JPH0324905B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a recording medium recorded using ink, and in particular, a medium that has high density images and characters recorded on the medium, clear color tones, and excellent ink absorption ability, especially for multicolor recording. The present invention relates to a suitable inkjet recording medium. The inkjet recording method uses various operating principles to eject minute droplets of ink and attach them to a recording medium such as paper to record images, characters, etc.; It has the characteristics of easy printing, great flexibility in recording patterns, and no need for development or fixing, and is rapidly becoming popular for various uses as a recording device for various figures including Chinese characters, color images, etc. Furthermore, images formed using the multicolor inkjet method can produce records that are comparable to multicolor printing using the plate making method or printing using the color photographic method, making it ideal for applications that require fewer copies to be produced. Since it is cheaper than using photographic technology, it is being widely applied to the field of full-color image recording. Efforts have been made in terms of equipment and ink composition to use high-quality paper or coated paper used for ordinary printing and writing as the recording medium used in this inkjet recording method. However, as the performance of inkjet recording devices has improved and their applications have expanded, such as higher speeds, higher definitions, and full-color inkjet recording devices, more sophisticated characteristics have come to be required of recording media. In other words, the recording medium must have high ink dot density, bright and colorful colors, and must absorb ink quickly so that even when ink dots overlap, the ink will not run out or smudge. , the lateral diffusion of the ink dots is not unnecessarily large, the periphery is smooth and does not become blurred, and furthermore, the resistance of the dye does not decrease when the recorded image is exposed to ultraviolet rays, oxygen in the air, or water. , preferably to be enhanced. Several proposals have been made to solve these problems. For example, JP-A-52-
No. 53012 describes inkjet recording paper, which is made by moistening a low-size base paper with a coating for surface treatment.
Further, JP-A-53-49113 discloses an inkjet recording paper in which a sheet containing urea-formalin resin powder is impregnated with a water-soluble polymer. Although these general paper type inkjet recording papers absorb ink quickly, they have the disadvantage that the periphery of dots tends to become blurred and the dot density is low. Further, JP-A-55-5830 discloses an inkjet recording paper in which an ink-absorbing coating is provided on the surface of the support, and JP-A-55-51583 discloses non-colloidal silica as a pigment in the coating layer. An example using a powder is disclosed in Japanese Patent Application Laid-open No. 55-11829, and an example of a smear paper using a two-layer structure with different ink absorption speeds is disclosed. These coated paper-type inkjet recording papers are improved over ordinary paper-type inkjet recording papers in terms of dot diameter, dot shape, dot density, and color tone reproducibility, but they are inferior to ordinary paper-type inkjet recording papers in terms of absorption capacity. It was found that the paper type was not as good as the paper type, and even the coated type had superiority and inferiority. Therefore, the present inventors proposed a coat type structure with high absorption speed and large absorption capacity in Japanese Patent Application Laid-Open No. 58-110287, but after that, intensive studies were conducted to improve the absorption capacity and the size of the dot diameter. We succeeded in adjusting the (bleeding rate) and achieved the present invention. That is, the present inventors have proposed an inkjet recording method in which a recorded image is obtained by jetting inkjet ink onto a recording medium, in which the recording medium has at least one ink-receiving layer and voids are formed in the ink-receiving layer. By incorporating synthetic amorphous silica that has been surface-treated with a silane coupling agent as a constituent material, it is possible to maintain sufficient ink absorption speed and ink absorption capacity while suitably controlling dot bleeding, which has a large effect on resolution. It was discovered that this can be adjusted, and the present invention was created. Although it is not clear how the synthetic amorphous silica surface-treated with a silane coupling agent can adjust the degree of bleeding of dots according to the present invention, it is thought to be as follows. Synthetic amorphous silica usually has an extremely large surface area of 80 to 800 m ² /g by the BET method, and has a structure in which hydroxyl groups are coordinated on the surface, and has a large ability to adsorb water molecules, so it can be said to be an extremely hydrophilic pigment. When these are used in the ink-receiving layer, the ink-absorbing capacity increases, but at the same time they also have a large affinity with the ink vehicle, so there is a competition between absorption and penetration, and the absorption depends on the surface area of the pigment used and the thickness of the ink-receiving layer. When the ability is decided, the degree of blurring of the dots is also decided at the same time. However, as in the present invention, by treating the pigment used with a silane coupling agent, it is possible to finely adjust the affinity with the ink vehicle without changing the absorption capacity of the ink vehicle, resulting in moderate bleeding. It is possible to form an ink-receiving layer with certain properties. This can be understood by considering affinity as the difference between the surface energy of the solid and the surface energy of the ink vehicle. Generally, when the solid surface energy is close to or larger than the liquid surface energy, the affinity is considered to be high, and the smaller the solid surface energy is than the liquid surface energy, the weaker the affinity becomes. As mentioned above, the surface of silica is thought to have a very high affinity for water molecules, but treating the surface with a substance that is thought to lower the surface energy, such as a silane coupling agent, is difficult to achieve with the surface-treated pigment. It is thought that this acts to reduce the affinity with the ink vehicle, and by adjusting the difference in surface energy depending on its content, the degree of bleeding of the dots can be adjusted. The synthetic amorphous silica referred to in the present invention refers to dry process silica produced by thermal decomposition of silicon tetrachloride, so-called white carbon such as metathesis precipitation products with sodium silicate acid, carbon dioxide, ammonium salts, etc., and sodium silicate acid. Silica sol obtained through thermal decomposition or through an ion-exchange resin layer, or colloidal silica obtained by heating and aging this silica sol. Silica gel whose primary particles become three-dimensional secondary particles with siloxane bonds, and also so-called synthetic molecules produced by heating silica sol, sodium silicate, sodium aluminate, etc. as starting materials at 80°C to 120°C. Synthetic silicon compounds mainly composed of silicon dioxide, such as Larsieve, are mixed with an aqueous solution of a silane coupling agent during the production process or after production, or are sprayed with an aqueous solution of a silane coupling agent to the surface of synthetic amorphous silica powder. It is possible to react by attaching the silica to synthetic amorphous silica treated with a silane coupling agent.
A silane coupling agent is represented by the following general formula, where OR represents a hydrolyzable group bonded to a silicon atom, and chlorine, R′Si(OR) ³ alkoxy group, and acetoxy group are generally used. . When these groups or atoms are made into an aqueous solution, they undergo hydrolysis to produce silanol, which is coordinated to the surface of the inorganic pigment through hydrogen bonds or the like. R′Si(OR) ³ +H ² O→R′Si(OH) ³ +3ROH Furthermore, in the above general formula, R′ represents various organic functional groups, such as a chloro group, an amino group, an aminoethyl group, A ureido group, a glycidoxy group, an epoxymicrohexyl group, a methacryloxy group, a vinyl group, etc. are generally used. The amount of the silane coupling agent to be added is a matter to be determined depending on the minimum coverage area of the silane coupling agent and the surface area of the synthetic amorphous silica, but in the present invention, it is 0.1 to 20% by weight, preferably 0.5 to 20% by weight.
The amount is 10% by weight, and if it is too large, the synthetic amorphous silica becomes too hydrophobic and cannot be dispersed in water, which is not preferable. In the present invention, the synthetic amorphous silica treated with a silane coupling agent can also be used in combination with the following inorganic or organic pigments. In this case, the silane coupling agent treated synthetic amorphous silica is 20% by weight of the total pigment.
It is preferably used in an amount of 40% by weight or more. Examples of inorganic pigments that can be used in combination include light calcium carbonate, heavy calcium carbonate, kaolin (white clay),
Talc, calcium sulfate, barium sulfate, titanium oxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, aluminum hydroxide, alumina, lithopone. Examples of white pigments and organic pigments include water lily plastic pigments, acrylic plastic pigments, microcapsules, and urea resin pigments. The ink-receiving layer in the present invention refers to a coating layer with voids, which is formed by mixing the inorganic pigment or organic pigment with an adhesive and is provided in a layered manner on a support. Examples of aqueous adhesives used in the ink receiving layer include oxidized starch, etherified starch, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, casein, gelatin, soybean protein, polyvinyl alcohol and its derivatives, and maleic anhydride. Resin, regular styrene
Conjugated diene polymer latex such as butadiene copolymer, methyl methacrylate-butadiene copolymer, acrylic polymer latex such as polymer or copolymer of acrylic acid ester and methacrylic acid ester, ethylene vinyl acetate copolymer, etc. vinyl-based polymer latexes, functional group-modified polymer latexes using monomers containing functional groups such as carboxyl groups of these various polymers, and water-based adhesives such as thermosetting synthetic resins such as melamine resins and urea resins. , and synthetic resin adhesives such as polymethyl methacrylate, polyurethane resin, unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, and alkyd resin, may be used alone or in combination. These adhesives are pigmented
2 parts to 100 parts per 100 parts, preferably 5 parts to 30 parts
However, the ratio is not particularly limited as long as the amount is sufficient to bind the facial mass. However, if 100 parts or more of adhesive is used, the adhesive film forms, which reduces the void structure or makes the voids extremely small, which is not preferable. In addition, when the ink used is a water-based ink, it is preferable that the image does not flow in water after being formed on the ink-receiving layer. activator,
It is also possible to add cation-modified inorganic particles. In addition, if necessary, pigment dispersants, thickeners, fluidity improvers, antifoaming agents, foam inhibitors, mold release agents, foaming agents, penetrants, colored pigments, colored dyes, optical brighteners, and ultraviolet absorbers. , antioxidants, preservatives, anti-bacterial agents, etc. can also be blended as appropriate. The support used is a sheet material such as paper or thermoplastic resin film. In the case of paper, it is paper with no sizing agent added or with appropriate sizing, and may or may not contain a filler. In the case of thermoplastic films, transparent films such as polyester, polystyrene, polyvinyl chloride, polymethyl methacrylate, cellulose acetate, polyethylene, polycarbonate, etc., and white opaque films filled with white pigment or made by fine foaming are used. . As the white pigment to be filled, many pigments are used, such as titanium acetate, calcium sulfate, calcium carbonate, silica, clay, talc, and zinc oxide. It is also possible to use so-called laminated paper, which is obtained by pasting these resin films on the surface of paper or by processing it with molten resin. A subbing layer or corona discharge processing may be applied to improve the adhesion between the resin surface and the ink receiving layer. When forming an ink-receiving layer on these supports by applying a pigment coating liquid, etc., a blade coater, an air knife coater, a roll coater, a brush coater, a curtain coater, which are generally used as coating machines, are used. A bar coater, gravure coater, spray device, etc. are usually used. Furthermore, when the support is paper, it is also possible to apply a size press on a paper machine, a gate roll, a spray, etc. A sheet simply provided with an ink-receiving layer on a support can be used as it is as a recording sheet according to the present invention, but it can be heated and/or
Alternatively, it is also possible to provide surface smoothness by passing between roll nips under pressure. In this case, the degree of processing may be limited because excessive processing by supercalendering will reduce the ink absorbency due to the gaps between the particles. Measurement of various physical property values in Examples was carried out in the following manner. First, use a Sharp inkjet printer (IO-700) to print cyan (C) and magenta.
(M), yellow (Y), and black (Bl) inks were immersed in running water for 5 minutes, and the image density before and after immersion was measured using a Macbeth densitometer RD514. The percentage obtained by dividing the concentration by the concentration before immersion was used as a measure of water resistance. Also,
The dot diameter was determined by measuring the area of a single dot in the black ink area of the same inkjet printer using a dot area meter, calculating the diameter assuming a perfect circle, and using that value. The ink absorption speed was determined using the same printer by bringing the solid print diameter (after about 1 second) of the red print area (magenta + yellow) into contact with a paper presser roll and determining whether stains appeared or not. Furthermore,
The ink absorption capacity is measured at 20℃ using a 1/1 solution of polyethylene glycol (PEG No. 400)/water.
Contact with a fixed area of the ink receiving layer for 10 seconds, remove excess liquid with blotting paper, measure the weight of the solution absorbed into the ink receiving layer, and use the value calculated as grams per square meter. there was. The present invention will be described below with reference to examples, but it is not limited to these examples. In addition, parts and percentages shown in the examples mean parts by weight and percentages by weight. Example 1 100 parts of synthetic amorphous silica (Carplex #67, manufactured by Shionogi Pharmaceutical Co., Ltd.) was dispersed in 400 parts of water, and while stirring at high speed, a silane coupling agent (r-
10 parts of Glycicloxypropyltrimethoxysilane (manufactured by Nippon Unicar) was added dropwise as a 5% aqueous solution, and after completion of the dropwise addition, high-speed stirring was continued for 30 minutes. The mixture was then allowed to stand, the supernatant liquid was discarded, and the mixture was filtered to form a cake, which was then dried with hot air at 105°C. After drying, it was dry-pulverized to obtain a silane coupling agent-treated pigment. 100 parts, 70 parts, and 40 parts of silane coupling agent-treated pigment, 0 parts of light calcium carbonate (Univer 70, manufactured by Shiraishi Kogyo),
Mix 30 parts and 60 parts, add 20 parts of polyvinyl alcohol (PVA117 manufactured by Kuraray), and make a concentration of 18.
% coating solution was prepared, applied with an air knife coater to a dry solid content of 13 g/m ^{2 ,} dried, passed through a super calender, and the surface was smoothed, and then the recording paper of Examples 1, 2, and 3 was prepared. And so. Table 1 shows the evaluation results of the obtained recording paper. Comparative Example 1 Light calcium carbonate (Univer
70 (manufactured by Shiraishi Kogyo), 20 parts of polyvinyl alcohol was added, and the recording paper of Comparative Example 1 was prepared in exactly the same manner as in Examples 1 to 3. Table 1 shows the evaluation results of the obtained recording paper. Examples 4 to 6 100 parts of synthetic amorphous silica (Syroid 404, manufactured by Fuji Devison Chemical) was dispersed in 400 parts of water, and while stirring at high speed, a silane coupling agent (γ-
Aminopropyltriethoxysilane, manufactured by Nippon Unicar)
1 part, 2 parts, and 5 parts of each were added to the above slurry as a 5% aqueous solution, and after the addition was completed, high-speed stirring was continued for 30 minutes to allow reaction. To this slurry, 30 parts of solid polyvinyl alcohol (PVA117 manufactured by Kuraray Co., Ltd.) dissolved at 10% was added and thoroughly stirred to prepare a coating liquid. Apply this coating liquid to art base paper at a solid content of 15g/
The recording sheets of Examples 4, 5, and 6 were coated with an air knife coater to a coating thickness of m ² , dried, and smoothed using a super calender. Table 1 shows the results of evaluating these. Comparative Example 2 Comparative Example 2 was a recording paper prepared in exactly the same manner as in Examples 4 to 6, except that a synthetic amorphous silica slurry to which no silane coupling agent was added was used. Table 1 shows the evaluation results for this product.

【table】

[Table] As is clear from Table 1, Examples 1 to 6 using synthetic amorphous silica surface-treated with a silane coupling agent were able to control the dot diameter to a small size while maintaining good ink absorption. is recognized.

Claims (1)

[Claims] 1. An inkjet recording paper comprising an ink-receiving layer made of synthetic amorphous silica and a water-based adhesive on a support, characterized in that the synthetic amorphous silica is surface-treated with a silane coupling agent. A recording medium for inkjet.