JP2001183913A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate peeling off of paper from an intermediate transfer belt by preventing a leading tip part of the paper from being closely adhered to the intermediate transfer belt. SOLUTION: In the image forming device, a multiple number of developing devices each developing an image onto a photoreceptor with a different color of toner that is contained to them, the intermediate transfer belt where each image formed on the photoreceptor is superposed and primary transferring is carried out and a transfer part where secondary transfer of the image transferred on the intermediate transfer belt is carried out to the paper P are provided. In this case, a secondary transfer is carried out to the leading tip part P1 in a carrying direction of the paper P at the transfer part of a forced image 82 of a specified pattern that is formed on the photoreceptor by the developing device and to which primary transfer to the intermediate transfer belt is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction peripheral thereof.

[0002]

2. Description of the Related Art Conventionally, a plurality of developing devices each containing a toner of a different color, a photoreceptor on which an image is developed with a toner of a different color by each developing device, and a toner of each color formed on the photoreceptor. A color image forming apparatus including an intermediate transfer belt on which images are primarily transferred in a superimposed state, and a transfer unit on which a multiplex image primary-transferred on the intermediate transfer belt is secondarily transferred onto paper as a transfer material. Are known.

In this type of image forming apparatus, an image forming area on a photoreceptor is exposed based on image information by an exposing means, so that an electrostatic latent image is formed in the image forming area. This electrostatic latent image is developed by supplying toner from a developing device to become a visible toner image. The toner image is temporarily transferred onto the intermediate transfer belt, and then transferred from the intermediate transfer belt to a sheet at a transfer unit.

[0004] In the above process, the sheet is superimposed on the intermediate transfer belt such that the leading end thereof coincides with the image forming area. Generally, the leading end of the image forming area on the intermediate transfer belt corresponds to the background portion of the document, and therefore, there is no toner on this portion of the intermediate transfer belt. When the leading edge of the sheet is superimposed on the portion where no toner is present, the sheet comes into close contact with the intermediate transfer belt, and as a result, there is a disadvantage that the sheet is not properly separated from the intermediate transfer belt after the completion of the transfer process.

In order to solve such inconvenience, in the prior art, as disclosed in Japanese Patent Application Laid-Open No. 1-138579, a very small amount of toner adhering means for adhering a very small amount of toner to the leading end of the image forming area is provided. An electrostatic recording device has been proposed.

[0006]

However, the types of paper used in image forming apparatuses have increased in recent years, and the basis weight of plain paper has conventionally been generally 60 to 70 g / m ² .
The use frequency of paper having a small basis weight of 40 to 50 g / m ² has been increased. With such a small basis weight paper, even if a small amount of toner is attached to the leading end area of the image forming area on the intermediate transfer belt and is interposed between the intermediate transfer belt and the paper as in the above-described conventional technique, Due to the weak stiffness, the leading end of the sheet and the intermediate transfer belt are attracted to each other, and there is a case where peeling cannot be performed properly.

Further, if a separating claw is provided as an auxiliary means, or if the roller diameter of the transfer section is increased for the purpose of separating the curvature, the cost and the size of the apparatus will be increased, resulting in a poor product concept. Become.

Further, in the prior art, a small amount of toner is deposited on the leading end of an image forming area corresponding to the leading end of a sheet. This is because there is a possibility that image quality is degraded due to information or image contamination.

[0009]

In order to solve the above-mentioned problems, an image forming apparatus according to the present invention comprises a plurality of developing devices each of which develops an image on an image carrier with a developer of a different color accommodated therein. And an intermediate transfer member on which each image formed on the image carrier is primarily transferred in a superimposed manner, and a transfer unit for secondarily transferring a multiplex image transferred on the intermediate transfer member to a transfer material, In the transfer section, a forced image of a predetermined pattern formed on the image carrier by the developing device and primarily transferred onto the intermediate transfer body is secondarily transferred to a leading end of the transfer material in a conveying direction. Things.

In the image forming apparatus according to the present invention, the predetermined pattern may be a halftone dot, a grid, a line, or a solid.

Further, in the image forming apparatus of the present invention, it is preferable that the color of the developer for forming the forced image is different depending on the ground color of the transfer material. In this case, when the ground color of the transfer material is white, it is preferable that the forced image is formed with a yellow developer.

[0012]

According to the image forming apparatus of the present invention, a forced image of a pattern such as a halftone dot, a grid, a line, or a solid pattern is secondarily transferred and formed at the leading end of the transfer material in the conveying direction. Due to the presence of the developing agent, a gap is formed between the transfer material and the intermediate transfer member. Thereby, it is possible to prevent the leading end of the transfer material from being in close contact with the intermediate transfer body in the transfer section,
The transfer material can be easily separated from the intermediate transfer member.

Further, if the forcible image is formed with a yellow developer when the background color of the transfer material is white, the forced image is not conspicuous because the difference in brightness between the forced image and the ground color of the transfer material is small. . Therefore, the forced image is not regarded as extra image information or image stain, and the image quality is not degraded.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing the overall configuration of a digital color copying machine (hereinafter, simply referred to as a "copying machine") 1 according to an embodiment of the present invention. In addition,
Here, a copying machine will be described as an example, but the present invention is also applicable to various image forming apparatuses such as a printer and a facsimile.

The copying machine 1 comprises an image reader section 10 for reading an original image and a copying section 30 for reproducing the image read by the image reader section 10.

The image reader 10 has a scanner 14 below a platen 12 on which a document is placed. The scanner 14 includes an exposure lamp 16 for irradiating the original on the platen 12, a rod lens array 18 for condensing light reflected from the original, and a contact type CCD color image sensor 20 for converting the condensed light into an electric signal. have. The scanner 14 is driven by a motor 22 at the time of reading a document, and scans a document placed on the platen 12 while moving in the direction of arrow a. The scanner 14 is electrically connected to the read signal processing unit 24. The read signal processing unit 24 converts the multi-valued electrical signals of the three colors R, G, and B photoelectrically converted by the color image sensor 20 into yellow (Y), magenta (M), cyan (C), and black (K). The data is converted into any of 8-bit gradation data.

The copying section 30 includes an endless intermediate transfer belt 32.
It has. The intermediate transfer belt 32 is wound around two parallel rollers 34 and 36 arranged at an interval, and is driven to rotate in the direction of arrow b.
The intermediate transfer member is not limited to a belt-shaped one, but may be another shape, for example, a drum-shaped one.

The upper belt 32a of the intermediate transfer belt 32
Above, four image forming units 40C and 40 corresponding to cyan, magenta, yellow, and black, respectively.
M, 40Y, and 40K are arranged along the belt moving direction (the direction of the arrow b). Each image forming unit 40C, 4
Reference numerals 0M, 40Y, and 40K denote photoconductors 42C, 42M, 42Y, and 42K that are driven to rotate in the direction of an arrow (clockwise).
Are provided. Each photoconductor 42C, 42M, 42
Around the Y and 42K, the chargers 44C, 44M, 44Y and 44K for uniformly charging the surfaces of the photoconductors 42C, 42M, 42Y and 42K and the uniformly charged photoconductors 42C and 42M Laser diodes 46 for exposing to form electrostatic latent images of cyan, magenta, yellow, and black on the surfaces of 42Y and 42K.
C, 46M, 46Y, 46K, photoconductors 42C, 42M,
Developing devices 48C, 48M, 48Y, which develop the electrostatic latent images formed on 42Y and 42K with cyan toner, magenta toner, yellow toner, and black toner, respectively.
48K, AIDC sensors 50C, 50M, 50Y, 50K for detecting the density of each toner image formed on the photoconductors 42C, 42M, 42Y, 42K, and photoconductors 42C, 42
Transfer brushes 52C, 52M, 52Y, 52 that are in contact with the back side of the intermediate transfer belt 32 for primary transfer of the toner images on M, 42Y, and 42K onto the intermediate transfer belt 32.
K, photoconductors 42C, 42M, 42Y, 42 after primary transfer
Cleaning device 54 for collecting toner remaining on K
C, 54M, 54Y, 54K, and photoconductor 42C,
Eraser lamps 56C, 56M, 56Y, 56K for erasing the electrostatic latent images on 42M, 42Y, 42K are arranged, respectively. Each laser diode 46C, 46
M, 46Y, and 46K are electrically connected to the reading processing unit 24 of the image reader unit 10 via the exposure control unit 58.

The main body of the copying section 30 is provided with paper feed cassettes 60 and 62 each containing paper as a transfer material, and a paper discharge tray 64 for discharging printed paper.

A secondary transfer roller 66 that constitutes a transfer section is sandwiched between the intermediate transfer belt 32 and the roller 34.
Is arranged. The paper fed from each of the paper feed cassettes 60 and 62 is transported along a paper transport path 68 and discharged through a nip portion of a timing roller 72, a nip portion of a secondary transfer roller 66, and a nip portion of a fixing roller 70. The paper is discharged onto the paper tray 64.

Next, the operation of the copying machine 1 having the above configuration will be described. Platen 1 of image reader unit 10
When a document is placed on the document 2 and a start button (not shown) is pressed, the scanner 14 reads the document while scanning in the direction of arrow a. The read document image is photoelectrically converted by the color image sensor 20 into multi-valued electrical signals of three colors of R, G, and B. The multi-valued electrical signals of these three colors are converted by the read signal processing unit 24 into 8-bit grayscale data of any of cyan, magenta, yellow, and black.

The exposure control unit 58 of the copying unit 30 determines the laser diode 46C of each of the image forming units 40C to 40K based on each gradation data from the read signal processing unit 24.
To 46K are sequentially emitted.

In the image forming unit 40C, the surface of the photoreceptor 42C uniformly charged by the charging charger 44C is exposed by the light emission of the laser diode 46C to form an electrostatic latent image. This electrostatic latent image is developed with cyan toner by the developing device 48C to become a toner image. Thereafter, the cyan toner image is primarily transferred from the photoconductor 42C onto the intermediate transfer belt 32 by the action of the transfer brush 52C.

In the image forming unit 40M, the surface of the photoconductor 42M uniformly charged by the charging charger 44M is exposed by the light emission of the laser diode 46M to form an electrostatic latent image. This electrostatic latent image is developed with magenta toner by the developing device 48M to become a toner image. Thereafter, the magenta toner image is primarily transferred from the photoconductor 42M onto the cyan toner image on the intermediate transfer belt 32 by the action of the transfer brush 52M.

In the image forming unit 40Y, prior to the emission of the laser diode 46Y based on the yellow gradation data from the read signal processing unit 24, the exposure control unit 58
Causes the laser diode 46Y to forcibly emit light. By the exposure by the forced light emission, a predetermined pattern (for example, solid, halftone dot, grid, line, etc.) is formed on the surface of the photoconductor 42Y.
Is formed. Subsequent to the formation of the electrostatic latent image for forced image, the surface of the photosensitive member on the upstream side in the rotation direction of the photosensitive member 42Y with respect to the electrostatic latent image for forced image is exposed by the light emission of the laser diode 46Y based on the gradation data. Then, an electrostatic latent image for a document image is formed. Both of these electrostatic latent images are developed with yellow toner by the developing device 48Y to become yellow toner images. Thereafter, the developed yellow toner forced image and yellow toner original image are primarily transferred onto the intermediate transfer belt 32 by the action of the transfer brush 52Y. At this time, the yellow toner original image is transferred so as to be superimposed on the cyan toner image and the magenta toner image, but the yellow toner forced image is transferred slightly forward in the moving direction of the intermediate transfer belt 32 with respect to these multiple toner images. Will be done. The area where the yellow toner forced image is transferred corresponds to the belt-shaped leading end P1 in the transport direction of the sheet P to be secondarily transferred, as shown in FIG.

In the image forming unit 40K, the surface of the photoreceptor 42K uniformly charged by the charger 44K is exposed by the light emission of the laser diode 46K to form an electrostatic latent image. This electrostatic latent image is developed with black toner by the developing device 48K to become a toner image. Thereafter, the black toner image is primary-transferred from the photoreceptor 42K to the cyan, magenta, and yellow toner images on the intermediate transfer belt 32 by the action of the transfer brush 52K.

The yellow toner forced image and the multi-toner image primary-transferred onto the intermediate transfer belt 32 in this manner are transferred to the secondary transfer roller 6 by the movement of the intermediate transfer belt 32.
6 is transferred to the nip portion. Into the nip portion, the paper with a ground color of white fed from the paper feed cassette 60 or 62 is fed with the timing adjusted by the timing roller 72. As a result, as shown in FIG. 3A, the yellow toner forced image 82 on the intermediate transfer belt 32 is superimposed and secondary-transferred on the leading end P1 of the paper P in the transport direction, and is transferred to the image area P2 of the paper P. Multiple toner image 84
Is secondarily transferred. At the time of this secondary transfer, the leading edge P of the sheet P is
A gap 86 is formed between the transfer belt 1 and the intermediate transfer belt 32.

The sheet P on which the yellow toner forced image 82 and the multiple toner image 84 have been secondarily transferred is fixed to the fixing roller 7.
After these images are fixed when passing through the nip portion 0, they are discharged onto the paper discharge tray 64.

In the prior art described above, as shown in FIG. 3B, even if a small amount of toner 88 is interposed between the leading end P1 of the sheet P and the intermediate transfer belt 32, a gap is formed between them. The sheet P is hardly formed, and particularly in the case of a sheet P having a small basis weight, the stiffness is very weak, so that the sheet leading end portion P1 and the intermediate transfer belt 32 may be attracted to each other, and a separation failure may occur. On the other hand, according to the copying machine 1 of the present embodiment, the forced image 82 of the predetermined pattern is secondarily transferred and formed on the leading end P1 of the sheet P in the transport direction.
A gap 86 is formed between the sheet P and the intermediate transfer belt 32 due to the presence of the yellow toner. Thereby, it is possible to prevent the leading end portion P1 of the sheet P from coming into close contact with the intermediate transfer belt 32 in the transfer section, and to transfer the sheet P to the intermediate transfer belt 32 without providing a separation claw or increasing the diameter of the roller 34.
Can be easily peeled off.

In the present embodiment, the forcible image 82 is formed with yellow toner on the paper P whose ground color is white. The reason why the forced image 82 is formed with the yellow toner is as follows. FIG. 4 shows color measurement values L, A, and B measured using a generally used colorimeter for each solid image of cyan, magenta, and yellow formed on white paper. Here, the L value represents the brightness and is generally called lightness, and the A and B values represent the color of the measurement color and generally called the hue. As shown in FIG.
Yellow has a smaller lightness difference than white paper,
The yellow color on the white background is less irritating to the human eye and the difference is hard to discern and inconspicuous. Therefore, in order to minimize the deterioration of the image quality due to the forced image 82 and obtain the effect of the present embodiment described above, it is optimal to form the forced image 82 with yellow toner. For the same reason, when the ground color of the paper is a blue color, the forced image 82 is formed with cyan toner, and when the ground color of the paper is a red color, the forced image 82 is formed with magenta toner. Is preferred.

In the present embodiment, each of the image forming units 40C, 40M, 40Y, and 40K is provided with a photosensitive member 42C,
Although the copying machine having each of 42M, 42Y, and 42K has been described, as shown in FIG.
The rotation of the rack 90 holding C, 48M, 48Y, and 48K causes each of the developing devices 48C, 48M, 48Y,
The present invention is also applicable to an image forming apparatus of a type in which toner images of each color are sequentially formed on one photoconductor 42 at 48K and are superimposed on the intermediate transfer belt 32. Also, as shown in FIG. 6A, an image forming apparatus of a type in which each of the developing devices 48C, 48M, 48Y, 48K is moved in the direction of the arrow c with respect to the photoconductor 42, or as shown in FIG. Each of the developing devices 48C, 48M, 4
The present invention can be applied to an image forming apparatus of a type in which 8Y and 48K are fixedly arranged.

The present invention is not limited to the electrophotographic image forming apparatus, but can be applied to other methods, for example, an electrostatic recording type image forming apparatus.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a copying machine according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a leading end portion of a sheet on which a forced image is formed in a conveying direction and a pattern example of the forced image.

FIG. 3A is an enlarged view of a transfer section in the present embodiment, and FIG. 3B is an enlarged view of a transfer section when a conventional technique is applied.

FIG. 4 is a chart showing color measurement values of a white background, cyan, magenta, and yellow.

FIG. 5 is a schematic configuration diagram showing another image forming apparatus to which the present invention can be applied.

FIG. 6 is a schematic diagram of still another image forming apparatus to which the present invention can be applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Copy machine (image forming apparatus), 10 ... Image reader part, 30 ... Copy part, 32 ... Intermediate transfer belt (intermediate transfer body), 40C, 40M, 40Y, 40K ... Image forming unit, 42C, 42M, 42Y, 42K: photosensitive member (image carrier), 48C, 48M, 48Y, 48K: developing device
66: Secondary transfer roller.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Futa Hamada 2-3-1-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Yasuyuki Inada Azuchi-cho, Chuo-ku, Osaka-shi, Osaka 2-3-13 Osaka International Building Minolta Co., Ltd. (72) Inventor Yoshinobu Hata 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Osaka International Building Minolta Co., Ltd. F-term (reference) 2H030 AB02 AD05 AD17 BB02 BB23 BB42 BB44 BB46 2H032 AA05 AA15 BA09 BA11 BA18 BA23 CA02 CA13 DA17 DA22 DA30

Claims (4)

[Claims] 1. A plurality of developing devices each for developing an image on an image carrier with a developer of a different color accommodated therein, and an intermediate unit in which each image formed on the image carrier is superimposed and primary-transferred. A transfer unit for transferring the multiplexed image transferred onto the intermediate transfer body to a transfer material in a secondary transfer manner. An image forming apparatus, wherein a forced image of a predetermined pattern formed on a body and primarily transferred onto the intermediate transfer body is secondarily transferred. 2. The image forming apparatus according to claim 1, wherein the predetermined pattern is a halftone dot, a grid, a line, or a solid. 3. The color of a developer for forming the forced image is as follows:
The image forming apparatus according to claim 1, wherein the image forming apparatus differs depending on a ground color of the transfer material. 4. The image forming apparatus according to claim 3, wherein when the ground color of the transfer material is white, the forced image is formed with a yellow-based developer.