Thermal transfer foil

Abstract

Provided is a thermal transfer foil capable of ensuring the solvent resistance and wear resistance of a transfer layer adhered to an object. A thermal transfer foil 100 comprises a substrate 4 and a transfer layer 10 arranged on the substrate 4. The transfer layer 10 comprises a release layer 1, a color layer 2, and an adhesive layer 3 which are laminated in order of proximity to the substrate 4. The release layer 1 contains an isocyanate compound (A) and a polyol compound (B). The isocyanate compound (A) contains a first isocyanate compound (A1) and a second isocyanate compound (A2) different from each other. The first isocyanate compound (A1) does not have an isocyanate group blocked with a blocking agent. The second isocyanate compound (A2) has an isocyanate group blocked with a blocking agent.

Description

Heat transfer foil

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to heat transfer foils, and more particularly to heat transfer foils used to decorate objects.

[0002] Patent Document 1 discloses a transfer foil that is used by adhering it to the outer surface of a rod-shaped object having a first outer surface and a second outer surface with different taper angles, and that has a base sheet and a transfer layer laminated on the base sheet, and that the transfer layer has a release layer for surface protection, an ink layer for forming a pattern, an adhesive layer, etc.

[0003] Japanese Patent Application Laid-Open No. 2020-163861

[0004] An object of the present disclosure is to provide a thermal transfer foil that can ensure solvent resistance and abrasion resistance of a transfer layer attached to an object.

[0005] A thermal transfer foil according to one embodiment of the present disclosure includes a substrate and a transfer layer disposed on the substrate. The transfer layer includes a release layer, a color layer, and an adhesive layer, stacked in order from closest to the substrate. The release layer contains an isocyanate compound (A) and a thermoplastic polyol compound (B). The isocyanate compound (A) contains a first isocyanate compound (A1) and a second isocyanate compound (A2), which are different from each other. The first isocyanate compound (A1) does not have an isocyanate group blocked with a blocking agent. The second isocyanate compound (A2) has an isocyanate group blocked with a blocking agent.

[0006] Fig. 1 is a schematic cross-sectional view of a thermal transfer foil according to an embodiment of the present disclosure. Fig. 2 is a schematic cross-sectional view showing a process for transferring the thermal transfer foil according to an embodiment of the present disclosure. Fig. 3 is a schematic cross-sectional view showing a process for transferring the thermal transfer foil according to an embodiment of the present disclosure, following Fig. 2.

[0007] [Embodiments] Hereinafter, embodiments of the present disclosure will be described. However, the present disclosure is not limited to the following embodiments. The following embodiments are merely examples of various embodiments of the present disclosure, and various modifications are possible depending on the design as long as the object of the present disclosure can be achieved. Furthermore, the scope of the present disclosure is not limited by the development history described below. Furthermore, the mechanism of action described in the following description is speculated, and the present disclosure is not bound by the mechanism of action described below.

[0008] (Overview) First, the background to the present disclosure will be described.

[0009] Conventionally, the outer surface of a shaft or the like has often been decorated to enhance the product's distinctiveness and added value.

[0010] As a method for applying this decoration, in addition to methods of applying a pattern by painting or printing, a method of applying decoration using thermal transfer foil has also been proposed (Patent Document 1). Thermal transfer foil has the advantage of high degree of freedom in decoration and easy handling. In particular, since shafts require designs consisting of various patterns and colors as well as letters such as product logos, decoration using thermal transfer foil is preferably used.

[0011] Conventional thermal transfer foils have a transfer film composed of multiple layers, such as a release layer, an ink layer, and an adhesive layer, and decoration is achieved by attaching the transfer film to a shaft or the like. Typically, shafts or the like to which the transfer film is attached are often exposed to harsh environments. For this reason, an overcoat is sometimes applied to protect the transfer film. However, the overcoat application process is problematic in that it requires time and cost.

[0012] In response to the above problem, the inventors have conducted extensive research and development and have developed a thermal transfer foil 100 that can ensure the solvent resistance and abrasion resistance of the transfer layer 10 attached to the object 20.

[0013] The thermal transfer foil 100 according to this embodiment includes a substrate 4 and a transfer layer 10 disposed on the substrate 4. The transfer layer 10 includes a release layer 1, a color layer 2, and an adhesive layer 3, stacked in order from the substrate 4 side (see FIG. 1 ). The release layer 1 contains an isocyanate compound (A) and a thermoplastic polyol compound (B). The isocyanate compound (A) contains a first isocyanate compound (A1) and a second isocyanate compound (A2), which are different from each other. The first isocyanate compound (A1) does not have an isocyanate group blocked with a blocking agent. The second isocyanate compound (A2) has an isocyanate group blocked with a blocking agent.

[0014] The reason why the thermal transfer foil 100 having the above configuration exhibits the above effects is not entirely clear, but can be inferred as follows.

[0015] The release layer 1 contains the first isocyanate compound (A1). Therefore, by attaching the transfer layer 10 to the object 20 while heating it, the first isocyanate compound (A1) contained in the release layer 1 can react with the polyol compound (B). This can increase the abrasion resistance of the release layer 1.

[0016] Then, by further heating the transfer layer 10 after attaching it to the object 20, the blocking agent contained in the second isocyanate compound (A2) can be efficiently released. In this case, the reaction between the second isocyanate compound (A2) and the polyol compound (B) can be efficiently promoted. Therefore, the curing of the release layer 1 can be further promoted. This can further improve the abrasion resistance of the release layer 1 and also improve its solvent resistance.

[0017] By this mechanism, the thermal transfer foil 100 can ensure the solvent resistance and abrasion resistance of the transfer layer 10 attached to the object 20 .

