JPS6339914B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a static eliminator that eliminates static electricity by electrically neutralizing an electrostatic latent image formed on a dielectric material with a charge having a polarity opposite to that of the latent image charge.

FIG. 1 is a schematic diagram of an electrostatic transfer type recording device used in conventional facsimile machines, copying machines, and the like. The drum 1 is rotatably provided in the direction of arrow A, and as the drum 1 rotates, an electrostatic latent image charge is first applied by the recording head 4 to the dielectric 2 which has been neutralized in the vicinity of OV. be done. Next, the toner in the developing device 5 adheres to the latent image on the dielectric 2 due to Crohn's force and is visualized. The transfer device 8 is for transferring the toner 6 on the dielectric material 2 developed by the clone force of the generated corona onto the transfer paper 7.
The transfer paper 7 is fed out in the direction of arrow B from the transfer paper stacking table 13 by a feeding means 14 such as a feeding roller,
It is in contact with the dielectric 2 at the location where the transfer device 8 is provided. The transfer paper 7 on which the transfer has been completed is peeled off from the dielectric 2 by corona generated by the peeler 9.
Thereafter, the sheet is further fed out in the direction of arrow B by the feeding means 14 and fixed by the fixing device 11. This means that the transfer to the transfer paper 7 is complete,
After the transfer is completed, the dielectric material 2 on the drum 1 is fully charged with the same polarity as the latent image charge by the pre-charger 10, and after the potential on the surface of the dielectric material 2 is made almost uniform, the cleaning device 12 removes residual toner. The dielectric 2 that has been cleaned is charged to the opposite polarity to the latent image charge by the static eliminator 3 for reuse, and the surface charge is neutralized.

By the way, as the static eliminator 3 conventionally used, a corona charger as shown in FIG. 2 has been used. The structure of the corona charger is roughly divided into a corotron consisting of a shield plate 15 and a corona wire 16 as shown in FIG. . The corotron is made by applying a DC high voltage of opposite polarity to the latent image charge, which is usually around 7 Kv, to the corona wire 16, so that the corona wire 16 is approximately 1.5 kW.
A corona discharge is caused between the shield plate 15, which is located cm away, and charged particles (ozone O _3, etc.) are converted into corona beams.
The dielectric material 2 is sprayed and charged at a distance of 1.6 to 1.7 cm. However, in static elimination using a corotron, it has been difficult to uniformly eliminate static electricity at a set potential because the distribution of an electrostatic latent image is not uniform and the amount of static elimination increases when humidity is high.

The scorotron shown in FIG. 2 is used to remove static electricity more uniformly than the corotron. Static elimination using the scorotron first involves parallel line grid 1.
When a DC voltage is applied to 7, a corona current flows through the dielectric 2 and the parallel wire grid 17. When the surface potential of the dielectric 2 exceeds the grid potential, all corona current flows to the parallel grid 17, and no further discharge occurs. Usually parallel grid 1
7 voltage is set to OV. However, static elimination using a scorotron has the disadvantage that most of the corona current flows through the parallel wire grid 17, resulting in extremely poor static elimination efficiency and slow static elimination speed.

In general, when removing charges using a corona charger, it is desirable to keep the potential difference between the latent image area and the non-latent image area below a certain value in order to prevent uneven charge removal. There is a problem in that precharging with a corona charger is required. Furthermore, a large amount of ozone O ₃ is generated due to corona discharge, which causes a bad odor and is harmful to the human body.Also, high voltage switching is required to turn on and off the corona charger that performs discharge. There were also problems such as this causing noise generation.

The present invention has been made in view of these conventional points, and provides a static eliminator that does not require precharging, can completely eliminate latent image charges at low voltage, and does not generate ozone or noise. The purpose is to provide.

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIG. 3 shows a static eliminator according to an embodiment of the present invention. The static eliminator 20 is composed of a main electrode 18 made of a conductive plate and an insulator 19 sandwiching the main electrode 18. Next, the principle of operation of the static eliminator 20 will be explained with reference to FIGS. 4 to 9. First, in FIG. 4, the main electrode 1
8 is provided close to a dielectric material 22 having a latent image charge 24 of approximately -100V, and is connected to a positive power source 21. Note that whether the latent image charge 24 is positive or negative, the main electrode 18
Since the difference is only in the polarity of the voltage applied and is not essentially different, only the case where the latent image charge is negative will be explained here. On the other hand, the dielectric 22 is placed on a grounded conductor 23 (corresponding to the drum 1 in FIG. 1). When the gap length and potential difference between the main electrode 18 and the dielectric 22 are set within a range that satisfies the Patsien curve according to Patsien's law shown in FIG.
8 and the surface of the dielectric 22, a positive charge is ionically conducted, and the dielectric 22 is charged. In other words, the Patsien curve shown in Fig. 5 shows the relationship between the gap length and the discharge voltage required to discharge the gap length.
It can be seen that when set to (μ), discharge is performed at the lowest voltage. Therefore, the gap length between the main electrode 18 and the dielectric 22 in the present invention is most preferably C(μ), which is the minimum value of the Patsien curve, but is not limited thereto; What is necessary is to determine a preferable gap length and a voltage according to the gap length. As a result of experiments, the upper limit of this gap length is about 30 (μ),
Good results are obtained between 8 (μ) and 14 (μ).

By the way, the positive charges that have moved to the dielectric body 22 and are charged are electrically neutralized with the negative charges 24 of the latent image. FIG. 6 schematically shows this charge movement, and indicates the start of direct discharge between the main electrode 18 and the dielectric 22, and a positive charge 25 is generated between the main electrode 18 and the dielectric 22. ing. This figure shows how the dielectric body 22 is charged with positive charges 25 generated by the discharge, and electrically neutralized with the negative latent image charges 24. The surface potential of the dielectric 22 is
Even if it becomes a little high due to the first discharge, the main electrode 1
The potential difference between 8 and the dielectric 22 is large enough to satisfy the Patsien curve, and furthermore, a discharge occurs and is electrically neutralized. The above process is shown in FIGS. In other words, as long as the sum of the voltage applied to the main electrode 18 and the latent image potential of the dielectric 22 satisfies Patsien's law, the positive charge 25 generated by the discharge
continues to neutralize the latent image charge 24 on the dielectric 22,
Thereafter, the surface potential of the dielectric 22 becomes higher, the potential difference between the main electrode 18 and the dielectric 22 becomes smaller, and the sum of the applied voltage and the latent image potential becomes less than the threshold for causing discharge according to Patsien's law. , 6th
The discharge stops as shown in the figure. The threshold value of the potential difference that causes this discharge is determined by the distance between the main electrode 18 and the dielectric 22 according to Patsien's law.

Next, FIG. 7 shows the applied voltage Vo applied to the main electrode 18 when the distance between the main electrode 18 and the dielectric 22 is kept constant, and the surface potential of the dielectric 22 after static elimination.
This shows the relationship between Va. When the voltage applied to the main electrode is equal to or higher than V _T , the applied voltage affects the surface potential of the dielectric 22, and when the voltage Vo is applied, the dielectric surface voltage becomes Va. That is, when the distance between the main electrode 18 and the dielectric 22 is kept constant, the threshold value of the potential difference that causes a discharge is V _T , the surface voltage of the dielectric 22 before discharge is V _S , and the saturation potential of the dielectric 22 after discharge is V T . If Va is the voltage applied to the main electrode and Vo is the voltage applied to the main electrode, then
Discharge occurs at Vo which satisfies Vo-V _S >V _T , and the discharge stops when the surface voltage V _S of the dielectric 22 reaches Vo-V _S =V _T . At this time, V _S =Va. As is clear from the figure, the saturation potential Va is approximately OV, but this is done in order to avoid affecting the re-formation of the image by the recording head after charge removal by not making Va a very large value. be. Also, the polarity of Va is set to be opposite to the electrostatic latent image, but this is because the gap length between the main electrode 18 and the dielectric 22 is not constant due to slight differences in the unevenness of the dielectric surface. This is generally done in order to prevent the generation of areas where discharge does not occur in the concave portions and from which static electricity cannot be removed, and to ensure static electricity removal. FIG. 8 shows the relationship between the time from the start of the discharge and the surface potential of the dielectric 22. It can be seen from the figure that when the distance between the main electrode 18 and the dielectric 22 is kept constant, the surface potential of the dielectric 22 saturates over time and does not rise above a constant value Va. Therefore, this
If Vo is selected so that Va is close to OV, the latent image charge on the dielectric 22 will be reliably removed by discharge.

