JPH03218887A - Ink jet recording medium - Google Patents

Abstract

PURPOSE:To enhance the preservability of a recording image, to especially reduce the deterioration thereof due to indoor discoloration and to enhance image density by adding magnesium-containing inorg. pigment surface-treated with an aluminum or silicon compound to an ink receiving layer. CONSTITUTION:An ink receiving layer containing magnesium-containing inorg. pigment surface-treated with an aluminum or silicon compound is formed on a support. As a magnesium-containing inorg. pigment, for example, magnesium oxide, magnesium hydroxide, magnesium silicate, magnesium oxalate or magnesium calcium carbonate are designated but it is desirable to use basic magnesium carbonate. The surface treatment of basic magnesium carbonate is concretely performed by a method wherein basic magnesium carbonate is treated using an organoaluminum compound or an inorg. aluminum compound such as aluminum oxide or aluminum hydroxide or a silicon compound such as a silane coupling agent and absorbing the above mentioned compound on the surface thereof by an electrical method or other method or making the same react on the hydroxyl group of said surface.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a recording medium suitably used in an inkjet recording method, and in particular has excellent absorbency and coloring properties for water-based inks, and also has excellent clarity of recorded images. Regarding excellent recording media.

Furthermore, the present invention relates to a recording medium that provides images with less indoor discoloration and excellent elasticity retention.

(Prior Art) Conventionally, recording media for inkjet use include (1) paper made from ordinary paper whose main component is valves to a low size, such as filter paper or blotting paper; 2) As disclosed in Japanese Patent Application Laid-Open No. 56-148585, there are known ink-absorbing layers using porous inorganic pigments on a base paper with low ink-absorbing properties such as 1M high-quality paper. ing.

In addition, in the inkjet recording method that forms high-quality and high-resolution color images, particularly good image preservation is required, and due to such requirements, it is difficult for images to fade due to irradiation with sunlight, visible light, ultraviolet light, etc. Methods for improving this are known (for example, see Japanese Patent Laid-Open No. 60-49990, Japanese Patent Laid-Open No. 61-57380, etc.).

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

Light resistance, which has traditionally been a problem, is, for example, the problem of fading of images due to irradiation with ultraviolet light or visible light.
This problem occurs with images printed on any kind of paper, from PC paper and high-quality paper to coated paper for inkjet use.
The problem of indoor discoloration referred to in the present invention occurs, for example, when an image formed on coated paper is stored in a place where it is not exposed to direct sunlight, but it occurs when an image printed on non-coated paper such as so-called general PPC paper This does not occur, and is a separate issue from the above-mentioned light resistance.

Since the problem of indoor discoloration is a problem specific to coated paper, it is thought that the problem is caused by the pigment that forms 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 common fillers for paper, such as calcium carbonate, kaolin, and talc, which have a low specific surface area. However, when the above-mentioned filler is used, there are problems in that the image density is low and images with high quality and resolution cannot be obtained.

On the other hand, coated paper using highly active silica with a large specific surface area as disclosed in JP-A No. 56-185690, for example, can provide images with high optical density, but at the same time may cause indoor discoloration. The disadvantage was that the problem became more obvious.

As described above, suppressing indoor discoloration and increasing image density are contradictory problems, which cannot be solved by conventional techniques.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a recording medium that has a high image density and has low storage stability of recorded images, especially deterioration due to indoor discoloration, and is particularly suitable for inkjet use.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention provides an inkjet recording medium comprising an ink-receiving layer on a support, wherein the ink-receiving layer contains a magnesium-containing inorganic pigment whose surface is treated with an aluminum compound or a silicon compound. It is a medium.

(Function) According to the findings of the present inventors, indoor discoloration of recorded images is due to oxidative decomposition of the dye, and when the dye is captured on the surface layer of the recording medium, the more the dye comes into contact with the air. In particular, when it is captured by a pigment with a large specific surface area, the contact area with the air becomes correspondingly large, making indoor discoloration more likely to occur.

However, when conventional pigments with a small specific surface area are used, their adsorption power for dyes is insufficient, and the dyes penetrate deeply from the surface layer together with the solvent in the ink, reducing the color development of the dyes, that is, the density of the recorded image. Resulting in.

In general, it is difficult to obtain magnesium-containing inorganic pigments with a high BET specific surface area. Therefore, when used as the main pigment of an ink-receiving layer, indoor discoloration is good, but it is difficult to obtain a high image density. was there.

Therefore, as a result of intensive investigation into a method that could obtain high image density while maintaining excellent indoor discoloration resistance when using magnesium-containing inorganic pigments, we found that the surface of magnesium-containing inorganic pigments was treated with an aluminum compound or a silicon compound. The present invention was developed based on the knowledge that good results could be obtained by using the same method.

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

The present invention is characterized by using a magnesium-containing inorganic pigment whose surface has been treated with an aluminum compound or a silicon compound when forming an ink-receiving layer on a support.

The support used in the present invention is preferably a base paper having ink-absorbing properties, but is not particularly limited thereto, and may be, for example, a commonly used polymer film. However, in this case, it is preferable to use a pigment with good absorbency so that the ink can be completely absorbed in the ink-receiving layer, to increase the coating thickness, or to adopt a combination of the two. The configuration of the present invention will be explained in more detail below regarding a preferred embodiment of the present invention in which the support is a base paper having ink absorbing properties.

The inkjet recording medium of the present invention is constructed by forming an ink-receiving layer containing a magnesium-containing inorganic pigment surface-treated with an aluminum compound or a silicon compound on the support.

The magnesium-containing inorganic pigment referred to in the present invention is, for example,
Examples include magnesium oxide, magnesium hydroxide, magnesium silicate, magnesium oxalate, magnesium calcium carbonate, etc., but it is more preferable to use basic magnesium carbonate. The basic magnesium carbonate which is preferably used will be explained below as a representative example.

Specifically, the surface treatment of basic magnesium carbonate is carried out using an organic aluminum compound, an inorganic salt of aluminum, an aluminum compound such as aluminum oxide, or aluminum hydroxide, or a silicon compound such as a silane clumping agent. This is carried out by treating magnesium so that the above compound is adsorbed onto the surface of basic magnesium carbonate by electrical or other methods, or by reacting with the hydroxyl groups on the surface.

The organoaluminum compound used for the surface treatment of basic magnesium carbonate may be any conventionally known organoaluminum compound, but preferred are aluminum compounds such as aluminum alcoholate compounds, aluminum chelate compounds, and cyclic aluminum oligomers. , has reactivity with adsorbed components and surface functional groups present on the surface of basic magnesium carbonate.

Preferred specific examples of the organoaluminum compound used in the present invention include aluminum ethylate, aluminum isobrobylate, monosec-butoxyaluminum diisobrobylate, aluminum sec-
Aluminum alcoholate compounds such as butyrate; ethyl acetoacetate aluminum diisobutyrate;
Aluminum chelate compounds such as aluminum tris (ethyl acetoacetate), alkyl acetoacetate aluminum diisobutyrate, aluminum monoacetylacetonate bis (ethyl acetoacetate), aluminum tris (acetylacetonate); cyclic aluminum oxydeutroxybropyrate, cyclic Examples include cyclic aluminum oligomers such as aluminum oxide stearate. In addition to these, aluminum stearates, laurates, etc. may also be used.

In addition, inorganic salts of aluminum include chlorides, sulfates, nitrates, ammonium salts, acetates, carbonates, nitrates, etc., as well as aluminates such as sodium aluminate and potassium aluminate, and alum. Examples include double salts, which may also contain water of crystallization.

In addition, aluminum oxide is industrially known as aluminum hydroxide obtained by treating bauxite, a natural mineral, with hot caustic soda, or aluminum hydroxide obtained by spark discharge of metallic aluminum pellets in pure water, etc. The manufacturing method itself is conventionally known, and it can be obtained with various crystal systems (α-form, γ-form, δ-form, η-form, θ-form), and with various particle sizes, bulk densities, and ratios. Aluminas having various surface areas are commercially available, and the present invention includes all of these aluminas.

For example, in addition to general alumina powder, fused alumina, spherical alumina particles, α-alumina, and γ-alumina that are used as materials for ceramics, porcelain, and abrasive materials, ultrafine alumina produced by vapor phase method (manufactured by Aerosil ■), and catalysts. Examples include activated alumina for use as an adsorbent (manufactured by Iwatani Chemical Industry Co., Ltd.), colloidal aqueous dispersion of alumina hydrate (alumina: manufactured by Nissan Chemical Company, Ltd.), and any of them can be used in the present invention.

