DE4013057C2 - - Google Patents

Description

The invention relates to a heat-sensitive Recording paper, which in terms of Heat reaction ability is excellent, which is a high Sensitivity, and in which a mist at high Temperatures are essentially not caused.

Generally include heat-sensitive Recording papers a carrier on which a heat-sensitive recording layer is provided, the an electron donating, colorless or weak colored dye precursor, an electron pulling Color developer and, if necessary, a sensitizer includes. When heating the heat-sensitive Recording paper by a thermal head, a Thermostift or a laser beam react the dye precursor and the color developer immediately with each other while preserving the recorded images.

Such heat-sensitive recording papers are in JP-AS 43-4160, 45-14 039 known.

When using such heat-sensitive Recording papers can record with the help of a be obtained comparatively simple device whereby the maintenance of the plant is easy, and this plant runs quietly. Therefore, such heat-sensitive Recording papers in a wide range of areas, such as B. Meßaufzeichner, facsimile equipment, printers,  Computer terminals, labeling machines, automatic Ticket vending machines, used. In particular, the Demand for heat-sensitive recording papers increased significantly in the field of facsimile equipment.

In the field of facsimile equipment was the improvement the sensitivity of the heat-sensitive Recording papers, that is, the ability to Recording image with a sufficient optical density to obtain when the low-energy pressure (the means a small amount of heat) is carried out, urgently required to meet the need for a high Print speed and a reduction of Energy required to comply with the energy required to make the plant small in size.

In general, the sensitivity of the to improve heat-sensitive recording papers, an intermediate layer between the carrier and the heat-sensitive recording layer laid, or it becomes, as shown in JP-PS 52-1 40 483, a Developer or dye precursor with a low Melting point used. In addition, as it is in the JP-OS No. 53-39 139 and No. 54-1 39 740, a so-called sensitizer, which has a strong affinity for the dye precursor and the developer and has a sharp melting point at 80 to 140 ° C and in terms of its Heat activity is excellent, used.

If such a developer with a low melting point or such a sensitizer will be used then the sensitivity improved considerably. But when  the heat-sensitive recording papers of a high Temperature will be exposed, then will be a strong fog caused.

Recently, heat-sensitive recording systems used on a wider scale. For example These systems are also used in facsimile systems that are in Automobiles and in automatic vending machines that are installed outdoors. The Facsimile equipment for automobiles or automatic Sales facilities also carry printing with one low energy input due to their size small to design. As a result of this, the heat-sensitive recording papers for this purpose be required to have the highest possible Have sensitivity. To this request will be a developer with a low Melting point or a sensitizer used. Because the Temperature rises slightly within these plants, cause heat-sensitive recording papers with a higher sensitivity, a stronger fog, and the recorded pictures can be in an extreme case not be read, so that the value of heat-sensitive recording papers as a commodity is greatly reduced.

In general, in thermosensitive recording materials as the dye precursor, a triarylmethane compound, a representative example of which is 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (ie, crystal violet lactone); an aromatic ether compound such as 4,4-bis-dimethylaminobenzhydrin benzyl ether; a diphenylmethane compound such as benzoylleucomethylene blue; a spiro compound such as 3-methyl spiro-dinaphthopyran; and a fluoran compound such as rhodanmin B-anilinolactam, 3- diethylamino-7-dibenzylaminofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-ethyl-tolylamino-6-methyl-7-anilinofluoran, 3-N-ethyl- N-isoamilamino-6-methyl-7-anilinofluoran. In practice, the fluoran compound is widely used.

As developers are phenols, such as p-phenylphenol (especially bisphenols, such as 2,2-bis (p-hydroxyphenyl) 4,4'-dihydroxydiphenylsulfone) and aromatic Carboxylic acid derivatives, such as benzyl p-hydroxybenzoate, far common.

The sensitizers are alkylphenols, higher Fatty acid amides, and naphthalenesulfonic acid esters containing a have sharp melting point at 80 to 140 ° C, far common.

To the sensitivity of the heat-sensitive It is appropriate to improve the recording papers Develop color at a lower temperature by adding a dye precursor or a developer with a low melting point. Currently however, low melting point dye precursors hard to use. Benzyl p-hydroxybenzoate is referred to as Developers with a low melting point practically used, as it has a good heat response.

In general, the sensitivity of the to improve heat-sensitive recording papers,  widespread an intermediate layer that exists between the Carrier and the heat-sensitive recording layer is placed, or used a sensitizer.

