JPH0421486A - Thermal recording body - Google Patents

Abstract

PURPOSE:To prevent the deterioration of color reproducing properties of heat- sensitive paper even if a waste paper pulp is incorporated in a substrate by using a compound selected out of groups made of bis(4-hydroxyphenyl)acetate-n- butyl, 4-hydroxy-4-isopropoxydiphenylsulfone, 4,4'-thiobis(3-methyl-6-tert- butyphenol), and N,N'-diphenyl thiourea as a color-developing organic acid. CONSTITUTION:A leuco compound is a colorless or light-colored substance reacting with an organic acid to produce a color. As the leuco compound, a mixture of one or more compounds can be used. The leuco compound is preferably incorporated in the amount of 1-20wt.%, pref. 5-15wt.%, of all the solid content of a thermal recording layer. As the organic acid, a mixture of one or more compounds selected out of KFB, D-8, BPSR, and 17C can be used. The organic acid is preferably incorporated in the amount of 1-50%, pref. 5-40wt.%, of all the solid content of the thermal recording layer.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention mainly consists of a colorless or light-colored organic dye, generally called a leuco compound, and an organic acid that develops a color by reacting with the leuco compound. This paper relates to the improvement of thermal recording paper.

(Prior Art) A thermosensitive recording paper containing a leuco compound and an organic acid is already known, for example, from Japanese Patent Publication No. 14039/1983. This recording paper applies thermal energy to the recording layer to soften or melt the leuco compound, organic acid, and binder.
It is based on the principle of bringing both coloring components into contact to cause a coloring reaction, and has recently been used in various fields such as printers and facsimile machines.

Various types of supports for thermal paper have been proposed, but in response to recent demands for paper resource issues, it is desired that the supports contain waste paper pulp.

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

However, when a support containing waste paper pulp is used as a support for thermal paper, the recoloring ability of thermal paper (when thermal paper is stored under certain conditions, how much the recording properties after storage decrease compared to before storage) It has been found that there is a problem in the characteristics that [expressed as sample recording density after storage/recording density before storage lX100%] decreases.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide a thermal recording paper in which the recoloring ability of the thermal paper does not deteriorate even when the support contains waste paper pulp.

[Means to solve the problem]

The above problem is solved in a thermal recording paper in which a thermosensitive recording layer containing a leuco compound, an organic acid that reacts with the leuco compound to develop a color, and a binder is provided on a support containing waste paper pulp. (4-human D + diphenyl)acetic acid-
n-Butyl, 4-hydroxy-4-isopropoxydiphenylsulfone, 4,4'-thiobis(3-methyl-5
-tert-butylphenol) and N,N'-diphenylthiourea.

In the present invention, various waste paper pulps can be used, but those obtained by deinking printed paper such as newspaper are mainly used.

Incidentally, waste paper pulp is generally produced by a combination of the following three steps. That is, (1) Disintegration: The waste paper is treated with mechanical force and chemicals in a pulper to loosen it into fibers, and the printing ink is separated from the fibers.

(2) Dust removal: Remove foreign substances (such as plastic) and garbage contained in waste paper.

(3) Deinking: The printing ink peeled off from the fibers is removed from the system by a flotation method or a cleaning method.

Incidentally, if necessary, bleaching can be carried out simultaneously with deinking or in a separate step.

Using 100% of the thus obtained waste paper pulp or a mixture of the waste paper pulp and 50% or less of virgin pulp, a support for a heat-sensitive recording material is formed by a conventional method.

The leuco compounds used in the present invention are colorless to light-colored substances that develop color by reacting with organic acids. Examples include various derivatives such as phenoxazine-based, phenoxazine-based, spiropyran-based, indoline-based, and indigo-based. Preferred leuco compounds include, for example, 3-diethylamino-6-methyl-7-anilinofluorane, 3(N
-ethyl-P-)luidino)-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-ynamyl-N-ethylamino)-6
Examples include fluoran compounds such as -methyl-7anilinofluorane, 3-dibutylamino-6methyl-7-anilinofluorane, and 3-(furanylmethyl-N-ethylamino)-6-methyl-7anilinofluorane. 3-dibutylamino-6-methyl 7-anilinofluorane (OD
B-2), 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-methyl7-anilinofluorane is particularly preferred.

The above leuco compound can be used alone or as a mixture of two or more, and is contained in an amount of 1 to 20% by weight (hereinafter abbreviated as %), preferably 5 to 15% of the total solid content of the heat-sensitive recording layer. It is better.

In the present invention, specific organic acids, namely the above-mentioned KFB, D
-8, BPSR, or 17C, or a mixture of two or more thereof is used.

The amount of this organic acid can be set arbitrarily, but it is preferably 1 to 50%, preferably 5 to 40% of the total solid content of the heat-sensitive recording layer.

As the sensitizer, known thermofusible substances with a melting point of 80 to 120°C can be used, but in particular m-terphenyl, parabasil biphenylene 2-naphthol benzyl ether, bis(P-methylbenzyl oxalate) , dibenzyl terephthalate, and 2-bis(3-methylphenoxy)ethane are preferred.

The sensitizer is preferably contained in an amount of 1 to 50%, preferably 5 to 40% of the total solid content of the heat-sensitive recording layer.

The binder used in the present invention mainly consists of a water-soluble binder, which binds the coloring agent dispersed in fine particles by releasing it from each other. , polyacrylic acid, casein,
Examples include gelatin, starch and derivatives thereof. The binder accounts for 1 to 35% of the total solid content of the heat-sensitive recording layer, preferably 1
It is preferably 0 to 30%.

The heat-sensitive recording layer of the present invention may contain other additives as necessary, such as inorganic or organic pigments such as clay, calcium carbonate, synthetic silica, aluminum hydroxide, talc, titanium oxide, and zinc oxide, waxes, and anti-stick additives. Various fatty acid metal salts for water resistance, water resistance agents for water resistance improvement, phenol resins, surfactants, etc. can be added.

In addition, various antioxidants and ultraviolet absorbers can be added for storage stability, especially 1,1°3-tris.
(2-methyl-4-hydroxy-5cyclohexylphenyl)butane, 1,1.3-tris(2-methyl-4-
Hydroxy-5-tert-butylphenyl)butane is preferred.

The leuco compounds, sensitizers, various antioxidants and ultraviolet absorbers for storage stability that are used in the present invention have been illustrated above, and combinations of the leuco compounds, sensitizers, and storage stabilizers described as particularly preferred. By doing so, the heat-sensitive recording material of the present invention can obtain particularly excellent effects.

The paint for the heat-sensitive recording layer of the present invention separates the leuco compound and organic acid, and contains additives such as pigments and sensitivity adjusters as necessary, and a binder such as polyvinyl alcohol at an appropriate concentration. It is generally prepared by pulverizing and dispersing in an aqueous medium using a pulverizer such as a ball mill or a sand grinder, and then mixing and stirring a dye dispersion and an organic acid dispersion.

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

Coating can be performed using a conventional blade coater, air knife coater, bar coater, reverse roll coater, or the like.

Providing an intermediate layer containing baked clay, silica, plastic pigment, etc. between the support and the heat-sensitive layer;
It is also a preferable configuration to provide an overcoat layer on the heat-sensitive layer.

(Effect) The cause of the decrease in coloring ability of the support containing waste paper pulp is not clear, but it is presumed that the color developer is inactivated by the surfactant contained in the waste paper pulp. . In particular, 2,2'-bis (
It is presumed that because 4-hydroxyphenyl)propane (BPA) is relatively highly water-soluble, it easily reacts with surfactants and is easily deactivated.

On the other hand, it seems that the organic acid used in the present invention effectively prevents the color developer from becoming inactivated.

(Effects of the Invention) According to the present invention, an excellent heat-sensitive recording material is provided in which the problem of coloring ability of a heat-sensitive recording material using a support containing waste paper pulp has been solved.

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

〔Example〕

Example 1 a) Production of heat-sensitive recording material A liquid A and a liquid B having the following compositions were separately dispersed in a paint shaker (manufactured by Toyo Seiki Co., Ltd.) 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: [Developer] Bis(4-hydroxyphenyl) (n-butyl acetate) 15g Zinc stearate 3g Polyvinyl alcohol 12% solution 35g Water
47g, then 100g of liquid A,
105g of liquid B and 50g of 12% polyvinyl alcohol liquid1
Synthetic silica p832 (manufactured by Mizusawa Kagaku ■) 15g, water 60g
was mixed and stirred to make a coating liquid, and then this coating liquid was mixed with 50g/m' of 80% waste paper pulp and NBKP20.
% was coated on the surface of medium-quality paper using a Mayer bar so that the coated amount after drying was 8 g/m', and dried to obtain heat-sensitive recording paper.

Examples 2 to 8 Thermosensitive recording paper was obtained by changing the dye and developer used in Example 1 as shown in Table 1.

Example 9 Silica 1 (10 parts by weight and PVA30
An undercoat of 6 g/m'' consisting of parts by weight was used.

Comparative Examples 1 to 4 Thermosensitive recording papers were obtained by changing the developer used in Example 1 as shown in Table 1.

Reference Examples 1-2 NBKP 50% as a support in Example 1 and Comparative Example 1
, LBKP 50% was used to obtain thermal paper.

The thermal paper obtained by surface treatment in this way was heated for 100 m (1
After completing the winding process (inch core winding), the following coloring ability test was conducted. The results are shown in Table 1.

Color development test (1) Roll up using a commercially available personal facsimile spora)
V (manufactured by Toshiba) and measure the density (D6).

(2) The same roll is stored for one week at 50°C and 80%, and after storage, the second rotation from the row side is similarly recorded at spot V, and the density is measured (D,).

(3) Evaluation Db/D, XIOO=R% The larger R is, the higher the coloring ability is. Practically speaking, 80% or more is required.

Claims (1)

[Claims] A heat-sensitive recording material in which a heat-sensitive recording layer comprising a leuco compound, an organic acid that reacts with the leuco compound to develop a color, and a binder is provided on a support, the support containing waste paper pulp, and the organic acid is bis(4-hydroxyphenyl)
n-butyl acetate, 4-hydroxy-4-isopropoxydiphenylsulfone, 4,4'-thiobis(3-methyl-6-tert-butylphenol) and N,N'-
At least one selected from the group consisting of diphenylthiourea
A thermosensitive recording medium characterized by being a seed.