JPH01225589A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance the preservability of a developed color image in a visible and near infrared region, by containing at least one kind of a fluorenephthalide compound and at least one kind of a fluorene compound as color formers. CONSTITUTION:At least one kind of a fluorenephthalide compound represented by formula (1) (wherein R<1>, R<2>, R<3>, R<4>, R<5> and R<6> are an alkyl group, a cycloalkyl group, a benzyl group or a phenyl group, and R<1> and R<2>, R<3> and R<4>, and R<5> and R<6> may be respectively bonded to form a pyrrolidino or pyperidino group along with an adjacent nitrogen atom) and at least one kind of a fluorene compound represented by formula (2) (wherein R<7>, R<8>, R<9> and R<10> are an alkyl group, a cycloalkyl group, a benzyl group or a phenyl group, and R<7> and R<8>, and R<9> and R<10> may be respectively bonded to form a pyrrolidino or pyperidino group along with an adjacent nitrogen atom) are contained in a thermal recording material composed of a colorless - light- colored color former and a coupler as color formers.

Description

[Detailed Description of the Invention] [Industrial Application Field] In recent years, with the rationalization of Ba processing, optical character readers (OCR, OMR), barcode readers, etc. have come to be frequently used as human power media for computers. As a result, there is a strong demand for heat-sensitive recording materials that have a readable wavelength range, especially in the near-infrared region.Traditionally, an electron-accepting substance (developer) and an electron-donating substance (color-forming agent), which are almost colorless themselves, have been used.
As thermosensitive recording materials that produce color by heating and melting, there are thermosensitive recording papers based on paper, synthetic paper, film, etc., and electrically conductive thermosensitive recording papers.Currently used in facsimiles, printers,
It is widely used for POS labels, prepaid cards, train tickets, etc., and demand for it is rapidly increasing. The present invention provides a heat-sensitive recording material that can be read by the reader having a reading wavelength range in the near-infrared region.

[Prior Art] and [Problem to be Solved by the Invention] When using the above-mentioned reader as a manual medium for transmitting information to a computer, near-infrared light is better than visible light in terms of speed and accuracy in reading the information. It is much more advantageous to use it. Further, the reading rock having a reading wavelength range in the near-infrared region is small and inexpensive. However, in this case, in order to manually record with near-infrared light, it is necessary to record with a recording material that has strong absorption in the near-infrared region, and to maintain color development and color images in the visible and near-infrared regions. It is required to have excellent properties such as coloring properties, background coloration (fogging), and light resistance of the background, and in particular, those that develop a blackish color are strongly desired. However, among known heat-sensitive recording materials using color formers having absorption in the near-infrared region, no one has been found that satisfies all of these properties.

For example, 2-anilino-3-methyl-6, which is one of the fluoran compounds widely used as a coloring agent.
-(N-Ethyl-N-1so-amylamino)fluoran itself is an almost colorless crystal, with almost no background coloring, and develops a blackish color. Although it is extremely excellent, it has the drawback that it has almost no absorption in the near-infrared region. In addition, a color former having absorption in the near-infrared region, such as a fluorene phthalide compound, may be used.
3,6,6'-tris(dimethylamino)fluorenespiro(9,3')phthalide (JP-A-59-19
9757) is a type of styryl methanesulfinate compound, which has little coloration on the background, but has a bluish-green color, and has a marked lack of preservation of colored images in the visible and near-infrared regions. Bis(p-dimethylaminostyryl)-p-methylphenylsulfonylmethane
-230890) has strong background coloring and blue-ish coloring, and the storage stability of colored images in the visible and near-infrared regions is generally poor. 3,3-bis[2,2-bis(p-dimethylaminophenyl)ethynyl]-4.5,6.7-titrachlorophthalide (Japanese Patent Publication No. 58-5940), which is one of the divinyl compounds, is Although it has excellent storage stability of colored images in the visible and near-infrared regions, it has the disadvantage that the coloring is greenish and the background is strongly colored. -2-Cdimethylaminophenyl)ethynyl]-4,5゜6.7-titrachlorphthalide (JP 62-243653) and 3.3-bis[2-(p
-Methoxyphenyl)-2-(pyrrolidinophenyl)ethynyl]-4.5.6.7-titrachlorphthalide (Japanese Unexamined Patent Publication No. 1983-243652) has a blackish color with almost no skin coloring and is visible. Although they are generally excellent in color development in the near-infrared region, they have the disadvantage that the storage stability of colored images is extremely poor.

