JP2001328346A - Water-based ink jet recording sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based ink jet recording sheet, which is excellent in the water resistance, color foring properties and absorbency of a water-based ink jet ink, with which a clear and high density image can be formed. SOLUTION: This water-based ink jet recording sheet is formed by having an ink accepting layer on a base material. The ink accepting layer consists of a resin and fine hydrophilic inorganic particles, which are dispersed in the resin and, in addition, covered with substance with anion trapping properties.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous ink jet recording sheet, and more particularly, to an aqueous ink jet recording sheet which is excellent in water resistance, color development and absorption of an aqueous ink jet ink and can form a clear and high density image. Regarding the sheet.

[0002]

2. Description of the Related Art An aqueous ink jet recording system in which an aqueous ink is directly jetted from a nozzle toward a recording sheet and adheres to the recording sheet to record an image, a character, or the like has a small noise at the time of recording and is easy to record a color image. It has various advantages such as high-speed recording, miniaturization of the recording device, and easy maintenance of the device. It has been widely used for printers for computer terminals, facsimile machines, plotters, form printing, and the like.

Conventionally, this aqueous ink jet recording sheet is typically prepared by applying an aqueous coating liquid mainly comprising a binder resin composed of a pigment such as fine powder silica and a water-soluble resin on a substrate sheet. The ink-receiving layer is prepared by dispersing the pigment in the resin and forming an ink receiving layer on the substrate (Japanese Patent Application Laid-Open No. 63-265680, Japanese Patent Publication No. 3-26665). Gazette).

On the other hand, aqueous ink-jet inks for color image recording use dyes, pigments or both as colorants as appropriate additives such as polyhydric alcohols for preventing nozzle clogging and improving discharge stability. And a water-soluble dispersing agent dissolved or dispersed in water, and blue,
The required color tone is expressed by overlapping four colors of red, yellow and black inks.

However, according to the ink jet recording sheet as described above, since the surface of the ink receiving layer is generally covered with a continuous resin layer, the water-based ink jet ink described above has a low absorbency and the ink has a low absorbency. The drying property is poor, and the water resistance and color development of the ink are not sufficient.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the conventional water-based ink jet recording sheet, and is intended to improve the water resistance, color development and absorptivity of the water-based ink-jet ink. It is an object of the present invention to provide an aqueous ink jet recording sheet capable of forming a clear, high-density image.

[0007]

According to the present invention, there is provided an ink receiving layer on a base material, the ink receiving layer comprising a resin and hydrophilic inorganic fine particles dispersed in the resin. An aqueous inkjet recording sheet is provided, wherein the inorganic fine particles are coated with a substance having an anion-capturing property.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the aqueous ink jet recording sheet according to the present invention, the ink receiving layer comprises a resin and hydrophilic inorganic fine particles dispersed in the resin, and the hydrophilic inorganic fine particles have a substance having an anion-capturing property. It is covered with.

The above resin functions as a binder, and when the ink receiving layer is formed on the base material, mainly absorbs the water in the aqueous inkjet ink,
It contributes to the absorbability of the ink jet ink.

In the present invention, an aqueous resin is used as such a resin. This water-based resin may be either a water-soluble resin or a water-insoluble resin. Specific examples of the water-soluble resin include, for example, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethylcellulose, hydroxyethylcellulose, casein, gelatin, starch, sodium alginate, polyethylene oxide, polyethylene oxide, polypropylene oxide copolymer, and the like. When forming the ink receiving layer, it is used as an aqueous solution.

On the other hand, as the water-insoluble resin, for example,
An acrylic resin, a urethane resin, a polyester resin, and the like can be given. These resins are used as an emulsion when forming the ink receiving layer.

According to the present invention, the ink receiving layer is formed by dispersing hydrophilic inorganic fine particles in the above resin, and the hydrophilic inorganic fine particles have a substance having an anion-capturing property (hereinafter referred to as an anion-capturing substance). It is characterized in that it is covered with.

In the present invention, the substance having an anion-capturing property (hereinafter referred to as an anion-capturing substance) refers to a substance having a water-soluble dye such as an acid dye or a direct dye widely used as a coloring agent of an aqueous inkjet ink. A substance that captures an anionic group such as a sulfonic acid group or a carboxyl group, and specific examples include, for example, a cationic substance such as a cationic resin or a cationic coupling agent, and a glycidyl group. Coupling agents having the same.

Examples of the cationic resin include homopolymers and copolymers of cationic monomers having primary to tertiary amino groups. Specific examples of such a monomer include, for example, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate,
Examples thereof include diethylaminoethyl acrylate, diethylaminoethyl methacrylate, methylethylaminoethyl acrylate, methylethylaminoethyl methacrylate, dimethylaminostyrene, diethylaminostyrene, and methylethylaminostyrene. Further, a homopolymer or a copolymer of a monomer having a quaternary ammonium base corresponding to the monomer having a tertiary amino group is also used as the cationic resin in the present invention.

