JPH08207446A - Thermal recording material - Google Patents

Abstract

PURPOSE: To provide a thermal recording material having excellent coloring property, high whiteness, only a little blush which generates due to heat, and excellent preservability (particularly plasticizer resistance and oil resistance). CONSTITUTION: A thermal recording material has, on a support body, a thermal coloring layer consisting of, as main components, a coloring compound which is normally colorless or has light color and a developing compound which can make the coloring compound color with heat. For the coloring compound, a 2-(O-chloroanilino)-6-dibutyl aminofluoran, a 2-(O-fluoroanilino)-6-diethyl aminofluoran or a 2-anilino-3-methyl-6-dibutyl aminofluoran are used. As a developer, a bis-(3-allyl-4-hydroxyphenyl)-sulfone or a 2,2-bis(4-hydroxyphenyl) benzyl acetate is used.

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, 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 the products handled by the POS system, the labels attached to instant foods or processed foods may cause the image part to be discolored by contact with packaging wrap or cooking oil, or the background fogging due to heat or humidity during heating or thawing. There is a problem that it is easy to wake up.

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 responding to high-speed recording has been strongly demanded. Generally, if the sensitivity of the heat-sensitive recording material is improved and the thermal response is improved, the background fog will be fogged. 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.

For example, Japanese Examined Patent Publication No. 52-20142 describes that the heat-sensitive color forming layer is supercalendered to increase the smoothness and improve the thermal response. However, this process complicates the operation and also reduces the smoothness. On the contrary, if it is improved, there is an adverse effect that the matching with the thermal head becomes defective. Further, Japanese Patent Application Laid-Open No. 56-164890 discloses a method of using a leuco dye having a low melting point. Although this method improves the thermal response, it has a drawback that thermal fog increases. . As another method, a method of providing a resin layer containing inorganic hollow fine particles between a support and a thermosensitive recording layer is described in JP-A-59-5093 and JP-A-60-248390. In these cases, The particle distribution of the inorganic hollow fine particles is not uniform, and the smoothness is rather deteriorated, resulting in defective printing and uneven printing. Furthermore, JP-A-1-
113282 and JP-A-2-214688 disclose a method of providing a resin layer containing organic hollow fine particles between a support and a heat-sensitive recording layer. The glass transition temperatures 40 to 90 described in the former method are disclosed. The hollow fine particles of ° C have a poor heat resistance and thus easily cause sticking, and the latter, which has the same glass transition temperature of 40 to 90 ° C, has a poor sticking.

[0006]

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.

[0007]

The present inventor has completed the present invention as a result of various studies to achieve the above object. That is, the present invention relates to (1) a thermosensitive recording material comprising a support and a thermosensitive coloring layer containing a colorless or light-colored coloring compound and a color-developing compound capable of coloring the coloring compound under heat as a main component. And the color-forming compound is 2
-(O-Chloroanilino) -6-dibutylaminofluorane, 2- (o-fluoroanilino) -6-diethylaminofluorane or 2-anilino-3-methyl-6-dibutylaminofluorane, and the developer As a compound,
It is characterized by containing bis- (3-allyl-4-hydroxyphenyl) sulfone or benzyl 2,2-bis (4-hydroxyphenyl) acetate, and further providing an intermediate layer between the heat-sensitive recording layer and the support. (2) The heat-sensitive recording material according to (1) above, characterized in that the intermediate layer contains non-expandable spherical single hollow fine particles made of a hydrophobic resin.
(3) The average particle diameter of the non-expandable spherical single hollow fine particles is 1.
The heat-sensitive recording material according to (2) above, which has a porosity of 50 to 60% and a glass transition temperature of 100 to 110 ° C.

The above-mentioned color-forming compounds used in the color-forming layer of the heat-sensitive recording material of the present invention may be used in combination, but from the viewpoint of performance, it is preferable to use each independently. It is also preferable to use the above-mentioned color developer compound alone. 2- (o-chloroanilino) -6-dibutylaminofluorane or 2-
A combination of (o-fluoroanilino) -6-diethylaminofluorane and benzyl 2,2-bis (4-hydroxyphenyl) acetate is used in a field requiring relatively high heat resistance, and 2-anilino-3 A combination of -methyl-6-dibutylaminofluorane and bis- (3-allyl-4-hydroxyphenyl) sulfone is suitable for a field requiring particularly high sensitivity and fastness.

