JP5741731B1 - Thermal transfer sheet - Google Patents

Abstract

A thermal transfer sheet excellent in printability and boil resistance of printed matter is provided. At least a transferable release layer and a transferable colored layer are arranged in this order from one side of the substrate on the one side of the substrate, and a back layer is arranged on the other side of the substrate. The transferable colored layer is a thermal transfer sheet containing a colorant, a phenol resin having a softening point of 100 ° C. or higher, and a bisphenol compound. [Selection] Figure 1

Description

  The present invention relates to a thermal transfer sheet.

  Conventionally, a thermal transfer sheet in which a heat-melting ink layer (transferable colored layer) in which a colorant such as a pigment is dispersed in a binder such as a heat-meltable wax or resin is supported on a base sheet such as a plastic film is used. In addition, there is known a hot-melt transfer method in which energy corresponding to image information is applied to a heating device such as a thermal head and a colorant is transferred onto a transfer paper such as paper or a plastic sheet together with a binder (Patent Document 1). . An image formed by the hot-melt transfer method has high density and excellent sharpness, and is suitable for recording binary images such as characters and line drawings. Further, by using a thermal transfer sheet of yellow, magenta, cyan, black or the like and recording it on a transfer paper, it is possible to form a multicolor or color image.

In the hot-melt transfer method, various prints can be easily formed with a thermal head, etc., so it is also used for printing characters, barcodes, etc., for managing products etc. at factories etc. Yes. When printing is performed by a hot-melt transfer method using a thermal transfer sheet on a packaging material that is subjected to a boil sterilization process after packaging the food or a plastic film that is used as a packaging material for retort food. It is required to have boil resistance so that the product is not lost even if it is stirred in boiling water.
Further, as the printing speed of the thermal transfer printer is increased, the thermal transfer sheet used in the thermal melting type transfer system is required to have excellent printability that can cope with the increased printing speed. On the other hand, as the speed of the printer increases, the thermal energy generated from the thermal head tends to increase more and more. For this reason, since the load applied to the thermal head is increased, there is a problem that the thermal head is consumed significantly and the life of the thermal head is shortened. Therefore, there is a demand for printability that can cope with an increase in printing speed while suppressing thermal energy generated from the thermal head.

  A binder resin having a bisphenol skeleton is disclosed as a binder resin for the transferable colored layer of the thermal transfer sheet. For example, in Patent Document 2, a heat-meltable ink layer provided with a thermal transfer recording medium has a magenta dye having a specific structure, a glass transition point of 35 to 100 ° C., and a number average molecular weight within a specific range. In addition, by including a polyether resin having a bisphenol skeleton and a hydroxyl group at the molecular end, a transfer image excellent in sharpness and friction fastness can be obtained. It is described that a halftone dot can be printed neatly, a transfer image excellent in gradation can be obtained, and a multicolor print image can be formed.

  Further, in Patent Document 3, in a thermal transfer recording medium in which a thermal transfer layer composed of an ink layer containing a colorant is provided on a support, a saturated polyester resin having a bisphenol S structure is contained in the thermal transfer layer, whereby an image is obtained. It is described that the transferability is excellent and the resistance of the image to the solvent is very excellent.

JP-A-57-105395 JP-A-11-321123 JP 2002-111961 A

However, conventional thermal transfer sheets have insufficient boil resistance. Also, with conventional thermal transfer sheets, if high-speed printing is performed while suppressing thermal energy during printing, it is difficult to obtain high-quality printed matter, such as missing or crushed portions in the printed matter. It was.
The present invention has been accomplished in view of the above-described actual circumstances, and an object thereof is to provide a thermal transfer sheet excellent in printability and boil resistance of printed matter.

In the thermal transfer sheet according to the present invention, at least a transferable release layer and a transferable colored layer are arranged in this order from one side of the substrate, and a back layer is arranged on the other side of the substrate. And
The transferable colored layer includes a colorant, a phenol resin having a softening point of 100 ° C. or higher, and a bisphenol compound.

  In the thermal transfer sheet according to the present invention, a transferable protective layer is further disposed between the transferable release layer and the transferable colored layer, and the transferable protective layer has an annular shape having a glass transition temperature of 100 ° C. or higher. It is preferable from the viewpoint of excellent boil resistance and scratch resistance of the printed matter that an olefin polymer is included as a main component and further an incompatible resin for the cyclic olefin polymer is included.

  ADVANTAGE OF THE INVENTION According to this invention, the thermal transfer sheet excellent in printability and the boil resistance of printed matter can be provided.

It is a schematic sectional drawing which shows an example of the thermal transfer sheet of this invention. It is a schematic sectional drawing which shows another example of the thermal transfer sheet of this invention.

  In the thermal transfer sheet according to the present invention, at least a transferable release layer and a transferable colored layer are arranged in this order from one side of the substrate, and a back layer is arranged on the other side of the substrate. The transferable colored layer is a thermal transfer sheet containing a colorant, a phenol resin having a softening point of 100 ° C. or higher, and a bisphenol compound.

The thermal transfer sheet according to the present invention includes a phenol resin having a softening point of 100 ° C. or higher as a binder resin of the transferable colored layer, and the transferable colored layer further includes a bisphenol compound, so that it is excellent in printability and boil resistance. There is an effect.
Although the mechanism by which the thermal transfer sheet according to the present invention exhibits the above effects has not been elucidated, it is presumed as follows. The phenol resin has good adhesion to a plastic film used as a packaging material, and improves the printability. Further, by using a phenol resin having a softening point of 100 ° C. or higher, transfer of a very fine character pattern is also improved. For example, a 1-dot character pattern printability is excellent with a thermal head having a resolution of 300 dpi. The present inventors have found that the printability is further improved by using a bisphenol compound in combination with the phenol resin, and have completed the present invention. The combination improves the printability because the bisphenol compound has a lower molecular weight than the phenol resin and is excellent in affinity with the phenol resin and the transferred material. In addition, the effect is not clear, but the adhesion of the colored layer to the transferred material can be improved by adding a bisphenol compound to the transferred colored layer because the adhesion of the low molecular weight substance to the transferred material is improved. Is estimated to improve.
The thermal transfer sheet according to the present invention improves the printability by combining the bisphenol compound with the phenol resin, so that a printed matter with good printing can be obtained even when high-speed printing is performed while suppressing thermal energy during printing. Can be obtained.
Further, the boil resistance of the printed matter obtained using the thermal transfer sheet according to the present invention is good because the transferable colored layer itself is selected by selecting a phenol resin having a softening point of 100 ° C. or higher as the binder of the transferable colored layer. It is presumed to be due to a synergistic effect of improving the heat resistance of the film and further having a transferable release layer. When the colored layer is the outermost layer in the printed matter, the boil resistance tends to be insufficient due to rubbing at the time of boiling, but when printing is performed using the thermal transfer sheet according to the present invention, the transferable peeling layer peels off from the substrate. Then, the transferable release layer is laminated and transferred on the transferable colored layer, and the transferable release layer is disposed on the outermost layer of the printed matter. For this reason, the printed matter is considered to have good boil resistance because the scratch resistance during boiling is improved in addition to the heat resistance of the transferable colored layer itself.

