JPH039390A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a clear image without generating the uneveness of density and fogging by providing a separating device which gives alternating current charges in the case of forming the image and for the time after the images are continuously formed until the subsequent image forming process. CONSTITUTION:The subject device is provided with a transfer device 17, which gives positive charges at the time of image formation opposing an image supporting body 11 as an image forming means 13 for the image supporting body 11 possessing a negative organic photoconductive body 10, and the separating device 22, which gives the alternating current charges at the time of the image formation and for the time after the images are continually formed until the subsequent image forming process opposing the image supporting body. Namely, the positive charges of the photosensitive body 10 are removed by the alternating current charges charged by a separating charger 22 and the photosensitive body 10 starts the subsequent copying after uniformly destaticized and exposed by a destaticizing lamp 24. Thus, the uniform excellent image is obtained without allowing the image density of a part whose image is enlarged to be dense and without generating the fogging.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Field of Application) The present invention is directed to forming an image using an image support having a negative polarity organic photoconductor in an image forming apparatus such as an electrophotographic apparatus. The present invention relates to an image forming apparatus.

(Prior Art) In image forming apparatuses, particularly color copying machines and laser printers, a photoconductor, which is a negatively charged image support, is fogged to form an electrostatic latent image on the photoconductor. However, this electrostatic latent image is further developed with a 1 to 1 toner having the same polarity as the 4G polarity of the photoreceptor, so that a visible image is often obtained by a reversal development method. In such a device, at the time of transfer, a visible image is transferred onto the sheet paper by applying an electric charge with a polarity opposite to that of the photoreceptor from the back side of the sheet paper in the transfer section, thereby obtaining an image. There is.

- In recent years, photoreceptors suitable for such image forming devices have become non-polluting and do not require collection processing, and the spectral sensitivity can be changed by selecting the material, increasing versatility. At the same time, photoreceptors in which a low-cost organic photoconductor is coated on a drum-shaped or belt-shaped conductive support are increasingly being used. Compared to conventional organic photoconductors such as selenium (Se), this organic photoconductor has the drawbacks of low sensitivity and rapid deterioration of properties, resulting in a short service life. Although it was only applied to low-cost image forming apparatuses, recent efforts have been made to improve sensitivity and life by selecting materials and improving layer configurations. Moreover, with the need for miniaturization of image forming apparatuses in which an organic leading conductor is applied to a photoconductor,
There is a demand for miniaturization of drum-shaped photoreceptors, and the diameter of the photoreceptor is being reduced. Moreover, since each image forming means for forming an image on the photoreceptor is all provided around the photoreceptor, the time required for the image forming process by each image forming means is shortened as the diameter of the photoreceptor is reduced. This results in deterioration of the image. Especially if the direct t ¥ is 60φ to 40
In the case of a photoreceptor having a negative polarity organic photoconductor formed by sequentially laminating a charge generation layer and a charge transport layer on a conductive support, the image forming process is repeated to form a After continuously forming images on sheets of paper of the same size, if you try to form an image on a sheet of paper of a larger size, the enlarged part of the 5th image will be compared with the other if it is the image part. However, if the image density is high and the area is a white pond, a phenomenon of fogging occurs, which significantly reduces the image quality and has been reported to cause problems.

(Problems to be Solved by the Invention) As mentioned above, in the past, a photoreceptor containing a negative polarity organic photoreceptor with a small diameter was also used, and after image formation was performed in continuous L by the 1 reversal development method, Large size sheet・
When an image is formed on paper, there is a problem in that the larger portion of the image has a higher density than the other parts, or fogging or artifacts occur, resulting in a decrease in image quality due to density unevenness.

Therefore, in order to eliminate the above-mentioned drawbacks, the present invention has been developed by continuously forming images on a sheet or paper of any size when forming an image using a photoreceptor having a negative polarity organic photoconductor.
Next, even if an image is formed on a larger sheet of paper, uneven density or fogging will occur in the larger portion of one image, but it is possible to obtain a clear image.
The purpose is to provide F[k forming equipment "t".

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above-mentioned problems, the present invention provides an image forming means for forming an image on an image support having a negative polarity organic photoconductor. at the time of image formation, and a transfer device that applies a positive charge, and a
A peeling device is provided for applying an AC charge after continuous image formation until the image forming step after continuous image formation. After continuous image formation on a sheet of arbitrary size using an image support, when forming an image on a larger sheet of paper, there may be uneven density or fog in the sharp areas of the image. This does not occur and a good image can be obtained.

