JPH0930115A - Recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a recording sheet for an ink jet printer good in ink absorbability, showing excellent color forming properties and capable of rapidly absorbing ink. SOLUTION: A porous layer wherein a pore vol. with a radius of 1-30nm is 0.3-1.2cc/g, a pore vol. with a radius of 10-30nm is 0.2-1.0cc/g, a pore vol. with a radius of 30-100nm is 0.3cc/g or less and boehmite crystals are oriented is provided on a base material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium, and more particularly to a recording medium capable of clear recording by a printing method using a dye as a coloring material such as an ink jet method.

[0002]

2. Description of the Related Art In recent years, in order to obtain a small amount of printed matter such as a sheet for an overhead projector, a method of editing an original with a personal computer or a word processor and printing with a printer has been widely used. As the printer, it is easy to make full color,
The inkjet method has begun to spread because of its relatively low price.

As a recording medium in this case, it is necessary to sufficiently absorb a large amount of ink. Therefore, coated paper or film provided with an inorganic porous powder or a water-absorbent resin on the surface as an ink receiving layer has been developed. There is. For example, an ink jet recording medium having a porous alumina xerogel having pores having a radius of 4 to 100 nm in an ink receiving layer (Japanese Patent Laid-Open No. Sho 60).
No. 245588) has been developed.

Further, in order to improve the color density of an image and obtain a higher quality image, the total volume of pores having a radius of 10 to 100 nm is 0.1 cc / g or less, mainly. A recording sheet provided with a highly transparent adsorption layer made of pseudo-boehmite has been developed (JP-A-2-2).
76670 gazette).

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
A recording sheet provided with an adsorption layer made of pseudo-boehmite having a total pore volume of 0 nm of 0.1 cc / g or less produces a high-quality full-color image by printing in an appropriate environment using an appropriate inkjet printer. However, depending on the inkjet printer used and the environment in which it is used, the ink absorption rate is insufficient, and so-called beading may occur, making it impossible to obtain high-quality images. Beading is a phenomenon in which dots are distorted by joining droplets on the surface of a recording medium. An object of the present invention is to obtain a recording medium having an ink receiving layer which has a sufficient absorption speed without impairing transparency.

[0006]

The present invention is a porous layer containing boehmite on a substrate, having a pore radius of 1 to 3.
The pore volume of 0 nm is 0.3 to 1.2 cc / g, the pore volume of pore radius 10 to 30 nm is 0.2 to 1.0 cc / g,
Pore volume of 30 to 100 nm is 0.3 cc / g
A recording medium having at least one porous layer in which the b axis of boehmite crystals is oriented perpendicular to the substrate surface is as follows.

Boehmite has the composition formula Al ₂ O ₃ .nH ₂
It is a crystal of alumina hydrate represented by O (n = 1 to 1.5), and the colloidal aggregate of boehmite is also called pseudo-boehmite. Since boehmite is excellent in ink absorbency and dye fixing, the boehmite-containing porous layer is suitable as an ink receiving layer. In particular, the recording medium of the present invention is suitable as a recording sheet for an inkjet printer, since it exhibits a high adsorptivity for water-soluble anionic dyes that are often used in inkjet printers.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The porous layer containing boehmite is required to have a pore volume of 0.3 to 1.2 cc / g in the range of pore radius of 1 to 30 nm. .
Pore volume in the range of 1 to 30 nm is 0.3
If it is less than cc / g, the ink absorbency and the dye fixing property become insufficient, which is not suitable. When the pore volume in this range exceeds 1.2 cc / g, the light scattering in the porous layer containing boehmite becomes large, the transparency of the porous layer is impaired, and the dye is adsorbed to this layer. This is not suitable because the formed image becomes whitish. The pore volume of the pores having a pore radius in the range of 1 to 30 nm is 0.5 to
The case of 1.2 cc / g is more preferable.

The boehmite-containing porous layer has a pore volume of 0.
It is necessary to be 2 to 1.0 cc / g. Pore volume in the range of 10 to 30 nm is 0.2 cc /
If it is less than g, the absorption speed of the ink becomes slow, which is not suitable. When the pore volume in this range exceeds 1.0 cc / g, the light scattering in the porous layer containing boehmite becomes large, the transparency of the porous layer is impaired, and the dye is adsorbed to this layer. This is not suitable because the formed image becomes whitish. It is further preferable that the pore volume of the pores having a pore radius of 10 to 30 nm is 0.3 to 0.5 cc / g.

