JP2003260862A - Ink jet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recording medium which has outstanding ink absorption capacity, high ink absorption rate, superb glossiness and is free from a feathering phenomenon or surface cracks after printing. <P>SOLUTION: A silica-encapsulated hybrid emulsion which is an aqueous dispersion composed of a silica superparticle, especially a particle of a core/shell structure obtained by bonding a vinylic polymer to the surface of a colloidal silica particle, stably dispersed in an aqueous medium, is added to an ink receiving layer. In addition, an undercoat layer composed mainly of silica used together with a gas phase silica or a colloidal silica is formed between a support and the ink receiving layer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording medium, which is excellent in ink absorption capacity and ink absorption speed, has no bleeding after printing and has no surface cracks, and has high glossiness.

[0002]

2. Description of the Related Art The ink jet recording system is a technique in which minute droplets of ink are ejected according to various operating principles and adhered to recording paper such as paper to record images and characters. Recording devices using this technology operate rapidly and at low noise, and because they do not require image forming processing using chemicals such as development and fixing, they have rapidly spread in various applications. There is. In particular, recently, with the spread of computers and digital cameras, an image similar to a silver halide photograph has been demanded, and ink jet recording paper is required to have high color developability, resolution, color reproducibility and gloss. There is.

On the other hand, in the field of full-color recording, a printer using a so-called dye-based ink in which a dye having excellent color developability is dissolved in a solvent is mainstream, whereas a printer using a so-called pigment-based ink is light-resistant. Due to its excellent properties and water resistance, it has come to be used for posters and printing proofs. Large-format recording media such as posters are required to have image quality close to that of silver salt photographs, and for applications such as proofing of printing, those that are close to the gloss of general coated paper are required. There is a need for an inkjet recording medium having the same.

By the way, in the pigment-based ink, since the pigment, which is a coloring material, has a specific size, it does not have a dyeing property on the surface of the recording medium like a dye, and the coloring material is a surface layer portion of the recording medium. Difficult to stay in In order to improve the fixability, if the ink absorbency is increased and the coloring material is deeply penetrated into the paper, the color developability is poor, and the ink solvent overflows in the recording medium that emphasizes color developability, and sufficient absorbency can be obtained. Without high-speed printing. Inkjet recording using a pigment-based ink as described above has a problem that color reproducibility is inferior because color development and ink absorption cannot be achieved at the same time.

When the precipitation-type silica or gel-type silica, which has been used as a recording medium for dyes, is used, the particle size of the silica is larger than that of the coloring material of the pigment ink. There was a problem that the image permeated and the image looked whitish. Further, there is a problem that it is difficult to obtain the required high gloss because of the large particle size.

As a method for obtaining a high-gloss ink jet recording medium, the use of vapor phase silica is disclosed in Japanese Patent Publication No. 3-56.
No. 552, JP-A-10-81064, JP-A-11-48602, and JP-A-11-58938. Vapor phase silica is also called dry method silica or fumed silica as opposed to the wet method, and is generally made by flame hydrolysis. Specifically, a method of burning silicon tetrachloride with hydrogen and oxygen is generally known. However, instead of silicon tetrachloride, silanes such as methyltrichlorosilane and trichlorosilane may be used alone or in the form of silicon tetrachloride. It can be used as a mixture with. However, when vapor phase silica is used, the primary particles are present in a state of network structure or chain-like structure and secondarily aggregated, which increases voids per unit volume and improves ink absorption capacity. However, it has drawbacks such as lack of film strength and lack of gloss on the surface of the film due to its lack of binding force.

As a method for obtaining a high-gloss ink jet recording medium, a technique using colloidal silica is
JP-A-8-67064 and JP-A-8-207423.
JP-A-8-267907, JP-A-11-
It is disclosed in Japanese Patent No. 58938. In addition, JP 20
JP-A-00-37944 discloses an inkjet recording medium having a layer containing vapor grown silica and a layer containing colloidal silica in this order from the side closer to the support. Colloidal silica is a synthetic silica having a primary particle diameter of about several nm to 100 nm synthesized by a wet method.

