JPS58130358A - Device for image formation - Google Patents

Abstract

PURPOSE:To enable a good image to be formed in accordance with its use in multicolor copying machine, by executing high contrast developing to form a multicolor image, and low contrast developing to form a single color image. CONSTITUTION:A variable resistor 172 is connected in series with the magnetic brush developing device 171 of a developing apparatus 17, and its resistance is changed to change image gradation. A V-D characteristic curve for relationship btween photoreceptor surface potential (X) and image density (Y) is shown in the figure. As a value of the variable resistor 172 is raised, the curve shifts toward the right side. In 2-color copying, a resistance value is made zero, and high contrast development is made to prevent color mixing, but in single color copying, a resistance value is increased to make low contrast developement in accordance with the right side curve because of reproducibility of a line original or the like, thus permitting a good image adapted for its use to be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus, which has an integrated O development: L ets, and selectively performs multicolor image formation and monochrome image formation. Concerning statue-shaped majesty devices.

Conventionally, there have been various types of single image forming devices with two-color reproduction function.
l ≠ ru. One is a full-color copying machine that also has the ear wing function, and is equipped with a color reproduction function, and the other is a case where the two-color reproduction function is exclusively used as a beak. be.

By the way, an image forming device ID with such a two-color reproduction function is effective for document copying in the office. This often happens, but in cases like this, multiple colors are not necessary, or by dividing them into two colors,
The effect of calling attention to this is very effective.

Capri, there is no color mixing, and calligraphy that is color-coded by itself dramatically increases its usefulness.

Therefore, in order to obtain two-color document copies, it is desirable that the image quality of each color be high contrast, especially in order to prevent fogging and color mixing.

On the other hand, when copying a general original, a soft-tone image is required in order to reproduce not only a line original but also a photographic original.

11. When black toner is used for monochromatic copying, it is desirable to adjust the Kll image reproducibility by increasing the degree of softness because the lightness, li: degree is low, so that photographic image reproduction is possible. However, there has been no conventional method that meets this purpose.

This Todoro@ was created in consideration of the above points, and it is possible to selectively obtain high-tone development and soft-tone development by switching between multicolor image formation and monochrome image formation. It is an object of the present invention to provide an apparatus for forming iii*.

This product is equipped with an image forming apparatus that has a plurality of developing units and selectively forms multicolor ms shadows and monochrome images. It is characterized by forming 31 images in soft tone 1 during formation.

The details of the present invention will be explained below by way of specific examples with reference to the drawings.
I will clarify.

This is a surface N of a variant image forming apparatus OII having a two-color reproduction function according to the present invention.

Part 1 - Basics of l#i insulating layer, photoconductive layer and conductive layer -
The photosensitive drum rotates in the direction of the arrow to increase the power. m is the manuscript table, 3 is the manuscript table illumination lamp, 6Fi its reflective shade, 4, 5
The movable mirror of the document table scanning optical system is a lens, and s e
9 F! Hard 5ii! It's a mirror. 10 is a control section. 1lFi-next 11 electric appliances, 12#i secondary corona electric appliances,
13#i Complementary color ° filter provided on the secondary corona discharge sow' surface (in the case of red and black two-color reproduction, Kj-j is cyan, the complementary color of red), 14 is a monochrome filter provided in the subsequent position (in the case of red and black reproduction 110 mentioned above) is red). Reference numeral 15 indicates a monochrome (red in the illustrated example) toner supplying and developing device, 16#i full-surface exposure lamp, and 1F indicates a black toner supplying and developing device. Reference numeral 18 indicates a paper feeding timing, 1G, 9' indicates a transfer material feeding roller, and 0 indicates a transfer material feeding force. 21#
i transfer coat discharger, 22 is separation means 0 minute 10-ra, 2
It is a 3Fi fixing device. 24 is a transfer material static eliminator, 25 is a paper discharge roller, and 5oFi paper discharge tray. It is also a 26#i cleaning device.

The operation of the above device will be described below. A document (for example, a two-color image consisting of black and red) placed on the document table glass 2 is irradiated by the amm clamp 3, and the reflected light is light @ 27 &! 'FbK split and movable Mira number one.

5, lens filter, mirrors 8 and 9, 1 cyan filter 13 (OIF) and red filter 14 respectively
(II?) onto the surface of the photoreceptor drum 1. Since the WI1 unit 2tj is scanned in the direction of the arrow X, each point on the document first passes through the path of the light m2 and then the light ll
It passes through the path 1127b and is projected onto the photoreceptor drum. The photoreceptor drum 1#'i is uniformly charged with a predetermined polarity by the next charger 911, and simultaneously exposed to a light image (cyan filter) from the path of light @I 27 m, and simultaneously exposed to the next image. Coptic discharge with reverse polarity component (it, reverse polarity D
O, MU0, etc.) to the secondary corona cheer 1112! given by.

Of course, the document is scanned in synchronization with the movement of the photoreceptor drum l, but the photoreceptor drum l is subjected to neutralization or reverse polarity electricity, and the photoreceptor drum l is exposed to light beams two times.
The original image passing through the red filter 14 is irradiated through the 1i path. That is, as a result, a light image in which all light other than red is cut is irradiated, and a developable potential image is formed on the red corresponding S of the formed electrostatic charge.

The original image is developed into a red color by a developing device 1115.

The photoreceptor drum 1 is then illuminated by a full-surface exposure lamp 16, and a high potential image is formed on the photoreceptor portion corresponding to the black color of the original document. Next, the negatively charged black tinner is 3
The original image is developed using a J imager. On the other hand, the transfer material is fed from the transfer material cassette 20 or Fi 20' by the paper feed roller 19 or Fi 19', and is sent to the transfer position after being timed by the timing roller 1B. At the transfer position, the developed image is transferred to the transfer material by the transfer corona discharger 21. After the transfer is completed, the transfer material is also separated from the photoreceptor drum l by the separation roller 23. The transferred image on the transfer material is fixed onto the paper by a contact heating type fixing device 20, and the paper is ejected p.
- It is discharged to the tray 30 by the roller 25.

Drum surface 0 after transfer is complete! ! ! The remaining toner is removed by the cleaning device 26 and accumulated at - locations.

The gradation switching control in the present invention will be described below.

FIG. 2 shows an embodiment of gradation control of development according to the present invention. FIG. 2 shows a magnetic sleeve in which a fixed magnetic pole is arranged in the second developing section in FIG. 1 and a non-magnetic cylinder is rotated. This sleeve table IjK! A Dunnett brush is formed. Magnet brush 04111 has 11Ei because the carrier in the developer acts as a group of minute contact electrodes.
The li effect OS has good halftone image reproducibility. Of course, it is possible to change the paper image reproducibility by changing the development value.

Section 3m is a graph showing the tonality of development, and is a v-n@ characteristic curve showing the relationship between the photoreceptor surface potential and image density.

For example, if the resistance value is gradually increased during image formation, V-D
, *-moves to the right of the Fiv axis, and the eta area is gradually corrected.

In FIG. 3, if (3-&)#i the resistance value of the variable resistor 172 is 00, (3-b) means that the resistance value of the variable resistor 1720 is 10? The case of Ω is shown.

For two-color copying, set the resistance value to OK and use high contrast development.

The above objective can be achieved by turning off (OIFF) the dynamics of one developer at a time when copying a single color and switching the resistance value to 10Ω.

FIG. 4 shows an embodiment of the present invention in which a developing device 31 of another type is used as the second developing device. In the figure, 32t
j A developing roller that forms a thin layer of toner on the surface to develop the latent image on the photosensitive drum L, and an applicator ruler that coats the surface of the 33Fi developing roller with toner. When the toner polarity is negative, the developing roller 32@f
A negative voltage is biased to the lc positive and applicator roller 33 side by a variable power supply 34, and the negative toner on the applicator roller 33 is transferred to the developing roller 32.
K::I-ting is performed. When the toner polarity is positive, the bias is applied in the opposite way. By changing the value of the bias voltage 34 for both rollers, the thickness of the toner coated on the surface of the developing roller can be changed, and the developing characteristics can be changed.

#i, bias voltage of 600v is applied at once for two-color copying,
The above purpose can be achieved by thickening the toner coating to achieve high-contrast development, turning off (oyP) the operation of the first developing device and lowering the bias voltage by 450vK and thinning the toner coating to achieve soft-contrast development during the monochrome lobby. can be reached.

In addition, magnetic toner O with a thickness of about 100μ on the sleeve surface rI7JK
Form a thin layer of about 300μ on the sleeve surface and photoreceptor surface.
Japanese Patent Application Laid-Open No. 1855-186 develops by applying an AC bias voltage while maintaining a narrow interval of 1[K, m to cause toner to fly.
In the case of the jumping development method described in Publication No. 56, etc.,
The developing characteristics can be changed by changing the frequency of the AC bias voltage in accordance with changes in the adjustment dial.

Two-color copy temporary KIIi, bias frequency 800-16
The above object can be achieved by setting high contrast development as 00 &, controlling the operation of the monochrome copy temporary KIIi and the first developing device to oy (oyy) pc, and setting the bias frequency to 200 to 5QQlim to perform soft contrast development.

As described above in detail in the specific MK section, the apparatus of the present invention forms a high contrast image during multicolor development and forms a soft contrast AM image during monochrome development, thereby making it possible to obtain a good image depending on the application.

[Brief explanation of drawings]

115ii1 is a side view of a specific example image forming apparatus according to the present invention; FIG. 2 is an explanatory diagram of development gradation control-Sakaki of the actual wA specific example apparatus; an explanatory diagram of the third factor FiV-D characteristic curve; FIG. 4 is an explanatory diagram of different embodiments of the apparatus of the present invention. In the figure, 1: photosensitive drum (image carrier), 2: document table, 3:
Original case IIIlj11 lamp, 4, 5: Movable mirror. Applicant Canon Co., Ltd.

Claims (1)

[Claims] (1) The image forming apparatus Kjl, which has a 11110 developing unit and selectively performs multicolor image formation and monochrome image formation, produces a high contrast image when forming a multicolor image, and produces a soft contrast image when forming a single color image. An image forming apparatus characterized in that the image forming apparatus is formed in the following manner.