JPH11119554A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to assure a sufficient triboelectrostatic charge quantity and transportation quantity for a magnetic toner of a one-component developer on a developing sleeve of a developing device even if a metallic layer is formed on the surface of the developing sleeve and to obtain images maintaining densities and image quality for a long period of time even in image formation of a reversal development system using the magnetic positive toners by using an amorphous silicon drum as an image carrying member. SOLUTION: The surface of the developing sleeve is subjected to surface roughening and is subjecting plating of a nonmagnetic metal. The difference ΔW(eV) of the work function after the work function of the magnetic toner is subtracted from the work function of the plating layer and the center line average height Ra(μm) of the developing sleeve surface after the plating satisfy the relations Ra-13|ΔW|+0.6<=0; Ra-6|ΔW|+6>=0; 19Ra-|ΔW|-0.9>=0; Ra<=0.7. More preferably, the thickness of the plating layer is specified to 3 to 20 μm and the hardness Hv thereof to 450 to 1000. The photosensitive drum is formed of an a-Si drum and the developing sleeve is made of aluminum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for developing an electrostatic latent image on an image carrier such as a photoreceptor to obtain an image, and more particularly to an image forming apparatus with improved development.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, an electrostatic latent image is formed on an image carrier made of a photoreceptor.
The latent image is developed by a developing device.
The developing device uses a non-magnetic metal developing sleeve containing a magnet roller for transporting the developer.

The surface of the developing sleeve is provided with appropriate irregularities for the purpose of improving the transportability and charging property of the developer. Inexpensive nonmagnetic metal pipes such as aluminum and aluminum alloys are often used for the developing sleeve. However, since these are relatively soft metals (Vickers hardness Hv = 70 to 120), if the developing sleeve is used for a long time, Further, there is a disadvantage that the unevenness of the surface is reduced or the state of the unevenness is changed due to the abrasion caused by the developer, so that a high quality image as obtained in the early stage of use cannot be obtained.

[0004] This will be described in detail with reference to the drawings.
FIG. 2 is a cross-sectional view showing a developing sleeve conventionally used. The developing sleeve 6 is made of non-magnetic metal aluminum, and contains a magnet roller 7 as a magnetic field generating means inside. The developing sleeve 6 is rotatably arranged around a magnet roller 7 in a developing device, while the magnet roller 7 is arranged non-rotatably.

FIG. 9 is a cross-sectional view of the surface of the developing sleeve 6. The surface of the developing sleeve 6 is provided with irregularities 11 by blasting using glass beads.
The surface of the developing sleeve 6 having the irregularities 11 is as follows.
For example, when the surface roughness Ra was about 1.0 μm in the early stage of use, the number of prints was about 10,
After development of an amount equivalent to 000 sheets, Ra is reduced to about 0.5 μm. As a result, the transportability and chargeability of the developer are reduced from the initial settings, and the obtained image density is reduced.

Here, Ra is the average roughness of the center line. As shown in FIG. 11, a portion of the measured length L is extracted from the roughness curve f (x) in the direction of the center line. This is a value obtained by arithmetically averaging the absolute value of the deviation between the center line of the extracted portion and the roughness curve, and is represented by the equation shown in FIG.

When the developing sleeve 6 is used for a long period of time, fragments of resin, which is a main component of the toner, may be embedded in the surface of the developing sleeve during the blasting process, in particular, in a small recess formed in a concave portion of the surface. Do you get it. When the resin fragment of the toner exists on the surface of the developing sleeve,
As for the toner in contact with the surface of the developing sleeve, the resin in the toner frequently comes into contact with the resin on the surface of the developing sleeve, and therefore, the toner is not provided with a sufficient triboelectric charge, so that the toner is not sufficiently charged. The charge amount decreases. As a result, similarly to the above, there is a problem that a satisfactory image density cannot be obtained.

As a countermeasure against such a problem, as shown in FIG. 10, a hard metal layer 12 such as Cr or Cu-Ni-Cr having a hardness Hv of about 450 is formed on the uneven surface of the developing sleeve 6. It has been proposed (Japanese Unexamined Patent Publication No.
1485).

[0009]

However, when the metal layer 12 such as Cr or Cu-Ni-Cr is formed on the surface of the developing sleeve 6, depending on the type of the developer, the developer is rubbed by friction with the surface of the developing sleeve. It cannot be sufficiently charged, and an image of good density and quality cannot be obtained.

This problem is particularly caused by a photosensitive drum (image carrier).
In a reversal development system using an amorphous silicon drum, when a magnetic positive toner (one-component positive magnetic developer) is used for development, it becomes more remarkable.

That is, the photosensitive drum made of amorphous silicon is superior in durability to the OPC drum that has been frequently used in the past, but has a lower charging ability. In order to form an electrostatic latent image on the photosensitive drum, even if the drum surface is charged by the charging means, it is charged only from about + 400V to about + 450V. As a result, the latent image potential becomes shallower and the image density becomes lower. Therefore, if the DC component of the developing bias is set higher in order to increase the image density, the positively charged toner becomes a white background area other than the latent image area on the photosensitive drum. Also adheres to
So-called "fogging" occurs remarkably, and image quality deteriorates. Therefore, if a toner with enhanced magnetism is used to reduce fog, as described at the beginning, the amount of charge required to secure a sufficient density cannot be obtained.

An object of the present invention is to provide a magnetic toner of a one-component developer having a sufficient amount of triboelectric charge and a sufficient transport amount even when a metal layer is formed on the surface of a developing sleeve of a developing device. An image that uses an amorphous silicone drum as a carrier, performs good development even in the reversal development system image formation using a magnetic positive toner, and makes it possible to obtain a high-quality image that maintains the density and image quality for a long time. It is to provide a forming device.

[0013]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention has an image carrier having a photosensitive layer on the surface, and a cylindrical developing sleeve made of a non-magnetic metal material in which a magnet is arranged in a non-rotating manner. A developing unit that carries a magnetic toner of a component developer and transports the toner to a developing unit facing the image carrier, and develops a latent image formed on the surface of the image carrier with the toner. The developing sleeve has a roughened surface and is plated with a non-magnetic metal, and a work function difference ΔW (eV) obtained by subtracting the work function of the toner from the work function of the plating layer; Surface center line average roughness Ra (μm)
Is an image characterized by satisfying the following relationship: Ra-13 | ΔW | + 0.6 ≦ 0 Ra-6 | ΔW | + 6 ≧ 019 Ra− | ΔW | −0.9 ≧ 0 Ra ≦ 0.7 It is a forming device.

According to the present invention, preferably, the coating amount of the toner per unit area on the developing sleeve is a (m
g / cm ² ) and the ratio of the peripheral speed of the developing sleeve to the image carrier is b (unitless), the product of a and b can satisfy the relationship of 1.0 ≦ ab. . Further, the thickness of the plating layer can be 3 μm or more and 20 μm or less, and the hardness Hv of the plating layer can be 450 or more and 1000 or less. The photosensitive layer of the image carrier may be made of amorphous silicon, and the developing sleeve may be made of aluminum.

