JP2992139B2 - Color electrophotographic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color electrophotographic apparatus in which a plurality of single-color toner images are superimposed and transferred to an intermediate transfer member, and then the full-color toner image is further transferred to a recording medium.

In order to express a color image with toner, for example, a total of four primary colors of yellow, magenta, and cyan and black are used.
The color toner images may be transferred onto the recording medium in a superimposed manner. However, it is not easy to perform such superimposed transfer directly from the photoreceptor to the recording medium because color mixing and misregistration are likely to occur. Therefore, there is an image transfer apparatus that transfers a full-color toner image via an intermediate transfer member.

[0003]

2. Description of the Related Art In such a conventional color electrophotographic apparatus, an image is first divided into dots, and the color to be expressed is separated into four colors of yellow, magenta, cyan and black for each dot. I do. Then, yellow, magenta, cyan, and black single-color toner images are formed on the surfaces of the four photosensitive drums, and are transferred to the intermediate transfer member while being superimposed in the order of the colors. Therefore, on the surface of the intermediate transfer member, the yellow toner is the lowermost layer, and the portion without the yellow toner is the lowermost layer of the magenta toner.

[0004]

As described above, if the toner adheres to any number of layers on the intermediate transfer member, the lowermost layer of the toner ( In particular, the transfer voltage applied to the portion of the intermediate transfer member where only one layer of toner adheres is lower than the voltage applied to the upper layer toner.

Further, the intermediate transfer member must be formed of a viscoelastic member such as rubber in order to smoothly rotate by pressing against the hard photosensitive drum, so that the adhesion of toner is strong.

For this reason, when a full-color toner image is transferred from the intermediate transfer member to the recording medium, a part of the toner in the lowermost layer remains on the surface of the intermediate transfer member, and the amount of transfer to the recording medium is reduced. There is a drawback that the color image is less than the toner layer, and as a result, the color reproducibility of the color image is deteriorated.

Therefore, the present invention provides a color electronic device capable of obtaining a high-quality color image with good color reproducibility on a recording medium even if a phenomenon that a part of the toner in the lowermost layer remains on the intermediate transfer member. It is intended to provide a photographic device.

[0008]

In order to attain the above object, an intermediate transfer member of an electrophotographic apparatus according to the present invention forms a single color toner image with toners of different colors as shown in FIG. A plurality of monochromatic toner image forming means 1
And an intermediate transfer body 2 on which the single-color toner images are transferred from the single-color toner image forming means 1 in a superimposed manner, and the superimposed toner image is transferred to a recording medium 100; A lowermost layer color detecting means 3 for detecting in advance whether or not the toner of the color becomes a lowermost layer; and developing the lowermost layer on the intermediate transfer body 2 in response to the detection result of the lowermost layer color detecting means 3. And a developing amount increasing unit for correcting the developing amount so that the amount is increased in each of the single-color toner image forming units.

The monochromatic toner image forming means 1 develops an electrostatic latent image formed by exposing the charged photoreceptor 10 to image light with toner. The development amount may be increased by lengthening the exposure time of the image light exposed on the photoconductor 10,
Alternatively, the development amount may be increased by increasing the exposure brightness of the image light exposed on the photoconductor 10.

[0010]

The lowermost layer color detecting means 3 detects in advance which color of the plurality of color toners superimposed on the intermediate transfer member 2 will be the lowermost layer and contacts the surface of the intermediate transfer member 2. Then, in response to the detection result of the lowermost layer color detecting unit 3, the developing amount increasing unit 4 increases the developing amount of the color forming the lowermost layer on the intermediate transfer body 2 to the single color toner image forming unit 1.

[0011]

An embodiment will be described with reference to the drawings.

FIG. 2 shows a color electrophotographic apparatus using four color toners of yellow (Y), magenta (M), cyan (C) and black (B).

This apparatus comprises four monochromatic toner image forming means 1 (1) for forming a toner image with four color toners.
Y, 1M, 1C, 1B) and each single-color toner image forming unit 1
The photosensitive drum 10 (10Y, 10M, 10
C, 10B) and the intermediate transfer drum 2 which is driven to rotate simultaneously.

The toner images of each color are transferred from the photosensitive drum 10 to the intermediate transfer drum 2 in the order of yellow (Y), magenta (M), cyan (C), and black (B) from the lower layer side.
After the transfer, the color toner image (full color toner image) is transferred onto the recording paper 100 from the intermediate transfer drum 2. Therefore, the toner images of the respective colors are formed on the recording paper 100 in the reverse order of the order on the intermediate transfer drum 2.

Each photosensitive drum 10 (10Y, 10M, 10
C, 10B), a pre-charger 11 for charging the photosensitive drum 10, an exposure unit 12 for irradiating the photosensitive drum 10 with image light to form an electrostatic latent image, and a toner When the intermediate transfer drum 2 comes into contact with the photosensitive drum 10, the toner image on the surface of the photosensitive drum 10 is transferred to the intermediate transfer drum 2.
Is transferred to Reference numeral 14 denotes a cleaner for removing the toner remaining on the surface of the photosensitive drum 10.

In the exposure unit 12 and the developing unit 13,
12Y and 13Y are for yellow toner, 12M and 13M are for magenta toner, 12C and 13C are for cyan toner, and 12B and 13B are for black toner.

The intermediate transfer drum 2 is formed, for example, by lining an elastic conductive rubber 2a outside the aluminum tube 2b, and is driven to rotate in a direction opposite to the photosensitive drum 10 by a drive motor (not shown). Is done.
Therefore, the outer peripheral surface of the intermediate transfer drum 2 and the photosensitive drum 1
The outer peripheral surface moves in the same direction at the contact portion,
Then, the toner image is transferred from the photosensitive drum 10 to the intermediate transfer drum 2.

The recording paper 100 travels while being sandwiched between the intermediate transfer drum 2 and the transfer roller 17, where the full-color toner image is transferred from the intermediate transfer drum 2 to the recording paper 100, and is further fixed by the fixing device 16. The full-color toner image is fixed on the recording paper 100.

Reference numeral 8 designates a new transfer portion A to the recording sheet 100 and then a new image to the intermediate transfer drum 2 to remove residual toner remaining on the surface of the intermediate transfer drum 2 after transferring the toner image onto the recording sheet 100. Photosensitive drum 1 for transferring toner image
This is a residual toner cleaner provided between 0 and 0.

As shown in FIG. 3, exposure units 12Y, 12M and 12 for yellow, magenta, cyan and black are used.
The exposure circuits 12Y, 12M,
Light emission time indicating unit 3 for controlling the light emission time of 12C and 12B
3Y, 33M, 33C and 33B are connected.

In the frame memory 30, a full-color image to be expressed is color-separated for each dot, and information on the presence / absence of yellow, magenta, cyan and black is stored in dot units. Then, a signal indicating whether or not yellow exists (“1”) is sent from the frame memory 30 to the light emission time instruction unit 33Y for yellow.
Or, “0”) is directly input, and a signal indicating the presence or absence of black is directly input from the frame memory 30 to the light emission time instruction unit 33B for black.

A magenta determination circuit 31 for determining whether or not magenta is the lowermost layer on the intermediate transfer drum 2 is connected between the magenta light emission time instruction section 33M and the frame memory 30. Flashing time indicator 3
Between the 3C and the frame memory 30, a cyan determination circuit 32 for determining whether or not cyan is the lowermost layer on the intermediate transfer drum 2 is connected.

In the magenta determination circuit 31, first and second AND circuits 31a and 31b are juxtaposed, each of which is provided with a yellow presence / absence signal ("1") from the frame memory 30.
Or "0") and a signal indicating the presence or absence of magenta ("1" or "0"), and an output signal is sent to the magenta light emission time instruction unit 33M. However, the second AND circuit 3
For 1b, the signal indicating the presence or absence of yellow is inverted and input via an inverter.

Therefore, when both yellow and magenta are present, that is, when magenta is not the lowermost layer, the first AND circuit 31a outputs the magenta light emission time indicating section 33.
When a signal of "1" is sent to M and there is no yellow and there is only magenta, that is, when magenta is on the lowermost layer on the intermediate transfer drum 2, a magenta light emission time indicating unit is output from the second AND circuit 31b. A signal of "1" is sent to 33M.

The cyan determination circuit 32 includes first and second AND circuits 32a and 32b and an OR circuit 32c. Then, a signal (“1” or “0”) indicating the presence or absence of yellow and a signal (“1” or “0”) indicating the presence or absence of magenta are input from the frame memory 30 to the OR circuit 32c.

The first AND circuit 32a receives the cyan non-existence signal ("1" or "0") from the frame memory 30 and the output signal from the OR circuit 32c. The AND circuit 32b includes a frame memory 30
, And an output signal from the OR circuit 32c inverted by the inverter is input. Then, the first and second AND circuits 32
a, 32b are output signals for cyan light emission time instructing section 33
Sent to C.

Therefore, when there is at least one of yellow and magenta in addition to cyan, that is, when cyan is not the lowermost layer, the output from the OR circuit 32c is "1", so that the first AND circuit 32a When the signal of "1" is sent to the cyan light emission time instructing unit 33C, and there is no yellow and magenta, and there is cyan, that is, when cyan is the lowest layer on the intermediate transfer drum 2, the OR circuit Since the output from 32c is "0", a signal of "1" is sent from the second AND circuit 32b to the light emission time instruction unit 33C for cyan.

In each of the magenta and cyan emission time indicating sections 33M and 33C to which such a signal is input, the first and second magenta determination circuits 31 and cyan determination circuits 32, respectively.
When the signal of "1" is received from the AND circuits 31a and 32a, that is, when those colors do not become the lowermost layer, the light emission time of the exposure units 12M and 12C for each color is controlled to a normal length, and When the signal of "1" is received from the AND circuits 31b and 32b of the second color, that is, when those colors are in the lowermost layer, the light emission time of the exposure units 12M and 12C for each color is increased by a predetermined time to increase the light emission time of each color. The developing amount developed by the developing units 13M and 13C is increased.

On the other hand, since yellow is always in the lowermost layer, the light emission time indicator 33Y for yellow always increases the light emission time of the exposure unit 12Y for yellow by a predetermined factor. In addition, since black is preferably expressed in clear black which is not mixed with other colors, a black light emission time indicating unit is also used so that the light emission time of the black exposure unit 12B is always increased by a predetermined time. 33B is set in advance.

FIG. 4 is a time chart concretely showing an example of the operation of the above embodiment. When there is a yellow component which is the lowermost layer like the first, second, third, fourth, seventh and eighth dots, FIG. In this case, the light emission time of the exposure units 12M and 12C for magenta and cyan remains normal, and the light emission time of the exposure unit 12Y for yellow becomes longer.

When there is no yellow component and there is a magenta component as in the fifth and sixth dots, the light emission time of the magenta exposure device 12M remains the normal light emission time of the cyan exposure device 12C. Becomes longer.

When the yellow and magenta components are not present and there is a cyan component as in the ninth and tenth dots, the light emission time of the exposure unit 12C for cyan becomes long.

In the embodiment apparatus thus constructed, the light emission time of the color component exposure device 12 which is the lowermost layer on the intermediate transfer drum 2 is increased by a predetermined time, and the color component developing device 13 The color component which does not become the lowermost layer is exposed by each of the exposure devices 12 with the light emission time according to the normal setting value except for black, and the color component which does not become the lowermost layer is subjected to normal development by the development device 13 of the color component. Development is performed with the development amount.

In this way, the development of each color component is performed on the photosensitive drums 10Y, 10M, 10C, 10B for each color, and these are transferred to the intermediate transfer drum 2. Then, when the full-color toner image is transferred from the intermediate transfer drum 2 to the recording paper 100, a part of the toner in the lowermost layer remains on the intermediate transfer drum 2 and the toner of that color is transferred to the recording paper 100. Transfer is reduced, and as a result, recording paper 1
In the full-color image on 00, appropriate color reproduction is performed.
Therefore, the magnification for extending the exposure time is preferably determined by the adhesion rate of the toner to the surface of the intermediate transfer drum 2.

The present invention is not limited to the above embodiment. For example, in order to increase the amount of development, instead of changing the light emission time, the light emission brightness of the exposure unit is increased to increase the amount of development. May be increased.

In the present specification, the "toner to be the lowermost layer" means not only the toner of the lowermost layer when the toners of a plurality of colors overlap, but also includes the toner of a single color portion.

[0037]

According to the color electrophotographic apparatus of the present invention,
Since the amount of development of the color that becomes the lowermost layer on the intermediate transfer body is increased, even if a part of the toner that becomes the lowermost layer remains on the intermediate transfer body when a full-color toner image is transferred to the recording medium, the recording medium In this case, accurate color reproduction can be performed, and a high-quality full-color image can be obtained.

[Brief description of the drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is an overall configuration diagram of an embodiment.

FIG. 3 is a circuit block diagram of the embodiment.

FIG. 4 is a time chart of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Monochromatic toner image forming means 2 Intermediate transfer body 3 Bottom layer color detecting means 4 Developing amount increasing means 100 Recording medium

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-45994 (JP, A) JP-A-4-194961 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/01 111 G03G 15/01 112 G03G 15/01 114 G03G 15/00 303

Claims (3)

(57) [Claims] A plurality of single-color toner image forming means for forming a single-color toner image with toners of mutually different colors; and each single-color toner image from the single-color toner image forming means is transferred in a superimposed manner. An intermediate transfer member for transferring the formed toner image to a recording medium, and each portion where a plurality of color toners overlap on the intermediate transfer member.
A bottom layer color detecting means for detecting in advance the color of the toner forming the lowermost layer in each minute; and in response to the detection result of the lowermost layer color detecting means, each portion where the plurality of color toners overlap on the intermediate transfer body. And a developing amount increasing means for correcting the developing amount so that the developing amount of the lowermost layer is increased in each of the single-color toner image forming means. 2. The method according to claim 1, wherein the monochromatic toner image forming means develops an electrostatic latent image formed by exposing the charged photoreceptor to image light with toner. 2. The color electrophotographic apparatus according to claim 1, wherein the development amount is increased by lengthening the exposure time of the image light to be exposed. 3. The monochromatic toner image forming means develops an electrostatic latent image formed by exposing a charged photoreceptor to image light with toner, and the developing amount increasing means comprises 2. The color electrophotographic apparatus according to claim 1, wherein the development amount is increased by increasing the exposure brightness of the image light to be exposed.