JP6327391B2 - Thermal transfer sheet - Google Patents

Description

  The present invention relates to a thermal transfer sheet.

  Conventionally, images such as letters, symbols, diagrams, and patterns have been formed on a substrate using a thermal transfer method, and as a thermal transfer method, a thermal sublimation transfer method and a thermal fusion transfer method are widely used. ing. The heat-sensitive transfer method uses a heat transfer sheet in which a heat-meltable ink layer containing a colorant such as a pigment and a binder resin is provided on a base film, which is overlaid on a transfer target, and a heating device such as a thermal head. In this method, an image according to image information is applied to transfer a softened heat-meltable ink layer component onto a transfer medium to form an image. The heat-sensitive transfer method is preferred when producing IDs such as identification cards, especially when forming monotonous images such as letters and numbers.

  When forming images using the heat-sensitive melt transfer method, if the heat-meltable ink layer is not releasable from the base material, problems such as problems with heat-meltable ink not being transferred onto the transfer target, It is known that transfer problems occur, and various attempts have been made to improve the releasability of the hot-melt ink layer from the substrate. For example, Patent Document 1 proposes a thermal transfer sheet in which a release layer is provided between a base film and a hot-melt ink layer to improve the release property of the hot-melt ink.

  However, even if a release layer is provided between the base material and the hot-melt ink layer, if the release force of the release layer is too light, the ink of the hot-melt ink layer is excessively transferred. Ink crushing may occur during image formation. On the other hand, when the peeling force of the release layer is too heavy, the ink of the hot-melt ink becomes difficult to transfer, and the ink may be blurred during image formation. Adjustment of the release force of the release layer is generally performed by controlling the drying temperature at the time of forming the release layer, but the management margin of the drying conditions for adjusting the release force is narrow, Since the peeling force fluctuates due to minute fluctuations, it is difficult to adjust the peeling force by controlling the drying conditions. In particular, recently, for example, a release layer is widely formed using a reaction system material such as a silicone material, but when a reaction system material is used, it is dried under the same conditions. Even if it performs, peeling force will fluctuate.

  As with the above drying condition margin, the control margin for the coating amount of the heat-meltable ink layer for adjusting the transferability of the heat-meltable ink layer is also very narrow, and the coating amount as small as the target coating amount can be applied. When the amount of work is reached, the ink is crushed during image formation, and when the amount of coating is less than the target coating amount, the ink is faded during image formation.

JP 2003-127558 A

  The present invention has been made in such a situation, and it is possible to prevent the occurrence of ink crushing or fading at the time of image formation without being affected by the drying conditions of the release layer and the coating amount. It is a main object to provide a thermal transfer sheet that can be formed.

The present invention for solving the above problems is a thermal transfer sheet comprising a base material, a release layer provided on the base material, and a hot-melt ink layer provided to be peelable on the release layer. The release layer contains cellulose acetate and a citrate ester.
Moreover, the release layer of the thermal transfer sheet may contain the citrate within a range of 7% by mass to 30% by mass with respect to the total solid content of the cellulose acetate.
The release layer of the thermal transfer sheet may contain polyethylene wax, and the release layer of the thermal transfer sheet is 3% by mass or more and 12% by mass or less with respect to the total solid content of the cellulose acetate. The polyethylene wax may be contained within the range of. In the thermal transfer sheet, a part of the surface of the polyethylene wax may protrude from the surface of the release layer.
In the thermal transfer sheet, the degree of polymerization of cellulose acetate may be 100 or more and 300 or less.
Moreover, the thermal transfer sheet of one embodiment is a thermal transfer sheet comprising a base material, a release layer provided on the base material, and a hot-melt ink layer provided to be peelable on the release layer. The release layer contains cellulose acetate, citrate ester, and a cellulose resin having a melting point exceeding 165 ° C.
Moreover, the thermal transfer sheet of one embodiment is a thermal transfer sheet comprising a base material, a release layer provided on the base material, and a hot-melt ink layer provided to be peelable on the release layer. The release layer contains cellulose acetate.

  Further, the release layer may contain a citrate ester and / or a cellulose resin having a melting point exceeding 165 ° C. Moreover, the said release layer may further contain the polyethylene wax within the range of 3 mass% or more and 12 mass% or less with respect to the solid content total amount of the said cellulose acetate.

  The degree of polymerization of the cellulose acetate may be 100 or more and 300 or less.

  Moreover, a part of the surface of the polyethylene wax may protrude from the surface of the release layer.

  According to the thermal transfer sheet of the present invention, it is possible to prevent the ink from being crushed or blurred during image formation without being affected by the drying conditions and the coating amount when forming the release layer, and forming a good image. Can do.

  Further, according to one embodiment of the thermal transfer sheet of the present invention, even when an image is formed on an intermediate transfer medium using the thermal transfer sheet of the present invention, and the formed image is retransferred onto a transfer medium, Good transfer performance can be exhibited.

It is a schematic sectional drawing which shows an example of the thermal transfer sheet of this invention. (A) is a schematic sectional drawing which shows an example of the thermal transfer sheet of this invention, (b) is a top view of the thermal transfer sheet of this invention. (A) is a schematic sectional drawing which shows the state at the time of transferring a heat-meltable ink on an intermediate transfer medium, (b) is the outline which shows the state at the time of retransferring a heat-meltable ink on a to-be-transferred body. It is sectional drawing.

  Hereinafter, the thermal transfer sheet of the present invention will be described in detail. As shown in FIG. 1, the thermal transfer sheet 10 of the present invention includes a base material 1, a release layer 2 provided on the base material 1, and a hot-melt ink layer provided on the release layer 2 so as to be peelable. 3. In particular, the thermal transfer sheet 10 of the present invention is characterized in that the release layer 2 contains cellulose acetate, and the thermal transfer sheet 10 is not limited to this embodiment as long as this requirement is satisfied. For example, in the form shown in FIG. 1, the back layer 5 is provided on a surface different from the surface on which the release layer of the substrate 1 is provided, but the back layer 5 is an arbitrary configuration in the thermal transfer sheet 10 of the present invention. It is. Hereafter, each structure of the thermal transfer sheet 10 of this invention is demonstrated concretely.

