JP2001219654A - Thermal transfer recording medium and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal transfer recording medium (a heat-sensitive thermal transfer ribbon) sufficiently and simultaneously achieving the prevention of lowering of resolution generated by the bleeding of an ink, the improvement of the points of the insufficient durability, the tendency in which an image is easily removed and eliminated when a wax is used and the transferred image is rubbed by a hand to increase the durability. SOLUTION: A thermal transfer recording layer 3 composed of a color pigment, a vinyl chloride-vinyl acetate copolymer resin and colorless or light-color fine particles as main components and having the film thickness in the range of 0.2-1.0 μm is formed on a substrate 2, and the average molecular weight of the vinyl chloride-vinyl acetate copolymer resin is in the range of 10,000-20,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head printer, in which a thermal transfer recording layer containing a color pigment is thermally transferred onto an image receiving sheet. The present invention relates to a thermal transfer recording medium for forming a color image and the like and an image forming method.

[0002]

2. Description of the Related Art Hitherto, as a thermal transfer recording system for forming a gradation image using a thermal head printer, a sublimation transfer system and a fusion transfer system are known.

In the sublimation transfer system, a thermal transfer recording medium having a sublimable (heat transferable) dye and a binder resin provided on a support is superimposed on an image receiving sheet, and the thermal transfer recording is performed in accordance with the amount of heat of a thermal head. The sublimation dye in the layer is transferred onto the image receiving sheet to form a gradation image.

However, when an image is formed using such a sublimable (heat-migrating) dye, the formed image is inferior in durability and its use in fields requiring heat resistance and light resistance is limited. You. In addition, the thermal recording sensitivity is lower than that of the melt transfer method, so the printer is driven by a battery such as a dry battery, making it smaller and lighter, and is not suitable as a high-speed recording material using a high-resolution thermal head expected to be used in the future. have.

[0005] On the other hand, the melt transfer method uses a transfer sheet having a heat-meltable ink transfer layer formed of a coloring material such as a pigment or a dye and a binder such as a wax on a support. In this method, an image is formed by applying energy corresponding to image information to a device and fusing an ink transfer layer on an image receiving sheet. An image formed by the fusion transfer method has high density and excellent sharpness, and is suitable for recording a binary image such as a character or a line drawing. In addition, by using a thermal transfer sheet made of yellow, magenta, cyan, and black and forming an image on the image receiving sheet by superimposing,
It is also possible to form a color image. Japanese Patent Publication No. 63-65029 discloses such a thermal transfer sheet for forming a color image.

[0006]

However, in the case of the thermal transfer sheet described in JP-B-63-65029,
Since a crystalline wax having a low melting point is used as a binder for the ink layer, the resolution is likely to decrease due to bleeding of the ink. In addition, the fixing strength of the transferred image is low, and if the image portion is rubbed strongly by hand, the image portion is removed.

Various proposals have been made as methods for solving such a phenomenon. For example, JP-A-61-24459
No. 2 proposes a heat-sensitive transfer sheet having a heat-sensitive ink layer comprising 65% or more of an amorphous polymer, a release material and a colorant.

However, the above-mentioned Japanese Patent Application Laid-Open No. 61-2445 discloses
The thermal transfer sheet described in Japanese Patent Publication No. 92-92 also contains a crystalline wax, and thus has insufficient fixing strength at a portion where the superimposed printing of each color is performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and is intended to reduce the reduction in resolution due to ink bleeding caused by the use of a low-melting crystalline wax as a binder for an ink layer. In addition, if wax is used, the durability of the transferred image is insufficient when the transferred image is rubbed with the hand, and the image is easily removed and improved, and the durability is increased, and In particular, the thermal transfer recording layer has good foil-cutting property during thermal transfer, has high optical density of the transferred image, and has excellent halftone expression by dot area gradation. It is an object of the present invention to provide a thermal transfer recording medium (thermal transfer ribbon) that can be used.

