JP2006240035A - Manufacturing method of inkjet recording matter - Google Patents

Abstract

The present invention provides a method for producing an ink jet recording material having high whiteness and a smooth surface free from irregularities and excellent in ink absorbability.
In a method for producing an ink jet recording material having a coating layer containing inorganic fine particles on a support, the coating layer comprises an aqueous dispersion of inorganic fine particles having an average secondary particle size of 1 μm or less, and a degree of polymerization. Is mixed with an aqueous solution of polyvinyl alcohol having a molecular weight of 2000 or more, the fluorescent whitening agent is mixed in a state where the mixed liquid is 30 ° C. or higher and 65 ° C. or lower, and then an inorganic fine particle coating solution mixed with water-soluble salts is applied and dried. A method for producing an ink jet recording material, wherein the layer is a layer obtained as described above.

Description

  The present invention relates to a method for manufacturing an ink jet recording material.

  The ink jet recording method is a recording method in which ink droplets are ejected onto a recording medium and directly adhered to the recording medium, and since multicolor recording can be easily performed, as an output method of characters and various figures from a computer. In recent years, it has been rapidly spread for general use and office use. Multi-color recording by inkjet can form complex images accurately and quickly, and the color image formed is not inferior to that of multi-color printing by plate-making method or printing by color photographic method. It is possible to obtain When used in applications where the number of printed copies is small, it also has the advantage that it can be used at a lower cost than printing and photographic technologies.

  Since ink used in the ink jet system contains a large amount of solvent, it is necessary to eject a large amount of ink in order to obtain a high printing density. Therefore, the ink receiving layer formed on the recording surface of the ink jet recording body is required to be a material that can sufficiently absorb the ejected ink. In addition, since ink droplets are ejected continuously, if the next droplet is ejected before the first droplet is absorbed, bleeding or density unevenness is caused, and a clear image cannot be obtained. Therefore, the ink receiving layer is required to have a high absorption speed as well as an absorption amount. Furthermore, in addition to the above-described requirements for image quality, various performances such as ink drying properties, water resistance of printed matter, and image storage stability are required.

  In order to satisfy the above requirements, many ink jet recording materials provided with a resin-based or pigment-based ink receiving layer have been proposed and are commercially available. The resin-based ink receiving layer is generally formed by applying an aqueous solution of a water-soluble resin such as polyvinyl alcohol, polyvinyl pyrrolidone, a water-soluble cellulose derivative, or gelatin to a support and drying it, and has high transparency. For this reason, there are advantages such as high printing density and high gloss, but on the other hand, there are disadvantages in that the ink absorption rate is slow and the image quality is poor, and the ink drying rate is slow and the water resistance is poor. For this reason, it is difficult to obtain a print quality equivalent to a silver salt photograph required in recent years, and the pigment-based ink receiving layer described below has become mainstream recently.

  The pigment-based ink receiving layer is formed by adding a water-soluble resin such as polyvinyl alcohol or cellulose derivative as a binder resin to a pigment such as silica, alumina, pseudoboehmite, calcium carbonate, or kaolin. As the form of the pigment, those in which primary particles are aggregated to form secondary particles are preferably used. In such a pigment-based ink receiving layer, the ink is quickly absorbed by the capillary phenomenon between the primary particles and the secondary particles of the pigment to form an image, so that the image quality is good and the ink drying property is also good. .

  In general, many commercially available pigments have a secondary particle diameter of more than 1 μm, and when these are used in a pigment-based ink receiving layer, a large void between the secondary particles is formed. Is expensive. However, since the secondary particle size is large, the smoothness of the surface of the ink receiving layer is low and the gloss is low. Therefore, it is not suitable for the purpose of obtaining a high gloss of photographic printing paper tone that has been demanded in recent years. In addition, since the transparency of the ink receiving layer is low, there is also a disadvantage that the print density is low.

  In order to overcome the drawbacks as described above, an ink jet recording body provided with a pigment-based ink receiving layer using a fine pigment having an average particle size of 0.1 μm or less and polyvinyl alcohol having a high degree of polymerization has been proposed (for example, Patent Document 1). In addition, the agglomerated silica particles are pulverized to a fine particle diameter to form an ink receiving layer (see, for example, Patent Document 2), and active silica is used as a fine pigment in terms of high ink absorbability and transparency. Silica produced by condensation has been proposed (see, for example, Patent Document 3).

  In addition, an ink receiving layer containing a water-soluble salt for improving the ink absorbability of the ink receiving layer using fine pigments and preventing cracks in the coating film has been proposed (for example, see Patent Documents 4 and 5).

  Furthermore, recently, due to the widespread use of digital cameras and the availability of inexpensive inkjet printers that can output high-definition images equipped with photo ink, there is a demand for inkjet recording media that output images comparable to silver salt photographs. Is growing. With higher definition, higher speed, and full color of printers, more advanced characteristics are required for recording media. Especially when a human sees other than high ink absorption speed and absorption capacity, roundness of dots, high density of image, high gloss of surface, high smoothness to give image and texture comparable to silver salt photograph Therefore, there is a strong demand for an ink jet recording material that is excellent in whiteness (visual whiteness).

  In particular, in order to obtain a bright and high-contrast image, it is necessary to increase the whiteness of the ink jet recording material. In the case of an output product in which a blank paper portion is left, if the color of the white portion is dull, the impression of the entire image is impaired. Recently, so-called “borderless printing” such as a silver salt photograph is preferred, but in this case as well, the color development in a portion where the amount of ink is small is easily affected by the background.

  Conventionally, fluorescent whitening agents such as fluorescent dyes and fluorescent pigments have been used as means for obtaining suitable whiteness. Specifically, a fluorescent whitening agent is contained in the ink receiving layer (recording layer) (Patent Documents 6 to 8), a resin-coated paper is used as a support, and a fluorescent whitening agent is contained in the resin coating layer. (Patent Documents 9 to 11).

However, when an optical brightening agent is contained in the ink receiving layer mainly containing inorganic fine particles, if an application layer is formed by applying to a support for an ink jet recording body and then drying, a coating layer having a diameter of 20 to A problem (hereinafter also referred to as “pops”) that 100 μm protrusions are generated or cracks occur, and an ink receiving layer having a smooth surface cannot be obtained.
Japanese Patent Laid-Open No. 7-117334 JP-A-9-286165 JP 2001-354408 A JP 2003-182209 A JP 2004-1463 A JP 2000-2111247 A JP 2000-43404 A Japanese Patent Laid-Open No. 2004-50617 JP 2004-50501 A JP 2004-34634 A Japanese Patent Laid-Open No. 2004-74535

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing an ink jet recording material having high whiteness, no cracks and no flaws, a smooth surface, and excellent ink absorbability.

The present invention has been achieved by the following configurations as a result of intensive studies to solve the above-described problems.
[1] In a method for producing an ink jet recording material having a coating layer containing inorganic fine particles on a support, the coating layer has an inorganic fine particle aqueous dispersion having an average secondary particle diameter of 1 μm or less, and a degree of polymerization. A mixture of 2000 or more aqueous solutions of polyvinyl alcohol is mixed, and the mixture is mixed with a fluorescent brightening agent in a state of 30 ° C. or more and 65 ° C. or less, and then an inorganic fine particle coating solution mixed with water-soluble salts is applied and dried. A method for producing an ink jet recording material, comprising:
[2] The method for producing an ink jet recording material according to [1] or [2], wherein the optical brightener is a stilbene compound.
[3] The method for producing an ink jet recording material according to [1] or [2], wherein the inorganic fine particles have an average secondary particle diameter of 0.5 μm or less and 0.01 μm or more.
[4] Any one of [1] to [3], wherein the inorganic fine particles are at least one selected from wet silica, gas phase silica, silica produced by condensing activated silicic acid, and mesoporous silica. 2. A method for producing an ink jet recording material according to 1.
[5] The method for producing an ink jet recording material according to any one of [1] to [4], wherein the inorganic fine particles are at least one selected from wet-process silica and silica produced by condensing activated silicic acid. .
[6] The method for producing an ink jet recording material according to any one of [1] to [5], wherein the water-soluble salt is a sodium salt, a potassium salt or an ammonium salt.
[7] The method for producing an ink jet recording material according to any one of [1] to [6], wherein a second coating layer having a pigment, an adhesive, and a cationic compound is formed on the coating layer.

