JPS6370238A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent toner from sticking on a no-image area by turning off an exposure source in the no-image area and holding a photosensitive body uniformly at a dark potential. CONSTITUTION:Reflecting mirrors 4 and 5 begin to move and a halogen lamp 2 is turned off as copying operation is started. The surface of the drum 6, on the other hand, is discharged electrostatically and uniformly by an exposure lamp 9 and then charged uniformly by a primary electrostatic charger 10. Then, the lamp 2 is turned off in the no-image area and the drum 6 is not exposed to any image. The photosensitive body is held at the dark potential uniformly. Then, toner forming a visual image on the drum 6 is transferred to transfer paper 12 by a transfer charger 14 which is applied with a voltage having the opposite polarity from the drum 6. This transfer paper 12 is discharged after fixation. Then the toner remaining on the drum 6 is removed by a cleaner 13 and then the drum 6 is discharged electrostatically and uniformly by being irradiated by the lamp 9.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention [Field of Industrial Application] The present invention relates to a microreader printer that performs reversal development.

[Conventional technology]

In reversal development, a developer adheres to the exposed portion of the photoreceptor to form a visible image.

However, in a microreader printer that performs reversal development, when the scanning optical system moves, part of the non-image area existing before and after the image area is also irradiated with image exposure.

As a result, developer adheres to the non-image area of the photoreceptor and scatters into the device, causing image stains, staining the charger and causing image unevenness, or staining the separation belt. There were many problems such as increased toner consumption and increased toner consumption.

Therefore, as shown in FIG. 6, conventionally a method has been adopted in which a light shielding means such as a shutter is used to prevent image exposure from being applied to the non-image area of the photoreceptor. In the non-image area, the shutter closes the slit 7 as shown by the solid line 15a,
In the zero image area where the image exposure 8 to the photosensitive drum 6 is blocked, the shutter is opened to the position indicated by the dotted line 15b by a plunger (not shown), and the image exposure 8 is irradiated onto the photosensitive drum 6.
It forms an electrostatic latent image.

[Problem that the invention seeks to solve]

However, this method has the following problems. Since the exposure lamp is turned on regardless of whether it is an image area or a non-image area, the film surface temperature rises, which tends to cause discoloration of the film, especially in diazo films and the like.

Further, a light shielding member, a plunger, etc. are required to open and close the shutter, making the structure complicated and the device expensive. Furthermore, in order to block image exposure, the location where the shutter can be installed is limited and a considerable amount of space is required.

In addition, simply blocking image exposure to non-image areas will not work.
When trying to obtain a proper image by varying the developing bias depending on the document, the potential difference between the photosensitive drum potential in the non-image area and the developing bias may be too large depending on the developing bias setting.
In the case of a high-resistance magnetic toner for the first order, reversal fog occurs, and carrier adhesion occurs for the second order. In particular, when an image is copied onto a portion of the transfer paper such as a designated area, the above-mentioned reverse fog toner adheres outside the designated area, resulting in an unsightly image on the transfer paper.

An object of the present invention is to provide an image forming method that eliminates the following drawbacks.

SUMMARY OF THE INVENTION [Means for Solving Problems] The present invention is an image forming apparatus that is a microreader printer that performs reversal development and is characterized in that an image exposure light source is turned off in non-image areas.

Further, at the same time as the image exposure light source is turned off, the developing bias may also be controlled to a predetermined value of the non-developing level.

[For production]

In the non-image areas before and after the image area, the photosensitive drum is not exposed to light by turning off the exposure light source, so the photosensitive member potential is maintained at a substantially uniform dark potential and toner adhesion is prevented.

At the same time, by switching the developing bias to a non-developing level below the photoreceptor potential in non-image areas, toner adhesion to non-image areas is prevented.

〔Example〕

The present invention will be explained below based on illustrated embodiments. 1st
The figure is a schematic diagram of a microreader printer to which the present invention is applied.

1 is a negative film that is an original, 2 is a halogen lamp for exposing the negative film 1, 3 is a projection lens for enlarging the negative film, 4 and 5 are the stations of the circumferential speed of the photosensitive drum 6, which move in the direction of the arrow. The projected image of the negative film 1 is irradiated onto the photosensitive drum 6 through the exposure slit 7 by plane mirrors arranged to face each other at right angles.

First, during the league, a projected image of a negative film 1 is enlarged and projected by a halogen lamp 2 onto a screen (not shown) via a projection lens 3.

At this time, the optical system including the reflecting mirrors 4 and 5 is at home positions 4a and 5a and is off the optical path 8, so that the photosensitive drum 6 is not exposed.

Therefore, the photosensitive drum 6 does not generate optical memory.

At the same time as the copying operation begins, the first reflecting mirrors 4 and 5 start moving and the halogen lamp 2 is turned off.

On the other hand, after the surface of the photosensitive drum 6 is uniformly neutralized by the pre-exposure lamp 9, it is uniformly charged by the primary charger 10. In the non-image area, the halogen lamp 2 is turned off and the photosensitive drum 6 is not irradiated with image exposure light, so that the photosensitive member potential uniformly maintains approximately the dark potential Vo.

In the image area, the halogen lamp 2 is turned on, and the projected image of the negative film is exposed to the photosensitive drum 6 through the projection lens 31, reflection mirrors 4 and 5, and slit, and an electrostatic latent image is formed.

The electrostatic latent image formed in the image area is visualized by toner charged to the same polarity as that of the photosensitive drum 6 in the developing device 11 .

The above description can also be applied to a cartridge (not shown) in which the photosensitive drum 6 and the primary charger 10, developer 11, etc. surrounding the photosensitive drum 6 are integrally attached.

Next, the toner visualized on the photosensitive drum 6 is transferred onto the transfer paper 12 by a transfer charger 14 to which a voltage of a different polarity than the photosensitive drum 6 is applied. This transfer paper 12 is ejected after being fixed by a fixing device (not shown). The toner remaining on the photosensitive drum 6 is removed by a cleaner 13, and then the residual charge on the photosensitive drum 6 is evenly removed by the irradiation light from the pre-exposure lamp 9.

FIG. 2 is a diagram showing the operational states of primary charging, image exposure (on/off of the rogen lamp 2), and developing bias with respect to the image area and the non-image area based on the transfer paper.

(a) The temporary copying photosensitive drum is uniformly charged, and both the image area and the non-image area are uniformly charged to the dark potential Vo.

(b), the 7-logen lamp for irradiating the image exposure is
It is on during league play, but turns off at the same time as copying starts, and turns on when it passes the leading edge of the transfer paper to expose the image. It also turns off just before the trailing edge of the transfer paper and lights up at the same time as copying is complete.

As a result of the above, image exposure is not performed at the leading edge and trailing edge of the transfer paper, and the dark potential Vo is uniformly maintained.

(C) Similarly, the developing bias is turned on at the same time as copying starts and turned off at the same time as copying ends.

At this time, a predetermined non-image bias slightly lower than the dark potential VD is applied to the non-image area, and an arbitrary bias depending on the document is applied to the image area (see the dotted line in FIG. 3).

FIG. 3 specifically shows the relative relationship between the developing bias (dotted line) and the photosensitive drum potential (solid line).

In the figure, in the image area, the literature potential V L = −+0
0V, background potential V D = -800V vs. -4
A proper image was obtained by applying a developing bias of 50V.

As is well known, this developing bias can be changed arbitrarily depending on the original.

In the non-image area, the photosensitive drum potential Vo = -800
By applying a predetermined developing bias of, for example, -700 to V, it is possible to prevent toner from adhering to non-image areas.

The developing bias of -700V in this embodiment is not limited to this, but may be set within a predetermined value range below the photosensitive drum potential of the non-image area.

Although only the DC component of the developing bias has been described, if the AC and DC components are superimposed, it is preferable not to apply the female wave component to the non-image area.

The above-mentioned on/off control of the exposure light source 2 and control of the bias potential are controlled by copy start/end signals and start/end signals of the leading and trailing non-image areas transmitted in conjunction with the transfer paper feed mechanism. , which is performed under computer control.

Figure 4 schematically shows the relationship between the developing bias, the potential difference with the photosensitive drum potential VD, and the amount of toner adhesion.The above potential difference is set to a range of about 200 V or less as the developing bias for the non-image area. This means that normal toner adhesion and reverse fog do not occur.

Figure 5 schematically shows the change in film surface temperature during continuous copying.Curve (c)) shows curve m(b) when the halogen lamp 2 is always on as in the past; These are the temperature rise curves for each film surface when the halogen lamp of the invention is turned on in the image area and turned off in the non-image area.

As is clear from the comparison of curves (a) and (b), non-ilj
By turning off the halogen lamp in the image area, it is possible to suppress the film surface temperature compared to conventional methods.

C1 Effects of the invention As mentioned above, the increase in film surface temperature can be prevented by a simple method of turning off the /h rogen lamp corresponding to the non-image area and setting the developing bias to a predetermined value for the non-image area. It is possible to suppress it.

In addition, it is possible to prevent toner from adhering to non-image areas, to form fog-free leading and trailing margins, and to easily erase parts of the image, eliminating the drawbacks of the conventional method described in the problem section above. It has the effect of

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a microreader printer to which the present invention is applied, FIG. 2 is a chart explaining the operation of the present invention, FIG. 3 is a curve diagram illustrating the relative relationship between the photoreceptor potential and the developing bias potential, and FIG. The figure is a curve diagram showing the relationship between the difference between the two potentials and the amount of toner adhesion, FIG. 5 is a curve diagram of temperature rise on the film surface during continuous copying, and FIG. 6 is a schematic diagram of a conventional example. 1... Negative film, 2... Exposure lamp, b...
Photoreceptor, 12...transfer paper. Fig. 5 Fig. 6 Fig. 1 (c) Fig. 4 +f, trG ( (-10200 (+) (v) Main optical F pay 1 sill - development, assembly as) Fig. 2 T S Fig. 3

Claims (2)

[Claims] (1) An image forming apparatus in a microreader printer that performs reversal development, characterized in that an image exposure light source is turned off in non-image areas. (2) In a microreader printer that performs reversal development, an image forming apparatus is characterized in that in a non-image area, an image exposure light source is turned off and at the same time, a development bias is also controlled to a predetermined value of a non-development level.