JP4490256B2 - Inkjet recording medium and method for producing the same - Google Patents

Description

  The present invention relates to an ink jet recording medium, and more particularly to an ink jet recording medium excellent in surface strength of an ink receiving layer, particularly in wet surface strength, and a method for producing the same.

  Inkjet recording method is a method of recording characters, images, etc. by ejecting ink droplets from nozzles and landing and fixing them on the surface of the recording medium. Full color printing is easy and running cost is low. Because of its many advantages such as low noise, it is widely used in home and office printers. Furthermore, in recent years, printing speed and resolution have improved dramatically. Along with this, recording media have been required to have more advanced characteristics such as ink absorptivity and dot shape uniformity. So-called ink-jet paper having an ink receiving layer provided on a material has come to be used.

  Today, inkjet recording media are (1) matte paper: a support substrate provided with an ink receiving layer mainly composed of inorganic fine particles and a binder resin, and (2) glossy paper: matte paper on a support substrate. (3) Photo-like glossy paper: Resin film or resin-coated paper is used as the supporting substrate, and inorganic fine particles and binder resin are the main components on it. The ink receiving layer and the glossy layer are provided, and are classified into three types depending on the application.

  In any recording medium, the ink receiving layer is a void type mainly composed of inorganic fine particles and a binder resin. As such a binder resin, polyvinyl alcohol which has excellent affinity for water-soluble ink and excellent binder power of inorganic fine particles. Resin (hereinafter, polyvinyl alcohol is abbreviated as PVA), and particularly modified PVA having a silanol group having high affinity with the surface of inorganic fine particles is widely used (for example, Patent Documents 1 and 2 and 3).

In addition, the present applicant also has a resin containing an acetoacetate group-containing PVA resin (hereinafter, the acetoacetate group-containing PVA resin is abbreviated as AA-PVA), a polyhydric hydrazide compound, an inorganic acid, and an inorganic powder. An ink jet recording medium in which the composition is coated on the surface of a supporting substrate is proposed (for example, see Patent Document 4).
JP-A-7-276784 JP 2000-15924 JP 2003-291502 A JP 2004-230609 A

In recent years, with the spread of digital cameras and the increasing demand for personal printing of photographed digital photographs, inkjet prints are required to have the same expressive power as silver halide photographs, that is, higher definition of images and higher printing speed. It has become.
In order to increase the image definition, a method of increasing the printing density and simultaneously controlling the ink discharge amount, and a method of printing low density ink multiple times at the same location and controlling the number of times have been developed. In any case, since the ink discharge amount per unit area of the recording medium increases, the recording medium tends to require the ability to absorb a larger amount of ink than in the past. For this purpose, the porosity of the ink receiving layer must be increased, and development is proceeding in the direction of increasing the amount of inorganic fine particles, that is, reducing the amount of binder resin.

  Further, for the problem of improving the printing speed, a recording medium having a surface strength that can withstand a high-speed transport mechanism has been required. This is because if the surface strength of the recording medium is weak, the ink receiving layer peels off from the support substrate during transportation, or inorganic fine particles fall off when passing through the paper feed roller, and this adheres to the roller surface, resulting in transportation failure. This is because there is a case of doing. Therefore, in order to improve the surface strength while the amount of the binder resin for increasing the porosity is reduced, a binder resin having an excellent binder power against inorganic fine particles is desired.

  Also, as described above, the amount of ink absorbed per unit area tends to increase, and the wet state after printing lasts longer than the conventional one, preventing the ink receiving layer from peeling off due to rubbing during that time. Therefore, there has been a strong demand for a binder resin having excellent binder strength when wet and an ink jet recording medium having a strong wet strength of the ink receiving layer.

However, it has been found that the techniques described in Patent Documents 1 to 3 do not provide sufficient surface strength of the ink receiving layer when the amount of the binder resin is reduced.
In addition, the ink jet recording medium based on the technique described in Patent Document 4 can obtain good surface strength even if the amount of the binder resin is reduced, but there is still room for improvement with respect to the surface strength when wet. found.
That is, there is a demand for an ink jet recording medium having an ink receiving layer having a strong surface strength even when the amount of the binder resin is low and a strong surface strength when wet.

  However, the present inventor has conducted extensive studies in view of such circumstances, and as a result, the AA-PVA having a content of acetoacetate groups exceeding 3 mol% and a hydroxyl group average chain length of 25 or more on the support substrate. The above-mentioned problem can be solved by an ink jet recording medium having an ink receiving layer formed by applying a coating liquid containing a resin (A), a crosslinking agent (B), and inorganic fine particles (C). As a result, the present invention has been completed.

That is, the present invention is as follows.
[1] AA-PVA-based resin (A), cross-linking agent (B), inorganic fine particles having an acetoacetate group content of over 3 mol% and a hydroxyl group average chain length of 25 or more on a support substrate An ink jet recording medium comprising an ink receiving layer containing (C).
[ 2 ] The inkjet recording medium as described in [1 ] above, wherein the saponification degree of the AA-PVA-based resin (A) is 97 mol% or more.
[ 3 ] The AA-modified PVA resin (A) is obtained by reacting a diketene with a PVA resin obtained by saponification in the presence of a solvent having a dielectric constant of 30 or less. The inkjet recording medium according to [ 1] or [2] .
[ 4 ] AA-PVA-based resin (A) is 44 to 74, 74 to 105, 105 to 177, 177 to 297, 297 to 500, 500 to 1680 μm in maximum value of acetoacetate group content by particle size Is an AA-PVA-based resin (A) having a value within 3 times the minimum value, the inkjet recording medium according to any one of [1] to [ 3 ] above.
[ 5 ] The inkjet recording according to any one of [1] to [ 4 ], wherein the crosslinking agent (B) is any one of a polyvalent metal compound, a boron compound, an amine compound, or a hydrazine compound. Media.
[ 6 ] The above [1] to [ 5 ], wherein the inorganic fine particles (C) are any of amorphous silica, vapor phase method silica, colloidal silica, vapor phase method alumina, and alumina hydrate. The ink jet recording medium according to any one of the above.
[ 7 ] The ink jet recording medium according to any one of [1] to [ 6 ], wherein a gloss layer is further provided on the ink receiving layer.
[ 8 ] AA-PVA-based resin (A), cross-linking agent (B), inorganic fine particles having an acetoacetate group content of over 3 mol% and a hydroxyl group average chain length of 25 or more on the support substrate The method for producing an ink jet recording medium according to any one of [1] to [ 7 ], wherein a coating liquid containing (C) is applied to form an ink receiving layer.

“Hydroxyl group average chain length” [l (OH)] refers to 3- (trimethylsilyl) -2,2,3,3-d ₄ -propionic acid sodium salt (3- (trimethylsilyl) propionic- Absorption based on the methylene carbon moiety found in the range of 38-46 ppm in ¹³ C-NMR measurements (solvent: D ₂ O) using 2,2,3,3-d ₄ -acid sodium salt) ((OH, OH ) Absorption of dyad = absorption having a peak top between 43 and 46 ppm, Absorption of (OH, OR) dyad = absorption having a peak top between 41 and 43 ppm, Absorption of (OR, OR) dyad = 38 to 41 ppm It is a value calculated from the following formula.
l (OH) = {2 (OH, OH) + (OH, OR)} / (OH, OR)
(However, the absorption intensity ratios of (OH, OR) and (OH, OH) are all calculated as mole fractions.)
Regarding such an average hydroxyl chain length and a measuring method thereof, Poval (publisher: Kobunshi Shuppankai, 1981) and Macromolecules, Vol. 10, p532 (1977).

  The ink jet recording medium of the present invention is useful as an ink jet recording medium for printing a high-definition image at a high speed because the surface strength of the ink receiving layer and the surface strength when wet are strong even with a low binder resin amount.

The AA-PVA-based resin (A) having an acetoacetate group content of more than 3 mol% and a hydroxyl group average chain length of 25 or more used in the present invention will be described in detail.
The AA-PVA-based resin (A) used in the present invention is one in which an acetoacetate group is introduced into PVA, and in order to obtain such an AA-PVA-based resin (A), a method of reacting the PVA-based resin with diketene, A method of transesterification by reacting a PVA resin with acetoacetate, a method of saponifying a copolymer of vinyl acetate and vinyl acetoacetate, etc. can be mentioned, but the production process is simple and AA is of good quality. Since PVA-type resin (A) is obtained, it is preferable to manufacture by the method of making PVA-type resin and diketene react, and although this method is demonstrated, it is not limited to this.

  As a PVA resin used as a raw material, a saponified product obtained by saponifying a lower alcohol solution of polyvinyl acetate with a saponification catalyst such as an alkali or an acid or a derivative thereof is generally used, and further, copolymerizable with vinyl acetate. It is also possible to use a saponified product of a copolymer of a monomer having a vinyl acetate and vinyl acetate.

Examples of such monomers include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-octadecene, vinylene carbonates, acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, Unsaturated acids such as itaconic acid and undecylenic acid or salts thereof, mono- or dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as acrylamide and methacrylamide, ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid Such as olefin sulfonic acid or salt thereof, alkyl vinyl ethers, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethyldiallylammonium chloride, Polyoxyalkylene (meth) allyl ethers such as methyl allyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl ether, polyoxyethylene (meth) Polyoxyalkylene (meth) acrylates such as acrylate, polyoxypropylene (meth) acrylate, polyoxyalkylene (meth) acrylamides such as polyoxyethylene (meth) acrylamide, polyoxypropylene (meth) acrylamide, polyoxyethylene (1- (Meth) acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxy Lopylene allylamine, polyoxyethylene vinylamine, polyoxypropylene vinylamine, isopropenyl acetate, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, glycerol monoallyl ether, 3,4-diacetoxy- Examples include 1-butene and 1,4-diacetoxy-2-butene.

  The saponification of the obtained polyvinyl acetate can be carried out by a known method, but usually it is carried out in the presence of an alkali catalyst or an acid catalyst after dissolving the polyvinyl acetate in an alcohol solvent. As the alcohol solvent, for example, methanol, ethanol, butanol, isopropanol, a mixed solvent of various alcohols such as methanol and methyl acetate, and a mixed solvent of methyl acetate can be used. The concentration of polyvinyl acetate in the alcohol solvent is selected from the range of 10 to 60% by weight.

As the alkali catalyst, alkali catalysts such as alkali metal hydroxides and alcoholates such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate and potassium methylate can be used. As the acid catalyst, an inorganic acid aqueous solution such as hydrochloric acid or sulfuric acid, or an organic acid such as p-toluenesulfonic acid can be used. The amount of the alkali catalyst used is preferably 1 to 100 mmol (more preferably 1 to 40 mmol, particularly 1 to 20 mmol) with respect to 1 mol of polyvinyl acetate or a vinyl acetate structural unit in the copolymer. When the amount of the alkali catalyst used is less than 1 millimolar, it tends to be difficult to increase the saponification degree to the target saponification degree, and when it exceeds 100 millimoles, it becomes higher than the target saponification degree. This is not preferable because it tends to be excessive and control becomes difficult.
The temperature at which saponification is carried out is not particularly limited, but is preferably 10 to 70 ° C and more preferably 20 to 50 ° C.

Next, in order to cause the PVA resin obtained by saponification of polyvinyl acetate to react with the diketene, the PVA resin and the gaseous or liquid diketene may be reacted directly, or an organic acid is converted into the PVA resin. After adsorbed and occluded in advance, gaseous or liquid diketene is sprayed and reacted in an inert gas atmosphere, or a mixture of an organic acid and liquid diketene is sprayed and reacted with a PVA resin.
As a reaction apparatus for carrying out the above reaction, any apparatus that can be heated and has a stirrer is sufficient. For example, a kneader, a Henschel mixer, a ribbon blender, other various blenders, and a stirring and drying apparatus can be used.

  The average polymerization degree (according to JIS K6726) of the AA-PVA-based resin (A) thus obtained is preferably 300 to 4000 (more preferably 400 to 4000, particularly 500 to 4000). When the average polymerization degree is less than 300, In some cases, sufficient surface strength may not be obtained. On the other hand, if it exceeds 4000, the viscosity of the coating solution becomes too high, and coating may be difficult.

  Further, the saponification degree of the AA-PVA-based resin (A) of the present invention is preferably 97 mol% or more (more preferably 98 mol% or more, particularly 99 mol% or more), and the saponification degree is 97 mol%. If it is less than%, the average chain length of the hydroxyl group tends to be short, and sufficient surface strength when wet may not be obtained.

  In addition, the content of acetoacetate groups in the AA-PVA-based resin (A) of the present invention (degree of acetoacetate esterification, hereinafter abbreviated as AA degree) exceeds 3 mol% (moreover 3 mol%). And more than 3 mol%, particularly more than 3 mol% and 8 mol% or less). When the content is 3 mol% or less, sufficient surface strength when wet cannot be obtained, and the object of the present invention cannot be achieved. The upper limit of the AA conversion degree is not particularly limited, but if it exceeds 10 mol%, the dispersibility of the inorganic fine particles is lowered, and the ink absorbability may be lowered.

Also, AA-PVA-based resin (A) of the present invention, it is necessary that the hydroxyl group average chain length of the 2 5 more than, with such hydroxyl chain length of less than 15, and surface strength, surface strength when wet Is insufficient to achieve the object of the present invention.

The method for controlling the hydroxyl group average chain length of the AA-modified PVA resin (A) of the present invention is not particularly limited, but the dielectric constant is 30 in the saponification step of polyvinyl acetate during the production of the PVA resin used as a raw material. it is preferable to perform alkali saponification in the presence of a solvent such as a lower, more preferably the dielectric constant is from 6 to 30, particularly preferred dielectric constant is 12 to 30. When the dielectric constant exceeds 32, the block property of the arrangement of the remaining acetic acid groups in the PVA-based resin is lowered, and the hydroxyl chain length of the AA-PVA-based resin (A) obtained as a final product tends to be shortened. Absent.

The dielectric constant of 30 or less of the solvent, acetic acid methyl / methanol = 1/3 (27.1), methyl acetate / methanol = 1/1 (21.0), methyl acetate / methanol = 3/1 (13. 9), methyl acetate (7.03), isopropyl acetate (6.3), trichlorethylene (3.42), xylene (2.37), toluene (2.38), benzene (2.28), acetone (21 .4). Of these, a mixed solvent of methyl acetate / methanol is preferably used.

  In addition, the AA-PVA-based resin (A) of the present invention preferably has a smaller distribution of the degree of AA conversion by particle size, specifically, 44 to 74, 74 to 105, 105 to 177, 177 to 297, The AA conversion degree of each AA-modified PVA resin (A) fractionated into particle sizes of 297 to 500 and 500 to 1680 μm was calculated from the alkali consumption by neutralization titration, and the highest AA conversion degree was the lowest. A value obtained by dividing by the AA degree (AA degree degree distribution by particle size) is 3.0 to 1.0 (more preferably 2.5 to 1.0, particularly 2.0 to 1.0). This is particularly preferable because a uniform dispersed state of inorganic fine particles can be obtained, and as a result, an ink receiving layer having good ink absorbability can be obtained.

  The particle size of 44 to 74 μm means a particle size screened by 350 mesh (44 μm) on a standard wire mesh and a 200 mesh (74 μm) pass, and 74 to 105 μm means 200 mesh (74 μm) on, A particle size screened by a 145 mesh (105 μm) pass is 105 to 177 μm is 145 mesh (105 μm) on, and a particle size screened by an 80 mesh (177 μm) pass is 177 to 297 μm. Mesh (177 μm) on, particle size screened by 48 mesh (297 μm) pass, 297-500 μm is 48 mesh (297 μm) on, particle size screened by 32 mesh (500 μm) pass, 500 ~ 1680μm is 32 mesh (500μm) On means having a particle size screened by 10.5 mesh (1680 μm) pass.

