JPH0444598B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-sensitive recording paper characterized by containing at least one type of novel fluoran compound as a color former (electron-donating coloring agent). Thermosensitive recording paper is a recording paper with a structure in which a so-called thermosensitive coloring layer that develops color when heated is formed on a support such as paper.Thermal printers with a built-in thermal head are used to heat the layer to develop the color. is used. A recording paper having such a structure having a heat-sensitive coloring layer is inexpensive compared to other recording papers;
It is widely used in facsimile machines, printers, etc. due to its low noise and ability to record in a short time. The most important thing for thermal recording paper is that it has excellent color development sensitivity, but recently
It is also beginning to be used for display labels for POS (point of sale), etc., and it is becoming an essential condition that the colored image has good storage stability. The minimum properties that should be possessed by a coloring layer of thermal recording paper are excellent self-coloring resistance (resistance to background skin fogging), pressure coloring resistance, coloring sensitivity, moisture decoloring resistance, heat decoloring resistance, oil resistance, and light resistance. However, we have not yet achieved anything that fully satisfies these requirements. Color formers that produce black color are often used in the heat-sensitive coloring layer, but fluoran compounds as color formers were developed in Japanese Patent Application Laid-Open No.
No. 23204, Special Publication No. 51-29180, Special Publication No. 56-52769
No., JP-A-57-53562, JP-A-58-7453, and USP-3681390.
Regarding heat-sensitive recording paper using color formers, Japanese Patent Publication No. 4160/1980, Japanese Patent Publication No. 3680/1982, and Japanese Patent Publication No. 17748/1989 are known. The present inventors manufactured thermal recording paper using known fluoran compounds as color formers according to conventionally known methods or the methods described in the above-mentioned patent publications, and the performance aspects that thermal recording paper should have. When tested, each of these thermal recording papers had drawbacks such as coloring sensitivity, moisture and decoloring resistance, oil resistance, and surface fog resistance. The inventors of the present invention have conducted extensive studies on thermal recording paper that improves these drawbacks, and have discovered that the performance of thermal recording paper can be significantly improved by using a specific fluoran compound.
That is, the present invention provides the following general formula (), (In the formula, R ₁ is a heterocyclic alkyl group excluding a tetrahydrofurfuryl group, R ₂ is a hydrogen atom; an alkyl group having 1 to 8 carbon atoms; an alkoxyalkyl group; a cycloalkyl group; a cyclohexylalkyl group; or a halogen R ₃ and R ₄ are hydrogen atoms; alkoxy groups having 1 to 4 carbon atoms; alkoxy groups having 1 to 4 carbon atoms; alkoxy Alkyl group; or phenyl group or benzyl group that can be substituted with a halogen atom, lower alkyl group, or alkoxyalkyl group,
R ₅ and R ₆ are hydrogen atoms; alkyl groups having 1 to 12 carbon atoms; alkoxyalkyl groups; cyanoalkyl groups;
Heterocyclic group; heterocyclic alkyl group; or phenyl group or aralkyl group that can be substituted with a halogen atom, lower alkyl group, alkoxyalkyl group, or acyl group. ) is a heat-sensitive recording paper characterized by containing at least one type of novel fluoran compound having a heterocyclic alkyl group other than a tetrahydrofurfuryl group at the 6-position as a color former. The fluoran compound represented by the general formula () is almost colorless itself, but has the property of rapidly developing color when it comes into contact with an electron-accepting substance. That is, it develops a blackish color due to phenol derivatives such as bisphenol A and organic carboxylic acid esters such as benzyl p-hydroxybenzoate. Representative examples of the novel fluoran compound represented by the general formula (), which is a color former used in the thermal recording paper of the present invention, are shown below. The hue indicates the hue when the color is developed on a thin layer of silica gel.

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[Table] To synthesize the fluoran compound represented by the general formula () according to the present invention, the general formula (In the formula, R ₃ , R ₄ , R ₅ , and R ₆ are the same as defined above, and R ₇ represents a hydrogen atom or a lower alkyl group.) A diphenylamine derivative represented by the general formula (In the formula, R ₁ and R ₂ are the same as defined above.) is reacted with a benzophenone derivative represented by the formula in a condensing agent such as sulfuric acid, phosphoric acid, or polyphosphoric acid, and then treated in alkaline water. It will be done. For example, 2
-Anilino-3-methyl-6-N-(tetrahydropyran-2-methyl)-N-methyl-aminofluorane is synthesized as follows. 2-(2-hydroxy-4-
Add 16.5 g of N-(tetrahydropyran-2-methyl)-N-methylphenylcarbonylbenzoic acid,
After completely dissolving it while keeping it at about 8-14℃, 2-
Add 10 g of methyl-4-methoxydiphenylamine and react at 20-25°C for 10 hours.
Then, an aqueous sodium hydroxide solution was added to adjust the pH to 10 or higher. The precipitate was collected by filtration. 450 ml of toluene and 340 g of 10% aqueous sodium hydroxide solution were added to the cake, and after stirring under reflux for 2 hours, the toluene layer was separated and washed with water, and the toluene was distilled off by steam distillation. The precipitated crystals were collected by filtration, and after washing by adding 150 ml of methanol to the cake, the crystals were collected again by filtration. The crystals were dried and a pale pink 2-anilino-3-methyl-
6-N-(tetrahydropyran-2-methyl)-N
-Methyl-aminofluorane, 12 g was obtained. The melting point of this fluoran compound was 134°C to 139°C. A solution of this substance dissolved in toluene is colorless and quickly develops color due to pisphenol A.
It appeared black. In addition, color developers used in combination with these fluoran compounds include 4-t-butylphenol, 4-phenylphenol, methyl-4-hydroxybenzoate, 4,4'-isopropylidene diphenol, 4,4 '-isopropylidene bis(2,6-dibromophenol), bis(4-hydroxyphenyl) sulfone, benzyl p-hydroxybenzoate, p-hydroxybenzoic acid-sec-
Conventionally known color developers such as butyl and 3-(α-methylbenzyl)salicylic acid can be used. Furthermore, various water-soluble or water-insoluble binders are used in the thermosensitive coloring layer of the present invention for binding onto the support. Typical examples include polyvinyl alcohol, methyl cellulose,
Hydroxyethylcellulose, carboxymethylcellulose, gum arabic, starch, gelatin,
Casein, polyvinylpyrrolidone, styrene-maleic anhydride copolymer, etc. are used, but the binder that can be particularly preferably used in the present invention is a water-soluble binder, a typical example of which is polyvinyl alcohol. . In addition, in the heat-sensitive coloring layer, if necessary, auxiliary additives such as fillers such as aluminum hydroxide, calcium carbonate, magnesia, barium sulfate, calcium stearate, dimethyl terephthalate, dibenzyl terephthalate, β-naphthol, etc. Conventionally known sensitivity improvers such as benzyl ether, stearamide, and benzyl p-benzyloxybenzoate can be added to improve the clarity or color density of a colored image. The thermosensitive recording paper of the present invention is produced by applying and drying a coating liquid for forming a thermosensitive coloring layer containing the above-mentioned components onto a support such as paper. The heat-sensitive recording paper of the present invention thus produced was particularly excellent in coloring sensitivity, moisture decoloring resistance, and oil resistance. The performance of the thermal recording paper was determined by the following test method. In other words, the color density in terms of the background density, the decoloring density of the coloring agent in humidity after color development by heating at each temperature (moisture decoloring resistance), the decoloring density when it comes into contact with castor oil (oil resistance), etc. , Macbeth RD
Measurements were made using a -514 reflection densitometer. Thermal coloring was performed using a low-day aceta type thermotest tester (manufactured by the French National Textile Research Institute) at a heating temperature of 60 to 170°C.
The heating time was 3 seconds and the load was 100 g/cm ² . Further, decoloring of the coloring agent after coloring by heating was carried out using a constant temperature and humidity tester. Next, the present invention will be explained in detail with reference to Examples. Example 1 A mixture consisting of the following composition was separately applied with a paint conditioner (trade name Red Devil).
The mixture was ground for 3 hours to prepare liquid, liquid, and liquid. Composition formula 2-anilino-3-methyl-6-N-(thiolane-2-methyl)-N-methyl-aminofluorane 4 parts by weight 10% polyvinyl alcohol aqueous solution 34 parts by weight 5% antifoaming agent (Sannopco 1407, Sannobco 2 parts by weight Liquid composition Bisphenol A 6 parts by weight 10% polyvinyl alcohol aqueous solution 20 parts by weight Water 14 parts by weight Liquid composition Aluminum hydroxide 10 parts by weight 10% polyvinyl alcohol aqueous solution 20 parts by weight Water 10 parts by weight Liquid, liquid, The liquid and water were mixed at a weight ratio of 3:9:5:3 to obtain a paint for heat-sensitive recording paper. This paint was applied to the surface of high-quality paper using a wire bar so that the solid content after drying was 5 g/ ^m2 , and the paint was placed in a blow dryer and dried at room temperature to obtain the thermal recording paper (A) of the present invention. Ta. Comparative Example 1 Comparative thermal recording papers (Y) to (T) were obtained in exactly the same manner except that a liquid or liquid was used instead of the liquid in Example 1. Liquid composition 2-anilino-3-methyl-6-diethylaminofluorane 4 parts by weight 10% polyvinyl alcohol aqueous solution 34 parts by weight 5% antifoaming agent (Sannobuco 1407) 2 parts by weight Liquid composition 2-anilino-3-methyl-6- N-cyclohexyl-N-methyl-amino-fluorane 4 parts by weight 10% polyvinyl alcohol aqueous solution 34 parts by weight 5% antifoaming agent (Sannobuco 1407) 2 parts by weight Thermal recording paper of the present invention and comparative thermal recording paper obtained as above The color development sensitivity, moisture decolorization resistance, and oil resistance were tested. The results are shown in Table 1. Example 2 2-anilino-3-methyl-6-N-(thiolane-2-methyl)-N-methylaminofluorane used in Example 1 was replaced with 2-anilino-3-
Ethyl-6-N-(1-methylpyrrolidine-2-
methyl)-N-methylaminofluorane, 2-anilino-3-chloro-6-N-(1,3-dioxane-2-methyl)-N-methylaminofluorane, 2-(-fluoroanilino)- 4-methoxy-
6-N-(tetrahydropyran-2-methyl)-N
-methylaminofluorane, 2-anilino-3-
Methyl-6-N-(morpholine-N-propyl)-
N-methylaminofluorane, 2-anilino-3
-methoxy-6-N-furfuryl-N-n-octylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N-(tetrahydropyran-2-methyl)-amino-fluorane, 2-( 4-
butylanilino)-3-ethyl-6-N,N-di(thiolane-2-methyl)aminofluorane, 2
-anilino-3-benzyl-6-N,N-di(morpholine-N-propyl)aminofluorane, 2
-(N-n-octyl-N-methyl)-amino-3
-ethoxyethyl-6-N-(morpholine-N-
propyl)-N-ethoxyethylaminofluorane, 2-N,N-dicyanoethyl-3,4-dimethyl-6-N-hexyl-N-furfurylaminofluorane, 2-N-benzyl-N-tetrahydrofuran Furylamino-4-phenyl-6-N-
(1,3-dioxane-2-methyl)-N-cyclohexylmethyl-aminofluorane or 2-
(4-acetylanilino)-4-phenyl-6-N
Thermal recording papers (B) to (W) were obtained in the same manner as in Example 1 using -ethyl-N-(thiolane-2-methyl)-aminofluorane. Performance tests were conducted on these thermal recording papers of the present invention in the same manner as in Example 1.
The results are shown in Table 1.

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[Table] The thermal recording paper of the present invention had characteristics such as extremely excellent coloring sensitivity, moisture decoloring resistance, and oil resistance. Therefore, the thermal recording paper of the present invention has sufficient practical durability as a thermal recording paper for various recording fields, particularly for high-speed recording and POS. Example 3 2-anilino-3-methyl-6-N-(thiolane-2-methyl)-N-methylaminofluorane used in Example 1, 4 parts by weight was replaced with 2-anilino-3-methyl- 6-N-(thiolane-2-methyl)-N-methylaminofluorane, 2 parts by weight and 2-anilino-3-methyl-6-N-(morpholine-N-propyl)-N-methylaminofluorane, Example 1
A thermosensitive recording paper (f) was obtained in the same manner as above. When the performance test of the thermal recording paper of the present invention was carried out in the same manner as in Example 1, the color development sensitivity was 100, the moisture decolorization resistance was 106, and the oil resistance was 92. It also showed extremely superior performance compared to paper.

Claims (1)

[Claims] 1. General formula (In the formula, R ₁ is a heterocyclic alkyl group excluding a tetrahydrofurfuryl group, R ₂ is a hydrogen atom; an alkyl group having 1 to 8 carbon atoms; an alkoxyalkyl group; a cycloalkyl group; a cyclohexylalkyl group; or a halogen a phenyl group or aralkyl group that can be substituted with an atom, a lower alkyl group, an alkoxy group, or an acyl group, R ₃ and R ₄ are hydrogen atoms; alkyl groups having 1 to 4 carbon atoms; alkoxy groups having 1 to 4 carbon atoms; alkoxy an alkyl group; or a phenyl group or benzyl group that can be substituted with a halogen atom, lower alkyl group, or alkoxyalkyl group;
R ₅ and R ₆ are hydrogen atoms; alkyl groups having 1 to 12 carbon atoms; alkoxyalkyl groups; cyanoalkyl groups;
Heterocyclic group; heterocyclic alkyl group; or phenyl group or aralkyl group that can be substituted with a halogen atom, lower alkyl group, alkoxyalkyl group, or acyl group. 1. A heat-sensitive recording paper containing, as a color former, at least one type of novel fluoran compound having a heterocyclic alkyl group other than a tetrahydrofurfuryl group at the 6-position represented by the following formula: