JPH0789251A - Manufacture of image receiving sheet for thermal transfer recording - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing an image receiving sheet for thermal transfer recording with a satisfactory image quality by allowing a thermally foaming resin particle in a coated layer to foam uniformly and efficiently and providing an intermediate layer with superb properties. CONSTITUTION:A method of manufacturing an image receiving sheet for thermal transfer recording is to apply a coating liquid containing a thermally foaming resin particle to the surface of a base, then allow the coat to foam by a near- infrared beam emission device as a heating means to prepare an intermediate layer, and form an image receiving layer on the intermediate layer. Consequently, the intermediate layer thus obtained has a large sheet thickness and an adequately foamed state both on the surface and internally. In addition, the quality of an image obtained by a thermal transfer to the image receiving sheet for thermal transfer recording is satisfactory without roughness in the highlighted portion. Further, the image is visually of high color density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an image-receiving sheet for thermal transfer recording provided with an intermediate layer containing heat-expandable resin particles, and in particular, the heat-expandable resin particles from the surface layer to the inner surface of the coating layer. The present invention relates to a production method for obtaining an intermediate layer having excellent properties by uniformly and efficiently foaming the entire area of the layer to obtain an image-receiving sheet for thermal transfer recording having good image quality.

[0002]

2. Description of the Related Art The thermal recording system, which can increase the number of records at the same time as an input signal, is used in various fields such as a facsimile, a computer terminal printer, a measuring instrument printer, etc., because it is relatively simple and inexpensive and has low noise. Has been done. As the recording medium used in these thermal recording systems, so-called color-developing type thermal recording paper is most commonly used, which is provided with a recording layer that undergoes a physical or chemical change by heating to develop a color. However, color-type thermosensitive recording paper is liable to cause unwanted color development during the manufacturing process and storage, and also the storage stability of the recorded image is poor, causing discoloration due to contact with organic solvents and chemicals. There are drawbacks.

Therefore, a recording method using a colored coloring material itself has been proposed as a recording medium to replace the color-developing type thermosensitive recording paper. JP-A-51-15446 discloses a solid or semi-solid recording medium. Is applied on a support such as paper or polymer film, the color material on the support is brought into contact with the recording paper, and the color material on the support is heated by the thermal recording head to produce this color. A method has been proposed in which a material is selectively transferred to recording paper to obtain a recorded image.

In this recording method, a coloring material on a support is melted, evaporated or sublimated by heat, transferred to recording paper, and a recorded image is obtained by adhesion, adsorption or dyeing.
Plain paper can be used as recording paper. And
In particular, in a recording method using a sublimable dye as a color material, an image excellent in gradation can be obtained, and therefore application to high-grade full-color recording has been attempted.

For the purpose of obtaining a high-quality full-color recorded image,
When plain paper is used as the recording paper, dyeing is not particularly likely to occur, and not only the color density of the recorded image is low, but also a marked fading phenomenon occurs over time. Therefore, JP-A-57-107885 and U.S. Pat. No. 360180
An image-receiving sheet having an image-receiving layer containing a thermoplastic resin as a main component is used as described in Japanese Patent No. 4 or the like, which improves recording sensitivity and storability.

However, in the case of transferring an image having gradation, even if an image receiving layer is provided on a base material having a low smoothness such as high quality paper, an image having a beautiful gradation having no transfer omission is obtained. I can't get it. In particular, in the case of an image such as a photograph or an image having a solid colored portion, the transfer omission remains as a defect.

Various efforts have heretofore been made to improve this drawback. Japanese Patent Application Laid-Open No. 61-172795 discloses a method in which an intermediate layer below an image receiving layer is provided with an organic solvent barrier property, and at the same time, the maximum surface height R _max measured according to JIS B 0601 is set to 7 μm or less. Japanese Patent Application Laid-Open No. 61-144394 proposes a method in which the 100% modulus defined by JIS K 6301 of the intermediate layer mainly composed of resin is 100 Kg / cm ² or less. There is. Furthermore, JP-A-64-
Japanese Patent No. 27996 proposes an intermediate layer using thermally expandable resin particles and has been noted as an effective method.

[0008]

It has been found that the performance of the intermediate layer using the thermally expandable resin particles also varies greatly depending on the foaming means. The volume of the heat-foamed resin particles expands several tens of times by applying a temperature exceeding the minimum foaming temperature. However, if the exposure time to the high temperature is too long, the thermally expanded resin particles become excessively foamed near the surface of the intermediate layer and eventually burst and lose their volume. In order for the heat-expandable resin particles to fully exhibit their performance in the intermediate layer, the foamed state is unsuitable whether unexpanded or ruptured.

That is, it is necessary to expose the temperature of the intermediate layer using the heat-expandable resin particles to a temperature higher than the minimum foaming temperature for a time as short as possible. However, according to the observations of the present inventors, in the case of the means of drying and heating using a hot air dryer, such short-time heating causes sufficient foaming in the vicinity of the surface of the intermediate layer, but The resin particles are still in a non-foaming state. Then, when the heating time was extended until the internal particles foamed, it became clear that at that time, the particles near the surface had already begun to burst.

[0010]

According to the present invention, a coating liquid containing thermally expandable resin particles is applied onto a base material and foamed by a heating means to form an intermediate layer, and an image receiving layer is provided on the intermediate layer. In the method for producing a thermal transfer recording image-receiving sheet, a near-infrared irradiation device is used as a heating means for producing the thermal transfer recording image-receiving sheet.

That is, a coating material containing heat-expandable resin particles is applied onto a base material, and the heat-expandable resin particles are heat-foamed to provide an intermediate layer of an image-receiving sheet for thermal transfer recording. As a result of using a near-infrared irradiation device, the expandable resin particles are uniformly and efficiently foamed from the surface of the intermediate layer over the entire area to obtain an intermediate layer with excellent characteristics, and thermal transfer with good image quality. Recording paper can be obtained.

[0012]

The operation of the intermediate layer will be described below. The intermediate layer in the present invention contains the heat-expandable resin particles, further the pigment,
A water-based resin, other auxiliaries and the like are appropriately used in combination depending on the purpose to apply as a coating liquid onto a substrate and heated to obtain thermally expandable resin particles, which are obtained.

The thermally expandable resin particles referred to herein are hollow particles having a capsule wall made of a thermoplastic resin such as vinylidene chloride, acrylonitrile, or methyl methacrylate,
Includes a volatile swelling agent such as isobutane or n-pentane,
It expands when heated. As a concrete example,
For example, Matsumoto Microsphere F80, F30 (Matsumoto Yushi-Seiyaku Co., Ltd.), Expancel 551, 64
2 (manufactured by Kemanobel Co., Ltd.).

Examples of pigments include kaolin, calcined kaolin, calcium carbonate, calcium sulfate, calcium sulfite, barium sulfate, titanium oxide, zinc oxide, magnesium carbonate, alumina, silica, polystyrene resin, urea resin, melamine resin, benzoguanamine resin, It is appropriately selected from acrylic resins and the like according to the purpose. In general, the coating suitability is often improved by adding these pigments within a range that does not impair the foamability.

As the aqueous resin, for example, polyacrylamide, various resins containing carboxyl group or hydroxyl group, for example, carboxyl group-containing polyethylene, polyvinyl alcohol, cellulose resin, polyacrylic acid ester, polymethacrylic acid ester, polyolefin, polybutadiene, polystyrene, Polyvinyl acetate, polyvinyl chloride,
Alkali-soluble type, alkali-swelling type, alkali-non-swelling type, deformed polymers and copolymers such as polyvinylidene chloride, polyurethane, and polyester can be used.

If necessary, a starch, a modified starch, a binder such as a protein adhesive, an antioxidant, a dye, a defoaming agent, a surfactant, and other auxiliaries are added.

The content of the heat-expandable resin particles with respect to 100 parts of the intermediate layer is preferably 20 to 70 parts, and the coating amount of the heat-expandable resin particles as the intermediate layer is 1 to a dry solid content.
The range is 10 g / m ² , and more preferably 2 to 6 g / m ² .

This coating solution uses a known blade coater, air knife coater, bar coater, rod blade coater, roll coater, gravure coater, curtain coater, etc., and has a dry weight of 3 g / m ² or more,
Desirably, it is formed by coating and drying 8 to 30 g / m ² . When the coating amount is less than 3 g / m ² as a dry weight, it is insufficient to obtain the intended effect, and when it exceeds 30 g / m ² , there is no significant change in the effect and it is not desirable from the economical point of view. Conceivable.

The following effects can be obtained when the intermediate layer is provided between the support and the image receiving layer. By smoothing the surface of the support or imparting cushioning properties to improve the adhesion between the thermal transfer recording sheet and the image receiving sheet,
Improve image quality. The image receiving layer is prevented from penetrating into the support and not sufficiently covering the surface of the image receiving sheet, thereby improving the image quality. The heat applied from the thermal head is prevented from escaping to the support, and the thermal efficiency of the image receiving sheet is improved. In particular, depending on the nature of the support or the quality required for the image-receiving sheet, it is also possible to adopt a structure having two or more intermediate layers.

Next, the heating means for the intermediate layer will be described. As means for heating and drying, conventionally, steam heating, hot air heating, gas heater heating, electric heater heating,
Various methods such as infrared heater heating, high frequency heating, laser heating, and electron beam heating are adopted. Infrared rays have a wavelength of 0.75 to 2.5 μm, and near infrared rays of 2.5 to 25 μm.
Of the mid-infrared and far-infrared of 25-2000 μm (Guidance for instrumental analysis Kagaku Dojin / April 2, 1979)
In the infrared dryer which has been conventionally used (see Issue 0), infrared rays in the mid-infrared region or far-infrared region with a wavelength of 2.5 μm or more are exclusively used, and the near infrared rays used in the present invention are the Infrared drying in the infrared region is a relatively new drying method.

In the method of the present invention, infrared rays in the near infrared region are selected and used, and the wavelength is 0.75 to 0.75.
Near infrared rays of 2.5 μm, preferably 1.0 to 2.0 μm are used. When the wavelength of near-infrared rays is shorter than 0.75 μm, the heating effect of the coating layer is extremely small, while when the wavelength of near-infrared rays is longer than 2.5 μm, it is effective for mere heating, but the effect of the present invention is intended. Will not be able to get.

Although the reason why the heat-foamable resin particles in the coating layer are uniformly foamed by the method of the present invention is not clear, near-infrared rays have a strong penetrating power to the coating layer and a high energy density. It is presumed that the heat instantly penetrates into the coating layer, and the thermally expandable resin particles expand uniformly from the surface to the inside of the coating layer.

In the present invention, the image receiving layer provided on the intermediate layer functions to receive the dye transferred from the color material transfer sheet, and so-called dyeing resins in the technical field are used. It is used and specifically contains the following synthetic resins. As those having an ester bond, polyester resin, polyacrylic ester resin, polycarbonate resin, polyvinyl acetate resin, styrene acrylate resin, vinyltoluene acrylate resin and the like. Polyurethane resin, etc. as having a urethane bond.
Polyamide resin etc. having an amide bond. Urea resins, etc. that have a urea bond.

As the image receiving layer provided on the intermediate layer,
The image receiving layer that receives the hot-melt ink has the same effect, and the image receiving layer can be provided by applying a coating liquid containing an inorganic-organic pigment and an adhesive as the main components onto the substrate. For the inorganic and organic pigments, adhesives and other auxiliaries, all known techniques in the art can be used.

For the image-receiving layer, for example, a blade coater, an air knife coater, a bar coater, a rod blade coater, a roll coater, a gravure coater or a curtain coater is used, and the dry weight is 1 g / m ² or more, more preferably 2 to It is formed by applying and drying about 10 g / m ² . If necessary, an antistatic agent, an ultraviolet absorber, an anti-fusing agent, an antioxidant, a dye, an antifoaming agent, a surfactant, a pigment such as colloidal silica, a cross-linking agent and other auxiliaries may be added. Is also good.

Next, the support will be described. For the support, general paper, for example, art paper, coated paper, lightweight coated paper, coated paper such as lightly coated paper, cast coated paper, coated paper such as dull type and matte type, fine paper, medium-quality paper , Super calendered paper, uncoated paper such as single-gloss base paper. Further, general synthetic paper, film, or a composite support obtained by laminating these with paper can be used.

[0027]

EXAMPLES Examples will be described below to more specifically describe the present invention, but the present invention is not limited thereto. Further, "parts" and "%" in the text represent "parts by weight" and "% by weight", respectively, converted into solid content, unless otherwise specified.

Example 1 An intermediate layer coating material was prepared and coated as follows to form an intermediate layer. Kaolin [Product Name: Ultra White-90, E.I.
M. C. Made by the company] 20 parts dispersed in water, solid concentration 50%
And In addition, expandable resin particles (trade name: Matsumoto Microsphere F30, Matsumoto Yushi-Seiyaku Co., Ltd.)
20 parts and acrylic resin emulsion [Product name:
Nicazole RX-941 (A), Nippon Carbide Co., Ltd.
Manufacturing] 60 parts was added, and water was added to make the solid content concentration 40%. This was dried on a fine paper of 85 g / m ^{2 with} a dry weight of 2
An intermediate layer was formed by coating and drying with a wire bar so as to obtain 0 g / m ² .

For drying, first, a hot air dryer was used until the paper surface temperature reached 65 ° C. Next, this is irradiated with a near infrared ray irradiation device (infrared wavelength of 1.2 μm) at a paper surface temperature of 90 to 100.
The temperature was controlled to ℃ and the conditions for foaming the intermediate layer and maximizing the paper thickness were determined. The foaming state is confirmed by measuring the paper thickness (based on “ISO 534”), examining the foaming state of the surface with an optical microscope / reflected light, and the foaming state inside the intermediate layer with an optical microscope / transmitted light, and confirming the result. The results are shown in Table 1. It should be noted that the evaluations were evaluated as ◯ and those inferior were evaluated as Δ.

Next, an image receiving layer coating material was prepared in the following manner, and this was coated on the surface of the intermediate layer to form an image receiving layer. 100 parts of polyester resin [trade name: Vylon 200, manufactured by Toyobo Co., Ltd.], amino-modified silicone [trade name: KF-
393, manufactured by Shin-Etsu Chemical Co., Ltd.] 0.5 parts, epoxy-modified silicone [trade name: X-22-343, manufactured by Shin-Etsu Chemical Co., Ltd.] 0.5 parts methyl ethyl ketone / toluene (weight ratio 1: 1 ) Was dissolved in the mixture with stirring with a mixer to obtain an image receiving layer coating liquid having a solid content of 15%. This was coated on the surface of the barrier layer with a wire bar so as to have a dry weight of 7 g / m ² and dried, and then subjected to a super calendar treatment to obtain an image-receiving sheet for thermal transfer recording.

A sublimation transfer type printer [trade name: color video printer GZ-
21B, manufactured by Sharp Co., Ltd.] and image quality was evaluated, and the results are shown in Table 1. The quality of the image was evaluated by evaluating the roughness of the highlight portion and the visual color density, and evaluated as ◯ when it was excellent and Δ when it was inferior.

Example 2 The coating solution of Example 1 was applied to the same base paper as in Example 1 in the same manner, and the surface of the paper was kept wet with an infrared irradiator (infrared wavelength 1.2 μm) and a circulating air dryer. Temperature 90-100 ℃
The intermediate layer was obtained in the same manner as in Example 1, except that the drying and the foaming were simultaneously performed under the control of No. 1, and the foaming state thereof was examined. Further, an image receiving layer was formed in the same manner as in Example 1 and the evaluation results are shown in Table 1.

Comparative Example 1 The same as Example 1 except that a hot air dryer was used as the foaming means of the intermediate layer and the temperature of the paper surface was adjusted to 100 ° C. so that the paper thickness was maximized. Similarly,
Table 1 shows the results of the evaluation and evaluation of the image-receiving sheet for thermal transfer recording.
It was shown to.

Comparative Example 2 An image receiving sheet for thermal transfer recording was prepared in the same manner as in Example 1 except that a hot air dryer having a set temperature of 100 ° C. was used as a means for drying and foaming the intermediate layer. The evaluation results are shown in Table 1.

[0035]

[Table 1]

[0036]

As is clear from Table 1 as a result of the examples, the thermal transfer image-receiving sheet obtained by the production method of the present invention has a high paper thickness and the intermediate layer has a sufficiently foamed state both on the surface and inside. Therefore, the quality of the image obtained by thermal transfer was excellent with no roughness in the highlight portion, and the visual color density was high and excellent.

Claims (1)

[Claims] 1. An image receiving sheet for thermal transfer recording in which a coating liquid containing thermally expandable resin particles is applied onto a substrate and foamed by a heating means to provide an intermediate layer, and an image receiving layer is formed on the intermediate layer. The method for producing an image-receiving sheet for thermal transfer recording according to claim 1, wherein a near infrared ray irradiation device is used as the heating means.