JP2000229963A - Alkylidenebis-coumarin derivative and its use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new compound capable of providing heat-sensitive recording material excellent in storage stability such as resistance to plasticizer, oil resistance, etc. of colored image and having sufficient coloring concentration and useful as a developer for coloring dyes. SOLUTION: This compound is represented by formula I (R1 is an alkyl or an aralkyl; and R2 is H, OH, an alkyl or the like), e.g. 3,3'-propylidenebis-(4- hydroxycoumarin). The compound of formula I is obtained by reacting a compound of the formula R1CHO (e.g. propionic aldehyde) with a compound of formula II (e.g. 4-hydroxycoumarin) in an organic solvent such as ethanol, preferably at 40-70 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a specific bis-coumarin derivative useful for coloring a color-forming dye such as a leuco dye, a novel color developer comprising the same and a thermosensitive recording material containing the bis-coumarin derivative. About. A report that this type of derivative can be synthesized from alkyl aldehydes or aralkyl aldehydes [W. R. Sul
Livan, C.I. F. Huebner, M .; A. Sta
hmann and K.H. P. Link, J. et al. Ame
r. Chem. SOC. , 65, 2288-2291
Page (1943)], but there is no disclosure of the compound of the present invention or its use.

[0002]

2. Description of the Related Art A thermosensitive recording medium is provided with a thermosensitive coloring layer mainly composed of a color developing agent such as an electron-donating leuco dye and a color developing agent composed of an organic acidic substance such as a phenolic compound on a support. The heat-sensitive coloring layer can obtain a color-recorded image by a reaction between the developer and the coloring dye by heat. But the developer,
The thermosensitive recording medium obtained by applying a heat-sensitive coloring layer containing a color-forming dye and a binder as active ingredients to a support has a reversible color-forming reaction. It is known that the color is erased.

[0003] Many techniques have been disclosed to suppress this decoloring phenomenon. For example, those using a hydrophobic polymer compound emulsion or the like for the protective layer (Japanese Patent Application Laid-Open No. 56-14 / 1981)
No. 6796) or provided with a surface layer containing a hydrophobic polymer compound as a resin component (Japanese Patent Application Laid-Open No. 58-199189).
No.). These protective layers, the thermosensitive recording medium provided with the surface layer, can suppress the decoloration of the image to short-time contact with oil, plasticizer, but decoloration due to long-term contact is inevitable Is not an essential solution. Various auxiliaries such as plasticizer-resistant and oil-resistant color-forming dyes, developers, and storage stabilizers have been developed, but none of them have been found to be sufficiently satisfactory.

[0004] For this reason, there is a strong demand for improving the storage stability of color images in recording materials, especially the resistance to plasticizers and oils.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a recording material which is excellent in storage stability of a color image and has a sufficient color density, a color developer thereof, and a novel compound suitable therefor. It is in.

[0006]

Means for Solving the Problems A first aspect of the present invention is the following general formula (1):

Embedded image (Wherein R ¹ is a group selected from the group consisting of linear or branched alkyl groups or aralkyl groups;
² is a group selected from the group consisting of a hydrogen atom, a hydroxy group, a linear or branched alkyl group, an alkoxy group and a dialkylamino group. )).

A second aspect of the present invention relates to a developer for a color-forming dye comprising the alkylidenebis-coumarin derivative according to the first aspect.

A third aspect of the present invention relates to a heat-sensitive recording material comprising the alkylidene bis-coumarin derivative according to claim 1.

The following general formula (1) of the present invention:

Embedded image (Wherein R ¹ is a group selected from the group consisting of linear or branched alkyl groups or aralkyl groups;
² is a group selected from the group consisting of a hydrogen atom, a hydroxy group, a linear or branched alkyl group, an alkoxy group and a dialkylamino group. The alkylidene bis-coumarin derivative represented by the following general formula (2)

Embedded image An aldehyde derivative represented by R ¹ CHO (2) (wherein, R ¹ is a group selected from the group consisting of a linear or branched alkyl group or an aralkyl group) and the following general formula: (3)

Embedded image (Wherein R ² is a group selected from the group consisting of a hydrogen atom, a hydroxy group, a linear or branched alkyl group, an alkoxy group, and a dialkylamino group). , In an organic solvent.

The straight-chain or branched R ¹ described above,
Examples of the alkyl group include a methyl group, an ethyl group, n
-Propyl group, iso-propyl group, n-butyl group, i
Examples thereof include a so-butyl group and a sec-butyl group, and the number of carbon atoms is preferably 1 to 8. Examples of the aralkyl group include a phenylethyl group and a phenylpropyl group.

R ² is a straight-chain or branched alkyl group such as a methyl group, an ethyl group, an n-propyl group or an n-butyl group. Is preferred. As the alkoxy group,
For example, it may be the same as the alkoxy group shown for R ¹ . Examples of the dialkylamino group include a dimethylamino group, a diethylamino group, and a di-n-propylamino group.

Specific examples of the alkylidene bis-coumarin derivative represented by the above general formula (1) used in the present invention include the following compounds. 3,3'-methylenebis- (4-hydroxycoumarin), 3,3'-ethylidenebis- (4-hydroxycoumarin), 3,3'-n-propylidenebis- (4
-Hydroxycoumarin), 3,3'-iso-propylidenebis- (4-hydroxycoumarin), 3,3'-n
-Butylidenebis- (4-hydroxycoumarin), 3,
3'-iso-butylidenebis- (4-hydroxycoumarin), 3,3'-n-pentylidenebis- (4-hydroxycoumarin), 3,3'-iso-pentylidenebis- (4-hydroxycoumarin), 3,3'-n-hexylidenebis- (4-hydroxycoumarin), 3,3 '
-(2-ethylhexylidene) bis- (4-hydroxycoumarin), 3,3'-n-heptylidenebis- (4-
Hydroxycoumarin), 3,3'-n-octylidenebis- (4-hydroxycoumarin), 3,3'-n-nonylidenebis- (4-hydroxycoumarin), 3,3'-
n-decylidenebis- (4-hydroxycoumarin),
3,3'-phenylethylidenebis- (4-hydroxycoumarin), 3,3'-phenylpropylidenebis-
(4-hydroxycoumarin) and the like.

The following general formula (2)

Embedded image As the aldehyde derivative represented by R ¹ CHO (2) (wherein R ¹ is the same as described above), formaldehyde, paraformaldehyde, trioxymethylene, acetaldehyde, propionaldehyde, n-butyraldehyde , Iso-
Butyraldehyde, n-pentylaldehyde, 2-ethylhexylaldehyde, n-hexylaldehyde, n-
Heptyl aldehyde, n-octyl aldehyde, n-nonyl aldehyde, n-decyl aldehyde, phenylacetaldehyde, phenyl propionaldehyde and the like can be mentioned.

The above reaction is usually carried out at room temperature to 100 ° C., preferably at 40 to 70 ° C., and the organic solvent used includes lower aliphatic alcohols, dioxane, tetrahydrofuran and the like.

The following general formula (3)

Embedded image (In the formula, R ² is the same as described above.) Specific examples of the 4-hydroxycoumarin derivative represented by the formula: 4-hydroxycoumarin, 4,7-dihydroxycoumarin, 4-hydroxy-7-dimethylaminocoumarin, 4-hydroxy-7-diethylaminocoumarin, 4-hydroxy-7
-Di-n-propylaminocoumarin, 4-hydroxy-
Examples thereof include 7-methoxycoumarin, 4-hydroxy-7-ethoxycoumarin, and 4-hydroxy-7-n-propoxycoumarin.

In the present invention, a conventionally known developer can be used in combination with the compound of the formula (1). These conventional developers include, for example, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [1-methyl-1- (4′-hydroxyphenyl) ethyl] benzene, Dihydroxydiphenyl ether, benzyl 4-hydroxybenzoate, 4-hydroxy-4'-isopropyloxydiphenylsulfone, 1,1-di (4-hydroxyphenyl) cyclohexane, 1,7-di (4-hydroxyphenylthio) -1,1 Examples thereof include 3,5-trioxaheptane and 3,3'-diallyl 4,4'-dihydroxydiphenyl sulfone. In this case, although it depends on the amount of the compound of the general formula (1) of the present invention, a considerable image storage stabilizing effect is exhibited according to the amount used.

Although there is no particular limitation on the dye precursor which is a color-forming dye, leuco dyes are typical, and examples thereof include triphenylmethane type, fluoran type,
Examples include diphenylmethane. For example, 3- (4
-Diethyl-2-ethoxyphenyl) -3- (1-phenyl-2-methylindol-3-yl) -4-azaphthalide, crystal violet lactone, 3- (N-
Ethyl-N-isopentylamino) -6-methyl-7-
Anilinofluoran, 3-diethylamino-6-methyl-7- (4-diethylanilino) fluoran, 3- (N
-Ethyl-N-4-methylanilino) -6-methyl-7
-Anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluoran, 3-diethylamino- 7- (2-chloroanilino) fluoran, 3-diethylamino-7- (3-trifluoromethylanilino) fluoran, 3-dibutylamino-7- (2-chloroanilino) fluoran, 3-
Diethylamino-6-methyl-7-chlorofluoran,
3-cyclohexylamino-6-chlorofluoran, 3
-(N-ethyl-N-hexylamino) -6-methyl-
7- (4-chloroanilino) fluoran and the like can be mentioned.

The thermosensitive coloring layer of the thermosensitive recording medium of the present invention contains, as its main components, a dye precursor and a developer comprising the compound of the above formula (1). The heat-sensitive coloring layer may contain a conventionally known sensitizer, image stabilizer, antioxidant, light stabilizer, and metal deactivator, if necessary, in addition to the binder.

The sensitizer which may be used in the present invention is not particularly limited, but for example, 1-hydroxy-2
-Phenyl naphthoate, 4-benzylbiphenyl, benzylnaphthyl ether, benzyl 4-benzyloxybenzoate, diphenyl carbonate, ditolyl carbonate, terphenyls, 1,2-bis (4-tolyloxy) ethane, 1,5-bis (4-methoxyphenoxy) -3-oxapentane, oxalic acid diester, higher fatty acid amide, higher fatty acid anilide, acetoacetic anilide, phthalic diester, terephthalic diester, bis (ter)
t-butylphenol), 1,2-bis (phenoxy)
Ethane, diphenylamine, carbazole, 4,4'-
Dimethyl biphenyl and diethers of 4,4'-dihydroxydiphenyl sulfone can be exemplified.

Other image stabilizers that may be used in the present invention are not particularly limited, and include, for example, 4-benzyloxy-4 '-(2-methylglycidyloxy) diphenylsulfone and 4,4'- Examples thereof include diglycidyloxydiphenyl sulfone, 1,4-diglycidyloxybenzene, a 2-propanol derivative, and a salicylic acid derivative.

The antioxidant which may be used in the present invention is not particularly limited, but for example, 2,6-di-t
tert-butyl-4-methylphenol, 2-tert
-4,6-dimethylphenol, 2,6-di-tert
-Butyl-4-ethylphenol, 2,6-di-ter
t-butyl-4-n-butylphenol, 2,6-di-
tert-butyl-4-isobutylphenol, 2,6
-Dicyclopentyl-4-methylphenol, 2- (α
-Methylcyclohexyl) -4,6-dimethylphenol, 2,6-dioctadecyl-4-methylphenol,
2,4,6-tricyclohexylphenol, 2,6-
Dinonyl-4-methylphenol, 2,6-di-ter
t-butyl-4-methoxymethylphenol, 2,4-
Dimethyl-6- (1'-methyl-undec-1'-yl) -phenol, 2,4-dimethyl-6- (1'-methyl-heptadec-1'-yl) -phenol, 2,4
2,4-di-, such as -dimethyl-6- (1'-methyl-trideca-1'-yl) -phenol and mixtures thereof.
Octylthiomethyl-6-tert-butylphenol, 2,4-dioctylthiomethyl-6-methylphenol, 2,4-di-octylthiomethyl-6-ethylphenol, 2,6-di-dodecylthiomethyl-4- 2,6-di-te, such as nonylphenol and mixtures thereof
rt-butyl-4-methoxyphenol, 2,5-di-
tert-butyl hydroquinone, 2,5-di-ter
t-amylhydroquinone, 2,6-diphenyl-4-
Octadecyloxyphenol, 2,6-di-tert
-Butylhydroquinone, 2,5-di-tert-butyl-4-hydroxyanisole, 3,5-di-tert
-Butyl-4-hydroxyanisole, 3,5-di-t
tert-butyl-4-hydroxyphenylstearate, bis (3,5-di-tert-butyl-4-hydroxyphenyl) adipate and mixtures thereof,
4-bis-octylmercapto-6- (3,5-di-t
tert-butyl-4-hydroxyanilino) -1,3,3
5-triazine, 2-octylmercapto-4,6-bis (3,5-di-tert-butyl-4-hydroxyanilino) -1,3,5-triazine, 2-octylmercapto-4,6-bis (3,5-di-tert-butyl-4-hydroxyphenoxy) -1,2,3-triazine, 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) -iso Shanulate,
1,3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) -isoshanulate, 2,4,6-tris (3,5-di-tert-butyl-4-) (Hydroxyphenylethyl) -1,3,5-triazine, 1,3,5-tris (3,5-di-tert)
-Butyl-4-hydroxyphenylpropionyl) -hexahydro-1,3,5-triazine, 1,3,5-tris (3,5-dicyclohexyl-4-hydroxybenzyl) -isoshanulate and the like, 2,2'- Methylene bis (6-tert-butyl-4-methylphenol),
2,2'-methylenebis (6-tert-butyl-4-
Ethylphenol), 2,2'-ethylidenebis (4,
6-di-tert-butylphenol), 2,2'-ethylidenebis (6-tert-butyl-4-isobutylphenol), 4,4'-methylenebis (2,6-di-
tert-butylphenol), 4,4'-methylenebis (6-tert-butyl-2-methylphenol),
1,1-bis (5-tert-butyl-4-hydroxy-2-methylphenyl) butane, ethylene glycol bis [3,3'-bis (3'-tert-butyl-4'-)
Hydroxyphenyl) butyrate], 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) -2,4,6-trimethylbenzene, 1,4
-Bis (3,5-di-tert-butyl-4-hydroxybenzyl) -2,3,5,6-tetramethylbenzene, 2,4,6-tris (3,5-di-tert-4-
(Hydroxybenzyl) phenol and the like.

The light stabilizer that may be used in the present invention is not particularly limited, and examples thereof include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole,
-(3 ', 5'-di-tert-butyl-2'-hydroxyphenyl) benzotriazole, 2- (5'-te
rt-butyl-2'-hydroxyphenyl) benzotriazole, 2- [2'-hydroxy-5 '-(1,1,
3,3-Tetramethylbutyl) phenyl] benzotriazole, 2- (3 ', 5'-di-tert-butyl-
2'-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3'-tert-butyl-2'-hydroxy-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-4 '-Octoxyphenyl) benzotriazole, 2- (3', 5'-di-tert-pentyl-2'-hydroxyphenyl) benzotriazole, 2- (3'-tert-butyl-
2'-hydroxy-5'-octyloxycarbonylethylphenyl) -5-chlorobenzotriazole, etc.
-Hydroxy-, 4-methoxy-, 4-octoxy-,
4-decyloxy-, 4-dodecyloxy-, 4-benzyloxy-, 4,2 ', 4'-trihydroxy-,
2'-hydroxy-4,4'-dimethoxy-, or 4
-(2-ethylhexyloxy) -2-hydroxybenzophenone derivative, such as 4-tert-butylphenyl salicylate, phenyl salicylate, octylphenyl salicylate, dibenzoylresorcinol, bis (4
-Tert-butylbenzoyl) resorcinol, 2,
4-di-tert-butylphenyl-3,5-di-te
tert-butyl-4-hydroxybenzoate, hexadecyl-3,5-di-tert-butyl-4-hydroxybenzoate, etc., ethyl-α-cyano-β, β-diphenylacrylate, isooctyl-α-cyano-β, β
-Diphenyl acrylate, methyl-α-carbomethoxycinnamate, methyl-α-cyano-β-methyl-p
Bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl)
2,6,6-tetramethyl-4-piperidyl) succinate, bis (1,2,2,6,6-pentamethyl-4-)
Piperidyl) sebacate, bis (1-octyloxy-
2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4)
-Piperidyl) adipate, 4,4'-di-octyloxyoxanilide, 2,2'-diethoxyoxyoxanilide, 2,2'-di-octyloxy-5,5'-
Di-tert-butyl oxanilide, 2,2'-di-dodecyloxy-5,5'-di-tert-butyl oxanilide, 2-ethoxy-2'-ethyl oxanilide,
N, N'-bis (3-dimethylaminopropyl) oxanilide, 2-ethoxy-5-tert-butyl-2'-
2,4,6-tris (2-hydroxy-4-octyloxyphenyl) -1,3,5 such as ethoxyoxanilide
-Triazine, 2- (2-hydroxy-4-octyloxyphenyl) -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, 2- (2,4-dihydroxyphenyl)- 4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, 2,4-bis (2-hydroxy-4-propyloxyphenyl) -6
-(2,4-dimethylphenyl) -1,3,5-triazine, 2- (2-hydroxy-4-dodecyloxyphenyl) -4,6-bis (2,4-dimethylphenyl)-
1,3,5-triazine and the like can be mentioned.

The metal deactivator which may be used in the present invention is not particularly limited. For example, N, N'-diphenyloxalyldiamide, N-sartilal-N'-
Salicyloylhydrazine, N, N'-bis (salicyloyl) hydrazine, N, N'-bis (3,5-di-ter
t-butyl-4-hydroxyphenylpropionyl) hydrazine, 3-salicyloylamino-1,2,3-triazole, bis (benzylidene) oxalyl hydrazide, isophthalloyl dihydrazide, N, N'-bis-
Salicyloyl oxalyl dihydrazide, N, N'-bis-salicyloyl-thiopropionyl dihydrazide and the like can be mentioned.

Examples of the binder include starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer and the like. Latex polymers such as a water-soluble polymer, a styrene-butadiene copolymer, an acrylonitrile-butadiene copolymer, and a methyl acrylate-butadiene copolymer are exemplified.

The thermosensitive recording medium of the present invention is used in the form of a layer on an arbitrary support, and any known support can be used as the support. For example, paper, especially neutral paper, plasticizer paper coated with synthetic resin on one or both sides of the paper, various synthetic papers, cellulose derivative films such as cellulose triacetate film, polyester films such as polyethylene terephthalate,
Examples include a poly-α-olefin film such as a polystyrene film, polyethylene, and polypropylene, or a laminate thereof.

Prior to forming the heat-sensitive recording layer of the present invention, an undercoat layer can be formed. As the undercoat layer, known undercoat materials such as gelatin, synthetic polymer latex, and nitrocellulose (see JP-B-60-27590, column 4, line 24 to column 5, line 16) can be used.

Further, a protective layer can be provided on the heat-sensitive recording layer of the present invention, if necessary. Specific examples of the polymer used for the protective layer include methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, starches, gelatin, gum arabic, casein, and styrene.
Maleic anhydride copolymer hydrolyzate, styrene-maleic anhydride copolymer half ester hydrolyzate, polyvinyl alcohol, silica-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, polyacrylamide derivative, polyvinylpyrrolidone, sodium polystyrene sulfonate, alginic acid Examples include water-soluble polymers such as sodium and water-insoluble polymers such as styrene-butadiene rubber latex, acrylonitrile-bradiene rubber latex, methyl acrylate-butadiene rubber latex, and polyvinyl acetate emulsion. The protective layer has improved matching with the thermal head during thermal printing,
Pigments, metal soaps, waxes, crosslinking agents, and the like are added for the purpose of improving the water resistance of the protective layer. In the protective layer,
A surfactant, a polymer electrolyte or the like for preventing electrification of the heat-sensitive recording material may be added.

When a multi-color heat-sensitive recording material is formed by providing a heat-sensitive layer on a multilayer, a layer having the same composition as the protective layer may be provided as an intermediate layer. As the intermediate layer, in particular,
As disclosed in No. 301282, it is preferable to use a layer obtained by gelling a water-soluble polyanionic polymer with a polyvalent cation.

The alkylidene bis- (4) used in the present invention
-Hydroxycoumarin) derivative is an alkylidenebis-
According to a general method for producing coumarins, for example, it can be obtained by reacting a corresponding alkyl aldehyde or aralkyl aldehyde with a corresponding 4-hydroxy coumarin in an organic solvent such as an alcohol by heating.

[0030]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by these.

Synthesis Example 3,3'-propylidenebis-
Synthesis Example of (4-hydroxycoumarin) 40.0 parts by weight of 4-hydroxycoumarin and 8.4 parts by weight of propionaldehyde are added to 500 parts by weight of ethanol, and the mixture is refluxed for 6 hours. After completion of the reaction, ethanol is recovered, and the residue is recrystallized from 250 parts by weight of 50% methanol to obtain 31.5 parts by weight of a target bis compound. 144-145 ° C

Example 1 (Preparation of Thermal Recording Paper) Dye Dispersion (Solution A) 2-anilino-3-methyl-6-dibutylaminofluoran 6.0 g Polyvinyl alcohol 20% aqueous solution 30.0 g Calcium carbonate 10.5 g 53.5 g water Developer dispersion (Solution B) 3,3'-propylidenebis- (4-hydroxycoumarin) 6.0 g 20% aqueous solution of polyvinyl alcohol 30.0 g Calcium carbonate 10.5 g Water 53.5 g Mixture of the above composition Are sufficiently ground with a sand grinder to prepare respective dispersions of Solution A and Solution B.
The coating solution was prepared by mixing parts by weight and 1 part by weight of the solution B. The coating liquid was applied to white paper using a wire rod (No. 12), dried and calendered to prepare a thermosensitive recording paper.

Comparative Example 1 Instead of 3,3'-propylidenebis- (4-hydroxycoumarin) in the developer dispersion, 4-hydroxy-4 '
Thermal recording paper was made using isopropoxydiphenyl sulfone.

Example 2 (Plasticizer resistance test of thermal recording paper) For each of the thermal recording papers produced in Example 1 and Comparative Example 1, a thermal paper coloring tester (TH-PMD type, manufactured by Okura Electric Co., Ltd.) was used. The color used under the conditions of a printing voltage of 26 V and a pulse width of 1.8 ms was infiltrated into di (2-ethylhexyl) phthalate. In this state, a plasticizer resistance test was performed by leaving the device for 40 hours in an atmosphere at 25 ° C. The color density before and after the test was measured using Macbeth reflection densitometer RD-514 (filter used: # 1)
06). The results are shown in Table 1.

[0035]

Table 1 Thermal recording paper Colored image area Measurement value before test Measurement value after plasticizer resistance test (residual rate) Example 1 1.07 0.88 (82%) Comparative Example 1 1.06 0.12 (11%)

In the above table, the larger the measured value after the test, the higher the color density. The larger the value of the residual ratio, the less the fading. These results indicate that the heat-sensitive recording paper using the compound of the present invention as a color developer has extremely excellent plasticizer resistance in a color image. In calculating the residual ratio, the measured value of the image density after the test was divided by the measured value before the test to obtain a percentage.

[0037]

According to the present invention, a novel alkylidenebis-coumarin derivative can be provided. (2) The alkylidene bis-coumarin derivative is useful as a developer in a thermosensitive recording medium and can also be used as an image storage stabilizer. (3) The heat-sensitive recording material of the present invention has extremely excellent image storage stability such as plasticizer resistance and oil resistance.

Claims (3)

[Claims] 1. A compound of the general formula (1) (Wherein R ¹ is a group selected from the group consisting of linear or branched alkyl groups or aralkyl groups;
² is a group selected from the group consisting of a hydrogen atom, a hydroxy group, a linear or branched alkyl group, an alkoxy group and a dialkylamino group. ) An alkylidene bis-coumarin derivative represented by the formula: 2. A developer for a color-forming dye comprising the alkylidene bis-coumarin derivative according to claim 1. 3. A heat-sensitive recording material comprising the alkylidene bis-coumarin derivative according to claim 1.