JPS6030941B2 - Surface coating of contact metal parts of transport transfer paper in electrophotographic copying machines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface coating of contact metal parts of a transport transfer paper in an electrophotographic copying machine.

Metal parts of electrophotographic copiers in general, especially heating low-fu,
The metal plate (slide plate), etc. used to improve the slipperiness of the transfer paper feeding claw and conveyance transfer paper (hereinafter referred to as transfer paper) is heated under high temperatures (130 to 240℃) during the practical use of electrophotographic copying machines.
00), the surfaces of these parts vary depending on the application, but at least have one of the following properties: heat resistance, non-adhesiveness, slipperiness, electrical conductivity (antistatic properties), and abrasion resistance. Or, it is required to have two or more properties at the same time.

In particular, with the recent increase in the speed of copying performance in electrophotographic copying machines, the metal parts of the copying machines are not only unavoidably charged due to friction with the conveying transfer paper, but also suffer from wear and abrasion of the coating under high temperatures. How to solve various problems became an important issue. Non-adhesiveness is necessary to prevent the adhesion of toner heat-fused substances, and for this purpose, fluorine resins, which have excellent non-adhesive properties, are generally used as the optimal coating material.
Furthermore, among the fluorine resins, tetrafluoroethylene resin (hereinafter referred to as PTFE) and perfluoroalkoxytetrafluoroethylene resin (hereinafter referred to as PFA), which can be stably used up to temperatures around 250 qo, are used. However, although coatings made of these resins can withstand the above-mentioned high temperatures, they suffer from relatively high abrasion at the high temperatures and, furthermore, have the disadvantage that they are not electrically conductive and therefore become charged even by slight surface friction.

For this reason, even though the heating roller, transfer paper feed pawl, slide plate, etc. coated with a PTFE or PFA resin coating has superior sliding properties with the transfer paper compared to resin coatings other than these resins, contact with the transfer paper may be difficult. It has been pointed out that there is a drawback in that the coated surface is charged due to slippage, and the transfer paper is therefore likely to wrap around the surface, or that this tends to spread between parts. In order to solve the above-mentioned drawbacks caused by the electrical conductivity and abrasion resistance of this type of fluororesin, various ideas have been made from the viewpoint of fluororesin (PTFE, P
Aluminum powder,
1 or 2 of copper powder, stainless steel powder, carbon black, graphite powder, polonitride powder, etc.
A method of adding a species or more, and a method of adding a molybdic acid compound, etc. are known (hereinafter, the above substances are collectively referred to as additives). However, according to experiments conducted by the present inventors, when the additive is used in the known method, if the amount added deviates from a predetermined amount relative to the fluororesin and becomes excessive, the non-adhesive property of the resin deteriorates. Not only this, but also the coating strength decreases, leading to a decrease in the adhesion strength to metal parts.

For this reason, the amount of the additive to be added to the resin must be determined depending on the type, particle size, specific gravity, etc. of the additive, but in the case of fluorine-containing fat, the weight ratio is about 15% at most. Therefore, in order to obtain the desired electrical conductivity by adding metal powder or graphite powder among the additives to a fluororesin, it is necessary to increase the amount of the powder considerably relative to the resin. If it is a liquid, the particle size of STFE in the dispersion is about 0.1 mm, so the particle size of the additive powder needs to be about the same. Since it is substantially difficult to obtain the additive powder, it is impractical.

Furthermore, regardless of whether this additive is a molybdic acid compound such as a soda compound, an ammonium compound, or a potash compound, since they are water-soluble, it is possible to contain a large amount of such compound in the resin coating. This is undesirable because it impairs the stability of the coating. This applies, for example, to sodium molybdate versus PTFEII. It is obvious that if a coating liquid containing % red by weight is applied to a desired metal surface and washed with water after firing, the surface of the coating will change color and be impractical.
Therefore, the electrical conductivity of the resin coating obtained was confirmed by the following method. In other words, the conductivity can be measured with a meter, but since it is extremely unstable depending on the measurement date and time and measurement conditions, the above-mentioned additives are added to the surface of the test piece (aluminum plate 100 side x 200 ribs x 3 sides) in advance. After forming a material film, rub the surface of the film 20 times with a white cotton cloth, place a piece of white paper (unused transfer machine) cut into 15 square strips on the surface, and lightly roll the strip of paper from the top surface with your fingers. By holding the paper and pulling it towards you, it was confirmed whether or not the transfer paper was stuck due to static electricity. As a result, the additives that have been considered effective in the past, such as powders of aluminum, copper, and stainless steel, powders of inorganic substances, and their compounds, are charged by friction unless they are contained at least about 15% by weight relative to the resin. This was recognized. As a result of further research on the additive, the present inventors found that the amount added was less than 15% by weight based on the resin, and that fine tin oxide powder (particle size 0.1 μm), which is conventionally known to have good electrical conductivity, was used. ) has been experimentally found to have extremely excellent abrasion resistance under high temperatures.In addition to its single use, it has also been found that by mixing it with an appropriate amount of other electrically conductive substances such as sodium tungstate or graphite fiber powder. Mixed use (added amount of tin oxide less than 15% by weight)
By doing so, the resulting film was successfully provided with desired electrical conductivity and abrasion resistance at the same time. Tables 1 and 2 show examples of tests conducted on the electrical conductivity and abrasion resistance (display of wear amount) of the thus obtained resin coatings and related coatings.

Table 1 (Appendix) This table shows the test pieces (aluminum plate low cape x 20 enemies x 3
This figure shows the amount of wear caused by the transfer paper and the generation of static electricity at 13,000 (load).
'o is the average measured value after 100,000 runs under the conditions of 150 skins/running under the ground and 2 running/seconds.
'To check whether the transfer paper has adhered due to static electricity, rub the donor piece with a white cotton cloth 20 times, place an unused transfer paper cut into 15 strips on the surface, and gently press the surface of the transfer paper with your fingertips. The presence or absence of the substance was determined by checking as soon as it adhered to the offering piece.

Shiichi: Quality is determined by the amount of additive added to the resin (less than 15% by weight)
, shows the three-way comprehensive judgment results of the amount of wear and adhesion of transfer paper due to static electricity, ◎: best, 0: good, ×: poor (unsuitable).

Table 2 (Appendix) This table shows the amount of wear caused by the transfer paper and the generation of static electricity on the test piece (same as the note in Table 1) at 180°C. The presence or absence of adhesion of the transfer paper due to static electricity and its quality were determined according to the method described in Table 1.

As is clear from Tables 1 and 2 above, the amount of wear varies depending on the type of resin and the applied temperature, but the electrical conductivity (antistatic property)
In terms of wear resistance (display of wear amount), a coating containing less than 15% by weight of tin oxide (single substance) relative to the resin (PTFE, PFA), that is, 1% by weight of the box, is optimal (Table 1 M.
2. Second outer material. 2), there is no transfer paper adhesion due to static electricity, and the amount of wear is as low as 20.7 to 26.5 (9).
It turns out to be the best.

Following tin oxide (single substance), under the same addition conditions as above, sodium tungstate alone and a mixed film of this and tin oxide had good electrical conductivity and wear resistance (first rhombic rule o.3, N
o. However, the former (sodium tungstate alone) is disadvantageous because the amount added to the resin is 16.5% by weight, and a large amount of water-soluble substances is contained in the coating film. On the other hand, it is known that the desired results can be obtained with the latter by mixing tin oxide. In addition, good electrical conductivity can be obtained by mixing sodium molybdate with sodium tungstate (first
Front ship. 5, No. However, the wear amount of the coating is particularly large in the latter case, and is more than twice as much as that of tin oxide alone or a mixture of tin oxide and sodium tungstate, which is impractical.

