Thermal recording materials

Abstract

To provide a thermosensitive recording material which substantially contains no dye precursor and color developer and has excellent whiteness, coloring density, oil resistance and printing adaptability.SOLUTION: There is provided a thermosensitive recording material which has a support including at least one colored surface and a light scattering layer disposed on the colored surface, wherein the light scattering layer contains polymer particles having a hollow and a transparency agent, the content ratio of the polymer particles having a hollow is 6 to 35 mass% of the total solid content of the light scattering layer, 1 pt.mass or more of the transparency agent is contained in terms of solid content per 1 pt.mass of the polymer particles having a hollow, the light scattering layer substantially contains no dye precursor or developer, A) the transparency agent comprises only a fatty acid amide or B) the transparency agent is a combination of a fatty acid amide and at least one selected from the group consisting of a compound represented by the following formula (1): (wherein, X represents CH3 or Cl identically or differently) and 1,2-phenoxymethylbenzene.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a thermal recording material. [Background technology]

[0002] Thermal recording materials that record colored images using a heating-induced color reaction between a colorless or light-colored dye precursor and phenols or organic acids are widely used. Because such thermal recording materials form colored images simply by heating, they offer advantages such as compact recording devices, easy maintenance, and low noise generation. Therefore, thermal recording materials are widely used as information recording materials in various applications, including label printers, automatic ticket vending machines, CD / ATM machines, order slip output machines in restaurants, and data output machines for scientific research equipment.

[0003] Other thermal recording materials besides those that utilize the color development reaction between a dye precursor and a color developer include, for example, the thermal recording material reported in Patent Document 1.

[0004] Patent Document 1 reports a recording material comprising a) a support having at least one colored surface; and b) a layer disposed thereon, wherein the layer comprises polymer particles having a core / shell structure and an opacity reducing agent having a melting point from 45°C to 200°C, in an amount from 1% to 90% by weight based on the weight of the polymer particles, wherein the particles have an outer first polymer shell having a calculated Tg from 40°C to 130°C, and the particles contain at least one void when dry.

[0005] In such thermal recording materials, the colored surface is concealed by an opaque layer. When heated, an opacity-reducing agent melts, causing the layer on the colored surface to become transparent, allowing the colored surface to be seen and thus enabling printing.

[0006] However, conventional thermal recording materials that substantially do not contain dye precursors and color developers have insufficient whiteness, color density, oil resistance, and printability, and there is room for improvement. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Special Publication No. 2014-512290 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The main objective of the present invention is to provide a thermal recording material that is substantially free of dye precursors and color developers, and that exhibits excellent whiteness, color density, oil resistance, and printability. [Means for solving the problem]

[0009] The present inventors, after diligent research to solve the above-mentioned problems, have found that the above-mentioned problems can be solved by incorporating 6 to 35% by mass of hollow polymer particles into a light scattering layer, incorporating 1 part by mass or more of a clearing agent per 1 part by mass of hollow polymer particles, and using a fatty acid amide alone or in combination with a specific compound as the clearing agent, thereby completing the present invention. That is, the present invention relates to the following thermal recording material.

[0010] Item 1: A thermal recording material comprising a support including at least one colored surface, and a light-scattering layer disposed on the colored surface, wherein the light-scattering layer contains hollow polymer particles and a clearing agent, the proportion of the hollow polymer particles is 6 to 35% by mass of the total solid content of the light-scattering layer, the clearing agent is contained in an amount of 1 part by mass or more on a solid content basis per 1 part by mass of the hollow polymer particles, and the light-scattering layer substantially does not contain a dye precursor and a color developer. A) The clearing agent consists solely of a fatty acid amide, or B) The transparency agent is a fatty acid amide and a compound represented by the following general formula (1):

[0011] [Chemical formula] (wherein X is the same or different and represents CH₃ or Cl) and a combination with at least one selected from the group consisting of 1,2- bis( phenoxymethyl ) benzene is a heat-sensitive recording material. Item 2: The heat-sensitive recording material according to Item 1, wherein the content ratio of the transparency agent is 20 to 35% by mass in the total solid content of the light-scattering layer. Item 3: The heat-sensitive recording material according to Item 1 or 2, wherein the content ratio of the polymer particles having hollow portions is 20 to 30% by mass in the total solid content of the light-scattering layer. Item 4: The heat-sensitive recording material according to any one of Items 1 to 3, further containing polymer particles having no hollow portions in the light-scattering layer, and the content ratio of the polymer particles having no hollow portions is 10 to <, 45% by mass in the total solid content of the light-scattering layer. Item 5: The heat-sensitive recording material according to Item 4, wherein the average particle diameter of the polymer particles having no hollow portions is 0.4 to 2.0 μm. Item 6: The heat-sensitive recording material according to any one of Items 1 to 5, wherein the fatty acid amide contains at least one selected from the group consisting of stearic acid amide and palmitic acid amide. Item 7: The heat-sensitive recording material according to any one of Items 1 to 6, wherein the polymer particles having hollow portions are made of a polymer selected from the group consisting of polystyrene, polymethyl methacrylate, polyvinyl chloride, and polyvinylidene chloride. [Advantages of the Invention]

[0012] The heat-sensitive recording material of the present invention is a heat-sensitive recording material substantially free of a colorant precursor and a developer, and is excellent in whiteness, color density, oil resistance, and printing suitability. [Modes for Carrying Out the Invention]

[0013] In this specification, the expression "comprising" includes the concepts of "comprising", "consisting essentially of", and "consisting of".

[0014] It should be noted that there seems to be some inaccuracies in the original text where some numbers are not properly formatted in the tags (e.g., etc. which might be a display issue). This translation is based on the best understanding of the provided text.In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value.

[0015] The latex in the present invention includes a state of a gel or a dried film formed by drying a dispersion medium.

[0016] In the present invention, the "average particle diameter" refers to the volume-based median diameter measured by the laser diffraction method. More simply, an electron microscope may be used to measure the particle diameters from particle images (SEM images) respectively, and the average value of 10 may be shown.

[0017] The present invention is a heat-sensitive recording material having a support including at least one colored surface and a light-scattering layer disposed on the colored surface thereof, wherein the light-scattering layer contains polymer particles having a hollow and a clarifying agent, the content ratio of the polymer particles having a hollow is 6 to 35% by mass in the total solid content of the light-scattering layer, the clarifying agent is contained in an amount of 1 part by mass or more in terms of solid content with respect to 1 part by mass of the polymer particles having a hollow, and the light-scattering layer does not substantially contain a dye precursor and a developer. A) The clarifying agent consists only of a fatty acid amide, or B) The clarifying agent is a combination of a fatty acid amide and at least one selected from the group consisting of a compound represented by the following general formula (1):

[0018] [Chemical formula] [[ID=2३]] (In the formula, X represents CH3 or Cl, which may be the same or different.) and 1,2- bis( phenoxymethyl ) benzene, and is characterized by being a combination of at least one selected from the group consisting of.

[0019] [Support] The support in this invention is not particularly limited in terms of type, shape, dimensions, etc., and can be appropriately selected and used from among, for example, high-quality paper (acidic paper, neutral paper), medium-quality paper, coated paper, art paper, cast-coated paper, glassine paper, resin-laminated paper, polyolefin-based synthetic paper, synthetic fiber paper, nonwoven fabric, synthetic resin film, and various transparent supports. In embodiments of this invention, the support may have a colored surface on one side, or both sides may be colored. The color may be imparted, for example, by a pigment, dye, or the inherent color of the support, and the support may be immersed in a coloring agent to provide a colored surface. The thickness of the support is not particularly limited, and is usually about 20 to 200 μm. The density of the support is also not particularly limited, and is 0.60 to 0.85 g / cm³. 3 A certain degree is desirable.

[0020] [Colored side] The thermal recording material of the present invention has at least one colored surface on the support. This makes it possible to print when the light scattering layer becomes transparent due to heat.

[0021] The support may have a colored surface on one side, or it may have colored surfaces on both sides. The colored surface only needs to have a sufficient color density that is visually contrasting with the light scattering layer placed on it. The colored surface may have a uniform color density, a varying color density, or a patterned surface. The type of color of the colored surface is not particularly limited and any color is acceptable.

[0022] The colored surface may be a colored layer formed on a support. The colored layer may contain dyes, pigments, carbon black, etc., as colorants to impart color. The proportion of the colorant can be selected from a wide range, but generally it is preferably about 5 to 50% by mass, and more preferably about 7 to 30% by mass, of the total solid content of the colored layer.

[0023] The colored layer may contain pigments other than colorants. Examples of pigments include inorganic pigments such as calcium carbonate, magnesium carbonate, kaolin, calcined kaolin, clay, talc, calcined clay, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface-treated calcium carbonate, silica, hollow polymer particles, and non-hollow polymer particles. The pigment content can be selected from a wide range, but generally, it is preferably about 30 to 80% by mass, and more preferably about 40 to 70% by mass, of the total solid content of the colored layer.

[0024] The colored layer is generally formed by applying and drying a coating solution for the colored layer onto a support, which is prepared by mixing and stirring a colorant, other pigments, adhesives, auxiliary agents, etc., with water as a medium. The amount of coating solution for the colored layer applied is not particularly limited, but is 2 to 15 g / m² by dry mass. 2 A suitable amount is 3-10 g / m². 2 A more moderate degree is preferable.

[0025] Examples of adhesives include water-soluble polymer materials such as polyvinyl alcohol and its derivatives, starch and its derivatives, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and their derivatives, as well as emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, and ethylene-vinyl acetate copolymer, or latex of water-insoluble polymers such as styrene-butadiene copolymer and styrene-butadiene-acrylic copolymer. The content of the adhesive can be selected from a wide range, but generally it is preferably about 5 to 40% by mass, and more preferably about 10 to 30% by mass, of the total solid content of the colored layer.

