JPH0792815A - Developing device - Google Patents

Abstract

PURPOSE:To suppress the deterioration rate of a developer by specifying the peak value of each magnetic flux density of plural carrying poles of a magnet arranged in a standstill state inside a developer carrying member. CONSTITUTION:18 Kinds of magnet rollers 10 having the different magnetic flux densities of first, second and third magnetic poles N1, S2 and N2 are prepared and in each magnet roller 10, the carrying properties of the developer in a developing device 9 and the degradation of an image after 100,000 copies of A-4 size paper at a printing ratio of 10% are evaluated. Consequently, when each magnetic flux density of the second and third magnetic poles S2 and N2 is 10%-49% to that of the first magnetic pole N1, it is judged that the carrying properties of the developer are excellent as well and the degradation of the image can be prevented. In other words, the deterioration of the developer can be prevented for a long period. At this time, the magnetic flux of the magnetic pole is of the peak value on the surface of a sleeve (developer carrying member) 3 of the magnetic flux density distribution of a magnetic filed formed by the magnetic pole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for developing an electrostatic latent image using a developer containing toner particles and magnetic carrier particles.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIG. 1, which is an explanatory view of a developing device to which the present invention can be applied.

In FIG. 1, a developing device 9 has a container 8 for containing a two-component developer 7 in which non-magnetic toner particles and magnetic carrier particles are mixed.

A first stirring chamber 13 and a second stirring chamber 14 are provided in the container 8, and the first stirring chamber 13 and the second stirring chamber 14 are provided.
A partition wall 6 is provided between them. The partition wall 6 is provided with developer passage openings at both ends in the longitudinal direction (perpendicular to the paper surface), and the developer is supplied to the first stirring chamber 13 and the second stirring chamber 14 respectively.
Cycle between.

As a means for moving and stirring the developer in the longitudinal direction of the sleeve 3 (direction perpendicular to the paper surface), which will be described later, the developer is rotated between the first stirring chamber 13 and the second stirring chamber 14 in the directions of the arrows. Screws 11 and 12 are arranged.

By the rotation of the screw 11, the developer in the first stirring chamber 13 moves and is stirred in the longitudinal direction and enters the second stirring chamber 14 through the one opening.
Then, the developer in the second stirring chamber 14 moves in the longitudinal direction while being stirred by the rotation of the screw 12, and enters the first stirring chamber 13 again through the other opening. Screw 11, 1
The moving direction of the developer by 2 is the opposite direction. In any case, the toner and the carrier are uniformly mixed by the agitation, and the toner obtains a triboelectric charge having a sufficient polarity for developing the latent image by friction with the carrier.

Toner is supplied to the second stirring chamber 14 from a toner replenishing means (not shown).

At the opening of the container 8, a non-magnetic sleeve 3 made of aluminum, stainless steel or the like is used as a developer carrying member.
Are arranged. This sleeve 3 rotates in the direction of the arrow.

A magnet 10 is arranged stationary inside the sleeve 3. The magnet 10 has a plurality of magnetic poles on its peripheral surface. In the illustrated example, two north poles N ₁ and N ₂ and three S poles are provided.
There are poles S ₁ , S ₂ , S ₃ .

In the rotation path of the sleeve 3, there are a supply position 31, a regulating position 32, a developing position 33 and a removing position 34. The sleeve 3 rotates through each of the above positions in the above order.

The developing position 33 also passes through the electrophotographic photosensitive member 4 as an image bearing member. At this position 33, toner adheres to the electrostatic latent image on the photoconductor 4 and the latent image is developed.

The first magnetic pole N ₁ is a developing magnetic pole that forms a magnetic field at the developing position 33. The magnetic brush of the developer formed by this magnetic field contacts the photoconductor 4.

A vibration bias voltage is applied to the sleeve 3 from a developing bias voltage source 15 in order to improve the developing efficiency. As the vibration bias voltage, a voltage obtained by superimposing a DC voltage on an AC voltage can be used. However, a DC bias voltage may be applied to the sleeve 3.