EP 03 06 916 A2 discloses heat-sensitive recording materials which comprise a heat-sensitive recording layer ( 1 ) comprising a dye precursor ( 2 ), a developer ( 3 ), a sensitizer ( 4 ) and a binder. As an essential developer there is called bis (3-allyl-4-hydroxyphenyl) sulfone, a benzyl ester of oxalic acid and optionally also the di-p-chlorobenzyl ester of oxalic acid.

The object of the invention is a heat-sensitive Recording paper to provide that a has excellent heat activity, a high Having sensitivity, and wherein one Receives a recording image with a high optical density, and essentially no at high temperatures Mists is caused.

This task is performed by a heat sensitive Recording paper according to claim 1.  

The heat-sensitive recording paper of the present invention Invention comprises a carrier and a heat-sensitive Recording layer. Preferably, one is Interlayer between the carrier and the heat-sensitive recording layer attached.

The heat-sensitive layer comprises a Dye precursor, a developer, a sensitizer and a binder.

In the present invention, the proportions of Dye precursor, developer and Sensitizer not critical, but they are preferably at 1: 0.5: 0.2 to 1: 5: 10 with respect to Mass.

The heat-sensitive recording paper of the present invention Invention can be obtained as follows.

The dye precursor and the developer are separated added to water with a dispersant made up of a water-soluble polymer or a surfactant composition. Every one of them Mixtures prepared in a device, such as pulverized by a ball mill or a sand mill. At this time, the sensitizer may be together with pulverized the dye precursor or the developer  or he can be powdered separately from these become.

To the obtained dispersion, if necessary, a pigment such as kaolin, calcium carbonate; on Wax, such as paraffin wax, microcrystalline wax, Polyethylene wax, higher fatty acid amide; a multi-valued Metal salt of a higher fatty acid such as zinc stearate and other additives are added. It will continue to a water-soluble binder, such as polyvinyl alcohol, Hydroxyethyl cellulose, hydroxypropyl cellulose, Ethylene maleic anhydride copolymer, Styrene-maleic anhydride copolymer, Isobutylene-maleic anhydride copolymer, polyacrylic acid, Starch derivatives, casein and gelatin, added to obtain a coating composition.

In addition, to improve the water resistance a water resistance improving agent (for example a gelling agent, a crosslinking agent) Styrene-butadiene latex, an acrylic resin emulsion to which Coating composition can be added.

To prevent sticking to the thermal head, it is preferred that an intermediate layer, the one oil absorptive pigment.

As a carrier paper is generally used. however can also use different types of non-woven fabrics, Plastic films, synthetic papers, metal foils or a combination of these are used.  

A coating device, such as a Doctor blade coater, an air knife coater, one Roll painting, a bar coater or a Paint casting machine, can be used to the Intermediate layer and the heat-sensitive Form recording layer. Furthermore, a Device like a machine calender, a supercalender, or a gloss calender can be used, around the surface flatness of the heat-sensitive To improve recording paper. This remains find that a protective layer that is in the essentially from a water-soluble polymer composed, on the heat-sensitive Recording layer can be formed by a through to prevent a solvent-related color development.

The present invention will be described in the examples described. Parts and percent mean parts by weight or percent by weight.

example 1 Preparation of the solution A

A mixture of the following components became one average grain size of 2 microns in one Sand grinder pulverized.

3-dibutyl-amino-6-methyl-7-anilinofluoran: 10 parts 10% aqueous PVA solution 10 parts water 30 parts

Preparation of solution B

A mixture of the following components was added to a average grain size of 2 μm in one Sand grinder pulverized:

2,2-bis (4-hydroxyphenyl) propane 10 parts 10% aqueous PVA solution 10 parts water 30 parts

Preparation of the solution C

It was a mixture of the following components an average grain size of 2 μm in one Sand grinder pulverized.

Di-p-chlorobenzyl ester of oxalic acid 10 parts 10% aqueous PVA solution 10 parts water 30 parts

15 parts of the solution A thus obtained, 20 parts of the like solution B obtained, 25 parts of the solution C thus obtained, 20 parts of a 20% aqueous PVA solution and 10 parts of calcium carbonate were added to 45 parts water added and under training a Coating composition stirred.

The coating composition thus obtained was applied to a wood-free paper having a basis weight of 50 g / m ² so that 4.8 g of the solid portion thereof was coated per m ² , dried at 50 to 60 ° C, and then the coated side thereof became one Furnace treatment, achieving a Beck smoothness of 400 to 500 s.

Example 2

It became a mixture of the following components stirred sufficiently to obtain a dispersion.

calcined kaolin 100 parts Natriumhexa metaphosphate 0.5 parts water 150 parts

100 parts by weight of a 15% polyvinyl alcohol solution was added to the dispersion thus obtained to obtain an intermediate layer coating composition. The coating composition thus obtained was applied to a wood-free paper having a basis weight of 50 g / m ² so that 6 g of solid portion per m ^{2 was} thereon. The same heat-sensitive recording layer formed in Example 1 was applied to the obtained intermediate layer, and the surface treatment thereof was carried out in the same manner as in Example 1 to obtain a heat-sensitive recording paper.

Comparative Example 1

It became the same procedure as in Example 1 carried out, with the exception that p-benzylbiphenyl instead of the di-p-chlorobenzyl ester of oxalic acid, which in the solution C of Example 1 was used has been.

Comparative Example 2

It became the same procedure as in Example 1  repeated, except that ethylenebisstearic acid amide instead of the di-p-chlorobenzylesters of oxalic acid, which in the solution C of Example 1 was used has been.

Comparative Example 3

It became the same procedure as in Example 1 repeated, except that 3-N-ethyl-N-isoamylamino-6-methyl-7-anilinofluoran instead of 3-dibutylamino-6-methyl-7-anilinofluoran, the in solution A of Example 1 was used, was used.

Comparative Example 4

It became the same procedure as in Example 1 repeated, except that 3-diethylamino-6-methyl-7-anilinofluoran instead of 3-dibutylamino-6-methyl-7-anilinofluoran, described in the Solution A of Example 1 was used.

Comparative Example 5

It became the same procedure as in Example 1 repeated, except that 4,4'-dihydroxydiphenylsulfone instead of 2,2-bis (4-hydroxyphenyl) propane, which in solution B of the Example 1 was used was used.

Comparative Example 6

It became the same procedure as in Example 1 repeated, except that the benzyl ester of the  p-hydroxybenzoic acid instead of 2,2-bis (4-hydroxyphenyl) propane, which in solution B of the Example 1 was used was used.

Table 1 shows the results of the test, in terms of the sensitivity of the thus formed heat-sensitive recording papers and in terms performed at high temperature mist has been.

Table 1

As shown in Table 1, the effect of Comparative examples, the higher sensitivity exhibit, a strong mists at high temperature, and Comparative Examples, the low fogging at high Temperatures are in terms of the Sensitivity weak, whereas the Examples 1 and 2, which  3-dibutylamino-6-methyl-7-anilinofluoran, 2,2-bis (4-hydroxyphenyl) propane and di-p-chlorobenzyl ester of oxalic acid, in terms of heat reactivity are excellent and have a high sensitivity and a little misting at high temperatures cause. In particular, Example 2, which is the Interlayer, between the carrier and the heat-sensitive recording layer is provided in terms of sensitivity in particular prefers.

Claims (4)

A heat-sensitive recording paper comprising a support and a heat-sensitive recording layer provided on at least one side of the support, wherein the heat-sensitive recording layer ( 1 ) is a dye precursor which is colorless or slightly colored in the normal state, ( 2 ) a developer compatible with the Dye precursor when heated to color, ( 3 ) a sensitizer, and ( 4 ) a binder, characterized in that the dye precursor is 3-dibutylamino-6-methyl-7-anilinofluoran, the developer is 2,2-bis (4) Hydroxyphenyl) propane and the sensitizer is di-p-chlorobenzyl ester of oxalic acid. 2. A heat-sensitive recording paper according to claim 1, characterized in that an intermediate layer which is an oil-absorbing pigment comprises, between the carrier and the heat-sensitive Recording layer is provided. 3. A heat-sensitive recording paper according to claim 1, characterized in that the carrier paper, a non-woven fabric, a Plastic film, synthetic paper, a metal foil or a combination of them. 4. A heat-sensitive recording paper according to claim 1, characterized in that the binder is polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, Ethylene maleic anhydride copolymer, Styrene-maleic anhydride copolymer, Isobutylene-maleic anhydride copolymer, Polyacrylic acid, a starch derivative, casein or Gelatin is.