JP2993977B2 - Water resistant inkjet recording sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ink jet recording sheet used for an image printer or a print printer using an aqueous ink, wherein the base material and the coating layer are strong and water resistant. It can be processed and written in the same manner as ordinary high-quality paper and coated paper, but has a large absorption rate and absorption capacity of ink attached to the sheet surface, and sharp images and prints with vivid ink color development Excellent ink jet recording characteristics such as giving
The present invention relates to a novel recording sheet having excellent image water resistance and storage stability.

[Conventional technology]

2. Description of the Related Art The technology of an ink jet color printer that creates a color hard copy at a high speed using an ink jet recording method has been advanced. In order to obtain high-quality recorded images, paper provided with a layer mainly composed of a pigment and an adhesive so that the water-based ink adhering to the paper is quickly absorbed without spreading on the surface is particularly suitable. A number of proposals have been made in the past, such as a coating layer comprising non-colloidal silica (flow diameter: 0.1 to 10 μm) and a polymer binder disclosed in Japanese Patent Laid-Open No. 55-51583.

In addition, in order to improve the clarity and water resistance of an image printed using an aqueous ink, a cationic water-soluble polymer has recently been added. However, due to the cationic polymer, pigments, adhesives,
Even if the water resistance of the image itself composed of other additives is obtained, since the base material is a paper containing cellulose pulp as a main component, the paper is broken by being wet with water, and the paper is stretched, wrinkled, and curled. However, practically, it cannot be said that the color hard copy has water resistance.

Using a recording paper with a coating layer provided on paper made of such cellulose pulp as a main material, a color hard copy sheet that can be used in an environment exposed to high humidity and water droplets while utilizing the full color performance of an ink jet printer. It was difficult to get. In order to provide such a sheet, the present inventors have first prepared a polyolefin containing inorganic pigment as a main component and a mono- or biaxially stretched multi-layered film on which 30 to 88% by weight of fine powdered silica A water-based adhesive, preferably containing 5 to 40% by weight of a vinyl alcohol copolymer containing silanol groups, and 2 to 10% by weight of a cationic water-soluble polymer. A full-color recording sheet for an ink jet printer provided with a coating layer of 10 to 40 g / m ² was proposed.

[Problems to be solved by the invention]

The present invention has good inkjet recording suitability, that is, the absorption rate and the absorption capacity of the aqueous ink attached to the recording sheet surface are large, the color development of the ink is clear, the ink dot bleed is small, and the ink dot shape is small. This is a recording sheet for inkjet printers that gives circular and sharp images, and thus enables high-resolution printing and color printing of images at a high speed. An object of the present invention is to provide an ink jet recording sheet which has good workability and is excellent in water resistance and moisture resistance of an image and a substrate and can solve the above-mentioned disadvantages.

When a film mainly containing a hydrophobic polymer such as polyolefin is used, bleeding occurs when a hard copy sheet is stored. In particular, it was remarkable when stacked. This is presumably because the non-volatile organic solvent such as polyhydric alcohol is contained in the component of the aqueous ink. After printing, when the image is dried, polar components such as water in the ink are almost completely evaporated or adsorbed, and the ink of the image is almost dissolved in the nonvolatile organic solvent, and the polyolefin and the like are dissolved. It is considered that when the film is in contact with a film containing a hydrophobic polymer as a main component, the film has a high affinity and bleeds or spreads.

[Means for solving the problem]

 The present invention includes the following aspects.

1. A stretched film support containing an inorganic pigment containing a thermoplastic polymer as a main component and an aqueous ink receptive coating layer on one surface, and a hydrophilic polymer as a main component on the opposite surface. An ink jet recording sheet provided with a coating layer, wherein the coating layer mainly composed of a hydrophilic polymer on the opposite side contains polyvinyl alcohol or a vinyl alcohol copolymer in an amount of 10 to 100% by weight.

2. The ink jet recording sheet according to 1, wherein the support is a multilayer structure including a stretched film containing a polyolefin and an inorganic pigment.

3. The ink jet recording sheet according to 1 or 2, wherein the ink receptive coating layer contains a vinyl alcohol copolymer containing a silanol group.

4. The ink jet recording sheet according to any one of 1 to 3, wherein the ink receptive coating layer contains a cationic polymer.

5. The ink jet recording sheet according to any one of items 1 to 4, wherein the coating amount of the coating layer containing the hydrophilic polymer on the opposite side is 0.1 to 10 g / m ² .

The present invention relates to a thermoplastic polymer film, preferably a polyolefin containing an inorganic pigment as a main component.
Water-resistant ink-jet recording sheet characterized in that a water-based ink-receiving coating layer is provided on one surface of an axially stretched multi-layer film sheet, and a layer mainly composed of a hydrophilic polymer is provided on the other surface. It is.

As a layer mainly composed of a hydrophilic polymer, a coating amount of 10 to 100% by weight containing a copolymer of vinyl alcohol is 0.1 to 10 g / m ^2.
Are preferred.

