JPH0880685A - Image receiving sheet for thermal transfer - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a high-sensitivity image receiving sheet for thermal transfer, which is free from white spots and uneven density. In a thermal transfer image-receiving sheet provided with an image-receiving layer that receives a dye that migrates from a thermal transfer medium by heat melting or sublimation upon heating, a spherical hollow particle having a main component between a support made of pulp paper and the image-receiving layer. And a rubber elastic fine particle, and an intermediate layer having a density of less than 0.8 is provided. Preferably, the particle diameter ratio of the spherical hollow particles and the rubber elastic fine particles is 1: 0.5 to 1: 2.
Is.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer image-receiving sheet, and more particularly to a high-sensitivity thermal transfer image-receiving sheet which is free from white spots and uneven density in an image.

[0002]

2. Description of the Related Art In recent years, as a means for color hard copy, an apparatus using a thermal transfer recording system has been widely used because of its advantages such as light weight, compact size, no noise, excellent operability and maintainability. . This thermal transfer recording system is roughly classified into two types, which are a heat melting type and a heat transfer type or a sublimation type. In particular, the latter is excellent in reproducibility of multicolor gradation images and is printed by using a sublimation type thermal transfer type printer. The principle of such a sublimation-type thermal transfer type printer is that an image is converted into an electric signal, and this electric signal is further converted into a heat signal by a thermal head, and a thermal transfer medium coated with a heat transferable dye (hereinafter , An ink donor sheet) is heated, and dye is transferred from the ink donor sheet to the image-receiving layer of the thermal transfer image-receiving sheet by sublimation or diffusion in a medium, thereby recording information.

[0003]

Conventionally, an image-receiving sheet for thermal transfer having an image-receiving layer formed on a support made of pulp paper has uneven thickness of the support or unevenness of the surface, resulting in white spots and uneven density. It is known that this produces a rough texture in the halftone. Further, it was impossible to obtain a high transfer density due to the lack of heat insulation of the support.

In particular, in recent years, from the viewpoint of increasing the printing speed, it has been required to improve the sensitivity, that is, the transfer density, and such high sensitivity is disclosed in, for example, JP-A-62-87390.
JP-A No. 3-2666691 and the like. In this publication, synthetic resin films and synthetic papers such as polypropylene, polyester and polyethylene terephthalate having a void structure produced by a biaxial stretching method are used.
It is described as effective because it has excellent cushioning properties and heat insulating properties.

However, since such a synthetic film or synthetic paper is inferior in heat resistance, heat shrinkage may occur due to, for example, a drying process in laminating when a support has a multi-layer structure or an applied energy heat in printing. However, there are problems such as surface irregularities. The voids of such synthetic resin film or synthetic paper are generally several to several tens of μm in thickness and several to several tens of μm in length, but the platen pressure is applied to the thermal transfer image receiving sheet during printing. When it was compressed due to cracking, minute density unevenness due to the density unevenness of the void structure occurred. Further, in consideration of curl suitability, paper feeding property and handling property in a printer, it is not possible to provide an inexpensive thermal transfer image-receiving sheet with a support which is laminated with paper, resin-coated paper, PET film or the like. It was difficult.

Therefore, in JP-A-62-151393 and JP-A-63-98494, cushioning properties are imparted by providing an elastic layer between the support and the image-receiving layer to prevent uneven density and white spots. It shows that a high-sensitivity image-receiving sheet can be obtained. Also, JP-A-2-248289
In JP-A No. 2-286290 and JP-A No. 2-286290, by providing an intermediate layer containing hollow particles on a support, the heat insulating property of the image receiving sheet is improved and the sensitivity is increased.

However, simply providing an elastic intermediate layer lacks heat insulation and cannot achieve the high sensitivity required in recent years. Further, merely providing the intermediate layer containing hollow particles did not completely suppress unevenness in density and blank areas.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly sensitive image-receiving sheet for thermal transfer which is free from white spots and uneven density by using pulp paper mainly composed of wood pulp and synthetic pulp as a support. I am trying.

