JPS63265685A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance a high speed recording property, to make the fading of a recording image with the elapse of time hard to develop and to enhance the whiteness of a recording layer, by using high purity 3,4'-(1-methylethylidene) bisphenol (m,p-bisphenol A) having a specific m.p. range as an electron acceptive coupler. CONSTITUTION:High purity m,p-bisphenol A to be used is obtained by reacting m-isopropenylphenol and phenol in the presence of an acid catalyst and has a m.p. of 120-140 deg.C. In thermal recording material, m,p-bisphenol A being a coupler is used along with a colorless-light-colored electron donating dye precursor (color former) but, as the dye precursor, a triarylmethane type compound, a diphenylmethane type compound, a xanthene type compound, a spiropyrane type compound or the like are designated. A coating solution is generally prepared by together or separately dispersing the dye precursor and the coupler in water being a dispersing medium. By this method, a serious drawback such that a formed recording image is faded with the elapse of time is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat-sensitive recording material. More specifically, the present invention relates to an electron-accepting color developer that develops a color when it comes into contact with a colorless or light-colored electron-donating dye precursor.

[Conventional technology and problems]

2. Description of the Related Art Conventionally, recording materials utilizing a color reaction between a colorless or light-colored electron-donating dye precursor (color former) and an electron-accepting color developer are well known.

Among such recording media, heat-generating recording media that utilize thermal contact between two substances, particularly two-component color-forming thermosensitive recording media, have become increasingly important in recent years as facsimiles and the like have become more popular.

The two-component color-forming thermosensitive recording material is made by dispersing a colorless or light-colored electron-donating dye precursor and an electron-accepting color developer in the form of fine particles.
This is mixed with a binder, etc., and coated on a support so that these two types of heat-reactive compounds are separated from each other by the binder, and one or both of them melt and come into contact with each other by heating, causing a coloring reaction. It is used to obtain recorded images. A thermal printer or the like with a built-in thermal head is used for heating.

Recently, due to advances in thermal recording methods, thermal facsimile,
Thermal printers and other devices have all become faster. Thermal recording materials used in the hardware field are also required to have excellent recording sensitivity, that is, to have high thermal reactivity, to prevent static recording from occurring in low-temperature regions, and to avoid recording caused by dust adhesion. Characteristics such as no cutting are required.

4. As an electron-accepting color developer that has been widely used in the past.
4'-(1-methylethylidene)bisphenol (P
, sometimes abbreviated as ρ-bisphenol A), but thermosensitive recording materials using this have a problem of low recording sensitivity and cannot cope with the recent increase in speed. In order to improve the recording sensitivity, some bisphenol compounds such as p,p-bisphenol A are combined with sensitizers such as stearic acid amide. This had the disadvantage that static records were more likely to appear.

On the other hand, 4-hydroxybenzoic acid ester, 4-tert
- Heat-sensitive recording materials using monophenolic compounds such as butylphenol as electron-accepting color developers are known, but although such heat-sensitive recording materials have high recording sensitivity, the recorded image produced fades over time. It has a serious drawback that it does.

Furthermore, in order to improve these drawbacks, a method of using a monophenol compound and a bisphenol compound such as P,P-bisphenol A in combination has been proposed, but a sufficient improvement has not necessarily been achieved.

Further, according to JP-A-60-220787, 3.4' having a melting point of 97 to 99°C is used as an electron-accepting color developer.
-(1-methylethylidene)bisphenol (hereinafter 1+
A method using m+P-bisphenol A (sometimes abbreviated as P-bisphenol A) has been proposed.The present inventors investigated this method in detail and found that m+P-bisphenol A with a melting point of 97 to 99°C was used with electron-accepting color development. It has been found that when used as an agent, it is possible to obtain heat-sensitive recording paper that has a fast color development rate and is suitable for high-speed recording, but it has the drawback of lacking storage stability.

