ADHESIVE LAYER TRANSFER SHEET AND UTILIZATION OF THE SAME

Abstract: A transfer sheet, for an adhesive layer, for use in the formation of an image by a thermal transfer process, an image forming method using the transfer sheet for an adhesive layer, and an object with an image formed thereon are disclosed. A transfer sheet 1 for an adhesive layer comprises: a substrate sheet 2; and an adhesive layer 3 and an interposing layer 4 laminated in that order on the substrate sheet 2. The substrate sheet 2 and the adhesive layer 3 are separable from each other. The use of the transfer sheet for an adhesive layer in combination with an intermediate transfer medium enables a desired image having a high quality to be efficiently formed on a particular article.

Description: TECHNICAL FIELD The present invention relates to a transfer sheet for an adhesive layer, particularly a transfer sheet, for an adhesive layer, which has a combination of excellent adhesion to a transfer material and excellent adhesion to an image-forming object or releasability of an adhesive layer from the transfer sheet for an adhesive layer, and an image-forming method and an object, with an image formed thereon, using the transfer sheet for an adhesive layer. BACKGROUND ART Further, the present invention relates to a transfer sheet for an adhesive layer, particularly a transfer sheet, for an adhesive layer, which can conduct temporary bonding and separation a plurality of times in bonding a transfer material to a different material through an adhesive layer transferred onto the transfer material, an image-forming method using the transfer sheet for an adhesive layer, and an object, with an image formed thereon, and, an intermediate thereof, that is, an intermediate image-forming object, formed using the transfer sheet for an adhesive layer. A melt type thermal transfer system and a sublimation type thermal transfer system have hitherto been used extensively as a thermal transfer system. In the sublimation type thermal transfer system, a thermal transfer sheet comprising a substrate sheet, such as a plastic film, bearing a dye layer formed of a binder resin with a sublimable dye as a colorant melted or dispersed therein is used with an image-forming object comprising a support, such as paper or a plastic sheet, bearing an image-receptive layer, and energy corresponding to image information is applied by means of a heating device, such as a thermal head, to transfer a sublimable dye contained in a dye layer of the thermal transfer sheet onto an image-receptive layer of the image-forming object, thereby recording an image. According to the sublimation type thermal transfer system, the amount of the dye transferred can be regulated on a dot basis by regulating the amount of energy applied to the thermal transfer sheet, enabling tone reproduction by taking advantage of density gradation. Further, since the colorant used is a dye, the recorded image has good transparency and, at the same time, the reproduction of an intermediate color created by superposition of colors using a plurality of dye layers is excellent. Therefore, a high-quality, full-color image can be recorded by using a thermal transfer sheet(s) for three colors of yellow, magenta, and cyan or four colors of yellow, magenta, cyan, and black to superpose these three or four colors on top of one another on an object. In the formation of an image by the sublimation type thermal transfer system, an image can be formed on image-forming materials having various shapes by once forming an image on an intermediate transfer medium having an image-receptive layer and transferring the image-receptive layer, with an image formed thereon, onto an image-forming object. The formation of an image using the intermediate transfer medium by the sublimation type thermal transfer system, however, often suffers form a drawback that the adhesion between the image-receptive layer and the image-forming object in its image-forming surface is unsatisfactory. In this case, it is preferred to transfer the image-receptive layer onto the image-forming object through an adhesive layer. EP-A-0487727 relates to a heat transfer cover film, enabling heat transferred images to show durability such as rub resistance and allow them to develop colour and luster and a heat transfer process making use of said cover films. The heat transfer cover film comprises a substrate film, a transparent resin layer and a heat-sensitive adhesive layer further provided on the transparent resin layer, said heat-sensitive adhesive layer being made of a resin having a glass transition temperature lying in the range of 40 to 75° C. JP-05-177994 relates to a heat transfer material for transferring marks having specific shape and colour, said material comprising a releasable base material made of paper or a synthetic resin film, a patterned heat-sensitive adhesive layer temporarily bonded with said releasable base material, a patterned adhesive layer comprising a strong adhesive having stretching properties, a fibre planted layer. JP 07-052522 relates to an intermediate transfer recording medium that forms an image acceptable layer on one surface of a base material sheet so that the image acceptable layer can be peeled off. JP 04-078599 relates to thermally transferring method for video print image to T-undershirts. DISCLOSURE OF INVENTION According to the present invention, a transfer sheet for an adhesive layer is used in the formation of an adhesive layer used in the above transfer of an image-receptive layer onto an image-forming object. Specifically, the transfer sheet, for an adhesive layer, according to the present invention basically comprises a substrate sheet and an adhesive layer provided on the substrate sheet. It is put on top of an image-receptive layer in an intermediate transfer medium so as for the adhesive layer to face the image-receptive layer, and, in this state, heat and pressure are applied through the substrate sheet to transfer the adhesive layer onto the image-receptive layer in the intermediate transfer medium. The transferred adhesive layer is in direct contact with the image-receptive layer in the intermediate transfer medium. Therefore, the adhesive layer should be formed of a resin which has good adhesion to the resin constituting the image-receptive layer and into which the dye constituting the image is not bled. This greatly limits the material usable for the adhesive layer. Further, an adhesive layer, which is easily adhered to the image-receptive layer, is in many cases difficult to be adhered to an image-forming object, such as paper. In this respect as well, there is a limitation on the selection of the material. Furthermore, when the image-forming object is one having a fiber texture, such as paper, the transfer of an image-receptive layer onto an image-forming object through an adhesive layer causes the adhesive layer to be penetrated into the image-forming object, posing a problem that the fiber texture of the image-forming object appears on the surface of the formed image. Good releasability of the adhesive layer from the substrate sheet is required of the thermal transfer sheet for an adhesive layer. If the transferred adhesive layer has a smaller thickness than a desired one or poor surface smoothness, the adhesion of the transferred image-receptive layer to an image-forming object is poor, or irregularities are created on the image-receptive layer, resulting in deteriorated image quality. Further, when the image-receptive layer with an adhesive layer formed thereon by transfer is transferred onto an image-forming object through the adhesive layer, or when an image-receptive layer is transferred onto an image-forming object, with an adhesive layer formed thereon by transfer, through the adhesive layer, registration is necessary between the image-receptive layer and the image-forming object. In the case of an adhesive layer formed by transfer using the transfer sheet for an adhesive layer, when the image-receptive layer or the image-forming object once comes into contact with and adhered to the adhesive layer of the transfer sheet for an adhesive layer, there is a possibility that the adhesive layer cannot be separated from the sheet, making it impossible to release and again adhere the adhesive layer for more accurate registration. For this reason, registration while repeating contact and separation between the image-receptive layer and the image-forming object a plurality of times becomes impossible, imposing restriction on registration work at the time of transfer of the image-receptive layer onto the image-forming object. In view of the above situation, the present invention has been made, and an object of the present invention is to provide a transfer sheet, for an adhesive layer, which can transfer an adhesive layer and has excellent adhesion to a transfer material (an intermediate transfer medium), is free from bleeding of dyes, has excellent adhesion to an image-forming object, and is free from penetration into the image-forming object, and an image-forming method and an object, with an image formed thereon, using said transfer sheet for an adhesive layer. Another object of the present invention is to provide a transfer sheet, for an adhesive layer, which can transfer and form an adhesive layer, with desired thickness, possessing very good releasability and having uniform thickness and high surface smoothness. A further object of the present invention is to provide a transfer sheet, for an adhesive layer, which is excellent in transferability and adhesion of an adhesive layer onto a transfer material and enables temporary bonding and separation to be repeated a plurality of times to achieve satisfactory positioning for bonding of a transfer material to a different object, an image-forming method, which can form a high-quality image using said transfer sheet for an adhesive layer, and an object, with an image formed thereon, and an intermediate thereof, that is, an intermediate image-forming object, formed using the transfer sheet for an adhesive layer. The transfer sheet for an adhesive layer according to the present invention basically comprises a substrate sheet and an adhesive layer separably provided on the substrate sheet. Further, it embraces transfer sheets, for an adhesive layer, improved for solving the above technical problems. Thus, according to one aspect of the present invention, there is provided a transfer sheet for an adhesive layer, comprising: a substrate sheet; and an adhesive layer and an interposing layer laminated in that order on at least part of one surface of the substrate sheet, the substrate sheet and the adhesive layer being separable from each other, the interposing layer having a glass transition point higher than that of said adhesive layer. According to a preferred embodiment of the present invention, the interposing layer has a glass transition point in the range of from 50 to 115°C and the adhesive layer has a glass transition point in the range of from 35 to 100°C, the glass transition point of the interposing layer being above that of the adhesive layer; at least one of the interposing layer and the adhesive layer contains a filler; or the transfer sheet for an adhesive layer further comprises a back surface layer on the surface of the substrate sheet remote from the adhesive layer. According to another aspect of the present invention, there is provided an image forming method comprising the steps of: forming an image on a releasable image-receptive layer in an intermediate transfer medium by a thermal sublimation transfer process; putting the intermediate transfer medium and the above transfer sheet, for an adhesive layer, on top of the other so as for the image-receptive layer to abut against the interposing layer on the intermediate transfer medium and applying heat and/or pressure to the laminate by transfer means to transfer the adhesive layer onto the image-receiving layer through the interposing layer; and putting an image-forming object onto the intermediate transfer medium so as for the image-forming object to abut against the adhesive layer and applying heat and/or pressure to the laminate by transfer means to transfer the image-receptive layer onto the image-forming object through the adhesive layer. According to a further aspect of the present invention, there is provided an object with an image formed thereon, comprising: an image-forming object; an adhesive layer and an interposing layer laminated in that order on a desired site of the image-receiving object; said interposing layer having a glass transition point higher than that of the adhesive layer and an image-receptive layer provided on the interposing layer, the image-receptive layer having an image formed by a thermal sublimation transfer process. According to a preferred embodiment of the present invention, in the object with an image formed thereon, the interposing layer has a glass transition point in the range of from 50 to 115°C and the adhesive layer has a glass transition point in the range of from 35 to 100°C, the glass transition point of the interposing layer being above that of the adhesive layer; or at least one of the interposing layer and the adhesive layer contains a filler. The adhesive layer provided on the substrate sheet has thereon an interposing layer which has good adhesion to a transfer material, onto which the adhesive layer is to be transferred, and, at the same time, can prevent bleeding of dyes. Therefore, the transfer of the adhesive layer onto a transfer material is very good, and, for the adhesive layer, importance can be placed on the adhesion to the image-forming object and properties which enable prevention of penetration of the adhesive layer, thus realizing a transfer sheet, for an adhesive layer, which can develop good transfer onto a transfer material by virtue of the interposing layer and good transfer onto an image-forming object by virtue of the adhesive layer. BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1, 2, 5, are schematic cross-sectional views showing embodiments of the transfer sheet for an adhesive layer according to the present invention; and Figs. 3A to 3C, Figs. 4A to 4C, are cross-sectional views showing embodiments of the image-forming method according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION Fig. 1 is a schematic cross-sectional view showing an embodiment of the transfer sheet, for an adhesive layer, according to the first aspect of the present invention. In Fig. 1, a transfer sheet 1 for an adhesive layer comprises a substrate sheet 2, an adhesive layer 3 separably provided on the substrate sheet 2, and an interposing layer 4 provided on the adhesive layer 3. The transfer sheet 1 for an adhesive layer according to the present invention is characterized in that the interposing layer 4 is further provided on the adhesive layer 3 separably provided on the substrate sheet 2. By virtue of the above construction of the transfer sheet 1 for an adhesive layer according to the present invention, good adhesion to a transfer material and a capability of preventing bleeding of dyes can be imparted to the interposing layer 4, the adhesive layer 3 can be transferred to a transfer material (an intermediate transfer medium) through the interposing layer 4, and, at the same time, after transfer to an image-forming object, has good adhesion to the image-forming object and a capability of preventing penetration into the image-forming object. Thus, various properties required of the adhesive layer of the conventional transfer sheet for an adhesive layer can be shared by the adhesive layer 3 and the interposing layer 4. Therefore, even though the adhesive layer 3 penetrates into the image-forming object, the presence of the interposing layer 4 prevents the surface state of the image-forming object from appearing on the surface of the image. This increases the degree of freedom for the selection of material for the adhesive layer 3 (not to mention the degree of freedom of material for the interposing layer 4), realizing a transfer sheet, for an adhesive layer, which can stably develop various required properties. Preferably, the adhesive layer 3 constituting the transfer sheet for an adhesive layer is formed of a material which develops adhesion upon heating, for example, a thermoplastic synthetic resin, natural resin, rubber, or wax. More specific examples of the material usable for constituting the adhesive layer 3 include synthetic resins, for example, cellulose derivatives, such as ethyl cellulose and cellulose acetate propionate, styrene resins, such as polystyrene and poly-α-methylstyrene, acrylic resins, such as polymethyl methacrylate and polyethyl acrylate, vinyl resins, such as polyvinyl chloride, polyvinyl acetate, vinyl chloride/vinyl acetate copolymer, polyvinyl butyral, and polyvinyl acetal, polyester resins, polyamide resins, epoxy resins, polyurethane resins, ionomers, ethylene/acrylic acid copolymer, and ethylene/acrylic ester copolymer; and natural resins and derivatives of synthetic rubbers, usable as a tackifier, such as rosin, rosin-modified maleic acid resins, ester gums, polyisobutyrene rubber, butyl rubber, styrene/butadiene rubber, butadiene/acrylonitrile rubber, polyamide resins, and polychlorinated polyolefins. The adhesive layer 3 may be formed of a composition comprising one or more materials described above. The thickness thereof can be determined by taking into consideration the necessary adhesive property and the processability. In general, however, it is preferably about 0.1 to 200 µm. The interposing layer 4 provided on the adhesive layer 3 comes into direct contact with a dye image formed on the image-receptive layer of the transfer material (intermediate transfer medium) and, hence, is formed of a resin into which a dye is not bled. For this reason, preferably, a resin commonly used for constituting a dye-receptive layer in the art is employed as a resin for constituting the interposing layer. When paper is used as the image-forming object, the adhesive layer 3 often penetrates into paper. In this case, when the interposing layer 4 is formed of a resin having a high glass transition point, it does not penetrate into paper, preventing paper texture from appearing on the surface of the interposing layer 4. Therefore, preferably, the resin for constituting the interposing layer 4 has a glass transition point above that of the resin for constituting the adhesive layer 3. For example, a resin having a glass transition point of 50 to 115°C, preferably 60 to 90°C, may be used for constituting the interposing layer 4, with a resin having a glass transition point of 35 to 100°C, preferably 35 to 70°C, more preferably 45 to 65°C, being used for constituting the adhesive layer 3. Specific examples of resins usable for the interposing layer 4 include vinyl chloride resin, vinyl chloride/vinyl acetate copolymer, polyester resin, polyvinyl acetal, and polymethyl methacrylate. Preferred examples of combinations of the resin for constituting the adhesive layer 3 with the resin for constituting the interposing layer 4 are as follows. (Adhesive layer 3) (Interposing layer 4) polyamide resin / vinyl chloride-vinyl acetate copolymer polyethyl acrylate / polyester resin polyvinyl butyral / polyvinyl acetal ethylene-acrylic acid copolymer / polymethyl methacrylate polychlorinated polyolefin / polyvinyl chloride The thickness of the interposing layer 4 can be determined by taking into consideration necessary properties, for example, adhesion to a transfer material (an intermediate transfer medium) and a capability of preventing bleeding of dyes, processability and the like. In general, however, it is preferably about 0.1 to 200 µm. In the present invention, a filler is preferably added to the adhesive layer 3 and the interposing layer 4 from the viewpoint of improving the transferability. In this case, conventional organic or inorganic fillers may be used. Examples of fillers usable herein include organic fillers, such as acrylic, nylon, and teflon fillers and polyethylene wax, and inorganic fillers, such as fine particles of various metal oxides including titanium oxide, zinc oxide, kaolin clay, calcium carbonate, finely divided silica, zinc oxide, and tin oxide. The particle diameter of the filler is preferably in the range of from 0.05 to 10 µm, and the amount of the filler added is preferably in the range of from 10 to 300 parts by weight based on 100 parts by weight of the resin for constituting the adhesive layer 3 or the interposing layer 4. The substrate sheet 2 constituting the transfer sheet 1 for an adhesive layer may be any substrate sheet commonly used in the conventional transfer sheet for an adhesive layer. Examples of preferred substrate sheets usable herein include thin papers, such as glassine, capacitor, and paraffin papers; stretched or unstretched plastic files of polyesters having high heat resistance, such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyphenylene sulfide, polyether ketone, and polyether sulfone, polypropylene, polycarbonate, cellulose acetate, polyethylene derivatives, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, polyimide, polymethylpentene, and ionomers; and laminates of the above sheets. The thickness of the substrate sheet 2 may be properly selected, depending upon the material, so as to provide proper properties such as strength and heat resistance. In general, however, it is preferably about 1 to 100 µm. In the thermal transfer sheet for an adhesive layer according to the present invention, a release layer may be provided between the substrate sheet and the adhesive layer. In this case, the release layer may be formed of a resin, examples of which include: thermoplastic resins, for example, acrylic resins, such as polymethyl methacrylate, polyethyl methacrylate, and polybutyl methacrylate, vinyl resins, such as polyvinyl acetate, vinyl chloride/vinyl acetate copolymer, polyvinyl alcohol, polyvinyl butyral, and polyvinyl acetal, cellulose derivatives, such as ethyl cellulose, nitrocellulose, and cellulose acetate; and thermosetting resins, for example, unsaturated polyester resins, polyester resins, polyurethane resins, and aminoalkyd resins. When no satisfactory release effect can be attained by the sole use of the thermoplastic resin, it is preferred to add a release agent to the release layer. Release agents usable herein include silicone compounds, wax, melamine resin, fluororesin, talc, finely divided silica, and lubricants, such as surfactants and metal soaps. Among them, silicone compounds are particularly preferred. Specific examples of silicone compounds include silicone oils, such as dimethyl silicone, epoxy-modified silicone, reactive silicone, alkyl-modified silicone, and amino-modified silicone oils, reaction products of a polyester resin or an epoxy resin with a silane coupling agent, silicone rubbers, silicone compounds, and silicone waxes. The addition of the above release agent to the adhesive layer 3 can improve the release effect. This, however, deteriorates the adhesive property of the adhesive layer 3 when the adhesive layer 3 and paper are adhered to each other. Therefore, as described above, the addition of the release agent to the release layer is preferred. The above release layer can be formed by coating a coating liquid comprising a binder resin or a coating liquid comprising a binder resin, with a release agent incorporated therein, onto a substrate sheet 2 by a conventional method such as gravure printing, screen printing, or reverse roll coating using a gravure plate, and the thickness thereof is preferably about 0.05 to 5 µm. As shown in Fig. 2, the transfer sheet for an adhesive layer according to the present invention may comprise: a substrate sheet 2; an adhesive layer 3 and an interposing layer 4 provided on one surface of the substrate sheet 2; and a back surface layer 5 provided on the other surface of the substrate sheet 2. The back surface layer 5 is provided on the substrate sheet 2 for the purpose of preventing the substrate sheet 2 from being heat-fused to a heating device, such as a thermal head, at the time of transfer of the adhesive layer 3 and the interposing layer 4 onto a transfer material, enabling the transfer sheet to be smoothly carried. Examples of resins usable for the back surface layer 5 include natural or synthetic resins, for examples, cellulosic resins, such as ethyl cellulose, hydroxy cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, cellulose acetate butyrate, and nitrocellulose, vinyl resins, such as polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, and polyvinyl pyrrolidone, acrylic resins, such as polymethyl methacrylate, polyethyl acrylate, polyacrylamide, and acrylonitrile/styrene copolymer, polyamide resins, polyvinyltoluene resins, coumarone/indene resins, polyester resins, polyurethane resins, and silicone-modified or fluorine-modified urethanes. They may be used alone or as a mixture of two or more. In order to enhance the heat resistance of the back surface layer, preferably, a resin, having a hydroxyl reactive group, among the above resins is used in combination with a crosslinking agent, such as polyisocyanate, to form a crosslinked resin layer. Further, in order to render the thermal sheet slidable on a thermal head, a solid or liquid release agent or lubricant is added to the back surface layer so that the transfer sheet have a thermal slip property. Release agents or lubricants usable herein include, for example, various waxes, such as polyethylene and paraffin waxes, higher aliphatic alcohols, organopolysiloxanes, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, fluorosurfactants, organic carboxylic acids and derivatives thereof, fluororesins, silicone resin, and fine particles of inorganic compounds, such as talc and silica. The content of the lubricant in the back surface layer 5 is about 5 to 50% by weight, preferably about 10 to 30% by weight. The thickness of the back surface layer 5 may be about 0.1 to 10 µm, preferably about 0.5 to 5 µm. One embodiment of the image-forming method using a transfer sheet for an adhesive layer according to the present invention will be described with reference to Figs. 3 and 4. At the outset, an intermediate transfer medium 31 is put on top of a sublimation type thermal transfer sheet 21 so that a dye layer 23 in the thermal transfer sheet 21 comes into contact with an image-receptive layer 33 in the intermediate transfer medium 31. In this state, the intermediate transfer medium 31 and the thermal transfer sheet 21 are passed through between a thermal head 11 and a platen roller 12 and brought into press-contact with each other by means of the thermal head 11 and the platen roller 12. In this case, the thermal head 11 is heated according to image data (Fig. 3A). Thus, a sublimable dye contained in the dye layer 23 is transferred onto the image-receptive layer 33 in the intermediate transfer medium 31 to form an image A (Fig. 3B). In the embodiment shown in the drawings, the thermal transfer sheet 21 comprises a substrate sheet 22, a dye layer 23 provided on one surface of the substrate sheet 22, and a back surface layer 24 on the other surface of the substrate sheet 22. On the other hand, the intermediate transfer medium 31 comprises a substrate sheet 32 bearing an image-receptive layer 33. Then, a thermal transfer sheet 1 for an adhesive layer is put on top of the intermediate transfer medium 31 with the image A formed thereon so that an interposing layer 4 in the transfer sheet 1 for an adhesive layer comes into contact with the image-receptive layer 33 in the intermediate transfer medium 31 with the image A formed thereon. In this state, the intermediate transfer sheet 31 with the image A formed thereon and the transfer sheet 1 for an adhesive layer are passed through between the thermal head 11 and the platen roller 12 and brought into press-contact with each other by means of the thermal head 11 and the platen roller 12, and the thermal head 11 is heated (Fig. 3C). This causes separation between the substrate sheet 2 and the adhesive layer 3, resulting in transfer of the adhesive layer 3 onto the image-receptive layer 33 in the intermediate transfer medium 31 as a transfer object through the interposing layer 4 (Fig. 4A). As described above, in the transfer of the adhesive layer 3, the interposing layer 4 has good adhesion to the image-receptive layer 33 and a capability of preventing bleeding of dyes, and, hence, there is no need to impart such properties to the adhesive layer 3. Then, the intermediate transfer medium 31 is put on top of an image-forming object 41 so that the adhesive layer 3 in the intermediate transfer medium 31 faces the image-forming object 41, and heat and pressure are applied to the laminate by means of the heat roller 15 and the platen 16 (Fig. 4B). This result in the transfer of the image-receptive layer 33 in the intermediate transfer medium 31 onto the image-forming object 41 to transfer and form the image A on the image-forming object 41 through the adhesive layer 3, thereby preparing an object 40 with an image formed thereon according to the present invention (Fig. 4C). Thus, the object 40 with an image formed thereon has such a construction that the adhesive layer 3 and the interposing layer 4 are laminated in that order on a desired site of the image-forming object 41, and the image-receptive layer 33 with the image A formed thereon is provided on the interposing layer 4. In the transfer of the image-receptive layer 33 onto the image-forming object 41, the adhesion of the adhesive layer 3 to the image-forming object 41 is so good that the adhesion of the image-receptive layer 33 to the image-forming object 41 is very good. Further, even though the adhesive layer 3 penetrates into the image-forming object 41, there is no fear of the image quality being deteriorated by appearance of the surface state of the image-forming object 41 on the image A because, as described above, the interposing layer 4 has a capability of preventing penetration and the like. There is a mirror image relationship between the image A formed on the image-forming object 41 and the image A formed on the image-receptive layer 33 in the intermediate transfer medium 31. Therefore, regarding an image, a letter, or a mark, a reverse image should be previously formed. The above intermediate transfer medium 31 used in the image-forming method according to the present invention comprises a substrate sheet 32 and an image-receptive layer 33 provided on the substrate sheet 32. A peelable protective layer may be provided between the substrate sheet 32 and the image-receptive layer 33. The peelable protective layer may be formed in the same manner as described above in connection with the formation of the peel layer of the transfer sheet for an adhesive layer according to the present invention. The thickness of the peelable protective layer may be, for example, about 2 to 3 g/m 2 on a dry basis. When such a peelable protective layer is provided, in the transfer of the image-receptive layer 33, the peelable protective layer is transferred together with the image-receptive layer 33 and, after transfer, functions as a layer for protecting the image-receptive layer 33. In all the above embodiments of the transfer sheet according to the present invention, an adhesive layer and an interposing layer are provided on substantially the whole area of one surface of the substrate sheet. The transfer sheet for an adhesive layer according to the present invention is not limited to these embodiments only. For example, as shown in Fig. 5, a laminate of an adhesive layer 3 and an interposing layer 4, a dye layer 7Y, a dye layer 7M, and a dye layer 7C are formed in a face serial manner on a substrate sheet 2 to constitute a transfer sheet for an adhesive layer (a thermal transfer sheet integral with an adhesive layer) 1'. The use of the thermal transfer sheet 1' integral with an adhesive layer is advantageous in that, in the above image formation, an image is formed on the image-receptive layer in the intermediate transfer medium by the transfer of the dye layer and the thermal head for the formation of an image as such may be used to continuously transfer and form an adhesive layer on the image-receptive layer. Example A Preparation of transfer sheets for adhesive layer (samples 1 to 5) A 6 µm-thick polyethylene terephthalate film (Lumirror, manufactured by Toray Industries, Inc.) with a back surface layer coated thereon was provided as a substrate sheet. A coating liquid, for an adhesive layer, having the following composition was coated by gravure coating on the substrate sheet, and the coating was dried (coverage on a dry basis: 3 g/m 2 ) to form an adhesive layer. (Composition of coating liquid X for adhesive layer) Polyamide resin (Tg: 50°C) (Macromelt 6240, manufactured by Henkel Hakusui Corp.) 100 parts by weight Methyl ethyl ketone 500 parts by weight (Composition of coating liquid Y for adhesive layer) Polyester resin (Tg: 75°C) (UE3600, manufactured by Unitika Ltd.) 100 parts by weight Methyl ethyl ketone 500 parts by weight Then, different resin coating liquids, for an interposing layer, having the following respective compositions were coated by gravure coating on the adhesive layer, and the coatings were dried (coverage on a dry basis: 2 g/m 2 ) to form interposing layers, thereby preparing transfer sheets for an adhesive layer according to the present invention (samples 1 to 5). (Coating resin liquid A for interposing layer) Vinyl chloride/vinyl acetate copolymer (1000 ALK, manufactured by Denki Kagaku Kogyo K.K.) 100 parts by weight Methyl ethyl ketone 500 parts by weight (Coating resin liquid B for interposing layer) Polymethyl methacrylate resin (BR-85, manufactured by Mitsubishi Rayon Co., Ltd.) 100 parts by weight Methyl ethyl ketone 500 parts by weight (Coating resin liquid C for interposing layer) Polyester resin (Vylon 600, manufactured by Toyobo Co., Ltd.) 100 parts by weight Methyl ethyl ketone 500 parts by weight (Coating resin liquid D for interposing layer) Polymethyl methacrylate resin (LP-45M, manufactured by Soken Chemical Engineering Co., Ltd.) 100 parts by weight Methyl ethyl ketone 500 parts by weight Preparation of transfer sheets for adhesive layer (comparative samples 1 to 3) For comparison, a transfer sheet for an adhesive layer (comparative sample 1) was prepared in the same manner as described above in connection with the preparation of sample 1, except that no interposing layer was formed. Further, for comparison, transfer sheets for an adhesive layer (comparative examples 2 and 3) were prepared in the same manner as described above in connection with the preparation of sample 1, except that, as the resin used in the coating liquid for an interposing layer, a releasable resin (Gosenol NH-8, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) or a resin having a low glass transition point (AE 322, manufactured by Japan Synthetic Rubber Co., Ltd.) was used instead of the vinyl chloride/vinyl acetate copolymer. Furthermore, a transfer sheet for an adhesive layer (comparative sample 4) was prepared using the following coating liquid Z as the coating liquid for an adhesive layer and the above coating liquid A as the resin coating liquid for an interposing layer. (Composition of coating liquid Z for adhesive layer) Acrylic resin (BR-85 (Tg: 105°C), manufactured by Mitsubishi Rayon Co., Ltd., ) 100 parts by weight Methyl ethyl ketone 500 parts by weight Preparation of intermediate transfer medium sheets A 6 µm-thick polyethylene terephthalate film (Lumirror, manufactured by Toray Industries, Inc.) with a back surface layer coated thereon was provided as a substrate sheet. A coating liquid, for a peelable protective layer, having the following composition was coated by gravure coating on the untreated surface of the substrate sheet, and the coating was dried (coverage on a dry basis: 3 g/m 2 ) to form a peelable protective layer. (Composition of coating liquid for peelable protective layer) Polymethyl methacrylate resin (BR-83, manufactured by Mitsubishi Rayon Co., Ltd.) 100 parts by weight Methyl ethyl ketone 500 parts by weight Then, the following coating liquid for a receptive layer was coated by gravure coating on the releasable protective layer, and the coating was dried (coverage on a dry basis: 3 g/m 2 ) to form a dye-receptive layer, thereby preparing an intermediate transfer medium. (Composition of coating liquid for receptive layer) Vinyl chloride/vinyl acetate copolymer (VYHD, manufactured by Union Carbide Corporation) 100 parts by weight Epoxy-modified silicone (KF-393, manufactured by The Shin-Etsu Chemical Co., Ltd.) 1 part by weight Amino-modified silicone (KS-343, manufactured by The Shin-Etsu Chemical Co., Ltd.) 1 part by weight Methyl ethyl ketone 500 parts by weight Thereafter, a thermal sublimation transfer sheet was used to form an image on the image-receptive layer in the intermediate transfer medium sheet, and an adhesive layer was transferred thereon using the above transfer sheets for an adhesive layer (samples 1 to 5 and comparative samples 1 to 3) under the following transfer conditions. (Transfer conditions) Thermal head 6 dots/mm Thermal energy 1.0 mJ/dot The image-receptive layer and the releasable protective layer were then transferred through the transferred adhesive layer onto a postal card as an image-forming object under the above transfer conditions to prepare objects with an image formed thereon. In this case, at the time of the transfer, separation occurred between the peelable protective layer and the substrate sheet in the intermediate transfer medium sheet. The images thus obtained were evaluated for the adhesion and image quality by the following methods. The results are given in Table A1. (Adhesion) A pressure-sensitive adhesive tape (Cello-Tape 545, manufactured by Nichiban Co., Ltd.) having a width of 12 mm was adhered to the image, and 180° peeling was then carried out at a peel rate of 100 cm/sec to evaluate the adhesion. Evaluation criteria ○: No separation occurred between the image-receptive layer and the interposing layer, and the pressure-sensitive adhesive tape alone was separated, or alternatively the image-receptive layer and the interposing layer, together with pressure-sensitive adhesive tape, were taken away, resulting in ruined surface of the card. X: Separation occurred between the image-receptive layer and the interposing layer or between the adhesive layer and the card. (Image quality) The image quality was evaluated by visual inspection. Evaluation criteria ○: The surface of the image was smooth, and no fiber texture of the card was observed in the image per se. X: The influence of fiber texture of the card appeared in the image, and the creation of a streak pattern having a higher density than the area around the pattern or a streak pattern having a lower density than the area around pattern was observed. Transfer sheet for adhesive layer Coating liquid for adhesive layer Coating liquid/resin for interposing layer Adhesion Image quality Sample 1 X A ○ ○ Sample 2 X B ○ ○ Sample 3 X C ○ ○ Sample 4 X D ○ ○ Sample 5 Y D ○ ○ Comparative sample 1 X - - × × Comparative sample 2 X Peelable resin × ○ Comparative sample 3 X Low Tg resin ○ × Comparative sample 4 Z A × ○ As is apparent from Table A1, both the adhesion and the image quality were good for all the transfer sheets for an adhesive layer (samples 1 to 5) according to the present invention. By contrast, both the adhesion and the image quality were poor for the transfer sheet, having no interposing layer, for an adhesive layer (comparative sample 1). For the comparative sample 2 using a releasable resin for constituting the interposing layer, the adhesion of the image-receptive layer transferred onto the postal card was unsatisfactory due to poor adhesion between the interposing layer and the image-receptive layer. For the comparative sample 3 using a resin, having a low glass transition point, for constituting the interposing layer, although the adhesion was good, bleeding of the dye into the interposing layer occurred resulting in poor image quality. For the comparative sample 4, the adhesion of the adhesive layer to the image-forming object was unsatisfactory. As is apparent from the foregoing detailed description, according to the present invention, an interposing layer is provided on the adhesive layer, and the adhesive layer is transferred onto a transfer material through the interposing layer. Therefore, when necessary properties, such as adhesion to a transfer material and prevention of bleeding of dye, are imparted to the interposing layer, properties required of the adhesive layer may be limited to those such as adhesion to the image-forming object and prevention of penetration of the adhesive, markedly increasing the degree of freedom in selection of materials for the adhesive layer and thus making it possible to provide a transfer sheet, for an adhesive layer, which has excellent properties such as excellent adhesion in the transfer to the transfer material and resistance to bleeding of the dye and, at the same time, has excellent adhesion to the image-forming object and prevention of penetration of the adhesive. The transfer of an interposing layer and an adhesive layer using the above transfer sheet, for an adhesive layer, onto an image-receptive layer of an intermediate transfer medium with an image formed thereon by transfer, followed by transfer of the image-receptive layer onto an image-forming object through the interposing layer and the adhesive layer can provide an object, with an image formed thereon, which is free from bleeding of the image and has a smooth image surface independently of the surface profile of the image-forming object.

Claims: An adhesive layer transfer sheet for forming an image on a releasable image-receptive layer in an intermediate transfer medium by a thermal sublimation transfer process by means of a thermal heat, said adhesive layer transfer sheet comprising: a substrate sheet; an adhesive layer formed on the substrate sheet; and an interposing layer formed on the adhesive layer, said interposing layer having a glass transition point higher than that of said adhesive layer. The adhesive layer transfer sheet according to claim 1, wherein the interposing layer has a glass transition point in the range of from 50 to 115°C and the adhesive layer has a glass transition point in the range of from 35 to 100°C. The adhesive layer transfer sheet according to claim 1 or 2, wherein at least one of the interposing layer and the adhesive layer contains a filler. An adhesive layer transfer sheet according to one of claims 1 to 3, which further comprises a back surface layer on the surface of the substrate sheet remote from the adhesive layer. An image forming method comprising the steps of: forming an image on a releasable image-receptive layer in an intermediate transfer medium by a thermal sublimation transfer process; putting the intermediate transfer medium and an adhesive layer transfer sheet according to any one of claims 1 to 4 on top of the other so as for the image-receptive layer to abut against the interposing layer and applying heat and/or pressure to the laminate by transfer means to transfer the adhesive layer onto the image-receiving layer through the interposing layer; and putting an image-forming object onto the intermediate transfer medium so as for the image-forming object to abut against the adhesive layer and applying heat and/or pressure to the laminate by transfer means to transfer the image-receptive layer onto the image-forming object through the adhesive layer. An object with an image formed thereon, comprising: an image-forming object; an adhesive layer and an interposing layer formed in this order on a desired site of the image receiving object, said interposing layer having a glass transition point higher than that of said adhesive layer, and an image-receptive layer provided on the interposing layer, the image-receptive layer having an image formed by a thermal sublimation transfer process. The object with an image formed thereon according to claim 6, wherein the interposing layer has a glass transition point in the range of from 50 to 115°C and the adhesive layer has a glass transition point in the range of from 35 to 100°C, the glass transition point of the interposing layer being above that of the adhesive layer. The object with an image formed thereon according to claim 6 or 7, wherein at least one of the interposing layer and the adhesive layer contains a filler.

Inventors: KITA TATSUYA, SHIBASAKI NAOJI, UENO TAKESHI, KITA, TATSUYA, SHIBASAKI, NAOJI, UENO, TAKESHI, KITA, Tatsuya Dai Nippon Printing Co., Ltd., SHIBASAKI, Naoji Dai Nippon Printing Co., Ltd., UENO, Takeshi Dai Nippon Printing Co., Ltd.
Applicants: DAINIPPON PRINTING CO LTD, DAI NIPPON PRINTING CO., LTD.
Application year: 1996
Main classification: B44C1
IPC codes: B44C1, B41M7