JPH0437582A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having a high compatibility with colorless dye, developer, sensitizer, etc., a good coloring sensitivity, little texture fog, and a good image maintenance by constituting the thermal recording material in such a manner that a dye precursor is a specific compound and at least one of specific two sorts of compounds is contained in a thermal coloring layer. CONSTITUTION:In this thermal recording material, a thermal coloring layer containing a colorless or light-colored electron donative dye precursor and an electron acceptable substance for reacting on the dye precursor to color the precursor is provided on a support. The dye precursor is a compound represented by formula I and at least one sort of compounds represented by formulae II and III is contained in the thermal coloring layer. As a developer, 1, 1'-bis(p-hydroxyphenyl)propane is especially preferable. When the compound of the formula I is used as colorless dye and the thermal coloring layer using at least one sort of the compounds of the formulae II, III as a sensitizer is contained, it is possible to obtain the thermal recording material having a high coloring concentration and high coloring sensitivity at the time of thermal recording and the obtained material is excellent in image maintenance.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to heat-sensitive recording materials.

(Prior Art) Conventional general heat-sensitive recording materials consist of a colorless or light-colored electron-donating dye precursor (hereinafter abbreviated as "colorless dye") and an electron-accepting substance ( A two-component coloring system consisting of a color developer (hereinafter abbreviated as a "color developer") is further provided with a heat-sensitive coloring layer in which a binder, a sensitivity improver, a lubricant, a filler, and other auxiliaries are dispersed. Kosho 43-41
No. 60, U.S. Patent No. 554585 (Special Publication No. 45-14
No. 039).

This type of two-component color-forming heat-sensitive recording material allows a color image to be easily obtained by heating with a heating element (thermal head, thermal pen, etc.), and has the following characteristics.

(1) - Secondary color development, no need for development or fixing.

(2) There is no need to replenish toner, etc., and maintenance of the recording machine is easy.

(3) When paper is used as a support, the quality of the paper is similar to that of ordinary paper, so there is no discomfort.

(4) High color density and clear images can be obtained.

(5) By changing the type of colorless dye, different color tones can be easily obtained.

Due to these advantages, two-component color-forming heat-sensitive recording materials are the most widely used of all heat-sensitive recording materials, and in recent years,
Its use in fields such as facsimiles, printers, measurement records, and labels has increased significantly.

By the way, for example, in the recent field of facsimile communication,
Along with the increase in speed, the recording speed is also increasing.
There is also a strong demand for improved thermal responsiveness of thermal recording paper so that sufficient color density can be obtained with less thermal energy.

Research has been conducted on various coloring sensitivity improvers to improve thermal responsiveness, but generally speaking, improving thermal responsiveness increases the undesirable tendency of increasing background fog. At present, a heat-sensitive recording material that satisfies both the fogging and fogging issues has not been obtained.

Examples of components contained in the heat-sensitive coloring layer of heat-sensitive recording materials currently generally proposed and used include colorless dyes such as triarylmethane compounds such as 3,3-bis(p-dimethylamino phenyl)−
6-dimethylaminophthalide (i.e. crystal violet lactone), 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(P-dimethylaminophenyl)-3-(1,3-dimethylindole-3- yl)phthalide, 3-(p-dimethylaminophenyl)-3-(
Examples include 2-methylindol-3-yl)phthalide.

Examples of diphenylmethane compounds include 4,4 bis-dimethylaminohenzhydrin benzyl ether, N-herophenyl leuco auramine, and N-2,4,5-1-lichlorophenyl leuco auramine.

