JPH0528190B2 - - Google Patents

Description

[Detailed description of the invention]

(A) Industrial Application Field The present invention relates to a highly sensitive recording material with excellent thermal responsiveness. (B) Prior art A heat-sensitive recording material generally has a heat-sensitive recording layer on a support, the main components of which are an electron-donating, usually colorless or light-colored dye precursor and an electron-accepting color developer. By heating with a head, thermal pen, laser light, etc., the dye precursor and developer react instantly.
This allows recorded images to be obtained, and is designated as Special Publication No. 43-4160.
It is disclosed in Japanese Patent Publication No. 14039/1983. Such heat-sensitive recording materials have the advantages of being able to record with relatively simple equipment, being easy to maintain, and producing no noise, and are suitable for measurement recorders, facsimile machines, printers, and computer terminals. ,
It is used in a wide range of fields such as labels, ticket vending machines, etc. Particularly in facsimile, the demand for heat-sensitive methods is increasing rapidly, and speeds are being increased to reduce transmission costs. In response to such increased speed of facsimile, there has been a demand for higher sensitivity of heat-sensitive recording materials. Since high-speed facsimile machines can receive and send standard A4 documents in a few seconds to 20 seconds, the current that flows through the facsimile thermal head is repeated over a very short period of time, less than a few milliseconds, and the thermal energy generated by this is extremely short. is transmitted to a heat-sensitive recording sheet to cause an image-forming reaction. In order to carry out an image forming reaction using thermal energy transmitted in such a short time, it is necessary to use a heat-sensitive recording material with excellent thermal responsiveness. In order to increase the thermal reactivity, it is necessary to improve the compatibility between the color developer and the dye precursor. A sensitizer is used for this purpose if necessary. When the sensitizer itself melts due to the transferred thermal energy, it dissolves or encapsulates nearby dye precursors and color developers to promote the color reaction, so the thermal responsiveness of the sensitizer increases. Improving the compatibility with dye precursors and color developers is also one method for increasing the sensitivity of heat-sensitive recording materials. As such a method, waxes are used in JP-A-48-19231, JP-A-49-34842 and JP-A-Sho.
No. 50-149353, JP-A-52-106746, JP-A-53-
5636, etc., nitrogen-containing compounds, carboxylic acid esters, etc. are described in JP-A-57-64593, JP-A-58-
No. 87094 discloses naphthol derivatives in JP-A-57-
No. 64592, JP-A-57-185187, JP-A-57-
191089 and JP-A-58-110289 disclose naphthoic acid derivatives, JP-A-57-148688 and JP-A-57-
No. 182483, JP-A No. 112788, JP-A-58-
Publication No. 162379 discloses the addition of a benzoic acid ester derivative. However, the heat-sensitive recording materials produced using these methods are still unsatisfactory in terms of color density and color sensitivity. (C) Purpose of the Invention The present inventors investigated various sensitizers with the aim of obtaining a highly sensitive heat-sensitive recording material with further excellent thermal responsiveness. (D) Structure of the Invention In a heat-sensitive recording material containing a color developer that reacts with a normally colorless or light-colored dye precursor upon heating to cause the dye precursor to develop color, a compound represented by the following general formula is used as a sensitizer. By containing this, a highly sensitive heat-sensitive recording material with excellent thermal responsiveness could be obtained. general formula (However, X represents hydrogen or OR'. R and R' represent a substituted or unsubstituted alkynyl group.) Specific examples of the compound represented by the above general formula include those shown below. The compound of the above general formula can be easily obtained by a known method. The sensitizer according to the present invention is usually added in an amount of 5% by weight or more based on the color developer. Preferred amounts are 10-400% by weight, particularly 20-300% by weight. If the amount added is less than 5% by weight, the effect of improving sensitivity will not be sufficient, and if the amount added is more than 400% by weight, it may be economically disadvantageous. The main components used in the heat-sensitive recording material of the present invention will be specifically explained below, but are not limited thereto. As a dye precursor, triphenylmethane type,
Examples include fluoran-based, diphenylmethane-based, thiazine-based, and spiropyran-based compounds. For example, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1
-ethyl-2-methylindol-3-yl)-
4-Azaphthalide, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3-(N-cyclohexylamino)-7-methylfluorane, 3-diethylamino-7-methyl Fluoran, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-6-methyl-7-dibenzylaminofluorane, 3-(N-ethyl -N
-p-toluidino)-7-anilinofluorane,
3-diethylamino-7-(o-chloroanilino)
Fluoran, 3-dibutylamino-7-(o-chloroanilino)fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-
(N-ethyl-N-p-toluidino)-6-methyl-7-anilinofluorane, 3-(N-methyl-
N-cyclohexylamino)-6-methyl-7-
Anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-
6-Methyl-7-anilinofluorane, 3-diethylamino-7-(m-trifluoromethylanilino)fluorane, 3-(N-ethyl-N-isopentylamino)-6-methyl-7-anilino Fluoran, 3-diethylamino-6-methyl-7
-(p-phenetidino)fluoran, 3-dibutylamino-7-(o-fluoroanilino)fluoran, and the like. As the color developer, acidic substances generally used in thermal paper, ie, electron-accepting compounds, are used, and in particular, phenol derivatives and aromatic carboxylic acid derivatives are used. Preferred compounds among the phenol derivatives are those having at least one phenolic hydroxyl group, and more preferably phenol derivatives in which both or one of the ortho positions of the phenolic hydroxyl group are unsubstituted. For example, phenol, p-t-butylphenol, p-phenylphenol, 1-naphthol, 2-naphthol, p-hydroxyacetophenone, 2,2'-dihydroxybiphenyl, 4,4'-isopropylidene di Phenol, 4,4'-isopropylidene diphenol, 4,4'-isopropylidene bis(2-
t-butylphenol), 4,4'-isopropylidene bis(2-chlorophenol), 4,4'-cyclohexylidene diphenol, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis (4-hydroxyphenyl)pentane, 2,2
-Bis(4-hydroxyphenyl)hexane, diphenol acetic acid methyl ester, bis(4-hydroxyphenyl)sulfone, bis(3-allyl-
4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-isopropyloxydiphenyl sulfone, bis(4-hydroxyphenyl) sulfide, 4,4'-thiobis( Examples of aromatic carboxylic acid derivatives include 2-t-butyl-5-methyl)phenol, 7-bis(4-hydroxyphenylthio)-3,5-dioxyheptane, and novolac type phenolic resin. Benzoic acid, p-t
-butylbenzoic acid, p-hydroxybenzoic acid, p
-Hydroxybenzoic acid methyl ester, p-hydroxybenzoic acid isopropyl ester, p-hydroxybenzoic acid benzyl ester, gallic acid lauryl ester, gallic acid stearyl ester, salicylanilide, 5-chlorosalicylanilide,
Examples include metal salts of 5-t-butylsalicylic acid such as zinc, metal salts of hydroxynaphthoic acid such as zinc, and the like. As binders, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol,
Styrene-maleic anhydride copolymer, ethylene-
Examples include water-soluble binders such as maleic anhydride copolymers, latex-based water-soluble binders such as styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, and methyl acrylate-butadiene copolymers. Examples of pigments include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin, and the like. In addition, higher fatty acid metal salts such as zinc stearate and calcium stearate, paraffin,
Waxes such as paraffin oxide, polyethylene, polyethylene oxide, stearamide, castor wax, dispersants such as sodium dioctyl sulfosuccinate, ultraviolet absorbers such as benzophenone and benzotriazole, surfactants, and fluorescent Examples include dyes. Paper is mainly used as the support for the heat-sensitive recording material according to the present invention, but various non-woven fabrics,
Plastic film, synthetic paper, metal foil, etc., or a composite sheet made of a combination of these may be used as desired. (E) Synthesis Examples and Examples The present invention will be explained in more detail with reference to Synthesis Examples and Examples. However, the present invention is not limited to the following synthesis examples and examples. Synthesis Example 1 Synthesis of compound (1) 10.2 g of paraphenylphenol was added to 100 g of acetone.
ml, add 34.1% sodium hydroxide aqueous solution to this
12.9 g and 9.6 g of propargyl bromide were added.
The system was kept under reflux conditions for 5 hours under stirring. After cooling, benzene and water were added to separate the layers. The organic layer was washed with an aqueous sodium bicarbonate solution and dried over anhydrous potassium carbonate. The solvent and unreacted raw materials were distilled off under reduced pressure, and the residue was treated with n-hexane to obtain crystals of the desired product. This was recrystallized with n-hexane to obtain the desired product.
8.6g was obtained. mp=80.5-83°C Mass spectrum (FD method) m/e=208 Example 1 20 g of 3-diethylamino-6-methyl-7-anilinofluorane was dispersed in a ball mill with 80 g of a 1% polyvinyl alcohol aqueous solution. On the other hand 4,
50 g of 4'-isopropylidene diphenol was dispersed in a ball mill with 200 g of a 1% aqueous polyvinyl alcohol solution, and 50 g of compound (1) was similarly dispersed with 200 g of a 1% aqueous polyvinyl alcohol solution. After mixing these three types of dispersions, 125 g of a 40% dispersion of calcium carbonate was added, and 40 g of a 25% dispersion of zinc stearate and 285 g of a 10.5% polyvinyl alcohol aqueous solution were added, and the mixture was sufficiently stirred to form a coating solution. . The coating liquid was applied to a base paper having a basis weight of 55 g/m ² so that the solid content coating amount was 6 g/m ² , dried, and treated with a supercalender to obtain a heat-sensitive recording material. Comparative Example 1 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that N-(hydroxymethyl)stearamide was used in place of Compound (1) in Example 1. Comparative Example 2 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the dispersion of compound (1) in Example 1 was omitted. Evaluation The heat-sensitive recording materials obtained in Example 1 and Comparative Examples 1 and 2 were used with a facsimile machine FACOM manufactured by Fujitsu Limited.
The optical density of the image printed using FAX-621C was measured using Macbeth RD-514. The results were tabulated.

[Table] (F) Effects of the Invention As shown in the table, by using the sensitizer according to the present invention, a heat-sensitive recording material with excellent heat responsiveness can be obtained.

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording material containing a color developer that reacts with a normally colorless or light-colored dye precursor upon heating to cause the dye precursor to develop color, containing a compound represented by the following general formula: A heat-sensitive recording material characterized by: general formula (However, X represents hydrogen or OR'. R and R' represent a substituted or unsubstituted alkynyl group.)