JPH03120089A - Thermal recording paper - Google Patents

Abstract

PURPOSE:To achieve improvement of heat resistant, moisture resistance and colouring sensitivity by a method wherein 4,4'-thio bis is used as a developer in a thermal recording layer and further, a specified compound is contained therein. CONSTITUTION:4,4'-thio bis(6-t-butyl-3-methylphenol) as a developer which develops colour by reacting on a basic leuco dye, and either one type of di(P- chlorobenzyl) oxalate as a sensitizer are used in a thermal colouring layer. Then, 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane is contained as an auxiliary component therein. Either one type of di(P-methylbenxyl) oxalate or di(P-chlorobenxyl) oxalate acts as a colour accerator, generates a melting point lowering phenomenon between it and organic acid substance, and shows an action as a sensitizer which generates reaction on the leuco dye at lower temperature than respective melting points. Thereby, thermal recording paper which is excellent in points such as colouring sensitivity, heat resistant moisture resistance of an image part and a non-image part, etc., can be obtained.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to heat-sensitive recording paper, and more specifically, the present invention relates to heat-sensitive recording paper. This paper relates to a thermal recording paper that has few colors, has good heat resistance and moisture resistance, and has high color development sensitivity.

[Prior Art] It has been known for a long time that basic leuco dyes and organic acidic substances undergo a melting reaction under heat to produce color, and an example of applying this color reaction to recording paper is disclosed in Japanese Patent Publication No. 4160/1983. , is disclosed in Japanese Patent Publication No. 45-14039 and is well known.

These thermal recording papers are used in measurement recorders, terminal printers such as word processors, facsimile machines, automatic ticket vending machines,
It has been applied to a wide range of fields such as bar code labels, but as these recording devices become more diversified and more sophisticated, demands on thermal recording paper also become more sophisticated. Specifically, with the advancement of POS, when thermal recording paper is used to print barcodes, weights, unit prices, prices, etc. on printers in stores, supermarkets, etc. ,salt,
It is desired that the non-image area does not develop color or the image area discolors even when exposed to vinegar, soy sauce, water, etc.

As a method to prevent color development in non-image areas and decolorization in image areas caused by such wrap films and oils, we have created a film-forming layer on a heat-sensitive coloring layer provided on ordinary paper, which also has chemical resistance. A method of applying a water emulsion of a certain resin (Japanese Unexamined Patent Publication No. 54-128347), a method of applying a water-soluble polymer compound such as polyvinyl alcohol (Japanese Unexamined Patent Publication No. 56-1988)
A method of providing a protective layer is known, as shown in Japanese Patent Publication No. 125354).

However, these methods can prevent color development in non-image areas and color development in image areas due to the cling film and oils on the protective layer; In this case, in reality, the level that can meet the demands cannot be obtained.

Recently, high-speed recording has been made possible by increasing the recording speed by shortening the heating time of the thermal head and producing sufficient density with low power, and reducing the power applied to the thermal head. This increases the lifespan of the thermal head, so there is a demand for highly sensitive thermal recording paper.

On the other hand, it has been proposed to incorporate benzylbiphenyls, alkylbenzylbiphenyls, or hydrides thereof into the heat-sensitive coloring layer (Japanese Patent Laid-Open No. 82382/1982). However, with this method, a highly sensitive recording paper with good thermal response can be obtained, but when the recorded image is immersed in water,
It is not possible to prevent the image from fading when left in high temperature and high humidity conditions for a long period of time.

Another possible method is to mix two or more types of acidic substances to prevent the recorded image from decoloring, but this method causes a large amount of coloring of the white paper and is a practical problem.

[Problems to be Solved by the Invention] The present invention provides highly sensitive recording, and even if the recorded image is left under high temperature and high humidity conditions for a long period of time, there is little fading of the colored image.
The object of the present invention is to obtain a heat-sensitive recording paper in which the white paper is less colored.

[Means and Effects for Solving the Problems] In response to these requirements, the present inventor has developed a method that will prevent non-image areas from developing color and image areas from discoloring even if left under high temperature and high humidity conditions for a long period of time. We also conducted studies to develop highly sensitive thermal recording paper. 4,4'-thiobis(6
-t-butyl-3-methylphenol), di(p-methylbenzyl) oxalate or di(p-methylbenzyl) oxalate as a sensitizer.
~chlorobenzyl) and contain 1.1.3-tris(2-methyl-4hydroxy-5-cyclohexylphenyl)butane as an auxiliary component to achieve this purpose. The present inventors have discovered that it is possible to do this, and have completed the present invention.

In order to achieve the above objective, the organic acidic substance used to develop the color of the leuco dye by heating must have a high heat-resistant storage stability for the colored image and must not fade even when immersed in water. The inventor has identified 4,4 as such substances.
'-Thiobis(6-t-butyl-3-methylphenol) is extremely excellent, and this substance has high sensitivity and
In order to exhibit excellent effects with high storage stability, either di(p-methylbenzyl oxalate) or di(p-chlorobenzyl oxalate) is used as a sensitizer, and additionally, It has been found that it is effective to combine 1.1.3-)lis(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane as a component. Either di(p-methylbenzyl oxalate) or di(p-chlorobenzyl oxalate) acts as a color development promoter and causes a melting point depression phenomenon with organic acidic substances, lowering the melting point of each. It acts as a sensitizer, causing a reaction with leuco dyes at low temperatures.

Furthermore, by blending 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, sensitivity and storage stability can be further improved.

These 4.4'-thiobis(6-t-butyl3-methylphenol) and di(p-methylbenzyl) oxalate or di(p-chlorobenzyl) oxalate and 1.1.3-
The three-component formulation of tris(2-methyl-4-hydroxy-5-cyclohexyl phenyl)butane is leuco dye 1
4,4'-thiobis(6-t-butyl-
3-methylphenol) is 0.5 to 10 parts by weight, di(p-methylbenzyl) oxalate or di(p-chlorobenzyl) oxalate is 0.2 to 10 parts by weight, 1.1.3-tris( Suitably, the amount of 2-methyl-4-hydroxy-5-cyclohexylphenyl)butane is 0.05 to 2 parts by weight.

The dye used in the heat-sensitive coloring layer in combination with these substances may be a general leuco dye, for example, a commonly used fluoran dye. Such fluorane-based leuco dyes include 3-diethylamino-6-methyl-7-anilinofluoran, 3-(N-ethyl-P-toluidino)-6-methyl-
7-anilinofluorane, 3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-anilinofluorane, 3-diethylamino-7-(ortho-chloroanilino)fluorane, 3-diethylamino-7-(metaltrifluoromethylanilino)fluorane, 3-diethylamino-6-methyl-7-(ortho , para-dimethylanilino) fluorane, 3-pyrrolidine-6-methyl-7-anilinofluorane, 3-piperidine-6-methyl-7-anilinofluorane, 3-dibutylamino-6-metal-7-anilino Fluorane etc.

As this external filler, inorganic or organic pigments commonly used in coatings and the like can be used. Typical examples include calcium carbonate, fired clay, aluminum hydroxide, talc, magnesium carbonate, silica, polystyrene particles, and urea-formalin resin powder. As binders, water-soluble resins such as various polyvinyl alcohols, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, styrene-acrylic copolymers, isobutylene maleic anhydride, starches, styrene-butadiene copolymers, and vinyl acetate copolymers can be used. Although aqueous emulsions such as ethylene vinyl acetate copolymers and ethylene vinyl acetate copolymers can be used, it is preferable to select a binder with good water resistance, and it is also possible to use these in combination and to mix a crosslinking agent. It is also effective to use various waxes to impart coating properties.

The support used in the heat-sensitive recording paper of the present invention may be paper, plastic film, synthetic paper, or the like. The heat-sensitive recording layer of the present invention can be formed by applying the coating liquid for forming a heat-sensitive recording layer as described above onto these supports and drying it.

In the present invention, the heat-sensitive recording layer 2 may be provided with a protective layer for protecting this layer, if necessary. This protective layer is generally used to prevent color development in non-image areas and decolorization of image areas due to packaging films, oils, and the like. As such a protective layer, a water-soluble resin with film-forming ability and a chemical-resistant aqueous emulsion can be used, and the above-mentioned pigments, lubricants, etc., and crosslinking to prevent sticking, smoothness, and improve the strength of the water-resistant coating can be used. It is also possible to incorporate agents.

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

Preparation of Coating Liquid for Heat-Sensitive Coloring Layer Each of the compositions having the following compositions was ground with a sand grinder to an average particle size of 1.0 to prepare liquids A to F.

Part A 3-dibutylamino-6-methyl-7-anilinofluorane 200 parts Polyvinyl alcohol 10% solution 200 parts Water
600 parts of liquid B 4.4'-thiobis(6-tert-butyl-3-methylphenol) 100 parts (manufactured by Yoshitomi Pharmaceutical Co., Ltd., Yoshinox SR) Di(p-methylbenzyl oxalate) (manufactured by Dainippon Ink, M.S. -3520) 100 parts 1.1.3-tris(2-methyl-4-hydroxy-5
-cyclohexylphenyl)butane (manufactured by Adica Argus, D H-43) 10 parts Calcium carbonate (Shiraishi Kogyo, Brilliant-15) Polyvinyl alcohol 10% liquid water 90 parts 200 parts 500 parts C liquid 4.4'-thiobis ( 1.1.3-Tris (2-methyl-4-hydroxy-
5-cyclohexylphenyl)butane (Adica Argus, D H-43) 10 parts Calcium carbonate (Shiraishi Kogyo, Brilliant-15) 90 parts Polyvinyl alcohol 10% liquid water solution 200 parts 500 parts 4.4'-thiobis (6-tert-butyl-3-methylphenol) 100 parts (Yoshitomi Pharmaceutical Co., Ltd., Yoshinox SR) Parabenzylbiphenyl (Nippon Steel Chemical Co., Ltd., PBBP) 100 parts 1.1.3-Tris(2-methyl-4-hydroxy-
5-Cyclohexylphenyl)butane (Adica Argus, D H-43) 10 parts Calcium carbonate (Shiraishi Kogyo, Brilliant-15) Polyvinyl alcohol 10% liquid water 90 parts 200 parts 500 parts E liquid 4.4'- Isobylidene diphenol (Mitsui Toatsu, Bisphenol A) 100 parts Parabenzylbiphenyl (Nippon Steel Chemical, PBBP) 100 parts 1.1.3-Tris(2-methyl-4 hydroxy-5-cyclohexylphenyl)butane (Manufactured by Adica Argus, DH-43) 10 parts Polyvinyl alcohol 10% solution 200 parts Water 500 parts Example I 75 parts by weight of solution A, 200 parts by weight of solution B, styrene-butadiene copolymer latex (solid content 50%) ) and 25 parts by weight of zinc stearate emulsion (solid content 20%) were mixed to prepare a heat-sensitive coloring coating liquid. The dry coating amount of this heat-sensitive coloring coating liquid was 5 g/f on high-quality paper with a basis weight of 64 g/r+f.
rr? Then, on this coloring layer, a protective layer coating solution having the following composition was applied at a dry weight of 3 g/rrr.
It was coated and dried to obtain heat-sensitive recording paper.

(Protective layer coating liquid) 10% polyvinyl alcohol solution (degree of polymerization 1100, degree of saponification 98.5%) 100 parts oleinite clay (HG clay) 6 parts zinc stearate emulsion (20% solution) 2 parts glyoxal (
40% liquid) 1 part Example 2 75 parts by weight of liquid A, 200 parts by weight of liquid C, 40 parts by weight of styrene-butadiene copolymer latex (solid content 50%), zinc stearate emulsion (solid content 20%) 25 parts by weight were mixed to prepare a heat-sensitive coloring coating liquid. The dry coating amount of this coloring coating liquid was 5 g/rrr on high-quality paper with a basis weight of 64 g/rrr.
The coating solution for a protective layer having the composition shown in Example 1 was applied on this coloring layer at a dry weight of 3 g/r.
A heat-sensitive recording paper was obtained by coating and drying so as to obtain rr.

Comparative Example I 75 parts by weight of liquid A, 200 parts by weight of liquid D, 40 parts by weight of styrene-butadiene copolymer latex (solid content 50%), 25 parts by weight of zinc stearate emulsion (solid content 20%) were mixed to form a heat-sensitive coloring coating liquid.

This color-forming coating liquid was coated and dried on high-quality paper with a basis weight of 64 g/rd so that the dry coating weight was 5 g/rn'', and then a protective layer having the composition shown in Example 1 was coated on this color-forming layer. The liquid was applied to a dry weight of 3 g/rd and dried to obtain a thermosensitive recording paper.

Comparative Example 2 75 parts by weight of liquid A, 200 parts by weight of liquid E, 40 parts by weight of styrene-butadiene copolymer latex (solid content 50%), and 25 parts by weight of zinc stearate emulsion (solid content 20%) were mixed. , a heat-sensitive coloring coating liquid.

This color-forming coating liquid was coated on a high-quality paper with a basis weight of 84 g/rri' and dried so that the dry coating was 5 g/m'', and then a layer containing the composition shown in Example 1 was applied on this color-forming layer. A protective layer was coated and dried to give a dry weight of 3 g/r+f to obtain a heat-sensitive recording paper.

The heat-sensitive recording paper produced in each of the above Examples and Comparative Examples was heated to a smoothness of 450 seconds (Oken Beck (JI)) using a super calender.
Calendar treatment was performed to obtain a product (measured according to S-8123). Table 1 shows the results of performance tests on this product.

Note that these tests were conducted as follows. The color development sensitivity was determined using a label printing machine D-805P manufactured by Ishida Koki Seisakusho, with a head voltage of 22.2 V and a pulse width of 2. em, 5ecs
Period 3.0m5ec, applied energy 1.64W/da
Recording was performed using a solid black staircase pattern in test mode under the conditions of t, and the color density was measured using a Macbeth reflection densitometer (RD-514). Regarding heat and humidity resistance, heat-sensitive recording paper recorded under the above recording conditions was treated in a constant temperature and humidity chamber controlled at 50°C and 90% RH for 7 days, then taken out and heated at 20°C.
After conditioning the humidity at 65% RH for 2 hours, the density of the image area and non-image area was measured using the above-mentioned reflection densitometer.

Table 1 [Effects of the Invention] According to the present invention, it has become possible to provide a thermosensitive recording paper that is excellent in terms of color development sensitivity and heat and humidity resistance of image areas and non-image areas.

Claims (1)

[Claims] In a thermal recording paper, a heat-sensitive recording layer containing a colorless or light-colored leuco dye and a color developer is provided on a support, and a protective layer is further provided on the heat-sensitive recording layer as required. 4,4'-thiobis(6-tert-butyl-3-methylphenol) was used as a color developer, and di(p-methylbenzyl) oxalate and di(p-
chlorobenzyl) and 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane. Thermal recording paper.