JPS58222887A - Heat-sensitive recording material - Google Patents

Abstract

PURPOSE:To provide the titled material improved in oil resistance and fat resistance of an image, wherein a specified thiourea derivative is incorporated as a color developing substance for developing the color of a leuco dye when being heated. CONSTITUTION:A heat-sensitive recording material comprises a leuco dye and a thiourea derivative of formula I (e.g., a compound of formula II or III) as a color developing substance for developing the color of the leuco dye when being heated which are provided on a base. The recording material is comparable or superior in density of an image and superior in oil resistance and fat resistance of the image, as compared to a heat-sensitive recording material wherein a conventional phenolic substance such as bisphenol A is used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in heat-sensitive recording materials containing leuco dyes as color formers.

Thermosensitive recording materials generally consist of a support such as paper, synthetic paper, or plastic film provided with a thermosensitive coloring layer containing a thermochromic composition as a main component, and can be heated with a thermal head, thermal pen, laser beam, etc. A colored image is obtained. Compared to other recording materials, this type of recording material does not require complicated processing such as development and fixing, can produce records in a short time using relatively simple equipment, and generates less noise and pollutes the environment. ,
Due to its low cost and other advantages, it is used not only for copying books and documents, but also as a recording material in a wide range of applications such as electronic computers, facsimiles, ticket vending machines, labels, and recorders. Thermochromic compositions used in such heat-sensitive recording materials generally consist of a coloring agent and a color developer that causes the coloring agent to develop color when heated, and the coloring agent includes:
For example, colorless or light-colored leuco dyes having a lactone, lactam or spiropyran ring are used, and various acidic substances such as organic acids and phenolic substances are used as color developers. A recording material that combines a color former and a color developer has the advantage that the resulting image has a particularly clear color tone, has a high background whiteness, and has excellent weather resistance of the image (dye image). and is widely used.

However, in recent years, heat-sensitive recording methods have replaced other conventional recording methods, and as demand has increased, demands for improving the quality of heat-sensitive recording materials used in this method have also increased. Stability against fingerprints and the like has become a major issue. By the way, the materials that affect the quality of the heat-sensitive recording material as mentioned above include color formers, color developers, binders that bind or protect these, and other auxiliary agents (for example, dispersants, pigments). However, the color developer has the greatest influence. Conventionally, bisphenol A has been commonly used as a color developer due to its excellent color development properties, but on the other hand, when bisphenol A is attached to fats and oils, such as olive oil and salad oil, the image disappears in the attached area. It is well known to those skilled in the art that there is a problem of image instability in which the image of the fingerprint trace disappears.

The present inventors have conducted various studies on the development of a color developer that exhibits excellent color development and is free from the above-mentioned drawbacks, and as a result, has completed the present invention.

That is, the heat-sensitive recording material of the present invention is a heat-sensitive recording material in which a heat-sensitive coloring layer containing a colorless or light-colored leuco dye and a color developer is provided on a support. Sign 4 A tension 1/ηt + 7% 7'
- and tsu composition Lpdguma η.

By using the compound of the present invention, the image density is equal to or higher than that using conventional phenolic compounds such as bisphenol A, and the heat-sensitive image has greatly improved oil resistance and compatibility resistance. Recording materials can be obtained.

In the present invention, the strong color developing ability of the compound represented by the general formula (I) is considered to be due to the active hydrogen of the amino group.

Furthermore, the reason why the background is extremely white is thought to be because the active hydrogen of the amine group is weak at room temperature and rather shows basicity, which has the effect of making the dye colorless.

The synthesis of the compounds of the present invention can be carried out, for example, by
Tterman, Wieland p. 151)
It is described in etc.

The colorless or light-colored leuco dye used in the present invention may be used alone or in combination as a coloring agent. Specific examples thereof include leuco dyes such as triphenylmethane, fluoran, phenothiazine, auramine, and spiropyran dyes.More specifically, 3.3'-bis(p-dimethylaminophenyl)-6-
Dimethylaminophthalide (also known as crystal violet), 3,3-his(p-dimethylaminophenyl) phthalide, 3,3-bis(p-dimethylaminophenyl) phthalide, 3,3-bis(p-dimethylaminophenyl) -6-dimethylaminophenyl, 3.3-bis(p-dimethylaminophthalide)-6-chlorophthalide, 3-(N-p-tolyl-N-ethylamino)-6-meth
7-(N-phenylamino)fluorane, 3-diedylamino-7-chlorofluorane, pensoylleucomethylene blue, 6-chloro-8'-methoxy-benzoindolino-pyrylospirane, 6-bromo-3-methoxy-benzoindoly Examples include no-pyrillospiran, 2-[3,6-bis(diethylamino)-9-(O-chloroanilino)]xantylbenzoic acid lactam, and the like.

In addition to the above-mentioned materials, the thermosensitive coloring layer usually also contains a binder. As the binder, all known binders in the field of thermosensitive recording can be used, such as gelatin, starch, hydroxyethyl cellulose, polyacrylic acid, carboxyethyl cellulose, methoxy cellulose, polyvinyl alcohol, polyvinylpyrrolidone, and the like.

To produce the heat-sensitive recording material of the present invention, an aqueous solution containing a leuco dye, a compound of the above general formula, and a binder as main components may be coated on a support such as paper or synthetic paper and dried. Here, the amounts of the leuco dye, the compound of the above general formula, and the binder used are 5
-30% by weight, 40-80% by weight, 2-20% by weight are suitable. In addition, the amount of adhesion of the thermosensitive coloring layer to be formed is 2 to 2.
Approximately 10 cm is appropriate. In addition, talc, wax,
Auxiliary agents such as surfactants and antifoaming agents can be added.

Examples are shown below. Incidentally, parts and ratios are parts by weight and weight %, respectively.

Examples 1 to 2 [Liquid A] 10 parts of hydroxyethylcellulose 30 parts of aqueous solution Dispersed in a ball mill for 20 hours.

[Liquid B]

30 parts of the indicated color developer component: 10 parts of LD-,

[Liquid C]

Calcium carbonate 40 parts Stearamide 15 parts Zinc stearate
5 parts polyvinyl alcohol 10 parts aqueous solution 6
0 parts water 180
Part i-'1ivT"°"611. Mix the A, B, and C solutions obtained as above and apply on a piece of high-quality paper weighing 50 mm to a dry adhesion of 61 mm. After drying, a heat-sensitive coloring layer was formed and heat-sensitive recording paper was obtained. The evaluation results are shown in the table below. Note that the maximum density is the image density when printed at 120C using a commercially available thermal gradient tester, and the background density at that time is also shown. Concentrations were measured using a Macbeth densitometer. Oil resistance was determined by applying cottonseed oil to the surface of the image and observing changes after storage at 60C for one day. Grease resistance was determined by applying strong pressure to a fingerprint and observing changes after storage at 60C for one day. The symbols in the table indicate the following.

○・・・・・・・・・There is almost no change △・・・・・・
. . . There is a slight decrease in density × . I understand.

Patent applicant Rico Co., Ltd. Representative Patent Attorney Toshiaki Ikeura

Claims (1)

[Claims] (1) A heat-sensitive recording material in which a leuco dye and a color-developing substance that causes the leuco dye to develop color when heated are supported on a support, characterized in that the color-developing substance is a compound represented by the general formula. heat-sensitive recording material.