[0010]

Means for Solving the Problems As a result of intensive studies, the present inventors have made it possible to solve the above problems by using a fusion transfer method.

That is, the invention according to claim 1 of the present invention comprises, on a support, a color pigment, a vinyl chloride-vinyl acetate copolymer resin, and colorless or light-colored fine particles as main components, and has a film thickness of 0.1. A thermal transfer recording medium having a thermal transfer recording layer in the range of 2 to 1.0 μm, wherein the vinyl chloride-vinyl acetate copolymer resin has an average molecular weight in the range of 10,000 to 20,000.

The invention according to a second aspect of the present invention is the invention according to the first aspect, wherein the composition for forming the thermal transfer recording layer is based on 100 parts by weight of the total solid content.
20 to 60 parts by weight of a coloring pigment, 40 to 70 parts by weight of a vinyl chloride-vinyl acetate copolymer resin, colorless or pale color fine particles 1
A thermal transfer recording medium characterized by having a composition of up to 30 parts by weight.

According to a third aspect of the present invention, in the first or second aspect, the vinyl chloride-vinyl acetate copolymer resin contains maleic acid as a copolymer component in an amount of 1 to 5 or less. % Of a vinyl chloride-vinyl acetate-maleic acid copolymer resin.

According to a fourth aspect of the present invention, there is provided the heat transfer recording layer according to any one of the first to third aspects, wherein the colorless or light-colored fine particles of the thermal transfer recording layer have an average particle size of 10%. A thermal transfer recording medium, wherein the average particle diameter is in a range of from about 300 nm to less than 300 nm.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the colorless or light-colored fine particles of the thermal transfer recording layer are silica. This is a characteristic thermal transfer recording medium.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the thermal transfer recording layer includes three colors of cyan, magenta, and yellow, or A thermal transfer recording medium characterized in that four colors of black, cyan, magenta and yellow are repeatedly arranged on a support in an appropriate order along the longitudinal direction.

Next, according to a seventh aspect of the present invention, there is provided a thermal transfer recording layer of the thermal transfer recording medium according to any one of the first to sixth aspects, wherein the thermal transfer recording layer is image-received by using a thermal head printer. In an image forming method in which an image is thermally transferred onto a sheet and an image is formed based on an area gradation, an image receiving layer containing a vinyl chloride-vinyl acetate copolymer resin as a main component is formed on the image receiving layer of the image receiving sheet by coating. This is an image forming method characterized by thermal transfer.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle of transfer of a thermal transfer recording medium according to the present invention is as follows. Heat is applied to a thermal transfer recording material by a thermal medium such as a thermal head, and the acrylic resin in the thermal transfer recording layer is thermally melted. Rather, rather than become a softened or semi-molten state, at the same time as the adhesion to the image receiving layer is expressed,
The adhesiveness to the medium substrate is reduced, and the image is recorded by the thermal transfer recording layer being adhered to the image receiving sheet. This transfer principle is considered to be related to the fact that the thickness of the thermal transfer recording layer is very thin, and rather than the traditional so-called thermal fusion transfer, a thermal adhesive thin film peeling method (this method) Is disclosed in Japanese Unexamined Patent Publication (Kokai) No. 7-117359).

As a result, when printing is performed by overlapping at least two or more colors, clear printing can be obtained without ink bleeding. Further, the transferred recorded image is excellent in mechanical strength and excellent in halftone expression power by dot area gradation.

Hereinafter, the thermal transfer recording medium of the present invention will be described in detail. FIG. 1 shows a thermal transfer recording medium 1 according to the present invention in which a thermal transfer recording layer 3 is provided on a support 2.

As the support 2 that can be used in the present invention, those generally used for sublimation transfer type and melt transfer type can be used. In particular,
Polyethylene terephthalate, polyethylene naphthalate, polypropylene, cellophane, polycarbonate,
Examples thereof include plastic films such as polyvinyl chloride, polystyrene, polyimide, nylon, and polyvinylidene chloride, and papers such as condenser paper and paraffin paper. Particularly preferred is polyethylene terephthalate (PET; saturated polyester).

The thickness of the support 2 is 2 to 50 μm, more preferably 2 to 16 μm. The thermal transfer recording layer 3 is composed of a color pigment, vinyl chloride resin and colorless or light-colored fine particles.

The polyvinyl chloride resin contained in the thermal transfer recording layer 3 has a Tg of 50 to 90 ° C. in consideration of printing aptitude for a heat medium such as a thermal head and durability of an image after transfer recording.
It is preferable to use one in the range of ° C. Further, vinyl chloride vinyl chloride resin used as a main material in the thermal transfer recording layer of the present invention,
Preferably, those having an average molecular weight of 10,000 to 20,000 are good. Here, the average molecular weight means a weight average molecular weight, and in the present invention, this is hereinafter simply referred to as an average molecular weight.

If the average molecular weight of the polyvinyl chloride resin is lower than the lower limit (less than 10,000), the stability of the vinyl chloride resin is usually too low, and the resin is decomposed at room temperature to yellow, brown, Discoloration occurs greatly in black and the like. Further, the durability of the image to rubbing is not sufficient, and if the image is rubbed by hand, tailing tends to occur in the transferred image, which is not preferable. On the other hand, if the average molecular weight is higher than the upper limit (exceeding 20,000), the transferability is deteriorated because the heat-sensitive transfer layer is poorly cut, and the resolution of the obtained image is deteriorated. Would.

Further, when a vinyl chloride / vinyl acetate / maleic acid copolymer resin containing 1 to 5% of a maleic acid component is used as the vinyl chloride / vinyl acetate resin, the alcohol resistance of the image is high, which is particularly preferable.

The vinyl chloride vinyl acetate resin used in the present invention may be copolymerized so that the total of the vinyl chloride component and the vinyl acetate component is at least 70%, and the remaining components are various known vinyl resins. May be copolymerized.

The coloring pigment contained in the thermal transfer recording layer 3 is
Various known pigments can be used. As an example,
Carbon black is preferable for black single-color printing, and pigments forming yellow, magenta, and cyan, and four-color pigments obtained by adding black to these three-color pigments are used for multi-color printing. These pigments can be used alone or in combination of two or more.

The colorless or light-colored fine particles contained in the thermal transfer recording layer 3 are necessary for improving the transferability at the time of thermal transfer, more specifically, the dot shape on which a transferred image is formed, and the gradation reproducibility. The reason why the colorless or light-colored component is used is to prevent the coloring of a colored image formed by thermal transfer from being impaired.

Examples of such colorless or light-colored fine particles include silica, calcium carbonate, kaolin, clay, starch, zinc oxide, Teflon powder, polyethylene powder, polymethyl methacrylate resin beads, polyurethane resin beads, benzoguanamine and melamine resins. Beads and the like can be mentioned. Among the above, silica fine particles are particularly preferred. These fine particles can be used alone or in combination of two or more.

In the present invention, the colorless or light-colored fine particles are added for the purpose of improving transferability (foil breakability).
This size is preferably smaller than the average particle size of the color pigment when the average particle size is in the range of 10 to 300 nm. Since the average particle diameter of the fine particles is smaller than that of the coloring pigment, the effect of improving the foil-cutting property (film-cutting property) of the thermal transfer recording layer, which cannot be achieved only with the coloring pigment without impairing the coloring property of the pigment, is extremely high. Specifically, the dot shape on which the transfer image is formed and the tone reproducibility are very good.

Further, as compared with the case where the amount of the coloring pigment is increased, since the average particle diameter is small, the weakening of the adhesive force to the image receiving layer can be minimized. If the average particle size is more than 300 nm, the effect of improving the cut-off property of the foil is weak, and the color development of the colored image formed by the thermal transfer is not preferred.

The average particle size mentioned here can be measured by a method such as AUTOSIZER2C manufactured by MARVERUN by a light scattering method, a Coulter counter method, image processing from SEM observation images, and the like.

The composition of the composition for forming the thermal transfer recording layer 3 is such that the color pigment is 20 to 60 parts by weight, the polyvinyl chloride resin is 40 to 70 parts by weight, and the total solid content is 100 parts by weight. The colorless or light-colored fine particles are 1 to 30 parts by weight.

When the amount of the coloring pigment is less than the above range, a desired printing density cannot be obtained, and when the amount is too large, the film strength is unfavorably lowered. If the polyvinyl chloride resin is less than the above range, the film strength is not preferred in that the film strength is reduced. Absent. When the amount of colorless fine particles is less than the above range, transferability, in particular, the dot shape on which a transferred image is formed, and the gradation reproducibility are not preferable, and when the amount is large, good ink fluidity is obtained. Absent.

In the thermal transfer recording layer, various additives such as a pigment dispersant, a coating film stabilizer, an antioxidant, an antistatic agent, a leveling agent, and a sensitizer may be added, if necessary. It can also be blended. The amount of addition is preferably 10 parts by weight or less based on 100 parts by weight of the composition for forming the thermal transfer recording layer.

The method for producing a thermal transfer recording medium of the present invention comprises the steps of: dispersing or dissolving a colorant, a vinyl acetate resin and colorless fine particles in a solvent on a substrate such as coated paper or plastic; It is formed by applying a solvent coat method such as a coat, a blade coat, an air knife coat, a gravure coat, a roll coat and the like, and drying to form a thermal transfer recording layer.

The thickness of the thermal transfer recording layer 3 is 0.2 to 1.0.
μm is desirable. When the film thickness is less than 0.2 μm, it is difficult to obtain a sufficient density, and when the film thickness is more than 1.0 μm, it becomes difficult to perform transfer according to the heat-generating portion of the thermal head. The gradation reproducibility is inferior.

Further, heat is applied from the side of the support 2 on which the thermal transfer recording layer 3 is not provided using a thermal head, and when the thermal transfer recording layer 3 is transferred onto the image receiving sheet, the thermal head adheres to the support 2. In order to prevent the smooth running of the thermal transfer recording medium 1 from being hindered, it is desirable to provide the back coat layer 4 on the side of the support 2 where the thermal transfer recording layer 3 is not provided.

Materials used for the back coat layer 4 include nitrocellulose, saturated polyester resin (polyethylene terephthalate resin; PET resin),
An acrylic resin, a vinyl resin, or the like containing silicon oil, a silicon-modified resin, or the like can be given. Further, a crosslinking agent may be used in combination for the purpose of improving heat resistance.

The coating thickness when providing the back coat layer 4 is as follows:
It is preferably about 0.1 to 4 μm. As the image receiving sheet used to form an image using the thermal transfer recording medium 1 as described above, papers such as high quality paper and coated paper, saturated polyester films (PET film; polyethylene terephthalate film), polyvinyl chloride film And a plastic film such as a polypropylene film, or paper or a plastic film coated with an image receiving layer.

The image receiving layer used here is preferably composed mainly of vinyl chloride vinyl chloride resin. That is, by using the image receiving layer containing vinyl chloride resin as a main component, the heat transfer recording layer and the image receiving layer are satisfactorily formed by the heat during the thermal transfer even if the thermal transfer recording layer of the thermal transfer recording medium is not sufficiently melted during the thermal transfer. Since the printing is performed by bonding and sufficient foil cutting, transferability, more specifically, dot shape on which a transferred image is formed, gradation reproducibility, and the like are improved. Furthermore, the formed image has abrasion resistance,
It is excellent in image resistance such as scratch resistance.

Here, the range mainly composed of polyvinyl chloride resin is
This means that among the components contained in the image receiving layer, the polyvinyl chloride resin component is contained more than any other component.

When it is difficult to form an image directly on a sheet on which an image is to be formed, it is possible to form an image on the image receiving sheet once and then re-transfer the transferred image onto the final sheet. good. Such an indirect transfer method not only widens the selectivity of the final sheet, but also provides a protective layer on the final transfer image by providing a protective layer on the image receiving sheet, thereby improving the image resistance and improving image resistance. By providing a security layer such as a hologram forming layer on the sheet, it is possible to improve the security of the final transfer image.

The means for applying thermal energy used to obtain a gradation image expression by area gradation using the thermal transfer recording medium of the present invention as described above and the image receiving sheet as described above may be any of conventionally known applying means. Can be used, and a gradation image can be obtained by controlling the heat energy.

[0045]

Next, the present invention will be described more specifically with reference to examples. In the description, “parts” or “%” is based on weight (parts by weight or% by weight) unless otherwise specified.

Example 1 First, an ink composition for a thermal transfer recording layer having the following composition was prepared. (Cyan ink) Phthalocyanine blue 9 parts PVC resin (VROH, manufactured by Union Carbide) 20 parts Molecular weight Mn 15000 Colorless fine particles (silica) 5 parts (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) Methyl ethyl ketone 67 parts (magenta) Ink) Carmine 6B 9 parts PVC resin (VROH manufactured by Union Carbide) 20 parts Molecular weight Mn 15000 Colorless fine particles (silica) 5 parts (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) Methyl ethyl ketone 67 parts (yellow ink) Disazo Yellow 9 parts PVC resin (VROH, manufactured by Union Carbide Co., Ltd.) 20 parts Molecular weight Mn15000 Colorless fine particles (silica) 5 parts (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) Methyl ethyl ketone 67 parts

The ink for a thermal transfer recording layer having the above formulation was applied to a 5.4 μm-thick polyethylene terephthalate film having a heat-resistant back surface and dried to a dry film thickness of 0.7 μm. A thermal transfer recording medium was obtained.

Next, the following image-receiving layer ink was applied to the easily-adhesive surface of a 100-μm easily-adhesive polyester film (saturated polyester film; polyethylene terephthalate film) so as to have a dry film thickness of 5 μm and dried. An image receiving sheet was obtained. (Image receiving layer ink) PVC resin (manufactured by Union Carbide: VMCC) 20 parts Molecular weight Mn19000 Methyl ethyl ketone 70 parts

First, the surface of the thermal transfer recording layer of the obtained cyan thermal transfer recording medium and the image receiving sheet are overlapped and heated using a thermal head, and a cyan image is formed on the image receiving sheet by area gradation according to the heat generating portion of the thermal head. I got Next, using a magenta thermal transfer recording medium, a magenta image based on area gradation was formed on an image receiving sheet on which a cyan image was formed in the same manner as for cyan. Similarly, a yellow image was formed, and a color image consisting only of area gradation was formed on the image receiving sheet.

Example 2 Example 1 was the same as Example 1 except that the ink for the thermal transfer recording layer was changed to the following formulation.
A thermal transfer recording medium was prepared in the same manner as described above to form a color image. (Cyan ink) Phthalocyanine blue 9 parts PVC resin (VMCC manufactured by Union Carbide) 20 parts Molecular weight Mn19000 Colorless fine particles (silica) 5 parts (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) Methyl ethyl ketone 67 parts (magenta) Ink) Carmine 6B 9 parts PVC resin (Union Carbide: VMCC) 20 parts Molecular weight Mn19000 Colorless fine particles (silica) 5 parts (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) Methyl ethyl ketone 67 parts (yellow ink) Disazo Yellow 9 parts PVC resin (Union Carbide: VMCC) 20 parts Molecular weight Mn19000 Colorless fine particles (silica) 5 parts (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) Methyl ethyl ketone 67 parts

The obtained image had the same image performance as in Example 1, and was particularly excellent in the alcohol resistance test (water / ethanol = 1/1, immersion for 12 hours). Alcohol resistance test evaluation result Example 1 ... acceptable ... level at which no peeling occurs in the image Example 2 ... excellent ... no change in image and image quality

Example 3 In Example 1, a color image consisting of four primary colors was prepared by adding the following black inks to three colors of cyan, magenta and yellow as the ink composition for the thermal transfer recording layer. (Black ink) Carbon black 9 parts PVC resin (VROH, manufactured by Union Carbide Co., Ltd.) 20 parts Molecular weight Mn15000 Colorless fine particles (silica) 4 parts (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) Methyl ethyl ketone 67 parts

The obtained image was confirmed to have the same performance as in Example 1.

<Embodiment 4> The color image in Embodiment 3 is created from three colors of cyan, magenta and yellow.
Binary images of characters and barcodes were created in black. It was confirmed that the obtained image had excellent resistance to characters and barcode portions in addition to the performance of Example 1.

Example 5 Using the thermal transfer recording medium obtained in Example 1, an image was formed on the following image receiving sheet. (Construction of Image Receiving Sheet) Each of the following prescription inks was sequentially applied to a 25 μm polyester film (saturated polyester film; polyethylene terephthalate film) and dried to obtain an image receiving sheet in which a release layer and an image receiving layer were sequentially laminated. (Ink for release layer) Acrylic resin ... 20 parts Methyl ethyl ketone ... 40 parts Toluene ... 40 parts (Ink for image receiving layer) Vinyl chloride vinegar resin (manufactured by Union Carbide: VMCC) ... 20 parts Molecular weight Mn19000 Methyl ethyl ketone ... 70 parts

The image-receiving sheet on which the image was formed was superimposed on the sheet for the final product, and thermal transfer was performed from the back of the image-receiving sheet with a heat roller, and only the polyester film (polyethylene terephthalate film) was peeled off. A protective layer was provided on the surface. A good transfer product could be obtained.

Example 6 Using the thermal transfer recording medium obtained in Example 1, an image was formed on the following image receiving sheet. (Image receiving sheet configuration) The following release layer ink and hologram formation layer ink were sequentially applied to a 25 μm polyester film (saturated polyester film; polyethylene terephthalate film) and dried to obtain a release layer and a hologram formation layer. A hologram was formed on the surface of the hologram-forming layer by heat embossing using an uneven shape. (Ink for release layer) Acrylic resin ... 20 parts Methyl ethyl ketone ... 40 parts Toluene ... 40 parts (Ink for hologram forming layer) Vinyl chloride-vinyl acetate copolymer ... 20 parts Urethane resin ... 15 parts Methyl ethyl ketone ... 70 parts Toluene ... 30 parts

Further, ZnS was provided as a transparent thin film layer on the surface of the hologram forming layer by vapor deposition, and then the following ink for an image receiving layer was applied and dried to laminate the image receiving layers to obtain an image receiving sheet. (Ink for image receiving layer) PVC vinyl chloride resin (manufactured by Union Carbide: VMCC) ... 20 parts Molecular weight Mn19000 Urethane resin ... 10 parts Methyl ethyl ketone ... 70 parts The final surface of the image receiving sheet on which an ultraviolet light emitting fluorescent agent is printed Thermal transfer was performed with a heat roller from the back of the product sheet and the image receiving sheet, and only the polyester film (polyethylene terephthalate film) was peeled off. As a result, a good transfer body having a protective layer on the surface was obtained. The obtained transfer body had a hologram image as a security function, and had high security.

