JPS6083054A - Electronic photographing device - Google Patents

Abstract

PURPOSE:To form a copy picture of appropriate quality from an original of low density to an original of high density by providing a copy density adjusting device that adjusts the copy density by changing the amount of exposure and developing bias voltage increasing or decreasing them in linkage. CONSTITUTION:A photosensitive drum 1 is charged uniformly by a primary charging device 11 and the charge of the primary charging device is removed by a destaticizer 12 projecting picture light of a microfilm 2, and then exposed uniformly by a lamp 13. Thus, an electrostatic image corresponding to a projected picture pattern is formed on the photosensitive drum 1, and developed by a positively charged toner by a reversing developing method by a developing device 14. When a copy density adjusting dial 30 in a copy density adjusting device 22 is rotated, gears 32, 33 are rotated in the direction shown by the arrow through an intermediate gear 31. The resistance value of connected resistance 35 for controlling the quantity of light of the lamp and resistance 36 for controlling developing bias voltage changes and controls voltage supply circuits 18, 19, and determines a supply voltage to the lamp 3 and developing a bias voltage for the developing device 14.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic apparatus, in particular, to an electrophotographic apparatus, which applies a light pattern of reflected light or transmitted light from an original to a photoreceptor to form a predetermined latent image potential pattern on the photoreceptor. The present invention relates to an electrophotographic apparatus that obtains a visible image by developing using a normal development method or a reversal development method.

Conventionally, electrophotographic devices control the amount of exposure of the original illumination light, that is, the exposure of the photoreceptor, in order to obtain a proper copy image. The charges should be of the same polarity, and when developing by attaching toner to the area of the photoreceptor with a low surface potential, that is, the area corresponding to the image area of the original, exposure should be done to avoid blurring of low-density negative film originals. If the exposure amount is controlled to increase the image density, the potential contrast becomes insufficient and the density of the copied image becomes extremely low, and if the exposure amount is controlled to increase the image density, fogging occurs in the non-image area, that is, the background area. In high-density negative film originals, the density of the copied image area is high, and images such as characters become thick and illegible. Therefore, when controlling the exposure amount, an appropriate copy image can be obtained with a negative film L/original having an appropriate density, but an appropriate copy image cannot be obtained with a negative film original with a low or high density.

Hereinafter, the reason why the above-mentioned appropriate copy image cannot be obtained will be specifically explained with reference to the drawings. Figure 1 shows the case where an image of a negative film original is exposed to a charged photoconductor to form a latent image on the photoconductor, and this latent image is developed by applying an Iasumi pressure of 650 mm and performing reversal development. This figure shows the relationship between the exposure amount E of the photoreceptor L, the surface potential B of the photoreceptor, and the developed density.

The negative film original mentioned in 2. (1) General film (hereinafter referred to as FIJL/J, F) with an image of νJ density contrast I, suitable for relatively high-density back Jet (IIrf part). ).

(2) A film with a high density as a whole having a high density image on a high 6 degree background (hereinafter referred to as film F2).

(3) A film with an overall low density that has a low density image on a low density background (hereinafter referred to as film F).

There is.

When the above-mentioned filter F1 is illuminated with a constant amount of illumination light and copied, the exposure amount of photoreceptor-2 becomes E shown on the left side of FIG. 1, and El-a to E of I)-V curve B.

-b range, and the background Q[j of film F1 is compared to:
The portion of the photoreceptor that corresponds to the image area of the film 1 has a surface potential that allows development to occur without fogging, and the portion of the photoreceptor that corresponds to the image area of the film 1 has a potential that allows appropriate image density to be obtained. Therefore, the developed image has a high density contrast and good intermediate density reproducibility.

However, when copying film F2 by illuminating it with the same amount of illumination light as described in Section 12, the exposure end becomes E2 as shown in FIG.
(The range is E2-a-E>-b of DV curve B,
This causes fog in the background of the copied image. In this case, by reducing the original illumination light amount and setting the exposure amount to E2 as shown in FIG.
b, and it is possible to prevent fog from occurring in the background of the copied image, but the density of the copied image is low and the image cannot be reproduced correctly.

