JP3276093B2 - Developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device such as an electrophotographic or electrostatic recording type copier or printer for visualizing a latent image formed on an image carrier by attaching a developer to the latent image. About.

[0002]

2. Description of the Related Art One embodiment of a conventional developing device is shown in FIG.
In the apparatus shown in FIG.
The developer is supplied to the surface of the developing sleeve 3, and the developer is held in a state of a magnetic brush by the magnetic force of the magnet roller 13, and the developer is opposed to the photosensitive drum 4 based on the rotation of the developing sleeve 3. When the magnetic brush is conveyed to the developing area, the magnetic brush is cut off by the developer return member 1 and the spike height restricting member 2 that regulate the amount of the accumulated developer on the developing sleeve 3.
The amount of the developer conveyed to the developing area is appropriately maintained.

[0003] The magnet roller 13 is composed of five magnetic poles and restrains and conveys the developer. First, the developer stirred by the developing chamber stirring screw 11 is constrained by the magnetic force of the pumping pole S <b> 2, and is conveyed to the developer reservoir 5 by the rotation of the developing sleeve 3. The amount of the developer conveyed to the developer reservoir 5 is regulated by the developer return member 1 and cut by a cut pole N2 having a magnetic flux density of a certain level or more in order to restrain the developer having a stable charge amount. Be fully restrained. As a result, the developer is conveyed while forming a magnetic brush on the developing sleeve 3, is cut off by the spike height regulating member 2 to have an appropriate amount of the developer, and is conveyed to the developing area by the conveying magnetic pole S <b> 1.

In the developing region, the developer confined to the developing pole N1 is a direct current or an alternating current applied to the developing sleeve 3 via a bias power supply 15 provided on the image forming apparatus main body side, or a superimposed direct current and alternating current. With the bias voltage, of the developer on the developing sleeve 3, the toner moves to the electrostatic latent image side of the photosensitive drum 4 in the two-component system including the toner and the carrier, and in the one-component system, the developer moves as it is.
The electrostatic latent image is visualized as a toner image.

To form a high-quality image in such a developing device, it is essential to stabilize the charge amount of the developer. For this reason, in the two-component system, the charge amount is stabilized by the friction between the carrier and the toner in the stirring screw portions 11 and 12 and the developer reservoir 5, and in the one-component system, the development is performed in the developer reservoir 5. The friction between the sleeve 3 and the ear height regulating member 2 and the developer stabilizes the charge amount.

[0006]

However, in the above-mentioned conventional example, the developer returned from the pumping pole S2 by the magnetic restraining force in the developing device 9 is used as the developer return member 1.
In addition, there is a problem that the image quality deteriorates in the developer reservoir 5 formed by the cut pole N2, and when the image is formed for a long period of time, the image quality is significantly reduced.

[0007] As shown in FIG.
2. Bottom of developer magnetically bound at cut pole N2
Layer or developer confined on the surface of developing sleeve 3
Is the normal direction of the developing sleeve 3, that is,
The current that depends on the absolute value of the magnetic flux density of the gnet roller.
F acting toward the center of the image sleeve 3 r and developing sleeve 3
F acting in the direction of travel θ (f in S2 r to f r1, f θ
f f at θ1, N2 r to f r2, f θ is f θ2)
Is strongly rubbed with the developing sleeve 3.

As a result, in the case of the two-component system, the carrier in which the toner resin is fused to the carrier surface is spent, or silica or titanium oxide or the like externally added to the toner to improve the fluidity of the toner is used. A phenomenon such as the additive being buried in the toner occurs, so that stable charging of the toner cannot be performed, and there is a disadvantage that scattering, fogging occurs, and the image quality of the entire image is significantly reduced. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which solves the above-mentioned problems, stabilizes the charge amount of a developer, and prevents scattering, fogging, and deterioration of image quality.

[0010]

SUMMARY OF THE INVENTION According to the present invention, there is provided a toner and a magnetic recording medium for developing a latent image on an image carrier.
A developer carrying member that carries and transports a developer including a carrier ,
A magnetic field generating means provided in the developer carrier for generating a magnetic field; and a developer regulating means for regulating a layer thickness of the developer carried on the developer carrier. The magnetic field generating means comprises a first magnetic pole and A second magnetic pole provided downstream of the first magnetic pole and upstream of the developing magnetic pole in the rotation direction of the developer carrier and adjacent to the first magnetic pole and having the same polarity as the first magnetic pole. The developing device further includes a stirring unit provided at a position where the first magnetic pole and the second magnetic pole allow the developer to drop from the developer carrier, and agitating the developer .
Countercurrent arranged above the developer regulating means is accomplished by regulating the developer drawn up to the developer carrying member by the second magnetic pole from being agitated by the agitating means.

[0011]

According to the present invention, the developer in the developing container is agitated by the developer agitating means to make the concentration uniform, and the developer-carrying member is actuated by the magnetic restraining force generated by the magnetic field of the predetermined second magnetic pole for supply. Supplied to The supplied developer is developed with respect to the second magnetic pole located on the downstream side in the rotation direction of the developer carrier among the first and second magnetic poles located at the same polarity and adjacent to each other. The height of the spike is immediately regulated by the agent regulating means, and the spike is transported to the developing position by a predetermined transport magnetic pole in a state of being coated in a thin layer by a predetermined amount. As described above, since the developer supplied to the developer carrier is immediately thinned, the sliding force due to the magnetic restraining force acting on the lowermost developer in the transport magnetic pole is small, and the deterioration of the developer is prevented.
Therefore, the charge amount of the developer conveyed to the developing position is stable, and favorable development is performed at a predetermined developing magnetic pole provided at the developing position.

[0012]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

<First Embodiment> First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram illustrating a main part of an image forming apparatus according to a first embodiment of the present invention, and illustrates a laser beam printer having an optical scanning unit using a plurality of laser beams and a plurality of photosensitive drums.

In this printer, four image forming stations corresponding to the colors are provided around an electrophotographic photosensitive member and have image forming means, and a photosensitive drum formed at each image forming station is provided. The upper toner image is configured to be transferred to a recording material conveyed by a belt-shaped moving body that moves opposite to the photosensitive drum.

Image forming stations Pm, Pc, P corresponding to each color of magenta, cyan, yellow, and black
y and Pk are photosensitive drums 4M, 4C, 4Y,
4K is arranged rotatably in the direction of the arrow (clockwise). Around the photosensitive drums 4M, 4C, 4Y, 4K, corona chargers 16M, 16C, 16Y, 16K,
Further, scanning optical devices 17M and 17 as optical scanning means.
C, 17Y, 17K, and developing devices 9M, 9C, 9
Y, 9K, and cleaning devices 18M, 18C, 18
Image forming means having Y, 18K is provided.

The transfer section 6 constituting one of the image forming means includes a transfer belt 19a and a transfer charger 19 for each drum commonly used for each image forming station.
M, 19C, 19Y, and 19K. Each color is sequentially formed on the photosensitive drum on a recording material (not shown) that is supplied from the paper supply cassette 20 and supported on the transfer belt 19a. Is transferred to form a full-color image. The recording material that has completed the transfer process is separated from the transfer belt 19a, and is transferred to the tray 2 via the fixing device 21.
It is discharged to 2.

The scanning optical devices 17M, 17C, 17
Y and 17K are laser light sources (not shown) as light sources,
A rotating polygon mirror that scans the laser beam from the laser light source, an fθ lens that focuses the scanning beam on the generatrix of the surface of the photosensitive drum, a reflection mirror that changes the light flux, and a specific position of the scanning beam is detected. And a beam detector.

Next, a developing device in the above-described image forming apparatus will be described with reference to FIG. 2 taking a magenta developing device 9M as an example. In the following description, the developing device is simply referred to as “developing device 9”.

As shown in FIG. 2, a developing device 9 disposed opposite the photosensitive drum 4 includes a developing sleeve 3 as a developer carrier and a blade as a spike height regulating member in a developing container. Two. The inside of the developing device 9 is provided with a developing chamber (first chamber) 1 by a partition 6 extending in the vertical direction.
6 and a stirring chamber (second chamber) 17. Partition wall 6
The upper portion of the developing chamber 16 is open so that the excess two-component developer in the developing chamber 16 is collected in the stirring chamber 17 side. In this embodiment, the developing chamber 16 and the stirring chamber 17 contain a two-component developer containing a non-magnetic toner and a magnetic carrier.

In the developing chamber 16 and the stirring chamber 17, first and second screw-type developer stirring and conveying means 11 and 12 are disposed, respectively.

The first agitating / conveying means 11 is disposed substantially parallel to the bottom of the developing chamber 16 along the axial direction of the developing sleeve 3 (the developing width direction). It has a screw structure in which the blade member is provided in a spiral shape, and rotates the developer in the developing chamber 16 to agitate the developer in the developing chamber 16 at one end along the axial direction of the developing sleeve 3 at the bottom of the developing chamber 16. Transport.

The second stirring / transporting means 12 is also a screw having the same structure as that of the screw-type first stirring / transporting means 11 (a blade member is provided around the rotation axis by the first stirring / transporting means 11). It is a screw structure provided in a spiral shape in the opposite direction, and is disposed substantially parallel to the first stirring and conveying means 11 at the bottom in the stirring chamber 17. Then, the toner rotates in the same direction as the first stirring and conveying unit 11 and is supplied from a toner supply tank (not shown) to the upstream side of the stirring and conveying unit 12 under the control of the developer concentration control device. The developer already in the stirring chamber 17 is stirred and the toner concentration is made uniform while being conveyed in the direction opposite to the first stirring and conveying means 11.

In the partition 6, a developer passage (not shown) is formed at the front and rear ends in FIG. 1 for communicating the developing chamber 16 and the stirring chamber 17 with each other. The toner in the developing chamber 16 in which the toner is consumed by the development and the toner density is reduced by the conveying force of 11 and 12 moves from the other passage into the developing chamber 16. That is, the first and second stirring and conveying means 1
By the rotation of 1 and 12, the developer is circulated between the developing chamber 16 and the stirring chamber 17.

An opening is formed in the developing chamber 16 of the developing device 9 at a position corresponding to a developing area facing the photosensitive drum 4, and the developing sleeve 3 is rotatable so as to be partially exposed at the opening. The developing sleeve 3 is made of a non-magnetic material, rotates in the direction of the arrow in the developing operation, and includes a magnet 1 serving as a magnetic field generating means.
3 is fixed. The developing sleeve 3 is formed of the blade 2
The developer transports and transports the layer of the two-component developer, the height of which is regulated, and supplies the developer to the photosensitive drum 4 in a development area facing the photosensitive drum 4 to develop the latent image. In order to improve the development efficiency, that is, the toner application rate to the latent image, a development bias voltage in which a DC voltage and an AC voltage are superimposed is applied to the development sleeve 3 from the power supply 15.

In this embodiment, the magnet 13 is used as the developing magnetic pole N1.
And magnetic poles S2, N2, S2 and S3 for transporting the developer. The magnetic pole S <b> 2 is a pumping cut pole, and draws up the developer agitated and transported with the rotation of the first agitating and transporting means 11 to the developing sleeve 3 by a magnetic restraining force. At this pumping position, a blade 2 provided on the developer return member 1 is disposed so as to regulate the height of the developer pumped by the magnetic pole S2.

The blade 2 is made of aluminum (Al)
And is arranged on the upstream side in the rotation direction of the developing sleeve 3 from the photosensitive drum 4. By adjusting a gap between the developing sleeve 3 and the surface of the developing sleeve 3, the developing on the developing sleeve 3 is performed. The thickness of the developer transported to the area is regulated. Therefore, in this embodiment, the developer carried on the developing sleeve 3 by the magnetic pole S2 as described above allows both the non-magnetic toner and the magnetic carrier to pass between the tip of the blade 2 and the developing sleeve 3. As a result, the height of the spikes is regulated and sent to the developing area.

The developer whose height has been regulated is coated with a constant amount of a thin layer by the transporting magnetic poles N2 and S1 to form the main developing pole N.
The developer which has been developed in 1 and is not subjected to the development in the developing area is conveyed again to the developing chamber 16 by the developing sleeve 3 and scraped from the developing sleeve 3 into the developing chamber 16 by the repulsive magnetic poles S3 and S2. Collected.

The developer agitated and transported by the rotation of the first agitating and transporting means 11 is pumped up by the magnetic restraining force exerted by the magnetic field of the pumping cut pole S2. The height of the pumped developer is regulated by a blade 2 provided on the developer return member 1. The developer whose ear height is regulated is developed at the main development pole N1 by the transport magnetic poles N2 and S1 in a state where a certain amount of the thin layer is coated.

More specifically, the developer supplied to the developing sleeve 3 at the pumping cut pole S2 is immediately thinned by the blade 2, so that the lowermost developer at the transport magnetic poles N2 and S1, ie, on the sleeve 3, The rubbing force due to the magnetic binding force acting on the developer is small, so that the developer is not easily deteriorated. However, if the magnetic flux density of the pump cut pole S2 is low, the developer will not be pumped up, and if the magnetic flux density is high, deterioration will occur. Therefore, from the results of the experiment, the magnetic flux density of the pump cut pole S2 is 300 to 700.
In a state where the half width of G (Gaussian) was 25 ° to 45 °, the thin film coating of the developer was most possible. The distance between the blade 2 and the sleeve 3 was optimally 600 to 1300 μm for thinning the developer. Further, the positional relationship between the tip of the blade 2 and the pumping cut pole S2 is optimally ± 15 ° with respect to the pumping cut pole S2.

The number of magnetic poles related to the height control is not particularly limited. If there is a magnetic pole related to the height control by the pumping of the developer and the blade 2 and a magnetic pole related to transport other than the main development pole, the deterioration of the developer is reduced. For the purpose of prevention, the developer can be transported in a thin layer by the height restriction. That is, assuming that the total number of magnetic poles is n, it is better to control the height of the magnetic poles up to the (n-1) th pole upstream of the main developing pole. After the development at the main developing pole, if there is a magnetic pole for collecting the developer into the developing device, it is desirable to remove the magnetic pole. In this embodiment, there is a total of five magnetic poles, and there is a magnetic pole S3 for collecting the developer to the developing device after the main developing pole N1, so that the collecting magnetic pole S3 is removed in addition to the main developing pole N1. For this reason, it is preferable that the magnetic poles for which the height is regulated are magnetic poles up to n-2 poles upstream of the main developing pole.

Next, the developer used in this embodiment will be described. The carrier used in the present invention has a smaller average particle size and a sharper particle size distribution than conventional general carriers. Due to the small particle size, the number of times of contact between the carrier and the toner increases, the rise of the toner charge becomes faster, and the uncharged toner is not developed even if the supply amount increases. Further, the rise of the charging speed can prevent the uncharged toner from scattering and fogging under high humidity. Therefore, by combining with the toner described below, a magenta developer which is resistant to humidity and does not cause scattering or fogging even when continuous copying of a document having a large image area is obtained.

Further, by sharpening the particle size distribution, it is possible to solve the problem that the fine powder carrier is generated along with the small particle size carrier and adheres to the photoconductor together with the toner during development. The image quality is prevented from deteriorating due to the charging failure.

20% by weight of ultrafine powder of 400 mesh or less
Or less, preferably 16% by weight or less. If the content is 20% by weight or more, the carrier adheres to the photoreceptor, hinders smooth triboelectric charging with the toner, and promotes the edge effect. The fine powder having a size of 350 mesh or less is 30% by weight or less, preferably 25% by weight or less, more preferably 20% by weight or less. If the content is 30% by weight or more, the rise of the toner charge becomes extremely poor, and the edge effect also increases.

Further, the amount of coarse powder of 250 mesh or more is
It is closely correlated with the sharpness of the image. When the content is 10% by weight or more, the scattering of the toner to the non-image portion increases, and the resolution of the image is likely to be reduced and the image is likely to be rough. Therefore, the content of 250 mesh or more is 10% by weight or less, preferably 7% by weight or less, more preferably 5% by weight or less.

The average particle size of the carrier is preferably from 20 to 60 μm, more preferably from 30 to 56 μm. 20
When the average particle diameter is less than μm, the image density decreases due to charge-up of the toner and the carrier adhesion to the photoreceptor increases.
An average particle size of 0 μm or more deteriorates reproducibility of fine lines in copying.

The magnetic characteristics of the carrier greatly affect the developing characteristics and transport of the developer, and the uniformity and gradation of the image are emphasized.

When the saturation magnetization is 75 emu / g or more (for an applied magnetic field of 3,000 Oersteds), the toner is composed of a carrier and a toner on a developing sleeve facing an electrostatic latent image on a photoreceptor at the time of development. The resulting brush-like ears are firmly tightened, and the gradation and the reproduction of halftone are deteriorated. In addition, when it is 55 emu / g or less, it becomes difficult to hold the toner and the carrier on the developing sleeve,
There is a disadvantage that fog and toner scattering are worsened. Further, when the residual magnetization and the coercive force of the carrier are too high, the transport of the developer in the developing device is deteriorated, and image blurring and uneven density in a solid image are likely to occur. Therefore, the residual magnetization and the coercive force are reduced to 10 emu / g or less, respectively.
It is necessary that the temperature be not more than Oersted (for an applied magnetic field of 3,000 Oersted), preferably not more than 5 emu / g and not more than 6.0 Oersted.

As the binder resin to be used in the toner of the present invention, any known resins can be used. For example, polystyrene, poly-p-chlorostyrene, polyvinyltoluene and other styrenes and their substituted homopolymers, styrene -P-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, Styrene-butyl acrylate copolymer, stinene-
Octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-
Acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile- Indene copolymer,
Styrene-maleic acid copolymer, styrene-based copolymer such as styrene-maleic acid ester copolymer, polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, Epoxy resin, polyvinyl butyral, polyamide, polyacrylic acid resin, rosin, modified rosin, terpene resin,
Phenol resins, aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, paraffin waxes and the like can be used alone or in combination.

Further, a charge control agent may be added to the toner of the present invention as needed. As an example, in the case of a magenta toner, in the case of a negative toner, a dye having an anthraquinone-based magenta color, or a metal chelate of alkyl salicylic acid, or the like, in the case of a positive toner, a magenta basic dye, or And their lake pigments can be used.

In the developer in which the toner of the present invention is used, a charge controlling agent such as colloidal silica and a fluidity modifier are added in an amount of 0.01 to 5% by weight (preferably 0.1 to 5% by weight) based on the toner. It is preferable to add about 2% by weight).

As the carrier used in the present invention, known materials can be used as long as the gist of the present invention is not hindered. For example, surface-oxidized or unoxidized iron, nickel, copper,
Metals such as zinc, cobalt, manganese, chromium, and rare earths, and alloys or oxides thereof, and ferrites are preferable. Ferrites selected from zinc, copper, nickel, and cobalt metals can be preferably used. In addition, there is no particular limitation on the manufacturing method.

Further, the surface of the carrier can be covered with a resin or the like. As the method, a method of dissolving or suspending a coating material such as a resin in a solvent and applying it and attaching it to a carrier, a method of simply mixing with a powder, and the like,
Any of the conventionally known methods can be applied.

The substance fixed to the carrier surface varies depending on the toner material. Examples thereof include polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicone resin, polyester resin, metal complex of ditersharry butylsalicylic acid, and styrene-based. It is appropriate to use a resin, an acrylic resin, a polyamide, polyvinyl butyral, nigrosine, an aminoacrylate resin, a basic dye and its lake, a silica fine powder, an alumina fine powder, or the like alone or in combination, but it is not necessarily limited thereto. .

The amount of the compound to be treated may be appropriately determined so that the carrier satisfies the above conditions, but is generally 0.1 to 30% by weight (preferably 0.5 to 20% by weight) based on the carrier of the present invention. % By weight) is desirable.

In the present invention, a particularly preferred embodiment is a ternary ferrite of Cu—Zn—Fe whose surface is formed by a combination of a resin such as a fluororesin and a styrene resin, for example, polyvinylidene fluoride and styrene-ferrite. Methyl methacrylate resin, polytetrafluoroethylene and styrene-methyl methacrylate resin, fluorine-based copolymer and styrene-based copolymer 90:10 to 20:
80, preferably 70:30 to 30:70, in a mixture of 0.01 to 5% by weight, preferably 0.1 to 5% by weight.
One that is a coated ferrite carrier coated with 1 to 1% by weight. As the fluorine-based copolymer, a vinylidene fluoride-tetrafluoroethylene copolymer (10:90 to 90:10) is exemplified, and as the styrene-based copolymer, styrene-2-ethylhexyl acrylate (20:80 to 80:20), styrene-2-ethylhexyl acrylate-methyl methacrylate (20-6)
0: 5 to 30:10 to 50).

The method for measuring the particle size distribution of the carrier in the present invention is as follows. 1. Weigh about 100 samples to the nearest 0.1 g. 2. As the sieve, a standard sieve of 100 Mesh to 400 Mesh (hereinafter referred to as a sieve) is used.
The trays are placed on the bottom of the stack in the order of 00, 250, 350, 400, and the sample is put on the top sieve and capped. 3. Using a vibrator, the number of horizontal turns is 285 ± 6 per minute.
And shake at 150 ± 10 times per minute for 15 minutes. 4. After sieving, weigh the iron powder in each sieve and tray to the nearest 0.1 g. 5. Calculated to the second decimal place by weight percentage, JIS-Z8
401 rounds to the first decimal place.

The size of the sieve frame is 200 mm in inner diameter above the sieve surface and 45 mm in depth from the upper surface to the sieve surface. Also, the sum of the weights of the iron powders in each part must not be less than 99% of the mass of the sample initially taken.

The average particle size is determined from the above-mentioned measured particle size distribution according to the following equation.

[0049]

(Equation 1)

As a device for measuring the magnetic properties of the carrier, a BHU-60 type magnetization measurement device (manufactured by Riken Keisoku) is used. About 1.0 g of the measurement sample was weighed, the inner diameter was 7 mm, and the height was 1
Pack in a 0 mm cell and set in the above device.

In the measurement, first, an applied magnetic field is gradually applied to change the maximum to 3,000 Oe. Next, the applied magnetic field is reduced, and finally a hysteresis curve of the sample is obtained on the recording paper. As a result, saturation magnetization, residual magnetization,
Find the coercive force.

In this example, carriers shown in Table 1 by A to C and toners shown in Table 2 by a to c were prepared.

[0053]

[Table 1]

[0054]

[Table 2]

The toner was melt-kneaded with a roll mill, cooled, and then finely pulverized and classified with a jet mill.
A classified product having an average particle size of 8 to 15 μm was obtained. For this classifier,
0.5% by weight of hydrophobic silica (trade name: R-972, manufactured by Nippon Aerosil Co., Ltd.) was externally added with a Henschel mixer to obtain the toner of the present invention. Further, the toner and the carrier were mixed to obtain a developer having a toner concentration of 6%. Using this developer, a copy test was performed using the image forming apparatus shown in FIG. 1 equipped with the developing device shown in FIG. The results are shown below.

( Examination Example 1 ) A developer having a carrier indicated by A in Table 1 and a toner having a carrier indicated by a in Table 2 was used. A printing durability test of 10,000 sheets was performed. As a result, even after copying 20,000 sheets,
An image with little edge effect was obtained, and no image deterioration such as fogging or scattering occurred. Further, using the same developer and original, a printing durability test of 10,000 sheets was conducted at 30 ° C. and high temperature and high humidity of 80%, but no scattering or fogging occurred.

( Study Example 2 ) The same printing durability as in Study Example 1 was carried out using a developer shown in Table 1 as B for the carrier and a developer shown in Table 2 for the toner as b. But the image is
It was satisfactory enough.

( Study Example 3 ) The same printing durability as in Study Example 1 was carried out using a developer shown in Table 1 with A as the carrier and a toner shown in Table 2 with c as the toner. However, there was no image deterioration and the result was good.

( Examination Example 4 ) The same printing durability as in Examination Example 1 was carried out using a developer shown in Table 1 as C and a toner as shown in Table 2 as a toner. However, 1.
Fog occurred on 50,000 sheets. Further, in the same manner as in Study Example 1, a printing durability test was performed on 50,000 sheets at 30 ° C. and high temperature and high humidity of 80%, and fog and scattering were remarkably deteriorated on 1,000 sheets.

[0060]

<Embodiment 2> Next, Embodiment 2 of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description is omitted.

In the first embodiment, the edge of the blade 2 corresponds to the normal direction of the sleeve 3, but in this embodiment, the edge of the blade 2 is set to be tangential to the sleeve 3 as shown in FIG. It is characterized by the following. This has an effect of reducing the shearing force of the pumped-up developer at the blade portion as compared with the blade direction of the first embodiment, and thus has an even more effective effect on the deterioration of the developer.

At this time, the distance between the sleeve side surface at the edge of the blade 2 and the sleeve 3 is 600 to 13 as in the first embodiment.
00 μm is optimal.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description is omitted.

In this embodiment, it will be described that the present invention is applicable to a developing device different from the developing device of the image forming apparatus described above. As shown in FIG. 5, the rotation directions of the photosensitive drum 4 and the developing sleeve 3 are opposite (counter). The magnetic pole for pumping up the developer is S2, and the developer return member 1
The magnetic pole N2 is used to convey the developer compressed by the magnetic pole force to the blade 2 in order to cut the developer. The developer coated in a thin layer with the pumping cut pole S2 is transferred to the developing main pole S while keeping the thin layer by the transport magnetic pole N2.
It is transported to 1.

[0066]

As described above, according to the present invention,
The first magnetic pole and the second magnetic pole allow the developer from the developer carrier
攪developer it by the stirring means is provided at a position falling
Stir to adjust concentration , then pump onto developer carrier
By controlling the size of the developer, it is possible to provide a high quality image in a configuration in which the lowermost layer of the developer carried on the developer carrier is prevented from deteriorating.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a schematic configuration of a developing device in the apparatus of FIG. 1;

FIG. 3 is a diagram illustrating a schematic configuration of an image forming apparatus used in an experiment according to the first embodiment of the present invention.

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

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

FIG. 6 is a diagram showing a schematic configuration of a conventional developing device.

FIG. 7 is a schematic diagram showing a force acting on a developer near the surface of a developing sleeve of the apparatus in FIG. 6;

[Explanation of symbols]

 Reference Signs List 2 blade (developer spike height regulating means) 3 developing sleeve (developer carrier) 4 photosensitive drum (latent image carrier) 9 developing device 11 first stirring and conveying means (developer stirring means) 12 second stirring and conveying means (developing) Agent stirring means) 13 magnet

Continuation of the front page (56) References JP-A-2-110484 (JP, A) JP-A-1-142775 (JP, A) JP-A-64-40970 (JP, A) JP-A-3-172858 (JP) , A) JP-A-1-223471 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/09

Claims (7)

(57) [Claims] 1. A toner for developing a latent image on an image carrier.
And a developer carrying member for carrying and transporting a developer containing a magnetic carrier, a magnetic field generating means provided in the developer carrying body for generating a magnetic field, and a developing device for regulating a layer thickness of the developer carried on the developer carrying member And a magnetic field generating unit, which is adjacent to the first magnetic pole and downstream of the first magnetic pole and upstream of the developing magnetic pole in the rotating direction of the developer carrier. A developing device provided with a first magnetic pole and a second magnetic pole having the same polarity, provided at a position where the developer falls from the developer carrier by the first magnetic pole and the second magnetic pole to stir the developer. The developer regulating means disposed opposite to the second magnetic pole;
Developing apparatus is characterized in that to regulate the developer drawn up to the developer carrying member by the second magnetic pole from being agitated by the agitating means. 2. The developing device according to claim 1, wherein a tip of said developer regulating means is provided in said second portion.
The developing device according to claim 1, wherein the developing device is provided at a position of ± 15 ° with respect to the magnetic pole. 3. The developing device according to claim 1, wherein the magnetic flux density of the second magnetic pole is 300 gauss to 600 gauss. 4. A half-value width of the second magnetic pole is 25 ° to 45 °.
The developing device according to claim 3, wherein 5. The carrier has an average particle size of 20 to 60 μm.
The particle size of 400 mesh or less is 20% by weight or less, preferably 16% by weight or less, and the particle size of 350 mesh or less is 3% by weight.
0% by weight or less, preferably 25% by weight or less, more preferably 20% by weight or less,
Wt% or less, preferably 7 wt% or less, more preferably 5 wt% or less. Further, the saturation magnetization is 50 emu / g or more and 75 emu / g (with respect to an applied magnetic field of 3000 Oersted), and the residual magnetization and the coercive force are 10 emu. / G
10 oersted or less (for an applied magnetic field of 3000 oersted), preferably 5 emu / g or less,
The method of claim 6, wherein the temperature is 6.0 Oersted or less.
The developing device according to claim 1 . At 6. developing, a developing device according to any one of claims 1 to 5 for the developer carrying member and a voltage obtained by superimposing a DC voltage and an AC voltage is applied. 7. according to any one of claims 1 to 6, wherein the rotational direction of the developer carrying member and the upper <br/> Kizo carrier in the developing unit is opposite to each other Developing device.