Thermal transfer sheet and manufacturing method for transfer product

Abstract

Provided is a thermal transfer sheet capable of inhibiting breakage of or an increase in the resistance value of a transferred conductive layer accompanying deformation of a substrate to which to transfer, even when printing a conductive pattern of thin wire. Also provided is a manufacturing method for a transfer product.　This thermal transfer sheet is disposed between a foil stamping plate on which a pattern is formed and a substrate to which to transfer, and performs thermal transfer. The thermal transfer sheet comprises a substrate and a transfer layer, and the transfer layer comprises, in order from the substrate side, a conductive layer containing carbon nanotubes or a conductive polymer, and an adhesive layer which melts due to the heating of the foil stamping plate. Alternatively, this thermal transfer sheet is stacked on a substrate to which to transfer on which a pattern is formed using a hot-melt material, and performs thermal transfer. The thermal transfer sheet comprises a substrate and a transfer layer, and the transfer layer comprises a conductive layer containing carbon nanotubes or a conductive polymer.

Description

Thermal transfer sheet and method for manufacturing a transferred product

[0001] The present invention relates to a thermal transfer sheet and a method for manufacturing a transferred product.

[0002] In gravure printing or the like, printing over a large area is possible. However, due to the influence of the viscosity of the ink, for example, being low viscosity, the thickness in a single application is thin. Therefore, when applying a functional ink such as a conductive ink, overcoating is required to reduce the resistivity to a predetermined value and achieve low resistance.

[0003] Particularly when performing pattern printing by gravure printing, in the case of a thin line, increasing the number of lines of the printing plate makes the plate depth shallower, while to apply thickly to achieve low resistance, it is necessary to deepen the plate depth of the printing plate. It is difficult to satisfy both of these two requirements with a single printing plate, so overcoating or the like is necessary, but problems such as an increase in the cost of the printing plate, misalignment, and pattern collapse may occur.

[0004] Even if printing of a thin line and low resistance can be achieved, in gravure printing or the like, basically it is premised on printing on a flat surface, and it is difficult to print on an uneven shape or pinpoint.

[0005] As a technology capable of addressing the above problems, a technology using a thermal transfer sheet has been proposed (Patent Document 1).

[0006] Japanese Patent No. 7194336

[0007] However, in the technology described in Patent Document 1, since a metal-based material such as a vapor deposition layer of aluminum or copper is used as the conductive layer for thermal transfer, the conductive layer after thermal transfer has poor elongation characteristics. When the transferred substrate is stretched for molding or the like, there is a high risk that the conductive layer formed as a thin line will break or the resistance value will increase. Not limited to stretching, a technology for suppressing disconnection of the conductive layer and increase in the resistance value accompanying deformation of the transferred substrate such as bending has been desired.

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to provide a thermal transfer sheet and a method for manufacturing a transferred product that can suppress disconnection of the transferred conductive layer and increase in the resistance value accompanying deformation of the transferred substrate even when printing a thin conductive pattern.

[0009] To solve the above problems, this disclosure provides the following inventions: [1] A thermal transfer sheet that is placed between a foil stamping plate on which a pattern is formed and a substrate to be transferred, comprising a substrate and a transfer layer, wherein the transfer layer comprises a conductive layer containing carbon nanotubes or a conductive polymer and an adhesive layer that melts when the foil stamping plate is heated, in this order from the substrate side. [2] A thermal transfer sheet that is placed between a foil stamping plate on which a pattern is formed and a substrate to be transferred, comprising a substrate and a transfer layer, wherein the transfer layer comprises a conductive layer containing carbon nanotubes or a conductive polymer and an adhesive that melts when the foil stamping plate is heated. [3] A thermal transfer sheet that is laminated on a substrate to be transferred on which a pattern is formed with a heat-melting material, and thermal transfer, comprising a substrate and a transfer layer, wherein the transfer layer comprises a conductive layer containing carbon nanotubes or a conductive polymer. [4] The thermal transfer sheet according to [3], wherein the transfer layer further comprises an adhesive that melts when the substrate to be transferred is heated during the thermal transfer. [5] A heat transfer sheet according to any one of [1] to [4], further comprising a release layer between the substrate and the transfer layer. [6] A heat transfer sheet according to any one of [1] to [4], wherein the transfer layer further comprises a resin layer laminated on the conductive layer. [7] A method for manufacturing a transfer product using the heat transfer sheet according to [1] or [2], wherein the heat transfer sheet is placed between the foil stamping plate and the substrate to be transferred, with the side opposite to the substrate facing the substrate to be transferred, the adhesive layer according to [1] or the adhesive according to [2] is melted by the heated foil stamping plate, and the transfer layer is heat-transferred onto the substrate to be transferred in the pattern shape of the foil stamping plate. [8] A method for manufacturing a transfer product according to [7], further comprising a release layer between the substrate and the transfer layer. [9] A method for manufacturing a transfer product according to [7], wherein the transfer layer further comprises a resin layer laminated on the conductive layer.

[10] A method for manufacturing a transfer product using the heat transfer sheet described in [3] or [4], comprising: laminating the substrate to be transferred and the heat transfer sheet such that the side opposite to the substrate and the side of the substrate on which the pattern is formed are in contact; melting the heat-melting material with the heated substrate to be transferred; and heat-transferring the transfer layer to the substrate in the shape of the pattern of the substrate.

[11] The method for manufacturing a transfer product according to

[10] , further comprising a release layer between the substrate and the transfer layer.

[12] The method for manufacturing a transfer product according to

[10] , wherein the transfer layer further comprises a resin layer laminated on the conductive layer.

[0010] According to the present invention's method for manufacturing a thermal transfer sheet and a transferred material, by using a conductive layer containing carbon nanotubes or a conductive polymer as the conductive layer to be transferred to the substrate, it is possible to suppress disconnection of the transferred conductive layer and an increase in resistance value due to deformation of the substrate, even when printing a conductive pattern of fine lines.

[0011] This figure schematically shows the manufacturing process of a transfer product using a thermal transfer sheet in an embodiment of the present invention. This figure schematically shows the manufacturing process of a transfer product using a thermal transfer sheet in an embodiment of the present invention. (A) is a photograph showing an example of a transfer plate used in the evaluation of the embodiment, (B) is a micrograph showing an example of a foil-stamped conductive layer, (C) is a photograph showing an example of a molding machine used to mold the APET sheet after pattern transfer, and (D) is a photograph showing a substrate to be transferred with a fine line pattern toner printed on it. (A) is a graph showing the surface resistance value with respect to the stretching ratio when the APET sheet after pattern transfer is stretch-molded, and (B) is a graph showing the difference in the change in surface resistance value with respect to the stretching ratio (Evaluation 1). (A) is a graph showing the surface resistance value with respect to the stretching ratio when the APET sheet after pattern transfer is stretch-molded, and (B) is a graph showing the difference in the change in surface resistance value with respect to the stretching ratio (Evaluation 2).

[0012] The embodiments for carrying out the present invention will be described in detail below. Figures 1(A) to 1(C) are schematic diagrams showing the manufacturing process of a transfer product using a heat transfer sheet in an embodiment of the present invention. The heat transfer sheet 1 in the embodiment shown in Figure 1(A) comprises a base material 2 and a transfer layer 3 (3a and 3b).

[0013] The base material 2 is not particularly limited in terms of material or thickness as long as it is in the form of a sheet, and can be appropriately selected considering thermal conductivity from the foil stamping plate 4, mechanical strength, heat resistance during thermal transfer, solvent resistance, etc. For example, resin film, paper, etc. can be used. Examples of resin materials for the resin film include polyester resins such as amorphous polyethylene terephthalate resin (A-PET), polyolefin resins such as polypropylene resin, polystyrene resin, polyamide resin, polyvinyl chloride resin, polycarbonate resin, acrylonitrile-butadiene-styrene copolymer resin (ABS resin), etc. These may be used individually or in combination of two or more. These resin materials may contain additives known to exist.

[0014] A release layer 2a may be further provided between the substrate 2 and the transfer layer 3 (3a and 3b). The release layer 2a is provided to improve the peelability of the transfer layer 3 (3a and 3b) from the substrate 2 and to improve the transferability to the substrate 5 to be transferred. The release layer 2a is not particularly limited and can be appropriately selected considering that it should not adhere to the transfer layer 3 (3a and 3b) side during heat transfer but remain on the substrate 2 side. For example, conventionally known resin materials can be used as release agents. As such resin materials, for example, fluorine-based or silicone-based resins, waxes, etc. can be used depending on the type of resin that makes up the substrate 2. These may contain additives known in resin materials. The thickness of the release layer 2a is not particularly limited, but is preferably 0.1 to 5 μm, more preferably 1 to 3 μm. The release layer 2a can be provided on the substrate 2, for example, by applying an ink containing the material of the release layer 2a onto the substrate 2. The application method is not particularly limited, but for example, a gravure printing press, reverse gravure, comma coater, lip coater, etc., can be used. After applying the ink containing the material for the release layer 2a, the release layer 2a can be formed by drying.

[0015] The transfer layer 3 (3a and 3b) comprises a conductive layer 3a and an adhesive layer 3b in that order from the substrate 2 side. The conductive layer 3a contains carbon nanotubes or a conductive polymer. Due to the properties of the fibrous carbon nanotubes and the polymer conductive polymer, the conductive layer 3a containing these exhibits excellent flexibility, stretchability in the planar direction, and ability to follow curved surfaces and shape deformations. Therefore, even when printing a conductive pattern of fine lines, it is possible to suppress disconnection of the transferred conductive layer 3a and increase in resistance value due to deformation of the substrate 5 to be transferred.

[0016] The carbon nanotubes are not particularly limited as long as they are conductive, but examples include single-walled carbon nanotubes (SWCNTs), which have a structure of a single graphene sheet, multi-walled carbon nanotubes (MWCNTs), which are composed of multiple layers of graphene sheets, fullerene tubes, bucky tubes, graphite fibrils, etc. These may be chemically modified to increase their affinity for solvents, etc., or they may be concentrated from a mixture of metallic carbon nanotubes and semiconducting carbon nanotubes. These may be used individually or in combination of two or more. Among these, single-walled carbon nanotubes are preferred because they have good flexibility, stretchability in the planar direction, and ability to follow curved surfaces and shape deformations. The conductive layer 3a containing carbon nanotubes may contain other components such as carbon nanotube dispersants, within a range that does not impair the effects of the present invention. The conductive layer 3a containing carbon nanotubes exhibits conductivity through the formation of a network of carbon nanotubes, i.e., an entanglement of carbon nanotube fibers. The conductive layer 3a containing carbon nanotubes may further contain conductive polymers as described below to complement its conductivity.

[0017] The conductive polymer is not particularly limited, but examples include polyanilines, polythiophenes, polypyrroles, polyazulenes, polyindoles, polycarbazoles, polyacetylenes, polyfurans, polyp-phenylenevinylenes, polyazulenes, polyp-phenylenes, polyp-phenylene sulfides, polyisothianaphthenes, and polythiazils. These may be used individually or in combination of two or more.

[0018] The conductive layer 3a is a layer formed by coating and drying a conductive ink containing carbon nanotubes or a conductive polymer. This conductive ink is a dispersion in which a conductive material is dispersed in a liquid, and contains carbon nanotubes or a conductive polymer and a solvent such as water or an organic solvent, and may also contain other components such as a binder resin or a dispersant. For example, a known conductive ink can be used.

[0019] The thickness of the conductive layer 3a is not particularly limited, but is preferably 0.01 to 5 μm, more preferably 0.05 to 1 μm, considering factors such as conductivity when a fine line pattern is formed, and suppression of disconnection of the transferred conductive layer 3a and increase in resistance due to deformation of the substrate 5 to be transferred.

[0020] The adhesive layer 3b melts upon heating of the foil stamping plate 4, and heat-transfers the transfer layer 3 (3a and 3b) to the substrate 5 to be transferred. The adhesive layer 3b is not particularly limited as long as it has adhesive properties that allow the conductive layer 3a to be transferred from the substrate 2 to the substrate 5 by melting upon heating of the foil stamping plate 4 during heat transfer and solidifying again after foil stamping. Since the conductive layer 3a does not have high adhesive properties on its own, and the substrate 2 has a release layer 2a which makes it easy to peel off, conventionally known adhesives can be used for the adhesive layer 3b. The adhesive is not particularly limited as long as it has properties such as melting point and softening temperature that melt upon heating of the foil stamping plate 4, for example, a resin material can be used. Specifically, examples include emulsion-type adhesives in which a resin is dispersed in an aqueous solvent, and solvent-type adhesives in which a resin is dissolved in a solvent. As the resin material of the adhesive component, thermoplastic resins, thermosetting resins, etc. can be used, and heat sealing technologies such as heat-seal resin inks can be applied. Examples of resin materials include saturated copolymer polyester resins and polyolefin resins. These may contain additives known in adhesives.

[0021] The thickness of the adhesive layer 3b is not particularly limited, but is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.

[0022] The adhesive layer 3b can be formed on the conductive layer 3a, for example, by applying ink to the conductive layer 3a provided on the substrate 2. The application method is not particularly limited, but for example, a gravure printing machine, reverse gravure, comma coater, lip coater, etc., can be used. The adhesive layer 3b can be formed by applying the ink containing the material for the adhesive layer 3b and then drying it.

[0023] As shown on the left side of Figure 1(A), the thermal transfer sheet 1 can be manufactured by providing a release layer 2a, a conductive layer 3a, and an adhesive layer 3b on a base material 2 in that order. If a release layer 2a is not required, the conductive layer 3a and adhesive layer 3b can be printed on a separate release film and transferred to the base material 2 to produce the thermal transfer sheet 1.

[0024] When manufacturing a transfer product using the heat transfer sheet 1, as shown on the right side of Figure 1(A), the heat transfer sheet 1 is placed between the foil stamping plate 4 and the substrate to be transferred 5, with the side opposite to the substrate 2 facing the substrate 5. The heated foil stamping plate 4 melts the adhesive layer 3b via the substrate 2, release layer 2a, and conductive layer 3a, and the portion of the adhesive layer 3b that melts into the shape of the foil stamping plate 4's pattern 4a adheres to the substrate to be transferred 5. This heat transfers the transfer layer 3 to the substrate to be transferred 5 in the shape of the foil stamping plate 4's pattern 4a. Subsequently, by peeling the substrate to be transferred 5 from the heat transfer sheet 1, the portion of the adhesive layer 3b that conforms to the shape of the foil stamping plate 4's pattern 4a and the conductive layer 3a in that portion are separated from the release layer 2a, and a transfer product can be obtained.

[0025] The foil stamping plate 4 can be configured using a conventionally known structure, and one can be used that has a printed pattern 4a formed by relief on one side. The material is not particularly limited as long as it has the desired thermal conductivity, and metal plates and the like can be used.

[0026] The material and shape of the transfer substrate 5 are not particularly limited, and materials such as resin and paper can be used. Examples of shapes include sheets, three-dimensional shapes, and molded products. In the case of molded products, it can be suitably used for molded products in which stretching is performed after transferring the transfer layer 3 from the heat transfer sheet 1. The stretching molding method is not particularly limited, but known methods such as vacuum forming, press forming, compressed air forming, and vacuum compressed air forming can be used.

[0027] The temperature of the foil stamping plate 4 during heat transfer is not particularly limited, but is preferably 60 to 180°C, and more preferably 80 to 150°C.

[0028] The thermal transfer sheet 1 of the embodiment shown in Figure 1(B) comprises a transfer layer 3(3c) which includes a conductive layer 3c containing carbon nanotubes or a conductive polymer and an adhesive. Except for the absence of an adhesive layer 3b and the inclusion of the adhesive of the adhesive layer 3b within the conductive layer 3c, the configuration is the same as the thermal transfer sheet 1 of Figure 1(A). According to this embodiment, the transfer layer 3(3c) transferred to the substrate 5 is electrically conductive in the vertical direction.

[0029] The thermal transfer sheet 1 shown in Figure 1(B) can be manufactured by providing a release layer 2a and a conductive layer 3c on a base material 2 in that order, as shown on the left side of Figure 1(B). If a release layer 2a is not required, the conductive layer 3c can be printed on a separate release film and transferred to the base material 2 to produce the thermal transfer sheet 1. When manufacturing a transfer using the thermal transfer sheet 1, as shown on the right side of Figure 1(B), the thermal transfer sheet 1 is placed between the foil stamping plate 4 and the substrate 5 to be transferred, with the side opposite to the base material 2 facing the substrate 5. The heated foil stamping plate 4 melts the adhesive in the conductive layer 3c via the base material 2 and the release layer 2a, and the portion of the conductive layer 3c that melts in the shape of the pattern 4a of the foil stamping plate 4 adheres to the substrate 5. This allows the transfer layer 3 (3c) to be heat-transferred onto the substrate 5 in the shape of the foil stamping plate 4. Subsequently, by peeling the substrate 5 from the heat transfer sheet 1, the portion of the conductive layer 3c that corresponds to the pattern 4a of the foil stamping plate 4 separates from the release layer 2a, thereby obtaining the transferred material.

