JPH02282279A - Contact electrifying device - Google Patents

Abstract

PURPOSE:To allow an effective and stable operation with simple constitution by forming a part to come into contact with the band to be charged of an elastic material and forming a part having electrostatic influence of a resistance layer having a large resistance. CONSTITUTION:The contact electrifying device is constituted of a conductive support 20 to be impressed with a voltage. The front end part 2c of the charging blade 2 of this support 20, which part comes into contact with an image carrier 1, such as photosensitive body, of the band to be charge is formed of the elastic material to prevent giving damages to the carrier 1. The damaging of the blade 2 from the carrier 1 is prevented as well. On the other hand, the charge material layer 2a of the blade 2 having the electrostatic influence is parted from the carrier 1 and is coated with the resistance layer 2b of the large resistance value so that a charge drop-out is eliminated even if a pinhole, etc., exist on the surface of the carrier 1. The charge operation is effectively and stably executed with the simple constitution and the good image formation is executed.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a method for charging (including static electricity removal) the surface of a charged object by bringing a contact charging member to which a voltage is applied into contact with the surface of the charged object and moving it relatively. ) related to a contact charging device.

(Prior Art) For convenience, image forming apparatuses such as electrophotographic copying apparatuses and electrostatic recording apparatuses will be described as examples.

As is well known, electrophotographic copying devices and electrostatic recording devices use an electrophotographic photoreceptor as an image carrier or an electrostatic recording dielectric material (rotating drum type, rotating belt type, running web type, etc.) to make the surface uniform. 1 by applying an image forming process means including a means for charging
] An image corresponding to the image information of the target is formed either indirectly (transfer type) or directly.

As a means for uniformly charging the surface of an image bearing member, which is a body to be charged, a corona'M: electric device such as a corotron or scorotron, which has good uniform charging properties, is widely used. However, corona dischargers require expensive high-voltage power supplies, which themselves require 4...
17, which requires space such as shielding space for high voltage power supply and
There are many cases of corona products such as 1.7 + additional measures for dealing with the occurrence of corona products, and -4.
There are several problems, such as factors such as increased size and cost of the hardware.

Therefore, in recent years, a contact charging method (direct charging method) has been adopted in place of the corona discharger, which has many problems. In contact charging, a voltage (
For example, by contacting a conductive member (charging member) to which a DC voltage of about 1 to 2 KV, or a superimposed voltage of a DC voltage and an AC voltage, etc. is applied, charges are directly injected into the image carrier surface. A roller charging type (JP-A No. 58-91253), a blade charging type (JP-A No. 58-194349, No. 80-14775)
Publication No. 8) Charging-cleaning type (Unexamined Japanese Patent Publication No. 56-1
6518fi) etc. have been devised.

(Problems to be Solved by the Invention) (1) However, when a conductive member is used as a contact charging member as in the conventional example above, a part of the object to be charged may cause dielectric breakdown or foreign matter may occur. Pinholes may occur due to scratches caused by contamination. In this way, when a pinhole occurs in the charged object, the electrical resistance of that part decreases, so when a conductive member as a contact charging member to which a voltage is applied comes close to the pinhole, a spark discharge occurs between them. arise. While a spark discharge occurs, the charge that should be charged on the charged object passes through the surface of the conductive member and leaks to the pinhole, so the surface of the charged object is not charged in a band-like manner, a so-called "charge" phenomenon occurs. "missing" occurs. This charge loss can result in image defects if the object to be charged is an image carrier such as a photoreceptor of an image forming apparatus.

Regarding such "charge loss", by coating the surface of the conductive member with a thin film having an appropriate volume resistivity (10"Qcm or more), it is possible to prevent charge loss and improve charging performance. It becomes possible to charge without significant loss.

For this purpose, it is necessary to select a material with electrical resistance that can be used as the surface layer.