Examples of the cationic coupling agent include a silane coupling agent having an amino group and a titanium coupling agent. Silane coupling agents having a preferred amino group used in the present invention, the general formula (I) in R _m -Si-Y _n (wherein, R is an alkoxyl group (preferably, methoxy or ethoxy group), m is 1 Represents an integer of from 3 to 3, and a part of the alkoxyl group may be an alkyl group (preferably a methyl group or an ethyl group), and Y is an aminoalkyl group (preferably, the alkyl group has 1 to 5 carbon atoms). ), N represents an integer of 1 to 3, and the nitrogen atom of this aminoalkyl group may be further substituted with an aminoalkyl group or a hydroxyalkyl group, provided that m + n = 4.

As specific examples of such a silane coupling agent having an amino group, for example, specific examples of a silane coupling agent having an amino group include γ-aminopropyltrimethoxysilane and γ-aminopropyltrimethoxysilane. Ethoxysilane, N-β- (aminoethyl) γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ
-[Bis (β-hydroxyethyl)]-aminopropyltriethoxysilane and the like, but are not limited thereto.

The same applies to the titanium coupling agent in which a silicon atom is replaced by a titanium atom in the above formula.

A coupling agent having a glycidyl group is also
The sulfonic acid group and the carboxyl group can be effectively captured by the reaction with the glycidyl group. Specific examples of such a silane coupling agent having a glycidyl group include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, and the like.

In the present invention, the hydrophilic inorganic fine particles assist the ink absorption of the resin when the ink-jet ink adheres to the ink-jet recording sheet.
It mainly adsorbs colorant components such as dyes and pigments in the inkjet ink, thereby contributing to the coloring and fixing properties of the ink, and further imparts water resistance to an image formed by the aqueous inkjet ink due to its anion trapping property.

When the average particle size of the hydrophilic inorganic fine particles coated on the surface with such an anion-trapping substance is larger than 1 μm, such hydrophilic inorganic fine particles are mixed with the resin composition particles, Even if the surface of the particles is coated, it is difficult to uniformly coat the resin composition particles, and the ratio of the surface that is not coated with the hydrophilic inorganic fine particles coated with the anion-trapping substance increases. As a result, the resin composition particles do not have sufficient anion-capturing properties, so that images and characters on a recording sheet formed by the aqueous inkjet ink are inferior in water resistance, and the ink has poor color developability.

As such hydrophilic inorganic fine particles having an average particle diameter of 1 nm to 1 μm, anhydrous silica, alumina, titanium dioxide, calcium carbonate and the like are preferably used. Such hydrophilic inorganic fine particles can be easily obtained as a commercial product. Specific examples of commercially available products include, for example, Aerosil (registered trademark) 50, 90G, 130, 200, 200 V, and 2 V, which are anhydrous silica manufactured by Nippon Aerosil Co., Ltd.
00CF, 200FAD, 300, 300CF, 38
0, OX50, TT600, MOX80, MOX17
0, COK84, etc., prominent aluminum C, titanium dioxide P25, etc., anhydrous silica S manufactured by Clariant Japan
13, V15, N20, T30, T40 and the like.

According to the present invention, among these, they are produced by a gas phase method (dry method) and have a BET specific surface area of 40 to 50.
Anhydrous silica in the range of 0 m ² / g, that is, so-called fumed silica is particularly preferably used.
As is well known, the gas phase method is a method for producing anhydrous silica (silicon dioxide) by subjecting silicon tetrachloride to gas phase hydrolysis in an oxyhydrogen flame at a high temperature.

Such hydrophilic inorganic fine particles are made of resin 10
For 0 parts by weight, 50 to 180 parts by weight, preferably,
It is used in the range of 50 to 150 parts by weight. When the proportion of the hydrophilic inorganic fine particles in the ink receiving layer is less than 50 parts by weight per 100 parts by weight of the resin, the formed ink receiving layer still has insufficient water absorption, and therefore, such an ink receiving layer When the ink-jet ink adheres to the layer, the ink does not dry well and the ink-jet ink bleeds, so that a high quality recorded image is not provided. On the other hand, the ratio of the hydrophilic inorganic fine particles is 180 per 100 parts by weight of the resin.
When more than parts by weight, such an ink receiving layer is
The surface is easily cracked, and the obtained ink jet recording sheet is inferior in quality.

In particular, according to the present invention, the hydrophilic inorganic fine particles are mixed with the above-mentioned silane coupling agent or titanium coupling agent having an amino group or a glycidyl group, and the mixture is heated if necessary. The ring agent is chemically reacted with the hydrophilic inorganic fine particles, usually with the hydroxyl group on the surface thereof, and thus the coupling agent is bonded to the surface of the hydrophilic inorganic fine particles by a chemical bond. It can be coated with a ring agent. In the present invention, among the hydrophilic inorganic fine particles whose surface is coated with an anion-capturing substance, particularly, as described above, the hydrophilic inorganic fine particles have a coupling agent bound to the surface thereof by a chemical bond, Those coated with a coupling agent are preferably used.

In the present invention, the thickness of such an ink receiving layer is usually in the range of 5 to 50 μm, preferably in the range of 10 to 30 μm.

In the present invention, examples of the substrate include various papers including plain paper, synthetic paper, sheets made of thermoplastic resin or thermosetting resin, sheets made of metal such as iron and aluminum, and the like. However, the present invention is not limited to these.

The aqueous ink jet recording sheet according to the present invention comprises, in addition to the hydrophilic inorganic fine particles obtained by coating the aqueous solution or emulsion of the aqueous resin with the above-mentioned anion-capturing substance, if necessary, a dispersant, a humectant, a coloring agent, An ink receiving layer can be obtained by preparing a coating liquid by adding an additive, applying the coating liquid on a base material by an appropriate means, and drying it to form an ink receiving layer. The base material may be subjected to a corona discharge treatment or an appropriate primer applied as necessary to enhance the adhesion to the ink receiving layer.

[0028]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by these examples.

Example 1 (Preparation of hydrophilic inorganic fine particles whose surface is coated with a silane coupling agent) Hydrophilic anhydrous silica (380 manufactured by Nippon Aerosil Co., Ltd. (average particle size: 7 nm, BET)
100 parts by weight of a specific surface area of 380 m ² / g) were charged into a mixer, 10 parts by weight of γ-aminopropyltrimethoxysilane was added dropwise with stirring under a nitrogen atmosphere, heated at 150 ° C. for 2 hours, and then cooled. A hydrophilic anhydrous silica whose surface was coated with the above-mentioned γ-aminopropyltrimethoxysilane was obtained.

(Preparation of Aqueous Coating Solution) To an aqueous solution containing 100 parts by weight of a polyvinyl alcohol resin, 100 parts by weight of hydrophilic anhydrous silica fine particles coated with the silane coupling agent are added and stirred to prepare an aqueous coating solution. did.

(Preparation of Inkjet Recording Sheet) The above coating solution was applied to a corona-discharged polyethylene terephthalate film using a bar coater and dried to prepare an inkjet recording sheet having an ink receiving layer having a thickness of 20 μm.

(Inkjet Recording Characteristics) Using a commercially available inkjet printer (Epson PM-750C), inkjet recording of a predetermined image is performed on the inkjet recording sheet to form an ink-jet ink for forming an image. And investigated.

The water resistance of the ink was determined by dropping a water droplet on the image immediately after ink-jet recording of the image and visually checking whether the ink forming the image flows. The case where ink did not flow was defined as “good”, and the case where ink flowed easily was defined as “bad”. The color developability of the ink is evaluated by visually observing the sharpness and density of the image, and is defined as “good” when the image is clear and sufficiently dark, and “bad” when the image is not clear or the density is insufficient. And In addition, the surface condition of the obtained ink jet recording sheet was visually observed. When there was no crack, "good" was given, and when there was cracking, "bad" was given. Table 1 shows the results.

Example 2 In Example 1, 50 (manufactured by Nippon Aerosil Co., Ltd., coated with γ-aminopropyltrimethoxysilane as hydrophilic inorganic fine particles coated with a silane coupling agent (average particle diameter: 30 nm, BET specific surface area) An aqueous coating liquid was prepared in the same manner as in Example 1 except that 50 m ² / g) was used.
Using this, an ink jet recording sheet was prepared.
In the same manner as in Example 1, the water resistance and color development of the ink were examined. Table 1 shows the results.

Example 3 Example 1 was repeated except that alumina (aluminum oxide C manufactured by Nippon Aerosil Co., Ltd., average particle size: 13 nm) was treated with γ-aminopropyltrimethoxysilane in place of hydrophilic anhydrous silica. Similarly, an aqueous coating solution was prepared, and an ink jet recording sheet was prepared using the same. In the same manner as in Example 1, the water resistance and color development of the ink were examined. Table 1 shows the results.

Example 4 (Preparation of hydrophilic inorganic fine particles whose surface is coated with a silane coupling agent having a glycidyl group) In the same manner as in Example 1, hydrophilic anhydrous silica (380 available from Nippon Aerosil Co., Ltd.)
(Average particle diameter 7 nm, BET specific surface area 380 m ² / g) 1
00 parts by weight was treated with 10 parts by weight of γ-glycidoxypropyltrimethoxysilane to obtain hydrophilic anhydrous silica whose surface was coated with the silane coupling agent. An aqueous coating liquid was prepared using this hydrophilic anhydrous silica in the same manner as in Example 1, and an ink jet recording sheet was prepared using the aqueous coating liquid. In the same manner as in Example 1, the water resistance and color development of the ink were examined. Table 1 shows the results.

Comparative Example 1 In Example 1, a hydrophilic anhydrous silica (380, manufactured by Nippon Aerosil Co., Ltd., having an average particle diameter of 7 nm and a BET specific surface area of 38) which was not subjected to a surface treatment with a silane coupling agent was used.
0 m ² / g), except that the same was used as in Example 1.
An aqueous coating liquid was prepared, and using this, an ink jet recording sheet was prepared. In the same manner as in Example 1, the water resistance and color development of the ink were examined. Table 1 shows the results
Shown in

Comparative Example 2 An aqueous coating solution was prepared by adding 25 parts by weight of hydrophilic anhydrous silica fine particles coated with a silane coupling agent to an aqueous solution containing 100 parts by weight of a polyvinyl alcohol resin in Example 1. An ink jet recording sheet was prepared using this aqueous coating liquid in the same manner as in Example 1, and the water resistance and color development of the ink were examined in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 3 An aqueous coating solution was prepared by adding 200 parts by weight of hydrophilic anhydrous silica fine particles coated with a silane coupling agent to an aqueous solution containing 100 parts by weight of a polyvinyl alcohol resin in Example 1. An ink jet recording sheet was prepared using this aqueous coating liquid in the same manner as in Example 1, and the water resistance and color development of the ink were examined in the same manner as in Example 1. Table 1 shows the results.

[0040]

[Table 1]

[0041]

In the aqueous ink jet recording sheet according to the present invention, the ink receiving layer comprises a resin and hydrophilic inorganic fine particles dispersed in the resin, and the hydrophilic inorganic fine particles are coated with a substance having an anion-capturing property. Have been. That is, it has cationicity. Preferably, according to the present invention, the hydrophilic inorganic fine particles are coated with a silane coupling agent or a titanium coupling agent having an amino group or a glycidyl group, which is bonded to the surface by a chemical bond. .

Accordingly, in the ink jet recording using such an ink jet recording sheet, if the aqueous ink jet ink adheres to the surface of the recording sheet, the dye in the ink is rapidly dispersed by the cationic hydrophilic inorganic fine particles in the ink receiving layer. Is captured by Similarly, water is not only quickly captured by the cationic hydrophilic inorganic fine particles, but also absorbed by the aqueous resin. Thus, according to the ink jet recording sheet of the present invention, since the ink is ionically captured by the hydrophilic inorganic fine particles in the receiving layer, it has excellent water resistance and color development.

Continued on the front page F term (reference) 2C056 EA13 FC06 2H086 BA01 BA15 BA33 BA35 BA37 BA45 4J002 AB031 AB041 AB051 AD011 AD021 BE041 BG001 BJ001 CF001 CH021 CK021 DE136 DE146 DE146 DJ236 FB136 FB146 FB166 FB266 FD016

Claims (8)

[Claims] An ink receiving layer is provided on a substrate, the ink receiving layer comprising a resin and hydrophilic inorganic fine particles dispersed in the resin, and the hydrophilic inorganic fine particles are used as a substance having an anion-capturing property. A water-based inkjet recording sheet, characterized in that the sheet is coated with water. 2. The method according to claim 1, wherein the hydrophilic inorganic fine particles have an average particle size of 1 nm to 1 nm.
The aqueous inkjet recording sheet according to claim 1, wherein the aqueous inkjet recording sheet is anhydrous silica, alumina, titanium oxide, or calcium carbonate in a range of μm. 3. The aqueous ink jet recording sheet according to claim 1, wherein the ink receiving layer has 50 to 180 parts by weight of hydrophilic inorganic fine particles based on 100 parts by weight of the resin. 4. The aqueous ink jet recording sheet according to claim 1, wherein the substance having an anion-capturing property is a cationic substance. 5. The aqueous ink jet recording sheet according to claim 3, wherein the cationic substance is a cationic resin or a cationic coupling agent. 6. The aqueous ink jet recording sheet according to claim 4, wherein the cationic coupling agent is a silane coupling agent having an amino group in the molecule or a titanium coupling agent. 7. The aqueous ink jet recording sheet according to claim 1, wherein the substance having an anion trapping property is a silane coupling agent having a glycidyl group. 8. The aqueous ink jet recording sheet according to claim 1, wherein the hydrophilic inorganic fine particles are anhydrous silica produced by a gas phase method.