JP2007069593A - Inkjet recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording material having a photolike high gloss, excellent in ink absorbing property, color developability, and productivity, and generating no color change in the periphery of printing position. <P>SOLUTION: An inkjet recording material comprises a base and formed thereon one or more ink-receiving layers at least one of which comprises fine inorganic particles having an average secondary-particle diameter of 500 nm or smaller, a resin binder having an acetoacetyl group, and a compound having two or more terminal hydrazino groups, wherein at least one of the ink-receiving layers contains at least one organic acid having a pKa of 2-5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording material, and more particularly to an ink jet recording material having high photo-like glossiness, excellent ink absorbability, no surface cracks and no discoloration of a printed portion, and high productivity.

  As a recording material used in the ink jet recording method, a recording material in which an ink receiving layer is provided on a support such as paper or a plastic resin film is known. The ink receiving layer is roughly classified into two types. One type is an ink receiving layer mainly composed of a water-soluble polymer, and the other type is an ink receiving layer mainly composed of an inorganic pigment and a resin binder.

  The former type of ink receiving layer absorbs ink by swelling the water-soluble polymer. The latter type of ink receiving layer absorbs ink in voids formed by inorganic pigments. Due to such a difference in ink absorption mechanism, the former type is called a swelling type (or polymer type), and the latter type is called a void type.

  The former polymer type ink-receiving layer is excellent in gloss because it is a continuous and uniform film, but is inferior in ink absorptivity (ink absorption speed; drying speed after printing). On the other hand, the latter void type has excellent ink absorbability but poor gloss.

  In recent years, there has been a demand for a recording material excellent in both ink absorbency and gloss, and a void-type recording material using extremely fine inorganic fine particles as a pigment has been proposed. For example, it has been proposed to use inorganic ultrafine particles such as gas phase method silica or wet method silica, which are pulverized and dispersed so as to have an average secondary particle diameter of 500 nm or less, as a pigment component of the ink receiving layer. For example, JP-A-3-56552, JP-A-10-119423, JP-A-2000-2111235, and JP-A-2000-309157 disclose examples of using vapor phase silica. JP-A-9-286165, JP-A-10 JP-A No. 181190 discloses an example of using precipitated silica, and JP-A No. 2001-277712 discloses an example of using gel silica. JP-A-62-174183, JP-A-2-276670, JP-A-5-32037, JP-A-6-199034 and the like disclose recording materials using alumina or alumina hydrate.

  However, the use of ultrafine inorganic fine particles as described above can provide high gloss, but the viscosity of the coating solution tends to be high, and since it is applied at a low solid content concentration, there are surface defects such as wind ripples and cracks during drying. It tends to occur. In particular, when using a non-water-absorbent support such as polyolefin resin-coated paper (polyolefin resin such as polyethylene laminated on both sides of the paper) or polyester film in order to obtain high gloss and good texture, the support is ink. Ink absorbability of the ink receiving layer provided on the support is important. Therefore, in order to increase the void ratio and void volume of the ink receiving layer, the ink receiving layer needs to be composed of a large amount of pigment and a low ratio of binder, and as a result, wind ripples and cracks occur when the ink receiving layer is applied and dried. Increasingly more likely.

  In order to prevent such surface defects, a method is known in which a coating liquid containing a crosslinking agent is applied to a support and then dried under relatively mild conditions. For example, in JP-A-10-119423, JP-A-2000-27093, JP-A-2001-96900, etc., a boron compound such as boric acid, borate, or borax is used as a crosslinking agent for polyvinyl alcohol, and the coating solution is used. A method is disclosed in which it is applied and cooled once to increase the viscosity of the coating solution and then dried at a relatively low temperature. Further, aldehyde compounds, epoxy compounds, isocyanates and the like are also known as crosslinking agents. However, it is difficult to achieve both crosslinkability and various properties as an ink jet recording material. Depending on the conditions during coating and drying, defects in the coating often occur, and coating failures may become noticeable with slight changes in drying temperature. It was. In addition, since the film quality is rigid, there is a drawback such as so-called folding that the coating film breaks when the recording material is bent. Furthermore, since a long time is required especially in the drying process, there is a problem that productivity cannot be increased.

  On the other hand, it is known to use a resin binder having an acetoacetyl group as a technique for preventing surface defects such as cracks as described above. For example, Japanese Patent Application Laid-Open No. 2003-335043 (Patent Document 1), Japanese Patent Application Laid-Open No. 2004-230609 (Patent Document 2), Japanese Patent Application Laid-Open No. 2004-268576 (Patent Document 3), Japanese Patent Application Laid-Open No. 2004-268777 (Patent Document 4). Etc. are described.

However, it has been newly found that an ink jet recording material using such a binder discolors the printed part over time when printing with ink jet ink.
JP 2003-335043 A JP 2004-230609 A JP 2004-268576 A JP 2004-268777 A

  An object of the present invention is to provide an ink jet recording material which has a photo-like high gloss, excellent ink absorbability, color developability and productivity, and does not cause discoloration of a printing portion.

The above object of the present invention has been achieved by the following invention.
(1) At least one of the ink receiving layers provided on the support contains inorganic fine particles having an average secondary particle diameter of 500 nm or less, a resin binder having an acetoacetyl group, and a compound having two or more terminal hydrazino groups An ink jet recording material, wherein at least one of the ink receiving layers contains an organic acid having a pKa value of 2 to 5.
(2) The inkjet recording material according to (1), wherein an addition amount of the organic acid having a pKa value of 2 to 5 is 0.01 to 1 g per 1 m ² of the inkjet recording material.
(3) The inkjet recording material according to (1) or (2), wherein the inorganic fine particles are amorphous synthetic silica.
(4) In the ink receiving layer containing an organic acid having a pKa value of 2 to 5, the amount of the alkali metal ion is 10 to 120 mol% with respect to the organic acid having a pKa value of 2 to 5. The inkjet recording material according to (1), which also contains an alkali metal salt.
(5) The ink jet recording material according to (4), wherein the amount of the organic acid having a pKa value of 2 to 5 is 0.01 to 3.0 g per 1 m ² of the ink jet recording material.
(6) The inkjet recording material according to (4) or (5), wherein the inorganic fine particles are alumina or alumina hydrate.

  By carrying out the present invention, it is possible to obtain an ink jet recording material which has a photo-like high gloss, is excellent in ink absorbability, color developability and productivity, and does not cause discoloration of the printed part during storage after printing.

  Hereinafter, the present invention will be described in detail. An ink jet recording material provided with at least one ink receiving layer containing inorganic fine particles, a resin binder having an acetoacetyl group, and a compound having two or more terminal hydrazide groups on a support, a sheet printed with ink jet ink, When stored for a long period of time, there was a problem that the printed portion was discolored. As a result of intensive studies on the improvement method, it was found that discoloration of the printed portion can be prevented by incorporating an organic acid having a pKa value of 2 to 5 in at least one ink receiving layer of the ink jet recording material. It is a thing.

  Further, by adding together an alkali metal salt in an amount such that the amount of alkali metal ions is 10 to 120 mol% with respect to the organic acid added to at least one ink receiving layer of the ink jet recording material. Furthermore, it discovered that discoloration can be prevented and production efficiency can be improved more.

  The color change of the print unit, which is a problem of the present invention, is a phenomenon in which the print unit and the periphery of the print unit are changed to red. This phenomenon is a problem peculiar to an ink jet recording material using a resin binder having an acetoacetyl group as a resin binder and further using a compound having two or more terminal hydrazino groups.

  In particular, the above discoloration is greatly affected by the amount of the compound having two or more terminal hydrazino groups. If the amount of the compound having two or more terminal hydrazino groups is large, the discoloration becomes remarkable. If the amount is small, the discoloration may be acceptable.

  However, if the addition amount of the compound having two or more terminal hydrazino groups is too small, the crosslinking reaction of the resin binder having the acetoacetyl group becomes insufficient, resulting in insufficient ink absorbability or cracking during coating and drying. Or the application surface becomes non-uniform due to the wind in the dryer.

  When the organic acid of the present invention and further an alkali metal salt are present during coating and drying of the ink jet recording material, the crosslinking reaction between the compound having two or more terminal hydrazino groups and the resin binder having the acetoacetyl group is promoted. Therefore, an ink jet recording material can be produced with a compound having a smaller amount of two or more terminal hydrazino groups, and as a result, it is considered that discoloration can be suppressed.

  Examples of inorganic fine particles having an average secondary particle diameter of 500 nm or less used in the ink receiving layer of the present invention include various known fine particles such as amorphous synthetic silica, alumina, alumina hydrate, calcium carbonate, magnesium carbonate, titanium dioxide. Among them, amorphous synthetic silica, alumina, or alumina hydrate is preferable in terms of ink absorbability and productivity.

  Amorphous synthetic silica can be roughly classified into wet method silica, gas phase method silica, and others depending on the production method. Wet method silica is further classified into precipitation method silica, gel method silica, and sol method silica according to the production method. Precipitated silica is produced by reacting sodium silicate and sulfuric acid under alkaline conditions, and the silica particles that have grown are agglomerated and settled, and are then commercialized through the steps of filtration, washing, drying, pulverization and classification. Precipitated silica is commercially available, for example, from Tosoh Silica Co., Ltd. as a nip seal and from Tokuyama Co., Ltd. as a Toxeal. Gel silica is produced by reacting sodium silicate and sulfuric acid under acidic conditions. During aging, the microparticles dissolve and reprecipitate so as to bind the other primary particles, so that the distinct primary particles disappear and form relatively hard aggregated particles having an internal void structure. For example, it is commercially available as nip gel from Tosoh Silica Co., Ltd. and as syloid and silo jet from Grace Japan Co., Ltd. The sol method silica is also called colloidal silica, and is obtained by heating and aging a silica sol obtained through metathesis of sodium silicate acid or the like through an ion exchange resin layer. For example, it is commercially available as Snowtex from Nissan Chemical Industries, Ltd. Yes.

  Vapor phase silica is also called a dry method as opposed to a wet method, and is generally made by a flame hydrolysis method. Specifically, a method of making silicon tetrachloride by burning with hydrogen and oxygen is generally known, but silanes such as methyltrichlorosilane and trichlorosilane can be used alone or silicon tetrachloride instead of silicon tetrachloride. Can be used in a mixed state. Vapor phase silica is commercially available as Aerosil from Nippon Aerosil Co., Ltd. and QS type from Tokuyama Co., Ltd.

In the present invention, vapor phase silica is particularly preferably used. The average primary particle diameter of the vapor phase silica used in the present invention is preferably 30 nm or less, and preferably 15 nm or less in order to obtain higher gloss. More preferably, an average primary particle diameter of 3 to 15 nm (especially 3 to 10 nm) and a specific surface area by the BET method of 200 m ² / g or more (preferably 250 to 500 m ² / g) are used. The average primary particle diameter as used in the present invention is an average particle diameter obtained by observing the diameter of a circle equal to the projected area of each of 100 primary particles existing within a certain area by observation of fine particles with an electron microscope. The BET method referred to in the present invention is one of the powder surface area measurement methods by the vapor phase adsorption method, and is a method for determining the total surface area of a 1 g sample from the adsorption isotherm, that is, the specific surface area. is there. Usually, nitrogen gas is often used as the adsorbed gas, and the most frequently used method is to measure the amount of adsorption from the change in pressure or volume of the gas to be adsorbed. The most prominent expression for expressing the isotherm of multimolecular adsorption is the Brunauer, Emmett, and Teller formula, called the BET formula, which is widely used for determining the surface area. The adsorption amount is obtained based on the BET equation, and the surface area is obtained by multiplying the area occupied by one adsorbed molecule on the surface.

  In the ink receiving layer of the present invention, the vapor phase method silica is used in the presence of a cationic compound, and the average secondary particle size of the vapor phase method silica is 500 nm or less, preferably 30 to 300 nm, more preferably 30 to 200 nm. Dispersed ones can be used. As a dispersion method, gas phase method silica and a dispersion medium are premixed by ordinary propeller stirring, turbine type stirring, homomixer type stirring, etc., and then a media mill such as a ball mill, a bead mill, a sand grinder, a high pressure homogenizer, an ultrahigh pressure, etc. It is preferable to perform dispersion using a pressure disperser such as a homogenizer, an ultrasonic disperser, a thin film swirl disperser, or the like. The average secondary particle diameter as used in the present invention is an average particle diameter of dispersed aggregated particles observed by observing the ink receiving layer of the obtained recording material with an electron microscope. It is.

  In the present invention, wet method silica pulverized so that the average secondary particle diameter is 500 nm or less can also be preferably used. The wet process silica particles used in the present invention are preferably wet process silica particles having an average primary particle diameter of 50 nm or less, preferably 3 to 40 nm, and an average aggregate particle diameter of 5 to 50 μm. It is preferable to use wet method silica fine particles finely pulverized to an average secondary particle diameter of 500 nm or less, preferably 30 to 400 nm, more preferably about 30 to 300 nm in the presence of.