  According to the present invention, it is possible to provide a method for producing an ink jet recording material having high whiteness, a coating layer free from cracks and irregularities, a smooth surface and excellent ink absorbability.

  The inorganic fine particles are stably dispersed in a colloidal form in the water-based paint, but when the inorganic fine particle dispersion is mixed with an aqueous polyvinyl alcohol solution having a high polymerization degree of 2000 or more, and coated and dried, There is a drawback in that film formation failure due to cracking is likely to occur due to capillary contraction force. In order to increase the ink absorbency, it is necessary to have a large number of pores having a large diameter.

  In order to eliminate these drawbacks, water-soluble salts are included in the paint. When water-soluble salts are included, water-soluble salts are adsorbed on the pigment surface in the process of increasing the concentration of water-based paint during the drying process, reducing the amount of charge on the surface, making the dispersion unstable and large. Produce an aggregate structure. In this way, the presence of many large-diameter pores generated by the influence of water-soluble salts alleviates capillary contraction force, and the presence of many large-diameter pores reduces the pore volume that contributes to ink absorption. A large amount of ink once absorbed can be taken in immediately, and ink can be absorbed without overflowing even if ink is ejected one after another.

However, when a fluorescent brightening agent is mixed to increase the whiteness of the coating layer, the resulting coating layer is cracked or flawed, and a uniform coating layer cannot be formed. Occurred.
In the present invention, an inorganic fine particle aqueous dispersion having an average secondary particle size of 1 μm or less and an aqueous solution of polyvinyl alcohol having a degree of polymerization of 2000 or more are mixed, and the fluorescence is increased in a state where the mixture is from 30 ° C. to 65 ° C. An ink jet recording material obtained by such a manufacturing method is characterized by forming a coating layer by mixing a white agent and then coating and drying an inorganic fine particle coating solution mixed with a water-soluble salt. It is possible to form an excellent coating layer surface in which cracks of the working layer are hardly generated and no flaws are generated.
The lower the viscosity of the mixed liquid of inorganic fine particles and polyvinyl alcohol when the fluorescent brightening agent is mixed, the less the thickening occurs. In order to lower the viscosity, it is desirable that the temperature of the mixed solution is high. However, if the temperature of the mixed solution exceeds 65 ° C., aggregates are likely to be generated. On the other hand, when the temperature is lower than 30 ° C., the fluorescent brightening agent is difficult to be mixed evenly. For this reason, if the stirring is strengthened, aggregates are generated and fibrillation of the paint occurs. In addition, it is preferable to perform stirring at the time of adjustment of a coating liquid in the range whose peripheral speed is about 40-80 m / sec.

  After blending the optical brightener, water-soluble salts are added. When the water-soluble salt is added to the mixed solution, the liquid temperature of the mixed solution is 40 ° C. or lower, preferably 30 ° C. or lower, preferably 15 ° C. or higher, preferably 20 ° C. or higher. preferable.

  The polyvinyl alcohol used in the coating layer is not limited in terms of the degree of saponification and the degree of polymerization as long as the degree of polymerization is 2000 or more, but the preferred degree of saponification is 80 to 99.9%, and the degree of polymerization is more than 3500, more preferably. Is 4000 or more. The upper limit of the degree of polymerization is not particularly limited, but is preferably 7500 or less, and preferably 5000 or less because the viscosity does not become high when the coating solution is adjusted. It is also possible to use modified polyvinyl alcohol such as hydrophobic group modification or anion modification.

  The concentration of the polyvinyl alcohol aqueous solution is not particularly limited, but it is preferably as high as possible when used as a coating solution for an inkjet recording material. The coating layer of the ink jet recording body needs to sufficiently absorb ink components at the time of recording, for example, an ink solvent, and therefore has a higher coating amount than a general coated paper for printing. Therefore, unless the concentration of the coating solution is as high as possible, it is necessary to make the drying conditions harsh, and the coating layer will crack. The concentration of the polyvinyl alcohol aqueous solution may be adjusted to 5% or more, preferably about 7 to 10%.

  Usually, when adjusting polyvinyl alcohol to an aqueous solution, depending on the degree of saponification and polymerization of polyvinyl alcohol, solid polyvinyl alcohol is added to water, heated to around 95 ° C. with stirring, and held for about 1 to 2 hours. To dissolve completely. If the temperature of the polyvinyl alcohol aqueous solution before mixing is adjusted to a range of 60 to 80 ° C., it is easy to mix with the inorganic fine particle dispersion. If it is less than 60 degreeC, a viscosity will become high and it will become difficult to mix a high concentration inorganic fine particle uniformly. If the stirring is increased and mixed forcibly, fibrillation will occur due to the high viscosity of polyvinyl alcohol.

  On the other hand, the aqueous dispersion of inorganic fine particles having an average particle diameter of 1 μm or less is not particularly limited. The dried inorganic fine particles may be added to water for pulverization and dispersion, or the slurry-like inorganic fine particles may be pulverized and dispersed as they are. The concentration of the aqueous dispersion of inorganic fine particles is not particularly limited, but it is preferable to adjust the concentration within the range of 10% to 28%, preferably 15% to 25%. When the concentration is low, the adjustment of the coating solution is easy, but the concentration of the inorganic fine particles in the resulting coating solution is low, and it becomes difficult to form a coating layer having a large coating amount. When the concentration is high, it is difficult to adjust the aqueous dispersion of inorganic fine particles.

  By using inorganic fine particles having an average particle diameter of 1 μm or less, high print density and high smoothness can be obtained, but 800 nm or less is more preferable, and 500 nm or less is particularly preferable. Ultrafine particles having an average particle diameter of 500 nm or less can be obtained by pulverizing and dispersing commercially available pigments by mechanical means. It can also be produced by synthesizing silica by condensing activated silicic acid. Mechanical means include: ultrasonic homogenizer, pressure homogenizer, liquid collision homogenizer, high-speed rotary mill, roller mill, container drive medium mill, medium agitator mill, jet mill, mortar, disintegrator (covered in a bowl-shaped container) And a mechanical method such as a sand grinder or the like.

  The average particle diameter referred to in the present invention is a number average particle diameter, and in the case of secondary particles, it is a number average average secondary particle diameter. In addition, the average particle diameter in the case of containing a plurality of types of inorganic pigments refers to the average particle diameter of all inorganic pigments.

  The average primary particle size of the inorganic fine particles in the present invention is not particularly limited, but is preferably about 3 to 50 nm. The average pore diameter of the inorganic fine particles is not particularly limited, but is, for example, 20 nm or less, preferably 15 nm or less in terms of glossiness and printing density.

  Examples of inorganic fine particles having an average particle diameter of 1 μm or less used in the present invention include wet-process silica, gas-phase process silica, silica produced by condensing activated silicic acid, mesoporous silica, alumina, pseudo-boehmite, calcium carbonate, Among them, kaolin and the like are mentioned, and among them, wet-process silica, vapor-phase process silica, and silica produced by condensing activated silicic acid are preferable in terms of ink absorbability.

The wet process silica is manufactured using silicon dioxide (SiO ₂ ), mainly silica sand, as a raw material, and a typical manufacturing method is a gel method or a sedimentation method.
The gel method amorphous silica is produced, for example, as follows. First, silicate sol is produced by mixing sodium silicate and sulfuric acid using high-purity silica sand as a raw material. The silicic acid sol gradually polymerizes to form primary particles, and further, a three-dimensional aggregate is formed and gelled. This silica is micronized and pulverized. That is, in the gel method, reaction polymerization is performed on the acidic side, and the mixture is allowed to stand until it becomes a gel (sorbet shape), washed with water and dried to obtain an amorphous silica of the gel method.
The precipitated amorphous silica is obtained by reaction polymerization on the alkali side, sedimentation as it is, and drying. Gel silica has a small pore size between primary particles, and precipitated silica is large.

  Silica produced by condensing activated silicic acid, for example, after adding alkali to a dispersion having silica seed particles formed by heating the first activated silicic acid aqueous solution, further adding a second activated silicic acid aqueous solution Then, it is obtained by growing silica seed particles. The first active silicic acid aqueous solution and the second active silicic acid aqueous solution may be the same. The silica seed particles may be obtained by a method in which the first active silicic acid aqueous solution is dropped into hot water at 70 ° C. or higher.

No particular limitation is imposed on the rate of addition of the second active silicic acid aqueous solution, with respect to SiO ₂ 1 mole contained in the silica seed particles in terms of SiO ₂ 0.001 to 0.2 mol / min are preferred.

The first active silicic acid aqueous solution and the second active silicic acid aqueous solution are silicic acid having a pH of about 2 to 4 obtained by ion exchange treatment of a sodium silicate aqueous solution having a molar ratio of about 2 to 4 with a hydrogen cation exchange resin. An acid aqueous solution may be mentioned. The alkali metal silicate may be one that can be obtained as a commercial industrial product. In particular, sodium silicate having a molar ratio of SiO ₂ / M ₂ O (where M represents an alkali metal atom) of about 2 to 4 is used. Is preferred.
The first active silicic acid aqueous solution and the second active silicic acid aqueous solution are preferably 1 to 6% by mass, more preferably 2 to 5% by mass as the SiO ₂ concentration.
The concentration of the seed particles is preferably 0.05 to 10.0% by mass in terms of silica.

The amount of alkali added to the dispersion having silica seed particles is not particularly limited, but the amount of alkali necessary to make the pH of the dispersion 6.5 or more, more preferably pH 8 or more, more specifically silica. It is desirable that the amount of alkali is 1 × 10 ^{−3 to} 1.0 mol, more preferably 0.01 to 0.1 mol with respect to 1 mol of the silica component (SiO ₂ ) in the seed particles. Examples of the alkali include sodium hydroxide, potassium hydroxide, ammonium hydroxide and the like. Of these, ammonium hydroxide is preferable.

  Vapor phase process silica can make silicon tetrachloride as a raw material relatively high in purity by distillation, and can be manufactured by combustion hydrolysis of silicon tetrachloride in the gas phase using a closed system. It is possible to prevent contamination with impurities. For this reason, it is suitable for obtaining excellent transparency. Thus, high printing density and high gloss can be obtained by using high-purity gas phase method silica.

The specific surface area of these silicas is 50 to 500 m ² / g (according to the nitrogen adsorption method). If the specific surface area is less than 50 m ² / g, light scattering becomes strong, the transparency is lowered, and the recording density may be lowered. There is. Further, if it exceeds 500 meters ² / g, the ink absorbency is remarkably lowered, 200 to 400 m ² / g is more preferable.

  Moreover, it is desirable that the pore volume with a pore diameter of 100 nm or less is 0.4 to 2.0 ml / g. When the pore volume is less than 0.4 ml / g, the ink absorbency is inferior, and when the pore volume exceeds 2.0 ml / g, the mechanical strength is inferior. A nitrogen adsorption method was used to measure the pore volume and pore diameter.

  In the present invention, in particular, silica produced by condensing gel method silica or active silicic acid is preferable from the viewpoint of ink absorbability.

  The fluorescent whitening agent used in the present invention is a substance that absorbs a part of ultraviolet rays and converts it into visible blue light, erases the yellowishness of the object and makes it appear white. is there. Examples include stilbene, coumarin, oxazole, naphthalimide, carbostyril, and pyrazoline compounds, and have been used for whitening of various fibers and paper and pulp whitening for a long time. It is known that it is also blended into sucrose. The fluorescent whitening agent used in the present invention is not particularly limited, and known ones disclosed in JP-A-2004-50617, JP-A-2004-181714, JP-A-2004-50501, etc. Commercially available products such as Yakuhin, Clariant Japan, Ciba Geigy and Sumitomo Chemical can be used, but water-based stilbene or coumarin brighteners that are easy to add to paints are particularly preferred. Two or more fluorescent brighteners can be used in combination as required.

The content of the fluorescent brightening agent is preferably 0.01~0.2g / ^{m 2.} Most preferably, it is 0.03-0.15 g / m < ² >. If it is less than 0.01 g / m ² , the whitening effect is insufficient, and if it exceeds 0.2 g / m ² , the fluorescence intensity is decreased, which is not suitable.

  As means for increasing the whiteness or visual whiteness, a white pigment or a colored pigment can be used in combination with the fluorescent whitening agent. Examples of the white pigment include titanium oxide, zinc oxide, zinc sulfate, barium sulfate, and calcium carbonate, and examples of the colored pigment include ultramarine (ultraviolet), cobalt blue, cerulean blue, phthalocyanine blue, and dioxazine violet. . Phthalocyanine blue that exhibits a clear blue color and excellent light resistance is particularly preferred. However, if such a pigment is added too much, the absorbency is reduced, or even if it looks white at first glance, the whiteness and L * values are substantially reduced. It is.

  Examples of water-soluble salts used in the present invention include sodium sulfate, sodium chloride, sodium hydrogen sulfate, sodium nitrate, sodium acetate, sodium formate, sodium carbonate, sodium hydrogen carbonate, sodium dihydrogen phosphate, dihydrogen phosphate. Sodium, trisodium phosphate, sodium thiosulfate, potassium sulfate, potassium chloride, potassium hydrogen sulfate, potassium nitrate, potassium acetate, potassium formate, potassium carbonate, potassium hydrogen carbonate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, phosphoric acid Alkali metal salts such as tripotassium and potassium thiosulfate, calcium sulfate, calcium chloride, calcium nitrate, calcium acetate, calcium formate, calcium carbonate, calcium hydrogen phosphate, calcium dihydrogen phosphate, tricalcium phosphate, barium sulfate, chloride Alkaline earth metals such as barium, barium nitrate, barium acetate, barium formate, barium carbonate, barium hydrogen phosphate, barium dihydrogen phosphate, tribarium phosphate, magnesium sulfate, magnesium chloride, magnesium nitrate, magnesium acetate, magnesium carbonate Salt, manganese chloride, manganese acetate, manganese formate, cupric chloride, copper sulfate, cobalt chloride, nickel sulfate, nickel chloride, aluminum sulfate, aluminum sulfite, aluminum thiosulfate, polyaluminum chloride, aluminum nitrate, aluminum chloride, bromide Examples thereof include ferrous chloride, ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, zinc bromide, zinc chloride, zinc nitrate, and zinc sulfate. These water-soluble salts can be used alone or in combination of two or more.

  In particular, among these, alkali metal salts and alkaline earth metal salts can be easily mixed with water-based paints, and easily cause aggregation in the drying process after application of the water-based paint, so that the porous ink receiving layer of the present invention can be easily formed. Sodium salt, potassium salt or ammonium salt is preferably used because it can be obtained. Further, strong alkali metal salts, that is, hydrochlorides, sulfates, nitrates, and the like can be most preferably used because they can exist most stably in water-based paints and do not settle even in alkaline.

  The present invention is characterized in that an inorganic fine particle aqueous dispersion and a polyvinyl alcohol aqueous solution are mixed, a fluorescent brightening agent is mixed in a specific temperature range, and then the water-soluble salts are mixed. The content of polyvinyl alcohol in the inorganic fine particle coating solution is about 5 to 40% by weight, preferably 10 to 25% by weight, based on the inorganic fine particles, and the fluorescent brightening agent is 0.1 to 1% by weight. The water-soluble salts are preferably contained in a range of about 0.01 to 10% by mass, more preferably 0.05 to 5% by mass.

  The coating layer coated with the inorganic fine particle coating solution thus obtained is a uniform coating layer having high whiteness and no cracks or irregularities. This coating layer is excellent in the absorptivity of the ink for inkjet recording.

A known method can be adopted as the coating method, and it is not particularly limited. For example, there are a slide bead method, a curtain method, an extrusion method, an air knife method, a roll coating method, and a Ked bar coating method. Coating amount is not particularly limited, a dry weight, 3~60g / ^{m 2,} preferably 10 to 50 g / ^{m 2} approximately.

  In the inorganic fine particle coating solution, other pigments may be used in combination according to the purpose such as adjustment of transparency and absorbability of the ink receiving layer. In this case, it is preferable to mainly contain inorganic fine particles having an average particle diameter of 1 μm or less. Here, “mainly contained” means that the inorganic fine particles are contained in an amount of 50% by mass or more, particularly 60% by mass or more based on the total solid content of the ink receiving layer.

  Such pigments include titanium oxide, barium sulfate, kaolin, clay, calcined clay, silica, zinc oxide, aluminum oxide, aluminum hydroxide, calcium carbonate, satin white, aluminum silicate, alumina, colloidal silica, zeolite, and synthetic zeolite. , Sepiolite, smectite, synthetic smectite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, styrene plastic pigment, hydrotalcite, urea resin plastic pigment, benzoguanamine plastic pigment, etc. can do.

  Furthermore, in addition to polyvinyl alcohol, the coating solution may be blended with a binder known for coating layers of ink jet recording materials as long as the function of polyvinyl alcohol is not impaired. In that case, the addition amount of the other hydrophilic binder is preferably 20% by mass or less with respect to polyvinyl alcohol.

  Examples of such binders include soy protein, synthetic proteins, starch, cellulose derivatives such as carboxymethyl cellulose and methyl cellulose, or water-dispersible resins such as styrene-butadiene copolymer and methyl methacrylate-butadiene copolymer. Various known and commonly used adhesives in the field of coated paper, such as conjugated diene polymer latex, acrylic polymer latex, and vinyl copolymer latex such as styrene-vinyl acetate copolymer, etc. .

  In addition, various auxiliary agents such as a dispersant, a thickener, an antifoaming agent, an antistatic agent, and a corrosive agent that are generally used in the production of coated paper are appropriately added.

  The coating solution may contain a known ink fixing agent for an ink jet recording body. However, when the inorganic fine particles are silica, aggregation is likely to occur. Therefore, only a small amount is added, and another coating solution is applied later. It is good to apply on the work layer. In particular, it is preferable to provide a second coating layer containing an ink fixing agent on the coating layer coated with the inorganic fine particle coating solution.

  The second coating layer is a layer containing a pigment, an adhesive, and an ink fixing agent. As the pigment, those exemplified in the above-mentioned inorganic fine particle coating solution can be used, but vapor phase silica or alumina having an average particle diameter of 1 μm or less which is excellent in dispersibility is preferable. As the adhesive, known water-soluble binders such as the above-mentioned polyvinyl alcohol can be used.

As the ink fixing agent, a known material for an ink jet recording material can be used, and for example, a cationic compound can be exemplified. Examples of the cationic compound include 1) polyalkylene polyamines such as polyethylene polyamine and polypropylene polyamine or derivatives thereof, 2) acrylic polymers having secondary amino groups, tertiary amino groups, and quaternary ammonium groups, 3) Polyvinylamine and polyvinylamidines, 4) Dicyan-based cationic compounds represented by dicyandiamide / formalin copolymer, 5) Polyamine-based cationic compounds represented by dicyandiamide / polyethyleneamine copolymer, 6) Epichlorohydrin / dimethylamine copolymer, 7) diallyldimethylammonium -SO ₂ double condensate, 8) diallylamine salt -SO ₂ double condensate, 9) diallyldimethyl ammonium chloride polymers, 10) diallyldimethyl ammonium chloride Acrylamide copolymer, 11) Copolymer of allylamine salt, 12) Dialkylaminoethyl (meth) acrylate quaternary salt copolymer, 13) Acrylamide-diallylamine copolymer, 14) Cationic having 5-membered ring amidine structure Examples thereof include cationic compounds such as resins.

  When silica and an ink fixing agent are blended, they are prone to agglomerate, so silica and an ink fixing agent are mixed in advance, and the agglomerated particles are finely divided with a high-pressure pulverizer such as a pressure homogenizer, ultrasonic homogenizer, microfluidizer, or nanomizer. It is good to adjust to the shape.

  Further, a gloss layer containing a colloidal pigment may be further provided on the second coating layer. Layers such as an undercoat layer, an intermediate layer, and an overcoat layer may be provided between each layer or in the outermost layer.

  The support of the ink-receiving layer used in the present invention is not particularly limited with respect to its type, shape, dimensions, transparency / opacity, etc., but from the viewpoint of cockling after printing or photographic texture. A non-absorbent substrate is preferred, and in the case of an absorbent support, it is preferred that the paper thickness and sizing degree are higher.

  Examples of the absorbent support include fine paper, medium paper, coated paper, art paper, and cast coated paper. Examples of the non-absorbent support include plastic films such as polyethylene terephthalate, polyvinyl chloride, polycarbonate, polyethylene, and polypropylene, synthetic paper, and white films. Further, a non-absorbent resin-coated sheet obtained by coating these supports with a non-ink medium absorbent resin may be used. As the non-ink medium-absorbing resin, a polyolefin resin such as polyethylene and polypropylene, a cellulose diacetate resin, a polyester resin, or a mixture thereof can be used as a main component. It is preferable because of good adhesion, and polyethylene is particularly preferable.

  In addition, in the resin of the non-ink medium absorbing resin to be coated, white pigments such as titanium oxide, zinc oxide, talc and calcium carbonate, fatty acid amides such as stearic acid amide and arachidic acid amide, zinc stearate, calcium stearate, Fatty acid metal salts such as aluminum stearate and magnesium stearate, antioxidants such as Irganox 1010 and Irganox 1076, blue pigments and dyes such as cobalt blue, ultramarine blue, cecilian blue, and phthalocyanine blue, cobalt violet, fast violet, It is preferable to add various additives such as magenta pigments and dyes such as manganese purple, fluorescent brighteners and ultraviolet absorbers in appropriate combinations.

  The resin coating is produced by, for example, a so-called extrusion coating method in which a polyolefin resin is cast on a traveling support in a heated and melted state, and both surfaces thereof are coated with the resin. Further, before the resin is coated on the support, it is preferable to subject the support to an activation treatment such as corona discharge treatment or flame treatment. Although it is not necessary to coat the resin on the back surface, it is preferable to coat the resin from the viewpoint of curling prevention. The back surface is usually a matte surface, and an active treatment such as corona discharge treatment or flame treatment can be applied to the front surface or both the front and back surfaces as required. Moreover, there is no restriction | limiting in particular as the thickness of the resin coating layer, but it is generally coated on the surface or both sides of the surface to a thickness of 5 to 50 μm.

  In addition, the surface of the support on which the ink receiving layer is formed may be subjected to an adhesion treatment or an adhesion treatment in advance for the purpose of improving the adhesion between the support and the ink receiving layer. In particular, when resin-coated paper is used as the non-absorbent support, it is preferable to subject the surface of the resin coating layer to corona discharge treatment or to provide an undercoat layer made of gelatin, polyvinyl alcohol or the like.

  Various back coat layers can be coated on the support used in the present invention for antistatic properties, transport properties, anticurling properties, and the like. The backcoat layer can contain an appropriate combination of inorganic antistatic agent, organic antistatic agent, hydrophilic binder, latex, curing agent, pigment, surfactant and the like.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Moreover, unless otherwise indicated, the part and% in an example are solid content except water, and show a mass part and mass%, respectively.
In the examples, the specific surface area, pore volume, pore diameter, and average particle diameter of the inorganic fine particles are values obtained as follows.

[Measurement method of specific surface area, pore volume and pore diameter of inorganic fine particles]
The sample was dried, and the specific surface area, pore volume, and pore diameter were measured using a gas adsorption method specific surface area / pore distribution measuring apparatus (SA3100plus type manufactured by Coulter). As the pore volume, the total pore volume value of pores having a pore diameter of 100 nm or less was used. The pore diameter was defined as the pore diameter of the maximum volume fraction in the pore distribution curve obtained from the analysis of the desorption isotherm.