In the present invention, the above-mentioned color-developing compound and color-developing compound are the main components, and a thermosensitive color-developing layer is prepared by using the following binder and optionally other additives such as filler and heat-soluble substance. Is prepared. The ratio in the heat-sensitive color-developing layer is as follows:
The color-developing compound is 1 to 20 parts by weight, preferably 1 to 5 parts by weight.

In forming the thermosensitive coloring layer in the present invention, the color forming compound is 1 to 50% by weight, the color developing compound is 1 to 80% by weight, the binder is 1 to 90% by weight, the filler and the heat fusible substance. 0 to 80% by weight of each of the functional compounds, other lubricants,
Surfactants, defoamers, ultraviolet absorbers and the like are used in arbitrary proportions (% by weight is the weight ratio of each component in the thermosensitive color developing layer).

Examples of the binder include methyl cellulose, methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, cellulose, polyvinyl alcohol (PVA), carboxyl group-modified polyvinyl alcohol, sulfonic acid group-modified polyvinyl alcohol, polyvinylpyrrolidone, Polyacrylamide, polyacrylic acid,
Water-soluble substances such as starch and its derivatives, casein, gelatin water-soluble isoprene rubber, alkali salts of styrene / maleic anhydride copolymers, alkali salts of iso (or diiso) butylene / maleic anhydride copolymers, or ethylene / Vinyl acetate copolymer, polystyrene, polyacrylic acid ester, polyurethane, styrene / butadiene (S
B) Copolymer, carboxylated styrene / butadiene (SB) copolymer, styrene / butadiene / acrylic acid copolymer, acrylonitrile / butadiene copolymer,
Water-soluble emulsions such as ethylene / acrylic acid copolymer, styrene / acrylic acid copolymer, and composite particles of colloidal silica and acrylic resin are used.

Examples of usable fillers are, for example, 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 can be mentioned.

Examples of heat-soluble substances that can be used include higher fatty acids or their esters, amides or metal salts, as well as various waxes, condensates of aromatic carboxylic acids and amines, phenyl benzoate esters, and higher linear chains. Glucol, dialkyl 3,4-ethoxy-hexahydrophthalate, higher ketones, P-benzenebiphenyl, m-terphenyl, and other heat-meltable organic compounds of 50 to 200
One having a melting point of about ° C can be mentioned.

Specific examples of these compounds include caproic acid amide, capric acid amide, palmitic acid amide,
Stearic acid amide, oleic acid amide, erucic acid amide, linoleic acid amide, N-methyl stearic acid amide, stearic acid anilide, N-methyl oleic acid amide, benzanilide, linoleic acid anilide, N-ethylcaprylic acid amide, N-butyllaurin Acid amide, N-
Octadecylacetamide, N-oleinacetamide, N-oleinbenzamide, N-stearylcyclohexylamide, erucic acid amide, methylolbehenic acid amide, methylolstearic acid amide, methylenebisstearic acid amide, ethylenebisstearic acid amide, p-acetotoluidide, polyethylene Glycol,
1-benzyloxynaphthalene, 2-benzyloxynaphthalene, 1-hydroxynaphthoic acid, 1,2-bis (3-methylphenoxy) ethane, 1,2-bis (4-
Methoxyphenoxy) ethane, 1,2-bis (3,4-
Dimethylphenyl) ethane, 1-phenoxy-2- (4
-Chlorophenoxy) ethane, 1-phenoxy-2-
(4-methoxyphenoxy) ethane, 1- (2-methylphenoxy) -2- (4-methoxyphenoxy) ethane, terephthalic acid dibenzyl ester, oxalic acid dibenzyl ester, oxalic acid di (4-methylbenzyl) ester , P-benzyloxybenzoic acid benzyl ester,
p-benzylbiphenyl, m-terphenyl, 1,5-
Bis (p-methoxyphenoxy) -3-oxa-pentane, 1,4-bis (2-vinyloxyethoxy) benzene, p-biphenyl-p-tolyl ether, benzyl-
p-methylthiophenol, phenylmesitylene sulfonate, 4-methylphenyl mesitylene sulfonate,
Examples thereof include compounds such as 4-benzyloxy-4 ′-(2-methylglycidyloxy) diphenyl sulfone.

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 intermediate layer provided between the thermosensitive color developing layer and the support is a thin coating of a binder resin (white pigment such as kaolin or clay is optionally added) on the support. It is preferable to add non-foaming spherical single hollow fine particles to this intermediate layer because the whiteness, sensitivity, heat resistance, storability, etc. are improved. The non-expandable spherical single hollow fine particles are fine particles that do not foam at the heating temperature of the thermal printer and have only one space like rubber mull and are formed of a thermoplastic resin. The non-expandable spherical single hollow fine particles have a particle size of 1.0 μm or less, preferably an average particle size of 0.4 to
0.6 μm, more preferably an average particle size of about 0.5 μm,
The porosity is about 50 to 60%. Further, for example, if the glass is deformed by heat during recording or pressure during calendering, the desired effect of the present invention may be impaired. Therefore, glass transition temperature in the range of 100 to 110 ° C., preferably 100 to 105 ° C. Is good.

The non-foaming spherical single hollow fine particles are made of a thermoplastic resin such as polystyrene, poly-α-methylstyrene, poly-β-methylstyrene and other styrene resins, and polymethylmethacrylate. In addition to acrylic resins such as, polyethylmethacrylate, polyisopropylmethacrylate, polyisobutylmethacrylate, polyacrylonitrile, polymethacrylo
Polyvinyl chloride, polytetrafluoroethylene, polyvinyl alcohol, poly-o-vinylbenzyl alcohol, poly-m-vinylbenzyl alcohol, poly-p-
Vinyl benzyl alcohol, polyvinyl formal, polyvinyl acetal, polyvinyl propional, polyvinyl butyral, polyvinyl isobutyral, polyvinyl-tert-butyl ether, polyvinyl pyrrolidone, polyvinyl carbazole, cellulose acetate, cellulose triacetate, polycarbonate and copolymers of these Can be mentioned. Of these thermoplastic resins, hydrophobic resins are preferred.

Of these substances, styrene resins, acrylic resins or styrene-acrylic copolymer resins are preferred, and single hollow fine particles made of polystyrene or styrene-methyl methacrylate copolymer have a suitable hardness. Since it has elasticity and heat resistance, it is particularly preferably used.

The heat-sensitive recording material of the present invention is prepared by using the above-mentioned material by the following method, for example. That is, the above-mentioned non-expandable spherical single hollow fine particles, and if necessary, an inorganic or organic pigment or the like within a range that does not impair the effects of the present invention, is dispersed in a binder liquid to form a coating liquid for the intermediate layer, and this coating is performed. The solution is applied on a support such as paper, plastic sheet or synthetic paper in a dry coating amount of ² to 20 g / m ² , preferably 3 to 7 g.
/ M ² and then dried to obtain an intermediate layer coated paper. Next, the color-developing compound and the color-developing compound are separately pulverized and dispersed together with a binder or, if necessary, other additives by a disperser such as a ball mill, an attritor, or a sand mill. When it is carried out by a wet method, water is usually used as a medium), and the coating solution for the thermosensitive color developing layer prepared by mixing is applied onto the present intermediate layer, usually in a dry weight of 1 to 20.
Coating with a bar coater, a blade coater, or the like so as to be g / m ² (the ratio of the color-forming compound to the color-developing compound is usually 2: 1 to 1:10 in dry weight ratio), followed by drying to obtain the heat-sensitive material of the present invention. Obtain recording material. In the heat-sensitive recording material of the present invention, an overcoat layer may be provided on the heat-sensitive color developing layer, if necessary.

The mixing ratio of the single hollow fine particles in the coating liquid for the intermediate layer is not particularly limited, but the single hollow fine particles are 30 to 90% by weight based on the total solid content of the intermediate layer. It is preferable to mix it in the range of 60 to 85% by weight. Examples of the binder include the binders that form the above-mentioned thermal recording layer. In particular, an emulsion (latex) binder gives a good coating solution stability and an intermediate layer excellent in elasticity. It is more preferably used because it is obtained.

[0021]

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

Example 1 A mixture [A] and a solution [B] were prepared by pulverizing and dispersing a mixture having the following composition using a sand grinder so that the average particle diameter was 2 μm or less. [A] liquid: 2- (o-chloroanilino) -6-dibutylaminofluorane 25 parts 25% PVA aqueous solution 20 parts water 55 parts [B] liquid: bis- (3-allyl-4-hydroxyphenyl) sulfone 25 parts 25 % PVA aqueous solution 20 parts Water 55 parts

Next, the respective preparation solutions were mixed in the following proportions to prepare a thermosensitive color developing layer coating solution. Liquid [A] 10 parts Liquid [B] 25 parts Zinc stearate dispersion 15 parts (Chukyo Yushi Co., Ltd. Hydrin Z-730; solid content 30%) 50% Calcium carbonate dispersion 25 parts 25% PVA aqueous solution 10 parts Water 15 Parts ----------------------------------------

Next, the following mixture was stirred and dispersed to obtain an intermediate layer coating liquid [C] liquid. Liquid [C]; emulsion of single hollow fine particles 83 parts (styrene and acrylic copolymer resin) (solid content 30%, average particle size 0.5 μm, porosity 55%, glass transition temperature 105 ° C.) Styrene / Butadiene copolymer latex (solid content 48%) 17 parts

The above-mentioned coating solution for the intermediate layer is applied to the surface of a commercially available high-quality paper (basis weight: 55 g / m ² ) so that the weight after drying becomes 3 g / m ^2, and dried to obtain an intermediate-layer coated paper. It was Next, the thermosensitive coloring layer coating solution prepared above was applied and dried on the present intermediate layer so that the weight after drying was 7 g / m ² to obtain a thermosensitive recording sheet (a) of the present invention.

Example 2 A thermosensitive recording sheet (b) of the present invention was obtained in the same manner as in Example 1 except that the following liquid [D] was used instead of the liquid [A] in Example 1.

Liquid [D]: 2- (o-fluoroanilino) -6-diethylaminofluorane 25 parts 25% PVA aqueous solution 20 parts water 55 parts

Example 3 The following solution [E] was used in place of the solution [A] of Example 1,
A thermosensitive recording sheet (c) of the present invention was obtained in the same manner as in Example 1 except that the following liquid [F] was used instead of the liquid [B].

Liquid [E]: 2-anilino-3-methyl-6-dibutylaminofluorane 25 parts 25% PVA aqueous solution 20 parts water 55 parts

[F] liquid: 2,2-bis (4-hydroxyphenyl) benzyl acetate 25 parts 25% PVA aqueous solution 20 parts water 55 parts

Comparative Example 1 A comparative thermal recording sheet (d) was obtained in the same manner as in Example 1 except that the coating of the liquid [C] of Example 1 was omitted.

Comparative Example 2 A thermosensitive recording sheet for comparison (e) was obtained in the same manner as in Comparative Example 1 except that the following liquid [G] was used instead of the liquid [A] of Example 1.

Liquid [G]: 2-anilino-3-methyl-6-cyclohexylmethylaminofluorane 25 parts 25% PVA aqueous solution 20 parts water 55 parts

Comparative Example 3 A thermosensitive recording sheet (f) for comparison was obtained in the same manner as in Comparative Example 1 except that the following [H] solution was used instead of the [F] solution of Example 3.

Liquid [H]: Bisphenol A 25 parts 25% PVA aqueous solution 20 parts Water 55 parts

Comparative Example 4 Instead of the solution [A] of Example 1, the solution [G] was replaced with the solution [B].
A comparative thermal recording sheet (g) was obtained in the same manner as in Example 1 except that the above [H] solution was used in place of the solution and the following [I] solution was used in place of the [C] solution.

Liquid [I]: Styrene / acrylic copolymer resin 50 parts (solid content 49.5%, average particle size 1.0 μm, porosity 0%, glass transition temperature 120 ° C.) Styrene / butadiene copolymer Latex (solid content 48%) 17 parts Water 33 parts

Table 1 shows the test results of the sensitivity and heat resistance of the thermosensitive recording sheet obtained as described above, and Table 2 also shows the test results of the storage stability (plasticizer resistance and oil resistance).

