Thermal recording medium and image recording method

Abstract

To provide a thermal recording medium that can improve printing defects caused by the adhesion of printhead residue. [Solution] The thermal recording medium of the present disclosure is a thermal recording medium having a first direction and a second direction perpendicular to the first direction in a plan view, comprising a support having a first surface and a second surface facing the first surface, a thermal layer disposed in a part of the area of ​​the first surface of the support, a protective layer disposed on at least the upper surface of the thermal layer, and a cleaning layer disposed in a part of the area of ​​the first surface of the support and in a different area from the thermal layer, wherein at least a part of the first surface of the support has an exposed portion that is exposed from the thermal layer, the cleaning layer and the protective layer, and in a cross-sectional view when the thermal recording medium is cut toward the first direction at a predetermined position in the second direction, the thermal layer and the cleaning layer are disposed in a different area from the thermal layer.

Description

[Technical Field]

[0001] This disclosure relates to a thermal recording medium and an image recording method. [Background technology]

[0002] Conventionally, thermal recording media are widely known in which a thermal layer is provided on a support made of paper, synthetic paper, etc., utilizing the color reaction between electron-donating compounds and electron-accepting compounds. Conventional thermal recording media are manufactured by mixing electron-donating compounds and electron-accepting compounds with resins such as polyvinyl alcohol, pigments such as calcium carbonate, dispersants such as surfactants, etc., and then atomizing and dispersing the resulting thermal layer-forming liquid onto the entire surface of the support using coating methods such as air knife coaters, bar coaters, blade coaters, curtain coaters, and gravure printing, and then drying it.

[0003] Conventional thermal recording media have a problem in terms of cost and environmental impact because the thermal layer forming liquid is applied to the entire surface of the support, resulting in waste of the thermal layer forming liquid applied to areas that are not printed. Furthermore, when thermal recording media with a transparent support are used as packaging material for various containers such as PET bottles, forming the thermal layer on the entire surface of the support makes it difficult to see inside the packaging material. In addition, when thermal recording media are heat-sealed and packaged in containers, if the thermal layer is formed on the entire surface of the support, there is a problem that it will change color due to the heating during heat sealing.

[0004] Therefore, a thermal recording medium has been proposed in which, for example, by applying a heat-sensitive layer-forming liquid to a portion of the support where printing is required, the amount of heat-sensitive layer-forming liquid in the non-printed areas can be reduced, thereby reducing costs and environmental impact. Furthermore, when using a transparent support, the inside of the packaging material can be seen from the area of ​​the support where the heat-sensitive layer is not provided, and color development due to heating during heat sealing can also be reduced.

[0005] As a technique for providing a heat-sensitive layer on a portion of a support, for example, a heat-sensitive film has been proposed in which a heat-sensitive layer is partially provided on at least one surface of a substrate, and a protective layer is applied to the entire surface of the heat-sensitive layer (see Patent Document 1). This proposed heat-sensitive film can suppress wear of the protective layer of the thermal head due to contact with the heat-sensitive film during printing. [Overview of the project] [Problems that the invention aims to solve]

[0006] The present invention aims to provide a thermal recording medium that can improve printing defects caused by the adhesion of printhead residue. [Means for solving the problem]

[0007] The thermal recording medium of the present invention, as a means for solving the aforementioned problems, is a thermal recording medium having a first direction and a second direction perpendicular to the first direction in a plan view, comprising: a support having a first surface and a second surface facing the first surface; a thermal layer disposed in a part of the area of ​​the first surface of the support; a protective layer disposed on at least the upper surface of the thermal layer; and a cleaning layer disposed in a part of the area of ​​the first surface of the support and in a different area from the thermal layer, wherein at least a part of the first surface of the support has an exposed portion that is exposed from the thermal layer, the cleaning layer and the protective layer, and in a cross-sectional view when the thermal recording medium is cut toward the first direction at a predetermined position in the second direction, the thermal recording medium is disposed in a different area from the thermal layer and the cleaning layer. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a thermal recording medium that can improve printing defects caused by the adhesion of head residue. [Brief explanation of the drawing]

[0009] [Figure 1A]FIG. 1A is a schematic top view showing an example of the first surface of the heat-sensitive recording medium according to the first embodiment of the present disclosure. [Figure 1B] FIG. 1B is a schematic cross-sectional view in the thickness direction of the heat-sensitive recording medium along line IB-IB of FIG. 1A. [Figure 2A] FIG. 2A is a schematic top view showing another example of the first surface of the heat-sensitive recording medium according to the first embodiment of the present disclosure. [Figure 2B] FIG. 2B is a schematic cross-sectional view in the thickness direction of the heat-sensitive recording medium along line IIB-IIB of FIG. 2A. [Figure 3A] FIG. 3A is a schematic top view showing another example of the first surface of the heat-sensitive recording medium according to the first embodiment of the present disclosure. [Figure 3B] FIG. 3B is a schematic cross-sectional view in the thickness direction of the heat-sensitive recording medium along line IIIB-IIIB of FIG. 3A. [Figure 4A] FIG. 4A is a schematic top view showing another example of the first surface of the heat-sensitive recording medium according to the first embodiment of the present disclosure. [Figure 4B] FIG. 4B is a schematic cross-sectional view in the thickness direction of the heat-sensitive recording medium along line IVB-IVB of FIG. 4A. [Figure 5] FIG. 5 is a diagram showing the size relationship among the support 1, the protective layer 3, and the cleaning layer 4 in FIG. 1A. [Figure 6] FIG. 6 is a diagram showing the size relationship among the support 1, the protective layer 3, and the cleaning layer 4 in FIG. 3A. [Figure 7A] FIG. 7A is a schematic top view showing an example of the first surface of the heat-sensitive recording medium according to the second embodiment of the present disclosure. [Figure 7B] FIG. 7B is a schematic cross-sectional view in the thickness direction of the heat-sensitive recording medium along line VIIB-VIIB of FIG. 7A. [Figure 8A] FIG. 8A is a schematic top view showing another example of the first surface of the heat-sensitive recording medium according to the second embodiment of the present disclosure. [Figure 8B] FIG. 8B is a schematic cross-sectional view in the thickness direction of the heat-sensitive recording medium along line VIIIB-VIIIB of FIG. 8A. [Figure 9A]Figure 9A is a schematic top view showing an example of the first surface of a thermal recording medium according to the second embodiment of this disclosure. [Figure 9B] Figure 9B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the IXB-IXB line in Figure 9A. [Figure 10A] Figure 10A is a schematic top view showing an example of the first surface of a thermal recording medium according to the second embodiment of this disclosure. [Figure 10B] Figure 10B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the XB-XB line in Figure 10A. [Figure 11A] Figure 11A is a schematic top view showing an example of the first surface of a thermal recording medium according to the second embodiment of this disclosure. [Figure 11B] Figure 11B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line XIB-XIB in Figure 11A. [Figure 12A] Figure 12A is a schematic top view showing an example of the first surface of a thermal recording medium according to the third embodiment of this disclosure. [Figure 12B] Figure 12B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the XIIB-XIIB line in Figure 12A. [Figure 13A] Figure 13A is a schematic top view showing an example of the first surface of a thermal recording medium according to the third embodiment of this disclosure. [Figure 13B] Figure 13B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line XIIIB-XIIIB in Figure 13A. [Figure 14A] Figure 14A is a schematic top view showing an example of the first surface of a thermal recording medium according to the third embodiment of this disclosure. [Figure 14B] Figure 14B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line XIVB-XIVB in Figure 14A. [Figure 15A] Figure 15A is a schematic top view showing an example of the first surface of a thermal recording medium according to the third embodiment of this disclosure. [Figure 15B] Figure 15B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line XVB-XVB in Figure 15A. [Figure 16A]Figure 16A is a schematic top view showing an example of the first surface of a thermal recording medium according to the third embodiment of this disclosure. [Figure 16B] Figure 16B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line XVIB-XVIB in Figure 16A. [Figure 17A] Figure 17A is a schematic top view showing an example of the first surface of a thermal recording medium according to the third embodiment of this disclosure. [Figure 17B] Figure 17B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line XVIIB-XVIIB in Figure 17A. [Figure 18A] Figure 18A is a schematic top view showing an example of the first surface of the thermal recording medium of this disclosure. [Figure 18B] Figure 18B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line XVIIIB-XVIIIB in Figure 18A. [Figure 19A] Figure 19A is a schematic top view showing an example of the first surface of the thermal recording medium of this disclosure. [Figure 19B] Figure 19B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line XIXB-XIXB in Figure 19A. [Figure 20A] Figure 20A is a schematic top view showing an example of the first surface of the thermal recording medium of this disclosure. [Figure 20B] Figure 20B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line XXB-XXB in Figure 20A. [Figure 21A] Figure 21A is a schematic top view showing an example of the first surface of the thermal recording medium of Comparative Example 1. [Figure 21B] Figure 21B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the XXIB-XXIB line in Figure 21A. [Figure 22] Figure 22 is a schematic top view showing an example of the first surface of the thermal recording medium of this disclosure. [Modes for carrying out the invention]

[0010] A common method for partial printing is gravure printing. In gravure printing, liquid ink is supplied to the surface of a cylinder that has a printing plate surface with numerous tiny recesses called cells formed on its surface according to the image. The ink on the surface other than the recesses is scraped off, and only the ink in the cells is transferred to the material to be printed. The doctor blade used for this scraping is pressed against the printing plate surface at the appropriate angle and pressure during printing in order to make uniform contact between the blade tip and the plate surface. However, as the plate rotates during printing, the blade tip of the doctor blade wears down, and it may not be able to scrape off all the ink in the non-image areas, causing ink to remain on the plate surface other than the image area, a phenomenon known as "ink bleed."

[0011] The inventors conducted thorough research and discovered that the layer transferred to the substrate by plate smearing has poor film-forming properties, and when printed with a thermal printer, it is rubbed against the thermal head and adheres to the head as residue, causing a problem. When residue adheres to the heating element of the head, printing smudges occur. The inventors also discovered that this phenomenon tends to occur especially after the doctor blade has worn down due to continuous production.

[0012] Conventionally, thermal recording materials have generally been those in which at least a thermal layer is provided over the entire upper layer of a support, and a protective layer is provided on top of that. In recent years, thermal recording media have come into use that have at least a partially provided thermal layer and a protective layer partially provided to cover the thermal layer.

[0013] By partially incorporating a heat-sensitive layer and a protective layer, the amount of material used can be reduced, and by omitting the heat-sensitive layer in the heat-sealed portion of the heat-seal packaging material, the heat-induced color change caused by heat sealing can be eliminated. Partially incorporating a heat-sensitive layer of any shape can improve design, and especially when using a transparent substrate as a support, it offers various benefits such as improved visibility of the areas without a heat-sensitive layer, and has been widely utilized.

[0014] Furthermore, by providing a color ink layer simultaneously with the heat-sensitive layer and protective layer, it is possible to provide a heat-sensitive recording medium with various design features. Various printing methods can be used to partially provide the heat-sensitive layer and protective layer. Among these, flexographic printing and gravure printing are particularly preferable for partially providing the heat-sensitive layer and protective layer together with the color ink layer.

[0015] On the other hand, the inventors have also found that when a thermal head is used to print with a partially thermal layer and protective layer, printing defects due to head residue are likely to occur due to foreign matter introduced from the outside or trace amounts of foreign matter adhering to the film.

[0016] Conventionally, it has been common practice to provide a protective layer suitable for head matching to improve printing characteristics and remove head debris with thermal heads. However, our research has revealed that when a protective layer is applied only partially, the function of removing head debris may not be sufficient.

[0017] While it is also possible to apply a protective layer to the entire surface, the significant advantage of partially applying a thermal layer is that it minimizes the amount of material used and allows for the creation of a thermal recording medium with excellent design, whether through a color ink layer or a partial thermal layer. In particular, when using a transparent support, the transparency of the support without a thermal layer or color ink layer makes it easier to see the contents when used in packaging materials, etc.

[0018] Since layers such as the heat-sensitive layer and protective layer contain at least colorants, pigments, lubricants, etc., they inevitably reduce transparency to some extent. Therefore, considering the visibility of the transparent area, it is preferable to apply the heat-sensitive layer and protective layer to the minimum area necessary for the display.

[0019] Furthermore, in the case of packaging materials, the areas near the ends in the width direction and flow direction are often not used in the final form. Therefore, if protective layers are placed outside these areas, it is possible to avoid impairing the visibility of the final product.

[0020] In contrast, the thermal recording medium of this disclosure, by having the configuration described below, can improve printing defects caused by head residue adhesion without compromising the design.

[0021] Embodiments of this disclosure will be described below with reference to the drawings.

[0022] This disclosure is not limited to the embodiments shown below, and may be modified to the extent that a person skilled in the art can conceive of other embodiments, additions, modifications, or deletions, and any such embodiment is included in the scope of this disclosure insofar as it produces the functions and effects of this disclosure.

[0023] The dimensions, materials, shapes, and relative arrangements of the components described in the embodiments are merely illustrative examples and not intended to limit the scope of this disclosure unless otherwise specified. The size and positional relationships of the components shown in each drawing may be exaggerated for clarity. Furthermore, in the following description, the same name and reference numeral indicate the same or identical components, and detailed explanations are omitted as appropriate. To avoid overly complex drawings, schematic diagrams may be used with some elements omitted, or end views showing only the cross-section may be used as cross-sectional views.

[0024] Furthermore, in this disclosure, the term "polygon" refers to polygons such as rectangles, triangles, and quadrilaterals, including shapes where the corners of the polygon have been rounded, chamfered, or otherwise modified. Similarly, shapes where modifications have been made not only to the corners (ends of the sides) but also to the middle parts of the sides will also be referred to as polygons. In other words, shapes that retain the shape of a polygon but have been partially modified are included in the interpretation of "polygon" as described in this disclosure.

[0025] Furthermore, the same applies not only to polygons but also to terms describing specific shapes such as trapezoids, circles, and convex shapes. The same also applies when dealing with each side that forms such a shape. In other words, even if a side has been processed at a corner or in the middle, the interpretation of "side" includes the processed part. When distinguishing a "polygon" or "side" without partial processing from a processed shape, the term "strictly" should be added, for example, "strictly quadrilateral."

[0026] Furthermore, the following description uses terms to indicate specific directions or positions as needed (e.g., "up," "down," "side," "top surface," "bottom surface," "side," "X," "Y," "Z," and other terms including these terms). However, the use of these terms is for the purpose of facilitating the understanding of the invention with reference to the drawings, and the meaning of these terms does not unduly limit the technical scope of this disclosure. For example, if "top surface" is mentioned, the invention must not always be used in a way that faces upwards. Also, in the embodiments, "covering" is not limited to direct contact, but also includes indirect covering, for example, through other components.

[0027] (Thermal recording medium) The thermal recording medium of this disclosure is a thermal recording medium having a first direction and a second direction perpendicular to the first direction in a plan view, comprising: a support having a first surface and a second surface opposite to the first surface; a thermal layer disposed in a portion of the area of ​​the first surface of the support; a protective layer disposed on at least the upper surface of the thermal layer; and a cleaning layer disposed in a portion of the area of ​​the first surface of the support and in a region different from the thermal layer, wherein at least a portion of the first surface of the support has an exposed portion that is exposed from the thermal layer, the cleaning layer, and the protective layer, and in a cross-sectional view when the thermal recording medium is cut toward the first direction at a predetermined position in the second direction, the thermal layer and the cleaning layer are disposed in a region different from the thermal layer and the cleaning layer. The thermal recording medium of this disclosure may further comprise other layers or members as necessary.

[0028] In the thermal recording medium of this disclosure, the thermal layer, the protective layer disposed on its upper surface, and the cleaning layer may be disposed at only one location on the first surface of the support, or they may be disposed at multiple locations, as long as the arrangement of the thermal layer and the cleaning layer is satisfied.

[0029] In the thermal recording medium of this disclosure, the exposed area refers to a region where the thermal layer, protective layer, cleaning layer, and optionally a color ink layer are not present, and where the support is exposed on the first surface when viewed from above. This has the advantage that the support is transparent, and when the thermal recording medium is used as packaging material for various containers, the inside can be seen.

[0030] In the thermal recording medium of this disclosure, there are no particular restrictions on the arrangement of the exposed portion, and it can be appropriately selected according to the purpose. In the first direction, at least one of the sides of the thermal layer and the protective layer is not in contact with the side of the cleaning layer, and the space between the thermal layer and the protective layer and the cleaning layer in the first direction may be the exposed portion.

[0031] [First Embodiment] A thermal recording medium according to the first embodiment of this disclosure has a first direction and a second direction perpendicular to the first direction. In the thermal recording medium according to the first embodiment of this disclosure, it is preferable to use the first direction as the transport direction in a thermal printer.

[0032] The shape of the thermal recording medium according to the first embodiment of this disclosure is not particularly limited and can be appropriately selected depending on the purpose, for example, it can be in the form of a label, a sheet, a roll, etc.

[0033] A thermal recording medium according to the first embodiment of the present disclosure comprises a support, a thermal layer, a protective layer, and a cleaning layer. At least a portion of the first surface of the support has an exposed portion that is exposed from the thermal layer, the cleaning layer, and the protective layer, and in a cross-sectional view when the thermal recording medium is cut toward the first direction at a predetermined position in the second direction, the thermal layer and the cleaning layer are arranged in different regions.

[0034] <Support> The support has a first surface and a second surface opposite the first surface. The support supports a heat-sensitive layer, a protective layer, a cleaning layer, and, if necessary, other layers or components.

[0035] There are no particular restrictions on the shape of the support, and it can be appropriately selected according to the purpose. Examples include polygons such as squares and rectangles, circles, ellipses, flat plates, and sheets.

[0036] There are no particular restrictions on the structure of the support, and it can be appropriately selected according to the purpose. It may be a single-layer structure or a laminated structure of two or more layers made of two or more different materials.

[0037] There are no particular restrictions on the structure of the support, and it can be appropriately selected according to the purpose. It may be a single-layer structure or a multi-layer structure of two or more layers.

[0038] There are no particular restrictions on the dimensions of the support, and it can be appropriately selected according to the dimensions of the desired thermal recording medium.

[0039] There are no particular restrictions on the material of the support, and it can be appropriately selected according to the purpose. Examples include paper, synthetic paper, and plastic film.

[0040] There are no particular restrictions on the plastic film used, and it can be appropriately selected depending on the purpose. Examples include polyester resins such as polyethylene terephthalate (PET), polycarbonate, polystyrene (PS), polymethyl methacrylate (PMMA), polyethylene (PE), polypropylene (PP), and vinyl chloride. These may be used individually or in combination of two or more types.

[0041] Among these, polyethylene terephthalate (PET) or polypropylene (PP) is preferred as the support material from the viewpoint of flexibility, and biaxially oriented polyethylene terephthalate (PET) is preferred from the viewpoint of superior strength, heat resistance, dimensional stability, etc.

[0042] Furthermore, examples of supports having a multilayer structure of two or more layers include laminates of cellulose fibers and synthetic paper, and laminates of cellulose fibers and plastic film or plastic film and synthetic paper.

[0043] The support may be surface-modified by treatments such as corona discharge treatment, oxidation reaction treatment (such as chromic acid), etching treatment, easy-adhesion treatment, and antistatic treatment, for the purpose of improving adhesion to the heat-sensitive layer, protective layer, cleaning layer, and, if necessary, other layers or components.

[0044] The support material may be a white opaque film or a foamed sheet obtained by adding additives such as a white raw material and a filler to the aforementioned material.

[0045] Furthermore, the support material may contain inorganic materials, organic compounds, etc., to improve heat resistance and mechanical strength.

[0046] There are no particular restrictions on the inorganic material contained in the support, and it can be appropriately selected depending on the purpose. Examples include glass, quartz, and inorganic single crystals. These may be used individually or in combination of two or more.

[0047] There are no particular restrictions on the organic compounds contained in the support material, and they can be appropriately selected depending on the purpose. Examples include benzotriazole compounds, triazine compounds, benzophenone compounds, and hindered amine compounds. These may be used individually or in combination of two or more.

[0048] The support is preferably a transparent film, as this allows for easy confirmation of the contents when the thermal recording medium is used as packaging material for food and the like. In this specification, "transparent" of the support means that a haze (turbidity) of 10% or less, measured according to ASTM D1003 or ISO 14782 for film transparency, is acceptable, but 5% or less is more preferable. The haze of the support can be measured using a haze meter (for example, device name: HZ-V3, manufactured by Suga Test Co., Ltd.).

[0049] There are no particular restrictions on the average thickness of the support material, and it can be appropriately selected depending on the purpose. However, from the viewpoint of transparency and ease of processing, a thickness of 3 μm to 300 μm is preferred. When the average thickness of the support material is 3 μm or more, the strength is high, and when it is 300 μm or less, the transparency is high and the rigidity is low, resulting in good processability.

[0050] In this specification, the "average thickness" of the support refers to the average value calculated from the thicknesses of 20 points arbitrarily selected from the support. The thickness of the support can be measured using a film thickness gauge (for example, K-402B STAND and electronic micrometer K351C, manufactured by Anritsu Corporation).

[0051] <Heat-sensitive layer> The heat-sensitive layer is placed in a portion of the first surface of the support.

[0052] In this specification, the term "displayed on the first surface" of the support means not only that the heat-sensitive layer is directly laminated on one surface of the support, but also that the heat-sensitive layer may be laminated on one surface of the support via another layer or component. For example, the heat-sensitive layer may be located on the upper surface of a color ink layer placed on the support.

[0053] In this specification, when the thermal layer is said to be placed in a "partial area" of the first surface of the support, it means that the area of ​​the thermal layer is placed such that it is less than 100% of the total area of ​​the first surface of the support.

[0054] The shape, structure, dimensions, number, and arrangement of the heat-sensitive layer are not particularly limited, as long as they are placed in a portion of the first surface of the support, and can be appropriately selected according to the purpose.

[0055] The heat-sensitive layer contains electron-donating compounds and electron-accepting compounds, and may also contain other components as needed.

[0056] <<Electron-donating compounds>> There are no particular restrictions on the electron-donating compound; it can be appropriately selected from those commonly used in thermal recording media, depending on the purpose. Examples include leuco compounds of dyes such as triphenylmethane, fluorane, phenothiazine, auramine, spiropyran, and indolinophthalide. These may be used individually or in combination of two or more.

[0057] Examples of black dye compounds include 6-(diethylamino)-2-[3-(trifluoromethyl)anilino]spiro[9H-xanthene-9,3'(1'H)-isobenzofuran]-1'-one, 2'-anilino-3'-methyl-6'-(dipentylamino)spiro[isobenzofuran-1(3H),'-[9H]xanthene]-3-one, and 2'-anilino-6'-dibutylamino-3'-methylspiro[phthalido-3,9'-[9H]xanthene Examples include 2'-anilino-6'-(N-ethyl-N-isopentylamino)-3'-methylspiro[phthalide-3,9'-[9H]xanthene], 2-(phenylamino)-3-methyl-6-[ethyl(p-tolyl)amino]spiro[9H-xanthene-9,1'(3'H)-isobenzofuran]-3'-one, 3-diethylamino-6-methyl-7-anilinofluorane, and 3-dibutylamino-6-methyl-7-anilinofluorane. These may be used individually or in combination of two or more.

[0058] Examples of red dye compounds include 6'-(diethylamino)-1',2'-benzofluorane, 9-(N-ethyl-N-isopentylamino)spiro[benzo[a]xanthene-12,3'-phthalide], 2'-methyl-6'-(Np-tolyl-N-ethylamino)spiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one, 2'-chloro-6'-(diethylamino)spiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one, 6'-(dibutylamino)-2'-bromo3'-methylspiro[phthalide-3,9'-xanthene], and 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide. These may be used individually or in combination of two or more.

[0059] Examples of blue dye compounds include 3-[4-(diethylamino)-2-hexyloxyphenyl]-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide, and 3',6'-bis(diphenylamino)spiro[phthalide-3,9'-xanthene]. These may be used individually or in combination of two or more.

[0060] Examples of green dye compounds include 1-ethyl-8-[N-ethyl-N-(4-methylphenyl)amino]-2,2,4-trimethyl-1,2-dihydrospiro[11H-chromeno[2,3-g]quinoline-11,3'-phthalide], 2'-(dibenzyloamino)-6'-(diethylamino)fluorane, and 2'-(N-phenyl-N-methylamino)-6'-(Np-tolyl-N-ethylamino)spiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one. These may be used individually or in combination of two or more.

[0061] Examples of yellow or orange dye compounds include F.Color Yellow-17, Orange 100, and Orange-DCF. These may be used individually or in combination of two or more.

[0062] Electron-donating compound 50% cumulative volume particle size (D 50 There are no particular restrictions on the particle size (D) and it can be appropriately selected according to the purpose, but 0.05 μm or more and 0.5 μm or less is preferred, and 0.1 μm or more and 0.3 μm or less is more preferred. 50% cumulative volume particle size (D) of electron-donating compound 50 This can be measured, for example, using a laser diffraction / scattering particle size distribution analyzer (e.g., device name: LA-960, manufactured by Horiba, Ltd.).

[0063] There are no particular restrictions on the content of the electron-donating compound, and it can be appropriately selected depending on the purpose. However, it is preferably 5% to 40% by mass, and more preferably 10% to 30% by mass, relative to the total mass of the heat-sensitive layer.

[0064] <<Electron-accepting compounds>> As for the electron-accepting compound, there are no particular restrictions as long as it has electron-accepting properties that cause the electron-donating compound to react and produce color when heated. It can be appropriately selected from those commonly used in thermal recording media depending on the purpose, but it is preferable that it be a color developer.

[0065] There are no particular restrictions on the color developer, and it can be appropriately selected depending on the purpose. Examples include phenolic substances, non-phenolic substances, organic or inorganic acidic substances, esters or salts thereof.

[0066] Specific examples of color developers include gallic acid, salicylic acid, 3-isopropylsalicylic acid, 3-cyclohexylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4'-isopropylidenediphenol, 1,1'-inopropylidenebis(2-chlorophenol), 4,4'-isopropylidenebis(2,6-dibromophenol), 4,4'-isopropylidenebis(2,6-dichlorophenol), 4,4'-isopropylidenebis(2-methylphenol), and 4,4'-isopropyl Redenbis(2,6-dimethylphenol), 4,4-isopropylidenebis(2-tert-butylphenol), 4,4'-sec-butylidenediphenol, 4,4'-cyclohexylidenebisphenol, 4,4'-cyclohexylidenebis(2-methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 3,5-xylenol, thymol, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, novolac type phenyl Nol resin, 2,2'-thiobis(4,6-dichlorophenol), catechol, resorcinol, hydroquinone, pyrogallol, phlologlysine, phlologlysine carboxylic acid, 4-tert-octylcatechol, 2,2'-methylmbis(4-chlorophenol), 2,2'-methylmbis(4-methyl-6-tert-butylphenol), 2,2,-dihydroxydiphenyl, p-hydroxybenzoate ethyl, p-hydroxybenzoate propyl, p-hydroxybenzoate butyl, p-hydroxybenzoate benzyl, p-hydroxybenzoate p-chlorobenzyl benzoate, p-o-chlorobenzyl hydroxybenzoate, p-methylbenzyl hydroxybenzoate, p-n-octyl hydroxybenzoate, benzoic acid, zinc salicylate, 1-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic acid, zinc 2-hydroxy-6-naphthoate, 4-hydroxydiphenyl sulfone, 4-hydroxy-4'-chlorodiphenyl sulfone, bis(4-hydroxyphenyl) sulfide, 2-hydroxy-p-toluic acid, zinc 3,5-di-tert-butylsalicylate, 3,5-di-tert-butylsalicylate tin, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, boric acid, thiourea derivatives, 4-hydroxythiophenol derivatives, bis(4-hydroxyphenyl)acetic acid, bis(4-hydroxyphenyl)ethyl acetate, bis(4-hydroxyphenyl)n-propyl acetate, bis(4-hydroxyphenyl)m-butyl acetate, bis(4-hydroxyphenyl)phenyl acetate, bis(4-hydroxyphenyl)benzyl acetate, bis (4-Hydroxyphenyl)Phenethyl Acetate, Bis(3-Methyl-4-Hydroxyphenyl)Acetate, Bis(3-Methyl-4-Hydroxyphenyl)Methyl Acetate, Bis(3-Methyl-4-Hydroxyphenyl)N-Propyl Acetate, 1,7-Bis(4-Hydroxyphenylthio)3,5-Dioxaheptane, 1,5-Bis(4-Hydroxyphenylthio)3-Oxaheptane, Dimethyl 4-Hydroxyphthalate, 4-Hydroxy-4'-Methoxydiphenyl Sulfone, 4-Hydroxy-4'-Ethoxydiphenyl Nylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'-propoxydiphenylsulfone, 4-hydroxy-4'-butoxydiphenylsulfone, 4-hydroxy-4'-isobutoxydiphenylsulfone, 4-hydroxy-4'-butoxydiphenylsulfone, 4-hydroxy-4'-tert-butoxydiphenylsulfone, 4-hydroxy-4'-bendyloxydiphenylsulfone, 4-hydroxy-4'-phenoxydiphenylsulfone, 4-hydroxy C-4'-(m-methylbenzyloxy)diphenylsulfone, 4-hydroxy-4'-(p-methylbenzyloxy)diphenylsulfone, 4-hydroxy-4'-(O-methylbenzyloxy)diphenylsulfone, 4-hydroxy-4'-(p-chlorobenzyloxy)diphenylsulfone, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1,1-tris(4-hydroxyphenyl)ethane, N,Examples include N'-di-[3-(p-toluenesulfonyl)oxy]phenylurea and [3-(3-phenylureido)phenyl]-4-methylbenzenesulfonate. These may be used individually or in combination of two or more.

[0067] 50% cumulative volume particle size (D) of electron-accepting compounds 50 There are no particular restrictions on the particle size (D) and it can be appropriately selected according to the purpose, but 0.05 μm or more and 0.5 μm or less is preferred, and 0.1 μm or more and 0.3 μm or less is more preferred. 50% cumulative volume particle size (D) of the electron-accepting compound 50 This can be measured, for example, using a laser diffraction / scattering particle size distribution analyzer (e.g., device name: LA-960, manufactured by Horiba, Ltd.).

[0068] There are no particular restrictions on the content of the electron-accepting compound, and it can be appropriately selected depending on the purpose. However, it is preferably 5% to 40% by mass, and more preferably 10% to 30% by mass, relative to the total mass of the heat-sensitive layer.

[0069] There are no particular restrictions on the mass ratio of the electron-donating compound to the electron-accepting compound, and it can be appropriately selected depending on the purpose. However, from the viewpoint of transparency stability, it is preferable that the electron-accepting compound is in an amount of 1 to 20 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 1 to 4 parts by mass, per 1 part by mass of the electron-donating compound.

[0070] There are no particular restrictions on the average thickness of the heat-sensitive layer, and it can be arbitrarily selected as needed, but it is preferably 1 μm to 20 μm, and more preferably 2 μm to 10 μm.

[0071] In this specification, the "average thickness" of the heat-sensitive layer refers to the average value calculated from the thicknesses of 20 points arbitrarily selected from the heat-sensitive layer. The thickness of the heat-sensitive layer can be measured using a film thickness gauge (e.g., K-402B STAND and electronic micrometer K351C, manufactured by Anritsu Corporation). Alternatively, the thickness of the heat-sensitive layer may be measured by using a cross-sectional sample preparation device (e.g., cross-section polisher SM-09020CP, manufactured by JEOL Ltd.) to cut the heat-sensitive recording medium in the thickness direction (stack direction) to expose the cross-section, and observing the cross-section with a scanning electron microscope (SEM) (e.g., S-3700, manufactured by Hitachi High-Tech Corporation).

[0072] <<Other ingredients>> Other components in the heat-sensitive layer are not particularly limited and can be appropriately selected from those commonly used in heat-sensitive recording media, depending on the purpose. Examples include photothermal conversion materials, ultraviolet absorbing materials, binder resins, auxiliary additives, thermofusible substances, lubricants, fillers, ultraviolet absorbers, antioxidants, sensitizers, and light stabilizers.

[0073] There are no particular restrictions on the content of other components in the heat-sensitive layer, and they can be appropriately selected depending on the purpose.

[0074] - UV absorbing material - There are no particular limitations on the UV-absorbing material, and it can be appropriately selected depending on the purpose. Examples include salicylic acid-based UV absorbers, benzophenone-based UV absorbers, and benzotriazole-based UV absorbers.

[0075] Specific examples of UV-absorbing materials include phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis(2-methoxy-4-hydroxy-5-benzoylphenyl)methane, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di- Examples include tert-butylphenyl)chlorobenzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-{2'-hydroxy-3'-(3'',4'',5'',6''-tetrahydrophthalimidomethyl)-5'-methylphenyl}benzotriazole, 2,2'-methylenebis{4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazole-2-yl)phenol}, 2-(2'-hydroxy-5'-methacryloxyphenyl)-2H-benzotriazole, 2-(3,5-di-t-amyl-2-hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole, and 2-(5-methyl-2-hydroxyphenyl)benzotriazole. These can be used individually or in combination of two or more.

[0076] -Binding resin- There are no particular restrictions on the binder resin, and it can be appropriately selected depending on the purpose. Examples include thermoplastic resins, thermosetting resins, and photocurable resins. These resins can be water-soluble, water-dispersible, or solvent-soluble resins, regardless of their properties.

[0077] Examples of binder resins include acrylic resins, polyvinyl alcohol resins, starch or its derivatives; cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose; water-soluble polymers such as sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylic ester copolymer, styrene-acrylic copolymer, acrylamide-acrylic ester-methacrylic acid ternary copolymer, styrene-maleic anhydride copolymer alkali salt, isobutylene-maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and casein; emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, and ethylene-vinyl acetate copolymer; and latexes such as styrene-butadiene copolymer and styrene-butadiene-acrylic copolymer. These may be used individually or in combination of two or more. Among these, acrylic resins and styrene-acrylic copolymers are preferred as binder resins when transparency is required.

[0078] -Auxiliary additives- Examples of auxiliary additives include various hindered phenol compounds and hindered amine compounds that are electron-accepting but have relatively low color-developing ability.

[0079] Specific examples of auxiliary additives include 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 4,4'-butylidenebis(6-tert-butyl-2-methylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, and 4,4'-thiobis(6-tert-butyl-2-methyl Examples include tetrabromobisphenol, tetrabromobisphenol A, tetrabromobisphenol S, 4,4'-thiobis(2-methylphenol), 4,4'-thiobis(2-chlorophenol), tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, and tetrakis(1,2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate. These may be used individually or in combination of two or more.

[0080] -Thermofusible substance- Examples of thermofusible substances include fatty acids such as stearic acid and behenic acid; fatty acid amides such as stearamide and palmitamide; fatty acid metal salts such as zinc stearate, aluminum stearate, calcium stearate, zinc palmitate, and zinc behenate; p-benzyl biphenyl, terphenyl, triphenylmethane, benzyl p-benzyloxybenzoate, benzyloxynaphthalene, phenyl benzylnaphthoate, and 1-hydroxy-2-naphthic acid. Phenyl, methyl 1-hydroxy-2-naphthoate, diphenyl carbonate, glycol carbonate, dibenzyl terephthalate, dimethyl terephthalate, 1,4-dimethoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dibendyloxynaphthalene, 1,2-diphenoxyethane, 1,2-bis(3-methylphenoxy)ethane, 1,2-bis(4-methylphenoxy)ethane, 1,4-diphenoxy-2-butene, 1,2-bis(4-methoxyphenyl Thio)ethane, dibenzoylmethane, 1,4-diphenylthiobutane, 1,4-diphenylthio-2-butene, 1,3-bis(2-vinyloxyethoxy)benzene, 1,4-bis(2-vinyloxyethoxy)benzene, p-(2-vinyloxyethoxy)biphenyl, p-aryloxybiphenyl, p-propagyloxybiphenyl, dibenzoyloxymethane, dibenzoyloxypropane, dibenzyl disulfide, 1,1-diphenylethanol, 1, Examples include 1-diphenylpropanol, p-benzyloxybenzyl alcohol, 1,3-phenoxy-2-propanol, N-octadecylcarbamoyl-p-methoxycarbonylbenzene, N-octadecylcarbamoylbenzene, 1,2-bis(4-methoxyphenoxy)propane, 1,5-bis(4-methoxyphenoxy)-3-oxapentane, dibenzyl oxalate, bis(4-methylbenzyl oxalate), and bis(4-chlorobenzyl oxalate. These may be used individually or in combination of two or more.

[0081] - Lubricant - Examples of lubricants include higher fatty acids or their metal salts, higher fatty acid amides, higher fatty acid esters, animal waxes, vegetable waxes, mineral waxes, and petroleum-based waxes. These may be used individually or in combination of two or more.

[0082] Examples of animal-derived waxes include beeswax, lanolin, and whale wax.

[0083] Examples of plant-based waxes include candelilla wax, carnauba wax, rice wax, wood wax, and jojoba oil.

[0084] Examples of mineral waxes include ceresin or its derivatives.

[0085] Examples of petroleum-based waxes include paraffin, petrolatum, microcrystalline wax, and petrolactam.

[0086] Examples of synthetic hydrocarbon waxes include Fischer-Tropsch wax.

[0087] Examples of hydrogenated waxes include hydrogenated castor oil and hydrogenated castor oil derivatives.

[0088] -Filler- Examples of fillers include inorganic fine powders such as calcium carbonate, silica, zinc oxide, titanium dioxide, zirconium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, kaolin, talc, surface-treated calcium, and surface-treated silica; and organic fine powders such as urea-formaldehyde resin, styrene-methacrylic acid copolymer, polystyrene resin, and vinylidene chloride resin. These may be used individually or in combination of two or more.

[0089] There are no particular restrictions on the content of the filler in the heat-sensitive layer, and it can be appropriately selected depending on the purpose. However, it is preferable that the content be 0.4 parts by mass or less, and more preferably 0.2 parts by mass or less, per 1 part by mass of the binder resin.

[0090] <Protective layer> The protective layer is disposed on at least the upper surface of the heat-sensitive layer. The heat-sensitive recording medium of this disclosure can improve the abrasion resistance of the heat-sensitive layer by the thermal head by having a protective layer.

[0091] In this specification, the "upper surface" of the heat-sensitive layer means the surface opposite to the surface on which the support is placed relative to the heat-sensitive layer.

[0092] In this specification, "the protective layer is positioned on the upper surface" of the heat-sensitive layer means not only that the protective layer is directly laminated on one surface of the heat-sensitive layer, but also that the protective layer may be laminated on one surface of the heat-sensitive layer via another layer or component.

[0093] Furthermore, the statement that the protective layer is positioned on "at least the top surface" of the heat-sensitive layer means that the protective layer may be positioned on surfaces other than the top surface of the heat-sensitive layer, such as the sides, the top surface of other layers, or the first or second surface of the support. If the protective layer is positioned on the side surface of the heat-sensitive layer, the protective layer positioned on the top surface of the heat-sensitive layer and the protective layer positioned on the side surface of the heat-sensitive layer may or may not be positioned consecutively.

[0094] Furthermore, the statement that the protective layer is placed "at least on the upper surface" of the heat-sensitive layer means that the protective layer may be placed so that its area is 100% of the total area of ​​the upper surface of the heat-sensitive layer (i.e., the protective layer covers at least the entire upper surface of the heat-sensitive layer), or it may be placed so that its area exceeds 100% (i.e., the protective layer extends beyond the upper surface of the heat-sensitive layer). However, it is preferable that the protective layer does not extend beyond the upper surface of the support.

[0095] Therefore, there are no particular restrictions on the shape of the protective layer, and it can be appropriately selected according to the purpose. Examples include polygons such as squares and rectangles, circles, ellipses, flat plates, and sheets.

[0096] For example, if the protective layer is laminated directly onto the upper surface of the heat-sensitive layer and positioned directly on the side surface of the heat-sensitive layer, the protective layer on the upper surface of the heat-sensitive layer and the protective layer on the side surface of the heat-sensitive layer may be positioned continuously. On the other hand, if the protective layer is laminated onto the upper surface of the heat-sensitive layer via another layer or component and positioned directly on the side surface of the heat-sensitive layer, the protective layer on the upper surface of the heat-sensitive layer and the protective layer on the side surface of the heat-sensitive layer may not be positioned continuously.

[0097] There are no particular restrictions on the composition of the protective layer, and it can be appropriately selected from known compositions used as protective layers for thermal recording media. However, it is preferable that it contains a binder resin and a pigment (filler), and it is even more preferable that it contains a crosslinking agent, wax, etc., and it may also contain other components as needed. When the protective layer contains a pigment, the scratch resistance of the thermal layer, the matching with the thermal head can be improved, and the heat resistance can also be improved.

[0098] <<Binding resin>> There are no particular restrictions on the binder resin, and it can be appropriately selected depending on the purpose. Examples include thermoplastic resins, thermosetting resins, and photocurable resins. These resins can be water-soluble, water-dispersible, or solvent-soluble resins, regardless of their properties.

[0099] The binder resin contained in the protective layer may be the same as the binder resin described in the "-Binding Resin-" section of "<<Other Components>>" of the <Heat-Sensing Layer> mentioned above.

[0100] The content of the binder resin in the protective layer is not particularly limited, as long as it does not impair the effects of this disclosure, and can be appropriately selected depending on the purpose.

[0101] <<Pigment>> There are no particular restrictions on the pigment (filler), and it can be appropriately selected according to the purpose; it may be an inorganic filler or an organic filler.

[0102] Examples of inorganic fillers include carbonates, silicates, metal oxides, and sulfate compounds.

[0103] Specific examples of inorganic fillers include zinc oxide, calcium carbonate, barium sulfate, titanium dioxide, lithopone, talc, pyrophyllite, kaolin, aluminum hydroxide, and calcined kaolin.

[0104] Examples of organic fillers include silicone resin, cellulose, epoxy resin, nylon resin, phenolic resin, polyurethane resin, urea resin, melamine resin, polyester resin, polycarbonate resin, styrene resin, acrylic resin, polyethylene resin, formaldehyde resin, polymethyl methacrylate resin, crosslinked polystyrene resin, urea resin, crosslinked polymethyl methacrylate resin, and melamine-formaldehyde resin.

[0105] These pigments (fillers) may be used individually or in combination of two or more.

[0106] The pigment content in the protective layer is not particularly limited as long as it does not impair the effects of this disclosure, and can be appropriately selected depending on the purpose. However, it is preferably 5 parts by mass or more and 200 parts by mass or less, and more preferably 10 parts by mass or more and 100 parts by mass or less, per 100 parts by mass of the binder resin.

[0107] <<Crosslinking agent>> There are no particular restrictions on the crosslinking agent, and it can be appropriately selected depending on the purpose. However, it is preferable that the crosslinking agent can reduce the solubility of the water-soluble resin in water by reacting with it.

[0108] Specific examples of crosslinking agents include glyoxal derivatives, methylol derivatives, epichlorohydrin, polyamide epichlorohydrin, epoxy compounds, aziridine compounds, hydrazine, hydrazide derivatives, oxazoline derivatives, and carbodiimide derivatives. These may be used individually or in combination of two or more. Among these, polyamide epichlorohydrin is preferred as a crosslinking agent due to its high safety in handling and short curing time required for water resistance.

[0109] The crosslinking agent content in the protective layer is not particularly limited as long as it does not impair the effects of this disclosure, and can be appropriately selected depending on the purpose. However, it is preferably 10 parts by mass or more and 60 parts by mass or less, and more preferably 20 parts by mass or more and 50 parts by mass or less, per 100 parts by mass of the binder resin.

[0110] <<wax>> The presence of wax in the protective layer is preferable in terms of improving lubricity for the thermal head.

[0111] Examples of waxes include animal waxes, plant waxes, mineral waxes, petroleum-based waxes, polyethylene oxide waxes, montan waxes, zinc stearate, and silicone waxes. These may be used individually or in combination of two or more. Among these, polyethylene oxide wax is preferred.

[0112] Examples of animal-derived waxes include beeswax, lanolin, and whale wax.

[0113] Examples of plant-based waxes include candelilla wax, carnauba wax, rice wax, wood wax, and jojoba oil.

[0114] Examples of mineral waxes include ceresin or its derivatives.

[0115] Examples of petroleum-based waxes include paraffin, petrolatum, microcrystalline wax, and petrolactam.

[0116] Examples of synthetic hydrocarbon waxes include Fischer-Tropsch wax.

[0117] Examples of hydrogenated waxes include hydrogenated castor oil and hydrogenated castor oil derivatives.

[0118] Examples of oxidized polyethylene waxes include polyethylene wax that has been oxidized by air oxidation and / or ozone oxidation (introducing carboxyl groups, hydroxyl groups, and / or formyl groups).

[0119] There are no particular restrictions on the weight-average molecular weight of the polyethylene oxide wax, and it can be appropriately selected depending on the purpose, but it is preferably 500 to 10,000, more preferably 600 to 9,000, and particularly preferably 700 to 8,000. The weight-average molecular weight of the polyethylene oxide wax can be measured using a static light scattering photometer (for example, product name: SLS-6000, static light scattering photometer, manufactured by Otsuka Electronics Co., Ltd.) with 1-chloronaphthalene as the solvent and a measurement temperature of 160°C.

[0120] Examples of commercially available polyethylene oxide waxes include product names such as RP-960 (manufactured by Chukyo Oils Co., Ltd., solid content: 30%) and L-787 (manufactured by Chukyo Oils Co., Ltd., solid content: 30%).

[0121] There are no particular restrictions on the volume-average particle size of the wax, and it can be appropriately selected depending on the purpose, but it is preferably between 0.3 μm and 6 μm. The volume-average particle size of the wax can be measured using a laser diffraction / scattering particle size distribution analyzer (for example, product name: LA-960, manufactured by Horiba, Ltd.).

[0122] There are no particular restrictions on the wax content in the protective layer, and it can be appropriately selected depending on the purpose, but it is preferably 100 parts by mass or less, and more preferably 25 parts by mass or less, per 100 parts by mass of the binder resin.

[0123] The wax in the protective layer may be used in combination with other known lubricants as needed. Other lubricants that can be combined with the wax in the protective layer include, for example, the wax described as a lubricant as another component in the heat-sensitive layer.

[0124] <<Other ingredients>> Other components in the protective layer are not particularly limited as long as they do not impair the effects of this disclosure, and can be appropriately selected depending on the purpose. Examples include auxiliary additives such as surfactants, thermofusible substances, lubricants, and pressure color inhibitors. These can be the same as the other components of the heat-sensitive layer.

[0125] The content of other components in the protective layer is not particularly limited, as long as it does not impair the effects of this disclosure, and can be appropriately selected depending on the purpose.

[0126] There are no particular restrictions on the average thickness of the protective layer, and it can be arbitrarily selected as needed, but it is preferably 0.5 μm to 5 μm, and more preferably 1 μm to 3 μm.

[0127] In this specification, the "average thickness" of the protective layer refers to the average value calculated from the thicknesses of 20 points arbitrarily selected from the protective layer. The thickness of the protective layer can be measured by using a cross-sectional sample preparation device (e.g., cross-section polisher SM-09020CP, manufactured by JEOL Ltd.) to cut the thermal recording medium in the thickness direction (stack direction) to expose the cross-section, and then observing the cross-section with a scanning electron microscope (SEM) (e.g., S-3700, manufactured by Hitachi High-Tech Corporation).

[0128] <Cleaning layer> The cleaning layer is located in a portion of the first surface of the support and in a region different from the thermal layer. In a cross-sectional view when the thermal recording medium is cut toward the first direction at a predetermined position in the second direction, the cleaning layer is located in a region different from the thermal layer. The first direction is preferably the transport direction of the thermal printer. When the first direction is the transport direction of the thermal printer, the cleaning layer is partially located on the transport direction of the thermal printer, aligned with the thermal layer.

[0129] The thermal recording medium of this disclosure has a cleaning layer, which prevents trace amounts of ink material, thermal layer material, or protective layer material adhering to the support due to plate overflow from accumulating as head residue when in contact with the thermal head, thereby improving printing defects.

[0130] The predetermined position in the second direction refers to a position arbitrarily selected from the second direction of the thermal recording medium. The thermal recording medium can be cut by any means, such as a cutter, scissors, razor blade, cutting machine, or laser. Furthermore, the arrangement of the thermal layer and the cleaning layer can be confirmed by observing the cross-section of the thermal recording medium with a laser microscope, optical microscope, scanning electron microscope, or by measuring with a scale. In addition, the thermal layer and the cleaning layer can be identified and their arrangement confirmed by using methods such as thermal color development and X-ray fluorescence measurement.

[0131] There are no particular restrictions on the shape of the cleaning layer, and it can be appropriately selected according to the purpose. Examples include polygons such as squares and rectangles, circles, ellipses, flat plates, and sheets. Among these, a rectangle with a longer side in the second direction is preferable because it can make broad contact with the width direction of the thermal printer and clean the thermal head over a wide area.

[0132] There are no particular restrictions on the dimensions of the cleaning layer on the first surface of the support, and they can be appropriately selected according to the purpose. However, it is preferable that the minimum length Xc of the cleaning layer in the first direction, the minimum length Xp of the protective layer in the first direction, and the maximum length Xs of the support in the first direction satisfy (Xc + Xp) / Xs ≥ 0.25. This can further significantly improve the adhesion of head dust.

[0133] Furthermore, there are no particular restrictions on the minimum length Xc of the cleaning layer in the first direction and the maximum length Xs of the support 1 in the first direction, but it is preferable that Xc / Xs ≥ 0.05. This further enhances the effect of preventing printing defects caused by head debris.

[0134] In the case of a thermal recording medium, if there are multiple areas for placing cleaning layers in the first direction, the minimum length Xc of the cleaning layer in the first direction refers to the minimum total length of the multiple cleaning layers in the first direction. The total length of the cleaning layers can be determined from the total length of the multiple cleaning layers along the cross-sectional line in the first direction when the thermal recording medium is cut toward the first direction at a predetermined position in the second direction.

[0135] In a thermal recording medium, if there are multiple areas for placing protective layers in a first direction, the minimum length Xp of the protective layers in the first direction refers to the minimum total length of the multiple protective layers in the first direction. The total length of the protective layers can be determined from the total length of the multiple protective layers along the cross-sectional line in the first direction when the thermal recording medium is cut toward the first direction at a predetermined position in the second direction.

[0136] Furthermore, there are no particular restrictions on the maximum length Yc of the cleaning layer in the second direction and the maximum length Ys of the support in the second direction, but it is preferable that Yc = Ys be satisfied. This can further significantly improve the adhesion of head debris.

[0137] In the case of a thermal recording medium, if there are multiple areas for placing cleaning layers in the second direction, the maximum length Yc of the cleaning layers in the second direction refers to the maximum total length of the multiple cleaning layers in the second direction. The total length of the cleaning layers can be determined from the total length of the multiple cleaning layers on the cross-sectional line in the second direction when the thermal recording medium is cut toward the second direction at a predetermined position in the first direction.

[0138] There are no particular restrictions on the haze in the region where the support and the cleaning layer are laminated, and it can be appropriately selected depending on the purpose, but it is preferably 30% or less, more preferably 20% or less, and even more preferably 10% or less. The haze in the region where the support and the cleaning layer are laminated can be measured using a haze meter (for example, device name: HZ-V3, manufactured by Suga Test Co., Ltd.).

[0139] There are no particular restrictions on the composition of the cleaning layer, and it can be appropriately selected depending on the purpose. However, it is preferable that it contains a binder resin and a pigment (filler), and it is even more preferable that it contains a crosslinking agent, wax, etc., and it may also contain other components as needed. Among these, it is particularly important that the cleaning layer contains a pigment (filler) in order to achieve the effects of this disclosure. By containing a pigment in the cleaning layer, the adhesion of head residue to the thermal head can be effectively prevented.

[0140] For the materials used in the cleaning layer, such as binder resins, pigments, crosslinking agents, and waxes, those listed under the <Protective Layer> section can be suitably used. The same applies to other components in the cleaning layer.

[0141] The composition of the cleaning layer material and the protective layer material may be the same or different. Among these, it is preferable that the composition of the cleaning layer and the protective layer be the same. This allows the cleaning layer and protective layer to be provided simultaneously within a single unit of a gravure printing press, thereby improving productivity.

[0142] Furthermore, the cleaning layer and the protective layer may be arranged separately in different areas, or they may be arranged continuously.

[0143] The composition and arrangement of the materials for these cleaning and protective layers can be combined. For example, the composition of the cleaning layer material and the protective layer material may be the same, and the cleaning layer and protective layer may be arranged separately in different regions; the composition of the cleaning layer material and the protective layer material may be the same, and the cleaning layer and protective layer may be arranged continuously; the composition of the cleaning layer material and the protective layer material may be the same, and the cleaning layer and protective layer may be arranged in different layers and separated in different regions (i.e., the cleaning layer and protective layer may be laminated via another layer or component); the composition of the cleaning layer material and the protective layer material may be... Examples include: being identical, with the cleaning layer and protective layer arranged in different layers and being arranged continuously; having different material compositions for the cleaning layer and protective layer, with the cleaning layer and protective layer arranged in different layers and being spaced apart in different regions (i.e., the cleaning layer and protective layer are laminated via another layer or component); and having different material compositions for the cleaning layer and protective layer, with the cleaning layer and protective layer arranged in different layers and being arranged continuously.

[0144] Furthermore, if the composition of the cleaning layer material and the composition of the protective layer material are different, the boundary between them can be distinguished even if the cleaning layer and the protective layer are arranged continuously. On the other hand, in the thermal recording medium of this disclosure, if the composition of the cleaning layer material and the composition of the protective layer material are the same, and the cleaning layer and the protective layer are arranged continuously, the boundary between them cannot be distinguished. The cleaning layer is arranged on at least a portion of the upper surface of at least one of the other layers, such as the support or the color ink layer, and the protective layer is arranged on at least the upper surface of the thermal layer. However, if the composition of the cleaning layer material and the composition of the protective layer material are the same, and the cleaning layer and the protective layer are arranged continuously, the cleaning layer and the protective layer may not be distinguished and may function as a single "protective section".

[0145] If the composition of the protective layer differs from that of the cleaning layer, the boundary between them can be confirmed by analyzing the composition of the materials, such as the shape and elemental types of pigments (fillers) in the cleaning layer and the protective layer, using scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDX).

[0146] Furthermore, if the composition of the cleaning layer material and the composition of the protective layer material are different, for example, the cleaning layer may contain at least a binder resin, a crosslinking agent, a pigment (filler), and a wax, and the protective layer may also contain at least a binder resin, a crosslinking agent, a pigment (filler), and a wax.

[0147] If the composition of the cleaning layer material and the composition of the protective layer material are the same, for example, both the cleaning layer and the protective layer may have a composition that contains at least a binder resin and a crosslinking agent, or both may have a composition that contains at least a binder resin, a crosslinking agent, a pigment (filler), and a wax.

[0148] There are no particular restrictions on the shape, structure, dimensions, number, or arrangement of the cleaning layer, and these can be appropriately selected according to the purpose. The cleaning layer is preferably layered.

[0149] There are no particular restrictions on the average thickness of the cleaning layer, and it can be arbitrarily selected as needed, but it is preferably 0.5 μm to 5 μm, and more preferably 1 μm to 3 μm.

[0150] In this specification, the "average thickness" of the cleaning layer refers to the average value calculated from the thicknesses of 20 points arbitrarily selected from the cleaning layer. The thickness of the cleaning layer can be measured by using a cross-sectional sample preparation device (e.g., cross-section polisher SM-09020CP, manufactured by JEOL Ltd.) to cut the thermal recording medium in the thickness direction (stack direction) to expose the cross-section, and observing the cross-section with a scanning electron microscope (SEM) (e.g., S-3700, manufactured by Hitachi High-Tech Corporation).

[0151] <Other components> Other components in the thermal recording medium according to the first embodiment of this disclosure are not particularly limited and can be appropriately selected depending on the purpose, and examples include a back layer, under layer, heat seal layer, release layer, adhesive layer, etc.

[0152] <<Back layer>> If a thermal recording medium has a back layer, curling of the thermal recording medium can be suppressed. On the other hand, if transparency is required for the thermal recording medium, it is preferable not to have a back layer.

[0153] When a back layer is placed on a thermal recording medium, it is preferable to place the back layer on the side of the support opposite to the side on which the thermal layer is placed, i.e., on the bottom surface of the support.

[0154] The back layer is not particularly limited and can be appropriately selected depending on the purpose, but it contains a binder resin and a pigment (filler), and may also contain other components such as a lubricant and a coloring pigment as needed. The binder resin and lubricant can be the same as those used in the heat-sensitive layer. The pigment (filler) can be the same as those used in the protective layer. The coloring pigment is not particularly limited and can be appropriately selected from known pigments.

[0155] There are no particular restrictions on the average thickness of the back layer, and it can be appropriately selected depending on the purpose, but it is preferably 0.1 μm to 20 μm, and more preferably 0.3 μm to 10 μm.

[0156] <<Underclass>> An underlayer can improve the color sensitivity of a thermal recording medium. On the other hand, if the thermal recording medium requires transparency, it is preferable not to include an underlayer.

[0157] When an underlayer is placed on a thermal recording medium, it is preferable to place the underlayer between the support and the thermal layer.

[0158] When an underlayer is provided, there are no particular restrictions on the underlayer, and it can be appropriately selected according to the purpose. However, it is preferable that the underlayer contains adhesive resin, thermoplastic hollow resin particles, and further contains other components as needed.

[0159] Thermoplastic hollow resin particles are tiny hollow particles that are already in a foamed state, with a thermoplastic resin shell containing air or other gases inside.

[0160] There are no particular restrictions on the average particle size (outer diameter) of the thermoplastic hollow resin particles, and they can be appropriately selected depending on the purpose. However, a size of 0.2 μm to 20 μm is preferred, and a size of 2 μm to 5 μm is more preferred. When the average particle size of the thermoplastic hollow resin particles is 0.2 μm or larger, it is technically easy to make them hollow, and the undercoat layer functions adequately. On the other hand, when the average particle size is 20 μm or smaller, the smoothness of the surface after coating and drying does not decrease, the coating of the heat-sensitive layer is less likely to become uneven, and it is not necessary to apply more heat-sensitive layer forming liquid than is required to make it uniform. Therefore, it is desirable that the average particle size of the thermoplastic hollow resin particles is within the above range, and that they have a uniform distribution peak with little variation.

[0161] There are no particular restrictions on the hollowness ratio of the thermoplastic hollow resin particles, and they can be appropriately selected depending on the purpose, but 30% to 95% is preferred, 50% to 95% is more preferred, and 80% to 95% is even more preferred. When the hollowness ratio of the thermoplastic hollow resin particles is 30% or more, sufficient heat insulation is achieved, and thermal energy from the thermal head is not released outside the heat-sensitive recording medium through the support, thus providing a sufficient sensitivity improvement effect.

[0162] In this specification, the hollowness ratio of thermoplastic hollow resin particles is expressed by the following formula 1, based on the ratio of the outer diameter of the thermoplastic hollow resin particle to the inner diameter (diameter of the hollow portion) of the thermoplastic hollow resin particle. [Formula 1] Hollowness of thermoplastic hollow resin particles (%) = (Inner diameter of thermoplastic hollow resin particle / Outer diameter of thermoplastic hollow resin particle) × 100

[0163] As mentioned above, thermoplastic hollow resin particles have a thermoplastic resin as a shell. However, there are no particular restrictions on the thermoplastic resin, and it can be appropriately selected depending on the purpose. Examples include styrene-acrylic resin, polystyrene resin, acrylic resin, polyethylene resin, polypropylene resin, polyacetal resin, chlorinated polyether resin, polyvinyl chloride resin, and copolymer resin mainly composed of vinylidene chloride and acrylonitrile. Among these, styrene-acrylic resin and copolymer resin mainly composed of vinylidene chloride and acrylonitrile are preferred as thermoplastic resins because they have a high hollowness ratio, small variation in particle size, and are suitable for blade coating.

[0164] <<Heat seal layer>> The heat-seal layer is formed by laminating LDPE (low-density polyethylene) films used as sealants. By heating the heat-seal layers in close contact with each other, they can be welded together. This property allows a bag-shaped packaging sheet to be sealed, or heat-sealed, by heating it in the same manner. Therefore, any material that is heat-sealable, i.e., has heat-seal properties, can be used to form the heat-seal layer, and is not limited to LDPE.

[0165] When a heat seal layer is placed on a thermal recording medium, it is preferable to place it on the side of the support opposite to the side on which the thermal layer is placed, i.e., the bottom surface of the support; or, if placed on the side of the support on which the thermal layer is placed, between the support and the thermal layer or the color ink layer. The heat seal layer may be placed on one side of the thermal layer or on both sides.

[0166] Suitable materials for heat sealing include films such as HDPE (high-density polyethylene), CPP (unoriented polypropylene), OPP (biaxially oriented polypropylene), and EVA (ethylene-vinyl acetate copolymer). However, polyolefin resins such as polyethylene and polypropylene; vinyl acetate resins such as ethylene-vinyl acetate copolymer (olefin-vinyl acetate copolymer, etc.); and acrylic resins such as ethylene-(meth)acrylic acid copolymer and ionomer [olefin-(meth)acrylic acid copolymer, or its metal crosslinked product, etc.] may also be used. Alternatively, known heat-sealable adhesives may be used for formation. It is preferable to use a material that becomes transparent after formation, as the packaged contents will be visible.

[0167] There are no particular restrictions on the average thickness of the heat seal layer, and it can be appropriately selected depending on the purpose. However, from the viewpoint of transparency and seal strength, a thickness of 5 μm to 50 μm is preferred, and a thickness of 10 μm to 30 μm is more preferred.

[0168] <<Exfoliation layer>> A release layer may be placed on the thermal recording medium to protect it from scratches and other damage. The release layer is removed when the thermal recording medium is in use.

[0169] When a release layer is placed on a thermal recording medium, it is preferable to place the release layer on the protective layer and / or on the upper surface of the protective layer.

[0170] The release layer contains a release agent. There are no particular restrictions on the release agent, and it can be appropriately selected depending on the purpose. Examples include UV-curing silicones, thermosetting silicones, solvent-free silicones, solvent-based silicones, emulsion-type silicones, and fluorine-based release agents.

[0171] <<Adhesive layer>> When a thermal recording medium is used by adhesion, an adhesive layer may be provided. Preferably, the adhesive layer is provided on the side of the support opposite to the side on which the thermal layer is provided, i.e., on the underside of the support. If the thermal recording medium has a back layer, it is preferable to provide the adhesive layer on the underside of the back layer, i.e., on the side opposite to the side on which the back layer is in contact with the support.

[0172] The main component of the adhesive contained in the adhesive layer is preferably at least one selected from acrylic resin obtained by emulsion polymerization of monomers mainly consisting of at least one alkyl (meth)acrylate ester having an alkyl group, acrylic ester-styrene copolymer, and acrylic ester-methacrylate-styrene copolymer.

