JP2020055287A - Thermal transfer sheet, thermal transfer printer and cleaning method of thermal head - Google Patents

Abstract

To provide a thermal transfer sheet capable of preventing foil peeling at a detection mark part, with high thermal head cleaning properties, and capable of effectively preventing an irregularity from occurring at a printed matter, and also to provide a thermal transfer printer suitable for using the thermal transfer sheet and a cleaning method of a thermal head.SOLUTION: A thermal transfer sheet includes a base material 11, and a dye layer 12 and a transfer layer 13 field-sequentially on one side of the base material 11. The thermal transfer sheet further includes a detection mark 14 at least at one location from among an unwinding initiation region, a vicinity of a boundary between the unwinding initiation region and the dye layer, and a non-transfer region in a vicinity of a boundary between the dye layer 12 and the transfer layer 13, which is on the other side of the base material 11. The detection mark 14 includes a filler with an average particle diameter of 0.3 μm or larger.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thermal transfer sheet, a thermal transfer printer, and a method for cleaning a thermal head.

2. Description of the Related Art Conventionally, a sublimation type thermal transfer method is known as a method for producing a print having an image formed on a transfer target.
This is a thermal transfer sheet having a back layer, a base material and a dye layer, and a transfer object are superimposed, and then, when these are passed between a thermal head provided in a thermal transfer printer and a platen roller, the thermal transfer sheet By transferring the sublimable dye in the dye layer to the transfer target by heating the transfer target by the thermal head from the back side of the thermal transfer sheet by the thermal head and pressing the thermal transfer sheet against the transfer target, image formation is achieved. Done.

In addition, a transfer layer is transferred onto an image formed on an object to be transferred, for the purpose of improving the durability and the like of a printed matter produced by a sublimation thermal transfer method.
Specifically, the transfer target, a back layer, a substrate and a thermal transfer sheet having a transfer layer are superimposed, and then, when these are passed between a thermal head provided in a thermal transfer printer and a platen roller, The transfer layer is transferred onto the image formed on the transfer body by pressing the thermal transfer sheet against the transfer body and heating the thermal transfer sheet from the back layer side by the thermal head.
Further, a thermal transfer sheet provided with a dye layer and a transfer layer in a plane-sequential manner is also widely known (Patent Document 1).

  In such a thermal transfer sheet, detection marks are provided between the dye layers and between the dye layers and the transfer layer, whereby the transfer start position and the transfer end position of the thermal head are determined (Patent Document 2).

  In recent years, from the viewpoint of cost reduction and improvement in printing speed, there has been no provision for a blank portion for providing a detection mark such as a thermal transfer sheet proposed in Patent Document 2, and the formation of the detection mark on the dye layer and the transfer layer has been improved. Is being done.

  However, in such a thermal transfer sheet, there is a possibility that foil may fall off at the detection mark portion formed on the transfer layer. This is considered to be due to the fact that the coating liquid for forming the detection mark applied onto the transfer layer permeates the transfer layer during the formation of the detection mark, resulting in a decrease in the adhesion between the transfer layer and the base material.

In addition, when continuously producing a print using such a thermal transfer sheet, head residues are deposited on a thermal head provided in the printer, and a formed image may be missing or blurred, thereby deteriorating the quality of the print. There was a need for improvement.
For example, in the thermal transfer sheet proposed in Patent Document 3, the thermal head can be cleaned by providing a back layer containing a curable resin and a filler on the opposite side of the transfer layer with the base material interposed therebetween. Further, in Patent Document 3, a layer containing carbon black and a fluorescent color former is formed on the entire surface of the substrate on the back layer side, which corresponds to the position of the dye layer.

  However, when trying to produce a print using the thermal transfer sheet proposed in Patent Document 3, when forming an image and transferring the transfer layer, the thermal head applies the back layer containing the filler to the transfer target body. Is pressed in a heated state, so that irregularities due to the filler contained in the back layer and color unevenness due to the irregularities may occur on the surface of the print, and the quality thereof may be impaired.

JP 2018-051914 A JP 2012-240278 A JP 2011-56893 A

The present invention has been made in view of the above problems, and a problem to be solved is to prevent the detection mark portion from falling off the foil, have a high thermal head cleaning property, and have irregularities on a printed material. An object of the present invention is to provide a thermal transfer sheet that can effectively prevent occurrence of the heat transfer sheet.
Another object of the present invention is to provide a thermal transfer printer suitable for using the thermal transfer sheet and a method for cleaning a thermal head using the thermal transfer sheet.

  The thermal transfer sheet of the present invention is provided with a base material, a dye layer and a transfer layer on one surface of the base material in a plane sequence, and on the other surface of the base material, an unwinding start area, an unwinding start A detection mark is provided in at least one portion of the non-transfer region near the boundary between the region and the dye layer, and near the boundary between the dye layer and the transfer layer, and the detection mark includes a filler having an average particle diameter of 0.3 μm or more. It is characterized by the following.

  In one embodiment, the average particle diameter of the filler is 2 μm or more and 100 μm or less.

  In one embodiment, the content of the filler in the detection mark is 2% by mass or more and 40% by mass or less.

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

  In one embodiment, the thermal transfer sheet of the present invention further includes a detection mark on the other surface of the base material, near a boundary between the dye layers, and in a non-transfer area.

  In one embodiment, the thermal transfer sheet of the present invention further includes a back layer so as to be surface-sequential with the detection mark or between the base material and the detection mark.

  In one embodiment, the width of the detection mark is equal to or larger than the printing margin width of the transfer target body and equal to or smaller than the width of the heating portion provided in the thermal head.

The thermal transfer printer of the present invention is used for producing a print using the thermal transfer sheet,
It is characterized by comprising a thermal head, a platen roller, a detection mark detection sensor, and means for controlling opening and closing of the thermal head and the platen roller.

  In one embodiment, the thermal transfer printer of the present invention further includes a transfer object detection sensor.

