JPH106639A - Cast coated paper for ink jet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cast coated paper for ink jet recording especially with high blank face luster, outstanding ink jet recording (print) suitability and high recorded image preservability. SOLUTION: A coated layer containing pigment and an adhesive is formed on a base paper, and a cast coated layer is formed by applying a cast coating liquid containing a polymer resin and at least, one type of metal salt selected from zinc, aluminum, magnesium and calcium. In addition, the cast coated layer is press-contacted with a heated mirror drum and then is finished by drying.

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 having excellent white paper surface gloss, excellent ink jet recording (printing) suitability, and preservation of recorded images. About paper.

[0002]

2. Description of the Related Art In recent years, recording by an ink-jet printer has been used in various fields because of low noise, high-speed recording, and easy multi-color printing. As the paper for ink jet recording, high quality paper devised to be rich in ink absorbency, coated paper having a surface coated with a porous pigment, or the like is used. By the way, these papers are mainly made of so-called matte-tone ink jet recording paper having a low surface gloss.

However, recently, with the expansion of applications such as high-speed ink-jet recording, high-definition of recorded images, and full-color printing, ink-jet recording paper having high surface gloss and excellent appearance characteristics has been desired. On the other hand, ink jet recording papers having high gloss include those using a casting method disclosed in JP-A-63-264391 and JP-A-7-149038 and JP-A-6-16-138.
Japanese Patent Application Laid-Open No. 55892 discloses a method in which surface treatment of general cast paper is performed. The inkjet recording paper having such a high gloss is not always satisfactory in terms of image quality after printing, ink absorbency, and water resistance after printing.

That is, in general cast coated paper, gloss is obtained by copying the glossy surface of a mirror drum, so that a large amount of a film-forming substance such as casein or latex is used in the coated layer. Since these film-forming substances hinder the absorption of the inkjet ink, a phenomenon occurs in which the ink bleeds or flows out on the surface. For this reason, the ink disclosed in JP-A-6-155892 has insufficient ink absorbency.
No. 391 discloses an ink having excellent absorbability by specifying a pigment, but has a drawback that it is difficult to obtain a sufficient gloss value. Japanese Patent Application Laid-Open (JP-A) No. 7-149038 has a drawback that, although good gloss and good ink absorbency can be obtained, a sufficient print density cannot be obtained.

[0005]

SUMMARY OF THE INVENTION The present inventors have maintained the high smoothness and excellent gloss inherent in cast coated paper,
Further, the present invention provides a cast coated paper excellent in inkjet recording (printing) suitability and preservation of a recorded image. Disclosed is a cast coated paper which has the original high smoothness and excellent glossiness of cast coated paper, and has excellent ink jet print recording suitability and excellent recorded image storage stability.

[0006]

The present invention includes the following aspects. [1] A base paper is provided with a coating layer containing a pigment and an adhesive,
Further, a coating liquid containing a polymer resin and at least one metal salt selected from zinc, aluminum, magnesium and calcium was applied to form a coating layer for casting, and the coating layer for casting was heated. Cast coated paper for inkjet recording, which is pressed against the mirror drum, dried and finished.

[2] The cast coated paper for inkjet recording according to [1], wherein the polymer resin is a copolymer of styrene and acrylate. [3] The cast coated paper for inkjet recording according to [1], wherein the polymer resin is a copolymer of styrene and an acrylate ester, and the copolymer forms a composite with colloidal silica.

[4] The polymer resin has a glass transition point of 40
[1], [2] or [3] which is a polymer resin having a temperature of at least
The cast coated paper for inkjet recording according to the above. [5] A coating liquid for casting is applied to form a coating layer for casting, and while the coating layer for casting is in a wet state,
The cast coated paper for ink jet recording according to [1], [2], [3] or [4], which is a coated paper for ink jet recording by a wet cast method, which is pressed against a heated mirror-surface drum, dried and finished. paper.

[6] The metal salt selected from zinc, aluminum, magnesium and calcium is sulfate, nitrate, acetate or formate [1], [2],
The cast coated paper for inkjet recording according to [3], [4] or [5]. [7] The inkjet recording method according to [1], [2], [3], [4] or [5], wherein the metal salt is selected from zinc sulfate, calcium sulfate, magnesium sulfate, calcium formate and calcium acetate. Cast coated paper. [8] The coating layer for casting, based on 100 parts by weight of the polymer resin (and the total amount of the pigment when containing a pigment),
[1], [2], containing 0.1 to 5 parts by weight of a metal salt
The cast coated paper for inkjet recording according to [3], [4], [5], [6] or [7].

[0010]

[9] On a base paper having a coating layer mainly composed of a pigment and an adhesive on the base paper, a glass transition point of 40
° C. or more as a main component, and zinc, magnesium, or a coating agent for casting containing at least one kind of a metal salt composed of calcium as an auxiliary to form a coating layer for casting, A method for producing a cast coated paper for ink-jet recording, characterized in that the cast coated layer is pressed against a heated mirror drum and dried to finish while the cast coated layer is in a wet state.

The metal coated with zinc, magnesium, or calcium is preferably a water-soluble metal salt. The cast coated paper for inkjet recording according to any one of the above [1] to [8], It is preferable in terms of the effects of the present invention.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A coating composition containing a polymer resin and a specific salt is coated, and while the coating composition is in a wet plasticized state, it is pressed against a heated mirror drum and cast. By finishing, it was found that a cast coated paper having both the excellent gloss desired by the present inventors and the suitability for ink jet recording (printing) was obtained, and the present invention was completed.

The polymer resin used as the coating composition for casting includes conjugated diene latex such as styrene-butadiene copolymer, styrene-acrylate copolymer, and styrene-methacrylate copolymer. , An acrylic polymer latex such as an acrylate polymer and a methacrylate copolymer, and a polyurethane resin. A styrene-acrylic acid ester copolymer is preferably used from the viewpoint of good releasability at the time of casting. Further, the styrene-acrylate copolymer is further polymerized in the presence of colloidal silica at the time of polymerization, and is used in the form of a complex formed by Si-OR (R: polymer component) bonds, which is more favorable. High releasability can be obtained. As described above, a pigment such as colloidal silica can be added to the coating composition for casting as long as the effects of the present invention are not impaired. The pigment is polymer resin 100
It is adjusted to about 200 parts by weight or less based on parts by weight.

The above polymer resin has a glass transition point of 40
C. or higher, and the glass transition point can be adjusted by the monomer composition. That is, in the production of conventional cast coated papers generally used for printing and the like, in order to obtain excellent surface gloss, when performing a cast finish, the resin component in the coating composition is sufficiently formed into a film, High gloss was obtained. However, in such a method, the porosity of the surface of the cast coating layer tends to decrease, and as a result, the absorbability of the ink during inkjet recording may decrease. Therefore, in a preferred embodiment of the present invention, by using a polymer resin having a high glass transition point and performing a cast finish in a state where the copolymer composition does not completely form a film, more excellent ink absorbency Is obtained.

Next, in the present invention, one of the important requirements is to obtain desired characteristics as product quality.
The metal salt will be described. The above-mentioned cast polymer resin generally has many anionic properties, and the dye used in the inkjet ink also has anionic property, so the cast coating layer cannot fix the dye. Therefore, the dye passes through the cast coating layer and is fixed in the undercoating layer mainly composed of a pigment and an adhesive described later. For this reason, the ink jet image can be seen through the cast coating layer with the dye formed in the undercoat layer, and the print density is lower than in the case of using only the undercoat layer.

However, in the present invention, by adding a metal salt to the cast coating composition, the dye of the inkjet ink can be fixed in the cast coating layer,
As a result, the print density can be significantly improved. Further, these metal salts accelerate the immobilization of the paint by being heated at the time of cast finishing, and the viscosity increases even if the solid content of the coating liquid is relatively low. For this reason, the coating liquid for casting hardly permeates the undercoat layer. As a result, the porosity and opacity of the undercoat layer are not hindered, and the cast coating layer itself is also porous, so that the ink absorption is improved,
In addition, it can be estimated that the print density becomes higher.

As the metal salts used in the present invention, at least one metal salt selected from the group consisting of zinc, magnesium and calcium is used. Specific examples of metal salts include sulfate, nitrate, acetate and formate. Preferably, it is a water-soluble metal salt. Particularly, zinc sulfate, calcium sulfate, magnesium sulfate, calcium formate, calcium acetate and the like are preferably used. The amount of addition of these metal salts is 100% of the above-mentioned polymer resin (in the case of including a pigment such as colloidal silica, the total amount of the pigment)
It is adjusted in the range of 0.1 to 5 parts by weight with respect to parts by weight. By the way, if the amount is too small, a sufficient effect of improving the print density and the effect of improving the ink absorbency cannot be obtained.

In order to control the whiteness, viscosity, fluidity, etc. of the coating composition for casting, dispersants and thickeners used in general printing coated paper and ink jet recording paper are used. Various auxiliaries such as a defoaming agent, a coloring agent, an antistatic agent and a preservative can be added as appropriate.

The coating composition used in the undercoat layer contains a pigment and an adhesive. As such a pigment, for example, kaolin, clay, calcined kaolin, amorphous silica, zinc oxide, aluminum hydroxide, aluminum oxide, zeolite, hydrotalcite, hectorite, calcium carbonate generally used in the coated paper manufacturing field , Satin white, aluminum silicate, magnesium silicate, magnesium carbonate, plastic pigment and the like can be used as appropriate. Among them, amorphous silica and aluminum oxide are preferably used.

Examples of the adhesive include proteins such as casein, soybean protein, and synthetic protein; various starches such as starch and oxidized starch;
Polyvinyl alcohol, 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, vinyl such as ethylene-vinyl acetate copolymer Conventionally known adhesives generally used for coated paper, such as a polymer latex, may be used alone or in combination of two or more. The amount of the adhesive was 1 pigment.
About 5 to 50 parts by weight, preferably 1 to 100 parts by weight
It is adjusted in the range of 0 to 30 parts by weight.

A cationic resin may be added to the undercoat layer. As a result, the water resistance of the recorded image and the print color density can be improved. Examples of the cationic resin include polyalkylene polyamines such as polyethylene polyamine and polypropylene polyamine, or derivatives thereof, acrylic resins having a tertiary amino group and a quaternary ammonium group, and diacrylamine. The addition amount of the cationic resin is not limited, but is adjusted in the range of 1 to 30 parts by weight, preferably 5 to 20 parts by weight, based on 100 parts by weight of the pigment. In addition, various auxiliaries such as a dispersant, a thickener, an antifoaming agent, a coloring agent, an antistatic agent, and a preservative used in the production of general coated paper can also be appropriately added.

The undercoat coating layer composition composed of the above-mentioned materials is generally adjusted to have a solid content of about 1 to 65% by weight, and has a base paper of about 20 to 400 g / m ² in base weight. ^{2 to} 30 g / m ² by dry weight, preferably 4 to
Blade coater so that the order of 10 g / m ^2, an air knife coater, roll coater, brush coater,
Coating and drying are performed by various known and publicly used coating devices such as a champlex coater, bar coater, and gravure coater. Further, if necessary, a smoothing treatment such as super calendering, brushing, or cast finishing can be performed after the undercoat layer is dried.

The base paper serving as the support is not particularly limited, and may be an acidic paper, a neutral paper, a synthetic paper, a porous film having air permeability, etc., used for general coated paper. Is appropriately used. On the coated surface of the undercoated paper thus obtained, a cast coating liquid comprising the specific polymer composition described above, a blade coater, an air knife coater, a roll coater, a brush coater, a champlex coater, a bar coater, Coating is performed by various known coating devices such as a gravure coater, and while the coating layer is in a wet state as described above, it is pressed against a heated mirror-surface drum and dried to perform a cast finish. The coating amount of the cast coating liquid in this case is 0.2 to
30 g / m ^2, preferably from 3 to 10 g / m ^2.
In the wet method among the casting methods, particularly excellent recording properties can be obtained.

[0024]

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 High-purity alumina (AKP-G01 manufactured by Sumitomo Chemical Co., Ltd.) was used as a pigment.
5) 100 parts, polyvinyl alcohol 1 as an adhesive
5 parts, dicyandiamide resin as a cationic resin (trade name: Neofix FY / Nichika Chemical Co., Ltd.)
10 parts) and 0.5 parts of sodium polyphosphate as a dispersant were added to prepare an undercoating coating liquid having a solid content of 18%. This undercoating coating liquid was applied to a base paper of 100 g / m ² of rice tsubo with a dry weight of 8 g / m ² by an air knife coater and dried to obtain a base paper. On the other hand, styrene-2 having a glass transition point of 80 ° C. was used as a cast coating liquid.
Composite of methylhexyl acrylate copolymer and colloidal silica (Movinyl 8050 manufactured by Hoechst) 10
A casting coating liquid having a solid content concentration of 30%, comprising 0 parts, 1 part of calcium stearate as a release agent, 1 part of carboxymethyl cellulose as a thickener, and 1 part of zinc sulfate as a metal salt was prepared. After this coating liquid was applied on the base paper using a roll coater, the coating liquid was immediately pressed against a mirror drum having a surface temperature of 85 ° C., dried, and released from the mold.
A cast coated paper for inkjet recording was obtained. The coating amount at this time was 7 g / m ² in terms of solid content weight.

Example 2 A cast coated paper for ink jet recording was obtained in the same manner as in Example 1, except that 1 part of zinc sulfate in the cast coating liquid was changed to 1 part of calcium acetate. The coating amount at this time was 6 g / m ² in terms of solid content weight. Example 3 A cast coated paper for ink jet recording was obtained in the same manner as in Example 1, except that 1 part of zinc sulfate in the cast coating liquid was changed to 1 part of zinc formate. The coating amount at this time was 6 g / m ² in terms of solid content weight.

Example 4 A solid content consisting of 100 parts of a styrene-methyl methacrylate copolymer having a glass transition point of 50 ° C. as a cast coating liquid, 2 parts of ammonium oleate as a release agent, and 3 parts of zinc sulfate as a metal salt. A coating solution for casting having a concentration of 25% was prepared. This coating liquid was applied onto the base paper obtained in Example 1 using a roll coater, immediately pressed against a mirror drum having a surface temperature of 60 ° C., dried, and released.
A cast coated paper for inkjet recording was obtained. The coating amount at this time was 4 g / m ² in terms of solid content weight.

Example 5 100 parts of a polyurethane emulsion having a glass transition point of 70 ° C. as a cast coating liquid, 1 part of ammonium oleate as a release agent, 5 parts of casein dissolved with ammonia as a thickener, and zinc sulfate as a metal salt 4 parts were added to prepare a coating liquid for casting having a solid concentration of 40%. This coating liquid was coated on the base paper obtained in Example 1 using a roll coater, immediately pressed against a heated mirror-surface drum having a surface temperature of 65 ° C., dried, released, and used for inkjet recording. A cast coated paper was obtained. The coating amount at this time was 6 g / m ² in terms of solid content weight.

Example 6 As a pigment of a coating liquid for undercoat, 100 parts of amorphous silica were used.
13 parts of polyvinyl alcohol as adhesive, cationic
Diacrylamine acrylamide resin (trademark)
Product name: Sumireze Resin 1001 / Sumitomo Chemical Co., Ltd.
15 parts) and 0.3 parts of sodium polyphosphate as a dispersant.
To prepare an undercoating coating solution having a solid content of 30%.
This coating solution was prepared by adding 80 g / m^TwoBy dry weight on base paper
6g / m ^TwoCoat with a blade coater and dry
After drying, a base paper was obtained. Example 1 on this base paper
Apply the coating liquid for casting used in Step 1.
A cast coated paper for inkjet recording was obtained by the method. this
The amount of coating at the time is 5 g / m^TwoMet.

Comparative Example 1 A cast coated paper for ink jet recording was obtained in the same manner as in Example 1 except that zinc sulfate was not added. Comparative Example 2 100 parts kaolin, casein 10 as a cast coating liquid
Parts, a methyl methacrylate-butadiene copolymer having a glass transition point of 0 ° C., 13 parts of ammonium oleate as a mold release agent, and a solid coating concentration of 45%. Immediately after coating on the base paper using a roll coater, it was pressed against a mirror-surface drum having a surface temperature of 85 ° C., dried, and released to obtain a cast coated paper for inkjet recording. The coating amount at this time was 12 g / m ² in terms of solid content weight.

Comparative Example 3 A cast coated paper for ink jet recording was obtained in the same manner as in Example 1 except that zinc sulphate was replaced with sodium oxalate. Comparative Example 4 A cast coated paper for inkjet recording was obtained in the same manner as in Example 1, except that zinc sulphate was replaced with potassium oxalate.

Table 1 summarizes the results of the glossiness of white paper, suitability for ink jet recording, and operability of the cast coated paper thus obtained. In addition, about the said evaluation, evaluation was performed by the following methods. (White paper gloss) Measured according to JIS-P8142. (Absorptivity of Ink for Inkjet Recording) Printing was performed with a color image jet IO-735X (inkjet recording apparatus) manufactured by Sharp Corporation, and the drying property of the ink was visually evaluated. ：: No stain at all even if touched with a finger immediately after printing. ：: Slightly soiled when touched with a finger immediately after printing, but almost dry. Δ: Immediately after printing, the ink portion slightly glows, but there is no practical problem. ×: Due to poor drying of the ink, the ink flowed during printing and was not practical.

(Printing Color Development of Inkjet Recording Ink after Recording) Printing was performed with a color image jet IO-735X manufactured by Sharp Corporation, and the density of the ink was visually evaluated. A: Print density is good. ：: The color density is slightly low, but there is no practical problem. ×: The coloring density is too low to be practical. (Cast operability) A: Continuous operation for one day or more is possible without any problem. ○: Operation is possible for the time being, but demolding is slightly inferior.
It is a continuous operation for less than a day. ×: Inoperable due to poor mold release (drum picking and sticking).

[0034]

[Table 1]

[0035]

As is clear from the results shown in Table 1, the cast coated paper of the present invention was excellent in surface glossiness and ink jet recording suitability, and could be produced efficiently. The present invention was excellent in ink jet printability such as print density and ink absorbency in ink jet.

Claims (4)

[Claims] 1. A base paper is provided with a coating layer containing a pigment and an adhesive, and further coated with a coating liquid containing a polymer resin and at least one metal salt selected from zinc, aluminum, magnesium and calcium. A cast coated layer for ink jet recording, comprising forming a coated layer for casting by pressing, and pressing the coated layer for coating onto a heated mirror drum, followed by drying. 2. The cast coated paper for ink jet recording according to claim 1, wherein the metal salt is at least one selected from sulfate, nitrate, acetate and formate. 3. The metal salt is a water-soluble metal salt.
Or the cast coated paper for inkjet recording according to 2. 4. The cast coated paper for ink-jet recording according to claim 1, wherein the polymer resin is a copolymer of styrene and acrylate.