JPH02156267A - Forming method for developer layer and developing device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a white stripe by bringing the surface of a film material into press-contact with the surface of a developer carrier with pressure, passing magnetic developer between the surface of the film material and the surface of the developer carrier, and forming a thin layer of magnetic developer on the developer carrier. CONSTITUTION:Dry magnetic developer D replenished in a developing device 2 where it is agitated, triboelectrified and uniformized, is carried to a developing sleeve 3 which rotates in an arrow direction. Although the developer D is almost held on the surface of the developing sleeve 3 with its rotation and is carried to a developing area 12, the developer D passes between the film material 52 of a layer thickness regulating member 5 and the surface of the developing sleeve 3 because there is the layer thickness regulating member 5 being in press-contact with the surface of the developing sleeve 3 by a coil spring 57 on the way. Then, the layer thickness of the developer D is regulated, and the developer which turns into a stable and uniform thin layer, reaches the developing area 12, and is electrostatically attracted to the latent image part of a photosensitive body drum 1, where development is performed. Thus, a picture free of a white stripe can be obtained.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a developing device that develops a latent image formed on an image carrier by an electrophotographic method, and a developer carrier (developing sleeve) of the developing device. ) A developer layer forming method for forming a thin layer of magnetic developer on top of the present invention.

[Background of the invention]

Dry developers used when developing a latent image on an image carrier by electrophotography are broadly classified into l-component developers and two-component developers.

The l-component developer is further classified into magnetic or non-magnetic one-component developer. Further, two-component developers generally consist of a magnetic carrier such as iron powder and toner. The developer used in the present invention is a one-component or two-component magnetic developer, and these developers are provided with a magnet inside the developing device, and a layer is formed on the surface of the developer carrier rotating around the outer circumference of the developing device. The latent image is deposited on the surface of the image carrier, is conveyed to a development area facing the image carrier, and is deposited on the latent image formed on the surface of the image carrier, where development is performed. Development is divided into contact development methods, in which the developer attached to the surface of the developer carrier directly contacts the latent image area, and non-contact development methods, in which development is performed by applying a development bias in a non-contact state. be done.

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

In addition, even if a non-contact development method using an l-component developer is used,
In order to improve image quality, the amount of charge per unit weight of developer (
Q/M) needs to be high, and also from the relationship between Q/M and the amount of developer conveyed to the development area, it is necessary to form a thin layer of developer on the surface of the developer carrier.

Many proposals have been made regarding means for forming a thin layer of developer.

(a) The developer layer forming apparatus described in Japanese Patent Application Laid-Open No. 54-43037 proposes using a magnetic member for the doctor blade, which is a layer thickness regulating member. If it is attempted to form a thin layer using such a proposal, it will be difficult to maintain the gap, and excessive processing precision will be required for the parts.

(b) The developer layer forming device described in Japanese Patent Application Laid-open No. 54-43038 is one in which a developer layer thickness regulating member made of a plate-shaped elastic body having a free end on one side is bent and pressed. This proposal utilizes the pressing force generated by bending the layer thickness regulating member made of an elastic body, so the pressing force varies depending on the rotational speed of the developer carrier and the pressure contact position! It is easy to change due to changes in the developer layer thickness, etc., and it is easy to vibrate, and no means have been taken to suppress the vibration, so the image forming device! There is a problem in that the vibration generated inside the machine resonates and vibrates, making it difficult to obtain a developer layer with a uniform thickness.5Also, it is susceptible to impurities such as lint and dust. has.

(c> The developer layer forming device described in JP-A-63-155065 proposes forming a thin layer of developer by bringing a stretched sheet-like member into direct contact with the circumferential surface of a developer layer carrier. In the other proposal, in order to form a thin layer, a considerable amount of tension is required in the toe-shaped member, and the rotational torque applied to the developer carrier becomes large.Also, unevenness in layer thickness occurs. Furthermore, it is susceptible to impurities such as lint and dirt, and white streaks are likely to appear.

(d) The developer layer forming device described in JP-A-62-17774 bends a thin plate-like elastic member at a predetermined curvature.
This is a proposal in which one thickness is regulated by making elastic contact with the developer carrier. Such a proposal requires precision in longitudinal linearity and curvature of the elastic member, and there is a problem in that it is not easy to satisfy these requirements.

[Purpose of the invention]

The present invention solves these problems and stably forms a good image by uniformizing the layer thickness of the developer on the developer carrier, and preventing the aggregated developer from reaching the development area. It is an object of the present invention to provide a method for forming a developer layer and a developing device that can prevent movement of the developer layer.

[II Hiroshi of invention]

An object of the present invention is to apply pressure to the back surface of a film material using a working medium made of magnetic particles or a magnetic fluid, and to bring the developer carrier into pressure contact with the surface of a developer carrier moving on the surface of the film material. A magnetism generating means is disposed on the back side of the working medium, a magnetic field is formed between the working medium and the magnetism generating means, and a magnetic developer is placed between the surface of the film material and the surface of the developer carrier. A developer layer forming method in which a thin layer of magnetic developer is formed on the developer carrier by allowing the magnetic developer to pass through the developer carrier, the peak of the magnetic flux density distribution on the developer carrier of the magnetism generating means being The developer layer forming method is characterized in that the surface of the film material is brought into pressure contact with a magnetic flux density B such that 1/2 Bp<B≦Bp, where Bp is the value, and such a developer layer forming method. A developing device that performs development by forming a thin layer of developer using a magnetic developer, that is, a movable developer carrier that carries a magnetic developer on its surface and transports it to a development area, and a developer disposed on the back side of the developer carrier. a magnetism generating means having a plurality of magnetic poles, and a film disposed on the surface side of the developer carrier upstream of the development area so that the surface thereof is in contact with the developer carrier. and a developer layer thickness regulating means for regulating the layer thickness of the magnetic developer, which comprises a support for holding a working medium made of magnetic particles or magnetic fluid on the back side of the film material. This is achieved by a developing device characterized by the following.

〔Example〕

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

FIG. 1 is a sectional view of a main part showing an embodiment of the present invention, and FIG. 2 is a perspective view of the layer thickness regulating member 5 shown in FIG.

In the figure, 1 is a photosensitive drum which is an image carrier, 2 is a developing device, 3 is a development sleeve which is a rotatably supported developer carrier made of non-magnetic metal such as aluminum or stainless steel, and 4 is a developing device. A magnet roller is fixedly installed inside the sleeve 3 and has a plurality of magnetic poles on the circumferential surface; 5 is a layer thickness regulating member; 6 is a housing of the developing device 2; 51 is a rectangular cross section (width: approximately 5 mm) and is made of synthetic resin or aluminum. The support 52, which is a rod-shaped member made of material, is a flexible strip-shaped film material with a thickness of 45 to 70 μm, which is bent so that the cross section is U-shaped, and the upper part of both sides is attached to the support 51. Use adhesive or double-sided tape, etc., to fix it to the side of the board.

56 is a guide member for always holding the layer thickness regulating member 5 in the correct position; 57 is a coil spring serving as pressure applying means;
9 is a thin developer layer formed by the layer thickness regulating member 5;
is the developing sleeve 3. A developing bias circuit for applying a developing bias voltage to 12, a developing area where the photoreceptor drum l and the developing sleeve 3 face each other, D a magnetic developer, Ds
d is the interval between the developing areas, and θ is the angle between the position of the layer thickness regulating member 5 in contact with the surface of the developing sleeve 3 and the position of the magnetic pole on the upstream side with respect to the rotation center of the developing sleeve 3, which is called the magnetic pole angle. That's what I will say.

The dry magnetic developer replenished into the developing device 2 is stirred within the developing device 2, triboelectrically charged, and made uniform.
The image is sent to the developing sleeve 3 which rotates in the direction of the arrow. As the developing sleeve 3 rotates, the developer particles are carried on the surface of the developing sleeve 3 and try to be transported to the developing area 12, but because there is a layer thickness regulating member 5 in pressure contact with the surface of the developing sleeve 3 by a coil spring 57 on the way. The developer layer passes between the film material 52 of the layer thickness regulating member 5 and the surface of the developing sleeve 3, thereby regulating the layer thickness of the developer layer and forming a stable and uniform thin layer into the developing area 12. The latent image is electrostatically attracted to the latent image portion of the photoreceptor drum 1, and development is performed.

3 to 5 are enlarged perspective views showing a first embodiment, a second embodiment, and a third embodiment of the layer thickness regulating member. 3 to 5 are shown in an inverted state compared to FIG. 1 for ease of understanding.

FIG. 3 shows a first embodiment of the envelope which is the main body of the layer thickness regulating member. In the figure, 53 is a side end member for preventing the outflow of the working medium 54, which will be described later, and has a semicircular cross-sectional shape. It is made of a block member such as a rubber material or a sponge material, and the peripheral surface is fixed to both side ends of the support body 51 and the film material 52 using an adhesive. One end is fixed first, and the other end is filled with a working medium 54 made of magnetic powder or magnetic fluid and then fixed to form the envelope 5a.

When using a magnetic fluid working medium 54, air-tightness of the bond is particularly required. As the adhesive, a rubber adhesive or adhesive double-sided tape is preferably used.

FIG. 4 shows a second embodiment of the envelope of the layer thickness regulating member, and in this embodiment, the support body 51 and the side end members 53 shown in FIG. 3 are integrally constructed using a rubber material or an elastic synthetic resin. It is something.

In the figure, 51a is the support A having the above-mentioned integral structure,
A film material 52 is bonded to the bonded portion indicated by diagonal lines. 51
b is a filling port provided at the bottom or side end of the support A 51a for filling the working medium 54, and after being filled with the working medium 54, it is closed using a stopper made of the same material as the support A 31a.

FIG. 5 shows a third embodiment of the envelope of the layer thickness regulating member, and in the figure, 52a is a pipe-shaped film material with a wall thickness of about 60 μm, 53a is a side end member made of a cylindrical elastic material,
After one side end of the film material 52a is closed with the side end member 53a and adhesive and filled with the working medium 54, the other side end is similarly closed. With this configuration, the support 5I and the film material 52 shown in FIG. 3 are rolled together to form the envelope 5b.

When assembling the layer thickness regulating member 5 as shown in the enlarged view of FIG.
Incidentally, an auxiliary member 51c shown by a dashed line may be used.

The above-mentioned respective envelopes 5a and 5b are shown in the enlarged view of FIG. 6 in order to prevent deformation when pressing and sliding on the developing sleeve 3 and to smoothly slide between the guide members 56. Side plates 55 and 55a are fixed to both sides of the envelopes 5a and 5b using an adhesive or machine screws to form the layer thickness regulating member 5. As shown in the enlarged view of FIG. 6, the side plate 55a on the downstream side of the rotation of the developing sleeve 3
It is bent so that the width of the part contacting the filled part of film material 54 becomes narrower, and when it is attached, it presses the part filled with the working medium 54 and increases the internal pressure of the film material 52. It is.

Since the layer thickness regulating member 5 as described above is used, the pressing force by the coil spring 57 is uniformly propagated to the contact surface by the working medium 54, and external vibrations are also absorbed by the working medium 54, so that resonance does not occur. Nor.

The dry type developer used in this developing device 2 is an l-component magnetic developer: (1) Thermoplastic resin (binder) 30 to 70 wt% Examples: polystyrene, styrene acrylic polymer, polyester,
Polyvinyl butyral, epoxy resin, polyamide resin, polyethylene, ethylene vinyl acetate copolymer, etc., or mixtures of the above.

(2) Magnetic agent 30-7 Qvt% Example 2 Triiron tetroxide, γ-ferric oxide, chromium dioxide, nickel 7-erite, iron alloy powder with particle size 0.1 μlT1-1 μm.

(3) Pigment (coloring agent) θ~15wt% Example: Black ・
・Carbon black yellow ・Benzidine derivative magenta ・Cyan such as rhodamine B lake, carmine 6B ・Copper 7 lysocyanine, sulfonamide derivative dye, etc.

(4) Charge control agent Qwt%-5vt% plus toner:
Nigrone-based electron-donating dyes, alkoxylated amines, alkylamides, chelates, pigments, ammonium salts, etc., negative toners, electron-accepting rust bodies, chlorinated paraffins, chlorinated polyesters, excess bases, etc. polyester, chlorinated steel phthalocyanine, etc.

(5) Examples of fluidizing agents: colloidal silica, hydrophobic silica, silicone varnish, metallparic acid, nonionic surfactants, etc.

(6) Cleaning agent (prevents toner filming on the photoconductor) Examples: fatty acid metal salts, silicic acid with an organic group on the surface,
Fluorine surfactants, etc.

(7) Fillers (improving image surface gloss, reducing raw material costs) Examples: calcium carbonate, clay talc, pigments, etc.

5) o to 0.8 per 100 parts of granules obtained by mixing, kneading, crushing, and classifying each material of (1), (2), (3), (4), and (7). 1 part, (6)O to 0.3 parts are added, mixed and stirred to obtain an l component magnetic developer.

In the two-component developer, a non-magnetic toner with a particle size of 6 μm to 18 μm and a ferrite core coated with a resin material with a particle size of 10 μm to 100 μm (preferably 30 μm to 60 μm) are used.
A developer comprising a carrier (m) is preferably used.

The toner will be explained as follows.

(1) Thermoplastic resin (binder) 80-9 (ht% Examples: polystyrene, styrene acrylic polymer, polyester,
Polyvinyl butyral, Epoquine resin, polyamide resin, polyethylene, ethylene vinyl acetate copolymer, etc., or mixtures of the above.

(2) Pigment (coloring agent) 0-15wt% Example: Black ・
・Carbon black yellow ・Benzidine derivative magenta ・Cyan such as rhodamine B lake, carmine 6B ・Copper phthalocyanine, sulfonamide derivative dye, etc.

(3) Charge control agent Qvt% to 5wt% plus donor:
Nigrosine-based electron-donating dyes, alkoxylated amines, alkylamides, chelates, pigments, quaternary ammonium salts, etc., negative toners: electron-accepting organic complexes, chlorinated paraffins, chlorinated polyesters, overbased polyesters, chlorinated copper phthalocyanine, etc.

(4) Examples of fluidizing agents: colloidal silica, hydrophobic silica, silicon face, metal soap, nonionic surfactants, etc.

(5) Cleaning agent (prevents toner filming on the photoreceptor) Examples: fatty acid metal salts, silicic acid with an organic group on the surface,
Fluorine surfactants, etc.

(6) Filler (Improves image surface gloss, reduces raw material cost) Examples: Calcium carbonate, clay talc, pigments, etc. In addition to these materials, a small amount of magnetic powder is used to prevent fogging on the image surface and toner scattering. It may be included. As this magnetic powder, triiron tetroxide, γ-ferric oxide, chromium dioxide, nickel 7-erite, iron alloy powder, etc. with a particle size of 0.1 μm to 1 μm are used, and the powder contains Q, 1 wt% to 5 wt%. but,
In order to maintain clear colors, it is desirable to keep it below lvt%.

Mix the ingredients (1), (2), (3), and (6) above.
4 per 100 parts of granules obtained by grinding, crushing, and classifying
) 0 to 0.8 parts and (5) O to 0.3 parts are added and mixed to obtain a toner.

Note that resins suitable for pressure fixing toner, which is plastically deformed and fixed to paper with a force of about 20 kg/cm, include wax,
Adhesive resins such as polyolefins, ethylene vinyl acetate copolymers, and polyurethane rubber are used.

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

Using the developer, the film material 52 of the layer thickness regulating member 5 is made of polyimide (Kapton, trade name manufactured by Toshi Co., Ltd.), nylon, polyester tele7 tallate (PET), U7-h.
(Product name), using glass fiber paper coated with rubber material, etc.
Although liquid or gas may be used as the working medium 54, in this experiment, magnetic powder with a particle size of 45-200 mm was used.
μm, iron particles with a magnetic susceptibility of 55 to loOemu/g, glass particles with a particle size of 350 μm or 500 μm, or SU3 particles with a particle size of 90.120.180 μm as the non-magnetic powder, and the developing sleeve 3 has an outer diameter of 20 mm. SUS materials with surface roughness Rz of 2 μm, 3 μm, 4 μm, and 5 μm were used, and the number of magnetic poles of the magnet roller 4 was 2°4.
, 6, 8.10.12, the magnetic flux density on the surface of the developing sleeve 3 was 650 to 800 Gauss (G), and as a result of experiments on each combination, it was found that the magnetic working medium 54 was used. Compared to a non-magnetic working medium, the dependence on the layer thickness is greater depending on the contact position of the layer thickness regulating member 5. When examining the performance at the appropriate contact position, magnetic materials were found to be superior to non-magnetic materials in all aspects, including stability of developer layer thickness, layer uniformity, durability during long-term use, and stability against foreign matter contamination. was gotten.

In the case of non-magnetic films, when used for a long period of time, the toner will fuse to the surface of the film and cause white smudges, but in the case of magnetic films, the contact pressure is small and can be made uniform, so even in a dry run test equivalent to 200,000 copies, white smudges are produced. Neither sushi nor toner fusion occurred. Abrasion of the film surface occurred evenly at the abutting portion, and the extent of the abrasion was also good.

Furthermore, no toner fusion, filming, etc. occurred on the developing sleeve. Furthermore, in an experiment in which lint was mixed in, white streak-like conveyance unevenness occurred immediately in the case of a non-magnetic working medium, but this did not occur at all in the case of a magnetic working medium. Observation experiments revealed that in the case of magnetism, lint does not enter the abutting portion, but instead flows through a curved and circular flow path. Furthermore, even if the lint accidentally entered the inlet, it was found that it did not remain in the abutment area but slipped through.

It has been found that when the contact position is near the magnetic pole, the regulated developer layer becomes more homogeneous without microscopically agglomerating.

Although the above performance was particularly noticeable in the l-component magnetic developer, similar results were obtained with the two-component developer. The most typical configurations are as follows.

Film material 52: Polyimide with a film thickness of 50 μm Working medium 54: Surface roughness of magnetic powder developing sleeve 3 with particle size of 120 μm and magnetic susceptibility of 60 emu/g: Rz-3 μm Magnet roller 4: Number of magnetic poles 4. It was a combination of magnetic flux density of 750G.

Next, the developing device 2 using the l-component developer and the layer thickness regulating member 5 transports the developer by the conveyance amount M/A (toner weight per unit area of the surface of the developing sleeve 3, that is, mg/
cm2) and charge rate Q/M (charge per unit weight, i.e. μ
c/g), as shown in FIG. 7, the stronger the contact force of the layer thickness regulating member 5 and the smaller the amount of developer conveyed, that is, the thinner the layer thickness, the higher the charge. The result was that the ratio was obtained.

Although the absolute values differ depending on the specific gravity and particle size of the toner or changes in the toner formulation, such a relationship was obtained regardless of whether the toner is non-magnetic or magnetic. Under any of the development conditions 1 and 2 shown below, images excellent in sharpness and gradation could be obtained.

Development conditions l ■Development gap Gap between photoreceptor and development sleeve 0.1-0
．． 15mm ■Conveyance amount of toner layer 1 mg/am2
■Surface potential of photoreceptor Non-image area -400 to -600V Image area -100 to -50V ■Developing bias voltage -300 to -500V■
Speed ratio Vs of developing sleeve (V, ) and photoreceptor (V P)
/Vp-1~2 ■Height of developer in developing area 0.15~0.25mm
It may be in contact with the photoconductor or in a non-contact state.

■Toner composition (1) Polyester 47.5wt% (
2) Magnetite 52.5wt%
(4) Bontron E 82 (1) + (2) 10
After mixing, kneading, crushing, and classifying 1 part to 0 part, the granules are spheroidized by mechanical impact force and the average particle size is 10 to 15 μm. (6) Hydrophobic silica 0.4vt -0.8v
t% (7) Zinc stearate 0.05wt~0
．． Toner obtained by adding and mixing 10 wt % Development conditions 2 The conditions different from development conditions 1 are as follows, and the other conditions are the same.

■Surface potential of photoconductor Non-image area V H= -600V Image area V H= -100V ■Development bias voltage DC component -350v AC component V ppm 400V Waveform Rectangular wave frequency I KHz-10KHz Also, the magnetic pole angle θ was changed. Layer thickness regulating member 5 in case
Magnetic flux density (G) at the contact position and conveyance amount of developer M/
A is shown in FIG. 8 in the case of a l-component developer, and as shown in FIG. 9 in the case of a two-component developer. In other words, with the l-component developer, the conveyance amount decreases monotonically when the magnetic pole angle θ is from 0 to around 45°, but when the magnetic pole angle θ exceeds 45'', the conveyance amount increases rapidly, and then reverses and decreases from around 60°. death,
The range of magnetic pole angle θ that forms a good thin layer of developer is 0.
°~20° and 706~90°.

In two-component developer, the conveyance amount is minimum when the magnetic pole angle θ is around 45°, and a good magnetic pole angle θ ranges from 0° to 20°.
and 70° to 90°.

When the magnetic pole angle θ is 0°, the magnetic flux density reaches its maximum value (peak value), but a slightly thicker developer layer is obtained. When the magnetic pole angle θ is around 15° and around 75°, a thin developer layer 59 with good development can be obtained.

Examining the magnetic pole angle θ that shows the above-mentioned good results, we find that the absolute value of the peak value of the magnetic flux density distribution due to the magnetic roller 4 is defined as Bp, and the absolute value of the magnetic flux density at the position where the film material 52 contacts the developing sleeve 3. Assuming that B is B, a good developer thin layer 59 is formed when B is in the range between the peak value and 1/2 of the peak value, that is, in the range of the magnetic pole angle θ such that 1/2 Bp<B≦Bp. There was found.

When the magnetic pole position as described above is taken, the magnetic pole position near the developing area 12 of the magnet roller 4 can be adjusted to deteriorate the developing conditions by making the magnetic pole intervals unequal or increasing the number of magnetic poles. You can take a position that does not allow

〔Effect of the invention〕

According to the present invention, as explained above, the layer thickness regulating member that holds the working medium between the support body and the film material is pressed against the surface of the developing sleeve, and the magnetic flux density at the pressure-contact position of the film material changes according to the magnetic flux density distribution. It was set between the peak value and 1/2 of the peak value. Therefore, external vibrations are absorbed by the working medium, and no resonance phenomenon occurs.
The pressing force against the developing sleeve becomes uniform, forming a stable and uniform thin layer of developer for good development on the surface of the developing sleeve, and preventing aggregated developer from moving to the developing area. Therefore, it has been possible to provide a developer layer forming method and a developing device that can provide an image having high resolution and free from self-streaks.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of essential parts showing an embodiment of the present invention. FIG. 2 is a perspective view of the layer thickness regulating member shown in FIG. 1. 3 to 5 are enlarged perspective views showing a first embodiment, a second embodiment, and a third embodiment of the layer thickness regulating member. FIG. 6 is an enlarged sectional view of the layer thickness regulating member shown in FIG. 1. FIG. 7 is a graph showing the relationship between the amount of developer conveyed and the charging rate obtained by an example of the present invention. FIGS. 8 and 9 are graphs showing the relationship between the magnetic flux density and the conveyance amount with respect to the magnetic pole angle obtained by the embodiment of the present invention. ■... Photosensitive drum 3... Developing sleeve 5... Layer thickness regulating member 7... Developing bias circuit 51... Support body 51b... Filling port 53, 53a... Side end member 55 , 55a... Side plate 57... Fill spring D... Developer 2... Developing device 4... Magnet roller 6... Housing 12... Developing area 51a... Support body A 52, 52a ...Film material 54...Working medium 56...Guiding member 59...Developer thin layer θ...Magnetic pole angle (Fig. 1)

Claims (3)

[Claims] (1) Pressure is applied to the back surface of the film material by a working medium made of magnetic particles or magnetic fluid, and the back surface of the developer carrier is brought into pressure contact with the surface of the developer carrier moving on the surface of the film material. A magnetism generating means is disposed in the magnetic field, and a magnetic field is formed between the working medium and the magnetism generating means, so that the magnetic developer slips between the surface of the film material and the surface of the developer carrier. A method for forming a developer layer, comprising: forming a thin layer of magnetic developer on the developer carrier. (2) If the peak value of the magnetic flux density distribution on the developer carrier of the magnetism generating means is B_p, 1/2B_p<
2. The method for forming a developer layer according to claim 1, wherein the surface of the film material is pressed onto a magnetic flux density B such that B≦B_p. (3) a movable developer carrier carrying magnetic developer on its surface and transporting it to a development area; a magnetism generating means having a plurality of magnetic poles disposed on the back side of the developer carrier; A film material disposed upstream of the development area on the surface side of the developer carrier and disposed so that the surface is in contact with the developer carrier, and a magnetic particle or the like on the back side of the film material. A developing device comprising: a support for holding a working medium made of a magnetic fluid; and a developer layer thickness regulating means for regulating the layer thickness of the magnetic developer.