JPH0785945B2 - Thermal recording - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is mainly composed of a colorless or light-colored organic dye generally called a leuco compound, and an organic acid which develops color by reacting with the leuco compound. The present invention relates to an improvement of thermal recording paper.

(Prior Art) A thermal recording paper containing a leuco compound and an organic acid is already known, for example, from Japanese Patent Publication No. 4514039.
This recording paper is based on the principle that heat energy is applied to the recording layer to soften or melt the leuco compound, organic acid and binder, and both color forming components are brought into contact with each other to cause a color forming reaction. It is used in such fields.

Various proposals have been made for the support of the thermal paper, but it is desired that the support contains waste paper pulp due to the recent demand for paper resources.

The inclusion of waste paper pulp in the support of thermal paper has already been described in JP-A-58-25986.

However, when a support containing waste paper pulp is used as a support for thermal paper, the recolorability of the thermal paper (when the thermal paper is stored under certain conditions, how much the recording characteristics after storage deteriorate compared to before storage) It was found that a problem arises that [representation density after storage / recording density before storage] × 100% decreases in characteristics.

(Problems to be Solved by the Invention) Accordingly, it is an object of the present invention to provide a thermosensitive recording paper in which the recolorability of the thermosensitive paper does not decrease even if the support contains waste paper pulp.

[Means for Solving the Problems]

The above problem is a thermal recording paper provided with a thermal recording layer containing a binder and a leuco compound and an organic acid that develops a color by reacting with the leuco compound on a support containing waste paper pulp, and bis as the organic acid. (4-hydroxyphenyl) acetic acid-n-
Butyl, 4-hydroxy-4-isopropoxydiphenyl sulfone, 4,4'-thiobis (3-methyl-6-tert
-Butylphenol) and N, N'-diphenylthiourea.

In the present invention, various waste paper pulps can be used, but deinked printed paper such as newsprint is mainly used.

In addition, waste paper pulp is generally produced by a combination of the following three steps. That is, (1) disaggregation: The waste paper is treated with mechanical force and chemicals using a pulper to disintegrate into a fibrous form, and the printing ink is separated from the fibers.

(2) Dust-remove foreign matter (plastic etc.) and dust contained in the waste paper.

(3) Deinking: The printing ink separated from the fibers is removed to the outside of the system by the flotation method or cleaning method.

If necessary, bleaching can be performed simultaneously with deinking or in a separate step.

A support for a thermosensitive recording medium is formed by a conventional method using 100% of waste paper pulp thus obtained or a mixture of waste paper pulp and virgin pulp in an amount of 50% or less.

The leuco compound used in the present invention is a colorless or light-colored substance that reacts with an organic acid to form a color, and is triphenylmethane-based, triphenylmethanephthalide-based, fluorane-based, leucoauramine-based, diphenylmethane-based, phenothiazine. System, phenoxazine series, spiropyran series, indoline series, indigo series and the like. Examples of preferable leuco compounds include 3-diethylamino-6-methyl-7-anilinofluorane and 3-diethylamino-6-methyl-7-anilinofluorane.
(N-Ethyl-P-toluidino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-
7- (ortho, para-dimethylanilino) fluorane,
3-piperidino-6-methyl-7-anilinofluorane, 3- (N-cyclohexyl-N-methylamino)-
6-methyl-7-anilinofluorane, 3-diethylamino-7- (ortho-chloroanilino) fluorane, 3
-Diethylamino-7- (meta-trifluoromethylanilino) fluorane, 3-diethylamino-6-methyl-chlorofluorane, 3-diethylamino-6-methyl-fluorane, 3- (N-isoamyl-N-ethylamino)- 6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3
-(Furanylmethyl-N ethylamino) -6-methyl-
Examples thereof include fluorane compounds such as 7-anilinofluorane, but especially 3-dibutylamino-6-methyl-7-anilinofluorane (ODB-2) in terms of background density, background fogging after storage, and fading. , 3-diethylamino-6-methyl-7-anilinofluorane (ODB), 3- (N-isoamyl-N-ethylamino) -6-methyl-7-anilinofluorane (S-205), 3- (N-Cyclohexyl-N-methylamino) -6-methyl-7-anilinofluorane (PSD-150) and 3- (furanylmethyl-N-
Ethylamino) -6-methyl-7-anilinofluorane is particularly preferred.

