JP2009196365A - Method of manufacturing inkjet recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a recording sheet suitable for inkjet recording which prepares an ink acceptance layer excellent in transparency and water resistance. <P>SOLUTION: The method of manufacturing an inkjet recording sheet includes: applying a coating liquid containing polyvinyl pyrrolidone, an anion monomer having an ethylene unsaturated group and a carboxy group, a polymerization initiator, a crosslinking agent having a functional group which can react with the carboxy group on a support; and carrying out heating polymerization to prepare an ink acceptance layer containing a crosslinked anion polymer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing an ink jet recording sheet, and is intended to enhance the water resistance and transparency of the ink receiving layer so as to have good water resistance and transparency.

  Printers that output image information created by a computer, particularly inkjet printers, are excellent in terms of quietness, cost, image quality, and the like. Inkjet recording is a method of recording by ejecting water-based ink from a nozzle and attaching it to an inkjet recording sheet.

  With the rapid spread of inkjet printers, various types of inkjet recording sheets have been studied in order to satisfy diversifying needs. For example, highly transparent inkjet recording sheets are desired for applications or forms such as OHP, electrical panels, posters, stickers, and labels.

  A transparent plastic sheet is suitable for the support of the highly transparent ink jet recording sheet, but it has almost no property of absorbing water-based ink. For this reason, it is necessary to provide on the sheet an ink receiving layer having a property of quickly absorbing and drying water-based ink (ink drying property). In addition to transparency, the ink receiving layer is required to have a characteristic (water resistance) that prevents printing even when wet by rain when an inkjet recording sheet is used outdoors.

  However, it is difficult to obtain an ink receiving layer that simultaneously satisfies ink drying properties, transparency, and water resistance. The background is described below.

  In general, a water-soluble polymer that easily absorbs water-based ink is used as the material of the ink receiving layer. Examples thereof include polyvinyl alcohol, cation-modified polyvinyl alcohol, polyvinyl pyrrolidone, polyallylamine, polyethylene oxide, polyacrylic acid and the like. However, when these water-soluble polymers are used as they are in the ink-receiving layer, the printed image immediately bleeds when wet.

  A method of adding a filler capable of quickly absorbing ink and drying it to the ink receiving layer is well known. For example, highly water-absorbing polymer particles (Patent Document 1), silica fine particles (Patent Document 2), alumina hydrate fine particles (Patent Document 3) and the like can be mentioned, but the transparency of the ink receiving layer and cracking are likely to occur. Furthermore, these fillers do not modify the water-soluble polymer itself contained in the ink receiving layer and improve its water resistance.

  As a specific example of the method for modifying the water-soluble polymer to provide the ink receiving layer with water resistance, a method of synthesizing a polymer complex that is hardly soluble in water from the water-soluble polymer can be mentioned. For example, Patent Document 4 describes that an ink receiving layer having a structure (polymer complex) in which a polyvinyl pyrrolidone that is a cationic polymer and a (meth) acrylic acid polymer that is an anionic polymer are ion-bonded is excellent in water resistance. Yes. Moreover, the combination of the cationic polymer and the styrene- (meth) acrylic acid polymer described in Patent Documents 5 and 6 have the same principle.

  Specifically, an ink receiving layer is obtained by applying a polymer complex solution or dispersion obtained by mixing a cationic polymer solution and an anionic polymer solution to a support and drying. Is. Since the ion-bonded polymer complex is hardly soluble in water, it is considered to be an effective method for improving the water resistance of the ink receiving layer.

However, an ink-receiving layer having satisfactory water resistance even under outdoor conditions cannot be obtained only with an ion-bonded polymer complex. Furthermore, since the polymer complex is generally poorly soluble, a polar solvent such as dimethylformamide or cellosolve, which is unfavorable for hygiene, is required for the coating liquid when preparing the coating liquid.
In addition, the rate at which both cationic and anionic polymers are ion-bonded is remarkably fast, and an ory or massive polymer complex is likely to be formed during mixing. In order to suppress the aggregation of the polymer complex, the composition of the polymer complex may be limited. As a result, it becomes difficult to impart water resistance to the ink receiving layer.

