JPH0251748B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material with improved color development. Heat-sensitive recording materials using an electron-donating colorless dye and an electron-accepting compound are disclosed in Japanese Patent Publications No. 14039-1982, Japanese Patent Publication No. 4160-43-1972, and the like. The minimum performance that such a heat-sensitive recording material should have is (1) sufficient color density and color development sensitivity, (2) no fogging (color development phenomenon during storage before use), and (3) The coloring material must have sufficient fastness after coloring, but currently no product has been obtained that completely satisfies these requirements. Particularly in recent years, as thermal recording systems have become faster, research on the above (1) has been intensively conducted. One way to do this is to raise the melting point of the electron-accepting compound itself from 60 to 100°C. However, it is difficult to control the melting point of phenolic compounds, which are currently the most widely used electron-accepting compounds, and the phenolic compounds themselves are expensive and impractical. Other methods include the combined use of organic acids and phenolic compounds as electron-accepting substances, as described in Japanese Patent Publications No. 49-17748 and No. 51-39567;
Alternatively, it is described that a polyvalent metal salt of a compound having an alcoholic hydroxyl group is used. Furthermore, Japanese Patent Publication No. 51-29945 describes the use of a copolymer of hydroxyethyl cellulose and maleic anhydride. Furthermore, JP-A-49-34842, JP-A-49-115554, JP-A-50-149353, JP-A-52
−106746, JP-A No. 53-5636, JP-A-53-
No. 11036, JP-A-55-48751 and JP-A-56-
72996 etc., nitrogen-containing organic compounds such as thioacetanilide, phthalonitrile, acetamide, di-β-naphthyl-p-phenylenediamine, fatty acid amide, acetoacetanilide, diphenylamine, benzamide, carbazole, etc. or 2,3- It is described that thermofusible substances such as di-m-tolylbutane and 4,4'-dimethylbiphenyl, or carboxylic acid esters such as dimethyl isophthalate, diphenyl phthalate, and dimethyl terephthalate are added as sensitizers. has been done. However, heat-sensitive recording materials produced using these methods are insufficient in color density and color sensitivity. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a heat-sensitive recording material which has sufficient color density and color sensitivity and satisfies other requirements. The present inventors have discovered a compound completely different from these amide compounds, aromatic amines, aromatic hydrocarbons, or carboxylic acid esters, that is, aryl ethers, which have never been studied in the past, and which have a specific melting point range. The present inventors have discovered that the material exhibits unexpectedly favorable performance and have completed the present invention. The object of the present invention was achieved by a heat-sensitive recording material characterized by containing an electron-donating colorless dye, an electron-accepting compound, and a divalent phenol derivative represented by the following general formula () and having a melting point of 40 to 150°C. . In the above formula, R ₁ is an alkyl group or an aralkyl group,
R ₂ represents a hydrogen atom, an alkyl group, an aralkyl group, an aryl group or an alkylcarbonyl group,
The groups represented by R ₁ and R ₂ may contain an ether bond or an ester bond. In the above general formula (), the benzene ring may have a substituent, and examples of the substituent include an alkyl group, an aryl group, and a halogen atom. In the above general formula (), the alkyl group represented by R ₁ or R ₂ preferably has 1 to 20 carbon atoms, and the aralkyl group represented by R ₁ or R ₂ preferably has 7 to 20 carbon atoms, and R ₂ The alkylcarbonyl group represented by is preferably one having 2 to 20 carbon atoms. In the divalent phenol derivative represented by the general formula () according to the present invention, the substituent represented by OR ₂ may be substituted at any of the ortho, meta, and para positions with respect to the OR ₁ group, but especially the para-substituted Preferably. Among the above phenol derivatives, those having a melting point of 40°C to 150°C are preferred, particularly 50°C to 120°C.
