JPS6296956A - Method for forming developer thin layer - Google Patents

Abstract

PURPOSE:To prevent photographic fog by moving endlessly a developer holding member to form a thin layer of a developer on the developer holding member in the downstream of a blade in the moving direction of the holding member. CONSTITUTION:A blade 6 has an end part which is energized to come into contact with the developer holding member below a magnetic pole 5 of a magnetic field generating means in the rotation direction of the developer holding member, and the blade is inclined down in the rotation direction from the end part. The particle size of magnetic particles 7 is set to 50-200mum, and the quantity of them is set to 0.01-0.5g/cm per unit length of the developer holding member near the blade, and the developer holding member is moved endlessly to form the thin layer of the developer on the developer holding member in the downstream of the blade in the moving direction of the holding member. Thus, good copy pictures without photographic fog are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a thin layer of developer 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.
Because the developer itself contains a magnetic material (magnetic material is usually black), there are problems such as poor color reproduction and dullness during color reproduction.

For this reason, one method for forming a thin layer of non-magnetic developer is to use a cylindrical brush made of soft hair such as beaver hair, and apply the developer to the brush.

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 fogging and resulting in poor images.

11 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, providing a magnetic particle restraining member opposite to a developer holding member, and controlling the direction of movement of the surface of the holding member. Regarding this, a magnetic brush of magnetic particles is formed upstream of the magnetic particle restraining member by the magnetic force of a magnetic field generating means, the magnetic brush is restrained by the magnetic particle restraining member, and a thin layer of non-magnetic developer is formed on the developer holding member. We have already proposed a developer thin layer forming device.

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 method for forming a thin layer of developer by which a good copy image can be obtained.

A further object of the present invention is to provide a method for forming a thin layer of developer, which has a simple configuration and can provide 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-magnetic container provided in the opening and capable of endlessly moving inside and outside the container. In the developer thin layer forming method using a developer holding member, a magnetic field generating means provided inside the developer holding member, and a blade elastically abutting on the developer holding member, the blade is configured to generate a magnetic field. The magnetic pole of the generating means has an end biased to come into contact with the developer holding member at a downstream position in the rotational direction of the developer holding member, and is inclined from the end to the downstream side in the rotational direction. , the particle size of the magnetic particles is 50 to 200 Bm, the amount thereof is 0.01 to 0.5 g/cm per unit length of the developer holding member near the blade, and the developer holding member is moved endlessly. Accordingly, there is provided a method for forming a thin layer of developer, which is characterized in that a thin layer of developer is formed on the developer holding member downstream of the blade in the moving direction of the holding member, so that the method is simple and satisfactory. Since the developer can be sufficiently charged while ensuring the binding of magnetic particles, it is possible to provide a good image without background fog.

ACTUAL 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 l serving as a latent image carrier rotating in the direction of arrow a. As the photoreceptor 1, for example, a so-called xerographic photoreceptor on which an electrostatic latent image is formed by the Carlson process, N described in Japanese Patent Publication No. 42-23910,
A photoreceptor having an insulating layer on its surface on which an electrostatic latent image is formed by the P process, an insulator on which a latent image is formed by an electrostatic recording method,
It is an insulator to which an electrostatic latent image is transferred by a transfer method, or a member to which an electrostatic latent image (or potential latent image) or magnetic latent image is formed and retained by any other appropriate method.

The developer thin layer forming device includes a developer supply container 2. It has 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, the right half circumferential surface is inserted into the container z through the opening, and the left half circumferential surface is exposed outside the container, and is horizontally installed with a freely rotatable 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 provided in the developing sleeve 3, and in this embodiment is a fixed permanent magnet, 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 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 exposed to the developer. More specifically, this opening is such that 90% or more of the surface of the developer carrier is released from magnetic particles in the area where magnetic particles exist near 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. This causes agitation of the adhering developer and forms a thin layer of developer on the surface of the developer carrier leading to the development 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, the negative part of the developer is consumed by the developing operation, and the other developer is collected from the lower part of the sleeve 2 as the sleeve 3 rotates. A sealing member 9 is provided in this collection portion to allow the developer not consumed during development to pass into the container z, and also to prevent the magnetic particles 7 and developer 8 in the container 2 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 2, and an alternating current with a superimposed direct current is applied between them. A method of imagewise transferring a thin layer of developer onto 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 rotation direction of the sleeve 3 (forward direction with respect to the sleeve rotation direction). In this configuration, when the sleeve 3 rotates, the magnetic particles 7 are The developer 8 in the upper part of the container 2 is clogged near the tip of the container 2, and the magnetic particles 7 are not circulated and vibrated. Therefore, sufficient triboelectric charging is not achieved. It has been found that because the developer cannot be taken in, 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 The particles 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, causing the magnetic particles 7 to vibrate significantly near the magnetic pole 5. confirmed.

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, the material and rule of the elastic blade 6 are, for example, JIS
Rubber with a hardness of 40 to 80 degrees, preferably 50 to 70 inches, is suitable for stable formation of a thin layer of developer.The thickness of the elastic blade 6 is such that the magnetic particles 7 ride on the back surface of the elastic blade 6. In order to prevent this, it is preferable to have a certain degree of thickness, 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 between the elastic blade 6 and the sleeve 3 and the center of the sleeve 3, a straight line, or a straight line passing through the center of the sleeve 3 and the center of the magnetic pole 5.

The 0 plane T, where the angle between the straight mm and the straight line n is X, and the angle between the straight line n and the straight line is y, is the 1 elastic blade 6 when the 1 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 recurving due to frictional force when the sleeve 3 rotates.
The range is θ°.

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＞.

For z+y<90° angle Due to the relationship of zero gravity, it was found that the angle X
The preferred range of is 5<x<40°.

Regarding the angle y, it has been found that when y≦00, 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 was confirmed that particularly good circulation and vibration were achieved when '''<y<so''.

Regarding the angle It has been found that the circulating and vibrating magnetic particles 7 are no longer present, which is undesirable.

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

5°<x<40"30'"<y<5O6x+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 ILm. Below 50 ILm, the fluidity of the magnetic particles 7 is poor;
It was confirmed that sufficient circulation and vibration were not obtained, the amount of developer 8 taken in was reduced, and a stable thin layer of developer 8 was not formed. In addition, if the particle size is 200 μm or more, although the developer 8 can be sufficiently supplied, the frictional charging is not sufficient, so it is not preferable. Particularly preferred for obtaining circulation and vibration.

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

The sleeve 3 used was an aluminum sleeve with a diameter of 20 mm whose surface was subjected to amorphous sandblasting treatment 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°. Silicone rubber (rubber hardness JIS 60', thickness 2 mm) was used as the elastic body blade 6 used. These mounting positions are θ=lO”, d=1.0mm, x=15”,
y=50''.

The magnetic particles have a particle size of 100 to 80 μm (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 μm 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 to the powder was used.
A uniform coating layer of 1 Lm was obtained. When the amount of charge on this layer was measured using the blow-off method, the amount of charge was +12 #LC
/g, which is a sufficient value.

The developing method used here is
The method described in 7.5 is preferred, and a voltage is applied between the electrophotographic photoreceptor and the sleeve 3 by bias N, alt. 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 is manufactured by Canon Co., Ltd.
20 built into a copying machine, frequency 160 as a bias power supply
0Hz, AC voltage with peak-to-peak voltage of 1300V,
Using a superimposed DC current of -300V, the surface potential of the latent image L on the photoconductor is set to -540V in the dark area and -220V in the bright area, and the distance between the sleeve 3 and the photoconductor 1 (organic photoconductor) is set to 2.
When development was carried out at a setting of 501 parts m, a good red image with a reflection density of 1.2 could be obtained. Furthermore, when 100 images were continuously formed, 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 mixed at a rate of 0.1 g per unit length of the developer holding member (total of 2
．． 1g) Pour into the developing device, and add 5g of the above red toner.
Table 1 shows the results of developing with 0 g added and a developing distance of 210 mm (corresponding to A4 lengthwise).

Table 1 Particle size and image quality of magnetic particles As a result, for magnetic particles with a particle size of 50 gm or less, the magnetic particles stay near the end of the elastic blade 6, hardly any circulation or vibration of the magnetic particles is observed, and the development The agent layer is very thin, resulting in an image with noticeable development unevenness, which is undesirable.
At ~100 gm, some development unevenness was observed, but the image was quite good. A very good image was obtained at 80 to loo μm. At 200 lm or more, fogging was observed, which was thought to be due to insufficient triboelectric charging.

Next, in order 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 gm (0.01 g per unit length (longitudinal direction) of the developer holding member) were added. cm), 1.0 (0,05), 2.1
(0,1), 10°5 ((15), 21.5 (1
, 0) input (the total amount of magnetic particles (g )
When the above-mentioned red toner was used together with 50 g for development, the results shown in Table 2 were obtained for the case where the magnetic particles were divided by the effective length of the sleeve (cm) and when no magnetic particles were added.

Table 2: Magnetic particle input amount and image quality According to the results, when no magnetic particles are present and a thin layer is formed only by the elastic blade 6, development unevenness is significant, and 0.01 to 0.5 g/cm. In this range, the development unevenness is not noticeable, and in this range, the magnetic particles have magnetic pole 5.
Because there is nothing that can move freely within the developer thin layer forming device, even when an impact is applied to the developer thin layer forming device, the magnetic particles are not biased. Particularly good results were obtained in the range of 0.05 to 0.1 g/cm. Moreover, at 1.0 g/am or more, uneven development, which is thought to be caused by sleeve ghost, becomes noticeable. At this time, although the magnetic particles covered a considerable portion of the surface of the sleeve 3 and circulated slowly, no significant vibration was observed.

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 relationship between magnetic particles and developer application, that is, formation of a thin developer layer, will be explained. If the amount of magnetic particles is too small, that is, about 0.1 g or less, the magnetic particles will concentrate on the tip surface of the elastic blade 6 and circulate only in this part, and the magnetic particles will be concentrated near the upstream magnetic pole of the circulating part. vibration was observed.

When magnetic particles of 0.5 g/cm or more are present, the circulation area expands to the vicinity of the magnetic pole position, and the vibrations of the magnetic particles are considerably reduced. Furthermore, 1.0g/cm
In the above case, complete circulation occurred because the magnetic particles completely covered the magnetic pole position, but almost no vibration of the magnetic particles was observed. In addition, the circulation speed is also slower than in the case of 0.5 g/cm or less.From these results, the vibration of the magnetic particles plays an important role in scraping off the toner that was not consumed in development and supplying the toner. It is understood that

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.

Furthermore, as shown in FIG. 6, the number of magnetic poles of the magnet 4 inside the sleeve 3 is further increased, and a magnetic pole is also provided on the photoreceptor l 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 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 By using this in the developing operation, good images can be stably obtained.

Also, the magnetic particles are o, oi-o per unit length.

Since only a minute amount of 5 g/cm is used, the magnetic particles are strongly restrained by the magnetic poles1, and even if a strong impact is applied to the developer thin layer forming device, the magnetic particles will not be biased and a stable thin layer will be obtained. be able to.

[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. 1) Takashi - Figure 1 Figure 2 Figure 2 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. In a developer thin layer forming method using a holding member, a magnetic field generating means provided inside the developer holding member, and a blade elastically abutting on the developer holding member, the blade has a magnetic field generating means provided inside the developer holding member. The magnetic pole has an end portion biased so as to come into contact with the developer holding member at a downstream position in the rotational direction of the developer holding member, and is inclined from the end portion toward the downstream side in the rotational direction, and the magnetic The particle size of the particles is 50 to 200 μm, and the amount is 0.0 per unit length of the developer holding member near the blade.
1 to 0.5 g/cm, and the developer holding member is moved endlessly to form a thin layer of developer on the developer holding member downstream of the blade in the moving direction of the holding member. Method for forming a thin layer of developer.