[0039]

[Table 1] Table 1. Sensitivity and heat resistance test results Recording sheet Background 1) Dynamic sensitivity 2) Heat resistance 3) 21V 23V 25V Example 1 (a) 0.06 1.12 1.37 1.54 0.07 Example 2 (b) 0.06 0.95 1.36 1.55 0.08 Example 3 (c) 0.06 1.07 1.40 1.58 0.08 Comparative Example 1 (d) 0.07 0.82 1. 22 1.37 0.14 Comparative Example 2 (e) 0.15 0.79 1.19 1.43 0.24 Comparative Example 3 (f) 0.08 0.46 0.90 1.38 0.13 Comparative Example 4 (g) 0.09 0.90 1.31 1.48 0.18

[0040]

[Table 2] Table 2. Preservation test result 4) Recording sheet Image density before test 5) Plasticizer resistance 6) Oil resistance 7) Example 1 (a) 1.54 (100) 1.38 (89.6) 1.31 (85.1) Example 2 (b) 1.55 ( 100) 1.50 (96.8) 1.30 (83.9) Example 3 (c) 1.58 (100) 1.55 (98.1) 1.51 (95.6) Comparative Example 1 (d) 1.37 (100) 1.03 (75.2) 0.77 (56.2) Comparative Example 2 ( e) 1.43 (100) 1.12 (78.3) 0.99 (69.2) Comparative Example 3 (f) 1.38 (100) 0.37 (26.8) 0.24 (17.4) Comparative Example 4 (g) 1.48 (100) 0.77 (52.0) 0.92 (62.2)

1) Background: A value (reflection density) obtained by measuring the unprinted portion of the sample with a Macbeth reflection densitometer (RD-914 type manufactured by Macbeth Co.) 2) Dynamic sensitivity: thermal printer (D by Koki Ishida Co., Ltd.) -805P) Macbeth reflection density of the sample printed.
In addition, V shows an applied voltage. 3) Heat resistance: Macbeth reflection density of the unprinted part of the sample after standing in a thermostat at 70 ° C. for 24 hours. 4) Storability test: A protective layer comprising a polyvinyl alcohol aqueous solution, a filler, zinc stearate, and a water-proofing agent was coated on the thermosensitive recording sheet so that the dry coating amount was 2 g / m ² , and the storability was evaluated. A thermal recording sheet for testing was prepared. The test of the items described in Table 2 was carried out on this heat-sensitive recording sheet. 5) Image density before test: Macbeth reflection density of a sample printed with a thermal printer (D-805P) 25V manufactured by Ishida Koki Co., Ltd. 6) Plasticizer resistance: A value measured by the above Macbeth reflection densitometer on the printed part after sandwiched from both sides with PVC wrap and left at 40 ° C. for 15 hours under a load of 0.3 kg / cm ² . The value in parentheses is the density ratio (%) to the image density before the test. 7) Oil resistance: Apply salad oil on the printed part,
A value measured by the Macbeth reflection densitometer after printing for 15 hours. The value in parentheses is the density ratio (%) to the image density before the test.

As is clear from Tables 1 and 2, the thermosensitive recording material of the present invention exhibits excellent effects such as the whiteness of the background, the coloring sensitivity, the heat resistance and the storability of the image area. That is, Examples 1 to 1
The recording sheet of No. 3 is superior to the recording sheets of Comparative Examples 1 to 4 in all test items.

[0043]

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

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display section 108

Claims (3)

[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 developing a color when the coloring compound is heated, as a main component.
As the color forming compound, 2- (o-chloroanilino)-
6-dibutylaminofluorane, 2- (o-fluoroanilino) -6-diethylaminofluorane or 2-anilino-3-methyl-6-dibutylaminofluorane, and bis- (3 -Allyl-4-hydroxyphenyl) sulfone or 2,2-bis (4-hydroxyphenyl) benzyl acetate, further comprising an intermediate layer between the heat-sensitive recording layer and the support. Recording material. 2. The heat-sensitive recording material according to claim 1, wherein the intermediate layer contains non-expandable spherical single hollow fine particles made of a thermoplastic resin. 3. The heat-sensitive recording material according to claim 2, wherein the non-expandable spherical single hollow fine particles have an average particle diameter of 1.0 μm or less, a porosity of 50 to 60%, and a glass transition temperature of 100 to 110 ° C.