JP2005205763A - Image recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser-thermal-transfer image recording method which enables stable color reproduction and gradation reproduction, even in halftone dot reproduction and FM screening. <P>SOLUTION: This image recording method comprises: a step (a) of converting applied laser light into heat by a photothermal conversion layer of a thermal transfer sheet, and of transferring an image to an image receiving sheet by the heat; and a step (b) of retransferring the image to a final image carrier (printing paper for running-on). The image recording method is characterized as follows: in the thermal transfer sheet, at least the photothermal conversion layer and an ink layer are provided on a substrate; a melt viscosity at a retransfer temperature of a composition of the ink layer is in the range of 50-1,000 Pa s; a density area of at least a part of gradation expression is expressed by density gradation using a minute dot of a size of 30 μm or less, when the image is exposed to light; and a rubber hardness of a transfer roll for use in retransfer is in the range of 10-60°. Preferably, the thickness of the printing paper for running-on, which is subject to retransfer, is set at 20-50 g/m<SP>2</SP>or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image recording method, and more specifically, the image is transferred from a thermal transfer ink sheet to an image receiving sheet by laser light, and the image is further retransferred to a final image carrier (printing paper) to perform DDCP (Direct Digital Color Proof). The present invention relates to an image recording method suitable for creation.

  In recent years, with the digitization of the plate making process, the demand for DDCP has been increasing rapidly. Among them, the laser melting thermal transfer type DDCP is attracting attention as a method capable of accurately reproducing even the texture because halftone dots can be reproduced on the same paper as the printed matter.

  Incidentally, there is a method called FM screening as a gradation reproduction method by printing. Unlike the conventional halftone dot method, this method is a method in which the image density is controlled by the density of minute dots, and has advantages such as less moire. However, the printing plate process was difficult because the minute dots had to be expressed accurately, but since the stability of dot reproduction was significantly improved with the introduction of CTP (Computer-to-Plate), it has been attracting attention. Yes.

  In the case of DDCP, it is desirable that images created by FM screening have the same reproducibility and texture as printing, but the transfer pressure, ink physical properties, etc. are not exactly the same as in a printing machine, so a conventional halftone screen With the same setting, the subtle color tone may not approximate the printed matter. In particular, it is stable when expressing density by mixing density gradation and area gradation in one image, or when reproducing dots with different sizes in high density part and low density part, etc. There arises a problem that smooth gradation reproduction cannot be obtained.

In this regard, in a thermal transfer recording system using a high-power, multi-channel laser, as a laser thermal transfer film capable of obtaining stable color reproducibility in a wide range of environmental temperatures and humidity, the melt viscosity and content of the thermoplastic binder of the thermal transfer ink layer, and A technique for defining absorption at the exposure wavelength of the ink layer (see Patent Document 1) also binarizes the pixel of interest into an AM halftone signal and an FM halftone signal, and generates an AM halftone signal based on the color component signal. By selecting FM halftone signal and outputting it as recorded image data, a method for forming recorded image data that suppresses visually conspicuous moire and obtains a desired color tone without using fine paper (Patent Document) 1) and the like, but it was not sufficient to solve the problems in the DDCP.
JP-A-11-289465 JP 2001-199170 A (Claim 3)

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a laser thermal transfer type image recording method capable of obtaining stable color reproduction and gradation reproduction in both halftone reproduction and FM screening. There is.

  The above object of the present invention is achieved by the following configurations.

(Claim 1)
A step (a) of converting the laser light irradiated on the light-to-heat conversion layer of the thermal transfer sheet into heat, and transferring the image to the image receiving sheet by this heat, and a step of retransferring the image to the final image carrier (printing paper) ( In the image recording method including b), the thermal transfer sheet has at least a photothermal conversion layer and an ink layer on a support, and the melt viscosity at the retransfer temperature of the ink layer composition is 50 to 1,000 Pa · s. In the image exposure, at least a part of the density area of the gradation expression is expressed by a density gradation of fine dots of 30 μm or less, and the transfer roll used for retransfer has a rubber hardness of 10 to 60 °. A characteristic image recording method.

(Claim 2)
^2. The image recording method according to claim 1, wherein the thickness of the printing paper to be retransferred is 20 to 50 g / m < ² >.

  According to the present invention, it is possible to provide a color proof that is close to the original color reproduction and good image expression in both halftone dot reproduction and FM screening.

  Hereinafter, the present invention will be sequentially described in detail for a thermal transfer sheet, an image receiving sheet, and an image forming method.

<Thermal transfer sheet>
The thermal transfer sheet of the present invention comprises a photothermal conversion layer and an ink layer on a support, and further has a thermal softening layer, an intermediate layer, etc. between these layers and the support, if necessary.

(Support)
As the support of the thermal transfer sheet, any material can be used as long as it has good dimensional stability and can withstand the heat during image formation, and a conventionally known support can be used without particular limitation. The material, layer structure, size, etc. are appropriately selected and used.

  Examples of the support include various papers such as paper, coated paper, and synthetic paper (polypropylene, polystyrene, or a composite material obtained by bonding them to paper), vinyl chloride resin sheets, ABS resin sheets, polyethylene terephthalate films. , Polybutylene terephthalate film, polyethylene naphthalate film, polyarylate film, polycarbonate film, polyether ketone film, polysulfone film, polyether sulfone film, polyetherimide film, polyimide film, polyethylene film, polypropylene film, polystyrene film, stretched A single layer of nylon film, polyacetate film, etc., or various plastic films or sheets obtained by laminating two or more layers thereof, formed of various metals Film or sheet, film or sheet made of various ceramics, metal plates such as aluminum, stainless steel, chromium, nickel, etc., laminated or vapor-deposited metal thin film on resin-coated paper, kneaded white pigment Examples generally include white PET. A conventionally known surface modification technique can be suitably used for the support.

  In the present invention, since the adhesion to the lower layer can be obtained stably, it is also preferable to use a support that has been subjected to adhesion treatment or provided with an adhesion layer.

Examples of the adhesion treatment include flame emission treatment, sulfuric acid treatment, corona discharge treatment, and plasma treatment. Among these, corona discharge treatment is preferable, and the output is preferably ²⁰ to 80 W / m ² , particularly preferably 30 to 70 W / m ² .

  A conventionally well-known thing can be especially used as a contact bonding layer without a restriction | limiting. Examples of the method for providing the adhesive layer include water-based resin coating, solvent-based resin coating, water-based latex coating, and hot melt coating.

  The preferred film thickness of the support is 25 to 200 μm, more preferably 25 to 100 μm.

  If an image is formed by irradiating laser light from the thermal transfer sheet side, the support of the thermal transfer sheet is desirably transparent. If the image is formed by irradiating laser light from the image receiving sheet side, the support of the thermal transfer sheet does not need to be transparent.

(Photothermal conversion layer)
The photothermal conversion layer is composed of a binder and a photothermal conversion material. As a photothermal conversion substance, although it changes with light sources, the substance which absorbs light and converts into heat efficiently is good, for example, when using a semiconductor laser as a light source, the substance which has an absorption band in near infrared is preferable. Near-infrared light absorbers include, for example, carbon black, cyanine-based, polymethine-based, azulenium-based, squalium-based, thiopyrylium-based, naphthoquinone-based, anthraquinone-based organic compounds such as phthalocyanine-based, azo-based, and thioamide-based organic metals. Complexes and the like are preferably used, and specifically, JP-A-63-139191, JP-A-64-33547, JP-A-1-160683, JP-A-1-280750, JP-A-1-293342, and JP-A-2-2074. 3-26593, 3-30991, 3-34891, 3-36093, 3-36094, 3-36095, 3-42281, 3-97589, Examples include compounds described in No. 3-103476. These can be used alone or in combination of two or more.

  As a binder for the photothermal conversion layer, a resin having a high Tg and a high thermal conductivity, such as polymethyl methacrylate, polycarbonate, polystyrene, ethyl cellulose, nitrocellulose, polyvinyl alcohol, polyvinyl chloride, polyamide, polyimide, polyetherimide, polysulfone, Common heat resistant resins such as polyethersulfone and aramid can be used.

  Moreover, a water-soluble polymer can also be used as a binder of a photothermal conversion layer. The water-soluble polymer is preferable in that it has good releasability from the ink layer, good heat resistance during light irradiation, and less so-called scattering even when excessively heated. When a water-soluble polymer is used, it is desirable that the photothermal conversion substance is modified to be water-soluble (for example, by introduction of a sulfo group) or dispersed in water. Among water-soluble resins, gelatin is preferable because it hardly causes aggregation of water-soluble infrared absorbing dyes and does not cause stable coating of a light-to-heat conversion layer, storage of a recording medium, color turbidity due to aggregation of infrared absorbing dyes, and sensitivity reduction. Further, increasing the peelability between the photothermal conversion layer and the ink layer leads to an improvement in sensitivity, and therefore it is effective to incorporate various release agents into the photothermal conversion layer. Examples of release agents include silicone release agents (polyoxyalkylene-modified silicone oil, alcohol-modified silicone oil, etc.), fluorine-based surfactants (perfluorophosphate ester-based surfactants), and other various surfactants. Etc. are effective.

  The film thickness of the photothermal conversion layer is preferably from 0.1 to 3 μm, more preferably from 0.2 to 1.0 μm. The content of the photothermal conversion substance in the photothermal conversion layer is usually determined such that the absorbance at the wavelength of the light source used for image recording is 0.3 to 3.0, more preferably 0.7 to 2.5. it can.

  In addition to this, a vapor deposition film can also be used as the photothermal conversion layer. Carbon black, gold, silver, aluminum, chromium, nickel, antimony, tellurium, bismuth described in JP-A No. 52-20842, A vapor deposition layer of metal black such as selenium can be used. The photothermal conversion substance may be the color material itself of the ink layer, and is not limited to the above, and various substances can be used.

(Ink layer)
The ink layer means a layer which can be transferred for each layer containing a colorant, a binder and the like by being melted or softened when heated, and may not be transferred in a completely melted state.

  Examples of the colorant include inorganic pigments (titanium dioxide, carbon black, graphite, zinc oxide, Prussian blue, cadmium sulfide, iron oxide and lead, zinc, barium and calcium chromates) and organic pigments (azo, Pigments and dyes (acid dyes, direct dyes, disperse dyes, oil-soluble dyes) such as thioindigo, anthraquinone, anthanthrone, triphendioxazine pigments, vat dye pigments, phthalocyanine pigments and derivatives thereof, quinacridone pigments, Metal-containing oil-soluble dyes or sublimable dyes).

  For example, when a color proof material is used, yellow, magenta, and cyan are C.I. I. 21095 or C.I. I. 21090, C.I. I. 15850: 1, C.I. I. 74160 pigment is preferably used.

  The content of the color material in the ink layer is not particularly limited, but is usually in the range of 5 to 70% by mass, preferably 10 to 60% by mass.

  Examples of the binder for the ink layer include a heat-meltable substance, a heat-softening substance, and a thermoplastic resin. The hot-melt material is usually a solid or semi-solid material having a melting point measured using Yanagimoto MJP-2 type in the range of 40 to 150 ° C. Specifically, plant waxes such as carnauba wax, wood wax, aucuric wax and espal wax; animal waxes such as beeswax, insect wax, shellac wax and whale wax; paraffin wax, microcrystal wax, polyethylene wax, ester wax, acid Petroleum waxes such as waxes; and waxes such as mineral waxes such as montan wax, ozokerite, and ceresin. In addition to these waxes, palmitic acid, stearic acid, margaric acid, behenic acid, etc. Higher fatty acids; higher alcohols such as palmityl alcohol, stearyl alcohol, behenyl alcohol, marganyl alcohol, myricyl alcohol, eicosanol; higher fatty acid esters such as cetyl palmitate, myricyl palmitate, cetyl stearate, myricyl stearate; acetamide Amides propionic acid, palmitic acid amide, stearic acid amides such as amide wax; and stearylamine, behenylamine, like higher amines such as palmityl amine.

  Thermoplastic resins include ethylene copolymers, polyamide resins, polyester resins, polyurethane resins, polyolefin resins, acrylic resins, vinyl chloride resins, cellulose resins, rosin resins, polyvinyl alcohol resins. Resins such as resins, polyvinyl acetal resins, ionomer resins, petroleum resins; elastomers such as natural rubber, styrene butadiene rubber, isoprene rubber, chloroprene rubber, diene copolymer; ester gum, rosin maleic resin, rosin phenol resin And rosin derivatives such as hydrogenated rosin; and polymer compounds such as phenol resin, terpene resin, cyclopentadiene resin, and aromatic hydrocarbon resin.

  A thermal transfer layer having a desired thermal softening point or thermal melting point can be formed by appropriately selecting the above-mentioned hot-melt material and thermoplastic material.

  In the present invention, it is essential that the melt viscosity at a temperature at which the ink layer composition is retransferred is 50 to 1,000 Pa · s. When the melt viscosity is less than 50 Pa · s, the fluidity of the ink layer microdots to be transferred is too high, so that bleeding, displacement, etc. occur, and stable dots cannot be formed. On the other hand, if the melt viscosity seems to exceed 1,000 Pa · s, the melt heat transferability deteriorates and normal image formation cannot be achieved. The melt viscosity of this thermoplastic binder can be measured using a BH viscometer manufactured by Tokimec Co., Ltd.

  When the temperature of the heat roll of the retransfer apparatus is 120 ° C., the melt viscosity of the measurement object can be known by setting the measurement object to 120 ° C. The range of the thermoplastic binder having a melt viscosity of 50 Pa · s or more varies depending on the type of polymer, but among the thermoplastic binders described above, the weight average molecular weight (Mw) is 10,000 or more and the glass transition temperature (Tg) is 60 ° C. The above polymers are preferred. Of these, ethylene resins, styrene resins, acrylic resins, polyvinyl acetal resins such as polyvinyl butyral, and ionomer resins are preferable. Elastomers such as styrene butadiene are preferred because of their high viscosity at high temperatures even at low Tg.

  In order to secure the dispersibility of the pigment and obtain a good color reproduction, it is effective to use various dispersants. Other additives include a plasticizer that increases the sensitivity by plasticizing the ink layer, a surfactant that improves the coatability of the ink layer, and submicron to micron order particles that prevent blocking of the ink layer. (Matte material) can be added.

  The thickness of the ink layer is preferably 0.2 to 2 μm, more preferably 0.3 to 1.5 μm, and high sensitivity can be obtained particularly when the thickness is 0.8 μm or less.

(Back coat layer)
In order to provide functions such as running stability, heat resistance, and antistatic properties, a back coat layer described in the image receiving sheet described later can be provided on the back surface of the support.

<Image-receiving sheet>
Next, an image receiving sheet that receives an image transferred imagewise from a thermal transfer sheet will be described. The image-receiving sheet basically has an image-receiving layer on a support. However, in order to improve adhesion to the thermal transfer sheet, transportability, transferability, etc., a thermal softening layer is provided between the image-receiving layer and the support. The back coat layer can be provided on the surface (back surface) opposite to the image receiving layer.

(Support)
As the support for the image receiving sheet, the same materials as those described for the thermal transfer sheet can be used. The preferred film thickness of the support is 25 to 200 μm, more preferably 25 to 100 μm.

(Image receiving layer)
The image receiving layer is usually composed of a binder, a mat material, and various additives added as necessary. The image receiving layer preferably has a softening point of 100 ° C. or less as measured by TMA (thermogravimetric analysis) (for example, contains a thermoplastic resin having a TMA softening point of 100 ° C. or less), more preferably 80 ° C. or less, and 60 ° C. It is particularly preferred that

  The TMA softening point can be obtained by raising the temperature of the measurement object while applying a constant heating rate and a constant load and observing the phase of the measurement 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. Measurement of the softening point by TMA can be performed using an apparatus such as Thermoflex (manufactured by Rigaku Corporation). For example, when using Thermoflex, measuring temperature range 25-200 ° C., and heating rate 5 ° C./min, TMA softening point with temperature at which phase starts to change when a constant load is applied to a 1 mmφ quartz glass pin And

  Specific examples of binders used in the image receiving layer include polyvinyl acetate emulsion adhesives, chloroprene adhesives, epoxy resin adhesives, natural rubber, chloroprene rubber, butyl rubber, polyacrylate , Nitrile rubber, polysulfide, silicone rubber, petroleum resin, etc., recycled rubber, vinyl chloride resin, SBR, polybutadiene resin, polyisoprene, polyvinyl butyral resin, polyvinyl ether, ionomer resin, SIS, SEBS , Acrylic resin, ethylene copolymer, ethylene-vinyl chloride copolymer, ethylene-acrylic copolymer, ethylene-vinyl acetate resin (EVA), PVC graft EVA resin, EVA graft PVC resin, vinyl chloride resin, various modified Olefin, polyvinyl butyler Etc. The.

  The above resins may be used alone or in combination of two or more, but may be used in combination with additives and the like.

  Although the sensitivity can be improved by setting the TMA softening point of the image receiving layer low, fog may occur on the other hand. In addition, it is effective to add a mat material to the image receiving layer for the purpose of improving the removal of gas generated during exposure as the output image is enlarged. The average particle size of the mat material is preferably 0.3 to 10.0 μm larger than the average film thickness of the portion of the image receiving layer where the mat material does not exist, more preferably 0.3 to 8.0 μm. Of these, those larger by 1 to 5.5 μm are effective and particularly preferable.

  If it is less than 0.3 μm, the effect on fog and gas removal is small, and if it exceeds 10.0 μm, the sensitivity is deteriorated. A particle having a distribution in which the particle mass that is twice or more the average particle size is 20% or less is preferable, and a particle having a distribution in which the particle mass that is twice or more the average particle size is 5% or less is more preferable.

  If the mat material has a particle mass of 20% or less that is twice or more the average particle size, the pressure is uniformly relieved, so that deterioration in storage stability such as blocking can be suppressed. It is more preferable in terms of storage stability to use a particle having a particle mass that is twice or more the average particle size and 5% or less.

  When such a mat material is selected, if the film thickness of the image receiving layer is set to 3.0 μm or more, if an appropriate mat material is added in accordance with the thickness, the mat material is too much and a yellowish image is obtained. The film thickness of the image receiving layer is preferably 3.0 μm or less.

  As the material of the mat material, both organic and inorganic materials can be used, and known organic fine particles such as acrylic resin such as PMMA (polymethyl methacrylate), fluorine-based resin, and silicon resin can be used. In order to increase the strength and solvent resistance of the particles, crosslinked organic fine particles are more preferable.

(Middle layer)
It is also preferable to provide an intermediate layer between the image receiving layer and the support. Specific examples of the binder for the intermediate layer include polyester, polyvinyl acetal, polyvinyl formal, polyparabanic acid, polymethyl methacrylate, polycarbonate, ethyl cellulose, nitrocellulose, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, polyvinyl chloride, and polystyrene. , Styrenes such as acrylonitrile styrene and those obtained by crosslinking these resins, polyamides, polyimides, polyetherimides, polysulfones, polyethersulfones, aramids and other thermosetting resins having a Tg of 65 ° C. or higher, and cured products of these resins. It is done. As the curing agent, general curing agents such as isocyanate and melamine can be used.

  When the binder for the intermediate layer is selected according to the above physical properties, polycarbonate, acetal, and ethyl cellulose are preferable in terms of storage stability. Further, when an acrylic resin is used for the image receiving layer, releasability is improved when the image after laser thermal transfer is retransferred. Particularly preferred.

