JPH0564968A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material which is almost free from a texture fog and allows an image to be preserved in satisfactory condition with high thermal sensitivity by adding an electron-receptive compound expressed by a specific formula. CONSTITUTION:An electron-donative dye precursor such as fluoran compound and at least, one type of either electron-receptive compound, alone or in a mixed state, of those expressed by formula I and formula II (R is H, an alkyl group, an aralkyl group, an aryl group or an alkenyl group; X1 and X2 are H, a halogen atom or an alkyl group) and formula III (X3 and X4 are H, an alkyl group, an aralkyl group, an aryl group or a halogen atom) are crushed to the grain size of 1.5mum or smaller in a dispersion medium to obtain a dispersion liquid. If this dispersion liquid is used, it is possible to obtain an extremely high sensitive thermal recording material which allows an image to have high developed color density without sacrificing its preservability at normal temperature and is almost free from a texture contamination.

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 high sensitivity and improved image storability.

[0002]

2. Description of the Related Art Recording materials using an electron-donating dye precursor and an electron-accepting compound are pressure-sensitive paper, thermal paper, photosensitive pressure-sensitive paper,
It is already well known as an electric heat-sensitive recording paper, a heat-sensitive transfer paper, etc., and for example, British Patent No. 2,140,449, U.S. Patent Nos. 4,480,052, 4,436,920,
Japanese Patent Publication No. 60-23,992, Japanese Patent Laid-Open No. 57-17
No. 9,836, No. 60-123,556, No. 60-
No. 123,557 and the like.

In these recording materials, in recent years,
(1) Color density and color sensitivity, (2) Robustness of color body,
Although researches for improving the characteristics such as the above have been actively carried out, there is a strong demand for improving the storability of the non-image area and the image area in particular, and the performance of the above (1) and (2) is maintained and the background fog is eliminated. It is desired to reduce the number.

[0004]

Therefore, the present inventors have
For each of the electron-donating dye precursor and the electron-accepting compound, their oil solubility, water solubility, partition coefficient, pKa,
The polarities of the substituents, the positions of the substituents, the results of diligent study focusing on characteristics such as crystallinity and solubility change when mixed.
In particular, they have found that the background fog can be reduced and the thermal sensitivity can be improved by mixing a certain kind of electron-accepting compound, and the present invention has been completed. Therefore, an object of the present invention is to provide a heat-sensitive recording material which has less background fog and has good image storability and has high heat sensitivity.

[0005]

The above objects of the present invention are as follows.
The present invention is achieved by a heat-sensitive recording material containing an electron-donating dye precursor and at least one electron-accepting compound represented by the following general formulas 4 and / or 5 and 6, respectively.

[0006]

[Chemical 4]

[Chemical 5] However, R in Chemical formulas 4 and 5 is H, an alkyl group, an aralkyl group, an aryl group or an alkenyl group, and X ₁ and X
₂ is H, a halogen atom or an alkyl group.

[Chemical 6] However, X ₃ and X ₄ in Chemical formula 6 are H, an alkyl group, an aralkyl group, an aryl group or a halogen atom.

The electron-donating dye precursor of the present invention includes
Various compounds such as triphenylmethanephthalide compounds, fluorane compounds, phenothiazine compounds, indolylphthalide compounds, leukoauramine compounds, rhodamine lactam compounds, triazene compounds, spiropyran compounds, fluorene compounds There is.

Specific examples of the phthalide compound include US Reissue Patent Specification No. 23,024 and US Patent Specification No. 3,49.
No. 1,111, No. 3,491,112, No. 3,4
91,116 and 3,509,174.

Specific examples of fluoran compounds are shown in US Pat. Nos. 3,624,107 and 3,627,787.
No. 3,641,011, No. 3,462,82
No. 8, No. 3,681,390, No. 3,920,5
No. 10 and No. 3,959,571. Specific examples of spiropyran compounds are described in US Pat. No. 3,971,808, and further specific examples of fluorene compounds are described in Japanese Patent Application No. 61-240,989.

Of these, fluoran compounds are particularly preferable in the present invention. According to the present invention,
The electron-accepting compound of Chemical formula 6 may be used in combination with other phenol derivative, metal salt of aromatic carboxylic acid, acid clay, bentonite, novolac resin, metal-treated novolac resin, metal complex and the like.

Examples of these phenol derivatives which can be used in combination are Japanese Patent Publication Nos. 40-9,309 and 45-14,03.
No. 9, No. 52-140, 483, No. 48-51,
No. 510, No. 57-210, 886, No. 58-8.
No. 7,089, No. 59-11,286, No. 60-
Nos. 176,795 and 61-95,988.

As described above, when another electron-accepting compound represented by Chemical formulas 4 to 6 is used in combination, 10 weight parts of the electron-accepting compound represented by Chemical formulas 4 to 6 are used. % Or more, preferably 30% by weight or more.

Specific examples of the electron-accepting compound represented by the above chemical formula 4 include the compounds of the following chemical formulas 7 to 10.

[Chemical 7]

[Chemical 8]

[Chemical 9]

[Chemical 10]

Further, as specific examples of the electron-accepting compound represented by the chemical formula 5, compounds represented by the chemical formulas 11 and 12 below can be mentioned.

[Chemical 11]

[Chemical formula 12] Further, as the electron-accepting compound of Chemical formula 6,
The compound of Chemical formula 18 can be mentioned.

[Chemical 13]

[Chemical 14]

[Chemical 15]

[Chemical 16]

[Chemical 17]

[Chemical 18]

In the present invention, the electron-accepting compound is
It is preferably used in an amount of 50 to 1000% by weight, particularly preferably 100 to 500% by weight, based on the electron-donating dye precursor.

In the present invention, a sensitizer can be used in combination. Examples of sensitizers that can be used in combination include JP-A-58
-57,989, 58-87,094, 63-
39,375, etc., and the like.
Particularly, a diphenyl ether compound or a benzyl ether compound is preferable.

When a heat-sensitive recording material is produced using these materials, as described in JP-A Nos. 62-144,989 and 1-87291, an electron-donating dye precursor and an electron-donating dye are used. The receptive compound or the like is used alone or in a mixture, and the dispersion medium is 3 μm or less, preferably 1.5 μm or less.
It is pulverized to a particle size of less than μm and dispersed for use. As the dispersion medium, an aqueous solution containing a water-soluble polymer at a concentration of about 0.5 to 10% by weight is generally used, and the dispersion is performed using a ball mill, a sand mill, a horizontal sand mill, an attritor, a colloid mill or the like.

Examples of the water-soluble polymer include polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, epichlorohydrin-modified polyamide, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, and isobretin-maleic salicylic anhydride. Examples thereof include copolymers, polyacrylic acid, polyacrylic acid amide, methylol-modified polyacrylamide, starch derivatives, casein, gelatin and the like.

In particular, after the developer is dissolved in a sparingly or insoluble water-soluble solvent, it is mixed with an aqueous solution containing a surfactant and a water-soluble polymer as a protective colloid, and the resulting mixture is emulsified and dispersed. When used as a product, the heat-sensitive layer can have excellent transparency.

The water-soluble polymer also contributes as a binder for the heat-sensitive layer, but if necessary, other water-soluble polymer or the like may be used as a binder in the coating liquid.
Further, for the purpose of imparting water resistance to these binders, a water resistant agent may be added, or a hydrophobic polymer emulsion, specifically, styrene-butadiene rubber latex or acrylic resin emulsion may be added.

Various additives are further added to the coating liquid thus obtained, if necessary. Examples of additives include dispersing an oil-absorbing substance such as an inorganic pigment or polyurea filler in a binder for the purpose of preventing stains on the recording head at the time of recording, or a fatty acid for improving releasability to the head. Or a metal soap, or a heat-fusible substance or the like is added to improve the heat response sensitivity.

Therefore, in general, in addition to the electron-donating dye precursor and the electron-accepting compound that directly contribute to color development, a heat-fusible substance, a pigment, a wax, an antistatic agent, an ultraviolet absorber, an antifoaming agent, A coating liquid containing additives such as a conductive agent, a fluorescent dye, and a surfactant is applied on the support to form a recording layer.

In the present invention, a protective layer may be provided on the surface of the thermosensitive recording layer, if necessary. Further, two or more protective layers may be laminated if necessary. Further, a layer similar to the protective layer may be provided on the back surface for the purpose of correcting the curl balance of the support or improving the chemical resistance from the back surface. Alternatively, an adhesive may be applied to the back surface and a release paper may be combined to form a label. The coating liquid for the heat-sensitive layer is
It is applied on base paper, high quality paper, synthetic paper, plastic sheet, resin coated paper or neutral paper.

[0024]

In the heat-sensitive recording material of the present invention, a specific compound is used as an electron-accepting compound, so that the color density can be significantly increased without sacrificing the storage stability at room temperature. The sensitivity is extremely high, and there is little background stain.

[0025]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.
In the following description,% means% by weight unless otherwise specified.
Represents.

Example 1. Preparation of Electron-Donating Dye Precursor Liquid Dispersion 20 g of 2-anilino-3-methyl-6-dibutylaminofluorane (electron-donating dye precursor) was added to polyvinyl alcohol (PVA-105: manufactured by Kuraray Co., Ltd.) having a concentration of 5%. The product was kneaded in 100 g of an aqueous solution for 16 hours using a ball mill to prepare an electron-donating dye precursor dispersion having an average particle size of 0.7 μm.

Preparation of Electron-Accepting Compound / Sensitizer Dispersion (1) Electron-accepting compound 10 represented by Chemical Formula 7 in the specification
g and β-naphthylbenzyl ether 10 g concentration 5%
Electron-accepting compound / sensitizer represented by Chemical formula 7 having an average particle diameter of 0.8 μm, which is obtained by kneading in an aqueous solution of 100 g of polyvinyl alcohol (PVA-105: Kuraray Co., Ltd.) aqueous solution for 16 hours using a ball mill. A dispersion liquid of was obtained.

(2) The average particle size is the same as in (1) above except that the electron-accepting compound represented by Chemical formula 12 in the specification is used in place of the compound represented by Chemical formula 7. 0.8
A μm dispersion of the electron-accepting compound / sensitizer represented by Chemical formula 12 was obtained.

Preparation of Pigment Dispersion 40 g of calcium carbonate (trade name: Univer 70) manufactured by Shiraishi Kogyo Co., Ltd., 60 g of water and 1 g of an aqueous solution of sodium hexametaphosphate having a concentration of 40% are rotated at a rotation speed of 15,000 rpm
The resulting mixture was stirred for 15 minutes with a homogenizer to prepare a calcium carbonate dispersion liquid.

Preparation of coating liquid for heat-sensitive layer : 3 g of an electron-donating dye precursor dispersion liquid, 6 g each of a dispersion liquid containing an electron-accepting compound represented by Chemical formula 7 and 6 g each containing an electron-accepting compound represented by Chemical formula 12, respectively. 7 g of the pigment dispersion liquid and 1.5 g of zinc stearate dispersion (trade name: Hydrin Z-7) manufactured by Chukyo Yushi Co., Ltd. having a concentration of 21% were mixed to obtain a heat-sensitive layer coating liquid.

Preparation of thermosensitive recording paper A thermosensitive layer after drying was 5 g / m on a paper support weighing 50 g.
^After applying the heat-sensitive layer coating solution using a wire bar so as to be ^2, and drying in an oven at 50 ° C, the smoothness is 200
Calendar processing was performed so that it would be seconds.

Example 2. A thermal recording paper was obtained in exactly the same manner as in Example 1 except that the compound of Chemical formula 13 was used in place of the compound of Chemical formula 12 used in Example 1.

Example 3. Example 1 except that the compound of Formula 14 was used in place of the compound of Formula 12 used in Example 1.
A heat-sensitive recording paper was obtained in the same manner as in.

Example 4. A thermosensitive recording paper was obtained in exactly the same manner as in Example 1 except that the compound of Chemical formula 11 was used in place of the compound of Chemical formula 7 used in Example 1.

Example 5. A protective layer having the composition shown in Table 1 below was further provided on the surface of the thermosensitive recording paper obtained in Example 1 so that the dry film thickness was 2 μm.

[Table 1]

Comparative Example 1. A thermosensitive recording material was obtained in exactly the same manner as in Example 1 except that the compound of Chemical formula 7 used in Example 1 was not used and the compound of Chemical formula 12 was used in a double amount.

Comparative Example 2. A thermosensitive recording material was obtained in exactly the same manner as in Example 1 except that the compound of Chemical formula 12 used in Example 1 was not used and the compound of Chemical formula 7 was used in a double amount.

Comparative Example 3. A thermosensitive recording material was obtained in exactly the same manner as in Example 2 except that the compound of Chemical formula 7 used in Example 2 was not used and the compound of Chemical formula 13 was used in a double amount.

Comparative Example 4. A thermosensitive recording material was obtained in exactly the same manner as in Example 4 except that the compound of Chemical formula 12 used in Example 4 was not used and the compound of Chemical formula 11 was used in a double amount.

Comparative Example 5. A thermosensitive recording material was obtained in exactly the same manner as in Example 3 except that the compound of Chemical formula 7 used in Example 3 was not used and the compound of Chemical formula 14 was used in a double amount. Table 2 shows the results of the following performance comparison of the heat-sensitive recording materials obtained in Examples and Comparative Examples.

Performance comparison Chemical resistance: The degree of erasing with Fluorescent Pen-2 Yellow manufactured by Zebra Co., Ltd. was evaluated. ◯: Printed characters are not erased at all. Δ: The color is a little erased, but the characters can be read. ×: The color was erased so that the characters could not be read.

Heat resistance: 2 at 40 ° C. and 90% RH
When the print density residual rate (%) after standing for 4 hours was evaluated using a Macbeth densitometer, the residual rate of 90% or more was evaluated as good. However, the initial print density was 1.1.

Light resistance: Fluorescent lamp tester (32000lu
x) When the print density residual rate (%) after irradiation for 16 hours was evaluated by using a Macbeth densitometer, the residual rate of 95% or more was evaluated as good. However, the initial print density was 1.1.

Color density: When a voltage of 25 V was applied to a KLT head manufactured by Kyocera Corporation and printing was performed with a pulse width of 1.0 msec, a color density of 1.2 or more was evaluated as good.

[0045]

[Table 2] As is clear from the results in Table 2, it is understood that the recording material of the present invention is excellent in color developability, stability over time and chemical resistance.

Claims (1)

[Claims] 1. A heat-sensitive recording material containing an electron-donating dye precursor and at least one electron-accepting compound represented by the following general formulas 1 and / or 2 and 3, respectively. [Chemical 1] [Chemical 2] However, R in the chemical formulas 1 and 2 is H, an alkyl group, an aralkyl group, an aryl group or an alkenyl group, and X ₁ and X
₂ is H, a halogen atom or an alkyl group. [Chemical 3] However, X ₃ and X ₄ in Chemical formula ₃ are H, an alkyl group, an aralkyl group, an aryl group or a halogen atom.