JPH0655847A - Thermal recording material - Google Patents

Abstract

(57) [Summary] [Structure] A heat-sensitive recording material containing a colorless leuco dye having a lactone ring in the molecule and developing a color by the cleavage reaction thereof, and a developer capable of developing the color by the lactone ring cleavage when the leuco dye is heated. In, a decarboxylation reaction accelerator such as N, N-dimethylformamide or cyclohexanone is included. [Effect] Since the decarboxylation reaction is promoted, a ring-closing reaction (decoloring reaction) of the lactone ring does not occur, and a stable color-developed state is maintained. Therefore, the storability of the color image, especially the plasticizer resistance, is excellent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material having significantly improved image stability against oil and plasticizer.

[0002]

2. Description of the Related Art Generally, a heat-sensitive recording material is mainly composed of a color-forming system comprising a colorless or light-colored color-forming dye as a color-forming agent on a support such as paper, synthetic paper, plastic film and a color-developing agent which makes the color develop when heated. A thermosensitive coloring layer as a component is provided, and a colored image can be obtained by heating with a hot pen, a thermal head, a laser beam, a strobe lamp, or the like. Compared with other recording materials, this recording material does not require complicated processing such as development and fixing, and recording can be obtained in a short time with a relatively simple device, noise generation and environmental pollution are small, and cost is low. It is used for copying books, documents, etc. due to its low price, electronic calculator, facsimile, ticket vending machine,
It is useful as various recording materials such as labels and recorders.

As the color-forming dye used in this heat-sensitive recording material, for example, a colorless or light-colored leuco dye having a lactone, lactam or spiropyran ring, and as a color developer, a phenolic compound has been conventionally used. . The recording material using the color former and the color developer is widely used because of its high image density and high whiteness of the background.

However, an image formed by such a leuco dye and a phenol-based developer has a reversible process in its color-developing system, so that the storage stability is poor and the printed image is left as it is for a long time. , The image fades.
Further, there is a big drawback that the image is easily discolored even when it comes into contact with water, oil, a plasticizer or the like.

In order to improve the storability of such a leuco dye-based color image, various studies have been made so far on the color developer. For example, JP-A-57-199686 proposes to improve the plasticizer resistance by using a benzophenone derivative having a sulfonyl group. However, such a sulfonic acid type developer is not used in the non-image area. It is hard to say that it is not practical and has poor storability.

Further, Japanese Patent Laid-Open No. 59-185693 proposes a method of improving the plasticizer resistance by using a metal salt of an aromatic carboxylic acid and an aliphatic carboxylic acid. It cannot be said that it is practical, and it cannot be said that it is practical. JP-A-63-45087 discloses a sulfonium salt compound, and JP-A-1-294088 discloses a sulfonium salt compound of a type having a benzyl group as one of the substituents and an aromatic ammonium organic acid salt as a developer. As a result, a method of improving image stability with respect to a plasticizer and preventing coloring of a non-image area due to an organic solvent has been proposed. It is considered that such a type of color developing agent produces a cation species such as a benzyl cation by thermal decomposition during heating, thereby developing an electron-donating leuco dye. However, since such a thermal decomposition process requires a considerable amount of heat energy, it cannot be said that the heat source used for ordinary heat-sensitive recording has poor color development and is practical.

Further, in JP-A-59-109388 and JP-A-1-178489, it has been proposed to use a sulfonic acid ester derivative as a developer, but the color developability and image strength are not sufficient. It is hard to say that there is and it is not practical.

Further, in JP-A-2-120086, a hydrogen-bonding molecular complex is formed between bisphenol A and another phenolic compound or an amine compound to use a developer, whereby color development and plasticizer resistance are achieved. It has been proposed to improve, but in such a system, since the phenolic compound such as bisphenol A acts as a developer, the plasticizer resistance of the image is not fundamentally improved, The current situation is that it is not practical.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording material which makes the color forming reaction irreversible and is excellent in storage stability of a color image, particularly in image stability against oil and plasticizer. To do.

