JP2003098810A - Image forming device - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide an image forming apparatus capable of preventing reverse charge injection from a transfer roller to an image carrier in a transfer section. An image forming apparatus includes a voltage control device (CPU).
The voltage control device 10 is provided between the paper 5 and the next paper 5 during printing, for example, when the next paper 5
When the transfer roller 6a is in contact with the image carrier 2 in a paper non-passing state where the transfer roller 6a does not reach between the image carrier 2 and the transfer roller 6a, the transfer voltage applied to the transfer roller 6a is applied to the writing electrode 3b. Control is performed so that the applied voltage is equal to or lower than the maximum applied voltage. Thereby, the transfer roller 6a in the transfer portion
, The reverse charge injection into the charging layer 2b of the image carrier 2 is prevented, and a current exceeding the withstand voltage of the high-voltage IC driver 8 is prevented from flowing to the writing electrode 3b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of an image forming apparatus for forming an image by forming an electrostatic latent image on an image carrier by a write electrode of a write head section.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrostatic copying machine or a printer, the surface of a photosensitive member is generally charged uniformly by a charging device, and a laser beam is applied to the surface of the uniformly charged photosensitive member. Alternatively, an electrostatic latent image is written on the surface of the photoconductor by exposing the light of an exposure device such as LED lamp light. Then, the electrostatic latent image on the surface of the photoconductor is developed by a developing device to form a developer image on the surface of the photoconductor, and the developer image is transferred to a transfer material such as paper by a transfer device to form an image. Is forming. In such a conventional general image forming apparatus, since the exposure device, which is a writing device for the electrostatic latent image, is composed of a laser light generator, an LED lamp light generator, or the like, the image formation device is large. And it has a complicated structure.

Therefore, as an electrostatic latent image writing device, an image forming device for writing an electrostatic latent image on the surface of an image bearing member by electrodes without using laser light or LED lamp light is disclosed in Japanese Patent Publication No. 63-
It is proposed in Japanese Patent No. 45104. The image forming apparatus disclosed in this publication includes a multi-stylus having a large number of needle electrodes, and the multi-stylus needle electrodes are simply brought into contact with the inorganic glass layer on the surface of the image carrier. Then, when a voltage is applied to the corresponding needle electrode of the multi-stylus by the input signal of the image information, an electrostatic latent image is formed on the image carrier by the needle electrode. According to the image forming apparatus disclosed in this publication, the conventional exposure apparatus is not used as the writing apparatus.
Therefore, the image forming apparatus has a small size and a relatively simple structure.

In addition, the ion generated by the corona discharger is controlled by an ion control electrode which is provided at the tip of the insulating substrate and is not in contact with the image carrier, so that an electrostatic latent image is written on the image carrier. The forming device is disclosed in Japanese Patent Laid-Open No. 06-1662.
No. 06 publication. Also in the image forming apparatus of this publication, since the exposure device is not used as the writing device, the image forming apparatus has a small size and a relatively simple structure.

[Problems to be Solved by the Invention]

However, in the image forming apparatus of the above-mentioned publication, since many needle electrodes of the multi-stylus are simply brought into contact with the inorganic glass layer on the surface of the image carrier, many needle electrodes are imaged. Stable contact with the inorganic glass layer on the surface of the carrier is difficult. Therefore, it is difficult to stably charge the surface of the image carrier and it is difficult to obtain a good image.

Further, in order to prevent the surface of the image carrier from being damaged by the contact of a large number of needle electrodes, it is inevitable to provide an inorganic glass layer on the surface of the image carrier, and the structure of the image carrier becomes complicated accordingly. Become. Moreover, since the inorganic glass layer has very good physical adsorption water properties, moisture is well adsorbed on the surface of the inorganic glass, and the adsorbed moisture increases the electrical conductivity of the glass surface and leaks the charged charges of the image carrier. Therefore, it is necessary to provide a means for drying the surface of the image carrier on which water is adsorbed to prevent the influence of the physically adsorbed water.
Therefore, there is a problem that not only the device becomes larger, but also the number of parts increases, the structure becomes more complicated, and the cost becomes higher.

In addition, since a large number of needle electrodes are discharged,
There is also a problem that ozone (O ₃ ) is likely to be generated. This ozone not only causes rust to occur in parts inside the apparatus, but also nitric acid (HN) generated by reacting with NO _x.
O ₃ ) may melt the resin parts. Moreover, there is a possibility that ozone produces an offensive odor. For this reason, ozone must be discharged from the inside of the device, but for that purpose it is necessary to provide a duct and an ozone filter to make the exhaust system sufficient, and not only the device becomes large, but also the number of parts increases and the configuration is increased. It becomes more complex and costly.

Further, in the image forming apparatus disclosed in the above-mentioned publication, the ion control electrode controls the ions generated in the corona discharger and does not directly inject the charge into the image carrier, so that the image is formed. There is a problem that not only the forming apparatus becomes large, but also the configuration becomes extremely complicated. Moreover, it is difficult to stably write the electrostatic latent image on the image carrier because of the charging by the ions. Furthermore, since ions are basically generated and ozone is basically generated, the same problems as those of the image forming apparatus of the above-mentioned publication occur.

Therefore, in view of these problems, the present applicant intends to further reduce the size, and further reduce the number of parts to make the configuration simpler and cheaper.
Moreover, the electrostatic latent image can be written more stably,
Furthermore, a patent application has been filed for an image forming apparatus capable of further suppressing the generation of ozone (Japanese Patent Application No. 2001-227).
630).

The details of the image forming apparatus according to this patent application can be easily understood by referring to the specification and the drawings of the patent application, and therefore, the detailed description thereof will be omitted here, but the parts directly related to the present invention will be described. I will briefly explain.

FIG. 1 is a diagram schematically showing the basic structure of an image forming apparatus according to this patent application. As shown in FIG. 1, the image forming apparatus 1 is provided with an insulating property on the outer periphery of a base material 2a made of a conductive material such as aluminum and grounded, and an electrostatic latent image is formed. Image carrier 2 having a charging body layer 2b, and an FPC (Flexible Pris
nt Circuit, abbreviated as FPC hereinafter) or PET
An image carrier is supported by a flexible base material 3a having a high insulating property, such as polyethylene terephthalate (hereinafter abbreviated as PET), a relatively soft and elastic material, and a weak elastic restoring force due to the bending of the base material 3a. The second write head portion 3 having a write electrode 3b for writing an electrostatic latent image on the charged body layer 2b, which is lightly pressed and brought into surface contact with the second charged body layer 2b; At least a developing device 4 having a transfer roller 6a and a transfer device 6 having a transfer roller 6a are provided.

In the image forming apparatus 1 having the above-described structure, after the charge layer 2b of the image carrier 2 is brought into a uniform charge state, the voltage is applied from the write electrode voltage applying device 7 to the write electrode 3b. Applied via the IC driver 8 of the write electrode 3b,
An electrostatic latent image is formed on the image carrier 2 mainly due to charge transfer between the image carrier 2 and the write electrode 3b of the write head unit 3 which are in surface contact with each other (hereinafter, also referred to as contact charge transfer). It is written on the charged body layer 2b. Then, the electrostatic latent image on the charged body layer 2b of the image carrier 2 is developed with the developer conveyed by the developing roller 4a of the developing device 4, and the developer image is applied with a voltage from the transfer voltage applying device 9. Transfer roller 6a
Is transferred to a transfer material 5 such as paper. In the following description of the present invention, the present invention will be described by using the paper 5 as a representative of the transfer material 5, but it goes without saying that the transfer material 5 may be other than the paper 5.

By the way, in the writing of the electrostatic latent image by the write electrode 3b of the write head unit 3 as described above, for example, when continuous printing is performed in monochrome image formation, as shown in FIG. After the printing is completed, the transfer roller 6a is arranged on the charged body layer 2 of the image carrier 2 until the next paper 5 arrives at the transfer device 6.
It comes into contact with b. At this time, if the transfer voltage is continuously applied to the transfer roller 6a, a potential according to the transfer voltage is generated in the charged body layer 2b of the image carrier 2. When writing is performed by the write electrode 3b in this state, a current exceeding the withstand voltage of the high-voltage IC driver 8 connected to the write electrode 3b flows to the write electrode 3b, and the write head portion is formed. 3 may be destroyed. Especially at low temperatures (eg 15
C.) and low humidity (23% RH) environment (LL environment), when the transfer voltage is increased when the transfer is performed,
The IC driver 8 may be damaged.

When reverse charge injection occurs from the transfer roller 6a to the charged body layer 2b of the image carrier 2 at the transfer portion of the transfer device 6, the reference of the write potential in the subsequent selective charge writing is disturbed, The ghost image is developed, and at the time of writing the latent image, a voltage drop occurs between the image carrier 2 and the writing electrode 3b due to discharge, and the electrostatic latent image is disturbed.

Further, when the write electrode 3b and the image carrier 2 come into contact with each other in the state where the reverse charge injection is occurring in the transfer portion, a potential difference exceeding the discharge start voltage is applied. Moreover, vibration is generated in relation to the frequency of the ON / OFF signal applied to write the electrostatic latent image on the write electrode 3b.
When such vibration occurs, the write electrode 3b and the image carrier 2
Contact instability between the two increases and the reproducibility of latent image formation becomes unstable.

The present invention has been made in view of such circumstances, and an object thereof is to provide an image forming apparatus capable of preventing reverse charge injection from a transfer roller to an image carrier at a transfer portion. It is to be.

[0017]

In order to solve this problem, the invention of claim 1 provides an image carrier having a charged body layer on the surface of which a latent electrostatic image is formed. A write head portion having a write electrode for writing the electrostatic latent image in contact with the charged body layer of the image carrier, and developing for developing the electrostatic latent image on the image carrier with a developer At least a device and a transfer device having a transfer roller that is in contact with the charged body layer of the image carrier and transfers the developed developer image on the image carrier to a transfer material, wherein the transfer roller is The transfer voltage applied to the transfer roller when in contact with the image carrier is set to be equal to or less than the maximum applied voltage applied to the write electrode.

According to a second aspect of the present invention, an image carrier having a charged body layer having an electrostatic latent image formed on the surface of the dielectric layer and a contact with the charged body layer of the image carrier. And a writing head unit having writing electrodes for writing the electrostatic latent image, a developing device for developing the electrostatic latent image on the image carrier with a developer, and the charged body layer of the image carrier. At least an intermediate transfer medium that is transferred to the developed developer image on the image carrier and a transfer device having a transfer roller that transfers the developer image of the intermediate transfer medium onto a transfer material. The intermediate transfer voltage applied to the intermediate transfer medium when the intermediate transfer medium is in contact with the image carrier is set to be equal to or lower than the maximum applied voltage applied to the write electrode. There is.

[0019]

In the image forming apparatus of the present invention configured as described above, the transfer roller may come into contact with the image carrier between the transfer material and the next transfer material in the state where the transfer voltage is applied. Alternatively, even if the non-image portion of the intermediate transfer medium comes into contact with the image carrier, the transfer voltage applied to the transfer roller or the intermediate transfer voltage applied to the intermediate transfer medium is applied to the write electrodes, respectively. Since it is set below the maximum applied voltage, the reverse charge injection from the transfer roller or the intermediate transfer medium to the image carrier does not occur, and the IC of the write electrode is
No current will exceed the withstand voltage of the driver. Therefore, destruction of the write head portion is prevented, a ghost image does not occur, and a voltage drop due to discharge between the image carrier and the write electrode disappears during writing of the latent image, so that the electrostatic latent image is formed. Disturbance will be prevented. Further, when the transfer is performed in a low temperature and low humidity (LL) environment, even if the transfer voltage is increased, the IC driver of the write electrode is not damaged.

Further, since the reverse charge injection does not occur in the transfer portion, when the write electrode and the image carrier contact each other, a potential difference exceeding the discharge start voltage is not applied, so that the voltage is applied to the write electrode. Vibration does not occur in the write electrode regardless of the frequency of the on / off signal. As a result, the contact between the write electrode and the image carrier is stabilized, and good reproducibility of latent image formation can be obtained.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a view similar to FIG. 1, schematically showing the basic configuration of an example of an embodiment of the image forming apparatus according to the present invention. In the following description, the same components as those of the image forming apparatus of the example described before the described example will be denoted by the same reference numerals, and detailed description thereof will be omitted.

The image forming apparatus 1 of this example is basically shown in FIG.
The image forming apparatus 1 of this example has the same configuration as the image forming apparatus 1 of the above-mentioned patent application shown in FIG.
In, a voltage control device (CPU) 10 is provided.
The voltage controller (CPU) 10 is, for example, between the paper 5 and the next paper 5 during printing, that is, the next paper 5 is the transfer roller 6a.
When the transfer roller 6a is in contact with the image carrier 2 in the non-sheet-passing state where it has not reached between the transfer roller 6a and the image carrier 2, the transfer voltage applied to the transfer roller 6a is applied to the write electrode 3b. The applied voltage is controlled to be equal to or lower than the maximum applied voltage, that is, the transfer voltage in the non-sheet passing state ≦ the maximum applied voltage to the writing electrode 3b.

Further, in the image forming apparatus 1 of this example, the voltage control device (CPU) 10 causes the voltage applied to the transfer roller 6a to be applied to the IC driver 8 by the voltage controller (CPU) 10 at the time of initial operation such as when the transfer is completed or the machine is turned on. Voltage control is performed so that the voltage is lower than the withstand voltage. The other configuration of the image forming apparatus 1 of this example is the same as the image forming apparatus 1 of the above-mentioned patent application shown in FIG.

In the image forming apparatus 1 of this example configured as described above, as in the case of the image forming apparatus 1 of the patent application shown in FIG. 1, the charged body layer 2b of the image carrier 2 is uniform. After being brought into a charge state, a voltage is applied from the write electrode voltage applying device 7 to the write electrode 3b, and mainly the image carrier 2 and the write electrode 3b of the write head unit 3 are in surface contact with each other. An electrostatic latent image is written on the charged body layer 2b of the image carrier 2 by the charge transfer (hereinafter, also referred to as contact charge transfer) between them. Then, the electrostatic latent image on the charged body layer 2b of the image carrier 2 is developed with the developer conveyed by the developing roller 4a of the developing device 4, and the developer image is applied with a voltage from the transfer voltage applying device 9. It is transferred to the paper 5 by the transfer roller 6a.

Then, for example, in the case where continuous printing is performed on a paper, after the printing on the paper is completed as described above, the transfer roller 6 is in a non-sheet passing state until the next paper arrives at the transfer device 6.
Although a contacts the charged layer 2b of the image carrier 2, at this time, in the image forming apparatus 1 of this example, the transfer voltage in the non-sheet passing state is set to be equal to or lower than the maximum applied voltage to the writing electrode 3b. Therefore, even if the transfer voltage is continuously applied to the transfer roller 6a, reverse charge injection from the transfer roller 6a to the charged body layer 2b of the image carrier 2 does not occur in the transfer portion as described above, and in this state. Even if writing is performed by the write electrode 3b, a current exceeding the breakdown voltage of the high voltage IC driver 8 connected to the write electrode 3b does not flow to the write electrode 3b.

As described above, according to the image forming apparatus 1 of this example, the reverse charge injection does not occur in the transfer portion, and the current exceeding the withstand voltage of the IC driver 8 of the write electrode 3b does not flow. It is possible to prevent breakage of the insert head portion 3 and also to prevent generation of a ghost image. Further, since the voltage drop due to the discharge between the image carrier and the writing electrode is eliminated at the time of writing the latent image, the disturbance of the electrostatic latent image can be prevented. Further, when the transfer is performed in the environment of low temperature and low humidity (LL), even if the transfer voltage is increased, the damage of the IC driver 8 of the write electrode 3b can be prevented.

Further, since the reverse charge injection does not occur at the transfer portion, when the write electrode 3b and the image carrier 2 are brought into contact with each other, no potential difference exceeding the discharge start voltage is applied, so that the write electrode 3b is applied. It is possible to prevent vibration of the write electrode 3b regardless of the frequency of the on / off signal applied for writing. As a result, the contact between the write electrode 3b and the image carrier 2 can be stabilized, and good reproducibility of latent image formation can be obtained. Other operational effects of the image forming apparatus 1 of this example are the same as those of the image forming apparatus 1 of the above-mentioned patent application shown in FIG.

FIG. 4 is a view similar to FIG. 3, schematically showing the basic structure of another example of the embodiment of the image forming apparatus according to the present invention. The above-described example shown in FIG. 3 is an example in which the present invention is applied to the image forming apparatus 1 that does not perform intermediate transfer. However, as shown in FIG. 4, the image forming apparatus 1 of this example has a conventionally known image carrier. The developer image on the body 2 is primary-transferred onto the endless belt-shaped intermediate transfer medium 11 in contact with the image carrier 2 by the primary transfer device 6, and the developer image on the intermediate transfer medium 11 is transferred to the secondary transfer device 6 '. The secondary transfer roller 6'a performs secondary transfer on the paper 5.

The primary transfer device 6 comprises a primary transfer roller 6a for pressing the intermediate transfer medium 11 against the image carrier 6. Further, the primary transfer voltage from the transfer voltage applying device 9 is applied to the intermediate transfer medium 11 via the primary transfer roller 6a. The secondary transfer voltage is also applied to the secondary transfer roller 6'a from a secondary transfer voltage applying device (not shown).

An endless belt-shaped intermediate transfer medium 11 is stretched between a driving roller 12 and a driven roller 13, and is rotated by the driving roller 12 which is rotationally driven by a motor (not shown).

The voltage controller (CPU) 10 of this example is
The transfer voltage in the non-image portion of the intermediate transfer medium 11 is set to the write electrode 3
It is controlled so that it is less than or equal to the maximum applied voltage applied to b, that is, the transfer voltage in the non-image portion ≦ the maximum applied voltage to the writing electrode 3b.

Further, also in the image forming apparatus 1 of this example, the voltage control unit (CPU) 10 causes the voltage applied to the transfer roller 6a by the voltage driver (CPU) 10 of the IC driver 8 at the time of initial operation such as when the transfer is completed or the machine is turned on. Voltage control is performed so that the voltage is lower than the withstand voltage. The other configuration of the image forming apparatus 1 of this example is the same as that of the image forming apparatus 1 of the example shown in FIG.

In the image forming apparatus 1 of this example configured as described above, the charge electrode layer 2b of the image carrier 2 is brought to a uniform charge state and then the write electrode voltage is applied, as in the above-described examples. A voltage is applied from the application device 7 to the write electrode 3b, and the image carrier 2 and the write head unit 3 are mainly in surface contact with each other.
The charge transfer between the write electrode 3b and the write electrode 3b (hereinafter, also referred to as contact charge transfer) causes an electrostatic latent image to appear on the charged body layer 2 of the image carrier 2.
written on b. Then, the charged body layer 2 of the image carrier 2
The electrostatic latent image on b is developed by the developer conveyed by the developing roller 4a of the developing device 4, and the developer image is transferred from the transfer voltage applying device 9 to the primary transfer roller 6a by the transfer voltage applying device 9 in the primary transfer device 6. Intermediate transfer medium 1 applied via
Transferred to 1.

Then, for example, even if the non-image portion of the intermediate transfer medium 11 contacts the charged body layer 2b of the image carrier 2, at this time, in the image forming apparatus 1 of this example, the transfer voltage at the non-image portion is Since the voltage applied to the write electrode 3b is set to be equal to or lower than the maximum applied voltage, the intermediate transfer medium 11 in the transfer portion as described above is set.
Inverse charge injection into the charged body layer 2b of the image carrier 2 does not occur, and even if writing is performed by the writing electrode 3b in this state, a high voltage IC connected to the writing electrode 3b.
A current exceeding the withstand voltage of the driver 8 does not flow into the write electrode 3b. Other operational effects of the image forming apparatus 1 of this example are the same as those of the image forming apparatus 1 of the example shown in FIG.

In the image forming apparatus having the intermediate transfer medium of the example shown in FIG. 4, a portion excluding the intermediate transfer medium and the secondary transfer device is provided for each color of yellow, magenta, cyan, and black in FIG. FIG. 3 is a diagram schematically showing a full-color image forming apparatus configured by combining these.

As shown in FIG. 5, the full-color image forming apparatus 1 of this example has an image carrier 2 _Y , 2 _M , 2 _C , 2 _K for each color of yellow Y, magenta M, cyan C, and black _K. ,
Writing electrodes _{3b Y, 3b M, 3b C} , the writing head 3 _Y, having a _{3b K 3 M, 3 C,} 3 K, and the developing roller 4a _Y, 4a _M, 4
It has a _C and 4a _K. In addition, the full-color image forming apparatus 1 includes an endless belt-shaped intermediate transfer medium 11 that is common to all colors, and the intermediate transfer medium 11 is used for each color image carrier 2 _Y , 2 _M , 2 _C ,. The primary transfer rollers 6a _Y , 6a _M , 6a _C , and 6a _K for each color pressed against 2 _K are provided.

Further, the full-color image forming apparatus 1
Is the IC driver 8 _Y , 8 _M , 8 _C for each color on the write electrode 3 b _Y , 3 b _M , 3 b _C , 3 b _K of each color of each write head unit 3 _Y , 3 _M , 3 _C , 3 _K. write electrode voltage applying unit 7 for each color to be applied to the writing electrode voltage independently through 8 _{K Y,} 7 _M, 7 _C, 7
_K is provided, and the primary transfer rollers 6a _Y , 6a _M , 6a _C , 6 are provided on the intermediate transfer medium 11 independently for each color.
and a a transfer voltage applying device 9 for each _{color K} through the application of a transfer voltage _{Y, 9 M, 9 C,} 9 K. The write electrode voltage applying devices 7 _Y , 7 _M , 7 _C and 7 _K and the transfer voltage applying devices 9 _Y , 9 _M , 9 _C and 9 _K are connected to a common voltage control device (CPU) 10. The voltage control device (CPU) 10 is connected to each write electrode voltage application device 7 _Y ,
7 _M , 7 _C , 7 _K and transfer voltage applying devices 9 _Y , 9 _M , 9 _C , 9 _K
Are controlled so that their applied voltages are independently controlled. The full-color image forming apparatus 1 further includes a secondary transfer device 6 ′ that transfers the primary-transferred developer image on the intermediate transfer medium 11 to the paper 5.

Then, the image carriers 2 _Y , 2 _M , 2 _C and 2 _K , the writing head portions 3 _Y , 3 _M , 3 _C and 3 _K , and the developing rollers 4 are provided.
a _Y , 4a _M , 4a _C , and 4a _K are arranged in tandem in this order from the upstream side in the rotation direction of the intermediate transfer medium 11 (counterclockwise in FIG. 5). The arrangement order of the image forming apparatus of each color can be set in any order.

The endless belt-shaped intermediate transfer medium 11 is stretched around a driving roller 12 and a driven roller 13, and is rotated by the driving roller 12 which is rotationally driven by a motor (not shown). Secondary transfer is performed on the paper 5 by passing the paper 5 while sandwiching it between the intermediate transfer medium 11 and the secondary transfer roller 6'a at the position of the drive roller 12.

Although not shown in FIG. 5, in the full-color image forming apparatus 1 of this example, as in the image forming apparatus 1 of the example shown in FIG. A secondary transfer voltage applying device for applying a voltage is provided.

In the full-color image forming apparatus 1 of this example, the voltage controller (CPU) 10 sets the intermediate transfer voltage in the non-image portion of the intermediate transfer medium 11 to the write electrode 3 for each color.
_{b Y, 3b M, 3b C} , the minimum voltage among the maximum applied voltages applied to 3b _K below, that the intermediate transfer voltage ≦ writing electrodes 3b _Y in the non-image _{portion, 3b M, 3b C, 3b} K It is controlled to be the minimum voltage of the maximum applied voltage to the. The other configuration of the image forming apparatus 1 of this example is the same as that of the image forming apparatus 1 of the example shown in FIG.

In the full-color image forming apparatus 1 of this example configured as described above, first, the yellow Y writing electrode 3b _Y is used to charge the yellow Y image carrier 2 _{Y to} the charging layer 2b _Y. The latent image is written. Then, the yellow Y electrostatic latent image is developed by the yellow Y developing roller 4 _Y to form a yellow Y developer image on the charged body layer 2 b _Y of the image carrier 2 _Y. This yellow Y developer image is primarily transferred to the intermediate transfer medium 11.

Then, the electrostatic latent image of magenta M is written on the charged body layer 2b _M of the image carrier 2 _M of magenta M by the writing electrode 3b _M of magenta M. Then, the electrostatic latent image of magenta M is developed by the developing roller 4 _M of magenta M, and a developer image of magenta M is formed on the charged body layer 2b _M of the image carrier 2 _M. This magenta M developer image is the intermediate transfer medium 1
The image is primarily transferred so as to be superimposed on the first yellow Y developer image.

Subsequently, the cyan C writing electrode 3b _C writes an electrostatic latent image of cyan C on the charged body layer 2b _C of the cyan C image carrier 2 _C. Then, the cyan C electrostatic latent image is developed by the cyan C developing roller 4 _C to form a cyan C developer image on the charged body layer 2 b _C of the image carrier 2 _C. The cyan C developer image is yellow Y on the intermediate transfer medium 11.
And is primarily transferred so as to be superimposed on the developer image of magenta M.

Further, the black B write electrode 3b_BIn bra
Image carrier 2 of Bock B_BCharged body layer 2b _BAnd still black B
The latent image is written. And this black B electrostatic
Developing roller 4 with a black B latent image_BImage bearing by being developed with
Body 2_BCharged body layer 2b_BA black B developer image is formed on top
To be done. This black B developer image is the intermediate transfer medium 11
Yellow Y, magenta M, and cyan C developer images
Primary transfer is performed in a layered manner and full color is printed on the intermediate transfer medium 11.
The developer image of is formed. Furthermore, on the intermediate transfer medium 11
The formed full-color developer image is transferred to the secondary transfer roller 6 '.
It is secondarily transferred to the paper 5 by a.

Then, for example, the non-image portion of the intermediate transfer medium 11 is the charged body layer 2b _Y , 2 of each image carrier 2 _Y , 2 _M , 2 _C , 2 _K.
Even if it touches any of b _M , 2b _C and 2b _K , at this time,
In the image forming apparatus 1 of this example, the transfer voltage in the non-image portion of the intermediate transfer medium 11 is set to the write electrodes 3b _Y , 3b _M , 3b _C , for each color.
Since it is set to be equal to or lower than the minimum voltage among the maximum applied voltages applied to 3b _K , the image transfer members 2 _Y , 2 _M , and 2 _Y from the intermediate transfer medium 11 in the transfer portion of each color as described above.
Inverse charge injection into the charged body layers 2b _Y , 2b _M , 2b _C and 2b _{K of} 2 _C and 2 _K does not occur, and in this state, each write electrode 3b
_Y, 3b _M, 3b _C, even writing is performed by 3b _K, each write electrode _{3b Y, 3b M, 3b C} , a high voltage IC drivers that are respectively connected to 3b _K (not shown) A current exceeding the withstand voltage does not flow into each of the write electrodes 3b _Y , 3b _M , 3b _C and 3b _K. Other operational effects of the full-color image forming apparatus 1 of this example are the same as those of the example shown in FIG.

[0047]

As is apparent from the above description, according to the image forming apparatus of the present invention, the transfer roller forms an image between the transfer material and the next transfer material while the transfer voltage is applied. Even if the carrier is contacted or the non-image portion of the intermediate transfer medium is contacted with the image carrier, the transfer voltage applied to the transfer roller or the intermediate transfer voltage applied to the intermediate transfer medium is Since the maximum applied voltage applied to the write electrode is set to be equal to or lower than the maximum applied voltage, reverse charge injection from the transfer roller or the intermediate transfer medium to the image carrier can be prevented.

Therefore, it is possible to reliably prevent the flow of a current exceeding the withstand voltage of the IC driver of the write electrode. As a result, the write head section can be prevented from being destroyed and a ghost image can be prevented from being generated. Furthermore, at the time of writing the latent image, the voltage drop due to the discharge between the image carrier and the write electrode is eliminated to eliminate the electrostatic latent image. It becomes possible to prevent image distortion. Further, when the transfer is performed in a low temperature and low humidity (LL) environment, even if the transfer voltage is increased, it is possible to prevent the IC driver of the write electrode from being damaged.

Further, since the reverse charge injection does not occur at the transfer portion, a potential difference exceeding the discharge start voltage does not occur when the write electrode and the image carrier contact each other, so that the write electrode is applied. It is possible to prevent the write electrode from vibrating regardless of the frequency of the on / off signal. As a result, the contact between the write electrode and the image carrier can be stabilized, and good reproducibility of latent image formation can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a basic configuration of an image forming apparatus according to a patent application of Japanese Patent Application No. 2001-227630.

FIG. 2 is a diagram illustrating the behavior of the image forming apparatus shown in FIG.

FIG. 3 is a view similar to FIG. 1, schematically showing the basic structure of an example of an embodiment of an image forming apparatus according to the present invention.

FIG. 4 is a view similar to FIG. 3, schematically showing the basic structure of another example of the embodiment of the image forming apparatus according to the present invention.

5 is a diagram schematically showing a full-color image forming apparatus configured by combining image forming apparatuses having the intermediate transfer medium of the example shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Image carrier, 3 ... Writing head section,
3a ... Base material, 3b ... Writing electrode, 4 ... Developing device, 4a ... Developer carrier (developing roller), 5 ... Transfer material (paper etc.), 6 ...
Primary transfer device, 6a ... Primary transfer roller, 6 '... Secondary transfer device, 6'a ... Secondary transfer roller, 7 ... Write electrode voltage applying device, 8 ... IC driver, 9 ... Transfer voltage applying device, 10
... voltage control device (CPU), 11 ... intermediate transfer medium

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C162 AE21 AE31 AE44 AE47 AE69                       AF13 AF64 AF70 EA20                 2H027 DC04 EA03 ED24 EF09                 2H029 AA06 AB03 AB13 AB23 AD02                 2H200 FA03 FA09 GA10 GA12 GA20                       GA23 GA47 HA02 HB12 HB22                       JA02 JA29 JA30 JC03 JC07                       JC19 JC20 PA05 PA10 PA22                       PB12 PB16

Claims (2)

[Claims] 1. An image carrier having a charged body layer on which an electrostatic latent image is formed on the surface of a dielectric layer, and the electrostatic latent image in contact with the charged body layer of the image carrier. A writing head section having a writing electrode for writing the data, a developing device for developing the electrostatic latent image on the image carrier with a developer, and a developing device in contact with the charged body layer of the image carrier. And a transfer device having a transfer roller for transferring the developer image on the image carrier to a transfer material, the transfer being applied to the transfer roller when the transfer roller is in contact with the image carrier. An image forming apparatus, wherein a voltage is set to be equal to or lower than a maximum applied voltage applied to the write electrode. 2. An image carrier having a charged body layer on which an electrostatic latent image is formed on the surface of a dielectric layer, and the electrostatic latent image in contact with the charged body layer of the image carrier. A writing head section having a writing electrode for writing the data, a developing device for developing the electrostatic latent image on the image carrier with a developer, and a developing device in contact with the charged body layer of the image carrier. At least an intermediate transfer medium to which the developer image on the image carrier is transferred, and a transfer device having a transfer roller for transferring the developer image on the intermediate transfer medium to a transfer material, wherein the intermediate transfer medium is An image forming apparatus, wherein an intermediate transfer voltage applied to the intermediate transfer medium when in contact with the image carrier is set to be equal to or lower than a maximum applied voltage applied to the write electrode.