Thermosensitive recording medium

Abstract

To provide a thermal recording medium that can reduce the wear of a thermal head and has excellent sticking resistance.SOLUTION: A thermal recording medium includes a substrate 2, on which laminated are at least a thermal recording layer 4 and a protective layer 6 to be the uppermost layer. The surface of the protective layer 6 is provided with recesses, which are evaporation holes from moisture or cracks, which do not reach the thermal recording layer 4.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a thermal recording medium in which at least a thermal recording layer and a protective layer as the outermost layer are laminated on a substrate.

Background Art

[0002] Thermal recording media, for example, thermal paper having a thermal recording layer formed on a paper substrate, are used in various applications such as receipt paper, fax paper, or labels.

[0003] Some such thermal papers contain elastic particles in the outermost layer on the surface of the thermal paper in order to reduce wear of the thermal head of a printer, as disclosed in Patent Document 1, for example.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the thermal paper of Patent Document 1 above, it is necessary to blend elastic particles into the material constituting the outermost layer, and it is difficult to sufficiently prevent the sticking phenomenon caused by the components of the outermost layer melting due to the heat of the thermal head of the printer and sticking to the thermal head.

[0006] The present invention has been made paying attention to such circumstances, and an object thereof is to provide a thermal recording medium that does not require blending of elastic particles or the like into the material constituting the outermost layer, can reduce wear of the thermal head, and has good anti-sticking properties.

Means for Solving the Problems

[0007] In order to achieve the above object, the present invention is configured as follows.

[0008] (1) The thermal recording medium according to the present invention is a thermal recording medium in which at least a thermal recording layer and a protective layer serving as the outermost layer are laminated on a base material, and recesses that do not reach the thermal recording layer are formed on the surface of the protective layer.

[0009] According to the thermal recording medium of the present invention, since recessed portions are formed on the surface of the protective layer which is the outermost layer, the contact area between the protective layer and the thermal head can be reduced, wear of the thermal head is suppressed, and the anti-sticking property is improved.

[0010] Furthermore, since the recesses on the surface of the protective layer do not reach the thermal recording layer, even if oil or the like adheres to the surface of the protective layer, it does not reach the thermal recording layer, the thermal recording layer does not discolor, etc., and the print storage property is good.

[0011] (2) The thermal recording medium according to the present invention is a thermal recording medium in which at least a thermal recording layer and a protective layer serving as the outermost layer are laminated on a base material, and the protective layer is composed of hydrophobic resin particles.

[0012] According to the thermal recording medium of the present invention, in the outermost protective layer composed of hydrophobic resin particles, when a coating liquid in which the hydrophobic resin particles are dispersed is coated and dried, the hydrophobic resin particles aggregate and shrink, and cracks that become recesses are generated on the surface of the protective layer. By the cracks formed on the surface of this protective layer, the contact area between the protective layer and the thermal head can be reduced, wear of the thermal head can be suppressed, and the anti-sticking property can be improved.

[0013] (3) In a preferred embodiment of the present invention, the recess is at least one of a moisture evaporation hole and a crack.

[0014] According to this embodiment, when applying and drying the coating liquid for forming the protective layer, evaporation holes caused by evaporation of moisture and cracks caused by shrinkage become sunken concave portions on the surface of the protective layer.

[0015] (4) In one embodiment of the present invention, the protective layer does not contain a water-soluble polymer.

[0016] A coating liquid containing a water-soluble polymer does not easily aggregate and form a film without cracks when applied and dried. However, according to this embodiment, since the protective layer does not contain a water-soluble polymer, cracks can surely be caused on the surface of the protective layer.

[0017] (5) In another embodiment of the present invention, an intermediate layer is formed between the protective layer and the heat-sensitive recording layer.

[0018] According to this embodiment, since an intermediate layer is formed between the uppermost protective layer and the heat-sensitive recording layer, even if there are evaporation holes or cracks on the surface of the protective layer, oils or the like adhering to the surface of the protective layer are blocked by the intermediate layer and do not reach the heat-sensitive recording layer, so the print storage property is good.

[0019] (6) In still another embodiment of the present invention, an undercoat layer containing hollow particles is formed between the base material and the heat-sensitive recording layer.

