JPH06127139A - Heat-sensitive recording material - Google Patents

Abstract

PURPOSE:To obtain a heat-sensitive recording material which has especially excellent heat-sensitivity, chemical resistance and shelf stability life of printed images by having an electron donor dye precursor contain together at least one kind of plural numbers of electron acceptor compounds that are respectively indicated by a specific general formula. CONSTITUTION:An electron donor dye precursor and an electron acceptor compound are used for a heat-sensitive recording material. In this case, the heat- sensitive recording material contains at least one kind of the electron acceptor compounds that are respectively expressed by respective formulas I and II. In the formulas stated herewith, X1 and X2 denote respectively hydrogen atom, alkyl group, aralkyl group, alkenyl group, halogen atom or hydroxyl group. And, X3 and X4 respectively denote hydrogen atom, alkyl group, aralkyl group, halogen atom or hydroxy group. Further, R denotes cyclic alkyl group. Thus, the heat-sensitivity, chemical resistance and shelf stability life of printed images of the heat-sensitive recording material are specifically improved.

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 excellent in sensitivity, chemical resistance and image storability.

[0002]

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, and the like. For example, British Patent No. 2,140,449, US Patent Nos. 4,480,052, and 4,436,920,
Japanese Examined Patent Publication No. 60-23,992, Japanese Unexamined Patent Publication No. 57-17
No. 9,836, No. 60-123,556, No. 60-
No. 123,557 and the like.

In particular, the heat-sensitive recording material is used in various fields because the demand for the recording material has increased because a good image can be recorded without making noise, although the recording apparatus is inexpensive. . However, as the field of use expands, there are many cases where inconvenience occurs in terms of image storability and chemical resistance, and these improvements have been desired. Further, with the speeding up of the apparatus, there has been a demand for development of a heat sensitive recording material having higher sensitivity.

[0004]

Therefore, the present inventors
For each of the electron-donating dye precursor and the electron-accepting compound, their oil solubility, water solubility, partition coefficient, pKa,
Polarity of the substituent, the position of the substituent, as a result of earnest study focusing on characteristics such as crystallinity and solubility change when mixed,
In particular, it has been found that the use of an electron-accepting compound of a certain type can reduce background fogging, improve heat sensitivity, and improve chemical resistance and image storability. Reached Therefore, it is an object of the present invention to provide a heat-sensitive recording material which has good chemical resistance and image storability and also has high heat sensitivity.

[0005]

The above objects of the present invention are as follows.
The present invention has been achieved by a heat-sensitive recording material comprising an electron-donating dye precursor and at least one electron-accepting compound represented by the following general formulas 3 and 4, respectively.

[0006]

[Chemical 3] However, X ₁ and X ₂ in Chemical formula ₃ are hydrogen atoms, alkyl groups,
It is an aralkyl group, an alkoxy group, an alkenyl group, a halogen atom or a hydroxyl group.

[0007]

[Chemical 4] However, X ₃ and X ₄ in Chemical formula ₄ are each a hydrogen atom, an alkyl group, an aralkyl group, a halogen atom, or a hydroxy group, and R is a cyclic alkyl group.

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 are described in US Reissue Patent Specification No. 23,
No. 024, U.S. Pat. Nos. 3,491,111, 3,491,112, 3,491,116,
And No. 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.

In the present invention, among these, fluoran compounds are particularly preferable. The electron-accepting compounds of Chemical Formulas 3 and 4 according to the present invention are other phenol derivatives,
Aromatic carboxylic acid metal salt, acid clay, bentonite,
You may use together with a novolak resin, a metal treatment novolak resin, a metal complex, etc. Examples of these phenol derivatives which can be used in combination are described in JP-B-40-9,309 and JP-A-
5-14,039, 52-140,483, 48-51,510, 57-210,886.
No. 58-87,089, No. 59-11, 28
No. 6, No. 60-176, 795, No. 61-95,
No. 988 and the like.

As described above, when the electron-accepting compound represented by Chemical formulas 3 and 4 is used in combination with another electron-accepting compound, the electron-accepting compound represented by Chemical formulas 3 and 4 is
It is preferable to use 0% by weight or more, and particularly preferably 30% by weight or more. Specific examples of the electron-accepting compound represented by Chemical Formula 3 include compounds represented by Chemical Formula 5 to Chemical Formula 10 below.

[0012]

[Chemical 5]

[Chemical 6]

[Chemical 7]

[Chemical 8]

[Chemical 9]

[Chemical 10]

As specific examples of the electron-accepting compound represented by Chemical formula 4, compounds represented by Chemical formulas 11 to 13 below can be given.

[Chemical 11]

[Chemical 12]

[Chemical 13]

In the present invention, the electron-accepting compound is
50 to 1,000% by weight based on the electron-donating dye precursor
It is preferably used, and particularly preferably 100 to 500% by weight. In the present invention, a sensitizer can be used in combination. Examples of sensitizers that can be used in combination are:
JP-A-58-57,989 and 58-87,094
No. 63-39,375 and the like, and diphenyl ether compounds or benzyl ether compounds are particularly preferable.

In producing a heat-sensitive recording material using these materials, as described in JP-A-62-144,989 and JP-A-1-87291, an electron-donating dye precursor and an electron-donating dye precursor 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 crushed to a particle size of less than or equal to 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 by 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, isobutylene-maleic anhydride. Examples thereof include copolymers, polyacrylic acid, polyacrylic acid amide, methylol-modified polyacrylamide, starch derivatives, casein, gelatin and the like.

In particular, the developer is dissolved in an organic solvent which is sparingly soluble or insoluble in water, and then this is mixed as a protective colloid with an aqueous solution containing a water-soluble polymer and, if necessary, a surfactant. -When used as an emulsified dispersion with stirring, the heat-sensitive layer can have excellent transparency.
The above water-soluble polymer also contributes as a binder for the heat-sensitive layer, but if necessary, other water-soluble polymer or the like may also be used as a binder in the coating liquid.

Further, a water resistant agent may be added to these binders for the purpose of imparting water resistance, or an emulsion of a hydrophobic polymer, specifically, a styrene-butadiene rubber latex or an acrylic resin emulsion may be added. Various additives are further added to the coating liquid thus obtained, if necessary. For example, in order to prevent the recording head from becoming dirty at the time of recording, an oil-absorbing substance such as an inorganic pigment or polyurea filler is dispersed in the binder, or a fatty acid or a metal soap is used to enhance the releasability of the head. A thermofusible substance or the like is added to improve the thermal 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 coated on a 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, in order to correct the curl balance of the support or to improve the chemical resistance from the back surface, a layer similar to the protective layer may be provided on 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 applied on base paper, high-quality paper, synthetic paper, plastic sheet, resin-coated paper or neutral paper.

[0021]

Since the heat-sensitive recording material of the present invention is used by mixing a specific one as the electron-accepting compound, the color density can be remarkably increased without sacrificing the storage stability at room temperature and, therefore, extremely high. It has high sensitivity and good chemical resistance.

[0022]

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

Example 1. Preparation of electron-donating dye precursor 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 5 in the specification
g and β-naphthylbenzyl ether 10 g concentration 5%
Electron-accepting compound / sensitizer represented by Chemical formula 5 having an average particle diameter of 0.8 μm, which was kneaded in 100 g of an aqueous solution of polyvinyl alcohol (PVA-105: Kuraray Co., Ltd.) aqueous solution for 16 hours using a ball mill. A dispersion liquid of was obtained. (2) Instead of the compound represented by Chemical formula 5, Chemical formula 1 in the specification
(1) except that the electron-accepting compound represented by 1 is used.
In the same manner as in the case of, the average particle size of 0.8 μm
A dispersion liquid of the electron-accepting compound / sensitizer represented by 1 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 mixture was stirred for 15 minutes with a homogenizer to prepare a dispersion of calcium carbonate.

Preparation of Coating Solution for Heat- Sensitive Layer 3 g of electron-donating dye precursor dispersion, 6 g of dispersion containing the electron-accepting compound represented by Chemical formula 5 and 6 g of dispersion containing the electron-accepting compound represented by Chemical formula 11, respectively. 7 g of the pigment dispersion 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 thermosensitive recording paper was obtained in exactly the same manner as in Example 1 except that the compound of Chemical formula 10 was used in place of the compound of Chemical formula 5 used in Example 1, and the compound of Chemical formula 13 was used in place of the compound of Chemical formula 11. . Example 3. A thermosensitive recording paper was obtained in the same manner as in Example 1 except that the compound of Chemical formula 12 was used in place of the compound of Chemical formula 11 used in Example 1.

Example 4. A protective layer having the composition shown in Table 1 below was further provided on the surface of the thermal recording paper obtained in Example 1 so that the dry film thickness was 2 μm.

[Table 1]

Comparative Example 1. A thermosensitive recording paper was obtained in exactly the same manner as in Example 1 except that the compound of Chemical formula 5 used in Example 1 was not used and the compound of Chemical formula 11 was used in a double amount. Comparative example 2. A thermosensitive recording paper was obtained in exactly the same manner as in Example 1 except that the compound of Chemical formula 11 used in Example 1 was not used and the compound of Chemical formula 5 was used in a double amount.

Comparative Example 3. A thermosensitive recording paper was obtained in exactly the same manner as in Example 2 except that the compound of Chemical formula 10 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 paper was obtained in exactly the same manner as in Example 2 except that the compound of Chemical formula 13 used in Example 2 was not used and the compound of Chemical formula 10 was used in a double amount.

Comparative Example 5. A thermosensitive recording paper was obtained in exactly the same manner as in Example 2 except that the compound of Chemical formula 5 used in Example 3 was not used and the compound of Chemical formula 12 was used in a double amount. Table 2 shows the results of the following performance comparison performed on the thermal recording papers obtained in the respective examples and comparative examples.

Performance comparison Chemical resistance: The degree of erasing with Zebra Fluorescent Pen-2 Yellow 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 so erased that the characters could not be read. Heat resistance: When the print density residual ratio (%) after standing for 24 hours under the conditions of 40 ° C. and 90% RH is evaluated using a Macbeth densitometer, a residual ratio of 90% or more is good. Evaluated as. 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 and printing was performed with a pulse width of 1.0 msec, a color density of 1.2 or more was evaluated as good.

[0035]

[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 comprising an electron-donating dye precursor and at least one electron-accepting compound represented by the following general formulas 1 and 2 respectively; However, X ₁ and X ₂ in Chemical formula ₁ are a hydrogen atom, an alkyl group,
An aralkyl group, an alkoxy group, an alkenyl group, a halogen atom or a hydroxyl group; However, X ₃ and X ₄ in Chemical formula ₂ are each a hydrogen atom, an alkyl group, an aralkyl group, a halogen atom, or a hydroxy group, and R is a cyclic alkyl group.