JPH07108596B2 - 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] A heat-sensitive recording material is generally a paper, a synthetic paper, a film such as a plastic film provided with a thermosensitive coloring layer containing a thermochromic composition as a main component on a support, 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 color former, 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 is particularly advantageous in that the color tone of the obtained image is clear, the whiteness of the background is high, and the light resistance of the image (dye image) is excellent. It is widely used.

Conventionally, bisphenol A and p-hydroxybenzoic acid esters have been used as color developers for leuco dyes. However, these phenols have a high color density but lack stability in the color image, and thus are left unattended. In addition to the decrease in the concentration, there is a problem that the concentration is decreased even when the oil or fat such as fingerprints is contacted. These phenomena occur not only when phenols but also general organic acids are used, and it is strongly desired to overcome them.

In the field of pressure-sensitive paper as a developer that gives an image with good stability, the use of a metal compound of an aromatic carboxylic acid has been proposed as shown in Japanese Patent Publication No. 52-1327. When applied, the image stabilizes, but the contact with oils and fats causes the non-image part (background part) to develop color, which makes it difficult to distinguish the image. The current situation is difficult.

〔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 storage stability of an image and oil resistance, and has almost no background color development, and improved reliability. .

〔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, as the color developer, an acidic salt of zinc or tin, ammonium hydroxide, sodium hydroxide and potassium hydroxide is used. At least one selected from
There is provided a heat-sensitive recording material characterized by using an inorganic hydroxide of zinc or tin obtained by adding an alkaline salt of a seed, washed with water and dried.

That is, the present invention provides, as a developer, zinc obtained by adding at least one alkali salt selected from ammonium hydroxide, sodium hydroxide and potassium hydroxide to an acidic salt of zinc or tin, or It is characterized in that an inorganic hydroxide of tin is first washed with water and then dried (hereinafter, also referred to as crude zinc or tin inorganic hydroxide) as it is.

In this case, the acidic salt of zinc or tin is a salt that exhibits acidity in the state of an aqueous solution, and examples thereof include the following compounds.

Zinc carbonate, zinc sulfate, zinc chloride, zinc bromide, zinc sulfate,
Zinc acetate, zinc thiocyanate, zinc thiosulfate, zinc sulfite, zinc phosphate, zinc phosphite, zinc pyrophosphate and tin inorganic acids similar to zinc.

In addition, 1 selected from an acidic salt of zinc or tin and ammonium hydroxide, sodium hydroxide or potassium hydroxide
The ratio of the seed and the alkali salt used is at least 1 gram equivalent or more with respect to 1 gram equivalent of the former, and preferably the latter is used in a slightly excessive amount relative to 1 gram equivalent of the former.

The crude inorganic hydroxide of zinc of the present invention can be specifically produced as follows. That is, a little more ammonia water than the same gram equivalent as zinc chloride is added to the zinc chloride aqueous solution to form a precipitate. The precipitate obtained by filtration is washed with cold water and then air-dried to obtain crude zinc inorganic hydroxide.

The heat-sensitive recording material of the present invention, as described above, by using a crude inorganic hydroxide of zinc or tin as a developer,
There is almost no color development of the background with excellent oil resistance, which is an improved reliability, but in this case, when the dispersion of the leuco dye is added as the acidic salt, a large liquid fog is used, Further, it is possible to obtain a heat-sensitive recording material having excellent color development sensitivity and oil resistance. For example, crude zinc hydroxide obtained by adding ammonium hydroxide to zinc chloride having a large liquid fog gives better results than using zinc sulfate having a small liquid fog. It is also possible to use a crude inorganic hydroxide obtained by mixing two kinds of the above-mentioned acidic salts and adding the alkali to the aqueous solution thereof.

Even if commercially available purified zinc hydroxide or tin hydroxide is used as the developer, the oil resistance and the plasticizer resistance are inferior and the intended purpose of the present invention cannot be achieved.

In the present invention, as the developer, it is possible to use a conventionally known organic acidic substance as described below in addition to the crude inorganic hydroxide. Generally, it is known that when a color developing agent having a strong color developing ability, for example, zinc salicylate and the like and an organic acidic substance are used in combination, it is difficult to put into practical use due to a background fogging, but the crude inorganic hydroxide of the present invention. When used in combination with an organic acidic substance, it is possible to obtain a heat-sensitive recording material having no background fog and having good thermal response and good image stability.

The color developer used in the present invention is generally used in an amount of 1 to 10 parts by weight, preferably 2 to 6 parts by weight, based on 1 part by weight of the leuco dye. When used in combination with an organic acidic substance, the ratio is arbitrarily determined.

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 has been applied to this type of heat-sensitive material is arbitrarily applied, for example, triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, indolinophthalide-based dye leuco compounds 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 lactone), 3,3-bis (p- Dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3-cyclohexylamino-6-chloro Fluoran, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 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) Fluorane, 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) -6-phenylphthalide, 3-di (1-ethyl-2-methylyldol) -3 -Iloftalide, 3-diethylamino-6-phenyl-7-azafluorane, 3,3-bis (p-diethylaminophenyl) -6-dimethylaminophthalide, 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, etc.

In the present invention, as a developer that can be used in combination with the developer selected from the above-mentioned crude inorganic hydroxide of zinc or tin, various electron-accepting substances that react with the leuco dye at the time of heating to develop the color. Is applied, and 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-cyclohexylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4′-isopropylidenediphenol, 4,4′-isopropylidenebis (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'-cyclohexylidenebisphenol, 4,4'-cyclohexylidenebis (2-methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α
-Naphthol, β-naphthol, 3,5-xylenol,
Thymol, methyl-4-hydroxybenzoate, 4-
Hydroxyacetophenone, novolac type phenolic resin, 2,2'-thiobis (4,6-dichlorophenol), catechol, resorcin, hydroquinone, pyrogallol,
Phloroglucin, phloroglysin carboxylic acid, 4-tert
-Octylcatechol, 2,2'-methylenebis (4-chlorophenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-dihydroxydiphenyl, ethyl p-hydroxybenzoate, 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-di- t
ert-Butyl salicylate zinc, 3,5-di-tert-butyltin salicylate, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, boric acid, thiourea derivative, 4- Hydroxythiophenol derivative, etc.

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, methoxycellulose, hydroxyethyl cellulose, carboxymethyl cellulose,
Cellulose derivatives such as methylcellulose and ethylcellulose, 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 salt, poly In addition to water-soluble polymers such as acrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate,
Polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic acid 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 ° C for 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. Some of them have a melting point of some extent.

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. It is used as a heat-sensitive recording material for the 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.

If necessary, each layer such as an undercoat and an overcoat can be provided, and the materials that can be used here include auxiliary components such as the above-mentioned binder filler and wax.

〔effect〕

The heat-sensitive recording material of the present invention uses the above-mentioned specific crude inorganic hydroxide as a developer, so that the image erasing by the plasticizer or oil of the recorded image is extremely small as compared with the conventional heat-sensitive recording material. Moreover, it is also excellent in terms of thermal response.

〔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] 1.1 g equivalent of aqueous ammonium hydroxide solution was added to 1 g equivalent of zinc chloride aqueous solution to obtain hydroxide. Crude zinc hydroxide obtained by washing with water and then drying 10 parts 10% aqueous solution of polyvinyl alcohol 10 parts water 10 parts [solution C] N-stearylbenzamide 10 parts calcium carbonate 20 parts 10% aqueous solution of polyvinyl alcohol 10 parts water 60 Part A mixture having the above composition was pulverized and dispersed by a sand glider for 2 to 4 hours to obtain [A liquid], [B liquid] and [C liquid].
Liquid] was prepared.

Next, the weight ratio of [Liquid A], [Liquid B] and [Liquid C] is 1: 3: 3.
To prepare a heat-sensitive coating solution, and mix and stir so that
Commercially available high-quality paper of m ² (basis weight) was coated and dried with a lab coating rod 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 In place of zinc hydroxide, the composition of Example 1 was added 1.2 gram equivalent of sodium hydroxide aqueous solution to 1 gram equivalent of an aqueous solution of stannic thiocyanate, and the obtained hydroxide was washed with water and then dried. A heat-sensitive recording material of the present invention was obtained in the same manner except that the crude stannic hydroxide thus obtained was used.

Example 3 A thermosensitive recording material of the present invention was obtained in the same manner as in Example 1, except that benzyl p-hydroxybenzoate was used in place of the N-stearylbenzamide of [C liquid].

Example 4 1,7-Bis (4-hydroxyphenylthio) -3,5-instead of N-stearylbenzamide of [C liquid] of Example 1
A thermosensitive recording material of the present invention was obtained in the same manner except that dioxaheptane was used.

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

Comparative Example 2 A thermosensitive recording material for comparison was obtained in the same manner except that the [B liquid] of Example 4 was omitted.

Comparative Example 3 A thermal recording material for comparison was obtained in the same manner as in Example 1 except that zinc carbonate was used instead of the acidic zinc hydroxide in Example 1.

Comparative Example 4 A thermosensitive recording material for comparison was obtained in the same manner as in Example 1 except that commercially available purified zinc hydroxide (manufactured by Kanto Chemical Co., Inc.) was used instead of the crude zinc hydroxide in Example 1.

The above thermal recording sheet was printed under the condition of 150 ° C. for 1 second using a commercially available thermal tilt tester, and the image density and background density at this time were measured by 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-1.

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

(2) Plasticizer resistance: Dioctyl adipate (DOA) was adhered to the above color-developing sample with absorbent cotton, and the densities of the image part and the background part were measured after standing at 40 ° C. for 24 hours.

As is clear from the results in Table 1, the heat-sensitive recording material of the present invention is superior in stability of image and background to the conventional one.

Claims (1)

[Claims] 1. A heat-sensitive recording material utilizing a color-developing reaction between a leuco dye and a color developer, wherein the color developer is an acidic salt of zinc or tin, ammonium hydroxide, sodium hydroxide and potassium hydroxide. A heat-sensitive recording material comprising an inorganic hydroxide of zinc or tin obtained by adding at least one alkali salt selected from the above, washed with water and dried.