JP2003162092A - Developer and color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide developer used in a color image forming apparatus capable of uniformizing all the wear of photoreceptors for black and for colors other than black without causing the cost rise of the apparatus and the deterioration in maintainability. <P>SOLUTION: When the length of the outer periphery in the two-dimensional shape of toner is defined as L, the area in the two-dimensional shape of the toner is defined as S and the shape factor SF2 of the toner is defined as SF2=(L<SP>2</SP>/S)×(100/4π), the central value of the shape factor SF2 in the black toner is set to be ≥10 smaller than the central value of the shape factor SF2 in the color toner other than the black toner. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus such as a color printer, and more particularly to a developer and a color image forming apparatus used in a color image forming apparatus called a tandem system.

[0002]

2. Description of the Related Art Conventionally, based on color image information and multicolor image information, images formed of a plurality of component colors are sequentially laminated and transferred onto a sheet to form an image in which a color image and a multicolor image are combined and reproduced. Color image forming apparatuses that output objects have become widespread. Various methods have been adopted as a method for forming a color image, but hereinafter, a color image forming apparatus using an electrophotographic process will be described in particular.
In recent years, in a color electrophotographic process, a tandem type color image forming apparatus is used to obtain a color image by arranging a plurality of photosensitive drums corresponding to each toner color in order to realize a high printing speed. It has become to.

A conventional digital color copying machine will be described below as an example of such a color image forming apparatus. The digital color copying machine includes an image reading unit for reading image data of an original, an original feeding device for sequentially supplying the original to the image reading unit, and a paper on the basis of image information read by the image reading unit. In addition, the image forming unit for forming a color image is provided.

The image reading unit irradiates the original conveyed on the original table with light and reflects light reflected from the original on the CCD (Cha).
rge Coupled Device) and the like to obtain digital image data. The document feeder is a block that sequentially conveys documents onto a document table, and for example, RADF (Reversing Automatic Documen).
t Feeder) and so on.

The image forming section is composed of a conveyor belt for conveying the paper, and a plurality of image stations for forming an image of each color component on the paper conveyed by the conveyor belt. At each image station, an image is formed on a sheet as follows.
First, the photoconductor drum is uniformly charged by the charger. Then, for the uniformly charged photosensitive drum,
A laser beam modulated in accordance with image data is emitted from the laser unit to form an electrostatic latent image. A toner image is formed by applying toner to the electrostatic latent image by a developing device. After that, the toner image on the photosensitive drum is transferred onto the sheet by the transfer discharger.

A plurality of image stations having such a configuration are provided corresponding to each toner color, that is, black K, cyan C, magenta M, and yellow Y. And
These image stations are arranged side by side in order from the upstream side in the sheet conveyance path by the conveyance belt. As a result, in each image station, the toner images of the respective colors are formed so as to overlap each other, and the color image is formed on the sheet.

In the digital color copying machine as described above,
Actually, not only color images but also monochrome images are frequently output. When the monochrome image output is selected by the user, the operations of the photoconductors other than the black photoconductor are stopped, and the photoconductors are moved so as to be separated from the conveyor belt. As a result, when a monochrome image is output, it is possible to prevent film scraping by a cleaning blade or the like on a photoconductor other than the black photoconductor that does not need to be operated, and abrasion due to paper, a transport belt, or the like.

[0008]

However, there are cases where the output of a monochrome image is used more frequently than the output of a color image, and the photoconductor for black is compared with the photoconductors for other colors. However, there is a drawback that the wear is relatively fast. Further, the wear characteristics of the four photoconductors are usually different for each of the four color toners of Y, M, C, and K, and the deterioration of the photoconductor differs depending on the color of the toner. As described above, when the photoconductors corresponding to the colors of the toner are unevenly worn and deteriorated, color unevenness of the color image quality occurs with the number of copies.

Here, as described above, when only a certain specific photosensitive drum is deteriorated due to the wear deterioration speed of the photosensitive drum for each color, only that photosensitive drum is replaced. Can't do. This is because unless all the drums are replaced, the color balance between the replaced drum and the drum that is not replaced is upset, and an output image with good image quality cannot be obtained. That is, the interval at which the photoconductor drums are replaced is determined according to the wear and deterioration state of the photoconductor drums corresponding to the most severely deteriorated color among the four photoconductor drums, that is, the photoconductor drum for black. It will be.
Therefore, the photosensitive drums of other colors are replaced even when the degree of wear and deterioration is comparatively small, and there is a problem that the size becomes large.

As measures against this problem, there are techniques disclosed in Japanese Patent Application Laid-Open No. 10-333393, Japanese Patent Application Laid-Open No. 11-24358, and Japanese Patent Application Laid-Open No. 11-52599. In these publications, the black photoconductor is made of a photoconductor made of .alpha.-Si or .alpha.-SiC to prolong its service life, and OPC (organic photoconductor) is used for photoconductors for other colors except black. ) Is proposed. However, α-Si or α-S
There is a problem that the photoconductor made of iC has low chargeability.

As a method for solving this drawback, Japanese Unexamined Patent Publication No.
In JP-A-0-333393, the thickness of the photoconductor is set to 30 μm.
In view of the above, it has been proposed that the charging difference with the organic photoconductor be 200 V or less. Also, JP-A-11-24358
In the publication, it is proposed that the voltage applied to the α-Si photoconductor be 1.05 to 2.50 times that of the organic photoconductor. Further, in JP-A-11-52599, α-S
The chargeability is increased by adding a surface layer of iC. In this way, the black photoconductor is used for a long time, and α-
In order to compensate for the low chargeability of the Si or α-SiC photosensitive member, complicated charging control is required only for black, and as a result, a new problem arises that extra cost is required.

Further, the .alpha.-Si or .alpha.-SiC photoconductor and the organic photoconductor differ in how they are affected by photosensitivity and temperature / humidity. Therefore, it is necessary to make the exposure amount, the transfer condition, and the like different between the α-Si or α-SiC photoconductor for black and the organic photoconductor used for other than black. Therefore, different control methods must be adopted for the black photoconductor and the non-black photoconductor, and as a result, there is a problem that extra cost is required.

Further, Japanese Patent Laid-Open No. 10-333393,
JP-A-11-24358 and JP-A-11-5
The α-Si or α-SiC photoconductor described in Japanese Patent No. 2599, etc. also has a problem that the production cost is obviously higher than that of the organic photoconductor.

On the other hand, as another problem, as described above,
There is a problem that the black photoconductor is often consumed. As a solution to this problem, JP-A-2000-242056 and JP-A-2000-242057 propose to increase the drum diameter or the film thickness of the black photoconductor. There is. In addition, JP-A-200
In Japanese Patent Application Laid-Open No. 1-51467, a non-contact charging means is used only for a black photoconductor, a film thickness of the black photoconductor is increased, and a resin having a large viscosity average molecular weight is used for a charge transport layer of the black photoconductor. It has been proposed to use. Furthermore, JP-A-200
In JP-A-330303, it is stated that a copolymerized polycarbonate resin is used as a resin for a tandem photoreceptor. Also, a method of providing a protective layer only on the black photoconductor is being studied.

The use of a different photosensitive member only for black as described above increases the labor for management. Further, when a resin having a large viscosity average molecular weight is used for the charge transport layer, there is a problem that it is difficult to apply, and when the film thickness of the photoconductor is increased, there are problems that the charge amount of the photoconductor is lowered and the resolution is lowered. There is also a problem that the machine becomes large when the drum diameter is increased. Further, most of the photoconductors currently used do not have a protective layer. This means that no effective protective layer has been developed yet. Further, the cause of the abrasion of the photoconductor drum is abrasion of the transfer paper, the cleaning blade, the charging, the developing portion and the like, and the main cause thereof is considered to be abrasion by the cleaning blade. Therefore, even if the charging means which is not the main factor is the charging means which is non-contact only with black, the effect can be slightly improved, but it is not the main solution.

On the other hand, Japanese Patent Laid-Open No. 5-53414,
Japanese Unexamined Patent Publication No. 11-249452 discloses that a cleanerless system is adopted for a tandem image forming apparatus. However, these are performed only for the purpose of making the machine compact, and there is no idea to extend the life of the photoconductor.

Further, in Japanese Unexamined Patent Publication No. 8-106197, the charge amount or volume specific resistance value of the toner used in the image forming apparatus of the multiple transfer system is gradually changed from the development / transfer of the former stage to the development / transfer of the latter stage. Means for doing so are disclosed. However, here, in particular, OHP (O
(Verhead Projector) sheet is intended to improve transferability, and there is no suggestion as to the abrading property of the photoconductor and realization of same-time maintenance, which are the subjects of the present invention.

Further, Japanese Patent Application Laid-Open No. 9-319179 discloses that in a color image forming apparatus, the toner adhesion amount is controlled in the former transfer process and the latter transfer process. However, the purpose thereof is to improve the image quality by taking measures against the reverse transfer phenomenon of the toner, and there is no suggestion regarding the abradability of the photoreceptor and the realization of the same-time maintenance which are the subjects of the present invention.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a photosensitive member for black and a color other than black without increasing the cost of the apparatus and deteriorating the maintainability. It is an object of the present invention to provide a developer used in a color image forming apparatus and a color image forming apparatus capable of uniformizing all wear.

[0020]

In order to solve the above-mentioned problems, the developer according to the present invention forms an electrostatic latent image by exposing a photoreceptor according to image information,
A color image having a plurality of image forming stations for forming a toner image by adhering toner to the electrostatic latent image and transferring the toner image onto a sheet corresponding to black and colors other than black, respectively. The developer used in the forming apparatus is characterized in that the abradability of the black developer with respect to the photoreceptor is smaller than the abradability of the developer of colors other than black with respect to the photoreceptor.

According to the above construction, since the abradability of the black developer with respect to the photoconductor is made smaller than the abradability of the photoconductor with the non-black developer, the abrasion and deterioration of the photoconductor corresponding to black is deteriorated. It is possible to make the speed almost equal to the wear deterioration speed of the photoconductor corresponding to a color other than black. As a result, it is possible to make the intervals for replacing the photoconductors the same for the photoconductors corresponding to black and colors other than black, and to avoid the waste of replacing the photoconductors even though the degree of wear is small. It can be lost.

Further, as a means for making a difference in abrasion property between the photoconductor corresponding to black and the photoconductor corresponding to a color other than black, a method of making the abrasiveness of the developer itself different is adopted. Become. Therefore, for example, as in the past,
Since it is not necessary for the photoconductor itself to have different configurations for black and for colors other than black, it is possible to use a common photoconductor for black and for colors other than black. Therefore,
It is possible to improve the maintainability and reduce the device cost.

Further, in the developer according to the present invention, in the above constitution, the outer peripheral length of the toner contained in the developer in the two-dimensional shape is L, the area of the toner in the two-dimensional shape is S, and the shape is The coefficient SF2 is calculated as SF2 = (L ² /
When defined as (S) × (100 / 4π), the representative value of the shape factor SF2 of the black toner may be smaller than the representative value of the shape factor SF2 of the toner of a color other than black.

The above-mentioned SF2 has a value closer to 100 as the shape of the toner particles is closer to a circle, and has a larger value as the peripheral shape is more complicated. That is, SF2 is an index showing the toner surface area (irregularity). According to the above configuration, the black toner has a smaller surface irregularity as a whole than the toner of a color other than black. That is,
According to the above configuration, the abradability of the black developer with respect to the photoconductor can be made smaller than the abradability of the non-black developer with respect to the photoconductor.

Further, the developer according to the present invention has a constitution in which the representative value of the shape factor SF2 of the black toner is smaller than the representative value of the shape factor SF2 of the toner of a color other than black by 10 or more. Good.

With this setting, it is possible to make the wear deterioration rate of the photoconductor corresponding to black almost equal to the wear deterioration rate of the photoconductor corresponding to colors other than black from the experimental result described later. . Therefore, it is possible to use a common photoconductor for black and for a color other than black, and it is possible to improve the maintainability and reduce the device cost.

In the developer according to the present invention, the maximum diameter in the two-dimensional shape of the toner is D, the area in the two-dimensional shape of the toner is S, and the shape factor SF1 is SF1 = ( D ² / S) × (100π / 4)
, The shape factor SF1 of the black toner is defined as
The representative value of is the shape factor S for toner of colors other than black.
The configuration may be smaller than the representative value of F1.

The above SF1 has a value closer to 100 as the shape of the toner particle is closer to a circle, and conversely becomes larger as the shape is elongated. That is, SF1 is the major axis of the toner /
It is an index showing the difference (strainability) in the minor axis. Here, the smaller the distortability of the toner particles, that is, the closer it is to the spherical shape,
Since the fluidity of the toner is improved and cleaning is facilitated, the wear of the photoconductor is reduced. Therefore, according to the above configuration, the abradability of the black developer with respect to the photoconductor can be made smaller than the abradability of the photoconductor with the non-black developer. Therefore, it is possible to further reduce the difference between the wear deterioration rate of the photoconductor corresponding to black and the wear deterioration rate of the photoconductor corresponding to colors other than black.

Further, the developer according to the present invention has a constitution in which the representative value of the shape factor SF1 of the black toner is smaller than the representative value of the shape factor SF1 of the toner of a color other than black by 10 or more. Good.

When the above setting is made, the difference between the wear deterioration rate of the photoconductor corresponding to black and the wear deterioration rate of the photoconductor corresponding to colors other than black can be further reduced from the experimental result described later. It will be possible.

Further, the developer according to the present invention may have a constitution in which the black toner is spheroidized by a mechanical impact force in the above constitution.

When a mechanical impact force is applied to the toner, it has a characteristic that its shape becomes closer to a sphere.
Therefore, when a mechanical impact force is applied to the black toner as in the above configuration, the shape of the black toner can be approximated to a spherical shape, and thus the shape factor SF2
It becomes possible to realize the numerical limitation regarding SF1 and SF1.

Further, the developer according to the present invention may have a constitution in which the black toner is spheroidized by heat treatment in the above constitution.

When the heat treatment is applied to the toner, it has a characteristic that its shape becomes closer to a sphere. Therefore, when the heat treatment is applied to the black toner as in the above-described configuration, the shape of the black toner can be made close to a sphere, so that it is possible to realize the numerical limitation on the shape factors SF2 and SF1. Becomes

Further, the developer according to the present invention may have a constitution in which the black toner is formed by polymerization in the above constitution.

Generally, when the toner is formed by polymerization, it is possible to make the shape of the toner nearly spherical. Therefore, if the black toner is formed by polymerization as in the above configuration, the above shape factors SF2 and SF
It becomes possible to realize numerical limitation regarding 1.

