JPH0375356B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention uses a normally colorless or light-colored color-forming lactone compound and a phenolic substance that causes this color-forming lactone compound to develop color when heated, in order to reduce the amount of residue adhering to the thermal heads of thermal facsimiles, thermal printers, etc. The present invention relates to a thermal paper characterized in that a heat-sensitive layer is directly coated on the support of light calcium carbonate without smoothing it. The thermal paper of the present invention is basically colored by melting a lactone dye and a phenolic substance by the heat applied by a thermal head, and the molten material also adheres to the thermal head. Generally, waxes described in Japanese Patent Publication No. 0-14531 of 1978 are often used for the purpose of preventing color development under pressure, fogging, and sticking, and these waxes are thermofusible. Therefore, it becomes more likely to become debris and adhere to the thermal head. If the molten material adheres to the thermal head in the form of scum, the printing quality of thermal paper, especially in the case of long-term printing, will be significantly deteriorated, so there has been a strong desire for improvement. Generally, it is known to add inorganic or organic fillers such as talc, clay, starch, etc. 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 have found that by applying a heat-sensitive layer directly on a light calcium carbonate support without smoothing it, the properties of thermal paper such as print density deteriorate. It has been found that this method is surprisingly effective in preventing debris from adhering to the thermal head. The reason for this is not well understood, but it is probably because light calcium carbonate, which is overcoated with melted lactone dyes, phenolic substances, etc. in the coating layer on the support during printing with a thermal head, instantly absorbs oil. It is thought that this reduces the amount of residue adhering to the thermal head. Naturally, it is possible to incorporate these highly oil-absorbing substances into the heat-sensitive coating layer, and the present inventors have already proposed JP-A-53-105239 and JP-A-53-105239.
No. 118059, and is effective in preventing residue adhesion, but these highly oil-absorbing substances generally have large bulk and high water absorption, so when added to a heat-sensitive coating liquid, the liquid properties Other problems may occur. 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, and the present invention is an improvement on these points. It is also possible to internally add these inorganic powders to the support, but in order to prevent scum from adhering, it is necessary to have a certain amount or more of these inorganic powders on the support surface that is in close contact with the heat-sensitive layer, and it is effective if they are added internally in large quantities. However, if a large amount is added internally, the strength and other properties of the support will be impaired, which is not appropriate. 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, macarite green lactone, 3,3-bis(paradimethylaminophenol)-4,5,6,7-tetrachlorophthalide, 3-ethylamino-6-chlorofluoran, 3-benzylamino- 6-chlorofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-morpholino-5,6-benzofluorane, 3-diethylamino-6-methyl-7
-Chlorofluorane, 3-diethylamino-7-
Chlorofluorane, 3-diethylamino-6,7
-dimethylaminofluorane, 3-diethylamino-7,8-benzofluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-anilinofluorane , 3-diethylamino-5,6-benzo-7-dibenzylaminofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-7-dibenzylamino-3',4', 5′, 6′−
Tetrachlorofluorane, 3-ethyltolylamino-6-methyl-7-anilinofluorane, 3-
Pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilifluorane, 3-diethylamino-7-{N-methyl-N-(3-trifluoromethylphenyl)amino }Fluoran, 3-diethylamino-7-
(N-3'-trifluoromethylphenyl)aminofluorane The phenolic compound used in the present invention is 70
4,4'-isopropylidene diphenol, 4,4'-isopropylidene diphenol, 4,4'-isopropylidene diphenol,
4'-isopropylidene bis(2-chlorophenol), 4,4'-isopropylidene bis(2-ter-
butylphenol), 4,4'-sec-butylidene diphenol, 4,4'-cyclohexylidene diphenol, bisphenolsulfone, 4,4'-thiobis(4-ter-butyl-3-methylphenol), 2, 2-bis(4-hydroxyphenyl)-
Preferred examples include, but are not limited to, phenolic substances having two or more hydrogen groups in one molecule, such as n-heptane, novolac type phenolic resin, and halogenated novolac type phenolic resin. Examples of waxes used in the heat-sensitive layer of the present invention for the purpose of preventing pressure color development, preventing sticking, etc. include animal waxes such as Seratus wax described in Japanese Patent Publication No. 14531/1982, and plant waxes such as Carnauba wax. waxes, petroleum waxes such as paraffin, synthetic waxes such as polyethylene wax, and higher fatty acid amides, which can be used alone or in combination of two or more, as fine powder, or as an emulsion. Ru. As the adhesive used in the heat-sensitive layer of the present invention, thermofusible adhesives are generally difficult to use because they may stick to the thermal head; Water-soluble polymeric adhesives such as ethylcellulose, 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. In addition, it can be used as a sensitivity improver in thermal facsimile machines, thermal printers, etc., as necessary to reduce power consumption and increase printing speed.
It is also possible to add additives such as those described in No. -58842. In the heat-sensitive coating liquid used in the present invention, normally colorless or light-colored color-forming lactone compounds, phenolic substances, sensitivity improvers, and waxes are processed using a water-soluble polymer adhesive or surfactant in a pulverizer such as a ball mill. Therefore, to make the particles as small as possible, specifically 5 μ
It is desirable to grind the powder to the following particles: The support used in the present invention is generally paper, but synthetic resin films and woven fabric sheets can also be used. When the heat-sensitive coating liquid used in the present invention is applied, a coater head such as an air knife, rubber doctor, steel blade, roll, or Meyer bar is used, and the coating is dried at a relatively low temperature. And since the surface condition is generally not good just by coating,
It is common to treat the surface with a calendar 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, larger apparent volume, and bulkier structure than heavy calcium carbonate produced by mechanically crushing coal stone. It has a high value. When overcoating the light 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 solution on a paper machine. It is efficient to apply the liquid to the surface of the paper using a process, and it is generally best to apply the liquid to the surface of the paper in a section such as a size press section where the liquid is overcoated on the surface of the paper. However, the coating may not be applied on the paper machine, but may be applied to the surface of the paper using a coater having a coater head such as a steel blade, air knife, roll, flexo, or Meyer bar. A sizing agent can also be added when coating in the size press section of a paper machine. As for the coating amount of this light calcium carbonate, it is effective if it is 1.0 g/m ² or more on the surface to which the heat-sensitive coating liquid is applied, and the effect is not sufficient if it is less than 1.0 g/m ² .
The larger the amount, the greater the effect, but if the amount is too large, the workability during coating may be poor, and the strength and other properties of the support may be lost. Next, examples will be described to further specifically explain the present invention. Example 1 100 parts by weight of Shiroenka PC (light calcium carbonate manufactured by Shiroishi Calcium KK) 0.5 parts by weight of sodium hexametaphosphate 150 parts of water were sufficiently stirred with a stirrer to disperse, and then
Add 100 parts by weight of 15% polyvinyl alcohol solution,
Use as overcoat liquid. This liquid was applied to 40 g/m ² of high-quality paper using an air knife coater in a coating amount of 6 g/m ² and dried. On the other hand, as a heat-sensitive coating liquid, liquid A {3-piperidino-6-methyl-7-anilinofluorane 1 part by weight 5% hydroxyethyl cellulose aqueous solution 5 liquid B {4,4'-isopropylidene diphenol
1. 5% hydroxyethyl cellulose aqueous solution 5. C solution {Fatty acid amide S (Stearic acid amide manufactured by Nitto Kagaku KK) 1. 5% hydroxyethyl cellulose aqueous solution 5.
A heat-sensitive coating liquid was prepared by pulverizing the mixture for several days and mixing the mixture at a weight ratio of A:B:C=1:5:3.This heat-sensitive coating liquid was completely dried on the overcoated base paper using an air knife coater. The coating was applied in an amount of 3 g/m ² and dried at a temperature not exceeding 60°C. Furthermore, Beck smoothing is 200 ~ with super calendar.
The material was finished to a length of 300 seconds and slit into 180 mm width using a slitter to create a 100 m roll. At the same time, a heat-sensitive coating liquid was similarly applied to base paper that was not overcoated, and then a roll was created in the same manner. The winding was carried out using a Toshiba thermal FAX KB-500 using the standard chart No. 2 of the Institute of Image Electronics Engineers, at a main scanning speed of 500.
When observing the thermal head after printing for 100 m at a pm recording voltage of 20 V, the amount of debris adhering to the thermal head with overcoating on the support was 0.8 to 1.2 mm, which was extremely small, and the amount of debris adhering to the thermal head without overcoating was 5 mm. -6 mm length had a large amount of debris attached (see Table 1). Example 2 Similar results were obtained under the same conditions as in Example 1, using Shiroyahana PZ instead of Shiroyahana PC (see Table 1). Comparative Example 1 For comparison, the results obtained without any undercoating are also shown in Table 1. Comparative Examples 2 to 7 Shiroka PC, Shirokaa under the same conditions as Examples 1 and 2
The results of using various inorganic and organic powders in place of PZ are also shown in Table 1 for comparison.

[Table] As is clear from Table 1, when the support is overcoated with light calcium carbonate and the heat-sensitive layer is applied directly on top of the support without smoothing, it has a remarkable effect on preventing deposits of residue. I understand that there is something. Comparative Example 8 The overcoat liquid (referred to as liquid E) containing the white glossy PC of Example 1 and the heat-sensitive coating liquid were used as one layer,
Example 1 was repeated except that the coating was applied to the base paper at an absolute dry coating weight of 9 g/m ² . Note that A:B:C:E=1:5:3:18.2. Therefore, the absolute dry coating weight 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 amount of each component is the same for both. Macbeth densitometer RD-514, filter #106
The print density measured using was 1.0 in Example 1,
In Comparative Example 8, it was 0.7.

Claims (1)

[Scope of Claims] 1. A thermal paper comprising a heat-sensitive layer on a support, which basically contains a colorless or light-colored lactone compound or a phenol compound, and which may or may not contain waxes, scum adhesion to a thermal head characterized in that light calcium carbonate is applied to the body, a heat-sensitive layer is provided directly on it without smoothing, and the surface of the heat-sensitive layer is then finished; Thermal paper with less heat. 2. The thermal paper according to claim 1, wherein the coating amount of light calcium carbonate is 1.0 g/m ² or more. 3 Average particle size of light calcium carbonate is from 0.2
The thermal paper according to claim 1, which has a thickness of 5μ.