Image transfer sheet, sheet with adhesive layer, and image transfer method

Abstract

An image transfer sheet (1) is obtained by laminating a first release layer (11), a transfer layer (20) including an image layer (22), an adhesive layer (30), and a second release layer (12) in this order. The adhesive layer (30) includes an adhesive layer body part (31) and an adhesive force reduction part (32) provided on the surface of the adhesive layer body part (31). The adhesive layer body part (31) is in contact with the second release layer (12), and the adhesive force reduction part (32) is in contact with the transfer layer (20). When the adhesive force between the first release layer (11) and the transfer layer (20) is denoted by A, the adhesive force between the second release layer (12) and the adhesive layer body part (31) is denoted by C, the adhesive force between the adhesive force reduction part (32) and the transfer layer (20) is denoted by D, and the tensile strength of the adhesive layer (30) is denoted by F1, all of the following relational expressions (1) to (3) are satisfied.　(1): Adhesive force C < adhesive force D (2): Adhesive force C < adhesive force A (3): Tensile strength F1 < adhesive force C

Description

Image transfer sheet, sheet with adhesive layer, and image transfer method

[0001] The present invention relates to an image transfer sheet for transferring various images, a sheet with an adhesive layer, and an image transfer method.

[0002] Patent Document 1 describes an image transfer sheet for transferring an image to a transfer surface. In the image transfer sheet of Patent Document 1, an image layer is partially formed between a transfer film and an adhesive layer (paste layer), and the paste layer is protected by a release paper. When transferring the image layer to the transfer surface, the release paper is peeled off and then turned over, and the adhesive layer (paste layer) is adhered to the transfer surface. The transfer film has releasability with respect to the image layer and is easily peeled off, but has easy adhesiveness with respect to the adhesive layer (paste layer) and is difficult to peel off. Therefore, when the transfer film is peeled off, the image layer is easily peeled off from the transfer film and remains on the transfer surface, and the unnecessary adhesive layer (paste layer) around the image layer is peeled off together with the transfer film and removed from the transfer surface.

[0003] Japanese Patent No. 6260878

[0004] When manufacturing an image transfer sheet such as that of Patent Document 1, generally, a sheet with an adhesive layer in which an adhesive layer is provided on the release surface of a release sheet (release paper in Patent Document 1) is used. This type of sheet with an adhesive layer is provided as a product in a state where the surface of the adhesive is protected by a protective film. Therefore, at the time of use, the protective film is peeled off from the release surface.

[0005] The manufacture of an image transfer sheet such as that of Patent Document 1 is performed, for example, by the following procedure. First, a sheet with an adhesive layer from which the protective film has been peeled off to expose the adhesive is set in a printer, and ink is ejected onto the surface of the adhesive to print an image layer. Thereafter, another release sheet (transfer film in Patent Document 1) is laminated on the surface of the image layer. At this time, the release sheet laminated on the surface of the image layer is used as a product in which the release surface is covered with a protective film, similar to the sheet with an adhesive layer. Therefore, at the time of use, the protective film is peeled off from the release surface.

[0006] Therefore, in the conventional method of manufacturing image transfer sheets as described above, both the adhesive-coated sheet and the peelable sheet, which are the materials, require the protective film to be peeled off immediately before use, resulting in a large amount of protective film being generated as waste.

[0007] Furthermore, in the conventional method of manufacturing image transfer sheets as described above, the protective film is peeled off to expose the adhesive, and the sheet is set in the printer as a printing medium. Ink is then ejected onto the surface of the adhesive to print the image layer. When using a sheet with an adhesive surface as a printing medium in this way, it is not possible to supply the printing medium to the printer in a roll manner. Nor is it possible to set the printing medium in a stacked state in the paper cassette. Consequently, it is not possible to continuously supply the printing medium and print continuously, making it impossible to manufacture image transfer sheets efficiently.

[0008] Furthermore, with conventional image transfer sheets as described above, after the adhesive layer is bonded to the transfer surface, the transfer film is peeled off, simultaneously removing only the excess adhesive layer around the image layer. However, if the adhesive layer is difficult to cut, there is a risk that only the excess portion may not be removed. Also, if the transfer surface is highly adhesive to the adhesive, there is a risk that the excess adhesive layer cannot be peeled off the transfer surface, making it impossible to remove only the excess portion. To avoid such problems, it is necessary to cut and remove the excess adhesive layer around the image layer in advance, but such processing is time-consuming.

[0009] In view of the above, the present invention aims to propose an image transfer sheet that reduces waste generated during manufacturing, is suitable for continuous supply of printing medium when printing an image layer, and allows for easy removal of unwanted adhesive around the image layer.

[0010] Furthermore, the present invention aims to propose an adhesive-coated sheet suitable for manufacturing the above-mentioned image transfer sheet, and an image transfer method using the above-mentioned image transfer sheet.

[0011] To solve the above problems, the present invention provides an image transfer sheet comprising a first release layer, a transfer layer including an image layer, an adhesive layer, and a second release layer laminated in this order, wherein the adhesive layer comprises an adhesive layer body and an adhesive force reducing portion provided on the surface of the adhesive layer body, the adhesive layer body is in contact with the second release layer, the adhesive force reducing portion is in contact with the transfer layer, the adhesive force between the first release layer and the transfer layer is A, the adhesive force between the second release layer and the adhesive layer body is C, the adhesive force between the adhesive force reducing portion and the transfer layer is D, and the tensile strength of the adhesive layer is F1, and the present invention is characterized in that all of the following relational expressions (1) to (3) are satisfied: Adhesion force C < Adhesion force D ... (1) Adhesion force C < Adhesion force A ... (2) Tensile strength F1 < Adhesion force C ... (3)

[0012] In the image transfer sheet of the present invention, when transferring a transfer layer (a layer including the image layer) to a transfer surface, the second release layer protecting the adhesive layer is first peeled off to expose the adhesive layer. At this time, since relation (1) is satisfied, only the second release layer can be peeled off without the adhesive layer peeling off from the transfer layer. Also, since relation (2) is satisfied, the transfer layer and adhesive layer do not peel off from the first release layer together with the second release layer. Furthermore, since relation (3) is satisfied, when peeling off the second release layer, the surface of the adhesive layer is easily cut at the boundary between the area without the transfer layer and the area with the transfer layer, and the entire adhesive layer is easily cut starting from the cut point. As a result, the unnecessary adhesive layer around the transfer layer can be easily removed simply by peeling off the second release layer.

[0013] Furthermore, according to the present invention, since the adhesive layer surface is equipped with an adhesive strength reducing portion, when manufacturing an image transfer sheet, the adhesive-coated sheet used as a material does not need to have a protective film attached to the surface of the adhesive layer for protection. Therefore, the amount of protective film generated as waste when manufacturing an image transfer sheet can be reduced.

[0014] Furthermore, according to the present invention, since the adhesive layer has an adhesive strength reducing portion on its surface, it is possible to use an adhesive-coated sheet with an adhesive layer on one side of the first release layer as a printing medium for printing the image layer. When an adhesive-coated sheet is used as a printing medium, the adhesive strength reducing portion becomes the printing surface, and the printing surface is not adhesive. Therefore, the printing medium can be supplied to the printing device by either a roll method or by setting it in a stacked state in a paper cassette. Consequently, continuous printing is possible, and the image transfer sheet can be manufactured efficiently.

[0015] In the image transfer sheet of the present invention, the transfer layer comprises a protective layer laminated on the first release layer and an image layer laminated on the protective layer, the adhesive force A is the adhesive force between the first release layer and the protective layer, the adhesive force D is the adhesive force between the adhesive force reduction portion and the image layer, the adhesive force between the protective layer and the image layer is B, and the tensile strength of the protective layer is F2. In this case, it is preferable that the following relational expressions (4) and (5) are satisfied: Adhesive force A < Adhesive force B ... (4) Tensile strength F2 < Adhesive force A ... (5)

[0016] In this invention, when transferring the transfer layer to the transfer surface, the adhesive layer of the image transfer sheet is exposed, then it is turned over and attached to the transfer surface, and the first release layer is peeled off and removed. At this time, since relation (4) is satisfied, only the first release layer can be peeled off, leaving a protective layer on the surface of the image layer. Also, since relation (5) is satisfied, when the first release layer is peeled off, the protective layer is easily cut at the boundary between the area with the image layer and the area without the image layer. Therefore, the unnecessary protective layer around the image layer can be easily removed. Furthermore, when printing the image layer, it is sufficient to print on the surface of the protective layer, so there is no need to print on the adhesive side. Therefore, continuous printing is possible, and the image transfer sheet can be manufactured efficiently.

