JPH058545A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance the light fastness and storage stability of both of an image and a blank part by providing a thermal color forming layer containing a specific colorless or light-colored leuco dye and a developer on a support and adding a benzotriazole compound to said color forming layer. CONSTITUTION:A thermal color forming layer containing a specific colorless or light-colored leuco dye represented by formula I [wherein R1 is -N(C4H9)2 or -N(iso-C3H11)C2H5] and a developer represented by formula II [wherein R2 is -OCR(CH3)2 or -OH] is provided on a support and a color is formed by the contact of the leuco dye with the developer. Further, a benzotriazole compound represented by formula III (wherein R3, R4 and R5 are a halogen atom or a 1-8C alkyl group) is added to the thermal color forming layer. The leuco dye represented by the formula I has high sensitivity and excellent preservability and the developer represented by the formula II has high whiteness and excellent preservability and, by the addition of the compound represented by the formula III, background color development is prevented and sensitivity is kept.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material having good storage stability of images and blank areas.

[0002]

2. Description of the Related Art Various types of heat-sensitive recording materials have been published so far, which utilize the heat-coloring reaction of at least one colorless or light-colored basic dye with phenols, organic acids, etc. (Japanese Patent Publication No. 45-14039). It is widely used. These thermosensitive recording materials are applied to a wide range of fields such as measuring recorders, computers and information communication terminals, facsimiles, ticket vending machines.

These recording apparatuses are equipped with a thermal element such as a thermal head or a hot pen, and by heating this element, a color can be developed to obtain a recording.

Recently, the diversification of the uses and the higher performance of the apparatus have been advanced, and accordingly, the required quality of the heat-sensitive recording material paper has also become higher. For example, in the case of the facsimile, the A4 size recording is conventionally used. What used to take a few minutes is now possible within a minute.

Under the present circumstances, it has been proposed to add a sensitizer as a method for improving the sensitivity of the thermal recording paper, but the color developing sensitivity, the stability of the color image, the recording suitability, etc. However, there has not yet been obtained what satisfies the performance required for the thermal recording material in a well-balanced manner.

Further, these heat-sensitive recording materials have a defect in light resistance in the image area and the blank area. That is, when exposed to sunlight or a fluorescent lamp for a long time, the density of the image part is reduced and the white paper part is discolored. Particularly in applications such as heat-sensitive tickets, heat-sensitive coupons, and heat-sensitive recording labels for automatic ticket vending machines, there is a high possibility of being exposed to the above-mentioned sunlight and fluorescent lamps, which poses a problem. As a method for improving the light resistance, for example, JP-A-63-30
Although the addition of benzotriazole and the like is described in Japanese Patent No. 7981, there are drawbacks that the light resistance is not sufficient and the storage stability with respect to plasticizers and oils is poor.

[0007]

SUMMARY OF THE INVENTION The present invention aims to improve the light resistance of the image part and the white paper (background) when exposed to such sunlight and fluorescent light. The object of the present invention is to provide a heat-sensitive recording material having good storage stability.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result,
A colorless or light-colored leuco dye, and a thermosensitive recording material provided with a thermosensitive coloring layer containing a color developing agent which is brought into contact with the leuco dye to form a color, in the thermosensitive recording layer, as a leuco dye,

[Chemical 4] [Wherein R ₁ is -N (C ₄ H _{9) 2} or -N (iso-C
₅ H ₁₁ ) C ₂ H ₅ ] is also used as a developer.

[Chemical 5] [Wherein R ₂ represents -OCH (CH ₃ ) ₂ or -OH], and a compound of the formula

[Chemical 6] [Wherein R ₃ , R ₄ and R ₅ are halogen atoms or carbon atoms 1
It has been found that a heat-sensitive recording material having a high whiteness and good storage stability in the image and white paper portions can be obtained by incorporating a benzotriazole compound represented by [indicating 8 to 8 alkyl groups].

Formula used as leuco dye in the present invention

[Chemical 7] The compound represented by is particularly sensitive and has excellent storage stability.

Further, a formula used as a color developer

[Chemical 8] The compound represented by is highly white and has excellent storage stability.

In the present invention, in addition to the leuco dyes and the developers represented by the formulas (1) and (2), no further background color development occurs,
And in order not to reduce the sensitivity

[Chemical 9] A benzotriazole compound represented by is incorporated into the thermosensitive color developing layer. Examples of such compounds include the following. 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3) '-T-Butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-5'-t-octylphenyl) benzotriazole, 2- (2'-hydroxy-3', 5 '-T-amylphenyl) benzotriazole, 2- (2'-hydroxy-3', 5'-di-t
-Butylphenyl) benzotriazole, 2- (2'-
Hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di-t-butylphenyl) -5
-Chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-diphenylphenyl) benzotriazole.

Expression

[Chemical 10] Benzotriazole compounds of formula

[Chemical 11] It is added in a proportion of 0.1 to 2 parts by weight with respect to 1 part by weight of the leuco dye represented by. If it is less than 0.1%, there is no effect of improving the light resistance, and if it exceeds 2% by weight, there is no particular effect. Further, sensitivity is lowered and background color is generated.

By forming a thermosensitive coloring layer on a support by blending such a specific compound in a fixed ratio, the light resistance of the image area and the blank area is remarkably improved, and the storage stability becomes good. It was

In the heat-sensitive recording material of the present invention, it is safe to use a combination of auxiliary substances which can be generally added as a heat-sensitive recording material.

For example, as a sensitizer, parabenzyl biphenyl, dibenzyl terephthalate, 1-hydroxy-2
-Phenyl naphthoate, dibenzyl oxalate, di-o-chlorobenzyl adipate, 1,2-di (3-methylphenoxy) ethane, di-p-chlorobenzyl oxalate,
Di- (p-methylbenzyl) oxalate or the like can be used.

In the heat-sensitive recording material of the present invention, the material of the support that supports the heat-sensitive color forming layer may be any material. For example, paper, synthetic fiber paper, synthetic resin film and the like can be used as appropriate. Paper is generally preferred.

In preparing the thermosensitive coloring layer-forming coating liquid,
Using water as a dispersion medium, a dye, a color developer, and an additive are dispersed by a pulverizer such as a ball mill, an attritor, or a sand grinder to obtain a coating liquid.

In the coating liquid, starch, hydroxyethyl cellulose, methyl cellulose,
Carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene, maleic anhydride copolymer salt, styrene, butadiene copolymer emulsion and the like are used in an amount of 2 to 40% by weight, preferably 5 to 25% by weight, based on the total solid content. To do.

There is no problem in adding various auxiliary materials to the coating liquid, if necessary.

For example, dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate / sodium salt and fatty acid metal salt, other defoaming agents, fluorescent dyes, coloring dyes and the like can be added.

In order to make the heat-sensitive recording layer whiter, inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth and fine anhydrous silica can be added. Waxes such as a dispersion or emulsion of stearic acid, polyethylene, carnauba wax, paraffin wax, calcium stearate, zinc stearate, ester wax and the like can be added as necessary.

In the heat-sensitive recording material of the present invention, the method for forming the heat-sensitive color forming layer is not particularly limited. For example, when the heat-sensitive coating liquid is applied to the support, an appropriate coating device such as an air knife coater or a blade coater can be used.

The thermosensitive coloring layer generally has a dry weight of 2 to 12.
g / m ^2, preferably formed to be in the range of 3 to 8 g / m ^2.

If necessary, an undercoat layer,
There is no problem in making various known modifications such as providing an overcoat layer for the purpose of improving printability, water resistance and oil resistance.

[0025]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited thereto. Parts and% in the examples and comparative examples represent parts by weight and% by weight.

Preparation of Coating Liquid for Thermosensitive Coloring Layer Compositions A having the following composition were pulverized with a sand grinder to an average particle size of 1.0 μm to prepare liquids A to G.