  Since the wet process silica produced by a normal method has an average aggregate particle diameter of 1 μm or more, it is used after being finely pulverized. As a pulverization method, a wet dispersion method in which silica dispersed in an aqueous medium is mechanically pulverized can be preferably used. At this time, the increase in the initial viscosity of the dispersion is suppressed, high concentration dispersion is possible, and the pulverization / dispersion efficiency is increased so that the particles can be further pulverized. Therefore, the oil absorption is 210 ml / 100 g or less, the average aggregated particle diameter It is preferable to use precipitated silica of 5 μm or more. By using a high-concentration dispersion, the productivity of recording paper is also improved. The oil absorption is measured based on the description of JIS K-5101.

  As a specific method for obtaining wet method silica fine particles having an average secondary particle diameter of 500 nm or less according to the present invention, first, silica particles and a cationic compound are mixed in water (whichever comes first or at the same time). And each dispersion or aqueous solution may be mixed, and at least one dispersion device such as a sawtooth blade type dispersion device, a propeller blade type dispersion device, or a rotor stator type dispersion device is used. To obtain a preliminary dispersion. If necessary, an appropriate low boiling point solvent may be added. The higher the solid content concentration of the silica pre-dispersion, the higher the concentration. However, since the dispersion becomes impossible when the concentration is too high, the preferred range is 15 to 40% by mass, more preferably 20 to 35% by mass. Next, by applying a stronger mechanical means, a wet process silica fine particle dispersion having an average secondary particle diameter of 500 nm or less is obtained. As the mechanical means, a known method can be adopted, for example, a media mill such as a ball mill, a bead mill, a sand grinder, a high pressure homogenizer, a pressure disperser such as an ultra high pressure homogenizer, an ultrasonic disperser, and a thin film swirl disperser. Can be used.

  As the cationic compound used for the dispersion of the gas phase method silica and the wet method silica, a cationic polymer or a water-soluble metal compound can be used. Examples of the cationic polymer include polyethyleneimine, polydiallylamine, polyallylamine, alkylamine polymer, JP-A-59-20696, JP-A-59-33176, JP-A-59-33177, JP-A-59-155088. JP, 60-11389, JP 60-49990, JP 60-83882, JP 60-109894, JP 62-198493, JP 63-49478, 1 described in JP-A-63-115780, JP-A-63-280681, JP-A-1-40371, JP-A-6-234268, JP-A-7-125411, JP-A-10-193976, etc. A polymer having a tertiary amino group or a quaternary ammonium base is preferably used. In particular, diallylamine derivatives are preferably used as the cationic polymer. In terms of dispersibility and dispersion viscosity, the molecular weight of these cationic polymers is preferably about 2,000 to 100,000, and particularly preferably about 2,000 to 30,000.

  Examples of the water-soluble metal compound include water-soluble polyvalent metal salts, and among them, a compound made of aluminum or a group 4A metal (for example, zirconium or titanium) in the periodic table is preferable. Particularly preferred is a water-soluble aluminum compound. As a water-soluble aluminum compound, for example, as an inorganic salt, aluminum chloride or a hydrate thereof, aluminum sulfate or a hydrate thereof, ammonium alum and the like are known. Furthermore, a basic polyaluminum hydroxide compound which is an inorganic aluminum-containing cationic polymer is known and preferably used.

The basic polyaluminum hydroxide compound has a main component represented by the following general formula 1, 2, or 3, for example, [Al ₆ (OH) ₁₅ ] ³⁺ , [Al ₈ (OH) ₂₀ ] ⁴⁺ _{, [Al 13 (OH) 34} ] 5+, with _{[Al 21 (OH) 60]} 3+, basic water-soluble that contain polynuclear condensed ions of a polymer stable at of polyaluminum hydroxide as an equal is there.

[Al ₂ (OH) _n Cl _6-n ] _m General formula 1
[Al (OH) ₃ ] _n AlCl ₃ general formula 2
Al _n (OH) _m Cl _(3n-m) 0 <m <3n General formula 3

  These are water treatment agents from Taki Chemical Co., Ltd. under the name of polyaluminum chloride (PAC), from Asada Chemical Co., Ltd. under the name of polyaluminum hydroxide (Paho), and from Riken Green Co., Ltd. It is marketed under the name of Purachem WT and from other manufacturers for the same purpose, and various grades are readily available.

  As the water-soluble compound containing a Group 4A element of the periodic table used in the present invention, a water-soluble compound containing titanium or zirconium is more preferable. Examples of the water-soluble compound containing titanium include titanium chloride and titanium sulfate. Examples of water-soluble compounds containing zirconium include zirconium chloride, zirconium oxychloride, hydroxy zirconium chloride, zirconium nitrate, basic zirconium carbonate, zirconium hydroxide, zirconium carbonate / ammonium, zirconium carbonate / potassium, zirconium sulfate, zirconium fluoride compound, etc. Is mentioned. In the present invention, the term “water-soluble” means that 1% by mass or more dissolves in water at room temperature and normal pressure.

  As the alumina used in the present invention, γ-alumina which is a γ-type crystal of aluminum oxide is preferable, and among them, a δ group crystal is preferable. Although γ-alumina can reduce the primary particles to about 10 nm, normally, secondary particle crystals of several thousand to several tens of thousands nm are averaged by ultrasonic waves, a high-pressure homogenizer, a counter collision type jet crusher, or the like. Those whose size is pulverized to a particle size of 500 nm or less, preferably about 20 to 300 nm can be used.

The alumina hydrate of the present invention is represented by a constitutive formula of Al ₂ O ₃ .nH ₂ O (n = 1 to 3). The case where n is 1 represents an alumina hydrate having a boehmite structure, and the case where n is greater than 1 and less than 3 represents an alumina hydrate having a pseudo boehmite structure. It can be obtained by a known production method such as hydrolysis of an aluminum alkoxide such as aluminum isopropoxide, neutralization of an aluminum salt with an alkali, hydrolysis of an aluminate. The average secondary particle diameter of the alumina hydrate used in the present invention is 500 nm or less, preferably 20 to 300 nm.

  In the ink receiving layer of the present invention, the content of inorganic fine particles having an average secondary particle diameter of 500 nm or less is preferably 50% by mass or more, more preferably 60% by mass or more, based on the total solid content of the ink receiving layer. The range of 65 to 90% by mass is particularly preferable.

  The ink receiving layer of the present invention uses a resin binder having an acetoacetyl group as a binder resin for inorganic fine particles. A resin binder having an acetoacetyl group can be synthesized by introducing an acetoacetyl group by a polymer reaction. For example, an acetoacetyl group can be introduced by reaction of a hydroxy group with diketene. Specific examples of the resin binder having an acetoacetyl group include acetoacetyl-modified polyvinyl alcohol, acetoacetyl-modified cellulose derivatives, acetoacetyl-modified starch, diacetone acrylamide-modified polyvinyl alcohol and the like. In the present invention, modified polyvinyl alcohol having an acetoacetyl group is particularly preferable.