(2) When a blade-shaped object is used as a contact charging member, since the blade is of a fixed type, if the hardness of the part in contact with the object to be charged is large, uneven parts will occur in the way the contact is made. Therefore, if the pressure force is increased in an attempt to increase adhesion, a sliver-like scratch will be created on the charged object, which will cause uneven charging, which will reduce the quality of the image that can be obtained if the charged object is an image carrier. It may drop. In particular, materials with adequate resistance tend to have high hardness, resulting in damage to the 12-layer body.

(3) Furthermore, since the contact charging member is a fixed type, the resistance layer on the surface that is in contact with the charged object is worn away and the dielectric breakdown strength becomes weaker, so the effect of the resistance layer may be lost. there were.

The present invention solves the problems mentioned in (1) to (3) regarding the contact charging device, so that it can be effectively used without any problems as a device for uniformly charging the image bearing surface of an image forming apparatus, for example. The purpose is to

(Means for Solving the Problems) The present invention is a contact charging device that charges the surface of a charged object by bringing a contact charging member to which a voltage is applied into contact with the surface of the charged object and moving it relatively; The contact charging member is a blade-shaped member whose end portion is brought into contact with the object to be charged, and has a contact surface that is gradually separated from the contact portion.

A portion on the surface of the conductive member that is the base body that electrostatically affects the charged body is coated with one or more types of resistance layers having a large electric resistance value, and at least the charged body is in contact with the charged body. The contact charging device is characterized in that the end portion is made of an elastic body.

(Function) Since the conductive member that is the base of the blade-shaped contact charging member is covered with a resistive layer, even if there is a pinhole due to a scratch on the charged object, no charge will be lost.
Therefore, if the object to be charged is an image carrier such as a photoreceptor of an image forming apparatus, good images without defects due to charge loss can be stably obtained over a long period of time.

The end of the blade-shaped contact charging member, which is the part that comes into contact with the object to be charged, is made of an elastic material, so the adhesion between the object to be charged and the contact charging member is good, and furthermore, there is no damage to the object to be charged. Difficult to attach. Even if the contact edges of the blade-shaped contact charging member or the heavy body are worn away, the surface resistance layer will not be worn away, so the dielectric breakdown strength will not be weakened. The so-called white area caused by this does not cause the phenomenon.

In addition, since it is possible to set the contact charging member at a small angle with respect to the object to be charged, it is possible to widen the charging width, and it is possible to achieve the same charging performance as using a charging roller with a large outer diameter. I can do it.

Furthermore, since the configuration is simple, the device can be made small, lightweight, and space-saving, and the cost of the device can be significantly reduced.

(Examples) Example 1 (Figures 1 to 3) Figure 3 is a schematic diagram of the configuration of an image forming apparatus using a contact charging device according to the present invention as a charging processing means for an image carrier. This example is a transfer type electrophotographic copying apparatus with a removable process cartridge.

In the figure, fI! 1 is rotationally driven at a predetermined circumferential speed in the direction of the arrow around the support shaft 1a! , carrier (IP electric body)
It is a drum-type electrophotographic photoreceptor (hereinafter abbreviated as photoreceptor). Reference numeral 2 denotes a contact charging member as a means for uniformly charging the peripheral surface of the photoreceptor, 3 a short focus lens array as a photoimage exposure means, 4 a developing device, 5 a transfer device, and 51 a paper feeding section (not shown). A timing roller 52 synchronizes with the rotation of the photoconductor 1 and feeds the transfer material 10 conveyed one sheet at a time between the photoconductor 1 and the transfer device 5; a transfer material guide member disposed in the
53 is a conveying device that passes between the photoreceptor 1 and the transfer device 5 and introduces the transfer material 10 onto which the image has been transferred to a fixing device (not shown), and 6 is a cleaning device that cleans the surface of the photoreceptor 1 after the image has been transferred. It is a device.

The device of this example includes a photoreceptor 1, a contact charging member 2, a developing device 4,
The four process devices of the cleaning device 6 are assembled into a process cartridge 7 in a predetermined relationship with each other, and the process cartridge 7 can be inserted into the main body of the copying machine along support rails 8. On the contrary, it can be freely removed from the main body of the copying machine.

By fully inserting and mounting the process cartridge 7 into the copying machine main body, the copying machine main body side and the process car; ridge 7 side are mechanically and electrically coupled to each other, and the copying machine is ready to operate. Become.

During the rotation process, the photoreceptor l is sequentially and uniformly charged on its circumferential surface by the contact charging member 2 to which a voltage (bias) is applied by the high-voltage power source E, and then passes through the position of the optical image exposure means 3. By sequentially receiving light image exposure L (slit exposure of the original image), electrostatic latent images corresponding to the exposed image pattern are sequentially formed. Reference numeral 7a indicates a light transmitting window opening in a wall portion of the cartridge housing corresponding to the optical image exposure means 3.

The optical image exposure can also be performed by laser beam scanning. In the case of an electrostatic recording device, latent images are sequentially formed on a dielectric surface as an image carrier by the action of means such as an electrode array that selectively removes charges from the dielectric surface.

The latent image formed on the surface of the photoreceptor is then sequentially developed (developed) as a toner image by the developing device 4, and the toner image on the surface of the photoreceptor is transferred between the transfer device 5 and the photoreceptor 1 by the transfer device 5. One sheet of paper is conveyed from a paper feeder (not shown), and is registered in synchronization with the rotation of the photoreceptor 1 by a timing roller 51, and then transferred onto the surface of the fed transfer material 10.

The transfer material 10 that has passed through the transfer device 5 and has received the image transfer is sequentially separated from the surface of the photoreceptor, is introduced into a fixing device (not shown) by the conveyance device 53, is fixed with the image, and is output as one image formed product. Ru.

On the other hand, the surface of the photoreceptor after the image transfer is cleaned by a cleaning device 6 to remove residual toner, transfer material paper powder, and other adhered contaminants, and is used repeatedly for image formation.

The contact charging member 2 is a blade-shaped member (hereinafter referred to as a charging blade), and FIG. 1 is an enlarged cross-sectional perspective view of the charging blade portion.

The charging blade 2 includes a conductive member 2a as a base,
It consists of a resistive layer 2b covering the surface of the conductive member 2a facing the photoreceptor 1, and an elastic member 2C provided on the tip end surface of the charging blade.

The resistance layer 2b has a higher resistance than the conductive member 2a as a base.

The volume resistivity of the conductive member 2a is 10-Qcm or less2
/r? The resistance layer 2b is preferably set in a range of 10 to 109 cm, particularly 10 to μmoucm.

? The elastic member 2C may have a volume resistivity of 10r1cm or more, and a hardness of about 30° to 70° (JIS-A), preferably about 40″ to 656°.

20 is a conductive support supporting the charging blade 2;
The conductive member 2a of the charging blade 2 is connected to the conductive column support 20.
A voltage from a power source E is applied to the charging blade 2 via the charging blade 2 .

FIGS. 2(a) and 2(b) are explanatory diagrams of the state of contact between the charging blade 2 and the photoreceptor l, and the charging blade 2 is connected to the tip of the blade provided with the elastic member 2Ct as shown in FIG. 2(a). The lower surface side is in contact with one surface of the photoreceptor. (b) shows the contact pressure distribution in the contact area. As shown in this figure, the length b of the contact portion of the strip blade 2 with the photoreceptor l
(nip length) needs to be slightly longer than the length a of the elastic body 2C. Otherwise, charging properties will be poor.

Here, the conductive member 2a is made by dispersing carbon in chloroprene rubber and has a volume resistivity of 10'L! A blade material having Lcm, rubber hardness of 60°, and thickness ta=1 mm was used.

As for the material, there are no problems with other rubbers such as urethane, EPDM, and silicone rubber.

The surface of the conductive member 2a facing the photoreceptor 1 has a thickness of t.
It was coated with a resistive layer 2b of b. Materials for this resistance layer 2b include nylon-based substances such as Amilan (trade name) and Torezin (same), and materials in which they are dispersed in an appropriate ratio;
Polyurethane rubber/polyurethane elastomer - NBR
-Chloroprene rubber” PVdF-PVCI ・PET
etc. Resistance layer 2b made of such resistance layer material
The thickness tb is preferably about several 1 Ln1 to several 11001 L, and here it is set to 50 m.

Here, the elastic member 2C has a volume resistivity of ρ-1'6"
A polyurethane elastomer with a rubber hardness of 60° was used. The length a of the elastic member 2C is 500IL here.
m, but there was no problem even at 200 pm to IjLm.

The edge portion of the elastic member 2C in contact with the photoreceptor 1 has a thickness of several J.
The cutting process is performed with an edge precision of about Lm.

The setting angle θ of the charging blade 2 with respect to the photoconductor 1 is O~30' with respect to the tangent plane to the photoconductor, but here it is 20@
It was set to The contact pressure distribution between the charging blade and the photoreceptor at that time is shown in Figure 2 (b), where the nip length b =
Although i'm=, it can basically be said to be edge contact.

Under the above-mentioned configuration conditions of the charging blade 2 and setting conditions for the photoreceptor 1, the charging/1/- blade 2 was set at 50 mm.
Photosensitive drum 1 rotated by /sec
(a drum in which an organic photoreceptor is laminated on the surface of a pattern A drum), and the elastic member 2a of the charging blade 2
00V (7) A voltage in which a DC heavy pressure VI'llG and an AC voltage WAG having a beam-to-line type pressure vpP of 1400V are superimposed is applied to the photoreceptor surface to touch the contact zone! The charging properties, leakage properties, and damage to the photoconductor were investigated.

■Charging property is evaluated as follows. That is, a voltage obtained by superimposing an AC voltage VAC with a peak-to-peak voltage vPP that is more than twice the charging start voltage of the photoreceptor 1 on a DC voltage VDC was applied to the conductive member 2a of the charging blade 2 that was in contact with the photoreceptor 1. In this case, as described in Japanese Patent Application No. Sho EL-2H419, the surface potential of the photoreceptor is charged to be approximately equal to the direct current voltage VDC. Therefore, the charging property is considered to be good when the surface potential of the photoreceptor is near vDC.

■Leakage performance is considered good if there is no charge leakage even if there is a pinhole in the photoreceptor.

■The degree of damage to the photoreceptor is determined by looking at the image.

That is, the image obtained by the copying machine using the wood-contact charging device is considered to be good if no stains occur due to durability.

Actually, using a water contact charging device, an A4 image has a charge of 5,000
There were no problems with respect to chargeability or leakage when the battery was used for durability equivalent to a sheet of paper. Furthermore, the degree of damage to the photoreceptor was hardly noticeable. This is because the edge portion of the elastic member 2c is in contact with the photoreceptor l, so there is good adhesion, and it is possible to remove the poorly cleaned portion of the photoreceptor surface after cleaning.
Photoconductor 1 and plate 1 where dust and dirt in the air rotate
This is because the particles do not slip through to the charged area on the downstream side in the rotational direction of the photoreceptor than the contact portion with -2, so the particles do not become an abrasive and damage the photoreceptor.

Comparative Example: As shown in FIG. 6, cutting was performed using a charged blade 1/- without the elastic member 2c. The conditions are almost the same except that there is no elastic member 2c, but PV is used as the resistance layer 2d.
If a hard material such as dF is used, charging defects may occur locally, damage may occur to the photoreceptor, and smudges may appear on the image after about 3,000 sheets are printed. Furthermore, the edge portion P of the resistance layer 2d may be scraped due to wear, resulting in dielectric breakdown.

Example 2 (Figure 4) FIG. 4 shows another embodiment of the invention.

In this embodiment, the elastic body 2c explained in the first embodiment
Unlike the previous example, which included the entire end of the blade, only the edge that contacts the photoreceptor is included. Since the edge portion of the contact charging member 2a on the photoreceptor 1 side has an obtuse angle of 90° or more, the local electric field strength is weaker than in Example 1, and the resistance layer (2c in this case) may leak. Hateful. The chargeability and leakage properties were investigated using this product, and the result was good, and no damage to the photoreceptor was observed after copying approximately 5,000 sheets of A4 size.

Embodiment 3 (FIG. 5) FIG. 5 shows still another embodiment of the present invention. The charging blade 2 of this example includes a blade-like elastic body 2d, a conductive material layer 2a covering the side of the elastic body 2d facing the photoreceptor 1, and a resistance layer covering the surface of the conductive material layer 2a. 2b, and an elastic member 2C provided at the distal end in a form similar to that of Example 2 (FIG. 4).

The conductive material layer 2a is electrically connected to the conductive support 20. The blade-shaped elastic body 2d controls the overall elasticity of the charging blade 2, and unlike the elastic member 20 at the tip of the blade, there is no limit to the resistance value, and a material with an appropriate elastic modulus can be selected. It is possible. It may be made of the same material as the elastic member 2c.

Using this charging blade 2, make 500 copies of A4 size.
No problems were observed with regard to leakage or chargeability, and no damage to the photoreceptor was observed.

(Effects of the Invention) As described above, in the contact charging device, the contact charging member is made into a blade-like member, and the portion of the blade-shaped contact charging member that electrostatically affects the charged object is coated with a resistance layer, and the charged member is coated with a resistive layer. By making the part that comes into contact with the elastic material, ■Charged object number? Even if there is a pinhole due to a scratch or the like, charge loss does not occur; for example, in an image forming apparatus, a good image can be output without image defects caused by charge loss.

■The end of the blade-shaped contact charging member, which is the part that comes into contact with the object to be charged, is made of bone, so the adhesion between the object to be charged and the contact charging member is good. Even if the toner adheres to the surface of the image carrier, which is the object to be charged, and is carried, it is blocked here, and the toner is transferred to the charging section (discharging section).
It does not affect charging unevenness, etc.

■Furthermore, even if the edges are worn away, the resistance layer will not wear out, so the dielectric breakdown strength of the resistance layer will not weaken and there will be no leakage.

(2) Furthermore, thanks to this elastic body, even if an AC voltage is applied as the charging voltage, the vibration of the charged object is considerably alleviated and is hardly noticeable.

■Also, since the contact charging member is a blade-like object, the setting angle relative to the object to be charged can be made small, making it possible to widen the charging width, compared to using a charging roller with a large outer diameter. It can provide equivalent charging properties.

■Furthermore, because the configuration is simple, the device is small.

It is lightweight, space-saving, and can significantly reduce the cost of the device.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional perspective view of the contact charging device of the first embodiment;
Figures (a) and (b) are explanatory diagrams of the contact state between the charging blade and the photoreceptor;
) is a contact pressure distribution diagram, FIG. 3 is a schematic diagram of the configuration of an example of an image forming apparatus using the contact charging device, FIG. 4 is a cross-sectional perspective view of the contact charging device of the second embodiment, and FIG. 5 is a diagram of the third embodiment. FIG. 6 is a cross-sectional view showing the layer structure of the contact charging device of the example, and FIG. 6 is a cross-sectional view of the comparative example device. (2) is an image carrier such as a photoreceptor as a charged body, 2 is a charging blade as a contact charging member, 2a is a conductive member or a conductive material layer, 2b is a resistive layer, 2c and 2d are elastic bodies, 20
is a conductive support. Patent applicant: Canon Co., Ltd.

Claims (1)

[Claims] (1) A contact charging device that charges a surface of an object to be charged by bringing a contact charging member to which a voltage has been applied into contact with the surface of the object to be charged and moving it relatively, and the contact charging member has an end portion thereof connected to the surface of the object to be charged. A blade-shaped object that is brought into contact with a charged object and has a contact surface that is gradually separated from the contact part, and is connected to the charged object on the surface of the conductive member that is the base thereof and electrostatically A contact charging device characterized in that a portion that affects the electrical resistance is coated with one or more types of resistance layer having a large electrical resistance value, and at least the end portion that comes into contact with the charged object is made of an elastic material.