceeds 11 g / m ² , the generation of paper powder at the time of paper small judgment becomes severe, and when the coating amount is less than 2 g / m ² , the surface hardness is inferior.

  The gloss developing layer is formed by a known cast coating method. As the cast coating method, a wet method, a solidification method, and a rewetting method are known, and in this embodiment, a solidification method is preferable. The coagulation method is a method in which a gloss developing layer is applied and a coagulating liquid is applied to the cast drum while being in a wet state and subjected to coagulation treatment. Here, the coagulation liquid refers to an aqueous solution of a coagulant. It is important to select a coagulant that effectively coagulates with the binder component of the glossy layer. In the present embodiment, it is preferable to select a boron compound. More preferably, either or both of sodium borate and boric acid are used. A more uniform glossy surface can be obtained. The concentration of the coagulant is preferably 0.1% by mass or more. If it is less than 0.1% by mass, the coagulation force may be insufficient. More preferably, it is 0.5 mass% or more. Furthermore, the content of 1.0% by mass or more is particularly preferable because the coagulation force becomes stronger and the scratch resistance can be improved. In addition, it is preferable that the upper limit of the density | concentration of coagulating liquid shall be 10.0 mass% from the point of workability | operativity and cost.

  Further, a cationic polymer for fixing the ink can be added to the coagulating liquid. The addition amount of the cationic polymer is preferably 1 to 1000 parts by mass in dry mass with respect to 100 parts by mass of the coagulant contained in the coagulation liquid. More preferably, it is 10-800 mass parts.

  By adjusting the time from application of the glossy layer to application of the coagulation liquid, the time from application of the coagulation liquid to the arrival of the cast drum, the temperature of the cast drum, the pressure at the time of pressure bonding, or the line speed Further, the glossiness of the gloss developing layer can be further increased. About these various conditions, it is necessary to optimize by calculating | requiring optimal conditions according to the equipment to be used and a coating liquid.

  Depending on one or both of the components of the coagulant and / or the pH of the coagulant, the surface pH of the glossy layer after drying may have an effect. It is preferable that the surface pH of the glossy layer is adjusted to 6.4 or less from the viewpoint of reducing blank paper fading and discoloration. More preferably, the surface pH is 6.0 or less. The lower limit of the surface pH of the glossy layer is preferably 3.0 from the viewpoint of image clarity.

  In addition, calendar processing such as machine calendar, soft calendar, super calendar, etc. may be performed after casting processing, and for curl adjustment, water, curling agent etc. are applied on the back side and humidification is performed by humidification. It can also be done.

  In the glossy paper for ink-jet recording according to the present embodiment, an optical comb width of 2 mm is added according to JIS H 8686-2: 1999 “Image quality test method of anodized film of aluminum and aluminum alloy—Part 2: Instrument measurement method”. The image clarity of the glossy layer under the condition of a reflection angle of 60 ° is preferably 50% or more. More preferably, it is 60% or more. If the image clarity is 60% or more, it can be said that the glossiness is further improved. Here, the reason why the incident / reflection angle is changed from 45 ° described in JIS to 60 ° is because it is easy to evaluate the difference in glossiness.

  The glossy paper for ink-jet recording of this embodiment is provided with one or more ink receiving layers under the glossy expression layer. The ink receiving layer contains a pigment and a binder as main components.

  The pigment used in the ink receiving layer is either wet-process silica or dry-process silica or any one of them. Since wet method silica and dry method silica are excellent in ink absorbability and color developability, good image sharpness can be realized.

  Wet process silica is classified into precipitation (precipitation) process silica and gel process silica, and is generally synthesized by a neutralization reaction between sodium silicate and mineral acid (usually sulfuric acid). In this embodiment, the type of wet method silica is not limited, but gel method silica is more preferable in terms of ink absorbability.

  Dry process silica is also called gas phase process silica or fumed silica, and is generally produced by flame hydrolysis. Specifically, it is manufactured by gas-phase hydrolysis of volatile silane compounds such as silicon tetrachloride in an oxyhydrogen flame, and changes the conditions such as the flame temperature, the supply ratio of oxygen and hydrogen, and the supply of raw material silicon tetrachloride. It is obtained by doing.

