JP2638183B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Table of Contents] Outline Industrial field of application Conventional technology Problems to be solved by the invention Means to solve the problem Action Embodiment Effect of the invention [Overview] Image exposure from the back side of photoreceptor And develop at the same time
An image forming apparatus for obtaining a toner image on a photoreceptor, wherein a latent image charge that has moved to the photoreceptor surface during the first development is charged to the second
An object of the present invention is to provide an image forming apparatus that does not return to a conductive layer of a photoreceptor again during development. A photoreceptor comprising a transparent substrate, a transparent or translucent conductive layer, and a photoconductive layer, A first magnetic brush developing machine arranged on the side of the photoconductive layer and filled with a developer;
A first voltage applying means for applying a voltage between the magnetic brush developing machine and the conductive layer of the photoconductor, and a transparent substrate side of the photoconductor,
And an image exposing means provided at a position facing the first magnetic brush developing machine for performing image exposure based on image data, and a second exposing means arranged downstream of the first magnetic brush developing machine in the moving direction of the photoconductor. A second magnetic brush developing machine, and a second voltage applying means for applying a low voltage having a polarity opposite to that of the first voltage applying means between the second magnetic brush developing machine and the conductive layer of the photoconductor, An image exposing means for exposing the photoconductor sandwiched between the opposing first magnetic brush developing machines to image exposure, and at the same time, developing the toner with a first magnetic brush developing machine; In an image forming apparatus for performing a second development for collecting toner in a background portion in a portion of a brush developing machine and forming a toner image on a photoconductor, the photoconductive layer of the photoconductor has a large carrier movement during the first development. At the time of II development. Compared to when I developed for 1
It is constituted by using a photoreceptor having a carrier mobility smaller than an order of magnitude.

Alternatively, the photoconductive layer is composed of at least two layers having a small electric field dependence and different carrier mobilities, a photoconductive layer having a large carrier mobility on the transparent conductive layer side, and a carrier mobility of one or more digits higher than that. It is configured using a photoconductor formed by laminating small photoconductive layers.

[Industrial applications]

The present invention relates to an image forming apparatus that develops an image at the same time as exposing an image from a back surface of a photoconductor to obtain a toner image on the photoconductor.

Current copiers or high-speed, high-quality printers
An electrophotographic recording system is generally used. In this method, a photoconductor is used as a recording medium, and uniform charging, image exposure,
Recording is performed in the steps of transfer, fixing, static elimination, and cleaning. This is the so-called Carlson process.

In the Carlson process, a corona discharger is used for uniform charging, transfer, and static elimination. Since the corona discharger is configured to apply a high voltage of several KV to the corona wire, it requires a high-voltage power supply and is easily affected by humidity, dust, etc.
It has the disadvantage of low reliability. In addition, the ozone generated by the corona discharger generates an odor, and in recent years, the harmfulness of ozone to the human body has become a problem.

Further, since the above seven steps are required, there is a disadvantage that the apparatus becomes complicated and the size becomes large.

In view of the above problems, an image forming method has recently been proposed that focuses on miniaturization of an apparatus that does not require a corona discharger. Specifically, this method is a method in which a toner developing device and an image exposing unit are arranged opposite to each other with a photoconductor interposed therebetween, and image exposure and development are performed simultaneously. The present invention relates to one such system.

[Conventional technology]

 FIG. 12 shows a schematic diagram of the prior art.

In the figure, a photoconductor 1 has a transparent substrate 1a, a transparent conductive layer 1b,
It is composed of a photoconductive layer 1c, and the transparent conductive layer 1b is connected to the ground. The first photoconductor 1 provided on the photoconductive layer 1c side of the photoconductor 1
The magnetic brush developing machine 2 includes a magnet roller 2a and a sleeve 2b, and both the magnet roller 2a and the sleeve 2b are rotatable. A first recording voltage 3 having a polarity opposite to the photocarrier polarity (positive polarity in the figure) of the photoconductive layer 1c is applied to the first developing brush developing device 2,
The first magnetic brush developing machine 2 is filled with a one-component or two-component developer 4, and the developer 4 is conveyed by rotation of a magnet roller 2a and a sleeve 2b.

