JPH0761114A - Recording sheet - Google Patents

Abstract

PURPOSE:To provide a recording sheet excellent in ink drying properties, image properties and film strength. CONSTITUTION:In a recording sheet consisting of a base material sheet 2 and the ink receiving layer provided at least on one surface of the base material sheet 2, the ink receiving layer 3 is formed by irradiating a film containing water absorbable gel particles and a compd. having at least one or more functional group in its molecule with ionizing radiation to cure the same and the wt. compounding ratio of water absorbable gel particles and the compd. having at least one functional group in its molecule is 5:95-99.5:0.5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording sheet, which is excellent in recording mainly by an ink jet printer using a water-soluble ink, particularly excellent in ink drying property, color developability and the like, and further excellent in coating film strength. Recording sheet.

[0002]

2. Description of the Related Art Conventionally, as an output print of a computer or a word processor, a wire dot recording system,
Various systems such as a thermal color recording system, a thermal melt transfer recording system, a thermal sublimation transfer recording system, an electrophotographic recording system and an inkjet recording system have been developed. Among them, the ink jet recording method is characterized in that plain paper can be used as a recording sheet, the printing cost is low, the apparatus is compact and there is no noise, and high speed recording is possible. Therefore, its use as a printer that outputs image information such as characters and figures created by a computer or the like quickly and accurately is drawing attention. Also, since it is easy to colorize and the picture is clear, the image information created by the computer is recorded on a transparent recording sheet by an ink jet printer, and this is used as a manuscript for OHP (overhead projector) and the like, at conferences, various academic conferences, etc. The demand for use in announcements is also increasing.

In general, an ink jet printer ejects recording ink from a nozzle by the pressure of a fine piezoelectric element (piezo element) or the pressure of air (bubble jet) generated by heating a thermal head, and adheres to the recording sheet. By doing so, recording is performed. For this reason, as a recording ink used for inkjet recording, an ink that is difficult to dry is used in order to prevent defective ejection of ink from a nozzle due to an increase in viscosity due to drying of the ink. Usually, this ink component is a dye,
Resins, additives and the like dissolved in water and alcohol are generally used.

Therefore, a recording sheet for recording with an ink jet printer is required to absorb the moisture of the adhered ink and dry and solidify the ink. For this reason, a recording sheet is used in which an ink receiving layer is formed on a resin film to enhance the ink absorbency.

In particular, the ink receiving layer of a recording sheet for an ink jet printer is required to have the following characteristics.

It has excellent ink absorbency and does not cause bleeding, that is, it has good ink drying properties, it has excellent image clarity, and it has excellent scratch resistance, that is, it is easily recorded even if the recording surface is rubbed. The surface does not come off, and the sheet and image are water resistant, and even if water adheres, the image does not bleed or run off, and has excellent smoothness and gloss.

From this point of view, the conventional recording sheet is provided with an ink receiving layer on a substrate, a water-soluble polymer is used as the receiving layer, and a filler such as silica is added thereto. There have been proposed ones, ones in which a water-absorbent gel is dispersed in a water-insoluble polymer binder, and the like.

[0008]

However, the ink-receiving layer formed by coating the water-soluble polymer shows tackiness after absorbing the ink, and when overlaid immediately after recording,
Ink drying is insufficient, and blocking and image disorder often occur, and it cannot be said that the ink composition has sufficient performance. In addition, when a filler such as silica is added, the ink adsorbability is improved, and the drying property is improved, but the ink adsorbability becomes too strong, so the appropriate spread of dots cannot be obtained and the line is thin. There is a disadvantage that a desired image cannot be obtained because it becomes an image line.

Further, as a method for absorbing the water content of the ink, for example, an acrylic acid-vinyl alcohol copolymer and its salt are used (JP-A-62-9988).
And those using various superabsorbent resins (JP-A-62-9)
No. 988) is also proposed. Although these materials certainly have excellent absorption performance, they have a practical problem that the strength of the film after printing is weak. The present invention was created in view of such circumstances, and its purpose is to:
An object of the present invention is to provide a recording sheet excellent in ink drying property, image property and coating film strength.

[0010]

In order to achieve such an object, the present invention comprises a substrate sheet and an ink receiving layer provided on at least one surface of the substrate sheet,
The ink receiving layer is formed by curing a coating film containing water-absorbing gel particles and a compound having at least one functional group in the molecule by irradiating with ionizing radiation to cure the coating film. The compounding ratio of the hydrophobic gel particles to the compound having at least one functional group in the molecule is in the range of 5:95 to 99.5: 0.5.

[0011]

With the above-mentioned constitution, the ink receiving layer formed by curing by the irradiation of ionizing radiation has not only excellent ink drying property but also extremely excellent image quality and coating film strength.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view of the recording sheet of the present invention. In FIG. 1, a recording sheet 1 is a base sheet 2
And an ink receiving layer 3 formed on one surface of the base sheet 2.

When the recording sheet 1 is used as, for example, an OHP sheet, the base sheet 2 is preferably made of a thermoplastic resin having transparency, heat resistance, dimensional stability and rigidity. . Specifically, the thickness of polyethylene terephthalate resin, polycarbonate resin, acrylic resin, polyvinyl chloride resin, polypropylene resin, polystyrene resin, polyvinyl alcohol resin, polyethylene resin, diacetate resin, triacetate resin, polyimide resin or the like is about 5 to 250 μm. A film or plate having a thickness of preferably about 50 to 180 μm is used.

When the adhesion of the base sheet 2 to the ink receiving layer 3 formed on the surface of the base sheet 2 is insufficient, the surface of the base sheet 2 is preferably subjected to a primer treatment or a corona discharge treatment. Further, a curl prevention layer may be provided on the back surface of the base material sheet 2 on which the ink receiving layer 3 is not formed.

When the use of the recording sheet 1 is not limited to OHP, the base sheet is made of synthetic paper such as polystyrene, fine paper, art paper, coated paper, cast coated paper, wallpaper, backing paper, synthetic paper. It is also possible to use various colored or white papers such as resin-impregnated paper, emulsion-impregnated paper, synthetic rubber latex-impregnated paper, synthetic resin internal-addition paper, and paperboard.

The ink receiving layer 3 formed on the base sheet 2 is formed by irradiating a coating film containing water-absorbing gel particles and a compound having at least one functional group in the molecule with ionizing radiation. It is formed.

The water-absorbent gel particles used in the present invention are basically polymeric materials which are insoluble in water and absorb water, and have an absorption capacity of about 2 to 1000 times their own weight. Here, the particles do not necessarily have to be spherical, but the preferable particle size assuming that they are spherical is 0.01 to 100 μm.
It refers to a degree.

Examples of such water-absorbent gel particles include crosslinked polyacrylic acid and its salts, crosslinked polyvinyl alcohol (PVA), crosslinked polyacrylamide, crosslinked acrylamide such as propylacrylamide, crosslinked carboxymethylcellulose, crosslinked polyethylene glycol. System, isobutylene / maleic acid system, PVA / polyacrylic acid system, starch / polyacrylic acid salt system, hydrolyzate of starch / polyacrylonitrile polymer and the like are used.

The compound having at least one functional group in the molecule is not particularly limited as long as it basically reacts to ionizing radiation such as ultraviolet rays and electron beams, but especially in the molecule. Those having a radical-polymerizable unsaturated bond are preferred. The number of functional groups is applicable from monofunctional to polyfunctional, and the molecular weight is not particularly limited, and low molecular weight monomers, oligomers and polymers can be applied. The number of functional groups and the molecular weight are determined by the characteristics and amount of the water-absorbent gel particles to be used. For example, when a monofunctional compound is used alone and the required coating strength cannot be obtained, it is mixed with a bifunctional or more functional compound. Can also be used.

As the monofunctional monomer, acrylic acid, acrylic acid dimer, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl acrylate, 2-ethylhexyl acrylate, methoxyethyl acrylate, butoxyethyl acrylate, butyl acrylate, methoxybutyl acrylate. Acrylic acid and its esters such as phenyl acrylate; methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycerol methacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, methoxyethyl methacrylate, ethoxyethyl methacrylate, phenyl methacrylate, Methacrylic acid esters such as lauryl methacrylate Unsaturated carboxylic acid amides such as acrylamide, propylacrylamide, methacrylamide, propylmethacrylamide; 2- (N, N-dimethylamino) ethyl acrylate, 2- (N, N-dimethylamino) ethyl methacrylate, 2- (N, Substituted amino alcohol esters of unsaturated acids such as N-dibenzylamino) ethyl acrylate, (N, N-dimethylamino) methyl methacrylate, 2- (N, N-diethylamino) propyl acrylate; N-methylcarbamoyloxyethyl Acrylate, N-ethylcarbamoyloxyethyl acrylate, N-butylcarbamoyloxyethyl acrylate, N-phenylcarbamoyloxyethyl acrylate, 2- (N-methylcarbamoyloxy)
Carbamoyloxyalkyl acrylates such as ethyl acrylate and 2-carbamoyloxypropyl acrylate; Others, vinylbenzyltrimethylammonium chloride, N-methyl-4-vinylpyridinium chloride,
There are cationic vinyl monomers such as 2-methacryloyloxyethyltrimethylammonium chloride and 2-acryloyloxydimethylsulfonium chloride, and acryloylmorpholine. In addition, the polyfunctional monomer is 2
A polyfunctional (meth) acrylate having two or more radical-polymerized unsaturated groups, and particularly having two or more (meth) acryloyl groups is preferable. Specific examples include, for example, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane di (meth) acrylate, penta Erythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, polyethylene glycol diglycidyl ether di (meth) acrylate,
Propylene glycol diglycidyl ether di (meth)
Examples thereof include polyfunctional (meth) acrylates such as acrylate, polypropylene glycol diglycidyl ether di (meth) acrylate, sorbitol tetraglycidyl ether tetra (meth) acrylate, and melamine (meth) acrylate.

As the oligomer or polymer having a functional group, for example, a urethane acrylate obtained by combining a diisocyanate, a diol having a hydroxyl group at both ends and an acrylate compound having a hydroxyl group at both ends and a radically polymerizable unsaturated group is bonded. Yes, a urethane acrylate having an arbitrary molecular weight can be obtained by changing the molecular weight of the diol used. In addition, a 1: 1 adduct of acrylic acid chloride or 2-hydroxyethyl acrylate and diisocyanate is added to the hydroxyl group of the copolymer of polyester acrylate, epoxy acrylate, acrylic acid alkyl ester and acrylic acid-2-hydroxy ester. Acryloyl group-introduced copolymer, a copolymer obtained by adding glycidyl methacrylate to the carboxyl group of a copolymer of acrylic acid alkyl ester and acrylic acid, or acrylic acid chloride or acrylic acid on the residual hydroxyl group of polyvinyl butyral- Those obtained by adding a 1: 1 adduct of 2-hydroxyethyl and diisocyanate can be used.

The weight ratio of the water-absorbent gel particles to the compound having at least one functional group in the molecule is 5:95 to 99.5: 0.5, preferably 10: 9.
0-90: 10, more preferably 50: 50-90: 1
It is set within the range of 0. When the ratio of the water-absorbent gel particles is less than 5%, almost no water-absorbing performance is exhibited, and conversely, 99.
If it exceeds 5%, the effect of the compound having one or more functional groups to be used is not exhibited and the coating film is easily peeled off. The preferred range is determined by the water absorption capacity of the water-absorbent gel particles used, the coating strength and the film thickness of the compound having one or more functional groups.

In addition, various polymers and additives such as polymer fine particles, fine particle fillers such as micro silica and alumina sol, and various kinds of particles are added to the above composition for the purpose of improving blocking resistance, coating strength, adhesion and dyeing property. It is also possible to mix and use a surfactant, various modified oils having high hydrophilicity, etc. within a range that does not impair the effects of the present invention.

As a method of coating the above-mentioned composition on a substrate sheet, when the compound having one or more functional groups is a liquid having a low viscosity, water-absorbing gel particles are added to the composition. A well-dispersed product is prepared as a coating liquid. On the contrary, when the compound having one or more functional groups is a solid or highly viscous liquid, it is dissolved in a suitable solvent in which a compound other than water is dissolved. A solution in which water-absorbent gel particles are well dispersed is prepared as a coating solution and applied on a substrate sheet.

The coating method may be various conventionally known methods, for example, gravure coat, gravure reverse coat, roll coat, Meyer bar coat, blade coat, knife coat, air knife coat, comma coat, slot die coat, slide die coat. , Dip coating, etc. may be used. The thickness applied to the substrate sheet using these methods is 1 to 50 μm when dried.
m, preferably 3 to 30 μm. If this value is less than 1 μm, the ink absorption amount is not sufficient, while if it exceeds 50 μm, the economic demerit is simply increased, which is not preferable.

The coating film thus formed can be irradiated with ionizing radiation to crosslink the coating composition to obtain the recording sheet of the present invention. Ionizing radiation includes α rays, β rays and γ rays emitted from radionuclides, high energy particles generated from accelerators, neutrons and photons of uncharged particles,
Others include fission products. Of course, ultraviolet rays, electron beams, etc. are included as described above, but when ultraviolet rays are used, it is preferable to add a suitable photoinitiator, sensitizer, and the like.

Further, an antistatic layer, an anti-curl layer, etc. may be provided on the base sheet on the surface (rear surface) opposite to the surface on which such an ink receiving layer is formed.

Next, the present invention will be described in more detail with reference to specific examples. (Example 1) A coating liquid containing the following water-absorbent gel particles and an electron beam curable material (hereinafter simply referred to as EB curable material) was prepared.

Water-absorbent gel particles: polyvinyl alcohol / acrylic acid salt type SP-510 (manufactured by Sumitomo Chemical Co., Ltd.) 18 g EB curable material: urethane acrylate type Ebecryl 284 (manufactured by Daicel UCB Co., Ltd.) 2 g -Solvent: 30 g of methyl ethyl ketone This coating solution was applied onto a sheet base material (HP-7, manufactured by Teijin Ltd.) of a polyester film having a thickness of 100 μm to have a thickness of 20 μm after drying using a Meyer bar. It was applied as described above and dried at 80 ° C. for 10 minutes. After that,
Using an electron beam irradiation device (Curetron, manufactured by Nisshin High Voltage Co., Ltd.), an accelerating voltage of 175 KV and 5 Mra
The recording sheet of Example 1 was produced by irradiating the coating film with the electron beam of d. (Example 2) A recording liquid of Example 2 was prepared in the same manner as in Example 1 except that a coating liquid (ink receiving layer composition) having the composition shown below was prepared and this coating liquid was used. A sheet was prepared.

Water-absorbent gel particles: polyvinyl alcohol / acrylic acid salt system SP-510 (manufactured by Sumitomo Chemical Co., Ltd.) 2 g EB curable material: acrylic acid dimer system M-5600 (manufactured by Toagosei Co., Ltd.) ) 17 g: pentaerythritol triacrylate KAYARAD PET30 (manufactured by Nippon Kayaku Co., Ltd.) 1 g (Example 3) A coating liquid (ink receiving layer composition) having the composition shown below was prepared and used. A recording sheet of Example 3 was prepared in the same manner as in Example 1 except that the thickness of the coating film after drying was 25 μm.

Water-absorbent gel particles: polyvinyl alcohol GP-02 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 10 g-EB curable material: polyethylene glycol diacrylate M-245 (manufactured by Toa Synthetic Chemical Industry Co., Ltd.) ) 10 g: pentaerythritol triacrylate KAYARAD PET30 (manufactured by Nippon Kayaku Co., Ltd.) 1 g-Solvent: methanol 40 g (Example 4) A coating liquid (ink receiving layer composition) having the composition shown below was prepared, and A recording sheet of Example 4 was prepared in the same manner as in Example 1 except that the coating liquid was used and the thickness of the coating film after drying was 25 μm.

Water-absorbent gel particles: polyacrylate type Diawet I-400 (manufactured by Mitsubishi Petrochemical Co., Ltd.) 16 g EB curable material: urethane acrylate type Ebecryl 284 (manufactured by Daicel UCB Co., Ltd.) 4 g-Additive: polyvinyl butyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) 1 g-Solvent: methyl ethyl ketone 40 g (Example 5) A coating liquid (ink receiving layer composition) having the composition shown below was prepared, and this coating was prepared. A recording sheet of Example 5 was produced in the same manner as in Example 1 except that the coating liquid thickness after drying was changed to 25 μm using a working liquid.