[0173] Here, the "main component" of the adhesive refers to the component consisting solely of resin, excluding additives such as penetrating agents, film-forming aids, defoaming agents, rust inhibitors, thickeners, wetting agents, preservatives, UV absorbers, light stabilizers, pigments, and inorganic fillers that are added to the adhesive as needed. Furthermore, in this specification, "(meth)acrylic" means "acrylic or methacrylic."

[0174] Specific examples of alkyl (meth)acrylates include n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, and n-dodecyl (meth)acrylate. These may be used individually or in combination of two or more.

[0175] In this specification, the "average thickness" of each layer as other components refers to the average value calculated from the thicknesses of 20 points arbitrarily selected from each layer. The thickness of each layer can be measured by observing the cross-section with a scanning electron microscope (SEM) in the same manner as measuring the thickness of the heat-sensitive layer.

[0176] Next, examples of the layout configurations of each layer in the thermal recording medium according to the first embodiment of this disclosure will be described in detail with reference to the drawings. In Figures 1A to 4B, the Z-axis direction indicates the stacking direction of the thermal recording medium 100, that is, the thickness direction of the thermal recording medium 100. The X-axis direction and the Y-axis direction are perpendicular to the Z-axis direction. The X-axis direction indicates the first direction of the thermal recording medium, and the Y-axis direction indicates the second direction of the thermal recording medium. The X-axis direction is perpendicular to the Y-axis direction.

[0177] In addition, the thermal recording medium according to the first embodiment of this disclosure is preferably long in the first direction, and preferably has one layout laid out as a repeating pattern in the first direction. In Figures 1A to 4B, only one of these repeating patterns is illustrated and explained.

[0178] Preferably, the support material is continuous between one pattern and the subsequent other pattern, but a cleaning layer, protective layer, etc., may be placed between the two patterns.

[0179] [Layout Example 1] Figure 1A is a schematic top view showing an example of the first surface 1A of a thermal recording medium according to the first embodiment of the present disclosure. Figure 1B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the IB-IB line in Figure 1A. Figure 5 is a diagram showing the size relationship between the support 1, the protective layer 3, and the cleaning layer 4 in Figure 1A.

[0180] A thermal recording medium 100 having a first direction Fd and a second direction Sd perpendicular to the first direction Fd comprises a support 1 having a second surface 1B facing a first surface 1A, a thermal layer 2 disposed in a part of the area of ​​the first surface 1A of the support 1, a protective layer 3 disposed on at least the upper surface of the thermal layer 2, and a cleaning layer 4 disposed in a part of the area of ​​the first surface 1A of the support 1 and in a different area from the thermal layer 2. At least a part of the first surface 1A of the support 1 has an exposed portion that is exposed from the thermal layer 2, the cleaning layer 4, and the protective layer 3, and in a cross-sectional view when the thermal recording medium 100 is cut toward the first direction Fd at a predetermined position in the second direction Sd, the thermal layer 2 and the cleaning layer 4 are disposed in different areas. In a top view, since the thermal layer 2 is disposed below the protective layer 3, the outer edge 2a of the thermal layer 2 and the outer edge 3a of the protective layer 3 coincide.

[0181] In Layout Example 1, the cleaning layer 4 is positioned in a different region from the thermal layer 2 and the cleaning layer 4 when the thermal recording medium 100 is cut toward the first direction Fd at a predetermined position in the second direction Sd, and one side of the cleaning layer 4 (the side facing the thermal layer 2) is in contact with one side of the thermal layer 2 (the side facing the cleaning layer). Also, in a cross-sectional view in the second direction Sd, the length of the thermal layer 2 and the length of the cleaning layer 4 are the same. The exposed area refers to the area on the first surface 1A of the support 1 where the thermal layer 2, protective layer 3, and cleaning layer 4 are not located.

[0182] Here, as shown in Figure 5, there are no particular restrictions on the minimum length Xc of the cleaning layer 4 in the first direction Fd, the minimum length Xp of the protective layer 3 in the first direction Fd, and the maximum length Xs of the support 1 in the first direction Fd, but it is preferable that (Xc + Xp) / Xs ≥ 0.25. This can further significantly improve the adhesion of head debris.

[0183] Furthermore, there are no particular restrictions on the minimum length Xc of the cleaning layer 4 in the first direction Fd and the maximum length Xs of the support 1 in the first direction Fd, but it is preferable that Xc / Xs ≥ 0.05. This can further significantly improve the adhesion of head debris.

[0184] [Layout Example 2] Figure 2A is a schematic top view showing another example of the first surface 1A of a thermal recording medium according to the first embodiment of this disclosure. Figure 2B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line IIB-IIB in Figure 2A.

[0185] Layout example 2 differs from layout example 1 in that the protective layer 3 is located not only on the top surface of the thermal layer 2 but also on the sides. Therefore, in a top view, the outer edge 2a of the thermal layer 2 is inside the outer edge 3a of the protective layer 3.

[0186] [Layout Example 3] Figure 3A is a schematic top view showing another example of the first surface 1A of a thermal recording medium according to the first embodiment of the present disclosure. Figure 3B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line IIIB-IIIB in Figure 3A. Figure 6 is a diagram showing the size relationship between the support 1, the protective layer 3, and the cleaning layer 4 in Figure 3A.

[0187] Layout example 3 differs from layout example 1 in that one side of the cleaning layer 4 (the side facing the thermal layer 2) and one side of the thermal layer 2 (the side facing the cleaning layer) are not in contact, and the support 1 is exposed between the thermal layer 2 and the protective layer 3 and the cleaning layer 4.

[0188] Here, as shown in Figure 6, there are no particular restrictions on the minimum length Xc of the cleaning layer 4 in the first direction Fd, the minimum length Xp of the protective layer 3 in the first direction Fd, and the maximum length Xs of the support 1 in the first direction Fd, but it is preferable that (Xc + Xp) / Xs ≥ 0.25. This can further significantly improve the adhesion of head debris.

[0189] Furthermore, there are no particular restrictions on the minimum length Xc of the cleaning layer 4 in the first direction Fd and the maximum length Xs of the support 1 in the first direction Fd, but it is preferable that Xc / Xs ≥ 0.05. This can further significantly improve the adhesion of head debris.

[0190] [Layout Example 4] Figure 4A is a schematic top view showing another example of the first surface 1A of a thermal recording medium according to the first embodiment of the present disclosure. Figure 4B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line IVB-IVB in Figure 4A.

[0191] Layout example 4 differs from layout example 2 in that one side of the cleaning layer 4 (the side facing the thermal layer 2) and one side of the thermal layer 2 (the side facing the cleaning layer) are not in contact, and the support 1 is exposed between the thermal layer 2 and the protective layer 3 and the cleaning layer 4.

[0192] [Second Embodiment] The thermal recording medium according to the second embodiment of this disclosure differs from the thermal recording layer according to the first embodiment in that, in addition to the support, thermal layer, protective layer, and cleaning layer, it further comprises a color ink layer on the second surface of the support.

[0193] The thermal recording medium according to the second embodiment is preferable because it has a color ink layer on the second surface of the support, that is, the color ink layer is provided on the surface opposite to the support from the thermal layer etc. which is arranged on the first surface of the support, thereby improving the design of the thermal recording medium and suppressing ink bleed of the color ink layer on the first surface of the support on which the thermal layer is provided.

[0194] The following describes the differences between the thermal recording medium according to the second embodiment and the thermal recording medium according to the first embodiment.

[0195] <Color ink layer> The color ink layer is a layer on which color ink is printed and which consists of various colors, materials, and thicknesses. The color ink layer can provide design elements to images recorded on the thermal recording medium of this disclosure, or it can form the background of images printed on the thermal layer. Therefore, when the thermal recording medium is used for packaging printing, by providing a color ink layer, it is possible to include the product name, manufacturer name, ingredient list, etc., before product packaging, and to give the product an excellent design. The thermal recording medium of this disclosure is not limited to packaging applications, and the color ink layer may be printed with information such as text, marks, pictures, barcodes, or two-dimensional codes such as QR codes (registered trademarks).

[0196] There are no particular restrictions on the shape, structure, dimensions, number, or arrangement of the color ink layer, but it is preferable that it be arranged in a portion of the second surface of the support.

[0197] The color ink layer contains a colorant and a binder resin, and may also contain other components as needed. The binder resin and other components may be the same as those used in the heat-sensitive layer.

[0198] <<Colorants>> There are no particular restrictions on the colorants used; they can be appropriately selected according to the purpose, and known pigments or dyes can be used.

[0199] There are no particular restrictions on the content of colorants in the color ink layer, as long as the effects of this disclosure are not impaired, and can be appropriately selected depending on the purpose.

[0200] There are no particular restrictions on the average thickness of the color ink layer, and it can be arbitrarily selected as needed, but it is preferably 0.05 μm to 4 μm, and more preferably 0.1 μm to 2 μm.

[0201] In this specification, the "average thickness" of the color ink layer refers to the average value calculated from the thicknesses of 20 arbitrarily selected points within the color ink layer. The thickness of the color ink layer can be measured by using a cross-sectional sample preparation device (e.g., cross-section polisher SM-09020CP, manufactured by JEOL Ltd.) to cut the thermal recording medium in the thickness direction (stack direction) to expose the cross-section, and then observing the cross-section with a scanning electron microscope (SEM) (e.g., S-3700, manufactured by Hitachi High-Tech Corporation).

[0202] Next, examples of the layout configurations of each layer in the thermal recording medium according to the second embodiment of this disclosure will be described in detail with reference to the drawings. In Figures 7A to 11B, the Z-axis direction indicates the stacking direction of the thermal recording medium 100, that is, the thickness direction of the thermal recording medium 100. The X-axis direction and the Y-axis direction are perpendicular to the Z-axis direction. The X-axis direction indicates the first direction of the thermal recording medium, and the Y-axis direction indicates the second direction of the thermal recording medium. The X-axis direction is perpendicular to the Y-axis direction.

[0203] Furthermore, the thermal recording medium according to the second embodiment of this disclosure is preferably elongated in the first direction, similar to the thermal recording medium according to the first embodiment, and preferably has one layout laid out as a repeating pattern in the first direction. In Figures 7A to 11B, only one of these repeating patterns is illustrated and explained.

[0204] [Layout Example 5] Figure 7A is a schematic top view showing an example of the first surface 1A of a thermal recording medium according to the second embodiment of this disclosure. Figure 7B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line VIIB-VIIB in Figure 7A.

[0205] Layout example 5 differs from layout example 3 in that the color ink layer 5 is located on the second surface 1B of the support. The color ink layer 5 is located on the second surface 1B of the support 1 at a position facing the thermal layer 2 and at a position facing the exposed portion of the support.

[0206] [Layout Example 6] Figure 8A is a schematic top view showing another example of the first surface 1A of a thermal recording medium according to the second embodiment of this disclosure. Figure 8B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line VIIIB-VIIIB in Figure 8A.

[0207] Layout example 6 differs from layout example 5 in that the color ink layer 5 extends from a position facing the thermal layer 2 on the second surface 1B of the support 1 to the corresponding position of the cleaning layer 4.

[0208] [Layout Example 7] Figure 9A is a schematic top view showing an example of the first surface 1A of a thermal recording medium according to the second embodiment of this disclosure. Figure 9B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line IXB-IXB in Figure 9A.

[0209] Layout example 7 differs from layout example 4 in that the color ink layer 5 is located on the second surface 1B of the support. The color ink layer 5 extends from a position opposite the thermal layer 2 to the corresponding position of the cleaning layer 4 on the second surface 1B of the support 1.

[0210] [Layout Example 8] Figure 10A is a schematic top view showing an example of the first surface 1A of a thermal recording medium according to the second embodiment of this disclosure. Figure 10B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the XB-XB line in Figure 10A.

[0211] Layout example 8 differs from layout example 1 in that the color ink layer 5 is located on the second surface 1B of the support. The color ink layer 5 is located on the second surface 1B of the support 1 at a position facing the thermal layer 2, a position corresponding to the cleaning layer 4, and a position facing the exposed portion of the support 1 around the thermal layer 2 and the cleaning layer 4. Therefore, the outer edge 5a of the color ink layer 5 is outside the outer edge 2a of the thermal layer 2 and the outer edge 4a of the cleaning layer 4.

[0212] [Layout Example 9] Figure 11A is a schematic top view showing an example of the first surface 1A of a thermal recording medium according to a second embodiment of the present disclosure. Figure 11B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line XIB-XIB in Figure 11A.

[0213] Layout example 9 differs from layout example 2 in that the color ink layer 5 is located on the second surface 1B of the support. The color ink layer 5 is located on the second surface 1B of the support 1 at a position opposite to the protective layer 3, at a position corresponding to the cleaning layer 4, and at a position opposite to the exposed portion of the support 1 surrounding the protective layer 3 and the cleaning layer 4. Therefore, the outer edge 5a of the color ink layer 5 is outside the outer edge 3a of the protective layer 3 and the outer edge 4a of the cleaning layer 4.

[0214] [Third Embodiment] The thermal recording medium according to the third embodiment of this disclosure differs from the thermal recording layer according to the first embodiment in that, in addition to the support, thermal layer, protective layer, and cleaning layer, it further comprises a color ink layer on the first surface of the support.

[0215] In the thermal recording medium according to the third embodiment of this disclosure, the color ink layer is arranged in at least one of the following ways: (1) at least the upper surface of the color ink layer is exposed; (2) the thermal layer is arranged on at least the upper surface of the color ink layer; and (3) the cleaning layer is arranged on at least the upper surface of the color ink layer.

[0216] The thermal recording medium according to the third embodiment has a color ink layer on the first surface of the support, that is, the thermal layer etc. arranged on the first surface of the support has a color ink layer on the same surface of the support, so the design of the thermal recording medium can be improved.

[0217] The following describes the differences between the thermal recording medium according to the third embodiment and the thermal recording medium according to the second embodiment.

[0218] In this specification, the "top surface" of the color ink layer means the surface opposite to the surface on which the support is placed relative to the color ink layer.

[0219] The thermal recording medium according to the third embodiment of this disclosure comprises a color ink layer on the first surface of the support, and at least one of a cleaning layer and a protective layer may be disposed over at least the entire upper surface of the color ink layer. This improves the abrasiveness of the color ink layer by the thermal head and prevents printing defects caused by the accumulation of ink residue on the thermal head due to abrasion of the color ink layer.

[0220] In this specification, "displayed on the upper surface" of the color ink layer means not only that at least one of the cleaning layer and the protective layer is directly laminated on one side of the thermal layer, but also that at least one of the cleaning layer and the protective layer may be laminated on one side of the color ink layer via another layer or component.

[0221] Furthermore, the statement that at least one of the cleaning layer and the protective layer is positioned on "at least the top surface" of the color ink layer means that at least one of the cleaning layer and the protective layer may be positioned on a surface other than the top surface of the color ink layer, for example, on the side. If at least one of the cleaning layer and the protective layer is positioned on the side of the color ink layer, at least one of the cleaning layer and the protective layer positioned on the top surface of the color ink layer and at least one of the cleaning layer and the protective layer positioned on the side of the color ink layer may or may not be positioned consecutively.

[0222] Furthermore, the statement that at least one of the cleaning layer and the protective layer is positioned "at least on the upper surface" of the color ink layer means that the area of ​​at least one of the cleaning layer and the protective layer may be positioned such that it accounts for 100% of the total area of ​​the upper surface of the color ink layer (i.e., at least one of the cleaning layer and the protective layer covers the entire upper surface of the color ink layer), or it may be positioned so that it exceeds 100% (i.e., at least one of the cleaning layer and the protective layer extends beyond the upper surface of the color ink layer). However, it is preferable that at least one of the cleaning layer and the protective layer does not extend beyond the upper surface of the support.

[0223] For example, if at least one of the cleaning layer and the protective layer is laminated directly onto the upper surface of the color ink layer and positioned directly on the side surface of the color ink layer, then at least one of the cleaning layer and the protective layer on the upper surface of the color ink layer and at least one of the cleaning layer and the protective layer on the side surface of the color ink layer may be positioned continuously. Alternatively, if at least one of the cleaning layer and the protective layer is laminated onto the upper surface of the color ink layer via another layer or component and positioned directly on the side surface of the color ink layer, then at least one of the cleaning layer and the protective layer on the upper surface of the color ink layer and at least one of the cleaning layer and the protective layer on the side surface of the color ink layer may not be positioned continuously.

