JPH0240517B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-sensitive recording material, and more particularly, a heat-sensitive color-forming layer containing as main components a color-forming substance that is usually colorless or light-colored, and a color-developing substance that reacts with the color-forming substance and develops a color when heated. This invention relates to an improvement in a heat-sensitive recording material having a structure formed on a support. A thermosensitive recording material is a recording material having a structure in which a so-called thermosensitive coloring layer that develops color when heated is formed on a support such as paper, synthetic paper, or resin film. A thermal pen or the like is used. Compared to other recording materials, such recording materials can produce records in a relatively short time without complex processes such as development and fixing, do not generate noise, and are relatively inexpensive. Due to these advantages, it is widely used not only for copying books, documents, etc., but also as a recording material for various information and measuring instruments such as electronic computers, facsimiles, telex, and medical measuring instruments. The thermosensitive coloring layer that records an image by developing color when heated contains a combination of a coloring substance and a color developing substance that reacts with the coloring substance and develops color when heated. In this case, as the color-developing substance, for example, a colorless or light-colored leuco dye having a lactone, lactam or spiropyran ring is used, and as the color-developing substance, various acidic substances are used. Such a combination of a color-forming substance and a color-developing substance has been applied to many heat-sensitive recording materials because the color tone is clear and there is little fog. However, in recent years, with the development of society, there has been a growing demand for faster recording, so there is a strong desire not only to increase the speed of the recording apparatus itself, but also to develop recording materials that can meet this demand. Conventionally, such heat-sensitive recording materials for high-speed recording have been proposed, for example, containing stearic acid amide in the heat-sensitive coloring layer to increase heat sensitivity and develop heat-sensitive colors in a short heating time. Although this product is improved in terms of thermal sensitivity, the stearamide contained in the thermosensitive coloring layer impairs the runnability of the thermal head during recording, and the thermal melting in the coloring layer There are problems such as adhesion of objects to the heated head (residue adhesion), staking, etc. This heat-sensitive recording material containing stearic acid amide also has the disadvantage that it easily develops color (pressure coloring) when pressure is applied, for example, when it is scratched or rubbed. Furthermore, the coloring layer containing stearic acid amide has the drawback that it does not respond well to variations in head voltage or electricity application time, and has the disadvantage of large variations in coloring density, as well as causing blurring in colored images. There are also problems. The present inventors have already developed a formula for the heat-sensitive coloring layer of heat-sensitive recording materials. We have proposed a certain heat-sensitive recording material containing a fluoran compound shown in the following, which has solved most of the above-mentioned drawbacks and difficulties. Although it has the advantage of having a white background, it still has some drawbacks in that colored images tend to fade or discolor due to water or humidity. An object of the present invention is to solve the above-mentioned drawbacks of the prior art, that is, to provide a heat-sensitive recording material with high water resistance and high humidity resistance, in which colored images are not erased or faded due to moisture. . As a result of various studies to achieve the above object, the present inventors found that in the heat-sensitive coloring layer of the heat-sensitive recording material,
a fluoran compound represented by the above formula () and at least 10% by weight of the formula It has been found that the object can be achieved by containing an acidic substance containing a hydroxyphenylthioether compound represented by the above formula (), and a fluoran compound represented by the above formula () and at least 10% by weight of the above formula (). In addition to acidic substances containing compounds represented by the general formula (In the formula, R ₁ represents an alkyl group having 1 to 30 carbon atoms, A represents H or -CO ₂ R', and R' represents an alkyl group having 1 to 10 carbon atoms, respectively.) (In the formula, R ₃ and R ₄ each represent an alkyl group having 10 to 30 carbon atoms.) By containing at least one selected from the group of compounds represented by the following, the objective can be further achieved. They discovered this and completed the present invention. In the above, the hydroxyphenylthioether compound represented by the formula () is preferably used in an amount of 10 to 100% by weight, preferably 30 to 100% by weight of the total acidic substance. Further, the compound represented by the general formula () or () is preferably used in a weight range of 1 to 10 times the weight of the fluoran compound of the formula (). There are various specific examples of the compound represented by the general formula () used in the present invention, among which N-stearylbenzamide and N-stearyl-P-methoxy (or ethoxy) carbonylbenzamide are particularly preferred. Various specific examples of the compound represented by the general formula () include distearyl-4,5-epoxycyclohexane-1,2-
Particularly preferred are dicarboxylates. The heat-sensitive coloring layer used in the present invention may appropriately contain components such as the following commonly used acidic substances, binders, additive substances, etc., in addition to the above-mentioned compounds () to (). (A) Acidic Substances The following various acidic substances can be used as acidic substances that react with the above-mentioned leuco dye when heated to cause it to develop color. (a) Organic and inorganic acids boric acid, oxalic acid, maleic acid, tartaric acid,
Citric acid, succinic acid, benzoic acid, stearic acid, gallic acid, salicylic acid, 1-hydroxy-2-naphthoic acid, o-hydroxybenzoic acid, m-hydroxybenzoic acid, 2-hydroxy-p-toluic acid. (b) Phenolic substances 3,5-xylenol, thymol, p-
tert-butylphenol, 4-hydroxyphenoxide, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, α
-Naphthol, β-naphthol, catechol, resorcinol, hydroquinone, 4-tert-
Octinol, 2,2'-dihydroxydiphenyl, 2,2'-methylenebis(4-methyl-
6-tert-butylphenol), 2,2-bis(4-hydroxyphenyl)propane,
4,4-isopropylidene-bis(2-tert
-butylphenol), 4,4-sec-butylidene diphenol, pyrogallol, phloroglucin, phloroglucin carboxylic acid. (B) Binder The following various binders can be used to bind and support the thermosensitive coloring layer on the support. Water-soluble materials such as polyvinyl alcohol, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch, gelatin, etc., or polystyrene, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, etc. Aqueous emulsions such as . In addition, in the heat-sensitive coloring layer, if necessary, conventional auxiliary additives such as calcium carbonate, silica, alumina, magnesia, talc,
Fine powders such as titania, barium sulfate, aluminum stearate, and stearamide can be added to improve the clarity of colored images. The heat-sensitive recording material of the present invention is produced by applying a heat-sensitive layer-forming coating solution containing the above-mentioned components onto a suitable support such as paper, synthetic paper, or plastic film, and drying it. It is used in the recording field, especially as a heat-sensitive recording material for high-speed recording. Next, the present invention will be explained in more detail with reference to Examples. Example 1 [A] 20 g of 3-dinormalbutylamino-7-orthochloroanilinofluorane as liquid 20 g of 10% aqueous solution of hydroxyethylcellulose 60 g of water 2,2-bis(P-hydroxyphenyl) as liquid [B] Propane 20g 10% aqueous solution of hydroxyethylcellulose 20g Water 60g [C] As liquid, bis[P-hydroxy-m-t-butyl-o-
Prepare 20 g of methyl-phenyl]thioether (compound of formula ()), 20 g of 10% aqueous solution of hydroxyethyl cellulose, 60 g of water, 20 g of stearic acid amide as liquid [D], 20 g of 10% aqueous solution of hydroxyethyl cellulose, and 60 g of water. After dispersing each liquid in a magnetic ball mill for two days, liquid [A], liquid [B], liquid [C] and liquid [D] were mixed in a ratio of 1:2.1:0.9:2, and oxidized starch was added to this. A 20% aqueous solution of is added and mixed so that the dry weight ratio is as shown below to prepare a coating solution for a heat-sensitive coloring layer. Material Dry weight ratio 3-Di-Normalbutylamino-7-orthochloroanilinofluorane 1 2,2-bis(P-hydroxyphenyl)propane 2.1 Compound of formula () 0.9 Stearic acid amide 2 Oxidized starch 1.6 Next This coating liquid was applied to one side of a high-quality paper with a standard basis weight of 52 g/m ² using a wire bar so that the dry adhesion amount was 4 g/m ² and dried to obtain a heat-sensitive recording sheet. Example 2 The mixing proportions of liquid [A], liquid [B], liquid [C] and liquid [D] were adjusted so that the dry weight ratio of each material in Example 1 was as follows. A thermosensitive recording sheet was obtained in the same manner. Material Dry weight ratio 3-Di-n-butylamino-7-orthochloroanilinofluorane 1 2,2-bis(P-hydroxyphenyl)propane 0.3 Compound of formula () 2.7 Stearic acid amide 2 Oxidized starch 1.6 Examples 3 Do not use liquid [B] in Example 1, and make [A] so that the dry weight ratio of each material is as follows.
Adjust the mixing ratio of liquid, [C] liquid, and [D] liquid,
A thermosensitive recording sheet was obtained in the same manner as in Example 1. Material Dry weight ratio 3-di-n-butylamino-7-orthochloroanilinofluorane 1 Compound of formula () 3 Stearic acid amide 2 Oxidized starch 1.6 Comparative example 1 [C] solution in Example 1 was not used, So that the dry weight ratio of each material is as follows [A]
A thermosensitive recording sheet was obtained in the same manner as in Example 1 by adjusting the mixing ratio of the liquid, [B] liquid, and [D] liquid. Materials Dry weight ratio 3-Di-Normalbutylamino-7-orthochloroanilinofluorane 1 2,2-bis(P-hydroxyphenyl)propane 3 Stearic acid amide 2 Oxidized starch 1.6 Obtained as above Example 1 of the present invention,
When the thermal recording sheets of Examples 2 and 3 and the thermal recording sheets obtained in the comparative example were printed at high speed (head voltage 12.5 V) using a facsimile machine (OKI FAX-7100) manufactured by Oki Electric Industries, Ltd., Examples 1, 2,
3. All of the heat-sensitive recording sheets of Comparative Example 1 formed bright black images with high density. There was almost no difference in image density. Next, these image-forming parts were cut out, completely immersed in tap water kept at room temperature in a beaker, and left for 24 hours. As a result, the images of Comparative Examples showed significant decolorization, but the images of Examples 1, 2, and 3 showed almost no decolorization. Example 4 [A] 20 g of 3-dinormalbutylamino-7-orthochlorofluorane as liquid 20 g of 10% aqueous solution of hydroxyethylcellulose 60 g of water 20 g of 2,2-bis(P-hydroxyphenyl)propane as liquid [B] 10% aqueous solution of hydroxyethylcellulose 20g Water 60g [C] Compound of formula () as liquid 20g 10% aqueous solution of hydroxyethylcellulose 20g Water 60g [D] N-stearylbenzamide as liquid 20g 25% of polycarboxylic acid type polymer activator aqueous solution
Prepare 2g and 60g of a 5% aqueous solution of methylcellulose. Solutions obtained by dispersing each solution in a magnetic ball mill for 2 days, [A] solution, [B] solution, [C] solution,
[D] Mix the liquid at a ratio of 1:0.3:2.7:2, add and mix a 20% aqueous solution of oxidized starch so that the dry weight ratio is as shown below to obtain a coating liquid for the heat-sensitive coloring layer. . Material Dry weight ratio 3-Di-n-butylamino-7-orthochloroanilinofluorane 1 2,2-bis(P-hydroxyphenyl)propane 0.3 Compound of formula () 2.7 N-stearylbenzamide 2 Oxidized starch 1.6 Next, this coating liquid was applied to one side of a high-quality paper with a standard basis weight of 52 g/m ² using a wire bar so that the dry adhesion amount was 4 g/m ² and dried to obtain a heat-sensitive recording sheet. Comparative Example 2 The following liquid [E] was used instead of liquid [D] in Example 4, and liquid [A], liquid [B], and liquid [C] were mixed so that the dry weight ratio of each material was as follows. 〕liquid,
[E] The mixing ratio of liquid was adjusted and a heat-sensitive recording sheet was obtained in the same manner as in Example 4. [E] Stearic acid amide as liquid 20g 10% aqueous solution of hydroxyethylcellulose 20g Water 60g Materials Dry weight ratio 3-di-n-butylamino-7-orthochloroanilinofluorane 1 2,2-bis(P-hydroxyphenyl) ) Propane 0.3 Compound of formula () 2.7 Stearic acid amide 2 Oxidized starch 1.6 Each heat-sensitive recording sheet of Example 4 of the present invention and Comparative Example 2 obtained as described above was subjected to a facsimile machine manufactured by Oki Electric Industry Co., Ltd. ( When printing at high speed (head voltage 12.5V) with OKIFAX-7100), Example 4
This produced a bright black image with high density and no smearing. Comparative Example 2 had a bright black image with high density, but some bleeding was observed in the colored area. The image density of Example 4 was higher. Next, these image-forming parts were cut out, completely immersed in tap water kept at room temperature in a beaker, and left for 24 hours. As a result, in both Example 4 and Comparative Example 2, almost no decoloring of the images was observed. Example 5 [A] 20 g of 3-dinormalbutylamino-7-orthochloroanilinofluorane as liquid 20 g of 10% aqueous solution of hydroxyethyl cellulose 60 g of water 2,2-bis(P-hydroxyphenyl) as liquid [B] Propane 20g 10% aqueous solution of hydroxyethyl cellulose 20g Water 60g [C] Compound of formula () as liquid 20g 10% aqueous solution of hydroxyethylcellulose 20g Water 60g [D] P-methoxycarbonyl-N-stearylbenzamide as liquid 20g Polycarboxylic acid type 25% aqueous solution of polymer activator
Prepare 2g and 60g of a 5% aqueous solution of methylcellulose. After dispersing each solution in a magnetic ball mill for 2 days, [A] solution, [B] solution, [C] solution,
[D] Mix the liquid at a ratio of 1:0.3:2.7:2, add and mix a 20% aqueous solution of oxidized starch so that the dry weight ratio is as shown below to obtain a coating liquid for the heat-sensitive coloring layer. . Materials Dry weight ratio 3-Di-n-butylamino-7-orthochloroanilinofluorane 1 2,2-bis(P-hydroxyphenyl)propane 0.3 Compound of formula () 2.7 P-methoxycarbonyl-N-stearylbenzamide 2 Oxidized starch 1.6 Next, this coating solution was applied with a wire bar to one side of high-quality paper with a standard basis weight of 52 g/m ² so that the dry adhesion amount was 4 g/m ² and dried to obtain a heat-sensitive recording sheet. Ta. Comparative Example 3 The following liquid [E] was used instead of liquid [D] in Example 5, and liquid [A], liquid [B], and liquid [C] were mixed so that the dry weight ratio of each material was as follows. 〕liquid,
The mixing ratio of liquid [D] and liquid [E] was adjusted, and Example 5
A thermosensitive recording sheet was obtained in the same manner. [E] Stearic acid amide as liquid 20g 10% aqueous solution of hydroxyethyl cellulose 20g Water 60g Materials Dry weight ratio 3-di-n-butylamino-7-orthochloroanilinofluorane 1 2,2-bis(P-hydroxyphenyl) ) Propane 0.3 Compound of formula () 2.7 Stearic acid amide 2 Oxidized starch 1.6 Each of the thermal recording sheets of Example 5 of the present invention and Comparative Example 3 obtained as described above was processed using a thermal printer PU-1800 manufactured by Olivetsu Tei Co., Ltd. When printed at high speed, Example 5 produced a bright black image with no bleeding and high density. Comparative Example 3 had a bright black image with high density, but some bleeding was observed in the colored area. The image density of Example 5 was higher. Next, these image-forming parts were cut out, completely immersed in tap water kept at room temperature in a beaker, and left for 24 hours. As a result, in both Example 5 and Comparative Example 3, almost no decoloring of the images was observed. Example 6 Mixtures having the following compositions were each ground and dispersed for 24 hours using a ball mill to form liquid [A] and liquid [B].
Solution, [C] solution, and [D] solution were prepared.

[Table] Lohexane

[Table] Next, a thermosensitive color forming layer forming liquid was prepared by mixing these in the following proportions. [A] Solution 1 part by weight [B] Solution 4 [C] Solution 2 [D] Solution 2 20% polyvinyl alcohol aqueous solution 2 When dry, apply the solution to the surface of high-quality paper (basis weight 50 g/m ² ). A heat-sensitive recording material of the present invention was obtained by coating and drying to a coating weight of 6 g/m ² to form a heat-sensitive coloring layer. Comparative Example 4 A mixture having the following composition was prepared using a ball mill.
The mixture was crushed and dispersed for 24 hours to prepare liquid [E]. [E] Liquid 3-diethylamino-7-orthochloroanilinofluorane 20 parts by weight 10% hydroxyethyl cellulose aqueous solution
20 〃 Water 60 〃 A comparative heat-sensitive recording material was obtained in the same manner as in Example 6 except that liquid [E] was used instead of liquid [A]. Comparative Example 5 A mixture having the following composition was prepared using a ball mill.
The mixture was crushed and dispersed for 24 hours to prepare liquid [F]. [F] Liquid Bisphenol A 20 parts by weight 5% Polyvinyl alcohol 20 Water 60 A comparative heat-sensitive recording material was obtained in the same manner except that liquid [F] was used instead of liquid [B] in Example 6. . A facsimile machine [manufactured by Oki Electric Industry Co., Ltd.] was used for the heat-sensitive recording materials of the present invention and comparative heat-sensitive recording materials obtained as described above.
The product of the present invention obtained in Example 6 was printed at high speed using OKI FAX-7100].
514, a clear black image with an image density of 1.20 was obtained. On the other hand, in Comparative Example 4, the image density was 1.00.
The coloring properties were poor, and only blurred black images with insufficient density were obtained. On the other hand, in Comparative Example 5, the image density after printing was 1.20.
Although the product of the present invention obtained in Example 6 maintained a clear image with an image density of 1.20 when soaked in water at 20°C for one day, the product of Comparative Example 5 In the case of , the image area was discolored and only a blurred image with an image density of 0..5 was obtained. Example 7 Mixtures having the following compositions were ground and dispersed for 24 hours using a ball mill to form liquid [A] and liquid [B].
Solution, [C] solution, and [D] solution were prepared. [A] Liquid 3-Di-n-butylamino-7-orthochloroanilinofluorane 20 parts by weight 10% hydroxyethylcellulose aqueous solution
20 〃 Water 60 〃 [B] Compound of liquid formula () 20 parts by weight 10% hydroxyethyl cellulose aqueous solution
20 [C] Liquid P-methoxycarbonyl-N-stearylbenzamide 20 parts by weight 5% methylcellulose aqueous solution 60 [D] Liquid 3,4-epoxy-1,2-bis-stearyloxycarbonyl-cyclohexane 20 parts by weight Part 5% methyl cellulose aqueous solution 20 parts Water 60 parts Next, these were mixed in the following proportions to prepare a thermosensitive coloring layer forming liquid. [A] Solution 1 part by weight [B] Solution 4 [C] Solution 2 [D] Solution 2 20% polyvinyl alcohol aqueous solution 2 When dry, apply the solution to the surface of high-quality paper (basis weight 50 g/m ² ). The heat-sensitive recording material of the present invention was obtained by coating and drying to a coating weight of 6 g/m ² to form a heat-sensitive coloring layer. Comparative Example 6 A mixture having the following composition was prepared using a ball mill.
Solution E was prepared by crushing and dispersing for 24 hours. [E] Liquid 3-diethylamino-7-orthochloroanilinofluorane 20 parts by weight 10% hydroxyethyl cellulose aqueous solution
20 〃 Water 60 〃 A comparative heat-sensitive recording material was obtained in the same manner as in Example 7 except that liquid [E] was used instead of liquid [A]. Comparative Example 7 A mixture having the following composition was prepared using a ball mill.
The mixture was crushed and dispersed for 24 hours to prepare liquid [F]. [F] Liquid Bisphenol A 20 parts by weight 5% polyvinyl alcohol 20 Water 60 A comparative heat-sensitive recording material was obtained in the same manner except that liquid [F] was used instead of liquid [B] in Example 7. . A facsimile machine (manufactured by Oki Electric Industry Co., Ltd.) was used for the heat-sensitive recording materials of the present invention and comparative heat-sensitive recording materials obtained as described above.
OKI FAX-7100], the present invention product obtained in Example 7 was printed at high speed using a Maxbe RD-
514, a clear black image with an image density of 1.10 was obtained. On the other hand, in Comparative Example 6, the image density was 0.90.
The coloring properties were poor, and only blurred black images with insufficient density were obtained. On the other hand, Comparative Example 7 has an image density of 1.10, which is similar to Example 7, but the product of the present invention obtained in Example 7 after being immersed in water at 20°C for one day maintains a clear image with an image density of 1.10. was. On the other hand, in Comparative Example 7, the image area was discolored and only a blurred image with an image density of 0.4 was obtained.

Claims (1)

[Claims] 1. A heat-sensitive coloring layer containing a fluoran compound represented by the following formula () and an acidic substance containing at least 10% by weight of a hydroxyphenylthioether compound represented by the following formula () on a support. A heat-sensitive recording material formed by forming a heat-sensitive recording material. 2. A heat-sensitive recording formed by forming on a support a heat-sensitive coloring layer containing a fluoran compound represented by the following formula () and an acidic substance containing at least 10% by weight of a hydroxyphenylthioether compound represented by the following formula (). A heat-sensitive recording material characterized in that the material further contains at least one compound selected from the group of compounds represented by the following general formulas () and (). (In the formula, R ₁ represents an alkyl group having 1 to 30 carbon atoms, A represents H or -CO ₂ R', and R' represents an alkyl group having 1 to 10 carbon atoms, respectively.) (In the formula, R ₃ and R ₄ each represent an alkyl group having 10 to 30 carbon atoms.)