JP2005103893A - Imaging material and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging material which can be suitably used for an imaging method using laser beams; a thermal transfer sheet which has an especially uniform coating surface-like imaging layer with an improved transferability of an image formed in the imaging layer to an image receiving sheet; and an imaging method using the imaging material. <P>SOLUTION: In the imaging material, the image receiving sheet with at least an image receiving layer formed on a support and the thermal transfer sheet with at least a photothermal conversion layer and an imaging layer formed on the support, are used and the imaging layer of each thermal transfer sheet and the image receiving layer of each image receiving sheet are lapped together opposite to each other. In addition, an image is recorded by transferring a laser beam exposure region of the imaging layer to the surface of the image receiving layer of the image receiving sheet with the help of laser beam exposure from the thermal transfer sheet side. The thermal transfer sheet has a back coat layer formed on the opposite side to the imaging layer across the support and the back coat layer contains a surfactant with a branched perfluoroalkyl group in a molecule. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming material (thermal transfer sheet and image receiving sheet) suitable for an image forming method using laser light, and an image forming method using the same.

  The laser thermal transfer recording method is a dry process and has not only high continuous output stability and simple operation, but also a high-definition image comparable to a printed matter by a printing press in combination with an IR laser. In the case of this method, as described in JP-A-2002-347353, the image receiving sheet and / or the thermal transfer sheet is a method in which the image receiving sheet and the thermal transfer sheet are opposed to each other and irradiated with an IR laser from the back surface of the thermal transfer sheet. Discloses that a fluorine-based surfactant having a weight average molecular weight of 3,000 or more is contained.

  In addition, for the purpose of reducing the printing torque (coefficient of dynamic friction) of a thermal recording material that records images by supplying heat with a thermal head, etc., and obtaining a uniform surface with no coating unevenness, the protective layer of the thermal recording material has a silicone-based activity. Japanese Patent Application Laid-Open No. 2003-127541 also describes a technique for containing an agent.

These image forming methods can use printing paper provided with an image receiving layer (adhesive layer) as an image receiving sheet material, and can easily obtain multicolor images by transferring images of different colors onto the image receiving sheet one after another. It is useful for producing a color proof (DDCP: Direct Digital Color Proof) or a high-definition mask image. .
JP 2003-127541 A JP 2002-347353 A

  In the image forming material used in such an image forming method, the photothermal conversion layer and the image forming layer of the thermal transfer sheet are formed by a coating method. The image receiving layer of the image receiving sheet is also formed by a coating method. The image forming layer of the thermal transfer sheet is required to have a uniform coated surface in order to obtain stable transferability (sensitivity). If the coated surface is non-uniform, unevenness on the surface, surface energy, and adhesion force will be uneven, and the uniform transfer to the image receiving sheet will deteriorate.

  Accordingly, an object of the present invention is to provide an image forming material that can be suitably used in an image forming method using a laser beam, particularly an image receiving sheet for an image formed on an image forming layer, having an image forming layer having a uniform coated surface. It is an object of the present invention to provide a thermal transfer sheet having improved transferability to and an image forming method using the image forming material.

The inventor of the present invention pays attention to the fact that the coating property of the backcoat layer (BC layer) of the thermal transfer sheet on which the laser beam is incident and the uniformity of the film density are particularly important, and as a result of various studies, the present invention is completed. Arrived. That is, the above object of the present invention is achieved by the following configuration.
(Claim 1)
Using an image receiving sheet having at least an image receiving layer on a support and a thermal transfer sheet having at least a photothermal conversion layer and an image forming layer on the support, the image forming layer of each thermal transfer sheet and the image receiving layer of the image receiving sheet are opposed to each other. In an image forming material for superimposing and irradiating laser light from the thermal transfer sheet side to transfer the laser light irradiation area of the image forming layer onto the image receiving layer of the image receiving sheet and recording an image, the thermal transfer sheet sandwiches the support and the image An image forming material comprising a back coat layer on the side opposite to the forming layer, and the back coat layer containing a surfactant having a branched perfluoroalkyl group in the molecule.
(Claim 2)
Using an image receiving sheet having at least an image receiving layer on a support and a thermal transfer sheet having at least a photothermal conversion layer and an image forming layer on the support, the image forming layer of each thermal transfer sheet and the image receiving layer of the image receiving sheet are opposed to each other. In an image forming material for superimposing and irradiating laser light from the thermal transfer sheet side to transfer the laser light irradiation area of the image forming layer onto the image receiving layer of the image receiving sheet and recording an image, the thermal transfer sheet sandwiches the support and the image An image forming material comprising a back coat layer on the opposite side of the forming layer, and the back coat layer containing a surfactant having two or more perfluoroalkyl groups in the molecule.
(Claim 3)
Using an image receiving sheet having at least an image receiving layer on a support and a thermal transfer sheet having at least a photothermal conversion layer and an image forming layer on the support, the image forming layer of each thermal transfer sheet and the image receiving layer of the image receiving sheet are opposed to each other. In an image forming material for superimposing and irradiating laser light from the thermal transfer sheet side to transfer the laser light irradiation area of the image forming layer onto the image receiving layer of the image receiving sheet and recording an image, the thermal transfer sheet sandwiches the support and the image An image forming material comprising a back coat layer on the side opposite to the forming layer, and the back coat layer containing a surfactant having a C 1-7 perfluoroalkyl group.
(Claim 4)
Using an image receiving sheet having at least an image receiving layer on a support and a thermal transfer sheet having at least a photothermal conversion layer and an image forming layer on the support, the image forming layer of each thermal transfer sheet and the image receiving layer of the image receiving sheet are opposed to each other. In an image forming material for superimposing and irradiating laser light from the thermal transfer sheet side to transfer the laser light irradiation area of the image forming layer onto the image receiving layer of the image receiving sheet and recording an image, the thermal transfer sheet sandwiches the support and the image It has a back coat layer on the side opposite to the forming layer, and the back coat layer contains at least one surfactant represented by the following general formula (1) to general formula (7). Image forming material.

The general formula ₍₁₎ Rf 1 -OR 1
Formula _{(2) Rf 1 -O-L} -Rf 1

In the general formulas (1) to (4), Rf ₁ represents a [(CF ₃ ) ₂ C] ₂ C═C (CF ₃ ) — group or a (CF ₃ ) ₂ C═C (C ₂ F ₅ ) — group. L represents a linking group, and R ₁ represents a polar group. a, b, c, d, e, f and g each represent an integer of 1 to 40.

In Formula (5) ~ (7), Rf 2 represents a perfluoroalkyl group having 1 to 7 carbon atoms, R ₂ represents a polar group. m1, m2, m3 and n1 each represents an integer of 1 to 40.
(Claim 5)
Using an image receiving sheet having at least an image receiving layer on a support and a thermal transfer sheet having at least a photothermal conversion layer and an image forming layer on the support, the image forming layer of each thermal transfer sheet and the image receiving layer of the image receiving sheet are opposed to each other. In an image forming material for superimposing and irradiating laser light from the thermal transfer sheet side to transfer the laser light irradiation area of the image forming layer onto the image receiving layer of the image receiving sheet and recording an image, the thermal transfer sheet sandwiches the support and the image An image-forming material comprising a backcoat layer on the side opposite to the forming layer, and the backcoat layer contains an acetylene glycol surfactant and a silicone surfactant.
(Claim 6)
6. A method of forming an image using the image forming material according to claim 1, wherein the recording density of the laser beam is 1,250 dpi (dpi is the number of dots per inch = 2.54 cm) ) An image forming method as described above.

  According to the present invention, it is possible to obtain a transfer image that is excellent in fine line reproducibility and improved in environmental fluctuation (temperature / humidity fluctuation) and formed image surface variation.

  Hereinafter, the present invention will be described in more detail.

(Fluorine surfactant)
The fluorine-based surfactant contained in the BC layer on the side opposite to the image forming layer of the thermal transfer sheet of the present invention will be described. This fluorine-based surfactant includes a fluorine-based surfactant having a branched perfluoroalkyl group in the molecule, two or more perfluoroalkyl groups in the molecule, and a C 1-7 perfluoroalkyl group. Although the agent can be used, the compounds represented by the general formulas (1) to (7) are particularly preferable.

In the general formulas (1) to (4), examples of the linking group represented by L include divalent groups such as alkylene, alkyleneoxy, and phenylene, and an alkyleneoxy group having 1 to 4 carbon atoms is particularly preferable. Examples of the polar group represented by R ₁ include a hydrogen atom, an organic group containing a hydroxyl group, an alkyl carboxylate, a benzene carboxylate, an alkyl benzene carboxylate, an alkyl ammonium salt, a benzene ammonium salt, and an alkyl benzene ammonium salt. . a to g each represents an integer of 1 to 40, preferably 5 to 25.

Formula (5), (6), in (7), Rf ₂ is a perfluoroalkyl group having 1 to 7 carbon atoms, preferably a _{C 2 F 5 ~C 5 F 11} . m1, m2, m3 and n1 each represents an integer of 1 to 40, preferably 2 to 10.

  In the following, typical examples of the fluorine-based surfactants represented by the general formulas (1) to (7) are shown, but the invention is not limited thereto.

Some of the above compounds can also be obtained from Neos or Omniva. The amount of the fluorine-based surfactant used is preferably in the range of 0.5 to ²⁰ mg / m ^2, more preferably 1 to 10 mg / m ² as the solid content in the BC layer of the thermal transfer sheet.

(Silicone surfactant)
The BC layer of the thermal transfer sheet of the present invention preferably contains an acetylene glycol surfactant and a silicone surfactant.

  The silicone-based surfactant is a water-soluble compound in which a hydrophobic part is made of a silicone resin and a hydrophilic group is introduced into the terminal and / or side chain thereof. Typical examples of the silicone resin include poly (dimethyl) siloxane, methylphenyldimethylpolysiloxane, tetramethyltetraphenylpolysiloxane, dimethylpolysiloxane / polymethylphenylsiloxane copolymer, polymethylsiloxane, tetramethylpolymethylsiloxane, Examples thereof include polymethylsiloxane / polydimethylsiloxane copolymer in which a part or all of the side chain methyl groups are substituted with phenyl groups, hydrogen atoms, or the like. (However, among the above notations, a silicone resin having a low degree of polymerization is also included. For example, tetramethyltetraphenyltrisiloxane is also included in tetramethyltetraphenylpolysiloxane.) In addition, a hydrophilic group introduced into this silicone resin. Examples thereof include polyether groups, polyglycerin groups, pyrrolidone groups, betaine groups, sulfate groups, hydroxyl groups, carboxyl groups, phosphate groups, quaternary ammonium groups, and the like.

  These silicone resins and hydrophilic groups can be used in appropriate combination. In addition, regarding the structure of the surfactant, not only a hydrophilic group is simply introduced into the terminal and / or side chain of the above-mentioned silicone resin, but also a polymer in which a hydrophilic group is introduced and a polymer in which a hydrophilic group is not introduced are randomly copolymerized and blocked. It may be copolymerized by copolymerization.

  Specifically, for example, manufactured by Shin-Etsu Chemical Co., Ltd .: KF351 (A), KF352 (A), KF353 (A), KF354 (A), KF355 (A), KF615 (A), KF618, KF945 (A), KF6001, KF6004, KF6012, KF6013, KF6015, KF6016, KF6017, KF640, KF641, KF700, X-22-4959, X-22-4966, etc., manufactured by Toray Dow Corning Silicone: SYLGARD309, SH3746, SH3749, SH3749 SH8400, SH8410, SH8700, etc., manufactured by Nippon Unicar Co., Ltd .: SILWETL-77, L-720, FZ2122, L-7001, L-7002, FZ-2123, L-7604, FZ-2105, FZ-2104, FZ-211 , FZ-2110, FZ-2161, FZ-2162, FZ-2163, FZ-2164 and the like. Among these, a silicone surfactant in which polydimethylsiloxane is introduced as a silicone resin and a polyether group, polyglycerin group, or pyrrolidone group is introduced as a hydrophilic group is preferable.

The content of the silicone-based surfactant in the protective layer is preferably in the range of 0.005 to 0.20 g / m ² as the solid content in the applied BC layer. 10 g / m ² is more preferable.

(Acetylene glycol surfactant)
The acetylene glycol surfactant used in combination with the silicone surfactant is preferably a compound represented by the following general formula (8).

In the formula, each of R ^{1 to} R ⁴ represents a hydrogen atom, a linear, branched, or cyclic substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms. , EO represents an ethyleneoxy group which may be substituted, and m and n each represent an integer of 0-50.

Examples of the alkyl group represented by R ^{1 to} R ⁴ include groups such as methyl, ethyl, propyl group, i-propyl, butyl group, i-butyl group, and cyclohexyl. Specific examples of the aryl group include Examples include groups such as phenyl and naphthyl. m and n are preferably integers of 0 to 4.

Among these, R ² and R ³ are methyl groups, R ¹ and R ⁴ are i-butyl groups, and m and n are preferably 0.

  Specific examples of the acetylene glycol represented by the general formula (8) are given below.

The content of the acetylene glycol surfactant in the BC layer is preferably in the range of 0.005 to 0.2 g / m ² as the solid content in the applied BC layer. 0.1 g / m ² is more preferable. Moreover, as a compounding ratio of a silicone type surfactant and an acetylene glycol type surfactant, silicone type: acetylene glycol type is preferably 1:10 to 10: 1, and more preferably 1: 5 to 5: 1.

  Hereinafter, the image forming method using the image forming material of the present invention will be described in detail, and the thermal transfer sheet and the image receiving sheet will be described in more detail.

  The image forming method using the image forming material of the present invention realizes a thermal transfer image with sharp halftone dots, and can perform transfer on a paper and B2 size recording (515 mm × 728 mm, but B2 size is 543 mm × 765 mm). It is effective and suitable for the system. This thermal transfer image can be a halftone image corresponding to the number of printed lines at a resolution of 1,250 dpi. Since each halftone dot has almost no blur or chip and has a very sharp shape, a high range of halftone dots from highlight to shadow can be formed clearly. As a result, high-quality halftone dot output with the same resolution as the image setter and CTP setter is possible, and halftone dots and gradations with good printed matter approximation can be reproduced.

  In addition, since this thermal transfer image has a sharp halftone dot shape, the halftone dot corresponding to the laser beam can be faithfully reproduced, and the environment (temperature / humidity) dependence of the recording characteristics is very small, so a wide range of temperature / humidity environments. Under these conditions, it is possible to obtain stable repeatability in both hue and density. This thermal transfer image is formed using the color pigment used in the printing ink, and since it has good repeatability, a highly accurate CMS (color management system) can be realized. Furthermore, this thermal transfer image can be made to substantially match the hue of Japan color, SWOP color, etc., that is, the hue of the printed material, and the appearance of the color when the light source such as a fluorescent light or an incandescent light is changed is the same as that of the printed material. Change can be shown.

  In addition, since this thermal transfer image has a sharp dot shape, fine lines of fine characters can be reproduced well. The heat generated by the laser beam is transmitted to the transfer interface without diffusing in the surface direction, and the image forming layer is sharply broken at the interface between the heating part and the non-heating part. For this purpose, the thickness of the photothermal conversion layer in the thermal transfer sheet and the mechanical properties of the image forming layer are controlled. By the way, in the simulation, it is estimated that the photothermal conversion layer instantaneously reaches about 700 ° C., and if the film is thin, it is likely to be deformed or broken. When the deformation or destruction occurs, the photothermal conversion layer is transferred to the image receiving sheet together with the transfer layer, or the transfer image becomes non-uniform. On the other hand, in order to obtain a predetermined temperature, the photothermal conversion substance must be present in a high concentration in the film, and problems such as pigment precipitation and migration to an adjacent layer also occur. For this reason, it is preferable to reduce the thickness of the photothermal conversion layer to about 0.5 μm or less by selecting an infrared absorbing dye having excellent photothermal conversion characteristics and a heat-resistant binder such as polyimide.

  In general, when the photothermal conversion layer is deformed or when the image forming layer itself is deformed by high heat, the image forming layer transferred to the image receiving layer has uneven thickness corresponding to the sub-scanning pattern of the laser beam, As a result, the image becomes non-uniform and the apparent transfer density decreases. This tendency is more conspicuous as the image forming layer is thinner. On the other hand, when the thickness of the image forming layer is large, the sharpness of the dots is impaired and the sensitivity is also lowered. In order to achieve both of these conflicting performances, it is preferable to improve transfer unevenness by adding a low melting point material such as wax to the image forming layer. In addition, by adding inorganic fine particles in place of the binder, the layer thickness is appropriately increased, so that the image forming layer breaks sharply at the heated / unheated interface, maintaining the sharpness and sensitivity of the dots. In addition, the transfer unevenness can be improved.

  In general, a low-melting-point substance such as wax tends to ooze or crystallize on the surface of the image forming layer, which may cause a problem in image quality and stability over time of the thermal transfer sheet. In order to cope with this problem, it is preferable to use a low-melting-point material having a small Sp value difference from the polymer of the image forming layer, to increase compatibility with the polymer and to separate the low-melting-point material from the image forming layer. Can be prevented. It is also preferable to mix several kinds of low-melting substances having different structures so as to eutectify and prevent crystallization. As a result, an image with a sharp dot shape and less unevenness can be obtained. In general, when the coating layer of the thermal transfer sheet absorbs moisture, the mechanical properties and thermal properties of the layer change, and the humidity dependence of the recording environment occurs. In order to reduce the temperature / humidity dependency, it is preferable that the dye / binder system of the light-to-heat conversion layer and the binder system of the image forming layer be an organic solvent system. Further, it is preferable to select a polyvinyl butyral as a binder for the image receiving layer and introduce a polymer hydrophobization technique in order to reduce the water absorption. Examples of polymer hydrophobization techniques include reacting a hydroxyl group with a hydrophobic group as described in JP-A-8-238858, and crosslinking two or more hydroxyl groups with a hardener.

  In addition, the image forming layer is usually heated to about 500 ° C. or more during printing by laser exposure, and some of the conventionally used pigments are thermally decomposed. This can be prevented by adopting the above. In order to prevent the hue from changing when the infrared absorbing dye moves from the photothermal conversion layer to the image forming layer due to high heat during printing, as described above, the infrared absorbing dye / It is preferable to design the photothermal conversion layer with a combination of binders.

  In general, energy is insufficient in high-speed printing, and a gap corresponding to the interval of laser sub-scanning is generated. As described above, increasing the dye concentration in the photothermal conversion layer and reducing the thickness of the photothermal conversion layer and the image forming layer can increase the efficiency of heat generation / transfer. Furthermore, it is preferable to add a low-melting-point substance to the image forming layer for the purpose of slightly flowing the image forming layer during heating and filling the gap and improving the adhesion to the image receiving layer. Further, in order to increase the adhesion between the image receiving layer and the image forming layer and to give sufficient strength to the transferred image, it is preferable to employ, for example, the same polyvinyl butyral as the image forming layer as the binder of the image receiving layer.

  The image receiving sheet and the thermal transfer sheet are preferably held on the drum by vacuum contact. This vacuum contact is important because the image transfer behavior is very sensitive to the clearance between the image receiving layer surface of the image receiving sheet and the image forming layer surface of the transfer sheet because the image is formed by controlling the adhesive force between both sheets. If the clearance between materials increases due to foreign matter such as dust, image defects and image transfer unevenness occur. In order to prevent such image defects and image transfer unevenness, it is preferable to improve the air flow and provide uniform clearance by providing uniform irregularities on the thermal transfer sheet.

  As a method for forming irregularities on the thermal transfer sheet, there are generally post-treatment such as embossing treatment and addition of a matting agent to the coating layer, but the addition of the matting agent is preferred for simplifying the production process and stabilizing the material over time. The matting agent needs to be larger than the coating layer thickness, and if the matting agent is added to the image forming layer, there will be a problem that the image of the portion where the matting agent exists is lost. It is preferable to add to the conversion layer, whereby the image forming layer itself has a substantially uniform thickness, and an image having no defect can be obtained on the image receiving sheet.

  In order to reliably reproduce the sharp dots as described above, the recording apparatus side is also required to have a high-precision design. The basic configuration is the same as that of a conventional laser thermal transfer recording apparatus. This configuration is a so-called heat mode outer drum recording system in which a recording head having a plurality of high-power lasers irradiates and records laser on a thermal transfer sheet and an image receiving sheet fixed on the drum. Among them, the following aspect is a preferable configuration. The supply of the image receiving sheet and the thermal transfer sheet is a fully automatic roll supply. The image receiving sheet and the thermal transfer sheet are fixed to the recording drum by vacuum suction. A large number of vacuum suction holes are formed on the recording drum, and the inside of the drum is decompressed by a blower, a decompression pump, or the like, so that the sheet is attracted to the drum. Since the thermal transfer sheet is further adsorbed from the upper side where the image receiving sheet is adsorbed, the size of the thermal transfer sheet is made larger than that of the image receiving sheet. The air between the thermal transfer sheet and the image receiving sheet that has the greatest influence on the recording performance is sucked from the area of the thermal transfer sheet only outside the image receiving sheet.

  The absolute value of the difference between the surface roughness Rz of the surface of the image forming layer of the thermal transfer sheet and the surface roughness Rz of the surface of the back layer thereof is 3.0 or less, and the surface roughness Rz of the surface of the image receiving layer of the image receiving sheet and the back layer thereof The absolute value of the difference in surface roughness Rz between the surfaces is preferably 3.0 or less. With such a configuration, it is possible to prevent image defects in combination with the above-described cleaning means, to eliminate a conveyance jam, and to further improve dot gain stability.

  In the present invention, the surface roughness Rz refers to the ten-point average surface roughness corresponding to JIS Rz (maximum height), and the average surface of the portion extracted from the roughness curved surface by the reference area is used as a reference. As a surface, the distance between the average value of the altitude of the mountain from the highest to the fifth and the average value of the depth of the valley from the deepest to the fifth is input-converted. A stylus type three-dimensional roughness meter (Surfcom 570A-3DF) manufactured by Tokyo Seimitsu Co., Ltd. is used for the measurement. The measurement direction is the vertical direction, the cutoff value is 0.08 mm, the measurement area is 0.6 mm × 0.4 mm, the feed pitch is 0.005 mm, and the measurement speed is 0.12 mm / s.

  The absolute value of the difference between the surface roughness Rz of the surface of the image forming layer of the thermal transfer sheet and the surface roughness Rz of the surface of the back layer is 1.0 or less, and the surface roughness Rz of the surface of the image receiving layer of the image receiving sheet is The absolute value of the difference in the surface roughness Rz on the back layer surface is preferably 1.0 or less from the viewpoint of further improving the above effect.

  Furthermore, as another aspect, it is preferable that the surface roughness of the image forming layer surface and the back surface layer surface of the thermal transfer sheet and / or the surface roughness Rz of the front and back surfaces of the image receiving sheet is 2 to 30 μm. With such a configuration, it is possible to prevent image defects in combination with the above-described cleaning means, eliminate a conveyance jam, and further improve dot gain stability.

  The glossiness of the image forming layer of the thermal transfer sheet is also preferably 80 to 99. The glossiness greatly depends on the smoothness of the surface of the image forming layer, and can affect the uniformity of the thickness of the image forming layer. Higher glossiness is more suitable for use as a uniform and high-definition image as an image forming layer. However, when smoothness is high, resistance during conveyance becomes larger, and both are in a trade-off relationship. When the glossiness is in the range of 80 to 99, it is possible to achieve a balance between the two.

  In image formation, particularly multicolor image formation, the laser light used for light irradiation is preferably multi-beam light, and particularly preferably a multi-beam two-dimensional array. The multi-beam two-dimensional array uses a plurality of laser beams when recording by laser irradiation, and a plurality of spot arrays of these laser beams are arranged along the main scanning direction and along the sub-scanning direction. A two-dimensional planar array consisting of rows. By using laser light that is a multi-beam two-dimensional array, the time required for laser recording can be shortened.

  The laser beam used can be used without particular limitation as long as it is a multi-beam, solid state laser beam such as argon laser beam, helium neon laser beam, helium cadmium laser beam, etc., YAG laser beam, semiconductor, etc. Direct laser light such as laser light, dye laser light, and excimer laser light is used. Or the light etc. which converted these laser lights into the half wavelength through the 2nd harmonic element can also be used. In consideration of output power, ease of modulation, etc., it is preferable to use semiconductor laser light. In the multicolor image forming method, the laser beam is preferably irradiated under conditions such that the beam diameter on the photothermal conversion layer is in the range of 5 to 50 μm (especially 6 to 30 μm), and the scanning speed is 1 m / m. It is preferable to set it to 2 seconds or more, more preferably 3 m / second or more.

  As a method for forming a multicolor image, as described above, a multicolor image is formed by repeatedly superimposing a large number of image layers (image forming layers on which images are formed) on the same image receiving sheet using the thermal transfer sheet. Alternatively, a multicolor image may be formed by once forming an image on the image receiving layer of a plurality of image receiving sheets and then re-transferring it to a printing paper. For the latter, for example, a thermal transfer sheet having an image forming layer containing colorants having different hues from each other is prepared, and four types (four colors, Cyan, magenta, yellow, black). Each laminated body is irradiated with laser light according to a digital signal based on an image through, for example, a color separation filter, and then the thermal transfer sheet and the image receiving sheet are peeled off, and each color receiving image is separated into each image receiving sheet. Are formed independently. Next, a multicolor image can be formed by sequentially laminating each of the formed color separation images on an actual support such as a separately prepared printing paper or a similar support.

  Thermal transfer recording using laser light irradiation, if the laser beam can be converted into heat and the image forming layer containing the pigment is transferred to the image receiving sheet using the thermal energy, and an image can be formed on the image receiving sheet, The state change of the pigment, dye, or image forming layer at the time of transfer is not particularly limited, and includes any state of a solid state, a softened state, a liquid state, and a gas state, preferably a solid or softened state. Thermal transfer recording using laser light irradiation includes, for example, conventionally known melt transfer, transfer by ablation, sublimation transfer, and the like. Among these, the above-mentioned thin film transfer type and melting / ablation type are preferable in that an image having a hue similar to printing is created.

  In addition, a thermal laminator is usually used to perform a process of re-transferring the image-receiving sheet, on which the image has been transferred by the recording apparatus, to a printing main paper (referred to as “main paper”). When heat and pressure are applied to the image-receiving sheet and the paper sheet, both adhere to each other, and when the image-receiving sheet is peeled off from the paper sheet, only the image-receiving layer containing the image remains on the paper sheet. By connecting the above apparatuses on the plate making system, a system capable of exhibiting a function as a color proof is constructed.

  Hereinafter, a thermal transfer sheet and an image receiving sheet that are preferably used in the recording apparatus of the above system will be described.

<Thermal transfer sheet>
The thermal transfer sheet has at least a light-to-heat conversion layer and an image forming layer on a support, and further includes other layers as necessary.

(Support)
There is no particular limitation on the material of the support of the thermal transfer sheet, and various support materials can be used according to the purpose. The support preferably has rigidity, good dimensional stability, and can withstand heat during image formation. Preferred examples of the support material include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), polymethyl methacrylate (PMMA), polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC). And synthetic resin materials such as polyvinylidene chloride, polystyrene (PS), styrene-acrylonitrile copolymer, polyamide (aromatic or aliphatic), polyimide, polyamideimide, and polysulfone. Among these, biaxially stretched PET is preferable in view of mechanical strength and heat dimensional stability. When used for producing a color proof using laser recording, the support of the thermal transfer sheet is preferably formed from a transparent synthetic resin material that transmits laser light. The thickness of the support is preferably 25 to 130 μm, and particularly preferably 50 to 120 μm. The center line average surface roughness Ra (measured based on JIS B0601 using a surface roughness measuring instrument or the like) of the support on the image forming layer side is preferably less than 0.1 μm. The Young's modulus in the longitudinal direction of the support is preferably 2 to 12 GPa, and the Young's modulus in the width direction is preferably 2.5 to 16 GPa. The F-5 value in the longitudinal direction of the support is preferably 49 to 490 MPa, the F-5 value in the width direction of the support is preferably 9.4 to 294 MPa, and the F-5 value in the longitudinal direction of the support is supported. It is generally higher than the F-5 value in the body width direction, but this is not the case when it is necessary to increase the strength in the width direction. Further, the heat shrinkage rate at 100 ° C. for 30 minutes in the longitudinal direction and the width direction of the support is preferably 3% or less, more preferably 1.5% or less, and the heat shrinkage rate at 80 ° C. for 30 minutes is preferably 1% or less, more preferably 0.5% or less. The breaking strength is preferably 49 to 980 MPa in both directions, and the elastic modulus is preferably 0.98 to 19.6 GPa.

  The support of the thermal transfer sheet may be provided with a surface activation treatment and / or one or more undercoat layers in order to improve adhesion to the light-to-heat conversion layer provided thereon. Examples of the surface activation treatment include glow discharge treatment and corona discharge treatment. As the material for the undercoat layer, it is preferable that both surfaces of the support and the light-to-heat conversion layer exhibit high adhesion, have low thermal conductivity, and have excellent heat resistance. Examples of such a material for the undercoat layer include styrene, styrene-butadiene copolymer, gelatin and the like. The total thickness of the undercoat layer is usually 0.01 to 2 μm. A BC layer is provided on the surface of the thermal transfer sheet opposite to the photothermal conversion layer side.

(Back coat layer)
It is essential to provide a BC layer on the surface of the thermal transfer sheet of the present invention on the side opposite to the side on which the photothermal conversion layer is provided. The BC layer is also preferably composed of two layers: a first BC layer adjacent to the support and a second BC layer provided on the opposite side of the support of the first BC layer.

(Antistatic agent)
The BC layer preferably contains an antistatic agent in addition to the fluorine-based surfactant. Antistatic agents include nonionic surfactants such as polyoxyethylene alkylamines and glycerin fatty acid esters, cationic surfactants such as quaternary ammonium salts, anionic surfactants such as alkyl phosphates, and amphoteric surfactants. A compound such as an agent and a conductive resin can be used.

Conductive fine particles can also be used as an antistatic agent. Examples of such conductive fine particles include ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , MgO, BaO, CoO, CuO, Cu ₂ O, CaO, SrO, BaO, PbO, and PbO. ₂ , MnO ₃ , MoO ₃ , SiO ₂ , ZrO ₂ , Ag ₂ O, Y ₂ O ₃ , Bi ₂ O ₃ , Ti ₂ O ₃ , Sb ₂ O ₃ , Sb ₂ O ₅ , K ₂ Ti ₆ O ₁₃ , Oxides such as NaCaP ₂ O ₁₈ and MgB ₂ O ₅ ; sulfides such as CuS and ZnS; carbides such as SiC, TiC, ZrC, VC, NbC, MoC and WC; Si ₃ N ₄ , TiN, ZrN, VN, Nitrides such as NbN and Cr ₂ N; borides such as TiB ₂ , ZrB ₂ , NbB ₂ , TaB ₂ , CrB, MoB, WB, LaB ₅ ; TiSi ₂ , ZrSi ₂ , NbSi ₂ , TaSi ₂ , CrSi ₂ , MoSi _2, WSi silicide such as _{2; aCO 3, CaCO 3, SrCO 3} , BaSO 4, metal salts of CaSO ₄ and the like; SiN ₄ -SiC, complexes such 9Al ₂ O ₃ -2B ₂ O ₃ and the like, alone, or two or these one You may use the above together. Of these, SnO ₂ , ZnO, Al ₂ O ₃ , TiO ₂ , In ₂ O ₃ , MgO, BaO and MoO ₃ are preferred, SnO ₂ , ZnO, In ₂ O ₃ and TiO ₂ are more preferred, and SnO ₂ is preferred. Particularly preferred.

  When the thermal transfer material of the present invention is used in a laser thermal transfer recording system, it is preferable that the antistatic agent used for the back layer is substantially transparent so that the laser beam can be transmitted.

  When a conductive metal oxide is used as an antistatic agent, the particle size is preferably as small as possible to minimize light scattering, but is determined using the ratio of the refractive index of the particles and the binder as a parameter. It can be obtained using Mie's theory. In general, the average particle size is in the range of 0.001 to 0.5 μm, preferably in the range of 0.003 to 0.2 μm. The average particle size referred to here is a value including not only the primary particle size of the conductive metal oxide but also the particle size of the higher order structure.

  In addition, various additives such as surfactants, slipping agents and matting agents and binders can be added to the BC layer.

  Examples of the binder used for forming the BC layer include homopolymers and copolymers of acrylic acid monomers such as acrylic acid, methacrylic acid, acrylic ester, and methacrylic ester, nitrocellulose, methylcellulose, ethylcellulose, and cellulose acetate. Cellulose polymers such as polyethylene, polypropylene, polystyrene, vinyl chloride copolymers, vinyl chloride-vinyl acetate copolymers, polyvinyl pyrrolidone, polyvinyl butyral, vinyl alcohol polymers such as polyvinyl alcohol, and copolymers of vinyl compounds , Polymerizing condensation polymer such as polyester, polyurethane, polyamide, rubber thermoplastic polymer such as butadiene-styrene copolymer, photopolymerizable or thermopolymerizable compound such as epoxy compound, Bridges are allowed polymer, and melamine compounds.

(Photothermal conversion layer)
The photothermal conversion layer contains a photothermal conversion substance, a binder, and, if necessary, a matting agent, and further contains other components as necessary. The photothermal conversion substance is a substance having a function of converting irradiated light energy into heat energy. Generally, it is a dye (including a pigment) capable of absorbing laser light. When performing image recording with an infrared laser, it is preferable to use an infrared absorbing dye as the photothermal conversion substance. Examples of the dyes are black pigments such as carbon black, macrocyclic compound pigments 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 include organic dyes (cyanine dyes such as indolenine dyes, anthraquinone dyes, azulene dyes, phthalocyanine dyes), and organometallic compound dyes such as dithiol nickel complexes. Among them, cyanine dyes exhibit a high extinction coefficient for light in the infrared region, so that when used as a photothermal conversion substance, the photothermal conversion layer can be made thin, and as a result, the recording sensitivity of the thermal transfer sheet can be reduced. Since it can improve more, it is preferable. As the photothermal conversion substance, an inorganic material such as a particulate metal material such as blackened silver can be used in addition to the pigment.

  As the binder contained in the photothermal conversion layer, a resin having at least strength capable of forming a layer on a support and having high thermal conductivity is preferable. Further, when the image is recorded, the resin having heat resistance that is not decomposed by heat generated from the light-to-heat conversion substance can smooth the surface of the light-to-heat conversion layer after light irradiation even when light irradiation with high energy is performed. Can be maintained. Specifically, a resin having a thermal decomposition temperature (temperature at which the temperature is reduced by 5% in an air stream at a rate of temperature increase of 10 ° C./min by TGA method (thermal mass spectrometry)) of 400 ° C. or more is preferable. A resin having a decomposition temperature of 500 ° C. or higher is more preferable. Moreover, it is preferable that a binder has a glass transition temperature (Tg) of 200-400 degreeC, and it is more preferable to have a glass Tg of 250-350 degreeC. If Tg is lower than 200 ° C., fog may occur in the formed image, and if it is higher than 400 ° C., the solubility of the resin may be reduced and the production efficiency may be reduced. In addition, it is preferable that the heat resistance (thermal deformation temperature or thermal decomposition temperature) of the binder of the photothermal conversion layer is higher than materials used for other layers provided on the photothermal conversion layer.

  Specifically, acrylic resin such as polymethyl methacrylate, polycarbonate, polystyrene, vinyl chloride / vinyl acetate copolymer, vinyl resin such as polyvinyl alcohol, polyvinyl butyral, polyester, polyvinyl chloride, polyamide, polyimide, Examples include polyetherimide, polysulfone, polyethersulfone, aramid, polyurethane, epoxy resin, urea / melamine resin, and the like. Among these, a polyimide resin is preferable.

  Examples of the matting agent contained in the photothermal conversion layer include inorganic fine particles and organic fine particles. Examples of the inorganic fine particles include silica, titanium oxide, aluminum oxide, zinc oxide, magnesium oxide, barium sulfate, magnesium sulfate, aluminum hydroxide, magnesium hydroxide, boron nitride and other metal salts, kaolin, clay, talc, zinc white, Lead white, sieglite, quartz, diatomaceous earth, barlite, bentonite, mica, synthetic mica and the like can be mentioned. Examples of the organic fine particles include resin particles such as fluorine resin particles, guanamine resin particles, acrylic resin particles, styrene-acrylic copolymer resin particles, silicone resin particles, melamine resin particles, and epoxy resin particles.

The particle size of the matting agent is usually 0.3 to 30 μm, preferably 0.5 to 20 μm, and the addition amount is preferably 0.1 to 100 mg / m ² .

  If necessary, a surfactant, a thickener, an antistatic agent and the like may be further added to the photothermal conversion layer.

  The photothermal conversion layer is prepared by dissolving a photothermal conversion substance and a binder, preparing a coating liquid to which a matting agent and other components are added if necessary, and applying and drying the coating liquid on a support. Can do. The application / drying can be performed using a normal application / drying method. The drying is usually performed at a temperature of 300 ° C. or lower, and is preferably performed at a temperature of 200 ° C. or lower. When PET is used as the support, it is preferably dried at a temperature of 80 to 150 ° C.

  Further, it is preferable to make the light-to-heat conversion layer thin because the thermal transfer sheet can be highly sensitive as described above. The photothermal conversion layer is preferably 0.03 to 1.0 μm, and more preferably 0.05 to 0.5 μm. The photothermal conversion layer preferably has an optical density of 0.80 to 1.26 with respect to light having a wavelength of 808 nm because the transfer sensitivity of the image forming layer is improved. More preferably, it has an optical density of 0.92 to 1.15. When the optical density at the laser peak wavelength is less than 0.80, it becomes insufficient to convert the irradiated light into heat, and the transfer sensitivity may be lowered. On the other hand, if it exceeds 1.26, the function of the photothermal conversion layer is affected during recording, and fogging may occur.

(Image forming layer)
The image forming layer contains at least a pigment for forming an image by being transferred to the image receiving sheet, and further contains a binder for forming the layer and other components as required. Pigments are generally classified into organic pigments and inorganic pigments. The former is particularly excellent in transparency of the coating film, and the latter is generally excellent in hiding properties. That's fine. When the thermal transfer sheet is used for proofreading printing colors, organic pigments that match yellow color, magenta color, cyan color, and black color that are generally used for printing inks or have a close color tone are preferably used. In addition, metal powder, fluorescent pigments, etc. may be used. Examples of pigments that can be suitably used include azo pigments, phthalocyanine pigments, anthraquinone pigments, dioxazine pigments, quinacridone pigments, isoindolinone pigments, and nitro pigments. The pigments used in the image forming layer are listed below according to hue, but are not limited thereto.

1) Yellow pigment Pigment Yellow (Pigment Yellow) 12 (C.I. No. 21090)
Pigment Yellow 13 (C.I. No. 21100)
Pigment Yellow 14 (C.I.No. 21095)
Pigment Yellow 17 (C.I.No. 21105)
Pigment Yellow 155
Pigment Yellow 180 (C.I.No. 21290)
Pigment Yellow 139 (C.I.No. 56298)
2) Magenta pigment Pigment Red 57: 1 (C.I.No. 15850: 1)
Pigment Red 122 (C.I.No. 73915)
Pigment Red 53: 1 (C.I. No. 15585: 1)
Pigment Red 48: 1 (C.I. No. 15865: 1)
Pigment Red 48: 2 (C.I.No. 15865: 2)
Pigment Red 48: 3 (C.I.No. 15865: 3)
Pigment Red 177 (C.I.No. 65300)
3) Cyan Pigment Pigment Blue (Pigment Blue) 15 (C.I.No. 74160)
Pigment Blue 15: 1 (C.I.No. 74160)
Pigment Blue 15: 2 (C.I.No. 74160)
Pigment Blue 15: 3 (C.I. No. 74160)
Pigment Blue 15: 4 (C.I.No. 74160)
Pigment Blue 15: 6 (C.I.No. 74160)
Pigment Blue 60 (C.I.No. 69800)
4) Black pigment Pigment Black 7 (carbon black)
Further, as pigments that can be used in the present invention, refer to Pigment Handbook: Edited by Japan Pigment Technical Association, Seibundo Shinkosha, 1989, COLOR INDEX, THE SOCIETY OF DYES & COLORIST, THIRD EDITION, 1987, etc. You can select a product.

  The average particle diameter of the pigment is preferably 0.03 to 1 μm, more preferably 0.05 to 0.5 μm. If the particle size is less than 0.03 μm, the dispersion cost may increase or the dispersion may gel. On the other hand, if it exceeds 1 μm, coarse particles in the pigment adhere to the image forming layer and the image receiving layer. In some cases, the transparency of the image forming layer may be hindered.

The binder for the image forming layer is preferably an amorphous organic polymer having a softening point of 40 to 150 ° C. Examples of the amorphous organic polymer include butyral resin, polyamide resin, polyethyleneimine resin, sulfonamide resin, polyester polyol resin, petroleum resin, styrene, vinyltoluene, α-methylstyrene, 2-methylstyrene, chlorostyrene. Styrene and its derivatives such as vinylbenzoic acid, sodium vinylbenzenesulfonate, aminostyrene, homopolymers and copolymers of substituted products, methacrylic esters such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, and Acrylic esters such as methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, and α-ethylhexyl acrylate, and dienes such as acrylic acid, butadiene, and isoprene; Use vinyl monomers such as rilonitrile, vinyl ethers, maleic acid and maleic esters, maleic anhydride, cinnamic acid, vinyl chloride, vinyl acetate alone or copolymers with other monomers. Can do. These resins can be used in combination of two or more.

  The image forming layer preferably contains 30 to 70% by mass of pigment, more preferably 30 to 50% by mass. The image forming layer preferably contains 70 to 30% by mass of resin, more preferably 70 to 40% by mass.

  The image forming layer can be provided by preparing a coating solution in which a pigment and the binder or the like are dissolved or dispersed, and coating and drying the coating solution on the photothermal conversion layer. Examples of the solvent used for preparing the coating solution include propyl alcohol, methyl ethyl ketone, propylene glycol monomethyl ether, methanol, water and the like. The application / drying can be performed using a normal application / drying method.

  Next, an image receiving sheet that can be used in combination with the thermal transfer sheet will be described.

<Image-receiving sheet>
The image-receiving sheet is usually provided with a support and one or more image-receiving layers thereon. If desired, one or two of a cushion layer, a release layer and an intermediate layer are provided between the support and the image-receiving layer. It is the structure which provided the layer or more. In addition, it is preferable in terms of transportability to provide a BC layer on the surface of the support opposite to the image receiving layer.

(Support)
Examples of the support include ordinary sheet-like substrates such as plastic sheets, metal sheets, glass sheets, resin-coated paper, paper, and various composites. Examples of the plastic sheet include a polyethylene terephthalate sheet, a polycarbonate sheet, a polyethylene sheet, a polyvinyl chloride sheet, a polyvinylidene chloride sheet, a polystyrene sheet, a styrene-acrylonitrile sheet, and a polyester sheet. Further, as the paper, printing paper, coated paper or the like can be used.

  It is preferable that the support has fine voids because the image quality can be improved. Such a support is, for example, a mixed melt obtained by mixing a thermoplastic resin and a filler composed of an inorganic pigment or a polymer that is incompatible with the thermoplastic resin, by a single-layer or multi-layer using a melt extruder. It can be produced by forming a film and further stretching it in one or two axes. In this case, the porosity is determined by the selection of resin and filler, mixing ratio, stretching conditions, and the like.

  As the thermoplastic resin, a polyolefin resin such as polypropylene and a polyethylene terephthalate resin are preferable because of good crystallinity, good stretchability, and easy formation of voids. It is preferable to use the polyolefin resin or polyethylene terephthalate resin as a main component and to use a small amount of other thermoplastic resin in combination with it as appropriate. As the inorganic pigment used as the filler, those having an average particle diameter of 1 to 20 μm are preferable, and calcium carbonate, clay, diatomaceous earth, titanium oxide, aluminum hydroxide, silica and the like can be used. In addition, as the incompatible resin used as the filler, when polypropylene is used as the thermoplastic resin, it is preferable to combine polyethylene terephthalate as the filler. In addition, the content of fillers such as inorganic pigments in the support is generally about 2 to 30% by volume.

  The thickness of the support of the image receiving sheet is usually 10 to 400 μm, and preferably 25 to 200 μm. Further, the surface of the support is subjected to surface treatment such as corona discharge treatment or glow discharge treatment in order to improve the adhesion to the image receiving layer (or cushion layer) or the image forming layer of the thermal transfer sheet. It may be.

(Image receiving layer)
In order to transfer and fix the image forming layer on the surface of the image receiving sheet, it is preferable to provide one or more image receiving layers on the support. The image receiving layer is preferably a layer formed mainly of an organic polymer binder. The binder is preferably a thermoplastic resin. For example, homopolymers and copolymers of acrylic monomers such as acrylic acid, methacrylic acid, acrylic ester, and methacrylic ester, methyl cellulose, ethyl cellulose, and cellulose acetate. Cellulosic polymer, polystyrene, polyvinyl pyrrolidone, polyvinyl butyral, polyvinyl alcohol, polyvinyl chloride, styrene-maleic acid copolymer half-esterified product, styrene-fumaric acid copolymer half-esterified product, styrene-acrylic acid copolymer Examples include homopolymers of vinyl monomers such as esterified products of copolymers and copolymers thereof, condensation polymers such as polyesters and polyamides, and rubber polymers such as butadiene-styrene copolymers. Can. Among them, at least one selected from polyvinyl butyral or styrene-maleic acid copolymer half-esterified product, styrene-fumaric acid copolymer half-esterified product and styrene-acrylic acid copolymer esterified product is used as a polymer binder. It is preferable to use it. The above binder polymers may be used in combination of two or more, but polyvinyl butyral or styrene-maleic acid copolymer half-esterified product, styrene-fumaric acid copolymer half-esterified product and styrene-acrylic acid copolymer It is preferable to occupy 10% by mass or more, particularly 30% by mass or more, of the binder polymer in which at least one selected from the combined esterified product is used.

  The binder of the image receiving layer is preferably a polymer having a Tg lower than 90 ° C. in order to obtain an appropriate adhesive force with the image forming layer. For this purpose, it is also possible to add a plasticizer to the image receiving layer. The binder polymer preferably has a Tg of 30 ° C. or higher in order to prevent blocking between sheets. As the binder polymer of the image receiving layer, it is possible to use the same or similar polymer as the binder polymer of the image forming layer in terms of improving the adhesion with the image forming layer at the time of laser recording and improving sensitivity and image strength. Particularly preferred.

  The smoother value on the surface of the image receiving layer is preferably 0.0665 to 6.65 kPa at 23 ° C. and 55% RH, and Ra is preferably 0.05 to 0.4 μm, whereby the image receiving layer and the image are formed on the contact surface. A large number of microscopic voids that cannot be in contact with the forming layer can be reduced, which is preferable in terms of transfer and image quality. The Ra value can be measured based on JIS B0601 using a surface roughness measuring machine or the like.

  The surface resistance of the image receiving layer is preferably 109Ω or less at 23 ° C. and 55% RH. The coefficient of static friction on the surface of the image receiving layer is preferably 0.8 or less.

  When an image is once formed on the image receiving layer and then re-transferred to printing paper or the like, it is also preferable to form at least one of the image receiving layers from a photocurable material. Examples of the composition of such a photocurable material include: a) a photopolymerizable monomer comprising at least one of a polyfunctional vinyl or vinylidene compound capable of forming a photopolymer by addition polymerization, b) an organic polymer, c) The combination which consists of additives, such as a photoinitiator and a thermal-polymerization inhibitor as needed, can be mentioned. As the polyfunctional vinyl monomer, an unsaturated ester of polyol, particularly an ester of acrylic acid or methacrylic acid (ethylene glycol diacrylate, pentaerythritol tetraacrylate, etc.) is used.

(Other layers)
A cushion layer is preferably provided between the support and the image receiving layer. When a cushion layer is provided, the adhesion between the image forming layer and the image receiving layer can be improved during laser thermal transfer, and the image quality can be improved. In addition, even if foreign matter is mixed between the thermal transfer sheet and the image receiving sheet during recording, the gap between the image receiving layer and the image forming layer is reduced due to the deformation action of the cushion layer, and as a result, the size of image defects such as white spots is reduced. You can also Furthermore, when the image is transferred and then transferred to a separately prepared printing paper or the like, the image receiving surface is deformed according to the uneven surface of the paper, so that the transferability of the image receiving layer can be improved, By reducing the gloss of the material to be transferred, the closeness with the printed material can also be improved.

  The cushion layer is configured to be easily deformed when stress is applied to the image receiving layer, and in order to achieve the effect, a material having a low elastic modulus, a material having rubber elasticity, or a thermoplastic that is easily softened by heating. It is preferable to consist of resin. The elastic modulus of the cushion layer is preferably 0.5 MPa to 1.0 GPa, particularly preferably 1 MPa to 0.5 GPa, more preferably 10 to 100 MPa at room temperature. Further, in order to entrap foreign substances such as dust, the penetration (25 ° C., 100 g, 5 seconds) defined in JIS K2530 is preferably 10 or more. The Tg of the cushion layer is 80 ° C. or lower, preferably 25 ° C. or lower, and the softening point is preferably 50 to 200 ° C. In order to adjust these physical properties, for example, Tg, a plasticizer can be suitably added to the binder.

  Specific materials used as a binder for the cushion layer include rubbers such as urethane rubber, butadiene rubber, nitrile rubber, acrylic rubber, natural rubber, polyethylene, polypropylene, polyester, styrene-butadiene copolymer, ethylene -Vinyl acetate copolymer, ethylene-acrylic copolymer, vinyl chloride-vinyl acetate copolymer, vinylidene chloride resin, vinyl chloride resin with plasticizer, polyamide resin, phenol resin and the like. In addition, although the thickness of a cushion layer changes with resin and other conditions to be used, it is 3-100 micrometers normally, Preferably it is 10-52 micrometers.

  The image receiving layer and the cushion layer need to be bonded until the stage of laser recording, but are preferably provided so as to be peelable in order to transfer the image onto the printing paper. In order to facilitate peeling, it is also preferable to provide a peeling layer with a thickness of about 0.1 to 2 μm between the cushion layer and the image receiving layer. If the layer thickness is too large, the performance of the cushion layer will be difficult to exhibit, and it is necessary to adjust depending on the type of the release layer. Specific examples of binders for the release layer include polyolefin, polyester, polyvinyl acetal, polyvinyl formal, polyparabanic acid, polymethyl methacrylate, polycarbonate, ethyl cellulose, nitrocellulose, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, and polyvinyl chloride. , Urethane resins, fluorine resins, polystyrenes, styrenes such as polystyrene, acrylonitrile styrene, etc. and those crosslinked with these resins, polyamides, polyimides, polyetherimides, polysulfones, polyethersulfones, aramids, etc., with a Tg of 65 ° C. Resins and cured products of these resins are mentioned. As the curing agent, general curing agents such as isocyanate and melamine can be used.

  The image receiving sheet combined with the thermal transfer sheet may have a configuration in which the image receiving layer also serves as a cushion layer. In that case, the image receiving sheet is a support / cushioning image receiving layer or a support / undercoat layer / cushioning property. The image receiving layer may be configured. Also in this case, it is preferable that the cushioning image-receiving layer is provided so as to be removable so that retransfer to the printing paper can be performed. In this case, the image after retransfer to the printing paper is an image having excellent gloss. The thickness of the cushioning image-receiving layer is 5 to 100 μm, preferably 10 to 40 μm.

  In addition, it is preferable to provide a back layer on the surface of the image receiving sheet opposite to the surface on which the image receiving layer is provided because the transportability of the image receiving sheet is improved. It is preferable to add an antistatic agent such as a surfactant or tin oxide fine particles, or a matting agent such as silicon oxide or PMMA particles to the back layer in order to improve transportability in the recording apparatus. The additive may be added not only to the back layer but also to the image receiving layer and other layers as necessary. Although the kind of additive cannot be defined unconditionally depending on the purpose, for example, in the case of a matting agent, about 0.5 to 80% of particles having an average particle size of 0.5 to 10 μm can be added to the layer. The antistatic agent is appropriately selected from various surfactants and conductive agents so that the surface resistance of the layer is 1012Ω or less, more preferably 109Ω or less under the conditions of 23 ° C. and 50% RH. it can.

  Binders used in the back layer include gelatin, polyvinyl alcohol, methyl cellulose, nitrocellulose, acetyl cellulose, aromatic polyamide resin, silicone resin, epoxy resin, alkyd resin, phenol resin, melamine resin, fluorine resin, polyimide resin, urethane resin , Acrylic resin, urethane-modified silicone resin, polyethylene resin, polypropylene resin, polyester resin, Teflon (R) resin, polyvinyl butyral resin, vinyl chloride resin, polyvinyl acetate, polycarbonate, organic boron compounds, aromatic esters, fluorinated polyurethane In addition, general-purpose polymers such as polyethersulfone can be used. Using a crosslinkable water-soluble binder as a binder for the back layer is effective in preventing the matting agent from falling off and improving the scratch resistance of the back layer. It is also very effective for blocking during storage.

Organic or inorganic fine particles can be used as the matting agent preferably added to the back layer. Examples of the organic matting agent include polymethyl methacrylate (PMMA), polystyrene, polyethylene, polypropylene, fine particles of other radical polymerization polymers, and fine particles of condensation polymers such as polyester and polycarbonate. The back layer is preferably provided at a weight of about 0.5 to 5 g / m ² . If it is less than 0.5 g / m ² , the coating property is unstable, and problems such as powdering off of the matting agent are likely to occur. Also, when the coating is applied greatly exceeding 5 g / m ² , the particle size of a suitable matting agent becomes very large, resulting in embossing of the image receiving layer surface by the back layer during storage, and in particular thermal transfer for transferring a thin image forming layer Then, omission and unevenness of the recorded image are likely to occur.

  An antistatic agent is preferably added to the back layer in order to prevent adhesion of foreign matters due to frictional charging with the transport roll. Antistatic agents include cationic surfactants, anionic surfactants, nonionic surfactants, polymer antistatic agents, and conductive fine particles, as well as “11290 chemical products”, Chemical Industry Daily, 875- The compounds described on page 876 and the like are widely used. As the antistatic agent that can be used in combination with the back layer, among the above substances, metal oxides such as carbon black, zinc oxide, titanium oxide, and tin oxide, and conductive fine particles such as organic semiconductors are preferably used. In particular, it is preferable to use conductive fine particles because the antistatic agent is not dissociated from the back layer, and a stable antistatic effect can be obtained regardless of the environment. In addition, various activators, release agents such as silicone oil, fluorine-based resins, and the like can be added to the back layer in order to impart coatability and releasability. The back layer is particularly preferable when the softening point measured by TMA of the cushion layer and the image receiving layer is 70 ° C. or less.

  The TMA softening point is obtained by heating the measurement object at a constant heating rate while applying a constant load and observing the phase of the object. In the present invention, the TMA softening point is defined as the temperature at which the phase of the measurement object starts to change. The measurement of the softening point by TMA can be performed using a device such as Thermoflex manufactured by Rigaku Corporation.

  The thermal transfer sheet and the image receiving sheet are used for image formation as a laminate in which the image forming layer of the thermal transfer sheet and the image receiving layer of the image receiving sheet are superposed. The laminate of the thermal transfer sheet and the image receiving sheet can be formed by various methods. For example, it can be easily obtained by superposing the image forming layer of the thermal transfer sheet and the image receiving layer of the image receiving sheet and passing them through a pressure heating roller. In this case, the heating temperature is preferably 160 ° C. or lower, or 130 ° C. or lower.

  As another method for obtaining a laminate, the above-described vacuum contact method is also preferably used. In the vacuum contact method, an image receiving sheet is first wound on a drum provided with a suction hole for evacuation, and then a thermal transfer sheet slightly larger in size than the image receiving sheet, while air is uniformly pushed out by a squeeze roller, the image receiving sheet It is the method of making it vacuum-adhere to. Further, as another method, there is a method in which the image receiving sheet is mechanically attached to the metal drum while being pulled, and a thermal transfer sheet is similarly attached to the metal drum while being mechanically pulled to be in close contact therewith. Among these methods, the vacuum adhesion method is particularly preferable because it does not require temperature control of a heat roller or the like and is easy to laminate quickly and uniformly.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, the embodiment of this invention is not restrict | limited to these. Unless otherwise specified, “part” in the examples represents “part by mass” and “%” represents “% by mass”.

Example 1
<Preparation of thermal transfer sheet K>
<Formation of back layer>
(Back first layer coating solution)
Acrylic resin aqueous dispersion (Julimer ET410: Nippon Pure Chemical Industries, solid content 20%)
2 parts antistatic agent (tin oxide-antimony oxide aqueous dispersion, average particle size: 0.1 μm, 17%)
7.0 parts Polyoxyethylene phenyl ether 0.1 part Compound listed in Table 1 0.05 part Melamine compound (Sumitic Resin M-3: manufactured by Sumitomo Chemical Co., Ltd.) 0.3 part Total amount of distilled water is 100 parts Adjustment <Formation of back first layer>
Corona treatment is applied to one side (back side) of a biaxially stretched PET support of 75 μm thickness (Ra on both sides is 0.01 μm) so that the dried first layer coating solution has a dry layer thickness of 0.03 μm. After coating, the back first layer was formed by drying at 180 ° C. for 30 seconds. The Young's modulus in the longitudinal direction of the support is 4.4 GPa, and the Young's modulus in the width direction is 4.9 GPa. The F-5 value in the longitudinal direction of the support is 98 MPa, the F-5 value in the width direction is 127.4 MPa, and the thermal shrinkage rate of the support at 100 ° C. for 30 minutes is 0.3% in the longitudinal direction and the width The direction is 0.1%. The breaking strength is 196 MPa in the longitudinal direction, 245 MPa in the width direction, and the elastic modulus is 3.9 GPa.
(Back second layer coating solution)
Polyolefin (Chemical S-120: Mitsui Petrochemical Co., Ltd., 27%) 3.0 parts Antistatic agent (tin oxide-antimony oxide aqueous dispersion, average particle size: 0.1 μm, 17%)
2.0 parts Colloidal silica (Snowtex C: manufactured by Nissan Chemical Co., Ltd., 20%) 2.0 parts Epoxy compound (Dinacol EX-614B: manufactured by Nagase Kasei Co., Ltd.) 0.3 parts 0.05 parts of the compounds listed in Table 1 Adjust the total volume to 100 parts with distilled water <Formation of back second layer>
A back second layer coating solution was applied onto the back first layer so that the dry layer thickness was 0.03 μm, and then dried at 170 ° C. for 30 seconds to form a back second layer.

<Preparation of coating solution for photothermal conversion layer>
The following components were mixed while stirring with a stirrer to prepare a photothermal conversion layer coating solution.
(Coating solution composition for photothermal conversion layer)
Infrared absorbing dye (NK-2014: Cyanine dye manufactured by Nippon Senshoku Dye Co., Ltd.) 7.6 parts Polyimide resin (Lika Coat SN-20F: Shin Nippon Rika Co., Ltd., thermal decomposition temperature 510 ° C.)
29.3 parts Exon naphtha 5.8 parts N-methyl-2-pyrrolidone (NMP) 1500 parts Methyl ethyl ketone (MEK) 360 parts F-based surfactant (Megafac F-176PF: manufactured by Dainippon Ink & Chemicals, Inc.)
0.5 parts Matting agent dispersion liquid with the following composition * 14.1 parts * Matting agent dispersion liquid NMP 69 parts, MEK 20 parts, Styrene acrylic resin (John Crill 611: manufactured by Johnson Polymer Co., Ltd.), silica (Seahoster KEP150: Nippon Shokubai) (Silica gel particles) dispersion <Formation of photothermal conversion layer>
After coating the photothermal conversion layer coating solution on one surface of a PET support having a thickness of 75 μm using a wire bar, it is dried in an oven at 120 ° C. for 2 minutes, and photothermal conversion is performed on the support. A layer was formed. When the optical density of the obtained photothermal conversion layer at a wavelength of 808 nm was measured with a UV-spectrophotometer UV-240 manufactured by Shimadzu Corporation, OD = 1.03. When the cross section of the photothermal conversion layer was observed with a scanning electron microscope, the layer thickness was 0.3 μm on average.

<Preparation of coating solution for black image forming layer>
Each of the following components was put into a kneader mill, a shearing force was applied while adding a small amount of solvent, and a dispersion pretreatment was performed. A solvent was further added to the dispersion to prepare a final composition having the following composition, and sand mill dispersion was performed for 2 hours to obtain a pigment dispersion mother liquor.
[Black pigment dispersion mother liquor composition]
(Composition 1)
Polyvinyl butyral (ESREC B BL-SH: manufactured by Sekisui Chemical Co., Ltd.) 12.6 parts carbon black (Mitsubishi Carbon Black # 5: manufactured by Mitsubishi Chemical Corporation, PVC blackness 1)
4.5 parts Dispersing aid (Solsperse S-20000: manufactured by ICI) 0.8 parts 79.4 parts propyl alcohol (composition 2)
Polyvinyl butyral (ESREC B BL-SH: supra) 12.6 parts Carbon black (Mitsubishi Carbon Black MA100: manufactured by Mitsubishi Chemical Corporation, PVC blackness 10) 10.5 parts Dispersing aid (Solsperse S-20000: supra) 0.8 parts Propyl alcohol 79.4 parts Next, the following components were mixed with stirring with a stirrer to prepare a coating solution for a black image forming layer.
(Coating solution for black image forming layer)
Black pigment dispersion mother liquor (Composition 1: Composition 2 = 70: 30 parts) 185.7 parts Polyvinyl butyral (Eslec B BL-SH: supra) 11.9 parts Wax compound Stearic acid amide (Neutron 2: Nippon Seiki) 1.7 parts behenamide (diamond BM: manufactured by Nippon Kasei Co., Ltd.) 1.7 parts lauric acid amide (diamond Y: manufactured by Nippon Kasei Co., Ltd.) 1.7 parts palmitic acid amide (diamond KP: Nippon Kasei Co., Ltd.) 1.7 parts erucic acid amide (Diamid L-200: manufactured by Nippon Kasei Co., Ltd.) 1.7 parts Oleic acid amide (Diamid O-200: manufactured by Nippon Kasei Co., Ltd.) 1.7 parts Rosin (KE) -311: manufactured by Arakawa Chemical Co., Ltd.) 11.4 parts (component: resin acid 80-97%; resin acid component: abietic acid 30-40%, neoabietic acid 10-20%, dihydro Biechin acid 14%, 14% tetrahydroabietic acid)
Surfactant (compound described in Table 1) 1.5 parts Inorganic pigment (MEK-ST, 30% methyl ethyl ketone solution: manufactured by Nissan Chemical Industries, Ltd.) 7.1 parts Propyl alcohol 1050 parts Methyl ethyl ketone 295 parts For the obtained black image forming layer When the particles in the coating solution were measured using a laser scattering type particle size distribution analyzer, the average particle size was 0.25 μm, and the proportion of particles of 1 μm or more was 0.5%.

<Formation of black image forming layer>
After applying the black image forming layer coating liquid on the surface of the light-to-heat conversion layer for 1 minute using a wire bar, the coating is dried in an oven at 100 ° C. for 2 minutes to form a black on the light-to-heat conversion layer. An image forming layer was formed. Through the above steps, the photothermal conversion layer and the black image forming layer are provided on the support in this order in the order of the thermal transfer sheet (hereinafter referred to as the thermal transfer sheet K. Similarly, the yellow image forming layer, the magenta image forming layer, Those provided with a cyan image forming layer were respectively referred to as a thermal transfer sheet Y, a thermal transfer sheet M, and a thermal transfer sheet C).

  When the optical density (optical density: OD) of the black image forming layer of the thermal transfer sheet K was measured with a Macbeth densitometer “TD-904” (W filter), OD = 0.91. Further, the thickness of the black image forming layer was measured and found to be 0.60 μm on average.

  The physical properties of the obtained image forming layer were as follows. The surface hardness of the image forming layer is preferably 10 g or more with a sapphire needle, specifically 200 g or more. The smooth star value on the surface was preferably 66.5 to 6,650 Pa at 23 ° C. and 55% RH (relative humidity), specifically 1.24 kPa. The static friction coefficient of the surface is preferably 0.2 or less, specifically 0.08.

<Preparation of thermal transfer sheet Y>
In the production of the thermal transfer sheet K, a thermal transfer sheet Y was produced in the same manner as the production of the thermal transfer sheet K except that a yellow image forming layer coating liquid having the following composition was used instead of the black image forming layer coating liquid. . The film thickness of the image forming layer of the obtained thermal transfer sheet Y was 0.42 μm.
[Yellow pigment dispersion mother liquor]
(Composition 1)
Polyvinyl butyral (ESREC B BL-1SH: supra) 7.1 parts Yellow pigment (Novo Palm Yellow P-HG: manufactured by Clariant Japan)
12.9 parts Dispersing aid (Solsperse S-20000: supra) 0.6 parts Propyl alcohol 79.4 parts (Composition 2)
Polyvinyl butyral (ESREC B BL-1SH: supra) 7.1 parts Yellow pigment (Novo Palm Yellow M2R 70: manufactured by Clariant Japan)
12.9 parts Dispersing aid (Solsperse S-20000: supra) 0.6 parts 79.4 parts propyl alcohol (coating solution for yellow image forming layer)
Yellow pigment dispersion mother liquor (Composition 1: Composition 2 = 95: 5 parts) 126 parts Polyvinyl butyral (ESREC B BL-1SH: supra) 4.6 parts Wax compound Stearic acid amide (Neutron 2: Nippon Seika Co., Ltd.) 1.7 parts behenamide (diamond BM: manufactured by Nippon Kasei Co., Ltd.) 1.7 parts lauric acid amide (diamond Y: manufactured by Nippon Kasei Co., Ltd.) 1.7 parts palmitic acid amide (diamond KP: Nippon Kasei) 1.7 parts erucic acid amide (Diamid L-200: manufactured by Nippon Kasei Co., Ltd.) 1.7 parts oleic acid amide (Diamid O-200: manufactured by Nippon Kasei Co., Ltd.) 1.7 parts Nonionic surfactant (Chemist 1100; manufactured by Sanyo Chemical Co., Ltd.) 0.4 parts Rosin (KE-311: supra) 2.4 parts Surfactant (compound described in Table 1) 0.2 part Propyl alcohol Properties of 793 parts of methyl ethyl ketone 198 parts The obtained image-forming layer had the following. The surface hardness of the image forming layer is preferably 10 g or more with a sapphire needle, specifically 200 g or more. The surface smoother value was preferably 66.5 Pa to 6.65 kPa at 23 ° C. and 55% RH, specifically 310 Pa. The static friction coefficient of the surface is preferably 0.2 or less, specifically 0.1.

<Preparation of thermal transfer sheet M>
In the preparation of the thermal transfer sheet K, a thermal transfer sheet M was prepared in the same manner as the preparation of the thermal transfer sheet K, except that a magenta image forming layer coating liquid having the following composition was used instead of the black image forming layer coating liquid. . The film thickness of the image forming layer of the obtained thermal transfer sheet M was 0.38 μm.
[Magenta pigment dispersion mother liquor]
(Composition 1)
Polyvinyl butyral (Denka butyral # 2000-L: manufactured by Denki Kagaku Kogyo Co., Ltd., Vicat softening point 57 ° C.) 12.6 parts Magenta pigment (Shimla Brilliant Carmine 2B-229: manufactured by Dainippon Ink & Chemicals, Inc.) 15.0 parts Dispersing aid (Solsperse S-20000: supra) 0.6 parts Propyl alcohol 80.4 parts Composition 2
Polyvinyl butyral (Denka butyral # 2000-L: supra) 12.6 parts Magenta pigment (Lionol Red GB-4290G: manufactured by Dainippon Ink & Chemicals, Inc.)
15.0 parts Dispersing aid (Solsperse S-20000: supra) 0.6 parts Propyl alcohol 79.4 parts (Coating liquid for magenta image forming layer)
Magenta pigment dispersion mother liquor (Composition 1: Composition 2 = 95: 5 parts) 163 parts Polyvinyl butyral (Denkabutyral # 2000-L: supra) 4.0 parts Wax compound Stearamide (Neutron 2: Nippon Seikai) 1.0 part behenamide (diamond BM: manufactured by Nippon Kasei Co., Ltd.) 1.0 part lauric acid amide (diamond Y: manufactured by Nippon Kasei Co., Ltd.) 1.0 part palmitic acid amide (diamond KP: Japan) 1.0 part erucic acid amide (Diamid L-200: manufactured by Nippon Kasei Co., Ltd.) 1.0 part oleic acid amide (Diamid O-200: manufactured by Nippon Kasei Co., Ltd.) 1.0 part Nonionic surfactant Agent (Chemist 1100: supra) 0.7 parts Rosin (KE-311: supra) 4.6 parts Pentaerythritol tetraacrylate (NK ester A- TMMT (manufactured by Shin-Nakamura Chemical Co., Ltd.) 2.5 parts Surfactant (compound described in Table 1) 0.3 part Propyl alcohol 848 parts Methyl ethyl ketone 246 parts Physical properties of the resulting image forming layer were as follows. The surface hardness of the image forming layer is preferably 10 g or more with a sapphire needle, specifically 200 g or more. The smooth star value on the surface was preferably 66.5 Pa to 6.65 kPa at 23 ° C. and 55% RH, and specifically 470 Pa. The static friction coefficient of the surface is preferably 0.2 or less, specifically 0.08.