[0017] In the image transfer sheet of the present invention, the sheet comprises an image region in which the image layer is provided between the protective layer and the adhesive layer, and a non-image region in which the image layer is not provided between the protective layer and the adhesive layer, wherein in the non-image region, the adhesive force reducing portion is in contact with the protective layer, and when the adhesive force between the protective layer and the adhesive force reducing portion is E, it is preferable that the following relation (6) is satisfied: Adhesion force E < Adhesion force C ... (6)

[0018] As described above, in the present invention, when transferring a transfer layer to a transfer surface using an image transfer sheet, the second release layer protecting the adhesive layer is peeled off first. At this time, the adhesive layer in the non-image areas where there is no transfer layer is also peeled off and removed. If relation (6) is satisfied, it is possible to avoid the adhesive layer in the non-image areas remaining on the side of the protective layer.

[0019] In the image transfer sheet of the present invention, the image layer is preferably a UV-curable ink layer. In this case, the curing of the ink can increase the bonding force between the image layer and the adhesive-reducing portion. Therefore, the above relational equation (1) can be satisfied.

[0020] In the image transfer sheet of the present invention, the transfer layer may consist of an image layer laminated on the first release layer and a UV-curable clear ink layer laminated on the image layer. In this case, the adhesive force A is the adhesive force between the first release layer and the image layer, and the adhesive force D is the adhesive force between the adhesive force reduction portion and the clear ink layer. Thus, by using a UV-curable clear ink layer, the bonding force with the adhesive force reduction portion can be increased by the curing of the ink. Therefore, the above relational expression (1) can be satisfied. Furthermore, the entire transfer layer (image layer and clear ink layer) can be formed by printing.

[0021] In the image transfer sheet of the present invention, the sheet comprises an image region in which the image layer and the clear ink layer are provided between the first release layer and the adhesive layer, and a non-image region in which the image layer and the clear ink layer are not provided between the first release layer and the adhesive layer, wherein in the non-image region, the adhesive force reducing portion is in contact with the first release layer, and when the adhesive force between the first release layer and the adhesive force reducing portion is F, it is preferable that the following relation (7) is satisfied: Adhesion force F < Adhesion force C ... (7)

[0022] As described above, in the present invention, when transferring a transfer layer to a transfer surface using an image transfer sheet, the second release layer protecting the adhesive layer is peeled off first to expose the adhesive layer. At this time, if relation (7) is satisfied, the unnecessary portion of the adhesive layer does not remain on the side of the first release layer, but is removed together with the second release layer. Therefore, the unnecessary portion of the adhesive layer can be easily removed.

[0023] In the image transfer sheet of the present invention, when the tensile strength of the adhesive strength reduction portion is F3 and the tensile strength of the adhesive layer body portion is F4, it is preferable that the following relational expression (8) is satisfied: Tensile strength F3 < Tensile strength F4 ... (8)

[0024] Thus, by forming an adhesive layer that is non-adhesive only on its surface and easily cut, it is possible to obtain an adhesive layer that has the necessary adhesiveness to bond the transfer layer to the transfer surface, and that can be easily cut when pulled, allowing for easy removal of unwanted portions. In other words, if the tensile strength F3 of the adhesive-reducing portion is sufficiently small and less than the adhesive strength C, the adhesive-reducing portion (the layer with weak tensile strength) will easily cut at the boundary between the area without the transfer layer and the area with the transfer layer when the second release layer is peeled off. If the surface portion of the adhesive layer (the adhesive-reducing portion) is cut, the entire adhesive layer can be easily cut starting from the point of breakage.

[0025] In the image transfer sheet of the present invention, the adhesive strength reduction portion is preferably one of a foil layer, a water-soluble lacquer layer, or an oil-based lacquer layer. This makes it possible to easily form an adhesive layer that is non-adhesive only on the surface and easily torn.

[0026] To solve the above problem, the adhesive sheet of the present invention is an adhesive sheet in which an adhesive layer is laminated on a second release layer, wherein the adhesive layer comprises an adhesive layer body and an adhesive force reducing portion provided on the surface of the adhesive layer body, and when the adhesive layer body is in contact with the second release layer, and the tensile strength of the adhesive force reducing portion is F3 and the tensile strength of the adhesive layer body is F4, the following relational expression (8) is satisfied: Tensile strength F3 < Tensile strength F4 ... (8)

[0027] Thus, the adhesive-coated sheet of the present invention has an adhesive layer that is non-adhesive only on the surface and easily torn. Therefore, when used in the manufacture of the above-mentioned image transfer sheet, it is possible to provide an adhesive layer that has the necessary adhesiveness to bond the transfer layer to the transfer surface, and that can be easily torn when pulled, allowing for easy removal of unwanted portions.

[0028] In the adhesive sheet of the present invention, the adhesive strength reducing portion is preferably one of a foil layer, a water-soluble lacquer layer, or an oil-based lacquer layer. In this way, an adhesive layer with the characteristic of being non-adhesive only on the surface and easily torn can be easily formed.

[0029] In the adhesive sheet of the present invention, the adhesive strength reducing portion is a layer adhered to the surface of the transfer layer in an image sheet in which a transfer layer including an image layer is laminated on a first release layer, and when the adhesive strength between the adhesive strength reducing portion and the transfer layer is D, the adhesive strength between the first release layer and the adhesive strength reducing portion is F, and the adhesive strength between the second release layer and the main body of the adhesive layer is C, it is preferable that the following relational expressions (1) and (7) are satisfied: Adhesion C < Adhesion D ... (1) Adhesion F < Adhesion C ... (7)

[0030] Thus, if relation (1) is satisfied, when the adhesive-coated sheet of the present invention is used in the manufacture of the above-mentioned image transfer sheet, the adhesive layer does not peel off from the transfer surface, and only the second release layer can be peeled off. Furthermore, if relation (7) is satisfied, the unnecessary portion of the adhesive layer does not remain on the side of the first release layer, but is removed together with the second release layer. Therefore, the unnecessary portion of the adhesive layer can be easily removed.

[0031] Next, in order to solve the above problems, the image transfer method of the present invention performs a bonding step in which an image sheet having a transfer layer containing an image layer laminated on a first release layer and an adhesive sheet having an adhesive layer laminated on a second release layer are bonded together with the transfer layer and the adhesive layer facing each other, the adhesive layer comprises an adhesive layer body and an adhesive force reducing portion provided on the surface of the adhesive layer body, the adhesive layer body is in contact with the second release layer, the adhesive force reducing portion is in contact with the transfer layer by the bonding step, the transfer layer comprises a curable ink layer in contact with the adhesive force reducing portion, a curing step is performed after the bonding step to cure the curable ink layer and bond the curable ink layer and the adhesive force reducing portion, the image sheet is the The transfer layer comprises an image region on which an image layer is formed and a non-image region on which an image layer is not formed, and after the curing step, an unwanted adhesive layer removal step is performed to peel off the second release layer, in the unwanted adhesive layer removal step, the adhesive force reduction portion is cut along the boundary between the image region and the non-image region by the tensile force applied to the adhesive force reduction portion via the adhesive layer body portion, and the portion of the adhesive layer located in the non-image region is removed together with the second release layer to form an adhesive-coated image sheet on which the adhesive layer is applied to the surface of the transfer layer, and after the unwanted adhesive layer removal step, the adhesive layer of the adhesive-coated image sheet is bonded to the transfer surface, and then a transfer step is performed to peel off the first release layer.

[0032] Thus, in the image transfer method of the present invention, when manufacturing an image transfer sheet, the image sheet and the adhesive-coated sheet are bonded together. However, since the adhesive-coated sheet has an adhesive strength reducing portion on its surface, it does not need to be protected with a protective film. Therefore, the amount of protective film generated as waste during the manufacturing of the image transfer sheet can be reduced. Furthermore, when performing a transfer using the manufactured image transfer sheet, the second release layer is first peeled off to expose the adhesive layer. At this time, the adhesive strength reducing portion is easily cut, and the entire adhesive layer is easily cut starting from the cut point. Therefore, the unnecessary adhesive layer around the transfer layer can be easily removed.

[0033] In the image transfer method of the present invention, the transfer layer comprises a protective layer laminated on the first release layer and an image layer laminated on the protective layer, the image layer being the curable ink layer, the protective layer being formed in the image region and the non-image region, the adhesive force reducing portion being in contact with the protective layer in the non-image region, in the unwanted adhesive layer removal step, the adhesive force reducing portion in contact with the protective layer being peeled off from the protective layer, and in the transfer step, when peeling off the first release layer, the protective layer is preferably cut along the boundary between the image region and the non-image region by the tensile force applied to the protective layer through the first release layer, leaving the protective layer on the surface of the image layer in the image region and removing the protective layer together with the first release layer in the non-image region.

[0034] Thus, in the image transfer method of the present invention, since a protective layer is laminated on the first release layer before forming the image layer, an image layer protected by the protective layer can be transferred. The protective layer can be easily cut when the first release layer is peeled off, so any unnecessary protective layer around the image layer can be easily removed. Furthermore, when printing the image layer, it is only necessary to print on the surface of the protective layer, so there is no need to print on an adhesive surface. Therefore, continuous printing is possible, and the image layer can be formed efficiently.

[0035] In the image transfer method of the present invention, it is preferable that the adhesive strength reduction portion has a lower tensile strength than the main adhesive layer portion. By forming an adhesive layer that is non-adhesive only on the surface and easily cut, it is possible to obtain an adhesive layer that has the necessary adhesiveness to bond the transfer layer to the transfer surface, and that can be easily cut when pulled, allowing for easy removal of unwanted portions.

[0036] In the image transfer method of the present invention, the adhesive force reducing portion is preferably one of a foil layer, a water-soluble lacquer layer, or an oil-based lacquer layer formed on the surface of the adhesive layer body. In this way, an adhesive layer with the characteristic of being non-adhesive only on the surface and easily torn can be easily formed.

[0037] According to the present invention, waste generated during the manufacturing of image transfer sheets can be reduced. In addition, the unnecessary adhesive layer around the transfer layer can be easily removed. Furthermore, since there is no need to print on the adhesive surface when manufacturing the image transfer sheet, continuous printing is possible, and the manufacturing of image transfer sheets can be carried out efficiently.

[0038] This is a cross-sectional view of the image transfer sheet of Embodiment 1. This is an explanatory diagram of the image transfer method (unwanted adhesive layer removal step) of Embodiment 1. This is an explanatory diagram of the image transfer method (transfer step) of Embodiment 1. This is an explanatory diagram of a cross-sectional view of a sheet with an adhesive layer and its manufacturing method. This is an explanatory diagram of the process of printing the image layer. This is an explanatory diagram of the image transfer method (bonding step and curing step) of Embodiment 1. This is a cross-sectional view of the image transfer sheet of Embodiment 2. This is an explanatory diagram of the image transfer method (unwanted adhesive layer removal step) of Embodiment 2. This is an explanatory diagram of the image transfer method (transfer step) of Embodiment 2. This is an explanatory diagram of the process of printing the image layer and clear ink layer of Embodiment 2. This is an explanatory diagram of the image transfer method (bonding step and curing step) of Embodiment 2.

[0039] Embodiments of the present invention will be described below with reference to the drawings.

[0040] (Embodiment 1) Figure 1 is a cross-sectional view of the image transfer sheet 1 of Embodiment 1. Figure 2 is an explanatory diagram of the image transfer method (unnecessary adhesive layer removal step) of Embodiment 1. Figure 3 is an explanatory diagram of the image transfer method (transfer step) of Embodiment 1. As shown in Figure 1, the image transfer sheet 1 of Embodiment 1 comprises a transfer layer 20 having a first release layer 11 and a second release layer 12, an image layer 22 partially disposed between the first release layer 11 and the second release layer 12, and an adhesive layer 30 disposed between the transfer layer 20 and the second release layer 12. As will be described later, the adhesive layer 30 comprises an adhesive for bonding the image layer 22 to the transfer surface 40 (see Figure 3). As shown in Figure 1, before use, the adhesive layer 30 of the image transfer sheet 1 is protected by the second release layer 12.

[0041] The first release layer 11 and the second release layer 12 are made of, for example, release paper or a release film. At least one surface of the first release layer 11 and the second release layer 12 is a release surface 13. For the first release layer 11, the surface contacting the transfer layer 20 is the release surface 13. For the second release layer 12, the surface contacting the adhesive layer 30 is the release surface 13.

[0042] As shown in FIG. 1, the transfer layer 20 is composed of two layers. The transfer layer 20 includes a protective layer 21 contacting the release surface 13 of the first release layer 11, and an image layer 22 overlapping the protective layer 21 from the side opposite to the first release layer 11. The adhesive layer 30 overlaps the image layer 22 from the side opposite to the protective layer 21. As will be described later, the protective layer 21 covers and protects the surface of the image layer 22 after transfer (see FIG. 3).

[0043] Hereinafter, in the image transfer sheet 1, the region where the image layer 22 of the transfer layer 20 is disposed is defined as an image region R1, and the region where the image layer 22 is not disposed is defined as a non-image region R2. As shown in FIG. 1, the adhesive layer 30 is continuously disposed over the entire ranges of the image region R1 and the non-image region R2. Also, the protective layer 21 of the transfer layer 20 is continuously disposed over the entire ranges of the image region R1 and the non-image region R2.

[0044] The image layer 22 is an ink layer. More specifically, the image layer 22 is a curable ink layer made of UV-curable ink. The protective layer 21 has no adhesiveness on its surface and has the property of being easily torn when pulled. For example, the protective layer 21 is a coating film layer made of a transparent coating film material such as a urethane emulsion, and fine powder such as silica is dispersed in the layer.

[0045] As shown in FIG. 1, the adhesive layer 30 is composed of two layers. The adhesive layer 30 includes an adhesive layer main body portion 31 contacting the release surface 13 of the second release layer 12, and an adhesion reduction portion 32 overlapping the adhesive layer main body portion 31 from the side opposite to the second release layer 12. As will be described later, the adhesion reduction portion 32 is bonded to the image layer 22 when the image layer 22 is cured by UV light.

[0046] The adhesive layer main body portion 31 has adhesiveness. For example, the adhesive layer main body portion 31 is made of a pressure-sensitive adhesive that adheres to the transfer surface 40 with a force that is just enough to lightly press. The type of the pressure-sensitive adhesive is not particularly limited. For example, various adhesives used in known adhesive tapes can be used. In this embodiment, since UV light is irradiated when the image layer 22 is cured, it is preferable to use an adhesive having durability against UV light.

[0047] The adhesive force reduction portion 32 has no adhesiveness on the surface and has the property of being easily torn when pulled. The adhesive force reduction portion 32 is, for example, a thin film-like coating layer formed by an aqueous paint or an oil-based paint. As the aqueous paint or the oil-based paint, a quick-drying paint in which a coating film material such as an acrylic resin or other resin, or nitrocellulose, and additives are dissolved in an organic solvent or an aqueous solvent can be used. Alternatively, the adhesive force reduction portion 32 may be a thin film-like foil layer such as a metal foil.

[0048] (Relationship between adhesive force and tensile strength) As shown in FIG. 1, the adhesive forces A to E of adjacent layers in the image transfer sheet 1 of Embodiment 1 are defined as follows. - Adhesive force A: The adhesive force between the first release layer 11 and the transfer layer 20 (protective layer 21). - Adhesive force B: The adhesive force between the protective layer 21 and the image layer 22. - Adhesive force C: The adhesive force between the second release layer 12 and the adhesive layer 30 (adhesive layer main body portion 31). - Adhesive force D: The adhesive force between the adhesive layer 30 (adhesive force reduction portion 32) and the transfer layer 20 (image layer 22). - Adhesive force E: The adhesive force between the protective layer 21 and the adhesive layer 30 (adhesive force reduction portion 32).

[0049] Also, the tensile strengths F1 to F4 of the adhesive layer 30 and the protective layer 21 are defined as follows. The tensile strength means the force at which it is torn and cut when pulled. - Tensile strength F1: The tensile strength of the adhesive layer 30. - Tensile strength F2: The tensile strength of the protective layer 21. - Tensile strength F3: The tensile strength of the adhesive force reduction portion 32. - Tensile strength F4: The tensile strength of the adhesive layer main body portion 31.

[0050] The image transfer sheet 1 is constructed such that the adhesive strengths A to E and tensile strengths F1 to F4, as defined above, satisfy all of the following relationships (1) to (6) and (8). The intent of each relationship will be explained later. Adhesive strength C < Adhesive strength D ....(1) Adhesive strength C < Adhesive strength A ....(2) Tensile strength F1 < Adhesive strength C ....(3) Adhesive strength A < Adhesive strength B ....(4) Tensile strength F2 < Adhesive strength A ....(5) Adhesive strength E < Adhesive strength C .....(6) Tensile strength F3 < Tensile strength F4 ....(8)

[0051] (Image Transfer Method: Step to Remove Unwanted Adhesive Layer) An image transfer method using the image transfer sheet 1 will be explained with reference to Figures 2 and 3. First, as shown in Figure 2, the second release layer 12 protecting the adhesive layer 30 is peeled off to expose the adhesive layer 30. At this time, as shown in Figure 2, the adhesive layer 30 is pulled and cut at the boundary between the image area R1 and the non-image area R2, so the portion of the adhesive layer 30 located in the non-image area R2 is peeled off together with the second release layer 12. As a result, the unnecessary portion of the adhesive layer 30 is removed, and the adhesive layer 30 remains only on the surface of the image layer 22. This results in an image sheet 2 with an adhesive layer 30 applied only to the portion of the image layer 22.

[0052] - In relational equation (1), the intended image transfer sheet 1 has an adhesive strength C < adhesive strength D as shown in relational equation (1). Therefore, when the second release layer 12 is peeled off, the adhesive layer 30 does not peel off from the transfer layer 20, and the adhesive layer 30 remains on the surface of the transfer layer 20. In this embodiment, the adhesive strength D is the adhesive strength between the image layer 22 on the surface of the transfer layer 20 and the adhesive layer 30. Since the image layer 22 bonds with the adhesive layer 30 through the curing reaction of the UV-curable ink, the adhesive strength D is large. Therefore, relational equation (1) holds true.

[0053] • Intent of relational equation (2) Furthermore, as shown in relational equation (2), since adhesive strength C < adhesive strength A of the image transfer sheet 1, when the second release layer 12 is peeled off, the entire transfer layer 20 will not peel off from the first release layer 11 together with the adhesive layer 30. Therefore, as shown in Figure 2, the transfer layer 20 remains on the side of the first release layer 11.

[0054] - Intent of relation (4) Here, as shown in relation (4), adhesive strength A < adhesive strength B, so combining relations (2) and (4), we get adhesive strength C < adhesive strength A < adhesive strength B. Adhesive strength B, like adhesive strength D, is the bonding force due to the curing reaction of the UV-curable ink, so adhesive strength B is large. Therefore, relation (4) holds true. If adhesive strength C < adhesive strength B, then when the second release layer 12 is peeled off, the image layer 22 of the transfer layer 20 will not peel off together with the adhesive layer 30.

[0055] • Intent of relation (3) Furthermore, as shown in relation (3), the image transfer sheet 1 has a tensile strength F1 < adhesive strength C. When the second release layer 12 is peeled off, the adhesive layer 30, which is bonded to the second release layer 12 with adhesive strength C, is pulled. As a result, the adhesive layer 30 is subjected to a tensile force exceeding the tensile strength F1 at the boundary between the image region R1 and the non-image region R2, which are bonded to the image layer 22 with strong adhesive strength D, and tears. Consequently, as shown in Figure 2, the adhesive layer 30 in the non-image region R2 is peeled off and removed together with the second release layer 12.

[0056] - In relational equation (8), the adhesive layer 30, as shown in relational equation (8), has a layer (adhesion reduction portion 32) that is easily torn only on the surface portion in contact with the image layer 22. When the second release layer is peeled off, a tensile force is applied to the adhesion reduction portion 32 via the adhesive layer main body portion 31. Since the tensile strength F3 of the adhesion reduction portion 32 is weaker than the tensile strength F4 of the adhesive layer main body portion 31, the adhesion reduction portion 32 tears first along the boundary between the image area R1 and the non-image area R2. If the surface portion (adhesion reduction portion 32) of the adhesive layer 30 tears easily, the adhesive layer main body portion 31 also tears easily starting from the point where it was torn. In other words, the adhesive layer 30 is structured so that the adhesive layer main body portion 31 has the necessary adhesiveness to bond the transfer layer 20 to the transfer surface 40, while being easily torn when the second release layer 12 is peeled off.

[0057] The tensile strength F3 of the adhesive strength reducing portion 32 is sufficiently small, and is smaller than the adhesive strength C. That is, in the case of the structure of the adhesive layer 30 in this embodiment, relation (3) may be defined as tensile strength F3 < adhesive strength C. Tensile strength F3 < adhesive strength C means that the adhesive strength reducing portion 32 can be easily cut when the second release layer 12 is peeled off.

[0058] - As shown in relation (6), the intended image transfer sheet 1 has an adhesive force E < adhesive force C, so when the second release layer 12 is peeled off, the adhesive force reducing portion 32 that is in contact with the protective layer 21 can be peeled off from the protective layer 21. Therefore, the adhesive layer 30 in the non-image area R2 will not remain on the side of the first release layer 11. Thus, the unnecessary portion of the adhesive layer 30 can be removed together with the second release layer 12. As described above, the adhesive layer 30 of this embodiment is equipped with an adhesive force reducing portion 32. Since the adhesive force E is the adhesive force between the adhesive force reducing portion 32, which has no adhesive force, and the protective layer 21, relation (6) holds true.

[0059] (Image Transfer Method: Transfer Process) Next, as shown in the upper diagram of Figure 3, the adhesive-coated image sheet 2, on which the adhesive layer 30 is applied only to the surface of the image layer 22, is turned over and the adhesive layer 30 is pressed onto the transfer surface 40. This bonds the image layer 22 to the transfer surface 40 via the adhesive layer 30. After that, as shown in the lower diagram of Figure 3, the first release layer 11 is peeled off. When the first release layer 11 is peeled off, the protective layer 21 is pulled and cut at the boundary between the image region R1 and the non-image region R2, so that only the unnecessary protective layer 21 of the non-image region R2 can be peeled off and removed together with the first release layer 11. The protective layer 21 of the image region R1 remains on the surface of the image layer 22.

[0060] The intended image transfer sheet 1 in relation (5) has a tensile strength F2 < adhesive strength A, as shown in relation (5). When the first release layer 11 is peeled off, the protective layer 21, which is bonded to the first release layer 11 with adhesive strength A, is pulled through the first release layer 11. As a result, the protective layer 21 is cut along the boundary between the image region R1 and the non-image region R2, which are bonded to the image layer 22 with strong adhesive strength B, by a tensile force exceeding the tensile strength F2. Consequently, as shown in Figure 3, the protective layer 21 in the non-image region R2 is peeled off and removed together with the first release layer 11.

[0061] (Sheet with adhesive layer) Figure 4 is a cross-sectional view of the sheet with adhesive layer 3 and an explanatory diagram of its manufacturing method. When manufacturing the image transfer sheet 1, the sheet with adhesive layer 3, which has an adhesive layer 30, is used as the material. As shown in the lower part of Figure 4, the sheet with adhesive layer 3 is a sheet in which a second release layer 12, an adhesive layer main body 31, and an adhesive force reducing part 32 are laminated in this order. As described above, the second release layer 12 is made of release paper or release film, and the adhesive layer main body 31 is made of, for example, a pressure-sensitive adhesive (PSA).

[0062] Figure 4 shows a method for manufacturing an adhesive sheet 3 when forming an adhesive-reducing portion 32 consisting of a coating layer using lacquer spray 100. As shown in the upper part of Figure 4, a thin film-like adhesive-reducing portion 32 can be formed by spraying a water-based or oil-based paint in a mist-like manner onto the surface of the adhesive layer body portion 31 using lacquer spray 100.

[0063] (Image Transfer Method: Process of Printing the Image Layer) Figure 5 is an explanatory diagram of the process of printing the image layer 22. As described above, the image layer 22 is a UV-curable ink layer and is formed by printing. In this embodiment, a substrate (sheet with protective layer) is used as the printing medium 5, on which a protective layer 21 is formed on the release surface 13 of the first release layer 11. As shown in Figure 5, by ejecting UV-curable ink from the print head 101 toward the printing medium 5, the image layer 22 is partially printed on the surface of the protective layer 21. This gives rise to an image sheet 4. The printing medium 5 is not tacky on the surface of the protective layer 21. Therefore, it is possible to continuously supply the printing medium 5 and continuously print image sheets 4 by a roll system or by stacking the printing medium 5 in a paper cassette.

[0064] (Image Transfer Method: Bonding Process) Figure 6 is an explanatory diagram of the image transfer method (bonding process and curing process) of Embodiment 1. As shown in the upper part of Figure 6, the surface portion of the transfer layer 20 (image layer 22) of the image sheet 4 created in the previous process and the surface portion of the adhesive layer 30 (adhesion reduction portion 32) of the adhesive sheet 3 are placed opposite each other and the two sheets are bonded together. This bonding process is performed before curing the image layer 22. At this time, in areas where there is no image layer 22, the adhesive sheet 3 is pressed until the adhesive layer 30 (adhesion reduction portion 32) adheres to the protective layer 21. Note that it is not necessary to make the adhesive layer 30 adhere to the protective layer 21.

[0065] (Image Transfer Method: Curing Process) Next, as shown in the lower diagram of Figure 6, UV light is irradiated onto the image layer 22 from the side of the adhesive layer 30 and the second release layer 12 to cure the image layer 22. As described above, the image layer 22 is a curable ink layer made of UV-curable ink. Note that the UV light may also be irradiated from the side of the protective layer 21 and the first release layer 11. When the image layer 22 (curable ink layer) is cured, the image layer 22 and the layers above and below it (protective layer 21, adhesive strength reduction part 32) bond together. This completes the image transfer sheet 1.

[0066] The process of transferring the image layer 22 onto the transfer surface 40 using the completed image transfer sheet 1 (the process of removing the unnecessary adhesive layer and the transfer process) has already been explained with reference to Figures 2 and 3.

[0067] (Effects of Embodiment 1) As described above, the image transfer sheet 1 of Embodiment 1 is constructed by laminating a first release layer 11, a transfer layer 20 including an image layer 22, an adhesive layer 30, and a second release layer 12 in this order. The adhesive layer 30 includes an adhesive layer body 31 and an adhesive force reducing portion 32 provided on the surface of the adhesive layer body 31, with the adhesive layer body 31 in contact with the second release layer 12 and the adhesive force reducing portion 32 in contact with the transfer layer 20. When the adhesive force between the first release layer 11 and the transfer layer 20 is A, the adhesive force between the second release layer 12 and the adhesive layer body 31 is C, the adhesive force between the adhesive force reducing portion 32 and the transfer layer 20 is D, and the tensile strength of the adhesive layer 30 is F1, all of the following relational expressions (1) to (3) are satisfied. Adhesion force C < Adhesion force D ... (1) Adhesion force C < Adhesion force A ... (2) Tensile strength F1 < Adhesion force C ... (3)

[0068] The intent of relational equations (1), (2), and (3) has already been explained. With this configuration, when the second release layer 12 protecting the adhesive layer 30 is peeled off, the adhesive layer 30 does not peel off from the transfer layer 20, nor do the transfer layer 20 and the adhesive layer 30 peel off from the first release layer 11 together with the second release layer 12. Furthermore, since the adhesive layer 30 is easily cut at the boundary between the area without the image layer 22 and the area with the image layer 22, the unnecessary adhesive layer 30 around the image layer 22 can be easily removed.

[0069] Furthermore, the adhesive layer 30 of Embodiment 1 has an adhesive strength reducing portion 32 on its surface, and the surface is not adhesive. Therefore, the adhesive-coated sheet 3 used as a material when manufacturing the image transfer sheet 1 does not need to have a protective film attached to the surface of the adhesive layer 30 for protection. Consequently, the amount of protective film generated as waste when manufacturing the image transfer sheet 1 can be reduced.

[0070] Thus, if the surface of the adhesive layer 30 is not tacky, the process of printing the image layer 22 shown in Figure 5 can be performed using the adhesive layer sheet 3 as the printing medium instead of the protective layer sheet 5, which has a protective layer 21 on one side of the first release layer 11. In this case, the protective layer 21 of the protective layer sheet and the image layer 22 formed on the adhesive layer sheet 3 can be joined together, and then the curing process can be performed.

[0071] The transfer layer 20 of Embodiment 1 consists of a protective layer 21 laminated on the first release layer 11 and an image layer 22 laminated on the protective layer 21. Therefore, adhesive force A is the adhesive force between the first release layer 11 and the protective layer 21, and adhesive force D is the adhesive force between the adhesive force reduction section 32 and the image layer 22. When the adhesive force between the protective layer 21 and the image layer 22 (ink layer) is B, and the tensile strength of the protective layer 21 is F2, the following relationships (4) and (5) are satisfied: Adhesive force A < Adhesive force B ... (4) Tensile strength F2 < Adhesive force A ... (5)

[0072] The intent of relational equations (4) and (5) has already been explained. The image transfer sheet 1 of Embodiment 1 has a protective layer 21 between the first release layer 11 and the image layer 22, so that the image layer 22 can be protected by the protective layer 21 after transfer. The protective layer 21 remains on the surface of the image layer 22 when the first release layer 11 is peeled off and removed. Also, when the first release layer 11 is peeled off, the protective layer 21 is easily cut at the boundary between the area with the image layer 22 and the area without the image layer 22. Therefore, the unnecessary protective layer 21 around the image layer 22 can be easily removed.

[0073] The image transfer sheet 1 of Embodiment 1 comprises an image region R1 in which an image layer 22 is provided between a protective layer 21 and an adhesive layer 30, and a non-image region R2 in which an image layer 22 is not provided between the protective layer 21 and the adhesive layer 30. In the non-image region R2, the adhesive force reducing portion 32 is in contact with the protective layer 21, and when the adhesive force between the protective layer 21 and the adhesive force reducing portion 32 is E, the following relation (6) is satisfied: Adhesion force E < Adhesion force C ... (6)

[0074] As explained earlier, the purpose of relation (6) is to remove the unnecessary portion of the adhesive layer 30 along with the second release layer 12, so that no adhesive layer 30 remains on the protective layer 21 side.

[0075] The image layer 22 in Embodiment 1 is a UV-curable ink layer. Therefore, the curing of the ink can increase the bonding strength between the image layer 22 and the adhesive strength reduction portion 32.

[0076] The adhesive layer 30 of Embodiment 1 is a layer that is non-adhesive only on its surface and easily torn, and is provided with an adhesive strength reducing portion 32 on its surface. When the tensile strength of the adhesive strength reducing portion 32 is F3 and the tensile strength of the adhesive layer main body portion 31 is F4, the following relationship (8) is satisfied: Tensile strength F3 < Tensile strength F4 ... (8)

[0077] In this way, the adhesive layer body 31 has the necessary adhesive properties to bond the transfer layer 20 to the transfer surface 40, while the adhesive layer 30 can be easily cut when the second release layer 12 is peeled off.

[0078] In Embodiment 1, a water-soluble lacquer layer or an oil-based lacquer layer was used as the adhesion-reducing layer 32 having these characteristics. The adhesion-reducing layer 32 may also be a foil layer. Such a layer can be easily applied to the surface of the adhesive layer body 31.

[0079] (Modification of Embodiment 1) (1) The transfer layer 20 of Embodiment 1 includes a protective layer 21, but the protective layer 21 may be omitted. If the protective layer 21 is not present, the adhesive force A in relational expression (2) becomes the adhesive force between the image layer 22 and the first release layer 11. Alternatively, the protective layer 21 may be provided only in the image region R1. For example, the protective layer 21 made of a transparent ink (e.g., UV-curable ink) may be formed by printing in the same way as the image layer 22. If the protective layer 21 is not present, or if the protective layer 21 is provided only in the image region R1, it is not necessary to remove the unnecessary portion of the protective layer 21, so it is not necessary to satisfy relational expression (5). On the other hand, in the non-image region R2, the adhesive layer 30 (adhesion reduction portion 32) and the first release layer 11 are in contact, so instead of relational expression (6), it is sufficient to satisfy the relational expression < adhesive force C between the adhesive layer 30 (adhesion reduction portion 32) and the first release layer 11. In the second embodiment described later, the adhesive force between the adhesive force reducing section 32 and the first release layer 11 is defined as the adhesive force F.

[0080] (2) The adhesive layer 30 is not limited to the same as in Embodiment 1, as long as it satisfies relation (3). That is, it does not have to be a layer that is easily torn due to low tensile strength only on the surface, but may have low tensile strength throughout the entire adhesive layer 30 and be adhesive to the transfer surface 40.

[0081] (3) The image layer 22 may be made of a thermosetting ink that hardens with heat, rather than a UV-curing ink. In this case, the curing process should be performed to achieve the temperature conditions required for the thermosetting ink to harden.

[0082] (Embodiment 2) Figure 7 is a cross-sectional view of the image transfer sheet 1A of Embodiment 2. Figure 8 is an explanatory diagram of the image transfer method (unnecessary adhesive layer removal step) of Embodiment 2. Figure 9 is an explanatory diagram of the image transfer method (transfer step) of Embodiment 2. As shown in Figure 7, the image transfer sheet 1A of Embodiment 2 includes a transfer layer 20A having a first release layer 11 and a second release layer 12, an image layer 23 partially disposed between the first release layer 11 and the second release layer 12, and an adhesive layer 30 disposed between the transfer layer 20A and the second release layer 12. As can be seen by comparing Figures 1 and 7, the configuration of the transfer layer 20A including the image layer 23 in the image transfer sheet 1A of Embodiment 2 is different from that of Embodiment 1. Hereinafter, configurations that are different from those of Embodiment 1 will be denoted by different reference numerals and described, while configurations that are common to Embodiment 1 will be denoted by the same reference numerals and their description will be omitted.

[0083] As shown in Figure 7, the transfer layer 20A of Embodiment 2 comprises an image layer 23 in contact with the release surface 13 of the first release layer 11, and a clear ink layer 24 overlapping the image layer 23 from the side opposite to the first release layer 11. The adhesive layer 30 overlaps the clear ink layer 24 from the side opposite to the image layer 23. Both the image layer 23 and the clear ink layer 24 are arranged only in the image region R1.

[0084] The image layer 23 is an ink layer. The clear ink layer 24 is a curable ink layer made of transparent UV-curable ink. The clear ink layer 24 hardens when irradiated with UV light. Therefore, it is bonded to the adhesive layer 30, similar to the image layer 22 in Embodiment 1. The image layer 23 may be a UV-curable ink or another type of ink.

[0085] (Relationship between adhesive strength and tensile strength) As shown in Figure 7, the adhesive strengths A to D and F of adjacent layers in the image transfer sheet 1A of Embodiment 2 are defined as follows: ・Adhesive strength A: Adhesion between the first release layer 11 and the transfer layer 20A (image layer 23) ・Adhesive strength B: Adhesion between the image layer 23 and the clear ink layer 24 ・Adhesive strength C: Adhesion between the second release layer 12 and the adhesive layer 30 (adhesive layer main body 31) ・Adhesive strength D: Adhesion between the adhesive layer 30 (adhesion reduction part 32) and the transfer layer 20A (clear ink layer 24) ・Adhesive strength F: Adhesion between the first release layer 11 and the adhesive layer 30 (adhesion reduction part 32)

[0086] Furthermore, the tensile strengths F1, F3-F4 of the adhesive layer 30 are the same as in Embodiment 1. • Tensile strength F1: Tensile strength of the adhesive layer 30 • Tensile strength F3: Tensile strength of the adhesive force reduction section 32 • Tensile strength F4: Tensile strength of the adhesive layer main body section 31

[0087] Image transfer sheet 1 is constructed such that A to D, F and tensile strengths F1, F3 to F4, as defined above, satisfy all of the following relationships (1) to (4) and (7) to (8). The intent of each relationship will be explained later. Adhesion C < Adhesion D .... (1) Adhesion C < Adhesion A .... (2) Tensile strength F1 < Adhesion C .... (3) Adhesion A < Adhesion B .... (4) Adhesion F < Adhesion C .... (7) Tensile strength F3 < Tensile strength F4 .... (8)

[0088] (Image Transfer Method: Step to Remove Unwanted Adhesive Layer) Next, an image transfer method using the image transfer sheet 1A will be explained with reference to Figures 8 and 9. First, as shown in Figure 8, the second release layer 12 protecting the adhesive layer 30 is peeled off to expose the adhesive layer 30. At this time, as shown in Figure 8, the adhesive layer 30 is pulled and cut at the boundary between the image area R1 and the non-image area R2, so the adhesive layer 30 in the non-image area R2 is peeled off together with the second release layer 12. As a result, the unnecessary part of the adhesive layer 30 is removed, and the adhesive layer 30 remains only on the surface of the image layer 23. This gives rise to an image sheet 2A with an adhesive layer, in which the adhesive layer 30 is applied only to the image layer 23.

[0089] - In relation to relation (1), the image transfer sheet 1A satisfies relation (1) in the same way as in Embodiment 1. Therefore, when the second release layer 12 is peeled off, the adhesive layer 30 does not peel off from the transfer layer 20A, and the adhesive layer 30 remains on the surface of the transfer layer 20A. Similar to Embodiment 1, the adhesive strength D is the bonding force with the adhesive layer 30 due to the curing reaction of the UV-curable ink, so the adhesive strength D is large. Therefore, relation (1) is satisfied.

[0090] - Intent of relational equations (2) and (4) Furthermore, since relational equations (2) and (4) hold true for the image transfer sheet 1A, just as in Embodiment 1, when the second release layer 12 is peeled off, the entire transfer layer 20A does not peel off from the first release layer 11 together with the adhesive layer 30, and the transfer layer 20A remains on the side of the first release layer 11. Also, when the second release layer 12 is peeled off, the clear ink layer 24 of the transfer layer 20A does not peel off together with the adhesive layer 30.

[0091] • Intent of relational equation (3) Furthermore, since relational equation (3) holds true for the image transfer sheet 1A, just as in Embodiment 1, when the second release layer 12 is peeled off, the adhesive layer 30 is torn at the boundary between the image area R1 and the non-image area R2 by a tensile force exceeding the tensile strength F1. Therefore, as shown in Figure 8, the adhesive layer 30 of the non-image area R2 is peeled off and removed together with the second release layer 12.

[0092] - The adhesive layer 30 in relation to equation (8) has the same configuration as in Embodiment 1, and only the surface portion in contact with the clear ink layer 24 is a layer with easily cut properties (adhesion reduction portion 32). Therefore, the adhesive layer 30 has an adhesiveness in the main body portion 31 necessary for bonding the transfer layer 20A to the transfer surface 40, while being structured to be easily cut when peeling off the second release layer 12.

[0093] In the case of such an adhesive layer 30 structure, the relational expression (3) may be defined as tensile strength F3 < adhesive strength C, similar to Embodiment 1. Tensile strength F3 < adhesive strength C means that the adhesive strength reduction portion 32 can be easily cut when the second release layer 12 is peeled off.

[0094] - In relational equation (7), the intended image transfer sheet 1A has an adhesive force F < adhesive force C as shown in relational equation (7). Therefore, when the second release layer 12 is peeled off, the adhesive layer 30 in the non-image area R2 does not remain on the side of the first release layer 11. Thus, the unnecessary portion of the adhesive layer 30 can be removed together with the second release layer 12. As described above, the adhesive layer 30 in this embodiment is equipped with an adhesive force reducing portion 32. Since the adhesive force F is the adhesive force between the adhesive force reducing portion 32, which has no adhesive force, and the release surface 13, relational equation (7) holds true. As described above, in the modified embodiment of Embodiment 1, the adhesive force reducing portion 32 and the first release layer 11 are in contact, so relational equation (7) holds true in the same way as in Embodiment 2.

[0095] (Image Transfer Method: Transfer Process) Next, as shown in the upper diagram of Figure 9, the adhesive image sheet 2A, on which the adhesive layer 30 is applied only to the surface of the transfer layer 20A, is turned over and the adhesive layer 30 is pressed onto the transfer surface 40. This causes the clear ink layer 24 to be bonded to the transfer surface 40 via the adhesive layer 30. After that, the first release layer 11 is peeled off as shown in the lower diagram of Figure 3.

[0096] (Image Transfer Method: Process of Printing Image Layer and Clear Ink Layer) Figure 10 is an explanatory diagram of the process of printing the image layer 23 and the clear ink layer 24. In this embodiment, release paper or release film constituting the first release layer 11 is used as the printing medium. First, ink is ejected from the print head 101 toward the release surface 13 of the release paper or release film to partially form the image layer 23. Next, UV-curable ink is ejected toward the image layer 23 to form the clear ink layer 24. The clear ink layer 24 is formed only in the area where the image layer 23 is located. This results in an image sheet 4A having a transfer layer 20A.

[0097] (Image Transfer Method: Bonding Process) Figure 11 is an explanatory diagram of the image transfer method (bonding process and curing process) of Embodiment 2. As shown in the upper part of Figure 11, the surface portion (clear ink layer 24) of the transfer layer 20A of the image sheet 4A created in the previous process and the surface portion (adhesion reduction portion 32) of the adhesive layer sheet 3 are placed opposite each other and the two sheets are bonded together. This bonding process is performed before curing the clear ink layer 24. At this time, in areas where there is no image layer 23, the adhesive layer sheet 3 is pressed until the adhesive layer 30 (adhesion reduction portion 32) adheres to the release surface 13 of the first release layer 11. Note that it is not necessary to make the adhesive layer 30 adhere to the first release layer 11.

[0098] (Image Transfer Method: Curing Process) Next, as shown in the lower diagram of Figure 11, UV light is irradiated onto the clear ink layer 24 from the side of the adhesive layer 30 and the second release layer 12 to cure the UV-curable ink. Once the UV-curable ink has cured, the clear ink layer 24 and the layers above and below it (image layer 23, adhesive strength reduction section 32) bond together. This completes the image transfer sheet 1A.

[0099] The process of transferring the image layer 23 onto the transfer surface 40 using the completed image transfer sheet 1A (the process of removing the unnecessary adhesive layer and the transfer process) has already been explained with reference to Figures 8 and 9.

[0100] (Effects of Embodiment 2) As described above, the image transfer sheet 1A of Embodiment 2 is formed by laminating a first release layer 11, a transfer layer 20A including an image layer 23, an adhesive layer 30, and a second release layer 12 in this order. The adhesive layer 30 includes an adhesive layer body 31 and an adhesive force reducing portion 32 provided on the surface of the adhesive layer body 31, with the adhesive layer body 31 in contact with the second release layer 12 and the adhesive force reducing portion 32 in contact with the transfer layer 20A. When the adhesive force between the first release layer 11 and the transfer layer 20A is A, the adhesive force between the second release layer 12 and the adhesive layer body 31 is C, the adhesive force between the adhesive force reducing portion 32 and the transfer layer 20A is D, and the tensile strength of the adhesive layer 30 is F1, all of the following relational expressions (1) to (3) are satisfied. Adhesion strength C < Adhesion strength D ... (1) Adhesion strength C < Adhesion strength A ... (2) Tensile strength F1 < Adhesion strength C ... (3)

[0101] Similar to Embodiment 1, with this configuration, when the second release layer 12 protecting the adhesive layer 30 is peeled off, the adhesive layer 30 does not peel off from the transfer layer 20A, and the transfer layer 20A and the adhesive layer 30 do not peel off from the first release layer 11 together with the second release layer 12. Furthermore, since the adhesive layer 30 is easily cut at the boundary between the area without the image layer 23 and the area with the image layer 23, the unnecessary adhesive layer 30 around the image layer 23 can be easily removed.

[0102] Furthermore, since the adhesive layer 30 has no adhesive properties on its surface, it is possible to reduce the amount of protective film generated as waste when manufacturing the image transfer sheet 1A.

[0103] Furthermore, the adhesive layer 30 is not limited to the same one as in Embodiment 1, as long as it satisfies relational equation (3), as is the case with modification (2) of Embodiment 1.

[0104] The transfer layer 20A of Embodiment 2 consists of an image layer 23 laminated on the first release layer 11 and a UV-curable clear ink layer 24 laminated on the image layer 23. Adhesion A is the adhesion force between the first release layer 11 and the image layer 23, and adhesion D is the adhesion force between the adhesion force reduction section 32 and the clear ink layer 24. In this way, by using a UV-curable clear ink layer between the image layer 23 and the adhesion force reduction section 32, the bonding force between the image layer 23 and the adhesion force reduction section 32 can be increased by the curing of the ink.

[0105] The image transfer sheet 1A of Embodiment 2 comprises an image region R1 in which an image layer 23 and a clear ink layer 24 are provided between the first release layer 11 and the adhesive layer 30, and a non-image region R2 in which the image layer 23 and the clear ink layer 24 are not provided between the first release layer 11 and the adhesive layer 30. In the non-image region R2, the adhesive force reducing portion 32 is in contact with the first release layer 11, and when the adhesive force between the first release layer 11 and the adhesive force reducing portion 32 is F, the following relational expression (7) is satisfied: Adhesion force F < Adhesion force C ... (7)

[0106] In this way, the unnecessary portion of the adhesive layer 30 can be removed together with the second release layer 12, and no adhesive layer 30 remains on the side of the first release layer 11.

[0107] (Prototyping of Image Transfer Sheets and Measurement of Adhesion Strength) Prototypes of image transfer sheets 1 and 1A of Embodiments 1 and 2 were produced. The adhesion strengths A to C of image transfer sheet 1 of Embodiment 1 and the adhesion strengths D and F of image transfer sheet 1A of Embodiment 2 were measured by comparative tests with the adhesion strength of commercially available adhesive tapes. In both Embodiments 1 and 2, the adhesive layer body 31 is in contact with the second release layer 12, so the adhesion strength C is the same value in Embodiments 1 and 2. In addition, in the modified form of Embodiment 1 (when the protective layer 21 is omitted), the adhesion strength reduction part 32 is in contact with the first release layer 11, so the adhesion strength F, not the adhesion strength E, must be smaller than the adhesion strength C.

[0108] The adhesive strength of the adhesive tape used in this measurement, and the measurement results for adhesive strengths A to D and F, are as follows. <Adhesive strength of adhesive tapes used in the test> ・Adhesive tape 1: 0.9 (N / 10mm) ・Adhesive tape 2: 4.73 (N / 10mm) ・Adhesive tape 3: 5.25 (N / 10mm) <Measurement results of adhesive strengths A to D and F> ・Adhesive strength A: Adhesion between the first release layer and the protective layer A < 0.9 (N / 10mm) ・Adhesive strength B: Adhesion between the protective layer and the image layer 4.73 < B < 5.25 (N / 10mm) ・Adhesive strength C: Adhesion between the second release layer and the main body of the adhesive layer C < 0.9 (N / 10mm) ・Adhesive strength D: Adhesion between the adhesive strength reduction part and the clear ink layer 5.25 < D (N / 10mm) ・Adhesive strength F: Adhesion between the adhesive strength reduction part and the first release layer F < 0.9 (N / 10mm)

[0109] From the measurement results above, it was confirmed that the following relationship between the values ​​was achieved: Adhesive strength F, C, A < 0.9 to 4.73 < Adhesive strength B < 5.25 < Adhesive strength D. From this relationship between the values, it was confirmed that relational equations (1) and (4) hold true for both the prototype of Embodiment 1 and the prototype of Embodiment 2.

[0110] In addition, the above measurements did not use any tape with lower adhesive strength than adhesive tape 1, and the relative magnitudes of adhesive strengths F, C, and A were not measured.

Claims

1. An image transfer sheet comprising a first release layer, a transfer layer including an image layer, an adhesive layer, and a second release layer, laminated in this order, wherein the adhesive layer comprises an adhesive layer body and an adhesive force reducing portion provided on the surface of the adhesive layer body, the adhesive layer body is in contact with the second release layer, the adhesive force reducing portion is in contact with the transfer layer, the adhesive force between the first release layer and the transfer layer is A, the adhesive force between the second release layer and the adhesive layer body is C, the adhesive force between the adhesive force reducing portion and the transfer layer is D, and the tensile strength of the adhesive layer is F1, the image transfer sheet is characterized in that it satisfies all of the following relational expressions (1) to (3): Adhesion force C < Adhesion force D ... (1) Adhesion force C < Adhesion force A ... (2) Tensile strength F1 < Adhesion force C ... (3) 2. The image transfer sheet according to claim 1, wherein the transfer layer comprises a protective layer laminated on the first release layer and the image layer laminated on the protective layer, the adhesive force A is the adhesive force between the first release layer and the protective layer, the adhesive force D is the adhesive force between the adhesive force reduction portion and the image layer, the adhesive force between the protective layer and the image layer is B, and the tensile strength of the protective layer is F2, and the following relational expressions (4) and (5) are satisfied. Adhesive force A < Adhesive force B ... (4) Tensile strength F2 < Adhesive force A ... (5) 3. The image transfer sheet according to claim 2, comprising an image region in which the image layer is provided between the protective layer and the adhesive layer, and a non-image region in which the image layer is not provided between the protective layer and the adhesive layer, wherein in the non-image region, the adhesive force reducing portion is in contact with the protective layer, and when the adhesive force between the protective layer and the adhesive force reducing portion is E, the following relational expression (6) is satisfied: Adhesion force E < Adhesion force C ... (6) 4. The image transfer sheet according to claim 2, characterized in that the image layer is a UV-curable ink layer.

5. The image transfer sheet according to claim 1, wherein the transfer layer comprises the image layer laminated on the first release layer and the UV-curable clear ink layer laminated on the image layer, the adhesive force A is the adhesive force between the first release layer and the image layer, and the adhesive force D is the adhesive force between the adhesive force reduction portion and the clear ink layer.

6. The image transfer sheet according to claim 5, comprising an image region in which the image layer and the clear ink layer are provided between the first release layer and the adhesive layer, and a non-image region in which the image layer and the clear ink layer are not provided between the first release layer and the adhesive layer, wherein in the non-image region, the adhesive force reducing portion is in contact with the first release layer, and when the adhesive force between the first release layer and the adhesive force reducing portion is F, the following relational expression (7) is satisfied: Adhesion force F < Adhesion force C ... (7) 7. The image transfer sheet according to claim 1, characterized in that when the tensile strength of the adhesive strength reduction portion is F3 and the tensile strength of the adhesive layer main body portion is F4, the following relational expression (8) is satisfied: Tensile strength F3 < Tensile strength F4 ... (8) 8. The image transfer sheet according to claim 1, characterized in that the adhesive strength reducing portion is one of a foil layer, a water-soluble lacquer layer, and an oil-based lacquer layer.

9. An adhesive sheet comprising an adhesive layer laminated on a second release layer, wherein the adhesive layer comprises an adhesive layer body and an adhesive strength reducing portion provided on the surface of the adhesive layer body, the adhesive layer body is in contact with the second release layer, and when the tensile strength of the adhesive strength reducing portion is F3 and the tensile strength of the adhesive layer body is F4, the following relational expression (8) is satisfied: Tensile strength F3 < Tensile strength F4 ... (8) 10. The adhesive sheet according to claim 9, characterized in that the adhesive strength reducing portion is one of a foil layer, a water-soluble lacquer layer, and an oil-based lacquer layer.

11. The adhesive sheet according to claim 9, wherein the adhesive strength reducing portion is a layer adhered to the surface of the transfer layer in an image sheet in which a transfer layer including an image layer is laminated on a first release layer, and when the adhesive strength between the adhesive strength reducing portion and the transfer layer is D, the adhesive strength between the first release layer and the adhesive strength reducing portion is F, and the adhesive strength between the second release layer and the main body of the adhesive layer satisfies the following relational expressions (1) and (7). Adhesion strength C < Adhesion strength D ... (1) Adhesion strength F < Adhesion strength C ... (7) 12. A bonding step is performed to bond an image sheet, which has a transfer layer containing an image layer laminated on a first release layer, and an adhesive sheet, which has an adhesive layer laminated on a second release layer, with the transfer layer and the adhesive layer facing each other, wherein the adhesive layer comprises an adhesive layer body and an adhesive force reducing portion provided on the surface of the adhesive layer body, the adhesive layer body is in contact with the second release layer, and the adhesive force reducing portion is in contact with the transfer layer by the bonding step, the transfer layer comprises a curable ink layer in contact with the adhesive force reducing portion, and after the bonding step, a curing step is performed to cure the curable ink layer to bond the curable ink layer and the adhesive force reducing portion, the image sheet comprises an image region on which the image layer is formed and a non-image region on which the image layer is not formed. An image transfer method characterized in that, after the curing step, an unwanted adhesive layer removal step is performed to peel off the second release layer, in the unwanted adhesive layer removal step, the adhesive force reduction portion is cut along the boundary between the image region and the non-image region by the tensile force applied to the adhesive force reduction portion via the adhesive layer body portion, and the portion of the adhesive layer located in the non-image region is removed together with the second release layer to form an image sheet with an adhesive layer on the surface of the transfer layer, and after the unwanted adhesive layer removal step, the adhesive layer of the image sheet with an adhesive layer is bonded to the transfer surface, and then a transfer step is performed to peel off the first release layer.

13. The image transfer method according to 12, wherein the transfer layer comprises a protective layer laminated on the first release layer and an image layer laminated on the protective layer, the image layer being the curable ink layer, the protective layer being formed in the image region and the non-image region, the adhesive force reducing portion being in contact with the protective layer in the non-image region, the unwanted adhesive layer removal step being peeled off the adhesive force reducing portion in contact with the protective layer, and the transfer step being characterized in that, when peeling off the first release layer, the protective layer is cut along the boundary between the image region and the non-image region by the tensile force applied to the protective layer through the first release layer, leaving the protective layer on the surface of the image layer in the image region and removing the protective layer together with the first release layer in the non-image region.

14. The image transfer method according to claim 12, characterized in that the adhesive strength reducing portion has a lower tensile strength than the adhesive layer main body portion.

15. The image transfer method according to claim 12, characterized in that the adhesive strength reducing portion is one of a foil layer, a water-soluble lacquer layer, and an oil-based lacquer layer formed on the surface of the adhesive layer body.

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