The thermal head cleaning method of the present invention is a step of preparing the thermal transfer sheet and the thermal transfer printer, and a detection mark provided on the thermal transfer sheet, in a state where the thermal head and the platen roller sandwich the detection mark, The method includes a step of passing the thermal head so as to be in contact therewith.

  In one embodiment, the temperature of the heat generating portion of the thermal head in the passing step is less than 100 ° C.

  In one embodiment, in the passing step, the detection mark provided on the thermal transfer sheet is reciprocated between the thermal head and the platen roller.

According to the present invention, it is possible to provide a thermal transfer sheet that can prevent the foil of the detection mark from falling off, has high thermal head cleaning properties, and can effectively prevent the occurrence of irregularities or the like on a print.
Further, it is possible to provide a thermal transfer printer and a thermal head cleaning method suitable for using the thermal transfer sheet.

FIG. 1 is a schematic sectional view illustrating an embodiment of a thermal transfer sheet of the present invention. FIG. 1 is a schematic sectional view illustrating an embodiment of a thermal transfer sheet of the present invention. FIG. 1 is a schematic sectional view illustrating an embodiment of a thermal transfer sheet of the present invention. FIG. 1 is a schematic sectional view illustrating an embodiment of a thermal transfer sheet of the present invention. FIG. 1 is a schematic view illustrating an embodiment of a thermal transfer printer of the present invention. FIG. 3 is a schematic diagram for explaining an embodiment of the thermal head cleaning method of the present invention. FIG. 3 is a schematic diagram for explaining an embodiment of the thermal head cleaning method of the present invention. FIG. 3 is a schematic diagram for explaining an embodiment of the thermal head cleaning method of the present invention. FIG. 3 is a schematic diagram for explaining an embodiment of the thermal head cleaning method of the present invention. FIG. 3 is a schematic diagram for explaining an embodiment of the thermal head cleaning method of the present invention. FIG. 4 is a schematic cross-sectional view illustrating a thermal transfer sheet manufactured in Comparative Example 1. FIG. 9 is a schematic cross-sectional view illustrating a thermal transfer sheet manufactured in Comparative Example 2.

(Thermal transfer sheet)
The thermal transfer sheet according to the present invention is provided with a substrate, a dye layer and a transfer layer on one side of the substrate in a sequential order, and on the other side of the substrate, an unwinding start area (hereinafter, referred to as a case). The unwinding start area provided in the thermal transfer sheet is referred to as an unwinding start area A), a non-transfer area near a boundary between the unwind start area A and the dye layer, and a non-transfer area near a boundary between the dye layer and the transfer layer. At least one detection mark is provided in the area.

In one embodiment, a thermal transfer sheet 10 according to the present invention includes, as shown in FIG. 1, a substrate 11, a dye layer 12 and a transfer layer 13 on one surface of the substrate 11, and 11, on the other surface of the non-transfer area near the boundary between the unwinding start area A and the dye layer 12 and the non-transfer area near the boundary between the dye layer 12 and the transfer layer 13. Prepare.
In one embodiment, as shown in FIG. 2, the thermal transfer sheet 10 is provided with a plurality of dye layers 12 in a plane-sequential manner, and on the other surface of the substrate 11, a non-transfer area between the dye layers 12 is provided. Is provided with a detection mark 14.
In one embodiment, as shown in FIGS. 1 and 2, the thermal transfer sheet 10 includes a back surface layer 15 on the other surface of the base material 11 so as to be in the order of the detection marks 14.
Further, in one embodiment, as shown in FIG. 3, the thermal transfer sheet 10 includes a back layer 15 between the base material 11 and the detection mark 14.
Hereinafter, each layer included in the thermal transfer sheet according to the present invention will be described.

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

As the base material, for example, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), 1,4-polycyclohexylene dimethylene terephthalate, terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymer and the like Polyester such as polyester, nylon 6 and nylon 6,6, polyolefin such as polyethylene (PE), polypropylene (PP) and polymethylpentene, polyvinyl chloride, polyvinyl alcohol (PVA), polyvinyl acetate, vinyl chloride-vinyl acetate Copolymers, vinyl resins such as polyvinyl butyral and polyvinyl pyrrolidone (PVP), (meth) acrylic resins such as polyacrylate, polymethacrylate and polymethyl methacrylate, poly Imide resins such as imide and polyetherimide, cellophane, cellulose acetate, nitrocellulose, cellulose resins such as cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB), styrene resins such as polystyrene (PS), polycarbonate, In addition, a film composed of an ionomer resin or the like (hereinafter, simply referred to as “resin film”) can be used.
Among the above-mentioned resins, polyesters such as PET and PEN are preferred from the viewpoint of heat resistance and mechanical strength, and PET is particularly preferred.
In the present invention, “(meth) acryl” includes both “acryl” and “methacryl”. Further, “(meth) acrylate” includes both “acrylate” and “methacrylate”.

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

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

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

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

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

  Further, the dye layer can include additives such as a filler, a plasticizer, an antistatic material, an ultraviolet absorber, organic particles, a release agent, and a dispersant.

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

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

(Transfer layer)
The thermal transfer sheet of the present invention is provided with a transfer layer on a base material so that the transfer layer is arranged in the order of the dye layer.
In one embodiment, the transfer layer comprises a release layer.
In one embodiment, the transfer layer includes an adhesive layer on the outermost surface.

  The release layer contains at least one resin material, and examples thereof include (meth) acrylic resin, polyester, polyamide, vinyl resin, imide resin, and cellulose resin. Among them, (meth) acrylic resin is preferable from the viewpoint of transferability of the transfer layer.

  The content of the resin material in the release layer is not particularly limited, and may be, for example, 50% by mass or more and 100% by mass or less.

