JPH0532049A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material imparting sufficiently high developed color density, having sufficiently high color forming sensitivity and forming an image having good preservability by adding a specific compound to a thermal color forming layer containing a leuco dye being a color forming substance and a phenolic compound being a developer as a sensitizer. CONSTITUTION:A thermal color forming layer containing a colorless or light- colored leuco dye as a color forming substance and a phenolic compound as a developer is provided on a support such as paper, synthetic paper or a plastic film. In this case, at least one kind of a compound represented by formula I (wherein1, R1 R2 and R2, are hydrogen, halogen, an alkyl group, an alkenyl group, an alkoxy group, an acyl group, an alkoxycarbonyl group, a phenyl group or phenoxy group or phenylalkylene group which is substituted or not substituted with halogen, an alkyl group, an alkenyl group, an alkoxy group, an acyl group or an alkoxycarbonyl group) is added to the thermal color forming layer as a sensitizer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel heat-sensitive recording material, and more particularly to a heat-sensitive recording material having improved color forming property and image storability.

[0002]

2. Description of the Related Art In recent years, a thermosensitive recording material in which a thermosensitive coloring layer that develops color by heating is provided on a support such as paper, synthetic paper, plastic film, etc. is used for thermal printers such as facsimiles, calculators, microcomputers, electrocardiogram and analysis. It is widely used for thermopen recorders such as devices, tickets, and POS labels in supermarkets. This heat-sensitive recording material is usually a colorless or light-colored lactone-based, lactam-based, spiropyran-based leuco dye or the like, and a color developer which reacts with the color-developing substance to develop a color, separately. After crushing with a ball mill or sand mill and dispersing in a solvent, a binder is added and these dispersions are mixed, and if necessary, wax, sensitizer, surfactant, defoaming agent, inorganic pigment After adjusting the coating liquid by adding etc., apply this on a support such as paper,
It is manufactured by providing a thermosensitive coloring layer by drying. As the developer used in the heat-sensitive color-developing layer, a phenolic compound has been conventionally used, and particularly 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) is commonly used. However, this developer alone has a high color development temperature and insufficient sensitivity for high-speed facsimiles requiring high sensitivity. In this case, therefore, a sensitizer is added to this developer to develop the color development temperature. Is being lowered. Examples of sensitizers currently used for such purposes include paraffin wax, amides and esters such as fatty acid amides and dimethyl terephthalate, and ethers (Reference: Paper Processing Handbook, These sensitizers are not necessarily sufficient in terms of color density and color sensitivity.

[0003]

SUMMARY OF THE INVENTION The present invention overcomes the drawbacks of the conventional heat-sensitive recording materials, has sufficiently high color density and color sensitivity, is excellent in color developability, and has excellent image storability (weather resistance). ) Is also good, and the object is to provide a heat-sensitive recording material having excellent performance.

[0004]

The inventors of the present invention have conducted extensive studies to develop a heat-sensitive recording material having the above-mentioned excellent performance, and as a result, by using a specific compound as a sensitizer, the purpose thereof can be improved. The inventors have found what can be achieved and have completed the present invention based on this finding. That is, the present invention is a heat-sensitive recording material comprising a support, a colorless or light-colored leuco dye as a color-developing substance, and a heat-sensitive color-developing layer containing a phenolic compound as a color-developing substance. formula

[0005]

[Chemical 2]

(Wherein R ₁ , R ₁ ', R ₂ and R ₂ ' are hydrogen,
Halogen, alkyl group, alkenyl group, alkoxy group,
It represents a phenyl group, a phenoxy group or a phenylalkylene group which is substituted or unsubstituted with an acyl group, an alkoxycarbonyl group or a halogen, an alkyl group, an alkenyl group, an alkoxy group, an acyl group or an alkoxycarbonyl group. The present invention provides a heat-sensitive recording material containing at least one selected from the compounds represented by the formulas). Hereinafter, the present invention will be described in detail.

The heat-sensitive color-forming layer provided on the support in the heat-sensitive recording material of the present invention is selected from the compounds represented by the above formula [A] as a sensitizer together with a color-forming substance and a color-developing substance. The feature is that at least one kind is contained. The sensitizer, which is a feature of the present invention, is a compound having a basic skeleton in which the substituents of the benzene nucleus on both sides of the formula [A] are all hydrogen atoms (positions of two methylene groups bonded to the central benzine nucleus). Therefore, there are three kinds of basic skeletons, which are the compounds 1, 2, 3) in Table 1, and it is considered that the effect as a sensitizer is brought about by this basic skeleton.

