JPH0465792B2 - - Google Patents

Description

[Detailed description of the invention]

(A) Industrial Application Field The present invention relates to a recording medium recorded using ink, and in particular, the images and characters recorded on the medium have high density, clear color tone, and excellent ink absorption ability. Moreover, the strength of the coating layer is strong, preventing folding and cracking.
This invention relates to an inkjet recording medium with significantly less powder falling. (B) Prior Art Efforts have been made in terms of equipment and ink composition to use high-quality paper or coated paper, which is used for ordinary printing and writing, as the recording medium used in the inkjet recording method. However, as the performance of inkjet recording devices increases, such as higher speeds, higher definitions, and full-color inkjet recording devices, and their applications expand, more advanced characteristics are now required of recording media. In other words, the recording medium should have high ink dot density, bright and colorful tones, fast ink absorption, no ink flowing or smearing even when ink droplets overlap, and high quality after printing. Several proposals have been made in the past to meet these requirements, such as that images do not blur even when immersed in water. For example, JP-A-55-5830 discloses an inkjet recording paper in which an ink-absorbing coating layer 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 powder is disclosed, and furthermore, Japanese Patent Laid-Open No. 11829/1983 discloses an example of smear paper using a two-layer structure with different ink absorption speeds. Generally, in order to obtain print density and color clarity, synthetic amorphous silica, which has a low refractive index and a large specific surface area, is preferably used. Various adhesives ranging from natural, semi-synthetic to synthetic adhesives are used for smearing using synthetic amorphous silica. However, with both adhesives, the adhesion between silica particles is weak, especially when the ink-receiving layer is thickened to increase the ink absorption ability, and sufficient coating strength cannot be obtained. This not only causes problems such as peeling, powder falling, or peeling of the coating layer when feeding paper to the printer, or flaking of the coating layer when handling the image after printing, or peeling off the coating layer with a writing instrument, which not only damages the printed image. This was a practical problem because it also caused clogging of the inkjet nozzles. In order to eliminate the above-mentioned drawbacks such as powder falling off, increasing the amount of adhesive will improve powder falling off, but in this case, the adhesive will fill the voids in the ink receiving layer, so the ink absorbency, which is important for an inkjet recording medium, will be improved. The disadvantage was that the value decreased. (C) Problems to be Solved by the Invention The present invention does not cause the above-mentioned problems such as cracking and peeling of the coating layer during processing and handling, has strong coating layer strength, and has a high color quality of printed images. The object of the present invention is to provide an inkjet recording medium that has a high ink absorption capacity and excellent water resistance of recorded images. (D) Means for Solving the Problems The present invention provides the following advantages: (1) A polyvinyl alcohol polymer having a silanol group in the molecule has a higher resistance between synthetic amorphous silica particles and a support than conventionally known binders. It has extremely good adhesion to the paint, and it is possible to obtain an ink absorbing layer that maintains high ink absorbency and does not cause problems such as flaking of the coating layer or cracking.
(2) However, when the cationic resin used to obtain water resistance of images is mixed with an aqueous solution of polyvinyl alcohol polymer having silanol groups, it gels, forming a coating liquid for spreading on the support. Based on the knowledge that this is not possible, we will obtain an excellent recording medium that eliminates this drawback. Namely, 1. In an inkjet recording medium in which an aqueous ink absorbing layer is provided on a support, the ink absorbing layer is
(1) A first layer consisting of a pigment mainly composed of synthetic amorphous silica and a polyvinyl alcohol polymer having silanol groups in its molecules (silanol-containing PVA) alone or in a mixture with other adhesives;
(2) Pigments and pigments based on synthetic amorphous silica
An inkjet comprising a second layer consisting of 2 parts by weight or less of a polyvinyl alcohol polymer having a silanol group in the molecule (silanol-containing PVA) per 100 parts by weight, other adhesives, and a cationic resin. recoding media. 2. An inkjet recording medium in which the first layer contains 6 to 80 parts by weight of (silanol-containing PVA) and 15 to 90 parts by weight of the total binder based on 100 parts by weight of the pigment. 3 In the second layer, the total amount of binder is 100% pigment.
It is an inkjet recording medium in which the amount is 15 to 90 parts by weight. The above ink absorbing layer is obtained by adding and mixing a cationic resin and other additives if necessary to an aqueous slurry of a pigment and adhesive mainly composed of synthetic amorphous silica, and coating the mixture on a support. . In the first layer formed on the support, 6 to 80 parts by weight of a PVA polymer containing silanol groups in the molecule (silanol-containing PVA) is contained per 100 parts by weight of the pigment, and the total amount of adhesive is 15 to 90 parts by weight. Parts by weight are preferred. The total amount of adhesive
If it is less than 15 parts, adhesion between the pigments and to the support will be insufficient, resulting in powder falling off and cracking. Moreover, if the amount exceeds 90 parts by weight, the voids formed between the pigments will be filled with the adhesive, resulting in a marked decrease in ink absorbency. For the same reason as above, the amount of adhesive in the second layer is
It is preferably 15 to 90 parts by weight based on 100 parts by weight of the pigment.
Of this adhesive (PVA containing silanol), 2
If the amount exceeds parts by weight, the aqueous slurry will gel when the cationic resin is added and mixed, and it will no longer be possible to form an absorbent layer by coating on the support. Therefore, it is preferable not to add (silanol-containing PVA) to the second layer, and even if it is added, the amount is up to 2 parts by weight. The first layer having the above composition is coated on the support and dried, or the second layer is coated on the first layer and dried without drying. A sheet simply coated on a support can be used as it is as a recording sheet according to the present invention, but it may also be heated and/or passed between roll nips under pressure using a super calender, gloss calender, etc. to impart surface smoothness. It is possible.
In this case, excessive processing by supercalender processing may reduce the ink absorbency due to the voids between the particles, so the degree of processing may be limited. By adopting the above layer structure, the (silanol-containing PVA) in the first layer strengthens the adhesion between the silica and the silica to the support.
The cationic resin in the second layer formed thereon also permeates into the first layer, so that the entire layer satisfies the water resistance of the ink. Also, since a strong adhesive layer to the support has already been formed, adhesion of the second layer is also facilitated. Therefore, first a second layer is applied to the support,
It is also possible to create a first layer, but
In this case, the cationic resin exists only in the lower layer, and when printing with ink, the water-based dye is fixed only in the lower layer and not in the upper layer, resulting in printed dots concentrically, and the ink's water resistance is insufficient. However, the pigment adhesion is not sufficient. It is not necessary to form each of the first layer and second layer in one coating, and it is also possible to stack several layers of the composition of the first layer that satisfies the claimed range, and then to form several second layers. It is. The coating device may be any conventional coating device, such as a size press coater, gate roll coater, roll coater, air knife coater, blade coater, etc., which are appropriately selected and used in combination. The coating amounts of the first and second layers are appropriately determined depending on the required absorbency and ink dot smearing, but each is 3 to 30 g/m ² , preferably 5 to 25 g/m 2 .
^m2 . The coating amounts of each of the first layer and the second layer may also be appropriately combined. The polyvinyl alcohol polymer having a silanol group in the molecule as used in the present invention is, for example, radical copolymerization of an alkylene monomer containing a silanol group with a lower fatty acid vinyl ester such as vinyl acetate, and the resulting copolymer is saponified. It is a polyvinyl alcohol-based polymer obtained by methods such as
85% or more, and the degree of polymerization is preferably 500 or more and 2000 or less.
In addition, the content of silanol groups in the modified polyvinyl alcohol polymer having silanol groups in the molecule is preferably 0.05 to 1.5 mole% as monomer units containing silanol groups, and if it is less than 0.05 mole%, the strength of the coating will improve. The effect of
If it exceeds 1.5 mole%, the water solubility of the polymer decreases, which not only reduces the ink absorbency of the ink receiving layer, but also significantly increases the viscosity of the coating liquid due to interaction with synthetic amorphous silica. Practically unfavorable. Examples of adhesives other than the above-mentioned PVA polymers having silanol groups in the molecule include oxidized starch,
etherified starch, carboxymethyl cellulose,
Cellulose derivatives such as hydroxyethyl cellulose, casein, gelatin, soybean protein, polyvinyl alcohol and its derivatives, maleic anhydride resin, conjugated diene polymer latex such as ordinary styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, etc. , acrylic polymer latex such as a polymer or copolymer of acrylic acid ester and methacrylic acid ester, vinyl polymer latex such as ethylene vinyl acetate copolymer,
Alternatively, functional group-modified polymer latexes using monomers containing functional groups such as carboxyl groups of these various polymers, water-based adhesives such as thermosetting synthetic resins such as melamine resins and urea resins, and polymethyl methacrylate, Synthetic resin adhesives such as polyurethane resins, unsaturated polyester resins, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral, and alkyd resins can be used alone or in combination. 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 from sodium silicate acid, carbon dioxide, ammonium salts, etc. Silica sol obtained by thermal decomposition with acid or passing through an ion exchange resin layer, or colloidal silica obtained by heating and aging this silica sol, gelling the silica sol and changing the formation conditions to produce a size ranging from several millimicrons to several tens of millimicrons. A so-called synthetic product produced by heating at 80℃ to 120℃ using silica gel, silica gel, silica sol, sodium silicate, sodium aluminate, etc. as a starting material, which is a three-dimensional secondary particle with siloxane bonds. Refers to synthetic silicon compounds mainly composed of silicon dioxide, such as molecular sieves. In the present invention, in addition to synthetic amorphous silica, the following inorganic or organic pigments can be used in combination. However, from the viewpoint of color clarity and absorbency, it is preferable that the content of silica be 80% 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,
Examples of white pigments and organic pigments such as aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, aluminum hydroxide, alumina, and lithopone include styrene plastic pigments, acrylic plastic pigments, microcapsules, and urea resin pigments. be. The cationic resin referred to in the present invention refers to a monomer, oligomer, or polymer that dissociates and exhibits cationic properties when dissolved in water, preferably having a quaternary ammonium group, and particularly preferably the following () to () Refers to a compound having a structure represented by the general formula. In the formula, R ₁ , R ₂ , R ₃ are alkyl groups, m is 1 to 7,
n represents 2 to 20, and Y represents an acid group. In the formulas () to (), R ₁ and R ₂ are −CH ₃ and −CH _2
-CH3 , _-CH2 - _CH2 -OH and Y represent acid groups. () Polyalkylene polyamine dicyandiamide ammonium salt condensate Examples of the compound represented by the general formula () include Nalpoly 607 (manufactured by Nalco Chemical Co., Ltd.) and Polyfix 601 (manufactured by Showa Kobunshi Co., Ltd.). The compounds represented by the general formulas () to () are polydiallylamine derivatives, obtained by cyclopolymerization of diallylamine compounds, and Percoll 1697
(Allied Colloids), Cat Floe (Calgon)
Corp), PAS (Nitto Boseki), Neo Fixtures
Examples include RPD (manufactured by NICCA Chemical Co., Ltd.). Furthermore, examples of the compound represented by the general formula () include Neofix RP-70 (manufactured by NICCA Chemical Co., Ltd.). The content of the cationic resin represented by these general formulas () to () is usually 0.1 to 4 g/m ² , preferably 0.2 to 2 g/m ² . Other additives include pigment dispersants, thickeners,
Fluidity modifier, antifoaming agent, foam suppressor, mold release agent, foaming agent, penetrating agent, colored dye, colored pigment, fluorescent whitening agent,
UV absorbers, antioxidants, preservatives, anti-bacterial agents,
A waterproofing agent and the like may also 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, corona discharge processing, etc. may be applied to improve the adhesion between the resin surface and the ink receiving layer. The aqueous ink referred to in the present invention is a recording liquid comprising the following colorant, liquid medium, and other additives. As the coloring agent, water-soluble dyes such as direct dyes, acid dyes, basic dyes, reactive dyes, and food colorings are preferably used. For example, as a direct dye,

【table】

【table】

[Table] etc. In addition, water-based ink media include water and various water-soluble organic solvents, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol,
Alkyl alcohols having 1 to 4 carbon atoms such as sec-butyl alcohol, tert-butyl alcohol and isobutyl alcohol; Amides such as dimethylformamide and dimethylacetamide; Ketones or ketone alcohols such as acetone and diacetone alcohol; tetrahydrofuran and dioxane Ethers such as polyethylene glycol, polypropylene glycol, etc.; polyalkylene glycols such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol, etc. Alkylene glycols having 2 to 6 alkylenes; lower alkyl ethers of polyhydric alcohols such as glycerin, ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl ether, and the like. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether and triethylene glycol monoethyl ether are preferred. Examples of other additives include PH regulators, metal sequestrants, antifungal agents, viscosity regulators, surface tension regulators, wetting agents, surfactants, and rust preventives. Ink jet suitability was measured by the following method. The ink absorption capacity is 10% at 20°C using a 1/1 solution of polyethylene glycol (PEG No. 400)/water.
The solution was brought into contact with a fixed area of the ink-receiving layer for seconds, excess liquid was removed with absorbent paper, the weight of the solution absorbed into the ink-receiving layer was measured, and the value calculated as grams per square meter was used. The ink absorption speed is measured using a Sharp inkjet printer (IO-700), immediately after solid printing of the red printed area (magenta + yellow) (about 1 second later)
The paper was brought into contact with a paper presser roll, and judgment was made as to whether stains appeared or not. Adhesive strength was measured by pressing an adhesive tape with a width of 18 mm onto the coated layer surface at a constant pressure, and measuring the resistance force when peeling in a 180° direction. The adhesive strength is preferably 250g/18mm or more. The amount of powder falling is measured by wrapping a sample with a length of 100 mm and a width of 200 mm around a round rod with a diameter of 10 mm, and measuring it from 100 mm to 30 mm in the length direction.
The weight of the peeled coating layer was measured, and the value calculated as the number of grams per square meter was used. The smaller the amount of powder falling off, the better.If it is less than 0.5g/ ^m2 , there will be no practical problems in terms of folding during cutting, powder falling off when feeding printer paper, etc. The printed dot diameter was determined by measuring the area of a single dot printed with black ink using an inkjet printer (A-1210) manufactured by Canon Inc. using a dot area meter (Beauback manufactured by Toyo Ink Manufacturing Co., Ltd.). The area was assumed to be a perfect circle, and the diameter was calculated. The shape of the printed dots was determined visually by observing the printed dots under a microscope. Water resistance was measured using a Canon inkjet printer by printing a solid image with M ink, immersing it in running water at 30°C for 3 minutes, and measuring the density before and after immersion with a Macbeth densitometer RD514. The percentage obtained by dividing the concentration after immersion by the concentration before immersion was taken as the water resistance value. The higher the value, the better the water resistance. (E) Function In the present invention, synthetic amorphous silica is used as the main pigment, and a coating layer containing a polyvinyl alcohol polymer containing silanol groups as an adhesive is used as the first layer and as the second layer. The inkjet recording medium uses synthetic amorphous silica as the main pigment, contains an adhesive containing almost no silanol-containing polyvinyl alcohol, and has a coating layer containing a cationic resin as the second layer. Because it has a strong affinity for synthetic fine particle silica and the support due to the silanol group in the layer, it exhibits strong adhesion, and furthermore, if it is included in the coating solution for the first layer, it will cause gelation and cannot be included. By incorporating the cationic resin into the coating solution for the second layer and allowing it to substantially permeate into the first layer during coating of the second layer, it has excellent water resistance and improves ink jet properties such as ink absorbency and dot diameter. Excellent printing suitability, and significantly improves adhesion, powder shedding, etc. (F) Examples The present invention will be described below with reference to examples, but the invention is not limited to these examples. Note that parts and percentages shown in the examples mean parts by weight and percentages by weight. Comparative 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 (manufactured by Deitsku Hercules, Harcon W) 0.08
A base paper with a basis weight of 68 g/m ² was made from a slurry consisting of 1 part and 0.4 parts of a polyalkylene polyamine epichlorohydrin resin using a Fourdrinier paper machine, and 2 g/m ² of oxidized starch was attached as a solid content using a size press during paper making. The material was used as a support. Synthetic amorphous silica (Mizukasil) is deposited on this support.
P78-F (BET method specific surface area 340m ² /g, average particle size
12.8 μm) manufactured by Mizusawa Chemical Industry KK), 30 parts of polyvinyl alcohol (PVA117, manufactured by Kuraray), and a coating solution with a solid content concentration of 17% were applied using an air knife coater to give a dry solid content of 10 g/ ^m2 . After drying, a first layer coated paper was obtained. 100 parts of synthetic amorphous silica (Mizukasil P-78-A (BET method specific surface area 340 m ² /g, average particle size 3.6 μm), manufactured by Mizusawa Kagaku Kogyo KK), polyvinyl alcohol ( PVA117, manufactured by Kuraray Co., Ltd.) 60 copies, Polyfix
601 (cationic resin, manufactured by Showa Kobunshi KK) 20 parts,
A coating liquid with a solid content concentration of 12% was applied and dried to a solid content of 4 g/m ² to form a second coating layer, and the recording paper of Comparative Example 1 was prepared by lightly supercalendering. Table 1 shows the results of evaluating the inkjet suitability and coating layer strength of this recording paper. Examples 1 and 2 Comparative Example 1 except that 10 parts and 30 parts of the 30 parts of polyvinyl alcohol in the first layer coating solution of Comparative Example 1 were replaced with silanol group-containing polyvinyl alcohol (R1130, manufactured by Kuraray Co., Ltd.). Recording sheets prepared in the same manner were used as the recording sheets of Examples 1 and 2, respectively. Table 1 shows the results of evaluating inkjet suitability and coating layer strength for these recording papers. Comparative Example 2 An attempt was made to produce a sample in the same manner as Comparative Example 1, except that 5 parts of the 60 parts of polyvinyl alcohol in the second layer coating solution of Comparative Example 1 was replaced with silanol group-containing polyvinyl alcohol (R1130, manufactured by Kuraray Co., Ltd.). However,
The coating solution gelled and was difficult to coat. Example 3 Produced in the same manner as in Example 1 except that 2 parts of the 60 parts of polyvinyl alcohol in the second layer coating solution in Example 1 was replaced with silanol group-containing polyvinyl alcohol (R1130, manufactured by Kuraray Co., Ltd.) was used as the recording paper of Example 3. Table 1 shows the results of evaluating the inkjet suitability and coating layer strength of this recording paper. Comparative Example 3 Polyfix 601 of the second layer coating solution of Example 1
A recording sheet of Comparative Example 3 was prepared in the same manner as in Example 1 except that the following was removed. Table 1 shows the results of evaluating the inkjet suitability and coating layer strength of this recording paper.

【table】

[Table] (F) Effects of the Invention As is clear from Table 1, the recording medium according to the present invention satisfies the printing suitability required for inkjet recording media, and at the same time has strong coating layer strength and is easily absorbed by printers during processing such as cutting. Creases, peeling of the paint layer, falling powder, etc. when handling the paper and before and after image printing.
Furthermore, the present invention provides a good inkjet recording medium that does not cause clogging of inkjet nozzles due to paper dust generated by these.

Claims (1)

[Scope of Claims] 1. An inkjet recording medium having an aqueous ink absorbing layer on a support, wherein the ink absorbing layer is (1)
A first layer consisting of a pigment mainly composed of synthetic amorphous silica and a polyvinyl alcohol polymer having silanol groups in the molecule alone or a mixture with other adhesives; and (2) a pigment mainly composed of synthetic amorphous silica. An ink jet recording comprising: a second layer consisting of 2 parts by weight or less of a polyvinyl alcohol polymer having a silanol group in the molecule, other adhesives, and a cationic resin per 100 parts by weight of the pigment; Medium. 2. In the first layer, the polyvinyl alcohol polymer having a silanol group in the molecule is 6 to 80 parts by weight, and the total amount of adhesive is 15 to 90 parts by weight, based on 100 parts by weight of the pigment. Inkjet recording medium. 3. In the second layer, the total amount of adhesive is 15 to 90 parts by weight based on 100 parts by weight of the pigment.
Inkjet recording medium.