JPH0966660A - Recording sheet for pigment ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a recording sheet for pigment ink which has excellent pigment ink absorption and reveals excellent coloring property by uniformly fixing the pigment in the ink, by providing an alumina hydrate porous layer on a base material and layering thereon a porous layer whose average pore diameter is smaller than that of the alumina hydrate porous layer. SOLUTION: On a base material, an alumina hydrate porous layer and a porous layer (an upper layer) whose average pare diameter is smaller than that of the alumina hydrate porous layer are layered in sequence so as to form a recording sheet for pigment ink. As concrete examples of the base material, plastics such as a polyester resin and a polycarbonate resin, and various types of papers can be named. The alumina hydrate porous layer functions as an ink absorbing layer. For the alumina hydrate, a pseudo-boehmite is suitable due to its excellent ink absorption. A difference in average pore radius between the upper layer and the alumina hydrate porous layer is suitably about 1-14nm. As concrete examples of the material of the upper layer, an alumina hydrate, a silica, and an SBR latex can be named.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording sheet for pigment ink, and more particularly to a recording sheet suitable for an ink jet recording system using pigment ink.

[0002]

2. Description of the Related Art In recent years, with the spread of electronic still cameras or computers, a hard copy technique for recording those images on a paper surface has rapidly developed. The ultimate goal of these hard copies is silver halide photography, and in particular, how to bring color reproducibility, color density, resolution, gloss, weather resistance, etc. closer to those of silver halide photography is an issue for development. There are a variety of hard copy recording methods, such as a method of directly photographing a display displaying an image by a silver halide photograph, a sublimation type thermal transfer method, an ink jet method, and an electrostatic transfer method.

Ink jet printers have become rapidly popular in recent years because they are easy to produce in full color and have low printing noise. In this method, ink droplets are ejected from a nozzle toward a recording material at a high speed, and a large amount of solvent is contained in the ink. For this reason, a recording medium for an inkjet printer is required to quickly absorb the ink and have excellent color developability.
In the ink jet recording method, an ink of a type in which a dye is dissolved in a solvent has been used so far, but an ink of a type in which a pigment is dispersed in a solvent (a pigment ink) is also known.

[0004]

SUMMARY OF THE INVENTION According to the present invention, a pigment ink having a good absorbency, a pigment in the ink is uniformly fixed to exhibit excellent color developability, and a recorded matter having a high color density is obtained. The purpose is to obtain a recording sheet that can

[0005]

According to the present invention, an alumina hydrate porous layer is provided on a substrate, and a porous layer having an average pore size smaller than that of the alumina hydrate porous layer is provided thereon. A recording sheet for pigment ink is provided.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The base material is not particularly limited and various materials can be used. Specifically, polyester resins such as polyethylene terephthalate, polycarbonate resins, plastics such as ETFE and other fluorine resins, and various papers can be preferably used. Furthermore, cloth, glass or metal can also be used. These substrates may be subjected to corona discharge treatment or various undercoats for the purpose of improving the adhesive strength of the alumina hydrate layer.

When a transparent plastic film is used as a base material, a transparent recorded material that can be used as an OHP (overhead projector) sheet or the like can be obtained. When an opaque plastic film containing a white pigment, paper, or the like is used as the base material, a recorded matter comparable to a silver salt photograph can be obtained.

In the present invention, the alumina hydrate porous layer functions as an ink absorbing layer. As the alumina hydrate, pseudo-boehmite is preferable because it absorbs ink well. Here, pseudo-boehmite is Al ₂ O ₃ · nH ₂
It is an aggregate of alumina hydrate represented by a composition formula of O (n = 1 to 1.5).

A binder is preferably contained in the alumina hydrate porous layer. As a binder,
Starch or a modified product thereof, polyvinyl alcohol or a modified product thereof, SBR latex, NBR latex,
Organic substances such as carboxymethyl cellulose, hydroxymethyl cellulose and polyvinylpyrrolidone can be used.
The amount of the binder used is preferably about 5 to 50% by weight of the alumina hydrate. When the amount of the binder used is less than 5% by weight, the strength of the alumina hydrate layer may be insufficient, and when it exceeds 50% by weight, the ink absorption may be insufficient. Therefore, it is not preferable.

The alumina hydrate porous layer has sufficient absorbability when the average pore radius is 1 to 15 nm and the pore volume is 0.3 to 1.0 cc / g, and the alumina water The Japanese layer is also preferable because it has transparency. At this time, if the substrate is transparent, a recording medium having high transparency can be obtained. Even when the base material is opaque, it is possible to obtain a recording medium capable of obtaining an image with high quality and high color density without impairing the texture of the base material. The average pore diameter of the alumina hydrate porous layer is 3 to
More preferably, it is 10 nm. The pore radius distribution is measured by the nitrogen desorption method.

The porous layer (hereinafter referred to as the upper layer) provided on the alumina hydrate porous layer is required to have a smaller average pore radius than the alumina hydrate layer. The upper layer adjusts the ink absorption speed and absorbs the pigment ink while uniformly dispersing it, so that the fixing property of the pigment is improved. Further, it has a function of smoothing the ink surface after drying, and has an effect of improving image quality.

The difference between the average pore radius of the upper layer and the average pore radius of the alumina hydrate porous layer is preferably 1 to 14 nm. When the difference in average pore radius is less than 1 nm, the upper layer impairs the function of adjusting the solvent absorption rate in the ink, which is not preferable. When the difference in average pore radius exceeds 14 nm, the characteristics of the upper layer portion as the porous layer are substantially lost, which is not preferable.

The material of the upper layer is not particularly limited as long as it is porous, and for example, alumina hydrate, silica, SBR latex, NBR latex and the like can be used. Further, it may contain a binder component as required. Further, spherical particles may be mixed in order to impart automatic transportability to the recording sheet.

As a method for forming an alumina hydrate layer on a substrate, a method in which a binder and a solvent are added to alumina hydrate to form a sol-like coating solution, which is applied to the substrate and then dried. preferable. It is preferable to use alumina sol as a raw material for the alumina hydrate because an alumina hydrate layer having good transparency can be formed. The application method is, for example,
Die coater, roll coater, air knife coater,
It is preferable to use a blade coater, a rod coater, a bar coater, a comma coater, or the like. As a solvent for the coating liquid, either an aqueous system or a non-aqueous system can be adopted.

The thickness of the alumina hydrate layer is appropriately selected according to the specifications of each printer, etc., and is generally 5 to 100 μm.
It is preferable to adopt m. If the thickness of the alumina hydrate layer is less than 5 μm, the ink may not be sufficiently absorbed, which is not preferable. If the thickness of the alumina hydrate layer exceeds 100 μm, the transparency of the alumina hydrate layer may be impaired or the strength of the layer may be reduced, which is not preferable.

As a method for forming the upper layer, a coating solution is prepared by adding a solvent and optionally a binder to alumina hydrate, silica, SBR latex, NBR latex, etc., and coating this on the alumina hydrate layer. The method of drying after drying is preferable. As a coating method, a die coater, a roll coater, an air knife coater, a blade coater, a rod coater, a bar coater, a comma coater or the like can be adopted as in the case of forming the alumina hydrate layer. As a solvent for the coating liquid, either an aqueous system or a non-aqueous system can be adopted.

The thickness of the upper layer is appropriately selected according to the specifications of each printer and the like, and generally 0.2 to 10 μm is preferably adopted. If the thickness of the upper layer is less than 0.2 μm, the fixing property of the ink may not be sufficiently improved, which is not preferable. When the thickness of the upper layer is more than 10 μm, the ink absorbability may be deteriorated, which is not preferable.

[0018]

【Example】

Example 1 A coating liquid was prepared by mixing 100 g of an alumina sol having a solid content of 18% by weight synthesized by the hydrolysis / peptization method of aluminum alkoxide and 32 g of a 6.2% by weight aqueous solution of polyvinyl alcohol. This coating liquid was applied onto a polyethylene terephthalate film (thickness 100 μm, white) using a bar coater so that the coating amount after drying was 26 g / m ² , and dried to form a pseudo-boehmite layer. did. Further, a solid content of 5% by weight of a siligasol having a primary particle diameter of 10 to 20 nm and a polyvinyl alcohol copolymer having a silanol group (Kuraray Co., Ltd., trade name R-polymer R-1130) (the copolymer / SiO 2 ₂ = 0.3) of the silica sol coating solution was applied and dried so that the thickness of the silica gel layer after drying was 1 µm, and heat-treated at 140 ° C to obtain a recording sheet. The average pore radius of the lower layer (alumina hydrate layer) of the coating layer of the heat-treated sheet was 8 nm, and the average pore radius of the upper layer (silica gel layer) of the coating layer was 2 nm.

Example 2 On the pseudo-boehmite layer of Example 1, 100 g of an alumina sol having a solid content of 18% by weight synthesized by the hydrolysis / peptization method of an aluminum alkoxide and 6.2% by weight of polyvinyl alcohol.
A coating solution was prepared by mixing 60 g of the aqueous solution. This coating solution is applied and dried so that the coating amount after drying is 1 g / m ² .
A heat treatment was performed at 140 ° C. at 140 ° C. to obtain a recording sheet. The average pore radius of the lower layer of the coating layer of the heat-treated sheet is 8 nm
The average pore radius of the upper layer of the coating layer was 6 nm.

Example 3 (Comparative Example) A recording sheet was obtained in the same manner as in Example 1 except that the silica gel layer was not provided.

Printing Evaluation Regarding the recording sheets of Examples 1 to 3, an ink jet printer (made by Hewlett-Packard Company, trade name DeskWr
Iter550C) was charged with a pigment ink, and printing was performed in the same manner. In Example 3, the fixing property of the pigment ink was poor and the pigment peeled off when rubbed with a finger, and the image was unclear.
The recording sheets of Examples 1 and 2 had good fixability and good images were obtained.

[0022]

The recording sheet of the present invention has high absorptivity and fixability for pigment ink, and has good color developability. In particular, it is suitable as a recording medium for an inkjet printer.

Claims (1)

[Claims] 1. A recording sheet for a pigment ink, comprising a porous alumina hydrate layer on a substrate, and a porous layer having an average pore size smaller than that of the porous alumina hydrate layer on the porous layer.