Therefore, in the benzene nuclei at both ends of the formula [A],
In addition to R ₁ , R ₁ ′, R ₂ and R ₂ ′, those having 1 to 4 simple substituents, for example, methyl group, ethyl group and the like, naturally have the effects of the present invention. Expression [A]
Does not exclude such things as having no effect, and these compounds are included in the technical scope of the present invention as an invention in which the constitution of additional substituents is further added to the present invention. .. The melting points of several examples of the sensitizer used in the present invention are shown in Tables 1 and 2.

[0009]

[Table 1]

[0010]

[Table 2]

The sensitizer compound used in the present invention can be produced as a compound having a basic skeleton by, for example, reacting xylylene chloride with a potassium salt of phenol. By using a phenol having various substituents in the benzene nucleus of the phenol used here, a compound of the formula [A] having various substituents corresponding thereto can be produced. The sensitizer used in the present invention has an advantage that it has an action of improving color forming properties such as color density and color developing sensitivity, and also has an action of improving image storability (weather resistance).

In the present invention, the sensitizer compound is
Each of them can be used alone or in combination of two or more kinds at an appropriate ratio, and the amount of the developer can be 1
It can be usually used in the range of 50 to 300 parts by weight per 00 parts by weight. If the amount used is less than 50 parts by weight, the effect of the present invention is not sufficiently exhibited, and if it exceeds 300 parts by weight, the color development temperature may become too low.

There are no particular restrictions on the colorless or light-colored leuco dye used as a color-forming substance in the heat-sensitive color-forming layer of the heat-sensitive recording material of the present invention. For example, from among those conventionally used as color-forming substances in heat-sensitive recording materials. Any one can be selected and used. Examples of the leuco dye used in the present invention include crystal violet lactone, malachite green lactone, 3,3-bis (p-dimethylaminophenyl) -6-aminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-.
(p-toluenesulfonamide) phthalide, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-phenylfluorane, 3-cyclohexylamino-6-chlorofluorane, 3-N-methyl-N-cyclohexylamino -6-Methyl-7-anilinofluorane, 1,3,3-trimethyl-6'-chloro-8'-methoxyindolinobenzospiropyran and the like can be used. These coloring substances may be used alone or in combination of two or more kinds.
The amount used can be appropriately selected depending on the type of the color developer used.

The developer used in the thermosensitive color developing layer of the present invention is also not particularly limited, and for example, any known developer used in conventional thermosensitive recording materials can be selected and used. can do. Examples of such a developer include phenols, phenol resins, p-hydroxybenzoic acid esters, 4-hydroxyphthalic acid diesters, hydroxynaphthoic acid esters, bisphenol A derivatives, bisphenol S derivatives and the like. These color developers can be used alone or in combination of two or more.

In the present invention, the compound represented by the above formula [A] is used as the sensitizer, but other sensitizers may be optionally used in combination within the range not impairing the object of the present invention. You can also Examples of such sensitizers that can be used in the present invention include higher fatty acids or their esters, amides, metal salts, various waxes, condensates of aromatic carboxylic acids and amines, higher linear glycols, higher sensitizers. Ketones,
A bisphenol S derivative or the like can be used.

The heat-sensitive recording material of the present invention can be produced by using the heat-sensitive color-forming layer material in a commonly used method, for example, the color-forming substance, the color-developing substance and the sensitizer together with a suitable binder, and a medium such as an aqueous medium. It can be produced by a method in which a dispersion is prepared by dispersing in a medium, the dispersion is uniformly coated on an appropriate support, and then dried. Examples of the binder in this case include hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, starch, polyacrylic acid, polyacrylamide,
A styrene-maleic acid copolymer or the like can be used, and these binders can be used alone or in combination of two or more. The support used in the heat-sensitive recording material of the present invention is not particularly limited, and those conventionally used as a support in heat-sensitive recording materials, such as paper,
Synthetic paper, plastic film and the like can be used.

[0017]

The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The performance of the thermal recording papers obtained in Examples and Comparative Examples was evaluated by the following test methods. (1) Coloring property A thermal gradient tester (Toyo Seiki Seisakusho Co., Ltd.) was used to perform color development under the conditions of sample pressurization of 2 kg / cm ² , heating time of 5 seconds and color development temperature of 5 ° C, and then a color computer (Suga The color density C ′ was measured using a tester). The color density of the thermosensitive recording paper before color development was C ₀ '(background fog), and the color density after color development was C ₁ '. a) Background fog It is better that the background fog is small. b) Rise and end temperatures and color density C'The color density C'at that time with respect to the color development temperature is plotted on a graph, a correlation curve is drawn on the graph, and an intersection point obtained by drawing a tangent line from the plot before and after the rising curved portion From the coordinates of
The rising temperature and its color density C ′ were determined. In addition, the end temperature and the color density C'from the improvement coordinates obtained by subtracting a close battle from the plots before and after the curved portion on the high density saturation point side.
I asked. The smaller the difference between the rising temperature and the ending temperature, the better the heat-sensitive recording material. (2) Lightfastness A thermosensitive recording paper heated and colored by a thermal gradient tester was exposed for 20 hours at 63 ° C with a fade-o-meter (Suga tester), and then the color density C ′ of the background and the color development part was measured. did. In addition, the residual rate of the color development part is

[0018]

[Equation 1]

It is represented by The remaining rate should be close to 100.

Example 1 As a thermosensitive color forming layer forming liquid, the following liquids A, B and C were separately prepared and finely pulverized and dispersed for 3 hours using a sand mill. [Liquid A] (Coloring substance dispersion liquid) 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane 2.0 parts by weight 10% polyvinyl alcohol aqueous solution 4.3 parts by weight water 2 0.0 parts by weight [solution B] (developing substance dispersion) benzyl p-hydroxybenzoate 2.8 parts by weight 10% aqueous polyvinyl alcohol solution 12.0 parts by weight water 5.2 parts by weight [solution C] (sensitizer) Dispersion) Compound 1 (described in Table 1) 2.8 parts by weight 10% aqueous polyvinyl alcohol solution 12.0 parts by weight water 5.2 parts by weight

Next, solutions B and C were mixed to prepare solution D. [D liquid] B liquid 3.0 parts by weight C liquid 3.0 parts by weight 10% polyvinyl alcohol aqueous solution 0.8 parts by weight Kaolin 0.61 parts by weight Then, A liquid 0.78 parts by weight and liquid D 10 parts by weight are added. A thermosensitive color developing layer coating solution was prepared by mixing, coated on a high-quality paper having a basis weight of 65 g / m ^{2 so} that the dry coating amount was about 7 g / m ^2, and air-dried to obtain a thermosensitive recording paper. Table 3 shows the evaluation results of this heat-sensitive recording paper.

Example 2 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that the compound 4 shown in Table 1 was used instead of the sensitizer compound 1 of the liquid C in Example 1.

Comparative Example 1 Solution B in Example 1 was prepared, and this solution B was used to prepare E solution.
A liquid was prepared. [Solution E] Solution B 3.0 parts by weight 10% aqueous polyvinyl alcohol solution 2.6 parts by weight Water 1.2 parts by weight Kaolin 0.61 parts by weight Next, solution A in Example 1 0.78 parts by weight and solution E 10 In the same manner as in Example 1 except that parts by weight were mixed,
A thermal recording paper for comparison was obtained. Table 3 shows the evaluation results of this heat-sensitive recording paper.

Comparative Example 2 A thermal recording paper for comparison was obtained in the same manner as in Example 1 except that stearic acid amide was used in place of the sensitizer compound 1 of the liquid C in Example 1. Table 3 shows the evaluation results of this heat-sensitive recording paper.

[0025]

[Table 3]

Note Developer: p-benzyl benzoate () shows the background color density.

Example 3 Example 1 was repeated except that bisphenol A was used instead of the benzyl developer p-hydroxybenzoate of the liquid B in Example 1.
A thermosensitive recording paper was obtained in the same manner as in (1). Table 4 shows the evaluation results of this thermal recording paper.

Example 4 A thermosensitive recording paper was obtained in the same manner as in Example 3 except that the compound 4 was used in place of the sensitizer compound 1 of the liquid C in Example 3. Table 4 shows the evaluation results of this thermal recording paper.

Comparative Example 3 A thermosensitive recording paper for comparison was prepared in the same manner as in Comparative Example 1 except that the B solution prepared in the same manner as in Example 3 was used as the B solution in the preparation of the E solution in Comparative Example 1. Obtained. Table 4 shows the evaluation results of this thermal recording paper.

Comparative Example 4 A thermosensitive recording paper for comparison was obtained in the same manner as in Example 3 except that stearic acid amide was used in place of the sensitizer compound 1 of the liquid C in Example 3. Table 4 shows the evaluation results of this thermal recording paper.

[0031]

[Table 4]

Note Developer: Bisphenol A () shows background color density.

[0033]

INDUSTRIAL APPLICABILITY The present invention provides a heat-sensitive recording material excellent in image storability as well as color development sensitivity and color density by using a specific sensitizer.

Claims (1)

Claim: What is claimed is: 1. A thermosensitive recording material comprising a support and a thermosensitive coloring layer containing a colorless or pale-colored leuco dye as a coloring substance and a phenolic compound as a developing substance. The thermosensitive coloring layer has the formula: (In the formula, R ₁ , R ₁ ′, R ₂ and R ₂ ′ are hydrogen, halogen, alkyl group, alkenyl group, alkoxy group, acyl group, alkoxycarbonyl group or halogen, alkyl group, alkenyl group, alkoxy group, acyl group. Group or alkoxycarbonyl group-substituted or unsubstituted phenyl group, phenoxy group, or phenylalkylene group).