JPS5834308B2 - heat sensitive recording material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material in which a heat-sensitive coloring layer containing a colorless or light-colored leuco dye and an acidic substance that causes the leuco dye to develop color when heated is provided on a support.

A heat-sensitive recording material is a material in which a heat-sensitive coloring layer is provided on a support such as paper, synthetic paper, or plastic film, on which a colored image can be recorded by heating with a thermal head or a thermal pen. It is used not only for copying documents, etc., but also as a recording material for various information and measuring instruments such as electronic computers, facsimiles, telex machines, medical measuring instruments, etc.

Various kinds of heat-sensitive recording materials have been known so far, and among them, colorless or light-colored leuco dyes having a lactone, lactam, or spiropyran ring, and acidic substances such as organic acids or phenolic substances are used. A thermosensitive color forming layer containing the above is provided on a support, and is particularly useful because the image has a clear color tone and less fog.

However, since these conventional heat-sensitive recording materials do not have sufficient heat sensitivity, they cannot satisfactorily meet the recent demands for faster recording.

For this reason, several methods have been proposed to improve the heat sensitivity by adding certain substances to the heat-sensitive coloring layer of heat-sensitive recording materials, but while these conventional substances can increase the heat sensitivity to a certain degree, , the components of the thermosensitive coloring layer melt due to heating during recording, and this sticks to a thermal pen or thermal head (
Phenomena such as scum adhesion, sticking, and trailing occurred, and the running properties of the thermal head or thermal pen and the image became thick.

These phenomena become more significant as the recording speed increases.

The purpose of the present invention is to solve the above-mentioned conventional drawbacks,
More specifically, the object is to provide a heat-sensitive recording material that is highly sensitive to heat without causing phenomena such as the above-mentioned residue adhesion, sticking, and trailing, and is also capable of recording clear images with high density even during high-speed recording. The purpose of the present invention is to provide heat-sensitive recording materials.

As a result of various studies in view of the object of the present invention, we have found that a thermosensitive recording material having a thermosensitive coloring layer containing a colorless or light-colored leuco dye and an acidic substance that causes the leuco dye to develop color when heated; Among them, the general formula R1-X-R2 (where R1 and R2 are each a substituted or unsubstituted alkyl group having 10 or more carbon atoms, an aralkyl group, or -R3
COOR4 group, -R5COOR6 group, R3,R
5 represents an alkylene group, R4 and R6 represent a substituted or unsubstituted alkyl group having 10 or more carbon atoms, or an aralkyl group.

X represents a divalent bonding group selected from a sulfur atom or an S-5-S group.

) By adding the compound represented by (), the heat sensitivity is increased without causing phenomena such as adhesion of residue, sticking, and trailing, and it is excellent not only for low and medium speed recording but also for high speed recording. It has been found that clear images can be recorded, and the present invention has come to fruition.

Specific examples of the compound represented by the above general formula include dilauryl thiodipropionate (s<CH2CH2C00C12H25), shear, thea 1) #-f-CHCHCOOC1□H25 2 osi, and the like.

D2 onate (s<CH2CH2C00C08H3□)
and CH2CH2C00C48H3□ and didodecyl disulfide (C32T(25-8-8
-C, 2H25), etc.

In the present invention, conventionally known leuco dyes, acidic substances (organic acids, phenolic substances) and binders constituting the heat-sensitive coloring layer are used, and examples thereof are shown below.

1. Leuco dye 3.3-bisGp=dimethylaminophenyl)-phthalide, 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3.3-bis (p-dimethylaminophenyl) = 6-dimethylaminophenyl, 3-cyclohexylamino-6-chlorofluorane, 3-(N,N-diethylamino)-5-, methyl-7-
(N,N-dibenzylamino)fluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-(2'-hydroxy-47- dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)phthalide, 3-(2'hydroxy-4'-dimethylaminophenyl)-3-'(2'-methoxy-57-nitrophenyl) Phthalide, 2, organic acids diboric acid, oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid, benzoic acid, stearic acid, gallic acid, salicylic acid, 1-hydroxy-2-naphthoic acid, 0-hydroxybenzoic acid, m- Humanized xybenzoic acid, 2-hydroxy-p
-Toluic acid.

3. Phenolic substances: 3.5-xylenol, thymol, p-tertbutylphenol, 4-human xyphenoxide, methyl-4
-Hydroxybenzoate, 4-hydroxyacetophenone, α-naphthol, β-naphthol, catechol,
Resorcinol, hydroquinone, 4-tert-octylcatechol, 4.4-sec-butylidenephenol, 2
．． 2dihydroxydiphenyl, 2,2-methylenebis(
4-methyl-6-tert-butylphenol), 2.
2-bis(4'-hydroxyphenyl)furopane (also known as bisphenol A), 4,4'-isopropylidene-bis(2-tert-butylphenol), 4,4'
-5ec-Butylidene diphenol Pyrogallol Phloroglucin Phloroglucin carboxylic acid.

4. Binders: wood vinegar-based materials such as polyvinyl alcohol, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, DEAP 7, gelatin, etc.
Alternatively, aqueous emulsions such as polystyrene, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, etc. can be used as the binder.

In the heat-sensitive recording material of the present invention, fine powders such as calcium carbonate, silica, alumina, magnesia, talc, barium sulfate, and aluminum stearate are added to the heat-sensitive coloring layer to improve the clarity of the colored image. Also, lubricants such as linseed oil, tung oil, wax, paraffin, polyethylene wax, chlorinated paraffin, etc. can be added to further improve the runnability of the thermal head or thermal pen.

The heat-sensitive coloring layer of the present invention may be coated or pasted onto a support such as ordinary paper, plastic film, metallized paper, etc. to form a heat-sensitive recording material.

Further, a thinner protective layer made of a colorless or colored transparent polymeric material may be provided on the heat-sensitive coloring layer.

In some cases, it is also possible to use a self-supporting substance as a binder for the heat-sensitive coloring layer to provide a recording material without a support.

The present invention will be explained below using examples.

Example 1 The following components were mixed in a ball mill for 10 hours to prepare dispersion A and dispersion B, and then equal amounts of both dispersions were mixed to prepare a thermosensitive coloring layer forming liquid.

(Components of dispersion A) Crystal violet lactone 10% aqueous solution of 4,5 polyvinyl alcohol 22.0 water
23.5 (Components of dispersion B) Calibration part) Bisphenol A
16.6 hydroxyethyl cellulose 2,3 distearyl thiodipropionate 9, O water
22.1 Next, the above heat-sensitive color forming layer forming liquid was applied onto the surface of high-quality paper (basis weight 50 g/m) using a wire bar so that the dry adhesion amount was 5.2 g/tri', and dried. A heat-sensitive recording material of the invention was obtained.

Example 2 The following components were mixed in a ball mill for 10 hours to prepare dispersion C and dispersion liquid, and then equal amounts of both dispersions were mixed to prepare a thermosensitive coloring layer forming liquid.

(Components of dispersion liquid C) Mourning sound D)3
-Pyrrolidino-6-methyl-7-4,7anilinofluoran polyvinyl alcohol 10% water/ll!2
3.0 water 2
2, 3 (component of dispersion liquid) Mourning sound.

Bisphenol A 17.8 Oxidized starch 2,5 Dilauryl thiodipropionate 7, O Water 22,7
Next, the above heat-sensitive color forming layer forming liquid was applied using a wire bar.
The amount of adhesion on the surface of high-quality paper (basis weight 5o9/m) when dry is s
The heat-sensitive recording material of the present invention was obtained by coating and drying to give a weight of 5 g and 7 m.

Comparative Example A comparative heat-sensitive recording material was obtained in the same manner as in Example 1, except that distearyl thiodipropionate in dispersion B was not used.

When the heat-sensitive recording materials of the present invention and comparative heat-sensitive recording materials obtained as described above were printed and recorded using a thermal printer with a built-in thermal head, in the case of the heat-sensitive recording materials of the present invention obtained in Example 1 and Example 2, 90℃ and 135℃ respectively
Clear blue and black images were obtained at a heating temperature of .degree. C., and phenomena such as adhesion of residue, sticking, and tailing were hardly observed, and the running properties of the thermal head were extremely good.

On the other hand, in the case of Comparative Example, phenomena such as adhesion of residue, sticking, and trailing occurred when the heat-sensitive recording material of Example 1 was heated to 90° C., and only an unclear image with low density was obtained.

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording material having a heat-sensitive color-forming layer containing a colorless or light-colored leuco dye and an acidic substance that causes the leuco dye to develop color when heated, in which the heat-sensitive color-forming layer contains the general formula %. % (where R, R2 is a substituted or unsubstituted alkyl group having 10 or more carbon atoms, an aralkyl group, or -R3COOR4
group, -R6COOR6 group, R3°R6 represents an alkylene group, R4 and R6 represent a substituted or unsubstituted alkyl group having 10 or more carbon atoms, or an aralkyl group. X represents a sulfur atom or a divalent bonding group selected from -5-8- groups. ) A heat-sensitive recording material characterized by adding a compound represented by: