JP2967551B2 - Back exposure equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a back exposure apparatus in which an exposure means is provided in a photoconductor, and more particularly to a back exposure apparatus capable of smoothly forming an image even when an insulating toner or a high-resistance toner is used. To provide.

[0002]

2. Description of the Related Art Exposure means for generating a light output corresponding to image information is inserted in a photosensitive drum in which a light-transmitting conductive layer and a photoconductive layer are conventionally laminated on a light-transmitting support. At the same time or immediately after forming the latent image on the photoconductor layer by converging the light output of the exposure unit and immediately thereafter, the latent image is converted into a visible image through a developing unit disposed opposite the photosensitive drum. An image forming apparatus is known which is configured to transfer the toner image to plain paper via a transfer roller or other transfer means after forming the toner image. (Hereinafter referred to as back exposure apparatus)

In this type of image forming apparatus, in order to further simplify the structure and prevent ozone generation and the like, and to prevent ground fogging, the image forming apparatus faces the photosensitive drum without providing an independent charger. The conductive magnetic toner is carried on the developing sleeve arranged in the manner described above, and a so-called magnetic brush-like toner reservoir is provided immediately before the developing position by using a fixed magnetic pole or other magnetic force included in the sleeve, and the toner reservoir is provided. Almost at the same time as charging the photoconductive layer on the surface of the photoconductor drum while rubbing the photoconductor drum, an exposure image formed using an exposure head included in the drum is formed.
The image forming apparatus is configured to visualize an image using a developing bias applied from the developing sleeve side and to form a predetermined image.

[0004]

Therefore, it is premised that the toner used in the above-mentioned apparatus is a conductive toner. However, when the conductive toner is used, the electrostatic transfer means by corona discharge like the insulating toner is used. It is not possible to use a transfer roller, so a transfer roller is generally used, and a transfer bias,
The transfer efficiency is increased by applying heat or magnetic force at the same time, but the resistance value on the recording paper side is liable to fluctuate due to moisture and other environmental factors, so stable and smooth transfer cannot be performed, resulting in high image quality. However, it has a disadvantage that it is difficult to form a reliable image.

In order to solve such a disadvantage, a two-component developer composed of a combination of an insulating toner and a conductive carrier (Japanese Patent Laid-Open No. 22145/1985) and a combination of a conductive toner and an insulating toner are used. However, none of them have been put to practical use because it is difficult to uniformly charge the photosensitive drum side.

[0006] In addition, while maintaining the insulating properties until exposed,
An apparatus using a photoconductive toner that converts into a conductive toner by exposure (Japanese Patent Application Laid-Open No. 1-196076) has also been proposed. However, in such an apparatus, the toner cost becomes extremely large and the stability of the toner is problematic. There is still not practical.

Further, as a technique similar to the present invention, first and second magnetic brush developing means are arranged along the moving direction of the photosensitive member, and the recording voltage to be applied to the first developing means by the second developing means is determined. The developing voltage of the opposite polarity can be applied.
A predetermined toner image is carried on the photoreceptor side by performing development almost at the same time as exposure by the magnetic brush developing means, and then a developing voltage of the opposite polarity applied to the second developing means is applied to the background portion. It is configured to pull back the attached toner.
However, such a configuration merely obtains a high-contrast image and does not eliminate the difficulty of charging when an insulating toner is used.

SUMMARY OF THE INVENTION In view of the drawbacks of the prior art, an object of the present invention is to provide a backside exposure apparatus which can smoothly perform charging and development even when an insulating toner or a high-resistance toner is used. Another object of the present invention is to provide a backside exposure apparatus capable of cleaning residual toner simultaneously with charging without providing an independent cleaning unit.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the following problems and to attain stability and smoothness of charging and exposure when an insulating toner is used. That is, as described above, the developing method of the backside exposure device charges the drum surface using the toner pool, and charges the toner while the toner is in contact (sliding) with the drum surface at the developing position due to the toner pool. The toner of the charged portion (background portion) is electrically repelled by a so-called reversal development method using a developing bias on a latent image of 0 potential formed by exposing the photoconductive layer, which is being exposed, while causing electrical repulsion. Uncharged part (latent image part)
The toner is attached only to the toner. Therefore, in the above-mentioned method, the condition that the toner layer is in contact with the drum surface at the developing position is a condition for smooth development.

On the other hand, when the insulating toner is used, the necessary drum charging cannot be performed only by the rubbing of the toner pool. Therefore, an independent charging means must be provided on the upstream side in the drum moving direction. However, in such a configuration, in the above-described developing method, the charging polarity of the toner and the charging polarity of the drum are the same. Cannot be maintained, and stable smooth development is impossible.

[0011] Therefore, in the first aspect of the present invention, sensitive
Exposure means are provided inside the photoconductor, and the exposure means is moved along the photoconductor moving direction.
A charging unit and a developing unit are sequentially arranged so that they can face the photoconductor surface.
The developing means and the charging means.
Steps are connected to the developing bias and charging bias, respectively.
The charging means and the current
A resistance value of 10 ⁶ Ω so that the surface of the photoreceptor can be contacted between image means.
・ Carrying semiconductive endless toner of 10 to 10 ¹¹ Ωcm
Feed belt arranged toner transfer body was hung and the toner conveying
Or high-resistance toner between the photoconductor and the surface of the photoconductor
While holding the layer, perform exposure and development with a time lag.
It is characterized by having such a configuration.

Namely, as shown in FIG. 1, a developing unit 2
And the charging means 3 are marked with a developing bias and a charging bias, respectively.
Forming a pressurized electrically conductive roller, a developing position upstream in a separate provision of the charging unit 3 is also accessible to the resistance the the the charging means 3 in the surface of the photosensitive member 1 between the current <br/> image means 2 Value 10 ⁶ Ω
・ Carrying semiconductive endless toner of 10 to 10 ¹¹ Ωcm
A toner conveying body 4 on which a feeding belt is mounted is disposed.
Exposure and development are sequentially performed with a time lag while an insulating or high-resistance toner layer 6 is sandwiched between the photosensitive member 1 and the surface of the charged photosensitive member 1 .
This is characterized in that it is configured to perform this operation.
In a preferred embodiment of the present invention, the developing means 2 and the charging means 3 are formed of conductive rollers to which a developing bias BV and a charging bias AV are applied, respectively, and a semiconductive endless roller is formed between the rollers. Although the configuration is such that the toner transport belt 4 is mounted, the present invention is not limited to this.

The peripheral speed of the conveyor belt 4 is not particularly limited. By setting the peripheral speed at least higher than the moving speed of the photosensitive member 1, not only the amount of toner supplied to the developing position becomes larger, but also Relative rubbing speed increases, which leads to an increase in frictional charge to the toner and an increase in charge injection to the photoconductor 1 side.

The reason that the toner conveying belt 4 is formed of a semiconductive material is that a charging bias AV or a developing bias BV can be applied between the conveying belt 4 and the photosensitive member 1 by using a conductive roller on the back side. In order to form the belt 4, it is necessary to form at least a conductive material. In this case, if the belt 4 is formed of a good conductive material, a leak occurs between the charging roller 3 and the developing roller 2, which is preferable. Absent. Therefore, the present invention particularly adjusts the resistance value of the belt 4 to semiconductivity, specifically from about 10 ⁶ Ω · cm to 10 ¹¹ Ω · cm.
Set between.

[0015]

According to such a technical means, the charged insulating toner which repels each other after charging and the photoreceptor 1 are forcibly contacted, preferably rubbed, by the toner conveying means (hereinafter referred to as the conveying belt 4). While being guided to the developing position, smooth and stable development can be performed even in a back exposure apparatus employing the above-described reversal developing method.

According to the invention, since the insulating toner can be used, the transfer of the toner image can be stably performed without being influenced by environmental factors on the recording paper side. High quality image formation can be easily performed.

In the present invention, since the toner layer 6 is positively in contact with the photoreceptor 1 from the charging position to the developing position, it is not always necessary to perform development almost simultaneously with exposure as in the conventional apparatus. The exposure position can be set at an arbitrary position within the holding range of the toner layer 6, and the degree of freedom in assembly and design is increased accordingly.

Further, in the present invention, since the toner layer is always in contact from the charging position to the developing position, in other words, it is not necessary to form a toner pool or the like due to the fixed magnetic pole. Coloring is easy because non-magnetic toner can be used sufficiently.