JP 58-11284 A JP-A-57-14091 JP-A-2-276671 Japanese Patent Laid-Open No. 62-218181 Japanese Patent Laid-Open No. 62-122781 JP-A-9-99634

Highly transparent sheets for ink-jet recording do not have an ink-receiving layer that satisfies transparency and water resistance for the above reasons, etc., so that electrical panels, posters, and stickers that can be exposed to the rain outside of the interior such as OHP It is difficult to develop applications for labels and the like.
In view of these circumstances, an object of the present invention is to provide a method for producing an ink jet recording sheet provided with an ink receiving layer excellent in transparency and water resistance.

  As a result of earnest studies to achieve the above object, an ink receiving layer obtained by applying and heating a coating liquid containing polyvinylpyrrolidone as a cationic polymer, an anionic monomer, a polymerization initiator, and a crosslinking agent as essential components. It has been found that an ink jet recording sheet satisfying such a problem can be obtained by providing the above, and the present invention has been completed.

That is, in the method for producing an inkjet recording sheet of the present invention, a coating liquid containing polyvinylpyrrolidone, an anionic monomer, a polymerization initiator, and a crosslinking agent is applied on a support and heated to form an ink receiving layer. It is characterized by providing.
The anionic monomer preferably contains an ethylenically unsaturated group and a carboxyl group.
Furthermore, the crosslinking agent is preferably a compound having a functional group capable of reacting with a carboxyl group.
Moreover, it is preferable that the said support body has transparency.

  The method for producing an ink jet recording sheet of the present invention is such that an ink receiving layer satisfying transparency and water resistance is provided on a support, and if a transparent sheet is used as the support, the transparency and water resistance are excellent. An ink jet recording sheet is obtained. The ink receiving layer in the present invention is considered to be obtained through the following reaction process when the coating liquid containing the essential components is applied and dried by heating.

  That is, after an anionic monomer is polymerized by a polymerization initiator to become an anionic polymer, the anionic polymer is ionically bonded to polyvinyl pyrrolidone to form a polymer complex. Further, it is considered that the crosslinking agent reacts with a carboxyl group or the like to promote insolubilization in water, and an ink receiving layer having sufficient water resistance can be obtained on the support.

In the present invention, polyvinyl pyrrolidone and an anionic monomer are ion-bonded but are not a polymer complex. Therefore, compared with the conventional polymer mixing method of a cationic polymer and an anionic polymer, there is no need to worry about the orientation or lump of the polymer complex, and it is possible to keep the thixotropy of the coating solution low. preferable.
Further, since the composition of the polymer complex can be made arbitrarily, it is considered advantageous for imparting water resistance to the ink receiving layer. Furthermore, it is preferable in terms of hygiene in production and cost that a polar solvent such as dimethylformamide or cellosolve for dissolving the polymer complex is not required in the solvent of the coating solution.

  According to the present invention, an ink jet recording sheet provided with an ink receiving layer excellent in transparency and water resistance can be produced.

The ink receiving layer constituting the ink jet recording sheet obtained from the ink jet recording sheet manufacturing method of the present invention (hereinafter referred to as “the manufacturing method of the present invention”) is specifically polyvinyl pyrrolidone, an anionic monomer, polymerization It is obtained by applying a coating liquid comprising an initiator, a crosslinking agent and other materials to a support and heating and drying.
Hereinafter, the composition of the coating liquid will be described.

[Polyvinylpyrrolidone]
Examples of the polyvinyl pyrrolidone used in the present invention include polymers of N-vinyl-2-pyrrolidone, N-vinyl pyrrolidone, and N-vinyl piperidone, and these may be used alone or in combination. In particular, a polymer having an average molecular weight of 160,000 or more and 1,500,000 or less of N-vinyl-2-pyrrolidone is preferable. When the average molecular weight is low, the dried coating film has poor water resistance and is very brittle. When it is too high, the viscosity of the polymer solution (coating solution) is high and the leveling at the time of coating is poor.

[Anionic monomer]
The anionic monomer used in the present invention is a compound having an ethylenically unsaturated group and a carboxyl group, such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, 2- (meth) acryloyloxy. Monomers containing ethylenically unsaturated groups and carboxyl groups, such as ethyl maleic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, and neutralized products and parts thereof Although neutralized material etc. are mentioned, these may be used 1 type or 2 or more types, It is not limited to these.
The neutralized product or the partially neutralized product can be obtained by neutralizing a corresponding compound with sodium, potassium, ammonia, or an organic amine. Acrylic acid, methacrylic acid, and 2- (meth) acryloyloxyethyl succinic acid are preferable.

  The weight ratio of the polyvinyl pyrrolidone and the anionic monomer contained in the coating liquid in the present invention is 20:80 to 95: 5. When the weight ratio of polyvinyl pyrrolidone is less than this, the cationic property becomes poor, and therefore, the dye of the anionic water-based ink is generally difficult to fix to the ink receiving layer, and when it exceeds this, the water resistance of the ink receiving layer becomes poor. A particularly preferable mixing ratio is 30:70 to 90:10.

[Polymerization initiator]
Examples of the polymerization initiator used in the present invention include persulfates such as sodium persulfate, ammonium persulfate, and potassium persulfate; peroxides such as t-butyl hydroperoxide; 2,2-azobis (2-amidino- Propane) dihydrochloride, 2,2-azobis [2-methyl-N- (2-hydroxyethyl) propion-amide], 2,2-azobis [2- (2-imidazolin-2-yl) propane] dihydro Examples thereof include azo initiators such as chloride. Moreover, you may use together the reducing agent which accelerates | stimulates decomposition | disassembly of these polymerization initiators. Examples of the reducing agent include (bi) sulfurous acid (salt) such as sodium bisulfite, reducing metal (salt) such as L-ascorbic acid (salt) and ferrous salt, and amines.
These polymerization initiators and reducing agents may be used alone or in combination of two or more thereof, and the present invention is not limited to these. Preferred are 2,2-azobis (2-amidino-propane) dihydrochloride, ammonium persulfate, and potassium persulfate. Moreover, the polymerization initiator contained in a coating liquid is 0.01 to 10 weight% of a coating liquid, Preferably it is 0.1 to 5 weight%.

[Crosslinking agent]
The crosslinking agent used in the present invention is a compound that can react with a carboxyl group to form a crosslinked structure. For example, melamine compounds, oxazoline compounds, ethyleneimine compounds, carbodiimide compounds, glyoxal compounds, epoxy compounds , Isocyanate compounds, and the like. These may be used alone or in combination of two or more, but are not limited thereto. Hexamethoxymethylol melamine which is a melamine compound is preferred.
The crosslinking agent contained in the coating solution is 0.1 to 30% by weight, preferably 1 to 10% by weight of the coating solution excluding the crosslinking agent, but this weight range is not limited to the anionic monomer. This is not the case when a material such as acetic acid that can react with the crosslinking agent is added to the working solution. This is because, depending on the material, a certain amount of the crosslinking agent may be deactivated without contributing to the improvement of the water resistance of the ink receiving layer. It may be added. If the cross-linking agent is insufficient, the ink-receiving layer is not sufficiently cross-linked and has poor water resistance, and if it is excessive, the cross-linking proceeds so much that the ink absorbability is extremely lowered.

