JP7263741B2 - Thermal recording media, thermal recording liquids, and articles - Google Patents

Description

The present invention relates to a thermal recording medium, a thermal recording liquid, and an article.

2. Description of the Related Art Conventionally, highly transparent thermosensitive recording media (transparent thermosensitive recording media) have been used in the field of foods and the like from the viewpoint of improving the visibility of the inside of a package to which the thermosensitive recording medium is attached.
As such a transparent thermosensitive recording medium, for example, a highly transparent thermosensitive recording medium has been proposed by increasing the transparency (lowering the haze) of the support and the thermosensitive recording layer formed thereon. (See Patent Document 1, for example).

When transparent thermosensitive recording media are used in the food industry, they are expected to be exposed to various heat environments. It is strongly desired to be able to maintain
The various thermal environments include, for example, heating in a microwave oven (for example, 100° C. for 2 to 3 minutes) when used as a lunch box label, and the like, and when used as a PET bottle drink label. , hot melt gluing (for example, 130 ° C for several seconds), shrink wrap processing (for example, 200 ° C for several seconds), shrink label processing (for example, 90 ° C for several 10 seconds), environment inside the container during delivery (for example, 60 ° C (for several days at 90° C.), and left on the dashboard of a car in summer (for example, at 90° C. for 1 hour).

An object of the present invention is to provide a thermosensitive recording medium which has high transparency and can maintain high transparency even when exposed to a high temperature environment. The high-temperature environment is appropriately selected depending on the application, and for example, it corresponds to heating a label (eg, 90° C. for 1 hour) of an article (PET bottle, etc.) left on the dashboard of a car in summer.

ただし、前記一般式（１）中、Ｒ^１～Ｒ^５はそれぞれ独立に水素原子、ハロゲン原子、ニトロ基、アミノ基、アルキル基、アルコキシ基、アリールオキシ基、アルキルカルボニルオキシ基、アリールカルボニルオキシ基、アルキルカルボニルアミノ基、アリールカルボニルアミノ基、アルキルスルホニルアミノ基、アリールスルホニルアミノ基、モノアルキルアミノ基、ジアルキルアミノ基、及びアリールアミノ基のいずれかを表す。
Ｘ＝（Ａ－Ｂ）／Ａ×１００・・・式（１）
ただし、前記式（１）中、Ａは、前記感熱記録媒体を温度９０℃で加熱する前の全光線透過率であり、Ｂは、前記感熱記録媒体を温度９０℃で１時間加熱した後の全光線透過率である。

A thermosensitive recording medium of the present invention as a means for solving the above problems is a thermosensitive recording medium comprising a support and a thermosensitive recording layer on the support, wherein the thermosensitive recording layer comprises a leuco dye and a developer. containing a coloring agent, the developer being at least one compound represented by the following general formula (1), and having a 50% cumulative volume particle size (D50) of 0.05 μm or more and 0.12 μm or less; The heat-sensitive recording medium has a haze degree of 15 or less, and a change rate X of total light transmittance represented by the following formula (1) is 5.0% or less.

However, in the general formula (1), R ¹ to R ⁵ are each independently 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.
X=(AB)/A×100 Formula (1)
However, in the formula (1), A is the total light transmittance before heating the thermosensitive recording medium at a temperature of 90°C, and B is the total light transmittance after heating the thermosensitive recording medium at a temperature of 90°C for 1 hour. Total light transmittance.

According to the present invention, it is possible to provide a thermosensitive recording medium that has high transparency and can maintain high transparency even when exposed to a high-temperature environment.

(Thermal recording medium)
A thermosensitive recording medium of the present invention is a thermosensitive recording medium comprising a support and a thermosensitive recording layer on the support, wherein the thermosensitive recording layer contains a leuco dye and a developer, The medium has a haze degree of 15 or less, a rate of change X of total light transmittance represented by the following formula (1) of 5.0% or less, and, if necessary, a protective layer, an adhesive layer, and other have layers.
X=(AB)/A×100 Formula (1)
However, in the formula (1), A is the total light transmittance before heating the thermosensitive recording medium at a temperature of 90°C, and B is the total light transmittance after heating the thermosensitive recording medium at a temperature of 90°C for 1 hour. Total light transmittance.

In the prior art, in order to make the thermal recording medium transparent, the leuco dye and developer contained in the thermal recording layer are finely divided into particles of 0.15 μm or more and 0.2 μm or less. Warming by microwave oven (for example, 100 ° C. for 2 to 3 minutes), hot melt gluing (for example, 130 ° C. for several seconds), shrink wrapping (for example, 200 ° C. for several seconds), shrink label processing (for example, 90 ° C. for several 10 Seconds), environment inside a container during shipping (e.g. 60°C for several days), leaving on the dashboard of a car in summer (e.g. 90°C for 1 hour). There is a problem of not being able to maintain sexuality.

The present inventors have extensively studied a thermosensitive recording medium that has high transparency and can maintain high transparency even when exposed to a high-temperature environment. a recording layer, wherein the thermal recording layer contains a leuco dye and a developer, the thermal recording medium has a haze of 15 or less, and is represented by the above formula (1) It has been found that a thermosensitive recording medium having a total light transmittance change rate X of 5.0% or less has high transparency and can sufficiently maintain high transparency even when exposed to a high temperature environment. .

In the present invention, the heat-sensitive recording medium has a haze degree of 15 or less, preferably 10 or less from the viewpoint of high transparency.

The haze degree of the thermosensitive recording medium is a haze degree measured in accordance with ASTM D1003 or ISO 14782, and the haze degree is measured by, for example, a haze meter (device name: HZ-V3, manufactured by Suga Test Co., Ltd.). can be measured using

In the present invention, the change rate of the total light transmittance is represented by the above formula (1). The rate of change of the total light transmittance is 5.0% or less, preferably 3.0% or less, in order to sufficiently maintain high transparency even when exposed to a high-temperature environment.

The total light transmittance is the average value of the transmittance of each wavelength measured in increments of 1 nm in the wavelength range of 300 nm to 830 nm (D65 light source) in the background portion of the thermosensitive recording medium.
The total light transmittance can be measured, for example, using a spectrophotometer (U-4100, manufactured by Hitachi High-Technologies Corporation).

<Thermal recording layer>
The thermosensitive recording layer preferably contains a leuco dye and a developer, and preferably contains a photothermal conversion material and an ultraviolet absorbing material, and further contains other components as necessary.

－Leuco Dye－
The leuco dye is not particularly limited, and can be appropriately selected according to the purpose from those commonly used in thermosensitive recording media. Examples include leuco compounds of dyes such as spiropyran-based and indolinophthalide-based dyes. These may be used individually by 1 type, and may use 2 or more types together.

Examples of the leuco compound include 3,3-bis(p-dimethylaminophenyl)-phthalide, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3 ,3-bis(p-dimethylaminophenyl)-6-diethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)-6-chlorophthalide, 3,3-bis(p-dibutylaminophenyl)phthalide, 3 -cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8 -benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-(Np-tolyl-N-ethylamino)-6-methyl-7-anilinofluorane, 2-{N- (3′-trifluoromethylphenyl)amino}-6-diethylaminofluorane, 2-{3,6-bis(diethylamino)-9-(o-chloroanilino)xantylbenzoic acid lactam}, 3-diethylamino-6-methyl -7-(m-trichloromethylanilino)fluorane, 3-diethylamino-7-(o-chloroanilino)fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-di-n-butylamino- 7-o-chloroanilino)fluorane, 3-N-methyl-N,n-amylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilino Fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-(N,N-diethylamino)-5-methyl-7-(N,N-dibenzylamino)fluorane, benzoyl leuco methylene blue, 6 '-chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-3'-methoxy-benzoindolino-spiropyran, 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-( 2′-Methoxy-5′-chlorophenyl)phthalide, 3-(2′-hydroxy-4′-dimethylaminophenyl)-3-(2′-methoxy-5′-nitrophenyl)phthalide, 3-(2′- Hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl)phthalide, 3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4 '-Chloro-5'-methylphenyl)phthalide, 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl-7-anilinofluorane, 3-N-ethyl-N-(2-ethoxy propyl)amino-6-methyl-7-anilinofluorane, 3-N-methyl-N-isobutyl-6-methyl-7-anilinofluorane, 3-morpholino-7-(N-propyl-trifluoromethyl anilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-(N-benzyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-(di -p-chlorophenyl)methylaminofluorane, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluorane, 3-(N-ethyl-p-toluidino)-7-(α-phenylethylamino ) fluoran, 3-diethylamino-7-(o-methoxycarbonylphenylamino)fluorane, 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3-(N-methyltoluidino)-7-(pn-butylanilino)fluorane, 3-di-n-butylamino-6-methyl-7-anilinofluorane, 3,6-bis(dimethyl Amino)fluorene spiro(9,3′)-6′-dimethylaminophthalide, 3-(N-benzyl-N-cyclohexylamino)-5,6-benzo-7-α-naphthylamino-4′-bromofluoro Olan, 3-diethylamino-6-chloro-7-anilinofluorane, 3-diethylamino-6-methyl-7-mesitidino-4',5'-benzofluorane, 3-N-methyl-N-isopropyl-6 -methyl-7-anilinofluorane, 3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-(2',4'-dimethylani rhino)fluorane, 3-diethylamino-5-chloro-(α-phenylethylamino)fluorane, 3-diethylamino-7-piberidinofluorane, 3-(N-benzyl-N-cyclohexylamino)-5,6- Benzo-7-α-naphthylamino-4′-bromofluorane, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, 3-p-dimethylaminophenyl)-3 -{1,1-bis(p-dimethylaminophenyl)ethylene-2-yl}phthalide, 3-(p-dimethylaminophenyl)-3-{1,1-bis(p-dimethylaminophenyl)ethylene-2 -yl}-6-dimethylaminophthalide, 3-(p-dimethylaminophenyl)-3-(1-p-dimethylaminophenyl-1-phenylethylene-2-yl)phthalide, 3-(p-dimethylamino Phenyl)-3-(1-p-dimethylaminophenyl-1-p-chlorophenylethylene-2-yl)-6-dimethylaminophthalide, 3-(4′-dimethylamino-2′-methoxy)-3- (1″-p-dimethylaminophenyl-1″-p-chlorophenyl-1″,3″-butadien-4″-yl)benzophthalide, 3-(4′-dimethylamino-2′-benzyloxy)-3- (1″-p-dimethylaminophenyl-1″-phenyl-1″,3″-butadien-4″-yl)benzophthalide, 3-dimethylamino-6-dimethylamino-fluorene-9-spiro-3′-( 6′-dimethylamino)phthalide, 3,3-bis(2-(p-dimethylaminophenyl)-2-p-methoxyphenyl)ethenyl)-4,5,6,7-tetrachlorophthalide, 3-bis {1,1-bis(4-pyrrolidinophenyl)ethylene-2-yl}-5,6-dichloro-4,7-dibromophthalide, bis(p-dimethylaminostyryl)-1-naphthalenesulfonylmethane, bis(p -dimethylaminostyryl)-1-p-tolylsulfonylmethane, 2-(phenylamino)-3-methyl-6-[ethyl(p-tolyl)amino]spiro[9H-xanthene-9,1′(3′H )-isobenzofuran]-3′-one, 6-(diethylamino)-2-[3-(trifluoromethyl)anilino]spiro[9H-xanthene-9,3′(1′H)-isobenzofuran]-1 '-on and the like. These may be used individually by 1 type, and may use 2 or more types together.

The 50% cumulative volume particle diameter (D ₅₀ ) of the leuco dye is preferably 0.05 μm or more and 0.5 μm or less, more preferably 0.1 μm or more and 0.3 μm or less.

The 50% cumulative volume particle size (D ₅₀ ) of the leuco dye can be measured using, for example, a laser diffraction/scattering particle size distribution analyzer (device name: LA-920, manufactured by Horiba, Ltd.). can.

The content of the leuco dye is not particularly limited and can be appropriately selected depending on the intended purpose. % or less is more preferable.

- Color developer -
As the color developer, various electron-accepting substances that react with the leuco dye to develop color when heated can be applied, and may be used singly or in combination of two or more. may

The developer is not particularly limited and can be appropriately selected depending on the intended purpose. , 3-cyclohexylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4′-isopropylidenediphenol, 1,1′-inopropylidenebis (2-chlorophenol), 4,4'-isopropylidenebis (2,6-dibromophenol), 4,4'-isopropylidenebis (2,6-dichlorophenol), 4,4'-isopropylidenebis ( 2-methylphenol), 4,4′-isopropylidenebis(2,6-dimethylphenol), 4,4-isopropylidenebis(2-tert-butylphenol), 4,4′-sec-butylidenediphenol, 4 ,4′-cyclohexylidenebisphenol, 4,4′-cyclohexylidenebis(2-methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 3,5-xylenol, thymol, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, novolac-type phenolic resin, 2,2'-thiobis(4,6-dichlorophenol), catechol, resorcinol, hydroquinone, pyrogallol, phlologlycin , phloroglycin carboxylic acid, 4-tert-octylcatechol, 2,2′-methylnbis(4-chlorophenol), 2,2′-methylnbis(4-methyl-6-tert-butylphenol), 2,2,-dihydroxy Diphenyl, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-chlorobenzyl p-hydroxybenzoate, o-chloro p-hydroxybenzoate Benzyl, p-methylbenzyl p-hydroxybenzoate, n-octyl p-hydroxybenzoate, benzoic acid, zinc salicylate, 1-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic acid, 2-hydroxy -6-zinc naphthoate, 4-hydroxydiphenylsulfone, 4-hydroxy-4'-chlorodiphenylsulfone, bis(4-hydroxyphenyl)sulfide, 2-hydroxy-p-toluic acid, 3,5-di-tert- Zinc butylsalicylate, tin 3,5-di-tert-butylsalicylate, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, boric acid, thiourea derivatives, 4-hydroxythio Phenol derivatives, bis(4-hydroxyphenyl)acetic acid, ethyl bis(4-hydroxyphenyl)acetate, n-propyl bis(4-hydroxyphenyl)acetate, m-butyl bis(4-hydroxyphenyl)acetate, bis(4- hydroxyphenyl)phenyl acetate, bis(4-hydroxyphenyl)benzyl acetate, bis(4-hydroxyphenyl)phenethyl acetate, bis(3-methyl-4-hydroxyphenyl)acetic acid, bis(3-methyl-4-hydroxyphenyl) methyl acetate, n-propyl bis(3-methyl-4-hydroxyphenyl)acetate, 1,7-bis(4-hydroxyphenylthio)3,5-dioxaheptane, 1,5-bis(4-hydroxyphenylthio ) 3-oxaheptane, dimethyl 4-hydroxyphthalate, 4-hydroxy-4′-methoxydiphenylsulfone, 4-hydroxy-4′-ethoxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, 4-hydroxy -4'-propoxydiphenylsulfone, 4-hydroxy-4'-butoxydiphenylsulfone, 4-hydroxy-4'-isobutoxydiphenylsulfone, 4-hydroxy-4-butoxydiphenylsulfone, 4-hydroxy-4'-tert- butoxydiphenylsulfone, 4-hydroxy-4'-benzyloxydiphenylsulfone, 4-hydroxy-4'-phenoxydiphenylsulfone, 4-hydroxy-4'-(m-methylbenzyloxy)diphenylsulfone, 4-hydroxy-4' -(p-methylbenzyloxy)diphenylsulfone, 4-hydroxy-4'-(O-methylbenzyloxy)diphenylsulfone, 4-hydroxy-4'-(p-chlorobenzyloxy)diphenylsulfone, 1,1-bis (4-hydroxyphenyl)-1-phenylethane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1,1-tris(4-hydroxyphenyl)ethane, the following general A compound represented by the formula (1) and the like can be mentioned. Among these, compounds represented by the following general formula (1) are preferred from the viewpoint of heat resistance.

A compound represented by the following general formula (1) is disclosed as a color developer (see International Publication No. 2017/111032 pamphlet). However, the pamphlet of International Publication No. 2017/111032 is concerned with high heat resistance of opaque thermosensitive recording media, and the transparency of transparent thermosensitive recording media as in the present invention, and high even when exposed to high temperature environments Maintaining transparency is not a challenge.

ただし、前記一般式（１）中、Ｒ^１～Ｒ^５はそれぞれ独立に水素原子、ハロゲン原子、ニトロ基、アミノ基、アルキル基、アルコキシ基、アリールオキシ基、アルキルカルボニルオキシ基、アリールカルボニルオキシ基、アルキルカルボニルアミノ基、アリールカルボニルアミノ基、アルキルスルホニルアミノ基、アリールスルホニルアミノ基、モノアルキルアミノ基、ジアルキルアミノ基、及びアリールアミノ基のいずれかを表す。

However, in the general formula (1), R ¹ to R ⁵ are each independently 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.

Examples of the halogen atom include fluorine atom, chlorine atom, and bromine atom. Among these, a fluorine atom and a chlorine atom are preferable.

Examples of the alkyl group include linear, branched or cyclic alkyl groups. Among these, straight-chain or branched-chain alkyl groups are preferred, and straight-chain alkyl groups are more preferred. The number of carbon atoms in the alkyl group is preferably 1-12, more preferably 1-8, still more preferably 1-6, and particularly preferably 1-4.
Examples of the alkyl group include straight groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, n-undecyl and n-dodecyl. Chain alkyl group (preferably straight chain alkyl group having 1 to 6 carbon atoms); branched chain alkyl group (preferably C 3 to 10 branched chain alkyl groups); cyclic alkyl groups (preferably cyclic alkyl groups having 3 to 7 carbon atoms) such as cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.

Examples of the alkoxy group include linear, branched or cyclic alkoxy groups. Among these, straight-chain or branched-chain alkoxy groups are preferred, and straight-chain alkoxy groups are more preferred. The number of carbon atoms in the alkoxy group is preferably 1-12, more preferably 2-8, still more preferably 2-6, and particularly preferably 2-4.
Examples of the alkoxy group include linear alkoxy groups such as methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, n-hexyloxy, n-heptoxy, n-octyloxy, n-nonyloxy and n-decyloxy. (preferably a straight-chain alkoxy group having 2 to 6 carbon atoms); branched-chain alkoxy groups (preferably branched-chain alkoxy groups having 3 to 10 carbon atoms) such as octyloxy, 2-ethylhexyloxy, isononyloxy, and isodecyloxy; cyclic alkoxy groups such as cyclopropoxy, cyclobutoxy, cyclopentoxy, cyclohexyloxy, and cycloheptoxy; group (preferably a cyclic alkoxy group having 3 to 7 carbon atoms).

The aryloxy group preferably has 6 to 12 carbon atoms. Examples of the aryloxy group include phenoxy, naphthyloxy, biphenyloxy and the like.

Examples of the alkylcarbonyloxy group include linear, branched or cyclic alkylcarbonyloxy groups. Among these, straight-chain or branched-chain alkylcarbonyloxy groups are preferred, and straight-chain alkylcarbonyloxy groups are more preferred. The number of carbon atoms in the alkylcarbonyloxy group is preferably 1-10.
Examples of the alkylcarbonyloxy group include methylcarbonyloxy, ethylcarbonyloxy, n-propylcarbonyloxy, n-butylcarbonyloxy, n-pentylcarbonyloxy, n-hexylcarbonyloxy, n-heptylcarbonyloxy, n- octylcarbonyloxy, n-nonylcarbonyloxy, n-decylcarbonyloxy and other straight-chain alkylcarbonyloxy groups (preferably carbonyloxy groups having a straight-chain alkyl group having 1 to 6 carbon atoms); isopropylcarbonyloxy, isobutylcarbonyl oxy, sec-butylcarbonyloxy, t-butylcarbonyloxy, isoamylcarbonyloxy, t-amylcarbonyloxy, isohexylcarbonyloxy, t-hexylcarbonyloxy, isoheptylcarbonyloxy, t-heptylcarbonyloxy, isooctylcarbonyloxy , t-octylcarbonyloxy, 2-ethylhexylcarbonyloxy, isononylcarbonyloxy, branched-chain alkylcarbonyloxy groups such as isodecylcarbonyloxy (preferably a carbonyloxy group having a branched-chain alkyl group having 3 to 10 carbon atoms) cyclic alkylcarbonyloxy groups such as cyclopropylcarbonyloxy, cyclobutylcarbonyloxy, cyclopentylcarbonyloxy, cyclohexylcarbonyloxy, cycloheptylcarbonyloxy (preferably a carbonyloxy group having a cyclic alkyl group having 3 to 7 carbon atoms), etc. is mentioned.

The arylcarbonyloxy group preferably has 6 to 12 carbon atoms. Examples of the arylcarbonyloxy group include phenylcarbonyloxy, naphthylcarbonyloxy, biphenylcarbonyloxy and the like.

Examples of the alkylcarbonylamino group include linear, branched or cyclic alkylcarbonylamino groups. Among these, straight-chain or branched-chain alkylcarbonylamino groups are preferred, and straight-chain alkylcarbonylamino groups are more preferred. The number of carbon atoms in the alkylcarbonylamino group is preferably 1-10.
Examples of the alkylcarbonylamino group include methylcarbonylamino, ethylcarbonylamino, n-propylcarbonylamino, n-butylcarbonylamino, n-pentylcarbonylamino, n-hexylcarbonylamino, n-heptylcarbonylamino, n- straight-chain alkylcarbonylamino group (preferably a carbonylamino group having a straight-chain alkyl group having 1 to 6 carbon atoms) such as octylcarbonylamino, n-nonylcarbonylamino, n-decylcarbonylamino; isopropylcarbonylamino, isobutylcarbonyl amino, sec-butylcarbonylamino, t-butylcarbonylamino, isoamylcarbonylamino, t-amylcarbonylamino, isohexylcarbonylamino, t-hexylcarbonylamino, isoheptylcarbonylamino, t-heptylcarbonylamino, isooctylcarbonylamino , t-octylcarbonylamino, 2-ethylhexylcarbonylamino, isononylcarbonylamino, isodecylcarbonylamino (preferably a carbonylamino group having a branched alkyl group having 3 to 10 carbon atoms) a cyclic alkylcarbonylamino group (preferably a carbonylamino group having a cyclic alkyl group having 3 to 7 carbon atoms) such as cyclopropylcarbonylamino, cyclobutylcarbonylamino, cyclopentylcarbonylamino, cyclohexylcarbonylamino, cycloheptylcarbonylamino, etc.; is mentioned.

The arylcarbonylamino group preferably has 6 to 12 carbon atoms. Examples of the arylcarbonylamino group include phenylcarbonylamino, naphthylcarbonylamino, biphenylcarbonylamino and the like.

Examples of the alkylsulfonylamino group include linear, branched or cyclic alkylsulfonylamino groups. Among these, a linear or branched alkylsulfonylamino group is preferable, and a linear alkylsulfonylamino group is more preferable. The number of carbon atoms in the alkylsulfonylamino group is preferably 1-10. Examples of the alkylsulfonylamino group include methylsulfonylamino, ethylsulfonylamino, n-propylsulfonylamino, n-butylsulfonylamino, n-pentylsulfonylamino, n-hexylsulfonylamino, n-heptylsulfonylamino, n- straight-chain alkylsulfonylamino groups (preferably sulfonylamino groups having straight-chain alkyl having 1 to 6 carbon atoms) such as octylsulfonylamino, n-nonylsulfonylamino, n-decylsulfonylamino; isopropylsulfonylamino, isobutylsulfonylamino , sec-butylsulfonylamino, t-butylsulfonylamino, isoamylsulfonylamino, t-amylsulfonylamino, isohexylsulfonylamino, t-hexylsulfonylamino, isoheptylsulfonylamino, t-heptylsulfonylamino, isooctylsulfonylamino, t-octylsulfonylamino, 2-ethylhexylsulfonylamino, isononylsulfonylamino, isodecylsulfonylamino and other branched alkylsulfonylamino groups (preferably sulfonylamino groups having a branched alkyl group having 3 to 10 carbon atoms); Cyclic alkylsulfonylamino groups (preferably sulfonylamino groups having a cyclic alkyl group having 3 to 7 carbon atoms) such as cyclopropylsulfonylamino, cyclobutylsulfonylamino, cyclopentylsulfonylamino, cyclohexylsulfonylamino, cycloheptylsulfonylamino, etc. mentioned.

The arylsulfonylamino group preferably has 6 to 12 carbon atoms. Examples of the arylsulfonylamino group include phenylsulfonylamino, toluenesulfonylamino, naphthylsulfonylamino, biphenylsulfonylamino and the like.

