JP2002337447A - Ink jet recording cast-coated paper and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording cast-coated paper, which is excellent in the gloss of a white part, a surface strength and an ink jet recordability, and its manufacturing method. SOLUTION: In the ink jet recording paper having a sheet-like base material and an outer ink jet recording layer made of a pigment and an adhesive and at least one inside ink jet absorbing layer made of the pigment and the adhesive on the surface thereof, the pigment of the recording layer and of the absorbing layer adjacent thereto has an average primary particle diameter of 3 to 40 nm and an average secondary particle diameter of 10 to 500 nm, the adhesive of the absorbing layer includes a silanol-modified polyvinyl alcohol. In addition, the cast-coated paper has the surface strength measured by JIS K 6854-2 of 0.15 kN/m or more and the surface pH (measured by JAPAN TAPPI No.6-75) of 5.5 to 7.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cast coated paper for ink jet recording, and more particularly to a cast coated paper for ink jet recording which is excellent in glossiness and surface strength of a blank portion and excellent in ink jet recording and a method for producing the same.

[0002]

2. Description of the Related Art Recording by an ink jet printer is as follows.
It is used in various fields because of low noise, high-speed recording, and easy multicoloring. As the ink jet recording paper, high quality paper devised to be rich in ink absorbency, coated paper having a surface coated with a porous pigment, or the like is applied. By the way, since all of these papers are mainly ink jet recording papers having a low surface gloss, so-called matte tone, there is a demand for ink jet recording papers having a high surface gloss and an excellent appearance.

[0003] Generally, as a paper having a high surface gloss, a high gloss paper coated with a plate-like pigment coated on the surface and further subjected to a calender treatment as necessary, or a wet coated layer having a mirror surface is used. A so-called cast-coated paper obtained by copying a mirror surface by pressing and drying the surface of a heating drum having the same is known. This cast coated paper has higher surface gloss and better surface smoothness than super calendered normal coated paper, and provides excellent printing effect. However, when it is used as a cast coated paper for ink jet recording, it has various difficulties.

A general cast coated paper is, for example, US52
As disclosed in Japanese Patent No. 75846, a film-forming substance such as an adhesive in a pigment composition constituting a coating layer obtains a high gloss by copying the mirror drum surface of a cast coater. On the other hand, the presence of the film-forming substance causes a problem that the porosity of the coating layer is lost and the ink absorbency during ink jet recording is extremely reduced. In order to improve the ink absorbency, it is important to make the cast coating layer porous so that the ink can be easily absorbed. For this purpose, it is necessary to reduce the film forming property. By reducing the amount of the active substance, the gloss of the white paper is reduced as a result. As described above, it was extremely difficult to simultaneously satisfy both the surface gloss of the cast coated paper and the suitability for inkjet recording.

[0005] As a method for solving the above-mentioned problem, a secondary surface of ultrafine silica having a specific particle size is used for a cast coating layer, and a mirror-surface drum heated while the cast coating layer is in a wet state. It has been found that gloss and extremely excellent print quality can be obtained by pressing and drying to finish, and this method has been proposed in JP-A-11-34486. With the above technology, gloss and extremely excellent print quality can be obtained, but the surface strength is reduced as a result of including a porous pigment in the coating film on the base material to have high ink absorption However, various problems have been caused. For example, the surface of a cast coated paper for inkjet recording is easily damaged by a paper pick-up roll or the like installed in a transport unit of an inkjet printer, and even if a high-quality inkjet recorded image is obtained, the image quality is reduced as a result. Would. In addition, the glossiness once obtained may be reduced by various post-processes (printing, cutting, etc.) after the casting, which may cause a reduction in print quality.

Japanese Patent Application Laid-Open No. 7-117335 proposes a cast coated paper for ink jet recording containing colloidal particles having an average particle diameter of 300 nm or less as a main component.
However, in order to increase the surface strength, it is necessary to increase the amount of the adhesive added, but the average primary particle diameter is 3 to 40 n.
m, when a fine pigment having an average secondary particle diameter of 10 to 500 nm is used, and when a silanol-modified polyvinyl alcohol having excellent adhesiveness is used, agglomeration of the coating is likely to occur, and the target surface It was difficult to obtain strength.

Japanese Patent Application Laid-Open No. 2001-10220 discloses that either the recording layer or the outermost layer of the recording layer contains secondary particles of ultrafine silica having a specific particle diameter and silanol-modified polyvinyl alcohol. There is a description of a cast coated paper for ink jet recording, which is characterized by the fact that when silanol-modified polyvinyl alcohol is added to secondary particles of ultrafine silica having a specific particle size, the aggregation of the paint is easily caused, and the operability is difficult. was there.

[0008]

The present invention relates to a cast coated paper for ink jet recording, and more particularly to a cast coated paper for ink jet recording which is excellent in glossiness and surface strength of a blank portion and excellent in ink jet recording and a method for producing the same. About.

[0009]

Means for Solving the Problems The present inventor adopts the following configuration in order to solve the above problem. That is, the present invention has [1] a sheet-like substrate, and on its surface, an outermost inkjet recording layer composed of a pigment and an adhesive, and at least one inner inkjet absorbing layer composed of a pigment and an adhesive. In the cast coated paper for inkjet recording, the outermost inkjet recording layer and the inner inkjet absorbing layer adjacent thereto have an average primary particle diameter of the pigment of 3 to 40 nm and an average secondary particle diameter of 10 to 500.
nm, the adhesive of the inner inkjet absorbing layer contains silanol-modified polyvinyl alcohol, and the surface strength of the cast coated paper measured by the method described in JIS-K-6854-2 is 0. 15 kN / m or more and surface pH (JAPAN TAPPI No.
6-75) is 5.5 to 7.5.

The present invention includes the following aspects. [2] The cast coated paper for inkjet recording according to [1], wherein the pigment of the outermost inkjet recording layer and the inner inkjet absorbing layer is silica. [3] The cast coated paper for inkjet recording according to [1] or [2], wherein the inner inkjet absorbing layer contains a pH adjuster and is coated with a paint adjusted to pH 8 to 13. [4] The cast coating for inkjet recording according to [3], wherein the pH adjuster is at least one selected from the group consisting of aqueous ammonia, sodium hydroxide, potassium hydroxide, monoethanolamine, diethanolamine and triethanolamine. Papermaking. [5] 75 degree surface glossiness (JIS-P-8142)
50% or more and 20 degree surface gloss (JIS-Z-
8741) is 15% or more of the cast coated paper for inkjet recording according to any one of [1] to [4]. [6] Cast coating for inkjet recording having a sheet-like substrate, and on its surface an outermost inkjet recording layer composed of a pigment and an adhesive, and at least one inner inkjet absorbing layer composed of a pigment and an adhesive In the paper production method, the outermost inkjet recording layer and the inner inkjet absorbing layer adjacent thereto have an average primary particle diameter of the pigment of 3 to 40 nm and an average secondary particle diameter of 10 to 50.
0 nm, wherein the coating material for the inner inkjet absorbing layer contains a silanol-modified polyvinyl alcohol as an adhesive, and is coated with the pH adjusted to 8 to 13 to form a cast coated paper for inkjet recording. Manufacturing method.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The sheet-like base material used in the present invention is not particularly limited, and a paper base material such as acidic paper or neutral paper used for general coated paper is appropriately used. Is done. In addition, air-permeable resin sheets can also be used. The paper base is composed mainly of wood pulp and optionally containing pigment. As the wood pulp, various chemical pulp, mechanical pulp, regenerated pulp and the like can be used, and the degree of beating of these pulp can be adjusted by a beating machine in order to adjust paper strength, suitability for papermaking, and the like. The degree of beating (freeness) of the pulp is not particularly limited.
It is about 550 ml (CSF: JIS P-8121). The pigment is blended for the purpose of imparting opacity or the like or adjusting the ink absorbency, and calcium carbonate, calcined kaolin, silica, titanium oxide and the like can be used. In this case, the amount is preferably about 1 to 20% by weight based on the total solid content. If it is too large, the paper strength may be reduced.

As auxiliaries, various auxiliaries such as a sizing agent, a fixing agent, a paper strength enhancer, a cationizing agent, a retention improver, a dye and a fluorescent whitening agent can be added. Further, in the size press step of the paper machine, starch, polyvinyl alcohols, cationic compounds and the like may be applied and impregnated to adjust the surface strength, the degree of stiffening and the like. The degree of Stekigt sizing is preferably about 1 to 200 seconds. If the degree of Stigecht size is low, wrinkles may occur during coating, which may cause operational problems.If the degree is high, ink absorbency may decrease, curl after recording, or waving phenomenon, so-called cockling. May be significant. The basis weight of the sheet-shaped substrate is not particularly limited, but is about ²⁰ to 400 g / m ² .

In the present invention, on the sheet-like substrate,
An outermost inkjet recording layer and at least one inner inkjet absorbing layer comprising a pigment and an adhesive are provided. The inner inkjet absorbing layer is preferably provided for the purpose of increasing the absorption capacity and absorption speed of the ink. The outermost inkjet absorbing layer is a layer mainly for fixing a colorant, i.e., a dye or a coloring pigment, in the inkjet ink component, and the inner inkjet absorbing layer mainly refers to a layer that rapidly absorbs the solvent in the inkjet ink component. .
However, the distinction is not always clear, and when the amount of applied ink is large, a part of the colorant may be fixed in the inner inkjet absorbing layer or the sheet substrate. The inner inkjet absorbing layer provided on the substrate,
Contains pigment and adhesive as main components.

(Outermost Inkjet Recording Layer, Inner Inkjet Absorbing Layer) In the present invention, a pigment and an adhesive are formed on a sheet-like substrate or an undercoat layer provided on the sheet-like substrate as required. An outermost inkjet recording layer and at least one inner inkjet absorbing layer comprising a pigment and an adhesive are provided. The outermost inkjet recording layer and the inner inkjet absorbing layer contain a pigment having an average primary particle diameter of 3 to 40 nm and an average secondary particle diameter of 10 to 500 nm as a pigment. The method for adjusting the pigment used in the present invention is not particularly limited. For example, a commercially available synthetic amorphous silica or the like (for example, having a secondary particle diameter of about several microns) may be prepared by mechanical means. By giving a stronger force to reduce the average secondary particle diameter. As the mechanical means, an ultrasonic homogenizer, a pressure homogenizer, a high-speed rotation mill, a roller mill, a container driving medium mill, a medium stirring mill,
A jet mill and the like. The silica fine particles thus treated are generally obtained as an aqueous dispersion (slurry or colloid particles) having a solid content of about 5 to 20%.

In the present invention, the average particle diameter is a particle diameter observed with an electron microscope (SEM and TEM) (10,000 to 4).
An electron microscope photograph of a magnification of 10,000 times was taken, and the Martin diameter of particles within 5 cm square was measured and averaged. "Particle Handbook" (Asakura Shoten), p. 52, 1991, etc.). The pigment (substantially composed mainly of secondary particles) used in the present invention has an average secondary particle diameter of 10 to 500 nm, preferably 10 to 300 nm, more preferably 15 to 15 nm.
0 nm, most preferably 20-100 nm. When the average particle diameter of the secondary particles of the pigment exceeds 500 nm, the transparency of the outermost inkjet recording layer and the inner inkjet absorbing layer is reduced, and the colorant fixed in the outermost inkjet recording layer and the inner inkjet absorbing layer is reduced. The color developability decreases, and the desired print density cannot be obtained. Further, when an extremely small pigment having an average particle diameter of the secondary particles of less than 10 nm is used, the ink absorbency decreases,
The desired image quality cannot be obtained.

The average primary particle size of the pigment is 3
４０40 nm, preferably 5-30
nm, more preferably 7 to 20 nm. When the average primary particle diameter is less than 3 nm, the gap between the primary particles becomes extremely small, the ability to absorb the solvent and the colorant in the ink is reduced, and a desired image quality cannot be obtained. When the average primary particle diameter exceeds 40 nm, the aggregated secondary particles become large, the transparency of the outermost inkjet recording layer and the inner inkjet absorbing layer is reduced, and the outermost inkjet recording layer and the inner inkjet absorbing layer are reduced. The color developability of the fixed colorant is reduced, and a desired print density cannot be obtained. Examples of the pigment include silica and aluminosilicate, but silica is particularly preferred.

The proportion of silica in all the pigments in the outermost ink jet recording layer and the inner ink jet absorbing layer is desirably 50% or more in order to maintain the transparency of the recording layer. If the silica ratio in all the pigments is less than 50%, the transparency is significantly reduced, and the image quality such as print density may be reduced. As the adhesive, silanol-modified polyvinyl alcohol which is excellent in adhesion of the pigment to silica is preferable. However, with silanol-modified polyvinyl alcohol,
When a pigment having an average secondary particle diameter of about 100 nm is mixed, the pigment is aggregated. Therefore, a pH adjuster is added.

As the pH adjuster, lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide,
Alkali metal hydroxides such as cesium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide, strontium hydroxide and barium hydroxide, and alkali metals such as lithium hydrogen carbonate, sodium hydrogen carbonate and potassium hydrogen carbonate Bicarbonate, ammonia water, monoethanolamine,
Examples thereof include amine compounds such as diethanolamine and triethanolamine.Ammonia water is preferably used because of solubility in water, evaporation by casting, and difficulty in remaining on paper. Those selected from the group consisting of potassium, monoethanolamine, diethanolamine and triethanolamine are used alone or in combination. The paint pH is
It is preferably adjusted to 8 to 13, and more preferably adjusted to 10 to 11. When the paint pH is less than 8, agglomeration of the paint occurs, and when the paint pH is more than 13, more p is applied.
An H adjuster is required, and the suitability for inkjet recording may be impaired. Surface pH of Cast Coated Paper for Inkjet Recording (JAPAN TAPPI No. 6-7
5) is preferably 5.5 to 7.5, and more preferably 6.0 to 7.0. When the surface pH is less than 5.5,
When the amount of the pH adjuster is too small, the stability of the paint is poor, and when the surface pH of the outermost layer exceeds 7.5, the suitability for inkjet recording may be poor due to the excessive amount of the pH adjuster.

The adhesive may be silanol-modified polyvinyl alcohol alone, or a water-soluble resin (eg, polyvinyl alcohol, casein, soybean protein, synthetic proteins, starch, cellulose derivatives such as carboxymethylcellulose and methylcellulose), styrene-butadiene copolymer Water-dispersible resins such as conjugated diene-based polymer latex such as methyl methacrylate-butadiene copolymer, and vinyl-based copolymer latex such as styrene-vinyl acetate copolymer; water-based acrylic resin; water-based polyurethane resin; water-based polyester resin And the like, and may be used in combination with various publicly known adhesives generally used in the coated paper field. When a cationic compound is added to the ink fixing layer, a cationic or nonionic adhesive is preferable because the coating composition has good stability. The amount of the adhesive is adjusted in the range of 1 to 200 parts by weight, more preferably 5 to 100 parts by weight, based on 100 parts by weight of the pigment. When the amount of the adhesive is small, the strength of the coating layer is weakened, the surface is easily damaged, and powder fall may occur. Conversely, if the amount of the adhesive is large, the ink absorbency may decrease, and the desired inkjet recording suitability may not be obtained.

Here, when the amount of the adhesive in the outermost ink jet recording layer is larger than that in the inner ink jet absorbing layer,
It is preferable because it is easy to obtain one excellent in balance between surface strength and ink absorbency. The colorant for inkjet ink is
Since it is usually anionic, it is preferable to mix a cationic compound in the outermost inkjet recording layer and the inner inkjet absorbing layer for the purpose of fixing the colorant component in the ink. The compounding method may be that the pigment is mixed with the pigment, but the pigment is generally anionic, and aggregation may occur during mixing. For example, commonly available amorphous silica (having a secondary particle size of several microns)
When pulverizing into fine particles by giving a strong force by mechanical means, after mixing and dispersing the cationic compound together with the amorphous silica before the pulverizing treatment, or by dispersing and pulverizing by mechanical means,
Alternatively, it is mixed with a finely divided silica dispersion,
After coagulation, the particle diameter can be adjusted to a required particle size by using a method of mechanically dispersing and pulverizing again.

Examples of the cationic compound include a cationic resin and a low molecular weight cationic compound (for example, a cationic surfactant). In order to improve the printing density, a cationic resin is preferable and can be used as a water-soluble resin or an emulsion. Furthermore, the cationic resin can be used as a cationic organic pigment in the form of particles by insolubilizing the cationic resin by means such as crosslinking. Such a cationic organic pigment, when polymerizing a cationic resin, copolymerizes a polyfunctional monomer to form a crosslinked resin, or has a reactive functional group (hydroxyl group, carboxyl group, amino group, acetoacetyl group, etc.). A cross-linking agent is added to a cationic resin having the above as required, and the cross-linked resin is formed by heat, radiation or the like. Cationic compounds, especially cationic resins, may also serve as adhesives.

Examples of the cationic resin include the following. 1) polyalkylene polyamines such as polyethylene polyamine and polypropylene polyamine or derivatives thereof, 2) acrylic resin having a secondary amino group, tertiary amino group or quaternary ammonium group, 3) polyvinylamine, polyvinylamidines, 4) a dicyanic cationic compound represented by a dicyandiamide-formalin polycondensate; 5) a polyamine-based cationic compound represented by a dicyandiamide-diethylenetriamine polycondensate;
6) epichlorohydrin-dimethylamine addition polymer,
7) dimethyldiallylammonium chloride -S0 ₂
Copolymer, 8) diallylamine salt -S0 ₂ copolymer,
9) dimethyldiallylammonium chloride polymer,
10) Cationic compounds such as polymer of allylamine salt, 11) polymer of quaternary salt of dialkylaminoethyl (meth) acrylate, and 12) copolymer of acrylamide-diallylamine salt.

The cationic compound also has the effect of improving the water resistance of a printed image. The cationic compound blended in the outermost inkjet recording layer and / or the inner inkjet absorbing layer is 1 to 10 parts by weight based on 100 parts by weight of the pigment.
0 parts by weight, more preferably 5 to 50 parts by weight. If the blending amount is small, the effect of improving the print density is small, and if it is large, the print density may decrease or blurring of the image may occur. When the cationic compound is blended in the outermost inkjet recording layer, the desired effect is often obtained, but when the ink amount is large or the coating amount of the outermost inkjet recording layer is small, the inner inkjet absorbing layer is preferably used. It is also desirable to mix them.

When the coating liquid for the inner ink jet absorbing layer is applied on a sheet-like substrate or an undercoat layer provided on the sheet-like substrate, a blade coater, an air knife coater, a roll coater, a brush coater, a chaplex, etc. Various known coating apparatuses such as a coater, a bar coater, a lip coater, a gravure coater, and a curtain coater can be used. The coating amount of the inner inkjet absorbing layer is preferably 1 to 50 g / m ² , more preferably 1.5 to 30 g / m ² as a dry solid content. If it is less than 1 g / m ² , bleeding tends to occur during printing, and if it exceeds 50 g / m ² , the print density may be reduced. When an undercoat layer is provided, a sufficient effect is often obtained at 1 to 10 g / m ² .

The outermost inkjet recording layer is a cast coating layer formed by a casting method. The cast method means that the coating layer is a mirror-finished drum (drum of mirror-finished metal, plastic, glass, etc.), a mirror-finished metal plate, a plastic sheet or film,
This is a method of drying on a glass plate or the like and transferring a smooth surface onto the coating layer to obtain a smooth and glossy coating layer surface. As a coating method, a coating liquid for the outermost inkjet recording layer is applied onto the inner inkjet absorbing layer, and while the coating layer is in a wet state, pressed against a heated mirror-surface drum and dried. (Wet cast method) or a method of once drying, re-wetting, pressing against a heated mirror drum, drying and finishing (rewet cast method), and the like. In the wet casting method, the coating liquid for the outermost inkjet recording layer is provided between the drum and the inner inkjet absorbing layer on the pressing roll (press roll) side immediately before the outermost inkjet recording layer is pressed against the mirror drum. Is particularly preferable, since the penetration of the coating liquid is suppressed as much as possible and good gloss and print quality can be easily obtained with a small amount of coating.

Further, a method of applying a coating liquid for a cast coating layer directly onto a heated mirror-surface drum, pressing the base coating layer provided with an undercoat layer onto the base coating layer surface, and then drying and finishing the coating (precast method) is also employed. can do. The surface temperature of the mirror drum is preferably 40 to 200 ° C, and 70 to 150 ° C.
Is more preferred. When the temperature is lower than 40 ° C., it takes time for drying, the gloss is easily reduced, and the productivity is apt to be significantly reduced. If the temperature exceeds 200 ° C., the surface of the cast coated paper for inkjet recording may be roughened or the gloss may be reduced.

The coating solution for the outermost ink jet recording layer is
When the outermost inkjet recording layer is applied on the inner inkjet absorbing layer and pressed against a heated mirror drum while the outermost inkjet recording layer is in a wet state, and then dried and finished, the penetration of the outermost inkjet recording layer coating liquid is prevented. For the purpose of suppressing, a method of promoting immobilization of the coating liquid for the outermost inkjet recording layer can be adopted. As this method, for example, (1) a gelling agent that promotes immobilization of the coating liquid for the outermost inkjet recording layer is blended into the inner inkjet absorbing layer, and (2) the inner inkjet absorbing layer Is coated and impregnated with a gelling agent that promotes immobilization of the coating liquid for the outermost inkjet recording layer. (3) After coating the coating liquid for the outermost inkjet recording layer, Coating and impregnating the surface with a gelling agent that promotes the immobilization of the coating liquid for the recording layer. (4) The immobilization occurs in the process of drying the coating liquid in the outermost inkjet recording layer coating liquid. Incorporation of a gelling agent that promotes the above is mentioned.
Such a gelling agent is a crosslinking agent for the adhesive in the coating liquid for the outermost ink jet recording layer, and includes boric acid, formic acid and the like, salts thereof, aldehyde compounds, epoxy compounds and the like. When the wet casting method is used among the above methods, the coating liquid for the outermost ink jet recording layer is coated on the inner ink jet absorbing layer, and the time until the coating liquid is pressed against the mirror surface drum and dried is shortened as much as possible. Since the penetration of the outermost ink jet recording layer coating liquid is suppressed, gloss is more likely to be exhibited.

In order to adjust the whiteness, viscosity, fluidity, etc., pigments, defoamers, and pigments used in general printing coated papers and ink-jet papers are included in the coating liquid for the outermost ink jet recording layer. Various auxiliaries such as a coloring agent, a fluorescent whitening agent, an antistatic agent, a preservative and a dispersant, and a thickener are appropriately added. It is preferable to add a release agent to the outermost inkjet recording layer coating liquid for the purpose of imparting releasability from a mirror drum or the like.

Examples of the release agent include higher fatty acid amides such as stearic acid amide and oleic acid amide, polyolefin waxes such as polyethylene wax and polypropylene wax, sodium stearate, potassium stearate, ammonium stearate, calcium stearate and stearic acid. Examples include alkali salts of higher fatty acids such as zinc, sodium oleate, potassium oleate and ammonium oleate, silicone compounds such as lecithin, silicone oil and silicone wax, and fluorine compounds such as polytetrafluoroethylene. The compounding amount of the release agent is 0.1 to 50 parts by weight based on 100 parts by weight of the pigment,
Preferably 0.3 to 30 parts by weight, more preferably 0.5
It is adjusted in the range of ~ 20 parts by weight. If the amount is small,
It is difficult to obtain the effect of improving the releasability. Conversely, if the effect is large, the gloss may be reduced, the ink may repell, or the recording density may be reduced.

The coating amount of the outermost ink jet recording layer is
0.1 to 20 g / m ² , preferably 0.1 to 20 g / m ² on a dry solids basis.
5 to 10 g / m ² . Here, if it is less than 0.1 g / m ^2, it is difficult to obtain a sufficient gloss, and if it exceeds 20 g / m ² , bleeding occurs at the time of printing, and the print density tends to decrease. After the outermost inkjet recording layer is provided by a cast method, a smoothing treatment can be further performed by a super calendar or the like. The surface strength (JIS-K-6864-2) of the cast coated paper for inkjet recording is as follows.
0.15 or more, preferably 0.15 to 0.30 kN /
m, more preferably 0.17 to 0.25 kN / m. If it is less than 0.15 kN / m, the surface strength is weak,
If it exceeds 0.30 kN / m, the amount of the adhesive is excessive and the ink absorbency is poor.

75 degree surface glossiness (JIS-P-8142) of the cast coated paper for ink jet recording according to the present invention.
Is preferably 50% or more, and more preferably 60% or more, in order to impart the texture of photographic paper. Further, the 20-degree surface glossiness (JIS-Z-8741) is preferably 15% or more. When the 75 degree surface gloss is less than 50% or the 20 degree surface gloss is less than 15%, the glossiness of visual observation is liable to be impaired, and a cast coated paper for inkjet recording of desired quality may not be obtained. is there.

(Undercoat Layer) An undercoat layer may be provided between the sheet-like substrate and the inner ink jet absorbing layer, if necessary. Pigments of the undercoat layer include kaolin, clay, calcined clay, amorphous silica (also referred to as amorphous silica), zinc oxide, aluminum oxide, aluminum hydroxide, calcium carbonate, satin white, aluminum silicate, alumina, colloidal silica, Zeolites, synthetic zeolites,
Sepiolite, smectite, synthetic smectite, magnesium silicate, magnesium carbonate, magnesium oxide,
One or more of various publicly known pigments in the general coated paper manufacturing field, such as diatomaceous earth, styrene-based plastic pigment, hydrotalcite, urea resin-based plastic pigment, and benzoguanamine-based plastic pigment, can be used in combination. Among these, it is preferable to contain amorphous silica, alumina, and zeolite having high ink absorbency as main components.

The average particle size of the pigment (aggregated particle size in the case of agglomerated pigment) is preferably about 1 to 20 μm, more preferably 2 to 10 μm, and still more preferably 3 to 8 μm.
m. If it is less than 1 μm, the effect of improving the ink absorption speed is poor, and if it is more than 20 μm, the smoothness and gloss after providing the cast coating layer may be insufficient. However, a pigment having a small particle size can be blended as an auxiliary component for the purpose of adjusting the ink absorbency or controlling the penetration of the paint applied on the undercoat layer. Examples of such a pigment include colloidal silica, alumina sol, and silica fine particles contained in an ink fixing layer described later.

Examples of the adhesive for the undercoat layer include proteins such as casein, soybean protein and synthetic protein, various starches such as starch and oxidized starch, and modified polyvinyl alcohol such as polyvinyl alcohol, cationic polyvinyl alcohol and silanol-modified polyvinyl alcohol. Polyvinyl alcohols, cellulose derivatives such as carboxymethyl cellulose and methyl cellulose, styrene-butadiene copolymer, conjugated diene-based polymer latex of methyl methacrylate-butadiene copolymer, acrylic polymer latex, ethylene-vinyl acetate copolymer Conventionally known adhesives generally used for coated paper, such as a vinyl polymer latex such as a vinyl polymer latex, may be used alone or in combination.

The mixing ratio of the pigment and the adhesive depends on the kind thereof, but generally, the adhesive is 1 to 10 parts by weight based on 100 parts by weight of the pigment.
0 parts by weight, preferably in the range of 2 to 50 parts by weight. In addition, various auxiliaries such as a dispersant, a thickener, an antifoaming agent, an antistatic agent, and a preservative used in the production of general coated paper are appropriately added. A fluorescent dye and a coloring agent can be added to the undercoat layer.

The undercoat layer may contain a cationic compound for the purpose of fixing the colorant (dye or color pigment) component in the ink jet recording ink. However,
As described later, it is preferable that the colorant in the ink be fixed to a portion as close to the surface as possible, because the printing (recording) density is high.
In the outermost inkjet recording layer and the inner inkjet absorbing layer, especially in the outermost inkjet recording layer,
It is preferable to incorporate a large amount of a cationic compound. More preferably, the cationic compound is blended only in the outermost inkjet recording layer, and the cationic compound is preferably substantially absent in the undercoat layer and the inner inkjet absorbing layer. However, if necessary, a small amount of a cationic surfactant or the like may be added as an auxiliary agent. When a cationic compound is compounded only in the outermost inkjet recording layer,
Good gloss. The effect of the cationic compound is particularly effective when the colorant is anionic.

When the undercoat layer contains a composite of colloidal silica and a polymer resin obtained by polymerizing a monomer having an ethylenically unsaturated bond, gloss is further exhibited. The reason for this is not necessarily clear, but it is assumed that the presence of the composite suppresses penetration while maintaining the ink absorbency of the undercoat layer. Further, although the reason is unknown, when the cast coating layer is provided by the cast method, the releasability from the cast drum tends to be improved.

Examples of the polymer resin obtained by polymerizing a monomer having an ethylenically unsaturated bond include methyl acrylate, ethyl acrylate, butyl acrylate, and the like.
Acrylic acid ester having 1 to 18 alkyl groups such as 2-ethylhexyl acrylate, lauryl acrylate, 2-hydroxyethyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycidyl Alkyl groups such as methacrylates having 1 to 18 carbon atoms, methacrylic acid esters, styrene, α-methylstyrene, vinyltoluene, acrylonitrile, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl propionate, acrylamide, N-methylolacrylamide, ethylene And a polymer obtained by polymerizing an ethylenic monomer such as butadiene. The polymer may be a copolymer using two or more kinds of ethylenic monomers as needed, or may be a polymer or a substituted derivative of the copolymer. Incidentally, examples of the substituted derivative include, for example, those having a carboxyl group or those having been rendered alkali-reactive.

The complexation with colloidal silica is carried out by polymerizing the above-mentioned ethylenic monomer with a silane coupling agent or the like in the presence of colloidal silica to form a Si—O—R bond (R:
A polymer resin) or a polymer resin modified with a silanol group or the like and colloidal silica, if necessary, to form a Si—OR bond (R: polymer component)
To form a composite. The Tg (glass transition point) of the polymer component of the composite is preferably 40 ° C or higher, more preferably 50 to 100 ° C. If the Tg is low, the film formation may progress too much during drying, or the ink absorption may be slow and bleeding may occur. further,
Although the reason is not necessarily clear, when the Tg is 40 ° C. or higher, the releasability from the mirror drum when the cast coating layer is provided by the casting method tends to be improved.

The undercoat layer paint composed of the above materials is generally adjusted to have a solid content of about 5 to 50% by weight, and is dried on a paper substrate in a dry weight of ^{2 to} 100 g / m ² , preferably 5 to 50 g. / M ² , more preferably 10 to 20
g / m ² . If the coating amount is small, the effect of improving the ink absorbency may not be sufficiently obtained,
When the outermost inkjet recording layer is provided, the gloss may not be sufficiently obtained, and if it is large, the print density may be reduced, or the strength of the coating layer may be reduced and the powder may be easily dropped and scratched. is there. The composition for the undercoat layer is coated and dried by various known and publicly-known coating devices such as a blade coater, an air knife coater, a roll coater, a brush coater, a chaplex coater, a bar coater, a lip coater, a gravure coater, and a curtain coater. You. Further, if necessary, after the undercoat layer is dried, it may be subjected to a smoothing treatment such as super calendering or brushing.

[0041]

The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted thereto.
Parts and% in Examples are parts by weight and% by weight, respectively, unless otherwise specified.

Example 1 (Coating 1-1 for Undercoat Absorbing Layer) Amorphous silica having an average secondary particle diameter of 4.3 μm (trade name: Fine Seal X45, average primary particle diameter 15 nm, manufactured by Tokuyama) 100 as a pigment
Part, styrene-2- having a glass transition point of 75 ° C. as an adhesive
Methylhexyl acrylate copolymer resin and particle size 30
40 parts of a 40:60 composite of 40 nm colloidal silica,
Silanol-modified polyvinyl alcohol (trade name: R-1)
130, manufactured by Kuraray Co., Ltd.), 20 parts of a 10% aqueous solution, and 0.5 part of sodium phosphate (trade name: Nancarin S-1, manufactured by Rin Kagaku) as a dispersant were mixed and dispersed together with water to obtain a solid content of 20 parts.
% Paint 1-1 was obtained.

(Coating 1 for Inner Inkjet Absorbing Layer)
2) Amorphous silica having an average secondary particle diameter of 4.3 μm (trade name: Fine Seal X-45, average primary particle diameter 15 n)
m, manufactured by Tokuyama Co., Ltd.) and a pressure-type homogenizer (trade name: Ultra High Pressure Type Homogenizer GM-1 type, SMT)
Under the pressure condition of 500 kg / cm ² to obtain a silica dispersion having an average secondary particle diameter of 50 nm.
100 parts of this silica as a pigment and silanol-modified polyvinyl alcohol (trade name: R-113) as an adhesive
5 parts, polyvinyl alcohol (trade name: Kuraray)
PVA117, 10 parts by Kuraray), as a pH adjuster,
Aqueous ammonia (manufactured by Wako Pure Chemical Industries, Ltd.) (10 parts) was mixed and dispersed with water to obtain Paint 1-2 having a solid content of 10%. The pH of the paint at this time was 11.

(Coating for outermost ink jet recording layer 1-
3) Amorphous silica having an average secondary particle diameter of 4.3 μm (trade name: Fine Seal X-45, average primary particle diameter 15 n)
m, manufactured by Tokuyama Co., Ltd.) and a pressure-type homogenizer (trade name: Ultra High Pressure Type Homogenizer GM-1 type, SMT)
Under the pressure condition of 500 kg / cm ² to obtain a silica dispersion having an average secondary particle diameter of 50 nm.
100 parts of this silica as a pigment, 10 parts of a cationic compound (trade name: PAS-J-81, manufactured by Nitto Bo) as a dye fixing agent, and a cationic compound (trade name: Unisense C)
P-91, manufactured by Senka) 10 parts, cationic polyurethane resin (trade name: F-8564D, manufactured by Daiichi Kogyo Seiyaku) as an adhesive 80 parts, polyethylene wax emulsion (trade name: Pertol N-856, trade name) 10 parts (mixed with Hyundai Chemical Industry) together with water, and the solid content concentration is 1
0% of paint 1-3 was obtained.

(Preparation of paper) A dry weight of 15 g was applied to one side of a high-quality paper having a basis weight of 100 g / m ² using an air knife coater.
g / m < ² >, and the coating material 1-1 was applied and dried. A dry weight of 7 g /
The paint 1-2 was applied so as to obtain m ² and dried. At the same time that the coating material 1-3 is applied to the surface, while the coating material is in a wet state, it is pressed against the surface of a chrome-plated mirror surface drum having a surface temperature of 100 ° C., dried, peeled off, and cast coated paper for inkjet recording. I got At this time, the dry weight of the paint 1-3 was 3 g / m ² .

Example 2 In Example 1, the average secondary particle diameter of the paint 1-3 was 4.3.
μm amorphous silica (trade name: Fine Seal X-4)
5, using an amorphous silica (trade name: Fine Seal X-60, average primary particle diameter 15 nm, manufactured by Tokuyama) having an average secondary particle diameter of 3 μm instead of the average primary particle diameter 15 nm, manufactured by Tokuyama A cast coated paper for inkjet recording was obtained in the same manner as in Example 1 except that a silica dispersion having a particle diameter of 200 nm was obtained.

Example 3 The procedure of Example 1 was repeated, except that the silanol-modified polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray Co., Ltd.) of Paint 1-2 was changed from 5 parts to 15 parts. Thus, a cast coated paper for inkjet recording was obtained.

Example 4 (Paint 4-1 for Inner Inkjet Absorbing Layer) Water of amorphous silica (trade name: Fine Seal X-45, average primary particle diameter 15 nm, manufactured by Tokuyama) having an average secondary particle diameter of 4.3 μm The dispersion was pressurized with a pressure homogenizer (trade name: ultra high pressure homogenizer GM-1 type, manufactured by SMT) under a pressing condition of 50.
The pulverization treatment was repeated at 0 kg / cm ² to obtain a silica dispersion having an average secondary particle diameter of 50 nm. 100 parts of this silica as a pigment, 10 parts of a cationic compound (trade name: PAS-J-81, manufactured by Nitto Bo) as a dye fixing agent, 5 parts of a cationic compound (trade name: Unisense CP-91, manufactured by SENKA)
Parts, 15 parts of silanol-modified polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray) as an adhesive, and 15 parts of aqueous ammonia (manufactured by Wako Pure Chemical Industries) as a pH adjuster were mixed and dispersed together with water to obtain a solid content. 10% concentration paint 4-1
I got The pH of the paint at this time was 11.

(Preparation of Paper) A dry weight of 15 g was applied to one side of high quality paper having a basis weight of 100 g / m ² using an air knife coater.
g / m < ² >, and the coating material 1-1 was applied and dried. A dry weight of 7 g /
The coating material 4-1 was applied so as to obtain m ² and dried. At the same time that the coating material 1-3 is applied to the surface, while the coating material is in a wet state, it is pressed against the surface of a chrome-plated mirror surface drum having a surface temperature of 100 ° C., dried, peeled off, and cast coated paper for inkjet recording. I got At this time, the dry weight of the paint 1-3 was 3 g / m ² .

Comparative Example 1 In Example 1, a silanol-modified polyvinyl alcohol (trade name: R-1130, trade name) was used as an adhesive for paint 1-2.
Instead of 5 parts of Kuraray), use 15 parts of polyvinyl alcohol (trade name: PVA117, made by Kuraray),
A cast coated paper for inkjet recording was obtained in the same manner as in Example 1 except that no modifier was added. The pH of the paint at this time was 7.5.

Comparative Example 2 In Example 1, the coating material 1-3 had an average secondary particle diameter of 4.3.
μm amorphous silica (trade name: Fine Seal X-4)
5. Instead of the average primary particle diameter of 15 nm, manufactured by Tokuyama, amorphous silica having an average secondary particle diameter of 7.5 μm (trade name: Silojet P612, average primary particle diameter of 10 n)
m, manufactured by Grace Devison) to obtain a cast coated paper for inkjet recording in the same manner as in Example 1 except that a silica dispersion having an average secondary particle diameter of 600 nm was obtained.

Comparative Example 3 A cast coated paper for ink jet recording was obtained in the same manner as in Example 1, except that the pH adjuster was not added to the paint 1-2. PH of paint at this time
Was 7.5.

Comparative Example 4 (Comparative Paint 4-1 for Inner Inkjet Absorbing Layer) As a pigment, amorphous silica having an average secondary particle diameter of 4.3 μm (trade name: Fine Seal X45, average primary particle diameter 15 nm,
100 parts of Tokuyama), 20 parts of silanol-modified polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray) as an adhesive, 10% aqueous solution, and a cationic compound as a dye fixing agent (trade name: Unisense CP-103, manufactured by SENKA) 20 parts, and 0.5 part of sodium phosphate (trade name: Nancarin S-1, manufactured by Rin Kagaku) as a dispersant were mixed with water.
The dispersion was dispersed to obtain Comparative Paint 4-1 having a solid content of 20%. At this time, the pH of the paint was 6.0.

(Comparative paint 4-2 for outermost ink jet recording layer) 100 parts of a 50:50 composite of a styrene-2-methylhexyl acrylate copolymer resin having a glass transition point of 85 ° C. and colloidal silica having a particle diameter of 30 nm, 5 parts of an alkyl vinyl ether / maleic acid derivative resin as a viscosity modifier and 3 parts of lecithin as a release agent were mixed and dispersed with water to obtain Comparative Paint 4-2 having a solid content of 30%.

(Preparation of Paper) A dry weight of 10 g was applied to one side of a high-quality paper having a basis weight of 100 g / m ² using an air knife coater.
g / m ² of Comparative Paint 4-1 was applied and dried. On this surface, a comparative paint 4-
After coating No. 2, while the coating was in a wet state, the coating was pressed against the surface of a chrome-plated mirror drum having a surface temperature of 80 ° C., dried, and peeled to obtain a cast coated paper for inkjet recording. At this time, the dry weight of the comparative paint 4-2 was 5 g /
m ² .

[Evaluation Methods] The stability of the pH adjusting agent-containing paints used in Examples and Comparative Examples, and the surface strength, surface pH, white paper gloss, and ink jet recording suitability of the obtained cast coated paper for ink jet recording were evaluated. Table 1 shows the results
It was shown to. Each evaluation was performed by the following method.

[Stability of Paint for Inner Inkjet Absorbing Layer] The stability of the paint in each layer was evaluated as follows. ：: No viscosity increase after 1 day after coating preparation. Δ: The viscosity increases for 3 hours after the paint preparation. ×: Viscosity increases within 1 minute after preparation of paint.

[Surface strength] The surface of cast coated paper for ink jet recording and Scotch clear tape (trade name: CH
-24, manufactured by 3M) and adhered to JIS-K-68
It was measured by the method described in 54-2, and the 180-degree peel strength was taken as the surface strength. The test piece is 25 mm wide x 16 long
0 mm. The test piece was bonded to a plastic plate having a width of 25 mm and a length of 180 mm with a double-sided tape of the same width, taking care not to allow air bubbles to enter the surface of the test piece. Next, on the evaluation surface (glossy surface) side of the test, the above-mentioned scotch clear tape having a constant quality of 24 mm width (trade name: CH-24, manufactured by 3M)
Paste. The lamination is performed by rotating twice with a roller having a weight of 5 kg for a width of 25 mm without reciprocating (linear pressure: 2 kg / cm).

[Surface pH] The surface pH of the cast coated paper for ink-jet printing was measured according to JAPAN TAPPI No. 6
-75 Measured according to "2.1 Coating method" in "Method for testing surface pH of paper and paperboard". However, assuming that the solution penetrates into the cast coated paper for ink jet recording, the indicator solution for pH measurement (manufactured by Kyoritsu Rikagaku Kenkyusho) is applied to the surface, and after 1-2 minutes, the judgment is made. The surface pH was determined based on a standard color change table.

[75 ° Surface Gloss and 20 ° Surface Gloss] The 75 ° surface gloss of cast coated paper for ink jet recording was measured by the method described in JIS-P-8142. According to the method described in JIS-Z-8741, the 20-degree surface glossiness of the cast coated paper for inkjet recording was measured.

[Ink-jet recording suitability] The ink-jet recording suitability was measured by an ink jet printer BJ-F870.
(Canon) was used for printing. The ink cartridges are Canon BCI-6Y, BCI-6M, BC
I-6C, BCI-6BK, BCI-6PM photo, B
A CI-6PC photo was used. The evaluation was made by visually observing print unevenness in a solid printing portion of a mixture of two colors of cyan ink and magenta ink. ：: Good level without printing unevenness. ：: There is some printing unevenness, but there is no practical problem. Δ: There is uneven printing, which is a level that is somewhat problematic in practical use. X: Printing unevenness was remarkable, and it was not practical.

[Overall Evaluation] The stability of the paint, the surface strength of the cast coated paper for ink jet recording, the surface glossiness at 75 °, the surface glossiness at 0 °, and the suitability for ink jet recording were comprehensively evaluated. 5: Extremely excellent. 4: Excellent. 3: Normal. 2: Slightly inferior. 1: Poor.

[0063]

[Table 1]

[0064]

As is clear from Table 1, the cast coated paper for ink jet recording obtained according to the present invention is particularly excellent in glossiness and surface strength of a white paper portion, excellent in ink jet recording suitability, and extremely practical. It is expensive.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C056 FC06 2H086 BA16 BA31 BA33 BA34 BA41 BA46 4L055 AG18 AG64 AH02 AH37 AJ04 BE09 EA07 EA11 EA16 EA31 FA12 FA13 GA09

Claims (6)

[Claims] An ink jet recording cast comprising a sheet-like substrate, an outermost ink jet recording layer comprising a pigment and an adhesive, and at least one inner ink jet absorbing layer comprising a pigment and an adhesive on the surface thereof. In the coated paper, the outermost inkjet recording layer and the inner inkjet absorbing layer adjacent to the outermost inkjet recording layer have an average primary particle diameter of 3 to 40 nm and an average secondary particle diameter of 10 to 50 nm.
0 nm, the adhesive of the inner inkjet absorbing layer contains silanol-modified polyvinyl alcohol, and the cast coated paper has a surface strength of 0. 0 measured by the method described in JIS-K-6854-2. 15 kN / m or more and surface pH (JAPAN TAPPI No.
6-75) is 5.5 to 7.5. 2. The cast coated paper for ink jet recording according to claim 1, wherein the pigments of the outermost ink jet recording layer and the inner ink jet absorbing layer are silica. 3. The cast coated paper for ink-jet recording according to claim 1, wherein the inner ink-jet absorbing layer contains a pH adjuster and is coated with a paint adjusted to pH 8 to 13. 4. The method according to claim 1, wherein the pH adjuster is aqueous ammonia, sodium hydroxide, potassium hydroxide, monoethanolamine,
The cast coated paper for inkjet recording according to claim 3, which is at least one selected from the group consisting of diethanolamine and triethanolamine. 5. A 75 degree surface gloss (JIS-P-814)
2) is 50% or more and 20 degrees surface glossiness (JI
SZ-8741) is 15% or more.
The cast coated paper for inkjet recording according to any one of the above. 6. An inkjet recording cast comprising a sheet-like substrate, an outermost inkjet recording layer comprising a pigment and an adhesive, and at least one inner inkjet absorbing layer comprising a pigment and an adhesive on the surface thereof. In the method for producing a coated paper, the outermost inkjet recording layer and the inner inkjet absorbing layer adjacent to the outermost inkjet recording layer have an average primary particle size of 3 to 40 nm and an average secondary particle size of 10 to 40 nm.
To 500 nm, wherein the coating for the inner inkjet absorbing layer contains a silanol-modified polyvinyl alcohol as an adhesive, and is applied with the pH adjusted to 8 to 13 for cast coating for inkjet recording. Paper manufacturing method.