The present inventors have conducted various studies in order to solve the above-mentioned drawbacks of the prior art, and as a result, have found that the above-mentioned drawbacks can be solved by providing a layer mainly composed of a hydrophilic polymer on the opposite surface. Heading, the present invention has been made.

As an aqueous ink receptive coating layer, 30 to 30
A pigment containing 88% by weight of fine-particle silica, a 10-40% by weight aqueous adhesive containing preferably 5-40% by weight of the total paint solids containing a vinyl alcohol copolymer containing silanol groups;
10 to 10% by weight of a layer containing a cationic polymer as a main component is coated on a sheet-like support made of a multi-layered film biaxially stretched with a polyolefin containing an inorganic pigment as a main component.
When provided at a rate of 40 g / m ^2, a large absorption rate and absorption capacity of the aqueous ink, vivid color development of the ink, the ink dot shape small ink bleeding Dodd gives a sharp image in a circular, hence a high It is possible to obtain an ink jet recording sheet which enables high-speed printing and color printing of images at a high speed, and at the same time, has both the water resistance of an image and the water resistance of a base and excellent surface strength.

That is, in the present invention, a water-based ink-receiving coating layer is provided on the surface of a support made of synthetic paper having a multilayer structure, and a layer mainly composed of a hydrophilic polymer is provided on the opposite surface.

The support of the present invention is a thermoplastic resin film containing from 8 to 65% by weight of an inorganic fine powder, and may include a surface layer depending on the use in addition to the support, the base material layer and the paper-like layer. As a thermoplastic resin constituting each layer of the support, a polyolefin resin such as polyethylene, polypropylene, an ethylene-propylene copolymer, and an ethylene-vinyl acetate copolymer is a main component.
A thermoplastic resin such as an acrylate copolymer can be mixed and used. As the inorganic fine powder to be blended with the thermoplastic resin, the average grain system is used for the base material layer and paper-like layer.
20 μm or less calcium carbonate, calcined clay, diatomaceous earth,
Examples include talc and silica, and examples of the surface layer include calcium carbonate, titanium oxide, and barium sulfate.

The thickness of the support is preferably from 10 to 200 μm, the basis weight is preferably from 10 to ²⁰⁰ g / m ² , and those having good surface smoothness are preferred.

As the hydrophilic polymer in the layer mainly composed of the hydrophilic polymer on the opposite side, a vinyl alcohol (co) polymer is effective in improving the adhesive strength to the thermoplastic polymer film of the base material and stabilizing the image. There is. In addition, from vinyl acetate (co) polymers, starch and starch derivatives, cellulose derivatives, etc.,
Those having good adhesive strength to the thermoplastic polymer film of the substrate can be selected and used in combination, whereby the stability of the aqueous ink image can be improved.

By using a pigment in combination with the coating layer on the opposite surface, the stability of the aqueous ink image can be further improved.
Fine particles of silica, zeolite, calcium carbonate, diatomaceous earth, kaolin clay, talc, aluminum hydroxide, organic pigments (plastic pigments) and other pigments used in general paper coating can be used or used together, but the total amount of pigments Is preferably 0 to 50% by weight of the solid content of the coating layer.

The coating amount of the coating layer on the opposite side is 0.1 to 10 g / m ² , preferably
0.5 to 3 g / m ² . If the coating amount is small, the surface coating effect of the thermoplastic polymer is insufficient, and if it is too large, it is not only uneconomical, but also the strength of the coating layer is reduced.

Various water-soluble or water-dispersible adhesives can be used as the adhesive for the water-based ink-receiving coating layer, but a vinyl alcohol copolymer is preferable, and a vinyl alcohol copolymer containing a silanol group is particularly preferable. By using such a polyvinyl alcohol copolymer having an excellent adhesive specifically for silica, a specific synergistic effect can be obtained with the fine particle silica as the main component of the pigment and the cationic polymer. This is presumably because a specific interaction occurs in the coating layer of the inkjet paper. Furthermore, the vinyl alcohol copolymer containing a silanol group reacts with an active group such as a hydroxyl group of an inorganic pigment in the surface layer of the base multilayer film, and has an effect of dramatically improving surface strength and image water resistance. It is presumed that.

The vinyl alcohol-based copolymer containing a silanol group used as a preferred adhesive of the present invention is obtained by copolymerizing a vinyl compound containing silicon with vinyl acetate and then saponifying the vinyl acetate unit into vinyl alcohol. It is obtained by converting a silicon-containing monomer unit into a silanol group, respectively (see JP-A-58-59203). The silicon-containing monomer may be copolymerized in a small amount such as 0.1 to 1.0 mol%. Since the vinyl alcohol-based copolymer containing a silanol group binds specifically and firmly to silica, it is possible to realize sufficient coating film strength with a small amount that does not hinder color development and resolution.

Other water-soluble and water-dispersible polymers can be used as the adhesive together with the vinyl alcohol copolymer containing a silanol group. From among starch and starch derivatives, cellulose derivatives, polyvinyl alcohol, acrylic ester copolymers and the like, those having good compatibility with finely divided silica and cationic polymers can be selected and used in combination, whereby aqueous inks can be obtained. The adhesive strength of the receptive coating layer can be further improved.

When the amount of the adhesive in the aqueous ink-receiving coating layer is 40% or more, the resolution of an image is reduced. Therefore, the total amount of the adhesive including the vinyl alcohol-based copolymer having a silanol group is based on the solid content of the aqueous ink-receiving coating layer. 40% or less, preferably 30% by weight or less.

In the invention, it is preferable to add a cationic polymer to the water-based ink-receiving coating layer in order to make the image water-resistant. As the cationic polymer, a quaternary ammonium salt derivative of polyethyleneimine, an acrylate or methacrylate copolymer obtained by copolymerizing a monomer containing a quaternary ammonium group, or the like is suitable. Exist in a range. If the content is less than 2% by weight, a sufficient effect cannot be obtained. If the content is more than 10% by weight, the effect is saturated and no further improvement can be obtained, or a secondary problem such as a decrease in light resistance of an image may occur. .

The pigment used in the water-based ink receptive coating layer of the present invention is a white pigment having a high absorption and a high specific surface area, which is known to give a clear image when used on ink-jet paper. Fine particle silica mainly composed of particles having a secondary particle diameter of 1 to 5 μm is the most excellent. Suitably, the particulate silica is used in an amount of 30 to 88% by weight of the solid content of the aqueous ink receiving coating layer. To improve the image quality, the more the fine particle silica, the better. In addition, other white pigments such as zeolite, calcium carbonate, diatomaceous earth, kaolin clay, talc, aluminum hydroxide, organic pigments (plastic pigments), and other general paper coatings, depending on the purpose of the recording sheet and the requirements of the printer The total amount of the pigment may be 50 to 88% by weight of the solid content.

Generally, the coating amount of the water-based ink-receiving coating layer is 2 to 50 g /
m ² , preferably 5 to 30 g / m ² .

If the coating amount is small, the ink absorbency is insufficient, and if it is too large, not only is it uneconomical, but also the strength is reduced.

Hereinafter, the present invention will be described in more detail with reference to examples. In the examples, parts are parts by weight as solids.

Example 1 Paint-1 (water-based ink-receiving coating layer) Pigment Fine particle silica (Fine Seal Tokuyama Soda) 100 parts Silanolated vinyl alcohol copolymer (R-1130 Kuraray) 30 parts Polyvinyl alcohol (PVA-105 Kuraray) 10 parts Polyethyleneimine quaternary ammonium salt 5 parts A coating material-1 having a concentration of 12% by weight was prepared from the above components.

Paint-2 (back surface and coating layer) Polyvinyl alcohol (PVA-117 Kuraray) 100 parts Paint-2 having a concentration of 10% by weight was prepared from the above components.

YUPO FPG80 (80 μm thick Oji Yuka Synthetic Paper Co., Ltd.)
1.5 g / m ² coating on a solids paint -2 backside of Ltd.), dried, further recording surface coatings -1 with solids 20 g / m ² coating, and dried to obtain an ink jet sheet.

Comparative Example 1 An inkjet sheet was obtained in the same manner as in Example 1, except that the back surface was not coated.

The evaluation results of these inkjet recording sheets are shown in the table. The ink jet recording characteristics were evaluated using a commercially available ink jet printer (manufactured by PaintJet Hewlett-Packard) for ink absorbency and color clarity.

For the ink absorption evaluation, the time (speed) until the ink dries was measured.

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

The image storability was measured by superimposing five sheets for one month so that the print surface and the back surface were in contact with each other, and then observing image bleeding.

[Effects of the Invention] According to the present invention, it is possible to provide an ink jet recording sheet which does not cause image bleeding even when a hard copy sheet is stored for a long period of time.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B41M 5/00

Claims (5)

(57) [Claims] An aqueous ink-receiving layer is provided on one surface of a stretched film support containing a thermoplastic polymer as a main component and containing an inorganic pigment, and a hydrophilic polymer is provided on the other surface. A coating layer having a main component as a main component is provided, and the coating layer having a hydrophilic polymer as a main component on the opposite surface has a polyvinyl alcohol or vinyl alcohol copolymer content of 10 to 100% by weight.
An ink jet recording sheet comprising: 2. The ink jet recording sheet according to claim 1, wherein the support is a multilayer structure including a stretched film containing a polyolefin and an inorganic pigment. 3. The ink jet recording sheet according to claim 1, wherein the ink receptive coating layer contains a vinyl alcohol copolymer containing a silanol group. 4. The ink jet recording sheet according to claim 1, wherein the ink receiving coating layer contains a cationic polymer. 5. The ink jet recording sheet according to claim 1, wherein the coating amount of the coating layer containing the opposite hydrophilic polymer is 0.1 to 10 g / m ² .