Comparative Example 1 The following sublimation transfer type ink composition was prepared as an ink for a thermal transfer recording layer. (Cyan ink) C.I. I. Solvent Blue 63: 5 parts Butyral resin (BX-1 manufactured by Sekisui Chemical Co., Ltd.): 5 parts Methyl ethyl ketone: 60 parts Toluene: 30 parts (magenta ink) I. Disperse Red 60: 5 parts Butyral resin (BX-1 manufactured by Sekisui Chemical Co., Ltd.): 5 parts Methyl ethyl ketone: 60 parts Toluene: 30 parts (yellow ink) I. Disperse Yellow 201 5 parts Butyral resin (BX-1 manufactured by Sekisui Chemical Co., Ltd.) 5 parts Methyl ethyl ketone 60 parts Toluene 30 parts

The thermal transfer recording layer ink of the above formulation was applied to a 5.4 μm-thick polyester film (saturated polyester film; polyethylene terephthalate film) having a heat-resistant back surface so that the dry film thickness became 1.0 μm. The resultant was applied and dried to obtain a thermal transfer recording medium of Comparative Example 1.

Next, the following ink for a dye-receiving layer was applied to the easily-adhesive surface of a 100-μm easily-adhesive polyester film (saturated polyester film; polyethylene terephthalate film) so as to have a dry film thickness of 4 μm, followed by drying. Aging was performed at 45 ° C. for one week to obtain an image receiving sheet. (Ink for dye receiving layer) Acetal resin ... 10 parts Vinyl chloride-vinyl acetate copolymer resin ... 10 parts Silicone oil ... 2 parts Isocyanate resin ... 3 parts Methyl ethyl ketone ... 50 parts Toluene ... 25 parts

The surface of the thermal transfer recording layer of the obtained thermal transfer recording medium was superimposed on the surface of the dye receiving layer of the image receiving sheet, and an image was formed in the order of yellow, magenta and cyan using a thermal head to obtain a color image.

Comparative Example 2 A thermal transfer recording medium was produced in the same manner as in Example 1, except that the dry film thickness of the ink for the thermal transfer recording layer was changed to 1.2 μm for each of cyan, magenta and yellow. A color image was formed.

Comparative Example 3 The procedure of Example 1 was repeated except that the ink for the thermal transfer recording layer was changed to the following formulation.
A thermal transfer recording medium was prepared in the same manner as described above to form a color image. (Cyan ink) Phthalocyanine blue 9 parts PVC resin (Union Carbide: VROH) 20 parts Molecular weight Mn15000 Methyl ethyl ketone 71 parts (Magenta Ink) Carmine 6B 9 parts PVC resin (Union Carbide: VROH) 20 parts Molecular weight Mn 15000 Methyl ethyl ketone 71 parts (yellow ink) Disazo Yellow 9 parts Vinyl chloride vinegar resin (VROH, manufactured by Union Carbide Co., Ltd.) 20 parts Molecular weight Mn 15000 Methyl ethyl ketone 71 parts

Comparative Example 4 Example 1 was repeated except that the ink for the thermal transfer recording layer was changed to the following formulation.
A thermal transfer recording medium was prepared in the same manner as described above to form a color image. (Cyan ink) Phthalocyanine blue 9 parts PVC resin (VAGH, manufactured by Union Carbide Co., Ltd.) 20 parts Molecular weight Mn27000 Colorless fine particles (silica) 4 parts (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) Methyl ethyl ketone 67 parts (magenta) Ink) Carmine 6B 9 parts PVC resin (Union Carbide: VAGH) 20 parts Molecular weight Mn27000 Colorless fine particles (silica) 4 parts (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) Methyl ethyl ketone 67 parts (yellow ink) Disazo Yellow 9 parts PVC resin (VAGH, manufactured by Union Carbide Co., Ltd.) 20 parts Molecular weight Mn27000 Colorless fine particles (silica) 4 parts (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) Methyl ethyl ketone 67 parts

Comparative Example 5 Example 1 was repeated except that the ink for the thermal transfer recording layer was changed to the following formulation.
A thermal transfer recording medium was prepared in the same manner as described above to form a color image. (Cyan ink) Phthalocyanine blue ... 9 parts PVC resin (VYES-4 manufactured by Union Carbide) ... 20 parts Molecular weight Mn5500 Colorless fine particles (silica) ... 4 parts (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) Methyl ethyl ketone ... 67 parts (Magenta ink) Carmine 6B 9 parts PVC resin (VYES-4 manufactured by Union Carbide) 20 parts Molecular weight Mn5500 Colorless fine particles (silica) 4 parts (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) Methyl ethyl ketone 67 parts (Yellow Ink) Disazo Yellow 9 parts PVC resin (VYES-4 manufactured by Union Carbide) 20 parts Molecular weight Mn5500 Colorless fine particles (silica) 4 parts (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) Methyl ethyl ketone 67 parts

Example 1 and Comparative Examples 1, 2, 3, 4,
The image obtained in 5 was evaluated for image gradation, light fastness and security.

[0068]

[Table 1] As shown in the table, the heat-sensitive recording medium of Example 1 according to the present invention is excellent in that a color image produced in gradation reproducibility is faithfully reproduced from a highlight portion to a shadow portion, and has durability of an image after recording. Thus, a thermal transfer recording medium was obtained, and the object of the present invention was achieved.

[0069]

According to the present invention, the thermal transfer recording layer contains a color pigment, a binder resin, and colorless fine particles, and the thermal transfer recording layer is thermally transferred onto an image receiving sheet by a thermal head printer, and gradation reproduction by area gradation is performed. The present invention provides a thermal transfer recording medium capable of forming an image having excellent heat resistance, and further provides a thermal transfer recording medium having excellent preservability of an image after transfer, particularly excellent in light resistance and mechanical strength. You can do it.

[Brief description of the drawings]

FIG. 1 is a sectional view of a thermal transfer sheet of the present invention.

FIG. 2 is a cross-sectional view of the thermal transfer sheet of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Thermal transfer recording medium 2 ... Support 3 ... Thermal transfer recording layer
4: Back coat layer

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2H111 AA05 AA12 AA26 AA27 AA48 BA03 BA14 BA38 BA47 BA48 BA49 BA50 BA53 BA55 BA76 BA78 CA03 CA12 CA30 CA44

Claims (7)

[Claims] 1. A thermal transfer recording method comprising, as a main component, a color pigment, a vinyl chloride-vinyl acetate copolymer resin, and colorless or light-colored fine particles on a support, and a film thickness in the range of 0.2 to 1.0 μm. A thermal transfer recording medium, comprising a layer, wherein the vinyl chloride-vinyl acetate copolymer resin has an average molecular weight in the range of 10,000 to 20,000. 2. A composition for forming a thermal transfer recording layer, comprising: 20 to 60 parts by weight of a coloring pigment and 40 to 70 parts by weight of a vinyl chloride-vinyl acetate copolymer resin based on 100 parts by weight of the total solid content.
2. The thermal transfer recording medium according to claim 1, wherein the composition is 1 to 30 parts by weight of colorless or light-colored fine particles. 3. A vinyl chloride-vinyl acetate-maleic acid copolymer resin containing 1 to 5% of maleic acid as a copolymerization component. Or the thermal transfer recording medium according to claim 2. 4. The colorless or light-colored fine particles of the thermal transfer recording layer have an average particle size of 10 to 300 nm and are smaller than the average particle size of the color pigment. The thermal transfer recording medium according to any one of the above items. 5. The colorless or light-colored fine particles of the thermal transfer recording layer are silica.
The thermal transfer recording medium according to any one of the above items. 6. A thermal transfer recording layer in which three colors of cyan, magenta and yellow, or four colors of black, cyan, magenta and yellow are repeatedly arranged on a support in an appropriate order along the longitudinal direction. The thermal transfer recording medium according to any one of claims 1 to 5, wherein: 7. An image forming method, wherein the thermal transfer recording layer of the thermal transfer recording medium according to claim 1 is thermally transferred onto an image receiving sheet using a thermal head printer to form an image by area gradation. An image forming method, wherein an image receiving layer containing a vinyl chloride-vinyl acetate copolymer resin as a main component is thermally transferred onto the image receiving layer of an image receiving sheet formed by coating.