JPH0690568B2 - Electrophotographic charging device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic charging device used in a copying machine or a printer to which an electrophotographic process is applied.

2. Description of the Related Art Corotron charging devices as shown in FIGS. 19 and 20 are generally used in conventional electrophotographic devices such as electrophotographic copying machines.

In the above charging device, insulating blocks b are provided at both ends of a shield case a having a substantially U-shaped cross section, and a discharge wire c is stretched between the insulating blocks b so as to be located substantially in the center of the shield case a. With this configuration, when a high voltage of ± 4000 to ± 8000 V is applied to the discharge wire c, corona discharge is generated between the discharge wire c and the charge acceptor d such as a photoconductor. Ions generated by the discharge adhere to the charge acceptor d to charge it.

In addition, the shield case a surrounding the discharge wire c has a function of maintaining a constant spatial distance from the discharge wire c to strengthen and stabilize the electric field formed on the surface of the discharge wire c. There is.

Problems to be Solved by the Invention However, the charging device configured as described above requires a special device in order to stretch the discharge wire c having a small mechanical strength between the insulating blocks b, and therefore the cost is low. In addition, the discharge wire c is easily broken due to vibration during use, so that it is necessary to replace the discharge wire c frequently, and maintenance is troublesome.

Another problem is that a current also flows through the shield case a in addition to the charge acceptor d during discharge, so that the discharge current increases, resulting in an increase in the high-voltage current and cost, and an increase in the discharge current causes ozone generation. There is also a problem that the amount increases and causes environmental pollution.

Furthermore, in order for the charging device to operate stably, a sufficient distance is required between the discharge wire c and the shield case a and the charge acceptor d.

That is, the ionization region of the corona discharge is in the range from the surface of the discharge wire c to about 1 to several μm in the radial direction at most, and the space other than this region up to the shield case a and the charge acceptor d is filled with air during discharge. Spatial impedance is higher than in the ionization region, which was a drift region in which only ions of unidirectional polarity move without ionization.

A stable corona discharge can be maintained only when the drift region has a sufficient distance.

However, if the discharge wire c is moved too close to the charge acceptor d or the distance from the discharge wire c to the shield case a is reduced in an attempt to further reduce the size of the charging device, the ionization region widens and the spatial impedance decreases. As a result, a spark discharge is generated and damages the charge receptor d and the like.
The conventional charging device described above has a limit in downsizing.

On the other hand, as another charging device, JP-A-60-254172, JP-A-58-76851 and the like disclose a device using an electrode in which a conductive coating layer is formed on the surface of a conductor.

However, in the case where a conductive coating layer is provided like those disclosed in these publications, since the coating layer is formed by coating a resin or the like, it is possible to make the coating layer uniform in thickness and obtain surface flatness. Have difficulty.

In particular, when air bubbles are generated in the coating layer during resin application, the air bubbles impair the flatness of the surface, and the air bubbles easily discharge due to the thin film thickness of the air bubbles, resulting in uniform discharge. At the same time, the coating layer is destroyed by the abnormal discharge and the conductor is exposed, and a spark is generated between this conductor and the charge receptor to damage the charge receptor, or the abnormal discharge proceeds further from the damaged part. However, there was a problem that the life of the coating layer was shortened at an early stage.

The present invention has been made in order to improve the conventional problems, and an object thereof is to provide an electrophotographic charging device capable of uniformly and efficiently charging a charge receptor.

Means and Actions for Solving Problems In order to achieve the above object, the present invention has a volume resistance of 10 ⁶
A solid electrode plate is formed of a plate-shaped electric resistor having a surface resistance of 10 ¹³ Ωcm or more and a surface resistance of 10 ⁶ Ω or more, and a plate-shaped voltage application electrode is attached to the first surface of the solid electrode plate. The second surface of this solid electrode plate is charged to the charge receptor to be charged by 500μ
Since they are opposed to each other with a gap of m or less, the flatness of the second surface facing the charge acceptor can be obtained with high accuracy, so that the uniformity of the distance between the charge acceptor and the fixed electrode plate is improved. To do.

Further, since the plate-shaped voltage applying electrode is attached to the first surface of the solid electrode plate, the discharge is uniformly performed over the entire second surface of the solid electrode plate, so that the charge acceptor can be charged uniformly and efficiently. .

Embodiment 1 FIG. 1 is a basic configuration diagram of the charging device of the present invention and the application of the charging device as a charging means. In this figure, 1 is a solid electrode plate of a plate-shaped high electric resistance body having a volume resistivity of 10 ⁶ to 10 ¹³ Ωcm, and 2 is a plate-shaped solid electrode plate closely attached to the first surface of the solid electrode plate 1, for example, the back surface. A voltage application electrode made of a conductor such as a metal is connected to the DC power source 4 to apply a voltage to the solid electrode plate 1. Reference numeral 3 denotes a charge receptor which faces the second surface of the solid electrode plate 1, for example, the surface with a gap of 0.5 mm or less, for example, forms a photoconductive layer on a conductive substrate, and is grounded to the substrate. Corona discharge is generated between the solid electrode plate 1 and the solid electrode plate 1 as follows.

That is, when a DC voltage is applied to the solid electrode plate 1 via the voltage application electrode 2, air is ionized in the gap between the solid electrode plate 1 and the charge acceptor 3. If the positive polarity side of the DC power supply 4 is connected to the voltage application electrode 2, + ions flow to the charge acceptor 3 side and charge it, and − ions or electrons reach the solid electrode 1 side and are neutralized. To be done.

Further, since the solid electrode plate 1 has a large resistance, the discharge is stable and does not lead to a spark discharge, and the plate-shaped high electric resistance body is used for the solid electrode plate 1, so that any portion of the void is excessive. It is possible to prevent a current from flowing, and it is possible to charge the charge acceptor 3 more uniformly.

It is considered that this is because the gap between the solid electrode plate 1 and the charge acceptor 3 corresponds to the ionization region, and the solid electrode plate 1 itself corresponds to the high impedance drift region.

On the other hand, FIG. 2 shows an embodiment of an electrophotographic copying machine adopting the charging device of the present invention. Next, this will be explained. The charge acceptor 3 having a photoconductive layer formed on an aluminum substrate is drum-shaped. First, before the image information is irradiated, its surface is uniformly charged by a charging device 21, and a document table 11 on which a document 10 to be copied is placed is provided above it. Below the document table 11, a light source 12 for irradiating the document 10 and an optical system 9 for guiding the reflected light from the document 10 to the charge receptor 3 are installed.

Further, the electrostatic latent image formed on the surface of the charge receptor 3 by the exposure process is developed into a toner image by the developing device 13 installed in the periphery of the charge receptor 3 and then reaches the transfer device 14 to feed the image. The toner image is transferred onto the paper 16 fed from the device 15.

The paper 16 to which the toner image is transferred is discharged by the peeling charging device 17, peeled from the charge acceptor 3, and sent to the fixing device 18. The fixing device 18 fixes the toner image on the paper 16 to the paper 16. On the other hand, the untransferred toner remaining on the surface of the charge receptor 3 after the transfer step is neutralized by the precleaning corotron 19 and then removed from the surface of the charge receptor 3 by the cleaning device 20.

The above is the structure and operation of the copying machine adopting the electrophotographic method. In the copying machine, the charging device 21 for uniformly charging the surface of the charge receptor 3, the transfer device 14, the peeling charging device 17, and the pre-charging device are provided. Various charging devices such as a charging device 19 for cleaning are used, and the charging device of the present invention is applied to these charging devices. Next, a specific example thereof will be described with reference to FIGS. 2 and 3. The electrode plate 1 has a volume resistance of 10 ¹¹ Ωcm,
A plate-like electrode having a thickness of 1 mm, a width of 10 mm, and a length of 300 mm was used, and a plate-shaped voltage applying electrode 2 having the same width and the same length and a thickness of 3 mm was adhered thereto using a conductive adhesive.

Further, by fixing the voltage applying electrode 2 to the insulated support body 5,
When the DC power source 4 of about +3 KV was applied to the voltage applying electrode 2 while facing the charge acceptor 3 through the solid electrode plate 1 and the gap of about 200 μ, the surface potential of the charge acceptor 3 was about +.
It became 800V.

After uniformly charging the charge receptor 3 by using the charging device having the above-mentioned structure, an electrostatic latent image is formed on the surface of the charge receptor 3 by an exposure process, and the electrostatic latent image is developed into a toner image by the developing device 13. In the transfer step, the sheet 16 transferred from the sheet feeding device 15 was transferred, and the sheet 16 on which the toner image was transferred was sent to the fixing device 18 and the toner image was transferred to the sheet 16. As a result, it was confirmed that a good copy image was obtained.

Further, the same experiment was conducted by changing the volume resistivity of the solid electrode plate 1, and when the volume resistivity was less than 10 ⁶ Ωcm, intercalated discharge was apt to occur in a part of the solid electrode plate 1 and 10 ¹³ Ω.
It has been found that if the voltage exceeds cm, it is difficult to obtain a sufficient current required for charging, and therefore the power supply voltage must be considerably increased.

Therefore, the volume resistivity of the solid electrode plate 1 is 10 ⁶ Ωcm to 1
A range of 0 ¹³ Ωcm is suitable. As a material applicable to the solid electrode plate 1, plastic is preferable, and in order to obtain a necessary resistance value, it can be adjusted by adding an ion conductive material.

Next, regarding the surface resistance of the solid electrode plate 1, if a surfactant or the like is applied to the surface of the solid electrode plate 1 to prevent contamination, the surface resistance may decrease.

In such a case, for example, the surface resistance of the solid electrode plate 1 is 10 ⁶
Spark discharge may occur even if the bulk resistance is less than Ω.

Therefore, at least the surface resistance of the solid electrode plate 1 must be maintained at a value higher than 10 ⁶ Ω or higher.

If the gap between the solid electrode plate 1 and the charge acceptor 3 exceeds 500 μm, discharge may locally occur, and black spots may occur in the obtained copy. Therefore, it is desirable that the gap be 500 μm or less.

Modified Example On the other hand, FIG. 4 shows a modified example in which glass having a volume specific resistance of about 10 ¹⁰ Ωcm is used for the solid electrode plate 1. When glass is used, it has a light-transmitting property. The charging device can be realized.

In this case, the voltage application electrode 2 is provided at a position that does not obstruct the optical path of the light source 6.

Then, by using the above charging device, the charge of the developed toner image on the charge receptor 3 is controlled by discharge, and the charge is removed by exposure to improve transfer efficiency, or unnecessary toner is transferred to the back shadow portion. Will be able to prevent.

Example 2 The charging device described in Example 1 above employs the solid electrode plate 1 made of a high electric resistance material, so that the solid electrode plate 1
The current flowing between the charge acceptor 3 and the charge acceptor 3 is almost 100%, and the ineffective current becomes almost zero. Therefore, only the current necessary for decharging needs to be supplied, which reduces the size of the device itself. At the same time, the amount of ozone generated was reduced, and the environment was less polluted. However, the solid electrode 1 and the voltage application electrode 2 that supplies a voltage to the solid electrode 1
If the contact state is incomplete, the current flowing from the solid electrode plate 1 to the charge acceptor 3 becomes non-uniform. In order to solve the above problems, the solid electrode plate 1 and the voltage application electrode 2
Good results have been obtained by making them adhere as follows. The solid electrode plate 1 has a volume resistivity of 10 as in the first embodiment.
^A semiconductive material having a surface resistance of ⁶ to 10 ¹³ Ωcm and a surface resistance of 10 ⁶ Ω or more is used, and a voltage applying electrode 2 is adhered to the back surface of the solid electrode plate 1 to form an insulator as shown in FIG. It is housed in a protective case 25 consisting of.

Then, the charging device having the above-mentioned configuration was installed so that the solid electrode plate 1 was opposed to the charge acceptor 3 through a gap, and a DC power supply 4 of −3 KV was applied to the voltage applying electrode 2, and the surface of the charge acceptor 3 was found. Could be charged to -800V.

Modified Example In order to further enhance the adhesion between the solid electrode plate 1 and the voltage applying electrode 2, the voltage applying electrode 2 is formed by silk screen printing a conductive paste on the back surface of the solid electrode plate 1.
When a DC power source 4 was applied to the voltage applying electrode 2 as shown in FIG. 6, the surface of the charge acceptor 3 could be charged in the same manner as in Example 2 above.

Further, instead of printing the voltage applying electrode 2 on the back surface of the solid electrode plate 1, carbon or a conductive metal is deposited to form the voltage applying electrode 2
Similar results were obtained by forming

Embodiment 3 FIG. 7 shows an embodiment in which plural kinds of voltage applying electrodes 2 ₁ , 2 ₂ and 2 ₃ are provided on the back surface of the solid electrode plate 1 according to the size of the original 10 to be copied. This will be explained with reference to FIG.
When the original 10 is copied using the charge acceptor 3, it is necessary to use an eraser or the like to remove the charge except the image area of the charge acceptor 3, and an eraser or the like is required, and the power consumption is also increased by the eraser or the like. .

If the charge is not removed by using an eraser or the like, a portion other than the image area is developed, toner is wasted, and the load on the cleaning device 20 increases.

Therefore, in this embodiment, as shown in FIG. 7, a plurality of, for example, three voltage applying electrodes 2 ₁ , 2 ₂ , 2 ₃ having a length set for each document size are arranged in parallel on the back surface of the solid electrode plate 1. and, if these voltages applied electrodes 2 _1, 2 _2, 2 ₃ respectively terminals 2a, 2b, and 2c provided, in which so as selectively applying a DC power supply 4 by switching the switch 26 depending on the document size . 27 is an application switch.

As a result, the voltage application electrodes 2 ₁ , 2 to which the DC power source 4 is applied
_2, 2 ₃ and across the solid electrode plate 1 to the opposite charge receptor third surface, the voltage application electrode 2 ₁ selected, 2 _2, 2 ₃ of the ion from the solid electrode plate 1 according to the length release Then, the surface of the charge acceptor 3 is charged.

Further, since the voltage application electrodes to which the DC power supply 4 is not applied are in an electrically floating state, ions are not emitted from the solid electrode plate 1 facing these voltage application electrodes toward the charge acceptor 3.

As described above, a plurality of voltage applying electrodes 2 ₁ , 2 ₂ ,
Case of providing 2 _3, since may each voltage application electrode 2 _1, 2 _2, 2 voltage applied to the ₃ applied voltage as compared with the conventional charging device using the discharge wire is very low, the electrodes 2 ₁ , 2 ₂ , 2 ₃ may have a small interval, so that even if a plurality of voltage applying electrodes 2 ₁ , 2 ₂ , 2 ₃ are provided on the solid electrode plate 1, the solid electrode plate 1 itself may be small. The charging device does not become large.

Further, if the changeover switch 26 is intermittently turned on and off in accordance with the timing of image formation, unnecessary charges are not charged between the images, so that the inter-image lamp in the direction of the voltage application electrode 2 is used. The same function can be obtained, and the inter image lamp can be omitted.

Modified Example On the other hand, FIG. 9 shows a modified example of the above-mentioned third embodiment, in which a plurality of, for example, three, voltage applying electrodes 2 ′ ₁ , 2 ′ ₂ , 2 ′ ₃ are formed on the solid electrode plate 1.
Are bonded in a straight line with a conductive adhesive. The voltage applying electrodes 2 _'1, 2' _2, 2 'changeover switch 28 and 29 to ₃
Thus, the DC power source 4 can be applied according to the copy size.

For example, by turning on only the application switch 27 when copying a small size document, turning on the switches 27 and 28 for medium size, and turning on the switches 27, 28 and 29 for large size, a voltage application electrode 2 _'1, 2' _2, 2 _'3 towards the solid electrode plate 1 corresponding to the length of the charge receptor 3 release ions, charging the surface of the charge receptor 3 in response to the copy size become able to.

Needless to say, the number of voltage applying electrodes 2 is not limited to those in the above-described embodiments and modifications.

Example 4 FIG. 11 is an example showing a means for supporting the solid electrode plate 1, and the solid electrode plate 1 is a conductive polymer made of a polymer such as a π-conjugated system, a metal chelate system, a charge transfer type complex system, or a conductive polymer. Conductive polymer compounded by mixing a hydrophilic substance into a polymer, conductive polymer compounded with an antistatic agent in a polymer, conductive polymer compounded with a hydrophilic rubber and polymer, soda coal glass or boron It is made of glass such as silicate glass to which additives are added and whose resistance is adjusted.
The volume resistivity is 10 ⁶ to 10 ¹³ Ωcm, and the surface resistance is 10 ⁶ Ω or more. Further, the solid electrode plate 1 is formed in a substantially inverted triangular cross section, a voltage applying electrode 2 is closely attached to the upper surface of the bottom side, and a DC power supply 4 is applied to the voltage applying electrode 2. . And the solid electrode plate 1 is 200μ
It is attached to a support 30 made of an insulating material so as to face the charge receptor 3 with a space of m. As a mounting means, a concave groove 30a into which both side edges of the solid electrode plate 1 can be inserted is obliquely formed in the insulating support 30 in advance, and the solid electrode plate is inserted into the concave groove 30a from the end side of the insulating support 30. The fixed electrode plate 1 is fixed to the insulating support 30 by inserting both side edges of the solid electrode plate 1.
Even when the solid electrode plate 1 is twisted or warped, it can be corrected by inserting it into the insulating support 30.
The distance between the charge acceptor 3 and the charge acceptor 3 can be kept uniform over the entire length. Further, by forming the support body 3 with an insulating material, it is possible to prevent the current from leaking from the solid electrode plate 1 to the support body 30, and thus it is also possible to prevent the solid electrode 1 from being deteriorated due to the leak.

Fifth Embodiment FIG. 12 shows an embodiment in which foreign matter such as toner is prevented from adhering to the solid electrode plate 1 to deteriorate the discharge performance. The voltage application electrode 2 provided on the back surface of the solid electrode plate 1 is shown in FIG. The DC power source 4 and the AC power source 39 can be selectively applied by the changeover switch 38.

That is, the discharge surface of the solid electrode plate 1 facing the charge acceptor 3 is contaminated with foreign matter such as toner as the copy cycle increases, and the discharge performance deteriorates.

Therefore, during the copying cycle, the DC power supply 4 applies a voltage of −3 KV to the voltage application electrode 2 and the AC power supply 39 applies an AC voltage of 2 KV and 1000 Hz to the solid electrode plate 1 in the cycles other than the copying cycle. An electric field of a high frequency alternating electric field was formed in the periphery. As a result, foreign matter attached to the solid electrode plate 1 scatters toward the charge acceptor 3 side.
The discharge surface of can be always kept clean.
The reason why the foreign matter attached to the solid electrode plate 1 can be removed by applying the AC power supply 39 to the voltage application electrode 2 is as follows.
When the toner used is +, the toner attached to the solid electrode plate 1 flies toward the charge acceptor 3 in the + half cycle of the applied alternating current, and returns to the solid electrode plate 1 side again in the − half cycle. However, at this time, by colliding with the remaining toner adhering to the solid electrode plate 1, the remaining toner floats, and this toner flies to the charge acceptor 3 side again in the next + half cycle.

While the above operation is repeated, most of the toner adhered to the solid electrode plate 1 is adsorbed to the charge receptor 3 side, and the cleaning device 20 (see FIG. 2) for cleaning the surface of the charge receptor 3 is used. To be removed.

Modified Example In the above embodiment, a DC power source 4 of −3 KV was applied to the voltage applying electrode 2 to charge the charge acceptor 3, but from +2 KV to +5 KV.
Even when a DC voltage of V was applied, it was found that about 80% of the foreign matter attached to the solid electrode plate 1 moved to the charge acceptor 3 side, and the cleaning effect on the solid electrode plate 1 was confirmed.

Further, when 2 KV, an AC voltage with a frequency of 1000 Hz and a DC voltage of +0.5 KV were simultaneously applied to the voltage application electrode 2, 90 to 95% of the foreign matter adhering to the surface of the solid electrode plate 1 moved to the charge acceptor 3 side. The cleaning effect of the solid electrode 1 was confirmed.

FIG. 13 is a table showing the degree of dirt removal with respect to AC and DC applied voltages, and the effect was most recognized when the AC applied voltage was +1.5 to 2.5 KV and the DC applied voltage was +0.4 KV.

In this table, ◎ is the best, the ○ is good, △
It shows a little good.

Further, FIG. 14 is a diagram showing the relationship between the frequency of the applied alternating current and the dirt removal efficiency.

Embodiment 6 FIG. 15 shows an embodiment in which a ceramic layer is provided on the discharge surface of the solid electrode plate 1. Next, when explaining this layer, the solid electrode plate 1 made of a semiconductive material is Are exposed to plasma, and active oxygen and ions generated during discharge break the molecular bonds of the material, causing deterioration.

Therefore, if the entire solid electrode plate 1 is made of ceramic, deterioration of the discharge surface can be prevented, but the long solid electrode plate 1
When the whole is made of ceramic, the flatness is impaired by the heat during high-temperature sintering at 1500 to 2000 ° C., and when the solid electrode plate 1 is used, the distance from the charge acceptor pair 3 becomes non-uniform, resulting in a uniform Cannot be charged.

Further, since the long solid electrode plate 1 made of ceramic is fragile, there is a problem that it is easily damaged during manufacturing, cleaning or replacement.

Therefore, in this embodiment, a ceramic layer 40 having a thickness of about 1 μm is formed on the discharge surface 1a of the solid electrode plate 1 made of a semiconductive material by sputtering.

Participating silicon (SiO ₂ ),
Made of silicon nitride (Si ₃ N ₄ ), silicon carbide, etc.,
The sputtering time was controlled to obtain a film thickness of 1 μm.

The film thickness of 1 μm is a sufficient distance to separate the plasma from the discharge surface 1a of the solid electrode plate 1, but it is not limited to this distance.

The voltage applying electrode 2 is attached to the back surface of the solid electrode plate 1 manufactured as described above, and the DC power source 4 is attached to the voltage applying electrode 2.
Was applied and the time until the discharge surface 1a of the solid electrode plate 1 deteriorates was measured.

As a result, the surface of the solid electrode plate 1 not provided with the ceramic layer 40 on the discharge surface 1a deteriorated in about 10 hours, whereas the surface of the solid electrode plate 1 provided with the ceramic layer 40 was discharged even after 50 hours. No deterioration was observed.

Modification 1 Aluminum oxide (Al ₂ O ₃ ) is formed on the discharge surface 1a of the solid electrode plate 1.
Was deposited by reactive evaporation to form a ceramic layer 40 having a thickness of 1.5 μm.

The formation of the ceramic layer 40 was performed in an atmosphere of oxygen pressure of 10 ⁻⁵ to 10 ⁻² Torr using aluminum as the evaporation source, but a similar ceramic layer 40 can be obtained by performing reactive sputtering in oxygen. It is what is done.

Modification 2 On the discharge surface 1a of the solid electrode plate 1, a ceramic layer 40 made of silicon oxide (SiO ₂ ) having a thickness of 0.8 μm was formed by plasma chemical vapor deposition (CVD). The ceramic layer 40 is formed by performing high-frequency discharge using the solid electrode plate 1 as an electrode in a mixed gas of SiH ₄ and O ₂ .

It was found that, by any of the forming methods, by forming the ceramic layer 40 on the discharge surface 1a of the solid electrode plate 1, deterioration of the discharge surface 1a can be prevented.

Example 7 FIGS. 16 and 17 show a static elimination lamp 42 behind the solid electrode plate 1.
Another embodiment of the present invention will be described. Next, this will be described. A charging device is installed in front of the cleaning device 20 (see FIG. 16) and remains on the surface of the charge acceptor 3 after the transfer process. The untransferred toner is discharged, and a discharge lamp 42 is installed behind the solid electrode plate 1 so that the charge of the residual toner can be controlled.

That is, a voltage applying electrode 2 is attached to the back surface of the solid electrode plate 1, and a voltage is applied to the solid electrode plate 1 by a power source 4 via the voltage applying electrode 2, whereby charge reception from the solid electrode plate 1 is performed. 400 Hz, 0.3 to 0.5 μA toward body 3
/ cm of AC charge and 0.02 to 0.05 µA / cm of positive DC charge are applied, and the toner on the surface of the charge acceptor 3 is neutralized, and at the same time, neutralized by the neutralization lamp 42. .

As a result, the charge of the toner remaining on the surface of the charge receptor 3 is erased by the solid electrode plate 1, and the charge on the surface of the charge receptor 3 other than the portion where the toner remains is erased by the charge eliminating lamp 42, so that the cleaning device 20 As a result, good cleaning becomes possible.

The solid electrode plate 1 has a voltage applying electrode 2 formed by vapor-depositing SnO on the back surface of a semiconductive material having a volume specific resistance of 10 ⁶ -10 ¹³ Ωcm and having a light-transmitting property so that the light of the static elimination lamp 42 is transmitted. Is used.

Modified Example After the surface of the charge acceptor 3 is uniformly primary-charged by the solid electrode plate 1, the solid electrode plate 1 is irradiated with AC or negative DC charges to perform secondary charging, and It can also be applied to a charging device which exposes the charge receptor 3 from behind to form an electrostatic latent image on the surface of the charge receptor 3.

Embodiment 18 FIG. 18 shows an embodiment in which a shield electrode 45 is provided on the discharge surface 1a of the solid electrode plate 1. Next, this will be described. On the discharge surface 1a of the solid electrode plate 1, foreign matter such as floating toner adheres. It is easy, and if it adheres, there is a problem that the discharge becomes uneven.

Therefore, in this embodiment, a pair of shield electrodes 45 are provided on the discharge surface 1a of the solid electrode plate 1 so as to be parallel to each other along the longitudinal direction of the solid electrode plate 1 at intervals. The shield electrode 45 is formed by adhering a conductor having a width of about 1 mm with a conductive adhesive, and a high voltage of -1.0 KV is applied to the shield electrode 45 by a DC power supply 46.

A high voltage of about −3.0 KV is applied to the voltage application electrode 2 attached to the back surface of the fixed electrode plate 1 by the DC power source 4, and thus the surface of the charge acceptor 3 facing the fixed electrode plate 1 is −800 V. The charging potential of is obtained.

When a copying cycle is executed using the charging device as described above, foreign matter such as floating toner generated during the copying cycle adheres to the shield electrode 45 before adhering to the discharge surface 1a of the solid electrode plate 1. It was possible to prevent adherence to the discharge surface 1.

As a result, a good copy image can be obtained without frequently cleaning the discharge surface 1a of the solid electrode plate 1.

EFFECTS OF THE INVENTION As described in detail above, the present invention uses a plate-shaped electric resistor having a volume resistance of 10 ⁶ to 10 ¹³ Ωcm and a surface resistance of 10 ⁶ Ω or more as a solid electrode plate, so that the humidity increases. However, no spark discharge will occur between the solid electrode plate and the charge receptor, and the gap between the second surface of the solid electrode plate and the charge receptor to be charged should be 500 μm or less. Thus, the gap between the solid electrode plate and the charge acceptor corresponds to the ionization region, and it is possible to make the solid electrode plate itself correspond to the high impedance drift region between the second surface of the solid electrode plate and the charge acceptor. Since it is possible to cover the entire gap, uniform charging is possible without spark discharge.

Further, since the solid electrode plate has a plate shape having a thickness, the flatness of the second surface facing the charge acceptor can be obtained with high accuracy, and
Even if the surface of the second surface is damaged by foreign matter or paper dust, the plate-shaped voltage applying electrode attached to the first surface is not exposed to the second surface side, and thus the charge acceptor Since abnormal discharge does not occur between the voltage application electrode and the voltage applying electrode, it is possible to prevent the surface of the charge receptor from being damaged by the abnormal discharge.

Moreover, since the plate-shaped voltage application electrode is attached to the first surface of the plate-shaped solid electrode plate, discharge is generated across the front surface of the second surface of the solid electrode plate around the wide surface of the voltage application electrode. Therefore, the charge acceptor can be uniformly and efficiently charged, and since the voltage application electrode only needs to be attached to the first surface of the solid electrode plate, it can be easily manufactured and provided at low cost.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the basic structure of the present invention, FIG. 2 is an explanatory view showing an embodiment of an electronic copying machine using the electrophotographic charging device of the present invention, and FIG. 3 is an embodiment of the present invention. An explanatory view showing an example, FIGS. 4 to 18 are explanatory views showing another embodiment, and FIGS. 19 and 20 are conventional explanatory views. Reference numeral 1 is a solid electrode plate, 2 is a voltage applying electrode, and 3 is a charge acceptor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiichi Nashimoto 2274 Hongo, Ebina City, Kanagawa Fuji Zero Tsuxu Co., Ltd. Ebina Business Office (56) Reference JP 58-76851 (JP, A) JP 59- 3885 (JP, A) JP-A-60-254172 (JP, A)

Claims (2)

[Claims] 1. A volume resistance of 10 ⁶ to 10 ¹³ Ωcm and a surface resistance of 1
A fixed electrode plate is formed of a plate-shaped electric resistor having a resistance of 0 ⁶ Ω or more, and a plate-shaped voltage application electrode is attached to the first surface of the solid electrode plate. A charging device for electrophotography, characterized in that a surface is made to face a charge receptor to be charged with a gap of 500 μm or less. 2. The electron according to claim 1, wherein the plate-shaped voltage application electrode to be bonded to the first surface of the plate-shaped solid electrode plate is fixed to the solid electrode plate with a conductive adhesive. Photographic charging device.