JPH0486861A - Developing device - Google Patents

Abstract

PURPOSE:To prevent the change of the thickness of a developer thin layer on the surface of a developing roller and the deterioration in image quality from occurring even in the case of using a device over a long period by setting the hardness of a press-contact part which is made to press-contact with the surface of the developing roller by interposing the developer thin layer between them larger than that of the roller and setting the surface roughness thereof smaller than that of the roller. CONSTITUTION:The rubber hardness of the press-contact part of a developer thin layer forming means blade 16 is set larger than the hardness of the developing roller 12 and the surface roughness thereof is set smaller than that of the developing roller. Thus, sufficient charge is added to developer with low pressure. Therefore, a developing device in which the change of the thickness of the developer thin layer on the surface of the roller 12 and the deterioration of the image quality are not caused even when it is used over a long period is accomplished. By satisfying the relation of Rb>=Lb supposing that the radius of curvature of the semicircular cross sectional part of the press-contact part is Rb and abrasion width caused by friction with the developing roller is Lb, the change of a space with the developing roller caused by the abrasion of the press-contact part is kept to the minimum. Thus, the developing device in which the change of the thickness of the developer thin layer on the surface of the developing roller and the deterioration of the image quality are not caused even when it is used over a long period is accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Industrial Application Field) The present invention relates to a developing device for visualizing an electrostatic latent image in an electrophotographic device or an electrostatic recording device.

(Prior Art) One of the developing methods using a one-component developer is the pressure development method.
)It has been known. This pressure development method attaches the toner to the surface of the developing roller by applying an electric charge to the toner through friction with the developing roller and friction with a blade for forming a thin toner layer that is pressed against the surface of the developing roller. One of its characteristics is that it is transported toward the development area. Therefore, it has many advantages, such as not requiring a magnetic material, making it possible to simplify and downsize the device, and toners that can be made into colored toners.

In a developing device using such a pressure developing method, the developing roller is pressed against or brought into contact with the photoreceptor drum to perform development, so the developing roller is required to have elasticity and conductivity. Particularly when the photosensitive drum is a rigid body, it is essential that the developing roller be made of an elastic body to avoid damaging it. Further, in order to obtain the well-known developing electrode effect and bias effect, it is desirable to provide a conductive layer on or near the surface of the developing roller and apply a bias voltage as necessary. Furthermore, in order to impart sufficient charge to the toner, it is necessary to ensure a predetermined nip width between the developing roller and the blade for forming a thin toner layer.

By the way, when the developing roller is made of an elastic material, the surface of the developing roller is easily scratched due to pressure contact with the blade.
Particularly when a conductive layer is provided on the surface of the developing roller, scars from the conductive layer appear on the image. Therefore, attention is being paid to a method in which the pressure contact portion of the blade with the developing roller is made of resin or rubber elastic material.

However, when such a blade is used, the shape of the pressure contact portion of the blade changes due to wear after long-term use. Particularly in the case of a pressure contact part with a rounded tip, if the contact area with the developing roller increases due to wear, the first
As shown in FIG. 4, the space F for the toner pool formed by the tip of the pressure contact portion 2a of the developing roller 1 and the blade 2 becomes smaller, and as a result, the developing roller 1 and the blade 2
The amount of toner passing between the toner and the toner layer decreases, resulting in a thinner toner layer. Furthermore, due to the decrease in the amount of toner conveyed, there has also been a problem in that when so-called graphic images are printed, the image density decreases in the latter half of the image.

(Problem 8 to be Solved by the Invention) As described above, in the conventional developing device, there is a risk that image quality may deteriorate due to long-term use.

The present invention is intended to solve these problems, and aims to provide a developing device that does not cause changes in the thickness of the thin developer layer on the surface of the developing roller or deterioration of image quality even during long-term use. There is.

[Configuration of the Invention (Means for Solving the Problem) In order to achieve the above object, the developing device of the first invention has the following features:
A developing roller disposed opposite to the electrostatic latent image holder, and a developer thin layer forming means for forming a thin developer layer on the surface of the developing roller. In a developing device that visualizes an electrostatic latent image formed on an electrostatic latent image holder by bringing a thin layer of developer close to or in contact with the latent electrostatic image holder, the thin developer layer forming means includes a thin layer of developer formed on a developing roller. It has a pressure contact part that is pressed against the surface with a thin developer layer in between, and this pressure contact part is harder than the developing roller.
It is also characterized by low surface roughness.

Further, in order to achieve the above object, the developing device of the second invention includes a developing roller disposed opposite to the electrostatic latent image holder, and a developer forming a thin developer layer on the surface of the developing roller. an electrostatic latent image formed on the electrostatic latent image carrier by bringing a thin layer of developer formed on the surface of the developing roller close to or in contact with the electrostatic latent image carrier; In the developing device, the developer thin layer forming means has a pressure contact portion having a semicircular cross section that is pressed against the surface of the developing roller with the developer thin layer in between, and the semicircular shape of the pressure contact portion is It is characterized in that it satisfies the relationship Rb≧Lb, where Rb is the radius of curvature of the cross-sectional portion and Lb is the width of wear caused by friction with the developing roller.

(Function) According to the developing device of the first invention, the rubber hardness of the pressure contact portion of the developer thin layer forming means is made larger than the hardness of the developing roller,
In addition, by making the surface roughness of the pressure contact portion smaller than the surface roughness of the developing roller, it becomes possible to impart a sufficient charge to the developer with a low pressure. Therefore, it is possible to realize a developing device that does not cause changes in the thickness of the thin developer layer on the surface of the developing roller or deterioration of image quality even during long-term use.

According to the developing device of the second aspect of the invention, the relationship Rb≧Lb is satisfied, where Rb is the radius of curvature of the semicircular cross-sectional portion of the pressure contact portion, and Lb is the abrasion width caused by friction with the developing roller. Therefore, changes in the space between the developing roller and the developing roller due to wear of the pressure contact portion can be minimized.

As a result, it is possible to realize a developing device in which the thickness of the thin developer layer on the surface of the developing roller does not change and the image quality does not deteriorate even during long-term use.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing the overall structure of a contact type component nonmagnetic developing device (hereinafter simply referred to as a developing device) according to an embodiment of the present invention.

As shown in the figure, this developing device 10 uses non-magnetic toner (hereinafter simply referred to as toner) as a developer on an electrostatic latent image formed on the surface of a photoreceptor drum 11, which is an electrostatic latent image holder. ) A developing roller 12 for transferring toner A to visualize an electrostatic latent image, a toner container 13 containing toner A, a mixer 14 for stirring toner A in this toner container 13, and a toner The toner A in the container 13 is transferred to the developing roller 1.
2 and the developing roller 12.
The main part thereof consists of a blade 16 which is a means for forming a thin layer of developer to form a thin layer of I/ner on the surface.

Next, the developing process in this developing device 10 will be explained.

The toner A contained in the toner container 13 is transferred to the mixer 1.
4, the toner is sent toward the toner co-supply roller 15, and further supplied to the developing roller 12 by the toner supply roller 15. Here, the toner A is negatively charged due to friction with the surface of the rotating developing roller 12, is electrostatically attracted to the surface of the developing roller 12, and is transported. After this,
The toner A attached to the surface of the developing roller 12 is removed by the blade 1.
At the same time, the amount of conveyance is regulated by 6 and the layer is thinned, and at the same time 1. Due to the friction between the developing roller 12 and the blade 16, the toner is triboelectrically charged again and transported as a dense toner layer. Thereafter, the toner A adhering to the surface of the developing roller 12 is transferred onto the electrostatic latent image on the surface of the photoreceptor drum 11 due to contact with the photoreceptor drum 11 . This makes the electrostatic latent image visible. Toner A on the surface of the developing roller 12 that did not transfer
The recovery blade (Mylar film) 17 is scraped off and returned to the toner container 13.

