JPH01150576A - heat sensitive recording sheet - Google Patents

Abstract

PURPOSE:To enhance preservability and heat response, by using a compound selected from 3-dibutylamino-6-methyl-7-anilino fluorane and 3-dibutylamino-7- orthochloroanilinofluorane as a leuco dye, bis-(3-allyl-4-hydroxyphenyl) sulfone as a coupler and dibenzyl oxalate as a sensitizer. CONSTITUTION:A thermal recording layer containing a colorless or light-colored leuco dye, a coupler reacting with the leuco dye at the time of heating to form a color and a sensitizer is provided to a thermal recording sheet and a protective layer composed of a high molecular compound is provided on the thermal recording layer. As the leuco dye, one of 3-dibutylamino-6-methyl-7- anilinofluorane and 3-dibutylamino-7-orthochloroanilinofluorane and, as the coupler, bis-(3-allyl-4-hydroxylphenyl) sulfone is used and, as the sensitizer, dibenzyl oxalate is used. By this method, the thermal recording sheet excellent in thermal response, kept white without developing the color of a background part even during high temp. preservation and excellent in the preservability of a color forming part is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Application Field The present invention relates to a heat-sensitive recording sheet whose main components include a leuco dye and a color developer that develops color when the leuco dye is heated, and is particularly suitable for adhesive labels. The present invention relates to a heat-sensitive recording sheet that enables high-speed printing and prevents deterioration of blank areas and colored areas.

CB) Prior art and its problems Hitherto, heat-sensitive recording paper has been known which comprises a light-colored or colorless leuco dye on the surface of a sheet-like support and a color developer that develops color from the leuco dye by heating. This thermal recording paper is also used for applications such as adhesive labels. Such thermal recording paper for adhesive labels is usually printed using a thermal head.

This printing method has the advantage that it is more compact and can print more beautifully than conventional ink printing methods.

However, the recording layer of such thermal recording paper contains dioctyl adipate (DOA) and dioctyl phthalate (DOP).
) When a plastic film containing a plasticizer such as the above comes into contact with a plastic film, a problem arises in that the printed area (image area) becomes discolored.

That is, when selling fresh foods in supermarkets, meat, fish, vegetables, and side dishes are placed in plastic trays such as polystyrene sheets, and then a stretch film such as soft polyvinyl chloride is applied to the wrapper. It is common to affix an adhesive label printed on the surface using a measuring printer. If you use conventional heat-sensitive recording paper for adhesive labels when packaging and stacking products for display, when the adhesive label and wrap film come into close contact, the plasticizer in the wrap film will spread onto the surface of the adhesive label. It penetrates into the heat-sensitive coloring layer and over time the printed area (image area) disappears, creating a major hindrance to product sales.

In order to prevent the printed area (image area) from being discolored by this plasticizer, a coloring agent consisting of a leuco dye is placed on the support, and a color developer that develops color when the leuco dye is heated, such as an organic acid or a phenolic compound. It is known to provide a thermosensitive coloring layer containing a color developer and a water-soluble polymer layer as a protective layer on the thermosensitive coloring layer.

However, in the case of such a heat-sensitive recording material, although the storage stability against plasticizers is improved, the formation of a protective layer causes a drawback of poor thermal response.

Recent printing machines are becoming faster and more energy efficient, and along with this, there is a strong demand for improving the thermal responsiveness of thermal recording paper. The development of a heat-sensitive recording sheet that prevents deterioration of the coloring part has become an urgent issue.

(C) Purpose of the Invention The inventor of the present invention has arrived at the present invention as a result of extensive research into a thermosensitive recording sheet that has improved storage stability against plasticizers and the like and improved thermal responsiveness.

