JPH01174590A - Heat-sensitive recording material - Google Patents

Abstract

PURPOSE:To obtain the subject material having excellent color fading properties of low-temperature and high-temperature coloring layers, excellent storage properties, not suppressing coloring in low-temperature coloring, preventing blushing of ground, by using a specific piperidine compound as a color fading agent in a double - multi-color heat-sensitive coloring layer. CONSTITUTION:In a double - multi-color heat-sensitive coloring layer containing a usually colorless - light-colored electron donative dye precursor and an electron accepting compound to react with the precursor and to color, usually 0.1-10pts.wt. piperidine compound shown by formula I [R is group shown by formula II (R' is alkyl or acyl)] is used based on 1pt.wt. coloring dye to give the aimed material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-color or multicolor heat-sensitive recording material, and more particularly to a heat-sensitive recording material containing a piperidine compound as a decoloring agent.

[Conventional technology and problems]

Heat-sensitive recording materials usually contain a colorless or light-colored color-forming substance and a color developer that causes the color-forming substance to develop color when exposed to heat.
It is produced by coating the surface of a support such as paper, synthetic paper, plastic film or sheet with a sensitizer, binder and other additives in an isolated state. Then, in the recording apparatus, when a heat generating element such as a thermal head or a hot pen comes into contact with this recording medium, the dye and the color developer react to form a color such as black and are recorded.

Compared to other recording materials, this type of recording material does not require complicated processing such as development or fixing, can produce records in a short time using relatively simple equipment, and generates less noise and pollutes the environment. Because of its low cost, it is widely used as a recording material for various purposes such as copying books, documents, recording paper for various measurements, facsimile machines, ticket vending machines, prepaid cards, and labels.

Recently, two-color or more multicolor recording has been developed by utilizing differences in thermal temperature or thermal energy, and various methods have been proposed. Two-color or multi-color heat-sensitive recording materials are generally formed by stacking two types of high-temperature and low-temperature coloring layers that develop different tones with different coloring heat energies on a support such as paper or plastic. , can be roughly divided into the following two types. (1) When the high-temperature color-forming layer is colored, it is mixed with the color tone of the low-temperature color-forming layer to obtain a color tone different from that of the low-temperature color-forming layer. and(
2) When coloring the high-temperature color-forming layer, a decoloring agent that erases the color tone developed at a low temperature is used to obtain only the color tone of the high-temperature color-forming layer without color mixing of the color tone of the low-temperature color-forming layer.

Specific examples of these include (1) Japanese Patent Publication No. 49-69, Japanese Patent Publication No. 49-4342, Japanese Patent Publication No. 49-27708, Japanese Patent Publication No. 48-86543, Japanese Patent Publication No. 49-65239, (2) Japanese Patent Publication No. 17865-1786, Kosho 50-1786
6, Special Publication No. 51-29024, Special Publication No. 51-87542
, JP-A-50-18048, and JP-A-55-36529.

However, in the case of the former multicolor heat-sensitive recording material, the color tones that can be specifically achieved are red-black, blue-black, etc. because the color is mixed with the color tone of the low-temperature color layer when coloring at high temperatures. The drawback is that the high-temperature color tone is limited to a strong black color.

On the other hand, in the case of the latter multicolor heat-sensitive recording material, the combination of color tones can be freely selected, but when the coloring layer on the high temperature side develops color, the coloring layer containing a decoloring agent that decolorizes the coloring layer on the low temperature side is used. Although it is desirable to provide a layer, a material sufficient as a decolorizing agent has not yet been found.

Therefore, JP-A No. 62-279981 proposes the use of a specific polyalkylpiperidine compound as a color erasing agent, and when the compound described in this publication is used, problems such as color mixing during high-temperature color development, etc. Although the problem was improved to some extent, the color development tended to be suppressed during low temperature color development, and was not practically satisfactory.

In addition, JP-A-60-219086, JP-A-62-1
16182, etc., the above-mentioned Japanese Patent Application Laid-Open No. 62-27998
It has been proposed that various polyalkylpiperidine compounds, including the compound described in Publication No. 1, are effective in improving the storage stability of the colored part and preventing fogging on the background. There is no mention of whether or not it can be used as a decolorizing agent for recording materials.

[Means for solving problems]

In view of the above-mentioned current situation, the present inventors have made extensive studies to solve these problems, and have found that a specific polyalkylpiperidine compound has excellent color erasing properties of the low-temperature coloring layer during high-temperature coloring. Furthermore, the inventors have discovered that color development is not inhibited during low-temperature color development, and have arrived at the present invention.

Furthermore, when the specific piperidine compound of the present invention is used, it is extremely effective in improving the storage stability of the low-temperature coloring layer and the high-temperature coloring layer and preventing fogging on the background.

That is, the present invention provides a thermosensitive recording material having a two-color or multicolor thermosensitive coloring layer containing a normally colorless or light-colored electron-donating dye precursor and an electron-accepting compound that reacts with the electron-donating dye precursor to form a color. The present invention provides a heat-sensitive recording material characterized in that the material contains a compound represented by the following general formula as a decoloring agent.

C1h-COO-R CIl-Coo-R CH-COO-R cttz-coo-n or represents an acyl group. ) In the compound represented by the above general formula (1) used in the present invention, the alkyl group represented by R' includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, nibutyl, tertiary butyl groups, etc. Examples include acyl group, acetyl group, propionyl group, etc.

As mentioned above, the specific piperidine compound represented by the above-mentioned formula used in the present invention does not exhibit a decoloring effect when coloring occurs at low temperatures, but has the function of decolorizing the low temperature coloring portion when coloring occurs at high temperatures. Moreover, since it does not cause a color erasing effect before printing or during storage, if it is included in a layer adjacent to the heat-sensitive recording layer to be color-erased or in a layer between the heat-sensitive coloring layer and an intermediate layer, it improves color separation and storage stability. A heat-sensitive recording material with excellent properties can be obtained.

The piperidine compound represented by structure (1) above is a known compound, and can be easily synthesized, for example, by transesterification reaction between butanetetracarboxylic acid methyl ester and the corresponding piperiditul compound.

Next, a specific synthesis example of the piperidine compound used in the present invention will be shown.

Synthesis example 1 xylene 350d and 4-hydroxy 1.2°2.6
．． Add 8.55 g (0.21 mol) of 6-bentamethylbiperidine and 14.5 g (0.05 mol) of 1,2,3.4-butanetetracarboxylic acid methyl ester, and add titanium tetraisopropoxylate while stirring. Side 0.4m1
1 was added little by little, and the mixture was stirred for 2 hours under xylene reflux while removing generated methanol. Further under reduced pressure reflux
The reaction was completed by stirring for an hour. The solid precipitated upon cooling was filtered off, recrystallized using MSP, and dried to obtain a white solid with a melting point of 141°C.

Synthesis Example 2 1-acetyl-4-hydroxy-2, instead of 4-hydroxy-1,2,2,6,6-pentamethylpiperidine
2,6,6-titramethylpiperidine 41.8g (0
, 21 mol) was used, but the reaction was carried out in the same manner as in Synthesis Example 1,
Recrystallized from acetonitrile and dried to a melting point of 185-186
A white solid was obtained.

The amount of the piperidine compound represented by the above-mentioned formula of the present invention is determined according to the required performance and recording suitability, and is not particularly limited, but usually o, t- Use the to part.

Various dyes are well known as the normally colorless or light-colored electron-donating dye precursor used in the present invention, and there are no particular limitations as long as they are used in general heat-sensitive recording materials.

Specific examples of these dyes include (1) triarylmethane compounds; for example, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (crystal violet lactone'), a-( 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, (2) diphenylmethane compounds; for example,
4.4-bis-dimethylaminobenzhydrin benzyl ether, N-halophenylleucoolamine, N-2
,4,5-)lichlorophenylleucoolamine etc., (
3) Xanthine compounds; for example, rhodamine-β-anilinolactam, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-(2-chloroanilino)-fluorane, 3-diethylamino-6-
Methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-(β-ethoxyethylamino)-fluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-ethyl-tolylamino- 6-methyl-
7-anilinofluorane, 3-cyclohexylmethylanilino-6-methyl-7-anilinofluorane, 3-diethylamide/-6-chloro-7-γ-chloropropylaminofluorane, etc., (4) Thiazine type Compound; for example,
benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene→゛ru, etc., (5) spiro-based compounds;
Examples include 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho(3-methoxybenzo)spiropyran, and several types of these dyes can be mixed. It can also be used as

Further, as the electron-accepting compound that reacts with the electron-donating dye precursor to form a color, conventionally used color developers include:
p-octylphenol, p-tert-butylphenol,
p-phenylphenol, bisphenol AS1.1-
Bis(p-hydroxyphenylbutane)2,2-bis(
4-hydroxy-3,5-dichlorophenyl-propane, bis[2-(4-hydroxyphenylthio)-ethoxycomethane, p-(4-isopropoxybenzenesulfonyl)-phenol, 4-hydroxyphthalic acid dimethyl ester, bis (4-Hydroxyphenyl)-butyl acetate, sulfobis(3,4-dihydroxybenzene), benzyl p-hydroxybenzoate, zinc salicylic acid dodecyl ester salt, 3,5-di-tert-butylsalicylic acid, 4,4°-cyclohexyl cylidene diphenol, p
-Hydroxydiphenoxide, α-naphthol, β-naphthol, p-hydroxyacetophenone, p-tertiary octylcatechol, 2,2'-dihydroxybiphenyl, 2,2-bis(3-methyl-4-hydroxyphenyl)-propane , 2,2-bis(3,5-dimethyl-4-
hydroxyphenyl)-propane, 1.1.3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)-butane, 1,1°3-tris(2-methyl-4-
Phenols such as hydroxy-5-cyclohexylphenyl)-butane, organic acids, or metal salts thereof can be used alone or in combination.

The piperidine compound, the color-forming colorless to light-colored electron-donating dye precursor, and the electron-accepting compound of the present invention are pulverized by a grinder such as a ball mill, atlyzer, or sand grinder, or by an appropriate emulsifying device, and are made into fine particles according to the purpose. Add additive materials to make a coating liquid.

This coating solution usually contains polyvinyl alcohol, hydroxyethylcellulose, methylcellulose, polyacrylamide polymer, starch, styrene-maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer, styrene-butadiene copolymer. Binding agents such as coalescence, kaolin, diatomaceous earth,
Fillers such as silica, talc, titanium dioxide, calcium carbonate, magnesium carbonate, and aluminum hydroxide are blended, but in addition to these, 4-benzyloxybiphenyl, 4-benzylbiphenyl, 1,2-bis-(3-methylphenoxy) - sensitizers such as ethane, methylene bisbenzoate, 1-hydroxy-2-naphthylic acid benzyl ester,
Amines such as triethylenetetramine, N,N-bis-(3-aminopropyl)-ethylenediamine, amide compounds such as stearic acid amide, metal soaps such as zinc stearate, waxes, light stabilizers, waterproofing agents , dispersant,
Antifoaming agents etc. can be used.

The desired heat-sensitive recording material can be obtained by applying this coating liquid to paper, synthetic paper, plastic, and various other films or sheets.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example-1 Each of the following formulations was ground in a ball mill, and a dispersion liquid (A
From liquid) to dispersion liquid (liquid d) were obtained.

(Liquid A) Crystal violet lactone 10 parts 10%
Hydroxyethylcellulose aqueous solution 10 parts water
30 copies (B
Liquid) Bisphenol S monobenzyl ether 30 parts 10%
Hydroxyethyl cellulose aqueous solution 15 parts water
105 copies (
Solution C) Calcium carbonate 20 parts Zinc stearate, 2 parts lO% hydroxyethyl cellulose aqueous solution 11 parts Water
40 parts (Liquid D) Compound of Table 1 10 parts 10%
Hydroxyethylcellulose aqueous solution 10 parts water
30 parts (snake liquid) 3-diethylamino-6-methyl-7-10 parts Chlorofluorane 10% hydroxyethyl cellulose aqueous solution 10 parts Water
30
Part (F solution) Benzyl p-hydroxybenzoate 30 parts 10%
Hydroxyethylcellulose aqueous solution 15 parts water
Part 105 Mix (Liquid E), (Liquid B), and (Liquid C) in a ratio of 1:1:1 to create a coating liquid, and apply this coating liquid on high-quality paper with a basis weight of 50 g/m''. The mixture was dried in a room so that the amount of dye attached was 0.5 g/mg to obtain a high temperature thermosensitive coloring layer.

Next, (Liquid D) was coated and dried in a layered manner so that the amount of solid matter deposited was 4 g/ls''.

Furthermore, (Liquid A), (Liquid F), and (Liquid C) were mixed at a ratio of 1:l:l to create a coating liquid, and this coating liquid was coated with a dye adhesion amount of 0.4.
A two-color heat-sensitive recording material was obtained by laminating the coating and drying so as to give a ratio of "g/n+".

The thermal recording paper prepared as described above was printed at 1, Omj/d using a thermal printing simulator (manufactured by Matsushita Electronics)
ot and 3. Printing was performed with an energy of Omj/dot.

The colored recording paper was stored for 48 hours at a temperature of 50'' C1 and a humidity of 90%, and the density of the low temperature colored area was measured using a Macbeth densitometer RD-933 model.

In addition, the degree of color mixing in the high-temperature coloring area was visually determined.

The results are shown in Table-1.

As shown in Table 1, the color erasing agent of the present invention has clear separation of two colors, good color density during low temperature color development, and
It is clear that it also has excellent storage stability.

On the other hand, when a decolorizing agent is not used, color separation is not achieved and the high-temperature colored areas are mixed, and when a polyalkylpiperidine compound other than the present invention is used, color separation is not achieved and the high-temperature colored areas are mixed. or the color density during low-temperature color development was poor.

Claims (1)

[Scope of Claims] A thermosensitive recording layer having a two-color or multicolor thermosensitive coloring layer containing a normally colorless or light-colored electron-donating dye precursor and an electron-accepting compound that reacts with the electron-donating dye precursor to form a color. There are heat-sensitive recording materials characterized by containing a compound represented by the following general formula as a decolorizing agent ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ and R' represents an alkyl group or an acyl group.)