JPH0776162A - Recording sheet and manufacture of it - Google Patents

Abstract

PURPOSE:To obtain a recording sheet for ink jet printer, having high ink absorptive property, high coloring matter adsorptive property, excellent friction resistance of a recorded face, and excellent glossiness. CONSTITUTION:On a base material, a pseudo-boehmite porous layer having a thickness of 10-100mum is provided, which is coated with a silica sol together with a binder and dried, so as to form a recording sheet with a silica gel layer having a thickness of 0.1-30mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording sheet and its manufacturing method.

[0002]

2. Description of the Related Art In recent years, with the widespread use 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, image density, gloss, weather resistance, etc. closer to those of silver halide photography is an issue for development. As a hard copy recording method, various methods such as a sublimation type thermal transfer method, an ink jet method, an electrostatic transfer type method are known in addition to a method of directly photographing a display on which an image is displayed by a silver halide photograph.

An ink jet printer is
It has become popular rapidly in recent years because it can be easily converted into full-color and print noise is low. The inkjet method is a method of ejecting ink droplets from a nozzle toward a recording material at high speed, and the ink contains a large amount of solvent. Therefore, a recording sheet for an inkjet printer is required to quickly absorb the ink and have excellent color forming properties. For example, a recording sheet in which a porous layer of hydrated alumina is provided on a substrate is known (Japanese Patent Laid-Open No. HEI 2).
-276670, JP-A-2-27667, etc.).

[0004]

In a recording sheet having a porous ink absorbing layer made of alumina hydrate on a substrate, the porous layer of alumina hydrate is sharp. When they come into contact with each other, they may be scratched, which may impair the quality of recorded matter. An object of the present invention is to provide a recording sheet which has excellent ink absorbency and color developability and also excellent scratch resistance.

[0005]

DISCLOSURE OF THE INVENTION According to the present invention, a recording having a pseudo-boehmite porous layer having a thickness of 10 to 100 μm on a substrate and a silica gel layer having a thickness of 0.1 to 30 μm thereon. It provides a seat.

The pseudo-boehmite porous layer is preferably a colloidal aggregate of boehmite crystals (compositional formula Al ₂ O ₃ .nH ₂ O, n = 1 to 1.5). It preferably contains an organic binder component. The pseudo-boehmite porous layer has high ink absorbability and dye fixing property, and has high transparency, so that it is excellent in coloring property of the dye. Therefore, it is suitable as an ink receiving layer of a recording sheet. In the recording sheet, the boehmite crystals are preferably oriented with the b axis perpendicular to the sheet surface. In this case, particularly high absorbency and transparency are imparted.

The pseudo-boehmite porous layer has a sufficient absorption when the pore structure thereof is substantially composed of pores having a radius of 1 to 15 nm and the pore volume is 0.3 to 1.0 cc / g. It is preferable because it has properties and has high transparency. At this time, if the base material and the dye adsorption layer are transparent, a transparent recording sheet can be obtained. The pore radius distribution in the present invention is measured by the nitrogen adsorption / desorption method.

Means for providing the pseudo-boehmite porous layer on the substrate is, for example, a sol-like coating liquid obtained by adding a binder to boehmite sol and using a roll coater, an air knife coater, a blade coater, a rod coater, a bar coater or a comma. A method of coating using a coater or the like and drying can be adopted.

As the binder, organic substances such as starch, modified products thereof, polyvinyl alcohol and modified products thereof, SBR latex, NBR latex, carboxymethyl cellulose, hydroxymethyl cellulose, polyvinyl pyrrolidone and the like can be used. The amount of binder used is preferably about 5 to 50% by weight of pseudo-boehmite. If the amount of the binder used is less than 5% by weight, the strength of the pseudo-boehmite porous layer may be insufficient, and if it exceeds 50% by weight, the adsorbability of the dye may be insufficient. Therefore, it is not preferable.

In the present invention, the base material is not particularly limited, and various materials can be used. Specifically, various plastic sheets such as polyester resins such as polyethylene terephthalate and polyester diacetate, polycarbonate resins, fluorine resins such as ETFE, and various papers can be preferably used. In the case of an OHP recording sheet, the base material needs to be transparent, but an opaque base material can also be used, and in this case, a recording sheet that does not impair the texture of the base material can be obtained. Further, for the purpose of improving the adhesive strength of the pseudo-boehmite porous layer, corona discharge treatment or undercoating can be performed.

In the present invention, a silica gel layer is provided on the pseudo-boehmite porous layer. It is preferable that the silica gel layer has a structure in which spherical primary particles of silica are bonded to each other, and that the powder composed of secondary particles of silica is not substantially contained in the silica gel layer. When the powder composed of the secondary particles of silica is present, the transparency of the silica gel layer may be impaired, and the mechanical strength of the silica gel layer may be reduced to reduce the action of protecting the pseudo-boehmite layer. . Such a silica gel layer is obtained by adding a binder to silica sol and applying the binder. As the silica sol, sol particles have an average particle diameter of 10
~ 90 nm spherical primary particles with a solid concentration of 1-2
It is preferred to use 0% by weight.

As the binder, the same binder as that used for forming the porous layer of pseudo-boehmite can be used, and it is particularly preferable to use a polyvinyl alcohol copolymer having a silanol group. The amount of the binder used is 1 to the solid content of the silica sol (converted to SiO ₂ ).
30% by weight is preferred. The amount of binder used is 1% by weight
If it is less than the above range, the mechanical strength of the silica gel layer is insufficient and the protective effect of the pseudo-boehmite layer may be insufficient, which is not preferable. When the amount of the binder used exceeds 30% by weight, the absorptivity of the ink is insufficient, which may cause beading or the like, which is not preferable. With beading, when recording with an inkjet printer,
This is a phenomenon in which ink droplets attached to a recording sheet are fused on the surface of the recording sheet to deteriorate the image quality.

A silica gel layer can be formed by applying this coating solution onto the porous layer of pseudo-boehmite and drying it. As the coating method, the same method as for the pseudo-boehmite layer can be preferably adopted. The thickness of this silica gel layer is preferably about 0.1 to 30 μm. When the thickness of the silica gel layer is less than 0.1 μm, the effect of protecting the pseudo-boehmite porous layer is not sufficiently exhibited, and the scratch resistance may be insufficient, which is not preferable. When the thickness of the silica gel layer is more than 30 μm, the transparency of the coating layer may be impaired, and the absorptivity of the ink may be impaired to cause beading, which is not preferable. More preferable thickness of the silica gel layer is 0.1 to 10 μm.
m.

In the recording sheet of the present invention, the function of absorbing the ink and fixing the dye is mainly possessed by the pseudo-boehmite porous layer, and the silica gel layer functions as a protective layer thereof. When recording with an inkjet printer,
The ink penetrates the silica gel layer and penetrates into the pseudo-boehmite layer, and the dye is fixed in the pseudo-boehmite layer.

[0015]

In the present invention, although the mechanism of improving scratch resistance by providing the silica gel layer is not clear, the coated surface of the recording sheet of the present invention was observed by a scanning electron microscope to find that the pseudoboehmite layer surface was covered with silica gel. Since the silica gel layer is formed in a state where the spherical primary particles are regularly arranged, it is considered that the smoothness of the surface of the coating layer is improved and the slipperiness is imparted. The silica gel layer also has the effect of improving the glossiness of the recording sheet and contributes to the improvement of image quality.

[0016]

【Example】

Example Using boehmite sol synthesized by hydrolysis and deflocculation of aluminum isopropoxide and polyvinyl alcohol (saponification degree 99.8%, polymerization degree 4000), polyvinyl alcohol was 11% by weight based on solid content of boehmite, A coating liquid having a solid content concentration of 15% by weight was prepared. This coating solution was applied on a polyethylene terephthalate film having a thickness of 100 μm using a bar coater so that the coating thickness after drying was 30 μm, and dried to form a pseudo-boehmite layer.

Next, a silica sol in which the sol particles are spherical primary particles having a diameter in the range of 35 to 55 nm, and a polyvinyl alcohol copolymer having silanol groups (Kuraray Co., Ltd., trade name R-Polymer R-1130). Solid content of 5% by weight (polyvinyl alcohol copolymer / S
A silica sol coating solution with iO ₂ = 0.1 (weight ratio) was prepared. This coating solution is applied onto the above-mentioned pseudo-boehmite layer, dried, and then heat-treated at 140 ° C. to have a thickness of 1 μm.
A silica gel layer of was formed to obtain a recording sheet.

This recording sheet had sufficient ink absorbency for recording with an ink jet printer and had good transparency. For the coated surface of this recording sheet, use a friction tester (manufactured by Suga Test Instruments Co., Ltd.)
When a cotton gauze was pressed with a load of 00 g and a friction test was performed 100 times, no scratch was observed. The 60 ° specular gloss of this recording sheet was 50%.

When the cross section of this recording sheet was observed with a scanning electron microscope, the silica gel layer formed on the pseudo-boehmite layer had a structure in which spherical primary particles of silica were regularly arranged.

Comparative Example In the recording sheet of the example, a recording sheet having only the alumina layer without the silica gel layer was obtained. The ink absorbency and transparency were the same as those of the recording sheet of the example. When the same rubbing test was performed, it was observed that scratches were formed. The 60 ° specular gloss of this recording sheet was 40%.

[0021]

The recording sheet of the present invention has a high ink absorbency and a high dye adsorbing property, a high coloring property of the dye, and a good abrasion resistance of the recording surface. Also, the glossiness is good, and a high quality image comparable to a silver halide photograph can be obtained. The recording sheet of the present invention can be particularly preferably used as a recording medium for an inkjet printer.

Claims (6)

[Claims] 1. A pseudo-boehmite porous layer having a thickness of 10 to 100 μm is provided on a base material, and a thickness of 0.1 to 30 μm is provided thereon.
Recording sheet with m silica gel layer. 2. The recording sheet according to claim 1, wherein the silica gel layer has a structure in which spherical primary particles of silica are bonded to each other, and powder composed of secondary particles of silica is substantially not contained in the silica gel layer. 3. The average particle diameter of spherical primary particles of silica is
The recording sheet according to claim 2, which has a thickness of 10 to 90 nm. 4. The recording sheet according to claim 1, which is a recording medium for an inkjet printer. 5. A pseudo-boehmite porous layer is formed on a substrate,
A method for producing a recording sheet, comprising forming a silica gel layer by applying silica sol together with a binder thereon and then drying it. 6. The sol particles of silica sol have an average particle diameter of 1
The method for producing a recording sheet according to claim 5, wherein the spherical primary particles of silica have a particle size of 0 to 90 nm.