JP2727095B2 - Developing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a developing device for developing a latent image formed on an image carrier by an electrophotographic method, and a developer carrier (developing sleeve) of the developing device. And b) forming a thin layer of a magnetic developer thereon.

[Background of the Invention]

Dry developers used when developing a latent image on an image carrier by an electrophotographic method are roughly classified into a one-component developer and a two-component developer.

One-component developers are further classified into magnetic or non-magnetic one-component developers. Further, the two-component developer generally comprises a magnetic carrier such as iron powder and a toner. The developer used in the present invention is a one-component or two-component magnetic developer. These developers are provided with a magnet inside the developing device, and have a layered structure on the surface of the developer carrier rotating around the outer periphery thereof. And is conveyed to a development area facing the image carrier, and adheres on a latent image formed on the surface of the image carrier to perform development. The development is classified into a contact development method in which the developer adhered to the surface of the developer carrier directly contacts the latent image portion to perform development, and a non-contact development method in which development is performed by applying a development bias in a non-contact state. Is done.

In a non-contact developing method using a two-component developer, in order to increase the resolving power, the gap Dsd between the image carrier surface and the developer carrier surface in the development area is generally narrowed. It often adheres to the image carrier, and to prevent this, it is necessary to form a uniform and uniform thin layer of the developer on the surface of the developer carrier.

Even in the non-contact developing method using a one-component developer, the charge amount per unit weight (Q / M) of the developer needs to be high in order to improve the image quality. Therefore, it is necessary to form a thin layer of the developer on the surface of the developer carrying member also from the relation of the amount of transfer to the developing area.

There have been many proposals for means for forming a thin layer of developer.

(A) The developer layer forming apparatus described in JP-A-54-43037 proposes to use a magnetic member for a doctor blade which is a layer thickness regulating member. If a thin layer is to be formed by such a proposal, it is difficult to maintain a gap, and excessive processing accuracy is required for the component.

(B) The developer layer forming apparatus described in Japanese Patent Application Laid-Open No. Sho 54-43038 is designed to bend and press a developer layer thickness regulating member made of a plate-like elastic body having a free end on one side. Since such proposals use a pressing force generated by bending a layer thickness regulating member made of an elastic body, the pressing force varies depending on fluctuations in the rotation speed of the developer carrier, the pressure contact position, the developer layer thickness, and the like. Because it is easy to vibrate and vibrates, and there is no means for suppressing the vibration, the vibrator resonates with the vibration generated in the image forming apparatus and vibrates. Is difficult to obtain. Further, it has a disadvantage that it is weak against impurities such as thread waste and dust.

(C) The developer layer forming apparatus described in JP-A-63-155065 proposes to form a thin layer of developer by bringing a stretched sheet-shaped member into surface contact with the peripheral surface of a developer carrier. is there. In such a proposal, a considerable amount of tension is required for the sheet-like member to form a thin layer, and the rotational torque applied to the developer carrier becomes large. There is also a problem that layer thickness unevenness is likely to occur. Further, there is a problem in that it is vulnerable to impurities such as thread scraps and dust, and white stripes are easily generated.

(D) The developer layer forming apparatus described in Japanese Patent Application Laid-Open No. Sho 62-17774 discloses a method in which a thin plate-like elastic member is bent at a predetermined curvature and is elastically brought into contact with a developer carrier to regulate the layer thickness. It is a proposal made. Such a proposal requires accuracy in the linearity and curvature in the longitudinal direction of the elastic member, and has a problem that it is not easy to satisfy the requirements.

[Object of the invention]

The present invention is intended to solve these problems and to stably form a good image by uniformly forming the layer thickness of the developer on the developer carrier and forming the aggregated developer stably in the development area. An object of the present invention is to provide a developing device capable of preventing movement.

[Configuration of the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a movable developer carrier that carries a magnetic developer on a surface thereof and conveys the developer to a development area, and a magnetic generating means having a plurality of magnetic poles fixed on the back side of the developer carrier. A developing device having a layer thickness regulating means for the developer, which is disposed on the surface side of the developer carrier and upstream of the developing area, and is in contact with the developer carrier. The layer thickness regulating means includes a package substantially made of a film material filled with a working medium composed of magnetic particles or a magnetic liquid, a support for supporting the package, and a layer adjacent to the package. And a magnetic plate disposed downstream in the direction of movement of the developer carrier.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 (a) is a cross-sectional view of a main part showing a first embodiment of the present invention, FIG. 1 (b) is an enlarged view of the main part, and FIG. 2 is a perspective view showing a layer thickness regulating member of FIG. It is. In the figure, 1 is a photosensitive drum as an image carrier, 2 is a developing device, 3 is a developing sleeve which is made of a non-magnetic metal such as aluminum or stainless steel and is rotatably supported, and 4 is a developing sleeve. A magnet roller fixed inside the sleeve 3 and having a plurality of magnetic poles on the peripheral surface, 5 is a layer thickness regulating member, 6 is a developing device 2
The housing 51 has a rectangular cross section (width of about 5 mm) and is a support member which is a rod-shaped member made of synthetic resin or aluminum.
Reference numeral 52 denotes a flexible strip-shaped film material having a thickness of 45 to 70 μm, which is bent so that its cross section becomes U-shaped, and an adhesive or a double-sided tape or the like is provided on both sides of the upper surface of the support 51. Use to fix. Reference numeral 53 denotes a side end member (see FIG. 2) for preventing an outflow of the working medium 54 described later, which is made of a block member such as a rubber material or a sponge material having a semicircular cross section, and has a peripheral surface formed of an adhesive. Is fixed to both ends of the support body 51 and the film material 52 by using the. One end is fixed first, and the other end is working medium
Fix after filling 54. Support 51, film material
As shown in FIG. 4, the side member 53 and the side end member 53 together form a package 5a for holding a working medium 54 made of magnetic powder or magnetic liquid (shown inverted).

When the working medium 54 made of a magnetic fluid is used, airtightness is particularly required for the bonding portion. As the adhesive, a rubber-based adhesive or an adhesive double-sided tape is preferably used.

55 is a side plate, 56 is a guide member for always holding the layer thickness regulating member 5 at a correct position, 57 is a coil spring as a pressure acting means, 58 is a magnetic material which will be described later, and is made of a magnetic material downstream of the rotation of the developing sleeve 3. When the radius of a semicircular portion of the film material 52 that contacts the developing sleeve 3 is 2.5 mm, the thickness of the magnetic material is increased to about 3 mm above the contact surface so as to increase the thickness in a triangular shape. Have been. 59 is a developer thin layer formed by the layer thickness regulating member 5, 7 is a developing bias circuit for applying a developing bias voltage to the developing sleeve 3, and 12 is a developing area where the photosensitive drum 1 and the developing sleeve 3 are opposed to each other. , D is the developer, Dsd is the interval between the development areas, θ is the angle between the position of the layer thickness regulating member 5 in contact with the surface of the development sleeve 3 and the magnetic pole located upstream thereof with respect to the rotation center of the development sleeve 3 This is called the magnetic pole angle.

5 and 6 are enlarged perspective views showing a second embodiment and a third embodiment of the package of the layer thickness regulating member. FIG. 5 and FIG. 6 show a state of being inverted with respect to FIG. 1 for easy understanding.

FIG. 5 shows a second embodiment of a package serving as a main body of the layer thickness regulating member. In this embodiment, the support 51 and the side end members 53 of FIG. 4 are integrally formed using a rubber material or an elastic synthetic resin. It is configured. In the figure, reference numeral 51a denotes a support body A having the above-mentioned integral structure, and 51b denotes a filling port for filling a working medium 54 provided on the bottom surface or a side end of the support body A51a. It is closed using a stopper made of the same material as the body A51a.

FIG. 6 shows a third embodiment of the package of the layer thickness regulating member, in which 52a is a pipe-shaped film material having a wall thickness of about 60 μm, 53a is a side end member made of a cylindrical elastic material, After closing one side end of the film material 52a with the side end member 53a and the adhesive and filling the working medium 54, the other side end is similarly closed. With this configuration, the support body 51 and the film material 52 shown in FIG. 4 are integrated to form the package 5b. When the layer thickness regulating member 5 is assembled as shown in the enlarged view of FIG. 1B, an auxiliary member 51c shown by a dashed line in FIG. 5 may be used as a member corresponding to the support 51. Good.

Each of the above packages 5a and 5b is pressed against the developing sleeve 3
In order to prevent denaturation during sliding, the guide member 56
As shown in the enlarged view of FIG. 1 (b), the side plates 55 and the magnetic side plates 58 are formed on both sides of the packages 5a and 5b by using an adhesive or a small screw in order to smoothly slide the gap therebetween. The layer is fixed and becomes the layer thickness regulating member 5. The downstream magnetic side plate 58 is formed so that the width of the portion in contact with the portion filled with the working medium 54 is narrow, and when attached, presses the portion filled with the working medium 54 to cause the film material to be pressed. The internal pressure of 52 is raised.

The magnetic side plate 58 is used for the following reason. That is, when the magnetic working medium 54 is used, the magnetic pole angle θ is 5
When the angle is equal to or more than 0 °, auxiliary magnetic poles are generated on both sides of the working medium 54 as shown in FIG. Magnetic brush generated on the downstream side
Since 60 has an adverse effect on the developer thin layer 59, its generation must be suppressed. A magnetic side plate 58 is used to suppress the generation of the magnetic brush 60 on the downstream side. As a result, the lines of magnetic force on the downstream side do not concentrate, but move upward to increase the area, and only the extremely short magnetic brush 60 is generated, so that the above-mentioned adverse effects can be eliminated.

Accordingly, the magnetic pole angle θ can be freely set, and a thin developer layer having a desired transport amount can be obtained.
Further, since the working medium 54 made of a magnetic material is attracted by the magnetic field of the magnet roller 4, the pressing force of the coil spring 57 can be reduced, the dependency of the layer thickness on the pressing load is reduced, the load is reduced, and the rotational torque of the developing sleeve is reduced. And so on.

FIG. 3 is an enlarged sectional view showing a layer thickness regulating member according to a second embodiment of the present invention. In the second embodiment, a magnetic side plate 58a formed of a magnetic material so that the support 51 and the magnetic side plate 58 of the layer thickness regulating member 5 of the first embodiment are integrated is used as a magnetic plate. is there.

Since the working medium 54 made of a magnetic material is used for any of the above-mentioned layer thickness regulating members 5, the working medium 54 is attracted by the magnetic field of the magnet roller 4, and the coil spring 57 can be omitted.

Next, the operation of the developing device 2 will be described. The dry magnetic developer D supplied into the developing device 2 is
The toner is agitated, frictionally charged and made uniform, and sent to the developing sleeve 3 rotating in the direction of the arrow. Developer D is
As the developing sleeve 3 rotates, it is carried on the surface thereof and is conveyed to the developing area 12.
Alternatively, since the layer thickness regulating member 5 is pressed against the surface of the developing sleeve 3 by a magnetic force, the developer D slips through between the film material 52 of the layer thickness regulating member 5 and the surface of the developing sleeve 3,
As a result, the layer thickness of the developer D is regulated and becomes a stable and uniform thin layer, reaches the developing area 12, and is attracted to the latent image on the photosensitive drum 1 to perform development.

The dry magnetic developer D used in the developing device 2 includes:
For a one-component magnetic developer, (1) thermoplastic resin (binder) 30 to 70% by weight Example: polystyrene, styrene acrylic polymer, polyester, polyvinyl butyral, epoxy resin, polyamide resin, polyethylene, ethylene-vinyl acetate copolymer Such,
Or a mixture of the above.

(2) Magnetic agent 30 to 70 wt% Example: triiron tetroxide, γ-ferric oxide, chromium dioxide, nickel ferrite, iron alloy powder having a particle size of 0.1 μm to 1 μm.

(3) Pigment (colorant) 0 to 15% by weight Example: Black: carbon black Yellow: benzidine derivative Magenta: rhodamine B lake, carmine 6B, etc. Cyan: copper phthalocyanine, sulfonamide derivative dye, etc.

(4) Charge control agent 0 wt% to 5 wt% Plus toner: Nigrosine electron donating dye, alkoxylated amine, alkylamide, chelate, pigment,
Negative toners such as quaternary ammonium salts: electron-accepting organic complexes, chlorinated paraffins, chlorinated polyesters, polyesters with excess base, chlorinated copper phthalocyanines, and the like.

(5) Superplasticizer Examples: colloidal silica, hydrophobic silica, silicone varnish, metal soap, nonionic surfactant and the like.

(6) Cleaning agent (prevents filming of toner on photoreceptor) Examples: metal salts of fatty acids, silicon oxide having organic groups on its surface, fluorine-based surfactants, etc.

(7) Filler (improvement of surface gloss of image, reduction of raw material cost) Examples: calcium carbonate, clay, talc, pigment, and the like.

(5) 0 to 0.8 parts for 100 parts of granules obtained by mixing, milling, crushing and classifying each material of (1), (2), (3), (4), (7), (6) Add 0 to 0.3 part, mix and stir to obtain a one-component magnetic developer.

In the two-component developer, a developer comprising a nonmagnetic toner having a particle diameter of 6 μm to 18 μm and a carrier having a particle diameter of 10 μm to 100 μm (preferably 30 μm to 60 μm) obtained by coating a resin material on a ferrite core is preferable. Used.

 The toner will be described below.

(1) Thermoplastic resin (binder) 80 to 90 wt% Example: polystyrene, styrene acrylic polymer, polyester, polyvinyl butyral, epoxy resin, polyamide resin, polyethylene, ethylene-vinyl acetate copolymer, etc.
Or a mixture of the above.

(2) Pigment (colorant) 0 to 15% by weight Example: Black: carbon black Yellow: benzidine derivative Magenta: rhodamine B lake, carmine 6B, etc. Cyan: copper phthalocyanine, sulfonamide derivative dye, etc.

(3) Charge control agent 0 wt% to 5 wt% plus toner: Nigrosine electron donating dye, alkoxylated amine, alkylamide, chelate, pigment,
Negative toners such as quaternary ammonium salts: electron-accepting organic complexes, chlorinated paraffins, chlorinated polyesters, polyesters with excess base, chlorinated copper phthalocyanines, and the like.

(4) Superplasticizer Examples: colloidal silica, hydrophobic silica, silicone varnish, metal soap, nonionic surfactant and the like.

(5) Cleaning Agent (Prevents Filming of Toner on Photoconductor) Examples: Aliphatic metal salts, silicon oxide having an organic group on the surface, fluorine-based surfactant, etc.

(6) Filler (Improvement of surface gloss of image, reduction of raw material cost) Example: In addition to these materials such as calcium carbonate, clay, talc, and pigment, magnetic powder is used to prevent fogging and toner scattering on the image surface. A small amount may be contained. As the magnetic powder, triiron tetroxide, .gamma.-ferric oxide, chromium dioxide, nickel ferrite, iron alloy powder having a particle size of 0.1 .mu.m to 1 .mu.m is used, and is contained in an amount of 0.1 wt% to 5 wt%. In order to maintain a good color, it is desirable that the content be 1 wt% or less.

100 parts of granules obtained by mixing, milling, crushing, and classifying each material of (1), (2), (3), (6)
(4) 0 to 0.8 part and (5) 0 to 0.3 part are added and mixed to obtain a toner.

Adhesive resins such as wax, polyolefins, ethylene-vinyl acetate copolymer, and polyurethane rubber are used as the resin suitable for the pressure fixing toner that is plastically deformed with a force of about 20 kg / cm and fixed on paper.

 Next, experimental results of the developing device of the present invention will be described.

Using the developer, the film material 52 of the layer thickness regulating member 5 is coated with polyimide (Kapton, trade name, manufactured by Toray Industries Co., Ltd.), nylon, polyester terephthalate (PET), U sheet (trade name), and glass coated with a rubber material. Using fiber paper, etc.
In this experiment, as the working medium 54, iron particles having a particle diameter of 45 to 200 μm and a magnetic susceptibility of 55 to 100 emu / g were used as the magnetic powder.In addition, magnetic fine particles such as machine oil and ferrite were used. Mixed magnetic liquids can also be used.

The developing sleeve 3 is made of a SUS material having an outer diameter of 20 mm and has a surface roughness of Rz.
Are 2 μm, 3 μm, 4 μm, and 5 μm. The number of magnetic poles of the magnet roller 4 is 2, 4, 6, 8, 10, 12, and the magnetic flux density on the surface of the developing sleeve 3 is 650 to 800 gauss (G). As a result of conducting an experiment for each combination, the layer thickness varies depending on the contact position of the layer thickness regulating member 5, but by selecting an appropriate contact position, the stability of the layer thickness and the uniformity of the layer can be improved. Good results were obtained in all properties and durability in long-term use. Even in a long-term use test (free-running test equivalent to 200,000 copies), toner is fused to the film surface, no white streak-like transport unevenness occurs, and the abrasion of the film surface is uniform over the entire contact area and the amount is small. Was. Also, there was no fusion of the toner on the surface of the developing sleeve. No white streaks occurred in the experiment in which lint or the like was mixed. Observation showed that the lint did not flow into the inlet of the regulating portion but moved along a flow path bent upstream of the regulating portion. Also, it was found that even if it happened to flow into the contact portion, it would pass through without stopping. When the contact position was near the magnetic pole, the developer whose layer thickness was regulated was found to be microscopically homogeneous.

The above performance is the result obtained with both the one-component developer and the two-component developer. The tendency is more remarkable in the one-component developer. The most typical configuration is as follows.

Film material 52: polyimide having a thickness of 50 μm Working medium 54: magnetic powder having a particle size of 120 μm and magnetic susceptibility of 60 emu / g Surface roughness of the developing sleeve 3: Rz = 3 μm Magnet roller 4: combining four magnetic poles and magnetic flux density of 750 G Was something.

Next, by the developing device 2 using the one-component developer D and the layer thickness regulating member 5, the transport amount M / A of the developer D (toner weight per unit area of the surface of the developing sleeve 3, ie, mg / c
When the relationship between m ² ) and the charge ratio Q / M (charge per unit weight, ie, μc / g) was tested, as shown in FIG. As the transport amount was reduced, that is, as the layer thickness was reduced, a higher charging rate was obtained.

Although the absolute value differs depending on the change in the specific gravity, the particle size, or the toner prescription of the toner, such a relationship was obtained irrespective of non-magnetism and magnetism. Under any of the developing conditions 1 and 2 shown below, an image excellent in sharpness and gradation was obtained.

Developing condition 1 Developing gap Gaps between photoconductor and developing sleeve 0.1 to 0.15 mm Conveyance of toner layer 1 mg / cm ² Surface potential of photoconductor Non-image part -400 to -600 V Image part -100 V to -50 V Development bias voltage -300 ~-500V developing sleeve (V _S) and the photoconductor (V _P) speed ratio V _S / V _P = 1~2 of the developer in the developing region Hotaka 0.15~0.25mm photoreceptor in contact and non-contact state either will do.

Toner composition (1) Polyester 47.5wt% (2) Magnetite 52.5wt% (4) Bontron E82 (1) + (2) 1 for 100 parts
After mixing, milling, crushing, and classifying the granules, the granules are subjected to spheroidizing treatment with a mechanical impact force to obtain an average particle size of 10 to 15 μm. (6) Hydrophobic silica 0.4 wt to 0.8 wt% (7) Zinc stearate Toner obtained by adding and mixing 0.05 wt% to 0.10 wt% Developing condition 2 Conditions different from developing condition 1 are as follows, and others are the same.

Photoreceptor surface potential Non-image area VH = -600V Image area VH = -100V Development bias voltage DC component -350V AC component Vpp = 400V Waveform Square wave Frequency 1KHz to 10KHz Also, layer when magnetic pole angle θ is changed The magnetic flux density (G) at the contact position of the thickness regulating member 5 and the transport amount M /
A is as shown in FIG. 9 for the one-component developer D, and as shown in FIG. 10 for the two-component developer D. That is, in the one-component developer D, the magnetic pole angle θ monotonically decreases from 0 ° to around 45 °, but when the magnetic pole angle θ exceeds 45 °, the transport amount increases sharply, and reverses from around 60 °. The range of the magnetic pole angle θ which decreases and forms a good thin layer of the developer D is 0 °.
~ 20 ° and 75 ° ~ 90 °.

In the two-component developer D, the conveyance amount becomes minimum when the magnetic pole angle θ is around 45 °, and the preferable range of the magnetic pole angle θ is 0 ° to 20 °.
60 ° to 90 °.

When the magnetic pole angle θ is 0 °, a slightly thicker thin layer of the developer D is obtained. When the magnetic pole angle θ is around 15 ° and around 75 °, a thin developer layer 59 in which good development is performed can be obtained. When such a magnetic pole position is taken, the magnetic poles in the vicinity of the developing region 12 of the magnet roller 4 are positioned such that the developing conditions are not deteriorated by performing measures such as making the magnetic pole intervals uneven or increasing the number of magnetic poles. Can be taken.

〔The invention's effect〕

As described above, according to the present invention, the layer thickness regulating member in which the back surface of the film material is filled with the magnetic working medium and the magnetic plate is provided to cover the downstream side (developing area side) of the film material is used. To press the magnetic developer through the film material of the layer thickness regulating member and the surface of the developing sleeve, so that external vibration is absorbed by the working medium and is not affected by the vibration, Since the rotational load of the developing sleeve can be reduced, a very stable and uniform thin layer of developer is formed on the surface of the developing sleeve even when magnetic developer is used, and the aggregated developer is moved to the developing area. Thus, it is possible to provide a developing device which has a high resolving power and can obtain a good image free of white stripes or the like.

[Brief description of the drawings]

FIG. 1 is a sectional view of an essential part showing a first embodiment of the present invention. FIG. 2 is a perspective view showing a layer thickness regulating member of FIG. FIG. 3 is an enlarged sectional view showing a layer thickness regulating member according to a second embodiment of the present invention. FIG. 4 to FIG. 6 are enlarged perspective views showing the first to third embodiments of the package of the layer thickness regulating member of FIG. FIG. 7 is a sectional view showing a sub-magnetic pole generated when magnetic powder is used as a working medium of the layer thickness regulating member. FIG. 8 is a graph showing the relationship between the conveyance amount of a one-component developer thin layer obtained according to the embodiment of the present invention and the charge ratio. 9 and 10 are graphs showing the relationship between the magnetic flux density and the transport amount with respect to the magnetic pole angle obtained by the embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum, 2 ... Developing device 3 ... Developing sleeve, 4 ... Magnet roller 5 ... Layer thickness regulating member, 6 ... Housing 7 ... Developing bias circuit, 12 ... Developing area 51 ... Support member 51a Support member A 52, 52a Film material 53, 53a Side end member 54 Working medium 55 Side plate 56 Guide member 57 Coil spring 58, 58a Magnetic side plate, 59: developer thin layer D: developer, θ: magnetic pole angle

Claims (1)

(57) [Claims] A movable developer carrier that carries a magnetic developer on a surface thereof and conveys the developer to a development area; and a magnetic generating means having a plurality of magnetic poles fixedly provided on a back side of the developer carrier. A developer layer thickness regulating means disposed on the surface side of the developer carrier and upstream of the developing area, the layer thickness regulating means for the developer contacting the developer carrier; The regulating means includes a package substantially made of a film material filled with a magnetic medium or a working medium composed of a magnetic liquid, a support for supporting the package, an adjacent to the package, and And a magnetic plate disposed downstream in the moving direction of the developer carrier.