JPH0437589A - 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 heat-sensitive 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 heat- sensitive 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 heat-sensitive 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. 554565 (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,
With the increase in speed, the recording speed is 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-dimethylindol-3-yl) ) Phthalide, 3-(p-dimethylaminophenyl) -
Examples include 3-(2-methylindol-3-yl)phthalide.

As a diphenylmethane compound, 4.4°-bis-
Dimethylaminobenzhydrin benzyl ether, N-
herophenyl leukoolamine, N-2,4,5-
)-lichlorophenylleucoauramine, etc. are exemplified.

As xanthine compounds, rhodamine-B-anilinolactam, rhodamine (p-nitrino)lactam, 2
-(dibenzylamino)fluorane, 2-phenylamino-6-dimethylaminofluorane, 2-(o-chloroanilino)-6-dinithylaminofluorane, 2-(3
, 4-dichloroanilino)-6-dinithylaminofluorane, 2-anilino-3-methyl-6-piperidinofluorane, 2-phenyl-6-dinithylaminofluorane, 2-anilino-3-methyl- 6-dimethylaminofluorane, 2-anilino-3-methyl-6-N-methyl-
N-ethylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N-(isopropyl)aminofluorane, 2-anilino-3-methyl-6-N-methyl-
N-pentylaminofluorane, 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-dinithylaminofluorane, 2- Anilino-3-chloro-
6-N-methyl-N-dithylaminofluorane, 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-dithylaminofluorane, 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-(p-methylanilino)
-3-chloro-6-N-methyl-N-(isopropyl)
Aminofluorane, 2-(P-methylanilino)-3-
Chloro-6-N-methyl-N-(isopropyl)aminofluorane, 2-(p-methylanilino)-3-chloro,
Rho 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, 2-anilino-3-ethyl-6-N-methyl-N-
Examples include furylmethylaminofluorane.

Further, examples of the thiazine-based compound include benzoloucomethylene blue, p-nitrobenzylleucomethylene blue, and the like.

As a spiropyran compound, 3-methyl-spiro-
dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3°-cyclolose bilodinaphthopyran, 3-
Examples include benzylspiro-dinaphthopyran, 3-methyl-naphtho-(3-methoxybenzo)-spiropyran, and 3-propyl-spiro-dibenzobilane.

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°-hydroxy-3°,5°-dichlorophenyl)propane, 1.1-bis(4°-hydroxyphenyl)cyclohexane, 2.2-bis(4°-hydroxyphenyl)hexane, 1.1-bis (4°-hydroxyphenyl)propane, 1.1-bis(4°-hydroxyphenyl)butane, 1.1-bis(4°-hydroxyphenyl)pentane, 1.1-bis(4′-hydroxyphenyl)hexane , 1. l-bis(4°-hydroxyphenyl)hebutane, 1.1bis(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. l-bis(4°-hydroxyphenyl)
Sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 1,1-bis(4'-hydroxyphenyl)ether, 2,2-bis(4'-hydroxy-3
", 5'-dichlorophenyl)butane, phenyl 2,4-dihydroxybenzoate, 2,4-dihydroxy-4
゜Methyl-phenyl benzoate, 2,4-dihydroxy-
4゛-Phenyl chlorobenzoate, 2.4 dihydroxy-
Phenyl 6-methylbenzoate, 2.4.6-phenyl trihydroxybenzoate, 2.4-dihydroxy-6,
Phenyl 4°-dimethylbenzoate, phenyl 2.4-dihydroxy-6-methyl-4°-chlorobenzoate, 2.
Benzyl 4-dihydroxybenzoate, benzyl 2.4-dihydroxy-4°-methylbenzoate, benzyl 2,4-dihydroxy-4°-chlorobenzoate, benzyl 2.4-dihydroxy-6-methylbenzoate, 2. 4.6-
Benzyl trihydroxybenzoate, 2,4-dihydroxy-6,4°-dimethylbenzoate, 2,4-
Benzyl dihydroxy-6-methyl-4'-chlorobenzoate, 4-hydroxybenzoic acid ethyl ester, 4-hydroxybenzoic acid propyl ester, 4-hydroxybenzoic acid isopropyl ester, 4-hydroxybenzoic acid benzyl ester, 4-hydroxy- Compounds such as 4'-chlorobenzoic acid benzyl ester, 4-hydroxy-4'-methylbenzoic acid benzyl ester, and 4-hydroxy-4'-ethylbenzoic acid benzyl ester are mentioned.

