JPH0971059A - Image receive sheet and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image receive sheet having a high sensitivity with which irregular sensitivity and defective images can be reduced, and high quality transfer images can be obtained, and provide an image forming method using the sheet. SOLUTION: An image receive sheet is used for an image forming method wherein an ink layer of a thermal transfer sheet having on a support body the ink layer having as main components a pigment and a thermoplastic resin is transferred on the image receive sheet by irradiation with a laser beam modulated by a digital signal. The image receive sheet is a laminated body comprising a plastic support body having fine cells inside and an image receiving layer. On the ink layer of the thermal transfer sheet, the image receiving layer of the image receive sheet is superposed. Thereafter, the laser beam modulated by the digital signal is emitted from the rear face of the transfer sheet (or the laser beam is emitted by ablation method) so as to form a transferred image on the image receiving layer of the image receive sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image receiving sheet and an image forming method using the image receiving sheet and a thermal transfer sheet. In particular, the present invention is intended to form a high quality multi-tone color image (full color image) by transferring an ink image formed on a thermal transfer sheet by using laser light onto an image receiving sheet by area gradation recording. The present invention relates to an advantageous image receiving sheet and an image forming method using the image receiving sheet and a thermal transfer sheet.

[0002]

2. Description of the Related Art In recent years, with the progress of OA, copiers and printers using various recording systems such as an electrophotographic system, an ink jet system, and a thermal transfer recording system have been used in accordance with their respective applications. A coloring material is used in these image formations, and a composition containing the coloring material is usually melted, or the coloring material is evaporated or sublimated to have a recording medium such as paper or film by an action such as adhesion, adsorption or dyeing. I got an image on a sheet.

The thermal transfer recording system has advantages such as easy operation and maintenance, downsizing of the apparatus, and cost reduction. As a thermal transfer recording system, two systems, a thermal fusion type transfer system and a sublimation type dye transfer system, have been conventionally known. The heat-melt transfer method is a method in which a transfer sheet having a meltable ink layer on a support is image-wise heated by a thermal head or a laser beam to melt-transfer the meltable ink to a heat-sensitive transfer recording image-receiving sheet. On the other hand, the sublimation type dye transfer method uses a thermal transfer recording ink sheet having an ink layer containing a heat diffusible dye (sublimable dye) on a support, and heats the thermal transfer recording image receiving sheet to the above This is a method of diffusion transfer of a heat diffusible dye.

As a method of forming a transfer image using a thermal transfer sheet, a method using a laser beam, that is, a digital image forming method has been developed in recent years. In this method, an image receiving sheet is superposed on the ink layer (image forming layer mainly composed of pigment and thermoplastic resin) of the thermal transfer sheet, and a laser beam modulated by a digital signal is irradiated from the back surface of the thermal transfer sheet to obtain the image receiving sheet. It is a method of forming a transfer image on top. In this case, in order to convert the light energy of the laser beam into heat energy with high efficiency, a carbon black layer between the ink layer of the thermal transfer sheet and the support,
It is also common practice to provide a photothermal conversion layer composed of a metal vapor deposition layer or the like. Furthermore, in order to further improve the image quality of the transferred image (uniformity of image density, edge sharpness, etc.), as described in JP-A-6-219052, between the photothermal conversion layer and the ink layer, Further, a so-called ablation method in which a heat-sensitive peeling layer is interposed and peeled locally and transferred to an image receiving sheet is also used.

As the material to be transferred (image-receiving sheet) used in combination with the thermal transfer sheet in the thermal transfer method using the laser as described above, the above-mentioned JP-A-6-21905 is used.
As disclosed in Japanese Unexamined Patent Publication No. 2 (1999), an organic high molecular polymer is contained in order to prevent uneven transfer and dot omission due to the smoothness of the image receiving surface which is the transfer surface and the ink acceptability. An image receiving sheet provided with a thermal adhesive layer (image receiving layer) is generally used. The material for the support of the image-receiving sheet is, for example, paper, synthetic paper, or polymer film (eg, polyethylene terephthalate, polycarbonate, polyethylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, styrene-acrylonitrile copolymer). Are used. In particular, it is described that biaxially stretched polyethylene terephthalate is preferable from the viewpoint of dimensional stability against water and heat.

[0006]

However, the transfer image sensitivity (the recording line width becomes wider as the sensitivity becomes higher) obtained by using the laser beam is still not sufficient. Laser recording is performed after the ink layer side of the heat-sensitive transfer sheet and the image receiving layer side of the image receiving sheet are superposed under pressure to form a laminated body. It was also noticed that uneven sensitivity between the image-receiving layer and the image-receiving layer may cause unevenness in the sensitivity, and dust may be caught in the overlapping process to cause image defects. Such sensitivity unevenness and image defects can be improved to some extent by thickening the image receiving layer of the image receiving sheet, but on the other hand, increasing the layer thickness increases the manufacturing cost of the image receiving sheet. Therefore, it is not preferable (usually the layer thickness is 50 μm or less). Further, the above method is insufficient for image defects caused by relatively large dust.

Therefore, an object of the present invention is to provide an image-receiving sheet which has higher sensitivity, can reduce sensitivity unevenness and image defects, and can obtain a high quality transferred image, and an image forming method using the same. is there.

[0008]

As a result of the research conducted by the present inventor,
The present invention has been accomplished by finding that a transfer image having high sensitivity and good image quality can be obtained by using an image receiving sheet having a plastic support containing fine air bubbles inside. An image-receiving sheet having a support having such characteristics has low thermal conductivity, and therefore the thermal energy converted on the thermal transfer sheet is less likely to be lost due to thermal diffusion, and the temperature at the thermal transfer interface becomes higher, resulting in high sensitivity. Turn into. This makes it possible to obtain a highly sensitive transferred image. Further, since the image receiving sheet is also provided with properties such as high cushioning property and flexibility, in the step of superposing the transfer sheet and the image receiving sheet, a superposing operation by more uniform pressure is realized. Then, the laminated body is formed in a state where the ink layer and the image receiving layer are in close contact with each other. As a result, the followability with respect to the thermal information by the laser beam is improved, and sensitivity unevenness can be suppressed. Further, even when a relatively large amount of dust is caught in the superposing step, the deformation of the adhesive surface due to the dust is alleviated due to the above properties, and the image defects due to the dust can be reduced.

In the present invention, the ink layer of a heat-sensitive transfer sheet having an ink layer mainly composed of a pigment and a thermoplastic resin on a support is transferred onto an image receiving sheet by irradiation with a laser beam modulated by a digital signal. An image receiving sheet for use in the image forming method, wherein the image receiving sheet is a laminate comprising a plastic support having fine air bubbles inside and an image receiving layer.

