JP2007301890A - Inkjet recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording material which has an ink accepting layer being free from cracking of the surface and having high glossiness, excellent ink absorbency and high transparency. <P>SOLUTION: The inkjet recording material is prepared by coating a base with a water-based dispersion containing a vinyl alcohol polymer (A) and a vapor-phase-method silica (B). At the time when the viscosity of a water solution wherein the concentration of the vinyl alcohol polymer (A) is 8 wt.% is measured by a BL type viscometer under the condition of the number of revolutions of a rotor being 60 rpm, the ratio η<SB>1</SB>/η<SB>2</SB>between the viscosity η<SB>1</SB>at the temperature of 60°C and the viscosity η<SB>2</SB>at the temperature of 40°C is 0.8 or above. The vapor-phase-method silica (B) is coated with a cationic treating agent which has acetic acid ions as counter ions, and the water-based dispersion contains the vinyl alcohol polymer (A) of 10-100 pts.wt. to 100 pts.wt. of the vapor-phase-method silica (B). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording material obtained by coating a base material with an aqueous dispersion containing vapor-phase silica coated with a vinyl alcohol polymer and a cationic treating agent.

  A vinyl alcohol polymer represented by polyvinyl alcohol (hereinafter, the vinyl alcohol polymer may be abbreviated as “PVA”) is known as a water-soluble synthetic polymer, and uses its strength characteristics. Used as a raw material for synthetic fiber vinylon, and by utilizing its excellent film forming ability, surface activity ability, hydrogen bond forming ability, etc., paper processing agents, fiber pastes, dispersants, adhesives, films, etc. Has been used. Among these, vinyl alcohol polymers are used for paper processing, as surface sizing agents for general paper, undersize agents for art paper / coated paper, dispersants for fluorescent dyes, and binders for fillers in inkjet recording materials. Has been used for.

  Recently, the use of inkjet printers has expanded, and inkjet recording materials have been used for color proofing in commercial printing, design image output in the design field, and documents for overhead projectors. The properties required for ink jet recording materials in these applications include high gloss of the ink receiving layer surface, high transparency of the ink receiving layer, high image density, good color reproducibility, ink Examples thereof include high absorptivity and good dot reproducibility.

  In response to the above requirements for ink jet recording materials, recording materials are known in which a void layer composed of inorganic fine particles and a hydrophilic binder is provided as an ink receiving layer (Patent Documents 1 and 2). This recording material achieves both high ink absorbability and water resistance by an ink absorption mechanism utilizing capillary action. However, in order to form a capillary tube in the ink receiving layer, it is usually necessary to contain a large amount of fine particles with respect to the binder. In this case, the ratio of the binder to the fine particles is low, and the ink receiving layer is very rigid and hard. Therefore, when an ink receiving layer is formed by applying a coating liquid composed of inorganic fine particles and a hydrophilic binder to the base material, due to the generation of internal stress in the drying stage of the coating film, or the inclusion of minute foreign matter, There was a problem that the ink receiving layer was easily cracked.

  To solve such cracking problem of the coating film, a method of preventing the cracking by thickening the coating film before drying the coating film can be considered, and a coating obtained by adding boric acid as a curing agent to a high polymerization degree polyvinyl alcohol. A method has been proposed in which a coating liquid is used and the coating film is cooled to 20 ° C. or lower after coating (Patent Document 3). In this method, when the coating film is cooled to 20 ° C. or less, a strong three-dimensional structure is formed in the coating film due to the interaction between polyvinyl alcohol and boric acid, and as a result, cracking can be prevented. However, in this method, since it is necessary to lower the temperature of the coating film once after coating, there is a problem that energy loss is large, and it takes time to form the coating film, and the production speed cannot be increased. Furthermore, in this method, since polyvinyl alcohol having a high degree of polymerization is used, the viscosity of the coating solution is high, and it is necessary to keep the concentration of the coating solution low in view of its handleability. For this reason, this method has a problem that it takes time to dry the coating film and the production rate cannot be increased.

  In order to solve these problems, a method using a viscosity change with respect to a temperature change of an aqueous solution of a vinyl alcohol polymer having a polyoxypropylene group is disclosed (Patent Document 4). However, this method has problems in that the miscibility is inferior depending on the type of silica to be blended, and the transparency and glossiness of the obtained film are lowered.

Japanese Patent Laid-Open No. 3-56552 JP-A-7-137434 JP 2001-150805 A Japanese Patent Laid-Open No. 2005-42008

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording material having an ink receiving layer that has no cracks on the surface, high gloss, excellent ink absorbability, and high transparency.

According to the present invention, the above-mentioned problem is an ink jet recording material obtained by coating a base material with an aqueous dispersion containing a vinyl alcohol polymer (A) and gas phase method silica (B). When the viscosity of the aqueous solution containing the polymer (A) of 8% by weight was measured with a BL type viscometer under the condition that the rotor rotation speed was 60 rpm, the viscosity η ₁ at a temperature of 60 ° C. and the viscosity η ₂ at a temperature of 40 ° C. The gas phase method silica (B) is coated with a cationic treating agent having an acetate ion as a counter ion, and the aqueous dispersion liquid has a ratio η ₁ / η ₂ of 0.8 or more. Has been found to be solved by an ink jet recording material characterized by containing 10 to 100 parts by weight of a vinyl alcohol polymer (A) with respect to 100 parts by weight of vapor-phase process silica (B).

（Ｒ^１は炭素数１または２のアルキル基を表し、Ｒ^２は水素原子または炭素数１〜４のアルキル基を表し、ｎは１〜１００の整数である。）で示されるポリオキシアルキレン基を有する単量体単位を含有するビニルアルコール系重合体であることが好適である。 At this time, as the vinyl alcohol polymer (A), the following general formula (I)

(R ¹ represents an alkyl group having 1 or 2 carbon atoms, R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 100). A vinyl alcohol polymer containing a monomer unit having the above is preferable.

