JPH0632999B2 - 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 thermosensitive recording material utilizing a heat-coloring reaction between a colorless or light-coloring colorless dye (leuco dye), a phenol, and an organic acid is disclosed in JP-B-43-4160, JP-B-45-14039 and JP-A-48-39. -Published in No. 27736, etc., and widely used. 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.

A thermal printer having a built-in thermal head, a facsimile machine, or the like is used for heating the heat-sensitive recording material for color development. In comparison with other recording materials, such a recording material 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. It is widely used not only for copying books and documents, but also for recording information of electronic calculators, facsimiles, telexes, medical measuring instruments and the like, as well as recording materials of measuring instruments due to its advantages such as low cost. However, such a conventional heat-sensitive recording material which is a combination of a leuco dye and a phenolic substance has a drawback that the color-developed portion thereof is reduced in density or erased by oils and fats. In addition, contact with a substance containing a plasticizer, such as polyvinyl chloride film, has the drawbacks of decoloring the color-developed portion and lowering the density.

On the other hand, it has been proposed to improve such a point in the conventional thermal recording material 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. Further, in a heat-sensitive ticket or heat-sensitive label produced by subjecting a heat-sensitive recording material coated with such an overcoat layer to a cutting process, an adhesive process, etc., oil or a plasticizer penetrates from the cut surface to decolorize the image area. The application of such an overcoat layer is not an essential solution because it causes a decrease in density and a decrease in density.

〔Purpose〕

The present invention overcomes the drawbacks found in the above-mentioned prior art, in particular, the concentration of the color-developed portion is not reduced or erased by oils and fats, and the reduction of the image density is also caused by contact with a plasticizer or the like. It is an object of the present invention to provide a heat-sensitive recording material with almost no decoloring.

〔Constitution〕

According to the present invention, in a heat-sensitive recording material utilizing a color-forming reaction between a leuco dye and its color developer, a general formula is used as the color developer. 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 10 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 kind of heat-sensitive material is arbitrarily applied, and for example, leuco compounds of 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) Fluoran, 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'-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-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) The phenolic compound can be produced by converting a disulfide compound synthesized from monothiohydroquinone and a corresponding dihalogenoalkylene into a disulfoxide by applying the method described in JP-B-57-48115.

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 on a suitable support such as paper, synthetic paper, plastic film, and drying. It is used in various recording fields, especially as a heat-sensitive recording material 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 color image is very stable without decoloring with time or developing white powder.

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

(3) The color image does not decrease in density or disappear due to contact with a plasticizer.

〔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% hydroxyethyl cellulose aqueous solution 20〃 water 60〃 [B] liquid 1,3-bis (p -Hydroxyphenylthionyl) propane
(Compound example (2), melting point 123-125 ° C) 20 parts 10% hydroxyethyl cellulose aqueous solution 20〃 water 60〃 [C] liquid calcium carbonate 20 parts 5% methyl cellulose aqueous solution 20〃 water 60〃 Using the obtained liquids [A] to [C], a thermosensitive coloring layer liquid having the following composition was prepared so that a dry coating amount of 4 to 5 g / m ² was obtained on a commercially available high-quality paper having a standard basis weight of 50 g / m ^2. A wire bar was selected, coated, dried, and then calendered so that the smoothness of the surface of the thermosensitive color developing layer was 500 to 600 seconds in terms of flat smoothness, to prepare the thermosensitive recording material sheet (a) of the present invention. .

Exothermic color development layer solution [A] solution 10 parts [B] solution 30〃 solution [C] solution 30〃 20% alkaline aqueous solution of isobutylene-maleic anhydride copolymer 10〃 Example 2 [B] solution of Example 1 A thermal recording material (b) was prepared in the same manner as in Example 1 except that the following liquid [D] was used.

[D] Liquid 1,5-bis (p-hydroxyphenylthionyl) -pentane
(Substance of compound example (3), melting point, 98 to 100 ° C.) 20 parts 10% aqueous solution of hydroxyethyl cellulose 20 〃 water 60 〃 Comparative example 1 The following solution [E] is used instead of the solution [B] of Example 1. A thermal recording material (c) was produced in the same manner as in Example 1 except that the above was carried out.

[E] Liquid Bisphenol A 20 parts 10% Hydroxyethyl cellulose aqueous solution 20〃 Water 60〃 Comparative Example 2 Same as Example 1 except that the following [F] solution was used instead of the [B] solution of Example 1. To prepare a thermosensitive recording material (d).

[F] liquid p-hydroxybenzoic acid benzyl ester 20 parts 10% aqueous solution of hydroxyethyl cellulose 20〃 water 60〃 The thermal recording materials (a) to (d) obtained as described above were subjected to a thermal gradient tester (manufactured by Toyo Seiki Co., Ltd.). ) At a pressure of 2 kg and a contact time of 1 second at 150 ° C
It was printed with. Cotton seed oil was thinly applied to the color development part and the background part of the heat-sensitive recording materials (a) to (d) and stored in a storage test room at 60 ° C dry for 24 hours, and changes in the color development part and the background part were observed. As a result, no change was observed in the background portion in all of the heat-sensitive recording materials (a) to (d). On the other hand, the color-developed portion is the heat-sensitive recording material of the comparative example.
(c) and (d) disappeared almost completely.

Next, the thermal recording materials (a) to (d) were printed in the same manner, and a 4 cm square was cut out centering on the printed part, and polyvinyl chloride film (Shin-Etsu Polymer Co., Ltd.Polyrap V-300) After stacking the sheets and applying a load of 500 g / cm ² for 24 hours at room temperature, they were taken out and the density of the color development part was measured with a Macbeth densitometer (RD-514), and compared with the density before the test, and the results are shown in Table-1. Described in.

From Table 1, the heat-sensitive recording material of the present invention has not only the decolorization of the color-developed part due to the oils and fats such as cottonseed oil, but also the image stability of the color-developed image with very little deterioration even when the film is contacted with polyvinyl chloride film. 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 thermosensitive recording material comprising a phenolic compound represented by the formula (wherein R represents an alkylene group having 1 to 10 carbon atoms).