<Preparation of thermal transfer sheet C>
In the preparation of the thermal transfer sheet K, a thermal transfer sheet C was prepared in the same manner as the preparation of the thermal transfer sheet K, except that a cyan image forming layer coating liquid having the following composition was used instead of the black image forming layer coating liquid. . The film thickness of the image forming layer of the obtained thermal transfer sheet C was 0.45 μm.
[Cyan pigment dispersion mother liquor composition]
(Composition 1)
Polyvinyl butyral (ESREC B BL-SH: supra) 12.6 parts Cyan pigment (cyanine blue 700-10FG: manufactured by Toyo Ink Co., Ltd.) 15.0 parts Dispersing aid (PW-36: manufactured by Enomoto Kasei Co., Ltd.) 8 parts propyl alcohol 110 parts (composition 2)
Polyvinyl butyral (ESREC B BL-SH: supra) 12.6 parts Cyan pigment (Lionol Blue 7027: manufactured by Toyo Ink Co., Ltd.) 15.0 parts Dispersing aid (PW-36: supra) 0.8 parts Propyl 110 parts of alcohol (coating solution for cyan image forming layer)
Cyan pigment-dispersed mother liquor (Composition 1: Composition 2 = 90: 10 parts) 118 parts Polyvinyl butyral (ESREC B BL-SH: supra) 5.2 parts Inorganic pigment (MEK-ST) 1.3 parts Wax compound Stearin Acid amide (Neutron 2: Nihon Seika Co., Ltd.) 1.0 part Behenamide (Diamid BM: Nihon Kasei Co., Ltd.) 1.0 part Lauric acid amide (Diamid Y: Nihon Kasei Co., Ltd.) 1.0 Part Palmitic acid amide (Diamid KP: manufactured by Nippon Kasei Co., Ltd.) 1.0 part Erucic acid amide (Diamid L-200: manufactured by Nippon Kasei Co., Ltd.) 1.0 part Oleic acid amide (Diamid O-200: Nippon Kasei Co., Ltd.) 1.0 parts Rosin (KE-311: supra) 2.8 parts Pentaerythritol tetraacrylate (NK ester A-TMMT: supra)
1.7 parts Surfactant (compound described in Table 1) 0.4 part Propyl alcohol 890 parts Methyl ethyl ketone 247 parts <Preparation of image receiving sheet>
A cushioning layer coating solution and an image receiving layer coating solution having the following composition were prepared.
(Coating liquid for cushion layer)
Vinyl chloride-vinyl acetate copolymer (MPR-TSL: manufactured by Nissin Chemical) 20 parts Plasticizer (Paraplex G-40: manufactured by CP. HALL.COMPANY) 10 parts Fluorosurfactant (Megafac F-) 177: manufactured by Dainippon Ink and Chemicals, Inc.) 0.5 parts Antistatic agent (SAT-5 Super (IC): manufactured by Nippon Pure Chemicals Co., Ltd.) 0.3 parts Methyl ethyl ketone 60 parts Toluene 10 parts N, N-dimethylformamide 3 parts (Image-receiving layer coating solution)
Polyvinyl butyral (ESREC B BL-1: manufactured by Sekisui Chemical Co., Ltd.) 117 parts Styrene-maleic acid half ester (oxylac SH-128: manufactured by Nippon Shokubai Co., Ltd.)
63 parts Antistatic agent (Chemistat 3033: Sanyo Chemical Industries) 16 parts Surfactant (Megafac F-176PF: Dainippon Ink & Chemicals) 1.2 parts Propyl alcohol 570 parts Methanol 1200 parts 1-Methoxy- 2-Propanol 520 parts On a white PET support (Lumirror # 130E58: manufactured by Toray Industries, Inc., 130 μm thick), the above-mentioned cushion layer forming coating solution is applied and dried, and then used for an image receiving layer. The coating solution was applied and dried. The coating amount was adjusted so that the thickness of the cushion layer after drying was about 20 μm and the thickness of the image receiving layer was about 2 μm.

  The white PET support is a laminate (total thickness 130 μm,) of a void-containing PET layer (thickness 116 μm, porosity 20%) and a titanium oxide-containing PET layer (thickness 7 μm, titanium oxide content 2%) provided on both sides thereof. A void-containing plastic support having a specific gravity of 0.8).

  The produced image receiving sheet was wound up in roll form and stored at room temperature for 1 week, and then used for image recording with the following laser beam.

<Formation of transfer image>
The image-receiving sheet (56 cm × 79 cm) prepared above was wound around a rotating drum having a diameter of 35 cm in which a vacuum section hole having a diameter of 1 mm (one surface density in an area of 3 cm × 8 cm) was formed and vacuum-adsorbed. Next, the thermal transfer sheet K (black) cut to 61 cm × 84 cm was stacked so as to protrude evenly from the image receiving sheet, and squeezed with a squeeze roller, and closely adhered and laminated so that air was sucked into the section holes. The degree of vacuum in the state where the section hole was blocked was −81.13 kPa with respect to 101.3 kPa (= 1 atm). The drum is rotated, and a semiconductor laser beam having a wavelength of 808 nm is focused on the surface of the laminated body on the drum from the outside so as to be a 7 μm spot on the surface of the photothermal conversion layer. A laser image (image line) was recorded on the laminate while moving in the direction perpendicular to the scanning direction (sub-scanning). The laser irradiation conditions are as follows. The laser beam used in this example was a multi-beam two-dimensional array of parallelograms consisting of 5 rows in the main scanning direction and 3 rows in the sub-scanning direction.

Laser power: 10m0mW
Drum rotation speed: K = 580, Y = M = 550, C = 560 rpm
Sub-scanning pitch: 6.35 μm
Environmental temperature and humidity: 2 conditions of 16 ° C. and 30% RH (LL), 27 ° C. and 70% RH (HH) The diameter of the exposure drum is preferably 360 mm or more, specifically, 380 mm. The image size is 515 mm × 728 mm, and the resolution is 4,000 dpi (supra).

  When the laser-recorded laminate is removed from the drum and the thermal transfer sheet K is manually peeled off from the image receiving sheet, only the light irradiation area of the image forming layer of the thermal transfer sheet K is transferred from the thermal transfer sheet K to the image receiving sheet. It was confirmed that The obtained image receiving sheet was superposed on Tokuhishi art paper, and the image was retransferred with a laminator TP-400 (manufactured by Konica Medical and Graphic) to obtain an evaluation sample.

  In the same manner as described above, an image was transferred from the thermal transfer sheet Y, the thermal transfer sheet M, and the thermal transfer sheet C onto the image receiving sheet. Also for these, the transfer image of each image-receiving sheet was re-transferred to Tokishi art paper, and used as an evaluation sample.

<Performance evaluation>
The following evaluation was performed about the sample for evaluation (K, Y, M, C).

<< Reproducibility of fine lines >>
The reproducibility of the 6 μm and 12 μm fine lines was evaluated in three stages according to the following criteria under the above-described exposure to retransfer conditions.

○: Defect in thin line, no “gassiness” △: Part of fine line is missing ×: Over half of thin line is missing << ΔDG (environment) >>
The environmental variation of the dot gain was evaluated under the above exposure to retransfer conditions. As an evaluation chart, a solid patch of 5 cm × 5 cm and a 50% halftone patch were exposed at the center of the image with a standard exposure amount, re-transferred with a laminator TP-400, and the density of each patch was measured.

  The exposure was performed under the above LL and HH conditions, and the dot gain (DG) was calculated from the respective densities. Table 1 shows the difference in DG under the LL and HH conditions as ΔDG.

<< ΔDG (in-plane) >>
Under the same conditions as the environmental evaluation, an in-plane variation evaluation pattern (5 cm × 5 cm solid, 5 cm × 5 cm 50% halftone dot repeat pattern) was exposed to re-transferred to obtain an evaluation sample. DG was calculated by measuring the density of the solid patch and the density of the flat patch immediately below it with the top of the exposure at the top. The DG of all the patches in the repetitive pattern was calculated, and the difference between the maximum value and the minimum value was shown as ΔDG (in-plane).

M-1: Acetylene glycol surfactant (Dinol 604 5% solution: manufactured by Air Products Japan) 0.5% and silicone surfactant (SLYGARD309 5% methanol solution: manufactured by Toray Dow Corning) 0.5% mixtures of _{F-a: C 8 F 17} CH 2 CH 2 O (CH 2 CH 2 O) 8 CH 3
From Table 1, it can be seen that according to the implementation of the present invention, both fine line reproducibility and dot gain fluctuation due to the environment are improved.

Example 2
<Preparation of thermal transfer sheet>
<Preparation of yellow transfer sheet>
Using a transparent PET (T100, # 38: manufactured by Mitsubishi Polyester) with a thickness of 38 μm as a support, a release layer coating solution having the following composition is applied and dried on the reverse roll coater, and the dry weight is 0.3 g. A release layer of / m ² was formed.
(Release layer coating solution)
Release layer binder liquid * 22.9 parts Crosslinker (Smileze Resin 613: manufactured by Sumitomo Chemical Co., Ltd.) 0.2 parts Pure water 69.2 parts i-Propyl alcohol 7.7 parts * Release layer binder liquid: aqueous polyvinyl alcohol solution (Nippon Synthetic Chemical Industry Co., Ltd .: 9.5% aqueous solution of Gohsenol EG-30) 97.2 parts, Cross-linking accelerator (Sumitex Accelerator ACX-P: Sumitomo Chemical Co., Ltd.) 1.3 parts, Fluorosurfactant (Unidyne) (TG-810: manufactured by Daikin Industries, Ltd.) A binder liquid having a solid content of 9.5% was prepared from 0.3 part and 1.2 parts of water.

On the release layer, a yellow ink layer coating liquid having the following composition was applied and dried by wire bar coating to form an ink layer having a dry weight of 0.65 g / m ² .
(Yellow ink layer coating liquid)
Yellow pigment dispersion (10 parts of Seika First Yellow H-7055 dispersed in MEK 88 parts with 2 parts of dispersant) 18.24 parts Styrene resin (Himmer ST-95: manufactured by Sanyo Chemical Industries) 5.05 parts Acrylic Resin (Dianar BR-102: manufactured by Mitsubishi Rayon Co., Ltd.) 0.40 parts Styrene-butadiene block copolymer (kraton D-1101CU: manufactured by Shell Japan Co., Ltd.) 0.24 parts Fluorine-based surfactant (Megafac F-178K: Dainippon Ink and Chemicals)
0.09 parts Methyl ethyl ketone 11.52 parts Cyclohexanone 64.47 parts On the yellow ink layer, the photothermal conversion layer coating liquid 1 having the following composition was applied and dried by wire bar coating, and the drying weight was 0.73 g. A photothermal conversion layer of / m ² was formed.
(Photothermal conversion layer coating solution 1)
Polyvinyl alcohol (Gohsenol EG-30: supra, volatile content 4%)
3.85 parts carbon black aqueous dispersion (CAB-O-JET300: manufactured by CABOT)
13.32 parts Boric acid 0.24 parts Fluorosurfactant (FT-251: Neos) 0.06 parts Pure water 63.73 parts i-Propyl alcohol 18.80 parts On the other hand, a transparent PET (thickness 75 μm) Using T100, # 75: manufactured by Mitsubishi Polyester Co., Ltd.), a backcoat layer coating solution 1 having the following composition was applied by wire bar coating to form a backcoat layer having a drying weight of 0.65 g / m ² . .
(Backcoat layer coating solution 1)
Polyvinyl alcohol (GOHSENOL EG-05: manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
4.72 parts Antistatic agent (Efcol 214: manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) 1.49 parts Mat material (57% aqueous solution of PMMA particles having a volume average particle size of 5.6 μm) 0.63 parts Fluororesin aqueous solution (Smiles) Resin FP-150: manufactured by Sumitomo Chemical Co., Ltd.) 1.99 parts Compounds listed in Table 2 0.03 parts Pure water 81.74 parts i-propyl alcohol 9.40 parts On the opposite side of the backcoat layer, The intermediate layer coating liquid 1 was applied by wire bar coating to form an intermediate layer having a dry weight of 7 g / m ² .
(Intermediate layer coating solution 1)
Styrene-ethylene-butylene block copolymer (kraton G1657: manufactured by Shell Japan) 10.0 parts tackifier (superester A100: manufactured by Arakawa Chemical Industries) 4.3 parts methyl ethyl ketone 17.1 parts toluene 68.6 parts Next Further, after the light-to-heat conversion layer of each sheet provided with the yellow ink layer and the light-to-heat conversion layer is combined with the intermediate layer by roll touch, the film with the release layer is peeled off, and the yellow transfer sheet Got.