At this time, the content S (mol%) of the monomer unit having a polyoxyalkylene group with respect to all the monomer units in the vinyl alcohol polymer (A) is 0.01 to 1 mol%. Is preferred. In a preferred embodiment, the vinyl alcohol polymer (A) has a viscosity average polymerization degree P and a monomer unit having a polyoxyalkylene group relative to all monomer units in the vinyl alcohol polymer (A). The product P × S with the S content (mol%) satisfies the following formula (1).
5 <P × S <1500 (1)

Further, at this time, the vinyl alcohol polymer (A) has a polyoxypropylene group in which R ¹ in the general formula (I) is a methyl group and R ² is an alkyl group having 1 to 4 carbon atoms. It is also a preferred embodiment to contain a monomer unit. In a more preferred embodiment, R ¹ is a methyl group and R ² is a methyl group. In another preferred embodiment, the vinyl alcohol polymer (A) is a monomer having a polyoxypropylene group in which R ¹ in the general formula (I) is a methyl group and R ² is a hydrogen atom. Contains units.

In a preferred embodiment of the present invention, gas phase method silica having a specific surface area of 70 m ² / g or more is treated as a cationic method as gas phase method silica (B) coated with a cationic treatment agent having acetate ions as counter ions. It is a preferred embodiment to use one coated with an agent.

  The aqueous dispersion used in the present invention has good miscibility, and when the aqueous dispersion is heated to room temperature or higher, the viscosity of the aqueous dispersion is obtained when a general vinyl alcohol polymer is used. It has the characteristic that it becomes high compared. Therefore, the aqueous dispersion used in the present invention increases the viscosity of the coating before the coating is dried when the coating obtained by applying the aqueous dispersion to a substrate is heated and dried. Therefore, the crack of the coating film can be prevented. And by applying the aqueous dispersion used in the present invention, it is possible to produce an inkjet recording material having high gloss, excellent ink absorption, and a highly transparent ink receiving layer with high productivity. And has high industrial value.

The ink jet recording agent of the present invention is obtained by coating a base material with an aqueous dispersion containing a vinyl alcohol polymer (A) and gas phase method silica (B), and comprises a vinyl alcohol polymer (A ) Is the ratio η ₁ of the viscosity η ₁ at a temperature of 60 ° C. and the viscosity η ₂ at a temperature of 40 ° C. when the viscosity of an aqueous solution of 8% by weight is measured with a BL-type viscometer under the condition that the rotor speed is 60 rpm. / Η ₂ is 0.8 or more, gas phase method silica (B) is coated with a cationic treatment agent having acetate ions as counter ions, and the aqueous dispersion is a gas phase method It contains 10 to 100 parts by weight of vinyl alcohol polymer (A) with respect to 100 parts by weight of silica (B).

The vinyl alcohol polymer (A) used in the present invention has a viscosity η ₁ at a temperature of 60 ° C. and a temperature when the viscosity of an 8% by weight aqueous solution is measured with a BL type viscometer under the condition that the rotor rotational speed is 60 rpm. The ratio η ₁ / η ₂ to the viscosity η ₂ at 40 ° C. is 0.8 or more. As a result, when the vinyl alcohol polymer (A) used in the present invention is used as a recording material or the like, a coated product having excellent physical properties such as no cracks on the coating surface can be obtained. The viscosity ratio η ₁ / η ₂ is preferably 1 or more, and more preferably 2 or more. The vinyl alcohol polymer (A) has a special property that the viscosity is large even in a high temperature range as compared with a general vinyl alcohol polymer having a viscosity ratio η ₁ / η ₂ of less than 0.8. By using such a polymer, effects such as prevention of cracks on the coating surface and high gloss can be achieved.

（Ｒ^１は炭素数１または２のアルキル基を表し、Ｒ^２は水素原子または炭素数１〜４のアルキル基を表し、ｎは１〜１００の整数である。）で示されるポリオキシアルキレン基を有する単量体単位を含有するビニルアルコール系重合体であることが好ましい。上記ポリオキシアルキレン基のＲ^１としては、本発明で用いられる水性分散液を皮膜とした時に高い透明性が得られる観点から、メチル基であることが好ましい。また、一般式（Ｉ）で示されるポリオキシアルキレン基のＲ^２としては水素原子またはメチル基であることが好ましく、塗膜乾燥時における、粘度上昇による塗膜ひび割れ防止の観点からは、メチル基であることがより好ましい。 As described above, the vinyl alcohol polymer (A) used in the present invention is required to have a viscosity ratio η ₁ / η ₂ of 0.8 or more, and among them, the following general formula (I)

(R ¹ represents an alkyl group having 1 or 2 carbon atoms, R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 100). It is preferable that it is a vinyl alcohol-type polymer containing the monomer unit which has this. R ¹ of the polyoxyalkylene group is preferably a methyl group from the viewpoint of obtaining high transparency when the aqueous dispersion used in the present invention is used as a film. Further, R ² of the polyoxyalkylene group represented by the general formula (I) is preferably a hydrogen atom or a methyl group. From the viewpoint of preventing cracking of the coating film due to an increase in viscosity at the time of drying the coating film, the methyl group It is more preferable that

  In the vinyl alcohol polymer (A) used in the present invention, the number n of oxyalkylene repeating units in the monomer unit having a polyoxyalkylene group is an integer of 1 to 100. When the number n of oxyalkylene repeating units exceeds 100, the solubility of the vinyl alcohol polymer (A) in water becomes low, and the stability of the aqueous dispersion used in the present invention becomes insufficient. . N preferably satisfies 5 <n <80, more preferably satisfies 8 <n <50, further preferably satisfy 10 <n <40, and particularly preferably satisfy 15 <n <35. . When the number n of oxyalkylene repeating units exceeds 5, a high transparency film can be obtained when the film is formed, and the effect of preventing cracking of the coating film can be obtained.

