JP5885906B2 - Thermal transfer sheet - Google Patents

Description

  The present invention relates to a thermal transfer sheet, and more particularly to a thermal transfer sheet in which a dye transferred (kicked) from a dye layer to the opposite side of a substrate does not retransfer (back) to a protective layer transfer body.

  As a simple printing method, various thermal transfer recording methods are widely used. In each thermal transfer recording method, when obtaining a color image, a thermal transfer sheet in which a large number of color material layers of, for example, yellow, magenta, and cyan (black if necessary) are repeatedly provided in a surface sequence on a continuous base sheet. Is mainly used. In the thermal transfer recording method, the color material layer is melted and softened by heating and transferred onto the transfer target to form an image, and the dye in the color material layer is sublimated by heating and transferred to the transfer target. And sublimation type that forms an image.

  Recently, for the purpose of improving the light resistance, plasticizer resistance, etc. of a printed material, a protective layer transfer body having at least a protective layer is provided on a continuous base sheet in the surface order with the above-described color material layer. An image is formed on a transfer medium by a thermal printer using a body-shaped thermal transfer sheet, and then a protective layer transfer body is transferred onto the formed image. Such an integrated thermal transfer sheet has the advantage that the formation of an image on the transfer target and the transfer of the protective layer onto the formed image can be performed in the same volume, Since it is possible to reduce the size and time of ribbon replacement, it is widely used.

  On the other hand, the above-described integrated thermal transfer sheet has a plurality of winding processes in the manufacturing process, for example, winding immediately after ink coating, winding at the slitter, winding on a bobbin that is a product form, Etc. exist. By the way, while the thermal transfer sheet is stored in a rolled state, the opposite layer, specifically, the color material layer or protective layer transfer body provided on one surface of the substrate, and the opposite surface of the substrate There is a slight transfer of dye between the sides (for example, the heat resistant slipping layer if a heat resistant slipping layer is provided on the back of the substrate). When the winding process is performed a plurality of times, the opposing surfaces are different in each process. Therefore, the dye that has moved (kicked) from the color material layer to the opposite surface side of the base material is transferred to the protective layer transfer body after the winding process. The phenomenon of re-migration (back) occurs. When the protective layer transfer body containing the dye retransferred (backed) in this way is transferred to an image, there is a problem that the image is colored and the image quality is greatly impaired.

  Under such circumstances, Patent Document 1 discloses that a color material layer is provided on one surface of a base material, and the other surface of the base material is composed of cellulose acetate butyrate resin, acrylic resin, and polyvinyl acetal resin. A thermal transfer sheet provided with a heat-resistant slipping layer containing at least one resin selected from the following is disclosed. Patent Document 2 discloses that the Tg of the polyvinyl acetal resin used for the heat resistant slipping layer is limited to 80 ° C. or higher, and the melting point of the phosphoric ester used as a lubricant is limited to 35 ° C. or higher, so that the transition to the protective film is possible. A thermal transfer sheet that suppresses (back) is disclosed.

  However, these thermal transfer sheets suppress the transfer (kick) of the dye layer to the heat-resistant slip layer, and as a result, prevent the re-transfer (back) of the dye from the heat-resistant slip layer. When the dye layer is transferred (kick) to the protective layer, it is no longer possible to prevent retransfer (back) of the dye to the protective layer transfer body.

JP 2008-105371 A JP-A-9-300827

  The present invention has been made in view of such a situation, and even if the opposite side of the base material to which the dye has transferred (kicked) and the protective layer transfer body are rolled back so as to face each other, the opposite side of the base material The main object is to provide a thermal transfer sheet in which the dye does not re-transfer (back) from the side to the outermost surface of the protective layer transfer body.

The present invention for solving the above problems is a thermal transfer in which a protective layer transfer body provided on one surface of a base material so as to be peelable from the base material and one or more dye layers are formed in a surface sequence. The protective layer transfer body has a laminated structure in which a release layer, a protective layer, and an outermost surface layer are laminated in this order from the base material side, and the surface of the outermost surface layer is exposed. to which, on the outermost layer located on the outermost surface of the layer constituting the protective layer transfer member, inorganic pigment ultrafine particles contained in the range of 50 to 100 wt% relative to the total weight of the outermost surface layer are, the inorganic pigment ultrafine particles, alumina, either hydrated alumina, and colloidal silica, the average particle diameter of the inorganic pigment ultrafine particles, 3 nm to 100 nm der is, the transferable protective layer Is located closest to the substrate among the layers constituting The serial release layer, are contained in a polymethyl methacrylate resin, the protective layer, a vinyl chloride - wherein the vinyl acetate copolymer is contained.

  According to the present invention, since the outermost surface layer of the protective layer transfer body constituting the thermal transfer sheet contains the inorganic pigment ultrafine particles, the opposite surface side of the substrate on which the dye has migrated (kicked) and the protective layer transfer body Even if it is rolled back so as to face the outermost surface, the dye does not re-transfer (back) from the opposite surface side of the substrate to the protective layer transfer body.

It is a schematic cross section which shows the thermal transfer sheet which concerns on embodiment of this invention. It is a schematic cross section which shows the thermal transfer sheet which concerns on embodiment of this invention. It is a schematic cross section which shows the thermal transfer sheet which concerns on embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings. 1 and 2 are schematic cross-sectional views showing the thermal transfer sheet according to the embodiment of the present invention, and FIG. 1 is a schematic cross-sectional view showing the thermal transfer sheet in which the protective layer transfer body 2 is composed of one layer. FIG. 2 is a schematic cross-sectional view showing a thermal transfer sheet in which the protective layer transfer body 2 is composed of two layers.

  As shown in FIGS. 1 and 2, the thermal transfer sheets 10 and 20 of the present invention are detachably provided on one surface of the substrate 1 (the upper surface of the substrate 1 in the case shown in FIG. 1). Protective layer transfer body 2 composed of one or more layers (in the case shown in FIG. 1, the protective layer transfer body 2 consisting only of the outermost surface layer 30; in the case shown in FIG. A protective layer transfer body 2 in which two layers including the surface layer 30 are laminated) and one or more dye layers 23 (yellow 23Y, magenta 23M, cyan 23C in the case shown in FIGS. 1 and 2) Are formed in a surface sequential manner. In particular, in the thermal transfer sheet of the present invention, the outermost surface layer 30 located on the outermost surface among the layers constituting the protective layer transfer body 2 is within the range of 50 to 100% by mass with respect to the total mass of the outermost surface layer 30. The present invention is not limited to the present embodiment as long as it is characterized in that it contains ultrafine inorganic pigment particles and satisfies this requirement.

