JPH0460559A - Image forming device - Google Patents

Abstract

PURPOSE:To properly expose an image without receiving the effect of residual developer by making a substrate in the inside of an image carrier of a light transmitting substrate and making an exposure part exposing the image face to the light transmitting substrate side. CONSTITUTION:A developing part 2, an electrostatic charging brush 4, an expo sure device 5 and a transfer roller 6 are provided against a photosensitive drum 1. Then, a fixing device is provided above the roller 6. The drum 1 is obtained by forming a transparent electrical conductive layer, for example, an aluminum vapor-deposited thin film 12 on a transparent glass substrate 11 and forming an electric charge generation layer 13 and an electric charge transportation layer 14 on it. In such a way, the image carrier is electrostatically charged from the outside surface side thereof by an electrostatic charge device. Besides, the image is exposed without receiving the effect of the residual devel oper from the inside light transmitting substrate side and an electrostatic latent image is formed. The latent image is developed by a developing device and made a visible image. Besides, the visible image is transferred to a transfer material and fixed. Thus, the image is properly exposed without receiving the effect of the residual developer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus such as an electrophotographic printer or a copying machine.

[Conventional technology]

Conventionally, this type of image forming apparatus uses a charging device to charge the outer surface (
An electrostatic latent image carrier charged so that its surface (surface) has a negative potential is exposed to light corresponding to the image to be copied or printed, thereby increasing the electrostatic latent image formed on the image carrier. The image is developed into a visible image by a developing device, and this visible image is transferred onto a transfer material and fixed.

In this case, all the developer on the electrostatic latent image carrier is not transferred to the transfer material, and the transfer efficiency is usually 80 to 90%.
Approximately 10 to 20% of the developer remains without being transferred. This residual developer is generally removed by a cleaning device.

As the cleaning device, there are known types such as a web rubbing type, a fur brush type, a roller type, and a blade type.

However, the conventional cleaning device has the following problems.

- The existence of a cleaning device limits the ability to make image forming apparatuses smaller and cheaper.

(2) It is not always possible to remove the residual developer sufficiently, especially when the developer is small-diameter, spherical toner, and it is difficult to remove it.

(2) When the removed developer is discarded, there is a large loss of the developer, and when it is to be reused, a separate means must be added to return it to the developing device.

(2) Whether the removed developer is disposed of or returned to the developing device, a container for once collecting the removed developer and a space for its installation are required, which increases the size of the image forming device.

(2) The surface of the electrostatic latent image carrier is abraded due to contact with the cleaning member, and the life of the carrier is shortened accordingly.

In order to solve these problems related to the leaning device, an image forming apparatus has been proposed in which the residual developer is collected by the developing device.

[Problems to be Solved by the Invention] However, when the residual developer is collected by the developing device, there is a new problem.

That is, when the electrostatic latent image carrier is imagewise exposed before the residual developer reaches the developing device, there is a risk that the residual developer may interfere with proper exposure. In particular, when the transfer efficiency deteriorates and the amount of residual developer increases, missing portions may occur in the final image G.

As a method to solve this problem, Japanese Patent Application Laid-Open No. 6420587
As disclosed in the above publication, a method has been proposed in which a memory removing member is provided in contact with the image carrier and disturbs the residual developer thereon before exposure.

However, in the method of providing a memory removal member, the member must be provided separately, which increases the cost accordingly.

In addition to the above, as disclosed in Japanese Unexamined Patent Publication No. 1-94377, it has also been proposed that the amount of light irradiated onto the image carrier by the exposure means be four times or more the half-exposure amount of the image carrier. .

In the present invention, the outer surface of an electrostatic latent image carrier is charged by a charging device, imagewise exposed to form an electrostatic latent image on the outer surface of the image carrier, and the latent image is developed by a developing device to form a transfer material. In the image forming apparatus, the developer is transferred to the image carrier, and after the transfer, the developer remaining on the image carrier is removed by the developing device,
It is an object of the present invention to make it possible to perform appropriate image exposure without being affected by residual developer without the need for the memory removal member or the adjustment of the exposure amount, thereby making it possible to obtain good images. shall be.

[Means to solve the problem]

The image forming apparatus of the present invention that achieves the above object is characterized in that the inner substrate of the image carrier is a translucent substrate, and the exposure section for performing the image exposure is made to face the translucent substrate side. .

(Function) According to the apparatus of the present invention, the image bearing member is charged from the outer surface side by the charging device, and imagewise exposed from the inner transparent substrate side without being affected by residual developer, thereby forming an electrostatic latent image. is formed, and this latent image is developed by a developing device to become a visible image, and this visible image is transferred to a transfer material and fixed.

After the transfer, the developer remaining on the image carrier is re-charged by a charging device from above, and then the non-image portion is collected by the developing device.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

The first part shows a schematic configuration of a printer P which is an embodiment of the present invention, FIG. 2 shows a part of the printer shown in FIG. 1 in an enlarged manner, and FIG. It shows the structure of

This printer P is equipped with a photosensitive drum 1 that is driven to rotate clockwise in the figure, and a developing section 2, a charging brush 4, an exposure device 5, and a transfer roller 6 are provided to the drum. A fixing device 7 is provided above the fixing device 6 .

As shown in FIG. 3, the photosensitive drum 1 includes a transparent conductive layer (for example, an aluminum vapor-deposited thin film) on a transparent glass substrate 11.
12, and CGLI3 (charge generation layer, approximately 0
．． 2μm or less) and CTL14 (charge transport layer, approx.
0 μm or less).

The charging brush 4 is supported by a protruding arm portion 20 formed integrally with the developing section 2 and is in contact with the photosensitive drum 1 .

These developing section 2 and charging brush 4 form a charging and developing unit A, which is detachable from the printer body.

The developing section 2 includes a drive roller 22 supported by a unit casing 2A and driven to rotate counterclockwise in the figure, and a flexible developing sleeve 2 having an inner diameter slightly larger than the outer diameter of the roller.
1 is fitted onto the outside, and both ends of the sleeve are pressed against the drive roller 22 from the inside of the casing 2A by the pressure contact heald member 27 to form a slack portion 210 on the opposite side, and this slack portion is brought into contact with the photoreceptor drum 1. It is something that The width of this contact nip is about one cylinder or more, preferably about 1.5 mm.
That's all. Further, a metal regulating blade 24 is in contact with the developing sleeve 21 inside the casing 2A.

The developing sleeve 21 is a nickel sleeve manufactured by electroforming, and has a thickness of about 35 μm. The regulating blade 24 is made of stainless steel and has a thickness of 0.1 mm.
The free length is 18 holes, and the pressing force on the developing sleeve is 3 g/
It is mm.

A non-magnetic component insulating toner 3 as a developer is housed in the unit casing 2A, and the toner is agitated by agitators 25 and 26 which are driven to rotate clockwise in the figure, while being moved onto the toner conveying roller 23. and is supplied onto the sleeve 21 by rotation of the roller 23 in the counterclockwise direction in the figure.

The developing sleeve 21 rotates as the drive roller 220 rotates.
The regulating blade 24 rotates in the same direction as the driving roller due to the frictional force, while the regulating blade 24 frictionally charges the toner 3 and deposits a certain amount onto the developing sleeve 21 . In this example, the adhesion amount M/S of the toner 3 is approximately 0.6 mg/cr! +, charge amount Q/M = approximately -20 μc/g. The developing sleeve 21 transfers this toner 3 to the photosensitive drum 1 by its rotation.
It is sequentially supplied to the contact area with the

-1 (KV) is applied to the charging brush 4 from a power source (not shown) within the printer body, thereby making it possible to charge the surface of the photosensitive drum 1 to about -600 (V).

On the other hand, a developing bias voltage of about -250 (V) is applied to the developing sleeve 21 from a power supply (not shown) inside the printer body, and this bias voltage causes the toner 3 to adhere to the electrostatic latent image on the photoreceptor drum 1. I can do it.

The exposure device 5 utilizes a generally known semiconductor laser, and is disposed within the photosensitive drum 1 and faces the glass substrate 11 of the drum 1 .

The device 5 applies laser irradiation to the surface of the photoreceptor drum 1, which is charged to about -600 (V), to about -50 (V) in the image area.
The light is adjusted to lower the temperature to V).

In FIG. 1, numerals 81 and 82 each represent a pair of paper guide rollers.

According to the printer P described above, the surface of the photoreceptor drum l, which is rotationally driven in the clockwise direction in the drawing, is uniformly charged to a surface potential of about -600 (V) by the charging brush 4, and then the glass is charged by the exposure device 5. Image exposure is performed from the base 11 side, and an electrostatic latent image is formed. The surface potential of the exposed portion drops to about -50 (V). The electrostatic latent image thus formed is applied at a developing bias voltage of about -25 in the developing section 2.
It is developed after 0 (V) and becomes a toner image. In this development, the toner 3 on the developing sleeve 21 adheres to the electrostatic latent image at a developing gear potential Δ■ - about 200 (V).

Toner image 31 formed in this way (see FIG. 2)
is paper 9 supplied from a transfer paper supply means (not shown).
The image is transferred by a transfer roller 6, fixed by a fixing device 7, and then discharged.

However, all of the toner on the photosensitive drum 1 is not transferred onto the paper 9 by the transfer roller 6;
20% of the toner remains on the photosensitive drum 1 as residual toner. This residual toner 32 (see FIG. 2) is charged by a charging brush 4, and further subjected to image exposure by an exposure device 5 if necessary, and then reaches the developing section 2 again. will be collected.

In this case, depending on the potential gap between the photoreceptor drum surface potential and the sleeve potential in the developing area, the toner is transferred to the developing sleeve 21 side with a difference of about 350 (V) for the non-image area, and toner for the image area (character area). is transferred to the photoreceptor 1 side with a difference of about 200 (V), and unnecessary residual toner 32 is substantially cleaned.

During the process, the charging brush 4 passes the residual toner 32 attached to the photoreceptor drum 1, but it captures paper dust depending on the density of the brush bristles, thereby preventing paper dust from entering the developing section 2. . Furthermore, when the residual toner 32 passes through the charging brush 4, it collides with each brush bristle and its position is disturbed, and as a result, the charging brush 4 uniformly charges the entire surface of the photoreceptor drum.

Further, when image exposure is performed after charging, it is performed from the glass substrate 11 side of the photoreceptor drum 1 where residual toner 32 does not exist, so that the exposure is appropriately performed without being affected by the residual toner 32.

In order to clearly understand the difference between the conventional exposure method from the surface of the photoreceptor drum 1 and the exposure method from the photoreceptor drum base 11 side in this embodiment, a pattern shown in FIG. 5 is printed and the two are compared. did.

That is, first, a solid black image X was printed, and then a line image Y was printed. The state of the line image Y at this time is shown in Part 6 (a) for this example, and in Figure 6 (b) for the conventional method, and the charge disappearance process is shown in Figure 3 for this example. The conventional method is also shown in No. 40.

As can be seen from this, when exposure is performed from the photosensitive drum base 11 side, carrier generation within the photosensitive layer is divided according to the exposure amount and exposure width, as shown in FIG. In the method of exposing the surface of the photoreceptor, as shown in Fig. 4, the image exposure is blocked by the area where untransferred toner (residual toner) exists, and the surface charge is not dissipated properly, as shown in Fig. 6(b). As shown in Figure 611D(a), the line width was narrower than in the case of this example shown in 611D(a), and toner missing portions occurred within the lines.

The charging brush 4 itself has a very simple structure and does not require an expensive high-voltage power source required for a corona charger, so the charging and developing unit I-A as a whole can be manufactured with a simple structure and at low cost. The charging brush 4 also has the advantage that it does not generate ozone, unlike a corona charger.

Furthermore, when the charging brush 4 and the developing section 2 are integrated into a unit as in the embodiment, maintenance related to adhesion of paper dust etc. to the charging brush 4, deterioration of toner in the developing section 2, mixing of paper dust, replenishment of toner, etc. This can be done extremely easily and all at once by replacing the unit 7, and as a whole it is possible to provide stable images over a long period of time.

〔Effect of the invention〕

As explained above, according to the present invention, the outer surface of an electrostatic latent image carrier is charged by a charging device, and then imagewise exposed to form an electrostatic latent image on the image carrier, and the latent image is transferred by a developing device. In an image forming apparatus in which the image is developed and transferred to a transfer material, and after the transfer, the developer remaining on the image carrier is removed by the developing device, conventionally proposed memory removing members and exposure amounts are Without the need for adjustment, appropriate image exposure can be performed without being affected by residual developer, and thereby good images can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a printer according to an embodiment of the present invention, and FIG.
The figure is an enlarged view of a part of the printer shown in Figure 1, Figure 3 is an explanatory diagram of the structure of the photoreceptor drum, Figure 4 is an explanatory diagram of the conventional exposure method, and Figure 5 is an image according to the embodiment of Figure 1. FIG. 6, an image pattern diagram used to examine the formation state, is a comparison diagram of the line image formation state between the exposure method of the embodiment and the conventional exposure method. P...Print...Photosensitive drum 11...Glass substrate A...Charging and developing unit 2...Developing section 3...Toner 31...Toner image 32...Residual toner 4...・Charging brush 5...Exposure device 6...Transfer roller 7...Fuser Applicant Minolta Camera Co., Ltd. Figure (b)

Claims (1)

[Claims] (1) After the outer surface of the electrostatic latent image carrier is charged by a charging device, an electrostatic latent image is formed on the image carrier by image exposure, and the latent image is developed by a developing device and transferred to a transfer material. In the image forming apparatus, in which the developer remaining on the image carrier is removed by the developing device after the transfer, the inner substrate of the image carrier is a light-transmitting substrate, and the image exposure is performed. An image forming apparatus characterized in that an exposure section for performing exposure faces the light-transmitting substrate side.