  The acetoacetyl-modified polyvinyl alcohol can be produced by a known method such as a reaction between polyvinyl alcohol and diketene. The degree of acetoacetylation is preferably from 0.1 to 20 mol%, more preferably from 1 to 15 mol%. The saponification degree is preferably 80 mol% or more, more preferably 85 mol% or more. As a polymerization degree, the thing of 500-5000 is preferable, and the thing of 1000-4500 is especially preferable.

  In the present invention, in addition to the resin binder having an acetoacetyl group, another known resin binder may be used in combination. For example, cellulose derivatives such as carboxymethyl cellulose and hydroxypropyl cellulose, starch and various modified starches, gelatin and various modified gelatins, chitosan, carrageenan, casein, soy protein, polyvinyl alcohol, various modified polyvinyl alcohols, polyvinylpyrrolidone, polyacrylamide, etc. are required It can be used together depending on the situation. Furthermore, various latexes may be used in combination as the binder resin.

  In this case, it is preferable to use a resin binder having an acetoacetyl group and a highly compatible resin binder in terms of gloss. When using the modified polyvinyl alcohol having an acetoacetyl group, complete or partially saponified polyvinyl alcohol or cationic modified polyvinyl alcohol can be preferably used in combination. In particular, those having a saponification degree of 80% or more and an average polymerization degree of 200 to 5000 can be preferably used.

  Examples of the cation-modified polyvinyl alcohol include polyvinyl alcohol having a primary to tertiary amino group or a quaternary ammonium group in the main chain or side chain of polyvinyl alcohol as described in JP-A-61-110483. It is.

  The amount of the resin binder to be used in combination is not particularly limited as long as the action of the resin binder having an acetoacetyl group and a compound having two or more terminal hydrazino groups described below can be obtained.

  The total content of the resin binder is preferably in the range of 5 to 40% by mass, and particularly preferably 10 to 30% by mass with respect to the inorganic fine particles. By setting the ratio of the resin binder in the above range, it is preferable because the void volume (void ratio) in the ink receiving layer is increased and the ink absorbability is increased.

  A terminal hydrazino group is a hydrazino group in which one nitrogen atom of the hydrazino group is unsubstituted and the other nitrogen atom is bonded to the other structural part of the molecule. Examples of the partial structure containing the terminal hydrazino group of the present invention include partial structures such as hydrazine, carboxylic acid hydrazide, semicarbazide, carbohydrazide, sulfonic acid hydrazide, imido acid hydrazide, and the like, particularly carboxylic acid hydrazide and semicarbazide structures. It is preferable. The two or more hydrazino groups are connected by any organic group such as an aliphatic group, an aromatic group, or a heterocyclic group. Specific examples of the compound having two or more terminal hydrazino groups of the present invention include 4,4′-methylenebis (phenylhydrazine), 2,4,6-trihydrazino-1,3,5-triazine, carbohydrazide, thiocarbo Hydrazide, diaminoguanidine, succinic acid dihydrazide, adipic acid dihydrazide, citric acid trihydrazide, sebacic acid dihydrazide, polyphthalic acid hydrazides such as isophthalic acid dihydrazide, 4,4'-ethylene disemicarbazide, 4,4'-hexamethylenedi Reaction products of polyisocyanate such as semicarbazide and hydrazine, polymer type hydrazide such as polyacrylic acid hydrazide, and the like can be mentioned. In particular, succinic acid dihydrazide and adipic acid dihydrazide are preferable in terms of water solubility and reactivity.

  The content of the compound having two or more terminal hydrazino groups of the present invention is not particularly limited, but 0.1% of the resin binder having an acetoacetyl group in terms of productivity and characteristics of the obtained ink receiving layer. The range of -50 mass%, and further 1-20 mass% is preferable.

  In the present invention, other known hardeners may be used in combination. When modified polyvinyl alcohol is used as the resin binder, the polyvinyl alcohol cross-linking agent (hardener) includes aldehyde compounds such as formaldehyde and glutaraldehyde, ketone compounds such as diacetyl and chloropentanedione, and bis (2-chloroethyl). Urea), 2-hydroxy-4,6-dichloro-1,3,5-triazine, a compound having a reactive halogen as described in US Pat. No. 3,288,775, divinyl sulfone, US Pat. No. 3,635 , Compounds having reactive olefins as described in US Pat. No. 2,718,316, N-methylol compounds as described in US Pat. No. 2,732,316, isocyanates as described in US Pat. No. 3,103,437, US Pat. No. 3,017,280, U.S. Pat. No. 2,983,611 Lysine compounds, carbodiimide compounds as described in US Pat. No. 3,100,704, epoxy compounds as described in US Pat. No. 3,091,537, halogen carboxaldehydes such as mucochloric acid, dioxanes such as dihydroxydioxane Inorganic cross-linking agents such as derivatives, chromium alum, zirconium sulfate, boric acid, borates and borax can be used in combination.

In the present invention, an organic acid having a pKa value of 2 to 5 is contained in the ink receiving layer. Specific examples of organic acids include formic acid (pKa = 3.75), acetic acid (pKa = 4.76), citric acid (pKa ₁ = 3.13), lactic acid (pKa = 3.86), malonic acid (pKa) ₁ = 2.85), succinic acid (pKa ₁ = 4.19), malic acid (pKa ₁ = 3.40), tartaric acid (pKa ₁ = 3.04), fumaric acid (pKa ₁ = 3.03), Examples include benzoic acid (pKa = 4.20), ascorbic acid (pKa = 4.10), benzenesulfonic acid (pKa = 2.55), and 2,4-dinitrophenol (pKa = 4.10).

  In the present invention, it is preferable to further contain an alkali metal salt in the ink receiving layer. Examples of alkali metal salts that can be used in the present invention include sodium formate, potassium formate, sodium acetate, potassium acetate, sodium lactate, potassium lactate, sodium benzoate, potassium benzoate, sodium ascorbate, sodium benzenesulfonate, benzene And potassium sulfonate.

  The amount of the alkali metal salt used in the present invention is preferably 10 to 120 mol% of the alkali metal ion with respect to the content of the organic acid having a pKa value of 2 to 5 added in the ink receiving layer. is there. In the case of less than 10 mol%, there may be almost no effect of adding an alkali metal salt. More preferably, it is 35-100 mol%.

  The discoloration which is a problem in the present invention is a phenomenon in which the print portion and the periphery of the print portion are red when seen with a long-term storage after printing with an inkjet printer. This is a phenomenon peculiar to an ink jet recording material in which a resin binder having an acetoacetyl group and a compound having two or more terminal hydrazino groups are used in combination. The reason for this is not clear, but it is considered that one of the mechanisms of discoloration is probably that alkaline ink droplets are injected and the pH of the ink receiving layer partially rises, and organic acids having a pKa of 2 to 5 are used in the present invention. This is also advantageous in that it can be added without impairing the coating properties, color developability and gloss of the inkjet recording material. It is thought that this is because a buffer is formed by adding the organic acid having a pKa value of the present invention to prevent an increase in pH. Such an effect was not obtained when an ink jet recording paper was prepared using an acid having a pKa of less than 2.

When no alkali metal salt is added, the content of the organic acid having a pKa value of 2 to 5 is preferably 0.01 to 1 g, and 0.1 to 0.6 g per 1 m ^{2 of the} inkjet recording material. Is particularly preferred. Moreover, the range of 0.2-25 mass% is preferable with respect to the resin binder which has an acetoacetyl group. By setting the ratio of the organic acid within the above range, discoloration of the printed portion over time can be effectively prevented.

When the alkali metal salt is added, the content of the organic acid having a pKa value of 2 to 5 is preferably 0.01 to 3.0 g per 1 m ^{2 of the} ink jet recording material, and 0.1 to 2 Particularly preferred is 0.7 g. It is believed that the addition amount of an organic acid having a pKa value of 2 to 5 can be increased by suppressing the pH of the ink receiving layer from being lowered too much by adding an alkali metal salt.

  As an alkali metal salt, a mixture of an organic acid and an alkali may be added instead. Examples of the alkali that can be used in the present invention include sodium hydroxide, potassium hydroxide, barium hydroxide, magnesium hydroxide, calcium hydroxide and the like.

  As a coating method of the ink jet recording material of the present invention, a resin binder having an acetoacetyl group and a compound having two or more terminal hydrazino groups may be contained in one coating solution, or an acetoacetyl group may be coated. Alternatively, the resin binder and the compound having two or more terminal hydrazino groups may be contained in different coating solutions and mixed at the time of production. However, the resin binder having an acetoacetyl group and hydrazide react to increase the viscosity of the coating solution, which makes it difficult to apply, so a different coating solution, and a method of simultaneous multilayer coating using a coating device described later, Or the method of apply | coating each coating liquid one by one is preferable. In the sequential coating, a coating solution containing a compound having two or more terminal hydrazino groups is applied after the coating solution containing the inorganic fine particles and the resin binder having an acetocetoacetyl group is applied and before drying is completed. Need to be done. If the coating solution containing the inorganic fine particles and the resin binder having an acetocetoacetyl group is dried in the absence of the compound having two or more terminal hydrazino groups, cracking occurs, which is not preferable. As a specific coating sequence in sequential coating, coating containing inorganic fine particles and a resin binder having an acetocetacetyl group on a support that has been coated with a coating solution containing a compound having two or more terminal hydrazino groups in advance and dried. Applying a coating solution, coating a coating solution containing a compound having two or more terminal hydrazino groups on a support and drying the coating solution containing inorganic fine particles and a resin binder having an acetocetacetyl group Applying a coating liquid containing inorganic fine particles and a resin binder having an acetocetoacetyl group on a support, and coating a coating liquid containing a compound having two or more terminal hydrazino groups before the coating liquid dries To do.

  As a method for adding an organic acid having a pKa value of 2 to 5 to the ink receiving layer, it may be added in advance to the coating solution, and as described above, two resin binders having an acetoacetyl group and two terminal hydrazino groups are used. When the compound having the above is contained in a different coating solution, the coating solution containing a compound having two or more terminal hydrazino groups can be added to the coating solution containing a resin binder having inorganic fine particles and an acetoacetyl group. It may be added. Further, when forming an ink receiving layer containing inorganic fine particles, a resin binder having an acetoacetyl group, and a compound having two or more terminal hydrazino groups by the above-described simultaneous multilayer coating method, a coating liquid containing the organic acid is used. You may apply | coat simultaneously. Further, a liquid containing the organic acid may be sprayed on the surface of the ink receiving layer by spraying before or after drying the ink receiving layer, or a support on which a coating liquid containing the organic acid has been applied in advance. A coating solution containing a resin binder having an inorganic fine particle and an acetocetoacetyl group and a coating solution containing a compound having two or more terminal hydrazino groups may be applied.

  As a method of adding an alkali metal salt to the ink receiving layer of the present invention, it is necessary to add the alkali metal salt after adjusting the pH to the acidic side, so that all or a part of the organic acid having a pKa value of 2 to 5 is previously added. It is preferable to add after mixing. If only the alkali metal salt is added, aggregates may be generated in the coating liquid, which is not preferable. The method for adding the mixed solution of the alkali metal salt and the organic acid having a pKa value of 2 to 5 may be added to the coating solution containing the inorganic fine particles and the resin binder having an acetocetoacetyl group, or the terminal hydrazino group. You may add to the coating liquid containing the compound which has 2 or more. Also, a coating containing a resin binder having inorganic fine particles and an acetocetacetyl group on a support on which a coating solution containing a mixture of the alkali metal salt and an organic acid having a pKa value of 2 to 5 has been coated in advance. A liquid and a coating liquid containing a compound having two or more terminal hydrazino groups may be applied. The timing of addition needs to be from the time of production of the coating liquid containing the inorganic fine particles and the resin binder having an acetocetoacetyl group to the end of drying after coating.

  Moreover, after apply | coating these coating liquids, the manufacturing method of making a coating liquid gel by heating and drying after that is preferable. In the present invention, gelation refers to a state in which the viscosity of the coating liquid increases and the coating liquid does not flow due to the wind blown in the drying process. Preferably, the state which does not show fluidity substantially is pointed out.

  As a method of heating after applying to the support, a method of passing through high-temperature air, a method of closely contacting a heat roll, a method of using an infrared heating device, a microwave heating device, or the like can be used. The heating temperature depends on the composition of the coating solution such as the amount of the resin binder having an acetoacetyl group and the amount of the compound having a hydrazino group, but when the coating solution is aqueous, it is preferably 30 to 100 ° C., particularly 40 to 95. A range of ° C is preferred. In general, the reaction between an acetoacetyl group and a hydrazine or hydrazide group proceeds rapidly, and from the viewpoint of productivity, the heating time is preferably 1 second to 10 minutes, and more preferably 5 seconds to 5 minutes.

The dry coating amount of the ink receiving layer of the present invention is in the range of 8 to 40 g / m ² , particularly 10 to 30 g / m ² as the solid content of the inorganic fine particles in terms of ink absorbability, ink receiving layer strength, and productivity. A range of m ² is preferred.

  In the present invention, it is preferable that the ink receiving layer further contains a cationic compound for the purpose of improving the water resistance of the ink dye. Examples of the cationic compound include the cationic polymer and the water-soluble metal compound mentioned in the description of the dispersion of silica. Examples of water-soluble metal compounds include water-soluble salts of metals selected from calcium, barium, manganese, copper, cobalt, nickel, iron, zinc, chromium, magnesium, tungsten, and molybdenum. Specifically, for example, calcium chloride, calcium sulfate, barium sulfate, barium phosphate, manganese chloride, manganese ammonium sulfate hexahydrate, cupric chloride, ammonium copper (II) chloride dihydrate, copper sulfate, chloride Cobalt, cobalt thiocyanate, cobalt sulfate, nickel sulfate hexahydrate, nickel chloride hexahydrate, nickel ammonium sulfate hexahydrate, nickel amidosulfate tetrahydrate, ferrous bromide, ferrous chloride, Ferric chloride, ferrous sulfate, ferric sulfate, zinc bromide, zinc chloride, zinc nitrate hexahydrate, zinc sulfate, zinc p-phenolsulfonate, chromium sulfate, magnesium sulfate, magnesium chloride hexahydrate , Sodium phosphotungstate, 12 tungstophosphoric acid n hydrate, 12 tungstosilicic acid 26 hydrate, molybdenum chloride, 12 molybdophosphoric acid n hydrate And the like. Among these, a cationic polymer having a molecular weight of about 5,000 to 100,000 and a compound made of aluminum or a Group 4A metal (for example, zirconium or titanium) in the periodic table are preferable, and an aluminum compound is particularly preferable. One type of cationic compound may be used, or a plurality of compounds may be used in combination.

  In the present invention, the ink jet recording material may be provided with a layer having other functions such as an ink absorbing layer or a protective layer as another ink receiving layer in addition to at least one ink receiving layer.

  In the present invention, the ink receiving layer of each layer further includes a surfactant, a coloring dye, a coloring pigment, an ink dye fixing agent, an ultraviolet absorber, an antioxidant, a pigment dispersant, an antifoaming agent, a leveling agent, an antiseptic. Various known additives such as an agent, a fluorescent brightening agent, and a viscosity stabilizer can also be added.

  Examples of the support used in the present invention include polyethylene, polypropylene, polyvinyl chloride, diacetate resin, triacetate resin, cellophane, acrylic resin, polyethylene terephthalate, polyethylene naphthalate and other water resistant supports such as polyolefin resin-coated paper, Water-absorbing supports such as high-quality paper, art paper, coated paper, cast coated paper and the like are used. A water resistant support is preferably used. Among water-resistant supports, polyolefin resin-coated paper is particularly preferable. The thickness of these supports is preferably about 50 to 250 μm.

  When a non-water-absorbing support such as a film or resin-coated paper is used as the support, a primer layer mainly composed of a natural polymer compound or a synthetic resin is preferably provided on the surface on which the ink receiving layer is provided. The primer layer provided on the support is mainly composed of natural polymer compounds such as gelatin and casein and synthetic resins. Examples of such synthetic resins include acrylic resins, polyester resins, vinylidene chloride, vinyl chloride resins, vinyl acetate resins, polystyrene, polyamide resins, polyurethane resins, and the like. The primer layer is provided on the support with a film thickness (dry film thickness) of 0.01 to 5 μm. Preferably it is the range of 0.01-2 micrometers.

  Various back coat layers can be coated on the support in the present invention for writing properties, antistatic properties, transport properties, anticurling properties and the like. The backcoat layer can contain an appropriate combination of inorganic antistatic agents, organic antistatic agents, hydrophilic binders, latexes, pigments, curing agents, surfactants, and the like.

  When the ink receiving layer coating solution is applied to a film support or resin-coated paper, corona discharge treatment, flame treatment, ultraviolet irradiation treatment, plasma treatment or the like is preferably performed prior to coating.

  In the present invention, a known coating method can be used as a coating method of each layer constituting the ink receiving layer. For example, there are a slide bead method, a curtain method, an extrusion method, an air knife method, a roll coating method, a rod bar coating method, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, the content of this invention is not restricted to an Example. In addition, a part and% show a mass part and the mass%.

<Preparation of polyolefin resin-coated paper support>
A 1: 1 mixture of hardwood bleached kraft pulp (LBKP) and softwood bleached sulfite pulp (NBSP) was beaten to 300 ml with Canadian Standard Freeness to prepare a pulp slurry. As a sizing agent, alkylketene dimer is 0.5% to pulp, polyacrylamide is 1.0% to pulp, and cationized starch is 2.0% to pulp. Polyamide epichlorohydrin resin is 0 to pulp. 0.5% was added and diluted with water to make a 1% slurry. This slurry was made with a long paper machine to a basis weight of 170 g / m ² , dried and conditioned to obtain a polyolefin resin-coated paper base paper. A polyethylene resin composition in which 10 parts of anatase-type titanium is uniformly dispersed in 100 parts of resin of low density polyethylene having a density of 0.918 g / cm ³ is melted at 320 ° C. and then thickened at 200 m / min. The surface was extrusion-coated using a cooling roll that had been extrusion-coated to a thickness of 35 μm and was processed with a finely roughened surface. Melted at similarly 320 ° C. The blend resin composition of the low density polyethylene resin 30 parts of a density 0.962 g / cm 70 parts high density polyethylene resin of ³ and a density 0.918 g / cm ³ on the other surface, the thickness Extrusion-coating to a thickness of 30 μm, and extrusion coating using a cooling roll having a roughened surface was used as the back surface.

After subjecting the polyolefin resin-coated paper surface to a high-frequency corona discharge treatment, a primer layer coating solution in which the following composition is added to water is applied and dried so that gelatin is 50 mg / m ² (about 0.05 μm) Was made.

<Primer layer coating solution>
Composition of primer layer coating solution Lime-processed gelatin 100 parts Sulfosuccinic acid-2-ethylhexyl ester salt 2 parts Chrome alum 10 parts

<Recording sheet 1>
<Silica dispersion>
After adding 4 parts of dimethyldiallylammonium chloride homopolymer (molecular weight 9,000) and 100 parts of vapor phase silica (average primary particle diameter 7 nm, specific surface area 300 m ² / g) to water to prepare a preliminary dispersion, a high-pressure homogenizer To prepare a silica dispersion 1 having a solid content concentration of 20%.

<Inorganic fine particle-containing coating solution 1>
The silica dispersion liquid 1 and other chemicals dissolved in water were mixed to adjust the inorganic fine particle-containing coating liquid 1 having the following composition so that the solid content concentration was 13.5%.
Inorganic fine particle-containing coating liquid 1 composition Silica dispersion (as silica solid content) 100 parts Acetoacetyl-modified polyvinyl alcohol 20 parts (Acetyacetylation degree 3%, Saponification degree 98%, Average polymerization degree 2350)

<Upper layer coating solution 1>
As the upper layer coating solution 1, the following composition was added to water to adjust the solid content concentration to 5.0%.
Upper layer coating solution 1 composition Adipic acid dihydrazide Nonionic surfactant Small amount (Polyoxyethylene alkyl ether)

The inorganic fine particle-containing coating solution 1 is prepared so that the silica fine particle-containing coating solution 1 has a silica particle coating amount of 20 g / m ² , and the adipic acid dihydrazide coating amount is 0.4 g / m ^2. On the lower layer, the upper layer coating solution 1 is coated on the support so as to be the upper layer by simultaneous multi-layer coating using a slide bead type coating device, and first heated at 80 ° C. for 15 seconds to gel the coating solution, The recording sheet 1 was obtained by blowing air at 70 ° C. and drying.

<Recording sheets 2 to 11>
Recording sheets 2 to 11 were obtained in the same manner as the recording sheet 1 except that the composition of the inorganic fine particle-containing coating liquid 1 was changed to each composition of the following inorganic fine particle-containing coating liquid 2. In addition, as described in Table 1, an acid was added.

<Inorganic fine particle-containing coating solution 2>
Inorganic fine particle-containing coating liquid 2 composition Silica dispersion 1 (silica solid content) 100 parts Acetoacetyl-modified polyvinyl alcohol 20 parts (Acetyacetylation degree 3%, Saponification degree 98%, Average polymerization degree 2350)
Acids described in Table 1 Amounts described in Table 1 The addition amounts described in each table are amounts per 1 m ² of the recording sheet, and are amounts of substantial components.

  Each of the obtained recording sheets was evaluated as follows. The results are shown in Table 1. The average secondary particle diameter of the silica fine particles in each recording sheet was 70 nm.

<Blank paper gloss>
The glossiness of the blank paper before printing on the recording sheet was observed obliquely and evaluated according to the following criteria.
○: High glossiness equivalent to glossy color photographic printing paper.
Δ: Slightly glossy.
X: There is no glossiness.

<Ink absorbability>
Red, blue, green, and black solids are printed with a commercially available inkjet printer (Seiko Epson Corp., PM-G800). Immediately after printing, PPC paper is layered on the print section and lightly crimped, then transferred to PPC paper. The degree of the ink amount was visually observed. Evaluation was made according to the following criteria.
○: Not transferred.
Δ: A thin transfer is observed on the entire printed portion.
X: A dark transfer is observed over the entire printed part.

<Color development>
Using the above printer, solid printing of cyan, magenta, yellow, red, blue, green, and black was performed, and each color was measured with a colorimeter and the reproduced color spaces were compared. The evaluation was made in three stages, with ◯ indicating that the reproduction color space was wide, △ indicating that the color space was slightly inferior, and X indicating clearly inferior.

  Discoloration with time is a phenomenon that occurs when stored for a long time in a relatively mild environment. The following accelerated test method was used as an evaluation method.

<Discoloration of printed part>
The recording sheet printed by the printer was stored for 3 months under the condition of 40 ° C., and the change in color tone of the printed part and its periphery was evaluated.
○: No change.
Δ: Discoloration but slight.
X: Discoloration is remarkable.

  From the results shown in Table 1, the ink-receiving layer having the constitution of the present invention yielded an inkjet recording material having high gloss, excellent ink absorbability and color developability with high production efficiency, and an organic material having the pKa value of the present invention. It can be seen that the inclusion of the acid suppresses discoloration of the printed portion over time.

<Recording sheets 12 to 21>
Recording sheets 12 to 21 were obtained in the same manner as the recording sheet 1 except that the composition of the upper layer coating liquid 1 was changed to each composition of the upper layer coating liquid 2 described below.

<Upper layer coating solution 2>
Upper layer coating solution 2 composition Adipic acid dihydrazide Nonionic surfactant Small amount (Polyoxyethylene alkyl ether)
Acids listed in Table 2 Amounts listed in Table 2

  Each recording sheet obtained was evaluated in the same manner as in Example 1. The results are shown in Table 2.

  Even in the results shown in Table 2, the ink-receiving layer having the constitution of the present invention yielded an inkjet recording material having high gloss, excellent ink absorbability and color developability with high production efficiency, and the organic acid having the pKa value of the present invention. It can be seen that discoloration of the printed portion over time is suppressed by containing.

<Recording sheets 22 to 41>
<Alumina hydrate dispersion>
Nitric acid (1.5 parts) and 100 parts of pseudoboehmite-structured alumina hydrate (average primary particle size 14 nm) are added to water, and an alumina water having a solid content concentration of 32% using a sawtooth blade type disperser. A Japanese dispersion was prepared.

<Inorganic fine particle-containing coating solution 3>
The alumina hydrate dispersion and other chemicals dissolved in water were mixed to adjust each coating solution of the inorganic fine particle-containing coating solution 3 having the following composition so that the solid content concentration was 24%.
Composition of inorganic fine particle-containing coating liquid 3 Alumina hydrate dispersion (as alumina hydrate solid content) 100 parts Acids (1) listed in Table 3 Amounts listed in Table 3 Acetacetyl-modified polyvinyl alcohol 12 parts (Degree of acetoacetylation 3 %, Saponification degree 98%, average polymerization degree 2350)
Mixed solution of acid (2) and alkali metal salt described in Table 3 Amount described in Table 3

<Upper layer coating solution 3>
As the upper layer coating solution 3, the following composition was added to water to adjust the solid content concentration to 3.0%.
Upper layer coating solution 3 composition Adipic acid dihydrazide Nonionic surfactant Small amount (Polyoxyethylene alkyl ether)

The inorganic fine particle-containing coating solution 3 is coated with inorganic fine particles such that the coating amount of alumina hydrate particles is 35 g / m ² and the upper coating solution 3 is coated with adipic acid dihydrazide so that the coating amount is 0.2 g / m ^2. Simultaneously apply multiple layers on the support with a slide bead type coating device so that the liquid 3 becomes the lower layer and the upper layer coating liquid 3 becomes the upper layer. First, the coating liquid is gelled by heating at 80 ° C. for 8 seconds. And then dried by blowing air at 70 ° C. to obtain recording sheets 22 to 41.

  Each of the obtained recording sheets was evaluated in the same manner as in Example 1 except for the glossiness of the blank paper portion. Evaluation of the glossiness of the white paper portion was performed as shown below. The results are shown in Table 3.

<Blank paper gloss>
The 75-degree specular gloss specified by ISO-8254 on the surface of the ink-receiving layer of the recording sheet was measured and judged according to the following criteria.
◎: 75 or more ○: 50 or more and less than 75 Δ: 40 or more and less than 50 ×: less than 40

  From the results shown in Table 3, the ink-receiving layer having the constitution of the present invention yields an inkjet recording material having high gloss, excellent ink absorbability and color developability with high production efficiency, and has the pKa value of the present invention. It can be seen that the inclusion of the acid suppresses discoloration of the printed portion over time. Furthermore, a sample with higher gloss could be obtained by adding an appropriate amount of an alkali metal salt. This is because gelation has occurred sufficiently despite the gelation time after coating being 8 seconds, which is about half that of Examples 1 and 2, suggesting that production efficiency is further improved. Yes. In the recording sheets 27 to 29 to which only the organic acid having the pKa value of the present invention is added, the gloss is slightly lower than that to which the alkali metal salt is added. It is speculated that the gelation is slightly insufficient. In the recording sheets 23 and 24 to which nitric acid was added, the gelation reaction was suppressed, so that the gloss was lowered. The recording sheets 32, 38, and 39 to which an excessive amount of alkali metal salt was added had a slight agglomeration when the mixed solution of the organic acid and alkali metal salt having the pKa value of the present invention was added to the coating solution. Slightly affected gloss.

<Recording sheets 42 to 57>
Recording sheets 42 to 57 were obtained in the same manner as the recording sheet 22 except that the composition of the upper layer coating liquid 3 was changed to each composition of the upper layer coating liquid 4 described below.

<Upper layer coating solution 4>
Top coating solution 4 composition Adipic acid dihydrazide Nonionic surfactant Small amount (Polyoxyethylene alkyl ether)
Solutions of acids and alkali metal salts listed in Table 4 Amounts listed in Table 4

  Each recording sheet obtained was evaluated in the same manner as in Example 3. The results are shown in Table 4.

  As shown in Table 4, it can be seen that the same result as in Example 3 can be obtained even when the mixed solution of the organic acid and alkali metal salt having the pKa value of the present invention is added to the upper coating solution.

<Recording sheets 58 to 74>
After coating the following lower layer coating solution 1 with a rod bar in advance so that the coating amount of adipic acid dihydrazide is 0.2 g / m ² , the coating solution 4 containing inorganic fine particles is hydrated with alumina. It is applied with a slide bead type application device so that the amount of particles to be applied is 35 g / m ² , first heated at 80 ° C. for 8 seconds to gel the coating solution, and then dried by blowing air at 70 ° C. Sheets 58 to 74 were obtained.

<Lower layer coating solution 1>
As the lower layer coating solution 1, the following composition was added to water to adjust the solid content concentration to 4.0%.
Lower layer coating solution 1 composition Adipic acid dihydrazide 100 parts Partially saponified polyvinyl alcohol 100 parts (saponification rate 88%, average polymerization degree 500)

<Inorganic fine particle-containing coating solution 4>
The above-mentioned alumina hydrate dispersion and other chemicals dissolved in water were mixed to adjust each coating solution of the inorganic fine particle-containing coating solution 4 having the following composition so that the solid content concentration was 24%.
Inorganic fine particle-containing coating solution 4 composition Alumina hydrate dispersion (as alumina hydrate solid content) 100 parts Acids (1) listed in Table 5 Amounts listed in Table 5 Acetacetyl-modified polyvinyl alcohol 12 parts (Degree of acetoacetylation 3 %, Saponification degree 98%, average polymerization degree 2350)
Mixed solution of acid and alkali metal salt described in Table 5 Amount described in Table 5 Nonionic surfactant Small amount (Polyoxyethylene alkyl ether)

  Each recording sheet obtained was evaluated in the same manner as in Example 3. The results are shown in Table 5.

  As shown in Table 5, it can be seen that the same result as in Example 3 can be obtained even when the coating method is changed from the simultaneous multilayer coating to the sequential coating.

<Recording sheets 75 to 88>
The recording sheet 22 was used except that the lower layer coating solution 2 described below was coated on the support with a rod bar so that the coating amount of partially saponified polyvinyl alcohol was 0.2 g / m ² and dried. In the same manner, recording sheets 75 to 88 were produced.

<Lower layer coating solution 2>
As the lower layer coating solution 2, the following composition was added to water to adjust the solid content concentration of partially saponified polyvinyl alcohol to 2.0%.
Composition of lower layer coating solution 2 Mixed solution of acid and alkali metal salt described in Table 6 Amount described in Table 6 Partially saponified polyvinyl alcohol (saponification rate 88%, average polymerization degree 500)

  Each recording sheet obtained was evaluated in the same manner as in Example 3. The results are shown in Table 6.

  As shown in Table 6, it can be seen that the same effect as in Example 3 can be obtained by using a support in which a mixed solution of an organic acid and an alkali metal salt having a pKa value of the present invention is applied and dried in advance. When the alkali metal salt was added excessively, the gloss decreased slightly.

Claims (6)

  Ink jet recording in which at least one of the ink receiving layers provided on the support contains inorganic fine particles having an average secondary particle diameter of 500 nm or less, a resin binder having an acetoacetyl group, and a compound having two or more terminal hydrazino groups An ink jet recording material, characterized in that at least one of the ink receiving layers contains an organic acid having a pKa value of 2 to 5. The ink jet recording material according to claim 1, wherein the addition amount of the organic acid having a pKa value of 2 to 5 is 0.01 to 1 g per 1 m ² of the ink jet recording material.   The inkjet recording material according to claim 1, wherein the inorganic fine particles are amorphous synthetic silica.   In the ink-receiving layer containing an organic acid having a pKa value of 2 to 5, the amount of alkali metal salt is such that the amount of alkali metal ions is 10 to 120 mol% with respect to the organic acid having a pKa value of 2 to 5. The ink jet recording material according to claim 1, further comprising: The ink jet recording material according to claim 4, wherein the addition amount of the organic acid having a pKa value of 2 to 5 is 0.01 to 3.0 g per 1 m ² of the ink jet recording material.   6. The ink jet recording material according to claim 4, wherein the inorganic fine particles are alumina or alumina hydrate.