Conventionally, as a method of improving the storage stability of colored images, mixing two or more types of coloring agents has been proposed, for example, in Japanese Patent Publication No. 59-1999.
53193, JP-A-56-195990, JP-A-57
-123085, JP-A-58-71192, JP-A-5
No. 8-119892, JP-A No. 61-76387, etc. are known, but all of these are mixtures of fluoran compounds and do not have absorption in the near-infrared region. Also, the mixture of divinyl compounds described in JP-A-62-288078, the mixture of a divinyl compound and a fluorene phthalide compound, etc., in JP-A-62-148287, and JP-A-62-148287, a mixture of divinyl compounds and fluorene phthalide compounds, etc.
Although it is known to mix a divinyl compound with a fluorene compound or a phenylenediamine compound as disclosed in Japanese Patent No. 2-184881, the above drawbacks have not yet been overcome.

[Means for Solving the Problem] and [Operation] The present inventors have conducted intensive research to overcome the drawbacks of heat-sensitive recording materials using surface compounds, and as a result, the following heat-sensitive recording material develops a blackish color. It has also been found that it has strong absorption in the near-infrared region (700 to 900 nm), has little coloring of the background, and has excellent storage stability of colored images in the visible and near-infrared regions.

That is, the present invention (1) provides at least one fluorene phthalide compound represented by the general formula (1) as a color former in a heat-sensitive recording material comprising a colorless or light-colored color former and a color developer; A heat-sensitive recording material characterized by containing at least one fluorene compound represented by 2).

/N\Rfi R6 [In the formula, 11', r(2, R3, R4, R5, R6 represent an alkyl group, a cycloalkyl group, a benzyl group, a phenyl group, and R' and R2, R5 and R4, R5 and R6 may each bond with the adjacent nitrogen atom to form a pyrrolidino group or a piperidino group.] [In the formula, 87% R8, R9, RIG are an alkyl group, a cycloalkyl group, a benzyl group, Indicates a phenyl group, and R
7 and R8, and R9 and RID may each be bonded together to form a pyrrolidino group or a piperidino group with the adjacent nitrogen atom. It is intended to provide the following.

In this case, the PC3 (Print Contrast Signal) value required for a colored image is usually in the range of 0.7 to 1.0, although it varies depending on the model of the inscription reader.

The compounds of general formula (1) and general formula (2) described above are disclosed in, for example, JP-A-59-199757, JP-A-61-22076,
This is known from Japanese Patent Laid-Open No. 62-184881.

As a precaution, examples of the vine compounds used in the present invention are as follows.

Specific examples of fluorene phthalide compounds represented by general formula (1) 3.6.6'-tris(dimethylamino)fluorenespiro(9,3')phthalide, 3.6-bis(dimethylamino)-6'-diethylaminofluorenespiro(9,3')phthalide,3.6-bis,(diethylamino)-6fudimethylaminofluorenespiro(9,3')phthalide,3.6,6'-tris(diethylamino)fluorenespiro(9,3')phthalide,3.6-bis(dimethylamino)-6fudibrobylaminofluorenespiro(9,3')phthalide, 3.3.
6'-trispyrrolidinofluorenespiro(9,3')
Phthalide, 3,6-bis(dimethylamino)-6'-pyrrolidinofluorenespiro(9,3')phthalide, 3,6-bis(
dimethylamino)-6'-piperidinofluorenespiro(9,3')phthalide, 3,6-bis(diethylamino)-6'-pyrrolidinofluorenespiro(9,3')phthalide, 3-dimethylamino-6 -ethylamino-6
'-Dimethylaminofluorene spiro(9,3') phthalide, 3-dimethylamino-6-pyrrolidino 6'-dimethylaminofluorene spiro(9,3') phthalide, 3-dimethylamino-6-dipensylamino-6 '-Dimethylaminofluorenespiro(9,3')phthalide, 3-dimethylamino-6-(N-methyl-N-cyclohexylamino-6'-dimethylaminofluorenespiro(9,3')phthalide, 3-dimethyl Amino-6-(N-methyl-N-methoxyethylamino-6'-dimethylaminofluorenespiro(9,3')phthalide, 3,3-bisdimethylamino-6-phenylfluorenespiro(9,3')phthalide , Specific examples of fluorene compounds represented by general formula (2) 3.6-pisdimethylamino-9-(p-dimethylaminophenyl)fluorene, 3.6-pisdimethylamino-9-(p-diethylaminophenyl)fluorene , 3.6-pisdiethylamino-9-(p-pyrrolidinophenyl)fluorene, 3.6-pisdimethylamino-9-(p-diethylaminophenyl)fluorene 5 3.6-pisdiethylamino-9-(p-dimethylaminophenyl) ) fluorene, 3.6-pisdimethylamino-9-(p-pyrrolidinophenyl)fluorene, 3.6-pisdimethylamino-9-(p-dimethylaminophenyl)fluorene, 3.6-bisdiethylamino-97(p-pyrroli dinophenyl)fluorene, 3.6- and dimethylamino-9-[p-(N-methyl-N-phenylamino)phenyl]fluorene, 3.6-bis(N-methyl-N-phenylaminophenyl)- 9-[p-(N-methyl-N-phenylamino)
] Fluorene, 3.6- and sudiethylamino-9-[p-(N-methyl-N-phenylamino)phenyl]fluorene, 3.6-bis(N-methyl-N-cyclohexylamino)-9-[ p-(N-methyl-N-cyclohexylamino)phenylphenol, 3.6- and dimethylamino-9-[p-(N-methyl-N-hensylamino)phenyl]fluorene, 3.6-bis(N -Methyl-N-pencylamino)-9
-[p-(N-methyl-N-pensylamino)]fluorene When producing a heat-sensitive recording material using these color formers, the color formers may be mixed in advance by melting or melting, The crystals may be mixed before or after crushing. In addition, in order to improve color tone, color density, stability of color images, etc., other color formers that develop various hues, such as 3.3
-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide, disubstituted fluorane (UK Patent No. 118)
No. 2743, Belgian Patent No. 815291, No. 815
294) and bisindolyl phthalide compounds (described in German Patent Publication No. 2259711).

In addition, in manufacturing thermal recording paper, polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, gum arabic, gelatin, casein, starch, polyvinylpyrrolidone, styrene-maleic anhydride group polymer, etc. are used as binders. I can do it.

In this case, the color developer includes 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenyl ether, 4-hydroxybenzoic acid methyl ester, 4-hydroxybenzoic acid pencil ester, 2.2
-Bis(hydroxyphenyl)propane, 4,4'-thiodiphenol, bis-(4-hydroxy-3-methylphenyl) sulfide, 4,47-cyhydroxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl Sulfone, 4-hydroxy-47-itubroboxydiphenylsulfone, 4,4'-dihydroxy-3°;
3'-dimethyldiphenylsulfone, 4.4'-dihydroxy-3,37-diallyldiphenylsulfone, 1.
5-di(4-hydroxyphenylthio)-3-oxapentane, 1,7-di(4-hydroxyphenylthio)-
3,5-dioxahebutane, 1,8-cy(4-hydroxyphenylthio)-3,6-thioxaoctane, bis(
Hydroxy compounds such as 4-hydroxy-3-methylphenyl) sulfide can be used alone or in combination.

Sensitivity improvers include acetanilide, paraffin wax, carnauba wax, higher fatty acids, higher fatty acid esters, higher fatty acid amides, phthalic esters, terephthalic esters, benzyl 4-benzyloxybenzoate, dibenzyl oxalate, naphthol benzyl ether, 1.4 -dialkoxynaphthalene, 1,5-dialkoxynaphthalene, m
-terphenyl, p-benzylbiphenyl, dihenzylbenzene, ■-hydroxy-2-naphthoic acid ester,
2-Hydroxy-3-naphthoic acid ester, l-phenoxy-2-naphthoxy(1)ethane, 1,2-di(3-
methylphenoxy)ethane, 1-(2-isopropylphenoxy)-2-naphthoxy(2)ethane, bis(P-
methoxyphenoxyethyl) ether, 4,4'-dialkoxydiphenyl sulfone, penzamide, diphenylamine, benzenesulfonamide, benzenesulfonanilide, phenyl p-toluenesulfonate, hydroquinone dibenzyl ether, used alone or in combination I can do things.

In addition, addition of antioxidants, anti-deterioration agents, ultraviolet absorbers, etc., or overcoating with polymeric substances, etc., are effective in improving the light resistance and storage stability of images.

As a method for producing heat-sensitive recording paper using a fluorene phthalide compound represented by general formula (1) and a fluorene compound represented by general formula (2), there are known methods such as Japanese Patent Publication No. 14039/1983, The method described in Japanese Unexamined Patent Publication No. 59-33186 can be adopted. EXAMPLES The present invention will be specifically explained below by way of comparative tests, using examples of producing heat-sensitive recording paper as examples of the present invention.

[Production Example (1) l) Preparation of color former dispersion (liquid A) 3.6'-Tris(dimethylamino)fluorenespiro(9,3')phthalide 3.75 parts 3.6 -Pisdimethylamino-9-(p-dimethylaminophenyl)fluorene 1.25 parts
15 parts 10% polyvinyl alcohol aqueous solution 100 parts water
85 parts The above mixture was pulverized using a paint shaker (manufactured by Toyo Seiki Co., Ltd.) until the average particle size was 2 microns.

2) Preparation of color developer dispersion (liquid B) Bisphenol A 15 parts Stearamide 20 parts Zinc stearate 10 parts 10% polyvinyl alcohol aqueous solution 150 parts The above mixture was mixed in a paint shaker until the average particle size became 3 microns. Shattered.

3) Preparation and Coating of Heat-Sensitive Coating Liquid 10 parts of liquid A and 6.5 parts of liquid B were mixed and stirred to obtain a heat-sensitive coating liquid. The weight after drying this liquid on paper with a wire bar is 6g/
It was coated uniformly to give a thickness of m2 and dried to obtain heat-sensitive recording paper. This thermosensitive recording paper had no coloring on the background, and developed a deep black color when heated with a thermal pen or the like. This colored image has excellent light resistance and moisture resistance, and has excellent light resistance and moisture resistance in the near-infrared region (700 to 9
00 nm), and showed the reflection spectrum shown in Figure 1.

Production example (2) Fluorene phthalide compound 3°6.6' as a coloring agent
-tris(dimethylamino)fluorenespiro(9,3
') 2.5 parts of phthalide, 3.6 parts of fluorene compound
A thermosensitive recording paper was obtained in the same manner as in JEi Example (1) except that 2.5 parts of psdimethylamino-9-(p-dimethylaminophenyl)fluorene was used. The color image of this thermal recording paper shows a deep black-red color, and the near-infrared region (7
It also had strong absorption in the wavelength range of 00 to 900 nm) and had excellent light resistance and moisture resistance.

Production Example (3) A thermosensitive recording paper was obtained in the same manner as Production Example (1) except that the fluorene compound as the color former was replaced with 3,6-pisbyrrolidino-9-(p-pyrrolidinophenyl)fluorene. The colored image of this thermal recording paper shows a deep black-blue color, and has strong absorption in the near-infrared region (700 to 900 nn).
It had excellent properties such as light resistance and moisture resistance.

A thermosensitive recording paper was obtained in the same manner as in Production Example (1) except that s(dimethylamino)-6'-dipropylaminofluorenespiro(9,3')phthalide was used. The colored image of this thermal recording paper shows a deep black color, and the near-infrared region (7
It also had strong absorption in the wavelength range of 00 to 900 nm) and had excellent light resistance, moisture resistance, etc.

Comparative Example A thermosensitive recording paper was prepared in the same manner as in Production Example (1) except that only 3,6,6'-tris(dimethylamino)fluorenespiro(9,3')phthalide 5iTIS was used as the coloring agent. Obtained. The colored image of this thermal recording paper shows blue-green, and the colored image is in the near-infrared region (700 to 900 stops).
Although it had absorption in , and showed the reflection spectrum shown in FIG. 1, it had poor light resistance and moisture resistance.

[Comparative Test] The thermal recording paper obtained in the above production example and comparative example was tested using a thermal coloring tester (manufactured by Matsushita Electronic Components Co., Ltd.) at an applied voltage of 16 V.
Color was developed with a pulse width of 3.6 msec. After leaving this colored image indoors for a day, we exposed it to sunlight and measured the density of the colored image and the reflectance of the colored image and the background at each hour.
The cs value was calculated.

(+) Density table 1 of color image by time, Density table 26 in the visible region using a Macbeth reflection densitometer (manufactured by Macbeth) Near infrared region (830 nm) measured by a spectrophotometer (Model UV-365, manufactured by Shimadzu Corporation) ) Concentration (2) Hourly PCS Value Table 31 Calculated from the reflectance (%) at 830 nm using a spectrophotometer using the following formula.

Reflectance of background − Reflectance of colored image PC8f direct = Reflectance of background As shown in Tables 1.2 and 3, manufacturing examples (1) and (2)
) Compared with the comparative example, the colored image shows strong light resistance in the visible and near infrared regions, and the decrease in PCS fU is also small.

[Effects of the Invention] As described above, the heat-sensitive recording material of the present invention not only forms a highly desired black colored image and also has absorption in the near-infrared region, but also has particularly low light resistance. It exhibits excellent properties and has high utility value in the industrial world as a heat-sensitive recording material that can be read by the reader having a reading wavelength range in the near-infrared region.

[Brief explanation of the drawing]

FIG. 1 shows the reflection spectra of colored images of Production Example 1 and Comparative Example.

Claims (1)

[Claims] (1) In a heat-sensitive recording material consisting of a colorless or light-colored color former and a color developer, at least one fluorene phthalide compound represented by the general formula (1) and a color developer represented by the general formula (2) are used as the color former. 1. A heat-sensitive recording material comprising at least one fluorene compound. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(1) [In the formula, R^1, R^2, R^3, R^4, R^5, R
^6 is an alkyl group, a cycloalkyl group, a benzyl group,
Indicates a phenyl group, and also R^1 and R^2, R^3 and R^4
, R^5 and R^6 may each be bonded to an adjacent nitrogen atom to form a pyrrolidino group or a piperidino group. ] ▲There are mathematical formulas, chemical formulas, tables, etc.▼(2) [In the formula, R^7, R^8, R^9, R^1^0 represent an alkyl group, a cycloalkyl group, a benzyl group, a phenyl group. In addition, R^7 and R^8, R^9 and R^1^0 may each be bonded to form a pyrrolidino group or piperidino group with the adjacent nitrogen atom. ]