JP2832207B2 - Thermal recording material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat-sensitive recording material, and more particularly to a high-sensitivity heat-sensitive recording material having excellent heat response.

[Conventional technology]

The heat-sensitive recording material generally comprises a support provided with a heat-sensitive recording layer mainly composed of an electron-donating, usually colorless or pale-colored leuco dye and an electron-accepting developer. When heated with light or the like, the leuco dye and the color developer react instantaneously to obtain a recorded image, which is disclosed in JP-B-43-4160 and JP-B-45-14039. Such a heat-sensitive recording material has the advantages that recording can be obtained with a relatively simple device, maintenance is easy, and there is no noise.The recording device for measurement, facsimile, printer, and computer terminal It is used in a wide range of fields, such as automatic ticket vending machines such as machines, labels, and tickets. In particular, in the case of facsimile machines, the demand for the heat-sensitive system has been greatly increased, and the speed has been increased to reduce transmission costs. In response to such speeding up of the facsimile, it has been required to increase the sensitivity of the heat-sensitive recording material.

Since the accelerated facsimile sends and receives A4 standard documents in a few seconds to 20 seconds, the current flowing through the facsimile thermal head is also a very short cycle of less than a few milliseconds, and the thermal energy generated by this Is transmitted to the heat-sensitive recording sheet to cause an image forming reaction.

In order to perform an image forming reaction with the thermal energy transmitted in such a short time, it is necessary that the thermal recording material has excellent thermal responsiveness. In order to increase the thermal response, the compatibility between the developer and the leuco dye must be improved. For this, a sensitizer is used if necessary. When the sensitizer itself is melted by the transmitted thermal energy, it has a function of dissolving or encapsulating a nearby leuco dye and a developer to promote a color-forming reaction. Improving is also one method of increasing the sensitivity of a heat-sensitive recording material.

As such a method, waxes are disclosed in JP-A-48-19231, JP-A-49-34842 and JP-A-50-149353.
JP-A-52-106746 and JP-A-53-5636 disclose nitrogen-containing compounds, carboxylate esters, and the like.
No. 64593, JP-A-58-87094, etc., naphthol derivatives, JP-A-57-64592, JP-A-57-185187, JP-A-57-191089, JP-A-58-110289 Publications include naphthoic acid derivatives, JP-A-57-148688, JP-A-57-1824.
No. 83, JP-A-58-112788, JP-A-58-162379, etc., benzoate derivatives, JP-A-60-122193, parabenzylbiphenyl, JP-A-61-272189. The publication discloses 4-allyloxybiphenyl and the like,
Japanese Patent No. 56588 discloses diphenoxyethanes disclosed in JP-A-61-2.
42884 discloses sulfides, JP-A-62-48588,
JP-A-62-53876 discloses cinnamic acid esters,
JP-A-63-21181 discloses adding a styrene derivative.

[Problems to be solved by the invention]

However, it is difficult to say that the heat-sensitive recording materials manufactured based on these methods are still sufficient in terms of color sensitivity and color density.

Therefore, the present invention has sufficient color sensitivity and color density,
An object of the present invention is to provide a heat-sensitive recording material suitable for high-speed recording.

[Means for solving the problem]

According to the present invention, a heat-sensitive recording material containing a colorless or pale-colored leuco dye and a color developer which causes the leuco dye to develop a color when heated, further comprises a compound represented by the following general formula. Is provided.

(Wherein R ¹ and R ² represent a hydrogen atom, a lower alkoxy group, a halogen atom, an acyloxy group, an aralkyloxy group or an aryloxy group, respectively, provided that both R ¹ and R ² are hydrogen atoms R ³ represents an alkyl group, an aralkyl group or an aryl group.) That is, the heat-sensitive recording material of the present invention contains a compound represented by the above general formula as a sensitizer, thereby providing color sensitivity and color development. It has a sufficient concentration and high sensitivity with excellent thermal response.

The compound represented by the general formula used in the present invention has a melting point of 50 from the viewpoint of storage stability and sensitivity as a heat-sensitive recording material.
-150 ° C is preferred, and 70-130 ° C is particularly preferred. The preferred specific examples of the compound represented by the above general formula of the present invention and the melting points thereof are shown below, but the present invention is not limited to these. Compound Nos. 2 to 8, 10,
20, 22, 26 and 28 are reference examples The compound of the above general formula can be easily obtained by a known method.

The sensitizer according to the present invention usually contains 5% by weight of the developer.
The above is added. The preferred amount is 10-400% by weight,
Particularly, 20 to 300% by weight is preferable. If the amount is less than 5% by weight, the effect of improving sensitivity is not sufficient. If the amount is more than 400% by weight, economically disadvantageous cases may occur, and the amount of the heat-fusible substance increases. Color density cannot be obtained.

The leuco dye used in the present invention is applied alone or as a mixture of two or more kinds. As such a leuco dye, those applied to this kind of heat-sensitive material are arbitrarily applied, for example, triphenyl dye. Leuco compounds of dyes such as methane, fluoran, phenothiazine, auramine and spiropyran are preferably used. Specific examples of such leuco dyes include, for example, 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-dimethyl Aminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chloro Fluoran, 3-dimethylamino-5,7-dimethylfluoran, 3-N-methyl-N-isobutyl-6-methyl-7-
Anilinofluoran, 3-N-ethyl-N-amino-6-methyl-7-anilinofluoran, 3-diethylamino-7-chlorofluoran, 3-dielmamino-7-methylfluoran, 3-diethylamino- 7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluoran, 3- (Np-tolyl-N-ethylamino) -6-methyl-7-anilinofluoran, 3- Pyrrolidino-6-methyl-7-anilinofluoran, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluoran, 2- {3,6-bis (diethylamino) -9- (O-chloroanilino) lactam xanthylbenzoate, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluoran, 3-diethy Amino-7- (o-chloroanilino) fluoran, 3-dibutylamino-7- (o-chloroanilino) fluoran, 3-N-methyl-N-isoamylamino-6-methyl-7-anilinofluoran, 3-N -Methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (2 ', 4' −
Dimethylanilino) fluoran, 3- (N, N-diethylamino) -5-methyl-7-
(N, N-dibenzylamino) fluoran, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-
Pyrirospiran, 6'-bromo-3'-methoxy-benzoindolino-
Pyrirospiran, 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) fluoran, 3-pyrrolidino-7-trifluoromethylanilinofluoran, 3-diethylamino-5-chloro-7- (N -Benzyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluoran, 3-diethylamino-5-chloro-7- (α-phenylethylamino) fluoran, 3 -(N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluoran, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluoran, 3-diethylamino-5-methyl-7- (α -Phenylethylamino) fluoran, 3-diethylamino-7-piperidi Fluoran, 2-chloro-3-(N-Mechirutoruijino) -7-
(Pn-butylanilino) fluoran, 3- (N-methyl-N-isopropylamino) -6
Methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluoran, 3,6-bis (dimethylamino) fluorenespiro (9,
3 ')-6'-dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino)-
5,6-benzo-7-α-naphthylamino-4′-bromofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-N-ethyl-N- (2-ethoxypropyl) amino -6-methyl-7-anilinofluoran, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluoran and the like.

Examples of the developer used in the present invention include various electron-accepting compounds that cause the leuco dye to develop a color when heated, such as phenolic compounds, thiophenolic compounds, thiourea derivatives, organic acids and metal salts thereof. It is preferably applied, and specific examples thereof include the following.

4,4'-isopropylidenebisphenol, 4,4'-isopropylidenebis (o-methylphenol), 4,4'-secondarybutylidenebisphenol 4,4'-isopropylidenebis (2-tert-butylphenol), 4 4,4'-cyclohexylidenediphenol, 4,4'-isopropylidenebis (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'-diphenolsulfone, 4,4'-isopropoxy-4'-hydroxydiphenylsulfone, 4- Benzyloxy-4'-hydroxydiphenylsulfone, 4,4'-diphenolsulfoxide, isopropyl P-hydroxybenzoate, benzyl P-hydroxybenzoate, benzyl protocatechuylate, 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, salicyl-0-chloroanilide, 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'-diphenolsulfone, 3,3'-diallyl-4,4'-di Phenol sulfone, α, α-bis (4-hydroxyphenyl) -α-methyltoluene, an antipyrine complex of zinc thiocyanate, Tiger bromo bisphenol A, tetrabromobisphenol S, and the like.

In the present invention, various conventional binders can be appropriately used to supply and support the leuco dye, the developer and the sensitizer on a support. For example, polyvinyl alcohol, starch and derivatives thereof, methoxycellulose,
Hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, cellulose derivatives such as ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylate copolymer,
Water solubility of acrylamide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein, etc. In addition to the molecule, polyvinyl acetate,
Emulsions such as polyurethane, polyacrylate, polymethacrylate, vinyl chloride / vinyl acetate copolymer, ethylene / vinyl acetate copolymer, styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer, etc. Latex and the like.

Further, in the present invention, together with the leuco dye, the developer and the sensitizer, if necessary, further auxiliary additives commonly used in this type of heat-sensitive recording material, for example, fillers, lubricants,
Dispersants, ultraviolet absorbers, surfactants, fluorescent dyes and the like can be used in combination. In this case, as the filler, for example,
Calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay,
In addition to inorganic fine powders such as talc, surface-treated calcium and silica, organic fine powders such as urea-formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin can be mentioned. As the lubricant, for example, in addition to higher fatty acids or their esters, amides or metal salts,
Various waxes are included.

In the present invention, a layer containing a filler, a binder and the like can be provided as an undercoat layer between the support and the thermosensitive coloring layer, if necessary. In this case, specific examples of the filler and the binder include those similar to those exemplified in the thermosensitive coloring layer.

Further, the heat-sensitive recording material of the present invention can be provided with a protective layer on the heat-sensitive coloring layer for the purpose of improving the matching property with a thermal head or the like and further improving the storage stability of the recorded image. In this case, the above-mentioned fillers, binders and surfactants can also be used as components constituting the protective layer.

The heat-sensitive recording material of the present invention is produced, for example, by applying a heat-sensitive color-forming layer-forming coating solution containing the above-described components on a suitable support such as paper, synthetic paper, or plastic film, and drying. .

〔The invention's effect〕

The heat-sensitive recording material of the present invention has high color sensitivity and color density, is suitable for high-speed recording, and has high thermal response and high sensitivity.

〔Example〕

Next, the present invention will be described in more detail by way of examples. The percentages shown below are based on weight.

Reference Example 1 2-benzoyloxycinnamic acid methyl ester (trans
-From) Synthesis of Compound Specific Example No. 1 17.8 g of trans-0-coumaric acid methyl ester was dissolved in 200 ml of anhydrous benzene, and 20 ml of anhydrous pyridine was added thereto and stirred. Further, 16.9 g of benzoyl chloride was slowly dropped,
After the dropwise addition, the mixture was refluxed for 1 hour. Next, the reaction solution is poured into 300 ml of an ice-cooled 1N aqueous hydrochloric acid solution and stirred for a while. After standing for a while, the organic layer is separated, washed with a 5% aqueous sodium carbonate solution, washed well with water, and dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure, and the residue was recrystallized from a mixture of cyclohexane and benzene.
I got 87-87.5 ° C.

Reference Example 2 4-chlorocinnamic acid benzyl ester [Compound specific example N
o.33] 18.3 g of P-chlorocinnamic acid and benzyl bromide 18.
8 g was dissolved in 200 ml of dioxane by heating, 14.7 g of a 40% aqueous potassium hydroxide solution was added dropwise over 15 minutes with stirring, and the mixture was refluxed for 5 hours. Then, the solvent is distilled off under reduced pressure, ethyl acetate and water are added to the residue, and the mixture is separated. The organic layer is washed with a 5% aqueous solution of sodium carbonate, washed well with water, and dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure, and the residue was recrystallized from cyclohexane to obtain 21.4 g of the desired product as white crystals. 74.5 melting point
~ 75.5 ° C.

Reference Example 3 Synthesis of 4-methoxycinnamic acid-2'-methoxyphenyl ester [Compound Specific Example No. 34] 17.8 g of P-methoxycinnamic acid, 24.9 g of o-methoxyphenol and 0.1 g of methanesulfonic acid were xylene anhydride. 200ml
, And the mixture was boiled under reflux for 12 hours. Then, the reaction solution is poured into 160 ml of a 5% aqueous sodium hydroxide solution and stirred for a while. After standing for a while, the organic layer is separated, washed well with water, and dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure, and the residue was recrystallized from a mixed solution of cyclohexane and benzene to obtain 21.1 g of the target substance as white crystals. 102-103 ° C.

Reference Example 4 Synthesis of 4-benzoyloxycinnamic acid-4'-chlorobenzyl ester [Compound Specific Example No. 38] 28.9 g of P-coumaric acid-P-chlorobenzyl ester was dissolved in 200 ml of anhydrous benzene, and anhydrous 20 ml of pyridine
Was added and stirred. Further, 16.9 g of benzoyl chloride was slowly added dropwise, and after the addition, the mixture was refluxed for 1 hour. Then, the mixture is poured into 300 ml of an ice-cooled 1N aqueous hydrochloric acid solution and stirred for a while. After standing for a while, the organic layer was separated, washed with a 5% aqueous sodium carbonate solution, washed well with water, and dried over anhydrous sodium sulfate. Next, the solvent was distilled off under reduced pressure, and the residue was recrystallized from a mixed solution of cyclohexane and benzene to obtain 31.8 g of the target substance as white crystals. 95.5-96 ° C.

Example 1 20 g of 3-diethylamino-6-methyl-7-anilinofluoran was dispersed in a ball mill together with 80 g of a 1% aqueous solution of polyvinyl alcohol. On the other hand, 50 g of 2,2-bis (4-hydroxyphenyl) propane was dispersed in a ball mill together with 200 g of a 1% aqueous solution of polyvinyl alcohol, and 50 g of the compound of Reference Example 1 was further dispersed in 200 g of a 1% aqueous solution of polyvinyl alcohol.
And dispersed similarly.

After mixing these three dispersions, the calcium carbonate
125 g of a 40% dispersion was added, 40 g of a 25% dispersion of zinc stearate, and 300 g of a 10% aqueous polyvinyl alcohol solution were further added, followed by sufficient stirring to obtain a coating liquid. The coating liquid is applied to a base paper having a basis weight of 48 g / m ^{2 so} as to have a solid content of 6 g / m ² and dried.
It was processed with a super calender to obtain a heat-sensitive recording material of the present invention.

Example 2 A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1, except that 50 g of the compound of Reference Example 2 was used instead of 50 g of the compound of Reference Example 1 used in Example 1.

Example 3 A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1, except that 50 g of the compound of Reference Example 3 was used instead of 50 g of the compound of Reference Example 1 used in Example 1.

Example 4 A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1, except that 50 g of the compound of Reference Example 4 was used instead of 50 g of the compound of Reference Example 1 used in Example 1.

Comparative Example 1 N instead of 50 g of the compound of Reference Example 1 used in Example 1
A comparative heat-sensitive recording material was obtained in the same manner as in Example 1, except that 50 g of -hydroxymethylstearic acid amide was used.

Comparative Example 2 A comparative thermosensitive recording material was obtained in the same manner as in Example 1, except that the dispersion of the compound of Reference Example 1 was omitted.

Evaluation The thermal recording materials obtained in Examples and Comparative Examples were
Using a thermal facsimile tester (Matsushita Electronic Components Co., Ltd.), applied pulse width of 1.0 and 1.2 milliseconds, applied voltage of 1600 V
The image was printed under the following conditions, and the optical density of the obtained image was measured using a Masbeth densitometer RD-918. Table 1 shows the results.

From the results shown in Table 1, it can be seen that the heat-sensitive recording material of the present invention has high thermal response and high sensitivity.

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Claims (1)

(57) [Claims] 1. A heat-sensitive recording material containing a generally colorless or pale-colored leuco dye and a color developer which causes the leuco dye to develop a color when heated and contacted, further comprising a compound represented by the following general formula: Heat-sensitive recording material. (Wherein R ¹ and R ² represent a hydrogen atom, a lower alkoxy group, a halogen atom, an acyloxy group, an aralkyloxy group or an aryloxy group, respectively, provided that both R ¹ and R ² are hydrogen atoms R ³ represents an alkyl group, an aralkyl group or an aryl group.)