Reference numeral 5 denotes an image exposing means, and the first magnetic brush developing machine 2
Is disposed on the side of the transparent substrate 1a of the photoconductor 1 opposite to the photoconductor 1.
As the image exposure means 5, an LED array optical system, a laser optical system, an EL optical system, a liquid crystal shutter optical system, or the like can be used.

Reference numeral 8 denotes a second magnetic brush developing machine, which is provided downstream of the first magnetic brush developing machine 2 in the moving direction of the photoconductor 1. The second magnetic brush developing device 8 includes, similarly to the first magnetic brush developing device 2, a magnet roller 2a and a sleeve 2b.
, And both the magnet roller 2a and the sleeve 2b are configured to be rotatable. Further, a second recording voltage 9 having a polarity opposite to that of the recording voltage 3 of the first magnetic brush developing machine 2 is applied to the second magnetic brush developing machine 8. This second
One-component or two-component developer 10 in magnetic brush developing machine 8
And the developer 10 is transported by the rotation of the magnet roller 8a and the sleeve 8b.

 Next, the principle of image formation will be described.

In the first magnetic brush developing machine 2 of the above-described apparatus, when the photosensitive member 1 is image-exposed, photocarriers are generated in the photoconductive layer 1c, and of the photocarriers, the polarity of which is opposite to the first recording voltage 3. The photocarriers move to the vicinity of the surface of the photoconductive layer 1c and become latent image charges 6. For this reason, in the exposed portion, the capacitance of the photoconductive layer 1c apparently increases, so that the amount of adhered toner increases, and a toner image 7 having a certain level of contrast between the exposed portion and the non-exposed portion is formed. This step is referred to as first development.

Next, the photosensitive member 1 is moved to the second magnetic brush developing machine 8.
By applying the reverse voltage 9 to the sleeve 8b, the excess toner on the non-exposed portion adhered in the first magnetic brush developing machine 2 is collected by electrostatic force. At this time, the toner in the exposed portion is also slightly recovered, but the latent image charge 6
Most of the toner remains on the photoreceptor 1 due to the electrostatic restraining force of the toner charges and the toner image 11 is formed. This step is referred to as “second development”.

[Problems to be solved by the invention]

In the prior art, in the first developing step, since image exposure and development are performed simultaneously, photocarriers generated in the photoconductor need to move at a high speed, so that the photoconductive layer 1c having a high carrier mobility was required. This photoconductive layer 1c has a small change with respect to the electric field as shown in FIG. 13, and shows a large carrier mobility even in a weak electric field.

When such a photoconductor 1 is used, in the first magnetic brush developing machine 2, as shown in FIG. 14 (a), photocarriers generated in the photoconductor move at a high speed toward the surface of the photoconductor 1. As a result, latent image charge 6 is obtained. Next, as shown in FIG. 14 (b), in the second magnetic brush developing machine 8 for collecting the toner in the background, the charge (latent image charge) is applied despite the weak electric field applied to the photoconductive layer 1c. 6) move. Therefore, the latent image charges 6 on the photoreceptor surface move to the conductive layer 1b side of the photoreceptor 1 again, and act to weaken the adhesion of the toner on the photoreceptor surface. As a result, the amount of toner adhering to the photoconductor 1 decreases,
There is a problem that the density of the image 11 is reduced.

Accordingly, an object of the present invention is to provide an image forming apparatus in which a latent image charge that has moved to the photoconductor surface during the first development does not return to the conductive layer of the photoconductor again during the second development.

[Means for solving the problem]

As shown in FIGS. 1 and 2, the problem is that the photocarriers move at high speed during the first development, that is, at the time of high electric field, and the electric charges in the photoconductor move at the time of the second development, that is, at the time of low electric field. Or use a photosensitive member 1 that is difficult to move. Specifically, as shown in FIG. 2, the photoreceptor has a carrier mobility dependent on an electric field. That is, the photoreceptor has a large carrier mobility in a high electric field and a small carrier mobility in a low electric field.

Alternatively, as shown in FIGS. 7 and 8, the photoconductive layer is composed of a plurality of layers, and the photoconductors 11A and 13A have a low electric field dependency and a large carrier mobility on the transparent conductive layer 1b side. Of photoconductive layers 11c and 13d, and second photoconductive layers 11d and 13e having a carrier mobility that is smaller than the first photoconductive layers 11c and 13d by one digit or more and has less electric field dependence. Photoreceptor 1
1A and 13A.

[Action]

By using the photoreceptor 1 shown in FIG. 1 having a carrier mobility characteristic as shown in FIG. 2, the first brush developing machine 2 of the first development of FIG. The photocarriers generated in the photoconductive layer 1c of the body 1 move at high speed toward the surface of the photoconductor 1 and become latent image charges 6.

Next, in the second magnetic brush developing machine 8 of the II development of FIG. 1B, a weak electric field is applied to the photoconductive layer 1c to collect the toner in the background portion. Conventionally, at this time, the latent image charges 6 move in the direction of the conductive layer 1b of the photoconductor 1, so that the amount of toner in the image area has been reduced. However, in the present invention, since the photosensitive member having a small carrier mobility is used in a low electric field, the latent image charges 6 cannot move. Therefore, the latent image charge 6
And the electrostatic binding force of the toner charge can be strongly maintained,
The amount of adhered toner is large and the development density is high.

In the photoconductors 11A and 13A shown in FIGS. 7 and 8, when a high electric field of the first development is applied as shown in FIG. Carriers move at high speed through the first photoconductive layer 11c or the first charge transporting photoconductive layer 13d, and enter the outer second photoconductive layer 11d or the second charge transporting photoconductive layer 13e to be trapped. , The latent image charge becomes 6,
The toner charge of the developer 4 on the surface is absorbed to form a toner image 7.
To form

Next, as shown in FIG. 9 (b), by applying a low electric field in the second development, the toner in the background portion (non-exposed portion) of the latent image charge 6 drops off and is collected, and at the same time, the carrier moving speed becomes 1 A second photoconductive layer 11d or a second charge transporting photoconductive layer 13e
The latent image charges 6 trapped in the first photoconductive layer 11c
Or, it cannot move to the first charge transporting photoconductive layer 13d side, and most of the latent image remains trapped in the outer second photoconductive layer 11d or the second charge transporting photoconductive layer 13e. The electrostatic binding force between the charge 6 and the toner charge is strongly held,
The toner image 7 has a large amount of adhered toner and a high development density.

〔Example〕

FIG. 3 shows an embodiment in which the present invention is applied to an image recording apparatus.

In the figure, reference numeral 12 denotes a photosensitive drum. This photosensitive drum 12
As shown in FIG. 4, a transparent conductive layer 12b of an ITO (indium oxide) deposited film is provided on a transparent substrate 12a of a glass substrate, and further, as a photoconductive layer, a charge generation photoconductive layer 12c and a charge transport light It has a function-separated organic photoconductive layer having a thickness of about 13 μm and made of a conductive layer 12d. A phthalocyanine-based material was used for the charge generating photoconductive layer, and a hydrazone-based material was used for the charge transporting photoconductive layer. The transparent conductive layer 12b of the photoconductor drum 12 as described above is connected to the ground, and the photoconductor drum 12 itself is transported by a drum drive system (not shown) in the direction of the arrow in the figure.

Reference numeral 13 denotes a first magnetic brush developing machine, which comprises an inner magnet roller and an outer sleeve, and the sleeve is rotatable. The first magnetic brush developing machine 13 has a first recording voltage 1 having a polarity opposite to the photocarrier polarity of the photoconductive layer 12c.
4 is applied. A hole transfer type was used for the photoconductive layers 12c and 12d in this example. Therefore, a negative voltage is applied to the first magnetic brush developer 13 as the first recording voltage 14. This voltage is suitably from -100V to -600V. The first magnetic brush developing machine 13 is filled with a developer 15 in which a conductive carrier and an insulating toner are mixed, and is conveyed by rotation of a sleeve.

