JPS59155097A - Heat-sensitive paper freed from adhesion of scum to thermal head - Google Patents

Abstract

PURPOSE:To prevent adhesion of scum to a thermal head from occurring while maintaining characteristics as a heat-sensitive paper, by a method wherein a composition comprising an inorganic particulate material having an oil absorption in a specified range is applied onto a base, and then a heat-sensitive layer is provided thereon. CONSTITUTION:(A) a composition comprising an inorganic particulate material having an oil absorption determined by the method of JIS K-5101 of 50-80ml/ 100g, preferably fired kaolin or the like, is applied onto the surface of the base, then (B) a heat-sensitive coating liquid containing (i) a colorless or light-colored color forming lactone compound, (ii) a phenolic compound and, if required, (iii) a wax is applied thereon to produce a heat-sensitive layer, thereby obtaining the objective heat-sensitive paper. The composition B preferably comprises, if required, a dispersant, a binder or the like in addition to the inorganic material, and is preferably applied as an overcoating material onto the base in the form of an aqueous coating liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION In order to reduce the amount of residue adhering to the thermal heads of thermal facsimile machines, thermal printers, etc., the present invention uses a normally colorless or light-colored color-forming lactone compound, and a method for heating the color-forming lactone compound. In thermal paper consisting of a phenolic substance that develops color, 'the support +' = Jx
Oil absorption amount by sK-5101 method is 50/100 S'
The present invention relates to a thermal paper characterized by being overcoated with the above inorganic powder and coated with a heat-sensitive layer 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, and since these waxes are thermofusible, , it becomes more likely to become debris and adhere to the thermal head. If the molten material becomes scum and adheres to the thermal paper, the printing quality of the thermal paper will deteriorate.
In particular, in the case of long-term printing, the printing quality deteriorates significantly, so there has been a strong desire for improvement.

Generally, it is 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 found that the oil absorption amount according to the JISK-5101 method was 50R/! /100P or more 8Qml/100
By coating an inorganic powder with a particle size of less than 1i' on the support and applying a heat-sensitive layer on top of it, it is surprisingly effective in preventing residue from adhering to the thermal head without degrading the properties of the thermal paper, such as print density. I found that it was effective.゛The reason is not well understood, but it is probably due to the inorganic powder overcoating the support with the melted lactone dye, phenolic substance, etc. in the coating layer when printing with a thermal head due to its oil absorbing properties. It is thought that this reduces the amount of residue adhering 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 residue adhesion, but
These highly oil-absorbing substances generally have large bulk;
It also has high water absorption, which may cause problems with liquid properties and other issues when added to heat-sensitive coating liquids. 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, malachite green lactone, 3,3-bis(paradimethylaminophenol)-4,5,6,7-titrachlorphthalide, 3-
Ethylamino-6-chlorofluoran, 3-benzylamino-6-chlorofluoran, 3-cyclohexylamino-6-chlorofluoran, 3-morpholino-5,6-
Benzofluorane, 3-diethylamino-6-methyl-
7-riμrofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6,7-dimethylaminofluorane, 3-diethylamino-7,8-benzofluorane, 3-diethylamino-7-methoxyfluoran Orane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-5,6-pendi-thu-dibenzylaminofluorane, 3-diethylamino-6-methyl- i-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-anilinofluorane, 3-diethylamino-7-(N-methyl-N-(3-trifluoromethylphenyl)amino)fluorane, 3-diethylamino-
7-(N-3'-)lifluoromethylphenyl)aminofluorane.

The phenolic compound used in the present invention is one that liquefies or vaporizes at 70°C or higher and reacts with the color-forming lactone compound to develop color, and includes 4,4'-isopropylidenediphenol, 4,4'- Impropylidene bis(2)
-chlorophenol), 4.4'-isopropylidene bis(2-ter-butylphenol), 4.4' 5
ec-butylidene diphenol, 4.4'-cyclohexylidene diphenol, bisphenol sulfone, 4.
1 molecule of 4'-thiobis(4-ter-butyl-3-methylphenol), 2.2-bis-(4-hydroxyphenyl)-n-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 therein.

Waxes used in the heat-sensitive layer of the present invention for the purpose of preventing color development, scratching, etc.
Examples include animal waxes such as shellac wax as described in No. 4531, 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 strains can be used in combination as fine powder or as an emulsion.

As for the adhesive used in the heat-sensitive layer of the present invention, there is a risk that thermofusible adhesives may stick to the thermal head. Water-soluble polymer adhesives such as agglomerates, hydroxyethyl cellulose, casein, gelatin, and gum arabic are commonly used.In addition, talc, clay, starch granules, etc. can be added to heat-sensitive coating fluids as brighteners and fillers. .

In addition, in thermal facsimiles, thermal printers, etc., in order to reduce the power consumption and increase the printing speed, as necessary, it can be used as a sensitivity improver. -58842
It is also possible to add additives such as those described in No.

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, it is carried out using a coater head such as an air knife, rubber doctor, steel blade, roll, or Meyer bar, and dried at a relatively low temperature. Since the surface condition is generally not good just by coating, it is common to treat the surface with a calender or the like to improve the smoothness of the coated surface.

Inorganic powders with an oil absorption of 50d/1005' or more and less than 80m1/100y according to the JISK-5101 method used in the present invention are generally effective in preventing scum adhesion, but among them, active clays such as montmorillonite, bentonite,
Particularly suitable are those obtained by acid treatment of frozen soil containing kaolin, etc., and various calcined kaolins prepared by calcining kaolin minerals as calcined kaolins.

Oil absorption of the present invention is Om/l o o Li- or more 8
When overcoating a support with an inorganic powder of less than oIILl/100 lid, disperse it using a dispersant or surfactant such as a phosphate as necessary, and add an adhesive to form an aqueous coating liquid. It is efficient to apply the liquid to the surface of the paper on the paper machine, and it is generally best to apply the liquid at a portion such as the 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.

The coating amount of this inorganic powder should be 1.0 g/m or more on the surface to be coated with the heat-sensitive coating liquid, as the effect will be greater and the coating will be 1.0 ff.
If it is less than -/rr1, the effect will be slightly reduced, 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. There is.

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

Example 1 150 parts by weight of water was thoroughly stirred in a machine to disperse the mixture to obtain an overcoat liquid. This overcoat liquid was applied in an absolute dry coating amount of 5 in the size press section of the paper machine that had produced 40 f/d high-quality paper.
One product was manufactured with the surface coated to a thickness of 1/m''.

On the other hand, as a heat-sensitive coating liquid, liquid Δ and liquid B were separately ground in a ball mill for two days, and mixed at a weight ratio of A:B=1:5 to prepare a heat-sensitive coating liquid.

This heat-sensitive coating liquid was applied to the above-mentioned overcoated base paper using an air knife coater to give an absolute dry coating of 143 P/m', and was dried at a temperature not higher than 60°C. Furthermore, Beck smoothing 200 to 300 with a super calendar.
The film was finished to have a width of 180 mm and was slit to a width of 180 mm 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 is sent by Toshiba thermal fax machine.
The main scanning speed was 500 Jpm using the KB-500 and the standard chart graph 2 of the Institute of Image Electronics Engineers.

After printing for 100 m at a recording voltage of 20 V, when adjusting the thermal head, the amount of residue adhering to the support was 0.4 to 0.7 Korean length for the support with an overcoat, and the head was foggy, which was very small. was very common, with 3 to 4 dragon lengths.

Thoroughly stir Example 2゜ with a stirrer to disperse it, and then add 15%
Add 1 part by weight of polyvinyl alcohol S solution B solution O to obtain an overcoat solution. Apply this liquid with an air knife coater for 4
Of-/? Coat on high quality paper at a coating amount of 6y-/vl and dry.

On the other hand, as a heat-sensitive coating liquid, liquids A, B, and C were each ground separately in a ball mill for 2 days, mixed at a weight ratio of A:B:C=1:5:3, and prepared in the same manner as in Example 1. As a result of coating, calendaring, rolling, and facsimile testing, the support was overcoated.
As shown in Table 1, the amount of debris adhering to the thermal head is 0.8 to 1.2 as shown in Table 1, and there is very little debris. There were many.

In addition, cases in which the support was overcoated with something other than the inorganic powder were similar to cases in which the support was not overcoated.

Table 1 *The amount of deposited debris indicates the length of deposits that adhered to the thermal head after printing on the thermal paper 100711. In actual use, 2 fl or less is desirable.

**Dust adhesion is the state of dregs adhering to the thermal head.
○ indicates that there is almost no residue attached, which is good for practical use, and × indicates that there is a lot of residue attached, and that it is not practical. ◎ indicates that there is virtually no residue attached.

As is clear from Table 1, the oil absorption amount according to JISK-s1o1 method is 5011 Ll/1005' or more 80 m7/1
00f! It can be seen that a support with a heat-sensitive layer coated on a support with less than 100% inorganic powder has a remarkable effect on preventing the adhesion of residue.

In addition, the oil absorption amount according to the JISK-5101 method refers to sample 1.
~5y- is placed on a glass plate (approximately 250 x 250 x 5 plates), and a small amount of boiled linseed oil is dripped onto the center of the sample from a buret, and the whole is thoroughly kneaded with a spatula each time. The dropping and kneading operations are repeated, and the end point is when the whole becomes a hard putty-like lump that can be rolled up into a spiral shape with a steel spatula, and the amount of boiled linseed oil used so far is determined. The oil absorption amount G is determined from the following formula.

Also, depending on the type of pigment, if the putty-like lump cannot be rolled up in a spiral shape, it will suddenly soften with a drop of boiled linseed oil, and the end point will be calculated as the point just before it sticks to the glass plate.

Comparative Example 1゜ Overfoot liquid (D
Example 1 was repeated except that the heat-sensitive coating solution and the heat-sensitive coating solution were coated as one layer on the base paper to give an absolutely dry coating layer of 8 y-/l.

The solids concentration of Dow 636 is 50%.

Note that the weight ratio of A:B:D=1:5:0.1.

Therefore, the absolute dry coating amount of the layer provided on the base paper of Example 1 and Comparative Example 1 was 8P/- in both cases, and the absolute dry coating amount of each component was the same in both cases.

The thermal paper of Example 1 and Comparative Example 1 was printed using Toshiba Thermal FAXKB-500 in the same way as the printing in the residue adhesion test of Example 1.
Printing was carried out at a printing speed of 500 Apm and a recording voltage of 20 V using the standard chart NQ2 of the Institute of Image Electronics Engineers of Japan.

The print density was 1.1 in Example 1 and 0.8 in Comparative Example 1.

The print density was measured with a Macbeth densitometer RD-514 using filter #106.

Claims (1)

[Claims] (1) A thermal paper comprising a heat-sensitive layer on a support that basically contains a colorless or light-colored lactone compound or phenol compound, and may or may not contain waxes. , oil absorption amount according to JISK-5101 method is 50m
J/1005' or above, 80! 1. A thermal paper which reduces the adhesion of residue to Thermano and Rehead, characterized in that a composition containing an inorganic powder having a particle size of less than Ll/1001i' is coated and a heat-sensitive layer is provided thereon. ω) The thermal paper according to claim 1, wherein the amount of inorganic powder applied is 1.0 f/m' or more. (3) The thermal paper according to claim 1, wherein the inorganic powder is one or more selected from the group consisting of activated clay and calcined kaolin.