JPS62167082A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance preservability along with thermal characteristics, heat resistance and water resistance, in a thermal recording paper using colorless electron donating leuco dye as a color former, by containing at least one kind of a phenol compound represented by a specific formula in a recording layer as an acidic substance. CONSTITUTION:At least one kind of colorless electron donating leuco dye being a color former and at least one kind of a phenol compound represented by general formula I (wherein R1 and R2 are a hydrogen atom, a 1-5C alkyl group, a 1-5C alkoxy group or a halogen atom and n is an integer of 1-9) are made present in one thermal recording layer as fine particles in a uniform state. As a binder for bonding a mixture of the color former and the coupler to a support sheet, a water-soluble or water-insoluble binder such as polyvinyl alcohol is used. The wt. ratios of both components and the binder are set so that the amount of the phenol compound represented by the general formula I is 1-10 times, pref. 1-5 times and the binder is 0.3-3 times with respect to the color former.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material that has excellent heat resistance and water resistance, and has improved heat-sensitive characteristics. Yes, especially color development sensitivity, moisture resistance,
This invention relates to heat-sensitive recording paper with improved storage properties such as oil resistance and plasticizer resistance.

(Conventional technology) The minimum performance required for thermal recording paper and recording layers is excellent self-coloring resistance, pressure coloring resistance, heat sensitivity, light resistance, heat decoloring resistance, moisture decoloring resistance, and water resistance. However, at present we have not found anything that completely satisfies these requirements.

Specific examples of electron-accepting compounds in heat-sensitive recording materials include phenolic compounds, organic acids or metal salts thereof, and hydroxybenzoic acid esters, and phenolic compounds are particularly widely used.

Specifically, 4-1-butylphenol, 4-phenylphenol, 2,2'-hydroxyphenol, p
- to:)'omethyloxybenzoate, 2,2-bis(4-
hydroxyphenyl)propane [bisphenol A],
4,4'-impropylidene bis(2-methylphenol), 4,4'-impropylidene diphenol, bis-
Examples include 4-hydroxyphenyl sulfone. However, these phenolic compounds cannot necessarily be said to be satisfactory materials for heat-sensitive recording materials.

That is, these phenolic compounds have drawbacks such as insufficient color density when combined with t-m child-donating colorless dyes and poor image storage stability.

As a method for improving the storage stability of images, the following proposal has been made in which a sensitizer, a color developer, a storage stabilizer, or the like is added to a color developer.

First, as a method for improving moisture and heat resistance storage stability, JP-A-60
-46.292, addition of 7-tole derivatives such as 1-benzyl-2-hydroxynaphthalene, JP-A-60
79.996 describes a method of adding 4-benzyloxyphenylphenol and 4-hydroxybenzoic acid biphenyl ester.

As a method for improving plasticizer resistance, JP-A-60-
144388 describes a method of adding 2,2',4,4'-tetraoxyacybophenone, and JP-A-60-176.794 describes a method for improving oil-resistant storage stability. The publication describes examples of adding 4-hydroxyphenylarylsulfones and 4-hydroxyarylsulfonates.

(Problems to be Solved by the Invention) The present inventors used a known electron-donating colorless dye as a coloring agent to produce a thermosensitive recording medium according to a conventionally known method and the method described in each of the above-mentioned patent publications. When paper was manufactured and tested for the performance aspects that thermal recording paper should have, it was found that paper with excellent color development sensitivity and excellent storage properties such as moisture resistance, oil resistance, and plasticizer resistance had good resistance to background fog and humidity. As a result, the background fog was large, and there was no practical thermal recording paper. The present invention provides a heat-sensitive recording paper that has improved these properties without staining the background.

(Means for Solving the Problems) The present inventors have completed the present invention as a result of intensive research to improve the above-mentioned drawbacks of heat-sensitive recording materials using known electron-donating colorless dyes. be. That is, the present invention provides a recording medium that basically comprises at least one type of colorless or slightly pale electron-donating colorless dye and an acidic substance that causes the electron-donating colorless dye to develop color when heated. In the thermal recording paper, the acidic substance in the recording layer is represented by the following general formula (1) (wherein R, R, is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms,
It represents an alkoxy group having 1 to 5 carbon atoms or a halogen atom, and n represents a strain number of 1 to 9. ) contains at least -alt- of a phenolic compound represented by '
j&: A characteristic heat-sensitive recording material.

The conventionally known p-phenylphenol (hereinafter referred to as pp
p), bisphenol A (hereinafter abbreviated as BPA)
, benzyl hydroxybenzoate (hereinafter abbreviated as POB) and the like, and the various sensitizers described in the above-mentioned publications as auxiliaries to the heat-sensitive recording material of the present invention do not interfere with the present invention. do not have.

Specific examples of the heptanoyl compound of the above general formula (1) according to the present invention are shown below, but the present invention is not limited thereto.

Compound example of general formula CI) OHOH
2881, above (1), (2), (3), (4), (5
) about 19:18 + 15:15 with i0H
:29:6 mixture) OHs OHs Electron-donating colorless dyes used in the present invention are conventionally known ones, such as triarylmethane compounds,
Diphenylmethane compounds, xanthine compounds, thiazine compounds, oxazi/spiropyran compounds, and the like are known.

Some examples of these include triarylmethane compounds such as 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (C!VL), 6.3
-bis(p-dimethylamino)7thalide, 5-Cp-dimethylaminophenyl)-3-(1,3-dimethylindol-3-yl)phthalide, and xanthine compounds include rhodamine B-anilinolactam. , rhodamine (p-nitroanilino)''7cutam, 2-anilino-3-methyl-6-dinithylaminofluorane, 2-anilino-3-methyl-6-(N-cyclohexyl-N-
ethyl)aminofluorane, 2-anilino-3-methyl-6-(N-ethyl-N-isoamyl)aminofluorane, 2-anilino-3-methyl-6-di(n)butylaminofluorane, etc. Examples of thiazine compounds include benzoylleucomethylene blue and p-nitrobenzylleucomethylene blue, and examples of spiro compounds include 5-)tylspirodinaphthopyran, 3-benzylspiro-cinnaphthopyran, and ! l-7' lopyrususpirogipenzopyra y and the like.

The present invention is not limited to these electron-donating colorless dyes. Further, these may be used alone or in combination.

Next, a specific example of manufacturing a heat-sensitive recording paper using the heat-sensitive recording material of the present invention will be shown.

'A water-soluble or water-insoluble binder is used as the binder for binding the mixture of color forming agent and color developer onto the support sheet. Typical examples include polyvinyl alcohol, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, gum arabic, starch, gelatin, casein, polyvinylpyrrolidone, styrene-maleic anhydride copolymer, polyacrylic acid amide, polyacrylate, Although there are terpene resins and petroleum resins, the binder that can be particularly preferably used in the present invention is a water-soluble binder, a typical example of which is polyvinyl alcohol.・An electron-donating colorless binder that is a coloring agent. at least one dye;
According to the present invention, a method of providing a layer in which each component consisting of at least one type of phenol compound represented by the general formula (1) exists in a uniform state as fine particles in one heat-sensitive layer is a method for producing heat-sensitive recording paper. Favorable in terms of performance.

When producing heat-sensitive recording paper, the weight ratio of each of the above-mentioned components and binder in the recording layer is such that the amount of the phenol compound represented by general formula (1) is 1 to 10 to the color former.
The binder is used at 13-3 times, preferably 1 to 5 times.

The color former, developer, and additive are preferably each separately dispersed in a dispersing machine such as a ball mill, dyno mill, sand mill or paint conditioner in water or an organic medium containing a binder, preferably a binder. is dispersed in water as a medium and ground to form a suspension with a particle size of 1-6μ, preferably 2-4μ. If necessary, add an antifoaming agent, dispersant, or brightener to disperse.
It may be crushed.

Next, each of the above components is separately dispersed, and a suspension of the pulverized components is mixed so that the weight ratio of each component in the recording layer is as described above to prepare a paint for forming a heat-sensitive recording layer. . Apply this paint to the surface of the paper using a wire burner 6~
20, and the weight of the solid after drying is 3 to 717 m1.
A heat-sensitive recording paper is produced by coating the mixture so as to give the following properties and drying it in a blow dryer at room temperature to 70°C. If necessary, inorganic or organic fillers may be added to the paint to improve the fusing resistance, writability, etc. of the thermal head.

(Effects of the Invention) The thermal recording paper thus obtained has excellent thermal properties, heat resistance, and water resistance, and is particularly excellent in storage properties such as moisture resistance, oil resistance, and plasticizer resistance. This paper successfully overcomes the drawbacks of conventionally known thermosensitive recording papers without the whitening phenomenon that impairs its commercial value as a thermosensitive recording paper.

(Examples) The present invention will be specifically explained below using Examples, but the present invention is not limited to these Examples.

Solution A (dye dispersion) Solution B (developer dispersion) Solution C (comparative developer dispersion) Solution D (additive dispersion) The canned liquid of the above composition was milled into particles with a particle size of 2 to 3 using a ball mill. Grind down to microns.

Example 1 The above dispersions are mixed in the proportions shown below to form a paint.

However, for liquid B, the above numerical values were added in the case of one type, 4.5 parts each in the case of two types, and 3 parts equivalent in the case of three types.

Example 2 The above dispersions are mixed in the proportions shown below to form a paint.

However, for liquid B, the above values were added in the case of one type of gold, and 3 parts and the same amount of gold were added in the case of two electrodes.

Comparative Example 1 For comparison purposes, the following proportions were dispersed and mixed to form a paint, and a heat-sensitive coating liquid was obtained.

These paints were applied to the surface of high-quality paper using a wire percoater with 18 scraps, and the solid content after drying was 5 f/lr?
I applied it so that it looked like this and put it in a blow dryer to dry it. Each of the obtained thermal recording papers was subjected to performance tests.

The results are shown in Table I.

Note■ Heating color development is based on Rhodiaceta type thermotest test @
(Manufactured by the French National Textile Research Institute) at a heating temperature of 70 to 1
The coloring was carried out under the conditions of 60° C., heating time of 5 seconds, and load of 100 f/11, and the uncolored portion under these conditions was designated as background D1.

Further, the reflection density was measured using a Macbeth reflection densitometer model RD-514.

Note ■ Indicates the moisture decoloring resistance after heat color development, partial sound of reflection density 1.0 developed under the conditions of Note ■ 40℃, relative humidity 90
% atmosphere, the color density of the colored part after 24 hours (Dz
), and the remaining color rate (to) = (Dv'1.0) x 1
00 was determined, and this was defined as the moisture decoloring resistance.

Note ■ The uncolored thermosensitive recording paper was measured with an uncolored partial total reflection densitometer after 24 hours in the atmosphere of Note ■ and was named 1IIIt wetland skin (Ds).

Note: Apply a 5% castor oil-chloroform solution to the entire surface of the polyester using a film applicator, and after air drying,
Color was developed using castor oil f 1.5 cm x 1G rubber stamp on the film under the conditions specified in Note 2. Stamp the area with a reflection density of 1.0, and test it at 40℃ and relative humidity of 90℃ using a constant temperature constant temperature tester.
%, and the color density (D4) after 3 hours of treatment was measured to determine the color retention rate (CDa/1.0) x 100, which was defined as oil resistance.

Note ■ Evenly cover the area with a reflection density of 1.0 that was colored under the conditions specified in Note ■ with Saran wrap (Asahi Kasei @ J product) at 50℃, 2
Color density after 24 hours of treatment with a load of 0 f/d (
Ds) t-measurement, and the residual color rate eQ = (Ds/1
．． 0)X100'i was determined and this was taken as the plasticizer resistance.

As is clear from s-1, the thermal recording paper obtained in Example 1.2 of the present invention has the following characteristics compared to the thermal recording paper of Comparative Example 1.
The storage performance of IIfft moisture, oil resistance, and plasticizer resistance was improved.

Hodogaya Chemical Industry Co., Ltd.

Claims (1)

[Claims] A recording layer is provided on a support, which basically includes at least one colorless or slightly pale electron-donating colorless dye and an acidic substance that causes the electron-donating colorless dye to develop color when heated. In thermal recording paper, the following general formula [I]▲mathematical formula, chemical formula, table, etc. is included as an acidic substance in the recording layer▼
[I] (In the formula, R_1 and R_2 represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a halogen atom, and n represents an integer of 1 to 9.) A heat-sensitive recording material characterized by containing at least one of the phenolic compounds shown below.