JPS60147388A - Thermal recording material - Google Patents

Abstract

PURPOSE:To greatly enhance plasticizer resistance of a developed color image part, by incorporating a specified substance in a thermal recording layer as a phenolic substance in a thermal recording material. CONSTITUTION:A substance of the formula, wherein (n) is 1-10, is incorporated as a phenolic substance in a thermal recording layer of a thermal recording material provided with a thermal recording layer which comprises a colorless or light-colored color forming substance and a phenolic substance capable of a developing the color of the color forming substance when being heated. The phenolic substance is used in an amount of 1-40wt% to the total amount of solid matter. From the viewpoint of color forming efficiency, it is advantageous to use a leuco compound such as triphenylmethane as the color forming substance and pulverize each constituent as possible, preferably, to a particle diameter of 1- 3mum. Accordingly, even when a developed color image is brought into contact with a plasticizer for a long period of time, the image will not disappear or be discolored.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material in which the stability of a colored image against plasticizers is improved.

It has been known for a long time that a color-forming substance such as crystal violet lactone reacts with a phenolic substance to form a color, and it is also possible to thermally develop a color using these substances, for example, as described in US Pat. No. 3,539,375. However, colored images obtained by a thermal reaction between a color-forming substance and a phenolic substance or an organic acid are generally very unstable against changes in light, temperature, and humidity. It is also unstable to various plasticizers used in rubber and plastics, such as dioctyl phthalate, dibutyl phthalate, dihexyl phthalate, butylbenzyl heptathalate, tricresyl phosphate, and dioctyl adipate. However, when a colored image comes into contact with rubber, plastic, etc. to which these plasticizers are added, the image disappears or becomes discolored, which is a major drawback. Improving the stability of colored images against changes in light, temperature, and humidity is of course important, and therefore there are still problems to be solved at least simultaneously or independently. This invention relates to improving the stability of colored images against plasticizers (hereinafter referred to as plasticizer resistance).

In recent years, heat-sensitive recording materials have been increasing in use as recording media used at the input/output end of information equipment such as facsimiles, computers, and telex machines, as well as in transportation-related fields such as railway station labor equipment. Opportunities for these heat-sensitive recording materials to directly or indirectly come into contact with plastic sheets containing various plasticizers, periodical rolls, etc. are increasing.

Therefore, there is an urgent need to improve the reliability of heat-sensitive recording materials as recording media when they are colored, used for long periods of time, and brought into contact with plasticizers. Efforts have been made to improve these required performances, but the current situation is that nothing with satisfactory performance has yet been obtained.

As a result of various studies to improve this drawback, the inventors of the present invention found that
By incorporating a substance represented by the general formula (where n is 1 to 10) into the heat-sensitive layer as a phenol substance of the heat-sensitive recording material,
We discovered that the plasticizer resistance of the colored part was significantly improved.
The present invention has been accomplished.

In the present invention, the object can be achieved by containing the substance represented by the above general formula in an amount of 1 to 40% by weight in the total solid content of the heat-sensitive recording layer. It is also possible to use the substance represented by the above general formula in combination with other known heptaenolic substances.

The colorless to light-colored color-forming substance used in the present invention is a substance that develops color by reacting with a phenolic substance when heated,
Examples include various leuco compounds such as triphenylmethane, triphenylmethanephthalide, fluor-7rane, leucoauramine, and spiropyran.

The color-forming substance and the phenolic substance dispersed in the form of fine particles are separated and fixed to each other by an adhesive so as not to develop color during storage as a heat-sensitive recording material. The adhesive used in the heat-sensitive recording medium of the present invention includes, for example, casein, gelatin, modified starch, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, styrene-maleic anhydride copolymer and its alkali melt, polyacrylamide. , styrene-butadiene copolymer, polyvinyl acetate, polyacrylic acid ester latex, and the like.

The heat-sensitive recording material of the present invention may optionally contain other additives in the recording layer, such as various waxes to improve recording properties, fatty acid amides, various fatty acid metal salts to prevent sticking, and surface whiteness. White pigments, fillers, and water-resistant agents to improve water resistance are added to improve naturalness and sharpness.

The heat-sensitive recording material of the present invention is produced as follows. A heat-sensitive composition is obtained by pulverizing and dispersing color-forming substances, phenolic substances, sensitivity regulators, and other additives in an aqueous medium containing an appropriate concentration of adhesive using a pulverizer such as a ball mill.

It is advantageous in terms of color development efficiency to make each component material as fine as possible, and preferably to have a particle size of 1 to 3 microns.

The heat-sensitive recording composition thus obtained is applied to a suitable support and dried to obtain the heat-sensitive recording material of the present invention. Examples of the support include papers such as wood-free paper, medium-quality paper, and coated paper, plastic films, film-laminated papers, and woven fabric sheets. The heat-sensitive recording material of the present invention thus obtained exhibits excellent plasticizer resistance against various plasticizers, and the image does not fade or discolor even if the colored image is brought into contact with these plasticizers for a long period of time. Moreover, other properties such as background fogging are also good.The present invention will be explained in more detail with reference to Examples.

Example 1 (a) Production of heat-sensitive recording composition □ Part A Fluoran black coloring dye 5 parts by weight (PSD 150 manufactured by Shin Nisso Kako) Stearic acid amide 15 parts by weight Clay 20 1 Polyvinyl alcohol 10% aqueous solution 40 #Water 20
# Solution B 2, 2.4.4-tetraoxyacybophenone 20 parts by weight Clay 20 I Negative polyvinyl alcohol 10% aqueous solution 40 g Water 20
l Liquids A and B were separately dispersed in a centrifugal ball mill for 4 hours, and then the liquids A and B were mixed to prepare a heat-sensitive recording composition (paint).

(b) Apply this heat-sensitive recording composition to 50 t/nl general paper. The coating amount after drying is 7f/I? A heat-sensitive recording material was obtained by applying the resin to obtain a heat-sensitive recording material.

(e) Next, the plasticizer resistance of this heat-sensitive recording material was examined according to the following procedure. First, the thermosensitive recording material was colored using a static coloring tester (stamp type) at a pressure of 2 KICD, a temperature of 130° C., and a time of 1 second. Next, as a plasticizer resistance test, a commercially available plastic eraser was placed on the colored part of the heat-sensitive recording material.
Furthermore, a 30Of weight was placed on the eraser and left for one day.

Thereafter, the density of the colored part before and after the test was measured using a Macbeth reflection densitometer RD-514, and the results shown in the table were obtained. A thermosensitive recording material was obtained in exactly the same manner as in Example 1 except that 2.2t4.4'-tetraoxysebatiphenone was used instead of 2.2t4.4'-tetraoxysebatiphenone, and a plasticizer resistance test was conducted. The results are shown in the table.

Comparative Example 1, Comparative Example 2 Bisphenol A was used instead of 2,2-4,4'-tetrao-t-xyaziboenone in Solution B of Example 1. Comparative Example 1 used benzyl P-hydroxybenzoate. This was designated as Comparative Example 2, and a heat-sensitive recording material was obtained in exactly the same manner as in Example 1, and a plasticizer resistance test was conducted. The results are shown in the table.

From the results shown in the table, it is clear that the thermosensitive recording material using the phenolic substance of the present invention has extremely excellent plasticizer resistance.

Claims (1)

[Claims] A thermosensitive recording material having a heat-sensitive layer containing a color-forming substance that is normally colorless or light-colored and a phenolic substance that causes the color-forming substance to develop color when heated, as the phenolic substance (where n is 1 to 1). 10) A heat-sensitive recording material characterized by containing a substance that is abrasive.