JPH0336087A - Thermal recording material - Google Patents

Abstract

PURPOSE:To improve the storage stability against heat, hygroscopic moisture and an oil component by incorporating at leat one kind of a tetraphenol compound represented by a specific formula in the color forming layer of a thermal recording material. CONSTITUTION:At least one kind of a tetraphenol compound represented by formula (wherein R1 is a tertiary butyl group, a tertiary amino group or a cyclohexyl group) is contained in the color forming layer of a thermal recording material. A color forming leuco dye, a coupler, the tetraphenol compound and other additives such as a sensitizer or the like are treated by a grinding machine such as a ball mill, an atomizer mill or a sand grinder or a proper emulsifying apparatus to prepare a coating solution containing fine particles, for example, having a particle size of 0.1 - 10mum. This coating solution is applied to paper or various films to obtain an objective 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, the present invention relates to a heat-sensitive recording material that has improved storage stability against heat, moisture, and oil by adding a specific tetraphenol compound. Regarding heat-sensitive recording materials.

[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 color developing system consisting of a color developer, a sensitizer,
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. It is widely used as a recording material for ticket vending machines, etc.

However, these heat-sensitive recording materials have the disadvantage that the printed areas turn white or the non-printed areas develop color during storage, and this phenomenon is particularly likely when stored at high temperatures or when stored in a humid atmosphere. If there are fingerprints or if there is contact with vinyl chloride sheets, heat, heat, etc.
It is thought that the influence of moisture or oil is significant.

It is extremely important to improve the stability during storage, and attempts have been made to improve the storage stability by adding various third components.

For example, JP-A-58-57990 and Jikai-58-
Publication No. 87089 proposes adding a specific trisphenol compound for the purpose of improving storage stability.
Furthermore, JP-A-59-185693 proposes the use of metal salts of aliphatic organic acids in order to improve solvent resistance when aromatic carboxylic acids are used as color developers.
JP-A No. 59-39593 proposes the combined use of a specific metal benzoate in order to improve the storage stability when a phenolic color developer is used;
No. 2-169683 proposes the use of specific cyclohexylphenol derivatives.

However, the improvement effects achieved by these methods are not sufficient, and there has been a strong desire to find a more effective method.

[Means to solve the problem]

As a result of extensive research to find additives that improve the storage stability of heat-sensitive recording materials, the present inventor found that a specific tetraphenol compound has an extremely superior effect and develops color even after storage under harsh conditions. The inventors have discovered that there is very little whitening of the area and very little background fog, and have arrived at the present invention.

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 color-forming layer containing a color developer that causes the substance to develop color when heated, the color-forming layer contains the following formula (I
) The present invention provides a heat-sensitive recording material with improved storage stability, which is characterized by containing at least one type of tetraphenol compound represented by the following.

(In the formula, R represents a tertiary butyl group, a tertiary amyl group, or a cyclohexyl group.) Hereinafter, the present invention having the above-mentioned summary will be explained in more detail.

The compound represented by the above formula (I) used in the present invention can be easily synthesized by, for example, reacting 2R15-methylphenol with terephthalaldehyde or isophthalaldehyde, and representative examples thereof include: The following are listed.

Zenno(I,4-bis[bis(3-tert-butyl-4-hydroxy-6methylphenyl)methyl]benzene)(I,4-
Bis[bis(3-tertiary amyl-4-hydroxy-6methylphenyl)methyl]benzene) Among these compounds, a compound in which R1 is a cyclohexyl group is preferred because of its great effect.

less than, Specific examples of the effectiveness of the compounds of the present invention are shown below. figure.

Bottom example (No. 1 compound bottom) Take 40 g of methanol, 40 g (0.21 mol) of 2-cyclohexyl-5 methylphenol, and 14 g of concentrated hydrochloric acid, heat it to 60"C, and then Aldehyde 6.
A methanol solution of 7 g (0.05 mol) was added dropwise over a period of 2 hours, and after the addition was completed, the reaction was continued for an additional hour under reflux.

After adding 200 g of an aromatic hydrocarbon solvent and removing methanol and hydrogen chloride, the mixture was washed with water. After removing the solvent, the obtained solid was treated with butanol under reflux.

The obtained powder was filtered and dried to obtain 40 g of white powder product.
(yield 93%).

The product showed no melting point and decomposed at 295°C.

Various dyes are well known as the usually colorless or light-colored color-forming substances used in the present invention, and there are no particular limitations as long as they are used in general pressure-sensitive recording paper, heat-sensitive recording paper, etc. .

Specific examples of these dyes include (I) triarylmethane compounds; for example, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (commonly known as crystal violet lactone), 3-( p-dimethylaminophenyl)-3-(I,2-dimethyl-3-indolyl)phthalide, 3-(P-dimethylagodiphenyl)-3-(2-phenyl-3-indolyl)phthalide, 33-bis(9 -ethyl-3-carbazolyl)-5 dimethylaminophthalide, 33-bis(2-phenyl-3
-indolyl)-5-dimethylaminophthalide etc., (2
) diphenylmethane compounds; for example, 4,4-bis(
Dimethyla)) 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-dimethylamine-7-chlorofluoran,
3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6 -chloro-
7-(β-ethoxyethylamino)fluoran, 3-diethylamino-6-chloro-7-anilinofluoran,
3-diethylamino-6-chloro-7-γ-chloropropylagonofluorane, 3-diethylamino-6,7-
Dimethylfluorane, 3-diethylamino-7-medoxyfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3-diethylamino-
7-N-methylaminofluorane, 3-diethylamino-7-sibenzylaminofluorane, 3-diethylamino-2-N-methyl-N-benzylaminofluorane,
3-diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-diethylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-(
2-chloroanilino)fluoran, 3-diethylamino-7-(2-carbomethoxyphenylamino)fluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-dibutylamino-7-(2-chloroanilino) Fluoran, 3-dibutylamino-7-(2-fluoroanilino)fluoran, 3-(N-methyl-N-
n-amylami))-6-methyltoanilinofluorane, 3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluorane, 3-(N-methyl-N
(N-hexylamino))-6-methyl-7-anilinofluorane, 3-(N-methyl-N-cyclohexylamino)-6-methyl-7-anilinofluorane, 3-(N
-ethyl-p-toluidino)-6-methyl-7-(p-
toluidino)fluorane, 3-(N-ethyl-p-toluidino)-7-methylfluorane, 3-(N-ethyl-
p-)luidino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isoamylamino)-6
-Methyl-7-anilinofluorane, 3-(N-ethyl-N-n-amyl))-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-n-hexyl) -6-methyl-7-anilinofluorane, 3-(N
-ethyl-N-β-ethylhexylluaξ))-6-methyl-7-anilinofluorane, 3-(N-ethyl-N
-isopropylamino)-6-methyl-7-anilinofluorane, 3-(N~ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluorane,
3-piperidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl 7-T)-butylphenylagonofluorane, etc. (4 ) Thiazine compounds; for example, benzoylleucomethylene blue, p-nitrohendiylleucomethylene blue, etc.; (5) Spiro compounds; for example, 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3-benzylspirodini Examples include naphthopyran and 3-methylnat(3-methoxybenzo)spiropyran, and several types of these dyes may be used in combination.

As the color developer used in the present invention, for example, 4.4
°-dihydroxybiphenyl, 4.4"methylenebisphenol, 4,4"~butoxycarbonylmethylenebisphenol, 2.2-bis(p-hydroxyphenyl)
Propane (bisphenol A), 1.1-bis(p-hydroxyphenyl)butane, 2.2-bis(4-hydroxyphenyl)hebutane, 2.2-bis(3-methyl 4
-hydroxyphenyl)propane, 2,2-bis(3,
5-dimethyl-4-hydroxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, bis(3-allyl-4-hydroxyphenyl)sulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4
, 4'-cyclohexylidene bisphenol, bis(4
-hydroxyphenyl)ether, 4.4'-thiobis(2-tert-butyl-5-methylphenol), 1. 2bis(4-hydroxyphenylthio)ethane, 1.5-bis(4-hydroxyphenylthio)3-oxapencune, 1. 7-bis(4-hydroxyphenylthio)-3
, 5-dioxahebutane, 1.8-bis(4-hydroxyphenylthio)3.6-thioxaoctane, ethyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, 1. 5-pentamethylene bis(p-hydroxybenzoate), 1.6-
Examples include hexamethylene bis(p-hydroxybenzoate).

Furthermore, conventionally used sensitizers can also be added to the heat-sensitive recording material of the present invention. Examples of the sensitizer include thermofusible substances with a melting point of 60 to 200"C, such as 2.6-isopropylnaphthalene, 2,3.6-)dimethylnaphthalene, 2°3-dimethylnaphthalene, 1,
2,3.4-tetramethylnaphthalene, 4-benzylbiphenyl, m-terphenyl, 1.2-bis(4-methylphenyl)ethane, 1,2-bis(2,3-dimethylphenyl)ethane, 1. 2-bis(3,4-dimethylphenyl)ethane, 1,2-bis(2,4゜5-trimethylphenyl)ethane, dibenzyl terephthalate, methylene dibenzoate, 1,2-bis(3-methylphenoxy)ethane , 14bis(benzyloxy)henzen, β
-hensyloxynaphthalene, dibenzyl oxalate, phenyl-α-hydroxy-β-naphthalate, stearic acid amide, and the like.

Other additives used in the present invention, such as a color-forming colorless dye, a color developer, a tetraphenol compound, and a sensitizer, can be granulated using a grinding machine such as a ball mill, an atlyzer, or a sand grinder, or a suitable emulsifying device. Diameter 0.1~1
It is used as a coating liquid as fine particles of 0μ.

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

Furthermore, in addition to these, waxes, light stabilizers, waterproofing agents, dispersants, antifoaming agents, etc. can be used as appropriate depending on the purpose.

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

The amounts of the color developer and tetraphenol compound used in the present invention are not particularly limited, as they vary depending on the required performance and recording suitability, as well as the type and amount of other additives used together, but are usually , 0.1 to 10 parts by weight are used per 1 part by weight 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-isoamylami)=6-methyl-7-anilinofluorane and 100 g of a 10% polyvinyl alcohol aqueous solution were thoroughly ground to obtain a dye dispersion (liquid A). I got it.

Benzyl-4-hydroxybenzoate 20g and 10
% polyvinyl alcohol aqueous solution was sufficiently ground to obtain a color developer dispersion (liquid B).

20 g of 1.2-bis(3-methylphenoxy)ethane and 100 g of a 10% polyvinyl alcohol aqueous solution were thoroughly ground to obtain a sensitizer dispersion (liquid C).

Thoroughly grind 20 g of the sample compound and 100 g of 10% polyvinyl alcohol aqueous solution, and prepare a storage stabilizer dispersion (liquid B).
I got it.

Liquids A, B, C, B and finely powdered silica were mixed at a weight ratio of 1:2:2:O, Sho, 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 produce a heat-sensitive recording material.

Using the obtained thermal paper, a pulse width of 0.7 m5 was printed using a thermal printing device (THPMD: manufactured by Okura Electric Co., Ltd.).
The color density of the recorded image printed by EC was measured using a Macbeth densitometer (model RD-933, manufactured by Macbeth).

In addition, this colored thermal paper was stored for 4 hours each under 60'C1 drying conditions and 60°C1 90% relative humidity conditions, and changes in density of the background and colored areas were measured to determine storage stability. evaluated.

The results are shown in Table-1.

Example-2 20 g of 3-dibutylamino-6-methyl-7-anilinofluorane and 10% aqueous polyvinyl alcohol solution
0 g was 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 1.2-bis(3-methylphenoxy)ethane and 100 g of a 10% polyvinyl alcohol aqueous solution were thoroughly ground to obtain a sensitizer dispersion (liquid C).

Thoroughly grind 20 g of the sample compound and 100 g of 10% polyvinyl alcohol aqueous solution, and prepare a storage stabilizer dispersion (liquid D).
I got it.

Liquids A, B, C, D and fine powdered silica were mixed in a weight ratio of 1:2:2:0. They were mixed in a ratio of 6 parts and 5 parts, and were sufficiently dispersed to obtain a coating liquid.

This coating liquid was applied to a thickness of 32 μm on a 50 g/rrr base paper.
T? A heat-sensitive recording material was created by coating and drying.

Using the obtained thermal paper, a thermal printing device (TH to PMD
: manufactured by Okura Electric Co., Ltd.) with pulse widths of 0 and 7.
The color density of the recorded image printed with m5ec was measured using a Macbeth densitometer (model RD-933, manufactured by Macbeth).

In addition, this colored thermal paper was stored for 4 hours each under 60°C 1 dry condition and 60°C and 90% relative humidity, and the change in density of the colored area was measured to evaluate storage stability. .

Furthermore, the colored area was pasted on a wrap film made of vinyl chloride resin and stored for 4 hours under dry conditions of 60°C3, and the change in concentration was measured to evaluate plasticizer resistance.

The results are shown in Table-2.

Example-3 1,2-bis(3,4-dimethylphenyl)ethane (Example 3-■) or 4-phenylphenyl methacrylate (Example 3-2) was used as a sensitizer, and 1 was used as a storage stabilizer. ．． 4-bis[bis(3-cyclohexyl-4-
A heat-sensitive recording material was prepared in the same manner as in Example 2 except that hydroxy-6-methylphenyl)methyl]benzene was used.

The same test as in Example 2 was conducted using the obtained thermal paper.

The results are shown in Table-3.

Table 3 Example 4 The compounds listed in Table 4 were used as color developers, and 1,4-bis[bis(3-cyclohexyl-4-
Hydroxy-6-methylphenyl)methyl]benzene (
each example) or 1,1,3°3-tetrakis (3-cyclohexyl-4-hydroxy-6-methylphenyl)
A heat-sensitive recording material was produced in the same manner as in Example-2 except that propane (each comparative example) was used.

Using the obtained thermal paper, a thermal printing device (THPMD:
(manufactured by Okura Electric Co., Ltd.) with a pulse width of 0 and 7 m.
The color density of the recorded image printed at 5ec was measured using a Macbeth densitometer (
Measured using Macbeth Co., Ltd. RD-933 model).

In addition, the colored thermal paper was stored for 4 hours under dry conditions at 60"C5 and 90% relative humidity at 60°C, and changes in density of the colored area were measured to evaluate storage stability. .

The results are shown in Table 4.

〔Effect of the invention〕

When using conventional storage stabilizers in which 3 or 4 phenol groups are bonded to an aliphatic chain, the effect is insufficient, and the coloring part is significantly decolored after dry heat or hot storage. Moreover, the plasticizer resistance is also not satisfactory.

On the other hand, the heat-sensitive recording material using a specific tetraphenol compound having an aromatic ring as a bond according to the present invention prevents the colored portion from decoloring after storage under dry heat or heat, and
Not only is the plasticizer resistance good, but also there is almost no capri on the background, and it is clear that the specific tetraphenol compound of the present invention is extremely excellent as a storage stabilizer for heat-sensitive recording materials.

Claims (1)

[Scope of Claims] 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, wherein the color-forming layer contains the following formula (I): A heat-sensitive recording material with improved storage stability, characterized by containing at least one type of tetraphenol compound represented by: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (In the formula, R_1 represents a tertiary butyl group, tertiary amyl group, or cyclohexyl group.)