JPH0696342B2 - 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 color development.

[Prior art]

A general heat-sensitive recording material is a colorless or light-coloring coloring dye such as leuco dye as a coloring agent on a support such as paper or film, and a phenolic compound (especially bisphenol A) as a color developing agent for coloring the same when heated. A thermosensitive coloring layer in which a binder, a filler, a sensitivity improver, a lubricant, and other auxiliaries are dispersed in a coloring system made of an acidic substance such as an organic acid.For example, JP-B-43-4160, Kosho 45-14039,
It was introduced in Japanese Patent Laid-Open No. 48-27736 and is widely put to practical use. This type of heat-sensitive recording sheet obtains a color image by a momentary chemical reaction between a color developer and a color developer at the time of heating (a thermal printer or a facsimile having a thermal head is used for heating). Therefore, compared to other recording materials, recording can be obtained in a short time with a relatively simple device without performing complicated processing such as development and fixing, there is little noise and environmental pollution, and cost is low. Because of its advantages such as low price, it is useful for copying books, documents and the like, and is also useful as a recording material for various information and measuring instruments such as electronic calculators, facsimiles, telexes and medical measuring instruments.

On the other hand, in recent years, the demand for high-speed recording and high-density recording has increased with the development of society. For this reason, it is strongly desired to develop a recording material capable of coping with the speedup of the recording apparatus itself. The first method is to lower the melting point of the electron-accepting compound as a color developer to a practically acceptable level such as storage stability (for example, 80 to 120 ° C.), and set the melting start temperature with the leuco dye. It is to lower the speed and increase the speed. However, it is difficult to control the melting point of a phenolic compound, which is a color developing agent that is widely used in the field of thermal recording materials, and the phenolic compound itself is expensive and is not practical. The second method is, for example, JP-A-53-39139 and JP-A-53-26139.
As described in JP-A No. 53-5636, JP-A No. 53-11036, etc., various waxes, fatty acid amides, alkylated biphenyls, substituted biphenylalkanes, coumarinic acid, diphenylamine are used in the thermosensitive coloring layer. There is a method of adding a heat-melting substance having a low melting point such as a class as a sensitizer (or a melting point depressant). However, it is hard to say that the thermosensitive recording materials produced by these methods are still sufficient in terms of color density, color sensitivity, background whiteness and the like.

〔Purpose〕

An object of the present invention is to provide a heat-sensitive recording material which has sufficient color density and color sensitivity, is suitable for high-speed recording, has high background whiteness, and is extremely practical.

〔Constitution〕

The heat-sensitive recording material of the present invention is a heat-sensitive recording material utilizing a color-forming reaction between a leuco dye and a color developer, and is characterized by using a naphthalene thioether compound represented by the following general formula (I) as an auxiliary component.

In the above formula, R is an unsubstituted aralkyl group or an aralkyl group substituted with a lower alkyl group. The naphthalene thioether compound represented by the general formula (I) used as an auxiliary component in the present invention is widely used. Has a high ability to dissolve a phenolic compound that is a color developer (electron-accepting compound) and a leuco dye (electron-donating colorless dye) when heated, and by adjusting the melting point of the naphthalene thioether compound used in combination, A heat-sensitive recording material having high sensitivity can be obtained.

The naphthalene thioether compound used in the present invention has a melting point of 40 to 40 from the viewpoint of storage stability and sensitivity as a thermal recording material.
A temperature of 150 ° C is preferable, and a temperature of 50 to 120 ° C is particularly preferable. Specific examples of the naphthalene thioether compound of the present invention are shown below, but the present invention is not limited thereto.

The leuco dyes used in the present invention may be used alone or as a mixture of two or more, and as such leuco dyes,
What is applied to this type of heat-sensitive material is arbitrarily applied, and for example, leuco compounds of dyes such as triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, indolinophtalide-based dyes are preferably used. . Specific examples of such leuco dyes include those shown below.

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, 3-cyclohexylamino-6-chloro Fluoran, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3- Diethylamino-6-methyl-7-chlorofluorane, 3- (Np-tolyl-N-ethylamino) -6-methyl- -Anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluorane, 2- {3,6 -Bis (diethylamino) -9- (o-chloroanilino) xanthylbenzoic acid lactam}, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) Fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 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) fluorane, benzoyl leuco methylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrrolispirane, 6'-bromo-3'-methoxy-benzoindolino-pyrrolispirane, 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, 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluorane, 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) fluorane, 3 -(N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluorane, 3-diethylamino-5-methyl-7- (α -Phenylethylamino) fluorane, 3-diethylamino-7-piperidi Fluoran, 2-chloro-3-(N-Mechirutoruijino) -7 (p-
n-butylanilino) fluorane, 3- (N-benzyl-N-cyclohexylamino)-
5,6-benzo-7-α-naphthylamino-4′-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluorane and the like.