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 colorless dyeing and a coloring reaction between the color developer and the coloring agent to occur due to the eutectic point effect, thereby improving the coloring sensitivity. Examples of conventionally known sensitizers include waxes, nitrogen-containing compounds, and carboxylic acid esters such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, valmitic acid amide, and coconut fatty acid amide. , naphthol derivatives, naphthoic acid derivatives, benzoic acid ester derivatives, 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. 1. It satisfies the demand for good color development sensitivity with no printing unevenness and good image reproducibility, as required by the industry, and on the other hand, it reduces the negative effects of background fogging that accompanies improvement in color development sensitivity. Thermosensitive recording materials having a structure that satisfies various 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 has the following structural formula (1) (R2, R2'' are H, CHs At least one of the compounds represented by R2, R, " may be the same or different," or a compound represented by the following in the heat-sensitive coloring layer: General formulas (!i) and (III) (R+, R+' are any group of H, C9, CH3. However, R,, R,' may be the same or different.) It has a composition containing eight elements.

As the color developer contained in the heat-sensitive coloring layer, the conventionally known color developer mentioned above can be used, but in particular 1.
Preferably l-bis(p-hydroxyphenyl)propane is used, a compound of formula (I) is used as colorless dye and at least one of the compounds of formula (11) and (III) or (IV The reason why the heat-sensitive recording material having the heat-sensitive coloring layer of the present invention using the compound of the formula ) as a sensitizer shows a remarkable sensitizing effect is thought to be as follows, although the details are not necessarily clear.

That is, the above formula (II) or (III'') or (IV
) Not only does the heat dissolution rate of the sensitizer itself as shown by the formula (1) above be high, but also the heat dissolution diffusion rate and saturation solubility for the colorless dye shown in the above formula (1) are high, so the sensitizer acts as a medium during heating. This is thought to be because the colorless dye and color developer quickly form a color-forming composition.

The following are representative examples of the compounds of formulas (II) and (m) above.

... (n-1) ... (TI-2) H3 ... (III-2) In the heat-sensitive coloring layer of the present invention, together with the above-mentioned sensitizer, a sensitizing agent may be added to the extent that the desired effect is not inhibited. Fatty acid amides such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, balmitic acid amide, coconut fatty acid amide, etc., which have a sensitizing effect, 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 set it as g/ln2.

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. In addition to inorganic white parts such as magnesium, barium sulfate, and surface-treated silica, organic fine particles such as starch, polystyrene resin, and urea-formalin resin may be mentioned.

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 derivatives, hydroxyl ethyl cellulose, ethyl cellulose, methyl cellulose, carboxymethyl cellulose. Water-soluble polymers such as cellulose derivatives such as styrene maleic anhydride copolymer alkali salts, isobutylene maleic anhydride copolymer alkali salts, polyacrylic acid alkali salts, alginate alkali salts, polyacrylamide, casein, gelatin, etc. 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 methylol stearamide, and lubricants such as zinc stearate and calcium stearate can be added. , 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.

Conventional methods such as a blade coater, an air knife coater, and a roll coater are used to form a heat-sensitive coloring layer on a support using a heat-sensitive paint produced using colorless dyes, color developers, pigments, binders, and other auxiliary agents. A known method such as a coater rod coater can be used, and the preparation can be similarly adjusted by a conventional method.

As the support used to constitute the heat-sensitive recording material of the present invention, paper, synthetic paper, plastic film, non-woven fabric, old resin 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 the coloring sensitivity and to prevent dust from being deposited on 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 to D in which the following colorless dyes were dispersed, dispersions P to H in which color developers were dispersed, and dispersions U to Z in which sensitizers were dispersed were prepared. . That is, the 8 liquids were wet-dispersed using a sand grinder until the average particle size became 1 to 2 microns, to prepare a dispersion liquid. As the modified polyvinyl alcohol, sulfonated PV (trade name: Goselan L-3266) manufactured by Nippon Synthetic Chemical Industry Co., Ltd. was used.

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

10% denatured polyvinyl alcohol water [Liquid B] 3-n-dibutylamino-6-methyl-7-anilinofluorane 10% denatured polyvinyl alcohol water [Liquid C] Fluoran 10 % Modified polyvinyl alcohol water 10 parts 20 parts 10 parts 10 parts 20 parts 10 parts 20 parts [Df night] Fluoran 10% modified polyvinyl alcohol water dish L1 [P solution] 10 parts 20 parts Enlargement agent dispersion [ U liquid] 10% modified polyvinyl alcohol water [V liquid] 10 parts 20 parts 10% modified polyvinyl alcohol water [Q liquid] 10 parts 20 parts 10% denatured polyvinyl alcohol water 10 parts 20 parts [R liquid] 10% modified polyvinyl alcohol Water: 10 parts, 20 parts, 10% modified polyvinyl alcohol water [W liquid, 10% modified polyvinyl alcohol water, 10 parts, 20 parts, 10 parts, 20 parts] [X liquid, CH.

10% modified polyvinyl alcohol 10 parts water

20 parts [Liquid Y] p-benzylbiphenyl 10 parts 10
% modified polyvinyl alcohol 10 parts water

20 parts [Z liquid co-terphenyl 10 parts 1
0% modified polyvinyl alcohol 10 parts water

20 parts of the above colorless dye dispersions of A, B, C, and D;
P, Q, R color developer dispersion, U, V.

Sensitizer dispersions of W, Polyvinyl alcohol (average degree of polymerization approximately 100
0) 10 parts of a 10% solution was added to prepare thermal paints having the combinations shown in Table 1 below. As calcium carbonate, Callite S^ manufactured by Shiraishi Kogyo was used.

The intermediate layer and the heat-sensitive paint were each coated on 45 g/cm2 of paper as a support with a dry weight of 9 to 9.
10g/+'' and 4~5g/■2!!! cloth to obtain a heat-sensitive recording material.The above-mentioned intermediate layer used an inorganic filler layer mainly composed of fired clay, and the ratio of the inorganic filler to the binder was Zo
o: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 00 to 600 seconds, the coloring sensitivity was measured using a thermal head printing device manufactured by Daiichi Denki.

The color density was measured using a Macbeth densitometer (RD-5143 manufactured by Macbeth) with an applied power of 0.4 W/dot, a pulse period of 4.0 ms, and a thermal head resistance of 1.
The test was carried out at 191Ω, and the results shown in Table 1 were obtained as the level of color development sensitivity.

Table 1 As is clear from the results in this table, the heat-sensitive recording materials of each example having a specific structure of the present invention exhibited superior color development sensitivity compared to the comparative examples, and the heat-sensitive recording materials of Examples 1 to 5 The recording material showed particularly excellent color 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.

4 others Procedural amendment 7813, 1990 Supplementary Positive book We will amend the following matters in the specification of this application.

Record 1990 Special permission wish 1st Buddha No. 33ρ2 28th page, 2nd line from the bottom r RD-5143, it says r　RD-514 ” he corrected.

2.

“Table 1” on page 29 is corrected as follows.

Name: Daio Paper Co., Ltd. 4゜Agent address: 3308゜Shigesu Building, 2-6-2 Marunouchi, Chiyoda-ku, Tokyo Contents of amendments As per attached sheet

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. A heat-sensitive recording material in which a heat-sensitive coloring layer containing a colorless or light-colored electron-donating dye precursor and an electron-accepting substance that reacts with the dye precursor to form a color is provided on a support, in which the dye precursor The body is a compound represented by the structural formula (I) according to claim 1, and the thermosensitive coloring layer has the following structural formula (IV) ▲ Numerical formula, chemical formula, table, etc. ▼... (IV) A heat-sensitive recording material characterized by containing a compound that 3. In claim 1 or 2, the electron-accepting substance is 1,1
A heat-sensitive recording material characterized in that it is '-bis(p-hydroxyphenyl)propane. 4. The heat-sensitive recording material according to any one of claims 1 to 3, wherein the heat-sensitive coloring layer contains ▲a mathematical formula, a chemical formula, a table, etc.▼ as the compound of the general formula (II). 5. The heat-sensitive recording material according to any one of claims 1 to 3, wherein the heat-sensitive coloring layer contains ▲a mathematical formula, a chemical formula, a table, etc.▼ as the compound of the general formula (II). 6. In any one of claims 1 to 3, the heat-sensitive coloring layer has the compound of the general formula (III) ▲ mathematical formula, chemical formula,
A heat-sensitive recording material characterized by containing ▼. 7. In any one of claims 1 to 3, the heat-sensitive coloring layer has the compound of general formula (III) ▲ mathematical formula, chemical formula,
A heat-sensitive recording material characterized by containing ▼.