JPS60138574A - Developing device - Google Patents

Abstract

PURPOSE:To form developed image of high quality by using a developer consisting of only nonmagnetic toner and prevent contamination in a machine frame and a waste of toner by pressing a prescribed surface of an elastic blade except the edge against the surface of a developing roll. CONSTITUTION:One end side of the elastic blade 23 is fixed on a base 25 with a fitting screw 24 and the other end side is brought into press contact so that its flank contacts the surface of the developing roll 21 to a fixed area while the edge is not in contact. One end side of the elastic blade 26 is fixed on the base 27, and the other end side is pressed against the roll 21 as well as the blade 23. Then, when the roll 21 and a photosensitive body 33 are rotated, toner 28 in a toner container 28 is specified with the blade 23 into a thin layer and also charged negatively by friction, and toner carried according to the rotation of the roll 21 comes close to an electrostatic latent image on the drum 33 and scatters to stick on the surface of the drum 33, thereby forming the developed image.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a developing device, and more specifically, in an electrophotographic device or an electrostatic recording device, an electrostatic latent image formed on a photoreceptor or a dielectric material is transferred to a non-magnetic toner. This invention relates to an improvement in a developing device that produces a visible image using a one-component developer consisting of only one component.

[Technical background of the invention and its problems]

This type of developing device has undergone technological advances, including those that use a two-component developer consisting of toner and carrier, and those that use a single-component developer that consists only of magnetic toner. A developing device using a one-component state image side made only of non-magnetic toner has been developed, which can eliminate the drawbacks of the above. However, since non-magnetic toner is used, the only major problem is that it is difficult to stably form a uniform thin toner layer on the surface of the movable wound carrier. Practical implementation was hindered.

Based on these advantages, the present inventors have already invented the developing device shown in FIG. 1 (Japanese Patent Application No. 155934/1982) and succeeded in making it possible to form a thin layer of nonmagnetic toner.

In this invention, a rubber blade 2 as an elastic blade is attached to a developing roll 1 as a movable sight and an image side carrier so that its free end, that is, the surface excluding the edge located on the downstream side of the developer flow, faces the roll 1. By arranging the toner containers 3 and 2 in contact with each other, for example, a thin toner layer is formed by applying the toner from the toner container 3 to the toner 2 onto the surface of the developing roll 1. This is a device that develops electrostatic latent images.

According to the above-mentioned developing device, it is possible to set a large contact area between the developing roll surface and the elastic blade, and since the edge of the elastic blade does not come into contact with the developing roll surface, it is possible to prevent pressure from being applied locally. It can be avoided. As a result, it is possible to alleviate the non-uniformity of the pressure contact force caused by subtle imperfections in setting conditions or machine precision, wear, etc., making it possible to form a more uniform developer layer. In addition, since the contact area between the developing roll surface and the elastic blade is large, when the image side passes through this contact area, it is subjected to friction under pressure contact force for a long time. The image forming agent is provided with a uniform and sufficient triboelectric charge.

Therefore, it is possible to form a uniform thin layer of developer having sufficient charge, so that the electrostatic latent image can be developed satisfactorily.

However, subsequent experiments by the present inventors revealed the following problems with the above-mentioned developing device.

That is, according to the same invention, as shown in FIG. 1, a toner container 3 is constituted by a part of the surface of the f[j roll 10, the elastic blade 2, the rigid metal piece 6, and the side wall 7. The rigid metal piece 6 has a minute gap, for example 0, between the fA image crawls 1.
．． 111111 is fixed across the gap, and the toner (
As the developing roll 1 rotates, residual toner (hereinafter referred to as residual toner) slips through this gap and returns to the toner container 3. However, since the metal piece 6 is a rigid body, the following problems arose.

■ To prevent the toner in the container from melting away, the gap between the developing roll 1 and the rigid metal piece 6 must be kept to a very small value of 0.1 fl or less, and sophisticated machinery is required to manufacture and assemble the parts. O ■ During repeated development, the gap between the developing roll 1 and the rigid metal piece 6 may become clogged with toner particles≠ aggregates or foreign matter. Toner adheres to the surface of the developing roll 1 due to frictional heat and pressure between the toner and the developing roll 1. Such stuck objects are
Since static latent fib cannot be transferred, the image quality of the developed image deteriorates. However, the adhered matter prevents the elastic blade 2 from forming a uniform layer of toner, causing background fog, white spots, etc. to appear on the image.