It is preferable to have a melting point of . The heat-sensitive recording material containing the divalent phenol derivative represented by the general formula () according to the present invention has sufficient color development density and color development sensitivity, and has little deterioration in color development sensitivity over time and fog, and has good fastness of the color former after color development. is also sufficient. Next, specific examples of the divalent phenol derivative according to the present invention will be shown, but the present invention is not limited thereto. (1) p-benzyloxyphenylhexyl ether (2) p-benzyloxyphenyl octyl ether (3) p-benzyloxyphenyl decyl ether (4) p-anisylbenzyl ether (5) p-anisyl tetra Decyl ether (6) p-anisyl dodecyl ether (7) m-benzyloxyphenyl decyl ether (8) m-benzyloxyphenyl dodecyl ether (9) m-benzyloxyphenyl tetradecyl ether (10) m- Benzyloxyphenylstearyl ether (11) 1,3-bis-(2-benzoyloxyethoxy)benzene (12) m-anisylbenzyl ether (13) m-anisylstearyl ether (14) 3-t-butyl- 4-Hydroxyphenylbenzyl ether (15) 3-t-butyl-1,4-bisbenzyloxybenzene (16) 3-t-butyl-4-n-butyloxyphenylbenzyl ether (17) 3-t- Octyl-4-hydroxyphenylbenzyl ether (18) 3-t-octyl-1,4-bisbenzyloxybenzene (19) 3-t-octyl-4-n-butyloxyphenylbenzyl ether (20) 3, 6-di-t-butyl-1,4-bisbenzyloxybenzene (21) 1-methoxy-4-myristoyloxybenzene (22) 1-methoxy-4-capryloyloxybenzene (23) Resorcin dibenzyl ether (24) ) 1-Butyloxy-4-myristoyloxybenzene (25) 1-butyloxy-4-capryloyloxybenzene (26) 1-benzyloxy-4-α-phenoxypropionyloxybenzene (27) 1-benzyloxy-4 -Propionyloxybenzene (28) 1-benzyloxy-4-butyryloxybenzene (29) 1-benzyloxy-4-capryloyloxybenzene (30) 2,4-di-t-butyl-5-hydroxyanisole ( 31) 2,4-di-t-hexyl-5-hydroxyanisole, etc. Examples of the electron-donating colorless dye used in the present invention include triarylmethane compounds, diphenylmethane compounds, xanthene compounds, thiazine compounds, and spiropyran compounds. To illustrate some of these, triarylmethane compounds include 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (i.e., crystal violet lactone);
3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3
-(1,3-dimethylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3
-(2-methylindol-3-yl)phthalide,
etc., and diphenylmethane compounds include:
There are 4,4'-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl-leucoauramine, N-2,4,55-trichlorophenylleucoauramine, and xanthene compounds include rhodamine-B. -anilinolactam, rhodamine (p-nitroanilino)lactam, rhodamine B (p-chloroanilino)lactam, 2-
Dibenzylamino-6-diethylaminofluorane, 2-anilino-6-diethylaminofluorane, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6
-cyclohexylmethylaminofluorane, 2-
o-chloroanilino-6-diethylaminofluorane, 2-m-chloroanilino-6-diethylaminofluorane, 2-(3,4-dichloroanilino)-6-diethylaminofluorane, 2-octylamino-6-diethylaminofluorane ,2
-dihexylamino-6-diethylaminofluorane, 2-m-trichloromethylanilino-6-
Diethylaminofluorane, 2-butylamino-
3-chloro-6-diethylaminofluorane, 2
-ethoxyethylamino-3-chloro-6-diethylaminofluorane, 2-anilino-3-chloro-6-diethylaminofluorane, 2-diphenylamino-6-diethylaminofluorane, 2
-anilino-3-methyl-6-diphenylaminofluorane, 2-phenyl-6-diethylaminofluoran, etc. Thiazine compounds include benzoylleucomethylene blue, p-nitrobenzylleucomethylene blue, etc. The compounds include 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3'-dichloro-spiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-
Examples include methyl-naphtho-(3-methoxy-benzo)spiropyran and 3-propyl-spiro-dibenzopyran. These may be used alone or in combination. Examples of electron-accepting compounds include phenol compounds, organic acids or their metal salts, oxybenzoic acid esters, etc. Phenol compounds in particular have melting points near the desired recording temperature, so it is necessary to use compounds with particularly low melting points. It is preferable to use it because there is no or only a small amount is needed, for example,
