JPH053393B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material that is prevented from being contaminated by various solvents and has improved safety. Traditionally, basic dyes such as phthalide or fluoran and bisphenol A or p-
Thermal recording paper, which uses a color reaction caused by thermal contact with acidic phenolic compounds such as oxybenzoic acid esters, has been extensively studied and has come to be widely put into practical use. This type of thermal recording paper is widely used for facsimiles and printers because of its rapid thermal coloring properties and ease of handling, but the colored images based on acid-base reactions are unstable. In some cases, contact with organic substances, especially organic solvents, easily causes undesirable decolorization or color development. Specifically, the colored image disappears when it comes into contact with plasticizers, oils and fats, or body fat, and even the unprinted areas become completely colored when it comes into contact with volatile solvents such as alcohol and lower ketones. Improvements have been made, such as considering the composition of the thermal paper or the paint used, and introducing a solvent-resistant protective layer, but there is still no prospect of a fundamental solution, and therefore, there is still no prospect of a fundamental solution. There are major practical problems in applications where there are many opportunities for contact or frequent contact with body fat. On the other hand, the diazo method, which has been studied in recent years,
Thermal recording materials produced by the thermal transfer method have excellent stability of colored images, but their alternative uses are extremely limited due to the instability of the diazo compound to light and the handling and storage aspects of the thermal transfer system. be done. Based on the current situation, the present inventors have proposed the following patent application:
No. 14273, etc., we proposed a copying system using a new redox coloring method and reported that the colored images produced by such a copying system were extremely stable when in contact with organic solvents. Problems remained in its practical application. That is, although the stability of the colored image was good, the uncolored surface had a tendency to gradually develop color upon contact with the organic solvent. The inventors of the present invention have conducted intensive studies on methods for preventing contamination of the fabric (uncolored surface) of such redox coloring heat-sensitive recording materials by organic solvents, and have found that the use of quaternary bases has resulted in solvent-resistant contamination of the background. The present invention was achieved by discovering that a remarkable effect on sex can be obtained. The color-forming compound and color developer used in the heat-sensitive recording material of the present invention have the general formula () as described in JP-A-57-107882, etc. (In the formula, X, Y, and Z may be the same or different from each other and are benzene rings, naphthalene rings, or aromatic heteroaromatic rings, and as substituents are alkyl groups,
It has a cycloalkyl group, a halogen atom, an alkoxy group, an amino group or a substituted amino group. ), and methine compounds represented by the general formula (). (In the formula, R ₁ to _{R 4} represent a hydrogen atom, a halogen atom, an alkoxycarbonyl group, an acyl group, or a substituted sulfonyl group.) Among the expressed benzoquinone derivatives, specific examples of methine compounds include:
4-4′-4″-tris-dimethylamino-triphenylmethane, 4-4′-bis(dimethylamino)-
Triphenylmethane, 4-dimethylaminophenyl-bis-(3'-methyl-4'-methylaminophenyl)-methane, 3-methyl-4-ethoxyphenyl-bis-(4'-dimethylaminophenyl) )-methane, 3-methyl-4-methoxyphenyl-bis-(4'-N-pyrrolidylphenyl)-methane, 4-
Methoxy-1-naphthyl-bis-(4'-dimethylaminophenyl)-methane, 4-dimethylaminophenyl-bis-(4'-methoxyphenyl)-methane, 4-dimethylaminophenyl-bis-( 4′−
N-methyl-N-benzylaminophenyl)-methane, 4-dimethylaminophenyl-bis-
(1'-ethyl-2'-methylindol-3'-yl)
-methane, 4-ethoxyphenyl-bis-(1'-
Examples include, but are not limited to, ethyl-2'-methylindol-3'-yl)-methane. Specific examples of benzoquinone derivatives represented by the general formula () include 3.6-dibromo-2.5-
Diethoxycarbonyl-1,4-benzoquinone, 3.6
-dibromo-2.5-dicyclohexyloxycarbonyl-1.4-benzoquinone, 2.5-dibenzoyl-1.4-benzoquinone, 2.5-dibenzoyl-3-
Bromo-1,4-benzoquinone, 2,5-dibenzoyl-3,6-dichloro-1,4-benzoquinone, 3-benzoyl-1,4-benzoquinone, 3,6-di-p-toluenesulfonyl-2,5-diethoxycarbonyl-
Examples include 1,4-benzoquinone. In the present invention, the quaternary salt compound used as an essential component together with the methine compound and the benzoquinone derivative has the general formula () (In the formula, X is an anion residue, R ₁ to _{R 4} are each,
Indicates an organic residue. ), examples of anionic residues include halogen anions, sulfate groups, etc.
Examples of organic residues include alkyl groups, aryl groups, aralkyl groups, cycloalkyl groups, hydroxyalkyl groups, unsaturated ring residues, polyalkylene oxide groups, cyclic alkylene groups, and oxygen-containing or nitrogen-containing cyclic alkylene groups. . Among these, for example, a long-chain alkyl quaternary base R-N (R ₁ R ₂ R ₃ )Cl (R is a long-chain alkyl group such as dodecyl or stearyl) benzyl trialkylammonium salt

[Formula] Quaternary polyalkylene oxide H (OCH ₂ CH ₂ )N
(R ₁ R ₂ R ₃ )Cl, quaternary pyridine salt

[Formula] etc. are easily available. Among these quaternary salt compounds, those that do not cause any major trouble in the production of heat-sensitive recording materials are appropriately selected and used. Specific compounds used in the present invention include dodecyltriethylammonium chloride, stearyltrimethylammonium chloride, oleyltrimethylammonium chloride, benzyltrimethylammonium chloride, benzylmethyldihydroxyethylammonium chloride, trimethylpolyoxyethylene ammonium chloride, benzylpyridinium Examples include chloride, dodecylpyridinium chloride, etc. Among these, one suitable for the properties of the coating liquid is arbitrarily selected and used. The amount of these quaternary compounds used is 1 to 50 parts, preferably 5 to 30 parts, per 100 parts of the methine compound of general formula (). The heat-sensitive recording material of the present invention includes a methine compound represented by the general formula (), a benzoquinone derivative represented by the general formula (),
In addition to the quaternary salt compound of the general formula (), colorless organic or inorganic pigments are generally mixed and used in order to improve paper properties, writing properties, and matching properties to a thermal head. As such pigments, many substances have been proposed and are known, and can be selected and used as appropriate. In the present invention, suitable pigments include light or heavy calcium carbonate, magnesium carbonate, oxidized Examples include neutral or weakly basic pigments such as zinc and particulate urea formaldehyde resin fillers. Pigments that are themselves acidic, such as certain types of kaolin and acid clay, tend to stain the background of heat-sensitive recording materials and must be handled with care. The heat-sensitive recording material of the present invention can be made into paper, film, etc. by adding various coloring sensitivity improvers, lubricants, waterproofing agents, surfactants, etc. in addition to the above-mentioned components, as well as a binder component. It is manufactured by coating it on a support and drying it. As binders used with the above various components, water-soluble polymer binders such as polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, and starch, or synthetic resin binders such as acrylic emulsion and synthetic rubber latex are generally used. Preferably used in the present invention is polyvinyl alcohol, particularly partially saponified polyvinyl alcohol. Partially saponified polyvinyl alcohol, which is the most preferred binder in the present invention, is obtained by partially saponifying polyvinyl acetate, and has a degree of saponification of 60 to 90% and an average degree of polymerization of 500 to 2000. These are readily available on the market. EXAMPLES Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited thereto. First, a method for preparing a heat-sensitive paint and an evaluation method will be shown. [A] Preparation of water-based paint and heat-sensitive recording paper Part by weight Methine compound (10% water dispersion) 8.5 Benzoquinone derivative (20% water dispersion) 7.0 Stearamide (same as above) 10.0 Zinc stearate (same as above) 5.0 Pigment (50% aqueous dispersion) 49.5 Binder (10% aqueous solution) 11.5 Water 8.5 Create a water-based paint by mixing well in the above proportions. Note that the methine compound, benzoquinone derivative, stearamide, and zinc stearate are used as an aqueous dispersion obtained by wet pulverization in the presence of a small amount of a surfactant. The water-based paint obtained in this way has a basis weight of 50 g/m ²
The mixture was coated on high-quality paper using a Mayer bar coater to a dry coating weight of 6.0 g/m ² and dried, and the surface was smoothed using a super calender to obtain heat-sensitive recording paper. [B] Plasticizer resistance coloring test method Microcapsules prepared by the gelatin-CMC complex coacervation method using dioctyl phthalate as the core material were coated on high-quality paper so that the dry coating amount was 5 g/ ^m2 . The microcapsule surface of the coated paper (plasticizer resistance test paper) and the coated surface of the heat-sensitive recording paper of each example or comparative example were superimposed and supercalendered (linear pressure 100 kg/cm ² ) to destroy the microcapsules. After a certain period of time, the reflectance of the coated surface [X ₁ ] was measured using a Hunter colorimeter (using an amber filter).
, and using the reflectance before the test [X ₀ ],
Calculate the rate of color development due to contact with dioctyl phthalate Color rate _[ K] = X _{0 −} is large. Comparative Example 1 In the above water-based paint composition, 4-4'-4''-tris-dimethylaminotriphenylmethane (Ryuco Crystal Violet) was used as the methine compound and 2.5-dibenzoyl-1.4-benzoquinone was used as the benzoquinone derivative. The binder had a saponification degree of 100% and a viscosity of a 10% aqueous solution.
1360CPS polyvinyl alcohol was used. When the thermal recording paper prepared above was colored using a thermal printer (applied voltage 20 V, current application time 1.4 msec), a deep blue thermally colored image was obtained. The results of the plasticizer coloring test were 26.5% after 24 hours.
The rate was 59.2% after 120 hours, and a significant tendency for skin color to develop over time was observed. Example 1 2.5 parts of a composition containing stearyltrimethylammonium chloride as a main component (trade name Cortamine 86P, manufactured by Kao Soap Co., Ltd.) was added to the water-based paint of Comparative Example 1, and the paint was applied in the same manner as Comparative Example 1. A thermosensitive recording paper was obtained. With the thermal recording paper of this example, it was possible to obtain a dark colored image similar to that of Comparative Example 1 using a thermal printer. The results of the plasticizer coloring test were 8.3% after 24 hours.
After 120 hours, a significant inhibitory effect of 16.4% was observed. Examples 2 to 4 In place of stearyltrimethylammonium chloride in Example 1, the same amounts of dodecylammonium chloride [Example 2], dodecylpyridinium chloride [Example 3], and benzyltriethylammonium chloride [Example 4] were used, respectively. A thermosensitive recording paper was obtained in the same manner as in Example 1 except for this. As a result of the plasticizer coloring resistance test for each thermal recording paper, superior suppressive effects were observed compared to the thermal recording paper of Comparative Example 1. Plasticity resistance coloring test result values after 24 hours (after 24 hours) Example 2 7.6% Example 3 9.4% Example 4 10.1% Example 5 As a binder, a saponification degree of 82% (viscosity of 10% aqueous solution 2500CPS) was used. A thermosensitive recording paper was obtained in the same manner as in Example 1 except that partially saponified polyvinyl alcohol was used. The results of the plasticizer coloring resistance test for the heat-sensitive recording paper of this example were 6.4% after 24 hours and 14.2% after 120 hours, indicating an extremely excellent inhibitory effect. Comparative Example 2 A thermosensitive recording paper was obtained in the same manner as in Comparative Example 1, except that calcined kaolin (Ansirex, manufactured by Engelhard) was used instead of calcium carbonate. The results of the plasticizer coloring test for the thermal recording paper in this example are
After 24 hours, it was 51% and the entire surface turned blue. Example 6 A thermosensitive recording paper was obtained in the same manner as in Example 1, except that calcined kaolin (Ansirex, manufactured by Engelhard) was used in place of calcium carbonate. The results of the plasticizer coloring test of the thermal recording paper of this example,
It showed a color development rate of 26% after 24 hours, compared to Comparative Example 2,
An improvement effect was observed. Example 7 3-4′-4″-tris-dimethylamino-triphenylmethane was used as a methine compound.
A thermosensitive recording paper was prepared in the same manner as in Example 1 except that methyl-4-ethoxyphenyl-bis-dimethylaminophenylmethane was used. When the thermal recording paper of this example was colored by the method described in the comparative example, a dark green colored image was obtained. Furthermore, the result of the plasticizer coloring resistance test for the thermosensitive recording paper of this example was 7.3% after 24 hours, which was good. Comparative Example 3 A thermosensitive recording paper was obtained in the same manner as in Example 7 except that stearyltrimethylammonium chloride was not used. The thermal recording paper of this example is colored dark green by a thermal printer, as in Example 7. However, as a result of the plasticizer coloring test, 24 hours after 24 hours.
% color development and the whole turned green, which was inconvenient. Example 8 As a methine compound, 4-4′-4″-trisdimethylamino-triphenylmethane was used instead of 4-4′-4″-trisdimethylamino-triphenylmethane.
dimethylaminophenyl-bis-(1'-ethyl-
A thermal recording paper was obtained in the same manner as in Example 5 except that 2'-methylindol-3'-yl)-methane was used. The thermal recording paper of this example is colored deep red by a thermal printer. The result of the plasticizer coloring test was 2.1% after 24 hours.
It was an excellent product with almost no background coloration. Comparative Example 4 As a methine compound, 4-4′-4″-tris-
4 instead of dimethylamino-triphenylmethane
A thermal recording paper was obtained in the same manner as in Comparative Example 1 except that -dimethylaminophenyl-bis-(1'-ethyl-2'-methylindol-3'-yl)-methane was used. As in Example 8, the thermal recording paper of this example was colored deep red using a thermal printer. The result of the plasticizer coloring resistance test was 10.6% after 24 hours, and the entire background was colored red.

Claims (1)

[Scope of Claims] 1 [A] Color-forming compound represented by general formula () (In formula (), X, Y, and Z may be the same or different from each other and are benzene rings, naphthalene rings, or aromatic heterocyclic rings, and as substituents, an alkyl group, a cycloalkyl group, or a halogen atom) , has an alkoxy group, an amino group, or a substituted amino group.) [B] Color developing compound represented by the general formula () (In formula (), R ₁ to _{R 4} represent a hydrogen atom, a halogen atom, an alkoxycarbonyl group, an acyl group, or a substituted sulfonyl group.) [C] A heat-sensitive recording material containing a quaternary salt compound as an essential component .