The second, third, fourth and fifth magnetic poles S ₂ , N ₂ ,
S ₃ and S ₁ function as carrier magnetic poles that magnetically attract the developer onto the sleeve 3 so that the developer can be transported by the rotation of the sleeve 3.

The second magnetic pole S ₂ draws up the developer in the first stirring chamber 13 by the magnetic field, and magnetically attaches the drawn developer on the surface of the sleeve 3 at the supply position 31.

The developer magnetically attached to the surface of the sleeve 3 at the supply position 31 is regulated by the rotation of the sleeve 3 at the regulating position 3.
It is transported to 2.

At the regulating position 32, the developer layer thickness regulating member 2 is arranged so as to face the sleeve 3. For this member 2, a non-magnetic doctor blade such as aluminum can be used. The gap between the blade 2 and the sleeve 3 is 600 to 130.
0 μm is preferable for thinning the developer.

The blade 2 regulates the thickness of the developer layer conveyed to the developing position 33.

The third magnetic pole N ₂ forms a magnetic field at the regulation position 32 so that the blade 2 can regulate the thickness of the developer layer smoothly.

The developer, which has been prevented from passing through the gap between the blade 2 and the sleeve 3 at the regulating position 32, is reversed in the direction substantially opposite to the rotating direction of the sleeve 3 and enters the first stirring chamber by the action of gravity. To fall.

The reverse movement of the developer is guided by the developer guide surface 1'of the guide member 1.

The fourth magnetic pole S ₃ is located upstream of the second magnetic pole S _{2 with} respect to the rotation direction of the sleeve 3 and is adjacent to the second magnetic pole S ₂ . The fourth magnetic pole S ₃ has the same polarity as the second magnetic pole S ₂ . Therefore, a repulsive magnetic field is formed between the magnetic poles S ₂ and S ₃ . The developer remaining on the sleeve 3 after the development and returning to the container 8 is removed by the repulsive magnetic field.
At 4, the sleeve 3 is separated from the sleeve 3 and falls into the first stirring chamber 13.

The fifth magnetic pole S ₁ is located between the regulating position 32 and the developing position, and contributes to the stable conveyance of the developer layer passing through the regulating position 32 to the developing position 33. If the distance between the regulation position 32 and the developing position 33 is short, the fifth magnetic pole S ₁ is unnecessary. In any case, in an apparatus using a two-component developer, the developer deteriorates as the operation of the apparatus is repeated.

[0024]

By the way, the feeding position 3
A relatively thick developer layer is present on the surface of the sleeve 3 between 1 and the regulating position 32. The developer near the surface of the lowermost sleeve 3 of the developer layer contains the magnetic poles S ₂ , N.
The magnetic force of ₂ attracts the developer layer and applies a magnetic pressure toward the sleeve center.

It has been found that the action of this pressure exerts a strong stress on the toner particles and the magnetic carrier particles in the vicinity of the sleeve surface, and as a result, carrier deterioration in which the resin component of the toner is fused to the carrier particle surface is promoted. .

When an external additive such as silica fine particles or titanium oxide fine particles is externally added to the toner in order to improve fluidity, the stress accelerates deterioration of the toner by embedding the external additive in the toner. It turned out that it was done. When such carrier deterioration and / or toner deterioration occur, the toner cannot obtain sufficient triboelectric charge, the image quality of the developed image deteriorates, fog occurs in the background portion of the developed image, and the toner is exposed outside the container. The toner is likely to be scattered from the surface of the sleeve.

An object of the present invention is to provide a developing device capable of suppressing the deterioration rate of the developer.

Another object of the present invention is to provide a developing device which can suppress the deterioration rate of the developer and form a developed image of good quality for a long period of time.

Still another object of the present invention is to provide a developing device capable of suppressing the deterioration rate of the developer and suppressing fog and toner scattering for a long period of time.