[0010]

According to the present invention, a colorless leuco dye having a lactone ring in the molecule and developing a color by the cleavage reaction thereof, and the leuco dye are colored by the lactone ring cleavage when heated. Provided is a heat-sensitive recording material containing a color developer, which further contains a decarboxylation reaction accelerator.

Generally, this type of heat-sensitive recording material has a lactone ring in the molecule, and a colorless leuco dye that develops a color in the cleavage reaction of the lactone ring is a color developer contained in the heat-sensitive color-developing layer and when heated. Upon contact, the lactone ring is cleaved and color is developed. However, since this color development reaction is a reversible reaction as shown by the following reaction formula, the reverse reaction (ring closure of the lactone ring) easily proceeds, and the color image disappears.

[Chemical 3] Therefore, in the present invention, in a system in which a lactone ring is cleaved by a color developer to develop a color (state (II) above), a compound that enables the decarboxylation reaction to proceed promptly (hereinafter, By including a carbonic acid reaction accelerator), the leuco dye develops color as shown in the following reaction formula, and at the same time, the decarboxylation reaction proceeds, thereby making the color development process irreversible.

[0012]

[Chemical 4] The (III) obtained in the above reaction formula does not cause a ring-closing reaction (decoloring reaction) of the lactone ring because the carboxylate anion portion (COO ⁻ ) is lost due to the decarboxylation reaction, and its coloring state Is stable.

It can be confirmed from the infrared absorption spectrum (IR spectrum) that such decarboxylation reaction is actually proceeding. In other words, stretching vibration at around 1720 cm ^-1 of the lactone ring carbonyl of the leuco dyes before coloring (C = 0), also in the colored state (II) in which the lactone ring is cleaved by the developer, 1600 cm ^-1 and around 1400 cm ^-1 near the carboxylate anion (CO
O ^-) stretching vibration occurs of. However, from the color-developed state (III) obtained by the method of the present invention, the absorption derived from carbonyl generated in this region has disappeared, and the decarboxylation reaction has progressed to the state of (III). Shows.

The decarboxylation reaction accelerator used in the present invention is N, N-dimethylformulamide (DM
F), N, N-diethylformulamide, diethylformulamide malonate, cyclohexanone, cycloheptane, cyclooctanone, 1,4-cyclohexanedione mono-2,2-dimethyltriethylene ketal, 1,4
Examples thereof include cyclohexanedione monoethylene ketal, but the present invention is not limited thereto.

The leuco dyes used in the present invention are applied singly or as a mixture of two or more kinds, and such leuco dyes are applicable to the recording material of this kind, and any one having a lactone ring is arbitrary. Applied to, for example, triphenylmethanephthalide-based, fluorane-based, thiofluorane-based, indophthalyl-based, spiropyran-based,
Leuco compounds such as azaphthalide and bislactone are preferably used. Examples of such compounds include those shown below.

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-N-methyl-N-isobutyl-6-
Methyl-7-anilinofluorane, 3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluorane, 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, 3-pyrrolidino-6-
Methyl-7-anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluorane, 2- {3,6-bis (diethylamino) -9- (o-
Chloranilino) xanthylbenzoic acid lactam}, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o -Chloranilino) fluorane, 3-N-methyl-N-amylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N
-Cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (2 ', 4'-dimethylanilino ) Fluoran, 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
-Morpholino-7- (N-propyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethyl) Anilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl)
Methylaminofluorane, 3-diethylamino-5-chloro-
7- (α-phenylethylamino) fluorane, 3- (N-ethyl
-p-toluidino) -7- (α-phenylethylamino) fluorane, 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-
(N-methyl-N-isopropylamino) -6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3,6-bis (dimethylamino) fluorene spiro ( 9,3 ')-6'-Dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7-α
-Naphthylamino-4'-bromofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-N-ethyl-N
-(2-Ethoxypropyl) amino-6-methyl-7-anilinofluorane, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, 3-diethylamino
-6-methyl-7-mesitidino-4 ', 5'-benzofluorane, 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-
Dimethylaminophenyl) -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 ''-butadiene-4 ''-yl) benzophthalide, 3-
(4'-Dimethylamino-2'-benzyloxy) -3- (1 ''-p-dimethylaminophenyl-1 ''-phenyl-1 '', 3 ''-butadiene-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, 3- (N, N-diethylamino) -6-methyl-7-anilino-3 ', 4', 5 ', 6'-tetrachlorofluorane, 3- (N, N
-Diethylamino) -6-methyl-7-anilino-3 ', 6'-
Dichlorofluorane, 3- (N, N-diethylamino) -6-
Methyl-7-anilino-3 ', 4', 5 ', 6'-tetrabromofluorane, 3- (N, N-diethylamino) -6-methyl-7-anilino-3', 6'-dibromofuran Oran, 3- (N, N-dinormalbutylamino) -6-methyl-7-anilino-3 ', 4',
5 ', 6'-Tetrachlorofluorane, 3- (N, N-dinormalbutylamino) -6-methyl-7-anilino-3', 6'-dichlorofluorane, 3- (N, N-di Normal butylamino)-
6-Methyl-7-anilino-3 ′, 4 ′, 5 ′, 6′-tetrabromofluorane, 3- (N, N-dinormalbutylamino) -6-
Methyl-7-anilino-3 ', 6'-dibromofluorane, 3
-(N, N-Dinormal pentylamino) -6-methyl-7-
Anilino-3 ', 4', 5 ', 6'-tetrachlorofluorane, 3-
(N, N-Dinormalpentylamino) -6-methyl-7-anilino-3 ', 6'-dichlorofluorane, 3- (N, N-Dinormalpentylamino) -6-methyl-7-anilino- 3 ',
4 ', 5', 6'-Tetrabromofluorane, 3- (N, N-Dinormalpentylamino) -6-methyl-7-anilino-3 ', 6'
-Dibromofluorane, 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilino-3 ', 4', 5 ', 6'-tetrachlorofluorane, 3- (N- Ethyl-N-isopentylamino) -6-methyl-7-anilino-3 ', 6'-dichlorofluorane, 3- (N-ethyl-N-isopentylamino)
-6-Methyl-7-anilino-3 ', 4', 5 ', 6'-tetrabromofluorane, 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilino-3' , 6'-Dibromofluorane, 3- (N-normalpropyl-N-isopropylamino) -6-methyl-7-anilino-3 ', 4', 5 ', 6'-tetrachlorofluorane, 3- (N-Normalpropyl-N-isopropylamino) -6-methyl-7-anilino-3 ', 6'-dichlorofluorane, 3- (N-normalpropyl-N-isopropylamino) -6-methyl-7- Anilino-3 ', 4', 5 ', 6'
-Tetrabromofluorane, 3- (N-normalpropyl-N-isopropylamino) -6-methyl-7-anilino-
3 ', 6'-dibromofluorane, 3- (N-normalhexyl-N-isopropylamino) -6-methyl-7-anilino-
3 ', 4', 5 ', 6'-Tetrachlorofluorane, 3- (N-normalhexyl-N-isopropylamino) -6-methyl-7-
Anilino-3 ', 6'-dichlorofluorane, 3- (N-normalhexyl-N-isopropylamino) -6-methyl-7-
Anilino-3 ', 4', 5 ', 6'-Tetrabromofluorane, 3-
(N-Normalhexyl-N-isopropylamino) -6-
Methyl-7-anilino-3 ', 6'-dibromofluorane, 3
-(N-methyl-N-normalpropylamino) -6-methyl-7-anilino-3 ', 4', 5 ', 6'-tetrachlorofluorane, 3- (N-methyl-N-normalpropylamino) ) -6-
Methyl-7-anilino-3 ', 6'-dichlorofluorane, 3
-(N-methyl-N-normalpropylamino) -6-methyl-7-anilino-3 ', 4', 5 ', 6'-tetrabromofluorane, 3- (N-methyl-N-normalpropylamino) ) -6-
Methyl-7-anilino-3 ', 6'-dibromofluorane, 3
-(N-ethyl-N-isobutylamino) -6-methyl-7-
Anilino-3 ', 4', 5 ', 6'-tetrachlorofluorane, 3-
(N-ethyl-N-isobutylamino) -6-methyl-7-anilino-3 ', 6'-dichlorofluorane, 3- (N-ethyl-
N-isobutylamino) -6-methyl-7-anilino-3 ',
4 ', 5', 6'-Tetrabromofluorane, 3- (N-ethyl-N
-Isobutylamino) -6-methyl-7-anilino-3 ', 6'
-Dibromofluorane, 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilino-3 ', 4', 5 ', 6'-
Tetrachlorofluorane, 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilino-3 ', 6'-dichlorofluorane, 3- (N-methyl-N-cyclohexylamino) -6 -Methyl-7-anilino-3 ', 4', 5 ', 6'-tetrabromofluorane, 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilino-3', 6 ' -Dibromofluorane, 3- (N-ethyl-N-4-oxohexylamino) -6-methyl-7-anilino-3 ', 4', 5 ', 6'-tetrachlorofluorane, 3- ( N-ethyl-N-4-oxohexylamino) -6-methyl-7-anilino-3 ', 6'-dichlorofluorane, 3- (N-ethyl-N-4-oxohexylamino) -6-methyl -7-anilino-3 ', 4', 5 ', 6'-tetrabromofluorane, 3- (N-ethyl-N-4-oxohexylamino) -6-methyl-7-anilino-3', 6 '-Dibromful Oran, 3- (N-isopentyl-N-3-oxopentylamino) -6-methyl-7-anilino-3 ', 4', 5 ', 6'
-Tetrachlorofluorane, 3- (N-isopentyl-N-
3-oxopentylamino) -6-methyl-7-anilino-
3 ', 6'-dichlorofluorane, 3- (N-isopentyl-N
-3-Oxopentylamino) -6-methyl-7-anilino-3 ', 4', 5 ', 6'-tetrabromofluorane, 3- (N-isopentyl-N-3-oxopentylamino) -6 -Methyl-
7-anilino-3 ', 6'-dibromofluorane, 3-piperidino-6-methyl-7-anilino-3', 4 ', 5', 6'-tetrachlorofluorane, 3-piperidino-6- Methyl-7-anilino-3 ', 6'-dichlorofluorane, 3-piperidino-
6-methyl-7-anilino-3 ', 4', 5 ', 6'-tetrabromofluorane, 3-piperidino-6-methyl-7-anilino-3', 6'-dibromofluorane, 3- (N-ethyl-N-furfurylamino) -6-methyl-7-anilino-3 ', 4', 5 ',
6'-Tetrachlorofluorane, 3- (N-ethyl-N-furfurylamino) -6-methyl-7-anilino-3 ', 6'-dichlorofluorane, 3- (N-ethyl-N-fluor Furylamino) -6-methyl-7-anilino-3 ', 4', 5 ', 6'-tetrabromofluorane, 3- (N-ethyl-N-furfurylamino) -6-methyl-7-anilino −3 ′, 6′-dibromofluorane and the like.