The method for controlling the AA degree distribution according to particle size is not particularly limited, but the degree of swelling as a raw material is 1.0 or more (more preferably 1.0 to 500, particularly 3.0 to 200), and the elution rate is It is preferable to use a PVA-based resin that is 3.0% or more (more preferably 3.0 to 97.0%, particularly 5.0 to 60.0%). Here, the swelling degree and elution rate of the raw material PVA-based resin are shown in the following formulas (i) and (ii).
(I) Swelling degree = (X−Y) /Y≧1.0
(Ii) Elution rate (%) = (Z / 30) × 100 ≧ 3.0
X: 270 g of water was added to 30 g of PVA resin and left at 25 ° C. for 24 hours, then filtered for 10 minutes with a vacuum of 100 mmHg and left on the filter paper (No. 2).
Weight of existing water-absorbed PVA resin (g)
Y: Weight of the PVA-based resin swollen by water absorption at 105 ° C. and having a constant weight (g)
Z: 270 g of water was added to 30 g of PVA-based resin, left at 25 ° C. for 24 hours, and then filtered for 10 minutes with a vacuum of 100 mmHg.
Weight of non-volatile component when distilling off volatile component (g)

  When the degree of swelling is less than 1.0 or the elution rate is less than 3.0%, it becomes difficult to obtain an AA-PVA-based resin having an AA degree distribution by particle size of 3.0 or less.

  In order to control the degree of swelling and elution rate of the raw material PVA-based resin, there is a method of adjusting the crystallization degree by heating the raw material PVA-based resin while standing or flowing. A fluidized heat treatment method is preferred.

Next, a crosslinking agent (B) is demonstrated.
Examples of the crosslinking agent (B) contained in the ink receiving layer of the ink jet recording medium of the present invention include, for example, polyvalent metal compounds, boron compounds, amine compounds, hydrazine compounds, silane compounds, methylol group-containing compounds, and aldehyde groups. A compound, an epoxy compound, a thiol compound, an isocyanate compound, and the like can be mentioned, and a polyvalent metal compound, a boron compound, an amine compound, and a hydrazine compound are particularly preferable.

The polyvalent metal compound is a compound containing an aluminum atom, a zinc atom, an iron atom, a zirconium atom, a titanium atom, a gallium atom, an indium atom, a ruthenium atom, or a hafnium atom, and a compound having a zirconium atom is particularly preferable. It is.
The compound having a zirconium atom may be any one of a single salt and a double salt of an inorganic acid or an organic acid, an organic metal compound, a metal complex, an oxide compound (zirconyl compound), etc. Zirconium, zirconium chloride, zirconium bromide, zirconate, zirconate, zirconyl chloride ("Zircosol ZC" manufactured by Daiichi Rare Element Chemical Co., Ltd.), basic zirconyl chloride ("Zircosol ZC-2" manufactured by Daiichi Elemental Chemical Co., Ltd.) , Zirconyl sulfate, zirconyl nitrate ("Zircosol ZN" manufactured by Daiichi Rare Element Chemical Co., Ltd.), zirconyl carbonate, ammonium zirconium carbonate ("Zircosol AC-7" manufactured by Daiichi Rare Element Chemical Co., Ltd.), potassium zirconium carbonate (first rare element chemistry) "Zircosol ZK-10"), zirconyl acetate, and stearic acid Nil, zirconyl octylate, zirconyl citrate, zirconyl lactate, zirconyl oxalate, zirconyl phosphate, zirconium tetraacetylacetonate ("Orgatrix ZC-150" manufactured by Matsumoto Pharmaceutical Co., Ltd.), zirconium monoacetylacetonate (Matsumoto Pharmaceutical "Orgatics ZC-540"), zirconium bisacetylacetonate (Matsumoto Pharmaceutical Co., Ltd. "Orgachix ZC-550"), zirconium monoethyl acetoacetate (Matsumoto Pharmaceutical Co., Ltd. "Orgatics ZC-560") , Zirconium acetate (“Orgachix ZC-115” manufactured by Matsumoto Pharmaceutical Co., Ltd.), and the like.
Among these compounds containing zirconium atoms, zirconyl compounds such as ammonium zirconium carbonate, zirconium potassium carbonate, zirconyl acetate, basic zirconyl chloride, zirconyl oxychloride, zirconyl nitrate, etc. are preferable, and basic zirconyl chloride and zirconyl nitrate are particularly preferred. It is preferably used in that the object of the invention can be remarkably exhibited.

  Such boron compounds include boric acid, metal salts such as sodium and potassium borate, polyhydric alcohol esters such as ethylene glycol and glycerin boric acid, borax and the like, in particular boric acid, borate and boron. Sand is preferably used in that the object of the present invention can be remarkably exhibited.

  Such hydrazine compounds include hydrazine, hydrazine hydrochloride, sulfuric acid, nitric acid, sulfurous acid, phosphoric acid, thiocyanic acid, carbonic acid and other inorganic acid salts, and formic acid, oxalic acid and other organic acid salts, hydrazine methyl, ethyl, propyl, Hydrazine derivatives such as mono-substituted compounds such as butyl and allyl, symmetrical di-substituted compounds such as 1,1-dimethyl and 1,1-diethyl, carbohydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, glutaric acid dihydrazide, succinic acid dihydrazide, Adipic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, diglycolic acid dihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid hydride Zido, trihydrazide citrate, 1,3-bis (hydrazinocarbonoethyl) -5-isopropylhydantoin (such as “Amicure VDH” manufactured by Ajinomoto Finetechno Co., Ltd.), 7,11-octadecadien-1,18-di And hydrazide compounds such as carbohydrazide (“Amicure UDH” manufactured by Ajinomoto Fine Techno Co., Ltd.), polyacrylic acid hydrazide, N-aminopolyacrylamide, N-aminoacrylamide / acrylamide copolymer, and the like. Polyhydric hydrazide compounds such as dihydrazide, 1,3-bis (hydrazinocarbonoethyl) -5-isopropylhydantoin, N-aminopolyacrylamide, N-aminoacrylamide / acrylamide copolymer, and the like, remarkably achieve the object of the present invention. It is preferably used in that it can be demonstrated That.

  Examples of such amine compounds include fats such as ethylenediamine, hexamethylenediamine, diethylenetriamine, dipropylenetriamine, triethylenetetramine, tetraethylenepentamine, N-aminoethylpiperazine, bisaminopropylpiperazine, trimethylhexamethylenediamine, and polyoxypropylenediamine. Polyamines, alicyclic polyamines such as 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane, 4,4′-diaminodicyclohexylmethane, isophoronediamine, 1,3-bisaminomethylcyclohexane, norbornanediamine, 4 , 4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, diaminodiphenyl sulfone, m-phenylenediamine, 2,4'-toluylene diene Examples include amino group-containing water-soluble polymers such as aromatic diamines such as amine and metaxylylenediamine, amino group-modified PVA resins, polyvinylamine, polyallylamine, and polyethyleneimine. Particularly, 1,3-bisaminomethylcyclohexane , Metaxylylenediamine, amino group-modified PVA resin, polyethyleneimine and the like are preferably used in that the object of the present invention can be remarkably exhibited.

Next, the inorganic fine particles (C) will be described.
The inorganic fine particles (C) contained in the ink receiving layer of the ink jet recording medium of the present invention are not particularly limited, but calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, oxidation Zinc, zinc hydroxide, zinc sulfide, zinc carbonate, hydrotalcite, aluminum silicate, magnesium silicate, calcium silicate, amorphous silica, vapor phase silica, colloidal silica, vapor phase alumina, alumina hydrate, alumina sol, Aluminum hydroxide, zeolite, magnesium hydroxide, zirconium oxide, zirconium hydroxide, cerium oxide, and the like are preferably used, and these can be used alone or in combination of two or more.
In particular, when the ink jet recording medium is mat paper or glossy paper, the ink absorbency is important. Therefore, amorphous silica capable of obtaining a high porosity and a large pore size is preferably used, and photo-like gloss In the case of paper, since glossiness and smoothness are regarded as important as well as ink absorbability, inorganic ultrafine particles such as colloidal silica, gas phase method silica, gas phase method alumina, and alumina hydrate are preferably used. It is done.

  A preferable average particle diameter of the amorphous silica (C) is 1 to 15 μm (more preferably 2 to 12 μm, particularly 2 to 10 μm). When the average particle diameter is less than 1 μm and more than 15 μm, the ink absorbability is increased. Is unfavorable because it tends to decrease and ink bleeding tends to increase.

  As such colloidal silica (C), those having a surface imparted with an anionic property or a cationic property by a surface treatment with an organic compound such as ammonium ion or a metal ion are preferable. Can be mentioned. Further, those having an average particle diameter of 2 to 500 nm (more preferably 3 to 200 nm, particularly 4 to 100 nm) are preferable. When the average particle diameter is less than 2 nm, a uniform dispersion state may be difficult to obtain. On the other hand, if it exceeds 500 nm, the ink absorptivity may decrease, which is not preferable.

As the gas phase method silica (C), those having a BET specific surface area of 50 m ² / g or more (more preferably 100 m ² / g or more, particularly 200 m ² / g or more) are preferable, and the average particle diameter is 1 to The thing of 30 nm (further 2-20 nm, especially 3-10 nm) is preferable. When the BET specific surface area is less than 50 m ² / g, the ink absorbability may be lowered, which is not preferable. Further, when the average particle diameter is less than 1 nm, it is difficult to obtain a uniform dispersed state. Conversely, when the average particle diameter exceeds 30 nm, the ink absorptivity decreases, ink bleeding tends to increase, and glossiness tends to decrease. This is not preferable.

  The preferable average particle diameter of the vapor phase alumina (C) is 30 nm or less (more preferably 25 nm or less, particularly 20 nm or less). When the average particle diameter exceeds 30 nm, the ink absorptivity decreases and the ink bleeds. Is unfavorable because it tends to increase or gloss decreases.

  As such an alumina hydrate, pseudoboehmite is preferable, its average pore radius is preferably 1 to 30 nm (more preferably 2 to 20 nm, particularly 2 to 15 nm), and its pore volume is 0.3 to 2 cc / g. (Furthermore, 0.4 to 1.8 cc / g, particularly 0.5 to 1.5 cc / g) is preferable. When the average pore radius is less than 1 nm, it may be difficult to obtain a uniform dispersed state. When the average pore radius exceeds 30 nm, the ink absorptivity, gloss, and transparency may be deteriorated. Further, when the pore volume is less than 0.3 g / cc, the ink absorbability may be lowered, and when it exceeds 2 cc / g, the transparency may be insufficient.

The ink receiving layer of the ink jet recording medium of the present invention has an AA degree of more than 3 mol% and a hydroxyl group chain length of 25 or more, AA PVA (A), a crosslinking agent (B), and inorganic fine particles as described above. (C) is contained, and the content ratio (A / B) (weighted) of the AA-PVA-based resin (A) and the crosslinking agent (B) in the layer is 100/200 to 100 / 0.1 (more preferably 100/100 to 100/1, particularly 100/50 to 100/2), and when the content ratio (A / B) exceeds 100 / 0.1, it is sufficient. The surface strength and water resistance may not be obtained. On the other hand, if it is less than 100/200, the dispersibility of the inorganic fine particles may be lowered, and the ink absorbability may be lowered.

  The content ratio (A / C) (weight ratio) of the AA-PVA-based resin (A) and the inorganic fine particles (C) in the layer is an ink receiving layer of matte paper or glossy paper. It is preferably 5/100 to 100/100 (more preferably 10/100 to 50/100, particularly 10/100 to 30/100). When the content ratio (A / C) exceeds 100/100, the ink absorption ability may be reduced due to the reduction of voids, which may cause feathering and bleeding. When the strength decreases, the inorganic particles fall off, or when a glossy layer is applied on such a layer, the layer peels off due to a decrease in the surface strength in the wet state, or the adhesive force at the interface between the ink receiving layer and the glossy layer is reduced. This is not preferable because interface peeling due to shortage and ink bleeding at the interface may occur.

  When the ink receiving layer is an ink receiving layer and gloss layer of photo-like glossy paper, the content ratio (A / C) (weight ratio) of the AA-PVA-based resin (A) and inorganic fine particles (C) is It is preferably 10/100 to 100/10 (more preferably 20/80 to 80/20, particularly 30/70 to 50/50). When the content ratio (A / C) exceeds 100/10, voids in the glossy layer are reduced, ink permeability is deteriorated, feathering and image spots occur, and image areas are sharp. On the other hand, if the ratio is less than 10/100, the smoothness of the surface is impaired, the gloss is lowered, the gloss layer is cracked, the surface is not strong enough to blow the dry wind due to insufficient surface strength. This is not preferable because it may be broken or rough.

  The method for forming the ink receiving layer in the ink jet recording medium of the present invention is not particularly limited, but usually the AA-PVA-based resin (A), the crosslinking agent (B) and the inorganic fine particles (C) as described above are used. What is necessary is just to apply | coat the containing coating liquid on a support base material, and to form an ink receiving layer, and the manufacturing method is demonstrated concretely.

  The supporting substrate is not particularly limited. For example, paper (manila balls, white balls, liners and other paperboards, general fine papers, medium papers, gravure papers and other printing papers, upper / middle / lower grades) Paper, newsprint, release paper, carbon paper, non-carbon paper, glassine paper, etc.), resin-coated paper, synthetic paper, non-woven fabric, cloth, metal foil, polyolefin resin (eg, polyethylene, PET, polypropylene, polyvinyl chloride, ethylene- Films and sheets made of thermoplastic resins such as propylene copolymers and ethylene-vinyl acetate copolymers) can be used. In the case of matte paper or glossy paper, the paper substrate made of cellulose is used as photo-like glossy paper. In some cases, film or resin-coated paper is mainly used.

  The coating liquid is obtained by dissolving and dispersing the PVA resin (A), the crosslinking agent (B), and the inorganic fine particles (C) in a medium mainly containing water. There is no particular limitation on the method for dissolving and dispersing in the medium. Usually, an aqueous solution of PVA resin (A) is produced, and the crosslinking agent (B) is added. After the preparation, inorganic fine particles (C) are dispersed therein. In this dispersion, a known mixing apparatus / method such as a high-speed homogenizer can be used.

As a method of providing an ink receiving layer on a support substrate and a method of providing a glossy layer on an ink receiving layer, known coating methods such as a bar coater method, an air knife coater method, a blade coater method, and a curtain coater method are available. Used.
The total solid content in the coating liquid is not particularly limited, but is preferably 5 to 60% by weight (more preferably 10 to 50% by weight, and particularly 10 to 30% by weight) of the entire coating liquid. If the total solid content is less than 5% by weight, the drying load increases and the uniformity of the coating layer thickness may decrease. Conversely, if the total solid content exceeds 60% by weight, the coating liquid becomes highly viscous, and at high speed. Coating is difficult, and workability may be reduced.
In the case of an ink receiving layer of matte paper or glossy paper, the coating amount of the coating liquid should be 3 to 100 μm after drying (more preferably 5 to 80 μm, especially 10 to 50 μm). In the case of photo-like glossy paper, the thickness after drying is preferably 1 to 20 μm (more preferably 1 to 10 μm, particularly 1 to 5 μm). It is possible to form an ink receiving layer by multilayer coating.

  Such a coating liquid can be used in combination with other water-soluble or water-dispersible resins. Examples of water-soluble or water-dispersible resins that can be used in combination include starch derivatives such as starch, oxidized starch, and cation-modified starch, natural proteins such as gelatin and casein, methylcellulose, ethylcellulose, hydroxyethylcellulose, and CMC. Cellulose derivatives, unmodified PVA, cation-modified PVA, carboxylic acid-modified PVA, sulfonic acid-modified PVA, diacetone acrylamide-modified PVA, silanol-modified PVA, low ethylene-modified PVA having an ethylene content of 15 mol% or less, ethylene-vinyl acetate copolymer PVA derivatives such as partially saponified compounds, water-soluble resins such as poly (meth) acrylate, natural polymeric polysaccharides such as sodium alginate and pectic acid, polyvinyl pyrrolidone, poly (meth) acrylate, SBR latex, NBR latex , Vinyl acetate resin emulsion, ethylene-vinyl acetate copolymer emulsion, (meth) acrylic ester resin emulsion, vinyl chloride resin emulsion, urethane resin emulsion, and the like. is not.

  In addition, it is possible to use a cationic resin in combination with the coating liquid as a fixing agent for anionic ink. Examples of such cationic resins include polyalkylene polyamines such as polyethylene polyamine and polypropylene polyamine or derivatives thereof, acrylic polymers having secondary amino groups, tertiary amino groups, and quaternary ammonium salts, polyvinylamine copolymer Examples include, but are not limited to, polymers, polyvinylamidine copolymers, dicyandiamide / formalin copolymers, dimethylamine / epichlorohydrin copolymers, acrylamide / diallylamine copolymers, diallyldimethylammonium chloride copolymers, and the like. It is not a thing.

  What is necessary is just to dry after coating, and although it does not restrict | limit especially as drying conditions, Usually, what is necessary is just to dry for about 1 to 30 minutes at 90-120 degreeC.

In the case of glossy paper, after the ink receiving layer is formed by the above-described method, a glossy layer is further formed thereon. Such a gloss layer is mainly composed of inorganic fine particles and a binder resin, and examples of the inorganic fine particles include colloidal silica, gas phase method silica, gas phase method alumina, alumina hydrate, hydrotalcite, amorphous silica and Examples of such finely pulverized products include colloidal silica and alumina hydrate. Examples of the binder resin include PVA resins and known modified PVA resins, gelatin, casein, cellulose derivatives such as carboxymethylcellulose and methylcellulose, diene such as styrene-butadiene copolymer and methylmethacrylate-butadiene copolymer. Examples thereof include polymer polymer latex, acrylic polymer latex, vinyl polymer latex such as ethylene-vinyl acetate copolymer, and aqueous urethane resin.
The mixing ratio of the inorganic fine particles and the binder resin in the glossy layer is not particularly limited. Generally, however, the inorganic fine particles are contained in an amount of 0 to 200 parts by weight (weight solid content) with respect to 100 parts by weight of the binder resin. Furthermore, it is preferably 2 to 200 parts by weight, particularly 5 to 150 parts by weight.

In the case of photo-like glossy paper, it is preferable to impart high gloss to the outermost ink receiving layer / glossy layer by a cast coating method or the like. Here, the cast coating method is a method in which a coated surface in a wet state is pressed onto a heated mirror surface and dried. (1) The coated layer is in a wet state before drying and is bonded to the heated mirror surface (direct method). ), (2) Re-wet the dried coating layer and press-bond to the heated mirror surface (re-wetting method). (3) Gelate the wet coating layer and leave it in the wet state on the heated mirror surface. Three types of pressure bonding (coagulation method) are generally known.
In the case of the above method (3), the PVA resin is usually subjected to gelation treatment by coating an aqueous liquid containing boric acid or borate on the coating layer. Although this method can be used for an ink jet recording medium, in the case of the present invention, the coating layer already contains the crosslinking agent (B) together with the PVA-based resin. Even without using a gelling solution containing an acid compound, it is possible to easily create a gel state by heating at room temperature or by infrared rays after forming the coating layer.
Moreover, after making a coating layer into a gel similarly to the above-mentioned method, it is also possible to provide glossiness by making it dry only by applying a drying wind, without making it press-fit with a heating mirror surface.

  The ink jet recording medium of the present invention thus obtained has excellent surface strength of the ink receiving layer even in the case of a low binder amount, and has excellent ink absorbability and high surface strength when wet. High gloss production for high-definition image printing at high speed because the ink receiving layer does not peel off and the production yield is high even when applying gloss by gloss coating by gloss coating. Suitable as a medium.

Hereinafter, the present invention will be specifically described with reference to examples.
In the examples, “%” means weight basis unless otherwise specified.

Production Example 1: AA-PVA-based resin (A1)
A reaction vessel equipped with a reflux condenser, a dropping funnel, and a stirrer was charged with 1000 g of vinyl acetate, 200 g of methanol, and 0.05 mol% of azobisisobutyronitrile (vs. vinyl acetate charged) and stirred under a nitrogen stream. While raising the temperature, polymerization was carried out at the boiling point for 3 hours. When the polymerization rate of vinyl acetate reaches 50%, the polymerization is completed by adding m-dinitrobenzene, and then the unreacted vinyl acetate monomer is removed from the system by blowing methanol vapor. A methanol solution (41% resin content) was obtained. Subsequently, the solution was diluted with methyl acetate (dielectric constant 7.03), adjusted to a concentration of 29.5% (dielectric constant of saponification solvent 23.7), charged into a kneader, and the solution temperature was raised to 40 ° C. While maintaining, sodium hydroxide was added for neutralization. Further, 50 mmol of sodium hydroxide is added to 1 mol of vinyl acetate unit in the polymer to saponify, and the precipitate is filtered off, washed thoroughly with methanol, dried in a hot air dryer, and further at 80 ° C. A PVA resin was obtained by heat treatment for 60 minutes.
The saponification degree of the obtained PVA-based resin was 99.7 mol% when analyzed by the alkali consumption required for hydrolysis of residual vinyl acetate, and the average polymerization degree was analyzed according to JIS K6726. As a result, it was 2300, and the content of sodium acetate was 0.8%. Further, the degree of swelling was 2.0 and the elution rate was 5.0%.

444 parts of the PVA-based resin is charged into a kneader, and 100 parts of acetic acid is added to the kneader. The mixture is swelled, and stirred at a rotation speed of 20 rpm. The solution was added dropwise over a period of time, and further reacted for 30 minutes. After completion of the reaction, the reaction product was washed with 500 parts of methanol and dried at 70 ° C. for 6 hours to obtain an AA-modified PVA resin (A1) having a saponification degree of 99.7 mol% and an AA degree of 5.0 mol%. The average chain length of the hydroxyl group determined from the ¹³ C-NMR spectrum of the AA-PVA-based resin (A1) was 30. Further, when the AA-PVA-based resin (A1) was subjected to 7 types of sieves as described above, 6 types of fractions were taken out and the AA conversion degree was measured. 44-74 μm: 6.0 mol%, 74-105 μm : 5.5 mol%, 105 to 177 μm: 5.3 mol%, 177 to 297 μm: 4.8 mol%, 297 to 500 μm: 4.5 mol%, 500 to 1680 μm: 4.0 mol% The AA degree distribution (maximum AA degree / lowest AA degree) was 1.5.

