JP2016064575A - Recording medium and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording medium which has a texture of silver halide baryta paper, a small gloss difference, excellent ink absorbency and high color developability.SOLUTION: There is provided a recording medium which comprises a support, a first layer, a second layer and a third layer in this order, in which the first layer contains first inorganic particles, the second layer contains at least one type of second inorganic particles selected from alumina hydrate and silica and a binder, the third layer is obtained by applying a coating liquid for the third layer containing core-shell type polymer particles A having an average particle diameter of 20 to 95 nm and a glass transition point of 60°C or less and polymer particles B having an average particle diameter of 95 nm or more and a glass transition point of 60°C or less on the second layer, the oil absorption of the first inorganic particles is 100 mL/100 g or less, the arithmetic average roughness Ra of the surface is 0.50 to 0.80 μm and the 60-degree specular glossiness of the surface is 60% to 80%.SELECTED DRAWING: None

Description

  The present invention relates to a recording medium and a manufacturing method thereof.

  2. Description of the Related Art In recent years, as an ink jet recording method, a method of recording images, characters, and the like by causing ink droplets to fly by various operating principles and attaching them to a recording medium such as paper has been widely used. The recording apparatus used in this method has features such as high speed, low noise, easy multi-coloring, great flexibility in recording patterns, and no need for development and fixing. For this reason, the recording device is rapidly spreading as various image recording devices in various applications including information equipment. Furthermore, an image formed by the multicolor ink jet recording method is not inferior to the multicolor printing by the plate making method or the printing by the color photographic method. For this reason, an image formed by the ink jet recording method is cheaper than multicolor printing or printing when the number of produced copies is small, and is widely applied to the field of full color image recording.

  On the other hand, further high speed and high image quality are widely demanded in the ink jet recording system, and an ink jet recording medium as a final output product has been studied. In addition, since silver salt baryta paper with high gloss and appropriate roughness is used for photographs, the surface quality of the inkjet recording medium that affects the image quality is not limited to the glossy surface or matte surface. Barita-like surface quality is required. In order to obtain an inkjet recording medium having a silver salt baryta-like surface quality, it has a high glossiness and an appropriate roughness, is excellent in printability of dye ink, and has a printing portion and a blank paper generated when pigment ink is printed. It is necessary to eliminate the gloss difference from the part.

  In Patent Document 1, an ink jet recording material having a surface layer composed of organic fine particles, or organic fine particles and inorganic fine particles, and having an arithmetic average roughness of the surface is specified. It is disclosed that printability is exhibited and gloss difference can be eliminated.

JP 2008-126550 A

  The present inventors examined the surface properties of the silver salt baryta paper in detail, and the silver salt baryta paper was measured with a standard length of 2.5 mm and a cut-off value of 0.8 mm as defined in JIS-B-0601. It was found that the arithmetic average roughness Ra of the surface was in the range of 0.50 μm or more and 0.80 μm or less, and the 60 degree specular gloss specified by JIS-Z-8741 was 60% or more and 80% or less. .

  However, in the ink jet recording material described in Patent Document 1, the surface properties of silver salt baryta paper having a 60 ° specular gloss of 60% or more in the range where the arithmetic average roughness Ra of the recording surface is 0.50 μm or more. Cannot be achieved. Thus, high glossiness could not be achieved at the same time in the inkjet recording medium having rough surface properties.

  An object of the present invention is to provide a recording medium having a texture of silver salt baryta paper, having a small gloss difference, excellent ink absorbability, and high color developability.

The recording medium according to the present invention is a recording medium having a support, a first layer, a second layer, and a third layer in this order,
The first layer contains first inorganic particles,
The second layer contains at least one second inorganic particle selected from alumina hydrate and silica, and a binder,
The third layer has core-shell polymer particles A having an average particle size of 20 nm or more and 95 nm or less and a glass transition point higher than 60 ° C., and a polymer having an average particle size of more than 95 nm and a glass transition point of 60 ° C. or less. Obtained by coating the second layer with the third layer coating solution containing the particles B,
The amount of oil absorption based on the measurement method defined in JIS-K-5101 of the first inorganic particles is 100 mL / 100 g or less,
Arithmetic average roughness Ra (cutoff value 0.8 mm) based on the measurement method defined in JIS-B-0601 on the surface of the recording medium on which the third layer is disposed is 0.50 μm or more and 0.80 μm And
60 degree specular glossiness based on the measuring method defined by JIS-Z-8741 on the surface of the recording medium on which the third layer is disposed is 60% or more and 80% or less.

  The method for producing a recording medium according to the present invention applies a third-layer coating solution containing a core-shell type emulsion containing the core-shell type polymer particles A and a resin emulsion containing the polymer particles B, followed by drying. And a step of forming the third layer.

  According to the present invention, it is possible to provide a recording medium having the texture of silver salt baryta paper, having a small gloss difference, excellent ink absorbability, and high color developability.

  The recording medium according to the present invention has a support, a first layer, a second layer, and a third layer in this order. The first layer contains first inorganic particles. The second layer contains at least one second inorganic particle selected from alumina hydrate and silica, and a binder. The third layer has core-shell polymer particles A having an average particle size of 20 nm or more and 95 nm or less and a glass transition point higher than 60 ° C., and a polymer having an average particle size of more than 95 nm and a glass transition point of 60 ° C. or less. It is obtained by coating the second layer with a third layer coating liquid containing particles B. The oil absorption amount of the first inorganic particles based on the measurement method defined in JIS-K-5101 is 100 mL / 100 g or less. The arithmetic average roughness Ra (cut-off value 0.8 mm) based on the measurement method defined in JIS-B-0601 on the surface of the recording medium on the side where the third layer is disposed is 0.50 μm or more and 0.80 μm. It is as follows. The 60-degree specular glossiness based on the measurement method defined by JIS-Z-8741 on the surface of the recording medium on which the third layer is disposed is 60% or more and 80% or less.

  As a result of investigations by the present inventors, in the conventional method, in order to achieve a 60 ° specular glossiness of 60% or more in the range where the arithmetic average roughness Ra of the recording surface is 0.50 μm or more, the recording surface is used. It needed to be thicker. However, in this case, it has been found that problems such as a decrease in ink absorbability (also referred to as absorbability) occur. In order to achieve both high gloss and high absorbency in the region where the arithmetic average roughness Ra of the recording surface is high, the present inventors have studied in detail the organic resin material. As a result, the core-shell type polymer particle A having a high glass transition point (also indicated as Tg) and a small average particle size (also indicated as particle size) according to the present invention, and the polymer particle B having a low Tg and large particle size according to the present invention It was found that by using together, high absorptivity was maintained while high gloss was obtained.

  Although it is not clear why the core-shell type polymer particle A having a high Tg and a small particle size and the polymer particle B having a low Tg and a large particle size can achieve both high gloss and high absorbency. The present inventors consider as follows. For example, when a core-shell type emulsion containing core-shell type polymer particles A having a high Tg and a small particle size is used alone as a raw material, the core-shell type emulsion does not form a film and remains on the recording medium as a particle, although it has high absorbency. Sex does not improve. In addition, when a resin emulsion containing polymer particles B with a low Tg and a large particle size is used alone as a raw material, the resin emulsion forms a film, but the polymer particle B has a large particle size, so that the transparency of the film itself is high. Low and high gloss cannot be achieved. Further, in this case, since the film is firmly formed, the absorbency is likely to be lowered. However, when these two materials are used in combination, the core-shell type emulsion that does not form a film is formed into a film so as to be mixed with the resin emulsion, so that high gloss is obtained. Moreover, since it partially remains as a core-shell type polymer particle while being formed into a film, the film does not impair the high absorbability. As described above, the effects of the present invention can be obtained by synergistically effecting the core-shell type polymer particle A having a high Tg and a small particle size and the polymer particle B having a low Tg and a large particle size. The emulsion indicates a state where polymer particles are dispersed in a solvent.

  Moreover, by having the structure which concerns on this invention, the gloss difference of the printing part by a pigment ink and a blank paper part can be reduced. In the prior art, it has been impossible to obtain a recording medium having the texture of silver salt baryta paper and having a small gloss difference between the printed portion and the white paper portion by the pigment ink. In dye inks, the dye is a single molecule and penetrates into the porous ink-receiving layer to form an image, so that a film is not formed on the surface of the recording medium like pigment ink. The difference in gloss is hardly observed. The effect of improving glossiness by the third layer according to the present invention is manifested in the entire print density region, and an image having uniform glossiness can be obtained.