[Other materials]
In addition to polyvinyl pyrrolidone, an anionic monomer, a polymerization initiator, and a crosslinking agent, other materials may be added to the coating liquid for the purpose of improving the production method and modifying the ink receiving layer suitable for the application. For example, a water-soluble polymer excluding the polyvinyl pyrrolidone, a monomer having an ethylenically unsaturated group excluding the anionic monomer, a polymerization inhibitor, a polymerization regulator, inorganic fine particles for improving water absorption, reduction of friction characteristics and prevention of blocking Matting agents, plasticizers, antioxidants, ultraviolet absorbers, surfactants, antifoaming agents, antiseptics, diluting solvents and the like.
However, these materials should be used so as not to significantly impair the transparency and water resistance, which are the characteristics of the ink receiving layer in the present invention.

  Examples of the water-soluble polymer other than the polyvinylpyrrolidone include natural polymers such as albumin, gelatin, casein, starch, gum arabic, chitosan organic acid salt, sodium alginate; methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxybutylcellulose. Synthetic polymers such as polyacrylamide, polydimethylacrylamide, polydimethylaminoacrylate, polyvinyl methyl ether, polyethyleneimine, polyallylamine, polyvinyl alcohol, cation-modified polyvinyl alcohol, polyethylene oxide, polyacrylic acid soda, acrylate copolymer, etc. These may be used alone or in combination of two or more. However, it should be 0 to 20% by weight or less based on the total weight of the polyvinylpyrrolidone and the anionic monomer contained in the coating liquid so that the coating liquid does not separate or disproportionate.

Examples of monomers having an ethylenically unsaturated group other than the anionic monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. , Polyethylene glycol (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, glycidyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, (meth) Acrylonitrile, (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, diacetone acrylamide Monomer having one ethylenically unsaturated group in the molecule, such as styrene, vinyl acetate, 2-acrylamido-2-methylpropanesulfonic acid, 2- (meth) acryloyloxyethylsulfonic acid, p-styrenesulfonic acid; ethylene glycol Di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri Ethylenically unsaturated groups such as (meth) acrylate, neopentyl glycol di (meth) acrylate, N, N-methylenebisacrylamide, N, N′-methylenebis (N-vinylcarbonylamide) In the molecule can be mentioned a monomer having two or more, they may be used alone or two or more, also not limited thereto.
Although these monomers can contribute to prevention of cracking due to softening of the ink receiving layer or improvement in water resistance, they should be used so as not to impair the transparency and ink drying properties of the ink receiving layer. It should be 0 to 50% by weight or less based on the total weight of the polyvinylpyrrolidone and the anionic monomer contained in the coating solution.

  Examples of the polymerization inhibitor include hydroquinone, hydroquinone monomethyl ether, mono-t-butylhydroquinone, catechol, t-butylcatechol, and N-nitrosophenyl salt.

  Examples of the polymerization regulator include 2-mercaptoethanol, isopropyl alcohol and the like.

  Silica fine particles and alumina fine particles can be added as inorganic fine particles for improving water absorption. However, fine particles having a primary particle diameter of 30 nm or less are preferred so as not to impair transparency.

  Examples of the matting agent for reducing friction characteristics and preventing blocking include inorganic fine particles such as silica fine particles and alumina fine particles, or organic fine particles.

  Examples of the plasticizer include organic acids such as acetic acid, lactic acid, propionic acid and adipic acid; alcohols such as ethylene glycol, diethylene glycol, triethylene glycol and glycerin.

  As other materials that can be added to the coating liquid in the present invention, in addition to the above, known additives such as antioxidants, ultraviolet absorbers, surfactants, antifoaming agents, preservatives, and diluting solvents are added. be able to.

  The procedure for preparing the coating liquid is preferably the order in which the anionic monomer and other materials are added to the polyvinylpyrrolidone solution in order and mixed, and finally the polymerization initiator and the crosslinking agent are added and mixed. The present invention is not necessarily limited to this order.

[Support]
The support used in the present invention is preferably a thermoplastic film, sheet or plate having transparency, heat resistance and moderate rigidity. Examples thereof include polyester, cellophane, polycarbonate, polyimide, vinyl chloride, polyvinylidene chloride, polyacrylate, polyethylene, polypropylene and the like having a thickness of 10 to 200 μm. And more preferably, it is a polyester sheet having a thickness of 20 to 150 μm.
Further, in order to improve the adhesion between the support and the ink receiving layer, surface activation by corona discharge or easy adhesion treatment by providing a primer layer may be performed on the support surface. Examples of the resin for the primer layer include polyester, vinylidene chloride, and acrylic.

[Application]
Examples of methods for applying the coating liquid to the support include known roll coating methods, bar coating methods, spray coating methods, air knife coating methods, gravure coating methods, reverse coating methods, pipe coating methods, and comma coating methods. Can be mentioned.

[Heat drying]
The heat drying after coating the coating liquid on the support is preferably performed by a hot air dryer at 50 to 180 ° C. for 1 to 30 minutes, preferably at 90 to 150 ° C. for 5 to 15 minutes. If the drying temperature is lower and the time is shorter, the polymerization initiator and the cross-linking agent do not react sufficiently, resulting in insufficient water resistance of the ink receiving layer. Coloration of the layer becomes a problem.
The thickness of the dried coating film, that is, the ink receiving layer in the present invention is 2 to 100 μm, preferably 5 to 40 μm. If the thickness is thin, the ink drying property is insufficient, and if it is too thick, the production cost becomes a problem.

  Further, in the present invention, for the purpose of reducing the amount of monomer remaining in the ink receiving layer, the obtained ink jet recording sheet is immersed in an aqueous solution bath of the polymerization initiator, a warm water bath or a weak basic bath. You may perform the process dried by heating later. In addition, a photopolymerization initiator such as 1- (4- (2-hydroxyethoxy) -phenyl) -2-hydroxy-2-methyl-1-propan-1-one is used in combination, and treatment with ultraviolet rays or electron beam irradiation is performed. May be performed.

  The ink jet recording sheet obtained by the production method of the present invention can perform multicolor recording by ink jet recording. The ink jet recording in the present invention may be any system as long as it can eject water-based ink from a nozzle and adhere to the ink jet recording sheet regardless of a continuous system or an on-demand system such as bubble jet (registered trademark) or piezo.

As described above, the method for producing an ink jet recording sheet of the present invention comprises applying a coating liquid containing polyvinylpyrrolidone, an anionic monomer, a polymerization initiator, and a crosslinking agent as essential components on a support and heating. Since the ink receiving layer is provided, the ink receiving layer is excellent in ink drying property, transparency and water resistance. If a transparent sheet is used as a support, the ink receiving layer is excellent in ink drying property, transparency and water resistance. An ink jet recording sheet is obtained.
In the present invention, since the coating solution is not prepared by mixing both cationic and anionic polymers, there is no need to worry about gelation due to the formation of a polymer complex in the coating solution.

  The present invention will be described in detail by the following examples, but the present invention is not limited to these examples. Hereinafter, unless otherwise indicated, “%” and “parts” indicate “% by weight” and “parts by weight”.

[Example 1]
700 parts of a 20% aqueous solution of polyvinylpyrrolidone (PVPK-90, manufactured by GAF), 80 parts of water, 75 parts of 80% acrylic acid (80% GAA, manufactured by Toagosei), 2,2-azobis (2-amidino-propane) di A coating solution comprising 40 parts of a 10% aqueous solution of hydrochloride (V-50, manufactured by Wako Pure Chemical Industries) and 40 parts of a 40% aqueous solution of a melamine compound (Smitex Resin M-3, manufactured by Sumitomo Chemical Co., Ltd.) is prepared. . This coating solution was applied to a corona discharge-treated surface of a 125 μm thick biaxially stretched polyester film (A4300, manufactured by Toyobo Co., Ltd.) so that the dry coating film had a thickness of 25 μm, and dried with a hot air dryer at 110 ° C./10 minutes, An ink jet recording sheet according to the present invention was obtained.

[Example 2]
500 parts of a 20% aqueous solution of polyvinylpyrrolidone, 80 parts of water, 20 parts of acetic acid, 40 parts of 2-methacryloyloxyethyl succinic acid (acrylic ester SA, manufactured by Mitsubishi Chemical), 75 parts of 80% acrylic acid, 2,2-azobis (2 -Amidino-propane) A coating solution comprising 35 parts of a 10% aqueous solution of dihydrochloride and 70 parts of a 40% aqueous solution of a melamine compound is prepared. An ink jet recording sheet according to the present invention was obtained in the same manner as in Example 1 except for the preparation of the coating solution.

[Comparative Example 1]
An attempt was made to prepare a coating solution from 700 parts of a 20% aqueous solution of polyvinylpyrrolidone and 150 parts of a 40% aqueous solution of polyacrylic acid (Durimer AC-10P, average molecular weight 7,000, manufactured by Nippon Pure Chemical). Due to solidification, an ink jet recording sheet could not be obtained.

[Comparative Example 2]
The coating liquid was changed from the coating liquid of Example 1 to a coating liquid in which a 10% aqueous solution of 2,2-azobis (2-amidino-propane) dihydrochloride and a 40% aqueous solution of a melamine compound were omitted. An ink jet recording sheet was obtained in the same manner as in Example 1.

[Comparative Example 3]
An ink jet recording sheet was obtained in the same manner as in Example 1 except that the coating liquid was changed from the coating liquid of Example 1 to a 40% aqueous solution of the melamine compound.

[Comparative Example 4]
The same method as in Example 1 except that the coating liquid is a coating liquid in which a 10% aqueous solution of 2,2-azobis (2-amidino-propane) dihydrochloride is omitted from the coating liquid in Example 1. Thus, an ink jet recording sheet was obtained.

  The ink-drying property, transparency, and water resistance of the ink-jet recording sheets obtained in the above Examples and Comparative Examples were evaluated by printing a magenta pattern with an ink-jet printer (PM-770C, manufactured by Seiko Epson). . The evaluation method is described below.

  The ink drying property was evaluated by finger touch on the dry state of the ink jet recording sheet surface left for 20 minutes after printing (stickiness due to non-absorption of water-based ink). ○: Dry. X: The pattern is blurred and unclear because it is not dry.

  Transparency evaluated the part except a pattern by visual observation. ○: Transparent. Δ: Slightly opaque X: Opaque.

The water resistance was evaluated by visual observation after the ink-jet recording sheet left for 1 hour after printing was immersed in a water bath for 3 days and the change after touching it. ○: Almost no change after bathing, and the pattern does not easily fall off when touched with a finger. Δ: Almost no change after bathing, but the pattern falls off easily when touched with a finger. X: The pattern disappears completely after bathing. XX: The pattern is severely blotted immediately after the start of bathing, and the pattern disappears completely after bathing.
The results are shown in Table 1.

From the results in Table 1, it can be seen that according to the present invention, an ink jet recording sheet having good ink drying properties, transparency, and water resistance can be obtained.

Claims (4)

  A method for producing an inkjet recording sheet, comprising: coating a coating liquid containing polyvinylpyrrolidone, an anionic monomer, a polymerization initiator, and a crosslinking agent on a support, and providing an ink receiving layer by heating.   2. The method for producing an ink jet recording sheet according to claim 1, wherein the anionic monomer contains an ethylenically unsaturated group and a carboxyl group.   3. The method for producing an ink jet recording sheet according to claim 1, wherein the crosslinking agent is a compound having a functional group capable of reacting with a carboxyl group.   The said support body has transparency, The manufacturing method of the sheet | seat for inkjet recording in any one of Claims 1-3 characterized by the above-mentioned.