JPH0575113B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD 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. BACKGROUND ART Conventionally, various devices have been proposed and put into practical use as dry one-component developing devices. However, in any of the development methods, it is extremely difficult to form a thin layer of dry one-component developer, and for this reason, a developing device has been constructed by forming a relatively thick layer. However, as improvements in the clarity and resolution of developed images are currently being sought, it is essential to develop a method for forming a thin layer of a dry one-component developer and an apparatus therefor. As a method of forming a thin layer of a conventionally known dry type one-component developer, Japanese Patent 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. Magnetic developers must have a magnetic substance added to them to have magnetism, and this is due to poor fixing properties when thermally fixing the developed image transferred to transfer paper, and because the developer itself contains magnetic substances (magnetic substances do not contain magnetic substances). Since the color (usually black) is added internally, 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 is a method of using a cylindrical brush made of soft bristles like beaver hair and applying the developer to it.
A method has been proposed in which the coating is applied to a developing roller whose surface is made of fibers such as velvet using a doctor blade or the like. 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 fog and resulting in poor images. Purpose of the Invention The present applicant uses a non-magnetic developer and magnetic particles as a developing device that is completely different from the conventional method described above.
A magnetic particle restraining member is provided opposite to the developer holding member, and a magnetic brush of magnetic particles is formed by the magnetic force of the magnetic field generating means upstream of the magnetic particle restraining member with respect to the moving direction of the surface of the holding member. A developer thin layer forming apparatus has already been proposed in which a magnetic brush is restrained by a particle restraining member and a thin layer of non-magnetic developer is formed on a developer holding member. 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 makes it possible to stably form a thin developer layer on the surface of a developer holding member over a long period of time. It is an object of the present invention to provide a developer thin layer forming device that can form a thin layer of developer and obtain 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 can produce good copy images without background fog. SUMMARY OF THE INVENTION According to the present invention, there is provided a developer supply container having an opening and containing a developer and a minute amount of magnetic particles, and a non-magnetic container provided in the opening and capable of endlessly moving inside and outside the container. A developer holding member, a magnetic field generating means provided inside the developer holding member and generating a temporally varying magnetic field, and an end portion urged to come into contact with the developer holding member. a blade that is inclined from the end toward the downstream side in the rotational direction and elastically contacts the developer holding member; A developer thin layer forming device is provided, which forms a thin layer of developer on a developer holding member downstream of the blade in the direction of the blade, thereby ensuring good magnetic particle restraint with a simple configuration. While doing so,
Since the developer can be sufficiently charged, it is possible to provide a good image without background fog. Embodiment 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 includes a photoconductor 1 as a latent image carrier rotating in the direction of arrow a.
This is to develop the electrostatic latent image on the top. As the photoreceptor 1, for example, a so-called xerographic photoreceptor, which forms an electrostatic latent image by the Carlson process,
A photoreceptor having an insulating layer on the surface on which an electrostatic latent image is formed by the NP process described in Publication No. 42-23910,
An insulator on which a latent image has been formed using an electrostatic recording method, an insulator on which an electrostatic latent image has been transferred using a transfer method, or an insulator on which an electrostatic latent image (or potential latent image) or a magnetic latent image has been formed and retained using any other appropriate method. It is a member. 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. In the figure, the sleeve 3 is installed horizontally in the opening, with its right half-circumferential surface protruding into the container 2, and its left half-circumferential surface exposed to the outside of the container so that it can freely rotate and is supported by a bearing, and is rotatably driven in the direction of arrow b. be done. The developer holding member 3 is not limited to the above-mentioned cylindrical body (sleeve), but may be in the form of an endless belt that is rotatably driven. Alternatively, a conductive rubber roller may be used. The surface of the developing sleeve 3 exposed outside the container faces or contacts the surface of the photoreceptor 1 with a small gap therebetween. The magnet 4 is rotatably provided within the developing sleeve 3, and in this embodiment is a permanent magnet having a plurality of magnetic poles 5, and is rotatable in the direction of arrow e as the sleeve 3 rotates. The magnetic field formed by the magnetic field changes over time at a fixed position. As the magnet 4, an electromagnet may be provided instead of a permanent magnet. In the present invention, the magnet 4 is assumed to rotate in the opposite direction to the rotation of the sleeve 2, but the invention is not limited to this. The elastic blade 6 is provided in contact with the outer surface of the sleeve 3, and is inclined downstream in the direction of rotation of the sleeve 3 (i.e., opposite to the direction of rotation of the sleeve).
It is provided. Further, a minute amount of magnetic particles 7 and a developer 8 are placed inside the container 2, and the magnetic particles 7 are placed in a magnet 4.
is restrained on the surface of the container 2 by the action of the magnetic field. 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 in the vicinity of the blade and does not cause any development in the vicinity. 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 area where the magnetic particles exist near the blade portion. According to an embodiment of the present invention, a small amount of magnetic particles are contained in the developer container near the tip of the blade that is brought into elastic contact with the surface of the developer carrier, and a small amount of magnetic particles are circulated near the tip of the blade. The developer adhering to the surface of the developer carrier is stirred, and 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 arrow b and the magnet 4 rotates in the direction of arrow e, 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 do not come out of the container 2, but 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 sleeve surface inside the container 2. Here, since the magnet 4 is rotating inside the sleeve 2, the state of the magnetic field inside the container 2 changes over time, and as a result, the magnetic particles vibrate violently near the surface of the sleeve 3. Here, the rotational speed of the magnet is preferably 10 to 1000 rpm, particularly 50 to 500 rpm. On the other hand, the developer 8 mixed between the magnetic particles 7
enters the contact area 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 the vibrations described above occur, the developer 8 is agitated 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 area between the elastic blade 6 and the sleeve 3, it
It is rubbed against the surface 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 seal member 9 is attached to this recovery part.
is provided to allow the developer that has not been consumed during development to pass into the container 2, and to prevent the magnetic particles 7 and the developer 8 in the container 2 from leaking from the lower part of the container 2. The collected developer on the sleeve 3 is once scraped off by the circulation and intense vibration of the magnetic particles 7, and then stirred and mixed by the magnetic particles 7, and then applied again as a thin layer of developer on the surface of the sleeve 3. Ru. In this way, the developer that is 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 of the sleeve after passing through the contact area A thin layer of developer of uniform thickness is formed thereon. Further, since the developer is once scraped off in this manner, the developer on the sleeve 3 is replaced, thereby preventing excessive charging of the developer, that is, charge-up. 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 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 rotates, the magnetic particles 7 become clogged near the tip of the elastic blade 6, preventing circulation and vibration of the magnetic particles 7. Therefore, in addition to insufficient triboelectrification, the container It has been found that because the developer 8 on the upper part of the magnetic particles 2 cannot be sufficiently captured between the magnetic particles 7, 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 inclined 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 conveyed by the rotation of the sleeve 3 are lifted upward by the tip of the elastic blade 6, fall down due to gravity and magnetic force, and can repeat the circulation in the direction of arrow c. It was confirmed that near the tip of the blade 6, the magnetic particles 7 vibrated significantly due to the above-mentioned temporal change in the magnetic field. Due to the circulation and vibration of the magnetic particles 7,
The developer is sufficiently triboelectrically charged and the container 2
is stably supplied onto the surface of the sleeve 3 from the top of the sleeve. Furthermore, due to the above 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. can. Next, as a material for the elastic blade 6, for example, rubber having a JIS hardness of 40 to 80 degrees, preferably 50 to 70 degrees, is suitable for stably forming a thin developer layer. The thickness of the elastic blade 6 is set to prevent the magnetic particles 7 from riding on the back surface of the elastic blade 6.
It is preferable to have a certain degree of thickness, and according to the inventor's experiments and considerations, it is preferably 1 mm or more.
It is 2.0mm or more. FIG. 4 is a cross-sectional view showing the configuration for attaching the elastic blade. 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 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, and the straight line n is a straight line passing through the contact portion Q between the elastic blade 6 and the sleeve 3 and the center of the sleeve 3. Let x be the angle formed by straight line m and straight line n. Surface T is the bottom surface of the elastic blade 6 in a state where the elastic blade 6 is in contact with the sleeve 3 and is not deformed. Point P is plane 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 length of the surface T entering into the inside of the sleeve 3. . Here, straight line m passes through point P, but
This is not necessarily necessary. The angle θ is in the range of 0° to 40°, preferably 2° to 20°, in order to prevent problems such as the elastic blade 6 bending back due to frictional force when the sleeve 3 rotates. . Further, the penetration amount d of the elastic blade 6 is 0.5 to 1
mm is preferable, 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 if the edge of the tip of the elastic blade 6 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. This is because it has become clear. Furthermore, regarding the above angle x, 0≦x<90°
It is preferable that the following conditions are satisfied. When x<0, the direction of gravity at the tip of the elastic blade 6 is directed toward the elastic blade 6, so the magnetic particles 7 tend to stay near the tip of the elastic blade 6, and the magnetic particles 7 It has been found that this prevents good vibration and circulation of particles 7. Due to gravity, the preferred range of angle x is 5<x<40°. In addition, when x > 90°, the magnetic particles 7 are not well conveyed on the sleeve 3 to the position of the elastic blade 6, and due to gravity, the magnetic particles 7 are dispersed within the sleeve 3 and circulate and vibrate just before the elastic blade 6. It has been found that the magnetic particles 7 that do this are no longer present, which is undesirable. From the above considerations, more preferable ranges are as follows. 5°<x<30° 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 even more preferable to coat these with a resin in accordance with the charging polarity of the developer 8. The particle size of the magnetic particles 7 is 50~
200 μm can be used. It was confirmed that when the diameter is less than 50 μm, the fluidity of the magnetic particles 7 is poor, sufficient circulation and vibration cannot be obtained, the amount of developer 8 taken in is small, and a stable thin layer of developer 8 is not formed. Further, in the case of a particle size of 200 μm or more, although the developer 8 can be sufficiently supplied, triboelectric charging is not sufficient, which is not preferable. Within this range, 80 to 150 μm 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. As the sleeve 3, we used an aluminum sleeve with a diameter of 20 mm whose surface was subjected to amorphous sandblasting treatment using alundum abrasive grains, and as the magnet 4, we used 6 magnetic poles with a peak magnetic flux density of 700 Gauss.
A piece having equal parts was used. As the elastic blade 6, silicone rubber (rubber hardness JIS 60°, thickness 2 mm) was used. These mounting positions are θ=
10°, d=1.0mm, and x=15°. The magnetic particles used were iron particles (maximum magnetization = 190 emu/g) coated with acrylic and fluorine resin with a particle size of 100 to 80 μm (150/200 mesh), and the developer was styrene/acrylic resin. Styrene butadiene resin copolymer 100
Average particle size consisting of 5 parts of perylene red pigment
When a red toner in which 1.0% colloidal silica was externally added to a 13 μm toner powder was used, a uniform coating layer of about 50 μm was obtained on the sleeve by the above-mentioned coating action. When the amount of charge on this layer was measured by a blow-off method, the amount of charge was +12 μc/g, which is a sufficient value. The developing method used here is
32375 is preferred. A voltage is applied between the electrophotographic photoreceptor and the sleeve 3 by a bias power source. The bias power source 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 1. This developer thin layer forming device was installed in a PC-20 copying machine manufactured by Canon Inc., and a bias power supply consisting of -300V DC superimposed on an AC voltage with a frequency of 1600Hz and a peak-to-peak voltage of 1300V was used.
The surface potential of latent image 1 on the photoconductor was set to -540V in the dark area and -220V in the bright area, and development was performed with the distance between the sleeve 3 and photoconductor 1 (organic photoconductor) set to 250μm, and the reflection density was We were able to obtain a good red image of 1.2. 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 particle size of magnetic particles in the developer thin layer forming device of the present invention, magnetic particles of various particle sizes were measured at 0.1 g per unit length of the developer holding member.
(2.1g in total) into the developing device, and then add 50g of the red toner mentioned above to make the developing width 210mm.
(corresponding to A4 portrait size) and the results of development are shown in Table 1.

[Table] As a result, for magnetic particles with a particle size of 50 μm or less,
The thin developer layer is very thin, resulting in an image with noticeable uneven development, which is undesirable. At 50 to 100 μm, some unevenness in development was observed, but the images were quite good. Almost good images were obtained at 80 to 100 μm. In the case of 200 μm, fogging was observed, which appeared to be due to insufficient triboelectric charging. Next, to investigate the effect of the amount of magnetic particles,
In the same developing device, 0.2 g of magnetic particles with a particle size distribution of 80 to 150 μm (per unit length of developer holding member (longitudinal direction 0.01 g/cm), 1.0 (0.05), 2.1 (0.1), 10
.Five
(0.5), 21.5 (1.0) Insertion (Total magnetism existing in the space inside the container between 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 The amount of particles (g) divided by the effective length of the sleeve (cm)) and the case where no magnetic particles are added,
When developed using 50 g of the sample, the results shown in Table 2 were obtained.

