JPH0632998B2 - 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) Usually a colorless or light-colored colorless dye (leuco dye) and phenols, a heat-sensitive recording sheet using a heat color reaction of an organic acid, JP-B-43-4160, JP-B-45-14039,
It was announced in Japanese Patent Laid-Open No. 48-27736 and is widely put into practical use. Generally, a thermal recording sheet is prepared by pulverizing and dispersing a leuco dye and a color developing agent such as a phenolic substance into fine particles, respectively, and then mixing them together to form a binder, a filler, a sensitivity improver, a lubricant and other auxiliary agents. Is applied to a support such as paper and film, and color recording is obtained by an instantaneous chemical reaction by heating.

For heating the color recording of such a heat-sensitive recording sheet, a thermal printer having a built-in thermal head, a facsimile machine or the like is used. In comparison with other recording materials, such a recording sheet can obtain a recording in a relatively short time without complicated processing at the time of development and fixing, no noise is generated, and a comparison is made. Due to the advantage of being relatively inexpensive, not only copying books, documents, etc., but also electronic computers,
It is widely used as a recording material for information such as facsimiles, telex, and medical measuring instruments, and measuring instruments. However, such a conventional thermosensitive recording sheet comprising a combination of a leuco dye and a phenolic substance has drawbacks in that the color-developed portion is reduced in density or erased by oils and fats.

On the other hand, it has been proposed to improve such a point in the conventional thermosensitive recording sheet by providing a water-soluble polymer overcoat layer on the thermosensitive coloring layer. Therefore, the thermal sensitivity is deteriorated, and the coating process of the overcoat layer is required, resulting in high cost.

〔Purpose〕

The present inventor has conducted extensive studies to overcome the drawbacks found in the prior art, and as a result, when a phenolic compound represented by the following general formula is used as a developer, the concentration of the color-developed part is lowered by oils and fats. It has been found that a heat-sensitive recording sheet that does not bleach or lose color can be provided, and the present invention has been completed.

〔Constitution〕

That is, according to the present invention, in a heat-sensitive recording material utilizing a color-forming reaction between a leuco dye and its developer, a general formula as the developer is used. There is provided a heat-sensitive recording material characterized by using a phenolic compound represented by the formula (wherein R represents an alkylene group having 1 to 6 carbon atoms).

The leuco dyes used in the present invention may be used alone or as a mixture of two or more kinds.
What is applied to this type of heat-sensitive material is arbitrarily applied, and for example, leuco compounds of various dyes such as triphenylmethane type, fluorane type, phenothiazine type, auramine type and spiropyran type 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 letolactone), 3,3-bis ( p-dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexyl Amino-6-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benz Fluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3- (Np-tolyl-N-ethylamino) -6-methyl-7-
Anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) amino}
-6-diethylaminofluorane, 2- {3,6-bis (diethylamino) -9 (o-chloroanilino) xanthylbenzoate 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 Leucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrrilospirane, 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'-dimethylaminophenyl)
-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-prolidino-7-trifluoromethylanilinoflu Oran, 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-methoxycarbonylphenyl) Amino) fluorane, 3-diethylamino-5-methyl-7- (α-phenylethylamino) fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro -3- (N-methyltoluidino) -7- (pn-butylanilino) fluorane, 3- (N-benzyl-cyclohexylamino) -5,6-benzo-7-α-naphthylamino-4'-bromofur Oran, 3-diethylamino-6-methyl-7-mesitidino-4 ',
5'-benzofluorane and the like.

These may be used alone or in combination of two or more.

Specific examples of the phenolic substance represented by the above general formula include those shown below.

(1) (2) (3) (Four) (Five) (6) (7) The phenolic compound used in the present invention is not limited to these, and these may be used alone or in admixture of two or more. The phenolic substance represented by the above general formula has never been used as a material for a thermal recording sheet until now.
In the present invention, the color-developing substance comprising the above-mentioned phenolic compound is generally used in an amount of 1 to 10 parts by weight, preferably 2 to 6 parts by weight, based on 1 part by weight of the leuco dye.

In the present invention, in order to bond and support the leuco dye and the color developer on a support, various conventional binders can be appropriately used, and examples thereof include polyvinyl alcohol, starch and its derivatives, methoxycellulose and hydroxy. Cellulose derivatives such as ethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid ternary copolymer, stellene / Maleic anhydride copolymer alkali salt,
Isobutylene / maleic anhydride copolymer Alkaline salt, polyacrylamide, sodium alginate, gelatin, casein and other water-soluble polymers, polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic acid ester A latex such as a vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer, or styrene / butadiene / acrylic copolymer can be used.

Further, in the present invention, together with the leuco dye and the color developer, if necessary, further auxiliary components commonly used in this type of heat-sensitive recording material, for example, a filler, a surfactant, a heat-fusible substance ( Alternatively, a lubricant) or 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 carbonate and silica, urea-formalin resin, styrene / methacrylic acid copolymer , An organic fine powder such as polystyrene resin,
Examples of heat-fusible substances include higher fatty acids or their esters, amides or metal salts, as well as various waxes,
50-200 of condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, 3,4-epoxy-dialkyl hexahydrophthalates, higher ketones, other heat-fusible organic compounds, etc. Those having a melting point on the order of ° C.

The heat-sensitive recording material of the present invention can have various structures, and all of the conventionally known structures utilizing the color-forming reaction between the leuco dye and the color developer are included. For example, the heat-sensitive recording material of the present invention has a structure in which a leuco dye and a developer are supported on the support as the same coating layer or separate coating layers, or a leuco dye is supported as a transfer layer. It can be used as a thermal transfer type heat-sensitive recording material comprising a transfer sheet formed by being supported by a body and a receiving sheet formed by supporting a color developer as a receiving layer on the support.
In the case of thermal transfer type thermal recording material,
A desired color image can be formed on the receiving layer side of the receiving sheet by superposing the receiving sheet so that the receiving layer is in contact with the transfer layer of the transfer sheet and performing thermal printing from the front surface or the back surface of the polymerized sheet.

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 as a heat-sensitive recording material for various recording fields, especially for high-speed recording which requires high image stability.

The heat-sensitive recording material of the present invention is used in various fields, and in particular, it utilizes the above-mentioned excellent color image stability,
It can be advantageously used as a heat-sensitive recording type label sheet or a heat-sensitive recording type magnetic ticket paper. In the case of a thermosensitive recording type label sheet, a thermosensitive coloring layer containing the above-mentioned fluoran compound and a phenolic compound is provided on one surface of the support,
On the other surface of the support, a release liner may be provided via an adhesive layer. In the case of magnetic ticket paper, instead of this release liner,
A magnetic recording layer containing a ferromagnetic material and an adhesive as main components may be provided.

[Effect]

According to the present invention, the use of the phenolic compound represented by the above general formula makes it possible to obtain a thermosensitive recording material having the following excellent properties.

(1) The colored image is very stable without decoloring with time or self-developing.

(2) The density of the developed image does not decrease or disappear due to contact with oils and fats.

〔Example〕

Examples of the present invention will be shown below. Parts and% are parts by weight and% by weight, respectively.

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

[A] liquid 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluorane 20 parts 10% aqueous solution of hydroxyethyl cellulose 20 parts water 60 parts [B] liquid p-hydroxybenzoic acid-2 -(P-hydroxyphenylthio) -ethyl ester (substance of compound example (2), melting point 147
~ 148 ° C) 20 parts 10% hydroxyethyl cellulose aqueous solution 20 parts water 60 parts [C] liquid calcium carbonate 20 parts 5% methyl cellulose aqueous solution 20 parts water 60 parts The above-obtained [A]-[C] liquids are Using, to prepare a thermosensitive color developing layer liquid of the following composition, select a wire bar so as to be a dry coating amount of 4 ~ 5 g / m ^{2 on} a commercial high-quality paper with a standard basis weight of 50 g / m ^2, and then dried, then, A thermosensitive recording sheet (a) of the present invention was prepared by calendering so that the surface of the thermosensitive coloring layer had a smoothness of 500 to 600 seconds.