Water-absorbent gel particle: polyvinyl alcohol / acrylic acid salt system SP-520 (manufactured by Sumitomo Chemical Co., Ltd.) 1 g EB curable material: urethane acrylate type UV-3000B (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 16 g-Solvent: Methyl isobutyl ketone 30 g (Example 6) A coating liquid (ink receiving layer composition) having the composition shown below was prepared, and the coating film thickness after drying was 20 μm using this coating liquid. A recording sheet of Example 6 was prepared in the same manner as in Example 1 except that the above was used.

Water-absorbent gel particles: polyvinyl alcohol / acrylic acid salt type SP-510 (manufactured by Sumitomo Chemical Co., Ltd.) 50 g EB curable material: urethane acrylate type Ebecryl 284 (manufactured by Daicel UCB Co., Ltd.) 1 g Solvent: methyl ethyl ketone 50 g (Comparative Example 1) A coating solution (ink-receiving layer composition) having the composition shown below was prepared and compared in the same manner as in Example 1 except that this coating solution was used. The recording sheet of Example 1 was prepared.

Water-absorbent gel particles: polyvinyl alcohol / acrylic acid salt type SP-510 (manufactured by Sumitomo Chemical Co., Ltd.) 1 g EB curable material: urethane acrylate type Ebecryl 284 (manufactured by Daicel UCB Co., Ltd.) 50 g Solvent: methyl ethyl ketone 70 g The recording sheets of Examples and Comparative Examples prepared as described above were evaluated for dryness, image quality and coating strength under the following conditions.

The results are shown in Table 1 below. (Drying property) A test pattern was printed by a desk writer C (manufactured by Hured Packer Co., Ltd.), and immediately after that, a sensory test was conducted by touching the printed surface.

Evaluation criteria: ⊚: completely dry after printing ○: completely dry to some extent ×: it takes 3 minutes or more to completely dry (image quality) A test pattern is written by a desk writer C (manufactured by Hured Packer) It was printed and evaluated visually.

Evaluation criteria: ⊚: No ink bleeding, no flow, moderate dot spread ◯: Moderate size dot is obtained, but ink bleeding is somewhat bad ×: Ink bleeding is remarkable ( (Coating strength) Immediately after printing, a sensory test was conducted in which the printed surface was palpated 10 times.

Evaluation criteria: ◯ ... No change is observed on the printed surface. Δ: Film peeling and surface defects are recognized after 5 to 10 times. X ... Film peeling and surface defects are recognized after less than 5 times.

[0041]

[Table 1]

[0042]

The effect of the present invention is clear from the results shown in Table 1. That is, the recording sheet of the present invention comprises a substrate sheet and an ink receiving layer provided on at least one surface of the substrate sheet, and the ink receiving layer contains at least water-absorbing gel particles and molecules. Weight of the water-absorbent gel particles and the compound having at least one functional group in the molecule, which is formed by curing a coating film containing a compound having one or more functional groups by irradiation with ionizing radiation. Since the compounding ratio is in the range of 5:95 to 99.5: 0.5, the ink has excellent drying properties and image quality, and the coating film strength is extremely strong.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a recording sheet of the present invention.

[Explanation of symbols]

 1 ... Recording sheet 2 ... Substrate sheet 3 ... Ink receiving layer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshio Yoshihara 1-1-1, Ichigaya-Kagacho, Shinjuku-ku, Tokyo Within Dai Nippon Printing Co., Ltd. No. 1 within Dai Nippon Printing Co., Ltd. (72) Inventor Kiyoshi Oguchi 1-1-1 Ichigayaka-cho, Shinjuku-ku, Tokyo Within Dai Nippon Printing Co., Ltd.

Claims (1)

[Claims] 1. A substrate sheet, and an ink receiving layer provided on at least one surface of the substrate sheet, wherein the ink receiving layer contains water-absorbing gel particles and at least one or more functional groups in the molecule. A compound having a group and a coating film containing the compound formed by curing by irradiation with ionizing radiation, the water-absorbing gel particles, and a compound having at least one or more functional groups in the molecule Weight ratio is 5: 95 ~
A recording sheet having a range of 99.5: 0.5.