Furthermore, if the film F3 is illuminated and copied with the same amount of illumination light as above, the exposure amount will be E3 as shown in FIG.
Curve B (7) E 3 a - E 3 b (7)
As a result, the density of the copied image is low and an appropriate density contrast cannot be obtained. In this case, increase the amount of light for illuminating the original and set the exposure amount to E:l as shown in FIG.
From z, DV curve B (7:l'E3'-a-E3'-
b, and it is possible to increase the density of the copied image, but it requires a large amount of illumination light, so it is necessary to use a large-capacity illumination light source, and in the case of character images, the characters become thicker and difficult to read. become unable to do so.

This invention was proposed in view of the above, and the exposure amount and the developing bias voltage are increased or decreased in conjunction with each other so that a copy image of appropriate quality can be obtained from a low-density original to a high-density original. It is an object of the present invention to provide an electrophotographic apparatus characterized by having a copy density adjusting device that adjusts the copy density by changing the density.

Hereinafter, the above-mentioned FIG. 1 to tjtJ3 will be explained in detail. :51 As shown in Figure 11, in the case of a negative film original, when the exposure amount is increased, the photoreceptor surface potential decreases and the image density increases, and when the developing bias voltage is changed, the apparent photoreceptor surface potential decreases. It can be changed.

The uninvented method takes advantage of this phenomenon, and when the original is a low-density Nekafilm F2, first, the exposure is performed by controlling the light i- so that 1 image i2 becomes high. r11
E2 (Figure 2), two ijJ, V-D curve B (7)
E.

-a-E, -b, and 11) When the resulting latent image is developed by the reversal development method by applying a developing bias pressure of 650 V, the density of the developed image becomes high, but the background part (non-image part or haze part) Fog may occur.

Therefore, the present invention is as described above! 1. Is it possible to control the Meiko J type and at the same time lower the surface potential of the photoreceptor in conjunction with that control? Control the city use.

In this case, when the development bias Ichikawa is set to 550■ and reverse development is performed, the relationship among the exposure M E , the surface potential V of the toner photoreceptor, and the development density is as shown by the dotted line polarity B in Figure 2, and the point is V-.
Moving to D curve B (1) B-a-B-b, the developed image had no fog and the density contrast was appropriate.

If the illumination light 1d is controlled so that the potential contrast of the image area of the photoreceptor is approximately 300V, the density contrast of the developed image will be appropriate.

In the case of high 1 ÷ degree fill As F, conventionally, Fig. 3 shows 2
No ＼ like Kaburi or Ushi 1ko W light II! E3(
Conventionally, this was appropriately set to 11 exposures (9 degrees), and for this reason, as mentioned above, 6 degrees was too high, causing the problem that characters, etc. in multi-key images became large.

Therefore, V-D curve B (T) E 3a -E A
-b, that is, the exposure amount E3//(
The exposure amount is smaller than the conventional appropriate exposure amount E3, E//, <
When exposure is performed at E3/<E3) and the obtained latent image is developed by reversal development by applying a development bias voltage of 650 V, the density of this developed image becomes low and the image becomes thick and difficult to read. However, when the density contrast of the developed image is low and the latent image potential is between 659V and 810V, images such as thin characters and thin characters cannot be reproduced correctly.

In the present invention, as described above, the illumination light ψ is controlled, and at the same time, the development 7\ias voltage is controlled so as to lower the photoreceptor surface potential in conjunction with the controlled amount of illumination light. In this case, if the developing via droplet voltage is set to 810 V and reverse development is performed, the relationship between the exposure amount E, the photoreceptor surface potential V, and the developed density becomes as shown by the dotted line curve B in FIG. D curve B E number-a-E3-bc
The r+ point moved to B-a-B-b of the V-D curve B, and the developed image was fog-free and had an appropriate density contrast.

FIG. 4 shows a schematic diagram of the above-mentioned photocopying machine, in which 1 is a photosensitive tram rotating clockwise at a circumferential speed of V, 2 is a microfilm that is covered with originals, and 3 is a microfilm 2.
4 is a focusing lens, 5 is a projection lens,
Reference numeral 6 denotes a movable stage that supports orthogonal reflecting mirrors 7.8, and 9 denotes an exposure slit plate disposed between the projection lens 5 and the photosensitive drum l. The moving table 6 is coupled to a motor (not shown),
By reciprocating at a speed of >>V, the entire image of one frame of the film is exposed onto the photosensitive drum l.

1. The photosensitive drum 1 is composed of a three-layered photosensitive member consisting of a conductive layer, a photoconductive layer, and a transparent insulating layer in this order, and has an insulating layer on its surface.

This photosensitive drum 1 is uniformly charged with a primary (tF) upper device It, and then an image light of the microfilm 2 is projected by a static eliminator 12 of AC or primary (DC with opposite polarity to the 17 electric device). The charge on the primary battery is removed, and then uniformly exposed to light by the lamp 13, an electrostatic image corresponding to the projected image pattern is formed on the photosensitive drum l. The electrostatic latent image (potential of the exposed area and potential of the non-exposed area) on the drum 1 is developed by a developing device 14 using regular commercial toner by a reversal development method, and then transferred to a transfer paper 16 by a transfer device 15.
transcribed into. Using the reversal development method, the toner is transferred to a photosensitive drum.
- is exposed to the low potential exposure area, and is developed in step 6.

22 denotes a copy density adjusting device 71, and a voltage supply circuit 1.
8.19 is controlled to determine the supply voltage to the -1- lamp 3 and the developing bias pressure to the developing device 14. 20 is a cleaning device.

FIG. 5 shows an example of the copy density adjusting device 22. As shown in FIG. When the copy density adjustment dial 3o is rotated, @
+32.33 rotates in the direction of the arrow, and 32.33 rotates in the direction of the arrow.
4 for controlling the light end of the lamp connected to the legs 32a and 33a of 33
1, the resistance f〆1 of the resistor 35 and the developing bias voltage control resistor 36 change.

In the illustrated example, for example, when the gouillage 30 is turned clockwise,
The lamp voltage supply circuit 18 and the development/''-ias supply circuit 19 are controlled so that the lamp light ji (and development bias voltage) are high, that is, both of them are high. When turned in the counterclockwise direction, the lamp voltage supply circuit 18 and the development bias supply circuit 19 are controlled so that the lamp light [I- and development] ζ asumi pressure decreases, that is, the copy density becomes lower in both cases. 'It is structured so as to be F.

The table shows the relationship between the lamp opening force lI Ifi pressure, the developing/\iasu city pressure, and the dial 1 scale.The user should check the density of the original and decide whether to set it to The decision is made by judging the image quality of the copy image obtained by cutting or making a trial copy. For example, if you are copying a light original, set the dial [1] to (1), and if you are copying a dark original, set the dial [11] to (5).

In addition, a measuring device to measure the density of the original (measures one transmitted light of the original or nine fouls) is provided, the measuring device of this measuring device is displayed, and the density of the original is determined based on the values shown in this table. The concentration may also be determined.

FIG. 6 shows the relationship between the developing bias voltage and the lamp applied voltage, and the developing bias upper pressure and the lamp applied voltage are changed in conjunction so that the linear relationship shown in FIG. 6 is achieved.

Note that the electrophotographic copying machine is not limited to the embodiment, and various known electrophotographic copying machines can be applied. Further, the present invention can also be applied to a slitting 11-light type copying machine and a copying machine capable of full-surface simultaneous exposure η1.

In the above embodiments, the exposure section is controlled by changing the voltage applied to the lamp, but the amount of exposure may be controlled by changing the slit width, exposure time, etc.

Furthermore, the present invention can be applied to general copying machines that use reflective originals; 4. Is the base (non-image area) colored in ν? This is especially effective when using colored paper or discolored manuscripts such as new NL, blueprints, etc.

As described in detail above, according to the present invention, the exposure amount and the developing bias voltage are adjusted in conjunction with each other, so that even if an original with an inappropriate density such as a low-density original or a high-density original is used, it is possible to obtain an optimal image without fogging. This has the effect of easily obtaining a high-density copy image.

[Brief explanation of the drawing]

Figures 1 to 3 are diagrams showing the relationship between exposure IE, photoreceptor surface potential (■), and development density, Figure 4 is a schematic diagram of the electrophotographic apparatus of the present invention, and Figure 5 is an example of a copy density adjustment device. The perspective view and FIG. 6 are diagrams showing the relationship between the developing bias voltage and the lamp applied voltage. 22 is a copy density control device, 18 is a lamp voltage supply circuit, and 19 is a developing bias voltage supply circuit. Figure 4 Figure 6 Figure 3 Figure 5

Claims (1)

[Claims] (1) An electrophotographic apparatus comprising a copy density adjusting device 41 that adjusts copy density by increasing or decreasing the exposure amount and the developing bias voltage in conjunction with each other.