JPS6157387A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having excellent color forming property and preservability and capable of giving favorable black-colored images, by using a specified fluoran substance as a color forming substance and a specified diphenylpropane as a color developer in a leuco thermal recording material. CONSTITUTION:A combination of 3-di-N-butylamino-7-(2-difluorophenylamino) fluoran and a fluoran substance of formula I, wherein each of R1 and R2, which together may form a ring, is hydrogen, alkyl, aycloalkyl, allyl or aralkyl, in a mixing ratio of 10/90-90/10 is used as a color forming substance, and 4,4'-dihydroxy-3,3'-diisopropyldiphenyl-2,2'-propane of formula II, wherein R1 is isopropyl, is used as a color deeloper. The color forming substance and the color developer are applied to a base such as a paper and a glass fiber sheet together with a known color developer accelerator, binder or other additives to obtain a thermal recording material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material that has excellent high-speed recording suitability and storage stability, and is capable of obtaining a good black image.

[Prior art]

A thermosensitive recording paper containing a normally colorless to light-colored color-forming substance (hereinafter referred to as a leuco compound) and a color-developing substance is already known, for example, from Japanese Patent Publication No. 14039/1983. This recording paper applies thermal energy to the recording layer to soften or melt the leuco compound, organic acid, and binder.
It is based on the principle of bringing both coloring components into contact to cause a coloring reaction, and has recently been used in various fields such as printers and facsimile machines. The recording characteristics of the recording paper differ depending on the use, but for example, in order to increase the recording speed, it is necessary to improve the recording device and promote the color development of the recording paper itself, and in recent years there has been a demand for the development of thermal paper in this direction. It is being

Conventionally, bisphenol A has been commonly used as a color developer, but bisphenol A has a high melting point of 157°C and is not suitable for high-speed recording, so various sensitizers are sometimes added to improve suitability for high-speed recording. Although many proposals have been made, none are yet sufficiently effective.

In addition, many proposals have been made for color developers with lower melting points to improve suitability for high-speed recording, and P-
Hydroxybenzoic acid ester (JP-A-56-14419
No. 3) and 4-hydroxyphthalic acid diester (JP-A-58-153692). However, all of these materials have the disadvantage that the resulting images have significantly poor fading resistance. Therefore, the addition of various chemicals such as antioxidants has been proposed in order to improve the fading property, but nothing satisfactory has been obtained.

For the above reasons, the present inventors first used 4,4' as a color developer.
-dihydroxy-3,3'-diisopropyldiphenyl-2,2-propane (Patent application 1301/1989)
35).

Even when this color developer is used, it has much better color development and storage stability than P-hydroxybenzoic acid ester and 4-hydroxyphthalic acid diester, but the hue of the resulting image is reddish. This has the disadvantage that it is impossible to obtain a good black image due to the tinge of color, and that the fingerprint-attached area is easily discolored.

[Problem that the invention seeks to solve]

The inventor has discovered that the color developer 4,4'-dihydroxy-3,3'-
The object of the present invention is to provide a heat-sensitive recording material that retains the excellent characteristics of diisopropyldiphenyl-2,2-propane and is capable of obtaining a good black image, and furthermore, a heat-sensitive recording material that is resistant to discoloration in areas where fingerprints are attached. As a result of intensive research, the present invention has been completed.

[Means for solving problems]

That is, the present invention provides a heat-sensitive recording material having a heat-sensitive recording layer containing a normally colorless or light-colored color-forming substance and a color developer that causes the color-forming substance to develop color when heated.
-di-N-butylamino-7-(2-fluorophenylamino)fluoran and one or more fluoran substances represented by the formula (1), and the color developer is 4.4' -Dihydroxy-3,3-diimpropyldiphenyl-2,2-propane (R represents an inglovir group).

The heat-sensitive recording material obtained by combining the fluoran compound represented by formula (1) and 4,4-dihydroxy-3,3-diisopropylphenyl-2,2-propane has a reddish color hue and a color-forming area. There was a problem that the color would disappear if fingerprints were attached to it.

In addition, 4,4-dihydroxy-3,3-diisopropylphenyl-2,2-propyf was used as a color developer, and 3-di-N-butylamino-7-(2-fluorophenylamino)fluoran was used as a color former. Even when the color was removed, the hue became greenish, and the fading resistance of the fingerprint-attached area was not significantly improved.
Image density was also not good. Therefore, it was unexpected that by combining these three materials as in the present invention, it was possible to obtain a heat-sensitive recording material that solved all of the above-mentioned drawbacks.

In the present invention, the fluoran compound of formula (1) may be one or more, and may be 3-di-N-butylamino-7-(2-
The mixing ratio with fluorophenylamino) fluorane is 1
A ratio of 0/90 to 90/10 is preferred. If this ratio is exceeded, it will not be possible to obtain a strong greenish or reddish hue or a good black image. Furthermore, it is not possible to improve the decolorization caused by fingerprints.

Next, the substances used in the present invention will be described.

(1) Leuco compound of formula (1) 3-diethylamino-6-methyl-7-anilinofluorane, 3-(N-cyclohexyl-N-methylamino)
-6-Methyl-7-anilinofluorane, 3-(N-inamyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3-(N-inbutyl-N-ethylamino)-6- Methyl-7-anilinofluorane, 3-? '
loricino-6-methyl-7-anilinofluorane, 3-
piperidino-6-methyl-7-anilinofluorane, 3
Examples thereof include -dipropylamino-6-methyl-7-anilinofluorane, 3-dibenzylamino-6-methyl-7-anilinofluorane, and the like.

(2) Color development accelerator In order to further improve the recording properties of the heat-sensitive recording medium of the present invention, conventionally known color development accelerators such as fatty acid amides such as stearamide, terephthalate esters, terphenyl, Parabenzylbiphenyl, octahydroanthracene, benzylmandelic acid, various naphthalene derivatives, etc. are used.

(3) Binder A water-soluble binder is used to isolate and fix the coloring agent dispersed in fine particles from each other (t'), polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid. , casein, gelatin, starch and derivatives thereof.

(4) Other additives The heat-sensitive recording material of the present invention may contain other additives in the heat-sensitive layer as necessary, such as inorganic or organic pigments such as clay, calcium carbonate, aluminum hydroxide, Merck, titanium oxide, zinc oxide, etc. , waxes, antioxidants for storage stability,
It is also possible to add a phenol resin, an ultraviolet absorber, various fatty acid metal salts to prevent stickiness, a water resistance agent to improve water resistance, a phenol resin, a surfactant, and the like.

(5) Substrate The present invention is produced by coating a substrate with a heat-sensitive paint containing the above-mentioned substances. The substrate is generally high quality paper, medium quality paper,
Paper such as coated paper is used, but other materials such as glass fiber sheets, plastic sheets, film-laminated papers, etc. can also be used as the substrate.

〔Effect of the invention〕

The heat-sensitive recording material of the present invention satisfies both high-speed recording performance and storage stability, and can also obtain good black images.
Furthermore, it is an extremely useful heat-sensitive recording material having the characteristic that the fingerprint-attached portion is resistant to discoloration.

□ [Example] The effects of the present invention will be explained in more detail below with reference to Examples.

Example 1 a) Production of heat-sensitive recording material Liquids A and B having the following compositions were separately dispersed in a paint shaker (manufactured by Toyo Sayaki Co., Ltd.) for 10 hours.

Solution A: 3-di-N-butylamino-7-(2-fluorophenylamino)fluorane 2.513-(N-cyclohexyl-N-methyl)amino-6-methyl-7-
Aniritsu fluoran
2,5? Aluminum hydroxide 282
Zinc stearate 52 holvinyl alcohol 12%i 3sy water
522B solution: 4,4-dihydroxy-3,37-diimbrobyldiphenyl-2,2-propane 152 kaolin
209 Zinc stearate
32 polyvinyl alcohol 12 liquid 3
52 water
521 Next is A liquid 125? , B liquid 125? And polyvinyl alcohol 12% liquid 50? , add 4°2 of water, mix and stir to adjust and coat the coating solution. Next, apply this coating solution to the surface of 509/- high quality paper using a Meyer bar until the coating amount after drying is 8.
1Ar? The mixture was coated and dried to obtain a heat-sensitive recording material.

Example 2 Among the formulations of AM used in Example 1, 3-(N-ynamyl-N-
A thermosensitive recording material was obtained in the same manner as in Example 1 except that ethyl)amino-6-methyl-7-anilite fluorane was used.

Example 3 Among the liquid A formulations m- in Example 2, 3-G-N-7'F-
7-(2-fluoro2enylamino)fluorane and 3-(N-ynamyl-N-ethyl]amino-6-
Mixing ratio with methyl-7-anilite fluorane is 1:2.
A thermosensitive recording material was obtained in the same manner as in Example 1 except that

Example 4 A thermosensitive recording material was obtained in the same manner as in Example 1 except that the mixing ratio of the fluoran dye in Example 3 was changed to 2:1.

Example 5 The same amounts of the coating liquid of Example 1 and the coating liquid of Example 2 were mixed to obtain a new coating liquid, and a heat-sensitive recording material was obtained in the same manner as in Example 1.

Comparative Example 1 In the formulation of Solution A used in Example 1, 3-(N-cyclohexyl-N-methyl)amino- was used instead of 3-di-N-butylamino-7-(2-fluorophenylamino)fluorane. A thermosensitive recording material was obtained in the same manner as in Example 1, except that 6-methyl-7-anilite fluorane was used.

Comparative Example 2 3-di-N-butylamino-7 was used in place of 3-(N-cyclohexyl-N-methyl)amino-6-methyl-7-anilite fluorane in the formulation of Solution A used in Example 1. −
A thermosensitive recording material was obtained in the same manner as in Example 1 except that (2-fluorophenylamino)fluoran was used.

Comparative Example 3.4.5 In Comparative Example 3, P-hydroxybenzoic acid benzyl ester Comparative Example 4 was used in place of 4,4-dihydroxy-3,3-diimprobil difer in the formulation of Solution B used in Example 1. In Comparative Example 5 of 4-hydroxyphthalic acid dimethyl ester, a thermosensitive recording material was obtained in the same manner as in Example 1 except that bisphenol A was added all around.

The heat-sensitive recording bodies obtained in the above Examples and Comparative Examples were surface-treated with a test super calender so that the recording surface had a Bekk smoothness of 500 seconds.

Next, regarding the heat-sensitive recording material obtained by surface treatment, commercially available
Printing was performed using the m7 axis device FACOM FAX6210 (manufactured by Fujitsu ■) under the conditions of recording power 0.96 W/''dat, current conduction time 0.45 m5ec, periodicity of 5 m3ec/L, and the image density and background density when printed. was measured using a Macbeth densitometer RD-514, and the color hue was observed.

Further, in order to check the fingerprint fading resistance, a fingerprint was attached to the printed surface and stored at 40°C and 90% RH for 48 hours, and the degree of fading at that time was visually judged.

The results are shown in Table 1.

As described above, it has been demonstrated that the heat-sensitive recording material of the present invention has excellent characteristics.

Table 1

Claims (1)

[Scope of Claims] A heat-sensitive recording material having a heat-sensitive recording layer containing a normally colorless or light-colored color-forming substance and a color developer that causes the color-forming substance to develop color when heated, wherein the color-forming substance is 3-di-N -Butylamino-7-(2-fluorophenylamino)fluorane and formula (1) ▲ Contains mathematical formulas, chemical formulas, tables, etc. ▼ (1
) (In the formula, R_1 and R_2 represent a hydrogen atom, an alkyl group, an alicyclic group, an allyl group, and an aralkyl group, and R_1 and R_2 can also mutually form a ring.) 4,4-dihydroxy-3,3-diisopropyldiphenyl-2,2-propane is used as a color developer ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (R_1 represents an isopropyl group). ) A heat-sensitive recording material characterized by using.