JPS6283178A - Ink jet recording sheet - Google Patents

Abstract

PURPOSE:To obtain a printed character or an image with high resolving power, by using fine powdery silicic acid as the main component of pigment and containing a cationic polymer in a part of an adhesive. CONSTITUTION:In an ink jet recording sheet wherein a coating layer containing an adhesive in an amount corresponding to 20-50% of a paint solid component and the greater part of the remainder as pigment having a good water absorbing property and an excellent color forming property is provided on a support, 50-80% by wt. of the paint solid component of fine powdery silicic acid pref. based on a secondary particle size of 1-6mum is used as the pigment main component having a good color forming property of aqueous ink and, pref., 5-25wt% of diatomaceous earth is together used as other pigment and, as the adhesive, 20-50wt% of an emulsion polymer is used and, as a part or whole of a polymer, 5-50% by wt. of the paint solid component of a cationic copolymer having effect improving the color forming property of the ink (pref., a cationic acrylic copolymer emulsion containing 5-30% by wt. of the polymer of an acrylic monomer containing a quaternary ammonium salt or tertiary amine as a functional group) is used.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an inkjet recording sheet, and more specifically, in an inkjet recording method using water-based ink and used for high-quality image recording and printing printers, the present invention relates to an inkjet recording sheet. The ink absorption speed and absorption capacity are large,
The spreading and bleeding of ink dots is small, the color of the ink is bright, and the dot shape is circular, making it possible to provide images and prints with sharp edges, thus making it possible to record high-resolution images at high speed. . The present invention relates to an inkjet recording sheet.

[Conventional technology]

In order to obtain high-quality recorded images with the inkjet recording method, pigments and adhesives are used to ensure that the ink adhered to the substrate (mainly paper) is quickly absorbed in the thickness direction without spreading over the surface. A number of proposals have been made in the past regarding providing a fenced layer (coating layer) mainly composed of (binder) on a base material.

For example, in JP-A-55-51585, a layer made of non-silica silica C (particle size 0.1 to 10 μm) and a polymer binder is disclosed, and in JP-A-55-144172, a water-based ink is used. Coating layer with a pigment that adsorbs the coloring components of , zirconium salts, ion-exchange resin powders, urea-formalin resin powders, etc.) JP-A-56-99692 discloses a coating layer (advanced) in which 60% by weight or more of filler fine particles are added to the binder. JP-A-5BS6-145854 discloses porous inorganic pigments (natural zeolite, synthetic zeolite, Japanese Patent Publication No. 145856/1986 discloses that a recording liquid receiving layer containing particles of silicic acid, fine silicic acid, silicic acid, synthetic mica) should be provided, or may be made of fine silicic acid and a non-aqueous solvent soluble resin. Providing a recording liquid-receiving layer on the substrate comprising silicic acid, other #B-free kerosene and a non-aqueous solvent soluble resin,
Disclosed.

However, most of these proposals have problems in that the writability (pencil writability in %) is not good and the coating layer is cracked.

The problem of writability can be solved by selecting and using other blended pigments)
However, it is difficult to improve the cracking problem because it is necessary to increase the blending ratio of W and white carbon and to increase the coating amount in order to improve ink absorption and resolution.

[Purpose of the invention]

The present invention is an inkjet recording method using water-based ink, which has a high absorption speed and absorption capacity for ink adhering to the surface of a recording sheet, has small ink dot spreading and bleeding, has a bright ink color, and has an ink dot shape. This is an inkjet recording sheet that can give circular images with sharp edges, thus making it possible to print and record high-resolution prints and images at high speed, and also has good writability. An object of the present invention is to provide an inkjet recording sheet that can eliminate the drawbacks.

[Structure of the invention]

In the present invention, pigments and adhesives are used as main components on a sheet-like support, 20 to 50% of the solid content of the paint is adhesive, and most of the rest is pigments that have good water absorption and excellent color development. In an inkjet recording sheet having a coating layer of
Fine particle silicic acid, mainly having a particle size of 1 to 6μ, is used in an amount of 50 to 80% by weight based on the solid content of the paint, preferably diatomaceous earth is used in combination with 5 to 25% by weight as another pigment, and 20% by weight is used as an adhesive.
An emulsion polymer (preferably self-crosslinkable and Tg of 0°C or less) with a weight of ~50 wt. 11% is used, and a cationic copolymer (preferably is a cationic acrylic copolymer emulsion containing 5 to 30.lii% of the polymer of an acrylic monomer containing a quaternary ammonium salt or a tertiary amine as a functional group (P 岑郎→倭→゛゛) with a paint solid content of 5 to 30.lii%.
This is an inkjet recording sheet designated as 411 for use with a weight of $50.