  Hereinafter, the recording medium according to the present invention will be described in detail. The recording medium according to the present invention is a recording medium in which a first layer, a second layer, and a third layer are provided on a support in order from the side closer to the support. The first layer, the second layer, and the third layer may be provided on one side of the support, or may be provided on both sides. The recording medium according to the present invention can be preferably used as an inkjet recording medium.

  The recording medium according to the present invention corresponds to a recording medium referred to as a bariter surface, and is measured when measured with a reference length of 2.5 mm and a cutoff value of 0.8 mm as defined in JIS-B-0601. The arithmetic average roughness Ra of the surface on which the third layer is disposed (also referred to as a recording surface) is 0.50 μm or more and 0.80 μm or less. By satisfying this range, a recording medium having a texture comparable to silver salt baryta paper can be obtained. When Ra is 0.50 μm or more and 0.80 μm or less, the reflected light is diffused so that the difference in glossiness between the print portion and the blank paper portion is difficult to be visually recognized. On the other hand, if Ra exceeds 0.80 μm, the sharpness of the formed image is impaired. Further, when Ra is less than 0.50 μm, it is recognized as a “glossy surface”, and external light is reflected. Ra is preferably 0.50 μm or more and 0.75 μm or less, more preferably 0.55 μm or more and 0.70 μm or less, and further preferably 0.55 μm or more and 0.65 μm or less. Ra is a value measured by a method described later.

  Further, from the viewpoint of obtaining a recording medium having the texture of silver salt baryta paper, the 60 ° specular glossiness based on the measurement method defined in JIS-Z-8741 on the surface on which the third layer of the recording medium is disposed. Is from 60% to 80%, preferably from 62% to 78%, and more preferably from 65% to 75%. The 60 degree specular gloss is a value measured by the method described later.

<Support>
Although it does not specifically limit as a support body which concerns on this invention, For example, the paper support body, resin film, sheet material, etc. which have air permeability can be used. Among these, a paper support is preferable as the support from the viewpoint of air permeability. As the paper support, for example, used for high-quality paper, art paper, coated paper, cast coated paper, kraft paper, Kent paper, baryta paper, board paper, impregnated paper, vapor-deposited paper, and general coated paper. And acidic paper and neutral paper. The paper support can contain wood pulp as a main component. The paper support can also include a filler. Further, the paper support may contain a sizing agent, pigment, paper strength enhancer, fixing agent, fluorescent whitening agent, wet paper strength agent, cationizing agent, and the like as required.

Examples of the wood pulp include chemical pulp, mechanical pulp, and regenerated pulp. Examples of the filler include calcium carbonate, calcined kaolin, silica, and titanium oxide. These may use 1 type and may use 2 or more types together. Among these, as the filler, calcium carbonate is preferable from the viewpoint of obtaining a paper support with high whiteness and increasing the gloss of the recording medium. The content of the filler in the paper support is preferably 1 to 20% by mass. When the content is within the above range, the smoothness, air permeability, paper strength and rigidity can be balanced, so that a recording medium excellent in the balance of glossiness, image clarity and rigidity can be obtained. Although the basic weight of a paper support body is not specifically limited, 20-400 g / m < ² > is preferable and 100-300 g / m < ² > is more preferable.

<First layer>
(First inorganic particles)
The first layer according to the present invention includes first inorganic particles. The oil absorption amount of the first inorganic particles based on the measurement method defined in JIS-K-5101: 1991 is 100 mL / 100 g or less. In the recording medium according to the present invention, by providing the first layer containing the first inorganic particles having an oil absorption of 100 mL / 100 g or less on the support, the first layer absorbs the solvent of the third layer coating liquid. Functions as a delay layer. Although the mechanism is not clear, when the third layer coating solution is applied, the absorption rate is high and the solvent is absorbed in the second layer with a large absorption capacity, but the absorption rate of the first layer is slow, The solvent necessary for film formation of the third layer can be retained on the second layer. Thus, for example, when an emulsion as described later is used as the third layer coating solution, it is presumed that the emulsion is melted and easily formed into a film. When the oil absorption exceeds 100 mL / 100 g, the first layer does not function as a solvent absorption delay layer of the third layer coating solution. That is, the solvent in the coating solution for the third layer easily penetrates to the support, the solvent is not retained on the second layer, and a layer made of particles is obtained as the third layer without being formed into a film.

  The oil absorption amount of the first inorganic particles is preferably 90 mL / 100 g or less, more preferably 80 mL / 100 g or less, and further preferably 70 mL / 100 g or less. Moreover, the lower limit of the oil absorption amount of the first inorganic particles is not particularly limited, but may be, for example, 5 mL / 100 g or more. When two or more kinds of first inorganic particles are used, the oil absorption amount of the first inorganic particles is a value calculated by conversion based on the blending ratio of each first inorganic particle. Therefore, when two or more types of first inorganic particles are used, even if the oil absorption amount of one kind of first inorganic particles is 100 mL / 100 g or less, the oil absorption amount as a whole of the first inorganic particles is 100 mL. / 100g or less is not included in the scope of the present invention.

  Examples of the first inorganic particles include kaolin clays, heavy calcium carbonates, light calcium carbonates, inorganic pigments such as titanium oxide, barium sulfate, satin white, and silica, and organic pigments such as plastic pigments. These may use 1 type and may use 2 or more types together. The first layer can contain the first inorganic particles as a main component. For example, the first layer can contain 40 mass% or more and 98 mass% or less of the first inorganic particles.

  The first layer may contain a binder (also referred to as a first binder) and an auxiliary agent in addition to the first inorganic particles.

(First binder)
Examples of the first binder include casein, soybean protein, starch, oxidized starch, esterified starch, etherified starch, cationized starch, enzyme-modified starch and other modified starches, natural adhesives such as cellulose derivatives, and styrene-butadiene series. Synthetic adhesives such as copolymers, conjugated diene polymer latexes such as methyl methacrylate-butadiene copolymers, acrylic polymer latexes such as acrylic acid esters, methacrylic acid ester polymers or copolymers, and polyvinyl alcohol Etc. These may use 1 type and may use 2 or more types together.

  When the first layer contains the first binder, the content of the first binder is not particularly limited as long as it is an amount sufficient for bonding of the first inorganic particles. For example, the first layer can include 10 to 50 parts by mass of the first binder with respect to 100 parts by mass of the first inorganic particles. When the content is 10 parts by mass or more, sufficient surface strength can be obtained. Moreover, when the content is 50 parts by mass or less, the viscosity of the first layer coating liquid is reduced, and the first layer coating liquid is easy to pass through a pipe or a screen, so that operability is improved.

(Auxiliary)
As auxiliary agents, dispersants, antifoaming agents, water retention agents, thickeners, lubricants, wetting agents, mold release agents, water resistance agents, colorants, preservatives, fluorescent whitening agents, antistatic agents, printability An improving agent etc. are mentioned. These may use 1 type and may use 2 or more types together.

(Coating method for first layer coating solution)
The first layer is a coating liquid for the first layer containing the first inorganic particles, for example, blade coater, roll coater, reverse roll coater, air knife coater, die coater, bar coater, gravure coater, curtain coater, champ. It can be formed by single-layer or multi-layer coating by an off-machine coater or an on-machine coater by a coating method such as a flex coater, a lip coater, or a rod coater. From the viewpoint of appropriate coating, the coating method is preferably an air knife coater, a curtain coater, or a rod coater, and more preferably an air knife coater.

The coating amount of the first-layer coating solution is preferably applied so that the coating amount after drying per side is 5 to 20 g / m ² . When the coating amount is 5 g / m ² or more, the coating surface can be sufficiently covered with the first layer coating liquid, and printing unevenness is reduced. Moreover, a coating amount can be reduced because a coating amount is 20 g / m < ² > or less.

  The drying method after coating is not particularly limited, and examples thereof include hot air drying, infrared drying, room temperature drying, and freeze drying. Among these, infrared drying and hot air drying are preferable as drying methods from the viewpoint of drying efficiency.