(Base material)
The substrate 1 used in the thermal transfer sheet 10 of the present invention is not particularly limited as long as it has a certain degree of heat resistance and strength, and is the same base as that used in a conventionally known thermal transfer sheet. The material can be used as it is. Examples of such a substrate 1 include polyester films such as polyethylene terephthalate (PET), polycarbonate, polyamide, polyimide, cellulose acetate, polyvinylidene chloride, polyvinyl chloride, polystyrene, fluororesin, polypropylene, polyethylene, ionomer, and other plastic films; glassine Papers such as paper, condenser paper, paraffin paper; cellophane and the like. Further, the base material may be composed of only one kind of the above-mentioned resin, or may be composed of two or more kinds of resins. The base material may be a composite film in which two or more of the plastic film, paper, and cellophane are laminated.

  The thickness of the base material can be appropriately set depending on the material so that the strength and heat resistance thereof are appropriate, and for example, it is preferably about 2 to 100 μm.

(Protective layer transfer body)
As shown in FIGS. 1 and 2, a protective layer transfer body 2 that can be peeled off from the base material 1 is provided on the base material 1. The protective layer transfer body 2 is an essential component in the thermal transfer sheet of the present invention, and is composed of one or more layers including at least the outermost surface layer 30 and is transferred onto the transfer medium during thermal transfer.

  In addition, the outermost surface layer as used in the field of this invention is a layer located in the outermost surface among the layers which comprise the protective layer transfer body 2, and among the layers which comprise the protective layer transfer body 2 provided on the base material 1 Means the layer located at the farthest distance from the substrate 1. That is, as shown in FIG. 1, when the protective layer transfer body 2 is composed of one layer, the one layer becomes the outermost surface layer 30, and as shown in FIG. In the case of the above layer, the layer located at the farthest distance from the base material is the outermost surface layer 30.

(Outermost layer)
The outermost surface layer 30 constituting the thermal transfer sheets 10 and 20 of the present invention contains inorganic pigment ultrafine particles. Since the inorganic pigment ultrafine particles contained in the outermost surface layer 30 is an inorganic material, it is difficult to be dyed by a dye, and since it is a particle, the surface of the outermost surface layer 30 becomes uneven and contacts the heat resistant slipping layer 25. The area can be reduced. Thereby, according to the thermal transfer sheet of the present invention provided with the outermost surface layer 30, even when the dye of the dye layer 23 moves (kicks) to the opposite surface side of the substrate 1 during winding and storage, The dye transferred to the opposite surface side of the substrate 1 is transferred to the outermost surface layer when it is rolled back so that the opposite surface side of the substrate 1 to which the dye has been transferred and the protective layer transfer body 2 face each other. (Back) can be prevented.

  Here, when the content of the inorganic pigment ultrafine particles is less than 50% by mass with respect to the total mass of the outermost surface layer 30, the content of the material more easily dyed by the dye than the content of the inorganic pigment ultrafine particles is Therefore, it is impossible to effectively prevent the dye transferred (kicked) to the opposite surface side of the substrate 1 from retransferring (backing) to the outermost surface layer (protective layer transfer body 2). Therefore, the outermost surface layer 30 constituting the thermal transfer sheet 10 of the present invention is inorganic in the range of 50% by mass to 100% by mass, preferably 60% by mass to 90% by mass with respect to the total mass of the outermost surface layer 30. Pigment ultrafine particles are contained.

  In addition, this invention is not limited by the name of the layer located in the outermost surface among the layers which comprise the protective layer transcription | transfer body 2, Everything located in the outermost surface among the layers which comprise the protective layer transcription | transfer body 2 The name layer can be the outermost layer.

  For example, in the field of thermal transfer sheets, when a layer called an adhesive layer is located on the outermost surface of the protective layer transfer body 2, the adhesive layer becomes the outermost surface layer, and the adhesive layer is within a range of 50 to 100% by mass. The adhesive layer is included in the scope of the present invention as long as it contains inorganic pigment ultrafine particles.

  The inorganic pigment ultrafine particles contained in the outermost surface layer need only have an effect that the dye transferred to the opposite surface side of the substrate 1 does not migrate to the outermost surface layer 30 as described above. Examples of ultrafine particles include silica (colloidal silica), alumina or alumina hydrate (alumina sol, colloidal alumina, cationic aluminum oxide or hydrate, pseudoboehmite, etc.), aluminum silicate, magnesium silicate, magnesium carbonate, Examples thereof include magnesium oxide and titanium oxide. The above inorganic pigment ultrafine particles may be used alone or in combination of two or more. In particular, considering the adhesiveness between the outermost surface layer 30 and the transfer target during thermal transfer, the outermost surface layer 30 contains at least one of colloidal silica and alumina sol as inorganic pigment ultrafine particles, or both. Is preferred.

  The average particle diameter of the inorganic pigment ultrafine particles is not particularly limited, but is 100 nm or less, preferably 50 nm or less, and more preferably 3 to 30 nm. The shape of the inorganic pigment ultrafine particles may be any shape such as a spherical shape, a needle shape, a plate shape, a feather shape, or an amorphous shape.

  For the purpose of facilitating dispersion in a solvent, the above-mentioned inorganic pigment ultrafine particles may be processed into an acidic type by adding a dispersion stabilizer such as hydrochloric acid or acetic acid, or the fine particle charge is a cation. Alternatively, it may be surface-treated. The inorganic pigment ultrafine particles in the present invention may be commercial products such as alumina sol 100 (manufactured by Nissan Chemical Industries, Ltd.) and alumina sol 200 (manufactured by Nissan Chemical Industries, Ltd.).

  In addition, since the outermost surface layer 30 of the present invention containing inorganic pigment ultrafine particles as the main component has adhesiveness, the protective layer transfer body can be transferred onto the transfer body during thermal transfer. That is, the outermost surface layer 30 of the present invention has a function of preventing the dye transferred to the opposite surface side of the substrate 1 from transferring (backing) to the outermost surface layer 30, as well as transferring the protective layer onto the transfer target. It plays a role as an adhesive layer for transferring and bonding the body 2.

  Moreover, the outermost surface layer 30 can contain other components in a proportion of less than 50% by mass, if necessary, in addition to the inorganic pigment ultrafine particles as the main component. Hereinafter, examples of other components contained as necessary will be described.

(Other ingredients)
In order to improve the powder fall off of the outermost surface layer 30 and to improve the adhesiveness, the outermost surface layer 30 is allowed to contain other component A exemplified below within a range not impeding the content of the above-mentioned inorganic pigment ultrafine particles. Also good.

(Other component A)
Examples of the other component A include polyester resins, polyacrylate resins, polyurethane resins, styrene acrylate resins, ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, and butyric acid cellulose. Examples thereof include cellulose resins, polyvinyl acetal resins such as polyvinyl acetoacetal and polyvinyl butyral, polyvinyl pyrrolidone resins, and polyvinyl alcohol resins. These resins may be used alone or in combination of two or more.

  In order to improve the adhesiveness and light resistance of the outermost surface layer 30, the outermost surface layer 30 may contain other component B exemplified below as long as the content of the inorganic pigment ultrafine particles is not hindered. .

(Other component B)
As other component B, ethylene-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate copolymer resin, maleic acid-modified vinyl chloride-vinyl acetate copolymer resin, polyamide resin, polyester resin, polyethylene resin, ethylene-isobutyl acrylate copolymer Polymer resins, butyral resins, polyvinyl acetate and its copolymer resins, ionomer resins, acid-modified polyolefin resins, acrylic and methacrylic (meth) acrylic resins, acrylic ester resins, ethylene (meth) Acrylic acid copolymer, ethylene / (meth) acrylic acid ester copolymer, polymethyl methacrylate resin, cellulose resin, polyvinyl ether resin, polyurethane resin, polycarbonate resin, polypropylene resin, epoxy resin, phenol resin, vinyl Resin, maleic acid resin, alkyd resin, polyethylene oxide resin, urea resin, melamine resin, melamine alkyd resin, silicone resin, rubber resin, styrene butadiene styrene block copolymer (SBS), styrene isoprene styrene block copolymer ( SIS), styrene ethylene butylene styrene block copolymer (SEBS), styrene ethylene propylene styrene block copolymer (SEPS), and other thermoplastic resins. These resins may be used alone or in combination of two or more.

  Further, in order to impart plasticizer resistance and scratch resistance to the image formed on the transferred body, the following examples are given as long as the content of the above-mentioned inorganic pigment ultrafine particles in the outermost surface layer 30 is not hindered. Another component C may be contained.

(Other component C)
Examples of other components C include acrylic resin, cellulose resin, polyvinyl acetal resin, polyester resin, polyethylene, polypropylene, polyvinyl fluoride, polyvinylidene fluoride, polyvinyl chloride, polyvinylidene chloride, ethylene-vinyl alcohol, polyvinyl alcohol, Examples include polymethyl methacrylate, polyether sulfone, polyether ether ketone, polyamide, tetrafluoroethylene-perfluoroalkyl vinyl ether, polyethylene terephthalate, and polyimide. These resins may be used alone or in combination of two or more.

  Further, other components A to C exemplified above may be used in combination. In addition, the other component which can be contained in the outermost surface layer is not limited to the other components A to C exemplified above, and is not limited to the resin. Depending on the function desired for the outermost surface layer 30, a conventionally known component used in the field of the thermal transfer sheet, for example, an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, etc. may be appropriately selected and used. Can do.

  The method for forming the outermost surface layer 30 is not particularly limited, and a gravure coating is prepared by dispersing inorganic pigment ultrafine particles in a solvent and dispersing or dissolving other components contained in the solvent as necessary. It can be formed by applying and drying by a conventionally known forming means such as a method, a roll coating method, a screen printing method, or a reverse roll coating method using a gravure plate.

  It does not specifically limit as a solvent in the said coating liquid, For example, water; Alcohols, such as ethanol and a propanol, and the mixture of water; Furthermore, as a solvent other than the above water-based solvents, cellosolves such as methyl cellosolve and ethyl cellosolve; aromatic solvents such as toluene, xylene and chlorobenzene; ketones such as acetone and methylethylketone; ester solvents such as ethyl acetate and butyl acetate Ethers such as tetrahydrofuran and dioxane; chlorine-based solvents such as chloroform and trichloroethylene; nitrogen-containing solvents such as dimethylformamide and N-methylpyrrolidone; and organic solvents such as dimethyl sulfoxide; Or it is preferable that it is a mixture of water and alcohol.

  Next, another embodiment of the thermal transfer sheet in which the protective layer transfer body 2 is composed of a plurality of layers including the outermost surface layer will be described with reference to FIG. In FIG. 2, a protective layer transfer body in which a protective layer 21 and an outermost surface layer 30 are laminated in this order on one surface of a base material and a dye layer of one or more colors are formed in the surface order. This is a thermal transfer sheet 20.

  When the protective layer transfer body 2 is composed of a plurality of layers including the outermost surface layer 30, the outermost surface layer 30 contains inorganic pigment ultrafine particles in the range of 50 to 100% by mass. For example, the outermost surface layer 30 can be superposed on any conventionally known layer in the field of thermal transfer sheets. For example, as shown in FIG. 2, the resin exemplified by the other component A is mainly used so that the layer containing the inorganic pigment ultrafine particles in the range of 50 to 100% by mass becomes the outermost surface layer 30. The protective layer transfer body 2 may be formed by laminating with the protective layer 21.

  In addition, although not shown, the resin exemplified by the above other component B such that the layer containing the inorganic pigment ultrafine particles in the range of 50 to 100% by mass becomes the outermost surface layer 30 instead of the protective layer 21. The protective layer transfer body 2 may be superposed with a release layer mainly composed of the base material side so that the layer containing the inorganic pigment ultrafine particles in the range of 50 to 100% by mass becomes the outermost surface layer 30. Alternatively, the protective layer transfer body 2 may be formed by laminating the release layer, the protective layer 21, and the outermost surface layer 30 in this order. That is, if the outermost surface layer 30 positioned on the outermost surface of the protective layer transfer body 2 is a layer containing inorganic pigment ultrafine particles in the range of 50 to 100% by mass, any limitation is imposed on the layer configuration of the protective layer transfer body 2. It will never be done.

(Release layer)
In addition, as shown in FIG. 3, a release layer 24 may be provided between the base material 1 and the protective layer transfer body 2 to make the transferability of the protective layer transfer body 2 suitable. The release layer 24 is an arbitrary structure in the thermal transfer sheet of the present invention, and the release layer 24 is unnecessary when the transferability of the protective layer transfer body 2 is high.

  As the release layer 24, a conventionally known resin can be appropriately selected and used as long as it is a resin having excellent release properties. Examples of such resins include waxes, silicone waxes, silicone resins, silicone-modified resins, fluorine resins, fluorine-modified resins, polyvinyl alcohol, acrylic resins, heat-crosslinkable epoxy-amino resins, and heat-crosslinkable alkyd-amino resins. Is mentioned. Moreover, the said resin may be used independently and may mix and use 2 or more types of resin. Further, in addition to the above resin, a cross-linking agent such as an isocyanate compound and a catalyst such as a tin-based catalyst may be used.

The release layer is, for example, a coating solution obtained by dissolving the resin in a solvent, in a region of the surface of the base material where the protective layer transfer body 2 is formed, a gravure coating method, a roll coating method, a screen printing method, It can be formed by applying by a conventionally known forming means such as a reverse roll coating method using a gravure plate so that the coating amount after drying is about 0.5 to 5 g / m ² and drying. . Moreover, a coating liquid can be prepared by dissolving the said resin and the crosslinking agent or catalyst mix | blended as needed in suitable solvents, such as methyl ethyl ketone, toluene, and isopropyl alcohol. Such a coating liquid preferably has a solid content concentration of about 5 to 50% by mass.

  Further, the transfer body is opposed so as to be in contact with the outermost surface layer 30 of the thermal transfer sheet 10, and the protective layer transfer body 2 is transferred onto the transfer body from the heat-resistant slipping layer side by a heating means such as a thermal head or a laser. In this case, the release layer 24 remains on the substrate 1 side.

(Dye layer)
As shown in FIGS. 1 to 3, on one surface of the substrate 1 (on the upper surface of the substrate 1 in the case shown in FIG. 1), one or more dye layers are transferred to the above protective layer. The body 2 and the surface are formed in order. The dye layer 23 is an essential component in the thermal transfer sheet of the present invention. The dye layer 23 may be formed of only one color layer appropriately selected as the dye layer 23 when the desired image is monocolor, or yellow 23Y when the desired image is a full color image. A plurality of dye layers 23 containing dyes having different hues such as magenta 23M, cyan 23C, and black as necessary may be repeatedly formed on the same surface of the same base material in the surface order.

  It does not specifically limit about the dye used for the dye layer 23, A conventionally well-known dye can be selected suitably and can be used. For example, such dyes include diarylmethane dyes; triarylmethane dyes; thiazole dyes; merocyanine dyes; pyrazolone dyes; methine dyes; indoaniline dyes; Azomethine dyes such as azomethine and pyridone azomethine; xanthene dyes; oxazine dyes; cyanostyrene dyes such as dicyanostyrene and tricyanostyrene; thiazine dyes; azine dyes; acridine dyes; benzeneazo dyes; Azo dyes such as azo, isothiazole azo, pyrrole azo, pyrazole azo, imidazole azo, thiadiazole azo, triazole azo, disazo; spiropyran dyes; indolinospiropyran Fee; fluoran dyes; rhodamine lactam dyes; naphthoquinone dyes; anthraquinone dyes; quinophthalone dyes; and the like.

  In the dye layer 23, the dye is 5 to 90% by mass, preferably 10 to 70% by mass, based on the total solid content of the dye layer 23. If the amount of the dye used is less than the above range, the printing density may be lowered, and if it exceeds the above range, the storage stability and the like may be deteriorated.

  As the binder resin for supporting the dye, generally, a resin having heat resistance and appropriate affinity with the dye can be used. Examples of the binder resin include cellulose resins such as ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate and cellulose butyrate; polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetoacetal, polyvinyl pyrrolidone and the like. Vinyl resins; acrylic resins such as poly (meth) acrylates and poly (meth) acrylamides; polyurethane resins; polyamide resins; polyester resins; Among them, cellulose resin, vinyl resin, acrylic resin, urethane resin, polyester resin, etc. are preferable, heat resistance, dye transfer property, etc., vinyl resin is more preferable, polyvinyl butyral, polyvinyl acetoacetal Etc. are more preferable.

  The dye layer 23 may use additives such as a release agent, inorganic fine particles, and organic fine particles as desired. Examples of the release agent include silicone oil and phosphate ester, examples of the inorganic fine particles include carbon black, aluminum, and molybdenum disulfide. Examples of the organic fine particles include polyethylene wax.

The dye layer 23 is prepared by dissolving or dispersing the above-described dye and binder resin in an appropriate organic solvent or water together with an additive to be added as necessary. It can be formed by applying the coating liquid on one surface of the substrate film and drying it by known means such as a reverse roll coating printing method using a printing method, a screen printing method, or a gravure plate. . Examples of the organic solvent include toluene, methyl ethyl ketone, ethanol, isopropyl alcohol, cyclohexanone, dimethylformamide [DMF] and the like. The coating amount of the dye layer 23 is about 0.2 to 6.0 g / m ² , preferably about 0.2 to 3.0 g / m ^{2 on} a dry solid basis.

  According to the thermal transfer sheet of the present invention, even if the dye of the dye layer 23 is transferred (kicked) to the opposite side of the substrate during winding and storage, the outermost surface layer of the protective layer transfer body 2 has an inorganic surface layer. Since the ultrafine pigment particles are contained, the dye transferred to the opposite side of the base material when the opposite side of the base material and the outermost surface layer of the protective layer transfer body 2 face each other It does not re-migrate (back) to the layer. Therefore, even a dye that easily shifts to the opposite side of the substrate 1 (easy to kick) can be suitably used as the dye layer 23 of the present invention.

