JPH0141514B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a heat-sensitive recording material using a colorless or light-colored leuco dye and an acidic substance that causes the leuco dye to develop color when heated as a coloring component.

A thermosensitive recording material is a recording material in which a so-called thermosensitive coloring layer that develops color is formed on the surface of a support such as paper by heating, and a thermal printer with a built-in thermal head or the like is used for heating.

The thermal recording method using the recording material described above is used not only for copying books and documents, but also for recording output machines such as electronic computers, facsimile machines, and measuring machines. , a colorless or light-colored leuco dye having a lactam or spiropyran ring and an acidic substance such as an organic acid or a phenolic substance formed on a support, resulting in a recorded image with clear color tone and excellent contrast. It is especially widely used because of its

However, recently, with the increase in speed of output machines, there has been a strong demand for recording materials with high heat sensitivity that can always record clear images even after long-term use with very little thermal energy. cannot be fully satisfied.

Therefore, in order to improve the heat sensitivity of heat-sensitive recording materials, several methods have been proposed in which a heat-sensitive coloring layer contains a heat-sensitive sensitizer. For example, a method using acetoacetanilide (Japanese Unexamined Patent Publication No. 106746/1983), melting point
A method of incorporating a thermofusible substance at 60 to 200°C into particles of at least one of a dye and a color developer (Japanese Patent Application Laid-Open No. 1983-1999)
48751), a method using alkylated biphenyl and substituted biphenyl alkane with a melting point of 60 to 200°C (Japanese Patent Application Laid-open No. 53-39139), and a method using a fatty acid amide having 12 carbon atoms.
Adding ~22 saturated fatty acids (Japanese Patent Application Laid-Open No. 139740
Methods such as No. 1) have been used, but they are all ineffective, and further solutions are desired. Furthermore, if a large amount of these conventional heat sensitivity sensitizers is used, scum may adhere to the heat-sensitive head, causing a staking phenomenon, resulting in poor color clarity and defects that significantly impede running performance. ing.

Therefore, in order to consistently obtain clear, high-density images even when used for long periods of time with very little heat energy at low temperatures, especially in high-speed facsimile machines, it is necessary to lower the coloring temperature and at the same time reduce the amount of adhesive substances that adhere to the heat-sensitive head. It is necessary to select a sensitizer with a heat sensitivity that does not generate any.

The present invention has been made in view of the above-mentioned current situation. Specifically, the present invention records high-density clear images using a small amount of thermal energy at low temperatures without causing dust adhesion or staking phenomena during long-term recording. The object of the present invention is to provide a heat-sensitive recording material with high heat sensitivity.

As a result of repeated research in view of the above objects of the present invention, we have found a heat-sensitive recording material in which a heat-sensitive color-forming layer containing a colorless or light-colored leuco dye and an acidic substance that causes the leuco dye to develop color when heated is provided on a support. It has been found that the above-mentioned conventional drawbacks can be solved and the objects of the present invention can be achieved by containing at least one compound represented by the following general formulas (1) to (5) in the heat-sensitive coloring layer.

general formula X: O or S General formula (2) Z: O or S Y: H, OH or acetyl group General formula (3) General formula (4) In the heat-sensitive recording material of the present invention, the compound represented by the above general formula can prevent scum from adhering to the thermal head.
By increasing the thermal sensitivity of the color-forming layer and lowering the color-forming temperature without causing statesking, it is possible to quickly obtain high-density, clear images with a small amount of thermal energy at a lower temperature. It does not cause adhesion or staking that impairs image clarity and head runnability.

Therefore, when such a recording material is used in a machine that outputs a small amount of thermal energy, such as a high-speed fax machine, it is extremely useful because it can always provide clear images for a long time.

The details of why such an effect was obtained in the present invention are unknown, but by adding the compound represented by the above general formula, the melting point of the main coloring component is lowered by the eutectic effect, and the compound represented by the general formula It is believed that because of the high mutual solubility between the coloring component and the coloring component, the melting rate was accelerated and the coloring rate was significantly improved, and an image with particularly high density was obtained with low thermal energy.

Examples of compounds represented by the above general formula that can be used in the present invention include the following.

Xanthene 9-phenylxanthene 2-benzylxanthene 9-benzylxanthenethioxanthene dibenzofuran dibenzothiofuran 2-oxythiofuran dibenzothiofene 4-oxythiofene 4-acetylthiophene phenanthrene 3-oxyphenanthrene 1-methylphenanthrene acenaphthene However, the amount of these compounds used is 0.1 to 5.0 parts by weight of the leuco dye contained in the heat-sensitive coloring layer.
It is preferably contained in the heat-sensitive coloring layer in a proportion of parts by weight. If the amount is less than 0.1 part by weight, the effect of improving the thermal sensitivity of the colored image is small, and if the amount is more than 5.0 parts by weight, no further effect of improving the thermal sensitivity can be expected.

In the present invention, conventionally used leuco dyes, acidic substances, and binders are used, and specific examples thereof are shown below.

1 Leuco dye: (a) Leuco base of triphenylmethane dye: Compound represented by the following general formula: In the formula, R _x , R _y and R _z are hydrogen, hydroxyl group,
Halogen, alkyl group, nitro group, amino group, dialkylamino group, monoalkyl group,
It is an allyl group.

Specific examples of the above compounds are as follows.

3,3-bis(p-dimethylaminophenyl)-phthalide 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone) 3,3-bis(p- dimethylaminophenyl)-6-diethylaminophthalide 3,3-bis(p-dimethylaminophenyl)-6-chlorophthalide 3,3-bis(p-dibutylaminophenyl)phthalide (b) Fluoran dye leuco Body base: Compound represented by the following general formula: In the formula, R _x , R _y and R _z are the same as in (a) above.

Specific examples of the above compounds are as follows.

3-Cyclohexylamino-6-chlorofluorane 3-(N,N-diethylamino)-5-methyl-7-(N,N-dibenzylamino)fluorane 3-dimethylamino-5,7-dimethylfluorane 3- Diethylamino-7-methylfluorane 3-diethylamino-7,8-benzfluorane (iii) Fluoran dye: 3-diethylamino-6-methyl-7-chlorofluorane 3-pyrrolidino-6-methyl-7-anilino Fluoran 2-{N-(3'-trifluoromethylphenyl)amino}-6-diethylaminofluorane 2-{3,6-bis(diethylamino)-9
-(o-chloroanilino)xantylbenzoic acid lactam}.

(d) Lactone compound represented by the following general formula: In the formula, R ₁ and R ₂ are hydrogen, a lower alkyl group substituted or unsubstituted aralkyl group, a substituted or unsubstituted phenyl group, a cyanoethyl group,
or represents a β-halogenated ethyl group, or R ₁ and R ₂ combine to form (-CH ₂ )- ₄ , (-CH ₂
) _-5 also represents ( _-CH2 ) _-2O ( _-CH2 ) _-2 , _R3 and _R4 represent hydrogen, lower alkyl group, alkyl group, amyl group or phenyl group,
Either one of R ₃ and R ₄ is hydrogen, and X ₁ ,
X ₂ and X ₃ represent hydrogen, a lower alkyl group, a lower alkoxyl group, a halogen atom, a halogenated methyl group, a nitro group, an amino group, or a substituted amino group, and X ₄ represents hydrogen, a halogen, a lower alkyl group, or It represents a lower alkoxyl group, and n represents 0 or an integer of 1-4.

Specific examples of the above compounds are as follows.

3-(2'-Hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)phthalide 3-(2'-hydroxy-4'-dimethylaminophenyl)-3- (2'-methoxy-5'-nitrophenyl)phthalide 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl)phthalide 3-(2'-methoxy- 4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'-methylphenyl)phthalide.

2 Acidic substances: boric acid, oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid, benzoic acid, stearic acid,
Gallic acid, salicylic acid, 1-hydroxy-2-
naphthoic acid, o-hydroxybenzoic acid, m-hydroxybenzoic acid, 2-hydroxy-p-toluic acid, 3,5-xylenol, thymol, p
-tert-butylphenol, 4-hydroxyphenoxide, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, α-naphthol, β-naphthol, catechol, resorcinol, hydroquinone, 4-tert-octylcatechol, 4, 4'-sec-butylidene diphenol, 2,2'-dihydroxydiphenyl, 2,
2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2-bis(4-hydroxyphenyl)propane (also known as bisphenol A), 4,4'-isopropylidene-bis(2-
tert-butylphenol), 4,4'-sec-butylidene diphenol, pyrogallol, phloroglucin, phloroglucin carboxylic acid.

3 Binder: polyvinyl alcohol, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylmide, polyacrylic acid, starch,
Water-soluble materials such as gelatin or aqueous emulsions such as polystyrene, vinyl chloride-vinyl acetate copolymers, polybutyl methacrylate, etc. can be used as binders.

In the heat-sensitive recording material of the present invention, fine powders such as calcium carbonate, silica, alumina, magnesia, talc, barium sulfate, and aluminum stearate are added to the heat-sensitive coloring layer to improve the clarity of the colored image. Furthermore, the running properties of the thermal head can be further improved by adding a lubricant such as linseed oil, tung oil, wax, paraffin, polyethylene wax, or chlorinated paraffin.

Examples of the present invention are shown below.

Example 1 The following components were mixed for 10 hours using a ball mill to prepare dispersions A and B, and then dispersions A and B were further mixed to prepare a thermosensitive coloring layer forming liquid.

Dispersion A (parts by weight) Crystal Violet 5.2 Polyvinyl alcohol (10% aqueous solution) 23.0 Water 21.8 Dispersion B Bisphenol A 19.0 Starch oxide 2.8 Calcium carbonate 2.0 Acenaphthene 7.8 Water 18.4 Thermosensitive coloring layer forming liquid prepared as above Using a wire bar, high-quality paper (basis weight 50g/m ² )
A heat-sensitive coloring layer was formed by coating and drying on top, to obtain a heat-sensitive recording material of the present invention.

When the recording material thus obtained was printed at a temperature of 90°C using a thermal printer equipped with a built-in thermal head, a clear blue image was obtained.

In addition, a comparison heat-sensitive recording material was prepared using the same method described above except that acenaphthene was removed, and a comparative study revealed that the product of the present invention was able to produce sufficiently high-density colored images even with a small amount of thermal energy at low temperatures. scum (adhesive) on the heat-sensitive head.
The recording material of the present invention was shown to be superior, with no occurrence of stagnation or statesking phenomenon, and excellent running properties with the heat-sensitive head. Not only was the density of the colored image low at low temperatures, but also the runability with the heat-sensitive head was poor.

Examples 2 to 4 In place of the acenaphthene used in Example 1, heat-sensitive recording materials were prepared using 2 xanthene, 3 dibenzothiofuran, and 4 phenanthrene, and each heat-sensitive recording material was printed in the same manner as in Example 1. As a result, a clear blue image was quickly obtained, and the above-mentioned recording suitability was also excellent as in Example 1.

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording material in which a heat-sensitive coloring layer containing a colorless or light-colored leuco dye and an acidic substance that causes the leuco dye to develop color when heated is formed on a support, wherein the heat-sensitive coloring layer In the following general formula (1)
A heat-sensitive recording material characterized by containing at least one of the compounds shown in (4). General formula (1) X: O or S General formula (2) Z: O or S Y: H, OH or acetyl group General formula (3) General formula (4)