JPS58211496A - Heat-sensitive recording material - Google Patents

Abstract

PURPOSE:To enhance heat sensitivity and degree of whiteness, by using at least one phenolic compound and a specified amino compound in combination as color developer components in a color forming layer, in a heat-sensitive recording material comprising a leuco dye. CONSTITUTION:At least one phenolic compound such as 4,4'-isopropylidene-bisphenol and compounds of formulas I , II (wherein each of R1, R2, R3 is hydrogen, an alkyl group, an aromatic group, an acyl group or halogen; X is a sulfur or oxygen atom) are used as color developer components for a leuco dye such as a triphenylmethane base dye or a fluoran base dye. The ratios of the quantities of the above components are such that the quantity of the phenolic compound is 20-80wt%, while the quantity of the compounds of formulas I and II is 80- 20wt%, and in the entire body of the color forming layer, the quantity of the leuco dye is 5-30wt%, that of the compounds of formulas I , II is 40-80wt% and that of a binder is 2-20wt%. An additive, an adjuvant or the like is appropriately added, in addition to the above components.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a heat-sensitive recording material containing a leuco dye as a coloring agent, and an object thereof is to provide a heat-sensitive recording material having high sensitivity and high whiteness.

Thermosensitive recording materials generally consist of a support such as paper, synthetic paper, or plastic film provided with a thermosensitive coloring layer containing a thermochromic composition as a main component, and can be heated with a thermal head, thermal pen, laser beam, etc. A colored image is obtained. Compared to other recording materials, this type of recording material does not require complicated processing such as development and fixing, can produce records in a short time using relatively simple equipment, and generates less noise and pollutes the environment. ,
Due to its low cost and other advantages, it is used not only for copying books and documents, but also as a recording material in a wide range of applications such as electronic computers, facsimiles, ticket vending machines, labels, and recorders. Thermochromic compositions used in such heat-sensitive recording materials generally consist of a color former and a color developer that causes the color former to develop color when heated. Examples of the color former include lactone, lactam, or colorless or spiropyran ring-containing compositions. Light-colored leuco dyes are used, and various acidic substances such as organic acids and phenolic substances are used as color developers. A recording material using a combination of a color forming agent and a color developing agent has the advantage that the resulting image has a particularly clear color tone, has a high background whiteness, and has excellent weather resistance of the image (dye image). , is widely used.

However, in recent years, heat-sensitive recording methods have replaced other conventional recording methods, and as demand has increased, so has the demand for improved quality of heat-sensitive recording materials used in this method. There is a strong demand for improvements in whiteness, storage stability, etc. By the way, materials that affect the quality of the heat-sensitive recording material as mentioned above include color formers, color developers, binders that bind or protect these, and other auxiliary agents (such as dispersants and pigments). However, the color developer has the greatest influence. Conventionally, bisphenol A has been commonly used as a color developer due to its excellent color-forming properties. A whiteness of 1 is insufficient, and improvements in this respect have become necessary. In order to further increase the sensitivity of this heat-sensitive recording material using bisphenol A, the present inventors have continued to conduct extensive research into using other phenolic compounds in combination. Although the sensitivity can be further improved by using the phenolic compound in combination, there is a problem in that the greater the color developing ability of the phenolic compound, the greater the fog on the background. That is, although this problem is observed even in the coating liquid state, fogging is even more severe after the thermal paper is stored over time.

The inventors have overcome the aforementioned drawbacks found in the prior art,
As a result of intensive research in order to develop a heat-sensitive recording material that does not cause background fog, has excellent whiteness, and has significantly increased thermal sensitivity, we found that the general formula (n) (where "l + R2 + R3 is hydrogen, It has been discovered that the object can be achieved by using a combination of a compound represented by (representing an alkyl, aromatic group, anru or halogen, and X represents a sulfur or oxygen atom) and a phenolic compound as a color developer component. , we have completed the present invention.

In the general formulas (1) and (I+), "l + "
The alkyl in 2 +R3 has 1 to 30 carbon atoms.
．． Preferably, those of 1 to 4 are mentioned, and... Examples of rogens include chlorine, bromine, fluorine, etc., and aromatic groups include phenyl, methylphenyl, ethylphenyl, fluorobylphenyl, isopropylphenyl. Such aryl groups and their nuclear substituted products, such as . General formula (1)
Specific examples of the compound represented by and ([1)] include those shown below, but of course the compounds are not limited to these.

1,3-diphenylthiourea, 1,3-di(p-methylphenyl)thiourea, 1,3-di(p-chlorophenyl)thiourea, 1,3-di(m-chlorophenyl)thiourea, 3-di(0-methylphenyl)thiourea, 1.
3-di(m-methylphenyl)thiourea, 1,3-di(
o-chlorophenyl)thiourea, 1,3-di(p-bromophenyl)thiourea, 1,3-di(m-bromophenyl)thiourea, 1,3-di(0-bromophenyl)thiourea, 1 .3-di(p-ethylphenyl)thiourea, 1
, 3-di(m-ethylphenyl)thiourea, 113-di(o-ethylphenyl)thiourea, ], 3-di(p-isopropylphenyl)thiourea, ■, 3-di(p-isobutylphenyl) Thiourea, 1,3-di(p-yneamylphenyl)thiourea, 1,3-di(p-octylphenyl)thiourea, 1,3-di(p-lauryl phenyl)
Thiourea, 1,3-di(p-stearylphenyl)thiourea, 1-phenylthiourea, l-6-(p-methylphenyl)thiourea, and l-(p- chlorophenyl)thiourea, 1-(
m-chlorophenyl)thiourea.

In the present invention, a combination of the urea or thiourea derivative and a phenolic compound is used as a color developer component, and specific examples of the phenolic color developer in this case are as follows.

4147-Ingropylidene-bisphenol 4.4'
-(1,1-chlorohexylidene)bisphenol 4I4
7-isopropyritine bis(2-+e10-butylphenol) 4.4'-impropylide/bis(2-isopropylphenol) 4.4'-isopropyritine bis(2
-5ee-butylphenol)4.47-thiobis(2
-1crt-butyl-5-methylphenol)4.4'
-thiobis(2-isopropyl-5-methylphenol)4I4'-thiobis(2-jcrt-butylphenol)4.4'-thiobis(2-sec-butylphenol)4.4'-bisphenol sulfo/4I4'-his(2 -Methylphenol) sulfone4.
4'-bis(2-isopropylphenol)sulfone 4
-Hydroxy-4'l' lorodiphenylsulfone 7
- 4-hydroxy-4'-promodiphenylsulfone 4-hydroquine-4'-benzyloxy-diphenylsulfone 4-hydroxy-inodyl benzoate 4-hydroxy-phenethyl benzoate 4-hydroquine-benzoate α-phenethyl glotocatechu Phenethyl acid benzyl protocatechuate.

In the present invention, a phenolic compound and general formula (1)
The ratio of the compounds of (II) and (II) is arbitrary, but preferably 20 to 80% by weight of the phenolic compound and the general formula (+)
The proportion of the compounds (■) and (■) is 80 to 20% by weight.

The leuco dye used in the present invention is usually a colorless or light-colored leuco dye.

(a) Leuco compound of triphenylmethano dye represented by the following general formula (1): (wherein X, Ry and 8 are hydrogen, hydroxyl group, halogen, alkyl group, nitro group, amine group, dialkylamine group, monoalkyl group, and allyl group.) Specific examples of the above-mentioned leuco 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-dimethylamino phenyl)-6-dibutylaminophenyl 3.3-bis(p-dimethylaminophenyl)-6-chlorophthalide 3.3-bis(p-dibutylaminophenyl)phthalide (b) Fluoran dyes represented by the following general formula Leuco compound: 9-tz In the formula, R.IRY and 几. are the same as in the above (a).

Specific examples of the above compounds are as follows.

3-Cyclohexylamino-6-chlorofluorane 3- (N,N-diethylamino)-5-methyl-7-
(N,N-dibenzylamino)fluoran 3-dimethylamino-5,7-dimethylfluoran 3-diethylamino-7-methylfluoran 3-diethylamino-7,8-benzfluoran ←→ Fluoran dye leuco Compound: 10- 3-diethylamino-6-methyl-7-chlorofluoran 3-pyrrolidino-6-methyl-7-anilinofluoran 2-i N-(3'-)'J chloromethylphenyl)amine) -6-dinithylaminofluorane 2-i 3,6-bis(diethylamino)-9-(o
-chloranilino)xanthylbenzoic acid lactam) lactone compound represented by the following general formula: R2H.
4 11 X.

In the formula, 几1 and 几2 represent hydrogen, a lower alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted phenyl group, a cyanethyl group, or a β-no-rogenated ethyl group, or R11 and R2 combine to form +CH2
*-4+ +OH2+5 or +OH2+,, o
(Represents 7cl-12+i!, 几3 and 几4 represent hydrogen, a lower alkyl group, an alkyl group, an amino group or a phenyl group, and either one of Ha and 几4 is hydrogen, and XI + X2 and X3 is hydrogen, lower alkyl group,
Represents a lower alkoxyl group, a halogen atom, a halogenated methyl group, a nitro group, an amine group, or a substituted amine group; Represents an integer from ~4.

Specific examples of the above compounds are as follows.

3-(2'-hydroxy-4'-dimethylaminophenyl) -3-(2'-methoxy-57-chlorophenyl)phthalide a -(2'-hydroxy-5'-dimethylaminophenyl) -3-(2 '-methoxy-5'-nitrophenyl)phthalide 3- (2'-hydroxy-4'-diethylaminophenyl) -3-(2'-methquine-5'-methylphenyl)phthalide 3- (2'-methoxy- 47-dimethylaminophenyl)-3-(2'-hydroxy-47-chloro-5'
-methylphenyl)phthalide.

As the binder for bonding and supporting the thermosensitive coloring layer on the support, various binders as shown below can be used.

Water-soluble ones such as hollyhinyl alcohol, methoxycellulose, hydroquine ethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch, gelatin, etc.
Alternatively, aqueous emulsions such as polystyrene, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate-1, etc. can be used as the binder.

Furthermore, if necessary, conventional auxiliary additives such as fine powders of calcium carbonate, silica, alumina, magnenia, talc, titania, 13-barium sulfate, and aluminum stearate may be added to the heat-sensitive coloring layer. , the clarity of colored images can be improved.

To produce the heat-sensitive recording material of the present invention, an aqueous solution containing a leuco dye, a compound of the above general formula, and a binder as main components may be coated on a support such as paper or synthetic paper and dried. Here, the amounts of the leuco dye, the compound of the above general formula, and the binder used are 5
-30% by weight, 40-800-80% by weight and 0% by weight are suitable. In addition, the amount of adhesion of the thermosensitive coloring layer to be formed is 2 to 2.
Approximately 101/go is appropriate. The coating liquid contains talc, wax,
Auxiliary agents such as surfactants and antifoaming agents can be added.

Examples are shown below. Note that parts and q are parts by weight and % by weight, respectively.

Example [Liquid A] 10% aqueous solution of 3-(N~methyl-N-cyclohexyl-14-hydroxyethyl cellulose 10
Department water
Disperse in a 30 part ball mill for 20 hours.

[Liquid B]

Color developer [I] in the table 15 parts 10% aqueous solution of hydroquine ethyl cellulose 15 parts water
45
Disperse in a ball mill for 10 hours.

[Liquid C]

Color developer marked with [+1] in the table 15 parts 10% aqueous solution of hydroxyethyl cellulose 15 parts water
4
Disperse in a 5-part ball mill for 10 hours.

[Liquid D]

Carbonic acid 40 parts Ammonia adduct of isobutylene/maleic anhydride copolymer 10 parts
Aqueous solution 20 parts carunium stearate 5 parts water
160 parts ball mill 10
Distribute time.

The A liquid, B liquid, C liquid and D liquid obtained as above were mixed, and the mixture was coated and dried on soil paper with a basis weight of 50 f/m'' so that the dry adhesion amount was 6 f/m''. A heat-sensitive coloring layer was provided to obtain heat-sensitive recording paper. The evaluation results are shown in the table below.

The maximum concentration is 120% using a commercially available heat 44 group tester.
The image density when printed at ℃ is also shown, along with the background density at that time. Concentrations were measured using a Macbeth densitometer.

From the above results, it can be seen that the heat-sensitive recording material of the present invention not only improves the sensitivity but also significantly improves the whiteness of the background.

Patent applicant Ricoh Co., Ltd. Agent: Patent Attorney Toshiaki Ikeura 18-

Claims (1)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive color-forming layer containing a leuco dye and a color developer component that causes the leuco dye to develop color when heated is provided on a support, the heat-sensitive color-forming layer contains, as a color developer component, A heat-sensitive recording material comprising a combination of at least one phenolic compound and at least one amino compound represented by the following general formulas (I) and (I+). (In the formula, 几1 + "2 + "3 is hydrogen, alkyl,
represents an aromatic group, acyl or )-rogen, and X represents a sulfur or oxygen atom)