By the way, in this embodiment, since a reversal development method using a negatively charged organic photoreceptor drum 11 is adopted, a negatively charged toner is used as the toner A, and the blade 16
A material that easily charges the toner A negatively is used. Further, the surface potential of the photosensitive drum 11 is -550
In contrast, -200 V is applied to the metal shaft 12a of the developing roller 12 via a protective resistor as a developing bias potential. Further, the developing roller 12 is always 1 to 5 mm away from the surface of the photoreceptor drum 11.
It rotates at a speed that is about 1 to 4 times the diameter of the rotation speed of the photosensitive drum 11 while having a contact width (developing nip) of about 100 to 100 m.

In addition, if toner A falls from the developing roller 12 for some reason in the above-mentioned development process, it will stain the inside of the main unit or the transfer paper. A member 18 is attached to the lower part of the developing device 10. Also, this allows
Even when the developing device 10 is placed upside down, scattering of the toner A can be prevented.

The above blade 16 is attached to a first blade holder 16a1.
It is supported by the device main body by a spacer 16b and a second blade holder 16c. Reference numeral 19 denotes a baffle plate attached to the first blade boulder 16a to sandwich a foam material 20 made of maltbrene or the like between it and the back surface of the blade 16. By sandwiching the foam material 20 between the baffle plate 19 and the back surface of the blade 16 in this manner, leakage of toner A from the toner container 13 and vibration of the blade 16 are prevented.

Further, this blade 16 has a tip portion (tip 162).
) to press the surface of the developing roller 12 with an appropriate force.
It is constantly biased by a plurality of compression springs 22 with the rotating shaft 21 as a fulcrum. Since the spring constant of these compression springs 22 is lower than the spring constant of the blade 16 (thin plate spring 161), even if the tip 162 of the blade 16 wears, there is almost no effect on its pressing force.

Next, the blade 16 and its surroundings in the developing device 10 of this embodiment will be explained.

FIG. 2 is a perspective view showing details of the blade 16.

As shown in the figure, this blade 16 has a thickness of, for example, 2
Thin plate spring 1 made of urethane resin with a length of 20 mm
A tip 162 made of urethane resin and having a semicircular cross section is mounted in the longitudinal direction on the tip of the tip 61, and sealing material 163 made of urethane foam is attached to both ends of the tip 162. Note that the radius of curvature of the chip 162 is 1
．． It is 5mm. Further, the urethane resin of the chip 162 is made of a rubber hardness higher than that of the JISA standard, compared to the urethane resin of the thin plate spring 161, so as not to impair the elasticity of the thin plate spring 161.

In this embodiment, the thin plate spring 161 has a JIS-A standard 75° angle.
urethane resin to the chip 162 according to JIS-A standard 50.
°Uses urethane resin.

Furthermore, since the sealing material 163 has a thicker cross-section than the height of the chip 162, it can reliably seal the movement of toner toward both ends when the chip 162 is pressed against the developing roller 12, and also seal the tip of the blade 16. Since it is attached so as to wrap around the toner, there is no need to worry about it coming off when the toner is transported.

Furthermore, in this blade 16, if the chip 162 is not securely pressed against the surface of the developing roller 12, uneven formation of a thin toner layer will occur, so precision is required for the contact area between the chip 162 and the developing roller 12. Ru. Experiments have shown that if the straightness is 50 μm or less, the unevenness in the formation of a thin toner layer can be ignored.

Therefore, in this embodiment, as shown in FIG.
62 is mounted from a position dl away from the tip of the thin plate spring 161. That is, this thin plate spring 161
The tip portion is used for holding and positioning when mounting the chip 162 on the thin plate spring 161 by molding or adhesion. This makes it possible to improve the mounting accuracy of the thin plate spring 161 in the lateral direction, as well as the accuracy in the tangential direction with respect to the developing roller 12.

Note that if di is too large, the pressure caused by the toner flow may cause defective toner layer formation, so it is appropriate to set di to be about 0.5 to 5 mm.

The optimal thickness is desirably about 0.5 to 2 mm. Furthermore, there are portions at both ends of the thin plate spring 161 in the longitudinal direction where the chip 162 is not mounted. The above-described seal member 163 is attached to this portion.

That is, the length Lp of the chip 162 in the longitudinal direction is shorter than the length Lc of the thin plate spring 161 by d2 + d3. The length of d2 + d3 needs to be at least 2 mm on each side considering sealing performance, but if it is too long, the developing device 10 itself will become large, so the length should be 4 to 30 mm.
The thickness is preferably about 4 to 20 mm.

Further, the length Lp of the chip 162 at this time is greater than the effective development width of the developing roller 12, and the length Lc of the thin plate spring 161 is equal to the width of the developing roller 12 or the side seal of the developing roller 12 (not shown). ).

Furthermore, if the radius of curvature of the chip 162 in the portion that contacts the developing roller 12 is too small, the amount of toner charge will be small and fog on the transfer paper will increase; if it is too large, the width of contact with the developing roller 12 will be large. The required rotational torque increases accordingly, and the toner layer thickness on the developing roller 12 becomes too thin, resulting in a decrease in image density, so it is necessary to keep it within an appropriate range.

FIG. 4 shows the surface roughness of the developing roller 12 of 3. While fixing OBmRz, the surface roughness of the chip 162 is set to 1.0.2,
0.3.0.4. Change to OBmRz, develop roller 1
2 is a graph showing the state of an image when printing is performed after adjusting the pressing force of the blade 16 so that the amount of charge of the toner on the toner is 10.0 μc/g. Here, the surface roughness (center line average roughness) of the chip 162 and the developing roller 12 was measured using the apparatus shown in FIG. This device is (
Product name “Surfcoder 5E-40D” manufactured by Koita Research Institute Co., Ltd.
"This is a contact type surface roughness meter, and is composed of a detector 201, an amplification calculation device 202, a recorder 203, and a support for the object to be measured 204. When measuring surface roughness using this device, the measurement An object is placed on the object to be measured 204 and the contact needle 205 of the detector 201 is brought into contact with the surface of the object under a predetermined pressure. The signal is then output to the recorder 203.

Note that the measurement conditions are as follows.

Cutoff value (mm): 0.8 Measurement length (mm): 2.5 Experiments have shown that if the toner charge amount is less than 10.0μc/g, the density will decrease and fog will increase under humid conditions. Confirmed by. Further, the amount of charge of the toner was determined by measuring the charge m for 10 revolutions of the developing roller.

From this graph, it was confirmed that when the surface roughness of the chip 162 was smaller than the surface roughness of the developing roller 12, a good image without density unevenness, white spots, etc. could be obtained. In addition, the surface roughness of the chip 162 and the developing roller 12 is 3 μm each.
When Rz was equal, white spots on the image were developed when the image was left for about one week. However, in this case, a normal good image could be obtained by performing interlacing on several images.

In these developments, the greater the surface roughness of the chip 162, the more it is necessary to press the blade 16 against the developing roller 12 with a stronger force in order to sufficiently charge the toner. This is caused by distortion.

FIG. 6 shows that while the rubber hardness of the developing roller 12 is fixed at 36°, the rubber hardness of the chip 162 is set at 30°, 40°, 50°.
The charge amount of the toner on the developing roller 12 is 10.
．． It is a graph showing the state of an image when printing is performed after adjusting the pressing force of the blade 16 so that it becomes 0 μc/g. Note that the surface roughness of the chip 162 is 1.
It was fixed at 0 μmRz.