The charge polarity of the magnetic toner is positive, and the work function difference ΔW (eV) and the center line average roughness Ra (μm) are Ra-13ΔW + 0.6 ≦ 0 Ra-6ΔW + 6. .Gtoreq.0 19Ra-.DELTA.W-0.9.gtoreq.0Ra.ltoreq.0.7, the charging polarity of the magnetic toner is negative, the work function difference .DELTA.W (eV) and the center line average roughness are satisfied. Ra (μm) satisfies the following relationship: Ra + 13ΔW + 0.6 ≦ 0 Ra + 6ΔW + 6 ≧ 019Ra + ΔW−0.9 ≧ 0 Ra ≦ 0.7

Further, the photosensitive layer of the image carrier is made of an amorphous material, and means for heating and controlling the surface of the image carrier is provided. The magnetic toner has a positive polarity, and the magnetic toner has a positive polarity. The polarity is positive, and the work function difference ΔW (eV) and the center line average roughness Ra (μm) are Ra-13ΔW + 0.6 ≦ 0 Ra-6ΔW + 6 ≧ 0 19Ra-ΔW-0.9 ≧ 0 Ra ≦ 0.7 is satisfied.

[0017]

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

Embodiment 1 FIG. 1 is a schematic structural view showing an embodiment of the image forming apparatus of the present invention. In the figure, reference numeral 1 denotes an image carrier, which in this embodiment is an electrophotographic photosensitive drum. Around this photosensitive drum 1, a latent image forming section 2 for forming an electrostatic latent image on the surface of the photosensitive drum 1, a developing device 3 for developing the latent image, and a method for transferring a toner image obtained by development to a transfer material A transfer separation unit 4 for separating the transfer material from the photosensitive drum 1; and a cleaning unit 5 for cleaning the transfer residual toner remaining on the photosensitive drum 1.

In order to form an image, the photosensitive drum 1 is rotated in the direction of arrow A. First, the surface of the photosensitive drum 1 is charged by the latent image forming section 2, and image exposure is performed to form an electrostatic latent image. I do. The latent image formed on the photosensitive drum 1 is moved to the position of the developing device 3 as the photosensitive drum 1 rotates, and is developed by the developing device 3 using a magnetic toner of a one-component developer.

According to the present embodiment, the developing device 3 contains a positively charged magnetic toner. The developing device 3 carries the magnetic toner and rotates in the direction of arrow B, so that the developing sleeve 6 conveys the toner to the developing section facing the photosensitive drum 1, and is arranged in the developing sleeve 6 non-rotatably. A magnet roller 7 serving as a magnetic field generating means, a stirring means 8 for stirring the toner in the developing device 3 to increase the fluidity and conveying the toner to the developing sleeve 6, and a toner layer carried on the developing sleeve 6 It comprises a magnetic blade 9 for regulating the thickness and a bias power supply 10 for applying a developing bias to the developing sleeve 6. The developing sleeve 6
The photosensitive drum 1 is opposed to the photosensitive drum 1 with a predetermined minimum gap. The magnet roller 7 has magnetic poles N1, S1, N
It has four poles of 2, S2.

The magnetic blade 9 is opposed to the magnetic pole N1 of the magnet roller 7 in the developing sleeve 6 with a predetermined gap therebetween, and is developed by the magnetic field formed between the magnetic blade 9 and the magnetic pole N1 (regulating pole). The layer thickness of the toner carried on the sleeve 6 is regulated. After the layer thickness is regulated, the toner conveyed to the developing section rises on the surface of the developing sleeve 6 by the magnetic pole S1 (developing pole) of the magnet roller 7 disposed in the developing section. The spiked toner flies and adheres to the latent image portion due to a potential difference between the latent image on the photosensitive drum 1 and the developing sleeve 6, and the latent image is developed as a toner image.

At this time, in order to promote the development, a developing bias in which an AC voltage is superimposed on a DC voltage is applied between the developing sleeve 6 and the photosensitive drum 1 by the bias power supply 10. The toner on the developing sleeve 6 flies due to the developing bias and repeatedly adheres to and separates from the photosensitive drum 1. The latent image portion on the surface of the photosensitive drum 1 corresponds to the potential of the latent image until the latent image portion leaves the developing portion. The residual toner adheres and remains, and thus the latent image is favorably developed.

The toner image formed on the photosensitive drum 1 in this manner is transferred to a transfer material (not shown) supplied to the photosensitive drum 1 in the transfer separation section 4. The transfer material is separated from the photosensitive drum 1 while the toner image is transferred from the photosensitive drum 1 by the transfer / separation unit 4, and is then conveyed to a fixing unit by a conveyance unit (not shown), where the toner image is transferred to the transfer material by fixing. Fixation is performed. After the transfer, the photosensitive drum 1 is cleaned by the cleaning unit 5 to remove the transfer residual toner remaining on the surface, and prepares for the formation of a latent image of the next image.

An example of the specifications of the apparatus according to the present embodiment is as follows.

Magnetic force of the magnetic pole of the magnet roller (on the surface of the developing sleeve): N1 = 850 Gauss, S1 = 950 Gauss, N2 = 75
0 Gauss, S2 = 550 Gauss Minimum distance between photosensitive drum and developing sleeve: 230 μm Distance between developing sleeve and magnetic blade: 240 μm Development bias: DC voltage + AC voltage. DC voltage = +25
0V, AC voltage = peak-to-peak voltage 1.4k, frequency 2.7
kHz photosensitive drum: a-Si. Dark area potential = + 400 V, bright area potential + 50 V Image forming speed: A4 size 40 sheets / min

In the present invention, the material of the sleeve base used for the developing sleeve 6 is not particularly limited as long as it is a non-magnetic metal, but a relatively Vickers hardness Hv of an aluminum alloy, a copper alloy or the like having a hardness of about 70 to 120 is used. A soft nonmagnetic metal material is suitable for exhibiting the effects of the present invention, and is particularly preferable as a material for the sleeve base.

The use of an aluminum developing sleeve is
This is found in high-speed, high-durability image forming apparatuses using an amorphous silicon (a-Si) drum as an image carrier. In a high-speed, high-durability image forming apparatus, the corotron or scorotron charging method is frequently used for charging the photosensitive drum because of its high charging efficiency.However, during the charging process, discharge products are generated, which adhere to the surface of the photosensitive drum. Then, the image obtained by changing the potential of the attached portion becomes uneven.
Therefore, the photosensitive drum is set to 4 so that the discharge product does not adhere.
It is necessary to control the heating temperature to 0 ° C., and there is a concern about the thermal deformation of the developing sleeve.
This is because even if the temperature is adjusted to 40 ° C., it can be used without any problem.

According to the simulation calculation, when the developing sleeve diameter is 24.5 mm and the gap between the developing sleeve and the photosensitive drum is about 240 μm, the amount of deflection of the developing sleeve is 25 μm when the material of the developing sleeve is SUS. On the other hand, it was about 5 μm for aluminum.
It has been confirmed that when the gap between the developing sleeve and the photosensitive drum is set to 240 μm, if the amount of deflection of the developing sleeve exceeds 20 μm, the density unevenness of the image becomes remarkable.

