JPH03290287A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material which is excellent in plasticity resistance of a coloring image by a method wherein a thermal recording layer having colorless or light colored coloring compound and sulphonium salt as given by the formula (1) as main component is provided on a base material. CONSTITUTION:A thermal recording coloring layer having a colorless or light colored coloring compound and sulphonium salt as given by the formula (1) as main components is provided on a base material for a thermal recording material. After dispersing independently coloring material, sulphonium salt expressed by formula (1), further as required, thermally fusible compound and other additives together with a binder, water, or organic solvent with a dispersing device, by mixing or simultaneously dispersing the coloring material, sulphonium salt expressed by formula (1), etc., a thermal coloring layer forming applicable liquid is prepared. By applying and drying it on the base materials of paper, plastic sheet, synthetic paper, etc., so as to obtain 5-40g/m<2> by dry wt. the excellently plasticizer resistant thermal recording material on which color disappearance and fading of the color image are not generate with a plasticizer or the like, can be obtained.

Description

[Detailed description of the invention] Industrial applications be.

Prior Art A heat-sensitive recording material using a colorless or light-colored color-forming substance and a color-developing substance capable of coloring the color-forming substance when heated is disclosed in Japanese Patent Publication No. 43.
It was published in Japanese Patent Publication No. 4514039 and has been widely put into practical use.

In general, heat-sensitive recording materials: Leuco dyes and complexing agents such as phenolic substances are separately dispersed into fine particles, and then both are mixed and additives such as binders, sensitizers, fillers, and lubricants are added. The leuco dye and/or the color developer melt and come into contact with each other when heated, and color recording is obtained through a chemical reaction that is applied to a support such as paper, film, or synthetic paper as a coating solution. A heat-sensitive recording material, usually in the form of a sheet, is prepared. In order to color the heat-sensitive recording sheet (C), a thermal printer with a built-in thermal head or the like is used.

Compared to other recording methods, this thermal recording method has (1) no noise during recording; (2) There is no need for developing and fixing, (3
) It is maintenance free, (4) The machine is relatively inexpensive, etc.! Depending on the characteristics, facsimile field, computer output, printer field such as calculator, etc.
It is widely used in the field of medical measurement recorders, automatic ticket vending machines, thermal recording labels, etc.

Among these fields of use, their use is increasing for labels, etc., with the expansion of POS systems in retail stores, supermarkets, etc., and for train tickets, etc. in automated station service systems. A problem in these applications is that the colored image disappears or fades due to the presence of plasticizers and the like.

- Conventionally, various methods have been proposed to improve the plasticizer resistance of colored images, but no satisfactory method has yet been established.

Problems to be Solved by the Invention An object of the present invention is to solve the above-mentioned drawbacks of the prior art. That is, it is an object of the present invention to provide a heat-sensitive recording material having good so-called plasticizer resistance, which does not cause color erasure or fading of colored images due to plasticizers or the like.

Means for Solving the Problems The present inventors have completed the present invention as a result of various studies to achieve the above object.

That is, the present invention provides a heat-sensitive recording material characterized in that a heat-sensitive recording layer containing a colorless or light-colored color-forming compound and a sulfonium salt represented by the following general formula (I) as main components is provided on a support. It is.

(In the formula, R1 is hydrogen, methyl, acetyl, methoxycarbonyl, ethoxycarbonyl, tert-methoxycarbonyl, benzoyl, benzyloxycarbonyl, 4-
Methoxybenzyloxycarbonyl, phenoxycarbonyl or naphthylmethylene, R2 and R3 independently represent hydrogen, halogen, or alkyl having 1 to 4 carbon atoms, and R4 and lR5 independently represent 1 to 4 carbon atoms. alkyl; methyl, ethyl, methoxyethoxy, benzyl or naphthylmethylene optionally substituted with halogen or nitro;

Also, X is BF4. PF6. SbF6 or CL 04
shows. ) Detailed explanation of the present invention.

The heat-sensitive recording material of the present invention mainly contains a sulfonium salt of the above general formula (I) and a colorless or light-colored color-forming substance, and further contains a thermofusible compound, a filler, a surfactant, etc. as a binder, if necessary. It can be obtained by incorporating it into the heat-sensitive recording coloring layer.

Examples of the sulfonium salt of the above general formula (I) used in the present invention include compounds shown in Table 1 below.

These sulfonium salts may be used alone or in combination. In addition, conventionally known color developers, such as 4,4
It can also be used in combination with -isopropylidene diphenol, 2,2'-sialyl-4,4-sulfonyl diphenol, 4-hydroxybenzoic acid benzyl ester, etc.

The preferred amount of these to be used is 3 to 25% by weight, more preferably 10 to 22% by weight, based on the total weight of the heat-sensitive coloring layer.

Further, as the color-forming substance, xanthine compounds, triarylmethane compounds, spiropyran compounds, diphenylmethane compounds, thiazine compounds, fluorene compounds, etc. are used, and specific examples thereof are given below.

2-anilino-3-methyl-6-dinithylaminofluoran, 2-anilino-3- as a xanthine compound
Methyl-6-(methylcyclohexylamino)-fluorane, 2-anilino-3-methyl-6-(ethylisopentylamino)fluorane, 2-anilino-3-methyl6-sibutylaminofluorane, 2-(pchloroanilino /)-3-methyl-6-dinithylaminofluorane,
2-(p-fluoroanilino)-3-methyl-6-dinithylaminofluorane, 2-anilino-3-methyl-6
-(p-toluidinoethylamine)fluorane, 2(p
-Toluidino)-3-methyl-6-dinithylaminofluorane, 2-(0-chloroanilino)-6-sibutylaminofluorane, 2(0-fluoroanilino)-6-dinithylaminofluorane, 2 ．． -(0-fluoroanilino)6-sibutylaminofluorane, 2-anilino-3
-Methyl-6-piperidinofluorane, 2-anilino-
3-Methyl-6-pyrrolidinofluorane, 2-ethoxyethylamino-3-chloro-6-dinithylaminofluorane, 2-a=IJ/-3-chloro-6-dinithylaminofluorane, 2- 3,3-bis(p-dimethylaminophenyl) 6-dimethylaminophthalide (as a triarylmethane compound such as chloro-6-eneethylaminofluorane, 2-methyl-6-dinithylamine fluoran, etc.) Other name: crystal violet lactone),
3.3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1゜2
-dimethylaminoindol-3-yl)phthalide, etc.
3-methyl-3-spiro- as a spiropyran compound
dinaphthopyran, 1.33 trimethyl-6-nitro-8
-Methoxyspiro(indoline-2,2-benzopyran), he-halophenylleukoolamine as a diphenylmethane compound, thiazine compound and cytenopenzoylleucomethylene flue, 3,6-bis(dimethylamino) as a fluorene compound. ) Fluorene spiro(9,3)-6-dimethylaminophthalide, 3,6-
Bis(dimethylamino)fluorenespiro(9,3)-
Examples include 6-pyrrolidinophthalide, 3-dimethylamino-6-ethylaminofluorenespiro(9,3)-6pyrrolidinophthalide, and these 10-ico dyes can be used alone or in combination. It will be done.

Methyl cellulose, methoxy cellulose as binders,
Hydroxyethylcellulose, carboxymethylcellulose, polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, silica-modified polyvinyl alcohol, alkali salts of acrylic acid styrene copolymer, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch and Derivatives thereof, water-soluble ones such as casein, gelatin, alkali salts of styrene-maleic anhydride copolymer, alkali salts of iso(or diiso)butylene-maleic anhydride copolymer, or polyvinyl acetate, vinyl chloride/acetic acid Water-insoluble emulsions such as vinyl copolymers, polystyrene, polyacrylic esters, polyurethanes, and styrene/phtadiene/acrylic acid copolymers are used.

Fillers include calcium carbonate, magnesium carbonate, magnesium oxide, silica, white carbon, talc,
Examples include clay, alumina, magnesium hydroxide, aluminum hydroxide, aluminum oxide, barium sulfate, polystyrene resin, urea-formalin resin, and the like.

Thermofusible compounds include waxes such as animal and vegetable waxes, polyethylene wax, and synthetic waxes, higher fatty acids, higher fatty acid amides, higher fatty acid metal salts, acetylated aromatic amines, aromatic ether compounds, biphenyl derivatives, etc. Those that are solid and have a melting point of 80° C. or higher are preferred.

Other additives include lubricants such as zinc stearate, calcium stearate, and aluminum stearate;
Various surfactants, antifoaming agents, etc. are added as necessary.

The heat-sensitive recording material of the present invention can be obtained using the above-mentioned material, for example, by the following method.

That is, a color-forming substance, a sulfonium salt represented by the general formula (I), and if necessary, a heat-fusible compound and other additives are separately mixed with a binder and water or an organic solvent using a ball mill, an attritor sand mill, etc. After dispersing with a dispersing machine, it is mixed or a color-forming substance and the general formula (
A coating solution for forming a heat-sensitive coloring layer is prepared by simultaneously dispersing the sulfonium salt shown in I), and the dry weight is 5 to 40 g on a support such as paper, plastic sheet, synthetic paper, etc.
/m2 by coating with a bar coater or the like and drying to obtain the heat-sensitive recording material of the present invention.

Note that the ratio of the color-forming substance to the sulfonium salt represented by the general formula (I) is usually 1=1 to 1:10 in terms of dry weight ratio.

Further, if necessary, an intermediate layer may be provided between the support and the thermosensitive coloring layer, or an overcoat layer may be provided on the thermosensitive coloring layer.

The colored image of the heat-sensitive recording sheet of the present invention containing the sulfonium salt represented by the general formula (I) in the heat-sensitive coloring layer is produced by the decolorization of the plasticizer due to the action of the sulfonium salt represented by the general formula (CI). action is inhibited and shows good plasticizer resistance.