  Moreover, after the coating of the first layer coating solution, a roughening treatment or a smoothing treatment can be performed using a calendar device such as a super calender, a machine calender, or a soft calender. Here, the arithmetic average roughness Ra of the surface of the first layer is preferably 0.2 μm or more and 3.0 μm or less. When the Ra is 0.2 μm or more, the surface roughness after formation of the second layer and the third layer is moderately rough, and a recording medium having a texture of silver salt baryta paper is easily obtained. Further, when the Ra is 3.0 μm or less, the surface roughness after the formation of the second layer and the third layer is moderately smooth, and a recording medium having a texture of silver salt baryta paper is also easily obtained. . The Ra is more preferably 0.3 μm or more and 2.0 μm or less, further preferably 0.4 μm or more and 1.5 μm or less, and particularly preferably 0.5 μm or more and 1.0 μm or less. The Ra is a value measured by the same method as Ra on the recording surface of the recording medium.

<Second layer>
The second layer according to the present invention includes at least one second inorganic particle selected from alumina hydrate and silica, and a binder (also referred to as a second binder). The second layer can be a porous ink receiving layer. In addition to the second inorganic particles and the second binder, the second layer can contain a crosslinking agent, a pH adjuster, other additives, and the like. Hereinafter, these components will be described in detail.

(Second inorganic particles)
The second layer according to the present invention contains at least one selected from alumina hydrate and silica as the second inorganic particles from the viewpoint of ink absorbability, color developability, and gloss.

  The crystal structure of the alumina hydrate includes amorphous, kibsite, and boehmite types depending on the heat treatment temperature. Among these, alumina hydrates having any crystal structure can be used, but alumina hydrates exhibiting a boehmite structure or amorphous by analysis by an X-ray diffraction method are preferable. Examples of silica include vapor phase method silica and colloidal silica.

  When the second layer has pores, it is preferable that pores having a radius of 25.0 nm or more do not exist in the pores. That is, all the pores in the second layer preferably have a radius of less than 25.0 nm. When the pore radius is less than 25.0 nm, an increase in the haze of the second layer can be suppressed, and particularly good color developability can be obtained. The pore radius is a value obtained by using a BJH (Barrett-Joyner-Halenda) method from an adsorption / desorption isotherm of nitrogen gas measured on a recording medium by a nitrogen adsorption / desorption method.

Moreover, in order to obtain the pore radius at the time of forming the second layer, second inorganic particles having a BET specific surface area measured by a BET method of 100 m ² / g or more and 200 m ² / g or less are used. preferable. In particular, it is more preferable to use an alumina hydrate having a BET specific surface area of 125 m ² / g or more and 175 m ² / g or less.

  The BET method is a method for measuring the surface area of a powder by a vapor phase adsorption method, and is a method for obtaining the total surface area, that is, the specific surface area of a 1 g sample from an adsorption isotherm. In this BET method, nitrogen gas is usually used as the adsorbed gas, and the most frequently used method is to measure the amount of adsorption from the change in pressure or volume of the gas to be adsorbed. At this time, the most prominent expression representing the isotherm of multimolecular adsorption is the Brunauer, Emmett, and Teller equation, which is called the BET equation and is widely used for determining the specific surface area. In the BET method, the specific surface area is obtained by calculating the amount of adsorption based on the BET formula and multiplying the area occupied by one adsorbed molecule on the surface. In the BET method, in the nitrogen adsorption / desorption method, the relationship between the adsorption amounts at a certain relative pressure is measured at several points, and the specific surface area is derived by obtaining the slope and intercept of the plot by the least square method.

  Although the quantity of the 2nd inorganic particle contained in a 2nd layer is not specifically limited, For example, it is 50 to 98 mass%.

(Second binder)
The second layer according to the present invention contains a second binder from the viewpoint of binding the second inorganic particles and forming a film. Any binder can be used without particular limitation as long as it is a material capable of binding the second inorganic particles and forming a film and does not impair the effects of the present invention. However, from the viewpoint of coating suitability, the second binder is preferably a water-soluble binder.

  As the second binder, polyvinyl alcohol (PVA), oxidized starch, etherified starch, phosphate esterified starch, carboxymethylcellulose, hydroxyethylcellulose, casein, gelatin, soybean protein, polyvinylpyrrolidone, maleic anhydride resin, styrene-butadiene Copolymers, conjugated polymer latexes such as methyl methacrylate-butadiene copolymer, acrylic polymer latexes such as acrylic acid ester and methacrylic acid ester polymers, and vinyl polymer latexes such as ethylene-vinyl acetate copolymer , Melamine resin, urea resin, acrylic acid ester such as polymethyl methacrylate, methacrylic acid ester polymer or copolymer resin, polyurethane resin, unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer, poly Butyral, alkyd resins.

  Said 2nd binder can be used individually or in mixture of multiple types. Among these, as the second binder, polyvinyl alcohol (PVA) is preferable from the viewpoint of ink absorbability. As polyvinyl alcohol, for example, polyvinyl alcohol synthesized by hydrolyzing polyvinyl acetate can be used. The average degree of polymerization of polyvinyl alcohol is preferably 1500 or more, and more preferably 2000 or more and 5000 or less. The saponification degree of polyvinyl alcohol is preferably 80 mol% or more and 100 mol% or less, and more preferably 85 mol% or more and 100 mol% or less. In the present invention, the average degree of polymerization is the viscosity average degree of polymerization determined by the method of JIS-K-6726.

  Further, as the second binder, modified polyvinyl alcohols such as polyvinyl alcohol having a cation-modified terminal and an anion-modified polyvinyl alcohol having an anionic group can also be used.

  Although the quantity of the 2nd binder contained in a 2nd layer is not specifically limited, For example, it can be 5.0 mass% or more and 50.0 mass% or less with respect to content of a 2nd inorganic particle.

(Crosslinking agent)
The crosslinking agent is not particularly limited as long as it does not impair the effects of the present invention. However, when polyvinyl alcohol is used as the second binder, a compound capable of curing by causing a crosslinking reaction with polyvinyl alcohol is preferable. As the compound, boric acid is preferable. Examples of boric acid include orthoboric acid (H ₃ BO ₃ ), metaboric acid, and hypoboric acid. Among these, as the boric acid, orthoboric acid is preferable from the viewpoint of the temporal stability of the coating solution for the second layer and the effect of suppressing the occurrence of cracks.

  When polyvinyl alcohol is used as the second binder and boric acid is used as the cross-linking agent, the content of boric acid in the second layer is 0.2 equivalent or more with respect to the polyvinyl alcohol in the second layer. .2 equivalent or less is preferable. In addition, about "equivalent", the quantity of the crosslinking agent which reacts completely with the quantity of the hydroxyl group which polyvinyl alcohol has theoretically shall be 1 equivalent. By making the amount of boric acid used within the above range, the temporal stability of the coating solution for the second layer can be improved. When forming the second layer, the coating solution is used for a long time. By setting the content of boric acid in the coating solution for the second layer within the above range, the coating solution for long-time use is used. It is possible to prevent an increase in the viscosity of the working fluid and generation of gelled products. For this reason, it is not necessary to frequently change the coating liquid or clean the coater head, thereby improving productivity. Furthermore, if the content of boric acid in the coating liquid for the second layer is within the above range, a point-like surface defect is hardly generated in the second layer, and a uniform and good surface can be obtained. The boric acid content in the second layer coating solution is the same as the boric acid content in the second layer.

(PH adjuster)
Examples of the pH adjuster include formic acid, acetic acid, glycolic acid, oxalic acid, propionic acid, malonic acid, succinic acid, adipic acid, maleic acid, malic acid, tartaric acid, citric acid, benzoic acid, phthalic acid, isophthalic acid, Examples include inorganic acids such as terephthalic acid, glutaric acid, gluconic acid, lactic acid, aspartic acid, glutamic acid, pimelic acid, suberic acid, methanesulfonic acid, hydrochloric acid, nitric acid, and phosphoric acid. These may use 1 type and may use 2 or more types together. For example, when alumina hydrate is used as the second inorganic particles, it is preferable to use a monobasic acid as a pH adjuster in order to disperse the alumina hydrate in water. From this viewpoint, as the pH adjuster, formic acid, acetic acid, glycolic acid, methanesulfonic acid and other organic acids, hydrochloric acid, nitric acid and the like are preferable.

(Other additives)
Examples of other additives include pigment dispersants and fastness improvers. These can be used as appropriate as long as the contact angle with respect to pure water on the surface of the second layer does not change greatly.

(Coating method of coating solution for second layer)
As a coating method of the coating liquid for the second layer, from the viewpoint of obtaining an appropriate coating amount, for example, various curtain coaters, coaters using an extrusion method, coaters using a slide hopper method, etc. And a method of coating by on-machine or off-machine. In addition, the coating liquid for 2nd layers may be heated for the purpose of viscosity adjustment etc. of the coating liquid for 2nd layers at the time of coating, and a coater head may be heated.

  Moreover, for drying the coating liquid for the second layer after coating, for example, a hot air dryer such as a straight tunnel dryer, an arch dryer, an air loop dryer, a sine curve air float dryer, or the like can be used. Further, a dryer using infrared rays, a heated dryer, a microwave, or the like can be used.

The coating amount after drying of the coating liquid for the second layer is 15 g / m ² or more and 50 g / m ² or less, although it varies depending on the target ink absorption amount, gloss, composition of the second layer, and the like. It is more preferable that it is 25 g / m ² or more and 35 g / m ² or less. When the coating amount is 25 g / m ² or more, the ink absorbability of the entire second layer is improved. Moreover, if this coating amount is 35 g / m < ² > or less, generation | occurrence | production of a crack can be reduced more effectively.

<Third layer>
In the present invention, the third layer has a core-shell type polymer particle A having an average particle diameter of 20 nm or more and 95 nm or less and a glass transition point higher than 60 ° C., and an average particle diameter larger than 95 nm and a glass transition point of 60 ° C. or less. It is obtained by coating the second layer with a third layer coating solution containing polymer particles B. As a result, a recording medium having a high glossiness, a small gloss difference between the printed portion and the white paper portion when printing with pigment ink, and a high color development property and a surface quality of silver salt baryta paper can be obtained.

  When the third layer is in contact with the second layer, the third layer is formed on a part of the surface of the second layer in order to maintain the excellent absorbency of the second layer without inhibiting the ink absorbency. It is preferable. Specifically, the third layer is not continuously formed on the entire surface of the second layer, but the third layer is partially formed on the surface of the second layer, and the pores on the surface of the second layer are formed. The state in which remains is preferable. The coverage of the second layer by the third layer is preferably 40% or more and 90% or less, and more preferably 50% or more and 80% or less. When the coverage is 90% or less, the area of the surface of the second layer is not reduced and the ink absorbability is improved.

  The coverage is a value measured by the following method. Using an electron microscope (SEM), the area ratio of the third layer to the entire surface of the second layer by image processing of 10 or more observation images (size of one location; 5.00 mm × 5.00 mm) And the average value is taken as the coverage. The coverage is preferably almost constant over the entire surface of the second layer. That is, when 10 or more places are observed using an electron microscope, it is preferable that the coverage at 40% or more of the places is 40% or more and 90% or less. It is more preferable that the coverage at all the observed locations is 40% or more and 90% or less.

(Core-shell polymer particle A)
The core-shell type polymer particle A is a polymer particle in which a shell part is formed so as to cover the outside of the core part serving as a nucleus. In addition to functioning as a glossy layer, the third layer according to the present invention is required to have high transparency of ink components in order to be used as a recording medium. In the present invention, the third layer coating liquid, which is a raw material for the third layer, contains core-shell polymer particles A having an average particle diameter of 20 nm to 95 nm and a glass transition point higher than 60 ° C. Thereby, the third layer can have a uniform and dense porous structure, and the third layer can function as a glossy expression layer having high permeability of the ink component.

  If the average particle diameter exceeds 95 nm, the Rayleigh scattering intensity by the particles becomes high, so it is difficult to obtain a gloss having the texture of silver salt baryta paper, and the difference in gloss between the printed part and the white paper part at the time of pigment ink printing Becomes easy to be visually recognized. Further, when the printed part is observed, haze that appears to be slightly cloudy is likely to occur. On the other hand, when the average particle diameter is less than 20 nm, the particles are densely present and the pores contained in the third layer tend to be small, so that the ink absorbability is lowered. In addition, when the glass transition point is 60 ° C. or lower, the third layer is completely formed into a film when the third layer is formed, and the pores are blocked, so that the ink absorbability is lowered.

  The average particle diameter is preferably 30 nm or more and 80 nm or less, more preferably 35 nm or more and 70 nm or less, and further preferably 40 nm or more and 60 nm or less. The glass transition point is preferably 65 ° C. or higher, more preferably 70 ° C. or higher, and further preferably 75 ° C. or higher. The upper limit of the glass transition temperature is not particularly limited, but can be, for example, 130 ° C. or lower. In addition, the said glass transition point shows the glass transition point as the core-shell type polymer particle A whole.

  The average particle diameter in the present invention is measured by a dynamic light scattering method, and is described in “Structure of Polymer (2) Scattering Experiments and Morphological Observation Chapter 1 Light Scattering” (edited by Kyoritsu Publishing Polymer Society) Chem. Phys. , 70 (B), 15Apl. 3965 (1979), etc., and obtained from analysis using the cumulant method. The dynamic light scattering method has a distribution in the decay of the time correlation function from the scattered light when fine particles having different particle sizes are mixed. By analyzing this time correlation function using the cumulant method, the average (<Γ>) and variance (μ) of the decay rate can be obtained. Since the decay rate (Γ) is expressed as a function of the particle diffusion coefficient and the scattering vector, the hydrodynamic average particle diameter can be obtained using the Stokes-Einstein equation. The average particle diameter in the present invention is a value measured using a zeta potential / particle diameter measurement system ELS Z-2 (manufactured by Otsuka Electronics Co., Ltd.).

  In addition, the method for measuring the glass transition point in the present invention is a method described in “J. Brandrup, EH Immergut Co., Polymer Handbook, 2nd Edition, III-139 to III-192 (1975)”. In the case of a copolymer, the glass transition point is a value determined by the following formula.

1 / Tg = W ₁ / Tg ₁ + W ₂ / Tg ₂ +... W _n / Tg _n
Tg _n : Glass transition point of homopolymer in polymer W _n : Weight fraction of monomer n in polymer where W ₁ + W ₂ +... + W _n = 1.

  The glass transition point of the shell part of the core-shell type polymer particle A is preferably 60 ° C. or less. At this time, when a core-shell emulsion containing the core-shell type polymer particles A and a resin emulsion containing the polymer particles B described later are used as raw materials, film formation is likely to proceed while the core-shell type emulsion and the resin emulsion are mixed, and a desired film is formed. Glossiness is easy to obtain. The glass transition point is more preferably 57 ° C. or less, and further preferably 55 ° C. or less.

  Examples of the material forming the core portion of the core-shell type polymer particle A (hereinafter also referred to as a core polymer) include a hydrophobicized acrylic polymer, styrene-acrylic copolymer, and polyvinyl chloride. Specific examples of hydrophobic acrylic polymers, styrene-acrylic copolymers, and polyvinyl chloride include styrene derivatives such as styrene, α-methylstyrene, vinyltoluene, methyl acrylate, ethyl acrylate, and propyl acrylate. Alkyl acrylates having a linear, branched or cyclic alkyl group having 1 to 18 carbon atoms, such as butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate and stearyl acrylate , Having 1 to 18 carbon atoms, such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, Chain, methacrylic acid alkyl esters having a branched or cyclic alkyl group, vinyl acetate, vinyl propionate, vinyl butyrate, acrylonitrile, methacrylonitrile, methyl vinyl ether, vinyl chloride, vinyl bromide and the like. These may use 1 type and may use 2 or more types together.

  Examples of the material forming the shell portion of the core-shell type polymer particle A (hereinafter also referred to as shell polymer) include hydrophilic resins. Although it does not specifically limit as this hydrophilic resin, From a viewpoint of quality design, such as transparency, film forming property, safety | security, a glass transition point, a particle diameter, and molecular weight control, the hydrophilic acrylic polymer Is preferred. Specific examples of hydrophilic monomers for the hydrophilic acrylic polymer include acrylic acid, methacrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, maleic acid and fumaric acid. Group-containing monomer and derivative thereof, styrene sulfonic acid, sulfonic acid-2-propylacrylamide, monomer having sulfonic acid group such as vinyl sulfonic acid and derivatives thereof, monomer having phosphoric acid group such as vinyl phosphonic acid and derivatives thereof, and the like Is mentioned. Further, lithium salts, sodium salts, potassium salts, ammonium salts, organic ammonium salts, and the like of the above monomers can be mentioned. These may use 1 type and may use 2 or more types together. As a material for forming the shell portion, a hydrophobic polymer used for the core portion can be used together with the hydrophilic polymer.

  As will be described later, when the core-shell type emulsion is formed by emulsion polymerization and the core-shell type polymer particles contained therein are used, the core polymer and the shell polymer are close in polarity, and in a combination in which both are compatible. In some cases, the target core-shell structure cannot be sufficiently formed. In order to sufficiently form the core-shell structure, it is preferable to select a material in which the core polymer and the shell polymer are hardly compatible.

  At least one of the core polymer and the shell polymer contained in the core-shell type polymer particle A may be cross-linked. In this case, the molecular weight of the core polymer and shell polymer can be adjusted as appropriate. When the core polymer and the shell polymer are uncrosslinked, the weight average molecular weight of the polymer contained in the core-shell polymer particle A varies depending on the type of monomer and the synthesis conditions, but is preferably 5000 to 2 million. The weight average molecular weight is a value measured by GPC (Gel Permeation Chromatography). Depending on the purpose, the molecular weight can be adjusted with a chain transfer agent or the like.

  The ratio of the amount of the core polymer to the shell polymer in the core-shell type polymer particle A can be arbitrarily changed. For example, the core polymer: shell polymer can be from 20:80 to 80:20 by weight.

  The core-shell type polymer particles A according to the present invention are further emulsion-polymerized by, for example, charging or dropping monomers, which are raw materials of the shell polymer, into an aqueous dispersion obtained by emulsion polymerization of monomers, which are raw materials of the core polymer. And it can obtain easily by manufacturing a core-shell type emulsion. In the emulsion polymerization, the monomer is preferably emulsion polymerized in at least one emulsifier in water or a mixed solvent of water and an organic solvent such as methanol, ethanol, and acetone that is miscible with water. The emulsion polymerization can be carried out at a temperature of 30 ° C. to 100 ° C., preferably 40 ° C. to 90 ° C., using a radical polymerization initiator. When using a mixed solvent, the amount of the organic solvent that can be mixed with water in the mixed solvent is preferably 0 to 50% by volume with respect to water. In the polymerization reaction, 0.05 to 5% by mass of a radical polymerization initiator and, if necessary, 0.1 to 10% by mass of an emulsifier can be used with respect to the monomer to be polymerized.

(Polymer particle B)
The average particle diameter of the polymer particles B is larger than 95 nm, and the glass transition point is 60 ° C. or lower. When the average particle diameter is 95 nm or less, if a core-shell type emulsion containing the core-shell type polymer particles A is used as a raw material, the core-shell type emulsion may not be successfully formed, and desired glossiness cannot be obtained. When the glass transition point exceeds 60 ° C., film formation does not proceed and high gloss cannot be obtained. The average particle size is preferably 96 nm or more, and more preferably 98 nm or more. The glass transition point is preferably 50 ° C. or lower, more preferably 40 ° C. or lower, and further preferably 30 ° C. or lower. Although the upper limit of this average particle diameter is not specifically limited, For example, it can be 300 nm or less. Although the minimum of this glass transition point is not specifically limited, For example, it can be -50 degreeC or more. Further, from the viewpoint of easily developing gloss, the average particle diameter of the polymer particles B is preferably 30 nm or more, more preferably 35 nm or more, and further preferably 40 nm or more larger than the average particle diameter of the core-shell polymer particles A. . From the viewpoint of glossiness, the glass transition point of the polymer particle B is preferably 200 ° C. lower than the glass transition point of the core-shell polymer particle A, and more preferably 150 ° C. lower.

  Examples of the material of the polymer particle B include acrylic polymer, styrene-acrylic copolymer, vinyl acetate-acrylic copolymer, vinyl acetate polymer, ethylene-vinyl acetate copolymer, chlorinated polyolefin polymer, and ethylene-acetic acid. Multi-component copolymers such as vinyl-acrylic, styrene / butadiene rubber (SBR), acrylonitrile / butadiene rubber (NBR), methyl methacrylate / butadiene rubber (MBR), polyvinylidene chloride, polyester, polyolefin, polyurethane, polymethacrylate, polytetra Examples include fluoroethylene, polymethyl methacrylate, polycarbonate, polyvinyl acetal resin, rosin ester resin, episulfide resin, epoxy resin, silicone resin, and silicone-acrylic resin. These may use 1 type and may use 2 or more types together.

  The weight average molecular weight of the polymer contained in the polymer particle B is preferably 100 to 2 million.

  When the resin emulsion containing the polymer particles B is used when forming the third layer, the resin emulsion is preferably an aqueous emulsion. A small amount of an organic solvent may be included as a film forming aid.

  As the polymer particles B, it is also possible to use heterophasic structure particles containing a plurality of polymers having different compositions and degrees of polymerization of monomers as raw materials in a single particle. The structure of the heterophasic particles is not particularly limited. Structural examples and preparation methods of heterostructure particles are described in “Application of Synthetic Latex (Takaaki Murasugi, Ikuo Kataoka, Junichi Suzuki, Keiji Kasahara Publishing Co., Ltd., published by Kobunshi Publishing Co., Ltd. (1933))”. Examples of the heterostructure particles include a core-shell structure, a composite structure, a localized structure, a daruma structure, a raspberry-like structure, a multiparticulate composite structure, a mizukaki structure, and an IPN (interpenetrating network structure).

(3rd layer coating solution)
The third layer according to the present invention can be formed by applying a third layer coating solution containing the core-shell polymer particles A and the polymer particles B. In particular, the third layer according to the present invention is formed by a step of applying and drying a third layer coating solution containing a core-shell type emulsion containing core-shell type polymer particles A and a resin emulsion containing polymer particles B. It is preferable to do. The mass ratio between the core-shell emulsion and the resin emulsion is preferably 30:70 to 70:30. By satisfying the range of the mixing ratio, film formation of the core-shell type emulsion proceeds, high gloss is obtained, and high absorbency is obtained. The mass ratio is more preferably 40:60 to 60:40. The solid content concentration of the third layer coating solution is preferably 0.05 to 5.00% by mass. When the solid content concentration is 0.05% by mass or more, the concentration of the coating liquid is stabilized, which is preferable in production, and the glossiness is improved. Further, when the solid content concentration is 5.00% by mass or less, the particles are not densely packed and the ink absorbability is improved. The solid content concentration of the third layer coating solution is more preferably 0.10 to 1.00% by mass.

  In addition to the core-shell type polymer particles A and the polymer particles B, the third layer coating solution includes a thickener, an antifoaming agent, a dot adjusting agent, a preservative, a pH adjusting agent, an antistatic agent, a conductive agent, and the like. These various additives may be included.

(Coating method of third layer coating solution)
As a coating method of the third layer coating solution, various coating methods used for coating the first layer coating solution and the second layer coating solution can be used. In addition, the third layer coating solution is applied at any timing after the formed second layer is cured when the formed second layer is semi-cured simultaneously with the formation of the second layer. It is possible to work. However, in order to avoid mixing the second layer and the third layer, it is preferable to apply the third layer coating solution after curing the second layer. The coating amount after drying of the third layer coating solution is preferably 10 mg / m ² or more and 500 mg / m ² or less, more preferably 30 mg / m ² or more and 100 mg / m ² or less. When the coating amount is 10 mg / m ² or more, the glossiness is good. Further, when the coating amount is 500 mg / m ² or less, the ink absorbability is good. The method for curing the third layer is not particularly limited, and a drying method used for curing the second layer can be suitably used.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

<Production of support>
20 parts by weight of light calcium carbonate was added to a slurry containing 100 parts by weight of hardwood bleached kraft pulp. 2 parts by weight of cationic starch and 0.3 parts by weight of an alkenyl succinic anhydride neutral sizing agent were added to the slurry and mixed well to obtain a papermaking raw material. The paper raw material was dried using a long mesh multi-cylinder paper machine until the water content was 10% by mass. A solution containing 7% by mass of oxidized starch with a size press was applied to both sides at 4 g / m ² and dried until the water content became 7% by mass. Thereby, a support having a basis weight of 230 g / m ² was produced.