[Measurement method of average particle size of inorganic fine particles]
Measurement was performed using a laser particle size distribution meter (trade name: LPA3000 / 3100, manufactured by Otsuka Electronics Co., Ltd.) by a dynamic light scattering method in a state where the aqueous dispersion of inorganic fine particles was sufficiently diluted with distilled water. As the average particle size, a value calculated from an analysis using a cumulant method was used.

[Create support]
"Base paper"
A ratio of 2: 8 by weight between softwood bleached kraft pulp (NBKP) beaten to 250 ml of Canadian standard freeness (JIS P8121) and hardwood bleached kraft pulp (LBKP) beaten to Canadian standard freeness of 280 ml Were mixed to prepare a pulp slurry having a concentration of 0.5%. In this pulp slurry, cationized starch 2.0%, alkyl ketene dimer 0.4%, anionized polyacrylamide resin 0.1%, polyamide polyamine epichlorohydrin resin 0.7% is added to the pulp dry mass, and sufficient Stirred and dispersed. The pulp slurry having the above composition was made with a long net machine and passed through a dryer, a size press, and a machine calendar to produce a base paper having a basis weight of 180 g / m ² and a tenacity of 1.0 g / cm ³ . The size press solution used in the size press step was prepared by mixing carboxyl-modified polyvinyl alcohol and sodium chloride at a mass ratio of 2: 1, adding this to water and dissolving it by heating to a concentration of 5%. A size press solution was applied in a total of 25 cc on both sides of the paper to obtain a base paper.

"Polyolefin resin composition 1"
35 parts by mass of long-chain low-density polyethylene resin (density 0.926 g / cm ³ , melt index 20 g / 10 min), 50 parts by mass of low-density polyethylene resin (density 0.919 g / cm ³ , melt index 2 g / 10 min) , 15 parts by mass of anatase-type titanium dioxide (Ishihara Sangyo Co., Ltd., trade name: A-220), 0.1 parts by mass of zinc stearate, 0.03 parts by mass of antioxidant (manufactured by Ciba Geigy, trade name: Irganox 1010), Ultramarine (Daiichi Kasei Co., Ltd., trade name: Aoguchi Ultramarine No. 2000) 0.09 parts by mass, fluorescent whitening agent (Ciba Geigy, trade name: UVITEX OB) 0.3 parts by mass are mixed with a Banbury mixer. Dispersed to obtain polyolefin resin composition 1.

"Polyolefin resin composition 2"
65 parts by mass of high density polyethylene resin (density 0.954 g / cm ³ , melt index 20 g / 10 min) and 35 parts by mass of low density polyethylene resin (density 0.924 g / cm ³ , melt index 4 g / 10 min) A polyolefin resin composition 2 was obtained by mixing and dispersing with a mixer.

"Production of non-permeable substrates"
After performing corona discharge treatment on both sides of the base paper, the polyolefin resin composition 1 is applied to the felt side of the base paper so that the coating amount is 27 g / m ^2, and the polyolefin resin composition 2 (resin for back side) The composition) is applied to the wire side of the base paper so that the coating amount is 30 g / m ^2, and is applied with a melt extruder (melting temperature 320 ° C.) having a T-shaped die. Cooling roll, solidified by cooling the wire side with a rough surface cooling roll, smooth coated (Oken type, J.TAPPI No. 5) for 6000 seconds, opacity (JIS P8138) 93% resin coated support The body was manufactured.

Example 1
[Preparation of aqueous dispersion (A) of inorganic fine particles]
(Preparation of first active silicic acid aqueous solution)
Distilled water was mixed with a sodium silicate solution (No. 3 sodium silicate, manufactured by Tokuyama Corporation) having a SiO ₂ concentration of 30 mass% and a SiO ₂ / Na ₂ O molar ratio of 3.1, and a SiO ₂ concentration of 4.0 mass. % Dilute aqueous sodium silicate solution was prepared. This aqueous solution was passed through a column packed with a hydrogen-type cation exchange resin [manufactured by Mitsubishi Chemical Corporation, Diaion SK-1BH] to prepare a first active silicic acid aqueous solution. The SiO ₂ concentration in the first active silicic acid aqueous solution was 4.0% by mass, and the pH was 2.9.

(Preparation of second active silicic acid aqueous solution)
The same thing as the 1st active silicic acid aqueous solution was prepared as 2nd active silicic acid aqueous solution.

(Preparation of seed solution)
In a 5 liter glass reaction vessel equipped with a reflux, a stirrer, and a thermometer, 500 g of distilled water was heated to 100 ° C. While maintaining this hot water at 100 ° C., a total of 450 g of the first active silicic acid aqueous solution was added at a rate of 1.5 g / min to prepare a seed solution. The physical properties of the seed particle aggregate in the seed solution were an average particle diameter of 184 nm, a specific surface area of 832 m ² / g, a pore volume of 0.60 ml / g, and a pore diameter of 4 nm.

(Preparation of inorganic fine particle dispersion (A))
In the glass reaction vessel, 0.015 mol of ammonia was added to 950 g of the seed solution to stabilize it, and the mixture was heated to 100 ° C. A total of 550 g of the second active silicic acid aqueous solution was added to the seed solution at a rate of 1.5 g / min. After completion of the addition of the second aqueous active silicic acid solution, the solution was kept at 100 ° C. and heated to reflux for 9 hours to obtain an amorphous silica dispersion. The dispersion was a bluish clear solution with a pH of 7.2. The amorphous silica dispersion had an average particle diameter of 100 nm, a specific surface area of 240 m ² / g, a pore volume of 0.67 ml / g, and a pore diameter of 12 nm. This dispersion was concentrated with an evaporator to a silica concentration of 20% to obtain a dispersion (A) of inorganic fine particles.

[Preparation of aqueous polyvinyl alcohol solution]
Polyvinyl alcohol (manufactured by Kuraray Co., Ltd., trade name: PVA140) was heated and dissolved at 95 ° C. so as to be an 8% aqueous solution, kept at 90 ° C. or higher for 2 hours, and then cooled to 70 ° C.

[Preparation of coating solution for inorganic fine particles]
Further, 195 parts of an 8% aqueous polyvinyl alcohol solution having a liquid temperature of 65 ° C. after cooling was stirred with 500 parts of a 20% amorphous silica aqueous dispersion (liquid temperature 26 ° C.), which is a dispersion of inorganic fine particles (A). While mixing gradually. The liquid temperature after mixing was about 40 ° C. Next, 10 parts of a 10% aqueous solution of a fluorescent brightener (manufactured by Sumika Chemtex, Whitex BPS) was gradually added and stirred for 10 minutes. Then, after cooling to 28 ° C., 4 parts of 5% potassium chloride aqueous solution was gradually added and stirred and cooled for 30 minutes until the temperature reached 26 ° C. to prepare a coating solution having a concentration of 16% to obtain an inorganic fine particle coating solution.

[Formation of inorganic fine particle coating layer]
The obtained inorganic fine particle coating solution is applied to the above support using a die coater so that the dry coating amount is 20 g / m ^2, and the coating after drying is performed using hot air at 120 ° C. using a hot air dryer. The coating surface of inorganic fine particles was formed by drying so that the surface temperature of the surface to be worked was 80 ° C. or higher and the coating surface was not disturbed by hot air.

[Preparation of inkjet recording material]
(Preparation of cationic silica sol)
Commercially available vapor phase silica (manufactured by Tokuyama Corporation, trade name: Leolosil QS-30, specific surface area 300 m ² / g, average primary particle size: about 10 nm) was pulverized and dispersed with a sand grinder, and then nanomizer (manufactured by Nanomizer) was used. Then, pulverization and dispersion were repeated, and a 10% dispersion having an average secondary particle size of 80 nm after classification was prepared.
Next, 10 parts of a cationic compound having a 5-membered ring amidine structure (trade name: SC-700M, manufactured by Hymo Co., Ltd.) was added to cause aggregation of the pigment and thickening of the dispersion. Again, pulverization and dispersion were repeated using a nanomizer to prepare a 10% aqueous solution having an average secondary particle diameter (aggregated particle diameter) of 250 nm, thereby obtaining a cationic silica sol.

(Formation of second coating layer)
A 0.5% borax aqueous solution was applied onto the inorganic fine particle coating layer so that the coating amount was 0.15 g / m ^2, and polyvinyl alcohol (trade name, manufactured by Kuraray Co., Ltd.) was added to 100 parts of the cationic silica sol. : PVA140) 18 parts are mixed and the coating solution prepared to a concentration of 8% is applied and dried under the conditions of Wet on Wet so that the coating amount is 5 g / m ² , thereby forming a second coating layer. An ink jet recording material was obtained.

Comparative Example 1
[Preparation of aqueous dispersion (A) of inorganic fine particles]
In the same manner as in Example 1, an aqueous dispersion (A) of inorganic fine particles was obtained.
[Preparation of aqueous polyvinyl alcohol solution]
After preparation in the same manner as in Example 1, an 8% aqueous polyvinyl alcohol solution at 90 ° C. was obtained without cooling.

[Preparation of coating solution for inorganic fine particles]
To 195 parts of an 8% aqueous polyvinyl alcohol solution having a liquid temperature of 90 ° C., 500 parts of a 20% amorphous silica aqueous dispersion (liquid temperature of 26 ° C.), which is a dispersion of inorganic fine particles (A), was gradually mixed with stirring. . The liquid temperature after mixing was about 67 ° C. Next, 10 parts of a 10% aqueous solution of a fluorescent brightener (manufactured by Sumika Chemtex, Whitex BPS) was gradually added and stirred for 10 minutes. Then, after cooling to 50 ° C., 4 parts of 5% potassium chloride aqueous solution was gradually added and stirred and cooled for 120 minutes until the temperature reached 30 ° C. to prepare a coating solution having a concentration of 16%, thereby obtaining an inorganic fine particle coating solution.

[Formation of inorganic fine particle coating layer]
In the same manner as in Example 1, a coating layer of inorganic fine particles was formed.
[Preparation of inkjet recording material]
An ink jet recording material was prepared in the same manner as in Example 1.

Comparative Example 2
[Preparation of aqueous dispersion (A) of inorganic fine particles]
In the same manner as in Example 1, an aqueous dispersion (A) of inorganic fine particles was obtained.
[Preparation of aqueous polyvinyl alcohol solution]
Polyvinyl alcohol (manufactured by Kuraray Co., Ltd., trade name: PVA140) was heated and dissolved at 95 ° C. so as to be an 8% aqueous solution, kept at 90 ° C. or higher for 2 hours, and then cooled to 50 ° C.

[Preparation of coating solution for inorganic fine particles]
To 195 parts of an 8% aqueous polyvinyl alcohol solution cooled to a liquid temperature of 50 ° C., 500 parts of a 20% amorphous silica aqueous dispersion (liquid temperature of 26 ° C.), which is a dispersion of inorganic fine particles (A), is gradually mixed with stirring. did. The liquid temperature after mixing was about 27 ° C. Next, 10 parts of a 10% aqueous solution of a fluorescent brightener (manufactured by Sumika Chemtex, Whitex BPS) was gradually added and stirred for 10 minutes. Further, 4 parts of a 5% potassium chloride aqueous solution was gradually added, and the mixture was stirred and cooled for 30 minutes until the temperature reached 25 ° C., thereby preparing a coating solution having a concentration of 16% to obtain an inorganic fine particle coating solution.

[Formation of inorganic fine particle coating layer]
In the same manner as in Example 1, a coating layer of inorganic fine particles was formed.
[Preparation of inkjet recording material]
An ink jet recording material was prepared in the same manner as in Example 1.

Example 2
[Preparation of aqueous dispersion (B) of inorganic fine particles]
In the same manner as in Example 1, a first active silicic acid aqueous solution and a second active silicic acid aqueous solution were obtained.
(Preparation of seed solution)
In a 5 liter glass reaction vessel equipped with a reflux, a stirrer, and a thermometer, 400 g of the first active silicic acid aqueous solution was heated to 100 ° C. at a rate of 2 ° C./minute, and then at 100 ° C. for 40 minutes. The seed solution was prepared. The physical properties of the seed particle aggregate in the seed solution were an average particle size of 113 nm, a specific surface area of 480 m ² / g, a pore volume of 0.91 ml / g, and a pore size of 7 nm.
(Preparation of inorganic fine particle dispersion (B))
In the glass reaction vessel, 0.1 mol of ammonia was added to 400 g of the seed solution to stabilize, and the mixture was heated to 100 ° C. A total of 600 g of the second active silicic acid aqueous solution was added to the seed solution at a rate of 1.5 g / min. After completion of the addition of the second active silicic acid, the solution was kept as it was at 100 ° C. and heated to reflux for 9 hours to obtain a dispersion of amorphous silica. The pH of the dispersion was 6.7. The amorphous silica dispersion had an average particle size of 106 nm, a specific surface area of 268 m ² / g, a pore volume of 0.76 ml / g, and a pore size of 12 nm. This dispersion was concentrated with an evaporator to a silica concentration of 20% to obtain a dispersion (B) of inorganic fine particles.
[Preparation of aqueous polyvinyl alcohol solution]
In the same manner as in Example 1, an 8% aqueous polyvinyl alcohol solution at 70 ° C. was obtained.

[Preparation of coating solution for inorganic fine particles]
Further, 195 parts of an 8% aqueous solution of polyvinyl alcohol having a liquid temperature of 65 ° C. was stirred with 500 parts of a 20% amorphous silica aqueous dispersion (liquid temperature 26 ° C.), which is a dispersion of inorganic fine particles (B). While mixing gradually. The liquid temperature after mixing was about 40 ° C. Next, 10 parts of a 10% aqueous solution of a fluorescent brightener (manufactured by Sumika Chemtex, Whitex BPS) was gradually added and stirred for 10 minutes. Then, after cooling to 28 ° C., 4 parts of 5% potassium chloride aqueous solution was gradually added, and the mixture was stirred and cooled for 30 minutes until it became 26 ° C. to prepare a coating solution having a concentration of 16%, thereby obtaining an inorganic fine particle coating solution. .

[Formation of inorganic fine particle coating layer]
In the same manner as in Example 1, a coating layer of inorganic fine particles was formed.
[Preparation of inkjet recording material]
An ink jet recording material was prepared in the same manner as in Example 1.

Example 3
[Preparation of aqueous dispersion (C) of inorganic fine particles]
In the same manner as in Example 1, a first active silicic acid aqueous solution and a second active silicic acid aqueous solution were obtained.
(Preparation of seed solution)
In a 5 liter glass reaction vessel equipped with a reflux, a stirrer, and a thermometer, 200 g of distilled water was heated to 100 ° C. While maintaining this hot water at 100 ° C., a total of 256 g of the first active silicic acid aqueous solution was added at a rate of 4.3 g / min to prepare a seed solution.
(Preparation of inorganic fine particle dispersion (C))
In the glass reaction vessel, 0.025 mol of ammonia was added to 456 g of the seed solution, stabilized, and heated to 100 ° C. A total of 1044 g of the second active silicic acid aqueous solution was added to the seed solution at a rate of 4.3 g / min. After completion of the addition of the second aqueous active silicic acid solution, the solution was kept at 100 ° C. and heated to reflux for 6 hours to obtain an amorphous silica dispersion. The dispersion was a bluish clear solution with a pH of 8.5. The amorphous silica dispersion had an average particle size of 110 nm, a specific surface area of 170 m ² / g, a pore volume of 0.65 ml / g, and a pore size of 14 nm. This dispersion was concentrated with an evaporator to a silica concentration of 20% to obtain a dispersion (C) of inorganic fine particles.
[Preparation of aqueous polyvinyl alcohol solution]
In the same manner as in Example 1, an 8% aqueous polyvinyl alcohol solution at 70 ° C. was obtained.

[Preparation of coating solution for inorganic fine particles]
Further, 195 parts of an 8% aqueous solution of polyvinyl alcohol having a liquid temperature of 65 ° C. cooled to 500 parts of a 20% amorphous silica aqueous dispersion (liquid temperature 26 ° C.), which is a dispersion of inorganic fine particles (C), was stirred. Mix slowly. The liquid temperature after mixing was about 40 ° C. Next, 10 parts of a 10% aqueous solution of a fluorescent brightener (manufactured by Sumika Chemtex, Whitex BPS) was gradually added and stirred for 10 minutes. Then, after cooling to 28 ° C., 4 parts of 5% potassium chloride aqueous solution was gradually added, and the mixture was stirred and cooled for 30 minutes until it became 26 ° C. to prepare a coating solution having a concentration of 16%, thereby obtaining an inorganic fine particle coating solution. .

[Formation of inorganic fine particle coating layer]
In the same manner as in Example 1, a coating layer of inorganic fine particles was formed.
[Preparation of inkjet recording material]
An ink jet recording material was prepared in the same manner as in Example 1.

Example 4
[Preparation of aqueous dispersion (D) of inorganic fine particles]
Synthetic amorphous silica (produced by Grace Devison, trade name: Silojet P612, specific surface area 290 m ² / g, primary particle size 9 nm) produced by the gel method and dispersed in water at a concentration of 20%. Then, the slurry whose pH was adjusted to 9.0 by adding ammonia water was repeatedly pulverized and dispersed by a horizontal bead mill (Dynomill KDL-Pilot, manufactured by Shinmaru Enterprises Co., Ltd.), and 20% of the average secondary particle size of 300 nm. An aqueous silica dispersion was produced. The pore volume of this silica was 0.70 ml / g. This silica dispersion was used as an aqueous dispersion (D) of inorganic fine particles.
[Preparation of aqueous polyvinyl alcohol solution]
Polyvinyl alcohol (manufactured by Kuraray Co., Ltd., trade name: PVA140) was heated and dissolved at 95 ° C. so as to be an 8% aqueous solution, kept at 90 ° C. or higher for 2 hours, and then cooled to 80 ° C.

[Preparation of coating solution for inorganic fine particles]
To 195 parts of an 8% aqueous polyvinyl alcohol solution having a liquid temperature of 80 ° C., 500 parts of a 20% amorphous silica aqueous dispersion (liquid temperature 26 ° C.), which is a dispersion of inorganic fine particles (D), is gradually mixed with stirring. did. The liquid temperature after mixing was about 45 ° C. Next, 10 parts of a 10% aqueous solution of a fluorescent brightener (manufactured by Sumika Chemtex, Whitex BPS) was gradually added and stirred for 10 minutes. Then, after cooling to 30 ° C., 3 parts of a 5% sodium chloride aqueous solution was gradually added, and the mixture was stirred and cooled for 30 minutes until it reached 27 ° C. to prepare a coating solution having a concentration of 16%, thereby obtaining an inorganic fine particle coating solution. .

[Formation of inorganic fine particle coating layer]
In the same manner as in Example 1, a coating layer of inorganic fine particles was formed.
[Preparation of inkjet recording material]
An ink jet recording material was prepared in the same manner as in Example 1.

Example 5
[Preparation of aqueous dispersion (E) of inorganic fine particles]
Synthetic amorphous silica (produced by Grace Devison, trade name: Silojet 703A (20% aqueous dispersion)) having an average particle diameter of about 300 nm produced by the gel method was used as an aqueous dispersion (E) of inorganic fine particles. The properties of this silica dispersion were a specific surface area of 270 m ² / g, a pore volume of 0.70 ml / g, a primary particle diameter of 10 nm, and a pore diameter of 14 nm.
[Preparation of aqueous polyvinyl alcohol solution]
In the same manner as in Example 4, an 8% aqueous polyvinyl alcohol solution at 70 ° C. was obtained.

[Preparation of coating solution for inorganic fine particles]
To 195 parts of an 8% aqueous polyvinyl alcohol solution having a liquid temperature of 80 ° C., 500 parts of a 20% amorphous silica aqueous dispersion (liquid temperature 26 ° C.), which is a dispersion of inorganic fine particles (E), is gradually mixed with stirring. did. The liquid temperature after mixing was about 45 ° C. Next, 10 parts of a 10% aqueous solution of a fluorescent brightener (manufactured by Sumika Chemtex, Whitex BPS) was gradually added and stirred for 10 minutes. Then, after cooling to 29 ° C., 2 parts of a 10% aqueous sodium chloride solution was gradually added, and stirred and cooled for 30 minutes until the temperature reached 27 ° C. to prepare a coating solution having a concentration of 16%, thereby obtaining an inorganic fine particle coating solution. .

[Formation of inorganic fine particle coating layer]
In the same manner as in Example 1, a coating layer of inorganic fine particles was formed.
[Preparation of inkjet recording material]
An ink jet recording material was prepared in the same manner as in Example 1.

Example 6
[Preparation of aqueous dispersion (A) of inorganic fine particles]
In the same manner as in Example 1, an aqueous dispersion (A) of inorganic fine particles was obtained.
[Preparation of aqueous polyvinyl alcohol solution]
In the same manner as in Example 1, an 8% aqueous polyvinyl alcohol solution at 70 ° C. was obtained.

[Preparation of coating solution for inorganic fine particles]
An inorganic fine particle coating solution is obtained in the same manner as in Example 1 except that 15 parts of 10% aqueous solution of Kayahol JB Liq manufactured by Nippon Kayaku Co., Ltd. is used instead of 10 parts of 10% aqueous solution of Whitex BPS manufactured by Sumika Chemtex Co., Ltd. It was.

[Formation of inorganic fine particle coating layer]
In the same manner as in Example 1, a coating layer of inorganic fine particles was formed.
[Preparation of inkjet recording material]
An ink jet recording material was prepared in the same manner as in Example 1.

Comparative Example 3
[Preparation of aqueous dispersion (A) of inorganic fine particles]
In the same manner as in Example 1, an aqueous dispersion (A) of inorganic fine particles was obtained.
[Preparation of aqueous polyvinyl alcohol solution]
In the same manner as in Example 1, an 8% aqueous polyvinyl alcohol solution at 70 ° C. was obtained.

[Preparation of coating solution for inorganic fine particles]
Further, 195 parts of an 8% aqueous polyvinyl alcohol solution having been cooled to a liquid temperature of 65 ° C. and 500 parts of an aqueous dispersion of 20% inorganic fine particle dispersion (A) obtained by adding 4 parts of an aqueous 5% potassium chloride solution (liquid temperature 26 C.) was gradually mixed with stirring. The liquid temperature after mixing was about 40 ° C. Next, 10 parts of a 10% aqueous solution of a fluorescent brightener (manufactured by Sumika Chemtex, Whitex BPS) was gradually added and stirred for 10 minutes. Thereafter, it was cooled to 30 ° C. to prepare a coating solution having a concentration of 16%, and an inorganic fine particle coating solution was obtained.

[Formation of inorganic fine particle coating layer]
In the same manner as in Example 1, a coating layer of inorganic fine particles was formed.
[Preparation of inkjet recording material]
An ink jet recording material was prepared in the same manner as in Example 1.

Comparative Example 4
[Preparation of aqueous dispersion (A) of inorganic fine particles]
In the same manner as in Example 1, an aqueous dispersion (A) of inorganic fine particles was obtained.
[Preparation of aqueous polyvinyl alcohol solution]
In the same manner as in Example 1, an 8% aqueous polyvinyl alcohol solution at 70 ° C. was obtained.

[Preparation of coating solution for inorganic fine particles]
To 195 parts of an aqueous 8% polyvinyl alcohol solution having a liquid temperature of 70 ° C., 500 parts of a 20% amorphous silica aqueous dispersion (liquid temperature of 26 ° C.), which is a dispersion of inorganic fine particles (A), was gradually mixed with stirring. . The liquid temperature after mixing was about 45 ° C. Subsequently, 4 parts of a 5% aqueous sodium chloride solution was gradually added and stirred for 20 minutes. After cooling to 29 ° C, 10 parts of a 10% aqueous solution of fluorescent brightener (manufactured by Sumika Chemtex Co., Ltd., Whitetex BPS) is gradually added and stirred and cooled for 30 minutes until the temperature reaches 27 ° C. And an inorganic fine particle coating solution was obtained.

