JPH03295682A - Recording medium - Google Patents

Abstract

PURPOSE:To record an image at high absorption speed and capacity of water-soluble ink and with superior water-proofing properties and sharpness by forming the ink absorption layer of a medium for recording with water0swelling resin and hydrophobic binder. CONSTITUTION:A polymeric polystyrene having a methacryloyl group as alpha, beta-ethylene unsaturated groups at the end, polymeric polybutylmethacrylate having a methacryloyl group as alpha, beta-ethylene unsaturated groups at the end, acrylic acid, soda acrylate and (polystyrene)-(polybutadiene)-(polystyrene) type block copolymers are added to a mixed solution and the mixture is copolymerized. Thus a solution of dispersed water-swelling resin A is obtained. Next a hydrophobic rubber elastic binder(20 to 500 pts.wt. for 100 pts.wt. of water swelling resin A) and a solvent are added to the water swelling resin A to prepare an application liquid. This prepared liquid is applied to polyester film using a roll coater and dried to obtain a medium for recording of an ink absorption layer.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a recording medium, and more specifically, it is suitable for recording with water-based ink, such as an inkjet recording method, and has excellent absorption speed and ink absorption capacity for water-based ink. The present invention also relates to a recording medium capable of recording images with excellent water resistance, image clarity, etc.

(Prior art and its problems) Conventionally, various recording methods using water-based ink have been known, and inkjet recording methods in particular produce less noise (and can form high-definition, full-color images). It has the advantage of being possible.

Paper, synthetic paper, plastic film, etc. are used as recording media for such inkjet recording, and water is mainly used as the ink used for recording from the viewpoint of recording properties and safety. Water-based ink is used as a medium, and polyhydric alcohol or the like is added to prevent nozzle clogging and drying of the nozzle tip.

When recording with such water-based ink, if the recording medium is paper with high ink absorption, there is no problem with the ink absorption, but there is a problem that the ink bleeds along the fibers of the paper. If the recording medium is a non-absorbent plastic film or metal, it will not absorb ink, so it may take a long time to dry, or it may contaminate other items, especially when forming color images. However, there is a problem that a clear and high-resolution image cannot be formed due to mixing of two or more colors of ink.

As a method to solve this problem, a method has been proposed to provide an ink absorbing layer made of hydrophilic resin on the non-absorbing surface of a plastic film, etc. However, this method does not allow the recording surface to have poor water resistance, and the base material Various problems occur, such as poor adhesion to the sheet and low ink absorption capacity, and a recording medium with sufficient performance has not yet been provided.

Therefore, an object of the present invention is to provide a recording medium that is suitable for recording with water-based ink using an inkjet method, has excellent water-based ink absorption speed and ink absorption capacity, and is capable of recording images with excellent water resistance and clarity. The goal is to provide the following.

[Means to solve problems] The above objects are achieved by the present invention as described below.

That is, the present invention provides a recording medium comprising a water-based ink absorbing layer formed on at least one surface of a base sheet, wherein the ink absorbing layer is made of a water-swellable resin and a hydrophobic binder. It is a medium.

[Function] By forming the ink absorbing layer of the recording medium from a water-swellable resin and a hydrophobic binder, it is possible to record images with excellent water-based ink absorption speed and ink absorption capacity, as well as excellent water resistance and clarity. It is possible to provide a recording medium that allows

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

In addition to various ordinary papers, base sheets used in the present invention include synthetic paper, polyester, cellulose acetate, polyethylene, polypropylene, plastic films or sheets such as polyvinyl chloride, metallized films or molded products, and metal. foil, metal film, metal products,
Plywood, woven fabric, non-woven fabric, etc. can be used in the present invention, and any conventionally known base sheet for recording media can be used in the present invention. In particular, in the present invention, when a transparent plastic film is used as the base sheet, it is very suitable for OHP use. Provides an excellent recording medium.

The present invention is characterized in that an ink absorbing layer made of a water-swellable resin and a hydrophobic binder is formed on one or both surfaces of the base sheet.

The water-swellable resin used in the present invention has hydrophilic groups, such as
Anionic hydrophilic groups such as carboxyl, sulfonic acid group, sulfuric acid ester group, phosphoric acid ester group and their alkali metal salts, ammonium salts, or lower amine salt groups; cationic hydrophilic groups such as primary, secondary, tertiary amino group,
It is a resin having a large number of hydrophilic groups such as quaternary ammonium groups and their acid salts, nonionic groups such as hydroxyl groups and ether groups.

Examples of useful water-swellable resins include starch-sodium polyacrylate grafts, saponified starch-polyacrylonitrile grafts, cellulose-sodium polyacrylate grafts, and vinyl alcohol-sodium acrylate grafts. Polymers, vinyl alcohol-sodium methacrylate copolymers, partially crosslinked sodium polyacrylates, sodium salts of carboxymethylcellulose, and the like.

A particularly preferred water-swellable resin in the present invention is a polymer chain or copolymer chain having a hydrophilic group and a hydrophobic polymer chain or copolymer chain in the form of a block copolymer or a graft copolymer. For example, a block type water-swellable resin has a bonding format of (hydrophobic segment) - (hydrophilic segment) - (hydrophobic segment), and a typical example is , (polystyrene) −(
Examples include those obtained by addition or addition polymerization of thioglycolic acid, maleic anhydride, acrylic acid, methacrylic acid, etc. to the double bond of a block copolymer of (polybutadiene)-(polystyrene) and then neutralizing it with an alkali. .

Another preferred water-swellable resin has α at the end.

A copolymer of a hydrophobic polymer chain having a β-ethylenically unsaturated group and an a,β-ethylenically unsaturated monomer having a hydrophilic group or a group capable of easily generating a hydrophilic group. Typical examples include polystyrene, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, etc., which have α,β-ethylenically unsaturated groups, and (meth)acrylic acid, as necessary. Furthermore, a graft type water-swellable product is produced by copolymerizing polyethylene glycol mono(meth)acrylate and/or polyethylene glycol monoalkyl ether (meth)acrylate with a monomer as the main component, and forming a salt with an alkali metal salt or a hydrophilic amine. Examples include resin.

A preferred method for forming an ink absorbing layer containing a water-swellable resin as described above is a method of dispersing the water-swellable resin in an organic solvent containing a binder, applying the dispersion to the surface of a base sheet, and drying it. It is.

The fine dispersion of the water-swellable resin described above can be obtained by synthesizing the resin in an organic solvent and neutralizing it with a base if necessary. It may also be simply dispersed in the medium.

The organic solvent used in the above dispersion is one commonly used in the fields of paints, printing inks, coatings, etc., such as acetone, methyl ethyl ketone,
Methyl isobutyl ketone, butyl cellosolve, ethyl cellosolve, cyclohexane, toluene, xylene, methyl alcohol, ethyl alcohol, isopropyl alcohol, butyl alcohol, dioxane, tetrahydrofuran, etc. can be used alone or in mixtures, and the water swelling properties of their dispersions The solid content of resin is usually 5 to 70% by weight.
and preferably 10 to 65% by weight.

Furthermore, this dispersion liquid contains colorants, optical brighteners, fungicides, plasticizers such as dioctyl phthalate, dioctyl adipate, and process oil, extender pigments such as calcium carbonate and silica, white pigments such as titanium oxide, and ultraviolet rays. Known additives such as absorbents can be added.

The water-swellable resin swells by absorbing water, which is the main component of the aqueous ink medium. For this reason, the particle size and swelling ratio of the water-swellable resin dispersed in the ink absorption layer are
Affects ink dot diameter, absorption capacity, etc. In other words, if the particle size and swelling ratio are too high, the ink dot diameter becomes too large (which is not preferable because not only fine color expression cannot be achieved but also color density distribution occurs). Therefore, the average particle size of the water-swellable resin The diameter is 10 μm or less, especially 0.01 to 1 μm,
The swelling ratio is preferably about 10 to 1000 times, particularly about 20 to 100 times. If the swelling ratio exceeds the above range, there will be a problem that the particles will peel off from the ink absorbing layer, and if the swelling ratio is less than the above range, the absorption capacity of water-based ink will be extremely high when using the binder described below. This is not preferable because the absorption rate of water-based ink also decreases.

In forming the ink absorbing layer, it is preferable to use a hydrophobic binder in order to impart water resistance and improve adhesion to the base sheet. If a large amount of binder is used, the ink absorption speed and absorption capacity will decrease, while if the amount used is too small, the strength and water resistance of the ink absorption layer will decrease.
The amount of the binder used is 20 to 500 parts by weight, preferably 50 to 200 parts by weight, per 100 parts by weight of the water-swellable resin.

The binder used in the present invention is preferably a hydrophobic elastic material. Particularly preferable binders include materials that reduce the rate of water absorption and expansion of water-swellable resins and reduce absorption capacity, such as urethane rubber, acrylic rubber, polybutadiene, polyisoprene, polyisobutylene, butadiene-acrylonitrile copolymer rubber, and styrene. Butadiene copolymer rubber, styrene-isoprene copolymer rubber, chloroprene rubber, nitrile rubber, raw rubber,
These are elastic materials such as ethylene-vinyl acetate copolymer rubber and its chlorinated products. These copolymers may be of any bond type, such as block type, graft type, or random type.

Examples of methods for applying the coating liquid to the base sheet surface include conventionally known coating methods such as roll coating, blade coating, knife coating, squeeze coating, air doctor coating, gravure coating, rod coating, spray coating, and impregnation. The ink absorbing layer is formed by drying after coating. If the thickness of the ink absorbing layer is too thin, ink absorbency, absorption capacity, etc. will be insufficient, while if it is too thick, it will be uneconomical, so the preferred thickness is 0.5.
It is about 100 μm.

[Example] Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the text, parts or percentages are based on weight unless otherwise specified.

[Preparation of water-swellable resin A] 10.0 parts of polymerizable polystyrene having a molecular weight of about 7,000 having a methacryloyl group as an α1 β-ethylenically unsaturated group at the end, and 10.0 parts of polymerizable polystyrene having a methacryloyl group as an α,β-ethylenically unsaturated group at the end. 15.2 parts of polymerizable polybutyl methacrylate having a methacryloyl group and a molecular weight of approximately 6.000, 2 parts of acrylic acid
5.0 parts of sodium acrylate, 99.3 parts of sodium acrylate, 1.2 parts of a (polystyrene)-(polybutadiene)-(polystyrene) type block copolymer (polystyrene content 30%, molecular weight approximately 200,000), cyclohexane/toluene /Methyl ethyl ketone = 80/10/10 weight ratio for copolymerization.The solid content is about 30% and the average particle size is 0.
A 3 μm water-swellable resin dispersion was obtained. The degree of water swelling of this water-swellable resin was about 70 times.

[Preparation of water-swellable resin B] 25 parts of polymerizable polystyrene having a molecular weight of about 7.000 having a methacryloyl group as an α,β-ethylenically unsaturated group at the terminal, 7.5 parts of acrylic acid, and 29.9 parts of sodium acrylate.
4 parts, polyethylene glycol monomethacrylate (P
70 parts of EG (molecular weight: approx. 300), 1 part of (polystyrene)-(polybutadiene)-(polystyrene) type block copolymer (polystyrene content: 30%, molecular weight: approx. 200,000) at a weight ratio of cyclohexane/methyl ethyl ketone of 60/4.
Copolymerization was carried out in a mixed solvent of 0.0 to obtain a water-swellable resin dispersion having a solid content of 53%. The average particle diameter of the dispersed particles was 0.3 μm. The water swelling degree of this product was about 25 times.

[Preparation of water-swellable resin C] 5.0 parts of polymerizable polystyrene having a molecular weight of about 7,000 having a methacryloyl group as an α,β-ethylenically unsaturated group at the end, α,β-ethylenically unsaturated group at the end 12.0 parts of polymerizable polybutyl acrylate having a molecular weight of about 6,000 and having a methacryloyl group, 6.0 parts of acrylic acid, 23.4 parts of sodium acrylate, and 60.0 parts of polyethylene glycol monomethacrylate (PEG molecular weight of about 300).
0 parts, (polystyrene)-(polybutadiene)-(polystyrene) type block copolymer (polystyrene content 30
%, molecular weight approximately 200,000) was added to a mixed solvent with a weight ratio of cyclohexane/methyl ethyl ketone = 60,740 to copolymerize, and the solid content was approximately 50%, and water with an average particle size of 0.5 μm was copolymerized. A swellable resin dispersion was obtained. The degree of water swelling of this water-swellable resin was about 30 times.