In order to eliminate the drawbacks of the prior art described above, the present invention [i, etc.]
As a result of repeated studies by woodcutter, a coating liquid whose main component is an adhesive containing the above-mentioned color-forming white pigment and color-forming adhesive was applied to a sheet-like support and dried, resulting in high speed and high resolution. It has been found that an inkjet recording sheet that enables inkjet recording and has excellent writing characteristics can be obtained. That is, it has been experimentally found that when recording by an inkjet method, a recording sheet with excellent properties can be obtained when the above-mentioned pigment and adhesive are used on the recording sheet.

These remarkable effects are due to the unique surface structure and hydrophilicity of fine particle silica that has been reagglomerated to an appropriate secondary particle size, and the cationic nature of cationic functional groups that are omnipresent on the surface of the particulate polymer. It is thought that this is because a synergistic effect of the polymers causes a unique interaction with the inkjet ink, especially the dye component, but the details are not clear.

The materials used in the present invention will be explained.

- Pigment: Pigment Fi used in the present invention? IJJet is a color-developing white pigment with oil content and high specific surface area, and the secondary particle size is 1.
The main component is t-baozi silicic acid, which has particles of ~6μ as the main component,
It is suitable to use an appropriate amount of diatomaceous pigment in combination, but other white pigments may be added depending on the purpose.

These white pigments include pigments commonly used for paper coating, such as kaolin clay, talc, zeolite, calcium carbonate, aluminum hydroxide, white carbon,
Examples include organic pigments (glasstic pigments).

- Adhesive The adhesive (binder) of the present invention is preferably an emulsion polymer. Acrylic copolymer emulsions with Tg < D C are most suitable; they have self-crosslinking groups and exhibit sufficient water resistance and adhesive strength after processing under normal coating and drying conditions, so-called self-crosslinking properties. Preferably, acrylic emulsions are used.

Furthermore, when a polymer containing 5 to 95% vinyl acetate as a comonomer is used, the adhesive strength can be further improved.

In addition to natural or processed adhesives such as proteins such as casein, starch, and starch derivatives, binders such as polyvinyl alcohol, polyvinyl acetate, and styrene-butadiene rubber can also be used in combination.

・Colorable adhesive emulsion When a polymer emulsion with a cationic group is used as a part of the adhesive.

The coloring properties of the ink can be improved without causing problems such as cracking of the coating layer or deterioration of writing properties. It is already known to use cationic surfactants, cationic water-soluble polymer substances, cationic emulsions, etc. by simply mixing them with pigments, but these are unstable when used alone, and are insufficient. Shows no effect.

On the other hand, it is thought that by using an acrylic emulsion polymer and a cationic polymer together as an adhesive, cationic groups will be ubiquitous on the surface of the adhesive film, reinforcing the coloring effect of the dye in the ink. It will be done. In particular, polymers with tertiary amine groups as functional groups of acrylic monomers,
Polymers with grade ammonium bases show excellent effects.

In addition, those polymerized in the presence of cationic surfactants,
Similarly, it is known that cationic groups exist on the surface of polymer fine powder, and they exhibit similar effects.

Next, the support, which is another material used in the present invention, will be explained.

A sheet-like support The sheet-like support used in the present invention is made of ordinary natural pulp paper, plastic film sheets such as polyglopyrene, polyethylene, and polyester, synthetic fibers, synthetic pulp, and synthetic resin films, which are made into pseudopaper (surface treatment method). , surface coating method, pigment embedding method, etc.) may be used. The sheet-like support preferably has a thickness of 10 to 2003 m, a basis weight of 10 to 201 Jl/m, and preferably has a good surface smoothness.

The blending ratio of components such as pigments and adhesives depends on the operational characteristics of the resulting coating solution (e.g. concentration, -1 viscosity, fluidity) and the characteristics of the coating layer obtained by drying after coating on the base paper, especially It is largely limited by the characteristics of the inkjet recording layer.

Generally speaking, the coating weight for the support base paper is 2 to 50
．． 9/FIL2, preferably 5 to 501/11L2.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, in the actual examples, parts indicate parts by weight.

Example 1 100 parts of fine particle silicic acid (Fine Sea M Tokuyama Soda) with a secondary rice grain diameter of 2 to 5 μm or more was used as a pigment, and 1.5 parts of sodium polyacrylate and 300 parts of water were used as a dispersant. In addition, after performing high-speed dispersion mixing, 50 parts (as solid content) of a self-crosslinking acrylic copolymer emulsion (Movinyl 730 Nihext Synthesis) and an acrylic copolymer containing a quaternary ammonium salt (Tg- A coating liquid was obtained by adding and mixing 10 parts (as solid content) of 10Ce' class ammonium salt (25 mol %). Ko Om [-1651/ 112 (D
High quality MkVC201//rn2 was coated to obtain inkjet paper.

