JPH07304255A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain excellent thermal response and storage stability by adding a compd. selected from specific 4-hydroxy-4'-isopropoxydiphenyl sulfone and a sulfonic ester derivative to a thermal color forming layer containing an org. acidic substance reacting with a leuco dye by heating to develop a color. CONSTITUTION:A compd. selected from 4-hydroxy-4'-isopropoxydiphenyl sulfone represented by formula I and a sulfonic ester derivative represented by formula II (wherein R1 is an aryl group, a 1-8C alkyl group or a cycloalkyl group, R2 is an aryl group, a 1-8C alkyl group or a cycloalkyl group and j and k are an integer of 0-5) is added to the thermal color forming layer of a thermal recording material containing a leuco dye colorless or light-colored at the normal temp. and an org. acidic substance reacting with the leuco dye by heating to develop a color.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material excellent in thermal response of a recorded image and storage stability (moisture resistance, plasticizer resistance) with less fog on the background.

[0002]

2. Description of the Related Art In recent years, the amount of information has increased with the diversification of information, and various recording systems and recording materials have been studied and put into practical use in the field of information recording for recording such information. There is. Among them, the thermal recording method can obtain a recorded image by simply heating the thermal recording material and does not require a complicated developing step. It is easy and cheap, and cheap paper is often used as a support for the heat-sensitive recording material, but in this case, there is an advantage that the obtained recording material has a feeling similar to plain paper, It is used in many fields such as computer output, printers such as calculators, recorders for various measuring instruments, facsimiles, automatic ticketing machines, thermal copying machines, and labels.

However, with the spread of these OA equipment,
Recently, sales competition for thermal paper has intensified, and thermal paper manufacturers have been forced to compete in cost. In addition, for OA equipment manufacturers, the spread of word processors in general households has almost reached a stage, and in order to popularize a plurality of units, a high function that is different from the conventional function has been demanded. As one of them, when a conventional thermal recording material is used as a label or the like in a POS system or the like, the label particularly used in the supermarket or the like comes into contact with water, wrap films or oils. In many cases, there was a defect that the recorded image was significantly discolored. For this reason, there has been a demand for a chemical agent which has good thermal response and is inexpensive and which can stabilize printed images.

Therefore, as an attempt to solve the problems in the conventional heat-sensitive recording material, it has been proposed to add various substances to the heat-sensitive color forming layer to improve the storage stability of a recorded image. ing. Japanese Examined Japanese Patent Publication No. 63-4606
JP-A-59-73 discloses a method in which a diphenyl sulfone derivative having a phenol skeleton as a color developer and a dibenzyl ester of phthalic acid as a sensitizer are contained in JP-A-59-73.
990, JP-A-61-160292, JP-A-60-
176794, JP-A-1-209184, JP-A-4
In Japanese Patent Laid-Open No. 37589, it is proposed to use sulfonic acid ester as a sensitizer for storage stability. However, as a representative of commercially available developers, a combination of bisphenol A and a sulfonate ester is used, and as a developer, a phenol is used.
Although the storage stability is improved by any of the techniques in which a diphenylsulfone derivative having a skeleton of a skeleton and a commercially available sensitizer are combined, it is not satisfactory and it cannot be said that the performance of each drug is sufficiently brought out.

[0005]

SUMMARY OF THE INVENTION The present invention was devised in view of such a viewpoint, and its purpose is to:
It is an object of the present invention to provide an inexpensive heat-sensitive recording material which has excellent thermal responsiveness, has less fog on the background, and has excellent storage stability (humidity resistance, plasticizer resistance).

[0006]

That is, according to the present invention, a thermosensitive coloring layer containing a colorless or pale-colored leuco dye at room temperature and an organic acidic substance which reacts with the above leuco dye to develop a color when heated is provided on a support. In the heat-sensitive recording material obtained by

[Chemical 4] 4-hydroxy-4'-isopropoxydiphenyl sulfone represented by the following general formula (2)

[Chemical 5] (Wherein R ₁ is an aryl group, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group, X ₁ is a benzene ring, a naphthalene ring, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group, Y ₁ Is a benzene ring, a naphthalene ring, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group, R ₂ is an aryl group,
It shows an alkyl group or a cycloalkyl group having 1 to 8 carbon atoms, j is an integer of 0 to 5, and k is an integer of 0 to 5. ) A heat-sensitive recording material containing one or more compounds selected from the sulfonic acid ester derivatives represented by

In the present invention, the leuco dye used as a color former is a colorless or pale color at room temperature and is a substance that reacts with an acidic substance under heating to develop a color, and 3,3-bis (p-dimethylamino) Phenyl) -6-dimethylaminophthalide and other triallylmethane dyes, 4,4'-bisdimethylaminobenzhydridobenzyl ether and other diphenylmethane dyes, benzoyl leuco methylene blue and other thiazine dyes, and 3-methyl Examples thereof include spiro-based dyes such as spirodinaphthopyran, fluoran-based dyes, and other leucoauramine-based, indoline-based, and indigo-based dyes. When used, these color formers may be used alone or in combination of two or more.

Further, the organic acidic substance used together with the above leuco dye is a substance which comes into contact with the leuco dye by heating and becomes a developer, and in the present invention, 4- represented by the above formula (1) is used.
Hydroxy-4'-isopropoxydiphenyl sulfone is used. In addition, various phenol compounds, organic acids and the like can be mentioned as the organic acidic substance, and these can be used together with 4-hydroxy-4′-isopropoxydiphenyl sulfone.

In the present invention, the thermosensitive coloring layer is selected from 4-hydroxy-4'-isopropoxydiphenyl sulfone represented by the above formula (1) and the sulfonate derivative represented by the above general formula (2). Compounds as sensitizers 1
One kind or two or more kinds are mixed. Preferably, the following general formula (3)

[Chemical 6] One or more compounds selected from the sulfonate derivative represented by are blended.

In the general formula (2), R ₁ is an aryl group, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group,
X ₁ is a benzene ring, naphthalene ring, alkyl group or cycloalkyl group having 1 to 8 carbon atoms, Y ₁ is benzene ring, naphthalene ring, alkyl group or cycloalkyl group having 1 to 8 carbon atoms, R ₂ is aryl Group, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group, j is an integer of 0 to 5, and k is 0.
Indicates an integer of ˜5. In the general formula (3), R ₃ is an alkyl group having 1 to 4 carbon atoms, X ₂ is a benzene ring, a naphthalene ring or an alkyl group having 1 to 4 carbon atoms, and Y ₂ is a benzene ring, a naphthalene ring or a carbon number 1 ~ 4 alkyl groups, R ₄
Represents an aryl group or an alkyl group having 1 to 4 carbon atoms,
Is an integer of 0 to 5, and m is an integer of 0 to 5. Where X
_{When 1} , Y ₁ , X ₂ and Y ₂ are a benzene ring or a naphthalene ring, j, k, l and m can be integers of 1 or more, but they must be 5 or less. Further, X ₁ and Y ₁ , and X ₂ and Y ₂ may be the same or different.

A preferred specific example is a compound having a melting point of 70 to 110 ° C. among the sulfonic acid ester derivatives represented by the above general formula (3), and more specifically, the following (compound 1), (Compound 2), (Compound 3), (Compound 4), (Compound 5), (Compound 6) and (Compound 7) may be mentioned.

[Chemical 7] (Compound 1) Melting point = 95 ° C.

[Chemical 8] (Compound 2) Melting point = 105 ° C.

[Chemical 9] (Compound 3) Melting point = 89 ° C.

[Chemical 10] (Compound 4) Melting point = 78 ° C.

[Chemical 11] (Compound 5) Melting point = 75 ° C.

[Chemical 12] (Compound 6) Melting point = 98 ° C.

[Chemical 13] (Compound 7) Melting point = 103 ° C.

These compounds are prepared by converting phenolic compounds into phenol in a solvent such as sodium hydroxide and water or THF.
It is obtained by reacting this with sulfonic acid chloride. For example, phenol is reacted with sodium hydroxide in THF, and paratoluenesulfonic acid chloride is reacted with it to synthesize paratoluenesulfonic acid phenyl ester. When using, one or two or more selected from these can be used. The amount of these used varies depending on the type of leuco dye, sensitizer, organic acidic substance used, etc.
The sensitizer is usually 1 to 6 parts by weight, preferably 1.5
~ 2.5 parts by weight.

In addition to the above, it is added for the purpose of ensuring the storage stability of the color-developed portion, and although the thermal response is slightly inferior, it is possible to use organic acidic substances such as epoxy resin, zinc stearate and zinc salicylate. You may use together a metal salt. Further, various additives can be added to the heat-sensitive recording material of the present invention depending on its use and the like. Examples of such an additive include, for example, polyvinyl alcohol (PVA) for fixing the leuco dye and the organic acidic substance dispersed in fine particles in a state of being isolated from each other, methyl cellulose, carboxymethyl cellulose, polyacrylic acid casein, gelatin, starch or Binders such as these derivatives, whiteness of the thermosensitive coloring layer, slipperiness of writing instruments, calcium carbonate added for the purpose of sticking, kaolin, clay,
There are white pigments such as talc and titanium oxide. These additives are mixed or separately coated on a support such as a paper film to form a thermosensitive color developing layer. Further, the thermosensitive coloring layer may have other layers such as a protective layer.

[0014]

In the thermosensitive recording material of the present invention, when the leuco dye constituting the thermosensitive coloring layer is colored by the organic acidic substance, the sulfonic acid ester derivative contained in the thermosensitive coloring layer makes the printed image fast. It is thought to cause sex.

[0015]

EXAMPLES The present invention will be specifically described below based on Examples and Comparative Examples. Example 1 (1) Preparation of solution A 11.5 parts by weight of the sulfonic acid ester (Compound 1),
4-hydroxy-4'-isopropoxydiphenyl sulfone 1
1.5 parts by weight, 46 parts by weight of 5 wt% -PVA aqueous solution and 46 parts by weight of water were pulverized and mixed by using a sand mill to obtain an average particle size of 0.6.
A μm solution A was prepared. (2) Preparation of solution B 7'-anilino-3 '-(dibutylamino) -6'-methylfluorane (5.5 parts by weight) and 5 wt% -PVA aqueous solution (49.5 parts by weight) were ground and mixed using a paint shaker. And the average particle size is 0.
An 8 μm solution B was prepared. (3) Preparation of thermosensitive recording paper 20 parts by weight of liquid A, 10 parts by weight of liquid B, 1 part by weight of paraffin wax emulsion (Hydrin Z-7 manufactured by Chukyo Yushi), paraffin wax emulsion (Hydrin P-7 manufactured by Chukyo Yushi) 4 parts by weight, 10 parts by weight of 50% calcium carbonate dispersion and 11.5 parts by weight of 10 wt% -PVA aqueous solution are mixed to prepare a coating solution, and the coating solution is applied onto a base paper and dried. A thermal recording paper having a coating amount of 6 g / m ² was obtained. The thermal recording paper thus obtained was subjected to a dynamic color development test at 24 V and 1.0 ms for sensitivity and humidity resistance test, and at 27 V and 1.9 ms for plasticizer resistance test. At the same time, the color density of the background was measured. The results of the humidity resistance test are shown in Table 1, and the results of the plasticizer resistance test are shown in Table 2.

In the dynamic color development test, a printing tester (manufactured by Okura Electric Co., Ltd.) was used, and the color development density was measured by Macbeth reflection densitometer RD
914 was used for the measurement. (4) Humidity resistance test method The thermosensitive recording paper that had been subjected to the dynamic color development test was placed in a thermo-hygrostat (40
C., relative humidity 90%) was stored for 10 hours, and then the color density of the printed portion was measured using a Macbeth reflection densitometer RD-914. The residual rate was calculated by the following mathematical formula (1). Residual rate = (AB) / C-(1) (In the formula, A represents the dynamic color density after the humidity resistance test, and B represents
Indicates the value obtained by subtracting the color density of the background before the humidity resistance test from the color density of the background after the humidity resistance test, and C indicates the dynamic color density before the humidity resistance test. (5) Test method for plasticizer resistance A vinyl chloride wrap is adhered to the entire printing surface of the thermosensitive recording paper subjected to the dynamic color development test. This test thermal recording paper was stored in a dryer (50 ° C.) for 10 hours, and then the color density of the printed portion was measured by using a Macbeth reflection densitometer RD-914. The residual rate was calculated by the following mathematical formula (2). Residual rate = (D−E) / F ── (2) (In the formula, D indicates the dynamic color density after the plasticizer resistance test, and E
Indicates a value obtained by subtracting the background color density before the plasticizer resistance test from the background color density after the plasticizer resistance test, and F represents the dynamic color density before the plasticizer resistance test. )

Example 2 A thermal recording paper was prepared in exactly the same manner as in Example 1 except that (Compound 2) was used in place of (Compound 1) in the preparation of the liquid A of Example 1. A color development test was conducted in the same manner as in Example 1. The results of the humidity resistance test are shown in Table 1, and the results of the plasticizer resistance test are shown in Table 2.

Example 3 A thermosensitive recording paper was prepared in exactly the same manner as in Example 1 except that (Compound 3) was used in place of (Compound 1) in the preparation of the solution A of Example 1. A color development test was conducted in the same manner as in Example 1. The results of the humidity resistance test are shown in Table 1, and the results of the plasticizer resistance test are shown in Table 2.

Comparative Example 1 Except that 11.5 parts by weight of bisphenol A was used in place of 11.5 parts by weight of 4-hydroxy-4'-isopropoxydiphenylsulfone in the preparation of the liquid A of Example 1. A thermosensitive recording paper was prepared in exactly the same manner as in Example 1, and a color development test was conducted in the same manner as in Example 1. The results of the humidity resistance test are shown in Table 1, and the results of the plasticizer resistance test are shown in Table 2.

Comparative Example 2 Except that 11.5 parts by weight of bisphenol A was used in place of 11.5 parts by weight of 4-hydroxy-4'-isopropoxydiphenylsulfone in preparing the liquid A of Example 2. A thermosensitive recording paper was prepared in exactly the same manner as in Example 1, and a color development test was conducted in the same manner as in Example 1. The results of the humidity resistance test are shown in Table 1, and the results of the plasticizer resistance test are shown in Table 2.

Comparative Example 3 Except that 11.5 parts by weight of bisphenol A was used instead of 11.5 parts by weight of 4-hydroxy-4'-isopropoxydiphenylsulfone in the preparation of the liquid A of Example 3. A thermosensitive recording paper was prepared in exactly the same manner as in Example 1, and a color development test was conducted in the same manner as in Example 1. The results of the humidity resistance test are shown in Table 1, and the results of the plasticizer resistance test are shown in Table 2.

Comparative Example 4 In the preparation of solution A of Example 1, (Compound 1) 11.
A thermosensitive recording paper was prepared in exactly the same manner as in Example 1 except that 11.5 parts by weight of parabenzyl biphenyl was used instead of 5 parts by weight, and a color development test was conducted in the same manner as in Example 1.
The results of the humidity resistance test are shown in Table 1, and the results of the plasticizer resistance test are shown in Table 2.

Comparative Example 5 In preparing the solution A of Example 1, (Compound 1) 11.
A thermosensitive recording paper was prepared in the same manner as in Example 1 except that metatriphenyl was replaced by 11.5 parts by weight instead of 5 parts by weight, and a color development test was conducted in the same manner as in Example 1. The results of the humidity resistance test are shown in Table 1, and the results of the plasticizer resistance test are shown in Table 2.

Comparative Example 6 In preparing the solution A of Example 1, (Compound 1) 11.
A thermosensitive recording paper was prepared in the same manner as in Example 1 except that 11.5 parts by weight of dibenzyl terephthalate was used instead of 5 parts by weight, and a color test was conducted in the same manner as in Example 1. . The results of the humidity resistance test are shown in Table 1, and the results of the plasticizer resistance test are shown in Table 2. (Hereafter, margin)

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

The sulfonic acid ester derivative of the present invention is
It has excellent thermal responsiveness as an image stabilizer for heat-sensitive recording materials and has improved image stability (moisture resistance, plasticizer resistance). (Hereafter, margin)

Claims (2)

[Claims] 1. A thermosensitive recording material comprising a support, and a thermosensitive coloring layer containing a colorless or pale-colored leuco dye at room temperature and an organic acidic substance which reacts with the leuco dye to produce a color when heated. The coloring layer has the following formula (1): 4-hydroxy-4'-isopropoxydiphenyl sulfone represented by the following general formula (2) (Wherein R ₁ is an aryl group, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group, X ₁ is a benzene ring, a naphthalene ring, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group, Y ₁ Is a benzene ring, a naphthalene ring, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group, R ₂ is an aryl group,
It shows an alkyl group or a cycloalkyl group having 1 to 8 carbon atoms, j is an integer of 0 to 5, and k is an integer of 0 to 5. ) A heat-sensitive recording material containing one or more compounds selected from sulfonic acid ester derivatives represented by 2. A sulfonate derivative is represented by the following general formula (3): (Wherein R ₃ is an alkyl group having 1 to 4 carbon atoms, X ₂ is a benzene ring, a naphthalene ring or an alkyl group having 1 to 4 carbon atoms, Y ₂ is a benzene ring, a naphthalene ring or 1 to 4 carbon atoms.
Alkyl group, R ₄ is ants - indicates group or an alkyl group having 1 to 4 carbon atoms, l is an integer of 0 to 5, m is an integer of 0-5. The heat-sensitive recording material according to claim 1, which is one kind or two or more kinds of compounds selected from the sulfonic acid ester derivatives represented by (4).