JPS6012240B2 - Method for manufacturing heat-sensitive recording material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a heat-sensitive recording material, and more specifically, the present invention relates to a method for producing a heat-sensitive recording material, and more specifically, it includes a colorless or slightly pale leuco body and an organic acid or phenolic substance that reacts with the leuco body under heat to develop a color. The present invention relates to a method for producing a heat-sensitive recording material in which a heat-sensitive coloring layer is provided on a support.

A thermosensitive recording material is a material in which a thermosensitive coloring layer that can record a colored image by heat is provided on a support, and it can be used in calculators, computer terminals, thermal printers, thermal pen recorders such as medical measuring instruments, thermal facsimiles, etc. It is widely used as a recording material for automatic ticket vending machines, etc.

Such heat-sensitive recording materials usually contain a colorless or light coloring agent,
For example, a leuco compound and a color developer, such as an organic acid or a phenolic substance, which reacts with the color former to produce a color under heat, are separately used in combination with polyvinylene, methyl, and styrene-maleic acid. Polymer, hydroxyethylcellulose, polyvinylpyrrolidone, ethylcellulose, carboxycellulose, etc. are dispersed in a polymer compound, and then mixed with a resin binder, and if necessary, a surfactant, antifoaming agent, wax, and inorganic pigment. etc. to form a heat-sensitive coloring layer liquid, which is then coated onto a support such as paper, synthetic paper, plastic film, etc., and dried to form a heat-sensitive coloring layer. It has been put to practical use.

However, we have not yet obtained anything satisfactory. For example, in heat-sensitive recording materials, the color forming agent and color developer are separated by the polymer compound etc. so that they cannot come into direct contact with each other until they are heated, and it is not until heating during recording that the color forming agent and the color developer are separated by the polymer compound etc. It is desirable for the color former and the complexion agent to come into direct contact and react when the color former or color developer is melted, but in reality this is difficult and the color former and color developer are already mixed before heating. When they came into direct contact with each other, a reaction occurred, causing the heat-sensitive coloring layer liquid or the heat-sensitive coloring layer to develop color, resulting in so-called liquid fogging phenomenon or background fogging phenomenon. This phenomenon greatly reduces the contrast of colored images,
The clarity was lost. For this reason, in the past, the heat-sensitive coloring layer solution was kept alkaline (see Samurai Seki No. 49-11,141), or amines were added to the same solution (Japanese Unexamined Patent Publication No. 48-118).
01,943) Adding a basic inorganic pigment (
Methods have been proposed (see JP-A-49-90-142), but none of these methods prevent direct contact between the coloring agent and the complexion agent before heating, but merely reduce their reactivity. Therefore, it is not possible to sufficiently prevent liquid fog or skin fog during long-term storage or storage under high temperature and humidity.

An object of the present invention is to provide a method for producing a heat-sensitive recording material that does not cause the above-mentioned conventional drawbacks, particularly liquid fog or background fog. As a result of various studies in view of the purpose of the present invention, it was found that a colorless or slightly light-colored leuco compound and an organic acid or phenolic substance that reacts with the leuco compound under heat to develop a color are separately dispersed in a polymer compound, and then mixed. In the method for producing a heat-sensitive recording material in which the obtained heat-sensitive color forming layer liquid is coated on a support and dried to form a heat-sensitive color forming layer, if an aqueous etherified starch solution is used only for the leuco body, the above-mentioned isolation is sufficiently achieved. It was found that liquid fog and skin capri can be suppressed, leading to the completion of the present invention.

When an aqueous etherified starch solution is used after dispersing leuco bodies as in the present invention, it is possible to suppress the above-mentioned liquid fog and background capri, and not only improve the storage stability of the recording material, but also greatly improve the dispersion of leuco bodies into the polymer compound. It was easy to use, and it was possible to obtain a high-concentration dispersion of the oico-isomer in a short dispersion time, and in the end, it was possible to record a clear image with high contrast and high concentration.

Furthermore, the coating suitability of the heat-sensitive color forming layer liquid of the present invention was also extremely excellent. Colorless or slightly light-colored leuco bodies that can be used in the present invention include leuco bodies of triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based dyes, etc.;
3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis(p-dimethylaminophenyl) phthalide, 3,3-pis(p-dimethylaminophenyl) )
-6-diethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)-6-chlorophthalide, 3-(
N-ptolyl-N-ethylamino)-6-methyl-7
-(N-phenylamino)fluoran, 3-diethylamino-7-chlorofluoran, penzoylleucomethylene blue, 6-chloro-8'-methoxy-penzoindolinotapyrillospiran, 6-bromo8'-methoxybenzoindolino -pyrylospirane, 2-[3,6-bis(diethylamino)-9-(0-chloroanilino)
Examples include lactam xantylbenzoate.

These are dispersed in etherified starch to form a color former solution which is then mixed with an organic acid or phenolic compound. As the organic acid or phenolic substance that reacts with the leuco form under heat to cause the leuco form to develop color, any organic acid or phenolic substance that is normally used in combination with the leuco form can be used, such as benzoic acid, salicylic acid, tartaric acid, gallic acid,
Q-naphthol, P-naphthol, 4-t-butylphenol, 4-t-octylphenol, 4-phenylphenol, 2,2'-bis(p-hydroxyphenyl)propane, 2,2-bis( p-hydroxyphenyl)
Butane, 4,4'-cyclohexylidene diphenol,
2,2-bis(2,5-dipromo-4-hydroxyphenyl)propane, 4,4'-imptalopylidene bis(
2-t-butylphenol), 2,2'-methylenebis(4-chlorophenol), and the like.

To prepare mauve liquid using these organic acids or phenolic substances, they may be dispersed in conventional polymeric compounds. 0 or more color forming agent liquid and color developing agent liquid, resin binder usually used in this type of heat-sensitive recording material, and if necessary, surfactant, antifoaming agent, wax, inorganic pigment, etc. are added as usual. A thermosensitive coloring layer liquid is prepared to obtain the thermosensitive recording material of the present invention.

Examples and comparative examples will be shown below to specifically explain the present invention.

Example 1 Mixtures having the following compositions were separately dispersed using a ball mill for 4 hours and 2 hours to obtain a coloring agent solution and a complexion agent solution.

Color former liquid: Crystal violet lactone 2 parts by weight 20% etherified starch aqueous solution 1 Water 7
Color developer liquid: Bisphenol A 2.5
Part by weight 10% polyvinyl alcohol aqueous solution 1.5
J Water 65〃Next, a heat-sensitive color forming layer liquid having the following composition was prepared using the above color forming agent liquid and color developing agent liquid, and the dry coating amount of the liquid was 7 mm on commercially available high-quality paper (basis weight 52 mm/end). The mixture was coated in a uniform manner and dried at 90°C to obtain a heat-sensitive recording material of the present invention.

Thermosensitive color forming layer liquid: Z color forming agent liquid 5 parts by weight color developing agent liquid
18 25% stearamide aqueous solution 10 30% kaolin aqueous solution
10 50% styrene-butadiene rubber Terrax aqueous solution J solution 5 Water
20 Examples 2 to 7 The heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1, except that the polymer compound shown in Table 1 was used as the polyvinyl alcohol in the head colorant solution.

Comparative Examples 1 to 5 Comparative heat-sensitive samples were prepared in the same manner as in Example 1, except that the etherified starch and polyvinyl alcohol in the coloring agent liquid and complexing agent liquid were changed to the polymer compounds shown in Table 1. Obtained recording materials.

Using the heat-sensitive recording materials of the present invention and comparative heat-sensitive recording materials obtained as described above, a heat gradient tester (manufactured by Toyo Seiki Co., Ltd.) heated to 150°C was pressed for 1 second at a pressure of 2k9/me to develop color. , 40℃, 90%R to test the whiteness (%) of the background area, the density of the colored area, and the storage stability.
After storage for 2 hours, the skin reflectance and image density were measured using a Photoport densitometer (using a Green filter) and a Macbeth densitometer. The results are shown in Table-1. Table 1 As is clear from the above results, the product of the present invention had high whiteness, no background capri, and was able to record clear images with high contrast.

Claims (1)

[Claims] 1. A colorless or slightly light-colored leuco compound and an organic acid or phenolic substance that reacts with the leuco compound under heat to develop color are separately dispersed in a polymer compound and then mixed, and the resulting thermosensitive coloring layer liquid is supported. 1. A method for producing a heat-sensitive recording material in which a heat-sensitive coloring layer is formed by coating and drying the heat-sensitive recording material, characterized in that an aqueous solution of etherified starch is used only for the leuco body.