[0026] [Light scattering layer] The thermal recording material of the present invention has a light-scattering layer on a colored surface. The light-scattering layer contains hollow polymer particles and a clearing agent. Furthermore, the light-scattering layer substantially does not contain dye precursors or color developers.

[0027] (Hollow polymer particles) By including hollow polymer particles, light scattering occurs in the light scattering layer, resulting in the concealment of the colored surface.

[0028] Polymer particles with hollow bodies can be classified into foamed and non-foamed types depending on their manufacturing method. Of these two types, foamed hollow polymer particles generally have a larger average particle diameter and a higher hollowness ratio than non-foamed hollow polymer particles.

[0029] Non-foaming, hollow polymer particles can be manufactured by polymerizing seeds in a solution, then polymerizing another resin to surround the seeds, and finally swelling and dissolving the internal seeds to remove them, thereby forming a cavity inside. Alkaline aqueous solutions are used to swell and dissolve the internal seeds. By alkali-swelling core particles coated with a shell layer that does not swell with alkali, non-foaming, hollow particles with a relatively small average particle size can also be obtained.

[0030] Foamed, hollow polymer particles can be manufactured by creating particles in which a volatile liquid is sealed inside a resin, and then heating the resin to soften it while simultaneously vaporizing and expanding the liquid inside the particles.

[0031] The hollowness ratio of polymer particles containing hollows can be exemplified as being around 30-99%. Here, the hollowness ratio is given by the following formula (d 3 / D 3 This value is obtained by multiplying by ) × 100. In the formula, d represents the inner diameter of the hollow polymer particle, and D represents the outer diameter of the hollow polymer particle.

[0032] The average particle diameter of the hollow polymer particles in this invention is preferably 0.2 to 5.0 μm, more preferably 0.4 to 2.0 μm. Here, the average particle diameter is the median diameter, which is the diameter at which the volume occupied by the larger particle and the smaller particle are equal when the particle is divided into two groups based on its diameter, i.e., the particle diameter at which the 50% volume frequency occurs, and is also referred to as D50. The average particle diameter (D50) of the hollow polymer particles can be measured using a laser diffraction particle size distribution analyzer. Alternatively, the particle diameter may be measured from particle images (SEM images) using an electron microscope, and the average value of 10 values ​​may be shown.

[0033] In the present invention, the content of hollow polymer particles is 6 to 35% by mass of the total solid content of the light scattering layer, preferably 10 to 30% by mass, and more preferably 20 to 30% by mass. When the content of hollow polymer particles is 6% by mass or more, whiteness and oil resistance can be improved. On the other hand, when the content of hollow polymer particles is 35% by mass or less, the color density can be increased and printability can be improved.

[0034] (Clearing agent) By including a clearing agent, when heat is applied, the clearing agent melts, changing the refractive index of the light scattering layer. As a result, the light scattering layer becomes transparent, and the colored surface becomes visible.

[0035] The clearing agent is A) The clearing agent consists solely of a fatty acid amide, or B) The clearing agent is a fatty acid amide and a compound represented by general formula (1) and 1,2- bis( Phenoxymethyl ) This is a combination with at least one substance selected from the group consisting of benzene. This increases the contrast between the transparent and opaque areas, thereby improving printability.

[0036] Examples of fatty acid amides include myristic acid amide, palmitic acid amide, stearic acid amide, arachidin acid amide, and behenic acid amide. Among these, stearic acid amide and palmitic acid amide are preferred from the viewpoint of excellent printability, and the combined use of stearic acid amide and palmitic acid amide is particularly preferred because it can increase the color intensity. Of course, the options are not limited to these, and two or more compounds can be used in combination as needed.

[0037] The compound represented by general formula (1) is not particularly limited and includes at least one selected from the group consisting of di-p-chlorobenzyl oxalate and di-p-methylbenzyl oxalate.

[0038] The content ratio of the transparentizing agent is not particularly limited, but is preferably about 20 to 35% by mass, and more preferably about 25 to 30% by mass, of the total solid content of the light scattering layer. A concentration of 20% by mass or more can increase the color intensity. A concentration of 35% by mass or less can increase the color intensity and improve printability.

[0039] The content of the clearing agent is 1 part by mass or more per 1 part by mass of hollow polymer particles. On the other hand, in the case of A) above, the content of the clearing agent is preferably 3.5 parts by mass or less, more preferably 2.5 parts by mass or less, and even more preferably 1.5 parts by mass or less per 1 part by mass of hollow polymer particles. On the other hand, in the case of B) above, the content of the clearing agent is preferably 4 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less per 1 part by mass of hollow polymer particles. By using 1 part by mass or more, the color development density can be increased.

[0040] (Polymer particles that do not have a hollow core) The light scattering layer in this invention can contain polymer particles that do not have hollow spaces. This makes it possible to increase the whiteness.

[0041] Resins that can be used for polymer particles without hollows generally include acrylic resins and polystyrene resins, with styrene-acrylic copolymers being particularly preferred.

[0042] The average particle diameter of the polymer particles without hollows in this invention is preferably 0.4 to 2.0 μm, more preferably 0.6 to 1.5 μm. Here, the average particle diameter is the median diameter, which is the diameter at which the volume occupied by the larger particles and the smaller particles are equal when the particle diameter is divided into two groups, i.e., the particle diameter at 50% volume frequency, and is also referred to as D50. The average particle diameter (D50) of the polymer particles without hollows can be measured using a laser diffraction particle size distribution analyzer. Alternatively, the particle diameter can be measured from particle images (SEM images) using an electron microscope, and the average value of 10 particles can be shown. When the average particle diameter of the polymer particles without hollows is 0.4 to 2.0 μm, the whiteness of the thermal recording material can be improved.

[0043] In the present invention, the content of non-hollow polymer particles is preferably 10 to 45% by mass, more preferably 15 to 35% by mass, and even more preferably 20 to 30% by mass, of the total solid content of the light scattering layer. When the content of non-hollow polymer particles is 10% by mass or more, the whiteness of the thermal recording material can be improved. On the other hand, when the content of non-hollow polymer particles is 45% by mass or less, the color intensity can be increased.

[0044] Adhesives can be used as other component materials for the light scattering layer, and auxiliary agents such as crosslinking agents, lubricants, water-resistant agents, and dispersants can be used as needed.

[0045] Examples of adhesives include water-soluble polymer materials such as polyvinyl alcohol and its derivatives, starch and its derivatives, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and their derivatives, as well as emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, and ethylene-vinyl acetate copolymer, or water-insoluble polymer latex such as styrene-butadiene copolymer and styrene-butadiene-acrylic copolymer. Among these, polyvinyl alcohol and latex are preferred. The content of the adhesive can be selected from a wide range, but generally it is preferably about 7 to 60% by mass, and more preferably about 10 to 45% by mass, of the total solid content of the light scattering layer.

[0046] By incorporating a crosslinking agent into the light scattering layer, the water resistance of the light scattering layer can be improved. Examples of crosslinking agents include aldehyde compounds such as glyoxal, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, glyoxylates, dimethylolurea compounds, aziridine compounds, and blocked isocyanate compounds; inorganic compounds such as ammonium persulfate, ferric chloride, magnesium chloride, sodium tetraborate, and potassium tetraborate; boric acid, trysterol borate, boron-based polymers, hydrazide compounds, and glyoxylates. These may be used individually or in combination of two or more.

[0047] Metallic soaps may be used as lubricants. Examples of metallic soaps include polyvalent metal salts of higher fatty acids, namely zinc stearate, aluminum stearate, calcium stearate, and zinc oleate.

[0048] The light-scattering layer is, for example, prepared by dispersing a water-soluble synthetic polymer compound such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, methylcellulose, styrene-maleic anhydride copolymer salt, etc. together with a surfactant in water as a dispersion medium using various stirring and wet grinding machines such as a ball mill, a coball mill, an attritor, vertical and horizontal sand mills, etc. After obtaining respective dispersions, the dispersions are refined so that the average particle diameter becomes 2 μm or less, and polymer particles having a hollow are mixed. If necessary, an adhesive, polymer particles having no hollow, an auxiliary agent, etc. are mixed. After applying a coating liquid for the light-scattering layer thus prepared, it is dried to form on the colored surface. The coating amount of the coating liquid for the light-scattering layer is not particularly limited, and the coating amount after drying is preferably about 1 to 15 g / m 2 preferably about 2 to 10 g / m 2 more preferably about 2.5 to 8 g / m 2 even more preferably about 3 to 5 g / m 2 and particularly preferably about 3 to 5 g / m. Note that the light-scattering layer can be formed in two or more layers if necessary, and the composition and coating amount of each layer may be the same or different.

[0049] [Protective layer] In the heat-sensitive recording material, a protective layer can be provided on the light-scattering layer if necessary. The protective layer preferably contains a pigment and an adhesive. Further, for the purpose of preventing sticking to the thermal head, it is preferable to contain a lubricant such as polyolefin wax and zinc stearate in the protective layer, and an ultraviolet absorber can also be contained. Also, by providing a protective layer having gloss, the added value of the product can be increased.

[0050] The pigment contained in the protective layer is not particularly limited, and examples thereof include inorganic pigments such as amorphous silica, kaolin, clay, light calcium carbonate, heavy calcium carbonate, calcined kaolin, titanium oxide, magnesium carbonate, aluminum hydroxide, colloidal silica, synthetic phyllosilicate, etc., and plastic pigments such as urea-formalin resin fillers, etc.

[0051] The adhesive contained in the protective layer is not particularly limited, and water-soluble or water-dispersible aqueous adhesives can be used. The adhesive can be appropriately selected from those that can be used in the light scattering layer. Among these adhesives, various modified polyvinyl alcohols such as acetoacetyl-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and diacetone-modified polyvinyl alcohol are more preferably used.

[0052] The protective layer is formed on the light scattering layer by applying a protective coating solution, prepared by mixing a pigment, adhesive, and auxiliary agents as needed, using water as a dispersion medium, and then drying it. The amount of protective coating solution applied is not particularly limited, but is approximately 0.3 to 15 g / m² by dry mass. 2 A suitable amount is 0.3-10 g / m². 2 A more preferable degree is 0.5-8 g / m 2 A more preferable degree is 1-8 g / m 2 A degree of 1-5 g / m is particularly preferable. 2 A higher degree is preferable. The protective layer can be formed in two or more layers as needed, and the composition and application amount of each layer may be the same or different.

[0053] [Other layers] In the present invention, it is preferable to have an adhesive layer on at least one side of the support. This can increase the added value of the thermal recording material. As the adhesive layer, for example, by applying an adhesive, re-wettable adhesive, delayed-tack type adhesive, etc. to one side, adhesive paper, re-wettable adhesive paper, delayed-tack paper, etc. can be made. Alternatively, by utilizing the side of the support opposite to the light scattering layer and imparting it functions as thermal transfer paper, inkjet recording paper, carbonless paper, electrostatic recording paper, zeography paper, etc., it is possible to make recording paper that can record on both sides. Of course, it can also be a double-sided thermal recording material. Furthermore, a back layer can be provided to suppress the penetration of oil and plasticizer from the back surface of the thermal recording material, control curl, and prevent static charge. It is also possible to make a linerless label that does not require release paper by applying a release layer containing silicone on the protective layer and applying an adhesive to one side.

[0054] [Thermal recording material] The thermal recording material can be manufactured by forming the above-mentioned layers on a support. Any known coating method can be used to form the above-mentioned layers on the support, such as the air knife method, blade method, gravure method, roll coater method, spray method, dip method, bar method, curtain method, slot die method, slide die method, or extrusion method. In addition, each coating may be applied and dried one layer at a time to form each layer, or the same coating may be applied in two or more layers. Furthermore, simultaneous multilayer coating, in which two or more layers are applied at the same time, may be performed. In addition, after each layer has been formed, or at any stage after all layers have been formed, a smoothing treatment can be performed using a known method such as a supercalender or softcalender. [Examples]

[0055] The present invention will be described in more detail by reference to examples, but the present invention is not limited thereto. Unless otherwise specified, "parts" and "%" refer to "parts by mass" and "mass%", respectively. The average particle size was measured using a laser diffraction particle size distribution analyzer SALD2200 (manufactured by Shimadzu Corporation). Here, the average particle size is the median diameter (D50).

[0056] (Example 1) (1) Preparation of coating solution for colored layer A coating solution for a colored layer was obtained by mixing a composition consisting of 169.8 parts of a plastic hollow particle dispersion (product name: Lowpake SN-1055, hollowness ratio: 55%, average particle size: 1.0 μm, manufactured by Dow Chemical, solid content concentration 26.5% by mass), 40.0 parts of a 50% aqueous dispersion of calcined kaolin (product name: Ansilex 93, manufactured by BASF) (average particle size: 0.6 μm), 41.7 parts of styrene-butadiene latex (product name: L-1571, manufactured by Asahi Kasei Chemicals, solid content concentration 48% by mass), 50.0 parts of a 10% aqueous solution of oxidized starch, 26.3 parts of a carbon black dispersion (product name: Black FLTB, manufactured by Dainichi Seika Kogyo Co., Ltd., solid content concentration 38.0%), and 20 parts of water.

[0057] (2) Preparation of the clearing agent dispersion 12.5 parts stearic acid amide, 12.5 parts palmitic acid amide, 25.0 parts 10% aqueous solution of partially saponified PVA (product name: Kuraray Poval 5-88, manufactured by Kuraray Co., Ltd.) Department The mixture was combined with 50 parts of water and ground using a sand mill (AIMEX, Sand Grinder) until the median diameter measured by a laser diffraction particle size analyzer SALD2200 (Shimadzu Corporation) was 1.0 μm to obtain a clarifying agent dispersion.

[0058] (3) Preparation of coating solution for light scattering layer A coating solution for a light scattering layer was obtained by mixing a composition consisting of 33.9 parts of a plastic hollow particle dispersion (product name: Lowpake UltraE, hollowness ratio: 44%, average particle size: 0.4 μm, manufactured by Dow Chemical, solid content concentration 29.5% by mass), 140.0 parts of the clarifying agent dispersion obtained in (2), 415.0 parts of a 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.), 27.8 parts of an aqueous dispersion of zinc stearate (product name: Hydrin Z-9-36, manufactured by Chukyo Oil & Fat Co., Ltd., solid content concentration 36.0%), and 50.0 parts of water.

[0059] (4) Preparation of thermal recording material Basis weight 42g / m 2 On one side of the high-quality paper, the coating liquid for the colored layer and the coating liquid for the light scattering layer were applied at a dry amount of 6.0 g / m² each. 2 3.5g / m 2 The material was coated and dried in such a manner to sequentially form a colored layer and a light scattering layer, thereby obtaining a thermal recording material.

[0060] (Example 2) In preparing the coating solution for the light scattering layer in Example 1, the amount of plastic hollow particle dispersion (product name: Lowpake UltraE, hollowness: 44%, average particle size: 0.4 μm, manufactured by Dow Chemical, solid content concentration 29.5% by mass) was changed from 33.9 parts to 67.8 parts, and the amount of 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 415.0 parts to 315.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0061] (Example 3) In preparing the coating solution for the light scattering layer in Example 1, the amount of plastic hollow particle dispersion (product name: Lowpake UltraE, hollowness: 44%, average particle size: 0.4 μm, manufactured by Dow Chemical, solid content concentration 29.5% by mass) was changed from 33.9 parts to 101.7 parts, and the amount of 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 415.0 parts to 215.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0062] (Example 4) In preparing the coating solution for the light scattering layer in Example 1, the amount of plastic hollow particle dispersion (product name: Lowpake UltraE, hollowness: 44%, average particle size: 0.4 μm, manufactured by Dow Chemical, solid content concentration 29.5% by mass) was changed from 33.9 parts to 118.6 parts, and the amount of 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 415.0 parts to 165.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0063] (Example 5) In the preparation of the coating solution for the light scattering layer in Example 1, the amount of the clearing agent dispersion obtained in (2) was changed from 140.0 parts to 80.0 parts, and the amount of the 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 415.0 parts to 580.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0064] (Example 6) In preparing the coating solution for the light scattering layer in Example 1, the amount of the clearing agent dispersion obtained in (2) was changed from 140.0 parts to 60.0 parts, and the amount of the 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 415.0 parts to 635.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0065] (Example 7) In preparing the coating solution for the light scattering layer in Example 1, a composition consisting of 101.7 parts of hollow plastic particle dispersion (product name: Lowpake UltraE, hollowness: 44%, average particle size: 0.4 μm, manufactured by Dow Chemical, solid content concentration 29.5% by mass), 18.9 parts of dense plastic particle dispersion (product name: Grossdale 130S, manufactured by Mitsui Chemicals, solid content concentration 53.0%), 120.0 parts of the clearing agent dispersion obtained in (2), 170.0 parts of a 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.), 27.8 parts of aqueous zinc stearate dispersion (product name: Hydrin Z-9-36, manufactured by Chukyo Oil & Fat Co., Ltd., solid content concentration 36.0%), and 50.0 parts of water was mixed to obtain a coating solution for the light scattering layer. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0066] (Example 8) In preparing the coating solution for the light scattering layer in Example 7, the amount of dense plastic particle dispersion (product name: Grossdale 130S, manufactured by Mitsui Chemicals, Inc., solid content concentration 53.0%) was changed from 18.9 parts to 37.7 parts, and the amount of 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 170.0 parts to 70.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 7.

[0067] (Example 9) In preparing the coating solution for the light scattering layer in Example 1, a composition consisting of 33.9 parts of a plastic hollow particle dispersion (product name: Lowpake UltraE, hollowness: 44%, average particle size: 0.4 μm, manufactured by Dow Chemical, solid content concentration 29.5% by mass), 84.9 parts of a plastic dense particle dispersion (product name: Grossdale 130S, manufactured by Mitsui Chemicals, solid content concentration 53.0%), 120.0 parts of the clearing agent dispersion obtained in (2), 40.0 parts of a 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.), 22.2 parts of an aqueous dispersion of zinc stearate (product name: Hydrin Z-9-36, manufactured by Chukyo Oil & Fat Co., Ltd., solid content concentration 36.0%), and 50.0 parts of water was mixed to obtain a coating solution for the light scattering layer. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0068] (Example 10) (5) Preparation of the clearing agent dispersion 44 parts of di-p-methylbenzyl oxalate, 44 parts of a 10% aqueous solution of partially saponified PVA (product name: Kuraray Poval 5-88, manufactured by Kuraray Co., Ltd.), and 12 parts of water were mixed and ground using a sand mill (Aimex Co., Ltd., sand grinder) until the median diameter measured by a laser diffraction particle size analyzer SALD2200 (Shimadzu Corporation) was 1.0 μm to obtain a clarifying agent dispersion.

[0069] In the preparation of the coating solution for the light scattering layer in Example 1, 101.7 parts of plastic hollow particle dispersion (product name: Lowpake UltraE, hollowness ratio: 44%, average particle size: 0.4 μm, manufactured by Dow Chemical, solid content concentration 29.5% by mass), 37.7 parts of plastic dense particle dispersion (product name: Grossdale 130S, manufactured by Mitsui Chemicals, solid content concentration 53.0%), 40.0 parts of the clarifying agent dispersion obtained in (2), and obtained in (5) A thermal recording material was obtained in the same manner as in Example 1, except that a composition consisting of 45.5 parts of a clearing agent dispersion (solid content concentration 44.0%), 70.0 parts of a 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.), 27.8 parts of an aqueous dispersion of zinc stearate (product name: Hydrin Z-9-36, manufactured by Chukyo Oil & Fat Co., Ltd., solid content concentration 36.0%) was mixed to obtain a coating solution for the light scattering layer.

[0070] (Example 11) A thermal recording material was obtained in the same manner as in Example 10, except that in the preparation of the clearing agent dispersion (5) in Example 10, di-p-methylbenzyl oxalate was replaced with di-p-chlorobenzyl oxalate.

[0071] (Example 12) In the preparation of the clearing agent dispersion in Example 10 (5), di-p-methylbenzyl oxalate was used, 1,2- bis A thermal recording material was obtained in the same manner as in Example 10, except that it was changed to (phenoxymethyl)benzene.

[0072] (Example 13) In preparing the coating solution for the light scattering layer in Example 8, a thermal recording material was obtained in the same manner as in Example 8, except that 57.1 parts of a dense plastic particle dispersion (product name: Grossdale 204S, manufactured by Mitsui Chemicals, solid content concentration 35.0%) were used instead of 37.7 parts of a dense plastic particle dispersion (product name: Grossdale 130S, manufactured by Mitsui Chemicals, solid content concentration 53.0%).

[0073] (Example 14) In preparing the coating solution for the light scattering layer in Example 8, a thermal recording material was obtained in the same manner as in Example 8, except that 75.5 parts of a dense plastic particle dispersion (product name: Saibinol PG-5, manufactured by Saiden Chemical Co., Ltd., solid content concentration 26.5%) were used instead of 37.7 parts of a dense plastic particle dispersion (product name: Grossdale 130S, manufactured by Mitsui Chemicals, Inc., solid content concentration 53.0%).

[0074] (Example 15) A thermal recording material was obtained in the same manner as in Example 3, except that the amount of stearic acid amide was changed from 12.5 parts to 25.0 parts and the amount of palmitic acid amide was changed from 12.5 parts to 0 parts in the preparation of the clearing agent dispersion of Example 3.

[0075] (Example 16) A thermal recording material was obtained in the same manner as in Example 3, except that the amount of stearic acid amide was changed from 12.5 parts to 0 parts, and the amount of palmitic acid amide was changed from 12.5 parts to 25.0 parts.

[0076] (Comparative Example 1) In preparing the coating solution for the light scattering layer in Example 1, the amount of plastic hollow particle dispersion (product name: Lowpake UltraE, hollowness: 44%, average particle size: 0.4 μm, manufactured by Dow Chemical, solid content concentration 29.5% by mass) was changed from 33.9 parts to 16.9 parts, the amount of the clearing agent dispersion obtained in (2) was changed from 140.0 parts to 120.0 parts, and the amount of 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 415.0 parts to 520.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0077] (Comparative Example 2) In preparing the coating solution for the light scattering layer in Example 8, the amount of plastic hollow particle dispersion (product name: Lowpake UltraE, hollowness: 44%, average particle size: 0.4 μm, manufactured by Dow Chemical, solid content concentration 29.5% by mass) was changed from 101.7 parts to 0 parts, and the amount of 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 70.0 parts to 370.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 8.

[0078] (Comparative Example 3) In preparing the coating solution for the light scattering layer in Example 1, the amount of plastic hollow particle dispersion (product name: Lowpake UltraE, hollowness: 44%, average particle size: 0.4 μm, manufactured by Dow Chemical, solid content concentration 29.5% by mass) was changed from 33.9 parts to 135.6 parts, the amount of the clearing agent dispersion obtained in (2) was changed from 140.0 parts to 160.0 parts, and the amount of 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 415.0 parts to 60.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0079] (Comparative Example 4) In the preparation of the coating solution for the light scattering layer in Comparative Example 3, the amount of the clearing agent dispersion obtained in (2) was changed from 160.0 parts to 140.0 parts, and the amount of the 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 60.0 parts to 115.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Comparative Example 3.

[0080] (Comparative Example 5) In the preparation of the clearing agent dispersion in Example 10 (5), di-p-methylbenzyl oxalate was used, 1,2- bis A thermal recording material was obtained in the same manner as in Example 10, except that it was changed to (3-methylphenoxy)ethane.

