JPH02229083A - Production of thermal transfer image-receiving paper - Google Patents

Abstract

PURPOSE:To improve god blocking and curling characteristics and to prevent a change with time by a method wherein a radical polymerizable composition is applied on at least one surface of a sheet substrate and cured by an ultraviolet light or electron beam irradiation and, thereafter, treated with a radical polymerization inhibitor. CONSTITUTION:The coating weight of a radical polymerizable composition to be applied on a substrate is not particularly limited, but determined to be 1 - 20g/m<2> and more preferably 2 - 10g/m<2>. When the radical polymerizable composition layer is irradiated with an electron beam to be cured, an electron beam accelerator with an accelerating voltage of 100 - 1,000kV is used from the standpoint of a transmission power and a curing power. An ink accepting layer with the radical polymerizable composition cured by an ultraviolet light or electron beam irradiation is further treated with a radical polymerization inhibitor, thereby being improved to a great extent so as to not to change with time in acceptability of ink.

Description

[Detailed Description of the Invention] [A] Industrial Application Field The present invention provides gloss, smoothness, and heat resistance using sheet-like substrates such as paper, mica paper, glass paper, synthetic paper, nonwoven fabric, and synthetic resin sheets. The present invention relates to a method for producing an image-receiving paper for sublimation type heat-sensitive transfer, which has excellent image sharpness, image storage stability, and blocking property.

CB) Prior Art In recent years, sublimation type thermal transfer printers have been used as a means of color hard copying, particularly for reproducing multicolor gradation images. The principle of a sublimation type thermal transfer printer is to convert an image into an electrical signal, and then convert this electrical signal into a thermal signal using a thermal head to print a sheet coated with sublimation ink (ink donor sheet). The heated and sublimated ink is fixed on an image-receiving paper that is in close contact with an ink donor sheet, and the image is reproduced.

The surface of such receiving paper contains saturated copolymer polyester,
An image receiving layer is provided for immobilization of the ink by a polymer such as polyacetate.

(C) Problems to be Solved by the Invention The need to increase printing speed is an unavoidable problem in dye-sublimation thermal transfer printers, but this requires an increase in processing temperature.

However, when performing high-temperature heat treatment on a thermal transfer image-receiving paper that uses paper or synthetic resin as a base, it goes without saying that the base needs to be heat resistant, and the ink image-receiving layer made of a polymer provided on the image-receiving paper is exposed to heat. There are problems in that the ink donor sheet melts, causing blocking between the ink donor sheet and the image-receiving paper, resulting in only hard copies with poor image reproducibility, and that significant curling occurs after copying. As a means to solve such problems, there is known a sublimation type thermal transfer image-receiving paper in which a radically polymerizable oligomer is coated on a substrate and cross-linked by radiation (Japanese Patent Laid-Open No. 62-173).
295), however, in the case of thermal transfer image-receiving papers that use radically polymerizable oligomers to receive ink, as has been known up to now, the cured layer may be crosslinked if the amount of ultraviolet or electron beam irradiation is excessive. If polymerization progresses too much, the ink-receiving ability will be extremely reduced, and if polymerization is carried out to the extent that it has a moderate ink-receiving ability, the change over time after creation will be significant, and if a certain period of time has passed after creation, the ink-receiving ability will deteriorate. There was a problem in that the performance was lowered and the density of the reproduced image was lowered. This tendency was particularly noticeable when the material was held at high temperatures. This problem is fatal when dealing with image-receiving paper for thermal transfer as a commercial product.

Generally, electron beam curable resins contain hydroquinone monomethyl ether or phenothiazine compounds as polymerization inhibitors, but these compounds that already exist before electron beam irradiation lose their polymerization prevention function due to electron beam irradiation. However, the above-mentioned problems have not been solved because of problems such as coloring or discoloration over time.

In addition, the sheet used for the substrate is a porous material, glassine paper, which facilitates the diffusion of sublimation ink during printing, and has appropriate cushioning properties and promotes adhesion with the ink donor sheet. Coated paper, synthetic paper, or nonwoven fabric is preferred, but if the radically polymerizable oligomer is applied to these porous substrates, the radically polymerizable oligomer will seep into the porous substrate, making it difficult to obtain a smooth surface. When the surface quality of the image-receiving paper decreases in a dye-sublimation thermal transfer printer system, the image reproducibility decreases.
It is obvious that image sharpness deteriorates. More importantly, such resin seepage inevitably causes a decrease in opacity and whiteness of the porous material. This deteriorates the sharpness of the image after printing and particularly deteriorates the characteristics of white areas. This becomes a fatal problem when sublimation type thermal transfer printing is viewed as a means of color hard copying.

That is, an object of the present invention is to provide an image-receiving paper for thermal transfer that has good blocking and curling properties, is smooth, has good image reproducibility, and does not change over time.

(D) Means for Solving the Problems As a result of intensive research into means for solving the above-mentioned problems, the inventors have discovered the following method. That is, an invention of a method for producing an image-receiving paper for thermal transfer, characterized in that a radically polymerizable composition is applied to at least one side of a sheet-like substrate, cured by ultraviolet rays or electron beam irradiation, and then treated with a radical polymerization inhibitor. It is. A water-soluble polymer intermediate layer can also be provided between the sheet-like substrate and the radically polymerizable composition layer.

The present invention will be explained in detail below.

Substrates used in the present invention include glassine paper, high quality paper,
Paper strip porous substrates such as art paper and coated paper, so-called synthetic paper made of synthetic fiber or synthetic resin film, resin-coated paper with a water-resistant resin coating layer on the surface of base paper, or synthetic resin sheet. Refers to nonwoven fabrics, mica paper, glass paper, etc. There are no particular restrictions on the thickness of the substrate, but paper with good smoothness is preferred, and its basis weight is 50
g/go to 250 g/go is preferred.

The base paper mainly composed of natural pulp, which is advantageously used in the method of the present invention, can contain various polymeric compounds and additives. For example, starch derivatives, polyacrylamides, polyvinyl alcohol derivatives, dry paper strength agents such as gelatin, sizing agents such as fatty acid salts, rosin derivatives, dialkyl ketene dimer emulsions, and wet papers such as melamine resins, urea resins, and epoxidized polyamides. Strength enhancers, stabilizers, pigments, dyes, antioxidants, optical brighteners, various latexes, inorganic electrolytes, pH adjusters, and the like can be contained in appropriate combinations.

A water-soluble polymer layer can be provided by applying a water-soluble polymer solution onto the substrate of the present invention and drying it.

The water-soluble polymer mentioned here includes, for example, the following substances.

Starch as natural and semi-synthetic polymers, as well as modified starch compounds, alginate compounds, casein, gelatin, pullulan, dextran, chitin, chitosan,
Examples include rubber latex, gum arabic, french, natural gum, dextrin, and modified cellulose compounds.

Examples of synthetic polymers include modified polyvinyl alcohol compounds, polyethylene glycol, polyacrylic acid amide, polyacrylic acid compounds, polyvinylpyrrolidone, polyethyleneimine, polyvinyl ether, polymaleic acid copolymers, and water-soluble alkyd resins. Although not water-soluble polymers in the strict sense, styrene/maleic anhydride copolymers, styrene/butadiene copolymers,
An emulsion in which a synthetic polymer such as a butadiene/methacrylate copolymer is dispersed in water can be used instead of a water-soluble polymer solution. As the water-soluble polymer, the above-mentioned polymers can be used alone or in combination as an aqueous solution.

The dry coating amount of the water-soluble polymer to be applied onto the substrate is not particularly limited, but is 0.1 to 20 g/rrF, more preferably 0.2 to 10 g/rrF, and is more preferably 0.2 to 10 g/rrF. If the amount is extremely small, such as less than 0.1 g/rn', the effects of the present invention cannot be fully exhibited, and pinholes are likely to be generated. Also, 20g/rr? If it exceeds this, the burden on the porous substrate during drying will be large, and the shrinkage will be too large, making it difficult to adjust the curl.

In addition, in the present invention, there is no problem with surface treatment such as corona treatment on the surface to improve the adhesion and wettability between the porous substrate provided with the water-soluble polymer layer and the radically polymerizable composition. There is no problem in coating the porous substrate with an inorganic white pigment, a filler such as calcined kaolin such as Ansilex, a plastic pigment hollow organic pigment, etc. to provide cushioning properties and heat insulation properties.

The radically polymerizable composition constituting the ink receiving layer is mainly composed of ultraviolet polymerizable or electron beam polymerizable resins shown below, and these resins can be used without a solvent or diluted with a solvent. , and if necessary, a reaction initiator is used in combination.

The ultraviolet or electron beam polymerizable resin used in the present invention is a compound having a reactive group such as an acryloyl group, a methacryloyl group, or an epoxy group at the end of the molecule or in a side chain of the molecule, such as an unsaturated polyester or a modified unsaturated polyester. , acrylic polymer, acrylic monomer,
Methacrylic polymers, methacrylic onomers, monomers having vinyl unsaturated bonds, or oligomeric epoxy compounds can be used alone or in combination with other solvents. Typical examples are shown below.

(a) Polyester acrylate, polyester methacrylate, (b) Urethane acrylate, urethane methacrylate, (C) Monofunctional acrylate, monofunctional methacrylate, (d) Polyfunctional acrylate, polyfunctional methacrylate, (e) Epoxy compound (f>carboxylic acid) Modified acrylates, carboxylic acid-modified methacrylates (g>Other monomers such as vinylpyrrolidone, acryloylmorpholine, etc.) may be mentioned.

As the radically polymerizable composition, the above-mentioned resins can be used alone or in combination, taking into consideration the receptivity of sublimation ink. In addition, these resins can be used alone in the radically polymerizable composition, or pigments and dyes such as ultramarine and cobalt violet, and antioxidants can be added to improve opacity, hue, writability, antistatic properties, etc. A suitable combination of various additives can be added, such as a fluorescent whitening agent, an antistatic agent, a release agent such as colloidal silica or siloid, and a plastic pigment such as barmary.

In the present invention, the photoreaction initiators contained in the radical polymerizable composition for ultraviolet irradiation include ethyl anthraquinone, methylbenzoyl formate, 1-hydroxycyclohexylphenyl ketone, acetophenone, jetoxyacetophenone, di- and trichloroacetophenone. Acetophenones such as 0-benzoylmethylbenzoate, benzophenone, Michler's ketone, benzyl, benzoin, benzoin alkyl ether, benzyl dimethyl ketal, tetramethylthiuram monosulfide, xanthone, thioxanthone, azo compounds,
etc., and the amount of photoreaction initiator used is usually in the range of 0.1 to 10% based on the ultraviolet curable resin. Furthermore, a storage stabilizer such as hydroquinone may be used in combination with the photoreaction initiator.

In addition, in the present invention, when electron beam irradiation is performed to cure the radically polymerizable composition layer, a photoreaction initiator is naturally not required in the radically polymerizable composition, but even if it is contained, However, there is no problem with curing by electron beam irradiation.

The amount of the radically polymerizable composition applied to the substrate is not particularly limited, but is 1 to 20 g/m', more preferably 2 to Log/rr1', and the amount of the radically polymerizable composition applied to the substrate is not particularly limited. If it is extremely low, below Ig/nf, it is difficult to uniformly apply the radically polymerizable composition and pinholes are likely to be generated, and even if it is increased to above 20g/nIQ, the properties will not change and only the cost will increase. Curl adjustment becomes difficult.

Examples of ultraviolet irradiation devices for curing the radically polymerizable composition layer include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, metal halide lamps, and ozone-less types that generate less ozone. Generally output 30 w/c
Use multiple lamps of rn or higher in parallel.

When performing electron beam irradiation to cure the radically polymerizable composition layer, the acceleration voltage is
00~1000KV, more preferably 100~3
It is preferable to use an electron beam accelerator with a voltage of 0.00 KV so that the absorbed dose in one pass is 0.2 to 20 Mrad. If the accelerating voltage or electron beam irradiation amount is lower than this range, the penetrating power of the electron beam will be too low and sufficient curing will not occur, and if it is too high than this range, energy efficiency will not only deteriorate, but also the strength of the base paper will decrease. Unfavorable effects on quality, such as decomposition of the resin and decomposition of the resin, may occur. The electron beam accelerator may be, for example, an electrocurtain system, a scanning type, a double scanning type, or the like.

Note that during electron beam irradiation, if the oxygen concentration is high, curing of the electron beam curable composition will be hindered, so replacement with an inert gas such as nitrogen, helium, carbon dioxide, etc. is performed to reduce the oxygen concentration to 600 ppm or less, preferably 4,000 ppm or less. )L) Although irradiation is generally carried out in an atmosphere controlled to below m, if only the surface layer is cured by ultraviolet irradiation, and the inside of the layer is cured by electron beam irradiation, oxygen is generally used. No need for replacement.

However, it is preferable to circulate the cooling gas in order to avoid overheating within the electron beam irradiation device and to exhaust generated ozone.

In the radically polymerizable composition of the present invention, various additives such as pigments and dyes such as ultramarine blue and cobalt violet, antioxidants, optical brighteners, and antistatic agents can be added in appropriate combinations.

A general pigment kneading machine can be used as a method for preparing an electron beam curable composition by mixing a white pigment with an electron beam curable resin. For example, two-roll, three-roll, ball mill, Ni-Goo, high-speed mixer, homogenizer, etc.

The ink-receiving layer in which the radically polymerizable composition is cured by ultraviolet rays or electron beam irradiation as described above can be further treated with a radical polymerization inhibitor to significantly reduce the deterioration of the ink-receiving ability of the cured ink-receiving layer over time. It can be improved. This is probably due to the fact that unreacted radical species trapped in the resin cured by ultraviolet or electron beam irradiation are inactivated by the radical polymerization inhibitor. Such radical polymerization inhibitors include dichlorobenzoquinones, trinitrobenzenes, nitrosobenzenes, butylcatechols, picric acids, nitrobenzoic acids, oxygen and active oxygen, secondary chlorides, ferric chlorides, and halogenated Cobalt, diphenylpicrylhydrazyl, tetraethylphenylenediamine,
Generally known radical polymerization inhibitors such as chloranil and iodine can be used. These radical polymerization inhibitors can be used alone or as a solution,
Furthermore, after the treatment, it can be washed with water or a solvent.

Examples of methods for applying a water-soluble polymer solution, a radical polymerizable composition, or a radical polymerization inhibitor onto a substrate include blade coating, air doctor coating, squeeze coating, air knife coating, reverse roll coating, and gravure roll coating. Methods such as transfer roll coating, bar code, curtain coating, kiss coating, gate roll coating, and tab size are also used.

[E] Function The present invention provides an ink donor sheet and an image-receiving paper by the action of a water-soluble polymer intermediate layer provided on a substrate and an uncured radically polymerizable composition provided thereon in an image-receiving paper for thermal transfer. It has good adhesion and prevents blocking, resulting in images with good reproducibility. In addition, it has appropriate firmness and cushioning properties, does not overheat during manufacturing, and suppresses seepage of the radical polymerizable composition, so it has good flatness and does not curl, and has good image quality such as opacity and whiteness. Various characteristics necessary for reproduction can be satisfied at the same time.

Furthermore, the action of the radical polymerization inhibitor can inactivate unreacted radical species in the target MM that has been cured by ultraviolet rays or electron beam irradiation. Receptivity can be maintained for a long period of time.

[F] Examples The present invention will be explained in detail below using examples, but the content of the present invention is not limited to the examples.

Example 1 Using an air knife coater, a 5% gelatin solution containing formaldehyde and a hardening agent was applied to one side of coated paper (basis weight 110 g/rn') as a substrate at a dry weight of 0.8 g/r1.
12, and dried after setting.

5g/m of the following composition as a radically polymerizable composition
” and cured by UV irradiation (3 80w).

(Radical polymerizable composition) Acrylic oligomer M'-620'0 98 parts (product of Toagosei Chemical Industry Co., Ltd.) Benzyl dimethyl ketal IRGAC11RE951
2 parts (Ciba Geigy Co., Ltd. product) Cured radically polymerizable composition layer surface at 45°C, 0.5%
The 2,6-cyclopenzoquinone alcohol solution was coated and dried to obtain a thermal transfer image receiving paper treated with a radical polymerization inhibitor, and evaluated.

Example 2 A 5% solution of polyvinyl alcohol was applied to one side of the base synthetic paper (basis weight 90 g/n?) using an air knife coater to a dry weight of 0.5 g/n? I applied it and let it dry.

Acrylic oligomer=M-6 as radically polymerizable composition
500 (produced by Toagosei Kagaku Kogyo Co., Ltd.) and 10 parts of anatase-type titanium oxide (produced by Tohoku Kagaku Kogyo Co., Ltd.) were mixed and coated using a U comma coater at a concentration of 3 g/♂, and then coated with an electron beam. It was cured by irradiation acceleration voltage: 175 kV, absorbed dose: 2 Mrad).

Cured radically polymerizable composition layer surface at 45°C, 0.5%
A 2,6-cyclopenzoquinone alcohol solution was coated and dried to obtain a thermal transfer image-receiving paper treated with a radical polymerization inhibitor and evaluated.

Example 3 Using a tab on one side of a porous substrate art paper (basis weight 120 g/rr) 2), apply a 5% pullulan solution to a dry weight of 0.5 g.
/rn' and dried.

Acrylic oligomer APG as radically polymerizable composition
-400 (product of Shin Nakamura Chemical Co., Ltd.) was applied using a U comma coater at a rate of 3 g/rf, and then irradiated with an electron beam (
Curing was performed using an accelerating voltage of 175 kV and an absorbed dose of IMrad.

Cured radically polymerizable composition layer surface at 45°C, 065%
A 2,6-cyclobenzoquinone alcohol solution was coated and dried to obtain a thermal transfer image receiving paper treated with a radical polymerization inhibitor and evaluated.

Comparative Example An image-receiving paper for thermal transfer was prepared with a radical polymerizable composition layer provided in the same manner as in Example 1-3 except that the treatment with a radical polymerization inhibitor was not performed. Comparative examples 1 to 3 were prepared in correspondence with the numbers of the examples, and evaluations were conducted in the same manner as in the examples.

Evaluation That is, an object of the present invention is to provide an image-receiving paper for thermal transfer that has good blocking and curling properties, is smooth, has good image reproducibility, and does not change over time.

The smoothness of the thermal transfer image receiving paper (B6 version) obtained in Example 1-3 and Comparative Example 1-3 was measured using a three-dimensional surface roughness meter (manufactured by Koita Institute, 5PA210), and then After copying the video image using a dye-sublimation thermal transfer printer, the curl height was measured, and the sharpness of the reproduced image and the presence or absence of sticking were visually evaluated. In addition, in order to observe changes over time, the thermal transfer receiving papers obtained in Example 1-3 and Comparative Example 1-3 were kept at 40°C for 3 weeks, and then copies of video images were made using a sublimation thermal transfer printer. The sharpness of the reproduced image was evaluated.

The results are summarized in Table 1.

Results The thermal transfer image-receiving papers obtained in Examples and Comparative Examples all had excellent smoothness, and were practically satisfactory in terms of curl, whiteness, and opacity.

However, regarding image reproducibility (ink receptivity), the thermal transfer image-receiving paper obtained in the example has good image reproducibility both after preparation and after aging. It has become clear that although paper has good image reproducibility after it is made, its ink-receiving ability significantly decreases over time, and the image reproducibility is particularly poor in terms of ink transfer density.

=19= Table 1 Evaluation results of each thermal transfer paper By curing with electron beam irradiation and then treating with a radical polymerization inhibitor, it has excellent properties such as smoothness, curling, and whiteness after creation and after aging, and there is no blocking or sticking even after receiving a sublimation type heat-sensitive transfer image. The purpose of the present invention is to provide a heat-sensitive transfer image-receiving paper with good image reproducibility and image sharpness.

Claims (2)

[Claims] (1) A radically polymerizable composition is applied to at least one side of a sheet-like substrate, and after being cured by ultraviolet rays or electron beam irradiation, the cured radically polymerizable composition layer is treated with a radical polymerization inhibitor. A method for producing an image receiving paper for thermal transfer. (2) providing a water-soluble polymer intermediate layer on at least one side of a sheet-like substrate, applying a radically polymerizable composition thereon;
2. The method for producing an image-receiving paper for thermal transfer according to claim 1, wherein the cured radically polymerizable composition layer is treated with a radical polymerization inhibitor after being cured by ultraviolet rays or electron beam irradiation.