(Heat resistant slipping layer)
Moreover, as shown in FIGS. 1-3, on the other surface of the base material 1 (the lower surface of the base material 1 in the case shown in FIG. 1), heat resistance, running performance of the thermal head during printing, etc. You may provide the heat-resistant slipping layer 25 for improving. The heat-resistant slip layer 25 has an arbitrary configuration in the thermal transfer sheet of the present invention.

  The heat-resistant slip layer 25 can be formed by appropriately selecting a conventionally known thermoplastic resin or the like. Examples of such thermoplastic resins include polyester resins; polyacrylate resins; polyvinyl acetate resins; styrene acrylate resins; polyurethane resins; polyolefin resins such as polyethylene resins and polypropylene 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 resin; thermoplastic resins such as these, and silicone-modified products thereof. Among these, from the viewpoint of heat resistance, a polyamideimide resin or a modified silicone product thereof can be preferably used.

  In addition to the thermoplastic resin, the heat-resistant slip layer 25 is a mold release agent such as wax, higher fatty acid amide, ester, metal soap, silicone oil, surfactant, etc. for the purpose of improving slip properties; Various additives such as organic powders such as silica; clay, talc, calcium carbonate, etc .;

The method for forming the heat-resistant slip layer 25 is not particularly limited, and a coating liquid obtained by dispersing or dissolving the thermoplastic resin (added with an additive that is optionally blended if necessary) in a solvent is used. It is applied to the other surface of the material 1 (that is, on the surface opposite to the protective layer transfer body 2) by a known means such as a gravure printing method, a screen printing method, a reverse roll coating printing method using a gravure plate, It can be formed by drying. Further, the thickness of the heat resistant slipping layer 25 is preferably ² g / m ² or less in terms of the coating amount after drying, from the viewpoint that a heat transfer sheet having excellent heat resistance and the like is obtained. ² is more preferable.

  Even when the heat resistant slipping layer 25 is formed using a thermoplastic resin from which the dye of the dye layer 23 is likely to migrate (kick) from among the above thermoplastic resins, as described above, the protective layer Since the outermost surface layer of the transfer body 2 contains ultrafine inorganic pigment particles, when the roll is rolled back so that the heat-resistant slipping layer side of the substrate and the outermost surface layer of the protective layer transfer body 2 face each other. The dye that has migrated to the heat-resistant slip layer 25 does not migrate (back) to the outermost surface layer. Therefore, even a thermoplastic resin in which the dye of the dye layer 23 is easy to migrate (easy to kick) can be suitably used as the material of the heat-resistant slip layer 25 of the present invention.

(Heat resistant primer layer)
In addition, a primer layer (not shown) may be provided between the heat resistant slipping layer 25 and the substrate 1 for improving the adhesion between the heat resistant slipping layer 25 and the substrate 1. The primer layer is generally made of a thermoplastic resin, and the thermoplastic resin is not particularly limited as long as it exhibits adhesive properties such as a polyester resin and an acrylic resin.

(Transfer)
The transfer target that can be used for the transfer of the thermal transfer sheet of the present invention is not particularly limited, and examples thereof include those in which a receptor layer having dye acceptability is provided on a conventionally known substrate. Examples of the substrate in the transfer target include plain paper, high-quality paper, tracing paper, plastic film, and the like, and the substrate is not particularly limited. The receiving layer in the transfer target can be formed by a coating method, a forming method using a thermal head, a hot roll, or the like. In addition, as long as the base material itself has dye receptivity, it is not necessary to provide a receiving layer for the transfer target.

(Transfer method)
The thermal transfer sheet 10 of the present invention heats and pressurizes a predetermined portion on the opposite surface side of the substrate 1 (a surface different from the surface on which the protective layer transfer body 2 is provided) by heating means such as a thermal head. Thereby, the dye of the location corresponded to a printing part among the protective layer transfer body 2 and the dye layer 23 can be transcribe | transferred on a to-be-transferred body. There is no particular limitation on the heating means, and transfer may be performed using a heating plate such as a thermal head, a hot plate, a hot stamper, a heat roll, a line heater, or an iron.

Next, an Example is given and this invention is demonstrated further more concretely. Hereinafter, unless otherwise specified, parts or% is based on mass.
(Preparation of coating solution for outermost layer)
Coating solutions 1 to 12 for the outermost surface layer having the following compositions were prepared.

<Coating liquid 1 for outermost layer>
40 parts of alumina sol (alumina sol 200, solid content 10%, manufactured by Nissan Chemical Industries, Ltd.)
Water 12 parts IPA 48 parts

<Coating liquid 2 for outermost surface layer>
30 parts of alumina sol (alumina sol 200, solid content 10%, manufactured by Nissan Chemical Industries, Ltd.)
1 part of polyvinyl pyrrolidone resin (PVP K-90 manufactured by ASP Japan)
Water 21 parts IPA 48 parts

<Coating solution 3 for outermost surface layer>
Alumina sol 20 parts (Alumina sol 200 Nissan Chemical Co., Ltd. solid content 10%)
Polyvinylpyrrolidone resin 2 parts (PVP K-90 manufactured by ASP Japan Co., Ltd.)
Water 30 parts IPA 48 parts

<Coating solution 4 for outermost surface layer>
10 parts of alumina sol (alumina sol 200, solid content 10%, manufactured by Nissan Chemical Industries, Ltd.)
3 parts of polyvinyl pyrrolidone resin (PVP K-90 manufactured by ASP Japan)
Water 39 parts IPA 48 parts

<Coating liquid 5 for outermost layer>
Alumina sol 20 parts (Alumina sol 200 Nissan Chemical Co., Ltd. solid content 10%)
4 parts of vinyl acetate / vinyl pyrrolidone copolymer resin (PVP / VA E-335 manufactured by IPS Japan Co., Ltd., solid content 50%)
Water 30 parts IPA 46 parts

<Coating liquid 6 for outermost surface layer>
10 parts of alumina sol (alumina sol 200, solid content 10%, manufactured by Nissan Chemical Industries, Ltd.)
6 parts of vinyl acetate / vinyl pyrrolidone copolymer resin (PVP / VA E-335 manufactured by ASP Japan Co., Ltd., solid content 50%)
Water 39 parts IPA 45 parts

<Coating solution 7 for outermost surface layer>
Alumina sol 20 parts (Alumina sol 200 Nissan Chemical Co., Ltd. solid content 10%)
2 parts of polyvinyl alcohol resin (Gohsenol KH-20 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
Water 30 parts IPA 48 parts

<Coating liquid 8 for outermost surface layer>
10 parts of alumina sol (alumina sol 200, solid content 10%, manufactured by Nissan Chemical Industries, Ltd.)
3 parts of polyvinyl alcohol resin (Gohsenol KH-20 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
Water 39 parts IPA 48 parts

<Coating liquid 9 for outermost surface layer>
Alumina sol 20 parts (Alumina sol 200 Nissan Chemical Co., Ltd. solid content 10%)
8 parts of polyamide epoxy resin (Sumirez resin 675A, Sumika Chemtex Co., Ltd. solid content 25%)
Water 24 parts IPA 48 parts

<Coating liquid 10 for outermost surface layer>
10 parts of alumina sol (alumina sol 200, solid content 10%, manufactured by Nissan Chemical Industries, Ltd.)
12 parts of polyamide epoxy resin (Sumirez resin 675A, Sumika Chemtex Co., Ltd. solid content 25%)
Water 30 parts IPA 48 parts

<Coating liquid 11 for outermost surface layer>
Alumina sol 20 parts (Alumina sol 200 Nissan Chemical Co., Ltd. solid content 10%)
Polyurethane resin 5 parts (Hydran CP-7020 DIC Corporation solid content 40%)
Water 27 parts IPA 48 parts

<Coating liquid 12 for outermost surface layer>
10 parts of alumina sol (alumina sol 200, solid content 10%, manufactured by Nissan Chemical Industries, Ltd.)
Polyurethane resin 7.5 parts (Hydran CP-7020 DIC Corporation solid content 40%)
Water 34.5 parts IPA 48 parts

Example 1
As a base sheet, a polyethylene terephthalate film having a thickness of 6 μm (manufactured by Lumirror Toray Co., Ltd.) was used. On one surface of the base sheet, the following heat-resistant slipping layer coating solution was applied to a gravure coater. The heat-resistant slipping layer was formed by applying and drying after drying so that the coating amount after drying was 1.0 g / m ² . Next, on the surface opposite to the surface on which the heat-resistant slip layer of the substrate sheet is formed, the above outermost layer coating solution 1 is applied as a protective layer transfer body after drying using a gravure coater. The outermost surface layer was formed by coating and drying so that the work amount was 0.2 g / m ² , thereby forming a protective layer transfer body consisting only of the outermost surface layer, and the thermal transfer sheet of Example 1 was manufactured.

<Coating fluid for heat resistant slipping layer>
13.6 parts of polyvinyl butyral resin (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
0.6 parts of polyisocyanate curing agent (Takenate D218, manufactured by Mitsui Chemicals Polyurethanes)
Phosphate 0.8 parts (Plysurf A208N, Daiichi Kogyo Seiyaku Co., Ltd.)
Toluene 42.5 parts Methyl ethyl ketone 42.5 parts

(Example 2)
A thermal transfer sheet of Example 2 was produced in the same manner as in Example 1 except that the outermost surface layer coating liquid 1 was changed to the outermost surface layer coating liquid 2 described above.

(Example 3)
A thermal transfer sheet of Example 3 was produced in the same manner as in Example 1 except that the outermost surface layer coating solution 1 was changed to the outermost surface layer coating solution 3 described above.

Example 4
A thermal transfer sheet of Example 4 was produced in the same manner as in Example 1 except that the outermost surface layer coating solution 1 was changed to the outermost surface layer coating solution 5 described above.

(Example 5)
A polyethylene terephthalate film (Lumirror, manufactured by Toray Industries, Inc.) having a thickness of 6 μm was used as the base sheet, and the same heat-resistant slipping layer coating liquid as that of Example 1 was applied to one surface of the base sheet. Was coated with a gravure coater so that the coating amount after drying was 1.0 g / m ^2, and dried to form a heat-resistant slipping layer. Next, on the surface opposite to the surface on which the heat-resistant slip layer of the substrate sheet is formed, the following release layer coating solution is applied using a gravure coater, and the coating amount after drying is 1.0 g / A release layer is formed by applying and drying to m ^2, and the coating solution 1 for the outermost surface layer is coated on the release layer with a gravure coater and the coating amount after drying is 0.2 g. / M ² is applied and dried to form the outermost surface layer, thereby forming a protective layer transfer body in which the release layer and the outermost surface layer are laminated in this order, and the thermal transfer sheet of Example 5 is manufactured. did.

<Coating liquid for release layer>
20 parts of polymethyl methacrylate resin (Dianar BR-87, manufactured by Mitsubishi Rayon Co., Ltd.)
Toluene 40 parts Methyl ethyl ketone 40 parts

(Example 6)
A thermal transfer sheet of Example 6 was produced in the same manner as in Example 5 except that the outermost surface layer coating liquid 1 was changed to the outermost surface layer coating liquid 2 described above.

(Example 7)
A thermal transfer sheet of Example 7 was produced in the same manner as in Example 5 except that the outermost surface layer coating liquid 1 was changed to the outermost surface layer coating liquid 3 described above.

(Example 8)
A thermal transfer sheet of Example 8 was produced in the same manner as in Example 5 except that the outermost surface layer coating liquid 1 was changed to the outermost surface layer coating liquid 5 described above.

Example 9
A polyethylene terephthalate film (Lumirror, manufactured by Toray Industries, Inc.) having a thickness of 6 μm was used as the base sheet, and the same heat-resistant slipping layer coating liquid as that of Example 1 was applied to one surface of the base sheet. Was coated with a gravure coater so that the coating amount after drying was 1.0 g / m ^2, and dried to form a heat-resistant slipping layer. Next, on the surface opposite to the surface on which the heat-resistant slip layer of the base material sheet is formed, the coating liquid for the release layer similar to that of Example 5 is applied using a gravure coater, and the coating amount after drying is A release layer is formed by applying and drying to 1.0 g / m ^2, and the following protective layer coating solution is dried on the release layer using a gravure coater and the coating amount after drying is 1 A protective layer is formed by applying and drying to 0.0 g / m ^2, and the coating liquid 1 for the outermost surface layer is coated on the protective layer using a gravure coater and the coating amount after drying is By applying and drying to form 0.2 g / m ² to form an outermost surface layer, a protective layer transfer body in which a release layer, a protective layer, and an outermost surface layer are laminated in this order is formed. 9 thermal transfer sheets were produced.

<Coating liquid for protective layer>
24 parts of vinyl chloride-vinyl acetate copolymer (Solvine CNL, manufactured by Nissin Chemical Industry Co., Ltd.)
6 parts of UV absorber (Chinubine 900, manufactured by Ciba Japan Co., Ltd.)
Toluene 35 parts Methyl ethyl ketone 35 parts

(Example 10)
A thermal transfer sheet of Example 10 was produced in the same manner as in Example 9, except that the outermost surface layer coating liquid 1 was changed to the outermost surface layer coating liquid 2 described above.

(Example 11)
A thermal transfer sheet of Example 11 was produced in the same manner as in Example 9, except that the outermost surface layer coating solution 1 was changed to the outermost surface layer coating solution 3 described above.

(Example 12)
A thermal transfer sheet of Example 12 was produced in the same manner as in Example 9, except that the outermost surface layer coating solution 1 was changed to the outermost surface layer coating solution 5 described above.

(Example 13)
A thermal transfer sheet of Example 13 was produced in the same manner as in Example 9, except that the outermost surface layer coating solution 1 was changed to the outermost surface layer coating solution 7 described above.

(Example 14)
A thermal transfer sheet of Example 14 was produced in the same manner as in Example 9 except that the outermost surface layer coating solution 1 was changed to the outermost surface layer coating solution 9 described above.

(Example 15)
A thermal transfer sheet of Example 15 was produced in the same manner as in Example 9, except that the outermost surface layer coating liquid 1 was changed to the outermost surface layer coating liquid 11.

(Comparative Example 1)
A thermal transfer sheet of Comparative Example 1 was produced in the same manner as in Example 1 except that the outermost surface layer coating solution 1 was changed to the outermost surface layer coating solution 4 described above.

(Comparative Example 2)
A thermal transfer sheet of Comparative Example 2 was produced in the same manner as in Example 1 except that the outermost surface layer coating solution 1 was changed to the outermost surface layer coating solution 6 described above.

(Comparative Example 3)
A thermal transfer sheet of Comparative Example 3 was produced in the same manner as in Example 5 except that the outermost surface layer coating solution 1 was changed to the outermost surface layer coating solution 4 described above.

(Comparative Example 4)
A thermal transfer sheet of Comparative Example 4 was produced in the same manner as in Example 5 except that the outermost surface layer coating solution 1 was changed to the outermost surface layer coating solution 6 described above.

(Comparative Example 5)
A thermal transfer sheet of Comparative Example 5 was produced in the same manner as in Example 9, except that the outermost surface layer coating solution 1 was changed to the outermost surface layer coating solution 4 described above.

(Comparative Example 6)
A thermal transfer sheet of Comparative Example 6 was produced in the same manner as in Example 9, except that the outermost surface layer coating solution 1 was changed to the outermost surface layer coating solution 6 described above.

(Comparative Example 7)
A thermal transfer sheet of Comparative Example 7 was produced in the same manner as in Example 9, except that the outermost surface layer coating solution 1 was changed to the outermost surface layer coating solution 8 described above.

(Comparative Example 8)
A thermal transfer sheet of Comparative Example 8 was produced in the same manner as in Example 9, except that the outermost surface layer coating solution 1 was changed to the outermost surface layer coating solution 10 described above.

(Comparative Example 9)
A thermal transfer sheet of Example 9 was produced in the same manner as in Example 9, except that the outermost surface layer coating solution 1 was changed to the outermost surface layer coating solution 12 described above.

(Comparative Example 10)
A thermal transfer sheet of Comparative Example 10 was produced in the same manner as in Example 9 except that the adhesive protective layer was not applied.

  In the right column of Table 1, the content (%) of the inorganic pigment ultrafine particles contained in the outermost surface layer of the thermal transfer sheets of Examples 1 to 15 and Comparative Examples 1 to 10 and the protective layer transfer body are configured. Indicates the number of layers.

<< Back evaluation test >>
The ink ribbon of Canon Inc. color ink / paper set KP-36IP (trade name) is placed with the heat-resistant slipping layer and the magenta dye layer facing each other, a 20 kg / cm ² load is applied, 40 ° C., and humidity 90%. It was stored for 96 hours under the environment, and a heat-resistant slipping layer in which the dye in the dye layer was transferred (kicked) was prepared. The heat-resistant slipping layer and the thermal transfer sheets of Examples 1 to 15 and Comparative Examples 1 to 10 were opposed to the heat-resistant slipping layer and the protective layer transfer body, applied with a load of 20 kg / cm ² , 60 ° C., humidity Stored in a 20% environment for 24 hours. Thereafter, the protective layer transfer body to which the dye of the heat resistant slipping layer has transferred (backed) and the image receiving surface of the image receiving paper are superposed, and using a laminating tester (Lamipacker LPD2305PRO, manufactured by Fuji Plastics), 105 ° C., 4 mm. Transfer was performed at / sec / line. Further, the substrate sheet was peeled off from the image receiving paper, and the hue of the transfer portion was measured using Gretag Spectrolino (D65 light source, viewing angle 2 °) manufactured by Gretag, and the color difference was calculated by the following formula and evaluated based on the following criteria. . The evaluation results are shown in Table 1. As the image receiving paper, Canon Inc. color ink / paper set KP-36IP (trade name) was used.

(Color difference calculation formula)
ΔE ^* = ((difference between L ^* values before and after facing) ² + (difference between a ^* values before and after facing) ² + (difference between b ^* values before and after facing) ² ) ^1/2

(Evaluation criteria)
◎: Color difference ΔE ^* between the transfer product transferred from the unpreserved protective layer and the transfer product transferred from the backed protective layer transfer material is less than 1.5 ○: The transfer product transferred from the non-preserved protective layer and the back The color difference ΔE ^* of the transferred product obtained by transferring the transferred protective layer transfer product is 1.5 or more and less than 2.5 Δ: the transferred product obtained by transferring the unprotected protective layer and the transferred product obtained by transferring the backed protective layer transfer product color difference Delta] E ^* is 2.5 or more and 3.5 or less × a: unsaved and transcripts transferring the protective layer, the color difference of the transcripts transferred protective layer transfer member was back Delta] E ^* is 3.5 or more

<< Adhesion evaluation test >>
Using the thermal transfer sheets of Examples 1 to 15 and Comparative Examples 1 to 10, combined with a thermal transfer image receiving sheet of a color ink / paper set KP-36IP (trade name) manufactured by Canon Inc., and a protective layer transfer body under the following conditions After 30 minutes have passed after printing, attach a cellophane tape (registered trademark) on the protective layer transfer area by rubbing it twice with your thumb, and then perform 90 ° vertical peeling immediately, and then the protective layer for each gradation. The presence or absence of the transfer member was examined and evaluated based on the following criteria. The evaluation results are shown in Table 1.

(Printing conditions)
Thermal head: KGT-217-12MPL20 (manufactured by Kyocera Corporation)
Heating element average resistance value: 2994 (Ω)
Main scanning direction printing density; 300 dpi
Sub-scanning direction print density; 300 dpi
Applied power: 0.10 (w / dot)
1 line cycle: 5 (msec.)
Printing start temperature; 40 (° C)
Applied pulse (gradation control method): Using a multi-pulse test printer that can vary the number of divided pulses from 0 to 255 in one line period and having a pulse length obtained by equally dividing one line period into 256 The duty ratio of the divided pulses was fixed at 70%, and the number of pulses per line period was fixed at 180.

(Evaluation criteria)
◯: A protective layer transfer body remained on the printed matter.
X: The protective layer transfer body was peeled off by tape peeling.

<< Light resistance evaluation >>
Printing similar to the above adhesive evaluation test, except that the color transfer ink / paper set KP-36IP (trade name) manufactured by Canon Inc. was combined with the thermal transfer image receiving sheet and the number of applied pulses per line cycle was changed to the following. Thermal transfer was performed under the conditions to form a gray 16 gradation gradation image.

(Number of applied pulses)
By increasing the number of pulses per line period from 0 to 0, 17 in 2 steps, 34 in 2 steps, and 17 pulses from 0 to 255, depending on the gradation, from 0 steps to 15 steps Up to 16 gradations were controlled.

  Next, using the thermal transfer sheets of Examples 1 to 15 and Comparative Examples 1 to 10 on the gradation image formed by the above method, the adhesive evaluation test and the above except that the number of pulses per line cycle was fixed to 180. The protective layer transfer body was transferred under the same printing conditions.

The printed matter obtained by transferring the protective layer transfer body obtained above was subjected to a light resistance test using a xenon fade meter under the following conditions.
Irradiation tester: Atlas Ci35
Light source: Xenon lamp Filter: Inside = IR filter, Outside = soda lime glass black Panel temperature: 45 ° C
Irradiation intensity: 1.2 (W / m ² ) Measured value at 420 (nm) Irradiation energy: 400 (kJ / m ² ) Measured value at 420 (nm)

Next, the optical reflection density of the gray image is measured with a visual filter using an optical densitometer (manufactured by GretagMacbeth, Macbeth RD-918), and the optical reflection density before and after irradiation is measured for a step where the optical reflection density before irradiation is around 1.0. The change in density was measured, the remaining rate was calculated by the following formula, and the light resistance of each thermal transfer image-receiving sheet was evaluated. The evaluation results are shown in Table 1.
Residual rate (%) = (optical reflection density after irradiation / optical reflection density before irradiation) × 100

(Evaluation criteria)
◎: Residual rate 80% or more ○: Residual rate 70% or more and less than 80% ×: Residual rate less than 70%

<< Plasticizer resistance test >>
The image surface of the printed matter to which the protective layer transfer body obtained by the same method as the light resistance evaluation was transferred and Altron (sheet made of vinyl chloride) manufactured by Mitsubishi Chemical Corporation were overlapped to obtain 0.78 N / cm ^2. The condition after leaving for 48 hours in a storage environment of 50 ° C. dry was observed with the naked eye, and the plasticizer resistance was evaluated according to the following criteria. The evaluation results are shown in Table 1. The plasticizer resistance test was performed only on the thermal transfer sheets of Examples 5 to 15 and Comparative Examples 3 to 10 in which the protective layer transfer body was composed of two or more layers.

(Evaluation criteria)
A: No missing image was observed.
○: Some missing images were observed.
X: Image omission is remarkable and the original image cannot be distinguished.

As is clear from Table 1, the thermal transfer sheets of Examples 1 to 15 in which the content of the inorganic pigment ultrafine particles is included in the scope of the present application are all less than 2.5 in color difference ΔE ^* and effectively prevent the back. I was able to confirm.

  Moreover, it has confirmed that the thermal transfer sheet of Examples 1-15 obtained favorable evaluation in both adhesiveness and light resistance. Moreover, it has confirmed that the thermal transfer sheet of Examples 5-15 in which the number of layers which comprise a protective layer transfer body is 2 or more obtains favorable plasticizer resistance.

DESCRIPTION OF SYMBOLS 1 Base material 2 Protective layer transfer body 10 and 20 Thermal transfer sheet 21 Protective layer 23 Dye layer 24 Release layer 25 Heat resistant slipping layer 30 Outermost surface layer

Claims (2)

A thermal transfer sheet in which a protective layer transfer body provided on one surface of a base material so as to be peelable from the base material and a dye layer of one or more colors are formed in a surface sequence,
The protective layer transfer body has a laminated structure in which a release layer, a protective layer, and an outermost surface layer are laminated in this order from the base material side, and the outermost surface layer has its surface exposed,
The outermost layer located on the outermost surface of the layer constituting the protective layer transfer member, which is contained in the inorganic pigment ultrafine particles in the range of 50 to 100 wt% relative to the total weight of the outermost surface layer,
The inorganic pigment ultrafine particles are any of alumina, alumina hydrate, and colloidal silica,
The average particle diameter of the inorganic pigment ultrafine particles, Ri 3nm~100nm der,
The release layer located closest to the base material among the layers constituting the transferable protective layer contains a polymethyl methacrylate resin,
A thermal transfer sheet , wherein the protective layer contains a vinyl chloride-vinyl acetate copolymer .   The heat transfer sheet according to claim 1, wherein a heat-resistant slip layer is formed on the other surface of the substrate.

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