Further, examples of silicon compounds include silane coupling agents, and specific examples include vinyltrichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane,
Vinylsilanes such as vinyltriacetoxysilane, γ-
Methacrylic oxysilanes such as methacrylate-trimethoxysilane, N-β (aminoethyl)-aminobrobyltrimethoxysilane, N-β (aminoethyl)-γ-aminobutylmethyldimethoxysilane, γ −
Aminopropyltriethoxysilane, N-phenyl-γ
Examples include aminosilanes such as -aminobrobyltrimethoxysilane, epoxysilanes, mercabutosilanes, chloroprobylsilanes, etc., but are not limited to these, of course.

There are two methods for treating basic magnesium carbonate with aluminum compounds or silicon compounds: dry method and wet method.
There are two methods, and any method may be used. The dry method is a method in which an aqueous solution or an organic solvent solution of an aluminum compound or a silicon compound is sprayed onto the solution uniformly while stirring and mixing basic magnesium carbonate. On the other hand, the wet method involves immersing the basic magnesium carbonate in a treatment solution containing an aluminum compound or a silicon compound during the manufacturing process.
This method involves adding an aluminum compound or silicon compound to the slurry or spraying it during the drying process to treat the surface. The aluminum compounds or silicon compounds used in these methods may be used alone or in combination of one or more.
It is preferable to use the pigment in an amount of 0.1 to 15 parts by weight per 100 parts by weight of the basic magnesium carbonate,
Particularly preferred is a proportion of 0.5 to 10 parts by weight. If the amount used is less than 0.1 parts by weight, the effect of the present invention will be insufficient, while if it is more than 15 parts by weight, the ink absorbency and indoor discoloration resistance of the inkjet recording medium will decrease, so it is preferable.
do not have.

The average particle diameter of the treated pigment used in the present invention is preferably lnm to 20 μm, more preferably lnm
- 12 μm, most preferably 0. 1-12μm
It is. According to the findings of the present inventors, the smaller the particle size of the pigment, the less the problem of powder falling when forming coated paper, and the smaller the coefficient of friction between the sheets, and the smaller the particle size of the pigment, the less the problem of powder falling when forming coated paper, and the smaller the coefficient of friction between sheets. This is preferable because it solves the problem of double feeding in which two or more sheets of paper are conveyed in an overlapping manner when the sheets are set and fed.

The pigment forming the ink-receiving layer constituting the inkjet recording medium of the present invention may be the upper treated pigment alone, or
For the purpose of improving other recording characteristics, other conventionally known inorganic pigments and organic pigments can be used in combination without hindering the achievement of the objectives of the present invention. Examples of these other pigments include:
Examples include inorganic pigments such as silica, alumina, aluminum silicate, calcium silicate, clay, kaolin, talc, and diatomaceous earth, and organic pigments such as urea resin.

The ink-receiving layer of the inkjet recording medium of the present invention is mainly composed of the above-mentioned pigment and binder, and examples of the binder include conventionally known polyvinyl alcohol,
One or more water-soluble polymers such as starch, oxidized starch, cationized starch, casein, carboxymethyl cellulose, gelatin, hydroxyethyl cellulose, acrylic resin, and water-dispersible polymers such as SBR latex and polyvinyl acetate emulsion. are used in combination.

In the present invention, the preferred ratio of pigment and binder used is a weight ratio of pigment/binder (P/B) of 10/1 to 10/1.
The binder amount is within the range of 1/4, more preferably within the range of 6/1 to 1/1, and if the amount of binder is greater than 1/4, the ink absorbency of the ink receiving layer decreases; If the amount of pigment is larger, powder falling off of the ink-receiving ink will be severe, which is not preferable.

In preparing the inkjet recording medium of the present invention, an aqueous coating solution containing the pigment, binder, and other additives as described above is coated using a known method such as a roll coater method, a blade coater method, an air knife coater method, etc. , gate roll coater method, size press method, etc. to coat the surface of the support.

Thereafter, the recording medium of the present invention is obtained by drying using, for example, a hot air drying oven or a hot drum.

Furthermore, in order to smooth the surface of the ink-receiving layer or to increase the surface strength of the ink-receiving layer, supercalender treatment may be performed during the process.

