JPH0511599A - Developing device using nonmagnetic one-component developer - Google Patents

Abstract

PURPOSE:To maintain an average toner electrifying quantity in a proper range over a long period. CONSTITUTION:A developer holding container 36a, a conductive elastic body developing roller 36b provided inside the developer holding container 36a rotatively, a layer thickness regulating member 36c press-contacted to the elastic body developing roller 36b are provided. A charge injecting voltage having the same polarity as that obtained by triboelectrification and the injection of a charge into a developer layer is applied to the layer thickness regulating member 36c, at the time of regulating layer thickness, and a developing bias voltage so as to develop the electrostatic latent image of an image carrier 30 by the developer layer whose thickness is regulated by the layer thickness regulating member 30 and which has the injection of the charge, is applied to the elastic body developing roller 36b. The application of the charge injecting voltage to the layer thickness regulating member 36c is executed so as to form an electric field within the range of 5,0(X)10<4> or 1.5X10<5>V/cm, between the elastic body developing roller 36b and the layer thickness regulating member 36c.

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 held on an image carrier such as a photoconductor or a dielectric with a non-magnetic one-component developer.

[0002]

2. Description of the Related Art Referring to FIG. 6, there is schematically shown an example of a basic structure of a conventional electrostatic recording apparatus. In this example, a photosensitive drum 10 is used as an image carrier. The photoconductor drum 10 has a photosensitive material layer such as an organic photosensitive material layer (OPC) 10b formed on the surface of a cylindrical substrate 10a made of, for example, aluminum, and is rotated in a direction indicated by an arrow a during a recording operation. Around the photosensitive drum 10, along the direction of rotation thereof, a corona charger 12, an optical electrostatic latent image writing means such as a laser beam scanning optical system 14, a developing roller 16, a corona transfer device 18, a discharge lamp 20 and a cleaner are provided. 22 are sequentially arranged. The recording medium, that is, the recording paper P is introduced between the photosensitive drum 10 and the corona transfer device 18 in the direction of the arrow b, and the fixing device 24 is arranged on the downstream side in the traveling direction of the recording paper P.

The corona charger 12 is composed of a corona charger, and the corona charger 12 allows the photoconductor drum 10 to operate.
Negative or positive charges are applied to the photosensitive material layer 10b, and charged regions having a uniform charge are formed in the publication material layer 10b. In the illustrated example, since the organic photosensitive material layer 10b is formed on the photosensitive drum 10, a negative charge is applied thereto. In FIG. 6, negative charges are indicated by a minus sign “−”. A laser beam LB is emitted from the laser beam scanning optical system 14, and this laser beam LB is sequentially deflected along the generatrix direction of the photoconductor drum 10, whereby the charged area of the photoconductor drum 10 is scanned by the deflection laser LB. To be done. During scanning, the deflected laser beam LB is blinked based on binary image data from, for example, a word processor or a microcomputer, whereby a binary electrostatic latent image is written in the charged area of the photosensitive drum 10. That is, the electric charge at the portion irradiated with the laser beam LB is released (the aluminum cylindrical base of the photoconductor drum 10 is grounded), whereby a binary electrostatic latent image is formed by the potential difference in the charging area. Will be. Incidentally, a portion where the electric charge is removed by the irradiation of the laser beam LB is called a charge well, and in the illustrated example,
The potential of such a charge well will be higher than the potential of the background region.

The developing roller 16 is arranged in a developer container (not shown) for containing the developer, and a part of the surface thereof is exposed so as to be in contact with the photosensitive drum 10.
When the developing roller 16 is rotated in the direction indicated by the arrow c, the charged developer carried on the surface thereof, that is, the negative charged toner, is conveyed to the area facing the photosensitive drum 10, that is, the developing area, where the electrostatic latent image is formed. It will be electrostatically developed with charged toner. More specifically, the developing roller 16
Is applied with a negative developing bias voltage which is lower than the potential of the electrostatic latent image area of the photosensitive drum 10 but higher than the potential of the background area thereof. It attaches in a manner that charges the image area (charge well), but is electrostatically repelled in the background area,
Thus, only the electrostatic latent image areas will be visualized or developed with charged toner particles. In addition, in FIG.
Charged toner particles are indicated by white circles with a minus sign "-".

Like the corona charger 12, the corona transfer device 18 is also composed of a corona discharger.
The recording paper P is given an electric charge having a polarity opposite to that of the charged toner image, that is, a positive electric charge, so that the charged toner image is electrostatically transferred from the photosensitive drum 10 to the recording paper P side. The transferred toner image is sent together with the recording paper P to, for example, the thermal fixing device 24 and is thermally fixed there. On the other hand, from the region where the charged toner image is transferred from the photoconductor drum 10, the charge removal lamp 20 removes the residual charge, and then the cleaner 22 removes the residual toner from the surface of the photoconductor drum 10. The area thus cleaned is again charged by the corona charger 12 and the above process is repeated. In the illustrated example, the heat fixing device 24 comprises a heat roller 24a and a backup roller 24b, and the cleaner 22 comprises a fur brush. In FIG. 6, the positive charge applied to the recording paper P is indicated by a plus sign “+”, and the fixed toner image is indicated by a small black solid rectangle.

[0006]

By the way, when a non-magnetic one-component developer is used in the developing process of the electrostatic recording apparatus as described above, the developing apparatus as shown in FIG. Be incorporated into. In such a developing device, the developing roller 16 is configured as a conductive elastic developing roller, and preferably a conductive porous elastic rubber material is used. The elastic developing roller 16 is rotatably arranged in a developer container 26 containing a non-magnetic one-component developer, that is, a toner. A part of the elastic developing roller 16 is exposed from the developer container 26 and is exposed to a predetermined pressing force. The drum 10 is elastically contacted. When the elastic developing roller 16 is rotationally driven, toner adheres to the rotating surface by frictional force to form a toner layer, and such a toner layer 28 has a predetermined layer thickness by the layer thickness regulating member 28. After being regulated, the sheet is conveyed to a contact area with the photosensitive drum, that is, a developing area. The layer thickness regulating member 28 also has a function of charging the toner particles in the toner layer to a predetermined amount by frictional charging when the layer thickness of the toner layer is regulated. However, the charging of the toner due to such charging friction is easily affected by fluctuations in temperature and humidity. That is, as shown in the graph of FIG. 8, if the toner charging depends only on the triboelectric charging, the average toner charge amount is
In the environment where the temperature is 25 ° C or more and the relative humidity is 60% RH or more, it is out of the lower limit of the range of 7 to 17 μC / g where good developing quality is obtained. When the average toner charge amount becomes 7 μC / g or less, the toner particles include non-charged toner particles or toner particles close thereto, and such toner particles are not restricted by the developing bias voltage applied to the elastic developing roller 16. Therefore, it adheres to the background area other than the electrostatic latent image area,
So-called fog will occur.

Therefore, as shown in FIG. 9, by applying a voltage of a predetermined polarity to the layer thickness regulating member 28, the layer thickness regulating member 2
It has been proposed to positively inject charges into toner particles when the layer thickness of toner layer 8 is regulated. Although FIG. 9 shows an example of injecting negative charges into the toner particles indicated by white circles, it is needless to say that positive charges may be injected if necessary. In short, in the example shown in FIG. 9, charge injection and triboelectric charging by the layer thickness regulating member 28 are used together to negatively charge the toner. In such a case, as shown in FIG. Therefore, the average toner charge amount characteristic is improved, and thus, even under an environment of a temperature of 25 ° C. or more and a relative humidity of 60% RH or more, good developing quality can be maintained without causing fog.

However, the average toner charge amount greatly varies depending on the potential relationship between the layer thickness regulating member and the elastic developing roller, and when the charge injection is small, the development density is lowered and fog is generated, and the charge injection is performed. When the amount is excessive, discharge may occur at the layer thickness regulation portion of the toner layer.
In the latter case, the electric charge is removed from the toner layer to cause fogging, or the surface of the elastic developing roller is melted and damaged. Further, even if the predetermined charge injection voltage and the developing bias voltage are applied to the layer thickness regulating member and the elastic developing roller, respectively, the potential relation between them changes with the deterioration of the elastic developing roller, and therefore the elastic body Even though the life of the developing roller is not exhausted, there is a case where the developing device cannot be used due to deterioration of developing quality. In short, the charge injection of toner is controlled not by the electric potential but by the electric field between the developing roller and the tank thickness regulating member, and the above problems occur even if the potential difference is constant. Therefore, in the developing device using the non-magnetic one-component development, the present invention uses the triboelectric charging by the layer thickness regulating member and the charge injection for charging the non-magnetic one-component developer, that is, the toner, and the average toner charging. It is to maintain the amount in a proper range for a long time.

[0009]

To achieve the above object, according to the present invention, there is provided a developing device for developing an electrostatic latent image carried on an image carrier with a non-magnetic one-component developer. A developer holding container containing a non-magnetic one-component developer,
A conductive elastic developing roller provided rotatably in the developer holding container is provided, and the elastic developing roller is partially exposed from the developer holding container and contacts the image carrier. And a non-magnetic one-component developer is adhered to the peripheral surface of rotation during rotation driving to form a developer layer, and the development layer is conveyed to a contact area with the image carrier,
Further, a layer thickness regulating member is provided which regulates the developer layer on the elastic developing roller to a predetermined layer thickness and is brought into pressure contact with the elastic developing roller to frictionally charge the developer layer. When the layer thickness is regulated, a charge injection voltage having the same polarity as that of triboelectrification that causes charge injection into the developer layer is applied to the member, and the elastic developer roller is layer thickness regulated and injected by the layer thickness regulating member. In a developing device to which a developing bias voltage for developing an electrostatic latent image on an image bearing member is applied with a developed developer layer, an elastic developing roller is used for applying a charge injection voltage to a layer thickness regulating member. There is provided a developing device characterized in that an electric field in the range of 5.0 × 10 ⁴ to 1.5 × 10 ⁵ V / cm is formed between the layer thickness regulating member and the layer thickness regulating member.

[0010]

According to the present invention, when the charge injection voltage is applied to the layer thickness regulating member, 5.0 × 10 ⁴ to 1.5 × 10 ⁵ V / cm is applied between the elastic developing roller and the layer thickness regulating member. Since it is performed so as to form an electric field within the range, it is possible to maintain the average charge amount of the non-magnetic one-component developer, that is, the toner for a long period of time.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 5 of the accompanying drawings. First, referring to FIG. 1, a basic configuration of a laser printer is schematically shown as an example of an electrostatic recording apparatus to which a developing device according to the present invention is applied. In this laser printer, a photosensitive drum 30 is used as an image carrier. Be done. The photosensitive drum 30 is formed by forming a photoconductive material layer, that is, a photosensitive material layer on the surface of a cylindrical base body made of aluminum having a diameter of 40 mm, and examples of such a photosensitive material include an organic photosensitive material, a selenium-based photosensitive material, Although an amorphous silicon photosensitive material or the like is used, in this embodiment, the photosensitive drum 30 is an OPC photosensitive drum using an organic photosensitive material. During the recording operation, the photosensitive drum 30 is rotated in the direction indicated by the arrow a so that the peripheral speed of the photosensitive drum 30 is 70 mm / s.

A negative charge is applied to the photosensitive material layer of the photosensitive drum 30 by a suitable charger such as a corona charger 32, and the surface potential of the charged area is set to -600V, for example. In this embodiment, since the organic photosensitive material is used as the photosensitive material, the photosensitive drum 30 is provided with a negative charge, but the selenium-based photosensitive material is provided with a positive charge. In the case of an amorphous silicon photosensitive material, negative or positive charges are given. Photoconductor drum 3
An electrostatic latent image is written in the charging area of 0 by the laser beam scanning unit 34, and the electrostatic latent image is written with the laser beam LB emitted from the laser beam scanning unit 34 along the generatrix direction of the photosensitive drum 30. And the laser beam LB is blinked based on binary image data from a word processor or a microcomputer. That is, the electric charge at the portion irradiated with the laser beam LB is released (the aluminum cylindrical base of the photoconductor drum 30 is grounded), whereby a binary electrostatic latent image is formed by the potential difference in the charging area. Will be. Incidentally, a portion where the electric charge is removed by the irradiation of the laser beam LB is called a charge well, and its potential is increased from about −600V to about −100V (decreased as an absolute value).

The electrostatic latent image written by the laser beam scanning unit 34 is developed as a charged toner image by the developing device 36. The developing device 36 includes a developer container 36a containing a non-single-component developer consisting of only toner, and a developing roller 36b arranged in the developer container 36a and rotated in the direction of the arrow shown in the drawing. .. As shown in the drawing, a part of the developing roller 36b is the developer container 3
It is exposed from 6a and is elastically brought into contact with the photosensitive drum 30 with a predetermined pressing force. The shaft of the developing roller 36b is drivingly connected to the same drive source (not shown) as the photosensitive drum 30 via an appropriate transmission gear train (not shown), and the peripheral speed thereof is the peripheral speed of the photosensitive drum 30.
It is rotated to 175 mm / s, which is about 2.5 times 70 mm / s. The developing roller 36b can be configured as a conductive elastic roller, but is preferably formed of a conductive porous rubber material, and examples of such a conductive porous rubber material include polyurethane sponge, urethane rubber sponge, and the like. Carbon black or the like as a conductivity-imparting agent may be mixed into silicon rubber or sponge. In this example, a porous urethane sponge (trade name: Rubicell made by Toyo Polymer) is used.
The average pore diameter of the sponge is 10 μm and the number of pore cells is 200 cells.
/ inch, volume resistance is 10 ⁴ to 10 ⁷ Ωcm, and Asker C hardness is 23 degrees. The developing roller 36b made of such a material has good toner transportability, and the developing roller 36b
When b is rotated, toner adheres to the surface of rotation and toner layers are sequentially formed. At the time of developing the electrostatic latent image, a developing bias voltage of -300 V is applied to the developing roller 36b, so that the charged toner is electrostatically attached to the electrostatic latent image area, but is attached to the background area. Is blocked. As the non-magnetic one-component developer used here, a polyester-based negative polarity toner having a volume resistance of 4 × 10 ¹⁴ Ωcm, an average particle diameter of 12 μm and silica external addition of 0.5% is used.

Further, the developing device 36 is provided with a layer thickness regulating member 36c for regulating the layer thickness of the toner layer formed on the developing roller 36b to a predetermined thickness, and this layer thickness regulating member 36c is made of an appropriate metal material. However, in the present embodiment, the leaf spring member is made of stainless steel (SUS304-CSP-3 / 4H) and has a thickness of 0.1 mm. The layer thickness regulating member, namely the leaf spring member 36c, is supported at one end by a rigid supporting member 36d, and is elastically brought into pressure contact with the developing roller 36b at the other end side thereof with a linear pressure of, for example, 35 gf / cm. The toner layer is regulated to a predetermined layer thickness of about 10 μm, and the layer thickness of such a toner layer corresponds to the thickness of one toner particle. As described above, the average particle diameter of the toner is 12 μm.
However, since the toner particles enter into the pores on the surface of the developing roller 36b, the toner layer thickness is 12 m
It can be smaller than μm. The tip end edge on the other end side of the leaf spring member 36c is chamfered and rounded (so-called R
Chamfering), and the developing roller 36 with its rounded tip.
It is positioned so as to scrape off the excess toner from b. In the present embodiment, a charge injection voltage of −400 V is applied to the leaf spring member 36c, so that when the layer thickness of the toner layer is regulated by the leaf spring member 36c, negative charge is positively injected into the toner. Friction charging between the leaf spring member 36c and the toner is also used. Here, the point to be noted is that by applying −400V to the leaf spring member 36c, 5.0 × 10 10 is generated between the developing roller 36b and the leaf spring member 36c.
An electric field within the range of ⁴ to 1.5 × 10 ⁵ V / cm is formed, and therefore, the average charge amount of the toner can be included in the range of 7 to 17 μC / g where good developing quality can be obtained. This will be described in detail later.

The developing device 36 is further provided with a toner collecting / supplying roller 36e and a paddle rotating body 36f. The toner collecting and supplying roller 36e is preferably a conductive sponge, for example, the number of pore cells is about 40 cells / inch, and the volume resistance is 10 ⁴ Ω.
cm conductive sponge (Bridgestone Everlight TS-
It is formed of E), is pressed against the developing roller 36b, and is rotated in the same direction as the developing roller 36b. The toner collecting / supplying roller 36e is the developing roller 36b.
The toner that has not been used for development is scraped off from the developing roller 36b on one side of the pressure contact area against the developing roller 36b, and the toner is positively supplied to the developing roller 36b on the opposite side, that is, the right side of FIG. It functions to attach. -400V for the toner collection and supply roller 36e
The voltage is applied to prevent the toner particles from entering the sponge material of the toner collecting and supplying roller 36e, and the toner is electrostatically supplied to the developing roller 36b. The paddle rotating body 36f collects the toner in the developer container 36a from the toner collecting and supplying roller 36e.
It is rotated so as to be fed to the toner supply side of.

The charged toner image obtained in the developing process is then electrostatically transferred onto a recording medium such as recording paper P by a suitable transfer device such as corona transfer device 38. That is, a voltage of about 7 kV is applied to the corona transfer device 38, and thereby the recording paper P is given a charge having a polarity opposite to that of the charged toner image, that is, a positive charge, and the charged toner image is transferred from the photosensitive drum 30. It is electrostatically transferred onto the recording paper P. In addition,
The recording paper P is fed from a paper feed cassette (not shown) and then temporarily stopped at the pair of registration rollers 40, 40, and then the pair of registration rollers 40, 40.
Is driven at a predetermined timing, the recording paper P
Is introduced into the contact area between the photoconductor drum 30 and the corona transfer device 38, whereby the charged toner image can be transferred onto the recording paper P at the predetermined position. Immediately after passing through such a transfer process, a part of the positive charge of the recording paper P is neutralized by the AC static eliminator 42 on the recording paper P, and thus the electrostatic charge between the recording paper P and the photosensitive drum 30 is discharged. The attractive force is weakened, and the recording paper P can be separated from the photosensitive drum 30 without being electrostatically attracted thereto. continue,
The recording paper P is sent to the thermal fixing device 44, where the transferred toner image is thermally fixed on the recording paper P. That is, the heat fixing device 44
Is the heat roller 44a and the backup roller 4
4b, and when the recording paper P is passed between them,
The transferred toner image is melted by heat and firmly fixed on the recording paper P. In FIG. 1, reference numeral 46 indicates a charge eliminating lamp for removing the residual charge from the photosensitive drum 10, and reference numeral 48 indicates a toner scraping blade for removing the residual toner from the photosensitive drum 26. The toner removed by the take-off blade 48 is stored in the toner storage container 50.

Next, the developing roller 36b and the leaf spring member 36.
When a charge injection voltage is applied to the leaf spring member 36c so that an electric field in the range of 5.0 × 10 ⁴ to 1.5 × 10 ⁵ V / cm is formed between the leaf spring member 36c and c, the average charge amount of the toner is good. The inclusion within the range of 7 to 17 μC / g which guarantees the development quality is described below. First, a developing device as shown in FIG. 2 was prepared, and the potential of the toner layer at the time of development was measured. 2, the same reference numerals are used for the same components as the components of the developing device 36 shown in FIG. 1, and this developing device has a rigid support in which the leaf spring member 36c is rotatable. It is the same as that shown in FIG. 1 except that it is supported by the member 36d and its rounded tip end is elastically pressed against the developing roller 36b by the coil spring S.

To measure the potential of the toner layer during development
, Where the developing roller 36b contacts the photosensitive drum.
With the surface potentiometer 52 installed (note that in FIG.
The outline of the optical drum is shown by the broken line), the developing device is actually
Was operated by. The potential of the toner layer is as shown in FIG.
Measured by the method. To be more specific, first, the developing device is started.
Done, V_b, V_blAnd V_rIs the developing roller 3
6b, leaf spring member 36c, toner collecting and supplying roller
When applied to 36e, the surface potential of the developing roller 16b becomes
As shown in FIG._bsRise to. This potential
V_bsIs a developing bias voltage V to the developing roller 36b.
_bHowever, the electric power to the leaf spring member 16c is
Load injection voltage V_blAnd to the toner collection / supply roller 36e
Voltage V _rWas influenced by. Leaf spring member 36
The surface potential of the toner layer that first received charge injection from c
Immediately after passing the installation location of the difference meter 52, stop the developing device
Made me V_b, V_blAnd V_rIs the ground level (zero
Default), the surface potential of the developing roller 36b is V_bsOr
Et V_tDown to this potential V_tIs the potential of the toner layer
Which is due to frictional charge and electric charge by the leaf spring member 36c.
Obtained from injection.

After the potential of the toner layer was measured in this way, the layer thickness of the toner layer was measured. The layer thickness of the toner layer was measured by using a laser scanning micro measuring device 54 as shown in FIG. The measurement procedure there will be described below. (1) First, the developing roller 36b was gently taken out from the developing device of FIG. 2, and the developing roller 16b was installed in the laser scanning micro measuring device 54 of FIG. The laser scanning micro measuring device 54 includes a light emitting section 54a and a light receiving section 5.
4b are provided, and a reference shield wall 54c that shields a part of the laser beam emitted from the light emitting portion 54a is provided in the center between them. In FIG. 4, the toner layer formed around the developing roller 36b is illustrated in an exaggerated manner, which is indicated by reference numeral TL.
Indicated by. The developing roller 36b is installed on the laser scanning micro measuring device 54 so that a predetermined region of the toner layer, that is, a region whose layer thickness is regulated by the leaf spring member 36c is located above the reference shielding wall 54c. (2) The distance L1 was measured in such an installed state. (3) Subsequently, the developing roller 36b is attached to the laser scanning micro-measuring device 54, and the developing roller 3
6b is blown with nitrogen gas to completely remove the toner layer, and the distance L2 is measured there. (4) L2-L1 was calculated to calculate the layer thickness of the toner layer.

Next, the charge amount of the toner layer was calculated from the measured potential of the toner layer and the calculated layer thickness of the toner layer by the following formula. Toner charge amount q / m = 2ε ₀ ε _rl (toner layer potential) / δ
P (toner layer thickness) ² where ε ₀ is the dielectric constant of vacuum, ε _rl is the relative dielectric constant of the toner,
δ is the mass of the toner per unit volume, and P is the toner occupation rate. After performing the above-described measurement while changing the potential difference between the developing roller 36b and the leaf spring member 36c variously, the charge amount of the toner layer in each case was calculated. The above measurements were performed on a new developing roller and a developing roller at the end of its life.

The above results are shown in the graph of FIG. In the graph, the horizontal axis represents the developing roller 36a and the leaf spring member 36.
The potential difference from c is replaced by the electric field, and the vertical axis represents the toner charge amount replaced by the potential of the toner layer by the above formula. The shaded area in the graph corresponds to the shaded area in FIG. As is clear from the graph in FIG.
In order to charge the toner with a charge amount capable of guaranteeing good developing quality, an electric field within the range of 5.0 × 10 ⁴ to 1.5 × 10 ⁵ V / cm is formed between the developing roller 36b and the leaf spring member 36c. It is understood that the charge injection voltage may be applied to the leaf spring member 36c as described above.

[0022]

As is apparent from the above construction, in the developing device according to the present invention, it is possible to guarantee the developing quality up to the life of the developing roller for a long time.

[Brief description of drawings]

FIG. 1 is a schematic view of a laser printer to which a developing device according to the present invention is applied.

FIG. 2 is a schematic view showing the arrangement of a surface potentiometer for measuring the potential of the toner layer on the developing roller.

FIG. 3 is a graph illustrating a method of measuring the potential of a toner layer with the surface potentiometer of FIG.

FIG. 4 is a schematic view of a laser scanning micro measuring device for measuring the layer thickness of a toner layer.

FIG. 5 is a graph showing the relationship between the electric field between the developing roller and the layer thickness regulating member and the potential of the toner layer.

FIG. 6 is a schematic diagram illustrating a recording principle of a conventional electrostatic recording device.

FIG. 7 is a schematic view of a conventional developing device using a non-magnetic one-component developer.

FIG. 8 is a graph showing the relationship between the average charge amount of toner and temperature and humidity.

FIG. 9 is an explanatory diagram illustrating injection of an electric field into toner. 30 ... Photosensitive drum 32 ... Corona charger 34 ... Laser beam scanning unit 36 ... Developing device 36a ... Developer container 36b ... Developing roller 36c ... Layer thickness regulating member

Front page continuation (72) Inventor Masatoshi Kimura 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (1)

Claim: What is claimed is: 1. A developing device for developing an electrostatic latent image carried on an image bearing member (30) with a non-magnetic one-component developer, the non-magnetic one-component developer being contained therein. Developer holding container (3
6a) and a conductive elastic developing roller (36b) rotatably provided in the developer holding container, and the elastic developing roller is partially exposed from the developer holding container. And is arranged so as to be in contact with the image carrier, and a non-magnetic one-component developer is adhered to the peripheral surface of the rotation during rotation to form a developer layer. A layer thickness regulating member that is conveyed to the contact area and further regulates the developer layer on the elastic developing roller to a predetermined layer thickness and press-contacts the elastic developing roller to frictionally charge the developer layer. (36c), a charge injection voltage for injecting charges into the developer layer is applied to the layer thickness regulating member with the same polarity as the frictional charging polarity when the layer thickness is regulated. Is the layer thickness due to the layer thickness control member In a developing device to which a developing bias voltage is applied so as to develop an electrostatic latent image on the image carrier with the developer layer which is restrained and injected with electric charge, the electric charge is injected into the layer thickness regulating member (36c). The voltage is applied so as to form an electric field within the range of 5.0 × 10 ⁴ to 1.5 × 10 ⁵ V / cm between the elastic developing roller (36b) and the layer thickness regulating member. Characteristic developing device.