JPS6042093A - Thermal recording sheet - Google Patents

Abstract

PURPOSE:To provide a thermal recording sheet for facsimiles or the like, having excellent thermal response characteristic and improved in color forming sensitivity and image stability, wherein a naphthalenesulfonic acid ester is incorporated as a sensitizer together with a dye precursor and a color developer. CONSTITUTION:A naphthalenesulfonic acid ester, e.g., p-cumylphenyl 1-naphthalenesulfonate, is added as a sensitizer to a thermal recording sheet comprising a normally colorless or light-colored dye precursor, e.g., 3-diethylamino-6-methyl-7- anilinofluoran, and a color developer for developing the color of the dye precursor by reacting therewith when being heated, e.g., 2,2-bis(4-hydroxyphenyl) propane. The ester is preferably added in an amount of 1-80wt% to the color developer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording sheet, and more particularly to a heat-sensitive recording sheet with improved color development sensitivity characteristics and image stability.

In recent years, thermal recording methods are non-impact and do not produce noise during recording. Does not require development and fixing.

Because it has many features such as easy maintenance and management, it is used in a wide variety of applications, including handheld printers and telephone facsimile machines. Particularly in telephone facsimiles, the demand for heat-sensitive systems is rapidly increasing, and speeds are being increased to reduce transmission costs. In response to such increased speed of facsimile, there has been a demand for higher sensitivity of thermal recording materials 1 and 4.

The high-speed facsimile is an A4 size original (116 to 1
Because the facsimile's thermal head receives and sends data in 0 to 20 seconds, the current that flows through the facsimile's thermal head is repeated over a very short time of 1 to 2 milliseconds, and the resulting thermal energy is transferred to the thermal recorder or limp sheet. , which performs an image forming reaction.

In order to perform an image forming reaction using thermal energy transmitted in such a short period of time, it is necessary to use a heat-sensitive recording sheet with excellent thermal responsiveness.

Normally, thermal paper requires a dye precursor and a color developer.
In order to improve thermal responsiveness, it is necessary to lower the melting point of the color developer and improve its compatibility with the dye precursor. Furthermore, a sensitizer is used if necessary. When the sensitizer itself melts due to the transferred thermal energy, it has the function of dissolving or enclosing the nearby dye precursor and color developer to promote the coloring reaction, so the thermal response of the sensitizer is Improving the sensitivity is also one way to make a heat-sensitive recording sheet highly sensitive.

The name of the present invention was created as a result of various studies on sensitizers suitable for heat-sensitive sheets for high-speed recording.The name of the present invention was developed as a result of various studies on sensitizers suitable for heat-sensitive sheets for high-speed recording. By using naphthalene sulfonic acid ester as a sensitizer in the recording sheet, a highly sensitive recording material with excellent thermal responsiveness could be obtained.

Examples of the naphthalenesulfonic acid ester of the present invention include 1-naphthalenesulfonic acid p-cumylphenyl ester, 1-naphthalenesulfonic acid p-acetylphenyl ester, 1-naphthalenesulfonic acid, 2-naphthyl ester, and 1-naphthalenesulfonic acid. Octyl ester, benzyl ester, 1-naphthalenesulfonic acid phenyl ester, 1-naphthalenesulfone 12-naphthalenesulfone Np-cumylphenyl ester, 2-naphthalenesulfonic acid p-acetylphenyl ester, 2-naphthalenesulfonic acid 2-naphthyl ester etc. There is no problem even if the naphthalene ring has other substituents, and examples of the other substituents include an alkyl group, a halogen atom, and an aralkyl group.

The sensitizer according to the present invention is preferably added in an amount of 1 to 80% by weight based on the color developer. If it is less than 1% by weight, the above-mentioned effect will be small, and if it is more than 80% by weight, the dilution effect will be greater (which is also economically disadvantageous).

The main components used in the present invention will be specifically explained, but the present invention is not limited thereto unless it exceeds the gist of the present invention.

(1) Dye precursor Dye precursors commonly used for thermal paper can be used, such as crystal violet lactone, 3-diethylamino-7-methylfluoran, 3-diethylamino-6-
Chloro-7-methylfluorane, 3-diethylamine-
6-methyl-7-chlorofluoran, 3-diethylamine-7-aniIJ/fluoran, 3-diethylamino-7-(2'-chloroanilino)fluoran, 3-dibutylamino-7-(2'-chloroanilino)fluoran, 3-diethylamino-7-(3'-chloroanilino)
Fluoran, 3-diethylamino-6-methyl-7-anilinofluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluorane, 3-(N-
methylcyclohexylamino)-3-medy-7-anilinofluorane, 3-piperidino-3-methyl-7-anilinofluorane, etc.

(2) Binders such as starches, hydroxyethyl cellulose, methyl cellulose, hollyvinyl alcohol, styrene-maleic anhydride copolymer, styrene-butadiene copolymer,
polyacrylamide, etc.

(3) Pigments such as diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin, and the like.

(4) Color developer An acidic substance commonly used in thermal paper can be used, for example (
Yo, phenol, p-tart-butylphenol,
p-phenylphenol, α-naphthol, p-hydroxyacetophenone, 2.2'-dihydroxydiphenol, 4.4'-isopropylidene (2-tCrt-butylphenol), 4.4'-isopropylidene diphenol, 4. 4'-cyclohexylidene diphenol, nophorac type phenol at fat, benzoic acid, p-t
ert -butylbenzoic acid, p--A-xybenzoic acid,
p-oxybenzoic acid benzyl ester, p-,! xybenzoic acid methyl ester, etc.

(5) Other additives Stearin 11 is used for the purpose of adding ingredients (1) to (4) above, preventing head wear, and preventing sticking.
Zinc, fatty acid metal salts such as calcium stearate, paraffin, paraffin oxide, polyethylene, t+2 polyethylene, stearamide, carnauba wax, castor wax, waxes such as dioctyl sulfo/sodium monophosphate, etc. Ultraviolet absorbers such as minute jh agents, benzophenone type, penzotriazole type, etc.
Further examples include antifoaming agents and fluorescent dyes.

Paper is mainly used as the support for the heat-sensitive recording sheet according to the present invention, but various nonwoven fabrics, plastic films, synthetic papers, metal foils, etc., or composite sheets of combinations of these can also be used as desired.

The present invention will be specifically explained below with reference to Synthesis Examples and Examples. In addition, "parts" and "%" in the examples are parts by weight, respectively.
Indicates weight percentage.

Synthesis example ↓ (Synthesis of 1-naphthalenesulfonic acid p-cumyl enyl ester) 12 parts of 1-naphthalenesulfonyl chloride was dissolved in 100 parts of methyl ethyl ketone, and 7 parts of p-cumylphenol and 4 parts of potassium carbonate were added thereto. The mixture was stirred and refluxed for 4 hours.

Extraction was performed using a water-benzene system, and the organic layer was collected.

After distilling off the solvent, the precipitate was recrystallized from ethyl acetate. Yield: 7496 mp 124-126°C Example 1 (1) Solution A (dispersion of dye precursor) 150 parts of 3-diethylamino-6-methyl-7-anilinofluorane was mixed with 25 parts of styrene-maleic anhydride copolymer. % aqueous solution and 332 parts of water, and pulverized in a ball mill for 48 hours.

(2) Solution B (dispersion of color developer) 2.2-bis(4-hydroxyphenyl)furopane 15
(0 parts is styrene-maleic anhydride copolymer) IJ
The mixture was dispersed in 30 parts of a 25% aqueous solution of um salt and 320 parts of water, and pulverized and dispersed in a ball mill for 48 hours.

(3) Solution C (dispersion of sensitizer) 1-naphthalenesulfonic acid p-cumylphenyl ester 15C1 was added to 25% of the styrene-maleic anhydride copolymer.
Disperse in 30 parts of aqueous solution and 320 parts of water, and use a ball mill to
Grinding and dispersing for hours.

(4) Formation of heat-sensitive recording layer 20 parts of liquid A, 50 parts of liquid B, 20 parts of liquid C, 20 parts of calcium carbonate, 93 parts of 12% PVA aqueous solution, and 80 parts of water were mixed (the heat-sensitive Coating liquid: M 50 y/wt
The mixture was coated on base paper at a dry coating weight of 4.0 P/d, dried, and treated with a supercalender to obtain a heat-sensitive recording sheet.

Example 2C Example 1 (Thermosensitive) in the same manner as in Example 1 except that 1-naphthalenesulfonic acid p-acetylphenyl ester was used instead of 1-naphthalenesulfonic acid p-cumylphenyl ester of E'FIji. I got a record sheet.

Example 3 1-naphthalenesulfonic acid 2-naphthyl ester 'i: used in place of 1-naphthalenesulfonic acid p-cumylphenyl ester in Solution C of Example 1 Example 1
A thermosensitive recording sheet was obtained in the same manner as above.

Comparative Example 1 A thermosensitive recording sheet was obtained in the same manner as in Example 1 except that the liquid C of Example 1 was not added.

Comparative Example 2 A heat-sensitive recording sheet was obtained in the same manner as in Example 1 except that stearic acid amide was used as a thickening agent instead of 1-naphthalenesulfonic acid p-cumylphenyl ester in Solution C of Example 1.

Example 4 The heat-sensitive sheets of Examples 1 to 3 and Comparative Examples 1.2 were recorded using Facom Fax 621C manufactured by Fujitsu, and the color density was evaluated and the results were displayed.

As shown in the table, it can be seen that when naphthalene sulfonic acid ester is added as a sensitizer, the color development sensitivity is improved.

1. Indication of the case 3. Relationship between the person making the amendment and the case Patent applicant 4. Agent residence Mitsubishi Paper Mills Co., Ltd., 5-4-2 Marunouchi, Chiyo 11-ku, Tokyo 100 7. Target of correction (+): -j in L, 1o i 2 te treasure price tag - 4 shi drunken et al. .

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Claims (1)

[Claims] A heat-sensitive recording sheet containing a color developer that reacts with a normally colorless or light-colored dye precursor upon heating to cause the dye precursor to develop color, characterized in that a naphthalene sulfonic acid ester is used in combination.