(Example) First, a photoreceptor having a negative polarity organic photoconductor was used,
The causes of density unevenness and fog that occur when copying is performed on a larger sheet of paper after continuous copying is performed using reversal development will be explained. That is, if continuous copy n,'f is developed by a reversal development method in which development is performed using a loading toner having the same polarity as the surface charge of the photoreceptor, the image after the reversal development method is a visible image. When transferring a toner image to a sheet of paper, a transfer device applies a positive charge from the back side of the sheet, so that the toner image is electrostatically attracted to the sheet and transferred. For example, if the sheet paper that is continuously supplied to the transfer unit is of size [^・4], the area of the 11: charge applied by the transfer device is wider than the width of the sheet paper. Therefore, in the area outside the [A4] size width on the photoreceptor.

A positive charge is directly applied by the transfer device, resulting in a positive charge. When the paper sheet reaches the peeling device in this state, an alternating current charge is applied to the paper sheet from its back surface, and the paper sheet is peeled off due to the static electricity removal and the stiffness of the sheet paper. At the same time, the part of the photoreceptor outside the width of the (A4) size is directly given an alternating current charge, and the positive charge given by the transfer device is directly neutralized, but the diameter of the photoreceptor is Because it is small and the time required for the alternating current charge to be applied by the peeling device is 911 seconds, the positive charge (j) remains without being neutralized.On the other hand, the negative polarity organic photoconductor of the photoreceptor is A charge generation layer and a charge transport layer are sequentially stacked to form a layer structure. There is a characteristic that holes are transparent but electrons cannot pass through them, and from this,
When a negative organic photoconductor is positively charged, the positive charge cannot be removed by light irradiation. Therefore, the area outside the [A4] size width on the photoreceptor has positive charges that were not completely neutralized during peeling and will start the next copy cycle without being neutralized. Even if it is charged by -1...the surface potential is reduced compared to the part inside the supplied [A/4] size width, and this state is repeated continuously as 2. When copying, the part of the photoconductor on the side closer to the [A/4] size is directly charged with a positive charge each time it is transferred.
Although the stripping device neutralizes it to some extent, the positive charge gradually increases, and the surface potential when charged increases.

It will be further reduced. When all the preceding continuous copies have been completed in this way, the next copy is to be performed in a row, but at this time, if there is a part outside the [A4] size width of the photoreceptor 1Z, Even if the charging device is used to charge 41+f, it is not possible to obtain the desired surface potential required during charging due to the positive charge received from the transfer device during the transfer of the previous continuous copy. This causes uneven density and fog. For this reason, for example, the paper used for the next] paper is [A
-3] size, the image density will be higher in areas wider than the [A-4] size, further causing fog.

Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic explanatory diagram showing a part of a laser printer that is an image forming apparatus, and 10 is an image supporter. A conductive support 11, which is a photosensitive body and is made of a drum-shaped aluminum [AI] tube with a diameter of 60φ, and a charge generation layer 12a and a charge transport layer 12b are sequentially supported by this conductive support 11. The photoconductor has a negative polarity organic photoconductor 12 having a laminated structure 1. Incidentally, the occurrence of ffi loading [12a is an azo pigment represented by the formula and a binder resin, and the phenoxy represented by the formula (2nd formula) is mixed L5, and this is mixed with 1.1.2-
]-] The conductive support 11 is immersed in a liquid dissolved in a solvent of dichloroethane, and then dried to form the conductive support 11. Next, the charge transport layer 12b is formed by mixing hydrazone represented by the formula (3rd formula) and phenoxy represented by (2nd formula), and further dissolving 4L of hydrazone in a cyclohexane solvent. The conductive support 11 having the generation layer 12a is immersed and dried to form. Furthermore, five image forming means 13 are provided around the photoreceptor 10.

The image forming means 13 includes a charging device 14 to which a voltage of -6 (kV) is applied, an exposure device 17 that irradiates image information from a document (not shown), etc., and a magnet roller 18a.
A developing bias of 450 (V) is applied to the negative polarity toner 1.
81) on the right, a developing device 18, which is a transfer device provided in the transfer section, and a transfer charger 21 to which a DC voltage is applied by a +5K (V) DC power supply 21a, and a peeling device, which is a ±4K (V) AC power supply. A peeling charger/jar 22 to which an alternating current voltage is applied by 228 and a cleaning device 2
3. A static eliminating lamp 24 provided in the static eliminating section is provided.