Exothermic Coloring Layer Liquid [A] Liquid 10 parts [B] Liquid 30 〃 [C] Liquid 30 〃 Isobrylene-maleic anhydride copolymer 20% alkaline aqueous solution 10 〃 Example 2 Instead of the liquid [A] of Example 1 A thermal recording sheet (b) was prepared in the same manner as in Example 1 except that the following liquid [D] was used.

[D] Liquid 3-diethylamino-6-methyl-7-anilinofluorane 20 parts 10% aqueous solution of hydroxyethyl cellulose 20 parts water 60 parts Example 3 Example 1 [B] solution was replaced with the following [E] solution. A thermal recording sheet (c) was prepared in the same manner as in Example 1 except for the above.

[E] Liquid p-hydroxybenzoic acid-3- (p-hydroxyphenylthio) -n-propyl ester (substance of compound specific example (3), 14
2 to 143 ° C.) 20 parts 10% aqueous solution of hydroxyethylcellulose 20 parts water 60 parts Example 4 The same procedure as in Example 1 was carried out except that the following solution [F] was used instead of the solution [B] in Example 1. I made a recording sheet (d).

[F] Liquid p-Hydroxybenzoic acid-4- (p-hydroxyphenylthio) -n-butyl ester (Compound Specific Example (4) Substance Melting point
116 to 119 ° C.) 20 parts 10% hydroxyethyl cellulose aqueous solution 20 parts water 60 parts Example 5 The same as Example 1 except that the following [G] solution was used instead of the [B] solution of Example 1. Thermal recording sheet (e)
Made.

[G] Liquid p-hydroxybenzoic acid-6- (p-hydroxyphenylthio) -n-hexyl ester (substance of compound example (5), melting point 88 to 90 ° C.) 20 parts 10% hydroxyethyl cellulose aqueous solution 20 parts water 60 parts Comparative Example 1 A thermosensitive recording sheet (f) was prepared in the same manner as in Example 1 except that the following solution [H] was used instead of the solution [B] of Example 1.

[H] Solution Bisphenol A 20 parts 10% Hydroxyethylcellulose aqueous solution 20 parts Water 60 parts Comparative Example 2 All the same as Example 1 except that the following solution [I] was used instead of the solution [B] of Example 1. A thermosensitive recording sheet (g) was made.

[I] liquid p-hydroxybenzoic acid benzyl ester 20 parts 10% hydroxyethyl cellulose aqueous solution 20 parts water 60 parts The thermosensitive recording sheets (a) to (g) obtained as described above were subjected to a thermal gradient tester (manufactured by Toyo Seiki Co., Ltd.). ), Pressure 2kg, contact time 1 second 15
Printed at 0 ° C. A thin layer of cottonseed oil was applied to the color-developed portion and the background portion of the heat-sensitive recording sheets (a) to (g), and stored in a dry storability test room at 60 ° C for 24 hours, and changes in the color-developed portion and the background portion were observed. The results are shown in Table-1. Further, the thermal recording sheet of (a) ~ (g), in a thermal printing experimental device having a thin film head manufactured by Matsushita Electronic Parts Co., Ltd., head power 0.45w / dot, 1 line recording time 20msec / l, scanning line The pulse width was printed at 1.6, 2.0, and 2.4 mesc under the condition of a density of 8.times.3.85 dots / mm, and the print density was measured by a Macbeth densitometer RD-514 (filter W-106). The results are shown in Table-2.

As described above, the heat-sensitive recording material of the present invention has high image stability against contact with oils and fats, and is also highly practical in high-speed color development as in Examples 4 and 5. It can be seen that it is a thermosensitive recording material.

Claims (1)

[Claims] 1. A thermosensitive recording material utilizing a color-forming reaction between a leuco dye and a color developing agent thereof, wherein the color developing agent is a compound represented by the general formula: A heat-sensitive recording material comprising a phenolic compound represented by the formula (wherein R represents an alkylene group having 1 to 6 carbon atoms).