[0009]

Means for Solving the Problems As a result of intensive studies on such problems, the present inventors have found that spherical hollow particles and rubber elastic fine particles are contained as main components between a support and an image receiving layer. By providing an intermediate layer having a density of less than a specific value, it was found that even if inexpensive pulp paper is used as a support, there is no white spot and density unevenness, and it is possible to provide a high-sensitivity thermal transfer image-receiving sheet, leading to the invention. It was

That is, the image-receiving sheet for thermal transfer of the present invention is an image-receiving sheet for receiving a dye which is transferred from the thermal transfer medium by heat melting or sublimation at the time of heating on a support made of pulp paper mainly composed of wood pulp and synthetic pulp. In a thermal transfer image-receiving sheet having a layer, an intermediate layer is provided between the support and the image-receiving layer, the intermediate layer containing spherical hollow particles and rubber elastic fine particles as main components, and JIS According to P8118, the density defined by the following equation 2 (Formula 1) is 0.8 g.
It is characterized by less than / cm ³ .

[Formula 2] D = W / T (Equation 1) D: Density of intermediate layer (g / cm ³ ) W: Dry coating amount of intermediate layer (g / m ² ) T: Thickness of intermediate layer (μm)

In the thermal transfer image-receiving sheet of the present invention, the ratio of the spherical hollow particles contained in the intermediate layer to the rubber elastic fine particles is preferably 1: 0.5 to 1: 2.

In the present invention, the density (D) of the intermediate layer is
It is defined by Equation 1 above. In Formula 1, D is the density of the intermediate layer (g / cm ³ ), W is the dry coating amount of the intermediate layer (g / cm ³ ).
m ² ), T is the thickness (μm) of the intermediate layer. This density (D) is defined according to JIS P8118. The dry coating amount (W) of the intermediate layer is the mass (g /
It is obtained by subtracting the basis weight (g / m ² ) of the support from m ² ). Similarly, the thickness (T) of the intermediate layer is obtained by subtracting the thickness (μm) of the support from the thickness (μm) after coating the intermediate layer. Conversely, by peeling off the image receiving layer and the intermediate layer in this order, the dry coating amount (W) and the thickness (T) can be obtained.

Hereinafter, the present invention will be described in detail. Examples of the spherical hollow particles used in the present invention include capsule-shaped hollow polymers made of a styrene resin, an acrylic resin, a urea resin, a melamine resin, a styrene-acrylic copolymer resin, or the like. The capsule-shaped hollow polymer has, for example, a resin as a wall material and contains water inside,
It is a polymer that evaporates water when dried to form spherical hollow particles.

The spherical hollow particles used in the present invention preferably have a particle size of 0.3 to 5 μm, more preferably 0.5 to 2 μm. When it is less than 0.3 μm, a sufficient heat insulating effect cannot be obtained as hollow particles, and when it exceeds 5 μm, the smoothness is remarkably deteriorated. Further, the hollow rate is preferably 30% or more, and if the hollow rate is less than 30%, the heat insulating effect cannot be sufficiently obtained because the pores are small.

The rubber elastic fine particles in the present invention are partially cross-linked in a three-dimensional network and show deformation or limited fluidity due to the application of stress. Suitable rubber elastic particles include, for example, silicone rubber,
Butadiene rubber, styrene / butadiene rubber, high styrene / butadiene rubber, butyl rubber, fluororubber, nitrile rubber, chloroprene rubber, acrylic rubber, urethane rubber, isoprene rubber, emulsions obtained by damaging the bark of rubber trees are dried and coagulated. Fine particles containing the resulting natural rubber, chlorosulfonated polyethylene, chlorinated polyethylene, chlorinated butyl rubber, polysulfide rubber, epichlorohydrin rubber, propylene oxide rubber, ethylene-vinyl acetate rubber, etc.
You may use more than one kind.

The particle size suitable for the rubber elastic fine particles is
The range is 0.1 to 5 μm, and more preferably 0.2 to
It is in the range of 2 μm. If the particle size is too small, sufficient cushioning properties will not be obtained, and if it is too large, the surface smoothness will deteriorate significantly. Therefore, even if the rubber elastic particles have elasticity, the adhesion between the thermal head and the image receiving sheet Since it becomes impossible to compensate for this, density unevenness and white spots occur.

The weight ratio of the spherical hollow particles and the rubber elastic fine particles contained in the intermediate layer in the present invention is 1: 9 to 9: 1.
Is preferable, and more preferably 2: 8 to 8: 2. When the content of the rubber elastic fine particles is too small, the cushioning property imparted to the thermal transfer image receiving sheet is insufficient, and white spots and density unevenness cannot be suppressed. On the other hand, if the content of the spherical hollow particles is too small, the heat insulating property imparted to the thermal transfer image-receiving sheet is insufficient, and high sensitivity cannot be achieved.

The ratio of the particle diameters of the spherical hollow particles and the rubber elastic fine particles contained in the intermediate layer is 1: 0.5 to 1: 2. If the particle size of the rubber elastic microparticles is too small compared to the particle size of the spherical hollow particles, the rubber elastic microparticles will be embedded between the spherical hollow particles, so that the original elasticity of the rubber elastic microparticles should be exhibited. And white spots and uneven density cannot be completely suppressed. Further, if the particle size of the rubber elastic fine particles is too large as compared with the particle size of the spherical hollow particles, the local balance between the spherical hollow particles and the rubber elastic fine particles will be lost, causing a slight concentration unevenness. Will be.

To form the intermediate layer in the present invention, the spherical hollow particles and the rubber elastic fine particles are mixed with the binder resin described below as needed for the purpose of maintaining the film strength. Examples of the binder resin include styrene / butadiene / acrylic copolymer, polyurethane, acrylic, vinyl chloride, vinyl acetate, vinyl chloride / vinyl chloride.
Resins such as vinyl acetate copolymer, polyvinyl alcohol, polyvinyl butyral, alkyd, polyester and starch can be used alone or in admixture of two or more.

In the present invention, the density of the intermediate layer defined by the above formula 1 is less than 0.8 g / cm ³ . 0.8 g
When it is / cm ³ or more, the amount of pores is insufficient and the heat insulation is insufficient, so that high sensitivity cannot be achieved.
The density of the intermediate layer can be controlled by the compounding ratio of the spherical hollow particles, the rubber elastic fine particles, and the binder resin. The lower limit of the density of the intermediate layer is not particularly limited, but is naturally limited by the densities of the spherical hollow particles and the rubber elastic fine particles which are the main constituent elements of the intermediate layer.

The intermediate layer may contain silica, alumina, titanium oxide, kaolin, or the like for the purpose of improving whiteness and opacity.
Inorganic pigments such as clay, talc, zinc oxide, and barium sulfate, starch particles, cellulose powder, melamine-based resin particles, guanamine-based resin particles, urethane-based resin particles,
Organic pigments such as epoxy resin particles, silicone resin particles and vinyl resin particles can be added.

In the intermediate layer, if necessary, a dye, a pigment, a fluorescent whitening agent or the like for color tone control, an ultraviolet absorber, an antioxidant, an antiseptic agent or the like for improving storage stability, A dispersant, a surfactant, an antifoaming agent, a thickener, etc. may be added to improve the liquidity, a cross-linking agent, etc. may be added to improve the film strength, and a conductive agent, etc. may be added to prevent static electricity. it can.

Examples of the method for providing the intermediate layer of the present invention include an air knife coater, a curtain coater, a die coater, a blade coater, a gate roll coater, a bar coater, a rod coater, a roll coater, a bill blade coater and a short dwell blade coater. Can be used.

The coating amount of the intermediate layer of the present invention is preferably 1 to 70 g / m ² , and more preferably 5 to 5 in terms of dry coating amount.
It is in the range of 0 g / m ² .

As the support in the present invention, pulp paper mainly composed of wood pulp or synthetic pulp is used. Examples of pulp paper include various papers such as high-quality paper, art paper, coated paper, cast coated paper, thermal transfer paper, photographic paper, and Kent paper. For example, NBK
P, LBKP, NBSP, LBSP, GP, TMP, C
For wood pulp such as GP and DIP and synthetic pulp such as vinylon, polyester and polyethylene, conventionally known fillers,
Chemicals such as sizing agents, dyes, dry paper strength enhancers, wet paper strength enhancers, fixing agents, and yield improvers are added as necessary, and fourdrinier paper machines, twin wire paper machines, hybrid paper machines, round nets. Paper made by a paper machine or the like can be used.

As the filler, for example, light calcium carbonate, heavy calcium carbonate, kaolin, clay, talc,
Of calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic silica, aluminum hydroxide, alumina, lithopone, zeolite, magnesium carbonate, magnesium hydroxide White inorganic pigment, styrene plastic pigment,
Examples include acrylic plastic pigments, polyethylene, microcapsules, organic pigments such as urea resins and melamine resins, and the like.

Examples of sizing agents include rosin sizing agents for acidic papermaking, modified rosin sizing agents for neutral papermaking, and AK.
D, ASA, cationic polymer type sizing agent and the like can be mentioned.

Further, on the surface, inorganic pigments such as silica, alumina, titanium oxide, kaolin, clay, talc, zinc oxide, barium sulfate, starch granules, cellulose powder, melamine resin microparticles, guanamine resin microparticles, urethane resin. Fine particles, epoxy resin fine particles, silicone resin fine particles, vinyl resin fine particles and other organic pigments, vinyl resin hollow fine particles, melamine resin hollow fine particles and other hollow pigments, starch, casein, gelatin, polyvinyl alcohol, carboxymethyl cellulose, hydroxy Water-soluble resins such as ethyl cellulose, styrene-butadiene-based, acrylic-based, vinyl acetate-based resin emulsions, dispersants,
A gravure coater, a roll coater, a rod coater, a pigment coating layer containing a crosslinking agent, a dye, a fluorescent agent, an ultraviolet absorber, an antioxidant, a preservative, a surfactant, a defoaming agent, a thickener, a conductive agent, etc. Those coated with a die coater, curtain coater, blade coater or the like can be used.

An image-receiving layer having a dyeing property for a dye which is melted or sublimated by heat and migrates is provided on the intermediate layer of the present invention to form an image-receiving sheet for thermal transfer, and the dye constituting the image-receiving layer. As the dyeable binder resin, any binder resin having strong interaction with the dye and capable of stably diffusing the dye into the resin can be preferably used.

For example, as those having an ester bond, polyester resin, polyacrylic ester resin,
Polycarbonate resin, polyvinyl acetate resin, styrene acrylate resin and the like; polyurethane resin having urethane bond; polyamide resin (nylon) having amide bond; urea resin having urea bond A polycaprolactone resin having a bond with other high polarity,
Polystyrene resin, polyvinyl chloride, polyacrylonitrile resin or the like can be used, or a copolymer containing at least one of the structural units of the resin as a main component, for example, vinyl chloride-vinyl acetate copolymer, styrene- It can also be used as a butadiene copolymer or the like, and the above resins can be used alone or in combination of two or more kinds.

The above resin is dissolved or emulsified and dispersed in an organic solvent or water to obtain an emulsion, which is a gravure coater, roll coater, rod coater, die coater,
The intermediate layer can be coated using a curtain coater, a blade coater, an air knife coater, a slide hopper, or the like. The dry coating amount of the image receiving layer is 0.5 to 15
It is preferably in the range of g / m ² . If necessary, the intermediate layer may be subjected to an easy-adhesion treatment to improve the adhesiveness to the image receiving layer.

