JPS5820493A - Heat-sensitive recording paper - Google Patents

Abstract

PURPOSE:To obtain heat-sensitive recording paper which can form clear color at a low temperature, by incorporating a color-forming substance and 4-butoxy- 4'- hydroxydiphenyl sulfone. CONSTITUTION:A normally colorless or light-colored color-forming substance which can form color by reacting with a phenol compound, such as Crystal Violet lactone or benzo-beta-naphthospiropyran, and 4-butoxy-4'-hydroxydiphenyl sulfone of the formula are crushed in water or in an organic solvent with a ball mill, a sand grinder, or the like, together with, if necessary, a surface active agent, a binding agent, or a dispersing agent, applied on a support and dried, to obtain heat-sensitive recording paper. By a combination of the color-forming substance and the specified phenol compound described above, clear color formation can be performed even at a temperature of 90-120 deg.C which is lower than the conventional one.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording paper, and more particularly to a heat-sensitive 11S1S sheet which has improved color development sensitivity and which produces clear color development at low temperatures.

It has been known for a long time that a colorless or light-colored color-forming substance such as crystal violet lactone reacts with a phenol compound to form a color, and the application of this reaction to 16-thermal paper has been proposed, for example, in U.S. Pat. No. 3,539. ,375-
8.

However, with the recent advances in recording devices and the diversification of their uses,
It has many drawbacks such as high speed response and high sensitivity. For example, in thermal printers, thermal facsimiles, etc., if the coloring sensitivity of thermal recording paper is insufficient, power consumption increases and printing speed decreases, so it is necessary to increase the coloring sensitivity.

As a method for improving the color development of 16 degrees of heat-sensitive recording paper, an example of using a wax in combination of a color-forming substance and a phenol compound is disclosed in Japanese Patent Application Laid-Open No. 48-1.
No. 9231, and an example of using a sensitivity improver such as a nitrogen-containing compound is described in JP-A-49-34S 42Ji+.

In heat-sensitive recording paper, the color-forming substance and the heptanoyl compound are dispersed in the form of fine particles in the heat-sensitive coating layer, or are stably separated and present in different layers, but when heated, one component of the two melts or sublimates. Alternatively, it is thought that both components melt or sublimate, come into close contact with each other, mix, and develop thermal color. Therefore, each component of the reactive coloring agent needs to be colorless to light-colored crystals or solids at room temperature, and the melting point is 7.
It is preferable to completely liquefy and/or still vaporize at 0°C or higher and between 50 and 200°C.

U.S. Pat. No. 3,539,375 lists 4 as one example of a suitable phenolic compound for use in this purpose.
, 4°-isopropylidenediphenol (melting point 156°
C) is a compound that has been described and is widely used today, but as mentioned above, in order to develop color by thermal melting, it requires a considerably high temperature (for example, 140 to 150'C).
If you don't do this, it will be difficult to develop bright colors. however,
As mentioned above, in order to increase the color development sensitivity of thermal recording paper in response to the increasing speed of t in recording devices, the melting point of each component of the reactive coloring agent must be as low as possible, and the common point must be higher than any of the components. It is preferable to react even at a low temperature (for example, 90 to 120°C) and to obtain a bright color development. In addition, methyl p-hydroxybenzoate (melting point 126-12
8° C.), but even though the melting point is low, the molecular weight is small and the heat volatility is considered, which is not very preferable from a practical standpoint.

The present inventor has studied various phenol compounds and found that by combining a color-forming substance and a specific phenol compound, it is possible to reduce
), it has been found that a thermal recording paper with excellent sensitivity and vivid colors can be obtained. The phenol compound of the present invention referred to herein is 4-butoxy-4'-hydroxy-diphenylsulfone represented by the formula.

The color-forming substance may be any substance as long as it reacts with a phenol compound to form a color, such as crystal violet lactone, malachite green lactone, 3,3-bis(paradimethylaminophenyl) to
4.5.6.7-Titrachlorphthalide, benzo-β-
Naphthospiropyran, 3-methyl-di-β-su7tospirobilane, 1.3.3-trimethyl-6°-chloro-8
°-Methoxyindolinobenzospiropyran, N-phenylrhodamine lactam, 3-ethylamino-6-chlorofluoran, 3-morpholino-5,6-benzofluorane, 3-diethylamino-6-methyl-7-chlorofluoran , 3-diethylamino-6,7-dimethylfluorane, 3-dimethylamino-7,8-benzofluorane, 3-diethylamino-6-methoxyfluorane, 3
-diethylamino-7-dibenzylaminofluorane,
3-diethylamino-7-anilinofluorane, 3-diethylamino-5,6-pendi-tupendylaminofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl -7-anilinofluorane, 3-N-ethyl tolylamino-6-methyl-7-anilinofluorane, 3-diethylamino-
Examples include, but are not limited to, 7-(N-3-)lifluoromethylphenyl)aminofluorane.

In addition, the phenol compound of the present invention generally has the property of liquefying or vaporizing at 70° C. or higher and reacting with the color-forming substance to develop a color, such as 4
, 4°-isopropylidene diphenol, 4.4'-isopropylidene bis(2-chlorophenol), 4,4
°-isopropylidene bis(2-tert-butylphenol), 4.4°-sec-butylidene diphenol, 4.4'
-Cyclohexylidene diphenol, 4-phenylphenol, 4-hydroxycyphenol, methyl p-hydroxybenzoate, phenyl p-hydroxybenzoate, 4-hydroxyacetophenone, salicylic acid anilide, novolac type phenolic resin, halogenated novolak Invited phenolic resin, α-su7thol, β-naphthol,
It can also be used in combination with 2,2-bis-(4-hydroxyphenyl)-n-hebutane.

The heptadol compound of the present invention and the color-forming substance are separately ground in water or in an organic solvent together with a surfactant, binder, or dispersant if necessary using a ball mill, sand grinder, etc., and supported by a conventional method. Heat-sensitive recording paper is obtained by applying it to the body and drying it.

The phenol compound of the present invention is produced, for example, by the following method.

Bisphenol sulfone 5gs Ethanol 40me1 Sodium ethoxide 10me, Butyl bromide 2.7
Heat to reflux for 5 hours. The reaction solution is then concentrated under reduced pressure, and after diluting the residue with water, unreacted butyl bromide and the by-product 4,4'-dibutoxy-diphenyl sulfone are removed with an organic solvent. The aqueous layer is made acidic and extracted with chloroform (unreacted bisphenolsulfone is insoluble in chloroform and is therefore removed). When the resulting crude product is purified by silica gel column chromatography, it has a melting point of 118-1
4-Butoxy-4''-hydroxydiphenylsulfonate at 19°C.

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

Comparative example Liquid A Crystal violet lactone 1 part 5% polyvinyl alcohol 5 parts water
40 parts B liquid 4.4'-isopropylidene diphenol 5% polyvinyl alcohol 25 parts water
211 Example 1 Solution A Comparative Example A Solution B Solution 4-7') xy-4-hydroxy-diphenylsulfone 5% polyvinyl alcohol 25 Tosui
20 copies each A,
After pulverizing in a ball mill for 2 days without mixing B liquid, liquid AXB is mixed to obtain a coating liquid for heat-sensitive recording paper. The coating liquid is applied to the surface of a high-quality paper having a basis weight of 50 g/door so that the dry coating amount is 4 g/77Z'. The obtained thermal paper was dried at 50°C in a dryer, and the temperature of this thermal paper was 80-15°C.
Color was developed on a hot plate heated to 0° C. at a pressure of 1.5 Kg/cn for a pressing time of 5 seconds, and the density was measured using a photodensitometer. The results are shown in FIG.

Furthermore, when the thermal recording papers obtained in Examples 1 and 2 were recorded by facsimile, the dynamic color density was high and clear images were obtained.

[Brief explanation of the drawing]

FIG. 1 shows the relationship between temperature and color density measured with a photodensitometer, where ■ indicates a comparative example, and ■ indicates a thermal paper treated with the recipe of Example 1. Agent Patent Attorney Masaru Takamiyagi 11- Akira 11 included / 60 / RiOra Ai
le ((0 and) 1

Claims (1)

[Claims] Usually colorless to light colored chromogenic substance and 4-butoxy-4
1. A thermal recording paper with improved color development sensitivity, characterized by containing '-hydroxydiphenylsulfone.