JPH04101888A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material forming a color at low temp. and imparting a developed color image excellent in fastness by using 2-(4- hydroxyphenyl)-2-(3'-phenyl-4'-hydroxyphenyl)propane as a developer. CONSTITUTION:2-(4-hydroxyphenyl)-2-(3'-phenyl-4-hydroxyphenyl)propane is used in a thermal recording sheet as a developer. 2-(4-hydroxyphenyl)-2-(3'- phenyl-4'-hydroxyphenyl)propane can be obtained by reacting p-isopropylphenol with o-phenylphenol under an acidic condition. As a color former used along with the developer, an electron donating dye of every kind forming a color by the melt reaction with the developer is used and a triphenylmethane type compound, a fluorane type compound, a thiazine type compound and a spiropirane compound are designated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a color developer for heat-sensitive recording materials, and particularly to a heat-sensitive recording material with excellent color development sensitivity and image stability.

[Conventional technology]

In recent years, thermal paper has been used in facsimiles, printers, medical measurement,
Demand is growing for POS labels and transportation tickets. Among these, facsimile applications account for more than 70% of the total demand for heat-sensitive sheets, and the performance required of heat-sensitive sheets is also high.

Conventionally, various methods have been proposed as heat-sensitive recording methods, and among these, a two-component coloring method in which a lactone compound is used as a coloring agent and a phenol compound is used as a color developer is widely used.

2,2-bis(4-hydroquinphenyl)propane (hereinafter referred to as bisphenol A), which is widely used as a color developer.
Thermal paper using bisphenol A has a high melting point of 157°C, so in order to obtain a sufficiently colored image,
It is necessary to improve the sensitivity by increasing the coloring temperature or by using a sensitizer in combination.

Furthermore, when p-hydroquine benzoic acid benzyl ester is used as a color developer, there are problems such as insufficient storage stability of the colored image (with respect to light, plasticizers, humidity, etc.), and improvements are needed. Ta.

In particular, recently the speed of facsimile has increased (C, -111,
■) As a color developer for heat-sensitive sheets with a short heating pulse width, it develops color at low temperatures, reaches sufficient color density within a narrow temperature range from the color initiation temperature, and develops color instantly when heated. The appearance of a color developer was desired.

[Problem to be solved by the invention]

An object of the present invention is to provide a heat-sensitive recording material that develops color at low temperatures and has excellent fastness of colored images.

[Means to solve the problem]

As a result of various studies, the present inventors found that by using 2-(4-hydroxyphenyl)-2-(3°-phenyl-4°-hydroxyphenyl)propane as a color developer,
The present invention was achieved based on the discovery that a heat-sensitive recording material with significantly superior performance can be obtained.

That is, the present invention uses 2 as a color developer in the swear recording sheet.
-(4-hydroxyphenyl)-2-(3phenyl-4
It is characterized by the use of (hydroxyphenyl)propane, and has a lower melting point (melting point 119-121°C) compared to the conventional heat-sensitive recording sheet that uses bisphenol A as a color developer. Therefore, when applied to heat-sensitive sheets, the amount of auxiliary agents such as sensitizers used can be significantly reduced, or the coloring start temperature can be lowered without the need for their use at all, allowing for a narrow temperature range from the coloring starting temperature. Achieves sufficient color density. In addition, compared to ρ-hydroxybenzoic acid benzyl ester, the color image has excellent storage stability (against light, plasticizers, humidity, etc.), and it also has less sublimation, making it extremely easy to handle and store. A thermosensitive recording sheet can be obtained.

The present invention not only solves the problems of conventional heat-sensitive recording sheets, but also has great industrial merits in that it makes it possible to reduce the cost of recording sheets.

2-(4-hydroxyphenyl)-2(3'-
Phenyl-4°-hydroxyphenyl)propane is p
-It can be obtained by reacting isopropenylphenol and 0-phenylphenol under acidic conditions (Collect, Czech, Chew).

Commun, 342843-48 (1969)
).

The color forming agent used together with the color developer of the present invention includes:
Various electron-donating dyes that develop color through a melt reaction with a color developer are used, and specific examples include triphenylmethane-based, fluoran-based, diphenylmethane-based, thiazine-based, and spiropyran-based compounds.

For example, 3,3-bis(p-dimethylaminophenyl)
-6-dimethylaminophthalide, 3-(4-'; ethylamino-2-methylindole)-3-(1ethyl-2
-methylindol-3-yl) = 4-azaphthalide,
3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3-
(cyclohexylamino)-7-methylfluorane, 3
-diethylamine-6-chloro-7-anilinofluorane, 3-diethylamino-7-anilinofluorane, 3
-diethylamino-7-o-chloroanilinofluorane, 3-dibutylamino-7-o-chloroanilinofluorane, 3-(N-ethyl-N-p-)luidino)-6-
Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl 7-anilinofluorane, 3-(N
-Methyl-N-cyclohexylamino)-6-methyl-
7-anilinofluorane, 3-piperidino-6-methyl 7-anilinofluorane, 3-pyrrolidino-6methyl-7-anilinofluorane, 3-diethylamino-7-(
m-)lifluoromethylanilino)fluorane, 3-(
Examples include N-ethyl-N-isoamylamino)fluoran.

The heat-sensitive recording material of the present invention is produced by the following method.

First, the color developer of the present invention and the usually colorless to light color former are separately prepared in a medium that does not dissolve them (for example, water,
Oil etc. available! A dispersion is prepared by thoroughly mixing or pulverizing the compound with a dispersant or binder in a solvent (solvent).

Dispersants or binders used in the preparation of these dispersions include polyvinyl alcohol and its modified products, methylcellulose, hydroquine ethylcellulose, carboxymethylcellulose, gum arabic, salts of styrene-maleic anhydride copolymer, isobutylene-acrylic acid- Examples include synthetic polymers, natural polymers, and modified polymers such as copolymers of maleic anhydride, sodium alginate, modified starches, gum arabic, styrene-butadiene rubber latex, and cyclized rubber.

Coating the obtained dispersion onto a support such as paper or film,
Dry to create a heat-sensitive recording sheet. Generally, the two types of dispersions are mixed and applied to the support, but both dispersions may be applied separately in two parts.

Appropriate amounts of the color former, color developer and binder used are 1 to 15 parts by weight of the color former, 1 to 95 parts by weight of the color developer, and 1 to 40 parts by weight of the binder.

When producing the heat-sensitive recording material of the present invention, talc, kaolin, calcined kaolin, calcium carbonate, titanium oxide, zinc oxide mica group minerals, diatomaceous earth, urea-formaldehyde resin, acrylic resin, etc. may be added to the coating if necessary. Inorganic and organic pigments, water-soluble binders with crosslinking properties,
Dialdehyde starch or crosslinking accelerator, compounds with two or more ethyleneimine groups, compounds with two or more 1,2-epoxy rings, protein adhesives and waterproofing agents such as glutaraldehyde, beeswax, Animal waxes such as shellac wax, vegetable waxes such as carnauba wax, petroleum waxes, paraffin waxes, polyethylene waxes, microcrystalline waxes, lubricants such as metal soaps such as zinc stearate, anti-pressure agents, stearic acid amide, ethylene Bisstearamide, 1-hydroxy-2-naphthoic acid phenyl ester, p-penzylhyphenyl, β-naphthylbenzyl ether, terephthalic acid dibenzyl ester, di-p-methylphenyl carbonate, 1,4-butanediol- It is also possible to use aggravating agents such as P-methylphenyl ether, various surfactants, antifoaming agents, etc. in combination to improve the coating suitability and the properties of the recording paper.

〔Effect of the invention〕

The color developer of the present invention can be used at a lower temperature than bisphenol A.
It is a color developer that develops deep colors, has excellent fastness of colored images to light and plasticizers, and causes very little scumming on recording sheets.

Hereinafter, the method of the present invention will be explained in detail with reference to Examples.
The present invention is not limited thereby.

Example 1 (1) Method for preparing a heat-sensitive recording sheet Liquid A (dye dispersion) 3-dibutylamino-6-methyl 7-anilinofluoran polyvinyl alcohol (Kuraray 1117) 10% aqueous solution 0 g 0 g Water total 100 g Liquid B (color developer dispersion) 2-(4-hydroquinphenyl)-2-(3'-phenyl-4'-hydroxyphenyl)propane 20 g Light calcium carbonate (Okuta ff1TP-123) 4
0 g polyvinyl alcohol (Kuraray 1117) 10%
Aqueous solution 60 g Water - 1 "Saishi" L - Total 500 g Prepare a dispersion of the above A and B solutions using a sand grinding mill so that the average particle size is 1.5μ or less, A solution 100 g
g, 500 g of liquid B, and 23 g of 30% paraffin wax were mixed, and the dry coating amount was 4.5 ± 0.5 on high-quality paper.
The coating was coated and dried to obtain a swear record notebook with a thickness of 7 m''.

(II) Performance evaluation method of leisurely recording sheet (1) Color development density The recording sheet obtained by coating is brought into contact with a metal block for 5 seconds at a surface temperature of 150°C to develop color. After 1 hour of color development, a Macbeth densitometer is used. to determine the color density.

(2) Dynamic coloring properties The recorded notes obtained by coating were coated with Yuzen Paper Coloring System W (TH-PMD manufactured by Daii Denki), with an applied voltage of 26V and an average head resistance of 2985Ω, with a pulse width of O: 3-1.9m5
Print with ec, and determine the print density using a Macbeth densitometer after 1 hour.

(3) Storage Stability of Colored Image The recording sheet colored in (1) is stored in a constant temperature incubator at 60°C/90% RH for 24 hours, and then the change in color density is measured.

(4) Light fastness of colored image The colored recording sheet (1) is exposed for 4 hours using a carbon arc fade meter. Thereafter, the change in color density is measured.

(5) Plasticizer resistance of colored images Capsule-coated paper containing dioctyl phthalate as a plasticizer component is layered on top of the recording sheet colored in (1), passed through a pressure roll, and color develops after 5 days. Measure changes in concentration.

(6) Degree of scumming on the recording sheet The degree of scumming on the recording sheet obtained by coating is measured.

(7) Storage stability of recording sheet The recording sheet obtained by coating is stored in a constant temperature and humidity chamber at 40° C./90% RH for 24 hours, and the degree of self-coloring is then measured. The higher the reflection density after the test, the greater the natural color development under humidification.

Example 2 Thermal recording was carried out in the same manner as in Example 1, except that 3-(N-ethyl-Nisoamylamino)fluoran was used instead of the dye 3-dibutylamino-6-methyl-7-anilinofluoran. I created a sheet.

Comparative Example 1 Color developer 2-(4-hydroxyphenyl)-2-(3°
A leisurely recording sheet was prepared in the same manner as in Example 1 except that bisphenol A was used instead of -phenyl-4'-hydroxyphenyl)propane.

Comparative Example 2 Color developer 2-(4-hydroxyphenyl)-2-(3'
A leisurely recording sheet was prepared in the same manner as in Example 1, except that p-hydroxybenzoic acid benzyl ester was used instead of -phenyl-4'-hydroxyphenyl)propane.

Table 1 shows the performance evaluation results of each example and comparative example.

Table 1 Table 1 (continued)

Claims (1)

[Claims] 1) A heat-sensitive recording material characterized in that 2-(4-hydroxyphenyl)-2-(3'-phenyl-4'-hydroxyphenyl)propane is used as a color developer.