[0027] Liquid A   3- (N-ethyl-N-isopentylamino) -6-     Methyl-7-anilinofluorane 20 parts   Polyvinyl alcohol 10% liquid 20 parts   60 parts of water

[0028] B liquid   3-dibutylamino-6-methyl-7-anilinofluorane 20 parts           (Yamamoto Kasei ODB-2)   Polyvinyl alcohol 10% liquid 20 parts   60 parts of water

[0029] C liquid   3-dibutylamino-7- (0-chloroanilino) fluorane 20 parts         (Hodogaya Chemical TH-107)   Polyvinyl alcohol 10% liquid 20 parts   60 parts of water

[0030] D liquid   4-hydroxyphenyl-4'-isopropoxyphenyl     Sulfone (Nippon Soda, D-8) 10 parts   10 parts of di (p-methylbenzyl) oxalate       (HS-3520, manufactured by Dainippon Ink)   10 parts calcium carbonate       (Shiraishi Industry, Brilliant-15)   Polyvinyl alcohol 10% liquid 20 parts   50 parts of water

[0031] E liquid   Bis (4-hydroxyphenyl) sulfone 10 parts   10 parts of di (p-methylbenzyl) oxalate       (HS-3520, manufactured by Dainippon Ink)   10 parts calcium carbonate       (Shiraishi Industry, Brilliant-15)   Polyvinyl alcohol 10% liquid 20 parts   50 parts of water

[0032] F liquid   2,2-bis (4'-hydroxyphenyl) propane 10 parts   10 parts of di (p-methylbenzyl) oxalate       (HS-3520, manufactured by Dainippon Ink)   10 parts calcium carbonate       (Shiraishi Industry, Brilliant-15)   Polyvinyl alcohol 10% liquid 20 parts   50 parts of water

[0033] G liquid   2- (2'-hydroxy-5'-methylphenyl)     Benzotriazole 20 parts   Polyvinyl alcohol 10% liquid 20 parts   60 parts of water

Example 1 Liquid A 75 parts by weight, liquid D 200 parts by weight, liquid G 10 parts by weight,
Styrene-butadiene copolymer latex (solid content 50
%) 40 parts by weight and 25 parts by weight of zinc stearate emulsion (solid content 20%) were mixed to prepare a coating liquid for the thermosensitive color developing layer. This thermosensitive color developing layer coating solution was coated and dried on a high-quality paper weighing 64 g / m ^{2 so} that the dry coating amount was 5 g / m ² , and a protective layer coating solution having the following composition was further applied on this color developing layer. A thermosensitive recording paper was obtained by coating and drying so that the dry weight was 3 g / m ² .

[0035] (Coating liquid for protective layer)   Polyvinyl alcohol 10% liquid     (Polymerization degree 1100, saponification degree 98.5%) 100 parts   Kaolinite clay (HG clay) 6 parts   Zinc stearate emulsion (20% liquid) 2 parts   Glyoxal (40% liquid) 1 part

Example 2 Solution B 75 parts by weight, Solution E 200 parts by weight, Solution G 10 parts by weight,
Styrene-butadiene copolymer latex (solid content 50
%) 40 parts by weight and 25 parts by weight of zinc stearate emulsion (solid content 20%) were mixed to prepare a coating liquid for the thermosensitive color developing layer. This thermosensitive color developing layer coating solution was coated and dried on a high-quality paper weighing 64 g / m ^{2 so} that the dry coating amount was 5 g / m ² , and the color developing layer was further protected by the composition shown in Example 1. The layer coating solution was applied and dried to a dry weight of 3 g / m ² to obtain a thermosensitive recording paper.

Comparative Example 1 Liquid C 75 parts by weight, liquid D 200 parts by weight, liquid G 10 parts by weight,
Styrene-butadiene copolymer latex (solid content 50
%) 40 parts by weight and 25 parts by weight of zinc stearate emulsion (solid content 20%) were mixed to prepare a coating liquid for the thermosensitive color developing layer. This thermosensitive color developing layer coating solution was applied and dried on a high-quality paper weighing 64 g / m ^{2 so} that the dry coating amount was 5 g / m ^2, and the composition shown in Example 1 was formed on the thermosensitive color developing layer. The protective layer coating solution was applied and dried to a dry weight of 3 g / m ² to obtain a thermosensitive recording paper.

