JPS6082382A - Thermal recording material - Google Patents

Abstract

PURPOSE:To improve thermal responsiveness by making a thermal color development layer contain benzyl biphenyl, alkyl benzyl biphenyl or hydride of them. CONSTITUTION:A thermal color development layer containing a leuco dye and an organic acid material is made to contain benzyl biphenyl, alkyl benzyl biphenyl or a compound of one or two or more kinds of hydride of them. Benzyl biphenyl, alkyl benzyl biphenyl and hydride of them contained in the thermal color development layer act as a color development accelerator, respectively. The mechanizm of the action thereof is such that: they have a melting or subliming point lower than both or one of the leuco dye and the organic acid material and have the solvency for the leuco dye and/or the organic acid material, thus dissolving one or both of these materials and accelerating the reaction between them. The recording material thus prepared is excellent in the rise of a reflective density to the rise of temperature and in the thermal responsiveness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material suitable for high-speed recording due to its heat sensitivity.

In recent years, with the diversification of information, the amount of information has increased, and in order to record this information, the field of information recording (2) has seen various recording methods and recording materials being researched, developed, and put into practical use. Among them, the heat-sensitive recording method is: - A recorded image can be obtained by simply heating the heat-sensitive recording material, and it does not require a complicated development process. It is easy and inexpensive compared to other recording materials. In many cases, inexpensive paper is used as a support for heat-sensitive recording materials, but the recording material obtained in this case also has a feel similar to that of ordinary paper. It has the following advantages, and is widely used in computer output, printers such as calculators, recorders of various measuring instruments, facsimile machines, automatic distribution machines, thermal copying machines, etc.

Heat-sensitive recording materials used for this purpose have conventionally contained a leuco dye that is colorless or light-colored at room temperature and an organic acidic substance such as a phenol compound that reacts with the leuco dye to develop color when heated. It is known that a coloring layer is provided on a support such as paper, synthetic paper, or synthetic resin film.

However, in the field of information recording, the recording speed can be improved by heating the thermal head in a short time and producing sufficient density with a low voltage. There has been a strong demand for the development of recording materials.

In view of this, the inventors of the present invention have conducted extensive research on heat-sensitive recording materials that have excellent thermal responsiveness and are capable of recording clear images with good density even during high-speed recording. By incorporating benzylbiphenyls, alkylbenzylbiphenyls, or their hydrides into the heat-sensitive coloring layer containing leuco dye and an organic acidic substance that reacts with the leuco dye to develop color when heated, these compounds act as color development accelerators. The present invention has been completed based on the discovery that the thermal response is significantly improved and the object is achieved.

The leuco dye used as a coloring agent in the present invention is
Substances that are colorless or light-colored at room temperature (at room temperature) and develop color by reacting with acidic substances under heating; for example, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, etc. triallylmethane dyes, diphenylmethane dyes such as 4,4.'-bis-dimethylaminobenzhydryl benzyl ether, 7-diethylamino-3-
Fluoran dyes such as chlorofluorane, benzoyl C
Examples include thiazine dyes such as Icomethylene blue, spiro dyes such as 3-methyl-spiro-dinaphthopyran, and leucoauramine, indoline, and indigo dyes.

The organic acidic substance used together with the leuco dye is a substance that becomes a color developer when it comes into contact with the leuco dye upon heating, and includes various phenolic compounds, organic acids, and the like.

These are preferably solid at room temperature and liquefied or vaporized at 50° C. or higher. Examples of these organic acidic substances include phthalic anhydride, gallic acid, salicylic acid, 4,4
'-isopropylidene diphenol, 4,4'-isopropylidene bis(2-chlorophenol), 4,4'-
Isopropylidene bis(2-t-butylphenol),
hand.

4'-5ec-butylidene diphenol, 4'-(
1-methyl-n-hexylidene) diphenol, 4-phenyl phenol, 4-hydroxydiphenoxide,
Methyl-4-hydroxybenzoate, phenyl-4-
Hydroxybenzoate, 4-hydroxy acetophenone, salicylic acid anilide, 4,4'-cyclohexylidene diphenol, 4,4'-cyclohexylidene bis(2-methylphenol), 4,41-benzylidene diphenol, Φ, 4 '-thiobis(6-t-butyl-
8-methylphenol), novolac type phenol resin, halogenated novolac type phenol resin, α-naphthol, β-naphthol, and the like.

The heat-sensitive coloring layer containing a leuco dye and an organic acidic substance contains one or more compounds of benzylbiphenyls, alkylbenzylbiphenyls, or hydrides thereof.

The benzylbiphenyls, alkylbenzylbiphenyls, and their hydrides used in the present invention are contained in the heat-sensitive coloring layer and act as coloring accelerators. It has a melting point or sublimation point lower than both or one of the acidic substances, and has a solubility relative to the leuco dye and/or the organic acidic substance (''', and dissolves the leuco dye and/or the organic acidic substance (100,000 or both) and facilitates the reaction between them. Therefore, compounds with a melting point in the range of 50 to 150°C are preferable.As these benzylbiphenyls, alkylbenzylbiphenyls, and their hydrides, for example, m-
Benzylbiphenyl (mp, 56°C), p-benzylbiphenyl (mp'-86°C), p-cyclohexylmethylbiphenyl (mp, 58°C), 0-cyclohexylmethyldicyclohexyl (perhydro-〇-benzylbiphenyl) ( mp-62°C), m-cyclo\quinlemethyldicyclohexyl (perhydro-n1-pendylbiphenyl) (mp, 65°C) and alkyl substituted products thereof, preferably one or two methyl or ethyl substituted products, etc. can be mentioned. These benzylbiphenyls, alkylbenzylbiphenyls, and hydrides thereof can be used alone or in combination of two or more. The color development accelerator made of these compounds is used in an amount of 05 to 30 parts by weight, preferably 1 to 10 parts by weight, based on one part of the leuco dye, although it varies depending on the type of leuco dye and organic acidic substance used. Ru. It may also be used in combination with a conventionally known color accelerator.

Various additives can be added to the heat-sensitive recording material of the present invention depending on its use. The additives mainly include binders that isolate and fix the leuco dye dispersed in fine particles and the organic acidic substance from each other, such as polyvinyl alcohol (PVA), methyl cellulose, carboxynotyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, etc. Acrylic acid, casein, gelatin, starch,
Alternatively, derivatives thereof can be mentioned. In addition, white pigments such as calcium carbonate, kaolin, clay, talc, titanium oxide, etc. are used for the purpose of increasing the whiteness of the heat-sensitive coloring layer, preventing the slippage of writing instruments, and preventing sticking. There are fatty acid metal salts, etc.

These materials are mixed or separately coated on a support such as paper or film to form a thermosensitive coloring layer.

Hereinafter, the present invention will be specifically explained based on Examples and Comparative Examples.

[Example 1] (11A liquid preparation 15 parts by weight of crystal violet lactone, 50 parts by weight of p-benzylbiphenyl, 5 parts by weight of 10% PVA aqueous solution)
00 parts by weight were pulverized and mixed in a ball mill for 5 hours to prepare Solution A.

+2+ Br & Preparation 75 parts by weight of bisphenol A and 500 parts by weight of a solution in 15% PVA7 were ground and mixed in a ball mill for 5 hours,
A liquid was prepared.

(3) Preparation of thermal recording paper Prepare a coating liquid by mixing 100 parts by weight of liquid A and 100 parts by weight of liquid B, apply this coating liquid to 50 g/m2 base paper-1, and dry. A thermal recording paper with a coating weight of 5 g/rn' after drying was obtained.

[Examples 2 and 3] In place of p-benzylbiphenyl in Example 1, Example 2
Well then. -benzylbiphenyl, also in Example 8.

A thermosensitive recording paper was obtained in exactly the same manner as in Example 1 using -cyclohexylmethylcyclo to quinle, respectively.

[Comparative example]

15 parts by weight of crystal violet lactone and 10 parts by weight
A'tL was prepared with 250 parts by weight of VA aqueous solution 'tL, and 75 parts by weight of bisphenol A and 500 parts by weight of 15% PVA aqueous solution.
A coating liquid was prepared by mixing 100 parts by weight of the above liquid A and 200 parts by weight of liquid B, and a heat-sensitive coating was prepared in the same manner as in the above example with a coating amount of 5 g/n12 after drying. Recording paper was prepared.

Each heat-sensitive recording paper obtained in each of the above Examples and Comparative Examples was colored using a stamp-type coloring tester in the range of 60 to 180°C, and the coloring density was measured as the reflection density. 1 (-9-Kura Digital Reflection Densitometer PDA-45). The results are shown in Figure 1.

As is clear from FIG. 1, the thermal recording paper of each example has a higher reflection density with respect to an increase in temperature than that of the comparative example.
It was found that the film had excellent heat response and excellent heat response.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between temperature and reflection density of the thermal recording paper of each Example and Comparative Example. Proceedings 1N Correct - ■ November 1980 J] 1 (i II Commissioner of the Patent Office Kazuo Wakasugi 1 Indication of the case 1988 Patent No. 1 No. 191033 2 Name of the invention Thermal recording material 3 Person making the amendment Relationship with matter 1'1 Special AII applicant address (residence) 6-17-2 Ginza, Chuo-ku, Tokyo Name ((i 64) Nippon Steel Chemical Industry Co., Ltd. 4 Agent 〒104 Telephone 03 (543)167
5 (1 location 14-2 Gin P Door-chome, Chuo-ku, Tokyo 3rd floor of Ebara Pill 5? Ill positive command day i 1 Internal light correction 6 Increased by amendment Number of inventions covered None 7 Target of amendment i4 female σ) Trace \-1・ Nerlt, tF contents explanation! 11g1, page 6, line 6, "m-benzylbiphenyl" is corrected to "0-benzylbiphenyl".

Claims (1)

[Claims] A heat-sensitive recording material comprising a heat-sensitive color-forming layer provided on a support, which contains a leuco dye that is colorless or light-colored at room temperature, and an organic acidic substance that reacts with the leuco dye to develop color when heated (2) the heat-sensitive color-forming layer 1. A heat-sensitive recording material, characterized in that the material contains one or more compounds selected from the group consisting of benzylbiphenyls, alkylbenzylbiphenyls, and hydrides thereof.