JP2026002018A - Ink set for thermal transfer sheet, thermal transfer sheet, method for manufacturing thermal transfer sheet, and method for manufacturing transfer print - Google Patents

Abstract

[Problem] The present invention provides a thermal transfer sheet that can produce a transfer print with excellent wash fastness even at low transfer temperatures, an ink set for the thermal transfer sheet, a method for producing a thermal transfer sheet, and a method for producing a transfer print. [Solution] The present invention provides an ink set for a thermal transfer sheet that includes a water-based ink and a water-based adhesive, wherein the water-based adhesive contains a nonionic surfactant (A), and the content of the nonionic surfactant (A) in the water-based adhesive is in the range of 1.5 to 10 mass %. [Selected Figures] None

Description

This disclosure relates to an ink set for a thermal transfer sheet, a thermal transfer sheet, a method for manufacturing a thermal transfer sheet, and a method for manufacturing a transfer-printed material.

DTF printing has been gaining attention in recent years as a method for printing images such as text, pictures, and patterns onto woven, knitted, and nonwoven fabrics. DTF stands for Direct To Film, and is specifically a printing method that uses a thermal transfer sheet. Compared to methods that print directly onto fabric, DTF printing has the advantage of producing higher image clarity and a wider selection of printable fabrics and colors.

Thermal transfer sheets for DTF printing are generally produced by printing the desired image in color on a base sheet, printing white ink on top of the image, applying hot melt powder to the white ink before it dries, and then heating to melt the hot melt powder. Printing on fabric is done by placing the hot melt powder layer of the thermal transfer sheet on the fabric side and transferring the image using a heat press.

As a prior art example of a thermal transfer sheet for DTF printing using hot melt powder, Patent Document 1 describes an example that uses a resin powder of a grade that is heat-meltable and adheres to the entire surface of the ink without any gaps - specifically, a resin powder of a grade in which 87% or more of the particles are 75 μm or less in diameter and does not contain any powder with a particle size exceeding 150 μm - and a transfer sheet that is impermeable to ink and sufficient to maintain the adhesive properties of the resin powder.

Japanese Patent Application Laid-Open No. 2019-171840

As described in Patent Document 1, one of the technical challenges facing DTF printing is the creation of a transfer image without any missing parts. The method described in Patent Document 1 uses a special grade of hot melt powder to prevent image loss, and a highly impermeable base sheet to ensure the hot melt powder adheres well. However, the preferred grade of hot melt powder has a small particle size and is prone to scattering, making it difficult to handle. Furthermore, the use of a highly impermeable base sheet makes it easy for the color inks forming the image to mix with the white ink applied on top of it, posing another challenge in that image reproducibility can easily deteriorate.

As mentioned above, in DTF printing, images are transferred and printed using a heat press, and from the perspective of energy conservation, a lower transfer temperature is preferable. However, when transfer is performed at a low temperature, there are issues such as image loss being more likely to occur and the wash fastness of the transfer print is reduced.

One of the objectives of the present disclosure is to provide a thermal transfer sheet, an ink set for the thermal transfer sheet, a method for manufacturing a thermal transfer sheet, and a method for manufacturing a transfer print that can produce a transfer print with excellent washing fastness even at low transfer temperatures.

One embodiment of the present disclosure relates to an ink set for thermal transfer sheets that includes an aqueous ink and an aqueous adhesive, wherein the aqueous adhesive includes a nonionic surfactant (A), and the content of the nonionic surfactant (A) in the aqueous adhesive is in the range of 1.5 to 10% by mass.

Another embodiment of the present disclosure relates to a thermal transfer sheet having a substrate sheet, an aqueous ink image formed on the substrate sheet, and an area to which an aqueous adhesive is applied, the aqueous adhesive containing a nonionic surfactant (A) and a resin, and the proportion of the nonionic surfactant (A) relative to the total mass of the resin is in the range of 8 to 50 mass%.

Another embodiment of the present disclosure relates to a method for producing a thermal transfer sheet, which includes applying an aqueous ink onto a substrate sheet and then applying an aqueous adhesive by a wet-on-wet method, wherein the aqueous adhesive contains a nonionic surfactant (A), and the content of the nonionic surfactant (A) in the aqueous adhesive is in the range of 1.5 to 10% by mass.

Another embodiment of the present disclosure relates to a method for producing a transfer print, which includes placing the above-mentioned thermal transfer sheet on a cloth, heating it to transfer an image, and peeling off the base sheet.

The present disclosure provides a thermal transfer sheet, an ink set for the thermal transfer sheet, a method for manufacturing a thermal transfer sheet, and a method for manufacturing a transfer print that can produce a transfer print with excellent washing fastness even at low transfer temperatures.

Embodiments of the present disclosure are described in detail below, but the present disclosure is not limited to these embodiments and may be modified and altered in various ways.

In one embodiment, the ink set for thermal transfer sheets (hereinafter sometimes referred to as the "ink set") is an ink set for thermal transfer sheets that includes an aqueous ink and an aqueous adhesive, wherein the aqueous adhesive includes a nonionic surfactant (A), and the content of the nonionic surfactant (A) in the aqueous adhesive is in the range of 1.5 to 10% by mass.

In one embodiment of the ink set, the aqueous adhesive (hereinafter sometimes referred to as "adhesive") contains a nonionic surfactant (A), and the content is relatively high, ranging from 1.5 to 10% by mass. This allows the adhesive-applied portion of the resulting thermal transfer sheet to have adequate fluidity and easily penetrate into fabric, even under low-temperature conditions of around 120°C. This creates an anchoring effect on the fabric in the adhesive-applied portion, improving adhesion of the transferred image to the fabric and allowing for a transfer print with excellent washing fastness. Furthermore, because the surfactant component in the adhesive promotes the anchoring effect on the fabric, it becomes possible to select a resin component that is preferable from other perspectives, thereby expanding the design options for the adhesive and making it possible to further improve, for example, the image quality of the transferred image and its ability to conform to highly stretchable fabrics.

The content of nonionic surfactant (A) in the aqueous adhesive is more preferably 2.0% by mass or more, and particularly preferably 2.5% by mass or more, since this results in a transfer print with even better washing fastness. Furthermore, since this results in a transfer print with excellent image quality, it is more preferably 8% by mass or less, and particularly preferably 5% by mass or less. It is even more preferable that the content of nonionic surfactant (A) in the aqueous adhesive be in the range of 2.5 to 5% by mass.

The nonionic surfactant (A) may be any compound that is nonionic, has a hydrophilic portion and a lipophilic portion, and can function as a surfactant; its specific structure is not particularly limited. The HLB value of the nonionic surfactant (A) may be, for example, in the range of 10 to 20. One type of nonionic surfactant (A) may be used alone, or two or more types may be used in combination. Specific examples of the nonionic surfactant (A) include ester-type surfactants such as (poly)glycerin fatty acid esters and sorbitan fatty acid esters; ether-type surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxypropylene alkyl ethers; ether-ester-type surfactants such as polyoxyethylene sorbitan fatty acid esters; acetylene-based surfactants; silicone-based surfactants; and fluorine-based surfactants.

Examples of commercially available (poly)glycerin fatty acid esters include "NIKKOL Hexaglyn 1-L," "NIKKOL Decaglyn 1-M," "NIKKOL Decaglyn 1-OV," and "NIKKOL Decaglyn 1-SV" manufactured by Nikko Chemicals Co., Ltd.

Examples of polyoxyethylene sorbitan fatty acid esters include "NIKKOL TL-10," "NIKKOL TI-10V," and "NIKKOL TO-10V" manufactured by Nikko Chemicals Co., Ltd.

For polyoxyethylene alkyl ethers, the number of repeating units in the oxyethylene chain is not particularly limited, but may be, for example, in the range of 10 to 30. The number of carbon atoms in the alkyl group of the polyoxyethylene alkyl ether may be in the range of 10 to 30. Examples of commercially available polyoxyethylene alkyl ethers include Nikko Chemicals' "NIKKOL BT-12," "NIKKOL BO-20V," "NIKKOL BS-20," "NIKKOL BB-20," and "NIKKOL BC-20," as well as Kao's "EMULGEN 120," "EMULGEN 150," "EMULGEN 350," "EMULGEN 430," "EMULGEN 707," and "EMULGEN 709."

Examples of acetylene-based surfactants include acetylene glycol-based surfactants, acetylene alcohol-based surfactants, and surfactants having an acetylene group. Acetylene glycol-based surfactants are glycols having an acetylene group, preferably glycols with a symmetrical structure in which the acetylene group is located in the center, and may have a structure in which ethylene oxide is added to acetylene glycol. Commercially available acetylene-based surfactants include the Surfynol series manufactured by Evonik Industries (such as "Surfynol 104E," "Surfynol 104H," "Surfynol 420," "Surfynol 440," "Surfynol 465," and "Surfynol 485"), and the Olfin series manufactured by Nissin Chemical Industry Co., Ltd. (such as "Olfin E1004," "Olfin E1010," and "Olfin E1020").

Examples of silicone surfactants include polyether-modified silicone surfactants, alkyl-aralkyl co-modified silicone surfactants, and acrylic silicone surfactants. Commercially available silicone surfactants include "Silface SAG002" and "Silface SAG503A" manufactured by Nissin Chemical Industry Co., Ltd.

Examples of nonionic fluorosurfactants include perfluoroalkyl alkylene oxide adducts and perfluoroalkyl group-containing oligomers. Commercially available fluorosurfactants include perfluoroalkyl ethylene oxide adducts such as "Surflon S-242" and "Surflon S-243" manufactured by AGC Seimi Chemical Co., Ltd., and perfluoroalkyl group-containing oligomers such as "Surflon S-386."

Among these, it is preferable that the nonionic surfactant (A) contains one or more types selected from the group consisting of silicone-based surfactants and fluorine-based surfactants, as this allows the aqueous adhesive to be applied more uniformly to the aqueous ink image during production of the thermal transfer sheet and improves the washing fastness of the transferred image as a whole. The total proportion of the silicone-based surfactant and fluorine-based surfactant in the nonionic surfactant (A) is preferably 0.5% by mass or more, more preferably 0.7% by mass or more, and particularly preferably 0.9% by mass or more, as this provides an excellent balance between the washing fastness of the transferred print and the image quality of the transferred image. It is also preferable that the total proportion be 5% by mass or less, more preferably 4% by mass or less, and particularly preferably 3.5% by mass or less.

The proportion of silicone surfactant in nonionic surfactant (A) is preferably 0.5% by mass or more, more preferably 0.7% by mass or more, and particularly preferably 0.9% by mass or more, as this provides an excellent balance between the washing fastness of the transfer print and the image quality of the transferred image. It is also preferably 5% by mass or less, more preferably 4% by mass or less, and particularly preferably 3.5% by mass or less.

The proportion of the fluorine-based surfactant in the nonionic surfactant (A) is preferably 0.5% by mass or more, more preferably 0.7% by mass or more, and particularly preferably 0.9% by mass or more, as this provides an excellent balance between the washing fastness and color development of the image in the transfer print. It is also preferably 3% by mass or less, more preferably 2% by mass or less, and particularly preferably 1.5% by mass or less.

The aqueous adhesive may contain surfactants other than nonionic surfactants, as long as the effects of the invention are not impaired. The proportion of nonionic surfactant (A) in the surfactants contained in the aqueous adhesive is preferably 60% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more, and may even be 100% by mass.

Aqueous adhesives contain water. Examples of water include ion-exchanged water, distilled water, and ultrapure water. The water content of the aqueous adhesive is adjusted appropriately depending on the desired viscosity, etc., but may be, for example, in the range of 30 to 90% by mass.

In addition to water and the nonionic surfactant (A), the aqueous adhesive may contain other components. Examples of other components include resins, water-soluble organic solvents, colorants, pH adjusters, fixing agents, and preservatives.

When the water-based adhesive contains a resin, the resin is preferably a water-dispersible resin. One type of water-dispersible resin may be used alone, or two or more types may be used in combination.

The type and physical properties of the water-dispersible resin are not particularly limited and are adjusted appropriately depending on the desired performance of the thermal transfer sheet. For example, to further enhance the washing fastness of the transfer print, it is preferable to use a water-dispersible resin (B) (hereinafter sometimes referred to as "resin (B)") with a thermal melting temperature of 100°C or less, as this further reinforces the anchoring effect on the fabric. The thermal melting temperature of resin (B) is more preferably 80°C or less, and particularly preferably 70°C or less. Furthermore, to achieve an excellent balance between the anchoring effect on the fabric and the image quality of the transferred image, the thermal melting temperature of resin (B) is preferably 30°C or more, more preferably 40°C or more, and particularly preferably 50°C or more. The thermal melting temperature of resin (B) may be in the range of 30 to 100°C.

In this disclosure, the thermal melting temperature of a resin is the half-wave temperature calculated from the flow curve measured in a temperature rise test using a high-temperature flow tester in accordance with JIS K7121:2012. For example, the high-temperature flow tester "CFT-500D" manufactured by Shimadzu Corporation can be used as the flow tester.

Resin (B) is preferably capable of forming a transparent coating film. Specific examples of resin (B) include conjugated diene resins such as styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, and vinyl chloride-vinyl acetate copolymer; acrylic resins such as polymers of acrylic acid esters and methacrylic acid esters, or copolymers of these with styrene; vinyl resins such as ethylene-vinyl acetate copolymer; functional group-modified resins obtained by modifying these resins with monomers having functional groups such as carboxyl groups; melamine resins; urea resins; polyurethane resins; polyester resins; polyolefin resins; silicone resins; polyvinyl butyral resins; and alkyd resins. Among these, polyurethane resins are preferred due to their superior anchoring effect on fabrics.

Examples of water-dispersible resins with a thermal melting temperature of 100°C or less include Daiichi Kogyo Seiyaku Co., Ltd.'s "Superflex 500M" (thermal melting temperature 67°C), "Superflex 740" (thermal melting temperature 53°C), and "Superflex 860" (thermal melting temperature 93°C).

The content of resin (B) in the aqueous adhesive is not particularly limited, but may be, for example, 5% by mass or more, 8% by mass or more, or 12% by mass or more. It may also be 30% by mass or less, 25% by mass or less, or 20% by mass or less. The content of resin (B) in the aqueous adhesive may be in the range of 5 to 30% by mass.

The aqueous adhesive may contain resins other than resin (B). The proportion of resin (B) in the resins contained in the aqueous adhesive is preferably 60% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more, and may even be 100% by mass.

The ratio of resin to nonionic surfactant (A) in the aqueous adhesive can be any ratio, but to achieve an excellent balance between washing fastness and image color development in transfer prints, the ratio of the nonionic surfactant (A) to the total mass of resin is preferably 8% by mass or more, more preferably 10% by mass or more, and particularly preferably 15% by mass or more. It is also preferably 50% by mass or less, more preferably 35% by mass or less, and particularly preferably 25% by mass or less. The ratio of the nonionic surfactant (A) to the total mass of resin may be in the range of 8 to 50% by mass.

The aqueous adhesive may contain a water-soluble organic solvent. Any water-soluble organic solvent commonly used in the fields of aqueous adhesives or aqueous inks can be used without any particular limitation. A single water-soluble organic solvent may be used alone, or two or more may be used in combination. Among these, water-soluble organic solvents that are liquid at room temperature and can be uniformly mixed with an equal volume of water at 20°C under 1 atmosphere are preferred. Examples of such water-soluble organic solvents include lower alcohol compounds such as methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, and 2-methyl-2-propanol; glycol compounds such as ethylene glycol, diethylene glycol, trimethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol; glycerin compounds such as glycerin, diglycerin, and triglycerin; acetin compounds such as monoacetin, diacetin, and triacetin; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, and ethylene glycol monobutyl ether. glycol ether compounds such as tetraethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol dimethyl ether, and tetraethylene glycol diethyl ether; triethanolamine, 1-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, β-thiodiglycol, and sulfolane.

The content of the water-soluble organic solvent in the aqueous adhesive may be, for example, 1% by mass or more, 5% by mass or more, or 10% by mass or more. It may also be 30% by mass or less, 25% by mass or less, or 20% by mass or less. The content of the water-soluble organic solvent in the aqueous adhesive may be in the range of 1 to 30% by mass.

The aqueous adhesive may contain a colorant. One type of colorant may be used alone, or two or more types may be used in combination. The type of colorant is not particularly limited and is selected appropriately depending on the desired image on the thermal transfer sheet, etc. For example, if the printing target is a dark-colored fabric, the color of the fabric can be concealed by including a white pigment in the aqueous adhesive, resulting in a transferred image with excellent color reproducibility.

Examples of white pigments include white inorganic pigments such as titanium oxide, zinc oxide, zinc sulfide, antimony oxide, and zirconium oxide. Among these, titanium oxide is preferred because it has excellent concealing properties for the color of the fabric to be transferred. There are no particular restrictions on the average particle size of titanium oxide, but it may be in the range of 100 to 600 nm, for example.

There are no particular restrictions on the colorant content of the aqueous adhesive, and it can be used in the same range as general aqueous inks. For example, if the colorant is a white pigment, the colorant content of the aqueous adhesive may be in the range of 1 to 30% by mass.

When the aqueous adhesive contains a colorant, it may contain a dispersant to stably disperse the colorant. A single dispersant may be used, or two or more dispersants may be used in combination. When the colorant is a pigment, various pigment dispersants can be used, such as polymer dispersants and surfactant-type dispersants.

Examples of commercially available polymer dispersants include the TEGO Disperse series from EVONIK (TEGO Disperse 740W, TEGO Disperse 750W, TEGO Disperse 755W, TEGO Disperse 757W, TEGO Disperse 760W, etc.), and the Solsperse series from Lubrizol Japan Corporation (Solsperse 20000, Solsperse 27000, Solsperse 41000, Solsperse 41090, Solsperse 43000, Solsperse 44000, Solsperse 45000, Solsperse 46000, Solsperse 47000, Solsperse 48000, Solsperse 49000, Solsperse 5000, Solsperse 51000, Solsperse 52000, Solsperse 53000, Solsperse 54000, Solsperse 55000, Solsperse 56000, Solsperse 57000, Solsperse 58000, Solsperse 59000, Solsperse 6000, Solsperse 61000, Solsperse 62000, Solsperse 63000, Solsperse 64000, Solsperse 65000, Solsperse 66000, Solsperse 67000, Solsperse 68000, Solsperse 69000, Solsperse 7000, Solsperse 71000, Solsperse 72000, Solsperse 73000, Solsperse 74000, Solsperse 75000, Solsperse 6000), BASF Japan Ltd.'s JONCRYL series (JONCRYL 57, JONCRYL 60, JONCRYL 62, JONCRYL 63, JONCRYL 71, JONCRYL 501, etc.), BYK Japan Ltd.'s DISPERBYK-102, DISPERBYK-185, DISPERBYK-190, DISPERBYK-193, DISPERBYK-199, etc., and Dai-ichi Kogyo Seiyaku Co., Ltd.'s Polyvinylpyrrolidone K-30 and Polyvinylpyrrolidone K-90, etc.

Examples of commercially available surfactant-type dispersants include anionic surfactants such as Kao Corporation's Demol series (Demol P, Demol EP, Demol N, Demol RN, Demol NL, Demol RNL, Demol T-45, etc.); and nonionic surfactants such as Kao Corporation's Emulgen series (Emulgen A-60, Emulgen A-90, Emulgen A-500, Emulgen B-40, Emulgen L-40, Emulgen 420, etc.).

When a pigment dispersant is used, the amount used is adjusted appropriately depending on the type of pigment and pigment dispersant, but may be, for example, in the range of 0.05 to 20 parts by weight per 100 parts by weight of pigment.

The method for producing the water-based adhesive is not particularly limited, and it can be produced using the same production method as general water-based inks. Specifically, if the water-based adhesive does not contain a colorant, it can be produced by blending and stirring the various components contained in the water-based adhesive. If the water-based adhesive contains a colorant, it can be produced by first producing an aqueous dispersion of the colorant using a bead mill or the like, and then blending and stirring this with the other components, or by adding all of the components of the water-based adhesive to a mixer such as a three-one motor and dispersing them all at once or in portions. After production, the water-based adhesive may be passed through a filter such as a membrane filter, if necessary.

As described below, there are no particular limitations on the method for applying the aqueous adhesive when producing a thermal transfer sheet, but one preferred method is application by inkjet printing. In this case, from the perspective of inkjet ejection properties, the viscosity of the aqueous adhesive may be in the range of 1 to 30 mPa·s measured at 23°C.

In one embodiment, the ink set includes aqueous inks. The ink set may include one or more aqueous inks depending on the desired transfer image. For example, if the aqueous adhesive does not include a colorant, the ink set may include one or more non-white inks and a white ink as the aqueous inks. If the aqueous adhesive includes a white pigment, the ink set may include one or more non-white inks as the aqueous inks, and the white portions of the image may be formed with the aqueous adhesive instead of the white aqueous ink. Also, even if the aqueous adhesive includes a white pigment, the ink set may include one or more non-white inks and a white ink as the aqueous inks.

Non-white inks among aqueous inks contain non-white colorants. A single colorant may be used, or two or more may be used in combination. Examples of non-white pigments among non-white colorants include organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments, and dye lake pigments, as well as inorganic pigments such as carbon black and metal oxides. Examples of azo pigments include soluble azo lake pigments, insoluble azo pigments, and condensed azo pigments. Examples of phthalocyanine pigments include metal phthalocyanine pigments and metal-free phthalocyanine pigments. Examples of polycyclic pigments include quinacridone pigments, perylene pigments, perinone pigments, isoindoline pigments, isoindolinone pigments, dioxazine pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments, metal complex pigments, and diketopyrrolopyrrole (DPP). Examples of carbon black include furnace carbon black, lamp black, acetylene black, and channel black.

As will be described later, there are no particular limitations on the method for applying the aqueous ink in the production of thermal transfer sheets, but one preferred method is application by inkjet printing. In this case, from the standpoint of ink ejection stability and storage stability, the average particle size of the non-white pigment particles may be 300 nm or less, 200 nm or less, or 150 nm or less, as the volume-based average value in the particle size distribution measured by dynamic light scattering.

The non-white pigment may be a self-dispersing pigment or a microencapsulated pigment in which the pigment is coated with a resin. Self-dispersing pigments are pigments in which hydrophilic functional groups have been introduced onto their surfaces by chemical or physical treatment. The hydrophilic functional groups introduced into self-dispersing pigments are preferably ionic. By charging the pigment surface anionic or cationic, electrostatic repulsion can be utilized to stably disperse pigment particles in water. Examples of anionic functional groups include carboxyl groups, sulfo groups, sulfino groups, sulfate ester groups, phosphate groups, phosphate ester groups, phosphite groups, and phosphite ester groups. Examples of cationic functional groups include quaternary ammonium groups and quaternary phosphonium groups. These hydrophilic functional groups may be bonded directly to the pigment surface or via other atomic groups. Examples of other atomic groups include alkylene groups, phenylene groups, and naphthylene groups. Examples of pigment surface treatment methods include diazotization, sulfonation, hypochlorite treatment, humic acid treatment, and vacuum plasma treatment.

Examples of self-dispersible non-white pigments include Cabot Corporation's "CAB-O-JET" series (such as "CAB-O-JET200," "CAB-O-JET300," "CAB-O-JET250C," "CAB-O-JET260M," "CAB-O-JET270Y," "CAB-O-JET450C," and "CAB-O-JET465M"), and Orient Chemical Industries Co., Ltd.'s "BONJET" series (such as "BONJET BLACK CW-1," "BONJET BLACK CW-2," "BONJET BLACK CW-3," and "BONJET BLACK CW-4").

There are no particular restrictions on the content of non-white pigment in non-white ink, and it can be used in the same range as in general non-white inks. For example, it may be in the range of 1 to 10% by mass of the total amount of non-white ink.

Various pigment dispersants may be used to stably disperse non-white pigments in non-white inks. A single pigment dispersant may be used, or two or more may be used in combination. Specific examples of pigment dispersants include those exemplified in the explanation of water-based adhesives. Commercially available pigment dispersions in which non-white pigments are pre-dispersed with a pigment dispersant include the HOSTAJET series manufactured by Clariant and the FUJI SP series manufactured by Fuji Pigment Co., Ltd.

For the white ink among the water-based inks, the type of white pigment, particle size, amount of white pigment in the ink, type and amount of pigment dispersant used, etc. are the same as those for the water-based adhesive containing a white pigment described above.

Water-based inks contain water. Examples of water include ion-exchanged water, distilled water, and ultrapure water. The water content of water-based inks is adjusted appropriately depending on the desired viscosity, etc., but may be in the range of 30 to 90% by mass, for example.

Water-based inks may contain colorants, water, and pigment dispersants (if used as needed), as well as other components. Examples of other components include resins, surfactants, water-soluble organic solvents, pH adjusters, fixing agents, and preservatives.

When the water-based ink contains a resin, the resin is preferably a water-dispersible resin. One type of water-dispersible resin may be used alone, or two or more types may be used in combination.

The type and physical properties of the water-dispersible resin are not particularly limited and are adjusted appropriately depending on the desired performance of the thermal transfer sheet. For example, in order to reduce the likelihood of miscibility between the aqueous ink image and the aqueous adhesive during transfer printing using the thermal transfer sheet and thereby obtain a higher-quality transfer image, it is preferable to include a water-dispersible resin (C) (hereinafter sometimes referred to as "resin (C)") having a thermal melting temperature equal to or higher than that of resin (B) contained in the aqueous adhesive. The thermal melting temperature of resin (C) is preferably higher than that of resin (B), and the difference between the thermal melting temperature of resin (C) and that of resin (B) may be 50°C or higher, or 100°C or higher. It may also be 200°C or lower, 180°C or lower, or 160°C or lower. The difference between the thermal melting temperature of resin (C) and that of resin (B) may be in the range of 0 to 200°C.

Resin (C) is preferably one that can form a transparent coating film, as this results in an aqueous ink with superior color development. Specific examples of resin (C) include conjugated diene resins such as styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, and vinyl chloride-vinyl acetate copolymer; acrylic resins such as polymers of acrylic acid esters and methacrylic acid esters, or copolymers of these with styrene; vinyl resins such as ethylene-vinyl acetate copolymer; functional group-modified resins obtained by modifying these various resins with monomers having functional groups such as carboxyl groups; melamine resins; urea resins; polyurethane resins; polyester resins; polyolefin resins; silicone resins; polyvinyl butyral resins; and alkyd resins. Among these, polyurethane resins are preferred due to their excellent adhesion to aqueous adhesives.

Water-dispersible resins include the polyurethane dispersion "DAOTAN" series from Daicel Allnex Corporation (e.g., "DAOTAN TW6450," "DAOTAN TW6460," "DAOTAN TW6490," "DAOTAN VTW1262," etc.), and the "Implanil" series from Sumika Covestro Urethane Co., Ltd. (e.g., "Implanil DLP," "Implanil DLP-R," "Implanil DLV," "Implanil DLI," "Implanil 1016," "Implanil 1116," "Implanil DLS," "Implanil DL1537," "Implanil DL1554," "Implanil DL1380," "Implanil LP CGL 105," "Implanil DLN-SD," "Implanil LP DSB," etc.). 1069, Impranil DLN-W50, etc.), Daiichi Kogyo Seiyaku Co., Ltd.'s "Superflex" series (for example, "Superflex 420", "Superflex 150HS", "Superflex 460", "Superflex 470", "Superflex E2000", "Superflex 740", "Superflex 500M", "Superflex 300", "Superflex 860", etc.), Unitika Ltd.'s "Elitel" series (for example, "Elitel KT9204", "Elitel KT8803", etc.), DSM's "NeoRez" series (for example, "NeoRez R-966", "NeoRez R-4000, etc.), BYK's AQUACER series (e.g., AQUACER 507, etc.), and Japan Coating Resins Co., Ltd.'s Mowinyl series (e.g., Mowinyl 6750, Mowinyl 6751D, Mowinyl 6763, Mowinyl 6770, Mowinyl 6775, etc.).

The content of resin (C) in the aqueous ink is adjusted appropriately depending on the type of pigment, etc., but may be, for example, 5% by mass or more, 8% by mass or more, or 10% by mass or more. It may also be 30% by mass or less, 25% by mass or less, or 20% by mass or less. The content of resin (C) in the aqueous ink may be in the range of 5 to 30% by mass.

The aqueous ink may contain resins other than resin (C). The proportion of resin (C) in the resins contained in the aqueous ink is preferably 60% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more, and may even be 100% by mass.

When the aqueous ink contains a surfactant, examples of the surfactant include anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants. The surfactant may be either a low-molecular-weight surfactant or a high-molecular-weight surfactant. One type of surfactant may be used alone, or two or more types may be used in combination. Of these, nonionic surfactants are preferred. The HLB value of the surfactant is preferably 10 to 20.

Specific examples of nonionic surfactants include those exemplified in the explanation of the water-based adhesive. Of these, it is preferable for the water-based ink to contain a silicone-based surfactant, as this allows for transfer prints with even better image quality to be obtained. The content of the silicone-based surfactant in the water-based ink may be, for example, 0.05% by mass or more, 0.1% by mass or more, or 0.5% by mass or more. It may also be 10% by mass or less, 5% by mass or less, or 3% by mass or less. The content of the silicone-based surfactant in the water-based ink may be in the range of 0.05 to 10% by mass.

When the aqueous ink contains a water-soluble organic solvent, specific examples of the water-soluble organic solvent include those exemplified in the description of the water-based adhesive. A single water-soluble organic solvent may be used, or two or more may be used in combination. The content of the water-soluble organic solvent in the aqueous ink may be, for example, 1% by mass or more, 5% by mass or more, or 10% by mass or more. It may also be 35% by mass or less, 30% by mass or less, or 25% by mass or less. The content of the water-soluble organic solvent in the aqueous ink may be in the range of 1 to 35% by mass.

The method for producing the aqueous ink is not particularly limited, and it can be produced by the same method as general aqueous inks. For example, it can be produced by first producing an aqueous dispersion of the colorant in a bead mill or the like, and then mixing and stirring this with other ingredients, or by adding all of the ingredients of the aqueous ink all at once or in portions to a mixer such as a three-one motor and dispersing them. After the aqueous ink is produced, it can be passed through a filter such as a membrane filter, if necessary.

When applying aqueous ink using an inkjet method, the viscosity of the aqueous ink may be in the range of 1 to 30 mPa·s measured at 23°C, from the perspective of inkjet ejection properties.

In one embodiment, the ink set may include a pre-treatment liquid, a post-treatment liquid, etc. in addition to the aqueous adhesive and aqueous ink. The pre-treatment liquid and the post-treatment liquid may each be, for example, a liquid commonly used in the field of aqueous inkjet inks.

One embodiment of the thermal transfer sheet has a substrate sheet, an aqueous ink image formed on the substrate sheet, and an aqueous adhesive application section. The aqueous adhesive contains a nonionic surfactant (A) and a resin, and the ratio of the nonionic surfactant (A) to the total mass of the resin is in the range of 8 to 50 mass%. In one embodiment of the thermal transfer sheet, the aqueous adhesive contains a nonionic surfactant (A), and the ratio of the nonionic surfactant (A) to the total mass of the resin is relatively high, in the range of 8 to 50 mass%, so that the aqueous adhesive application section has hot-melt properties and can adequately penetrate the fabric during thermal transfer, achieving an anchoring effect. Therefore, the thermal transfer sheet of one embodiment enables the formation of a transfer image without any missing parts, even without a hot-melt powder layer, and produces a transfer print that also has excellent wash fastness.

In the thermal transfer sheet, the aqueous inks that form the aqueous ink images and the aqueous adhesives that form the aqueous adhesive application areas are as described above. That is, the aqueous ink images and aqueous adhesive application areas of the thermal transfer sheet can be formed using the ink set described above.

The thermal transfer sheet may have a hot melt powder layer, similar to general thermal transfer sheets. The hot melt powder can be any of a wide variety of hot melt powders commonly used for DTF printing, for example. On the other hand, as mentioned above, the thermal transfer sheet does not need to have a hot melt powder layer because the water-based adhesive application portion has hot melt properties and plays a role similar to that of a hot melt powder layer. In other words, the thermal transfer sheet may be a hot melt powder-free type that does not use hot melt powder.

The thermal transfer sheet of one embodiment can be manufactured by the method for manufacturing a thermal transfer sheet of another embodiment. The method for manufacturing a thermal transfer sheet of one embodiment includes applying an aqueous ink onto a substrate sheet and then applying an aqueous adhesive by a wet-on-wet method, wherein the aqueous adhesive contains a nonionic surfactant (A), and the content of the nonionic surfactant (A) in the aqueous adhesive is in the range of 1.5 to 10 mass %.

In the method for producing a thermal transfer sheet, the water-based ink and water-based adhesive are as described above. That is, the thermal transfer sheet can be produced using the ink set described above.

The type of substrate sheet is not particularly limited, and may be any type that can be printed using the ink set of one embodiment, is resistant to the pressure and temperature conditions during thermal transfer, and is removable after transfer. Specific examples of substrate sheets include those commonly used as substrate sheets for DTF printing. The printing surface of the substrate sheet may also be provided with a primer layer, an easily removable layer, or the like.

The substrate sheet may have a primer layer containing a cationic resin, as this provides excellent color development and allows for the production of high-quality transferred images. The primer layer may contain one or more types of cationic resin. Examples of cationic resins include cationic urethane resins, cationic acrylic resins, and polyallylamine-based resins. Specific examples of polyallylamine resins include polyallylamine, polyallylamine sulfate, polyallylamine hydrochloride, allylamine diallylamine copolymer, allylamine diallylamine copolymer sulfate, allylamine diallylamine copolymer hydrochloride, allylamine dimethylallylamine copolymer, allylamine dimethylallylamine copolymer sulfate, allylamine dimethylallylamine copolymer hydrochloride, polydiallylamine, polydiallylamine sulfate, polydiallylamine hydrochloride, polymethyldiallylamine amide, polymethyldiallylamine amide sulfate, polymethyldiallylamine amide hydrochloride, polydiallylamine sulfur dioxide copolymer, polydiallylamine sulfur dioxide copolymer sulfate, polydiallylamine sulfur dioxide copolymer hydrochloride, polymethyldiallylamine sulfur dioxide copolymer, polymethyldiallylamine sulfur dioxide copolymer sulfate, polymethyldiallylamine sulfur dioxide copolymer hydrochloride, and polydimethyldiallylammonium chloride.

The cationic resin preferably contains a polyallylamine resin, as this results in a highly uniform image density and a high-quality transferred image. Furthermore, it is preferable to use a combination of a polyallylamine resin and a cationic acrylic resin. In this case, the proportion of the polyallylamine resin relative to the total mass of the polyallylamine resin and the cationic acrylic resin may be 1% by mass or more, 5% by mass or more, or 10% by mass or more. It may also be 50% by mass or less, 30% by mass or less, or 20% by mass or less. The proportion of the polyallylamine resin relative to the total mass of the polyallylamine resin and the cationic acrylic resin may be in the range of 1 to 50% by mass.

The thickness of the primer layer on the substrate sheet may be, for example, in the range of 1 to 10 μm. The primer layer can be formed, for example, by applying a coating liquid containing a cationic resin onto the substrate sheet and then drying it.

The method for applying the aqueous ink to the substrate sheet is not particularly limited, and application can be performed by various printing methods such as screen printing, roller printing, and inkjet printing. Among these, application can be performed by inkjet printing, which allows for efficient production of thermal transfer sheets and easy control of the amount applied. The type of inkjet method is not particularly limited, and can be any method such as piezo, electrostatic, or thermal. Application of each ink and ink condensate by inkjet printing can be performed, for example, by using a general inkjet printer to eject droplets from an inkjet head based on a digital signal and allowing the ejected droplets to adhere to a cloth.

The amount of water-based ink applied can be adjusted as appropriate depending on the type of substrate sheet, the design of the transferred image, etc., but may be, for example, in the range of 5 to 50 g/m ^2. When multiple types of water-based ink are used, the amount of each may be in the range of 5 to 50 g/m ² .

After the application of the aqueous ink, the aqueous adhesive is applied using a wet-on-wet method. In the wet-on-wet method, the aqueous adhesive is applied without any special drying process after the application of the aqueous ink. There are no particular limitations on the method for applying the aqueous adhesive, and it can be applied using the same method as for the aqueous ink. The amount of aqueous adhesive applied can be adjusted appropriately depending on the type of substrate sheet, the design of the transferred image, etc., but may be, for example, in the range of 50 g/m ² to 300 g/m ² .

In addition to the aqueous ink and aqueous adhesive, other materials may be used in the method for manufacturing a thermal transfer sheet. Examples of other materials include a pre-treatment liquid applied to the substrate sheet before applying the aqueous ink, a post-treatment liquid applied after applying the aqueous adhesive, and hot melt powder. As mentioned above, hot melt powder is not required in one embodiment of the method for manufacturing a thermal transfer sheet, and can be used optionally.

The method for manufacturing a thermal transfer sheet may include a drying step. The drying step may be performed after applying the aqueous adhesive. Furthermore, if a post-treatment liquid is used, the drying step may be performed after applying the post-treatment liquid. The drying temperature and drying time are optional, but may be, for example, drying at a temperature in the range of 50 to 150°C for approximately 10 seconds to 10 minutes. Drying may remove 90% by mass or more of the solvent components, such as water and water-soluble organic solvents, contained in the aqueous ink and aqueous adhesive.

In one embodiment, the method for producing a transfer print includes placing the aforementioned thermal transfer sheet on a cloth, heating it to transfer the image, and peeling off the base sheet.

There are no particular limitations on the type of fabric, and a wide variety of fabrics can be used. Examples of fibers that make up the fabric include natural fibers such as cotton, silk, wool, and linen; chemical fibers such as polyester, acrylic, polyurethane, nylon, rayon, cupra, and acetate; and blends of these fibers. Examples of types of fabric include woven fabrics, knitted fabrics, and nonwoven fabrics.

The transfer conditions, such as pressure, temperature, and press time, are adjusted appropriately depending on the type of fabric. For example, when using a Stahls Photoronix Fusion Heat Press, the pressure may be in the range of 3 to 12 psi, the temperature may be in the range of 90 to 160°C, and the press time may be in the range of 5 to 30 seconds. As mentioned above, the thermal transfer sheet of one embodiment can produce a transfer print with excellent wash fastness even at a low transfer temperature of around 120°C.

After transferring the image, it is preferable to cool the printed transfer material to room temperature before peeling off the base sheet.

Some embodiments of the present disclosure are set forth below.
<1> An ink set for a thermal transfer sheet, comprising an aqueous ink and an aqueous adhesive, wherein the aqueous adhesive comprises a nonionic surfactant (A), and the content of the nonionic surfactant (A) in the aqueous adhesive is in the range of 1.5 to 10 mass %.

<2> The ink set for thermal transfer sheets described in <1> above, wherein the content of the nonionic surfactant (A) in the aqueous adhesive is in the range of 2.5 to 5% by mass.

<3> The ink set for thermal transfer sheets according to <1> or <2>, wherein the nonionic surfactant (A) includes one or more surfactants selected from the group consisting of silicone-based surfactants and fluorine-based surfactants.

<4> The ink set for thermal transfer sheets described in any one of <1> to <3>, wherein the aqueous adhesive contains a water-dispersible resin (B) having a thermal melting temperature of 100°C or less.

<5> The ink set for thermal transfer sheets described in any one of <1> to <4>, wherein the aqueous ink contains a water-dispersible resin (C), and the thermal melting temperature of the water-dispersible resin (C) is higher than the thermal melting temperature of the water-dispersible resin (B).

<6> A thermal transfer sheet having a substrate sheet, an aqueous ink image formed on the substrate sheet, and an aqueous adhesive application portion, wherein the aqueous adhesive contains a nonionic surfactant (A) and a resin, and the ratio of the nonionic surfactant (A) to the total mass of the resin is in the range of 8 to 50 mass%.

<7> The thermal transfer sheet described in <6> above, which is free of hot melt powder.

<8> A method for producing a thermal transfer sheet, comprising applying an aqueous ink onto a substrate sheet and then applying an aqueous adhesive by a wet-on-wet method, wherein the aqueous adhesive contains a nonionic surfactant (A), and the content of the nonionic surfactant (A) in the aqueous adhesive is in the range of 1.5 to 10 mass%.

<9> The method for producing a thermal transfer sheet according to <8>, which is hot melt powder-free.

<10> A method for producing a transfer print, comprising: placing the thermal transfer sheet described in <6> or <7> on a cloth, heating it to transfer an image, and peeling off the base sheet.

Embodiments of the present disclosure will be described in detail below using examples. The present disclosure is not limited to the following examples. In the following description, "%" indicates "% by mass" unless otherwise specified. The content shown in each table indicates the total amount of raw materials blended as a solution, dispersion, etc.

In this example, the thermal melting temperature of the resin is the half-wave temperature calculated from the flow curve measured in a temperature rise test using a Shimadzu Corporation high-speed flow tester "CFT-500D" in accordance with JIS K7121:2012.

[Production of ink set for thermal transfer sheet]
Water-based adhesives (1) to (10) and (1') to (3') and water-based inks (1) and (2) were prepared in the following manner, and these were combined to form an ink set for thermal transfer sheets.

[Production of water-based adhesive]
The raw materials were mixed in the compounding ratios shown in Table 1 and filtered through a cellulose acetate membrane filter with a pore size of 3 μm to obtain aqueous adhesives (1) to (10) and (1′) to (3′).

Details of the raw materials listed in Table 1 are as follows.
Nonionic surfactant (A-1): Silicone surfactant, "Silface SAG503A" manufactured by Nissin Chemical Industry Co., Ltd., HLB value 11, active ingredient 100% by mass
Nonionic surfactant (A-2): Fluorine-based surfactant, AGC Seimi Chemical Co., Ltd.'s "Surflon S-243", active ingredient 100% by mass
Nonionic surfactant (A-3): acetylene glycol surfactant, "Surfynol 465" manufactured by Nissin Chemical Industry Co., Ltd., HLB value 13, active ingredient 100% by mass
Nonionic surfactant (A-4): Polyoxyethylene alkyl ether (secondary alkyl ether with 12 to 14 repeating oxyethylene chains), "NIKKOL BT-12" from Nikko Chemicals Co., Ltd., HLB value 14.5, active ingredient 100% by mass
Nonionic surfactant (A-5): Polyoxyethylene oleyl ether (oxyethylene chain repeat number: 20), "NIKKOL BO-20V" from Nikko Chemicals Co., Ltd., HLB value: 17, active ingredient: 100% by mass
Nonionic surfactant (A-6): Polyoxyethylene sorbitan fatty acid ester (sorbitan monolaurate ethylene oxide addition polymer, oxyethylene chain repeat number 20), "NIKKOL TL-10" from Nikko Chemicals Co., Ltd., HLB value 17, active ingredient 100% by mass
Nonionic surfactant (A-7): Polyglycerin fatty acid ester (hexaglyceryl monolaurate), "NIKKOL HEXAGLYN 1-L" from Nikko Chemicals Co., Ltd., HLB value 14.5, active ingredient 100% by mass
Anionic surfactant: Special polycarboxylic acid type polymer surfactant, "Demol EP" by Kao Corporation, active ingredient 25% by mass
White pigment dispersion: 350 g of titanium oxide (Sakai Chemical Industry Co., Ltd. "R62N") as a white pigment and 14 g (3.5 g of active ingredient) of pigment dispersant (Kao Corporation "Demol EP") were mixed with 636 g of ion-exchanged water, and dispersed using a bead mill (Shinmaru Enterprises Co., Ltd. "DYNO-MILL KDL A-type") with 0.5 mm diameter zirconia beads at a filling rate of 80% and a residence time of 2 minutes. Pigment content: 35% by mass
Water-dispersible resin (B-1): Daiichi Kogyo Seiyaku Co., Ltd. "Superflex 420", a water dispersion of urethane resin with a thermal melting temperature of 205°C, resin content 32% by mass
Water-dispersible resin (B-2): Daiichi Kogyo Seiyaku Co., Ltd. "Superflex 500M", a water dispersion of urethane resin with a thermal melting temperature of 67°C, resin content 45% by mass
・Water-soluble organic solvent: Diethylene glycol from Fujifilm Wako Pure Chemical Corporation

[Production of water-based ink]
The raw materials were mixed in the blending ratios shown in Table 2 and filtered through a cellulose acetate membrane filter with a pore size of 3 μm to obtain non-white inks (1) and (2).

Details of the raw materials listed in Table 2 are as follows:
Magenta pigment dispersion: "CAB-O-JET 260M" manufactured by Cabot Corporation, pigment content 10% by mass
Water-dispersible resin (C-1): Daiichi Kogyo Seiyaku Co., Ltd. "Superflex 420", a water dispersion of urethane resin with a thermal melting temperature of 205°C, resin content 32% by mass
Water-dispersible resin (C-2): Daiichi Kogyo Seiyaku Co., Ltd. "Superflex 500M", a water dispersion of urethane resin with a thermal melting temperature of 67°C, resin content 45% by mass
Silicone surfactant: "Silface SAG503A" manufactured by Nissin Chemical Industry Co., Ltd., HLB value 11
・Water-soluble organic solvent: Diethylene glycol from Fujifilm Wako Pure Chemical Corporation

[Production of thermal transfer sheet]
Aqueous ink and aqueous adhesive were applied sequentially onto a substrate sheet (DTF print film manufactured by Toyo Corporation) using a wet-on-wet method. The aqueous ink and aqueous adhesive were applied by inkjet printing using a Mastermind MMP-8130 inkjet printer. The aqueous ink was ejected at a rate of 25 g/ ^m² , and a 10 cm x 20 cm solid image was printed. The aqueous adhesive was ejected at a rate of 100 g/ ^m² , and a 10 cm x 20 cm solid image was printed on top of the area where the aqueous ink had been applied. The sheet was then dried for 5 minutes in an ESPEC thermostatic chamber set at 110°C to obtain a thermal transfer sheet. The types of aqueous ink and aqueous adhesive used in each example are shown in Table 3.

[Production and evaluation of transfer prints]
The printed side of the thermal transfer sheet obtained above was placed on a white cotton T-shirt or a black cotton T-shirt manufactured by Tom's Co., Ltd., and heat-pressed using a Stahls Phototronix "Hotronix Fusion Heat Press" at a pressure setting of 7 psi, 120°C, and 20 seconds. After cooling to room temperature, the substrate sheet was peeled off to obtain a transfer print. The transfer print was subjected to the following evaluation tests. The results are shown in Table 3.

[Evaluation of washing fastness]
The transfer print was washed according to the standard of AATCC 61 2a and then evaluated according to the following criteria.
S: Washing fastness grade 4.5 or higher A: Washing fastness grade 3.5 to 4 B: Washing fastness grade 2.5 to 3.0 C: Washing fastness grade 2.0 or lower

[Evaluation of image quality of transferred image]
The image quality of the transfer print was visually observed and evaluated according to the following criteria.
A: High color development, high color reproducibility of the transferred image B: Slightly high color development, with a decrease in color reproducibility observed only in part of the transferred image C: Low color development, overall poor image quality

In Examples 1 to 11, which used aqueous adhesives (1) to (10) containing 1.5 to 10% by mass of nonionic surfactant (A), transfer prints with excellent washing fastness were obtained. On the other hand, in Comparative Examples 1 to 3, in which the content of nonionic surfactant (A) was less than 1.5% by mass, the transfer prints had poor washing fastness. Comparative Example 2 contained a large amount of anionic surfactant, but this was not effective in improving washing fastness.

Claims (10)

An ink set for a thermal transfer sheet, comprising a water-based ink and a water-based adhesive,
The aqueous adhesive contains a nonionic surfactant (A),
The ink set for a thermal transfer sheet, wherein the content of the nonionic surfactant (A) in the aqueous adhesive is in the range of 1.5 to 10 mass %. The ink set for thermal transfer sheets according to claim 1, wherein the content of the nonionic surfactant (A) in the aqueous adhesive is in the range of 2.5 to 5% by mass. The ink set for thermal transfer sheets according to claim 1, wherein the nonionic surfactant (A) includes at least one selected from the group consisting of silicone-based surfactants and fluorine-based surfactants. The ink set for thermal transfer sheets according to claim 1, wherein the aqueous adhesive contains a water-dispersible resin (B) having a thermal melting temperature of 100°C or less. The ink set for thermal transfer sheets according to any one of claims 1 to 4, wherein the aqueous ink contains a water-dispersible resin (C), and the thermal melting temperature of the water-dispersible resin (C) is higher than the thermal melting temperature of the water-dispersible resin (B). a substrate sheet and a water-based ink image and a water-based adhesive application portion formed on the substrate sheet;
the aqueous adhesive comprises a nonionic surfactant (A) and a water-dispersible resin (B),
A thermal transfer sheet, wherein the ratio of the nonionic surfactant (A) to the resin solid content of the water-dispersible resin (B) is in the range of 8 to 50 mass %. The thermal transfer sheet according to claim 6, which is hot melt powder-free. A method for producing a thermal transfer sheet, comprising applying an aqueous ink onto a substrate sheet, and then applying an aqueous adhesive to the substrate by a wet-on-wet method,
The aqueous adhesive contains a nonionic surfactant (A),
The method for producing a thermal transfer sheet, wherein the content of the nonionic surfactant (A) in the aqueous adhesive is in the range of 1.5 to 10 mass %. The method for producing a thermal transfer sheet according to claim 8, which is hot melt powder-free. A method for producing a transfer print, comprising: placing the thermal transfer sheet according to claim 6 or 7 on a cloth, heating it to transfer the image, and peeling off the base sheet.