The leuco dye preferably used in the present invention is represented by the general formula (I) (Formula 1), and the leuco dye more preferably used is represented by the formula (II) (Formula 2): 3- ( N, N-diethylamino) -6-methyl-7
-Anilino-3 ', 4', 5 ', 6'-tetrachlorofluorane.

[Chemical 1]

[Chemical 2]

Further, as the color developer used in the thermosensitive color developing layer of the present invention, various electron-accepting compounds which develop the above leuco dye upon contact, such as phenolic compounds, thiophenolic compounds, thiourea derivatives, organic compounds. Acids and metal salts thereof are preferably applied, and specific examples thereof include those shown below.

4,4'-isopropylidene bisphenol,
4,4'-isopropylidene bis (o-methylphenol),
4,4'-secondary butylidene bisphenol 4,4'-isopropylidene bis (2-tert-butylphenol), 4,4'-cyclohexylidene diphenol,
4,4'-isopropylidene bis (2-chlorophenol),
2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 4,4'-butylidenebis
(6-tert-butyl-2-methylphenol), 1,1,3
-Tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 4,4'-thiobis ( 6-tert-butyl-2-methylphenol),
4,4'-diphenol sulfone, 4-isopropoxy-4'-hydroxydiphenyl sulfone, 4-benzyloxy-4'-hydroxydiphenyl sulfone, 4,4'-diphenol sulfoxide, P-hydroxybenzoic acid isopropyl, P -Benzyl hydroxybenzoate, benzyl protocatechuate, stearyl gallate, lauryl gallate, octyl gallate, 1,7-bis (4-hydroxyphenylthio) -3,
5-dioxaheptane, 1,5-bis (4-hydroxyphenylthio) -3-oxapentane, 1,3-bis (4-hydroxyphenylthio) -propane, 1,3-bis (4-hydroxyphenylthio) ) -2-Hydroxypropane, N, N'-diphenylthiourea, N, N'-di (m-chlorophenyl) thiourea, salicylanilide, 5-chloro-salicylanilide, 2-hydroxy-3-naphthoic acid, 2 -Hydroxy-1
-Naphthoic acid, 1-hydroxy-2-naphthoic acid, metal salts of hydroxynaphthoic acid such as zinc, aluminum and calcium, bis- (4-hydroxyphenyl) acetic acid methyl ester, bis- (4-hydroxyphenyl) acetic acid benzyl ester , 1,3-bis (4-hydroxycumyl) benzene, 1,4
-Bis (4-hydroxycumyl) benzene, 2,4'-diphenol sulfone, 3,3'-diallyl-4,4'-diphenol sulfone, α, α-bis (4-hydroxyphenyl) -α- Methyltoluene, zinc thiocyanate antipyrine complex,
Tetrabromobisphenol A, tetrabromobisphenol S, 4,4'-thiobis (2-methylphenol), 4,4'-
Thiobis (2-chlorophenol) etc.

In order to produce the heat-sensitive recording material of the present invention,
When the leuco dye and the color developer are bound and supported on the support, various commonly used binders can be appropriately used, and specific examples thereof include the following.

Polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose and ethyl cellulose, polyacrylic acid sodium -Da, polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer, styrene /
Maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, soda alginate, gelatin, other water-soluble polymers such as casein, polyvinyl acetate, polyurethane, polyacrylic acid, Polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene /
Emulsion such as vinyl acetate copolymer, latex such as styrene / butadiene copolymer and styrene / butadiene / acrylic copolymer.

In the present invention, various heat-fusible substances can be used as the sensitivity improver, and specific examples thereof include the followings, but the present invention is not limited thereto. . Fatty acids such as stearic acid and behenic acid, fatty acid amides such as stearic acid amide and palmitic acid amide, fatty acid metal salts such as zinc stearate, aluminum stearate, calcium stearate, zinc palmitate and zinc behenate, p-benzyl Biphenyl, terphenyl, triphenylmethane, benzyl p-benzyloxybenzoate, β-benzyloxynaphthalene, phenyl β-naphthoate, phenyl 1-hydroxy-2-naphthoate, methyl 1-hydroxy-2-naphthoate, diphenyl Carbonate, Greacol 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) bifer, p-aryloxypphenyl, p-propargyloxybiphenyl, dibenzoyloxymethane, dibenzoyloxypropane, dibenzyl disulfide, 1,1-diphenylethanol, 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, oxalic acid Bis (4-chlorobenzyl) and the like.

In the case of obtaining a heat-sensitive recording material according to the present invention, a leuco dye, a color developer, the compound of the present invention and, if necessary, additional components commonly used in this kind of heat-sensitive recording material such as fillers and surface active agents are used. Agents can be used in combination. In this case, as the filler, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide,
In addition to barium sulfate, clay, kaolin, talc, inorganic fine powder such as surface-treated calcium and silica, urea-
Examples include organic fine powders such as formalin resin, styrene-methacrylic acid copolymer, polystyrene resin, and vinylidene chloride resin. Regarding the layer structure, it may be a single layer or multiple layers, and if necessary, an over layer,
An under layer and a back layer can be provided.

[0024]

EFFECT OF THE INVENTION The heat-sensitive coloring material of the present invention containing a compound having a lactone ring in the molecule, which accelerates the decarboxylation reaction in a system that develops a color by cleaving the lactone ring with a color developer. The recording material is extremely practicable in that the storability of a color image, particularly the storability of an image with respect to oil and a plasticizer, is remarkably improved as compared with conventional recording materials.

[0025]

EXAMPLES Next, the present invention will be described in more detail by way of examples. The parts and% shown below are based on weight. Examples 1-5 According to the microencapsulation method (coacervation method) shown below, uncured microcapsules containing a decarboxylation accelerator are formed, and the uncured microcapsules are subjected to a curing treatment to have a particle size of 1 to 3 μm.
Microcapsules of the decarboxylation reaction accelerator of were obtained.

"Microencapsulation method" (i) Production of uncured encapsulant The decarboxylation reaction accelerator solution, which is the core substance, is added to a gelatin aqueous solution containing sodium dodecyl sulfate as a surfactant at 40 ° C in an ultrasonic emulsifier. Emulsify and disperse using. The particle size of the decarboxylation reaction accelerator solution is measured by a light scattering method and always emulsified and dispersed so as to have a constant particle size. Next, this emulsion is quickly dispersed in an aqueous solution of gum arabic at 40 ° C.
Set to l. While stirring, the system p
When H is made to be equal to or lower than the isoelectric point of gelatin, coacervation occurs, and a coacervate phase composed of gelatin and gum arabic is deposited around the decarboxylation reaction accelerator solution to form a film, and uncured microcapsules are formed. (Ii) Curing treatment of uncured encapsulated product After the uncured microcapsules produced above were set at 20 ° C. below the set point of gelatin, 1 ml of 37% formalin aqueous solution was added to the system, and then the pH of the system was adjusted. 2.
When it is raised to 8.5 with a 5% sodium carbonate aqueous solution, gelatin is hardened and becomes insoluble in water. After the capsule dispersion is centrifuged, the obtained capsule slurry is dried by spray drying to obtain a hardened encapsulated product in which the target decarboxylation reaction accelerator solution is encapsulated. Decarboxylation reaction accelerator solution: Prepared by dissolving 1 part of decarboxylation reaction accelerator in 5 parts of acetone. This is the core substance. Then, the following [solution A] to [solution D] were prepared. In addition,
[Liquid A] was thoroughly mixed with a stirrer, and [Liquid B], [Liquid C] and [Liquid D] were each pulverized in a magnetic ball mill for 2 days.

[Solution A] Microcapsules of decarboxylation accelerator shown in Table 1 30 parts 10% aqueous solution of polyvinyl alcohol 20 parts Water 50 parts [Solution B] Leuco dye shown in table 1 20 parts 10% aqueous solution of polyvinyl alcohol 20 Part Water 60 parts [Solution C] 4,4'-isopropylidenediphenol 20 parts 10% aqueous solution of polyvinyl alcohol 20 parts Water 60 parts [Solution D] Calcium carbonate 20 parts 5% aqueous solution of methylcellulose 20 parts Water 60 parts Next [Liquid A] 30 parts, [Liquid B] 10 parts, [Liquid C] 30
Parts, 30 parts of [D liquid] and 10 parts of a 20% aqueous solution of an isobutylene / maleic anhydride copolymer are mixed to prepare a thermosensitive color forming layer-forming liquid, which is dried on a wood free paper having a basis weight of 50 g / m ² . A thermosensitive recording material is prepared by coating and drying the coating so that the amount of dye deposited is 0.5 g / m ^2, and then calendering the layer surface so that the surface smoothness is 500 to 600 seconds. It was created.

Comparative Example 1 The following mixtures were pulverized in a magnetic ball mill for 2 days to prepare [E liquid] and [F liquid]. [Solution E] 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane 20 parts 10% aqueous solution of polyvinyl alcohol 20 parts Water 60 parts [Solution F] 4,4'-isopropyloxy 20 parts of 10% aqueous solution of polyvinyl alcohol 20 parts of water 60 parts of [solution E], 30 parts of [solution F], 30 parts of [solution D] and 20% of isobutylene / maleic anhydride copolymer 10 parts of an alkaline aqueous solution is mixed to form a thermosensitive color forming layer forming liquid,
This was coated and dried on a high-quality paper having a basis weight of 50 g / m ² so that the amount of dye adhering after drying was 0.5 g / m ² to form a thermosensitive coloring layer, and then the surface smoothness was 500 to 600. The surface of the layer was calendered to prepare a heat-sensitive recording material in seconds.

Comparative Example 2 A thermosensitive recording material was prepared in the same manner as in Comparative Example 1 except that the following [G liquid] was used instead of [F liquid] in Comparative Example 1. [Liquid G] Bis (4-hydroxy-3-allylphenyl) sulfone 20 parts 10% aqueous solution of polyvinyl alcohol 20 parts water 60 parts

The heat-sensitive recording material obtained as described above was heated at a temperature of 150 ° C. using a thermal gradient tester manufactured by Toyo Seiki Seisakusho.
Printing was performed under the condition that a pressure of 2 kg / cm ^{2 was} applied for 5 seconds, and the image density was measured by a Macbeth densitometer RD-914 (filter:
W-106). Next, the printed samples were tested for oil resistance and plasticizer resistance as follows.
The results are shown in Table 1. [Oil resistance] Apply cottonseed oil to the printed part,
The density of the image area after storage for 48 hours under dry conditions was measured. [Plasticizer resistance] A plasticizer (DOA: dioctyl adipate) was applied to the printed area, and the density of the image area was measured after storing at a temperature of 40 ° C for 48 hours under dry conditions. Incidentally, the concentration measurement after each of the above-mentioned storage stability tests was also carried out with a Macbeth densitometer RD-914 (filter: W-106).

[Table 1]

From Table 1, the heat-sensitive recording material of the present invention suppresses the ring-closing reaction of the lactone ring, that is, the color erasing reaction, as compared with the conventional color-developing system, and can maintain a stable color-developed state and the storage stability of the image area. In particular, it can be seen that it is extremely excellent, with no discoloration due to the oil plasticizer in the image area.

Claims (4)

[Claims] 1. A heat-sensitive recording material comprising a colorless leuco dye having a lactone ring in the molecule, which develops a color by the cleavage reaction thereof, and a developer which causes the leuco dye to develop a color when the lactone ring is cleaved when heated. A heat-sensitive recording material containing a carbonic acid reaction accelerator. 2. The heat-sensitive recording material according to claim 1, wherein the decarboxylation reaction accelerator is N, N-dimethylformamide or cyclohexanone. 3. The heat-sensitive recording material according to claim 1, wherein the colorless leuco dye is a compound represented by the following general formula (I). [Chemical 1] 4. The heat-sensitive recording material according to claim 1, wherein the decarboxylation reaction accelerator is N, N-dimethylformamide, and the leuco dye is a compound represented by the following chemical formula 2. [Chemical 2]