JPH0723026B2 - Thermal recording material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-sensitive recording material, and more specifically, it comprises a colorless or slightly pale leuco dye at room temperature and a developer which reacts with the leuco dye to form a color when heated. The present invention relates to an improvement in a heat-sensitive recording material utilizing a color development reaction during the heat treatment.

[Prior art]

The heat-sensitive recording material generally comprises a support such as paper, synthetic paper, plastic film and the like, provided with a heat-sensitive color-forming layer containing a thermo-color-forming composition as a main component, a thermal head, a thermal pen, a laser beam,
A colored image can be obtained by heating with a strobe lamp or the like. This kind of recording material develops more than other recording materials,
Due to the advantages of being able to obtain recording in a short time with a relatively simple device without performing complicated processing such as fixing, low noise and environmental pollution, and low cost,
In addition to being used for copying books and documents, it is widely used as a recording material in various fields such as electronic computers, facsimiles, ticket vending machines, labels and recorders. The thermochromic composition used for such a heat-sensitive recording material is generally composed of a color former and a developer that allows the color former to develop color when heated.
As the color former, for example, a colorless or light-colored leuco dye having a lactone, lactam or spiropyran ring is used, and as the developer, an organic acid or a phenolic substance is conventionally used. The recording material in which the color-developing agent and the color-developing agent are combined has an advantage that the color tone of the obtained image is particularly clear, the whiteness of the background is high, and the light fastness of the image is excellent. It's being used.

Conventionally, bisphenol A and p-hydroxybenzoic acid esters have been used as developers for leuco dyes, but these phenols have a high color density but lack stability of a color image, and thus are naturally colored. In addition to the decrease in concentration when left to stand, there is a problem in that the concentration is decreased even when it comes into contact with oils and fats such as fingerprints. These developments occur not only when using phenols but also when using general organic acids, and it is strongly desired to overcome them. As disclosed in JP-A-59-38091, it has been proposed to use a metal compound such as aluminum chloride as a developer that gives an image with good stability. However, when this is applied to a heat-sensitive recording material. Although the image is stabilized, there is an initial background coloration, which makes it practically difficult to apply it to a heat-sensitive recording material.

〔Purpose〕

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording material which overcomes the problems of the prior art, that is, has excellent oil resistance and has little background coloration, and improved reliability.

〔Constitution〕

According to the present invention, in a heat-sensitive recording material utilizing a color development reaction between a leuco dye and a color developer, at least one selected from barium salt of hydroxynaphthoic acid, strontium salt, or magnesium salt is used as the color developer. There is provided a thermosensitive recording material characterized by being used.

The color developer used in the present invention is selected from barium salts of naphthoic acid, strontium salts and magnesium salts, and specific examples of such compounds include, for example, barium 2-hydroxy-1-naphthoate, 2- Hydroxy-
1-Strontium naphthoate, 2-hydroxy-1-
Magnesium naphthoate, barium 1-hydroxy-2-naphthoate, strontium 1-hydroxy-2-naphthoate, magnesium 1-hydroxy-2-naphthoate, 2-hydroxy-3-barium naphthoate, 2-hydroxy-3- Examples thereof include, but are not limited to, strontium naphthoate and magnesium 2-hydroxy-3-naphthoate.

Further, in the present invention, as an auxiliary component for the color developer, at least one metal compound selected from zinc, aluminum and tin is used, if necessary. As shown below, various organic and inorganic metal compounds can be mentioned.

Zinc, aluminum or saturated or unsaturated carboxylic acids such as stearic acid, palmitic acid, myristic acid, lauric acid, behenic acid, acetic acid, caproic acid, octylic acid, propionic acid, linoleic acid, oleic acid, sebacic acid, and sorbic acid. Tin salts; zinc, aluminum or tin salts of polyvalent carboxylic acids such as malonic acid, oxalic acid, succinic acid, tartaric acid; zinc, aluminum or tin salts of polymeric acids such as polyacrylic acid and styrene-acrylic acid copolymers. Zinc, aluminum or tin salts of aromatic carboxylic acids such as benzoic acid and naphthoic acid; zinc, aluminum or tin salts of sulfonic acids such as benzene sulfonic acid; zinc oxide, zinc hydroxide, zinc carbonate, zinc sulfoxylate, sulfite Zinc, zinc sulfate, zinc thiosulfate, zinc dithionate, zinc trithionate, zinc nitrate, zinc carbonate hydroxyl Mining, zinc phosphate, zinc sulphate amine, basic zinc sulphate amine, zinc phosphite, zinc pyrophosphate, zinc halides such as zinc chloride and zinc bromide, and the same hydroxylation of aluminum and tin as zinc. Various compounds such as compounds, oxides, and inorganic acid salts.

The zinc, aluminum or tin compound used as an auxiliary component in the present invention is 0.1 to 10 in molar ratio with respect to the color developer.
It is preferably used in a double range.

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-pyrroispirane, 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.

As the developer used in the present invention, in addition to the metal salt of hydroxynaphthoic acid, if necessary, a conventionally known phenolic substance, or a developer consisting of an inorganic / organic acidic substance and its derivative is used. It can also be used together. 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. The developer containing a metal salt accounts for 20% by weight or more, preferably 50% by weight or more, of all the developers.

In the present invention, as the developer that can be used in combination with the metal salt of hydroxynaphthoic acid, various electron-accepting substances that react with the leuco dye when heated to develop a color thereof are applied, and specific examples thereof will be given. Examples thereof include phenolic substances, organic or inorganic acidic substances, and their esters and salts as shown below.

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'-isopropylidenebis (2-tert-butylphenol), 4,4'-sec-butylidenephenol, 4,4'-cyclohexylidenebisphenol, 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 phenol 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, 1-hydroxy-2-naphthoic acid,
2-hydroxy-6-naphthoic acid, 4-hydroxydiphenyl sulfone, 4-hydroxy-4'-chlorodiphenyl sulfone, bis (4-hydroxyphenyl) sulfide, 2-hydroxy-p-toluic acid, tartaric acid, shu Acid, maleic acid, citric acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, boric acid, thiourea derivative, 4-hydroxythiophenol derivative 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, as well as 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, in addition to calcium carbonate, silica, titanium oxide, barium sulfate, clay, talc, inorganic fine powder such as surface-treated calcium or silica,
Examples thereof include organic fine powders of urea-formalin resin, styrene / methacrylic acid copolymer, polystyrene resin and the like. Examples of the heat-fusible substance include higher fatty acids or their esters, amides or metal salts. , Various waxes, condensation products of aromatic carboxylic acid and amine, benzoic acid phenyl ester, higher linear glycol, 3,4-epoxy-dialkyl hexahydrophthalate, higher ketone,
Other examples include heat-fusible organic compounds having a melting point of about 50 to 200 ° 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 on a suitable support such as paper, synthetic paper, plastic film, and drying. It is used as a heat-sensitive recording material for various recording fields, especially for high-speed recording which requires high image stability.

The heat-sensitive recording material of the present invention is used in various fields, and in particular, it utilizes the above-mentioned excellent color image stability,
It can be advantageously used as a heat-sensitive recording type label sheet or a heat-sensitive recording type magnetic ticket paper. In the case of a heat-sensitive recording type label sheet, a thermosensitive coloring layer containing the above-mentioned leuco dye and a color developer is provided on one surface of the support, and a release mount is provided on the other surface of the support via an adhesive layer. In the case of a magnetic ticket paper, a magnetic recording layer containing a ferromagnetic material and a binder as main components may be provided instead of the release mount.

Further, in the present invention, the leuco dye, the color developer, and the auxiliary component used as necessary can be contained in the same coating layer, or can be contained in separate coating layers.

〔effect〕

The heat-sensitive recording material of the present invention uses at least one of barium salt, strontium salt and magnesium salt of hydroxynaphthoic acid as a developer, so that image erasing due to oil or the like is less than that of the conventional heat-sensitive recording material. Becomes
The image reliability is remarkably improved.

〔Example〕

The invention will now be described in more detail by way of examples. In addition,
All parts and percentages below are by weight.

Example 1 [Liquid A] 3- (N-methyl-N-cyclohexyl) amino-6-
Methyl-7-anilinofluorane 10 parts 10% aqueous solution of hydroxyethyl cellulose 10 parts Water 80 parts [Solution B] 2-Hydroxy-3-barium naphthoate 10 parts Calcium carbonate 20 parts 10% Polyvinyl alcohol aqueous solution 10 parts Water 60 parts [C liquid] N-stearin benzamide 10 parts 10% polyvinyl alcohol aqueous solution 10 parts water 80 parts A mixture composed of the above composition is pulverized and dispersed by a sand glider for 2 to 4 hours to prepare [A liquid], [B liquid] and [B liquid]. C
Liquid] was prepared.

Next, the weight ratio of [Liquid A], [Liquid B] and [Liquid C] is 1: 3: 3.
Prepare a heat-sensitive coating liquid by mixing and stirring so that it becomes 52 g / m ²
Commercially available high-quality paper (basis weight) was coated and dried with a Labo Cotain Globe so that the dry coating amount was 6.5 g / m ² . The coated paper was calendered so as to have a surface smoothness of 700 to 1200 sec to prepare a heat-sensitive recording material of the present invention.

Example 2 A thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that barium 2-hydroxy-3-naphthoate in [solution B] was replaced with strontium 2-hydroxy-1-naphthoate.

Example 3 A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that barium 2-hydroxy-3-naphthoate in [Solution B] was replaced with magnesium 1-hydroxy-2-naphthoate. .

Example 4 A thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the following [Solution D] was used instead of [Solution B].

[D liquid]

2-Hydroxy-3-naphthoate strontium 7 parts Benzyl P-hydroxybenzoate 3 parts Calcium carbonate 30 parts 10% Polyvinyl alcohol 10 parts Comparative Example 1 In Example 1, [B liquid] 2-hydroxy-3-naphthoic acid. A heat-sensitive recording material for comparison was obtained in the same manner except that barium was replaced with benzyl P-hydroxybenzoate.

Comparative Example 2 A thermosensitive recording material for comparison was obtained in the same manner as in Example 1 except that bisphenol A was used instead of barium 2-hydroxy-3-naphthoate in [B liquid].

Comparative Example 3 A heat-sensitive recording material for comparison was obtained in the same manner as in Example 1, except that the barium 2-hydroxy-3-naphthoate of [B liquid] was replaced with zinc 2-hydroxy-3-naphthoate.

The above thermal recording materials were tested for image density, background density and decoloring property with oil. Table of the results
Shown in 1. Each test method was performed as follows.

(1) Image density: Using a commercially available thermal tilt tester,
It was heated at 150 ° C. for 1 ^{second under} a load of ² g / cm ² , and the color-developed portion at that time was measured with a Macbeth densitometer RD-514 (filter: W-106).

(2) Background density: The undeveloped area was similarly measured with a Macbeth densitometer.

(3) Oil resistance: Cottonseed oil was adhered to the sample whose image density was measured in (1) above with absorbent cotton, and the density of the image part and the background part was measured after standing at 40 ° C. for 24 hours.

As is clear from the results shown in Table 1, the thermal recording material of the present invention is superior in stability of image and background to the conventional recording materials.

Example 5 In Example 1, the following [C 'solution] was used instead of [C solution].
Was obtained, and a thermal recording material of the present invention was obtained in the same manner except that the coating amount was 8.0 g / m ² .

[C 'liquid]

N-stearylbenzamide 10 parts Zinc stearate 10 parts 10% aqueous solution of polyvinyl alcohol 20 parts Water 60 parts Example 6 In Example 5, barium 2-hydroxy-3-naphthoate was added to 2-hydroxy-1-. A heat-sensitive recording material of the present invention was obtained in the same manner except that zinc stearate in [C 'solution] was replaced with aluminum benzoate instead of strontium naphthoate.

Example 7 In Example 5, barium 2-hydroxy-3-naphthoate in [B liquid] was replaced with magnesium 1-hydroxy-2-naphthoate, and zinc stearate in [C 'liquid] was changed to stannic sulfate. A thermal recording material of the present invention was obtained in the same manner except that it was replaced.

Example 8 In Example 5, barium 2-hydroxy-3-naphthoate of [solution B] was replaced with strontium 2-hydroxy-3-naphthoate, and zinc stearate of solution [C] was replaced with zinc xanthate. Other than the above, a heat-sensitive recording material of the present invention was obtained in the same manner.

Comparative Example 4 A thermosensitive recording material for comparison was obtained in the same manner as in Example 5, except that benzyl P-hydroxybenzoate was used instead of barium 2-hydroxy-3-naphthoate in [B liquid].

Comparative Example 5 A thermosensitive recording material for comparison was obtained in the same manner as in Example 5, except that bisphenol A was used instead of barium 2-hydroxy-3-naphthoate in [B liquid].

Comparative Example 6 A thermosensitive recording material for comparison was obtained in the same manner as in Example 5 except that barium 2-hydroxy-3-naphthoate was replaced by zinc 2-hydroxy-3-naphthoate in [B liquid].

The above thermal recording sheet was printed under the condition of 150 ° C. for 1 second using a commercially available thermal gradient tester, and the image density and background density at this time were measured with a Macbeth densitometer RD-514 (filter: W
-106). The color-developing samples were examined for decoloring property by oil and plasticizer as follows. The results are shown in Table-2.

(1) Oil resistance: Cottonseed oil was adhered to the above color-developed sample with absorbent cotton, and the densities of the image area and the background area were measured after leaving at 40 ° C. for 24 hours.

(2) Plasticizer resistance: Dioctyl adipate (DOA) was attached to the above color-developing sample with absorbent cotton, and it was placed at 40 ° C for 24 hours.
The densities of the image area and the background area after standing for a period of time were measured.

As is clear from the results shown in Table 2, the thermal recording material of the present invention is superior in stability of images and background to the conventional recording materials.

Claims (2)

[Claims] 1. A heat-sensitive recording material utilizing a color-developing reaction between a leuco dye and a color developing agent, wherein the color developing agent is at least one selected from barium salt, strontium salt and magnesium salt of hydroxynaphthoic acid. A thermosensitive recording material characterized by being used. 2. A thermosensitive recording material utilizing a color-developing reaction between a leuco dye and a color developing agent, wherein the color developing agent is at least one selected from barium salt, strontium salt and magnesium salt of hydroxynaphthoic acid. A heat-sensitive recording material characterized by being used as an auxiliary component, at least one metal compound selected from zinc, aluminum and tin.