Production Example 2: AA-PVA-based resin (A2)
A reaction vessel equipped with a reflux condenser, a dropping funnel, and a stirrer was charged with 1000 g of vinyl acetate, 200 g of methanol, and 0.05 mol% of azobisisobutyronitrile (vs. vinyl acetate charged) and stirred under a nitrogen stream. While raising the temperature, polymerization was carried out at the boiling point for 3 hours. When the polymerization rate of vinyl acetate reaches 50%, the polymerization is completed by adding m-dinitrobenzene, and then the unreacted vinyl acetate monomer is removed from the system by blowing methanol vapor. A methanol solution (41% resin content) was obtained. Subsequently, the solution was diluted with methyl acetate (dielectric constant 7.03), adjusted to a concentration of 29.5% (dielectric constant of saponification solvent 23.7), charged into a kneader, and the solution temperature was raised to 35 ° C. While maintaining, sodium hydroxide was added for neutralization. Further, 15 mmol of sodium hydroxide is added to 1 mol of vinyl acetate unit in the polymer to saponify, the precipitate is filtered, washed well with methanol, dried in a hot air dryer, and further at 80 ° C. A PVA resin was obtained by heat treatment for 60 minutes.
The saponification degree of the obtained PVA resin was 97.5 mol% when analyzed by the alkali consumption required for hydrolysis of the residual vinyl acetate, and the average polymerization degree was analyzed according to JIS K6726. As a result, it was 2300, and the content of sodium acetate was 0.8%. Moreover, the swelling degree was 5.0 and the elution rate was 12.0%.

444 parts of the PVA-based resin is charged into a kneader, and 100 parts of acetic acid is added to the kneader. The mixture is swollen, and stirred at a rotation speed of 20 rpm. The solution was added dropwise over 5 hours, and further reacted for 30 minutes. After completion of the reaction, the reaction product was washed with 500 parts of methanol and dried at 70 ° C. for 6 hours to obtain an AA-modified PVA resin (A2) having a saponification degree of 97.5 mol% and an AA degree of 3.2 mol%. The average chain length of the hydroxyl group determined from the ¹³ C-NMR spectrum of the AA-PVA-based resin (A2) was 25. In addition, when the AA-PVA-based resin (A2) was taken out by using seven types of sieves as described above, six types of fractions were taken out and the degree of AA conversion was measured. 44-74 μm: 3.7 mol%, 74-105 μm : 3.5 mol%, 105 to 177 μm: 3.3 mol%, 177 to 297 μm: 3.0 mol%, 297 to 500 μm: 2.9 mol%, 500 to 1680 μm: 2.6 mol% The AA degree distribution (maximum AA degree / lowest AA degree) was 1.4.

Production Example 3: AA-PVA-based resin (A3)
A reaction vessel equipped with a reflux condenser, a dropping funnel and a stirrer was charged with 1000 g of vinyl acetate, 600 g of methanol, and 0.05 mol% of azobisisobutyronitrile (vs. vinyl acetate charged) and stirred under a nitrogen stream. While raising the temperature, polymerization was carried out at the boiling point for 7 hours. When the polymerization rate of vinyl acetate reaches 80%, m-dinitrobenzene is added to complete the polymerization, and then unreacted vinyl acetate monomer is removed from the system by blowing methanol vapor. A methanol solution (41% resin content) was obtained. Subsequently, the solution was diluted with methanol (dielectric constant 31.2) and methyl acetate (dielectric constant 7.03) to a concentration of 29.5% (dielectric constant of saponified solvent 31.0). The solution was neutralized by adding sodium hydroxide while keeping the solution temperature at 40 ° C. Further, 50 mmol of sodium hydroxide is added to 1 mol of vinyl acetate unit in the polymer to saponify, and the precipitate is filtered off, washed thoroughly with methanol, dried in a hot air dryer, and further at 80 ° C. A PVA resin was obtained by heat treatment for 60 minutes.
The saponification degree of the obtained PVA-based resin was 99.7 mol% when analyzed by the alkali consumption required for hydrolysis of residual vinyl acetate, and the average polymerization degree was analyzed according to JIS K6726. As a result, it was 1200, and the content of sodium acetate was 0.8%. Further, the degree of swelling was 2.0 and the elution rate was 5.0%.

444 parts of the PVA-based resin is charged into a kneader, and 100 parts of acetic acid is added to the kneader. The mixture is swelled, and stirred at a rotation speed of 20 rpm. The solution was added dropwise over a period of time, and further reacted for 30 minutes. After the completion of the reaction, the reaction product was washed with 500 parts of methanol and then dried at 70 ° C. for 6 hours to obtain an AA-modified PVA resin (A3) having a saponification degree of 99.7 mol% and an AA degree content of 5.0 mol%. . The average chain length of the hydroxyl group determined from the ¹³ C-NMR spectrum of the AA-PVA-based resin (A3) was 16. In addition, when the AA-PVA-based resin (A3) was taken out by using seven types of sieves as described above, six types of fractions were taken out and the degree of AA conversion was measured. 44-74 μm: 6.0 mol%, 74-105 μm : 5.5 mol%, 105 to 177 μm: 5.3 mol%, 177 to 297 μm: 4.8 mol%, 297 to 500 μm: 4.5 mol%, 500 to 1680 μm: 4.0 mol% The AA degree distribution (maximum AA degree / lowest AA degree) was 1.5.

Production Example 4: AA-PVA-based resin (A4)
A reaction vessel equipped with a reflux condenser, a dropping funnel, and a stirrer was charged with 1000 g of vinyl acetate, 200 g of methanol, and 0.05 mol% of azobisisobutyronitrile (vs. vinyl acetate charged) and stirred under a nitrogen stream. While raising the temperature, polymerization was carried out at the boiling point for 3 hours. When the polymerization rate of vinyl acetate reaches 50%, the polymerization is completed by adding m-dinitrobenzene, and then the unreacted vinyl acetate monomer is removed from the system by blowing methanol vapor. A methanol solution (41% resin content) was obtained. Subsequently, the solution was diluted with methyl acetate (dielectric constant 7.03), adjusted to a concentration of 29.5% (dielectric constant of saponification solvent 23.7), charged into a kneader, and the solution temperature was raised to 40 ° C. While maintaining, sodium hydroxide was added for neutralization. Further, 50 mmol of sodium hydroxide is added to 1 mol of vinyl acetate unit in the polymer to saponify, the precipitate is filtered, washed well with methanol, dried in a hot air dryer, and further at 105 ° C. A PVA resin was obtained by heat treatment for 120 minutes.
The saponification degree of the obtained PVA-based resin was 99.7 mol% when analyzed by the alkali consumption required for hydrolysis of residual vinyl acetate, and the average polymerization degree was analyzed according to JIS K6726. As a result, it was 2300, and the content of sodium acetate was 0.8%. Further, the degree of swelling was 1.1, and the elution rate was 3.1%.

444 parts of the PVA-based resin is charged into a kneader, and 100 parts of acetic acid is added to the kneader. The mixture is swelled, and stirred at a rotation speed of 20 rpm. The solution was added dropwise over a period of time, and further reacted for 30 minutes. After completion of the reaction, the reaction product was washed with 500 parts of methanol and then dried at 70 ° C. for 6 hours to obtain an AA-modified PVA resin (A4) having a saponification degree of 99.7 mol% and an AA degree of 5.0 mol%. The average chain length of the hydroxyl group determined from the ¹³ C-NMR spectrum of the AA-PVA-based resin (A4) was 30. Further, when the AA-PVA-based resin (A4) was taken out using the seven types of sieves as described above, six types of fractions were taken out and the degree of AA conversion was measured. : 6.5 mol%, 105 to 177 µm: 5.5 mol%, 177 to 297 µm: 4.5 mol%, 297 to 500 µm: 3.5 mol%, 500 to 1680 µm: 3.0 mol% The AA degree distribution (maximum AA degree / lowest AA degree) was 2.8.