As described above, since the rigid metal piece 6 is a rigid body, it deteriorates the image quality and causes a problem in the reliability of the apparatus.

On the other hand, in the toner powder applicator disclosed in JP-A-53-23638, a flexible blade is used as a device corresponding to the above-mentioned elastic blade 2 and rigid metal piece 6. By strongly pressing the edge of the toner against the developing roll, a uniform layer of toner is applied to the surface of the developing roll and a toner container is formed. In this invention, by using a flexible blade instead of a rigid metal piece, it is possible to solve some of the above-mentioned problems, especially the problem (2) above. The following problems still remain with the device.

■ When the edge of the blade is pressed against the surface of the object roll, the nip width is very narrow and the contact pattern is almost line contact. When forming a thin layer of toner using this contact method, the pressure force is concentrated on the edge of the blade, so the shape of the edge, wear condition, contact condition, etc. may have a subtle effect on the uniformity of the thin layer formed. This makes it difficult to stably form a uniform layer of toner with a constant thickness. 1. For the same reason that the pressing force is concentrated, the toner layer must be very thin, which has the disadvantage that the image density of the developed image will be insufficient.

Furthermore, when applying a charge to the toner by frictional charging with the developing roll or blade, in the conventional method described above, the contact area between the developing roll and the blade is small, so the developer does not adhere to the surface of the developing roll. It is not possible to obtain sufficient triboelectric charge when passing through the contact portion of the developer roll and blade.

(2) The toner that contributes most to the development of the latent image remains on the surface of the developing roll and is conveyed, passing under the blade and returning into the toner container. Therefore, the pressure of the blade must be set directly within a range that allows residual toner to pass through and does not allow toner in the container to leak out of the container. When using the edge of the blade, it is difficult to maintain such an appropriate pressure uniformly and stably, and due to subtle changes in the shape of the edge, wear condition, contact condition, etc., residual toner on the surface of the developing roll may A situation may occur in which the passage of toner is blocked or the toner in the toner container is allowed to leak. For these reasons, the pressure, contact condition, and wear condition of the blade must be extremely strictly controlled, and a great deal of effort must be spent on maintenance of the device.

As mentioned above, developing devices that use a single-component developer that uses only non-magnetic toner cannot apply magnetic force to the toner, so they have two major problems: creating a uniform thin layer of toner. It has been said that it is difficult to put it into practical use because it is difficult to form and the toner C7 leaks from the toner container or developing roll.

[Purpose of the invention]

The present invention aims to provide a developing device that can stably obtain high-quality images using a one-component nonmagnetic developer.

[Private invention]

The present invention relates to a developing roll that rotates while carrying a one-component developer consisting only of non-magnetic toner on its surface and develops a latent image by supplying the developer to an electrostatic latent image; a first elastic blade disposed so as to be in pressure contact with the surface of the developing roll in order to uniformly apply the developer to the surface; and a part of the surface of the object roll and the first elastic blade for developing. and a second elastic blade disposed in pressure contact with the surface of the developing roll so as to form a developer container, the first and second elastic blades having a predetermined surface other than their edges. By disposing the developing roll so as to be in pressure contact with the surface, it is possible to stably form a uniform and sufficient density image, and to obtain a developing device that is free from toner and blemish. Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to FIG.

Reference numeral 21 in the figure is a developing roll supported rotatably in the clockwise direction (arrow), and the developing roll 21 is connected to a DC power supply 22, and a developing bias of 100V is applied. There is. The developing roll 21 is made by roughening the surface of an aluminum cylinder having a diameter of 24 fi by sandblasting, and further has a 5 μm thick layer on the surface.
hard chrome plating with a final surface roughness of 3 μm. Here, the surface roughness is JIS standard 10
Based on point average roughness (JISBO 601). In addition, 23 in the figure has a thickness O, ? 1I11゜Length Q 7 Q r
ran, the first elastic grade consisting of a phosphor bronze plate with a width of 35+Im. One end of the elastic blade 23 is fixed to a support 25 by a screw 24, and the other end is used for developing so that a certain area of its side surface is in contact with the surface of the developing roll 21. It is pressed against the roll 21. However, the edge and free end of the elastic blade 23 do not contact the surface of the developing roll 21. The developing roll 21 of the first elastic blade 23
The pressure contact force P1 is set to, for example, 78'i-/sub. Here, PI is the total pressure Pt of the grade, the length A (27 cm) of the developing roll of the Boulade in the rotational axis direction, the linear pressure calculated as Pt = Pt/4b, and the linear pressure calculated by Pt/4b. It's pressure.

Furthermore, 26 in the figure is a second elastic blade made of a polyester film having a thickness of 75 μm, for example. One end side of this elastic blade 26 is fixed to a support body 27.
Similarly to the first elastic blade 23, the other end is pressed against the developing roll 21 so as to be in contact with anything including the edges. The pressing force P2 of the second elastic blade 26 against the developing roll 2 is set to 1077 cm. The relationship between the pressure contact force PI r P2 between the first elastic blade 23 and the second elastic blade 26 is Px
>P+. 28 in the figure is a toner container that stores toner 29. This toner container 28 is basically located above the developing roll 21, the first. In this embodiment, a pair of elastic blades (not shown) are arranged parallel to the supports 25, 27, the container wall 30, 31, and both ends of the developing roll 21. It is composed of side frames. In addition,
The support body 25.27 and the container wall 30.31 are fixed to the pair of side frames, and the developing roll 21 is also rotatably supported by the same side frames. Furthermore, stirring blades 32 are disposed within the toner container 28 to stir the toner 29 contained therein.
The stirring blades 32 are rotatably supported by the pair of side frames.

The developing device having the above-mentioned configuration is arranged such that the minimum gap between the developing roll 2 and the drum 33 is 0.2 mm with respect to the selenium-based photosensitive drum 33 having an outer diameter of 78 W+, for example. The drum 33 rotates counterclockwise, and an electrostatic latent image having a maximum surface potential of 900 V is formed on its surface by a corona charger and an image exposure device (not shown). In the subject section consisting of such a developing device and a photosensitive drum, "JL image roll 2 and photosensitive drum 33"
When the toner 29 in the toner container 28 is rotated, the toner 29 in the toner container 28 is rotated.
The layer is thinned by the elastic blade 23, and at the same time, a negative electrostatic charge is applied by frictional electrification. Developing port, -21
The toner conveyed as the rotation of the photosensitive drum 33
Approaching the upper electrostatic latent image, the developing roll 21 and the photosensitive drum 3
A developed image is formed by flying through the gap between the drums 33 and 33 by Coulomb force and adhering to the surface of the drum 33.

Accordingly, the developing device having the above structure has the functions and effects listed below.

■ The first and second elastic grades 23.26 are placed in pressure contact with the surface of the developing roll 21 so that a certain area of the j-plane, which does not include any edges, is in contact with the surface of the developing roll 21. 2 and each elastic grade 23.2
6 can be made larger, and since the edges of the elastic blades 23 and 26 are not in contact with the surface of the developing roll 21, it is possible to prevent the pressing force from concentrating on a minute area. Therefore, the appropriate range of the set pressure required for each elastic blade 23.26 is widened, and at the same time, the strictness of the mechanical viscosity required for each blade 23.26 is relaxed.

That is, even if the set pressure of each elastic blade 23, 26 changes or the first elastic grade 23 is worn out due to friction with the developing roll 21, the toner thin layer by the first elastic blade 23 The formation of is maintained in good condition. The residual toner on the surface of the developing roll 21 is
The toner particles pass under the elastic blade 26 and are returned to the toner container 28 without falling apart (hereinafter, this process is referred to as residual toner recovery). Furthermore, the toner 2 in the toner container 28
9 can be prevented from falling outside the container 28.

