JPH0696348B2 - Thermal recording material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-sensitive recording material utilizing a color-forming reaction between a leuco dye and a color developer.

[Prior art]

Recently, various recording sheets 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) A color image is recorded by simply heating and a complicated developing process is not required, (2) It can be manufactured using a relatively simple and compact device,
Further, the obtained recording sheet is easy to handle and the maintenance cost is low. (3) In many cases, paper is used as the support, in which case not only the support cost is low, but also the obtained Due to the advantage that the recording sheet feels like plain paper, it is used in the fields of computer output, calculators and other printers, medical measurement recorders, low and high speed facsimiles, automatic ticket vending machines, and thermal copying. Widely used.

The thermosensitive recording sheet is usually produced by coating a substrate such as paper, synthetic paper or synthetic resin film with a thermosensitive coloring layer liquid containing a coloring component capable of causing a coloring reaction by heating and drying. A color-developed image is recorded on the heat-sensitive recording sheet thus obtained by heating it with a hot pen or a thermal head. As a conventional example of such a heat-sensitive recording sheet, for example, JP-B-43-4160 or JP-B-45-4.
Examples of the thermal recording sheet disclosed in JP-14039-
Such a conventional heat-sensitive recording sheet has a low thermal responsiveness, for example, and a sufficient color density cannot be obtained at 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,
A p-oxybenzoic acid ester derivative is disclosed in JP-A-59-68295.
Contains 1,7-bis (4-hydroxyphenylthio) -3,5
-A method for achieving high speed and high sensitivity by containing dioxaheptane is disclosed. Among these, benzyl p-hydroxybenzoate and 1,7-bis (4-hydroxyphenylthio) are disclosed. The most effective method is to use -3,5-dioxaheptane as a developer.

However, although these color developers can provide a high-sensitivity heat-sensitive recording material, the developed image is discolored or white powder is generated (hereinafter, referred to as whitening), resulting in extremely poor image stability.

Further, JP-B-59-53193 describes that by mixing two or more kinds of leuco dyes, fading of an image is prevented, but it is difficult to obtain high sensitivity with these leuco dyes.

〔Purpose〕

In view of the above situation, the present inventors have made earnest studies as to a heat-sensitive recording material having high sensitivity and less fading of images and fading due to fingerprints, and as a result, the present invention has been accomplished. Therefore, an object of the present invention is to provide a heat-sensitive recording material having high sensitivity and less fading of images and fingerprints.

〔Constitution〕

According to the present invention, in a heat-sensitive recording material containing, as a main component, a normally colorless or slightly pale leuco dye and a developer capable of coloring the leuco dye under heat on a support, the compound represented by the general formula [ There is provided a heat-sensitive recording material comprising at least one type of fluoran compound represented by the formulas [I] and [II].

General formula (I) (In the above formula, R ₁ represents an alkyl group having 1 to 10 carbon atoms, R ₂ represents an alkyl group having 1 to 4 carbon atoms, R ₃ represents an alkylene group having 1 to 4 carbon atoms, R ₄ represents a methyl group, and R represents ₂ and R ₃ may combine to form a ring) General formula (II) (In the above formula, R ₅ is an alkyl group having 1 to 10 carbon atoms, R ₆ is an alkyl group having 1 to 10 carbon atoms, R ₇ is a hydrogen atom or a methyl group, Y
Represents a hydrogen atom or halogen. ) In the present invention, in particular, at least a part of the color developer is a highly sensitive heat-sensitive material using benzyl p-hydroxybenzoate or 1,7-bis (4-hydroxyphenylthio) -3,5-diohexaheptane. Recording material is provided.

The leuco dye of the general formula [I] used in the present invention has the effect of preventing image fading and fingerprint fading by combining it with the leuco dye of the formula [II], but especially the dye having a melting point of 170 ° C. or less has high sensitivity. From the point of, it is preferable. The ratio of the leuco dyes represented by the general formulas [I] and [II] is 9: 1 by weight.
It may be used in the range of 1: 9, but preferably in the range of 8: 2 to 2: 8.