Colloidal silica has more isolated primary particles than vapor-phase method silica, and when a coating film is formed, the particles are present in a dense state. Therefore, the ink fixing efficiency that affects the ink fixing property and the color forming property is good, and the close clogging causes the good scratch resistance. However, colloidal silica has a small amount of voids, and the ink absorption capacity is inferior to that of vapor-phase method silica, and if the film thickness of the ink receiving layer is increased to secure the absorption capacity, cracks may occur in the film,
It has a drawback that the strength of the coating becomes weak. Further, when a binder is added, a problem is more likely to occur in the absorbability of the ink receiving layer, and when the binder is reduced, cracks are likely to occur in the recording layer.

[0009]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a high gloss ink jet recording medium which is excellent in ink absorption capacity and ink absorption speed and does not cause ink bleeding or cracking when printed by an ink jet printer. In particular, it is to provide an inkjet recording medium suitable for inkjet recording using a pigment ink.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a recording layer contains a silica-containing hybrid emulsion in which the surface of colloidal silica is coated with a vinyl polymer. By doing so, even if the film thickness of the ink receiving layer is increased, cracking does not occur, the film strength of the layer does not decrease, ink absorption capacity and ink absorption speed are excellent, and a high-gloss inkjet that does not bleed after printing It has been found that a recording medium can be obtained.
Further, when further improvement in ink absorption capacity, ink absorption rate and bleeding after printing is desired, it is effective to use a vapor phase method silica in combination, and in order to further improve glossiness and surface strength, colloidal silica is used in combination. As a result, they have found that it is effective to use the above, and have completed the present invention.

[0011]

The support used in the present invention is not particularly limited and may be transparent or opaque. For example, plastic films such as cellophane, polyethylene, polypropylene, soft polyvinyl chloride, hard polyvinyl chloride, polyester, fine paper, photographic paper base paper, drawing paper, art paper, coated paper, cast coated paper,
Examples include kraft paper, impregnated paper, synthetic paper, and the like, which can be appropriately used depending on the application. In particular, it is desirable to use a support having excellent ink absorbency.

The silica-containing hybrid emulsion referred to in the present invention is an aqueous dispersion in which particles of a core / shell structure in which a vinyl polymer is bonded to the surface of silica super particles, particularly colloidal silica particles, are stably dispersed in an aqueous medium. It is the body. The manufacturing method is disclosed in JP-A-59-71316, JP-A-63-37168, JP-A-9-71316, JP-A-9-194208, and JP-A-11-20.
It is disclosed in Japanese Patent No. 9622 and Japanese Patent Laid-Open No. 2000-290464. A preferred method for producing a silica-containing hybrid emulsion used in the present invention is disclosed in Japanese Patent Laid-Open No. Hei 11
No. 209622 and Japanese Patent Application Laid-Open No. 2000-290464, the surface of the colloidal silica is coated with a vinyl polymer without using a silane monomer to form a shell. Those whose molecules are acrylic polymers are preferred.

As an example of the production method, a cationic radical polymerization initiator is adsorbed on the surface of colloidal silica particles in an aqueous solvent in the presence of a nonionic surfactant,
Methyl methacrylate / n-butyl acrylate / methacrylic acid is used as a monomer having a vinyl bond in a weight ratio of 4
It can be obtained by polymerizing or copolymerizing by a conventionally known emulsion polymerization method using 9/50/1 at a weight ratio of about 1: 1 with colloidal silica. The particle size of the colloidal silica is 5 nm to 1 μm, preferably 10 to 100 nm, and the particle size of the hybrid emulsion after polymer coating is 10 to 1
The thickness is preferably 50 to 200 nm in μm, and the polymer / silica weight ratio is preferably 100/50 to 100/150.

In the present invention, the ink receiving layer contains a known white pigment in addition to the silica-containing hybrid emulsion.
You may contain 1 or more types. For example, light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate,
Diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, colloidal alumina, boehmite, pseudoboehmite, aluminum hydroxide,
Alumina, lithopone, zeolite, hydrohaloysite,
White inorganic pigments such as magnesium carbonate and magnesium hydroxide, organic white pigments such as styrene plastic pigments, acrylic plastic pigments, polyethylene, microcapsules, urea resins and melamine resins can be used.

The silica-encapsulated hybrid emulsion alone is excellent in print density, glossiness, ink absorption, surface strength, etc., but when higher color density or ink absorption is required, it is preferable to mix vapor phase method silica. When high gloss and surface strength are required, it is preferably mixed with colloidal silica.

In the former case, the ratio of silica-containing hybrid emulsion / gas phase method silica is 100/0 to 20/8.
The case of 0 is preferable. If the content of the silica-containing hybrid emulsion is less than 20%, the film strength may not be obtained, or the gloss of the film surface may be significantly reduced. Vapor phase silica is commercially available from Nippon Aerosil Co., Ltd. as Aerosil series and Tokuyama Co., Ltd. as Reorosil series, and is easily available.

In the latter case, the silica-containing hybrid emulsion / colloidal silica ratio is 100/0 to 20.
The case of / 80 is preferable. If the content of the silica-containing hybrid emulsion is less than 20%, problems such as cracking of the coating film and reduction of coating strength occur. Colloidal silica is commercially available from Nissan Chemical Industries, Ltd. as the Snowtex series, Catalytic Chemical Industry Co., Ltd. as the cataloid series, and is easily available.

The silica-encapsulated hybrid emulsion used in the ink jet recording medium of the present invention itself has a binding force, but a binder is used as necessary in order to maintain the characteristics as a coating film. You may. The binder is not particularly limited, for example, starch derivatives such as oxidized starch, etherified starch, phosphate esterified starch, cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, casein, gelatin, soybean protein, etc. Protein, polyvinyl alcohol, polyvinylpyrrolidone, water-soluble resin such as maleic anhydride resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, vinyl chloride-vinyl acetate copolymer, etc. Combined latex, acrylic copolymer latex such as polymers or copolymers of acrylic acid ester and methacrylic acid ester, vinyl copolymer latex such as ethylene-vinyl acetate copolymer, or various copolymers thereof. Functional group-containing, such as carboxy groups of the body monomer by functionally modified copolymer latex, melamine resin,
A water-based adhesive such as a thermosetting synthetic resin such as a urea resin, a polyurethane resin, an unsaturated polyester resin, a polyvinyl butyral, an alkyd resin latex and the like can be mentioned.

In the present invention, at least one of these binders may be used, but the compounding amount thereof is preferably 0 to 50 parts by weight based on 100 parts by weight of the above-mentioned pigment, It is more preferably 0 to 30 parts by weight. If the amount of the binder used is 50 parts by weight or more, the ink absorbency becomes insufficient.

Further, in an ink jet recording system using a dye ink, in order to fix the ink and impart print density and water resistance of the print, it is desirable to contain a metal salt or a cationic compound in addition to the above. . The cationic compound in this case is not particularly limited, and forms a salt insoluble with the sulfonic acid group, carbosyl group, etc. in the water-soluble direct dye or water-soluble acid dye contained in the aqueous dye ink. It is a so-called dye fixing agent containing a secondary amine, a tertiary amine or a quaternary ammonium salt. You may use a cationic compound individually or in combination of 3 or more types.

The coating amount of the ink receiving layer can be determined on the basis of the ink absorption capacity of the ink receiving layer and the adhesive strength between the recording layer and the support that can be practically used.
Dry coating amount is preferably in the range of 3~40g / m ^2, when less than 3 g / m ^2, it is difficult to completely cover the underlying surface of the ink receiving layer, the ink by the coating layer Absorption unevenness occurs, which adversely affects inkjet printing performance. Further, when the dry coating amount exceeds 40 g / m ² , the adhesive strength between the ink receiving layer and the support becomes a level that cannot be practically used, and peeling of the coating layer from the support, which is called powder falling, occurs. However, serious problems arise. Therefore, it is particularly preferable that the coating amount is usually about 5 to ²⁰ g / m ² .