Next, FIG. 9 schematically shows the surface potential along an arbitrary straight line on the dielectric 22 (e.g., corresponding to one arbitrary main scan of recording by the recording head), divided into before and after static elimination. It is something that
From the same figure, it can be seen that the residual potential in the area where the electrostatic latent image exists forms part of the discharge voltage, and the above-mentioned discharge is mainly performed directly on the area where the electrostatic latent image exists. It can be understood that the potential increases and converges to the saturation potential Va like the other parts. That is, the surface potential at the location where the electrostatic latent image charge is applied by the recording head 4 in FIG.
_VS , and the surface potential elsewhere is OV
It's getting old. However, the dielectric 2 after static elimination
The surface potential of No. 2 has a substantially constant value Va that does not affect the re-formation of the electrostatic latent image by the recording head, both in the area where the electrostatic latent image charge is applied and in other areas. This can be easily understood from FIG.

Specific experimental values are as follows. for example,
If the electrostatic latent image potential V _S is -100V, the gap length between the electrode and the dielectric is 10μ, and the saturation potential Va is 10V, the applied voltage for static elimination is approximately 360V (350V +
(350V is the discharge starting voltage when the gap length is 10μ). In other words, the potential difference between the electrostatic latent image on the dielectric and the electrode is initially 460V (360V - (100V))
Therefore, when the discharge starts and the potential of the latent image rises to 10V, the potential difference between the electrostatic latent image and the electrode becomes 350V, which is less than the threshold in the Patsien curve, so the discharge stops.

FIG. 10 shows a static eliminator 20 according to the present invention applied in place of the static eliminator 3 of the electrostatic transfer recording device used in the conventional facsimile machine, copying machine, etc. shown in FIG. It is. The operation of this electrostatic transfer type recording apparatus is similar to that of the apparatus shown in FIG. 1, and will not be described here. Note that the static eliminator 20 according to the present invention is not limited to that shown in FIG. 3, but may include a main electrode 18 as shown in FIG. The static eliminator 27 may have a sub-electrode 26 provided close to and parallel to the main electrode 18 . In addition, the main electrode 18
A sub-electrode 26 may be provided at a position facing the auxiliary electrode 26 to eliminate static electricity. (In this case, the dielectric material 22 will be interposed between the main electrode 18 and the sub-electrode 26.) As is clear from the above description, the present invention is applicable to the dielectric material surface on which the electrostatic latent image is formed. and discharge means for applying a voltage of opposite polarity to the electrostatic latent image to the electrode to cause a direct discharge between the electrode and the surface of the dielectric. The distance to the electrode is set near the minimum value of the discharge voltage according to Patsien's law so that the saturation potential of the dielectric is opposite to the electrostatic latent image polarity and approximately OV. It neutralizes residual charges, does not require pre-charges, does not generate ozone or noise, and has the effect of being able to completely eliminate latent image charges efficiently at low voltage.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of an electrostatic transfer recording device used in conventional facsimile machines, copying machines, etc., Fig. 2 is a diagram showing a conventional static eliminator, and Fig. 3 is an embodiment of the present invention. Static eliminator according to example, Figures 4 to 9
The figure shows the operating principle of the static eliminator shown in FIG. 3, FIG. 10 is a schematic configuration diagram when the static eliminator according to the present invention is applied to a conventional electrostatic transfer recording device, and FIG. This is another embodiment of the static eliminator according to the present invention. 1...Drum, 2, 22...Dielectric, 4...Recording head, 5...Developer, 8...Transfer device, 9...
Peeling device, 10... Pre-charging device, 11... Fixing device, 1
2...Cleaning device, 18...Main electrode, 19
... Insulator, 20, 27 ... Static eliminator, 23 ...
Conductor, 26... Sub-electrode.

Claims (1)

[Claims] 1. A discharge in which a voltage of opposite polarity to the electrostatic latent image is applied to an electrode provided close to the dielectric surface on which the electrostatic latent image is formed, and a discharge is caused directly between the electrode and the dielectric surface. The means is disposed at a position immediately before the electrostatic latent image is formed, and a discharge voltage is obtained by the applied voltage and the residual potential at the location where the electrostatic latent image exists, and discharge is started, and the residual potential is removed by the discharge. Stopping the discharge by neutralizing the potential to reduce the discharge voltage below the discharge voltage threshold according to Patsien's law,
The distance between the electrode and the dielectric is set near the minimum value of the discharge voltage according to Patsien's law, such that the potential on the surface of the dielectric after discharge is opposite in polarity to the electrostatic latent image polarity and approximately OV. A static eliminator characterized by: