JPS6296977A - Developer thin layer forming device - Google Patents

Abstract

PURPOSE:To obtain good images without ground fog by forming circulation of a minute quantity of magnetic particles near the front end part of a blade to agitate a developer to be stuck to the surface of a developer carrier. CONSTITUTION:When a sleeve 3 is rotated in the direction of an arrow (b), magnetic particles 7 are carried in the rotation direction of the sleeve 3 while being restrained by the magnetic field formed with a magnet 4. Magnetic particles 7 are dropped to a part near a magnetic pole 5 by gravity and magnetic force, and at this time, magnetic particles 7 are not only circulated near the end face of an elastic body blade 6 but also oscillated intensively near the magnetic pole 5. A developer 8 is agitated in a vessel 2 and is charged frictionally by rubbing against magnetic particles 7, and the developer 8 is charged frictionally furthermore by rubbing against the surface of the sleeve 3 and the elastic body 6 when passing the contacting part between the elastic body blade 6 and the sleeve 3. Thus, the image density of a developed image is secured and ground fog is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developer thin layer forming device that can be used in a developing device that develops an electrostatic latent image using a non-magnetic developer.

Various types of dry-component developing devices have been proposed and put into practical use. However, in any of the development methods, it is extremely difficult to form a thin layer of dry-component developer, and for this reason, a developing device has been constructed by forming a relatively thick layer. However, as improvements in the clarity, resolution, etc. of developed images are currently being sought, it is essential to develop a method for forming a thin layer of a dry component developer and an apparatus therefor.

As a method of forming a thin layer of a conventionally known dry component developer, Japanese Patent Application Laid-Open No. 54-43037 has been proposed and has been put into practical use. However, this concerned the formation of a thin layer of magnetic developer. In order to make magnetic developers magnetic, a magnetic material must be added inside them, which causes poor fixing properties when heat fixing the developed image transferred to transfer paper.
Since a magnetic material (the magnetic material is usually black) is added to the developer itself, there are problems such as poor color reproduction during color reproduction.

For this reason, as a method for forming a thin layer of non-magnetic developer, there are two methods: using a cylindrical brush made of soft bristles like beaver's hair, and applying the developer to the brush. A method of coating the developing roller with a doctor blade or the like has been proposed. However, when an elastic blade is used as a doctor blade for the above-mentioned fiber brush, it is possible to regulate the amount of developer, but uniform application is not achieved, and the fibers of the brush are simply rubbed by the fiber brush on the developing roller. Since no triboelectric charge is imparted to the developer present in between, there is a problem in that fogging and the like are likely to occur.

In addition, in this type of development method, since the developer comes into contact with the surface of the image carrier regardless of the presence or absence of an electrostatic image, developer adhesion occurs even in non-image areas, that is, areas with no electrostatic charge. Insufficient amount of developer tends to adhere to non-image areas, resulting in fogging and resulting in poor images.

l1 Nijo J The present applicant has developed a developing device that is completely different from the conventional method described above, using a non-magnetic developer and magnetic particles, and providing a magnetic particle restraining member opposite to a developer holding member. Regarding the moving direction, a magnetic brush of magnetic particles is formed upstream of the magnetic particle restraining member by the magnetic force of the magnetic field generating means, the magnetic brush is restrained by the magnetic particle restraining member, and a thin layer of non-magnetic developer is transferred to the developer holding member. We have already proposed an apparatus for forming a thin layer of developer.

The present invention further improves this developer thin layer forming device, ensures good binding properties and stability of magnetic particles with a simple configuration, and stably forms a thin developer layer on the surface of a developer holding member over a long period of time. An object of the present invention is to provide a developer thin layer forming device that can form a good copy image.

A further object of the present invention is to provide a developer thin layer forming apparatus that has a simple configuration and is capable of producing good copy images without blurring.

According to the present invention, there is provided a developer supply container having an opening and containing a developer and a small amount of magnetic particles, and a non-container provided in the opening and capable of moving endlessly inside and outside the container. a magnetic developer holding member, a magnetic field generating means provided inside the developer holding member, and a magnetic pole of the magnetic field generating means such that the magnetic pole comes into contact with the developer holding member at a downstream position in the rotational direction of the developer holding member. a blade having an end biased toward the developer holding member, the blade being inclined downstream from the end in the rotational direction, and elastically abutting the developer holding member; Since there is provided a developer thin layer forming device which is characterized in that it moves endlessly to form a thin layer of developer on the developer holding member downstream of the blade in the direction of movement of the holding member, it has a simple structure. Since the developer can be sufficiently charged while ensuring good binding of the magnetic particles, it is possible to provide a good image without background fog.