[0030] The heat transfer sheet 1 of the embodiment shown in Figure 1(C) further comprises a resin layer 3d between the substrate 2 and the conductive layer 3c in the transfer layer 3 (3c and 3d). The resin layer 3d reinforces the conductive layer 3c and can suppress disconnection of the transferred conductive layer 3c and increase in resistance value due to deformation of the substrate 5 to be transferred, even when printing a fine-line conductive pattern. As the resin material for the resin layer 3d, it is preferable to use one that acts with a force in the opposite direction to the stretching when it follows the stretching of the substrate 5 to be transferred together with the conductive layer 3c, and in particular, one that generates tension when the substrate 5 to be transferred is molded. Such a resin material is not particularly limited, but elastomers, urethane resins, etc. can be used. Among these, elastomers are preferred in that they have excellent elasticity. As the elastomer, an elastic polymer, such as a thermoplastic or thermosetting elastomer, can be used. Specifically, examples include styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-propylene-styrene block copolymer (SEPS, hydrogenated SIS), styrene-ethylene-propylene block copolymer (SEP, hydrogenated styrene-isoprene block copolymer), styrene-isobutylene-styrene block copolymer (SIBS), styrene-silicone-based elastomers, olefin-based elastomers, urethane-based elastomers, polyester-based elastomers, polyamide-based elastomers, acrylic elastomers, and rubber-modified epoxy resins. These may be used individually or in combination of two or more. The resin layer 3d may contain other components such as known additives, as long as they do not impair the effects described above.

[0031] The thickness of the resin layer 3d is not particularly limited, but is preferably 0.01 to 5 μm, and more preferably 0.1 to 1 μm.

[0032] The resin layer 3d can be formed on the substrate 2, for example, by dispersing the resin layer 3d material in an aqueous solvent or the like to form an emulsion, or by applying an ink dissolved in a solvent, after the release layer 2a has been provided on the substrate 2. The application method is not particularly limited, but for example, a gravure printing machine, reverse gravure, comma coater, lip coater, etc., can be used. The resin layer 3d can be formed by applying an ink containing the resin layer 3d material and then drying it.

[0033] The position of the resin layer 3d in the transfer layer 3 is not particularly limited, but it is preferable that it is laminated on either the front or back surface of the conductive layer 3c (or the laminate of conductive layer 3a and adhesive layer 3b in Figure 1(A)), that is, on the surface of the conductive layer 3c (or the laminate of conductive layer 3a and adhesive layer 3b in Figure 1(A)) that is on the substrate 2 side, or on the surface of the conductive layer 3c (or the laminate of conductive layer 3a and adhesive layer 3b in Figure 1(A)) that is on the side opposite to the substrate 2. However, from the viewpoint of adhesion, it is preferable that the conductive layer 3c (or adhesive layer 3b) be on the outer surface of the transfer layer 3.

[0034] The thermal transfer sheet 1 shown in Figure 1(C) can be manufactured by providing a release layer 2a, a resin layer 3d, and a conductive layer 3c on a base material 2 in that order, as shown on the left side of Figure 1(C). If a release layer 2a is not required, the resin layer 3d and conductive layer 3c can be printed on a separate release film and transferred to the base material 2 to produce the thermal transfer sheet 1. When manufacturing a transfer using the thermal transfer sheet 1, as shown on the right side of Figure 1(C), the thermal transfer sheet 1 is placed between the foil stamping plate 4 and the substrate 5 to be transferred, with the side opposite to the base material 2 facing the substrate 5. The heated foil stamping plate 4 melts the adhesive in the conductive layer 3c via the base material 2 and the release layer 2a, and the melted portions of the conductive layer 3c and resin layer 3d that conform to the pattern 4a shape of the foil stamping plate 4 adhere to the substrate 5. This heat transfers the transfer layer 3 (3c and 3d) onto the substrate 5 in the shape of the pattern 4a on the foil stamping plate 4. Subsequently, by peeling the substrate 5 from the heat transfer sheet 1, the portion of the conductive layer 3c that conforms to the pattern 4a of the foil stamping plate 4 and the resin layer 3d of that portion are separated from the release layer 2a, thereby obtaining the transferred material. The conductive layer 3c may be replaced with the conductive layer 3a and adhesive layer 3b shown in Figure 1(A). In this case, the heated foil stamping plate 4 melts the adhesive layer 3b via the substrate 2 and the release layer 2a, and the portion of the adhesive layer 3b that has melted into the shape of the pattern 4a of the foil stamping plate 4 adheres to the substrate 5. This allows the transfer layers 3 (3b, 3a, and 3d) to be heat-transferred onto the substrate 5 in the shape of the pattern 4a of the foil stamping plate 4. Subsequently, by peeling the substrate 5 from the heat transfer sheet 1, the portion of the adhesive layer 3b that is shaped like the pattern 4a of the foil stamping plate 4, along with the conductive layer 3a and resin layer 3d of that portion, are separated from the release layer 2a, thereby obtaining the transferred material.

[0035] According to the method for manufacturing the thermal transfer sheet and transfer material in the embodiments shown in Figures 1(A) to (C), by using a conductive layer containing carbon nanotubes or a conductive polymer as the conductive layer 3a or 3c transferred to the substrate 5, even when printing a fine-line conductive pattern, it is possible to suppress disconnection of the transferred conductive layer and increase in resistance due to deformation of the substrate 5. By using thermal transfer technology, even if gravure printing or the like is used to form the transfer layer 3 (3a and 3b in Figure 1(A), 3c in Figure 1(B), and 3c and 3d in Figure 1(C)), solid printing is also acceptable, making it possible to produce a transfer material with fine lines and low resistance. Furthermore, since conductivity can be imparted to objects other than flat surfaces by transfer, there are fewer restrictions on the object. Compared to conventional fine-line printing, it is possible to manufacture at a lower cost, the printing area can be large, and it has higher resistance to stretching and bending compared to metal-based conductive layers, suppressing the decrease in conductivity. In addition, since the conductive layer containing carbon nanotubes or a conductive polymer has high transparency, the range of applications in various fields can be expanded.

[0036] Figures 2(A) to 2(C) schematically show the manufacturing process of a transfer product using a heat transfer sheet in another embodiment of the present invention.

[0037] The thermal transfer sheet 1 of the embodiment shown in Figure 2(A) comprises a base material 2 and a transfer layer 3(3a). The base material 2 is not particularly limited in material or thickness as long as it is in the form of a sheet, and the details described in the embodiments of Figures 1(A) to (C) are referred to. A release layer 2a may be further provided between the base material 2 and the transfer layer 3(3a), and the details described in the embodiments of Figures 1(A) to (C) are referred to. The transfer layer 3(3a) comprises a conductive layer 3a. The conductive layer 3a contains carbon nanotubes or a conductive polymer, and the details described in the embodiments of Figures 1(A) to (C) are referred to.

[0038] As shown on the left side of Figure 2(A), the thermal transfer sheet 1 can be manufactured by providing a release layer 2a and a conductive layer 3a on a base material 2 in that order. If a release layer 2a is not required, the conductive layer 3a can be printed on a separate release film and transferred to the base material 2 to produce the thermal transfer sheet 1.

[0039] When manufacturing a transfer product using the thermal transfer sheet 1, as shown on the right side of Fig. 2(A), the transfer substrate 5 and the thermal transfer sheet 1 are laminated such that the surface on the opposite side of the substrate 2 and the surface of the transfer substrate 5 on which the pattern 5a is formed are in contact with each other, and the pattern 5a of the heat-meltable material is melted by the heated transfer substrate 5, and the portion of the conductive layer 3a melted in the shape of the pattern 5a of the transfer substrate 5 adheres to the transfer substrate 5. Thereby, the transfer layer 3(3a) is thermally transferred onto the transfer substrate 5 in the pattern shape of the transfer substrate 5, and then the transfer substrate 5 is peeled off from the thermal transfer sheet 1, so that the portion of the conductive layer 3a in the shape of the pattern 5a of the transfer substrate 5 is separated from the release layer 2a, and a transfer product can be obtained.

[0040] As the transfer substrate 5, its material and shape are not particularly limited. As the material, for example, resin, paper, etc. can be used. Examples of the shape include film shape, three-dimensional shape, molded product, etc. In the case of a molded product, it can be suitably used for a molded product that undergoes a process involving stretching after transferring the transfer layer 3(3a) from the thermal transfer sheet 1. The molding method involving stretching is not particularly limited, but for example, known methods such as vacuum molding, press molding, pressure-air molding, vacuum-pressure-air molding, etc. can be used.

[0041] The pattern 5a of the transfer substrate 5 is formed by a heat-meltable material. As the heat-meltable material, toner, saturated copolymerized polyester resin, polyolefin resin, etc. can be used. The pattern 5a of the transfer substrate 5 can be formed as a thin line or the like by pattern printing on the transfer substrate 5 using a heat-meltable toner or the like by digital printing. Since toner can be used as the heat-meltable material, it is also possible to control the conductivity according to the density.

[0042] The temperature of the transfer substrate 5 during thermal transfer is not particularly limited, but considering the heat-melting temperature of toner or the like, it is preferably 60 to 180°C, more preferably 80 to 150°C.

[0043] The thermal transfer sheet 1 of the embodiment shown in FIG. 2(B) is, similar to FIG. 1(B), provided with a conductive layer 3c in which the transfer layer 3(3c) contains carbon nanotubes or a conductive polymer and an adhesive. It has the same configuration as the thermal transfer sheet 1 of FIG. 2(A) except that the adhesive is contained in the conductive layer 3c. According to this embodiment, even when toner or the like is used as the heat-melting material of the pattern 5a of the substrate 5 to be transferred, the transferability of the transfer layer 3(3c) can be further enhanced. For the adhesive of the conductive layer 3c, the content of the adhesive layer 3b described in the embodiments of FIGS. 1(A) to 1(C) is referred to.

[0044] The thermal transfer sheet 1 of the embodiment shown in FIG. 2(C) is, similar to FIG. 1(C), provided with a resin layer 3d between the substrate 2 and the conductive layer 3a or 3c in the transfer layer 3(3a and 3d, or 3c and 3d). The resin layer 3d reinforces the conductive layer 3a or 3c and can suppress disconnection or an increase in resistance value of the transferred conductive layer 3a or 3c due to deformation of the substrate 5 to be transferred even when printing a fine conductive pattern. As the resin material of the resin layer 3d, a material that applies a force in the direction opposite to the stretching when following the conductive layer 3a or 3c during stretching of the substrate 5 to be transferred, particularly a material that generates tension during stretching when molding the substrate 5 to be transferred, can be preferably used. For the resin layer 3d, the content of the resin layer 3d described in the embodiments of FIGS. 1(A) to 1(C) is referred to.

[0045] The position of the resin layer 3d in the transfer layer 3(3a and 3d, or 3c and 3d) is not particularly limited, but it is preferably laminated on either the front or back surface of the conductive layer 3a or 3c, that is, on the surface of the conductive layer 3a or 3c on the substrate 2 side or on the surface of the conductive layer 3a or 3c opposite to the substrate 2.

[0046] When manufacturing a transfer product using the heat transfer sheet 1 shown in Figures 2(B) and 2(C), as shown on the right side of Figures 2(B) and 2(C), the substrate to be transferred 5 and the heat transfer sheet 1 are laminated so that the side opposite to the substrate 2 and the side of the substrate to be transferred 5 on which the pattern 5a is formed are in contact. The heated substrate to be transferred 5 melts the pattern 5a of the heat-melting material, and if a conductive layer 3c is used, the adhesive in the conductive layer 3c is melted, and the portion of the conductive layer 3a or 3c and the resin layer 3d that has melted into the shape of the pattern 5a of the heat-melting material adheres to the substrate to be transferred 5. This heat transfers the transfer layer 3 (3a and 3d, or 3c and 3d) to the substrate to be transferred 5 in the shape of the pattern 5a of the substrate to be transferred 5. Subsequently, by peeling the substrate to be transferred 5 from the heat transfer sheet 1, the portion of the conductive layer 3a or 3c that has the shape of the pattern 5a of the heat-melting material and the resin layer 3d in that portion are separated from the release layer 2a, and a transfer product can be obtained.

[0047] According to the method for manufacturing the thermal transfer sheet and transfer material in the embodiments shown in Figures 2(A) to (C), by using a conductive layer containing carbon nanotubes or a conductive polymer as the conductive layer 3a or 3c transferred to the substrate 5, even when printing a fine-line conductive pattern, it is possible to suppress disconnection of the transferred conductive layer and increase in resistance due to deformation of the substrate 5. By using thermal transfer technology, even if gravure printing or the like is used to form the transfer layer 3 (3a in Figure 2(A), 3c in Figure 2(B), and 3a(3c) and 3d in Figure 2(C)), solid printing is also acceptable, making it possible to produce a transfer material with fine lines and low resistance. Furthermore, since conductivity can be imparted to objects other than flat surfaces by transfer, there are fewer restrictions on the object. Compared to conventional fine-line printing, it is possible to manufacture at a lower cost, the printing area can be large, and it has higher resistance to stretching and bending compared to metal-based conductive layers, suppressing the decrease in conductivity. In addition, since the conductive layer containing carbon nanotubes or a conductive polymer has high transparency, the range of applications in various fields can be expanded. In particular, by using digital printing or the like during heat transfer, it becomes possible to form and transfer fine line patterns without creating or using printing plates. Conventionally, printing plates had to be created and purchased for each of the several colors printed, but according to this embodiment, a pattern is printed digitally onto a transfer substrate 5 using heat-meltable toner, and then the transfer layer 3 of the heat transfer sheet 1 (3a in Figure 2(A), 3c in Figure 2(B), and 3a(3c) and 3d in Figure 2(C)) is heat-transferred onto the transfer substrate 5, thereby allowing the fine line pattern to be heat-transferred onto the substrate 5. Since toner can be used as the heat-meltable material, it is also possible to control conductivity by varying the density.

[0048] In the embodiments of Figures 1(A) to (C) and Figures 2(A) to (C), the method for manufacturing the heat transfer sheet and the transfer product is suitable for transferring a fine line pattern transfer layer 3 to a transfer substrate 5, and is particularly suitable for transferring a fine line pattern transfer layer 3 having a fine line width of 5 mm or less, 3 mm or less, and moreover, 0.1 to 1 mm to a transfer substrate 5.

[0049] In the embodiments shown in Figures 1(A) to (C) and Figures 2(A) to (C), the thermal transfer method is not particularly limited, and methods such as up-down thermal transfer, roll thermal transfer, and vacuum press transfer can be used.

[0050] In the embodiments shown in Figures 2(A) to (C), when a pattern 5a of a heat-melting material is formed on the transfer substrate 5 by digital printing, any known digital printing method that prints directly from data without using a printing plate can be applied, such as electrophotography or inkjet printing. When using toner for a heat-melting material, electrophotography can be suitably used.

[0051] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. (Carbon nanotube (CNT) ink) 11.7 g of single-walled carbon nanotubes (product name TUBALL CNT 93% manufactured by OCSiAl) and 17.5 g of PAA (polyacrylic acid) as a dispersant were dropped into 150 g of a mixed solvent of 2-propanol:ethanol = 9:1, and then dispersed using an ultrasonic disperser to prepare a CNT ink. (Polyaniline ink) 27 g of polymethyl methacrylate resin (PMMA: polymethyl methacrylate polymer manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in 63 g of a mixed solvent of toluene:methyl ethyl ketone = 1:1 to prepare a PMMA solution. A mixture of 120 g of deionized water, 15 g of dodecylbenzenesulfonic acid, 3.36 g of aniline, and 3 g of sulfuric acid was prepared. 22.5 g of deionized water and 10.26 g of ammonium persulfate were added dropwise, and the water was removed to prepare a polyaniline pigment. This polyaniline pigment was mixed with a PMMA solution and dispersed in a high-speed stirrer for 10 minutes to obtain a polyaniline ink. (CNT + Resin Ink) 0.1 g of single-walled carbon nanotubes (OCSiAl Co., Ltd., product name TUBALL CNT 93%) and 7.5 g of poly(3,4-ethylenedioxythiophene) (PEDOT) ink (Tosoh Corporation, SELFTRON S) were dropped into 50 g of pure water and dispersed using an ultrasonic disperser. 50 g of 2-propanol was added and the mixture was thoroughly stirred. Then, 15 g of heat-seal resin (adhesive B: Unitika Corporation, product name SB-1230) was added to prepare the CNT + resin ink. (Adhesive A) Arrowbase SB-1230N (Unitika Corporation) was used as the heat-seal resin ink. (Silver Ink) A silver ink made by mixing silver powder and binder resin was used. (Silver-copper ink) Electromagnetic wave shielding ink (Eleas EMI 51ac, manufactured by Edogawa Gosei Co., Ltd.) was used as the silver-copper ink. (Resin layer) Using the reverse gravure method, an ink made by dissolving styrene-butadiene-styrene (SBS) elastomer in a THF solvent was applied and dried to produce a resin layer.

[0052] <Example 1> CNT ink was printed on a release film, adhesive A was applied on top of it, and the resulting sheet was transferred onto coated paper to obtain the thermal transfer sheet of Example 1. <Example 2> CNT ink was printed on a release film, adhesive A was applied on top of it, and the resulting sheet was transferred onto a PET sheet to obtain the thermal transfer sheet of Example 2. <Example 3> A mixture of CNT ink and resin ink (adhesive B) was applied to a release film, and the resulting sheet was transferred onto a PET sheet to obtain the thermal transfer sheet of Example 3. <Example 4> A resin layer of styrene-butadiene-styrene copolymer (SBS) was applied to a release film, a mixture of CNT ink and resin ink (adhesive B) was applied on top of it, and the resulting sheet was transferred onto a PET sheet to obtain the thermal transfer sheet of Example 4. <Example 5> Polyaniline ink was printed on a release film, adhesive A was applied on top of it, and the resulting sheet was transferred onto a PET sheet to obtain the thermal transfer sheet of Example 5. <Example 6> CNT ink was printed on a release film, and the sheet was placed on coated paper that had a resin ink (adhesive A) pattern printed on it beforehand and heat-transferred to obtain the heat transfer sheet of Example 6. <Example 7> CNT ink was printed on a release film, and the sheet was heat-transferred onto a PET sheet that had a resin ink (adhesive A) pattern printed on it beforehand to obtain the heat transfer sheet of Example 7. <Example 8> A resin layer of styrene-butadiene-styrene copolymer (SBS) was applied to a release film, CNT ink was printed on it, and the sheet was heat-transferred onto a PET sheet that had a resin ink (adhesive A) pattern printed on it beforehand to obtain the heat transfer sheet of Example 8. <Example 9> Polyaniline ink was printed on a release film, and the sheet was heat-transferred onto a PET sheet that had a resin ink (adhesive A) pattern printed on it beforehand to obtain the heat transfer sheet of Example 9. <Comparative Example 1> Silver ink was printed on a release film, adhesive A was applied on it, and the sheet was transferred onto coated paper to obtain the heat transfer sheet of Comparative Example 1. <Comparative Example 2> Silver ink was printed on a release film, adhesive A was applied on top of it, and the resulting sheet was transferred onto a PET sheet to obtain the thermal transfer sheet of Comparative Example 2. <Comparative Example 3> Silver copper ink was printed on a release film, adhesive A was applied on top of it, and the resulting sheet was transferred onto a PET sheet to obtain the thermal transfer sheet of Comparative Example 3.<Comparative Example 4> Silver ink was printed on a release film, and the sheet was placed on coated paper that had been pre-patterned with resin ink (adhesive A) and heat-transferred to obtain the heat transfer sheet of Comparative Example 4. <Comparative Example 5> Silver ink was printed on a release film, and the sheet was placed on a PET sheet that had been pre-patterned with resin ink (adhesive A) and heat-transferred to obtain the heat transfer sheet of Comparative Example 5. <Comparative Example 6> Silver copper ink was printed on a release film, and the sheet was placed on a PET sheet that had been pre-patterned with resin ink (adhesive A) and heat-transferred to obtain the heat transfer sheet of Comparative Example 6.

[0053] Evaluation 1: In the following evaluations, a two-terminal resistance meter was used to measure surface resistivity. A cylinder foil stamping machine (Heidelberg HS-1 modified model) was used for thermal transfer, and thermal transfer was performed under the conditions of a temperature of 150°C and foil stamping pressure: weak and strong.

[0054] The transfer layer of a heat transfer sheet was heat-transferred onto a substrate (amorphous polyethylene terephthalate resin (A-PET sheet), 0.4 mm thick, with a transmittance of 89.45% at a wavelength of 550 nm and a total wavelength transmittance of 89.42%), and the transparency of the heat-transferred substrate was evaluated. In solid transfer, a ○ was given if the transfer was successful based on the appearance after transfer, and a × was given if there was a transfer defect. In addition, the transmittance was measured using a spectrophotometer: UV-1800 (Shimadzu Corporation), and a ○ was given if the total wavelength transmittance after transfer was 50% or more, and a × was given if it was less than 50%.

[0055] The conductivity was evaluated from the surface resistivity of the heat-transferred substrate. In solid transfer, the change in value before and after transfer was 10 3 Ω / □ or less is ○, 10 3A value greater than Ω was marked as "fail". The fineness of the lines was also evaluated. A transfer layer was heat-transferred from a thermal transfer sheet to a foil stamping plate (foil stamping plate shape: fine line plate (0.1-5.0 mm, an example is shown in Figure 3(A)) onto a transfer substrate (paper: commercially available coated paper, or release film: A-PET sheet with a thickness of 50 μm). The surface resistivity and the line width that could be thinned were confirmed. The appearance of the fine lines was examined under a microscope, and the condition of the fine lines was scored: 1 point: fine lines were not acceptable, 2 points: edges remained, 3 points: clean fine lines. An example of the evaluation criteria is shown in Figure 3(B). As a fine line criterion, a line width of 3.0 mm was considered acceptable. The fineness of the lines up to 3.0 mm was evaluated based on the change in surface resistivity before and after transfer and the printing condition (solid transfer was not acceptable), as described above.

[0056] The performance of the heat-transferred substrate during stretching was evaluated based on changes in appearance and conductivity. The transfer layer of the heat transfer sheet was heat-transferred solidly onto the APET sheet, the substrate to be transferred. The A-PET sheet after heat transfer was then molded using a foil plate (shape: solid plate, an example is shown in Figure 3(C)) on a molding machine (tabletop molding machine, manufactured by Rayama Pack) to stretch the transfer layer. For appearance, ○ was used if the result was equivalent to that of a PET sheet without transfer when the stretching ratio was 1.5 times, and × was used if the result was not the same as that of a PET sheet without transfer when the stretching ratio was 2.5 times. For conductivity, the change in surface resistance value (difference) before and after stretching was 10 4 Ω / □ is less than ○, 10 4 A value of Ω / □ or greater was marked as ×. Figure 4(A) is a graph showing the surface resistance value as a function of the stretching ratio, and Figure 4(B) is a graph showing the difference in the change in surface resistance value as a function of the stretching ratio. The evaluation results are shown in Table 1.

[0057]

[0058] Evaluation 2 In the following evaluations, a two-terminal resistance meter was used to measure surface resistivity. For thermal transfer, a Multi Dry Coater DC-X (manufactured by Yukos Co., Ltd.) was used, and solid heat transfer was performed under the following conditions: temperature 150°C, transfer speed 7 rpm, foil plate shape: fine line pattern with toner printing (an example is shown in Figure 3(D)).

[0059] The transfer layer of a thermal transfer sheet was thermally transferred to a substrate (A-PET sheet, 0.4 mm thick, 89.45% transmittance at 550 nm, 89.42% total wavelength transmittance) on which a fine line pattern had been formed by toner printing. The transparency of the thermally transferred substrate was then evaluated. In solid transfer, a ○ was given if the transfer was successful based on the appearance after transfer, and a × was given if there was a transfer failure. In addition, transmittance was measured using a spectrophotometer: UV-1800 (Shimadzu Corporation), and a ○ was given if the total wavelength transmittance after transfer was 50% or higher, and a × was given if it was less than 50%.

[0060] The conductivity was evaluated from the surface resistivity of the heat-transferred substrate. In solid transfer, the change in value before and after transfer was 10 3 Within Ω / □, ○, 10 3 A value greater than Ω was marked as "fail". The fineness of the lines was also evaluated. A transfer layer was heat-transferred from a thermal transfer sheet to a transfer substrate (paper: commercially available coated paper, or release film: 50 μm thick A-PET sheet) on which a fine line pattern (0.1-5.0 mm) had been formed by toner printing. The surface resistivity and the line width that could be thinned were then confirmed. The appearance of the fine lines was examined under a microscope, and the condition of the fine lines was scored as follows: 1 point: fine lines were unacceptable, 2 points: edges remained, 3 points: clean fine lines. An example of the evaluation criteria is shown in Figure 3(B). As a fine line criterion, a line width of 3.0 mm was considered acceptable. The fineness of the lines up to 3.0 mm was evaluated based on the change in surface resistivity before and after transfer and the printing condition (solid transfer was unacceptable), as described above.

[0061] The performance of the heat-transferred substrate during stretching was evaluated based on changes in appearance and conductivity. The transfer layer of the heat transfer sheet was heat-transferred onto an A-PET sheet of the substrate, which had been toner-printed in solid colors. The A-PET sheet after heat transfer was then molded using a molding machine (desktop molding machine, manufactured by Rayama Pack) with a foil plate (shape: solid plate, an example is shown in Figure 3(C)) to stretch the transfer layer. For appearance, a ○ was used if the result was equivalent to that of a PET sheet without transfer when the stretching ratio was 1.5 times, and a × was used if the result was not the same as that of a PET sheet without transfer when the stretching ratio was 1.5 times. For conductivity, the change in surface resistance value (difference) before and after stretching was 10 when the stretching ratio was 2.5 times. 4 Ω / □ is less than ○, 10 4A value of Ω / □ or greater was marked as ×. Figure 5(A) is a graph showing the surface resistance value as a function of the stretching ratio, and Figure 5(B) is a graph showing the difference in the change in surface resistance value as a function of the stretching ratio. The evaluation results are shown in Table 2.

[0062]

[0063] 1. Thermal transfer sheet 2. Substrate 2a. Release layer 3a. Conductive layer 3b. Adhesive layer 3c. Adhesive-containing conductive layer 3d. Resin layer 4. Foil stamping plate 4a. Pattern 5. Substrate to be transferred 5a. Pattern

Claims

1. A thermal transfer sheet that is placed between a foil stamping plate on which a pattern has been formed and a substrate to be transferred, and which comprises a substrate and a transfer layer, wherein the transfer layer comprises a conductive layer containing carbon nanotubes or a conductive polymer and an adhesive layer that melts when the foil stamping plate is heated, in this order from the substrate side.

2. A thermal transfer sheet that is placed between a foil stamping plate on which a pattern is formed and a substrate to be transferred, and heat-transferred, comprising a substrate and a transfer layer, wherein the transfer layer comprises a conductive layer containing carbon nanotubes or a conductive polymer and an adhesive that melts when the foil stamping plate is heated.

3. A thermal transfer sheet that is laminated onto a transfer substrate having a pattern formed on it using a heat-melting material, and heat-transferred, comprising a substrate and a transfer layer, wherein the transfer layer comprises a conductive layer containing carbon nanotubes or a conductive polymer.

4. The heat transfer sheet according to claim 3, wherein the transfer layer further comprises an adhesive that melts upon heating of the substrate to be transferred during the heat transfer.

5. The thermal transfer sheet according to any one of claims 1 to 4, further comprising a release layer between the substrate and the transfer layer.

6. The thermal transfer sheet according to any one of claims 1 to 4, wherein the transfer layer further comprises a resin layer laminated on the conductive layer.

7. A method for manufacturing a transfer product using a heat transfer sheet according to claim 1 or 2, comprising: placing the heat transfer sheet between the foil stamping plate and the substrate to be transferred, with the side opposite to the substrate facing the substrate to be transferred; melting the adhesive layer according to claim 1 or the adhesive according to claim 2 with the heated foil stamping plate; and heat-transferring the transfer layer onto the substrate to be transferred in the pattern shape of the foil stamping plate.

8. The method for producing a transfer product according to claim 7, further comprising a release layer between the substrate and the transfer layer.

9. The method for manufacturing a transfer product according to claim 7, wherein the transfer layer further comprises a resin layer laminated on the conductive layer.

10. A method for manufacturing a transfer product using a heat transfer sheet according to claim 3 or 4, comprising: laminating the substrate to be transferred and the heat transfer sheet such that the side opposite to the substrate and the side of the substrate on which the pattern is formed are in contact; melting the heat-melting material with the heated substrate to be transferred; and heat-transferring the transfer layer to the substrate in the shape of the pattern of the substrate.

11. The method for producing a transfer product according to claim 10, further comprising a release layer between the substrate and the transfer layer.

12. The method for manufacturing a transfer product according to claim 10, wherein the transfer layer further comprises a resin layer laminated on the conductive layer.

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