[0224] As shown in the second embodiment, the color ink layer is often placed on the side of the support opposite to the thermal layer, but depending on the configuration of the thermal recording layer, it may be placed on the same side as the recording layer on the first upper surface of the support. In particular, when the color ink is placed on the first surface of the support, it is preferable to have it between the support and the cleaning layer or protective layer, or between the support and the thermal layer.

[0225] Furthermore, the thermal recording medium according to the third embodiment of this disclosure allows for partial printing by arranging the color ink layer in a portion of the first surface of the support, thus enabling the color ink layer to be formed simultaneously with the thermal layer. In addition, by arranging the color ink layer in a portion of the first surface of the support, the thermal recording medium according to the third embodiment of this disclosure makes it easy to visually inspect the contents from areas where the color ink layer is not provided when the contents are packaged using the thermal recording medium as a packaging sheet.

[0226] Next, examples of the layout configurations of each layer in the thermal recording medium according to the third embodiment of this disclosure will be described in detail with reference to the drawings. In Figures 12A to 19B, the Z-axis direction indicates the stacking direction of the thermal recording medium 100, that is, the thickness direction of the thermal recording medium 100. The X-axis direction and the Y-axis direction are perpendicular to the Z-axis direction. The X-axis direction indicates the first direction of the thermal recording medium, and the Y-axis direction indicates the second direction of the thermal recording medium. The X-axis direction is perpendicular to the Y-axis direction.

[0227] Furthermore, the thermal recording medium according to the third embodiment of this disclosure is preferably elongated in the first direction, similar to the thermal recording medium according to the first embodiment, and preferably has one layout laid out as a repeating pattern in the first direction. In Figures 12A to 19B, only one of these repeating patterns is illustrated and explained.

[0228] [Layout Example 10] Figure 12A is a schematic top view showing an example of the first surface 1A of a thermal recording medium according to the third embodiment of this disclosure. Figure 12B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line XIIB-XIIB in Figure 12A.

[0229] Layout example 10 differs from layout example 3 in that the color ink layer 5 is positioned between the support 1 and the thermal layer 2. That is, in layout example 10, the thermal layer 2 is positioned at least on the upper surface of the color ink layer 5. On the first surface 1A of the support 1, the color ink layer 5 is larger in dimensions than the thermal layer 2 in the first direction Fd and the second direction Sd.

[0230] [Layout Example 11] Figure 13A is a schematic top view showing an example of the first surface 1A of a thermal recording medium according to the third embodiment of this disclosure. Figure 13B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line XIIIB-XIIIB in Figure 13A.

[0231] Layout example 11 differs from layout example 10 in that the protective layer 3 is placed in an area on the upper surface of the color ink layer where the thermal layer 2 is not placed. That is, in layout example 11, the thermal layer 2 and the protective layer 3 are placed on at least the upper surface of the color ink layer.

[0232] [Layout Example 12] Figure 14A is a schematic top view showing an example of the first surface 1A of a thermal recording medium according to the third embodiment of this disclosure. Figure 14B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line XIVB-XIVB in Figure 14A.

[0233] In layout example 12, a cleaning layer 4 is placed on a portion of the first surface 1A of the support 1, a color ink layer 5, a thermal layer 2, and a protective layer 3 are laminated in this order on another portion of the support 1, and another color ink layer 5 is placed on yet another portion of the support 1. In layout example 12, at least the upper surface of one of the color ink layers 5 is exposed. The thermal layer 2 is placed on at least the upper surface of the other color ink layer 5.

[0234] [Layout Example 13] Figure 15A is a schematic top view showing an example of the first surface 1A of a thermal recording medium according to the third embodiment of this disclosure. Figure 15B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line XVB-XVB in Figure 15A.

[0235] Layout example 13 differs from layout example 12 in that a color ink layer 5 is also placed between the support 1 and the cleaning layer 4. Therefore, in layout example 13, at least the upper surface of one color ink layer 5 is exposed. The cleaning layer 4 is placed at least on the upper surface of the other color ink layer 5.

[0236] [Layout Example 14] Figure 16A is a schematic top view showing an example of the first surface 1A of a thermal recording medium according to the third embodiment of this disclosure. Figure 16B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line XVIB-XVIB in Figure 16A.

[0237] Layout example 14 differs from layout example 13 in that a color ink layer 5 is also placed between the support 1 and the thermal layer 2. Therefore, at least the upper surface of one of the color ink layers 5 in layout example 13 is exposed. Another color ink layer 5 has a cleaning layer 4 placed at least on its upper surface. Yet another color ink layer 5 has a thermal layer 2 placed at least on its upper surface.

[0238] [Layout Example 15] Figure 17A is a schematic top view showing an example of the first surface 1A of a thermal recording medium according to the third embodiment of this disclosure. Figure 17B is a schematic cross-sectional view of the thermal recording medium in the thickness direction along the line XVIIB-XVIIB in Figure 17A.

[0239] Layout example 15 differs from layout example 1 in that the color ink layer 5 is positioned between the support 1 and the cleaning layer 4, and between the support 1 and the thermal layer 2. In layout example 15, the cleaning layer 4 and the protective layer 3 are positioned over at least the entire upper surface of the color ink layer 5.

[0240] Next, a more preferable form of the cleaning layer 4 will be described.

[0241] [Layout Form Example 16] FIG. 18A is a schematic top view showing an example of the first surface 1A of the thermal recording medium of the present disclosure. FIG. 18B is a schematic cross-sectional view in the thickness direction of the thermal recording medium along the line XVIIIB-XVIIIB in FIG. 18A.

[0242] Layout Form Example 16 is different from Layout Form Example 3 in that the length Yc of the cleaning layer 4 in the second direction Sd matches the length Ys of the support 1 in the second direction Sd, that is, it satisfies Yc = Ys. Thereby, the cleaning layer 4 can widely contact in the width direction of the head of the thermal printer, and it is possible to improve printing defects due to the adhesion of head dust.

[0243] [Layout Form Example 17] FIG. 19A is a schematic top view showing an example of the first surface 1A of the thermal recording medium of the present disclosure. FIG. 19B is a schematic cross-sectional view in the thickness direction of the thermal recording medium along the line XIXB-XIXB in FIG. 19A.

[0244] Layout Form Example 17 is different from Layout Form Example 1 in that the length Yc of the cleaning layer 4 in the second direction Sd matches the length Ys of the support 1 in the second direction Sd, and the length Xc of the cleaning layer 4 in the first direction Fd is approximately the same as the length Xs of the thermal layer 2 in the first direction Fd, and the area of the cleaning layer 4 with respect to the support 1 is large. That is, Layout Form Example 17 satisfies Yc = Ys, satisfies (Xc + Xp) / Xs ≧ 0.25, and satisfies (Xc + Xp) / Xs ≧ 0.25. Thereby, the cleaning layer 4 can widely contact in both the width direction and the conveyance direction of the head of the thermal printer, and it is possible to improve printing defects due to the adhesion of head dust.

[0245] [Layout Form Example 18] Figure 22 is a schematic top view showing an example of the first surface 1A of the thermal recording medium of the present disclosure. Figure 22 shows that multiple patterns are arranged in a continuous manner in the first direction Fd. The thermal recording medium of the present disclosure can be in the form of a label, a sheet, a roll, etc., but a roll is preferred when there are multiple long patterns in the first direction Fd.

[0246] <Application> There are no particular restrictions on the uses of the thermal recording medium disclosed herein, and can be appropriately selected according to the purpose. Examples include labels affixed to fresh food products, bento boxes, and prepared foods in the POS (Point of Sales) field, and bands wrapped around fresh food products, bento boxes, and prepared foods. By using it in the above-mentioned form, the visibility of the contents is improved, and consumers can select products while checking the contents. Other forms include tickets, tags, and cards. More specifically, examples include ticket vending machines, receipt and invoice issuing fields, packaging tags, pill cases, and pill bottles in the aircraft industry, and facsimile output paper in the book and document copying field.

[0247] There are no particular restrictions on the method for manufacturing the thermal recording medium, and any known method can be appropriately selected; however, the method for manufacturing the thermal recording medium described later in this disclosure can be preferably used.

[0248] (Method of manufacturing a thermal recording medium) The method for manufacturing a thermal recording medium according to the present disclosure includes forming a thermal layer, forming a cleaning layer, and forming a protective layer. The method for manufacturing a thermal recording medium according to the present disclosure may further preferably include forming a color ink layer, and may further optionally include other processes.

[0249] The method for manufacturing a thermal recording medium according to the present disclosure can suitably manufacture the thermal recording medium according to the present disclosure.

[0250] <Forming a heat-sensitive layer> To form a heat-sensitive layer, a heat-sensitive layer forming solution is applied to a portion of the first surface of the support to form the heat-sensitive layer.

[0251] In this specification, "applying the heat-sensitive layer-forming liquid to the first surface of the support" means not only applying the heat-sensitive layer-forming liquid directly to the first surface of the support, but also applying the heat-sensitive layer-forming liquid to the first surface of the support via another layer or component. For example, the heat-sensitive layer-forming liquid may be applied to the upper surface of a color ink layer placed on the support.

[0252] In this specification, applying a heat-sensitive layer-forming liquid to a "partial area" of the first surface of the support means applying it in such a way that the area to which the heat-sensitive layer-forming liquid is applied is less than 100% of the total surface area of ​​the first surface of the support.

[0253] There are no particular restrictions on the method for forming the heat-sensitive layer, and it can be appropriately selected depending on the purpose. For example, one method is to apply a heat-sensitive layer forming liquid onto a support and dry it to form the heat-sensitive layer.

[0254] There are no particular limitations on the method for applying the heat-sensitive layer forming liquid to a portion of the first surface of the support, and it can be formed using a generally known printing method. In the method for manufacturing a heat-sensitive recording medium of this disclosure, since the heat-sensitive layer and the cleaning layer are formed in a portion of the first surface of the support, the heat-sensitive layer and the cleaning layer can be formed simultaneously.

[0255] There are no particular restrictions on the printing method, and any known printing method can be used, but among these, gravure printing and flexographic printing are preferred. Generally, these printing methods are often used for paper substrates and film substrates for packaging, and furthermore, because multiple printing colors are required, equipment equipped with print heads for 5 to 12 colors in a single process is commonly used. For example, several color inks can be printed using the print head for design printing, and the remaining print head can be used to print the heat-sensitive layer forming liquid and the cleaning layer forming liquid simultaneously in one pass. This results in better design positioning accuracy and significantly improved productivity compared to production using two or more passes.

[0256] These studies can be conducted more efficiently by combining lab-scale, pilot-scale, and production-scale studies. At the lab scale, evaluation can be performed using laboratory printing presses (such as the PRINTABILITY TESTER from IGT Corporation or the FLEXIPROOF from Matsuo Sangyo Co., Ltd.), but the evaluation equipment is not limited to these; commercially available laboratory printing presses can be used for evaluation. Furthermore, at the pilot-scale and production-scale, more practical evaluations can be performed by creating various gravure rolls and flexographic plates according to the design and adhesion amount required for the evaluation.

[0257] There are no particular restrictions on the amount of heat-sensitive layer-forming liquid that adheres after drying, and it can be appropriately selected depending on the purpose, but 1 g / m² is the preferred amount. 2 More than 20g / m 2 The following is preferable: 2 g / m 2 More than 10g / m 2 The following are preferable.

[0258] <<Thermosensitive layer forming liquid>> The heat-sensitive layer-forming liquid preferably contains an electron-donating compound, an electron-accepting compound, and a solvent, and further contains a surfactant and a binder resin, and may also contain other components as needed.

[0259] Regarding the electron-donating compound, electron-accepting compound, binder resin, and other components, they are as described in the <thermal layer> section of the aforementioned (thermal recording medium).

[0260] - Solvent - There is no particular limitation on the solvent, and it can be appropriately selected according to the purpose. For example, water, aromatic solvents, ester solvents, ketone solvents, alcohol solvents, aliphatic hydrocarbons, glycol solvents, paraffin solvents, petroleum solvents with less than 1% aromatic components mainly composed of naphthene, or mixed solvents thereof can be mentioned. These can be used alone or in combination of two or more. Among these, from the viewpoints of the solubility of the electron-accepting compound and reduction of environmental load, as the solvent, alcohol solvents, ester solvents, or a mixed solvent of water and alcohol solvents are preferably used. Aromatic solvents such as toluene have low solubility in the electron-accepting compound, but their use is restricted from the point of reducing the environmental load of VOC emissions in the printing industry.

[0261] Examples of the alcohol solvent include methanol, ethanol, isopropyl alcohol, n-propyl alcohol, butanol, etc. Among these, ethanol is particularly preferred.

[0262] Examples of the ester solvent include ethyl acetate, propyl acetate, isopropyl acetate, isobutyl acetate, butyl acetate, isoamyl acetate, amyl acetate, hexyl acetate, phenyl acetate, benzyl acetate, etc.

[0263] Examples of water include pure water such as ion-exchanged water, ultrafiltration water, reverse osmosis water, distilled water, or ultrapure water.

[0264] There is no particular limitation on the content of the solvent in the thermal layer forming liquid, and it can be appropriately selected according to the purpose.

[0265] - Surfactant - If the heat-sensitive layer-forming liquid contains a surfactant, the surface tension of the heat-sensitive layer-forming liquid can be adjusted, and when applying the heat-sensitive layer-forming liquid to a portion of the first surface of the support, the desired shape and structure can be obtained with greater precision.

[0266] There are no particular restrictions on the surfactant used; it can be appropriately selected depending on the purpose. Examples include anionic surfactants, nonionic surfactants, amphoteric surfactants, and fluorinated surfactants.

[0267] Examples of anionic surfactants include polyoxyethylene alkyl ether acetates, dodecylbenzenesulfonates, lauryl salts, and polyoxyethylene alkyl ether sulfates. These may be used individually or in combination of two or more.

[0268] Examples of nonionic surfactants include acetylene glycol-based surfactants, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, and polyoxyethylene sorbitan fatty acid esters. These may be used individually or in combination of two or more types.

[0269] Examples of acetylene glycol-based surfactants include 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimethyl-4-octin-3,6-diol, 3,5-dimethyl-1-hexine-3-diol, and 2,5,8,11-tetramethyl-6-dodecine-5,8-diol. These may be used individually or in combination of two or more.

[0270] There are no particular restrictions on the surfactant content in the heat-sensitive layer-forming solution, and it can be appropriately selected depending on the purpose.

[0271] There are no particular limitations on the method for preparing the heat-sensitive layer forming liquid, and known methods can be used. For example, an electron-donating compound, an electron-accepting compound, a solvent, and other components as needed can be ground and dispersed using a disperser such as a ball mill, attritor, or sand mill until a desired dispersion particle size is achieved.

[0272] There are no particular restrictions on the dispersion particle size of the heat-sensitive layer forming liquid, but it is preferably 0.1 μm or more and 3 μm or less.

[0273] <Forming a protective layer> To form a protective layer, a protective layer-forming liquid is applied to at least the upper surface of the heat-sensitive layer.

[0274] The protective layer is formed after the heat-sensitive layer is formed.

[0275] In this specification, "applying a protective layer-forming liquid to the upper surface of the heat-sensitive layer" means not only directly applying the protective layer-forming liquid to one surface of the heat-sensitive layer, but also applying the protective layer-forming liquid to one surface of the heat-sensitive layer via another layer or component. For example, if an intermediate layer is formed on at least the upper surface of the heat-sensitive layer, the protective layer-forming liquid may be applied to at least a portion of the upper surface of the intermediate layer. In this case, the protective layer is formed in at least a portion of the upper surface of the intermediate layer and in a region facing at least a portion of the heat-sensitive layer.

[0276] Furthermore, applying the protective layer-forming liquid to "at least the upper surface" of the heat-sensitive layer means that the protective layer-forming liquid may also be applied to surfaces other than the upper surface of the heat-sensitive layer, such as the sides. When applying the protective layer-forming liquid to the sides of the heat-sensitive layer, the protective layer-forming liquid applied to the upper surface and the protective layer-forming liquid applied to the sides may be applied simultaneously or separately. When forming the protective layer on the upper surface of the heat-sensitive layer and the protective layer on the sides of the heat-sensitive layer to be continuous, it is efficient to apply the protective layer-forming liquid applied to the upper surface and the protective layer-forming liquid applied to the sides of the heat-sensitive layer simultaneously.

[0277] In this specification, applying the protective layer forming liquid to "at least the upper surface" of the heat-sensitive layer means that, with respect to the total area of the upper surface of the heat-sensitive layer, the area to which the protective layer forming liquid is applied may be 100% (i.e., the protective layer forming liquid is applied to the entire upper surface of at least the heat-sensitive layer), or it may be applied so as to exceed 100% (i.e., the protective layer forming liquid is applied beyond the upper surface of the heat-sensitive layer). However, it is preferable that the protective layer forming liquid is not applied beyond the first surface of the support.

[0278] There is no particular limitation on the method for forming the protective layer, and it can be appropriately selected according to the purpose. For example, there is a method of forming the protective layer by applying the protective layer forming liquid on the support and drying it.

[0279] There is no particular limitation on the method for applying the protective layer forming liquid to at least the upper surface of the heat-sensitive layer, and the same method as the method for applying the heat-sensitive layer forming liquid to a partial region of the upper surface of the support can be used.

[0280] There is no particular limitation on the adhesion amount after drying of the protective layer forming liquid, and it can be appropriately selected according to the purpose, but it is preferably 0.1 g / m 2 to 10 g / m 2 or less, more preferably 0.5 g / m 2 to 3.0 g / m 2 or less. If the adhesion amount is too small, a sufficient effect of head matching cannot be obtained, and if the adhesion amount is too large, the heat transfer property in printer printing decreases, so there is a risk of deterioration of the printed image quality and density.

[0281] <Forming a cleaning layer> In forming the cleaning layer, a cleaning layer forming liquid is applied to at least a partial region of the first surface of the support to form the cleaning layer.

[0282] In this specification, "applying the cleaning layer-forming liquid to the first surface of the support" means not only applying the cleaning layer-forming liquid directly to the first surface of the support, but also applying the cleaning layer-forming liquid to the first surface of the support via another layer or component. For example, the cleaning layer-forming liquid may be applied to the upper surface of a color ink layer placed on the support.

[0283] In this specification, applying the cleaning layer forming solution to "a portion of the area" of the first surface of the support means applying it in such a way that the area to which the cleaning layer forming solution is applied is less than 100% of the total surface area of ​​the first surface of the support.

[0284] There are no particular restrictions on the method for forming the cleaning layer, and it can be appropriately selected depending on the purpose. For example, one method is to apply a cleaning layer forming solution onto a support and dry it to form the cleaning layer.

[0285] There are no particular limitations on the method for applying the cleaning layer forming solution to a portion of the first surface of the support, and it can be formed using a generally known printing method. In the method for manufacturing a thermal recording medium of this disclosure, since the thermal layer and the cleaning layer are formed in a portion of the first surface of the support, the thermal layer and the cleaning layer can be formed simultaneously.

[0286] There are no particular restrictions on the printing method, and any known printing method can be used. Among these, gravure printing and flexographic printing are preferred, and can be carried out in the same manner as printing the thermal layer.

[0287] There are no particular restrictions on the amount of cleaning layer-forming solution that adheres after drying, and it can be appropriately selected depending on the purpose, but 0.1 g / m² is recommended. 2 More than 10g / m 2 The following is preferable: 0.5 g / m 2 More than 3.0g / m 2 The following are preferable.

[0288] <<Cleaning layer forming solution and protective layer forming solution>> The composition of the cleaning layer forming solution and the composition of the protective layer forming solution may be the same or different. The cleaning layer forming solution and the protective layer forming solution preferably contain a binder resin and a solvent, and further preferably contain a crosslinking agent, pigment (filler), wax, etc., and may also contain other components as needed.

[0289] The cleaning layer forming liquid preferably contains at least a binder resin, a solvent, and a pigment (filler), and more preferably a crosslinking agent and a wax.

[0290] The protective layer forming liquid preferably contains a binder resin, a solvent, a crosslinking agent, a pigment (filler), and a wax.

[0291] The binder resin, crosslinking agent, and other components are as described in the <Cleaning Layer> or <Protective Layer> section of the (Thermal Recording Medium) mentioned above. Furthermore, the solvent can be the same as that used for the thermal layer forming solution.

[0292] There are no particular limitations on the method for preparing the cleaning layer forming solution and the protective layer forming solution; known methods can be used, for example, by mixing a binder resin, a solvent, and other components as needed.

[0293] If at least one of the cleaning layer-forming liquid and the protective layer-forming liquid contains wax, it is preferable to use a dispersion obtained by wet dispersion with a dispersant in order to disperse the wax.

[0294] There are no particular restrictions on the dispersion, and it can be appropriately selected depending on the purpose. Examples include (i) an aqueous dispersion obtained by dispersing wax, preferably polyethylene oxide wax, in water using polyvinyl alcohol as a dispersant, and (ii) an emulsion obtained by emulsifying and dispersing wax, preferably polyethylene oxide wax, using an anionic emulsifier.

[0295] <Forming a colored ink layer> To form the color ink layer, a color ink is applied to a portion of the first surface, the second surface, or both of the support material. There are no particular restrictions on the order in which the color ink layer is formed and the heat-sensitive layer is formed.

[0296] In this specification, applying color ink to a support means not only applying the color ink directly to one surface of the support, but also applying the color ink to one surface of the support via another layer or component.

[0297] In this specification, applying color ink to "a portion of the upper surface of the support" means applying the color ink in such a way that the area to which the color ink is applied is less than 100% of the total area of ​​the first surface of the support.

[0298] There are no particular restrictions on the method for forming the color ink layer, and it can be appropriately selected depending on the purpose. For example, one method is to apply color ink to a support and dry it to form the color ink layer.

[0299] There are no particular limitations on the method for applying color ink to a portion of one or both sides of the support, and a method similar to the method for applying a heat-sensitive layer-forming liquid to a portion of the first surface of the support can be used.

[0300] There are no particular restrictions on the amount of color ink that adheres after drying, and it can be selected appropriately depending on the purpose, however, the average thickness of the color ink layer should be 0.05 g / m². 2 More than 10g / m 2 The following is preferable: 0.5 g / m 2 More than 4.0g / m 2 The following are preferable.

[0301] <<Color Ink>> The color ink contains a colorant and a solvent, and preferably further contains a surfactant and a binder resin, and may also contain other components as needed.

[0302] The colorants, binder resins, and other components are as described in the <Color Ink Layer> section of the aforementioned (Thermal Recording Medium). Furthermore, the solvent and surfactant can be the same as those used in the thermal layer forming liquid.

[0303] The colored ink may be prepared as appropriate by known methods, or a commercially available product may be used.

[0304] <Other processing> Other processes in the method for manufacturing a thermal recording medium according to this disclosure are not particularly limited and include, for example, processes for forming other layers in the thermal recording medium, such as a back layer, underlayer, heat seal layer, release layer, and adhesive layer.

[0305] There are no particular restrictions on the method of forming these other layers, and one method is to apply a layer-forming liquid, which is a mixture of the constituent materials of each layer, in the same manner as the method of applying a heat-sensitive layer-forming liquid, color ink, etc., and then laminate them.

[0306] (Image recording method) The image recording method disclosed herein records an image on a thermal recording medium according to the disclosure using a thermal head. Preferably, the transport direction of the thermal head is the first direction of the thermal recording medium. This makes it possible to further improve printing defects caused by the adhesion of head residue. [Examples]

[0307] The present disclosure will be specifically described below with reference to preparation examples, examples, and comparative examples, but the present disclosure is not limited in any way to these preparation examples, examples, and comparative examples.

[0308] (Preparation Example 1) <Preparation of the heat-sensitive layer forming solution> A heat-sensitive layer-forming solution was prepared by dispersing the following ingredients using a sand mill: 6.2 parts by mass of a black dye (ODB2, manufactured by Yamamoto Kasei Co., Ltd.) as an electron-donating compound, 18.7 parts by mass of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea represented by the following structural formula (1) as an electron-accepting compound, 40.0 parts by mass of acrylic resin (A-1125, manufactured by DSM, 19.5% solids by mass in aqueous solvent), 4.6 parts by mass of styrene-acrylic resin (Joncryl PDX-7741, manufactured by BASF, 41.5% solids by mass in aqueous solvent), 1.9 parts by mass of surfactant (PD-001, manufactured by Nisshin Chemical Industry Co., Ltd., 10% solids by mass), 15 parts by mass of water, and 13.6 parts by mass of ethanol. [ka]

[0309] (Preparation Example 2) <Preparation of Pigment Dispersion> 84.2 parts by mass of calcium carbonate as a pigment, 20.2 parts by mass of styrene-acrylic resin (Joncryl PDX-7741, manufactured by BASF, 41.5% solids by mass, aqueous solvent), 0.4 parts by mass of surfactant (PD-001, manufactured by Nisshin Chemical Industry Co., Ltd., 10% solids by mass), 51.1 parts by mass of water, and 51.1 parts by mass of ethanol were dispersed by a sand mill so that the 50% cumulative volume particle size (D50), measured by a laser diffraction / scattering particle size distribution analyzer (device name: LA-960, manufactured by Horiba, Ltd.), was 0.2 μm, to obtain a pigment dispersion (45% solids by mass, 44.8% by mass of ethanol in the solvent).

[0310] (Preparation Example 3) <Preparation of protective layer forming solution> A protective layer-forming solution was prepared by mixing and stirring 20.7 parts by mass of the pigment dispersion prepared in Preparation Example 2, 47.7 parts by mass of acrylic resin (A-1125, manufactured by DSM, 19.5% by mass solids, aqueous solvent), 9.5 parts by mass of oxazoline derivative as a crosslinking agent (Epocross® WS-500, manufactured by Nippon Shokubai Co., Ltd., 39% by mass solids), 4.7 parts by mass of oxidized polyethylene wax (30% by mass solids, aqueous solvent), 5 parts by mass of water, and 40 parts by mass of ethanol.

[0311] (Preparation Example 4) <Preparation of Cleaning Layer Forming Solution 1> A cleaning layer-forming solution was prepared by mixing and stirring 20.7 parts by mass of the pigment dispersion prepared in Preparation Example 2, 47.7 parts by mass of acrylic resin (A-1125, manufactured by DSM, 19.5% solids by mass, aqueous solvent), and 31.4 parts by mass of ethanol. (Preparation Example 5) <Preparation of Cleaning Layer Forming Solution 2> A cleaning layer-forming solution was prepared by mixing and stirring 20.7 parts by mass of the pigment dispersion prepared in Preparation Example 2, 47.7 parts by mass of acrylic resin (A-1125, manufactured by DSM, 19.5% by mass solids, aqueous solvent), 9.5 parts by mass of oxazoline derivative as a crosslinking agent (Epocross® WS-500, manufactured by Nippon Shokubai Co., Ltd., 39% by mass solids), 4.7 parts by mass of oxidized polyethylene wax (30% by mass solids, aqueous solvent), 5 parts by mass of water, and 31.4 parts by mass of ethanol.

[0312] (Printing method) In Examples 1 to 9 and Comparative Example 1 below, the thermal layer 2, protective layer 3, cleaning layer 4, and color ink layer 5 were all printed using the following gravure printing method.

[0313] -Preparing for Doctor Blade- To simulate the latter half of the actual production process for the thermal recording medium 100, a cylinder was set in a small gravure printing test machine manufactured by Chiba Machinery Industry Co., Ltd., and after adding the thermal layer forming liquid, protective layer forming liquid, and cleaning layer forming liquid, the machine was operated for 2 hours at a line speed of 40 m / min with the doctor blade in place.

[0314] -Gravure Printing- A gravure roll with an outer diameter of 200 mm was set in a small gravure printing test machine manufactured by Chiba Machinery Industry Co., Ltd., and using a doctor blade that had been prepared after 2 hours of operation, gravure printing was performed to create the layouts shown in Examples 1 to 9 and Comparative Example 1 at a line speed of 40 m / min and a drying temperature of 70°C, and then the prints were dried.

[0315] (Example 1) <Fabrication of thermal recording media> In Example 1, the thermal recording medium 100 shown in Figures 1A and 1B was fabricated using the following method.

[0316] <<Formation of heat-sensitive layer 2>> On a polyethylene terephthalate (PET) film (product name: E5102, average thickness: 12 μm, manufactured by Toyobo Co., Ltd., haze: 2.3%) serving as a support 1 with a length of 20 cm in the second direction, a portion of the central area of ​​the first surface 1A had a drying adhesion amount of 4 g / m² of the heat-sensitive layer-forming liquid obtained in Preparation Example 1. 2 To achieve this, printing was performed using the gravure printing method described above, and the material was dried to form a heat-sensitive layer 2 as shown in Figures 1A and 1B, with a length Xh of 25 cm in the first direction, a length of 10 cm in the second direction, and a rectangular shape when viewed from above.

[0317] <<Formation of protective layer 3>> The protective layer-forming solution obtained in Preparation Example 3 was applied to the entire upper surface of the heat-sensitive layer 2, with a dry adhesion amount of 2 g / m². 2 To achieve this, printing was performed using the gravure printing method described above, and the material was dried to form a protective layer 3 as shown in Figures 1A and 1B. Specifically, a protective layer 3 with a length of 25 cm in the first direction and a length of 10 cm in the second direction was formed on the upper surface of the heat-sensitive layer 2.

[0318] <<Formation of cleaning layer 4>> In a portion of the central area of ​​the first surface 1A of the support 1, and in a region different from the heat-sensitive layer 2, the cleaning layer forming liquid 1 obtained in Preparation Example 4 was applied, and the amount of adhesion after drying was 2 g / m². 2To achieve this, printing was performed using the gravure printing method described above, and the material was dried to form a cleaning layer 4 as shown in Figures 1A and 1B, with a length of 5 cm in the first direction, a length of 10 cm in the second direction, and a rectangular shape when viewed from above. The cleaning layer 4 was positioned so as to be aligned with the heat-sensitive layer 2 along the first direction, and one side of the cleaning layer 4 (the side facing the heat-sensitive layer 2) was in contact with one side of the heat-sensitive layer 2 (the side facing the cleaning layer). Furthermore, the length of the heat-sensitive layer 2 in the second direction and the length of the cleaning layer 4 were the same.

[0319] (Example 2) In Example 2, the thermal recording medium 100 shown in Figures 3A and 3B was manufactured using the following method. Specifically, in forming the cleaning layer 4 in Example 1, the cleaning layer 4 was arranged to be aligned with the thermal layer 2 along the first direction, and a gap was left between it and one side of the cleaning layer 4 (the side facing the thermal layer 2) so that it did not come into contact with one side of the thermal layer 2 (the side facing the cleaning layer). Otherwise, the thermal recording medium 100 was manufactured using the same method as in Example 1.

[0320] (Example 3) In Example 3, the thermal recording medium 100 was manufactured in the same manner as in Example 1, except that the formation of the thermal layer 2 and the protective layer 3 were modified as follows.

[0321] <<Formation of heat-sensitive layer 2>> In forming the heat-sensitive layer 2 in Example 1, the heat-sensitive layer 2 was formed in the same manner as in Example 1, except that the heat-sensitive layer forming liquid was gravure printed onto the first surface 1A of the support 1 so that its length in the first direction was 28 cm.

[0322] <<Formation of protective layer 3>> In forming the protective layer 3 in Example 1, the protective layer 3 was formed in the same manner as in Example 1, except that the protective layer forming solution was gravure printed onto the upper surface of the heat-sensitive layer 2 so that its length in the first direction was 28 cm.