(Base material)
As the base material 1 used for the thermal transfer sheet 10 of the present invention, a conventionally known base material can be appropriately selected and used as long as it has heat resistance and mechanical properties that do not hinder handling. Examples of such a substrate include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyarylate, polycarbonate, polyurethane, polyimide, polyetherimide, cellulose derivative, polyethylene, ethylene / vinyl acetate copolymer, polypropylene, polystyrene, and acrylic. , Polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, nylon, polyether ether ketone, polysulfone, polyether sulfone, tetrafluoroethylene / perfluoroalkyl vinyl ether, polyvinyl fluoride, tetrafluoroethylene / ethylene, tetrafluoro Ethylene / hexafluoropropylene, polychlorotrifluoroethylene, polyvinylidene fluoride Mention may be made of various plastic films or sheets. Each of these materials can be used alone, but may be used as a laminate in combination with other materials. The thickness of the base material 1 can be appropriately set according to the material so that the strength and heat resistance thereof are appropriate, and is generally about 2.5 to 100 μm.

  Further, the base material 1 may be subjected to an adhesion treatment on the surface on which the release layer 2 is formed. By performing the adhesion treatment, the adhesion between the substrate 1 and the release layer 2 can be improved.

  Examples of the adhesion treatment include known resin surfaces such as corona discharge treatment, flame treatment, ozone treatment, ultraviolet treatment, radiation treatment, surface roughening treatment, chemical treatment, plasma treatment, low temperature plasma treatment, primer treatment, and grafting treatment. The reforming technique can be applied as it is. Two or more of these treatments can be used in combination.

(Release layer)
A release layer 2 is provided on the substrate 1, and in the present invention, the release layer 2 contains cellulose acetate. According to the release layer 2 containing cellulose acetate, it is possible to stably transfer the hot-melt ink contained in the hot-melt ink layer 3 onto the transfer target. Specifically, the heat-meltable ink is transferred with a peeling force that does not cause crushing or fading to the heat-meltable ink without being affected by the drying temperature and the coating amount when forming the release layer 2. Can be transferred onto the body.

  The cellulose acetate contained in the release layer 2 preferably has a degree of polymerization of 100 or more and 300 or less, and more preferably 130 or more and 190 or less. By using cellulose acetate having a degree of polymerization of 100 or more, particularly 130 or more, a preferable release property can be imparted to the release layer 2.

  There is no particular limitation on the content of cellulose acetate with respect to the total solid content of the release layer 2, but when the mass of cellulose acetate is less than 60% by mass with respect to the total solid content of the release layer 2, the hot-melt ink Therefore, the effect of transferring the hot-melt ink with a peeling force that does not cause crushing or fading tends to be reduced. Considering this point, the cellulose acetate is preferably contained in an amount of 60% by mass or more, particularly preferably 70% by mass or more, based on the total solid content of the release layer 2. The upper limit of the content of cellulose acetate with respect to the total solid content of the release layer 2 is not particularly limited and is 100% by mass, but can be appropriately adjusted according to the content of any component described later.

  The release layer 2 containing cellulose acetate can transfer the hot-melt ink onto the transfer target material without being crushed or fainted at the time of printing in a normal temperature and normal humidity environment and a high temperature and high humidity environment. Under a low-temperature and low-humidity environment, the heat-meltable ink layer 3 becomes difficult to peel off from the release layer 2, and the heat-meltable ink layer and the transfer target may stick to each other during printing.

  In one embodiment of the thermal transfer sheet 10 of the present invention in consideration of the above points, as shown in FIG. 2 (a), polyethylene wax 20 is protruded from the release layer 2 and a part thereof protrudes from the surface of the release layer 2. To be contained. In other words, polyethylene wax exists at the interface between the release layer 2 and the hot-melt ink layer 3 as shown in FIG. FIG. 2B is a top view of the thermal transfer sheet 10 of the present invention, and the heat-meltable ink layer 3 is omitted for convenience of explanation.

  The polyethylene wax has a characteristic that the adhesiveness with the hot-melt ink layer 3 is low. Accordingly, by causing the polyethylene wax to protrude from the surface of the release layer 2, that is, by causing the polyethylene wax to exist at the interface between the release layer 2 and the hot-melt ink layer 3, the hot-melt ink from the release layer 2. The peeling force of the layer 3 can be lightened. As a result, even when the heat-meltable ink is transferred onto the transfer medium in a low-temperature and low-humidity environment, the heat-meltable ink is applied to the transfer medium without the transfer medium and the heat-meltable ink layer 3 sticking. It becomes possible to transfer.

  The content of the polyethylene wax is not particularly limited, but when the content of the polyethylene wax is less than 3% by mass with respect to the total solid content of cellulose acetate, the release layer 2 and the hot-melt ink layer 3 There is less polyethylene wax present at the interface, and the effect of improving sticking tends to decrease. On the other hand, when the content of polyethylene wax exceeds 12% by mass relative to the total solid content of cellulose acetate, the amount of polyethylene wax present at the interface between the release layer 2 and the hot-melt ink layer 3 increases. In some cases, the peeling force becomes too light, and when transferring the hot-melt ink, the resolution may be reduced due to the crushing of the ink. Further, when the content of the polyethylene wax contained in the release layer 2 is large, or when the polyethylene wax protrudes not only from the surface of the release layer 2 but also from the surface of the hot-melt ink layer 3, Polyethylene wax is also transferred onto the transfer medium along with the meltable ink, and white turbidity may occur on the surface of the transfer medium onto which the hot-melt ink has been transferred.

  In particular, when the intermediate transfer medium 50 is used as a transfer medium as shown in FIG. 3A, when the polyethylene wax is transferred onto the intermediate transfer medium 50 together with the hot-melt ink, the hot-melt ink The polyethylene wax 20 with low adhesiveness protrudes from the surface of the film. Then, as shown in FIG. 3B, when the heat-meltable ink transferred onto the intermediate transfer medium 50 is re-transferred onto the transfer target 60, the polyethylene wax protruding from the surface of the heat-meltable ink is removed. Due to the presence, the adhesion between the other transfer target 60 and the hot-melt ink to be retransferred is remarkably lowered.

  Therefore, considering such points, the polyethylene wax is preferably contained in the range of 3% by mass to 12% by mass with respect to the solid content mass of cellulose acetate, and is preferably 3% by mass to 8% by mass. The following range is particularly preferable.

  As the polyethylene wax, polyethylene wax particles having a density of 0.94 to 0.97, for example, those obtained by micronizing polyethylene wax into particles can be suitably used. Polyethylene wax includes high-density or low-density polyethylene wax, and low-density polyethylene includes many ethylene polymers that have branches in the structure. On the other hand, high-density polyethylene is relatively polyethylene. It is mainly composed of a straight chain structure.

