JPS5925673B2 - Thermal recording paper with improved color sensitivity - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal recording paper, and more specifically, to improve the color sensitivity of a thermal recording paper that combines a colorless or light-colored color-forming lactone compound and a phenol compound. Fluorene, benzyl, benzoin,
The present invention relates to a thermal recording paper characterized in that it contains mandelic acid, diphenylsulfone, acetovanillone, or ethyl anthraquinone (hereinafter referred to as a new sensitivity improver).

It has been known for a long time that color-forming compounds such as crystal violet lactone react with phenols to produce colors, and the application of this reaction to heat-sensitive recording paper was described, for example, in Japanese Patent Publication No. 14039/1983. It is publicly known.

This type of thermal recording paper develops color when a color-forming lactone compound and a phenol compound are compatible with each other. Color-forming lactone compounds and phenol compounds, in addition to their ability to react and develop color, have a high degree of whiteness when made into thermal recording paper, and their whiteness does not easily decrease even when stored.
If colored, it is necessary that the color does not easily fade during storage. In addition, in thermal printers, thermal facsimiles, etc. that use heat-sensitive recording paper, if the coloring sensitivity is insufficient, power consumption increases and printing speed decreases, so it is necessary to increase the coloring sensitivity. As a result of examining various compounds, the present inventors have discovered a method for improving color development sensitivity that is practical and can be used in a wide range of applications, by directly using a color-forming lactone compound and a phenol compound, which have traditionally been considered a preferred combination. That is, novel sensitivity enhancers such as fluorene, benzyl, benzoin, mandelic acid, diphenylsulfone, acetovanican, and ethyl anthraquinone are added to the heat-sensitive layer which is a combination of at least one colorless to light-colored color-forming lactone compound and at least one phenolic compound. It is characterized by containing at least one of these.

The colorless or light-colored color-forming lactone compound mentioned here is
It is capable of developing color by reacting with a phenol compound, and specific examples are described below, but the invention is not limited thereto. Crystal violet lactone, malachite green lactone, 3,3-bis(1-ethyl-2-methylindol-3-yl)phthalide, 3-indolino-3-P-dimethylaminophenyl-6-dimethylaminophthalide, 3-methyldi mono-beta naphthospiropyran, 3
-diethylamino-J chlorofluorane, 3-diethylamino-J
[Anilinofluorane, 3-diethylamino-6-methyl-Jio-butylanilinofluorane, 2-(N-phenyl-N-methylamino)-6-(N-P-tolyl-
N-ethyl)aminofluorane, 3-diethylamino
J Me[dibenzylaminofluorane, spiro(xanthine-9,1'-putalan)-6-diethylamino-2-phenyl-3-one, 3,6-pis(diethylamino)fluoran-r-anilinolactam, 3 -cyclohexylamino-6-chlorofluorane, 3-diethylamino-
Benzo[a]fluorane, spiro{chromeno[2.

3-c]pyrazole-4[H]-1'putalan}-J me
[diethylamino-3-methyl-1-(P-tolyl)-
3'-one, 3-diethylamino-6-methyl-J-[xylidinofluorane, 2-anilino-3-methyl-6-
(N-ethyl-P-toluidino)fluoran, 2-P-toluidino-3-methyl-6-(N-ethyl-P-toluidino)fluoran, 3-pyrrolidino-b-methyl-J
[Anilinofluorane, 3-pyrrolidino-J [cyclohexylaminofluorane, 3-piperidino-6-methyl-J][anilinofluorane, 3-piperidino-6-methyl-J][toluidinofluoran, spiro-1] 11H-benzo[b]thieno[3.2-b]chromeno-1.1.1putalan}-3-diethylamino-J-methyl-3'-one.

On the other hand, phenol compounds generally liquefy or vaporize at temperatures above 70°C and develop color by reacting with the colorless to light-colored lactone compounds. Specifically, 4-phenylphenol, 4-hydroxyacetophenone, 2.2'-dihydroxydiphenyl 2.
2'-dihydroxydiphenyl, 2.2'-methylenebis(4-chlorophenol), 2.2/-methylenebis(4-methyl-6-t-butylphenol), 4.4'
-isopropylidene diphenol, 4.4'-isopropylidene bis(2-chlorophenol), 4.4'-yripropylidene bis(2-methylphenol), 4.4
'-Sec butylidenephenol, 4.

4'-ethylenebisphenol, 4.4'-ethylenebis(2-methylphenol), 4.4'-thiobis(6
-t-butyl-3-methylphenol), 1.1'-bis(4-hydroxyphenyl)-cyclohexane, 2.
Examples include 2'-bis(4-hydroxyphenyl)-n-heptane, 4,4'-cyclohexylidene bis(2-isopropylphenol), salicylic acid anilide, novolac type phenolic resin, halogenated novolac type phenolic resin, etc. It will be done.

However, these do not limit the scope of the present invention. Next, a general method for manufacturing the thermal recording paper of the present invention will be described.

The lactone compound, the phenol compound, and the novel sensitivity enhancer are added separately, or the novel sensitivity enhancer is added to one or both of the lactone compound, the phenol compound, and the mixture is mixed in water or in an organic solvent with a surfactant or a binder if necessary. , and pulverize with a dispersant using a ball mill, attritor, sand grinder, etc. In some cases, the powder may be ground and dispersed in water containing a surfactant and a binder. The following methods can be used for coating the support. (1) Mix each of the pulverized solutions and apply to a support. (2) Without mixing the lactone compound liquid and the phenol compound liquid, the novel sensitivity improver pulverized liquid is mixed with one or both of them and sequentially applied onto the same sheet. (3) Either a lactone compound or a phenol compound is made to exist in the sheet by impregnating or rolling into a support, and a pulverized solution of the new sensitivity improver is added to the other solution and applied onto the sheet.

(4) Applying only the lactone compound liquid or a mixture of the pulverized liquid of the new sensitivity improver and the phenol compound liquid alone or the mixture of the pulverized liquid of the new sensitivity improver and the phenol compound liquid on one sheet, respectively; Make sure the applied surface is in close contact with the surface.

In this case, at least one sheet contains the novel sensitivity enhancer. Examples of the binder used in the present invention include starch, polyvinyl alcohol, hydroxyethylcellulose, methyl cellulose, alkali salts of styrene-maleic anhydride copolymers, styrene-acrylic acid copolymers, modified polyacrylamide, etc. Polymeric compounds and latexes are used, and dispersants and surfactants can be selected from anionic and nonionic types.

If necessary, clays, starches, waxes, surfactants, binders, waterproofing agents, etc. may be added to the heat-sensitive coating liquid to improve the coating state or heat-sensitive recording state. As the support sheet, robustness is required, and paper is considered to be optimal in terms of opacity, price, etc., but it goes without saying that synthetic resin films, woven fabric sheets, etc. can also be used depending on requirements. do not have. The ratio of the lactone compound to the phenol compound used in the present invention is generally from 1:2 to 1:10, and the amount of the color-forming lactone compound on the support is usually from 0.1 to 0.6 t/d. be.

On the other hand, the new sensitivity improver is effective when applied in an amount equal to or 10 times the weight of the color-forming lactone compound.
Preferably it is in the range of 2 to 7 parts by weight.

Next, in order to explain the present invention more specifically, examples will be described and the effects thereof will be shown, but the present invention is not limited to these examples.

Example As a color-forming lactone compound, crystal violet lactone and 3-piperidino-6-methyl-J-anilinofluorane were each mixed separately with 1 part of the lactone compound, 1 part of a 5% hydroxyethyl cellulose aqueous solution, and 1 part of water and milled in a ball mill. It was crushed for 2 days.

On the other hand, bisphenol A was mixed with 1 part of bisphenol A, 1 part of a 5% hydroxyethyl cellulose aqueous solution, and 1 part of water and ground in a ball mill for 2 days. Listed as a new sensitivity enhancer
Compounds 1 to 9 of No. 1 were each ground in a ball mill for 2 days using 1 part of the new sensitivity improver, 1 part of a 5% hydroxyethyl cellulose aqueous solution, and 1 part of water. And lactone compounds:
Bisphenol A: The new sensitivity improver was mixed at a ratio of 1:5:3, and a 5% aqueous hydroxyethyl cellulose solution was added as a binder so that the binder amount was 25% of the total solid content. A heat-sensitive coating liquid was created. It was applied as a lactone compound to a 50t/d high-quality paper to a thickness of 0.2 to 0.25%, dried in a dryer at 50°C, and supercalendered to a Beck smoothness of 100 to 200 seconds. A thermosensitive recording paper was obtained. The whiteness of the thermal recording paper was measured using a Sakura photodensitometer PDA after storage under heat and humidity conditions (conditions will be described later).
-30 type (manufactured by Konishiroku Co., Ltd.).

In addition, the sensitivity was expressed as a numerical value that corresponds well to the practical sensitivity. That is, color was developed at 100°C and 50°C using a stamp-type color developer at a pressure of 250 t/Cd and a pressure contact time of 5 seconds, and the density was measured using Roku Konishi's Sakura photoelectric densitometer PDA-30.
The ratio (percentage) of the concentration of 100'CilC to the concentration of 1C was taken. The results are shown in Table-1.
Table 1: Characteristics of the new sensitivity improver and its thermosensitive recording paper A: Using crystal violet lactone as a lactone compound.

B: 3-biperidino-6-methyl-J-anilinofluorane was used as a lactone compound.

Whiteness: The smaller the number, the better, and anything over 0.15 is not practical (the number is reflection density D).

Whiteness after storage: The smaller the number, the better; anything over 0.45 is not practical.

Conditions are 600C24hrs and 45C90(f)RH2
The worse value was obtained at 4 hrs (the value is reflection density D).

Sensitivity: The larger the number, the better the sensitivity, and preferably 80% or more (the number is DatlOO8C/Datl5O℃ x 10
0(f)).

As is clear from Table 1, the novel sensitivity improver of the present invention was found to improve the sensitivity of thermal recording paper in a wide range of lactone compounds without reducing the whiteness or the whiteness after storage.

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording paper that combines a colorless or light-colored kraton compound and a phenolic compound, a compound selected from the group consisting of fluorene, benzyl, benzoin, mandelic acid, diphenylsulfone, acetovanillone, and ethyl anthraquinone. 1. A thermal recording paper with improved color development sensitivity, characterized by containing one or more of the following. 2 Fluorene, benzyl, benzoin, mandelic acid,
One or two compounds selected from the group consisting of diphenyl sulfone, acetovanillone and ethyl anthraquinone
2. The heat-sensitive recording paper according to claim 1, wherein the thermosensitive recording paper contains the color-forming lactone compound in an amount equal to to 10 times the weight of the color-forming lactone compound.