As the color developer used in the present invention, various electron-accepting compounds such as phenolic compounds, thiophenolic compounds, and thiourea derivatives are preferably applied, and specific examples thereof are shown below.

4,4'-isopropylidene bisphenol, 4,4'-isopropylidene bis (o-methylphenol) 4,4'-secondary butylidene bisphenol 4,4'-isopropylidene bis (2-tert-butylphenol), 4,4'-Cyclohexylidenediphenol, 4,4'-Isopropylindenebis (2-chlorophenol), 2,2'-Methylenebis (4-methyl-6-tert-butylphenol), 2,2'-Methylenebis ( 4-ethyl-6-tert-butylphenol), 4,4'-butylidene bis (6-tert-butyl-2)
-Methyl) phenol 4,4'-thiobis (6-tert-butyl-2-methyl) phenol, 4,4'-diphenol sulfone, 4,4'-diphenol sulfoxide, isopropyl p-hydroxybenzoate, p- Benzyl hydroxybenzoate, benzyl protocatechuate, stearyl gallate, lauryl gallate, octyl gallate, N, N'-diphenylthiourea, N, N'-di (m-chlorophenyl) thiourea, salicylanilide, 5-chloro -Salicylanilide, salicyl-o-chloroanilide, 2-hydroxy-3-naphthoic acid, 2-hydroxy-1-naphthoic acid, 1-hydroxy-2-naphthoic acid, 1,7-di (4-hydroxyphenylthio) -3,5-dioxaheptane, 1,5-di (4-hydroxyphenylthio) -3-oxaheptane, Zinc Dorokishinafutoe acid, aluminum, metal salts such as calcium acid.

In the present invention, in order to bond and support the leuco dye, the color developer and the auxiliary component on the support, various conventional binders can be appropriately used, and examples thereof include polyvinyl alcohol, starch and its derivatives, and methoxy. Cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose and other cellulose derivatives, sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer , Styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate,
Water-soluble polymers such as gelatin and casein, polyvinyl acetate, polyurethane, styrene / butadiene copolymer,
Polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer, styrene / butadiene /
A latex such as an acrylic copolymer can be used.

Further, in the present invention, together with the leuco dye, the color developer, and the auxiliary component, if necessary, further, an auxiliary additive component commonly used in this type of heat-sensitive recording material, for example, a filler, a surfactant, a heat-fusible component It is possible to use together a volatile substance (or a lubricant) and the like. 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 include organic fine powders such as urea-formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin.

The heat-sensitive recording material of the present invention is produced, for example, by applying a coating solution for forming a heat-sensitive layer containing each of the above-mentioned components onto a suitable support such as paper, synthetic paper, plastic film and drying. In this case, the leuco dye, the color developer, and the color-sensitivity increasing agent are appropriately used in amounts of 5-40% by weight, 20-60% by weight, and 20-60% by weight, respectively.

[Effect]

The heat-sensitive recording material of the present invention has improved sensitivity, is suitable for high-speed recording, has high background whiteness, and is extremely practical.

〔Example〕

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

Example 1 A mixture having the following composition was separately pulverized and dispersed for 2 days using a magnetic ball mill to prepare the following liquids [A] to [D].

[Liquid A]

3- (N-cyclohexyl-N-methylamino-6-methyl-7-anilinofluorane 20 parts 10% aqueous solution of hydroxyethyl cellulose 20 〃 water 60 〃 [solution B] Bisphenol A 20 parts 10% aqueous solution of hydroxyethyl cellulose 20〃 Water 60〃 [Liquid C] 2-benzylthionaphthalene 20 parts (Compound No1, melting point 85-86 ° C) 20〃 5% aqueous solution of methylcellulose 20〃 Water 60〃 [Liquid D] Calcium carbonate 20 parts 5% aqueous solution of methylcellulose 20 parts Water 60 parts Water mixed with 10 parts A solution, 30 parts B solution, 30 parts C solution, 20 parts D solution and 10 parts 20% alkali aqueous solution of isobutylene-maleic anhydride copolymer to form a thermosensitive coloring layer As liquid, weigh 50
After coating and drying on a quality paper of g / m ^{2 so} that the dry adhesion amount becomes 4 to 5 g / m ² , a thermosensitive coloring layer is provided, and then the surface of the layer is further adjusted so that the surface smoothness becomes 500 to 600 seconds. A thermosensitive recording material (a) was prepared by calendering.

Example 2 A thermosensitive recording material (b) was prepared in the same manner as in Example 1 except that the following solution [E] was used instead of the solution [B] of Example 1.
It was created.

[E] Liquid p-hydroxybenzoic acid benzyl ester 20 parts 10% aqueous solution of hydroxyethyl cellulose 20〃 water 60〃 Example 3 All the operations were carried out except that the following liquid [F] was used instead of the liquid [B] of Example 1. Thermal recording material (C) as in Example 1
It was created.

[F] liquid 1,7-di (4-hydroxyphenylthio) -3,5-dioxaheptane 20 parts 10% aqueous solution of hydroxyethyl cellulose 20 parts water 60 parts Example 4 [B] liquid of Example 1 Thermal recording material (d) was prepared in the same manner as in Example 1 except that the following [G] solution was used.
It was created.

[G] liquid 4,4'-dihydroxydiphenyl sulfone 20 parts 10% aqueous solution of hydroxyethyl cellulose 20〃 water 60〃 Comparative example 1 Example 1 except that water was used instead of the liquid [C] of Example 1.
A heat-sensitive recording material (e) was prepared in the same manner as.

Comparative Example 2 A thermosensitive recording material (f) was prepared in the same manner as in Example 2 except that water was used instead of the liquid [C] of Example 2.

Comparative Example 3 Example 3 except that water was used instead of the liquid [C] of Example 3.
A heat-sensitive recording material (g) was prepared in the same manner as.

Comparative Example 4 Example 4 except that water was used instead of the [C] liquid of Example 4.
A thermal recording material (h) was prepared in the same manner as in.

Comparative Example 5 A thermosensitive recording material (i) was prepared in the same manner as in Example 1 except that the following [H] solution was used instead of the [C] solution of Example 1.

[H] Solution 20 parts of stearic acid amide 5% aqueous solution of methylcellulose 20〃 water 60〃 Comparative Example 6 The same as Example 2 except that the above [H] solution was used instead of the [C] solution of Example 2. A thermal recording material (i) was prepared.

Comparative Example 7 A thermosensitive recording material (k) was prepared in the same manner as in Example 3 except that the above [H] solution was used instead of the [C] solution of Example 3.

Comparative Example 8 A thermosensitive recording material (l) was prepared in the same manner as in Example 4 except that the above [H] solution was used instead of the [C] solution of Example 4.

Example 5 A thermosensitive recording material (m) was prepared in the same manner as in Example 1 except that the liquid [I] was used instead of the liquid [C] in Example 1.

[I] Liquid 2- (p-methylbenzyl) thionaphthalene (Compound N
o.3, melting point 96-97 ° C) 20 parts 5% aqueous solution of methyl cellulose 20 parts water 60 parts The thermal recording materials (a) to (m) obtained as described above are
Head thermal power 0.45W / dot, 1 line recording time 20 in a thermal printing experimental device with a thin film head manufactured by Matsushita Electronic Components Co., Ltd.
The pulse width was printed at 1.6, 2.0, and 2.4 (msec) under the conditions of msec / l and scanning line density of 8 × 3.85 dots / mm, and the print density was measured with a Macbeth densitometer RD-514 (filter W-106). . The results are shown in Table-1.

Next, heat-sensitive recording materials (a) to (m) were dried at 60 ° C under dry conditions.
A 24-hour storability test was conducted to examine changes in background density. The results are shown in Table-2.

From the above results, it can be seen that the heat-sensitive recording material of the present invention has a high color-developing sensitivity and is suitable for high-speed recording, and also has a high background whiteness and is a highly practical heat-sensitive recording material.

Claims (1)

[Claims] 1. A heat-sensitive recording material utilizing a color-forming reaction between a leuco dye and a color-developing agent thereof, wherein a general formula as an auxiliary component, (In the formula, R represents an unsubstituted aralkyl group or an aralkyl group having lower alkyl as a substituent.) A heat-sensitive recording material comprising a naphthalene thioether compound represented by the formula: