JPH01168489A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having excellent sensitivity and preservation stability, by incorporating ethylene glycol benzyl diphenyl ether as a color forming accelerator into a thermal recording layer. CONSTITUTION:A thermal recording material comprises a thermal recording layer provided on a base by coating, the recording layer comprising a leuco compound, an organic acid as a color developer, a binder, and ethylene glycol benzyl diphenyl ether of formula I as a color forming accelerator. The amount of the ether is preferably 1-50wt.% based on the total solids content of the thermal recording layer, from the viewpoint of the color forming accelerating property. The ethylene glycol benzyl diphenyl ether can be synthetized by, for example, etherifying the OH group of p-phenylphenol by ethylene chlorohydrin or ethylene oxide, and etherifying the OH group of the resultant compound by a benzyl halide.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention uses a colorless or light-colored organic dye generally referred to as a leuco compound, and an organic acid such as a phenol compound that develops a color by reacting with the leuco compound. This invention relates to improvements in thermosensitive recording materials.

(Prior Art) A thermosensitive recording paper containing a leuco compound and an organic acid is already known, for example, from Japanese Patent Publication No. 14039/1983. This recording paper applies thermal energy to the recording layer to soften or melt the leuco compound, organic acid, and binder.
It is based on the principle of bringing color components into contact and causing a color reaction, and has recently been used in various fields such as printers and facsimile machines. The recording characteristics of this recording paper vary depending on the use, but in order to increase the recording speed, for example, it is necessary to improve the recording apparatus and to promote the color development of the recording paper itself.

A commonly used method for promoting color development is to include a low melting point substance in the recording layer. As a low melting point substance, that is, a color accelerator or a sensitizer,
No. 60 uses urea, phthalic anhydride, and acetanilide; JP-A-48-19231 uses paraffin wax, carnauba wax, beeswax, wood wax, higher fatty acids, and higher fatty acid esters; and JP-A-49-17748 uses salicylic acid. , anisic acid, phthalic acid monophenyl ester, phthalic acid monobenzyl ester, and recently fatty acid amides have also been widely used as color accelerators. That is, Japanese Patent Publication No. 51-27599 describes the sensitizing effect of fatty acid amide by the combination of paraffin or microwax and fatty acid amide, and JP-A-54-139740 describes the sensitizing effect of fatty acid amide such as stearic acid amide and oleic acid amide. A sensitizing effect has been described and is well known.

(Problems to be Solved by the Invention) However, the effects of conventional color development accelerators cannot be said to be sufficient, and there has been a strong demand for a technique that provides even better color development.

The present inventors confirmed the effects of these conventional color accelerators, and in order to discover substances with even better properties,
As a result of extensive and deep studies, we have discovered a new color development accelerator that has remarkable effects, and based on this knowledge, we have accomplished the present invention.

(Means for Solving the Problems) That is, the present invention provides a heat-sensitive recording material mainly composed of a leuco compound and an organic acid that develops color by reacting with the leuco compound, in which color development is promoted in the heat-sensitive recording layer. It is constructed to contain ethylene glycol benzyl diphenyl ether represented by the following structural formula (I) as an agent.

The present invention will be explained in detail below.

The heat-sensitive recording material of the present invention has a heat-sensitive recording layer containing a leuco compound, an organic acid as a color developer, a binder, and ethylene glycol benzyl diphenyl ether as a color development promoter on a support. It is made of coated material.

Ethylene glycol benzyl diphenyl ether as a color development accelerator used in the present invention is excellent in the effect of promoting color development, and also has other properties as a heat-sensitive recording material, such as background density, background fogging after storage, discoloration,
It also has properties that pose no problem in practical use.

The content of this ethylene glycol benzyl diphenyl ether is preferably 1 to 50% by weight of the total solid content of the heat-sensitive recording layer from the viewpoint of promoting color development.

Ethylene glycol benzyl diphenyl ether as a color accelerator of the present invention can be synthesized by various methods. For example, p-phenylphenol OH
It can be synthesized by etherifying the group with ethylene chlorohydrin or ethylene oxide and then etherifying the OH group of the resulting compound with benzyl halide.

The leuco compounds used in the present invention are colorless to light-colored substances that develop color by reacting with organic acids. Examples include various derivatives such as phenoxazine-based, phenoxazine-based, spiropyran-based, indoline-based, and indigo-based. Preferred leuco compounds include crystal violet lactone, 3-diethylamino-6-methyl-
7-anilinofluorane, 3-(N-ethyl-P-toluidino)-6-methyl-7-anilinofluorane, 3
-diethylamino-6-methyl-7-(ortho, para-
dimethylanilino)fluoran, 3-pyrrolidino-6-
Methyl-7-anilinofluorane, 3-piperidino-6
-Methyl-7-anilinofluorane, 3-(N-cyclohexyl-N-methylamine)-6-methyl-7-anilinofluorane, 3-diethylamine-7-(ortho-
chloroanilino)fluoran, 3-diethylamino-7
-(meth-trifluoromethylanilino)fluorane,
3-diethylamino-6-methyl-chlorofluorane,
3-diethylamino-6-methyl-fluorane, 3-cyclohexylamino-6-chlorofluorane, 3-(
N-ynamyl-N-ethylamino)-6-methyl-7
-anilinofluorane and 3-dibutylamino-6-methyl-7-anilinofluorane.

The organic acid used in the present invention is a substance that is solid at room temperature, melts by heating, and becomes a color developer when it comes into contact with a leuco compound, and includes various phenolic substances, fatty acids, aromatic carboxylic acids, and the like. Examples include gallic acid, salicylic acid, 1-hydroxy-2-naphthoic acid, 0-hydroxybenzoic acid, m-hydroxybenzoic acid, 2-hydroxy-
p-Toluic acid, 3.5-xylenol, thymol, p
-tert-butylphenol, 4-hydroxyphenoxide, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, α-naphthol, β-naphthol, catechonoperezorcin, hydroquinone, 4-t
ert-octylcatechol, 4゜4'-5ec-butylidenephenol, 2,2'-dihydroxydipheninope 2,2'-methylenebis(4-methyl-6-tert
-butylphenol), 2,2'-bis(4'-hydroxyphenyl)propane (also known as bisphenol A),
4.4'-Impropylidene-bis(2-tert-butylphenol), pyrogallonoheflologlucin, phloroglucincarboxylic acid, p-methylphenol, p-
Phenylphenol, 4,4'-cyclohexylidene diphenol 4,4'-(1-methyl-n-hexylidene) diphenol, 4,4'-isopropylidene dicateconope 4,4'-benzylidene Diphenol, 4.
4'-isopropylidene bis(2-chlorophenol)
, 3-phenylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 1-oxy-2-naphthoic acid, gallic acid ester, salicylic acid ester, p-hydroxybenzoic acid ester, 4-hydroxyphthalic acid ester, 2-
(4-hydroxyphenyl)-2-(3'-hydroxyphenyl)propane, 4+4'-dihydroxy-3,3
'-diisopropyldiphenyl-2,2'-propane and the like.

The binder used in the present invention is mainly a water-soluble binder, which separates and fixes the coloring agent dispersed in fine particles from each other, and includes polyvinyl alcohol, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, Examples include acrylic acid, casein, gelatin, starch and derivatives thereof.

The heat-sensitive recording layer of the present invention may optionally contain other additives, such as clay, calcium carbonate, aluminum hydroxide, talc, titanium oxide, zinc oxide, and other inorganic or organic pigments, waxes, and storage-stable additives. antioxidants, ultraviolet absorbers, various fatty acid metal salts to prevent stickiness, water resistant agents to improve water resistance, phenolic resins,
Surfactants and the like can be added.

The paint for a heat-sensitive recording layer of the present invention comprises the above-mentioned leuco compound,
Organic acids, ethylene glycol benzyl diphenyl ether, and additives such as pigments and sensitivity adjusters as necessary are mixed in an aqueous medium containing an appropriate concentration of a binder such as polyvinyl alcohol using a ball mill or sand grinder. It is generally prepared by grinding and dispersing using a grinder such as a grinder.

It is advantageous in terms of color development efficiency to make each component material as fine as possible, and preferably to have a particle size of 0.5 to 3 microns. The heat-sensitive paint thus obtained is applied to a support described below and dried to obtain the heat-sensitive recording material of the present invention.

Coating can be done using a regular blade coater, air knife coater,
This can be done using a bar coater, reverse roll coater, or the like.

The support used in the present invention generally includes high-quality paper,
Papers such as medium-quality paper and coated paper are used, but other materials such as glass fiber sheets, plastic sheets, and film-laminated papers can also be used as the support.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

<Synthesis example> 250.0 g of p-phenylphenol,
236.5 g of ethylene chlorohydrin and 176.3 g of 95% sodium hydroxide were charged, stirred in a nitrogen stream, and heated. After continuing heating at a temperature of 70° C. for 4 hours, the mixture was cooled to room temperature, and excess ethylene chlorohydrin was distilled off under reduced pressure. After adding chloroform 1β to the residue and filtering off insoluble matter, chloroform was distilled off under reduced pressure.

The residue was recrystallized with acetone and 148.0 g of 2
-Hydroxyethyl diphenyl ether (white crystals)
I got it.

Next, 500+ with cooler, thermometer, and stirring device.
100.0 g of 2-hydroxyethyl diphenyl ether and 118.2 g of benzyl chloride obtained above were placed in a four-way flask of nj2.

37.5 g of 95% sodium hydroxide and 200 mf of dimethylformamide were charged, and heated and stirred at 100° C. for 3 hours. After cooling to room temperature, dimethylformamide was distilled off under reduced pressure. 500 mj' of toluene was added to the residue, washed three times with 200 ml of distilled water, dehydrated and dried over anhydrous magnesium sulfate, and then the solvent was distilled off under reduced pressure. The residue was recrystallized from ethanol to obtain 82.0% ethylene glycol benzyl diphenyl ether (white crystals, melting point 86.8°C).

(Analytical value) H'-NMR absorption spectrum (CDCf3. δ (ppm): 13.60-4.
00 (2H, m), 4.0 (]-4,30 (2H, m), 4.65
(2H,s), 6,85-7.75 (14H,m) IR absorption spectrum CKBr, wave number (cm-')) 2860, 1605.14g5.1240.1105°1035, 750. 695 Note that in combination with the color development accelerator according to the present invention, a known color development accelerator can be added and contained in the recording layer.

Example 1 a) Production of heat-sensitive recording material Liquids A and B having the following compositions were prepared by separately dispersing them in a paint shaker (manufactured by Toyo Seiki) for 10 hours.

Solution A: Leuco dye 3-(N-cyclohexyl-N-methyl)-
Amino-6-methyl-7-anilite fluorane
5g ethylene glycol benzyl diphenyl ether 8g aluminum hydroxide 20g zinc stearate 5g polyvinyl alcohol 12%
Liquid 35g water
52g Liquid B: Bisphenol A 15g Kaolin 20g Zinc stearate
3g hollyvinyl alcohol 12% liquid
35g water
52g Next, add 125g of liquid A, 125g of liquid B, 50g of 12% polyvinyl alcohol liquid, and 40g of water, mix, stir, and adjust to make a coating liquid.
The coating was coated on the surface of 0 g/m' high-quality paper using a Meyer bar so that the coating amount after drying was 8 g/m', and then dried to obtain heat-sensitive recording paper.

Example 2 Among the formulations of liquid A used in Example 1, 3 were used as leuco dyes.
A thermosensitive recording paper was obtained in the same manner as in Example 1, except that -(N-ynamyl-N-ethyl)amino-6-methyl-7-anilite fluorane was used.

Comparative Example 1 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that ethylene glycol benzyl diphenyl ether was excluded from the formulation of liquid A used in Example 1.

Comparative Example 2 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that ethylene glycol benzyl diphenyl ether linistearic acid amide was used in the liquid A formulation used in Example 1.

Comparative Example 3 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that rosebenzyl biphenyl was used instead of ethylene glycol benzyl diphenyl ether in the A liquid formulation used in Example 1.

The heat-sensitive recording papers obtained in the above Examples and Comparative Examples were surface-treated with a test super calender so that the recording surface had a Beck smoothness of 500 seconds.

Regarding the thermal recording paper obtained by this surface treatment, commercially available G
■Facsimile machine FACOM FAX 621C (manufactured by Fujitsu), recording power 0.90w/dat, power supply time Q, 45 m5ec, cycle approximately 5 m5ec/I
Printing was performed under the conditions of t, and the image density and background density at the time of printing were measured using a Macbeth densitometer. The storage stability was the concentration after 24 hours of storage in a constant temperature room maintained at 60°C in a dry state. The results shown in the table below were obtained for the Examples and Comparative Examples.

(Effects of the Invention) From the table, it was demonstrated that the heat-sensitive recording material of the present invention has excellent characteristics in terms of sensitivity and storage stability.

Claims (1)

[Scope of Claims] A heat-sensitive recording material comprising, on a support, a heat-sensitive recording layer containing a leuco compound, an organic acid that develops a color by reacting with the leuco compound, and a binder, wherein the heat-sensitive recording layer A heat-sensitive recording medium characterized by containing ethylene glycol benzyl diphenyl ether represented by the following structural formula (I): ▲Mathematical formulas, chemical formulas, tables, etc.▼