The color image forming apparatus according to the present invention includes a photoconductor, an exposure device which forms an electrostatic latent image by exposing the photoconductor according to image information, and a photoconductor. A plurality of developing devices that form a toner image by adhering toner to the formed electrostatic latent image, and an image forming station that forms an image by transferring the toner image to a sheet, A color image forming apparatus provided in plurality corresponding to colors other than black, wherein each of the developing devices forms a toner image using the developer according to the present invention.

In the above structure, an image is formed by using a developer capable of making the abradability of the black developer with respect to the photoconductor less than the abradability of the photoconductor with the non-black developer. ing. Therefore, it is possible to make the wear deterioration speed of the photoconductor corresponding to black substantially equal to the wear deterioration speed of the photoconductor corresponding to colors other than black. As a result, the interval for exchanging the photoconductor is
It is possible to make all the photoconductors corresponding to black and colors other than black the same, and it is possible to eliminate waste such as replacement even though the degree of wear is small.

Further, as a means for making a difference in abrasion property between the photoconductor corresponding to black and the photoconductor corresponding to a color other than black, the method of making the abrasiveness of the developer different is adopted. Become. Therefore, for example, as in the past,
Since it is not necessary for the photoconductor itself to have different configurations for black and for colors other than black, it is possible to use a common photoconductor for black and for colors other than black. Therefore,
It is possible to improve the maintainability and reduce the device cost.

[0040]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a sectional view showing the structure of a digital color copying machine (hereinafter simply referred to as a copying machine) 1 as a color image forming apparatus according to this embodiment. This copier 1 is a double-sided automatic document feeder (RADF; Reversing Auto).
matic Document Feeder) 112, image reading unit 11
0 and the image forming unit 210.

A document table 111 and an operation panel described later are provided on the upper surface of the main body of the copying machine 1. Further, the double-sided automatic document feeder 112 is supported on the upper surface of the document table 111 so as to be openable and closable with respect to the document table 111.

The double-sided automatic document feeder 112 first conveys the document so that one surface of the document faces the image reading section 110 at a predetermined position of the document table 111. Then, after the image reading on the one surface is completed, the original is turned over and conveyed toward the original table 111 so that the other surface faces the image reading unit 110 at a predetermined position of the original table 111. It is like this. Then, the double-sided automatic document feeder 112 discharges this document after the image reading on both sides of one document is completed, and executes the double-sided conveyance operation for the next document. The above-described operations of conveying the document and inverting the front and back sides are performed by the copying machine 1.
It is controlled in relation to the overall movement.

The image reading section 110 is arranged below the document table 111 in order to read the image of the document conveyed onto the document table 111 by the double-sided automatic document feeder 112. The image reading unit 110 includes a document scanning unit 1 that reciprocates in parallel along the lower surface of the document table 111.
13 and 114, an optical lens 115, and a CCD line sensor 116 which is a photoelectric conversion element.

The document scanning bodies 113 and 114 are composed of a first scanning unit 113 and a second scanning unit 114. The first scanning unit 113 has an exposure lamp that exposes the image surface of the document, and a first mirror that reflects the reflected light image from the document in a predetermined direction. Then, the first scanning unit 113 is controlled so as to reciprocate in parallel at a predetermined scanning speed while maintaining a constant distance from the lower surface of the document table 111.

The second scanning unit 114 includes second and third mirrors that further reflect the reflected light image from the original reflected by the first mirror of the first scanning unit 113 in a predetermined direction. Have The second scanning unit 114 is controlled so as to reciprocate in parallel with the first scanning unit 113 while maintaining a constant speed relationship.

The optical lens 115 reduces the reflected light image from the document reflected by the third mirror in the second scanning unit 114, and forms the reduced light image at a predetermined position on the CCD line sensor 116. It is a thing. The optical lens 115 is composed of, for example, a plurality of lens groups.

The CCD line sensor 116 sequentially photoelectrically converts the formed light image and outputs it as an electric signal. The CCD line sensor 116 reads, for example, a black and white image or a color image, and R (red), G (green),
It is composed of a three-line color CCD capable of outputting line data obtained by color-separating each color component of B (blue). The document image information converted into an electric signal by the CCD line sensor 116 is further transferred to an image processing unit (not shown) and subjected to predetermined image data processing.

Next, the structure of the image forming section 210 and the structure of each section related to the image forming section 210 will be described.
Below the image forming unit 210, a paper feeding mechanism 211 is provided, which separates the sheets (recording media) P stacked and accommodated in the sheet tray one by one and supplies them toward the image forming unit 210. Then, the sheet P that has been separated and supplied one by one is controlled in timing by a pair of registration rollers 212 arranged in front of the image forming section 210, and the image forming section 21 is controlled.
Transported to 0. Further, the sheet P having an image formed on one side is re-supplied and conveyed to the image forming unit 210 at the same timing as the image formation of the image forming unit 210.

Below the image forming section 210, a transfer / conveying belt mechanism 213 is arranged. The transfer / transport belt mechanism 213 is configured such that the transfer / transport belt 21 is stretched between the drive roller 214 and the driven roller 215 so as to extend substantially in parallel.
The sheet P is electrostatically adsorbed on the sheet 6 and conveyed. Then, in the vicinity of the lower side of the transfer / transport belt 216,
A pattern image detection unit is provided.

Further, on the downstream side of the transfer / transport belt mechanism 213 in the paper transport path, a fixing device 217 for fixing the toner image transferred and formed on the paper P onto the paper P.
Are arranged. The sheet P that has passed through the nip between the pair of fixing rollers in the fixing device 217 passes through the switching gate 218 that switches the transport direction, and the sheet discharge tray 220 attached to the outer wall of the main body of the copying machine 1 by the discharging roller 219. Discharged on top.

The switching gate 218 is used for the sheet P after fixing.
Is selectively switched between a path for discharging the paper P to the copying machine main body 1 and a path for re-supplying the paper P toward the image forming unit 210. The sheet P whose conveyance direction has been switched again toward the image forming unit 210 by the switching gate 218 is turned upside down through the switchback conveyance path 221 and then the image forming unit 21.
It is supplied again to 0.

Further, above the transfer / transport belt 216 in the image forming section 210, in the vicinity of the transfer / transport belt 216, the first image forming station Pa, the second image forming station Pb, and the third image forming station are provided. P
c and the fourth image forming station Pd are arranged in parallel in order from the upstream side of the paper transport path. The transfer / transport belt 216 is frictionally driven by the drive roller 214 in the direction indicated by the arrow Z in FIG. 1 to carry the sheet P fed through the sheet feeding mechanism 211 as described above, and to transfer the sheet P to the image forming stations Pa. It is sequentially transported to Pd.

The image forming stations Pa to Pd have substantially the same structure. Each image station P
Reference characters a, Pb, Pc, and Pd denote photoconductor drums (photoconductors) 222a and 222 that are rotationally driven in the arrow F direction shown in FIG.
b, 222c, and 222d, respectively.

Around the photosensitive drums 222a to 222d, chargers 223a, 223b, 223c, and 223d for uniformly charging the photosensitive drums 222a to 222d, and the photosensitive drums 222a to 222d are formed. Developing device 224 for developing each electrostatic latent image
a, 224b, 224c, and 224d and transfer dischargers 225a, 225b, and 225 for transferring the developed toner images on the photosensitive drums 222a to 222d to the paper P.
c and 225d, and the photosensitive drums 222a to 222
Cleaning device 22 for removing the toner remaining on d
6a, 226b, 226c, and 226d are sequentially arranged along the rotation direction of the photoconductor drums 222a to 222d.

The above cleaning devices 226a and 226
The cleaning method used in b, 226c, and 226d is a blade cleaning method. As a method for collecting the residual toner on the photoconductor, it is possible to use a fur brush method. Further, the fur brush method and the blade cleaning method may be used together.

Further, each of the photosensitive drums 222a to 222d
Above the above, laser beam scanner unit 227
a, 227b, 227c, and 227d are provided, respectively. Laser beam scanner units (exposure devices) 227a to 227d are semiconductor laser elements (not shown) that emit dot light modulated according to image data,
Polygon mirror (deflecting device) 240a for deflecting the laser beam from the semiconductor laser element in the main scanning direction
-240d and the laser beams deflected by the polygon mirrors 240a-240d, the photosensitive drums 222a-222d.
Fθ lens 241a to form an image on the surface of 222d
241d and mirrors 242a to 242d and 243a to 24
It is composed of 3d and the like.

The laser beam scanner 227a receives a pixel signal corresponding to the black component image of the color original image, the laser beam scanner 227b receives a pixel signal of the cyan component image of the color original image, and the laser beam scanner 227c receives the pixel signal. Pixel signals corresponding to the magenta color component image of the color original image, and the laser beam scanner 2
Pixel signals corresponding to the yellow color component image of the color original image are input to 27d. As a result, electrostatic latent images corresponding to the color-converted document image information are formed on the photoconductor drums 222a to 222d. The developing device 227a contains black toner, the developing device 227b contains cyan toner, the developing device 227c contains magenta toner, and the developing device 227d contains yellow toner. Photoreceptor drums 222a-22
The electrostatic latent image on 2d is developed with toner of each of these colors. As a result, the document image information color-converted by the image forming unit 210 is reproduced as a toner image of each color.

Further, a sheet suction charger 228 is provided between the first image forming station Pa and the sheet feeding mechanism 211. The adsorption charger 228 charges the surface of the transfer / transport belt 216. The sheet P supplied from the sheet feeding mechanism 211 due to the charging by the suction charger 228 is securely adsorbed on the transfer / conveying belt 216 from the first image forming station Pa to the fourth image forming station Pd. They will be transported without any gap between them.

On the other hand, a static eliminator 229 is provided in a region between the fourth image station Pd and the fixing device 217, which is just above the drive roller 214.
An alternating current is applied to the static eliminator 229 to separate the paper P electrostatically attracted to the transfer belt 216 from the transfer transfer belt 216.

In the digital color copying machine having the above-mentioned configuration, cut sheet-shaped paper is used as the paper P. This paper P is sent out from the paper feed cassette and fed to the paper feed mechanism 2
When the sheet 11 is fed into the guide of the sheet feeding / conveying path, the tip portion of the sheet P is detected by a sensor (not shown),
Based on the detection signal output from this sensor, the pair of registration rollers 212 temporarily stops. And
The sheet P is sent onto the transfer / conveying belt 216 rotating in the direction of arrow Z in FIG. 1 at a timing with each of the image stations Pa to Pd. At this time, since the transfer / conveying belt 216 is charged by the suction charger 228 as described above, the sheet P is stabilized by the electrostatic suction force while passing through the image stations Pa to Pd. And then transported.

In each of the image stations Pa to Pd, the toner images of the respective colors are formed, and the toner images of the respective colors are superposed on each other on the supporting surface of the sheet P which is electrostatically attracted by the transfer and transport belt 216 and is transported. Is transcribed. When the transfer of the image by the fourth image station Pd is completed, the paper P is sequentially transferred from the leading end portion thereof.
It is peeled off from the transfer / conveying belt 216 by the discharger for discharging electricity and guided to the fixing device 217. Finally, the paper P having the toner image fixed thereon is ejected onto the paper ejection tray 220 from a paper ejection port (not shown).

In the structure described above, the laser beam scanner units 227a to 227d scan and expose the laser beam to perform optical writing on the photosensitive drums 222a to 222d. . On the other hand, instead of the laser beam scanner unit, a writing optical system (LED head) including a light emitting diode array and an imaging lens array may be used. The LED head is smaller in size than the laser beam scanner unit and has no moving parts, so it is excellent in quietness. Therefore, the LED head can be preferably used in an image forming apparatus such as a tandem type digital color copying machine which requires a plurality of optical writing units.

Next, the flow of processing in the copying machine 1 having the above configuration will be described. In a color image forming apparatus such as the copying machine 1 described above, in actuality, not only color printing but also monochrome (black) printing is frequently performed. Therefore, in the following, operation control executed according to the user's mode designation will be described with reference to the flowchart shown in FIG.

First, in step 1 (hereinafter referred to as S1), the mode designated by the user is
It is determined whether or not the color mode is for outputting a color image. If YES in S1, that is, if the color mode is designated by the user, first in S2, black K, cyan C, magenta M, and yellow Y are selected.
Each of the photoconductors 222a, 222b, 222 corresponding to each color of
c and 222d are arranged at a normal position in contact with the transfer / conveying belt 216. Then, in S3, each of the photoconductors 222a, 222b, 222c, and 222d.
To rotate. Then, in accordance with the electrophotographic process, the corresponding charging / developing operation or the like is performed on each of the photoconductors 222a, 222b, 222c, and 222d (S4). With the above operation, a color image is formed on the paper P.

On the other hand, if NO in S1, that is, if the monochrome mode for outputting a monochrome image is designated,
First, in S5, by driving the contact / separation mechanism, the photoconductors 222b, 2b corresponding to the colors C, M, Y
22c and 222d are separated from the transfer / transport belt 216. Further, each of these photoconductors 222b, 222
The rotation drive of c and 222d is turned off and brought into a stopped state (S6). In addition, each of these photoconductors 222b, 222
Also, the charging / developing operations for c and 222d are turned off (S7). In this state, the black photoconductor 222a
Is driven to rotate (S8), and according to the electrophotographic process,
A charging / developing operation or the like is performed on the black photoconductor 222a (S9). With the above operation, a black and white monochrome image is formed on the paper P.

Thus, when the monochrome mode is designated,
Photoconductors 222b, 222 other than the black photoconductor 222a
c and 222d are controlled to be in a non-operating state such as stopping the rotation operation thereof and to be separated from the transfer / conveying belt 216. As a result, in the monochrome mode, the photoconductors 222b, 222c, 22 that do not need to operate are
Film scraping with a cleaning blade for 2d,
It is possible to minimize wear due to the transfer paper, the transfer / transport belt 216, and the like.

Next, the toner used in this embodiment will be described. In the present embodiment, a toner having a different shape from the black toner and a shape other than black, that is, the shapes of the Y, M, and C toners is used. As a result, the abradability of the black toner to the photoconductor drum is made less than the abradability of the other development color toners to the photoconductor drum, and the life of the black photoconductor drum can be extended.

In this embodiment, an image analyzer (manufactured by Nippon Regulator Co., model name: Luzex 5000) is used as an apparatus for analyzing the shape of toner. This image analyzer is a device capable of highly accurately quantitatively analyzing the area, length, shape, etc. of an image captured by an optical microscope or the like based on a statistical method called image analysis.

In this embodiment, the representative value of the shape factor SF2 of the black toner measured by this image analyzer is 10 or more smaller than the representative value of the shape factor SF2 of the toner other than black toner. Then, the shape of the toner is set. Also,
Further, the shape factor SF1 of the representative value for black toner is
Is a shape factor S of a representative value in toner of colors other than black
It is preferable to set the shape of the toner so that it is smaller than F1 by 10 or more. Here, for example, an average value is adopted as the representative value.

SF1 is a value obtained by squaring the maximum value D of the diameter of the toner particles in the two-dimensional shape, which is 2 of the toner particles.
A value obtained by dividing the value obtained by dividing the area S in the dimensional shape by π / 4 and further multiplying it by 100 is shown. Expressed as a formula, it is as follows. SF1 = (D ² / S) × (100π / 4) (1) This SF1 has a value closer to 100 as the shape of the toner particles is closer to a circle, and conversely has a larger value as the shape of the toner particle is elongated. That is, SF1 is an index showing the difference (distortion) between the long diameter and the short diameter of the toner.

SF2 is a value obtained by squaring the length L of the outer periphery of the toner particle in the two-dimensional shape, divided by the area S of the toner particle in the two-dimensional shape, and then multiplying by 1 / 4π. It shows the doubled value. Expressed as a formula, it is as follows. SF2 = (L ² / S) × (100 / 4π) (2) This SF2 has a value closer to 100 as the shape of the toner particles is closer to a circle, and is larger as the peripheral shape is more complicated. That is, SF2 is an index showing the toner surface area (irregularity). If the toner has a perfect spherical shape, SF1 = SF2 = 100.

In general, a toner having a larger unevenness on the surface of the toner has a higher abradability of the toner on the coating film of the photoreceptor than a toner having a smooth surface. Therefore, in order to have a sufficient difference in the abrasiveness between the black toner and the toners other than the black color, as described above, the shape factor SF2 of the black toner is the shape of the toner other than the black color. It is necessary to be smaller than the coefficient SF2 by 10 or more. Further, if the toner has a large distortion property and a toner having a smaller distortion property, the fluidity of the toner is improved and cleaning is facilitated. Therefore, as described above, it is preferable to set the shape of the toner so that the shape factor SF1 of the black toner is smaller than the shape factor SF1 of the toner other than black by 10 or more.

Although the optimum ranges for SF1 and SF2 have been shown above, the present invention is not limited to this. Basically, the shape factor SF for black toner is
If the representative value of 2 is smaller than the representative value of the shape factor SF2 of the toner of colors other than black, it is possible to give the abrasiveness different between the black toner and the toner of colors other than black. In addition, the shape factor SF1 of the black toner is
The representative value of is the shape factor S for toner of colors other than black.
Even if it is smaller than the representative value of F1, it is possible to give a difference in abrasivity between black toner and toner of colors other than black.

The shape of the toner greatly changes depending on the material and the manufacturing method. Generally, the toner obtained by polymerization is more spherical than the toner obtained by the pulverization method. Further, a method is known in which the toner obtained by the pulverization method is spheroidized by mechanical impact force or heat treatment. The spheroidizing method includes a known method, for example, a method in which heat treatment is performed in a high-temperature air flow using a sfusion system or a spray drying apparatus, and a method using a mechanofusion apparatus such as a hybridizer or an Ong mill.

The toner used in the present invention is specifically composed of the following constituent materials. As the binder resin, a known resin generally used for toner can be adopted. That is, as the binder resin,
Specifically, for example, polystyrene, polychlorostyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, Styrene-vinyl acetate copolymer, styrene-acrylic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl acrylate Copolymer, styrene-acrylonitrile-
Styrene resins such as acrylic ester copolymers; vinyl chloride resins; rosin-modified maleic acid resins; phenol resins; epoxy resins; saturated polyester resins; unsaturated polyester resins; polyethylene, polyethylene such as ethylene-ethyl acrylate copolymer System resins; polypropylene resins; ionomer resins; polyurethane resins; silicone resins; ketone resins; xylene resins; polyvinyl butyral resins; polycarbonate resins;
It is not particularly limited.

The above styrene resin is a homopolymer or copolymer of styrene or its derivative. As the styrene-acrylic acid ester copolymer, specifically, for example, styrene-methyl acrylate copolymer,
Examples thereof include a styrene-ethyl acrylate copolymer, a styrene-butyl acrylate copolymer, a styrene-octyl acrylate copolymer, and a styrene-phenyl acrylate copolymer. Specific examples of the styrene-methacrylic acid ester copolymer include styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, and styrene-octyl methacrylate. Examples thereof include copolymers and styrene-phenyl methacrylate copolymers.

These binder resins may be used alone or in combination of two or more. Of the binder resins exemplified above, styrene resins, saturated polyester resins, and unsaturated polyester resins are more preferable. The method for producing the binder resin is not particularly limited.

As the colorant, known pigments and dyes generally used for toner can be adopted.
That is, specific examples of the colorant include inorganic pigments such as carbon black, iron black, navy blue, yellow lead (chrome yellow), titanium oxide, zinc white, alumina white, calcium carbonate; phthalocyanine blue, Victoria. Organic pigments such as blue, phthalocyanine green, malachite green, Hansa yellow G, benzidine yellow, lake red C, quinacridone magenta; organics such as rhodamine dyes, triallylmethane dyes, anthraquinone dyes, monoazo dyes, diazo dyes dye;
However, it is not particularly limited.

These colorants may be used alone or in appropriate combination depending on the color to be colored in the toner. The colorant may be pretreated by a known method such as a so-called masterbatch method. The amount of the colorant used is not particularly limited, but the lower limit is 100 parts by weight of the binder resin.
It is 1 part by weight or more, more preferably 3 parts by weight or more, and the upper limit is preferably 25 parts by weight or less, more preferably 20 parts by weight or less.

As the charge control agent, those having a negative charging property include monoazo metal compounds, organometallic compounds, chelate compounds, styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, aromatic hydroxycarboxylic acids, esters. And phenol derivatives such as bisphenol. Above all, a colorless or pale color charge control agent that does not affect the color tone of the color toner is particularly preferable. Examples of the negative charge control agent include organic metal complexes such as metal complexes of alkyl-substituted salicylic acid (for example, chromium complex or zinc complex of diethyl butyl salicylic acid).

Examples of positively chargeable ones include nigrosine type dyes, triphenylmethane type dyes, quaternary ammonium salts, imidazole compounds, metal salts of higher fatty acids, etc., but are not particularly limited thereto. . These charge control agents may be used by simultaneously containing one kind or a plurality of kinds. The amount of the charge control material used is not particularly limited, but the lower limit is 0.1 part by weight or more, and more preferably 0.5 part by weight or more, relative to 100 parts by weight of the binder resin. And the upper limit is 20
It is suitable if it is not more than 10 parts by weight, and more preferably not more than 10 parts by weight.

Further, a dispersant / release agent may be contained in order to obtain sufficient release / release properties of the toner from the fixing roller or the fixing belt. Examples of the dispersant / release agent include synthetic waxes such as polypropylene and polyethylene, paraffin wax and derivatives thereof, petroleum waxes such as microcrystalline wax and derivatives thereof and modified wax thereof, carnauba wax, rice wax, can wax. A plant wax such as delilla wax is used. By maintaining sufficient releasability with such a dispersant / release agent, high temperature / low temperature offset can be prevented.

The toner particles are produced by a step of forming a toner particle by dispersing a colorant and optionally other materials in the binder resin as described above. Specifically, a known method of powderizing a toner material composed of a binder resin, a colorant, and other materials is used. That is, in order to form toner particles, a kneading and pulverizing method, a suspension polymerization method of polymerizing particles in which a binder resin monomer, a colorant, and other materials are dispersed in an aqueous medium, an emulsion of a binder resin It may be an emulsion coagulation method in which the particles are coagulated and fixed together with a colorant and other materials.