Examples of the fluorane compound of the general formula [I] include 3- (N-ethyl-N-ethoxypropyl) amino-6
-Methyl-7-anilinofluorane, 3- (N-ethyl-N-ethoxyethyl) amino-6-
Methyl-7-anilinofluorane, 3- (N-ethyl-N-methoxypropyl) amino-6
-Methyl-7-anilinofluorane, 3- (N-ethyl-N-ethoxypropyl) amino-6
Examples thereof include, but are not limited to, -chloro-7-anilinofluorane, 3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-anilinofluorane, and the like.

Examples of the fluorane compound of the general formula [II] include 3-diethylamino-7-o-chloroanilinofluorane, 3-dibutylamino-7-o-chloroanilinofluorane, 3-dibutylamino-7-o. -Fluoroanilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N-octyl-N-i-propyl) amino-6-
Methyl-7-anilinofluorane, 3- (N-ethyl-N-i-amyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-Nn-hexyl) amino- Examples thereof include 6-methyl-7-anilinofluorane, but are not limited thereto.

Further, the following compounds other than the leuco dyes of the above formulas [I] and [II] can be appropriately used in combination.

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-cyclohexylamino -6-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluor Oran, 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, benzoylleuco 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 and the like.

Examples of the color developer used in the present invention include 2,2′-
Dihydroxydiphenyl, 2,2-methylenebis (4-methyl-6-t-butylphenol), 2,2'-bis (4
-Hydroxyphenyl) propane, 4,4'-cyclohexylidene diphenol, 4-phenylphenol, 2,2
-Bis (3,5-dibromo-4-hydroxyphenyl) propane, bis (3,5-dibromo-4-hydroxyphenyl) sulfone, p-hydroxybenzoic acid methylbenzyl ester, p-hydroxybenzoic acid chlorobenzyl ester, p -Benzyl hydroxybenzoate, isopropyl p-hydroxybenzoate, dimethyl 4-hydroxyphthalate, 1,7-di (4-hydroxyphenylthio) -3,5-
Dioxaheptane, 4,4'-isopropylidene diphenol, bisphenol sulfone, 4,4'-thiobis (4
-T-butyl-3-methylphenol), 2,2-bis (4-hydroxyphenyl) -n-heptane, N, N'-
Diphenylthiourea and the like can be mentioned, but from the viewpoint of high sensitivity, benzyl p-hydroxybenzoate, 1,7-di (4
More preferred is the use of -hydroxyphenylthio) -3,5-dioxaheptane. Also, two or more kinds of these color developers may be mixed and used, if necessary.

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, polyvinyl chloride, polyvinylidene chloride,
Styrene / butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, styrene / acrylic acid ester copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer, styrene / butadiene / A latex such as an acrylic copolymer can be used.

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, inorganic fine powder of calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, surface-treated calcium carbonate, silica or the like is used. Others, urea-formalin resin, styrene / methacrylic acid copolymer,
Examples thereof include organic fine powders such as polystyrene resin, and examples of the heat-fusible substance include higher fatty acids or esters thereof, amides (including methylolated products thereof) or metal salts, various waxes, and dimethyl. Terephthalate, condensate 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 70 to 120 ° C. If necessary, an undercoat layer made of a filler or a water-soluble binder may be provided between the support and the thermosensitive color developing layer.

In order to obtain the heat-sensitive recording material of the present invention, a commonly known method can be used. That is, a leuco dye, a color developer, a binder, and other additives alone or in a mixture other than the leuco dye, a protective colloid substance such as polyvinyl alcohol, a surfactant and the like are added to a ball mill, attritor, sand mill. After dispersing with a disperser such as, a thermosensitive color developing layer coating solution is prepared according to the formulation, coated on a support such as paper, synthetic paper, or film, dried, and then calendered to obtain the thermosensitive recording material of the present invention. Is obtained.

〔effect〕

The heat-sensitive recording material of the present invention can be used in combination with the leuco dyes represented by the general formulas [I] and [II], and particularly, benzyl p-hydroxybenzoate or 1,7-di (4-hydroxyphenylthio) -3. By using 5,5-dioxaheptane as a developer, it is possible to obtain a heat-sensitive recording material with high sensitivity and with little image fading and fingerprint fading.

