JPH035190A - Thermal recording paper - Google Patents

Abstract

PURPOSE:To obtain thermal recording paper having excellent thermal response, high sensitivity and superior texture fog at a high temperature by containing a specific dye precursor, a developer and a sensitizer. CONSTITUTION:3-dibutylamino-6-methyl-7-anilinofluorene is contained as a dye precursour, 2,2-bis(4-hydroxyphenyl) propane as a developer and oxalic acid-di-p- chlorobenzyl ester as a sensitizer. The dye precursour and the developer are pulverized and dispersed together with a water-soluble high-molecular agent or a surface-active agent and the sensitizer together with either one of them or separately through a means such as a ball mill, a sand mill, etc. respectively. The dispersion is mixed properly, a pigment such as kaolin, calcium carbonate, etc., waxes such as paraffine wax, higher fatty acid amide, etc., higher fatty acid polyvalent metallic salt such as zinc stearate and other additives are added as required, and the whole is dispersed into water-soluble adhesives such as polyvinyl alcohol and applied. It is favorable that the intermediate layer of an oil absorptive pigment, etc. is formed with the object of the prevention, etc. of the adhesion of work-up onto a thermal head.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a thermal recording paper that has excellent thermal response, high sensitivity, and excellent background fogging at high temperatures.

(B) Prior art thermal recording paper generally consists of an electron-donating, usually colorless or light-colored dye precursor, an electron-accepting color developer, and, if necessary, a sensitizer, on a support. It is equipped with a heat-sensitive recording layer, and when heated with a thermal head, thermal pen, laser beam, etc., the dye precursor and color developer react instantly and a recorded image is obtained. ,6
No. 0, Japanese Patent Publication No. 4.5-14.039, etc.

Such thermal recording paper has the advantages of being able to record with a relatively simple device, being easy to maintain, and not generating noise, and is suitable for measurement recorders, facsimiles, printers,
It is widely used in computer terminals, automatic ticket vending machines for label tickets, etc. Particularly in the field of facsimile, demand for thermal recording methods has increased by 11 times.

In order to increase the printing speed and reduce the size of the device by reducing the applied energy, it has become essential to increase the sensitivity of thermal recording paper (color development at low temperature and low energy).

In order to achieve high sensitivity, generally an intermediate layer is provided between the support and the heat-sensitive layer, or a developer or dye precursor with a low melting point is used (Japanese Patent Publication No. 52-1./1.0483 ). Or has a strong affinity with the dye precursor and color developer, and has a melting point of 80 to J40.
A substance with a sharp melting point of 'C and a good thermal response, a so-called sensitizer, is used (Japanese Patent Application Laid-Open No. 53-391
-39, special 1) N. 1974, 3974.0).

The use of a color developer or sensitizer with a low melting point is effective in increasing sensitivity, but it also worsens background fogging at high temperatures. In recent years, the range of use of thermal recording has expanded, and it has begun to be used in fields with harsh environmental conditions, such as in-vehicle fax machines and vending machines, especially in places that are prone to high temperatures such as outdoors and inside cars. At present, it is not possible to be satisfied with products that provide excellent background fogging.

For recording materials that develop color when heated, dye precursors generally include 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (crystal violet lactone). lylmethane compounds, diphenylmethane compounds such as 4,4 bis-dimedylaminobenzhydrin benzyl ether, diphenylmethane compounds such as benzoylleucomethylene blue, spiro compounds such as 3-methyl-spiro-dinaphthopyran, and O-rhodamine B-ani linolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-
diethylamino-6-methyl 7-anilinofluorane,
3-ethyl-tolylamino-6-methyl-7-anilinofluorane, 3-N ethyl-Nisoamylamino-6-
Fluoran compounds such as methyl 7-anilinofluorane are known, and in reality, fluoran compounds are often used.

In addition, as a color developer, phenols such as p-phenylphenol, particularly bisphenols such as 2,2-bis(+)-hydroxyphenyl)propane, 4,4'-dihydroxydiphenylsulfone, and I]-hydroxy Aromatic carboxylic acid derivatives represented by benzyl benzoate are well known and often practically used.

As the sensitizer, alkyl biphenyls, higher fatty acid amides, naphthalene sulfonic acid esters, etc., which have a sharp melting point of 80 to 40°C, are widely used.

To increase the sensitivity of thermal recording paper, it is conceivable to use dye precursors and color developers with low melting points to develop color at lower temperatures, but in reality, dye precursors are rarely used, and color developers are Among the agents, benzyl p-hydroxybenzoate has good thermal responsiveness and has been put into practical use.

Generally, the sensitivity of heat-sensitive recording paper is increased by providing an intermediate layer between the support and the heat-sensitive layer or by using a sensitizer in combination.

(C) Problems to be Solved by the Invention An object of the present invention is to obtain a thermal paper that has excellent thermal responsiveness, high sensitivity, high color density, and less background fogging at high temperatures.

(D) Means for Solving the Problems In order to improve the above-mentioned drawbacks, the inventor of the present invention, as a result of intensive research, discovered that 3-dibutylamino-6-methyl-7-anilinofluorane was used as a dye precursor. By containing 2,2-bis(4-hydroxyphenyl)propane as a coloring agent and di-p-chlorobenzyl oxalate as a sensitizer, it has excellent thermal response and high sensitivity, and it is also sensitive to skin at high temperatures. It was possible to obtain thermal recording paper with excellent bending properties.

Even more preferred were those in which an intermediate layer was provided between the support and the heat-sensitive layer.

For automobile fax machines, vending machines, etc., thermal recording paper is required to have as high sensitivity as possible due to the miniaturization of equipment and the reduction in applied energy, and it is necessary to use low melting point color developers and sensitizers to achieve high sensitivity. Aim for sensitization.

On the other hand, these machines have severe environmental conditions, especially in the equipment, which tends to reach high temperatures, and deviations in high sensitivity can cause fogging of the thermal recording paper, which can significantly reduce the value of the product and cause damage to people. At times it becomes illegible.

As a result of various tests, the present inventor discovered that a specific tooth piece 51 precursor, a color developer and a sensitizer, that is, 3-dibutylamino-6-methyl-7-anilinofluorane and a developer as a dye precursor, By containing 2,2-his(4-hydroxyphenyl)propane as a colorant and oxalic acid di-I]-chlorobenzyl ester as a sensitizer, it has good thermal response and high sensitivity. It has also been discovered that a thermal recording paper with excellent background fogging at high temperatures can be obtained. Particularly preferred were those in which an intermediate layer was provided between the support and the heat-sensitive layer.

The ratio of the dye precursor to the developer and the sensitizer in the present invention is not particularly limited, and the weight ratio is from 10.50.2 to
1510 is preferred.

The method for producing the thermal recording paper of the present invention will be described.

The dye precursor and the color developer are separately pulverized and dispersed together with a water-soluble polymer agent or a surfactant using a ball mill, a sand mill, etc., and the sensitizer is pulverized and dispersed either one of them or separately.

This dispersion is mixed appropriately, and if necessary, pigments such as kaolin and charcoal, waxes such as paraffin wax, microcrystalline wax, polyethylene wax, and higher fatty acid amides, and higher fatty acid polyvalent metal salts such as zinc stearate, In addition to other additives, polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, ethylene-maleic anhydride copolymer,
Disperse and apply in a water-soluble adhesive such as styrene-maleic anhydride copolymer, isobutylene maleic anhydride copolymer, polyacrylic acid, starch derivative, casein, gelatin, etc.

Further, for the purpose of imparting water resistance to the binder, a water resistance agent (gelling agent, crosslinking agent), styrene butadiene latex, acrylic resin emulsion, etc. may be added.

Further, it is preferable to provide an intermediate layer such as an oil-absorbing pigment for the purpose of preventing residue from adhering to the thermal head.

Paper is generally used as the support, but various nonwoven fabrics, plastic films, synthetic papers, metal foils, etc., or composite sheets made of a combination of these may also be used as desired.

As the apparatus used for coating the intermediate layer and the heat-sensitive layer, a coater head such as a blade coater, air knife coater, roll coater, rod coater, curtain coater, etc. can be used. Furthermore, in order to improve the surface smoothness of the coated product, machine calender, super calender,
Equipment such as gloss calenders and brush brushing can be used. Incidentally, in order to prevent color development due to solvents or the like, a protective layer mainly composed of a water-soluble polymer or the like may be provided on the heat-sensitive layer.

(E) Examples Next, the present invention will be explained in more detail with reference to Examples. Note that all parts and percentages shown below are based on weight.

Example 1 ■ Preparation of liquid A 3-dibutylamino-6-medyru 7 Anilinofluorane 10 parts 10% polyvinyl alcohol aqueous solution 1-0 parts water
30 parts of this composition was ground with a sand grinder to an average particle size of 2 μm.

■Preparation of liquid B 2.2-bis(4-hydroxyphenyl)propane
10 parts 10% polyvinyl alcohol aqueous solution 1-0 parts water
30 parts of this composition was ground to a particle size of 2 μm using a sand grinder.

■Preparation of Solution C 10 parts of oxalic acid di-p-chlorobenzyl ester 10% polyvinyl alcohol aqueous solution 10 parts of water
30 parts of this composition was ground to an average particle size of 2 .mu.m using a sand cleaner.

15 parts of Δ liquid, 20 parts of liquid ■3, 25 parts of liquid C, and 10% O.
20 parts of polyvinyl alcohol aqueous solution and 1 part of calcium carbonate
0 parts and 45 parts of water were mixed and stirred to prepare a coating liquid.

The obtained coating liquid was applied to double-quality paper with a basis weight of 50 g/nf.
Apply so that the solid content amount is 4.8 g/i, 5
After drying at 0 to 60℃, Beck smoothness of heat-sensitive coating surface is 40.
A heat-sensitive recording paper was obtained by surface treatment so that the temperature was 0 to 500 seconds.

Example 2 As the intermediate layer, Ansilex (manufactured by Engelhard, calcined kaolin)
100 Sodium hexametaphosphate 0.5 water
Thoroughly stir and disperse 150, add 00 parts by weight of 15% polyvinyl alcohol solution, and coat this solution with an air knife coater to a basis weight of 50.
g/Id high quality paper so that the solid content was 6 g/rd, the heat-sensitive layer of Example 1 was applied thereon, and the same procedure was carried out thereafter.

Comparative Example The same procedure as in Example 1 was carried out except that oxalic acid di-p-chlorobenzyl ester in Solution C of Example 1 was changed to I]-benzylbiphenyl.

Comparative Example 2 The same procedure as in Example 1 was carried out except that oxalic acid di-p-chlorobenzyl ester in Solution C of Example 1 was changed to ethylene bisstearamide.

Comparative Example 3 3-dibutylamino-6-Mediru 7 of Solution A of Example 1
The same procedure as in Example 1 was carried out except that -anilinofluorane was changed to 3-N-ethyl or N-isoamylamino-6-methyl-7-anilinofluorane.

Comparative example 4 3-dibutylamino-6-methyl-7 of solution A of Example 1
The same procedure as in Example 1 was carried out except that -anilinofluorane was changed to 3-diethylamino-6-methyl-7-anilinofluorane.

Comparative Example 5 The same procedure as in Example 1 was carried out except that 2,2-bis(4-hydroxyphenyl)propane in Solution B of Example 1 was changed to 4,4'-dihydroxydiphenylsulfone.

Comparative Example 6 The same procedure as in Example 1 was carried out except that 2,2-his(4-hydroxyphenyl)propane in Solution B of Example 1 was changed to p-hydroxybenzoic acid benzyl ester.

The prepared thermal recording paper was tested for sensitivity and background fog at high temperatures, and the results are shown in Table 1.

(Left below) Table 1 *Sensitivity is based on Oshoku Denki thermal printing device (TH-PMD)
Kyocera thin film thermal head (KST-8MGD,)
], pulse IIIQ with Oms period, 3m
This value is the density measured by a Macbeth densitometer when printing with +, and there is a correlation with actual facsimile machines.

**The background fogging at high temperatures is based on the Macbeth concentration, which was previously measured as the density of the background fogging at 85°C using a stamp coloring device with a pressure of 200 g/cn and a pressure contact time of 5 seconds. There is a correlation with this, and the higher the number, the greater the background fogging. ○ indicates that there is no practical problem, and × indicates an unusable level.

(f?) Effects of the invention As is clear from the results in Table 1, the conventional products with high sensitivity have poor skin fogging at high temperatures, and the products with good skin fogging at high temperatures have poor sensitivity. 3-dibdelamino-6-methyl-7-anilinofluorane and 2,2-
Thermal recording paper containing bis(4-hydroxyphenyl)propane and oxalic acid-di-■)-chlorobenzyl ester had good thermal response, high sensitivity, and little background fogging at high temperatures. . Those in which an intermediate layer was provided between the support and the heat-sensitive layer were more preferable in terms of sensitivity.

Procedural amendment written spontaneously) March 28, 1990 1 - Display of the case 1999 Patent Application No. 1-40555 2, Name of the invention Thermal recording paper 3, Person making the amendment Relationship with the case Patent applicant address Tokyo 4-2 Marunouchi Otsu-chome, Chiyoda-ku, Tokyo Name <598) Mitsubishi Paper Mills Co., Ltd. Contact information: 4-1 Higashiganemachi-chome, N-Shikaku-ku, Tokyo Patent Department, Gobishi Paper Mills Co., Ltd. 125 ff103 (600) 2481-5 7 ) Specification, 3M, line 9 "3). Or" [r3), or blade 2) Akira Haru, page 8, line 1 "One hand and J r one hand and again" 3) Mei S, page 9, 11 Line “Flushing J r Brushing” 4) Specification, page 11, line 18 “1.0 parts by weight” r100 parts by weight J

Claims (1)

[Claims] 1. A thermosensitive recording paper containing a color developer that reacts with a normally colorless or light-colored dye precursor under heat to cause the dye precursor to develop a color, in which 3-dibutylamino-6 is used as the dye precursor. −
Methyl-7-anilinofluorane and as a color developer, 2,
A heat-sensitive recording paper comprising a heat-sensitive layer containing 2-bis(4-hydroxyphenyl)propane and di-p-chlorobenzyl oxalate as a sensitizer on a support. 2. 3-dibutylamino-6-methyl-7-anilinofluorane as a dye precursor and 2,2- as a color developer.
Claim 1: The heat-sensitive layer containing bis(4-hydroxyphenyl)propane and di-p-chlorobenzyl oxalate as a sensitizer is formed with an intermediate layer containing an oil-absorbing pigment interposed between the support and the heat-sensitive layer. Thermal recording paper described.