As described above, in the high-speed and high-durability image forming apparatus using the a-Si drum, the developing sleeve is made of aluminum having a small thermal deformation, and the hardness is increased by applying a plating layer on the surface of the developing sleeve. The present invention is effective because it can reduce image unevenness and extend the life of the developing sleeve. Of course, according to the present invention, it is a high-grade material used when a long life is required for the developing sleeve.
Even with stainless steel having a hardness Hv of about 150 to 190, the durability is improved.

In the present invention, the surface of the developing sleeve 6 is roughened in order to improve the toner transportability by the developing sleeve 6. The surface of the developing sleeve can be roughened by various methods. In the present invention, the surface is sandblasted as follows.

As the abrasive grains serving as the blast material, regular abrasive grains (preferably spherical or flat particles having a smooth surface) are preferable, and glass beads having a particle size of # 100 to # 600 are preferably used. The blast nozzle is positioned at a distance of 7 mm from the developing sleeve, the developing sleeve is rotated at 12 rpm, and glass beads are blown from the nozzle at an air pressure of 3 kg / m ² . During this spraying, the nozzle is moved along the developing sleeve surface for a distance of 30 cm in 1 to 2 minutes parallel to the axis. Thus, the surface of the developing sleeve is blasted to obtain a rough surface. After the blast processing is completed, the developing sleeve is dried after cleaning the surface.

In the present invention, the surface roughness (center line average roughness) Ra applied to the surface of the developing sleeve 6 is set to 0.7 μm or less. The lower limit of Ra is 0.05, which is specifically determined by the relationship between the work function difference between the non-metal plating layer applied to the surface of the developing sleeve described later and the magnetic toner used. Hereinafter, description will be made based on experiments performed by the present inventors.

A stainless steel (SUS316) developing sleeve is sandblasted on the surface with # 300 glass beads and subjected to development, and continuous image formation is performed using a small particle size toner (6 μm) capable of improving image quality. Was repeated. The following phenomenon occurred. (1) When the number of prints is 2000 to 5000,
The image density dropped from 1.3 to 1.0. (2) When the image is formed by changing the original to black on one side at the time when the image density is reduced, the print image becomes a partially blank image having a low density portion corresponding to the rotation cycle of the developing sleeve. . (3) When the toner on the developing sleeve at the time when the image density was reduced was removed, and the developing sleeve was washed with a solvent and then used again for development, the image density was recovered.

Then, first, when the amount of triboelectric charge of the toner at the time when the image density was reduced in (1) was measured, it was less than half of the amount of toner charge at the start of image formation. The decrease was found to be the cause of the decrease in image density. Similarly, when the occurrence of a partial white spot image in (2) was examined, the white spot was also caused by a decrease in the toner charge amount. However, it is assumed that the recovery of the image density by the toner removal and the cleaning of the developing sleeve in (3) is not caused by the deterioration of the toner including a decrease in the charge amount, but is caused by a change in the property of the surface of the developing sleeve.

In order to confirm the change in the properties of the surface of the developing sleeve, the surface of the developing sleeve was observed with an electron microscope when the image density was lowered. Then, as schematically shown in FIG. 2, there are a plurality of small recesses 14 having a diameter of about 5 μm in the recesses 13 of the surface irregularities, in particular, the recesses 13 having a diameter of about 40 μm and a depth of about 1 μm. Dent 14
It was found that a resin fragment (debris) of the toner main component was embedded therein.

When the resin fragments of the toner are embedded in the surface of the developing sleeve in this manner, the toner in contact with the surface of the developing sleeve often causes the resin of the toner to come into contact with the resin on the surface of the developing sleeve. Therefore, a sufficient triboelectric charge is not given to the toner, and the charge amount of the toner decreases. Hereinafter, the phenomenon that the toner resin fragments are embedded in the surface of the developing sleeve is referred to as “sleeve contamination”.

Then, the surface of the developing sleeve was blasted under different conditions to obtain a smoother surface having a surface roughness Ra of 0.7 μm and subjected to development, and continuous image formation was carried out. Did not. Considering this, in order to increase Ra, it is necessary to increase the air pressure used for spraying the abrasive grains. As a result, the generation of a small dent having a diameter of about 5 μm on the surface of the developing sleeve increases. Therefore, it is considered that sleeve contamination occurs when Ra is 0.7 μm or more.

In this embodiment, the surface roughness Ra is 0.1
Prepare a plurality of developing sleeves ranging from ~ 0.9 μm,
Each image was used for development to form a continuous image of 5,000 sheets, and sleeve contamination was examined. Table 1 shows the results.

In Table 1, the symbols in the column of sleeve contamination are as follows: ：: The toner charge amount on the developing sleeve has about 80% or more of the initial value at the end of image formation, Δ: 60% or more
X: Less than 80%, meaning less than 60%.

In general, if a continuous image is formed on 5,000 sheets and the charge amount of the toner on the developing sleeve has about 80% of the initial charge amount at the end of the image formation, then the toner is used for a long time. However, the charge amount of the toner does not greatly decrease, and it is considered that there is no problem in long-term use.

[0041]

[Table 1]

As shown in Table 1, in order to prevent sleeve contamination during continuous image formation and maintain a stable image density, the surface roughness Ra of the developing sleeve must be 0.7 μm or less. Is preferable. However,
When the surface roughness is in such a range, the fluctuation of the charge amount of the toner is not large, but the toner transport property on the developing sleeve is not sufficiently obtained, and an appropriate image density cannot be secured in terms of the toner amount. Problems arise.

In this embodiment, an aluminum developing sleeve containing a magnet roller is
Was blasted using the glass beads described above to roughen the surface. At this time, the surface roughness Ra of the developing sleeve was changed variously by changing the air pressure at which the glass beads were blown. These developing sleeves were used in the developing device 3 of FIG. 1, and the transportability of the positively charged magnetic toner contained in the developing device 3 was examined. The results are shown in FIG.

As shown in FIG. 3, the toner transportability of the developing sleeve is substantially determined by the degree of surface roughness, and the transport amount increases as the surface roughness increases. In the present invention,
The surface of the roughened developing sleeve is plated with a non-magnetic metal. If the plating thickness is small and uniform, the surface roughness of the developing sleeve is almost unchanged, and the toner transportability is not affected.

In general, it has been found that when the toner amount per unit area on the photosensitive drum is 0.5 mg / cm ² or more, a sufficient density as a printed image can be obtained.
Therefore, the toner coating amount per unit area on the developing sleeve is amg / cm ² , and the ratio of the rotational speed of the developing sleeve to the photosensitive drum (peripheral speed ratio) is b (unitless), and the maximum 50% of the toner on the developing sleeve is Assuming that the amount of toner has been subjected to development, 0.5 ≦ ab · 0.5, thus:
When the condition of 0 ≦ ab is satisfied, a print image with a sufficient density can be obtained.

Table 2 shows the results of examining the densities of print images when developing sleeves having various surface roughnesses were used with various changes in the toner coating amount a and the peripheral speed ratio b. In Table 2, the symbols are as follows: 初期: Initial density (maximum density at the beginning of development) is 1.3 or more; Δ: 1.2 or more to less than 1.3; X: Less than 1.2 Show.

[0047]

[Table 2]

Here, a developing sleeve having a surface roughness Ra of greater than 0.7 can secure an appropriate value for the initial image density, but as described above, sleeve contamination occurs at any peripheral speed ratio. Therefore, it is not an appropriate developing sleeve because the density is remarkably reduced. The developing sleeve having a surface roughness of 0.05> Ra (for example, Ra = 0.03 μm) has a toner charge amount of 15 μC / at any peripheral speed ratio.
g, and the toner is not uniformly coated on the developing sleeve, which causes unevenness in the image.

In the present invention, in order to increase the hardness of the surface of the developing sleeve, as described above, the surface of the developing sleeve is roughened and then plated with a non-magnetic metal. There are various plating treatments for hardening the surface, but in the present invention, electroless plating is used instead of electroplating. As the electroless plating of the non-magnetic metal, for example, electroless Ni-P plating, electroless Ni-B plating, and electroless Cr plating are suitable.

As described above, the developing sleeve 6 is made of a non-magnetic material because it uses a magnetic toner, but the metal plating applied to the surface of the developing sleeve has a thickness of several μm.
Since it is as thin as m, it can be used even if it is magnetic. It is preferably non-magnetic. Nickel (Ni) is a ferromagnetic substance by itself, but in an electroless Ni-P or Ni-B plating layer, nickel is phosphorus (P) or boron (B).
And becomes amorphous and becomes non-magnetic.
The phosphorus content in the Ni-P plating film required for such demagnetization is 8 to 10 wt%, and the boron content in the Ni-B plating film is 5 to 7 wt%.

The plating may be applied uniformly on the entire surface of the developing sleeve 6, but may be formed into a mesh having an arbitrary hole shape. By plating after performing a mesh-like masking process, a mesh-like plating is obtained. Further, as is often performed to enhance the adhesion between the plating film and the surface of the developing sleeve, a zincate treatment for forming a zinc alloy film on the surface of the developing sleeve can be performed before plating.

In the present invention, electroless plating rather than electroplating is used because the deposited plating metal adheres to the roughened uneven surface of the developing sleeve 6 to a uniform thickness without being affected by the unevenness. This is because a plated film having a uniform thickness can be obtained, and the surface roughness obtained by roughening can be maintained with almost no change. In electroplating, the plating metal is not easily deposited on the concave portions of the roughened surface of the developing sleeve, and is preferentially adhered to the convex portions and only the convex portions are plated thickly, so that a plating film having a uniform thickness is obtained. And the surface roughness changes.

In the present invention, the thickness of the nonmagnetic metal plating layer applied to the surface of the developing sleeve 6 is 3 to 20 μm.
In a developing sleeve having a surface roughness Ra of 0.05 to 0.7 μm, when plating is performed with a thickness of 3 μm or more, a small recess 14 in which the toner resin of FIG. 2 is embedded can be filled with a plating metal. Therefore, at the time of continuous image formation, the resin fragments of the toner are not present on the surface of the developing sleeve, so that the toner can be satisfactorily charged on the surface of the developing sleeve, and a decrease in the charge amount can be prevented. . The upper limit of the plating thickness is 20 μm. If the thickness is more than 20 μm, a uniform plating film cannot be obtained on the surface of the developing sleeve, and large irregularities necessary for toner conveyance are buried. .

The effect of eliminating the small recess 14 in the recess 13 on the surface of the developing sleeve by embedding the plating metal is particularly useful in the case of a developing sleeve using SUS having a relatively high hardness of Hv = 150 to 190. this is,
Even if sand blasting with fixed-size particles is performed, if the hardness of the material of the developing sleeve is high, the surface of the developing sleeve cannot be blasted smoothly according to the outer shape of the particles, and there are few small dents such as toner resin embedded in the surface. This is because it occurs.

The hardness of the metal plating is Hv = 450.
The above is preferable, and required wear resistance can be obtained. The upper limit is preferably as high as possible. However, if annealing of means for increasing the hardness of plating, which is often used, is performed, the developing sleeve will be warped and the deflection during rotation will be large. preferable.

As described above, in the present invention, the surface of the developing sleeve 6 is roughened and plated with a non-magnetic metal to form a non-magnetic metal having a plating layer having a thickness of 3 to 20 μm. The developing sleeve has a Ra of 0.05 to 0.7 μm. However, depending on the type of the combination of the plating metal and the magnetic toner, the toner may not be sufficiently charged on the surface of the developing sleeve in some cases. This will be described below.

Two types of toners A and B (manufactured by Canon Inc.) were prepared as positively chargeable magnetic toners (one-component magnetic developer), each of which was stored in a developing unit 3 and subjected to development to form an image. The developing sleeve 6 used was subjected to electroless Ni-P plating. Table 3 shows the measurement results of the charge amount of the toner at that time.

[0058]

[Table 3]

As shown in Table 3, there is no problem with the combination of the toner A and the developing sleeve coated with the electroless Ni-P plating, but the combination of the toner B and the developing sleeve coated with the electroless Ni-P plating. In this case, the charge amount of the toner B was very small, so that sufficient image density and image quality could not be obtained. Generally, in order to obtain a sufficient image density and image quality, the charge amount of the toner needs to be about 6.0 μC / g or more. The image density and image quality also depend on the amount of toner transported on the developing sleeve, but both toners A and B obtained 0.70 g / cm ² or more, and the toner transport amount was sufficient.

In order to investigate the cause of the difference in the charge amounts of the toners A and B, a work function measuring device utilizing the photoelectric effect (Surface Analyzer AC-1S, manufactured by Riken Keiki Co., Ltd.) was used. Work function of metal plating such as electrolytic Ni-P plating. F. Was examined. The work function of the toner was measured by melting the toner in a plate shape on an aluminum plate. Table 4 shows the results.

[0061]

[Table 4]

In general, when two substances are brought into contact, a substance having a small work function tends to be positively charged. Therefore, when a positively charged toner is used, the plating agent applied to the surface of the developing sleeve is It is necessary to use one having a larger work function than toner.

Table 5 shows the amount of toner charge obtained when the type of plating applied to the surface of the developing sleeve and the combination of the toners were changed, and the developing sleeve coated with these platings and the toner A and B were developed. The image density and the coating unevenness of the toner on the developing sleeve when an image is formed by performing the above steps are shown. The developing sleeve has a surface roughness Ra =
The thing of 1.1 μm was used. FIG. 4 shows a graph in which the difference between the work functions is plotted on the horizontal axis, and the charge amount of the toner is plotted on the vertical axis.

[0064]

[Table 5]

In Table 5, the symbols in the column of density are: ○: Initial development, maximum density is 1.3 or more, Δ: 1.2 or more,
Less than 1.3, ×: Less than 1.2. The symbols in the column of coat unevenness are as follows: ：: No toner coat unevenness is seen on the developing sleeve, Δ: Even toner coat unevenness is seen on the developing sleeve, but not bothersome in the image, ×:
This indicates that coat unevenness appears as image unevenness. The amount of toner transported on the developing sleeve was approximately 0.6 mg / cm ² in any combination.

In general, in order to obtain a sufficient image density, the charge amount of the toner is required to be at least about 6 μC / g. However, if it exceeds 15 μC / g, the toner is concentrated on a part of the developing sleeve. Would be coated. Also in this experiment, when the surface roughness Ra of the developing sleeve is 0.7 and the plating agent is copper electroplating, the charge amount of the toner is 17
μC / g, and uneven toner coating was confirmed.

Here, the surface roughness R of the developing sleeve
a is lower than 0.7, and Ra = 0.5, 0.3,.
An experiment was performed when the ratio was set to 1, 0.05. The peripheral speed ratio of the developing sleeve was set to an appropriate value obtained from the previous experiment. As a result, when the surface roughness Ra of the developing sleeve and the work function difference ΔW between the plating layer of the developing sleeve and the toner are combined so as to be within the rectangular area G shown in FIG. 5, a sufficient image density can be obtained. It was also confirmed that there was no uneven coating of the toner on the developing sleeve.

The square area G in FIG. 5 is the work function difference ΔW
Are enclosed by two upper and lower straight lines g2 and g1 that are lower left with respect to the surface roughness Ra of the developing sleeve. This is because when the surface roughness Ra of the developing sleeve is reduced (lowered),
The effective friction area with the toner on the surface of the developing sleeve increases, so that the charge amount of the toner increases. Therefore, in order to prevent the occurrence of uneven toner coating, the work function difference ΔW
(Work function of plating layer−work function of toner).

The four vertical lines g2, 1, 3, and 4 that define the quadrangular region G are expressed as follows.

G1: Ra-13ΔW + 0.6 = 0 g2: Ra-6ΔW + 6 = 0 g3: 19Ra-ΔW-0.9 = 0 g4: Ra = 0.7

Accordingly, the rectangular area G is represented by the following four inequalities.

Ra-13ΔW + 0.6 ≦ 0 Ra-6ΔW + 6 ≧ 019 Ra−ΔW−0.9 ≧ 0 Ra ≦ 0.7 where Ra is μm and ΔW is eV.

The above description is for the case where the toner is charged positively. In the case where the toner is negatively charged, ΔW may be replaced with −ΔW and the following operation may be performed.

Ra + 13ΔW + 0.6 ≦ 0 Ra + 6ΔW + 6 ≧ 019 Ra + ΔW−0.9 ≧ 0 Ra ≦ 0.7

If it is generalized so that it can be applied to a toner having a positive charging polarity and a toner having a negative charging polarity, Ra-13 | ΔW | + 0.6 ≦ 0 Ra-6 | ΔW using the absolute value of the difference between the work functions. | + 6 ≧ 0 19 Ra− | ΔW | −0.9 ≧ 0 Ra ≦ 0.7.

Hereinafter, the magnetic toner used in the present invention will be described.

The particle diameter of the magnetic toner ranges from 4 to
It is 9 μm, preferably 4 to 8 μm. When the volume average particle diameter of the toner is 4 μm or less, when the toner is used for an application having a high image area ratio such as a graphic image, a problem that the toner density on the transfer material is small and the image density is low tends to occur.
This is considered to be due to the same reason as when the density of the inside is reduced as compared with the edge portion of the latent image. When the volume average particle diameter of the toner is 9 μm or more, the resolution is not good, and the image quality is likely to deteriorate as the image is formed at the beginning of image formation and the use is continued.

Although the particle size distribution of the toner can be measured by various methods, in the present invention, the Coulter counter TA-
II (manufactured by Coulter Inc.). A personal computer CX-i (manufactured by Canon) for outputting the number distribution and volume distribution of the toner was connected to the coulter counter. The electrolyte is 1% Na using primary grade sodium chloride.
A Cl aqueous solution was prepared.

To 100 to 150 ml of the electrolytic solution, 0.1 to 5 ml of a surfactant, preferably an alkyl benzene sulfonate, is added as a dispersant, and 2 to 20 mg of a magnetic toner as a measurement sample is further added. The electrolytic solution in which the measurement sample was suspended was subjected to dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and the particle size distribution of toner particles of 2 to 40 μm on the basis of the number was measured using the above-mentioned collocator counter with an aperture of 100 μm. Was measured and the volume particle size distribution was determined therefrom.

The true density of the magnetic toner is 1.45 to 1.7.
Is preferably 0 g / cm ^3, more preferably from 1.50~1.65g / cm ^3. If the true density of the magnetic toner is less than 1.45, the weight of the magnetic toner particles themselves is too light, which tends to cause reverse fogging and crushing and scattering of fine lines due to excessive loading of toner particles, and deterioration of resolution. If the true density of the magnetic toner is greater than 1.70, the image density is low, and an image lacking sharpness such as breaks in fine lines is obtained. In addition, since the magnetic force of the toner is relatively large, the spikes of the toner become long or branch off, and the image is easily disturbed in development, and the image quality is likely to be rough.

There are several methods for measuring the true density of a magnetic toner. In the present invention, the following method is employed, which can accurately and simply measure the true density of a fine powder.

A stainless steel cylinder having an inner diameter of 10 mm and a length of about 5 cm, and an outer diameter of about 10 mm capable of being closely fitted into the cylinder.
A disk (A) having a height of 5 mm and a height of 5 mm, and a piston (B) having an outer diameter of about 10 mm and a length of about 8 cm are prepared. The disk (A) is placed at the bottom of the cylinder, then about 1 g of the magnetic toner of the sample to be measured, and then the piston (B) is gently pushed.
400 kg / cm ² by hydraulic press on piston (B)
Is applied to compress the toner, and the compressed state is maintained for 5 minutes before the toner is taken out.

The weight W (g) of this compressed sample was weighed, and the diameter D (cm) and height L of the compressed sample were measured with a micrometer.
(Cm), and the true density of the magnetic toner is calculated from the equation: affinity (g / cm ³ ) = W / {π × (D / 2) ² × L}.

In order to obtain better developability with the magnetic toner, the magnetic toner has a residual magnetization σr of 1 to 5 em.
u / g, preferably 2 to 4.5 emu / g, a saturation magnetization .sigma. of 20 to 40 emu / g, and a high magnetic force Hc of 40 to 100 Oe (Oe).

In the present invention, the following resins can be used as the binder resin for the toner in consideration of the use of a heat and pressure roller fixing device for applying oil.

For example, homopolymers of styrene such as polystyrene, poly-p-chlorostyrene and polyvinyltoluene and their substituted products; styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene Copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, Styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-
Styrene-based copolymers such as isoprene copolymer and styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenolic resin, natural modified phenolic resin, natural resin modified maleic resin, acrylic resin, methacrylic resin, polyvinyl acetate, Silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, coumaroindene resin, petroleum resin and the like can be used.

