JPH0671833B2 - Thermal recording material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-sensitive recording material, and more specifically, it produces a colorless or slightly pale leuco dye at room temperature and an acidic substance that reacts with the leuco dye to produce a color when heated. The present invention relates to an improvement of a thermosensitive recording material having a thermosensitive coloring layer contained as a component on a support.

[Prior art]

Recently, various recording materials have been researched and developed and put into practical use in the information recording field in response to social demands such as diversification and increase of information, resource saving, pollution-free, etc. , (1) Color image is recorded only by heating and no complicated development process is required, (2) Manufacture using a relatively simple and compact device, and easy handling of the obtained recording material Maintenance cost is low, and (3) paper is often used as a support,
In this case, not only the support cost is low, but also the feel of the obtained recorded material is close to that of plain paper, so the output of computers, the field of printers such as calculators, the field of recorders for medical measurement, etc. Widely used in low and high speed facsimile fields, automatic ticket vending machine fields, thermal copying fields and the like.

The heat-sensitive recording material is manufactured by applying and drying a heat-sensitive color forming layer liquid containing a color-forming component capable of causing a color-forming reaction by heating on a support such as ordinary paper, synthetic paper or synthetic resin film. A color image is recorded on the heat-sensitive recording material thus obtained by heating it with a hot pen or a thermal head. As a conventional example of such a heat-sensitive recording material, for example, JP-B-43-4160 or JP-B-45-14039.
The heat-sensitive recording material disclosed in Japanese Patent Laid-Open Publication No. JP-A-2003-13869 is mentioned, but such a conventional heat-sensitive recording material has a low thermal response, for example, and a sufficient color density cannot be obtained during high speed recording.

As a method for improving such defects, for example, Japanese Patent Laid-Open No. 49-3484.
No. 2 discloses nitrogen-containing compounds such as acetamide, stearamide, m-nitroaniline, and dinitrile phthalate.
Japanese Unexamined Patent Publication No. 52-106746 discloses acetoacetic anilide, Japanese Unexamined Patent Publication No. 53-11036 discloses N, N-diphenylamine derivatives, benzamide derivatives, carbazole derivatives, and Japanese Unexamined Patent Publication No. 53-39139. Is an alkylated biphenyl, a biphenylalkane, and in JP-A-56-144193,
Although a method of increasing the speed and increasing the sensitivity by incorporating a p-oxybenzoic acid ester derivative is disclosed, among these, the method of using the p-oxybenzoic acid ester derivative as a developer is the most effective. Was known as a method.

However, these various color developers have a drawback that a recorded image is discolored due to temperature and humidity, or is erased by a plasticizer, oil or the like.

〔Purpose〕

An object of the present invention is to provide a high-sensitivity thermal recording material in which the above-mentioned conventional drawbacks have been improved, that is, a high-sensitivity and recorded image is discolored, or is erased with a plasticizer or oil. The object is to provide less heat-sensitive recording material.

〔Constitution〕

According to the present invention, in a heat-sensitive recording material utilizing a color-developing reaction between a leuco dye and a color developer, a 2,3-dihydroxynaphthalene compound represented by the following general formula is used as a main component of the external color developer. A heat-sensitive recording material is provided.

In the above formula, R ₁ represents hydrogen. R ₂ is (In the formula, R ₃ is alkyl or halogen, and m is 1 to 3.
, And when R ₃ is plural, each R ₃ may be the same or different).

The present invention is represented by the general formula (I) as described above.
It is characterized in that a 2,3-dihydroxynaphthalene compound is used as all or a main component of the color developer. Specific examples of the compound represented by the general formula (I) include, for example,
The following can be shown:

The 2,3-dihydroxy compound represented by the general formula (I) has excellent stability in the color image area as compared with the conventional color developing agent such as bisphenol A. Almost no deterioration or image erasing due to plasticizer, oil, etc.

As the developer used in the present invention, in addition to the compound represented by the general formula (I), a developer comprising a conventionally known phenolic substance, an inorganic / organic acidic substance and a derivative thereof may be used, if necessary. A colorant can also be used in combination.
The color developer used in the present invention is generally used in the range of 1 to 10 parts by weight, preferably 2 to 6 parts by weight, relative to 1 part by weight of the leuco dye. 20% by weight of the total color developer
Or more, preferably 50% by weight or more.

The leuco dyes used in the present invention may be used alone or as a mixture of two or more, and as such leuco dyes,
What is applied to this type of heat-sensitive material is arbitrarily applied, and for example, leuco compounds of dyes such as triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, indolinophtalide-based dyes are preferably used. . Specific examples of such leuco dyes include those shown below.

3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet letolactone), 3,3-bis ( p-Dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexyl Amino-6-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benz Fluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3- (Np-tolyl-N-ethylamino) -6-methyl- -Anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluorane, 2- {3, 6-bis (diethylamino) -9- (o-chloroanilino) xanthylbenzoic acid lactam}, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino ) Fluoran, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N, N-diethylamino) ) -5-Methyl-7- (N, N
-Dibenzylamino) fluorane, benzoyl leuco methylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrrolispirane, 6'-bromo-3'-methoxy-benzoindolino-pyrrolispirane, 3- (2'-hydroxy) -4'-Dimethylaminophenyl) -3- (2'-methoxy-5'-chlorophenyl)
Phthalide, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5'-nitrophenyl)
Phthalide, 3- (2'-hydroxy-4'-diethylaminophenyl) -3- (2'-methoxy-5'-methylphenyl)
Phthalide, 3- (2'-methoxy-4'-dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-
Methylphenyl) phthalide, 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7- (N- Benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluorane, 3-diethylamino-5-chloro-7- (α-phenylethylamino) fluorane, 3- (N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluorane, 3-diethylamino-5-methyl-7- ( α-phenylethylamino) fluorane, 3-diethylamino-7-piperidi Fluoran, 2-chloro-3-(N-Mechirutoruijino)-7-(p
-N-butylanilino) fluorane, 3- (N-benzyl-N-cyclohexylamino)-
5,6-benzo-7-α-naphthylamino-4′-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluorane, 3,6-dimethoxyfluorane, 3- (p-dimethylaminophenyl) -3-phenylphthalide, 3-di (1-ethyl-2-methylyldol) -3- Iyl-phthalide, 3-diethylamino-6-phenyl-7-azafluorane, 3,3-bis (p-diethylaminophenyl) -6-dimethylamino-phthalide, 2-bis (p-dimethylaminophenyl) methyl-5. −
Dimethylamino-benzoic acid, 3- (p-dimethylaminophenyl) -3- (p-dibenzylaminophenyl) phthalide, 3- (N-ethyl-Nn-amyl) amino-6-methyl -7- Anilino fluoran and the like.

In the present invention, as the developer that can be used in combination with the developer represented by the general formula (I), various electron-accepting substances that react with the leuco dye when heated to develop the color are applied. Specific examples thereof include the following phenolic substances, organic or inorganic acidic substances, and their esters and salts.

Gallic acid, salicylic acid, 3-isopropylsalicylic acid,
3-cyclohexyl salicylic acid, 3,5-di-tert-butyl salicylic acid, 3,5-di-α-methylbenzyl salicylic acid, 4,4′-isopropylidene diphenol, 4,4′-isopropylidene bis (2-chloro Phenol), 4,4 '
-Isopropylidene bis (2,6-dibromophenol), 4,4'-isopropylidene bis (2,6-dichlorophenol), 4,4'-isopropylidene bis (2-methylphenol), 4,4'- Isopropylidene bis (2,6-
Dimethylphenol), 4,4'-isopropylidene bis (2-tert-butylphenol), 4,4'-sec-butylidene diphenol, 4,4'-cyclohexylidene bisphenol, 4,4'-cyclohexyl Denbis (2-methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α
-Naphthol, β-naphthol, 3,5-xylenol,
Thymol, methyl-4-hydroxybenzoate, 4-
Hydroxyacetophenone, novolak type phenolic resin, 2,2'-thiobis (4,6-dichlorophenol), catechol, resorcin, hydroquinone, pyrogallol,
Phloroglysin, phloroglysin carboxylic acid, 4-tert
-Octylcatechol, 2,2'-methylenebis (4-chlorophenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-dihydroxydiphenyl, p-hydroxybenzoic acid Ethyl, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-chlorobenzyl p-hydroxybenzoate, o-chlorobenzyl p-hydroxybenzoate, p-hydroxybenzoic acid −
p-methylbenzyl, p-hydroxybenzoic acid-n-octyl, benzoic acid, zinc salicylate, 1-hydroxy-
2-naphthoic acid, 2-hydroxy-6-naphthoic acid, 2
Zinc-hydroxy-6-naphthoate, 4-hydroxydiphenyl sulfone, 4-hydroxy-4'-chlorodiphenyl sulfone, bis (4-hydroxyphenyl) sulfide, 2-hydroxy-p-toluic acid, 3,5 -Ge-t
Zinc ert-butylsalicylate, tin 3,5-di-tert-butylsalicylate, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, boric acid, thiourea derivative, 4- Hydroxythiophenol derivatives and the like.

In the present invention, in order to bond and support the leuco dye and the color developer on a support, various conventional binders can be appropriately used, and specific examples thereof include the following. You can

Polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, sodium polyacrylate,
Polyvinylpyrrolidone, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali Water-soluble polymers such as salts, polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic ester, vinyl chloride / vinyl acetate copolymer , Polybutyl methacrylate, ethylene / vinyl acetate copolymer, styrene / butadiene / acrylic copolymer, and the like.

Further, in the present invention, together with the leuco dye and the color developer, if necessary, further auxiliary additives commonly used in this type of heat-sensitive recording material, for example, a filler, a surfactant, a heat-fusible substance ( Alternatively, a lubricant) or the like can be used in combination. In this case, as the filler, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, inorganic fine powder such as surface-treated calcium or silica, etc. , Urea-formalin resin, styrene / methacrylic acid copolymer, polystyrene resin, and other organic fine powders,
Examples of heat-fusible substances include higher fatty acids or their esters, amides or metal salts, as well as various waxes,
50-200 of condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, 3,4-epoxy-dialkyl hexahydrophthalates, higher ketones, other heat-fusible organic compounds, etc. Those having a melting point on the order of ° C.

The heat-sensitive recording material of the present invention is produced, for example, by applying a heat-sensitive layer-forming coating liquid containing each of the above-mentioned components onto a suitable support such as paper, synthetic paper, or a plastic film, and drying it. Applied to the recording field of.

[Effect]

The heat-sensitive recording material of the present invention uses the 2,3-dihydroxy compound represented by the general formula (I) as all or a part of the color developing agent, so that a recording image is improved as compared with the conventional heat-sensitive recording material. Very little discoloration due to temperature and humidity and image erasing due to plasticizer or oil, and it is also excellent in thermal responsiveness.

〔Example〕

Next, the present invention will be described in more detail with reference to Examples. The parts and% shown below are based on weight.

Example 1 [Liquid A] 3-N-methyl-3-N-cyclohexylamino-6-
Methyl-7-anilinofluorane 300 parts 10% polyvinyl alcohol aqueous solution 300〃 water 400〃 [B liquid] 4,4'-thiobis (3-methyl-6-t-butylphenol) 50〃 calcium carbonate 250〃 10% polyvinyl alcohol aqueous solution 200〃 water 350〃 [C liquid] N-stearylbenzamide 200 parts 10% polyvinyl alcohol aqueous solution 200 〃 Water 600〃 The mixture having the above composition was pulverized and dispersed by a sand grinder for 2 to 4 hours to prepare solutions A, B and C. Next, the weight ratio of A liquid, B liquid and C liquid is A: B: C = 1: 7: 2.
Was mixed and stirred to prepare a heat-sensitive coating solution, and coated on a 52 g / m ² (basis weight) commercial high-quality paper with a wire bar so that the coating amount after drying was 5 g / m ² . These coated papers have a smoothness of 70
A thermal recording material of the present invention was prepared by calendering for 0 to 1200 seconds.

Example 2 Instead of 4,4′-thiobis (3-methyl-6-t-butylphenol) of [solution B] in Example 1, A thermal recording material of the present invention was prepared in the same manner as in Example 1 except that was used.

Example 3 In the same manner as in Example 1 except that the weight ratio of [Liquid A], [Liquid B] and [Liquid C] in Example 1 was changed to A liquid: B liquid: C liquid = 1: 7: 0. A thermosensitive recording material was prepared.

Example 4 Instead of the 2,3-dihydroxy compound of [B liquid] in Example 1 A thermal recording material of the present invention was prepared in the same manner as in Example 1 except that was used.

Comparative Example 1 Same as Example 1 except that 4,4′-thiobis (3-methyl-6-t-butylphenol) was used in place of the 2,3-dihydroxy compound of [B liquid] in Example 1. Then, a thermosensitive recording material of Comparative Example 1 was prepared.

Comparative Example 2 A thermosensitive recording material of Comparative Example 2 was prepared in the same manner as in Example 1 except that bisphenol A was used instead of the 2,3-dihydroxy compound of [B liquid] in Example 1.

The above heat-sensitive recording sheets were tested for dynamic color density, background density, image fading and oil erasability. The results are shown in Table-1. Each test method was performed as follows.

(1) Dynamic color density: Matsushita Electronics Co., Ltd., thermal printing experiment device with thin film head, head power 0.45 W / dot, 1 line recording time 20 ms /, scanning line density 8 × 3.85 dots / mm The pulse width was printed at 2.0 msec under the conditions, and the print density was measured with a Macbeth densitometer RD-514 (filter: W-106).

(2) Discoloration of image: The sample for which the dynamic color density of (1) above was measured was allowed to stand at 40 ° C. and 90% RH for 48 hours, and then the density was measured.

(3) Decoloring property by oil: Cottonseed oil was adhered to the sample whose dynamic color density was measured in (1) above with absorbent cotton, and the density was measured after leaving it for 24 hours under a dry condition at 40 ° C.

Claims (1)

[Claims] 1. A heat-sensitive recording material utilizing a color-forming reaction between a leuco dye and a color developer, wherein a 2,3-dihydroxynaphthalene compound represented by the following general formula is used as a main component of the color developer. A heat-sensitive recording material characterized by: [In the formula, R ₁ represents hydrogen. R ₂ is [In the formula, R ₃ represents alkyl or halogen, and m is 1 to 3.
, And when R ₃ is plural, each R ₃ may be the same or different). ]