[Formation of inorganic fine particle coating layer]
In the same manner as in Example 1, a coating layer of inorganic fine particles was formed.
[Preparation of inkjet recording material]
An ink jet recording material was prepared in the same manner as in Example 1.

Comparative Example 5
[Preparation of aqueous dispersion (F) of inorganic particles]
Synthetic amorphous silica (trade name: Mizukasil P-527, specific surface area 55 m ² / g, pore volume 0.08 ml / g, pore diameter 7 nm, manufactured by Mizusawa Chemical Industry Co., Ltd.) produced by a sedimentation method. ) Was dispersed in water at a concentration of 20%. This silica dispersion was used as an aqueous dispersion (F) of inorganic particles.
[Preparation of aqueous polyvinyl alcohol solution]
In the same manner as in Example 1, an 8% aqueous polyvinyl alcohol solution at 70 ° C. was obtained.

[Preparation of coating solution for inorganic fine particles]
To 195 parts of an 8% aqueous polyvinyl alcohol solution having a liquid temperature of 65 ° C., 500 parts of a 20% amorphous silica aqueous dispersion (liquid temperature 26 ° C.), which is a dispersion of inorganic particles (F), is gradually mixed with stirring. did. The liquid temperature after mixing was about 40 ° C. Next, 10 parts of a 10% aqueous solution of a fluorescent brightener (manufactured by Sumika Chemtex, Whitex BPS) was gradually added and stirred for 10 minutes. Then, after cooling to 28 ° C., 4 parts of 5% aqueous potassium chloride solution was added and stirred and cooled for 30 minutes until the temperature reached 26 ° C. to prepare a coating solution having a concentration of 16% to obtain an inorganic fine particle coating solution.

[Formation of inorganic fine particle coating layer]
In the same manner as in Example 1, a coating layer of inorganic fine particles was formed.
[Preparation of inkjet recording material]
An ink jet recording material was prepared in the same manner as in Example 1.

Comparative Example 6
[Preparation of aqueous dispersion (A) of inorganic fine particles]
In the same manner as in Example 1, an aqueous dispersion (A) of inorganic fine particles was obtained.
[Preparation of aqueous polyvinyl alcohol solution]
A polyvinyl alcohol aqueous solution was obtained in the same manner as in Example 1 except that polyvinyl alcohol having a polymerization degree of 1700 (trade name: PVA117, manufactured by Kuraray Co., Ltd.) was used instead of polyvinyl alcohol having a polymerization degree of 4000.

[Preparation of coating solution for inorganic fine particles]
An inorganic fine particle coating solution was obtained in the same manner as in Example 1 except that a polyvinyl alcohol aqueous solution having a polymerization degree of 1700 was used.
[Formation of inorganic fine particle coating layer]
In the same manner as in Example 1, a coating layer of inorganic fine particles was formed.
[Preparation of inkjet recording material]
An ink jet recording material was prepared in the same manner as in Example 1.

Comparative Example 7
[Preparation of aqueous dispersion (A) of inorganic fine particles]
In the same manner as in Example 1, an aqueous dispersion (A) of inorganic fine particles was obtained.
[Preparation of aqueous polyvinyl alcohol solution]
In the same manner as in Example 1, an 8% aqueous polyvinyl alcohol solution at 70 ° C. was obtained.

[Preparation of coating solution for inorganic fine particles]
Further, 195 parts of an 8% aqueous polyvinyl alcohol solution having a liquid temperature of 65 ° C. after cooling was stirred with 500 parts of a 20% amorphous silica aqueous dispersion (liquid temperature 26 ° C.), which is a dispersion of inorganic fine particles (A). While mixing gradually. The liquid temperature after mixing was about 40 ° C. Then, after cooling to 28 ° C., 4 parts of 5% potassium chloride aqueous solution was gradually added, and the mixture was stirred and cooled for 30 minutes until it became 26 ° C. to prepare a coating solution having a concentration of 16%, thereby obtaining an inorganic fine particle coating solution. .

[Formation of inorganic fine particle coating layer]
In the same manner as in Example 1, a coating layer of inorganic fine particles was formed.
[Preparation of inkjet recording material]
An ink jet recording material was prepared in the same manner as in Example 1.

[Evaluation]
The following evaluation was performed about the coating layer in the case of manufacture, and the obtained inkjet recording material.
"Evaluation of coating layer"
The obtained coating layer was viewed obliquely, and the surface quality was determined according to the following criteria. The results are shown in Table 1.
○: No defects are observed, and the surface quality is good.
Δ: There are some spots.
X: Cracks and bumps are seen as a whole and the surface quality is poor.

"Glossiness"
The glossiness of the coated surface of the ink jet recording material was visually evaluated.
○: Glossiness similar to that of a silver salt photograph Δ: Slightly dull glossiness
×: Matte tone

"Ink absorbability"
The ink jet recording medium was green solid printed with a dye ink printer (trade name: PM-950C, PM photographic paper mode) manufactured by Epson Corporation, and the ink absorbability (whether there was no unevenness or uniformity) was visually evaluated.
○: Unevenness is not seen.
Δ: Unevenness is observed, but there is no problem in practical use.
X: Unevenness is noticeable.

"Whiteness"
According to the measuring method (ISO 2470) of whiteness, it was measured with a color difference meter (manufactured by Suga Test Instruments, spectral whiteness colorimeter SC-10WN, C light source, 2 ° visual field).

Evaluation results The evaluation results are shown in Table 1. As shown in Table 1, all of the coating layers of Examples 1 to 6 had a smooth surface. Furthermore, the ink-jet recording material provided up to the second coating layer had good ink absorbability.
On the other hand, the coating surface of Comparative Example 1 to which the fluorescent whitening agent was added at 67 ° C. had spots. An ink jet recording material was prepared by providing a second coating layer, but glossiness similar to silver salt photographs was not obtained.
The coating surface of the comparative example 2 which added the fluorescent whitening agent at 27 degreeC showed the spot in some places. An ink jet recording material was prepared by providing a second coating layer, but glossiness similar to silver salt photographs was not obtained.
In the case of Comparative Example 3 in which a water-soluble salt was previously mixed with a silica dispersion, when the fluorescent whitening agent was mixed, the coated surface was found to be fuzzy.
In Comparative Example 4 in which a water-soluble salt was added and then a fluorescent brightening agent was mixed, the coated surface was also found to be rough.
In Comparative Example 5, the coated surface was matte and the pore volume was small due to the large particle size of the inorganic particles, so the ink absorbability was poor and unevenness was observed on the printed surface.
In Comparative Example 6, dry cracks occurred on the coated surface.
Comparative Example 7 containing no optical brightener had poor visual whiteness and low whiteness.

Claims (6)

In the method for producing an ink jet recording material having a coating layer containing inorganic fine particles on a support, the coating layer comprises an inorganic fine particle aqueous dispersion having an average secondary particle size of 1 μm or less, and a polymerization degree of 2000 or more. It was obtained by mixing with an aqueous solution of polyvinyl alcohol, mixing the fluorescent whitening agent in a state where the mixed solution was 30 ° C. or more and 65 ° C. or less, and then coating and drying an inorganic fine particle coating solution mixed with water-soluble salts. A method for producing an ink jet recording material, comprising a layer. 2. The method for producing an ink jet recording material according to claim 1, wherein the optical brightener is a stilbene compound. The method for producing an ink jet recording material according to claim 1, wherein the inorganic fine particles have an average secondary particle diameter of 0.5 μm or less and 0.01 μm or more. 4. The method according to claim 1, wherein the inorganic fine particles are at least one selected from wet process silica, gas phase process silica, silica produced by condensing activated silicic acid, and mesoporous silica. The manufacturing method of the inkjet recording body of description. The method for producing an ink jet recording material according to any one of claims 1 to 4, wherein the water-soluble salt is a sodium salt, a potassium salt or an ammonium salt. The method for producing an inkjet recording material according to claim 1, wherein a second coating layer having a pigment, an adhesive, and a cationic compound is formed on the coating layer.