Next, we will discuss the effect. First, when continuous copying onto [A.4] size sheet paper (not shown) is started, the photoreceptor 10 is rotated in the direction of arrow X, and the photoreceptor 1 is rotated accordingly.
0 is uniformly charged to about 650 [V] by the charging device 14. Next, the photoreceptor 10 is exposed to the frost light device 174.
The 81jim portion is irradiated with light, and an electrostatic latent image of approximately -50 (V) is formed. After this, the photoreceptor No. is applied with negative polarity toner to the image portion irradiated with light by the developing device 18, and is subjected to 1 reversal development. A toner image is formed by scraping. Then, while the photoreceptor 10 carrying the I.color image reaches the transfer section, this 1.
- A sheet of paper is also fed to the transfer section in synchronization with the color image. Then, when a positive charge is applied from the back surface of the sheet 1-M by the transfer charger 21, the image on the photoreceptor io'- is
Electrostatically attracted to a sheet/paper (not shown) and transferred]
1. It becomes Rokoto. (Since the charge width of the photosensitive charger 21 spans the entire axial length of the photoreceptor lO, in the part wider than the width of the sheet paper, the photoreceptor lO
is directly charged with a positive charge by the transfer charger 21, and is charged to a positive polarity. Next, the sheet paper (not shown) is given an alternating current charge by a peeling charger 22.

The photoreceptor 1 is peeled off due to the strength of its elasticity.
The part j wider than the width of the 0 sheet paper is directly given an alternating current charge, and the positive charge caused by the transfer charger 21 is neutralized, but because the passage time is short, some of the positive charge is The remaining particles reach the cleaning device v123.

After peeling off, the paper is fixed with a fixing device (not shown) to complete the copy image. 7. After the residual toner is removed from the photoreceptor 10 by the cleaning device 23, the charge is removed by the charge removal lamp 24, and the photoconductor 10 is made ready for the next copy. However, at this time, the positive charge remaining on the outside of the sheet paper of photoreceptor IO1 and IO2 cannot be removed by the static elimination lamp, and the positive charge remains in the state.
During the next charging, the surface potential is not raised to -650 [V], but is reduced compared to the portion through which the photoreceptor 1C-0C-I-paper has passed. Then, if you repeat the continuous copying further,
The area on the photoreceptor lO outside the width of the paper is positively charged each time it is transferred, cannot be completely neutralized by the peeling charger 22, and the remaining positive charges are gradually accumulated. Next Charge degree - surface potential is gradually reduced, in this way all it! After the next copy is completed, another new copy will be started, but at this time, the first part 1 of the width [A4] shown in the third time on the surface of the photoreceptor 10
0a, the residual charge is of negative polarity, so the residual charge is completely eliminated by the static elimination lamp 24, but in the second portion 10b outside the width [A.4] , No. 7 positive charge is accumulated and remains without charge removal. Therefore, before starting the next new copy, the other image forming means 13 except the peeling charger 22 and the static elimination lamp 24 are stopped for a while, and the photoreceptor 10 is rotated once in the direction of the arrow X. As a result, the photoreceptor 10 is given an alternating current charge in the peeling charger z2, and the positive charges remaining on the second portions 10b on both sides of the photoreceptor 10 are neutralized and removed. After the rotation for removing the positive charge is completed, the image forming means 13, which had been stopped in #1, is activated again and the next copying operation is started. . As a result, the photoreceptor 10 is rotated in the direction of the arrow X. Uniformly 1650 over the entire area from the charging device 144! :V). Therefore, even if the next copy size is [A. The image is roaring. Surface, like this [1.
τ, [A.3] size sheet (After completing all the repeated copies using paper, and before starting the next copy, with the image forming means 131 other than the peeling charger 22 and the static elimination lamp 24 stopped, 1 in the direction of arrow X.
Rotate. According to Jl, the photoreceptor 10 is 3&+!
Jl due to the alternating current charge provided by the separation charger 22
:@The load is removed and the next copy is started after being uniformly exposed to light by the static eliminator 24.

