JPH0720732B2 - Thermal recording material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-sensitive recording material, and more specifically, a colorless or slightly pale leuco dye at room temperature and a color developer that reacts with the leuco dye to form a color when heated. The present invention relates to an improvement of a heat-sensitive recording material in which a heat-sensitive coloring layer containing a coloring component is provided on a support.

[Prior art]

The heat-sensitive recording material is generally a paper, synthetic paper, plastic film, or other support provided with a heat-sensitive color-forming layer containing a thermo-color-forming composition as a main component, and should be heated with a thermal head, a thermal pen, laser light, or the like. Thus, a color image is obtained. Compared to other recording materials, this type of recording material can perform recording in a short time with a relatively simple device without performing complicated processing such as development and fixing, and has less noise and environmental pollution. ,
Due to its low cost, it is used not only for copying books and documents, but also 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 material is generally composed of a color former and a color developer that allows the color former to develop color when heated, and examples of the color former include a lactone, a lactam or a spiropyran ring having a colorless color. Alternatively, a light-colored leuco dye is used, and as the developer, various acidic substances such as organic acids and phenolic substances are used. The recording material obtained by combining the color-developing agent and the color-developing agent has the advantages that the color tone of the obtained image is particularly clear, that the whiteness of the background is high, and that the weather resistance of the image is excellent, and is widely used. Has been done.

Conventionally, bisphenol A, p-hydroxybenzoic acid esters, etc. have been used as a developer for leuco dyes. However, these phenols have high color density but lack stability of a color image, and thus are left unattended. However, there are drawbacks such as a decrease in concentration and a decrease in temperature and humidity.

On the other hand, it has been proposed to use an organic metal salt as a color developer as described in JP-A-59-145189 and 59-145190, but this product has good stability but poor sensitivity. There is a drawback such as.

〔Purpose〕

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermal recording material that overcomes the problems of the prior art, that is, has high sensitivity and improved reliability with less image deterioration over time.

〔Constitution〕

According to the present invention, as a first invention, in a heat-sensitive recording material utilizing a color-forming reaction between a leuco dye and a developer thereof,
Further provided is a heat-sensitive recording material characterized by using benzyl bis (4-hydroxyphenyl) acetate.
As a second invention, in a heat-sensitive recording material utilizing a color-developing reaction between a leuco dye and a color developer, bis (4-hydroxyphenyl) acetic acid is further used, and p is used as a color developer.
-Benzyl hydroxybenzoate, bisphenol A and
Provided is a heat-sensitive recording material characterized by using at least one compound selected from 1,7-bis (4-hydroxyphenylthio) -3,5-dioxaheptane.

The amount of benzyl bis (4-hydroxyphenyl) acetate used in the present invention is 0.02 to 5 parts by weight, preferably 0.2 to 0.5 parts by weight, based on 1 part by weight of the color developer, and the amount of use is 0.
If it is less than 02 parts by weight, the storage stability and sensitivity of the image will be inferior, and if it exceeds 5 parts by weight, problems such as easy color development of the background will occur.

Further, in the present invention, benzyl P-hydroxybenzoate, bisphenol A and 1,7-bis (4-hydroxyphenylthio) -3,5- When at least one compound selected from dioxaheptane is used in combination, an image with higher sensitivity and higher reliability can be obtained.

In this case, when 1,7-bis (4-hydroxyphenylthio) -3,5-dioxaneheptane is used as the color developer, an image with higher sensitivity and improved reliability can be obtained.

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.

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-dimethyl) Aminophenyl) -6- (diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) 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'-natrophenyl)
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'-promofluorane, 3-diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluorane, 3,6-dimethoxyfluorane, 3- (p-dimethylaminophenyl) -3-phenylphthalide, 3-di (1-ethyl-2-methylyldol) -3 -Yl-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, etc.

As the developer used in the present invention, a conventionally known developer composed of a phenolic substance, an inorganic / organic acidic substance or a derivative thereof can be used. Specific examples thereof include the following phenolic substances, organic or inorganic acidic substances, their esters and salts, and also metal complexes. As mentioned above, preferably, benzyl p-hydroxybenzoate is used. , Bisphenol A and 1,7-bis (4-hydroxyphenylthio) -3,5
Preference is given to using dioxaheptane.

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'-isopropylidenebis (2-tert-butylphenol), 4,4'-sec-butyldendiphenol, 4,4'-cyclohexylidenebisphenol, 4,4'-cyclohexylidenebis (2-methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α
-Naphthol, β-naphthol, 3,5-chitylenol,
Thymol, methyl-4-hydroxybenzoate, 4-
Hydroxyacetophenone, novolac 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, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-hydroxybenzoate Acid-p-chlorobenzyl,
p-Hydroxybenzoate-o-chlorobenzyl, p-hydroxybenzoate-p-methylbenzyl, p-hydroxybenzoate-n-octyl, benzoic acid, zinc salicylate, 1,7-bis (4-hydroxyphenylthio) −3,5−
Dioxaheptane, 1-hydroxy-2-naphthoic acid,
2-hydroxy-6-naphthoic acid, 2-hydroxy-6
-Zinc naphthoate, 4-hydroxydiphenyl sulfone, 4-fudroxy-4'-chlorodiphenyl sulfone, bis (4-hydroxyphenyl) sulfide, 2-
Hydroxy-p-toluic acid, zinc 3,5-di-tert-butylsalicylate, tin 3,5-di-tert-butylsalicylate, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid, 4- Hydroxyphthalic acid, boric acid,
Metal complexes such as thiourea derivatives, 4-hydroxythiophenol derivatives, calcium 2-hydroxy-3-naphthoate, and antipyrine-zinc thiocyanate.

In the present invention, the developer 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.

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 thermosensitive recording type label sheet, a thermosensitive coloring layer containing the above-mentioned leuco dye, a developer and a metal compound is provided on one surface of the support, and an adhesive layer is provided on the local surface of the support. It is only necessary to provide a release mount, and 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.

In addition, 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, an undercoat, an overcoat, or the like can be provided, and as the material to be used, the above-mentioned binder, filler, and wax can be used.

〔effect〕

The heat-sensitive recording material of the present invention is a heat-sensitive recording material utilizing a color reaction between a leuco dye and a color developer, and further comprises bis (4-
Since it contains benzyl hydroxyphenyl) acetate, it has higher sensitivity, less image deterioration with time, and excellent storage stability under high temperature and high humidity, as compared with conventional thermal recording materials.

Further, in the present invention, benzyl P-hydroxybenzoate, bisphenol A and 1,7-bis (4-hydroxyphenylthio) -3,5- When at least one compound selected from dioxaheptane is used in combination, an image with higher sensitivity and higher reliability can be obtained.

In this case, when 1,7-bis (4-hydroxyphenylthio) -3,5-dioxaheptane is used as the color developer, an image with higher sensitivity and improved reliability can be obtained.

〔Example〕

The invention will be explained in more detail by the following examples. In addition,
All parts and percentages below are by weight.

[Liquid A]

3- (N-methyl-N-cyclohexyl) amino-6-
Methyl-7-anilinofluoran 20 parts 10% aqueous solution of hydroxyethyl cellulose 20 parts Water 60 parts [Solution B] Benzyl P-hydroxybenzoate 10 parts 10% Polyvinyl alcohol aqueous solution 15 parts Calcium carbonate 20 parts Bis (4-hydroxyphenyl) ) Benzyl acetate 5 parts Water 50 parts A mixture consisting of the above composition was ground and dispersed by a sand glider for 2 to 4 hours to prepare [solution A] and [solution B].

Next, the [A liquid] and the [B liquid] are mixed and stirred so that the weight ratio is 1: 3 to prepare a thermosensitive color developing layer coating liquid, and the basis weight is 52 g / m ²
After being dried, the commercially available high-quality paper of No. ³ was coated with a lab coating rod so that the coating amount was 6.5 g / m ² and dried. The coated paper was calendered so as to have a smoothness of 700 to 1200 seconds to prepare a heat-sensitive recording material of the present invention.

Example 2 1,7-bis (4-hydroxyphenylthio) was used in place of benzyl P-hydroxybenzoate in [B liquid] of Example 1.
A thermal recording material of the present invention was prepared in the same manner except that -3,5-dioxaheptane was used.

Example 3 Instead of benzyl P-hydroxybenzoate of Example 1,
A heat-sensitive recording material of the present invention was prepared in the same manner except that bisphenol A was used.

Comparative Example 1 Bis (4-hydroxyphenyl) of [B liquid] of Example 1
A thermal recording material for comparison was prepared in the same manner except that benzyl acetate was omitted.

Comparative Example 2 Bis (4-hydroxyphenyl) of [solution B] of Example 2
A thermal recording material for comparison was prepared in the same manner except that benzyl acetate was omitted.

The above thermal recording materials were tested for image density, background density, and resistance to heat and humidity. The results are shown in Table-1.

Image density In Matsushita Electronics Co., Ltd., a printing experiment device with a thin film head, head power 0.60 W / dot, 1 line recording time 5 ms /
, Pulse width 0.5m under the condition of scanning line density 8 × 7.7 dots / mm
The print density was measured with a Macbeth densitometer RD-514 (filter-wratten-106).

Samples printed in the moisture and heat resistance test were stored at 40 ° C and 90% RH or less.
The concentration after standing for a time was measured and evaluated.

As is clear from the results in Table 1, the heat-sensitive recording material of the present invention has higher sensitivity and excellent heat-resistant storage stability than conventional ones,
It can be seen that the image stability is also excellent.

Claims (2)

[Claims] 1. A heat-sensitive recording material utilizing a color-forming reaction between a leuco dye and a color-developing agent thereof, further comprising benzyl bis (4-hydroxyphenyl) acetate. 2. A heat-sensitive recording material utilizing a color-developing reaction between a leuco dye and a developer thereof, wherein bis (4-hydroxyphenyl) acetic acid is further used and benzyl P-hydroxybenzoate, bisphenol A and 1,7−
A heat-sensitive recording material characterized by using at least one compound selected from bis (4-hydroxyphenylthio) -3,5-dioxaheptane.