Regarding the physical properties and film thickness of the binder used for the intermediate layer, when the Tg of the binder is 140 ° C. or higher or the tensile strength is 5.0 kg / cm ² or higher, the film thickness is preferably 0.2 to 10 μm. Is 80 to 140 ° C. or a tensile strength of 3.5 to 5.0 kg / cm ² , the film thickness is preferably 0.2 to 15 μm.

  In addition, by adjusting the average particle size, particle size distribution, addition amount, shape, and material of the mat material contained in the image receiving layer, a layer that has extremely low adhesion to the image receiving layer during cooling can be used as an intermediate layer. Can do. Specifically, it can be a layer mainly composed of a heat-melting compound such as waxes and a binder, or a thermoplastic resin.

  Examples of the hot-melt compound include substances described in JP-A-63-193886. In particular, microcrystalline wax, paraffin wax, carnauba wax and the like are preferably used. As the thermoplastic resin, an ethylene copolymer such as an ethylene-vinyl acetate resin, a cellulose resin, or the like is preferably used.

  Examples of the method for forming the intermediate layer include a blade coater, a roll coater, a bar coater, a curtain coater, a gravure coater, and the like, in which the material is dissolved in a solvent or dispersed in a latex form, an extrusion lamination method using hot melt, and the like. It can be applied and can be applied and formed on the lower layer. Alternatively, there is a method in which a material obtained by dissolving the raw material in a solvent or dispersed in a latex form on a temporary base is bonded to a layer applied with the above method and the lower layer, and then the temporary base is peeled off.

(Thermo-softening layer)
The thermosoftening layer is preferably made of a material that does not exhibit fluidity at room temperature and exhibits elasticity. Further, in a high temperature region exceeding 100 ° C., it is required to show a remarkable change in fluidity.

  As long as such physical properties can be achieved, it can be achieved with a single layer or with two or more composite layers, and can be achieved with a single material or with multiple materials. .

  The preferred properties of the heat softening layer are not necessarily specified by the type of material, but the preferred properties of the material itself include ethylene copolymers, ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, Polybutadiene resin, styrene-butadiene copolymer (S), styrene-ethylene-butene-styrene copolymer (SEBS), acrylonitrile-butadiene copolymer (N), polyisoprene resin (IR), styrene-isoprene copolymer (SIS), acrylate copolymer, polyester resin, polyurethane resin, acrylic resin, butyl rubber, polynorbornene and the like.

  Even with materials other than those described above, preferable characteristics can be obtained by adding additives. Examples of the additive include a low melting point material such as wax, a plasticizer, a thermal solvent, and a tackifier.

  Specific examples of waxes include plant waxes such as carnauba wax, wood wax, aucuric wax, and espal wax; animal waxes such as beeswax, insect wax, shellac wax, and whale wax; paraffin wax, microcrystal wax, and polyethylene wax And waxes such as mineral waxes such as montan wax, ozokerite, and ceresin. Besides these waxes, palmitic acid, stearic acid, margaric acid Higher fatty acids such as behenic acid; higher alcohols such as palmityl alcohol, stearyl alcohol, behenyl alcohol, marganyl alcohol, myricyl alcohol, eicosanol; higher fatty acids such as cetyl palmitate, myricyl palmitate, cetyl stearate, myricyl stearate D Ether; acetamide, amides propionic acid, palmitic acid amide, stearic acid amides such as amide wax; and stearylamine, behenylamine, like higher amines such as palmityl amine.

  Among these, those having a solid at room temperature are preferred, those having a melting point of 40 to 130 ° C. are particularly preferred, and those having a melting point of 70 to 110 ° C. are more preferred.

  The wax may be used after being melted and mixed with a thermoplastic resin having a TMA softening point of less than 100 ° C., or may be present in the resin as a dispersion. When present in the resin as a dispersion, the wax itself preferably has a fine dispersion average particle size, preferably 0.01 to 3 μm, more preferably 0.05 to 1 μm.

  When such a solid wax is used, the addition amount can be used in the range of 1 to 70% by mass, and more preferably in the range of 5 to 50% by mass. The compound which is liquid at normal temperature is used at 10% by mass, more preferably 5% by mass or less.

  Specific examples of the plasticizer, thermal solvent, and tackifier include phthalic acid ester, adipic acid ester, glycol ester, fatty acid ester, phosphoric acid ester, and chlorinated paraffin. In addition, various additives described in, for example, “Practical Handbook for Additives for Plastics and Rubber”, Chemical Industry Co., Ltd. (published in 1970) can be added.

  What is necessary is just to select the addition amount of these additives, etc. required in order to express a preferable physical property in combination with the lower layer raw material used as a base.

  Even with materials other than those described above, preferable characteristics can be obtained by adding additives. Examples of the additive include a low melting point material such as wax, a plasticizer, a thermal solvent, and a tackifier.

  Specific examples of waxes include plant waxes such as carnauba wax, wood wax, aucuric wax, and espal wax; animal waxes such as beeswax, insect wax, shellac wax, and whale wax; paraffin wax, microcrystal wax, and polyethylene wax And waxes such as mineral waxes such as montan wax, ozokerite, and ceresin. Besides these waxes, palmitic acid, stearic acid, margaric acid Higher fatty acids such as behenic acid; higher alcohols such as palmityl alcohol, stearyl alcohol, behenyl alcohol, marganyl alcohol, myricyl alcohol, eicosanol; higher fatty acids such as cetyl palmitate, myricyl palmitate, cetyl stearate, myricyl stearate D Ether; acetamide, amides propionic acid, palmitic acid amide, stearic acid amides such as amide wax; and stearylamine, behenylamine, like higher amines such as palmityl amine.

  Among these, those having a solid at normal temperature are preferable, and those having a melting point of 40 to 130 ° C are particularly preferable, and those having a melting point of 70 to 110 ° C are more preferable.

  The wax may be used after being melted and mixed with a thermoplastic resin having a TMA softening point of less than 100 ° C. or may be present in the resin as a dispersion. When present in the resin as a dispersion, the wax itself preferably has a fine dispersion average particle size, preferably 0.01 to 3 μm, more preferably 0.05 to 1 μm.

  When such a solid wax is used at room temperature, the addition amount can be used in the range of 1 to 70% by mass, and more preferably in the range of 5 to 50% by mass. The compound which is liquid at normal temperature is used at 10% by mass, more preferably 5% by mass or less.

  Specific examples of the plasticizer, thermal solvent, and tackifier include phthalic acid ester, adipic acid ester, glycol ester, fatty acid ester, phosphoric acid ester, and chlorinated paraffin. In addition, various additives described in, for example, “Practical Handbook for Additives for Plastics and Rubber”, Chemical Industry Co., Ltd. (published in 1970) can be added.

  What is necessary is just to select the addition amount of these additives, etc. required in order to express a preferable physical property in combination with the lower layer raw material used as a base.

  As a method for forming the lower layer, the above materials dissolved in a solvent or dispersed in a latex form are applied to coating methods such as blade coaters, roll coaters, bar coaters, curtain coaters, gravure coaters, extrusion lamination methods using hot melt, etc. it can.

  The preferred thickness of the lower layer is 5 μm or more, more preferably 10 μm or more. If the thickness of the lower layer is 5 μm or less, missing or chipping may occur at the time of retransfer to the final transfer target.

  The preferable film thickness of the heat softening layer is 5 μm or more, more preferably 10 μm or more. If the thickness of the heat softening layer is less than 5 μm, omission or chipping may occur during retransfer to the final image carrier.

(Back coat layer)
A back coat layer is preferably provided on the back surface of the support to provide functions such as running stability, heat resistance, and antistatic properties.

  As the antistatic agent that can be used, for example, metal oxides such as carbon black, graphite, tin oxide, zinc oxide and titanium 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 backcoat layer and a stable antistatic effect can be obtained regardless of the environment such as temperature.

  Since the image-receiving sheet performs close-contact recording with the thermal transfer sheet, it is preferable that the back coat layer is roughened and the smoother value (suction pressure) is set to an appropriate value.

As means for obtaining the appropriate smoother value, for example, the following method can be employed.
(A) After providing the backcoat resin layer, the backcoat surface is roughened by embossing.
(B) The matte material is added to the back coat layer to make the back coat surface uneven.
(C) A support having an unevenness from the beginning is used as a support, and a backcoat layer having unevenness is provided by providing a backcoat layer having the unevenness or less.

  In thermal transfer recording that requires a particularly fine image, it is preferable to use a smooth film or sheet as the support for the recording material. Therefore, the suction pressure value required by the method (b), which is 40 kPa in the present invention, is used. It is particularly preferable to obtain (= 300 mmHg) or less. A more preferable value is 20 kPa (= 150 mmHg) or less.

  The suction pressure on the backcoat layer surface can be measured using Smoother SM-6B (manufactured by Toei Electric Industry Co., Ltd.).

  Binders used in the back coat 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, Teflon (R) resin, polyvinyl butyral resin, vinyl chloride resin, polyvinyl acetate, polycarbonate, organic boron compounds, aromatic esters, fluorinated polyurethane, poly General-purpose polymers such as ether sulfone, polyester resin, and polyamide resin can be used.

  Using a crosslinkable binder as the binder for the backcoat layer is effective in preventing powder fall of the mat material contained and improving the scratch resistance of the backcoat. It is also very effective for blocking during storage.

  This cross-linking means can employ any one of heat, actinic light, pressure, or a combination without particular limitation depending on the characteristics of the cross-linking agent used. Depending on the case, in order to provide the adhesiveness to a support body, you may provide arbitrary easy-adhesion layers in the side which provides the backcoat layer of a support body.

  As the mat material preferably added to the back coat layer, organic or inorganic fine particles can be used. Examples of the organic mat material include polymethyl methacrylate (PMMA), polystyrene, polyethylene, polypropylene, fine particles of other radical polymerization polymers, fine particles of condensation polymers such as polyester and polycarbonate, and the like.

The back coat layer is preferably provided at a weight of about 0.5 to 3 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 mat material are likely to occur. Further, if the coating material is applied greatly exceeding 3 g / m ² , the particle size of a suitable mat material becomes very large, and the image receiving layer surface is embossed by back coating during storage, and in particular a thin film for transferring a thin colorant layer In the melt thermal transfer recording, missing or unevenness of the recorded image is likely to occur.

The mat material preferably has a number average particle size larger by 5 μm or more than the film thickness of only the binder of the backcoat layer. Among the mat members, foreign matter failure is particularly improved by making particles having a particle diameter of 8 μm or more 5 mg / m ² or more. Also, as the particle size number average particle value divided by diameter sigma / r _n the standard deviation of the distribution (= coefficient of variation of particle size distribution) is 0.3 or less, by using a narrow particle size distribution In addition to improving defects caused by particles having an abnormally large particle size, desired performance can be obtained with a smaller addition amount. The variation coefficient is more preferably 0.15 or less.

An antistatic agent is preferably added to the backcoat layer in order to prevent adhesion of foreign matter due to frictional charging with the transport roll. The amount of the antistatic agent added is preferably such that the surface resistivity of the layer or support of the intermediate transfer medium at a relative humidity of 80% or less is 10 ⁸ to 10 ¹² Ω / m ² .

  In addition, various activators, mold release agents such as silicone oil, fluorine-based resins, and the like can be added to the back coat layer in order to impart coatability and mold release properties.

<Image recording method>
In the image recording method of the present invention, an image formed on the image receiving layer of the image receiving sheet is transferred from the ink layer of the thermal transfer sheet onto the final image carrier to form an image.

  As an exposure method using a laser, there are a method of exposing from the support side of the thermal transfer sheet while the thermal transfer sheet and the image receiving sheet are in close contact, and a method of exposing via the image receiving sheet.

  When exposed from the support side of the thermal transfer sheet, the colorant capable of absorbing heat rays in the image receiving layer and / or the thermal softening layer so that light that could not be absorbed by the thermal transfer sheet is absorbed by the image receiving layer and / or the thermal softening layer. Adding heat to efficiently use heat also has an effect of improving transferability.

  In the latter case, the transmittance with respect to the wavelength of the light source through the image receiving sheet is preferably 70% or more, more preferably 80% or more in order to allow the ink layer to absorb the energy of the light source without waste. For this purpose, it is necessary to use a support and a heat softening layer having good transparency and to reduce reflection at the back coat surface of the support and the interface between the support and the heat softening layer. As a method for reducing the reflection at the interface between the support and the thermal softening layer, it is preferable to reduce the refractive index of the thermal softening layer by 0.1 or more relative to that of the support.

(FM screening)
FM screening is a method of expressing light and shade based on the density of minute dots. The minimum dot size used in FM screening is preferably 5 to 30 μm in diameter. If it is smaller than 5 μm, dot formation is not stable and there is a concern about tone jump. On the other hand, if the size is larger than 30 μm, dots are observed with the naked eye, resulting in unnatural graininess in the image.

  In the present invention, known FM screening can be used. Specifically, FAIRDOT (Dainippon Screen Mfg. Co., Ltd.), Staccato (Creo), Co-Re Screening (Fuji Photo Film Co.), Sublima (Agfa), A diamond screen (manufactured by Heidelberg), crystal raster (Agfa) or the like is preferably used.

  In these commercially available FM screens, not all density areas are expressed in density gradation, but the highlight area is density-oriented in consideration of density stability and printing durability when printing many sheets. Some of them have their own tuning, such as using gradation, and using halftone to shadow areas with area gradation. In this way, screening using both density gradation and area gradation needs to precisely match the dot gain at small dots that were not a problem with conventional area gradation (halftone dot) screening. In addition, since area gradation is also used, it is necessary to maintain a balance with a large point characteristic having a large area in one image.

  In addition, in order to respond quickly and accurately to various printing presses and various screening printing data as a proof, it is possible to use small screen dots for FM screens without degrading the appropriate output of screening data based on area gradations. The dot gain characteristics of the printing machine and the proofer having different ink viscosities, printing pressures, transfer speeds, and the like have been very difficult to achieve.

  In the present invention, even when two or more dot sizes or two or more gradation reproduction techniques are mixed in one image, natural reproducibility approximated to a printed matter can be obtained without special adjustment. The final output can be obtained.

(Laminator)
A laminator for retransferring an image created on an image receiving sheet to a final image carrier (printing paper) is a device shown in Japanese Patent Laid-Open Nos. 2000-37911, 2000-62332, 2000-71634, 2003-18221, and the like. It can be preferably used.

  As disclosed in these patents, retransfer is a process in which the image receiving sheet and the final image carrier are superposed, and the image receiving layer of the image receiving sheet is transferred to the final image carrier with heat and pressure by a laminator heat roll. To do.

The retransfer temperature in the present invention means the temperature of the surface of the heat roll, and more specifically, the surface temperature of the heat roll provided on the image receiving sheet side. The temperature of the hot roll surface is preferably 80 to 140 ° C. When transferring to a thin paper of 50 g / m ² or less, 80 to 120 ° C. is particularly preferable. The rubber hardness of the transfer roll is preferably in the range of 10 to 60 °. If the angle is less than 10 °, the transportability deteriorates due to the adhesiveness of the rubber, and if it exceeds 60 °, small-point transfer cannot be stably obtained.

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

<Preparation of image receiving sheet 1 for laser thermal transfer>
Apply a back coat layer on one side of a white PET film (U51L74: manufactured by Teijin Ltd.) with a thickness of 100 μm, and apply each coating solution for the thermal softening layer, intermediate layer and image receiving layer on the opposite side of the same layer with a wire bar. -Drying to obtain an image receiving sheet 1 for thermal transfer. The number of mat members on the image receiving layer of this image receiving sheet was 920 / mm ² .

Back coat layer: 100 ° C., 1 minute, film thickness after drying 3 μm
Thermal softening layer: 100 ° C., 5 minutes, film thickness after drying 15 μm
Intermediate layer: 80 ° C., 1 minute, film thickness after drying 3 μm
Image receiving layer: 80 ° C., 1 minute, film thickness after drying 1.3 μm
(Backcoat layer coating solution 1)
Polyester resin (Byron 200: manufactured by Toyobo Co., Ltd.) 11.5 parts Matt material (MX-1000: manufactured by Soken Chemical Co., Ltd.) 0.4 parts Carbon black dispersion (MHI Black # 273: manufactured by Mikuni Dye Co., Ltd.) 6.6 parts Cyclohexanone 40 parts Toluene 20 parts Methyl ethyl ketone 25 parts (thermal softening layer coating solution 1)
Polyethylene latex (Hitech S-3127: manufactured by Toho Chemical Industry Co., Ltd.) 95 parts Pure water 5 parts (intermediate layer coating solution 1)
Ethylcellulose (STD10: manufactured by Dow Chemical Co.) 9.5 parts Methanol-modified ethanol 90.5 parts (Image-receiving layer coating solution 1)
Acrylic resin latex (Yodosol A5801 manufactured by NSC Japan) 22.0 parts Fluororesin (Unidyne TG810: manufactured by Daikin Industries) 4.4 parts Mat material (MX40S-2: manufactured by Soken Chemical Co., Ltd.) 2.1 parts Pure water 62 .8 parts i-propyl alcohol 8.7 parts [Preparation of thermal transfer sheet set 1]
A yellow ink sheet 1, a magenta ink sheet 1, a cyan ink sheet 1, and a black ink sheet 1 were prepared by the following method, and a thermal transfer sheet set 1 composed of Y, M, C, and K thermal transfer sheets was obtained.

<Preparation of Yellow Ink Sheet 1>
A transparent PET film having a thickness of 38 μm (Mitsubishi Chemical Polyester: T100 # 38) was used as a support, and a release layer coating solution having the following composition was applied and dried on the reverse roll coater. A release layer of 3 g / m ² was formed.
(Release layer coating solution)
Release layer binder liquid * 22.9 parts Crosslinking agent (Sumitomo Chemical Co., Ltd .: Sumire's Resin 613) 0.2 parts Pure water 69.2 parts i-Propyl alcohol 7.7 parts (* release layer binder liquid)
Polyvinyl alcohol aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd .: 9.5% aqueous solution of Gohsenol EG-30) 97.2 parts Cross-linking accelerator (Sumitex Accelerator ACX-P: manufactured by Sumitomo Chemical Co., Ltd.) 1.3 parts Fluorine-based surface activity Agent (Daikin Kogyo Co., Ltd .: Unidyne TG-810) 0.3 parts Pure water 1.2 parts On the release layer, a yellow ink layer coating liquid having the following composition is applied and dried by wire bar coating, and then dried. An ink layer having a weight of 0.65 g / m ² was formed.
(Yellow ink layer coating solution 1)
Yellow pigment dispersion (10 parts of Seika First Yellow H-7055 dispersed in MEK88 parts with 2 parts of dispersant) 18.2 parts Styrene resin (Hymer SBM73F: manufactured by Sanyo Chemical Industries, Ltd., melt viscosity at 120 ° C is 5.6 parts Fluorine-based surfactant (Megafac F-178K: manufactured by Dainippon Ink & Chemicals, Inc.) 0.1 part Methyl ethyl ketone 11.5 parts Cyclohexanone 64.5 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 to form a photothermal conversion layer having a drying amount of 0.73 g / m ² .
(Photothermal conversion layer coating solution 1)
Polyvinyl alcohol (GOHSENOL EG-30: manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
4.0 parts carbon black dispersion (CAB-O-JET300: manufactured by CABOT)
13.5 parts Boric acid 0.2 parts Fluorine-based surfactant (FT-251: manufactured by Neos) 0.1 part Pure water 63.4 parts i-Propyl alcohol 18.8 parts On the other hand, 75 μm thick transparent PET ( A back coat layer coating liquid 1 having the following composition was applied by wire bar coating using a Mitsubishi Chemical Polyester Co., Ltd. product: T100 # 75) as a support to form a back coat layer having a drying weight of 0.65 g / m ² .
(Backcoat layer coating solution 1)
Polyvinyl alcohol (Gosenol EG-05: supra) 4.7 parts Antistatic agent (Efcol 214: manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) 1.5 parts Mat material (57% aqueous solution of PMMA particles having a volume average particle size of 5.6 μm) 0.6 parts Fluorine-based resin aqueous solution (Smileze Resin FP-150: manufactured by Sumitomo Chemical Co., Ltd.) 2.0 parts Fluorine-based surfactant (Megafac F-142D: manufactured by Dainippon Ink & Chemicals, Inc.)
0.1 part pure water 81.3 parts i-propyl alcohol 9.4 parts The intermediate layer coating solution 1 having the following composition is applied to the back surface of the back coat layer by wire bar coating, and the dry weight is 7 g / m ² . An intermediate layer was formed.
(Intermediate layer coating solution 1)
Styrenic block copolymer (Kraton G1657: manufactured by Kraton Polymer Japan Co., Ltd.) 10.0 parts Rosin ester (Superester A-100: 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 bonded to the intermediate layer by roll touch, the film with a release layer is peeled off to remove the yellow ink sheet 1 Obtained. In this ink sheet, an intermediate layer, a light-to-heat conversion layer, and a yellow ink layer are laminated on a PET support, and a back coat layer is provided on the side opposite to the ink layer (back surface).