■ First elastic blade 23 and second elastic blade 2
6 on the surface of the developing roll 21 so that the pressing force PI of the first elastic blade 23 against the developing roll 21 and the pressing force P2 of the second elastic blade 26 satisfy Pi > p2, the residual toner can be collected. You can definitely go there. In other words, the pressure contact force P by the first elastic blade 23
The thin toner layer formed by passing under the second elastic blade 26 is now able to pass under the second elastic blade 26 whose pressing force P2 is smaller than the contact P1.

■ If the first elastic blade 23 is made of a phosphor bronze plate, the bending elastic modulus is generally larger than that of an elastic material such as rubber, so the pressure contact force can be made uniform, and a uniform toner layer can be formed. It becomes possible. In addition, the first elastic grade 23
It is possible to electrically short-circuit between the first elastic blade 23 and the developing roller 21, thereby preventing the first elastic blade 23 from being charged up, and thus always imparting a constant triboelectric charge to the toner.

Furthermore, for the second elastic grade, residual toner can be efficiently collected by using a metal plate such as a phosphor bronze plate.

(2) Since the second elastic blade 26 is made of an elastic body, aggregated toner and foreign matter do not get stuck between the blade 26 and the developing roll 21, and therefore, toner sticking on the surface of the developing roll 21 can be prevented.

In fact, in the developing device shown in Figure 2, the electrical resistance is approximately 1
When using non-magnetic toner of 00・α, the developing roll 21
It was confirmed by the real part that a thin toner layer of about 50 μm was formed on the surface of the toner, and that the toner at that time had acquired a negative charge of 5 μe/9−. The non-magnetic toner used was made up of particles with an average particle diameter of 13 μm made of polyester resin, and contained ξ carbon in the resin, with hydrophobic silica powder adhered to the surface. .

Further, the photosensitive drum 33 is
When developed, the image density was 1.5° and the resolution was 5 Jlp.
It was possible to form a good developed image with no background spots. Images transferred to plain paper and fixed by a heat roll were also of high quality.

Furthermore, the developing device shown in FIG. 2 is installed in the copying machine, and B
When a run-and-back test was carried out equivalent to copying 10,000 sheets of plain paper of 4 sizes, no toner adhesion was observed on the surface of the developing roll 21, and there was no toner spillage, and good development was maintained. This was confirmed. Moreover, the charged area of the toner layer formed on the surface of the developing roll 21 was maintained within the range of 5±1 μc/9−, and no fluctuation was observed in the toner flight characteristics at the developing position.

〔Effect of the invention〕

As described in detail above, according to the present invention, high quality developed images can always be formed using a developer that has only non-magnetic toner.
Moreover, it is possible to provide a developing device that can prevent contamination of the interior of an image recording device such as a photographic machine due to toner from a toner container and breakage, and can prevent waste of toner.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a conventional developing device, and FIG. 2 is a schematic diagram showing an embodiment of the developing device according to the present invention. 21... Developing roll, 23... First elastic blade, 26... Second elastic blade, 28... Toner container, 29... Toner, 33... Photosensitive drum.

Claims (4)

[Claims] (1) A developing roll that rotates while carrying a one-component developer consisting only of non-magnetic toner on its surface and develops the latent image by supplying the developer to the electrostatic latent image;
a first elastic blade disposed so as to be in pressure contact with the surface of the developing roll in order to uniformly apply the developer to the surface of the developing roll; together with a part of the surface of the developing roll and the first elastic blade; and a second elastic blade disposed in pressure contact with the surface of the developing roll to form a developer container. A developing device, characterized in that the developing device is disposed so that its surface is in pressure contact with the surface of the developing roll. (2) When the pressure contact force of the first elastic blade with respect to the developing roll is Pl, and the pressure contact force of the second elastic blade with respect to the developing roll is P2, the above-mentioned 1° and the second elastic blade are relative to the developing roll p , >p2. The developing device of claim 1, wherein the developing device is arranged so that the following relationship is satisfied. (3) The developing device according to claim 1 or 2, wherein at least one of the first and second elastic blades is made of an elastic metal plate. (4) The developing device according to claim 3, wherein the elastic metal plate is made of phosphor bronze.