JPH02109072A - Developing device and developing sleeve - Google Patents

Abstract

PURPOSE:To prevent sleeve ghost and the lowering of density at the time of endurable use by forming a developing sleeve of compound material containing synthetic resin, carbon graphite and carbon black. CONSTITUTION:The developing sleeve 1 is formed of the compound material containing at least synthetic resin, carbon graphite and carbon black. Thus, the lowering of the image density and the sleeve ghost caused by the contamination of the sleeve 1 can be drastically reduced. It is desirable that the content of carbon graphite is 10-60wt.%, the content of carbon black is 0-40wt.% and the content of the total of two kinds of carbon powder is 10-60% in the sleeve 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a 5M, a developing wave and a developing sleeve in a secondary photographic device.

[Prior Art] Conventionally, in electrophotographic development, uniform charging of toner on a developer holding member and coating of a thin layer of toner to achieve this have affected image quality due to environmental changes and durability. This is an extremely important technology for stabilization regardless of the situation.

For this purpose, sandblasting is applied to the surface of a developer support member (hereinafter referred to as a developer sleeve) made of a widely used non-magnetic metal material (for example, in Japanese Patent Laid-Open No. 58-571
There are techniques such as applying plating containing abrasive grains (Japanese Patent Application Laid-Open No. 57-64764).

[Problem that the invention seeks to solve] However,
In the above conventional example, especially in a low humidity environment, the toner has a triboelectric charge (triboelectric charge) that is too large than necessary (so-called toner charge-up, and the particle size of the toner that becomes like this is usually 5 gm or less, and because of this, magnetite This causes a phenomenon in which these toners are strongly electrostatically restrained against the sleeve due to the reflection force, and as a result, other toners are prevented from being charged by friction with the sleeve and cannot have a triboelectric charge. There is a difference in toner tribo distribution between areas with charge-up toner and areas without charge-up toner.

For this reason, there was a problem in that so-called (positive) sleeve ghosts as shown in FIG. 3 occur.

In FIG. 53, the part (a) where the density is low is the part where the density has decreased because a state in which no toner was consumed from the sleeve continued and a fine powder layer was formed on the sleeve surface. In most cases, this layer is removed by one rotation of the sleeve during development, so the image density from the second rotation is higher than in (a), as shown in part (b).

Furthermore, as more prints are made, the developer rubs against the developing sleeve and as a result, the surface of the developing sleeve becomes contaminated with the resin components and external additives in the developer, resulting in poor developability of the developer. There were also problems such as the inability to coat the developer uniformly. This deterioration in developability due to excessive frictional electrification of the developer tends to be particularly noticeable in developing devices that use negative polarity developers, as resins or metals generally tend to be negatively charged by friction. Kawata.

[Means for Solving the Problems] According to the present invention, a resinous resin, in which carbon black, carbon graphite, and more preferably carbon fibers are dispersed, is used as a binder, such as nylon, polyethylene, or polystyrene. By performing development using a conductive sleeve, it is possible to reduce image density reduction and sleeve ghosts due to contamination of the developing sleeve, which have been considered drawbacks in electrophotographic dry development.

[Example] Figure 1 is a developing sleeve showing an example of the present invention, and in the figure, conductive carbon black (C0IIDIIICTEX manufactured by Columbian Co., Ltd.) with a weight ratio of 5% to nylon 66 is used.
900) Weight ratio: 40% (7) Kneaded with graphite (C3PE manufactured by Nippon Graphite), outer diameter 16mm Thickness 11mm
It is a conductive resin sleeve molded into the shape of a vibrator. In this case, of course, the flange portion 2 (2') in the figure may be integrally molded with conductive resin. The conductivity of this resin is 2xlO"Ωcm in volume resistivity and 1 in surface resistance.
×lO°Ω. The content of carbon powder is
When the weight ratio exceeds 60%, the wear resistance of the sleeve deteriorates significantly, making it unsuitable for practical use. Also, when the weight of the carbon powder is reduced, the resistance increases, but it is 10'Ω・C.
When the value exceeds (2), toner coating defects occur, making it unsuitable for practical use. Also, the sleeve surface is R, (J
IS standard 10 point average roughness) 7~l Othm, R
, (center line average roughness specified by JIS) is 0.8 to 1.
A roughness of about 2 gm is preferable from the viewpoint of toner transport.6 Methods of adding roughness to the surface include adding it in the mold in the molding process and adding it during injection. Alternatively, as a post-process, it may be added by blasting or the like. When the sleeve surface roughness becomes 3 μm or less in R2 or 0.51 Lm or less in R, the toner conveying force of the developing sleeve decreases, and the toner coating amount decreases to 0.6 m9/cy.
a” or less, and good development could not be performed.On the contrary, R,
When R is 18 pm or R is 3 gm or more, the amount of toner coating becomes too large as 3.5 In9/cl12 or more, resulting in the inconvenience that a uniform thin layer coating, which is one of the objects of the present invention, cannot be achieved.

The reason why graphite is used in the present invention is that experimental results have shown that graphite is resistant to contamination by resin components due to its solid lubricating properties. This effect is remarkable when the graphite content is 30 to 60% by weight, and the effect is also observed when the graphite content is in the range of 10 to 30%.

Next, this developing sleeve was assembled into the developing device shown in FIG. 2, and image formation was performed.

The toner used at this time was composed of styrene acrylic as a main component, to which 50 parts by weight of magnetite and 2 parts by weight of a metal-containing complex were internally added as a charge control agent. 0.6 parts by weight of hexamethylene deisilazane (hexamethylene deisilazane added and heat treated) was added to sexually charged vapor-phase silica.

A developing sleeve 1 rotates in the direction of the arrow, and carries the magnetic toner (-component developer) 5 supplied in the container 4 and conveys it to the developing section. In the developing section, the sleeve faces an electrophotographic photoreceptor 7 as an image carrier. This sleeve l
The distance between the photoreceptor 7 and the photoreceptor 7 is wider than the thickness of the toner layer carried on the sleeve l. And in sleeve 1? From llt source 8,
A bias voltage that is more important than the DC voltage is applied to the AC voltage, thereby forming an oscillating electric field in the developing section. This oscillating electric field causes the toner to vibrate and become attached to the image area of the latent image. The toner layer is regulated by the magnetic blade 3 in the magnetic field of the magnet 6 fixedly arranged inside the sleeve.
Images output by a developing device using a developing sleeve according to the present invention had significantly reduced sleeve boost compared to an image using a conventional sandblasted non-magnetic metal sleeve. Furthermore, conventionally, especially in a low temperature and low humidity environment, the solid black reflection density after printing 1000 sheets was 0.
Even after printing 20,000 sheets, we were able to suppress the decrease in durable use density, which had been about 3.3% due to sleeve contamination, to within 0.2.

The cause of this sleeve ghost reduction is that, according to the inventors' various experimental results, this is due to the chemically inert carbon particles acting as leak sites on the sleeve surface. It is thought that the charge-up of fine toner powder is suppressed.

On the other hand, since a conventional sandblasted metal sleeve has an oxide film formed on its surface, its contact resistance is higher than that of carbon, and it is thought that it is unable to sufficiently release the charge of fine powder toner.

In the developing device shown in Example 1, the amount of toner coated on the sleeve is regulated by a magnetic seal formed by a ferromagnetic plate and a developing magnet by arranging a ferromagnetic metal blade to face the sleeve surface with a minute interval. ing.

On the other hand, the fourth. As shown in FIG. 5, a method of controlling the 1-ner coating by bringing an elastic metal plate or rubber blade 30 into contact with the sleeve surface is also widely used.

This method attempts to mass-charge the toner in a seeding manner at the contact portion between the sleeve, toner, and plate, and is a method that can obtain a stable triboelectric charge μ of the toner even under high temperature and high humidity conditions. However, under low temperature and low humidity conditions, it had the disadvantage that the triboelectric charge was too high, sleeve ghosting and low durability density were increased.

When the developing sleeve of Example 1 was incorporated into this developing device and image formation was performed, the sleeve ghost in a low-temperature, low-humidity environment hardly changed, and the solid black reflection density in a high-temperature, high-humidity environment increased by about 0.15. , it became about 1.40. However, since it is pressed by an elastic blade, the surface of the sleeve will be 15 times smaller after 10,000 prints.
A problem arose in that ~20yLm was scraped off. Therefore, in order to improve the abrasion resistance, the present inventors added 40% by weight of carbon fiber pyrofil manufactured by Mitsubishi Rayon Co., Ltd. to the resin binder of the sleeve. As a result, the abrasion resistance has been improved, making it possible to keep the abrasion record to less than 10 JLm even after 10,000 prints, making it possible to provide a developing device with stable image quality even under environmental changes and long-term use. Ta. The carbon fiber content is suitably 10 to 90% by weight relative to the resin binder; too much carbon fiber is not preferred because the sleeve becomes brittle.

The resin binder may be a synthetic resin other than those used in this example, such as polyethylene, polyacrylic, polyester, etc. The graphite may be either natural or artificial, but has a fixed kR of 297% or more and an ash content of 2.0%. The following are more preferable in terms of conductivity and solid lubricity.

Further, in order to improve Pl wear resistance, the same effect can be obtained by adding glass fiber, although unlike carbon fiber, electrical conductivity cannot be imparted.

Note that the present invention can also be applied to those using a one-component nonmagnetic developer or a two-component developer. The present invention can also be applied to a developing device in which the gap between the developing sleeve and the photoreceptor is less than or equal to the thickness of the developer layer on the sleeve. Furthermore, the present invention can also be applied to a developing device that applies a DC bias voltage that does not change over an hour to the sleeve instead of forming an oscillating electric field as described above in the developing section.

[Effects of the invention] As stated in theory 1 and 1 above, by performing development using a conductive resin sleeve containing carbon graphite, sleeve ghosting, which has been considered a drawback of conventional development, and during long-term use can be avoided. It has become possible to significantly reduce the concentration drop. Note that this effect is not limited to the case of the negative polarity toner shown in the example, but also has the effect of significantly reducing sleeve ghost and durable density decrease in heat-treated toners such as aminosilane that are strongly charged to positive polarity.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a conductive resin sleeve according to an embodiment of the present invention. Fig. 2 is a sectional view of a developing device to which the present invention can be applied. Fig. 3 is a diagram for explaining sleeve ghost. Fig. 4, f : IS5 diagram is a diagram for showing another embodiment. 1 is a developing sleeve 5, and a toner 7 is a photoreceptor. V I 153 Whisper 2 eyes

Claims (1)

Claims: (1) A developing device characterized in that the developing sleeve is made of a composite material containing at least a synthetic resin, carbon graphite, and carbon black. (2) The carbon graphite content in the developing sleeve is 10% to 60% by weight, the carbon black content is also 0% to 40%, and the total content of these two carbon powders is 10% to 60%. The developing device according to claim 1, characterized in that: (3) The developing device according to claim 1 or 2, wherein the developing sleeve contains 10 to 90% carbon fiber by weight. (4) The surface roughness of the developing sleeve is a 10-point average roughness,
4. The developing device according to claim 1, wherein the developing device has a center line average roughness of 0.6 to 3.0 μm. (5) A developing sleeve that carries and transports a developer for developing an electrostatic latent image, and is made of a composite material containing at least synthetic resin, carbon graphite, and carbon black.