JPS61242890A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material having a high dynamic developed color density and excellent weatherability such as heat resistance, moisture resistance and light resistance of an image part, by using a specified thiourea derivative as a color developer and incorporating a specified naphthol derivative in a thermal color forming layer. CONSTITUTION:A thiourea derivative of general formula (I), wherein each of R1 and R2 is independently hydrogen, halogen, trifluoromethyl or 1-4C alkyl, is used as a color developer, in a thermal recording material wherein a thermal color forming layer comprising a leuco dye and a color developer is provided on a base. In addition, a naphthol derivative of general formula (II), wherein m is 1 or 2, and R3 is subst. or unsubst. alkyl, aryl or aralkyl, is incorporated in the color forming layer. The thiourea derivative may be N,N'- diphenylthiourea or the like, and examples of the naphthalene derivative include 1-benzyloxynaphthalene and 2,7-diisoacyloxynaphthalene.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a heat-sensitive recording material, and more particularly, to a heat-sensitive recording material containing a leuco dye and a color developer capable of coloring the leuco dye when heated as coloring components. This invention relates to improvements in thermal sensitivity and weather resistance of colored images.

[Prior art]

It has been known for a long time that color-forming leuco dyes, which are normally colorless or light-colored, and color developers such as organic acidic substances melt and react when heated, producing color. Examples of applications of this color-forming reaction to recording paper are published in Japanese Patent Publication No. 43-4160, Publication No. 45-
It is disclosed in Japanese Patent No. 14039 and the like and is well known. These thermal recording sheets are used in measurement recorders, computer terminal printers, etc.

It is applied to a wide range of fields such as facsimiles, automatic ticket vending machines, and barcode labels.Recently, as these recording devices have become more diverse and more sophisticated, the quality required for thermal recording sheets has also become more sophisticated. ing. For example, as the speed of thermal heads increases, there is a demand for thermal recording sheets that can record high-density, clear images even with minute thermal energy and that have good head matching properties such as sticking and head dregs.

Coloring of heat-sensitive recording sheets occurs when a color-forming leuco dye and/or a color developer dissolves and reacts with thermal energy supplied from a thermal head, and this is one method for improving coloring sensitivity. A widely known method is to add a compound (generally called a thermofusible substance) that melts at a lower temperature than the leuco dye and developer and has a high ability to dissolve both. The compound is disclosed in the following publications, for example, JP-A-49-34842.
The publication describes nitrogen-containing compounds such as acetamide, stearamide, --nitroaniline, dinitrile phthalate, etc., and JP-A-52-106746 describes acetoacetanilide,
JP-A-53-39139 discloses alkylated biphenyl alkanes and the like.

However, in recent years, speeds have increased particularly in the field of thermal facsimile, and it has become common to drive thermal heads at high speeds. Due to heat accumulation around the head, the background of heat-sensitive recording sheets may develop color during continuous recording ( Since there are disadvantages such as residual heat color development), it is a challenge to increase the dynamic color development sensitivity without lowering the color development start temperature. but.

These compounds improve the static coloring sensitivity, but unless they are added in large quantities to the thermosensitive coloring layer, sufficient dynamic coloring sensitivity cannot be obtained, and in that case, the adhesion of molten matter (head dregs) on the thermal head may occur. If the amount is too large, sticking occurs, or the melting point is too low, the storage stability (background fog) of the heat-sensitive recording sheet may be deteriorated, making it impossible to obtain sufficiently satisfactory results.

JP-A-56-144193 proposes the use of benzyl P-oxybenzoate as a color developer. In this case, although the thermal properties are improved, the weather resistance of the image, ie, heat resistance, moisture resistance, light resistance, etc., is insufficient, and the image is likely to fade during storage.

〔the purpose〕

The object of the present invention is to provide a heat-sensitive recording material with high dynamic coloring density that provides a clear image with high density even with minute thermal energy, and which also has excellent weather resistance such as heat resistance, moisture resistance, and light resistance in the image area. The purpose of the present invention is to provide heat-sensitive recording materials.

〔composition〕

According to the present invention, in a heat-sensitive recording material in which a heat-sensitive color forming layer containing a leuco dye and a color developer is provided on a support, a thiourea derivative represented by the following general formula (1) is used as the color developer, and , there is provided a heat-sensitive recording material characterized in that the heat-sensitive coloring layer contains a naphthol derivative represented by the following general formula (II).

(In the formula, R□ and R2 each independently represent hydrogen, a halogen, a trifluoromethyl group, or an alkyl group having 1 to 4 carbon atoms.) The following general formula (■): (In the formula, Peng is 1 or 2, R3 represents a substituted or unsubstituted alkyl group, aryl group, or aralkyl group) As a specific example of a thiourea derivative represented by the general formula (R) is N,N'-diphenylthiourea, N-P-ethylphenyl-N'-phenylthiourea, N-p-butylphenyl-N'-phenylthiourea, N,N'-di-chlorophenylthiourea, N , N'-CDI-tripleomethylphenylthiourea, N,N'-G-methylphenylthiourea, and the like.