Examples of the monoalkylamino group include linear, branched or cyclic monoalkylamino groups. Among these, linear or branched monoalkylamino groups are preferred, and linear monoalkylamino groups are more preferred. The number of carbon atoms in the monoalkylamino group is preferably 1-10.
Examples of the monoalkylamino group include methylamino, ethylamino, n-propylamino, n-butylamino, n-pentylamino, n-hexylamino, n-heptylamino, n-octylamino, n-nonylamino, straight-chain monoalkylamino groups (preferably straight-chain monoalkylamino groups having 1 to 6 carbon atoms) such as n-decylamino; isopropylamino, isobutylamino, sec-butylamino, t-butylamino, isoamylamino, t- branched monoalkylamino groups such as amylamino, isohexylamino, t-hexylamino, isoheptylamino, t-heptylamino, isooctylamino, t-octylamino, 2-ethylhexylamino, isononylamino, isodecylamino; (preferably a branched monoalkylamino group having 3 to 10 carbon atoms); a cyclic monoalkylamino group (preferably a C3 to 7 cyclic monoalkylamino group).

Examples of the dialkylamino group include linear, branched or cyclic dialkylamino groups. Among these, linear or branched dialkylamino groups are preferred, and linear dialkylamino groups are more preferred. The dialkylamino group preferably has 1 to 10 carbon atoms.
Examples of the dialkylamino group include dimethylamino, diethylamino, di-n-propylamino, di-n-butylamino, di-n-pentylamino, di-n-hexylamino, di-n-heptylamino, di -n-octylamino, di-n-nonylamino, di-n-decylamino and other straight-chain dialkylamino groups (preferably dialkylamino groups having two straight-chain alkyl groups having 1 to 6 carbon atoms); diisopropylamino, Diisobutylamino, di-sec-butylamino, di-t-butylamino, diisoamylamino, di-t-amylamino, diisohexylamino, di-t-hexylamino, diisoheptylamino, di-t-heptylamino , diisooctylamino, di-t-octylamino, di-(2-ethylhexyl)amino, diisononylamino, diisodecylamino, and other branched dialkylamino groups (preferably two branched-chain alkyl groups having 3 to 10 carbon atoms). cyclic dialkylamino groups (preferably two cyclic alkyl groups having 3 to 7 carbon atoms) such as dicyclopropylamino, dicyclobutylamino, dicyclopentylamino, dicyclohexylamino, dicycloheptylamino a dialkylamino group having a dialkylamino group).

Examples of the arylamino group include a monoarylamino group and a diarylamino group. Among these, a monoarylamino group is preferred.
The number of carbon atoms in the monoarylamino group is preferably 6-12. Examples of the monoarylamino group include phenylamino (anilino), naphthylamino, biphenylamino and the like.
The diarylamino group preferably has 6 to 12 carbon atoms. Examples of the diarylamino group include diphenylamino, dinaphthylamino, di(biphenyl)amino and the like.

R ¹ to R ⁵ in the general formula (1) are preferably an alkyl group or a hydrogen atom, more preferably a linear alkyl group having 1 to 8 carbon atoms or a hydrogen atom, and a linear alkyl group having 1 to 4 carbon atoms. A group or a hydrogen atom is more preferred, and a methyl group or a hydrogen atom is particularly preferred.
R ¹ , R ² , R ⁴ and R ⁵ in the general formula (1) are preferably hydrogen atoms. R ³ is 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 alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group; , a monoalkylamino group, a dialkylamino group, or an arylamino group. Among these, a hydrogen atom or an alkyl group is preferable, a hydrogen atom or an alkyl group having 1 to 8 carbon atoms (preferably a linear alkyl group) is more preferable, a hydrogen atom or an alkyl group having 1 to 4 carbon atoms (preferably is a linear alkyl group) is more preferred, and a methyl group is particularly preferred.

The compounds represented by the general formula (1) include, but are not limited to, compounds listed in Tables A1 to A9.

As the compound represented by the general formula (1), among the compounds of compound numbers 1 to 45, the compounds of compound numbers 1 to 3 are preferable from the viewpoint of transparency and heat resistance.

The compound represented by the general formula (1) can be synthesized by the method described in paragraphs [0028] to [0063] of WO2017/111032 pamphlet.

The 50% cumulative volume particle size (D ₅₀ ) of the developer is preferably 0.05 μm or more and 0.5 μm or less, more preferably 0.1 μm or more and 0.3 μm or less.

The 50% cumulative volume particle size (D ₅₀ ) of the developer is measured using, for example, a laser diffraction/scattering particle size distribution analyzer (device name: LA-920, manufactured by HORIBA, Ltd.). can be done.

The content of the developer is not particularly limited and can be appropriately selected according to the purpose. % by mass or less is more preferable.

The content ratio of the leuco dye and the color developer is not particularly limited and can be appropriately selected according to the purpose. The colorant is preferably 1 part by mass or more and 4 parts by mass or less.

- Photothermal conversion materials -
The photothermal conversion material means a material that absorbs laser light and converts it into heat, and can be roughly divided into inorganic materials and organic materials.

Examples of the inorganic material include particles of carbon black, metal borides, and metal oxides such as Ge, Bi, In, Te, Se, and Cr. Among these, the above metal borides and metal oxides are preferable because they absorb light in the near-infrared wavelength region more and absorb light in the visible wavelength region less.
Examples of the metal borides and metal oxides include hexaborides, tungsten oxide compounds, antimony tin oxide (ATO), indium tin oxide (ITO), and zinc antimonate.
Examples of the hexaboride include LaB ₆ , CeB _{6 ,} PrB ₆ , NdB 6 , GdB 6 , TbB ₆ , DyB ₆ , HoB ₆ , YB ₆ , SmB ₆ , EuB ₆ , ErB ₆ , TmB ₆ , _{YbB 6} , LuB ₆ , SrB ₆ , CaB ₆ , (La, Ce)B ₆ and the like.

Examples of the tungsten oxide compound include fine particles of tungsten oxide represented by the general formula: WyOz (where W is tungsten, O is oxygen, and 2.2≦z/y≦2.999), or the general formula: MxWyOz (where M is H, He, alkali metal, alkaline earth metal, rare earth element, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, one or more elements selected from Be, Hf, Os, Bi, and I, W is tungsten, O is oxygen, 0.001 ≤ x/y ≤ 1, 2.2 ≤ z/y ≤ 3.0 There are composite tungsten oxide particles represented by (International Publication No. 2005/037932 pamphlet, Japanese Patent Application Laid-Open No. 2005-187323). Among these, cesium-containing tungsten oxide is preferable because it has high absorption in the near-infrared region and low absorption in the visible region.
Among the antimony tin oxide (ATO), the indium tin oxide (ITO), and the zinc antimonate, ITO is preferable because it has high absorption in the near-infrared region and low absorption in the visible region.

As the organic material, various dyes can be appropriately used depending on the light wavelength to be absorbed. External absorption dyes are used, and examples thereof include cyanine dyes, quinone dyes, quinoline derivatives of indonaphthol, phenylenediamine nickel complexes, and phthalocyanine dyes. These may be used individually by 1 type, and may use 2 or more types together.
The photothermal conversion material may be contained in the thermosensitive recording layer or may be contained in a layer other than the thermosensitive recording layer. When it is contained in a layer other than the heat-sensitive recording layer, it is preferable to provide a layer containing the photothermal conversion material adjacent to the heat-sensitive recording layer.
The content of the photothermal conversion material is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.3% by mass or more and 5% by mass or less, relative to the heat-sensitive recording layer.

-Ultraviolet absorption material-
The ultraviolet absorbing material is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include salicylic acid-based ultraviolet absorbents, benzophenone-based ultraviolet absorbents, and benzotriazole-based ultraviolet absorbents.

Examples of the ultraviolet absorbing material include phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxy Benzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfo Benzophenone, bis(2-methoxy-4-hydroxy-5-benzoylphenyl)methane, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-butyl phenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl) Chlorobenzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert- amylphenyl)benzotriazole, 2-{2′-hydroxy-3′-(3″,4″,5″,6″-tetrahydrophthalimidomethyl)-5′-methylphenyl}benzotriazole, 2,2′-methylenebis {4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol}, 2-(2'-hydroxy-5'-methacryloxyphenyl)-2H -benzotriazole, 2-(3,5-di-t-amyl-2-hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole, 2-(5-methyl- 2-hydroxyphenyl)benzotriazole and the like. These may be used individually by 1 type, and may use 2 or more types together.

-Other ingredients-
The other components are not particularly limited and can be appropriately selected depending on the intended purpose. filler and the like.

--binder resin--
The binder resin is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include thermoplastic resins, thermosetting resins, and photocurable resins. These resins may be water-soluble resins, water-dispersible resins, solvent-soluble resins, or the like, regardless of their properties.
Examples of the binder resin include acrylic resins, polyvinyl alcohol resins, starch or derivatives thereof; cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, and ethyl cellulose; sodium polyacrylate, polyvinylpyrrolidone, and acrylamide-acrylic acid esters. copolymer, styrene-acrylic copolymer, acrylamide-acrylic ester-methacrylic acid terpolymer, styrene-maleic anhydride copolymer alkali salt, isobutylene-maleic anhydride copolymer alkali salt, polyacrylamide, Water-soluble polymers such as sodium alginate, gelatin, and casein; emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, ethylene-vinyl acetate copolymer, etc. and latexes of styrene-butadiene copolymers, styrene-butadiene-acrylic copolymers, and the like. These may be used individually by 1 type, and may use 2 or more types together.
Among these, acrylic resins and styrene-acrylic copolymers are preferred from the viewpoint of transparency.

--Heat fusible substance--
Examples of the heat-fusible substance include fatty acids such as stearic acid and behenic acid; fatty acid amides such as stearic acid amide and palmitic acid amide; zinc stearate, aluminum stearate, calcium stearate, zinc palmitate, behenate Fatty acid metal salts such as zinc acid; p-benzylbiphenyl, terphenyl, triphenylmethane, benzyl p-benzyloxybenzoate, β-benzyloxynaphthalene, phenyl naphthoate, phenyl 1-hydroxy-2-naphthoate, methyl 1-hydroxy-2-naphthoate, diphenyl carbonate, glycol carbonate, dibenzyl terephthalate, dimethyl terephthalate, 1,4-dimethoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dibenzyloxynaphthalene, 1, 2-diphenoxyethane, 1,2-bis(3-methylphenoxy)ethane, 1,2-bis(4-methylphenoxy)ethane, 1,4-diphenoxy-2-butene, 1,2-bis(4- methoxyphenylthio)ethane, dibenzoylmethane, 1,4-diphenylthiobutane, 1,4-diphenylthio-2-butene, 1,3-bis(2-vinyloxyethoxy)benzene, 1,4-bis(2 -vinyloxyethoxy)benzene, p-(2-vinyloxyethoxy)biphenyl, p-aryloxybiphenyl, p-propargyloxybiphenyl, dibenzoyloxymethane, dibenzoyloxypropane, dibenzyldisulfide, 1,1-diphenyl ethanol, 1,1-diphenylpropanol, p-benzyloxybenzyl alcohol, 1,3-phenoxy-2-propanol, N-octadecylcarbamoyl-p-methoxycarbonylbenzene, N-octadecylcarbamoylbenzene, 1,2-bis(4 -methoxyphenoxy)propane, 1,5-bis(4-methoxyphenoxy)-3-oxapentane, dibenzyl oxalate, bis(4-methylbenzyl) oxalate, bis(4-chlorobenzyl) oxalate and the like. . These may be used individually by 1 type, and may use 2 or more types together.

--Auxiliary Additives--
The auxiliary additive is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include hindered phenol compounds and hindered amine compounds. These may be used individually by 1 type, and may use 2 or more types together.

Examples of the auxiliary additives include 2,2′-methylenebis(4-ethyl-6-tertiarybutylphenol), 4,4′-butylidenebis(6-tertiarybutyl-2-methylphenol), 1,1, 3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 4,4'-thiobis (6-tert-butyl-2-methylphenol), tetrabromobisphenol A, tetrabromobisphenol S, 4,4' thiobis (2-methylphenol), 4,4'-thiobis (2-chlorophenol), tetrakis ( 1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, tetrakis(1,2,2,6,6-tetramethyl-4-piperidyl)- 1,2,3,4-butane tetracarboxylate and the like. These may be used individually by 1 type, and may use 2 or more types together.

--Surfactant--
The surfactant is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include anionic surfactants, nonionic surfactants, amphoteric surfactants, and fluorine-based surfactants. be done.

Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, laurate, polyoxyethylene alkyl ether sulfate, and the like. These may be used individually by 1 type, and may use 2 or more types together.

Examples of the nonionic surfactants include acetylene glycol-based surfactants, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, and the like. These may be used individually by 1 type, and may use 2 or more types together.

Examples of the acetylene glycol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3 ,5-dimethyl-1-hexyne-3-diol, 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol and the like. These may be used individually by 1 type, and may use 2 or more types together.

--Lubricant--
Examples of the lubricant include higher fatty acids or metal salts thereof, higher fatty acid amides, higher fatty acid esters, animal waxes, vegetable waxes, mineral waxes, and petroleum waxes. These may be used individually by 1 type, and may use 2 or more types together.

--filler--
Examples of fillers include calcium carbonate, silica, zinc oxide, titanium oxide, zirconium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, kaolin, talc, surface-treated calcium, and surface-treated silica. organic fine powders such as urea-formalin resin, styrene-methacrylic acid copolymer, polystyrene resin, and vinylidene chloride resin; These may be used individually by 1 type, and may use 2 or more types together.

The content of the filler is not particularly limited and can be appropriately selected according to the purpose. The following are more preferred.

The method for forming the thermosensitive recording layer is not particularly limited and can be appropriately selected according to the purpose. After pulverizing and dispersing with the disperser of No. 2, the mixture is further mixed with the above-mentioned other components as necessary to prepare a coating liquid for a heat-sensitive recording layer. Thereafter, the heat-sensitive recording layer coating liquid is applied onto the support and dried.

The coating method is not particularly limited and can be appropriately selected depending on the purpose. Examples include blade coating, gravure coating, gravure offset coating, bar coating, roll coating, knife coating, air knife. Coating method, comma coating method, U comma coating method, AKKU coating method, smoothing coating method, micro gravure coating method, reverse roll coating method, 4 or 5 roll coating method, dip coating method, curtain coating method, slide coating method , a die coating method, and the like.

The adhesion amount of ^the thermosensitive recording layer after drying is not particularly limited and can be appropriately selected depending on the purpose ^. /m ² or more and 10.0 g/m ² or less is more preferable, and 2.0 g/m ² or more and 4.0 g/m ² or less is particularly preferable.

<Support>
The support preferably has high transparency.
In the present invention, the transparency is represented by a haze degree measured according to ASTM D1003 or ISO 14782, and the haze degree is preferably 15 or less, more preferably 10 or less.

The method for measuring the haze degree is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include a haze meter (device name: HZ-V3, manufactured by Suga Test Co., Ltd.).

The support is not particularly limited, and the material, shape, structure, average thickness, etc. can be appropriately selected according to the purpose.

Examples of materials for the support include polyester resins such as polyethylene terephthalate (PET), polycarbonate, polystyrene (PS), polymethyl methacrylate (PMMA), polyethylene (PE), and polypropylene (PP). These may be used individually by 1 type, and may use 2 or more types together. Among these, polyethylene terephthalate (PET) and polypropylene (PP) are preferred from the viewpoint of flexibility, and polyethylene terephthalate (PET) is more preferred from the viewpoint of excellent heat resistance.

An inorganic material, an organic compound, or the like may be further added to the support from the viewpoint of improving heat resistance, mechanical strength, and the like.

The inorganic material is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include glass, quartz, and inorganic single crystals. These may be used individually by 1 type, and may use 2 or more types together.

The organic compound is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include benzotriazole-based compounds, triazine-based compounds, benzophenone-based compounds, hindered amine-based compounds, and the like. These may be used individually by 1 type, and may use 2 or more types together.

The shape of the support is not particularly limited and can be appropriately selected depending on the intended purpose.

The structure of the support is not particularly limited and can be appropriately selected depending on the intended purpose.

For the purpose of improving the adhesiveness of the thermosensitive recording layer, the support is subjected to surface modification such as corona discharge treatment, oxidation reaction treatment (chromic acid, etc.), etching treatment, easy adhesion treatment, antistatic treatment, and the like. preferred to ask.

The average thickness of the support is not particularly limited and can be appropriately selected depending on the intended purpose.

- Protective layer -
The protective layer is a layer provided on the heat-sensitive recording layer on the side not having the support in the heat-sensitive recording medium, and preferably contains a binder resin and a cross-linking agent. contains other ingredients.

--Binder resin--
The binder resin is not particularly limited and can be appropriately selected depending on the purpose, but water-soluble resins are particularly preferable.
Examples of the water-soluble resin include polyvinyl alcohol, modified polyvinyl alcohol, starch or derivatives thereof, cellulose derivatives such as methoxycellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose and ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, and acrylamide-acrylic acid. Ester copolymer, acrylamide-acrylate-methacrylic acid terpolymer, alkali salt of styrene-maleic anhydride copolymer, alkali salt of isobutylene-maleic anhydride copolymer, polyacrylamide, modified polyacrylamide , methyl vinyl ether-maleic anhydride copolymer, carboxy-modified polyethylene, polyvinyl alcohol-acrylamide block copolymer, melamine-formaldehyde resin, urea-formaldehyde resin, sodium alginate, gelatin, casein and the like. These may be used individually by 1 type, and may use 2 or more types together. Among these, modified polyvinyl alcohol is preferred.
Examples of the modified polyvinyl alcohol include carboxylic acid-modified polyvinyl alcohol such as diacetone-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, itaconic acid-modified polyvinyl alcohol, and maleic acid-modified polyvinyl alcohol.

--crosslinking agent--
The cross-linking agent is not particularly limited as long as it can reduce the solubility of the water-soluble resin in water by reacting with the water-soluble resin, and can be appropriately selected according to the purpose. Examples include glyoxal derivatives, methylol derivatives, epichlorohydrin, polyamide epichlorohydrin, epoxy compounds, aziridine compounds, hydrazine, hydrazide derivatives, oxazoline derivatives, and carbodiimide derivatives. These may be used individually by 1 type, and may use 2 or more types together. Among these, polyamide epichlorohydrin is preferable because of its high safety in handling and short curing time required for water resistance.
The content of the polyamide epichlorohydrin is not particularly limited and can be appropriately selected according to the purpose. 50 parts by mass or less is more preferable.

The protective layer is not particularly limited and can be formed by a generally known method.
The average thickness of the protective layer is not particularly limited and can be appropriately selected depending on the intended purpose.

-adhesive layer-
In the present invention, it is preferable to provide an adhesive layer between the heat-sensitive recording layer and the support in order to improve the adhesion between the support and the heat-sensitive recording layer.
The adhesive layer contains the binder resin as in the thermosensitive recording layer, and may further contain the ultraviolet absorbing material, the photothermal conversion material, and the like.

-adhesive layer-
When the thermosensitive recording medium is used as a label, an adhesive layer may be provided on either side of the thermosensitive recording medium.

The material of the adhesive layer is not particularly limited and can be appropriately selected according to the purpose. Coalescence, ethylene-vinyl acetate copolymer, acrylic resin, polyvinyl ether resin, vinyl chloride-vinyl acetate copolymer, polystyrene resin, polyester resin, polyurethane resin, polyamide resin, chlorinated polyolefin resin , polyvinyl butyral-based resins, acrylic acid ester-based copolymers, methacrylic acid ester-based copolymers, natural rubber, cyanoacrylate-based resins, silicone-based resins, and the like. These may be used individually by 1 type, and may use 2 or more types together. These materials may be crosslinked with a crosslinking agent. Also, the material of the adhesive layer may be a hot-melt type.

A method for forming the adhesive layer is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include ordinary coating methods and lamination methods.
The average thickness of the adhesive layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.1 μm or more and 20 μm or less.

The shape of the thermosensitive recording medium is not particularly limited and can be appropriately selected depending on the intended purpose.

<Application>
The use of the thermosensitive recording medium is not particularly limited, and can be appropriately selected according to the purpose. Labels, perishables, boxed lunches, obis wrapped around side dishes, etc. can be mentioned. By using it as the above aspect, the visibility of the contents is improved, and the consumer can select the product while confirming the contents. Other aspects include, for example, tickets, tags, and cards. More specifically, for example, in the field of issuing tickets such as ticket vending machines, receipts, receipts; package tags, pill cases, pill bottles, etc. in the aircraft industry; in the field of copying books, documents, etc., facsimile output paper, etc. .

A method for recording information on the thermosensitive recording medium of the present invention is not particularly limited and can be appropriately selected according to the purpose. For example, a thermal head printer, a _CO2 laser, a semiconductor laser, etc. can be used. Since the thermosensitive recording medium of the present invention uses a pigment other than a silicone resin pigment, it is superior in printing properties and writability to a thermosensitive recording medium using a silicone resin pigment. It can be suitably used for printing such as type.

(Thermal recording liquid)
The thermosensitive recording liquid of the invention is used for forming the thermosensitive recording medium of the invention.

"Used for forming the thermosensitive recording medium of the present invention" means being used for forming the thermosensitive recording layer of the thermosensitive recording medium of the present invention.
The thermal recording liquid of the present invention contains a leuco dye and a developer, and if necessary, other components.

(Goods)
The article of the present invention has the thermosensitive recording medium of the present invention.

Having the thermosensitive recording medium of the present invention means a state in which the thermosensitive recording medium of the present invention is attached, attached, or the like.

The article of the present invention is not particularly limited as long as it has the thermosensitive recording medium of the present invention, and can be appropriately selected according to the purpose. packaging materials, packaging materials, packaging products packed with wrapping paper, and the like.

Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Example 1)
<Production of thermal recording medium>
-Preparation of dye dispersion-
2-anilino-3-methyl-6-butylaminofluorane 30 parts by weight, 36% by weight carboxyl group-containing acrylic resin aqueous solution (trade name: HPD-196, manufactured by BASF) 16 parts by weight, and ion-exchanged water 54 parts by weight was added so that the 50% cumulative volume particle size (D ₅₀ ) measured with a laser diffraction/scattering particle size distribution analyzer (device name: LA-920, manufactured by HORIBA, Ltd.) was 0.116 μm. Dispersed with a sand mill to obtain a dye dispersion.

-Preparation of color developer dispersion-
30 parts by mass of the compound No. 1 below, 36 parts by mass of a 36% by mass carboxyl group-containing acrylic resin aqueous solution (trade name: HPD-196, manufactured by BASF), and 54 parts by mass of ion-exchanged water were added, and laser diffraction/scattering was added. The color developer is dispersed by a sand mill so that the 50% cumulative volume particle size (D ₅₀ ) measured with a type particle size distribution measuring device (device name: LA-920, manufactured by HORIBA, Ltd.) is 0.12 μm. A dispersion was obtained.

[Compound No. 1]

-Preparation of coating solution for thermosensitive recording layer-
Next, 66.7 parts by mass of the obtained dye dispersion, 33.3 parts by mass of the developer dispersion, acrylic emulsion (trade name: EK-301, solid content: 42%, manufactured by Saiden Chemical Co., Ltd.)10. 4 parts by mass and 29.6 parts by mass of deionized water were mixed and stirred to obtain a coating liquid for a heat-sensitive recording layer.

Next, on one side of a polyethylene terephthalate film (trade name: E5100, average thickness: 50 μm, manufactured by Toyobo Co., Ltd., haze degree: 4.5), the coating liquid for the thermosensitive recording layer was applied in an amount of 3.36 g after drying. The thermal recording medium 1 was prepared by coating with a bar coater and drying so as to have a thickness of 1/m ² .

(Example 2)
A color developer dispersion was prepared in the same manner as in Example 1, except that in preparing the color developer dispersion of Example 1, the compound of compound number 1 was changed to the compound of compound number 2 below. A thermosensitive recording medium 2 was prepared in the same manner as in Example 1, except that this developer dispersion was used to form the thermosensitive recording layer.

[Compound No. 2]

(Example 3)
A color developer dispersion was prepared in the same manner as in Example 1, except that in preparing the color developer dispersion of Example 1, the compound of compound number 1 was changed to the compound of compound number 3 below. A thermosensitive recording medium 3 was prepared in the same manner as in Example 1, except that this color developer dispersion was used to form the thermosensitive recording layer.

[Compound No. 3]

(Example 4)
In the preparation of the thermosensitive recording layer coating liquid of Example 1, except that 66.7 parts by mass of the dye dispersion was changed to 20 parts by mass and 33.3 parts by mass of the developer dispersion was changed to 80 parts by mass. A heat-sensitive recording layer coating solution was prepared in the same manner as in 1. A thermosensitive recording medium 4 was prepared in the same manner as in Example 1, except that this thermosensitive recording layer coating liquid was used to form the thermosensitive recording layer.

(Example 5)
In the preparation of the thermosensitive recording layer coating liquid of Example 1, except that 66.7 parts by mass of the dye dispersion was changed to 50 parts by mass and 33.3 parts by mass of the developer dispersion was changed to 50 parts by mass. A heat-sensitive recording layer coating solution was prepared in the same manner as in 1. A thermosensitive recording medium 5 was prepared in the same manner as in Example 1, except that this thermosensitive recording layer coating liquid was used to form the thermosensitive recording layer.

(Example 6)
Except for changing the 66.7 parts by weight of the dye dispersion to 33.3 parts by weight and changing the 33.3 parts by weight of the developer dispersion to 66.7 parts by weight in the preparation of the coating liquid for the thermosensitive recording layer of Example 1. prepared a coating solution for a thermosensitive recording layer in the same manner as in Example 1. A thermosensitive recording medium 6 was prepared in the same manner as in Example 1, except that this thermosensitive recording layer coating liquid was used to form the thermosensitive recording layer.

(Example 7)
In the preparation of the thermosensitive recording layer coating liquid of Example 1, except that 66.7 parts by mass of the dye dispersion was changed to 25 parts by mass and 33.3 parts by mass of the developer dispersion was changed to 75 parts by mass. A heat-sensitive recording layer coating solution was prepared in the same manner as in 1. A thermosensitive recording medium 7 was produced in the same manner as in Example 1, except that this thermosensitive recording layer coating liquid was used to form the thermosensitive recording layer.

(Example 8)
A thermosensitive recording medium 8 was prepared in the same manner as in Example 7, except that the following thermosensitive recording layer coating solution was used to form the thermosensitive recording layer.
<Coating liquid for thermosensitive recording layer>
Dye dispersion liquid 25 parts by weight, developer dispersion liquid 75 parts by weight, acrylic emulsion (trade name: EK-301, solid content 42%, manufactured by Saiden Chemical Co., Ltd.) 10.5 parts by weight, cesium tungsten oxide as a light-to-heat conversion material 6 parts by mass of dispersion (trade name: YMW-D20, solid content 28.5%, manufactured by Sumitomo Metal Mining Co., Ltd.) and 23.5 parts by mass of ion-exchanged water were mixed and stirred to prepare a coating liquid for heat-sensitive recording layer. bottom.

(Example 9)
In Example 7, the protective layer was formed by applying the following protective layer coating liquid onto the thermosensitive recording layer using a bar coater so that the coating amount after drying was 2.0 g/m ² . A thermosensitive recording medium 9 was produced in the same manner as in Example 7.
<Preparation of protective layer coating solution>
Acrylic emulsion (trade name: B-1000, solid content 20%, manufactured by Mitsui Chemicals, Inc.) 37.5 parts by mass, oxazoline group-containing polymer emulsion (trade name: WS-700, solid content 25%, manufactured by Nippon Shokubai Co., Ltd. ) and 37.5 parts by mass of deionized water were mixed and stirred to obtain a protective layer coating liquid.

(Example 10)
In Example 7, the following adhesive layer coating liquid was applied onto a support (polyethylene terephthalate film) using a bar coater so that the adhesion amount after drying was 1 g/m ² . A thermosensitive recording medium 10 was produced in the same manner as in Example 7, except that the same thermosensitive recording layer as in Example 7 was formed in .
<Preparation of adhesive layer coating liquid>
50 parts by mass of an acrylic polyol emulsion (trade name: Orester Q155, solid content 50%, manufactured by Mitsui Chemicals, Inc.) and 50 parts by mass of ethyl acetate were mixed to obtain an adhesive layer coating liquid.

(Example 11)
A thermosensitive recording medium 11 was prepared in the same manner as in Example 7, except that the following thermosensitive recording layer coating solution was used to form the thermosensitive recording layer.
<Coating liquid for thermosensitive recording layer>
Dye dispersion liquid 25 parts by weight, developer dispersion liquid 75 parts by weight, acrylic emulsion (trade name: EK-301, solid content 42%, manufactured by Saiden Chemical Co., Ltd.) 10.4 parts by weight, hydroxyphenyltriazine-based ultraviolet absorbing material (trade name: Tinuvin 477-DW, solid content 40%, manufactured by BASF) 1.8 parts by mass and 27.8 parts by mass of deionized water were mixed and stirred to prepare a coating solution for a thermosensitive recording layer.

(Comparative example 1)
In the preparation of the developer dispersion of Example 7, except that the compound of compound number 1 was changed to 4-hydroxy-4'-isopropoxydiphenylsulfone (trade name: D-8, manufactured by Nippon Soda Co., Ltd.), A developer dispersion was prepared in the same manner as in Example 7. A thermosensitive recording medium 13 was produced in the same manner as in Example 7, except that this developer dispersion was used to form the thermosensitive recording layer.

(Comparative example 2)
In the preparation of the developer dispersion of Example 7, the compound of compound number 1 was polymerized mainly with 4,4'-[oxybis(ethyleneoxy-p-phenylenesulfonyl)]diphenol (trade name: D -90, manufactured by Nippon Soda Co., Ltd.), in the same manner as in Example 7, to prepare a developer dispersion. A thermosensitive recording medium 14 was prepared in the same manner as in Example 7, except that this color developer dispersion was used to form the thermosensitive recording layer.

(Comparative Example 3)
In the preparation of the developer dispersion liquid of Example 7, the compound of compound number 1 was changed to bis-(3-allyl-4-hydroxyphenyl)-sulfone (trade name: TG-SH, manufactured by Nippon Kayaku Co., Ltd.). A developer dispersion was prepared in the same manner as in Example 7, except that A thermosensitive recording medium 15 was prepared in the same manner as in Example 7, except that this color developer dispersion was used to form the thermosensitive recording layer.

(Comparative Example 4)
In the preparation of the developer dispersion of Example 7, the compound of compound number 1 was added to 4,4'-thiobis(3-methyl-6-t-butylphenol (trade name: Sumilizer WX-R, manufactured by Sumitomo Chemical Co., Ltd.). A developer dispersion was prepared in the same manner as in Example 7, except that the heat-sensitive recording layer was formed in the same manner as in Example 7. A recording medium 16 was produced.

(Comparative Example 5)
Example 7 except that the compound of compound number 1 was changed to 2,4'-dihydroxydiphenylsulfone (trade name: BPS-24C, manufactured by Nicca Chemical Co., Ltd.) in the preparation of the developer dispersion of Example 7. A developer dispersion was prepared in the same manner as in 7. A thermosensitive recording medium 17 was prepared in the same manner as in Example 7, except that this color developer dispersion was used to form the thermosensitive recording layer.

(Comparative Example 6)
A developer dispersion was prepared in the same manner as in Example 7, except that the compound of Compound No. 1 was changed to bisphenol A. A thermal recording medium 18 was produced in the same manner as in Example 7, except that this color developer dispersion was used to form the thermal recording layer.

Next, using the thermal recording media of Examples 1 to 11 and Comparative Examples 1 to 6, the "change rate of total light transmittance", "haze degree" and "maximum coloring density" were evaluated. The results of Examples 1-11 are shown in Tables 1-2 below, and the results of Comparative Examples 1-6 are shown in Table 3 below.

<Rate of change in total light transmittance>
The rate of change in total light transmittance of the thermal recording media of Examples 1 to 11 and Comparative Examples 1 to 6 before and after the heat treatment was measured, and the degree of transparency maintenance against heating of the thermal recording media was evaluated. evaluated.
The total light transmittance was measured using a spectrophotometer (U-4100, manufactured by Hitachi High-Technologies Co., Ltd.) at a wavelength of 300 nm for the texture of the thermal recording media prepared in Examples 1 to 11 and Comparative Examples 1 to 6. Measurements were taken every 1 nm in the range of ~830 nm (D65 light source), and the average transmittance at each wavelength obtained was calculated. A is the total light transmittance before the heat treatment, and B is the total light transmittance after the heat treatment at a temperature of 90° C. for 1 hour. It was calculated by AB)/A×100 and evaluated based on the following evaluation criteria. If the rate of change in total light transmittance is "○" or more, it is at a level that poses no problems in use.
[Evaluation criteria]
◎: 3.0% or less ○: More than 3.0% and less than 5.0% ×: 5.0% or more

<Haze degree>
Using a haze meter (device name: HZ-V3, manufactured by Suga Test Co., Ltd.), the haze degree of the recording surface of the thermal recording media produced in Examples 1 to 11 and Comparative Examples 1 to 6 was measured and evaluated as follows. Evaluated based on criteria. If the "haze degree" is "O" or higher, it is at a level that poses no problems in use.
[Evaluation criteria]
◎: less than 10.0 ○: 10.0 or more and 15.0 or less ×: more than 15.0

<Maximum color density>
- Examples 1 to 7, 9 to 11, and Comparative Examples 1 to 6 -
Using a thermal gradient tester (device name: HG-100-2, manufactured by Toyo Seiki Co., Ltd.), the thermosensitive recording media produced in Examples 1 to 7, 9 to 11, and Comparative Examples 1 to 6 exhibit saturated densities. A pre-test image sample was prepared by printing in a heat block at a temperature of 2 kg/cm ² for 1 second. Then, using a Macbeth densitometer RD-914, the reflection density of the printed portion of the prepared image sample before the test was measured as the "maximum coloring density" and evaluated according to the following evaluation criteria. If the "maximum coloring density" is "O" or more, it is a level that poses no problem in use.
[Evaluation criteria]
◎: more than 1.85 ○: 1.65 or more and 1.85 or less ×: less than 1.65 -Example 8-
Using an LD laser marker (device name: Ricoh Rewritable Laser Marker LDM200, manufactured by Ricoh Co., Ltd.), the thermal recording medium prepared in Example 8 was printed under the following printing conditions to prepare a pre-test image sample. Then, using a Macbeth densitometer RD-914, the reflection density of the printed portion of the prepared image sample before the test was measured as the "maximum coloring density" and evaluated according to the following evaluation criteria. If the "maximum coloring density" is "O" or more, it is a level that poses no problem in use.
[Print condition]
Work distance: 150mm
Scanning speed: 3,000mm/s
Laser light wavelength: 980nm
Laser power: 70%
[Evaluation criteria]
◎: more than 1.85 ○: 1.65 or more and 1.85 or less ×: less than 1.65

ただし、前記一般式（１）中、Ｒ^１～Ｒ^５はそれぞれ独立に水素原子、ハロゲン原子、ニトロ基、アミノ基、アルキル基、アルコキシ基、アリールオキシ基、アルキルカルボニルオキシ基、アリールカルボニルオキシ基、アルキルカルボニルアミノ基、アリールカルボニルアミノ基、アルキルスルホニルアミノ基、アリールスルホニルアミノ基、モノアルキルアミノ基、ジアルキルアミノ基、及びアリールアミノ基のいずれかを表す。
＜５＞ 前記顕色剤が、下記構造式（１）から（３）のいずれかで表される化合物である前記＜４＞に記載の感熱記録媒体である。

＜６＞ 前記ロイコ染料と前記顕色剤の含有比が、前記ロイコ染料１質量部に対して、前記顕色剤１質量部以上４質量部以下である前記＜１＞から＜５＞のいずれかに記載の感熱記録媒体である。
＜７＞ 前記支持体を有していない側の前記感熱記録層上に保護層を有する前記＜１＞から＜６＞のいずれかに記載の感熱記録媒体である。
＜８＞ 前記感熱記録層と前記支持体との間に接着層を有する前記＜１＞から＜７＞のいずれかに記載の感熱記録媒体である。
＜９＞ 前記感熱記録層及び前記接着層の少なくともいずれかが、紫外線吸収材料を含有する前記＜８＞に記載の感熱記録媒体である。
＜１０＞ 前記感熱記録層及び前記接着層の少なくともいずれかが、光熱変換材料を含有し、レーザーで記録可能である前記＜８＞から＜９＞のいずれかに記載の感熱記録媒体である。
＜１１＞ 前記＜１＞から＜６＞のいずれかに記載の感熱記録媒体の形成に用いられることを特徴とする感熱記録液である。
＜１２＞ 前記＜１＞から＜１０＞のいずれかに記載の感熱記録媒体を有することを特徴とする物品である。 Embodiments of the present invention are, for example, as follows.
<1> A thermosensitive recording medium comprising a support and a thermosensitive recording layer on the support,
The thermosensitive recording layer contains a leuco dye and a developer,
The thermal recording medium has a haze degree of 15 or less,
A thermosensitive recording medium characterized in that the rate of change X of total light transmittance represented by the following formula (1) is 5.0% or less.
X=(AB)/A×100 Formula (1)
However, in the formula (1), A is the total light transmittance before heating the thermosensitive recording medium at a temperature of 90°C, and B is the total light transmittance after heating the thermosensitive recording medium at a temperature of 90°C for 1 hour. Total light transmittance.
<2> The thermal recording medium according to <1>, wherein the thermal recording medium has a haze of 10 or less.
<3> The thermal recording medium according to any one of <1> and <2>, wherein the rate of change X of the total light transmittance is 3.0% or less.
<4> The thermal recording medium according to any one of <1> to <3>, wherein the color developer is at least one compound represented by the following general formula (1).

However, in the general formula (1), R ¹ to R ⁵ are each independently 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.
<5> The thermosensitive recording medium according to <4>, wherein the developer is a compound represented by any one of the following structural formulas (1) to (3).

<6> Any one of <1> to <5>, wherein the content ratio of the leuco dye and the color developer is 1 part by mass or more and 4 parts by mass or less of the color developer with respect to 1 part by mass of the leuco dye. 1. A thermosensitive recording medium according to 1.
<7> The thermosensitive recording medium according to any one of <1> to <6>, further comprising a protective layer on the thermosensitive recording layer on the side not having the support.
<8> The thermal recording medium according to any one of <1> to <7>, further comprising an adhesive layer between the thermal recording layer and the support.
<9> The thermal recording medium according to <8>, wherein at least one of the thermal recording layer and the adhesive layer contains an ultraviolet absorbing material.
<10> The thermal recording medium according to any one of <8> to <9>, wherein at least one of the thermal recording layer and the adhesive layer contains a photothermal conversion material and is recordable with a laser.
<11> A thermosensitive recording liquid, which is used for forming the thermosensitive recording medium according to any one of <1> to <6>.
<12> An article comprising the thermal recording medium according to any one of <1> to <10>.

According to the thermal recording medium according to any one of <1> to <10>, the thermal recording liquid according to <11>, and the article according to <12>, the above-mentioned conventional problems are solved, The object of the present invention can be achieved.

JP-A-5-278329

Claims (8)

A thermosensitive recording medium comprising a support and a thermosensitive recording layer on the support,
The thermosensitive recording layer contains a leuco dye and a developer,
The color developer is at least one compound represented by the following general formula (1), and has a 50% cumulative volume particle diameter (D50) of 0.05 μm or more and 0.12 μm or less,
The thermal recording medium has a haze degree of 15 or less,
A thermosensitive recording medium characterized in that a change rate X of total light transmittance represented by the following formula (1) is 5.0% or less.

However, in the general formula (1), R ¹ to R ⁵ are each independently 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.
X=(AB)/A×100 Formula (1)
However, in the formula (1), A is the total light transmittance before heating the thermosensitive recording medium at a temperature of 90°C, and B is the total light transmittance after heating the thermosensitive recording medium at a temperature of 90°C for 1 hour. Total light transmittance. 2. The thermal recording medium according to claim 1, wherein the content ratio of said leuco dye and said color developer is 1 part by mass or more and 4 parts by mass or less of said color developer with respect to 1 part by mass of said leuco dye. 3. The thermal recording medium according to claim 1 , further comprising a protective layer on the thermal recording layer on the side not having the support. 4. The thermal recording medium according to claim 1, further comprising an adhesive layer between said thermal recording layer and said support. 5. The thermal recording medium according to claim 4 , wherein at least one of said thermal recording layer and said adhesive layer contains an ultraviolet absorbing material. 6. The thermal recording medium according to claim 4 , wherein at least one of said thermal recording layer and said adhesive layer contains a photothermal conversion material and is recordable with a laser. A thermosensitive recording liquid, which is used for forming the thermosensitive recording medium according to any one of claims 1 and 2 . An article comprising the thermosensitive recording medium according to any one of claims 1 to 6 .