JPH0452785B2 - - Google Patents

Description

[Detailed Description of the Invention] (A) Industrial Application Field The present invention relates to a method for manufacturing inkjet recording paper that records using inkjet ink, and particularly relates to a method for manufacturing inkjet recording paper that records using inkjet ink. The present invention relates to a method for producing an inkjet recording paper that has a high color tone, a clear color tone, excellent ink absorption ability, and no image staining due to discoloration of the 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 recording various shapes and color images of kanji. 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 photographic technology, it is being widely applied to the field of full-color image recording.

(B) Prior art and its problems 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. Ta. However, as the performance of inkjet recording devices has improved and their applications have expanded, such as higher speeds, higher definition, and full-color recording, the recording media have come to be required to have more advanced characteristics. In other words, the recording medium must have high ink dot density, bright and colorful tones, ink absorption is fast and the ink does not run out or smear even when ink dots overlap, and the ink dots must be The diffusion of the image should not be larger than necessary, and the surrounding area should be smooth and not blurred. Furthermore, the resistance of the dye when the recorded image is exposed to ultraviolet rays, oxygen in the air, or water should not be reduced, but should preferably be enhanced, and the recorded image should not change color, let alone change in color when the recording medium is stored, etc. is required.

Several proposals have been made to solve these problems. For example, JP-A-52-
No. 53012 describes an inkjet recording paper 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 No. 55-5830 discloses an inkjet recording paper having an ink-absorbing coating layer on the surface of the support, and JP-A No. 55-51583 discloses a non-colloidal pigment as a pigment in the coating layer. An example using silica powder is disclosed in JP-A-55-11829, and an example of smear paper using a two-layer structure with different ink absorption speeds is disclosed. These coated paper-type inkjet recording papers are improved over general paper-type inkjet recording papers in terms of dot diameter, dot shape, dot density, and color tone reproducibility, but they are not as absorbent. There are many things. Therefore, if you increase the amount of coating to increase the absorption capacity, the dot diameter will become smaller, and the ink will sink deeper, causing the color to become less uniform, making it difficult to improve the absorption capacity alone. It was hot.

Therefore, the present inventor proposed a coat-type structure with a fast absorption rate and large absorption capacity by providing an ink-receiving layer containing a porous inorganic pigment in JP-A-58-110287. Inorganic pigments have high surface activity and a high ability to absorb ink, but they also have the ability to adsorb various organic substances and microparticles that are diffused in the air. On this occasion,
It is possible that the adsorbed organic matter may react with the porous inorganic pigments and other additives in the ink-receiving layer, resulting in coloring or discoloration, and in fact, the recording medium may change color under special conditions. There was found. In particular, these recording papers are sometimes used with marks or ruled lines printed on the ink-receiving layer side, or marks are printed in a light color on the back side to make it easier to distinguish between the front and back sides. Recording paper is subject to special conditions during storage, which sometimes causes the recording paper to change color, especially a slight yellowing. After intensive study on these discolorations, we found a combination with a printing ink that does not cause this discoloration, and completed the present invention.

(D) Structure of the Invention The present invention is a method of printing marks and ruled lines on at least one of the front and back surfaces of recording paper having an ink-receiving layer containing a porous inorganic pigment using printing ink using a normal printing device. A method for producing an inkjet recording paper, characterized in that when printing at least one of the above, printing is performed using an aqueous printing ink that does not contain a lipophilic vehicle, that is, before inkjet recording. Although it is not certain whether the use of printing ink will not cause discoloration of the recording medium, as mentioned above, porous inorganic pigments have high surface activity and have the ability to adsorb organic substances to their surfaces. In that case, the concentration of various adsorbents increases on the pigment surface, and the catalytic action of the pigment surface itself is also involved.
It is conceivable that the adsorbed organic matter may change color or become colored. Therefore, recording paper with an ink-receiving layer containing a porous inorganic pigment can directly absorb the lipophilic vehicle in oil-based ink and the organic solvent remaining in the adhesive of adhesive tape manufactured using oil-based solvents. Or, if it comes into contact with a transparent film or the like, it is thought that a phenomenon of discoloration may occur.

The ordinary printing apparatus referred to in the present invention includes, for example, a letterpress, an intaglio, a lithography, a stencil, etc. when divided by plate type.
Letterpress-related printing includes letterpress printing, flexo printing, primary color printing, etc.; intaglio-related printing includes engraving intaglio printing and gravure printing. Further, offset printing is a typical example of lithographic printing, and stencil printing includes tweezers and stencil printing, as well as collotype printing and the like.

In the present invention, ordinary printing ink refers to ink used in the various printing methods mentioned above, but for example, when classified by drying type, it includes quick set ink, heat set ink, moist set ink,
Cold set ink, UV ink, IR ink,
Possible options include EB ink. Further, in classification according to vehicle composition, inks are divided into oil inks, solvent inks, and water-based inks, and the ink not containing a lipophilic vehicle as referred to in the present invention refers to water-based inks among these classifications.

Water-based printing inks generally consist of the following components.

water-soluble resins such as natural or synthetic resins such as starch, dextrin, alginate, cellulose ester, cellulose ether, polyvinyl alcohol, polyvinyl methyl ether, polyacrylamide, polyethylene oxidone, polyacrylate;
Shellac, styrenated shellac, styrene maleic acid resin, rosin maleic acid resin, casein and its derivatives, colloidal dispersions or water-solubilized resins such as acrylic copolymers, acrylic resins, vinyl acetate resins, styrene resins, Emulsions of vinyl chloride resins, SBR, NBR, etc., polyurethane, polyester, etc., as well as water solubilizers such as ammonia water, co-solvents for pigments, dyes, alcohols, etc., as well as defoaming agents and abrasion resistance as necessary. Improvers, fungicides, plasticizers, rust inhibitors, etc. are added. Printing inks other than water-based printing inks contain vegetable oil, mineral oil, and oil-soluble resin as vehicles, and also contain lipophilic solvents such as hydrocarbons and esters, but the water-based printing ink used in the present invention does not contain these lipophilic vehicles. First, pigments are dispersed in an aqueous vehicle mainly consisting of water, an aqueous resin, and an alcohol.

The ink-receiving layer as used in the present invention refers to a layered coating layer having an ink-absorbing ability and formed on a suitable support from a porous inorganic pigment and, if necessary, other pore-forming materials and an adhesive.

The porous inorganic pigment referred to in the present invention is made by aggregating primary particles of synthetic silica or synthetic alumina.
It is a dry powder with an average secondary particle size of 0.5 μm to 30 μm. When synthetic silica or synthetic alumina is synthesized from water-soluble raw materials in an aqueous solution, its primary particles have a size of several micrometers to several hundred micrometers. Porous inorganic pigments can be mixed with porous inorganic pigments by drying, pulverizing and classifying, or by adjusting the particle size to the desired size using a spray dryer etc. during drying. You can.

In addition, if synthetic silica or synthetic alumina is in the form of a fine powder of 1 μm or less, it can be dispersed in water, added with a binder or adhesive, dried, pulverized, classified, or spray-dried with a spray dryer. It is also possible to use a porous inorganic pigment having an average secondary particle diameter of 0.5 μm to 30 μm.

Furthermore, in order to form fine water-dispersed substances such as colloidal silica and colloidal alumina into particles of 0.5 μm or more, urea-formalin resin etc. are generated in the fine particle suspension water as disclosed in USP-3855172. By adjusting the production conditions, it is also possible to obtain a porous inorganic pigment granulated to a desired secondary particle size.

In the present invention, the above porous inorganic pigment can also be used in combination with the following inorganic or organic pigments. In this case, the porous inorganic pigment is used in an amount of 20% by weight or more, preferably 40% by weight or more of the total pigment. 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,
Examples of white pigments and organic pigments such as aluminum hydroxide, alumina, and lithopone include styrene plastic pigments, acrylic plastic pigments, microcapsules, and urea resin pigments.

In order to form an ink-receiving layer by applying these pigments onto a support, an adhesive is required to adhere the void-forming material to the support. Examples of adhesives include oxidized starch, etherified starch, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, casein, gelatin, soybean protein, polyvinyl alcohol and its derivatives, maleic anhydride resin, and ordinary 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. Water-based adhesion of vinyl polymer latexes, functional group-modified polymer latexes using monomers containing functional groups such as carboxyl groups, and thermosetting synthetic resins such as melamine resins and urea resins. agent,
and synthetic resin adhesives such as polymethyl methacrylate, polyurethane resin, unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, alkyd resin, etc., 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
The ratio is not particularly limited as long as the amount is sufficient to bind the pigment. However, if more than 100 parts of adhesive is used, the adhesive will form a film, which will reduce the void structure or make 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 not be washed away in water after being formed on the ink-receiving layer. An activator, cation-modified inorganic particles, etc. can also be added.

In addition, if necessary, pigment dispersants, thickeners, flow modifiers, antifoaming agents, inhibitors, mold release agents, foaming agents, penetrants, colored dyes, colored pigments, fluorescent whitening agents, and ultraviolet absorbers. , an antioxidant, a preservative, an anti-bacterial agent, a water-resistant agent, etc. may be added as appropriate.

As the support, a sheet material such as paper or thermoplastic resin film is used. In the case of paper, it is paper with no sizing agent added or with appropriate sizing, and may or may not contain fillers.

