Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
  • B41M5/42—Intermediate, backcoat, or covering layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
  • B41M5/323—Organic colour formers, e.g. leuco dyes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
  • B41M5/323—Organic colour formers, e.g. leuco dyes
  • B41M5/327—Organic colour formers, e.g. leuco dyes with a lactone or lactam ring
  • B41M5/3275—Fluoran compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
  • B41M5/333—Colour developing components therefor, e.g. acidic compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
  • B41M5/333—Colour developing components therefor, e.g. acidic compounds
  • B41M5/3333—Non-macromolecular compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
  • B41M5/333—Colour developing components therefor, e.g. acidic compounds
  • B41M5/3333—Non-macromolecular compounds
  • B41M5/3335—Compounds containing phenolic or carboxylic acid groups or metal salts thereof
  • B41M5/3336—Sulfur compounds, e.g. sulfones, sulfides, sulfonamides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
  • B41M5/42—Intermediate, backcoat, or covering layers
  • B41M5/44—Intermediate, backcoat, or covering layers characterised by the macromolecular compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M2205/00—Printing methods or features related to printing methods; Location or type of the layers
  • B41M2205/04—Direct thermal recording [DTR]
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M2205/00—Printing methods or features related to printing methods; Location or type of the layers
  • B41M2205/40—Cover layers; Layers separated from substrate by imaging layer; Protective layers; Layers applied before imaging

Definitions

• This invention relates to a thermal recording medium that utilizes the color-developing reaction between a colorless or light-colored electron-donating leuco dye (hereinafter also referred to as “leuco dye”) and an electron-accepting developer (hereinafter also referred to as “developer”), and that has good print running properties during long-run printing.
• leuco dye colorless or light-colored electron-donating leuco dye
• developer electron-accepting developer
• a thermal recording medium is prepared by coating a coating liquid containing a colorless or light-colored leuco dye and a color developer on a support such as paper, synthetic paper, film, plastic, etc., and a recorded image is obtained by instantaneous chemical reaction caused by heating with a thermal head, hot stamp, heat pen, laser light, etc.
• Thermal recording media are widely used as recording media for facsimiles, computer terminal printers, automatic ticket vending machines, measurement recorders, receipts at supermarkets and convenience stores, etc. In recent years, the use of thermal recording media has expanded to include a wide variety of applications, such as for various tickets, receipts, labels, bank ATMs, gas and electricity meter reading, and vouchers for car and horse racing betting.
• An object of the present invention is to provide a thermal recording medium which has good print running properties (particularly, resistance to head residue adhesion) during long-run printing.
• the present invention is a thermosensitive recording medium comprising a support, a thermosensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer, and a protective layer provided on the thermosensitive recording layer, the thermosensitive recording layer containing at least one urea compound represented by the following general formula (Chemical Formula 1), and the protective layer containing a phosphate ester compound.
• X represents -O- or -NH-
• R1 represents a hydrogen atom or -SO2 - R3
• R3 represents a substituted or unsubstituted alkyl group, aralkyl group or aryl group
• R2 represents a hydrogen atom or an alkyl group
• m represents 0 or 1.
• thermosensitive recording layer of the thermosensitive recording medium of the present invention contains at least one urea compound represented by the following general formula (Chemical Formula 1) as a developer.
• X represents -O- or -NH-
• R1 represents a hydrogen atom or -SO2 - R3
• R3 represents a substituted or unsubstituted alkyl group, aralkyl group or aryl group
• R2 represents a hydrogen atom or an alkyl group
• m represents 0 or 1.
• the urea compound is preferably the following (1) or (2): (1) A first urea compound represented by the following general formula (Chemical Formula 2): (wherein R 1 , R 2 and R 3 are defined as above.) (2) A second urea compound represented by the following formula (Chemical Formula 3): (In the formula, R2 is defined as above, and R4 to R8 are defined below.)
• the first urea compound used in the present invention is preferably represented by the following formula (Chemical Formula 4).
• R3 represents an alkyl group, an aralkyl group, or an aryl group, which may be substituted or unsubstituted, and is preferably a substituted or unsubstituted aryl group.
• the substituent is preferably an 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 a halogen atom.
• multiple R3s may be the same or different.
• the positions of R 1 -O- in the benzene ring of the general formula (Chemical Formula 2) may be the same or different, and are preferably the 3-position, 4-position or 5-position.
• the position of R 3 —SO 2 —O— in the benzene ring of the general formula (Chemical formula 2) and the general formula (Chemical formula 4) may be the same or different, and is preferably the 3-position, 4-position or 5-position.
• the alkyl group may be, for example, a linear, branched, or alicyclic alkyl group, and preferably has 1 to 12 carbon atoms.
• Examples of the alkyl group include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, cyclopentyl, hexyl, cyclohexyl, 2-ethylhexyl, and lauryl groups.
• the number of carbon atoms in this aralkyl group is preferably 7 to 12.
• Examples of this aralkyl group include benzyl, 1-phenylethyl, 2-phenylethyl, 3-phenylpropyl, p-methylbenzyl, m-methylbenzyl, m-ethylbenzyl, p-ethylbenzyl, p-i-propylbenzyl, p-t-butylbenzyl, p-methoxybenzyl, m-methoxybenzyl, o-methoxybenzyl, m,p-di-methoxybenzyl, p-ethoxy-m-methoxybenzyl, p-phenylmethylbenzyl, p-cumylbenzyl, p-phenylbenzyl, o-phenylbenzyl, m-phenylbenzyl, p-tolylbenzyl, m-tolylbenzy
• the number of carbon atoms in this aryl group is preferably 6 to 12.
• this aryl group include unsubstituted aryl groups such as phenyl group, p-tolyl group, m-tolyl group, o-tolyl group, 2,5-dimethylphenyl group, 2,4-dimethylphenyl group, 3,5-dimethylphenyl group, 2,3-dimethylphenyl group, 3,4-dimethylphenyl group, mesitylene group, p-ethylphenyl group, p-i-propylphenyl group, p-t-butylphenyl group, p-methoxyphenyl group, 3,4-dimethoxyphenyl group, p-ethoxyphenyl group, p-chlorophenyl group, 1-naphthyl group, 2-naphthyl group, and t-butylated naphthyl group, or aryl groups substituted
• R3 is preferably a group represented by the following formula:
• R 4 to R 8 may be the same or different and each represent 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.
• R2 represents a hydrogen atom or an alkyl group, preferably a hydrogen atom.
• the alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, or a t-butyl group.
• the positions of R2 in the benzene ring of the general formula (Chemical Formula 2) may be the same or different, and are preferably the 3-position, 4-position or 5-position.
• a urea compound represented by the following general formula (Formula 6) is more preferable.
• R9 is an alkyl group or an alkoxy group, preferably an alkyl group, and o represents an integer of 0 to 3, preferably 0 to 2, more preferably 0 to 1.
• the number of carbon atoms in this alkyl group is, for example, 1 to 12, preferably 1 to 8, more preferably 1 to 4.
• the positions of R 9 in the benzene ring of the general formula (6) may be the same or different, and are preferably the 3-position, 4-position or 5-position, and more preferably the 4-position.
• examples of the first urea compound of the present invention include N,N'-di-[3-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-4-methyl-phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-4-ethyl-phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-5-methyl-phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-4-propyl-phenyl]urea, N,N'-di-[3-(o-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(m-toluenesulfonyloxy)phenyl]urea, N,
• the second urea compound used in the present invention is preferably N-[2-(3-phenylureido)phenyl]benzenesulfonamide, which is represented by the following formula and is available, for example, from Nippon Soda Co., Ltd. under the trade name NKK1304.
• the content of the urea compound in the heat-sensitive recording layer of the present invention (solid content, total amount when a plurality of urea compounds are contained) is 1.0 to 70.0% by weight, preferably 5.0 to 65.0% by weight, more preferably 10.0 to 60.0 parts by weight.
• the content of the first urea compound in the heat-sensitive recording layer of the present invention is 1.0 to 50.0% by weight, preferably 5.0 to 40.0% by weight
• the content of the second urea compound is 5.0 to 50.0% by weight, preferably 5.0 to 40.0% by weight.
• the content of the second urea compound in the thermosensitive recording layer is preferably 0.1 to 30.0 parts by weight, more preferably 0.5 to 25.0 parts by weight, still more preferably 1.0 to 20.0 parts by weight, and particularly preferably 2.0 to 15.0 parts by weight, relative to 1.0 part by weight of the first urea compound.
• the thermal recording layer of the present invention may use a color developer other than the first or second urea compound.
• color developers include inorganic acidic substances such as activated clay, attapulgite, colloidal silica, and aluminum silicate, 4,4'-isopropylidenediphenol, 1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, 4-hydroxybenzoate benzyl, 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4,4'-dihydroxy ...
• color developers examples include thiourea compounds such as phenylthiourea, p-chlorobenzoic acid, stearyl gallate, bis[zinc 4-(n-octyloxycarbonylamino)salicylate] dihydrate, 4-[2-(p-methoxyphenoxy)ethyloxy]salicylic acid, 4-[3-(p-tolylsulfonyl)propyloxy]salicylic acid, and 5-[p-(2-p-methoxyphenoxyethoxy)cumyl]salicylic acid, and salts of these aromatic carboxylic acids with polyvalent metal salts such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel, as well as antipyrine complexes of zinc thiocyanate and complex zinc salts of terephthalaldehyde acid and other aromatic carboxylic acids.
• polyvalent metal salts such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and
• color developers can be used alone or in combination of two or more.
• 1-[4-(4-hydroxyphenylsulfonyl)phenoxy]-4-[4-(4-isopropoxyphenylsulfonyl)phenoxy]butane is available, for example, under the trade name JKY-214 manufactured by API Corporation, and the phenol condensation composition described in JP 2003-154760 A is available, for example, under the trade name JKY-224 manufactured by API Corporation.
• Compounds described in WO 02/081229 and the like are available under the trade names NKK-395 and D-100 manufactured by Nippon Soda Co., Ltd.
• metal chelate-type color-developing components such as higher fatty acid metal double salts and polyvalent hydroxy aromatic compounds described in JP 10-258577 A can also be contained.
• the total content (solid content) of the first and/or second urea compound used relative to the total color developer contained in the thermosensitive recording layer (including the first and/or second urea compound) is preferably 50% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more.
• the leuco dye used in the present invention can be any dye known in the field of conventional pressure-sensitive or heat-sensitive recording paper, and is not particularly limited. However, triphenylmethane-based compounds, fluoran-based compounds, fluorene-based compounds, divinyl-based compounds, etc. are preferred. Specific examples of representative colorless or light-colored dyes (dye precursors) are shown below. These dye precursors may be used alone or in combination of two or more types.
• Triphenylmethane leuco dye 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis(p-dimethylaminophenyl)phthalide (also known as malachite green lactone)
• ⁇ Fluorene-based leuco dyes > 3,6,6'-tris(dimethylamino)spiro[fluorene-9,3'-phthalide], 3,6,6'-tris(diethylamino)spiro[fluorene-9,3'-phthalide]
• ⁇ Divinyl leuco dye> 3,3-bis-[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethenyl]-4,5,6,7-tetrabromophthalide, 3,3-bis-[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethenyl]-4,5,6,7-tetrachlorophthalide, 3,3-bis-[1,1-bis(4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7-tetrabromophthalide, 3,3-bis-[1-(4-methoxyphenyl)-1-(4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide
• ⁇ Other> 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-octyl-2-methylindol-3-yl)-4-azaphthalide, 3-(4-cyclohexylethylamino-2-methoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3,3-bis(1-ethyl-2-methylindol-3-yl)phthalide, 3,6-bis(diethylamino)fluoran- ⁇ -(3′-nitro)anilinolactam, 3,6-bis(diethylamino)fluoran- ⁇ -(3′-nitro)anilinolactam, Fluoran- ⁇ -(4'-nitro)anil
• the sensitizer used in the present invention may be a conventionally known sensitizer.
• Examples of such sensitizers include fatty acid amides such as stearic acid amide and palmitic acid amide, ethylene bisamide, montanic acid wax, polyethylene wax, 1,2-bis-(3-methylphenoxy)ethane, p-benzylbiphenyl, ⁇ -benzyloxynaphthalene, 4-biphenyl-p-tolyl ether, m-terphenyl, 1,2-diphenoxyethane, dibenzyl oxalate, di(p-chlorobenzyl) oxalate, di(p-methylbenzyl) oxalate, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, di-p-tolyl carbonate, phenyl- ⁇ -
• Examples of the sensitizers include naphthyl carbonate, 1,4-diethoxynaphthalene,
• Pigments that can be used in the present invention include kaolin, calcined kaolin, calcium carbonate, aluminum oxide, titanium oxide, magnesium carbonate, aluminum silicate, magnesium silicate, calcium silicate, aluminum hydroxide, silica, etc., and they can be used in combination depending on the required quality.
• Binders that can be used in the present invention include polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, olefin-modified polyvinyl alcohol, nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, and other modified polyvinyl alcohols, silane-modified acrylic resins, and high Tg acrylic resins (preferably non-core-shell acrylic resins, the glass transition point (Tg) of which is higher than 50°C and lower than 95°C.
• polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated poly
• the Tg can be measured by differential scanning calorimetry (DSC).
• DSC differential scanning calorimetry
• C (meth)acrylic acid and other acrylic resins consisting of monomer components (excluding olefins) copolymerizable with (meth)acrylic acid, cellulose derivatives such as hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, ethyl cellulose, acetyl cellulose, and other starches such as oxidized starch, etherified starch, and esterified starch, styrene-maleic anhydride copolymers, styrene-butadiene copolymers, casein, gum arabic, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic acid esters, polyvinyl butyral, polystyrose and their copolymers, polyamide resins, silicone resins, petroleum resins, terpene resins,
• the types and amounts of the leuco dye, developer, sensitizer, and other various components used in the thermal recording layer of the present invention are determined according to the required performance and recording suitability, and are not particularly limited, but typically, 0.5 to 10 parts by weight of developer, 0.1 to 10 parts by weight of sensitizer, 0.5 to 20 parts by weight of pigment, 0.01 to 10 parts by weight of stabilizer, and 0.01 to 10 parts by weight of other components are used per 1 part by weight of leuco dye.
• the appropriate amount of binder is about 5 to 25% by weight of the solid content of the thermal recording layer.
• the leuco dye, developer, and materials added as necessary are pulverized to particle sizes of several microns or less using a grinding machine such as a ball mill, attritor, or sand grinder, or an appropriate emulsifying device, and a binder and various additives depending on the purpose are added to make a coating liquid.
• a grinding machine such as a ball mill, attritor, or sand grinder, or an appropriate emulsifying device
• a binder and various additives depending on the purpose are added to make a coating liquid.
• the solvent used for this coating liquid can be water or alcohol, and the solid content is about 20 to 40% by weight.
• the protective layer contains a phosphoric acid ester compound.
• the phosphate compound used in the present invention include monocaproyl phosphate, monooctyl phosphate, monocapryl phosphate, monolauryl phosphate, monomyristyl phosphate, monocetyl phosphate, monostearyl phosphate, monophosphate of tetraethylene glycol mononeopentyl ether, monophosphate of triethylene glycol monotridecyl ether, monophosphate of tetraethylene glycol monolauryl ether, monophosphate of diethylene glycol monostearyl ether, dicaproyl phosphate, dioctyl phosphate, dicapryl phosphate, dilauryl phosphate, dimyristyl phosphate, dicetyl phosphate, distearyl phosphate, diphosphate of tetraethylene glycol mononeopentyl ether, diphosphate of triethylene glycol monotridecyl ether,
• Sepal M835 is preferred. Since it is a liquid substance at room temperature and does not have a specific melting point, it is considered to be less likely to adhere to the thermal head during long-term printing compared to zinc stearate, which is normally used as a lubricant.
• the amount of the phosphate ester compound used in the present invention is preferably 2.5 to 15.0 parts by weight (hereinafter, parts by weight are calculated as solids content) and more preferably 2.5 to 11.5 parts by weight, based on 100 parts by weight of the total solids content of the coating layer of the outermost layer. If the amount of the phosphate ester compound is less than 2.5 parts by weight, good stick resistance cannot be obtained, and if it exceeds 11.5 parts by weight, print storage stability (plasticizer resistance) may decrease.
• the protective layer of the present invention may contain optional components such as binders and pigments as described for the heat-sensitive recording layer, if necessary.
• the amount of the binder or the total amount of the binder and pigment in the protective layer is usually 80.0 to 100.0% by weight, preferably 90.0 to 100.0% by weight, in terms of solid content.
• the amount of the binder is preferably about 30.0 to 300.0 parts by weight per 100 parts by weight of the pigment.
• a crosslinking agent can be used in combination in the protective layer of the present invention.
• the crosslinking agent include epichlorohydrin resins such as polyamine epichlorohydrin resins and polyamide epichlorohydrin resins, polyamide urea resins, polyalkylene polyamine resins, polyalkylene polyamide resins, polyamine polyurea resins, modified polyamine resins, modified polyamide resins, polyalkylene polyamine urea formalin resins, and polyalkylene polyamine polyamide polyurea resins, polyamine/polyamide resins such as glyoxal, methylol melamine, melamine formaldehyde resins, melamine urea resins, potassium persulfate, ammonium persulfate, sodium persulfate, ferric chloride, magnesium chloride, borax, boric acid, alum, and ammonium chloride.
• the protective layer contains an epichlorohydrin resin
• the thermosensitive recording medium of the present invention may have a backcoat layer on the opposite side of the support to the thermosensitive recording layer, which may contain a water-soluble polymer, a water-dispersible resin, a pigment, etc.
• a water-soluble polymer include polyvinyl alcohols other than ethylene-vinyl alcohol copolymers, such as fully saponified polyvinyl alcohol and partially saponified polyvinyl alcohol; proteins, such as casein, soybean protein, and synthetic protein; starches, such as oxidized starch, cationized starch, urea phosphate esterified starch, and hydroxyethyl etherified starch; cellulose derivatives, such as carboxymethyl cellulose, hydroxymethyl cellulose, and hydroxyethyl cellulose; polyvinylpyrrolidone; and sodium alginate.
• water-dispersible resin examples include natural rubber, diene rubber, non-diene rubber, and thermoplastic elastomer.
• this pigment any pigment that can be used in a heat-sensitive recording layer can be used appropriately, but aluminum hydroxide, silica, kaolin, and calcined kaolin are preferred, and aluminum hydroxide is more preferred.
• This backcoat layer may further contain, as necessary, lubricants, crosslinking agents, ultraviolet absorbers, dispersants, antifoaming agents, fluorescent dyes, and the like that can be used in the thermosensitive recording layer, within the scope of not impeding the desired effects for the above-mentioned problems.
• the backcoat layer preferably contains an ethylene-vinyl alcohol copolymer and an ethylene-acrylic copolymer.
• the ethylene-vinyl alcohol copolymer is a polymer having ethylene units and vinyl alcohol units.
• the ethylene-vinyl alcohol copolymer is usually obtained by polymerizing ethylene and a vinyl ester and saponifying the resulting ethylene-vinyl ester copolymer, and the ethylene content is preferably 3 to 20 mol %.
• the saponification degree is preferably 80 to 100 mol %. If the saponification degree is less than 80 mol %, sufficient barrier properties and moisture resistance cannot be obtained.
• the ethylene-acrylic copolymer used in the present invention is a copolymer obtained by emulsion polymerization of ethylene and an acrylic monomer.
• acrylic monomer acrylic acid and methacrylic acid are preferred, and acrylic acid is more preferred.
• the ethylene-acrylic copolymer is preferably at least one of ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene-butyl acrylate copolymer, and ethylene-butyl methacrylate copolymer.
• the content ratio (solid content) of the ethylene-acrylic copolymer relative to the ethylene-vinyl alcohol copolymer is preferably 2.5 to 40 parts, more preferably 10 to 40 parts, per 10 parts by mass of the ethylene-vinyl alcohol copolymer.
• the content (solid content) of the pigment in the backcoat layer is preferably 50 to 10% by weight, and more preferably 30 to 10% by weight.
• the coating amount of the backcoat layer is determined according to the required performance and recording suitability, and is not particularly limited, but a typical coating amount is about 0.1 to 5 g/m2 in solid content. Of this amount , about 2.5 to 4.5 g/m2 is preferable because it has excellent water vapor barrier properties and good quality as a thermal recording medium.
• the thermosensitive recording medium of the present invention may further have an undercoat layer between the support and the thermosensitive recording layer.
• the undercoat layer consists primarily of a binder and a pigment.
• the binder used in the undercoat layer may be an emulsion of a water-soluble polymer or a hydrophobic polymer that is generally used.
• Specific examples include cellulose derivatives such as polyvinyl alcohol, polyvinyl acetal, hydroxyethyl cellulose, methyl cellulose, and carboxymethyl cellulose, starch and its derivatives, sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide/acrylic acid ester copolymer, acrylic acid amide/acrylic acid ester/methacrylic acid copolymer, styrene/maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and casein, and emulsions of hydro
• the pigment used in the undercoat layer may be any known pigment that has been generally used, such as calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, magnesium hydroxide, calcined kaolin, clay, talc, or other inorganic pigments. These pigments may be used alone or in combination.
• the amount of the pigment in the undercoat layer is usually 50 to 95 parts by weight, preferably 70 to 90 parts by weight, based on 100 parts by weight of the total solid content.
• the coating solution for the undercoat layer may contain various auxiliary agents, such as dispersants, plasticizers, pH adjusters, defoamers, water retention agents, preservatives, coloring dyes, and ultraviolet protection agents, as required.
• the means for coating the thermosensitive recording layer and the coating layers other than the thermosensitive recording layer i.e., the protective layer, undercoat layer, etc.
• the means for coating the thermosensitive recording layer and the coating layers other than the thermosensitive recording layer is not particularly limited, and can be applied according to well-known conventional techniques.
• an off-machine coater or an on-machine coater equipped with various coaters such as an air knife coater, a rod blade coater, a bent blade coater, a bevel blade coater, a roll coater, or a curtain coater can be appropriately selected and used.
• the coating weights of the thermosensitive recording layer and the coating layers other than the thermosensitive recording layer are determined according to the required performance and recording suitability, and are not particularly limited.
• the typical coating weight of the thermosensitive recording layer is about 2 to 12 g/ m2 in solid content
• the coating weight of the protective layer is preferably 0.5 to 5.0 g/ m2 in solid content.
• various known techniques in the field of thermal recording media can be added as necessary, such as smoothing treatment such as supercalendering after coating of each coating layer.
• the developer dispersions (Liquids A1 and A2), leuco dye dispersion (Liquid B), and sensitizer dispersion (Liquid C) having the following compositions were each wet-ground in a sand grinder until the average particle size reached 0.5 ⁇ m.
• ⁇ Coating solution for protective layer Aluminum hydroxide dispersion (manufactured by Martinsberg, product name: Martyfin OL, solid content 50%) 9.0 parts Carboxy-modified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd., trade name: KL318, Degree of polymerization: approximately 1700, degree of saponification: 95-99 mol%, solid content 10%) 30.0 parts polyamide epichlorohydrin resin (manufactured by Seiko PMC Corporation, product name: WS4030, Solid content 25%) 4.0 parts Modified polyamine resin (manufactured by Sumitomo Chemical Co., Ltd., product name: Sumirez Resin SPI-102A, Solid content 45%) 2.2 parts Phosphate ester compound (manufactured by Chukyo Yushi Co., Ltd., Sepal M835, solid content 20%)
• ⁇ Coating solution for backcoat layer > Kaolin (Imeris Co., Ltd., product name: Contour 1500) 20 parts Ethylene-vinyl alcohol copolymer (Kuraray Co., Ltd., product name: Exeval RS4104) 10 parts ethylene-acrylic copolymer (manufactured by Sumitomo Seika Chemicals, trade name: ZAIKXEN AC, Melting point: 80-95°C) 40 parts
• Example 1 The undercoat layer coating liquid was applied to one side of a support (fine paper with a basis weight of 60 g/ m2 ) by the bent blade method so that the coating amount was 6.0 g/ m2 in solid content, and then dried to obtain an undercoat layer coated paper.
• the coating solution 1 for the thermosensitive recording layer was applied by the rod blade method so as to give a coating amount of 3.0 g/ m2 in terms of solid content, and then the coating was dried and treated with a super calendar so as to give a smoothness of 500 to 1000 seconds to produce a thermosensitive recording layer coated paper.
• the protective layer coating liquid was applied onto the thermal recording layer of this thermal recording layer coated paper by the rod blade method so as to give a coating amount of 3.0 g/ m2 in solid content, and then dried to prepare a thermal recording medium.
• thermosensitive recording medium was prepared in the same manner as in Example 1, except that the amount of the phosphoric ester compound in the protective layer coating liquid was changed from 3.5 parts to 1.75 parts.
• Example 3 A thermosensitive recording medium was prepared in the same manner as in Example 1, except that the amount of the phosphoric ester compound in the protective layer coating liquid was changed from 3.5 parts to 7.0 parts.
• Example 4 A thermal recording medium was prepared in the same manner as in Example 1, except that 3.5 parts of the phosphoric acid ester compound in the protective layer coating liquid was replaced with 3.5 parts of a stearyl phosphoric acid ester potassium salt emulsion (product name: U-Pol 1800, manufactured by Matsumoto Oil Co., Ltd., solids concentration 35%).
• thermosensitive recording medium was prepared in the same manner as in Example 1, except that Coating Solution 1 for Thermosensitive Recording Layer was replaced with Coating Solution 2 for Thermosensitive Recording Layer.
• the backcoat layer coating liquid was applied to the side opposite the protective layer by the rod blade method to a coating amount of 3.5 g/ m2 in solid content, and then dried to prepare a thermal recording medium. Except for this, a thermal recording medium was prepared in the same manner as in Example 1.
• Example 7 A thermal recording medium was prepared in the same manner as in Example 1, except that 30.0 parts of the carboxy-modified polyvinyl alcohol aqueous solution (KL318) in the protective layer coating liquid was replaced with 30.0 parts of a carboxy-modified polyvinyl alcohol aqueous solution (manufactured by Kuraray Co., Ltd., product name: KL118, polymerization degree: approximately 1700, saponification degree: 85-90 mol%, solids content: 10%).
• thermosensitive recording medium was prepared in the same manner as in Example 2, except that the developer (urea compound 1) in the thermal recording layer coating solution 1 was replaced with 4-hydroxy-4'-benzyloxydiphenylsulfone (manufactured by Nicca Chemical Co., Ltd., product name: BPS-MA3).
• thermosensitive recording medium was prepared in the same manner as in Example 1, except that 3.5 parts of the phosphoric acid ester compound in the protective layer coating liquid was replaced with 3.5 parts of zinc stearate (product name: Hydrin Z-7-30, solids content 30%).
• thermosensitive recording medium was prepared in the same manner as in Example 1, except that 3.5 parts of the phosphoric ester compound in the protective layer coating liquid was replaced with 1.75 parts of zinc stearate (manufactured by Chukyo Yushi Co., Ltd., Hydrin Z-7-30).
• thermosensitive recording medium was prepared in the same manner as in Example 1, except that 3.5 parts of the phosphoric ester compound in the protective layer coating liquid was replaced with 7.0 parts of zinc stearate (Hydrin Z-7-30).
• the prepared thermosensitive recording medium was evaluated as follows. ⁇ Color development performance (print density)> A checkered pattern was printed on the prepared thermal recording medium at an applied energy of 0.35 mJ/dot and a printing speed of 50 mm/sec using a TH-PMD (thermal recording paper print tester, equipped with a thermal head manufactured by Kyocera Corporation) manufactured by Okura Electric Co., Ltd. The print density of the printed area was measured with a Macbeth densitometer (RD-914, using an amber filter) to evaluate the color development performance.
• RD-914 Macbeth densitometer
• ⁇ Stick resistance> Using a TH-PMD manufactured by Okura Electric Co., Ltd., printing was performed on a thermal recording medium under conditions of applied energy of 0.34 mJ/dot, printing speed of 50 mm/sec, and temperature of -10°C. The stick condition and noise during recording were evaluated according to the following criteria. ⁇ : No whiteout occurs, and there is almost no noise. ⁇ : Some whiteout occurs, but there is almost no noise. ⁇ : Whiteout occurs frequently, and there is a lot of noise.
• the thermal recording medium of the present invention has excellent resistance to head residue adhesion, preventing the adhesion of residue to the head during long-run printing without adversely affecting color development sensitivity.

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