JPS58191191A - Heat sensitive recording material - Google Patents

Abstract

PURPOSE:To provide the titled material reduced in the color formation in the ground part thereof and excellent in heat sensitivity during storage, by providing a water soluble high molecular layer on the surface of a heat sensitive layer containing 3-di-n-butyl-7-o-chloroanilinofluorane as a leuco dye and the color coupler thereof. CONSTITUTION:A heat sensitive color forming layer containing 3-di-n-butyl-7-o- chloroanilinofluorane as a leuco dye and the color coupler thereof is provided on a support to constitute a heat sensitive recording material. By further providing a water soluble high molecular (e.g., polyvinyl alcohol) layer on the aforementioned heat sensitive color forming layer, the heat sensitive recording material reduced in the color formation in the ground part during storage and excellent in heat sensitivity is obtained. The aforementioned water soluble high molecular layer is provided within a range of 0.3-10g/m<2>, pref., 1-6g/m<2>.

Description

[Detailed description of the invention] The present invention relates to heat-sensitive recording materials.

A thermosensitive recording material is a recording material in which a so-called thermosensitive coloring layer that develops color when heated is formed on the surface of a support such as paper, and a thermal printer equipped with a built-in thermal head is used for heating.

The thermal recording method using the above-mentioned recording materials is used not only to copy books and documents, but also to record the output of electronic computers, facsimile machines, measuring instruments, etc. The recording materials include, for example, lactones, lactams, A heat-sensitive coloring layer containing a colorless or light-colored leuco dye having a spiropyran ring and an acidic substance such as an organic acid or a phenolic substance is formed on a support, which has the advantage that the color tone is clear and there is little fog. Although it is particularly widely used, many other types are also in practical use.

This type of heat-sensitive recording material is required to have high heat sensitivity, and dyes have been investigated as one means of solving this problem.As a dye with high heat sensitivity, 3-diethylamino-6-
Methyl-7-anilinofluorane, 3-N-methyl-
N-cyclohexylamino-6-methyl-7-anilinofluorane and the like are selectively used.

It does not exhibit sufficient thermal sensitivity to meet the high-speed recording performance required. Recently, 3-dinormalbutyl-7-orthochloroanilinofluorane has been proposed as a dye meeting this requirement. However, compared to other fluoran compounds, this fluoran compound has the disadvantage that the skin develops color during storage, which limits its use.

An object of the present invention is to provide a heat-sensitive recording material that has sufficient heat sensitivity and exhibits little color development in the background during storage.

That is, the present invention provides a leuco dye by further providing a water-soluble polymer layer on the surface of a heat-sensitive recording layer containing 3-dinormalbutyl-7-orthochloroanilinofluorane and its color developer. The object of the present invention is to provide a heat-sensitive recording material that exhibits little color development in the background during storage and has excellent heat sensitivity.

The water-soluble polymer layer provided on the surface of the heat-sensitive recording layer in the present invention is
083~lOg, preferably 1~6 g/rr? is within the range of

In addition to the leuco dye and the color developer, the thermosensitive coloring layer used in the present invention can contain a thermofusible substance, a binder, and a filler, if necessary.

Next, these components will be explained in detail.

(1) Color developer As the color developer in the present invention, commonly used electron-accepting substances can be used, such as those shown below.

Boric acid, oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid, benzoic acid, stearic acid, gallic acid, salicylic acid, 1-hydroxy-2-naphthoic acid, 0-hydroxybenzoic acid, m-hydroxybenzoic acid, 2 -Hydroxy-
p-) Ruylic acid, 3゜5-xylenol, thymol, I
) Iert-butylphenol, 4-hydroxyphenoxide, methyl-4-hydroxybenzoate, 4
-Hydroxyacetophenone, α-naphthol, β-naphthol, catechol, resorcinol, hydroquinone, 4
- tert-octinol, 2,2'-dihydroxydiphenyl, 2,2'-methylenebis(4-methyl-6
-Lerl-butylphenol), 2,2-bis(4-
Hydroxyphenyl) furopuff, 4.4-isopropylidene-bis(2-+crt-butylphenol), 4
+ 4-5ec-butylidene diphenol, pyrogallol, phloroglucin, phloroglucin carboxylic acid.

(2) Binder The following various binders can be used to bind and support the thermosensitive coloring layer on the support.

water-soluble ones such as polyvinyl alcohol, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch, gelatin, etc.
Alternatively, aqueous emulsions such as polystyrene, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, etc. can be used as the binder.

However, if necessary, conventional auxiliary additives, such as fine powders such as calcium carbonate, silica, alumina, magnesia, talc, titania, barium sulfate, and aluminum stearate, may be added to the heat-sensitive coloring layer to develop the color. Image clarity can be improved. Further, a heat sensitivity increasing agent such as a higher fatty acid amide can be included.

In the present invention, water-soluble polymers in the water-soluble polymer layer provided on the surface of the heat-sensitive coloring layer for improving storage stability include, for example, polyvinyl alcohol, methylcellulose, ethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, starch, gelatin, methoxycellulose, Examples include polyacrylamide. Further, inorganic or organic fine particles can be added to this water-soluble polymer layer, and a commonly used water resistance agent can also be added.

Furthermore, in the water-soluble polymer layer, an aqueous emulsion of a hydrophobic polymer can be used in combination with the water-soluble polymer described above. Examples of such aqueous emulsions include polyvinyl acetate, vinyl chloride/vinyl acetate copolymers, polyurethanes, polyacrylic esters, styrene/butadiene/acrylic copolymers, polyesters, and the like.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Dispersions A, B, and C were prepared by dispersing the following components for 24 hours using a ball mill, and then dispersions A and B were further mixed to prepare a thermosensitive coloring layer forming liquid.

Dispersion A: 3-di-n-butyl-7-ol 1.5 heavy i-part sochloroanilinofluoran calcium carbonate 1.0 120% oxidized starch aqueous solution 5. OI water
42.5N
Dispersion B: Bisphenol A 6.0 parts by weight 20% polyvinyl alcohol 8.0I water
360
#Dispersion C: Calcium carbonate 5.0 parts by weight 20%
Holihinyl alcohol il 25. OI The thermosensitive coloring layer forming liquid prepared as described above was coated on F-quality paper (approximately s.o.g.
/rr? ) and dried, the adhesion rate was s g/r
A thermosensitive coloring layer of nl (solid content) was formed, and then liquid C was applied on the thermosensitive coloring layer and dried to give an adhering area of 4 g/n.
Comparative Example 1: In place of 3-dinormalbutyl-7-orunchloroanilinofluorane in dispersion A, 3-diethylamino-6
- Sample B-1 in which only a thermosensitive coloring layer was provided on the support using methyl-7-anilinofluorane and other conditions similar to those in Example 1;
Sample B-2 was obtained by applying and drying Liquid C in the same manner as in Example (+), and Sample B-3 was obtained before applying Liquid C.

Next, the present product (B-]) and comparative products (B-1, B-2, B-3) obtained in steps 1 to 1 as described above were heated at 40°C and at a relative humidity of 9.
The sample was left in a 0% RH environment for 24 hours, and the density of the skin was measured using a photovolt densitometer. Also, using a thermal gradient tester (manufactured by Toyo Seiki Co., Ltd.) at 150°C, 2 kg/crrI? , l s
Table 1 shows the results of printing with EC and measuring the color density with a Macbeth densitometer. From these results, it can be seen that the product of the present invention has excellent thermal sensitivity and no problems in storage stability.

Table-1 Patent applicant Ricoh Co., Ltd. Representative: Patent Attorney Toshiaki Ikeura

Claims (1)

[Claims] (X) 3-dinormalbutyl-7-orthochloroanilinofluorane as a leuco dye on the support;
A heat-sensitive recording material comprising a heat-sensitive color forming layer containing the color developer, characterized in that a water-soluble polymer layer is further provided on the heat-sensitive color forming layer.