Specific examples of the naphthalene derivative represented by the general formula (II) include l-benzyloxynaphthalene, 2-benzyloxynaphthalene, 2-p-chlorobenzylnaphthalene, 2-p-isopropylbenzyloxynaphthalene, and 2-benzoyl. Oxynaphthalene, 2-(3-phenoxyprobionyloxy)naphthalene, 2-isoamyloxynaphthalene, l-phenyloxynaphthalene, 2
-Phenyloxynaphthalene, l-ρ-methylphenyloxynaphthalene, 2-p-methylphenyloxynaphthalene, 2,4-dinitrophenylthioxynaphthalene, 2-(l-naphthoxy)naphthalene, 2-(2-naphthoxy)naphthalene , 1,4-dimethoxynaphthalene,
1,4-jethoxynaphthalene, 1,4-dipropoxynaphthalene, 1,4-dibenzyloxynaphthalene, l
-methoxy-4-ethoxynaphthalene, l-ethoxy-
Examples include 4-benzyloxynaphthalene, 2,7-dibenzyloxynaphthalene, and 2,7-diituacyloxynaphthalene.

The leuco dyes used in the present invention can be applied singly or in combination of two or more types, but such leuco dyes include:
Those applied to this type of heat-sensitive material can be arbitrarily applied. For example, leuco compounds of dyes such as triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, and indolinophthalide-based dyes are preferably used. .

Specific examples of such leuco dyes include, for example.

Examples include those shown below.

3.3-bis(p-diethylaminophenyl)-phthalide, 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3.3-bis(p-dimethyl (aminophenyl)-6-diethylaminophenyl.

3.3-bis(p-dimethylaminophenyl)-6-chlorophthalide.

3.3-bis(p-dibutylaminophenyl)phthalide.

3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3
-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane.

3-diethylamino-7,8-benzfluorane, 3-
Diethylamino-6-methyl-7-chlorofluoran.

3-(N-p-tolyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2-(N-(3'- trifluoromethylphenyl)amino)-6-dinithylaminofluorane.

2-(3,6-bis(diethylamino)-9-(o-
Chloranilino)xantylbenzoic acid lactam).

3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran.

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

3-dibutylamino-7-(o-chloroanilino)fluoran, 3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluorane.

3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-(N,N-diethylamino)-5-methyl -7-(
N.

N-dibenzylamino)fluoran, benzoylleucomethylene blue, 6'-chloro-18'-methoxy-benzoindolino-
virillos biran, 6'-bromo-3'-methoxy-benzoindolino-biliros biran, 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-51-methylphenyl)phthalide, 3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-51
-methylphenyl)phthalide, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluoran.

3-pyrrolidino-7-trifluoromethylanilinofluorane.

3-diethylamino-5-chloro-7-(N-benzyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluorane, 3-diethylamino-5-chloro- 7-(α-phenylethylamino)fluoran.

3-(N-ethyl-p-toluidino)-7-(α-phenylethylamino)fluoran.

3-diethylamino-? -(o-methoxycarbonylphenylamino)fluoran.

3-diethylamino-5-methyl-7-(α-phenylethylamino)fluorane, 3-diethylamino-7-piperidinofluorane, 2-
Chloro-3-(N-methyltoluidino)-7-(p-n
-butylanilino)fluoran, 3-(N-benzyl-N-cyclohexylamino)-5
, 6-penzo 7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino 4
',5'-benzofluorane.

In the present invention, in order to bind and support the leuco dye and color developer on the support, various commonly used binders can be used as appropriate. For example, polyvinyl alcohol, starch and its derivatives, methoxy cellulose, hydroxy Cellulose derivatives such as ethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic amide/acrylic ester copolymer, acrylic amide/acrylic ester/methacrylic acid ternary copolymer, styrene Maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali salt,
In addition to water-soluble polymers such as polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, styrene/butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer, and Latex such as butyl methacrylate, ethylene/vinyl acetate copolymer, styrene/butadiene/acrylic copolymer, etc. can be used.

In addition, in the present invention, in addition to the leuco dye and color developer, if necessary, auxiliary additive components 1 commonly used in this type of heat-sensitive recording material, such as fillers, surfactants, thermofusible substances ( or 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. , urea-formalin resin, styrene/methacrylic acid copolymer, polystyrene resin, and other organic fine powders. Examples of thermofusible substances include higher fatty acids or their esters, amides, or metal salts. In addition, various waxes, condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, dialkyl 3,4-epoxy-hexahydrophthalates, higher ketones, and other thermofusible organics. Examples include 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 and drying a heat-sensitive layer-forming coating solution containing the above-mentioned components onto a suitable support such as paper, synthetic paper, or plastic lime.

〔effect〕

The heat-sensitive recording material of the present invention uses a specific color developer in combination with a specific thermofusible substance.

It is possible to provide colored images with excellent 1-speed recording performance and excellent weather resistance.

〔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.

Example 1 Dispersions A and B were prepared by pulverizing and dispersing the following components using a sand mill so that the volume average particle diameter was 2 to 3 μm.

[Dispersion A]

3-di-butylamino-7-(0-chloroanilino)fluoran 20 parts 10
% hydroxyethylcellulose aqueous solution 20〃water
60
[Dispersion B] 3.3'-dichlorophenylthiourea 12 parts 1
-Ethoxy-4-benzyloxynaphthalene 6 Calcium carbonate 12 parts 10%
Polyvinyl alcohol aqueous solution 30# water
40#
The dispersions A and B obtained as above were mixed and stirred so that the weight ratio of dispersion A:dispersion B:water was 1:5:4 to obtain a thermosensitive coloring layer forming liquid. Next, this heat-sensitive coloring layer forming liquid was applied and dried on commercially available high-quality paper with a basis weight of about 50 g/ITr so that the dry adhesion amount was 4.5 g/rrr, and further, the smoothness was 500 to 1500 seconds. The heat-sensitive recording material of the present invention was obtained by calendering.

Example 2 A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1, except that 1-nithoxy-4-benzyloxynaphthalene in dispersion B in Example 1 was changed to 1,4-dimethoxynaphthalene. .

Example 3 A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1, except that 1-nitoxy-4-benzyloxynaphthalene in Dispersion B in Example 1 was replaced with 2-benzyloxynaphthalene.

Comparative Example 1 A comparative heat-sensitive recording material was obtained in the same manner as in Example 1, except that 1-nitoxy-4-benzyloxynaphthalene in Dispersion B in Example 1 was replaced with stearic acid amide.

Comparative example 2 Dispersion C was prepared using the following components in the same manner as in the examples.

[Dispersion liquid C]

3.3'-Dichlorophenylthiourea 15 parts Calcium carbonate 10H2O%
Polyvinyl alcohol aqueous solution 30〃water
4o The weight ratio of the dispersions A and C is dispersion A: dispersion C: water =
The mixture was mixed and stirred in a ratio of 1:4:5 to obtain a comparative thermosensitive coloring layer forming liquid. This was then coated and dried on the same support as in Example 1 to a dry adhesion weight of 3.7 g/-, and then a comparative heat-sensitive recording material was obtained in the same manner as in Example.

Comparative Example 3 A comparative heat-sensitive recording material was obtained in the same manner as in Comparative Example 2, except that 3,3'-dichlorophenylthiourea in Dispersion C in Comparative Example 2 was replaced with benzyl p-oxybenzoate.

The heat-sensitive recording material obtained as described above was subjected to a dynamic color density test using 8 G-■ facsimile machines.
Furthermore, the weather resistance of the colored image area was tested. The results are shown in Table 1 below. The test machine had an 8 dot/l thermal head made by Kenshi Electronics Co., Ltd., and a heating resistor of about 4000/dot, with a main scanning recording speed of 20 m5ec/1 in and a sub-scanning of 3 .85Q/as, platen suppression 1, 5 kg/d, head input 1,
Tests were conducted under the conditions of OmJ/dot and 0.7a+J/dot. The weather resistance test was carried out on dynamic color density head input 1.0 J/dot test samples by storing them at 60°C for 24 hours and at 40°C and 90% RH for 24 hours.

The results are shown in Table 1 below.

Table 1 From the above results, it can be seen that the heat-sensitive recording material of the present invention has excellent color development against minute dynamic thermal energy, and also has very excellent image storage stability.

Claims (1)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive color forming layer containing a leuco dye and a color developer is provided on a support, the developer has the following general formula (I): ▲Mathematical formula, chemical formula, table, etc. ▼(I) (In the formula, R_1 and R_2 each independently represent hydrogen,
In addition to using a thiourea derivative represented by halogen, trifluoromethyl group, or alkyl group having 1 to 4 carbon atoms, the heat-sensitive coloring layer contains the following general formula (II): ▲Mathematical formula, chemical formula, table, etc. ▼(II) (In the formula, m is 1 or 2, R_3 represents a substituted or unsubstituted alkyl group, aryl group, or aralkyl group) A heat-sensitive recording material characterized by containing a naphthol derivative represented by the following: .