In the case of the emulsion aggregation method, the emulsion particles may be those produced by the emulsion polymerization method, or those obtained by dissolving the binder resin in a solvent and finely dispersing it in an aqueous medium. .

Further, a method may be adopted in which the binder resin, the colorant and other materials are dissolved and dispersed in a solvent, suspended and dispersed in an aqueous medium, and then the solvent is removed. Alternatively, a method may be adopted in which the binder resin, the colorant, and other materials are dissolved and dispersed in a solvent, dispersed in a gas with a spray dryer or the like, and the solvent is removed at the same time. Further, a method of precipitating the binder resin dissolved in the solvent by lowering the temperature or adding a poor solvent may be adopted.

Further, a method of dispersing and cooling the melted material in a medium may be adopted. Further, a technique of dispersion polymerization or seed polymerization may be used. Particularly, it is preferable that the black toner is formed by the polymerization method, and the toners of other developing colors are formed by the kneading and pulverizing method. Alternatively, it is preferable that the black toner is also spheronized by a kneading and pulverizing method and further by mechanical impact force or heat treatment.

According to the method described above, the volume average particle size (D50v) of 3 to 3 is obtained by measuring the particle size with a Coulter counter TA-II (trade name) manufactured by Coulter or a Coulter Multisizer (trade name) manufactured by Coulter.
Make toner particles that are 10 μm.

Next, colorless or white organic and inorganic fine particles may be dispersed / added to the toner surface in order to add functions such as fluidity and abrasiveness to the obtained toner particles. The amount of addition is preferably 0.3 to 5 parts by weight of organic or inorganic fine powder with respect to 100 parts by weight of toner.

Examples of the organic fine powder include acrylic resin, polyester resin, fluorine resin, styrene resin,
Melamine resin etc. are mentioned. Examples of the inorganic fine powder include silica fine powder, titanium oxide fine powder, and alumina fine powder. In particular, the inorganic fine powder having a specific surface area of 90 to 150 m @ 2 / g) gives good results by nitrogen adsorption measured by the BET method. Inorganic fine powder, if necessary, hydrophobicization, silicone varnish for the purpose of charge control, various modified silicone varnish, silicone oil, various modified silicone oil, silane coupling agent, silane coupling agent having a functional group, It is also preferably treated with a treating agent such as another organosilicon compound. Two or more kinds of treatment agents may be used. In particular,
A silica fine powder surface-treated with silicone oil or the like is preferable.

Other additives include, for example, Teflon (registered trademark), zinc stearate, polyvinylidene fluoride,
Lubricants such as silicone oil particles (containing about 40% silica) are preferably used. Further, abrasives such as cerium oxide, silicon carbide, calcium titanate and strontium titanate are preferably used. Further, a small amount of a conductivity-imparting agent such as zinc oxide, antimony oxide, or tin oxide may be used as white particles having a polarity opposite to that of the toner particles as a developing property improver.

As described above, in the present embodiment, by controlling the shape of the toner based on the shape factors SF1 and SF2, the abrasiveness of the black toner and the toner of colors other than black is changed. However, it is not limited to this. For example, a method of changing the abrasivity by controlling the amount and type of abrasive contained in the toner, a method of changing the abrasivity by changing the type of resin constituting the toner, a method of changing the abrasivity by changing the particle size of the carrier. It is possible to change the method.

[0093]

EXAMPLES The present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Preparation Example 1 of Black Toner 100 parts by weight of a styrene-butyl acrylate copolymer as a binder resin, 2 parts by weight of a metal salt of alkylsalicylic acid as a charge control agent, and 6 parts by weight of carbon black. 3 parts by weight of carnauba wax A as a release material was mixed with a Henschel mixer, and then melt-kneaded using a biaxial kneader. The kneaded product was pulverized by a jet pulverizer and then classified to prepare a black toner 1 having an average particle diameter of 8 μm.

Further, as a surface treatment agent for the toner, 1 part by weight of hydrophobic silica having a primary particle diameter of 15 nm and 1 part by weight of hydrophobic silica having a primary particle diameter of 40 nm were added, and then externally added with a Henschel mixer. . Then, the obtained black toner and ferrite carrier were mixed with a Nauta mixer to obtain a two-component developer having a toner concentration of 5%.

Preparation Example 2 of Black Toner 100 parts by weight of a polyester resin as a binder resin, 2 parts by weight of a metal salt of alkylsalicylic acid as a charge control agent, 6 parts by weight of carbon black, and carnauba wax A as a release agent. Was mixed with 3 parts by weight with a Henschel mixer and then melt-kneaded using a biaxial kneader. The kneaded product was crushed by a jet crusher and then classified to prepare a black toner 2 having an average particle diameter of 8 μm.

Further, as a surface treatment agent for the toner, 1 part by weight of hydrophobic silica having a primary particle diameter of 15 nm and 1 part by weight of hydrophobic silica having a primary particle diameter of 40 nm were added, and then externally added with a Henschel mixer. . Then, the obtained black toner and ferrite carrier were mixed with a Nauta mixer to obtain a two-component developer having a toner concentration of 5%.

(Preparation Example 3 of Black Toner) The black toner 2 obtained in Preparation Example 2 of black toner was placed in a Mechanofusion (trade name) processing apparatus manufactured by Hosokawa Micron Co., Ltd. and heated in a gas phase without heating. The black toner 2 was subjected to a spheroidizing treatment by repeatedly applying mechanical energy having an impact force to the black toner 2 for 5 minutes, thereby preparing a black toner 3.

Further, as a surface treatment agent for the toner, 1 part by weight of hydrophobic silica having a primary particle diameter of 15 nm and 1 part by weight of hydrophobic silica having a primary particle diameter of 40 nm were added, and then externally added with a Henschel mixer. . Then, the obtained black toner and ferrite carrier were mixed with a Nauta mixer to obtain a two-component developer having a toner concentration of 5%.

(Preparation Example 4 of Black Toner) The black toner 2 obtained in Preparation Example 2 of black toner was blown into a sffusion (trade name) system manufactured by NPK in the state of being dispersed in primary particles, and the toner and hot air were blown. The temperature at the point of collision is about 180 ℃
The black toner 4 was manufactured by applying spheroidizing treatment by applying hot air adjusted so that

Further, as a surface treatment agent for the toner, 1 part by weight of hydrophobic silica having a primary particle diameter of 15 nm and 1 part by weight of hydrophobic silica having a primary particle diameter of 40 nm were added, and then externally added with a Henschel mixer. . Then, the obtained black toner and ferrite carrier were mixed with a Nauta mixer to obtain a two-component developer having a toner concentration of 5%.

Preparation Example 5 of Black Toner In a flask equipped with a stirrer containing water and methyl cellulose as a dispersion stabilizer, 80 parts by weight of styrene monomer and 20 of n-butyl acrylate monomer were previously used as the binder resin monomer. Parts by weight, 2 parts by weight of a metal salt of alkylsalicylic acid as a charge control agent, 6 parts by weight of carbon black, 3 parts by weight of carnauba wax A as a release agent, and 2 parts by weight of azobisisobutyronitrile as a polymerization initiator. Then, the mixture was mixed and dispersed, and the mixture was stirred at 80 ° C. for 5 hours to carry out polymerization. After completion of the reaction, the produced toner particles are cooled to 5 to 6
After washing with water, filtration and drying, air classification was carried out to prepare black toner 5 having an average particle size of 8 μm.

Further, as a surface treatment agent for the toner, 1 part by weight of hydrophobic silica having a primary particle diameter of 15 nm and 1 part by weight of hydrophobic silica having a primary particle diameter of 40 nm were added, and then externally added with a Henschel mixer. . Then, the obtained black toner and ferrite carrier were mixed with a Nauta mixer to obtain a two-component developer having a toner concentration of 5%.

(Preparation Example 1 of color toner) 100 parts by weight of a polyester resin as a binder resin, 2 parts by weight of a metal salt of alkylsalicylic acid as a charge control agent, and the following colorants of cyan, magenta and yellow are selected. After mixing 4 parts by weight of the coloring agent for color and 4 parts by weight of carnauba wax A as a release material with a Henschel mixer,
Melt kneading was performed using a biaxial kneader. This kneaded product was pulverized by a jet pulverizer and then classified to prepare color toner 1 of three colors each having an average particle diameter of 8 μm. As the colorant, for cyan toner, C.I. I. Pig.
B-15 was used, and as the magenta toner, C.I. I. Pi
g. R-122 is used, and as a yellow toner, C.I.
I. Pig. Y-17 was used.

Further, 1 part by weight of hydrophobic silica having a primary particle size of 15 nm and 1 part by weight of hydrophobic silica having a primary particle size of 40 nm were added as a surface treatment agent for the toner, and then externally added with a Henschel mixer. . After that, the obtained toners of respective colors and the ferrite carrier were mixed by a Nauter mixer to obtain a two-component developer having a toner concentration of 5%.

(Preparation Example 2 of color toner) In the same manner as in Preparation Example 1 of color toner except that a styrene-butyl acrylate copolymer was used as the binder resin, three color toners each having an average particle diameter of 8 μm were prepared. Color Toner 2 was prepared.

Further, as a surface treatment agent for the toner, 1 part by weight of hydrophobic silica having a primary particle diameter of 15 nm and 1 part by weight of hydrophobic silica having a primary particle diameter of 40 nm were added, and then externally added with a Henschel mixer. . After that, the obtained toners of respective colors and the ferrite carrier were mixed by a Nauter mixer to obtain a two-component developer having a toner concentration of 5%.

Example 1 The black toner 1 prepared in Preparation Example 1 of black toner and the Y, M, and C color toners 1 prepared in Preparation Example 1 of color toner are used and shown in FIG. A copying operation in a normal use mode was performed using a full-color copying machine AR-C150 (trade name) manufactured by Sharp Corporation and having the same configuration as the copying machine 1.

Example 2 Using Black Toner 3 prepared in Preparation Example 3 of Black Toner and each of Y, M, and C color toners 1 prepared in Preparation Example 1 of Color Toner, The same copying machine was used to perform the copying operation in the normal use mode.

Example 3 Using Black Toner 4 prepared in Preparation Example 3 of Black Toner and each of Y, M and C color toners 1 prepared in Preparation Example 1 of Color Toner, The same copying machine was used to perform the copying operation in the normal use mode.

(Example 4) Using the black toner 5 prepared in Preparation Example 5 of black toner and the Y, M, C color toners 2 prepared in Preparation Example 2 of color toner, The same copying machine was used to perform the copying operation in the normal use mode.

Comparative Example 1 The black toner 2 prepared in Preparation Example 2 of black toner and the Y, M, and C color toners 1 prepared in Preparation Example 1 of color toner were used, and Comparative Example 1 was prepared. The same copying machine was used to perform the copying operation in the normal use mode.

Table 1 shows the experimental results in the above Examples 1 to 4 and Comparative Example 1. In each column of Table 1, the used toner name, the values of SF1 and SF2, and 10
It shows the film thickness of the photosensitive film in the photoconductor for each color when the copying operation is performed on 10,000 sheets. Here, the ratio of the full-color mode use and the monochrome mode use is set to 3: 1 in the normal use mode. The film thickness of the photoconductor for each color at the start is 25 μm.

[0114]

[Table 1]

In Example 1, the black toner 1 and the color toner 1 are formed by the crushing method. The results in Table 1 show that the color toner 1 and the black toner 1 have almost the same values for SF1, and the black toner 1 for the SF2 is about 10 to 13 for the color toner 1. It is small, that is, 10 or less.

Further, the difference between the polishing amount of the photoconductor corresponding to the color toner and the polishing amount of the photoconductor corresponding to the black toner is about 0.4 to 0.5 μm, which is almost the same. You can see.

In Example 2, the black toner 3 and the color toner 1 are formed by a pulverizing method, and the black toner 3 is spheroidized by a mechanical impact force. . In the results of Table 1, the black toner 3 is smaller than the color toner 1 by about 10 to 13, that is, 10 or more smaller than the color toner 1 for SF1, and the color toner 1 is smaller for SF2.
The value of the black toner 3 is smaller than that of the black toner 3 by about 20 to 23, that is, 20 or more.

Further, the difference between the polishing amount of the photoconductor corresponding to the color toner and the polishing amount of the photoconductor corresponding to the black toner is about 0.1 to 0.3 μm, which is more than that of the first embodiment. It can be seen that the difference in the polishing amount becomes small.

That is, as compared with Example 1, Example 2
Spheroidizes the black toner by applying mechanical impact to the black toner, which makes the shape of the black toner closer to a sphere and improves the abrasiveness of the black toner to the photoconductor. Therefore, it is smaller than the abradability for the photoconductor. For this reason, the difference in the polishing amount in Example 2 is smaller than that in Example 1.

In Example 3, the black toner 4 and the color toner 1 are formed by the pulverization method, and the black toner 4 is subjected to the spheroidizing treatment by the heat treatment. And in the result of Table 1, SF1
As for the color toner 1, the black toner 4 is 2 more than the color toner 1.
It is smaller by about 8 to 30, that is, by 25 or more, and with respect to SF2, the black toner 4 is smaller by 27 to 30 than the color toner 1, that is, by 25 or more.

The difference between the polishing amount of the photoconductor corresponding to the color toner and the polishing amount of the photoconductor corresponding to the black toner is ±.
It is about 0.1 μm, and it can be seen that the difference in the polishing amount is smaller than in Examples 1 and 2.

That is, as compared with Example 1, Example 3
In the case of, in the formation of the black toner, the spheroidizing treatment is applied by the heat treatment, so that the shape of the black toner becomes closer to the spherical shape, and the abradability of the black toner to the photoconductor is better than that of the color toner to the photoconductor. It will be even smaller. For this reason, the difference in the polishing amount in Example 3 is smaller than that in Example 1.

In Example 4, the black toner 5 is formed by polymerization, while the color toner 1 is formed by a pulverization method. Then, in the result of Table 1, as for SF1, the black toner 5 is smaller than the color toner 2 by about 40 to 42, that is, 4
The value is smaller by 0 or more, and the SF2 is smaller by about 21 to 22 in the black toner 5 than in the color toner 2, that is, is smaller by 20 or more.

Further, the difference between the polishing amount of the photoconductor corresponding to the color toner and the polishing amount of the photoconductor corresponding to the black toner is about 0.1 to 0.2 μm, which is more than that of the first embodiment. It can be seen that the difference in the polishing amount becomes small.

That is, as compared with Example 1, Example 4
, The black toner is formed by polymerization, which makes the shape of the black toner more spherical, and the abradability of the black toner to the photoconductor is smaller than that of the color toner to the photoconductor. become. For this reason, the difference in the polishing amount in Example 4 is smaller than that in Example 1.

In Comparative Example 1, with respect to SF1, the difference between the color toner 1 and the black toner 2 is about 1 to 2, and the values are substantially the same. With respect to SF2, the difference between the color toner 1 and the black toner 2 is also large. The difference is about 1 to 4, which is almost the same value.

Further, the difference between the polishing amount of the photoconductor corresponding to the color toner and the polishing amount of the photoconductor corresponding to the black toner is about 2.8 to 3 μm, which causes a large difference in the polishing amount. You can see that

That is, in Comparative Example 1, SF1 and SF
Regarding 2, the color toner 1 and the black toner 2 are almost the same. In this case, since the black toner and the color toner have substantially the same abrasivity with respect to the photoconductor, when the monochrome output increases, the photoconductor corresponding to the black toner has a large abrading amount.

From the above results, by optimizing the shape of the toner as described above, it becomes possible to control the polishing amount of the photoconductor, and to polish the coating film of the black photoconductor and other photoconductors for developing colors. It is possible to differentiate the quantity. Therefore, it is possible to make the wear deterioration rates of the respective photoconductors substantially equal to each other. For example, when only the black photoconductor is greatly worn and deteriorated, the photoconductors of the other colors are not deteriorated. Instead, it is possible to avoid the situation where all the photoconductors are replaced in order to adjust the color balance. That is, as described above, by making the wear and deterioration rates of the respective photoconductors substantially equal to each other, it is possible to make the intervals for exchanging all the photoconductors uniform, and it is possible to eliminate the need to perform wasteful exchange.

[0130]

As described above, the developer according to the present invention is
Since the abradability of the black developer with respect to the photoconductor is smaller than the abradability of the non-black developer with respect to the photoconductor, the interval for exchanging the photoconductor is set to black or a color other than black. It is possible to make the same for all the photoconductors corresponding to the above, and it is possible to eliminate the waste of exchanging the photoconductor although the wear is small. In addition, since it is possible to use a common photoconductor for black and a color other than black, it is possible to improve maintainability and reduce the cost of the device.

If the developer according to the present invention is configured such that the representative value of the shape factor SF2 for black toner is smaller than the representative value of the shape factor SF2 for toner of colors other than black, it relates to the shape of the toner. It is possible to detect information with high accuracy, and it is possible to accurately control the shape of the toner.

Further, if the developer according to the present invention is configured such that the representative value of the shape factor SF2 of the black toner is smaller than the representative value of the shape factor SF2 of the toner of the colors other than black by 10 or more, the above-mentioned is described. From the experimental results, it is possible to make the wear deterioration speed of the photoconductor corresponding to black substantially equal to the wear deterioration speed of the photoconductor corresponding to colors other than black.

When the developer according to the present invention is configured such that the representative value of the shape factor SF1 of black toner is smaller than the representative value of the shape factor SF1 of toner of colors other than black, the developer of black toner is used. It is possible to make the abradability of the photoconductor even smaller than the abradability of the photoconductor with a toner other than black.

Further, if the developer according to the present invention is configured so that the representative value of the shape factor SF1 of the black toner is smaller than the representative value of the shape factor SF1 of the toner of the colors other than black by 10 or more, the above-mentioned is described. From the experimental results, it is possible to further reduce the difference between the wear deterioration speed of the photoconductor corresponding to black and the wear deterioration speed of the photoconductor corresponding to colors other than black.

Further, if the black toner is made to have a spherical shape by a mechanical impact force, the shape of the black toner can be made close to a spherical shape, so that the numerical values relating to the above shape factors SF2 and SF1. The effect is that it becomes possible to realize the limitation.

If the black toner is spheroidized by the heat treatment, the shape of the black toner can be made close to a sphere, so that the above shape factors SF2 and SF
This brings about an effect that it is possible to realize numerical limitation regarding 1.

If the black toner is formed by polymerization, it is possible to make the shape of the black toner close to a sphere, so that the above shape factors SF2 and S are used.
It is possible to achieve the numerical limitation regarding F1.

Further, in the color image forming apparatus according to the present invention, each developing device is configured to form a toner image by using the above-mentioned developer according to the present invention. Since it is possible to make the speed almost equal to the wear and deterioration rate of the photoconductors corresponding to colors other than black, the intervals for exchanging the photoconductors are the same for black and photoconductors corresponding to colors other than black. There is an effect that it becomes possible to. In addition, since it is possible to use a common photoconductor for black and a color other than black, it is possible to improve maintainability and reduce the cost of the device.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram showing a configuration of a digital color copying machine according to an embodiment of the present invention.

FIG. 2 is a flowchart showing operation control executed in the above digital color copying machine in accordance with a user's mode designation.

[Explanation of symbols]

1 Copier (color image forming apparatus) 110 Image reading unit 210 Image forming units 222a to 222d Photosensitive drums (photosensitive members) 224a to 224d Developing devices 227a to 227d Laser beam scanner unit (exposure device) Pa to Pd Image forming station

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/01 G03G 9/08 331 15/08 503 15/08 507L 507 9/08 384 361 381 (72) Inventor Masanori Matsumoto 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture F-term within Sharp Corporation (reference) 2H005 AA01 CA08 EA03 2H030 AA03 AB02 AD01 BB02 BB22 BB53 BB56 2H068 AA03 AA08 AA13 AA28 BB25 GA49AD03AD14H0777AD02

Claims (9)

[Claims] 1. An electrostatic latent image is formed by exposing a photosensitive member according to image information, and a toner image is formed by attaching toner to the electrostatic latent image.
An image forming station that transfers the toner image onto paper,
A developer used in a color image forming apparatus, which includes a plurality of colors corresponding to black and a color other than black, wherein the abradability of the black developer with respect to the photoreceptor is A developer characterized by being less abrasive than the photoconductor. 2. The length of the outer periphery of the two-dimensional shape of the toner contained in the developer is L, the area of the toner in the two-dimensional shape is S, and the shape factor SF2 is SF2 = (L ² / S) × The developer according to claim 1, wherein, when defined as (100 / 4π), the representative value of the shape factor SF2 of the black toner is smaller than the representative value of the shape factor SF2 of the toner of a color other than black. . 3. A typical value of the shape factor SF2 for black toner is a shape factor SF2 for toner of colors other than black.
3. The developer according to claim 2, which is smaller than the representative value of 10 or more. 4. The maximum diameter of the toner contained in the developer in the two-dimensional shape is D, the area of the toner in the two-dimensional shape is S, and the shape factor SF1 is SF1 = (D ² / S) × ( 100π / 4), the representative value of the shape factor SF1 of the black toner is smaller than the representative value of the shape factor SF1 of the toner of a color other than black. The described developer. 5. A representative value of the shape factor SF1 for black toner is a shape factor SF1 for toner of colors other than black.
The developer according to claim 4, which is smaller than the representative value of 10 by 10 or more. 6. The developer according to claim 1, wherein the black toner is spheroidized by a mechanical impact force. 7. The developer according to claim 1, wherein the black toner is spheroidized by heat treatment. 8. The developer according to claim 1, wherein the black toner is formed by polymerization. 9. A photoconductor, an exposure device that forms an electrostatic latent image by exposing the photoconductor according to image information, and a toner for the electrostatic latent image formed on the photoconductor. A plurality of developing devices for forming a toner image by adhering the toner images to each other, and a plurality of image forming stations for forming an image by transferring the toner image onto paper are provided for black and for colors other than black, respectively. A color image forming apparatus provided with the developing device, wherein each of the developing devices forms a toner image by using the developer according to any one of claims 1 to 8.