The boehmite-containing porous layer must have a pore volume of 30 to 100 nm and a pore volume of 0.3 cc / g or less. When the pore volume with a pore radius of 30 to 100 nm exceeds 0.3 cc / g, the light scattering in the porous layer containing boehmite becomes large, and the transparency of the porous layer is impaired, It is unsuitable because the image formed by adsorbing the dye on it becomes whitish. It is preferable that the pores having a pore radius of more than 30 nm do not substantially exist, and the pore volume of the pore radius of 30 to 100 nm is 0.1.
It is more preferable if it is cc / g or less.

In the present invention, the pore volume is measured by a nitrogen adsorption / desorption method. According to this method, it is impossible to measure the pore volume exceeding 100 nm, but the porous layer containing boehmite has a pore radius of 10
It is preferable that substantially no pores exceeding 0 nm are also present.

In the porous layer containing boehmite,
The b axis of the boehmite crystal needs to be oriented perpendicular to the substrate surface. When the b-axis of boehmite is not oriented perpendicular to the sheet surface, the transparency of the porous layer is impaired even when it has the above-mentioned pore characteristics, and when the substrate is transparent, haze Is high, which is not preferable.
Here, the degree of orientation is [0 of boehmite obtained by X-ray diffraction.
The ratio of the peak heights due to the reflection of the [20] plane and the [200] plane (Equation 1) was measured on the surface of the recording medium by a thin film X-ray diffraction method, and defined by comparison with non-oriented boehmite powder. That is, the degree of orientation is defined by the following formula 2.

[0013]

(Equation 3)

[0014]

(Equation 4)

If the degree of orientation value is 1, the boehmite is non-oriented. The smaller this value, the higher the degree of orientation,
If so, it indicates perfect b-axis orientation, that is, the b-axes of all boehmite crystal grains are perpendicular to the sheet surface. If the degree of orientation of boehmite exceeds 0.5, the transparency of the boehmite layer will be insufficient, which is unsuitable. When the transparency of the boehmite layer is insufficient, the haze becomes high in the case of a transparent sheet, which is not preferable. In the recording medium of the present invention, the boehmite layer serves as a dye-supporting layer, even when an opaque material such as paper is used as the substrate, the dye is supported in a highly transparent layer. Recording with good color development and high color density is possible. The degree of orientation of boehmite is 0.
The case of 3 or less is more preferable.

The thus oriented porous layer containing boehmite is formed by applying a coating liquid containing boehmite sol and drying. This is mainly due to the anisotropy of the boehmite crystal, and it is considered that the b-axis is oriented vertically on the substrate during the drying process of the boehmite sol coating liquid. The same applies not only when the boehmite crystal particles are monodispersed in the boehmite sol but also when the sol particles are secondary aggregated to some extent. However, it is not possible to obtain such a oriented boehmite layer by applying the powder obtained by pulverizing the boehmite xerogel together with the binder onto the substrate.

It is necessary to select a boehmite sol that forms a porous layer having the above-mentioned pore volume, but in the case of general boehmite sol, the pore volume of pores having a pore radius in the range of 10 to 30 nm is selected. However, it is necessary to increase the pore volume. For example, in the case of a boehmite sol produced by the hydrolysis method of alkoxide, it is preferable to use one in which the crystal primary particles are grown more by making the hydrolysis time longer than that of the conventional boehmite sol.

The base material is not particularly limited and various materials can be used. Specifically, plastics and papers such as polyester resins such as polyethylene terephthalate, polycarbonate resins, and fluorine resins such as ethylene-tetrafluoroethylene copolymer can be preferably used. In addition to transparent bodies such as films and sheets of plastics or various kinds of glass, opaque bodies such as cloth, paper and metal, and translucent bodies such as fluororesin films such as ethylene-tetrafluoroethylene copolymer may be used as appropriate. Corona discharge treatment or various undercoats may be applied to these substrates for the purpose of improving the adhesive strength of the boehmite porous layer.

As the base material, a material having ink absorbability such as paper can be used, and a material having no absorbency such as polyester film can also be used. An ink-absorbing resin layer, a siliceous porous layer, or the like may be provided between the substrate and the porous layer containing boehmite. Another layer may be further provided on the porous layer containing boehmite.

The thickness of the porous layer containing boehmite depends on the ink absorption characteristics of the substrate, but is preferably in the range of 1 to 50 μm. If the thickness is less than 1 μm,
It is not preferable because there is a risk that the ink absorbency will be insufficient or the color development will be insufficient. When the thickness is more than 50 μm, the mechanical strength of the porous layer may be lowered and the color of the recorded matter may be hindered, which is not preferable. It is more preferable that the thickness of the porous layer containing boehmite is 5 to 30 μm.

When the porous layer containing boehmite is provided as the uppermost layer of the recording medium, it is preferable in the sense that a vivid color is obtained. A protective layer may be provided on the surface in order to further impart glossiness and scratch resistance of the recorded matter. As the surface protective layer, a silica gel layer having a thickness of 0.1 to 30 μm, which has a structure in which spherical primary particles of silica are bonded to each other, and powders composed of secondary particles of silica are not substantially contained in the layer. It is preferable to use.

As the porous layer containing boehmite, 50
It is preferable that the weight% or more is boehmite. Further, when boehmite is 80% by weight or more, vivid color is obtained, which is particularly preferable. It is preferable that the porous layer containing boehmite contains a binder in addition to the boehmite because the strength of the porous layer is improved. In addition to the boehmite and binder components, an inorganic pigment such as silica and various additives may be contained within a range that does not impair the characteristics of the porous layer.

The binder is generally starch or a modified product thereof, polyvinyl alcohol (PVA) or a modified product thereof, styrene butadiene rubber (SBR) latex, acrylonitrile butadiene rubber (NBR) latex,
Organic substances such as hydroxycellulose and polyvinylpyrrolidone can be used. Of these, the use of PVA is particularly preferable because it does not substantially impair the preferable physical properties of pseudo-boehmite and the mechanical strength of the ink receiving layer can be made sufficient. The content of the binder is 5 to 5 of boehmite.
It is preferable to use about 50% by weight. If the content of the binder is less than 5% by weight, the strength of the porous layer will be insufficient, and if it exceeds 50% by weight, the absorptivity of the ink may be impaired, which is not preferable. The more preferable content of the binder is 10 to 30% by weight.

As a means for providing a porous layer containing boehmite on a substrate, a method is preferred in which a binder and a solvent are added to boehmite sol to prepare a sol-form coating solution, which is applied to the substrate and then dried. As a coating method, for example, 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 the solvent of the slurry, either an aqueous system or a non-aqueous system can be adopted.

[0025]

【Example】

Example 1 900 g (50 mol) of water was placed in a glass reactor (separable flask, stirring blade, thermometer) with a volume of 2 liters.
And 751 g (12.5 mol) of isopropanol were charged, and the liquid temperature was heated to 75 ° C. by a mantle heater.
Aluminum isopropoxide 204.2 with stirring
5 g (1 mol) was added, and hydrolysis was performed for 120 hours while maintaining the liquid temperature at 75 to 78 ° C. After that, the temperature was raised to 95 ° C while distilling off isopropanol, and 6 g of acetic acid was added.
(0.1 mol) was added and the mixture was kept at 95 to 97 ° C. for 48 hours for peptization. Further, this liquid was concentrated to 400 g to obtain white boehmite sol. The solid content of the obtained sol liquid was 15% by weight.

Polyvinyl alcohol (saponification degree: 99.8%, polymerization degree: 4000) was added to this sol in an amount of 10% by weight based on the boehmite solid content, and the white polyethylene terephthalate film having a thickness of 100 μm was coated with a bar coater. A recording medium was obtained by drying at 140 ° C. The thickness of the coating layer after drying was 30 μm. Pore distribution of the coating layer of this recording medium (pore radius is 1 to 30 nm, 10
Table 1 shows the volume of pores of -30 nm and 30-100 nm) and the degree of orientation.

Example 2 A white boehmite sol having a solid content of 15% by weight was obtained in the same manner as in Example 1 except that the hydrolysis time was changed from 120 hours to 24 hours. A recording medium was obtained in the same manner as in Example 1 using this sol. Pore distribution of the coating layer of this recording medium,
The degree of orientation is shown in Table 1.

Example 3 900 g (50 mol) of water was charged in a glass reactor (separable flask, stirring blade, thermometer) having a volume of 2 liters.
And 751 g (12.5 mol) of isopropanol were charged, and the liquid temperature was heated to 75 ° C. by a mantle heater.
Aluminum isopropoxide 204.2 with stirring
5 g (1 mol) was added, and hydrolysis was performed for 96 hours while maintaining the liquid temperature at 75 to 78 ° C. Then, isopropanol was distilled off, and the mixture was cooled, filtered, and dried at 160 ° C. to obtain boehmite xerogel. Further, this was pulverized to obtain a white powder having an average particle size of 3 μm.

This powder was added to an aqueous solution of polyvinyl alcohol (saponification degree: 99.8%, polymerization degree: 4000) at a ratio of 10 parts by weight of polyvinyl alcohol to 100 parts by weight of the solid content, and the total solid content concentration was 15 A coating liquid of weight% was prepared. This coating solution was applied on a white polyethylene terephthalate film having a thickness of 100 μm using a bar coater and dried at 140 ° C. to obtain a recording medium. The thickness of the coating layer after drying was 29 μm. Table 1 shows the pore distribution and orientation of the coating layer of this recording medium.

EXAMPLE 4 Polyvinyl alcohol (saponification degree: 96.5%, degree of polymerization: 260) was added to the same boehmite sol having a solid content of 15% by weight as in Example 1.
0) was added to the boehmite solid content in an amount of 10% by weight, coated on a high-quality paper having a basis weight of 128 g / m ² using a bar coater, and dried at 140 ° C. to obtain a recording medium. The thickness of the coating layer after drying was 25 μm. Table 1 shows the pore distribution and orientation of the coating layer of this recording medium. Here, the pore distribution measures the pore distribution of only the recording medium including the base material and the base material,
The pore distribution of the coating layer was obtained by subtracting the amount of the base material.

Example 5 The same boehmite powder as in Example 5 was added to an aqueous solution of polyvinyl alcohol (saponification degree: 96.5%, degree of polymerization: 2,600) to 1 part by weight of polyvinyl alcohol per 100 parts by weight of the powder in terms of solid content.
2 parts by weight were added to prepare a coating liquid having a total solid content concentration of 15% by weight. This coating liquid was applied onto a high quality paper having a basis weight of 128 g / m ² using a bar coater and dried at 140 ° C. to obtain a recording medium. The thickness of the coating layer after drying is 25 μm
Met. Table 1 shows the pore distribution and orientation of the coating layer of this recording medium. The pore size distribution was measured in the same manner as in Example 4.

[0032]

[Table 1]

Evaluation For the recording media of Examples 1 to 3, a color ink jet printer MJ-700V2C manufactured by Seiko Epson Corporation is used.
Using, the test pattern of 5 cm × 5 cm was printed in black and green (mixed color of cyan and yellow). The reflection color density of the black pattern of the printed sheet is measured by the Konica Corporation Sakura Densitometer PDA45.
It was measured at. From the green pattern of the printed sheet,
There are 4 levels of beading (0: best, 3:
The worst was the relative evaluation.

[0034]

[Table 2]

In Examples 1 and 4 which are examples of the present invention, recording media having high color density and no beading were obtained. On the other hand, Example 2 given for comparison
Then, although the color density was better than that of Example 1, beading was slightly likely to occur. In addition, in Examples 3 and 5 listed for comparison, beading did not occur, but the color density was slightly low.

[0036]

The recording medium of the present invention has good ink absorbability, exhibits excellent color development, and can quickly absorb ink. Therefore, even when used as a recording medium of an inkjet printer, problems such as beading do not occur. When a transparent substrate is used, the recording medium has good transparency.

Claims (2)

[Claims] 1. A porous layer containing boehmite on a substrate, having a pore volume of 0.3 to 30 with a pore radius of 1 to 30 nm.
1.2 cc / g, pore volume of pore radius 10 to 30 nm is 0.2 to 1.0 cc / g, pore volume of pore radius 30 to 100 nm is 0.3 cc / g or less, and boehmite A recording medium having at least one porous layer in which the b-axis of crystals is oriented perpendicular to the surface of the substrate. 2. Boehmite [02 obtained by X-ray diffraction
The recording medium according to claim 1, wherein the degree of orientation defined by Equation 2 is 0.5 or less based on the peak height ratio (Equation 1) due to the reflection of the [0] plane and the [200] plane. [Equation 1] [Equation 2]