JPS6361195B2 - - 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, and a thermal head is used for heating to develop the color. 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, such heat-sensitive recording materials for high-speed recording have been proposed in which, for example, a heat-sensitive coloring layer contains stearic acid amide to increase heat sensitivity and develop heat-sensitive color in a short heating time. However, although this product is improved in terms of heat sensitivity, stearic acid amide contained in the heat-sensitive coloring layer impairs the runnability of the thermal head during recording, and the heat in the coloring layer There are problems such as adhesion of the molten material to the heated head (residue adhesion) and staking. 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 above object of the present invention, the present inventors have conducted various studies and found that the object can be achieved by incorporating a compound represented by the following general formula () and a higher fatty metal salt into the heat-sensitive coloring layer. It was discovered that a heat-sensitive recording material can be obtained, and the present invention was completed.

(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 compound represented by the general formula () used in the present invention, Although the position of alkoxycarbonyl ( _-COOR2 ) is arbitrary, it is generally preferable to bond to the para position with respect to the aminocarbonyl group ( _R1NHCO- ). 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 Higher fatty metal salts used in the present invention is preferably one having 10 to 30 carbon atoms, and the salt-forming metal in this case is a polyvalent metal such as zinc, magnesium, copper, aluminum, nickel, or iron. Specific examples of higher fatty acid metal salts include the following.

Octadecylcarboxylic acid aluminum salt, octadecylcarboxylic acid subsalt, octadecylcarboxylic acid nickel salt, hexadecylcarboxylic acid zinc salt, hexadecylcarboxylic acid nickel salt, hexadecylcarboxylic acid aluminum salt, etc.

In the present invention, the amount of higher fatty metal salt used is:
It is preferably used in a proportion of 0.05 to 2 parts by weight per 1 part by weight of the total amount of leuco dye and acidic substance contained in the heat-sensitive coloring layer; if it is less than 0.05 parts by weight, the effect of preventing pressure coloring will not be sufficiently achieved. , while 2
If the amount exceeds 1 part by weight, the color density will decrease and the amount of residue will increase when thermally colored. Further, the amount of the compound represented by the general formula () used is preferably 0.5 to 4 parts by weight per 1 part by weight of the higher fatty acid metal salt.
If it is less than 0.5 part by weight, the thermal sensitivity improvement effect is practically unsatisfactory, and if it is more than 4 parts by weight, the printed area will smear and the contrast of the colored image will deteriorate, and furthermore, the density of the colored image will decrease, and it will be difficult to improve the thermal sensitivity. The amount of adhesion also increases.

In the heat-sensitive recording material of the present invention, the compound represented by the above-mentioned general formula () and a higher fatty acid metal salt are contained in the heat-sensitive color forming layer together with the conventional heat-sensitive color forming layer-forming components. The thermosensitive color forming layer forming components will be specifically shown below.

(A) Leuco dye As the leuco dye, various colorless or light-colored leuco dyes shown below are usually 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, dialkylamino group, monoalkyl group,
It is an 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-chlorophthalide 3,3-bis(p-dibutylaminophenyl)phthalide (b) Represented by the following general formula Leuco compounds of fluoran dyes: In the formula, R _x , R _y and R _z are the same as in (a) above.

Specific examples of the above compounds are as follows.

3-Cyclohexylamino-6-chlorofluorane 3-(N,N-diethylamino)-5-methyl-7-(N,N-dibenzylamino)fluorane 3-dimethylamino-5,7-dimethylfluorane 3- Diethylamino-7-methylfluorane 3-diethylamino-7,8-benzfluorane (c) Leuco compound of fluoran dye: 3-diethylamino-6-methyl-7-chlorofluorane 3-pyrrolidino-6-methyl-7-ani Linofluorane 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 represent hydrogen, a substituted or unsubstituted lower alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted phenyl group, a cyanoethyl group, or a β-halogenated ethyl group, or , R ₁ and R ₂ combine to form (-CH ₂ )- ₄ , (-CH ₂ )- ₅ or (-CH ₂ )- ₂ O(
−
CH ₂ ) _-2 , R ₃ and R ₄ represent hydrogen, a lower alkyl group, an alkyl group, an amino group or a phenyl group, either one of R ₃ or R ₄ is hydrogen, and X ₁ , ₂ and _X3 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,
X ₄ represents hydrogen, halogen, a lower alkyl group or a lower alkoxyl group, and n represents 0 or an integer of 1-4.

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) Acidic substances The various acidic substances listed below are applicable.

(a) Organic acids 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.

(C) Binder Polyvinyl alcohol, methoxycellulose, hydroxylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch,
Water-soluble materials such as gelatin or aqueous emulsions such as polystyrene, vinyl chloride-vinyl acetate copolymers, polybutyl methacrylate, etc. can be used as binders.

Fine powder of calcium carbonate, silica, alumina, magnesia, talc, barium sulfate, 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 coating liquid for forming a heat-sensitive layer containing the above-mentioned components onto an appropriate 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 Zinc stearate 1.0 N-stearyl (p-methoxycarbonyl) benzamide 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 dry coating amount was 5 g/m ² The mixture was coated on the surface of commercially available high-quality paper (average basis weight 50 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 = amino group) were synthesized as follows.

Monomethyl terephthalate monochloride 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 flaky crystals (mp. 117.5°C) was recrystallized from ethanol. Yield 40.2g (yield 93%),
mp.117~118.5℃.

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 Aluminum stearate 1.0 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. Then, this was applied to the surface of commercially available high-quality paper (average basis weight 50 g/m ² ) to a dry coating weight of 60 g/m ² and dried to form a thermosensitive coloring layer. I got the material.

Comparative Example 1 In Example 1, stearamide was used instead of zinc stearate and N-stearyl(p-methoxycarbonyl)benzamide in the [B] solution.
A heat-sensitive recording material for comparison was obtained in exactly the same manner except that 2.0 parts by weight was used.

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.].
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, staking, pressure coloring, etc. Not recognized,
Clear blue and black images were obtained, respectively. Furthermore, such results were not impaired in any way even when the recording speed was increased.

On the other hand, the heat-sensitive recording material for comparison had poor runnability on the thermal head, and scum adhesion, staking, and pressure coloring occurred, making it impossible to obtain a clear blue image.

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording material having a structure in which a heat-sensitive color forming layer containing a leuco dye and an acidic substance as main components is formed on a support, in which the heat-sensitive color forming layer contains the general formula (In the formula, R ₁ is an alkyl group having 1 to 30 carbon atoms, R ₂ is a lower alkyl group having 1 to 5 carbon atoms) and a higher fatty acid metal salt. Heat-sensitive recording material.