[0020] According to this embodiment, the undercoat layer containing hollow particles can function as a heat insulation layer that prevents the dissipation of heat applied from the thermal head and also as an elastic layer having cushioning properties, improving the print quality.

Advantages of the Invention

[0021] According to the present invention, since concave portions are formed on the surface of the protective layer which is the uppermost layer, the contact area between the protective layer and the thermal head can be reduced, suppressing the wear of the thermal head and improving the anti-sticking property.

[0022] Furthermore, since the recesses on the surface of the protective layer do not reach the heat-sensitive recording layer, the print retention property is good.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0025] FIG. 1 is a schematic cross-sectional view of a heat-sensitive recording medium according to an embodiment of the present invention.

[0026] The heat-sensitive recording medium 1 has at least a heat-sensitive recording layer 4 that develops color by heating and a protective layer as the outermost layer laminated on a sheet-like substrate 2. In this embodiment, an intermediate layer 5 is formed between the heat-sensitive recording layer 4 and the protective layer 6, and an undercoat layer 3 is formed between the substrate 2 and the heat-sensitive recording layer 4, resulting in a laminated structure.

[0027] The base material 2 is, for example, paper, non-woven fabric, plastic film, metal foil, or a composite sheet combining these. In this embodiment, paper is used as the base material 2.

[0028] The undercoat layer 3 contains hollow particles and a binder.

[0029] The average particle diameter of the hollow particles is preferably 1 μm to 100 μm. If it is in such a range, an undercoat layer excellent in heat insulation can be formed. The average particle diameter is the weight average particle diameter measured by the laser diffraction method. The measurement of the average particle diameter by the laser diffraction method can be performed using the product name "MT3300EX-II" manufactured by Microtrac Bell Corporation.

[0030] The hollowness of the hollow particles is preferably 30% to 70%. If it is in such a range, an undercoat layer excellent in heat insulation can be formed, and a thermal recording medium excellent in printing quality can be provided.

[0031] The hollowness is calculated by the following formula.

[0032] Hollowness = {(Volume of voids) / (Volume of hollow particles)} × 100 The content ratio of the hollow particles is preferably 40 parts by weight to 90 parts by weight with respect to 100 parts by weight of the undercoat layer.

[0033] The coating amount (dry weight) of the undercoat layer 3 is preferably 1 g / m 2 ~10 g / m 2 is.

[0034] The thickness of the undercoat layer 3 is preferably 1 μm to 20 μm.

[0035] The hollow particles are composed of, for example, a thermoplastic resin. Examples of the material constituting the hollow particles include polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, polyvinyl acetate resins, polyacrylate ester resins, polyacrylonitrile resins, polybutadiene resins, and the like.

[0036] Examples of the binder contained in the undercoat layer 3 include acrylic-styrene copolymers, styrene-butadiene copolymers, acrylic-butadiene-styrene copolymers, vinyl acetate resins, vinyl acetate-acrylic acid copolymers, styrene-acrylic acid ester copolymers, acrylate resins, polyurethane resins, and the like.

[0037] Also, as the binder, polyvinyl alcohol; starch and its derivatives; cellulose derivatives such as methoxycellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose; sodium polyacrylate; polyvinyl pyrrolidone; acrylamide-acrylic acid ester copolymer; acrylamide-acrylic acid ester-methacrylic acid terpolymer; styrene-maleic anhydride copolymer alkali salt; isobutylene-maleic anhydride copolymer alkali salt; polyacrylamide; sodium alginate; gelatin; water-soluble polymers such as casein may be used.

[0038] The heat-sensitive recording layer 4 contains a color former that develops color upon heating, a developer, and the like. The heat-sensitive recording layer 4 may further contain a binder, a sensitizer, a lubricant, a filler, and the like as necessary.

[0039] As the color former that develops color by heating, known leuco dyes that are generally used can be employed. Examples of such leuco dyes include 3-(N-isobutyl-N-ethyl)amino-6-methyl-7-anilinofluoran, 3-(N-isopentyl-N-ethyl)amino-6-methyl-7-o-chloroanilinofluoran, 3-(N-ethyl-N-p-toluidino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isopentyl)amino-6-methyl-7-anilinofluoran, 3-(N-ethoxypropyl-N-ethyl)amino-6-methyl-7-anilinofluoran, 3-(N-cyclohexyl-N-methyl)amino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-n-propyl)amino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-p-toluidinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-8-methylfluoran, 3-diethylamino-7-(m-trifluoromethylanilino)fluoran, 3-diethylamino-7-(o-chloroanilino)fluoran, 3-diethylamino-7-chlorofluoran, 3-dibutylamino-6-methyl-7-bromofluoran, 3-dibutylamino-7-(o-chloroanilino)fluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3-dimethylamino-5-methyl-7-methylfluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, crystal violet lactone, etc., which can be used alone or in combination of two or more kinds.

[0040] As the developer, various electron-accepting substances that react with the leuco dye as described above upon heating to cause it to develop color can be used.Examples of such color developers include 1,1-bis(p-hydroxyphenyl)cyclohexane, 1,1-bis(p-hydroxyphenyl)propane, 2,2-bis(p-hydroxyphenyl)propane, 2,2-bis(p-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 2,2'-methylenebis(4-chlorophenol), 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 2,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-n-propoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxyphenyl-4'-benzyloxyphenyl sulfone, 4-hydroxy-4'-allyloxydiphenyl sulfone, bis(3-allyl-4-hydroxyphenyl) sulfone, poly(4-hydroxybenzoic acid), benzyl 4-hydroxybenzoate, 2,4-bis(phenylsulfonyl)phenol, α-{4-[(4-hydroxyphenyl)sulfonyl]phenyl}-ω-hydroxy poly(degree of polymerization n = 1 to 7)(oxyethylene oxyethylene oxy-p-phenylene sulfonyl-p-phenylene) 2,2-bis[(4-methyl-3-phenoxycarbonylaminophenyl)urea] diphenyl sulfone, 3,5-bis(α-methylbenzyl)salicylic acid, bis[4-(n-octyloxycarbonylamino)salicylic acid zinc], 4,4'-bis(p-tolylsulfonylaminocarbonylamino)diphenylmethane, 4-hydroxybenzenesulfonanilide, 2'-(3-phenylureido)benzenesulfonanilide, N-(2-hydroxyphenyl)-2-[(4-hydroxyphenyl)thio]acetamide, N-(4-hydroxyphenyl)-2-[(4-hydroxyphenyl)thio]acetamide, 4-[[4-[4-[4-[[4-(1-methylethoxy)phenyl]sulfonylphenoxy]butoxy]phenyl]sulfonyl]phenol, 4-tert-butylphenol·formaldehyde polycondensate, N-(p-toluenesulfonyl)N'-(3-p-toluenesulfonyloxyphenyl)urea, 1-phenyl-3-(4-methylphenylsulfonyl)urea, etc. can be used.

[0041] Examples of the binder included in the heat-sensitive recording layer 4 include polyvinyl alcohol, modified polyvinyl alcohol, starch, casein, gelatin, polyamide, polyacrylamide, modified polyacrylamide, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl acetate, polyacrylate ester, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, diisobutylene-maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer, methyl vinyl-maleic anhydride copolymer, isopropylene-maleic anhydride copolymer, styrene-butadiene copolymer, polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, polyurethane, polystyrene, polyvinyl pyrrolidone, acrylate ester, acrylonitrile, methyl vinyl ether, which can be used alone or in combination of two or more.

[0042] Examples of the sensitizer include stearic acid, stearic acid amide, stearic acid anilide, methylol stearic acid amide, methylene bis stearic acid amide, ethylene bis stearic acid amide, 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, 2,6-diisopropylnaphthalene, 1,2-diphenoxyethane, 1,2-diphenoxymethylbenzene, 1,2-bis(3,4-dimethylphenol)ethane, 1,2-bis(3-methylphenoxy)ethane, 1,2-bis(4-methylphenoxy)ethane, di(p-chlorobenzyl) oxalate, di(p-methylbenzyl) oxalate, dibenzyl oxalate, p-benzylbiphenyl, m-terphenyl, diphenyl sulfone, benzyl p-benzyloxybenzoate, dibenzyl terephthalate, p-toluenesulfonamide, etc., which are solid at room temperature and preferably have a melting point of about 70°C or higher, can be used.

[0043] As the lubricant, for example, fatty acids such as paraffin wax and oleic acid; polyolefin waxes such as polyethylene wax; metal soaps such as zinc stearate; ester waxes such as carnauba wax; oils such as silicone oil and whale oil can be used alone or in combination of two or more.

[0044] As the filler, for example, aluminum hydroxide, magnesium hydroxide, aluminum oxide, magnesium oxide, aluminum silicate, calcium carbonate, magnesium carbonate, titanium oxide, barium sulfate, silica gel, activated clay, talc, clay, kaolin, calcined kaolin, diatomaceous earth, white carbon, zinc oxide, silicon oxide, colloidal silica, polystyrene resin particles, urea-formalin resin particles, polyolefin resin particles, etc. can be used alone or in combination of two or more.

[0045] In this embodiment, the heat-sensitive recording layer 4 is simultaneously coated in three layers together with the intermediate layer 5 and the protective layer 6 by a curtain coater.

[0046] By providing the intermediate layer 5 on the heat-sensitive recording layer 4, a heat-sensitive recording medium 1 excellent in water resistance, chemical resistance, plasticizer resistance, etc. can be obtained.

[0047] Examples of the material constituting the intermediate layer 5 include aqueous resins such as polyvinyl alcohol, modified polyvinyl alcohol, starch, modified starch, casein, gelatin, glue, gum arabic, polyamide, polyacrylamide, modified polyacrylamide, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl acetate, polyacrylate ester, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, diisobutylene-maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer, methyl vinyl-maleic anhydride copolymer, isopropylene-maleic anhydride copolymer, styrene-butadiene copolymer, maleic acid copolymer, polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, polyurethane, polystyrene, polyvinyl pyrrolidone, acrylate ester, acrylonitrile, methyl vinyl ether, etc., which can be used alone or in combination of two or more kinds.

[0048] The coating amount (dry weight) of the intermediate layer 5 is preferably 0.3 g / m 2 ~10 g / m 2 is.

[0049] In this embodiment, the protective layer 6, which is the uppermost layer of the thermal recording medium 1, is configured as follows in order to reduce the wear of the thermal head and not shorten its life without blending elastic particles or the like, that is, to improve the thermal head fitness and to improve the anti-sticking property. Note that the anti-sticking property means that there are no defects such as partial non-printing or distortion of the printed surface caused by the components of the uppermost layer of the thermal recording medium melting due to the heat of the thermal head and sticking to the head.

[0050] The protective layer 6 of this embodiment has evaporation holes due to evaporation of moisture and cracks as recessed concave portions on its surface, thereby reducing the contact area between the surface of the protective layer 6 and the thermal head.

[0051] In this way, in order to form recesses, particularly cracks, on the surface of the protective layer 6, a coating liquid containing hydrophobic resin particles is used as the coating liquid for forming the protective layer 6.

[0052] That is, as the binder of the protective layer 6, an emulsion of hydrophobic resin particles is used. In this embodiment, an emulsion in which hydrophobic acrylic resin particles are dispersed in water is used.

[0053] In this way, as the binder of the protective layer 6, an emulsion of hydrophobic resin particles is used, and no water-soluble polymer is used.

[0054] A coating liquid containing a water-soluble polymer is less likely to aggregate and forms a flexible coating film when coated and dried, so cracks due to shrinkage do not occur.

[0055] On the other hand, when an emulsion of hydrophobic resin particles is coated and dried, the hydrophobic resin particles aggregate and shrink due to evaporation, and cracks that become recesses are formed on the surface of the protective layer 6.

[0056] Since these cracks are formed by the shrinkage due to the aggregation of the hydrophobic resin particles, they are limited to the protective layer 6 and do not reach the intermediate layer 5.

[0057] Also, in this embodiment, in order to form evaporation holes that become recesses due to the evaporation of moisture on the surface of the protective layer 6, the three layers of the heat-sensitive recording layer 4, the intermediate layer 5, and the protective layer 6 are simultaneously coated in three layers by a curtain coater as described above.

[0058] In a curtain coater, each coating liquid for forming the heat-sensitive recording layer 4, the intermediate layer 5, and the protective layer 6 is discharged from each slit and laminated, and the laminated coating liquid is freely dropped and coated onto an undercoat layer 3 formed in advance on a base material 2 that is continuously running.

[0059] In the simultaneous coating of three layers using such a curtain coater, when the protective layer 6 dries, the hydrophobic resin particles start to aggregate and cracks occur as described above. Water vapor escapes from the cracks, and the semi-dry intermediate layer 5 and the heat-sensitive recording layer 4 dry and solidify. Most of the water vapor in the intermediate layer 5 and the heat-sensitive recording layer 4 is released from the cracks, but a part of the water vapor forms evaporation holes in the protective layer 6 and is released. Therefore, cracks and evaporation holes are formed near the protective layer 6.

[0060] In this embodiment, the evaporation holes formed in the protective layer 6 stop at the intermediate layer 5. Therefore, even if oil or the like adheres to the surface of the uppermost protective layer 6, it does not reach the heat-sensitive recording layer 4, and the heat-sensitive recording layer 4 does not change color or the like.

[0061] The protective layer 6 contains additives such as a lubricant, a crosslinking agent, a dispersant, an antifoaming agent, and a water resistance agent as required.

[0062] Examples of the filler contained in the protective layer 6 include aluminum hydroxide, aluminum oxide, aluminum silicate, heavy calcium carbonate, light calcium carbonate, titanium oxide, barium sulfate, silica gel, activated clay, talc, clay, kaolinite, diatomaceous earth, white carbon, magnesium carbonate, magnesium oxide, magnesium hydroxide, zinc oxide, polystyrene resin particles, urea-formalin resin particles, polyolefin resin particles, etc., which can be used alone or in combination of two or more.

[0063] As an example of the coating liquid for forming the protective layer 6 of this embodiment, a water-dispersed suspension in which a hydrophobic acrylic resin is water-dispersed, polyethylene wax as a lubricant, and calcium carbonate as a pigment are blended at a mass ratio of 4:3:3 during drying was used to manufacture the heat-sensitive recording medium 1.

[0064] The coating amount (dry weight) of the protective layer 6 was 1 g / m 2 and so on.

[0065] Figure 2 is a scanning electron microscope (SEM) photograph of the surface of the protective layer 6 of the heat-sensitive recording medium 1 manufactured as described above, and Figure 3 is a scanning electron microscope (SEM) photograph of the surface of the protective layer of a heat-sensitive recording medium as a comparative example.

[0066] As shown in Figure 2, a large number of whitish streak-like cracks 10 and a small number of evaporation holes 11 are formed on the surface of the protective layer 6.

[0067] Among the cracks 10, there are some that are long and streak-like, but most of them are branched and extend in a streak-like manner.

[0068] The evaporation holes 11 are formed for the evaporation of moisture during drying as described above, and as shown in Figure 7 to be described later, they are recessed substantially circular holes.

[0069] In the comparative example of Figure 3, a water-soluble polymer was used instead of an emulsion in which a hydrophobic acrylic resin was dispersed in water as a binder, and each layer was formed sequentially instead of simultaneous multilayer formation by a curtain coater.

[0070] As shown in this Figure 3, the surface of the protective layer of the comparative example is a flat surface without any evaporation holes or cracks.

[0071] Figure 4 is a scanning electron microscope (SEM) photograph of an area near a crack 10 in one location of Figure 2, enlarged.

[0072] As shown in this Figure 4, the crack 10 has an open surface and extends into the interior of the protective layer 6, that is, in the thickness direction of the protective layer 6.

[0073] Figure 5 is a scanning electron microscope (SEM) photograph of an area other than the crack 10 in Figure 4, further enlarged.

[0074] As described above, the protective layer 6 uses a binder containing hydrophobic resin particles, and as shown in this Figure 5, it can be seen that innumerable hydrophobic resin particles are aggregated and arranged so as to be spread out.

[0075] According to this embodiment, as described above, cracks 10 serving as recesses and evaporation holes 11 for moisture are formed on the surface of the protective layer 6 which is the uppermost layer of the thermal recording medium 1. Therefore, the surface of the protective layer 6 becomes uneven. As a result, the contact area between the protective layer 6 and the thermal head is reduced, wear of the thermal head is reduced, thermal head suitability is improved, and sticking resistance is improved.

[0076] Also, as in Patent Document 1, it is not necessary to blend elastic particles or the like into the constituent material of the protective layer 6. Accordingly, the thickness of the protective layer 6 can be made thinner, for example, less than 1 μm, and in this embodiment, about 0.8 μm. As a result, costs can be reduced, and the distance from the surface of the protective layer 6 to the thermal recording layer 4 can be shortened, so that heat from the thermal head is efficiently conducted to the thermal recording layer 4.

[0077] Furthermore, since the cracks 10 on the surface of the protective layer 6 progress in the thickness direction inside the protective layer 6, the protective layer 6 is divided in the direction perpendicular to the thickness direction, that is, the lateral direction, by the cracks 10. As a result, heat from the thermal head is suppressed from radiating laterally and is efficiently conducted to the lower thermal recording layer 4 in the thickness direction.

[0078] In order to reduce the contact area between the protective layer 6 and the thermal head, it is preferable that the evaporation holes 11 which are substantially circular have an average diameter of 2 μm or more.

[0079] The average diameter of the evaporation holes 11 is calculated by observing the surface of the protective layer 6 with an electron microscope (SEM) and measuring the diameter of the evaporation holes 11 per unit area, for example, 1 mm 2 per unit area. Also, the number of evaporation holes 11 is preferably 30 or more, and more preferably 40 or more, per 1 mm 2 per unit area for evaporation holes 11 having an average diameter of 5 μm or more.

[0080] In the thermal recording medium 1 of the present embodiment, by adjusting the formulation of the protective layer 6 and the like, for example, as shown in the scanning electron microscope (SEM) photograph of FIG. 6, the surface of the protective layer 6 can be made into a surface having a large number of evaporation holes 11 and a small number of cracks 10, or, as shown in the scanning electron microscope (SEM) photograph of FIG. 7, the surface of the protective layer 6 can be made into a surface having only a large number of evaporation holes 11 without cracks 10.

[0081] In the above embodiment, the three layers of the thermal recording layer 4, the intermediate layer 5, and the protective layer 6 are simultaneously coated in multiple layers by a curtain coater. However, not limited to simultaneous multi-layer coating, each layer 4, 5, and 6 may be formed individually and sequentially.

[0082] In the above embodiment, the undercoat layer 3 and the intermediate layer 5 are formed on the base material 2. However, as another embodiment of the present invention, at least one of the undercoat layer 3 and the intermediate layer 5 may be omitted.

Explanation of Reference Numerals

[0083] 1 Thermal recording medium 2 Base material 3 Undercoat layer 4 Thermal recording layer 5 Intermediate layer 6 Protective layer 10 Crack (recess) 11 Evaporation hole (recess)

Claims

1. A method for manufacturing a thermal recording medium in which at least a thermal recording layer and a protective layer as the outermost layer are laminated on a substrate, wherein the thermal recording layer and the protective layer are simultaneously applied and formed by a curtain coater, recesses that do not reach the thermal recording layer are formed on the surface of the protective layer, and innumerable hydrophobic resin particles are aggregated in the protective layer, a method for manufacturing a thermal recording medium.

2. The method for manufacturing a thermal recording medium according to claim 1, wherein the recesses are at least one of water evaporation holes and cracks. The method for manufacturing a thermal recording medium according to claim 1.

3. The method for manufacturing a thermal recording medium according to claim 1 or 2, wherein the protective layer does not contain a water-soluble polymer. The method for manufacturing a thermal recording medium according to claim 1 or 2.

4. The method for manufacturing a thermal recording medium according to claim 1 or 2, wherein an intermediate layer is formed between the protective layer and the thermal recording layer. The method for manufacturing a thermal recording medium according to claim 1 or 2.

5. The method for manufacturing a thermal recording medium according to claim 1 or 2, wherein an undercoat layer containing hollow particles is formed between the substrate and the thermal recording layer. The method for manufacturing a thermal recording medium according to claim 1 or 2.

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