[Preparation of water-swellable resin] 10.0 parts of polymerizable polystyrene having a molecular weight of about 5,500 having a methacryloyl group as an α,β-ethylenically unsaturated group at the terminal, α,β-ethylenically unsaturated group at the end 15.2 parts of polymerizable polybutyl acrylate having a molecular weight of about 6,000 and having a methacryloyl group, and 18.2 parts of acrylic acid.
9 parts, sodium acrylate 92.8 parts, polyethylene glycol monomethacrylate (PEG molecular weight approximately 450) 1
0.0 part, (polystyrene)-(polybutadiene)-(
1.2 parts of polystyrene type block copolymer (40% polystyrene content, molecular weight approximately 150,000) was mixed with 30% cyclohexane/methyl ethyl ketone/toluene/methanol.
It was added to a mixed solvent in a weight ratio of 30/20/20 and copolymerized to obtain a water-swellable resin dispersion having a solid content of about 50% and an average particle size of 0.3 μm. The degree of water swelling of this water-swellable resin was about 100 times.

[Preparation of water-swellable resin E] Cross-linked sodium polyacrylate (particle size 3 μm, water swelling degree approximately 2)
00 times) [Binder A] Polyether type urethane resin [Binder B] Ethylene-vinyl acetate copolymer (vinyl acetate content: 55
%) [Binder C] Acrylic rubber [Hydrophilic resin D] Methyl methacrylate-2-hydroxyethyl methacrylate-methacrylic acid copolymer (acid value = 100) Example 1 Water-swellable resin A (nonvolatile content 30%) 44. 4 parts Binder A (non-volatile content 25%) 26.6 parts Solvent (methyl ethyl ketone/kijirole/isopropyl alcohol 30:5
0:20 29. 0 total (non-volatile content 20%)
100.0 parts of the above coating solution was prepared, applied to a polyester film (thickness: 100 μm) using a roll coater, and dried for 5 minutes to obtain a recording medium of the present invention having an ink absorbing layer thickness of 10 μm.

Example 2 Water-swellable resin B (non-volatile content 53%) 37.7 parts Binder A (non-volatile content 25%) 40.0 parts Solvent (methyl ethyl ketone/kijirol/isopropyl alcohol 30:5
0:20 so, 1 total (19% non-volatile content)
157.8 parts The above coating solution was prepared, applied to a polyester film (thickness 100 μm) using a roll coater, and dried for 5 minutes until the thickness of the ink absorbing layer was 10 μm.
A recording medium of the present invention having the following characteristics was obtained.

Example 3 Water-swellable resin B (non-volatile content 53%) 18.9 parts Binder A (non-volatile content 25%) 60.0 parts Solvent (methyl ethyl ketone/kijirol/isopropyl alcohol 30:5
0:20 46. 1 total (non-volatile content 20%)
125.0 parts The above coating solution was prepared and applied to a vinyl chloride resin film (thickness 101001L using a gravure coater, dried for 5 minutes to give an ink absorbing layer with a thickness of 20.0 parts).
A recording medium of the present invention having a diameter of μm was obtained.

Examples 4 to 8 Recording media of the present invention were obtained in the same manner as in Example 1 except that the materials shown in Table 1 below were used in place of the water-swellable resin and binder in Example 1.

Comparative Example 1 Water-swellable resin B (non-volatile content 53%) 40.0 parts Solvent (methyl ethyl ketone/kijirol/isopropyl alcohol 30:50:20 66, 0 total (non-volatile content 2
0%) 106.0 parts The above coating solution was prepared, applied to a polyester film (thickness 100 μm) using a roll coater, and dried for 5 minutes to obtain a recording medium of a comparative example with an ink absorbing layer thickness of 10 μm. Ta.

Comparative Examples 2 to 3 Recording media of comparative examples were obtained in the same manner as in Example 1, except that the water-swellable resin and binder in Example 1 were replaced with the materials shown in Table 1 below.

Comparative Example 4 Binder A (non-volatile content 25%) 100.0 parts Solvent (methyl ethyl ketone/kijirol/isopropyl alcohol 30:50:20 25.0 total (non-volatile content 20
%) 125.0 parts The above coating solution was prepared, applied to a polyester film (thickness 100 μm) using a roll coater, and dried for 5 minutes to obtain a recording medium of a comparative example in which the thickness of the ink absorbing layer was 10 μm. .

Comparative Example 5 Water-swellable resin B (non-volatile content 53%) 10.0 parts Hydrophilic resin D (solid content 100%) 10.6 parts Solvent (methyl ethyl ketone/kijirol/isopropyl alcohol 30:5
0:20 58.9 total (non-volatile content 20%)
79.5 parts The above coating solution was prepared, applied to a vinyl chloride resin film (thickness 100 μm) using a gravure coater, and dried for 5 minutes until the thickness of the ink absorption layer was 20 μm.
A recording medium of a comparative example was obtained.

Color printing was performed on the recording media obtained in the above Examples and Comparative Examples using a water-based inkjet printer, and the results were evaluated using the following evaluation method, and the results shown in Table 2 below were obtained.

Soil absorption performance: After inkjet recording, the ink was left to stand for 2 minutes, a blank paper was applied to the printed surface, the blank paper was rubbed with a finger, and judgment was made by whether or not the ink was transferred to the paper.

○: No transfer ×: Transfer process 1: Print each of yellow, magenta, and cyan water-based inkjet inks on the same surface,
Does ink flow when the recording medium is held vertically?
It was determined whether or not.

○: There is no run-off.

○: No change △ Partially peeled off ×: Completely peeled off After applying cellophane tape to the 1 Yuuni recording medium and adhering it well, tape it at an angle of 30° to the base sheet for about 2 cm/
The ink absorbing layer was peeled off at a peeling speed of 1.5 sec, and judgment was made based on whether or not the ink absorbing layer was transferred to the cellophane tape.

○: No transfer △ Partial transfer X: Complete transfer Week 1 A recording medium capable of recording an excellent image can be provided.

*l: Image is unclear *2: Image formation is not possible (effect)

Claims (1)

[Claims] 1. A recording medium comprising a water-based ink absorbing layer formed on at least one surface of a base sheet, characterized in that the ink absorbing layer is made of a water-swellable resin and a hydrophobic binder. recording medium. 2. The recording medium according to claim 1, wherein the water-swellable resin is a block or graft copolymer consisting of a hydrophilic segment having a hydrophilic group and a hydrophobic segment. 3. An anionic hydrophilic group in which the hydrophilic group is a carboxyl group, a sulfonic acid group, a sulfuric acid ester group, a phosphoric acid ester group, and a hydrophilic salt thereof, a primary, secondary, or tertiary amino group, or a quaternary One or two selected from the group consisting of cationic hydrophilic groups consisting of ammonium groups and their salts, and nonionic hydrophilic groups consisting of hydroxyl groups and ether groups.
The recording medium according to claim 2, which is a hydrophilic group of more than one species. 4. The water-swellable resin is a hydrophobic polymer chain having an α,β-ethylenically unsaturated group at the end and an α,β-ethylenically unsaturated group having an anionic, cationic and/or nonionic hydrophilic group. The recording medium according to claim 1, which is a copolymer with a monomer. 5. The water-swellable resin contains a hydrophobic polymer chain having an α,β-ethylenically unsaturated group at the end, (meth)acrylic acid, and, if necessary, polyethylene glycol mono(meth)acrylate and/or polyethylene. The recording medium according to claim 1, which is an alkali metal salt and/or a hydrophilic amine salt of a copolymer with a monomer containing glycol monoalkyl ether (meth)acrylate. 6. Claim 1, wherein the binder is a hydrophobic rubber elastic material.
Recording medium described in . 7. The recording medium according to claim 1, wherein the ratio of the water-swellable resin to the binder used is 100:20 to 500 in terms of solid content ratio.