Production Example 5: AA-PVA-based resin (A5)
A reaction vessel equipped with a reflux condenser, a dropping funnel and a stirrer was charged with 1000 g of vinyl acetate, 200 g of methanol, and 0.05 mol% of azobisisobutyronitrile (vs. vinyl acetate charged), and stirred under a nitrogen stream. While raising the temperature, polymerization was carried out at the boiling point for 3 hours. When the polymerization rate of vinyl acetate reaches 50%, the polymerization is completed by adding m-dinitrobenzene, and then the unreacted vinyl acetate monomer is removed from the system by blowing methanol vapor. A methanol solution (41% resin content) was obtained. Subsequently, the solution was diluted with methanol (dielectric constant 31.2) and water (dielectric constant 80.4), adjusted to a concentration of 29.5% (dielectric constant 35 of saponified solvent) and charged into a kneader. While maintaining the solution temperature at 35 ° C., it was neutralized by adding sodium hydroxide. Further, 15 mmol of sodium hydroxide is added to 1 mol of vinyl acetate unit in the polymer to saponify, the precipitate is filtered, washed well with methanol, dried in a hot air dryer, and further at 80 ° C. A PVA resin was obtained by heat treatment for 60 minutes.
The saponification degree of the obtained PVA-based resin was 97.5 mol% when analyzed by the alkali consumption required for hydrolysis of residual vinyl acetate, and the average polymerization degree was analyzed according to JIS K6726. As a result, it was 2300, and the content of sodium acetate was 0.7%. The degree of swelling was 5.0 and the elution rate was 13.0%.

444 parts of the PVA-based resin is charged into a kneader, 100 parts of acetic acid is added to the kneader, and the mixture is swollen. After stirring at a rotation speed of 20 rpm, the temperature is raised to 60 ° C., and a mixed solution of 22 parts of diketene and 7 parts of acetic acid is reduced to 0 The solution was added dropwise over 5 hours, and further reacted for 30 minutes. After completion of the reaction, the reaction product was washed with 500 parts of methanol and dried at 70 ° C. for 6 hours to obtain an AA-PVA-based resin (A5) having a saponification degree of 97.5 mol% and an AA conversion degree of 1.6 mol%. The average chain length of the hydroxyl group determined from the ¹³ C-NMR spectrum of the AA-PVA-based resin (A5) was 29. In addition, when the AA-PVA-based resin (A4) was taken out by using seven types of sieves as described above, six types of fractions were taken out and the degree of AA conversion was measured. 44-74 μm: 1.5 mol%, 74-105 μm : 1.8 mol%, 105 to 177 μm: 1.8 mol%, 177 to 297 μm: 1.6 mol%, 297 to 500 μm: 1.5 mol%, 500 to 1680 μm: 1.3 mol%, according to particle size The AA degree distribution (maximum AA degree / lowest AA degree) was 1.4.

Production Example 6: AA-PVA-based resin (A6)
A reaction vessel equipped with a reflux condenser, a dropping funnel, and a stirrer was charged with 1000 g of vinyl acetate, 200 g of methanol, and 0.05 mol% of azobisisobutyronitrile (vs. vinyl acetate charged) and stirred under a nitrogen stream. While raising the temperature, polymerization was carried out at the boiling point for 3 hours. When the polymerization rate of vinyl acetate reaches 50%, the polymerization is completed by adding m-dinitrobenzene, and then the unreacted vinyl acetate monomer is removed from the system by blowing methanol vapor. A methanol solution (41% resin content) was obtained. Subsequently, the solution was diluted with methyl acetate (dielectric constant 7.03), adjusted to a concentration of 29.5% (dielectric constant of saponification solvent 23.7), charged into a kneader, and the solution temperature was raised to 35 ° C. While maintaining, sodium hydroxide was added for neutralization. Further, 11 mmol of sodium hydroxide is added to 1 mol of vinyl acetate unit in the polymer to saponify, the precipitate is filtered, washed well with methanol, dried in a hot air dryer, and further at 80 ° C. A PVA resin was obtained by heat treatment for 60 minutes.
The saponification degree of the obtained PVA-based resin was 93.0 mol% when analyzed by the alkali consumption required for hydrolysis of the residual vinyl acetate, and the average polymerization degree was analyzed according to JIS K6726. As a result, it was 2300, and the content of sodium acetate was 0.6%. Further, the degree of swelling was 95, and the elution rate was 50%.

444 parts of the PVA-based resin is charged into a kneader, and 100 parts of acetic acid is added to the kneader. The mixture is swollen, stirred at a rotation speed of 20 rpm, heated to 60 ° C., and mixed with 82 parts of diketene and 30 parts of acetic acid. The solution was added dropwise over 5 hours, and further reacted for 30 minutes. After the completion of the reaction, the reaction product was washed with 500 parts of methanol and then dried at 70 ° C. for 6 hours to obtain an AA-modified PVA resin (A6) having a saponification degree of 93.0 mol% and an AA conversion degree of 7.1 mol%. The average chain length of the hydroxyl group determined from the ¹³ C-NMR spectrum of the AA-PVA-based resin (A6) was 8. In addition, when the AA-PVA-based resin (A4) was used with seven types of sieves as described above, six types of fractions were taken out and the degree of AA conversion was measured. 44-74 μm: 8.5 mol%, 74-105 μm : 7.8 mol%, 105 to 177 μm: 7.3 mol%, 177 to 297 μm: 6.9 mol%, 297 to 500 μm: 6.4 mol%, 500 to 1680 μm: 5.7 mol%, according to particle size The AA degree distribution (maximum AA degree / lowest AA degree) was 1.5.

Example 1
AA-PVA resin (A1) 4.3 parts dissolved in 200 parts of water was added to amorphous silica (C) [“Fine Seal X-45” manufactured by Tokuyama Corporation, average particle size 4.5 μm] 28 7 parts are gradually added while being dispersed, and 15.3 parts of polydiallyldimethylammonium chloride (“PAS-H-5L” manufactured by Nittobo Co., Ltd., 28% aqueous solution) as an ink fixing agent and a crosslinking agent (B 2.9 parts of basic zirconyl chloride ("Zircosol ZC-2" manufactured by Daiichi Rare Element Chemical Co., Ltd.) is added, and 10 minutes at 5000 rpm with a homogenizer ["TK ROBOMICS" manufactured by Tokushu Kika Kogyo Co., Ltd.]. The mixture was stirred for a minute to prepare a coating solution having a solid content of 15%.
This coating solution is applied to high-quality paper having a basis weight of 64 g / m ² with an applicator having a clearance of 75 μm so that the solid content is 13 g / m ^2, and then dried in a hot air dryer at 105 ° C. for 10 minutes. Thus, an ink receiving layer was formed to obtain an ink jet recording medium (matte paper type).
The obtained ink jet recording medium (matte paper type) was evaluated for surface strength of the ink receiving layer and ink bleeding during printing in the following manner. The results are shown in Table 1.

(Ink receiving layer surface strength)
“Cellophane tape” (width 18 mm) manufactured by Nichiban Co., Ltd. was applied to the coated surface of the obtained inkjet recording medium, and a hand roller (weight 2 kg) was reciprocated five times from above to apply a load. Was peeled in a 180 degree direction (test speed 100 mm / min) with an autograph “AG-100” manufactured by Shimadzu Corporation, and the peel strength (gf / mm) at that time was measured.

(Wet strength of ink receiving layer)
The coated surface of the obtained inkjet recording medium was rubbed with a wet cotton swab under a load of 100 gf, the number of times until the surface of the supporting substrate appeared was measured, and evaluated according to the following criteria.
○ ・ ・ ・ 50 times or more △ ・ ・ ・ 10 to 50 times × ・ ・ ・ less than 10 times

Examples 2 and 4
An ink jet recording medium (matte paper type) was used in the same manner as in Example 1 except that the AA-PVA resin (A2 , A4) according to Production Examples 2 and 4 was used as the AA-PVA resin (A) in Example 1. ) And evaluated in the same manner. The results are shown in Table 1.

Comparative Examples 1-2 and 10
Inkjet recording medium in the same manner as in Example 1, except that the AA-PVA-based resin (A5-A6 , A3 ) according to Production Examples 5-6 , 3 was used as the AA-PVA-based resin (A) in Example 1. (Matte paper type) was obtained and evaluated in the same manner. The results are shown in Table 1.

Comparative Example 3
In Example 1, an ink jet recording medium (matte paper type) was obtained in the same manner as in Example 1 except that the crosslinking agent (B) was not used, and evaluation was performed in the same manner. The results are shown in Table 1.

Comparative Example 4
In Example 1, in place of the AA-modified PVA resin (A1), a silanol-modified PVA resin (polymerization degree 1700, saponification degree 99.0 mol%, modification degree 0.2 mol%) was used. In the same manner as in Example 1, an ink jet recording medium (matte paper type) was obtained and evaluated in the same manner. The results are shown in Table 1.

Example 5
Vapor phase process silica (C) [“Aerosil 300” manufactured by Nippon Aerosil Co., Ltd., average particle diameter 7 nm] 150 parts was dispersed in 500 parts of water using a homogenizer [“TK ROBOMICS” manufactured by Tokushu Kika Kogyo Co., Ltd.] To this, 20 parts of AA-PVA-based resin (A1) dissolved in 480 parts of water was gradually added and mixed. Next, 40 parts of polydiallyldimethylammonium chloride (“PAS-H-5L” manufactured by Nittobo Co., Ltd., 28% aqueous solution) as an ink fixing agent, and a 10% aqueous solution of basic zirconyl chloride as a cross-linking agent (B) 20 parts of “Zircosol ZC-2” manufactured by Elemental Chemical Industries, Ltd.] was added, and the mixture was further stirred with a homogenizer to obtain a coating solution.
This coating solution is applied onto a PET film whose surface has been subjected to corona discharge treatment with an applicator having a clearance of 200 μm, and once the temperature of the coating film surface is cooled to 10 ° C. and gelled, then 20 ° C., 30 ° C. Air at a temperature of 40 ° C., 40 ° C., and 50 ° C. was blown for 1 minute each and dried to form a receiving layer and glossy layer to obtain an ink jet recording medium (photo-like glossy paper type).
For the obtained ink jet recording medium (photo-like glossy paper type), the surface strength of the ink receiving layer and glossy layer was evaluated in the following manner, and the wet strength was evaluated in the same manner as in Example 1. . The results are shown in Table 2.

The state of the ink receiving layer and glossy layer of the obtained inkjet recording medium (photo-like glossy paper type) was visually observed, and the number of cracks having a size of 0.2 mm or more per 10 × 10 cm ² was counted. It was evaluated as follows.
◎ ... 3 or less ○ ... 4-10 pieces △ ... 11-19 pieces × ... 20 pieces or more

Examples 6 and 8
In Example 5, except that the AA-PVA-based resins (A2 and A4) according to Production Examples 2 and 4 were used as the AA-PVA-based resin (A), the same as in Example 5, an inkjet recording medium (photo-like gloss) Paper type) was obtained and evaluated in the same manner. The results are shown in Table 2.

Example 9
In Example 5, instead of basic zirconyl chloride as a crosslinking agent, an aqueous borax solution (4%)
An ink jet recording medium (photo-like glossy paper type) was obtained in the same manner as in Example 5 except that 30 parts were used and evaluated in the same manner. The results are shown in Table 2.

Example 10
In Example 5, an ink jet recording medium (photo-like medium) was used in the same manner as in Example 5 except that 2 parts of metaxylylenediamine (“MXDA” manufactured by Mitsubishi Gas Chemical Co., Inc.) was used instead of basic zirconyl chloride as a crosslinking agent. A glossy paper type) was obtained and evaluated in the same manner. The results are shown in Table 2.

Example 11
In Example 5, an ink jet recording medium (photo-like glossy paper type) was obtained in the same manner as in Example 5 except that 2 parts of adipic acid dihydrazide was used in place of basic zirconyl chloride as a crosslinking agent, and evaluation was performed in the same manner. Went. The results are shown in Table 2.

Example 12
Ink jet recording medium (photo-like glossy paper type) in the same manner as in Example 5 except that colloidal silica ("Snowtex PS-50" manufactured by Nissan Chemical Industries, Ltd.) was used instead of vapor phase method silica in Example 5. Were similarly evaluated. The results are shown in Table 2.

Example 13
In Example 5, an inkjet recording medium (photo-like medium) was used in the same manner as in Example 5 except that gas phase method alumina (“CAB-O-SPERSE PG-003” manufactured by CABOT) was used instead of gas phase method silica. A glossy paper type) was obtained and evaluated in the same manner. The results are shown in Table 2.

Comparative Examples 5-6
Ink jet recording medium (photo-like gloss) in the same manner as in Example 5 except that the AA-PVA resin (A5 to A6) according to Production Examples 5 to 6 was used as the AA-PVA resin (A) in Example 5. Paper type) was obtained and evaluated in the same manner. The results are shown in Table 2.

Comparative Example 7
In Example 5, an inkjet recording medium (photo-like glossy paper type) was produced in the same manner as in Example 5 except that the crosslinking agent (B) was not used. However, even when the temperature of the coating film surface was cooled to 10 ° C., it did not gel, and the coating surface was waved by blowing dry air, and a smooth glossy layer could not be obtained. The results evaluated in the same manner as in Example 5 are shown in Table 2.

Comparative Example 8
In Example 9, instead of the AA-modified PVA resin (A1), a silanol-modified PVA resin (polymerization degree 1700, saponification degree 99.0 mol%, modification degree 0.2 mol%) was used. The working solution gelled rapidly and a uniform coating layer could not be obtained.

Comparative Example 9
In Example 9, in place of AA-PVA-based resin (A1), an unmodified PVA having a polymerization degree of 3500 and a saponification degree of 88 mol% was used in the same manner as in Example 9 to prepare an ink jet recording medium (photo-like). A glossy paper type) was obtained and evaluated in the same manner. The results are shown in Table 3.

  The ink jet recording medium of the present invention has a high surface strength of the ink receiving layer even when the amount of the binder resin is low, and also has a high surface strength when wet, so that the ink jet recording medium for printing a high-definition image at high speed Useful as.

Claims (8)

An acetoacetate group-containing polyvinyl alcohol resin (A) having a content of acetoacetate groups exceeding 3 mol% and a hydroxyl group average chain length of 25 or more, a crosslinking agent (B), inorganic An ink jet recording medium comprising an ink receiving layer containing fine particles (C). Claim 1 Symbol mounting of the ink jet recording medium, wherein the saponification degree of the acetoacetic ester group-containing polyvinyl alcohol-based resin (A) is 97 mol% or more. The acetoacetate group-containing polyvinyl alcohol resin (A) is obtained by reacting diketene with a polyvinyl alcohol resin obtained by saponification in the presence of a solvent having a dielectric constant of 30 or less. The ink jet recording medium according to claim 1 or 2 . The acetoacetate group-containing polyvinyl alcohol resin (A) has a maximum acetoacetate group content by particle size of 44 to 74, 74 to 105, 105 to 177, 177 to 297, 297 to 500, 500 to 1680 μm. The inkjet recording medium according to any one of claims 1 to 3 , wherein the value is an acetoacetate group-containing polyvinyl alcohol resin (A) having a value within 3 times the minimum value. The inkjet recording medium according to any one of claims 1 to 4, wherein the crosslinking agent (B) is any one of a polyvalent metal compound, a boron compound, an amine compound, or a hydrazine compound. The inkjet recording according to any one of claims 1 to 5, wherein the inorganic fine particles (C) are any one of amorphous silica, gas phase method silica, colloidal silica, gas phase method alumina, and alumina hydrate. Media. On the ink receiving layer, according to claim 1 to 6 for ink jet recording medium according to any one characterized by comprising further provided a gloss layer. An acetoacetate group-containing polyvinyl alcohol resin (A) having a content of acetoacetate groups exceeding 3 mol% and a hydroxyl group average chain length of 25 or more, a crosslinking agent (B), inorganic and applying a coating liquid containing fine particles (C), according to claim 1-7 method of manufacturing an ink jet recording medium according to any one characterized by forming an ink-receiving layer.