As a method of making the intermediate layer easily adhesive, a method of modifying the intermediate layer by corona treatment, plasma treatment or the like, or a method of applying a resin having good adhesiveness to both the intermediate layer and the image receiving layer, etc. There is. As such a resin, any resin having good adhesiveness to both layers can be preferably used, but, for example, acrylic resin, vinyl chloride resin, vinyl acetate resin, urethane resin, styrene butadiene resin,
Or the copolymer etc. can be illustrated.

In the present invention, a releasing agent may be added to the image receiving layer for the purpose of preventing blocking. Specific examples of such a releasing agent include higher fatty acids or esters thereof, amides or metal salts thereof, waxes such as shellac wax, montan wax, carnauba wax, polyethylene wax and Teflon powder; fluorine-based and phosphoric ester-based waxes. Surfactants; silicone oil and the like can be mentioned. Further, as the silicone oil, modified silicone oil such as amino-modified silicone, epoxy-modified silicone, alkyd-modified silicone, polyester-modified silicone and the like can be used. Also, as a silicone compound,
A curable silicone compound can also be used if necessary. Examples of the curable silicone compound include a reaction curable type, an ionizing radiation curable type, and a catalyst curable type.

Further, if necessary, additives such as dyes, pigments, wetting agents, defoaming agents, dispersants, antistatic agents, fluorescent whitening agents, ultraviolet absorbers and light stabilizers are added to the image receiving layer. It can also be contained. Especially for pigments, silica, alumina, titanium oxide, calcium carbonate, kaolin, clay,
Inorganic particles typified by zinc oxide, barium sulfate and the like can also be added.

Further, a backing layer containing an inorganic fine powder is provided on the side of the support opposite to the image receiving layer in order to provide roll slipperiness during transfer and writing on the back side, or for the purpose of preventing electrostatic charge. Then, an antistatic agent can be added to the backing layer. When an adhesive resin is mixed in the backing layer, the adhesive resin and an antistatic agent are mixed and bleeding on the resin surface,
As a result, it can be provided on the resin layer. Examples of the antistatic agent include surfactants such as cationic surfactants (quaternary ammonium salts, polyamine derivatives, etc.), anionic surfactants (alkyl phosphates, etc.), zwitterionic surfactants, or nonionics. Type surfactants and the like.

[0036]

The present invention relates to a thermal transfer image-receiving sheet comprising a support made of pulp paper and an image-receiving layer for receiving a dye which migrates from the thermal transfer medium by heat melting or sublimation upon heating, the support and the image receiving layer. By providing an intermediate layer having a density of less than 0.8, which is an intermediate layer containing spherical hollow particles and rubber elastic fine particles as a main component, the thermal transfer image-receiving sheet is provided with heat insulating properties and cushioning properties. However, a high-sensitivity image receiving sheet for thermal transfer having no density unevenness and white spots can be obtained.

[0037]

EXAMPLES Next, the present invention will be described in more detail by way of examples, but the contents of the present invention are not limited to these. Further, "parts" shown in the examples mean parts by weight.

The ink donor sheet for evaluation was prepared as follows. On a biaxially stretched polyester film having a film thickness of 5 μm and subjected to a heat treatment, the following heat resistant slipping layer coating liquid was prepared, and the dry coating amount was 0.5 with a wire bar.
The coating was applied at g / m ² and UV irradiation was performed with a high pressure mercury lamp of 140 W / cm ² to cure the composition.

[Preparation of coating liquid for heat resistant slipping layer] TMPTA (Daiichi Kogyo Seiyaku Co., Ltd.) 10 parts Lipoxy SP1509 (Showa High Polymer) 20 parts Trefil E500 (Toray, silicone fine particles) 9 parts KF-393 (Shin-Etsu Silicone, amino modified) Silicone oil) 0.3 part Coronate L (Japan polyurethane, isocyanate) 0.3 part Darocur 1173 (Merck, initiator) 0.4 part Ethyl acetate 40 parts Isopropyl alcohol 20 parts

Further, a sublimation dye solution having the following composition was prepared on the other surface of the heat resistant slipping layer, pulverized with a ball mill for 2 days, and dried with a wire bar to give a dry coating amount of 1.5 g / m ² . It was coated so that it became a donor sheet. [Preparation of Sublimation Dye Liquid] Kayaset Blue 906 (Nippon Kayaku, sublimation dye) 10 parts Ethyl Semellose 10 parts Sylysia 350 (Fuji Silysia Chemical Silica) 10 parts Isopropyl alcohol 30 parts

[0041] fine paper of Example 1 basis weight 100 g / m ^2, was coated with an air knife coater so that the intermediate layer coating solution having the following composition was prepared, and 20 g / m ² on a dry coating amount, An image-receiving layer coating liquid having the following composition was prepared and coated with an air knife coater so that the dry coating amount was 7 g / m ² . The thermal transfer image-receiving sheet thus obtained was used as the thermal transfer image-receiving sheet of Example 1. According to the above mathematical formula 1, the density was calculated from the thickness of the intermediate layer and the coating amount to be 0.58 g / cm ³ .

[Preparation of Coating Liquid for Intermediate Layer] Spherical hollow particles (HP-91: Rohm & Haas, average particle size 1 μm) 79 parts Rubber elastic fine particles (0561: JSR, average particle size 0.6 μm) 21 parts Polyvinyl alcohol (PVA-117: Kuraray) 2 parts Water 20 parts [Preparation of coating liquid for image-receiving layer] Polyester emulsion (Vylonal MD-1220: Toyobo) 60 parts Polyerylene emulsion (Hydrin G-314: Chukyo Yushi) 15 parts As inorganic fine particles Colloidal silica (Snowtex O: Nissan Chemical) 25 parts Surfactant 5 parts

Examples 2 to 4 Thermal transfer image-receiving sheets were prepared in the same manner as in Example 1 except that the spherical hollow particles and the rubber elastic fine particles were mixed as shown in Table 1. The image-receiving sheet for thermal transfer of The density was determined from the thickness of the intermediate layer and the coating amount, and the results are shown in Table 1.

Example 5 Example 1 was repeated except that the composition of the intermediate layer coating liquid was changed to the following composition.
An image receiving sheet for thermal transfer of Example 5 was obtained in the same manner as in. The density of the intermediate layer was 0.72 g / cm ³ . [Preparation of coating liquid for intermediate layer] Spherical hollow particles (OP-62: Rohm & Haas, average particle diameter 0.4 µm) 80 parts Rubber elastic fine particles (0561: JSR, average particle diameter 0.6 µm) 20 parts

Example 6 Example 1 was repeated except that the intermediate layer coating liquid had the following composition.
An image receiving sheet for thermal transfer of Example 6 was obtained in the same manner as in. The density of the intermediate layer was 0.60 g / cm ³ . [Preparation of coating liquid for intermediate layer] Spherical hollow particles (HP-91: Rohm & Haas, average particle diameter 1.0 µm) 79 parts Rubber elastic fine particles (DX33-411: Toray Dow Corning Silicone, particle diameter 1-2 µm) ) 21 copies

Example 7 Example 1 was repeated except that the composition of the intermediate layer coating solution was changed to the following composition.
An image receiving sheet for thermal transfer of Example 6 was obtained in the same manner as in. The density of the intermediate layer was 0.58 g / cm ³ . [Preparation of coating liquid for intermediate layer] Spherical hollow particles (HP-91: Rohm & Haas, average particle diameter 1.0 μm) 79 parts Rubber elastic fine particles (DX33-412: Toray Dow Corning Silicone, particle diameter 2 to 5 μm) ) 21 copies

Example 8 Example 1 was repeated except that the composition of the intermediate layer coating solution was changed to the following composition.
An image receiving sheet for thermal transfer of Example 8 was obtained in the same manner as in. The density of the intermediate layer was 0.71 g / cm ³ . [Preparation of coating liquid for intermediate layer] Spherical hollow particles (HP-91: Rohm & Haas, average particle size 1.0 µm) 80 parts Rubber elastic fine particles (L-1876: Asahi Kasei Corporation, average particle size 0.2 µm) 20 parts

Example 9 A dry coating amount of the intermediate layer was 30 on a coated paper having a basis weight of 110 g / m ^2.
An image receiving sheet for thermal transfer of Example 9 was obtained in the same manner as in Example 1 except that a roll coater was used so as to obtain g / m ² . The density of the intermediate layer was 0.61 g / cm ³ .

Comparative Examples 1-2 A thermal transfer image-receiving sheet was prepared in the same manner as in Example 1 except that the spherical hollow particles and the rubber elastic fine particles were mixed as shown in Table 1, and Comparative Examples 1-2. The image-receiving sheet for thermal transfer of

Comparative Example 3 Example 1 was repeated except that the composition of the intermediate layer coating solution was changed to the following composition.
An image-receiving sheet for thermal transfer of Comparative Example 3 was obtained in the same manner as in. The density of the intermediate layer was 0.90 g / cm ³ . [Preparation of intermediate layer coating liquid] Spherical hollow particles (OP-62: Rohm & Haas, average particle diameter 0.4 µm) 20 parts Rubber elastic fine particles (0561: JSR, average particle diameter 0.6 µm) 80 parts

Comparative Example 4 Example 1 was repeated except that the composition of the intermediate layer coating solution was changed to the following composition.
An image-receiving sheet for thermal transfer of Comparative Example 4 was obtained in the same manner as in. The density of the intermediate layer was 0.56 g / cm ³ . [Preparation of coating liquid for intermediate layer] 100 parts of spherical hollow particles (HP-91: Rohm & Haas, average particle size 1.0 µm) Polyvinyl alcohol (PVA-117: Kuraray) 2 parts Water 20 parts

Comparative Example 5 Example 1 was repeated except that the composition of the intermediate layer coating liquid was changed to the following composition.
An image-receiving sheet for thermal transfer of Comparative Example 5 was obtained in the same manner as in. The density of the intermediate layer was 1.1 g / cm ³ . [Preparation of coating liquid for intermediate layer] Rubber elastic fine particles (L-1876: Asahi Kasei Corporation, average particle size 0.2 μm) 100 parts Polyvinyl alcohol (PVA-117: Kuraray) 2 parts Water 20 parts

Comparative Example 6 An image receiving sheet for thermal transfer of Comparative Example 6 was obtained in the same manner as in Example 1 except that the image receiving layer was coated directly on the support.

Table 1 below shows Examples 1 to 9 and Comparative Examples 1 to 6.
The spherical hollow particles, rubber elastic fine particles, the particle diameter ratio, and the density of the intermediate layer are collectively shown.

[0055]

[Table 1]

[Evaluation Method] The thermal transfer image-receiving sheet thus obtained was allowed to stand at 45 ° C. for 3 days, and then an ink donor sheet was overlaid thereon, and a sublimation type thermal transfer printer S3600 manufactured by Mitsubishi Electric Corporation was used.
A step wedge was printed at -30, and the sensitivity, white spots and density unevenness were evaluated.

(Sensitivity) The maximum reflection density of the printed step wedge was measured with a Macbeth RD-919 type optical densitometer.

(Blank) The low-density portion of the printed step wedge was visually evaluated, and ⊚ when no white spot was observed, ○ when almost no white spot was observed, and when white spot was observed. Δ, and the case where remarkable white spots were observed was evaluated as x.

(Density unevenness) The low-density portion of the printed step wedge was visually evaluated. When no density unevenness was observed at all, ⊚, when almost no density unevenness was observed, at ○, density unevenness was recognized. Δ, the case where remarkable density unevenness was recognized was evaluated as x.

The thermal transfer image-receiving sheets produced in Examples and Comparative Examples were evaluated according to the above-mentioned evaluation methods, and the results are shown in Table 2 below.

[0061]

[Table 2]

[Evaluation] The thermal transfer image-receiving sheets of Examples 1 to 9 had higher transfer densities than the thermal transfer image-receiving sheets of Comparative Examples 1-3, 5, and 6. The thermal transfer image-receiving sheet of Comparative Example 4 had a high transfer density, but was inferior in cushioning property because the intermediate layer did not contain the elastic fine particles, and white spots and density unevenness remarkably occurred. Further, the image-receiving sheet for thermal transfer of Comparative Example 6 in which the image-receiving layer was directly provided on the support was inferior in heat insulating property and cushioning property, so that the density was low and white spots,
The occurrence of uneven density was remarkable. Since the thermal transfer image-receiving sheets of Comparative Examples 1 to 3 contained spherical hollow particles and elastic fine particles in the intermediate layer, white voids and density unevenness were slightly improved, but the mixing ratio of the spherical hollow particles was small. Therefore, the density is 0.
Since it was 8 g / m ² or more, the heat insulation was insufficient and the transfer density was low. On the other hand, Examples 1 to 9
The thermal transfer image-receiving sheet contains a well-balanced spherical hollow particle and elastic fine particle in the intermediate layer, so that the density is less than 0.8 g / m ² and the heat insulating property and cushioning property are excellent. It was high, and white spots and uneven density were improved.

Further, in the thermal transfer image-receiving sheet of Example 7, since the particle size of the elastic fine particles was larger than that of the spherical hollow particles, white spots and uneven density were observed as compared with the thermal transfer image-receiving sheets of Examples 1 to 6 and 9. Was slightly inferior. On the contrary, in the thermal transfer image-receiving sheet of Example 8, since the particle diameter of the elastic fine particles was smaller than that of the spherical hollow particles, white spots and uneven density were similarly observed as compared with the thermal transfer image-receiving sheets of Examples 1 to 6 and 9. Was slightly inferior. In the image-receiving sheets for thermal transfer of Examples 1 to 6 and 9, since the ratio of the particle diameters of the spherical hollow particles and the elastic fine particles was appropriate, there were no blank areas and no density unevenness.

[0064]

The present invention contains spherical hollow particles and rubber elastic fine particles as main components between the support and the image-receiving layer,
By providing the intermediate layer having a density of less than 0.8, it is possible to impart heat insulating properties and cushioning properties to the thermal transfer image receiving sheet,
Even if an inexpensive pulp paper is used as a support, a high-sensitivity image receiving sheet for thermal transfer can be obtained without white spots and uneven density.

Claims (2)

[Claims] 1. An image-receiving sheet for thermal transfer, comprising an image-receiving layer for receiving a dye which migrates from a thermal transfer medium by heat melting or sublimation at the time of heating, on a support made of pulp paper mainly composed of wood pulp or synthetic pulp. An intermediate layer is provided between the support and the image receiving layer, the intermediate layer containing spherical hollow particles and rubber elastic fine particles as main components, and JI
An image-receiving sheet for thermal transfer having a density defined by the following mathematical formula 1 (equation 1) according to SP8118 of less than 0.8 g / cm ³ . ## EQU1 ## D = W / T (Equation 1) D: Density of intermediate layer (g / cm ³ ) W: Dry coating amount of intermediate layer (g / m ² ) T: Thickness of intermediate layer (μm) 2. A thermal transfer image-receiving sheet according to claim 1, wherein the ratio of the particle diameters of the spherical hollow particles and the rubber elastic fine particles is 1: 0.5 to 1: 2.