JPS61171384A - Thermal recording paper - Google Patents

Abstract

PURPOSE:To provide a thermal recording paper generating little fogging and undergoing little decoloration of recorded images due to moisture or heat, by incorporating specified amounts of an organic acid (color developer) and a diphenylsulfone derivative into a thermal color forming layer. CONSTITUTION:In the thermal color forming layer is incorporated 3,3',5,5'- tetrabromo-4,4'-dihydroxydiphenylsulfone in an amount of 5-50wt% based on the amount of an organic acid. The color former is a triaryl, diphenylmethane, xanthene, thiazine or spiropyran compound or the like, while the color developer may be a phenol derivative or an aromatic carboxylic acid derivative, particularly, a bisphenol. To produce a coating liquid for a thermal recording paper, the components are put into a dispersant containing a water-soluble high molecular weight compound, followed by dispersing by a dispersing machine such as a ball mill and a colloid mill. Further, an oil- absorbing oil, a wax, a metallic soap or the like is added to the dispersed liquid, and the resultant liquid is applied to a base such as a paper and a plastic to obtain the thermal recording paper.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to a heat-sensitive recording paper, and more particularly to a heat-sensitive recording paper that prevents a recorded image from decoloring.

- (Prior Art) Thermosensitive recording paper is used to obtain images by utilizing physical and chemical changes in substances caused by thermal energy, and a large number of processes are being studied.

Recently, thermal recording paper has come to be used for facsimile output, computer output, and recording paper, taking advantage of its features such as primary color development and no need for a developing process. These are called dye types, such as Tokko Shogu J-4t/bu0, Tokko Shogu! -/Da03de, JP-A-272! It is disclosed in No.j etc.

In general, when thermosensitive recording paper is used as recording paper, it has the advantage that the recording device is lightweight and can be made into a compact size, and its use has been rapidly increasing in recent years. On the other hand, as a disadvantage of thermal recording paper,
One example of this is that the recorded image that has been obtained may become discolored due to the influence of external conditions such as humidity and heat. Discoloration of recorded images is a serious drawback in practical use as recording paper, and various proposals have been made to improve this drawback.

Special public Akira! /-41J3rg, the trick is to add phenol derivatives such as 2'-methylenebis (4t-methyl-4-tert-butylphenol), and
-773417 discloses the addition of a water-insoluble modified phenolic resin such as rosin modified phenol resin, published by JP-A-Sho! The t-72 Tatabu issue describes the addition of a terephthalate ester such as diethyl terephthalate. However, all of these methods have the disadvantage that not only are the effects of preventing color erasure insufficient, but also unnecessary color development, so-called "fogging" occurs during the production of recording paper or during storage of recording paper. Since this fog increases significantly especially under the influence of humidity and heat, the commercial value is significantly reduced under such conditions.

(Object of the Invention) An object of the present invention is to provide a heat-sensitive recording paper that does not cause fog and is less likely to lose color of a recorded image due to humidity or heat.

(Structure of the Invention) The above-mentioned object of the present invention is to combine an electron-donating dye precursor (hereinafter referred to as a color former) and an organic acid (hereinafter referred to as a color developer) that reacts with the color former when heated to produce a color. In the heat-sensitive color forming layer mainly composed of, j weight percent or more of organic acid,! Less than 0 weight percent! , 31, j, j'-tetrabromog 4tt-dihydroxydiphenylsulfone. Furthermore, it is preferably at least /θ weight percent and at most jO weight percent with respect to the organic acid.

The coloring agent used in the present invention is typically (
These include 1) triarylmethane compounds, (2) diphenylmethane compounds, (3) xanthine compounds, (4) thiazine compounds, and (5) spiropyran compounds. -27.2!3, etc. Numbers listed here are examples.

As the color developer used in the present invention, phenol derivatives and aromatic carboxylic acid derivatives are preferable, and bisphenols are particularly preferable. Specifically, as the FuZ/-Jb class, p-octi"""'-".

p-tert-butylphenol, p-phenylphenol, /, l-bis(p-hydroxyphenyl)propane, co-corbis(p-hydroxyphenyl)propane, /, /-bis(p-hydroxyphenyl)pentane,
/,/-bis(p-hydroxyphenyl)hexane, λ
, --bi-p-°hydroxyphenyl)hexane, /
, /-bis(p-hydroxyphenyl)-coethylhexane, co,2-bis(gu-hydroxy-3,j-dichlorophenyl)propane, and the like.

Examples of aromatic carboxylic acid derivatives include benzyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, butyl p-hydroxybenzoate, 3. Examples of j-tert-butylsalicylic di-methylbenzylsalicylic acid and carboxylic acids include their polyvalent metal salts.

When producing a coating liquid for heat-sensitive recording paper, it is necessary to disperse the above-mentioned material for heat-sensitive recording paper using water as a dispersion medium. At this time, it is preferable to use water-soluble polymers such as polyvinyl alcohol, hydroxyethyl cellulose, and starch derivatives.

The method of dispersing materials for heat-sensitive recording materials using these dispersion media generally ranges from /wt% to iowt%,
More preferably from 2% by weight! A coloring agent,
7 each of the color developer and the diphenylsulfone derivative of the present invention.
From 0 weight percent! Add 0% by weight and disperse using a dispersing machine such as a ball mill, sand mill, attritor, or colloid mill.

The color developer and the diphenylsulfone derivative of the present invention can also be mixed and dispersed at the same time.

To the mixture of the above dispersion liquid, oil-absorbing pigments, waxes, metal soaps, etc. are further added as necessary to make a coating liquid for heat-sensitive recording paper, and the coating liquid is applied onto a support such as paper or plastic.
Obtain the desired thermal recording paper.

The oil-absorbing pigment is selected from kaolin, calcined kaolin, talc, waxite, diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, titanium oxide, barium carbonate, urea-formalin filler, cellulose filler, etc. .

Examples of waxes include paraffin wax, cownapa wax, microcrystalline wax, polyethylene wax, and higher fatty acid amides such as stearic acid amide, ethylene bisstearamide, and higher fatty acid esters.

Examples of metal soaps include higher fatty acid polyvalent metal salts such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate.

(Examples of the Invention) Examples will be shown below, but the present invention is not limited thereto.

Example 1 50% of 3-diethylamino-6-chloro-7-(β-ethoxyethyl)aminofluoranco 0p in polyvinyl alcohol (degree of saponification? r% degree of polymerization -+00) aqueous solution 50%
051 in a JOOd ball mill overnight to obtain a dispersion liquid (5). Similarly, 2゜corbis(terhydroxyphenyl)propane 501 and stearic acid amide 50
was dispersed day and night in a 300IjL ball mill with 500ml of 50% polyvinyl alcohol aqueous solution to obtain a dispersion (
B) was obtained. Similarly, J, J',! , j' -tetrabromo-≠.

μ'-dihydroxydiphenylsulfone 20ft-50
30 with Ls polyvinyl alcohol aqueous solution 1ooy
Dispersion was carried out day and night in a 0ml ball mill to obtain a dispersion.

Dispersion was carried out several times, and the dispersion liquid ■ and the dispersion liquid Ot were mixed at a weight ratio of 3:20:6, and then for 200 tons of the mixed liquid! Of calcium carbonate fine powder? Add it, disperse it thoroughly and use it as a coating liquid.

Is this coating liquid for thermal recording paper? The mixture was coated onto a base paper having a basis weight of JOf/m2 using an air knife so as to obtain a coating weight of 6f/m2 in terms of solid content, and dried for a minute to obtain a heat-sensitive recording paper.

Example 2゜! Example 1. In Example 1, the mixing ratio of dispersion ① and dispersion 0 was adjusted to 3:20=2 by weight. A thermosensitive recording paper was obtained in the same manner as above.

Comparative example l.

Mix several times of dispersion of Example and dispersion @ at a weight ratio of 3:20, add calcium carbonate fine powder of toy to the mixed liquid λooy, sufficiently disperse it to make a coating liquid, and mix it with Example and l1.
A heat-sensitive recording paper was obtained by coating IJ.

Comparative example 2゜Example 1. 3+", 4's''-natrapromo≠,
2,2'-methylenebis(V-methyA/-6-ter) instead of μ'-dihydroxydiphenylsulfoncoOf
Example 1. A dispersion was obtained using 20ff of t-butylphenol. In the same way, you can obtain thermal recording paper.

Comparative Example 3゜Execution except that 20f'i of diethyl terephthalate was used in place of J, J', j, j'-tetrabromo-≠1hiro'-dihydroxydiphenylsulfoncoQy to obtain dispersion 0. Obtain thermal recording paper in the same manner as the example.

Comparative Tests Comparative experiments of the following thermal recording paper obtained in Examples and Comparative Examples were carried out as follows.

(1) Fog and color development Main scanning t dots/m, sub-scanning 6 dots/cod density, /
ms/dot, j OmJ/mm" to the recording element to record, and the Macbeth RD-ta/ri
Fog (ground density before recording) and chromophore density after recording (
initial concentration)? It was measured.

(2) Moisture resistance Chromogenic body f20''c obtained in a chromogenic test.

After leaving it in an atmosphere of RH for 2μ hours, fogging (
The density of the background) and the chromophore density were measured.

Also, calculate the residual rate of the coloring material using the following formula.

(3) 60°01RH CoO obtained in the heat resistance coloring property test.
% atmosphere for 2 hours and then measure the fog (ground density) and color former density. In addition, the total residual rate of the colored body was calculated using the following formula.

The results of the comparative test are shown in Table 1.

From the above table, it can be seen that the thermosensitive recording paper of the present invention is less likely to lose color due to humidity and heat in the color former than the comparative thermosensitive recording paper, and is also superior in terms of fogging.

Claims (1)

[Claims] In a thermosensitive recording paper in which a thermosensitive coloring layer containing an electron-donating dye precursor and an organic acid that reacts with the dye precursor under heat to form a color is provided on a support, 5% of the organic acid is contained in the thermosensitive coloring layer. 3,3% or more and 50% or less by weight
A thermosensitive recording paper characterized by containing ',5,5'-tetrabromo-4,4'-dihydroxydiphenylsulfone.