JPS6174886A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having high image stability, by combining a specific fluorane compound and an imidazole derivative complex of zinc thiocyanate. CONSTITUTION:At least one compound selected from fluorane compounds represented by formulae (I), (II) and an imidazole derivative complex of zinc thiocyanate represented by formula (III) are combined. By this method, a thermal recording material generating no background fog, showing no phenomenon such as the erasion of a color forming part or the color development of a ground color part even in the contact with oil and a plasticizer, further preventing the color development of the background part even by the adhesion and having extremely excellent image stability is obtained. In the formulae (I)-(III), R1 and R2 are a 1-6C alkyl group, R3 and R4 are a 1-2C alkyl group or a halogen atom, k and l are respectively independently 0-2, m is 0 or 1, R5, R6 are a 1-6C alkyl group or cycloalkyl, R7 is an 1-2C alkyl group or a halogen atom, n is 0-2 and R8 is a 1-6C saturated or unsaturated hydrocar bon group.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material with excellent image stability.

[Prior art]

In recent years, with the increase in the amount of information, and social demands such as resource saving, labor saving, and pollution-free production, various recording methods have been put into practical use and improved in the information recording field. Among them, thermal recording materials The thermal recording method uses (1) primary color development that does not require a developing process, (2) the hardware is simple and compact, and maintenance costs are low; (3) the sheet itself has a feel similar to that of plain paper. Due to its relatively low cost, it is widely used in computer output, medical measurement recorder fields, facsimile fields, printer fields, PO5
It has been put to practical use in travel labels, tickets for vending machines, etc. The heat-sensitive recording material used in such a method includes a heat-sensitive coloring layer containing a colorless or light-colored leuco dye having a lactone, lactam, or spiropyran ring and an acidic substance, such as an organic acid or a phenolic compound, on a support. (Special Publication No. 43-4160, 45-14)
No. 039 etc.) are publicly known. However, in the case of the above-mentioned leuco-based heat-sensitive recording material, the stability of the recorded image is poor and the color is easily erased. for example,
There is a problem in that the recorded image becomes discolored when it comes into contact with oil or a plasticizer (such as dioctyl phthalate) in a plastic film, and solving this problem is a major technical challenge for this type of recording material.

Several methods have been proposed in the past to solve this problem, such as increasing the stability of the heat-sensitive coloring layer by incorporating a large amount of resin with good water and chemical resistance into the heat-sensitive coloring layer. There are some types that increase the stability of the thermosensitive coloring layer by incorporating a resin that hardens with heat or light in the thermosensitive coloring layer, and there are also those that increase the stability of the thermosensitive coloring layer by forming a resin protective layer on the surface of the thermosensitive coloring layer. Some are protected from the effects of chemicals and water.

On the other hand, in the field of pressure-sensitive paper, one using a color developer with good chemical resistance has been proposed (Japanese Patent Application Laid-open No. 51716/1983,
(Japanese Patent Publication No. 51-25174), in this case, although the use of a specific color developer is effective for pressure-sensitive paper, it is not effective for heat-sensitive recording paper, and the color developing area is not stable when it comes into contact with a plasticizer. However, there is a problem in that color development occurs in the ground color area (non-color development area). JP-A-59-11286 also discloses certain color developers, which may be suitable for pressure-sensitive papers, but most of them are unsuitable for heat-sensitive recording materials. . That is, the initial density of the background color portion is high (background fog), and only an extremely low-quality heat-sensitive recording material can be obtained. Furthermore, many of them, like the color developers used in the pressure-sensitive paper field, develop color in the background color when they come into contact with plasticizers.

〔the purpose〕

The object of the present invention is to achieve the following by combining a specific fluoran compound and an imidazole derivative complex of zinc thiocyanate.
Not only does the coloring area not discolor when it comes into contact with oil or plasticizer, and the background color area does not develop color, but it also does not develop color in the background color area even when alcohol is attached, which is not seen in conventional thermal recording materials. The object of the present invention is to provide a heat-sensitive recording material with extremely high image stability.

〔composition〕

That is, the heat-sensitive recording material of the present invention has the general formula (1) (wherein,
R1+R2 represents an alkyl group having 1 to 6 carbon atoms, R3+R4 each represents an alkyl group having 1 to 2 carbon atoms or a halogen atom, and k and Q each independently represent 0, 1. or 2, m represents 0 or 1) and general formula (n) (wherein R5+REi each independently represents an alkyl group having 1 to 6 carbon atoms, R7 represents 1 carbon number ~2 alkyl groups or halogen atoms, n is O2l or the number of 2); and at least one fluoranic compound selected from fluoranic compounds represented by the formula (2) and thiocyanic acid represented by the following structural formula (m). A special method characterized by utilizing a color-forming reaction between zinc and an imidazole derivative complex (wherein R8 represents a saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms). Specific examples of the fluoran compound represented by the formula include the following.

3-(N-ethyl-phluidino)-6-methyl-7
- Aniritsufluoran.

3-(N-methyl-N-phenyl)-6-nityl-7-
(ρ-methylanilino)fluorane.

3-(N-normalhexyl-ρ-toluidino)-6-
Gloro 7-anilinofluorane.

3-(N-ethyl-N-phenyl)-6-methyl-7-
(p-chloroanilino)fluoran, 3-(N-n-n-butyl-〇, P-dimethylphenyl)-6-methyl-
7-Anilitufluoran.

3-(N-methyl-ρ-toluidino)-7-(o-chloroanilino)fluoran and the like.

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

3-diethylamino-7-(0-chloroanilino)fluoran.

3-dinormalbutylamino-7-(Q-chloroanilino)fluoran, 3-(N-isoamyl-N-ethylamino)-7-(o
.

P-dichloroanilino)fluoran, 3-(N-cyclohexyl-N-methylamino)-7-
(0-chloroanilino)fluoran, 3-diethylamino-7-(o-methylanilino)fluoran, and the like.

Specific examples of the imidazole derivative complex of zinc thiocyanate represented by the general formula (III) include the following.

Zinc thiocyanate l-methylimidazole complex, zinc thiocyanate l-ethylimidazole complex, zinc thiocyanate 1-vinylimidazole complex, zinc thiocyanate 1
-allylimidazole complex, zinc thiocyanate 1-n-n-butylimidazole complex, zinc thiocyanate l-isopropylimidazole complex, zinc thiocyanate 1-hexylimidazole complex, etc.

All of the above-mentioned fluoran compounds may be used alone or in combination or in a combination of two or more. Here, the weight ratio of the leuco dye to the imidazole derivative complex of zinc thiocyanate is suitably about 1:1 to 6.

In addition, in the heat-sensitive coloring layer of the present invention, various conventional binders to be bonded and supported on the support may be appropriately used, such as polyvinyl alcohol, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, ribinylpyrrolidone, etc. , 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 the binder. can.

In addition, in the present invention, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material, such as fillers,
A surfactant, a thermofusible substance, a lubricant, etc. can be used in combination. In this case, fillers include, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, and surface-treated inorganic fine powders such as calcium and silica. ,
Organic fine powders such as urea-formalin resin, styrene/methacrylic acid copolymer, and polystyrene resin can be mentioned, and examples of the thermofusible substance include higher fatty acids or their esters, amides, or metal salts. , various waxes, condensates of aromatic carboxylic acids and amines, phenyl benzoate, higher linear glycols, dialkyl 3,4-epoxy-hexahydrophthalates, higher ketones, and other thermofusible organic compounds. Examples include those having a melting point of about 50 to 200°C.

The heat-sensitive recording material of the present invention can be produced by, for example, coating a heat-sensitive layer-forming coating solution containing the above-mentioned components on a suitable support such as paper, synthetic paper, or plastic film, and drying it. In particular, it is used in the field of recording, such as thermal labels for PO5, which often come into contact with oil, plasticizers, and alcohol, thermal paper used in thermal tickets, and recorders for medical measuring instruments.

〔effect〕

The heat-sensitive recording material of the present invention has the following features.

(1) The imidazole derivative complex of zinc thiocyanate represented by the above-mentioned structural formula (III) is easy to synthesize, so there are no problems in obtaining it, and it can be obtained in high yield, high purity, and at a relatively low cost.

(2) At least one selected from the fluoran compounds of the general formulas (I) and (II) and the structural formula (m)
By combining zinc thiocyanate with an imidazole derivative complex represented by
A heat-sensitive recording material with extremely excellent image stability is obtained that does not cause decolorization of colored areas or color development of background color areas even when in contact with plasticizers, and does not develop color in the background color areas even when alcohol is attached. It will be done. In addition, the colored image does not fade over time or white powder phenomenon occurs, and is very stable.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. Note that all parts and percentages shown below are based on weight.

Reference Example: Dissolve 23.60 g of zinc thiocyanate in 400+n Q of water.

■-24.47g of vinylimidazole and 20g of ethanol
When the solution dissolved in mQ is added dropwise to the above solution under stirring, a white precipitate immediately forms. After filtering this precipitate and washing with water,
dry. The dried white powder was recrystallized from a mixed solvent of water and ethanol to obtain white crystals of 1-vinylimidazole complex of zinc thiocyanate with a melting point of 105 to 107°C (41.5°C).
I got g.

Example 1 A mixture consisting of the following compositions was separately ground for two days using a magnetic ball mill and dispersed to obtain [A) solution, [8) solution, [
C] Solution was prepared.

[A] Liquid 3-(N-ethyl-p-toluidino)-6-methyl-7
-Anilitsufluoran 20 parts 10% hydroxyethylcellulose aqueous solution 20 parts water
60 parts [B] Liquid 1-vinylimidazole complex of zinc thiocyanate 20 parts 5% methylcellulose aqueous solution 20 parts water
60 parts (C) Fine powder of liquid urea-formalin condensation resin 20 parts 5% methylcellulose aqueous solution 20 parts water
60
A heat-sensitive coloring layer solution having the following composition was prepared using the solutions I"A] to CC) obtained as above, and the standard basis weight was 50 g.
/rrr commercially available high-quality paper with a wire bar selected to give a dry coating weight of 4 to 5 g/m, and then dried, and then the smoothness of the surface of the heat-sensitive coloring layer was 500 to 60 in Bekk smoothness.
A heat-sensitive recording sheet (a) of the present invention was prepared by calendering so that the temperature was 0 seconds.