[0030]

The above-described objects are achieved by the developing device according to the present invention. In summary, the present invention provides an electrostatic latent device comprising a rotatable developer carrying member for carrying a developer containing toner particles and magnetic carrier particles, and a magnet statically arranged inside the developer carrying member. In a developing device for developing an image, the developer carrying member has a supply position where the developer is supplied to the surface thereof, a restriction position where a restriction member for restricting the layer thickness of the developer on the surface is arranged, and a static position. The magnet rotates with a developing position where the latent image is developed and a removing position where the developer remaining on the surface after development is removed in this order, and the magnet forms a magnetic field that forms a magnetic field at the developing position. ,
It has a plurality of carrier magnetic poles located between the supply position and the regulation position, and the peak value of the magnetic flux density of each of the plurality of carrier magnetic poles is 10 to 10 times the peak value of the magnetic flux density of the developing magnetic pole.
The developing device is characterized by being in the range of 49%. Preferably, the magnetic flux density peak value of the developing magnetic pole is 7
It is 50-1400 gauss. The carrier particles have an average particle size of 20 to 60 μm, carrier particles having a particle size of 400 mesh or less are 20 wt% or less, carrier particles having a particle size of 350 mesh or less are 30 wt% or less, 250
Carrier particles of mesh or more is 10% by weight or less,
The saturation magnetization of the carrier particles is 55 emu / g or more and 75 emu / g or more for an applied magnetic field of 3000 oersteds.
Hereinafter, the remanent magnetization is 10 emu / g or less for an applied magnetic field of 3000 oersteds, and the coercive force is 10 oersted or less for an applied magnetic field of 3000 oersteds.

According to another aspect of the present invention, a developer stirring chamber in which a stirring member for stirring the developer containing toner particles and magnetic carrier particles is arranged, and a rotatable developer carrying member for conveying the developer. In a developing device for developing an electrostatic latent image, comprising a magnet disposed stationary inside the developer carrying member, the developer carrying member regulates a layer thickness of the developer carried on the surface thereof. The regulation position where the regulation member is arranged,
The magnet rotates by passing through a developing position where the electrostatic latent image is developed and a removing position where the developer remaining on the surface after the developing is removed in this order, and the magnet forms a magnetic field at the developing position. A magnetic pole, a second magnetic pole for magnetically attracting the developer in the stirring chamber onto the surface of the developer carrying member at a position between the removing position and the restricting position, and a second magnetic pole with respect to the rotating direction of the developer carrying member. A third magnetic pole that is located downstream of the second magnetic pole and upstream of the regulation position and that forms a magnetic field at the regulation position, and has a magnetic flux density of each of the second magnetic pole and the third magnetic pole. The peak value is 10 to 4 of the peak value of the magnetic flux density of the first magnetic pole.
There is provided a developing device characterized by being in the range of 9%. Preferably, the magnetic flux density peak value of the first magnetic pole is 750 to 1400 gauss. Further, the magnet has a fourth magnetic pole located upstream of the second magnetic pole with respect to the rotation direction of the developer carrying member and adjacent to the second magnetic pole, and the fourth magnetic pole has the second magnetic pole. The developer is removed from the developer carrying member at the removal position by the repulsive magnetic field having the same polarity as the magnetic pole and formed by the second magnetic pole and the fourth magnetic pole. Further, the carrier particles have an average particle size of 20.
Carrier particles having a particle size of 400 mesh or less are 20% by weight or less, carrier particles having a particle size of 350 mesh or less are 30% by weight or less, carrier particles having a particle size of 250 mesh or more are 10% by weight or less, or The saturation magnetization of the carrier particles is 55 emu / g or more and 75 emu / g or less for an applied magnetic field of 3000 Oersted, and the residual magnetization is 10 em for an applied magnetic field of 3000 Oersted.
The coercive force is u / g or less, and the coercive force is 10 oersted or less for an applied magnetic field of 3000 oersted.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The developing device according to the present invention will be described in more detail below with reference to the drawings.

FIG. 1 is an explanatory view of an embodiment of the present invention, and the arrangement and function of each member are as described above.

[0034] However, the magnetic pole S _2, N ₂ causing the developer deterioration is the strength of the magnetic poles capable of preventing deterioration of the developer over a long period of time.

Therefore, regarding the magnet roller 10 shown in FIG. 1, 18 kinds of magnet rollers 10 having different magnetic flux densities of the first, second and third magnetic poles N ₁ , S ₂ and N ₂ are prepared. The developer transportability in the developing device 9 and the image deterioration after 100,000 copies of A4 size paper at a printing ratio of 10% were evaluated. The results are shown in Table 1.

In the present specification, the magnetic flux density of the magnetic pole means the magnetic flux density distribution of the magnetic field formed by the magnetic pole.
It refers to the peak value on the surface of the sleeve (developer carrying member).

Further, in Table 1, N ₂ / N ₁ is expressed by 100 × (magnetic flux density of magnetic pole N ₂ ) / (magnetic flux density of magnetic pole N ₁ ), S ₂ / N _1. What is done is 100
X (magnetic flux density of magnetic pole S ₂ ) / (magnetic flux density of magnetic pole N ₁ ).

In Table 1, the symbol ◯ means good, the symbol Δ means good, and the symbol x means bad.

[0039]

[Table 1]

As can be seen from Table 1, the second magnetic pole S ₂ and the third magnetic pole
1 magnetic flux density of people pole N ₂ husband of the magnetic flux density of the first magnetic pole N ₁
It can be seen that when the content is 0% or more and 49% or less, the developer transportability is good and image deterioration can be prevented. That is, the deterioration of the developer can be prevented for a long period of time.

The developers usable in the present invention will be described below. In this embodiment, 2 having carrier and toner
A component developer was used. The carrier used in the present invention preferably has a smaller average particle shape and a sharper particle size distribution than conventional general carriers. Due to the small particle size, the number of times the carrier and the toner contact each other increases, the charging of the toner rises faster, and the uncharged toner is not developed even if the replenishment amount increases. Furthermore,
By increasing the rate of rise of charging, it is possible to prevent scattering and fog due to uncharged toner under high humidity. Therefore, by combining with the toner described below, it is possible to obtain a developer which is free from scattering and fog and is less affected by a change in humidity even when an original having a large image area is continuously copied.

Further, by sharpening the particle size distribution of the carrier, the phenomenon that the fine powder carrier often accompanies with the toner and adheres onto the photosensitive drum during development, which often occurs in the small particle size carrier, is solved. This prevents deterioration of image quality due to poor charging due to powder carriers.

Fine powder carrier of 400 mesh or less is 2
It is 0% by weight or less, preferably 13% by weight or less. 20
When the content is more than 5% by weight, the carrier adheres to the photosensitive drum, and the smooth frictional electrification with the toner is disturbed to promote the edge effect. Fine powder carrier of 350 mesh or less,
It is 30% by weight or less, preferably 25% by weight or less, more preferably 20% by weight or less. When the amount is 30% by weight or more, the rise of the charging of the toner is significantly deteriorated and the edge effect is increased.

Further, the amount of coarse powder carrier of 250 mesh or more closely correlates with the sharpness of the image, and when it is 10% by weight or more, the scattering of the toner to the non-image area increases,
The resolution of the image is likely to be deteriorated and the image is likely to be rough. Therefore, the carrier of 250 mesh or more is 10% by weight or less, preferably 7% by weight or less, more preferably 5% by weight.
It is the following.

The average particle size of the carrier is preferably 20 to 60 μm, more preferably 30 to 56 μm. 20
If the average particle size is less than or equal to μm, the image density will decrease due to toner charge-up and carrier adhesion to the photosensitive drum will increase.

The magnetic characteristics of the carrier have a great influence on the developing characteristics and the transportation of the developer, and the uniformity and gradation of the image are important.

When the saturation magnetization is 75 emu / g (for an applied magnetic field of 3000 oersteds) or more, at the time of development, it is composed of carrier and toner on the developing sleeve facing the electrostatic latent image on the photosensitive drum. The brush-like spikes are in a tightly tightened state, resulting in poor reproduction of gradation and halftone. If it is less than 55 emu / g, it becomes difficult to hold the toner and carrier on the developing sleeve,
There is a drawback that fog and toner scattering are worsened. Further, if the residual magnetization and the coercive force (coercive force) of the carrier are too high, the conveyance of the developer in the developing device is deteriorated, and image blurring and uneven density in a solid image are likely to occur. Therefore, with respect to an applied magnetic field of 3000 oersteds, the carrier remanent magnetization and the coercive force are each 10 emu / g or less,
10 oersted or less, preferably 5 emu / g or less,
It should be below 6.0 oersted.

The method of measuring the particle size distribution of the carrier in this example is as follows. 1. Approximately 100 g of sample is weighed to the nearest 0.1 g. 2. As the sieve, a standard sieve of 100 mesh to 400 mesh (hereinafter simply referred to as “sieve”) is used, and 100 from the top,
145, 200, 250, 350 and 400 are stacked in this order, a saucer is placed on the bottom, and the sample is placed on the top sieve and covered. 3. This is oscillated by a vibrator and the number of horizontal turns per minute (285 ±
6) times, vibrating 15 times per minute (150 ± 10) times. 4. After sieving, the iron powder in each sieve and the pan is weighed to the nearest 0.1 g. 5. Calculated to the second decimal place in weight percentage, and JIS-Z8
Round up to the first decimal place by 401.

At this time, the size of the screen frame has an inner diameter of 200 mm above the screen surface and a depth of 45 from the top surface to the screen surface.
mm, and the total weight of the iron powder in each part must not be less than 99% of the mass of the sample initially taken.

The average particle size is obtained from the above-mentioned measured value of particle size distribution according to the following formula. Average particle size (μ) = 1/100 × {(remaining amount of 100 mesh sieve) × 140 + (remaining amount of 145 mesh sieve) × 122
+ (Remaining amount of 200 mesh sieve) x 90 + (remaining amount of 250 mesh sieve) x 68 + (remaining amount of 350 mesh sieve) x 5
2 + 400 mesh sieve remaining amount) × 38 + (total sieve passing amount)
X14} As a measuring device for magnetic properties of carriers, BHU-60
Type magnetization measuring device (manufactured by Riken Seisakusho) is used.

About 1.0 g of the measurement sample is weighed and the inner diameter is 7 m.
The cells are packed in a cell having a height of 10 mm and a height of 10 mm and set in the above apparatus.

In the measurement, first, the applied magnetic field is gradually added and changed up to 3000 Oersted. Next, the applied magnetic field is reduced, and finally the hysteresis curve of the sample is obtained on the recording paper. From this, the saturation magnetization, remanent magnetization, and coercive force are obtained.

As the carrier used in this embodiment,
Known materials can be used, for example, surface-oxidized or unoxidized iron, nickel, copper, zinc, cobalt, manganese,
Metals such as chromium and rare earths, their alloys or oxides, and ferrites are preferable, and ferrites selected from metals such as zinc, copper, nickel, and cobalt can be preferably used. Further, there is no particular limitation as a manufacturing method thereof.

It is also possible to coat the surface of the carrier with a resin or the like. As the method, any conventionally known method such as a method of dissolving or suspending a coating material such as a resin in a solvent and applying the coating material and attaching it to a carrier, or a method of simply mixing with a powder can be applied.

The substance adhered to the surface of the carrier varies depending on the toner material. For example, polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicone resin, polyester resin, metal complex of di-t-butylsalicylic acid, Styrene resin,
Acrylic resin, polyamide, polyvinyl butyral,
It is suitable to use nigrosine, amino acrylate resin, basic dye and its lake, fine silica powder, fine alumina powder, etc. alone or in combination, but not limited thereto.

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

In a particularly preferred embodiment which can be used in the present embodiment, Cu-Nn-Fe ternary ferrite is used, and the surface thereof is a combination of a resin such as a fluorine resin and a styrene resin, for example, polyfluoride. Vinylidene and styrene-methylmethacrylate resin, polytetrafluoroethylene and styrene-methylmethacrylate resin,
Fluorine-based copolymer and styrene-based copolymer 90: 1
A mixed ferrite carrier having a ratio of 0 to 20:80, preferably 70:30 to 30:70, which is a coated ferrite carrier of 0.01 to 5% by weight, preferably 0.1 to 1% by weight. Can be mentioned. Examples of the fluorine-based copolymer include vinylidene fluoride-tetrafluoroethylene copolymer (10:90 to 90:10), and examples of the styrene-based copolymer include styrene-2-ethylhexyl acrylate (20: 80-). 80:20), styrene-
2-Ethylhexyl acrylate-methyl methacrylate (20 to 60: 5 to 30:10 to 50) is exemplified.

As the binder resin applied to the toner, all known binder resins can be used. For example, polystyrene,
Poly-p-chlorostyrene, homopolymers of styrene such as polyvinyltoluene and its substitution products, styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers, styrene-vinylnaphthalene Copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-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 Styrene-based copolymers such as ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-acrylonitrile-indene copolymers, styrene-maleic acid copolymers, styrene-maleic acid ester copolymers Coalesce, polymethylmethacrylate, polybutylmethacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene,
Polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyamide, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, Paraffin wax and the like can be used alone or as a mixture.

Further, a charge control agent may be added to the toner, if necessary. Taking magenta toner as an example, in the case of negative toner, a dye having an anthraquinone-based magenta color, or a metal chelate of alkylsalicylic acid, in the case of positive toner, a magenta basic dye, Alternatively, those lake pigments and the like can be used. Further, with respect to the developer in which the toner is used, 0.01 to 5% by weight (preferably 0.1 to 2% by weight) of a charge control agent such as colloidal silica and a fluidity modifier are added to the toner. ) It is preferable to add about 10%.

The developer used in this embodiment will be described in detail below.

Carriers A to C shown in Table 2 and toners a to c shown below were prepared.

[0062]

[Table 2]

Toner a: Styrene-n-butyl 100 parts by weight Methacrylate copolymer Charge control agent 4.0 parts by weight Quinacridone pigment 4.0 parts by weight (CiPigment Red 122) Methine dye 1.0 parts by weight (CIBasic Red 12)

Toner b: Unsaturated polyester resin 100 parts by weight Electrostatic control agent 4.0 parts by weight Quinacridone pigment 3.5 parts by weight (CI Pigment Red 202) Methine dye 0.5 parts by weight (CIBasic Red 14 )

Toner c: Styrene resin 100 parts by weight Electrostatic control agent 4.0 parts by weight Quinacridone pigment 4.0 parts by weight (C.I. Pigment Red 122)

Each of the toners a, b, and c was melt-kneaded by a roll mill, cooled, and then finely pulverized and classified by a jet mill to obtain a classified product having an average particle size of 8 to 15 μm. 0.5% by weight of hydrophobic silica (trade name R-972, manufactured by Nippon Aerosil Co., Ltd.) was externally added to this classified product with a Henschel mixer to obtain a toner of the present invention. Further, the toner and a carrier were mixed to obtain a developer having a toner concentration of 6%.

In the present embodiment, when a combination of the developers (carrier A + toner a), (carrier B + toner b), and (carrier A + toner c) is used, the developing devices (a) to (r) are used. ), The evaluation results shown in Table 1 are obtained, and as a developer (carrier C + toner a)
When the combination of is used, each developing device (a)-
The overall evaluation for (r) was all x.

FIG. 2 shows another structural example of the developing device. This developing device is different from the developing device having the configuration shown in FIG.
The rotation direction of the sleeve 3 at the developing position 33 is opposite to the rotation direction of the photoconductor 4. The present invention can be applied to such a developing device.

In FIG. 2, the magnetic pole S ₁ functions as a developing magnetic pole, and the magnetic pole N ₁ functions as a magnetic pole that conveys the developer from the developing position 33 to the removing position 34.

In the developing device of FIG. 2, toner is supplied to the developer on the sleeve 3 at the removing position 34.

That is, the toner in the toner storage chamber 23 is applied to the supply roller 26 by the application roller 25. The thickness of the toner layer on the supply roller 26 is regulated by the blade 27. The supply roller 26 is in contact with the developer layer on the sleeve 3, and the toner on the roller 26 is applied to the developer layer as the supply roller 26 rotates.

The magnetic flux density of the developing magnetic pole (first magnetic pole) is preferably 750 gauss or more and 1400 gauss or less.

When the magnetic flux density of the developing magnetic pole is smaller than 750 gauss, the reproducibility of the image in the low density region is lowered, and 1400
This is because if it is larger than Gauss, streak-like unevenness occurs in the developed image.

FIG. 3 shows a color printer as an example of an electrophotographic apparatus in which the developing apparatus of the present invention can be used. The printer is provided with four image forming stations around the photosensitive drum, each of which has an image forming unit corresponding to a color, and the toner image formed on each of the image forming stations is formed on the photosensitive drum. A color image is formed by being transferred onto a transfer material that is conveyed by a belt-shaped moving body that moves opposite to the photosensitive drum.

That is, each of the magenta, cyan, yellow, and black image forming stations Pm, Pc, Py, and P.
A photosensitive drum 4 (4M, 4C, 4Y, 4K) that rotates in the arrow direction (clockwise direction) is arranged in k.
In addition, around each photosensitive drum 4M, 4C, 4Y, 4K,
Corona charger 16 (16M, 16C, 16Y, 16
K), a scanning optical device 17 (17M, as an optical scanning means)
17C, 17Y, 17K), developing device 9 (9M, 9C,
9Y, 9K), and cleaning device 18 (18M, 1
8C, 18Y, 18K) is arranged.

Further, the transfer portion constituting one of the image forming means is a transfer belt 19a commonly used in each image forming station and a transfer charger 19 (1 for each drum.
9M, 19C, 19Y, 19K) for forming a full-color image on the transfer material P supported on the transfer belt 19a.
This is achieved by successively superimposing and transferring the toner images of the respective colors formed on the photosensitive drum onto the above. It should be noted that the transfer material P is supplied from the paper feed cassette 20, and the transfer material P that has completed the transfer process is separated, and is passed through the fixing device 21 to the tray 2
It is discharged to 2.

The scanning optical devices 17M, 17C, 17
Reference numerals Y and 17K denote a laser light source which is a light source (not shown), a rotating polygon mirror which scans the laser light from the laser light source, an fθ lens which condenses the scanning beam on the generatrix of the surface of the photosensitive drum, and redirects the light flux. And a beam detection device for detecting a specific position of the scanning beam.

In the above example, the so-called contact development type apparatus for bringing the developer layer on the developer carrying member into contact with the image carrying member has been described. However, the present invention is the minimum of the developer carrying member and the image carrying member. It can also be applied to a so-called non-contact developing type device in which the gap is thinner than the layer thickness of the developer.

[0079]

As described above, in the developing device according to the present invention, the peak value of the magnetic flux density of each of the plurality of carrier magnetic poles of the magnet which is statically arranged inside the developer carrying member such as the developing sleeve is as follows. A second magnetic flux density within a range of 10 to 49% of the magnetic flux density peak value of the developing magnetic pole forming the magnetic field at the developing position, or magnetically attracting the developer in the stirring chamber onto the surface of the developer carrying member. And the magnetic flux density peak value of each of the third magnetic poles located downstream of the second magnetic pole and upstream of the regulation position in the rotation direction of the developer carrying member to form a magnetic field at the regulation position. Since it is configured to be within the range of 10 to 49% of the peak value of the magnetic flux density of the first magnetic pole that forms the magnetic field at the position, the deterioration rate of the developer is suppressed, and a developed image of good image quality is obtained for a long period Can be formed,
Further, it is possible to obtain an effect that fog and toner scattering can be suppressed for a long period of time.

[Brief description of drawings]

FIG. 1 is an illustration of an embodiment of a developing device of the present invention.

FIG. 2 is an explanatory view of another embodiment of the developing device of the invention.

FIG. 3 is an explanatory diagram of an example of an image forming apparatus that can utilize the developing device of the present invention.