  The size of the polyethylene wax is not particularly limited, but when the average particle diameter of the polyethylene wax contained is significantly larger than the total thickness of the release layer 2 and the hot-melt ink layer 3, the polyethylene wax is The protruding polyethylene wax may protrude from the surface of the heat-meltable ink layer 3 and may drop off from the thermal transfer sheet 10. Further, as described above, polyethylene wax may also be transferred onto the transfer target material together with the hot-melt ink. On the other hand, since polyethylene wax bleeds to the surface of the release layer 2 at the time of printing, the above effect is exhibited even when a polyethylene wax having an average particle diameter smaller than the thickness of the release layer 2 is selected. Can do.

  The polyethylene wax contained in the release layer 2 needs to be selected with an optimum average particle size in consideration of the above points. A preferable average particle diameter of the polyethylene wax is about 2 μm to 10 μm. The average particle diameter of polyethylene wax referred to in the present specification means “volume average particle diameter”. The same applies to the average particle diameter of the fine particles described in the hot-melt ink layer 3.

  The shape of the polyethylene wax particles can be spherical, square, columnar, needle-like, plate-like, indefinite or the like, and any shape can exhibit the effects described above.

  Further, as described above, even when the release layer 2 contains polyethylene wax, when the adhesiveness between the release layer 2 and the substrate 1 is low, more specifically, from the release layer 2 When the adhesive force between the release layer 2 and the substrate 1 is weaker than the peelability of the hot-melt ink layer, the release layer 2 is covered together with the hot-melt ink layer 3 during printing in a low temperature and low humidity environment. In some cases, the image is transferred onto the transfer body. Since the release layer 2 containing cellulose acetate generally has low adhesion to the transfer medium, when the release layer 2 is transferred together with the heat-meltable ink layer 3 onto the intermediate transfer medium, The retransfer property onto the transfer medium is significantly reduced.

  In one embodiment of the thermal transfer sheet 10 of the present invention considering such points, the release layer 2 contains a citrate ester. By including a citrate ester in the release layer 2, the adhesion between the release layer 2 and the substrate 1 can be improved, and the release layer 2 is transferred together with the hot-melt ink layer 3 during printing. Abnormal transfer that is transferred onto the body can be prevented.

  Further, by improving the adhesion between the release layer 2 and the substrate 1, the heat-meltable ink layer 3 is more easily peeled off from the release layer 2, so that the release at the time of printing in a low-temperature and low-humidity environment. The peelability of the hot-melt ink layer 3 from the mold layer 2 can be further improved. The polyethylene wax and citrate ester that can be contained in the release layer 2 are used for sticking the heat-meltable ink layer to the transfer target during printing in a low-temperature and low-humidity environment, abnormal transfer of the release layer, etc. It is a component for solving the problem, and when printing is performed in an environment other than a low temperature and low humidity environment, these components do not need to be contained.

  Examples of the citrate ester include acetyl tributyl citrate, acetyl triethyl citrate, triethyl O-acetyl citrate, tributyl O-acetyl citrate, and citric acid that is particularly excellent in adhesion to a substrate. Acetyltributyl is preferred. As acetyltributyl citrate, dimer acetyltributyl dicitrate is particularly preferred.

  The citrate ester is preferably contained within a range of 7% by mass or more and 30% by mass or less with respect to the solid content mass of cellulose acetate. This is because if the content is less than 7% by mass or more than 30% by mass, the adhesion to the substrate tends to be lowered.

  Moreover, the adhesiveness of the base material 1 and the release layer 2 can also be improved by making the release layer 2 contain a cellulose resin having a melting point exceeding 165 ° C. instead of the citrate ester. In other words, like the citrate ester, the release property of the heat-meltable ink layer 3 at the time of printing in a low-temperature and low-humidity environment can also be obtained by adding a cellulose resin having a melting point exceeding 165 ° C. to the release layer 2. Can be improved. In addition, by containing a cellulose resin having a melting point exceeding 165 ° C. in combination with the citrate ester in the release layer 2, the hot-melt ink layer from the release layer 2 during printing in a low-temperature and low-humidity environment. 3 can be further improved.

  The cellulose resin is not particularly limited as long as the condition that the melting point exceeds 165 ° C. is satisfied. Examples of the cellulose resin include nitrocellulose resins.

  Moreover, it is preferable that content of the cellulose resin in which the said melting | fusing point exceeds 165 degreeC is 5 mass% or more and 25 mass% or less with respect to the total mass of cellulose acetate and the cellulose resin in which melting | fusing point exceeds 165 degreeC, More preferably, it is 7 mass% or more and 15 mass% or less. If it is less than 5% by mass, the effect of improving the adhesion between the substrate 1 and the release layer 2 is small, and the peelability of the hot-melt ink layer 3 during printing in a low-temperature and low-humidity environment cannot be sufficiently satisfied. There is a case. In addition, it is preferable that the cellulose resin whose melting | fusing point exceeds 165 degreeC is contained in the range from which the content of a cellulose acetate with respect to the solid content total amount of the mold release layer 2 will be 60 mass% or more.

  When a citric acid ester and a cellulose resin having a melting point exceeding 165 ° C. are used in combination, the total mass of the citric acid ester and the cellulose resin having a melting point exceeding 165 ° C. with respect to the solid content mass of cellulose acetate is 7 mass% or more and 30 mass% or less is preferable.

  The method for forming the release layer 2 is not particularly limited, and optional components such as cellulose acetate which is an essential component, polyethylene wax added as necessary, citrate ester, and cellulose resin having a melting point exceeding 165 ° C. The coating liquid dissolved or dispersed in an appropriate solvent is coated and dried on the substrate 1 using a known means such as a gravure printing method, a screen printing method, a reverse roll coating method using a gravure plate, etc. Can be formed.

Although there is no particular limitation on the coating amount of the release layer ^2, 0.05~1g / m 2, preferably 0.07~0.8g / m ² approximately. In the present invention, since cellulose acetate is contained in the release layer 2, the release force of the release layer 2 can be increased without being affected by the drying conditions and the coating amount when forming the release layer 2. Further, the heat-meltable ink can have a peeling force that does not cause crushing or fading during transfer.

(Hot melt ink layer)
A heat-meltable ink layer 3 is provided on the release layer 2. The heat-meltable ink layer 3 is not particularly limited. For example, conventionally known colorants and binders, and if necessary, higher fatty acids such as mineral oil, vegetable oil, stearic acid, plasticizers, thermoplastic resins, fillers, and the like. Those added with various additives are used.

  Examples of the wax component used as the binder include microcrystalline wax, carnauba wax, and paraffin wax. In addition, Fischer-Tropsch wax, various low molecular weight polyethylene, wood wax, beeswax, whale wax, ibota wax, wool wax, shellac wax, candelilla wax, petrolactam, polyester wax, partially modified wax, fatty acid ester, fatty acid amide, etc. The wax is used. Among these, those having a melting point of 50 to 85 ° C. are particularly preferable. If it is 50 ° C. or lower, a problem occurs in storage stability, and if it is 85 ° C. or higher, sensitivity is insufficient.

  Examples of the resin component used as the binder include ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, polyethylene, polystyrene, polypropylene, polybutene, petroleum resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer. Examples include coalesce, polyvinyl alcohol, vinylidene chloride resin, acrylic resin, methacrylic resin, polyamide, polycarbonate, fluororesin, polyvinyl formal, polyvinyl butyral, acetyl cellulose, nitrocellulose, polyvinyl acetate, polyisobutylene, ethyl cellulose, or polyacetal. In particular, those having a relatively low softening point, for example, a softening point of 50 to 80 ° C., conventionally used as a heat-sensitive adhesive are preferable.

  The colorant can be appropriately selected from known organic or inorganic pigments or dyes. For example, a colorant having a sufficient color density and not discolored or discolored by light, heat or the like is preferable. Further, it may be a substance that develops color when heated or a substance that develops color when it comes into contact with a component applied to the surface of the transfer target. Further, the color of the colorant is not limited to cyan, magenta, yellow, and black, and various colorants can be used. The heat-meltable ink layer 3 composed of a black colorant (sometimes referred to as a heat-meltable black ink layer) can be preferably used because there is no need to perform density gradation.

  The hot-melt ink layer 3 preferably contains fine particles, and the fine particles are preferably contained so that a part of the surface protrudes from the surface of the hot-melt ink layer 3. According to this configuration, it is possible to prevent the occurrence of blocking that may occur between the heat-meltable ink layer 3 and the transfer target due to the presence of fine particles protruding from the surface of the heat-meltable ink layer 3. In particular, the occurrence of blocking when stored under high temperature conditions can be effectively prevented. It can be confirmed using, for example, a blocking tester that the blocking is improved by protruding a part of the surface of the fine particles from the surface of the hot-melt ink layer 3.

  The fine particles serve to prevent the occurrence of blocking by causing a part of the surface to protrude from the surface of the hot-melt ink layer 3. Therefore, the specific components of the fine particles are not particularly limited, and conventionally known fine particles can be appropriately selected and used. Examples of the fine particles include melamine / aldehyde condensate, polymethyl methacrylate cross-linked product, styrene-acrylic cross-linked product, benzoguanamine / formaldehyde condensate, silicone resin fine particle, polyethylene wax, talc and the like.

  The average particle size of the fine particles is not particularly limited, and those having a particle size that can be projected from the surface of the hot-melt ink layer 3 can be appropriately selected and used. Although depending on the thickness of the heat-meltable ink layer 3, an example of the average particle diameter of the fine particles is about 0.5 μm to 5 μm. Even if the average particle diameter of the fine particles is smaller than the thickness of the heat-meltable ink layer 3, the surface of the heat-meltable ink layer 3 depends on the dispersion state of the fine particles in the heat-meltable ink layer 3. Thus, a part of the surface of the fine particles can be projected. Therefore, the average particle diameter of the fine particles is not necessarily larger than the thickness of the hot-melt ink layer 3.

  The content of the fine particles with respect to the total solid content of the heat-meltable ink layer 3 is not particularly limited. However, as the content increases, the foil endurance of the heat-meltable ink layer decreases, and heat melting Problems such as dropping of fine particles from the conductive ink layer may occur. Therefore, the content of the fine particles in the heat-meltable ink layer 3 is preferably set in consideration of the balance between the blocking prevention effect and the problems that may occur due to the inclusion of the fine particles. A preferable example of the content of the fine particles is in the range of 0.5% by mass or more and 10% by mass or less.

  Furthermore, in order to give the heat-meltable ink layer 3 good heat conductivity and heat-melt transferability, a heat-conductive substance may be blended as a binder filler. Examples of such fillers include carbonaceous materials such as carbon black, metals such as aluminum, copper, tin oxide, and molybdenum disulfide, and metal compounds. The hot-melt ink layer is formed by coating the colorant component and the binder component as described above, and further adding a solvent component such as water or an organic solvent as necessary. Is performed by a conventionally known method such as hot melt coating, hot lacquer coating, gravure coating, gravure reverse coating or roll coating. The thickness of the heat-meltable ink layer can be appropriately set within a range where the required printing density and thermal sensitivity can be harmonized, and the thickness is not particularly limited, but may be in the range of 0.1 μm to 30 μm. Preferably, about 1 μm to 20 μm is more preferable. In the thermal transfer sheet 10 of the present invention, cellulose acetate is contained in the release layer 2, whereby the heat-fusible ink layer 3 contains the heat-meltable ink layer 3 regardless of the thickness of the heat-meltable ink layer 3. The ink can be transferred onto the transfer target without causing crushing or fading.

(Back layer)
Further, when a material lacking durability against high heat is used as the substrate 1, the surface of the substrate 1 on the side in contact with the thermal head, that is, the side opposite to the surface on which the release layer 2 of the substrate 1 is provided. It is preferable to provide the back layer 5 on the surface in order to improve the slipperiness of the thermal head and prevent sticking. The back layer 5 includes a heat-resistant resin and a substance that functions as a thermal release agent or a lubricant as basic components. By providing such a back layer, it is possible to transfer heat-meltable ink without causing sticking even in a heat transfer sheet using, for example, a heat-sensitive plastic film as a base material 1.

  The back layer 5 can be formed by suitably using a binder resin to which a slip agent, a surfactant, inorganic particles, organic particles, a pigment and the like are added. Examples of the binder resin used for the back layer 5 include cellulose resins such as ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, cellulose acetate butyrate, and nitrified cotton, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, and polyvinyl. Examples thereof include vinyl resins such as acetal, polyvinylpyrrolidone, acrylic resin, polyacrylamide, acrylonitrile-styrene copolymer, polyester resin, polyurethane resin, silicone-modified or fluorine-modified urethane resin.

Among these, it is preferable to use a crosslinked resin using several reactive groups, for example, those having a hydroxyl group, and using a polyisocyanate or the like as a crosslinking agent. The means for forming the heat-resistant layer is as described above, by dissolving or dispersing a material obtained by adding a slipping agent, surfactant, inorganic particles, organic particles, pigments, etc. to a binder resin in a suitable solvent, The coating solution is coated by a conventional coating means such as a gravure coater, roll coater, wire bar, etc., and dried. The coating amount of the heat-resistant layer is usually about 0.01 to 10 g / m ^{2 in} a dry state.

(Transfer material)
Examples of the transfer target that can be used in combination with the thermal transfer sheet 10 of the present invention when performing image formation include plain paper, high-quality paper, tracing paper, and plastic film. Moreover, according to the thermal transfer sheet 10 of one embodiment of the present invention, it is excellent in the retransferability of the hot-melt ink, and therefore can be used particularly suitably when forming an image on an intermediate transfer medium. Hereinafter, an example of an intermediate transfer medium that can be suitably used in combination with the thermal transfer sheet 10 of the present invention will be described.

  As an intermediate transfer medium, a medium in which a protective layer and a receiving layer are laminated on one surface of a base material is generally used.

  Examples of the resin material constituting the intermediate transfer medium include polyester resin, polycarbonate resin, acrylic resin, ultraviolet ray absorbing resin, epoxy resin, polystyrene resin, polyurethane resin, acrylic urethane resin, and resins obtained by modifying these resins with silicone. And a mixture of these resins, ionizing radiation curable resins, ultraviolet absorbing resins and the like.

  The ionizing radiation curable resin can be suitably used as a binder for the protective layer in terms of particularly excellent plasticizer resistance and scratch resistance. The ionizing radiation curable resin can be appropriately selected and used from conventionally known ionizing radiation curable resins. For example, a radically polymerizable polymer or oligomer is crosslinked and cured by irradiation with ionizing radiation. A photopolymerization initiator added and polymerized and cross-linked with an electron beam or ultraviolet light can be used. A protective layer containing an ultraviolet absorbing resin is excellent in imparting light resistance to a printed material.

  As the ultraviolet absorbing resin, for example, a resin obtained by reacting and bonding a reactive ultraviolet absorbent to a thermoplastic resin or the above ionizing radiation curable resin can be used. More specifically, addition-polymerizable double-reactive organic UV absorbers such as salicylates, benzophenones, benzotriazoles, substituted acrylonitriles, nickel chelates, hindered amines, etc. Examples thereof include a bond (for example, a vinyl group, an acryloyl group, a methacryloyl group, etc.), an alcoholic hydroxyl group, an amino group, a carboxyl group, an epoxy group, and a reactive group such as an isocyanate group.

If necessary, for example, colorants such as lubricants, plasticizers, fillers, antistatic agents, antiblocking agents, crosslinking agents, antioxidants, ultraviolet absorbers, light stabilizers, dyes, pigments, etc. Additives and the like may be added. As a method for forming the protective layer, one or two or more of the resin materials exemplified above are dissolved or dispersed in an appropriate solvent to prepare a protective layer coating solution, which is then gravure-coated on the substrate. It can be formed by applying and drying by a conventionally known means such as a printing method, a screen printing method or a reverse coating method using a gravure plate. Although there is no limitation in particular about the thickness of a protective layer, Usually, it is 0.1-50 g / m < ² > by the thickness after drying, Preferably it is about 1-20 g / m < ² >.

(Receptive layer)
A receiving layer is provided on the protective layer. On this receiving layer, the heat-meltable ink peeled from the heat-meltable ink layer 3 constituting the heat transfer sheet 10 of the present invention is transferred to form an image. Then, the receiving layer of the intermediate transfer medium on which the image is formed is retransferred onto the transfer medium, and as a result, a printed product is formed.

  As a material for forming the receiving layer, a conventionally known resin material that can easily accept the hot-melt ink can be used. For example, polyolefin resin such as polypropylene, halogenated resin such as polyvinyl chloride or polyvinylidene chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer or polyacrylate Vinyl resins, polyester resins such as polyethylene terephthalate or polybutylene terephthalate, polystyrene resins, polyamide resins, copolymers of olefins such as ethylene or propylene and other vinyl polymers, cellulose resins such as ionomers or cellulose diastases Polycarbonate and the like, and vinyl chloride resin, acrylic-styrene resin or polyester resin is particularly preferable.

  When the receiving layer is transferred to the transfer medium via the adhesive layer, the adhesiveness of the receiving layer itself is not necessarily required. However, when the receptor layer is transferred to the transfer medium without passing through the adhesive layer, it is preferable to form the receptor layer using an adhesive resin material such as vinyl chloride-vinyl acetate copolymer.

The receiving layer is a coating for the receiving layer, which is prepared by adding one or more materials selected from the above materials and various additives as necessary, and dissolving or dispersing them in an appropriate solvent such as water or an organic solvent. A liquid can be prepared, and this can be formed by applying and drying by means of a gravure printing method, a screen printing method or a reverse coating method using a gravure plate. Its thickness is about 1 to 10 g / m ^{2 in} a dry state.

  Hereinafter, the present invention will be described with reference to Examples, Reference Examples, and Comparative Examples. “Parts” in the text are based on mass unless otherwise noted.

(Reference Example 1)
Using a polyethylene terephthalate film having a thickness of 5 μm that has been subjected to an easy adhesion treatment as a base material, a release layer coating solution 1 having the following composition is applied on the substrate so as to be 0.2 g / m ² when dried, A release layer was formed. Next, a hot melt ink layer coating liquid 1 having the following composition was applied on the release layer so as to be 0.8 g / m ² upon drying to form a hot melt ink layer, thereby providing Reference Example 1. A thermal transfer sheet was obtained.

<Release layer coating solution 1>
・ Cellulose acetate (solid content: 8%, polymerization degree: 180) 30 parts (L-70 manufactured by Daicel Chemical Industries, Ltd.)
・ Methyl ethyl ketone (MEK) 6 parts ・ Propylene glycol monomethyl ether (PGM) 3 parts ・ Methanol 1 part

<Coating liquid 1 for hot melt ink layer>
-60 parts of vinyl chloride-vinyl acetate copolymer (Solvine CNL Nissin Chemical Industry Co., Ltd.)
・ Carbon black 40 parts ・ Toluene 200 parts ・ Methyl ethyl ketone 200 parts

(Reference Example 2)
A thermal transfer sheet of Reference Example 2 was obtained in the same manner as Reference Example 1 except that the release layer coating solution 1 was changed to the release layer coating solution 2 having the following composition.

<Release layer coating liquid 2>
・ Cellulose acetate (solid content: 8%, polymerization degree: 140) 30 parts (L-20 manufactured by Daicel Chemical Industries, Ltd.)
・ Methyl ethyl ketone (MEK) 6 parts ・ Propylene glycol monomethyl ether (PGM) 3 parts ・ Methanol 1 part

(Reference Example 3)
A thermal transfer sheet of Reference Example 3 was obtained in the same manner as Reference Example 1 except that the release layer coating solution 1 was changed to the release layer coating solution 3 having the following composition.

<Release layer coating solution 3>
・ Cellulose acetate (solid content: 8%, polymerization degree: 180) 30 parts (L-70 manufactured by Daicel Chemical Industries, Ltd.)
・ Polyethylene wax (solid content: 7%, particle size: 5 μm) 0.343 parts (FA-341-7, Gifu Serask Manufacturing Co., Ltd.)
・ Methyl ethyl ketone (MEK) 6 parts ・ Propylene glycol monomethyl ether (PGM) 3 parts ・ Methanol 1 part

(Reference Example 4)
A thermal transfer sheet of Reference Example 4 was obtained in the same manner as Reference Example 1 except that the release layer coating solution 1 was changed to the release layer coating solution 4 having the following composition.

<Release layer coating solution 4>
・ Cellulose acetate (solid content: 8%, polymerization degree: 180) 30 parts (L-70 manufactured by Daicel Chemical Industries, Ltd.)
・ Polyethylene wax (solid content: 7%) 1.029 parts (FA-341-7 Gifu Serask Manufacturing Co., Ltd.)
・ Methyl ethyl ketone (MEK) 6 parts ・ Propylene glycol monomethyl ether (PGM) 3 parts ・ Methanol 1 part

(Reference Example 5)
A thermal transfer sheet of Reference Example 5 was obtained in the same manner as Reference Example 1 except that the release layer coating solution 1 was changed to the release layer coating solution 5 having the following composition.

<Release layer coating solution 5>
・ Cellulose acetate (solid content: 8%, polymerization degree: 180) 30 parts (L-70 manufactured by Daicel Chemical Industries, Ltd.)
Polyethylene wax (solid content: 7%, particle size: 5 μm) 4.114 parts (FA-341-7, Gifu Serask Manufacturing Co., Ltd.)
・ Methyl ethyl ketone (MEK) 6 parts ・ Propylene glycol monomethyl ether (PGM) 3 parts ・ Methanol 1 part

(Reference Example 6)
A thermal transfer sheet of Reference Example 6 was obtained in the same manner as Reference Example 1 except that the release layer coating solution 1 was changed to the release layer coating solution 6 having the following composition.

<Release layer coating solution 6>
・ Cellulose acetate (solid content: 8%, polymerization degree: 180) 30 parts (L-70 manufactured by Daicel Chemical Industries, Ltd.)
・ Polyethylene wax (solid content: 7%, particle size: 5 μm) 6.857 parts (FA-341-7, Gifu Serask Manufacturing Co., Ltd.)
・ Methyl ethyl ketone (MEK) 6 parts ・ Propylene glycol monomethyl ether (PGM) 3 parts ・ Methanol 1 part

(Reference Example 7)
A thermal transfer sheet of Reference Example 7 was obtained in the same manner as in Reference Example 1 except that the release layer coating liquid 1 was applied at a dryness of 1.0 g / m ² to form a release layer.

(Reference Example 8)
A thermal transfer sheet of Reference Example 8 was obtained in the same manner as in Reference Example 1 except that the hot-melt ink layer was applied at 1.2 g / m ² when dried to form a hot-melt ink layer.

(Reference Example 9)
The release layer coating liquid 1 is applied to a dry layer of 1.0 g / m ² to form a release layer, and the hot-melt ink layer is applied to a dry layer of 1.2 g / m ^2. Then, a thermal transfer sheet of Reference Example 9 was obtained in the same manner as Reference Example 1 except that a hot-melt ink layer was formed.

(Example 10)
A thermal transfer sheet of Example 10 was obtained in the same manner as in Reference Example 1 except that the release layer coating solution 1 was changed to the release layer coating solution 7 having the following composition.

<Release layer coating solution 7>
・ Cellulose acetate (solid content: 8%, polymerization degree: 180) 30 parts (L-70 manufactured by Daicel Chemical Industries, Ltd.)
・ Acetyltributyl citrate 0.24 parts (ATBC manufactured by Asahi Kasei Finechem Co., Ltd.)
・ Methyl ethyl ketone (MEK) 6 parts ・ Propylene glycol monomethyl ether (PGM) 3 parts ・ Methanol 1 part

(Example 11)
A thermal transfer sheet of Example 11 was obtained in the same manner as in Reference Example 1 except that the release layer coating solution 1 was changed to the release layer coating solution 8 having the following composition.

<Release layer coating liquid 8>
・ Cellulose acetate (solid content: 8%, polymerization degree: 180) 30 parts (L-70 manufactured by Daicel Chemical Industries, Ltd.)
・ Acetyltributyl citrate 0.24 parts (ATBC manufactured by Asahi Kasei Finechem Co., Ltd.)
Polyethylene wax (solid content: 7%, particle size: 5 μm) 1.714 parts (FA-341-7 Gifu Serask Manufacturing Co., Ltd.)
・ Methyl ethyl ketone (MEK) 6 parts ・ Propylene glycol monomethyl ether (PGM) 3 parts ・ Methanol 1 part

(Example 12)
A thermal transfer sheet of Example 12 was obtained in the same manner as in Reference Example 1 except that the release layer coating solution 1 was changed to the release layer coating solution 9 having the following composition.

<Release layer coating solution 9>
・ Cellulose acetate (solid content: 8%, polymerization degree: 180) 30 parts (L-70 manufactured by Daicel Chemical Industries, Ltd.)
・ Acetyltributyl citrate 0.096 parts (ATBC Asahi Kasei Finechem Co., Ltd.)
Polyethylene wax (solid content: 7%, particle size: 5 μm) 1.714 parts (FA-341-7 Gifu Serask Manufacturing Co., Ltd.)
・ Methyl ethyl ketone (MEK) 6 parts ・ Propylene glycol monomethyl ether (PGM) 3 parts ・ Methanol 1 part

(Example 13)
A thermal transfer sheet of Example 13 was obtained in the same manner as in Reference Example 1 except that the release layer coating solution 1 was changed to the release layer coating solution 10 having the following composition.

<Coating liquid 10 for release layer>
-Cellulose acetate (solid content: 8%, polymerization degree: 180) 64.37 parts (L-70 manufactured by Daicel Chemical Industries, Ltd.)
・ Nitrocellulose (solid content 25%, melting point 165 ° C. <1.6) 1.6 parts acetyltributyl citrate 0.57 parts (ATBC Asahi Kasei Finechem Co., Ltd.)
・ Polyethylene wax (solid content: 7%, particle size: 5 μm) 4.1 parts (FA-341-7, Gifu Serask Manufacturing Co., Ltd.)
・ Methyl ethyl ketone (MEK) 6 parts ・ Propylene glycol monomethyl ether (PGM) 3 parts ・ Methanol 1 part

(Example 14)
A thermal transfer sheet of Example 14 was obtained in the same manner as in Reference Example 1 except that the release layer coating solution 1 was changed to the release layer coating solution 11 having the following composition.

<Release layer coating solution 11>
-Cellulose acetate (solid content: 8%, polymerization degree: 180) 59.37 parts (L-70 manufactured by Daicel Chemical Industries, Ltd.)
・ Nitrocellulose (solid content 25%, melting point 165 ° C. <3.2 parts) ・ Acetyltributyl citrate 0.57 parts (ATBC Asahi Kasei Finechem Co., Ltd.)
・ Polyethylene wax (solid content: 7%, particle size: 5 μm) 4.1 parts (FA-341-7, Gifu Serask Manufacturing Co., Ltd.)
・ Methyl ethyl ketone (MEK) 6 parts ・ Propylene glycol monomethyl ether (PGM) 3 parts ・ Methanol 1 part

(Example 15)
The hot melt ink layer coating liquid 1 is changed to a hot melt ink layer coating liquid 2 having the following composition, and the release layer coating liquid 1 is changed to a release layer coating liquid 10 having the above composition. A thermal transfer sheet of Example 15 was obtained in the same manner as in Reference Example 1 except that. In addition, it was confirmed that a part of the surface of the melamine / formaldehyde condensate protrudes from the surface of the hot melt ink layer formed using the hot melt ink layer coating liquid 2.

<Coating liquid 2 for hot-melt ink layer>
・ 60 parts of vinyl chloride-vinyl acetate copolymer (Solvine CNL Nissin Chemical Industry Co., Ltd.)
・ Carbon black 40 parts ・ Melamine ・ Formaldehyde condensate 1 part (Eposter S12 Nippon Shokubai Co., Ltd.)
・ Toluene 200 parts ・ Methyl ethyl ketone 200 parts

(Example 16)
The hot melt ink layer coating liquid 1 is changed to the hot melt ink layer coating liquid 2 having the above composition, and the release layer coating liquid 1 is changed to the release layer coating liquid 11 having the above composition. Except that, the thermal transfer sheet of Example 16 was obtained in the same manner as Reference Example 1.

(Reference Example 17)
The hot melt ink layer coating liquid 1 is changed to the hot melt ink layer coating liquid 2 having the above composition, and the release layer coating liquid 1 is changed to the release layer coating liquid 12 having the following composition. A thermal transfer sheet of Reference Example 17 was obtained in the same manner as Reference Example 1 except for the above.

<Coating liquid 12 for release layer>
-Cellulose acetate (solid content: 8%, polymerization degree: 180) 64.37 parts (L-70 Daicel Chemical Industries, Ltd.)
・ Nitrocellulose (solid content: 25%, melting point 165 ° C. <1.6 parts) ・ Methyl ethyl ketone (MEK) 6 parts ・ Propylene glycol monomethyl ether (PGM) 3 parts ・ Methanol 1 part

(Comparative Example 1)
A thermal transfer sheet of Comparative Example 1 was obtained in the same manner as Reference Example 1 except that the release layer coating solution 1 was changed to the release layer coating solution A having the following composition.

<Release layer coating liquid A>
40 parts of silicone-modified acrylic resin having an epoxy group (solid content: 50%) (Cell Top 226 Daicel Chemical Industries, Ltd.)
Vinyl chloride-vinyl acetate copolymer (solid content: 20%, Tg = 76 ° C., number average molecular weight: 30,000) 4 parts (Solvine A Nissin Chemical Industry Co., Ltd.)
・ Aluminum catalyst (solid content: 10%) 10 parts ・ Methyl ethyl ketone (MEK) 24 parts ・ Toluene 24 parts

(Preparation of intermediate transfer medium)
A polyethylene terephthalate film (Lumirror, manufactured by Toray Industries, Inc.) having a thickness of 16 μm is used as a base material, and a coating solution for a release layer having the following composition is dried on the base material to a thickness of 1.0 g / m ^2. Was applied to form a release layer. Next, the protective layer coating liquid 1 having the following composition was applied on the release layer so as to have a thickness of 10.0 g / m ^{2 in} a dry state to form a protective layer. Further, a receiving layer coating solution having the following composition was applied on the protective layer so as to have a thickness of 2.0 g / m ^{2 in} a dry state to form a receiving layer to obtain an intermediate transfer medium. The release layer coating solution, the protective layer coating solution, and the receiving layer coating solution were all applied by gravure coating.

<Coating liquid for release layer>
・ 95 parts acrylic resin (BR-87, Mitsubishi Rayon Co., Ltd.)
・ Polyester resin 5 parts (Byron 200, Toyobo Co., Ltd.)
・ Methyl ethyl ketone (MEK) 200 parts ・ Toluene 200 parts

<Coating liquid for protective layer>
・ Styrene-acrylic resin 150 parts (Muticle PP320P Mitsui Chemicals)
・ 100 parts of polyvinyl alcohol (C-318 DNP Fine Chemical Co., Ltd.)
・ 70 parts of water / ethanol (mass ratio 1/2)

<Coating liquid for receiving layer>
・ 95 parts of vinyl chloride-vinyl acetate copolymer (CNL, Nissin Chemical Industry Co., Ltd.)
・ Epoxy-modified silicone oil 5 parts (KP-1800U, Shin-Etsu Chemical Co., Ltd.)
・ Methyl ethyl ketone (MEK) 200 parts ・ Toluene 200 parts

(Crush evaluation)
The thermal transfer sheets of Examples, Reference Examples and Comparative Examples and the intermediate transfer medium prepared above were combined, and a sublimation type retransfer printer (CX-210 manufactured by Dai Nippon Printing Co., Ltd.) was used, and the temperature was 22.5. Transfer the heat-meltable ink layer onto the receiving layer of the intermediate transfer medium under the default conditions in an environment of ℃ and humidity of 50%, and visually check the state of the heat-meltable ink transferred onto the intermediate transfer medium Then, the crushing evaluation of the hot-melt ink was performed based on the following evaluation criteria. The evaluation results are shown in Table 1.

<< Evaluation criteria >>
○: The 2 dot thin line is not crushed.
Δ: The 2 dot thin line is partially crushed.
X: The 2 dot thin line is completely crushed.

(Fuzzy evaluation)
Transfer the hot-melt ink layer onto the intermediate transfer medium under the same transfer conditions as the above-mentioned crush evaluation, visually check the state of the hot-melt ink transferred onto the intermediate transfer medium, and meet the following evaluation criteria: Based on this, the hot-melt ink was evaluated for fading. The evaluation results are also shown in Table 1.

<< Evaluation criteria >>
○: There is no fading in the 2 dot thin line.
Δ: There is a part of the 2 dot thin line.
X: The 2 dot thin line is completely blurred.

(Retransferability evaluation)
The heat-meltable ink layer transferred onto the intermediate transfer medium in the above-described crushing evaluation and the PVC card are superimposed so that they face each other, and the heat-melting property is applied to the PVC card under the same transfer conditions as in the above-mentioned crushing evaluation. The ink layer was retransferred. A mending tape (Nichiban Co., Ltd.) with a width of 18 mm was applied to a PVC card on which a heat-meltable ink layer was retransferred, a 90-degree peel test was performed, and retransferability was evaluated according to the following criteria. . The evaluation results are also shown in Table 1.

<< Evaluation criteria >>
○: No peeling of the hot-melt ink layer was observed.
Δ: Partial peeling occurred in the hot-melt ink layer.
X: All of the hot-melt ink layer was peeled off.

  As is clear from Table 1, in the thermal transfer sheets of Examples and Reference Examples in which the release layer contains cellulose acetate, it can be confirmed that crushing and blurring can be suppressed, and that retransferability is excellent. It was. On the other hand, in the thermal transfer sheet of the comparative example containing a resin other than cellulose acetate, it was confirmed that crushing and blurring occurred. Also from this, the superiority of the release layer containing cellulose acetate is clear.

(Paste evaluation)
In combination with the thermal transfer sheets of Examples, Reference Examples and Comparative Examples and the intermediate transfer medium prepared above, a sublimation type retransfer printer (CX-210 manufactured by Dai Nippon Printing Co., Ltd.) was used, and the temperature was 5 ° C. Under a 20% humidity environment, the hot-melt ink layer was transferred three times onto the receiving layer of the intermediate transfer medium under default conditions. At this time, whether or not the hot-melt ink layer and the receiving layer were adhered was visually confirmed, and adhesion evaluation was performed based on the following evaluation criteria. The same evaluation was performed in an environment with a temperature of 22.5 ° C. and a humidity of 50%. The evaluation results are shown in Table 2.

<< Evaluation criteria >>
○: No sticking between the hot-melt ink layer and the receiving layer occurs.
Δ: Sticking between the hot-melt ink layer and the receiving layer occurred one or more times.
X: Sticking between the hot-melt ink layer and the receiving layer occurred every time.

(Releasing layer adhesion evaluation)
In combination with the thermal transfer sheets of Examples, Reference Examples and Comparative Examples and the intermediate transfer medium prepared above, a sublimation type retransfer printer (CX-210 manufactured by Dai Nippon Printing Co., Ltd.) was used, and the temperature was 5 ° C. The hot-melt ink layer was transferred onto the receiving layer of the intermediate transfer medium under the default conditions in an environment of 20% humidity. At this time, whether or not the release layer was taken on the intermediate transfer medium was confirmed with a microscope, and the adhesion of the release layer was evaluated according to the following evaluation criteria. A similar evaluation was performed under an environment of a temperature of 22.5 ° C. and a humidity of 50%. The evaluation results are also shown in Table 2.

<< Evaluation criteria >>
○: No release layer is formed on the intermediate transfer medium.
Δ: A slight release layer may be formed on the intermediate transfer medium, but at a level where there is no problem in use.
X: A release layer is formed on the intermediate transfer medium, which is a level that inhibits retransferability.

(Blocking evaluation)
In order to verify the superiority of thermal transfer sheets (thermal transfer sheets of Reference Examples 1 to 9, 17 and Examples 10 to 16) in which a part of the surface of the fine particles protrudes from the surface of the heat-meltable ink layer, blocking evaluation is performed. It was.

  For the evaluation of blocking, the heat-meltable ink layers of the thermal transfer sheets of each Example, Reference Example, and Comparative Example were stored for 48 hours in an environment of a temperature of 40 ° C. and a humidity of 90%. A mending tape was affixed onto the meltable ink layer, and then 90 ° vertical peeling was performed immediately, and evaluation was performed according to the following evaluation criteria. In addition, the same evaluation was performed for those stored for 48 hours in an environment of temperature 50 ° C. and humidity Free. The evaluation results are shown in Table 2. Humidity Free means that humidity is not controlled. Further, the fact that the hot-melt ink layer does not peel means that the occurrence of blocking can be prevented.

<< Evaluation criteria >>
○: The hot-melt ink layer did not peel off.
Δ: Some peeling occurred in the hot-melt ink layer.

  As is clear from Table 2, the effect of improving sticking in a low-temperature and low-humidity environment could be confirmed by further containing polyethylene wax in the release layer. Moreover, the improvement effect of the adhesiveness of the release layer in a low-temperature, low-humidity environment could be confirmed by containing a citrate ester or a cellulose resin having a melting point exceeding 165 ° C. Further, it was confirmed that the occurrence of blocking during high-temperature storage can be prevented by causing a part of the surface of the fine particles to protrude from the surface of the hot-melt ink layer.

DESCRIPTION OF SYMBOLS 10 ... Thermal transfer sheet 1 ... Base material 2 ... Release layer 3 ... Hot melt ink layer 5 ... Back layer

Claims (6)

A thermal transfer sheet comprising a base material, a release layer provided on the base material, and a heat-meltable ink layer provided to be peelable on the release layer,
The thermal transfer sheet, wherein the release layer contains cellulose acetate and citrate ester.   2. The thermal transfer according to claim 1, wherein the release layer contains the citrate ester within a range of 7% by mass to 30% by mass with respect to the total solid mass of the cellulose acetate. Sheet.   The thermal transfer sheet according to claim 1 or 2, wherein the release layer contains polyethylene wax.   The thermal transfer sheet according to claim 3, wherein the release layer contains the polyethylene wax in a range of 3% by mass to 12% by mass with respect to the total solid content of the cellulose acetate.   The thermal transfer sheet according to claim 3 or 4, wherein a part of the surface of the polyethylene wax protrudes from the surface of the release layer.   The thermal transfer sheet according to any one of claims 1 to 5, wherein a polymerization degree of the cellulose acetate is 100 or more and 300 or less.

Images