As xanthine compounds, rhodamine-B-anilinolactam, rhodamine (p-nitrino)lactam, 2
-(dibenzylamino)fluorane, 2-phenylamino-6-ethylaminofluorane, 2-(o-chloroanilino)-6-dinithylaminofluorane, 2-(
3,4-dichloroanilino)-6-ethylaminofluorane, 2-anilino-3-methyl-6-piperidinofluorane, 2-phenyl-6-dinithylaminofluorane, 2-anilino-3-methyl -6-Simethylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N-ethylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N-(isopropyl)amino Fluoran, 2-anilino-3-methyl-6-N-methyl-N-pentylaminofluoran, 2-anilino-3-
Methyl-6-N-methyl-N-cyclohexylaminofluorane, 2-anilino-3-methyl-6-dinithylaminofluorane, 2-anilino-3-chloro-6-dimethylaminofluorane, 2-anilino -3-methyl-6
-N-ethyl-N-isoamylaminofluorane, 2-
Anilino-3-methyl-6-N-methyl-N-isoamylaminofluorane, 2-anilino-3-chloro-6-
Dinitylaminofluorane, 2-anilino-3-chloro-6-N-methyl-N-ethylaminofluorane, 2-
Anilino-3-chloro-6-N-methyl-N-(isopropyl)aminofluorane, 2-anilino-3-chloro-6-N-methyl-N-pentylaminofluorane, 2
-anilino-3-chloro-6-N-methyl-N-cyclohexylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N-pentylaminofluorane, 2
-anilino-3-chloro-6-N-ethyl-N-pentylaminofluorane, 2-(p-methylanilino)-3
-Methyl-6-dimethylaminofluorane, 2-(p-
methylanilino)-3-methyl-6-dinithylaminofluorane, 2-(p-methylanilino)-3-methyl-
6-N-methyl-N-ethylaminofluorane, 2-(
p-methylanilino)-3-methyl-6-N-methyl-
N-(isopropyl)aminofluorane, 2-(p-methylanilino)-3-methyl-6-N-methyl-N-pentylaminofluorane, 2-(p-methylanilino)
-3-Methyl-6-N-methyl-N-cyclohexylaminofluorane, 2-(p-methylanilino)-3-methyl-6-N-ethyl-N-pentylaminofluorane, 2-(p-methylanilino) -3-chloro-6-dimethylaminofluorane, 2-(p-methylanilino)-
3-chloro-6-dinithylaminofluorane, 2-(P
-methylanilino)-3-chloro-6-N-methyl-N
-Dithylaminofluorane, 2-(pmethylanilino)
-3-chloro-6-N-methyl-N-(isopropyl)
Aminofluorane, 2-(p-methylanilino)-3-
Chloro-6-N-methyl-N-(isopropyl)aminofluorane, 2-(p-methylanilino)3-chloro-
6-N-methyl-N-cyclohexylaminofluorane, 2-(p-methylanilino)-3-chloro-6-N-
Methyl-N-pentylaminofluorane, 2-(p-methylanilino)-3-chloro-6-N-ethyl-N-pentylaminofluorane, 2-anilino-3-methyl-
6-N-methyl-N-furylmethylaminofluorane,
Examples include 2-anilino-3-ethyl-6-N-methyl-N-furylmethylaminofluorane.

Further, examples of the thiazine-based compound include benzoloucomethylene blue, P-nitrohensylleucomethylene blue, and the like.

As a spiropyran compound, 3-methyl-spiro-
dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3°-cyclolose bilodinaphthopyran, 3-
Examples include hensylspiro-dinaphthopyran, 3-methyl-naphtho-(3-methoxybenzo)-spiropyran, and 3-probyl-svirodihenzobilane.

In addition, the color developer that is used together with a colorless dye in the heat-sensitive coloring layer of a heat-sensitive recording material and causes the colorless dye to develop color is
An organic acidic substance that is solid at room temperature and heat-melting is used, -
Examples include phenolic compounds, aromatic carboxylic acid compounds, novolac type phenolic resins, etc.
Typical examples thereof include bisphenol derivatives, hydroxybenzoic acid esters, and salicylic acid esters. Further examples include inorganic acids such as activated clay and activated silica.

Among these color developers, some representative examples of phenolic compounds and aromatic carboxylic acid compounds are 2.2-
Bis(4°-hydroxyphenyl)propane, 2.2-
Bis(4°-hydroxyphenyl)pentane, 2.2-
Bis(4'-hydro-IF-C3',5'-dichlorophenyl)propane, 11-bis(4'-hydroxyphenyl)cyclohexane, 2.2-bis(4'-hydroxyphenyl)hexane, 1.1- Bis(4°-hydroxyphenyl)furopane, ], 1-bis(4°-hydroxyphenyl)butane, l,, 1-bis(4°-hydroxyphenyl)pentane, 1.1-bis(4°-hydroxyphenyl) ) hexane, 1.1-bis(4°-hydroxyphenyl)hebutane, 1.1-bis(4°-hydroxyphenyl)-2-methyl-pentane, 1.1-bis(4°-hydroxyphenyl)- 2-Ethyl-hexane, 1.1-bis(4°-hydroxyphenyl)dodecane, 3.3-bis(4°-hydroxyphenyl)pentane, 1.2-bis(4′-hydroxyphenyl)ethane, 1. 1-bis(4′-hydroxyphenyl) sulfide, 1.1-bis(3°-allyl-4°-hydroxyphenyl) sulfone, 1.1-bis(4°-hydroxyphenyl) sulfone, 4-hydroxy-4 “-isopropoxydiphenylsulfone, 1.1-bis(4′-hydroxyphenyl)ether, 2,2-bis(4″-hydroxy-3°,5°-dichlorophenyl)butane, 2.4
-Phenyl dihydroxybenzoate, phenyl 2.4-dihydroxy-4'-methyl-benzoate, phenyl 2.4-dihydroxy-4'-chlorobenzoate, phenyl 2.4-dihydroxy-6-methylbenzoate, 2.4 .6-
Phenyl trihydroxybenzoate, phenyl 2,4-dihydroxy-6,4°-dimethylbenzoate, phenyl 2,4-dihydroxy-6-methyl-4'-chlorobenzoate, benzyl 2,4-dihydroxybenzoate, 2 .4-
Benzyl dihydroxy-4°-methylbenzoate, 2.4
-benzyl dihydroxy-4'-chlorobenzoate, 2,
Benzyl 4-dihydroxy-6-methylbenzoate, 2.
4.6-1-Benzyl dihydroxybenzoate, 2.4-
benzyl dihydroxy-6,4-dimethylbenzoate,
2.4-dihydroxy-6-methyl-4'-benzyl chlorobenzoate, 4-hydroxybenzoic acid ethyl ester, 4-hydroxybenzoic acid propyl ester, 4-hydroxybenzoic acid isopropyl ester, 4-hydroxybenzoic acid benzyl ester, 4-Hydroxy-4'-chlorobenzoic acid benzyl ester, 4-hydroxy-4'-methylbenzoic acid henzyl ester, 4-hydroxy-
Examples include compounds such as 4°-ethylbenzoic acid hensyl ester.

Furthermore, in addition to the above-mentioned colorless dye and color developer, a sensitizer (color development sensitivity improver) is also added to the heat-sensitive coloring layer of the heat-sensitive recording material. By melting at a relatively low temperature, this sensitizer causes a color reaction between the colorless dye and the color developer to occur due to the eutectic point effect, thereby improving the color development sensitivity. Examples of conventionally known sensitizers include waxes such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, coconut fatty acid amide, nitrogen-containing compounds, and carboxylic acid esters. , naphtholic conductors, naphthoic acid derivatives, benzoic acid ester conductors, and the like.

(Problem to be Solved by the Invention) As mentioned above, various components are known to be contained in the thermosensitive coloring layer of a thermosensitive recording material, and conventionally, for example, they are commonly used in high-speed facsimiles and energy-saving facsimiles. It satisfies good color development sensitivity with no uneven printing and good image reproducibility, which is required by the industry, and on the other hand, it has fewer negative effects such as the occurrence of background fog that accompanies improvement in color development sensitivity. Thermosensitive recording materials having structures that satisfy technical issues have been researched, and various combinations of components have been proposed and put into practice.

However, the mechanism of the coloring reaction in the heat-sensitive coloring layer has not yet been elucidated in detail, and there are a wide variety of types of colorless dyes, color developers, and sensitizers, so it is necessary to find a good combination among them. That is not easy.

Under these circumstances, the present inventors particularly focused on the following dye precursor having a fluorane skeleton, which is a colorless dye with no uneven printing and excellent reproducibility, and sought to develop a component composition that is particularly compatible with this dye. The present invention was developed by intensively studying the specific structure of the heat-sensitive coloring layer.

That is, an object of the present invention is to provide a heat-sensitive recording material that has high compatibility with colorless dyes, color developers, sensitizers, etc., has good color development sensitivity, has little background fog, and has good image retention.

(Means for Solving the Problems) A feature of the heat-sensitive recording material of the present invention that achieves the above object is that a colorless or light-colored colorless dye (electron-donating dye precursor) is reacted with the colorless dye on the support. In a heat-sensitive recording material provided with a heat-sensitive coloring layer containing a color developer (electron-accepting substance) as a main component, the colorless dye is a compound represented by the following structural formula (I)... (I) and the following general formulas (II) and (III) (R+ + R1' are f(, CLCL. However, even if R,, R, and ° are the same, (They may be different.) R7 (R2 and R2° are either H or CH3. However, R2 and R2° may be the same or different.) At least one of the compounds represented by It has a structure containing the following.

As the color developer contained in the heat-sensitive color forming layer, the conventionally known color developer mentioned above can be used, but in particular 1.
Preference is given to using 1'-bis(p-hydroxyphenyl)propane. This is remarkable in the heat-sensitive recording material having the heat-sensitive color forming layer of the present invention, which uses the compound of formula (I) as a colorless dye and at least one selected from the compounds of formula (II) and (III) as a sensitizer. The reason for the sensitizing effect is thought to be as follows, although the details are not necessarily clear.

That is, the thermal dissolution rate of the sensitizer itself represented by the above formula (II) or (Irl) is not only extremely high, but also the sensitizer represented by the above (1)
This is thought to be because the thermal dissolution diffusion rate and saturation solubility for the colorless dye represented by the formula are high, so the sensitizer acts as a medium during heating, and the colorless dye and developer quickly form a coloring composition.

The following are representative examples of the compounds of formulas (TI) and (III) above.

... (II-1) ... (II-2) ... (III-2) In the heat-sensitive coloring layer of the present invention, sensitization may be carried out together with the above-mentioned sensitizer to the extent that the desired effect is not inhibited. Effective fatty acid amides such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, coconut fatty acid amide, etc. may be included.

In the heat-sensitive recording material of the present invention, the content of each colorless dye, color developer, and sensitizer in the heat-sensitive coloring layer is 0.
．． 2-4.0 g/m2, preferably 0.3-2゜2
It is appropriate to take it as g/m2.

The heat-sensitive coloring layer according to the present invention preferably contains a filler, and such fillers include calcium carbonate, clay, fired clay, silica, zinc oxide, titanium oxide, talc, aluminum hydroxide, and hydroxide. Examples include inorganic white pigments such as magnesium, barium sulfate, and surface-treated silica, as well as organic fine particles such as starch, polystyrene resin, and urea-formalin resin.

Binding agents for binding colorless dyes, color developers, white organic pigments, etc. on the support include polyvinyl alcohol and its derivatives, polyvinylpyrrolidone, starch and its rust conductors, hydroxyl ethyl cellulose, ethyl cellulose, methyl cellulose, Water-soluble polymers such as cellulose conductors such as carboxymethylcellulose, styrene maleic anhydride copolymer alkali salts, isobutylene maleic anhydride copolymer alkali salts, polyacrylic acid alkali salts, alginate alkali salts, polyacrylamide, casein, gelatin, etc. , also styrene/butadiene copolymer,
Various latexes such as polyurethane, polyvinyl acetate, and polyacrylic acid can be used.

Furthermore, depending on the application, waxes such as paraffin wax, carnauba wax, polyethylene wax, and methylolstearamide, and lubricants such as zinc stearate and calcium stearate can be added.Additionally, to improve water resistance, , a crosslinking agent for crosslinking the binder, etc. can be blended. For applications requiring good recording stability, it is preferable to incorporate a preservation improver such as a phenolic antioxidant.

As a method for forming a heat-sensitive coloring layer on a support from a heat-sensitive paint produced using colorless dyes, color developers, pigments, binders, and other auxiliary agents, there are conventional methods such as plate coater and air knife. Known methods such as a coater, roll coater, lot coater, etc. can be used, and the preparation can be similarly adjusted using conventional methods.

As the support used to constitute the heat-sensitive recording material of the present invention, paper, synthetic paper, plastic film, nonwoven fabric, resin-impregnated paper, etc. can be used. Further, in order to prevent curling of the product after coating the heat-sensitive coloring layer, it is also preferable to coat one or both sides of the support with a water-soluble polymer, latex, or the like. Furthermore, in order to improve coloring sensitivity and prevent residue from adhering to thermal elements such as thermal heads, it is preferable to provide an intermediate layer mainly composed of the above-mentioned inorganic or organic filler between the support and the thermosensitive coloring layer. There are many.

In order to improve the storage stability of the heat-sensitive recording material of the present invention, it is preferable to provide an overcoat layer on the heat-sensitive coloring layer. No. 39078, Special Public Interest 1
The method described in No.-17478 can be used.

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

First, dispersions A-D in which the following colorless dye was dispersed, dispersions P-R in which a color developer was dispersed, and dispersions U-Z in which a sensitizer was dispersed were prepared. . That is, in each method, wet dispersion was performed using a sand grinder until the average particle size became 1 to 2 μm, and a dispersion liquid was prepared. The modified polyvinyl alcohol is sulfonated PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.).
(trade name: Goselan L-3266) was used.

In addition, the number of blended parts indicates the number of parts by weight.

Colorless dye dispersion [Liquid A] 10 parts 10% modified polyvinyl alcohol water 20 parts [Liquid B] 10 parts 3-n-dibutylamino-6-methyl-7-anilinofluorane 10 parts 10% modified polyvinyl alcohol water 20 parts Parts [C-N] 3-(Toethyl-N-isoamyl) Amino-6-methyl-7-anilinofluorane 10 parts 10% modified polyvinyl alcohol water [Liquid D] 10 parts 20 parts 3-(N-Methyl-N -propyl) Amino-6-methyl-7-anilinofluorane 10 parts 10% modified polyvinyl alcohol water developer dispersion [P solution] 10 parts 20 parts 1.1'-bis(p-hydroxyphenyl)propane (
Bisphenol A) 10 parts 10% modified polyvinyl alcohol water [Q] 4-Hydroxy-4'-isopropoxydiphenyl sulfone 10% modified polyvinyl alcohol water 10 parts 20 parts 10 parts 10 parts 20 parts [R] 4. 4°-hydroxy-3,3°-allyl-diphenylsulfone 10 parts 10% modified polyvinyl alcohol water sensitizer dispersion [U solution] 10 parts 20 parts 10% modified polyvinyl alcohol 10 parts water 20 parts [■ solution] 10 % modified polyvinyl alcohol 10 parts water 20 parts [W solution] 10% modified polyvinyl alcohol water [X solution] 10 parts 20 parts 10% modified polyvinyl alcohol 10 parts water

20 parts [Y liquid co-m-terphenyl 10 parts l
O% modified polyvinyl alcohol 10 parts water

20 parts [Z solution] p-benzylbiphenyl 10 parts 10
% modified polyvinyl alcohol 10 parts water

20 parts A, B, C, D colorless dye dispersions, P, Q, R color developer dispersions, UVw, x, y, z sensitizer dispersions, 30% Calcium carbonate dispersions were mixed at blending ratios of 10 parts, 15 parts, 15 parts, and 10 parts, respectively, and 10 parts of a 10% solution of fully saponified polyvinyl alcohol (average degree of polymerization of about 1000) was added as the main binder. Heat-sensitive paints having the combinations shown in Table 1 below were prepared. Calcium carbonate is Callite S manufactured by Shiraishi Kogyo.
I used ^.

The intermediate layer and the heat-sensitive paint were coated on a 45 g/l 112 high-quality paper as a support at a dry weight of 9 to 5 g/m' and 4 to 5 g/m', respectively, to obtain a heat-sensitive recording material. Ta. The above-mentioned intermediate layer uses an inorganic filler layer mainly composed of fired clay, and the ratio of the inorganic filler to the binder is 1.
00:10 (dry weight ratio). Styrene-butadiene latex was used as the binder.

The heat-sensitive recording material on each side shown in Table 1 below, prepared as described above, was processed using a super calender until the Bekk smoothness was 4.
After adjusting the time to be 00 to 600 seconds, the color development sensitivity was measured using a thermal head printing device manufactured by Taishoku Denki.

The color density was measured using a Macbeth densitometer (RD-5143 manufactured by Macbeth) at an applied power of 0.4 W/dot, a pulse period of 4.0 ms, and a thermal head resistance of 11.
The test was carried out at 91Ω, and the results shown in Table 1 were obtained as the level of color development sensitivity.

Table 1 ◎...Particularly excellent.

○...Excellent.

△...Slightly inferior.

×...Inferior.

As is clear from the results in this table, the heat-sensitive recording materials of each example having a specific configuration of the present invention exhibited superior color development sensitivity compared to the comparative example, and the heat-sensitive recording materials of Examples 1 to 4 It showed particularly excellent color development sensitivity.

Although the above embodiments have been described with reference to specific examples and numerical values of the present invention, it is of course possible to make various changes and modifications without departing from the broad spirit and scope of the present invention.

(Effects of the Invention) As described above in detail, the present invention has the effect that it is possible to obtain a heat-sensitive recording material that has high color density during heat-sensitive recording and has high color development sensitivity. Further, the heat-sensitive recording material of the present invention has an effect of excellent image retention, and is extremely useful industrially.

Procedural amendment 1990 7+173 days

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording in which a heat-sensitive coloring layer containing a colorless or light-colored electron-donating dye precursor and an electron-accepting substance that develops color by reacting with the dye precursor is provided on a support. In the material, the dye precursor is a compound represented by the following structural formula (I) ▲Mathematical formula, chemical formula, table, etc.▼...(I), and the thermosensitive coloring layer contains the following general formula (II). ) and (III
) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(II) (R_1 and R_1' are any of the groups H, Cl, and CH_3. However, R_1 and R_1' may be the same or different.) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(III) (R_2 and R_2' are either H or CH_3. However, R_2 and R_2' may be the same or different.) A heat-sensitive recording material characterized by containing at least one of the compounds shown below. 2. The heat-sensitive recording material according to claim 1, wherein the electron-accepting substance is 1,1'-bis(p-hydroxyphenyl)propane. 3. The heat-sensitive recording material according to claim 1 or 2, wherein the heat-sensitive coloring layer contains ▲a mathematical formula, a chemical formula, a table, etc.▼ as the compound of the general formula (II). 4. The heat-sensitive recording material according to claim 1 or 2, wherein the heat-sensitive coloring layer contains ▲which has a numerical formula, chemical formula, table, etc.▼ as the compound of the general formula (II). 5. The heat-sensitive recording material according to claim 1 or 2, wherein the heat-sensitive coloring layer contains ▲a mathematical formula, a chemical formula, a table, etc.▼ as the compound of the general formula (III). 6. The heat-sensitive recording material according to claim 1 or 2, wherein the heat-sensitive coloring layer contains ▲a mathematical formula, a chemical formula, a table, etc.▼ as the compound of the general formula (III).