  In one embodiment, the release layer comprises a wax, for example, natural waxes such as beeswax, spermaceti, wood wax, rice bran wax, carnauba wax, candelilla wax and montan wax, paraffin wax, microcrystalline wax, oxidized wax, ozokerite. , Synthetic waxes such as ceresin, ester wax and polyethylene wax, higher saturated fatty acids such as margaric acid, lauric acid, myristic acid, palmitic acid, stearic acid, freunic acid and behenic acid, and higher saturated monohydric alcohols such as stearyl alcohol and behenyl alcohol And higher esters such as fatty acid esters of sorbitan and sorbitan, and higher fatty acid amides such as stearic acid amide and oleic acid amide.

  The content of the wax in the release layer is not particularly limited, but may be, for example, 20% by mass or more and 100% by mass or less. Thereby, the transferability of the transfer layer can be further improved.

  Further, the release layer can include the above-mentioned additive.

  The thickness of the release layer is preferably 0.1 μm or more and 3 μm or less, more preferably 0.3 μm or more and 1.5 μm or less. Thereby, the transferability of the transfer layer can be further improved.

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

  In one embodiment, the adhesive layer includes at least one type of thermoplastic resin that softens when heated and exhibits adhesion. Examples of the thermoplastic resin include, for example, vinyl resins such as polyester, ethylene-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, (meth) acrylic resin, polyurethane, cellulose resin, polyamide, polyolefin, and styrene resin. Chlorinated resin.

  The content of the thermoplastic resin in the adhesive layer is not particularly limited, but is, for example, preferably 50% by mass or more, and more preferably 60% by mass or more. Thereby, the adhesiveness of the adhesive layer to the transfer object can be improved.

  The adhesive layer may contain the above-mentioned additive within a range that does not impair the characteristics of the present invention.

  The thickness of the adhesive layer is not particularly limited, but may be, for example, 0.05 μm or more and 0.5 μm or less. Thereby, the adhesiveness of the adhesive layer to the transfer object can be improved.

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

(Detection mark)
In the thermal transfer sheet of the present invention, the detection mark includes a filler, and is a surface opposite to the surface on which the dye layer and the transfer layer of the base material are provided, and the unwinding start area A, the unwinding start area A and the dye It is provided in at least one of a non-transfer region near the boundary between the layers and a non-transfer region near the boundary between the dye layer and the transfer layer. When the thermal transfer sheet has a plurality of dye layers, the detection mark may be provided in a non-transfer area near a boundary between the dye layers.
With such a configuration, it is possible to effectively prevent the detection mark portion from falling off the foil. Further, in the thermal transfer sheet of the present invention, the detection mark is provided in a region that is not transferred to the transfer target by the thermal head provided in the printer, and the unevenness or the like on the print due to the filler included in the detection mark is provided. The thermal head can be cleaned while preventing occurrence.

  As shown in FIG. 1, the unwinding start area A of the thermal transfer sheet is an area provided before the dye layer of the unwinded thermal transfer sheet where transfer is not performed, and is used for determining a transfer position and the like. Refers to the area. Note that a dye layer and a transfer layer may be formed in the unwinding start area A, but transfer for forming a print is not performed.

In addition, as shown in FIG. 1 and the like, the vicinity of the boundary means both the unwinding start area A and the position where the dye layer is provided, both the positions where the adjacent dye layers are provided, and the dye layer and the transfer layer. The position may overlap with both of the provided positions.
Further, only one of the positions where the dye layer or the transfer layer is provided, for example, as shown in FIG. 4, may be a position overlapping with the leading end in the supply direction of the position where each dye layer and the transfer layer are provided.
Further, when a blank portion is provided between the dye layer and the dye layer and between the dye layer and the transfer layer, this region is also included near the boundary in the present invention.

  Further, in the thermal transfer sheet of the present invention, the detection mark includes the unwinding start area A, a non-transfer area near the boundary between the unwinding start area A and the dye layer, the vicinity of the boundary between the dye layer and the dye layer, and the dye layer. It is preferable to provide it in any of the non-transfer areas near the boundary with the transfer layer. Thereby, the thermal head cleaning effect of the thermal transfer sheet can be further improved.

The detection mark includes at least one type of filler, and the average particle diameter of the filler is 0.3 μm or more, whereby the thermal head cleaning effect and the blocking resistance of the thermal transfer sheet can be improved. The average particle size of the filler is preferably 2 μm or more and 200 μm or less, more preferably 5 μm or more and 100 μm or less.
Thereby, the thermal head cleaning effect and the blocking resistance of the thermal transfer sheet can be further improved.
In the present invention, the average particle diameter of the filler means a median diameter D50 measured by a laser diffraction method.

The filler is not particularly limited as long as it satisfies the condition of the average particle diameter, and may be an organic filler or an inorganic filler, for example, glass fiber, carbon fiber, talc, Clay, mica, kaolin, silicon nitride, potassium titanate, barium sulfate, calcium carbonate, sodium phosphate, fluorite, gold, silver, iron, aluminum, diamond, and (meth) acrylic resin, vinyl resin, polyester, polyolefin, etc. Resin particles composed of the above resin material.
Among them, talc is preferable because a high cleaning effect can be expected while preventing abrasion of the thermal head.

  The content of the filler in the detection mark is preferably 2% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 35% by mass or less. Thereby, the thermal head cleaning effect of the thermal transfer sheet can be further improved.

  The detection mark includes a detection material, and the detection material may be an optical detection material such as carbon black, graphite or titanium oxide, an invisible light absorbing material, or a magnetic detection material, It may be a sensing material that emits fluorescence in response to specific electromagnetic wave irradiation. Among them, carbon black is preferable.

  In one embodiment, the detection mark includes at least one type of resin material, and includes, for example, (meth) acrylic resin, polyester, polyamide, vinyl resin, imide resin, and cellulose resin. In one embodiment, the back layer contains, as a resin material, a two-part curable resin that is cured in combination with an isocyanate compound or the like. Examples of such a resin include polyvinyl acetal such as polyvinyl acetoacetal and polyvinyl butyral.

  The content of the resin material in the detection mark is preferably 10% by mass or more, more preferably 15% by mass or more. Thereby, the filler retention of the thermal transfer sheet can be improved.