<Preparation of magenta ink sheet 1>
A magenta ink sheet 1 was obtained in the same manner as the yellow ink sheet 1 except that the yellow ink layer coating liquid 1 was changed to the magenta ink layer coating liquid 1 having the following composition. The amount of magenta ink layer coating solution 1 with which the ink was dried was 0.67 g / m ² .
(Magenta ink layer coating solution 1)
Magenta pigment dispersion (15 parts of brilliant carmine 6B dispersed in 4.5 parts of dispersant in 80.5 parts of MEK) 13.9 parts Styrene resin (Himmer SBM73F: supra) 5.2 parts Surfactant (mega Fuck F-178K: supra) 0.1 part methyl ethyl ketone 16.7 parts cyclohexanone 64.0 parts Preparation of cyan ink sheet 1 The yellow ink layer coating liquid 1 was changed to the cyan ink layer coating liquid 1 having the following composition. Obtained a cyan ink sheet 1 in the same manner as in the preparation of the yellow ink sheet 1. The amount with dryness of the cyan ink layer coating liquid 1 was 0.70 g / m ² .
(Cyan ink layer coating solution 1)
Cyan pigment dispersion (30 parts of phthalocyanine blue PB15: 3 dispersed in 65 parts of MEK with 5 parts of dispersant) 5.2 parts Styrene resin (Himmer SBM73F: supra) 6.1 parts Fluorine-based surfactant (Megafuck) F-178K: supra) 0.1 part methyl ethyl ketone 24.1 parts cyclohexanone 64.1 parts <Preparation of black ink sheet 1>
Preparation of the yellow ink sheet 1 except that the yellow ink layer coating liquid 1 was changed to the black ink layer coating liquid 1 having the following composition and the photothermal conversion layer coating liquid 1 was changed to the photothermal conversion layer coating liquid 2 having the following composition. In the same manner, a black ink sheet 1 was obtained. The drying amount of the black ink layer coating liquid 1 was 0.87 g / m ² , and the drying amount of the conversion layer coating liquid 2 was 0.73 g / m ² .
(Black ink layer coating solution 1)
Black pigment dispersion (25 parts of carbon black dispersed in 70 parts of MEK with 5 parts of dispersant) 8.0 parts Cyan pigment dispersion (supra) 1.1 parts Violet pigment dispersion (10 parts of dioxazine violet) 1.5 parts styrene resin (Himmer SBM73F: supra) 7.4 parts fluorinated surfactant (Megafac F-178K: supra) 0.1 part methyl ethyl ketone 19.2 parts Cyclohexanone 62.6 parts (photothermal conversion layer coating solution 2)
Polyvinyl alcohol (GOHSENOL EG-30: supra) 3.7 parts Carbon black dispersion (CAB-O-JET300: supra) 14.3 parts Boric acid 0.2 part Fluorosurfactant (FT-251: supra) ) 0.1 part pure water 62.9 parts i-propyl alcohol 18.8 parts [Preparation of thermal transfer sheet set 2]
A yellow ink sheet 2, a magenta ink sheet 2, a cyan ink sheet 2, and a black ink sheet 2 were prepared by the following method, and a thermal transfer sheet set 2 composed of Y, M, C, and K thermal transfer sheets was obtained.

<Preparation of Yellow Ink Sheet 2>
A yellow ink sheet 2 was produced in the same manner as the yellow ink sheet 1 except that the yellow ink layer coating liquid 1 was changed to the yellow ink coating liquid 2.
(Yellow ink layer coating liquid 2)
Yellow pigment dispersion (10 parts of Seika First Yellow H-7055 dispersed in 2 parts of MEK in 88 parts of MEK) 18.2 parts Styrene / methyl methacrylate / butyl acrylate copolymer resin A (Mw is 12,000 and 32) , 2,000 parts Fluorosurfactant (Megafac F-) with two peaks of 1,000, Tg = 61.5 ° C., softening point 112.3 ° C., melt viscosity at 120 ° C. is about 1,000 Pa · s) 178K: supra) 0.1 part methyl ethyl ketone 11.5 parts cyclohexanone 64.5 parts <Preparation of magenta ink sheet 2>
A magenta ink sheet 2 was produced in the same manner as the magenta ink sheet 1 except that the magenta ink layer coating liquid 1 was changed to the magenta ink coating liquid 2.
(Magenta ink layer coating solution 2)
Magenta pigment dispersion (15 parts of brilliant carmine 6B dispersed with 4.5 parts of dispersant in 80.5 parts of MEK) 13.9 parts Styrene / methyl methacrylate / butyl acrylate copolymer resin A (supra)
5.2 parts Fluorosurfactant (Megafac F-178K: supra) 0.1 part Methyl ethyl ketone 16.7 parts Cyclohexanone 64.0 parts <Preparation of cyan ink sheet 2>
A cyan ink sheet 2 was produced in the same manner as the cyan ink sheet 1 except that the cyan ink layer coating liquid 1 was changed to the cyan ink coating liquid 2.
(Cyan ink layer coating solution 2)
Cyan pigment dispersion (supra) 5.2 parts Styrene / methyl methacrylate / butyl acrylate copolymer resin A (supra)
6.1 parts Fluorine-based surface activity (Megafac F-178K: supra) 0.1 part Methyl ethyl ketone 24.1 parts Cyclohexanone 64.1 parts <Preparation of black ink sheet 2>
A black ink sheet 2 was produced in the same manner as the black ink sheet 1 except that the black ink layer coating liquid 1 was changed to the black ink coating liquid 2.
(Black ink layer coating solution 2)
Black pigment dispersion (above) 8.0 parts Cyan pigment dispersion (above) 1.1 parts Violet pigment dispersion (10 parts of dioxazine violet dispersed in 85 parts of MEK with 5 parts of dispersant) 5 parts Styrene / methyl methacrylate / butyl acrylate copolymer resin A (supra)
7.4 parts Fluorosurfactant (Megafac F-178K: supra) 0.1 part Methyl ethyl ketone 19.2 parts Cyclohexanone 62.6 parts [Preparation of thermal transfer sheet set 3]
A yellow ink sheet 3, a magenta ink sheet 3, a cyan ink sheet 3, and a black ink sheet 3 were produced by the following method, and a thermal transfer sheet set 3 composed of Y, M, C, and K thermal transfer sheets was obtained.

<Preparation of Yellow Ink Sheet 3>
A yellow ink sheet 3 was produced in the same manner as the yellow ink sheet 1 except that the yellow ink layer coating liquid 1 was changed to the yellow ink coating liquid 3.
(Yellow ink layer coating solution 3)
Yellow pigment dispersion (supra) 18.2 parts Styrene resin (Hymer ST-95: manufactured by Sanyo Chemical Industries, MW = 4000, melt viscosity at 120 ° C. is 20 Pa · s) 5.6 parts Fluorine-based surfactant (Megafuck F-178K: supra) 0.1 part Methyl ethyl ketone 11.5 parts Cyclohexanone 64.5 parts <Preparation of magenta ink sheet 3>
A magenta ink sheet 3 was produced in the same manner as the magenta ink sheet 1 except that the magenta ink layer coating liquid 1 was changed to the magenta ink coating liquid 3.
(Magenta ink layer coating solution 3)
Magenta pigment dispersion (supra) 13.9 parts Styrene resin (Himmer ST-95: supra) 5.2 parts Fluorosurfactant (Megafac F-178K: supra) 0.1 part Methyl ethyl ketone 16.7 Part Cyclohexanone 64.0 parts <Preparation of cyan ink sheet 3>
A cyan ink sheet 3 was produced in the same manner as the cyan ink sheet 1 except that the cyan ink layer coating liquid 1 was changed to the cyan ink coating liquid 3.
(Cyan ink layer coating solution 3)
Cyan pigment dispersion (supra) 5.2 parts Styrene resin (Haimer ST-95: supra) 6.1 parts Fluorine-based surfactant (Megafac F-178K: supra) 0.1 part Methyl ethyl ketone 24.1 parts Cyclohexanone 64.1 parts <Preparation of black ink sheet 3>
A black ink sheet 3 was produced in the same manner as the black ink sheet 1 except that the black ink layer coating liquid 1 was changed to the black ink coating liquid 3.
(Black ink layer coating solution 3)
Black pigment dispersion (supra) 8.0 parts Cyan pigment dispersion (supra) 1.1 parts Violet pigment dispersion (supra) 1.5 parts Styrene resin (Heimer ST-95: supra) 7.4 Part Fluorosurfactant (Megafac F-178K: supra) 0.1 part Methyl ethyl ketone 19.2 parts Cyclohexanone 62.6 parts <Image formation>
Using the image receiving sheet and each thermal transfer sheet set, an image formed on the image receiving sheet was transferred to the following paper (final image carrier) using the following exposure machine and laminator. The temperature and humidity environment during exposure and lamination was 23 ° C. and 50% RH (relative humidity), and the rotation amount (rpm) of exposure was as follows for each ink sheet.

Exposure machine: Color Decision II EV-Laser Proofer II (manufactured by Konica) B2 size specification Screen used (2 types below)
FM screen: FAIRDOT (Dainippon Screen Mfg. Co., Ltd.) Minimum dot size 20 μm
Halftone screen: Square dot (manufactured by Creo)
Exposure rotation amount (rpm): Y (600), M (550), C (600), K (580)
Laminator: Color Decision II EV-Laminator II (manufactured by Konica)
Set temperature: listed in Table 1 Speed: 7 mm / sec
Pressure: as described in Table 1 Rubber hardness: as shown in Table 1 (measured according to JIS K6301)
The final transfer paper is as follows: Paper 1: OK Coat L (Oji Paper Co., Ltd.), 64.0 g / m ²
Paper 2: ND Excel (manufactured by Daio Paper Co., Ltd.), 38.0 g / m ²
Paper 3: New NPI fine quality (manufactured by Nippon Paper Industries Co., Ltd.), 104.7 g / m ²
The final image obtained was evaluated as follows.

《Color reproducibility》
In order to create a standard for color reproduction, ISO 12642 color patches were printed on the screens of FAIRDOT and square dots at CTP, and printed on the same conditions with an offset printer. Each color patch is output by DDCP with the output of the exposure machine adjusted so as to approximate the offset printed matter printed with square dots, and the L ^* , a ^* , b ^* values of each color are output by SPECTROLINO (manufactured by Gretag). The average color difference of 928 points between the offset printing and DDCP was measured, and the color reproducibility was evaluated. The results are shown in Table 1.

《Image expression》
Using an exposure machine adjusted to the above conditions, SCID N-1 and N-6 compliant with JIS X9201-1995 were output, and image reproduction was visually evaluated in three stages.

○: Tone jump in the highlight area and no collapse in the shadow area are observed. △: Tone jump in the highlight area and collapse in the shadow area are observed. ×: Tone jump in the highlight area and collapse in the shadow area are clear. The results are shown in Table 1.

  According to the present invention, color reproducibility and image expression are good both in halftone dot reproduction and FM screening. In particular, the suitability for thin final transfer paper is improved.

Claims (2)

A step (a) of converting the laser light irradiated on the light-to-heat conversion layer of the thermal transfer sheet into heat, and transferring the image to the image receiving sheet by this heat, and a step of retransferring the image to the final image carrier (printing paper) ( In the image recording method including b), the thermal transfer sheet has at least a photothermal conversion layer and an ink layer on a support, and the melt viscosity at the retransfer temperature of the ink layer composition is 50 to 1,000 Pa · s. In the image exposure, at least a part of the density area of the gradation expression is expressed by a density gradation of fine dots of 30 μm or less, and the transfer roll used for retransfer has a rubber hardness of 10 to 60 °. A characteristic image recording method. ^2. The image recording method according to claim 1, wherein the thickness of the printing paper to be retransferred is 20 to 50 g / m < ² >.