JPH0220433B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, and more specifically, it mainly uses 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. The present invention relates to an improvement in a heat-sensitive recording material having a structure in which a heat-sensitive coloring layer contained as a component is 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 a clear color tone and less fog, and has thus far been applied to many heat-sensitive recording materials. 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, as such heat-sensitive recording materials for high-speed recording, materials have been proposed in which, for example, a heat-sensitive coloring layer contains stearic acid amide to increase heat sensitivity and develop heat-sensitive colors in a short heating time. ,however,
Although this product has improved thermal sensitivity, stearic acid amide contained in the thermosensitive coloring layer impairs the runnability of the thermal head during recording, and the thermal molten material in the coloring layer There are problems such as adhesion (residue adhesion) and staking to the thermal head. 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.

The object of the present invention is to solve the above-mentioned conventional drawbacks, and more specifically, to solve the problems of scum adhesion, staining, and pressure coloring, and to provide a heat-sensitive recording material capable of recording excellent images even during high-speed recording. Our goal is to provide the following.

In view of the object of the present invention, the present inventors have conducted various studies and found that the desired heat-sensitive recording material can be obtained by incorporating compounds represented by the following general formulas () and () into the heat-sensitive coloring layer. The present inventors have discovered that the following can be obtained, and have completed the present invention.

(In the formula, R ₁ is an alkyl group having 1 to 30 carbon atoms, and R ₂ is a lower alkyl group having 1 to 5 carbon atoms.) (In the formula, R ₃ and R ₄ are alkyl groups having 10 to 30 carbon atoms.) In the compound represented by the general formula () used in the present invention, the position of the alkoxycarbonyl group (-COOR ₂ ) bonded to the benzene nucleus is Although optional, it is generally preferable to bond to the para position of the aminocarbonyl group (R ₁ NHCO-). Specific examples of such compounds include the following.

N-octadecyl (p-methoxycarbonyl)
Benzamide N-octadecyl (p-ethoxycarbonyl)
Benzamide N-hexadecyl (p-methoxycarbonyl)
Benzamide N-hexadecyl (p-ethoxycarbonyl)
Benzamide N-lauryl (p-methoxycarbonyl) benzamide N-octyl (p-methoxycarbonyl) benzamide N-octadecyl (p-propoxycarbonyl) benzamide N-stearyl (p-methoxycarbonyl) benzamide N-octadecyl (m-methoxycarbonyl)
Benzamide.

Specific examples of the compound represented by the general formula () include the following.

Didodecyl-4,5-epoxycyclohexane-1,2-dicarboxylate Ditetradecyl-4,5-epoxycyclohexane-1,2-dicarboxylate Dihexadecyl-4,5-epoxycyclohexane-1,2-dicarboxylate Octadecyl- 4,5-Epoxycyclohexane-1,2-dicarboxylate Octacosyl-4,5-epoxycyclohexane-1,2-dicarboxylate.

In the present invention, the compound represented by the general formula () is added in an amount of 0.05 parts by weight per 1 part by weight of the total weight of the color-forming substance and the color-developing substance contained in the heat-sensitive coloring layer.
It is preferably used in the heat-sensitive coloring layer in a proportion of 2.0 parts by weight. If the amount used is less than 0.05 parts by weight, the effect of preventing pressure coloring will be reduced, and
If the amount is more than 2.0 parts by weight, the density of the colored image will be low. The amount of the compound of the general formula () used is preferably 0.5 to 4 parts by weight per 1 part by weight of the general formula (), and if it is less than 0.5 parts by weight, the effect of improving thermal sensitivity is practically unsatisfactory. If the amount is more than 4 parts by weight, bleeding will occur in the printed area and the contrast will deteriorate.

The heat-sensitive recording material of the present invention contains the compounds represented by the above-mentioned general formulas () and () together with the conventional heat-sensitive coloring layer components such as a color-forming substance, a color-developing substance, a binder, etc., in the heat-sensitive coloring layer. The conventional heat-sensitive color forming layer components in this case will be specifically described below.

(A) Color-forming substance As the color-forming substance, various leuco dyes shown below, which are usually colorless or light-colored, are used.

(a) Leuco compound of triphenylmethane dye represented by the following general formula (): (In the formula, R _x , R _y and R _z are hydrogen, hydroxyl group,
halogen, alkyl group, nitro group, amino group,
They are dialkylamino group, monoalkyl group, and allyl group. ) Specific examples of the above leuco compounds are as follows.

3,3-bis(p-dimethylaminophenyl)
-phthalide 3,3-bis(p-dimethylaminophenyl)
-6-dimethylaminophthalide (also known as crystal violet lactone) 3,3-bis(p-dimethylaminophenyl)
-6-diethylaminophthalide 3,3-bis(p-dimethylaminophenyl)
-6-Chlorphthalide 3,3-bis(p-dibutylaminophenyl)
Phthalide (b) Leuco compound of fluoran dye represented by the following general formula: In the formula, R _x , R _y and R _z are the same as in the above (a).

Specific examples of the above compounds are as follows.

3-Cyclohexylamino-6-chlorofluorane 3-(N,N-diethylamino)-5-methyl-
7-(N,N-dibenzylamino)fluoran 3-dimethylamino-5,7-dimethylfluoran 3-diethylamino-7-methylfluoran 3-diethylamino-7,8-benzfluoran (c) Fluoran dye Leuco compounds: 3-diethylamino-6-methyl-7-chlorofluoran 3-pyrrolidino-6-methyl-7-anilinofluoran 2-{N-(3'-trifluoromethylphenyl)
amino}-6-diethylaminofluorane 2-{3,6-bis(diethylamino)-9-
(o-chloroanilino)xantylbenzoic acid lactam} (d) Lactone compound represented by the following general formula: In the formula, R ₁ and R ₂ are hydrogen, lower alkyl group,
Substituted or unsubstituted aralkyl group, substituted or unsubstituted phenyl group, cyanoethyl group, or β-
represents a halogenated ethyl group or R ₁ and R ₂
are combined to form (-CH ₂ )- ₄ , (-CH ₂ )- ₅ or (-CH ₂
)−
_2O ( _-CH2 ) _-2 , _R3 and _R4 represent hydrogen, a lower alkyl group, an alkyl group, an amino group or a phenyl group, and either one of _R3 and _R4 is hydrogen, X ₁ , X ₂ and X ₃ represent hydrogen, a lower alkyl group, a lower alkoxyl group, a halogen atom, a halogenated methyl group, a nitro group, an amino group, or a substituted amino group, and X ₄ represents hydrogen, a halogen,
It represents a lower alkyl group or a lower alkoxyl group, and n represents 0 or an integer of 1 to 4.

Specific examples of the above compounds are as follows.

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.

(B) Color-developing substance The various acidic substances shown below are applicable as the color-developing substance.

(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-octylcatechol, 4,4-sec-butylidenephenol,
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.

(C) Binding agent polyvinyl alcohol, methoxycellulose,
Water-soluble materials such as hydroxyethyl cellulose, carboxymethyl cellulose, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch, gelatin, etc., or water-based emulsions such as polystyrene, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, etc. can be used as a binder.

Fine powder of calcium carbonate, silica, alumina, magnesia, talc, barium sulfate, aluminum stearate, etc. can be further added to the thermosensitive coloring layer forming liquid to improve the clarity of the colored image.

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 mixture having the following composition was separately ground and dispersed using a ball mill for 24 hours to obtain [A] liquid,
[B] Solution was prepared.

[A] Liquid crystal violet lactone 1.5 parts by weight 20% polyvinyl alcohol aqueous solution 5.0 Water 43.5 [B] Liquid bisphenol A 6.0 parts by weight N-stearyl (p-methoxycarbonyl)
Benzamide 1.0 parts by weight Distearyl-4,5-epoxycyclohexane-1,2-dicarboxylate
1.0 〃 20% polyvinyl alcohol aqueous solution 5.0 〃 Water 37.0 〃 Next, 1.0 part by weight of the above liquid [A] and 1.0 part by weight of liquid [B] were mixed to prepare a thermosensitive coloring layer forming liquid, and the coating amount when dried was It was coated on the surface of commercially available high-quality paper (average basis weight 50 g/m ² ) at a concentration of 5 g/m ² and dried to form a heat-sensitive coloring layer, thereby obtaining the heat-sensitive recording material of the present invention.

In addition, the above N-stearyl (p-methoxycarbonyl) benzamide (in the general formula (),
R ₁ = stearyl group, R ₂ = methyl group) were synthesized as follows.

Terephthalic acid monomethyl chloride 20g
(0.1 mol) and 27 g (0.1 mol) of stearylamine in 100 ml of toluene were refluxed at 110°C for 2 hours, and the reaction product was cooled and filtered to obtain white scaly crude crystals (mp. ~117.5°C) was recrystallized from ethanol. Yield 40.2g (yield 93%),
mp.117~118.5℃.

In addition, distearyl-4,5-epoxycyclohexane-1,2-dicarboxylate (in the general formula (), R ₃ and R ₄ = stearyl group) is a commercially available product (manufactured by Shin Nippon Rika Kogyo Co., Ltd., trade name Ricaflow).
EP-18) was used.

Example 2 A mixture consisting of the following compositions was separately ground and dispersed using a ball mill for 24 hours to obtain liquid [C].
[D] Solution was prepared.

[C] Liquid 3-pyrrolidino-6-methyl-7-anilinofluorane 1.5 parts by weight Calcium carbonate 1.0 20% oxidized starch aqueous solution 5.0 Water 42.5 [D] Liquid bisphenol A 6.0 parts by weight N-stearyl (p -ethoxycarbonyl)
Benzamide 1.0 〃 Distearyl-4,5-epoxycyclohexane-1,2-dicarboxylate
1.0 part by weight 20% polyvinyl alcohol aqueous solution 5.0 Water 37.0 Next, 1.0 part by weight of the above liquid [C] and 1.0 part by weight of liquid [D] were mixed to prepare a thermosensitive coloring layer forming liquid, and the coating amount when dried was The heat-sensitive recording material of the present invention was obtained by coating the surface of commercially available high-quality paper (average basis weight 50 g/m ² ) with a weight of 6.0 g/m ² and drying to form a heat-sensitive coloring layer.

Comparative Example 1 In Example 1, N-stearyl (p-methoxycarbonyl)benzamide and distearyl-4,5-epoxycyclohexane in [B] solution
A comparative heat-sensitive recording material was obtained in exactly the same manner except that 2.0 parts by weight of stearamide was used instead of 1,2-dicarboxylate.

The heat-sensitive recording materials of the present invention and comparative heat-sensitive recording materials obtained as described above were used with a facsimile machine [Oki Electric Industry Co., Ltd.].
When printed using a printer manufactured by OKIFAX-6000], both the heat-sensitive recording materials of the present invention obtained in Examples 1 and 2 had excellent runnability on the thermal head, and almost no scum adhesion, sticking, pressure coloring, etc. were observed. Clear blue and black images were obtained.
Furthermore, such results were not impaired in any way even when the recording speed was increased.

On the other hand, the comparative heat-sensitive recording material had poor runnability on the thermal head, and it was not possible to obtain a clear blue image due to scum adhesion, sticking, and pressure coloring.

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording material having a structure in which a heat-sensitive color-forming layer containing as main components a color-forming substance and a color-developing substance that causes the color-forming substance to develop color when heated is formed on a support, A heat-sensitive recording material characterized in that a heat-sensitive coloring layer contains compounds represented by the following general formulas () and (). (In the formula, R ₁ is an alkyl group having 1 to 30 carbon atoms, and R ₂ is a lower alkyl group having 1 to 5 carbon atoms.) (In the formula, R ₃ and R ₄ are alkyl groups having 10 to 30 carbon atoms.)