JPH11348416A - Ink jet recording sheet and manufacture of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording sheet, excellent in the distinctness of quality of printed picture, ink absorbing property, resistance to water in a printed part, smoothness as well as luster, and the manufacturing method of the same. SOLUTION: A transparent porous layer is provided on a paper substrate while the transparent porous layer is provided with cracks, having the width of 5-30 μm and the length of 30-200 μm, on the surface of the same in the rate of 30-500 pieces/1 mm<2> . The sheet is obtained by a method wherein transparent porous layer coating solution is applied on the paper substrate, then, the moisture content of the coating solution layer is conditioned so as to be 30-50 wt.% and, thereafter, is heated and pressed against a specular roll to effect the finishing treatment of strong luster.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording sheet suitable for recording by an ink jet printer (hereinafter, appropriately referred to as an ink jet recording sheet) and a method for producing the same.

[0002]

2. Description of the Related Art Recording by an ink jet printer is as follows.
Since it is capable of high-speed recording, has no noise, is excellent in operability and maintainability, and is easy to be multicolored, it is widely used. As the ink jet recording sheet, high-quality paper devised to be rich in ink absorbency, coated paper having an ink receiving layer containing a porous pigment on the surface, or the like is applied. However, the porosity is high, or the ink receiving layer having a large porosity, although rich in ink receptivity, due to scattering of light on the layer surface, reduction in light transmittance, etc.
Light does not easily reach the ink that has permeated into the voids, the image tends to be whitish, and the vividness of the hue and the color density tend to decrease. Furthermore, since such an ink receiving layer has a porous surface, it is difficult to desire high gloss.

On the other hand, to impart high gloss to paper is
Appropriate in appearance, for example, as a method for imparting gloss to the paper surface, a method of providing a resin layer on the surface, or smoothing and increasing the gloss of the coating layer surface by passing paper between rolls that are pressed and heated Methods and the like are known. Provide a resin layer on the surface,
There are recording papers, films, and the like that absorb ink by swelling and dissolving. Such a resin-coated product, although glossy, can be absorbed and dried slowly, causing stains and bleeding due to ink transfer. In addition, if pigment coated paper is
When calendering is performed at high pressure, the gloss improves, but the voids in the coating layer decrease, the absorption of the ink slows down, and the drying delays. It is not preferable for a sheet. For this reason, the calendering process must select the conditions within the range of the allowable ink absorption capacity, and at present, it has not been achieved to simultaneously obtain the ink absorption and the gloss.

[0004] Other papers having a high surface gloss include the following.
By applying a coating solution containing a plate-like pigment to the base paper, pressing it on the mirror-surface drum surface heated in a wet state, and drying it,
A so-called cast-coated paper obtained by copying the mirror surface is known. For example, US Pat.
The conventional cast-coated paper disclosed in No. 6 obtains high gloss by forming a film-forming substance such as a binder in the pigment composition constituting the coating layer by copying the mirror surface drum surface of the cast coater. ing. When this cast-coated paper is used for ink jet recording paper, there is a problem that the presence of the film-forming substance reduces the porosity of the coating layer and extremely reduces ink absorption during recording. In order to improve the ink absorbency, it is conceivable to make the cast coat layer porous so as to improve the ink receptivity, but in order to provide a large number of voids, it is necessary to reduce the amount of the film-forming substance. . However, a decrease in the film-forming substance causes a decrease in film-forming properties and a decrease in gloss, and furthermore, scattering of incident light due to a porous surface and a decrease in image density may occur. As described above, it has been difficult to simultaneously satisfy both the surface gloss of cast-coated paper and the suitability for inkjet recording. As an improvement of cast coated paper having excellent appearance and gloss, see, for example, JP-A-61-209189.
Japanese Patent Application Laid-Open No. 2-274587 discloses a method of casting after treating with an aqueous solution containing a cationic polyelectrolyte to improve ink absorption, and Japanese Patent Application Laid-Open No. 2-274587. A cast finishing method after treatment with an aqueous solution containing a molecular electrolyte is disclosed in Japanese Patent Application Laid-Open No. 7-89220, which has an ethylenically unsaturated bond on a base paper provided with an undercoat layer mainly composed of a pigment and an adhesive. Methods using a coating liquid containing a copolymer resin having a glass transition point of 40 ° C. or higher obtained by polymerizing a monomer as a main component have been proposed. However, with the recent expansion of applications such as high-speed inkjet recording, higher definition of recorded images, and full-color printing, the inkjet recording sheet obtained by the above proposal is insufficient in recording adequacy, sharpness of hue, and the like.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and in particular, to have excellent clarity of printing image quality, good ink absorbency, good water resistance and smoothness of a printing portion, and An object of the present invention is to provide an ink jet recording sheet having excellent gloss. It is a further object of the present invention to provide a method for producing an ink jet recording sheet having excellent ink absorbency, water resistance of a printed portion, smoothness and gloss, and excellent workability.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have obtained an ink jet recording sheet which can achieve the above object by adjusting the physical properties of the surface of a transparent resin layer provided on a paper substrate. That is, the present inventors have found a suitable manufacturing method for obtaining the surface properties, and have completed the present invention.

That is, the ink jet recording sheet according to the first aspect of the present invention has a transparent porous layer on a paper substrate, and the surface of the transparent porous layer has a width of 5 to 30 μm and a length of 3 μm.
The crack 0~200μm characterized by having 30 to 500 pieces / 1 mm ^2. In addition, the inkjet recording sheet according to claim 2 of the present invention, after applying a transparent porous layer coating solution on a paper substrate, pressed against a heated mirror-finished roll,
It is characterized by a high gloss finish. here,
The transparent porous layer preferably contains inorganic fine particles and a water-soluble resin, the porosity is 40 to 80%, and the pore diameter of the porous layer is preferably 0.005 to 0.030 μm in median diameter. It is an aspect.

Further, according to a method of manufacturing an ink jet recording sheet according to claim 6 of the present invention, a coating liquid for a transparent porous layer containing a water-soluble resin and inorganic fine particles is coated on a paper substrate, and thereafter, After the heat treatment is performed to adjust the water content to 30 to 50%, a gelling agent solution is applied, and a high gloss finish treatment is performed by pressing against a heated mirror-finished roll. In this production method, the pH of the transparent layer coating solution is further adjusted.
Is preferably adjusted to 8 to 10 with ammonia.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The ink jet recording sheet of the present invention comprises a paper substrate and a transparent porous layer formed on the paper substrate, and has a crack having a width of 5 to 30 μm and a length of 30 to 200 μm on the surface of the transparent porous layer. It is characterized in that it is formed up to 500 pieces / 1 mm ² .

The substrate used in the present invention is not particularly limited. In addition to paper substrates such as acidic paper or neutral paper used for general coated paper, synthetic paper, air-permeable film, etc. may be used. Among them, a paper substrate is preferable. As the paper substrate in the present invention, LBKP, NBKP, LBS
Chemical pulp such as P, NBSP, GP, PGW, RMP,
Mechanical pulp such as TMP, CTMP, CMP, CGP, D
For wood pulp such as waste paper pulp such as IP, various conventionally known sizing agents, fillers, fixing agents, retention enhancers, paper strength enhancers, cationizing agents, whiteness improvers, bluing agents, defoaming agents, etc. Additives are appropriately compounded and mixed, fourdrinier,
Base paper manufactured by various apparatuses such as a round paper machine and a twin-wire paper machine, and further, paper having a size press with starch, polyvinyl alcohol gelatin, or an anchor coat layer on the base paper; Coated paper such as art paper, coated paper, cast-coated paper, and barrier paper further provided with a coat layer thereon is also included.

Such a base paper and a coated paper may be provided with a coating layer such as a transparent porous layer according to the present invention as they are, or a machine calendar, T
A calendar device such as a G calendar or a soft calendar may be used. The higher the smoothness of the paper base material before providing the coating layer according to the present invention, the better the flatness after the cast finish, and the Beck smoothness of the paper base material is desirably 80 seconds or more, preferably 120 seconds or more. Is more preferable. Also,
The air permeability is desirably 120 seconds or less, desirably 90 seconds or less from the viewpoint of drying properties, dirt, and operability on the cast drum. The basis weight of the paper substrate is usually 40 to 300 g /
While those of m ² are generally used, it is not particularly limited, may be selected according to the purpose.

The air permeability or air permeability of the paper substrate is necessary for transferring steam generated when the coating layer is cast to the back surface and drying the coating layer. Base paper is generally used because it is an important factor that determines the mold releasability of the resin. However, synthetic resins such as polyethylene, polypropylene, polyester, rayon, and polyurethane can be used as long as they have air permeability or air permeability. A nonwoven sheet or synthetic paper formed into a sheet after fibrillation may be used. The transparent porous layer provided on the paper substrate contains inorganic fine particles and a water-soluble resin. In the present invention, the term "transparent" means that the transparent porous layer has a haze value of 30 when applied on a transparent film.
% Or less, and preferably has a haze value of 20% or less.

Examples of the water-soluble resin include resins having a dissociable group such as a hydrophilic structural unit or a carboxyl group. Examples of the water-soluble resin include resins having a hydroxyl group as a hydrophilic structural unit, such as polyvinyl alcohol (PVA) and cellulose. Resin (methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HE)
C), carboxymethylcellulose (CMC), chitins and starch; polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PE) which are resins having an ether bond.
G) and polyvinyl ether (PVE); and polyacrylamide (PAAM) and polyvinylpyrrolidone (PV), which are resins having an amide group or an amide bond.
P). Also, polyacrylates having a carboxyl group as a dissociable group, maleic acid resins, alginates and gelatins; polystyrene sulfonates having a sulfone group, amino groups, imino groups,
Mention may be made of polyallylamine (PAA) with amines and quaternary ammonium salts, polyethyleneimine (PEI), epoxidized polyamide (EPAm), polyvinylpyridine and gelatins.

The inorganic fine particles include, for example, silica fine particles, colloidal silica, calcium silicate, zeolite,
Examples include kaolinite, halloysite, muscovite, talc, calcium carbonate, calcium sulfate, boehmite, pseudo-boehmite and the like. From the viewpoint of not lowering the transparency, those having a refractive index in the range of 1.40 to 1.60 are preferable. Among these, silica fine particles are preferred. The average primary particle diameter of the inorganic fine particles is 30 n from the viewpoint of transparency.
m or less is common, preferably 15 nm or less, particularly preferably about 3 to 10 nm. Further, the refractive index is preferably around 1.45.

The silica fine particles are liable to adhere to each other due to hydrogen bonding due to silanol groups on the surface. Further, when the average primary particle diameter is 10 nm or less, a structure having a particularly high porosity can be formed, so that the ink absorption is high. It is effective for improving characteristics. Silica fine particles that can be used are roughly classified into a wet method and a dry method according to the production method. In the wet method, the mainstream is a method in which active silica is generated by acid decomposition of a silicate, which is appropriately polymerized, coagulated and sedimented to obtain hydrous silica. On the other hand, dry silica is a method by high-temperature gas-phase hydrolysis of silicon halide (flame hydrolysis method), a method in which silica sand and coke are heated and reduced by an arc in an electric furnace and oxidized with air ( The method of obtaining anhydrous silica by the arc method is the mainstream. These hydrated silica and anhydrous silica have different properties in terms of the density of silanol groups on the surface, the presence or absence of vacancies, etc., and exhibit different properties, respectively. In the case of silicic anhydride (anhydrous silica), three-dimensional porosity is particularly high. It is known to form structures and is preferred for use in the present invention. The reason for this is not clear, but in the case of hydrous silica, the density of silanol groups on the surface is as large as 5 to 8 particles / nm ² and the particles are likely to be densely aggregated. 3 / n
It is presumed that a coarse soft agglomerate is easily formed and the structure has a high porosity because it is as small as m ² .

In the case of using preferred silica fine particles as the inorganic fine particles, for example, the type of resin to be combined with the silica fine particles is important from the viewpoint of the transparency of the porous layer. In the case of anhydrous silica, the water-soluble resin is used. It is preferable to use polyvinyl alcohol (PVA), and particularly, polyvinyl alcohol having a low saponification degree, specifically, a saponification degree of 70 to 90% is suitable in terms of light transmittance. P
VA has a hydroxyl group in the structural unit, and the hydroxyl group and a silanol group on the surface of the silica fine particles form a hydrogen bond,
It is considered that a three-dimensional network structure in which secondary particles of silica fine particles are used as a chain unit is easily formed, whereby a color material receiving layer having a structure with a high porosity can be obtained. The porous layer having a three-dimensional network structure rapidly absorbs ink by capillary action in ink jet recording, and enables not only fine recording without ink bleeding and ink accumulation, but also coloring material in thermal recording, Then, the toner in the electrophotographic recording can be firmly bonded. That is, the coloring material and the toner penetrate into the pores of the porous layer, and a shape anchor effect caused by the three-dimensional network structure occurs, whereby the coloring material and the like are firmly fixed. Further, since the ratio of the inorganic fine particles constituting the transparent layer is large, the heat resistance is high and the emboss resistance is high.

The ratio of the inorganic fine particles (preferably silica fine particles) to the water-soluble resin (PB ratio: the weight of the inorganic particles with respect to the weight of the water-soluble resin of 1) has a great influence on the film structure of the ink receiving layer. As the PB ratio increases, the porosity, pore volume, and surface area (per unit weight) increase. If the PB ratio exceeds 10, there is no effect on the film strength, and the film strength decreases because the number of cracks on the surface of the cast finish increases, while if it is less than 1.5, the voids are easily closed by the resin,
The porosity is reduced, the surface cracks are reduced, and the ink absorption performance is reduced. Since the cracks formed on the surface of the cast transparent porous layer vary depending on the PB ratio and the coating amount, the width of the cracks is 5 to 30 μm and the length is 30 to 200 μm.
μm, and such cracks are 30 to 500 mm in 1 mm ² .
The PB ratio is preferably adjusted to a range of 1.5 to 10 for the above-described reason.
It is preferably in the range of 5 to 5. Since the shape of the cracks formed on the surface from the structure of the recording paper is originally indefinite and is not composed of simple lines, it naturally includes many branches and crossovers. The "length of a crack" in the present invention has to be expressed including the length between branched or crossed portions. Therefore, the term "crack length" here means, in other words, a linear crack. In the case of (1), the length is indicated, and in the case of a branched or crossed crack, the length from the branched or crossed portion is indicated.

If the coating amount of the transparent porous layer is less than 10 g / m ² , the ink receiving amount is insufficient, so that beading occurs and the ink drying property deteriorates. Even if the coating amount exceeds 30 g / m ² , the printing performance and the ink drying property are not significantly affected, the operability is deteriorated, and only the cost is increased. Therefore, the coating amount of the transparent layer is preferably in the range of 10 to 30 g / m ² .

The transparent porous layer of the present invention is obtained by applying a coating solution containing inorganic fine particles and a water-soluble resin onto a paper substrate, and thereafter,
This layer is obtained by pressing against a heated mirror-finished roll and applying a high gloss finish. For example, anhydrous silica having an average primary particle diameter of 10 nm or less and a water-soluble resin having a PB ratio of 2
When the coating liquid of the transparent porous layer completely dispersed in the aqueous solution is applied to the coating solution at ~ 5 and pressed and pressed against a heated mirror-finished roll to dry and gloss the surface, the structure in the porous layer is silica fine particles. A three-dimensional network structure having the secondary particles as a chain unit is formed, a porous layer having an average pore size of 30 nm or less and a porosity of 50% or more is formed. Cracks are formed, which contribute to the ink absorption of the surface without significantly affecting the appearance and serve to introduce the ink into the voids inside the porous layer.

The porosity of the transparent porous layer thus formed is preferably 40 to 80%, and the pore diameter of the transparent porous layer is 0.005 to 0.030 μm in median diameter.
m is preferable. Here, the porosity and the median pore diameter can be determined by applying a coating solution of a transparent porous layer on a transparent film and measuring the mercury porosimeter (trade name: Pore Sizer 932).
0-PC2, manufactured by Shimadzu Corporation).

Next, the method for producing the ink jet recording sheet of the present invention will be described. The method for producing an ink jet recording sheet according to the present invention includes a step of applying a transparent porous layer coating solution containing a water-soluble resin and inorganic fine particles on a paper substrate, and a step of coating the paper substrate coated with the transparent porous layer coating solution. A step of heating to adjust the water content to 30 to 50%, a step of applying a gelling agent, and pressing the surface of the paper substrate coated with the water-adjusted transparent porous layer coating solution on the paper substrate onto a heated mirror roll to increase the strength. There is a step of performing a gloss finishing treatment.

The coating liquid for forming a transparent porous layer used here is prepared by a conventional method. For example, a predetermined amount of silica fine particles having an average primary particle diameter of 3 to 10 nm in water, for example,
After adding 10 to 15% by weight and using a high-speed rotating wet colloid mill to disperse for 10 to 30 minutes under a high-speed rotation condition of, for example, about 5,000 to 20,000 rpm, an aqueous polyvinyl alcohol solution is reduced to about １ ／ of the silica fine particles. It can be obtained by dispersing under the same conditions as described above in addition to the weight of PVA. The coating solution thus obtained is a uniform sol, which is applied on a paper substrate by the following coating method. Here, at the time of preparing the coating liquid for the transparent porous layer, the pH of the solution is controlled from the viewpoint that the hydrogen bonding property between the silica fine particles and the water-soluble resin is controlled under suitable conditions and the stability of the coating liquid can be maintained. It is preferable to adjust to 8 to 10. However, if the alkali agent used at this time remains in the coating liquid layer, it may adversely affect the subsequent gelling step. Therefore, as the alkaline agent used for adjusting the pH, it is preferable to use ammonia which is easily removed from the coating layer in the drying step of the coating solution.

The coating liquid for the transparent porous layer may further contain a water retention agent, a thickener, an antifoaming agent, a foam inhibitor, a release agent, a coloring agent, if desired.
Known additives such as a water-proofing agent, a wetting agent, a fluorescent whitening agent, an ultraviolet absorber, a writability improving agent, an antistatic agent, and a mordant can be added within a range that does not impair the effects of the present invention. These additions may be made during the preparation of the coating solution.

The application of the coating liquid for the transparent porous layer thus obtained can be performed by a known method, for example, an extrusion die coater, an air doctor coater, or the like.
Bread coater, rod coater, knife coater,
It can be performed using a squeeze coater, a reverse roll coater, a bar coater or the like.

After the application of the coating liquid for the transparent porous layer, drying is performed until the water content of the coating layer becomes 30 to 50%, preferably 35 to 45%. If dried until the water content becomes less than 30%, there is a risk that a desirable gloss may not be obtained in appearance even if the subsequent high glossing treatment is performed. Since the coating liquid flows and the uniformity of the transparent porous layer is reduced, none of them is preferable. Drying can be performed by a known method, and drying may be performed while measuring the amount of water with a contact type or non-contact type moisture meter, etc. Alternatively, the residence time (sheet transport condition) in the drying zone may be determined, and the drying process may be performed continuously under the same conditions. The drying conditions vary depending on the amount of the coating solution applied, but are usually performed at 40 to 100 ° C. 3 moisture
The transparent porous layer coating liquid portion adjusted to 0 to 50% and in a plastic state (hereinafter, appropriately referred to as a coating liquid layer) is then pressed and dried on a heated mirror-surface drum to perform a high gloss treatment. However, in the present invention, in order to improve the strength and characteristics of the transparent porous layer, it is preferable to provide a step of applying a gelling agent liquid to the coating liquid layer.

The gelling agent liquid may be applied to the surface of the coating liquid layer by a method such as dip coating or spray coating, or may be applied by other known coating methods.
For example, a curtain flow coater, an extrusion die coater, an air doctor coater, a bread coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, a bar coater and the like can be mentioned, but an extrusion die coater, a curtain flow coater, a bar It is preferable to use a method in which the coater does not directly contact the coating layer using a coater or the like. The applied gelling agent liquid permeates into the coating layer, reacts quickly with the water-soluble resin in the coating layer, and polymerizes (hardens) the water-soluble resin, thereby immediately increasing the film strength of the coating layer. Greatly improve.

The gelling agent solution is associated with the water-soluble resin used.
Selected, for example, in combination with polyvinyl alcohol
The cross-linking reaction occurs quickly when used together.
For example, a boron compound may be used. As a boron compound
Represents boric acid, borate (eg, orthoborate, InBO)_Three, S
cBO_Three, YBO_Three, LaBO_Three, Mg_Three(B
O_Three) _Two, Co_Three(BO_Three), Diborate (eg, Mg_TwoB
_TwoO_Five, Co_TwoB_TwoO_Five), Metaborate (eg, LiBO)
_Two, Ca (BO_Two)_Two, NaBO_Two, KBO_Two), Four bo
Acid salts (eg, Na_TwoB_FourO₇, 10H_TwoO), pentaborate
(Eg, KB_FiveO₈・ 4H_TwoO, Ca_TwoB₆O₁₁, 7H_Two
O, CsB_FiveO_Five) And the like.

When a boron compound is used as a gelling agent,
Further, the addition of a cationic substance such as a cationic polymer, cationic polymer fine particles, cationic inorganic particles, and a cationic silane coupling agent to the gelling agent solution from the viewpoint of improving the water resistance and vividness of the image. preferable.
Here, as the cationic substance, an amide group, an imide group, a primary amino group, a secondary amino group, a tertiary amino group,
It refers to a compound having at least one kind of cationic group selected from primary ammonium base, secondary ammonium base, tertiary ammonium base, and quaternary ammonium base, and examples thereof include polyvinylbenzyltrimethylammonium chloride and polydiallyldimethylammonium. Chloride, polymethacryloyloxyethyl-β-hydroxyethyldimethylammonium chloride, polydimethylaminoethyl methacrylate hydrochloride, polyamide-polyamine resin, cationized starch, dicyandiamide formalin condensate, dimethyl-2-hydroxypropylammonium salt polymer and the like. be able to. These compounds preferably have a molecular weight of about 1,000 to 20,000, and if the molecular weight is less than 1,000, the effect of improving water resistance is insufficient, and if the molecular weight exceeds 20,000, the viscosity is high and the handling properties are deteriorated, and neither is preferred. .

The cationic polymer fine particles are preferably crosslinked polymer fine particles having an average particle diameter of 200 nm or less, and usually contain at least one monomer selected from the group consisting of alkyl acrylates, alkyl methacrylates, styrene and styrene derivatives, It can be obtained by emulsion polymerization using an emulsifier having one or more (preferably two or more) carbon-carbon double bonds in the molecule. As such polymer fine particles,
The microgel described in JP-A-5-254251 can be suitably used. As examples of the alkyl acrylate and the alkyl methacrylate, alkyl (meth) acrylates having 1 to 18 carbon atoms in the alkyl are preferable, and for example, (meth) alkyl
Methyl acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, 2- (meth) acrylate Examples include ethylhexyl and stearyl (meth) acrylate. Examples of styrene and styrene derivatives include styrene, α-methylstyrene and vinyltoluene.

In addition to the above monomers, monomers copolymerizable with the above monomers may be used in an amount of 50% by weight or less based on the total amount of the monomers. For example, anionic vinyl monomers of acrylic acid, methacrylic acid, maleic anhydride, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid; dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate and quaternary ammonium Cationic vinyl monomers such as vinyl monomers having salts; and (meth) acrylic acid 2-
Examples include nonionic vinyl monomers such as hydroxyethyl, 2-hydroxypropyl (meth) acrylate and (meth) acryloyloxyphosphate.

In addition to the above monomers, a crosslinkable vinyl monomer may be used in an amount of 5% by weight or less of the total amount of monomers. For example, bifunctional monomers such as ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, hexamethylenebis (meth) acrylamide, and divinylbenzene; 1,3,5-triacryloylhexahydro-S-triazine And trifunctional monomers such as triallyl isocyanurate; tetramethylolmethanetetraacrylate and N, N, N ',
Examples include tetrafunctional monomers such as N'-tetraallyl-1,4-diaminobutane. Examples of the emulsifier having one or two or more carbon-carbon double bonds (hereinafter, appropriately referred to as double bonds) in the above molecule include (meth) allyl group and 1-propenyl group as the double bonds. , 2-methyl-1-propenyl group, vinyl group, isopropenyl group and (meth) acryloyl group. Among these, a (meth) acryloyl group is preferred.

The emulsifier has a hydrophobic group and a cationic group for exhibiting an emulsifying action. The cationic group is preferable because the function of retaining the ink is large, and the water resistance of the colorant receiving layer is improved. As the cationic group, those having the following structure are preferable.

-N (R ¹ ) (R ² ) (R ³ )

In the formula, R ¹ , R ² and R ³ each independently represent a hydrogen atom, an alkyl group or a hydroxyalkyl group, and at least one of R ^{1 to} R ³ is an alkyl group or a hydroxyalkyl group. The emulsifier generally plays a role of an emulsifier and a role of a polymerizable (crosslinkable) monomer, and thus the above-mentioned cationic group is present on the surface of the obtained crosslinked polymer fine particles. Of course, the cationic group may be present inside the polymer fine particles.

Examples of the emulsifier include a sulfosuccinate salt of a polyoxyethylene alkyl ether having two or more double bonds in a molecule, and a polyoxyethylene alkyl ether having two or more double bonds in a molecule. A sulfate salt, a sulfosuccinate salt of a polyoxyethylene alkylphenyl ether having two or more double bonds in a molecule, a sulfate salt of a polyoxyethylene alkylphenyl ether having two or more double bonds in a molecule, Acidic phosphoric acid (meth) acrylate dispersants, phosphates of oligoester (meth) acrylate or alkali salts thereof, and oligoester poly (meth) acrylates of polyalkylene glycol derivatives having a hydrophilic alkylene oxide group are exemplified. be able to. These emulsifiers are KAYAMER P
M-2 (Nippon Kayaku Co., Ltd.), New Frontier A-
229E (Daiichi Kogyo Seiyaku Co., Ltd.) and New Frontier N-250Z (Daiichi Kogyo Seiyaku Co., Ltd.).

When an emulsifier having two or more carbon-carbon double bonds in the molecule is used, one emulsifier having one double bond in the molecule is used.
The emulsifier may be contained in a proportion of 60% by weight or less of the total emulsifier. Further, the emulsifier having one or two or more double bonds in the molecule is a normal anionic emulsifier,
It may contain a cationic emulsifier and a nonionic emulsifier. The amount of the emulsifier having one or more carbon-carbon double bonds in the molecule is usually 1 to 20 parts by weight, preferably 3 to 10 parts by weight, based on 100 parts by weight of the total amount of the monomers. .

The crosslinked polymer fine particles of the present invention can be obtained by a known emulsion polymerization method using the above materials. As the cationic inorganic fine particles, an average particle size of 0.1.
Ultrafine zinc oxide, ultrafine barium sulfate, zirconium oxide, alumina sol, colloidal silica and the like having a particle diameter of 1 μm or less are preferred. As the cationic silane coupling agent, a compound having a quaternary ammonium salt and a di- or trialkoxysilanyl group is preferable.
Examples of preferred silane coupling agents include (1) 3
-(Trimethoxysilyl) propyldimethyloctadecyl ammonium chloride, (2) N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane, (3) 3- (trimethoxysilyl) propyldimethylhydroxyethyl Examples thereof include ammonium chloride and (4) a silane coupling agent having an imidazole group. These chemical formulas are shown below.

[0038]

Embedded image

The silane coupling agent is cured by converting a plurality of alkoxysilanyl groups into silanol groups in the presence of water (possible with moisture in the air), and the silane coupling agents are combined (preferably by heating). This is performed by forming a crosslinked structure by bonding by a condensation reaction between silanol groups.

When these cationic substances are added to the coating liquid for the transparent porous layer, they may interact with the anionic charges on the surface of the inorganic fine particles such as silica to cause agglomeration. However, they are contained in the coating liquid for the crosslinking agent. In such a case, there is no problem, and an effective amount can be added to improve the film quality of the transparent porous layer. The amount of the cationic substance added is 0.0
1 to 3.6 g / m ² , preferably 0.05 to
More preferably, it is about 2 g / m ² .

Other gelling agents include glyoxal, melamine / formaldehyde (eg, methylol melamine, alkylated methylol melamine), methylol urea, resole resin, polyisocyanate and the like. The gelling agent solution is prepared by dissolving the gelling agent in water and / or an organic solvent. The concentration of the gelling agent solution is preferably 0.05 to 10% by weight, particularly 0.1% by weight.
~ 7% by weight. Water is generally used as a solvent for the gelling agent liquid. As the organic solvent, those in which each material is dissolved may be used. Examples thereof include alcohols such as methanol and isopropyl alcohol; ketones such as methyl ethyl ketone; esters such as ethyl acetate; aromatic solvents such as toluene; ethers such as tetrahydrofuran; Examples thereof include halogenated solvents such as dichloromethane. The coating amount of the gelling agent liquid is preferably about ² to 40 g / m ² .

As described above, the coating liquid for the transparent porous layer applied on the paper substrate is adjusted in water content by drying, and if desired, a gelling agent liquid is applied thereto. It is pressed against the mirror-surface drum to be used, released from the mold, and subjected to high gloss processing. Mirror drum (cast drum)
Since the surface of the recording sheet is transferred as it is to form the surface of the transparent porous layer of the recording sheet, it is necessary that the surface be completely mirror-finished, but the hardness, corrosion resistance, chemical resistance,
From the viewpoint of abrasion resistance, it is preferable to apply a thick chrome plating, heat treatment, and surface polishing to finish the plating surface with a thickness of 80 to 100 μm. The temperature of the mirror drum at the time of pressing the sheet is preferably about 80 to 120 ° C. If the temperature exceeds 120 ° C., the coating liquid may boil on the surface and the coating layer may be broken, so that gloss may not be produced.

The pressure contact is performed by an elastic nip roll or the like, and the pressure is preferably about 30 to 150 kg / cm ² . The transparent porous layer to which the amount of water is adjusted and the gelling agent liquid is applied is heated by a mirror drum to remove water to about 3.5%, and the surface of the mirror roll is transferred to a highly smooth surface. And a transparent porous layer having excellent gloss is formed. In the case of overdrying with a water content of about 3.5%, curling becomes a problem during subsequent handling. Therefore, immediately before pressing with a cast drum, water is applied to the base paper surface, or after releasing from the cast drum, It is preferable to apply water to the paper surface or to humidify both surfaces with steam.

During the drying and pressing, many fine cracks are formed on the surface of the transparent porous layer. These cracks are extremely narrow and short cracks. Unlike amorphous pores caused by irregularities of fine particles or voids formed between inorganic fine particles, light scattering on a strongly glossy surface formed by a water-soluble resin hardly occurs, and the effect on surface gloss is extremely small.

According to the conditions of the production method of the present invention, the surface of the transparent porous layer has a width of 5 to 30 μm and a length of 30 to 200 μm.
The m crack 30 to 500 pieces / 1 mm ² to the occurrence, the width of the crack 30 [mu] m, and reduced surface gloss when the length exceeds 200 [mu] m, width 5 [mu] m, is less than the length 30 [mu] m,
Either of them is not preferred because the ink receptivity decreases.
Regarding the number of cracks, if the number is less than 30/1 mm ² , the ink receptivity decreases, and if the number of cracks exceeds 500 / mm ² , the appearance and the surface gloss are deteriorated.

[0046]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. Unless otherwise specified, “parts” means “parts by weight” and “%” means “% by weight”.

(Example 1) [Preparation of paper substrate] A wood pulp composed of 100 parts of LBKP was beaten to a Canadian freeness of 300 ml with a double disc refiner, and 0.5 parts of epoxidized behenamide and 1.0 part of anionic polyacrylamide were used. ,
0.1 parts of polyamide polyamine epichlorohydrin and 0.5 parts of cationic polyacrylamide were added at an absolute dry weight ratio to pulp, and the basis weight was 1 by a fourdrinier paper machine.
A base paper of 50 g / m ² was formed and polyvinyl alcohol was added to a fluorescent whitening agent (Sumitomo Chemical Industries, trade name: Whitex B).
B) was added at 0.04%, the surface was sized at 0.5 g / m ^{2 in} absolute dry weight, and the density was adjusted to 0.9, the Beck smoothness was 100 seconds, and the air permeability was adjusted to 81 seconds by calendering. A substrate was obtained.

[Preparation of Coating Solution for Transparent Porous Layer] 12 parts of anhydrous silica fine particles (Aerosil 300, manufactured by Nippon Aerosil) having an average primary particle diameter of 7 nm was added to 88 parts of water, and a high-speed rotating colloid mill (M Technic Co., Ltd.) was added. Cleamics)
After dispersing for 20 minutes under the conditions of 10,000 rotations using 1N, 1N aqueous ammonia was added to 82.5 parts of the silica dispersion liquid.
3 parts, 41.3 parts of 9% polyvinyl alcohol (PVA-420, Kuraray) having a saponification degree of 82% and a polymerization degree of 2,000 were further added, and further 10000 using the same high-speed rotating colloid mill as described above. The dispersion was performed for 20 minutes under the condition of rotation to obtain a coating liquid for a transparent porous layer of 10.7%. (Ratio of silica fine particles / polyvinyl alcohol: 3.5 / 1)

[Preparation of gelling solution] 98.8 of water was added to 1 part of the shelf sand.
Part and surfactant (F-14 manufactured by Dainippon Ink and Chemicals, Incorporated)
4D) 0.2 parts was added and stirred to obtain a gelled liquid. [Preparation of coated paper] 187 g / m ^{2 of the} coating liquid for the transparent porous layer was applied to the paper substrate using a three-reverse coater,
It was dried with an arch dryer at 0 ° C. so that the wet moisture content became 40%. After applying the gelling solution at 20 g / m ² , it was pressed against a cast drum at 110 ° C. and dried to obtain an ink jet recording sheet. .

Example 2 Anhydrous silica fine particles having an average primary particle diameter of 12 nm (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) instead of anhydrous silica fine particles having an average primary particle diameter of 7 nm
An ink jet recording sheet was obtained in the same manner as in Example 1 except for using.

Example 3 Anhydrous silica fine particles having an average primary particle diameter of 16 nm (Aerosil 130, manufactured by Nippon Aerosil Co., Ltd.) instead of anhydrous silica fine particles having an average primary particle diameter of 7 nm
An ink jet recording sheet was obtained in the same manner as in Example 1 except that

Example 4 Example 1 except that the ratio of silica fine particles / polyvinyl alcohol was adjusted to 2.5 / 1.
An ink jet recording sheet was obtained in the same manner as described above. (Example 5) An ink jet recording sheet was obtained in the same manner as in Example 1 except that the coating liquid for the transparent porous layer was applied at 112 g / m ² (coating amount after drying was 12 g / m ² ).

(Example 6) In addition to the shelf sand,
Further, 1.4% of diallyldimethylammonium chloride / sulfur dioxide copolymer is used as a cationic polymer.
An ink jet recording sheet was obtained in the same manner as in Example 1 except that the addition was performed. (Example 7) Mist Pearl C-1 manufactured by Arakawa Chemical Co., Ltd. was added as a cationic emulsion in addition to the shelf sand to the gelling agent liquid.
An ink jet recording sheet was obtained in the same manner as in Example 1 except that 1.0% was added.

(Example 8) In addition to the shelf sand,
Further, an ink jet recording sheet was obtained in the same manner as in Example 1, except that 1.0% of Nissan Chemical Snowtex AK was added as cationic inorganic particles. (Example 9) POL manufactured by Shin-Etsu Chemical Co., Ltd. was added as a cationic silane coupling agent to a gelling agent solution in addition to shelf sand.
An ink jet recording sheet was obtained in the same manner as in Example 1 except that 1.0% of ON-MF-50 was added.

Comparative Example 1 An ink jet recording sheet was obtained in the same manner as in Example 1 except that the ratio of silica particles / polyvinyl alcohol was adjusted to 1.5 / 1. Comparative Example 2 An ink jet recording sheet was obtained in the same manner as in Example 1 except that the ratio of silica particles / polyvinyl alcohol was adjusted to 7.5 / 1.

Comparative Example 3 The coating liquid for the transparent layer was 187 g /
m ^{2 was} applied and dried by an arch dryer at 80 ° C. so that the wet moisture content became 25%, and an ink jet recording sheet was obtained in the same manner as in Example 1. (Comparative Example 4) 187 g / m ^{2 of the} coating solution for a transparent layer was applied,
An ink jet recording sheet was obtained in the same manner as in Example 1 except that drying was performed with an arch dryer at 40 ° C. so that the wet moisture content became 63%.

(Evaluation of Inkjet Recording Sheet) The inkjet recording sheet obtained above was evaluated for its inkjet recording suitability by the following measuring method. (1) Haze haze meter (HGM-DP; manufactured by Suga Test Instruments Co., Ltd.)
Was used to measure the parallel light transmittance, and the haze was measured. The haze was obtained by forming a colorant receiving layer on a 100 μm-thick polyethylene terephthalate film instead of the paper substrate used as a support in each of Examples and Comparative Examples in order to facilitate the measurement. The measurement was performed using a recording sheet.

(2) Porosity, pore median diameter Mercury porosimeter (trade name: Pore Sizer 9320-
PC2, manufactured by Shimadzu Corporation). In addition, in order to facilitate the measurement, the measurement was performed on a recording sheet treated in the same manner as the haze measurement. (3) Gloss The gloss of each recording sheet was measured in accordance with the method described in JIS-P-8142 (test method for 60-degree specular gloss of paper and paperboard).

(4) Ink absorption speed Y was applied to the recording sheet by an ink jet printer (trade name: PM-700C, manufactured by Seiko Epson Corporation).
(Yellow), M (magenta), C (cyan), K (black), B
Solid printing was performed with the inks of (blue), G (green) and R (red), and immediately thereafter (approximately 10 seconds later), the paper was contact-pressed, and the presence or absence of transfer of the ink to the paper was determined according to the following criteria. .

：: No ink was transferred to the paper at all. Δ: Part of the ink was transferred to paper. X: Many inks were transferred to paper.

(5) Crack The ink image receiving layer was magnified 50 times with a scanning electron microscope, and the length from the portion where the crack was branched was 40 to 200 μm.
Numbers having a width of 5 to 30 μm in a 1 mm ² chamber were counted. (6) Water resistance The same printing pattern was formed on the recording sheet using the same printer as the measurement of the ink absorption rate, and after leaving for 3 hours,
Immerse in water for one minute, visually observe the flow of ink,
It was determined according to the following criteria.

：: Dye did not flow at all △: Dye flowed as a whole and color density decreased X: Dye flowed almost completely

(7) Vividness of Image Inkjet printer PM-7 manufactured by Seiko Epson
At 00C yellow, magenta, cyan, black, blue, red,
Green and a person were printed, and the vividness of the image was visually determined according to the following criteria.

：: Very vivid. Δ: Slightly vivid. ×: lacks vividness.

(8) Beck smoothness Measured according to the method described in JIS P8119. (9) Appearance The appearance of the surface of the transparent porous layer formed on the paper substrate was visually judged according to the following criteria.

：: There is no gloss unevenness or coating unevenness in appearance. Δ: Some unevenness in gloss and uneven application in appearance. ×: The gloss unevenness and the coating unevenness are conspicuous in appearance.

Table 1 to Table 3 show the evaluation results of the above items.
Shown in

[0068]

[Table 1]

[0069]

[Table 2]

[0070]

[Table 3]

As is clear from the results of Tables 1 to 3,
The inkjet recording sheet of the present invention was found to be excellent in the clarity of the image quality of printing, and excellent in all of ink absorbency, water resistance of a printed area, smoothness, and gloss.

[0072]

As described above, the ink jet recording sheet of the present invention was excellent in the clarity of the image quality of printing, the ink absorbency, the water resistance and smoothness of the printed area, and the gloss. Further, according to the method for producing an ink jet recording sheet of the present invention, an ink jet recording sheet having excellent ink absorbency, water resistance of a printed portion, smoothness and gloss can be produced with good workability.

Claims (8)

[Claims] A transparent porous layer is provided on a paper substrate, and the surface of the transparent porous layer has a width of 5 to 30 μm and a length of 30 to 200 μm.
ink-jet recording sheet, wherein the crack having 30-500 pieces / 1 mm ² of the [mu] m. 2. An ink jet recording sheet, which is obtained by applying a coating liquid for a transparent porous layer on a paper substrate and then pressing it against a heated mirror-finished roll to perform a high-gloss finishing treatment. 3. The ink jet recording sheet according to claim 1, wherein the transparent porous layer contains inorganic fine particles and a water-soluble resin. 4. The porosity of the transparent porous layer is 40 to 80.
%.
Item 6. An ink jet recording sheet according to item 1. 5. The ink-jet recording sheet according to claim 1, wherein the pore diameter of the transparent porous layer is 0.005 to 0.030 μm in median diameter. 6. A coating liquid for a transparent porous layer containing a water-soluble resin and inorganic fine particles is coated on a paper substrate, and then heated to adjust the water content to 30 to 50%. A method for producing an ink jet recording sheet, comprising applying a liquid, and pressing against a heated mirror-finished roll to perform a high gloss finish. 7. The method according to claim 6, wherein the gelling agent solution contains a cationic substance. 8. The method according to claim 6, further comprising the step of adjusting the pH of the coating liquid for the transparent porous layer to 8 to 10 with ammonia.