  Although there is no restriction | limiting in particular in the viscosity average polymerization degree P (henceforth a polymerization degree) of the vinyl alcohol-type polymer (A) used for this invention, Usually, it is 50-10000, Preferably it is 100-8000. More preferably, it is 300-5000. The present invention relates to an ink jet recording material obtained by coating an aqueous dispersion containing a vinyl alcohol polymer (A) and gas phase method silica (B) on a substrate. When the polymerization degree of A) is less than 50, there is a possibility that the adhesive strength as a binder between the vapor phase method silica (B) and the adhesive strength with the substrate cannot be obtained sufficiently. On the other hand, when the degree of polymerization of the vinyl alcohol polymer (A) exceeds 10,000, the viscosity of the aqueous dispersion may be too high and handling may be difficult, and the aqueous dispersion may be used as a base material. There is a possibility that a uniform coating layer is difficult to be obtained when coating is applied.

  In the vinyl alcohol polymer (A) used in the present invention, the content S (mol%) of the monomer unit having a polyoxyalkylene group represented by the general formula (I) is the total amount of the vinyl alcohol polymer. It is preferable that it is 0.01-1 mol% with respect to a monomer unit. In the inkjet recording material of the present invention, from the viewpoint of obtaining a more excellent effect of preventing cracking of the coating film, the lower limit of the content S (mol%) of the monomer unit having the polyoxyalkylene group is 0.03 mol. % Or more, more preferably 0.05 mol% or more, particularly preferably 0.07 mol% or more, and most preferably 0.08 mol% or more. On the other hand, when emphasizing the standing viscosity stability of the aqueous dispersion used in the present invention, the upper limit of the content S (mol%) is more preferably 0.9 mol% or less, and 0.8 mol%. More preferably, it is 0.6 mol% or less, and most preferably 0.4 mol% or less.

The vinyl alcohol polymer (A) used in the present invention is a product of the viscosity average polymerization degree P of the vinyl alcohol polymer and the content S (mol%) of the monomer unit having a polyoxyalkylene group ( P × S) preferably satisfies the following formula (1).
5 <P × S <1500 (1)
By using the vinyl alcohol polymer (A) in which the P × S exceeds 5, an ink jet recording material having an excellent effect of preventing cracking of the coating film can be obtained. Further, by using the vinyl alcohol polymer (A) having a P × S of less than 1500, the standing viscosity stability of the aqueous dispersion used in the present invention can be significantly improved.
The P × S more preferably satisfies the following formula (1 ′).
50 <P × S <1000 (1 ′)
Further, it is more preferable that the P × S satisfies the following formula (1 ″).
100 <P × S <800 (1 ″)

  Although there is no restriction | limiting in particular in the saponification degree of the vinyl alcohol type polymer (A) used for this invention, It is preferable that it is 80-99.99 mol%, and it is more preferable that it is 85-99.9 mol%. More preferably, it is 88-99.5 mol%. When the saponification degree of the vinyl alcohol polymer (A) is less than 80 mol% or when the saponification degree is greater than 99.99 mol%, the solubility of the vinyl alcohol polymer (A) in water decreases. As a result, handling of the aqueous dispersion used in the present invention may be difficult.

  The method for producing a vinyl alcohol polymer (A) containing a monomer unit having a polyoxyalkylene group represented by the above general formula (I) used in the present invention is not particularly limited. Is a method of saponifying a vinyl ester polymer containing a monomer unit having a polyoxyalkylene group represented by the general formula (I). As a method for producing a vinyl ester polymer containing a monomer unit having a polyoxyalkylene group, a method of copolymerizing an unsaturated monomer having a polyoxyalkylene group and a vinyl ester monomer is preferable. .

  Examples of the unsaturated monomer having a polyoxyalkylene group represented by the general formula (I) include unsaturated monomers represented by the following general formula (II).

（Ｒ^１は炭素数１または２のアルキル基を表し、Ｒ^２は水素原子または炭素数１〜４のアルキル基を表し、Ｒ^３は水素原子またはメチル基を表し、Ａはカルボニルオキシ基、カルボニルイミノ基、オキシ基、アルキレンオキシ基などの２価の連結基を表す。）

(R ¹ represents an alkyl group having 1 or 2 carbon atoms, R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ³ represents a hydrogen atom or a methyl group, A represents a carbonyloxy group, a carbonyl group, (Denotes a divalent linking group such as an imino group, an oxy group, and an alkyleneoxy group.)

Methyl group is preferable as R ¹ in the unsaturated monomer represented by the general formula (II). As the R ² of the unsaturated monomer represented by the general formula (II) hydrogen atom, preferably a methyl group and butyl group, more preferably a hydrogen atom and methyl group. Furthermore, it is particularly preferable that R ^{1 of the} unsaturated monomer represented by the general formula (II) is a methyl group and R ² is a methyl group.

For example, when R ² in the general formula (II) is a hydrogen atom, specific examples of the unsaturated monomer represented by the general formula (II) include polyoxypropylene monoacrylate, polyoxypropylene monomethacrylate, polyoxypropylene Monoacrylic acid amide, polyoxypropylene monomethacrylic acid amide, polyoxypropylene monoallyl ether, polyoxypropylene monomethallyl ether, polyoxypropylene monovinyl ether, polyoxybutylene monoacrylate, polyoxybutylene monomethacrylate, polyoxybutylene mono Acrylic amide, polyoxybutylene monomethacrylamide, polyoxybutylene monoallyl ether, polyoxybutylene monomethallyl ether, polyoxybutylene monovinyl ether, etc. It is. Of these, polyoxypropylene monoallyl ether and polyoxypropylene monoacrylic amide are preferably used.

When R ^{2 in the} general formula (II) is an alkyl group having 1 to 4 carbon atoms, specifically, as the unsaturated monomer represented by the general formula (II), R ^{2 in} the general formula (II) is Examples thereof include those in which the terminal OH group of the unsaturated monomer exemplified in the case of a hydrogen atom is substituted with an alkoxy group having 1 to 4 carbon atoms. Among them, an unsaturated monomer in which the OH group at the terminal of polyoxypropylene monoallyl ether or polyoxypropylene monoacrylic amide is substituted with a methoxy group is preferably used.

