JPS62268682A - Ink jet recording sheet - Google Patents

Abstract

PURPOSE:To obtain an ink jet recording sheet having high surface strength, generating no falling of a powder and excellent in a writing property and water resistance, by providing a coating layer, with pigment containing a specific ratio of fine powdery silica, an adhesive containing a polyvinyl alcohol copolymer having a silanol group and a cationic polymer as main components, on a sheet like support. CONSTITUTION:30-88wt% of a total paint solid of pigment containing fine powdery silica is used and 5-40wt% of the total paint solid of a polyvinyl alcohol copolymer having a silanol group is contained and, when both of then are used in combination with a cationic polymer, an ink jet recording sheet having excellent surface strength is obtained without damaging the effects of the fine powdery silica and the cationic polymer at all. As the cationic polymer, a quaternary ammonium salt derivative of polyethyleneimine and an acrylic or methacrylic ester copolymer containing a quaternary ammonium group as a copolymerized monomer etc. are pref. and allowed to be present in a range of 2-10wt%.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a coated paper for inkjet recording used in image printers, print printers, etc. using water-based ink, and the coated paper has a strong coating layer and is of a general high quality. This relates to an inkjet recording sheet that can be used and written on in the same way as paper, but has a high absorption speed and capacity for ink adhering to the sheet surface, and provides sharp images and prints with vivid ink colors. .

[Conventional technology]

The technology of inkjet color printers, which create color hard copies at high speed using an inkjet recording method, has advanced, and in order to obtain high-quality recorded images, water-based ink adhered to the recording sheet does not spread on the surface. A number of proposals have been made in the past regarding sheets provided with a coating layer mainly composed of pigments and adhesives so as to be rapidly absorbed in the thickness direction.

For example, JP-A-55-51588 discloses a coating layer consisting of non-silica silica (particle size 0.1 to 10 μm) and a polymer binder, and JP-A-55-144172 discloses a coating layer consisting of aqueous ink. A mineral layer containing pigments that adsorb coloring components (numerous pigments such as zeolite are exemplified) was disclosed in JP-A-56-
Publication No. 145856 discloses providing on a substrate a receiving layer consisting of particulate silicic acid and a non-aqueous solvent-soluble resin, or comprising particulate silicic acid, other inorganic pigment particles, and a non-aqueous solvent-soluble resin. .

However, in these proposed sheets, the surface strength of the coating layer is weak (the coating layer peels off under normal paper usage conditions,
It has problems such as powder falling off, poor pencil writability, and cracks in the coating layer.

Pencil compatibility can be improved to some extent by selecting pigments such as finely powdered silica, and the problem of cracking can be improved to some extent by changing drying conditions. However, it has been difficult to improve the strength of the coating layer. The reason for this is that in order to improve ink absorption and resolution, the blending ratio of fine powder silica in the paint has been increased to 3% of the solid content of the paint.
Although it was necessary to use a high coating amount of 0 to 88% by weight, sufficient improvement could not be obtained due to restrictions on the adhesive surface. For example, attempts have been reported to increase the strength by increasing the amount of adhesive to an extreme level, but such paper suffers from noticeable smearing of water-based ink, reduced image quality, and reduced resolution and mid-tone color reproduction in new formats. It has become difficult.

Attempts have also been made to improve adhesive strength by using hydrophobic adhesives such as latex. or,
Additional cationic polymers have recently been added to improve the clarity and water resistance of inkjet printed images. However, since cationic polymers are generally not compatible with latex emulsions of anionic hydrophobic polymers, strength cannot be improved by adding these latexes.

As a result, it has been impossible to provide paper that can be used in the same way as high-quality paper, which is ordinary business paper, while taking full advantage of the full-color performance of inkjet printers.

[Problem that the invention seeks to solve]

The present invention has a high absorption speed and absorption capacity for water-based ink attached to the surface of a recording sheet, provides vivid ink color development, small ink dot smearing, circular ink dot shape, and sharp images, and therefore has high resolution. This is a sheet for inkjet printers that enables high-speed color printing of characters and images, and it also has a coated layer with a surface strength as strong as ordinary high-quality paper, and has good writing properties without falling off. It is an object of the present invention to provide an inkjet recording sheet with excellent water resistance of images and capable of eliminating the above-mentioned drawbacks. A pigment containing silica at 30-88% by weight of the total paint solids and a polyvinyl alcohol copolymer containing silanol groups containing 5-88% by weight of the total paint solids.
The present invention relates to an inkjet recording sheet characterized by being provided with a coating layer containing 40% by weight of an adhesive and 2-10% by weight of a cationic polymer.

As a result of repeated studies in order to solve the above-mentioned drawbacks of the prior art, the present inventor discovered that the total paint solid content was 30-88% by weight.
cll, a pigment containing powdered silica, a polyvinyl alcohol copolymer having silanol groups in an amount of 5 to 40% by weight of the total paint solid content, and more preferably polyvinyl alcohol with a degree of polymerization of 1000 or less as another adhesive. When the adhesive containing the pigment is used in combination with a cationic polymer as an adhesive for a pigment mainly composed of fine-particle silica, the effect of the fine-particle silica and cationic polymer is not impaired at all.
It has also been found that an inkjet recording sheet with excellent surface strength can be obtained.

By using polyvinyl alcohol copolymer, which has excellent adhesion specifically to silica, as a binder for the coating layer, a unique synergistic effect with the fine particle silica and cationic polymer, which are the main components of the pigment, can be obtained, and it is This is thought to be due to the formation of a unique interaction within the coating layer.

The polyvinyl alcohol copolymer containing silanol groups used as the adhesive of the present invention is a silicon-containing vinyl compound and vinegar! It is obtained by copolymerizing with vinyl and saponifying it to convert vinyl acetate units into vinyl alcohol and silicon-containing monomer units into silanol groups, respectively. (Refer to Japanese Patent Application Laid-Open No. 58-59203). The silicon-containing monomer may be copolymerized in a very small amount of about 0.1-1.0 mol. Since the polyvinyl alcohol copolymer containing silanol groups specifically and strongly bonds with silica, sufficient coating film strength can be achieved with a small amount that does not interfere with color development or resolution. The amount of polyvinyl alcohol copolymer containing silanol groups is 5 to 40
Weight%. Even if it is used in an amount of 40% by weight or more, the strength does not increase and, on the contrary, the silica ratio decreases and the image deteriorates, which is not preferable.

If the amount is less than 5% by weight, sufficient effects cannot be obtained.

In the present invention, polyvinyl alcohol having a degree of polymerization of 1000 or less can be used together with a polyvinyl alcohol copolymer containing a silanol group. Degree of polymerization is 100
It is often preferable to add polyvinyl alcohol with a molecular weight of 0 or less because it has excellent compatibility and dispersibility.However, in the past, in order to ensure adhesive strength and strengthen the surface, polyvinyl alcohol has poor compatibility and dispersibility. It was necessary to blend a large amount of polyvinyl alcohol with a high polymerization degree of 11,100 to 2,000 with respect to silica. However, in the present invention, there is no such need, and polyvinyl alcohol having a degree of polymerization of 1000 or less can be included in an amount of 5 to 20M.

In addition, adhesives that have good compatibility with cationic polymers can be selected and used in combination with starch, starch derivatives, natural or processed adhesives such as cellulose derivatives, and acrylic copolymers. , the adhesive strength can be further improved.

In order to achieve high image resolution, the amount of adhesive, including the amount of polyvinyl alcohol copolymer having silanol groups, is 10-40% by weight, preferably 10-30% by weight of the solid content of the paint.
Weight%.

In the present invention, a cationic polymer is added to make the image waterproof. Suitable examples of the cationic polymer include quaternary ammonium salt derivatives of polyethyleneimine, acrylic containing a quaternary ammonium group as a copolymerizable monomer, or copolymers of methacrylic acid esters.
It is present in the range of 0% by weight. If it is less than 23% by weight, no sufficient effect can be obtained, and if it is more than 10% by weight, the effect is saturated and no further improvement is seen.

The pigment used in the present invention is used in inkjet paper,
Fine particle silica, which is a color-developing white pigment with high oil absorption and high specific surface area and which is known to give clear images, is the most excellent, and whose main component is particles with a secondary particle size of 1 to 5 μm. . Suitably, the finely divided silica is used in an amount of 30-88% by weight of the total paint solids. In terms of image quality, the more the better. Other white pigments can be used or used in combination depending on the purpose of use of the outer paper and the requirements of the printer, and the total amount of pigments is 50-88% by weight. Other white pigments include, for example, zeolite, calcium carbonate, diatomaceous earth, kaolin clay, talc, aluminum hydroxide,
Organic pigments (plastic pigments) and other pigments commonly used for paper coating can be used.

The sheet-like supports used in the present invention include ordinary natural pulp paper, plastic film sheets such as polypropylene, polyethylene, and polyester, synthetic paper sheets made of synthetic fibers, synthetic pulp, and synthetic resin films. Nine is fine. The thickness of the sheet-like support is 10 to 20
0 μm 1 tsubo indigo is preferably 10 to 200 g/rrL2,
Those with good surface smoothness are preferred.

Generally speaking, the coating weight for the support base paper is 2 to 50
97 m2, preferably 5-30 g/m''.

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

In the examples, parts indicate parts by weight as solid content.

Example 1 Paint - 1 A paint 1 with a concentration of 12% by weight was prepared from components of 1° or more, and the solid content was coated at 20 g/m2 on 65 g/m2 high-quality paper.
It was dried to obtain an inkjet sheet.

Example 2 Paint-2 with a concentration of 18% by weight consisting of 2° or more components,
6587 m2 of high-quality paper coated with a solid content of 20 g/m.
It was dried to obtain an inkjet sheet.

Comparative Example 1゜Paint - FC paint-3 with a concentration of 18% by weight consisting of components of 8゜ or higher was applied to a 65g/m'' high-quality paper at a solid content of 20 g/rn'', dried, and an inkjet sheet was prepared. Obtained.

Comparative Example 2゜Paint - 4゜se Lμ2l 700 no
(31%) or more with a concentration of 8% by weight, paint-4 was coated on high-quality paper of 55/l/m2 with a solid content of 20%.
g/rn” coating, drying, and inkjet sheet If
Obtained.

Comparative Example 3 Paint-5 with a concentration of 15 weight 7 o consisting of components of 5° or more was coated on high-quality paper of 65 g/rrL2 at a solid content of 20 i/w.
m2 coating and drying to obtain an inkjet sheet.

The evaluation results of these inkjet recording sheets are shown in the table. The inkjet recording characteristics were evaluated using a commercially available inkjet printer, and the ink absorption and color clarity were evaluated, and the strength of the coating layer was evaluated using a cellophane tape test and pencil writability.

Ink absorption evaluation was carried out by measuring the time it took for the ink to dry.

The clarity of color development was visually evaluated by the color development of yellow, magenta, and cyan color inks and the color development of green, blue, and red heavy colors.

Pencil writability was sensually judged based on the difficulty of writing with an H pencil.

The surface strength was evaluated by sensory evaluation of the degree of removal of the coating layer by peeling off Ceviap.

Water resistance was determined by immersing the image in running water for 5 minutes and then drying it to see if the image remained.

○ indicates excellent performance, Δ indicates general quality, and X
may have defects that may cause problems in use.

Effects of the Invention The inkjet recording sheet of the present invention has a strong surface.
This makes it possible to create a high-resolution, high-speed, general-purpose inkjet color printer that eliminates the shortcomings of conventional methods, allowing easy writing with a pencil, excellent ink absorption, and excellent color vividness.

Watch applicant: Oji Paper Co., Ltd. (1 other person)

Claims (1)

[Scope of Claims] 1. A pigment containing finely powdered silica in an amount of 30 to 88% by weight of the total paint solids and a polyvinyl alcohol copolymer containing silanol groups are placed on a sheet-like support in an amount of 5 to 88% by weight of the total paint solids. 40
1. An inkjet recording sheet comprising a coating layer containing as main components an adhesive containing 2% to 10% by weight of a cationic polymer. 2. Claim 1 containing 5 to 20% by weight of polyvinyl alcohol with a degree of polymerization of 1000 or less as another adhesive
The inkjet recording sheet described in Section 1.