[0019] As shown in FIG. 1 according to the present invention, the residual toner over adhering to the latent image forming portion of the photoreceptor 1 surface after the transfer (non-charging portion) is fed back to the charging position, the latent to charge together also image forming unit, electrostatically biasing <br/> adhesion of the residual toner over to the residual inter toner over the charged surface of the photosensitive member 1 is repel is released, Thus also the subsequent Due to the rubbing between the conveyor belt 4 and the surface of the photoreceptor 1, the surface of the photoreceptor 1 can be cleaned by being mixed with a newly supplied toner. This eliminates the need for providing an independent cleaning means.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. Not just.

FIG. 2 shows a cross-sectional structure of a printer according to an embodiment of the present invention. A paper cassette 11 is inserted, and a recording material conveyance path 10 is formed substantially in parallel with the cut surface from the insertion position. Roller 13, transfer roller 14, fixing roller pair 15
A pair of paper discharge rollers 16 are arranged, and a wall surface of the frame body facing the paper discharge roller pair 16 is opened so that paper can be discharged from the opening onto a paper discharge tray 17 attached to the frame body.

On the other hand, the photosensitive drum 1 is provided on the inner side of the transport path 10 so as to be able to face the transfer roller 14 with the transport path 10 interposed therebetween.
Are arranged respectively.

Next, these members will be described in detail. The transfer roller 14 uses a conductive roller to increase the transfer efficiency, applies a transfer bias having a polarity opposite to the charging potential of the toner, and uniformly presses the peripheral surface of the photosensitive drum 1 to synchronize with the drum. To be rotatable. The transfer roller 14 does not need to be formed of a conductive material because the toner to be transferred is an insulating toner, and it is possible to use a high-resistance or semiconductive roller. .

As shown in FIG. 1, a photosensitive drum 1 has a light transmitting conductive layer 1b and a photoconductive layer 1c (for example, positive amorphous silicon) grounded on a hollow sleeve-shaped light transmitting support 1a. ) as well as formed by laminating, said photoconductor
An exposure head 21 inserted in the drum 1 is formed by an LED array 22 for generating a light output corresponding to image information and a converging lens 23 (product name: Selfoc lens), and an image forming position of the lens 23 Is formed on the photoconductor layer 1c located on the focal line connecting the axes of the photosensitive drum 1 and the developing sleeve 2. The image forming position of the exposure head 21 is not particularly limited as long as it is between the charging position and the developing position as described above.

The developing unit 18 has an opening at a portion facing the second quadrant position of the photosensitive drum 1 and a toner container 19 containing an insulating magnetic toner. Along the charging roller 3 and the developing sleeve 2, which are arranged so as to be able to face the drum in order from below, and the driving roller 26 meshed with the shaft gear 25 of the motor together with the two rollers 2, 3. And a toner transport belt 4.

The toner conveying belt 4 is formed of an endless urethane or polyester belt 4 having a thickness of 1 μm to 1 mm and a resistance value of 10 ⁶ Ω · cm or more. And a plate spring-shaped applicator 29 that presses against the peripheral surface of the toner conveying belt 4 is provided, and while applying a weak charge to the insulating toner using frictional charge between the applicator 29 and 1000 μm
Hereinafter, the toner layer 6 whose thickness is regulated can be conveyed to the charging roller 3 side.

The surface of the belt 4 has a lattice-shaped hair line (fine irregularities) to facilitate the toner conveyance. The peripheral speed of the toner conveying belt 4 may be set to be the same as the peripheral speed of the photosensitive drum 1, but more preferably, the peripheral speed of the photosensitive drum 1 is increased in order to enable a sufficient amount of toner supply and smooth charging. It is set to a larger value, specifically, about 1 to 2.5 times.

On the other hand, each of the charging roller 3 and the developing roller 2 is formed of a conductive rubber roller having a resistance value of 10 ⁴ Ω · cm or less and a rubber hardness of 60 ° or less, but is not limited thereto. It is also possible to use a foaming urethane resin into which carbon or metal powder is kneaded, or a conductive material such as a silicon resin. The developing roller 2 is not limited to the above-mentioned roller, and uses a developing sleeve 2 having a large number of float electrodes formed on the surface of a dielectric layer.
It may be configured to develop by a developing method.

The charging roller 3 is configured to be capable of applying an alternating electric field, more specifically, an alternating bias AV having a rectangular wave having a potential level of about 1000 V from peak to peak and a frequency of 1.5 KHz. In this case, a DC bias having a bias value of 30 to 200 V may be used as the bias power source. However, it is preferable to apply an alternating electric field because charging the insulating toner becomes easy.

On the other hand, an alternating electric field can be applied to the developing roller 2 in the same manner as described above, more specifically, an alternating bias BV having a potential level of about 400 V from peak to peak and having a rectangular wave having a frequency of 1.5 KHz. To be configured. Also in this case, a DC bias having a bias value of 0 to 200 V may be used, but application of an alternating electric field facilitates development of the insulating toner, and is therefore preferable.

Next, the operation of the embodiment will be described with reference to FIG. First, when the layer thickness is regulated by the applicator 29 and the insulative toner carried on the conveyor belt 4 is guided onto the charging roller 3, the insulating toner is frictionally charged by rubbing with the photosensitive drum 1, and from the back side thereof. Since the charging bias AV is applied via the charging roller 3, charges are injected into the photoconductive layer 1c on the surface of the photosensitive drum 1 and positively charged, and simultaneously, positive charges are also injected into the toner side. You.

In this state, the drum 1 and the charged toner repel each other electrically. However, the conveyor belt 4 rubs against the drum peripheral surface until it reaches the developing position. The charged toner layer is guided to the developing position while frictional charging is continued while the toner layer 6 is held between the photosensitive drum 1 and the photosensitive drum 1. In the charging step, residual toner adhering to the peripheral surface of the drum after the transfer is removed as described in the section of the operation, and a so-called cleaning function also occurs.

By exposing the photoconductive layer 1c from the inner surface of the drum using the exposure head 21 at the developing position, the potential of the exposed portion becomes low. Since an alternating developing electric field is formed via the belt 4, toner adheres to the low-potential latent image to perform predetermined development.

Then, the toner image carried on the photosensitive drum 1 by the development is transferred onto the plain paper inserted through the transfer roller 14 by the registration roller 13 at appropriate timing, and then transferred to the recording paper. The unfixed image is fixed on the image by a fixing roller 15 and is discharged onto a discharge tray 17 via a discharge roller 16. On the other hand, the residual toner after the transfer is removed when returning to the charging position as described above, and the above operation is repeated thereafter.

According to this embodiment, unlike the conventional rear exposure apparatus, charging and development are separated without performing simultaneous charging exposure / development, and the transfer from the charging position to the developing position is also performed using a transport belt. Exposure and development can be performed at a time difference or almost simultaneously with the charged toner layer in contact with the drum side, so that the above-described effects can be achieved smoothly. Note that the number of the charging rollers is not necessarily limited to one, and a similar effect can be obtained by providing a plurality of charging rollers.

[0036]

As described above, according to the present invention, even when an insulating toner or a high-resistance toner is used, an image can be formed smoothly and stably, and the residual toner can be cleaned in the charging step. For this reason, a cleaning step is unnecessary, and only a conveyance belt is interposed between two or three rollers, so that the apparatus can be easily reduced in space without increasing the size of the apparatus. And so on.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of the present invention.

FIG. 2 shows a cross-sectional configuration of the printer according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Developing means 3 Charging means 4 Toner conveying means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 15/05 G03G 15/02 101 G03G 15/08 G03G 15/09

Claims (2)

(57) [Claims] An exposure means is provided inside a photoreceptor., Photoconductor
A charging hand is provided so as to be able to face the surface of the photoreceptor along the moving direction.
With steps and developing meansBack exposure equipment,The developing unit and the charging unit are connected to a developing bias and a band, respectively.
It is formed with a conductive roller to which an electric bias is applied.
To Said Between the charging means and the developing meansSaidContact the photoconductor surface
PossibleResistance value 10 ⁶ Ω · cm-10 ¹¹ Ω · cm semiconductive
Electrified endless toner transport beltToner carrier
And the saidtonerWith the carrierSaidInsulating or high between photoconductor surfaces
Keep the time difference while holding the resistance toner layerDewlight
Back exposure device characterized in that it is configured to perform
Place. 2. The back exposure apparatus according to claim 1, wherein a peripheral speed of the conveyor belt is set to be higher than a moving speed of the photoconductor.