  Examples of the vinyl ester monomer include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, vinyl versatate, and vinyl acetate is generally used.

  When copolymerizing an unsaturated monomer having a polyoxyalkylene group represented by the general formula (I) and a vinyl ester monomer, bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization A known method such as the above can be adopted. Among them, a bulk polymerization method in which polymerization is performed without a solvent, or a solution polymerization method in which polymerization is performed in a solvent such as alcohol is usually employed, and an emulsion polymerization method is employed in order to obtain a polymer having a high degree of polymerization. Examples of the alcohol used as a solvent at the time of solution polymerization include lower alcohols such as methanol, ethanol, and propanol. Among these, methanol is preferably used. As initiators used for the polymerization, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2) , 4-dimethylvaleronitrile), or other initiators such as benzoyl peroxide and peroxide initiators such as n-propyl peroxycarbonate. Although there is no restriction | limiting in particular about superposition | polymerization temperature, The range of -30-150 degreeC is suitable.

  As a method for saponifying a vinyl ester polymer, any of the conventionally known methods can be suitably used. Usually, a method of saponifying an alcohol solution of a vinyl ester polymer with an alkaline catalyst or an acidic catalyst is employed. Is done. Methanol is preferred as the alcohol used as the saponification solvent. As the saponification solvent, not only anhydrides but also those containing a small amount of water are used depending on the purpose, and those containing other organic solvents such as methyl acetate and ethyl acetate may be used. The saponification temperature is usually selected from the range of 10 to 70 ° C. As the saponification catalyst, alkaline catalysts such as sodium hydroxide, potassium hydroxide, sodium methoxide and potassium methoxide are preferable. The amount of the saponification catalyst used is appropriately determined depending on the desired degree of saponification, the amount of water, etc., but is 0.001 or more, preferably 0.002 or more, in molar ratio to the vinyl ester unit in the polymer. It is desirable.

  Vapor phase method silica is used as the silica raw material before coating with the cationic treating agent used in the present invention.

  As the above-mentioned vapor phase method silica, what is also called “fumed silica” obtained by burning a silane-based gas such as silicon tetrachloride in an oxyhydrogen flame is used without any limitation.

The specific surface area of the vapor phase silica used in the present invention is preferably 70 m ² / g or more, and more preferably 180 m ² / g or more. When the specific surface area is less than 70 m ² / g, there is a possibility that the gloss or transparency of the coating layer is difficult to be obtained when the aqueous dispersion used in the present invention is applied to the substrate. The specific surface area is S.I. Brunaure, P.M. H. Emmett, E.M. J. Teller. Am. Chem. Soc. , 60, 309 (1938), the BET specific surface area measured by applying the multi-layer adsorption theory.

  In the present invention, the gas phase method silica coated with a cationic treatment agent refers to silica obtained by coating a cationic treatment agent on the surface of the gas phase method silica by physical adsorption or chemical bonding. In general, the zeta potential of silica particles shows a negative value due to the influence of surface silanol groups. Therefore, as a method for confirming that the silica particles are coated with the cationic treating agent, the zeta potential of the vapor phase silica coated with the cationic treating agent is measured, and it is confirmed that the value becomes positive. A method can be mentioned.

  The cationic treating agent used in the present invention can be used without particular limitation as long as it dissolves in water and dissociates from acetate ions and exhibits a cationic property. A treating agent having a quaternary ammonium base is preferred. Among them, diallylamine derivatives such as diallylmethylamine acetate polymer are preferable.

  The cationic treatment agent is obtained by adding an acetate or the like to a polymer that is dissociated from chloride ions and exhibits a cationic property, and then performing an ion exchange treatment. The average molecular weight of such a cationic treatment agent Is preferably in the range of 10,000 to 100,000. Moreover, the said cationic processing agent should just contain an acetate ion as a counter ion, and other anions may be contained.

  The amount of the cationic treating agent used in the present invention is preferably 3 to 30 parts by weight with respect to 100 parts by weight of the vapor-phase process silica because the stability of the resulting aqueous dispersion can be obtained. Among these, 5 to 20 parts by weight is more preferable.

  The average agglomerated particle diameter of the vapor phase silica (B) used in the present invention is preferably less than 300 nm, and more preferably in the range of 50 to less than 300 nm. When the average aggregate particle size is 300 nm or more, there is a possibility that the gloss or transparency of the coating layer is difficult to obtain when the aqueous dispersion used in the present invention is applied to a substrate.

  The vapor-phase method silica (B) used in the present invention is obtained as an aqueous silica dispersion containing silica particles by uniformly coating the surface of the silica with a cationic treatment agent while atomizing the silica particles in a polar solvent. Is preferred.

  The method for preparing the above aqueous silica dispersion is not particularly limited. Specifically, a cation is prepared by premixing a polar solvent containing gas phase method silica and a cationic treating agent. A method of coating the surface of the silica uniformly with a cationic treatment agent by coating the gas phase method silica with a functional treatment agent, further subjecting it to atomization treatment, and atomizing the silica particles to a suitable average aggregate particle size Is preferably employed. By adopting the above method, it is presumed that the cationic treatment agent adheres mechanochemically to the silica surface and the treatment is performed more uniformly.

  The mixing apparatus used for the premixing process is not particularly limited, but a high speed rotary centrifugal agitator such as a general agitator having a propeller blade, a turbine blade, a paddle blade, etc., a disper mixer, a homogenizer, a homomixer, an ultra mixer, etc. Examples thereof include a method using an emulsifier such as a rotary shear type stirrer, a colloid mill, and a planetary mixer.

  Although the atomization apparatus used for said atomization process is not restrict | limited in particular, Atomization process using an ultrasonic emulsifier, a wet media type grinder, a high-pressure homogenizer, etc. is mentioned. Among these, a high-pressure homogenizer can be most preferably used.

  In order to improve the storage stability and dispersibility, the aqueous silica dispersion may be added with a small amount of a cationic treatment agent, a surfactant, an alcohol, an antifungal agent, etc., as long as the effects of the present invention are not impaired. Good.

  The aqueous dispersion used in the present invention contains 10 to 100 parts by weight of the vinyl alcohol polymer (A) with respect to 100 parts by weight of the vapor phase silica (B). The blending amount of (A) with respect to 100 parts by weight of (B) is preferably 15 to 45 parts by weight, and more preferably 20 to 40 parts by weight. When the blending amount of (A) is less than 10 parts by weight, a sufficient effect of preventing cracking of the coating film cannot be obtained. On the other hand, when the blending amount of the above (A) exceeds 100 parts by weight, the ink absorbability of the ink jet recording material of the present invention becomes insufficient.

  In the aqueous dispersion used in the present invention, a water-soluble salt can be used as an additive for preventing cracking of the coating film as long as other effects are not significantly reduced. Examples of such water-soluble salts include sodium salts, potassium salts, magnesium salts, zinc salts, zirconium salts and ammonium salts of sulfuric acid, hydrochloric acid, phosphoric acid, acetic acid, boric acid and sulfonic acid.

  The water-soluble salt is preferably used in an amount of 0.1 to 6.0 parts by weight, based on 100 parts by weight of the vapor phase silica (B) in the aqueous dispersion, and 0.3 to 4.0 parts by weight. More preferably, it is 0.6 to 2.0 parts by weight. When the amount used is less than 0.1 parts by weight, it is difficult to obtain the effect of preventing the coating layer from cracking when the aqueous dispersion used in the present invention is applied to the substrate. Moreover, when the usage-amount exceeds 6.0 weight part, when apply | coating the aqueous dispersion liquid used by this invention to a base material, there exists a possibility that the glossiness or transparency of a coating layer may become difficult to be obtained.

  The method for adding the water-soluble salt is not particularly limited, and the aqueous alcohol dispersion containing the vinyl alcohol polymer (A), the vapor phase silica (B), the vinyl alcohol polymer (A), and the vapor phase silica. It can be added when preparing any of the coating liquids obtained by mixing (B).

  The aqueous dispersion used in the present invention may contain a cationic treating agent as an ink fixing agent. Examples of the cationic treatment agent include monomers, oligomers, or polymers having primary to tertiary amine groups or quaternary ammonium bases that dissociate when dissolved in water and exhibit cationic properties. Or a polymer is preferable. Examples include dimethylamine / epichlorohydrin polycondensate, acrylamide / diallylamine copolymer, vinylamine polymer, allylamine polymer, diallyldimethylammonium chloride polymer, polyethyleneimine, and cationic group-containing modified polyvinyl alcohol. It is not limited.

  The solid content concentration of the aqueous dispersion used in the present invention is not particularly limited, but is preferably 10 to 30% by weight. The method for preparing the aqueous dispersion is not particularly limited, but a method of mixing an aqueous solution containing the vinyl alcohol polymer (A) and an aqueous silica dispersion containing vapor phase silica (B) is preferable. When gas phase method silica that has not been treated with a cationic treating agent and a vinyl alcohol polymer are mixed, there is a possibility that thickening of the aqueous dispersion due to vigorous aggregation may occur.

  The aqueous dispersion can contain any known additive as long as the effects of the present invention are not significantly reduced. Examples of typical additives include fluorescent brighteners, surfactants, pH adjusters, antifoaming agents, and antifungal agents. An ink jet recording material is obtained by coating the aqueous dispersion on a substrate.

  The aqueous dispersion used in the present invention may further contain other water-soluble or water-dispersible resins. Water-soluble resins include cellulose derivatives such as methylcellulose, hydroxyethylcellulose, carboxymethylcellulose (CMC), albumin, gelatin, casein, starch, cationized starch, arabic gum, poly (meth) acrylamide, polyvinylpyrrolidone, poly (meth) acrylic acid Examples include sodium, sodium alginate, water-soluble polyester resin, water-soluble polyamide resin, and water-soluble melamine resin. Examples of the water dispersible resin include SBR latex, NBR latex, vinyl acetate emulsion, ethylene / vinyl acetate copolymer emulsion, (meth) acrylic ester emulsion, and vinyl chloride emulsion.

  As the substrate used in the ink jet recording material of the present invention, any conventionally known transparent or opaque substrate can be used. Examples of the transparent substrate include polyester, polystyrene, polyvinyl chloride, polymethyl methacrylate, cellulose acetate, polycarbonate, polyimide, cellophane, celluloid and other films, sheets, or highly transparent paper. As an opaque substrate, general paper, pigment coated paper (art paper, coated paper, cast coated paper), cloth, wood, metal plate, synthetic paper, polyethylene laminated paper, opaque synthetic resin film or A sheet etc. are mentioned.

  As a method for producing the ink jet recording material of the present invention, a vinyl alcohol polymer (A), a gas phase method silica (B), and an ink fixing agent, if necessary, are dispersed in an aqueous medium to form an aqueous dispersion. And a method of coating the obtained aqueous dispersion on a substrate using a conventionally known size press, air knife coater, roll coater, bar coater, blade coater, curtain coater, cast coater, die coater, etc. Can be mentioned. Here, although there is no restriction | limiting in particular about coating temperature, it is preferable that it is 10 to 60 degreeC, More preferably, it is 20 to 60 degreeC, More preferably, it is 30 to 50 degreeC.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these. In Examples, unless otherwise specified, “%” and “part” are based on weight, and “polymerization degree” is a viscosity average polymerization degree.

I. Production and Evaluation of PVA PVA was produced by the following method, and the degree of polymerization, the degree of saponification, the content of monomer units having a polyoxyalkylene group, and the viscosity ratio η ₁ / η ₂ of the aqueous solution were determined.

[Degree of polymerization and degree of saponification]
The degree of polymerization and saponification of PVA were determined by the method described in JIS-K6726.

