JPH02284986A - Heat-sensitive recording material - Google Patents

Abstract

PURPOSE:To obtain the subject material excellent in coloring sensitivity and preservation stability with hardly any surface fog by blending a bis(2- arylthioethyl)oxalate in a coloring layer. CONSTITUTION:The objective material obtained by blending a bis(2-arylthioethyl) oxalate expressed by the formula (R is lower alkyl, lower alkoxy, aryl, aralkyl, acyloxy or halogen; n is 0-3) in an amount of normally 0.1-10 pts.wt. based on 1 pt.wt. coloring dye in a coloring layer. Furthermore, the above-mentioned compound is synthesized by, e.g. reacting oxalic acid (dichloride, dimethyl, diethyl or dilower alkyl ester) with a 2-arylthioethanol.

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 characterized in that bis(2-arylthioethyl) oxalate is blended as a sensitizer. .

[Prior art and problems to be solved by the invention] Thermosensitive recording materials consist of a support such as paper, synthetic paper, resin film, etc., and a color-forming substance that is normally colorless or light-colored, such as leuco dye, and which develops color when heated. A coloring system consisting of a color developer, an aggravating agent,
It is equipped with a heat-sensitive coloring layer in which a binder and other additives are dispersed, and when a heat-generating element such as a thermal head or a thermal pen comes into contact with this recording medium in a recording device, the dye and color developer react to produce a black color. etc., and are recorded.

Compared to other recording materials, heat-sensitive recording materials have advantages such as being able to record in a short time, generating less noise, and being inexpensive. Widely used as recording material for ticket vending machines, etc.

Conventionally, as colorless or light-colored color-forming substances, for example, leuco dyes having a lactone, lactam or spiropyran ring have been used, and various acidic substances have been proposed as color developers, and in particular, phenolic compounds, for example, Bisphenol A, p-hydroxybenzoic acid benzyl ester, etc. were used alone or in combination of several kinds, but
When these phenols are used, it is difficult to achieve high speed and high density recording, and there are also disadvantages of uneven coloring or discoloration during storage.

So the coloring property v! Attempts have been made to achieve high sensitivity by using a sensitizer, which is a third substance, as a color developer. For example, terphenyl, various waxes, dimethyl phthalate, stearamide, phenyl benzoate, bis(vinyloxyethoxybenzene, p-acetyloxybiphenyl, etc.) have been proposed.

However, these sensitizers are not effective unless used in large quantities, and do not fully satisfy the demands for high sensitivity of heat-sensitive recording materials.Furthermore, they may cause fogging or discoloration during storage. However, it has some disadvantages and is not practically satisfactory.

For this reason, studies have been conducted on sensitizers that eliminate these drawbacks. For example, JP-A-61-242884 discloses the use of bis(arylthio)alkanes, and JP-A-62-5879 discloses the use of bis(arylthio)alkanes. is bis(phenoxyethyl)
Although it has been proposed to use dibasic acid ester compounds such as oxalate, and oxalate esters such as dibenzyl oxalate in JP-A No. 64-1583, it has been proposed to use dibasic acid ester compounds such as oxalate. Even when it is used, it not only has insufficient sensitivity (but also has poor background fog and storage stability, and is also poor in oil resistance, so it is unsatisfactory for practical use).

[Means to solve the problem]

The inventors of the present invention have made extensive studies to eliminate these drawbacks, and have found that when bis(2-arylthioethyl) oxalate is used, not only is the color development sensitivity good, but there is little background fog. Furthermore, the present inventors have discovered that the storage stability is also significantly improved.

That is, the present invention generally comprises a color-forming substance that is colorless or light-colored;
In a heat-sensitive recording material provided with a coloring layer containing a color developer that causes the substance to color when heated, bis(2-arylthioethyl)oxalate represented by the following formula is contained in the coloring layer. The present invention provides a heat-sensitive recording material having the following characteristics.

(In the formula, R represents a lower alkyl group, a lower alkoxy group, an aryl group, an aralkyl group, an acyloxy group, or a halogen atom. n represents 0 to 3.) Hereinafter, the present invention having the above summary will be explained in more detail. do.

In the above formula, the lower alkyl group represented by R includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, nibutyl, tertiary butyl, etc., and the lower alkoxy group includes the lower alkyl groups listed above. examples include lower alkoxy groups, and examples of aryl groups include phenyl,
Tolyl, xylyl, etc. are mentioned, and aralkyl groups include benzyl, phenethyl, α-methylbenzyl, α, α
Examples of the acyloxy group include acetyloxy, propionyloxy, and benzoyloxy, and examples of the hydrogen atom include chlorine, bromine, and fluorine.

Therefore, the following compounds are representative examples of bis(2-allylthioethyl)oxalate used in the present invention.

Nα1 Bis(2-phenylthioethyl)oxalate koji 2 Bis(2-(4-methylphenylthio)ethyl)
Oxalate koji 3 Bis(2-(4-methoxyphenylthio)ethyl)oxalate 4 Bis(2-(2,4-dimethylphenylthio)ethyl)oxalate koji 5 Bis(2-(4-phenylphenylthio)ethyl) Oxalate Nα6 Bis(2-(4-benzylphenylthio)ethyl)oxalate Nα7 Bis(2-(4-acetoxyphenylthio)ethyl)oxalate N018 Bis(2-(4-chlorophenylthio)ethyl)oxalate Used in the present invention Bis(2-arylthioethyl)oxalate can be easily produced by a conventional esterification reaction in which oxalic acid, oxalic acid dichloride, or a di-lower alkyl ester of oxalic acid such as dimethyl oxalate or diethyl oxalate is reacted with 2-arylthioethanol. I can do it.

A specific synthesis example is shown below.

Synthesis example [Synthesis of bis(2-phenylthioethyl)oxalate] 2-phenylthioethanol 16.2g, oxalic acid 4.5g
, para-toluenesulfonic acid 0.2g and toluene 40d
The mixture was stirred under reflux for 8 hours while removing the water produced.

After removing the theoretical amount (1.8 d) of water, it was cooled and 50 Il of toluene was added. i! was added and washed sequentially with water, 10% aqueous sodium bicarbonate solution, and water. After dehydration, the solvent was distilled off and recrystallized from ethanol to obtain a white powder with a melting point of 86°C.
I got g.

As a result of infrared spectroscopic analysis, the following characteristic absorption was observed, confirming that it was the desired product.

176 QC! l-': Ester 740cn+-': Thioether Various dyes are well known as the normally colorless to light-colored coloring substance used in the present invention, and are used in general pressure-sensitive recording paper, heat-sensitive recording paper, etc. There are no particular restrictions as long as there are.

Specific examples of these dyes include (1) triarylmethane compounds; for example, 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (commonly known as crystal violet lactone), 3-( p-dimethylaminophenyl)-3(1,2-dimethyl-3-indolyl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-phenyl-3-indolyl)phthalide,
3゜3-bis(9-ethyl-3-carbazolyl)-5 dimethylaminophthalide, 3.3-bis(2-phenyl-
3-indolyl)-5-dimethylaminophthalide etc., (
2) Diphenylmethane compounds; for example, 4,4-bis(dimethylamino)benzhydrin benzyl ether,
N-2,4,5-trichlorophenylleucoauramine, etc., (3) xanthine compounds; for example, rhodamine-
β-anilinolactam, 3-dimethylamino-7-medoxyfluoran, 3-dimethylamino-6-medoxyfluoran, 3-diethylamine-7-medoxyfluoran, 3-dimethylamino-7-chlorofluoran Oran, 3-
diethylamino-6-methyl-7-chlorofluorane,
3-diethylamino-6,7-dimethylfluorane, 3
-(N-Ethyl-p-toluidino)-7-methylfluorane, 3-diethylaminolfur N-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-
Methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-
N-methyl-N-benzylaminofluorane, 3-diethylaminol 6-methyl-f-xylidinofluorane,
3-diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-diethylaminofluorane, 3-(N-ethyl-p-1-
luidino)-6-methyl-7-(p-)luidino)fluoran, 3-diethylamino-7-octylaminofluoran, 3-diethylamino-7-(2-chloroanilino)fluoran, 3-diethylamino-6-methyl-7
-Ayurinofluoran, 3-diethylamino-6-chloro-7-(β-ethoxyethylamino)fluoran, 3
-diethylamino-7-(2-carbomethoxyphenylamino)fluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilite fluoran, 3
-(N-methyl-N-n-amylamino)-6methyl-7-anilinofluorane, 3-(N-ethyl-N-n-
amylamino)-6-methyl-7-anilitofluorane, 3-(N-methyl-Nn-hexylamino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N
-n-hexylamino)-6-methyl-7-anilinofluorane, 1-(N-ethyl-N-β-ethylhexylulamino)-6-methyl-7-anilinofluorane, 3
-dibutylamino-6-methyl-7anilinofluorane, 3-dibutylamino-7-(2-chloroanilino)fluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3(N-ethyl-p -Toluidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6=
Methyl-7-anilinofluorane, 3-pyrrolidino-6
-methyl-7-p-butylphenylaminofluorane,
3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-anilinofluorane, 3-(N-isopropyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3-diethylamine-6-chloro-1-r-
(4) Thiazine-based compounds such as chloropropylaminofluorane; for example, benzoylleucomethylene blue ρ-
nitrobenzoylleucomethylene blue, etc., (5) spiro-based compounds; for example, 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylcapto(3-methoxybenzo)spiropyran, etc. These dyes can also be used as a mixture of several types.

Furthermore, the color developer used in the present invention includes, for example, p
-octylphenol, p-tert-butylphenol, p
-Phenylphenol, p-hydroxyacetophenone, α-naphthol, β-naphthol, p-tertiary octylphenol, 2°2°-dihydroxybiphenyl, bisphenol A, 1,1-bis(p-hydroxyphenyl)butane, 2,2 -bis(4-hydroxyphenyl)butane, 2,2-bis(3-methyl-4-hydroxyphenyl)butane, 2,2-bis(3゜5-dimethyl-4-hydroxyphenyl)propane, 2 .2-bis(
3,5-dichloro-4-hydroxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, bis(3
, 4-dihydroxyphenyl) sulfone, bis(4-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4-isopropoxydiphenyl sulfone, 1.1
-Bis(4-hydroxyphenyl)cyclohexane, bis(4-hydroxyphenyl)ether, p-hydroxybenzoic acid, ethyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, bis(4- Hydroxyphenyl)acetic acid butyl ester, 1.1°3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1. l, 3-1-
Phenols such as lis(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, bis(2-(4-hydroxyphenylthio)ethoxycomethane, 4-hydroxyphthalic acid dimethyl ester); oxalic acid, maleic acid acids, aliphatic carboxylic acids such as tartaric acid, citric acid, succinic acid, stearic acid, behenic acid; benzoic acid, tert-butylbenzoic acid, phthalic acid, gallic acid, salicylic acid, isopropyl salicylic acid, phenyl salicylic acid, 3.5-di Tertiary-butylsalicylic acid, 3-methyl-5-benzylsalicylic acid, 3,5-di(α-methylhensyl)salicylic acid, 3
- Aromatic carboxylic acid M such as phenyl-5-(α,α-dimethylbenzyl)salicylic acid and zinc, magnesium, aluminum, calcium,
Polyvalent metal salts such as titanium, manganese, tin, and nickel; inorganic color developer of acid clay, activated clay, acpal guide, hentonite, colloidal silica, aluminum silicate, magnesium silicate, zinc silicate, tin silicate, calcined kaolin, talc, etc. Examples include drugs.

Bis(2-arylthioethyl) used in the present invention
The oxalate, the color-forming colorless dye, and the color developer are processed using a grinding machine such as a ball mill, an atlyzer, or a sand grinder, or an appropriate emulsifying device, for example, with a particle size of 0.1 to 10.
It is made into microparticles with a diameter of μ, and is made into a coating liquid by adding various additive materials depending on the purpose.

This coating solution usually contains polyvinyl alcohol, hydroxyethylcellulose, methylcellulose, polyacrylamide polymer, starch, styrene-maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer, styrene-
Binders such as butadiene copolymers or modified products thereof, and fillers such as silane, kaolin, diatomaceous earth, talc, titanium dioxide, calcium carbonate, magnesium carbonate, aluminum hydroxide, and melamine are blended.

In addition, metal soaps, amides, waxes,
Light stabilizers, waterproofing agents, dispersants, antifoaming agents, etc. can be used.

The desired heat-sensitive recording material can be obtained by applying this coating liquid to the film and various films.

The amount of bis(2-arylthioethyl) oxalate used in the present invention varies depending on the required performance and recording suitability, as well as the type and amount of other additives used in combination.
Although not particularly limited, 1 to 10 parts of O is usually used for 1 part of the color-forming dye.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the present invention is not limited by the following examples.

Example-1 20 g of 3-(N-ethyl-N-isoamylamino)6-methyl-7-anilite fluorane and 100 g of a 10% polyvinyl alcohol aqueous solution were sufficiently ground to obtain a dye dispersion (liquid A). .

20 g of bisphenol A and 100 g of a 10% polyvinyl alcohol aqueous solution were sufficiently ground to obtain a color developer dispersion (liquid B).

20 g of the sample compound and 100 g of a 10% polyvinyl alcohol aqueous solution were sufficiently ground to obtain a dispersion liquid (liquid C).

20 g of zinc stearate and 100 g of a 10% aqueous polyvinyl alcohol solution were sufficiently ground to obtain a dispersion (liquid D).

Liquids A, B, C, D and finely powdered silica were mixed at a weight ratio of 11:2:0.2:0.5 and sufficiently dispersed to obtain a coating liquid.

This coating liquid was applied to a thickness of 32 μm on a 50 g/rrf base paper and dried to form a heat-sensitive recording material.

Using the obtained thermal paper, a thermal printing device (THPMD:
The color density of the recorded image printed by changing the pulse width using a Macbeth densitometer (R manufactured by Macbeth Co., Ltd.)
D-933 type).

Further, the colored thermal paper was stored for 8 hours under drying conditions of 60° C., and changes in density of the background and colored areas were measured to evaluate storage stability.

Further, the colored thermal paper was smeared with dioctyl phthalate and stored for 8 hours under drying conditions at 60° C., and changes in density in the background and colored areas were measured to evaluate oil resistance.

The results are shown in Table-1.

Table Example-2 3-(N,N-dibutylamino)-6-methyl-7-anirithufluoran was used instead of 3-(N-ethyl-N-isoamylamino)6-methyl-7-anilithufluoran. A heat-sensitive recording material was prepared in the same manner as in Example-1 except for the use, and the same tests as in Example-1 were conducted.

The results are shown in Table-2.

〔Effect of the invention〕

As is clear from the results in Tables 1 and 2, bis(2-phenoxyethyl) is a known oxalate ester compound.
Oxalates still have insufficient sensitivity and storage stability, and have the disadvantage of extremely poor oil resistance.

Furthermore, 1,4-bis(phenylthio)butane, which is a known sulfur-containing compound, has completely insufficient sensitivity, and furthermore, has the drawbacks of background fogging after storage and extremely poor oil resistance.

On the other hand, the heat-sensitive recording material of the present invention using bis(2-arylthioethyl) oxalate has extremely excellent effects in all test items of sensitivity, storage stability, and oil resistance. It is clear that there are

Claims (1)

[Scope of Claims] In a heat-sensitive recording material provided with a color-forming layer containing a normally colorless or light-colored color-forming substance and a color developer that causes the substance to develop color when heated, the color-forming layer has a color-forming layer represented by the following formula: screws (2)
- A heat-sensitive recording material characterized by containing arylthioethyl) oxalate. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R represents a lower alkyl group, lower alkoxy group, aryl group, aralkyl group, acyloxy group, or halogen atom. n represents 0 to 3.)