In one embodiment, the detection mark includes at least one curing agent, and includes, for example, an isocyanate compound, a carbodiimide compound, an epoxy compound, and an oxazoline compound.
Among the above curing materials, isocyanate compounds are preferable, and examples thereof include xylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), isophorone diisocyanate (IPDI), and diphenylmethane diisocyanate (MDI).

  The content of the curing agent in the detection mark is preferably 3% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 16% by mass or less.

  In one embodiment, the detection mark also includes at least one release material. Thereby, the blocking resistance of the thermal transfer sheet can be improved. Examples of the release material include a surfactant such as a phosphate ester, silicone oil, polyethylene wax, and polyamide wax.

  The content of the release material in the detection mark is preferably 30% by mass or less, and more preferably 20% by mass or less. As a result, the content of the resin material can be increased, so that the filler retention property can be improved, and the sliding property of the thermal head can also be improved.

  In addition, the detection mark may include the above-described additive within a range that does not impair the characteristics of the present invention.

  The thickness of the detection mark is preferably 0.1 μm or more and 5 μm or less, more preferably 1 μm or more and 3 μm or less. Thereby, the thermal head cleaning effect of the thermal transfer sheet can be further improved.

The width of the thermal transfer sheet (the length in the direction perpendicular to the supply direction of the thermal transfer sheet) of the detection mark is preferably equal to or greater than the printing margin width of the transferred body and equal to or less than the width of the heat generating portion provided in the thermal head. Accordingly, head scum adhering to the vicinity of both ends of the transfer object can be cleaned, and quality defects such as printing defects and scratches near the width edge of the printed material can be suppressed.
The length L in the direction perpendicular to the supply direction of the detection mark is, for example, assuming that the width of the transferred object is A, the meandering width of the right and left sides of the non-transferred body is B, and the maximum printing width of the heating portion of the thermal head is C. A + 2B ≦ L ≦ C. As a result, it is possible to more effectively clean the head residue adhering to the vicinity of both ends of the transfer object, and it is possible to suppress poor quality such as printing defects and scratches near the edge in the width direction of the print.
In the present invention, the printing margin width of the transfer target means a meandering allowable width of the transfer target.
Further, the heating portion width means a maximum printing width of the thermal head.

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

  Note that the thermal transfer sheet of the present invention may include a detection mark that does not include a filler.

(Back layer)
The thermal transfer sheet of the present invention can be provided with a back layer on the substrate so as to be face-sequential with the detection mark or between the substrate and the detection mark. Thereby, the blocking resistance of the thermal transfer sheet can be improved.

  In one embodiment, the back layer comprises at least one resin material, for example, cellulose resin, styrene resin, vinyl resin, polyester, polyurethane, silicone-modified polyurethane, fluorine-modified polyurethane, (meth) acrylic resin, and two-component curing Mold resin and the like.

  The content of the resin material in the back layer is not particularly limited, and may be, for example, not less than 50% by mass and not more than 90% by mass.

  In one embodiment, the back layer includes at least one hardener. Thereby, it is possible to prevent the back layer from being scraped due to contact with the thermal head at the time of printing, and it is possible to further improve the holdability of the release material.

  In one embodiment, the back layer also includes at least one of the release agents described above. Thereby, the sliding property of the thermal head at the time of printing can be improved.

  In addition, the back layer may contain the above-mentioned additive within a range that does not impair the characteristics of the present invention.

  The thickness of the back layer is preferably from 0.3 μm to 5 μm, more preferably from 0.5 μm to 1 μm. Thereby, the blocking resistance of the thermal transfer sheet can be further improved.

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

(Thermal transfer printer)
As shown in FIG. 5, the thermal transfer printer 20 of the present invention includes a thermal head 21, a platen roller 22, a detection mark detection sensor 23, and means for controlling the opening and closing of the thermal head 21 and the platen roller 22 (not shown). Prepare.
In one embodiment, the thermal transfer printer 20 includes a transferred object detection sensor 24.
In one embodiment, the thermal transfer printer 20 includes a thermal transfer sheet supply unit 25, a thermal transfer sheet winding unit 26, and a transfer medium supply unit 27.
In one embodiment, the thermal transfer printer 20 includes a cutter mechanism 28.
Further, in one embodiment, the thermal transfer printer 20 may include a thermal transfer sheet transport control unit (not shown) and a transfer target transport control unit (not shown).

(Thermal head)
In one embodiment, the thermal head includes a substrate and a plurality of heat generating portions on the substrate, and the heat generating portions extend substantially in parallel on the substrate.

In one embodiment, the thermal head includes a glaze layer between the substrate and the heat generating portion. Glaze layer _may include SiO 2, SiON, and SiN.

In order to improve abrasion resistance, the thermal head is preferably coated. Materials for forming the coating include, for example, SiC, SiN, SiO ₂ and SiON, BP, and the like. From the viewpoint of improving the chemical wear resistance during cleaning, a coating containing BP is more preferable.

(Platen roller)
The platen roller is provided to face the thermal head, and the thermal head and the platen roller sandwich the thermal transfer sheet and the transfer target. Specifically, the thermal transfer sheet and the transferred object are pressed against the thermal head by a rotating platen roller, and are conveyed according to the rotation.

(Detection mark detection sensor)
The detection mark detection sensor detects the start and the completion of the passage of the detection mark provided on the thermal transfer sheet, and sends a detection signal to the sandwiching opening / closing control unit. The detection signal is also sent to the thermal transfer sheet conveyance control means and the transfer object conveyance control means.

(Transfer object detection sensor)
The transfer object detection sensor detects the start of passage of the transfer object, and sends a detection signal to the transfer object transport control means.

(Thermal transfer sheet supply unit)
The thermal transfer sheet supply unit is for setting a roll-like thermal transfer sheet and unwinding the thermal transfer sheet by rotation of a driving roller or a recovery unit.

(The thermal transfer sheet winding section)
The thermal transfer sheet winding section winds and collects the used thermal transfer sheet.

(Transferring object supply unit)
The transfer medium supply unit is for setting a roll-shaped transfer medium and unwinding the transfer medium by rotation of a driving roller.

(Cut mechanism)
The cutting mechanism is for cutting a transfer-receiving body on which an image is formed into a desired size to produce a print.
Further, as described below, the cutting mechanism is also used for cutting between regions where an image is formed.

(Thermal transfer sheet conveyance control means)
The thermal transfer sheet conveyance control means receives a detection signal from the detection mark detection sensor and controls unwinding and rewinding of the thermal transfer sheet.

(Transfer object transfer control means)
The transfer object transport control means is for receiving detection signals from the transfer object detection sensor and the detection mark detection sensor, and controlling unwinding and rewinding of the transfer object.

(How to clean the thermal head)
The thermal head cleaning method of the present invention is a step of preparing the thermal transfer printer and the thermal transfer sheet, and a detection mark provided on the thermal transfer sheet, in a state where the thermal head and the platen roller sandwich the detection mark, The method includes a step of passing the thermal head so as to be in contact therewith.

(Preparation process)
Since the thermal transfer printer and the thermal transfer sheet have been described above, the description is omitted here.

(Passing process)
The method of the present invention includes the step of passing the detection mark of the thermal transfer sheet between the thermal head and the platen roller while holding the thermal transfer sheet in contact with the thermal head.

It is preferable that the temperature of the heat generating portion of the thermal head in the passing step is lower than 100 ° C. when the detection mark is passed. The temperature of the heat generating portion is preferably lower than 60 ° C, more preferably lower than 40 ° C.
Thus, cleaning can be performed by applying a surface pressure to the head residue adhering to the vicinity of the heat generating portion of the thermal head without generating new head residue caused by melting.
The temperature of the heat generating portion is adjusted by (1) adjusting the interval between the detection marks provided on the thermal transfer sheet, and (2) adjusting the time until the thermal head reaches the next detection mark after the transfer of the dye layer and the transfer layer (transport speed). (Adjustment, positioning time, etc.) (3) It can be performed by installing a heat generation control means (air cooling fan) in the printer.
When cleaning is performed using a detection mark or the like provided in the unwinding start area A provided on the thermal transfer sheet before the start of production of a printed material, the heat generation unit is not heated, so that temperature adjustment is unnecessary.

In one embodiment, the object to be transferred is passed between the thermal head and the platen roller together with the thermal transfer sheet. In this case, the thermal transfer sheet passes through the thermal head, and the transfer object passes through the platen roller. There is a possibility that scum may be attached to a portion of the transfer object corresponding to the detection mark portion provided on the thermal transfer sheet, and this may cause unevenness to be formed in the formed image. Therefore, this portion is preferably cut.

In the passing step, it is preferable that the detection mark provided on the thermal transfer sheet is reciprocated between the thermal head and the platen roller.
The scum generated by printing is melted by the heat generated by the heat generating portion, extruded by the pressing force of the platen roller, and adheres to the vicinity of the heat generating portion of the thermal head, particularly to the glaze surface on the transfer sheet winding side of the heat generating portion of the thermal head.
By reciprocating the detection mark between the thermal head and the platen roller, a surface pressure can be applied to the glaze surface on the transfer sheet winding side of the heat generating portion of the thermal head, and cleaning can be performed effectively.
In addition, since the reciprocating movement can improve the cleaning effect of one detection mark, it is not necessary to increase the length of the detection mark including the filler in the transport direction, and the production cost of the thermal transfer sheet of the present invention can be reduced. .

In one embodiment, the passing step can be performed before starting the production of the print. Thereby, the thermal head before use can be cleaned, and the occurrence of printing failure due to the adhesion of scum can be suppressed.
Further, in one embodiment, the passing step can be performed during the production of the print, and the head can always be kept in a clean state. Further, the passing step may be performed after the production of the print to shorten the cleaning time at the start of the next print.

Hereinafter, a method of cleaning the thermal head when the passing step is performed before and during the production of the printed matter will be described with reference to FIGS. 6 to 10, but the present invention is not limited to this.
It should be noted that the unwinding start area A, and the supply end of the supply direction at the position where each of the dye layer and the transfer layer is provided, including a yellow dye layer, a magenta dye layer, a cyan dye layer, and a transfer layer that are repeatedly provided in a plane-sequential manner. And a thermal transfer sheet provided with detection marks of the same size at regular intervals so as to overlap.

  First, the thermal transfer sheet is unwound, and the detection mark detection sensor 23 detects a detection mark 14 (hereinafter, referred to as a yellow dye layer detection mark) provided to overlap the leading end of the yellow dye layer in the supply direction. At this point, the unwinding of the thermal transfer sheet is stopped (FIG. 6A).

  Next, the transfer object is unwound in the direction opposite to the unwinding direction of the thermal transfer sheet, and when the start of passage of the leading end of the transfer object is detected by the transfer object detection sensor, the transfer object is detected. The unwinding is stopped (FIG. 6B).

  Next, a detection signal from the detection mark detection sensor 23 is sent to the nipping / opening / closing control means, and the thermal head 21 is lowered, and the thermal transfer sheet and the object to be transferred are nipped together with the platen roller 22 (FIG. 6C).

Next, in a state of being sandwiched between the thermal head 21 and the platen roller 22, the detection mark 14 provided in the unwinding start area A of the thermal transfer sheet is passed together with the transfer target, whereby the thermal head 21 is cleaned.
When the detection mark detection sensor 23 detects the completion of the passage of the yellow dye layer detection mark, the unwinding of the thermal transfer sheet and the rewinding of the transfer object are stopped, and the thermal head 21 is raised (FIG. 6). (D)).

Next, the thermal transfer sheet was unwound, and the detection mark detection sensor 23 detected a detection mark 14 (hereinafter, referred to as a magenta dye layer detection mark) provided so as to overlap the leading end of the magenta dye layer in the supply direction. At this point, unwinding of the thermal transfer sheet is stopped (FIG. 7E).

Next, the transfer object is unwound and cut by the cutting mechanism. Then, the transfer object is rewound and the alignment is performed.
The scum removed by the cleaning of the thermal head may adhere to the transfer target, or may have irregularities due to particles of the detection mark portion of the thermal transfer sheet. This can be prevented from occurring, and the quality of the printed matter to be produced can be improved.
Rewinding of the transfer object is stopped when the start of passage of the leading end of the transfer object is detected by the transfer object detection sensor (FIG. 7F).

  Next, a detection signal from the detection mark detection sensor 23 is sent to the holding / opening / closing control means, and the thermal head 21 descends to hold the thermal transfer sheet and the transfer object together with the platen roller 22 (FIG. 7 (G)).

Next, in a state of being sandwiched between the thermal head 21 and the platen roller 22, the yellow dye layer detection mark of the thermal transfer sheet is passed together with the transfer target, thereby cleaning the thermal head (FIG. 7 (H)).
In a later step, it is preferable that a portion (hatched portion) corresponding to the yellow dye layer detection mark portion of the transfer object is cut by a cutting mechanism.

  At the time when the detection mark detection sensor 23 detects the completion of the passage of the magenta dye layer detection mark, the temperature of the heat generating portion of the thermal head 21 is controlled to be equal to or higher than the sublimation transfer temperature of the yellow dye contained in the yellow dye layer. In this state, the thermal transfer sheet and the object to be transferred pass between the thermal head 21 and the platen roller 22, and the yellow dye contained in the yellow dye layer is sublimated and transferred onto the object to be transferred (FIG. 7 (I)). ).

  Next, when the detection mark detection sensor 23 detects the detection mark 14 (hereinafter, referred to as a cyan dye layer detection mark) provided so as to overlap the leading end of the cyan dye layer in the supply direction, the unwinding of the thermal transfer sheet and the detection mark 14 are performed. The rewinding of the transfer medium and the heating of the heat generating portion of the thermal head 21 are stopped, and the thermal head 21 is raised (FIG. 7 (J)).

  Next, the transfer object is unwound and the alignment is performed. Specifically, unwinding of the transfer object is stopped when the start of the passage of the leading end of the transfer object is detected by the transfer object detection sensor. (FIG. 8 (K)).

  Next, a detection signal from the detection mark detection sensor 23 is sent to the holding / opening / closing control means, and the thermal head 21 in a non-heated state descends to hold the thermal transfer sheet and the transfer object together with the platen roller 22 (FIG. 8 (L)). ).

Next, in a state of being sandwiched between the thermal head 21 and the platen roller 22, the magenta dye layer detection mark of the thermal transfer sheet is passed together with the transfer target, thereby cleaning the thermal head 21 (FIG. 8 (M)).
In a later step, it is preferable that a portion (hatched portion) corresponding to the magenta dye layer detection mark portion of the transfer object is cut by a cutting mechanism.

  At the time when the detection mark detection sensor 23 detects the completion of the passage of the cyan dye layer detection mark, the temperature of the heat generating portion of the thermal head 21 is controlled to be equal to or higher than the sublimation transfer temperature of the magenta dye contained in the magenta dye layer. In this state, the thermal transfer sheet and the object to be transferred pass between the thermal head 21 and the platen roller 22, and the magenta dye contained in the magenta dye layer is sublimated and transferred onto the object to be transferred (FIG. 8 (N)). ).

  Next, when the detection mark detection sensor 23 detects the detection mark 14 (hereinafter, referred to as a transfer layer detection mark) provided so as to overlap the leading end of the transfer layer in the supply direction, the thermal transfer sheet unwinding and the transfer target are performed. The heating of the heat generating portion of the thermal head 21 is stopped, and the thermal head 21 is raised (FIG. 8 (O)).

  Next, the transfer object is unwound and the alignment is performed. Specifically, unwinding of the transfer object is stopped when the start of the passage of the leading end of the transfer object is detected by the transfer object detection sensor. (FIG. 9 (P)).

  Next, a detection signal from the detection mark detection sensor 23 is sent to the holding / opening / closing control means, and the thermal head 21 descends to hold the thermal transfer sheet and the transfer object together with the platen roller 22 (FIG. 9 (Q)).

Next, in a state of being sandwiched between the thermal head 21 and the platen roller 22, the cyan dye layer detection mark of the thermal transfer sheet is passed together with the transfer target, thereby cleaning the thermal head 21 (FIG. 9 (R)).
In a later step, it is preferable that a portion (hatched portion) corresponding to the cyan dye layer detection mark portion of the transfer object is cut by a cutting mechanism.

  When the detection mark detection sensor detects that the transfer layer detection mark has passed, the temperature of the heat generating part is controlled to be equal to or higher than the sublimation transfer temperature of the cyan dye contained in the cyan dye layer. The transfer of the thermal transfer sheet and the transfer object between the platen rollers 22 is performed, and the cyan dye contained in the cyan dye layer is sublimated and transferred onto the transfer object (FIG. 9 (S)).

  Next, when the detection mark detection sensor 23 detects the yellow dye layer detection mark, the conveyance of the thermal transfer sheet and the transfer target, the heating of the heat generating portion of the thermal head 21 are stopped, and the thermal head 21 is raised. (FIG. 9 (T)).

  Next, the transfer object is unwound and the alignment is performed. Specifically, unwinding of the transfer object is stopped when the start of the passage of the leading end of the transfer object is detected by the transfer object detection sensor. (FIG. 10 (U)).

  Next, a detection signal from the detection mark detection sensor 23 is sent to the holding and opening / closing control means, and the thermal head 21 descends to hold the thermal transfer sheet and the transferred object together with the platen roller 22 (FIG. 10 (V)).

Next, in a state of being sandwiched between the thermal head 21 and the platen roller 22, the transfer layer detection mark of the thermal transfer sheet is passed together with the object to be transferred, thereby cleaning the thermal head 21 (FIG. 10 (W)).
In a subsequent step, it is preferable that a portion (hatched portion) corresponding to the transfer layer detection mark portion of the transfer object is cut by a cutting mechanism.

  When the detection mark detection sensor 23 detects the completion of the passage of the yellow dye layer detection mark, the temperature of the heat generating portion of the thermal head 21 is controlled to be equal to or higher than the transfer temperature of the transfer layer. The heat transfer sheet and the object to be transferred pass between the platen rollers 22, and the transfer layer is transferred onto the object to be transferred (FIG. 10 (X)).

Thereafter, the transfer target is cut by a cutting mechanism to produce a print. A region corresponding to the detection mark portion is between the regions where the image of the transfer receiving body is formed, and is cut by the cutting mechanism and discarded.
In this way, the thermal head 21 can be cleaned and a print can be formed on the transfer target.
Usually, when the detection mark passes between the thermal head and the platen roller, the detection mark is not sandwiched therebetween. In the present invention, the thermal head can be satisfactorily cleaned by allowing the detection mark to contain a filler having an average particle diameter of 0.3 μm or more and being sandwiched between the thermal head and a platen roller when the detection mark passes.

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

Example 1
On one side of a PET film having a thickness of 5 μm, a coating solution for forming a yellow dye layer, a coating solution for forming a magenta dye layer, and a coating solution for forming a cyan dye layer having the following composition are repeatedly and sequentially applied and dried. Then, a 0.7 μm thick yellow dye layer, magenta dye layer and cyan dye layer were formed.

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

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

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

A coating liquid for forming a release layer having the following composition was applied and dried to form a 1 μm-thick release layer so that the dye layer formed in the above-described manner was plane-sequentially formed. An adhesive layer forming coating liquid having the following composition was applied and dried to form an adhesive layer having a thickness of 0.5 μm, whereby a transfer layer was formed on the base material so as to be in the order of the dye layer.
<Coating liquid for release layer>
・ (Meth) acrylic resin 40 parts by mass (LP-45M, manufactured by Soken Chemical Co., Ltd.)
・ MEK 30 parts by mass ・ Toluene 30 parts by mass <Coating liquid for adhesive layer>
-20 parts by mass of polyester (manufactured by Toyobo Co., Ltd., Byron (registered trademark) 700)
・ Silicon dioxide 0.5 parts by mass (Fuji Silysia Chemical Ltd., Sylysia 310)
・ 5 parts by mass of UV absorber (ST-I UVA 40KT Daicel)
・ MEK 30 parts by mass ・ Toluene 30 parts by mass

On the other surface of the PET film, near the boundary between the dye layers and near the boundary between the dye layer and the transfer layer, and in the non-transfer area, apply the detection mark forming coating liquid A having the following composition, and dry. Then, a detection mark having a thickness of 1 μm was formed.
<Coating liquid A for forming detection mark>
・ Polyvinyl acetal 6 parts by mass (S-LEC (registered trademark) BX-1 manufactured by Sekisui Chemical Co., Ltd.)
-Isocyanate compound 22 parts by mass (manufactured by DIC Corporation, Vernock (registered trademark) D750-45, solid part 45%)
-Phosphate ester 5 parts by mass (Plysurf (registered trademark) A-208N, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
・ 10 parts by mass of carbon black (average particle diameter 20 nm)
-Talc A 5 parts by mass (Micro Ace (registered trademark) P-3, manufactured by Nippon Talc Co., Ltd., average particle size 5 m)
・ MEK 60 parts by mass ・ Toluene 60 parts by mass

A back layer forming coating liquid A having the following composition was applied on a PET film and dried to form a back layer having a thickness of 1 μm so that the detection marks formed in the above-described manner became face-sequential. Was produced.
<Coating liquid A for forming back layer>
・ Polyvinyl acetal 6 parts by mass (S-LEC (registered trademark) BX-1 manufactured by Sekisui Chemical Co., Ltd.)
-Isocyanate compound 22 parts by mass (manufactured by DIC Corporation, Vernock (registered trademark) D750-45, solid part 45%)
-Phosphate ester 5 parts by mass (Plysurf (registered trademark) A-208N, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
・ MEK 60 parts by mass ・ Toluene 60 parts by mass

Example 2
A dye layer and a transfer layer were formed on one surface of a 5 μm-thick PET film in the same manner as in Example 1.

  On the other surface of the PET film, a coating liquid A for forming a back layer having the above composition was applied and dried to form a back layer having a thickness of 1 μm.

  On the back layer formed as described above, near the boundary between the dye layers and near the boundary between the dye layer and the transfer layer, apply the detection mark forming coating liquid having the above composition, dry, and dry. A detection mark of 1 μm was formed, and a thermal transfer sheet shown in FIG. 3 was produced.

Example 3
A thermal transfer sheet was prepared in the same manner as in Example 1 except that the composition of the detection mark forming coating liquid was changed as follows.
<Coating liquid B for forming detection mark>
・ 6 parts by mass of polyvinyl acetal ・ 22 parts by mass of isocyanate compound ・ 5 parts by mass of phosphoric ester ・ 10 parts by mass of carbon black (average particle diameter 20 nm)
・ Talc B 5 parts by mass (PA-OG, manufactured by Nippon Talc Co., Ltd., average particle size 19 μm)
・ MEK 60 parts by mass ・ Toluene 60 parts by mass

Example 4
A thermal transfer sheet was prepared in the same manner as in Example 1 except that the composition of the detection mark forming coating liquid was changed as follows.
<Coating liquid C for detection mark formation>
・ 6 parts by mass of polyvinyl acetal ・ 22 parts by mass of isocyanate compound ・ 5 parts by mass of phosphoric ester ・ 10 parts by mass of carbon black (average particle diameter 20 nm)
・ 11 parts by mass of talc B ・ 60 parts by mass of MEK ・ 60 parts by mass of toluene

Comparative Example 1
A dye layer and a transfer layer were formed on one surface of a 5 μm-thick PET film in the same manner as in Example 1.

On the other surface of the PET film, a coating solution a for forming a back layer having the following composition was applied and dried to form a back layer having a thickness of 1 μm.
<Coating liquid a for forming back layer>
・ 6 parts by mass of polyvinyl acetal ・ 22 parts by mass of isocyanate compound ・ 5 parts by mass of phosphate ester ・ 5 parts by mass of talc A ・ 60 parts by mass of MEK ・ 60 parts by mass of toluene

  On the back layer formed as described above, the detection mark forming coating liquid A having the above composition is applied and dried so as to correspond to the position of the dye layer to form a detection mark having a thickness of 1 μm. The thermal transfer sheet shown in FIG.

Comparative Example 2
A dye layer and a transfer layer were formed on one surface of a 5 μm-thick PET film in the same manner as in Example 1.

  On the dye layer and the transfer layer formed as described above, around the boundary between the dye layers and near the boundary between the dye layer and the transfer layer, apply the detection mark forming coating liquid A having the above composition, After drying, a detection mark having a thickness of 1 μm was formed.

  On the other surface of the PET film, a coating liquid A for forming a back layer having the above composition was applied and dried to form a back layer having a thickness of 1 μm to obtain a thermal transfer sheet shown in FIG.

<< Foil fall prevention >>
The thermal transfer sheet obtained in the above Examples and Comparative Examples, valley fold in the direction in which the back side becomes convex at the position of the detection mark, visually observe the presence or absence of foil fall of the detection mark portion, based on the following evaluation criteria, evaluated. The evaluation results are summarized in Table 1.
(Evaluation criteria)
A: No foil falling was observed.
NG: Folding of the detection mark at the folded portion and the surrounding area was observed.

<< Evaluation of thermal head cleaning performance >>
Using the thermal transfer sheet and the thermal transfer printer (DS620, manufactured by Dai Nippon Printing Co., Ltd.) obtained in the above Examples and Comparative Examples, a black solid image (0/255 image gradation) was formed on a genuine image receiving paper of the thermal transfer printer. 200 prints were formed.
The heat-generating portion of the thermal head of the thermal transfer printer after use was observed with an electron microscope (Digital Microscope VHX-2000, manufactured by KEYENCE CORPORATION), and the produced print was visually observed. Based on the evaluation. The evaluation results are summarized in Table 1.
(Evaluation criteria)
A: Adhesion of scum to the heat generating portion of the thermal head was not confirmed.
B: Adhesion of scum to the heat-generating portion of the thermal head was slightly confirmed, but there was no problem in practical use.
NG: Adhesion of scum to the heat generating portion of the thermal head was confirmed.

<< Evaluation of unevenness prevention property >>
Using the thermal transfer sheet and the thermal transfer printer (DS620, manufactured by Dai Nippon Printing Co., Ltd.) obtained in the above Examples and Comparative Examples, a black solid image (0/255 image gradation) was formed on a genuine image receiving paper of the thermal transfer printer. The formed print was produced.
The produced print was visually observed and evaluated based on the following evaluation criteria. The evaluation results are summarized in Table 1.
(Evaluation criteria)
A: The occurrence of irregularities on the surface of the print was not observed.
B: Some irregularities were observed on the surface of the printed matter, but this was not a problem in practical use.
NG: Many irregularities were observed on the surface of the printed matter, and color unevenness was confirmed in the formed image, which was practically a problem.

10: thermal transfer sheet, 11: base material, 12: dye layer, 13: transfer layer, 14: detection mark, 15: back layer, 20: thermal transfer printer, 21: thermal head, 22: platen roller, 23: detection mark detection Sensor, 24: Transfer object detection sensor, 25: Thermal transfer sheet supply unit, 26: Thermal transfer sheet recovery unit, 27: Transfer object supply unit, 28: Cutter mechanism

Claims (12)

Substrate, on one side of the substrate, comprising a dye layer and a transfer layer in a sequential order,
On the other surface of the base material, at least one of a unwinding start area, a vicinity of a boundary between the unwinding start area and the dye layer, and a non-transfer area near a boundary between the dye layer and the transfer layer. Equipped with detection marks in several places,
A thermal transfer sheet, wherein the detection mark includes a filler having an average particle diameter of 0.3 μm or more.   The thermal transfer sheet according to claim 1, wherein the average particle size of the filler is 2 µm or more and 100 µm or less.   The thermal transfer sheet according to claim 1, wherein the content of the filler in the detection mark is 2% by mass or more and 40% by mass or less.   The thermal transfer sheet according to claim 1, wherein a thickness of the detection mark is 0.1 μm or more and 5 μm or less.   The thermal transfer sheet according to any one of claims 1 to 4, further comprising the detection mark on the other surface of the base material, near a boundary between the dye layers, and in a non-transfer area. .   The thermal transfer sheet according to any one of claims 1 to 5, further comprising a back layer so as to be surface-sequential with the detection mark or between the base material and the detection mark.   The thermal transfer sheet according to any one of claims 1 to 6, wherein a width of the detection mark is equal to or larger than a print margin width of the transfer target body and equal to or smaller than a width of a heat generating portion provided in the thermal head. A thermal transfer printer used for producing a printed matter using the thermal transfer sheet according to any one of claims 1 to 7,
A thermal transfer printer, comprising: a thermal head, a platen roller, a detection mark detection sensor, and a means for holding and opening and closing the thermal head and the platen roller.   The thermal transfer printer according to claim 8, further comprising a transfer object detection sensor. A step of preparing the thermal transfer sheet according to any one of claims 1 to 7 and the thermal transfer printer according to claim 8 or 9, wherein the detection mark provided on the thermal transfer sheet is provided by the thermal head and the platen. A method for cleaning a thermal head, comprising a step of passing between them while being held by a roller so as to contact the thermal head.   The method for cleaning a thermal head according to claim 10, wherein a temperature of a heat generating portion of the thermal head in the passing step is lower than 100 ° C. 11.   The method of cleaning a thermal head according to claim 10, wherein in the passing step, the detection mark provided on the thermal transfer sheet is reciprocated between the thermal head and the platen roller.