[Content of monomer unit having polyoxyalkylene group]
The gel-like material obtained by saponifying the vinyl ester polymer was pulverized, then subjected to Soxhlet washing with methanol for 3 days, and then dried under reduced pressure at 80 ° C. for 3 days to obtain purified PVA. Containing monomer units having a polyoxyalkylene group based on NMR spectrum measurement using a 500 MHz proton NMR measurement device (“GX-500” manufactured by JEOL) using the purified PVA dissolved in a heavy water solvent as a measurement sample The amount was determined.

[Viscosity ratio of aqueous solution η ₁ / η ₂ ]
An 8 wt% PVA aqueous solution was prepared, and the viscosity η ₂ of the aqueous solution was measured using a BL type viscometer under the conditions of a rotor rotation speed of 60 rpm and a temperature of 40 ° C. Next, the viscosity η ₁ of the aqueous solution was measured using a BL type viscometer under the conditions of a rotor rotation speed of 60 rpm and a temperature of 60 ° C., and the viscosity ratio η ₁ / η ₂ of the PVA aqueous solution was determined.

PVA-1
In a 6 liter reactor equipped with a reflux condenser, a stirrer, a thermometer, a nitrogen inlet tube, a charging port for a post-addition liquid and a pump, 2282 g of vinyl acetate, 198 g of methanol, R ¹ in the general formula (II) is a methyl group An unsaturated monomer having a polyoxypropylene group in which R ² is a methyl group, R ³ is a hydrogen atom, A is a methyleneoxy group, and the average value n of oxyalkylene repeating units is 24 (Polyoxypropylene monoallyl ether (hereinafter abbreviated as POPMA) 100 g was charged. The inside of the system was purged with nitrogen while stirring the polymerization liquid. When the polymerization liquid was heated and became constant temperature at 60 ° C. Then, 1.3 g of 2,2′-azobisisobutyronitrile (hereinafter abbreviated as AIBN) was added to initiate the polymerization, and the solid content concentration in the system was analyzed from the beginning of the polymerization. After 1.8 hours, the reactor was cooled to stop the polymerization, and the polymerization rate was 30% when the polymerization was stopped.The obtained polymerization paste was dropped into n-hexane to give a polymer. The precipitated polymer was collected, dissolved in acetone, and subjected to reprecipitation-purification operation for precipitation in n-hexane three times, and the polymer was dissolved in acetone and added dropwise to distilled water. After boiling and purification, it was dried at 60 ° C. to obtain purified polyvinyl acetate (hereinafter abbreviated as PVAc).

  Next, a 17.5% methanol solution of purified PVAc was prepared. While stirring this methanol solution of purified PVAc at 40 ° C., a methanol solution having a sodium hydroxide concentration of 10% was added so that the molar ratio of sodium hydroxide to vinyl acetate units in PVAc was 0.02. The saponification reaction was performed for 60 minutes. The obtained gel-like material was pulverized and then subjected to Soxhlet washing with methanol for 3 days, followed by drying under reduced pressure at 80 ° C. for 3 days to obtain purified PVA. When the polymerization degree and saponification degree of the PVA were measured according to JIS K6726 of a conventional method, the polymerization degree was 2400 and the saponification degree was 98.5 mol%. Moreover, when the content of the terminal methoxy substituted unit of POPMA in the purified PVA was determined from proton NMR spectrum measurement, it was 0.1 mol% with respect to the total monomer units. Hereinafter, the PVA obtained above is referred to as PVA-1. Table 2 shows the basic structure and aqueous solution viscosity of PVA-1.

PVA-2-15 and 18
Except for changing the polymerization reaction conditions (vinyl acetate and methanol charge amount, type and amount of monomer having polyoxyalkylene group, amount of polymerization initiator used, polymerization time) as shown in Table 1. Various PVAs were prepared by the same method as PVA-1. Table 2 shows the basic structure and aqueous solution viscosity of the obtained PVA.

PVA-16
The polymerization reaction conditions (amount of vinyl acetate and methanol, amount of monomer having a polyoxyalkylene group, amount of polymerization initiator used) were changed as shown in Table 1, and vinyl acetate units in PVAc PVA-16 was prepared by the same method as PVA-1, except that the molar ratio of sodium hydroxide to 0.01 was 0.01. Table 2 shows the basic structure and aqueous solution viscosity of the obtained PVA-16.

PVA-17
Except for changing the polymerization reaction conditions (addition amount of vinyl acetate and methanol, preparation amount of monomer having polyoxyalkylene group, type and amount of polymerization initiator, polymerization time) as shown in Table 1, PVA PVA-17 was prepared by the same method as -1. Table 2 shows the basic structure and aqueous solution viscosity of PVA-17.

II. Preparation and Evaluation of Aqueous Silica Dispersion An aqueous silica dispersion was prepared by the following method, and the obtained aqueous silica dispersion was evaluated.

[Average agglomerated particle size]
The average aggregate particle diameter of the silica fine particles dispersed in the dispersion was measured with a laser diffraction / scattering particle size distribution measuring device (“LA-910” manufactured by Horiba, Ltd.).

[Zeta potential]
The zeta potential of the silica fine particles dispersed in the dispersion was measured with a laser zeta potentiometer (“LEZA-600” manufactured by Otsuka Electronics Co., Ltd.).

(Preparation of aqueous silica dispersion-1)
240 g of gas phase method silica having a specific surface area of 300 m ² / g (“Leosil QS30” manufactured by Tokuyama Co., Ltd.) is mixed with 1760 g of ion-exchanged water so that the gas phase method silica concentration is 12%. A gas phase silica dispersion was obtained by dispersing with a disperser. While adding this gas phase method silica dispersion to 120 g of a 20% aqueous solution of diallylmethylamine acetate polymer (weight average molecular weight 20000), a premixed solution was obtained by mixing with a turbine-stator type disperser. The preliminary mixed liquid was subjected to atomization using a high-pressure homogenizer to obtain a milky white viscous slurry aqueous silica dispersion-1 (solid content concentration: 12.5% by weight). Table 3 shows the evaluation results of the obtained aqueous silica dispersion.