[Explanation of symbols]

 3 developer carrying member (developing sleeve) 4 image carrier (photoreceptor) 9 developing device 10 magnet 31 supply position 32 regulating position 33 developing position 34 removing position

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shigeru Oki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kunihiko Kitayama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (7)

[Claims] 1. An electrostatic latent image is developed, comprising a rotatable developer carrying member for carrying a developer containing toner particles and magnetic carrier particles, and a magnet disposed stationary inside the developer carrying member. In the developing device, the developer carrying member has a supply position where the developer is supplied to the surface thereof, a restriction position where a restriction member for restricting the layer thickness of the developer on the surface is arranged, and an electrostatic latent image. Through a developing position where the toner is developed and a removing position where the developer remaining on the surface after the developing is removed in this order, and the magnet forms a magnetic field at the developing position, and A plurality of carrier magnetic poles located between the position and the regulation position, and the peak value of the magnetic flux density of each of the plurality of carrier magnetic poles is in the range of 10 to 49% of the peak value of the magnetic flux density of the developing magnetic pole. A developing device characterized by being inside. 2. The magnetic flux density peak value of the developing magnetic pole is 75.
The developing device according to claim 1, wherein the developing device has a density of 0 to 1400 gauss. 3. The carrier particles have an average particle size of 20-6.
Carrier particles having a particle size of 0 μm and a particle size of 400 mesh or less are 20% by weight or less, carrier particles having a particle size of 350 mesh or less are 30% by weight or less, and carrier particles having a particle size of 250 mesh or more are 10% by weight or less. The saturation magnetization of particles is 5 for an applied magnetic field of 3000 oersteds.
5 emu / g or more and 75 emu / g or less, the residual magnetization is
10 emu / for an applied magnetic field of 3000 Oersted
3. The developing device according to claim 1, wherein the coercive force is not more than g and the coercive force is not more than 10 oersted with respect to an applied magnetic field of 3000 oersted. 4. A developer stirring chamber in which a stirring member for stirring a developer containing toner particles and magnetic carrier particles is arranged,
In a developing device for developing an electrostatic latent image, which comprises a rotatable developer carrying member for carrying a developer and a magnet arranged stationary inside the developer carrying member, the developer carrying member has a surface thereof. A regulating position where a regulating member for regulating the layer thickness of the developer carried on the sheet is arranged, a developing position where the electrostatic latent image is developed, and a removing position where the developer remaining on the surface after development is removed. , Rotating through this order, the magnet is configured to move the first magnetic pole forming a magnetic field at the developing position and the developer in the stirring chamber at a position between the removing position and the restricting position,
A second magnetic pole that magnetically attracts onto the surface of the developer carrying member, and a second magnetic pole that is located downstream of the second magnetic pole and upstream of the restricting position in the rotating direction of the developer carrying member and that forms a magnetic field at the restricting position. 3 magnetic poles, and the peak value of the magnetic flux density of each of the second magnetic pole and the third magnetic pole is within the range of 10 to 49% of the peak value of the magnetic flux density of the first magnetic pole. A developing device characterized by the above. 5. The peak value of the magnetic flux density of the first magnetic pole is 75.
The developing device according to claim 4, wherein the developing device has a density of 0 to 1400 gauss. 6. The magnet has a fourth magnetic pole located upstream of the second magnetic pole in the rotating direction of the developer carrying member and adjacent to the second magnetic pole, and the fourth magnetic pole. Is of the same polarity as the second magnetic pole, and the repulsive magnetic field formed by the second magnetic pole and the fourth magnetic pole removes the developer from the developer carrying member at the removal position. apparatus. 7. The carrier particles have an average particle size of 20 to 6
Carrier particles having a particle size of 0 μm and a particle size of 400 mesh or less are 20% by weight or less, carrier particles having a particle size of 350 mesh or less are 30% by weight or less, and carrier particles having a particle size of 250 mesh or more are 10% by weight or less. The saturation magnetization of particles is 5 for an applied magnetic field of 3000 oersteds.
5 emu / g or more and 75 emu / g or less, the residual magnetization is
10 emu / for an applied magnetic field of 3000 Oersted
7. The developing device according to claim 4, wherein the coercive force is not more than g and the coercive force is not more than 10 oersted with respect to an applied magnetic field of 3000 oersted.