  The content of either or both of the wet method silica and the dry method silica is 70% by mass or more in terms of dry mass among all the pigments in the ink receiving layer. More preferably, it is 80% by mass or more, and particularly preferably 90% by mass. If it is less than 70% by mass, ink absorbability is poor when ink jet printing is performed, and good image sharpness cannot be obtained.

  Also, one or more known white pigments can be used in combination as long as the ink absorbability and color developability are not impaired when ink jet recording is performed. Known white pigments include, for example, kaolin, talc, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, titanium dioxide, zinc oxide, zinc sulfate, zinc carbonate, calcium silicate, aluminum silicate, magnesium silicate, diatomaceous earth, aluminum hydroxide. White inorganic pigments such as magnesium hydroxide, satin white, colloidal silica, and alumina, and organic pigments such as acrylic, styrene, ethylene, vinyl chloride, and nylon.

  Examples of the binder used in the ink receiving layer include polyvinyl alcohol, polyvinyl acetal, oxidized starch, etherified starch, carboxymethyl cellulose, hydroxyethyl cellulose, casein, gelatin, soybean protein, polyethylene imide resin, polyvinyl pyrohydrin resin, poly Acrylic acid or its copolymer, maleic anhydride copolymer, acrylamide resin, acrylate ester resin, polyamide resin, polyurethane resin, polyester resin, polyvinyl butyral resin, alkyd resin, epoxy resin, epichlorohydrin Resin, urea resin, melamine resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, acrylic acid ester, methacrylic acid ester polymer or copolymer, etc. Acrylic polymer latexes, ethylene - resins of the vinyl polymer latexes such as vinyl acetate copolymers are exemplified, can be used alone or in combination. The amount of the binder used is determined in consideration of the printability of the ink jet recording medium, the strength of the ink receiving layer, and the paint liquid property. Usually, it is added in the range of 1 to 200 parts by mass with respect to 100 parts by mass of the total pigment dry mass in the ink receiving layer. Preferably, it is added in the range of about 5 to 100 parts by mass. If it is less than 1 part by mass, the coating layer strength may decrease. If it exceeds 200 parts by mass, the ink absorbability may decrease.

  It is preferable to add a cationic polymer to the ink receiving layer in addition to the pigment and the binder. The cationic polymer reacts with an anionic component in the dye used in the ink to form a salt that is insoluble in water, so that the ink is more firmly fixed on the ink receiving layer, resulting in water resistance. There is an effect to improve. Such cationic polymers include polyethyleneimine, epichlorohydrin-modified polyalkylamine, polyamine, polyamine polyamide epichlorohydrin, dimethylamine ammonia epichlorohydrin, polyvinylbenzyltrimethylammonium halide, polydiacryldimethylammonium halide, polydimethylaminoethyl methacrylate hydrochloride, polyvinyl Pyridium halide, cationic polyacrylamide, cationic polystyrene copolymer, diallyldimethylammonium chloride polymer, diallyldimethylammonium chloride sulfur dioxide copolymer, diallyldimethylammonium chloride amide copolymer, dicyandiamide formalin polycondensate, dicyandiamide diethylenetriamine Polycondensate Polyallylamine, polyallylamine hydrochloride, polyacrylamide resin, polyamide epoxy resin, melamine resin acid colloid, urea resin, cation-modified polyvinyl alcohol, amino acid type amphoteric surfactant, betaine type compound, and other quaternary ammonium salts It can be illustrated. The addition amount is not particularly limited, but it is preferably used in the range of 1 to 50 parts by mass on a dry basis with respect to 100 parts by mass of the total pigment in the ink receiving layer. Preferably, it adds in the range of about 5-40 mass parts. If it is less than 1 part by mass, the water resistance of the printed part may be lowered. If it exceeds 50 parts by mass, the ink absorbability may be inferior.

  In the ink-receiving layer, as an auxiliary agent, an antifoaming agent, a lubricant, a dispersant, a wetting agent, a fluorescent whitening agent, a coloring dye, a coloring pigment, a thickening agent, a preservative, and a water-resistant agent UV absorbers, antioxidants and the like can be added.

The ink receiving layer is prepared by blending various components contained in the ink receiving layer such as the pigments, binders, additives, etc., applying the ink receiving layer working solution adjusted to an appropriate solid content concentration, and drying. Can be provided. The coating method of the coating liquid for forming the ink receiving layer is not limited in the present embodiment, and a known coating machine such as an air knife, a roll coater, a bar coater, a comma coater, or a blade coater can be used. The coating amount is preferably ² to 11 g / m ² . More preferably from 3 to 10 g / ^{m 2,} particularly preferably 5~8g / ^{m 2.} If it is less than 2 g / m ² , the ink absorptivity may be inferior, and if it exceeds 11 g / m ² , the amount of paper dust generated at the time of paper small judgment may increase. Further, it is disadvantageous in terms of cost. When the coating amount of the glossy layer is the lower limit of 2 g / m ² , the ink receiving layer coating liquid is preferably 1.8 g / m ² or more and less than 2.0 g / m ² . Further, the ink receiving layer can be provided with the ink receiving layer coating liquid by one-step coating, two-step coating, or three-step coating or more. In the case of two-stage coating or more, the formulation of the first-stage and second-stage coating liquids may be different for the purpose of imparting various functionalities.

  The ink receiving layer is easily plastically deformed because of the large gap. Therefore, it is necessary to increase the coating amount of the glossy layer having a high surface hardness. From the diligent study of the present inventors, the ratio in terms of solid content represented by (coating amount of the glossy layer) / (coating amount of the ink receiving layer) exceeds 1.0, and scratch resistance It was found that sex could be maintained at a practical level. The ratio in terms of solid content represented by (the coating amount of the glossy layer) / (the coating amount of the ink receiving layer) is more preferably 1.1 or more, and particularly preferably 1.2. When the ratio in terms of solid content expressed by (coating amount of the glossy layer) / (coating amount of the ink receiving layer) is 1.0 or less, the lower layer when an impact is applied to the glossy layer is formed. The effect of plastic deformation of the provided ink receiving layer is increased, resulting in poor scratch resistance. However, the upper limit of the ratio is preferably 4.0 from the point of cutting paper powder.

  Examples of the drying method after coating include hot air drying, infrared drying, and drum drying, but are not particularly limited in the present embodiment.

  In addition, for the purpose of controlling the smoothness of the surface of the ink receiving layer, a calendar process may be performed as necessary. Examples of the calendar include a super calendar, a machine calendar, and a soft calendar, but are not particularly limited in the present embodiment.

  In the glossy paper for ink-jet recording according to this embodiment, since the glossy expression layer is formed by a casting process, it is preferable that the glossy paper has air permeability as a whole. The air resistance of the base paper for forming the glossy layer after forming the ink receiving layer (measured according to JIS P 8117: 1998 “Paper and paperboard—Air permeability and air resistance test method (intermediate region) —Gurley method”) Is preferably 5 to 200 seconds. More preferably, it is 10 to 150 seconds.

  In the glossy paper for ink jet recording according to the present embodiment, the ink receiving layer and the gloss developing layer are provided on at least one side of the substrate. A glossy paper for single-sided printing may be provided by providing the ink receiving layer and the glossy expression layer only on one side of the substrate, or a glossy paper for double-sided printing by providing on both sides. Also, when used as a postcard for ink jet recording, only one side is a glossy surface provided with an ink receiving layer and a glossy expression layer, and the other side is a non-glossy surface, so that the glossy surface is a communication surface. One surface is preferably a non-glossy surface having offset printing suitability and writing property.

  As a base material used in the present invention, a paper base material such as normal high-quality paper, medium-quality paper, and white paperboard is used. Examples of the pulp used for the base paper of the paper base include hardwood bleached sulfite pulp (LBSP), hardwood bleached kraft pulp (LBKP), softwood bleached sulfite pulp (NBSP), softwood bleached kraft pulp (NBKP), deinked pulp, etc. Of wood pulp is advantageously used. Moreover, you may use a non-wood pulp, a synthetic pulp, or a synthetic fiber other than a wood pulp as needed. Considering the case of being recycled as fuel, it is desirable to use ECF (Elemental Chlorine Free) pulp or TCF (Totally Chlorine Free) pulp having a low chlorine content as raw material pulp.

