JPS633989A - Thermal recording material - Google Patents

Abstract

PURPOSE:To improve oil resistance and plasticity resistance, by providing a thermal recording layer containing a leuco dye being a fluorane compound represented by a specific general formula and a phthalamide represented by a specific general formula on a support. CONSTITUTION:A fluorane compound represented by formula I(wherein R1 and R2 are a 1-9C alkyl group, a 3-6C cycloalkyl group, a phenyl group or a 1-4 alkyl substituted phenyl group and R3 and R4 are a 1-16c alkyl group, a phenyl group or cycloalkane having a 5-8 membered ring) as a leuco dye and a phthalmide compound represented by formula II(wherein R5 is hydrogen or a 1-6 alkyl group and R6 is a 2-12C alkyl group or a phenyl group) as a coupler are compounded to prepare a coating solution which is, in turn, applied to base paper and dried to obtain a thermal recording material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat-sensitive recording material, and more specifically, to a heat-sensitive recording material that utilizes a thermal coloring reaction between a leuco dye and a color developer.

(Prior Art) Conventionally, heat-sensitive recording materials that utilize a color-forming reaction between a colorless or light-colored basic dye and a color developer to melt and contact them with heat to obtain a colored image are generally well known. These thermal recording media are applied to a wide range of recording devices such as facsimiles, various printers, automatic ticket vending machines, and barcode labels.Recently, these recording devices have become more diversified and more sophisticated. As technology advances, the quality requirements for such heat-sensitive recording media are also becoming increasingly sophisticated.
Various heat-sensitive recording materials have been developed and used to date.

[Problem that the invention seeks to solve]

Currently, phenolic compounds such as bisphenol A, bisphenol S, and benzyl p-hydroxybenzoate are widely used as color developers for basic dyes. However, there are various problems such as image stability due to adhesion of oils and fats contained in hair styling products (image oil resistance), image stability due to adhesion of plasticizers contained in PVC rubber (image plasticizer resistance), etc. Recently, there has been a renewed demand for these properties, but a heat-sensitive recording material that can fully satisfy these demands has not yet been developed.

In order to solve these problems, the present inventors have conducted intensive studies and found that by using a combination of a specific fluoran compound as a leuco dye and a specific phthalic acid amide compound as a color developer, it is possible to improve the skin texture. It has been discovered that a heat-sensitive recording material can be obtained that can provide colored images with excellent oil resistance and plasticizer resistance without causing fog,
This has led to the completion of the present invention.

[Means for solving problems]

According to the present invention, there is provided a heat-sensitive recording material which contains a leuco dye and a color developer and which develops color by heating.

[In the above formula, R1 and R1 may be the same or different, and each represents C8-C, alkyl, 03-C6
Chloalkyl, phenyl or alkyl (CI-04)
represents substituted phenyl, R3 and R4 may be the same or different and each represent C1-C6 alkyl or phenyl, or R3 and R6 together with the carbon atom to which they are attached , may form a 5- to 8-membered cycloalkane.
As a color developer, the following general formula ) represents substituted phenyl, hydroxy-substituted phenyl, cyclohexyl, or pyridyl.

Specific examples of fluoran compounds of general formula I useful in the present invention include:

Further, the phthalic acid amide compound of the general formula (3) useful in the present invention can be easily synthesized from phthalic anhydride and a primary or secondary amine. Specific examples of such compounds include the following compounds.

In the present invention, the developer represented by the general formula (2) is used in an amount of 1 to 5 parts by weight, preferably 2 to 3 parts by weight, per 1 part by weight of the leuco dye represented by the general formula (1).

A commonly used filler may be added to the heat-sensitive recording material of the present invention. Examples of fillers include calcium carbonate, aluminum hydroxide, talc, kaolin, diatomaceous earth, titanium oxide, magnesium carbonate, silicon oxide, and the like. In addition, a dispersion of a salt such as zinc stearate or calcium stearate may be added to the recording material of the present invention as appropriate to prevent the recording layer from causing sticking upon contact with a recording head or the like. .

A sensitizer can also be added to the heat-sensitive recording material of the present invention. Examples of such sensitizers include, but are not limited to, diphenyl carbonate, phenyl 1-hydroxy-2-naphthoate, and dibenzyl terephthalate.

The sensitizer is preferably used in an amount of 1 to 5 parts by weight, preferably 2 to 4 parts by weight, per 1 part by weight of the leuco dye represented by formula 1.

Furthermore, starches, hydroxycellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, styrene-maleic anhydride copolymer, etc. can be used as a binder for the heat-sensitive recording material of the present invention, but are of course limited to these. It's not a thing.

Generally known methods can be used to obtain the heat-sensitive recording material of the present invention using the various heat-sensitive coloring layer forming components described above. For example, a leuco dye, a color developer, a sensitizer, a filler, and other additives may be used alone together with a binder, or only the leuco dye may be used alone and the remaining components may be mixed together with an aqueous polyvinyl alcohol solution, etc. in an aqueous medium. The coating liquid is prepared by adding the liquid into the liquid and pulverizing and dispersing it using a dispersing machine such as a ball mill or attritor.

Next, each dispersion liquid is mixed to prepare a heat-sensitive coloring layer coating liquid, and this is coated on a support such as paper according to a conventionally known technique.
By drying, the desired heat-sensitive recording material is obtained.

[Operation and effects of the invention]

Regarding the reason why the oil resistance and plasticizer resistance of the resulting colored image are improved when using a heat-sensitive recording material containing a specific fluoran compound and a phthalic acid amide compound as described above as a leuco dye and a color developer, respectively. is not clear. However, the fluoran compound represented by the general formula I has a relatively high molecular weight and therefore has lower solubility in organic solvents such as plasticizers than conventional fluoran compounds, so it has poor robustness such as oil resistance and plasticizer resistance. It is estimated that this will improve. Furthermore, since the phthalic acid amide compound represented by -(2) has poor solubility in water, the coating solution does not develop color, and background fogging can be suppressed. Furthermore, since this compound has a polar group, its solubility in organic solvents such as plasticizers is lower than that of conventional color developers, and its fastness such as oil resistance and plasticizer resistance is further improved. It is estimated that

Therefore, according to the present invention, it is possible to provide a heat-sensitive recording material that can provide a colored image with excellent fastness to plasticizers, oils, etc. in the colored portion.

〔Example〕

The present invention will be further explained below by showing synthesis examples of the color developer used in the present invention and examples of the present invention.

However, the present invention is of course not limited to these.

Synthesis Example I Synthesis of N-(2'-hydroxyphenyl)-2-carboxybenzamide 18 g of phthalic anhydride was dissolved in 200 ml of tetrahydrofuran, and while stirring at room temperature, O-aminophenol 1
3 g was added and stirred at room temperature for 24 hours. Add 37% of the reaction solution to water.
! The precipitated crystals were collected by filtration and dried under reduced pressure. The yield of the product obtained is 20 g and the melting point is 223-22
The temperature was 5°C.

Synthesis Example 2 Synthesis of N-lauryl-2-carboxybenzamide 4.0 g of phthalic anhydride was dissolved in 50 ml of tetrahydrofuran, and while stirring at room temperature, 5.0 g of laurylamine was added.
was added and stirred at room temperature for 24 hours. Anti-9 liquid to 200 parts water
The precipitated crystals were collected by filtration and dried under reduced pressure.

The yield of product was 8.6 g, and the melting point was 90-93°C.

Example 1 [Dispersion A] Compound having the above structural formula 25 parts by weight 15% polyvinyl alcohol aqueous solution 30 parts by weight Water
45 parts by weight (Dispersion B) N-(2'-hydroxyphenyl)-2-carboxybenzamide 25 parts by weight 15% polyvinyl alcohol aqueous solution 30 parts by weight Water
45 parts by weight [Dispersion C] Diphenyl carbonate 25 parts by weight 15% polyvinyl alcohol aqueous solution 30 parts by weight Water
Dispersions A, B and C were prepared by pulverizing and dispersing 45 parts by weight of each of these compositions using a paint conditioner for 24 hours. Next, 10 parts by weight of Dispersion A, 825 parts by weight of Dispersion, and 30 parts by weight of Dispersion C were mixed with 30 parts by weight of 50% calcium carbonate dispersion and 5 parts by weight of 15% polyvinyl alcohol aqueous solution, and stirred to prepare a coating liquid. .

The obtained coating liquid was applied to a 50 g/cd base paper using a wire bar, and the coating amount after drying was 10 g/+r? It was coated, dried, and calendered to produce heat-sensitive recording paper.

Example 2 [Dispersion D] Compound of the above structural formula B 25 parts by weight 15% polyvinyl alcohol aqueous solution 30 parts by weight Water
A 45 parts by weight dispersion was prepared in the same manner as in Example 1, containing 825 parts by weight of the dispersion DIO and 825 parts by weight of the dispersion.
A thermosensitive recording paper was prepared in the same manner as in Example 1 except that the dispersion liquid C was 30 parts by weight.

[Comparative Example 1] A thermosensitive recording paper was prepared in the same manner as in Example 1, except that bisphenol A was used instead of N~(2'-hydroxyphenyl)-2-carboxybenzamide in Dispersion B in Example 1. It was created.

[Comparative Example 2] In place of the compound of structural formula A in dispersion A in Example 1, 3-(N-methyl-N-cyclohexyl)amino-
A thermosensitive recording paper was prepared in the same manner as in Example 1 except that 6-methyl-7-fluorane was used.

The four types of thermal recording paper obtained as described above were colored using a label printer (manufactured by Ishida Kouki).
A colored image was obtained. Salad oil, a plasticizer (dioctyl phthalate), and a fluorescent pen were applied to the surface of the colored sample, and after leaving it at room temperature for 24 hours, the decolorization of the colored image and the coloring of the background were visually evaluated.

The above results are shown in the table below.

Comparative Example 1 0 0 0 Example 2 0 0 0 Comparative Example 1 △ △ △ Comparative Example 2
△ △ △ The above evaluation was performed based on the following criteria.

○ Very good results, with no discoloration in the colored areas and no discoloration on the background.

△ The coloring area is slightly faded or the background is slightly colored, but there is no problem in practical use.

× The coloring part is almost completely discolored, or the background color is intense, which poses a practical problem.

Claims (1)

[Claims] 1. In a heat-sensitive recording material that contains a leuco dye and a color developer and develops color by heating, the leuco dye has the following general formula I, ▲mathematical formula, chemical formula, table, etc.▼... I [ In the above formula, R_1 and R_2 may be the same or different, and each represents C_1_ to C_9 alkyl,
C_3_-C_6 represents cycloalkyl, phenyl or alkyl (C_1_-C_4) substituted phenyl, R_3
and R_4 may be the same or different,
C_1_-C_6 each represents alkyl or phenyl, or R_3 and R_4 may form a 5- to 8-membered cycloalkane together with the carbon atom to which they are bonded. Containing at least one fluoran compound,
The developer has the following general formula II, ▲mathematical formula, chemical formula, table, etc. C_1_-_2) represents substituted phenyl, alkoxy (C_1_-_2) substituted phenyl, hydroxy-substituted phenyl, cyclohexyl or pyridyl] A heat-sensitive recording material characterized by containing at least one phthalic acid amide compound represented by the following.