(Preparation of aqueous silica dispersion-2)
The cationic treating agent was a mixture of 120 g of 20% aqueous solution of diallylmethylamine acetate polymer (weight average molecular weight 20000) and 60 g of 20% aqueous solution of diallyldimethylammonium chloride-sulfur dioxide copolymer (polymerization average molecular weight 5000). Was the same as the aqueous silica dispersion-1 to obtain an aqueous silica dispersion-2 (solid content concentration 12.7% by weight) in the form of a milky white viscous slurry. Table 3 shows the evaluation results of the obtained aqueous silica dispersion.

(Preparation of aqueous silica dispersion-3)
By adding 60 g of denatured ethanol (ethanol 85.5%, methanol 4.9%, n-propanol 9.6%) to the aqueous silica dispersion-2 and mixing with a propeller mixer, a milky white viscous slurry is obtained. An aqueous silica dispersion-3 (solid content concentration 12.3% by weight) was obtained. Table 3 shows the evaluation results of the obtained aqueous silica dispersion.

(Preparation of aqueous silica dispersion-4)
A milky white viscous slurry aqueous solution in the same manner as the aqueous silica dispersion-1 except that the vapor phase method silica was changed to a vapor phase method silica having a specific surface area of 220 m ² / g (“Leosil QS20” manufactured by Tokuyama Corporation). Silica dispersion-4 (solid content concentration 12.5% by weight) was obtained. Table 3 shows the evaluation results of the obtained aqueous silica dispersion.

(Preparation of aqueous silica dispersion-5)
A milky white viscous slurry aqueous solution in the same manner as the aqueous silica dispersion-1 except that the gas phase method silica was changed to gas phase method silica having a specific surface area of 200 m ² / g (“Leosil QS102” manufactured by Tokuyama Corporation). Silica dispersion-5 (solid content concentration 12.5% by weight) was obtained. Table 3 shows the evaluation results of the obtained aqueous silica dispersion.

(Preparation of aqueous silica dispersion-6)
A milky white viscous slurry-like aqueous solution in the same manner as the aqueous silica dispersion-1 except that the vapor phase method silica was changed to a vapor phase method silica having a specific surface area of 140 m ² / g (“Leosil QS10” manufactured by Tokuyama Corporation). Silica dispersion-6 (solid content concentration 12.5% by weight) was obtained. Table 3 shows the evaluation results of the obtained aqueous silica dispersion.

(Preparation of aqueous silica dispersion-7)
A milky white viscous slurry aqueous solution in the same manner as the aqueous silica dispersion-1 except that the gas phase method silica was changed to a gas phase method silica having a specific surface area of 90 m ² / g (“Leosil QS09” manufactured by Tokuyama Corporation). Silica dispersion-7 (solid content concentration 12.5% by weight) was obtained. Table 3 shows the evaluation results of the obtained aqueous silica dispersion.

(Preparation of aqueous silica dispersion-8)
A milky white viscous slurry aqueous silica dispersion-8 (solid content concentration 12% by weight) was obtained in the same manner as the aqueous silica dispersion-1, except that the cationic treating agent was not used. Table 3 shows the evaluation results of the obtained aqueous silica dispersion.

(Preparation of aqueous silica dispersion-9)
An aqueous silica dispersion-9 in the form of a milky white viscous slurry in the same manner as the aqueous silica dispersion-1 except that the cationic treatment agent was changed to 120 g of a 20% aqueous solution of diallylmethylammonium chloride polymer (polymerization average molecular weight 20000). (Solid content concentration 12.5 wt%) was obtained. Table 3 shows the evaluation results of the obtained aqueous silica dispersion.

III. Preparation and Evaluation of Coating Solution A coating solution was prepared by the following method, and the obtained coating solution was evaluated.

[Stability of coating solution viscosity]
The viscosity (a) at 20 ° C. immediately after the preparation of the coating liquid and the viscosity (b) after standing at 20 ° C. for 16 hours are measured, and the viscosity stability according to the following criteria from the ratio (b) / (a) Evaluated.
A: The value of (b) / (a) was less than 2.
B: The value of (b) / (a) was 2 or more and less than 5.
C: The value of (b) / (a) exceeded 5.

[Coating fluid viscosity]
The solution viscosity of the coating solution was measured using a BL type viscometer under the conditions of a rotor rotation speed of 60 rpm, a temperature of 40 ° C., a rotor rotation speed of 60 rpm, and a temperature of 60 ° C.

(Preparation of coating liquid-1)
50 g of an aqueous solution having a solid content concentration of 10% by weight of PVA-1 was prepared, added to 200 g of aqueous silica dispersion-1 (solid content concentration of 12.5% by weight), and well mixed and stirred to obtain a dispersion. Thereafter, distilled water was added to prepare a coating solution having a solid content concentration of 11.6% by weight. Table 4 shows the evaluation results of the coating liquid.

(Preparation of coating liquids 2 to 24 and 27 to 33)
As shown in Table 4 and Table 5, a coating solution was obtained in the same manner as Coating solution-1, except that the type and number of PVA and the type of aqueous silica dispersion were changed. Table 4 shows the evaluation results of the coating liquid.

(Preparation of coating liquids 25 and 26)
A coating solution was obtained in the same manner as coating solution-1, except that the number of parts of PVA was changed and sodium acetate was added to a mixed dispersion of an aqueous solution of PVA and an aqueous silica dispersion. Table 4 shows the evaluation results of the obtained coating solution.

IV. Production and Evaluation of Inkjet Recording Material An inkjet recording material was produced by the following method, and the ink receiving layer was evaluated for cracks, glossiness, and transparency. Further, the ink absorbability when printing on the recording material using an ink jet printer was evaluated.

(1) Cracks The surface of the ink receiving layer was observed with an optical microscope (magnification 100 times), and evaluated according to the following criteria.
5: No cracks were observed on the surface.
4: Cracks were partially generated in an area of less than 30% of the surface.
3: Cracks were partially generated in a region of 30% to less than 50% of the surface.
2: Cracks were partially generated in the region of 50% or more on the surface.
1: Cracks occurred on the entire surface.

