JPH06179289A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material having high sensitivity and excellent in the preservability in its image part by providing a thermal color forming layer containing two kinds of specific color forming compds., a developing compd. and methylolbehenamide on a support. CONSTITUTION:A color forming compd. expressed by formula I, a color forming compd. expressed by formula II, a developing compd. and methylolbehenamide are separately ground and dispersed along with a binder such as polyvinyl alcohol by a dispersing machine such as a ball mill. Next, the respective dispersions are mixed to prepare a coating soln. for a thermal color forming layer. This coating soln. is applied to a support such as paper or a plastic sheet by a bar coater and dried to form the thermal color forming layer to obtain a thermal recording material. As examples of the developing compd. there are alpha-naphthol, beta-naphthol and p-octylphenol. Further, an intermediate layer may be provided between the thermal color forming layer and the support or an overcoat layer may be provided on the thermal color forming layer.

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 which is excellent in color developability, has little fog in heat resistance and wet heat resistance, and is also excellent in plasticizer resistance and oil resistance. .

[0002]

2. Description of the Related Art A heat-sensitive recording material using a colorless or light-colored color-forming substance and a color-developing substance capable of coloring the color-forming substance under heat is disclosed in JP-B-43-4160 and JP-B-45-14039.
It has been widely used in practice. Generally, in a heat-sensitive recording material, a leuco dye and a color developer such as a phenolic substance are separately dispersed in fine particles, and then both are mixed, and a binder, a sensitizer, a filler, a lubricant, etc. are added thereto. It is applied as a coating solution by adding an agent and applied on a support such as paper, film, synthetic paper, etc. Color is generated by a chemical reaction that occurs when one or both of the leuco dye and the developer melts and is heated by heating. A sheet-shaped heat-sensitive recording material is usually used to obtain a record. A thermal printer or the like having a built-in thermal head is used for coloring such a thermal recording sheet. Compared to other recording methods, this heat-sensitive recording method (1) does not generate noise during recording, (2) does not require developing and fixing, etc.
(3) Maintenance free. (4) Due to features such as relatively inexpensive machines, the field of facsimiles, computer output, printers such as calculators,
It is widely used in the fields of medical measurement recorders, automatic ticket vending machines, and heat-sensitive recording labels.

[0003] Among these fields of use, labels are being used with the expansion of POS systems in retail stores, supermarkets, etc., and their use is increasing in train tickets for station automation systems. Among commercial products handled by the POS system, commercialization of instant foods or processed foods is subject to the opportunity for the labels to come into contact with packaging wraps and edible oil, and to be heated and thawed. The contact of the above causes a problem that the image portion is discolored and the background is fogged by heat, humidity and the like.

Further, in recent years, the demand for high-speed recording has been further increased, and the development of a heat-sensitive recording material capable of sufficiently supporting high-speed recording has been strongly desired. It is easy to appear the drawback that occurs. In addition, many storage stability improvers added to improve plasticizer resistance and oil resistance also have the drawbacks of lowering sensitivity and causing background fog. Heretofore, various methods have been proposed in order to improve heat resistance and moist heat resistance, as well as to have excellent thermal responsiveness, excellent image storability, and yet heat resistance and moist heat resistance have not been established yet.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to overcome the drawbacks of the prior art. That is, it is to provide a heat-sensitive recording material having high sensitivity, excellent storability in the image area, and good storability to heat and humidity.

[0006]

The present inventor has completed the present invention as a result of various studies to achieve the above object. That is, the present invention provides a thermosensitive recording material in which a thermosensitive coloring layer containing a colorless or pale-colored coloring compound and a color-developing compound capable of coloring the coloring compound on heating is provided on the support. Formula (1)
And a compound of the following formula (2), and further contains methylol behenic acid amide.

[0007]

[Chemical 3]

[0008]

[Chemical 4]

The present invention will be described in detail. In the present invention, the color-forming compound and the color-developing compound of the above formulas (1) and (2) and methylol behenic acid amide as main components are the following binders and other fillers as necessary, and others. The heat-sensitive color forming layer is prepared by using the additives and the like.
The ratio in the heat-sensitive color forming layer is 1 to 20 parts by weight, preferably 1 to 5 parts by weight, and 0.5 to 1 part of methylol behenate amide with respect to 1 part by weight of the color forming compound.
0 parts by weight, preferably 2 to 5 parts by weight are suitable.

In the present invention, the use ratio of the color forming compounds of the formulas (1) and (2) is not particularly limited, but the color forming compound of the formula (1): the color forming compound of the formula (2) = 20 A range of: 80 to 80:20 is suitable.

Examples of the color-developing compound are generally used for pressure-sensitive recording paper and heat-sensitive recording paper and are not particularly limited. Specific examples include the following compounds. α-
Naphthol, β-naphthol, p-octylphenol, 4-t-octylphenol, pt-butylphenol, p-phenylphenol, 1,1′-bis-
(P-Hydroxyphenyl) propane 2,2'-bis-
(P-Hydroxyphenyl) propane, 2,2'-bis- (p-hydroxyphenyl) butane, 1,1'-bis- (p-hydroxyphenylcyclohexane, 4,4 '
-Thiobisphenol, 4,4'-cyclohexylidene diphenol, 2,2'-bis- (2,5-dibromo-
4-hydroxyphenyl) propane, 4,4'-isopropylidene bis- (2-t-butylphenol, 2,
2,2'-methylenebis- (4-chlorophenol),
4,4'-sulfonylfludiphenol, 4,4'-sulfonyl-bis- (2-allylphenol, furylamino) fluorane, 2- (p-chloroanilino) -3-methyl-6-4-hydroxy-4 ' -Methoxydiphenyl sulfone, 4-hydroxy-4'-ethoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-butoxydiphenyl sulfone, methyl bis- (4-hydroxyphenyl) acetate, Phenolic compounds such as bis- (4-hydroxyphenyl) butyl acetate, bis- (4-hydroxyphenyl) benzyl acetate, benzyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, dibenzyl 4-hydroxyphthalate, 4- Dimethyl hydroxyphthalate,
Ethyl 5-hydroxyisophthalate, 3,5-di-t-
Butylsalicylic acid, aromatic carboxylic acid derivatives such as 3,5-di-α-methylbenzylsalicylic acid, aromatic carboxylic acids or metal salts thereof, and the like, and these color-developing compounds may be used alone or in combination of two or more. Used.

Examples of the binder include methyl cellulose,
Methoxycellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, cellulose, polyvinyl alcohol (P
VA), carboxyl group-modified polyvinyl alcohol, sulfonic acid group-modified polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch and its derivatives, casein, gelatin water-soluble isoprene rubber, alkali salt of styrene / maleic anhydride copolymer , Water-soluble substances such as alkali salts of iso (or diiso) butylene / maleic anhydride copolymers, ethylene / vinyl acetate copolymers, polystyrene, polyacrylic acid esters, polyurethanes, styrene / butadiene (SB) copolymers , Carboxylated styrene / butadiene (SB)
Copolymers, styrene / butadiene / acrylic acid type copolymers, acrylonitrile / butadiene copolymers, ethylene / acrylic acid copolymers, water-soluble emulsions such as colloidal silica / acrylic resin composite particles, and the like are used.

Examples of usable fillers are calcium carbonate, magnesium carbonate, magnesium oxide, silica, white carbon, talc, clay, alumina, magnesium hydroxide, aluminum hydroxide, aluminum oxide, barium sulfate, polystyrene resin, Urea-formalin resin and the like.

Other additives that can be used include higher fatty acid metal salts such as zinc stearate and calcium stearate, animal and vegetable wax, polyethylene wax, for the purpose of preventing thermal head wear and sticking.
Waxes such as synthetic waxes, phenol derivatives that impart antioxidant or anti-aging properties, UV absorbers such as benzophenone-based and benzotriazole-based, various surfactants,
An antifoaming agent or the like is added as needed.

The heat-sensitive recording material of the present invention is prepared by using the above-mentioned material, for example, by the following method. That is, according to a conventional method, first, the color-forming compound of formulas (1) and (2), the color-developing compound, and methylol behenic acid amide are separately and separately added together with the above-mentioned binder or, if necessary, other additives and the like in a ball mill. After being pulverized and dispersed by a disperser such as an attritor or a sand mill, they are mixed to prepare a thermosensitive color developing layer coating liquid, which is usually dried on a support such as paper, a plastic sheet or synthetic paper at a weight of 1 to 1 Coated with a bar coater, blade coater, etc. so as to be 40 g / m ² (the ratio of the color-forming compound to the color-developing compound is usually 1: 1 by dry weight ratio).
˜1: 10) to obtain the thermal recording material of the present invention. If necessary, an intermediate layer may be provided between the thermosensitive coloring layer and the support, or an overcoat layer may be provided on the thermosensitive coloring layer.

The heat-sensitive recording material of the present invention using the color-forming compounds of the formulas (1) and (2), the color-developing compound, and methylol behenic acid amide has a higher sensitivity and a higher image sensitivity than the conventionally known ones. It has excellent storage stability and less fog against heat and wet heat.

[0017]

EXAMPLES The present invention will be described in more detail by way of examples, but the present invention is not limited thereto. In the examples, "part" indicates part by weight.

Example 1 A mixture having the following composition was separately pulverized and dispersed using a sand grinder so as to have an average particle size of 2 μm or less, and each of liquid [A], liquid [B] and liquid [C] [D]. ] The liquid was prepared. [A] liquid: 2- (O-chloroanilino) -6-dibutylaminofluorane 25 parts 25% PVA aqueous solution 20 parts water 55 parts [B] liquid: 2- (O-fluoroanilino) -6-diethylaminofluorane 25 parts 25% PVA aqueous solution 20 parts Water 55 parts [C] liquid: bis- (3-allyl-4-hydroxyphenyl) sulfone 25 parts 25% PVA aqueous solution 20 parts water 55 parts [D] liquid: Clover Ace KN (trade name, Nippon Kasei Co., Ltd., methylol behenate amide 25 parts 25% PVA aqueous solution 20 parts water 55 parts

Next, the respective preparation liquids were mixed in the following proportions to prepare a heat-sensitive color developing layer coating liquid, which was coated on a high quality paper having a basis weight of 50 g / m ^{2 so} that the dry weight was about 7 g / m ² . It was dried to obtain the heat-sensitive recording material of the present invention. [A] liquid 5 parts [B] liquid 5 parts [C] liquid 30 parts [D] liquid 10 parts 50% calcium carbonate dispersion 25 parts 25% PVA aqueous solution 10 parts water 15 parts ────────── ──────────────────────── 100 copies

Example 2 A thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the liquid [A] of Example 1 was 8 parts and the liquid [B] was 2 parts.

Comparative Example 1 A thermosensitive recording material for comparison was obtained in the same manner as in Example 1 except that the liquid [A] was changed to 10 parts and the liquid [B] was removed.

Comparative Example 2 A thermosensitive recording material for comparison was obtained in the same manner as in Example 1 except that the liquid [B] of Example 1 was 10 parts and the liquid [A] was omitted.

Comparative Example 3 A thermal recording material for comparison was obtained in the same manner as in Example 1 except that the liquid [D] of Example 1 was omitted.

Comparative Example 4 A thermosensitive recording for comparison was made in the same manner as in Example 1 except that the amount of the solution [A] of Example 1 was changed to 10 parts, the solution [B] was removed, and the solution [D] was removed. Got the material.

Comparative Example 5 A thermosensitive recording for comparison was made in the same manner as in Example 1 except that the amount of the solution [B] of Example 1 was changed to 10 parts, the solution [A] was removed, and the solution [D] was removed. Got the material.

With respect to the heat-sensitive recording material obtained as described above, Table 1 shows the test results of sensitivity and heat resistance, and Table 2 shows the storage stability (plasticizer resistance, oil resistance).

[0027]

[Table 1] Sensitivity and heat resistance test results Background 1) Dynamic sensitivity 2) Heat resistance 3) Moisture and heat resistance 4) 21V 23V 25V Example 1 0.07 1.09 1.46 1.52 0.08 0.12 Example 2 0.07 1.10 1.46 1.51 0.08 0.12 Comparative Example 1 0.07 1.10 1.45 1.51 0.08 0.12 Comparative Example 2 0.08 0. 98 1.27 1.48 0.10 0.14 Comparative Example 3 0.07 0.68 1.31 1.49 0.09 0.13 Comparative Example 4 0.07 0.88 1.36 1.480 0.08 0.12 Comparative Example 5 0.07 0.55 1.09 1.36 0.08 0.12

[0028]

[Table 2] Preservation test result 5) Pre-test image density 6) Plasticizer resistance 7) Oil resistance 8) Example 1 1.52 1.48 1.30 Example 2 1.51 1.46 1.25 Comparative Example 1 1.51 0.66 0.42 Comparative Example 2 1.48 1.35 0.98 Comparative Example 3 1.49 0.78 0.50 Comparative Example 4 1.48 0.60 0.38 Comparative Example 5 1.36 1.10 0.85

1) Background: A value (reflection density) obtained by measuring the unprinted portion of the sample with a Macbeth reflection densitometer RD-914 type. 2) Dynamic sensitivity: Macbeth reflection density of a sample printed with a thermal printer (D-805P) manufactured by Ishida Koki Co., Ltd. 3) Heat resistance: Macbeth reflection density of the unprinted part of the sample after standing for 24 hours in a thermo-hygrostat at 60 ° C. 4) Moisture and heat resistance: Macbeth reflection density of the unprinted part of the sample after being left in a thermo-hygrostat at 60 ° C. and a relative humidity of 100% for 24 hours. 5) Preservation test: A protective layer consisting of an aqueous polyvinyl alcohol solution, a filler and a water-proofing agent was coated on the thermosensitive recording material so as to have a dry coating amount of 2 g / m ² , and the thermosensitivity for preservability test was conducted. A recording material was prepared. 6) Image density before test: Macbeth reflection density of a sample printed with a thermal printer (D-805P) 25V manufactured by Ishida Koki Co., Ltd. 7) Plasticizer resistance: A value which was sandwiched from both sides with PVC wrap and left for 15 hours at 40 ° C. under a load of 0.3 kg / cm ² to measure the printed part with the above Macbeth reflection densitometer 8) Oil resistance: Apply salad oil on the printed part and
Value measured with the above Macbeth reflection densitometer on the printed part after left at 0 ° C for 15 hours

As is apparent from Tables 1 and 2, the heat-sensitive recording material of the present invention is excellent in color density, heat resistance and heat and humidity resistance, and storage stability of the image area.

[0031]

EFFECT OF THE INVENTION A heat-sensitive recording material having high sensitivity, less fog against heat and moist heat, and excellent in storage stability (particularly plasticizer resistance and oil resistance) was obtained.

Claims (1)

[Claims] 1. A thermosensitive recording material comprising a support and a thermosensitive coloring layer containing a colorless or pale color-developing compound and a color-developing compound capable of coloring the color-developing compound when heated as a main component. A heat-sensitive recording material comprising a compound of the following formula (1) and a compound of the following formula (2) as a polymerizable compound, and further containing methylol behenic acid amide. [Chemical 1] [Chemical 2]