In the present invention, two or more ink receiving layers may be provided on the support. The constitution is not particularly limited, and for example, two or more ink receiving layers may be provided on one side or both sides of the support. In the present invention, it is also possible to provide a coating layer on the surface opposite to the one provided with the ink receiving layer for the purpose of curl correction or improvement of transportability.

Further, in order to improve the ink absorbency and image quality of the ink jet recording medium of the present invention, and especially when the coating amount of the ink receiving layer is small, an under layer is further provided between the ink receiving layer and the support. It is preferable to provide. Examples of pigments used in the under layer include synthetic silica, alumina and alumina hydrate (alumina sol, colloidal alumina, pseudo-boehmite, etc.), aluminum silicate, magnesium silicate, magnesium carbonate, light calcium carbonate, heavy calcium carbonate, kaolin, talc, sulfuric acid. Not only inorganic pigments such as calcium, titanium dioxide, zinc oxide, zinc carbonate, calcium silicate, and aluminum hydroxide, but also styrene plastic pigments, acrylic plastic pigments,
Organic white pigments such as urea resin can also be used.
Further, as the binder for the under layer, the same binder as used for the above-mentioned ink receiving layer is preferably used.

Further, in order to further improve the glossiness of the ink jet recording medium of the present invention, an over layer may be provided on the ink receiving layer as needed. As the pigment and the binder that can be used in the over layer, all that can be used in the under layer can be used.

Further, in the ink jet recording medium of the present invention, a pigment dispersant, a thickener, a fluidity improver, a defoaming agent, and a support, an ink receiving layer, an under layer and an over layer may be added, if necessary. Foam suppressor, release agent, foaming agent, penetrant, coloring dye, coloring pigment, fluorescent dye, ultraviolet absorber, antioxidant,
Preservatives, antifungal agents, water resistance agents, surfactants, wet paper strength enhancers, dry paper strength enhancers and the like can be appropriately added as long as the effects of the invention are not impaired.

In the apparatus for coating or impregnating the coating composition for forming the ink receiving layer in the present invention, various blade coaters, roll coaters, air knife coaters, bar coaters, gate roll coaters, curtain coaters,
Various devices such as a die coater, a short dwell coater, a gravure coater, a flexo gravure coater, a spray coater, and a size press can be used on-machine or off-machine. In the present invention,
Machine calendar before or after coating each layer,
It is also possible to perform surface treatment with a calendar device such as a super calendar or a soft calendar.

[0027]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In addition, “part” and “%” shown in the examples
Indicates parts by weight and% by weight unless otherwise specified.

Example 1 Base paper 90% of hardwood bleached kraft pulp and 10% of softwood bleached kraft pulp were mixed and beaten to prepare pulp having a freeness of 350 ml, 4 parts of cationized starch and 0 of anionized polyacrylamide. 3 parts and 0.5 part of an alkyl ketene dimer emulsion were added, and a web was formed with a Fourdrinier paper machine. After press-drying this paper web, a liquid of 5% phosphoric esterified starch and 0.5% polyvinyl alcohol was applied using a size press so that the dry weight was 3.6 g / m ^2, and after drying it was machine calendered. Treated to 100 g basis weight
A base paper of / m ² was produced.

The under layer synthetic amorphous silica (Fine Seal X-37B (Ltd.)
Tokuyama made 100 parts, polyvinyl alcohol (PVA
-117, made by Kuraray) 40 parts, styrene butadiene latex (LX438C made by Zeon Corporation) 5 parts, cationic sizing resin (Polymaron 360 made by Arakawa Chemical Industries)
A dye fixing agent and an antifoaming agent are added to 2 parts to form a coating material having a solid content of 20%, and this coating solution is applied with a bar blade coater to a coating amount of 12 g / m ² and then applied. It was dried until the water content of the entire paper was 5.0% to obtain a base paper having an under layer.

Ink Receiving Layer On the base paper coated with the under layer prepared above, a silica-containing hybrid emulsion (manufactured by Mizutani Paint, polymer / silica ratio 100/85, nonvolatile content about 50%, minimum film forming temperature 5 ° C.) Below) 100 parts, polyvinyl alcohol (PVA-117, manufactured by Kuraray), and a coating liquid having a solid content concentration of 25% by adding dilution water to a coating amount of 6 g / m ² using a bar blade coater. To obtain a first ink-receiving layer. Next, as a second ink receiving layer, the above coating liquid was applied using a bar blade coater to a coating amount of 6 g / m ^2, and dried until the water content became 5.0%. An ink jet recording medium was obtained by performing a finishing surface treatment with a soft calendar device under a linear pressure of 100 kg / cm.

Example 2 Ink Receiving Layer The pigment composition of the ink receiving layer was a silica-containing hybrid emulsion (manufactured by Mizutani Paint Co., Ltd., polymer / silica ratio 1).
00/85, non-volatile content of about 50%, minimum film forming temperature of 5 ° C. or less) 25 parts, and the same procedure as in Example 1 except that 75 parts of vapor phase silica (Aerosil 50, manufactured by Nippon Aerosil) was used. A recording medium was obtained. <Example 3> Ink receiving layer The pigment composition of the ink receiving layer was a silica-containing hybrid emulsion (manufactured by Mizutani Paint Co., Ltd., polymer / silica ratio 1).
00/85, non-volatile content about 50%, minimum film formation temperature 5 ° C or less 25 parts, colloidal silica (Snowtex PS-
L, manufactured by Nissan Chemical Industries, Ltd.) Example 1 except that 75 parts
An inkjet recording medium was obtained in exactly the same manner as.

Example 4 Ink Receiving Layer The pigment composition of the ink receiving layer was a silica-containing hybrid emulsion (manufactured by Mizutani Paint Co., Ltd., polymer / silica ratio 1).
00/85, non-volatile content of about 50%, minimum film forming temperature of 5 ° C. or lower) 70 parts, and vapor-phase process silica (Aerosil 50, manufactured by Nippon Aerosil) 30 parts in the same manner as in Example 1 except that ink jet was used. A recording medium was obtained. <Example 5> Ink receiving layer The pigment composition of the ink receiving layer was a silica-containing hybrid emulsion (manufactured by Mizutani Paint Co., Ltd., polymer / silica ratio 1).
00/85, non-volatile content about 50%, minimum film formation temperature 5 ° C or less 40 parts, vapor phase silica (Aerosil 50, manufactured by Nippon Aerosil) 30 parts, colloidal silica (Snowtex PS-L, manufactured by Nissan Chemical Industries) An inkjet recording medium was obtained in exactly the same manner as in Example 1 except that the amount was 30 parts.

Comparative Example 1 Ink Receiving Layer On the base paper coated with the under layer produced in Example 1, vapor phase method silica (Aerosil 50, Nippon Aerosil) 100
Parts and 8 parts of polyvinyl alcohol (PVA-117, manufactured by Kuraray Co., Ltd.) were mixed to prepare a coating material having a solid content of 25%, and an inkjet recording medium was obtained in exactly the same manner as in Example 1. <Comparative Example 2> Ink receiving layer 100 parts of colloidal silica (Snowtex PS-L, manufactured by Nissan Chemical Industries) and polyvinyl alcohol (PVA-11) were applied to the base paper coated with the under layer prepared in Example 1.
An ink jet recording medium was obtained in exactly the same manner as in Example 1 except that 8 parts (7, made by Kuraray Co., Ltd.) were mixed to form a coating material having a solid content of 25%.

Evaluation items <Color development> Solid images of black, cyan, magenta, and yellow were printed using a pigment ink jet printer MC-2000 manufactured by Seiko Epson Corporation, and after leaving for one day, each image part was printed. The print density was measured with a reflection densitometer (MACHBETH RD914), and evaluated by the sum of the obtained measurement values. ⊚: The total of four colors is 8.0 or more. ◯: The total of four colors is 7.5 or more and less than 8.0. Δ: The total of four colors is 7.0 or more and less than 7.5. X: The total of four colors is less than 7.0.

<White paper glossiness> The 75 ° specular glossiness of the coated paper was measured by a Murakami Color Research Laboratory specular glossiness meter (GM-26 for 75 °) in accordance with JIS-P-8142. A: 75 ° specular gloss is 60% or more. ◯: 75 ° specular gloss is 50% or more and less than 60%. Δ: 75 ° specular gloss is 40% or more and less than 50%. X: 75 ° specular gloss is less than 40%.

<Ink Absorption> The solid images of the respective colors were printed side by side, and the degree of bleeding at the boundary was evaluated. ⊚: No bleeding is observed. ○: Some bleeding is observed. Δ: Bleeding is recognized. X: Bleeding is noticeable.

<Coating layer strength> 18 m wide on the recording surface of coated paper
m cellophane tape was affixed, rubbed strongly with a rubber roller 20 times, the end was fixed to a digital force gauge (FGX-2) manufactured by Nidec Shinpo Co., Ltd., and the strength of the coating layer in the direction of 180 ° was measured, The following criteria evaluated. A: The measured value is 900 gf or more. ◯: The measured value is 700 gf or more and less than 900 gf. Δ: The measured value is 500 gf or more and less than 700 gf. X: The measured value is less than 500 gf.

<Surface Crack> The image-printed portion was observed with a microscope, and the degree of cracking was evaluated. A: No crack is observed. ◯: A small number of independent cracks are observed, but it does not affect printing. Δ: Independent cracks are observed and the print density is slightly reduced. X: A plurality of cracks are continuously observed, and the print density is significantly reduced. The evaluation results are as shown in Table 1.

[0039]

[Table 1]

[0040]

From Table 1, the ink jet recording medium produced in Example 1 has good color density, white paper gloss, coating layer strength, and surface cracking. Furthermore, from Example 2, the addition of vapor phase silica improves the color density and ink absorbency, and from Example 3 the addition of colloidal silica improves the color density and the glossiness of white paper. I understand. In Example 4, the surface cracking was improved, and also in the ink jet recording medium produced by mixing the silica-encapsulating hybrid emulsion with the vapor phase method silica and colloidal silica as in Example 5, the color density, the white paper gloss,
A well-balanced inkjet recording medium is obtained with particularly excellent surface strength and surface cracking. On the other hand, in Comparative Example 1, the surface strength is poor, and the color density and the glossiness of the white paper are insufficient. Further, in Comparative Example 2, the ink absorption was insufficient and many cracks were observed on the surface of the paper surface, which is not suitable as an inkjet recording medium. These drawbacks can be greatly improved by using together with the silica-containing hybrid emulsion. As is clear from the above,
According to the method of the present invention, an ink jet recording medium which is excellent in ink absorption capacity, ink absorption speed and glossiness and has no bleeding after printing and surface cracking can be obtained.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenbun Tanaka             5-21-1 Oji, Kita-ku, Tokyo Nippon Paper Industries             Product Development Laboratory Co., Ltd. (72) Inventor Susumu Hagisawa             5-21-1 Oji, Kita-ku, Tokyo Nippon Paper Industries             Product Research Institute Co., Ltd. (72) Inventor Yoshihide Kimura             5-21-1 Oji, Kita-ku, Tokyo Nippon Paper Industries             Product Research Institute Co., Ltd. F-term (reference) 2C056 EA05 FB01 FC06                 2H086 BA12 BA15 BA33

Claims (5)

[Claims] 1. An inkjet recording medium having an ink receiving layer on a support, wherein the ink receiving layer contains a silica-containing hybrid emulsion. 2. The ink jet recording medium according to claim 1, wherein the ink receiving layer further contains fumed silica. 3. The ink jet recording medium according to claim 1 or 2, wherein the ink receiving layer further contains colloidal silica. 4. The ink jet recording medium according to claim 1, wherein an under layer mainly composed of silica is provided between the support and the ink receiving layer. 5. The inkjet recording medium according to claim 1, wherein the coating amount of the ink receiving layer is 3 g / m ² or more.