It is described in detail in No.-14039, Special Publication No. 51-29830, etc. Specifically, 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, methyl-4-hydroxybenzoate, 2,2′-dihydroxybiphenyl, 2,2
-bis(4-hydroxyphenyl)propane (bisphenol A), 4,4'-isopropylidene bis(2-methylphenol), 1,1-bis-(3
Examples include -chloro-4-hydroxyphenyl)cyclohexane, 1,1-bis-(3-chloro-4-hydroxyphenyl)-2-ethylbutane, and 4,4'-secondary isobutylidene diphenol. The heat-sensitive recording material according to the present invention has the general formula ()
It contains one or more types of divalent phenol derivatives represented by the formula below, and a specific example of its production method will be described next. The most common manufacturing method for heat-sensitive recording materials is
The above-mentioned colorless electron-donating dye and electron-accepting compound are each separately dispersed in a 1-10% by weight water-soluble polymer solution using a ball mill, sand mill, etc., and then mixed. , talc, calcium carbonate, and other inorganic pigments are added to create a coating liquid. If necessary, a paraffin wax emulsion, a latex binder, a sensitivity improver, a metal soap, an ultraviolet absorber, etc. can be added thereto. Coating fluids are most commonly applied onto base paper. Generally, the coating amount is 2 to 10 g/m ² as a solid content, with the lower limit determined by the density during color development by heating, and the upper limit determined mainly by economic constraints. Examples will be shown below, but the present invention is not limited only to these examples. Example (1) Preparation of Samples 1 to 7 5 g of the electron-donating colorless dye shown in Table 1 was
% polyvinyl alcohol (Saponity number: 99%, degree of polymerization: 1000) and 50 g of an aqueous solution was dispersed overnight in a ball mill. On the other hand, 20 g of the electron-accepting compounds (phenols) shown in Table 1 were similarly dispersed with 200 g of a 5% polyvinyl alcohol aqueous solution in a ball mill overnight, and then 20 g of the electron-accepting compounds shown in Table 1 were dispersed overnight.
20g of a polyvinyl alcohol derivative was dispersed with a 5% polyvinyl alcohol aqueous solution in a ball mill overnight, and after mixing these three types of dispersions, 20g of kaolin (diyodia kaolin) was added and dispersed well, followed by a 50% paraffin wax emulsion. Dispersion (Chukyo Yufat Cellosol #428) 5
g was added to prepare a coating liquid. The coating liquid was applied onto a base paper having a basis weight of 50 g/m ² so that the solid content was 6 g/m ² ,
After drying at 60° C. for 1 minute, a coated paper was obtained by supercalendering at a linear pressure of 60 KgW/cm. Coated paper is heated by facsimile
Color was developed by heating at 35 mJ/cm ² and the color density was determined. The results are shown in Table 1. (2) Preparation of Comparative Samples 1 to 2 A similar test was conducted using the exact same formulation as used to prepare Samples 1 to 5, except that only the divalent phenol derivative was replaced with a compound other than the present invention shown in Table 1. Ivy. The results are also shown in Table 1. It can be seen from Table 1 that the recording material according to the invention clearly has a high sensitivity. Furthermore, when the fog density in Table 1 exceeds 0.13, the commercial value is significantly reduced. From this point of view as well, it was found that the electron-accepting compound of the present invention provides an extremely excellent heat-sensitive recording sheet.

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Claims (1)

[Scope of Claims] 1. Electron-donating colorless dye, electron-accepting compound, and a melting point of 40 to 150°C represented by the following general formula ()
A heat-sensitive recording material characterized by containing a divalent phenol derivative of In the above formula, R ₁ is an alkyl group or an aralkyl group,
R ₂ represents a hydrogen atom, an alkyl group, an aralkyl group, an aryl group or an alkylcarbonyl group,
The groups represented by R ₁ and R ₂ may contain an ether bond or an ester bond.