JPH0248986A - Thermal recording paper free of adhesion of scum to thermal head - Google Patents

Abstract

PURPOSE:To prevent adhesion of scum to a thermal head by providing a thermal recording layer comprising a colorless or light-colored color developing lactone compound and a phenol compound on a base coated with light calcium carbonate. CONSTITUTION:A thermal recording layer comprising a colorless or light-colored color developing lactone compound and a phenol compound as fundamental constituents with or without a wax is provided on a base coated with light calcium carbonate, thereby producing a thermal recording paper. The lactone compound may be, for example, crystal violet lactone or Malachite green lactone. The light calcium carbonate is precipitated calcium carbonate obtained by a chemical method, and an effective coating weight of the light calcium carbonate on a surface to be coated with a thermal recording layer coating liquid is at least 1.0g/m<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION In order to reduce gas deposits that adhere to thermal heads in thermal facsimiles, thermal printers, etc., the present invention uses a color-forming lactone compound that is usually colorless or light-colored, and a color-forming lactone compound that is heated when heated. The present invention relates to a thermal paper made of a phenolic substance that develops color, characterized in that its support is overcoated with light calci-cum carbonate, and a heat-sensitive layer is applied thereon.

The thermal paper of the present invention basically develops color by melting a lactone dye and a phenolic substance by heat applied by a thermal head, and the molten material also adheres to the thermal head. Generally, waxes described in Japanese Patent Publication No. 14531/1983 are often used for the purpose of preventing pressure coloring, fogging, and scratching. This makes it easier to adhere to the thermal head. When molten Fa becomes a gas and attaches to the thermal head, the printing quality of thermal paper decreases.
In particular, in the case of long-term printing, the printing quality deteriorates significantly, so there has been a strong desire for improvement.

It is generally known to add an inorganic or organic filler such as talc, clay, or starch to the heat-sensitive layer in order to prevent the molten material from sticking to the thermal head, but the effect was not sufficient. .

As a result of various studies, the inventors of the present invention found this! By overcoating the support with calcium carbonate and applying a heat-sensitive layer on top of it, it is surprisingly effective in protecting the thermal head from heating without deteriorating its properties as a heat-sensitive paper, such as print density. I found this to be shocking. I don't really understand the reason, but it's probably due to tll when printing with the thermal head.
It is thought that light calcium carbonate, which is an overcoat of melted lactone dyes, phenolic substances, etc. on the support, instantaneously adsorbs it due to its oil absorbing properties, thereby reducing gas adhesion to the thermal head.

Naturally, it is conceivable to incorporate these highly oil-absorbing substances into the heat-sensitive coating layer, and the present inventors have already reported in JP-A-53-105239 and JP-A-53-11805.
It is proposed in No. 9 and is effective in preventing gas adhesion, but
These highly oil-absorbing substances generally have large bulk;
It has high water absorption, so when it is added to a heat-sensitive coating liquid, it may not cause any problems due to liquid properties or other problems. Furthermore, since these substances do not directly participate in the color development of lactone dyes and phenol compounds, they tend to have an adverse effect on the color development characteristics of the lactone dyes and phenol compounds, and the present invention is an improvement on these points.

It is also possible to add internally to the support, but in order to prevent gas adhesion, it is necessary to have a certain amount or more of these scorched powders on the surface of the support that will adhere to the heat-sensitive layer, and adding a large amount internally will not be effective. However, if it is added internally in large quantities, it will impair the strength and other properties of the support, making it unsuitable. Representative examples of the colorless or light-colored color-forming lactone compounds used in the present invention are as follows, but the invention is not limited thereto.

Crystal violet lactone, Makkai 1-green lactone, 3,3-bis(paradimethylaminophenol)-4,5,6,7-titrachlorophthalide, 3-
Ethylamino-6-chlorofluoran, 3-benzylamino-6-chlorofluoran, 3-cyclohexyl 7minor 6-chlorofluoran, 3-Tylpolynow 5,6
-benzofluorane, 3-jeboulamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluoran, 3-diethylamino-6, fucymethylaminofluorane, 3-diethylamino-7,8 −
Benzofluorane, 3-di-1-thylamino-7-medoxyfluoran, 3-diethylamino-7-sibenzylaminofluorane, 3-diethyl-7-minor-7-7-nylinofluorane, 3-diethylamino-5,6-pendi-two Dibenzylaminofluorane, 3-diethylamino-6-
Methyl-7-anilinofluorane, 3-diethylamino-7-cybenzylamino 3', 4'5'6'
-Tetrachlorofluorane, 3-ethyltolylamino-
6-Methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-diethylamino-7-(N-medylinofluorane) -(3-trifluoromethylphenyl)amino)fluoran, 3-diethylamino-7-(N-3'-trifluoromethiphenyl)aminofluoran, and the phenolic compound used in the present invention liquefies at 70°C or higher. Alternatively, it is vaporized and reacts with the color-forming lactone compound to avoid color development.
-chlorowa 1nol), 4.4'-isopropylidene bis(2tar-butylphenol), 4.4'-5
ec-butylidene diphenol, 4,4'-Schiff O hexylidene diphenol, bisla 1-norsulfone, 4.
1 such as 41-thiobis(4-·tQr-pudyl~3-methylphenol), 2,2-bis-(4-hydroxyphenyl)-〇-hebutane, novolac type phenol resin, halogenated novolac type phenol resin, etc. Preferred examples include, but are not limited to, phenolic substances having two or more hydroxyl groups in the molecule.

Waxes used for the purpose of preventing pressure coloring, scratching, etc. in the heat-sensitive layer of the present invention include Japanese Patent Publication No. 50-1
Animal waxes such as shellac wax as described in 4531M, vegetable waxes such as carnauba wax, petroleum waxes such as paraffin, synthetic waxes such as polyethylene wax, and higher fatty acid amides. Alternatively, two or more of them may be used in combination as fine powder or as an emulsion.

As the adhesive used for the heat-sensitive layer of the present invention, thermofusible adhesives may stick to the thermal head and are generally difficult to use;
Water-soluble polymeric adhesives such as polymers, human O-oxyethylcellulose, casein, gelatin, and gum arabic are commonly used. In addition, talc, clay, starch granules, etc. may be added to the heat-sensitive coating liquid as a whitening agent or filler.

It can also be used as a sensitivity improver in thermal facsimiles, thermal printers, etc., as necessary to reduce power consumption and increase printing speed.
No. 0, JP-A-48-19231, Special 1m 1972-58
It is also possible to add additives such as those described in No. 842.

In the heat-sensitive coating liquid used in the present invention, normally colorless or light-colored color-forming lactone compounds, phenolic substances, sensitivity enhancers, and waxes are removed by pulverizing with a water-soluble polymer adhesive or surfactant using a pulverizer such as a ball mill. It is desirable to grind the particles into particles as small as possible, specifically particles with a size of 5 μm or less. The support used in the present invention is generally paper, but synthetic resin films and woven fabric sheets can also be used. Further, when the heat-sensitive coating liquid used in the present invention is applied, an air knife, a rubber doctor, a steel blade, a roll, and a terhead made exclusively for Meyer Bar are used to apply the coating, and the coating is dried at a relatively low temperature. Since the surface condition is generally not good just by coating, it is best to treat the surface with a calender or the like to improve the smoothness of the coated surface.

In addition, the light calcium carbonate used in the present invention is precipitated calcium carbonate produced by a chemical method, and has a more uniform particle size distribution and a larger apparent volume than calcium carbonate obtained by mechanically crushing limestone. It is high in potash. When overcoating the IIL calcium carbonate of the present invention on a support, if necessary, it is dispersed using a dispersant such as a phosphate or a surfactant, and an adhesive is added to form an aqueous coating liquid on a paper machine. It is efficient to apply the liquid to the surface of the paper at the top, and it is generally best to apply it at a part where the liquid is applied over the surface of the paper, such as in a nice press part. However, the coating may not be applied on the paper machine, but may be applied to the surface of the paper using a coater with a steel blade, air knife, roll, flexo, Meyer bar, etc., having a tarhead. A sizing agent can also be added when coating in the size press section of the paper machine.

It is effective if the coating amount of light calcium carbonate is 1.0 g/TrL2 or more on the surface to be coated with the heat-sensitive coating liquid.
If it is less than 1.09/m, the effect will not be sufficient, and the more it is, the greater the effect will be, but if it is too much, the workability during coating will be poor and the strength and other properties as a support will be lost. Sometimes.

Next, examples will be described to further specifically explain the present invention.

Example 1 Sodium hexametaphosphate 0.5 water
150 was sufficiently stirred with a stirrer to disperse it, and 100 parts of a 15% polyvinyl alcohol solution was added thereto to obtain an overcoat solution. Apply 40g of this liquid using an air knife coater.
/TrL2 high-quality paper at a coating amount of 6 g/TrL and dried.

On the other hand, as a heat-sensitive coating liquid, -4'-isopropylidene aqueous solution 4'-isopropylidene aqueous solution A113 and C solutions were each ground separately in a ball mill for 2 days to obtain A, :B:C=1:5:3. A heat-sensitive coating liquid was prepared by heating to an extenuating ratio of , and dried at a temperature not exceeding 60°C. Furthermore, it was finished with a super calender to give a Beck smoothness of 200 to 300 seconds, and was slit to a standard width using a slitter C180 to create a 100 TrL winding. At the same time, a heat-sensitive coating liquid was similarly applied to a base paper that was not overcoated, and then a roll was prepared in the same manner. The winding was carried out using a Toshiba thermal FAX KB-500 using the standard chart NQ2 of the Institute of Image Electronics Engineers, at a main scanning speed of 500.
11) When observing the thermal head after printing for 100 m at a recording voltage of 20 V, it was found that the overcoated support had gas attached to the thermal head with a length of 0.8 to 1.21, and there was very little gas. 5 without an overcoat
At -6s length, there was a large amount of gas adhesion (see Table 1).

Example 2 When Shiroyahana PZ was used in place of Shiroyahana PC under the same conditions as in Example 1, similar results were obtained (see Table 1).

Comparative Example 1 For comparison, such an undercoat was used. Table 1 also shows the results in the case of no 7th line.

Comparative Examples 2 to 7 The results of using various inorganic and organic powders in place of Shiroyahana PC1 and Shiroyahana PZ under the same conditions as in Example 1.2 are also shown in Table 1 for comparison.

The amount of gas adhesion indicates the length of the adhesion that adhered to the thermal head after printing 100 m of thermal web paper. In actual use, it is desirable that the number is 2#1lll or less.

Kasamoto Gas adhesion is the state of gas adhesion to the thermal head.
O indicates that there is almost no gas adhesion, which is good for practical use; X indicates that there is a lot of gas adhesion, and that it is not practical.

As is clear from Table 1, it can be seen that a support coated with light calcium carbonate and a heat-sensitive layer coated thereon has a remarkable effect on preventing gas adhesion.

Comparative Example 8 Example except that the overcoat liquid (referred to as liquid E) containing the white glossy PC of Example 1 and the heat-sensitive coating liquid were applied as one layer on the base paper so that the absolute dry coating rate was m99/m2. 1 was repeated.

Note that A:B:C:E=1:5:3:18,2.

Therefore, the absolute dry coating position of the layer provided on the base paper of Example 1 and Comparative Example 8 was 9 g/m 2 in both cases, and the absolute dry coating depth of each component was the same in both cases.

Macbeth IIr! J, total RD-5141-, the print density measured using filter #106 was 1.
0, and 0.7 in Comparative Example 8.

Claims (4)

[Claims] (1) A thermal paper in which a heat-sensitive layer is provided on a support that basically contains a colorless or light-colored lactone compound or phenol compound, and that also contains or does not contain waxes, and the support is made of light carbonic acid. A thermal paper coated with calcium and having a heat-sensitive layer thereon, which reduces gas adhesion to the thermal head. (2) Application amount of light calcium carbonate is 1.0g/m^2
The thermal paper according to claim 1, which is the above. (3) The average particle size of light calcium carbonate is 0.2 to 5
The thermal paper according to claim 1, which is μ. (4) The thermal paper according to claim 1, which is obtained by coating a support with light shicum carbonate, directly providing a heat-sensitive layer thereon, and then finishing the surface of the heat-sensitive layer. .