JPH0657473B2 - Thermal recording material - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement in a heat-sensitive recording material containing a leuco dye as a color former.

[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 recording material is generally composed of a color former and a developer that allows the color former to develop color when heated.
For example, a colorless or light-colored leuco dye having a lactone, lactam or spiropyran ring is used, and various acidic substances such as organic acids and phenolic substances are used as color developers. The recording material in which the color-developing agent and the color-developing agent are combined has the advantages that the color tone of the obtained image is particularly clear, the whiteness of the background is high, and the weather resistance of the image is excellent, and it is widely used. Has been done.

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 concentration, there is a problem in that the concentration is decreased even when it comes into contact with oils and fats such as fingerprints. These phenomena occur not only when phenols but also general organic acids are used, 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〕

The present invention overcomes the problems of the prior art, that is, provides a heat-sensitive recording material having high sensitivity, excellent fingerprint color development resistance and oil resistance, and almost no background color development, and improved reliability. To aim.

〔Constitution〕

According to the present invention, in a heat-sensitive recording material utilizing a color development reaction between a leuco dye and a color developing agent, the color developing agent is bis (4-hydroxyphenyl) represented by the following general formula (I).
A heat-sensitive recording material characterized by using a monoester compound of sulfone is obtained.

(In the formula, R ₁ represents a hydrogen atom or a methyl group.) Specific examples of the compound of the general formula (I) used as a developer in the present invention include the following compounds.

(Bisphenol S monoacrylate) (Bisphenol S Monomethacrylate) The monoester compound of bis (4-hydroxyphenyl) sulfone represented by the general formula (I) is more stable in the color image area than a conventional developer such as bisphenol A. Therefore, the deterioration of the image due to temperature and humidity,
Almost no image discoloration 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 lactone), 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-dimethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8- Benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3- (Np-tolyl-N-ethylamino) -6-methyl 7-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- Chloranilino) fluorane, 3-dibutylamino-7- (o-chloranilino) 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-methoxycarbonylphenyamino) fluorane, 3-diethylamino-5-methyl-7- (α -Phenylethylamino) fluorane, 3-diethylamino-7-piperidino Ruoran, 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 and the like.

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.

In the present invention, one of the compounds represented by the above general formula
One kind or two or more kinds are used as a color developing agent, and these can be used in combination with a conventionally used color developing agent. As such a developer, various electron-accepting substances that react with the leuco dye when heated to develop a color thereof are applied.
Specific examples thereof include the following phenolic substances, organic or inorganic acidic substances, their esters and salts, and the like.

Gallic acid, salicylic acid, 3-isopropylsalicylic acid,
3-cyclohexylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3,5-di-α-methicbenzylbenzylsalicylic acid, 4,4'-isopropylidenediphenol, 4,4'-isopropylidenebis (2- Chlorophenol), 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,
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-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
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 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 examples thereof include polyvinyl alcohol, starch and its derivatives, methoxycellulose and hydroxy. Cellulose derivatives such as ethyl 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 salt, polyacrylamide, sodium alginate, gelatin, casein and other water-soluble polymers, polyvinyl acetate,
Polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutylmethacrylate, ethylene / vinyl acetate copolymer, styrene / butadiene / acrylic copolymer, etc. Latex can be used.

Further, in the present invention, together with the leuco dye and the color developing agent, if necessary, further auxiliary components commonly used in this type of heat-sensitive recording material, for example, a filler, a surfactant, a heat-fusible substance. (Or a lubricant) and 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 fluoran compound and a phenolic compound is provided on one surface of the support,
On the other surface of the support, a release liner may be provided via an adhesive layer. In the case of magnetic ticket paper, instead of this release liner,
A magnetic recording layer containing a ferromagnetic material and a binder as main components may be provided.

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, an undercoat or an overcoat may be provided, and as the material usable here, the above-mentioned binder, filler, wax or the like can be arbitrarily selected.

〔effect〕

The heat-sensitive recording material of the present invention has the general formula (I) as a developer.
By using a monoester compound of bis (4-hydroxyphenyl) sulfone represented by the following, the image erasing due to oil or oil marks is less than that of the conventional thermal recording material, and it is also excellent in thermal response. There is.

〔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 [Solution 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] Bisphenol S mono Acrylate 10 parts Calcium carbonate 20 parts 10% Polyvinyl alcohol 10 parts Water 60 parts A mixture of the above composition was pulverized 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] were mixed and stirred so that the weight ratio was 1: 3 to prepare a heat-sensitive coating liquid, and the dry coating amount was applied to 52 g / m ² (basis weight) of commercial fine paper. Was about 5.0 g / ² and was coated and dried with a lab coating rod. 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 the bisphenol S monoacrylate in [B liquid] was replaced with bisphenol S monomethacrylate.

Comparative Example 1 A heat-sensitive recording material for comparison was obtained in the same manner as in Example 1 except that bisphenol S monoacrylate of [B liquid] was replaced with benzyl P-hydroxybenzoate.

Comparative Example 2 A thermal recording material for comparison was obtained in the same manner as in Example 1 except that bisphenol S monoacrylate of [B liquid] was replaced with bisphenol S.

The above thermal recording materials were tested for image density and decoloring property with oil. The results are shown in Table-1. In addition, each test method was performed as follows.

Image density Matsushita Electronic Parts Co., Ltd., printing experiment device with thin film head, head power 0.45W / dot, 1 line recording time 20m
Pulse width under conditions of s / l and scanning line density of 8 x 3.85 dots / mm
Printed in 2.2ms, and the print density is Macbeth densitometer RD-514
(Filter Wratten-106).

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

Oil resistance: Cottonseed oil was adhered to the above-mentioned sample whose image density was measured with absorbent cotton, and the densities of the image part and the background part were measured after standing for 24 hours.

As is clear from the results shown in Table 1, the heat-sensitive recording material of the present invention has a higher density and is more stable in the image area than the conventional ones.

Claims (1)

[Claims] 1. A heat-sensitive recording material utilizing a color-forming reaction between a leuco dye and a color developer, wherein a monoester compound of bis (4-hydroxyphenyl) sulfone represented by the following general formula is used as the color developer. A heat-sensitive recording material characterized by: (In the formula, R ₁ represents a hydrogen atom or a methyl group.)