The above leuco compound can be used as one kind or as a mixture of two or more kinds, and is contained so as to be 1 to 20% by weight (hereinafter abbreviated as%), preferably 5 to 15% of the total solid content of the thermosensitive recording layer. Is good.

In the present invention, a specific organic acid, namely the aforementioned KFB, D-
8. One or a mixture of two or more of BPSR or 17C is used. The amount of the organic acid may be arbitrary, but it is preferably 1 to 50%, preferably 5 to 40% of the total solid content of the thermosensitive recording layer.

As the sensitizer, a known heat-fusible substance having a melting point of 80 to 120 ° C. can be used, but particularly m-terphenyl, para-benzyl biphenyl, 2-naphthol benzyl ether, bis (P-methylbenzyl oxalate). , Dibenzyl terephthalate and 1,2-bis (3-methylphenoxy) ethane are preferred. The sensitizer is contained in an amount of 1 to 50%, preferably 5 to 40% of the total solid content of the thermosensitive recording layer.

The binder used in the present invention is mainly composed of a water-soluble binder, which is used to release and fix the color formers dispersed in fine particles to each other, and polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, poly Examples include acrylic acid, casein, gelatin, starch and derivatives thereof. The binder is 1 to 35% of the total solid content of the thermosensitive recording layer, preferably 10 to 30%.
It is good to set it as%.

In the heat-sensitive recording layer of the present invention, if necessary, other additives such as clay, calcium carbonate, synthetic silica, aluminum hydroxide, talc, titanium oxide, zinc oxide, and other inorganic or organic pigments, waxes, and stick-preventing substances are used. For this purpose, various fatty acid metal salts, water-proofing agents for improving water resistance, phenolic resins, surfactants and the like can be added.

In addition, various antioxidants and ultraviolet absorbers for storage stability can be added, but especially 1,1,3-tris (2-
Methyl-4-hydroxy-5-cyclohexylphenyl) butane and 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane are preferred.

The leuco compound, the sensitizer and various antioxidants for storage stability and ultraviolet absorbers used in the present invention have been exemplified above, but the leuco compound, the sensitizer and the storage stabilizer described as being particularly preferable are combined. As a result, the thermosensitive recording medium of the present invention can obtain particularly excellent effects.

The coating material for the heat-sensitive recording layer of the present invention contains the leuco compound and the organic acid separately, if necessary, an additive such as a pigment and a sensitivity modifier, and a binder such as polyvinyl alcohol in an appropriate concentration. It is generally prepared by pulverizing and dispersing in a water-based medium using a pulverizer such as a ball mill and a sand grinder, and then mixing and stirring the dye dispersion and the organic acid dispersion. It is advantageous in terms of color development efficiency to make each constituent substance into fine particles as much as possible, and it is preferable to make the particles to have a particle diameter of 0.5 to 3 μm. The heat-sensitive paint thus obtained is applied to a support containing waste paper pulp, preferably 50% by weight or more, and dried to obtain the heat-sensitive recording material of the present invention.

The coating can be carried out by a normal blade coater, air knife coater, bar coater, reverse roll coater, or the like.

Providing an intermediate layer containing calcined clay, silica and plastic pigment between the support and the heat-sensitive layer,
Providing an overcoat layer on the heat-sensitive layer is also a preferable configuration.

(Working) The cause of the decrease in the coloring ability of the support containing waste paper pulp is not clear, but it is presumed that the developer contained in the waste paper pulp inactivates the color developer. . In particular, it is presumed that 2,2'-bis (4-hydroxyphenyl) propane (BPA), which has been widely used in the past, is likely to react with a surfactant and is likely to be inactivated, probably because of its relatively high water solubility. To be done.

On the other hand, the organic acid used in the present invention seems to effectively prevent the inactivation of the color developer.

(Effect of the Invention) According to the present invention, there is provided an excellent thermosensitive recording medium in which the problem of the color forming ability of the thermosensitive recording medium using a support containing waste paper pulp is solved.

Hereinafter, the present invention will be described in more detail with reference to Examples.

〔Example〕

Example 1 a) Manufacture of a thermal recording material A liquid and a B liquid having the following compositions were separately prepared and dispersed by a paint shaker (manufactured by Toyo Seiki) for 10 hours.

Solution A: [Leuco dye] 3-dibutylamino-6-methyl-7-anilinofluorane 5g Bis (p-methylbenzyl) oxalate 8g Zinc stearate 5g Polyvinyl alcohol 12% solution 35g Water 47g Solution B: Coloring agent] bis (4-hydroxyphenyl) acetic acid-n-butyl) 15
g Zinc stearate 3g Polyvinyl alcohol 12% liquid 35g Water 47g 1,1,3-Tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane 5g Next, liquid A 100g, liquid B 105 and polyvinyl alcohol 12% Liquid 5
0 g, synthetic silica p-832 (manufactured by Mizusawa Chemical Co., Ltd.) 15 g, water 60
Add g and mix and stir to prepare a coating solution, and then apply this coating solution to the surface of a medium-quality paper consisting of 50 g / m ² 80% waste paper pulp and 20% NBKP using a Meyer bar. A thermal recording paper was obtained by coating and drying so that the coating amount after drying was 8 g / m ² .

Examples 2 to 8 The dyes and color developer of Example 1 were replaced as shown in Table 1 to obtain thermosensitive recording paper.

Example 9 The undercoat of 100 parts by weight of silica and 30 parts by weight of PVA coated on the support of Example 5 at 6 g / m ² was used.

Comparative Examples 1 to 4 Thermosensitive recording papers were obtained by replacing the color developer of Example 1 as shown in Table 1.

Reference Examples 1-2 As a support of Example 1 and Comparative Example 1, NBKP 50%, LBKP
A thermal paper was obtained using a high-quality paper composed of 50%.

The thermal paper obtained by the surface treatment was finished into a roll of 100 m (1 inch core winding), and the coloring ability test shown below was conducted. The results are shown in Table 1.

Color development test (1) The winding is recorded with a commercially available personal facsimile spot V (manufactured by Toshiba) and the density is measured (D _a ).

(2) The same roll is stored under the condition of 50 ° C. and 80% for 1 week, and after storage, the second lap from the outside is similarly recorded at spot V and the density is measured (D _b ).

(3) Evaluation D _b / D _a × 100 = R% The larger the R, the higher the color forming ability and the better. Practically, 80% or more is required.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 58-25986 (JP, A) JP 61-22987 (JP, A) JP 61-120796 (JP, A) JP 61- 230983 (JP, A) JP 61-27287 (JP, A) JP 62-122784 (JP, A) JP 62-117788 (JP, A) JP 62-130878 (JP, A) JP 62-273885 (JP, A)

Claims (1)

[Claims] 1. A thermosensitive recording medium comprising a support and a thermosensitive recording layer comprising a leuco compound, an organic acid which develops color by reacting with the leuco compound, and a binder, wherein the support comprises waste paper pulp. It is mainly contained and the organic acid is bis (4
-Hydroxyphenyl) acetic acid-n-butyl, 4-hydroxy-4-isopropoxydiphenyl sulfone, 4,4 '
-Thiobis (3-methyl-6-tert-butylphenol) and at least one selected from the group consisting of N, N'-diphenylthiourea.