3 Examples The present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

In the examples, "1 part" indicates parts by weight.

Example 1 A mixture having the following composition was separately ground and dispersed using a sand grinder so that the average particle size was 2 μm or less to prepare an (Al-(C') solution).

(5) Solution (B) Solution (Q solution 4) 50 parts of water was applied onto the surface of high-quality paper (m2) so that the dry solid content was 10 g/m'' and dried to obtain a heat-sensitive recording sheet of the present invention. .

Examples 2 to 8 A thermosensitive recording sheet of the present invention was obtained in the same manner as in Example 1, except that a sulfonium salt of the following formula was used in place of the sulfonium salt shown in Table 1 used in Example 1.

(Example 2) Sulfonium salt of ■ in Table 1 (Example 3)
Sulfonium salt (■) in Table 1 (Example 4) Sulfonium salt (■) in Table 1 (Example 5) Sulfonium salt (■) in Table 1 (Example 6) Sulfonium salt (■) in Table 1 (Example 7)
) Sulfonium salt of ■ in Table 1 (Example 8) ■ in Table 1
Sulfonium salts Examples 9 to 10 Using 2(2-fluoroanilino)-6-sibutylaminofluorane in place of the 2-anilino-3 methyl-6-sibutylaminofluorane used in Example 1,
A heat-sensitive recording sheet of the present invention was obtained in the same manner as in Example 1, except that a sulfonium salt of the following formula was used in place of the sulfonium salt in Table 1.

(Example 9) Sulfonium salt of ■ in Table 1 (Example 10
) Sulfonium Salt Example 11 (■) in Table 1 A mixture having the following composition was separately ground and dispersed for 1 hour using a sand grinder to obtain a solid liquid and a liquid (B).

Liquid (A) and Liquid CB) were then mixed at the following mixing ratio to prepare a thermosensitive coloring layer forming liquid.

Thermosensitive color forming layer forming solution Next, this mixture was spread on a milky white polyester sheet for two times.
A heat-sensitive recording sheet of the present invention was obtained by applying 0 g/m2 and drying.

Example 12゜Example 1 except that the sulfonium salt shown in Table 1 (■) was used in place of the sulfonium salt shown in (■) in Table 1 used in Example 11.
A thermosensitive recording sheet of the present invention was obtained in the same manner as in Example 1.

Comparative Example 1゜Instead of the sulfonium salt in Table 1 of Example 1, 4.4-
A comparative heat-sensitive recording sheet was obtained in the same manner as in Example 1 except that impropylidene diphenol was used.

Comparative Example 2 Example 10 A comparative heat-sensitive recording sheet was obtained in the same manner as in Example 1, except that di-4-hydroxybenzoic acid benzyl ester was used in place of the sulfonium salt in Table 1.

Comparative Example 3゜In place of the sulfonium salt in Table 1 of Example 11, D4,4
A comparative heat-sensitive recording sheet was obtained in the same manner as in Example 11 except that - isofuropylidene diphenol was used.

Table 2 shows the test results for the heat-sensitive recording sheets obtained in the above Examples and Comparative Examples.

7 8 Table 2 ■) Ground Skin: Measure the uncolored sample using Macbeth reflection densitometer R.
Value measured with D-914 type.

2) Color density: printing pressure 1 kg/cm” using a hot plate
The color density was measured using a Macbeth reflection densitometer model RD-914 when the sample was pressed for 5 seconds at 140°C.

3) Thermoplastic properties: 1 with a printing pressure of 1 kg/cm2 on a hot plate.
Image density after pressing a polyvinyl chloride lamp film (approximately 30 g/cm') on both sides of a heat-sensitive recording sheet that was pressed against the sample for 5 seconds at 40°C to develop color, and leaving it at 40°C for 24 hours. was measured and expressed as a percentage of the image density before the test.

From the above comparative test results, it is clear that the heat-sensitive recording sheet of the present invention has sufficient color development and the image has improved plasticizer resistance.

Effects of the Invention A heat-sensitive recording material that provides a colored image with excellent plasticizer resistance was obtained.

Claims (1)

[Claims] (1) A heat-sensitive recording material characterized by having a heat-sensitive recording color-forming layer mainly composed of a colorless or light-colored color-forming compound and a sulfonium salt represented by the following general formula (I) on a support ▲Mathematical formula, chemical formula , tables, etc.▼(I) (In the formula, R_1 is hydrogen, methyl, acetyl, methoxycarbonyl, ethoxycarbonyl, tert-butoxycarbonyl, benzoyl, benzyloxycarbonyl, 4-
Methoxybenzyloxycarbonyl, phenoxycarbonyl or naphthylmethylene, R_2 and R_3 independently represent hydrogen, halogen or alkyl having 1 to 4 carbon atoms, and R_4 and R_5 independently represent 1 to 4 carbon atoms. alkyl; methyl, ethyl, methoxy, ethoxy, benzyl or naphthylmethylene optionally substituted with halogen or nitro; Also, X is BF_4,
PF_6, SbF_6 or ClO_4)