JP2020055178A - Thermal transfer sheet - Google Patents

Abstract

To provide a thermal transfer sheet capable of significantly preventing dregs from being generated at a heating unit provided for a thermal transfer printer and a vicinity thereof in producing a printed matter, and capable of significantly improving: kickback prevention properties in the thermal transfer sheet when a dye layer is provided; and glossiness of a printed matter when a transfer layer is provided.SOLUTION: A thermal transfer sheet includes a back surface layer, a base material, and at least one of a transfer layer and a dye layer. The back surface layer contains a polyvinyl acetal, an isocyanate composition, and an inorganic particle. An average number of isocyanate functional groups of the isocyanate composition is 4.0 or more. A mol equivalent ratio (-NCO/-OH) of hydroxyl groups included in a resin material contained in the back surface layer and isocyanate groups included in the isocyanate composition is 0.03-0.20.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thermal transfer sheet.

  Conventionally, a thermal transfer sheet having a dye layer containing a sublimable dye and a transfer target are superimposed on each other, and then the thermal transfer sheet is heated by a thermal head provided in a thermal transfer printer, whereby the sublimable dye in the dye layer is heated. There is known a sublimation type thermal transfer system in which an image is formed by transferring to a receiving layer provided in a thermal transfer image receiving sheet and forming an image.

Further, for the purpose of improving the durability and the like of the printed matter produced by the sublimation transfer method, the printed matter and a thermal transfer sheet having a transfer layer are overlapped, and then the thermal transfer sheet is heated by a thermal head provided in the thermal transfer printer. By doing so, a transfer layer is transferred onto a print.
Further, a thermal transfer sheet provided with a dye layer and a transfer layer in a plane-sequential manner is also widely known (Patent Document 1).

  Further, as proposed in Patent Document 2, etc., in order to prevent the occurrence of wrinkles in printing on the thermal transfer sheet, a back layer is provided on the surface of the substrate opposite to the surface provided with the dye layer and the transfer layer. Provision is being made.

When a large number of prints are produced using a conventional thermal transfer sheet having a back layer, the back layer may peel off, become scum, and adhere to the heating element of the thermal head and its vicinity.
When the amount of adhesion of the scum increases, the scum is pressed against the thermal transfer sheet by the thermal head during image formation, and the formed image is flawed, thereby significantly deteriorating the quality of the print. There was a problem.

By the way, the thermal transfer sheet is generally stored in a state of being wound up to a predetermined winding diameter. When the thermal transfer sheet has a dye layer, the dye contained in the dye layer is bleed or the like. When the dye is present in a localized state on the surface, a so-called “kick phenomenon” in which the dye migrates to the back layer of the thermal transfer sheet may occur.
Further, when the dye transferred to the back layer is transferred again to the dye layer or the transfer layer provided in the thermal transfer sheet, when a so-called "back phenomenon" occurs, a print having a hue different from the desired hue is produced. Therefore, the thermal transfer sheet is required to have such kickback preventing properties.

  Furthermore, in recent years, printed materials have been required to have various appearances in accordance with their uses and the like.For example, in order to impart a high-grade appearance to printed materials, it may be required to improve the glossiness of a transfer layer to be transferred. .

JP 2018-051914 A JP 2010-89491 A

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to solve the problem that, during the production of a printed material, generation of scum in a heating element provided in a thermal transfer printer and its vicinity can be significantly prevented, and a dye layer The object of the present invention is to provide a thermal transfer sheet capable of significantly improving the kickback prevention property of the thermal transfer sheet when the thermal transfer sheet is provided, and significantly improving the glossiness of the printed matter when the thermal transfer sheet is provided with the transfer layer.

The thermal transfer sheet of the present invention includes a back layer, a base material, and at least one of a transfer layer and a dye layer,
The back layer includes a polyvinyl acetal, an isocyanate composition, and inorganic particles,
The average number of isocyanate functional groups of the isocyanate composition is 4.0 or more;
The molar equivalent ratio (-NCO / -OH) of the hydroxyl group of the resin material contained in the back layer to the isocyanate group of the isocyanate composition is 0.03 or more and 0.20 or less.

  In one embodiment, the transfer layer includes a (meth) acrylic resin.

  In one embodiment, the (meth) acrylic resin has a glass transition temperature (Tg) of 90 ° C. or higher.

  In one embodiment, the weight average molecular weight (Mw) of the (meth) acrylic resin is 10,000 or more and 50,000 or less.

In one embodiment, the transfer layer further comprises a vinyl resin,
The ratio of the content of the (meth) acrylic resin to the content of the vinyl resin in the transfer layer is from 25/75 to 95/5 on a mass basis.

  In one embodiment, the vinyl resin is a vinyl chloride-vinyl acetate copolymer.

  In one embodiment, the back layer further includes a lubricant.

  In one embodiment, the thickness of the back layer is 0.1 μm or more and 5 μm or less.

  ADVANTAGE OF THE INVENTION According to this invention, when producing a printed material, generation | occurrence | production of the scum in the heating element with which a thermal transfer printer is provided and its vicinity can be prevented remarkably (it is only hereafter referred to as scum prevention property). When a transfer layer is provided with the kickback prevention property of the sheet, it is possible to provide a thermal transfer sheet capable of remarkably improving the glossiness of a print to be produced.

FIG. 1 is a schematic sectional view illustrating an embodiment of a thermal transfer sheet of the present invention.

(Thermal transfer sheet)
As shown in FIG. 1, the thermal transfer sheet 10 according to the present invention includes a back layer 11, a substrate 12, and at least one of a transfer layer 13 and a dye layer 14. FIG. 1 shows a thermal transfer sheet provided with a transfer layer 13 and a dye layer 14 in a plane-sequential manner, but may be a mode provided with only one of them. Further, FIG. 1 shows a thermal transfer sheet provided with a plurality of dye layers, but may be an embodiment provided with only one dye layer.
Hereinafter, each layer included in the thermal transfer sheet according to the present invention will be described.

(Back layer)
The back layer includes a polyvinyl acetal, an isocyanate composition, and inorganic particles. In one embodiment, the back layer further includes a lubricant.

In one embodiment, polyvinyl acetal can be obtained by acetalizing polyvinyl alcohol with an aldehyde, for example, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, 2-ethyl Examples include butyraldehyde, n-hexylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde, formaldehyde, acetaldehyde, benzaldehyde, and the like.
The back layer may include two or more kinds of polyvinyl acetal.

The hydroxyl value of the polyvinyl acetal is preferably from 50 to 500, more preferably from 100 to 300. Thereby, the heat resistance of the back layer can be improved, and the solubility in a solvent such as ethyl acetate or toluene can be improved.
In the present invention, the hydroxyl value is measured according to JIS K0070.

  The content of polyvinyl acetal in the back layer is preferably from 25% by mass to 65% by mass, and more preferably from 35% by mass to 60% by mass. As a result, it is possible to further improve the scum prevention property, and to improve the kickback prevention property of the thermal transfer sheet when the transfer layer is provided, and to further improve the glossiness of the printed matter produced when the transfer layer is provided.

  The isocyanate composition contains at least one type of isocyanate compound. And a copolymer, an adduct obtained by adding a polyhydric alcohol such as trimethylolpropane to the polymer and the copolymer, a buret-modified product of the polymer and the copolymer, and an isocyanurate-modified product of the polymer and the copolymer And allophanate modified products of the polymers and copolymers.

The average number of isocyanate functional groups in the isocyanate composition is 4.0 or more, and more preferably 4.5 or more and 5.0 or less. Thereby, the scum prevention of the thermal transfer sheet can be further improved.
In the present invention, the average number of isocyanate functional groups of the isocyanate composition is an average value of the number of isocyanate functional groups of the isocyanate compound contained in the isocyanate composition.
The average number of isocyanate functional groups in the isocyanate composition is determined by the following equation. Average number of isocyanate functional groups in isocyanate composition = [number average molecular weight (Mn) of isocyanate composition × isocyanate group content (% by mass) × 0.01] / 42

  In the present invention, the molar equivalent ratio (-NCO / -OH) between the hydroxyl group of the resin material contained in the back layer and the isocyanate group of the isocyanate composition is 0.03 or more and 0.20 or less. It is preferably from 05 to 0.15, more preferably from 0.07 to 0.13. This makes it possible to further improve the scum prevention property of the thermal transfer sheet, and to improve the kickback prevention property of the thermal transfer sheet when a dye layer is provided, and to further improve the glossiness of a print to be produced when the transfer layer is provided. it can.

The back layer contains at least one kind of inorganic particles, and thereby can remove scum adhered to the thermal head. Examples of the inorganic particles include talc, kaolin, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, titanium dioxide, molybdenum disulfide, calcium sulfate, silica, graphite, saltpeter, and boron nitride.
Among the above, talc is preferable because it can effectively remove the attached residue while preventing abrasion of the thermal head. In particular, talc is preferably high in purity and free of hard impurities, since wear of the thermal head can be further prevented. Specifically, the calcium content is preferably 0.5% by mass or less, and more preferably 0.1% by mass or less. The aluminum content is preferably 0.6% by mass or less, more preferably 0.2% by mass or less. The iron content is preferably at most 1% by mass, more preferably at most 0.2% by mass.

  The shape of the inorganic particles is not particularly limited, and may be spherical, non-spherical, acicular, polygonal, or the like.

The average particle size of the inorganic particles is preferably from 0.1 μm to 10 μm, more preferably from 0.5 μm to 7 μm. Thereby, the scum prevention of the thermal transfer sheet can be further improved.
In the present invention, the average particle diameter is a value of D50 on a volume basis measured by a laser diffraction method.

  The content of the inorganic particles in the back layer is preferably from 0.5% by mass to 15% by mass, more preferably from 5% by mass to 13% by mass. Thereby, the scum prevention of the thermal transfer sheet can be further improved.

The back layer preferably contains a sliding material, whereby the slipperiness of the thermal transfer sheet can be improved and the occurrence of print wrinkles can be prevented.
Examples of the lubricant include polyolefin waxes such as polyethylene wax and polypropylene wax, ethoxylated alcohol-modified wax, paraffin wax, montan wax, sucrose fatty acid ester, glycerin fatty acid ester, stearyl alcohol, stearamide, butyl stearate, and stear. Examples include calcium phosphate, zinc stearate, zinc stearyl phosphate, magnesium stearate, oleamide, erucamide, dimethyl silicone, and alkyl-modified silicone.
In addition, the back layer may include two or more kinds of lubricants.

  The content of the lubricant in the back layer is preferably 30% by mass or more and 50% by mass or less, and more preferably 35% by mass or more and 45% by mass or less. Thereby, the slipperiness of the thermal transfer sheet can be further improved.

  The back layer may contain a resin material other than polyvinyl acetal as long as the properties of the present invention are not impaired. For example, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), Polyesters such as 1,4-polycyclohexylene dimethylene terephthalate, terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymer, polyamides such as nylon 6 and nylon 6,6, polyethylene (PE), polypropylene (PP) and polymethylpentene Such as polyolefin, polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer and polyvinyl resin such as polyvinyl pyrrolidone (PVP), polyvinyl acetal, poly (meth) acrylate and polymethyl ( (Meth) acrylic resins such as acrylates, imide resins such as polyimides and polyetherimides, cellulose resins such as cellophane, cellulose acetate, nitrocellulose, cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB); Examples include styrene resins such as polystyrene (PS), polycarbonates, and ionomer resins.

  The back layer can contain additives such as fillers, plasticizers, antistatic materials, ultraviolet absorbers, organic particles, release agents, and dispersants as long as the properties of the present invention are not impaired.

  The thickness of the back layer is preferably 0.1 μm or more and 5 μm or less, more preferably 0.3 μm or more and 3 μm or less. This makes it possible to further improve the scum prevention property of the thermal transfer sheet, and to improve the kickback prevention property of the thermal transfer sheet when a dye layer is provided, and to further improve the glossiness of a print to be produced when the transfer layer is provided. it can.

  The back layer is obtained by dispersing or dissolving the above material in water or a suitable solvent, and applying a known method such as a roll coating method, a reverse roll coating method, a gravure coating method, a reverse gravure coating method, a bar coating method, and a rod coating method. It can be formed by applying a film on a substrate to form a coating film and drying the coating film.

(Base material)
The substrate has heat resistance enough to withstand the heat energy applied at the time of thermal transfer, and can be used without particular limitation as long as it has mechanical strength and solvent resistance that can support a transfer layer and the like provided on the substrate. .

As the substrate, for example, a film composed of polyester, polyamide, polyolefin, vinyl resin, (meth) acrylic resin, imide resin, cellulose resin, styrene resin, polycarbonate, ionomer resin and the like (hereinafter simply referred to as “resin film”) .) Can be used.
Among the above resins, polyester is preferable and PET is particularly preferable from the viewpoint of heat resistance and mechanical strength.
In the present invention, “(meth) acryl” includes both “acryl” and “methacryl”. Further, “(meth) acrylate” includes both “acrylate” and “methacrylate”.

  Further, a laminate of the above resin films can be used as a substrate. The laminated body of the resin film can be manufactured by using a dry lamination method, a wet lamination method, an extrusion method, or the like.

  When the substrate is a resin film, the resin film may be a stretched film or an unstretched film, but from the viewpoint of strength, a stretched film stretched in a uniaxial or biaxial direction. It is preferred to use.

  The thickness of the substrate is preferably 2 μm or more and 25 μm or less, more preferably 3 μm or more and 10 μm or less. This makes it possible to improve the mechanical strength of the substrate and the transmission of thermal energy during thermal transfer.

(Transfer layer)
In one embodiment, the thermal transfer sheet of the present invention includes a transfer layer, and the transfer layer includes a resin material, and includes, for example, (meth) acrylic resin, polyester, polyamide, vinyl resin, imide resin, and cellulose resin. Can be
Among the above, when a dye layer is provided, a (meth) acrylic resin is preferable since kickback prevention in a thermal transfer sheet can be further improved. Further, from the viewpoint of the transferability of the thermal transfer sheet, a (meth) acrylic resin is preferable.
In addition, it is particularly preferable to use a vinyl resin in combination, since the adhesion of the transfer layer to the transfer object can be improved even in low energy transfer.

Examples of the (meth) acrylic resin include poly (meth) acrylate, polymethyl (meth) acrylate, polyethyl (meth) acrylate, polypropyl (meth) acrylate, polybutyl (meth) acrylate, and ethylene-methyl (meth) acrylate. Examples include a polymer and a styrene-methyl (meth) acrylate copolymer.
Among the above, polymethyl (meth) acrylate is preferred from the viewpoints of kickback prevention and transferability.

  From the viewpoints of kickback prevention and transferability, the (meth) acrylic resin preferably has a glass transition temperature (Tg) of 90 ° C. or higher, more preferably 100 ° C. or higher.

The weight average molecular weight (Mw) of the (meth) acrylic resin is preferably 10,000 or more and 50,000 or less from the viewpoints of kickback prevention and transferability.
In the present invention, the glass transition temperature (Tg) means a temperature determined by DSC (differential scanning calorimetry) in accordance with JIS-K-7121, and the weight average molecular weight (Mw) is JIS-K It means a value in terms of polystyrene measured by gel permeation chromatography (GPC) according to -7252-1.

  From the viewpoints of kickback prevention and transferability, the content of the (meth) acrylic resin in the transfer layer is preferably 30% by mass or more and 100% by mass or less, and more preferably 50% by mass or more and 90% by mass or less. More preferred.

  Examples of the vinyl resin include polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polyvinylpyrrolidone, and the like. Among these, in the transfer at a low energy, the adhesion between the transfer layer and the transfer-receiving body is improved. In particular, a vinyl chloride-vinyl acetate copolymer is particularly preferable because the adhesion between the substrate and the transfer layer can be made higher.

  When the transfer layer contains a vinyl resin, the content is preferably 5% by mass or more and 70% by mass or less, more preferably 8% by mass or more and 50% by mass or less. Thereby, even in the transfer with low energy, the adhesion of the transfer layer to the transfer target body can be improved.

  When the transfer layer contains a (meth) acrylic resin and a vinyl resin, the ratio of the content of the (meth) acrylic resin to the content of the vinyl resin is 25/75 or more and 95/5 or less on a mass basis. It is more preferably 50/50 or more and 92/8 or less. Thereby, when a dye layer is provided, the kickback prevention property of the thermal transfer sheet can be further improved. In addition, even in the transferability of the transfer layer provided in the thermal transfer sheet and the transfer at a low energy, the adhesion of the transfer layer to the object to be transferred can be improved.

  The transfer layer may contain the above-mentioned additives as long as the properties of the present invention are not impaired.

  The thickness of the transfer layer is preferably from 0.3 μm to 2.5 μm, and more preferably from 0.5 μm to 1.5 μm. Thereby, when a dye layer is provided, the kickback prevention property of the thermal transfer sheet can be further improved. In addition, even in the transferability of the transfer layer provided in the thermal transfer sheet and the transfer at a low energy, the adhesion of the transfer layer to the object to be transferred can be improved.

  The transfer layer is obtained by dispersing or dissolving the above material in water or a suitable solvent, and applying a known method such as a roll coating method, a reverse roll coating method, a gravure coating method, a reverse gravure coating method, a bar coating method, and a rod coating method. It can be formed by applying a film on a substrate to form a coating film and drying the coating film.

(Other transfer layer)
In one embodiment, another transfer layer may be provided below the transfer layer.
The other transfer layer contains at least one resin material, and includes (meth) acrylic resin, polyester, polyamide, vinyl resin, imide resin, cellulose resin and the like.

In one embodiment, the other transfer layer can include a release agent. Thereby, the transferability of the other transfer layer and the transfer layer can be improved.
Examples of the release agent include a phosphate ester, an olefin-maleic acid copolymer, an aminopolyether-modified silicone oil, an epoxy-modified silicone oil, a carboxyl-modified silicone oil, a polyethylene wax, an amide wax, and the like.

  The content of the release agent in the protective layer is preferably 0.5% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 9% by mass or less. Thereby, the transferability of the other transfer layer and the transfer layer can be improved.

  The thickness of the other transfer layer is not particularly limited, and may be, for example, 0.5 μm or more and 10 μm or less.

(Dye layer)
In one embodiment, the thermal transfer sheet of the present invention includes a dye layer.
The dye layer contains a sublimation type dye, for example, diarylmethane dye, triarylmethane dye, thiazole dye, merocyanine dye, pyrazolone dye, methine dye, indoaniline dye, acetophenone azomethine dye, pyrazoloazomethine dye, xanthene dye, oxazine Dyes, thiazine dyes, azine dyes, acridine dyes, azo dyes, spiropyran dyes, indolinospiropyran dyes, fluoran dyes, naphthoquinone dyes, anthraquinone dyes and quinophthalone dyes are exemplified.

  The dye layer contains a resin material, and the resin material is not particularly limited as long as it can support the above-described sublimation dye. For example, (meth) acrylic resin, polyester, polyamide, vinyl resin, imide resin And cellulose resin.

  Further, the dye layer may include the above-mentioned additive.

  The thickness of the dye layer is not particularly limited, and can be, for example, 0.2 μm or more and 5 μm or less.

  The dye layer is obtained by dispersing or dissolving the above material in water or a suitable solvent, and applying a known method such as a roll coating method, a reverse roll coating method, a gravure coating method, a reverse gravure coating method, a bar coating method, and a rod coating method. It can be formed by applying a film on a substrate to form a coating film and drying the coating film.

  Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Reference Example 1
Coating liquids A to F and a to e having the following composition were prepared. Note that, after the back layer forming coating liquid B, the same material as that contained in the back layer forming coating liquid A is not described with the trade name or the like.

<Coating liquid A for forming back layer: molar equivalent ratio (-NCO / -OH) = 0.05>
7.37 parts by mass of polyvinyl acetal (manufactured by Sekisui Chemical Co., Ltd., Eslek (registered trademark) KS-1, hydroxyl value 12% by mass)
0.23 parts by mass of isocyanate composition A (manufactured by Asahi Kasei Chemicals Corporation, Duranate (registered trademark) MFA-100, NCO = 18.6% by mass, average isocyanate functional group 5.5)
・ Inorganic particles 1.39 parts by mass (Nihon Talc Kogyo Co., Ltd., Micro Ace P3, average particle diameter 5 μm)
・ Zinc stearyl phosphate 2.35 parts by mass (LBT-1830 purified by Sakai Chemical Industry Co., Ltd.)
-2.35 parts by mass of zinc stearate (SZ-PF, manufactured by Sakai Chemical Industry Co., Ltd.)
・ 0.69 parts by mass of polyethylene wax (Toyo Adress Co., Ltd., polyethylene wax 3000)
-1.63 parts by mass of ethoxylated alcohol-modified wax (Toyo Adress Co., Ltd., Unitox 750)
・ Methyl ethyl ketone (MEK) 70 parts by mass ・ Toluene 14 parts by mass

<Coating liquid B for forming back layer: molar equivalent ratio (-NCO / -OH) = 0.10>
-7.26 parts by mass of polyvinyl acetal-0.45 parts by mass of isocyanate composition A-1.37 parts by mass of inorganic particles-2.31 parts by mass of zinc stearyl phosphate-2.31 parts by mass of zinc stearate-polyethylene wax 0. 68 parts by weight, 1.61 parts by weight of ethoxylated alcohol-modified wax, 70 parts by weight of MEK, 14 parts by weight of toluene

<Coating liquid C for forming back layer: molar equivalent ratio (-NCO / -OH) = 0.15>
-7.16 parts by mass of polyvinyl acetal-0.66 parts by mass of isocyanate composition A-1.35 parts by mass of inorganic particles-2.28 parts by mass of zinc stearyl phosphate-2.28 parts by mass of zinc stearate-polyethylene wax 0. 67 parts by weight, 1.59 parts by weight of ethoxylated alcohol-modified wax, 70 parts by weight of MEK, 14 parts by weight of toluene

<Coating liquid D for forming back layer: molar equivalent ratio (-NCO / -OH) = 0.05>
・ 13.13 parts by mass of polyvinyl acetal ・ 0.4 parts by mass of isocyanate composition A ・ 2.47 parts by mass of inorganic particles ・ 70 parts by mass of MEK ・ 14 parts by mass of toluene

<Coating liquid E for forming back layer: molar equivalent ratio (-NCO / -OH) = 0.10>
• 7.27 parts by mass of polyvinyl acetal • 0.43 parts by mass of isocyanate composition B (manufactured by Tosoh Corporation, Coronate (registered trademark) 2785, NCO = 19.2% by mass, average isocyanate functional group number: 4.9)
1.37 parts by mass of inorganic particles 2.32 parts by mass of zinc stearyl phosphate 2.32 parts by mass of zinc stearate 0.68 parts by mass of polyethylene wax 1.61 parts by mass of ethoxylated alcohol-modified wax 1.6% by mass of MEK 70 parts by mass Parts / toluene 14 parts by mass

<Coating liquid a for forming back layer>
-7.48 parts by mass of polyvinyl acetal-1.41 parts by mass of inorganic particles-2.38 parts by mass of zinc stearyl phosphate-2.38 parts by mass of zinc stearate-0.7 parts by mass of polyethylene wax-ethoxylated alcohol-modified wax 1 .66 parts by mass ・ MEK 70 parts by mass ・ Toluene 14 parts by mass

<Coating liquid b for forming back layer: molar equivalent ratio (-NCO / -OH) = 0.30>
-6.88 parts by mass of polyvinyl acetal-1.27 parts by mass of isocyanate composition A-1.3 parts by mass of inorganic particles-2.19 parts by mass of zinc stearyl phosphate-2.19 parts by mass of zinc stearate-polyethylene wax 0. 65 parts by weight, 1.52 parts by weight of ethoxylated alcohol-modified wax, 70 parts by weight of MEK, 14 parts by weight of toluene

<Coating liquid c for forming back layer: molar equivalent ratio (-NCO / -OH) = 0.50>
6.54 parts by mass of polyvinyl acetal 2.01 parts by mass of isocyanate composition A 1.23 parts by mass of inorganic particles 2.08 parts by mass of zinc stearyl phosphate 2.08 parts by mass of zinc stearate 2.0 g of polyethylene wax 61 parts by weight, 1.45 parts by weight of ethoxylated alcohol-modified wax, 70 parts by weight of MEK, 14 parts by weight of toluene

<Coating liquid d for forming back layer: molar equivalent ratio (-NCO / -OH) = 0.05>
-8.07 parts by mass of polyvinyl acetal-0.25 parts by mass of isocyanate composition A-2.57 parts by mass of zinc stearyl phosphate-2.57 parts by mass of zinc stearate-0.76 parts by mass of polyethylene wax-ethoxylated alcohol-modified 1.79 parts by mass of wax, 70 parts by mass of MEK, 14 parts by mass of toluene

<Coating liquid e for forming back layer: molar equivalent ratio (-NCO / -OH) = 0.10>
-7.31 parts by mass of polyvinyl acetal-0.36 parts by mass of isocyanate composition a (Duranate (registered trademark) TPA-100, manufactured by Asahi Kasei Chemicals Corporation, NCO = 23.1% by mass, average isocyanate functional group number 3.3) )
-1.38 parts by mass of inorganic particles-2.33 parts by mass of zinc stearyl phosphate-2.33 parts by mass of zinc stearate-0.69 parts by mass of polyethylene wax-1.62 parts by mass of ethoxylated alcohol-modified wax-70 parts by mass of MEK Parts / toluene 14 parts by mass

<Coating liquid f for forming back layer: molar equivalent ratio (-NCO / -OH) = 0.15>
-7.22 parts by mass of polyvinyl acetal-0.54 parts by mass of isocyanate composition a-1.36 parts by mass of inorganic particles-2.3 parts by mass of zinc stearyl phosphate-2.3 parts by mass of zinc stearate-polyethylene wax 0. 68 parts by weight, 1.6 parts by weight of ethoxylated alcohol-modified wax, 70 parts by weight of MEK, 14 parts by weight of toluene

<Coating liquid g for forming back layer: molar equivalent ratio (-NCO / -OH) = 0.10>
-7.29 parts by mass of polyvinyl acetal-0.39 parts by mass of isocyanate composition B (Coronate (registered trademark) HX, manufactured by Tosoh Corporation, NCO = 21.3% by mass, average isocyanate functional group number 3.6)
-1.37 parts by mass of inorganic particles-2.32 parts by mass of zinc stearyl phosphate-2.32 parts by mass of zinc stearate-0.69 parts by mass of polyethylene wax-1.61 parts by mass of ethoxylated alcohol-modified wax-70 parts by mass of MEK Parts / toluene 14 parts by mass

Reference example 2
Transfer layer forming coating liquids A to E having the following compositions were prepared. Note that, after the transfer layer forming coating liquid B, the same material as that contained in the transfer layer forming coating liquid A is not described with the trade name or the like.

<Coating liquid A for forming transfer layer>
・ (Meth) acrylic resin 24.5 parts by mass (Dianal (registered trademark) BR-83, manufactured by Mitsubishi Chemical Corporation)
・ Vinyl resin 10.5 parts by mass (Solvain (registered trademark) CNL, vinyl chloride-vinyl acetate copolymer manufactured by Nissin Chemical Industry Co., Ltd.)
-52 parts by weight of MEK-13 parts by weight of normal propyl acetate

<Coating liquid B for forming transfer layer>
・ (Meth) acrylic resin 17.50 parts by mass ・ vinyl resin 17.50 parts by mass ・ MEK 52 parts by mass ・ Normal acetate 13 parts by mass

<Transfer layer forming coating liquid C>
・ (Meth) acrylic resin 31.5 parts by mass ・ vinyl resin 3.5 parts by mass ・ MEK 52 parts by mass ・ Normal acetate 13 parts by mass

<Coating liquid D for forming transfer layer>
-10.5 parts by mass of (meth) acrylic resin-24.5 parts by mass of vinyl resin-52 parts by mass of MEK-13 parts by mass of normal propyl acetate

<Coating liquid E for transfer layer formation>
・ (Meth) acrylic resin 35 parts by mass ・ MEK 52 parts by mass ・ Normal acetate 13 parts by mass

Example 1
A coating liquid A for forming a back layer was applied to one surface of a PET film having a thickness of 5 μm and dried to form a back layer having a thickness of 0.5 μm.

  On the other surface of the PET film, a coating solution for forming a yellow dye layer, a coating solution for forming a magenta dye layer, a coating solution for forming a cyan dye layer, and a coating solution A for forming a transfer layer, having the following composition, The resultant was coated and dried to form a 0.5 μm-thick yellow dye layer, a magenta dye layer and a cyan dye layer, and a 0.8 μm-thick transfer layer.

<Yellow dye layer forming coating liquid>
-Solvent Yellow 93 2 parts by mass-Disperse Yellow 231 2 parts by mass-Polyvinyl acetal 3.5 parts by mass (Eslek (registered trademark) KS-5, manufactured by Sekisui Chemical Co., Ltd.)
・ Polyethylene wax 0.1 parts by mass ・ MEK 45 parts by mass ・ Toluene 45 parts by mass

<Coating solution for magenta dye layer formation>
-1.5 parts by mass of disperse dye (MS Red G)-2 parts by mass of disperse dye (Macrolex Red Violet R)-4.5 parts by mass of polyvinyl acetal (manufactured by Sekisui Chemical Co., Ltd., Eslek (registered trademark) KS- 5)
・ Polyethylene wax 0.1 parts by mass ・ MEK 45 parts by mass ・ Toluene 45 parts by mass

<Coating solution for forming cyan dye layer>
-2 parts by weight of Solvent Blue 63-2 parts by weight of Disperse Blue 354-3.5 parts by weight of polyvinyl acetal (Eslek (registered trademark) KS-5, manufactured by Sekisui Chemical Co., Ltd.)
・ Polyethylene wax 0.1 parts by mass ・ MEK 45 parts by mass ・ Toluene 45 parts by mass

Examples 2 to 11 and Comparative Examples 1 to 8
A thermal transfer sheet was produced in the same manner as in Example 1 except that at least one of the back layer forming coating liquid and the transfer layer forming coating liquid was changed to one having the composition shown in Table 1.

Performance evaluation << Evaluation of scum prevention >>
The thermal transfer sheets obtained in the above Examples and Comparative Examples were allowed to stand for 2 weeks in an environment at 23 ° C. and a relative humidity of 50%.
Using a thermal transfer sheet after standing and a thermal transfer printer A (DS620, manufactured by Dai Nippon Printing Co., Ltd.), a black solid image (0/255 image gradation) was formed on a genuine image receiving paper of the thermal transfer printer A under the following conditions. Thus, 200 prints were formed.
(Printing conditions)
-Resolution: 300 x 300 dpi (high-speed mode)
-Print size: PC size-Finish: Gloss

The heating element of the thermal head provided in the thermal transfer printer A after use and the vicinity thereof were observed using an electron microscope (manufactured by KEYENCE CORPORATION, digital microscope VHX-2000), and the produced print was visually observed. Was evaluated based on the following evaluation criteria. The evaluation results are summarized in Table 1.
(Evaluation criteria)
A: Adhesion of scum to the heating element of the thermal head and its vicinity was not confirmed, and generation of color unevenness and scratches on the print was not confirmed.
B: Adhesion of scum to the heating element of the thermal head and the vicinity thereof was slightly confirmed, but generation of color unevenness and scratches on the print was not confirmed.
NG1: Adhesion of scum to the heating element of the thermal head and its vicinity was confirmed, and generation of color unevenness and scratches on the print was slightly confirmed.
NG2: A large amount of scum adhered to the heating element of the thermal head and its vicinity was confirmed, and the occurrence of color unevenness and scratches on the print was confirmed.

<< Kickback prevention evaluation >>
The yellow dye layer included in the genuine thermal transfer sheet of the thermal transfer printer A and the back layer included in the thermal transfer sheet obtained in Example 1 are overlapped so as to face each other, and a constant load compression tester (Toyo Seiki Seisakusho Co., Ltd.) Under a load of 1.96 MPa (20 kgf / cm ² ) under an environment of 40 ° C. and 90% relative humidity for 96 hours to transfer the yellow dye from the yellow dye layer to the back layer. (So-called kick).
After standing, the back layer of the thermal transfer sheet, to which the yellow dye has migrated, and the separately prepared transfer layer of the thermal transfer sheet obtained in Example 1 are overlapped so as to face each other. With a load of 1.96 MPa (20 kgf / cm ² ) applied, the substrate was allowed to stand for 24 hours in an environment of 50 ° C. and a relative humidity of 30%, and the yellow dye contained in the back layer was transferred again to the transfer layer. (So-called back).

  After standing still, using a thermal transfer sheet provided with a transfer layer to which the yellow dye has re-migrated and a lamination tester (Lamipacker LPD2305PRO, manufactured by Fujipla Co., Ltd.), the transfer layer is transferred onto the genuine image receiving paper of the thermal transfer printer at a transfer temperature of 110 ° C. , Transfer speed 1 m / min. Transfer was performed under the conditions described above to prepare a transcript A.

  Further, using a separately prepared thermal transfer sheet obtained in Example 1 and the laminating tester, a transfer layer was transferred onto a genuine image receiving paper of the thermal transfer printer under the same conditions to prepare a transfer product B. .

The color difference (ΔE) of the images formed on the transfer material A and the transfer material B is measured using a spectrometer (Spectrolino, manufactured by X-Rite) in accordance with JIS Z 8730, and based on the following evaluation criteria. ,evaluated.
The color difference (ΔE) is represented by ΔE = ((ΔL *) ² + (Δa *) ² + (Δb *) ² ) ^1/2 , and L *, a * and b * are international certification committee members. It is defined by numerical values in the L * a * b * color system of CIE.
In the formula, “ΔL *” means “the difference between the L * value of transcript A and L * value of transcript B”, and “Δa *” means “a * value of transcript A”. And “Δb *” represent the difference between the b * value of transcript A and the b * value of transcript B.
The color difference (ΔE) was similarly measured for the thermal transfer sheets obtained in the other Examples and Comparative Examples, and evaluated based on the following evaluation criteria. Table 1 summarizes the evaluation results.
(Evaluation criteria)
A: The color difference (ΔE) was less than 1.5.
B: The color difference (ΔE) was 1.5 or more and less than 3.0.
C: Color difference (ΔE) was 3.0 or more and less than 4.5.
NG1: Color difference (ΔE) was 4.5 or more and less than 6.0.
NG2: Color difference (ΔE) was 6.0 or more.

<< Glossiness evaluation >>
The thermal transfer sheets obtained in the above Examples and Comparative Examples were allowed to stand for one week under an environment of 35 ° C. and a relative humidity of 50%.
Using the thermal transfer sheet after standing and the thermal transfer printer A, a black solid image (0/255 image gradation) was formed in a glossy finish mode on the genuine image receiving paper of the thermal transfer printer A to produce a print. .
The glossiness of the produced printed matter was measured using a gloss meter (Nippon Denshoku Industries Co., Ltd., Gloss Meter VG2000), and evaluated based on the following evaluation criteria. The evaluation results are summarized in Table 1.
In the present invention, the glossiness means a specular glossiness at a measurement angle of 20 ° specified in JIS Z8741. The measurement is performed from a direction parallel to the transport direction of the print in the thermal transfer printer. Was.
(Evaluation criteria)
A: The glossiness was 50% or more.
B: The glossiness was 45% or more and less than 50%.
C: The glossiness was 40% or more and less than 45%.
NG: The glossiness was less than 40%.

<< Slipperiness evaluation >>
Using the thermal transfer sheets obtained in the above Examples and Comparative Examples and the thermal transfer printer with a dynamic friction coefficient measuring function disclosed in JP-A-2003-300338, a black solid image (0 / 255 image gradation) and a half-gray image (128/255 image gradation) were formed, and the dynamic friction coefficient of the back layer during each image formation was measured and evaluated based on the following evaluation criteria. The evaluation results are summarized in Table 1.
The printing conditions were as follows.
(Printing conditions)
-Thermal head (manufactured by Toshiba Hokuto Electronics Co., Ltd.): Head resistance value 5020Ω, resolution 300 dpi (dot per inch)
-Line speed: 1 msec. / Line (resolution in the image receiving paper transport direction is 300 line per inch)
・ Printing voltage: 32V
・ Printing pressure: 40N
(Evaluation criteria)
A: The kinetic friction coefficient of the back layer was less than 0.4 at the time of forming both the solid black image and the half-gray image.
B: The dynamic friction coefficient of the back layer was 0.4 or more when forming at least one of a solid black image and a half-gray image.

<< Evaluation of transferability >>
Using the thermal transfer sheets obtained in the above Examples and Comparative Examples and the thermal transfer printer B described below, the transfer layer was transferred onto a genuine image receiving paper of the thermal transfer printer A under the conditions of a printing voltage of 21.5 V and a gradation of 255/255. A transcript was prepared. The transcript after the preparation was visually checked and evaluated based on the following evaluation criteria. The evaluation results are summarized in Table 1.
(Thermal transfer printer B)
-Gradation control method: a multi-pulse method in which the number of divided pulses having a pulse length obtained by equally dividing a line cycle into 256 can be varied from 0 to 255-Thermal head: KEE-57-12GAN2-, manufactured by Kyocera Corporation STA
・ Main scanning direction resolution: 300 dpi
・ Sub-scanning direction resolution: 300 dpi
-Line speed: 2 msec. / Line
・ Pulse duty: 85%
(Evaluation criteria)
A: The transfer layer did not come off in the transfer product, and the transfer layer was successfully transferred.
B: The transfer layer was missing in the transfer product, and the sticking between the base material and the transfer layer in the thermal transfer sheet occurred.

<< Adhesion evaluation >>
Using the thermal transfer sheet obtained in the above example and the comparative example, and the thermal transfer printer B, on the genuine image receiving paper of the thermal transfer printer A, under the condition of low energy, specifically, a printing voltage of 16 V and 255/255 gradations. The transfer layer was transferred to prepare a transfer product C.
Also, the printing voltage was changed to 18 V, and a transfer product D was prepared in the same manner.
The produced transcript was visually checked and evaluated based on the following evaluation criteria. The evaluation results are summarized in Table 1.
(Evaluation criteria)
A: It was confirmed that the transfer layer was normally transferred to the image receiving paper in both the transfer material C and the transfer material D.
B: Although it was confirmed that the transfer layer of the transfer material D was normally transferred to the image receiving paper, the transfer material C of the transfer material C showed that the adhesion between the base material and the transfer layer was higher than that of the transfer layer and the transfer object. A portion higher than the adhesive force was formed, and the transfer layer was not normally transferred to the image receiving paper, and at least a part of the transfer layer remained on the thermal transfer sheet.
C: A portion where the adhesion between the base material and the transfer layer is higher than the adhesion between the transfer layer and the transfer-receiving body, and the transfer layer is normally transferred to the image receiving paper for both the transfer material C and the transfer material D However, at least a part of the transfer layer remained on the thermal transfer sheet.

10: thermal transfer sheet, 11: back layer, 12: base material, 13: transfer layer, 14: dye layer

Claims (8)

A back layer, a substrate, and at least one of a transfer layer and a dye layer,
The back layer includes a polyvinyl acetal, an isocyanate composition, and inorganic particles,
The average isocyanate functional group number of the isocyanate composition is 4.0 or more,
A thermal transfer sheet, wherein a molar equivalent ratio (-NCO / -OH) of a hydroxyl group of the resin material contained in the back layer to an isocyanate group of the isocyanate composition is 0.03 or more and 0.20 or less.   The thermal transfer sheet according to claim 1, wherein the transfer layer includes a (meth) acrylic resin.   The thermal transfer sheet according to claim 2, wherein the (meth) acrylic resin has a glass transition temperature (Tg) of 90C or more.   4. The thermal transfer sheet according to claim 2, wherein the (meth) acrylic resin has a weight average molecular weight (Mw) of 10,000 or more and 50,000 or less. 5. The transfer layer further includes a vinyl resin,
5. The transfer layer according to claim 2, wherein a ratio of the content of the (meth) acrylic resin to the content of the vinyl resin is from 25/75 to 95/5 on a mass basis. Item 6. The thermal transfer sheet according to item 1.   The thermal transfer sheet according to claim 5, wherein the vinyl resin is a vinyl chloride-vinyl acetate copolymer.   The thermal transfer sheet according to any one of claims 1 to 6, wherein the back layer further includes a lubricant.   The thermal transfer sheet according to claim 1, wherein the thickness of the back layer is 0.1 μm or more and 5 μm or less.