JPH0452754Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a dry developing device and is applicable to recording devices such as electrophotography and electrostatic recording, such as copying machines, printing machines, printers, etc. .

2. Background Art

The applicant has proposed a developing device in which a thin layer of developer is formed on a developer carrier, the developer in the thin layer is brought close to the latent image, and an alternating electric field is applied to this approaching portion to perform development. (Special Publication No. 58-32375, No. 58-32377
No. Specification).

This device has a high development efficiency (the ratio of toner that can be consumed for development out of the toner present in the development section) and is very useful in terms of miniaturization. However, the developer used in this device is one component. Since the toner is a magnetic toner, it is essential that the toner contains a magnetic material, and therefore has drawbacks such as poor fixability of developed images and poor reproducibility of color images.

As a device to compensate for this drawback, the applicant has developed a method and device that uses non-magnetic toner and forms a thin layer of only non-magnetic toner on a developer carrying member.
We proposed a developing method and device in which a thin layer of non-magnetic toner is placed facing a latent image and developed by applying an alternating electric field (Japanese Patent Laid-Open Nos. 143360-1982 and 101680-1980).
No. Specification).

This is useful because it eliminates the disadvantages caused by the toner containing magnetic materials while maintaining the advantages of the developing device using magnetic toner, but it also has the disadvantages of relatively low density of the developed image and the negative effects described below. It has been found that there are some drawbacks in the development characteristics, such as the fact that the image density may decrease as the latent image potential increases.

In addition, in what is known as the so-called two-component magnetic brush development method (for example, Japanese Patent Laid-Open No. 53-93841), a non-magnetic developer can be used, but the consumable toner in the magnetic brush in the development section is Since the ratio of .

As a means to solve these problems, the applicant
Japanese Patent Application Publication No. 1983-204605 filed on September 17, 1960, 1988
We proposed Japanese Patent Application Laid-open No. 60-217556-217562, filed on September 30, 2008. These inventions are different from conventional two-component development, and have excellent effects such as increased development density and development efficiency.

However, it is difficult to supply toner particles of the developer uniformly in the longitudinal direction with respect to the consumption rate of the developer.
Even in an excellent developing device with high developing efficiency, adverse effects were observed. Particularly noticeable is that the original size and developed image area are different from A series and B series.
Due to the difference between the series, density changes occur between the common area and the different differential areas during long-term use. This tendency was strong in two-component development, and was slightly observed in one-component development as well.

In order to prevent this, stirring of the developer may be considered, but this alone does not provide a sufficient effect, and in particular, these problems cannot be solved because small-sized developing devices cannot even stir the developer sufficiently.
On the other hand, if a large amount of developer is partially accumulated without being consumed, fogging and scattering are likely to occur.

〔the purpose〕

The present invention has been developed based on the above-mentioned problems, and provides a developing device that prevents developer from scattering into the main body of a copying device and forms high-quality visible images without fogging. The purpose is to do the following.

〔overview〕

The present invention achieves the above object, and includes a conveyance means for conveying toner particles into an area where carrier particles and toner particles are mixed, and a conveyance means that carries and conveys the mixed developer within this mixing area to generate an electrostatic charge. In a developing device that develops a plurality of electrostatic latent images of different sizes and is equipped with a developer carrying member that supplies developer to the latent image, the conveying means moves the developer into the mixing area corresponding to the common area of the different sizes. , the developing device is characterized in that more toner particles are sent to the mixed area portions corresponding to the non-common areas of different sizes.

〔Example〕

The present invention will be explained in detail below using the figures.

FIG. 1 shows a sectional view of an embodiment of a developing device based on the present invention. In the figure, 10 is a self-occurring lens of the optical system, 1 is a non-magnetic cylinder (hereinafter referred to as a non-magnetic sleeve) that rotates in the direction of arrow a,
2 shows a fixed magnet consisting of a plurality of magnetic poles contained in a non-magnetic sleeve, and what forms the developer layer is experimentally known as magnetic particles (carriers) 3.
As toner particles 4, which are ferrite particles having a particle diameter of 40 to 80 microns and whose surface is fatigued with silicone resin, non-magnetic toner having a particle diameter of about 10 microns consisting only of a resin component was used. 3,4
The toner particles 4 are agitated by the rotation of the non-magnetic sleeve and the magnetic field of the fixed magnet, and the toner particles 4 are charged to a desired charge polarity by frictional charging, and the toner particles 4 are made non-magnetic by the magnetic field of the fixed magnet. While forming a so-called magnetic brush on the outer peripheral surface of the sleeve 1, a magnetic brush is formed on the photosensitive drum 9, which is a latent image carrier.
A rectangular wave of 1300 Vpp 1800 Hz is applied to the gap between the non-magnetic sleeve 1 and the photosensitive drum 9 by a high-voltage power supply 8 as an alternating electric field generating means to improve the developing efficiency. Visualization is performed.

Reference numeral 5 indicates a developer regulating magnetic blade, and 11 indicates a developer regulating non-magnetic blade, both of which are located on the downstream side in the rotational direction of the sleeve 1 than the opposing magnetic field generating magnetic poles S. The surface of the non-magnetic sleeve 1 and these blades 5, 11 are arranged with a gap in between, and the blade 5 is located upstream of the blade 11 and has a large gap (approximately 300 μm) to prevent the magnetic developer from circulating in the developer container. In addition to limiting the non-magnetic sleeve 1
Apply an appropriate amount of magnetic developer consisting of a mixture of 3 magnetic particles and 4 toner particles on the outer peripheral surface (Japanese Patent Laid-Open No. 60-217561
No. 0.5 to 5×10 ^-2 g/cm ² ). Here, the magnetic particles 3 play the role of mixing with the circulating toner particles in the developer container, charging the toner particles, and holding and transporting the toner particles to the development area facing the photosensitive drum. Therefore, basically only the toner particles 4 are transferred to the photosensitive drum 9 depending on the alternating electric field.

6 and 7 use the above-mentioned mechanism to send toner particles from the magnetic particle group near the sleeve to the mixed area of magnetic particles and toner particles (toward the sleeve side) in order to compensate for the lack of toner consumed during development. A toner supplying member consisting of a rotating body for supplying toner is shown. The toner supply member has an area for toner conveyance and rotates clockwise.

In general, electronic copying machines have the maximum document size that can be copied such as A3 and B4 sizes.
There is a high frequency of copying small-sized originals in the longitudinal axis direction of copying machines such as B5, and when the original is centered, there is no toner consumption from the developing device at both ends of the apparatus, and when one side of the original is used, there is no toner consumption from the developing device. continues. Here, if the toner supply member 6 that supplies toner 4 to the magnetic particle group 3 near the non-magnetic sleeve 1 in the developing device uniformly supplies the toner in the longitudinal axis direction, the toner is not consumed in the area where no toner is consumed. Because it is forced into the mixer and stirred,
The ratio of the amount of toner to the amount of magnetic particles (T/C ratio) increases abnormally, and the amount of toner particles that do not adhere to the surface of the magnetic particles increases, causing internal contamination of the optical system 10, transfer paper supply system 11, etc. due to toner. Or, when copying a large-sized original after long-term copying of a small-sized original, fogging may occur in the difference area.

Of course, in order to make the mixing ratio of magnetic particles and toner particles uniform in the developing device, a plurality of spiral screws are used in the axial direction to stir the mixture, or a sensor detects the above mixing ratio and the insufficient toner particles are added as needed. If an ATR method or the like is used for supplying the photoresist, the above-mentioned problems are less likely to occur, but not only can they not be solved, but the developing device becomes larger and more complicated.

In order to prevent this, the above-mentioned developer supply means adjusts the amount of toner particles supplied to the developer carrying member in the longitudinal direction of the developer carrying member according to the size of the document used in the copying device. The difference in the area to be developed is varied to increase.

FIG. 2 shows a toner supply member 6 based on the present invention.
This shows an example of this.

Reference numeral 12 indicates a rotary support plate made of a rigid body such as metal or plastic stick, and 13 indicates an elastic sheet made of film, rubber, or the like stuck to the rotation support plate.

In this embodiment, a document is set at the center in a copying machine, and a step (L-l) is provided in the (A-B) area of the elastic sheet 13 in the longitudinal direction, and both end areas are Compared to the center, the specific magnetic sleeve has a smaller ability to supply toner to the magnetic particle group, that is, the area for conveyance is smaller.

The above (A-B) area means, for example, (A3-B4 for an A3 size machine) and (B4-B4 for a B4 size machine).
A4) shows the difference area of each size.

Figure 3 shows the results using Canon PC-30 (maximum original size B4) = B4, B = A4, L = 8 mm, l
Non-magnetic sleeve when copying an A4 size original using a toner supply member curve r of = 6 mm and a toner supply member (curves α, β) of L = 8 mm with no step in the longitudinal direction. 2 shows the variation in T/C ratio of the magnetic developer coated thereon.

The curve α is stable at the T/C ratio at the center position of the A4 document, but as seen in the curve β, when a toner supply member with L = 8 mm without a step is used (B4- A4) The T/C ratio at both ends will change significantly.

On the other hand, curve r shows that when using the toner supply member with steps at both ends based on the present invention (B4-A4), the T/C ratio fluctuation at both end regions is
Both ends are stable.

If there is no step at both ends, (B4−A4)
The T/C ratio is increasing in the area, with 200 to 300 sheets
When copying an A4 original, fogging at both ends of the B4 copy and toner falling onto the transfer paper supply system began to occur, but with the version with a step, the T/C ratio changed (r in the figure)
was small and the above-mentioned problem did not occur.

Note that the sizes of L and l and the balance of supply vary depending on factors such as the developing speed of each developing device and the size of the rotating sleeve, so the appropriate range differs depending on the design. As a guideline, as shown in this example, 25
It is best to make a difference of about %.

In addition, in this example, the mixing ratio of toner particles and carrier particles in the developing section is such that the carrier particles have a volume ratio of 1.5% to 30% in the developing section, and the developer is placed in an alternating electric field and in a magnetic field. (Developing magnetic pole N
etc.) (toner transfer by alternating electric field with or without direct brush contact), it has good development efficiency, and good images could be formed without impairing this effect.

A more preferable application target of the developing device of the present invention is a developing device that develops an electrostatic latent image on an electrolatent image carrier, and which contains a developer having toner particles and substantially spherical magnetic particles. a developer container facing the electrostatic latent image carrier and forming a developing section for supplying toner particles to the electrostatic latent image carrier, and carrying and transporting the developer from the container to the developing section. a first magnetic field generating means provided on a side of the developer carrying member opposite to the latent image carrier and bringing the magnetic particles into contact with the developer carrying member in the developing section; a developer regulating member having a regulating portion distal end located upstream of the developing section in the rotational direction of the developer carrying member and spaced apart from the surface of the developer carrying member; and a developer regulating member provided on a side of the developer carrying member opposite to the regulating member. a second magnetic field generating means located upstream of the developer regulating member with respect to the rotational direction of the developer carrier; an alternating electric field forming means for forming an alternating electric field in the developing section to transfer an alternating electric field to the image carrier; The volume occupied by the magnetic particles in the developing section is 1.5% to 30% of the volume;
The amount of developer applied on the developer carrying member downstream of the regulating member is 0.5 to 5×10 ^-2 g/cm ² , and the weight ratio of toner particles to magnetic particles is 4 to 40%. The developing device is particularly good, because in addition to toner particles, there are a small amount of magnetic particles (occupying 1.5 to 30% of the volume) in the developing section when applied to the present invention. In other words, it forms ears in a sparse state, and by this action, it is possible to maintain good development characteristics.

Here, the volume ratio of magnetic particles in the developing section will be explained. The "developing section" is a section where toner is transferred or supplied from the sleeve to the photosensitive drum 1. The "volume ratio" is the percentage of the volume occupied by the magnetic particles present in the developing area relative to the volume of the developing area. In the above developing device, this volume ratio has an important influence, and this
A content of 1.5 to 30%, particularly 2.6 to 26% is highly preferred.

If it is less than 1.5%, a decrease in the density of the developed image will be observed, sleeve ghost will occur, and panicle 5
A significant difference in density occurs between the part where 1 is present and the part where it is not, and the thickness of the developer layer formed on the sleeve surface becomes non-uniform as a whole.
It is unfavorable for the following reasons.

If it exceeds 30%, the degree of closure of the sleeve surface increases, which is undesirable because fogging may occur.

In particular, with this development, the image quality does not monotonically deteriorate or increase as the volume ratio increases or decreases, but sufficient image density can be obtained in the range of 1.5 to 30%, and even if it is less than 1.5%, it can exceed 30%. This is based on the fact that the inventor has discovered that in the range of the above numerical values where the image quality is sufficient, neither sleeve ghost nor fogging occurs. The former image quality deterioration is thought to be due to negative characteristics, while the latter is thought to occur because the amount of magnetic particles present becomes large and the sleeve surface cannot be opened, resulting in a significant decrease in the amount of toner supplied from the sleeve surface.

Also, if it is less than 1.5%, the reproducibility of line images will be poor,
There is a noticeable decrease in image quality and density. On the other hand, if it exceeds 30%, the magnetic particles may damage the photosensitive drum surface.
There are transfer and fixing problems that occur because the image is attached as part of the image.

And if the presence of magnetic particles is close to 1.5%,
When reproducing large area uniform high density images (solid black),
Since there are cases where partial development unevenness called "roughness" occurs (under special circumstances, etc.), it is preferable to set a volume ratio that makes it difficult for this to occur. This value indicates that the volume ratio of magnetic particles to the developing area is 2.6.
% or more, this range becomes a more preferable range. Also, if the presence of magnetic particles is close to 30%, there may be a delay in toner replenishment from the sleeve surface around the area where the ears of magnetic particles come into contact (at high development speeds, etc.), and scales may appear when solid black is reproduced. This may result in uneven density. As a reliable range for preventing this, it is more preferable that the volume ratio of the magnetic particles is 26% or less.

If the volume ratio is within the range of 1.5 to 30%, the bristles are formed on the surface of the sleeve in a sparse state to a desired degree, the toner on both the sleeve and the bristles is sufficiently released to the photosensitive drum, and the toner on the sleeve is also transferred by flying in the alternating electric field, so that almost all the toner is available for development, resulting in high development efficiency (the ratio of toner that can be consumed for development among the toner present in the development section) and high image density. Preferably, the bristles are vibrated slightly but violently, which loosens the toner adhering to the magnetic particles and the sleeve. In any case, it is possible to prevent the occurrence of sweep unevenness and ghost images as in the case of a magnetic brush. Furthermore, the vibration of the bristles activates the frictional contact between the magnetic particles and the toner, improving the frictional charging of the toner and preventing the occurrence of fogging. In addition, high development efficiency is suitable for miniaturizing the developing device.

The volume ratio of magnetic particles present in the development area can be determined as (M/h) x (1/ρ) x [(C/(T+C)]. Here, M is the amount of development per unit area of the sleeve. The coating amount (g/cm ² ) of the agent (mixture...when not standing), h is the height of the developing section space (cm),
ρ is the true density of the magnetic particles in g/cm ³ , and C/(T+C) is the weight ratio of the magnetic particles in the developer on the sleeve.

In addition, in the developing section defined above, the ratio of toner to magnetic particles is preferably 4 to 40% by weight.

When the alternating electric field is strong (the rate of change is large or Vpp is large) as in the above embodiment, the ears separate from the sleeve 22 or from its base, and the separated magnetic particles are trapped in the space between the sleeve and the photosensitive drum 1. Move back and forth. Since the energy of this reciprocating motion is large, the effect of the vibration described above is further promoted.

The above behavior was observed using a high-speed camera (manufactured by Hitachi).
Confirmed by performing an effect of 8000 frames per second.

Even if the gap between the surface of the photosensitive drum 1 and the surface of the sleeve 22 is reduced to increase the contact pressure between the photosensitive drum 1 and the brush 51 and to reduce vibration, the gap is large at the entrance and exit sides of the developing section. Sufficient vibration occurs to produce the above-mentioned effects.

[Effect of idea]

As explained above, according to the present invention, the amount of toner supplied to the developer carrying member of the developer supplying means is adjusted according to the size of the document used in the recording device or the area size to be developed in the longitudinal axis direction of the developer carrying member. In particular, by changing the toner, it was possible to realize a developing device that can reduce toner scattering within the machine and achieve stable image formation without fogging.

In particular, images with excellent color reproducibility can be obtained with two-component toner particles in which a color component is added.

The present invention is particularly effective in new development using a small amount of carrier particles in a two-component development system, but it is also applicable to conventional two-component development.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view for explaining the overall configuration of the developing device based on the present invention, FIG. 2 is a perspective view of the toner supply member in the developing device shown in FIG. 1, and FIG. FIG. 3 is a graph diagram showing changes in the /C ratio. 1 is a sleeve, 2 is a magnet, 3 is a magnetic particle, 4 is a toner particle, 6 and 7 are toner supply members,
8 is a high voltage power supply, 9 is a photosensitive drum.

Claims (1)

[Claims for Utility Model Registration] (1) A conveying means for conveying toner particles into a region where carrier particles and toner particles are mixed, and a means for carrying and conveying the mixed developer within this mixing region to carry out electrostatic latent In a developing device that develops a plurality of electrostatic latent images of different sizes and is equipped with a developer carrying member that supplies the developer to the image, the conveying means conveys the mixed area portion corresponding to the common area of the different sizes, A developing device characterized in that more toner particles are sent to said mixed area portions corresponding to said non-common areas of different sizes. (2) The conveyance means includes a rotary sheet for conveying the toner particles into the area where the carrier particles and the toner particles are mixed, and the rotary sheet has a width for conveying the toner particles at a portion corresponding to the common area. The developing device according to claim 1, which is larger than the portions corresponding to different areas. (3) The above-mentioned developing device includes a non-magnetic blade that regulates the developer layer thickness, and a second blade located upstream of the tip of the non-magnetic blade with respect to the moving direction of the developer-carrying member and on the back side of the developer-carrying member. Registration of a utility model comprising: (1) magnetic field generating means, (2) magnetic field generating means which applies a magnetic field to a developing section where the developer carrying member is close to the electrostatic image carrier, and (2) alternating electric field forming means which forms an alternating electric field in the developing section. A developing device according to claim 2.