By the way, regarding P-bisphenol A, there is
A manufacturing method proposed in the specification of Japanese Patent No. 98 is known. Among these are Imekaho, which uses 3-hydroxyphenyldimethylcarbinol and phenol as raw materials;
The yield of P-bisphenol A is low. ↓The Il+P-bisphenol A shown in both publications has a melting point of 97 to 98°C, and according to the findings of the present inventors, ■ and p-bisphenol A having such a melting point are It was recognized that it contained a considerable amount of impurities. In other words, the melting point of high-purity p-bisphenol A is not in the temperature range of 97 to 99°C as shown in these publications. High purity l+ with melting point in the range of 122℃
P-bisphenol A and its production method have been presented, but the method using I' + P-bisphenol A with a melting point of 97 to 99°C as a color developer proposed in JP-A No. 60-220787 ( In Example 1) of the publication, there is a problem that when this is used as a color developer, the storage stability as a thermosensitive recording paper decreases, probably because it contains a considerable amount of impurities.

[Purpose of the invention]

Therefore, the present inventors developed high-purity I as an electron-accepting color developer.
By using l+P-bisphenol A and investigating its effects, it is possible to obtain a heat-sensitive recording material with high recording sensitivity (and excellent storage stability in which the recorded image is resistant to fading and the whiteness of the recording layer is high). investigated.

[Summary of the invention]

As a result, it has a melting point of 120-140 as an electron-accepting color developer.
The object of the present invention was achieved by using high purity 3.4'-(1-methylethylidene)bisphenol (m+p-bisphenol A) in the range of °C.

That is, according to the method of the present invention, 1' t
A heat-sensitive recording material characterized by using P-bisphenol A is provided.

[Detailed description of the invention]

A high-purity method of ll+P-bisphenol A used as a color developer in the present invention having a melting point in the range of 120 to 140°C will be specifically shown.

High purity 1M + P-bisphenol A according to the present invention
can be obtained by reacting meta-isopropenylphenol and phenol, but when using a normal reaction method, purification becomes difficult due to the large amount of by-product of meta-isopropenylphenol polymer, which is an impurity. , Therefore, Japanese Patent Application Laid-Open No. 60-220787 and Reference Example 4 of the present invention
m, p-bisphenol A with a low melting point as shown in
6 to 111°C), which has a high content of impurities. High purity m,ρ-bisphenol A used in the present invention
can be obtained by reacting I-isopropenylphenol and phenol in the presence of an acid catalyst, for example, according to the method disclosed in JP-A-61-271236.

Specifically, the reaction method is to carry out the reaction at a temperature of about 20 to 60°C while adding metaisopropenylphenol/phenol (molar ratio) to a large excess of phenol containing hydrogen chloride as an acid catalyst. After the reaction is completed, hydrogen chloride, a hydrocarbon solvent, and phenol are sequentially removed by distilling the reaction product under reduced pressure, and then recrystallization is performed using a solvent such as an aromatic hydrocarbon or a halogenated hydrocarbon, and the melting point is 120. High purity 'l+P in the range of -140℃
- Bisphenol A can be obtained.

The purity of this In+P-bisphenol according to the present invention is usually 99% or more in area % as determined by gas chromatography analysis. Moreover, specifically as the above-mentioned hydrocarbon solvent, n-
Aliphatic hydrocarbons such as hexane and n-hebutane, alicyclic hydrocarbons such as cyclopenkune and cyclohexane, aromatic hydrocarbons such as benzene, toluene, xylene and cumene, halogenated hydrocarbons such as chloroform and chlorobenzene, etc. Among them, aromatic hydrocarbons,
Particular preference is given to using toluene.

High purity +1+P with a melting point of 120 to 140°C according to the present invention
-Bisphenol A is not necessarily limited to that obtained by the above method, but as shown in Reference Examples 1 to 3 below, a cation exchange resin is used as a catalyst and it is charged into a reactor together with phenol, and then methane is added. It can also be obtained by adding a mixed solution of isopropenylphenol and phenol to a reactor over time, allowing the reaction to occur, and then removing the catalyst and phenol after the reaction is complete and recrystallizing.

For example, the present inventors obtained a mixture of two types of crystals having different melting points, with '+P''- exhibiting two values of 122.2 DEG C. and 137.5 DEG C., using the reaction method described above.

In addition, the measurement of chloroform from toluene as a solvent was performed using a Mettler automatic melting point analyzer FP-61 and differential thermal analysis (using a Seiko DSC model-20), but considering the experimental results and analytical errors in the measurement, the purity was normal. 99
% or more of m+P-bisphenol A has a melting point of 120-1
It was considered appropriate to set the temperature to be in the range of 40°C. In the present invention, when the melting point of '+P-bisphenol A used as a color developer is lower than 120°C, the humidity stability of the colored image is poor, as shown in Comparative Example 4 described below, and the heat-sensitive recording paper is Melting point: 120-140 due to lack of storage stability
Highly purified p-bisphenol A at a temperature of <RTIgt;° C.</RTI> is used.

In the heat-sensitive recording material according to the present invention, m+p-bisphenol A as a color developer is used together with a colorless or light-colored electron-donating dye precursor (color former), and the dye precursor may include a triarylmethane compound, Examples include diphenylmethane compounds, xanthine compounds, and spiropyran compounds.

Some examples include 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide; 3.
3-bis(ρ-dimethylaminophenyl)phthalide, 3
-(ρ-dimethylaminophenyl) -3-(1,2-
dimethylindol-3-yl)phthalide, 3-(p-
dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3,3-bis(l,2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3-bis( 1,2-dimethylindole-3
-yl)-6-dimethylaminophthalide, 3,3-bis(9-ethylcarbazol-3-yl)-6-dimethylaminophthalide, 3,3-bis(2-phenylindol-3-yl)- 6-dimethylaminophthalide, 3-P
-Triarylmethane dyes such as dimethylaminophenyl-3-(1-methylpyrrol-3-yl)-6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydryl benzyl ether, N- Halophenyl
Diphenylmethane dyes such as leucoauramine and N-2,4,5-trichlorophenylleucoauramine, thiazine dyes such as benzoylleucomethylene blue and p-nitrobenzoylleucomethylene blue, 3-methyl-
Spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3
- Spiro dyes such as benzyl-spiro-dinaphthopyran, 3-methyl-naphtho(6'-methoxybenzo)spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B-anilinolactam, rhodamine(P-nitroanilino)lactam , lactam dyes such as rhodamine (0-chloroanilino)lactam, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-
Methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-chlorofluorane, 3-diethylamino-6,7-dithymelfluorane, 3 -(N-ethyl-p-toluidino)-7-methylfluorane, 3-diethylamino-7-N-acetylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3 -diethylamino-7-N-methyl-N-benzylaminofluorane, 3-diethylamino-7-N-chloroethyl-N
-Methylaminofluorane, 3-diethylamino-7-
N-diethylaminofluorane, 3-(N-ethyl-P
-)luidino)-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-P-toluidino)-6-methyl-7-(P-toluidino)fluorane, 3-diethylamino-6-methyl-7 -phenylaminofluorane, 3-dibutylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7-(2-carbomethoxy-phenylamino)fluorane, 3-(N-cyclohexyl-N-methylamino) )-6-methyl-7-
Phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-pyrrolidino-
6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane,
3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7-(o-chlorophenylamino)-fluorane, 3-dibutylamino-7-(
o-chlorophenylamino)-fluorane, 3-pyrrolidino-6-methyl-7-P-butylphenylaminofluorane, 3-(N-methyl-Nn-amyl)amino-
6-Methyl-7-phenylaminofluorane, 3-(N
-Methyl-N-n-amyl)amino-6-methyl-7-
Phenylaminofluorane, 3-(N-methyl-N-i
so-amyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-methyl-Nn-hexyl)
amino-6-methyl-7-phenylaminofluorane,
3-(N-ethyl-N-hexyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-
Examples include N-β-ethylhexyl)amino-6-methyl-7-phenylaminofluoran.

These may be used alone or in combination. In particular, many triarylmethane compounds and xanthine compounds such as crystal violet cause little fog and provide high color density (preferably).

In the heat-sensitive recording material of the present invention, in order to further increase the recording sensitivity, 4-cumylphenol, 4-phenylphenol, 4-
- Monophenol compounds such as tert-butylphenol, 4-hydroxybenzoic acid esters such as methyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, etc., or dimethyl 4-hydroxyphthalate, 4-hydroxyphthalic acid Hydroxyphthalic acid esters such as dibenzyl etc. may be added.Also, in order to make the recorded image more solid, 1.1.3-)lis(
2-Methyl-4-hydroxy-5-tert-butylphenyl)butane, 2,2'-methylenebis(6-tert
It may contain so-called hindered phenol compounds such as t-butyl-4-methylphenol), 4,4'-butylidenebis(6-tert-butyl-3-methylphenol), and the like.

Coating liquids containing these materials are generally prepared by dispersing dye precursors, color developers, etc. together or separately using water as a dispersion medium using a ball mill, an attritor, a sand mill, or the like. This coating solution usually contains methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, gelatin, starches, casein, gum arabic, styrene-maleic anhydride copolymer hydrolyzate, ethylene-maleic anhydride copolymer hydrolyzate, etc. Decomposed products, styrene-butadiene copolymer emulsion, polyvinyl alcohol, polyacrylamide, etc. are added in an amount usually in the range of 2 to 30% by weight based on the total solids.

Furthermore, the coating liquid may contain inorganic pigments such as zinc oxide, calcium carbonate, kaolin, talc, etc., water-insoluble binders such as synthetic rubber latex or synthetic resin emulsion, zinc stearate, calcium stearate, etc., as necessary. Metallic soaps, waxes such as paraffin wax, carnauba wax, etc., surfactants, ultraviolet absorbers, etc. can be added.

In the heat-sensitive recording material of the present invention, a generally known method using an air knife coater, a blade coater, etc. can be used to form the recording layer. In addition, the amount of coating liquid applied is usually 2 to 10 g/n as solid content. range is used.

〔Effect of the invention〕

The heat-sensitive recording material obtained by the present invention has excellent performance in that it has high recording sensitivity and excellent high-speed recording properties, is less likely to cause discoloration of recorded images over time, and has a high whiteness of the recording layer.

[Embodiments of the invention]

EXAMPLES Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited thereto.

m-isopropenylphenol in the mixture of Reference Example 1 48.9
A mixed solution of g and 71.3 g of phenol was added over 3 hours. During this time, the reaction temperature was maintained at 80°C. After the addition was complete, stirring was continued for 1 hour at 80°C to complete the reaction.
The catalyst (Amberlyst-15) was removed by filtration.

Most of the phenol was removed from the obtained filtrate under reduced pressure to obtain a concentrate containing 72.5 wt% of 3.4'-(1-methylethylidene)bisphenol (m,ρ-bisphenol A) and 20.8 wt% of phenol. I got it. This concentrate was recrystallized from toluene and then dried under reduced pressure to obtain 65.5 g of white crystals. This white crystal has a melting point (
Measured with Mettler automatic melting point analyzer FP-61) 121
℃ was shown. In addition, as a result of gas chromatography analysis, 3.4'-(
The purity of 1-methylethylidene) bisphenol is 99.
It was 1%.

Reference Example 2 When the white crystals obtained in Reference Example 1 were recrystallized from toluene, 3.4'-(1-methylethylidene)bisphenol with a purity of 99.95% was obtained as white crystals. As a result of measuring this product using DSC (Seiko DSC Model-20), sharp endothermic peaks appeared at 122.2°C and 137.5°C, indicating that it was a mixture of two types of crystals exhibiting different melting points.

Reference Example 3 When the white crystals obtained in Reference Example 2 were recrystallized from chloroform, 3.4'-(1-methylethylidene)bisphenol with a purity of 99.96% was obtained as white crystals.

This substance has a melting point (Mettler automatic melting point analyzer FP-61
(measured at ) only one endothermic peak appeared at 138°C.

Reference Example 4 10g of 75% sulfuric acid aqueous solution was charged into a reactor, and the temperature was set at 40°C.
-/(. Under stirring, a mixed solution of m-isoprope; 2 g of turtle phenol, 10 g of phenol, and 42 g of toluene was added over 30 minutes. During this time, the reaction temperature was maintained at 40°C. The reaction was completed by stirring at ℃ for 5 minutes.

After adding 70 g of ethyl ether to the reaction solution and removing the separated lower layer, the oil layer was washed with a saturated aqueous sodium bicarbonate solution.

After drying the oil layer over anhydrous magnesium sulfate, ether and most of the phenol were distilled off under reduced pressure to obtain 3.4'~(
1-methylethylidene) bisphenol 71.5wt%
, 14.6% phenol, 14.6% IIt%, and 13.9wt% impurities mainly consisting of I-isopropenylphenol dimer. When this concentrate was recrystallized from chloroform L, the purity was 96.7% by gas chromatography analysis, and the melting point (measured with Mettler automatic melting point analyzer FP-61) was 10.
3.4'-(1-methylethylidene)bisphenol having a temperature of 6-111°C was obtained as white crystals.

Example 1 (1) Preparation of liquid A Crystal violet lactone 20g 5% polyvinyl alcohol aqueous solution (Kuraray PVA-105) 100g
This composition was dispersed in a ball mill for 24 hours to obtain liquid A.

(2) Preparation of Solution B 3,4′-(1-methylethylidene)bisphenol obtained in Reference Example 1 80g 5% polyvinyl alcohol aqueous solution (Kuraray PVA-105) 600g
This composition was dispersed in a ball mill for 24 hours to obtain liquid B.

(3) Preparation of liquid C Calcium carbonate (Shiraishi/Brilliant-15) 80
g 1% sodium hexametaphosphate aqueous solution 80 g This composition was dispersed with a homogenizer to obtain liquid C.

(4) Liquids A, B, and C were mixed and stirred to obtain a heat-sensitive coating liquid.

This was coated on 50 g/rd high-quality paper with a dry coating weight of 5.
A heat-sensitive recording material was obtained by coating at a ratio of g/g.

Example 2 By preparing Bfi in Example 1, 3 and 4 obtained in Reference Example 2
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that '-(1-methylethylidene)bisphenol was used.

Example 3 3,4'- obtained in Reference Example 3 by preparing Solution B in Example 1
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that (1-methylethylidene)bisphenol was used.

Comparative Example 1 Heat-sensitive recording paper was prepared in the same manner as in Example 1, except that the low-melting point, low-purity 3.4'-(1-methylethylidene)bisphenol obtained in Reference Example 4 was used in the preparation of Liquid B in Example 1. I got it.

Comparative Example 2 In the BWL preparation of Example 1, 4.4'-(1-methylethylidene)bisphenol was replaced with 4.4'-(1-methylethylidene)bisphenol.
A thermosensitive recording material was obtained in the same manner as in Example 1 except that methylethylidene) bisphenol (p,p-bisphenol A) was used.

Comparative Example 3 A thermosensitive recording material was obtained in the same manner as in Example 1, except that benzyl 4-hydroxybenzoate was used instead of 3.4'-(1-methylethylidene)bisphenol in the preparation of liquid B in Example 1. Ta.

Comparative Example 4 In the preparation of Solution B in Example 1, 50 g of 4,4'-(1-methylethylidene)bisphenol and 30 g of dimethyl 4-hydroxyphthalate were used instead of 3.4'-(1-methylethylidene)bisphenol. A thermosensitive recording material was obtained in the same manner as in Example 1 except that the following was used.

Table 1 shows the results of performance evaluation of the heat-sensitive recording material thus obtained. The following evaluation method was used.

(1) Color density: Color was developed by contacting with a heat stamp at 180° C. for 5 seconds, and the color density was measured 10 minutes later using a Macbeth densitometer (RD-10OR, using an amber filter).

(2) Capri: The skin density of the heat-sensitive recording medium was measured using a Macbeth densitometer (all over the area). The smaller the numerical value, the less clutter and the higher the degree of whiteness.

(3) Moisture resistance stability of colored image: After leaving the heat-sensitive recording medium colored in (1) for 24 hours at 40°C and 90% relative humidity, measure the color density using a Macbeth density needle (gold ball). The remaining rate of color density was calculated using the following formula.

Claims (1)

[Claims] (1) A heat-sensitive recording material characterized in that highly purified 3,4'-(1-methylethylidene)bisphenol having a melting point in the range of 120 to 140°C is used as a color developer.