Thermal recording layer forming liquid, thermal recording medium, method for manufacturing the same, and image recording method

Abstract

To provide a thermosensitive recording layer forming liquid capable of forming a thermosensitive recording layer that has a sufficiently uniform texture without tailing and without coating unevenness and also has a small variation in thickness.SOLUTION: Provided is a thermosensitive recording layer forming liquid including an electron-donating compound, an electron-accepting compound, and a solvent. The solubility of the electron-accepting compound in 100% ethanol at 20°C is 5.0 mass% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermal recording layer forming liquid, a thermal recording medium, a method for manufacturing the same, and an image recording method. [Background technology]

[0002] Conventionally, thermal recording media have been widely known, which consist of a thermal recording layer on a support made of paper, synthetic paper, etc., that utilizes the color reaction between electron-donating compounds and electron-accepting compounds. The aforementioned thermal recording medium is manufactured by dispersing an electron-donating compound and an electron-accepting compound in a thermal recording layer-forming liquid, which is then atomized and dispersed with a resin such as polyvinyl alcohol, a pigment such as calcium carbonate, and a dispersant such as a surfactant. This liquid is then applied to the entire surface of a support using an air knife coater, bar coater, blade coater, curtain coater, gravure coater, etc., and dried.

[0003] In recent years, there has been a growing demand for adding a thermal recording layer to conventional thermal recording media using a printing method, for at least one of the following reasons. (1) Reduce costs and environmental impact by simultaneously producing design printing and thermal recording layer forming liquid using a standard printing press. (2) By partially applying the thermal recording layer only where necessary, the amount of thermal recording layer forming liquid is reduced, thereby reducing costs and environmental impact. (3) By partially and directly applying the thermal recording layer only where necessary, the label can be eliminated, and materials such as the substrate, adhesive, and release paper that were conventionally used can be removed, thereby reducing costs and environmental impact. (4) The design can be improved by freely arranging thermal recording layers of various shapes in parts of the structure. (5) The design can be improved by freely arranging the thermal recording layer that emits multiple colors. (6) When used as packaging material after heat sealing, a non-coloring packaging material can be provided by removing the thermal recording layer in the heat-sealed area where high temperatures are applied.

[0004] As a technique for printing a heat-sensitive recording layer by a printing method, for example, there has been proposed a heat-sensitive ink that contains at least a leuco dye, a developer that causes the leuco dye to develop color when heated, and an acrylic resin as a binder, uses toluene as a solvent, can be printed by a printing method, and enables partial printing (see, for example, Patent Document 1).

[0005] On the other hand, conventionally, as a developer which is an electron-accepting compound of a heat-sensitive recording medium, phenolic developers such as 4,4'-isopropylidenediphenol, which are excellent in the preservability and color development sensitivity of the background and images, have been widely used. However, since the phenolic developer is suspected of being an endocrine disruptor, in recent years, heat-sensitive recording media using developers having no phenolic skeleton (hereinafter sometimes referred to as "non-phenolic developers") have been variously proposed (see, for example, Patent Documents 2 and 3). The heat-sensitive recording layer forming liquid in these proposals is an aqueous dispersion.

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a heat-sensitive recording layer forming liquid that can form a heat-sensitive recording layer having excellent background uniformity without streaking and coating unevenness and a small thickness difference. Here, "without streaking" means a state where the boundary between the printed part and the non-printed part is clear, that is, a state of rank 4 or higher with less of the part indicated by the dotted line in the streaking evaluation rank table of FIG. 40.

Means for Solving the Problems

[0007] The heat-sensitive recording layer forming liquid of the present invention as a means for solving the above problems contains an electron-donating compound, an electron-accepting compound having a solubility of 5% by mass or less in 100% ethanol at 20°C, and a solvent The electron-donating compound is a leuco compound, and the electron-accepting compound is at least one non-phenolic color developer selected from compounds having a structure in which an aromatic group is bonded via a linking group, comprising either a (thio)urea group (-NH-CX-NH-) (wherein X represents O or S) or a sulfonyl(thio)urea group (-SO2-NH-CX-NH-) (wherein X represents O or S), and either a urethane group (-NHCOO-), an amide group (-NHCO-), a sulfonyl group (-SO2-), or a sulfonylamide group (-SO2-NH-), and the solvent is a mixed solvent of water and an alcohol solvent, wherein the alcohol solvent accounts for 20% by mass or more of the total mixed solvent. .

Effects of the Invention

[0008] According to the present invention, it is possible to provide a thermal recording layer forming liquid that can form a thermal recording layer that has excellent surface uniformity without trailing or uneven coating, and with small differences in thickness. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of a thermal recording medium according to the first embodiment. [Figure 2] Figure 2 is a schematic cross-sectional view showing an example of a thermal recording medium according to the second embodiment. [Figure 3] Figure 3 is a schematic cross-sectional view showing an example of a thermal recording medium according to the third embodiment. [Figure 4] Figure 4 is a schematic cross-sectional view showing an example of a thermal recording medium according to the fourth embodiment. [Figure 5] Figure 5 is a schematic cross-sectional view showing an example of a thermal recording medium according to the fifth embodiment. [Figure 6] Figure 6 is a schematic cross-sectional view showing an example of a thermal recording medium according to the sixth embodiment. [Figure 7] Figure 7 is a schematic cross-sectional view showing an example of a thermal recording medium according to the seventh embodiment. [Figure 8] Figure 8 is a schematic cross-sectional view showing an example of a thermal recording medium according to the eighth embodiment. [Figure 9] Figure 9 is a schematic cross-sectional view showing an example of a thermal recording medium according to the ninth embodiment. [Figure 10] Figure 10 is a schematic cross-sectional view showing an example of a thermal recording medium according to the tenth embodiment. [Figure 11A] Figure 11A is a schematic cross-sectional view showing an example of a thermal recording medium according to the eleventh embodiment. [Figure 11B] Figure 11B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 11th embodiment. [Figure 12A] Figure 12A is a schematic cross-sectional view showing an example of a thermal recording medium according to the twelfth embodiment. [Figure 12B]Figure 12B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the twelfth embodiment. [Figure 13A] Figure 13A is a schematic cross-sectional view showing an example of a thermal recording medium according to the thirteenth embodiment. [Figure 13B] Figure 13B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 13th embodiment. [Figure 14A] Figure 14A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 14th embodiment. [Figure 14B] Figure 14B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 14th embodiment. [Figure 15A] Figure 15A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 15th embodiment. [Figure 15B] Figure 15B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 15th embodiment. [Figure 16A] Figure 16A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 16th embodiment. [Figure 16B] Figure 16B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 16th embodiment. [Figure 17A] Figure 17A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 17th embodiment. [Figure 17B] Figure 17B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 17th embodiment. [Figure 17C] Figure 17C is a schematic plan view (back surface of the support) showing an example of a thermal recording medium according to the 17th embodiment. [Figure 18A] Figure 18A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 18th embodiment. [Figure 18B] Figure 18B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 18th embodiment. [Figure 18C]Figure 18C is a schematic plan view (back surface of the support) showing an example of a thermal recording medium according to the 18th embodiment. [Figure 19A] Figure 19A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 19th embodiment. [Figure 19B] Figure 19B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 19th embodiment. [Figure 19C] Figure 19C is a schematic plan view (back surface of the support) showing an example of a thermal recording medium according to the 19th embodiment. [Figure 20A] Figure 20A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 20th embodiment. [Figure 20B] Figure 20B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 20th embodiment. [Figure 20C] Figure 20C is a schematic plan view (back surface of the support) showing an example of a thermal recording medium according to the 20th embodiment. [Figure 21A] Figure 21A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 21st embodiment. [Figure 21B] Figure 21B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 21st embodiment. [Figure 21C] Figure 21C is a schematic plan view (back surface of the support) showing an example of a thermal recording medium according to the 21st embodiment. [Figure 22A] Figure 22A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 22nd embodiment. [Figure 22B] Figure 22B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 22nd embodiment. [Figure 22C] Figure 22C is a schematic plan view (back surface of the support) showing an example of a thermal recording medium according to the 22nd embodiment. [Figure 23A] Figure 23A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 23rd embodiment. [Figure 23B]Figure 23B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 23rd embodiment. [Figure 24A] Figure 24A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 24th embodiment. [Figure 24B] Figure 24B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 24th embodiment. [Figure 25A] Figure 25A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 25th embodiment. [Figure 25B] Figure 25B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 25th embodiment. [Figure 25C] Figure 25C is a schematic plan view (back surface of the support) showing an example of a thermal recording medium according to the 25th embodiment. [Figure 26A] Figure 26A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 26th embodiment. [Figure 26B] Figure 26B is a schematic plan view showing an example of a thermal recording medium according to the 26th embodiment (surface of the support). [Figure 27A] Figure 27A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 27th embodiment. [Figure 27B] Figure 27B is a schematic plan view showing an example of a thermal recording medium according to the 27th embodiment (surface of the support). [Figure 28A] Figure 28A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 28th embodiment. [Figure 28B] Figure 28B is a schematic plan view showing an example of a thermal recording medium according to the 28th embodiment (surface of the support). [Figure 29A] Figure 29A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 29th embodiment. [Figure 29B] Figure 29B is a schematic plan view showing an example of a thermal recording medium according to the 29th embodiment (surface of the support). [Figure 30A] Figure 30A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 30th embodiment. [Figure 30B] Figure 30B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 30th embodiment. [Figure 31A] Figure 31A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 31st embodiment. [Figure 31B] Figure 31B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 31st embodiment. [Figure 32A] Figure 32A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 32nd embodiment. [Figure 32B] Figure 32B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 32nd embodiment. [Figure 33] Figure 33 is a schematic diagram showing an example of an image recording device used in the image recording method of the present invention. [Figure 34] Figure 34 is a schematic diagram showing another example of an image recording device used in the image recording method of the present invention. [Figure 35] Figure 35 illustrates the arrangement state of the laser array of the image recording device used in the image recording method of the present invention. [Figure 36A] Figure 36A is a schematic diagram showing an example of a gravure roll used in gravure printing in the embodiment. [Figure 36B] Figure 36B is a schematic diagram showing the layout in gravure printing in the embodiment. [Figure 37] Figure 37 is a schematic diagram showing an example of a flexographic plate used for flexographic printing in the embodiment. [Figure 38] Figure 38 shows a ranking table for evaluating scalp uniformity. [Figure 39] Figure 39 shows a ranking table for evaluating image uniformity. [Figure 40] Figure 40 shows the evaluation ranking table for Ohiki. [Modes for carrying out the invention]

[0010] (Thermal recording layer forming liquid) The thermal recording layer forming liquid of the present invention contains an electron-donating compound, an electron-accepting compound having a solubility of 5% by mass or less in 100% ethanol at 20°C, and a solvent, and further contains other components as needed.

[0011] The thermal recording layer forming solution of the present invention is used in forming the thermal recording medium of the present invention. "Used in forming the thermal recording medium of the present invention" means used in forming the thermal recording layer of the thermal recording medium of the present invention.

[0012] In conventional technology, since the thermal recording layer forming liquid is an aqueous dispersion, when printed using a printing method, the thermal recording layer forming liquid does not spread smoothly, resulting in reduced leveling, tailing and uneven coating, large differences in the thickness of the printed thermal recording layer, and a decrease in the uniformity of the base surface due to uneven coating. Furthermore, when applying a thermal layer to a specific area, the forming liquid may not cut off sufficiently from the desired shape, leading to problems such as blurring of the shape and tailing. Furthermore, conventional technologies use aromatic solvents such as toluene, but the use of toluene is restricted in the printing industry due to concerns about reducing the environmental burden of VOC emissions. Furthermore, while conventionally known thermal recording layer-forming solutions are aqueous dispersions, changing to alcohol-based or ester-based solvents other than aromatic solvents for printability increases the solubility of electron-accepting compounds, reducing the proportion of electron-accepting compounds present as particles in the solvent. This results in a state similar to an electron-accepting compound solution, increasing the probability of contact with electron-donating compounds. Over time, the color reaction between electron-donating and electron-accepting compounds progresses, leading to the so-called "liquid fogging" phenomenon of the thermal recording layer-forming solution.

[0013] Therefore, the thermal recording layer forming liquid of the present invention contains an electron-donating compound, an electron-accepting compound whose solubility in 100% ethanol at 20°C is 5% by mass or less, and a solvent. As a result, the proportion of electron-accepting compounds remaining as particles in the solvent increases, reducing the probability of contact with the electron-donating compound. This suppresses the color development reaction between the electron-donating compound and the electron-accepting compound over time, thereby significantly suppressing the "liquid bleed" phenomenon. Furthermore, the thermal recording layer forming liquid of the present invention makes it possible to form a thermal recording layer with small thickness differences and excellent surface uniformity without trailing or uneven coating.

[0014] The thermal recording layer formed by the thermal recording layer forming solution of the present invention is obtained by printing a thermal recording layer forming solution containing an electron-donating compound, an electron-accepting compound having a solubility of 5% by mass or less in 100% ethanol at 20°C, and a solvent onto a support. In the present invention, it is preferable to coat a portion of the support with a thermal recording layer-forming liquid. That is, the thermal recording layer-forming liquid is applied to the portion of the support where image recording is required to form a thermal recording layer. Here, "a portion of the support" means a partial area where the area of ​​the thermal recording layer is less than 100% of the total surface area of ​​the support. There are no particular restrictions on the shape, size, number, arrangement, etc. of the thermal recording layer, and these can be appropriately selected according to the purpose.

[0015] The heat-sensitive recording layer-forming liquid of the present invention contains an electron-donating compound, an electron-accepting compound, and a solvent, and preferably contains a surfactant, a photothermal conversion material, and a binder resin, and further contains other components as needed.

[0016] <Electron-donating compounds> The electron-donating compound is not particularly limited and 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.

[0017] 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),9'-[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.

[0018] 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.

[0019] 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].

[0020] 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'-(dibenzylamino)-6'-(diethylamino)fluorane, and 2'-(N-phenyl-N-methylamino)-6'-(Np-tolyl-N-ethylamino)spiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one.

[0021] Examples of yellow and orange dye compounds include F.Color Yellow-17, Orange 100, and Orange-DCF.

[0022] The electron-donating compound may be used alone or in combination of two or more.

[0023] The electron-donating compound has a particle size of 50% cumulative volume (D 50 The particle size is preferably 0.05 μm or more and 0.5 μm or less, and more preferably 0.1 μm or more and 0.3 μm or less. The electron-donating compound has a particle size of 50% cumulative volume (D 50 This can be measured, for example, using a laser diffraction / scattering particle size distribution analyzer (device name: LA-960, manufactured by Horiba, Ltd.). There are no particular restrictions on the content of the electron-donating compound, and it can be appropriately selected depending on the purpose, but it is preferably 5% by mass or more and 40% by mass or less, and more preferably 10% by mass or more and 30% by mass or less, relative to the total amount of the thermal recording layer forming liquid.

[0024] <Electron-accepting compounds> The aforementioned electron-accepting compound is not particularly limited as long as it has electron-accepting properties and can be appropriately selected depending on the purpose, but it is preferably a color developer. The aforementioned color developer is not particularly limited as long as its solubility in 100% ethanol at 20°C is 5% by mass or less, and can be appropriately selected according to the purpose. Examples include non-phenolic color developers and bisphenolic color developers. Among these, non-phenolic color developers are preferred. The solubility in 100% ethanol at 20°C is preferably 4% by mass or less, more preferably 3% by mass or less, and particularly preferably 1% by mass or less.

[0025] <Measurement of solubility of electron-accepting compounds in ethanol> <<1. Preparation of saturated solution>> (1) Prepare approximately 100 g of solvent (100% ethanol) in a 150 mL to 300 mL beaker at an environment of 20 °C ± 3 °C. (2) While stirring with a stirrer and stirring rod, gradually add the electron-accepting compound, and stop adding the chemical when undissolved material remains at the bottom. (3) Cover the top to prevent evaporation and leave for at least one hour. (4) Stir with a stirring rod until all undissolved material is gone, then repeat steps (2) to (4). (5) If undissolved material remains after standing for more than one hour, the saturated solution is considered complete.

[0026] <<2. Measurement of Solubility>> Weigh the aluminum cup (A) to the nearest 1 mg. Using a dropper, take out the clear supernatant liquid portion of the saturated solution prepared in step 1 above, place approximately 0.8 to 1.3 g of the liquid into an aluminum cup, and weigh the liquid (B) to the nearest 1 mg. Weighing should be done quickly, taking care to prevent contamination with waste or other debris. Place the aluminum cup containing the liquid into a drying oven (120°C ± 10°C). Alternatively, place it on a hot plate (120°C ± 10°C) in an area where local exhaust ventilation is installed. Evaporate the solvent for at least 25 minutes (if using a hot plate, cover it to prevent debris from getting onto the sample). Remove the aluminum cup from the dryer or hot plate, leave it at room temperature for at least one minute, and then weigh the total weight (C) to the nearest 1 mg. Based on the measurement results of A, B, and C above, the solubility of the electron-accepting compound in ethanol is calculated using the following formula 1. Solubility (mass%) = [(CA) / B] × 100 ... Formula 1

[0027] Non-phenolic color developers are those that do not contain a phenol skeleton. Because non-phenolic color developers do not have the potential to be endocrine disruptors like phenolic color developers, they are superior in terms of environmental impact.

[0028] The non-phenolic color developer is preferably at least one selected from compounds having a structure in which an aromatic group is bonded via the linking group, comprising either a (thio)urea group (-NH-CX-NH-) (wherein X represents O or S) or a sulfonyl(thio)urea group (-SO2-NH-CX-NH-) (wherein X represents O or S), and either a urethane group (-NHCOO-), an amide group (-NHCO-), a sulfonyl group (-SO2-), or a sulfonylamide group (-SO2NH-). More preferably, the non-phenolic color developer is at least one selected from compounds having a structure in which an aromatic group is bonded via the linking group, comprising either a urea group (-NH-CO-NH-) or a sulfonylurea group (-SO2-NH-CO-NH-), and either an amide group (-NHCO-), a sulfonyl group (-SO2-), or a sulfonylamide group (-SO2NH-).

[0029] As the electron-accepting compound, various substances can be used that react with the electron-donating compound upon heating to produce color. One type may be used alone, or two or more types may be used in combination. The electron-accepting compound can be any of the conventionally known sulfur-containing bisphenol compounds, 4-hydroxybenzoic acid esters, benzoates, metal salicylates, hydroxysulfones, polyvalent metals of hydroxysulfones, hydroxynaphthoic acid esters, trihalomethylsulfones, sulfonylureas, and diphenylsulfone crosslinked compounds, as long as its solubility in ethanol at 20°C is 5% by mass or less.

[0030] The electron-accepting compound is preferably one of the following compounds (I) to (VI). [Compound (I)] The aforementioned compound (I) is represented by the following general formula (I). [ka] However, in the general formula (I) above, R1 is an unsubstituted phenyl group or a phenyl group substituted with an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a halogen atom, X is a group of the formula: -C(=O)-, and A is an unsubstituted phenylene group or a phenylene group substituted with an alkyl group having 1 to 8 carbon atoms, a halogen-substituted alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a halogen-substituted alkoxy group having 1 to 8 carbon atoms, an alkylsulfonyl group having 1 to 8 carbon atoms, a halogen atom, a phenyl group, a phenoxy atom, or a phenoxycarbonyl group. TIFF0007852277000002.tif19138R2 is an alkyl group having 1 to 4 carbon atoms; a halogen-substituted alkyl group having 1 to 4 carbon atoms; an unsubstituted phenyl group or a phenyl group substituted with an alkyl group having 1 to 4 carbon atoms or a halogen atom; or an unsubstituted benzyl group or a phenyl group substituted with an alkyl group having 1 to 4 carbon atoms or a halogen atom. However, if B is not a linking group of the formula -O-SO2-, R2 is an unsubstituted or substituted phenyl group or an alkyl group having 1 to 8 carbon atoms, and if B is of the formula -O-, R2 is not an alkyl group.

[0031] Of the compounds (I) mentioned above, the compound represented by the following structural formula is particularly preferred. [ka]

[0032] [Compound (II)] The aforementioned compound (II) is represented by the following general formula (II). [ka] However, in the above general formula (II), R 1 ~R 5 Each of these independently represents one of the following: a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group.

[0033] Among the compounds (II) mentioned above, the compound represented by the following structural formula is particularly preferred. [ka]

[0034] [Compound (III)] The aforementioned compound (III) is represented by the following general formula (III). [ka] However, in the above general formula (III), R and R 1 It is independently selected from the group consisting of (1) to (5). (1) a hydrogen atom, (2) a linear or branched alkyl group having 1 to 18 carbon atoms, (3) R 11 OR 12 — provided that R 11 and R 12 are each independently a linear or branched alkyl group having 1 to 8 carbon atoms), (4) (R 13 )2N-R 12 ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0036] Among the aforementioned compounds (III), the compound represented by the following structural formula is particularly preferred. [ka]

[0037] [Compound (IV)] The aforementioned compound (IV) is represented by the following general formulas (IV)-1 to (IV)-3. [ka] However, in the general formula (IV)-1, R1 to R3 represent a hydrogen atom, a halogen atom, a nitro group, a C1-C6 alkyl group, a C1-C6 alkoxy group, a C2-C6 alkenyl group, a C1-C6 fluoroalkyl group, an N(R4)² group (wherein R4 represents a hydrogen atom, a phenyl group, a benzyl group, or a C1-C6 alkyl group), an NHCOR5 (wherein R5 represents a C1-C6 alkyl group), an optionally substituted phenyl group, or an optionally substituted benzyl group, and n1 and n3 each independently represent an integer from 1 to 5, and n2 represents an integer from 1 to 4.

[0038] [ka] However, in the general formula (IV)-2, R1 to R3 represent the same values ​​as R1 to R3 in formula (I), n2 and n3 represent the same values ​​as n2 and n3 in formula (IV)-1, and n4 represents any integer from 1 to 7.

[0039] [ka] However, in the general formula (IV)-3, R1 to R3 represent the same values ​​as R1 to R3 in formula (IV)-1, and n2, n3, and n4 represent the same values ​​as n2, n3, and n4 in formulas (IV)-1 and (IV)-2.

[0040] Of the compounds (IV)-1 to (IV)-3 mentioned above, the one having the following structural formula (IV) is particularly preferred. [ka]

[0041] [Compound (V)] Compound (V) is represented by the following general formula (V). [ka] However, in the general formula (V) above, R2 is a linear, branched, or alicyclic alkyl group having 1 to 12 carbon atoms, an unsubstituted or alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms substituted with a halogen atom, and multiple R2s may be the same or different. A1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Multiple A1s may be the same or different.

[0042] Of the above structural formulas, the compound represented by the following structural formula (V) is particularly preferred. [ka]

[0043] [Compound (VI)] The compound (VI) is represented by the following general formulas (VI-1) to (VI-7).

[0044] [ka] However, in the general formula (VI-1) above, X and Z represent aromatic compound residues, and each residue may have substituents, and Y0 represents one of the group selected from the group consisting of a torylene group, a xylylene group, a naphthylene group, a -Φ-CH2-Φ- group, and the following structural formula (1). Note that -Φ- represents a phenylene group. [ka]

[0045] [ka] However, in the general formula (VI-2) above, X and Y represent aromatic compound residues, and each residue may have substituents.

[0046] [ka] However, in the general formula (VI-3) above, X and Y represent aromatic compound residues, A represents an aromatic compound residue having a valency of 2 or more, n represents an integer of 2 or more, and each residue may have substituents.

[0047] [ka] However, in the general formula (VI-4) above, Z and Y represent aromatic compound residues, B represents an aromatic compound residue having a valency of 2 or more, n represents an integer of 2 or more, and each residue may have substituents.

[0048] [ka] However, in the general formula (VI-5) above, the hydrogen atoms of the benzene ring may be substituted with aliphatic compound residues, and the residues may have substituents, C is one selected from the group consisting of -SO2-, -O-, -(S)n-, -(CH2)n-, -CO-, -CONH- and the group shown in the following structural formula, or is absent, and n is 1 or 2. [ka]

[0049] [ka] However, in the general formula (VI-6) above, the benzene ring may be substituted with a hydrogen atom, and the aliphatic compound residue may have substituents, where D is one selected from the group consisting of -SO2-, -O-, -(S)n-, -(CH2)n-, -CO-, -CONH-, -NH-, -CH(COOR1)-, -C(CF3)2-, and -CR2R3-, or is absent, where R1, R2, and R3 each represent an alkyl group, and n is 1 or 2.

[0050] [ka] However, in the general formula (VI-7) above, X, Y, and Z represent aromatic compound residues, and each residue may have substituents.

[0051] Of the compounds (VI-1) to (VI-7) mentioned above, the compound represented by the following structural formula (VI) is particularly preferred.

[0052] [ka]

[0053] There are no particular restrictions on the content of the electron-accepting compound, and it can be appropriately selected depending on the purpose, but it is preferably 1 to 20 parts by mass, and more preferably 2 to 10 parts by mass, per 1 part by mass of the electron-donating compound.

[0054] <Solvent> Examples of the aforementioned solvents include water, aromatic solvents, ester solvents, ketone solvents, alcohol solvents, aliphatic hydrocarbons, glycol solvents, paraffinic solvents, petroleum-based solvents mainly composed of naphthenes with an aromatic component content of 1% or less, or mixed solvents thereof. Among these, alcohol solvents, ester solvents, or mixed solvents of water and alcohol solvents are preferably used from the viewpoint of solubility of electron-accepting compounds and reduction of environmental impact. Aromatic solvents such as toluene have low solubility for electron-accepting compounds, but their use is restricted in the printing industry from the standpoint of reducing the environmental impact of VOC emissions.

[0055] Examples of the alcohol solvent include methanol, ethanol, isopropyl alcohol, n-propyl alcohol, and butanol. Among these, ethanol is particularly preferred. Examples of the ester solvent include ethyl acetate, propyl acetate, isopropyl acetate, isobutyl acetate, butyl acetate, isoamyl acetate, amyl acetate, hexyl acetate, phenyl acetate, and benzyl acetate. Examples of the water mentioned above include pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water, or ultrapure water.

[0056] In the present invention, a mixed solvent of the above-mentioned alcohol solvent and water can be used. By using an electron-accepting compound within the solubility range of the above-mentioned ethanol, the phenomenon of "liquid fogging" over time can be significantly suppressed. However, by using a mixed solvent with water, the risk of the "liquid fogging" phenomenon over time can be further reduced, allowing the cycle time of the thermal recording layer forming solution to be extended, which is advantageous in terms of production. However, from the viewpoint of leveling, it is preferable that the alcohol solvent contains 20% by mass or more of the total mixed solvent, and more preferably 40% by mass or more.