Furthermore, in the case of using graphite fiber fine powder (single substance) (see Table 2 No. 5), although the electrical conductivity was good at 13% by weight of the resin, the amount of wear was 78%.
This amount is about three times as high as that of tin oxide, making it unsuitable.

However, the mixture of graphite fiber fine powder, hatched carbon, and tin oxide (refer to Table 2.8) has a ratio of 1% by weight to the resin, which is the same amount as the graphite fiber fine powder (single substance). First, it can be seen that the conductivity is good and the amount of wear is 35.3 mm, which is about 1/2 or less when using fine graphite fiber powder. In order to improve the conductivity and abrasion resistance of the resin coating and obtain the desired effect, it is optimal to mix 15% by weight or less of tin oxide (single substance) with respect to the resin.

However, when the mixing ratio of tin oxide (single substance) to the resin is 16% by weight, the electrical conductivity is good, but the degree of surface assembly becomes large, so the amount of wear is 130 to 179 (9). The damage to the transfer paper (transfer paper) is particularly severe, making it completely unusable.

This is thought to be due to the deterioration of the physical properties of the film mentioned earlier, and from this point of view, the amount of tin oxide added was 15% by weight based on the resin.
It is desirable that it be less than

The present invention will be explained in more detail below with reference to Examples.
Example 1 An aluminum plate (10 ribs x 20 ribs x 3 sides) was used as a test piece, and its surface was blasted using a conventional method.
Tin oxide fine powder particle size 0 is applied to the PTFE paint primer on the surface.
．． 1 pile (Mitsubishi Metal ■: T-1) 500g and water 500g
The resulting paint was mixed with Takayo at a ratio of PTFEIO% to a coating thickness of about 7A, and then baked at 330°C for 10 minutes.

Then, on the top surface of the PTFE top coat, fine tin oxide powder (particle size 0.1) was applied in an amount of 1% by weight of the paint resin.
After coating, the resulting coating material was baked at a high temperature of 40,000 mm for 10 minutes to obtain a film with a thickness of 35 mm. This coating was subjected to an abrasion resistance test according to the method listed in Table 1, and the results were 20.
The surface was rubbed 20 times with a white cotton cloth, but no transfer paper was observed on the surface, which was satisfactory.

Example 2 A test piece similar to Example 1 was previously degreased with alkali, etched with hydrochloric acid (15%), washed with water, and then dried.

Next, tin oxide fine powder (particle size 0.1 French) was added to the PFA powder.
9.1 wt.
After firing for 5 minutes, a film with 50 peaks was obtained. When the amount of wear of this item was measured using the method described in Table 2, it was found to be 40.
~42 showed a good result of 9/100,000 times, whereas the result of rubbing the surface with a white cotton cloth showed that there was only a slight adhesion of transfer paper (electrification), and it was not possible to fully energize. It was possible to apply it to unnecessary parts. Example 3 A primer similar to Example 1 was applied to a test piece similar to Example 1 to a thickness of 7 mm.

Next, graphite fiber fine powder (particle size 10
(France) (manufactured by Nippon Carbon ■) to PFA8. % by weight of G, 2.6% by weight of tin oxide, and 1.7% by weight of carbon fluoride (manufactured by Nippon Carbon ■) were added and mixed in a ball mill for 5 hours to obtain a top coat. Electrostatic powder coating was applied to the surface of the same machine as in Example 2. 38
The coating was baked at a high temperature of 0 qo for 30 minutes to obtain a coating film with a thickness of 90 to 100 mm.

Claims (1)

[Claims] 1. Electrophotographic copying of a coating consisting of a fluororesin and a fine tin oxide powder alone or a mixture of the fine tin oxide powder and another electrically conductive substance, and containing less than 15% by weight of the fine tin oxide powder relative to the fluorine resin. A surface coating of a contact metal part of a conveyed transfer paper in an electrophotographic copying machine, characterized in that it is formed on the surface of a contact metal part of a transfer paper conveyed in the machine.