Thermosensitive coloring layer liquid (1) (A) liquid 1
0 parts (2) CB) liquid
30 parts (3) (C) liquid
30 parts (4) Isobutylene-maleic anhydride
Example 2 20% alkaline aqueous solution of 10 parts copolymer A thermosensitive recording sheet (b
)made.

[D] Liquid 3-di-n-butylamino-7-(o-gloroanilino)fluoran 20 parts 10% hydroxyethylcellulose aqueous solution 20 parts water
60 copies Example 3 A thermosensitive recording sheet (c
)made.

(E) Liquid 3-diethylamino-7-(0-chloroanilino)fluoran 20 parts 10% hydroxyethylcellulose aqueous solution 20 parts water
60 copies Comparative Example ■ A thermosensitive recording sheet (d
)made.

CF3 liquid 3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-anilinofluorane 20 parts lO% hydroxyethyl cellulose aqueous solution 20 parts water
60 parts Comparative Example 2 A thermosensitive recording sheet h(e
)made.

(G) Liquid 3-diethylamino-6-methyl-7-anilinofluorane 20 parts 10% hydroxyethylcellulose aqueous solution 20 parts water
60 parts Comparative Example 3 A thermosensitive recording sheet (f
)made.

(H) Liquid 3-(N-isoamyl-N-ethylamino)-6-methyl-7-anilinofluorane 20 parts 10% hydroxyethylcellulose aqueous solution 20 parts water
6 o parts Comparative Example 4 A thermosensitive recording sheet (g
)made.

CI) Liquid 3-diethylamino-7-(m-hlifluoromethylanilino)-fluoran 20 parts 10% hydroxyethylcellulose aqueous solution 20 parts water
60 parts Comparative Example 5 A thermosensitive recording sheet (h
)made.

(J) Liquid imidazole complex of zinc thiocyanate 20 parts (melting point 143-145°C) 5% methylcellulose aqueous solution 20 parts water
6
Comparative Example 6 A thermosensitive recording sheet (I
)made.

(K) Liquid bisphenol A 20 parts 1
0% hydroxyethyl cellulose aqueous solution 20 parts water
6
0 parts or more of heat-sensitive recording sheets (a) obtained as above
(i) was printed at 150° C. using a thermal gradient tester (manufactured by Toyo Seiki) at a pressure of 2 kg and a contact time of 1 second. A thin layer of cottonseed oil was applied to the color developing area and the ground color area of the heat-sensitive recording sheets of (a) to (1).

After leaving it indoors for 24 hours, we examined the state of change and found that the results of Examples (a-c) and Comparative Examples 1 to 4 (d)
=G) showed no decolorization in the colored area and no color development in the ground color area, whereas in Comparative Example 5 (h), there was no decoloration in the color development area, but color development was observed in the background color area. . Also, that of Comparative Example 6 (
In case of i), there was no color development in the ground color area.

Discoloration of the colored area was observed.

Next, print on heat-sensitive recording sheets (a) to (1) in the same manner, cut out a 4 cm square area around the printed area, and cover it with polyvinyl chloride film (manufactured by Shin-Etsu Polymer ■, Polywrap V).
-300) stacked, and a load of 500g/- is applied to the
After adding it for 4 hours, it was taken out and the density of the ground color part and the density of the colored part was measured using a Macbeth densitometer (RD-514), and the density of the colored part was compared with the density before the test.

The results are shown in Table-1.

Table 1 (Polyvinyl chloride film test) Next, a thin layer of ethanol (reagent, special grade) was applied to the thermosensitive recording sheets (a) to (1), and after the ethanol evaporated, the concentration of the applied area was measured. The results are shown in Table-2.

Table 2 (Alcohol application test) From the above, the heat-sensitive recording material of the present invention has no background fog;
It can be seen that it is a heat-sensitive recording material with extremely high image stability, with no decoloring of the colored area and no color development of the background color area even when in contact with oil or plasticizer, and no color development of the background color area even when attached with alcohol. .

Claims (1)

[Claims] (1) General formula (I) ▲Mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, R_1 and R_2 are alkyl groups having 1 to 6 carbon atoms,
R_3 and R_4 each represent an alkyl group having 1 to 2 carbon atoms or a halogen atom, and k and l each independently represent 0, 1, or 2.
(in which R_5 and R_6 each independently represent carbon At least one fluoran compound selected from among fluoran compounds represented by an alkyl group having 1 to 6 carbon atoms, R_7 represents an alkyl group having 1 to 2 carbon atoms or a halogen atom, and n represents a number of 0, 1 or 2.
Species of fluoran compounds and the following structural formula (III) ▲Mathematical formulas, chemical formulas, tables, etc.▼(III) (In the formula, R_8 represents a saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms.) A heat-sensitive recording material characterized by utilizing a color-forming reaction between zinc thiocyanate and an imidazole derivative complex.