FIG. 1 shows an example of the thermal transfer sheet of the present invention. The thermal transfer sheet 10 of FIG. 1 has a transferable release layer 2 and a transferable colored layer 3 arranged in this order on one surface of the substrate 1 from the substrate 1 side, and the back surface on the other surface of the substrate 1. The layer 4 is arranged.
FIG. 2 shows another example of the thermal transfer sheet of the present invention. In the thermal transfer sheet 10 of FIG. 2, a transferable release layer 2, a transferable protective layer 5, and a transferable colored layer 3 are arranged in this order on one surface of the substrate 1 from the substrate 1 side. This is a configuration in which the back layer 4 is disposed on the other surface.
In the thermal transfer sheet according to the present invention, as shown in FIGS. 1 and 2, each of the above layers has a laminated structure.
Hereinafter, each layer constituting the thermal transfer sheet of the present invention will be described in detail.

(Base material)
The substrate 1 of the thermal transfer sheet used in the present invention is not particularly limited as long as it has a conventionally known degree of heat resistance and strength.
Specific examples of the base material include, for example, polyesters such as polyethylene terephthalate, 1,4-polycyclohexylenedimethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polysulfone, polycarbonate, polyamide, polyimide, cellulose acetate, polyvinylidene chloride, There are resin base materials such as polyvinyl chloride, polyvinyl alcohol, polystyrene, fluororesin, polypropylene, polyethylene, and ionomer, and papers such as glassine paper, condenser paper, paraffin paper, cellophane, etc. A laminated composite substrate can also be used. Moreover, in the case of the said resin base material, it may consist only of 1 type of the above-mentioned resin, and may consist of 2 or more types of resin.
The thickness of these base materials may be appropriately changed depending on the material so that the strength and heat resistance thereof are appropriate, but is usually preferably about 0.5 to 50 μm, more preferably about 1 to 10 μm. is there.

(Transferable colored layer)
The transferable colored layer 3 contains at least a colorant, a phenol resin having a softening point of 100 ° C. or higher as a binder resin, and a bisphenol compound. By using a phenol resin with a softening point of 100 ° C. or higher as the binder resin for the transferable colored layer, and further containing a bisphenol compound, the fixing property to the transfer medium is improved and the printability is good while having heat resistance. become.

Examples of the phenol resin having a softening point of 100 ° C. or higher used in the transferable colored layer of the present invention include a phenol novolak resin, a cresol novolak resin, a bisphenol novolak resin, a biphenylene aralkyl resin, a naphthol aralkyl resin, and a phenol aralkyl resin (also known as xylylene-modified). Phenolic resins) and the like, and one or more of these may be used in combination. Among these, from the viewpoint of the balance between printability and boil resistance, it is preferable to use a phenol novolak resin, a cresol novolak resin, or a bisphenol novolak resin, and more preferably a phenol novolak resin.
The softening point of the phenol resin is 100 ° C. or higher from the viewpoint of boil resistance, but is preferably 110 ° C. or higher.
In addition, the softening point of the phenol resin in this invention means the softening point measured by the method prescribed | regulated to JISK7206: 1999.

  Examples of commercially available phenol resins having a softening point of 100 ° C. or higher include Phenolite TD-2091, Phenolite TD-2090, Phenolite VH4170, Phenolite KH6021, Phenolite KA1163, Phenolite KA1165 (and above, DIC Corporation). Product name).

  As a binder resin for the transferable colored layer, a phenol resin having a softening point of 100 ° C. or higher may be used in combination with a curing agent, and a reaction product of the phenol resin and the curing agent may be included. By cross-linking the phenol resin with a curing agent, a three-dimensional network structure can be constructed, and excellent heat resistance can be imparted to the printed matter. Examples of the curing agent include formaldehyde supply compounds such as hexamethylenetetramine and paraformaldehyde, polyisocyanate compounds, and the like. In the present invention, a polyisocyanate compound is preferably used as a curing agent combined with a phenol resin having a softening point of 100 ° C. or higher.

  In the transferable colored layer of the present invention, the equivalent ratio (NCO / OH) of the isocyanate group of the polyisocyanate compound to the hydroxyl group of the phenol resin having the softening point of 100 ° C. or higher is preferably from the viewpoint of good printability. It is preferable to use a combination of a phenol resin and an isocyanate compound so as to be in the range of 05 to 0.5 and further in the range of 0.1 to 0.25.

  In the present invention, the polyisocyanate compound used as a curing agent for the phenol resin can be appropriately used as long as it is a compound having two or more isocyanate groups in the molecule. For example, aromatic polyisocyanates such as tolylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; modified polyisocyanates such as adduct, biuret and isocyanurate Can be mentioned.

  In the present invention, the polyisocyanate compound used as a curing agent for the phenol resin is preferably an aliphatic polyisocyanate from the viewpoint of further improving the boil resistance, and among them, an adduct of an aliphatic polyisocyanate is used. It is preferable. By including a reaction product of a phenol resin having a softening point of 100 ° C. or higher and an adduct of an aliphatic polyisocyanate as a binder resin for the transferable colored layer, the boil resistance of the printed matter is good. Will be particularly good. When a curing agent is used in the phenolic resin, a three-dimensional network structure is built, and excellent heat resistance is imparted to the printed matter. At that time, when an aliphatic polyisocyanate is selected and combined, the three-dimensional phenolic resin is added. This is not because the network structure is flexible and the printed matter on the packaging material is affected by deformation such as shrinkage and expansion of the packaging material in boiling water. It is estimated that.

  Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, trimethylhexamethylene diisocyanate, and the like. Is preferably used.

  The adduct body is a reaction product of polyisocyanate and polyol. As the polyol used in the adduct body, alcohol having two or more hydroxyl groups in the molecule is used, for example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, Examples include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, and dimers thereof, polyester polyol, polycarbonate polyol, polyether polyol, and polyolefin polyol. As the polyol used for the adduct, alcohol having 3 or more hydroxyl groups in the molecule is preferably used from the viewpoint of boil resistance, and glycerin, trimethylolpropane, and trimethylolethane are particularly preferably used.

  The mass average molecular weight of the adduct of the aliphatic polyisocyanate is usually selected in the range of 100 to 100,000, preferably 500 to 10,000 from the viewpoint of boil resistance. In the present invention, the mass average molecular weight is a value calculated as a polystyrene equivalent value by gel permeation chromatography (GPC method).

As the binder resin in the transferable colored layer of the present invention, another binder resin may be further contained within a range not impeding the effects of the present invention. For example, as other binder resin, acrylic resin, polyester resin, polyurethane resin, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, polyethylene, polystyrene, polypropylene, polybudene, petroleum resin, vinyl chloride resin, Vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol, vinylidene chloride resin, methacrylic resin, polyamide, polycarbonate, fluororesin, polyvinyl formal, polyvinyl butyral, acetyl cellulose, nitrocellulose, polyvinyl acetate, polyisobutylene, ethyl cellulose, polyacetal, etc. Is mentioned.
As the binder resin in the transferable colored layer of the present invention, from the viewpoint of boil resistance, a phenol resin (solid content) having a softening point of 100 ° C. or higher may be contained by 20% by mass or more in the solid content of all binder resins. Preferably, it is further contained in an amount of 30% by mass or more, more preferably 40% by mass or more, and particularly preferably 50% by mass or more.
When a curing agent is not used, as the binder resin in the transferable colored layer of the present invention, a phenol resin (solid content) having a softening point of 100 ° C. or higher is 70% in the solid content of all binder resins from the viewpoint of boil resistance. It is preferably contained in an amount of at least 80% by mass, more preferably at least 80% by mass, even more preferably at least 90% by mass, and particularly preferably at least 95% by mass.
When a curing agent is used, a reaction product of a phenol resin having a softening point of 100 ° C. or higher and a curing agent, an unreacted phenol resin having a softening point of 100 ° C. or higher and an unreacted curing that may be further included. The total solid content with the agent is preferably 70% by mass or more of the total solid content of the binder resin, more preferably 80% by mass or more, and still more preferably 90% by mass or more, In particular, it is preferably contained in an amount of 95% by mass or more.
From the viewpoint of further improving the boil resistance, the binder resin in the transferable colored layer of the present invention is composed of two components of a solid resin, a phenol resin having a softening point of 100 ° C. or higher, and an adduct body of aliphatic polyisocyanate. The aspect which consists only of the hardened | cured material of the resin composition which becomes is used suitably.

  The transferable colored layer of the present invention further contains a bisphenol compound. A bisphenol compound is a compound having two hydroxyphenyl groups, and examples thereof include those represented by the following general formula (1).

（式（１）中、Ｌは直接結合又は２価の連結基であり、Ｒ^１、Ｒ^２、Ｒ^３及びＲ^４は、水素原子又は炭素数１〜２８の直鎖又は分岐のアルキル基である。）

(In formula (1), L is a direct bond or a divalent linking ^group, R ^1, R 2, ^{R 3} and ^{R 4} is a hydrogen atom or a linear or branched alkyl group having a carbon number of 1 to 28 is there.)

The divalent linking group in L is not particularly limited, but includes a linear, branched or cyclic group containing at least one selected from a linear, branched or cyclic alkylene group, a halogen atom, an oxygen atom and a sulfur atom. Examples include an alkylene group, an arylene group, a sulfonyl group, a carbonyl group, and an ether group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the linear or branched alkyl group having 1 to 28 carbon atoms in R ¹ , R ² , R ³ and R ⁴ include a methyl group, an ethyl group, a butyl group, a hexyl group, an octyl group, and a dodecyl group. It is done.

  Specific examples of the bisphenol compound include 2,2-bis (4-hydroxyphenyl) propane (bisphenol A), 1,1-bis (4-hydroxyphenyl) -1-phenylethane, and 2,2- Bis (4-hydroxyphenyl) hexafluoropropane, 2,2-bis (4-hydroxyphenyl) butane, 4,4′-dihydroxytetraphenylmethane, 2,2-bis (4-hydroxy-3-methylphenyl) propane (Bisphenol C), 1,1-dichloro-2,2-bis (4-hydroxyphenyl) ethylene, 4,4 ′-(α-methylbenzylidene) bisphenol, 4,4′-dihydroxydiphenylmethane (bisphenol F), 2 , 2-bis (4-hydroxy-3-isopropylphenyl) propane, 1,3-bis 2- (4-hydroxyphenyl) -2-propyl] benzene, bis (4-hydroxyphenyl) sulfone (bisphenol S), 1,4-bis [2- (4-hydroxyphenyl) -2-propyl] benzene, 4 , 4 ′-(3,3,5-trimethyl-1,1-cyclohexanediyl) bis (phenol), 1,1-bis (4-hydroxyphenyl) cyclohexane, and the like. Among them, 2,2-bis (4-hydroxyphenyl) propane (bisphenol A), 4,4′-dihydroxydiphenylmethane (bisphenol F), 2,2-bis (4-hydroxy-3-) are excellent in terms of printability. Methylphenyl) propane (bisphenol C) is preferred.

  Among the bisphenol compounds, those having a melting point of 100 ° C. or higher are preferable from the viewpoint of boil resistance. The bisphenol compound preferably has a melting point of 240 ° C. or less from the viewpoint of printing sensitivity.

  The bisphenol compound has a molecular weight of preferably 300 or less and more preferably 280 or less from the viewpoint of excellent printing sensitivity. The molecular weight of the bisphenol compound is not particularly limited, but is preferably 100 or more, and more preferably 200 or more.

  Although content of the said bisphenol compound is not specifically limited, It is preferable that it is 0.5-15 mass% with respect to the total solid contained in the said transferable colored layer, and it is 1-10 mass%. More preferred. When the content is equal to or higher than the lower limit value, printability is improved, and when the content is equal to or lower than the upper limit value, blocking is suppressed.

The colorant used in the transferable colored layer of the present invention can be appropriately selected from carbon black, inorganic pigments, organic pigments or dyes according to the required color tone. For example, in the case of barcode printing, it is particularly preferable to have a sufficiently black density and not discolor or fade by light, heat or the like. Examples of such a colorant include carbon black such as lamp black, graphite, and nigrosine dye. When color printing is required, other chromatic dyes or pigments are used. Furthermore, in order to give good thermal conductivity and antistatic properties within a range where the melt viscosity is not significantly increased, a carbonaceous material such as carbon black, or a heat conductive or conductive material such as metal powder can be blended.
Further, the transferable colored layer may further contain other components as long as the effects of the present invention are not hindered. For example, additives such as inorganic fine particles, organic fine particles, and a release agent may be contained.

In the transferable colored layer of the present invention, the mixing ratio of the colorant and the binder resin is not particularly limited, but the colorant is usually used at 20 to 70% by mass in the total solid content of the transferable colored layer. It is preferable to be used at 30 to 50% by mass.
The binder resin is preferably used in an amount of 30 to 80% by mass and more preferably 50 to 70% by mass in the total solid content of the transferable colored layer from the viewpoint of printability and boil resistance. preferable.
In addition, in the transferable colored layer of the present invention, the content ratio of the component having a softening point or melting point of less than 100 ° C. is 5% with respect to the total solid content contained in the transferable colored layer because of excellent boil resistance. It is preferable that it is below mass.

The transferable colored layer is obtained by applying a coating solution obtained by dispersing or dissolving the above-described materials in an organic solvent or the like by a conventionally known coating means such as gravure coating, gravure reverse coating, knife coating, air coating, roll coating, or die coating, and drying. Can be formed.
As said solvent, what can disperse | distribute or melt | dissolve the material mentioned above can be selected suitably, For example, aromatic solvents, such as ketone solvents, such as methyl ethyl ketone, toluene, these mixed solvents, etc. are mentioned. It is done.
The coating amount of the transfer colored layer is not particularly limited, but 0.6 g / ^{m 2} approximately in the normal drying, preferably 0.4g ^{/ m 2} ~3.0g ^/ m 2 in dry. If it is less than 0.4 g / m ² , the transfer printing density may be lowered, and if it is more than 3.0 g / m ² , the heat melting property of the film may be lowered, and thermal transfer may be difficult to occur. .

(Transferable release layer)
The transferable release layer 2 is disposed between the substrate 1 and the transferable colored layer 3. The thermal transfer sheet according to the present invention is excellent in the peelability of the layer to be transferred during thermal transfer due to the transferable release layer 2. The transferable release layer 2 is transferred together with the transferable colored layer 3 and the like during thermal transfer. Thereby, since the transferable peeling layer 2 covers the transferable colored layer 3 in the printed matter obtained using the thermal transfer sheet according to the present invention, the scratch resistance is improved and the boil resistance is improved.

The transferable release layer 2 is made of wax such as carnauba wax, paraffin wax, micro wax, silicone wax, silicone resin, fluororesin, acrylic resin, polyvinyl alcohol resin, cellulose derivative resin, urethane resin, acetate vinyl resin, acrylic resin. A coating solution containing at least one kind of vinyl ether resin, maleic anhydride resin, melamine resin, polyolefin resin, ionomer resin, styrene resin and copolymers of these resin groups, a conventionally known gravure coat, gravure reverse coat, etc. A carnauba wax having a high scratch resistance is preferably used.
Examples of the organic filler that can be added to the transferable release layer 2 as needed include acrylic fillers, polyamide fillers, fluorine fillers, and polyethylene waxes. Examples of the inorganic filler that can be added include talc, kaolin, clay, calcium carbonate, magnesium hydroxide, magnesium carbonate, magnesium oxide, and silica.
Moreover, it is preferable that the transferable peeling layer 2 contains a metal soap from the point that a boil resistance improves. Examples of the metal soap include alkali metal salts such as fatty acid, rosin acid, and naphthenic acid, alkaline earth metal salts, and metal salts such as aluminum and zinc, and in particular, alkaline earth metal salts of fatty acids. Aluminum salts or zinc salts are preferred. Among these, magnesium salts, zinc salts or aluminum salts of fatty acids are preferable, zinc salts are more preferable, and zinc stearate is still more preferable.
The coating amount of transferable peeling layer is a 0.5 g / ^{m 2} approximately in the normal drying, preferably 0.1g ^{/ m 2} ~1.0g ^/ m 2 in dry. If it is less than 0.1 g / m ² , the peelability may deteriorate and the effect of the release layer may not be obtained. On the other hand, if it exceeds 1.0 g / m ² , transfer for each release layer is likely to occur, and the transferability of the layer to be transferred may be deteriorated.

(Transferable protective layer)
In order to further improve the durability of the transferable colored layer such as heat resistance, friction resistance, scratch resistance, and boil resistance, the thermal transfer sheet of the present invention has a substrate 1 and transferability as shown in FIG. A transferable protective layer 5 may be provided between the colored layer 3. The transferable protective layer is transferred together with the transferable colored layer 2 during thermal transfer and covers the surface of the transferred image.

The transferable protective layer is preferably formed by appropriately selecting a resin that forms a tough film having high durability such as heat resistance, friction resistance, scratch resistance, and boil resistance. Resin that forms a tough coating with high durability, such as acrylic resin such as polymethylmethacrylate resin, polyurethane resin, polyester resin, polyamide resin, chlorinated polypropylene, etc., toughness such as heat resistance and friction resistance It can form from resin which forms a film. In addition, a resin that does not melt with heat after the coating is formed, for example, a thermosetting resin, a resin that is cross-linked and cured by a cross-linking agent, for example, an acrylic polyol, a phenol resin, and the like.
In the present invention, the transferable protective layer contains, as a main component, a cyclic olefin polymer having a glass transition temperature of 100 ° C. or higher, from the viewpoint of further improving the boil resistance and scratch resistance of the printed matter. It is preferable that the resin contains an incompatible resin for the cyclic olefin polymer. Here, the main component means that the cyclic olefin polymer is contained in 50% by mass or more of the solid content of the transferable protective layer. The cyclic olefin polymer is more preferably 70% by mass or more of the solid content of the transferable protective layer, and still more preferably 80% by mass or more of the solid content of the transferable protective layer.

The cyclic olefin polymer used in the present invention represents a polymer having a structural unit derived from a monomer comprising a cyclic olefin. That is, the cyclic olefin polymer has a cyclic structure in the main chain.
Specifically, the cyclic olefin polymer used in the present invention may be a cyclic olefin polymer or copolymer obtained by ring-opening polymerization of a cyclic olefin, and a cyclic olefin, a chain olefin, and a vinyl group. It may be a cyclic olefin copolymer obtained by addition polymerization with one or more selected from the aromatic compounds possessed, and some or all of them may be hydrogenated. In the cyclic olefin-based polymer, the cyclic olefin may be used alone or in combination of two or more.
The type of copolymerization is not limited in the present invention, and various known copolymerization types such as random copolymer, block copolymer, and alternating copolymerization can be applied.

The cyclic olefin used in the ring-opening polymerization or addition polymerization is preferably a polycyclic cyclic olefin, and more preferably a norbornene-based monomer having a norbornene ring structure. Examples of the norbornene-based monomer include bicyclo [2.2.1] hept-2-ene (common name: norbornene), 5-ethylidene-bicyclo [2.2.1] hept-2-ene (common name: ethylidene). Norbornene) and its derivatives (having substituents in the ring); tricyclo [4.3.0 ^1,6 . 1 ^2,5 ] deca-3,7-diene (common name dicyclopentadiene) and its derivatives and other tricyclic monomers; 7,8-benzotricyclo [4.3.0.1 ^2,5 ] Deca-3-ene (common name methanotetrahydrofluorene: also referred to as 1,4-methano-1,4,4a, 9a-tetrahydrofluorene) and its derivatives, tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene (common name: tetracyclododecene), 8-ethylidenetetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene and tetracyclic monomers such as derivatives thereof; and the like.
Examples of the substituent that the derivative has include an alkyl group, an alkylene group, a vinyl group, an alkoxycarbonyl group, an alkylidene group, a cyano group, and a halogenated alkyl group. Specific examples of the derivative include 8-methoxycarbonyl-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-methyl-8-methoxycarbonyl-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-ethylidene-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene and the like.

Examples of the chain olefin used in the addition polymerization type cyclic olefin copolymer include α-olefins having 2 to 20 carbon atoms, such as ethylene, propylene, 1-butene and 4-methyl. Examples include -1-pentene, 1-hexene, 1-octene, and 1-decene. Specific examples of the aromatic compound having a vinyl group include styrene, vinyl naphthalene, methyl styrene, propyl styrene, cyclohexyl styrene, dodecyl styrene, 2-ethyl-4-benzyl styrene, 4- (phenylbutyl) styrene, m-divinylbenzene, p-divinylbenzene, bis (4-vinylphenyl) methane and the like can be mentioned.
The chain olefin and the aromatic compound having a vinyl group can be used alone or in combination of two or more.

As the cyclic olefin polymer used in the present invention, a cyclic olefin polymer having a glass transition temperature (Tg) of 100 ° C. or higher is used from the viewpoint of excellent boil resistance. Especially, it is preferable that the glass transition temperature (Tg) of a cyclic olefin polymer is 140 degreeC or more from the point which improves boil resistance. If the glass transition temperature is high, the number of cyclic olefin-derived repeating units tends to increase, and it is estimated that heat resistance is improved and water absorption is further reduced.
On the other hand, the glass transition temperature (Tg) of the cyclic olefin polymer is preferably 200 ° C. or less from the viewpoint of printability. If the glass transition temperature is too high, it is presumed that the thermal response is hindered.
In addition, the glass transition temperature (Tg) in this invention is a temperature calculated | required based on the measurement (DSC method) of the calorie | heat amount change by DSC (differential scanning calorimetry).

  The cyclic olefin polymer used in the present invention is more preferably a cyclic olefin polymer having a structural unit represented by the following general formula (2) from the viewpoint of heat resistance and flexibility.

〔式（２）中、Ａ^１、Ａ^２、Ａ^３およびＡ^４は、それぞれ独立に、水素原子、炭素数１〜１０の炭化水素基、ハロゲン原子、ハロゲン原子で置換された炭素数１〜１０の炭化水素基、−（ＣＨ_２）_ｎＣＯＯＲ^１、−（ＣＨ_２）_ｎＯＣＯＲ^１、−（ＣＨ_２）_ｎＯＲ^１、−（ＣＨ_２）_ｎＣＮ、−（ＣＨ_２）_ｎＣＯＮＲ^３Ｒ^２、−（ＣＨ_２）_ｎＣＯＯＺ、−（ＣＨ_２）_ｎＯＣＯＺ、−（ＣＨ_２）_ｎＯＺ、−（ＣＨ２）_ｎＷ、またはＡ^２とＡ^３から構成された−ＯＣ−Ｏ−ＣＯ−、−ＯＣ−ＮＲ^４−ＣＯ−、もしくは（多）環状アルキレン基を示す。ここでＲ^１、Ｒ^２、Ｒ^３およびＲ^４は、炭素数１〜２０の炭化水素基、Ｚはハロゲン原子で置換された炭化水素基、ＷはＳｉＲ^５ _ｐＦ_３−ｐ（Ｒ^５は炭素数１〜１０の炭化水素基、Ｆはハロゲン原子、−ＯＣＯＲ^６または−ＯＲ^６（Ｒ^６は炭素数１〜１０の炭化水素基）、ｐは０〜３の整数を示す）、ｎは０〜１０の整数を示す。〕

[In the formula (2), A ¹ , A ² , A ³ and A ⁴ each independently represent a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms, a halogen atom, or a carbon atom having 1 to 1 carbon atoms substituted with a halogen atom. 10 hydrocarbon groups, — (CH ₂ ) _n COOR ¹ , — (CH ₂ ) _n OCOR ¹ , — (CH ₂ ) _n OR ¹ , — (CH ₂ ) _n CN, — (CH ₂ ) _n CONR ³ R ² , — (CH ₂ ) _n COOZ, — (CH ₂ ) _n OCOZ, — (CH ₂ ) _n OZ, — (CH ₂ ) _n W, or —OC—O—CO— composed of A ² and A ³ , —OC—NR ⁴ —CO—, or a (poly) cyclic alkylene group. Here, R ¹ , R ² , R ³ and R ⁴ are each a hydrocarbon group having 1 to 20 carbon atoms, Z is a hydrocarbon group substituted with a halogen atom, W is SiR ⁵ _p F _3-p (R ⁵ is A hydrocarbon group having 1 to 10 carbon atoms, F is a halogen atom, -OCOR ⁶ or -OR ⁶ (R ⁶ is a hydrocarbon group having 1 to 10 carbon atoms), p is an integer of 0 to 3), and n is An integer of 0 to 10 is shown. ]

In the cyclic olefin polymer having the structural unit represented by the general formula (2), among them, any of A ¹ , A ² , A ³ and A ⁴ has a cyclic olefin polymer having a substituent containing oxygen. The combination is preferable from the viewpoint of interlayer adhesion with the transferable colored layer. Examples of the substituent containing oxygen include the above-described — (CH ₂ ) _n COOR ¹ , — (CH ₂ ) _n OCOR ¹ , — (CH ₂ ) _n OR ¹ , — (CH ₂ ) _n CONR ³ R ² , — ( CH ₂ ) _n COOZ, — (CH ₂ ) _n OCOZ, — (CH ₂ ) _n OZ, or —OC—O—CO—, —OC—NR ⁴ —CO—, etc. composed of A ² and A ³ Among them, — (CH ₂ ) _n COOR ¹ or — (CH ₂ ) _n OCOR ¹ is preferable.

  The cyclic olefin polymer used in the present invention is an amorphous polyolefin resin and preferably has a mass average molecular weight in the range of 50,000 to 300,000.

The cyclic olefin polymer can be synthesized by ring-opening polymerization or addition polymerization of a cyclic olefin by a conventionally known method, and further hydrogenating as necessary. Or you may use a commercial item.
Examples of commercially available addition polymerization type cyclic olefin polymers include Apel manufactured by Mitsui Chemicals and TOPAS manufactured by Polyplastics. Examples of commercially available ring-opening polymerization type cyclic olefin polymers include ZEONEX manufactured by Nippon Zeon Co., Ltd. and ARTON manufactured by JSR Corporation.

On the other hand, the incompatible resin for the cyclic olefin polymer used in combination with the cyclic olefin polymer may be an incompatible resin that does not completely dissolve in the cyclic olefin polymer used in combination. If it does not specifically limit. The incompatibility is determined according to a conventional method in the resin industry. For example, a composition obtained by melting and mixing 5 parts by mass of a resin with respect to 100 parts by mass of a cyclic olefin polymer is magnified 100,000 times with an electron microscope, and a domain of 1 mm ² or more in a range of 10 cm × 15 cm or Those having at least one particle can be defined as incompatible.

  As the incompatible resin, other resins than the cyclic olefin polymer are usually used. Examples of other resins that are incompatible with norbornene resins include polyethers or polythioethers such as polyphenylene sulfide and polyphenylene ether; aromatic polyesters, polyarylate, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, and polyether ketone. Polyester polymers; Chain polyolefin polymers such as polyethylene, polypropylene, and poly-4-methyl-pentene-1; General-purpose transparent resins such as polyacrylonitrile styrene (AS resin); Cyclic olefins such as acrylic resins A resin that is incompatible with the polymer is appropriately selected and used. Among these, a polyol having a hydroxyl group is preferably used, and examples thereof include polyester polyol, polycarbonate polyol, polyether polyol, polyolefin polyol, and acrylic polyol.

  When an incompatible resin is added with a cyclic olefin polymer as a main component, a large number of dispersed microdomains or particles of the incompatible resin are formed in a coating film formed by coating the incompatible resin. From the viewpoint of improving the transparency of the transferable protective layer and the transferability of the transferable protective layer, the microdomain has an average particle diameter [(major axis + minor axis) / 2] observed with an electron microscope, The size is preferably 5 to 30 μm, more preferably 10 to 20 μm.

Since the boil resistance of the transferable protective layer, transparency, and transferability of the transferable protective layer can be exhibited in a balanced manner, the incompatible resin is the cyclic olefin polymer in the transferable protective layer. And 5 to 30 parts by mass, preferably 10 to 25 parts by mass, based on 100 parts by mass of the total amount of the incompatible resin.
If the amount of the incompatible resin is less than the above ratio, the film cutting property at the time of transfer is deteriorated, and the printability may be deteriorated. On the other hand, when there are too many said incompatible resins than the said ratio, there exists a possibility that application | coating suitability may deteriorate or boil resistance may deteriorate.

Moreover, as a transferable protective layer, in addition to the above-mentioned thermoplastic resin, a lubricant component such as metal soap, phosphate ester, polyethylene wax, talc, silicone resin fine particles and the like, and an auxiliary to lubricity are provided for the purpose of improving slip properties. For the purpose of adjustment, it is preferable that various additives such as inorganic or organic fine particles or silicone oil are contained, and it is particularly preferable that lubricant components such as polyethylene wax, talc, and silicone resin fine particles are contained. preferable.
When the lubricant component is contained in the transferable protective layer, the content of the lubricant component is preferably 1 to 20% by mass in the solid content of the transferable protective layer.

The coating amount of the transferable protective layer, so that the film breakage is sufficiently performed, so that a thin layer is preferably 0.1g ^{/ m 2} ~1.5g ^/ m 2 in dry. Further, in order to improve the film breakage, a transferable protective layer may be formed by adding a fine extender pigment such as silica, alumina, clay, calcium carbonate or the like.

(Back layer)
In the thermal transfer sheet of the present invention, a back layer is provided on the other surface of the substrate in order to prevent adverse effects such as sticking and printing wrinkles due to heat from a thermal head, a transfer hot plate or the like.
The back layer can be formed by appropriately selecting a conventionally known thermoplastic resin or the like. As such a thermoplastic resin, for example, polyester resins, polyacrylate resins, polyvinyl acetate resins, styrene acrylate resins, polyurethane resins, polyethylene resins, polypropylene resins, and other polyolefin resins, Polystyrene resin, polyvinyl chloride resin, polyether resin, polyamide resin, polyimide resin, polyamideimide resin, polycarbonate resin, polyacrylamide resin, polyvinyl chloride resin, polyvinyl butyral resin, polyvinyl acetoacetal resin, etc. Polyvinyl acetal resins, polyvinyl alcohol resins, ethyl cellulose resins, thermoplastic resins such as cellulose resins such as methyl cellulose resins, these silicone-modified products, and fluorine-modified polyurethane Resins.

  Moreover, you may add a crosslinking agent to above-described resin. As the polyisocyanate resin functioning as a cross-linking agent, conventionally known ones can be used without any particular limitation. Among them, it is desirable to use an adduct of an aromatic polyisocyanate. As the aromatic polyisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, or a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, Examples include p-phenylene diisocyanate, trans-cyclohexane-1,4-diisocyanate, xylylene diisocyanate, triphenylmethane triisocyanate, and tris (isocyanatophenyl) thiophosphate, particularly 2,4-toluene diisocyanate and 2,6-toluene diisocyanate. Or, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate is preferable.

  In addition to the above thermoplastic resin, the back layer is provided with a lubricant component such as metal soap, phosphate ester, polyethylene wax, talc, and silicone resin fine particles in addition to the thermoplastic resin, and an auxiliary to the slipperiness. For adjustment, it is preferable that various additives such as inorganic or organic fine particles or silicone oil are contained, and it is particularly preferable that at least one of phosphate ester or metal soap is contained. Moreover, you may contain electroconductive carbon for antistatic.

The back layer is, for example, a coating solution obtained by dispersing or dissolving the thermoplastic resin and various additives added as necessary in a suitable solvent by a conventionally known gravure coating, gravure reverse coating, or the like. It can be formed by drying.
The coating amount of the back layer is not particularly limited, from the viewpoint of improvement of heat resistance and the like, preferably 0.01g ^{/ m 2} ~0.2g ^/ m 2 in dry.
Moreover, in order to improve the adhesiveness of a back surface layer and a base material, or to further reduce the damage by the heat | fever of the thermal head which a base material sheet receives, you may provide further a back surface primer layer.

  The material to be transferred printed by the thermal transfer sheet of the present invention is not particularly limited and may be any of ordinary paper, barcode label paper, synthetic paper, plastic film, sheet, metal, wood, glass, resin molded product, and the like. However, since the thermal transfer sheet of the present invention is particularly excellent in boil resistance, it is particularly suitable for a packaging material that is subjected to a boil sterilization process after packaging food or a plastic film used as a packaging material for retort food. Preferably used. Examples of the packaging material as described above include various laminated films. For example, the surface to be printed includes nylon, and laminated films made of a plastic film mainly composed of a polyester resin such as polyethylene terephthalate. It is not limited to.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. These descriptions do not limit the present invention. In the text, “part” or “%” is based on mass unless otherwise specified.
(Example 1: Production of thermal transfer sheet 1)
Using a biaxially stretched polyethylene terephthalate film (hereinafter referred to as PET) (trade name: Lumirror, manufactured by Toray) with a thickness of 4 μm as a base material, a back layer coating solution having the following composition as a back layer is dried. The back layer was formed by applying and drying by a gravure printing method so that the amount of coating was 0.06 g / m ² . Next, on the surface opposite to the back layer of the substrate on which the back layer is formed, the transfer release layer coating liquid 1 having the following composition is gravure so that the coating amount when dried is 0.2 g / m ^2. It was applied and dried by a printing method to form a transferable release layer. Next, a transferable protective layer coating solution having the following composition was applied and dried by a gravure printing method so that the coating amount at the time of drying was 0.2 g / m ² to form a transferable protective layer. Subsequently, the transferable colored layer coating liquid 1 having the following composition on the transferable protective layer was applied and dried by a gravure printing method so that the coating amount at the time of drying was 0.7 g / m ² . The thermal transfer sheet 1 of Example 1 was formed.

<Coating liquid for back layer>
・ Acrylic modified silicone 10 parts by mass (polyalloy NSA-X55, manufactured by NATCO Corporation)
Silicone isocyanate 2 parts by mass (Diaroma SP901, manufactured by Dainichi Seika Kogyo Co., Ltd.)
・ Methyl ethyl ketone 20 parts by mass ・ Toluene 20 parts by mass

<Transferable release layer coating solution 1>
Carnava wax 75 parts by mass (WE-95, manufactured by Konishi Co., Ltd., melting point 86 ° C.)
Latex 10 parts by mass (Nippol LX430, manufactured by Nippon Zeon Co., Ltd.)
-Mixed solvent of water and isopropyl alcohol (mixed at a mass ratio of 1: 1) 100 parts by mass

<Coating liquid for transferable protective layer>
80 parts by mass of a cyclic olefin polymer having a structural unit derived from a norbornene monomer (Arton G 7810, manufactured by JSR Corporation, glass transition temperature: 165 ° C.)
20 parts by mass of incompatible resin (acrylic polyol resin) for the cyclic olefin polymer (Thermolac SU100A, manufactured by Soken Chemical Co., Ltd.)
-Polyethylene WAX 5 parts by mass (slip agent B, manufactured by Showa Ink Industries, Ltd.)
-Mixed solvent of toluene and methyl ethyl ketone (mixed at a mass ratio of 1: 1) 100 parts by mass

<Coating liquid 1 for transferable colored layer>
-Phenol resin (solid content: 50%) 2.40 parts by mass (phenol novolac resin, TD-2090, manufactured by DIC Corporation, softening point 118-122 ° C)
・ Bisphenol F 0.12 parts by mass (Bisphenol F Honshu Chemical Industry Co., Ltd., melting point 118 ° C., molecular weight 200)
-Carbon black (solid content: 35%) 2.29 parts by mass-Mixed solvent of toluene and methyl ethyl ketone (mixed at a mass ratio of 1: 1) 5.31 parts by mass

(Example 2: Production of thermal transfer sheet 2)
In the thermal transfer sheet of Example 1, Example 2 was performed in the same manner as Example 1 except that the transferable colored layer coating solution 2 having the following composition was used instead of the transferable colored layer coating solution 1. Thermal transfer sheet 2 was obtained.
<Transferable coloring layer coating solution 2>
-Phenol resin (solid content: 50%) 2.40 parts by mass (phenol novolac resin, TD-2090, manufactured by DIC Corporation, softening point 118-122 ° C)
・ Bisphenol A 0.12 parts by mass (Bisphenol A manufactured by Mitsubishi Chemical Corporation, melting point 153 ° C., molecular weight 228)
-Carbon black (solid content: 35%) 2.29 parts by mass-Mixed solvent of toluene and methyl ethyl ketone (mixed at a mass ratio of 1: 1) 5.31 parts by mass

(Example 3: Production of thermal transfer sheet 3)
Example 3 was the same as Example 1 except that the transferable colored layer coating solution 3 having the following composition was used in place of the transferable colored layer coating solution 1 in the thermal transfer sheet of Example 1. The thermal transfer sheet 3 was obtained.
<Transferable coloring layer coating solution 3>
-Phenol resin (solid content: 50%) 2.40 parts by mass (phenol novolac resin, TD-2090, manufactured by DIC Corporation, softening point 118-122 ° C)
・ Bisphenol C 0.12 parts by mass (Bisphenol C Honshu Chemical Industry Co., Ltd., melting point 138 ° C., molecular weight 256)
-Carbon black (solid content: 35%) 2.29 parts by mass-Mixed solvent of toluene and methyl ethyl ketone (mixed at a mass ratio of 1: 1) 5.31 parts by mass

(Example 4: Production of thermal transfer sheet 4)
A thermal transfer sheet 4 of Example 4 was obtained in the same manner as Example 1 except that the transferable protective layer was not formed in the thermal transfer sheet of Example 1.

(Example 5: Production of thermal transfer sheet 5)
Example 5 In the thermal transfer sheet of Example 1, Example 5 was carried out in the same manner as Example 1 except that the transferable release layer coating solution 2 having the following composition was used instead of the transferable release layer coating solution 1. A thermal transfer sheet 5 was obtained.
<Transferable release layer coating solution 2>
Carnava wax 75 parts by mass (WE-95, manufactured by Konishi Co., Ltd., melting point 86 ° C.)
・ Zinc stearate 15 parts by mass (trade name: Hi-micron F-930, manufactured by Chukyo Yushi Co., Ltd.)
Latex 10 parts by mass (Nippol LX430, manufactured by Nippon Zeon Co., Ltd.)
-Mixed solvent of water and isopropyl alcohol (mixed at a mass ratio of 1: 1) 100 parts by mass

(Comparative Example 1: Production of comparative thermal transfer sheet 1)
In the thermal transfer sheet of Example 1, in place of the transferable colored layer coating solution 1, a comparative transferable colored layer coating solution 1 having the following composition was used in the same manner as in Example 1 except that a comparative example was used. 1 comparative thermal transfer sheet 1 was obtained.
<Comparative Transferable Colored Layer Coating Solution 1>
-Phenol resin (solid content: 50%) 2.40 parts by mass (phenol novolac resin, TD-2090, manufactured by DIC Corporation, softening point 118-122 ° C)
-Carbon black (solid content: 35%) 2.29 parts by mass-Mixed solvent of toluene and methyl ethyl ketone (mixed at a mass ratio of 1: 1) 5.31 parts by mass

(Comparative Example 2: Production of comparative thermal transfer sheet 2)
In the thermal transfer sheet of Example 1, in place of the transferable colored layer coating liquid 1, a comparative transferable colored layer coating liquid 2 having the following composition was used in the same manner as in Example 1 except that the comparative example was used. 2 comparative thermal transfer sheet 2 was obtained.
<Comparison Transfer Colored Layer Coating Solution 2>
Polyester resin (solid content: 50%) 2.40 parts by mass (polyester, Byron 200, manufactured by Toyobo Co., Ltd.)
・ Bisphenol F 0.12 parts by mass (Honshu Chemical Industry Co., Ltd., bisphenol F, molecular weight 200)
-Carbon black (solid content: 35%) 2.29 parts by mass-Mixed solvent of toluene and methyl ethyl ketone (mixed at a mass ratio of 1: 1) 5.31 parts by mass

(Comparative Example 3: Production of Comparative Thermal Transfer Sheet 3)
A comparative thermal transfer sheet 3 of Comparative Example 3 was obtained in the same manner as in Example 1 except that the transferable release layer was not formed in the thermal transfer sheet of Example 1.

(Comparative Example 4: Production of comparative thermal transfer sheet 4)
In the thermal transfer sheet of Example 1, in place of the transferable colored layer coating solution 1, a comparative transferable colored layer coating solution 3 having the following composition was used in the same manner as in Example 1 except that a comparative example was used. 4 comparative thermal transfer sheet 4 was obtained.
<Comparison transfer coloring layer coating solution 3>
-Phenol resin (solid content: 50%) 2.40 parts by mass (phenol novolac resin, TD-2090, manufactured by DIC Corporation, softening point 118-122 ° C)
・ Polyester resin 0.12 parts by mass (polyester, Byron 200, manufactured by Toyobo Co., Ltd.)
-Carbon black (solid content: 35%) 2.29 parts by mass-Mixed solvent of toluene and methyl ethyl ketone (mixed at a mass ratio of 1: 1) 5.31 parts by mass

[Evaluation of thermal transfer sheet]
(1) Printability evaluation Each thermal transfer sheet obtained in Examples 1 to 5 and Comparative Examples 1 to 4 is overlapped with the nylon surface side of a nylon / low density polyethylene laminated film (thickness 100 μm, manufactured by DNP). Using a melt transfer type thermal transfer printer (manufactured by B-SX4T TEC), a 1-dot character pattern was printed with a thermal head having a resolution of 300 dpi at a printing speed of 10 IPS (inch / second). Printing was performed under conditions where the Heat Adjust of the printer was −2, −1, and 0, and the printability was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1. Note that the thermal energy of the thermal head of the printer increases in the order of Heat Adjust-2 <-1 <0.
<Evaluation criteria>
A: Printing is good at Heat Adjust-2.
B: Although there is a missing or crushed portion in the printed matter at Heat Adjust-2, printing is good at Heat Adjust-1.
C: Although there is a missing or crushed portion in the printed matter at Heat Adjust-1, printing is good at Heat Adjust 0.
D: In Heat Adjust 0, there is a missing part or a crushed part in the printed matter, but it can be read.
E: In Heat Adjust 0, a missing part or a crushed part occurs in the printed matter, and it is unreadable.

(2) Evaluation of boil resistance After leaving each of the printed matter formed using the thermal transfer sheets of Examples 1 to 5 and Comparative Examples 1 to 4 in boiling hot water for 10 minutes, the surface of the printed matter is made with paper waste. Rub 10 round trips. Thereafter, the printed matter was visually observed, and the boil resistance was evaluated based on the following evaluation criteria. The evaluation results are shown in Table 1.
<Evaluation criteria>
A: There is no change in the printed matter.
B: Although there is a part missing from the printed matter or a part where peeling occurs, it is easy to read.
C: Difficult to read due to missing or peeled parts in the printed matter.
D: Unreadable because there is a missing part or a peeled part in the printed matter.

(Summary of results)
In the thermal transfer sheets obtained in Examples 1 to 5, at least a transferable release layer and a transferable colored layer are arranged in this order on one side of the substrate from the substrate side, and the transferable colored layer is a colorant. And a phenol resin having a softening point of 100 ° C. or higher and a bisphenol compound, the printability is good even when high-speed printing is performed while suppressing the thermal energy during printing, and the printed matter is resistant to printing. The boilability was also good. In addition, it was revealed that the thermal transfer sheets obtained in Examples 1 to 3 and 5 having a transferable protective layer were particularly excellent in the boil resistance of printed matter.
Further, for each of the thermal transfer sheets obtained in Example 1 and Example 5, the boil resistance was evaluated by further extending the standing time in the hot water in the evaluation of the boil resistance. Compared to the obtained thermal transfer sheet, the thermal transfer sheet obtained in Example 5 did not change the printed matter for a longer time. Therefore, it was revealed that Example 5 containing metal soap in the transferable release layer was further excellent in boil resistance.
On the other hand, the thermal transfer sheet obtained in Comparative Example 1 was inferior in printability because the transferable colored layer did not contain a bisphenol compound.
The thermal transfer sheet obtained in Comparative Example 2 was inferior in the boil resistance and printability of the printed matter because the transferable colored layer did not contain a phenol resin having a softening point of 100 ° C. or higher. In Comparative Example 2, there were many portions where peeling occurred compared to Comparative Example 4.
The thermal transfer sheet obtained in Comparative Example 3 was not provided with a transferable release layer, so that the transferable colored layer was not uniformly released and printing could not be performed.
Since the thermal transfer sheet obtained in Comparative Example 4 used a polyester resin in place of the bisphenol compound in the transferable colored layer, the printed matter was inferior in boil resistance and printability.

DESCRIPTION OF SYMBOLS 1 Base material 2 Transferable peeling layer 3 Transferable colored layer 4 Back surface layer 5 Transferable protective layer 10 Thermal transfer sheet

Claims (2)

On one surface of the substrate, at least a transferable release layer and a transferable colored layer are disposed in this order from the substrate side, and a back layer is disposed on the other surface of the substrate,
The transferable colored layer is a thermal transfer sheet containing a colorant, a phenol resin having a softening point of 100 ° C. or higher, and a bisphenol compound.   A transferable protective layer is further disposed between the transferable release layer and the transferable colored layer, and the transferable protective layer contains a cyclic olefin polymer having a glass transition temperature of 100 ° C. or higher as a main component. The thermal transfer sheet according to claim 1, further comprising an incompatible resin for the cyclic olefin polymer.

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