JP2003118224A - Coating liquid and recording sheet using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording sheet having particularly not only high ink absorbability, a high image quality but also excellent durability such as water resistance, coating film strength and pencil writability in the sheet containing an amorphous silica and a binder made of an aqueous resin composition on a support. SOLUTION: The coating liquid which can form an ink acceptive layer comprising the amorphous silica, the aqueous binder and a cationic resin on a support in such a manner that a wet silica (A) manufactured by a precipitating method having a BET specific surface area of 270 to 400 m<2> /g and a mean particle diameter of 2.5 to 10.0 μm as the amorphous silica, the aqueous resin composition (B) and the cationic resin (C) are blended.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating liquid containing a binder composed of amorphous silica and an aqueous resin composition, and a recording sheet produced by using the same, and particularly to high image quality,
It is an object of the present invention to obtain a recording sheet which is excellent in water resistance, coating film strength and writability while at the same time having high ink absorption property and high ink absorption speed.

[0002]

2. Description of the Related Art Ink jet recording systems have been rapidly growing due to their convenience, but the demands for image quality and durability thereof have been extremely high in recent years. Image quality has come to a level desired for photography and high-quality printing, for example, in addition to image density, resolution, surface gloss, and the like, there is a demand for eliminating the graininess of images. On the other hand, regarding the durability of the recording sheet, the durability of the image (water resistance, weather resistance, gas resistance, etc.), the strength of the coating film against physical rubbing, and eventually the pencil writability are required. . As a promising technical method for coping with this, improvement research has been actively conducted by reexamining an old technology (that is, an ink receiving layer in which a porous pigment such as amorphous silica is combined with an aqueous resin as a binder). However, the difficulty of this system is that the image quality and the durability, especially the strength of the coating film tend to contradict each other, and there is a trade-off between the two. For example, Japanese Examined Patent Publication No. 04-052786 has long disclosed that polyvinyl alcohol containing a silanol group is used together with silica to improve both the blurring degree and water resistance of an image in a silica compounding system. The present invention discloses that the silanol-modified polyvinyl alcohol has a saponification degree of 50 to 100 mol% and a number average degree of polymerization of 500 to 3,000. The correlation between range and image characteristics is not specified.

As the times go by, inventions have recently emerged that address the issues of image quality and its durability by specifying silica species. For example, in Japanese Unexamined Patent Publication No. 09-277695, a specific silica having an average particle size of 10 to 15 μm is synthesized as a specific silica that simultaneously solves white spots in a solid print portion of a single color, ink bleeding in a solid print portion of mixed colors, and smoothness of a coating film surface. An invention is disclosed in which amorphous silica is used in combination with silanol-modified polyvinyl alcohol for reinforcing the water resistance of a coating film. This invention also discloses the combined use of silanol-modified polyvinyl alcohol and ordinary polyvinyl alcohol, the number average degree of polymerization of which is 300 to 2,400 and the degree of saponification of which is 80% or more. It is said that the most preferable degree of conversion is 100%. It is considered to prevent the water resistance of the coating film from being lowered when the silanol-modified polyvinyl alcohol is combined with polyvinyl alcohol having a low saponification degree. Japanese Unexamined Patent Publication No. 10-181186 is also the discovery of the effect of the combination of specific silicas. Here, the amorphous silica produced by the sedimentation method and the amorphous silica produced by the gel method are combined, and the large difference in cohesive force between the two causes the former to absorb ink, and the latter to share the coating strength due to cohesive force. It is an invention. Incidentally, here again, silanol-modified polyvinyl alcohol is also used for enhancing the adhesiveness to the support, but at the same time, it has been observed that too many silanol groups deteriorate recording characteristics.

In parallel with the technical direction of the specification of such silica species, silica is usually used, but the development to cope with it by dramatically improving the properties of the binder has been continued. 10-330601 etc., mainly composed of a modified resin obtained by polymerizing a hydrophilic vinyl monomer in an aqueous dispersion in which an aqueous urethane resin and a polyvinyl alcohol having a saponification degree of 75 to 100 mol% and a number average degree of polymerization of 500 to 5000 are mixed. The above-mentioned new binder was technically disclosed as a material excellent in water resistance, image sharpness and transparency of the recording layer. This binder also has a binding ability to porous pigments such as silica, and the present invention also discloses the incorporation of silica and the like. However, in this case, the target is expected to be a general porous pigment compounding effect, and it is not intended to select and use a silica type having a specific function in order to achieve higher quality. Moreover, in order to obtain high-quality images of photo quality, there must be a further breakthrough on the binder side.

Regarding the specification of silica species, Japanese Patent Laid-Open No. 10-
The combined use of the 181186 precipitated silica and the gel method silica is excellent, but according to the study of the present inventors, the image quality improved by the precipitated silica is deteriorated with the combined use of the gel silica. In this direction, compatibility between image quality and its durability cannot be solved satisfactorily, and there is a limit in devising only porous pigments, and in the future full-scale development pigment function and binder It is considered that integration with functions is essential. In particular, considering that an inkjet recording material has to undergo a wet coating process for its production, the stability of the recording material emulsion and the physical properties of the coated film or paper material after coating and drying (surface smoothness) It is a matter of course that the homogeneity of the layer structure, the flatness, etc.) are the prerequisites for industrialization, and the achievement of these prerequisites is predominantly related to the binder properties. A further leap forward is required on the binder design side.

[0006]

The present invention has been made in view of the above circumstances, and the problem to be solved by the present invention is to provide a binder comprising amorphous silica and an aqueous resin composition on a support. With respect to the recording sheet containing a particularly high ink absorbency, in addition to being able to obtain a high image quality, to obtain a recording sheet having excellent durability such as water resistance, coating strength and pencil writability. For example, it is to provide a recording sheet capable of high-speed printing of photo-quality images.

[0007]

The present invention provides a coating solution and a recording sheet including the following aspects. That is, the coating liquid is characterized by forming an ink receiving layer on a support and has a BET specific surface area of 270 to 40.
0 m ² / g and an average particle size of 2.5 to 10.0 μm
Wet silica (A) produced by the precipitation method in the range of
Aqueous resin composition (B) and cationic resin (B) obtained by polymerizing component (d) in an aqueous solution or an aqueous dispersion in which the three components (a), (b) and (c) shown below are mixed. C), the composition ratio of which is 10 to 500 parts by weight of (B) and 1 to 50 parts by weight of (C) based on 100 parts by weight of solid content. Working fluid. (A) Silanol-modified polyvinyl alcohol (b) Number average degree of polymerization is 500 to 5,000, degree of saponification is 8
9 mol% or less of polyvinyl alcohol (c) aqueous urethane resin (d) 100 to 60% by weight of N-vinylpyrrolidone and 0 to 40% by weight of a vinyl monomer which can be used together therewith (2) Monomer used in combination with N-vinylpyrrolidone A recording liquid obtained by coating the support with the coating liquid according to (1) or (2), which contains a radically polymerizable vinyl monomer containing an alkoxysilyl group as a substrate, and drying the coating liquid. Sheet.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Amorphous silica is roughly classified into a dry method and a wet method according to well-known manufacturing methods. The dry method silica is produced by combustion hydrolysis of silicon tetrachloride in a gas phase, and silica. A method is known in which sand and coke are heated and reduced and vaporized by an arc method in an electric furnace to air oxidize them.
The wet process silica can be obtained by generating active silica by acid decomposition of silicate, and then appropriately polymerizing it to cause aggregation / precipitation. Wet method silica is further divided into gel method silica and precipitation method silica which are manufactured by different methods. Gel method silica generally mixes sodium silicate and sulfuric acid to form a silicate sol. The silicic acid sol is gradually polymerized to form primary particles and further to form three-dimensional aggregates and gel. This is obtained by pulverizing to a micron size. On the other hand, the precipitation method silica is temperature, silica concentration, reaction conditions of the gel method silica,
By controlling the time and the like, the growth of the secondary aggregate is stopped and the precipitate is aged and aged. It is obtained by filtering, washing with water, drying, pulverizing and classifying.

In the present invention, the amorphous silica (A) is
Of the various silicas mentioned above, it is an essential requirement to use the precipitated silica among those synthesized by the wet method. Especially, the BET specific surface area is 270 to
400 m ² / g, more preferably 270 to 360
It must be in the range of m ² / g. The specific surface area is 2
When it is less than 70 m ² / g, the ink absorbency of the obtained recording sheet is lowered, and the circularity of ink dots cannot be maintained. In addition, the surface strength of the recording sheet decreases. BET on the contrary
If the specific surface area is larger than 400 m ² / g, the viscosity of the coating solution will be high and good workability cannot be obtained. Incidentally, the pore volume of the precipitated silica is usually 1.0 ml /
g or more, preferably 1.3 ml / g or more.
If the pore volume is less than 0.5 ml / g, the ink absorbency may be insufficient.

Further, the amorphous silica (A) in the present invention
It is also important that the average particle diameter is 2.5 to 10.0 μm. When the average particle diameter is 2.5 μm or less, the viscosity of the dispersion increases when the amorphous silica is dispersed in water or the aqueous resin composition (B) obtained by performing the polymerization reaction described below, In addition to the problem in the process in which it is difficult to sufficiently increase the liquid concentration, it is not possible to expect an effect to solve the graininess that is essential for high image quality, and the image density becomes low, which is not preferable. Further, the surface strength and writability of the obtained receiving layer are reduced. On the other hand, when the average particle diameter exceeds 10.0 μm, the surface of the receiving layer becomes uneven due to the amorphous silica powder, so that the smoothness is impaired and the circularity of the ink dot is also lowered. Is. As described above, by using such a specific silica, it is possible to realize an extremely satisfactory improvement in the characteristics that are important for image quality, that is, the ink absorption amount, the ink absorption speed, the print density, the hue, etc. You can do it.

It is considered that the reason why the precipitated silica is superior is that there is a structural difference when compared with the gel silica, for example, and the gel silica has relatively small dense primary particles and relatively dense secondary particles with large cohesive force. On the other hand, precipitated silica is easy to form relatively gentle secondary particles with large primary particles and small cohesive force, so that a structure with a large pore volume between primary particles can be realized, and therefore a larger ink receiving capacity can be achieved. It is thought that it has sex essentially. On the other hand, however, the precipitated silica gives loose agglomerated particles, resulting in a weak coating film strength due to its cohesive force compared to the gel silica, and the use of this silica poses a problem for practical use. .

In view of the above situation, in the present invention, by developing a binder having a special constitution described in detail below, the contradictory requirements of image quality and coating strength are simultaneously satisfied, and curling hardly occurs. A recording sheet is obtained,
Furthermore, it is possible to provide a coating liquid having excellent redispersibility with respect to the silica pigment, which is related to the stability of the coating.

First, an aqueous resin composition (B) which is a binder for adhering the above-mentioned amorphous silica (A).
The silanol-modified polyvinyl alcohol (a) is required as one of the components constituting the. Since this product has a silanol group as a functional group and has high reactivity with an inorganic substance, it is well known that this product alone is an excellent material as a binder for binding amorphous silica. However, when it is used as one component of the aqueous resin composition (B) as in the present invention, it is possible to maintain a balance not only with the quality relating to the binding force of silica but also with the quality relating to the image described later. .

The silanol-modified polyvinyl alcohol is generally a method in which a silyl group is introduced into polyvinyl alcohol or modified vinyl acetate having a carboxyl group or a hydroxyl group by a post-modification using a silylating agent, a vinyl ester and a silyl group-containing olefinically unsaturated monomer. It is produced by a method of saponifying a copolymer with a polymer or a method of saponifying a polyvinyl ester having a silyl group at a terminal obtained by polymerizing a vinyl ester in the presence of a mercaptan having a silyl group. Among them, the silanol-modified polyvinyl alcohol (a) used in the present invention has a number average degree of polymerization of 300 to 2500, preferably 500 to 1700, and a modification rate of 0.0 as a silyl group-containing monomer unit.
It is 1 to 10 mol%, preferably 0.1 to 2.5 mol%. When the number average degree of polymerization is less than 300, surface strength cannot be obtained with the coating layer obtained thereby. When it exceeds 2,500, the viscosity of the liquid increases, which hinders the polymerization reaction described later and the preparation of the coating liquid, which is unsuitable. Next, if the modification ratio is less than 0.01 mol%, the adhesion with the above-mentioned amorphous silica may be insufficient, and if it exceeds 5 mol%, the solubility in water may deteriorate.

Next, polyvinyl alcohol (b) is required as a component for obtaining the aqueous resin composition (B).
When the present inventors proceeded to study a binder to be combined with the amorphous silica (A), the characteristics relating to the image, particularly the print density, changed depending on the binder, that is, the type of polyvinyl alcohol, despite the same silica. experienced. A closer examination reveals that among ordinary polyvinyl alcohols (hereinafter sometimes abbreviated as “PVA”), so-called partially saponified PVA having a saponification degree of 89 mol% or less is used as a binder for the amorphous silica (A). It was found that the use was better than the one using the silanol-modified polyvinyl alcohol (a) (hereinafter sometimes abbreviated as “silanol PVA”).
However, since the ordinary partially saponified PVA alone does not have the binder strength and the water resistance of the film as much as the silanolized PVA, the present inventors initially thought that they should be used in combination to achieve the balance. That is, in the constituent components of the aqueous resin composition (B), the component that brings out the print density characteristics was assigned to the partially saponified PVA, and the silanol-modified PVA as the component for obtaining the coating film strength. However, this is still inferior to the performance of silanolated PVA alone in terms of coating strength and water resistance of the coating, and the printing density should be further improved. Therefore, it is impossible to exceed all the performances by such simple blending of polymers, and in order to satisfy these, in a polymer matrix in a system to which an aqueous urethane resin (c) which will be described in detail later is further added. It becomes necessary to carry out the reaction (polymerization) of the component (d).

Polyvinyl alcohol is generally obtained by saponifying polyvinyl acetate by an acid saponification method or an alkali saponification method. Among them, polyvinyl alcohol (b) used in the present invention has a number average degree of polymerization of 500 to 50.
00, the saponification degree is 89 mol% or less. If the number average degree of polymerization is lower than 500, the surface strength cannot be obtained with the coating layer obtained by using the silanol-modified PVA as a binder component, and if it exceeds 5,000, the viscosity of the liquid will increase. This is unsuitable because it increases the pH and hinders the polymerization reaction and the preparation of the coating liquid described later. A more preferable range of the number average degree of polymerization is 1000 to 3500.

Further, it is important that the polyvinyl alcohol (b) used in the present invention has a saponification degree of 89 mol% or less. A more preferable range is 75 mol% to 89 mol%. When the saponification degree exceeds 89 mol%, the above-mentioned image-related characteristics, that is, the print density is lowered. Further, the viscosity of the aqueous resin composition (B) thus obtained tends to increase with time, which is not preferable. This tendency becomes more remarkable as the number average degree of polymerization increases. Meanwhile, the degree of saponification is 75%
If it is less than the above range, the surface strength of the aqueous resin composition (B) obtained by carrying out the polymerization reaction described below tends to be poor and the water resistance may be insufficient, which is not preferable.

The aqueous urethane resin (c) is further required as one of the components for obtaining the aqueous resin composition (B). It is a well-known fact that urethane resin has features such as high elasticity and elasticity like rubber, excellent adhesion to base materials, and formation of a film with excellent water resistance. It has been confirmed by the present inventor that the presence of this component in the aqueous resin composition (B) exerts an excellent preventive effect particularly on coatability such as film wrinkles and curls associated with drying shrinkage. In addition to this, the redispersibility of silica cannot be obtained in a system in which the urethane resin component does not exist, and this component has a great influence on the compatibilization in the coating material, and the component is the aqueous resin composition (B). Is one of the important ingredients.

The term "redispersibility" as used herein means that when a coating material containing a pigment such as silica is left for a long period of time, the pigment is precipitated and deposited in the lower layer. This is the state of dispersion when the pigment is made uniform by stirring it again.For example, a coating with good redispersibility can be easily redispersed by dispersing the pigment deposited in the lower layer into the system. It is in the state of being. On the other hand, if the paint is inferior, the pigment may solidify (cake) in the lower layer, and re-stirring may not be easy, or stirring (dispersion) may not be possible at all. By the way, the coating composition of the present invention shows good redispersibility even after one year has passed from the production, and there is no problem in its coatability and the performance of the recording sheet obtained thereby.

The aqueous urethane resin is generally obtained by dissolving or dispersing in water a polyurethane resin synthesized from a polyhydroxyl compound, a diisocyanate, and a low molecular weight chain extender containing at least two hydrogen atoms which reacts with isocyanate. In a known method. A method of emulsifying and dispersing using an emulsifier as a means for dissolving or dispersing in water or a method of introducing an ionic functional group such as a carboxyl group into a urethane resin molecule as a hydrophilic group and dissolving or dispersing the urethane resin using an alkali However, the preferred embodiment used in the present invention is the latter type.

Examples of the polyhydroxyl compound used in the above urethane resin include organic acids such as phthalic acid, adipic acid, dimerized linolenic acid and maleic acid, and glycols such as ethylene glycol, propylene glycol, butylene glycol and diethylene glycol, and trimethylolpropane. , Hexatriol, glycerin, trimethylol ethane, polyester polyol obtained by dehydration condensation reaction with pentaerythritol, polyoxypropylene glycol, polyoxybutylene glycol,
Polytetramethylene glycol, polyoxypropylene triol, sorbitol, pentaerythritol, sucrose, starch, polyether polyols such as polyoxypropylene polyoxyethylene polyols with inorganic acids such as phosphoric acid, acrylic polyols, castor oil Examples include derivatives and other hydroxyl compounds.

As the diisocyanate, for example, 2,
4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-
Phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isilylen diisocyanate, lysine diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, 1,4-cyclohexylene diisocyanate,
4,4-dicyclohexylmethane diisocyanate,
3,3'-dimethyl 4,4'-biphenylene diisocyanate, 3,3'-dimethoxy 4,4'-biphenylene diisocyanate, 3,3'-dichloro 4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1 , 5-tetrahydronaphthalene diisocyanate and the like.

Examples of the chain extender include ethylene glycol, 1,4 butanediol, trimethylolpropane, triisopropanolamine, N, N-bis (2-
Hydroxypropyl) aniline, hydroquinone-bis (β-hydroxyethyl) ether, resorcinol-
Bis (β-hydroxyethyl) ether and other polyols, ethylenediamine, propylenediamine, hexamethylenediamine, phenylenediamine, tolylenediamine, diphenyldiamine, diaminodiphenylmethane,
Examples are polyamines such as diaminodicyclohexylmethane, piperazine, isophoronediamine, diethylenetriamine, dipropylenetriamine, hydrazines and water.

The method of introducing the anionic group for dissolving or dispersing the polyurethane resin in water includes a method of introducing an anionic hydrophilic group into the polymer chain using a chain extender such as diaminophenylcarboxylic acid salt, or an isocyanate group. A method of introducing a carbamoyl sulfonate group as a strong hydrophilic group by reacting a blocking agent such as sodium bisulfite, a tertiary amine after sulfonation of an aromatic ring of a polyurethane prepolymer obtained from a hydrophobic polyol and an aromatic isocyanate. The method of introducing an anionic group by neutralizing with a medium such as water and introducing an anionic group, by making a prepolymer from diol and diisocyanate and reacting with an acid having a hydroxyl group, and then neutralizing with an amine such as triethylamine Examples thereof include a method of introducing a group.

In order to form the aqueous resin composition (B), an aqueous solution or an aqueous dispersion obtained by mixing the three components of the silanol-modified polyvinyl alcohol (a), polyvinyl alcohol (b) and aqueous urethane resin (c). It is necessary to polymerize N-vinylpyrrolidone or a vinyl monomer that can be used together with N-vinylpyrrolidone. As the component (d), N-vinylpyrrolidone may be used alone, but other vinyl monomers may be used in combination. Other monomers that can be used in combination include vinyl acetate, vinyl propionate and other vinyl esters, vinyl chloride, vinyl bromide and other vinyl halides, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, methacrylic acid. Examples include unsaturated carboxylic acid esters such as butyl, olefins such as ethylene, propylene, styrene, and butadiene, and olefin compounds. Among them, a preferred embodiment used in the present invention is to use a vinyl monomer having an alkoxysilyl group in combination with N-vinylpyrrolidone. And polymerize. Specific examples of the monomer include dimethylvinylmethoxysilane, vinyltrichlorosilane, vinyltris (βmethoxyethoxy) silane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyl. Dimethoxysilane etc. can be raised. Thereby, water resistance and coating film strength can be further improved at the same time. The reason for this is considered to be cross-linking with an alkoxysilyl group and reaction with silica.

The inventors of the present invention are required to further improve the printing density of the binder obtained by the blend of the silanol-modified polyvinyl alcohol (a) and the polyvinyl alcohol (b) described above and the improvement of coating strength and insufficient water resistance of the coating. As a result of various investigations, regarding improvement of print density,
It has been found that it is effective to add polyvinylpyrrolidone to the three-component system of silanol-modified polyvinyl alcohol (a), polyvinyl alcohol (b), and aqueous urethane resin (c). Polyvinylpyrrolidone is generally prepared from acetylene and formaldehyde by the Reppe reaction.
An N-vinylpyrrolidone monomer was synthesized through 4-butanediol and γ-butyrolactone and polymerized. It is well known that this product forms a complex with an electron-donating substance such as tannin, flavonoid, and dye, and for example, a color transfer inhibitor by forming a complex with a dye released in laundry detergent for clothing, It is often used for controlling the decoloring and dyeing speed of dyes from textiles. Also in this study, when polyvinyl pyrrolidone of the same high molecular weight is simply added to the polymer in which the above three components are mixed, it is not clear whether the dye in the ink is well adsorbed, but it certainly contributes to the improvement of the print density. Admitted. However, although the above-mentioned advantages are obtained, since the product itself is a polymer having extremely high hydrophilicity, the formed film has a remarkable decrease in water resistance, and the system containing the amorphous silica (A) added thereto. However, the disadvantage that the coating film strength was lowered was revealed.

Therefore, the inventors of the present invention described above (a) and (b).
An attempt was made to polymerize N-vinylpyrrolidone or a combination thereof with a vinyl monomer having an alkoxysilyl group in the presence of an aqueous solution or an aqueous dispersion in which the three components of (c) were mixed. Then, it was found that the above-mentioned various phenomena such as poor water resistance and reduction in coating film strength were improved. Although the reason for this is not clearly understood, by polymerizing the component (d) in the three components (a), (b), and (c), the dispersed particle size of the component (d) polymer becomes small and the compatibilizer is formed. , And with the help of this, the three components are alloyed by compatibilization and have an affinity with the silica possessed by the component (a),
(B) and (d) component high print density action, (c)
I think that the effects of the components' adhesion to substrates and water resistance may have been synergistically exhibited. It may be said that the physical strength properties, which cannot be obtained by a film formed by simply blending polymers, are exhibited by polymerizing in a polymer matrix, which is a kind of microcomposite.

The silanol-modified polyvinyl alcohol (a), polyvinyl alcohol (b), aqueous urethane resin (c), N-vinylpyrrolidone and vinyl monomer (d) which can be used in combination with the silanol-modified polyvinyl alcohol (a) in the aqueous resin composition (B) of the present invention.
The proportion of the solid content is 100 to 200 parts by weight of the polyvinyl alcohol (b) and 3 to 100 parts by weight of the aqueous urethane resin (c) with respect to 100 parts by weight of the silanol-modified polyvinyl alcohol (a), and N-vinyl. The pyrrolidone and vinyl monomer (d) which can be used together with the pyrrolidone are 10 to 10
It is 100 parts by weight.

If the amount of polyvinyl alcohol (b) is 100 parts by weight or less, the above-mentioned characteristic relating to the image, that is, the printing density is lowered, and if it exceeds 200 parts by weight, the coating strength becomes insufficient. When the amount of the water-based urethane resin is 3 parts by weight or less, it is impossible to obtain the effect of preventing the coating property such as the above-mentioned wrinkles of the film and curl due to drying shrinkage, and the compatibilization of the system in the coating, and the amount exceeds 100 parts by weight. And the coating film strength and the sharpness of the image are adversely affected. Further, N-vinylpyrrolidone and vinyl monomer (d) which can be used in combination therewith are 10
If the amount is less than 100 parts by weight, the print density will decrease, and if it exceeds 100 parts by weight, insufficient coating film strength and poor water resistance will occur.

On the other hand, the proportion of N-vinylpyrrolidone and other vinyl monomers which can be used in combination is also important, and is 0 to 40% by weight with respect to 100 to 60% by weight of N-vinylpyrrolidone. When N-vinylpyrrolidone is 60% by weight or less, the above-mentioned decrease in print density is observed, which is not preferable. Further, the amount of the vinyl monomer containing an alkoxysilyl group used is 0.1 to 10 in all monomers.
% By weight. Below this, the effects of the above-mentioned crosslinking and reaction with silica will not be exhibited, and if it exceeds 10% by weight, a stable polymer such as gelation during polymerization cannot be obtained.

As a polymerization method for obtaining the aqueous resin composition (B), a conventionally known method can be used. For example, (1) N-vinylpyrrolidone alone or in combination therewith in an aqueous solution or aqueous dispersion in which three components of silanol-modified polyvinyl alcohol (a), polyvinyl alcohol (b), and aqueous urethane resin (c) are mixed (2) A silanol modification of (2) a pre-emulsified aqueous urethane resin (c) and N-vinylpyrrolidone (or a mixture of N-vinylpyrrolidone (or another vinyl monomer which can be used together)). Examples thereof include a method of adding the polyvinyl alcohol (a) and the polyvinyl alcohol (b) to an aqueous solution in which the polyvinyl alcohol is mixed, and polymerizing. The above N-vinylpyrrolidone (or a mixture with other vinyl monomer which can be used together with it) or a pre-emulsion may be charged at once and polymerized,
A part may be charged and the rest may be dropped to polymerize. Also,
In the polymerization, emulsion polymerization can be carried out using a small amount of an emulsifying dispersant, if necessary. Examples of the emulsifier include anionic surfactants (sodium dodecylbenzene sulfonate, sodium alkyl diphenyl ether disulfonate, sodium alkyl naphthalene sulfonate, sodium lauryl sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, dialkyl). Sodium sulfosuccinate, etc.) and nonionic surfactants (eg, polyoxyethylene lauryl ether, polyoxyethylene oleyl phenyl ether, polyoxyethylene nonyl phenyl ether, etc.) can be used.

The polymerization can be carried out using a polymerization initiator. As the polymerization initiator, general polymerization initiators such as water-soluble peroxides such as potassium persulfate, ammonium persulfate and hydrogen peroxide solution, or oil-soluble peroxides such as benzoyl peroxide and t-butyl hydroperoxide, Alternatively, azo compounds such as azobisisobutyronitrile can be used, but hydrogen peroxide solution and azo compounds are particularly preferable as the polymerization initiator of N-vinylpyrrolidone, and for example, 2,2′-azobis (2- Methyl butanamide oxime) dihydrochloride tetrahydrate, 1,1′-azobis (1-acetoxy-1phenylethane), 2,2′-azobis (2-amidinopropane) hydrochloride,
2,2'-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate, poly [polyoxyethylene 4,4'azobis (4-cyanopentanoate)], dimethyl 2,2 '-Azobis (2-methylpropionate) and the like are mentioned. Further, a chain transfer agent, for example, alcohols such as catechol, thiols, mercaptan and the like may be used to adjust the molecular weight of the polymer. The polymerization temperature and the polymerization time are, for example, 40 to 100 ° C., preferably 50 ° C. to 90 ° C., and more preferably 60 to 85 ° C., depending on the type of the polymerization initiator. The polymerization time is, for example, 1 to 24 hours, preferably 2 to 12 hours, and more preferably 3 to 8 hours.

In the present invention, a cationic resin (C) is required in addition to the amorphous silica (A) and the aqueous resin composition (B) described in detail above. This is because the addition of the cationic resin (C) can further improve the water resistance after printing, that is, the ink fixability, and prevent the migration of the ink in a high humidity atmosphere.

Examples of the cationic resin for this purpose include a polymer of a monomer having a quaternary ammonium salt group in its side chain or a copolymer of this and another polymerizable monomer. Examples of the monomer having a quaternary ammonium salt group include quaternary compounds of aminoalkyl acrylates and aminoalkyl methacrylates, such as dimethylaminoethyl methacrylate methyl chloride and quaternary dimethylsulfate, and dimethylaminopropyl (meth) acrylamide chloride. Examples include monomers having a quaternized ammonium group such as methyl, dimethylsulfate, benzyl chloride, monochloroacetic acid and the like, quaternary acrylamido-3-methylbutyldimethylamine, vinylbenzylammonium salt, diallyldimethylammonium salt and the like. To be As other cationic resins, conventionally known cationic resins such as polyallylamine, polyethyleneimine, polyamine sulfone, polyamine polyamide epichlorohydrin, cationic polystyrene copolymer and cationized starch can be used.

In determining the compounding ratio of the above-mentioned components of the amorphous silica (A), the aqueous resin composition (B) and the cationic resin (C) in the coating liquid of the present invention, the print density, ink absorbency, It was set as follows in consideration of granular feeling, water resistance, ink fixability, coating film strength, writing property, curl property, and redispersibility. That is, the aqueous resin composition (B) has a solid content of 10 parts by weight based on 100 parts by weight of the amorphous silica (A).
˜500 parts by weight, preferably 30 to 300 parts by weight. When the content of the aqueous resin composition (B) is less than 10 parts by weight, the ink absorbability is excellent, but the coating strength and writability cannot be obtained. On the other hand, if it exceeds 500 parts by weight, the ink absorbency and the graininess are deteriorated. The cationic resin (C) is added in an amount of 1 to 50 parts by weight in terms of solid content with respect to 100 parts by weight of the amorphous silica (A). If it is 1 part by weight or less, it is difficult to obtain the above-mentioned ink fixing effect and migration resistance, and if it is added in an amount of 50 parts by weight or more, it tends to cause a decrease in ink absorption of the receiving layer, yellowing with time, and a decrease in water resistance of the receiving layer itself.

Other components to be added to the ink receiving layer of the present invention include melamine resins, isocyanate compounds, epoxy compounds, carbodiimide, oxazoline, glyoxal and other crosslinking agents, and alumina, talc, kaolin clay, if necessary. , Inorganic fillers such as calcium carbonate, mica, polymethyl acrylate, polystyrene, polyacrylonitrile, urea, nylon, urea formalin resin, etc., titanium, chromium, tin inorganic pigments and organic Pigments, film-forming aids, thickeners,
Dispersant, penetrant, leveling agent, antiblocking agent,
Conventionally known additives such as antistatic agents, ultraviolet absorbers, amines as light stabilizers, antioxidants, defoaming agents and fluorescent whitening agents can be added.

As the support for producing the ink jet recording sheet of the present invention, for example, resin-based films or molded products of polyester, polyethylene, polypropylene, vinyl chloride, polycarbonate, nylon, polystyrene, cellophane, triacetate, etc., synthetic papers. And so on. Further, papers such as high-quality papers, medium-quality papers, coated papers, art papers and the like, cloths and non-woven fabrics such as woven fabrics and knitted fabrics, metal, glass plates, wood, ceramics, pottery and the like molded products are also possible. Further, in the present invention, in order to improve the adhesion between the support and the ink receiving layer, the surface of the support may be previously subjected to anchor coat treatment or corona discharge treatment.

The coating composition for the ink receiving layer of the present invention is usually applied on a support as water or a dispersion liquid containing water as a main component to form an ink receiving layer. As a coating device, for example, a roll coater, a reverse roll coater, a gravure coater, a bar coater, a knife coater, a curtain coater, a die slot coater, a blade coater or the like is used to coat and dry one side or both sides of the support. The thickness of the coating layer is preferably in the range of 2 to 80 μm. In the case of cloth or non-woven fabric, it can be processed by dipping treatment.

Examples of the printing ink to be printed on the present inkjet recording sheet include dye type and pigment type inks. Examples of the dye type ink include those obtained by dissolving a water-soluble dye such as a direct dye, an acid dye, a reactive dye or a basic dye in a mixed solvent of water and an organic solvent. Examples of the pigment type ink include those in which various known organic pigments such as azo, phthalocyanine, indigo, and anthraquinone are dispersed in water with a dispersant.

Next, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, part and% in an example represent a weight part and weight%.

Production of Aqueous Resin Composition (B) The aqueous resin compositions (B) of Production Examples 1 to 4 and Comparative Production Examples 5 to 11 were produced with the compositions shown in Table 1.

(Production of Production Examples 1 to 4) In a reaction vessel equipped with a cooling tube, a silanol-modified polyvinyl alcohol (a) aqueous solution, a polyvinyl alcohol (b) aqueous solution, an aqueous urethane resin (c), water and water were dissolved in advance. A water-soluble azo initiator (trade name: V-50, manufactured by Wako Pure Chemical Industries, Ltd.) was charged according to the composition shown in Table 1, and nitrogen gas was blown therein for 20 minutes to perform deoxidation. Then, after introducing N-vinylpyrrolidone alone or a mixture of N-vinylpyrrolidone and other vinyl monomers which can be used together with N-vinylpyrrolidone into the system, 70-
The temperature was raised to 80 ° C. and maintained at the same temperature for 4 hours, then cooled to 30 ° C. or lower to terminate the polymerization.

(Preparation of Comparative Production Examples 5 to 8) Silanol-modified polyvinyl alcohol (a) aqueous solution, polyvinyl alcohol (b) aqueous solution, aqueous urethane resin (c), polyvinylpyrrolidone aqueous solution, and water were used according to the compositions shown in Table 1. It was obtained by simple blending and the above reaction operation was not performed.

(Comparative Production Examples 9 to 11)
4) was prepared by the same operation. However, as shown in Table 1, Comparative Production Example 9 is a composition in which the silanol-modified polyvinyl alcohol (a) and polyvinyl alcohol (b) are not present, and Comparative Production Example 10 is a composition in which the aqueous urethane resin (c) is not present. Comparative Production Example 11 uses N- as the monomer.
It was replaced with another monomer other than vinylpyrrolidone.

[0045]

[Table 1]

(Example 1) Specific surface area 3 produced by sedimentation method
Amorphous silica (trade name: Fineseal X45, manufactured by Tokuyama) having a particle size of 00 m ² / g and an average aggregate particle size of 4.3 μm 100
Part, Production Example 1 (solid content 12%) 42 of the aqueous resin (B) 42
0 parts, 18 parts of polydiallyldimethylammonium chloride-based cation resin (C) (trade name: PAS-H5L, manufactured by Nitto Boseki, solid content 28%) were added, and after adding water, an ink receiving layer having a concentration of 16% A coating liquid for use was prepared. Thickness 1
An anchor treatment agent (trade name: PESRESIN A-513E, manufactured by Takamatsu Yushi Co., Ltd., 25% aqueous dispersion) as an easy-adhesion layer on a 00 μm polyester film (trade name: Melinex D534, manufactured by DuPont) has a film thickness after drying. It was applied to have a thickness of 1 μm and dried at 120 ° C. for 1 minute. The above-mentioned coating liquid for the ink receiving layer was applied thereon so that the film thickness after drying was about 40 μm, and dried at 120 ° C. for 3 minutes to obtain an inkjet recording sheet. (Example 2) An inkjet recording sheet was obtained in the same manner as in Example 1 except that the production method 2 was used instead of the aqueous resin (B). (Example 3) An ink jet recording sheet was obtained in the same manner as in Example 1 except that Production Example 3 was used instead of the aqueous resin (B). (Example 4) An inkjet recording sheet was obtained in the same manner as in Example 1 except that the production method 4 was used instead of the aqueous resin (B). (Example 5) Specific surface area 305 m ² / produced by the sedimentation method
g, amorphous silica with an average aggregate particle size of 5.9 μm (trade name:
An ink jet recording sheet was obtained in the same manner as in Example 1 except that 100 parts of Fineseal X60, manufactured by Tokuyama Corporation) and 200 parts of Production Example 1 (solid content 12%) of the aqueous resin (B) were used. (Example 6) Specific surface area 305 m ² / g produced by the sedimentation method,
To 100 parts of amorphous silica (trade name: Fineseal X60, manufactured by Tokuyama) having an average aggregate particle size of 5.9 μm, 3800 parts of Production Example 1 (solid content 12%) of the aqueous resin (B), polydiallyldimethylammonium chloride An inkjet recording sheet was obtained in the same manner as in Example 1 except that 150 parts of a cationic resin (C) (trade name: PAS-H5L, manufactured by Nitto Boseki, solid content 28%) was added. (Comparative Example 1) As amorphous silica, an amorphous silica pigment (trade name: Carplex BS-304N, manufactured by gel method) having a specific surface area of 400 m ² / g and an average aggregate particle size of 9 μm.
An inkjet recording sheet was obtained in the same manner as in Example 1 except that Shionogi (manufactured by Shionogi) was used. (Comparative Example 2) An amorphous silica pigment (trade name: Mizukasil P-526, manufactured by Mizusawa Chemical Industry Co., Ltd.) having a specific surface area of 140 m ² / g and an average aggregate particle diameter of 3 μm manufactured by a precipitation method was used as amorphous silica. An inkjet recording sheet was obtained in the same manner as in Example 1 except for the above. (Comparative Example 3) An ink jet recording sheet was obtained in the same manner as in Example 1 except that Comparative Production Example 5 was used instead of the aqueous resin (B). (Comparative Example 4) An inkjet recording sheet was obtained in the same manner as in Example 1 except that Comparative Production Example 6 was used instead of the aqueous resin (B). (Comparative Example 5) An inkjet recording sheet was obtained in the same manner as in Example 1 except that Comparative Production Example 7 was used instead of the aqueous resin (B). (Comparative Example 6) An inkjet recording sheet was obtained in the same manner as in Example 1 except that Comparative Production Example 8 was used instead of the aqueous resin (B). (Comparative Example 7) An inkjet recording sheet was obtained in the same manner as in Example 1 except that Comparative Production Example 9 was used instead of the aqueous resin (B). (Comparative Example 8) An ink jet recording sheet was obtained in the same manner as in Example 1 except that Production Example 10 was used instead of the aqueous resin (B). (Comparative Example 9) An ink jet recording sheet was obtained in the same manner as in Example 1, except that the water-based resin (B) was changed to Production Example 11. (Comparative Example 10) Amorphous silica was changed to 600 in Example 1.
An ink jet recording sheet was obtained in the same manner as in Example 1 except that some parts were used. (Comparative Example 11) In Example 1, the aqueous resin (B) was added to 45
An inkjet recording sheet was obtained in the same manner as in Example 1 except that 100 parts was used. (Comparative Example 12) An ink jet recording sheet was obtained in the same manner as in Example 1 except that the coating liquid containing no cationic resin (C) was used. (Comparative Example 13) An inkjet recording sheet was obtained in the same manner as in Example 6 except that 200 parts of the cationic resin (C) was added.

[Evaluation of Performance of Recording Sheet] The following evaluation tests were conducted on the recording sheets prepared in Examples and Comparative Examples,
The results are shown in Table 2, respectively. (1) Print Density Using Epson inkjet printer PM-770C, solid printing of each color of cyan, magenta, yellow, black, green (mixed color), red (mixed color) and navy blue (mixed color) is performed, and the color tone and density are visually inspected. The evaluation was made by the following three-stage evaluation. A: The print density is extremely high and the image is also very clear. ◯: The print density is high and the image is clear. B: The print density is low and the image is not clear. (2) Ink absorbency The pattern of green (mixed color) -red (mixed color) -green (mixed color) is solidly printed using an ink jet printer PM-770C manufactured by Epson Corporation, and the degree of ink bleeding at the boundary is visually observed as follows. It was judged in 3 stages and evaluated as ink absorbency. ◯: Ink is almost free from bleeding. B: The ink is slightly bleeding. X: Ink is bleeding remarkably. (3) Sample image of a person image taken with a digital camera with a granularity of 2 million pixels (1600 × 1200 dots full color JP
EG file) for Canon inkjet printer B
When printed with JF-850, the skin portion of the face of the sample image was visually observed and its quality was judged in the following two stages. ◯: Even when the sample images are approached, the printed particles (dots) are not visible or are hardly noticeable. B: When the sample images are viewed closely, the printed particles (dots) feel a little rough, but when they are separated a little, it is almost unnoticeable. (4) The state of the receiving layer when the water-resistant recording sheet was immersed in water for 1 day was evaluated by the following three-stage evaluation. ○: No change. Δ: Some elution of the receiving layer was observed. X: Elution of the receiving layer was remarkably observed. (5) Ink fixability The sample printed in the section of (1) Printing density above (1) is left to dry for 1 day and then immersed in running water for 1 minute. It was judged by the evaluation. ○: Almost no change was seen. Δ: Elution of ink is slightly observed. X: Elution of ink is remarkably observed. (6) Stick cellophane tape on the surface of the film strength recording sheet 180 °
The amount of silica adhering to the cellophane tape after it was quickly peeled off in the direction was visually observed and judged by the following three-stage evaluation. ◯: Almost no adhesion of silica is observed, but it is slight. Δ: A level at which silica adhesion is slightly seen. X: A large amount of silica adhered, which was a problem in practical use. (7) The writing quality when handwritten on a writable recording sheet with a pencil of hardness H was evaluated by the following three-stage evaluation. ○: Easy to write. △: It is a little difficult to write, but there is no practical problem. X: It is difficult to write and poor in writing, and there is a problem in practical use. (8) A curl recording sheet was cut into a size of 150 mm × 150 mm, and this was cut in an environment of a temperature of 20 ° C. and a humidity of 30% RH for 24 hours.
The curl state after standing for a period of time was visually evaluated and evaluated according to the following two stages. O: A level where there is some curl but practically no problem. C: Curling is at a level at which remarkably practical problems occur. (9) The paint redispersible coating liquid was placed in a 200 cc glass bottle and tightly stoppered, and the temperature was adjusted to 50
The silica was allowed to settle by allowing it to stand for 20 days in a warm storage at 0 ° C. Insert a glass rod into this and visually check whether the silica deposited in the lower layer is easily redispersed when re-stirred.
Evaluation was made at the stage. ◯: Silica is easily redispersed by stirring with a glass rod. B: Some silica lumps remained at the bottom of the bottle when stirred with a glass rod, but completely dispersed when sufficiently stirred. ×: When stirring with a glass rod, silica is deposited as a solid mass and stirring is difficult. (10) Moisture-resistant storage property When the sample printed in the above (3) Granularity is left to dry in a room for 1 day, and then stored in a thermostat at a temperature of 30 ° C. and a humidity of 80% RH for one week, The state of the image of the sample was observed. ○: Almost no change. Δ: The image looks slightly blurred. X: The image looks remarkably blurred.

[0048]

[Table 2]

As is clear from Table 2, Examples 1 to 6 which are ink jet recording sheets of the present invention showed good performance in all evaluation items. On the other hand, Comparative Example 1
-13 had some defects.

[0050]

INDUSTRIAL APPLICABILITY As described above, the ink jet recording sheets obtained in the examples of the present invention have high image quality and high ink absorbency, and at the same time, are excellent in water resistance, coating strength and writability. there were.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09D 175/04 D21H 19/56 D21H 19/56 19/64 19/64 B41J 3/04 101Y F term (reference) ) 2C056 EA04 EA13 FC06 2H086 BA01 BA15 BA19 BA33 BA35 BA37 BA45 BA48 4J038 CE022 CK031 HA446 MA08 MA10 4L055 AG18 AG39 AG64 AG65 AG85 AG89 AH02 AH37 AH50 AJ04 BE08 EA16 EA17 EA32 FA11 FA13 FA19 GA09

Claims (3)

[Claims] 1. A coating liquid for forming an ink receiving layer on a support, which has a BET specific surface area of 270.
˜400 m ² / g and an average particle size of 2.5-10.
Wet silica (A) produced by the precipitation method in the range of 0 μm and the following three components (a), (b) and (c) are mixed in an aqueous solution or an aqueous dispersion to give the component (d): It is composed of an aqueous resin composition (B) obtained by polymerization and a cationic resin (C), and the composition ratio thereof is 10 to 50 for (B) relative to 100 parts by weight of solid content (A).
0 parts by weight, 1 to 50 parts by weight of (C), a coating liquid. (A) Silanol-modified polyvinyl alcohol (b) Number average degree of polymerization is 500 to 5,000, degree of saponification is 8
9 mol% or less of polyvinyl alcohol (c) aqueous urethane resin (d) 100 to 60% by weight of N-vinylpyrrolidone and 0 to 40% by weight of a vinyl monomer which can be used together therewith 2. The coating liquid according to claim 1, which contains a radical-polymerizable vinyl monomer having an alkoxysilyl group as a monomer used in combination with N-vinylpyrrolidone. 3. A recording sheet obtained by coating the coating liquid according to claim 1 or 2 on a support and drying. [0001]