Comparative Example 2 Liquid A 75 parts by weight, liquid F 200 parts by weight, styrene-butadiene copolymer latex (solid content 50%) 40 parts by weight, zinc stearate emulsion (solid content 20%) 25 parts by weight. The mixture was mixed to obtain a coating liquid for the thermosensitive color developing layer. This thermosensitive color developing layer coating solution was applied and dried on a high-quality paper weighing 64 g / m ^{2 so} that the dry coating amount was 5 g / m ^2, and the composition shown in Example 1 was formed on the thermosensitive color developing layer. The protective layer coating solution was applied and dried to a dry weight of 3 g / m ² to obtain a thermosensitive recording paper.

The thermal recording paper produced in each of the above Examples and Comparative Examples was calendered with a super calender so as to have a smoothness of 450 seconds (measured in accordance with Oken Beck (JIS-8123)) to obtain a product. did. The results of performance tests conducted on this product are shown in Table 1.

These tests were conducted as follows. The thermosensitive recording paper obtained above was used with a label issuing machine D-805P manufactured by Ishida Koki Co., Ltd., and the head voltage was 22.2.
V, pulse width 2.6 msec, period 3.0 msec, and applied energy 1.64 W / dot were recorded in a solid black step pattern in a test mode, and color density was measured by a Macbeth reflection densitometer (RD-514).

Further, the preservability test was conducted using the printed matter obtained in the recording density test, and the residual ratio of the recording density was calculated by the following formula. (1) Oil resistance test: Salad oil was applied to a printed material and left at a predetermined temperature for a predetermined time. (2) Plasticizer resistance test: A polyvinyl chloride wrap film (manufactured by Nippon Carbite: trade name, HSS Soft) is overlaid on the surface of the printed matter, and it is sandwiched between the upper and lower glass plates with a load of 60 g.
A weight was placed so that the pressure would be / cm ² and the plate was allowed to stand for a predetermined time under a predetermined temperature condition. (3) Light resistance test: The printed matter was stuck on the inner side of the window glass at the time of fine weather and left for a predetermined time.

Further, in the light resistance test, not only the printed matter but also a white paper was exposed by the same method, and the measurement was carried out using a Hunter whiteness meter blue filter (JIS-P-8123). Then, the whiteness retention rate was calculated.

[0043]

[Table 1]

As is clear from Table 1, the heat-sensitive recording materials of the respective examples were superior in oil resistance and oil resistance to those of the comparative examples.
It shows that storage stability such as plasticizer resistance and light resistance are all excellent in a well-balanced manner. As described above, the heat-sensitive recording material of the present invention is excellent in storability in the image area and the blank area, and further has high whiteness and sensitivity. For this reason, it will be possible to use it in fields that have not been used until now.

[0045]

According to the present invention, it is possible to obtain a heat-sensitive recording material having good storage stability of an image and a blank portion and high whiteness and sensitivity.

Claims (2)

[Claims] 1. A thermosensitive recording material comprising a support and a thermosensitive coloring layer containing a colorless or pale-colored leuco dye and a color developer which is brought into contact with the leuco dye to develop a color. , As a leuco dye, the formula: [Wherein R ₁ is -N (C ₄ H _{9) 2} or -N (iso-C
₅ H ₁₁ ) C ₂ H ₅ ] is also used as a color developer. A compound represented by the formula: wherein R ₂ represents —OCH (CH ₃ ) ₂ or —OH, and is further represented by the formula: [Wherein R ₃ , R ₄ and R ₅ are halogen atoms or carbon atoms 1
A heat-sensitive recording material containing a benzotriazole compound represented by 2. The heat-sensitive recording material according to claim 1, wherein the compound of formula (3) is present in the heat-sensitive recording layer in a proportion of 0.1 to 2 parts based on the weight of the leuco dye of formula (1).