  The pulp is a pulp slurry having an appropriate beating degree. The pulp beating degree of each layer is not limited in this embodiment, but is 350 to 600 ml CSF at Canadian standard freeness (freeness) (JIS P 8121: 1995 “Pulp Freeness Test Method”). It is preferable that More preferably, it is 400 to 580 ml CSF. If it is less than 350 ml CSF, since the fiber-to-fiber bond of the pulp becomes strong, the porosity decreases, and there is a tendency that the air resistance increases and the ink absorbability decreases. If it exceeds 600 ml CSF, the strength of the substrate will be reduced, and paper dust will be easily generated during guillotine cutting.

  The pulp slurry preferably contains a filler. The type of filler is not particularly limited in the present embodiment, but known fillers such as hydrated silicic acid, white carbon, talc, kaolin, clay, calcium carbonate, titanium oxide, aluminosilicate, calcined clay, and synthetic resin filler are used in combination. can do. From the viewpoint of opacity and paper strength, the content of the filler in the paper substrate is preferably 1 to 15% by mass in terms of dry mass. More preferably, it is 2-12 mass%. When the filler content is less than 1% by mass, desired opacity may not be obtained. If the filler content exceeds 15% by mass, paper strength may be insufficient, and paper dust and fluffing during cutting may increase.

  Further, the pulp slurry preferably contains a paper strength enhancer. The paper strength enhancer is not particularly limited in the present embodiment, but a known paper strength enhancer such as cationized starch, amphoteric starch, grafted starch, polyacrylamide, polyamide polyamine-epichlorohydrin resin, melamine resin, urea formaldehyde resin or the like is used. Can be used together. The content of the paper strength enhancer in the paper substrate is preferably 0.1 to 2.5% by mass in terms of dry mass. More preferably, it is 0.2-2.0 mass%.

  Various additives such as a dispersant, a sizing agent, and a fixing agent can be added to the pulp slurry as necessary to the extent that the effects of the present invention are not impaired. Furthermore, if necessary, it is possible to add a pH adjusting agent, a dye, a colored pigment or a fluorescent brightening agent.

  The pulp slurry prepared by beating to a predetermined freeness is made into a single layer or multiple layers using a known paper machine such as a long net paper machine, a twin wire paper machine, or a circular net paper machine.

  In order to suppress excessive penetration of the coating solution at the time of cast coating, it is preferable to apply a sizing solution containing a water-soluble polymer such as starch or polyvinyl alcohol to one side or both sides of the paper web. The size liquid can be applied with a known coating machine such as a tab size, a size press, a gate roll coater, or a film transfer coater to form a paper substrate. They can be applied on-machine or off-machine.

Although the thickness of a paper base material is not specifically limited in this embodiment, It is preferable that it is 100-360 micrometers. More preferably, it is 120-340 micrometers. Moreover, it is preferable that a basic weight is 100-300 g / m < ² >, More preferably, it is 120-280 g / m < ² >.

  Although the ink receiving layer may be directly provided on the paper base material thus manufactured, in this embodiment, for the purpose of smoothing the surface of the paper base material, a process such as a machine calendar, a soft calendar, or a raster is performed in advance. It is preferable to apply.

  Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the examples, “parts” and “%” represent “parts by mass” and “mass%”, respectively, unless otherwise specified.

Example 1
(Formation of paper substrate)
To 100.0 parts of LBKP beaten to a Canadian standard freeness of 500 ml CSF, 5.0 parts of talc (T-light 83, manufactured by Taihei Talc Co., Ltd.) was added as an internal filler. Further, 3.0 parts of a sulfuric acid band, 0.25 parts of a rosin sizing agent (AL-120, manufactured by Seiko PMC), and 1.0 part of a cationized starch (Mermaid C-50, manufactured by Shikishima Starch) are added. A pulp slurry was prepared. The pulp slurry was made using a long paper machine to obtain a paper web. Then, oxidized starch (MS # 3800, manufactured by Nippon Food Processing Co., Ltd.) as a sizing solution was applied to both sides of the paper substrate with a size press so that the dry coating amount was 1.5 g / m ² per side, and a cylinder dryer was used. Dried. Thereafter, surface treatment was performed using a steel calender under the conditions of a linear pressure of 40 kg / cm, 25 ° C., and 2 nips and 1 pass, and high-quality paper having a basis weight of 180 g / m ² was used as a paper substrate.

(Formation of ink receiving layer)
On one side of the obtained paper base material, 80.0 parts of synthetic silica (SYLOJET P409, wet method silica, manufactured by Grace Devison) as a pigment, and aluminum hydroxide (Hydelite H-42M, manufactured by Showa Denko) 20. 0 part, 10.0 parts of polyvinyl alcohol (PVA117, manufactured by Kuraray Co., Ltd.), 30.0 parts of ethylene-vinyl acetate (Polysol EVA AD-10, Showa Kogyo Co., Ltd.), and a cationic polymer ( The ink-receiving layer coating solution was prepared by blending 10.0 parts of Papiogen P-105 (Senka) and adjusting the solid content concentration to 22% with industrial water. Subsequently, the ink receiving layer was formed by coating and drying with an air knife coater so that the dry coating amount was 9 g / m ² . The air permeability resistance (JIS P 8117: 1998) of the base paper for forming the glossy layer after forming the ink receiving layer was 70 seconds.

(Formation of glossy layer)
90.0 parts of spherical colloidal silica (SYLOJET 4000C, cationic, average primary particle size 30 to 40 nm, manufactured by Grace Devison Co.) as a pigment, 10.0 parts of dry process silica (Leosil QS-30, manufactured by Tokuyama Corporation), As a binder, 4.0 parts of styrene-acrylic resin emulsion (Movinyl 880, manufactured by Nichigo Mobile Vinyl), 10.0 parts of polyvinyl alcohol (PVA-235, manufactured by Kuraray Co., Ltd.), and a cationic polymer (Smileze Resin 1001, Sumitomo Chemical Co., Ltd. (10.0 parts) and polyethylene emulsion (SN Coat 287, San Nopco Co., Ltd.) 1.0 parts as a release agent were blended, and a glossy expression layer adjusted to a solid content concentration of 20% with industrial water. A coating solution was obtained. This coating solution is applied onto the ink receiving layer of the base paper so that the dry coating amount is 10 g / m ² on the ink receiving layer with an air knife coater, and then sodium borate as a coagulant. 1% and aqueous coagulation solution containing 1% boric acid (coagulating solution concentration 2%) applied to the absolute dry coating amount 1.0 g / m ² and comprising as the glossy layer coating liquid coated surface on After the coagulation treatment was performed, while the surface of the obtained coating layer was in a wet state, it was pressure-bonded to a cast drum having a surface temperature of 105 ° C. to produce glossy paper for ink jet recording.

(Example 2)
Glossy paper for ink-jet recording of Example 2 according to Example 1, except that the pigment used in the coating liquid for glossy layer in Example 1 is 100 parts of spherical colloidal silica (SYLOJET 4000C, manufactured by Grace Devison). Was made.

(Example 3)
In Example 1, the gloss developing layer coating solution was prepared by using 100 parts of spherical colloidal silica (cataloid SI-80P, anionic, average primary particle diameter 78 nm, manufactured by Catalyst Kasei Kogyo Co., Ltd.) as a pigment, and polyvinyl alcohol (as a binder). 10.0 parts of PVA-235 (manufactured by Kuraray Co., Ltd.) and 1.0 part of polyethylene emulsion (SN coat 287, made by San Nopco Co., Ltd.) as a release agent are blended, and the solid content concentration is 17% with industrial water. Example according to Example 1 except that the coagulation liquid was an aqueous solution containing 1% sodium borate as a coagulant, 1% boric acid and 2% cationic polymer (Smileze Resin 1001, manufactured by Sumitomo Chemical Co., Ltd.). No. 3 glossy paper for ink-jet recording was prepared.

Example 4
In Example 1, the pigment used in the coating liquid for the glossy layer was pearl necklace-like colloidal silica (Snowtex PS-MO, cationic, average primary particle size 18 to 25 nm, average secondary particle size 80 to 150 nm, Nissan Chemical Co., Ltd. A glossy paper for ink-jet recording of Example 4 was produced in the same manner as in Example 1 except that the amount was 100 parts.

(Example 5)
In Example 1, the binder used in the glossy layer coating solution was 10.0 parts of silanol-modified polyvinyl alcohol (PVA-R1130, manufactured by Kuraray Co., Ltd.). A glossy paper for ink jet recording was prepared.

( Reference Example 6)
Inkjet recording of Reference Example 6 according to Example 1 except that the pigment used in the ink receiving layer coating liquid in Example 1 was 100 parts of synthetic silica (SYLOJET P409, wet method silica, manufactured by Grace Devison). Glossy paper was prepared.

( Reference Example 7)
Ink jet of Reference Example 7 according to Example 1 except that the pigment used in the ink receiving layer coating liquid in Example 1 was 100 parts of synthetic silica (Leosil QS-30, dry silica, manufactured by Tokuyama Corporation). A glossy recording paper was prepared.

(Example 8)
In Example 1, the absolute dry coating amount of the glossy layer was 6 g / m ² and the absolute dry coating amount of the ink receiving layer was 4 g / m ² . A glossy paper for ink jet recording was prepared.

Example 9
In Example 1, the absolute dry coating amount of the glossy layer was 11 g / m ² and the absolute dry coating amount of the ink receiving layer was 9 g / m ² . A glossy paper for ink jet recording was prepared.

(Example 10)
In Example 1, the pigment used in the coating liquid for glossy layer is composed of 80.0 parts of spherical colloidal silica (SYLOJET 4000C, manufactured by Grace Devison) and 20.0 dry method silica (Leosil QS-30, manufactured by Tokuyama). A glossy paper for ink-jet recording of Example 10 was produced in the same manner as in Example 1 except that the parts were used.

(Example 11)
In Example 1, the pigment used in the ink-receiving layer coating solution was 70.0 parts of synthetic silica (SYLOJET P409, wet silica, manufactured by Grace Devison) and aluminum hydroxide (Hijilite H-42M, Showa Denko). (Product made) Except that it was 30.0 parts, the glossy paper for inkjet recording of Example 11 was produced according to Example 1.

(Example 12)
In Example 1, the pigments used in the ink receiving layer coating solution were 70.0 parts of synthetic silica (Leosil QS-30, dry silica, manufactured by Tokuyama Corporation) and aluminum hydroxide (Hijilite H-42M, Showa Denko). A glossy paper for ink-jet recording of Example 12 was produced according to Example 1 except that the amount was 30.0 parts.

(Comparative Example 1)
In Example 1, the pigment used in the coating liquid for the glossy layer is 70.0 parts of spherical colloidal silica (SYLOJET 4000C, manufactured by Grace Devison) and 30.0 dry silica (Reorosil QS-30: manufactured by Tokuyama). A glossy paper for ink-jet recording of Comparative Example 1 was produced in the same manner as in Example 1 except that the parts were used.

(Comparative Example 2)
In Example 1, 50.0 parts of synthetic silica (SYLOJET P409, manufactured by Grace Devison) and aluminum hydroxide (Hydelite H-42M, manufactured by Showa Denko) were used as pigments used in the ink receiving layer coating solution. A glossy paper for inkjet recording of Comparative Example 2 was produced in the same manner as in Example 1 except that the content was 0 part.

(Comparative Example 3)
Ink jet of Comparative Example 3 according to Example 1 except that the dry coating amount of the glossy layer in Example 1 was 20 g / m ² and the dry coating amount of the ink receiving layer was 10 g / m ^2. A glossy recording paper was prepared.

(Comparative Example 4)
Ink jet of Comparative Example 4 according to Example 1 except that the dry coating amount of the glossy layer in Example 1 was 7 g / m ² and the dry coating amount of the ink receiving layer was 10 g / m ^2. A glossy recording paper was prepared.

(Comparative Example 5)
Inkjet of Comparative Example 5 according to Example 1 except that the absolute dry coating amount of the gloss developing layer was 12 g / m ² and the absolute dry coating amount of the ink receiving layer was 9 g / m ² in Example 1. A glossy recording paper was prepared.

  The obtained glossy paper for ink-jet recording was subjected to the following test, and the results are shown in Table 1.

(1) Dynamic hardness of the glossy layer surface (dynamic hardness (when loaded) and (when unloaded))
The dynamic hardness of the glossy layer surface of the resulting glossy paper for inkjet recording was measured. The dynamic hardness was measured under the following conditions using an ultra-micro hardness meter (DUH-201, manufactured by Shimadzu Corporation). The dynamic hardness was determined from the indentation depth during loading or unloading according to the following calculation formula.
Working indenter: Triangular pyramid diamond indenter (angle between ridges 115 degrees, indenter shape factor: 3.8484)
Test force: 1.00mN
Loading speed: 1.42 mN / second Calculation of dynamic hardness: DH = α × P ÷ D ² (DH: dynamic hardness, P: test force (mN), D: indentation depth of indenter onto sample surface (μm), α: Indenter shape factor)

(2) The image clarity (image clarity) of the glossy layer surface
The image clarity was measured in order to evaluate the specularity of the glossy layer surface of the resulting glossy paper for ink jet recording. The image clarity was measured with an image clarity measuring instrument (ICM-1T, manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS H 8686-2 with an optical comb width of 2 mm and an incident / reflection angle of 60 °. The evaluation is as follows.
Image clarity is 50% or more: The reflected image is clearly visible, excellent in gloss, and practical.
Less than 50%: Reflected image is unclear, inferior in glossiness, and has a practical problem as glossy paper.

(3) Image sharpness An ISO standard image (ISO / JIS-SCID high-definition color digital standard image data, image name: portrait, image identification number: N1) is an Seiko Epson inkjet printer “PM-900C”. Used and printed on the glossy paper for ink-jet recording obtained. The printed image was visually evaluated.
(Double-circle): The recorded image is very clear and contrast is clear, and it can be used practically.
○: The recorded image is clear and the contrast is clear, and can be used practically.
(Triangle | delta): The recorded image is clear, but contrast is not clear, the color is sinking, and there exists a problem in practical use.
X: The recorded image is unclear and the color is sinking, impractical.

(4) Ink Absorbency Glossary for inkjet recording using Seiko Epson inkjet printer “PM-900C” to obtain CMYK ink, RGB (Red-Green-Blue) solid (100% density) and characters Printed on paper. The boundary of each color of the solid part and the degree of blurring of the characters were evaluated visually.
(Double-circle): A boundary is clear, there is no blur, a character is clear, and it can be used practically.
○: The blur of the boundary is not conspicuous, the characters are clear, and can be used practically.
(Triangle | delta): The blur of a boundary is conspicuous, a character is unclear, and there exists a problem practically.
X: The blurring of the boundary is severe, and the characters cannot be distinguished, so that it is not practical.

(5) Scratch resistance of gloss-expressing layer surface 20 sheets of the obtained glossy paper for ink-jet recording (Chrysanthemum (636 mm x 939 mm)) are set on an offset printing machine (LITHRON 40, manufactured by KOMORI) at high speed that easily causes scratches. The degree of scratches on the surface of the glossy layer that occurred when printing on the back side was performed at a printing speed (8500 sheets / hour) was visually evaluated.
(Double-circle): There is no scratch and it is favorable and can be used practically.
○: Scratches are slightly recognized but are not noticeable and can be used practically.
Δ: Scratches are clearly recognized, and there is a problem in practical use.
X: Scratches are remarkably recognized and impractical.

(6) Amount of paper dust generated during cutting (Amount of paper dust generated)
Twenty sheets of glossy paper for inkjet recording (A4 size) obtained were stacked and cut with a cutter (Electric cutting machine No. 709, manufactured by Lion Corporation), and the amount of generated paper dust was visually evaluated.
A: Paper dust hardly occurs and can be used practically.
○: Paper dust is generated a little, but it is practical.
Δ: Paper dust is generated, which is problematic in practical use.
×: A large amount of paper dust is generated, impractical.

(7) Surface pH of gloss developing layer
Using a pH meter for paper quality inspection (MPC, manufactured by Kyoritsu Riken Corporation), the surface pH of the glossy layer surface of the obtained glossy paper for ink jet recording was measured.

As can be seen from Table 1, in Examples 1 to 12, the ink-receiving layer was such that 70% by mass or more of the pigment was wet method silica and / or dry method silica, and the gloss developing layer was a pigment. 80% by mass or more is colloidal silica, contains polyvinyl alcohol as the binder, and the coating amount of the glossy layer is ² to 11 g / m ² in terms of solid content (the gloss The ratio in terms of solid content expressed by the expression layer coating amount) / (coating amount of the ink receiving layer) exceeds 1, and both are excellent in printing performance and glossiness, and also generate paper dust. The glossy layer was excellent in scratch resistance on the surface of the glossy layer, and was at a practical level as a glossy paper for ink jet recording.

  Further, in all of Examples 1 to 8, a triangular pyramid diamond indenter (inter-edge angle 115 degrees, indenter shape factor 3.8854) was used under the measurement conditions of a test force of 1.0 mN and a load speed of 1.42 mN / sec. The dynamic hardness of the surface of the glossy layer as measured by an ultra micro hardness meter was 5.0 or more when loaded and 20.0 or more when unloaded. These were more suitable for practical use.

In Example 9, the coating layer of the gloss developing layer was 11 g / m ² , and although the effect of image sharpness, ink absorbability and scratch resistance were excellent, the amount of paper dust was compared with Examples 1-8. However, it was a practically lower limit level. In Example 10, the content of colloidal silica in the pigment of the glossy layer was 80% by mass, and the scratch resistance was at the practical lower limit level. In Example 11, among the pigments in the ink receiving layer, the wet process silica was 70% by mass, and the ink absorbency was at the practical lower limit level. In Example 12, among the pigments in the ink receiving layer, the dry method silica was 70% by mass, and the ink absorbency was at the practical lower limit level.

  Comparative Example 1 was inferior in the scratch resistance of the glossy surface because the colloidal silica content was too small as a pigment used in the glossy layer. Comparative Example 2 was inferior in ink absorbency because the amount of wet process silica was too small as a pigment used in the ink receiving layer. In Comparative Examples 3 and 5, since the coating amount of the glossy layer was too large, the amount of paper dust was at a level that was problematic in practice. In Comparative Example 4, since the amount of the ink receiving layer applied was larger than that of the glossy layer, the scratch resistance was at a practically problematic level.

Claims (5)

One or more ink-receiving layers containing a pigment are provided on at least one side of the substrate, and a glossy expression layer containing the pigment and a binder is provided on the outermost layer of the ink-receiving layer by a cast coating method. In glossy paper for inkjet recording,
The ink receiving layer contains only wet process silica and / or dry process silica as a pigment and aluminum hydroxide, and 70% by mass or more of the total pigment in the ink receiving layer is wet process silica and dry process silica. And / or any one of the methods silica
The gloss developing layer is 80% by mass or more of the pigment is colloidal silica, and contains polyvinyl alcohol as the binder.
The coating amount of the gloss developing layer is ² to 11 g / m ² in terms of solid content,
A glossy paper for ink jet recording, wherein a ratio in terms of solid content expressed by (coating amount of the glossy layer) / (coating amount of the ink receiving layer) exceeds 1. The dynamic hardness test condition shown below is characterized in that the gloss dynamic layer has an on-load dynamic hardness of 5.0 or more and an unloading dynamic hardness of 20.0 or more by an ultra-micro hardness tester. Item 2. The glossy paper for ink jet recording according to Item 1.
(Dynamic hardness test conditions)
Indenter: Triangular pyramid diamond indenter (edge angle 115 degrees, indenter shape factor 3.8854)
Test load: 1.0mN
Load speed: 1.42 mN / sec   According to JIS H 8686-2: 1999 "Image clarity test method of anodized film of aluminum and aluminum alloy-Part 2: Instrument measurement method" The glossy paper for ink jet recording according to claim 1, wherein the image clarity is 50% or more.   The glossy paper for ink-jet recording according to any one of claims 1 to 3, wherein the cast coating method for forming the glossy expression layer is a coagulation method and contains a boron compound as a coagulant. .   The glossy paper for ink-jet recording according to any one of claims 1 to 4, wherein the glossy layer has a surface pH of 6.4 or less.