JPS63257681A - Heat-sensitive recording member - Google Patents

Abstract

PURPOSE:To improve anti-plasticizer performance and recording characteristic, by adding specific sulfonic compound and polyvinyl pyrolidone simultaneously to a recording layer in heat-sensitive recording member. CONSTITUTION:In a heat-sensitive recording member composed of colorless or faint coloring matter, an acid material for thermally coloring a dye, a water soluble binder and a pigment, the acid material is bis-(3-aryl-4-hydroxyphenyl)- sulfone 5wt.% or more of the water soluble binder is composed polyvinyl pyrolidone and 5wt.% or more of the pigment is composed of zinc oxide. When bis(3-aryl-4-hydroxyphenyl) sulfone, zinc oxide and polyvinyl pyrolidone are applied simultaneously to a recording layer in heat-sensitive recording member, a heat-sensitive recording member having high anti-plasticizer performance and high sensitivity can be obtained. 5-100wt.% of polyvinyl pyrolidone is required for entire solid state binder and 5-100wt.% of zinc oxide is required for entirely solid-state pigment.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material with improved stability of a colored image against plasticizers and high sensitivity. It has been known for a long time that a color-forming substance such as crystal violet lactone reacts with an acidic substance to form a color, and thermally developing color using these substances is also known, for example, in U.S. Pat. No. 3,539,375. It is.

However, colored images obtained by a thermal reaction between a coloring substance and an acidic substance such as a phenolic substance or an organic acid are generally very unstable with respect to changes in source, temperature, and humidity. In addition, it is unstable to various plasticizers used in rubber, plastics, etc., such as dioctyl phthalate, diptyl hepthalate, dihexyl phthalate, butylbenzyl phthalate, tricresyl phosphate, and dioctyl adipate. A major drawback is that when the above-mentioned colored image comes into contact with rubber, plastic, etc. to which a plasticizer has been added, the image disappears or changes color.

It is of course important to improve the stability of colored images against changes in source, temperature, humidity, etc., and therefore there are still problems to be solved at least simultaneously or independently. When it comes into contact with plasticizers used in plastics, etc., the stability of colored images with respect to plasticizers (
This paper relates to a heat-sensitive recording material having a plasticizer resistance (hereinafter referred to as plasticizer resistance).

In recent years, the use of thermal recording paper has increased as a recording medium 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. As a result, there are increasing opportunities for these thermosensitive recording papers to directly or indirectly come into contact with plastic sheets containing various plasticizers, commuter pass holders, and the like.

Recently, it has also been used for tags in supermarkets, etc., and the opportunities for contact with plastic films are increasing.

Therefore, there was an urgent need to improve the reliability of heat-sensitive recording paper as a temporary recording medium by coloring it, using it for a long time, and bringing it into contact with a plasticizer. 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 intensive research to improve this drawback, the present inventors have found that by simultaneously adding a sulfone diphenol compound, polyvinylpyrrolidone, and zinc oxide to the recording layer of a heat-sensitive recording material, the plasticizer resistance of the colored portion can be improved. He discovered that this could be improved and filed an application (Japanese Patent Application No. 35396-1982).

Although the invention does improve plasticizer resistance,
It was insufficient in terms of responding to recent high-speed recording ratios (increasing the sensitivity of heat-sensitive recording media).

Thereafter, the inventors of the present invention further conducted studies to improve this drawback, and as a result, they completed the present invention.

That is, as a result of a more detailed study on sulfonodiphenyl compounds, the bis-(3-allyl-4
It has been found that the above problems can be solved by selecting -hydroxyphenyl)-sulfone.

(Problems to be Solved by the Invention) An object of the present invention is to provide a heat-sensitive recording material having plasticizer resistance and a high sensitivity ratio of b.

(Means for Solving the Problems) That is, the present invention provides at least a colorless to light-colored color-forming substance, an acidic substance (4-hydroxyphenyl)-sulfone that causes the dye to develop color when heated, and a water-soluble binder. 5w
The sections above are related to polyvinyl vinyl.

An example of using bis-(3-allyl-4-hydroxyphenyl)-sulfone as a color developer in a heat-sensitive recording composition is described, for example, in JP-A-60-208286. Furthermore, the use of zinc oxide as a pigment in thermal recording paper is public policy, as described in, for example, Japanese Patent Publication No. 18635-1983, and the use of polyvinylpyrrolidone as a binder in thermal recording paper is also public policy. 3680
This is a matter that is publicly known from publications such as the above.

However, in the present invention, these substances are simply obtained by applying them to a bis-(3-allyl-4 recording layer), and such an effect was completely unexpected.

Polyvinylpyrrolidone used in the present invention.

Zinc oxide is usually commercially available and there are no particular restrictions, but polyvinylpyrrolidone has slightly different effects on plasticizer resistance depending on its molecular weight. It tends to be less effective. Therefore, the molecular weight of the polyvinylpyrrolidone used in the present invention is preferably 40,000 or less.

Although it varies depending on the property, polyvinylpyrrolidone should be added in a proportion of 5 to 50% based on the total Via F-solids content in order to maintain plasticizer resistance.
100 wt%, zinc oxide is 5 to 5% based on the total pigment solid content
100 wt% is required.

Judging only from the viewpoint of plasticizer resistance, the best combination of these is 100 wt'l of each.However, if the heat-sensitive recording grit is exposed to high temperature and humidity, the surface tends to darken. In order to maintain plasticizer resistance and improve stability against temperature and humidity of the skin, polyvinylpyrrolidone is particularly preferably used in an amount of 7% based on the total binder solid content.
10-50 wt ratio, zinc oxide is 30-7% relative to the total pigment
It is 0 wt%.

The colorless to light-colored color-forming substance used in the present invention is a substance that develops color by reacting with an acidic substance under heat, such as triphenylmethane type, triphenylmethane phthalide type,
Examples include various leuco compounds such as fluoran-based, leuco-auramine-based, and spiropyran-based.

Examples of binders other than polyvinylpyrrolidone used in the present invention include water-disintegrable binders such as casein, gelatin, modified starch, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, styrene-maleic anhydride copolymer and its alkaline solution, polyacrylamide, Examples include latexes of styrene-butadiene copolymers, polyvinyl acetate, and polyacrylic esters.

Pigments other than zinc arsenide used in the present invention include calcium carbonate, kaolin, clay, and other additives such as various waxes for improving recording properties, fatty acid amides, and various types for preventing stickiness. fatty acid metal salts,
It is also possible to add a water resistance agent or the like to improve water resistance.

As the support used in the present invention, various types of paper including high-quality paper, medium-quality paper, and coated paper can be used, and the type and weightage thereof are not limited at all. Further, the support in the present invention is
Paper is most commonly used, but other supports such as synthetic resin films, film-laminated papers, and woven fabric sheets can also be used.

The heat-sensitive recording material of the present invention is produced as follows. Color forming substances, acidic substances, zinc oxide and other pigments, sensitivity modifiers and other additives are mixed in an aqueous medium containing an appropriate concentration of polyvinylpyrrolidone and other binders using a pulverizer such as a ball mill or sand grinder. pulverized and dispersed,
Obtain heat-sensitive paint. It is advantageous in terms of color development efficiency to make each constituent material as fine as possible, and it is preferable that the particles have a particle size of 0.5 to 3 .mu.m. The heat-sensitive paint thus obtained is applied to a support and dried to obtain the heat-sensitive recording material of the present invention. The heat-sensitive recording material of the present invention thus obtained has excellent plasticizer resistance against various plasticizers. Even if a colored image is brought into contact with these plasticizers for a long period of time, the image will not disappear or change color, and the sensitivity is high.

The present invention will be explained in more detail with reference to Examples.

(Example) Example 1 (a) Production of heat-sensitive recording composition Liquid A fluoran black coloring dye (PSD-150 manufactured by Shin Nisso Hiko Co., Ltd.)
) triple front methylolamide (manufactured by Nippon Himei: a substance in which one molecule of formaldehyde is added to one molecule of fatty acid amide (general formula % formula % polyvinyl pyrrolidone (Gokyo Sangyo Rip ni -30; molecular weight 4)
0000) 10 width aqueous solution (as it is)
20 l water
40 IB liquid bis-(3-allyl-4-hydroxyphenyl)-sulfone lo l zinc oxide
2o #Polyvinylpyrrolidone (A
liquid (!: same) 10th grade aqueous solution (as such)
20 #Water
4o # After dispersing liquid A and liquid B separately in a centrifugal ball mill for 4 hours, mix liquid A and liquid B to form a paint. Apply the coating so that the coating amount is 89/rr?, and then smooth it with a super calender to achieve a Peck smoothness of 5.
A thermosensitive recording paper of 0.00 seconds was obtained.

fcl Next, this thermosensitive recording paper was examined for plasticizer resistance according to the following procedure. First, the heat-sensitive recording paper was colored using a static coloring tester (stamp type) at a pressure of 2 wheels/-1 at a temperature of 120 DEG 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 thermal recording paper, and then a 300
A weight No. 2 was placed on the tube and the tube was left at 40° C., 904 RH for one day.

Thereafter, the density of the colored portion before and after the test was measured using a Macbeth reflection densitometer R1)-514, and the results shown in the table were obtained.

In addition, in order to test the sensitivity of the obtained thermal recording paper, it was recorded using a commercially available GI facsimile device C0PIX6500 (manufactured by Toshiba), and the recorded density was measured using a Macbeth reflection densitometer RD-
514, and the results shown in the table were obtained.

Example 2 10 parts by weight of the 20 parts by weight of zinc oxide in Solutions A and B of Example 1 were replaced with clay, and 15 parts by weight of the 20 parts by weight of the aqueous solution of polyvinylpyrrolidone 10 was replaced with an aqueous solution of polyvinyl alcohol 10. A thermosensitive recording paper was obtained in the same manner as in Example 1 except for the above, and the test was conducted in the same manner. The results are shown in the table.

Comparative Examples 1 to 6 Thermosensitive recording paper was obtained in exactly the same manner as in Example except that the combinations of acidic substances, pigments, and binders in liquids A and B of Example 1 were changed as shown in the table. I conducted a test. The results are shown in the table.

(Effects of the Invention) From the results in the table, it can be seen that the heat-sensitive recording material of the present invention is superior to the comparative example in both plasticizer resistance and recording properties.

Claims (1)

[Claims] In a heat-sensitive recording material comprising at least a colorless or light-colored color-forming substance, an acidic substance that causes the dye to develop color when heated, a water-soluble binder, and a pigment, the acidic substance is bis-(3-allyl-4-hydroxyphenyl)-sulfone. A heat-sensitive recording material characterized in that 5 wt% or more of the water-soluble binder is polyvinylpyrrolidone, and 5 wt% or more of the pigment is zinc oxide.