Image exposure means 16 is disposed at a position facing the first magnetic brush developing machine 13 with the photoconductor drum 12 interposed therebetween.
The image exposure means 16 includes an LED that emits light according to an image signal.
It consists of an array and a selfoc lens array that focuses the image light of the LED array. Reference numeral 17 denotes a toner image, in which toner is still attached to the background.

Reference numeral 18 denotes a second magnetic brush developing machine, which is provided downstream of the first magnetic brush developing machine 13 in the moving direction of the photosensitive drum 12. The second magnetic brush developing machine 18, like the first magnetic brush developing machine 13, includes a magnet roller and a sleeve, and the sleeve is configured to be rotatable. Further, the second magnetic brush developing machine 18 has a first recording voltage.
A second recording voltage 19 having a polarity opposite to that of 14 is applied. The appropriate second recording voltage 19 is 0 to + 100V. The second magnetic brush developing machine 18 includes a first magnetic brush developing machine.
13 is filled with the same developer 20 as the filled one, and is conveyed by rotation of the sleeve.

Reference numeral 21 denotes a toner image formed on the photosensitive drum 12. 22 is a recording paper. Reference numeral 23 denotes a transfer conductive rubber roller to which a voltage (+200 V to +600 V) is applied by a power supply 24. 25 is a toner image electrostatically transferred to the recording paper 22,
The recording paper 22 is fixed on the recording paper 22 by a heat roller fixing machine 26 to form a semi-permanent recording image 27.

28 is a residual toner image remaining on the photosensitive drum 12 after transfer. Reference numeral 29 denotes a charge elimination light source for removing the charge of the residual toner image 28 and the latent image charge in the photoconductive layers 12c and 12d of the photosensitive film shown in FIG. Numeral 30 denotes a toner image which has been destaticized and has lost its electrostatic binding force.

 Next, an image recording procedure will be described.

The photosensitive drum 12 is transported in the direction of the arrow, and the first and second magnetic brush developing machines 13 and 18 are rotated to transport the respective developers 15 and 20 in the direction of the arrow, and the first and second recording are performed. With the voltages 14 and 19 applied, the photoconductor 12 is image-exposed by the image exposure means 16. Then, photocarriers are generated in the charge-generating photoconductive layer 12c shown in FIG. 4, and the holes move in the charge-transporting photoelectric layer 12d to the vicinity of the photoreceptor surface to become latent image charges. For this reason, in the exposed portion, the capacitance of the photoconductive layer apparently increases, so that the amount of adhered toner increases, and a toner image 17 having a certain level of contrast between the exposed portion and the non-exposed portion is formed.

Next, the photosensitive drum 12 is moved, and the second magnetic brush developing device 18 causes the toner image 17 formed in the first magnetic brush developing device 13 to adhere to the background portion, which is a non-exposed portion, of the toner image 17. Is collected by electrostatic force. On this occasion,
Although a small amount of the toner in the exposed portion is collected, most of the toner remains on the photosensitive drum 12 due to the electrostatic binding force between the latent image charge and the toner charge, and a toner image 21 is formed.

Next, the toner image 21 is electrostatically transferred to the recording paper 22 using a conductive rubber roller 23 for transfer. Transferred toner image
25 is fixed on the recording paper 22 by a heat roller fixing machine 26, and a semi-permanent recorded image 27 is obtained.

On the other hand, the residual toner image remaining on the photosensitive drum 12 after the transfer
28 is neutralized using a neutralizing light source 29. The neutralized toner image 30 is formed by the magnetic force of the magnetic brush developing machines 13 and 18 and the developer 1
It is collected and reused by the scraping of 5, 20 and the electrostatic force by the recording voltages 14 and 19. The next image formation is performed simultaneously with the collection of the residual static elimination toner image 30. Simultaneous recovery of the residual static elimination toner image 30 and formation of the next image are performed because the image exposure means 16 and the two magnetic brush developing machines 13 and 18 face each other with the photosensitive drum 12 interposed therebetween. No problem.

In the above-described image recording apparatus, a printing experiment was performed on two types of photosensitive film having carrier mobility characteristics of A type and B type as shown in FIG. A type photoreceptors have a large dependence on the electric field in the photoconductive layer. Further, in the B type photoreceptor, the change in carrier mobility with respect to the electric field is not so large as in the A type.

FIG. 6 shows the results of a printing experiment performed on these two types of photoconductors. The experiment was performed with the first recording voltage 14 kept constant at -400V. In the case of the A type photoreceptor, even when the second recording voltage 19 was changed, there was no significant change, and a sufficient print density could be obtained. On the other hand, the B type photoreceptor has a large change with respect to the second recording voltage 19 and has a low print density.

Considering the above in detail, assuming that the first recording voltage 14 is constant at −400 V and the second recording voltage 19 is +20 V (the thickness of the photoconductive layer is about 13 μm), Is about 29 V / cm during the first development and about 1.6 V / cm during the second development. In the case of B type photoreceptor,
The carrier mobility of the photoreceptor is high for both the first and second developments.
The density is as large as 10 ⁻⁶ cm ² / V · s or more, and the printing density is low because the latent image charge is lost as described in the related art.

On the other hand, the A type photoreceptor has a large carrier mobility of 10 ⁻⁶ cm ² / V · s or more during the first development, and the generated photocarriers move quickly toward the photoreceptor surface. At the time of the second development, the carrier mobility is 10 ⁻⁷ cm ² / V · s or less, so that the electric charge in the photoconductor is very difficult to move.
Therefore, the latent image charge generated during the first development is held near the surface of the photoconductor, and causes the toner to adhere to the photoconductor with a strong electrostatic force. Therefore, the print density increases.

From the above experimental results, it is understood that the photoconductor having the carrier mobility dependent on the electric field is useful for improving the print density. Further, it can be seen that if the difference between the carrier mobilities at the time of the first development and the second development is one digit or more, printing with sufficiently high density can be performed.

In another embodiment, as the photoconductive layer of the photoconductor, a photoconductor in which a plurality of photoconductive layers having small electric field dependence and different carrier mobilities are stacked is used.

 FIG. 10 shows a concrete example.

In the figure, as shown in FIG. 11, this photosensitive drum 21A is made of ITO (indium oxide) on a transparent substrate 21a of a glass substrate.
A transparent conductive layer 21b of a vapor-deposited film is provided, and as a photoconductive layer, a charge generating photoconductive layer 21c, a first charge transporting photoconductive layer 21d having a large carrier mobility, and a carrier mobility one digit higher than the first one. This is a function-separated type organic photoconductor in which the second small charge transporting photoconductive layer 21e is laminated. The thickness of the first charge transport photoconductive layer 21d having a large carrier mobility is about 12 μm,
The thickness of the second charge transporting photoconductive layer 21e having a small carrier mobility was about 8 μm. The photoreceptor material used was a phthalocyanine-based material for the charge-generating photoconductive layer 21c, and a hydrazone-based material for the charge-transporting photoconductive layers 21d and 21e. This is achieved by changing the amount of The carrier mobility of the first charge transporting photoconductive layer 21d is as large as 10 ^-6 to 10 ^-5 cm ² / V · s.
The carrier mobility of 21e was set to be 10 ⁻⁷ cm ² / V · s or less.

The transparent conductive layer 21b of the photosensitive drum 21A as described above is connected to the ground, and the photosensitive drum 21A itself is transported by a drum drive system (not shown) in the direction of the arrow in the figure. 13
Is composed of a first magnetic brush developing machine, an inner magnet roller and an outer sleeve, and the sleeve is rotatable. The first magnetic brush developing machine 13 has a first recording voltage 14 having a polarity opposite to the photocarrier polarity of the charge generating photoconductive layer 21c.
Is applied. A hole transfer type was used for the photoconductive layer of this example. Therefore, a negative voltage is applied to the first magnetic brush developing device 13 by the first recording voltage 14.
This voltage is suitably from -100V to -600V. The first magnetic brush developing machine 13 is filled with a developer 15 in which a conductive carrier and an insulating toner are mixed, and is conveyed by rotation of a sleeve.

The first magnetic brush developing machine 13 with the photosensitive drum 21A interposed therebetween
Image exposure means 16 is arranged at a position facing the image exposure means. This image exposure means 16 emits light in accordance with an image signal
It is composed of an LED array and a Selfoc lens array that collects image light from the LED array. Reference numeral 17 denotes a toner image, in which toner is still attached to the background.

Reference numeral 18 denotes a second magnetic brush developing machine, which is provided downstream of the first magnetic brush developing machine 13 in the moving direction of the photosensitive drum 21A. The second magnetic brush developing machine 18, like the first magnetic brush developing machine 13, includes a magnet roller and a sleeve, and the sleeve is configured to be rotatable. Further, the second magnetic brush developing machine 18 has a first recording voltage.
A second recording voltage 19 having a polarity opposite to that of 14 is applied. The appropriate second recording voltage 19 is 0 to + 100V. The second magnetic brush developing machine 18 includes a first magnetic brush developing machine.
13 is filled with the same developer 20 as the filled one, and is conveyed by rotation of the sleeve.

The arrangement of the two magnetic brush developing machines is such that the second magnetic brush developing machine 18 is provided above the first magnetic brush developing machine 13.
As a result, the toner collected by the second magnetic brush developing device 18 can be refilled into the first magnetic brush developing device 13 by its own weight and reused.

Reference numeral 21 denotes a toner image formed on the photosensitive drum 21A. 22 is a recording paper. Reference numeral 23 denotes a transfer conductive rubber roller to which a voltage (+200 V to +600 V) is applied by a power supply 24. Reference numeral 25 denotes a toner image electrostatically transferred to the recording paper 22, which is fixed on the recording paper 22 by a heat roller fixing device 26 to form a semi-permanent recording image 27.

28 is a residual toner image remaining on the photosensitive drum 21A after transfer. Reference numeral 29 denotes a static elimination light source for removing the charge of the residual toner image 28 and the latent image charge in the photoconductive layer. Numeral 30 denotes a toner image which has lost static electricity due to static elimination.

 Next, an image recording procedure will be described.

The photosensitive drum 21A is transported in the direction of the arrow, and
And the second magnetic brush developing machines 13 and 18 are rotated to transport the respective developers 15 and 20 in the directions of the arrows, and the first and second recording voltages 14 and 19 are applied. The exposure unit 16 exposes the photoreceptor 21A to an image. Then, photocarriers are generated in the charge-generating photoconductive layer 21c, and holes move in the charge-transporting photoconductive layers 21d and 21e in the direction of the photoconductor surface to become latent image charges.

For this reason, the capacitance of the hole conductive layer apparently increases in the exposed portion, so that the amount of adhered toner increases, and a toner image 17 having a certain level of contrast is formed between the exposed portion and the non-exposed portion.

Next, the photosensitive drum 21A is moved, and the second magnetic brush developing device 18 removes excess toner adhering to the non-exposed portion of the toner image 17 formed in the first magnetic brush developing device 13. Collect by electric power. At this time, the toner in the exposed portion is also slightly recovered. However, the latent image charge in the exposed area has a relatively low reverse voltage 19 and a second charge transporting photoconductive layer.
21e is a state where the carrier mobility is small and the charge is hard to move. Therefore, since the electrostatic binding force between the latent image charge and the toner charge is maintained, most of the toner is
A toner image 21 is formed on A.

Next, the toner image 21 is electrostatically transferred to the recording paper 22 using a conductive rubber roller 23 for transfer. Transferred toner image 25
Is fixed on the recording paper 22 by a heat roller fixing machine 26, and a semi-permanent recorded image 27 is obtained.

On the other hand, the residual toner image 2 remaining on the photosensitive drum 21A after the transfer
8 is neutralized using the neutralizing light source 29. The residual static-eliminated toner image 30 from which the static electricity has been removed is a magnetic force of the magnetic brush developing machines 13 and 18,
It is collected by the scraping of the developers 15 and 20 and the electrostatic force by the recording voltages 14 and 19, and is reused. In the next image formation, the simultaneous operation of collecting the residual static elimination toner image 30 and the next image formation is performed by the image exposure unit 1 with the photosensitive drum 21A interposed therebetween.
Since there are 6 and 2 magnetic brush developers facing each other, there is no problem.

In this embodiment, the CTL of the function-separated type organic photoreceptor has a two-layer structure having different carrier mobilities. By using a material having a small carrier mobility for the upper second charge transporting photoconductive layer 21e, the second charge transporting photoconductive layer 21e is formed.
e functions as a latent image charge trap layer, and makes it difficult for the latent image charges to move. Therefore, the electrostatic binding force between the latent image charge and the toner charge is maintained, and a clear print with a large print density can be obtained.

As described above, according to the present embodiment, no corona discharger that generates ozone harmful to the human body and requires a high voltage of several KV is used. In addition, since the number of steps is smaller than that of the Carlson process and the recording process is simple, the apparatus can be downsized. Furthermore, the recorded image formed on the recording paper also
A clear recorded image with a large print density was obtained.

In the embodiments described above, the photoreceptor material is an organic material such as a phthalocyanine-based material, PVK-TNF, an azo-based dye, or a thiapyrylium dye, and an inorganic material such as a selenium-based photoreceptor, a-Si. However, any photoconductor having the above characteristics can be used.

In the embodiment, the photosensitive member is used in the form of a drum,
It is needless to say that the same effect as described above can be obtained even when used in the form of a film.

As an image recording process, in the embodiment, the residual toner remaining on the photoreceptor after the transfer was collected by a magnetic brush developing machine. However, a recording process of removing the residual toner with a brush cleaner or a blade cleaner may be used. ,
Although the roller transfer method is used in the embodiment, the same effect as in the embodiment can be obtained by using the corona transfer method.

Further, the present invention is not limited to image recording by a printer or the like as in the above-described embodiment, and can be sufficiently effective even when applied to a display device for directly viewing a toner image on a photoconductor without a transfer step. it can.

〔The invention's effect〕

As described above, according to the present invention, a clear toner image having a large print density can be obtained in an image forming apparatus that performs image exposure from the rear surface of a photoconductor and toner development simultaneously.

[Brief description of the drawings]

1 (a) and 1 (b) show the behavior of a photocarrier according to the principle of the present invention, FIG. 2 shows the characteristics of the photoreceptor used in the present invention, FIG. 3 is an explanatory view of an embodiment of the present invention, and FIG. FIG. 5 is a cross-sectional view of the photosensitive drum of FIG. 3, FIG. 5 is a characteristic of the photosensitive member used in the embodiment of the present invention, FIG. 6 is a comparison of printing between two photosensitive members, FIG. 9 (a) and 9 (b) show the behavior of the photocarrier in the present invention, FIG. 10 is an explanatory view of another embodiment of the present invention, and FIG. 11 is the photoreceptor of FIG. FIG. 12 is a schematic view of a conventional technology, FIG. 13 is a characteristic of a conventionally used photoconductor, and FIGS. 14 (a) and (b) are behaviors of a photocarrier in a conventional photoconductor. . In the figure, 1,11A and 13A are photosensitive members, 1a and 12a are transparent substrates, 1b and 12b are transparent conductive layers, 1c is a photoconductive layer, 2,13 is a first magnetic brush developing machine, 2a is a magnet roller 2b Is a sleeve 3, 14 is a first recording voltage (voltage application means), 4, 10, 15, 20 is a developer, 5, 16 is an image exposure means, 6 is a latent image charge, 7, 11, 17, 21 is A toner image; 8,18 a second magnetic brush developing machine; 9,19 a second recording voltage (voltage applying means); 11c, a first photoconductive layer; 11d, a second photoconductive layer; 21A is a photosensitive drum, 12c, 13c, and 21c are charge generation photoconductive layers, 12d is a charge transport photoconductive layer, 13d and 21d are first charge transport photoconductive layers, and 13e and 21e are second charge transport photoconductive layers. Layer, 22 is recording paper, 23 is a conductive rubber roller, 24 is a power supply, 25 is a transfer toner image, 26 is a heat roller fixing machine, 27 is a recorded image, 28 is a residual toner image, 29 is a static elimination light source, and 30 is residual static elimination. 3 shows a toner image.

Claims (2)

(57) [Claims] 1. A photoconductor (1) comprising a transparent substrate (1a), a transparent or translucent conductive layer (1b) and a photoconductive layer (1c), and a photoconductive layer of the photoconductor (1). A first magnetic brush developing machine (2) arranged on the (1c) side and filled with a developer; and between the first magnetic brush developing machine (2) and the conductive layer (1b) of the photoconductor (1). A first voltage applying means (3) for applying a voltage to the photosensitive member (1) on the transparent substrate (1a) side of the photosensitive member (1), and
Is provided at a position facing the magnetic brush developing machine (2),
Image exposure means (5) for performing image exposure based on image data
And the photoconductor (1) of the first magnetic brush developing machine (2).
A second magnetic brush developing machine (8) arranged downstream of the moving direction of the photoconductor, and the first voltage between the second magnetic brush developing machine (8) and the conductive layer (1b) of the photoconductor (1). Second voltage applying means (9) for applying a low voltage with a polarity opposite to that of the applying means (3);
The photosensitive member (1) sandwiched between the first magnetic brush developing machines (2) facing each other by image exposing means (5) is image-exposed, and at the same time, the first magnetic brush developing machines (2) The first development which performs the toner development, and the second development which collects the toner in the background in the second magnetic brush developing machine (8) are performed, and the toner image (7) is formed on the photoconductor (1). In the image forming apparatus, the photoconductive layer (1c) of the photoreceptor (1) exhibits a large carrier mobility at the time of the first development and a carrier mobility which is at least one digit smaller at the time of the second development than at the time of the first development. An image forming apparatus using a photoconductor (1) showing the following. 2. A photoconductor comprising a transparent substrate (1a), a transparent or translucent conductive layer (1b) and a photoconductive layer, and a developer disposed on the photoconductive layer side of the photoconductor and filled with a developer. A first magnetic brush developing machine (2), and first voltage applying means (3) for applying a voltage between the first magnetic brush developing machine (2) and the conductive layer (1b) of the photoconductor.
Image exposure means (5) provided on the transparent substrate (1a) side of the photoreceptor and at a position facing the first magnetic brush developing machine (2), and performing image exposure based on image data; A second magnetic brush developing machine (8) disposed downstream of the first magnetic brush developing machine (2) in the moving direction of the photoconductor, and a second magnetic brush developing machine (8) and a photoconductor. A second voltage applying means (9) for applying a low voltage with a polarity opposite to that of the first voltage applying means (3) between the conductive layers (1b), and facing each other by an image exposing means (5). The photosensitive member sandwiched between the first magnetic brush developing machines (2) is image-exposed,
And a second magnetic brush developing machine (8), which performs toner development with a magnetic brush developing machine (2), and a second magnetic brush developing machine (8), which collects toner in the background. In the image forming apparatus for forming a toner image (7) thereon, the photoconductive layer is composed of at least two layers having low electric field dependence and different carrier mobilities, and a transparent conductive layer (1b).
A photoconductor (11A) comprising a photoconductive layer (11c) having a high carrier mobility on the side and a photoconductive layer (11d) having a carrier mobility lower by one digit or more than that is used. Image forming device.