Furthermore, in the present invention, dye fixing agents (water-resistant agents), optical brighteners, surfactants, antifoaming agents, pH adjusters, fungicides, ultraviolet absorbers, and antioxidants are added to the ink-receiving layer as necessary. Additives such as a bulking agent, a bulking agent, and a thinning agent may also be included. These additives may be arbitrarily selected from conventionally known compounds depending on the purpose.

The dry coating amount of the ink receiving layer is preferably 0, 2 to 50 g/rri, more preferably 0.5 to 3
It is within the range of 0glrd. In addition, when the coating amount is small, a part of the support may be exposed on the surface. Furthermore, when the coating amount is less than 0.2 g/rrr, there is no effect in terms of dye color development than when no ink-receiving layer, that is, a layer containing pigment, is provided; If it is provided beyond this range, problems with paper dust are likely to occur.

Furthermore, by using a base paper with high ink absorbency (for example, paper with low sizing) as the support, the amount of coating of the ink receiving layer can be reduced.

A suitable coating amount of the ink receiving layer can be defined as the maximum thickness in the cross-sectional direction of the recording medium, and the maximum thickness is 0.
．． It is about 5 to 100 μm, and about 0.5 to 20 μm when a base paper with high ink absorption property is used. Note that the maximum thickness referred to here is the maximum value of the thickness of the ink receiving layer in the depth direction in the cross section of the recording medium.

Note that the recording medium of the present invention may be one in which the pigment is included in the support, that is, a recording medium that contains the pigment in the support without providing an ink-receiving layer.

Using an inkjet recording method, the recording medium of the present invention obtained as described above is coated with water-based ink of multiple colors such as yellow (Y), magenta (M), cyan (C), and black (Bk). When an image is formed, the density of the image obtained is sufficiently high, no discoloration occurs indoors, and excellent storage stability is exhibited.

The ink itself used for recording on the recording medium of the present invention may be any known ink. For example, the recording agent may include direct dyes, acid dyes, basic dyes, reactive dyes, food colorings, etc. Water-soluble dyes can be used, and there are no particular limitations as long as they are used for normal inkjet recording.

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

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 a particularly preferable one is a mixed solvent of water and a water-soluble organic solvent. It contains polyhydric alcohol, which has the effect of preventing ink from drying. Further, as water, it is preferable to use deionized water rather than ordinary water containing various ions.

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

In addition to the above-mentioned components, the ink used for recording may contain a surfactant, a viscosity modifier, a surface tension modifier, etc., if necessary.

The method for performing recording by applying the above-mentioned ink to the above-mentioned recording medium is preferably an inkjet recording method, and this method effectively releases the ink from a nozzle to apply the ink to the recording medium, which is a projectile. Any method may be used as long as it can provide the following.

In particular, by the method described in Japanese Unexamined Patent Publication No. 54-59936, ink subjected to the action of thermal energy undergoes a rapid volume change, and the acting force due to this change in state causes the ink to be ejected from the nozzle. The method can be used effectively.

(Example) Next, the present invention will be explained in more detail by giving reference examples, examples, and comparative examples. All figures in the text, parts and percentages are by weight unless otherwise specified.

Reference Example 1 (Preparation of treated pigment) Magnesium hydroxide (manufactured by Kamishima Chemical Industry ■, magnesium hydroxide 500, BET surface area 60 rrr/g, average particle size 0.29 μm) was dissolved in a mixed solvent of water and methanol (1:1). was dispersed at a concentration of 10%. To this slurry, 5 parts of alkyl acetoacetate aluminum diisobutylate (aluminum chelate M, manufactured by Kawaken Fine Chemicals ■) was added as a solid content per 100 parts of magnesium hydroxide, and after stirring for 30 minutes, the slurry was added with continued stirring. The temperature was raised to 90° C. to volatilize methanol to obtain magnesium hydroxide treated with an organoaluminum compound.