[0081] (Comparative Example 6) (6) Preparation of the clearing agent dispersion 44 parts of di-p-methylbenzyl oxalate, 44 parts of a 10% aqueous solution of partially saponified PVA (product name: Kuraray Poval 5-88, manufactured by Kuraray Co., Ltd.), and 12 parts of water were mixed and ground using a sand mill (Aimex Co., Ltd., sand grinder) until the median diameter measured by a laser diffraction particle size analyzer SALD2200 (Shimadzu Corporation) was 1.0 μm to obtain a clarifying agent dispersion.

[0082] In preparing the coating solution for the light scattering layer in Example 10, a thermal recording material was obtained in the same manner as in Example 10, except that the amount of the clearing agent dispersion obtained in (2) was changed from 40.0 parts to 0 parts, and the amount of the clearing agent dispersion obtained in (5) was changed from 45.5 parts to 68.2 parts of the clearing agent dispersion obtained in (6) (solid content concentration 44.0%).

[0083] (Comparative Example 7) In the preparation of the coating solution for the light scattering layer in Comparative Example 5, the amount of plastic hollow particle dispersion (product name: Lowpake UltraE, hollowness: 44%, average particle size: 0.4 μm, manufactured by Dow Chemical, solid content concentration 29.5% by mass) was changed from 101.7 parts to 27.1 parts, and the amount of 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 70.0 parts to 290.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Comparative Example 5.

[0084] The above examples and comparative examples were evaluated using the following method. The results are shown in Tables 1 and 2.

[0085] [ISO whiteness] Four layers of the obtained thermal recording material were stacked, and the ISO whiteness was measured using a colorimeter SC-WT (manufactured by Suga Test Instruments Co., Ltd.). An ISO whiteness of 35 or higher is required, 40 or higher is desirable, and 50 or higher is even more desirable.

[0086] [Print density] Using a thermal recording evaluation machine (product name: TH-PMD, manufactured by Okura Electric Co., Ltd.), each thermal recording material was recorded with an applied energy of 0.24 mJ / dot, and the resulting printed area was measured in visual mode using a Macbeth densitometer (RD-914, manufactured by Macbeth Corporation). A higher value indicates a higher print density. For recording density, a value of 1.25 or higher is required, 1.30 or higher is desirable, and 1.40 or higher is even more desirable.

[0087] [Oil resistance] For each thermal recording material, 1 ml of salad oil was dropped onto the blank area, spread evenly with a cloth, and left at room temperature for 24 hours. The scalp density was then measured using the visual mode of a Macbeth densitometer (RD-914, manufactured by Macbeth). A scalp density of 0.90 or less is required, and 0.80 or less is desirable.

[0088] [Printability] Using a thermal printer (product name: Lesprit T-408v-ex, manufactured by Sato Corporation), a solid black area of ​​18 cm was printed six times at an applied energy of 3 A, and the amount of printhead residue adhering to the thermal head was determined according to the following criteria. ○: The amount of residue on the head is very small, and it is at a level that does not cause any problems in actual use. △: Some residue is generated on the head, but it is at a level that does not cause problems in actual use. ×: A large amount of printhead residue was generated, and printing problems occurred within the first 6 prints. This is a level that would cause problems in practical use.

[0089] [Table 1]

[0090] [Table 2]

Claims

1. A thermal recording material comprising a support containing at least one colored surface, and a light-scattering layer disposed on the colored surface, wherein the light-scattering layer contains hollow polymer particles and a clearing agent, the proportion of the hollow polymer particles is 6 to 35% by mass of the total solid content of the light-scattering layer, the clearing agent is contained in an amount of 1 part by mass or more on a solid content basis per 1 part by mass of the hollow polymer particles, the light-scattering layer substantially does not contain a dye precursor and a color developer, and when heat is applied, the clearing agent melts, the refractive index of the light-scattering layer changes, as a result the light-scattering layer becomes transparent and the colored surface becomes visible. A) The clearing agent consists solely of a fatty acid amide, or B) The clearing agent comprises a fatty acid amide and the following general formula (1): 【Chemistry 1】 (In the formula, X is the same as or different from CH) ３ A combination of a compound represented by (or Cl) and at least one selected from the group consisting of 1,2-bis(phenoxymethyl)benzene, A) and B) above, the fatty acid amides are a thermal recording material containing stearic acid amide and palmitic acid amide.

2. The thermal recording material according to claim 1, wherein the content of the transparentizing agent is 20 to 35% by mass of the total solid content of the light scattering layer.

3. The thermal recording material according to claim 1 or 2, wherein the content of the hollow polymer particles is 20 to 30% by mass of the total solid content of the light scattering layer.

4. The thermal recording material according to claim 1 or 2, further comprising polymer particles without hollows in the light scattering layer, wherein the content ratio of the polymer particles without hollows is 10 to 45% by mass of the total solid content of the light scattering layer.

5. The thermal recording material according to claim 4, wherein the average particle size of the polymer particles that do not have a hollow space is 0.4 to 2.0 μm.

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