In the present invention, the image-receiving layer of the above-mentioned image-receiving sheet is superposed on the ink layer of the heat-sensitive transfer sheet having an ink layer mainly composed of a pigment and a thermoplastic resin on a support. There is also an image forming method including irradiating a laser beam modulated by a digital signal from the back surface to form a transfer image on the image receiving layer of the image receiving sheet.

Further, in the present invention, the image-receiving layer of the above-mentioned image-receiving sheet is superposed on the ink layer of the heat-sensitive transfer sheet having an ink layer mainly composed of a pigment and a thermoplastic resin on a support to form a heat-sensitive transfer sheet. There is also an image forming method which comprises irradiating a laser beam modulated by a digital signal from the back surface and forming a transfer image on the image receiving layer of an image receiving sheet by an ablation method.

The present invention preferably has the following aspects. (1) The plastic support having fine air bubbles inside is polyester, polyamide, polycarbonate, polyether sulfone, polyimide, polyolefin,
Polyvinyl chloride, polyurethane, polyvinylidene chloride,
It is formed of a material selected from polyacrylate and cellulose acetate. (2) The thickness of the plastic support having fine bubbles inside is 50 to 300 μm (more preferably 75 to 300 μm).
200 μm).

(3) The image receiving layer has a two-layer laminated structure comprising a first image receiving layer and a second image receiving layer provided thereon.
The high molecular polymer constituting the first image receiving layer is selected from polyvinyl chloride, vinyl chloride / vinyl acetate copolymer, vinyl chloride / vinyl alcohol copolymer, and vinyl chloride / vinyl acetate / maleic acid copolymer. It is a resin. (4) The image-receiving layer has a two-layer laminated structure including a first image-receiving layer and a second image-receiving layer provided on the first image-receiving layer, and the high-molecular polymer forming the second image-receiving layer is polyvinyl butyral and It is a resin selected from alkyl acrylate / acrylamide copolymers. (5) In the case where the image receiving layer has a laminated structure composed of the first image receiving layer and the second image receiving layer provided thereon, the layer thickness of the first image receiving layer is 1 to 50 μm (preferably 5 to 5 μm). Thirty
μm), and the layer thickness of the second image receiving layer is 0.1 to 1
It is in the range of 0 μm (preferably 0.5 to 5 μm).

(6) The thermal transfer sheet and the image receiving sheet are superposed on each other under pressure, and the pressure is 1 to 30 kg / cm.
^It is in the range of ² (more preferably ^{2 to 10} kg / cm ² ).

(7) The ink layer comprises 30 to 70% by weight of pigment, and 70 to 30% by weight of a thermoplastic resin (preferably, an amorphous organic polymer having a softening point in the temperature range of 40 ° C to 150 ° C). Molecular polymer).

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The image-receiving sheet of the present invention will be described below. The image-receiving sheet of the present invention has a laminated structure of a plastic support and an image-receiving layer provided thereon. The plastic support of the image-receiving sheet of the present invention has fine air bubbles inside. The size of the fine bubbles is not particularly limited, but it is preferable that the fine bubbles are uniformly present over the entire area of the plastic support.
The plastic support having such a structure is, for example, a method of adding inorganic or organic fine particles to a thermoplastic resin, stretching, and generating voids around the fine particles, an organic solvent solution of a synthetic resin is extruded from an orifice, and then, It is produced by using various known methods such as a method of introducing into a coagulation bath to desolvate, coagulate, and generate voids by solvent removal, or a method of extruding a resin together with a foaming agent through an orifice to foam. be able to.

Examples of the plastic material for the support used in the image-receiving sheet of the present invention include polyester (eg,
Examples thereof include polyethylene terephthalate, polyethylene naphthalate), polyamide, polycarbonate, polyether sulfone, polyimide, polyolefin (eg polyethylene, polypropylene), polyvinyl chloride, polyurethane, polyvinylidene chloride, polyacrylate and cellulose acetate. Among these, polyethylene terephthalate and polypropylene are preferable,
In particular, polyethylene terephthalate is preferable from the viewpoint of dimensional stability.

The thickness of the plastic support used in the image-receiving sheet of the present invention is preferably in the range of 50 to 300 μm, more preferably 75 to 200 μm. In addition, the plastic support of the present invention,
It may have a plurality of layer structures composed of two or more layers such as a layer having minute bubbles inside and a layer not containing bubbles inside as described above. Further, the surface of the support on which the image receiving layer is provided may be subjected to an undercoating treatment so as to be advantageous for coating, or a surface treatment such as a corona discharge treatment or a glow discharge treatment for increasing the adhesive strength. It is also possible to provide an undercoat layer. The undercoat layer is not particularly limited as long as it enhances the adhesive force between the support and the image receiving layer, but a silane coupling agent is particularly preferable. Further, the support may be subjected to antistatic treatment and matte treatment.

The image-receiving layer provided on the support is a layer containing a polymer. The image receiving layer may be composed of a single layer, or may be composed of two or more layers. The image receiving layer having a two-layer laminated structure, which is a preferred embodiment of the present invention, will be described below. The image receiving layer having a two-layer laminated structure comprises a first image receiving layer formed on a support and a second image receiving layer formed on this layer. Both the first image receiving layer and the second image receiving layer are layers mainly composed of a polymer. In the present invention, it is preferable that either the first image receiving layer or the second image receiving layer has a cushioning property. Below, it demonstrates using the example in case a 1st image receiving layer has a cushioning property. First, the first image receiving layer (cushion layer) will be described.

Examples of the high molecular weight polymer which constitutes the first image receiving layer include polyolefins such as polyethylene and polypropylene; ethylene copolymers such as ethylene and vinyl acetate or ethylene and acrylate; polyvinyl chloride; and vinyl chloride. Vinyl chloride copolymer such as vinyl acetate; polyvinylidene chloride; vinylidene chloride copolymer,
Poly (meth) acrylic acid ester; Copolymerized nylon, N
-Polyamide resins such as alkoxymethylated nylon;
Synthetic rubber such as acrylic rubber; at least one selected from organic high molecular weight polymers such as chlorinated rubber is preferable.

Among these, the degree of polymerization is especially 200 to 2
000 high molecular weight polymers (polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl alcohol copolymers, vinyl chloride-vinyl acetate-maleic acid copolymers) are preferred. The reason for this is that polyvinyl chloride and vinyl chloride copolymers have almost no adhesiveness at room temperature, have a relatively low elastic modulus, and can easily follow the irregularities of the transferred image during thermal transfer. It is possible to easily control the interlayer adhesion force by the effect of the hydroxyl group or the carboxyl group, and particularly to easily control the elastic modulus by the plasticizer.

The thickness of the first image receiving layer is 1 μm to 50 μm.
(More preferably, 5 μm to 30 μm). The reason is that when transferring the image transferred on the image-receiving sheet to the permanent support, it is necessary to make it thicker than the unevenness on the surface of the permanent support, and it is necessary to make the relief step at the portion where the four color images overlap. In order to obtain sufficient cushioning properties, it is necessary to have a thickness capable of absorbing dust, and to have sufficient cushioning properties so that image defects due to dust do not occur even if dust adheres during image formation (absorption of dust) It can be mentioned that such thickness is required.

The first image receiving layer is preferably formed with an elastic modulus of 200 kg · f / cm ² or less. By reducing the elastic modulus, cushioning properties are generated in the image receiving layer, and recording sensitivity, dot quality, and gradation reproducibility are improved. Further, even when foreign matter such as dust is present between the thermal transfer sheet and the image receiving sheet during thermal transfer recording, there is an advantage that image defects are less likely to occur due to the cushioning property of the first image receiving layer. In addition, when the image transferred to the image receiving sheet is retransferred onto a printing paper such as paper under heating and pressure, the first image receiving layer is embedded according to the unevenness of the paper, so that high adhesion to the paper is obtained. Even after the second image-receiving layer is peeled off and the surface is not subjected to a special treatment such as matting, the surface gloss becomes an image similar to that of a printed matter.

A plasticizer may be added to the above organic polymer. Examples of the plasticizer include phthalic acid esters (eg, dibutyl phthalate, di-n phthalate).
-Octyl, butylbenzyl phthalate), aliphatic dibasic acid ester (eg, di (2-ethylhexyl) adipate, di (2-ethylhexyl) sebacate), phosphate triesters (eg, tricresyl phosphate), Examples thereof include polyol esters (eg, polyethylene glycol ester), epoxy compounds (eg, epoxy fatty acid ester), and acrylic acid esters (eg, polyethylene glycol dimethacrylate, pentaerythritol triacrylate). It is also possible to add various polymers, adhesion improvers, surfactants, and release agents to the organic high molecular weight polymer in order to adjust the adhesive strength to the support and the second image receiving layer. Further, it is also very effective to use a part of the adhesive polymer together for the purpose of lowering the elastic modulus.

When a vinyl chloride resin is used as the high molecular weight polymer, a butyl tin stabilizer or an octyl tin stabilizer generally known as a stabilizer for polyvinyl chloride and vinyl chloride copolymers, etc. It is also effective to add the above organic tin stabilizer.

Next, the second image receiving layer will be described. The purpose of the second image receiving layer is to be able to receive an image by thermal transfer,
When peeling the image-receiving sheet during retransfer to the permanent support, delamination is performed between the first image-receiving layer and the second image-receiving layer, leaving only a thin second image-receiving layer on the image on the permanent support, The unevenness of the support is to obtain an image similar to the gloss of the actual printed matter without performing a special matting treatment, and to improve the scratch resistance of the image.

The second image receiving layer is preferably made of a resin material like the first image receiving layer. Examples of the resin material that can form the second image receiving layer include, for example, various organic high molecular weight polymers used in the first image receiving layer, vinyl acetate copolymer, acetal resin such as polyvinyl butyral, and alkyl. Acrylate / acrylamide copolymer, modified polyvinyl alcohol, phenol resin, epoxy resin, urethane resin, polyester resin, urea resin, melamine resin, alkyd resin, maleic acid resin,
Hydroxystyrene copolymer, sulfonamide resin,
Mention may be made of cellulose resins, ester gums and rosins. In particular, the second image receiving layer is preferably composed of polyvinyl butyral and an alkyl acrylate / acrylamide copolymer.

Other adhesion improvers, plasticizers, release agents and surfactants can be added to these resins in order to satisfy the relationship of the adhesive strength at various interfaces. The coating solvent used for the second image receiving layer dissolves or swells the resin used for the first image receiving layer in order to prevent mixing of the first image receiving layer and the second image receiving layer due to penetration of the coating solvent into the lower layer during coating. It is preferable to use a coating solvent that does not cause this. For example, when a vinyl chloride resin having a relatively good solubility in various solvents is used for the first image-receiving layer, it is preferable to use an alcohol-based or water-based coating solvent.

The thickness of the second image receiving layer is 0.1 μm to 10 μm.
It is preferably in the range of m (more preferably 0.5 μm to 5 μm). If the film thickness is too thick, the unevenness of the surface of the permanent support will be impaired, and the glossiness will be too high and the approximation of the printed matter will tend to be reduced. When the image receiving sheet is composed of two layers, the thickness of the first image receiving layer and the thickness of the second image receiving layer can be arbitrarily set within the above range of film thickness.

In order to cause delamination between the organic polymer substance of the first image-receiving layer and the organic polymer substance of the second image-receiving layer by peeling the image-receiving sheet at the time of transfer to the permanent support, the adhesion force between the respective layers is required. The balance of is important. In order to control interlayer adhesion, in addition to selecting coating solvent to prevent mixing during multilayer coating, material selection such as hydrophilic polymer and lipophilic polymer or combination of polar polymer and nonpolar polymer, silane coupling It is effective to add an adhesion improver such as an agent, various additives having a fluorine-based or silicone-based release cure, and a surfactant to the first image receiving layer or the second image receiving layer.

On the second image receiving layer, for the purpose of improving the slipperiness and scratch resistance of the image receiving layer, various release agent or lubricant layers can be provided as an overcoat layer. Specifically, for example, higher fatty acids such as palmitic acid and stearic acid, fatty acid metal salts such as zinc stearate, fatty acid esters or partial saponification products thereof, fatty acid derivatives such as fatty acid amides, higher alcohols, polyhydric alcohols. Derivatives such as ether, waxes such as paraffin wax, carnauba wax, montan wax, beeswax, wood wax, and candelilla wax, and also cationic surfactants such as ammonium salts having a long-chain aliphatic group and pyridinium salts, or Similarly, one or more kinds of anions having a long-chain aliphatic group, nonionic surfactants, perfluorinated surfactants and the like can be selected and used.

An intermediate layer may be provided between the first image receiving layer and the second image receiving layer for the purpose of improving adhesion.
The above description is an example of the case where the first image receiving layer of the image receiving layer is provided with cushioning properties, but as shown in Example 1 below,
By configuring the second image receiving layer to be thicker and softer than the first image receiving layer, it is possible to give the second image receiving layer both a cushioning function and an image forming function. In such a case, the first image receiving layer will function as a peeling layer. Even when the image receiving layer has such a structure, the same kind of material as that described above can be used.

The image-receiving sheet of the present invention may have a single image-receiving layer. In this case, the above-mentioned second image receiving layer is directly provided on the support to form an image receiving layer. When the image receiving layer is composed of a single layer, the layer thickness of the image receiving layer is 0.2 to
It is preferably in the range of 50 μm (preferably 0.5 to 20 μm).

Next, the thermal transfer sheet will be described.
The heat-sensitive transfer sheet used in the present invention has a constitution in which an ink layer mainly containing a pigment and a thermoplastic resin is provided on a support. This heat-sensitive transfer sheet is advantageously used for forming a multi-tone image (particularly a full-color image) by area-wise tone by heat-sensitive transfer.

The support material of the heat-sensitive transfer sheet is preferably made of a transparent synthetic resin material which transmits laser light. Examples of such a material include polymers such as polyethylene terephthalate, polycarbonate, polyethylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, and styrene-acrylonitrile copolymer. In particular, biaxially stretched polyethylene terephthalate is preferable in terms of mechanical strength and dimensional stability against heat. The surface of the support may be subjected to physical surface treatment such as glow discharge treatment and corona discharge treatment. The support generally has a thickness of 10 to 2
It is preferably in the range of 00 μm, particularly 20 to 15
It is preferably in the range of 0 μm. If necessary, an undercoat layer may be provided on the surface of the support. The material of the undercoat layer is preferably a material having high adhesion and heat resistance. Further, in order to reduce the decrease in sensitivity due to heat conduction to the support, a material having a small heat conductivity such as polystyrene is preferable. The thickness of the undercoat layer is usually in the range of 0.01 to 2 μm.

Various known pigments can be used as the pigment contained in the ink layer of the heat-sensitive transfer sheet used in the present invention. Examples of these include pigments such as carbon black, azo, phthalocyanine, quinacridone, thioindigo, anthraquinone and isoindolinone pigments. These can be used in combination of two or more kinds, and a known dye may be added for adjusting the hue. In the heat-sensitive transfer sheet used in the present invention, the pigment content in the ink layer is 30% by weight to 70% by weight (preferably 30% by weight to 50% by weight) in order to obtain a predetermined concentration in a thin film. . Pigment ratio is 30% by weight
If it is less than the above range, it becomes difficult to obtain the concentration with the above-mentioned predetermined film thickness. The particle size of the pigment is 0.1 when 70% by weight or more of the pigment is
It is preferably in the range of ˜1.0 μm. When the particle size is large, the transparency of the overlapping portion of each color during color reproducibility is likely to be impaired, and it may be difficult to satisfy both of the relationship between the layer thickness and the density.

The thermoplastic resin contained in the ink layer of the heat-sensitive transfer sheet used in the present invention has a softening point of 40 ° C. to 15 ° C.
Amorphous organic polymer at 0 ° C. is preferable, for example, butyral resin, polyamide resin, polyethyleneimine resin, sulfonamide resin, polyester polyol resin, petroleum resin, styrene, α-methylstyrene, 2-methylstyrene, chlorostyrene, vinylbenzoic acid. , Styrene and its derivatives such as vinylbenzene sulfonate, amino styrene, etc., homopolymers or copolymers of substitution products,
Methacrylic acid esters such as methyl methacrylate, ethyl methacrylate and hydroxyethyl methacrylate, acrylic acid esters such as methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, α-ethylhexyl acrylate and dienes such as acrylic acid, butadiene and isoprene, acrylonitrile ,
Examples thereof include vinyl ethers, maleic acid and maleic acid esters, maleic anhydride, cinnamic acid, vinyl chloride, vinyl monomers such as vinyl monomers alone or copolymers of other monomers. Two or more kinds of these resins may be mixed and used. Of these, butyral resin and styrene / maleic acid half ester resin are preferable from the viewpoint of dispersibility. The softening point of these resins is 40 ° C
It is selected in the range of 150 ° C. If it exceeds 150 ° C, the thermal recording sensitivity tends to be low, while if it is less than 40 ° C, the scratch resistance of the ink layer tends to be poor. As a specific example of butyral resin, Denka butyral # 2000-L (degree of polymerization:
About 300), # 4000-1 (degree of polymerization: about 920) (above, manufactured by Denki Kagaku Kogyo KK), S-REC BX-10
(Tg: 74 ° C., degree of polymerization: 80, degree of acetalization: 69
Mol%), S-REC BL-S (Tg: 61 ° C., viscosity at 5% concentration of ethanol / toluene = 1/1: 12c
ps and above Sekisui Chemical Co., Ltd. can be mentioned.

In the present invention, the polymer binder of the ink layer preferably contains the same polymer binder as the polymer binder contained in the image receiving layer (second image receiving layer), from the viewpoint of adhesiveness to the image receiving layer.

In the heat-sensitive transfer sheet used in the present invention, the content of the amorphous organic high-molecular polymer in the ink layer is 7
It is 0 to 30% by weight (preferably 50 to 30% by weight).

The heat-sensitive transfer sheet used in the present invention includes
It is preferable that the ink layer contains a nitrogen-containing compound. Examples of the nitrogen-containing compound include amide compounds, amines, quaternary ammonium salts, hydrazines, aromatic amines, and heterocyclic aromatic compounds. Of these, amide compounds and quaternary ammonium salts are preferred. The nitrogen-containing compound is contained in the ink layer in an amount of 0.1 to 20% by weight (preferably 1 to 1).
0% by weight) is preferable.

In the ink layer of the heat-sensitive transfer sheet used in the present invention, various releasing agents and softening agents are added to the ink layer from the viewpoints of releasability of the ink layer from the support and thermal sensitivity at the time of thermal printing. It is also possible to add it in an amount of 20% by weight or less. Specifically, for example, palmitic acid, higher fatty acids such as stearic acid, fatty acid metal salts such as zinc stearate, fatty acid esters or partially saponified products thereof, fatty acid derivatives, higher alcohols, ether derivatives of polyhydric alcohols, and the like, Paraffin wax, carnauba wax,
Waxes such as montan wax, beeswax, wood wax, candelilla wax, etc., viscosity average molecular weight of about 1,000
To about 10,000 low molecular weight polyethylene, polypropylene, polybutylene, and other polyolefins, or olefin, α-olefins and maleic anhydride, organic acids such as acrylic acid and methacrylic acid, and low molecular weight copolymers such as vinyl acetate, Low molecular weight oxidized polyolefin, halogenated polyolefins, lauryl methacrylate, stearyl methacrylate, etc., methacrylic acid ester having a long-chain alkyl side chain, acrylic acid ester or acrylic acid ester having a perfluoro group, methacrylic acid ester alone or styrene etc. Copolymers with vinyl monomers, low-molecular-weight silicone resins such as polydimethylsiloxane and polydiphenylsiloxane, and silicone-modified organic substances, as well as ammonium salts having long-chain aliphatic groups, pyridinium Cationic surfactants such as salts, or similarly anion having a long chain aliphatic group, a nonionic surfactant, mention may be made of perfluoro-based surfactant. These can be used alone or in combination of two or more.

Regarding the dispersion of the above-mentioned pigment in the amorphous organic polymer, various dispersion methods used in the field of paints such as ball milling with the addition of a suitable solvent can be applied. A nitrogen-containing compound, a release agent, etc. are added to the obtained dispersion to prepare a coating liquid, and the coating liquid thus prepared is coated on a support by a known method to form an ink layer. be able to.

The ink layer of the heat-sensitive transfer sheet used in the present invention has a layer thickness of 0.2 to 1.5 μm (preferably, 0.
2 to 1.0 μm, more preferably 0.2 to 0.6 μm
m). When the thickness of the ink layer is thicker than 1.5 μm, the shadow portion is easily crushed and the highlight portion is easily skipped in the area gradation reproducibility, resulting in poor gradation reproducibility. On the other hand, the layer thickness is 0.2
If it is less than μm, it becomes difficult to obtain the desired concentration.

The ink layer of the heat-sensitive transfer sheet used in the present invention is mainly composed of a pigment and an amorphous organic polymer, and has a higher pigment ratio than the conventional wax-melting type.
Viscosity at the time of thermal transfer is 10 ² to 10 ³ c as compared with the normal melting type
It is never as low as ps and is at least above 10 ⁴ cps at a temperature of 150 ° C. Therefore, the image forming method by thermal transfer using the thermal transfer sheet is a thin film peeling development type image formation utilizing the thermal adhesiveness to the image receiving sheet or the thermal adhesiveness between the ink layers in the case of color image creation. It can be said that there is. This, combined with the effect of thinning the ink layer, enables a wide gradation reproduction from the shadow area to the highlight area while maintaining high resolution, improves the edge sharpness, and further increases the 100% Enables image transfer.

As described above, in the heat-sensitive transfer sheet used in the ablation method, between the support and the ink layer,
It is preferable that a photothermal conversion layer is provided. Further, in order to carry out the ablation method more advantageously, it is preferable to further provide a heat-sensitive peeling layer on the photothermal conversion layer. When the light-heat conversion layer also has the function of the heat-sensitive peeling layer, the heat-sensitive peeling layer is not always necessary. These layers will be described in detail below. In general, the photothermal conversion layer has a basic structure including a coloring material capable of absorbing laser light and a binder. Examples of usable coloring materials include black pigments such as carbon black, pigments of macrocyclic compounds having absorption in the visible to near infrared region such as phthalocyanine and naphthalocyanine, and laser absorbing materials for high density laser recording such as optical disks. Examples thereof include organic dyes (cyanine dyes such as indolenine dyes, anthraquinone dyes, azulene dyes, phthalocyanine dyes) and organic metal compound dyes such as dithiol nickel complexes. The photothermal conversion layer is preferably as thin as possible in order to increase the recording sensitivity. Therefore, it is desirable to use a cyanine dye or a phthalocyanine dye that exhibits a large absorption coefficient in the laser light wavelength region.

The material of the binder of the photothermal conversion layer is not particularly limited, but for example, acrylic acid, methacrylic acid,
Acrylic acid esters, homopolymers or copolymers of acrylic acid type monomers such as methacrylic acid esters, methyl cellulose, ethyl cellulose, cellulose type polymers such as cellulose acetate, polystyrene, vinyl chloride-vinyl acetate copolymer, polyvinylpyrrolidone, polyvinyl Butyral, copolymers of vinyl polymers and vinyl compounds such as polyvinyl alcohol, condensation polymers such as polyesters and polyamides, rubber thermoplastic polymers such as butadiene-styrene copolymers,
Examples thereof include polymers obtained by polymerizing and crosslinking a photopolymerizable or thermopolymerizable compound such as an epoxy compound.

When the photothermal conversion layer is composed of a coloring material and a binder, the weight ratio is 1: 5 to 10: 1 (pigment: binder).
It is preferable to be set to, and it is particularly preferable to set to 1: 3 to 3: 1. When the amount of the binder is too small, the cohesive force of the light-heat conversion layer decreases, and when the formed image is transferred to the image receiving sheet, it is easily transferred together, which causes color mixing of the image. Further, if the amount of the binder is too large, it is necessary to increase the layer thickness of the photothermal conversion layer in order to achieve a constant light absorption rate, which tends to cause a decrease in sensitivity. The layer thickness of the photothermal conversion layer comprising the above dye and binder is generally 0.05 to 2 μm.
m, preferably 0.1 to 1 μm. Further, the photothermal conversion layer preferably exhibits a light absorption rate of 70% or more at the wavelength of the laser light used for optical recording.

The heat-sensitive peeling layer is a layer containing a heat-sensitive material. As such a heat-sensitive material, a compound (polymer or low-molecular compound) that itself decomposes or deteriorates by heat to generate gas, or a characteristic of the material is to absorb or adsorb a considerable amount of easily vaporizable gas such as water. Compounds (polymers or low molecular weight compounds) that are used can be used. Note that they can be used in combination. Examples of the polymer that decomposes or degrades by heat to generate a gas include self-oxidizing polymers such as nitrocellulose, chlorinated polyolefins, chlorinated rubbers, halogens such as polyvinyl chloride, polyvinyl chloride, and polyvinylidene chloride. Containing polymers, acrylic polymers such as polyisobutyl methacrylate to which volatile compounds such as water are adsorbed, cellulose esters such as ethyl cellulose to which volatile compounds such as water are adsorbed, and volatile compounds such as water being adsorbed And natural polymer compounds such as gelatin. Examples of the low molecular weight compound which decomposes or degrades by heat to generate a gas include a compound which generates a gas upon exothermic decomposition such as a diazo compound or an azide compound. As described above, the decomposition and deterioration of the heat-sensitive material due to heat,
It is preferable that it occurs at 280 ° C or lower, particularly 230 ° C.
It preferably occurs in the following.

When a low molecular weight compound is used as the heat sensitive material in the heat sensitive release layer, it is desirable to combine it with a binder. In this case, the binder may be a polymer which itself decomposes or denatures by heat to generate a gas, or a normal polymer binder having no such property. When the heat-sensitive low molecular weight compound and the binder are used in combination, the weight ratio of the former to the latter is 0.02: 1 to 3: 1 and particularly 0.05: 1 to 2: 1.
Is preferably within the range. It is desirable that the heat-sensitive peeling layer covers the light-heat conversion layer almost entirely, and the thickness thereof is generally 0.03 to 1 μm, and particularly 0.0.
It is preferably in the range of 5 to 0.5 μm.

Next, the image forming method of the present invention will be described. The image forming method of the present invention can be carried out using a laser beam using the image receiving sheet and the thermal transfer sheet having the above characteristics. As an image forming method using a laser beam, for example, an image forming method utilizing so-called “ablation” disclosed in US Pat. No. 5,352,562 and JP-A-6-219052 can be used. This method is specifically a layer (photothermal conversion layer) that absorbs laser light and converts it into heat between the support and the ink layer (image forming layer), and the action of heat generated in the photothermal conversion layer. A heat-sensitive transfer sheet provided with a layer containing a heat-sensitive material (heat-sensitive peeling layer) that generates gas (or, when the light-heat converting layer contains a heat-sensitive material, a light-heat converting layer having the function of the heat-sensitive peeling layer is also provided). Heat-sensitive transfer sheet) and an image-receiving sheet laminated on the ink layer, and laser irradiation causes ablation due to alteration or melting of the conversion layer due to temperature rise of the photothermal conversion layer, resulting in heat-sensitive peeling. This utilizes a phenomenon in which the layer is partially decomposed and vaporized, the binding force between the ink layer and the photothermal conversion layer is weakened, and the ink layer in that region is transferred to the image receiving sheet.

When the above-mentioned image forming method is carried out, a laser recording device is used. First, the image receiving sheet is adhered to the laser recording drum with the image receiving layer of the image receiving sheet facing outside by vacuuming or the like. Fix it. Next, the ink layer of the transfer sheet is passed through a pressure (heating if necessary) roller in a state of being in contact with the image receiving layer of the image receiving sheet, and the image receiving sheet and the transfer sheet are integrated to form a laminate. . In addition,
The laminated body can be formed not in advance on the laser recording drum but by preliminarily bringing the image receiving sheet and the transfer sheet into contact with their film surfaces and passing them through a pressure (heating if necessary) roller and superposing them.

The pressurizing condition for forming the above-mentioned laminate is usually 1 to 30 kg / cm ² , preferably ^{2 to} 10 kg / cm ² .
cm ² . When passing through the pressure roller, it is also preferable to perform heating. In the case of a roller, the heating condition is that the surface temperature is 250 ° C. or lower, preferably 60 to
It is in the range of 150 ° C. Since the image-receiving sheet of the present invention uses a plastic support having fine air bubbles inside, the pressure treatment when forming the above-mentioned laminate is a cushioning property of the applied support, Due to properties such as flexibility, it is carried out in a more uniform pressure state, and therefore a uniform and highly adherent laminate is formed. Further, even when a relatively large amount of dust is entrained during the formation of the laminated body, the degree of deformation of the adhesive surface due to the dust is alleviated, and the image defect due to this is reduced.

Next, while rotating this recording drum,
A laser beam modulated into the color-separated image signal is scanned and recorded. The laminated body obtained in advance can be mounted on a laser recording drum and recording can be performed by the above procedure. Then, by peeling off the laser-recorded transfer sheet from the image receiving sheet, a transfer image composed of an ink image can be formed on the image receiving sheet. The transfer image thus obtained is composed of area gradations whose optical reflection density is 0.5 or more. In the image forming method utilizing the above method, the ink layer is melted by the heat generated by the absorption of the laser beam, and the area is melt-transferred to the image receiving sheet to form a transferred image on the image receiving sheet. You can also do it. Further, the transfer image on the image-receiving sheet obtained as described above is further overlaid on a white support, which is a separately prepared printing main sheet, and pressure and heat treatment is performed in this state to re-image on the white support. A transfer image can be obtained. As a result, the optical reflection density is 1.
A retransfer image having an area gradation of 0 or more can be formed.

[0054]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples. The following "parts"
Represents parts by weight.

[Example 1] (1) Preparation of image-receiving sheet 1) Preparation of coating liquid for forming first image-receiving layer The following components were mixed with a stirrer under stirring to prepare coating liquid for forming first image-receiving layer. did. Composition of coating liquid for first image-receiving layer Polyvinyl chloride (Zeon 25, manufactured by Nippon Zeon Co., Ltd.) 9 parts Surfactant 0.1 part (Megafuck F-177, manufactured by Dainippon Ink and Chemicals, Inc.) Methyl ethyl ketone 130 Part Toluene 35 parts Cyclohexanone 20 parts Dimethylformamide 20 parts

2) Formation of the first image-receiving layer on the surface of the support A polyethylene terephthalate film (Lumirror E60L, Toray Industries, Inc.) containing fine air bubbles having a thickness of 100 μm.
The above coating solution was applied onto one surface of the coating material) using a spin coater, and then the coated product was placed in an oven at 100 ° C. for 2 minutes.
After drying for 1 minute, the first image-receiving layer (thickness 1 μm was formed on the support.
m) was formed.

3) Preparation of Second Image Receiving Layer Forming Coating Liquid The following components were mixed with stirring with a stirrer to prepare a second image receiving layer forming coating liquid. Composition of coating liquid for second image-receiving layer Methyl methacrylate / ethyl acrylate / methacrylic acid copolymer (Dianal BR-77, manufactured by Mitsubishi Rayon Co., Ltd.) 17 parts Alkyl acrylate / alkyl methacrylate copolymer (Dianal RB-64, Mitsubishi Rayon Co., Ltd. 17 parts Pentaerythritol tetraacrylate (A-TMMTN, Shin-Nakamura Chemical Co., Ltd.) 22 parts Surfactant 0.4 parts (Megafuck F-177, Dainippon Ink and Chemicals, Inc.) Methyl ethyl ketone 100 parts Hydroquinone monomethyl ether 0.05 parts 2,2-dimethoxy-2-phenylacetophenone 1.5 parts (photopolymerization initiator)

4) Formation of the second image-receiving layer on the surface of the first image-receiving layer After coating the above-mentioned coating solution on the surface of the first image-receiving layer on the support using a whiler, the coated product was placed in an oven at 100 ° C. And dried for 2 minutes to form a second image receiving layer on the surface of the first image receiving layer (thickness 25 μm). Through the above steps, an image receiving sheet having a structure in which two image receiving layers were laminated on a plastic support having fine air bubbles inside was prepared.

(2) Preparation of Image Recording Transfer Sheet (Heat Sensitive Transfer Sheet) 1) Preparation of Photothermal Conversion Layer Forming Coating Liquid The following components are mixed with stirring with a stirrer to prepare a photothermal conversion layer forming coating liquid. did.

Composition of coating liquid Infrared absorbing dye (IR-820, manufactured by Nippon Kayaku Co., Ltd.) 1.7 parts Polyamic acid varnish (PAA-A, manufactured by Mitsui Toatsu Chemicals, Inc.) 13 parts 1-Methoxy-2 -Propanol 60 parts Methyl ethyl ketone 88 parts Surfactant (MegaFac F-177, Dainippon Ink and Chemicals, Inc.) 0.05 parts

2) Formation of a photothermal conversion layer on the surface of a support A styrene / butadiene copolymer undercoat layer (thickness: 0.5 μm) and a gelatin undercoat layer (on a surface of a polyethylene terephthalate film having a thickness of 75 μm) Thickness 0.1μ
and m) were formed in this order to prepare a support. Next, the above-mentioned coating liquid for forming a light-heat conversion layer was applied onto the undercoat layer of this support using a spin coater (whirler), and then the coated product was dried in an oven at 100 ° C. for 2 minutes. A photothermal conversion layer (thickness 0.2 μm: measured value by a stylus type film thickness meter, absorbance 1.4 at a wavelength of 830 nm) was formed on the support.

3) Preparation of coating solution for forming heat-sensitive release layer The following components were mixed with a stirrer under stirring to prepare a coating solution for forming heat-sensitive release layer.

Coating liquid composition Nitrocellulose (Type HIG120, manufactured by Asahi Kasei Co., Ltd.) 1.3 parts Methyl ethyl ketone 26 parts Propylene glycol monomethyl ether acetate 40 parts Toluene 92 parts Surfactant (MegaFac F-177, Dainippon Ink and Chemicals Incorporated) Co., Ltd.) 0.01 part

4) Formation of a heat-sensitive peeling layer on the surface of the light-heat converting layer: The surface of the light-heat converting layer provided on the above-mentioned support was coated with the above-mentioned coating solution using a whiler, and then a coating material was applied to 100
Layer in a thermosensitive release layer (thickness: 0.1 μm: the same coating solution was applied onto a flat surface of a hard sheet under the same conditions, and dried under the same conditions). Was measured by a stylus type film thickness meter).

5) Preparation of coating liquid for forming magenta image forming layer Each of the following components was applied to a paint shaker (Toyo Seiki Co., Ltd.).
Dispersion) for 2 hours to prepare a magenta pigment dispersion mother liquor. Then, the obtained dispersion mother liquor was diluted with n-propyl alcohol and measured with a particle size measuring device (laser light scattering method). As a result, the particle size distribution of the pigment was such that 70% by weight or more of the particles were in the range of 180 to 300 nm. there were. Pigment dispersion mother liquor composition Polyvinyl butyral (Denka Butyral # 2000-L, manufactured by Denki Kagaku Kogyo Co., Ltd.) 12.6 parts Coloring material (magenta pigment, CI PR 57: 1) 18 parts Dispersion aid (Solspers S -20,000, manufactured by ICI Japan Co., Ltd. 0.8 part n-propyl alcohol 110 parts Glass beads 100 parts

The following components were mixed with a stirrer under stirring to prepare a coating solution for forming a magenta image forming layer. Coating liquid composition The above pigment dispersion mother liquor 6 parts n-propyl alcohol 60 parts Surfactant (MegaFac F-177, Dainippon Ink and Chemicals, Inc.) 0.01 parts

6) Formation of a magenta image forming layer on the surface of the heat-sensitive peeling layer After coating the above-mentioned coating solution on the surface of the heat-sensitive peeling layer using a whaler, the coated product was dried in an oven at 100 ° C.
After being dried for a minute, a magenta image forming layer (thickness 0.3 μm: the same coating solution was applied to a hard sheet flat surface under the same conditions and dried under the same conditions) by a stylus method. The value measured by the film thickness meter) was formed. The optical density of the obtained image forming layer was 0.7 (measured by a green filter and a Macbeth densitometer). Through the above steps, a magenta image recording transfer sheet was prepared in which the photothermal conversion layer surface, the heat-sensitive peeling layer, and the magenta image forming layer were laminated in this order on the support.

[Image formation by laser and evaluation] (3) Preparation of laminate for image formation The image-receiving sheet and the image-recording transfer sheet prepared as described above were left at room temperature for one day respectively, and then the image-recording transfer sheet was prepared. 3. The image receiving layer side of the image receiving sheet is superposed on the magenta image forming layer, and in this state, the surface temperature is 70 ° C. and the pressure is 4.
They were passed through a 5 kg / cm ² heat roller at a speed of 200 cm / sec to integrate them, thereby forming a laminate. In addition,
The temperature reached by each of the image recording transfer sheet and the image receiving sheet when passing through the heat roller was measured by a thermocouple and was about 50 ° C.

(4) Mounting of Image Forming Laminate on Image Recording Forming Apparatus The laminate obtained above was left to stand at room temperature for about 10 minutes to be sufficiently cooled. Next, the laminated body is wound around a rotary drum provided with suction holes for vacuum suction so that the image receiving sheet surface side is in contact with the drum surface, and the inside of the drum is evacuated to form a drum. It was fixed on the surface.

(5) Image Recording on Image Forming Laminate A semiconductor laser beam having a wavelength of 830 nm is externally applied to the surface of the image forming laminate on the drum by rotating the drum.
A laser image (a sub-scan) is formed on the surface of the photothermal conversion layer so as to form a spot having a diameter of 7 μm and moved in a direction perpendicular to the rotation direction (main scanning direction) of the rotary drum (sub scanning). Streak) was recorded. The laser irradiation conditions are as follows. Laser power: 110 mW Main scanning speed: 10 m / sec Sub-scanning pitch (sub-scanning amount per rotation): 5 μm

(6) Formation of Transfer Image When the laminated body on which the laser image recording was performed was removed from the drum and the image receiving sheet and the image recording transfer sheet were peeled off by hand, the image (image line) forming layer was formed. Only the laser irradiation part was transferred from the transfer sheet to the image receiving sheet with a recording line width of 5.0 μm. As a result, the obtained transferred image was a high-density image, had less unevenness in sensitivity, and had few image defects such as white spots, and had good image quality.

[Example 2] (1) Preparation of image-receiving sheet 1) Preparation of coating liquid for forming first image-receiving layer The following components were mixed with a stirrer under stirring to form a coating liquid for forming first image-receiving layer. Prepared. Coating solution for forming first image-receiving layer Vinyl chloride / vinyl acetate copolymer 25 parts (MPR-TSL, manufactured by Nisshin Chemical Co., Ltd.) Dibutyloctyl phthalate 12 parts (DOP, manufactured by Daihachi Chemical Co., Ltd.) Surfactant 4 parts (Megafuck F-177, manufactured by Dainippon Ink and Chemicals, Inc.) Solvent (methyl ethyl ketone) 75 parts

2) Formation of the first image-receiving layer on the surface of the support A polyethylene terephthalate film (Lumirror E60L, Toray Industries, Inc.) containing fine air bubbles having a thickness of 100 μm.
The above coating solution was applied onto one surface of the coating material) using a spin coater, and then the coated product was placed in an oven at 100 ° C. for 2 minutes.
After drying for 1 minute, the first image-receiving layer (thickness 20 μm is formed on the support.
m) was formed.

3) Preparation of Second Image Receiving Layer Forming Coating Liquid The following components were mixed with stirring with a stirrer to prepare a second image receiving layer forming coating liquid. Second image receiving layer forming coating solution Polyvinyl butyral 16 parts (Denka Butyral # 2000-L, manufactured by Denki Kagaku Kogyo Co., Ltd.) N, N-dimethylacrylamide / butyl acrylate copolymer 4 parts Surfactant 0.5 part ( Megafac F-177, manufactured by Dainippon Ink and Chemicals, Inc. Solvent (n-propyl alcohol) 200 parts

4) Formation of the second image-receiving layer on the surface of the first image-receiving layer The above-mentioned coating solution was applied to the surface of the first image-receiving layer on the support using a whiler, and then the coated product was placed in an oven at 100 ° C. And dried for 2 minutes to form a second image receiving layer (thickness 2 μm) on the surface of the first image receiving layer. Through the above steps, an image receiving sheet having a structure in which two image receiving layers were laminated on a plastic support having fine air bubbles inside was prepared.

[Image formation and evaluation by laser] (3) to (6) in Example 1 above using the obtained image receiving sheet
A transfer image was formed on the image-receiving sheet in the same manner except that the above step was repeated. As a result, the obtained transferred image was a high-density image as in the case of the image receiving sheet of Example 1 described above, had less unevenness in sensitivity, and had few white spot-like image defects, and had good image quality. .

[Comparative Example 1] In Example 1, instead of the polyethylene terephthalate film (Lumirror E60L, manufactured by Toray Industries, Inc.) containing fine air bubbles having a thickness of 100 μm when the image-receiving sheet of (1) was prepared. A thickness of 10
Clear polyethylene terephthalate film (Lumirror # 100, Toray Industries, Inc.) that does not have microscopic bubbles of 0 μm
An image-receiving sheet for comparison was prepared in the same manner as in (1) of Example 1 except that (made by Japan) was used.

[Image Formation and Evaluation by Laser] Using the obtained comparative image-receiving sheet, (3) of Example 1 was used.
A transfer image was formed on the image-receiving sheet in the same manner except that the steps (6) to (6) were repeated. As a result, in the obtained transfer image, more unevenness in sensitivity and white spot-like image defects were recognized as compared with the transfer images obtained on the image receiving sheets of Examples 1 and 2. The line width of the transferred image was 4 μm, which was inferior to that of Example 1.

[0079]

EFFECT OF THE INVENTION By using the image-receiving sheet of the present invention, a high density image can be obtained (high sensitivity), uneven sensitivity,
It is possible to obtain a transferred image having good image quality with few image defects. Further, the obtained transferred image is composed of only area gradations and has excellent color reproducibility, and is a transferred image advantageous for color proof use and the like.

Claims (10)

[Claims] 1. An ink layer of a heat-sensitive transfer sheet having an ink layer mainly composed of a pigment and a thermoplastic resin on a support,
An image-receiving sheet for use in an image-forming method comprising transferring onto a image-receiving sheet by irradiation with a laser beam modulated by a digital signal, the image-receiving sheet being a plastic support having fine air bubbles inside. An image receiving sheet which is a laminated body composed of the image receiving layer and the image receiving layer. 2. The image-receiving sheet according to claim 1, wherein the ink layer contains 30 to 70% by weight of pigment and 70 to 30% by weight of thermoplastic resin. 3. A plastic support having fine air bubbles inside is made of polyester, polyamide, polycarbonate, polyether sulfone, polyimide, polyolefin, polyvinyl chloride, polyurethane, polyvinylidene chloride, polyacrylate and cellulose acetate. The image-receiving sheet according to claim 1, which is formed of a material selected. 4. The image receiving sheet according to claim 1, wherein the plastic support having fine air bubbles inside has a thickness of 50 to 300 μm. 5. The image-receiving sheet according to claim 1, wherein the image-receiving layer has a two-layer laminated structure. 6. The image-receiving layer according to claim 1 is superposed on the ink layer of a heat-sensitive transfer sheet having an ink layer mainly composed of a pigment and a thermoplastic resin on a support, and then, An image forming method comprising irradiating a laser beam modulated by a digital signal from the back surface of a thermal transfer sheet to form a transferred image on an image receiving layer of an image receiving sheet. 7. The image-receiving layer according to claim 1 is superposed on the ink layer of the heat-sensitive transfer sheet having an ink layer mainly composed of a pigment and a thermoplastic resin on a support, and then, An image forming method comprising irradiating a laser beam modulated by a digital signal from the back surface of a thermal transfer sheet and forming a transferred image on an image receiving layer of an image receiving sheet by an ablation method. 8. The image forming method according to claim 6, wherein the ink layer contains 30 to 70% by weight of the pigment and 70 to 30% by weight of the thermoplastic resin. 9. The image forming method according to claim 6, wherein the heat-sensitive transfer sheet further has a photothermal conversion layer containing a photothermal conversion substance between the support and the ink layer. 10. A thermal transfer sheet and an image receiving sheet are superposed on each other under pressure, and the pressure is 1 to 30 kg / cm.
The image forming method according to any one of claims 6 to 9, which is in the range of ² .