JP5663327B2 - Inkjet recording material - Google Patents

Description

  The present invention relates to an ink jet recording material and a method for producing the same, and further relates to an ink jet recording material excellent in surface strength, water resistance and ink absorbability, and a method for producing a crack that hardly occurs during production.

  Inkjet recording is a method in which small droplets of ink are sprayed from nozzles and fixed on the surface of the recording medium to record characters, images, etc. Color printing is easy, running costs are low, and noise during printing It is widely used in home and office printers because of its many advantages. Recently, with the spread of digital cameras, it has been established as a recording method to replace silver salt photography, and ink jet recording materials such as printing directly on the surface of optical discs such as CD / DVD / BD are also used depending on the purpose. Various materials have been selected, and the required quality has become more sophisticated and diverse.

  As a constitution of the ink jet recording material, an ink receiving layer is provided on a support such as paper, a plastic sheet or a plastic disk. The ink receiving layer is made of a porous inorganic material such as silica or alumina bound with a hydrophilic resin binder. The porous inorganic material quickly absorbs ink, suppresses bleeding, and forms a perfect circle-like dot. By doing so, a fine image can be expressed. Here, the performance required for the binder resin is required to be (1) high affinity for the ink, (2) high binder power for the inorganic fine particles, and the binder resin is polyvinyl alcohol (hereinafter referred to as PVA). Abbreviated.) System resins are widely used.

  In recent years, ink jet recording systems have been required to have high expressive power, that is, higher definition of images and higher printing speed. In order to achieve such high-definition images, a method of increasing the amount of ink discharged per unit area of the recording material is taken, and the recording material is required to have an ability to absorb a larger amount of ink than before. ing. Therefore, it is necessary to increase the porosity of the ink receiving layer, and development is proceeding in the direction of reducing the amount of the binder resin.

  On the other hand, regarding the problem of improving the printing speed, when printing at a high speed, the physical load on the surface of the recording material being conveyed by the printer increases, and a large amount of ink is absorbed in the wet state as described above to absorb a large load. Will take. That is, in addition to the above-mentioned (1) and (2), (3) a higher binder strength is exhibited by addition of a small amount in the binder resin, and the ink receiving layer surface does not crack during drying of the coating solution. (4) In order to ensure the porosity of the inorganic fine particles, it is a highly viscous aqueous solution that does not easily penetrate into the porous fine particles at the coating liquid stage, and (5) water resistance that can provide high surface strength even when wet. Performances such as high performance are further demanded.

  As a binder for the ink receiving layer of such an ink jet recording material, Patent Document 1 discloses a technique using PVA having a polymerization degree of 4000 or more. PVA having such a high degree of polymerization has a high binder strength and a high aqueous solution viscosity. Therefore, even when the amount of the binder is small, cracking during drying hardly occurs and the porosity of fine particles can be secured.

  However, the PVA has insufficient surface strength when wet, and the binder strength and aqueous solution viscosity are not sufficient. Furthermore, PVA with such a high degree of polymerization has a problem that production efficiency is extremely poor. The upper limit of the degree of polymerization of industrially produced PVA is about 4500, and PVA with a higher degree of polymerization is a method using special equipment or a method that sacrifices productivity (low yield). There is a problem that the production cost is extremely high and industrial disadvantageous.

  On the other hand, techniques using PVA and a boron compound are disclosed (for example, Patent Document 2 and Patent Document 3). This increases the viscosity of the PVA aqueous solution by using boric acid and / or borax as a cross-linking agent, and prevents the binder resin from penetrating into the porous inorganic fine particles, thereby ensuring the porosity of the inorganic fine particles, It is considered that even a small amount of use contributes to improvement of the binder strength and improvement of the surface strength when wet.

  However, recently, boron compounds such as boric acid have been pointed out to be reproductive toxic, and they have become difficult to use due to their toxicity and adverse effects on the environment, such as being listed as candidates for substances of very high concern under the European Chemical Regulation (REACH). There is a need for PVA-based resin binders that have a cross-linking system to replace PVA / boron compounds.

  In response to these problems, the present inventors have proposed an ink jet recording material (Patent Document 4) using a saponified diacetone acrylamide-fatty acid vinyl ester copolymer and a hydrazine compound. Patent Document 5 proposes an ink jet recording medium containing an acetoacetate group-containing PVA resin and a polyhydric hydrazide compound.

  A binder obtained by reacting a PVA resin having a keto group with a crosslinking agent such as a hydrazine compound is excellent in water resistance, and an ink jet recording material having a high surface strength when wet is obtained. The porous inorganic fine particles have penetrated, and a large amount of ink is hardly absorbed, and the fineness of the image is not sufficient, and improvement has been desired. Further, since the binder resin itself permeates into the voids of the fine particles, the amount of the binder as a binder between the fine particles is small, and the problem that cracking at the time of drying and the like has not been completely solved.

Japanese Patent Laid-Open No. 7-117334 JP-A-11-20306 Japanese Patent Laid-Open No. 11-192777 JP-A-11-348417 JP 2001-213045 A

  An object of the present invention is to provide an ink jet recording material capable of expressing a fine image even when the water resistance is high and the printing speed is high. Another object of the present invention is to provide a method for producing an ink jet recording material in which cracking does not easily occur in the receiving layer when the ink receiving layer is formed.

  As a result of intensive studies, the present inventor has made a method for producing an ink jet recording material having an ink receiving layer containing porous inorganic fine particles, a saponified vinyl acetate-diacetone acrylamide copolymer and a crosslinking agent on a support. Wherein the polyvinyl alcohol-based resin contains (A) a diacetone acrylamide unit in the molecule and (B) a monomer unit having a long-chain alkyl group having 6 to 22 carbon atoms in the side chain. The present inventors have found that the above-described problems can be solved at once by using a resin, and have further studied and completed the present invention.

That is, the present invention relates to the following inventions.
[1] In an inkjet recording material having an ink receiving layer comprising porous inorganic fine particles, polyvinyl alcohol resin and a crosslinking agent on a support, the polyvinyl alcohol resin has (A) diacetone acrylamide units and ( B) An inkjet recording material, which is a modified polyvinyl alcohol resin containing a monomer unit having a long-chain alkyl group having 6 to 22 carbon atoms in the side chain.
[2] The inkjet recording material according to the above [1], wherein the crosslinking agent is a compound having two or more functional groups selected from the group consisting of a hydrazino group, a hydrazide group or a semicarbazide group.
[3] The content of (A) diacetone acrylamide unit in the modified polyvinyl alcohol resin is 0.1 mol% or more and 15 mol% or less, and (B) a long chain having 6 to 22 carbon atoms in the side chain. Content of the monomer unit which has an alkyl group is 0.02 mol% or more and 5 mol% or less, The inkjet recording material as described in said [1] or [2] characterized by the above-mentioned.
[4] The viscosity of a 4% by weight aqueous solution of the modified polyvinyl alcohol resin measured by the method of JIS K-6726 is 50 mPa · s or more, according to any one of the above [1] to [3] Inkjet recording material.
[5] A porous inorganic fine particle on the support, (A) a diacetone acrylamide unit in the molecule, and (B) a monomer unit having a long chain alkyl group having 6 to 22 carbon atoms in the side chain. The inkjet recording material according to any one of [1] to [4], wherein an ink receiving layer is formed by applying a coating solution containing a modified polyvinyl alcohol resin and a crosslinking agent. Method.
[6] The method for producing an ink jet recording material according to [5], wherein the coating solution further contains a water-soluble basic compound.

  The ink jet recording material of the present invention comprises (A) a diacetone acrylamide unit in the molecule as a binder of the ink receiving layer and (B) a monomer unit having a long chain alkyl group having 6 to 22 carbon atoms in the side chain. Since the modified polyvinyl alcohol-based resin is used, the ketone group in the diacetone acrylamide unit of (A) is reactive with the cross-linking agent and forms a cross-linked structure. Strength increases. In addition, the aqueous solution becomes highly viscous because the long-chain alkyl groups in the monomer unit having a long-chain alkyl group having 6 to 22 carbon atoms in the side chain of (B) associate with each other in the aqueous solution, In order to prevent the binder from penetrating into the voids of the porous inorganic fine particles, the ink receiving layer is less likely to crack, the surface strength is increased, and the ink absorbency is excellent, so that even when printed at high speed, a fine image can be obtained. It is possible to display. Furthermore, in the present invention, since no boron compound is used, reproductive toxicity does not become a problem and safety is high.

  Hereinafter, the ink jet recording material of the present invention and the production method thereof will be described in detail.

  “Modified polyvinyl alcohol resin containing (A) diacetone acrylamide unit in the molecule and (B) a monomer unit having a long chain alkyl group having 6 to 22 carbon atoms in the side chain” (Hereinafter simply abbreviated as “modified PVA resin”) is a fatty acid vinyl ester, diacetone acrylamide, and an ethylenically unsaturated monomer having a long chain alkyl group having 6 to 22 carbon atoms in the side chain. Can be produced by saponification of a polymer obtained by terpolymerization of.

  The fatty acid vinyl ester used for the copolymerization is not particularly limited, and examples thereof include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and the like. Among these, vinyl acetate is industrially preferable.

  Next, an ethylenically unsaturated monomer having a long-chain alkyl group having 6 to 22 carbon atoms in the side chain used for copolymerization will be described. The long-chain alkyl group having 6 to 22 carbon atoms is n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, Not only linear alkyl groups such as n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-eicosyl group, but also i-hexyl group (4-methylpentyl group), sec-hexyl group, tert-hexyl group (1,1-dimethylbutyl group), i-heptyl group, sec-heptyl group, tert-heptyl group, n-octyl group, i-octyl group Group, sec-octyl group, tert-octyl group, i-nonyl group, sec-nonyl group, tert-nonyl group, neo-nonyl group, i-decyl group, sec-decyl group, ert-decyl group, neo-decyl group, i-undecyl group, sec-undecyl group, tert-undecyl group, neo-undecyl group, i-dodecyl group, sec-dodecyl group, tert-dodecyl group, neo-dodecyl group, i-tridecyl group, sec-tridecyl group, tert-tridecyl group, neo-tridecyl group, i-tetradecyl group, sec-tetradecyl group, tert-tetradecyl group, neo-tetradecyl group, i-pentadecyl group, sec-pentadecyl group, tert-pentadecyl group, neo-pentadecyl group, i-hexadecyl group, sec-hexadecyl group, tert-hexadecyl group, neo-hexadecyl group, i-heptadecyl group, sec-heptadecyl group, tert-heptadecyl group, neo-heptadecyl group, i A branched alkyl group such as an octadecyl group, a sec-octadecyl group, a tert-octadecyl group, or a neo-octadecyl group may be used, but the number of carbons needs to be 6 or more and 22 or less. It is preferable that it is 18 or less. When the number of carbon atoms is less than 6, the viscosity of the aqueous solution of the PVA-based resin is low, so that the binder in the coating liquid cannot be prevented from penetrating into the voids of the porous inorganic particles, and the ink receiving layer is cracked. The effect of preventing and improving ink absorbability is reduced. On the other hand, when the number of carbons increases, the viscosity of the aqueous solution of the PVA resin increases. However, if the amount is too large, the effect reaches a peak, and the ethylenically unsaturated monomer having a long-chain alkyl group having more than 22 carbons The body also has problems with productivity such as a decrease in solubility in methanol as a polymerization solvent and a decrease in copolymerization with fatty acid vinyl ester and / or diacetone acrylamide.

  The ethylenically unsaturated monomer having a long-chain alkyl group in the side chain includes the vinyl ether, vinyl ester, acrylic ester, methacrylic ester, α-olefins, acrylamides and methacrylamide having the long-chain alkyl group. Long chain alkyl vinyl ethers such as vinyl octyl ether, vinyl 2-ethylhexyl ether, vinyl decyl ether, vinyl dodecyl ether, vinyl lauryl ether, vinyl stearyl ether, vinyl octadecyl ether; capryl Long chain alkyl vinyl esters such as vinyl acid vinyl, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate; n-hexyl acrylate, 2-ethylhexyl acrylate, acrylic Long chain alkyl acrylates such as lauryl laurate, dodecyl acrylate, octadecyl acrylate, stearyl acrylate; long chains such as hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, tridecyl methacrylate, hexadecyl methacrylate Alkyl methacrylates; α-olefins having 8 to 24 carbon atoms, such as octene and decene, and acrylamides to which the long-chain alkyl group is added; methacrylamides to which the long-chain alkyl group is added, and the like Of these, long chain alkyl vinyl ethers are preferably used from the viewpoint of copolymerization with fatty acid vinyl esters and diacetone acrylamide and the stability of the structure during saponification. These ethylenically unsaturated monomers having a long chain alkyl group in the side chain can be used alone or in combination of two or more.

  The copolymerization method of the fatty acid vinyl ester, diacetone acrylamide, and the ethylenically unsaturated monomer having a long chain alkyl group having 6 to 22 carbon atoms in the side chain is not particularly limited. Various polymerization methods such as polymerization, solution polymerization, suspension polymerization, and emulsion polymerization are possible. Among them, solution polymerization using methanol as a solvent is industrially preferable. In addition, these monomers may be initially charged and polymerized at once, but diacetone acrylamide and ethylenically unsaturated monomers having a long chain alkyl group having 6 to 22 carbon atoms in the side chain may be used. It is preferable to use a polymerization method that continuously drops in accordance with the polymerization rate.

  The method for saponifying a polymer obtained by copolymerizing a fatty acid vinyl ester, diacetone acrylamide, and an ethylenically unsaturated monomer having a long chain alkyl group having 6 to 22 carbon atoms in the side chain is particularly limited. Conventionally known alkali saponification and acid saponification can be applied, and among them, a method in which an alkali hydroxide is added to a methanol solution of a polymer or a mixed solution of methanol, water, methyl acetate, benzene, etc. to perform an alcoholysis Is industrially preferred.

  The modified PVA resin used in the present invention is an ethylenic polymer having a fatty acid vinyl ester, diacetone acrylamide, and a long chain alkyl group having 6 to 22 carbon atoms in the side chain within a range not inhibiting the effects of the present invention. Olefins such as ethylene, propylene and isobutylene, vinylene carbonates, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid and undecylenic acid which can be copolymerized with saturated monomers Or salts thereof, mono- or dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as acrylamide and methacrylamide, olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid or salts thereof , Alkyl vinyl ethers, N Acrylamide methyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethyldiallylammonium chloride, dimethylallyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl ether, etc. Polyoxyalkylene (meth) allyl ether, polyoxyethylene (meth) acrylate, polyoxyalkylene (meth) acrylate such as polyoxypropylene (meth) acrylate, polyoxyethylene (meth) acrylamide, polyoxypropylene (meth) acrylamide Such as polyoxyalkylene (meth) acrylamide, polyoxyethylene (1- (meth) acrylamide-1,1-dimethyl) Propyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, polyoxypropylene vinylamine, isopropenyl acetate, vinylethylene carbonate, 2,2-dialkyl- One selected from 4-vinyl-1,3-diaxolane, glycerin monoallyl ether, 3,4-diacetoxy-1-butene, 3,4-diacyloxy-1-butene, 1,4-diacetoxy-2-butene, and the like It may be copolymerized with the above. In addition, the resulting modified PVA-based resin was post-modified by reactions such as acetalization, urethanization, etherification, grafting, phosphoric esterification, acetoacetylation, cationization and the like within a range not inhibiting the effects of the present invention. It may be a thing.

  The content of the (A) diacetone acrylamide unit in the modified PVA resin of the present invention is preferably 0.1 mol% or more and 15 mol% or less, more preferably 0, relative to the entire modified PVA resin. .5 mol% or more and 10 mol% or less. (A) When the content of diacetone acrylamide units is lower than 0.1 mol%, the water resistance, moisture resistance and surface strength of the ink receiving layer may be lowered, and diacetone acrylamide exceeds 15 mol%. However, there is a problem that the solubility in water is lowered and an aqueous coating solution cannot be prepared.

  The content of the monomer unit having a long chain alkyl group having 6 to 22 carbon atoms in the side chain (B) of the modified PVA resin of the present invention is 0.02 with respect to the entire modified PVA resin. It is preferable that they are mol% or more and 5 mol% or less, More preferably, they are 0.1 mol% or more and 3 mol% or less. (B) When the content of the monomer unit having a long-chain alkyl group having 6 to 22 carbon atoms in the side chain is lower than 0.02 mol%, the modified PVA system when mixing the porous inorganic fine particles Since the viscosity of the resin aqueous solution is low, there is a problem that the ink absorbability of the ink receiving layer is deteriorated. When the content exceeds 5 mol%, the viscosity of the modified PVA resin aqueous solution becomes too high and the water solubility decreases. There is a fear.

(A) Content of diacetone acrylamide unit and content of (B) monomer unit having a long chain alkyl group having 6 to 22 carbon atoms in the side chain are fatty acid vinyl ester and diacetone at the time of copolymerization. It can be controlled by changing the charge composition and polymerization yield of acrylamide and the ethylenically unsaturated monomer having a long chain alkyl group having 6 to 22 carbon atoms in the chain. The content of (A) diacetone acrylamide unit and (B) the content of monomer unit having a long chain alkyl group having 6 to 22 carbon atoms in the side chain can be measured by ¹ H-NMR analysis. it can.

  In addition, the degree of polymerization and the degree of saponification of the modified PVA resin used in the present invention can be various. The degree of polymerization is not particularly limited, but is preferably less than 4500 and more preferably less than 4000 from the viewpoint of industrial productivity. The viscosity of a 4% by weight aqueous solution at 20 ° C. is preferably 50 mPa · s or more, and more preferably exceeds 100 mPa · s from the viewpoint of higher ink absorbability of the ink receiving layer. The saponification degree is preferably 80 mol% or more, and more preferably 85 mol% or more and 99 mol% or less. The saponification degree and the 4% by weight aqueous solution viscosity of the modified PVA resin are values measured according to JIS K-6726, and the viscosity is a value measured using a B-type rotational viscometer.

The crosslinking agent used in the present invention is not particularly limited as long as the effects of the present invention are not hindered, but the following formula (1) which is a functional group having reactivity with the ketone group of the diacetone acrylamide unit of the modified PVA resin.
—NH—NH ₂ (1)
A hydrazino group represented by the following formula (2):
—CO—NH—NH ₂ (2)
And a hydrazide group represented by the following formula (3)
—NH—CO—NH—NH ₂ (3)
Preferred examples include compounds having two or more functional groups selected from the group consisting of semicarbazide groups represented by

  Specific examples of the crosslinking agent include carbohydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydride hydride , Hexadecanediohydrazide, terephthalic acid dihydrazide, isophthalic acid dihydrazide, 2,6-naphthoic acid dihydrazide, 4,4'-bisbenzenedihydrazide, 1,4-cyclohexanedihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, iminodiacetic acid dihydrazide, itaconic acid Dihydrazide, ethylenediaminetetraacetic acid tetrahydrazide, citric acid trihydrazide, butanetricarbohydrazide, 1,2,3-benzene Polyfunctional hydrazine and polyfunctional hydrazide compounds such as hydrazide, 1,4,5,8-naphthoic acid tetrahydrazide, nitriloacetic acid trihydrazide, cyclohexanetricarboxylic acid trihydrazide, pyromellitic acid tetrahydrazide, N-aminopolyacrylamide, and N , N'-hexamethylenebissemicarbazide, buretritri, and other semicarbazide compounds, and polyfunctional hydrazine derivatives, polyfunctional hydrazide derivatives, and polyfunctional hydrazides obtained by reacting these compounds with low-boiling ketones such as acetone and methyl ethyl ketone. Functional semicarbazide derivatives and the like are also included.

  Said crosslinking agent can be used 1 type or in combination of 2 or more types, As for the addition amount of a crosslinking agent, 1-20 weight part is preferable with respect to 100 weight part of modified PVA-type resin, 2-15 weight Part is more preferable, and 3 to 10 parts by weight is still more preferable. When the addition amount of the crosslinking agent is small, the water resistance and moisture resistance are lowered. On the other hand, when the addition amount of the crosslinking agent is too large, the viscosity of the coating liquid becomes poor and the productivity is lowered, so that it does not contribute to the reaction. Since the crosslinking agent is eluted, the water resistance may be lowered.

  As a method for adding a crosslinking agent to the modified PVA resin of the present invention, the crosslinking agent or an aqueous solution thereof is usually added to an aqueous solution of a modified PVA resin prepared in advance and mixed. As a method for preparing a modified PVA-based resin aqueous solution, the modified PVA-based resin is previously dispersed in water at room temperature, heated to 80 ° C. or higher while stirring, completely dissolved, and then cooled. Can be prepared by the method. On the other hand, the cross-linking agent may be added to the aqueous solution of the modified PVA resin as a solid. However, in order to react more uniformly, there is a method of preparing an aqueous solution of the cross-linking agent in advance and adding the aqueous solution to the aqueous solution of the modified PVA resin. preferable.

  When a crosslinking agent is added to the aqueous solution of the modified PVA resin of the present invention, the crosslinking reaction proceeds even in the aqueous solution, and the aqueous solution thickens with time. Thereafter, the porous inorganic fine particles and the mixed aqueous solution are mixed, and there is no problem as long as the time until coating on the base material is relatively short. The problem of pot life of gelation occurs. In order to prevent this, a basic compound can coexist in a water-soluble manner. The substance to be added for the above purpose may be any substance that raises the pH of the system (pH 7.5 or more). Among them, a water-soluble organic amine or ammonia has an effect of inhibiting the reaction between the modified PVA resin and the crosslinking agent. In addition to being high, it is preferable in that it has characteristics that it does not impair the physical properties and water resistance of the recording material because it volatilizes when it is applied and dried.

  Examples of water-soluble basic compounds include, in addition to water-soluble organic amines and ammonia, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkaline earth metal hydroxides such as calcium hydroxide. Thing etc. are mentioned. Examples of the water-soluble organic amine include monoethanolamine, aminoethylethanolamine, monoisopropanolamine, N- (2-hydroxypropyl) -ethylenediamine, 2-amino-1-butanol, 2-amino-2-methyl-1 -Propanol, 3-amino-1-propanol, 2-amino-2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol, tris (hydroxyethyl) -aminomethane, etc. Secondary alkanolamines such as diethanolamine, methylethanolamine, butylmethanolamine, N-acetylethanolamine, diisopropanolamine; triethanolamine, methyldiethanolamine, dimethylethanolamine, diethyl Tertiary alkanolamines such as ethanolamine, ethyldiethanolamine, and triisopropanolamine; primary alkylamines such as methylamine, ethylamine, isobutylamine, t-butylamine, and cyclohexylamine; secondaries such as dimethylamine, diethylamine, and diisopropylamine Tertiary alkylamines; tertiary alkylamines such as trimethylamine are listed, and one or more selected from these can be used.

  The method for adding the water-soluble basic compound is not particularly limited, and it is common to add the basic compound to the modified PVA resin aqueous solution, and after mixing, add the crosslinking agent, but the modified PVA resin Alternatively, after adding a crosslinking agent, the mixture may be allowed to stand for a certain period of time to proceed with a crosslinking reaction, and when the mixed solution has reached a desired viscosity, a water-soluble basic compound may be added. Although there is no restriction | limiting in particular about the addition amount at the time of adding a water-soluble basic compound, 0.01-10 weight part is preferable with respect to 100 weight part of modified PVA-type resin, and 0.05-5 weight part is more. preferable.

  Examples of the porous inorganic fine particles used in the present invention include amorphous synthetic silica, colloidal silica, light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, and carbonic acid. Zinc, satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, tin oxide sol, cerium oxide sol, lanthanum oxide sol, titanium oxide sol, neodymium sol, yttrium oxide sol, colloidal alumina, pseudoboehmite alumina, vapor phase method alumina, White inorganic pigments and inorganic sols such as aluminum hydroxide, alumina, alumina hydrate, lithobon, zeolite, hydrous halloysite, magnesium carbonate, magnesium hydroxide can be used. that's all It can be used in combination. As the porous inorganic fine particles, amorphous synthetic silica, alumina, and alumina hydrate are particularly preferable because of their large ink absorption capacity. Amorphous synthetic silica can be roughly classified into wet synthetic silica, vapor phase silica, and others depending on the production method.

  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.

  Wet synthetic silica is further classified into precipitated silica, gel silica, and sol silica depending on 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 filtration, water washing, drying, pulverization and classification. Precipitated silica is commercially available, for example, from Tosoh Silica Co., Ltd. as nip seal (trade name), from Tokuyama Co., Ltd. as Toku Seal, fine seal (trade name). 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 from Tosoh Silica Co., Ltd. as nip gel (trade name) and from Grace Japan Co., Ltd. as syloid and silo jet (trade name). The sol method silica is also called colloidal silica, and is obtained by heating and aging silica sol obtained through metathesis of sodium silicate acid or the like through an ion exchange resin layer. For example, Snowtex (trade name) from Nissan Chemical Industries, Ltd. Is commercially available.

  The particle diameter of the porous inorganic fine particles used in the present invention is not particularly limited as long as the effects of the present invention are not hindered, and is selected according to the type of inorganic fine particles used. For example, in the case of wet synthetic silica, those having an average particle diameter of 1 to 12 μm are preferable from the viewpoint of ink absorbency, and in the case of colloidal silica, the average particle diameter is 5 to 100 nm from the viewpoint of ink absorbency. The vapor phase method alumina and pseudoboehmite alumina preferably have an average particle size of 30 nm or less from the viewpoint of ink absorbability. The average particle diameter is a particle diameter observed with an electron microscope (taken an electron micrograph of 10,000 to 400,000 times, and measured and averaged the diameters of particles in a 5 cm square, for example. “Particle Handbook” , Asakura Shoten, p52, 1991).

  The ratio of the modified PVA resin used as a binder to the porous inorganic fine particles used in the present invention is set according to the type and purpose of the porous inorganic fine particles used, but the modified PVA resin / porous 1/100 to 100/100 is preferable, and 3/100 to 50/100 is more preferable.

  The porous inorganic fine particles are added to the mixed aqueous solution of the modified PVA-based resin and the crosslinking agent, and there is no particular limitation on the mixing method when mixing, but in order to disperse the porous inorganic fine particles as uniformly as possible in the mixed aqueous solution, By using a known mixing apparatus / method such as a high-speed homogenizer, an ink-receiving layer coating solution can be prepared.

  In such a coating solution, other water-soluble resins, water-dispersible resins, or inorganic fillers, plasticizers, ink fixing agents, surfactants, etc. are used in combination as long as they do not impair the effects of the present invention. It can also be used. Other water-soluble resins or water-dispersible resins that can be used in combination include albumin, gelatin, casein, starch, gum arabic, cellulose derivatives such as methylcellulose, hydroxyethylcellulose, polyamide resins, melamine resins, PVA, vinylpyrrolidone-modified PVA, N- Substituted or unsubstituted (meth) acrylamide-modified PVA, silanol-modified PVA, sulfonic acid-modified PVA, sodium poly (meth) acrylate, anion-modified PVA, sodium alginate, water-soluble polyester and other anionic water-soluble resins, polyethyleneimine, polyvinyl Amine, polyallylamine, polyallylamine sulfone copolymer or ammonium salts thereof, cationized starch, cationized poly (meth) acrylamide, cation-modified PVA, cationized polyamido Water-dispersible resins such as cationic water-soluble resins such as resins, SBR latex, NBR latex, vinyl acetate resin emulsion, ethylene / vinyl acetate copolymer emulsion, (meth) acrylic ester resin emulsion, vinyl chloride resin emulsion Is mentioned.

  The ink jet recording material of the present invention forms an ink receiving layer by coating an ink receiving layer coating solution comprising a modified PVA resin, a crosslinking agent, porous inorganic fine particles and water on a support and drying. is there. Such a support 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, high grade papers, intermediate papers, Lower grade paper, newspaper, release paper, carbon paper, non-carbon paper, glassine paper, etc.), resin-coated paper, synthetic paper, non-woven fabric, cloth, metal foil, polyethylene, polypropylene, PET, polycarbonate, polyvinyl chloride, ethylene-propylene Films, sheets and molded products made of thermoplastic resins such as copolymers are used.

  Coating methods of the coating liquid for providing the ink receiving layer on the support include air knife coater, curtain coater, slide lip coater, die coater, blade coater, gate roll coater, bar coater, rod coater, bill blade coater A known method using an apparatus such as a short dwell blade coater or a size press is used.

  The solid content in the coating solution is not particularly limited, but is preferably 5 to 60% by weight, more preferably 8 to 50% by weight, and still more preferably 10 to 30% by weight of the entire coating solution. If the amount of solids in the coating solution is small, not only will the drying load increase, but the uniformity of the coating layer thickness may be reduced. Conversely, if the amount of solids is large, the coating solution will have a high viscosity. Therefore, workability may be reduced, such as difficulty in high-speed coating.

  The drying method after coating the coating solution on the support is not particularly limited, but it is preferable from the viewpoint of productivity to use heat drying such as a method of blowing hot air or a method of irradiating infrared rays. The drying conditions in that case are not particularly limited, but may be usually dried at 90 to 120 ° C. for about 1 to 30 minutes.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these. In the examples, “%” and “parts” are based on weight unless otherwise specified.

A modified polyvinyl alcohol resin containing a monomer unit having (A) a diacetone acrylamide unit and (B) a long chain alkyl group having 6 to 22 carbon atoms in the side chain is synthesized by the following method. did. The saponification degree and 4% aqueous solution viscosity were measured according to JIS K-6726. Regarding the content of diacetone acrylamide units and the content of monomer units having a long chain alkyl group having 6 to 22 carbon atoms in the side chain, the sample was thoroughly washed with methanol and hexane. Then, ¹ H-NMR measurement was performed using DMSO-d ₆ as a solvent, and the value was calculated from the integrated value of the assigned peak.

A synthesis example of the modified PVA resin is shown below.
[Synthesis Example 1]
Into a flask equipped with a stirrer, thermometer, dropping funnel and reflux condenser, 950 parts by weight of vinyl acetate and 350 parts by weight of methanol were charged, and after replacing the nitrogen in the system, the internal temperature was raised to 60 ° C. Warm up. A solution prepared by dissolving 1 part by weight of 2,2-azobisisobutyronitrile in 35 parts by weight of methanol was added to the system, and polymerization was started. While maintaining the temperature in the system at 63 ° C. and continuing to flow nitrogen through the flask, a solution in which 15 parts by weight of vinyl stearyl ether was dissolved in 50 parts by weight of vinyl acetate was dropped at a constant rate over 2 hours immediately after the start of polymerization. Then, a solution obtained by dissolving 70 parts by weight of diacetone acrylamide in 50 parts by weight of methanol was dropped at a constant rate over 4 hours immediately after the start of polymerization, and 5 hours after the start of polymerization, m-dinitrobenzene was used as a polymerization terminator. The polymerization was stopped by adding. The polymerization yield was 90%.
While adding methanol vapor to the resulting reaction mixture, the remaining vinyl acetate was distilled off to obtain a 50% methanol solution of diacetone acrylamide-vinyl stearyl ether-vinyl acetate copolymer. To 500 parts by weight of this mixed solution, 70 parts by weight of methanol, 2 parts by weight of ion-exchanged water and 15 parts by weight of a 4% methanol solution of sodium hydroxide were added and mixed well, and a saponification reaction was carried out at 40 ° C. for 2 hours. The obtained gel-like material was pulverized, thoroughly washed with methanol, and then dried to obtain diacetone acrylamide-vinyl stearyl ether copolymer-modified PVA. The resulting modified PVA had a 4% aqueous solution viscosity at 20 ° C. of 245 mPa · s and a saponification degree of 98.8 mol%. The diacetone acrylamide content in the modified PVA was 3.9 mol%, and the vinyl stearyl ether content was 1.2 mol%.

[Synthesis Example 2]
Into a flask equipped with a stirrer, thermometer, dropping funnel and reflux condenser, 950 parts by weight of vinyl acetate and 350 parts by weight of methanol were charged, and after replacing the nitrogen in the system, the internal temperature was raised to 60 ° C. Warm up. A solution prepared by dissolving 1 part by weight of 2,2-azobisisobutyronitrile in 35 parts by weight of methanol was added to the system, and polymerization was started. While maintaining the temperature in the system at 63 ° C. and continuing nitrogen flow in the flask, a solution in which 30 parts by weight of vinyl 2-ethylhexyl ether was dissolved in 50 parts by weight of vinyl acetate was added at a constant rate over 3 hours immediately after the start of polymerization. A solution prepared by dissolving 40 parts by weight of diacetone acrylamide in 50 parts by weight of methanol was added dropwise at a constant rate over 4 hours immediately after the start of polymerization, and 5 hours after the start of polymerization, m-diamine was used as a polymerization terminator. Nitrobenzene was added to stop the polymerization. The polymerization yield was 87%.
While methanol vapor was added to the resulting reaction mixture, the remaining vinyl acetate was distilled off to obtain a 50% methanol solution of diacetone acrylamide-vinyl 2-ethylhexyl ether-vinyl acetate copolymer. To 500 parts by weight of this mixed solution, 70 parts by weight of methanol, 2 parts by weight of ion-exchanged water and 20 parts by weight of a 4% methanol solution of sodium hydroxide were added and mixed well, and a saponification reaction was performed at 40 ° C. for 2 hours. The obtained gel-like material was pulverized, thoroughly washed with methanol, and then dried to obtain diacetone acrylamide-vinyl 2-ethylhexyl ether copolymer-modified PVA. The resulting modified PVA had a 4% aqueous solution viscosity at 20 ° C. of 138 mPa · s and a saponification degree of 98.8 mol%. The diacetone acrylamide content in the modified PVA was 3.0 mol%, and the vinyl 2-ethylhexyl ether content was 2.5 mol%.

[Synthesis Examples 3 to 6]
Table 1 below shows the same method as in Synthesis Example 1 except that the type of ethylenically unsaturated monomer having a long-chain alkyl group having 6 to 22 carbon atoms, the charged composition and the polymerization yield were changed. Modified PVA was synthesized.

[Comparative Synthesis Example 1]
Copolymerization with diacetone acrylamide in the same manner as in Synthesis Example 1 except that vinyl stearyl ether was not used and the amount of 2,2-azobisisobutyronitrile was changed from 1 part by weight to 0.5 part by weight. Modified PVA was synthesized. The analytical values of the obtained modified PVA are shown in Table 1 below.

[Comparative Synthesis Example 2]
Vinyl stearyl ether copolymer modified PVA was synthesized in the same manner as in Synthesis Example 1 except that diacetone acrylamide was not used. The analytical values of the obtained modified PVA are shown in Table 1 below.

[Comparative Synthesis Example 3]
A diacetone acrylamide-vinyl n-butyl ether copolymer-modified PVA was synthesized in the same manner as in Synthesis Example 1 except that vinyl n-butyl ether was used instead of vinyl stearyl ether. The analytical values of the obtained modified PVA are shown in Table 1 below.

Production and evaluation of the ink jet recording material will be described below.
[Example 1]
Pure water was added to the modified PVA obtained in Synthesis Example 1, the temperature was raised while stirring, the solution was dissolved at 90 ° C. for 2 hours, and then cooled to 20 ° C. to obtain an 8% aqueous solution. To 100 parts of this aqueous solution, 4 parts of a 10% aqueous solution of adipic acid dihydrazide as a cross-linking agent was added, and amorphous silica [trade name: Fine Seal X-45, average particle diameter 4.5 μm, manufactured by Tokuyama Corporation] 70 parts are gradually added while being dispersed, and 5 parts of polydiallyldimethylammonium chloride [manufactured by Nittobo Co., Ltd., trade name: PAS-H-5L, 28% aqueous solution] and 430 parts of pure water are added as an ink fixing agent. The mixture was stirred at 5000 rpm for 10 minutes using a homogenizer to prepare an ink receiving layer coating solution having a solid content of 15%. The coating solution is applied to high-quality paper having a basis weight of 64 g / m ² using an air knife coater so that the solid content is 13 g / m ² and dried at 105 ° C. for 10 minutes to obtain an ink jet recording material. Produced.

[Example 2]
Ink prepared in the same manner as in Example 1 except that 2 parts of a 20% aqueous solution of hexamethylene semicarbazide [Hardener SC manufactured by Asahi Kasei Chemicals Corporation] was used in place of 4 parts of a 10% aqueous solution of adipic acid dihydrazide as a crosslinking agent. An ink jet recording material was prepared using the receiving layer coating solution.

[Example 3]
To 100 parts of the 10% aqueous solution of modified PVA obtained in Synthesis Example 2, 5 parts of a 10% aqueous solution of N-aminopolyacrylamide [APA-L manufactured by Otsuka Chemical Co., Ltd.] as a cross-linking agent was added, and further amorphous. Silica [manufactured by Tokuyama Co., Ltd., trade name: Fine Seal X-45, average particle size 4.5 μm] 70 parts are gradually added while being dispersed, and polydiallyldimethylammonium chloride [manufactured by Nittobo Co., Ltd.] as an ink fixing agent. , Trade name: PAS-H-5L, 28% aqueous solution] 5 parts and 440 parts of pure water were added and stirred for 10 minutes at 5000 rpm using a homogenizer to prepare an ink receiving layer coating solution having a solid content of 15%. In the same manner as in Example 1, an inkjet recording material was produced.

[Example 4]
To 100 parts of the 10% aqueous solution of modified PVA obtained in Synthesis Example 3, 0.2 part of isopropanolamine as a water-soluble basic compound was added and mixed, and then 8 parts of a 10% aqueous solution of adipic acid dihydrazide as a crosslinking agent. Further, 70 parts of amorphous silica [trade name: Fine Seal X-45, average particle size 4.5 μm] manufactured by Tokuyama Co., Ltd. is gradually added while being dispersed, and polydiallyldimethylammonium as an ink fixing agent. Add 5 parts of chloride [made by Nittobo Co., Ltd., trade name: PAS-H-5L, 28% aqueous solution] and 440 parts of pure water, stir at 5000 rpm for 10 minutes using a homogenizer, and accept ink with a solid content of 15%. A layer coating solution was prepared, and an ink jet recording material was prepared in the same manner as in Example 1.

[Example 5]
To 100 parts of 10% aqueous solution of modified PVA obtained in Synthesis Example 4, 5 parts of 10% aqueous solution of N-aminopolyacrylamide [APA-L manufactured by Otsuka Chemical Co., Ltd.] as a cross-linking agent was added and slowly added at 30 ° C. The mixture was allowed to stand for 2 hours with stirring, and 0.1 part of monoethanolamine was added and mixed as a water-soluble basic compound. 70 parts of amorphous silica [made by Tokuyama Co., Ltd., trade name: Fine Seal X-45, average particle size 4.5 μm] is gradually added thereto while being dispersed, and polydiallyldimethylammonium chloride [Nitto] as an ink fixing agent. 5 parts of PAS-H-5L, 28% aqueous solution] and 440 parts of pure water were added and stirred at 5000 rpm for 10 minutes using a homogenizer, and an ink receiving layer coating solution having a solid content of 15%. And an ink jet recording material was produced in the same manner as in Example 1.

[Example 6]
An ink jet recording material was produced in the same manner as in Example 1 except that the modified PVA obtained in Synthesis Example 5 was used instead of the modified PVA obtained in Synthesis Example 1.

[Example 7]
An ink jet recording material was produced in the same manner as in Example 1 except that the modified PVA obtained in Synthesis Example 6 was used instead of the modified PVA obtained in Synthesis Example 1.

[Comparative Example 1]
Instead of the modified PVA obtained in Synthesis Example 1, unmodified PVA [JP-18 manufactured by Nippon Vinegar Poval Co., Ltd., saponification degree 88.0 mol%, 4% aqueous solution viscosity 24.1 mPa · s] is used. An ink jet recording material was produced in the same manner as in Example 1 except that.

[Comparative Example 2]
An ink jet recording material was prepared in the same manner as in Example 1 except that the modified PVA obtained in Comparative Synthesis Example 1 was used instead of the modified PVA obtained in Synthesis Example 1.

[Comparative Example 3]
An ink jet recording material was prepared in the same manner as in Example 1 except that the modified PVA obtained in Comparative Synthesis Example 2 was used instead of the modified PVA obtained in Synthesis Example 1.

[Comparative Example 4]
An ink jet recording material was prepared in the same manner as in Example 1 except that no crosslinking agent was added.

[Comparative Example 5]
An inkjet recording material was produced in the same manner as in Example 1 except that the modified PVA obtained in Comparative Synthesis Example 3 was used in place of the modified PVA obtained in Synthesis Example 1.

  The following tests were conducted on the ink jet recording materials of Examples and Comparative Examples produced as described above. The results are shown in Table 2.

<Observation of crack>
The surface of the ink receiving layer of the produced ink jet recording material was observed with a microscope having a magnification of 100 times, and the degree of cracking on the surface of the ink receiving layer was evaluated according to the following criteria.
○: No surface cracks observed and no problem △: Multiple surface cracks observed and practically difficult level ×: Very many cracks observed, impractical

<Surface strength>
A mending tape (width 18 mm) manufactured by Sumitomo 3M Co., Ltd. was applied to the surface of the ink-receiving layer of the ink-jet recording material produced, and the state of the coating layer transferred to the mending tape when peeled was visually observed. The surface strength was evaluated according to the following criteria.
○: Almost no coating layer is transferred, and there is no problem in practical use. △: A part of the coating layer is transferred, and there is a problem level. ×: A considerable part of the coating layer is transferred, which is impractical. level

<Ink absorbability>
Set the prepared inkjet recording material on the printer “PX-V630” (trade name) manufactured by Seiko Epson Corporation, perform solid printing with black ink, and touch the printed part on the recording sheet with a finger at regular intervals after printing. The time until rubbing and the printed part did not change was measured. The shorter the time, the greater the ink absorption rate.

<Water resistance>
Whether water was applied to the printed portion of the ink jet recording material and it was rubbed with a finger was used to determine whether the printed portion was dissolved or smudged according to the following criteria.
○: There is no blur and the original shape remains.
X: Smear is large and the original shape is not retained.

  As is apparent from the results in Table 2, it can be seen that the ink jet recording materials of Examples 1 to 7 of the present invention show high surface strength without cracks on the surface of the ink receiving layer. Further, since the ink absorbency is high and the water resistance is also high, it becomes possible to display a fine image even when printing at high speed.

  Since the comparative example 1 uses PVA which does not have a diacetone acrylamide unit and the monomer unit which has a long-chain alkyl group in a side chain as a binder, a crosslinking reaction does not occur and surface strength and water resistance are Since the binder resin is low and the viscosity of the aqueous solution is low, the binder resin penetrates into the voids of the porous inorganic fine particles, so that the surface is easily cracked and the ink absorbability is also lowered.

  Since Comparative Example 2 uses diacetone acrylamide-modified PVA that does not have a monomer unit having a long-chain alkyl group in the side chain as a binder, a crosslinking reaction occurs by adding a crosslinking agent, and the surface The strength and water resistance are improved as compared with Comparative Example 1. However, since it does not have a monomer unit having a long-chain alkyl group in the side chain, the aqueous solution viscosity is low, and the binder resin penetrates into the voids of the porous inorganic fine particles, so that the surface is liable to crack and the ink absorbency is also high. It was low.

  Since PVA which does not contain a diacetone acrylamide unit and has a monomer unit having a long-chain alkyl group in the side chain is used, in Comparative Example 3, the crosslinking reaction with the crosslinking agent does not occur, and the surface strength is low. The water resistance is also low. Although PVA having a diacetone acrylamide unit and a monomer unit having a long-chain alkyl group in the side chain is used as a binder, the same phenomenon as in Comparative Example 3 occurs in Comparative Example 4 in which no crosslinking agent is used. The surface strength and water resistance did not reach practical levels.

  In Comparative Example 5, a modified PVA having a diacetone acrylamide unit and an alkyl group in the side chain is used for the binder, but the viscosity of the aqueous solution is low and the binder resin is porous because the alkyl group has 4 carbon atoms. Since it penetrates into the voids of the inorganic fine particles, the surface is liable to crack and the ink absorbency is low.

  Since the ink jet recording material manufactured by the manufacturing method of the present invention is excellent in ink absorbability, strength and water resistance, it is possible to display a fine image even when printing at high speed.

Claims (5)

In an inkjet recording material having an ink receiving layer comprising a porous inorganic fine particle, a polyvinyl alcohol resin and a crosslinking agent on a support, the polyvinyl alcohol resin has (A) diacetone acrylamide unit and (B) side in the molecule. An inkjet recording material comprising a modified polyvinyl alcohol-based resin containing a monomer unit having a long-chain alkyl group having 6 to 22 carbon atoms in the chain , wherein the modified polyvinyl alcohol-based resin is ( A) The content of diacetone acrylamide unit is 0.1 mol% or more and 15 mol% or less with respect to the whole modified polyvinyl alcohol resin, and (B) a long chain alkyl having 6 to 22 carbon atoms in the side chain. The content of the monomer unit having a group is 0.02 mol% or more with respect to the whole modified polyvinyl alcohol resin. Jet recording material comprising not more than mole%.   2. The ink jet recording material according to claim 1, wherein the crosslinking agent is a compound having two or more functional groups of at least one selected from the group consisting of hydrazino group, hydrazide group or semicarbazide group. The inkjet recording material according to claim 1 or 2 , wherein the viscosity of the 4 wt% aqueous solution of the modified polyvinyl alcohol resin measured by the method of JIS K-6726 is 50 mPa · s or more. A modified polyvinyl containing porous inorganic fine particles on a support, (A) a diacetone acrylamide unit in the molecule, and (B) a monomer unit having a long chain alkyl group having 6 to 22 carbon atoms in the side chain. coating a coating solution containing an alcohol-based resin and a crosslinking agent, method for producing an ink jet recording material which is according to any one of claims 1 to 3, characterized in that to form an ink-receiving layer. The method for producing an ink jet recording material according to claim 4 , wherein the coating liquid further contains a water-soluble basic compound.