(D) Structure of the Invention In other words, the present invention provides a heat-sensitive recording layer containing a colorless or light-colored leuco dye, a color developer and a sensitizer that react with the leuco dye upon heating, and a sensitizer. In a heat-sensitive recording sheet in which a protective layer of a polymer compound is provided on the recording layer, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-7-oline chloroaniline is used as the leuco dye. One type of linofluorane is used as a color developer, and bis-(3-allyl-
An object of the present invention is to provide a heat-sensitive recording sheet according to the claims, characterized in that 4-hydroxyphenyl)sulfone and dibenzyl chelate are used as a sensitizer.

Due to the above configuration, the speed of the printing machine increases, although the cause is unknown.
It has excellent thermal responsiveness that can be used for power saving, and can withstand high temperatures (7
We were able to develop a heat-sensitive recording sheet that does not develop color in the background area and remains white even when stored at 0°C), and has excellent storage stability in the colored area against plasticizers and the like.

If the above configuration was changed even in one place, any one of the three characteristics of thermal response, whiteness of the background part during high temperature storage, and preservation of the colored part would deteriorate, making it impossible to put it into practical use.

The main components used in the present invention will be explained in detail below, but the present invention is not limited thereto unless it exceeds the gist of the present invention.

Examples of binders include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, water-soluble binders such as styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, and styrene. -Butadiene copolymer, acrylonitrile-butadiene copolymer, methyl acrylate-
Examples include latex-based water-insoluble binders such as butadiene copolymers.

Examples of pigments include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin, and the like.

In addition, higher fatty acid metal salts such as zinc stearate and calcium stearate, paraffin, oxidized paraffin,
Waxes such as polyethylene, polyethylene oxide, stearamide, castor wax, dispersants such as sodium dioctyl sulfosuccinate, ultraviolet absorbers such as benzophenone and penzotriazole, surfactants, fluorescent dyes, etc. can be used.

Paper is mainly used as the support for the heat-sensitive recording material according to the present invention, but any type of nonwoven fabric, plastic film, synthetic paper, metal foil, etc., or a composite sheet made of a combination of these can also be used.

An undercoat layer may be provided between the heat-sensitive color forming layer and the support depending on safety.

Generally, a water-soluble polymer compound is good for the protective layer, and a polymer compound selected from among alginates, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol can be used alone or in combination of two or more types. good.

In addition, efforts are being made to introduce film-forming polymer emulsions such as acrylic latex, vinyl acrylic resin, vinyl acetate/ethylene copolymer, silicone/acrylate resin, and styrene/butadiene latex.
It is proving effective.

Furthermore, it is preferable to use one or more of a water resistance agent, an ultraviolet absorber, and a mold release agent in combination to impart water resistance and light resistance and to prevent film peeling (blocking) due to adhesion.

On the other hand, an adhesive is provided on the back side of the support by a conventional method so that it can be applied to a solid surface such as a cling film or wrapping paper, and a release mount is applied to the surface. Furthermore, a barrier layer can be provided between the adhesive layer and the support to prevent penetration of plasticizers and the like.

(B) Example 1 Liquids A and B were prepared by pulverizing and dispersing mixtures of the following compositions using a ball mill so that the average particle size was 1 to 3 μm.

(Parts by weight) Part A 3-dibutylamino-6-methyl-7-anilinofluorane 110% polyvinyl alcohol 1.5 water
2.5B liquid bis-(3-allyl-4-hydroxyphenyl) sulfone
2 Dibenzyl sieuate 2 Calcium carbonate 3 10 Tivolivinyl alcohol 10.5 Water
17.5A liquid and B'W
Mix L to make a coating liquid for the heat-sensitive coloring layer, and coat it on high-quality paper (tsubo i
50t/rr? ) on one side, dry, coating amount 5 f/r? A heat-sensitive coloring layer was formed, and calendering was performed so that the Bekk smoothness was 100 seconds or more to prepare a heat-sensitive recording paper.

C? Night 10% polyvinyl alcohol 1020% acrylic resin 5 30% zinc stearate 2 Coat the adhesive layer forming liquid Ci on the heat-sensitive coloring layer of the heat-sensitive recording paper and dry it to a coating amount of 3 f/rr? A protective layer is formed, and calendering is performed so that the Bekk smoothness is 300 seconds or more.Furthermore, on the back side of this heat-sensitive recording paper, a silicone resin coating amount of 20 f/rr? A heat-sensitive adhesive label was obtained by pasting together an acrylic adhesive layer with the adhesive layer interposed therebetween, and then cutting it out to an appropriate size.

Example 2 Dye 3-dibutylamino-6-methyl-7- of Example 1
3-dibutylamide/-7 instead of anilinofluorane
A heat-sensitive adhesive label was obtained in the same manner as in Example 1 except that -orun chloraninunofluorane was used.

Comparative Example 1 Dye 3-dibutylamino-6-methyl-7- of Example 1
3-(N-methyl-N-
A heat-sensitive adhesive label was obtained in the same manner as in Example 1 except that cyclohexylamino)-6-, >1 thyl-7-anilinofluorane was used.

Comparative Example 2 The dye 3-dibutylamino-6-methyl-7-
3-diethylamino-6 instead of anilinofluorane
A heat-sensitive adhesive label was obtained in the same manner as in Example 1 except that -methyl-7-anilinofluorane was used.

Comparative Example 3 The dye 3-dibutylamino-6-methyl-7-
3-(N-ethyl-N-
A heat-sensitive adhesive label was obtained in the same manner as in Example 1 except that iso-pentyl)amino-6-methyl-7-anilinofluorane was used.

Comparative Example 4 A heat-sensitive adhesive label was obtained in the same manner as in Example 1, except that bisphenol A' was used instead of the color developer bis-(3-allyl-4-hydroxyphenyl)sulfone.

Comparative Example 5 A heat-sensitive adhesive label was obtained in the same manner as in Example 2, except that bisphenol A was used instead of the color developer bis-(3-allyl-4-hydroxyphenyl)sulfone.

Comparative Example 6 In the same manner as in Example 1 except that stearamide was used instead of the sensitizer dibenzyl oxalate in Example 1,
A heat-sensitive adhesive label was obtained.

Comparative Example 7 In the same manner as in Example 1, except that stearamide was used in place of the sensitizer dibenzyl oxalate in Example 2,
A heat-sensitive adhesive label was obtained.

Thermal response, background fog, and plasticizer resistance tests were conducted using the nine types of heat-sensitive adhesive labels obtained as described above.

(1) Thermal responsive printing device TH-PMD (Daikane Denki■'!A)'(i-
Printing was carried out by changing the applied energy using the printer, and the color density was measured using a Macbeth densitometer RD-514.

The higher the value, the better.

(2) Skin fog After standing at 70°C for 24 hours, the skin density was measured. The lower the value, the better.

(3) Plasticizer-resistant digital scale D-805P (manufactured by Ishida Koki Seisakusho)
After printing using polyvinyl chloride wrap and leaving under pressure at 40°C for 24 hours, the density was measured and calculated using the formula %. The higher the value, the better.

Table 1 1) Applied energy unit mj/dot (F) Effect of the invention As is clear from Table 1, the heat-sensitive adhesive label of the present invention has improved thermal response, less background fog, and improved plasticizer resistance of the image. It was excellent.

Claims (1)

[Claims] A heat-sensitive recording layer containing a colorless or light-colored leuco dye and a color developer and a sensitizer that react with the leuco dye to form a color when heated is provided on the support, and a polymer compound is provided on the heat-sensitive recording layer. In a heat-sensitive recording sheet provided with a protective layer of 3-diptylamino-
One of 6-methyl-7-anilinofluorane and 3-dibutylamino-7-orthochloroanilinofluorane is used, and bis-(3-allyl-4-hydroxyphenyl) is used as a color developer. A heat-sensitive recording sheet characterized by using sulfone and dibenzyl oxalate as a sensitizer.