(2) Glossiness According to JIS-Z8714 (specular glossiness with an incident angle of 60 degrees), the glossiness of the ink receiving layer surface was measured with a gloss meter (manufactured by Nippon Denshoku Industries Co., Ltd.), and the average of the five measurements. The value was determined.

(3) Transmittance A recording material having an ink receiving layer on a polyethylene terephthalate (hereinafter abbreviated as PET) substrate using a spectrophotometer (“UV2100” manufactured by Shimadzu Corporation) is transmitted at a wavelength of 500 nm. The rate was measured.

(4) Ink Absorption Speed After black ink was solid printed on an inkjet recording material using an inkjet printer (Seiko Epson Corporation “PM3300C”), the print surface was rubbed with a finger at regular intervals, and the degree of blur was observed. The time until no fading occurred was measured and evaluated according to the following criteria.
5: Less than 5 seconds, 4: 5 seconds or more and less than 10 seconds, 3: 10 seconds or more and less than 30 seconds, 2:30 seconds or more and less than 1 minute, 1: 1 minutes or more.

Example 1
On the surface of the PET film that has been subjected to corona treatment, coating solution-1 is applied at 30 ° C. using a Mayer bar so that the coating amount (at the time of drying) is 20 g / m ² . An ink jet recording material was produced by drying at 100 ° C. for 5 minutes. Table 5 shows the evaluation results of the obtained ink jet recording material.

Examples 2 to 26
An ink jet recording material was produced in the same manner as in Example 1 except that the type of coating liquid was changed as shown in Table 5. Table 5 shows the evaluation results of the obtained ink jet recording material.

Comparative Examples 1-7
An ink jet recording material was produced in the same manner as in Example 1 except that the type of coating liquid was changed as shown in Table 5. Table 5 shows the evaluation results of the obtained ink jet recording material. Note that Comparative Examples 5 and 6 could not be applied because they gelled during the preparation of the coating solution.

From Table 1 and Table 2, PVA-1 to 17 had a viscosity ratio η ₁ / η ₂ of 0.8 or more. On the other hand, in PVA-18, the viscosity ratio η ₁ / η ₂ was less than 0.8. Moreover, in PVA117, PVA124, and PVA135H which are unmodified PVA, viscosity ratio (eta) ₁ / (eta) ₂ was less than 0.8.

  From Tables 4 and 5, coating liquids -1 to 26 prepared using PVA-1 to 17 and dispersions -1 to 7 were evaluated as A or B in terms of the stability evaluation of the coating liquid viscosity. . In contrast, PVA-1 and a cationic treating agent prepared using Dispersion-8 that did not use a cationic treating agent-31, a cationic treating agent having only PVA-1 and chlorine ions as counter ions. In the coating liquid-32 prepared using the obtained dispersion-9, the coating liquid gelled during the preparation.

From Table 6, in Examples 1 to 26 using the coating liquids 1 to 26, there is no surface cracking, high glossiness, excellent ink absorption, and ink jet recording having a highly transparent ink receiving layer. A material was obtained. On the other hand, in Comparative Example 1 using PVA 117 having a viscosity ratio η ₁ / η ₂ of less than 0.8 and Coating Solution-27 prepared with Dispersion-1, the film was brittle and did not form a film. Further, in Comparative Examples 2 to 4 using the coating liquids -28 to 30, cracks occur on the entire surface of the obtained ink jet recording material, or cracks partially occur in an area of 50% or more of the surface. did.

Claims (8)

An ink jet recording material obtained by coating a base material with an aqueous dispersion containing a vinyl alcohol polymer (A) and vapor phase silica (B), wherein the vinyl alcohol polymer (A) has a concentration of 8% by weight. When the viscosity of the aqueous solution was measured with a BL type viscometer under the condition that the rotor rotational speed was 60 rpm, the ratio η ₁ / η ₂ of the viscosity η ₁ at a temperature of 60 ° C. and the viscosity η ₂ at a temperature of 40 ° C. was 0. 8 or more, wherein the vapor phase silica (B) is coated with a cationic treating agent having acetate ions as counter ions, and the aqueous dispersion is 100 wt% of the vapor phase silica (B). An ink jet recording material comprising 10 to 100 parts by weight of a vinyl alcohol polymer (A) with respect to parts. The vinyl alcohol polymer (A) is represented by the following general formula (I)

(R ¹ represents an alkyl group having 1 or 2 carbon atoms, R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 100). The ink jet recording material according to claim 1, comprising a monomer unit having:   The content S (mol%) of the monomer unit having a polyoxyalkylene group relative to all the monomer units in the vinyl alcohol polymer (A) is 0.01 to 1 mol%. Inkjet recording material. Viscosity average polymerization degree P of the vinyl alcohol polymer (A), and content S (moles) of monomer units having polyoxyalkylene groups relative to all monomer units in the vinyl alcohol polymer (A) %)), The product P × S satisfies the following formula (1).
5 <P × S <1500 (1) The vinyl alcohol polymer (A) is a monomer unit having a polyoxypropylene group in which R ¹ in the general formula (I) is a methyl group and R ² is an alkyl group having 1 to 4 carbon atoms. An ink jet recording material according to any one of claims 1 to 4. The ink jet recording material according to claim 5, wherein the vinyl alcohol polymer (A) contains a monomer unit having a polyoxypropylene group in which R ² in the general formula (I) is a methyl group. The vinyl alcohol polymer (A) contains a monomer unit having a polyoxypropylene group in which R ¹ in the general formula (I) is a methyl group and R ² is a hydrogen atom. 4. The inkjet recording material according to any one of 4 above. The ink jet recording material according to any one of claims 1 to 7, wherein the gas phase method silica (B) is formed by coating gas phase method silica having a specific surface area of 70 m ² / g or more with a cationic treating agent.