JPS63303364A - Reversal image forming method - Google Patents

Abstract

PURPOSE:To form a reversal image without adding additional equipment to an ordinary copying machine by developing the image part of an electrostatic latent image with a white developer in a 1st operating process and developing the image on the 1st image with a developer except the white developer in the 2nd operating process. CONSTITUTION:An original image is exposed from an exposing machine 3 to a photosensitive drum 1 to form the electrostatic latent image. A 2nd developing machine 5 is held retreated from the photosensitive body 1 and the electrostatic latent image on the drum 1 is developed by the white toner in the 1st developing machine 4 in the 1st operating process. The surface of the drum 1 including the white toner image is then electrostatically charged by an electrostatic charger 2 in the 2nd operating process. The 1st developing machine 4 is then held retreated and the charged part of the drum 1 is developed by the black toner in the 2nd developing machine 5 so that the solid black toner is superposed on the white toner image. The image is then transferred onto transfer paper 10 by a transfer charger 6. The black toner exists in the lower layer and the white toner in the upper layer on the transfer layer 10. The reversal image is, therefore, formable by the ordinary copying machine and the utilization value of the copying machine is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a reversal image forming method using an electrophotographic image forming process.

(Background of the Invention) Conventionally, league printers and the like use both positive and negative microfilm as manuscripts, so in order to obtain positive or negative images from either, a microfilm that has both regular development and reversal development functions is used. There is.

However, copying machines only have the so-called regular development copying function, which creates a positive image from a blank original.
If a negative image can be obtained from a blank original, an image with an elaborate design can be obtained, and the utility value of the copying machine will be dramatically increased.

However, if a copying machine is equipped with normal development and reversal development functions, the size and cost of the copying machine will inevitably increase.

That is, if the charging polarity of the photoreceptor drum is limited to either positive or negative, two developing units contain toners with different polarities, and these are used for normal development and reversal development, and furthermore, it is necessary to Two high voltage power supplies are required to switch the polarity of the voltage applied to the charge wire.

Furthermore, when a bipolarly chargeable photoreceptor drum is used, two chargers and two high-voltage power supplies are required to switch the polarity of the voltage applied to the charger wire.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an image forming method capable of forming a reversed image using a copying machine having the same configuration as the conventional one.

(Means for Solving the Problems) The present invention has been made to achieve the above object, and in the first image forming process, the surface of the electrostatic latent image carrier is uniformly charged, and the charging portion After exposing the image to light to form an electrostatic 'Ah image, a white developer is supplied to the image area of the electrostatic latent image to form a first image, and in a second image forming process, the electrostatic latent image is The surface of the latent image carrier is uniformly charged again, and a developer other than the white developer is supplied to the charging section, so that one of the first images is coated with a second one.
A reverse image can be obtained by overlappingly forming the images 1 and 2 and transferring the images 1 and 2 to a sheet at once.

(Example) Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

FIG. 1 schematically shows an electrophotographic copying machine, in which a well-known electrophotographic photoreceptor drum (1) having a photoconductive layer on its outer periphery is installed approximately in the center of the copying machine in the direction of arrow (a). It is installed so that it can be rotated, and the members and devices described below are installed around it.

The charger (2) functions as a charging device that applies a constant potential charge (positive charge in this embodiment) to the surface of the photoreceptor drum (1).

The image exposure device (3) shines light onto a document placed on a document platen glass (35)-L that can be scanned in the direction of arrow (b) and exposes the photoreceptor drum (1) using a well-known slit exposure method. It is used to form an electrostatic latent image corresponding to the original image on the surface, and includes an exposure lamp (31) and a focusing light transmitter! It is composed of a lens array (32) having 4 (ζ) bodies.

The first developing device (4) and the second developing device (5) both use a magnetic plan method to develop an electrostatic latent image formed on the surface of the photoreceptor drum (1) into a toner image. It's from Mu.

The first developing device (4) contains a developer containing white toner, and the second developing device (5) contains a developer containing black I/toner. In the reverse image forming mode, the developing devices (4,) and (5) are selectively driven.3, developer +J, 6j! 1. It is made of a mixture of magnetic gearia and insulating toner, and has a 7.
In this embodiment, the insulation 81
-1 +-ner""M'j Ra , the electrostatic lfh image formed on the surface of the photoreceptor l/ram (1) is developed.

The transfer roller (6) applies an electric field from the back side to the copy paper conveyed from the direction of arrow (c), and the developing device (4) or 11:(5) applies an electric field to the photosensitive drum (1). This is for transferring the toner image (formed on the surface) onto the copy paper.

The separation claw (7) separates the copy paper immediately after transfer from the photoreceptor drum (
1) Peeling off from Table 1Tti! This is because the l-rotator can be evacuated from the photoreceptor drum (1).

The eraser lamp (9) is used to remove charges remaining on the surface of the photoreceptor drum (1) by irradiating light in preparation for the next copying process.

The cleaning device (8) uses a blade (8I) to remove residual I and toner from the surface of the photoreceptor) and plate A (1).
81) is brought into contact with and separated from the photoreceptor drum (1) two times.

The switching means (80) is shown in FIGS. 2 and 3, and the plate (81) is fixed to the tip of a lever (82), and the lever (82) is moved in the direction of the arrow (d) about the support shaft (83). ),
It is rotatable in the direction (d'). In addition, the lever (8
2) The other end of a spring (84) with one end fixed is locked to the rear end, and the lever (82) is always biased in the direction of arrow (d). Furthermore, a planter (86) of a solenoid (85) is connected to the rear end of the lever (82) via a connecting member (87).

When the solenoid (85) is in the OFF state, the lever (82) is urged in the direction of the arrow (d) by the spring (84), as shown in FIG. - Pressed against the outer peripheral surface of the ram (1).

Conversely, when the solenoid l' (85) is in the ON state, the lever (82) is rotated in the direction of the arrow (d') against the spring (84), and the blade (81) is rotated as shown in FIG. It is separated from the surface of the photoreceptor drum (1).

Next, the operation of a reversal image forming method for obtaining a net J image from a positive original using a copying machine having the following configuration will be described.

First, in the first image forming process, the second developing device (5) is retracted from the photoreceptor tram (1) and set to a non-developing state, and the separating claw (7) is removed from the photoreceptor tram (1). You should evacuate. Further, the switching means (8o) of the cleaning device (8) is a third
The plate (81) is set to the on state shown in the figure, the plate (81) is set to a spaced state from the surface of the photoreceptor drum (1), and the eraser lamp (9) is set to a non-operating state.

In this state, the photoreceptor tram (1) rotates in the direction of arrow (a), and the surface of the photoreceptor drum (1) is charged by the charger (2).
) is uniformly charged to positive polarity.

Next, light is irradiated from the exposure lamp (3I) onto the document placed on the document table glass (35), which scans in the direction of arrow (b), and the reflected light passes through the lens array (32) to the document table. The surface of the charged photoreceptor drum (1) is exposed to light, leaving only the potential of the portion corresponding to the image area of the document.
In addition, an electrostatic latent image is formed in which the potential of the background portion is erased.

When this electrostatic latent image reaches a portion facing the first developing device (4) based on the rotation of the photoreceptor l/ram (1), white toner is electrostatically supplied to the electrostatic latent image image area. , as shown in Figure 4,
A white toner image (41) is formed.

The photosensitive drum (1) continues to rotate in the direction of the arrow (a), and the white toner image passes through the portion facing the second developing device (5) and heads toward the portion facing the eraser lamp (9). However, in the first image forming process, the second developing device (5), transfer roller (6), and eraser lamp (9) are stopped, and the separating claw (7) and plate (81) are retracted. Therefore, the white toner image (41) passes through each device without being disturbed.

Next, the process moves to the second image forming process. Note that this process is performed on the document table glass (35) scanned in the direction of arrow (b).
) is executed while returning to the ho 13 position.

When entering the second image forming process, the first developer (4) is set to a non-developing state, and conversely, the second developer (5) is set to a developing state. Also, image exposure device (3)
stops, transfer charger (6), eraser lamp (9)
) is set to an operating state, and the separating claw (7) is set to a state capable of separating the copy paper from the surface of the photoreceptor drum (1).

In this state, the surface of the photoreceptor tram (1) is covered with a white toner image (4
It should be uniformly recharged to positive polarity, including the surface of I). However, this time, unlike the first image creation process in Ati,
No image is exposed from the optical system (3). Therefore, no new electrostatic latent image is formed, and
White toner is not supplied from the first developing device (4).

Next, in a portion facing the second developing device (5), black toner is uniformly supplied to the charged portion on the surface of the charged photoconductor (photoreceptor) and ram (1), and the black toner is uniformly supplied onto the charged portion of the surface of the photoreceptor (1). solid black l
・Nar image (51) is superimposed.

On the other hand, the copy paper (10) stored in the paper feed section (20)
The toner image (4) is fed one by one from the second layer by the paper feed roller (2I), and the toner image (4) is fed by the timing roller pair (22).
1) and (5I), the photoconductor tram (+
, ) and the transfer roller (6), where the toner images C41) and (51) are transferred all at once as shown in FIG.

Copy paper (1) to which the toner images (41,) and (51) have been transferred.
0) is separated from the photoreceptor drum (1) by a separation claw (7), sent to a fixing device (24) via a guide plate (23), where the toner is fixed, and then transferred to a tray (25). )
-4- be discharged.

Meanwhile, the photoreceptor drum ('') continues to rotate in the direction of the arrow (a), and after the residual toner is scraped off and cleaned by the plate (81) of the cleaning device (8), the photoreceptor drum ('') is cleaned by the eraser (9).
) The residual charge is erased by light irradiation.

In this way, on the photoreceptor drum ( ), the white) toner image (41) is the lower layer, and the black toner image (51) is superimposed on the lower layer, or the copy paper ( 10
), there is a black toner image (51) or a white toner image (4) on the bottom layer.
I) is located in the upper layer.

That is, an inverted image is formed on the copy paper (10) in which the image area is reproduced in white and the background area is reproduced in black.

By the way, when a white toner image with the same toner adhesion amount as the black toner and color toner images is transferred to a sheet, the background color of the sheet is visible. This is particularly noticeable when copying an area image with many solid areas.

Therefore, in the reversal image forming method of the present invention, it is necessary to make the amount of white toner adhered per unit area by the first developing device (4) larger than the amount of adhered black l/toner and color toner.

Therefore, as a first method, a developing cap (D
s) in the developing sleeve (52) in the second developing device (5).
) and the photoreceptor drum (]), which is the developing gap (
Ds').

Specifically, the development gap (D s) was changed from 0.6 mm to 0.
．． When the length was changed to 55 mm, the amount of white toner adhered could be increased as shown in FIG.

As a second method, a brush height regulating gap (Db) between a brush height regulating member (43) regulating the amount of developer on the developing sleeve (42) and the developing sleeve (42) is set in the second developing device (5). The developing sleeve (52) and the height regulating member (53)
and the height regulation gap (Db').

Specifically, when the height regulation gap (Db) is changed from 0.5 mm to 0.55 mm, the development gap (Ds)
Similarly to the case where , the amount of adhered white toner could be increased from the dotted line state to the solid line state in FIG. 5.

As a third method, the rotation speed of the developing sleeve (42) is made higher than the rotation speed of the developing sleeve (52) of the second developing device (5), and the developing sleeve (42) and the photoreceptor drum (
1) Increase the amount of developer conveyed to the opposing development area.

Specifically, when a developing sleeve with an outer diameter of 24.5 mm is used, the rotation speed is changed from 143.64 rpm to 17
Orpm, the amount of toner adhesion could be increased from the dotted line state to the solid line state in FIG. 5, similar to the case where the development gap (Ds) was changed.

A fourth method is to make the developing bias (vb) applied to the developing sleeve (42) smaller than the developing bias (vb') applied to the developing sleeve (52) of the second developing device (5). .

Specifically, the developing bias (vb) was changed from -150■ to -11
When the voltage was changed to 00V, the amount of white toner attached could be increased as shown in FIG.

Note that the developing bias (Vb) is as shown in FIG.
The developing sleeve (42) and the developing bias output (+00) on the copying machine main body side are connected via a resistor Rb when the first developing device (4) contains white toner, and when the first developing device (4) contains white toner, When toner is stored, the switch (SW) is changed to connect via a resistor Ra having a smaller resistance value than the resistor Rb, and the developing bias is lowered when white toner is stored. Just do it.

As a fifth method, during the first image forming process, that is, when developing with white toner, the charging voltage by the charging roller (2) is increased to increase the potential difference with the developing bias (Vs), and conversely, During the second image forming process, that is, during development with black toner, the potential difference is reduced to a normal potential difference, and the amount of white toner adhered is larger than that of black toner.

(Effects of the Invention) As is clear from the above description, according to the reversal image forming method according to the present invention, a conventional multicolor copying machine can be used, and
It is possible to form a reversed image without adding new equipment such as a charging charger or a transfer charger, and without installing a paper refeeding device, further increasing the utility value of the copying machine.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the general structure of the copying machine, Figures 2-3 are side views of the blade switching means, Figure 4 is a diagram showing the state of toner image transfer, and Figures 5 and 6 are views of the photosensitive drum. A diagram showing the relationship between surface potential and toner adhesion amount, and FIG. 7 is a diagram showing a method of switching the developing bias. 1. Photosensitive drum, 2. Charging-+-Yanoya, 3. Optical system, 4. 1st developing device, 5. 2nd developing device, 6.. Transfer charger, 8. Cleaning device, 10. Copying paper.
80... Switching means, 8 blade, 41... White toner image, 51... Black toner image.

Claims (1)

[Claims] (1) In the first image forming process, after uniformly charging the surface of the electrostatic latent image carrier and exposing an image to the charged portion to form an electrostatic latent image, an image of the electrostatic latent image is formed. A first image is formed by supplying a white developer to the charging section, and in a second image forming process, the surface of the electrostatic latent image carrier is uniformly charged again, and a developer other than the white developer is supplied to the charging section. A reversal image forming method characterized by supplying a developer, forming a second image overlappingly on the first image, and transferring the first and second images to a sheet at once. .