JPS60222288A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain developed color images having excellent stability with time, heat resistance and plasticizer resistance, by using a color developer together with a specified ethylidenediphenol. CONSTITUTION:A color developer is used together with 4,4',6,6'-tetra-t-butyl-2,2'- ethylidenediphenol, in a thermal recording material utilizing a color forming reaction of a leuco dye and a color developer. Accordingly, developed color images having excellent stability with time, heat resistance and plasticizer resistance can be obtained. Particularly when a compound of formula ( I ) or (II), wherein R is propyl, butyl or benzyl, and X is alkylene with or without ether group, carbonyl group or hydroxyl group, is used as the color developer, an extremely remarkable effect is produced on stability with time, oil resistance and plasticizer resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to improvements in heat-sensitive recording materials containing leuco dyes as color formers.

[Prior art]

A heat-sensitive recording material is a piece of paper, synthetic paper, plastic film, or other support with a heat-sensitive coloring layer containing a thermocoloring composition as its main component, and can be heated with a thermal head, thermal pen, laser beam, etc. By doing so, a colored image can be obtained. Compared to other recording materials, this type of recording material does not require complicated processes such as development and fixing, can obtain 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 variety of applications, including electronic counters, facsimiles, ticket vending machines, labels, and recorders. Thermochromic compositions used in such heat-sensitive recording materials generally consist of a coloring agent and a color developer that causes the coloring agent to develop specific heat color. One coloring agent includes:
For example, colorless or light-colored leuco dyes having a lactone, lactam or spiropyran ring are used, and various acidic substances such as organic acids and phenolic substances are used as color developers. A recording material that combines a color forming agent and a color developer 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). and is widely used.

However, although colored images can be easily obtained with such recording materials, there are problems with the stability of the recorded images, and the stability of the images over time and stability against oils, fats, fingerprints, etc. have become major problems. . Conventionally, in order to stabilize images, it has been proposed to use a metal salt of a salicylic acid derivative or a hydroxynaphthoic acid derivative as a color developer (Japanese Patent Application Laid-open Nos. 48-51716 and 49-55410). However, it is still not enough. In addition, when these color developers are used for thermal recording paper, the background part may be contaminated with oils, fats, etc.
It is difficult to apply because it is plastic and produces color.

Furthermore, a method has been proposed in which an attempt is made to improve this by using a phenolic color developer and adding a material that has an image stabilizing effect. For example, JP-A-57-83495 and JP-A-57-185187 disclose 2,2'-methylenebis-(4-methyl-6-tert-butylphenol) and 2-hydroxy-3-naphthoic acid anilide. It is disclosed that image stability can be improved by incorporating it into a heat-sensitive coloring layer. However, even in this case, it is still difficult to obtain sufficient image stability, and further improvements are desired.

〔the purpose〕

An object of the present invention is to provide a heat-sensitive recording material that exhibits excellent stability of colored images over time, heat resistance, and plasticizer resistance.

〔composition〕

According to the present invention, in a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye and a color developer, the color developer is
．． 6. A heat-sensitive recording material characterized in that it is used in conjunction with s'-tetra-t-butyl-2,2'-ethylidene diphenol is provided.

Various conventional color developers can be used as the color developer used in the present invention, such as phenolated metals, organic acids, Lewis acids, aromatic oxycarboxylic acids, and phenyl urea compounds.
When a compound represented by the following general formula 0→ or (n) is used, extremely remarkable effects are exhibited in terms of stability over time, oil resistance, and plasticizer resistance.

In the formula, R represents a propyl group, a butyl group or a benzyl group.

In the formula, X is an alkylene group or -〇-1-se mo? Ha-
Represents an alkylene group containing OH. The alkylene group usually has about 1 to 12 carbon atoms, and can contain about 1 to 5 ether, carbonyl, or hydroxyl groups.

Conventionally, color developers of general formulas (I) and (n) described above have been used in 2.
2'-methylenebis-(4-methyl-6-t-butyl-
6-t-butylphenol), or 2-hydroxyP/-
Although it is known that it is used in combination with 3-naphthoic acid anilide, etc., the combination of the present invention provides extremely excellent image stability compared to this.

Examples of the compounds represented by the above general formulas (1) and (II) include the following.

n-propyl p-hydroxybenzoate P-isopropyl hydroxybenzoate P-n-butyl hydroxybenzoate P-isobutyl hydroxybenzoate P-secandeributyl hydroxybenzoate P-benzyl hydroxybenzoate 1, Fuji (4- hydroxyphenylthio)-3,5-dioxyhebutane, 1,5-di(4-hydroxyphenylthio)-3-oxypentane, 1,5-di(4-hydroxyphenylthio)-3-oxopentane.

1,5-di(4-hydroxyphenylthio)-3-hydroxypropane, 1,5-di(4-hydroxyphenylthio)-3-oxopropane.

Examples of other color developers include the following.

4.4'-Isopropylidene bisphenol.

4.4'-Isopropylidenebis(0-methylphenol), 4.4'-Secondary-butylidenebisphenol.

4.4'-isopropylidene bis(2-tert-butylphenol), 4.4'-cyclohexylidene diphenol, 4.4
′ -isopropylidene bis(2-chlorophenol)
, N,N-diphenylthiourea, N,N-di(m-chlorophenyl)thiourea, N,N-
Di(m-methylphenyl)thiourea, N,N-di(m-
trichloromethylphenyl)thiourea, dimethyl 4-hydroxyphthalate, 4,4'-butylidenebis(6-tert-butyl-
m-cresol), 4,4'-thiobis(6-tert-butyl-m-
Cresol.

Cyclohexyl P-oxybenzoate, neopentylcatechol butylphenone P-oxybenzoate, propyl protocatechuate, benzyl protocatechuate, propyl gallate.

Lauryl gallate.

Stearyl gallate.

Ethyl 2-hydroxy-6-naphthoate, isopropyl 2-hydroxy-6-naphthoate, 2-hydroxy-6
- Isobutyl naphthoate.

Benzyl 2-hydroxy-6-naphthoate.

3-tert-butylsalicylic acid, 3-cumylsalicylic acid, 3.5-di-tert-butylsalicylic acid, 3.5-dicumylsalicylic acid, 5-octylsalicylic acid, 3-phenylsalicylic acid.

2-oxy-3-naphthoic acid, 1-oxy-2-naphthoic acid, 2-oxy-1-naphthoic acid, 4-hydroxydiphenylsulfone, 4-Hydroxy-41-methyldiphenylsulfone.

4.4'-dihydroxydiphenylsulfone, 4.4
'-Dihydroxy-diphenylsulfone monobenzyl ether, 4.4'-dihydroxy-Schiffenylsulfone monooctyl ether, 4-hydroxy-4'-chlorodiphenylsulfone.

4-Hydroxy-2'-chlorodiphenyl sulfone.

4-Hydroxy-4'-isopropyldiphenyls J Rehosofue The leuco dyes used in the present invention can be applied singly or in a mixture of two or more types, but such leuco dyes include:
Those which are applied to heat- or pressure-sensitive recording materials of this kind may optionally be applied, e.g.

Leuco compounds of triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, and spiropyran-based dyes are preferably used. Specific examples of such leuco dyes include those shown below.

3.3-his(P-dimethylaminophenyl)-phthalide, 3.3-bis(P-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3.3-bis(p- dimethylaminophenyl)-6-dibutylaminophenyl, 3.3-bis(p-dimethylaminophenyl)-6-chlorphthalide, 3.3-bis(p-dibutylaminophenyl)methane 3-cyclohexylamino-6-chlor fluorane,
- 3-dimethylamino-5,7-dimethylfluorane.

3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane.

3-diethylamino-6-methyl-7-chlorofluorane, 3-(N-p-tolyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7- Anilinofluorane, 2-(N-(3'-trifluoromethylphenyl)amino)-6-dinithylaminofluorane.

2-(3,6-bis(diethylamino)-9-(o-
chloranilino)xantylbenzoic acid lactam), 3-
diethylamino-6-methyl-7-chloromethylanilino)fluoran, 3-diethylamino-7-(0-chloroanilino)fluoran, 3-dibutylamino-7-(0-chloromethylanilino)fluoran, 3-N-methyl-N- Amylamino-6-methyl-7-
Anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane.

3-diethylamino-6-methyl-7-anilinofluorane.

3-(N,N-diethylamino)-5-methyl-7-(
N.

N-dibenzylamino)fluorane.

Benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrylospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrylospirane, 3-(2'-hydroxy-4'-dimethylaminophenyl) )-3-(2'-methoxy-51-chlorophenyl)phthalide, 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-nitrophenyl)
Phthalide.

3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl)phthalide, 3-(2'-methoxy-4'-dimethylaminophenyl)-3-( 2'-hydroxy-4'-chloro-5'
-methylphenyl)phthalide.

3-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-(N-benzyl-trifluoro methylanilino)fluorane, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluorane, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluorane, 3-(N-ethyl -p-toluidino)-7-(α-phenylethylamino)fluoran, 11. +IF:! p 7
/+1 enemy k filling →- 11ノ→zo i-phenylamino) fluoran, 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-piperidinofluorane , 2-
Chloro-3-(N-methyltoluidino)-7-(p-n
-butylanilino)fluorane, 3-(N-benzyl-N-cyclohexylamino)-5
, 6-penzo 7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino 4
',5'-benzofluorane etc.

In the recording material of the present invention, the proportions of (a) leuco dye, (b) color developer, and (c) 4.4', 6.6'-tetra-L-butyl-2,2'-ethylidene diphenol are as follows: ，
Component (A) is 10 to 50% by weight, component (I) is 30 to 80% by weight, and component (C) is 10 to 50% by weight based on the total of those components (A), (I), and (C). It is preferable that Further, the ratio of component (C) to component (C) is preferably 0.2 to 2 parts by weight per 1 part by weight of component (C).

The above component (c) is usually applied to a heat-sensitive recording material having a structure in which a heat-sensitive coloring layer containing components (a) and (b) is provided on a support, but the present invention is applicable to this type of heat-sensitive recording material. However, it is not limited to heat-sensitive recording materials having a structure in which components (a) and (b) are formed as separate layers on a support, and transfer sheets and components in which a transfer layer containing component (a) is provided on a support. It is also possible to apply the present invention to a thermal transfer type recording medium comprising a receptor sheet in which a receptor layer containing (b) is provided on a support.

In the first embodiment, component (c) is contained in the heat-sensitive coloring layer, or in the upper or lower layer of the heat-sensitive coloring layer. In the second embodiment, in addition to being contained in the layer containing component (B), it can also be contained in a layer separate from the layer containing component (A) and (B). In the third embodiment, component (c) is usually contained in the receiving sheet and the receiving layer.

In the present invention, in order to bind and support the leuco dye, color developer, etc. on the support, various commonly used binders can be used as appropriate, such as polyvinyl alcohol,
Starch and its derivatives, methoxycellulose, hydroxyethylcellulose.

Cellulose derivatives such as ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide/
Acrylic ester copolymer, acrylic amide/acrylic ester/methacrylic acid ternary copolymer, styrene/maleic anhydride copolymer alkali salt, isobutylene l
In addition to water-soluble polymers such as maleic anhydride copolymer alkal salt, polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, styrene/butadiene copolymer, polyacrylic acid, polyacrylic acid ester, and chloride Vinyl/vinyl acetate copolymer, polybutyl methacrylate, ethylene/vinyl acetate copolymer,
A latex such as styrene/butadiene/acrylic copolymer can be used.

In addition, in the present invention, in addition to the leuco dye, color developer, and 4.4',6.6'-tetra-t-2,2'-ethylidene diphenol, if necessary, this type of heat-sensitive recording Auxiliary additives commonly used in the material, such as fillers,
A surfactant, a thermofusible substance (or lubricant), etc. can be used in combination. In this case, fillers include, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, and surface-treated inorganic fine powders such as calcium and silica. , urea-formalin resin, starch, styrene-methacrylic acid copolymer, polystyrene resin, and other organic fine powders. Examples of thermofusible substances include higher fatty acids or their esters, amides, or metals. In addition to salts, various waxes, condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, dialkyl 3゜4-epoxy-hexahydrophthalates, higher ketones, and other thermofusible materials. 5 of organic compounds, etc.
Examples include those having a melting point of about 0 to 200°C.

The heat-sensitive recording material of the present invention can have various structures, and the conventionally known structure that utilizes a color-forming reaction between a leuco dye and a color developer is 4'''rJth. [Effects] The heat-sensitive recording material of the present invention has the effect of further improving the stability of colored images over time and the reliability of images against oils and fats and plasticizers compared to conventional ones.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. In the following, both "1 part" and "%" are based on weight.

Examples 1-2. Comparative Examples 1-2 (A) Liquid 3-(N-methyl-N-cyclohexylamino)-6-
Methyl-7-anilite fluorane 1 part Hydroxyethylcellulose 10% aqueous solution lou water 3Qa (B) Group A component in Liquid Table-1 30 parts Polyvinyl alcohol 10% aqueous solution 15//Water 10
5〃 (C) Components of Group B in Liquid Table-1 10 parts Polyvinyl alcohol 10% aqueous solution 7 parts Water 38〃 (D) Liquid calcium carbonate 30 parts Methyl cellulose 5% aqueous solution 30〃 Water 90I! (E) Liquid Isobutylene maleic anhydride copolymer ammonia solution (20%) 5 parts After dispersing each liquid except for (E) in a ball mill.

Mix liquids (A) to (E) and use a lab rod to coat paper with a basis weight of 50 g/rf so that the dye adhesion amount is 0.5 g/rrF.
Five types of heat-sensitive recording materials were obtained by coating and drying. Each heat-sensitive recording material was tested for color development and stability. The test results are shown in Table-1. Note that the color density shown in 5 is the solution obtained when the color was developed using a facsimile printer at a head energy of 2 mj/dat, and the density was measured using a Macbeth density needle. Image density over time is 50℃ and humidity 50℃ for facsimile.
This is the concentration after standing for 2 weeks in a constant temperature bath.

As is clear from Table 1, it can be seen that the heat-sensitive recording material according to the present invention has superior stability over time for one image compared to the comparative example.

Patent applicant Rico Co., Ltd. Representative Patent Attorney Toshiaki Ikeura

Claims (2)

[Claims] (1) In a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye and a color developer, the color developer is A heat-sensitive recording material characterized in that it is used together with ethylidene diphenol. (2) The heat-sensitive recording material according to claim 1, wherein the color developer is at least one compound represented by the following general formula (1) or (II). (In the formula, R represents a propyl group, a butyl group, or a benzyl group) (In the formula, X is an alkylene group, or an alkylene group having an ether group, a carbonyl group, or a hydroxyl group)