FIRST EXAMPLE FIG. 1 is a partial sectional view of a developer thin layer forming apparatus according to an embodiment of the present invention.

In this embodiment, the developer thin layer forming device develops an electrostatic latent image on a photoreceptor 1, which serves as a latent image carrier and rotates in the direction of arrow a. The photoreceptor 1 may be, for example, a so-called xerographic photoreceptor on which an electrostatic latent image is formed using the Carlson process, or a photoreceptor having an insulating layer on the surface on which an electrostatic latent image is formed using the NP process described in Japanese Patent Publication No. 42-23910. , an insulator on which a latent image is formed by an electrostatic recording method, an insulator on which an electrostatic latent image is transferred by a transfer method, an electrostatic latent image (or potential latent image) or a magnetic latent image is formed and retained by any other appropriate method. It is a member that has been installed.

The developer thin layer forming device includes a developer supply container 2, a sleeve 3 as a developer holding member, a magnet 4 as a magnetic field generating means, and an elastic blade 6.

The container 2 has an opening extending in the longitudinal direction (direction perpendicular to the plane of the paper) of the developer thin layer forming device, and a developing sleeve 3 as a developer holding member is provided in the opening. Made of non-magnetic material such as aluminum. sleeve 3
In the figure, it is installed horizontally in the opening with its right half-circumferential surface extending into the container 2 and its left half-circumferential surface exposed outside the container so that it can freely rotate on a bearing, and is driven to rotate in the direction of the arrow. . The developer holding member 3 is not limited to the above-mentioned cylindrical body (sleeve), but may be in the form of a rotationally driven endless belt, or may be a conductive rubber roller. face or are in contact with the surface of the photoreceptor l with a small gap.

The magnet 4 is a fixed permanent magnet provided in the developing sleeve 3 in this embodiment, and even when the sleeve 3 is rotated, it maintains a fixed position and attitude and generates a fixed magnetic field. This magnet 4 has a magnetic pole 5 (N pole). As the magnet 4, an electromagnet may be provided instead of a permanent magnet.

The elastic blade 6 is provided in contact with the outer surface of the sleeve 3. The contact point is located downstream of the position of the magnetic pole 5 of the magnet 4 in the direction of rotation of the sleeve 3, and the elastic blade 6 is provided inclined toward the downstream side (that is, opposed to the direction of rotation of the sleeve).

The magnet 4 has at least one magnetic pole upstream of the contact point.

Further, a small amount of magnetic particles 7 and developer 8 are placed inside the container 2, and the magnetic particles 7 are restrained on the surface of the container 2 by the action of the magnetic field of the magnet 4, forming a magnetic brush. There is. Here, the term "very small amount" refers to a very small amount that exists only in the vicinity of the regulating blade with respect to the surface of the developer carrier at the opening of the developer supply container, and more specifically, a minute amount that exists near the regulating blade and that is present in the vicinity of the blade. The amount is such that the surface of the agent carrier is hardly covered with magnetic particles and is open to the developer. More specifically, this release is such that 90% or more of the surface of the developer carrier is released from the magnetic particles in the vicinity of the blade portion. A small amount of magnetic particles are contained in the developer container near the tip of the blade, which is brought into contact with the surface of the developer carrier. At the same time, a thin layer of developer is formed on the surface of the developer carrier leading to the developing section.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

When the sleeve 3 rotates in the direction of the arrow A, the magnetic particles 7 are conveyed in the direction of rotation of the sleeve 3 while being restrained by the magnetic field formed by the magnet 4. However, the magnetic particles 7 are prevented from being conveyed by the ends of the elastic blades 6 and released outside the container 2, and fall toward the vicinity of the magnetic poles 5 due to gravity and magnetic force. At this time, the magnetic particles 7 circulate near the end face of the elastic blade 6 and vibrate violently near the magnetic pole 5.

Since the amount of magnetic particles is very small, this vibration is violent due to the conveying force of the sleeve 3, the reversing force of the blade 6, the pullback force of the magnetic force, and the pullback force of gravity. On the other hand, the developer 8 mixed between the magnetic particles 7 enters the contact portion between the elastic blade 6 and the sleeve 3 and is conveyed on the surface of the sleeve 3 to the outside of the container.

As the magnetic particles 7 circulate and vibrate, the developer 8 is stirred inside the container 2 and at the same time rubs against the magnetic particles 7, thereby being triboelectrically charged. Furthermore, when the developer 8 passes through the contact portion between the elastic blade 6 and the sleeve 3, it is rubbed against the surface of the sleeve 3 by the elastic blade 6, and is further subjected to frictional electrification. In this way, the developer 8 can receive sufficient triboelectric charging. As a result, image density can be ensured in the developed image, and background fog can be further reduced.

The developer 8 that has been sufficiently triboelectrically charged in this way passes through the contact portion, is formed as a thin layer of developer on the sleeve 3, and is carried on the sleeve 3 to a developing section facing the photoreceptor 1. In the developing section, some of the developer is consumed by the developing operation, and other developer is recovered from the lower part of the sleeve 3 as the sleeve 3 rotates. A sealing member 9 is provided in this recovery portion to allow the developer not consumed during development to pass into the container 2, and also to prevent the magnetic particles 7 and developer 8 in the container z from leaking from the lower part of the container 2. 0 The collected developer on the sleeve 3 is magnetic particles 7.
The developer is once scraped off by the circulation and vibration of the developer, and then stirred and mixed by the magnetic particles 7, and then applied again as a thin layer of developer onto the surface of the sleeve 3. In this way, the developer not consumed during development is once scraped off from the surface of the sleeve 3, so regardless of the variation in the amount of developer remaining on the surface of the sleeve 3 after development, the surface after passing through the contact area A thin layer of developer of uniform thickness is formed thereon. In addition, since the developer is once scraped off in this way, the sleeve 3
Since the upper developer is replaced, excessive charging of the developer, that is, charge-up is prevented.

The developing method is, for example, the method described in Japanese Patent Publication No. 58-32375, in which a minute gap is provided between the photoreceptor 1 and the developing sleeve 3, and an alternating current with a superimposed direct current is applied between them. A method in which a thin layer of the developer described above is imagewise transferred to an electrostatic latent image on a photoreceptor can be used, but a contact development method can also be used.

Next, the elastic blade 6 will be explained in detail.

FIG. 2 is a sectional view of the vicinity of the elastic blade of the developer thin layer forming device when the present invention is not used.

In this figure, the elastic blade 6 is tilted upstream with respect to the rotational direction of the sleeve 3 (forward direction with respect to the sleeve rotational direction). In this configuration, when the sleeve 3 is rotated, the magnetic particles 7 are The area near the tip of the body blade 6 is clogged, and the magnetic particles 7 are not circulated or vibrated, and therefore sufficient triboelectric charging is not achieved. It has been found that because the developer cannot be taken in sufficiently, unevenness tends to occur in the thin developer layer.

In addition, the magnetic particles 7 enter the contact portion between the elastic blade 6 and the sleeve 3, and as a result, the contact pressure between them becomes non-uniform, and streak-like unevenness occurs in the formed developer thin layer. Furthermore, in this case, the magnetic particles 7 are partially pressed against the sleeve 3, causing damage to the surface of the sleeve 3.

FIG. 3 is a sectional view of the vicinity of the elastic blade of the developer thin layer forming device when the present invention is used. In the configuration shown in this figure, the elastic blade 6 is tilted downstream in the direction of movement of the sleeve 3 (opposed to the direction of rotation of the sleeve). In this configuration, the magnetic particles 7 transported by the rotation of the sleeve 3 are It was confirmed that the magnetic particles 7 are lifted upward by the tip of the elastic blade 6, fall near the magnetic pole 5 due to gravity and magnetic force, and can repeat the circulation in the direction of arrow C, and that the magnetic particles 7 vibrate significantly near the magnetic pole 5. Ta.

Due to the circulation and vibration of the magnetic particles 7, the developer is sufficiently triboelectrically charged and is stably supplied onto the surface of the sleeve 3 from the top of the container 2. Further, due to the above-mentioned action, residual developer on the sleeve 3 can be scraped off, so that in combination with the effect of using the elastic blade described above, a thin layer of developer with a uniform thickness can be stably formed.

Next, as the material of the elastic blade 6, for example, JIS
Rubber having a hardness of 40 to 80°, preferably 50 to 70°, is suitable for stably forming a thin developer layer. The elastic blade 6 preferably has a certain thickness in order to prevent the magnetic particles 7 from riding on the back surface of the elastic blade 6, and according to the inventor's experiments and considerations,
It is 1 mm or more, preferably 2.0 mm or more.

FIG. 4 is a cross-sectional view showing the elastic blade mounting configuration.
Since the elastic blade 6 is pressed against and in contact with the surface of the sleeve 3, it is deformed as shown. This urges the end of the blade 6 to come into contact with the sleeve 3. Note that the term "blade end" as used herein refers to the tip of the blade, the vicinity including the tip, or the vicinity of the tip not including the tip.

The blade 6 is inclined downstream in the rotational direction of the sleeve from the end. The zero dotted line indicates the state of the elastic blade 6 assuming that the sleeve 3 does not exist. The straight line m is a vertical line passing through the center of the sleeve 3. n is a straight line passing through the contact portion Q of the elastic blade 6 and the sleeve 3 and the center of the sleeve 3, and the straight line is a straight line passing through the center of the sleeve 3 and the center of the magnetic pole 5.

0 plane T, where the angle between straight line m and straight line n is X, and the angle between straight line n and straight line is y, is the elastic blade 6 in a state where the elastic blade 6 is in contact with the sleeve 3 and is not deformed.
0 point P, which is the bottom surface of the sleeve 3, is the cross section of the intersection of the surface T and the surface of the sleeve 3, the angle θ is the angle between the tangent of the sleeve 3 passing through point P and the surface T, and the distance d is the cross section of the intersection between the surface T and the surface of the sleeve 3. This is the length that extends inside. Here, straight line m passes through point P, but
This is not necessarily necessary.

The angle θ is set at 40° from θ°, preferably from 2″ to 2°, in order to prevent problems such as the elastic blade 6 bending back due to frictional force when the sleeve 3 rotates.
0” range.

Further, the penetration amount d of the elastic blade 6 is preferably 0.5 to 2 mm, and it is preferable that the edge portion of the tip of the elastic blade 6 is in contact with the sleeve 3. This is because it has been found that if the edge of the tip is separated from the surface of the sleeve 3, the magnetic particles 7 will enter this gap, impairing the uniformity of contact pressure and potentially damaging the surface of the sleeve 3. .

Furthermore, it is preferable that the angles X and y satisfy the following conditions.

X≧O y＞.

Regarding z + y < 90° angle Due to the relationship of zero gravity, the angle
The preferred range of is 5<x<40''.

Regarding the angle y, it has been found that when y≦0°, the magnetic particles 7 stick to the vicinity of the tip of the elastic blade 6, preventing circulation and vibration, which is not preferable. In addition, 30
It has been found that particularly good circulation and vibration occur when <y<60°, which is preferred.

Regarding the angle x+y, if x+y>90°, the magnetic particles 7 will not be transported well on the sleeve 3 to the elastic body play 16 position, and the magnetic particles 7 will be moved inside the sleeve 3 due to gravity.
It has been found that the circulating and vibrating magnetic particles 7 no longer exist immediately before the dispersing elastic body brake roller, which is undesirable.

From the above considerations, more preferable ranges are as follows.

5@<x<40°30"<y<so@x+y<90" In this range, sufficient circulation and vibration of the magnetic particles 7 can be obtained, and therefore stable developer application can be obtained.

The surface of the sleeve 3 is preferably provided with minute irregularities rather than a mirror surface from the viewpoint of circulation and vibration of the magnetic particles 7.

As the magnetic particles 7, iron powder, ferrite powder, etc. can be used. Furthermore, it is more preferable that these are coated with a resin in accordance with the charging polarity of the developer 8.
The magnetic particles 7 may have a particle size of 50 to 200 gm. It was confirmed that if it is less than 50 gm, the fluidity of the magnetic particles 7 is poor, sufficient circulation and vibration cannot be obtained, the amount of developer 8 taken in is reduced, and a stable thin layer of developer 8 is not formed. In addition, if the particle size is 200 gm or more, although the developer 8 can be sufficiently supplied, the frictional charging is not sufficient, so it is not preferable.
0 to 150 pm is particularly preferred in order to obtain sufficient circulation and vibration of the magnetic particles 7.

FIG. 5 is a sectional view of a specific example of a developing device using the developer thin layer forming device according to the present invention. In this figure, the same reference numerals as in FIG. 1 are given to corresponding members and means, so detailed explanations thereof will be omitted.

The sleeve 3 used was an aluminum acid sleeve with a diameter of 20 mm whose surface was subjected to amorphous sandblasting with 7 random abrasive grains, and the magnet 4 used had a magnetic flux density peak value of 800 Gauss and a half width of 60°. The elastic blade 6 used was made of silicone rubber (rubber hardness JIS 60@, thickness 2 mm). These mounting positions are θ=10@, d=l, Omm, x=15
°, y=50°.

The magnetic particles have a particle size of 100 to 804 m (150/20
0 mesh) iron particles (maximum magnetization = 190 emu/g
) coated with acrylic and fluorine resin, and the developer is a toner with an average particle size of 13 ILm consisting of 100 parts of a copolymer of styrene/acrylic resin and styrene-butadiene resin and 5 parts of perylene red pigment. It is said that a red toner with 1.0% colloidal silica added externally to the powder was used.
A uniform coating layer of 0 Bm was obtained. When the amount of charge on this layer was measured using the blow-off method, the amount of charge was +12 g c
/g, which is a sufficient value.

The developing method used here is
A voltage is applied between the electrophotographic photoreceptor and the sleeve 3 by a bias power source.

The bias power supply may be alternating current or direct current, but preferably one in which direct current is superimposed on alternating current.The developing method is not limited to this, and development may be performed by bringing a thin layer of developer into contact with the photoreceptor l.

This developer thin layer forming device was installed on a PC manufactured by Canon Corporation.
-20 built into a copying machine, frequency 16 as a bias power supply
Using an AC voltage with a peak-to-peak voltage of 1300 Hz and a DC voltage of -300 V superimposed, the surface potential of the latent image 1 on the photoreceptor was set to -540 V in the dark area and -220 V in the bright area.
When development was carried out with the distance between the sleeve 3 and the photoreceptor 1 (organic photoconductor) set to 2504 m, a good red image with a reflection density of 1.2 could be obtained.

Furthermore, when images were continuously formed on 1000 sheets, good images without sleeve ghosts could be obtained up to the final image formation.

In order to investigate the influence of the amount of magnetic particles in the developer thin layer forming apparatus of the present invention, development unevenness (sleeve ghost) in the case of a solid black image was measured by reflection density. Table 1 shows the results.
Shown below.

Table 1: When magnetic particles are not present, development unevenness is significant; 0.01 to 0.5 g per unit length (longitudinal direction) of the developing sleeve
/cm (The total amount of magnetic particles (g) present in the space inside the container sandwiched by the plane connecting the center line of the sleeve 3 and the tip of the blade 6, and the plane connecting the center line of the sleeve 3 and the center line of the magnetic pole. At a concentration of 1.0 g/cm (value divided by the effective length (cm) of the sleeve), the uneven development is barely noticeable to the naked eye, and at 1.0 g/cm, the uneven development becomes noticeable again.

Because only a small amount of magnetic particles (0.01 to 0.5 g/cm) is used per unit length, the magnetic particles are strongly restrained by the magnetic poles, and even if a strong impact is applied to the developer thin layer forming device, the magnetic particles will not be biased. A stable thin layer can be obtained without any problems.

Although a non-magnetic developer was used in the above embodiment, a magnetic developer can also be used as long as it has weaker magnetism than magnetic particles and can be triboelectrically charged.

Furthermore, as shown in FIG. 6, the number of magnetic poles of the magnet 4 in the sleeve 3 is further increased, and a magnetic pole is also provided on the photoreceptor 1 side.
As the sleeve 3 rotates, a small amount of magnetic particles passing under the elastic blade 6 may be transported and collected into the sleeve 3.

As explained above, according to the present invention, a developer S layer having a uniform developer layer thickness and a uniform and sufficient amount of triboelectric charge is stably formed, and this developer thin layer By using this in the developing operation, good images can be stably obtained.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a developer thin layer forming apparatus according to an embodiment of the present invention. FIG. 2 is a sectional view of the vicinity of the elastic blade of the developer thin layer forming device when the present invention is not used. FIG. 3 is a sectional view of the vicinity of the elastic blade of the developer thin layer forming device when the present invention is used. FIG. 4 is a sectional view showing the mounting structure of the elastic plate. FIG. 5 is a sectional view of a specific example of a developing device using the developer thin layer forming device according to the present invention. FIG. 6 is a sectional view of a developer thin layer forming apparatus according to another embodiment of the present invention. 11 Stand 1" l: Photoreceptor 2: Container 3 Ni Sleeve 4: Magnet 5: Magnetic pole 6: Elastic blade Figure 1 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] A developer supply container having an opening and containing a developer and a small amount of magnetic particles, and a non-magnetic developer provided in the opening and capable of moving endlessly inside and outside the container. a holding member; a magnetic field generating means provided inside the developer holding member; and a magnetic pole of the magnetic field generating means that is biased so as to come into contact with the developer holding member at a downstream position in a rotational direction of the developer holding member. a blade that is inclined downstream from the end in the rotation direction and elastically contacts the developer holding member; and a blade that moves the developer holding member endlessly. A developer thin layer forming device, characterized in that a thin layer of developer is formed on a developer holding member downstream of the blade in the moving direction of the holding member.