<Preparation of magenta thermal transfer sheet>
A magenta transfer sheet was obtained in the same manner as the yellow transfer sheet except that the yellow ink layer coating solution was changed to a magenta ink layer coating solution having the following composition. The drying amount of the magenta ink layer coating solution was 0.67 g / m ² .
(Magenta ink layer coating solution)
Magenta pigment dispersion (15 parts of Brilliant Carmine 6B with 4.5 parts of dispersant MEK
Dispersed in 80.5 parts) 13.86 parts Styrene resin (Heimer ST-95: supra) 4.63 parts Acrylic resin (Dianal BR-102: supra) 0.40 parts Copolymer weight of styrene-butadiene block Combined (kraton D-1101CU: supra)
0.24 parts Fluorine-based surface activity (Megafac F-178K: supra) 0.09 parts Methyl ethyl ketone 16.38 parts Cyclohexanone 64.40 parts <Preparation of cyan transfer sheet>
A cyan transfer sheet was obtained in the same manner as the yellow transfer sheet except that the yellow ink layer coating solution was changed to a cyan ink layer coating solution having the following composition. The dry weight of the cyan ink layer coating solution was 0.70 g / m ² .
(Cyan ink layer coating solution)
Cyan pigment dispersion (30 parts of phthalocyanine blue dispersed in 65 parts of MEK with 5 parts of dispersant) 5.20 parts Styrene resin (Heimer ST-95: supra) 5.70 parts Acrylic resin (Dianal BR-102) 0.41 part styrene-butadiene block copolymer (kraton D-1101CU: supra)
0.25 parts Fluorine-based surface activity (Megafac F-178K: supra) 0.09 parts Methyl ethyl ketone 24.10 parts Cyclohexanone 64.26 parts <Preparation of black transfer sheet>
Except for changing the yellow ink layer coating liquid to a black ink layer coating liquid having the following composition and changing the photothermal conversion layer coating liquid 1 to the photothermal conversion layer coating liquid 2 having the following composition, the same as the preparation of the yellow transfer sheet. Thus, a black transfer sheet was obtained. The dry weight of the black ink layer coating solution was 0.87 g / m ² . The conversion amount of the conversion layer coating liquid 2 was 0.73 g / m ² .
(Black ink layer coating solution)
Black pigment dispersion (25 parts of carbon black dispersed in 70 parts of MEK with 5 parts of dispersant) 7.98 parts Cyan pigment dispersion (30 parts of phthalocyanine blue dispersed in 65 parts of MEK with 5 parts of dispersant) 1.07 parts Violet pigment dispersion (10 parts of dioxazine violet with 5 parts of dispersant MEK
1.47 parts Styrene resin (Haimer ST-95: supra) 6.22 parts Acrylic resin (Dianar BR-85: manufactured by Mitsubishi Rayon Co., Ltd.) 1.05 parts Styrene-isoprene block co-weight Combined (Kraton D-1117P: manufactured by Shell Japan Co., Ltd.) 0.21 part Fluorine-based surface activity (Megafac F-178K: supra) 0.11 part Methyl ethyl ketone 19.25 parts Cyclohexanone (Photothermal conversion layer coating solution 2)
Polyvinyl alcohol (Gohsenol EG-30: supra, volatile content 4%)
3.69 parts carbon black aqueous dispersion (CAB-O-JET300: manufactured by CABOT)
14.34 parts Boric acid 0.24 parts Fluorosurfactant (FT-251: supra) 0.06 parts Pure water 62.87 parts i-Propyl alcohol 18.80 parts <Preparation of image receiving sheet>
Backcoat layer coating liquid 2 having the following composition was applied by wire bar coating using a white PET (U51L74: manufactured by Teijin Ltd.) having a thickness of 100 μm as a support, and a backcoat layer having a dry weight of 2.3 g / m ^2. Formed.
(Backcoat layer coating solution 2)
Polyester resin (Byron 200: manufactured by Toyobo Co., Ltd.) 11.5 parts Black pigment dispersion (MHI Black # 273: manufactured by Gokoku Color Co., Ltd.) 6.6 parts Polyester-modified silicone (X-24-8300: manufactured by Shin-Etsu Chemical Co., Ltd.) 0.5 parts Polymethyl methacrylate particles (MX-1000: manufactured by Soken Chemical Co., Ltd.) 0.4 parts Methyl ethyl ketone 21.0 parts Toluene 20.0 parts Cyclohexanone 40.0 parts On the back surface of the back coat layer, a cushion layer having the following composition The coating liquid was applied by wire bar coating to form a cushion layer having a dry weight of 17.5 g / m ² .
(Cushion layer coating solution)
Polyethylene latex (Hitech S-3127: manufactured by Toho Chemical Industry Co., Ltd.) 94.3 parts Pure water 5.7 parts On the above cushion layer, the intermediate layer coating solution 2 having the following composition was applied by wire bar coating, and the dry weight was applied. An intermediate layer of 3.40 g / m ² was formed.
(Intermediate layer coating solution 2)
Ethylcellulose (STD10 (PREM): Dow Chemical Co., Ltd.) 9.5 parts Methanol-modified ethanol 90.5 parts On the intermediate layer, an image-receiving layer coating solution having the following composition was applied by wire bar coating, and the dry weight was 1. An image receiving layer of 35 g / m ² was formed.
(Image-receiving layer coating solution)
Acrylic resin (Iodozol A5801: manufactured by NSC Japan) 22.0 parts Fluororesin (Unidyne TG810: manufactured by Daikin Industries) 4.4 parts Polymethylmethacrylate particles (MX40S-2: manufactured by Soken Chemical Co., Ltd.) 2.1 parts pure water 62.8 parts i-propyl alcohol 8.7 parts <Formation of Transfer Image>
The image receiving sheet (56 cm × 79 cm) prepared above was wound around a rotating drum having a diameter of 35 cm in which a vacuum section hole having a diameter of 1 mm (one surface density per area of 3 cm × 8 cm) was opened and vacuum-adsorbed. Next, the thermal transfer sheet K (black) cut to 61 cm × 84 cm was overlapped so as to protrude evenly from the image receiving sheet, and squeezed with a squeeze roller and adhered and laminated so that air was sucked into the section holes. The degree of vacuum in the state where the section hole was blocked was −81.13 kPa with respect to 101.3 kPa (= 1 atm). The drum is rotated, and a semiconductor laser beam having a wavelength of 808 nm is focused on the surface of the laminated body on the drum from the outside so as to be a 7 μm spot on the surface of the photothermal conversion layer. A laser image (image line) was recorded on the laminate while moving in the direction perpendicular to the scanning direction (sub-scanning). The laser irradiation conditions are as follows. The laser beam used is a laser beam composed of a multi-beam two-dimensional array composed of parallelograms in five rows in the main scanning direction and three rows in the sub-scanning direction.

Laser power: 100mW
Drum rotation speed: K = 580, Y = M = 550, C = 560 rpm
Sub-scanning pitch: 6.35 μm
Environmental Temperature and Humidity: Two Conditions of 16 ° C./70% RH (LL), 27 ° C./70% RH (HH) The diameter of the exposure drum is preferably 360 mm or more, specifically, 380 mm. The image size is 515 mm × 728 mm, and the resolution is 4,000 dpi (supra). When the laser recording-completed laminate is removed from the drum and the thermal transfer sheet K is manually peeled off from the image receiving sheet, only the light irradiation area of the image forming layer of the thermal transfer sheet K is transferred from the thermal transfer sheet K to the image receiving sheet. Has been confirmed. The obtained image receiving sheet was superposed on Tokuhishi art paper, and the image was retransferred with a laminator TP-400 (manufactured by Konica Medical and Graphic) to obtain an evaluation sample.

  In the same manner as described above, an image was transferred onto the image receiving sheet from each of the thermal transfer sheets Y, M, and C. Also for these, the transfer image of each image-receiving sheet was re-transferred to Tokishi art paper, and used as an evaluation sample.

  The evaluation samples were evaluated in the same manner as in Example 1, and the results are shown in Table 2.

M-1: Mixture of 0.5% acetylene glycol surfactant (Dinol 604 5% solution: supra) and 0.5% silicone surfactant (SLYGARD309 5% methanol solution: supra) Fa: C ₈ F ₁₇ CH ₂ CH ₂ O (CH ₂ CH ₂ O) ₈ CH ₃
From Table 2, the advantages of the present invention are apparent.

Claims (6)

Using an image receiving sheet having at least an image receiving layer on a support and a thermal transfer sheet having at least a photothermal conversion layer and an image forming layer on the support, the image forming layer of each thermal transfer sheet and the image receiving layer of the image receiving sheet are opposed to each other. In an image forming material for superimposing and irradiating laser light from the thermal transfer sheet side to transfer the laser light irradiation area of the image forming layer onto the image receiving layer of the image receiving sheet and recording an image, the thermal transfer sheet sandwiches the support and the image An image forming material comprising a back coat layer on the side opposite to the forming layer, and the back coat layer containing a surfactant having a branched perfluoroalkyl group in the molecule. Using an image receiving sheet having at least an image receiving layer on a support and a thermal transfer sheet having at least a photothermal conversion layer and an image forming layer on the support, the image forming layer of each thermal transfer sheet and the image receiving layer of the image receiving sheet are opposed to each other. In an image forming material for superimposing and irradiating laser light from the thermal transfer sheet side to transfer the laser light irradiation area of the image forming layer onto the image receiving layer of the image receiving sheet and recording an image, the thermal transfer sheet sandwiches the support and the image An image forming material comprising a back coat layer on the opposite side of the forming layer, and the back coat layer containing a surfactant having two or more perfluoroalkyl groups in the molecule. Using an image receiving sheet having at least an image receiving layer on a support and a thermal transfer sheet having at least a photothermal conversion layer and an image forming layer on the support, the image forming layer of each thermal transfer sheet and the image receiving layer of the image receiving sheet are opposed to each other. In an image forming material for superimposing and irradiating laser light from the thermal transfer sheet side to transfer the laser light irradiation area of the image forming layer onto the image receiving layer of the image receiving sheet and recording an image, the thermal transfer sheet sandwiches the support and the image An image forming material comprising a back coat layer on the side opposite to the forming layer, and the back coat layer containing a surfactant having a C 1-7 perfluoroalkyl group. Using an image receiving sheet having at least an image receiving layer on a support and a thermal transfer sheet having at least a photothermal conversion layer and an image forming layer on the support, the image forming layer of each thermal transfer sheet and the image receiving layer of the image receiving sheet are opposed to each other. In an image forming material for superimposing and irradiating laser light from the thermal transfer sheet side to transfer the laser light irradiation area of the image forming layer onto the image receiving layer of the image receiving sheet and recording an image, the thermal transfer sheet sandwiches the support and the image It has a back coat layer on the side opposite to the forming layer, and the back coat layer contains at least one surfactant represented by the following general formula (1) to general formula (7). Image forming material.
The general formula ₍₁₎ Rf 1 -OR 1
Formula _{(2) Rf 1 -O-L} -Rf 1

In the general formulas (1) to (4), Rf ₁ represents a [(CF ₃ ) ₂ C] ₂ C═C (CF ₃ ) — group or a (CF ₃ ) ₂ C═C (C ₂ F ₅ ) — group. L represents a linking group, and R ₁ represents a polar group. a, b, c, d, e, f and g each represent an integer of 1 to 40.

In Formula (5) ~ (7), Rf 2 represents a perfluoroalkyl group having 1 to 7 carbon atoms, R ₂ represents a polar group. m1, m2, m3 and n1 each represents an integer of 1 to 40. Using an image receiving sheet having at least an image receiving layer on a support and a thermal transfer sheet having at least a photothermal conversion layer and an image forming layer on the support, the image forming layer of each thermal transfer sheet and the image receiving layer of the image receiving sheet are opposed to each other. In an image forming material for superimposing and irradiating laser light from the thermal transfer sheet side to transfer the laser light irradiation area of the image forming layer onto the image receiving layer of the image receiving sheet and recording an image, the thermal transfer sheet sandwiches the support and the image An image-forming material comprising a backcoat layer on the side opposite to the forming layer, and the backcoat layer contains an acetylene glycol surfactant and a silicone surfactant. 6. A method of forming an image using the image forming material according to claim 1, wherein the recording density of the laser beam is 1,250 dpi (dpi is the number of dots per inch = 2.54 cm) ) An image forming method as described above.