In a heat and pressure roller fixing device in which almost no oil is applied, so-called offset phenomenon in which a part of the toner image on the transfer material is transferred to the roller, and adhesion of the toner to the transfer material are important problems. . Toners that fix with less heat energy tend to block or cake during storage or in a developer, and these problems must also be considered.

The physical properties of the binder resin of the toner are most involved in these problems. According to the study of the present inventors, when the content of the magnetic substance in the toner is reduced, the adhesion to the transfer material at the time of fixing is improved, but offset tends to occur, and blocking and caking tend to occur.

For this reason, when using a heat and pressure roller fixing device of a type that hardly applies oil, it is important to select a binder resin for the toner.
A crosslinked styrenic copolymer or crosslinked polyester is used.

Examples of comonomers for the styrene monomer of the styrene copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, and acrylic acid. Phenyl acid,
Monocarboxylic acids having a double bond such as methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide and the like; substituted maleic acid, butyl maleate, Dicarboxylic acids having a double bond such as methyl maleate, dimethyl maleate, and the like;
Vinyl esters such as vinyl chloride, vinyl acetate and vinyl benzoate; ethylene olefins such as ethylene, propylene and butylene; vinyl ketones such as vinyl methyl ketone and vinyl hexyl ketone; vinyl methyl Vinyl monomers such as ether, vinyl ethyl ether, vinyl isobutyl ether and the like; and vinyl monomers such as one or more can be used.

As the crosslinking agent, a compound having two or more polymerizable double bonds is mainly used. Aromatic dinyl compounds such as, for example, divinylbenzene, divinylnaphthalene and the like; for example, ethylene glycol diacrylate, ethylene glycol dimethacrylate,
Carboxylic acid esters having two double bonds such as 3-butanediol dimethacrylate; divinyl compounds such as divinylaniline, divinylether, divinylsulfide, divinylsulfone, and the like; compounds having three or more vinyl groups; Used alone or as a mixture.

When a fixing device of the pressure fixing type is used, a binder resin for the pressure fixing toner can be used. For example, polyethylene, polypropylene, polymethylene,
Examples thereof include polyurethane elastomer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ionomer resin, styrene-butadiene copolymer, styrene-isoprene copolymer, linear saturated polyester, and paraffin.

The magnetic toner is preferably used with a charge control agent added. The charge control agent can be contained in the toner particles (internal addition), or the charge control agent can be mixed with the toner particles (external addition). .

Examples of the positive charge controlling agent include denatured products such as nigrosine and fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate; dibutyltin oxide ,
Diorganotin oxides such as dioctyltin oxide and dicyclohexyltin oxide; diorganotin borates such as dibutyltin borate, dioctyltin borate and dicyclotin borate alone or 2
More than one type can be used in combination. Among these, a charge control agent such as a nigrosine or quaternary ammonium salt can be particularly preferably used.

Also, the general formula

[0096]

Embedded image (Where R ₁ is H or CH ₃ ; R ₂ , R ₃
The substituted or unsubstituted alkyl group, preferably a C ₁ ~
Homopolymers of monomers represented by C ₄ a is), or styrene as described above with the monomer, acrylic acid esters, the use of a copolymer of a polymerizable monomer such as methacrylic acid ester as a positive charge control agent Can be. These charge control agents also act as part or all of the binder resin.

As the negative charge controlling agent which can be used in the present invention, for example, organometallic complexes and chelate compounds are effective. For example, aluminum acetylacetonate, iron (II) acetylacetonate, 3,5 -Chromium ditertiary butyl salicylate and the like. Particularly, an acetylacetone metal complex, a salicylic acid-based metal complex or a salicylic acid-based metal salt is preferable, and among them, a salicylic acid-based metal complex or a metal salt is preferable.

The charge control agent (having no action as a binder resin) is preferably used in the form of fine particles, and its number average particle size is preferably 4 μm or less, particularly preferably 3 μm or less.

The amount of the charge control agent added to the toner is
It is preferably 0.1 to 20 parts by weight, more preferably 0.2 to 10 parts by weight, based on 100 parts by weight of the binder resin.

The amount of the charge control agent externally added to the toner is
In the case of finely divided silica, the amount is preferably 0.01 to 8 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the toner. This silica also has an effect of remarkably reducing abrasion of the developing sleeve by being interposed between the toner particles and the surface of the developing sleeve.

Fine powder of a fluorine-containing polymer, for example, fine powder of polytetrafluoroethylene, polyvinylidene fluoride or the like, or fine powder of tetrafluoroethylene-vinylidene fluoride copolymer is added to the toner as an external additive. Is preferred. In particular, polyvinylidene fluoride fine powder is preferred from the viewpoint of improving the fluidity and abrasiveness of the toner. The addition amount of the fluorine-containing polymer fine powder to the toner is 0.01 to 2.0% by weight, particularly 0.0 to 2.0% by weight.
2 to 1.0% by weight is preferred.

In particular, when the silica fine powder and the fluorine-containing polymer fine powder are added in combination, although the reason is not clear, the state of the silica adhering to the magnetic toner is stabilized, and the adhering silica is removed from the toner. It is possible to reduce abrasion of the toner due to separation and contamination of the developing sleeve, and it is possible to further increase the charging stability of the toner.

In some cases, strontium titanate is added to the toner as an abrasive for the photosensitive drum. The abrasive has a function of preventing the toner from adhering to the surface of the photosensitive drum, and the amount of the abrasive added to the toner is preferably 0.01 to 0.01.
1.0% by weight.

The magnetic toner may also serve as a colorant, but contains a magnetic material. Examples of the magnetic material to be contained in the magnetic toner include magnetite, γ-iron oxide, ferrite, iron oxides such as iron-rich ferrite; metals such as iron, cobalt, and nickel; or these metals and aluminum, cobalt, copper, Lead, magnesium, tin,
Examples include zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, alloys with metals such as selenium, titanium, tungsten, and vanadium, and mixtures thereof. These are all ferromagnetic materials.

The average particle size of these magnetic materials is 0.1-1.
0 μm, preferably about 0.1 to 0.5 μm. The magnetic material content of the magnetic toner is from 60 to 110 parts by weight, preferably from 65 to 100 parts by weight, based on 100 parts by weight of the resin.

Hereinafter, an example of an image forming experiment in this embodiment will be described.

Experimental Example 1 According to this example, the surface of the aluminum sleeve was roughened by blasting with glass beads, and then subjected to electroless Ni-P plating (work function = 4.4 eV).
A developing sleeve having a plating thickness of 6 μm and a surface roughness Ra of 1.1 μm was obtained. This was incorporated into the developing device 3 as the developing sleeve 6 in FIG. 1 and subjected to development to form an image.

The photosensitive drum 1 uses an a-Si drum.
The gap between the photosensitive drum and the developing sleeve was 230 μm. The photosensitive drum was charged to a surface potential of +400 V and subjected to image exposure to form a latent image at a surface potential of +50 V. The latent image was developed using the above-described positively chargeable toner A (work function = 4.1 eV). The peripheral speed ratio b of the developing sleeve was 2.1. A developing bias in which a DC voltage of +250 V and an AC voltage having a peak-to-peak voltage Vpp = 1.4 kV and a frequency f = 2.7 kHz were superimposed was applied to the developing sleeve.

As a result, the toner on the developing sleeve
0.6 mg / cm ² sufficient toner transport amount (at this time, a
× b = 1.26) and a sufficient charge amount of 11.1 μC / g were obtained.
Even after performing the operation on the 1,000,000 sheets, almost no decrease in the density and no deterioration of the image were observed.

Experimental Example 2 According to this example, the surface of a stainless steel sleeve was roughened by glass bead blasting, electroless Ni-B plating (work function = 4.5 eV) was performed, and the plating thickness was 6 μm.
m, and a developing sleeve having a surface roughness Ra of 0.4 μm was obtained. Similarly, the developing sleeve was incorporated in the developing device 3 of FIG. 1 and subjected to development to form an image.

The photosensitive drum 1 was an OPC drum, and the gap between the photosensitive drum and the developing sleeve was 250 μm. A latent image was formed at a surface potential of -100 V with a surface potential of -600 V on the photosensitive drum, and developed using toner A (work function = 4.1 eV) described above. The peripheral speed ratio b of the developing sleeve was 1.8. A DC voltage of -450 V, a peak-to-peak voltage Vpp = 1.2 kV, and a frequency f
= 2.2 kHz AC bias voltage was applied.

As a result, the toner on the developing sleeve
0.57 mg / cm ² of toner transport amount (at this time, a × b
= 1.03) and 10.5 μC / g. In addition, even when 5,000,000 prints, which is about 5 times the amount of the developing sleeve without electroless Ni-B, are used, a decrease in density and image deterioration are almost observed. Did not.

Embodiment 2 FIG. 6 is a schematic structural view showing another embodiment of the image forming apparatus of the present invention. This apparatus is a digital copying apparatus.

The photosensitive drum 1 is provided with a photoconductive layer of amorphous silicon on a cylindrical conductive substrate, and is rotatably supported in the direction of arrow A. A scotron charger 15 for uniformly charging the surface of the photosensitive drum 1 around the photosensitive drum 1 along the rotation direction thereof, and a document 22 placed on a glass table 23 above the photosensitive drum 1 are read, and the color is read. An exposure device including an exposure lamp 21 and an image scanner 26 for subjecting the photosensitive drum 1 to image exposure 33 based on an image signal proportional to the density of the separated image, and the electrostatic latent image obtained by the image exposure is positively charged. A developing unit 3 for developing using toner; a corona charger 16 for transferring a toner image formed on the photosensitive drum 1 by developing the latent image onto a transfer material P supplied to the photosensitive drum 1; Transfer material P
And a cleaning device 5 for cleaning the surface of the photosensitive drum 1 after the transfer of the toner image to remove toner remaining after the transfer, and a residual device on the surface of the photosensitive drum 1. A pre-exposure device (lamp) 18 for removing charges is disposed.

The transfer material P separated from the photosensitive drum 1 is conveyed to a fixing device 19, where the transferred toner is fixed on the image transfer material P by being heated and pressurized to form a desired print image. Then, the sheet is discharged outside the image forming apparatus.

The exposure lamp 21 of the exposure apparatus is
While reading the original 22 while moving along 3,
The obtained image information is inserted into the image scanner 26 via the reflection mirrors 24a, 24b and 24c that move together with the exposure lamp 21, and the short focus lens 25. The image scanner 26 converts image information into an electric signal. The electric signal is digitized by an A / D converter 29 and then sent to a signal processing unit 28, where it is converted into a digital image of 256 gradations proportional to the image density. Converted to a signal.

This image signal is sent to a laser driver 29 as a drive signal generator, and the drive signal
The laser driver 29 is used to generate a drive signal for the laser 30 so as to modulate the emission of 0 according to the image signal. The laser light modulated in accordance with the image signal passes through a polygon mirror 31 and a reflection mirror 32, and passes through an image exposure 33
Is irradiated on the photosensitive drum 1 to form an electrostatic latent image on the photosensitive drum 1 according to an image signal.

The copying speed of the digital copying machine of this embodiment is
A4 size is 60 to 100 sheets per minute.

In this embodiment, an image was formed.
First, the photosensitive drum 1 is charged to +400 V by the charger 15 and the image exposure 33 is performed based on the image signal to attenuate the surface potential of the exposed portion to, for example, +50 V at the maximum to form a latent image. Next, a DC voltage of +250 V, for example, or a peak-to-peak voltage Vpp of 1.4 kV and a frequency f of 2.7 k is applied to the developing sleeve 6 of the developing device 3 as a developing bias.
A latent image was developed by a reversal development method using a black toner of a magnetic toner as a one-component developer by applying a voltage obtained by superimposing a rectangular wave AC voltage of Hz.

The surface of the developing sleeve 6 is roughened by blasting the surface of the aluminum sleeve with regular glass beads, and then subjected to electroless Ni-P plating to obtain a surface roughness R.
a0.5μm, plating thickness 6μm, hardness Hv is about 500
It is what it was. Other configurations of the developing device 3 are the same as those of the developing device 3 shown in FIG. The toner A described above was used as the magnetic toner. The peripheral speed ratio b of the developing sleeve was 1.6.

In this case, the toner transport amount on the developing sleeve is 0.65 mg / cm ² , and the toner charge amount is 10.5 μC
/ G, sufficient image density and image quality were obtained from the beginning. At the time of printing 1,000,000 sheets of A4 size, the amount of shaving of the plating on the surface of the developing sleeve is about 1.0 μm, and there is no toner resin or the like embedded on the surface of the developing sleeve, and sufficient density and image quality are maintained. We were able to.

Embodiment 3 In this embodiment, as shown in FIG. 7, an elastic blade 9a is used in place of a magnetic blade as a developer regulating member of the developing device 3 as shown in FIG. Directly contacted. Further, as a developing sleeve 6, a stainless sleeve was roughened by blasting glass beads, and then electroless Pd-P (work function = 4.5 eV) was applied.
A developing sleeve having a surface roughness Ra of 0.7 μm, a plating thickness of 6 μm, and a hardness Hv of 470 was prepared and used.

The mechanical structure of the image forming apparatus of this embodiment is basically the same as that of the first embodiment shown in FIG.

As the photosensitive drum 1, an OPC drum was used, and the gap between the photosensitive drum and the developing sleeve was set to 250 μm. The surface of the photosensitive drum was charged to -600 V, image exposure was performed, a latent image was formed at a surface potential of -100 V, and developed using the toner A (work function = 4.1 eV) described above.
A developing bias in which a DC voltage (−450 V) and an AC voltage (Vpp = 1.2 kV, f = 2.2 kHz) were superimposed was applied to the developing sleeve to form an image.

As a result, the toner on the developing sleeve
9. A proper toner conveyance amount of 0.70 g / cm ² and 10.
A charge amount of 5 μC / g was obtained, and sufficient density and image quality could be obtained from the beginning of image formation.

In this embodiment, since the elastic blade which comes into direct contact with the developing sleeve is used, there is a concern that the surface of the developing sleeve may be shaved due to long-term use.
The P plating has no problem because it has a high hardness of Hv = 470 as described above, and the amount of shaving is 2.5 μm at the time of printing 1,000,000 A4 size sheets. Image quality could be maintained. In addition,
Although the present embodiment has been described using a magnetic toner, the present invention defines the charging characteristics of the toner and the plating layer on the surface of the developing sleeve. It is effective and applicable to a non-magnetic one-component developing method using a developing sleeve having no magnet roller inside.

In this embodiment, the elastic blade 9a is used as the developer regulating member. However, a roller made of a single foamed elastic body may be used. Similarly, the roller is used in contact with the developing sleeve. The present invention is also effective when such a regulating roller having a single foam elastic structure is used.

[0128]

As described above, according to the present invention, the surface of the developing sleeve of the developing device is roughened, plated with a non-magnetic metal, and the work function of the plating layer and the magnetic toner of the one-component developer used. Ra-13 | ΔW | + 0.6 ≦ 0 Ra-6 | ΔW | + 6 ≧ 0 19 Ra− | ΔW | −0.9 ≧ 0 Ra ≦ The relationship between the work function difference and the surface roughness Ra of the developing sleeve is as follows. 0.7, so that a sufficient amount of charge and conveyance can be ensured for the magnetic toner on the developing sleeve, and an amorphous silicone drum is used as an image carrier, and image formation of a reversal developing system using a magnetic positive toner is performed. In this case, it was possible to provide an image forming apparatus in which satisfactory development was performed over a long period of time to obtain an image with sufficient density and image quality, and the durability of the developing device was increased.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of an image forming apparatus of the present invention.

FIG. 2 is a cross-sectional view schematically showing the surface of the developing sleeve when the developing sleeve with the sandblast processing is repeatedly used for continuous image formation.

FIG. 3 is a graph showing the relationship between the surface roughness of a developing sleeve of a developing device and the transportability of magnetic toner.

FIG. 4 is a graph showing a relationship between a difference in work function between a nonmagnetic metal plating layer on a developing sleeve surface and a magnetic toner and a charge amount of the toner.

FIG. 5 shows the work function difference ΔW and surface roughness R in the present invention.
It is explanatory drawing which shows the preferable range of the combination of a.

FIG. 6 is a schematic configuration diagram showing another embodiment of the present invention.

FIG. 7 is a schematic configuration diagram showing a developing device according to still another embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating a developing sleeve of a developing device of a conventional image forming apparatus.

FIG. 9 is a cross-sectional view showing a surface portion of the developing sleeve of FIG.

FIG. 10 is a cross-sectional view showing a state where a metal layer is provided on a surface portion of the developing sleeve of FIG. 8;

11 is an explanatory diagram showing a center line average roughness Ra of a rough surface of the surface of the developing sleeve of FIG. 8;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 latent image forming unit 3 developing unit 4 transfer separating unit 5 cleaning unit 6 developing sleeve 7 magnet roller 9 magnetic blade 9a elastic blade Ra center line average roughness ΔW work function difference

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takao Honda 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (9)

[Claims] An image bearing member having a photosensitive layer on a surface thereof; and a developing sleeve having a developing sleeve serving as a developer carrying member, the developing sleeve carrying a one-component developer and facing the image carrying member. And a developing means for developing the latent image formed on the surface of the image carrier with a developer, wherein the developing sleeve has a surface roughened and plated with metal. , The work function difference ΔW (eV) obtained by subtracting the toner work function from the work function of the plating layer, and the center line average roughness Ra (μm) of the surface of the developing sleeve after plating.
m) and Ra-13 | ΔW | + 0.6 ≦ 0 Ra-6 | ΔW | + 6 ≧ 019Ra− | ΔW | −0.9 ≧ 0Ra ≦ 0.7 Image forming apparatus. 2. An image carrier having a photosensitive layer on its surface, and a cylindrical developing sleeve made of a non-magnetic metal material in which a magnet is arranged non-rotatably, and a one-component developer is provided on the developing sleeve. A developing unit for carrying a magnetic toner of the type described above and transporting the toner to a developing unit opposed to the image carrier, and developing the latent image formed on the surface of the image carrier with the toner. Is obtained by roughening the surface and plating a non-magnetic metal, and subtracting the work function of the toner from the work function of the plating layer to obtain a work function difference ΔW (e
V) and the center line average roughness Ra (μm) of the developing sleeve surface after plating is Ra-13 | ΔW | + 0.6 ≦ 0 Ra-6 | ΔW | + 6 ≧ 0 19Ra- | ΔW | -0 An image forming apparatus satisfying a relationship of 0.9 ≧ 0Ra ≦ 0.7. 3. When the amount of toner coated per unit area on the developing sleeve is a (mg / cm ² ) and the ratio of the peripheral speed of the developing sleeve to the image carrier is b (no unit), a and a 3. The image forming apparatus according to claim 1, wherein a product of b satisfies a relationship of 1.0 ≦ ab. 4. When the thickness of the plating layer is 3 μm or more, 20
The image forming apparatus according to claim 1, wherein the thickness of the image forming apparatus is not more than μm. 5. The image forming apparatus according to claim 1, wherein the plating layer has a hardness Hv of 450 or more and 1000 or less. 6. The image forming position according to claim 1, wherein the photosensitive layer of the image carrier is made of amorphous silicon, and the developing sleeve is made of aluminum. 7. The charging polarity of the toner is positive,
The work function difference ΔW (eV) and the center line average roughness R
a (μm) satisfies the following relationship: Ra-13ΔW + 0.6 ≦ 0 Ra-6ΔW + 6 ≧ 019 Ra-ΔW-0.9 ≧ 0 Ra ≦ 0.7 7. Image forming apparatus. 8. The charging polarity of the toner is negative,
The work function difference ΔW (eV) and the center line average roughness R
The image forming apparatus according to claim 1, wherein a (μm) satisfies the following relationship: Ra + 13ΔW + 0.6 ≦ 0 Ra + 6ΔW + 6 ≧ 019 Ra + ΔW−0.9 ≧ 0 Ra ≦ 0.7. 9. A photosensitive layer of the image bearing member is made of amorphous material, and has means for heating and controlling the surface of the image bearing member. The toner has a positive polarity and the toner has a positive polarity. The work function difference ΔW (e
V) and the center line average roughness Ra (μm) satisfy the following relationship: Ra-13ΔW + 0.6 ≦ 0 Ra-6ΔW + 6 ≧ 019 Ra−ΔW-0.9 ≧ 0 Ra ≦ 0.7. Or the image forming apparatus of 2.