[Table] According to the results, when no magnetic particles are present and a thin layer is formed only by the elastic blade 6, the development unevenness is significant, but at 0.01 to 0.5 g/cm, the development unevenness is not noticeable. In addition, in this range, the magnetic particles are completely restrained by the magnetic pole 5, and there are no particles that can move freely within the developer thin layer forming device, so when an impact is applied to the developer thin layer forming device, However, the magnetic particles were not biased.
Particularly good results were obtained in the range of 0.05 to 0.1 g/cm.
Moreover, at 1.0 g/cm or more, uneven development, which is thought to be caused by sleeve ghost, becomes noticeable. However, since the magnetic particles are forcibly vibrated by the rotation of the magnet 5, the amount of frictional electrification of the developer is much larger than in areas without a magnet or in the case where the magnet is fixed, resulting in a good image. Summer. From the above experiments and considerations, it is understood that the presence of magnetic particles and their properties are important in the developer thin layer forming apparatus of the present invention. Next, the temporally changing magnetic field generated by the magnet 4 will be explained. In the present invention, the magnetic particles circulate and vibrate near the elastic blade due to the rotation of the sleeve 3. This vibration and circulation is greatly facilitated by changes in the magnetic field near the surface of the sleeve 3. As a result, compared to the case where the magnetic field is fixed, frictional charging, ability to scrape off residual toner, and ability to supply toner are improved, and image quality can be further improved. Therefore, even when the amount of magnetic particles is small, the effect can be performed effectively, and even when the amount is large, sufficient circulation and vibration can be ensured. From this point of view, the tolerance range for the amount of magnetic particles relative to the amount of developer becomes large. FIG. 6 is a cross-sectional view of a device according to another embodiment of the invention. In this embodiment, the magnet 4 is unipolar and has a magnetic pole 5, which is swingable around the center of the sleeve 3 by a drive means (not shown).
The oscillations create a time-varying magnetic field. The frequency of the oscillation was 100Hz. Since the other configurations of the device of the present invention are the same as those of the previous embodiment, detailed explanations will be omitted by assigning the same reference numerals to corresponding parts. In this embodiment as well, the same effects as in the above-mentioned embodiment can be obtained, and since only a small amount of magnets are used, the structure is simple and inexpensive. FIG. 7 shows yet another embodiment of the invention. In this embodiment, the magnet 5 is an electromagnet. This is energized by a coil to which an alternating voltage is applied,
Creates a time-varying magnetic field. The frequency of the alternating voltage was 200Hz. Since the other configurations of the device of the present invention are the same as those of the previous embodiment, detailed explanations will be omitted by assigning the same reference numerals to corresponding parts. In this embodiment as well, the same effects as in the above-mentioned embodiments can be obtained, and in particular, in this embodiment, mechanical movement parts such as rotation and swinging are not required, and the configuration can be extremely simplified. The applied voltage is not limited to an alternating voltage, and may be any voltage that can form a magnetic field that changes over time. Although a non-magnetic developer was used in the above embodiments, a magnetic developer can also be used as long as it has weaker magnetism than magnetic particles and can be triboelectrically charged. Effects of the Invention As explained above, according to the present invention, a thin developer layer having a uniform developer layer thickness and a uniform and sufficient amount of triboelectric charge is stably formed, and this thin developer layer is developed. By using it for operation, good images can be stably obtained. Furthermore, since the formed magnetic field changes over time, the magnetic particles actively vibrate, ensuring frictional electrification of the developer, and a stable thin layer can be obtained.

[Brief explanation of the drawing]

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 brake. 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. 7th
The figure is a sectional view of a developer thin layer forming apparatus according to still another embodiment of the present invention. Explanation of symbols, 1...photoreceptor, 2...container, 3...
...Sleeve, 4...Magnet, 5...Magnetic pole, 6...Elastic blade.

Claims (1)

[Scope of Claims] 1. 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 movable endlessly inside and outside the container. a developer holding member; a magnetic field generating means provided inside the developer holding member for generating a temporally varying magnetic field; and an end portion biased to come into contact with the developer holding member; a blade that is inclined from the end toward the downstream side in the rotational direction and elastically abuts on the developer holding member, and for endlessly moving the developer holding member,
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.