JPH0382589A - Water-resistant ink jet recording sheet - Google Patents

Abstract

PURPOSE:To obtain a recording sheet excellent in water resistance and moisture resistance of an image and a base material by providing a lower layer based on a hydrophilic polymer and an ink receiving coating layer being an upper layer on a sheet composed of a film having a multilayer structure based on polyolefin. CONSTITUTION:A recording sheet is formed by providing 0.1 - 10g/m<2> of a lower hydrophilic polymer layer and 7 - 40g/m<2> of an upper ink receiving coating layer on a sheet composed of a uniaxially or biaxially stretched film having a multilayer structure based on polyolefin containing inorg. pigment and a support is a thermoplastic resin film containing 8 - 65 wt.% of an inorg. fine power and, as a thermoplastic resin, polyethylene or polypropylene is mainly used. As the hydrophilic polymer used in the lower layer, starch or perfectly or partially saponified polyvinyl alcohol is used and, as the binder of the upper ink receiving coating layer, a polyvinyl alcohol copolymer containing a silanol group is especially pref.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is an inkjet recording sheet used in image printers, printing printers, etc. using water-based ink, which has a strong base material and coating layer, and is waterproof. Although it can be processed and written on in the same way as general high-quality paper or coated paper, it has a high absorption speed and capacity for ink adhering to the sheet surface, and produces sharp images and prints with vivid ink colors. It has excellent inkjet recording characteristics such as giving
The present invention relates to a new recording sheet with excellent water resistance of images.

[Conventional technology]

Inkjet color printer technology that uses an inkjet recording method to create color hard copies at high speed is progressing. In order to obtain high-quality recorded images, a coating layer consisting mainly of pigment and adhesive is used so that the water-based ink attached to the recording sheet does not spread over the surface and is quickly absorbed in the thickness direction. Many proposals have been made for the provided sheets.

For example, JP-A-55-51583 discloses a coating layer consisting of non-silica silica (particle size 0.1 to 10 μm) and a polymer binder, and JP-A-56-145856 discloses a coating layer consisting of fine particle silica It is disclosed that a receiving layer made of a non-aqueous solvent-soluble resin or a receiving layer made of fine silicic acid particles, other inorganic pigment particles, and a non-aqueous solvent-soluble resin is provided on a substrate.

Furthermore, it has been proposed to improve the surface strength of the coating layer of these proposed sheets, and the present inventors have also proposed
68682, proposed a method using polyvinyl alcohol copolymers containing silanol groups.

Furthermore, in order to improve the clarity and water resistance of images printed using water-based inks by inkjet printing, cationic polymers have recently been added.

However, even if the cationic polymer provides water resistance to the image itself, which is made up of the ink and the pigments, adhesives, and additive polymers in the coating layer, if the base material is natural paper, the paper will tear when wet. Even if water-resistant paper is used, problems such as stretching, wrinkling, and curling occur, and in practical terms, it cannot be said to have the water resistance as a color hard copy.

A recording sheet with a coating layer on a base paper made of natural valves as the main raw material is a recording sheet that can be used in environments exposed to high humidity and water droplets while taking advantage of the full color performance of inkjet printers. It was impossible to provide.

[Problem to be solved by the invention]

The present invention has good suitability for inkjet recording, that is, the absorption speed and absorption capacity of the aqueous ink attached to the surface of the recording sheet are high, the color of the ink is bright, and the shape of the ink dots is circular, giving a sharp image. This recording sheet for inkjet printers has small ink dot smearing, making it possible to print high-resolution prints and images in color at high speed. Furthermore, the surface strength of the coating layer is high, and there is no powder falling off, making it suitable for processing. It is an object of the present invention to provide a water-resistant inkjet recording sheet which can eliminate the above-mentioned drawbacks and has excellent water resistance and moisture resistance of images and substrates.

[Means for solving problems]

The present invention provides a lower layer mainly composed of a hydrophilic polymer and an ink-receptive coating layer as an upper layer on a sheet consisting of a mono- or biaxially stretched multilayer film mainly composed of polyolefin containing an inorganic pigment. This is a water-resistant inkjet recording sheet characterized by:

As a result of various studies in order to solve the above-mentioned shortcomings of the prior art, the present inventors have developed a method for forming a lower layer on a sheet consisting of a mono- or biaxially stretched film with a multilayer structure mainly composed of polyolefin containing an inorganic pigment. Hydrophilic polymer as 0.1-10
g/m2, with an ink-receptive coating layer as an upper layer of 7 to 40 g/m2.
The water-resistant inkjet recording sheet is characterized by having a water-based ink absorption rate of 1.2 g/m2, which has a high absorption speed and absorption capacity for water-based ink, has a bright ink color, and has circular ink dots to produce sharp images. , an inkjet with small ink dot smearing, which makes it possible to print high-resolution characters and images in color at high speeds, and at the same time has both the water resistance of the image and the water resistance of the base material, and has excellent surface strength. It has been found that a recording sheet can be obtained.

That is, in the present invention, a coating layer is provided on the surface of a support made of synthetic paper having a multilayer structure.

The support is a thermoplastic resin film containing 8 to 65% by weight of inorganic fine powder, and includes a base layer with strength and a paper-like layer with voids to provide printability and shielding properties. In addition, a surface layer may be included depending on the application.

The thermoplastic resin constituting each layer of the support is mainly composed of polyolefin resins such as polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-vinyl acetate copolymer, but also polystyrene and acrylic ester copolymer. It is possible to use a mixture of thermoplastic resins such as:

Inorganic fine powders to be blended into the thermoplastic resin include calcium carbonate, calcined clay, diatomaceous earth, talc, silica, etc. with an average particle size of 20 μm or less for the base layer and paper layer.
Examples of materials for the surface layer include calcium carbonate, titanium oxide, and barium sulfate.

The thickness of the sheet-like support used in the present invention is 10 to 20
The basis weight per 0 μm is preferably 10 to 200 g/m′, and the surface smoothness is preferably good.

The lower layer provided on the sheet-like support contains a hydrophilic polymer of 0.
1 to 10 g/m".

The role of the lower layer is to firmly adhere the base material, the ink-receptive coating layer, and the base material, and also to improve the fixation of the ink since it uses a synthetic paper base material that does not absorb water. I also have The coating amount of the lower layer hydrophilic polymer is 0.1g/r
If it is less than n2, the adhesion between the upper ink-receptive coating layer and the substrate is poor, and if it is more than 10 g/m2, the adhesion effect between the upper ink-receptive coating layer and the substrate is saturated, making it uneconomical. It is.

As the hydrophilic polymer used here, at least one type or a mixture of two or more types of starch, modified starch, completely saponified or partially saponified polyvinyl alcohol, derivatives thereof, acrylic ester emulsion, etc. can be used. . In addition, inorganic salts such as table salt, various commonly used inorganic and organic pigments, conductive polymers, etc. may be mixed with the hydrophilic polymer to the extent that it does not affect the image, water resistance, writability, etc. can not use.

Although various water-soluble or water-dispersible adhesives can be used as the binder for the ink-receptive coating layer, a polyvinyl alcohol copolymer containing a silanol group is particularly preferred.

By using a polyvinyl alcohol copolymer that has excellent adhesion specifically to silica, a unique synergistic effect with the fine particle silica and cationic polymer, which is the main component of the pigment, can be obtained, and it can be used in the coating layer of inkjet paper. This is thought to be due to the formation of a unique interaction.

The polyvinyl alcohol copolymer containing a silanol group, which is preferably used as an adhesive in the present invention, is obtained by copolymerizing a silicon-containing vinyl compound with vinyl acetate and saponifying it, so that the vinyl acetate units are converted into vinyl alcohol.
It is obtained by converting each silicon-containing monomer unit into a silanol group. (Refer to Japanese Patent Application Laid-Open No. 58-59203). Silicon-containing monomer is 0.1 to 1.0 mol%
It is sufficient to copolymerize a very small amount.

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.

Along with polyvinyl alcohol copolymers containing silanol groups, other water-soluble and water-dispersible polymers can be used as adhesives. Among starch and starch derivatives, cellulose derivatives, polyvinyl alcohol, and acrylic acid ester copolymers, those that have good compatibility with fine powder silica and cationic polymers can be selected and used together.
Adhesive strength can be further improved.

When the amount is 40% by weight or more, high resolution images are achieved. Therefore, the total amount of the adhesive, including the polyvinyl alcohol copolymer having silanol groups, should be 40% by weight or less, preferably 30% by weight or less, based on the solid content of the paint.

In the present invention, a cationic polymer is added to make the image waterproof. Suitable cationic polymers include quaternary ammonium salt derivatives of polyethyleneimine, acrylic containing a quaternary ammonium group as a copolymerized monomer, or copolymers of methacrylic acid esters, and 2 to 10% by weight.
Exist within the range of If it is less than 2% by weight, a sufficient effect will not be obtained, and if it is more than 10% by weight, the effect will be saturated and no further improvement will be obtained, or secondary problems such as a decrease in light fastness of the image may occur. .

The pigment used for the coating for the ink-receptive coating layer in the present invention is a color-developing white pigment with high oil absorption and high specific surface area, which is known to give clear images when used in inkjet paper. Particulate silica whose main component is particles with a certain secondary particle diameter of 1 to 5 μm is the best. Suitably, finely powdered silica is used in an amount of 30 to 88% by weight of the total coating solids. When evaluating only from image quality, the more finely powdered silica is used, the better. In addition, other white pigments may be used or used in combination depending on the purpose of use of the recording sheet and the requirements of the printer, and the total amount of pigments is 50 to 88% by weight. Other white pigments that can be used include, for example, zeolite, calcium carbonate, diatomaceous earth, kaolin clay, talc, aluminum hydroxide, organic pigments (plastic pigments), and other pigments commonly used in paper coating.

Generally speaking, the coating weight of the ink receptive coating layer provided on the non-ink absorbent substrate is 7 to 40 g/rn.
', preferably 7 to 30 g/m2.

If the coating amount is less than 7 g/m', the ink absorbency will be insufficient, and if it is more than 40 g/m', it will not only be uneconomical but also cause a decrease in surface strength.

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

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

Example 1 Paint-1 Pigment Fine particle silicic acid containing 70% or more of secondary particle diameters of 2 to 5μ (Fine Seal Tokuyama Soda) 0B Vinyl alcohol copolymer containing silanol groups (R-1130 Kuraray) 0B Polyvinyl alcohol (PVA) -105 Kuraray) I 0 parts Polyethyleneimine quaternary ammonium salt (SP-102 Nippon Shokubai) 5 parts Synthetic paper YUPO FPG80 (thickness: 80 μm) with a multilayer structure containing an inorganic pigment and having paper-like layers on the front and back sides of the base material layer Polyvinyl alcohol (PVA) is used as a hydrophilic polymer in Yuka Synthetic Paper Co., Ltd.
117 Kuraray Co., Ltd. 1K) was applied at 0.1 g/m'', and on top of that, Paint-21 with a concentration of 12% by weight was prepared, and the solid content was applied at 20.0 g/m', dried, and inkjet recorded. I obtained a sheet for use.

Example 2 Paint-2 20 parts of diatomaceous earth Multi-layered synthetic paper Yubo FPG80 (thickness: 80 μm, manufactured by Tamago Yuka Synthetic Paper Co., Ltd.) containing 20 parts of diatomaceous earth and an acrylic ester copolymer emulsion as a hydrophilic polymer (Movinyl 963 manufactured by Hoechst Godo Co., Ltd.) at 2.1g/rn2
Paint-2 with a concentration of 18% by weight was applied on top of the paint-2.
It was coated at 5 g/m' and dried to obtain an inkjet recording sheet.

Example 3 Paint-3 Vinyl alcohol 2 copolymer containing silanol groups (
R-2105 Kuraray) 20 parts polyethyleneimine No. 4
grade ammonium salt (SP-102 Nippon Shokubai) 5 parts Synthetic paper YUPO FPG80 (thickness 80 μm) with multilayer structure containing inorganic pigment
A lower layer containing 90% by weight of starch (Tamako Ace C Tamago Cornstarch) and 10% by weight of common salt was coated on a hydrophilic polymer (manufactured by Tamago Yuka Synthetic Paper Co., Ltd.) at 9.1 g/m", and the upper layer was coated with a concentration of 9.1 g/m". Paint-3 with a concentration of 14% by weight was 7.2g/m'
It was coated and dried to obtain an inkjet recording sheet.

Comparative Example 1 Paint-4 Pigment Fine particle silicic acid (Fine Seal Tokuyama Soda) 100 parts Dispersant
Paint-3 with a concentration of 18% by weight, consisting of 1.5 parts of sodium polyacrylate (A6310 Toagosei Co., Ltd.) and 50 parts or more of polyvinyl alcohol (PVA-117 Kuraray Co., Ltd.), was applied to a multi-layered synthetic paper containing inorganic pigments (Yuyu). Bo FPG80 (manufactured by Oji Yugoshu Paper Co., Ltd.) was coated with a solid content of 20g/m'', dried,
An inkjet recording sheet was obtained.

Comparative Example 2 An inkjet recording sheet was produced in the same manner as in Example 1 except that the amount of undercoat was not provided.

Comparative Example 3 Paint-1 of Example-1 was applied to a 65 g/m'' high-quality paper at a solid content of 20 g/m2 and dried to obtain an inkjet recording 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. The results are shown in Table 1.

For ink absorption evaluation, the time taken for the ink to dry was measured.

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 and blue-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 cellophane tape.

Image water resistance was determined by immersing the image in running water for 5 minutes, drying it, and checking whether the image remained.

O indicates excellent performance, △ indicates general quality, ×
indicates a defect that poses a problem for use.

The fixation of the image was determined by observing the printed image after it was stored in a dark place for one month.

× indicates that bleeding occurred.

Table [Effects of the Invention] The water-resistant inkjet recording sheet of the present invention has a strong surface, can be easily written on with a pencil, has water resistance, ink absorbency,
A high-resolution, high-speed, general-purpose inkjet printer that eliminates the shortcomings of conventional methods, with excellent color vividness.
This is what makes color printers possible.

Claims (1)

[Claims] 1. A layer containing a hydrophilic polymer is added as a lower layer at a rate of 0.1 to 10 g/m^2 on a sheet consisting of a 1- to 2-axis stretched film with a multilayer structure mainly composed of polyolefin containing an inorganic pigment.
, an ink-receptive coating layer as an upper layer of 7 to 40 g/m^2
A water-resistant inkjet recording sheet characterized by having a water-resistant inkjet recording sheet.