[0018] (Transfer Layer) The layers included in the transfer layer 10 will be described.

[0019] <Release Layer> As described above, the transfer layer 10 includes the release layer 1. The release layer 1 overlaps the substrate 4. The thickness of the release layer 1 is, for example, 2 μm or more and 6 μm or less. In this case, the solvent resistance and abrasion resistance of the release layer 1 can be sufficiently ensured. This thickness is preferably 3 μm or more. This thickness is preferably 5 μm or less.

[0020] The release layer 1 also contains an isocyanate compound (A) and a polyol compound (B). This allows the release layer 1 to harden. The isocyanate compound (A) contains two types of isocyanate compounds: a first isocyanate compound (A1) and a second isocyanate compound (A2). This increases the solvent resistance and abrasion resistance of the release layer 1. As a result, the solvent resistance and abrasion resistance of the transfer layer 10 attached to the object 20 can be ensured.

[0021] The content of the isocyanate compound (A) relative to the polyol compound (B) is preferably 10% by mass or more and 30% by mass or less. In this case, the solvent resistance and abrasion resistance of the release layer 1 can be further improved. This content is more preferably 15% by mass or more. This content is further preferably 25% by mass or less.

[0022] <First Isocyanate Compound> As described above, the isocyanate compound (A) contains a first isocyanate compound (A1). The first isocyanate compound (A1) does not have an isocyanate group blocked with a blocking agent. In this case, the isocyanate group of the first isocyanate compound (A1) can easily react with the hydroxyl group of the polyol compound (B). Therefore, when the transfer layer 10 is attached to the object 20 while being heated, the first isocyanate compound (A1) contained in the release layer 1 can react with the polyol compound (B). This can improve the abrasion resistance of the release layer 1. Note that the heating performed when attaching the transfer layer 10 to the object 20 is, for example, in the range of 190°C to 230°C. Furthermore, because the time required to attach the transfer layer 10 to the object 20 is relatively short, the blocking agent of the second isocyanate compound (A2) is unlikely to be released at this point.

[0023] The molecular form that the first isocyanate compound (A1) can take is not particularly limited. For example, the first isocyanate compound (A1) contains at least one selected from the group consisting of a monomer, an oligomer, a prepolymer, a polymer, and the like.

[0024] As described above, the first isocyanate compound (A1) may contain a monomer. The number of isocyanate groups contained in one molecule of the monomer contained in the first isocyanate compound (A1) is not particularly limited, but is preferably 2. In other words, the first isocyanate compound (A1) preferably contains a bifunctional isocyanate monomer. In this case, the abrasion resistance of the release layer 1 can be further improved. Furthermore, the bifunctional isocyanate monomer contains at least one selected from the group consisting of an aliphatic diisocyanate monomer, an alicyclic diisocyanate monomer, and an aromatic diisocyanate monomer. The bifunctional isocyanate monomer preferably contains at least one of an aliphatic diisocyanate monomer and an alicyclic diisocyanate monomer. In this case, the abrasion resistance of the release layer 1 can be further improved.

[0025] The aliphatic diisocyanate monomer contains at least one selected from the group consisting of, for example, butane diisocyanate, pentane diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate. The alicyclic diisocyanate monomer contains at least one selected from the group consisting of, for example, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate), hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and 1,4-cyclohexane diisocyanate. Furthermore, the aromatic diisocyanate monomer contains at least one selected from the group consisting of, for example, phenylene 1,4-diisocyanate, tolylene 2,4-diisocyanate, tolylene 2,6-diisocyanate, naphthylene 1,5-diisocyanate, diphenylmethane 2,2'-diisocyanate, diphenylmethane 2,4'-diisocyanate, and diphenylmethane 4,4'-diisocyanate. Among these, it is particularly preferable that the first isocyanate compound (A1) contains at least one of hexamethylene diisocyanate and 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate). In this case, the abrasion resistance of the release layer 1 can be particularly improved.

[0026] As described above, the first isocyanate compound (A1) may contain at least one of an oligomer, a prepolymer, and a polymer. In other words, the first isocyanate compound (A1) may contain a polyisocyanate resin. In this case, the abrasion resistance of the release layer 1 can be further improved. The polyisocyanate resin is a compound having two or more isocyanate groups in one molecule. The number of isocyanate groups in one molecule of the polyisocyanate resin is not particularly limited, and the number can be adjusted as appropriate. This allows the curing property of the release layer 1 to be adjusted. Furthermore, the polyisocyanate resin may have an isocyanate group at the molecular terminal or within the molecule.

[0027] The first isocyanate compound (A1) preferably contains both a monomer and a polyisocyanate resin, which further enhances the abrasion resistance of the release layer 1. It is particularly preferable that the first isocyanate compound (A1) contains hexamethylene diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, and a polyisocyanate resin.

[0028] The content of the first isocyanate compound (A1) relative to the isocyanate compound (A) is preferably 10% by mass or more and 30% by mass or less. If this content is 15% by mass or more, the abrasion resistance of the release layer 1 can be further improved. If this content is 25% by mass or less, the transferability of the thermal transfer foil 100 can be ensured.

[0029] In addition, when the release layer 1 does not contain the first isocyanate compound (A1) but contains only the second isocyanate compound (A2) as the isocyanate compound (A), the second isocyanate compound (A2) contained in the release layer 1 tends to seep out from the release layer 1 and come into contact with the color layer 2 or the adhesive layer 3. In contrast, the isocyanate compound (A) in the present disclosure contains the first isocyanate compound (A1) in addition to the second isocyanate compound (A2). Therefore, the abrasion resistance of the release layer 1 can be sufficiently ensured, and the seepage of the first isocyanate compound (A1) from the release layer 1 can be reduced.

[0030] Furthermore, if the surface of the substrate 4 that overlaps the release layer 1 has irregularities, for example, a matte surface, when the substrate 4 is peeled from the release layer 1 (see FIG. 3 ), the irregularities of the substrate 4 may be transferred to the release layer 1, resulting in an irregular surface on the release layer 1. However, if the release layer 1 does not contain the first isocyanate compound (A1) but contains only the second isocyanate compound (A2) as the isocyanate compound (A), when the transfer layer 10 is transferred to the object 20 (see FIG. 2 ), for example by pressing a heated transfer roll 6 against the substrate 4, the surface of the substrate 4 is likely to become smooth as the second isocyanate compound (A2) is heated and cured. As a result, the irregularities on the surface of the substrate 4 are unlikely to be transferred to the release layer 1. In contrast, the isocyanate compound (A) in the present disclosure contains the first isocyanate compound (A1) in addition to the second isocyanate compound (A2). This increases the coating strength of the release layer 1, so that the unevenness of the surface of the substrate 4 is maintained even after the second isocyanate compound (A2) is heat-cured, and the unevenness of the substrate 4 can be transferred to the release layer 1.

[0031] <<Second Isocyanate Compound>> As described above, the isocyanate compound (A) contains the second isocyanate compound (A2). At least a portion of the isocyanate groups in the second isocyanate compound (A2) are blocked with a blocking agent. That is, the second isocyanate compound (A2) is a blocked isocyanate compound.

[0032] As described above, when the second isocyanate compound (A2) is heated, the blocking agent can be efficiently released. In this case, by heating the transfer layer 10 after attaching it to the object 20, the hardening of the release layer 1 can be promoted. This can improve the abrasion resistance of the release layer 1.

[0033] More specifically, when heat is applied to the release layer 1, the abrasion resistance of which has been increased by attaching the transfer layer 10 to the object 20 while heating it, the reaction between the second isocyanate compound (A2) and the polyol compound (B) progresses, and the hardening of the release layer 1 progresses, thereby further increasing the abrasion resistance of the release layer 1. Note that the heating performed after attaching the transfer layer 10 to the object 20 referred to here may be performed at a temperature in the range of 80°C or higher and 150°C or lower, for example.

[0034] The second isocyanate compound (A2) may have isocyanate groups that are not blocked with a blocking agent, as long as at least a portion of the isocyanate groups are blocked with a blocking agent. The blocking agent may contain at least one selected from the group consisting of, for example, active methylene-based blocking agents, oxime-based blocking agents, alcohol-based blocking agents, acid amide-based blocking agents, acid imide-based blocking agents, phenol-based blocking agents, amine-based blocking agents, imidazole-based blocking agents, and pyrazole-based blocking agents. One of these blocking agents may be used alone, or two or more may be used in combination.

[0035] In addition, by appropriately selecting the blocking agent, the temperature at which the blocking agent desorbs from the second isocyanate compound (A2) can be adjusted. This allows the curing temperature of the release layer 1 to be adjusted. The temperature at which the blocking agent desorbs from the second isocyanate compound (A2) is preferably 80°C or higher and 120°C or lower. By setting the temperature at which the blocking agent desorbs to 80°C or higher, the release layer 1 can be prevented from over-curing until the transfer layer 10 is attached to the object 20. This ensures sufficient transferability of the thermal transfer foil 100. Furthermore, by setting the temperature at which the blocking agent desorbs to 120°C or lower, the release layer 1 can be heated and cured at a temperature that does not impair the quality of the object 20. The temperature at which the blocking agent desorbs is preferably 110°C or lower, more preferably 100°C or lower, and even more preferably 90°C or lower. The temperature at which the blocking agent contained in the second isocyanate compound (A2) desorbs can be confirmed as follows. First, a mixture of polyol compound (B) and second isocyanate compound (A2) is applied to a substrate (e.g., a sample-coated plate) and heated at a temperature between 90°C and 120°C for 60 minutes to form a coating film. The formed coating film is then cooled to room temperature. A rubbing test is then performed on the surface of the coating film by applying a load of 150 g to a cotton swab soaked in methyl ethyl ketone. The rubbing test is repeated, with one round trip over a distance of 20 mm. The test is continued until 50 rubbings are reached or until the coating film dissolves and the substrate surface is exposed. If the substrate surface is not exposed after 50 or more rubbings, it is determined that the blocking agent has been released and curing has progressed completely. In this case, the heating temperature after application of the mixture is reduced by 1°C, a coating film is re-formed, and the above rubbing test is repeated. Conversely, if the substrate surface is exposed after fewer than 50 rubbings, it is determined that the release of the blocking agent has not progressed sufficiently and curing has not progressed. In this case, the heating temperature after coating the mixture is increased by 1° C., a coating film is formed again, and the above rubbing test is repeated.In the method described above, when the mixture was heated to form a coating film, the lowest heating temperature at which the surface of the substrate was not exposed even after rubbing with a cotton swab dipped in methyl ethyl ketone 50 times or more was determined as the temperature at which the blocking agent contained in the second isocyanate compound (A2) was desorbed.

[0036] Furthermore, the molecular form that the second isocyanate compound (A2) can take is not particularly limited. For example, the second isocyanate compound (A2) contains at least one selected from the group consisting of a monomer, an oligomer, a prepolymer, a polymer, and the like. Among these, the second isocyanate compound (A2) preferably contains at least one of a prepolymer and a polymer. In other words, the second isocyanate compound (A2) preferably contains a blocked polyisocyanate resin. In this case, the abrasion resistance and solvent resistance of the release layer 1 can be further improved. The blocked polyisocyanate resin is a compound having two or more isocyanate groups in one molecule, at least one of which is blocked with a blocking agent.

[0037] The content of the second isocyanate compound (A2) relative to the isocyanate compound (A) is preferably 70% by mass or more and 90% by mass or less. In this case, the abrasion resistance and solvent resistance of the release layer 1 can be further improved. This content is more preferably 75% by mass or more. This content is more preferably 85% by mass or less.

[0038] <<Polyol Compound>> As described above, the release layer 1 contains the polyol compound (B). As described above, in the release layer 1, the first isocyanate compound (A1) and the polyol compound (B) can be reacted by attaching the transfer layer 10 to the object 20 while heating it. Note that, at the stage when the transfer layer 10 is attached to the object 20, the first isocyanate compound (A1) may be partially or entirely reacted with the polyol compound (B).

[0039] The polyol compound (B) has thermoplastic properties. In other words, the polyol compound (B) is a thermoplastic resin having a hydroxyl group. For example, the polyol compound (B) contains at least one selected from the group consisting of polyester polyols, acrylic polyols, polyether polyols, polyolefin polyols, fluorine-containing polyols, polycarbonate polyols, and vinyl chloride / vinyl acetate copolymer polyols. Furthermore, it is particularly preferable that the polyol compound (B) contains a vinyl chloride / vinyl acetate copolymer polyol (vinyl chloride / vinyl acetate polyol), in which case the solvent resistance and abrasion resistance of the release layer 1 can be particularly improved.

[0040] In this disclosure, vinyl chloride-vinyl acetate copolymer polyol refers to a vinyl chloride-vinyl acetate copolymer having two or more hydroxyl groups per molecule. The method for producing vinyl chloride-vinyl acetate polyol is not particularly limited. For example, vinyl chloride-vinyl acetate polyol can be produced by chemically modifying a portion of the vinyl chloride-vinyl acetate copolymer to add hydroxyl groups. Alternatively, vinyl chloride-vinyl acetate polyol can be produced by saponifying the vinyl chloride-vinyl acetate copolymer, thereby eliminating acetyl groups from the vinyl acetate-derived portion and generating hydroxyl groups.

[0041] The content of the polyol compound (B) in the entire release layer 1 is preferably 55% by mass or more and 65% by mass or less. In this case, the solvent resistance and abrasion resistance of the release layer 1 can be further improved. This content is more preferably 60% by mass or more. This content may be 70% by mass or less.

[0042] The mass ratio of the isocyanate compound (A) to the polyol compound (B) is preferably 10:90 to 30:70, which can improve the solvent resistance and abrasion resistance of the release layer 1. This mass ratio is more preferably 15:85 to 25:75.

[0043] <Solvent> A solvent (C) may be used when preparing the release layer 1. As a result, the solvent (C) may remain in the release layer 1. The solvent (C) is not particularly limited as long as it is a solvent used in paints, and may contain, for example, at least one selected from the group consisting of ester compounds, ether compounds, ketone compounds, hydrocarbon compounds, and glycol ether compounds. The hydrocarbon compound contains at least one of an aliphatic hydrocarbon compound and an aromatic hydrocarbon compound. The solvent (C) preferably contains at least one of a ketone compound and an aromatic hydrocarbon compound, and more specifically, it preferably contains at least one of isophorone, Solvesso 150, and cyclohexanone.

[0044] The content of the solvent in the entire release layer 1 is preferably 15% by mass or less, so that the transferability and printability of the thermal transfer foil 100 can be sufficiently ensured.

[0045] <<Additives>> The release layer 1 contains, for example, an additive (D) in addition to the isocyanate compound (A), the polyol compound (B), and the solvent (C). Examples of the additive (D) include an antifoaming agent and a leveling agent. The antifoaming agent contains, for example, a silicone resin. The leveling agent contains, for example, a silicone resin.

[0046] <Color Layer> As described above, the transfer layer 10 includes the color layer 2. The color layer 2 is laminated on the release layer 1. The color layer 2 may include multiple layers. The thickness of each layer included in the color layer 2 is 2 μm or more and 6 μm or less. In this case, the solvent resistance and abrasion resistance of the color layer 2 can be sufficiently ensured.

[0047] For example, the color layer 2 contains an isocyanate compound (E) and a polyol compound (F), which can improve the abrasion resistance and solvent resistance of the color layer 2.

[0048] It is preferable that the isocyanate compound (E) does not contain an isocyanate compound (E1) that does not have an isocyanate group blocked with a blocking agent. In this case, the color layer 2 can be formed on the release layer 1 without curing. This prevents the transferability of the thermal transfer foil 100 from being impaired.

[0049] The isocyanate compound (E) preferably contains an isocyanate compound (E2) having an isocyanate group blocked with a blocking agent. In this case, the color layer 2 can be cured by heating the transfer layer 10 after it has been attached to the object 20. This allows the solvent resistance and abrasion resistance of the color layer 2 to be improved while still ensuring sufficient transferability of the thermal transfer foil 100.

[0050] The isocyanate compound (E) contained in the color layer 2 is not particularly limited, but for example, a compound similar to the isocyanate compound (A) contained in the release layer 1 can be used.

[0051] The polyol compound (F) contained in the color layer 2 is not particularly limited, but may be the same compound as the polyol compound (B) contained in the release layer 1. The color layer 2 preferably contains a chloride-vinyl acetate polyol as the polyol compound (F), which can improve the solvent resistance and abrasion resistance of the color layer 2.

[0052] Furthermore, in addition to the isocyanate compound (E) and the polyol compound (F), the color layer 2 may contain at least one selected from the group consisting of an antifoaming agent, a thickener, a solvent, etc. The solvent contained in the color layer 2 may be the same compound as the solvent (C) that the release layer 1 may contain. The antifoaming agent contained in the color layer 2 may be the same compound as the antifoaming agent contained in the release layer 1. The color layer 2 may be the same compound as the thickener that the release layer 1 may contain.

[0053] <Adhesive Layer> As described above, the transfer layer 10 includes the adhesive layer 3. The adhesive layer 3 is laminated on the color layer 2. The thickness of the adhesive layer 3 is 2 μm or more and 6 μm or less. In this case, the solvent resistance and abrasion resistance of the adhesive layer 3 can be sufficiently ensured.

[0054] For example, the adhesive layer 3 contains an isocyanate compound (G) and a polyol compound (H). In this case, the abrasion resistance and solvent resistance of the adhesive layer 3 can be improved.

[0055] It is preferable that the isocyanate compound (G) does not contain the isocyanate compound (G1) that does not have an isocyanate group blocked with a blocking agent. In this case, the adhesive layer 3 can be formed on the color layer 2 without curing. This can further ensure the adhesion between the adhesive layer 3 and the object 20.

[0056] Furthermore, the isocyanate compound (G) preferably contains an isocyanate compound (G2) having an isocyanate group blocked with a blocking agent. In this case, the adhesive layer 3 can be cured by heating the transfer layer 10 after it has been attached to the object 20. This makes it possible to ensure the adhesion between the adhesive layer 3 and the object 20 while also improving the solvent resistance and abrasion resistance of the adhesive layer 3.

[0057] The isocyanate compound (G) contained in the adhesive layer 3 is not particularly limited, but for example, a compound similar to the isocyanate compound (A) contained in the release layer 1 can be used.

[0058] The polyol compound (H) contained in the adhesive layer 3 is not particularly limited, but may be, for example, the same compound as the polyol compound (B) contained in the release layer 1. The adhesive layer 3 preferably contains a chloride-vinyl acetate polyol as the polyol compound (H). In this case, the solvent resistance and abrasion resistance of the adhesive layer 3 can be improved.

[0059] In addition to the isocyanate compound (G) and the polyol compound (H), the adhesive layer 3 may contain at least one selected from the group consisting of an antifoaming agent, a thickener, a solvent, etc. The solvent contained in the adhesive layer 3 may be the same compound as the solvent (C) that the release layer 1 may contain. The antifoaming agent contained in the adhesive layer 3 may be the same compound as the antifoaming agent contained in the release layer 1. The adhesive layer 3 may be the same compound as the thickener that the release layer 1 may contain.

[0060] (Method of Producing Thermal Transfer Foil) A method of producing the thermal transfer foil 100 will now be described. Note that the method of producing the thermal transfer foil 100 is not limited to the following method, and any appropriate method can be adopted depending on the mode of use.

[0061] First, a composition for forming the release layer 1 (hereinafter, composition (L)) is prepared. The composition (L) contains an isocyanate compound (A) and a polyol compound (B), and, if necessary, contains components such as a solvent (C). Next, a composition for forming the color layer 2 (hereinafter, composition (M)) is prepared. The composition (M) contains components such as an isocyanate compound (E), a polyol compound (F), and a solvent. Then, a composition for forming the adhesive layer 3 (hereinafter, composition (N)) is prepared. The composition (N) contains components such as an isocyanate compound (G), a polyol compound (H), and a solvent.

[0062] Next, the composition (L) is applied onto the substrate 4 to form a coating film, and this coating film is left at room temperature for a while or heated to form the release layer 1. The heating temperature here is preferably a temperature at which the isocyanate compound (A) does not react with the polyol compound (B), and is preferably, for example, less than 80°C. The method for applying the composition (L) is not particularly limited, and any appropriate method can be applied. Examples of methods for applying the composition (L) include screen printing, reverse roll coating, gravure coating, die coating, roll splash coating, spray coating, air knife coating, and curtain coating.

[0063] Next, composition (M) is applied onto the release layer 1 to form a coating film, and this coating film is left at room temperature for a while or heated to form color layer 2. The heating temperature here is preferably a temperature at which the isocyanate compound (A) and the polyol compound (B) do not react, or, if composition (M) contains isocyanate compound (E), a temperature at which the isocyanate compound (E) and the polyol compound (F) do not react, for example, preferably below 80°C. In this way, color layer 2 is formed. Note that the method for applying composition (M) can be the same as the method for applying composition (L).

[0064] Next, composition (N) is applied to the color layer 2 to form a coating film, and this coating film is left at room temperature for a while or heated to form the adhesive layer 3. The heating temperature is preferably a temperature at which the isocyanate compound (A) and the polyol compound (B) do not react, or, if composition (M) contains an isocyanate compound (E), a temperature at which the isocyanate compound (E) and the polyol compound (F) do not react, or, if composition (N) contains an isocyanate compound (G), a temperature at which the isocyanate compound (G) and the polyol compound (H) do not react, for example, preferably below 80°C. In this way, the adhesive layer 3 is formed. The same method as that used to apply composition (L) can be used to apply composition (N).

[0065] (Decoration) A method for decorating the object 20 using the thermal transfer foil 100 will be described.

[0066] First, the thermal transfer foil 100 is placed on top of the object 20, with the adhesive layer 3 of the thermal transfer foil 100 facing the object 20. Next, the transfer roll 6 is pressed against the substrate 4 to transfer the transfer layer 10 to the object 20 (see FIG. 2). During this process, the first isocyanate compound (A1) and the polyol compound (B) may react. The temperature of the transfer roll 6 is not particularly limited, but is, for example, 190°C or higher and 230°C or lower. This prevents damage to the transfer layer 10 attached to the object 20. From the viewpoint of the heat resistance of the substrate 4, the heating time is preferably between 0.2 and 0.3 seconds. After the transfer layer 10 is transferred so as to contact the object 20, the substrate 4 is peeled off from the release layer 1 (see FIG. 3). In this manner, the transfer layer 10 is attached to the object 20. In this case, if the color layer 2 does not contain the isocyanate compound (E1), the viscosity of the composition (M) can be suppressed. Therefore, when the composition (M) is applied onto the release layer 1 to form the color layer 2, the previously formed release layer 1 can be made difficult to peel off. This can make it possible to further prevent defects from occurring in the transfer layer 10. Furthermore, if the adhesive layer 3 does not contain the isocyanate compound (G1), the viscosity of the composition (N) can be suppressed. Therefore, when the composition (N) is applied onto the color layer 2 to form the adhesive layer 3, the previously formed release layer 1 can be made difficult to peel off. This can make it possible to further prevent defects from occurring in the transfer layer 10.

[0067] Next, the object 20 to which the transfer layer 10 is attached is heated to bake the transfer layer 10. The heating method is not particularly limited, but can be performed, for example, by placing the object 20 to which the transfer layer 10 is attached in a heating furnace or the like and heating it in the furnace. At this time, the second isocyanate compound (A2) and the polyol compound (B) may mainly react. The heating temperature is, for example, 90°C or higher and 120°C or lower. The heating time is between 30 and 90 minutes, with 90 minutes being particularly preferred. If the heating temperature and heating time are within the above ranges, the transfer layer 10 can be sufficiently cured, thereby ensuring sufficient solvent resistance and abrasion resistance of the transfer layer 10.

[0068] Note that by baking the transfer layer 10, the color layer 2 and the adhesive layer 3 can also be cured. In particular, when the color layer 2 contains an isocyanate compound (E2), the isocyanate compound (E2) and the polyol compound (F) can react efficiently. Furthermore, when the adhesive layer 3 contains an isocyanate compound (G2), the isocyanate compound (G2) and the polyol compound (H) can react efficiently.

[0069] Furthermore, if the object 20 has low heat resistance, even if the object 20 is heated at a temperature of 90°C or higher and 120°C or lower, the solvent resistance and abrasion resistance of the transfer layer 10 can be sufficiently ensured, thereby suppressing deterioration in the quality of the object 20 due to heating.

[0070] According to the method described above, the thermal transfer foil 100 can be transferred to the object 20. Note that the method for transferring the thermal transfer foil 100 to the object 20 is not limited to the above method, and any suitable method and conditions can be adopted depending on the mode of use.

[0071] It should be noted that when the transfer layer 10 is attached to the object 20, the transfer layer 10 is exposed to the external environment. In the embodiment, the solvent resistance and abrasion resistance of the transfer layer 10 attached to the object 20 can be ensured, so that the transfer layer 10 can have good durability even when exposed to the external environment. This reduces the need to protect the transfer layer 10 with an overcoat layer or the like, and the process for providing the overcoat layer can be eliminated. However, this does not prevent the transfer layer 10 from being covered and protected with an overcoat layer or the like for purposes such as further improving durability.

[0072] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0073] (Composition) <Composition for forming release layer> A composition for forming a release layer (hereinafter referred to as a first composition) was prepared by mixing the components shown in Table 1 in the ratios shown in Table 1. Details of the components are as follows.

[0074] <Unblocked Isocyanate Compounds> Unblocked Isocyanate Compound #1: A mixture of hexamethylene diisocyanate and 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate) (hexamethylene diisocyanate 0.2% by mass, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate 0.3% by mass).

[0075] Unblocked isocyanate compound #2: hexamethylene diisocyanate 0.6% by weight, polyisocyanate 85.0% by weight, butyl acetate 14.4% by weight.

[0076] Unblocked isocyanate compound #3: 75.0% by weight of xylene diisocyanate, 25.0% by weight of ethyl acetate.

[0077] Unblocked isocyanate compound #4: polyisocyanate 75.0% by mass, ethyl acetate 24.5% by mass, 2,6-di-tert-butyl-4-methylphenol 0.5% by mass.

[0078] <Blocked Isocyanate Compounds> Blocked Isocyanate Compound #1: 70.0 mass % of blocked isocyanate compound (desorption temperature of blocking agent: 110° C.), 30.0 mass % of propylene glycol monomethyl ether acetate.

[0079] Blocked isocyanate compound #2: 55.0% by mass of blocked isocyanate compound (blocking agent desorption temperature 120°C), 45.0% by mass of 1-methoxy-2-propanol.

[0080] Blocked isocyanate compound #3: blocked isocyanate compound (blocking agent desorption temperature 110°C) 69.6% by mass, dipropylene glycol monomethyl ether 30.0% by mass, residual blocking agent 0.4% by mass.

[0081] Blocked isocyanate compound #4: 70.0% by mass of blocked isocyanate compound (blocking agent desorption temperature 110°C), 28.8% by mass of 1-methoxy-2-propyl acetate, 1.2% by mass of unreacted remaining blocking agent.

[0082] <Polyol Compounds> Polyol Compound #1: Chloride-Acid-Bipolyol.

[0083] <Solvents> Solvent #1: A mixed solvent of cyclohexanone, isophorone, and Solvesso 150 (cyclohexanone 25% by mass, isophorone 25% by mass, Solvesso 150 50% by mass).

[0084] Additives: Additive #1: Antifoaming agent (silicone resin (silicone oil)).

[0085] Additive #2: Leveling agent (acrylic polymer).

[0086] <Composition for Preparing Color Layer> The following components were mixed to prepare a composition for preparing a color layer (hereinafter referred to as the second composition).

[0087] Blocked isocyanate compound (blocking agent desorption temperature: 110°C) 8% by mass

[0088] Vinyl chloride vinyl acetate copolymer polyol, 76% by mass.

[0089] A mixed solvent of cyclohexanone, isophorone, and Solvesso 150 (cyclohexanone 25% by mass, isophorone 25% by mass, Solvesso 150 50% by mass) was 12% by mass.

[0090] Antifoaming agent (silicone resin (silicone oil)) 2% by mass.

[0091] Thickener (silica): 2% by mass.

[0092] <Composition for forming adhesive layer> The following components were mixed to prepare a composition for forming an adhesive layer (hereinafter referred to as third composition).

[0093] Blocked isocyanate compound (blocking agent desorption temperature: 110°C) 8% by mass

[0094] - A mixture of vinyl chloride / vinyl acetate copolymer and isocyanate compound, 75% by mass.

[0095] A mixed solvent of cyclohexanone, isophorone, and Solvesso 150 (25% by mass of cyclohexanone, 25% by mass of isophorone, 50% by mass of Solvesso 150). 15% by mass

[0096] Antifoaming agent (silicone resin (silicone oil)) 2% by mass.

[0097] (Preparation of Thermal Transfer Foil) Thermal transfer foils were prepared from the first composition, the second composition, and the third composition according to the following method.

[0098] First, the first composition was applied by screen printing to a release film (a PET film with a thickness of 25 μm and a release coating on both sides of which was a silicone resin) to prepare a coating film. Subsequently, the coating film was heated by hot air drying to prepare a release layer.

[0099] Next, the second composition was applied onto the release layer by screen printing to form a coating film, which was then heated by hot air drying to form a color layer.

[0100] Then, the third composition was applied onto the color layer by screen printing to form a coating film, which was then heated by hot air drying to form an adhesive layer.

[0101] As described above, a thermal transfer foil was produced by laminating a release layer, a color layer, and an adhesive layer in this order on a release film.

[0102] (Evaluation of Thermal Transfer Foil) The transfer layer from the prepared thermal transfer foil was attached to the target (shaft) using a silicone roller with a hardness of 75 to 85°, a silicone roller surface temperature of 190 to 230°C, a shaft rotation speed of 15 to 25 rpm, and a pressure of 15 to 25 kgf / cm. ２ The transfer was performed under the following conditions. Then, the object onto which the transfer layer was transferred was heated at 100° C. for 90 minutes. The object decorated with the transfer layer was evaluated as follows.

[0103] <Solvent Resistance Test> The area of ​​the object where the transfer layer was attached was rubbed six times with a cloth soaked in a solvent (ethyl acetate), and the state of the transfer layer at that time was evaluated according to the following criteria. The results are shown in Table 1.

[0104] A: No dissolution is observed in the transfer layer. B: Dissolution is observed in the transfer layer. <Abrasion resistance test> The area of ​​the object where the transfer layer was attached was rubbed continuously with a load of 1250 g at a distance of 150 mm, at an interval of 1 reciprocation per second, and evaluated according to the following criteria. The results are shown in Table 1.

[0105] A: The surface of the shaft was not exposed even after rubbing 75 times or more. B: The surface of the shaft was exposed before rubbing 75 times. <Confirmation of foil cracking> The transfer layer attached to the object was visually inspected and evaluated according to the following criteria. The results are shown in Table 1.

[0106] A: No defects are observed in the transfer layer. B: Defects are observed in the transfer layer.

[0107]

[0108] (Summary) As is clear from the above embodiment, the present disclosure includes the following aspects. In the following, reference numerals are given in parentheses only to clarify the correspondence with the embodiment.

[0109] A thermal transfer foil (100) according to a first aspect of the present disclosure comprises a substrate (4) and a transfer layer (10) disposed on the substrate (4). The transfer layer (10) comprises a release layer (1), a color layer (2), and an adhesive layer (3), stacked in order from closest to the substrate (4). The release layer (1) contains an isocyanate compound (A) and a thermoplastic polyol compound (B). The isocyanate compound (A) contains a first isocyanate compound (A1) and a second isocyanate compound (A2), which are different from each other. The first isocyanate compound (A1) does not have an isocyanate group blocked with a blocking agent. The second isocyanate compound (A2) has an isocyanate group blocked with a blocking agent.

[0110] According to this embodiment, it is possible to provide a thermal transfer foil (100) that can ensure the solvent resistance and abrasion resistance of the transfer layer (10) attached to the object (20).

[0111] A thermal transfer foil (100) according to a second aspect of the present disclosure is based on the thermal transfer foil (100) of the first aspect. The first isocyanate compound (A1) contains at least one of hexamethylene diisocyanate and 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate.

[0112] According to this embodiment, the abrasion resistance of the release layer (1) can be further improved.

[0113] A thermal transfer foil (100) according to a third aspect of the present disclosure is based on the thermal transfer foil (100) according to the first or second aspect. The first isocyanate compound (A1) contains a polyisocyanate resin.

[0114] According to this embodiment, the abrasion resistance of the release layer (1) can be further improved.

[0115] A thermal transfer foil (100) according to a fourth aspect of the present disclosure is based on the thermal transfer foil (100) according to any one of the first to third aspects. The temperature at which the blocking agent is desorbed from the second isocyanate compound (A2) is 100°C or higher and 120°C or lower.

[0116] According to this embodiment, by setting the temperature at which the blocking agent is desorbed from the first isocyanate compound (A1) to 90°C or higher, it is possible to prevent the release layer (1) from being excessively cured until the transfer layer (10) is attached to the object (20). This makes it possible to sufficiently ensure the transferability of the thermal transfer foil (100). Furthermore, by setting the temperature at which the blocking agent is desorbed from the first isocyanate compound (A1) to 120°C or lower, it is possible to heat and cure the release layer (1) at a temperature that does not impair the quality of the object (20).

[0117] A thermal transfer foil (100) according to a fifth aspect of the present disclosure is based on the thermal transfer foil (100) according to any one of the first to fourth aspects. The color layer (2) contains an isocyanate compound (E) and a polyol compound (F).

[0118] According to this embodiment, the solvent resistance and abrasion resistance of the color layer (2) can be improved.

[0119] A thermal transfer foil (100) according to a sixth aspect of the present disclosure is based on the thermal transfer foil (100) of the fifth aspect. The isocyanate compound (E) does not contain an isocyanate compound (E1) that does not have an isocyanate group blocked with a blocking agent.

[0120] According to this embodiment, the color layer (2) can be formed on the release layer (1) without hardening, thereby preventing the transferability of the thermal transfer foil (100) from being impaired.

[0121] A thermal transfer foil (100) according to a seventh aspect of the present disclosure is based on the thermal transfer foil (100) of the fifth or sixth aspect. The isocyanate compound (E) contains an isocyanate compound (E2) having an isocyanate group blocked with a blocking agent.

[0122] According to this embodiment, the color layer (2) can be hardened by heating the transfer layer (10) after it has been attached to the object (20). This allows the solvent resistance and abrasion resistance of the color layer (2) to be improved while still ensuring sufficient transferability of the thermal transfer foil (100).

[0123] A thermal transfer foil (100) according to an eighth aspect of the present disclosure is based on the thermal transfer foil (100) according to any one of the first to seventh aspects. The adhesive layer (3) contains an isocyanate compound (G) and a polyol compound (H).

[0124] According to this embodiment, the solvent resistance and abrasion resistance of the adhesive layer (3) can be improved.

[0125] A thermal transfer foil (100) according to a ninth aspect of the present disclosure is based on the thermal transfer foil (100) of the eighth aspect. The isocyanate compound (G) does not contain an isocyanate compound (G1) that does not have an isocyanate group blocked with a blocking agent.

[0126] According to this embodiment, the adhesive layer (3) can be formed on the release layer (1) without curing, thereby ensuring better adhesion between the adhesive layer (3) and the object (20).

[0127] A thermal transfer foil (100) according to a tenth aspect of the present disclosure is based on the thermal transfer foil (100) of the eighth or ninth aspect. The isocyanate compound (G) contains an isocyanate compound (G2) having an isocyanate group blocked with a blocking agent.

[0128] According to this embodiment, the adhesive layer (3) can be cured by heating the transfer layer (10) after the transfer layer (10) is attached to the object (20), thereby ensuring adhesion between the adhesive layer (3) and the object (20) and improving the solvent resistance and abrasion resistance of the adhesive layer (3).

[0129] The thermal transfer foil (100) according to an eleventh aspect of the present disclosure is any one of the first to tenth aspects, wherein the polyol compound (B) contains a vinyl chloride / vinyl acetate copolymer polyol.

[0130] REFERENCE SIGNS LIST 1 Peel layer 2 Color layer 3 Adhesive layer 4 Substrate 10 Transfer layer 20 Object 100 Thermal transfer foil

Claims

1. A thermal transfer foil comprising a substrate and a transfer layer disposed on the substrate, wherein the transfer layer comprises a release layer, a color layer, and an adhesive layer laminated in that order from closest to the substrate, wherein the release layer contains an isocyanate compound (A) and a thermoplastic polyol compound (B), wherein the isocyanate compound (A) contains a first isocyanate compound (A1) and a second isocyanate compound (A2) that are different from each other, wherein the first isocyanate compound (A1) does not have an isocyanate group blocked with a blocking agent, and wherein the second isocyanate compound (A2) has an isocyanate group blocked with a blocking agent.

2. The thermal transfer foil according to claim 1, wherein the first isocyanate compound (A1) contains at least one of hexamethylene diisocyanate and 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate.

3. The thermal transfer foil according to claim 1 or 2, wherein the first isocyanate compound (A1) contains a polyisocyanate resin.

4. The thermal transfer foil according to claim 1, wherein the temperature at which the blocking agent is desorbed from the second isocyanate compound (A2) is 100°C or higher and 120°C or lower.

5. The thermal transfer foil according to claim 1, wherein the color layer contains an isocyanate compound (E) and a polyol compound (F).

6. The thermal transfer foil according to claim 5, wherein the isocyanate compound (E) contains an isocyanate compound (E2) having an isocyanate group blocked with a blocking agent.

7. The thermal transfer foil according to claim 1, wherein the adhesive layer contains an isocyanate compound (G) and a polyol compound (H).

8. The thermal transfer foil according to claim 7, wherein the isocyanate compound (G) contains an isocyanate compound (G2) having an isocyanate group blocked with a blocking agent.

9. The thermal transfer foil according to claim 1, wherein the polyol compound (B) contains a vinyl chloride / vinyl acetate copolymer polyol.

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