With the initial setup as described above, continuous copying is performed on the photoreceptor 10 consisting of the negative polarity organic photoelectric material 12, and depending on the size of the sheet paper &, T, at the time of transfer, the transfer charger 21, a part of the photoreceptor 10 is directly positively charged υ,
Even if the photoreceptor 10 is charged to a positive polarity,
After the end of continuous copying, the photoreceptor 10 is given an AC charge by the peeling charger 22 during the next copy start method,
After the positive charge is removed, the charge is uniformly removed by the charge removal lamp 24. Follow・j：、Next copy、、g!
U. Even when copying onto a larger sheet of paper, the entire area of the light body can be charged at 41V, and unlike conventional methods, the image density will be higher in the larger part of the image, or It is possible to obtain uniform and good images without causing fog.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and the diameter of the image support member can be set arbitrarily.
In order to secure a space for attaching a peeling device to the face-sealing peeling section, the diameter is preferably between 60φ and 40φ.Also, the circumferential speed of the image support can be set arbitrarily, but the higher the speed, the less uneven the density will be. It is effective for higher speed equipment because it causes significant fog. .

Furthermore, when comparing the circumferential speed of the image support during image formation 9, the speed during positive charge removal is lower than that during image formation No. 1. If you set this setting, the remaining positive charge can be removed more reliably.Since the amount of remaining positive charge differs depending on the number of continuous copies, the image support when removing the positive charge depends on the number of copies. The number of rotations may be changed. At this time, a surface type position sensor may be provided around the image support, and while measuring the residual pressure charge, the positive charge removal operation may be repeated until the positive charge becomes zero. Furthermore, the applied voltage C1 of the peeling device is not limited either. In addition, in the example, after continuous copying, a cycle of applying alternating current charges to the entire surface of the image support is carried out; If the sizes are the same, or the next sheet paper size is smaller than the paper size of the preceding continuous copy, and the surface potential on the photoreceptor is uneven = -, during image formation, If it is in an area that will not be affected, a peeling device will apply an AC charge to shorten the image forming process time! It is not necessary to perform the cycle j. However, in this case, the preceding continuous copy - sea]
- It is necessary to provide one stage that detects and compares the paper size and the size of the next sheet. Furthermore, when charging the next copy following the preceding continuous copy, as long as the surface potential of the photoreceptor is at least a predetermined value, no fogging or overprinting of the image density will occur even if there is some variation. Therefore, it is possible to simply remove the positive charge after applying the AC charge uniformly using a peeling device, but as shown in the example, if the AC charge is applied by peeling 1 and 2 and then light is irradiated with a static elimination lamp, The photoreceptor &j- was subjected to light static electricity removal,
At the time of the next charging, the surface potential is made uniform, and image formation can be performed in a more stable state. Note that the material of the organic photoconductor is also arbitrary.

〔Effect of the invention〕

As described in detail above, according to the present invention, after a continuous image forming process is performed using an image support having a negative polarity organic photoconductor suitable for color copying machines, one-north printers, etc. Furthermore, even if a larger size sheet paper is used and the next image forming process is performed, a part of the image support remains positively charged and the next image forming process is started. It is possible to obtain at least the desired surface potential over the entire area during charging in the first image forming process, and there is no density restriction in the case of conventional image areas and white background areas. Eliminates fog during exposure and alignment, allowing you to obtain clear and good images.

[Brief explanation of the drawing]

Figures 1 and 3 show an embodiment of the present invention.
Fig. 1 is a schematic explanatory diagram of the surroundings of the photoreceptor, Fig. 2 is a partial sectional view of the photoreceptor, and Fig. 3 is a schematic perspective view of the photoreceptor. Support, 12a.
...Charge generation layer, 12b...Charge transport layer, 12...
Organic photoconductor, 13... Image forming means 1G... IW
Electrical device, 17... Transfer charger, 22... Peeling charger.

Claims (1)

[Claims] An image forming apparatus comprising an image support having a negative organic photoconductor on a conductive support, and an image forming means for forming an image on the image support, the image forming means comprising:
A transfer device that faces the image support at least in a transfer section and applies a positive charge during image formation, and a transfer device that faces the image support in a peeling section during image formation and after continuous image formation until the next image formation step. An image forming apparatus comprising: a peeling device that applies an alternating current charge between the two.