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 formed by fine foaming are used. As the white pigment to be filled, many pigments are used, such as titanium oxide, 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. Bar coaters, gravure coaters, and spray equipment are commonly 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 the surface smoothness can be improved by passing it between roll nips under heat and/or pressure using a super calender, gloss calender, etc. It is also possible to give. In this case, the degree of processing may be limited because excessive processing by supercalendering will reduce the ink absorbency due to the carefully formed voids between particles.

The various physical property values used in the present invention were measured in the following manner. First, using an inkjet printer (10-700) manufactured by Sharp Co., Ltd., we printed solid images using cyan (C), magenta (M), yellow (Y), and black (Bl) inks. Concentrations were measured with a Macbeth densitometer RD514. 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, converting it to an area assuming a perfect circle, and calculating the diameter. Also, the ink absorption speed is immediately after solid printing (about 1 second) of the red printed area (magenta + yellow) using the same color image printer.
It was then brought into contact with a paper presser roll and judged by whether stains appeared or not. Further, the ink absorption ability was determined by the degree of bleeding at the boundary of the solid printed area using the same inkjet printer.

Printing discoloration was determined by the degree of yellowing of the ink-receiving layer when flexographic printing was performed on the back side of recording paper using various inks and the paper was stored in a cardboard box for one month.

(E) Examples The present invention will be described below with reference to Examples, but the invention 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 80 parts of LBKP with water level 370mlcsf, water level 400mlcsf
20 parts of NBKP, 13 parts of heavy calcium carbonate, 1 part of cationic starch, alkyl ketene dimer sizing agent
0.12 parts and polyalkylene polyamine epichlorohydrin resin. A base paper with a basis weight of 68 g/m ² was made from the slurry consisting of 4 parts using a Fourdrinier paper machine, and 1.5 g/m ² of oxidized starch was deposited using a size press during paper making to produce a coated base paper.

As a porous inorganic pigment, 100 parts of synthetic silica (Syroid 74, manufactured by Fuji Davison Co., Ltd.) with an average secondary particle diameter of 7 μm, which is a micron-sized xerogel obtained by gelling silicic acid, and as an adhesive, polyvinyl alcohol (Kuraray) was used as a porous inorganic pigment. Company-made
A coating liquid consisting of 30 parts of PVA117) was prepared. This coating solution was applied to the coated base paper using an air knife coater so that the dry solid content was 18 g/m ² . Next, the paper was passed through four nips at a nip pressure of 50 kg/cm ² at a speed of 40 m/mm in a super calendar to prepare a recording paper.

The recording paper of Example 1 was prepared by printing marks on the back side of this recording paper by flexographic printing using water-based letterpress chart paper ink (gray color) diluted with alcohol and water.

This recording paper was evaluated and found to have good inkjet suitability and no yellowing at all.

Comparative Example 1 For printing on the back side of the recording paper used in Example 1, an oil-based ink (gray color) for letterpress chart paper was diluted with polymerized linseed oil and Rezur (mineral oil) as an auxiliary agent and marked by flexographic printing. was printed to obtain the recording paper of Comparative Example 1.

As a result of evaluating this recording paper, it was found that the inkjet suitability was the same as in Example 1, but the ink-receiving layer in the area where the mark was printed was found to be discolored to yellow.

Comparative Example 2 The same printing as in Comparative Example 1 was performed on the back side of a commercially available single-sided art paper (pigments were kaolin and heavy charcoal) to obtain a recording paper for Comparative Example 2. As a result of evaluation of this recording paper, it was found that the absorbency of the inkjet suitability was completely poor, but no discoloration of the coating layer was observed.

(F) Effect of the Invention As described above, in the case of inkjet recording paper having an ink-receiving layer using a porous inorganic pigment, printing with a printing ink containing an oil-based vehicle causes yellowing, so it is difficult to print with a water-based ink. Printing is a necessary condition, and it is clear that inkjet recording paper with excellent storage stability can be manufactured by printing marks and ruled lines with water-based ink.

Claims (1)

[Scope of Claims] 1. A method for printing at least one of marks and ruled lines on at least one of the front and back sides of an inkjet recording paper having an ink-receiving layer using printing ink using an ordinary printing device. ,
A method for producing inkjet recording paper, which comprises printing with a printing ink that does not contain a lipophilic vehicle on an inkjet recording paper provided with an ink-receiving layer containing a porous inorganic pigment before inkjet recording. 2 The porous inorganic pigment has an average secondary particle size of 0.5 μm or more
2. The method for producing an inkjet recording paper according to claim 1, wherein the inkjet recording paper is a powder of 30 μm of synthetic silica or synthetic alumina. 3. The inkjet recording paper according to claim 1 or 2, wherein the printing ink is an aqueous printing ink in which a pigment is dispersed in an aqueous vehicle mainly consisting of water, an aqueous resin, and an alcohol. manufacturing method.