From this graph, density unevenness was confirmed on the image when the rubber hardness of the chip 162 was 306. From this, even if the surface roughness of the chip 162 is smaller than that of the developing roller 12, the rubber hardness of the chip 162 is lower than that of the developing roller 12.
It was confirmed that good images could not be obtained unless the rubber hardness was greater than No. 2.

Further, in order to confirm the influence of the wear width of the tip 162 of the blade 16 on the image in the developing device 10 described above, the following experiment was conducted. In other words, the hardness of the tip 162 is 50'70°, and the pressing force of the blade 16 is 100g/
A running test was conducted on 20,000 sheets under each condition at 250 g/cm and 16 chips before and after the test.
The amount of wear and the condition of the image of No. 2 were confirmed. The wear width was calculated by measuring the amount of change (wear depth) due to wear of the tip 162 and using the following formula.

B-R-Nishitoji=(A/璽-2 Here, as shown in FIG. 7, A is the wear width of the tip 162, B is the wear depth, and R is the curvature of the semicircular cross section of the tip 162. The radius is 1.5 mm.

Further, the wear depth B was measured using a laser length measuring device manufactured by Tokyo Photonics Industry Co., Ltd.

In addition, in this experiment, the potential of the image part, that is, the potential of the exposed part of the photosensitive drum 11 was -40V, the potential of the non-image part, that is, the potential of the unexposed part was -550V, and the developing bias was -200V.
The contact width with the photoreceptor drum 11 was set to 1.5 mm.

The experimental results are shown in the graphs of FIGS. 8 and 9. From these graphs, it can be seen that the wear width A of the chip 162 after 10,000 sheets is equal to the radius of curvature R (1.5 m) of the semicircular cross section of the chip 162.
m), and it was confirmed that the image density decreased accordingly. On the other hand, when the abrasion width A is the same as or smaller than the radius of curvature R of the semicircular cross section, almost no change is observed in the image density, and an extremely sharp line image with an image density of 1.4 can be obtained. did it.

This is because as the wear width A of the chip 162 increases, the space for the toner reservoir formed between the developing roller 12 and the tip of the chip 162 becomes narrower, and the toner layer formed on the surface of the developing roller 12 becomes thinner. Because it will be.

The wear of the tip 162 is more likely to affect the quality of the image as the radius of curvature R of the semicircular cross section of the tip 162 becomes smaller. In other words, this means that when the radius of curvature R of the tip 162 is large, the toner reservoir is narrow from the beginning, so the range that can change due to wear is small;
When the radius of curvature R of the chip 162 is small, the chip 16
This is because the size of the toner reservoir changes rapidly due to wear.

The experimental results also confirmed that it is necessary to suppress the wear of the tip 162 as much as possible by changing the pressing force of the blade 16 according to the rubber hardness of the tip 162. In this embodiment, the pressing force of the blade 16 is set to 200 g/cm.

Next, the above-mentioned developing roller 12 will be explained in detail.

FIG. 10 is a perspective sectional view showing the developing roller 12.

The characteristics required of the developing roller 12 are that it has "conductivity and elasticity".

The simplest configuration that satisfies this requirement is, for example, one in which the outer periphery of a metal shaft is covered with a conductive rubber roller. However, in the developing system of this embodiment, the toner is pressed against the surface of the developing roller 12, Surface smoothness is required because it will be transported.

Therefore, in the developing roller 12 of this embodiment, an elastic layer 12b made of, for example, conductive silicone rubber or urethane rubber is provided on the outer periphery of the metal shaft 12a. Conductive layer 12
c is provided to create a two-layer structure.

The elastic layer 12b may be conductive or non-conductive, but it is preferable to use a conductive layer in consideration of the possibility of peeling or scratches on the conductive layer 12c.

The rubber hardness of the elastic layer 12b is a factor that directly affects the load and torque of the developing roller 12 to obtain an appropriate nip between the developing roller 12 and the photoreceptor tram 11.

In addition, Jl5K6301 may be damaged during packaging or when left unattended for a long time.
Regarding the permanent strain shown in , it is known that if the permanent strain exceeds 10%, uneven rotation period of the developing roller will occur in the image, so the compressive strain of the elastic layer 12b should be 10% or less, preferably 5% or less. There must be. Regarding the relationship between rubber hardness and permanent set, there is generally a tendency that the higher the rubber hardness, the smaller the permanent set, so the balance between the materials and each other is important.

As described above, conductive silicone was selected in this embodiment as a material that satisfies the characteristics required for the elastic layer 12b, but other materials such as conductive EPDM rubber and conductive urethane rubber also meet the required characteristics. It can be used as

The elastic layer 12b made of conductive silicon has a hardness of 28'' based on the A type hardness needle of 6301 according to the JIs standard, and has an outer diameter of 18 mm as an elastic roller.The electrical resistance value of the conductive silicon is The results were calculated by placing this elastic roller in parallel with a stainless steel roller with a diameter of 60 mm so that the contact width was 2 mm, and measuring the current observed when a potential difference of 100 V was established between the metal shafts of both rollers. It was 3.4×10 1 Ω·Cm.The permanent deformation was 1.8% as measured using the measurement method specified in JIS standard 6301.

Furthermore, since the conductive layer 12c is in direct contact with the toner and the photoreceptor drum 11, it is limited to materials that do not contaminate the surface of the toner or the photoreceptor drum 11 by seeping out plasticizers, sulfurizers, process oils, etc. Regarding the smoothness of the surface, it is desirable that the maximum surface roughness is 3 μm or less. If it exceeds this range, uneven patterns on the surface tend to appear in the image.

A method of achieving a smoothness of the conductive layer 12C with a maximum surface roughness of 3 μm or less is to apply the conductive layer 12c with a sufficient thickness on the elastic layer 12b, and then use post-processing (polishing) to obtain a predetermined surface roughness. There are ways to finish the outer diameter and surface roughness, but
This method increases costs. Therefore, a method of finishing without requiring post-processing is desired, and for this purpose, the surface roughness of the elastic layer 12b, the film thickness of the conductive layer 12c, and the viscosity of the paint for forming the conductive layer 12c are optimally selected. Must.

FIGS. 11 to 13 show a typical method for applying the conductive layer paint.

FIG. 11 shows a spray coating method, FIG. 12 shows a dipping coating method, and FIG. 13 shows a knife coating method.

The viscosity of the paint in each method is spray method, dipping method ≦ Naifetsu method,
Smoothness of the surface of the conductive layer 12c (maximum surface roughness 3 μm)
If the maximum surface roughness of the elastic layer 12b is Rz (μm), the paint film thickness T (μm) required to achieve this is T≧5XRz in the spray method, and T≧5XRz in the dipping method and the knife method. This is possible if T≧3XRz is satisfied.

In this example, as a paint for forming the conductive layer 12c, a conductive polyurethane paint having a conductivity of 10'Ω·cm by dispersing conductive powder particles in a polyurethane resin was used. Then, in the following steps, a conductive polyurethane paint was applied to the surface of the elastic layer 12b made of conductive silicone, and after drying, heat treatment was performed to form a conductive layer 12C.

First, Nippon Miractron ■ as a conductive polyurethane paint.
A diluting solvent prepared by mixing methyl ethyl ketone (MEK) and tetrahydrofuran (THF) in a ratio of 1:1 is added to the same amount of a diluting solvent. "Sparex DH202313" is a solution type conductive polyurethane paint based on thermoplastic polyurethane. After sufficiently stirring this diluted paint, it is applied onto the surface of the elastic layer 12b washed with a solvent using a dipping method. In addition, the pulling speed of the treated material in this dipping method was 5.5 mm/sec.
c. Thereafter, it was dried in air for about 30 minutes, and then heat-treated at 100° C. for 20 minutes. As a result, a conductive layer 12c having a layer thickness of about 80 μm was obtained. The layer thickness of the conductive layer 12c can be changed within the range of 10 μm to 300 μm by changing the pulling speed of the dipping method and the viscosity of the solvent.

Through the above steps, the metal shirt h 12 a and the conductive layer 1
The resistance value between 2c and 2c is 5X10"Ω・cm.

Rubber hardness is 36″ with A type hardness needle of 6301 according to JIS standard.
, the surface roughness was determined at 1TPl using the above-mentioned measuring device, and was found to be 3
A developing roller 12 of μmRz could be obtained.

In the above-described embodiment, the tip 162 having a semicircular cross section is used in the blade 16, but it may have any other cross-sectional shape as long as the surface in contact with the surface of the developing roller 12 is a curved surface.

Further, there is no problem even if the developing roller 12 has an insulating layer or a resistive layer on its surface.

Further, in the above embodiment, the metal shaft 12a is used as the support for the developing roller 12, but as long as the developing bias voltage can be supplied, it may be, for example, a conductive resin shaft. In the type of developing roller that supplies power to the layer 12b, the support need not be electrically conductive and may be made of an insulating material.

Further, the blade 16 is supported at a position against the rotation of the developing roller 12;
It may also be supported at the with position with respect to rotation.

[Effects of the Invention] As explained above, according to the present invention, it is possible to realize a developing device in which there is no change in the thickness of the thin developer layer on the surface of the developing roller and no deterioration in image quality even during long-term use. can do.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the overall configuration of a developing device according to an embodiment of the present invention, FIG. 2 is a perspective view showing a blade in the developing device shown in FIG. 1, and FIG. 3 is a front view of the blade shown in FIG. 2. figure,
Fig. 4 is a graph showing the relationship between the surface roughness of the chip and the developing roller and the state of the image, Fig. 5 is a diagram for explaining the device for determining the surface roughness, and Fig. 6 is a graph showing the relationship between the surface roughness of the chip and the developing roller and the state of the image. Graph showing the relationship between rubber hardness and image condition,
Figure 7 is an enlarged view of the chip, Figures 8 and 9 are graphs showing experimental results to confirm the influence of the wear width of the blade chip on the image, and Figure 10 shows the developing roller. A perspective sectional view and FIGS. 11 to 13 are views for explaining the method of forming the conductive layer of the developing roller, respectively, and FIG. 14 is a side view showing details of the pressure contact portion between the developing roller and the blade. 10...Developing device, 11...Photosensitive drum, 12.
-Developing roller, 16...blade, 161...thin plate spring, 162...chip. Applicant Toshiba Corporation Toshiba Intelligent Technology Corporation

Claims (2)

[Claims] (1) A developing roller disposed opposite to the electrostatic latent image holder, and a developer thin layer forming means for forming a developer thin layer on the surface of the developing roller, In a developing device that visualizes an electrostatic latent image formed on the electrostatic latent image carrier by bringing the formed thin developer layer close to or in contact with the electrostatic latent image carrier, the forming of the developer thin layer The developing means has a pressure contact portion that is pressed against the surface of the developing roller with a thin layer of developer interposed therebetween, and the pressure contact portion has greater hardness and less surface roughness than the developing roller. Device. (2) A developing roller disposed facing the electrostatic latent image holder, and a developer thin layer forming means for forming a developer thin layer on the surface of the developing roller, In a developing device that visualizes an electrostatic latent image formed on the electrostatic latent image carrier by bringing the formed thin developer layer close to or in contact with the electrostatic latent image carrier, the forming of the developer thin layer The means has a pressing part having a semicircular cross section that is pressed against the surface of the developing roller with a thin developer layer in between, and the radius of curvature of the semicircular cross section of the pressing part is set to R.
b, the wear width caused by friction with the developing roller is Lb
Then, a developing device that satisfies the relationship Rb≧Lb.