JPH03244587A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having good heat registance and humidity resistance wherein absorption spectrum is recognized in a visible ray part and a near infrared part when an spectrum of an image is inspected by using two different types of specific fluoran compound as a color former. CONSTITUTION:A thermal recording material consists of colorless or pale leuco dye as a color former which forms a color thermally through contact with a developer. The color former contains at least, one type of fluoran compound expressed by formula (I) as a color former and at least, one type of fluoran compound expressed by formula (2). In the formula (I), R<1>, R<2> are an alkyl group, a cycloalkyl group, an alkoxyalkyl group, an aralkyl group or an aryl group; R<3> is a hydrogen atom, an alkyl group, an alkoxyalkyl group or an aralkyl group. In addition, in the formula (II), R<4>, R<5> are an alkyl group, an alkoxyalkyl group, a cycloalkyl group, a tetrahydrofurfuryl group, an aralkyl group or an aryl group; X<1>, X<2> are a hydrogen atom, an alkyl group, a halogen atom or a trifuloromethyl group.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is applicable to various optical character reading devices (OCR) in which a colored image has light absorption in both the visible region and the near-infrared region.
The invention relates to a heat-sensitive recording material that can be read with .

Heat-sensitive recording materials that use a colorless or light-colored leuco dye as a coloring agent and are heated and brought into contact with a color developer to develop color are widely known, and have already been used for various purposes such as printers, facsimile machines, and labels. Although,
In particular, recording materials whose colored images have strong absorption not only in the visible region but also in the near-infrared region are expected to be used as recording materials for OCR using semiconductor lasers and the like, which have been in increasing demand in recent years.

[Prior Art] and [Problems to be Solved by the Present Invention] Recording materials whose colored images have absorption in both the visible region and the near-infrared region have already been disclosed in JP-A-59-199757 and JP-A-62-243653. No. 63-37158, Japanese Unexamined Patent Publication No. 63-37158, etc.

However, in these cases, the density of the colored image is weak,
Another problem was that the colored image was unstable and easily disappeared.

As a result of searching for a recording material to replace the above, the present inventor discovered a compound disclosed in JP-A No. 51,90608 (the following general formula (
It was found that the compound 1) gives a colored image that has absorption in the visible region as well as in the near-infrared region.

[In the formula, R1 and R2 each represent an alkyl group, a cycloalkyl group, an alkoxyalkyl group, an aralkyl group, or an aryl group, and R3 represents a hydrogen atom, an alkyl group, an alkoxyalkyl group, or an aralkyl group.

Further, R1 and R2 may be connected to form a heterocycle. ] However, in this case as well, when the above compound was used alone, the storage stability of the colored image was poor, and it could not be used as a coloring agent for heat-sensitive recording materials.

In view of the above circumstances, the inventors of the present invention have conducted further research and have arrived at a solution to the above-mentioned problems by using leuco dyes in combination.

[Means for solving the problem] and [action], that is, the present invention,
By manufacturing heat-sensitive recording paper using a combination of the compound represented by the general formula (1) above and a specific fluoran compound represented by the following general formula (2) as a coloring agent, light absorption of the colored image is necessary for machine reading. As a result of further research, we discovered that not only does it extend to a long wavelength region of 700 nm or more, but the color image is extremely stable.

Specific examples of the compound represented by the general formula (1) according to the present invention include those shown in the following table, but are not limited thereto.

[In the formula, R4 and R5 each represent an alkyl group, an alkoxyalkyl group, a cycloalkyl group, a tetravitrofurfuryl group, an aralkyl group, or an aryl group, and Xl and X2 each represent a hydrogen atom, an alkyl group, a halogen atom, or a trifluoromethyl group represents. Further, R4 and R5 may be connected to form a heterocycle.

Further, specific examples of the compound represented by the general formula (2) used in the present invention include the following.

2-anilino-6-dinithylaminofluorane, 2-anilino-6-(N-ethyl-N-n-hexylamino)
Fluoran, 2-anilino-3-methyl-6-dinithylaminofluorane, 2-anilino-3-methyl-6-d-n-butylaminofluorane, 2-anilino-3-methyl-6-d-n-pentyl Aminofluorane, 2-anilino3-methyl-6-(N-methyl-N-n-propylamino)fluorane, 2-anilino-3-methyl-6
-(N-ethyl-N-iso-pentylamino)fluoran, 2-anilino-3-methyl-6-(N-ethyl-
N-n-hexylamino)fluorane, 2-anilino-
3-Methyl-6-(N-ethyl-N-p-tolylamino)fluoran, 2-anilino-3-methyl-6-(N-
Ethyl-N-ethoxypropylamino)fluorane, 2
-anilino-3-methyl-6-(N-methyl-N-cyclohexylamino)fluoran, 2-anilino-3methyl-6-(N-ethyl-N-tetrahydrofurfurylamino)fluoran, 2-anilino-3- Methyl-6-pyrrolidinylfluorane, 2-anilino-3-chloro-6
-Dinithylaminofluorane, 2-m-trifluoromethylanilino-6-dinitylaminofluorane, 2-0
-Chloroanilino-6-di-n-butylaminofluoran When producing a heat-sensitive recording material using a fluoran compound represented by the general formulas (1) and (2) as a coloring agent, for example, A known method described in Japanese Patent No. 14039 can be employed. Furthermore, in order to improve the coloring hue, coloring density, image stability, etc., known coloring agents that form various hues can be used in combination as long as the performance of the compound according to the present invention is not impaired.

For example, 3,3-bis(aminophenyl)-6-aminophthalide, 3,3-bis(indolyl)phthalide, 3-aminofluorane, aminobenzofluorane, 2,6-diamitfluorane, 2,6-diamitsufluorane 3-methylfluorane, spiropyran, phenothiazine, phenoxazine, leukoolamine, diarylcarbazolylmethane, 3-indolyl-3-(aminophenyl)phthalide,
It is used in combination with a coloring agent having a basic skeleton such as 3-indolyl-3-(aminophenyl)azaphthalide.

The following binders can be used in the production of heat-sensitive recording materials.

Polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, gum arabic, gelatin, casein, starch, polyvinylpyrrolidone, styrene-maleic anhydride copolymer, etc.

As the sensitivity improver, the following known compounds may be used alone or in combination.

Paraffin wax, carnauba wax, higher fatty acid ester, higher fatty acid amide, dibenzyl oxalate, di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, phthalate ester, terephthalate ester, benzyl 4-benzyloxybenzoate, naphthol benzyl ether, 1
．． 4-dibenzyloxybenzene, 1,4-di(vinyloxyethoxy)benzene, 1,2-diphenoxybenzene, 1,4-ditolyloxybenzene, 1,4-dialkoxynaphthalene, 1,5-dialkoxy Naphthalene, m-terphenyl, p-benzylbiphenyl, dibenzylbenzene, l,2-dixylylethane, 1-hydroxy-2-naphthoic acid ester, 1. 2-diphenoxyethane, 1,2-di(3-methylphenoxy)ethane, 1-(2-isopropylphenoxy)-2-naphthoxy(2)ethane, 1-phenoxy-2-naphthoxy(
1) Bis(p-methoxyphenoxyethyl) in ethane
Ether, 2-hydroxy-3-naphthoate ester,
4. 4'-dialkoxydiphenylsulfone, penzamide, benzenesulfonamide, benzenesulfoneanilide, toluenesulfoneanilide, phenyl toluenesulfonate, tolyl mesitylenesulfonate, diphenyl carbonate, and the like.

As the color developer, the following known compounds can be used alone or in combination.

p-hydroxybenzoic acid methyl ester, p-hydroxybenzoic acid benzyl ester, 2,2-bis(p-hydroxyphenyl)propane (bisphenol A), 3.
4'-isopropylidenediphenol, 2,2-bis(p-hydroxyphenyl)-4-methylpentane, 2
, 2-bis(4-hydroxy-3-allylphenyl)propane, bis(4-hydroxyphenyl)acetic acid, 1.1
-Bis(4-hydroxyphenyl)butyl acetate, 4°4
゛-Cyclohexylidene diphenol, 4,4-thiodiphenol, bis-(4-hydroxy-3-methylphenyl) sulfide, bis(4-hydroxy-3-t
er t-butyl-6-methylphenyl) sulfide, 4. 4'-dihydroxydiphenylsulfone, 4-hydroxy-4-methyldiphenylsulfone, 3
, 4-dihydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4"-isopropoxydiphenylsulfone, 4,49-dihydroxy-3,3'-dimethyldiphenylsulfone, 4.4'-dihydroxy-
3,3'-diallyldiphenylsulfone dimethyl 4-hydroxyphthalate, bis[2-(4-hydroxyphenylthio)ethyl]ether, 4.4''-methylenebis(oxyethylenethio)diphenol, 1-benzyl-
2-naphthol 1.1゛-methylene di-2-naphthol, p-hydroxyphenylsalicylamide, 1,3-diphenylthiourea, 1,3-ditolylthiourea 1.3
-dichlorophenylthiourea, etc.

Further, an overcoat such as a polymer material is also an effective means for improving the light resistance and moisture resistance of an image.

Next, the present invention will be specifically explained by giving examples and comparative examples of heat-sensitive recording paper production, and further by showing comparative test examples. (Parts represent parts by weight.) Example 1 1) Preparation of color former dispersion (liquid A) Compound No. 6 above 0. Part 5 2-
Anilino-3-methyl-6-(N-ethylN-1so
-pentylamino)fluorane 0. Part 5 Papilol N
680C (Showa Denko ■ binder) 3.0 parts water 2o.
Part o: Add the above mixture to a sand grinder (Igarashi Machine ■
The coloring agent was ground to an average particle diameter of 1 micron.

2) Preparation of color developer dispersion (liquid B) Hydrin F-285 (Hysphenol A30X dispersion made by Middle East Oil Co., Ltd.) 5.0
Hydrin Z-7-30 (Nakamuro Yushi ■Fatty acid zinc 3
0% dispersion) 4/5 parts Mizuka Seal P-832 (calcium silicate manufactured by Mizusawa Chemical ■)
4.0 parts water 9.5
The above dispersion was thoroughly mixed using a magnetic stirrer.

3) Preparation of sensitizer dispersion (liquid C) p-benzylbiphenyl 2. 0 parts Papilol N680C3, 0 parts water 7.
0 parts The above mixture was grinded with a sand grinder until the average particle size was 1
．． It was ground to 5 microns.

4) Preparation and coating of heat-sensitive coating liquid 4 parts of liquid A, 3 parts of liquid B, and 2 parts of liquid C were mixed and stirred to obtain a heat-sensitive coating liquid. This coating liquid was evenly applied to paper using a wire bar so that the weight after drying was 6 g/m, and then dried to obtain heat-sensitive recording paper.

This thermal recording paper had no background fog and quickly developed a deep black edge color when heated with a thermal pen or the like. Another 700-8
Since it had strong absorption even at 00 nm, it was possible to read it by OCR. Furthermore, the coated surface also had excellent light resistance, and no coloring occurred due to sunlight irradiation.

Examples 2 to 4 In preparing Liquid A of Example 1, the compounds shown in Table 1 were used as color formers, and the other operations were the same as in Example 1 to obtain thermosensitive recording paper.

Table 1 Comparative Examples F to 3 In preparing Liquid A of Example 1, the compounds shown in Table 2 were used as color formers, and the other operations were the same as in Example 1 to obtain thermosensitive recording paper.

Table 2 Comparative Test The light resistance and moisture resistance of the heat-sensitive recording papers obtained in the above Examples and Comparative Examples were tested by the following method, and the results are shown in Tables 3 and 4.

(1) Heat resistance test Each heat-sensitive recording paper was tested using a heat-sensitive coloring tester (manufactured by Matsushita Electronic Components) at an applied voltage of 16 V and a pulse width of 2. Color was developed in 0 milliseconds. After leaving this colored image at 60°C for 2 days, the reflection density at 700 nm was measured using a spectrophotometer (@
Measurement was performed using a UV-365 model (manufactured by Shimadzu Corporation).

The image survival rate was determined by the following formula, and the heat resistance was determined.

Table 4 (2) Moisture resistance test The image area developed under the same conditions as in (1) was left in an atmosphere of 40°C and 90% relative humidity for 5 days, and then 700 nm
The reflection density was measured in the same manner as in (1), and the image survival rate was determined using the following formula, which was defined as moisture resistance.

Table 3 The above test confirmed that the heat-sensitive recording paper of the present invention has excellent light resistance and moisture resistance.

[Effects of the Invention] The heat-sensitive recording material of the present invention has a colored image that absorbs not only the visible region but also the near-infrared region, and has extremely excellent heat resistance and moisture resistance. It has high industrial value.

Claims (1)

[Scope of Claims] [1] A heat-sensitive recording material in which a colorless to light-colored leuco dye is used as a coloring agent and color is developed by contacting it with a color developer by heating, wherein the coloring agent is a compound represented by the general formula (1). At least one fluoran compound represented by the general formula (
2) A heat-sensitive recording material containing at least one fluoran compound represented by the following. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (1) [In the formula, R^1 and R^2 each represent an alkyl group, a cycloalkyl group, an alkoxyalkyl group, an aralkyl group, or an aryl group, and R^3 represents a hydrogen atom, Represents an alkyl group, an alkoxyalkyl group, or an aralkyl group. Further, R^1 and R^2 may be connected to form a heterocycle. ] ▲There are mathematical formulas, chemical formulas, tables, etc.▼(2) [In the formula, R^4 and R^5 each represent an alkyl group, an alkoxyalkyl group, a cycloalkyl group, a tetrahydrofurfuryl group, an aralkyl group, or an aryl group, ^1,X^
2 each represents a hydrogen atom, an alkyl group, a halogen atom, or a trifluoromethyl group. Moreover, R^4 and R^5 may be connected to form a heterocycle.