Reference Example 2 (Preparation of treated pigment) Commercially available basic magnesium carbonate (manufactured by Kamishima Chemical Industry ■, one star, B.ET surface area 22 resistance/g, average particle size 0.38
μm) was dispersed in a mixed solvent of water and methanol (1:1). In this slurry, basic magnesium carbonate lO
Alkyl acetoacetate aluminum diisopropylate (Alumichelate M, manufactured by Kawaken Fine Chemicals ■) was added at a solid content of 5 parts per O part, and after stirring for 30 minutes, the temperature of the slurry was raised to 90°C while stirring was continued. The mixture was heated to 0.degree. C. to volatilize methanol to obtain basic magnesium carbonate treated with an organoaluminum compound.

Reference Example 3 (Preparation of treated pigment) In a slurry in which commercially available basic magnesium carbonate was dispersed in water, N-
β(aminoethyl)-γ-aminobutyltrimethoxysilane (silane coupling agent SH6020, Toray
(manufactured by Silicone ■) was added in a solid content of 7 parts, and the mixture was stirred for 1 hour to obtain basic magnesium carbonate treated with a silicon compound.

Reference Example 4 (Preparation of treated pigment) While vigorously stirring commercially available basic magnesium carbonate,
γ-glycidoxib-biltrimethoxysilane (KBM
603, manufactured by Shin-Etsu Silicone ■) sprayed with an aqueous solution,
Thereafter, it was sufficiently dried at 110'C to obtain basic magnesium carbonate treated with a silicon compound.

Examples 1 to 4 As base paper, Steckigt size degree 5 seconds, basis weight 66 g /
rd, JIS-P-81 calcium carbonate as filler
The ash containing 9.0% in terms of ash content according to No. 28 was used.

A coating solution having the following composition was coated on the above base paper using a bar coater method at a dry weight of 5 g/rrr.
The inkjet recording medium of the present invention was obtained by drying at 0° C. for 5 minutes.

(Coating liquid composition) Pigment (pigments of Reference Examples 1 to 4) 9 parts polyvinyl alcohol (PVA-1 17, manufactured by Kuraray ■, degree of saponification 98.5 mol%, degree of polymerization 1,700)
4. 5 parts water
86.5 parts Comparative Example 1 A comparative inkjet recording medium was obtained in the same manner as in Example 1 except that commercially available basic magnesium carbonate was used as a pigment without treatment.

The inkjet recording suitability of the above recording medium is that it has 128 nozzles at a ratio of 16 nozzles to 1 mm,
An inkjet head that ejects ink particles by the action of thermal energy is manufactured by Y. M.C. Inkjet recording was performed using an inkjet printer with four colors of Bk and an ink having the following composition for evaluation.

Eeno ■kai dye 5 parts diethylene glycol 20 parts water
78 parts Heavy duty Y:C. I. Direct Yellow 86 M:C. I. Acid Red 35 c:c. r. Direct Blue 199 8k:C. I. Food Black 2 Evaluation was performed on the following items.

(1) Image Density The black (Bk) density of a print printed solidly using the above inkjet printer was evaluated using a Macbeth reflection densitometer RD-918.

(2) Indoor storage stability The printed matter obtained in (1) was pasted on the wall of an office and left for 6 months. The difference (8E''Mk) between the chromaticity of the image immediately after printing (before being left) and the chromaticity of the image after being left was determined to evaluate the indoor storage stability.

As shown in Table 1, the results showed that the images of Examples had high image density, clarity, and high resolution, and had good indoor storage stability. On the other hand, the images of the comparative examples had low image density and were not clear images.

In addition, in the cases of Examples 2 to 4, the circularity of the dots was maintained when two or more colors of ink were injected, and the size of the dots was also thicker than in Example I. 《Resolution was improved.

Table 1 (Effects of the Invention) As explained above, the present invention provides an inkjet recording medium that can provide images that do not suffer from the problem of indoor discoloration peculiar to coated paper.

In other words, even if images formed by an inkjet recording method using multi-colored inks are stored in a place out of direct sunlight for several months, there will be no problem of discoloration, and furthermore, the image density will be high (dots will be small). An inkjet recording medium is provided in which the dots are nearly perfect circles and a clear image with high resolution is formed because excessive bleeding and feathering do not occur from the dots.

Claims (2)

[Claims] (1) An inkjet recording medium comprising an ink-receiving layer provided on a support, wherein the ink-receiving layer contains a magnesium-containing inorganic pigment surface-treated with an aluminum compound or a silicon compound. (2) The inkjet recording medium according to claim 1, wherein the magnesium-containing inorganic pigment is basic magnesium carbonate.