JPH0232893A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance a color developing characteristic and to prevent background fog and fading after preservation by adding 1, 4-bis (phenylglyoxaloyl) benzene in a thermal recording layer containing a leuco compound, an org. acid coupler and a binder as a development promoter. CONSTITUTION:For example, 3-dibutylamino-6-methyl-7-anilinofluorane as a leuco dye, bisphenol A as a coupler and 1, 4-bis (phenylglyoxaloyl)benzene as a development promoter are added while zinc stearate, an aqueous polyvinyl alcohol solution and synthetic silica are added to prepare a coating solution which is, in turn, applied to paper to form thermal recording paper. By this method, the color development start temp. of the thermal recording paper rises and high image density is imparted and the preservability of said recording paper is also enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention is directed to a dyestuff containing as main components a colorless or light-colored organic dye generally called 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 heat-sensitive recording materials.

[Prior Art] A thermosensitive recording paper containing a leuco compound and a t11 acid is already known, for example, from Japanese Patent Publication No. 14039/1983. This recording paper is based on the principle that heat energy is applied to the recording layer to soften or melt the leuco compound, organic acid, and binder, and the two coloring components are brought into contact to cause a coloring reaction. It is used in fields such as The recording characteristics of this recording paper vary depending on the use, but for example, in order to increase the recording speed,
It can be said that it is necessary to improve the coloring properties of the recording paper itself as well as improve recording devices.

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, i.e. color accelerator or sensitizer,
In Japanese Patent Publication No. 43-4160, urea, phthalic anhydride,
Acetanilide is also used in JP-A-48-19231, paraffin wax, carnauba wax, beeswax, real wax,
Higher fatty acids and higher fatty acid esters were further
-17748, salicylic acid, anis i! IlI
, 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 discloses that the combination of paraffin or microcrystalline wax and fatty acid amide can increase the sensitizing effect of fatty acid amide.
The sensitizing effect of fatty acid amides such as stearic acid amide and oleic acid amide is also described in the publication, and is well known.

Furthermore, terphenyl is disclosed in JP-A-57-27785, and rose-benzylbiphenyl is disclosed in JP-A-60-82382@.

[Problems to be Solved by the Invention] However, the effects of the color development accelerators proposed so far are not sufficient, and improvements are still required. Also,
In recent years, as the uses of thermal recording paper have expanded, the environment in which it is used has become more severe, and the characteristics required of thermal paper have also become more sophisticated. For example, recent attempts have been made to install facsimile machines in general passenger cars, and thermal paper with a high color initiation temperature and high sensitivity is desired.

In developing thermal paper that satisfies the above requirements, the present inventors confirmed the effects of conventional color accelerators and extensively and deeply studied color accelerators that met the above required properties. We have discovered a novel color development accelerator having the following characteristics, and based on this knowledge, we have accomplished the present invention.

An object of the present invention is to provide a heat-sensitive recording material that provides better sensitivity and storage stability than conventional heat-sensitive recording materials using color development accelerators.

[Means for Solving the Problems 1] That is, the present invention provides a heat-sensitive recording material mainly composed of a leuco compound and an organic acid that develops a color by reacting with the leuco compound, in which ( 1,4-bis(phenylglyoxaloyl)benzene) (hereinafter abbreviated as bisbenzyl).

The present invention will be explained in detail below.

The heat-sensitive recording material of the present invention is obtained by coating a heat-sensitive recording layer containing a leuco compound, an organic acid as a color developer, an adhesive, and a compound represented by the following structural formula as a color development promoter on a support. It consists of

The color accelerator bisbenzyl used in the present invention has 11 points and 1
It has a temperature of 23 to 125°C, and is excellent in the effect of promoting color development, and also has particularly excellent properties as a heat-sensitive recording material, such as background density, background fogging after storage, and discoloration. .

The content of sobenzyl 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.

Further, the color development accelerator of the present invention can be contained in the recording layer in combination with a known color development accelerator.

The leuco compounds used in the present invention are colorless to light-colored substances that develop color by reacting with organic acids, such as triphenylmethane, triphenylmethanephthalide, fluoran, leucoolamine, diphenylmethane, and phenothiazine. Examples include various derivatives such as phenoxazine-based, phenoxazine-based, spiropyran-based, indoline-based, and indigo-based. Preferred leuco compounds include, for example, 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)fluorane, 3-piperidino-6
-Methyl-7-anilinofluorane, 3-(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-7-(ortho-
chloroanilino)fluoran, 3-diethylamino-7
-(meta-trifluoromethylanilino)fluorane,
3-diethylamino-6-methyl-chlorofluorane,
3-diethylamino-6-methyl-fluorane, 3-
(N-isoamyl-N-ethylamino)-6-methyl-
Examples include 7-anilinofluoran and 3-dibutylamino-6-methyl-7-anilinofluoran.

The organic acid used in the present invention is a substance that is solid at room temperature, melts when heated, and becomes a color developer when it comes into contact with a leuco compound, and includes various phenolic substances, fatty acids, aromatic carboxylic acids, etc. . 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,
o-tert-butylphenol, 4-hydroxyphenoxide, methyl-4-hydroxybenzoate, 4-
Hydroxyacetophenone, α-naphthol, β-naphthol, catechol, resorcinol, hydroquinone, 4-
tert-Okjiru force tecol, 4.4'-5ec-
Butylidenephenol, 2,2'-dihydroxydiphenyl, 2°2'-methylenebis(4-methyl-6-te
rt-butylphenol), 2,2'-bis(4-hydroxyphenyl)propane (also known as bisphenol A)
), 4,4'-isopropylidene-bis(2-ter
t-butylphenol), pyrogallol, phloroglucin, 70roglucincarboxylic acid, p-methylphenol, p-phenylphenol, 4.4'-cyclohexylidene diphenol, 4.4'-isopropylidene dicatechol, 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- and droxybenzoic 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 mainly consists of a water-soluble binder, which releases and fixes the coloring agent dispersed in fine particles to each other. Polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, Examples include acrylic acid, casein, gelatin, starch and derivatives thereof.

The heat-sensitive recording layer of the present invention may contain other additives as necessary, such as inorganic or organic pigments such as clay, calcium carbonate, synthetic silica, aluminum hydroxide, talc, titanium oxide, and zinc oxide, waxes, and anti-stick additives. Various fatty acid metal salts for water resistance, water resistance agents for water resistance improvement, phenol resins, surfactants, etc. can be added.

The coating material for the heat-sensitive recording layer of the present invention is prepared by separating the above-mentioned leuco compound and organic acid into bisbenzyl and, if necessary, a pigment.
Additives such as a sensitivity adjuster are mixed in a ball mill in an aqueous medium containing a binder such as polyvinyl alcohol at an appropriate concentration.
It is generally prepared by pulverizing and dispersing using a pulverizer such as a sand grinder, and then mixing and stirring a dye dispersion and an organic acid dispersion. It is advantageous in terms of color development efficiency to make each constituent material as fine as possible, and it is 0.5 to 3μ.
It is preferable to atomize the particles to a particle size of m. The heat-sensitive paint thus obtained is applied to the support described below and dried to obtain the heat-sensitive recording material of the present invention.

Coating can be performed using a conventional blade coater, air knife coater, bar coater, reverse roll coater, or the like.

The support used in the present invention generally includes paper such as wood-free paper, medium-quality paper, and coated paper, but other materials such as glass fiber sheets, plastic sheets, and film-laminated paper may also be used as supports. I can do it.

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

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: Oico dye 3-dibutylamino, 6-methyl-7-anilite fluorane 5g Bisbenzyl 8g Zinc stearate 5g
Polyvinyl alcohol 12%m
35g water
479B liquid: Bisphenol A
15g zinc stearate
3゜Polyvinyl alcohol 12% liquid
35g water
479 Next, 100g of liquid A, 100g of liquid B
g, 50 g of 12% polyvinyl alcohol solution, 15 g of synthetic silica P-832 (manufactured by Mizusawa Chemical Co., Ltd.), and water 609 were mixed and stirred to prepare a coating liquid. - The surface of high-quality paper was coated and dried using a Mayer bar so that the coating ω after drying was 8 g/TIt to obtain heat-sensitive recording paper.

Example 2 The formulation of Solution A used in Example 1 was the same as Example 1 except that 3-(N-isoamyl-N-ethyl)amino-6-methyl-7-anilite fluorane was used as the leuco dye. A thermosensitive recording paper was obtained in the same manner.

Comparative Example 1 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that hisbenzyl was not added to 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 stearamide was used instead of bisbenzyl in the formulation of Liquid A used in Example 1.

Comparative Example 3 A thermosensitive recording paper was obtained in the same manner as in Example 1, except that in the formulation of Liquid A used in Example 1, parabenzylbiphenyl was used instead of bisbenzyl.

Comparative Example 4 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that 2-benzyloxynaphthalene was used instead of bisbenzyl in the formulation of Liquid A used in Example 1.

The thermosensitive recording papers obtained in the above Examples and Comparative Examples were surface-treated using a test super calender so that the recording surface had a Peck smoothness of 500 seconds.

The heat-sensitive recording paper obtained by this surface treatment (X, commercially available (') 077) Equipment FACOM FAX
Recording power: 0.9014 at 621C (manufactured by Fujitsu Ltd.)
/dat, energizing time 0.45 m5ec, periodic 5m
Printing was performed under the condition of 5ec/j2, and the image density and background density of the printed image were measured using Macbeth density. The storage stability was determined by measuring the image density and background density after storing the film in a dry state for 24 hours in a constant temperature room maintained at 60°C. The color development start temperature is the value specified as the temperature at which the image density becomes 0.2 or higher, and is determined by printing with a new thermal gradient tester manufactured by Toyo Seiki and measuring the image density with a Macbeth densitometer. Ta. The results obtained for Examples and Comparative Examples are shown in the table (the following margins).

Table [Effects of the Invention] As mentioned above, the heat-sensitive recording material of the present invention has superior coloring properties compared to the conventional heat-sensitive recording material containing a coloration accelerator, and is also less susceptible to storage problems such as background fogging and discoloration due to storage corrosion. It is clear that it also has very excellent properties in terms of gender.

Claims (1)

[Claims] In a heat-sensitive recording material provided with a heat-sensitive recording layer containing a leuco compound, an organic acid that reacts with the leuco compound to develop a color, and a binder on a support, the heat-sensitive recording layer contains (1,4-bis( 1. A heat-sensitive recording material characterized by containing phenylglyoxaloyl)benzene).