〔Example〕

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

Examples 1 to 4 [Liquid A] 3- (N-ethyl-N-ethoxypropyl) amino-6
-Methyl-7-anilinofluoran 210 parts 3-diethylamino-7-o-chloroanilinofluorane 90 parts 10% aqueous polyvinyl alcohol solution 300 parts water 400 parts [solution B] benzyl p-hydroxybenzoate 100 parts 2, 2-bis (3,3 ', 5,5'-tetrabromo-4-hydroxyphenyl) propane 50 parts Calcium carbonate 150 parts Zinc stearate 25 parts 10% aqueous polyvinyl alcohol solution 300 parts water 375 parts [A solution] and [B solution] were prepared by pulverizing and dispersing for 2 to 4 hours with a sand glider.

Next, solution A and solution B were mixed and stirred so that the weight ratio was A: B = 1: 6 to prepare a heat-sensitive coating solution.

[Liquid C] Polystyrene 40% Dispersion 750 parts 10% Polyvinyl alcohol aqueous solution 200 parts Water 50 parts The above composition was dispersed by a sand glider for 30 minutes to obtain an undercoat coating liquid.

Next, this undercoat coating liquid is applied to a high-quality paper of 52 g / m ^{2 and} the coating amount is adjusted to be 4 g / m ² and then dried.
After forming the undercoat layer, the heat-sensitive coating liquid was applied and dried so that the coating amount of the leuco dye after drying was 0.5 g / m ² . These coated papers were calendered so that the Beck's smoothness was 700 to 1500 sec to prepare a thermal recording material of the present invention (Example 1).

In addition, the leuco dye in the solution A and the p- in the solution B are
Thermal recording materials of Examples 2 to 4 were prepared in the same manner as in Example 1 except that the leuco dyes and developers shown in Table 1 were used instead of benzyl hydroxybenzoate.

Comparative Examples 1 and 2 Thermal recording materials of Comparative Examples 1 and 2 were prepared in the same manner as in Example 1 except that the leuco dyes shown in Table 1 were used instead of the leuco dyes.

The above thermal recording sheets were tested for dynamic color development sensitivity, image fading and fingerprint fading as follows. The results are shown in Table-1.

Dynamic Color Sensitivity A printing experiment device with a thin film head manufactured by Matsushita Electronic Components Co., Ltd., a head power of 0.45w / dot, 1 line recording time 20ms
/ l, scanning line density 8 × 3.85 dots / mm pulse width
It prints at 0.6, 0.8, 1.0, 1.2, 1.4 (msec), and the print density is measured with a Masbeth densitometer RD-514 (filter wratten-10
Measured in 6).

The color-developed sample printed in the image fading test was left at 40 ° C and 90% RH for 24 hours, and evaluated by the rate of decrease in the density of the part developed in 1.4 ms.

In the fingerprint fading test, fingerprint sebum was adhered to the area where the color was printed in 1.4 ms, and the skin oil was left at room temperature and normal humidity for 1 week, and the density was measured, and the density decrease rate was evaluated.

As can be seen from Table-1, the thermosensitive recording material of the present invention has high dynamic color development sensitivity, and has little image fading and fingerprint fading.

Claims (2)

[Claims] 1. A heat-sensitive recording material comprising, as a main component, a colorless or slightly pale leuco dye and a developer capable of developing the color of the leuco dye when heated, as a main component. ) And at least one fluoran compound represented by the general formula (II), respectively. General formula (I) (In the above formula, R ₁ represents an alkyl group having 1 to 10 carbon atoms, R ₂ represents an alkyl group having 1 to 4 carbon atoms, R ₃ represents an alkylene group having 1 to 4 carbon atoms, R ₄ represents a methyl group, and R ₂ and R ₃ may combine to form a ring) General formula (II) (In the above formula, R ₅ is an alkyl group having 1 to 10 carbon atoms, R ₆ is an alkyl group having 1 to 10 carbon atoms, R ₇ is a hydrogen atom or a methyl group, Y
Represents a hydrogen atom or halogen. " 2. A patent characterized in that benzyl p-hydroxybenzoate or 1,7-bis (4-hydroxyphenylthio) -3,5-dioxaheptane is used as at least a part of the developer. The heat-sensitive recording material according to claim 1.