JPH0614221B2 - Development device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a dry developing device applied to an image forming apparatus such as a copying machine and an information recording device, and more specifically, a developer is uniformly coated on a developer supporting member. Of the electrostatic latent image formed on the latent image holding member arranged facing the developer supporting member at the developing position. , A developing device for developing the same.

[Background of the Invention]

Conventionally, as a developing method for developing the electrostatic latent image formed on the latent image holding member, a developing method using a one-component toner and a developing method using a two-component toner are known.

An example of a conventional developing device used in such a developing method is shown in FIG. In FIG. 3, 1 is a blade used for uniformly forming a toner layer on a developer supporting member, 2 is a developer supporting member (hereinafter referred to as a sleeve),
Reference numeral 3 denotes a toner layer formed thereon, 4 a fixed magnet arranged in the sleeve, 5 a latent image holding member for holding an electrostatic latent image, and 6 a bias power source.

In this developing device, in order to form a uniform toner layer 3 on the developer supporting member, that is, the sleeve 2, at the outlet of the toner container, one magnetic pole N ₁ of the fixed magnet 4 contained in the sleeve 2 is opposed. Is provided at a position where a magnetic substance is provided, the toner 3 is erected along the magnetic force line between the magnetic pole and the magnetic substance blade, and the toner 3 is cut at the edge portion of the blade to utilize the action of the magnetic force. , The thickness of the toner layer is regulated (for example, JP-A-54-430).
No. 37).

By these methods, the developer supporting member, that is, the sleeve 2
It has become possible to form a substantially uniform toner layer 3 on top. However, it has been experimentally found that it is difficult to stably form a uniform toner layer on the sleeve for a practically long term. In particular, when a toner having a remarkably poor fluidity was used, or when an aggregated toner was used, it was more difficult to form a uniform toner layer. If the toner layer thickness on the sleeve 2 is uneven, the visible image becomes uneven, and a good image cannot be expected.

The applicant of the present invention has proposed a new developing device as a very effective method for countering this unevenness (Japanese Patent Laid-Open No.
113172). This is to prevent uneven coating by providing irregularities along the moving direction of the sleeve surface. The reason why the unevenness of the sleeve surface along the moving direction is effective against unevenness is that the friction force between the sleeve surface and the toner increases and the sleeve becomes difficult to push, and the pushing force of the toner from the blade is stable, It is considered that the unevenness in the circumferential direction of the sleeve gives periodic fine vibrations to the toner pool in the upstream portion of the blade, loosens the toner lumps, and the toner is in a free-flowing state.

For example, as the sleeve, stainless steel (SUS 3
04) When an image development durability test was performed using a surface-roughened sleeve that had been sandblasted with amorphous particles having a particle size of # 600 on the sleeve, no unevenness occurred.

However, when images were continuously output using this developing device, the following development occurred.

(1) When 300 to 500 copies of an original with a lot of white background with extremely small toner consumption were continued, the image density D decreased from 1.1 to 0.9.

(2) When a black background copy (whole surface black) was continuously made with a developing device in which the image density was lowered, the image density began to recover to 1.1 after 30 to 50 sheets were continuously printed.

Then, first, when the particle diameter of the toner on the sleeve surface where the image density is lowered in the above (1) is measured, the toner having a particle diameter of 1 to 5 μ is mainly, and the toner in the hopper (average particle diameter 8 to 1
3 μ), the particle size is clearly smaller, and it was found that the change in the image density occurs due to the change in the toner particle size. This is because when the toner is charged by friction with the sleeve, the toner is attracted onto the sleeve by the mirroring force. At this time, the fine toner (1 to 5 μm) has a mean particle size (8 .About.13 .mu.), The fine toner is thinly coated on the surface of the sleeve. For this reason, the toner having a particle size of 5 μ or more, which contributes most to the development, is not sufficiently rubbed with the sleeve and is not charged. As a result, the image density gradually decreases. It has been found that in order to suppress the sleeve coating due to the reflection force of the fine toner, the sleeve surface may be made insulating or semiconductive.