<Preparation of coating liquid A for the first layer>
Synthetic amorphous silica (trade name: Mizukasil P603, manufactured by Mizusawa Chemical Co., Ltd., oil absorption 110 mL / 100 g) as first inorganic particles, 25 parts by mass, calcium carbonate (trade name: Brilliant-15, manufactured by Shiraishi Calcium Co., Ltd., oil absorption) (Amount 44 mL / 100 g) 75 parts by mass, styrene-butadiene copolymer latex (trade name: Luck Star DS226, manufactured by Dainippon Ink & Chemicals, Inc.) as the first binder, 7.5 parts by mass, phosphoric esterified Starch (trade name: MS4600, manufactured by Nippon Shokuken Kako Co., Ltd.) was mixed with 7.5 parts by mass in terms of solid content. This prepared the coating liquid A for 1st layers whose solid content concentration is 40 mass%. The oil absorption amount of the first inorganic particles contained in the first layer coating liquid A was 60.5 mL / 100 g in terms of a blending ratio.

<Preparation of coating liquid B for the first layer>
For the first layer, except that the compounding amount of the synthetic amorphous silica was changed to 3 parts by mass, and 97 parts by mass of barium sulfate (trade name: W-10, manufactured by Takehara Chemical Co., Ltd.) was used instead of calcium carbonate. In the same manner as the coating liquid A, a first layer coating liquid B was obtained. The oil absorption amount of the first inorganic particles contained in the first layer coating liquid B was 9.1 mL / 100 g in terms of the blending ratio.

<Preparation of coating liquid C for the first layer>
Except having changed the compounding quantity of calcium carbonate into 100 mass parts, it carried out similarly to the coating liquid A for 1st layers, and obtained the coating liquid C for 1st layers. The oil absorption amount of the first inorganic particles contained in the first layer coating liquid C was 44.0 mL / 100 g in terms of the blending ratio.

<Preparation of first layer coating solution D>
Except for changing the blending amount of the synthetic amorphous silica to 75 parts by mass and the blending amount of calcium carbonate to 25 parts by mass, the coating liquid D for the first layer was prepared in the same manner as the coating liquid A for the first layer. Obtained. The oil absorption amount of the first inorganic particles contained in the first layer coating liquid D was 93.5 mL / 100 g in terms of the blending ratio.

<Preparation of coating liquid E for the first layer>
Coating for the first layer, except that 100 parts by mass of synthetic amorphous silica (trade name: Mizukasil P752, manufactured by Mizusawa Chemical Industry Co., Ltd., oil absorption 160 mL / 100 g) having a different oil absorption amount was used as the synthetic amorphous silica. In the same manner as Liquid A, a first layer coating liquid E was obtained. The oil absorption amount of the first inorganic particles contained in the first layer coating liquid E was 160.0 mL / 100 g in terms of the blending ratio.

<Preparation of coating liquid A for the second layer>
Alumina hydrate (trade name: Dispersal HP14, manufactured by Sasol Co., Ltd.) was added to the pure water as the second inorganic particles so that the solid concentration was 30% by mass. Next, 1.5 parts by mass of methanesulfonic acid was added to 100 parts by mass of this alumina hydrate and stirred to obtain a colloidal sol. The obtained colloidal sol was diluted with pure water so that the solid content concentration of the alumina hydrate was 25% by mass to obtain a colloidal sol.

  On the other hand, polyvinyl alcohol (trade name: PVA235, manufactured by Kuraray Co., Ltd., polymerization degree: 3500, saponification degree: 88%) is dissolved in pure water as the second binder, and the solid content concentration is 8.0 mass. % PVA aqueous solution was obtained. And the said PVA aqueous solution is mixed with the colloidal sol prepared above so that the solid content conversion ((PVA) / (alumina hydrate) × 100) of PVA with respect to the solid content of alumina hydrate is 8% by mass. did. Next, a 5.0 mass% boric acid aqueous solution was mixed so that the solid content of boric acid was 1.5 parts by mass with respect to 100 parts by mass of the solid content of alumina hydrate. A working liquid A was obtained.

<Preparation of second layer coating solution B>
100 parts by mass of gas phase method silica (average primary particle diameter 7 nm, specific surface area 300 m ² / g) and 4 parts by mass of dimethyldiallylammonium chloride polymer (molecular weight 9,000) are added to the pure water as the second inorganic particles. And stirred to obtain a colloidal sol. The obtained colloidal sol was diluted with pure water so that the solid content concentration of the vapor phase method silica was 20% by mass to obtain a colloidal sol.

  On the other hand, polyvinyl alcohol (trade name: PVA235, manufactured by Kuraray Co., Ltd., polymerization degree: 3500, saponification degree: 88%) is dissolved in pure water as the second binder, and the solid content concentration is 8.0 mass. % PVA aqueous solution was obtained. And the said PVA aqueous solution is mixed with the colloidal sol prepared above so that the solid content conversion ((PVA) / (gas phase method silica) × 100) of PVA with respect to the solid content of gas phase method silica may become 23 mass%. did. Next, a 5.0% by mass boric acid aqueous solution and a nonionic surfactant (polyoxyethylene alkyl ether) with a solid content of boric acid of 4 parts by mass with respect to 100 parts by mass of the solid content of vapor-phase process silica Then, the nonionic surfactant was mixed so as to be 0.3 parts by mass to obtain a second layer coating solution B.

<Preparation of third layer coating solution A>
Styrene acrylic core-shell emulsion 50 parts by mass (trade name: JE-1056, manufactured by Hoshiko PMC, average particle diameter of core-shell polymer particles 50 nm, Tg = 82 ° C. (core portion 105 ° C., shell portion 53 ° C.))
Styrene acrylic core-shell emulsion 50 parts by mass (trade name, UE-1055, manufactured by Hoshiko PMC, average particle diameter of core-shell polymer particles 100 nm, Tg = 15 ° C. (core portion-33 ° C., shell portion 126 ° C.))
These were diluted with pure water so that the solid content concentration was 0.1% by mass to obtain a third layer coating solution A.

<Preparation of third layer coating solution B>
Styrene acrylic core-shell emulsion 50 parts by mass (trade name: JE-1056, manufactured by Hoshiko PMC, average particle diameter of core-shell polymer particles 50 nm, Tg = 82 ° C. (core portion 105 ° C., shell portion 53 ° C.))
Styrene acrylic core-shell emulsion 50 parts by mass (trade name: UE-1055, manufactured by Hoshiko PMC, average particle diameter of core-shell polymer particles 100 nm, Tg = 15 ° C. (core portion-33 ° C., shell portion 126 ° C.))
These were diluted with pure water so that the solid content concentration was 0.05% by mass to obtain a third layer coating solution B.

<Preparation of third layer coating solution C>
Styrene acrylic core-shell emulsion 50 parts by mass (trade name: JE-1056, manufactured by Hoshiko PMC, average particle diameter of core-shell polymer particles 50 nm, Tg = 82 ° C. (core portion 105 ° C., shell portion 53 ° C.))
Styrene acrylic core-shell emulsion 50 parts by mass (trade name: UE-1055, manufactured by Hoshiko PMC, average particle diameter of core-shell polymer particles 100 nm, Tg = 15 ° C. (core portion-33 ° C., shell portion 126 ° C.))
These were diluted with pure water so that the solid content concentration was 0.2% by mass to obtain a third layer coating solution C.

<Preparation of third layer coating solution D>
30 parts by mass of styrene-acrylic core-shell emulsion (trade name: JE-1056, manufactured by Seiko PMC, average particle diameter of core-shell polymer particles 50 nm, Tg = 82 ° C. (core portion 105 ° C., shell portion 53 ° C.))
70 parts by mass of a styrene acrylic core-shell emulsion (trade name: UE-1055, manufactured by Hoshiko PMC, average particle diameter of core-shell polymer particles 100 nm, Tg = 15 ° C. (core portion-33 ° C., shell portion 126 ° C.))
These were diluted with pure water so that the solid content concentration was 0.1% by mass to obtain a third layer coating solution D.

<Preparation of third layer coating solution E>
70 parts by mass of styrene acrylic core-shell emulsion (trade name: JE-1056, manufactured by Hoshiko PMC, average particle diameter of core-shell polymer particles 50 nm, Tg = 82 ° C. (core portion 105 ° C., shell portion 53 ° C.))
30 parts by mass of styrene-acrylic core-shell emulsion (trade name: UE-1055, manufactured by Seiko PMC Co., Ltd., average particle diameter of core-shell polymer particles 100 nm, Tg = 15 ° C. (core portion-33 ° C., shell portion 126 ° C.))
These were diluted with pure water so that the solid content concentration was 0.1% by mass to obtain a third layer coating solution E.

<Preparation of third layer coating solution F>
50 parts by mass of styrene acrylic core-shell emulsion (trade name: KE-1062, manufactured by Hoshimi PMC, average particle diameter of core-shell polymer particles 80 nm, Tg = 96 ° C. (core portion 59 ° C., shell portion 126 ° C.))
Styrene acrylic core-shell emulsion 50 parts by mass (trade name: UE-1055, manufactured by Hoshiko PMC, average particle diameter of core-shell polymer particles 100 nm, Tg = 15 ° C. (core portion-33 ° C., shell portion 126 ° C.))
These were diluted with pure water so that the solid content concentration was 0.1% by mass to obtain a third layer coating solution F.

<Preparation of third layer coating solution G>
Styrene acrylic core-shell emulsion 50 parts by mass (trade name: JE-1056, manufactured by Hoshiko PMC, average particle diameter of core-shell polymer particles 50 nm, Tg = 82 ° C. (core portion 105 ° C., shell portion 53 ° C.))
Urethane emulsion 50 parts by mass (trade name: SF-500M, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., average particle diameter of polymer particles 140 nm, Tg = −39 ° C.)
These were diluted with pure water so that the solid content concentration was 0.1% by mass to obtain a third layer coating solution G.

<Preparation of third layer coating solution H>
Styrene acrylic core-shell emulsion 50 parts by mass (trade name: JE-1056, manufactured by Hoshiko PMC, average particle diameter of core-shell polymer particles 50 nm, Tg = 82 ° C. (core portion 105 ° C., shell portion 53 ° C.))
Urethane emulsion 50 parts by mass (trade name: CP-6190, manufactured by DIC, average particle diameter of polymer particles 150 nm, Tg = 43 ° C.)
These were diluted with pure water so that the solid content concentration was 0.1% by mass to obtain a third layer coating solution H.

<Preparation of third layer coating liquid I>
Styrene acrylic core-shell emulsion 50 parts by mass (trade name: JE-1056, manufactured by Hoshiko PMC, average particle diameter of core-shell polymer particles 50 nm, Tg = 82 ° C. (core portion 105 ° C., shell portion 53 ° C.))
Styrene acrylic emulsion 50 parts by mass (trade name: HY-364, manufactured by DIC, average particle diameter of polymer particles 125 nm, Tg = 30 ° C.)
These were diluted with pure water so that the solid content concentration was 0.1% by mass to obtain a third layer coating solution I.

<Preparation of third layer coating solution J>
50 parts by mass of styrene acrylic core-shell emulsion (trade name: KE-1062, manufactured by Hoshimi PMC, average particle diameter of core-shell polymer particles 80 nm, Tg = 96 ° C. (core portion 59 ° C., shell portion 126 ° C.))
50 parts by mass of acrylic core-shell emulsion (trade name: AKW-107, manufactured by Taisei Fine Chemical Co., Ltd., average particle diameter of core-shell polymer particles 145 nm, Tg = 25 ° C.)
These were diluted with pure water so that the solid content concentration was 0.1% by mass to obtain a third layer coating solution J.

<Preparation of third layer coating solution K>
Styrene acrylic core-shell emulsion (trade name: UE-1055, manufactured by Seiko PMC, average particle diameter of core-shell polymer particles 100 nm, Tg = 15 ° C. (core portion-33 ° C., shell portion 126 ° C.))
This was diluted with pure water so that the solid content concentration was 0.1% by mass to obtain a third layer coating solution K.

<Preparation of third layer coating solution L>
Styrene acrylic core-shell emulsion (trade name: JE-1056, manufactured by Seiko PMC, average particle diameter of core-shell polymer particles 50 nm, Tg = 82 ° C. (core portion 105 ° C., shell portion 53 ° C.))
This was diluted with pure water so that the solid content concentration was 0.1% by mass to obtain a third layer coating solution L.

<Preparation of third layer coating solution M>
50 parts by mass of styrene acrylic core-shell type emulsion (trade name: VE-1122, manufactured by Hoshimi PMC, average particle diameter of core-shell type polymer particles 185 nm, Tg = 62 ° C. (core portion 79 ° C., shell portion 59 ° C.))
Styrene acrylic core-shell emulsion 50 parts by mass (trade name: UE-1055, manufactured by Hoshiko PMC, average particle diameter of core-shell polymer particles 100 nm, Tg = 15 ° C. (core portion-33 ° C., shell portion 126 ° C.))
These were diluted with pure water so that the solid content concentration was 0.1% by mass to obtain a third layer coating solution M.

<Preparation of third layer coating solution N>
Styrene acrylic core-shell emulsion 50 parts by mass (trade name: JE-1056, manufactured by Hoshiko PMC, average particle diameter of core-shell polymer particles 50 nm, Tg = 82 ° C. (core portion 105 ° C., shell portion 53 ° C.))
Urethane-based emulsion 50 parts by mass (trade name: SF-620, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., average particle diameter of polymer particles 30 nm, Tg = 43 ° C.)
These were diluted with pure water so that the solid content concentration was 0.1% by mass to obtain a third layer coating solution N.

[Example 1]
The coating solution A for the first layer was applied to the support with an air knife coater so that the coating amount after drying was 15 g / m ² . Then, it dried with hot air with the air dryer and provided the 1st layer. The arithmetic average roughness Ra of the surface of the first layer was 0.6 μm. On the first layer, the coating solution A for the second layer was applied so that the coating amount after drying was 30 g / m ² and dried at 60 ° C. to provide a second layer. Further, the third layer coating solution A was applied onto the second layer so that the coating amount after drying was 60 mg / m ² and dried at 60 ° C. to provide a third layer. Thus, the recording medium 1 was obtained.

[Example 2]
A recording medium 2 was obtained in the same manner as in Example 1 except that the first layer coating solution A was changed to the first layer coating solution B.

Example 3
A recording medium 3 was obtained in the same manner as in Example 1 except that the first layer coating solution A was changed to the first layer coating solution C.

Example 4
A recording medium 4 was obtained in the same manner as in Example 1 except that the first layer coating solution A was changed to the first layer coating solution D.

Example 5
After the first layer was provided, the recording medium 5 was obtained in the same manner as in Example 1 except that the calendar process was performed with a mirror roll and the arithmetic average roughness Ra of the surface of the first layer was changed to 0.3 μm.

Example 6
After the first layer was provided, the recording medium 6 was obtained in the same manner as in Example 1 except that the calendering process was performed with a rough surface roll and the arithmetic average roughness Ra of the surface of the first layer was changed to 2.2 μm. .

Example 7
A recording medium 7 was obtained in the same manner as in Example 1 except that the second layer coating solution A was changed to the second layer coating solution B.

Example 8
A recording medium 8 was obtained in the same manner as in Example 1 except that the third layer coating solution A was changed to the third layer coating solution B.

Example 9
A recording medium 9 was obtained in the same manner as in Example 1 except that the third layer coating solution A was changed to the third layer coating solution C.

Example 10
A recording medium 10 was obtained in the same manner as in Example 1 except that the third layer coating solution A was changed to the third layer coating solution D.

Example 11
A recording medium 11 was obtained in the same manner as in Example 1 except that the third layer coating solution A was changed to the third layer coating solution E.

Example 12
A recording medium 12 was obtained in the same manner as in Example 1 except that the third layer coating solution A was changed to the third layer coating solution F.

Example 13
A recording medium 13 was obtained in the same manner as in Example 1 except that the third layer coating solution A was changed to the third layer coating solution G.

Example 14
A recording medium 14 was obtained in the same manner as in Example 1 except that the third layer coating solution A was changed to the third layer coating solution H.

Example 15
A recording medium 15 was obtained in the same manner as in Example 1 except that the third layer coating solution A was changed to the third layer coating solution I.

Example 16
A recording medium 16 was obtained in the same manner as in Example 1 except that the third layer coating solution A was changed to the third layer coating solution J.

[Comparative Example 1]
A recording medium 17 was obtained in the same manner as in Example 1 except that the first layer coating liquid A was not applied.

[Comparative Example 2]
A recording medium 18 was obtained in the same manner as in Example 1 except that the first layer coating solution A was changed to the first layer coating solution E.

[Comparative Example 3]
After the first layer was provided, the recording medium 19 was obtained in the same manner as in Example 1 except that the calendar process was performed with a mirror roll and the arithmetic average roughness Ra of the surface of the first layer was changed to 0.1 μm.

[Comparative Example 4]
After the first layer was provided, the recording medium 20 was obtained in the same manner as in Example 1 except that the calendering process was performed with a rough surface roll, and the arithmetic average roughness Ra of the surface of the first layer was changed to 3.1 μm. .

[Comparative Example 5]
A recording medium 21 was obtained in the same manner as in Example 1 except that the second layer coating liquid A was changed to the first layer coating liquid B.

[Comparative Example 6]
A recording medium 22 was obtained in the same manner as in Example 1 except that the third layer coating solution A was not applied.

[Comparative Example 7]
A recording medium 23 was obtained in the same manner as in Example 1 except that the third layer coating solution A was changed to the third layer coating solution K.

[Comparative Example 8]
A recording medium 24 was obtained in the same manner as in Example 1 except that the third layer coating solution A was changed to the third layer coating solution L.

[Comparative Example 9]
A recording medium 25 was obtained in the same manner as in Example 1 except that the third layer coating solution A was changed to the third layer coating solution M.

[Comparative Example 10]
A recording medium 26 was obtained in the same manner as in Example 1 except that the third layer coating solution A was changed to the third layer coating solution N.

(Measurement of arithmetic average roughness Ra)
The arithmetic average roughness Ra of the surface of the recording medium (the surface on the third layer side) produced in Examples and Comparative Examples was JIS-B- using Surfcorder SE3500 (trade name, manufactured by Kosaka Laboratory Ltd.). 0601: Measured according to 2001. The cut-off value was set to 0.8 mm, and the reference length was set to 2.5 mm. The results are shown in Table 1.

(Measurement of 60 degree specular gloss)
The 60-degree specular glossiness of the surface of the recording medium (the surface on the third layer side) prepared in Examples and Comparative Examples was measured by the method described in JIS-Z-8741: 1997. VG2000 (trade name) manufactured by Nippon Denshoku Industries Co., Ltd. was used as the measuring device. The results are shown in Table 1.

<Evaluation>
The following evaluations were performed on the recording media obtained in the above examples and comparative examples. A list of evaluation results is shown in Table 1.

[Gloss uniformity of the resulting image]
Using a photo printer (trade name: PIXUS Pro1, manufactured by Canon Inc.) using an ink jet method, check the monochrome printing in the photo paper “silk tone” mode, and RGB is recorded on the obtained recording medium. 17 gradation patterns from (255, 255, 255) to (0, 0, 0) were formed. Note that RGB (255, 255, 255) is a blank paper portion. The 60-degree specular glossiness of each gradation pattern is measured by the above-described method, and the largest glossiness (this is referred to as “maximum glossiness”) and the smallest glossiness (this is referred to as “minimum glossiness”). ”) (This is referred to as“ gloss difference ”), and gloss uniformity was evaluated based on the following evaluation criteria.
A: The difference in glossiness was 20% or less, and the gloss uniformity was high.
B: The difference in glossiness was larger than 20% and 40% or less, and the gloss uniformity was relatively high.
C: The difference in glossiness was larger than 40%, and the gloss uniformity was low.

[Ink absorbency of recording medium]
The recording surface of the obtained recording medium was evaluated for the absorbability of the dye ink. Using a photo printer (trade name: PIXUS MG6130, manufactured by Canon Inc.) using an inkjet method, 100% Duty of black, cyan, magenta, and yellow on a recording medium in a photographic paper “silk-tone” mode. Each solid batch was printed. Since ink absorptivity and beading are substantially correlated, the ink absorptivity of the recording medium was evaluated by evaluating beading. Evaluation was performed visually, and the evaluation criteria were as follows.
A: No beading was observed.
B: Although beading was slightly observed, there was no practical problem.
C: Beading was clearly observed.

[Texture of silver salt baraita paper]
The texture of the silver salt baryta paper was evaluated based on the following criteria using arithmetic average roughness Ra and 60 degree specular gloss.
A: The arithmetic average roughness Ra was 0.55 to 0.75 μm, the 60 ° specular gloss was 65 to 80%, and the barita-like surface quality was sufficiently satisfied.
B: Outside the range of A, arithmetic average roughness Ra is 0.5 to 0.8 μm and / or 60 degree specular gloss 60 to 80%, 60 degree specular gloss and / or arithmetic average roughness Although Ra was slightly inferior, the surface quality of the barita was satisfied.
C: Arithmetic average roughness Ra is 0.5 to 0.8 μm, 60 degree specular gloss is not in the range of 60 to 80%, 60 degree specular gloss and / or arithmetic average roughness Ra is greatly inferior, and balita tone I was not satisfied with the face.

[Color development of the resulting image]
The color developability of the recording surface (surface on which the third layer is disposed) of the obtained recording medium was evaluated. Using a photo printer (trade name: PIXUS MG6130, manufactured by Canon Inc.) using an inkjet method, a black 100% Duty solid batch was printed on a recording medium in a photographic paper “silk tone” mode. Next, 25 ° C., 50% R.I. H. Stored for 3 days in (relative humidity) environment. Then, the OD value (optical density) of the obtained sample was measured using a spectrophotometer and Spectrolino (manufactured by Gretag Macbeth). The evaluation criteria were as follows.
A: The OD value was 2.10 or more.
B: The OD value was 2.00 or more and less than 2.10.
C: The OD value was less than 2.00.

Claims (8)

A recording medium having a support, a first layer, a second layer, and a third layer in this order,
The first layer contains first inorganic particles,
The second layer contains at least one second inorganic particle selected from alumina hydrate and silica, and a binder,
The third layer has core-shell polymer particles A having an average particle size of 20 nm or more and 95 nm or less and a glass transition point higher than 60 ° C., and a polymer having an average particle size of more than 95 nm and a glass transition point of 60 ° C. or less. Obtained by coating the second layer with the third layer coating solution containing the particles B,
The amount of oil absorption based on the measurement method defined in JIS-K-5101 of the first inorganic particles is 100 mL / 100 g or less,
Arithmetic average roughness Ra (cutoff value 0.8 mm) based on the measurement method defined in JIS-B-0601 on the surface of the recording medium on which the third layer is disposed is 0.50 μm or more and 0.80 μm And
A recording medium having a 60-degree specular glossiness of 60% to 80% based on a measurement method defined by JIS-Z-8741 on the surface of the recording medium on which the third layer is disposed .   The recording medium according to claim 1, wherein a glass transition point of a shell portion of the core-shell type polymer particle A is 60 ° C. or less.   The third layer is obtained by applying and drying a third layer coating solution containing a core-shell emulsion containing the core-shell polymer particles A and a resin emulsion containing the polymer particles B. Item 3. The recording medium according to Item 1 or 2. It is a manufacturing method of the recording medium given in any 1 paragraph of Claims 1-3,
Applying a third layer coating solution containing a core-shell type emulsion containing the core-shell type polymer particles A and a resin emulsion containing the polymer particles B, and forming the third layer by drying. A method of manufacturing a recording medium, comprising:   The method for manufacturing a recording medium according to claim 4, wherein a mass ratio of the core-shell type emulsion to the resin emulsion is 30:70 to 70:30.   6. The method for producing a recording medium according to claim 4, wherein the solid content of the third layer coating solution is 0.05 to 5.00% by mass.   Coating the first layer coating solution containing the first inorganic particles, and drying to form the first layer, and the arithmetic average roughness Ra of the surface of the formed first layer is The method for producing a recording medium according to any one of claims 4 to 6, wherein the recording medium has a thickness of 0.2 µm to 3.0 µm. Manufacturing method of the coating amount after drying of the third layer coating solution, a recording medium according to any one of claims 4 to 7 is 10 mg / ^{m 2} or more 500 mg / ^{m 2} or less.