Example 2 By the same operation as described in Example 1, 80 parts of the same fine-particle silicic acid and ±2Q parts of silica were used as pigments, and an acrylic copolymer emulsion (Movinyl 7) was used as an adhesive.
30, Hoechst synthesis), 8 parts of quaternary ammonium salt as an emulsifier, 30 parts of polymerized acrylic copolymer (as solid content), and 300 parts of water to prepare a coating solution. A coated paper was prepared in the same manner as in Example 1.

Example 3 By the same operation as described in Example 1, 80 parts of the same fine particle silicic acid as the pigment, +/- 20 parts of acrylic copolymer emulsion (Movinyl 7) as the adhesive were prepared.
30, Hoechst Synthesis) 20 parts (as solid content), 30 parts (as solid content) of vinyl acetate #polymer (Kanebo WSC CC-IB) containing 5 mol% of acrylic ester containing tertiary amine, and 300 parts of water. Use the coating liquid! /I
A coated paper was prepared in the same manner as in Example 1.

Comparative Example Coated paper was prepared in the same manner as in Example 1 using the coating components shown in the following table. These are referred to as Comparative Examples 1 and 2.

Table 1 shows the evaluation results for each coated paper in these cases.

Inkjet Recording Characteristic Evaluation Method The inkjet recording characteristics of each of the coatings described above were evaluated using a commercially available inkjet printer in terms of ink absorbency and the diameter and shape of recording dots.

Ink absorption evaluation was performed by measuring the number of dots (X number of overwrites) until the ink in the dotted area begins to bleed (flow).

The vividness of color development was evaluated by visually observing the color development of yellow, magenta, and cyan color inks.

The shape of the dots was determined by observing the dots made once on paper by an inkjet printer under a microscope, and the dots were indicated by O1Δ and X in descending order of the shape being close to a perfect circle.

Pencil writability was determined based on the difficulty of writing with an HB pencil.

Table 1 Inkjet paper quality evaluation example 1 20
#/1l12 0 0 0 Δ2 201/
TrL2 0 0 0 032 opym OO
OO Comparative example 120I/1rL2 Δ Δ Δ
×2 201/1+12 Δ Δ ×
Δ [Effect of the invention] Judging from the above examples and comparative examples, the inkjet recording sheet of the present invention has excellent ink absorption, brightness of color, and dot shape, and has a strong surface. It is a high-resolution, high-speed inkjet full-color printer that eliminates the shortcomings of conventional methods, making it possible to easily write on cars with a pencil, making it a major contribution to industry.

Claims (1)

[Scope of Claims] 1. On a sheet-like support, 50 to 80% by weight of pigment and 20 to 50% by weight of a polymer prepared by emulsion polymerization, based on the total paint solids, are added as the main component of the adhesive. In an inkjet recording sheet provided with a coating layer of paint, fine powder silicic acid is used as the main component of the pigment in an amount of 50 to 80% by weight of the total paint solid content, and as part of the adhesive, fine powder silicic acid is used as the main component of the total paint solid content. An inkjet recording sheet containing 5 to 50% by weight of a cationic polymer. 2. Claim 1 in which the polymer prepared by emulsion polymerization used as an adhesive is primarily an acrylic copolymer whose glass transition point after film formation is 0°C or lower. Inkjet recording sheet as described in section. 3. The inkjet recording sheet according to claim 2, wherein the copolymer used as the adhesive contains 5 to 95% by weight of vinyl acetate as a copolymer monomer. 4. The inkjet recording sheet according to claim 1, wherein most of the fine powder silicic acid has a secondary particle diameter of 1 to 6 μm. 5. As other pigments, diatomaceous earth is used as a paint solid content of 5 to 2
An inkjet recording sheet according to claim 1 or 2, in which 5% by weight of the inkjet recording sheet is used. 6. The ink jet recording sheet according to claim 1, wherein the cationic polymer is an acrylic copolymer containing 2 to 15% by weight of the copolymer of a vinyl monomer having a quaternary ammonium salt as a cationic group. . 7. The cationic polymer is a copolymer containing an acrylic ester or methacrylic ester of a C_1 to C_4 alcohol having a quaternary ammonium base as a monomer.
The inkjet recording sheet according to claim 6, which is an acrylic copolymer containing 30% by weight.