JPH078598B2 - Thermal recording material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material excellent in image stability.

[Prior art]

In recent years, along with social demands such as an increase in the amount of information, resource saving, labor saving, and pollution-free, various recording systems have been put to practical use and improved in the information recording field. The heat-sensitive recording method using (1) primary color development does not require a developing step, (2) hardware can be simple and compact, maintenance cost is low, (3) the feel is similar to plain paper, and the sheet itself Due to its relatively low price, it has been put to practical use in computer output, medical measurement recorder fields, facsimile fields, printer fields, POS labels, vending machine tickets, etc. As the thermosensitive recording material used in such a system, a colorless or light-colored leuco dye having a lactone, a lactam, or a spiropyran ring on a support and an acidic substance, for example, a thermosensitive coloring layer containing an organic acid or a phenolic compound. Those provided (Japanese Patent Publication No. 43-4160, 45-14039, etc.) are known. However, the above-mentioned leuco-type heat-sensitive recording material has the drawback that the stability of the recorded image is poor and the color is easily erased. For example, there is a problem that the recorded image is erased when it comes into contact with oil or a plasticizer (such as dioctyl phthalate) in a plastic film, and the solution of this problem becomes a major technical problem in this type of recording material. There is.

In the past, several proposals aimed at solving this problem have been proposed. For example, in the thermosensitive coloring layer, a large amount of a resin having good water resistance and chemical resistance was added to improve the stability of the thermosensitive coloring layer. In some cases, the thermosensitive coloring layer contains a resin that is cured by heat or light to improve the stability of the thermosensitive coloring layer.In addition, a resin protective layer is formed on the surface of the thermosensitive coloring layer to form a thermosensitive coloring layer. Some are protected from the effects of chemicals and water.

On the other hand, in the field of thermal paper, there has been proposed one using a developer having a good chemical resistance (Japanese Patent Application Laid-Open No. 48-51716, Japanese Patent Publication No.
1-25174), in this case, although the use of a specific developer is effective for pressure-sensitive paper, it is not effective for heat-sensitive recording paper, and the colored portion is stable when contacted with a plasticizer. However, there is a problem that the background color portion (non-coloring portion) is colored. Japanese Patent Laid-Open No. 59-11286 also discloses a specific developer, which may be suitable for pressure-sensitive paper, but most of them are not suitable for heat-sensitive recording materials. .
That is, the initial density of the background color portion is high (background fog), and only a very low-quality thermal recording material can be obtained. Further, many of them, like the color developing agents in the pressure sensitive paper field, cause the ground color portion to develop color upon contact with a plasticizer.

〔Purpose〕

The object of the present invention is not only that the combination of a specific fluorane compound and an isopropylantipyrine complex of zinc thiocyanate does not cause the decolorization of the color-developed portion or the ground-colored portion upon contact with oil or a plasticizer, and the alcohol It is an object of the present invention to provide a heat-sensitive recording material having extremely high image stability, which is not seen in the conventional heat-sensitive recording material in that the background color portion does not develop color even when adhered.

〔Constitution〕

That is, the heat-sensitive recording material of the present invention has the general formula (I) (In the formula, R ₁ represents a disubstituted amino group, and R ₂ has 1 to 1 carbon atoms.
2 represents an alkyl group, and R ₃ represents a hydrogen atom), and at least one fluorane compound selected from the group consisting of fluorane compounds represented by the formula (I) and an isopropylantipyrine complex of zinc thiocyanate represented by the following formula (II): It is characterized by utilizing the color development reaction between them.

In the fluorane compound represented by the general formula (I), in the formula, R ₁ represents a di-substituted amino group. Examples of the substituted amino group include, for example, alkyl groups, alkenyl groups, cycloalkyl groups and the like. And disubstituted amino groups each independently having a substituent such as a saturated or unsaturated heterocycle-containing group such as a formulaic or cyclic hydrocarbon group, a furfuryl group, or a tetrahydrofurfuryl group. Further, the alkyl group and cycloalkyl group may contain one or more ether bonds, and such groups include, for example, an oxaalkyl group, an oxacycloalkyl group and the like.

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

3-diethylamino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluorane, 3- (N-methyl-N-normalhexyl) Amino) -6
-Methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexylamino) -6-
Methyl-7-anilinofluorane, 3-dinormal butylamino-6-ethyl-7-anilinofluorane, 3- (N-ethyl-N-furfurylamino) -6-methyl-7-anilinofluor Olane, 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane, and the above-mentioned fluorane compounds are used alone or in admixture of two or more. Here, the weight ratio of the leuco dye and the isopropylantipyrine complex of zinc thiocyanate is appropriately about 1: 1 to 6.

In the thermosensitive color-developing layer of the present invention, various conventional binders may be appropriately used for binding and supporting on a support. It is preferable to use a water-soluble substance such as polyacrylamide, polyacrylic acid, starch, gelatin, etc., or an aqueous emulsion such as polystyrene, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, etc. as the binder. it can.

Further, in the present invention, if necessary, an auxiliary additive component such as a filler, which is commonly used in this type of heat-sensitive recording material, is further added.
A surfactant, a heat-fusible substance, a lubricant and the like can be used in combination. In this case, as the filler, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, inorganic fine powder such as surface-treated calcium or silica, etc. ,
Examples thereof include organic fine powders of urea-formalin resin, styrene / methacrylic acid copolymer, polystyrene resin and the like. Examples of the heat-fusible substance include higher fatty acids or their esters, amides or metal salts. , Various waxes, condensates of aromatic carboxylic acid and amine, benzoic acid phenyl ester, higher linear glycol, 3,4-epoxy-dialkyl hexahydrophthalate, higher ketone,
Other examples include heat-fusible organic compounds having a melting point of about 50 to 200 ° C.

The heat-sensitive recording material of the present invention is produced, for example, by applying a heat-sensitive layer-forming coating liquid containing each of the above-mentioned components onto a suitable support such as paper, synthetic paper, or plastic film, and drying. It is used in various recording fields, especially in thermal labels for POS, which often come into contact with oil, plasticizer, and alcohol, thermal ticket, and thermal paper applied to recorders for medical measuring instruments.

〔effect〕

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

(1) The isopropylantipyrine complex of zinc thiocyanate represented by the above formula (II) is easy to synthesize, and therefore has no problems in availability, and can be obtained in high yield and high purity at a relatively low cost.

(2) By combining at least one selected from the fluorane compounds of the general formula (I) with an isopropylantipyrine complex of zinc thiocyanate represented by the above formula (II), there is no background fog and oil, Even when contacted with a plasticizer, there is no phenomenon such as decolorization of the color-developed part or color development of the ground-colored part. Furthermore, even when contacted with water such as immersion in water, there is little decrease in image density and extremely excellent image stability. A thermosensitive recording material is obtained. In addition, the color image does not fade over time or the white powder phenomenon does not occur, and is very stable.

〔Example〕

Next, the present invention will be described in more detail with reference to Examples. The parts and% shown below are based on weight.

Synthesis Example 9.08 g of zinc thiocyanate was dissolved in 150 ml of water. Separately, 23.03 g of isopropyl antipyrine was added to a 50% aqueous solution of ethanol.
A solution dissolved in 200 ml was prepared, and a white precipitate was produced when the solution was added dropwise to the above solution under stirring. This precipitate was separated by filtration, washed with water, dried, and the obtained white powder was recrystallized with a mixed solvent of water and ethanol to obtain 22.8 g of white crystals of an isopropylantipyrine complex of zinc thiocyanate having a melting point of 113 to 115 ° C. .

Example 1 A mixture having the following composition was separately pulverized for 2 days using a magnetic ball mill, and dispersed to obtain [A] liquid, [B] liquid,
A liquid [C] was prepared.

[A] Liquid 3- (N-cyclohexyl-N-methylamine) -6-
Methyl-7-anilinofluorane 20 parts 10% Hydroxyethyl cellulose aqueous solution 20〃 Water 60 parts [B] liquid 20% isopropylantipyrine complex of zinc thiocyanate 5% Methyl cellulose aqueous solution 20〃 water 60〃 [C] liquid Urea-formalin condensation Resin fine powder 20 parts 5% aqueous solution of methylcellulose 20〃 water 60〃 Using [A] liquid to [C] liquid obtained as described above,
A thermosensitive color developing layer solution having the following composition was prepared, and a commercially available high-quality paper having a standard basis weight of 50 g / m ² was coated with a wire bar so that the dry coating amount was 4 to 5 g / m ² , dried, and then the surface of the thermosensitive color developing layer. The heat sensitive recording material (a) of the present invention was prepared by calendering so that the smoothness of No. 5 was Beck's smoothness of 500 to 600 seconds.

Thermosensitive coloring layer liquid (1) [A] liquid 10 parts (2) [B] liquid 30 parts (3) [C] liquid 30 parts (4) 20% of isobutylene-maleic anhydride copolymer
Alkaline aqueous solution 10 parts Example 2 A thermosensitive recording material (b) was prepared in the same manner as in Example 1 except that the following solution [D] was used instead of the solution [A] of Example 1.
made.

[D] liquid 3-diethylamino-6-methyl-7-anilinofluorane 20 parts 10% aqueous solution of hydroxyethyl cellulose 20〃 water 60〃 Example 3 The following liquid [E] was used instead of the liquid [A] of Example 1. Thermal recording material (c) in the same manner as in Example 1 except that it was used.
made.

[E] liquid 3- (N-isoamyl-N-ethylamino-6-methyl-7-anilinofluorane 20 parts 10% aqueous solution of hydroxyethyl cellulose 20〃water 60〃 Example 4 [A] liquid of Example 1 Instead, a thermal recording material (d) was prepared in the same manner as in Example 1 except that the following [F] solution was used.

[F] liquid 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane 20 parts 10% hydroxyethylcellulose aqueous solution 20 parts water 60 parts Comparative Example 1 [A of Example 1 ] The thermosensitive recording material (e) was prepared in the same manner as in Example 1 except that the following liquid [G] was used instead of the liquid.
made.

[G] Liquid 3- (N-ethyl-N-p-tolylamino) -6-methyl-7-anilinofluorane 20 parts 10% Hydroxyethylcellulose aqueous solution 20〃 Water 60〃 Comparative Example 2 [A] of Example 1 Thermal recording material (f) was prepared in the same manner as in Example 1 except that the following liquid [H] was used instead of the liquid.
made.

[H] liquid 3-dinormal butylamino-7- (o-chloroanilino) fluorane 20 parts 10% aqueous solution of hydroxyethyl cellulose 20〃 water 60〃 Comparative example 3 [B] liquid in Example 1 was replaced with the following liquid [I]. Thermal recording material (g) in the same manner as in Example 1 except that
made.

[I] Solution 20 parts of imidazole complex of zinc thiocyanate (melting point 143 to 145 ° C.) 5% aqueous solution of methylcellulose 20〃 water 60〃 Comparative Example 4 The following [J] solution is used instead of the [B] solution of Example 1. Thermal recording material (h) in the same manner as in Example 1 except for the above.
made.

[J] Solution 20 parts of antipyrine complex of zinc thiocyanate (melting point 118 to 120 ° C.) 5% aqueous solution of methylcellulose 20〃 water 60〃 Comparative Example 5 Instead of the solution [B] of Example 1, the following solution [K] was used. A thermal recording material (i) was prepared in the same manner as in Example 1 except that it was present.

[K] Liquid Bisphenol A 20 parts 10% Hydroxyethyl cellulose aqueous solution 20〃 Water 60〃 The thermosensitive recording materials (a) to (i) obtained as described above are subjected to a pressure of 2 kg with a thermal gradient tester (manufactured by Toyo Seiki). Printing was performed at 150 ° C with a contact time of 1 second. When cotton seed oil was thinly applied to the color-developed portion and the ground-colored portion of the heat-sensitive recording materials (a) to (i) and left in the room for 24 hours, the state of change was examined. And those of Comparative Examples 1-2 and Comparative Example 4 (e, f,
In the case of h), neither decoloring of the color-developed portion nor coloring of the ground-colored portion was observed, but in Comparative Example 3 (g), although the color-developed portion was not decolored, the ground-colored portion was colored. In Comparative Example 5 (i), the background color portion did not develop color, but the color development portion was decolored.

Next, the thermal recording materials (a) to (i) were printed in the same manner, and a 4 cm square was cut out around the printed portion, and a polyvinyl chloride film (Polylap V-300 manufactured by Shin-Etsu Polymer Co., Ltd.) was cut on this. After stacking one sheet and applying a load of 500 g / cm ² at room temperature for 24 hours, take it out, measure the density of the background color part and the density of the color development part with a Macbeth densitometer (RD-514), and determine the density of the color development part, The results are shown in Table 1 in comparison with the concentration before the test.

Next, print the thermosensitive recording materials (a) to (i) in the same way, cut out a 4 cm square centering on the printed part, immerse in a 100 ml beaker filled with tap water, store at room temperature for 24 hours, then take out. After drying, the density of the colored part was measured and the density of the colored part was compared with the density before the test.

The results are shown in Table-2.

As described above, the heat-sensitive recording material of the present invention has no decolorization of the color-developing part and no color-developing of the ground-color part even when contacted with oil or a plasticizer, and further, the color-developed part after contact with water such as immersion in water. It can be seen that the heat-sensitive recording material has extremely high image stability without any decrease in density.

Claims (1)

[Claims] 1. A general formula (I) (In the formula, R ₁ represents a disubstituted amino group, and R ₂ has 1 to 1 carbon atoms.
2 represents an alkyl group and R ₃ represents a hydrogen atom), and at least one fluorane compound selected from the group consisting of fluorane compounds represented by the following formula (II) A thermosensitive recording material characterized by utilizing a color-forming reaction between zinc thiocyanate represented by the formula and an isopropylantipyrine complex.