JP2621096B2 - recoding media - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a recording medium suitably used for an ink jet recording method, and particularly to a recording medium which is excellent in absorptivity and color developing property of a water-based ink and has excellent storage stability of a recorded image obtained. Also relates to an excellent recording medium.

(Prior Art) Conventionally, as a recording medium for inkjet, (1)
General paper made of pulp as the main component and made into a low-size paper to form filter paper or blotter paper. (2) As described in JP-A-56-148585, general high-quality paper 2. Description of the Related Art There is known an ink-absorbing layer provided with a porous inorganic pigment on a base paper having low ink absorption such as paper.

In addition, in the ink jet recording method for forming a high-quality and high-resolution color image, particularly good image storability is required, and from such a request, image fading due to irradiation with sunlight, visible light, ultraviolet light, or the like. Are known (for example, JP-A-60-49990, JP-A-61-5).
No. 7380).

(Problems to be Solved by the Invention) However, recently, the problem of indoor discoloration of a recorded image has been highlighted as a problem unique to coated paper.

Light resistance, which has been regarded as a problem in the past, is, for example, a problem of fading of an image due to irradiation of ultraviolet light or visible light, and a so-called general light resistance.
This is a problem that occurs on images printed on any type of paper, from PPC paper and high-quality paper to coated paper for ink jet printing.
The problem of indoor discoloration referred to in the present invention, for example, also occurs in an image formed on coated paper stored in a place not exposed to direct sunlight, but does not occur in an image printed on non-coated paper such as PPC paper. This is a separate issue from the lightfastness described above.

Since the problem of indoor discoloration is a problem peculiar to coated paper, it is considered that the problem is caused by the pigment forming the coat layer. It is known that indoor discoloration is related to the specific surface area of the pigment used, and indoor discoloration can be suppressed by using a general filler for paper such as calcium carbonate, kaolin, and talc having a low specific surface area. However, when the above filler is used, the image density and saturation are low, and high quality,
There is a problem that a high-resolution image cannot be obtained. Conversely, for example, coated paper using silica having a large specific surface area and strong activity as disclosed in JP-A-56-185690 can provide an image with high optical density and saturation, while discoloring indoors However, there is a disadvantage that the problem described above becomes significant.

As described above, the suppression of indoor discoloration and the problem of image density and saturation are contradictory problems, and cannot be solved by the conventional technology.

Therefore, an object of the present invention is to provide a storage medium having a high image density with little deterioration due to storage stability of a recorded image, particularly, indoor discoloration,
In particular, it is to provide a recording medium suitable for inkjet.

Another object of the present invention is to provide a recording medium which is excellent in the color developability of the applied ink, has a wide color reproduction range on chromaticity coordinates, and is suitable for providing clear and high-quality images. To provide.

(Means for Solving the Problems) The above object is achieved by the present invention described below.

That is, the present invention is a recording medium comprising aluminum oxide particles and basic magnesium carbonate particles, wherein the weight ratio thereof is in the range of former / latter = 1/5 to 3/1. .

(Action) According to the findings of the present inventors, the indoor discoloration of the recorded image is considered to be due to the oxidative decomposition of the dye, and the dye is captured on the surface layer of the recording medium, and in the case of coated paper for forming an image,
That is, it is presumed that the larger the specific surface relation of the pigment used in the ink receiving layer in the present invention is, the higher the probability of occurrence of the contact oxidation reaction by air is, and the more the indoor discoloration proceeds.

However, when a conventional pigment having a small specific surface area is used, the adsorptive power to the dye is insufficient, and the amount of the dye captured near the surface of the ink receiving layer is reduced, so that a high-density image cannot be obtained. In addition, the dye cannot have sufficient color developing properties and the color reproduction range is narrow, so that only an unclear image can be obtained.

In the present invention, by containing certain two types of inorganic pigments, without using a pigment having a high specific surface area, the dye-capturing effect of the pigment in the surface layer is enhanced, and the excellent indoor discoloration suppressing effect is provided on the recording medium. Enabled to be granted.

Further, the present inventors have found that when these pigments are contained in a recording medium at a specific ratio, an unexpected synergistic effect can be obtained from a combination of the respective properties, and the present invention has been accomplished. .

(Preferred Embodiment) Next, the present invention will be described in more detail with reference to preferred embodiments.

BE having aluminum oxide particles used in the present invention
T specific surface area of 40 to 200 m ² / g, more preferably 60~170m ² / g
By containing these pigments, the dye-trapping effect on the surface of the ink receiving layer can be enhanced.

When the specific surface area is less than 40 m ² / g, a sufficient dye-trapping effect cannot be provided. On the other hand, when the specific surface area exceeds 200 m ² / g, the problem of indoor discoloration becomes significant.

The preferred average particle size of the aluminum oxide particles is in the range of 1 nm to 10 μm, and more preferably in the range of 0.01 to 3 μm. When a particle having a large average particle diameter is used, blurring of printed dots becomes large, or feathering occurs, resulting in deterioration of print quality.

Further, the aluminum oxide particles themselves usable in the present invention are conventionally known, and a method of calcining aluminum hydroxide obtained by treating bauxite with hot caustic soda, and a method of producing a metal aluminum pellet by spark discharge in water. Those obtained by a method of baking aluminum hydroxide or a method of evaporating aluminum chloride and oxidizing it in a gas phase can be used. Also, α, γ,
Any crystal structure such as δ, η, and θ can be used.

Aluminum oxide particles have the property of being able to impart sufficient dye coloring even with particles having a low specific surface area, compared to silica, calcium carbonate, kaolin, etc., which have been conventionally used as fillers for paper. doing.

This is because, unlike other particles, aluminum oxide particles have a cationic surface, so it is possible to ionically adsorb a dye having an acidic functional group, and the dye adsorption capacity per unit surface area is increased. It is thought that it is high.

Since aluminum oxide particles can obtain sufficient dye coloring properties with such a relatively low specific surface area, indoor discoloration of a recording medium using such aluminum oxide particles requires the use of a pigment having a low specific surface area. That is, it is significantly improved over the conventional silica-based pigment.

The problem with the use of aluminum oxide particles as described above is that the particles themselves have low water absorption, resulting in insufficient ink absorbency. However, it is insufficient for indoor discoloration resistance.

Next, the basic magnesium carbonate particles used in the present invention preferably have a BET specific surface area in the range of 10 to 170 m ² / g. By including these, an excellent indoor discoloration suppressing effect can be imparted. That the specific surface area exceeds 170m ² / g has insufficient indoor discoloration inhibiting effect, whereas, 10 m ²
If less than / g, the dye capturing effect is insufficient even when used in combination with the aluminum oxide particles.

The preferred range of the average particle size of the basic magnesium carbonate particles is from 1 to 20 μm, more preferably from 1 to 8 μm. When the particles having a large average particle diameter are used, the bleeding of the printed dots becomes large, or feathering occurs, thereby deteriorating the printing quality.

The basic magnesium carbonate particles used in the present invention are conventionally known in general.For example, usually, for example, magnesium oxide is dispersed and stirred in water to obtain magnesium hydroxide, and then carbon dioxide gas is blown into the slurry to form a carbonate. It can be obtained by Not only those that have been completely carbonized, but also those that partially contain magnesium oxide or magnesium hydroxide can be used in the present invention.

The basic magnesium carbonate particles can also provide a high density image even with a low specific surface area as compared with conventional paper fillers such as silica, calcium carbonate and kaolin.

This is considered to be because the basic magnesium carbonate particles are basic and have high dye adsorption capacity per unit surface area.

Furthermore, the feature when using basic magnesium carbonate particles is that, compared to other inorganic pigments such as silica-based and alumina-based having similar specific surface area, they have a remarkable suppression effect on indoor discoloration of images and It has a unique petal-like particle shape and therefore has excellent water absorption.

When basic magnesium carbonate particles are used, the mechanism by which the effect of suppressing indoor discoloration is superior to other pigments is unknown, but in particular, by using basic magnesium carbonate particles in the ink receiving layer, recording using an inkjet method is possible. It has become possible to impart the same image fastness to general printing as images.

The problem with the use of the basic magnesium carbonate particles is that the coloring property of the dye is still insufficient, and there is a problem that the saturation is reduced particularly when the amount of ink adhered is large.

The recording medium of the present invention is characterized in that the aluminum oxide particles and the basic magnesium carbonate particles are contained at a weight ratio of 1/5 to 3/1. When contained within this range, despite the use of aluminum oxide particles, the indoor discoloration suppression effect is not different from the case of basic magnesium carbonate particles alone, and a small amount of coating using basic magnesium carbonate particles. It is also possible to greatly improve the problem of the decrease in the saturation characteristic of paper. In addition, there is no problem of insufficient ink absorbency due to the aluminum oxide particles and bleeding and feathering caused by the lack of the ink absorbency.

When the content of the aluminum oxide particles is higher than the above range, the coloring property of the dye is excellent, but the effect of suppressing indoor discoloration is insufficient, and when the amount of the basic magnesium carbonate particles is large, sufficient concentration and Images with saturation cannot be obtained.

The recording medium of the present invention is composed of a base material and an ink receiving layer provided on the base material.Generally, general paper is used as the base material, but using a resin film, glass, a metal plate, a wooden plate, or the like. Is also good.

The ink receiving layer is formed mainly of a pigment and a binder. As the pigment constituting the ink receiving layer, in addition to the aluminum oxide particles and the basic magnesium carbonate particles, not more than 40% by weight of the total amount of the pigment constituting the ink receiving layer, more preferably 20% Other inorganic pigments and organic pigments conventionally used generally can be used within the range not exceeding.

As the binder that can be used in the present invention, for example, conventionally known polyvinyl alcohol, starch, oxidized starch, cationized starch, casein, carboxymethylcellulose, gelatin, hydroxyethylcellulose, water-soluble polymers such as acrylic resins and SBR latex And one or more water-dispersible polymers such as polyvinyl acetate emulsions.

In the present invention, the preferred ratio of the pigment and the binder used is such that the pigment / binder (P / B) is 10 to 1/4 by weight.
In the range, more preferably in the range of 6/1 to 1/1, 1/4
When the amount of the binder is larger, the ink absorbing property of the ink receiving layer is reduced. On the other hand, when the amount of the pigment is larger than 10/1, the powder dropping of the ink receiving layer is unfavorably increased.

In preparing the recording medium of the present invention, an aqueous coating solution containing the pigment, the binder, and other additives as described above, a known method, for example, a roll coater method, a blade coater method, an air knife coater method, Coating is performed on the substrate surface by a gate roll coater method, a size press method, or the like.
Thereafter, drying is performed using, for example, a hot-air drying furnace or a hot drum to obtain the recording medium of the present invention.

Further, in order to smooth the surface of the ink receiving layer or to increase the surface strength of the ink receiving layer, a super calender treatment may be performed.

Further, in the present invention, if necessary, a dye fixing agent (waterproofing agent), a fluorescent brightener, a surfactant, an antifoaming agent, a pH adjuster, a fungicide, an ultraviolet absorber, an antioxidant may be added to the ink receiving layer. An additive such as an agent, a dispersant, or a viscosity reducing agent may be contained. These additives may be arbitrarily selected from conventionally known compounds according to the purpose.

As a preferable coating amount of the ink receiving layer, a dry coating amount is in the range of 0.2 to 50 g / m ² , more preferably 0.5 to 30 g / m ² . When the coating amount is small, a part of the substrate may be exposed on the surface. The ink receiving layer when the coating amount is less than 0.2 g / m ^2, i.e. there is no effect in terms of color development of the dye in comparison with the case where not provided a layer containing a pigment, whereas,
If the amount is more than 50 g / m ² , the problem of paper dust is likely to occur.

Also, if a base paper having a high ink absorbency (for example, a paper having a low degree of size) is used as the base material, the coating amount of the ink receiving layer can be reduced. The preferred coating amount in this case is 1
About 8 gm ² .

In the recording medium of the present invention, the particles are contained in the base paper, that is, the aluminum oxide particles and the basic magnesium carbonate particles are contained in the base paper in the above range without providing the ink receiving layer. Recording medium.

The recording medium of the present invention obtained as described above is subjected to ink-jet recording using, for example, a multi-color aqueous ink such as yellow (Y), magenta (M), cyan (C), and black (Bk). When an image is formed, the resulting image does not undergo indoor discoloration and exhibits excellent storage stability.

The ink itself used for recording on the recording medium of the present invention may be a known one, and examples thereof include direct dyes, acid dyes, basic dyes, reactive dyes, edible dyes and the like. Water-soluble dyes can be used,
There is no particular limitation as long as it is used for ordinary inkjet recording.

Such water-soluble dyes are generally used in conventional inks at a ratio of about 0.1 to 20% by weight,
In the present invention, this ratio may be the same.

The solvent used in the water-based ink used in the present invention is water or a mixed solvent of water and a water-soluble organic solvent, and particularly preferable are water and a mixed solvent of a water-soluble organic solvent, and as a water-soluble organic solvent. It contains a polyhydric alcohol having an ink drying prevention effect. As the water, it is preferable to use deionized water instead of general water containing various ions.

The content of the water-soluble organic solvent in the ink is generally in the range of 0 to 95% by weight, preferably 2 to 80% by weight, more preferably 5 to 50% by weight based on the total weight of the ink.

In addition, the ink used for recording may include a surfactant, a viscosity modifier, a surface tension modifier, and the like, if necessary, in addition to the above components.

The method for performing the recording by applying the ink to the recording medium may be any recording method, preferably an inkjet recording method, the method is to effectively detach the ink from the nozzle, Any system may be used as long as it can apply ink to the recording medium that is the projectile.

In particular, according to the method described in Japanese Patent Application Laid-Open No. 54-59936, the ink subjected to the action of thermal energy causes a sudden volume change, and an ink jet method in which the ink is ejected from the nozzle by the action force due to this state change. Can be used effectively.

(Examples) Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. The terms “part”, “part” and “%” are based on weight unless otherwise specified.

Examples 1 to 4 and Comparative Examples 1 to 3 Basis weight 80 g / m ² , thickness 100 μm, Stekigt sizing degree 0 to 2 seconds, and calcium carbonate as filler JIS-P
A material containing 7.0% in terms of ash content by -8128 was prepared.

A coating solution having the following composition was applied on the above base paper by a bar coater method so as to have a dry weight of 5 g / m ² ,
After drying for minutes, the present invention and a recording medium for comparison were obtained.

Pigment 54 parts Polyvinyl alcohol (PVA-117, manufactured by Kuraray Co., Ltd., 98% saponification degree, polymerization degree 1,700) 36 parts Dimethyl diallyl ammonium chloride / acrylamide Polymer (PAS J-41, manufactured by Nitto Boseki Co., Ltd.) 10 parts Water 1,000 parts As the pigment, a mixture of the following particles in the proportions shown in Table 1 was used.

Pigment A: Aluminum oxide particles (fine powder alumina, AKP-
G, manufactured by Sumitomo Chemical Co., Ltd., average particle size 0.5 μm, BET specific surface area 137 m ² / g) Pigment B: basic magnesium carbonate particles (basic magnesium carbonate, S type, manufactured by Ube Chemical Co., Ltd., average particle size 16μ
m, BET specific surface area 46 m ² / g) The inkjet recording suitability of the above recording medium is 1 mm
Using an inkjet printer having four nozzles of Y, M, C, and Bk, each of which has 128 nozzles at a nozzle interval of 6 ratios and ejects ink droplets by the action of thermal energy, using an ink having the following composition: Inkjet recording was performed and evaluated.

Ink composition Dye 3 parts Ethylene glycol 5 parts Diethylene glycol 25 parts Water 67 parts Dye Y: C.I. Direct Yellow 86 M: C.I. Acid Red 35 C: C.I. Direct Blue 199 Bk: C.I. Food Black 2 Evaluation was made on the following items.

(1) Color reproduction range Yellow (Y), magenta (M), cyan (C) and red (R) (mixed color of Y and M), green (G) of printed matter solid-printed using the above printer The hue and saturation of each of (mixed color of Y and C) and blue (Bl) (mixed color of M and C) were evaluated using a color analyzer CA-35 (manufactured by Murakami Color Research Laboratory). , M and R are shown in Table 2 below.

(2) Image preservability The printed matter obtained in the above (1) was stuck on the outside of the window facing the north side of the office and left for 3 months. The difference (ΔE ^* ) between the chromaticity of the image immediately after printing on the solid printing portion of Bk, Y, M and C and the chromaticity of the image after standing was determined and evaluated as image storability.
Are shown in Table 2.

In addition, it has been confirmed that the place where the printed matter is pasted is not directly exposed to sunlight or rain all year round, and that there is air circulation. FIG. 1 shows the color gamut of Examples 1 and 4 and Comparative Example 3 on the chromaticity diagram.

Examples 5 to 6 and Comparative Examples 4 to 5 Commercially available high quality paper (Silver Ring, manufactured by Sanyo Kokusaku Pulp Co., Ltd.) was used as the base paper, and the dry coating amount of the ink receiving layer was 15 g / m 2 on the base paper. except that the ² to obtain a recording medium of the present invention and comparative examples in the same manner as in example 1.

 The mixing ratio of the two pigments was as follows: Example 5 = A / B = 7/3 Example 6 = A / B = 2/8 Comparative Example 4 = A / B = 10/10 Comparative Example 5 = A / B B = 0/10.

Examples 7 to 8 and Comparative Examples 6 to 7 The same as Example 1 except that the following pigments were used as the pigments A and B, and the blending ratio was the same as that of Examples 5 to 6 and Comparative Examples 4 to 5. Recording media of the present invention and comparative examples were obtained.

Pigment A: ultrafine alumina (Aerosil aluminum oxide-C, manufactured by Degussa, average particle diameter 20 nm, BET specific surface area 100
m ² / g) Pigment B: Basic magnesium carbonate (Venus, Kamijima Chemical Co., Ltd.)
Manufactured, average particle diameter 5.9 μm, BET specific surface area 26 m ² / g) The above evaluation results are summarized in Table 3.

Comparative Example 8 As an example to be compared with a conventionally known recording medium, fine pigment silica (Fine Seal X-37, manufactured by Tokuyama Soda Co., Ltd., average particle diameter 2.5 nm, BET specific surface area 260 m ² / g) was used as the pigment. A recording medium of a comparative example was obtained in the same manner as in Example 1 except that the recording medium was used. The evaluation results are shown in Table 3.

(Effects of the Invention) As described above, since the recording medium of the present invention contains aluminum oxide particles and basic magnesium carbonate particles at a fixed ratio, the recording medium is excellent in image preservability and excellent in color development of the dye. It is possible to provide a color reproduction area in the latter half, and it is possible to obtain a recorded image which cannot be achieved by the conventional technique.

Therefore, by using the recording medium of the present invention, it is possible to provide a clear, high-quality color recording image with high saturation, and the obtained image is discolored even if it is stuck on an office wall or the like and left. This makes it possible to provide an image which is excellent in storability and does not cause bleeding.

[Brief description of the drawings]

FIG. 1 is a diagram showing a color reproduction range in Examples 1, 4 and Comparative Example 3.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hiroshi Sato 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-61-63477 (JP, A) JP-A-60 −54915 (JP, A)

Claims (2)

(57) [Claims] 1. A recording medium comprising aluminum oxide particles and basic magnesium carbonate particles, wherein the weight ratio thereof is in the range of the former / the latter = 1/5 to 3/1. 2. An ink-receiving layer comprising a substrate and an ink-receiving layer provided on the substrate, wherein the ink-receiving layer contains aluminum oxide particles and basic magnesium carbonate particles, and the weight ratio thereof is the former / the latter = A recording medium characterized by being in the range of 1/5 to 3/1.