JPH06149072A - Electrophotographic developing device - Google Patents

Abstract

(57) [Abstract] [Purpose] In a device that directly supplies toner from a toner hopper to a photoconductor, the image does not have uneven development even under high humidity, and the solid part density is uniform and a high-resolution, high-quality image is stable. Get it. [Configuration] 1. 1. an electrostatic latent image holder that contains a fixed magnet and moves; 2. a toner hopper having an opening facing the fixed magnet and supplying a magnetic developer to the surface of the electrostatic latent image holding member; 3. A structure comprising: a surface of the electrostatic latent image carrier and an electrode roller which is installed at a position having a predetermined gap and rotates. A developer outflow preventing member made of a magnetic material or a magnet, which is arranged in the vicinity of the electrostatic latent image holding member and is arranged on an upstream side wall of an opening of the toner hopper facing the electrostatic latent image holding member; ． A magnetic field is formed between the developer outflow prevention member and the magnetic developer in a portion of the electrostatic latent image holding member facing the toner hopper in the magnetic field, and the developer flows out from the toner hopper. And a fixed magnet fixedly arranged inside the electrostatic latent image carrier to prevent such a phenomenon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic developing apparatus applicable to printers, facsimiles and the like.

[0002]

2. Description of the Related Art Conventionally, a two-component developing method using a developer composed of a toner and a carrier has been widely used in an electrophotographic method, but in recent years, a one-component toner is used for the purpose of downsizing an image forming portion and reducing the cost. Development methods have come to be used. As an electrophotographic apparatus using such a one-component developing method, there is an apparatus shown in FIG. 6 proposed by the inventors in Japanese Patent Application No. 3-345990. In FIG. 6, 1 is an organic photoconductor drum in which phthalocyanine is dispersed in a polyester binder resin, and 2 is a magnet fixed coaxially with the photoconductor 1. 3 is a corona charger for charging the photoconductor, 4 is a grid electrode for controlling the charging potential of the photoconductor, 5 is signal light, 6 is a toner hopper, 7 is a magnetic one-component toner, 8 is a flow of the developer in the toner hopper. It is a damper for smoothing the toner and preventing the developer from being crushed by its own weight to be clogged between the photoconductor and the electrode roller. The magnet 2 has a magnetic pole formed at a portion facing the toner hopper 6 (θ = 10 °). Reference numeral 9 is an aluminum electrode roller having a magnet 10 inside, 11 is an AC high voltage power source for applying a voltage to the electrode roller, 12 is a scraper made of a polyester film for scraping off the toner on the electrode roller, and 13 is toner on the photoconductor. A transfer corona charger that transfers an image to paper.

This electrophotographic developing device is shown in FIG.
The operation will be described using. The photoconductor 1 is connected to the corona charger 3 (applied voltage -4.5 kV, grid 4 voltage -500).
V) and charged to -500V. The photoconductor 1 was irradiated with laser light 5 to form an electrostatic latent image. At this time, the exposure potential of the photoconductor was -90V. On the surface of this photoreceptor 1,
The toner 7 was magnetically attached in the toner hopper 6.
Next, the photoconductor 1 was passed in front of the electrode roller 9. At this time, the electrode high voltage power supply 11 applies −35 to the electrode roller 25.
An AC voltage (frequency: 1 kHz) of 750 V 0-p (peak-to-peak 1.5 kV) superposed with a DC voltage of 0 V was applied. Then, the toner was collected from the photoconductor 1 toward the electrode roller 9, and the negative-positive inverted toner image remained only on the image portion on the photoconductor 1. The toner attached to the electrode roller 9 rotating in the direction of the arrow was scraped off by the scraper 12 and returned to the toner hopper 6 again for the next image formation.

The toner image thus obtained on the photosensitive member 1 was transferred onto a sheet of paper (not shown) by a transfer charger 13 and then heat-fixed by a fixing device (not shown).

[0005]

When printing is carried out under high temperature and high humidity conditions using such an electrophotographic developing apparatus, there arises a problem that lateral unevenness occurs in an image.

An object of the present invention is to provide an electrophotographic developing device which can stably obtain a uniform image under all environmental conditions.

[0007]

In order to solve the above problems, the present invention provides: 1. an electrostatic latent image holder that contains a fixed magnet and moves; 2. a toner hopper having an opening facing the fixed magnet and supplying a magnetic developer to the surface of the electrostatic latent image holding member; An electrode roller which is installed at a position having a predetermined gap with the surface of the electrostatic latent image holding member and which rotates,
And a configuration having 4. A developer outflow preventing member made of a magnetic material or a magnet, which is arranged in the vicinity of the electrostatic latent image holding member and is arranged on an upstream side wall of an opening of the toner hopper facing the electrostatic latent image holding member; ． A magnetic field is formed between the developer outflow prevention member and the magnetic developer in the toner hopper on the electrostatic latent image holding member is restrained in the magnetic field to prevent the developer from flowing out of the toner hopper. And a fixed magnet fixedly arranged inside the electrostatic latent image carrier having the above-mentioned structure.

Further, the present invention relates to 1. 1. an electrostatic latent image holder that carries and moves an electrostatic latent image; 2. a toner hopper having an opening facing the electrostatic latent image carrier and supplying a magnetic developer to the surface of the electrostatic latent image carrier; 3. A structure comprising: a surface of the electrostatic latent image carrier and an electrode roller which is installed at a position having a predetermined gap and rotates. A developer outflow prevention member made of a magnet, which is arranged in the vicinity of the electrostatic latent image holding member and is arranged on an upstream side wall of an opening of the toner hopper facing the electrostatic latent image holding member. This is an electrophotographic developing device characterized by being processed.

[0009]

2 (b) is an enlarged view of the upstream side wall portion of the toner hopper 6 of the apparatus shown in FIG. In the conventional configuration, a toner seal 14 made of a urethane film is provided on the upstream wall of the toner hopper in contact with the photoconductor to prevent the magnetic toner from flowing out of the toner hopper. When the cause of image unevenness when printed under high temperature and high humidity is examined using the above-mentioned conventional apparatus, the urethane film 14 is
However, as shown in FIG. 2A, the photosensitive member 1 is bent in the longitudinal direction, and accordingly, the contact distance between the photosensitive member 1 on which the electrostatic latent image is written and the magnetic toner 7 is different in the toner hopper 6. Therefore, it was found that a difference occurs in the developing time, resulting in image unevenness. In order to make the contact time for developing the magnetic toner in the toner hopper uniform, a seal member having excellent straightness is required on the upstream side wall of the toner hopper. It has been found that the sealing method using magnetic force of the present invention is extremely effective for such a demand. The operation of the present invention will be described with reference to FIG. As shown in FIG. 3, when the magnetic body 15 and the magnet 16 are opposed to each other with the photoconductor 1 interposed therebetween, the magnetic lines of force generated from the magnet 16 inside the photoconductor 1 are concentrated at the tip of the magnetic body 15 used for the seal, Even if this magnetic body is set in non-contact with the photoconductor, the magnetic lines of force strongly restrain the magnetic developer and the developer does not flow out of the toner hopper through this gap. Moreover, since such a magnetic body 15 is a rigid body, it has an advantage that it is excellent in straightness unlike a film and is less likely to be bent due to temperature change or the like. When such a magnetic seal is used, the contact time between the developer and the photoconductor in the toner hopper becomes constant, so that the image can be uniformly developed. Furthermore, in the conventional seal structure using a film, the seal contacts and rubs against the surface of the photoconductor,
Although the surface of the photoconductor is damaged when it is used for a long time, such a magnetic seal does not scratch the surface of the photoconductor because the magnetic plate is set in a non-contact manner. Further, under high humidity conditions, dew may sometimes form on the surface of the photoconductor. When this happens
With the sticker made of a film, the electrostatic latent image formed is rubbed by water droplets on the film, so that the charge of the electrostatic latent image leaks and the image is disturbed, but the magnetic sticker of the present invention does not cause the disturbed image. .

[0010]

The present invention can be applied to any developing device using a magnetic developer. For example, the developing method using a photoreceptor containing a magnet proposed by the above-mentioned inventors in Japanese Patent Application No. 3-345990 can be applied. The magnet in the photoconductor does not rotate, but only the photoconductor rotates. The maximum magnetic flux density of the photoconductor internal magnet used is 300 at the photoconductor surface.
Gauss or higher is required, and preferably 500 to 1200 Gauss. If it is less than 300 gauss, the effect of the magnetic force is weakened, the uniformity of the image is lost, and the toner is easily clogged with the electrode roller. The magnetic toner inside the photoconductor attracts magnetic toner to the surface of the photoconductor. Needless to say, the present invention can also be applied to a developing method in which no magnet is provided inside the photoconductor.

As the photoreceptor used in the present invention, an organic photoreceptor using phthalocyanine or an azo pigment can be used.

When the magnetic one-component toner is used in the present invention, the device structure can be simplified. The magnetic toner of the present invention is composed of at least a binder resin and a magnetic material, and if necessary, a charge control agent, a release agent, a fluidizing agent, a colorant, and a second external additive. Styrene acrylic resin is used as the binder resin. Magnetic materials include iron such as ferrite, magnetite, and hematite, manganese, cobalt,
Alloys and compounds of nickel, copper, zinc, magnesium and the like, and substances known as ferromagnetic materials such as soft iron and nickel can be used. These magnetic materials have an average particle size of about 0.05 to 5
As a fine powder of μm, preferably 0.1 to 1 μm, 30 to 100 parts by weight, preferably 40 to 90 parts by weight, may be contained per 100 parts by weight of the binder resin. This toner may be a powder obtained by spray drying or a powder chemically obtained by a pearl polymerization method or the like. The average particle size of the toner used is preferably 15 μm or less, but 12 μm
If it is less than m, a sharper image can be obtained.

Hydrophobic silica fine particles on the surface of the toner,
The external addition of boron nitride particles, titanium oxide particles, or the like has the effect of covering the surface of the magnetic toner and making it difficult for fog to occur. Further, in the magnetic toner used in the present invention, if necessary, a charge control agent such as various dyes and pigments,
Mold release agents such as polyethylene and polypropylene, silica,
Various metal oxides such as alumina, zirconia and titania, and colorants such as carbon black may be contained or externally added.

As the material of the magnetic plate that seals the upstream side wall of the photoreceptor of the toner hopper, a magnetic material such as soft iron, nickel, magnetic stainless steel (SUS430) is used. The magnetic plate is placed at a position facing the magnet contained in the photoconductor.
Install at a distance of ~ 700 μm. With this configuration, the magnetic developer connecting the magnetic plate and the magnet blocks the outflow of the magnetic developer, and the magnetic developer does not leak out of the toner hopper.

The electrophotographic developing device of the present invention will be described below.
A description will be given with reference to the drawings. (Embodiment 1) FIG. 1 shows an embodiment of the electrophotographic developing apparatus of the present invention. In FIG. 1, 1 is a diameter of 30 mm
Was rotated at a peripheral speed of 65 mm / s.
The structure was such that oxytitanium phthalocyanine was dispersed in butyral resin and applied on an aluminum substrate to a thickness of about 0.1 μm to form a charge generation layer, and a hydrazone pigment was further dispersed using a polycarbonate resin as a binder resin. This is a function separation type structure in which a charge transfer layer is applied to a thickness of 25 μm. Reference numeral 2 is a magnet fixed coaxially with the photoconductor 1, 3 is a corona charger for negatively charging the photoconductor, 4 is a grid electrode for controlling the charging potential of the photoconductor, 5
Is a signal light, 6 is a toner hopper, and 7 is a negatively chargeable magnetic one-component toner having an average particle size of about 10 μm using styrene-acrylic resin as a binder resin. The magnetic one-component toner used was composed of 70% styrene-acrylic resin, 25% ferrite, 3% carbon black, and 2% oxycarboxylic acid metal complex, and 0.4% colloidal silica with a particle size of 0.02 μm. It was used as an external additive (all in weight%). Reference numeral 9 is a stainless steel electrode roller having a magnet 10 inside, 11 is an AC high-voltage power supply for applying a voltage to the electrode roller, 12 is a scraper made of a polyester film for scraping off the toner on the electrode roller, and 13 is toner on the photoconductor. A transfer charger that transfers an image onto the paper 17. Reference numeral 15 is a magnetic plate that seals the side wall of the toner hopper 6 upstream of the photoreceptor. The material of the magnetic plate 15 was soft iron. Magnetic plate 15
Is placed at a position facing the magnet 16 included in the photoconductor 1.
It was installed at a distance of 00 μm.

The operation of the electrophotographic developing apparatus configured as described above will be described below with reference to FIG. The photoconductor 1 was charged to -500V by the corona charger 3 (applied voltage -5.3kV, grid 4 voltage -500V).
The photoconductor 1 was irradiated with laser light 5 to form an electrostatic latent image. At this time, the exposure potential of the photoconductor 1 became -30V.
In the toner hopper 6, the magnetic one-component toner 7 was magnetically attached onto the surface of the photoconductor 1. At this time, the toner was charged to approximately −3 μC / g. Next, the photoconductor 1 having the toner layer attached thereto was passed in front of the electrode roller 9.
The electrode roller 9 was installed with a distance of 300 μm from the photoconductor 1. A high voltage power supply 11 is applied to the electrode roller 9 so that -3
800V 0-p (peak-to-peak 1.6kV) AC voltage (frequency 2kHz) superposed with 00V DC voltage
Was applied. The toner layer on the photoconductor 1 moves between the photoconductor 1 and the electrode roller 9, and the toner in the non-image area gradually moves to the electrode roller 9 side, and the toner image on the photoconductor 1 is negative-positive inverted only in the image area. Remained. The toner adhering to the electrode roller 9 rotating in the direction of the arrow was scraped off by the scraper 12 and returned to the toner hopper 6 again for the next image formation. The toner image thus obtained on the photoconductor 1 is
After being transferred to the paper 17 by the transfer charger 13, it was heat-fixed by a fixing device (not shown).

Such a printing operation is performed at 35 ° C90
It was performed under high temperature and high humidity of% RH. As a result, uneven development did not occur in the image, and an extremely high-resolution and high-quality image in which solid image density was uniform and an image line of 32 lines / mm was reproduced over the entire image area was stably obtained.

(Embodiment 2) FIG. 4 shows one embodiment of the electrophotographic developing apparatus of the present invention, which is an apparatus in which the construction of the seal portion of the toner hopper 6 of Embodiment 1 shown in FIG. 1 is simplified. is there. Here, a part of the magnetic force of the magnet 2 used for developing inside the optical body is used to form a magnetic seal with the magnetic plate 15. This configuration is not suitable for high-speed processes because the contact time of the toner 7 in the toner hopper 6 is short, but it is more suitable for low-speed small machines because the configuration is simpler.

(Embodiment 3) FIG. 5 shows an embodiment of the electrophotographic developing apparatus of the present invention. The construction of the seal portion of the toner hopper 6 of the concrete embodiment 1 shown in FIG. 1 is further simplified. It is a device. In this configuration, a magnet plate 18 is used instead of the magnetic plate 15 in FIG. 1, and the magnet inside the photoconductor is omitted.

[0020]

In the apparatus for directly supplying the magnetic developer from the toner hopper to the photosensitive member, the seal member on the upstream side wall of the photosensitive member of the toner hopper is made of a magnetic material or a magnet and is sealed by a magnetic force, so that the high temperature and high humidity can be maintained. In the above, there is an effect that image unevenness does not occur, a solid image density is uniform, and a high-resolution and high-quality image is stably obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electrophotographic developing device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a problem of a conventional example.

FIG. 3 is an explanatory diagram for explaining the function and effect of the present invention.

FIG. 4 is a configuration diagram of an electrophotographic developing device according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram of an electrophotographic developing device according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram of a conventional electrophotographic developing device.

[Explanation of symbols]

 1 Photosensitive Member 2/16 Magnet 3 Corona Charger 6 Toner Hopper 7 Magnetic Toner 9 Electrode Roller 10 Magnet 11 AC High Voltage Power Supply 15 Magnetic Plate 18 Magnet

Claims (2)

[Claims] 1. 1. An electrostatic latent image holder that includes a fixed magnet and moves; 2. a toner hopper having an opening facing the fixed magnet and supplying a magnetic developer to the surface of the electrostatic latent image holding member; 3. A structure comprising: an electrode roller which is installed at a position having a predetermined gap from the surface of the electrostatic latent image holding member and rotates; A developer outflow prevention member made of a magnetic material or a magnet, which is arranged in the vicinity of the electrostatic latent image holder and is arranged on an upstream side wall of an opening of the toner hopper facing the electrostatic latent image holder; ． A magnetic field is formed between the developer outflow prevention member and the magnetic developer in the toner hopper on the electrostatic latent image holding member is restrained in the magnetic field to prevent the developer from flowing out of the toner hopper. An electrophotographic developing device comprising: a fixed magnet fixedly arranged inside the electrostatic latent image carrier having the above-mentioned configuration. 2. 1. An electrostatic latent image holder that carries and moves an electrostatic latent image; 2. A toner hopper having an opening facing the electrostatic latent image holder and supplying a magnetic developer to the surface of the electrostatic latent image holder. 3. A structure comprising: an electrode roller which is installed at a position having a predetermined gap from the surface of the electrostatic latent image holding member and rotates; A developer outflow prevention member made of a magnet, which is arranged in the vicinity of the electrostatic latent image holder and is arranged on an upstream side wall of an opening of the toner hopper facing the electrostatic latent image holder. An electrophotographic developing device characterized in that