[0323] (Example 4) The thermal recording medium 100 was manufactured in the same manner as in Example 1, except that the formation of the cleaning layer 4 in the thermal layer 2 of Example 1 was modified as follows.

[0324] <<Formation of cleaning layer 4>> In forming the cleaning layer 4 in Example 1, the cleaning layer 4 was formed in the same manner as in Example 1, except that the cleaning layer forming liquid 1 was gravure printed onto the first surface 1A of the support 1 so that its length in the first direction was 7 cm.

[0325] (Example 5) <Fabrication of thermal recording media> In Example 5, a thermal recording medium 100 was fabricated as shown in Figures 7A and 7B. Specifically, in Example 5, the thermal recording medium 100 was fabricated in the same manner as in Example 1, except that the color ink layer 5 was formed on the second surface 1B of the support in the following manner as in Example 2.

[0326] <<Formation of color ink layer 5>> On a portion of the central area of ​​the second surface 1B, opposite to the surface on which the heat-sensitive layer 2 of the polyethylene terephthalate film (product name: E5102) used as support 1 is formed, gravure printing ink (product name: Finart R794 white, manufactured by DIC Graphics Co., Ltd.) is applied, with a dry adhesion amount of 1 g / m². 2 To achieve this, printing was performed using the gravure printing method described above, and the material was dried to form a color ink layer 5 as shown in Figures 7A and 7B, with a length of 30 cm in the first direction, a length of 12 cm in the second direction, and a rectangular shape when viewed from above. The color ink layer 5 was positioned such that, when viewed from above, one side of the color ink layer 5, which is approximately parallel to the second direction, coincides with the side of the thermal layer 2 opposite the support 1 (the side not adjacent to the cleaning layer 4), and the other three sides have their outer edges extending beyond the outer edge of the thermal layer 2.

[0327] (Example 6) <Fabrication of thermal recording media> In Example 6, the thermal recording medium 100 shown in Figures 12A and 12B was fabricated using the following method.

[0328] <<Formation of color ink layer 5>> A portion of the central area of ​​the first surface 1A of a polyethylene terephthalate (PET) film (product name: E5102, average thickness: 12 μm, manufactured by Toyobo Co., Ltd., haze: 2.3%), which serves as a support 1 with a length of 20 cm in the second direction, was coated with gravure printing ink (product name: Finart R794 white, manufactured by DIC Graphics Co., Ltd.) with a dry adhesion amount of 1 g / m². 2 To achieve this, printing was performed using the gravure printing method described above, and after drying, a color ink layer 5 was formed as shown in Figures 12A and 12B, with a length of 28 cm in the first direction, a length of 10 cm in the second direction, and a rectangular shape when viewed from above.

[0329] <<Formation of heat-sensitive layer 2>> On the upper surface of the color ink layer 5, the amount of heat-sensitive layer-forming liquid obtained in Preparation Example 1 that adhered after drying was 4 g / m². 2 To achieve this, printing was performed using the gravure printing method described above, and the material was dried to form a thermal layer 2 as shown in Figures 12A and 12B, with a length of 25 cm in the first direction, a length of 10 cm in the second direction, and a rectangular shape when viewed from above. The thermal layer 2 was positioned so that one side of the thermal layer 2 that is approximately parallel to the second direction (the side not adjacent to the cleaning layer 4) and two sides that are approximately parallel to the first direction coincide with the side of the color ink layer 5, while the other side that is approximately parallel to the second direction (the side adjacent to the cleaning layer 4) has its outer edge inward from the outer edge of the color ink layer 5.

[0330] <<Formation of protective layer 3>> The protective layer-forming solution obtained in Preparation Example 3 was applied to the entire upper surface of the heat-sensitive layer 2, with a dry adhesion amount of 2 g / m². 2 To achieve this, printing was performed using the gravure printing method described above, and the material was dried to form a protective layer 3 as shown in Figures 12A and 12B. Specifically, a protective layer 3 with a length of 25 cm in the first direction and a length of 10 cm in the second direction was formed on the upper surface of the heat-sensitive layer 2.

[0331] <<Formation of cleaning layer 4>> In a portion of the central area of ​​the first surface 1A of the support 1, and in a region different from the heat-sensitive layer 2, the cleaning layer forming liquid 1 obtained in Preparation Example 4 was applied, and the amount of adhesion after drying was 2 g / m². 2 To achieve this, printing was performed using the gravure printing method described above, and the material was dried to form a cleaning layer 4 as shown in Figures 12A and 12B, with a length of 7 cm in the first direction, a length of 10 cm in the second direction, and a rectangular shape when viewed from above. The cleaning layer 4 was positioned so as to be aligned with the heat-sensitive layer 2 along the first direction, and a gap was left between it and one side of the heat-sensitive layer 2 (the side facing the heat-sensitive layer 2) so as not to be in contact with the other side of the heat-sensitive layer 2 (the side facing the cleaning layer 4).

[0332] (Example 7) <Fabrication of thermal recording media> In Example 7, the thermal recording medium 100 shown in Figures 13A and 13B was manufactured using the following method. Specifically, in Example 7, the thermal recording medium 100 was manufactured using the same method as in Example 6, except that a protective layer 3 was formed in the area on the upper surface of the color ink layer 5 where the thermal layer 2 was not placed, using the following method.

[0333] <<Formation of protective layer 3>> In the area on the upper surface of the color ink layer 5 where the heat-sensitive layer 2 is not placed, the amount of protective layer-forming liquid obtained in Preparation Example 3 after drying was 2 g / m². 2Printing was carried out using the gravure printing method described above, and the material was dried to form a protective layer 3 as shown in Figures 13A and 13B. Specifically, a protective layer 3 with a length of 3 cm in the first direction and a length of 10 cm in the second direction was formed on the upper surface of the color ink layer 5. One side of the protective layer 3 that is in contact with the upper surface of the color ink layer 5 (the side opposite to the cleaning layer 4) was positioned to be in contact with one side of the thermal layer 2 (the side facing the cleaning layer 4). Furthermore, in a top view, the outer edge of the protective layer 3, which is a combination of the protective layer 3 positioned in contact with the upper surface of the thermal layer 2 and the protective layer 3 positioned in contact with the upper surface of the color ink layer 5, was positioned to coincide with the outer edge of the color ink layer 5.

[0334] (Example 8) <Fabrication of thermal recording media> In Example 8, the thermal recording medium 100 shown in Figures 20A and 20B was fabricated using the following method. Specifically, the thermal recording medium 100 of Example 8 was fabricated in the same manner as in Example 5, except that a cleaning layer 4 was formed as shown in Figures 20A and 20B, with a length of 7 cm in the first direction, a length of 20 cm in the second direction, and a rectangular shape when viewed from above. The length of the cleaning layer 4 in the second direction was the same as the length of the support 1 in the second direction, 8 (shown as "total width" in Table 1).

[0335] (Example 9) <Fabrication of thermal recording media> The thermal recording medium 100 of Example 9 was prepared in the same manner as in Example 8, except that the cleaning layer forming solution was changed to the cleaning layer forming solution 2 obtained in Preparation Example 5 during the formation of the protective layer 3 of Example 8.

[0336] (Comparative Example 1) <Fabrication of thermal recording media> In Comparative Example 1, the thermal recording medium 100 shown in Figures 21A and 21B was prepared. Specifically, in Comparative Example 1, the thermal recording medium 100 was prepared in the same manner as in Example 1.

[0337] [evaluation] The thermal recording media 100 of Examples 1-9 and Comparative Example 1 were printed using a thermal printer (model: DF6530, manufactured by VIDEOJET) at a printing speed of 150 mm / s, printing energy of 100%, and head pressure of 3.5 kg. For Examples 1-4 and Comparative Example 1, the obtained images were visually inspected by a professional evaluator for ink residue buildup on the thermal head and for the absence of printing on the thermal layer 2, and evaluated based on the evaluation criteria below. For Examples 5-9, the obtained images were visually inspected by a professional evaluator for peeling of the color ink layer 5, ink residue buildup on the thermal head, and for the absence of printing on the thermal layer 2, and evaluated based on the evaluation criteria below. The results are shown in Table 1 below. Note that ◎, ○, and △ are within the range of practical use.

[0338] -Evaluation criteria for head residue buildup on thermal heads- ◎: No head debris was observed across the entire width of the thermal head during 1,000m printing. ○: In 1,000m printing, no head residue was observed in the thermal head's printing area, but a small amount of head residue was observed outside the printing area. △: No head residue is observed across the entire width of the thermal head during 100m printing, but head residue is observed across the entire width of the thermal head during 1,000m printing. ×: After printing 100m, head residue was observed to be attached and accumulated across the entire width of the thermal head.

[0339] -Evaluation Criteria for Printing Defects- ◎: No printing smudging occurs even after printing 3,000m. ○: No printing smudging occurs when printing 1,000m, but smudging occurs when printing continuously from over 1,000m to 3,000m. △: No printing smudging occurs during 100m printing, but smudging occurs during continuous printing from over 100m to 1,000m. ×: Print smudging occurs when printing 100m.

[0340] [Table 1]

[0341] In the thermal recording media 100 of Examples 1 to 9 and Comparative Example 1, the layout formed from each layer is a repeating pattern in the first direction, and each figure in the Examples and Comparative Examples shows only one of these patterns. Therefore, in Table 1, "Support length Xs in the first direction", "Thermal layer length Xh in the first direction", "Protective layer length Xp in the first direction", and "Cleaning layer length Xc in the first direction", as well as "The length of the color ink layer 5 in the first direction", all represent the lengths within one layout pattern. Furthermore, "Support length Xs in the first direction" means "Maximum support length Xs in the first direction", "Protective layer length Xp in the first direction" means "Minimum protective layer length Xp in the first direction", and "Cleaning layer length Xc in the first direction" means "Minimum cleaning layer length Xc in the first direction".

[0342] Examples of the types of disclosures include the following: <1> A thermal recording medium having a first direction and a second direction perpendicular to the first direction in a plan view, A support having a first surface and a second surface opposite to the first surface, A heat-sensitive layer disposed in a portion of the first surface of the support, A protective layer disposed on at least the upper surface of the heat-sensitive layer, A cleaning layer is disposed in a region that is part of the first surface of the support and is different from the heat-sensitive layer, Equipped with, The first surface of the support has at least a portion that is exposed from the heat-sensitive layer, the cleaning layer, and the protective layer, The thermal recording medium is characterized in that, in a cross-sectional view when the thermal recording medium is cut toward the first direction at a predetermined position in the second direction, the thermal layer and the cleaning layer are arranged in different regions. <2> In the first direction, at least one of the sides of the heat-sensitive layer and the side of the protective layer is not in contact with the side of the cleaning layer. In the first direction, the space between the heat-sensitive layer, the protective layer, and the cleaning layer is the exposed portion. <1> It is a thermal recording medium as described in [reference]. <3> The minimum length Xc of the cleaning layer in the first direction, the minimum length Xp of the protective layer in the first direction, and the maximum length Xs of the support in the first direction satisfy (Xc + Xp) / Xs ≥ 0.25, <1> or <2> It is a thermal recording medium as described in [reference]. <4> The minimum length Xc of the cleaning layer in the first direction and the maximum length Xs of the support in the first direction satisfy Xc / Xs ≥ 0.05, <1> from <3> It is a thermal recording medium described in any of the following. <5> The second surface of the support is provided with a color ink layer, <1> from <4> It is a thermal recording medium described in any of the following. <6> The first surface of the support is provided with a color ink layer, The aforementioned color ink layer is (1) At least the upper surface of the color ink layer is exposed, (2) The heat-sensitive layer is arranged on at least the upper surface of the color ink layer, (3) The cleaning layer is placed on at least the upper surface of the color ink layer. The arrangement is selected from the group consisting of the above, <1> from <5> It is a thermal recording medium described in any of the following. <7> The first surface of the support is provided with a color ink layer, At least one of the cleaning layer and the protective layer is disposed over the entire upper surface of the color ink layer. <1> from <6> It is a thermal recording medium described in any of the following. <8> The maximum length Yc of the cleaning layer in the second direction and the maximum length Ys of the support in the second direction satisfy Yc = Ys, <1> from <7> It is a thermal recording medium described in any of the following. <9> The composition of the cleaning layer and the composition of the protective layer are the same, <1> from <8> It is a thermal recording medium described in any of the following. <10> The haze in the region where the support and the cleaning layer are laminated is 30% or less. <1> from <9> It is a thermal recording medium described in any of the following. <11> Using the thermal head, <1> from <10> This is an image recording method characterized by recording an image on a thermal recording medium described in any of the above. <12> The transport direction of the thermal head is the first direction of the thermal recording medium, <11> This is the image recording method described in [reference].

[0343] The aforementioned <1> from <10> The thermal recording medium described in any of the above <11> or <12> The image recording method described herein can solve the aforementioned problems in the conventional methodology and achieve the objectives of this disclosure. [Explanation of symbols]

[0344] 1...Support 1A…Side 1 1B…Second side 2…Thermosensitive layer 3…Protective layer 4…Cleaning layer 5…Color ink layer 100... Thermal recording media [Prior art documents] [Patent Documents]

[0345] [Patent Document 1] Japanese Patent Publication No. 2021-45972

Claims

1. A thermal recording medium having a first direction and a second direction perpendicular to the first direction in a plan view, A support having a first surface and a second surface opposite to the first surface, A heat-sensitive layer disposed in a portion of the first surface of the support, A protective layer disposed on at least the upper surface of the heat-sensitive layer, A cleaning layer is provided which is a part of the first surface of the support and is located in a region different from the heat-sensitive layer, Equipped with, The first surface of the support has at least a portion that is exposed from the heat-sensitive layer, the cleaning layer, and the protective layer, A thermal recording medium characterized in that, in a cross-sectional view when the thermal recording medium is cut toward the first direction at a predetermined position in the second direction, the thermal layer and the cleaning layer are arranged in different regions.

2. In the first direction, at least one of the sides of the heat-sensitive layer and the side of the protective layer is not in contact with the side of the cleaning layer. The thermal recording medium according to claim 1, wherein the space between the thermal layer, the protective layer, and the cleaning layer in the first direction is the exposed portion.

3. The thermal recording medium according to claim 1, wherein the minimum length Xc of the cleaning layer in the first direction, the minimum length Xp of the protective layer in the first direction, and the maximum length Xs of the support in the first direction satisfy (Xc + Xp) / Xs ≥ 0.

25.

4. The thermal recording medium according to claim 1, wherein the minimum length Xc of the cleaning layer in the first direction and the maximum length Xs of the support in the first direction satisfy Xc / Xs ≥ 0.

05.

5. The thermal recording medium according to claim 1, wherein the second surface of the support is provided with a color ink layer.

6. The first surface of the support is provided with a color ink layer, The aforementioned color ink layer is (1) At least the upper surface of the color ink layer is exposed, (2) The heat-sensitive layer is arranged on at least the upper surface of the color ink layer, (3) The cleaning layer is placed on at least the upper surface of the color ink layer. The thermal recording medium according to claim 1, arranged in at least one of the group consisting of the following.

7. The first surface of the support is provided with a color ink layer, The thermal recording medium according to claim 1, wherein at least one of the cleaning layer and the protective layer is disposed over the entire upper surface of at least the color ink layer.

8. The thermal recording medium according to claim 1, wherein the maximum length Yc of the cleaning layer in the second direction and the maximum length Ys of the support in the second direction satisfy Yc = Ys.

9. The thermal recording medium according to claim 1, wherein the composition of the cleaning layer and the composition of the protective layer are the same.

10. The thermal recording medium according to claim 1, wherein the haze in the region where the support and the cleaning layer are laminated is 30% or less.

11. An image recording method characterized by recording an image on a thermal recording medium according to any one of claims 1 to 10 using a thermal head.

12. The image recording method according to claim 11, wherein the transport direction of the thermal head is the first direction of the thermal recording medium.

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