[0057] <Photothermal conversion materials> The aforementioned photothermal conversion materials are materials that absorb laser light and convert it into heat, and can be broadly classified into inorganic materials and organic materials. Examples of the inorganic material include carbon black, metal borides, and particles of at least one of metal oxides such as Ge, Bi, In, Te, Se, and Cr. Among these, materials that have high absorption of light in the near-infrared wavelength region and low absorption of light in the visible wavelength region are preferred, and metal borides and metal oxides are more preferred. Examples of the metal borides and metal oxides include at least one selected from hexaboride, tungsten oxide compounds, antimony tin oxide (ATO), indium tin oxide (ITO), and zinc antimonate. Examples of the aforementioned hexaborides include LaB6, CeB6, PrB6, NdB6, GdB6, TbB6, DyB6, HoB6, YB6, SmB6, EuB6, ErB6, TmB6, YbB6, LuB6, SrB6, CaB6, and (La,Ce)B6. The tungsten oxide compound may be, for example, fine particles of tungsten oxide represented by the general formula: WyOz (where W is tungsten, O is oxygen, 2.2 ≤ z / y ≤ 2.999), as described in International Publication No. 2005 / 037932, Japanese Patent Publication No. 2005-187323, etc., or by the general formula: MxWyOz (where M is H, He, alkali metals, alkaline earth metals, rare earth elements, Mg, Zr, Cr, Mn, Fe, Examples include fine particles of composite tungsten oxide (where W is tungsten, O is oxygen, and 0.001≦x / y≦1, 2.2≦z / y≦3.0), which are represented by one or more elements selected from Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, and I, where W is tungsten, O is oxygen, and 0.001≦x / y≦1, 2.2≦z / y≦3.0). Among these, cesium-containing tungsten oxide is particularly preferred due to its large absorption in the near-infrared region and small absorption in the visible region. Furthermore, among antimony tin oxide (ATO), indium tin oxide (ITO), and zinc antimonate, ITO is particularly preferred because it has high absorption in the near-infrared region and low absorption in the visible region. These are formed in layers by vacuum deposition or by bonding particulate materials with resin or the like. As the aforementioned organic material, various dyes can be used as appropriate depending on the wavelength of light to be absorbed. However, when a semiconductor laser is used as the light source, near-infrared absorbing dyes having an absorption peak around 600 nm to 1,200 nm are used. Specifically, examples include cyanine dyes, quinone dyes, quinoline derivatives of indonaphthol, phenylenediamine nickel complexes, and phthalocyanine dyes. The aforementioned light and heat conversion materials may be used individually or in combination of two or more types. The aforementioned photothermal conversion material may be incorporated into the thermal recording layer or into a layer other than the thermal recording layer. When incorporated into a layer other than the thermal recording layer, it is preferable to provide the photothermal conversion layer adjacent to the thermal recording layer. The amount of the photothermal conversion material is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.3% by mass or more and 5% by mass or less, relative to the total amount of the thermal recording layer forming liquid.

[0058] - Surfactants - To obtain the shape of the partial coating of the present invention with greater precision, a surfactant may be added to adjust the surface tension of the thermal recording layer forming liquid.

[0059] The surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples include anionic surfactants, nonionic surfactants, amphoteric surfactants, and fluorinated surfactants. Examples of the anionic surfactants include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, lauryl salt, and polyoxyethylene alkyl ether sulfate salts. These may be used individually or in combination of two or more. Examples of the 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. Examples of the acetylene glycol-based surfactants include 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyne-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.

[0060] -Binder 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 resins, water-dispersible resins, solvent-soluble resins, etc., regardless of their properties. Examples of the binder resin include acrylic resin, polyvinyl alcohol resin, 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 terpolymer, 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 resin and styrene-acrylic copolymer are preferred when transparency is required.

[0061] <Other ingredients> Examples of the other components mentioned above include auxiliary additives, thermofusible substances, lubricants, fillers, ultraviolet absorbers, antioxidants, sensitizers, and light stabilizers.

[0062] As the auxiliary additives, for example, various hindered phenol compounds or hindered amine compounds that are electron-accepting but have relatively low color-developing ability may be added. Examples of the aforementioned 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-methylphenyl). Examples include thiobisphenol, 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.

[0063] -Thermofusible substance- Examples of the aforementioned heat-fusible 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, benzyl β-benzyloxynaphthalene, phenyl β-naphthoate, and 1-hydroxy-2-naphthoate. Phenyl acid, 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-methoxyphenoxy Luthio)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.

[0064] - Lubricant - Examples of the 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.

[0065] -Filler- Examples of fillers include inorganic fine powders such as calcium carbonate, silica, zinc oxide, titanium oxide, 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. There are no particular restrictions on the content of the filler, and it can be appropriately selected depending on the purpose, but it is preferably 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.

[0066] - UV absorber - There are no particular restrictions on the UV absorber, 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. Examples of the UV absorbers 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'- Examples include di-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.

[0067] (Method of manufacturing a thermal recording medium) The method for manufacturing a thermal recording medium of the present invention includes a thermal recording layer formation step of applying the thermal recording layer forming solution of the present invention onto a support to form a thermal recording layer, and further includes other steps as necessary. In the thermal recording layer formation step, it is preferable to apply the thermal recording layer forming liquid to a portion of the support. Here, "a portion of the support" refers to a partial area where the area of ​​the thermal recording layer is less than 100% of the total surface area of ​​the support. There are no particular restrictions on the shape, size, number, or arrangement of the thermal recording layer, and these can be appropriately selected according to the purpose.

[0068] There are no particular limitations on the method for forming the thermal recording layer, and it can be appropriately selected according to the purpose. For example, the electron-donating compound, an electron-accepting compound having a solubility of 5.0% by mass or less in 100% ethanol at 20°C, and the other components can be ground and dispersed together using a disperser such as a ball mill, attritor, or sand mill until the dispersed particle size is 0.1 μm or more and 3 μm or less. Then, if necessary, the mixture can be mixed with the filler or the like to prepare a thermal recording layer forming solution, and the thermal recording layer can be formed by applying the thermal recording layer forming solution onto a support and drying it. The coating method is not particularly limited and can be appropriately selected according to the purpose. Examples include the blade coating method, gravure coating method, gravure offset coating method, bar coating method, roll coating method, knife coating method, air knife coating method, comma coating method, U-comma coating method, AKKU coating method, smoothing coating method, microgravure coating method, reverse roll coating method, 4- to 5-roll coating method, dip coating method, curtain coating method, slide coating method, and die coating method.

[0069] The amount of the thermal recording layer forming liquid that adheres after drying is not particularly limited and can be appropriately selected depending on the purpose, but is 1 g / m². 2 More than 20g / m 2 The following is preferable: 2 g / m 2 More than 10g / m 2 The following are preferable.

[0070] (Thermal recording medium) The thermal recording medium of the present invention comprises a support and a thermal recording layer formed on the support with the thermal recording layer forming solution of the present invention, and further comprises other layers as necessary. In other words, the thermal recording medium of the present invention comprises a support and a thermal recording layer formed on the support containing an electron-donating compound and an electron-accepting compound having a solubility in 100% ethanol at 20°C of 5.0% by mass or less, and further comprises other layers as necessary. Furthermore, it is preferable that the thermal recording medium of the present invention has a thermal recording layer formed on a portion of a support using the thermal recording layer forming solution of the present invention. Here, "a portion of the support" refers to a partial area where the area of ​​the thermal recording layer is less than 100% of the total surface area of ​​the support. There are no particular restrictions on the shape, size, number, or arrangement of the thermal recording layer, and these can be appropriately selected according to the purpose.

[0071] The thermal recording medium of the present invention comprises a support and a thermal recording layer on the support containing an electron-donating compound and an electron-accepting compound having a solubility in 100% ethanol at 20°C of 5.0% by mass or less, wherein the thickness difference of the thermal recording layer in the region excluding the edges of the thermal recording layer, represented by the following formula, is 50% or less, and further comprises other layers as necessary. Furthermore, it is preferable that the thermal recording medium of the present invention has a thermal recording layer on a portion of the support containing an electron-donating compound and an electron-accepting compound having a solubility of 5.0% by mass or less in 100% ethanol at 20°C. Here, "a portion of the support" refers to a partial area where the area of ​​the thermal recording layer is less than 100% of the total surface area of ​​the support. There are no particular restrictions on the shape, size, number, or arrangement of the thermal recording layer, and these can be appropriately selected according to the purpose. There are no particular restrictions on the average thickness of the thermal recording layer, and it can be appropriately selected depending on the purpose. A thickness of 1 μm to 20 μm is preferred, and a thickness of 2 μm to 10 μm is more preferred.

[0072] The difference in thickness of the thermal recording layer in the region excluding the edges of the thermal recording layer, as expressed by the following formula, is 50% or less, preferably 30% or less, more preferably 20% or less, and even more preferably 10% or less. Thickness difference of thermal recording layer (%) = [(Maximum thickness of thermal recording layer or minimum thickness of thermal recording layer - Average thickness of thermal recording layer) / Average thickness of thermal recording layer] × 100 However, the thickness of the thermal recording layer is measured at any 20 points on the thermal recording medium, the maximum value is defined as the "maximum thickness of the thermal recording layer," and the minimum value is defined as the "minimum thickness of the thermal recording layer." The average value of the 18 points obtained by excluding the "maximum thickness of the thermal recording layer" and the "minimum thickness of the thermal recording layer" from the aforementioned 20 points is defined as the "average thickness of the thermal recording layer." The larger of the absolute values ​​of (maximum thickness of the thermal recording layer - average thickness of the thermal recording layer) and (minimum thickness of the thermal recording layer - average thickness of the thermal recording layer) is adopted. The thickness of the thermal recording layer can be measured, for example, by a film thickness gauge, but it is also possible to determine the film thickness from a cross-sectional photograph of the thermal recording medium taken with an electron microscope. Any method that can determine the film thickness can be applied, and is not particularly limited. As the aforementioned film thickness gauge, for example, the K-402B STAND and the electronic micrometer K351C (manufactured by Anritsu Corporation) can be used.

[0073] Furthermore, the thickness of the thermal recording layer in a thermal recording medium in which layers other than the thermal recording layer (such as a protective layer or printed layer) are formed on the support can be measured by one of the following methods. (1) A single layer is printed on the support under the set conditions, and after drying, the thickness is measured with a film thickness gauge. Since the same conditions are used during lamination, the measurement value for the single layer can be applied to the lamination process. (2) The thickness of the first layer on the support can be measured with a film thickness gauge, and the thickness of the second layer can be measured by measuring the total thickness with a film thickness gauge and subtracting the thickness of the first layer from the total thickness to determine the thickness of the second layer. (3) Using the Cross Section Polisher SM-0920CP (manufactured by JEOL Ltd.), the cross section of the thermal recording medium can be cut, and the cross section can be observed with a Scanning Electron Microscope (SEM) S-3700 (manufactured by Hitachi High-Tech Corporation) to measure the thickness of each layer.

[0074] It is preferable to minimize the thickness variations of the thermal recording layer. If the thickness variations are large, they may be visible in the uncolored state, but they will particularly appear as density differences in the colored state. If the thermal recording layer is partially provided and the thickness variation within the area exceeds 50% of the average value, it will be visible as a difference in density between the uncolored and colored areas, which is undesirable in appearance when printing various patterns such as lines, characters, figures, designs, barcodes, and solid colors. When the aforementioned thickness difference is between 30% and 50%, it becomes difficult to see in the uncolored areas, but unevenness in shade can be seen once color has developed. Furthermore, if the thickness difference is between 10% and less than 30%, it will only be noticeable as slight variations in shading in the colored area, affecting only limited patterns such as large areas of solid printing. Furthermore, if the thickness difference is 10% or less, it becomes difficult to visually distinguish between uncolored and colored versions, allowing it to be used without compromise for any design.

[0075] <Support> The support has no particular limitations on its shape, structure, size, material, etc., and can be appropriately selected according to the purpose. Examples of the shape include a flat plate or a sheet. The structure may be a single-layer structure or a laminated structure. The size can be appropriately selected according to the size of the thermal recording medium, etc.

[0076] As the support material, for example, in addition to ordinary paper, synthetic paper, or plastic films such as polyethylene, transparent polyethylene terephthalate, polypropylene, or polyvinyl chloride can be used. When using these plastic films, surface treatments such as matte treatment or corona treatment may be applied to the surface of the support material to improve the adhesion of the coating liquid. Among these, biaxially oriented polyethylene terephthalate sheets are preferred because they are excellent in terms of strength, heat resistance, and dimensional stability. Furthermore, white opaque films or foamed sheets obtained by adding white raw materials or fillers to these materials can also be used. Laminates of the above materials can also be used, and typical examples include laminates of cellulose fibers and synthetic paper, cellulose fibers and plastic film, or plastic film and synthetic paper. The support is preferably a transparent film, as this allows for easy confirmation of the contents when used as packaging material for food and the like. Here, transparency refers to a haze (turbidity) of 10% or less, which is an indicator of the transparency of the film. While this is generally acceptable, a haze of 5% or less is more preferable to achieve the objectives of the present invention. The average thickness of the support can be arbitrarily selected as needed, but from the viewpoint of transparency and ease of processing, it is preferably between 3 μm and 300 μm. If the average thickness of the support is less than 3 μm, the strength will be insufficient, and if it exceeds 300 μm, the transparency will decrease and the rigidity will become too high, resulting in poor processability.

[0077] <Protective layer> The protective layer contains a binder resin and a crosslinking agent, and may further contain other components as needed. The protective layer is preferably located on the thermal recording layer.

[0078] There are no particular restrictions on the binder resin, and it can be appropriately selected depending on the purpose. However, when applying a partial coating, it is preferable to select a binder resin used for the thermal recording layer. Examples of the binder resin include acrylic resin, polyvinyl alcohol resin, 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 terpolymer, 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 resin and styrene-acrylic copolymer are preferred when transparency is required.

[0079] When applying a protective layer to the entire surface, it is also possible to use water-soluble resins or similar materials. Examples of the water-soluble resins include polyvinyl alcohol, modified polyvinyl alcohol, starch or its derivatives, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic acid terpolymer, alkali salt of styrene-maleic anhydride copolymer, alkali salt of isobutylene-maleic anhydride copolymer, polyacrylamide, modified polyacrylamide, methyl vinyl ether-maleic anhydride copolymer, carboxy-modified polyethylene, polyvinyl alcohol-acrylamide block copolymer, melamine-formaldehyde resin, urea-formaldehyde resin, sodium alginate, gelatin, and casein. These may be used individually or in combination of two or more. Among these, modified polyvinyl alcohol is preferred. Examples of the modified polyvinyl alcohols include diacetone-modified polyvinyl alcohol; acetoacetyl-modified polyvinyl alcohol; carboxylic acid-modified polyvinyl alcohols such as itaconic acid-modified polyvinyl alcohol and maleic acid-modified polyvinyl alcohol; and the like.

[0080] The crosslinking agent can be appropriately selected depending on the purpose, such as heat resistance and thermal head matching. Examples 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, aziridine compounds and carbodiimide derivatives, which have very high reactivity with carboxyl groups such as acrylic resins and form a crosslinked structure with the resin, exhibiting excellent water resistance and solvent resistance, are particularly preferred. The content of the crosslinking agent is not particularly limited and can be appropriately selected depending on the purpose, but 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.

[0081] Furthermore, it is preferable to include a pigment (filler) in the protective layer as needed. Examples of pigments used in the protective layer include inorganic pigments such as zinc oxide, calcium carbonate, barium sulfate, titanium dioxide, lithopone, talc, pyrophyllite, kaolin, aluminum hydroxide, and calcined kaolin, as well as organic pigments such as cross-linked polystyrene resin, urea resin, silicone resin, cross-linked polymethyl methacrylate resin, and melamine-formaldehyde resin. In addition to the resin, crosslinking agent, and pigment mentioned above, the protective layer may also contain conventionally used auxiliary additives, such as surfactants, thermofusible substances, lubricants, and pressure-induced color inhibitors.

[0082] The protective layer is not particularly limited and can be formed by generally known methods. The average thickness of the protective layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.5 μm or more and 5 μm or less, and more preferably 1 μm or more and 3 μm or less.

[0083] <Print layer> The aforementioned printing layer is printed with ink or the like and comes in various colors, materials, and thicknesses, forming the background of the image printed on the thermal recording layer. By providing a printing 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. Furthermore, since the thermal recording layer of the present invention allows for partial printing, the printing layer can be formed simultaneously with the thermal recording layer. Preferably, the printed layer is located on the thermal recording layer, between the support and the thermal recording layer, and on at least one of the surfaces of the support opposite to the thermal recording layer. This makes it easy to see the contents from the portion without the printed layer when the contents are packaged with the thermal recording medium as a packaging sheet.

[0084] The printing layer contains a colorant, a binder resin, and a solvent, and further contains other components as needed. There are no particular restrictions on the aforementioned coloring material; it can be appropriately selected according to the purpose, and pigments or dyes can be used.

[0085] The binder resin and other components can be the same as those used for the thermal recording layer.

[0086] The printed layer is formed by gravure printing, flexographic printing, offset printing, UV printing, inkjet printing, etc.

[0087] There are no particular restrictions on the average thickness of the printed layer, and it can be appropriately selected depending on the purpose, but it is preferably 0.05 μm or more and 4 μm or less, and more preferably 0.1 μm or more and 2 μm or less.

[0088] <Other layers> The aforementioned other layers are not particularly limited and can be appropriately selected according to the purpose. Examples include a back layer, underlayer, heat seal layer, release layer, and adhesive layer.

[0089] -Back layer- A back layer may be provided to suppress curling of thermal recording media, but if transparency is required, it is preferable not to provide a back layer. When the back layer is provided, the back layer may be provided on the side of the support that does not have a thermal recording layer, if necessary. The back layer contains a filler and a binder resin, and optionally contains other components such as a lubricant and a coloring pigment. For example, inorganic fillers or organic fillers can be used as the filler. Examples of the inorganic fillers include carbonates, silicates, metal oxides, and sulfate compounds. Examples of the 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, and polymethyl methacrylate resin. There are no particular restrictions on the binder resin, and it can be appropriately selected depending on the purpose. For example, the same type of binder resin as that used for the thermal recording layer can be used. The average thickness of the back layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.1 μm or more and 20 μm or less, and more preferably 0.3 μm or more and 10 μm or less.

[0090] -Underclass- An underlayer may be provided to improve the color sensitivity of a thermal recording medium, but if transparency is required, it is preferable not to provide an underlayer. When the aforementioned underlayer is provided, there are no particular restrictions on the underlayer, and it can be appropriately selected according to the purpose, but it is preferable that it contains adhesive resin, thermoplastic hollow resin particles, etc., and further contains other components as needed.

[0091] The aforementioned thermoplastic hollow resin particles are microscopic hollow particles that have a thermoplastic resin shell and contain air or other gases inside, and are already in a foamed state.

[0092] 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, but a size of 0.2 μm or more and 20 μm or less is preferred, and a size of 2 μm or more and 5 μm or less is more preferred. If the average particle size is smaller than 0.2 μm, it becomes technically difficult to create a hollow structure, and the undercoat layer's role becomes insufficient. On the other hand, if the average particle size is larger than 20 μm, the smoothness of the surface after coating and drying decreases, resulting in uneven coating of the thermal recording layer. To achieve uniformity, it becomes necessary to apply more thermal recording layer coating solution than required. Therefore, it is desirable that the average particle size is within the above range, and that the distribution peak is uniform with little variation.

[0093] There are no particular restrictions on the hollowness of the thermoplastic hollow resin particles, and they can be appropriately selected depending on the purpose, but 50% to 95% is preferred, and 80% to 95% is more preferred. If the hollow ratio is less than 30%, the thermal insulation is insufficient, causing thermal energy from the thermal head to be released outside the thermal recording medium through the support, resulting in an insufficient improvement in sensitivity. The hollow ratio referred to here is the ratio of the outer diameter to the inner diameter (diameter of the hollow part) of the hollow particle, and is expressed by the following formula. Hollowness (%) = (Inner diameter of hollow particle / Outer diameter of hollow particle) × 100

[0094] As mentioned above, the 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 because they have a high hollowness ratio, small variation in particle size, and are suitable for blade coating.

[0095] There are no particular restrictions on the amount of the aforementioned hollow plastic particles that can be applied, and it can be appropriately selected depending on the purpose. However, in order to maintain sensitivity and uniformity of application, the amount applied to the support is 1 m 2 1g to 3g is needed per unit. 1g / m 2 If it is less than 3g / m, sufficient sensitivity cannot be obtained, and 2 Beyond a certain point, a decrease in the bonding strength of the layers occurs.

[0096] -Heat seal layer- The heat-seal layer is formed by laminating LDPE (low-density polyethylene) films used as sealants, and can be welded together by heating the heat-seal layers in close contact with each other. This property allows for the sealing, or heat-sealing, of a bag-shaped packaging sheet by heating it in a similar manner. Therefore, the heat-seal layer can be formed using any material that possesses the property of being heat-sealable, i.e., heat-sealable, and is not limited to LDPE. 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. The average thickness of the heat seal layer is preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm, from the viewpoint of transparency and seal strength.

[0097] -Exfoliation layer- The release layer contains a release agent. Examples of the release agent include UV-curable silicone, thermosetting silicone, solvent-free silicone, solvent-based silicone, emulsion-type silicone, and fluorine-based release agents.

[0098] -Adhesive layer- 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. Here, "main component" means 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, which are added as needed. Furthermore, in this specification, "(meth)acrylic" means "acrylic or methacrylic." 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. In addition to the above components, radical polymerizable unsaturated monomers containing carboxyl groups, alkyl (meth)acrylates, and radical polymerizable unsaturated monomers copolymerizable with each of the carboxyl group-containing radical polymerizable unsaturated monomers may be added as needed. Examples of carboxyl group-containing radical polymerizable unsaturated monomers include α,β-unsaturated carboxylic acids such as (meth)acrylic acid, and α,β-unsaturated dicarboxylic acids such as itaconic acid, maleic acid, and 2-methyleneglutaric acid. These may be used individually or in combination of two or more. The dry adhesion amount of the adhesive layer is 8 g / m². 2 ~30g / m 2 Preferably, it is 12 g / m 2 ~25g / m 2 It is more preferable that the dry adhesion amount of the adhesive layer be 8 g / m². 2 If the value is less than this, sufficient adhesive strength may not be achieved. There are no particular restrictions on the method of applying the adhesive layer-forming liquid, and it can be appropriately selected according to the purpose. Examples include coating methods such as roll coaters, knife coaters, bar coaters, slot die coaters, and curtain coaters, as well as printing methods such as gravure and flexographic printing. The adhesive layer can be formed by directly applying and drying the adhesive layer forming liquid to the side of the support that is not the release layer, or by applying the adhesive layer forming liquid to a release-resistant substrate, drying it, transferring it to the side of the support that does not have a release layer, and then peeling off only the substrate to form the adhesive layer.

[0099] There are no particular limitations on the form of the thermal recording medium of the present invention, and can be appropriately selected according to the purpose. For example, it may be used as a label as is, or a layer for printing information such as characters, marks, pictures, barcodes, or two-dimensional codes such as QR codes (registered trademarks) may be provided on the protective layer or on the support. Alternatively, a release layer may be provided on the same side as the thermal recording layer on the support, and an adhesive layer may be provided on the opposite side of the support from the thermal recording layer. Furthermore, there are no particular restrictions on the shape of the thermal recording medium of the present invention, and it can be appropriately selected depending on the purpose. Examples include label shape, sheet shape, roll shape, etc.

[0100] <Application> The thermal recording medium of the present invention can be used in a wide range of applications, such as packaging films for various containers including PET bottles for soft drinks, metal cans for canned coffee, bottles for beverages, pharmaceuticals, beer, etc., and packaging labels in the POS field for fresh food, bento boxes, and prepared foods.

[0101] [Method of forming layers] The thermal recording layer, overlayer, and printing layer can be formed using generally known printing methods. While the printing layer is not strictly necessary in this invention, its inclusion allows for the inclusion of product names, manufacturer names, ingredient lists, etc., before product packaging, and provides the product with superior design appeal. Furthermore, since the thermal color-developing layer of this invention allows for partial printing, the printing layer can be formed simultaneously with the thermal recording layer. Furthermore, the printing layer is provided between the support and the thermal recording layer, or on a part of the back side of the support. Therefore, when the contents are packaged in the packaging sheet, it is easy to see the contents from the parts where the printing layer is not provided. 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, a print head can be used for several printing inks for design printing, and the remaining print head can be used to print the thermal recording layer and the protective layer of the present invention simultaneously in a single pass. This results in better design positioning accuracy and significantly improved productivity compared to production using two or more passes. 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.

[0102] Herein, embodiments of the thermal recording medium of the present invention will be described with reference to the drawings. In each drawing, the same components are denoted by the same reference numerals, and redundant descriptions may be omitted. Furthermore, the number, position, shape, etc. of the following components are not limited to this embodiment, and can be set to a number, position, shape, etc. that is preferable for carrying out the present invention.

[0103] <First Embodiment> Figure 1 is a schematic cross-sectional view showing an example of a thermal recording medium according to the first embodiment. The thermal recording medium of this first embodiment has a thermal recording layer 2 on a support 1.

[0104] <Second Embodiment> Figure 2 is a schematic cross-sectional view showing an example of a thermal recording medium according to the second embodiment. The thermal recording medium of this second embodiment has a thermal recording layer 2 and a protective layer 3 on a support 1 in that order.

[0105] <Third Embodiment> Figure 3 is a schematic cross-sectional view showing an example of a thermal recording medium according to the third embodiment. The thermal recording medium of this third embodiment has a printed layer 4 and a thermal recording layer 2 on a support 1 in that order.

[0106] <Fourth Embodiment> Figure 4 is a schematic cross-sectional view showing an example of a thermal recording medium according to the fourth embodiment. This thermal recording medium of the third embodiment has a printing layer 4, a thermal recording layer 2, and a protective layer 3 on a support 1 in that order.

[0107] <Fifth Embodiment> Figure 5 is a schematic cross-sectional view showing an example of a thermal recording medium according to the fifth embodiment. The thermal recording medium of this fifth embodiment has a thermal recording layer 2 on a support 1, and a printing layer 4 on the side of the support 1 that does not have the thermal recording layer.

[0108] <Sixth Embodiment> Figure 6 is a schematic cross-sectional view showing an example of a thermal recording medium according to the sixth embodiment. This thermal recording medium of the sixth embodiment has a thermal recording layer 2 and a protective layer 3 on a support 1 in that order, and a printing layer 4 on the side of the support 1 that does not have the thermal recording layer.

[0109] <Seventh Embodiment> Figure 7 is a schematic cross-sectional view showing an example of a thermal recording medium according to the seventh embodiment. The thermal recording medium of this seventh embodiment has a thermal recording layer 2 and a printing layer 4 on a support 1 in that order.

[0110] <Eighth Embodiment> Figure 8 is a schematic cross-sectional view showing an example of a thermal recording medium according to the eighth embodiment. The thermal recording medium of this eighth embodiment has a thermal recording layer 2, a protective layer 3, and a printing layer 4 on a support 1 in that order.

[0111] <Ninth Embodiment> Figure 9 is a schematic cross-sectional view showing an example of a thermal recording medium according to the ninth embodiment. The thermal recording medium of this ninth embodiment has a thermal recording layer 2, a protective layer 3, and a release layer 8 on a support 1 in that order, and a printing layer 4 and an adhesive layer 7 on the side of the support 1 that does not have a thermal recording layer in that order.

[0112] <Tenth Embodiment> Figure 10 is a schematic cross-sectional view showing an example of a thermal recording medium according to the tenth embodiment. The thermal recording medium of this tenth embodiment has a printed layer 4, a thermal recording layer 2, a protective layer 3, and a release layer 8 on a support 1 in that order, and the printed layer 4 and the adhesive layer 7 are on the side of the support 1 that does not have a thermal recording layer in that order. In Figure 10, the release layer is located on the outermost surface on the same side as the thermal recording layer of the support, and the adhesive layer is located on the outermost surface on the opposite side of the support from the thermal recording layer.

[0113] <Embodiment 11> Figure 11A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 11th embodiment, and Figure 11B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 11th embodiment. The thermal recording medium of this eleventh embodiment has a thermal recording layer 2 on a portion of the support 1. The surface of the support refers to the side on which the thermal recording layer is not provided (the same applies hereinafter).

[0114] <Twelfth Embodiment> Figure 12A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 12th embodiment, and Figure 12B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 12th embodiment. The thermal recording medium of this twelfth embodiment has a thermal recording layer 2 and a protective layer 3 in this order on a portion of the support 1.

[0115] <13th Embodiment> Figure 13A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 13th embodiment, and Figure 13B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 13th embodiment. The thermal recording medium of this 13th embodiment has a thermal recording layer 2 on a portion of the support 1, and a protective layer 3 on the entire surface of the support including the thermal recording layer.

[0116] <Embodiment 14> Figure 14A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 14th embodiment, and Figure 14B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 14th embodiment. The thermal recording medium of this 14th embodiment has a printed layer 4 and a thermal recording layer 2 in this order on a portion of the support 1.

[0117] <Embodiment 15> Figure 15A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 15th embodiment, and Figure 15B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 15th embodiment. The thermal recording medium of this 15th embodiment has a printed layer 4, a thermal recording layer 2, and a protective layer 3 in this order on a portion of the support 1.

[0118] <Embodiment 16> Figure 16A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 16th embodiment, and Figure 16B is a schematic plan view (surface) showing an example of a thermal recording medium according to the 16th embodiment. The thermal recording medium of this 16th embodiment is the same as the 14th embodiment, except that the support 1, which includes the printing layer 4 and the thermal recording layer 2, has a protective layer 3 over its entire surface.

[0119] <Embodiment 17> Figure 17A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 17th embodiment, Figure 17B is a schematic plan view (front surface of the support) showing an example of a thermal recording medium according to the 17th embodiment, and Figure 17C is a schematic plan view (back surface of the support) showing an example of a thermal recording medium according to the 17th embodiment. The back surface of the support refers to the side on which the thermal recording layer is provided (the same applies hereinafter). The thermal recording medium of this 17th embodiment is the same as that of the 11th embodiment, except that the printed layer 4 is located on the back surface of the support 1.

[0120] <Embodiment 18> Figure 18A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 18th embodiment, Figure 18B is a schematic plan view (front surface of the support) showing an example of a thermal recording medium according to the 18th embodiment, and Figure 18C is a schematic plan view (back surface of the support) showing an example of a thermal recording medium according to the 18th embodiment. The thermal recording medium of this 18th embodiment is the same as that of the 12th embodiment, except that the printed layer 4 is located on the back surface of the support 1.

[0121] <Embodiment 19> Figure 19A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 19th embodiment, Figure 19B is a schematic plan view (front surface of the support) showing an example of a thermal recording medium according to the 19th embodiment, and Figure 19C is a schematic plan view (back surface of the support) showing an example of a thermal recording medium according to the 19th embodiment. The thermal recording medium of this 19th embodiment is the same as that of the 13th embodiment, except that the printed layer 4 is located on the back surface of the support 1.

[0122] <20th Embodiment> Figure 20A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 20th embodiment, Figure 20B is a schematic plan view (front surface of the support) showing an example of a thermal recording medium according to the 20th embodiment, and Figure 20C is a schematic plan view (back surface of the support) showing an example of a thermal recording medium according to the 20th embodiment. The thermal recording medium of this 20th embodiment is the same as in the 17th embodiment, except that the entire back surface of the support 1 including the printing layer 4 is laminated with polyethylene (PE) 6 via a lamination adhesive 5.

[0123] <21st Embodiment> Figure 21A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 21st embodiment, Figure 21B is a schematic plan view (front surface of the support) showing an example of a thermal recording medium according to the 21st embodiment, and Figure 21C is a schematic plan view (back surface of the support) showing an example of a thermal recording medium according to the 21st embodiment. The thermal recording medium of this 21st embodiment is the same as in the 18th embodiment, except that the entire back surface of the support 1 including the printing layer 4 is laminated with polyethylene (PE) 6 via a lamination adhesive 5.

[0124] <22nd Embodiment> Figure 22A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 22nd embodiment, Figure 22B is a schematic plan view (front surface of the support) showing an example of a thermal recording medium according to the 22nd embodiment, and Figure 22C is a schematic plan view (back surface of the support) showing an example of a thermal recording medium according to the 22nd embodiment. The thermal recording medium of this 22nd embodiment is the same as in the 19th embodiment, except that the entire back surface of the support 1 including the printing layer 4 is laminated with polyethylene (PE) 6 via a lamination adhesive 5.

[0125] <Embodiment 23> Figure 23A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 23rd embodiment, and Figure 23B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 23rd embodiment. The thermal recording medium of this 23rd embodiment has a printed layer 4 and a thermal recording layer 2 in that order on a portion of the support 1, a release layer 8 on the entire surface of the support including the printed layer 4 and the thermal recording layer 2, and an adhesive layer 7 on the entire back surface of the support 1. The thermal recording medium of this 23rd embodiment may further have a protective layer.

[0126] <24th Embodiment> Figure 24A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 24th embodiment, and Figure 24B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 24th embodiment. The thermal recording medium of this 24th embodiment has a printed layer 4 and a thermal recording layer 2 in that order on a portion of the support 1, a release layer 8 on the entire surface of the support including the printed layer 4 and the thermal recording layer 2, a printed layer 4 on a portion of the back surface of the support 1, and an adhesive layer 7 on the entire back surface of the support including the printed layer 4. The thermal recording medium of this 24th embodiment may further have a protective layer.

[0127] <Embodiment 25> Figure 25A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 25th embodiment, and Figure 25B is a schematic plan view (front surface of the support) showing an example of a thermal recording medium according to the 25th embodiment. Figure 25C is a schematic plan view (back surface of the support) showing an example of a thermal recording medium according to the 25th embodiment. The thermal recording medium of this 25th embodiment has a thermal recording layer 2 on a portion of the support 1, a release layer 8 on the entire surface of the support including the thermal recording layer 2, a printing layer 4 on a portion of the back surface of the support 1, and an adhesive layer 7 on the entire back surface of the support including the printing layer 4. The thermal recording medium of this 25th embodiment may further have a protective layer.

[0128] <26th Embodiment> FIG. 26A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 26th embodiment, and FIG. 26B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 26th embodiment. The thermal recording medium of this 26th embodiment has a black thermal recording layer 2b, a region without a thermal recording layer (support 1), and a blue thermal recording layer 2c on the support 1, respectively.

[0129] <The 27th Embodiment> FIG. 27A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 27th embodiment, and FIG. 27B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 27th embodiment. The thermal recording medium of this 27th embodiment has a black thermal recording layer 2b, a region without a thermal recording layer (support 1), a red thermal recording layer 2r, a region without a thermal recording layer (support 1), a blue thermal recording layer 2c, a region without a thermal recording layer (support 1), and a yellow thermal recording layer 2y on the support 1, respectively.

[0130] <The 28th Embodiment> FIG. 28A is a schematic cross-sectional view showing an example of a thermal recording medium according to the 28th embodiment, and FIG. 28B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to the 28th embodiment. The thermal recording medium of this 28th embodiment has a region without a thermal recording layer (support 1), a black thermal recording layer 2b, a region without a thermal recording layer (support 1), a green thermal recording layer 2g, a region without a thermal recording layer (support 1), a black thermal recording layer 2b, a region without a thermal recording layer (support 1), and a green thermal recording layer 2g, and has a region without a thermal recording layer (support 1), a yellow thermal recording layer 2y, a region without a thermal recording layer (support 1), a red thermal recording layer 2r, a region without a thermal recording layer (support 1), a yellow thermal recording layer 2y, a region without a thermal recording layer (support 1), and has a blue thermal recording layer 2c, a region without a thermal recording layer (support 1), an orange thermal recording layer 2o, a region without a thermal recording layer (support 1), a blue thermal recording layer 2c, a region without a thermal recording layer (support 1), and an orange thermal recording layer 2o on the support 1, respectively.

[0131] <Embodiment No. 29> FIG. 29A is a schematic cross-sectional view showing an example of a thermal recording medium according to Embodiment No. 29, and FIG. 29B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to Embodiment No. 29. The thermal recording medium of this 29th embodiment has a circular thermal recording layer 2-1, a square thermal recording layer 2-2, a triangular thermal recording layer 2-3, a star-shaped thermal recording layer 2-4, and a heart-shaped thermal recording layer 2-5 on the support 1, respectively.

[0132] <Embodiment No. 30> FIG. 30A is a schematic cross-sectional view showing an example of a thermal recording medium according to Embodiment No. 30, and FIG. 30B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to Embodiment No. 30. The thermal recording medium of this 30th embodiment is the same as the 11th embodiment, except that in the 11th embodiment, a printing layer 4 is provided on the surface of the support 1 and on the thermal recording layer 2.

[0133] <Embodiment No. 31> FIG. 31A is a schematic cross-sectional view showing an example of a thermal recording medium according to Embodiment No. 31, and FIG. 31B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to Embodiment No. 31. The thermal recording medium of this 31st embodiment is the same as the 12th embodiment, except that in the 12th embodiment, a printing layer 4 is provided on the surface of the support 1 and on the protective layer 3.

[0134] <Embodiment No. 32> FIG. 32A is a schematic cross-sectional view showing an example of a thermal recording medium according to Embodiment No. 32, and FIG. 32B is a schematic plan view (surface of the support) showing an example of a thermal recording medium according to Embodiment No. 32. The thermal recording medium of this 32nd embodiment is the same as the 13th embodiment, except that in the 13th embodiment, a printing layer 4 is provided on the protective layer 3.

[0135] (Image Recording Method) The image recording method of the present invention records an image on a thermal recording medium of the present invention using a thermal head. The thermal head is not subject to any particular restrictions regarding its shape, structure, size, etc., and can be appropriately selected according to the purpose. In this case, considering the durability of the thermal recording layer and its compatibility with the thermal head, it is preferable to provide a protective layer on top of the thermal recording layer. However, if a colorant system with high image and background preservation properties is applied, or if the thermal recording layer itself is given compatibility with the thermal head using fillers, lubricants, etc., then it is not always necessary to provide a protective layer. Furthermore, when a filler is added to the protective layer or thermal recording layer for the purpose of matching with the thermal head, the 50% cumulative volume particle size (D) is measured using a laser diffraction / scattering particle size distribution analyzer (device name: LA-960, manufactured by Horiba, Ltd.). 50 If the particle size is too small, it will not be possible to achieve the intended purpose of matching with the thermal head. Conversely, if the particle size is too large, the head will wear down easily and transparency will be difficult to impart. Therefore, a particle size of approximately 0.25 μm to 0.75 μm is preferable, but this is not an absolute requirement.

[0136] The image recording method of the present invention records an image by irradiating a thermal recording medium of the present invention with laser light. While various methods can be considered for heating with laser light, it is preferable to use laser light that can heat without contact. There are no particular restrictions on the laser light, and it can be appropriately selected according to the purpose. For example, various commonly known laser devices can be used, such as gas lasers using gases like CO2, solid-state lasers using solids like YAG or YVO4, and semiconductor lasers using III-V or IV-VI semiconductors. The device should be selected according to the intended use and method of use. Among these methods, CO2 lasers, with their 10,000 nm wavelength, are used because most materials absorb light from them, allowing for thermal recording without the need for special absorbent materials. Furthermore, while the addition of photothermal conversion materials, which absorb laser wavelengths of 800nm ​​to 1100nm and convert them into heat, is necessary for semiconductor lasers, solid-state lasers such as YAG and fiber lasers, transparent plastic films such as PET and OPP do not absorb laser light. Therefore, it is possible to record on the thermal recording layer on the opposite side of the film by irradiating it with a laser from the transparent film side, rather than directly irradiating the thermal recording layer with a laser. This expands the range of applications. There are no particular restrictions on the output power of the laser light irradiated in the image forming process of the image forming apparatus, and it can be appropriately selected according to the purpose, but 1W or more is preferred, 3W or more is more preferred, and 5W or more is particularly preferred. If it is less than 1W, image forming will take a long time, and if the image forming time is to be shortened, the output will be insufficient. Furthermore, there is no particular upper limit to the output power of the laser light, and it can be appropriately selected according to the purpose, but it is preferably 200W or less, more preferably 150W or less, and particularly preferably 100W or less. Exceeding 200W may lead to an increase in the size of the laser device.

[0137] Furthermore, when performing high-speed image recording on a thermal recording medium, it is preferable to use an image forming apparatus having a laser array in which multiple laser light-emitting elements are arranged in an array.

[0138] Next, as an example, we will describe a laser recording device that records images on a long thermal recording medium.

[0139] Here, Figure 33 is a schematic perspective view of the image recording system 100, which is a laser recording device. In the following explanation, the transport direction (movement direction) of the thermal recording medium will be described as the X-axis direction, the vertical direction as the Z-axis direction, and the direction perpendicular to both the movement direction and the vertical direction as the Y-axis direction. The image recording system 100 irradiates the thermal recording medium 101, which is the object to be recorded, with laser light to perform surface processing and image recording processing, as detailed below. As shown in Figure 33, the image recording system 100 includes a transport device 10, a recording device 20, a main unit 30, an optical fiber 42, an encoder unit 60, and the like. The recording device 20 irradiates the thermal recording medium 101, which is the object to be recorded, with laser light to perform processing on the surface of the object or to record a visible image on the object, and is equivalent to a laser irradiation device. The recording device 20 is located on the -Y side of the transport device 10, that is, on the -Y side of the transport path. The transport device 10 transports the thermal recording medium 101 using, for example, multiple rotating rollers. The main unit 30 is connected to the transport device 10, the recording device 20, and other components, and controls the entire image recording system 100. The encoder unit 60 acquires the movement speed of the thermal recording medium 101.

[0140] Figure 34 is a schematic perspective view showing the configuration of the image recording system 100. The image recording system 100 includes a laser processing device 30, which is a laser light source. The laser processing device 30 includes a laser irradiation device 14 having a laser array section 14a and a fiber array section 14b, and an optical section 43. Here, as the laser irradiation device 14, a fiber array recording device is used that performs surface processing and image recording using a fiber array in which the laser emission sections of multiple optical fibers are arranged in an array in the main scanning direction (Z axis direction) perpendicular to the sub-scanning direction (X axis direction), which is the movement direction of the thermal recording medium 101, which is the object to be recorded. The laser processing device 30 irradiates the thermal recording medium 101 with laser light emitted from the laser light-emitting element 41 via the fiber array and records an image (visible image) consisting of drawing units. The laser array unit 14a comprises a plurality of laser light-emitting elements 41 arranged in an array, a cooling unit 50 for cooling the laser light-emitting elements 41, a plurality of drive drivers 45 provided corresponding to the laser light-emitting elements 41 for driving the corresponding laser light-emitting elements 41, and a controller 46 for controlling the plurality of drive drivers 45. The controller 46 is connected to a power supply 48 for supplying power to the laser light-emitting elements 41 and an image information output unit 47 such as a personal computer that outputs image information. Normally, in the laser light-emitting element 41, energy that is not converted into laser light is converted into heat, causing heat generation. Therefore, the laser light-emitting element 41 is cooled by a cooling unit 50, which is a cooling means. Furthermore, the laser irradiation device 14 here uses a fiber array section 14b, making it possible to arrange each laser light-emitting element 41 separately. This makes it possible to reduce the heat influence from adjacent laser light-emitting elements 41, and to cool the laser light-emitting elements 41 efficiently, thereby avoiding temperature rise and variation in the laser light-emitting elements 41, reducing variations in laser light output, and improving density uniformity. Note that the laser light output is the average output measured by a power meter. There are two methods for controlling the laser light output: controlling the peak power and controlling the pulse emission ratio (duty cycle: laser emission time / period time). The cooling unit 50 is a liquid-cooling system that cools the laser light-emitting elements 41 by circulating a coolant. It comprises a heat receiving section 51 that receives heat from each laser light-emitting element 41 and a heat dissipation section 52 that dissipates the heat from the coolant. The heat receiving section 51 and the heat dissipation section 52 are connected by cooling pipes 53a and 53b. The heat receiving section 51 has a cooling pipe inside a case made of a material with good thermal conductivity through which a coolant made of a material with good thermal conductivity flows. Multiple laser light-emitting elements 41 are arranged in an array on the heat receiving section 51. The heat dissipation unit 52 includes a radiator and a pump for circulating the coolant. The coolant pumped out by the heat dissipation unit 52 flows through the cooling pipe 53a into the heat receiving unit 51. The coolant then moves through the cooling pipes within the heat receiving unit 51, absorbing heat from the laser light-emitting elements 41 arranged in the heat receiving unit 51 and cooling them. The coolant, whose temperature has risen after absorbing heat from the laser light-emitting elements 41 and flowing out of the heat receiving unit 51, moves through the cooling pipe 53b and flows into the radiator of the heat dissipation unit 52, where it is cooled by the radiator. The coolant cooled by the radiator is then pumped back into the heat receiving unit 51. The fiber array section 14b comprises a plurality of optical fibers 42 provided in correspondence with the laser light-emitting element 41, and an array head 44 that holds the vicinity of the laser emission portion 42a of these optical fibers 42 in an array shape in the vertical direction (Z-axis direction). The laser incident portion of each optical fiber 42 is attached to the laser emission surface of the corresponding laser light-emitting element 41. Furthermore, if an array head 44 were to attempt to hold all the optical fibers 42, the array head 44 would become long and prone to deformation. As a result, it would be difficult to maintain the linearity of the beam arrangement and the uniformity of the beam pitch with a single array head 44. For this reason, the array head 44 is designed to hold 100 to 200 optical fibers 42. In addition, it is preferable that the laser irradiation device 14 arranges multiple array heads 44, each holding 100 to 200 optical fibers 42, in the Z-axis direction, which is perpendicular to the direction of movement of the thermal recording medium 101.

[0141] Figure 35 is a diagram illustrating the arrangement of the laser array. As shown in Figure 35, the optical fibers 42 of the array head 44 in Figure 34 are arranged so that the dots of diameter R1 formed by irradiating a thermal recording medium with a laser and producing color are connected at the focal point where the light is focused by the optical unit 43. The scanning direction of the laser light has a primary scanning direction and a secondary scanning direction, and the primary and secondary scanning directions are orthogonal to each other. The primary scanning direction is the direction in which the multiple optical fibers 42 are arranged. The secondary scanning direction is the direction in which the thermal recording medium moves. In addition, in order to record an image on the thermal recording medium by relatively moving the array head 44 and the thermal recording medium, the array head 44 may move with respect to the thermal recording medium, or the thermal recording medium may move with respect to the array head 44. Even when the array head 44 is moved with respect to the thermal recording medium, if the array head 44 is taken as the observation point, the expression of the moving speed of the thermal recording medium can be used.

[0142] Also, as shown in FIG. 34, an optical unit 43 which is an example of an optical system has a collimating lens 43a that converts the laser light of the diverging light beam emitted from each optical fiber 42 into a parallel light beam, and a condensing lens 43b that condenses the laser light on the surface of the thermal recording medium which is the laser irradiation surface. Also, whether to provide the optical unit 43 or not may be appropriately selected according to the purpose.

[0143] An image information output unit 47 such as a personal computer inputs image information to the controller 46. The controller 46 generates a drive signal (control pulse) for driving each drive driver 45 based on the input image information. The controller 46 transmits the generated drive signal (control pulse) to each drive driver 45. Specifically, the controller 46 includes a clock generator. When the number of clocks oscillated by the clock generator reaches the specified number of clocks, the controller 46 transmits a drive signal (control pulse) for driving each drive driver 45 to each drive driver 45. Each drive driver 45, upon receiving a drive signal (control pulse), transmits a current pulse to drive the corresponding laser light-emitting element 41. The laser light-emitting element 41 outputs a light emission pulse and emits laser light in accordance with the drive of the drive driver 45. The laser light emitted from the laser light-emitting element 41 enters the corresponding optical fiber 42 and is emitted from the laser emission section 42a of the optical fiber 42. The laser light emitted from the laser emission section 42a of the optical fiber 42 passes through the collimating lens 43a and the focusing lens 43b of the optical section 43 and then irradiates the thermal recording medium, which is the object to be recorded. An image is recorded on the thermal recording medium by heating it with the laser light irradiated onto it.

[0144] Incidentally, when using a recording device that uses a galvanometer mirror to deflect laser light and record images onto an object, images such as characters are recorded by irradiating them with laser light in a single continuous line as the galvanometer mirror rotates. Therefore, when recording a certain amount of information onto an object, there is a constraint that the recording cannot be completed in time unless the transport of the object is stopped. On the other hand, the laser irradiation device 14 uses a laser array in which multiple laser light-emitting elements 41 are arranged in an array, and by controlling the ON / OFF state of the laser light-emitting elements corresponding to each pixel, an image can be recorded on the thermal recording medium. As a result, even with a large amount of information, an image can be recorded on the thermal recording medium without stopping the transport of the thermal recording medium. Therefore, with the laser irradiation device 14, even when recording a large amount of information on the object to be recorded, an image can be recorded without reducing productivity.

[0145] The laser irradiation device 14 records an image on a thermal recording medium by irradiating it with laser light and heating the medium, so it is necessary to use a laser light-emitting element 41 with a certain level of high output. As a result, the laser light-emitting element 41 generates a large amount of heat. In conventional laser array recording devices that do not have a fiber array section 14b, it is necessary to arrange the laser light-emitting elements 41 in an array at intervals corresponding to the resolution. Therefore, in conventional laser array recording devices, in order to achieve a resolution of 200 dpi, the laser light-emitting elements 41 must be arranged at a very narrow pitch. As a result, in conventional laser array recording devices, the heat from the laser light-emitting elements 41 does not dissipate easily, and the laser light-emitting elements 41 become hot. In conventional laser array recording devices, when the laser light-emitting elements 41 become hot, the wavelength and light output of the laser light-emitting elements 41 fluctuate, making it impossible to heat the object to be recorded to the specified temperature, and thus it becomes impossible to obtain a good image. Furthermore, in conventional laser array recording devices, in order to suppress such a temperature rise of the laser light-emitting elements 41, it is necessary to reduce the transport speed of the object to be recorded and increase the emission interval of the laser light-emitting elements 41, which does not sufficiently increase productivity.

[0146] Typically, the cooling unit 50 uses a chiller system, which only cools and does not heat. Therefore, the temperature of the light source will not exceed the chiller's set temperature, but the temperature of the cooling unit 50 and the laser light-emitting element 41 in contact with it will fluctuate from the ambient temperature. On the other hand, when a semiconductor laser is used as the laser light-emitting element 41, a phenomenon occurs where the laser output changes depending on the temperature of the laser light-emitting element 41 (the laser output increases when the temperature of the laser light-emitting element 41 decreases). Therefore, in order to control the laser output, it is preferable to measure the temperature of the laser light-emitting element 41 or the temperature of the cooling unit 50 and control the input signal to the drive driver 45 that controls the laser output so that the laser output remains constant, thereby achieving normal image formation. In contrast, the laser irradiation device 14 is a fiber array recording device using a fiber array section 14b. By using a fiber array recording device, the laser emission sections 42a of the fiber array section 14b only need to be arranged at a pitch corresponding to the resolution, eliminating the need to set the pitch between the laser light-emitting elements 41 of the laser array section 14a at a pitch corresponding to the image resolution. As a result, with the laser irradiation device 14, the pitch between the laser light-emitting elements 41 can be made sufficiently wide so that the heat from the laser light-emitting elements 41 can be adequately dissipated. As a result, with the laser irradiation device 14, it is possible to suppress the high temperature of the laser light-emitting elements 41 and suppress fluctuations in the wavelength and light output of the laser light-emitting elements 41. Consequently, with the laser irradiation device 14, a good image can be recorded on the thermal recording medium. Furthermore, even if the emission interval of the laser light-emitting elements 41 is shortened, the temperature rise of the laser light-emitting elements 41 can be suppressed, the movement speed of the thermal recording medium can be increased, and productivity can be improved.

[0147] Furthermore, in the laser irradiation device 14, by providing a cooling unit 50 and liquid-cooling the laser light-emitting element 41, the temperature rise of the laser light-emitting element 41 can be further suppressed. As a result, with the laser irradiation device 14, the emission interval of the laser light-emitting element 41 can be shortened, the movement speed of the thermal recording medium can be increased, and productivity can be improved. In the laser irradiation device 14, the laser light-emitting element 41 is liquid-cooled, but it may also be air-cooled using a cooling fan or the like. Liquid cooling has the advantage of higher cooling efficiency than air cooling, allowing for better cooling of the laser light-emitting element 41. On the other hand, air cooling has the advantage of lower cooling efficiency than liquid cooling, but allows for inexpensive cooling of the laser light-emitting element 41. [Examples]

[0148] The following describes embodiments of the present invention, but the present invention is not limited in any way to these embodiments.

[0149] <Measurement of solubility of electron-accepting compounds in solvents> <<1. Preparation of saturated solution>> (1) Approximately 100 g of solvent was prepared in a 150 mL to 300 mL beaker under conditions of 20 °C ± 3 °C. (2) While stirring with a stirrer and stirring rod, the electron-accepting compound was added little by little, and the addition of the chemical was stopped when undissolved material remained at the bottom. (3) The container was left for more than an hour with a lid on top to prevent evaporation. (4) After stirring with a stirring rod and ensuring that no undissolved material remains, repeat the above steps (2) to (4). (5) If the solution was left for more than one hour and undissolved material remained, the saturated solution was considered complete.

[0150] <<2. Measurement of Solubility>> The weight of the aluminum cup (A) was measured to the nearest 1 mg. Using a dropper, the clear supernatant liquid portion of the saturated solution prepared in step 1 above was taken out, approximately 0.8 to 1.3 g of the liquid was placed in an aluminum cup, and the weight of the liquid (B) was measured to the nearest 1 mg. Weighing should be done quickly, taking care to prevent contamination with waste or other debris. Place the aluminum cup containing the liquid into a drying oven (120°C ± 10°C). Alternatively, place it on a hot plate (120°C ± 10°C) in an area where local exhaust ventilation is installed. Evaporate the solvent for at least 25 minutes (if using a hot plate, cover it to prevent debris from getting onto the sample). The aluminum cups were removed from the dryer or hot plate and left at room temperature for at least one minute, after which the total weight (C) was measured to the nearest 1 mg. Based on the measurement results of A, B, and C described above, the solubility of the electron-accepting compound was calculated using the following formula 1. Solubility (mass%) = [(CA) / B] × 100 ... Formula 1

[0151] [Table 1] The results in Table 1 show that alcohol solvents and ester solvents have low solubility in non-phenolic electron-accepting compounds. Toluene, an aromatic solvent, has low solubility in electron-accepting compounds, but its use is restricted in the printing industry due to concerns about reducing the environmental impact of VOC emissions.

[0152] The detailed contents of the electron-accepting compounds in Table 1 are as follows:

[0153] -Electron-accepting compound 1- 9,9-Bis(4-hydroxyphenyl)fluorene [ka]

[0154] -Electron-accepting compound 2- N-(2-(3-phenylureido)phenyl)benzenesulfonamide [ka]

[0155] -Electron-accepting compound 3- N-benzyl-N'-3-(p-toluenesulfonyloxyphenyl)urea [ka]

[0156] -Electron-accepting compound 4- Np-toluenesulfonyl-N'-3-(p-toluenesulfonyloxyphenyl)urea [ka]

[0157] -Electron-accepting compound 5- N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea [ka]

[0158] -Electron-accepting compound 6- Bisphenol-S: 4,4'-Sulfonylbisphenol [ka]

[0159] (Example 1) -Preparation of thermal recording layer forming solution (without photothermal conversion material)- As an electron-donating compound, 6.2 parts by mass of a black dye (ODB2, manufactured by Yamamoto Kasei Co., Ltd.), 18.7 parts by mass of the above electron-accepting compound 1, 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 are measured using a laser diffraction / scattering particle size distribution analyzer (device name: LA-960, manufactured by Horiba, Ltd.) to determine the 50% cumulative volume particle size (D 50 The material was dispersed by a sand mill to a particle size of 0.25 μm to obtain a thermal recording layer forming liquid 1 (without photothermal conversion material, solid content 36% by mass, ethanol ratio in solvent 21% by mass).

[0160] (Comparative Example 1) In Example 1, the same procedure was used to obtain a heat-sensitive recording layer forming liquid 11, except that electron-accepting compound 1 was replaced with electron-accepting compound 6 shown in Table 2, and 15 parts by mass of water and 13.6 parts by mass of ethanol were replaced with 28.6 parts by mass of water.

[0161] (Examples 2-4 and Comparative Example 2) In Example 1, except that electron-accepting compound 1 was changed to one of the electron-accepting compounds shown in Table 2, and the amounts of water and ethanol were changed to 7 parts by mass and ethanol to 21.6 parts by mass respectively, the same procedure as in Example 1 was followed to obtain thermal recording layer forming solutions 2-4 and 12 (without photothermal conversion material, solid content 36% by mass, ethanol ratio in solvent 34% by mass).

[0162] (Example 5) In Example 1, the electron-accepting compound 1 was changed to electron-accepting compound 5 shown in Table 2, and the amount of pure water was changed to 0 parts by mass and ethanol to 28.6 parts by mass. Otherwise, the procedure was the same as in Example 1 to obtain a heat-sensitive recording layer forming liquid 5 (without photothermal conversion material, solid content 36% by mass, ethanol ratio in solvent 45% by mass).

[0163] (Example 6) In Example 5, a thermal recording layer forming liquid 6 (without photothermal conversion material, solid content 36% by mass, methanol ratio in solvent 45% by mass) was obtained in the same manner as in Example 5, except that ethanol was replaced with methanol.

[0164] (Example 7) In Example 5, a thermal recording layer forming liquid 7 (without photothermal conversion material, solid content 36% by mass, isopropyl alcohol ratio in solvent 45% by mass) was obtained in the same manner as in Example 5, except that ethanol was replaced with isopropyl alcohol.

[0165] (Examples 8-9) In Example 5, the same procedure was followed as in Example 5, except that the electron-donating compound shown in Table 2 was used to obtain thermal recording layer forming solutions 8-9 (without photothermal conversion material, solid content 36% by mass, ethanol ratio in solvent 45% by mass).

[0166] (Example 10) -Preparation of thermal recording layer forming solution (containing photothermal conversion material)- A thermal recording layer forming solution 10 (with photothermal conversion material, 36% solid content, 45% ethanol ratio in solvent) was obtained in the same manner as in Example 5, except that 6 parts by mass of cesium tungsten oxide dispersion (manufactured by Sumitomo Metal Mining Co., Ltd., YMW-D20, 28.5% solid content by mass, aqueous solvent) was added to 100 parts by mass of the thermal recording layer forming solution (without photothermal conversion material) prepared in Example 5.

[0167] [Table 2]

[0168] Details of the electron-donating compounds and photothermal conversion materials in Table 2 are as follows. -Electron-donating compounds- • ODB2: Black dye, manufactured by Yamamoto Kasei Co., Ltd. • RED40: Red dye, manufactured by Yamamoto Kasei Co., Ltd. • BLUE63: Blue dye, manufactured by Yamada Chemical Co., Ltd.

[0169] -Light and heat conversion materials- • YMW-D20: Tungsten cesium oxide dispersion, manufactured by Sumitomo Metal Mining Co., Ltd.

[0170] (Example 1 of preparation of protective layer forming solution) -Preparation of protective layer forming solution 1- 100 parts by mass of acrylic resin (DSM, A-1125, 19.5% solids by mass, aqueous solvent) and 50 parts by mass of ethanol were mixed and stirred to prepare protective layer coating solution 1 (13% solids by mass, 38.3% ethanol ratio in the solvent).

[0171] (Example 2 of preparation of protective layer forming solution) <Preparation of protective layer forming solution 2> -Preparation of Pigment Dispersion- The pigment consists of 84.2 parts by mass of calcium carbonate, 20.2 parts by mass of styrene-acrylic resin (BASF, Joncryl PDX-7741, solids content 41.5% by mass), 0.4 parts by mass of surfactant (Nisshin Chemical Industry Co., Ltd., PD-001, solids content 10% by mass), 51.1 parts by mass of water, and 51.1 parts by mass of ethanol, and the 50% cumulative volume particle size (D) is measured using a laser diffraction / scattering particle size distribution analyzer (device name: LA-960, Horiba, Ltd.). 50 The particles were dispersed using a sand mill so that they were 0.2 μm in size, to obtain a pigment dispersion (solid content 45%, ethanol ratio in solvent 44.8% by mass).

[0172] -Preparation of protective layer forming solution- 20.7 parts by mass of the above pigment dispersion, 47.7 parts by mass of acrylic resin (DSM, A-1125, 19.5% by mass solids in aqueous solvent), 4.7 parts by mass of lubricant (oxidized polyethylene wax, 30% by mass solids in aqueous solvent), 5 parts by mass of water, and 40 parts by mass of ethanol were mixed and stirred to prepare protective layer forming solution 2 (16.9% by mass solids, 40.8% by mass ethanol ratio in solvent).

[0173] (Example 11) <Manufacturing of thermal recording media> On a portion of the surface of the support 1 (white PET: polyethylene terephthalate film, manufactured by Toyobo Co., Ltd., Crisper K1212, average thickness 50 μm), the amount of heat-sensitive recording layer forming liquid 1 applied after drying was 3 g / m². 2 To achieve this, gravure printing was performed as described below, and the material was dried to form a thermal recording layer, thereby creating a thermal recording medium 1 as shown in Figures 11A and 11B.

[0174] Gravure printing The shape shown in Figure 36A has an engraved section of 50 lines / cm (target Wet: 7.5g / m²). 2 ~8.5g / m 2 A gravure roll with an outer diameter of 200 mm was prepared. Using a small gravure printing test machine manufactured by Chiba Machinery Industry Co., Ltd., the above gravure roll was set, 500g of each coating for evaluation was prepared, and gravure printing was performed in the layout shown in Figure 36B under conditions of a line speed of 40m / min and a drying temperature of 70℃, followed by drying.

[0175] <Flexographic printing> Anilox Roll 50 lines / cm (Target Wet: 7.5g / m) 2 ~8.5g / m 2 A flexographic plate measuring 90 mm wide × 260 mm long × 1.14 mm thick, as shown in Figure 37, was prepared. Using a flexoproof printing test machine manufactured by Matsuo Sangyo Co., Ltd., 10g of each coating solution for evaluation was prepared and printed on the above-mentioned anilox roll and flexo plate at a line speed of 40m / min. The plates were then dried for 1 minute in a constant temperature bath with a drying setting of 70°C.

[0176] (Examples 12-19 and Comparative Examples 3-4) <Manufacturing of thermal recording media> In Example 11, thermal recording media 2-9 and 19-20 were prepared in the same manner as in Example 11, except that thermal recording layer forming liquid 1 was replaced with thermal recording layer forming liquids 2-9 and 11-12 shown in Table 3. These thermal recording media were then prepared as shown in Figures 11A and 11B.

[0177] (Example 20) <Manufacturing of thermal recording media> A thermal recording medium 10, as shown in Figures 11A and 11B, was fabricated in the same manner as in Example 15, except that support 1 was replaced with support 2 (transparent PET: polyethylene terephthalate film, manufactured by Toyobo Co., Ltd., E5100, average thickness 50 μm).

[0178] (Comparative Examples 5-6) <Manufacturing of thermal recording media> In Example 20, thermal recording media 21-22 were prepared in the same manner as in Example 20, except that the thermal recording layer forming liquid 5 was replaced with the thermal recording layer forming liquids 11-12 shown in Table 3, as shown in Figures 11A and 11B.

[0179] (Example 21) <Manufacturing of thermal recording media> In Example 15, the amount of protective layer coating liquid 1 applied to the thermal recording layer after drying was 1.1 g / m². 2 To achieve this, gravure printing was performed in the same manner as described above, and the material was dried to form a protective layer. Thus, a thermal recording medium 11 was fabricated as shown in Figures 12A and 12B.

[0180] (Example 22) <Manufacturing of thermal recording media> In Example 21, the amount of printing layer ink (Finato R794 white, manufactured by DIC Corporation) applied to the surface of the support after drying was 1 g / m². 2 To that end, a thermal recording medium 12 as shown in Figures 15A and 15B was fabricated in the same manner as in Example 21, except that gravure printing was performed in the same manner as described above to form a printed layer, and a thermal recording layer and a protective layer were formed on the printed layer.

[0181] (Example 23) <Manufacturing of thermal recording media> A thermal recording medium 13, as shown in Figures 12A and 12B, was fabricated in the same manner as in Example 21, except that support 1 was replaced with support 2 (transparent PET: polyethylene terephthalate film, manufactured by Toyobo Co., Ltd., E5100, thickness 50 μm).

[0182] (Example 24) <Manufacturing of thermal recording media> In Example 23, the amount of printing layer ink (Finato R794 white, manufactured by DIC Corporation) applied to the back surface of the support was 1 g / m² after drying. 2 A thermal recording medium 14 as shown in Figures 18A to 18C was fabricated in the same manner as in Example 23, except that gravure printing was performed in the same manner as described above to form a printed layer.

[0183] (Example 25) <Manufacturing of thermal recording media> In Example 24, when the protective layer coating liquid 1 covers the entire thermal recording medium, the amount of coating liquid that adheres to the portion overlapping with the thermal recording layer after drying is 1.5 g / m². 2 The rest of the area is 3g / m 2 A thermal recording medium 15 as shown in Figures 19A to 19C was fabricated in the same manner as in Example 24, except that gravure printing was performed in the same manner as described above, and a protective layer was formed by drying.

[0184] (Example 26) <Manufacturing of thermal recording media> In Example 23, the amount of ink (Finato R794 white, manufactured by DIC Corporation) applied to the thermal recording layer after drying was 1 g / m². 2 A thermal recording medium 16 as shown in Figures 30A and 30B was fabricated in the same manner as in Example 23, except that gravure printing was performed in the same manner as described above to form a printed layer.

[0185] (Example 27) <Manufacturing of thermal recording media> In Example 24, a thermal recording medium 17 was fabricated in the same manner as in Example 24, except that protective layer coating liquid 1 was replaced with protective layer coating liquid 2, as shown in Figures 19A to 19C.

[0186] (Example 28) <Manufacturing of thermal recording media> In Example 27, a thermal recording medium 18 was prepared in the same manner as in Example 27, except that the sample preparation method was changed to the flexographic printing method described above. The thermal recording medium 18 shown in Figures 19A to 19C was prepared in the same manner as in Example 27.

[0187] (Comparative Example 7) <Manufacturing of thermal recording media> A thermal recording medium 23, as shown in Figures 19A to 19C, was prepared in the same manner as in Example 28, except that a thermal recording layer forming liquid 11 was used.

[0188] Next, the contents of the fabricated thermal recording media 1 to 23 are summarized in Table 3 below.

[0189] [Table 3]

[0190] Next, the thickness difference of the thermal recording layer was determined for the fabricated thermal recording media 1 to 23 as follows, and the uniformity of the background surface was evaluated. The results are shown in Table 4.

[0191] <Thickness difference of thermal recording layer> The thickness difference within the region excluding the edges of the thermal recording layer was calculated using the following formula. Thickness difference of thermal recording layer (%) = [(Maximum thickness of thermal recording layer or minimum thickness of thermal recording layer - Average thickness of thermal recording layer) / Average thickness of thermal recording layer] × 100 However, the thickness of the thermal recording layer was measured at any 20 points on the thermal recording medium, with the maximum value being defined as the "maximum thickness of the thermal recording layer" and the minimum value as the "minimum thickness of the thermal recording layer." The average value of the 18 points remaining after excluding the "maximum thickness of the thermal recording layer" and the "minimum thickness of the thermal recording layer" was defined as the "average thickness of the thermal recording layer." The larger of the absolute values ​​of (maximum thickness of the thermal recording layer - average thickness of the thermal recording layer) and (minimum thickness of the thermal recording layer - average thickness of the thermal recording layer) was adopted. In Examples 11-20 and Comparative Examples 3-6, the overall thickness of the thermal recording medium in the width direction or flow direction was measured at 20 arbitrary points using a film thickness gauge (K-402B STAND and electronic micrometer K351C, manufactured by Anritsu Corporation). The average thickness of the support (50 μm) that had been measured in advance was then subtracted to determine the "average thickness of the thermal recording layer," the "maximum thickness of the thermal recording layer," and the "minimum thickness of the thermal recording layer." In Examples 21-28 and Comparative Example 7, a Cross Section Polisher SM-0920CP (manufactured by JEOL Ltd.) was used to cut the cross section of the thermal recording medium. The cross section was observed using a Scanning Electron Microscope (SEM) S-3700 (manufactured by Hitachi High-Tech Corporation), and the thickness of the thermal recording layer was measured at 20 arbitrary locations to determine the "average thickness of the thermal recording layer," the "maximum thickness of the thermal recording layer," and the "minimum thickness of the thermal recording layer."

[0192] <Evaluation of scalp uniformity> Each thermal recording medium was visually inspected before image recording, and scalp uniformity was evaluated based on the following criteria and the scalp uniformity evaluation rank table shown in Figure 38. [Evaluation Criteria] Rank 5: No unevenness in the coating is visible; it is uniform. Rank 4: Slight unevenness in the coating is visible. Rank 3: Uneven coating is visible. Rank 2: Poor coating consistency, with some uncoated areas visible. Rank 1: Poor coating consistency, with many uncoated areas visible.

[0193] <Image Recording> As shown below, for Examples 11-24 and Comparative Examples 3-6, a thermal gradient was used to record a 10mm x 20mm solid image from either the thermal recording layer side or the protective layer side. For Example 25, a CO2 laser was used from the thermal recording layer side. For Example 26, a semiconductor laser was used from the transparent support side. For Examples 27, 28, and Comparative Example 7, a thermal printer was used from the protective layer side.

[0194] <<Thermal gradient>> A thermal gradient tester (device name: HG-100-2, manufactured by Toyo Seiki Co., Ltd.) was used to perform printing under the following printing conditions. [Printing conditions] ·Temperature: 180℃ • Pressure: 2 kg / cm² 2 • Time: 1s

[0195] <<CO2レーザー> > Printing was performed using a CO2 laser marker (device name: LP-435TU, manufactured by SUNX Corporation) under the following printing conditions. [Printing conditions] • Workpiece distance: 275mm • Scanning speed: 900 mm / s • Laser light wavelength: 10.6 μm • Laser power: 10%

[0196] <<Semiconductor Laser>> Printing was performed using an LD laser marker (device name: Ricoh Rewritable Laser Marker LDM200, manufactured by Ricoh Co., Ltd.) under the following printing conditions. [Printing conditions] • Workpiece distance: 150mm • Scanning speed: 3000 mm / s • Laser wavelength: 980 mm • Laser power: 70%

[0197] <<Thermal Printer>> A thermal printer (model: MP-104T, manufactured by MARKPOINT) was used, with a printing speed of 100 mm / s and a printing energy of 13.00 mJ / mm². 2 I printed it.

[0198] Next, for each obtained image, image uniformity, trailing pattern, and background density were evaluated as follows. The results are shown in Table 4.

[0199] <Evaluation of image uniformity> Each obtained image was visually inspected, and its image uniformity was evaluated based on the following criteria and the image uniformity evaluation rank table shown in Figure 39. [Evaluation Criteria] Rank 5: No unevenness in the coating is visible in the printed area; it is uniform. Rank 4: Slight coating inconsistencies are visible in the printed area. Rank 3: Image inconsistencies are visible. Rank 2: The image quality is poor, and some unpainted areas are visible. Rank 1: The image quality is poor, with many unpainted areas visible.

[0200] <Evaluation of Obiki> The state of the trailing pattern in the printed and unprinted areas of each obtained image was visually observed, and the trailing pattern was evaluated based on the following criteria and the trailing pattern evaluation ranking table shown in Figure 40. [Evaluation Criteria] Rank 5: No streaking whatsoever between the printed and unprinted areas. Rank 4: The printed and unprinted areas are slightly jagged. Rank 3: A trail of less than 10mm is visible in the non-printed area. Rank 2: A trailing pattern of 10mm to less than 30mm is visible in the non-printed area. Rank 1: A trail of 30mm or more is visible in the non-printed area.

[0201] <Scalp Concentration> The skin density of each obtained image was measured using a reflectance densitometer (X-Rite eXact, manufactured by X-Rite Corporation) and evaluated according to the following criteria. When a transparent film was used as the support, a contrast card (Typ 24 / 5) manufactured by Erichsen Corporation was placed under the image for measuring skin density. [Evaluation Criteria] 〇: 0.15 or less △: 0.16 or more and 0.30 or less ×: 0.31 or higher

[0202] [Table 4]

[0203] Examples of the present invention are as follows: <1> Electron-donating compounds, This is a thermal recording layer forming solution characterized by containing an electron-accepting compound having a solubility of 5.0% by mass or less in 100% ethanol at 20°C, and a solvent. <2> The electron-accepting compound has a linking group that is either a (thio)urea group (-NH-CX-NH-) (wherein X represents O or S) or a sulfonyl(thio)urea group (-SO2-NH-CX-NH-) (wherein X represents O or S), The compound is selected from at least one compound having a linking group of any of the following: a urethane group (-NHCOO-), an amide group (-NHCO-), a sulfonyl group (-SO2-), and a sulfonylamide group (-SO2-NH-), and having an aromatic group bonded via the linking group. <1> This is the thermal recording layer forming liquid described above. <3> The electron-accepting compound has a linking group that is either a urea group (-NH-CO-NH-) or a sulfonylurea group (-SO2-NH-CO-NH-), The compound having a linking group of any of the following: an amide group (-NHCO-), a sulfonyl group (-SO2-), and a sulfonylamide group (-SO2-NH-), wherein an aromatic group is bonded via the linking group, is at least one selected from the compounds having this structure. <1> from <2> This is a thermal recording layer forming liquid as described in any of the above. <4> The above, containing a photothermal conversion material <1> from <3> This is a thermal recording layer forming liquid as described in any of the above. <5> The support <1> from <4> A method for manufacturing a thermal recording medium, characterized by including a step of forming a thermal recording layer by applying a thermal recording layer forming liquid described in any of the above to form a thermal recording layer. <6> The thermal recording layer forming liquid is applied to a portion of the support, <5> This is a method for manufacturing a thermal recording medium as described above. <7> The device comprises a support and a thermal recording layer on the support containing an electron-donating compound and an electron-accepting compound having a solubility of 5.0% by mass or less in 100% ethanol at 20°C. The thermal recording medium is characterized in that the thickness difference of the thermal recording layer in the region excluding the edges of the thermal recording layer, as expressed by the following formula, is 50% or less. Thickness difference of thermal recording layer (%) = [(Maximum thickness of thermal recording layer or minimum thickness of thermal recording layer - Average thickness of thermal recording layer) / Average thickness of thermal recording layer] × 100 However, the thickness of the thermal recording layer is measured at any 20 points on the thermal recording medium, the maximum value is defined as the "maximum thickness of the thermal recording layer," and the minimum value is defined as the "minimum thickness of the thermal recording layer." The average value of the 18 points obtained by excluding the "maximum thickness of the thermal recording layer" and the "minimum thickness of the thermal recording layer" from the aforementioned 20 points is defined as the "average thickness of the thermal recording layer." The larger of the absolute values ​​of (maximum thickness of the thermal recording layer - average thickness of the thermal recording layer) and (minimum thickness of the thermal recording layer - average thickness of the thermal recording layer) is adopted. The "edge of the thermal recording layer" refers to the area 3 mm inward from the printed edge of the thermal recording layer. <8> A thermal recording medium characterized by comprising a support and a thermal recording layer on the support containing an electron-donating compound and an electron-accepting compound having a solubility of 5.0% by mass or less in 100% ethanol at 20°C. <9> The thermal recording layer is located on a portion of the support, <7> from <8> It is a thermal recording medium described in any of the following. <10> The support is a transparent film, <7> from <9> It is a thermal recording medium described in any of the following. <11> The thermal recording layer has a protective layer, <7> from <10> It is a thermal recording medium described in any of the following. <12> The thermal recording layer has a printed layer on at least one of the following: between the support and the thermal recording layer, and on the side of the support opposite to the thermal recording layer. <7> from <11> It is a thermal recording medium described in any of the following. <13> The support has a release layer on the outermost surface on the same side as the thermal recording layer, and an adhesive layer on the outermost surface on the opposite side of the support from the thermal recording layer. <7> from <12> It is a thermal recording medium described in any of the following. <14> The aforementioned <7> from <13> This is an image recording method characterized by recording an image by irradiating a thermal recording medium described in any of the above with laser light. <15> The aforementioned <7> from <13> This is an image recording method characterized by recording an image on a thermal recording medium described in any of the above using a thermal head.

[0204] The aforementioned <1> from <4> The heat-sensitive recording layer forming liquid described in any of the above, <5> from <6> A method for manufacturing a thermal recording medium as described in any of the above, <7> from <13> A thermal recording medium as described in any of the above, and the <14> from <15> According to any of the image recording methods described herein, the problems of the conventional methods can be solved and the objectives of the present invention can be achieved. [Explanation of Symbols]

[0205] 1 Support 2. Thermal recording layer 3 protective layer 4 printing layer 7. Adhesive layer 8. Delamination layer [Prior art documents] [Patent Documents]

[0206] [Patent Document 1] Japanese Patent Publication No. 2019-38206 [Patent Document 2] Japanese Patent Publication No. 2015-150764 [Patent Document 3] Japanese Patent Publication No. 2014-226848

Claims

1. Electron-donating compounds, It contains an electron-accepting compound having a solubility of 5.0% by mass or less in 100% ethanol at 20°C, and a solvent. The aforementioned electron-donating compound is a leuco compound, The electron-accepting compound is at least one non-phenolic color developer selected from compounds having a structure in which an aromatic group is bonded via the linking group, comprising either a (thio)urea group (-NH-CX-NH-) (wherein X represents O or S) or a sulfonyl(thio)urea group (-SO2-NH-CX-NH-) (wherein X represents O or S), and either a urethane group (-NHCOO-), an amide group (-NHCO-), a sulfonyl group (-SO2-), or a sulfonylamide group (-SO2-NH-). The solvent is a mixed solvent of water and an alcohol solvent, wherein the alcohol solvent makes up 20% by mass or more of the total mixed solvent. A thermal recording layer forming liquid characterized by the following features.

2. The electron-accepting compound comprises a urea group (-NH-CO-NH-) and a sulfonylurea group (-SO ２ A linking group of any of the following: -NH-CO-NH-) Amide group (-NHCO-), sulfonyl group (-SO ２ -), and sulfonylamide group (-SO ２ The thermal recording layer forming liquid according to claim 1, which is at least one selected from compounds having a linking group (-NH-) and a structure in which an aromatic group is bonded via the linking group.

3. A heat-sensitive recording layer forming liquid according to any one of claims 1 to 2, comprising a photothermal conversion material.

4. A method for manufacturing a thermal recording medium, characterized by including a step of forming a thermal recording layer by applying a thermal recording layer forming liquid according to any one of claims 1 to 3 onto a support to form a thermal recording layer.

5. A method for manufacturing a thermal recording medium according to claim 4, comprising applying the thermal recording layer forming liquid to a portion of the support.

6. The device comprises a support and a thermal recording layer on the support containing an electron-donating compound and an electron-accepting compound having a solubility of 5.0% by mass or less in 100% ethanol at 20°C. The aforementioned electron-donating compound is a leuco compound, The electron-accepting compound is at least one non-phenolic color developer selected from compounds having a structure in which an aromatic group is bonded via the linking group, comprising either a (thio)urea group (-NH-CX-NH-) (wherein X represents O or S) or a sulfonyl(thio)urea group (-SO2-NH-CX-NH-) (wherein X represents O or S), and either a urethane group (-NHCOO-), an amide group (-NHCO-), a sulfonyl group (-SO2-), or a sulfonylamide group (-SO2-NH-). A thermal recording medium characterized in that the thickness difference of the thermal recording layer in the region excluding the edges of the thermal recording layer, as expressed by the following formula, is 50% or less. Thickness difference of thermal recording layer (%) = [(Maximum thickness of thermal recording layer or minimum thickness of thermal recording layer - Average thickness of thermal recording layer) / Average thickness of thermal recording layer] × 100 However, the thickness of the thermal recording layer is measured at any 20 points on the thermal recording medium, the maximum value is defined as the "maximum thickness of the thermal recording layer," and the minimum value is defined as the "minimum thickness of the thermal recording layer." The average value of the 18 points obtained by excluding the "maximum thickness of the thermal recording layer" and the "minimum thickness of the thermal recording layer" from the aforementioned 20 points is defined as the "average thickness of the thermal recording layer." The larger of the absolute values ​​of (maximum thickness of the thermal recording layer - average thickness of the thermal recording layer) and (minimum thickness of the thermal recording layer - average thickness of the thermal recording layer) is adopted. The aforementioned "edge of the thermal recording layer" refers to the area 3 mm inward from the printed edge of the thermal recording layer.

7. The thermal recording medium according to claim 6, wherein the thermal recording layer is located on a portion of the support.

8. The thermal recording medium according to any one of claims 6 to 7, wherein the support is a transparent film.

9. A thermal recording medium according to any one of claims 6 to 8, further comprising a protective layer on the thermal recording layer.

10. A thermal recording medium according to any one of claims 6 to 9, wherein a printing layer is provided on the thermal recording layer, between the support and the thermal recording layer, and on at least one of the surfaces of the support opposite to the thermal recording layer.

11. A thermal recording medium according to any one of claims 6 to 10, wherein the support has a release layer on the outermost surface on the same side as the thermal recording layer, and an adhesive layer on the outermost surface on the opposite side of the support from the thermal recording layer.

12. An image recording method characterized by recording an image by irradiating a thermal recording medium according to any one of claims 6 to 11 with laser light.

13. An image recording method characterized by recording an image on a thermal recording medium according to any one of claims 6 to 11 using a thermal head.

Images