[Object of the Invention]

An object of the present invention is to eliminate the above-mentioned drawbacks in the conventional developing device, and to always form a stable and uniform developer thin layer on the surface of the developer supporting member, and to convey the developer. To provide a developing device capable of improving stability and uniform coating stability, preventing change in image density due to change in toner particle size, and exhibiting stable and high performance for a long period of time. .

[Outline of Invention]

The developing device of the present invention which achieves the above object carries a developer having a chargeable insulating toner on a developer supporting member and conveys it to a developing position, and opposes it without contacting the developer supporting member. In the device for developing the electrostatic latent image formed on the latent image holding member arranged with the above-mentioned developer,
Characterized by forming a thin film of an ultraviolet curable resin in which solid particles are dispersed on the surface of the developer supporting member and irradiating the thin film with ultraviolet rays to form a surface layer having fine irregularities on the surface of the developer supporting member. It is what

The solid particles dispersed in the ultraviolet curable resin described above are preferably conductive particles, and may contain conductive particles and particles for charge control. Further, it is preferable that the solid particles and the ultraviolet curable resin have different charging polarities with respect to the developer.

Since the developer used in the developing device according to the present invention is charged by friction with the developer supporting member, that is, the sleeve, from this viewpoint, it is necessary to use a one-component insulating toner. Further, magnetic toner is preferably rotated by the magnetic poles of the magnet, so that frictional rotation with the sleeve increases, so magnetic toner is preferable. On the other hand, the non-magnetic insulating toner of the two-component developer is mainly charged by contact with the carrier, but friction with the sleeve also occurs to some extent. The developer used in the developing device according to the present invention is not limited to the one-component insulating magnetic developer, because it has the ability to carry the agent and functions to generate friction. A two-component developer can be applied as long as it contains a toner.

Example of Invention

 Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show an embodiment of the present invention. In the figure,
The same parts as those shown in FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted.

A thin film of an ultraviolet curable resin in which solid particles are dispersed is formed on the surface of the developer supporting member, that is, the sleeve 2, and by irradiating the thin film with ultraviolet rays, the surface layer 7 having fine irregularities is formed on the surface of the sleeve 2. .

The details of the surface layer 7 are shown enlarged in FIG.

In FIG. 2, 8 indicates an ultraviolet curable resin and 9 indicates solid particles dispersed therein.

Hereinafter, an example of the developing device actually manufactured by using the device shown in FIG. 1 will be described.

Example 1 As the fixed magnet 4, the magnetic pole strength is N ₁ = 820 gauss,
S ₁ = 820 gauss, N ₂ = S ₂ = N ₃ = S ₃ = 500 g
Auss magnet roll was used. The gap between the sleeve 2 and the latent image holding member (hereinafter referred to as drum) 5 is set to 0.2.
The toner layer 3 having a thickness of 5 mm and a gap between the sleeve 2 and the blade 1 of 0.2 mm was held to form a toner layer 3 thinner than the gap between the sleeve 2 and the drum. As the bias power supply 6, AC is DC
, Which are superposed, V _PP (peak-to-peak) = 1300V, f = 1000Hz, DC = + 100
As (v), jumping development was performed and a copying process was performed at a speed of 30 sheets per minute.

The sleeve 2 is made of non-magnetic metal such as stainless steel or aluminum, and has a thin surface layer 7 containing solid particles applied to the surface thereof.

The sleeve 2 is the non-magnetic metal described above, and the solid particles 9 are dispersed in the resin 8. The resin 8 is a urethane-acrylate resin (for example, Seika Beam PHC-2210, trade name of Dainichi Seika Kogyo Co., Ltd.). It is a resin that cures with ultraviolet rays, and after application, strong ultraviolet rays are irradiated to complete the curing. The solid particles mixed in the resin 8 make the surface of the sleeve uneven, and are preferably resistant to abrasion and have a charge control effect to some extent. Such powder can be selected from ceramic powders such as alumina and boron nitride, glass beads, metal oxides such as TiO ₂ and Fe ₂ O ₃ .

When the latent image surface was actually developed using the developing device having the above-mentioned configuration, the toner coating on the sleeve surface was very good, and no coating unevenness occurred. Further, when 50,000 sheets of images were formed using the above-mentioned sleeve, good images were always obtained, and the image density did not decrease. This is because the surface of the sleeve is insulated with a polymer substance to prevent a decrease in image density.

UV curable resins such as urethane-acrylate resins have a pencil hardness of 6 to 7H and are hard to wear. Further, it is not necessary to heat the resin to cure it, and almost no heat is generated even when the resin is irradiated with ultraviolet rays.
Therefore, unlike the other methods, the sleeve is hardly thermally deformed, and the accuracy of the sleeve can be maintained.

Example 2 An experiment was conducted by changing various solid particles contained in the coating film applied to the sleeve surface.

It is possible to control the charging of the toner by mixing solid particles such as Teflon particles having a strong negative charge. For example, in a developing device that uses positive toner, if a urethane acrylate resin coating film having a relatively strong positive polarity is provided on the sleeve surface, the amount of charge of the positive toner decreases, but by incorporating Teflon powder, the toner is well charged. Became. In addition, the electric charges on the surface of the coating film, which are charged due to the friction between the coating film surface and the toner, are very close to each other and are charged in opposite polarities. It also has the effect.

In this case, Teflon particles having a particle size of about 0.1 to 5 μm are used, and the Teflon particles may be mixed at about 5 to 30 wt%.

Example 3 A case where carbon powder or metal powder is mixed as solid particles will be described.

By setting the volume resistance of the coating film to about 10 ⁶ to 10 ⁹ Ω · cm by using carbon powder or metal powder such as Al or Cu, the electric charge charged on the coating film surface can be released slowly. In this case, it is particularly effective in the case of being easily charged as in a low humidity environment.

〔The invention's effect〕

As described above, the developing device according to the present invention uses the ultraviolet curable resin obtained by mixing solid particles on the surface of the developer supporting member to irradiate the surface with ultraviolet rays to form a surface having fine irregularities on the surface of the developer supporting member. By forming the layer, it is possible to obtain a good image with less abrasion by the toner.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the developing device according to the present invention, and FIG.
The figure is an enlarged view of the surface of the developer supporting member of the embodiment of FIG.
FIG. 3 is a sectional view of a conventional developing device. 1 ... Magnetic blade 2 ... Developer supporting member (sleeve) 3 ... Toner layer, 4 ... Fixed magnet 5 ... Latent image holding member (drum) 6 ... Bias power supply, 7 ... Surface layer 8 ... UV curable resin, 9 ... Solid particles

Claims (5)

[Claims] 1. A latent image holding device, which carries a developer having a chargeable insulating toner on a developer supporting member and conveys the developer to a developing position, and which is arranged so as to face the developer supporting member without contacting the developer supporting member. In an apparatus for developing an electrostatic latent image formed on a member with the above-mentioned developer, a thin film of an ultraviolet curable resin having solid particles dispersed therein is formed on the surface of a developer supporting member, and this is irradiated with ultraviolet rays. The developing device is characterized in that a surface layer having fine irregularities is formed on the surface of the developer supporting member. 2. The developing device according to claim 1, wherein the solid particles dispersed in the ultraviolet curable resin are conductive particles. 3. The developing device according to claim 1, wherein the solid particles dispersed in the ultraviolet curable resin include conductive particles and particles for charge control. 4. The developing device according to claim 1, wherein the solid particles and the ultraviolet curable resin have different charging polarities with respect to the developer. 5. A bias voltage having an AC component is applied to the developer supporting member.
The developing device according to any one of items 1 to 4.