JP2003131444A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus applying a transfer control method in which using environment, the property and the kind of a transfer material and a printing rate are not regarded, and to provide an image forming apparatus which can prevent the insufficient density and the irregular transfer of a final image from occurring by eliminating toner amount reversely transferred from an intermediate transfer body to a photoreceptor even under such conditions that the properties of toner, the photoreceptor, the intermediate transfer body or a transfer roller or the like are varied because of the change of the environment or aging. SOLUTION: This image forming apparatus has a latent image forming means for forming an electrostatic latent image on the photoreceptor, and a developing means for forming a toner image by developing the electrostatic latent image, and has a transfer means for electrostatically transfering the formed toner image on the photoreceptor to an image supporting body. In the device, the value of a current applied to the transfer means is set according to the potential by electrification of the photoreceptor, length in an image forming width direction on the photoreceptor and the printing rate.

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 used in a copying machine, a printer or the like.

[0002]

2. Description of the Related Art At present, in most image forming apparatuses which are required to have high image quality at high speed, an electrostatic latent image type image forming method centering on an electrophotographic method is adopted.

The reason therefor is that high-quality images can be stably obtained at high speed, and that they can be applied to color images and digital image formation. Therefore, it is considered that the electrostatic latent image type image forming method will continue to occupy a large amount in the future.

However, the performance demand level of the image forming technology in the market is high and is increasing year by year. Therefore, further improvement in performance is required even in the electrostatic latent image system.

Needless to say, the greatest demand is to further improve the image quality. In this case, the problem is the problem in the step of transferring the toner image formed by development onto the transfer material. Is. There are roughly two types of problems that occur in the transfer process. The first one is how to keep the transfer rate of toner as a whole from being lowered, and the second one is how to maintain a high transfer rate. The problem is how to prevent image defects such as transfer loss, toner scattering, and image blurring that occur.

In order to increase the transfer rate of a toner image from a photoconductor (representing an electrophotographic photoconductor) to an intermediate transfer body or an image support, a voltage applied to a transfer roller or a transfer wire electrode is increased, and exposure is performed by pre-transfer exposure. A method of exposing the entire surface of the body and controlling the surface of the photosensitive member or the toner to an appropriate charge by charging before transfer has been used. However, each of these methods has a problem. For example, in the case where a leak occurs in a minute space and an image is missing, the toner in the image area is scattered to the peripheral area, and the charge of the photoconductor or the toner is appropriately controlled. Difficult to do. As described above, conventionally, there was a limit to increase the transfer rate without causing image defects, but recently, since a toner having a small particle size or a toner having a uniform particle size distribution and particle shape is used, the tendency becomes stronger. There is.

Particularly, in a color copying machine or a color printer, usually, a plurality of photoconductors are used, and monochromatic color images formed by the respective photoconductors are sequentially transferred to produce a superposed color image. If the transfer rate decreases in such a case, not only the image density decreases but also the color balance is disturbed, which is a serious problem.

If the value of the current flowing at the time of transfer is increased in order to increase the transfer rate, for example, the toner once transferred to the intermediate transfer member will also tend to be retransferred to the photosensitive member in the subsequent transfer.

In many cases, an intermediate transfer member is used for color image formation, and primary transfer to the intermediate transfer member and secondary transfer from the intermediate transfer member to the image support are performed twice. In this case, the influence of the transfer rate becomes greater.

In order to solve the above problems, a transfer failure does not occur even if a toner image formed by using a toner having a small particle size or a toner having a uniform particle size distribution and particle shape is transferred, and the transfer failure does not occur a plurality of times. It is necessary to find a method in which retransfer to the photoconductor does not occur even when a color image is transferred to form a superposed color image, and a sufficient transfer rate can be obtained even when they are collectively transferred.

[0011]

The present invention has been made to solve the above problems.

That is, an object of the present invention is to provide an image forming apparatus capable of obtaining a sufficient transfer rate without causing image defects such as transfer blank, toner scattering, and image blur, which are likely to occur in a transfer process. Further, even if a plurality of toner images are transferred in superposition to form a superposed color image, the toner image to be newly transferred to the transfer material is transferred at a high transfer rate, and the toner already transferred is transferred to the photoconductor. An object is to provide an image forming apparatus that is not retransferred.

An object of the first aspect of the present invention is to provide an image forming apparatus to which a transfer control method is applied regardless of the environment of use, characteristics / type of transfer material, printing rate and the like.

The second object of the present invention is to change the characteristics of the toner, the photosensitive member, the intermediate transfer member, the transfer roller and the like due to changes in the environment and the passage of time. On the contrary, eliminate the amount of toner transferred to the photoconductor,
An object of the present invention is to provide an image forming apparatus that prevents the density of the final image from becoming insufficient and transfer unevenness from occurring.

[0015]

Means for Solving the Problems As a result of intensive studies by the inventors, it was found that the object of the present invention can be achieved by adopting any of the following constitutions.

[1] A toner image formed on the photoconductor, which has a latent image forming unit for forming an electrostatic latent image on the photoconductor and a developing unit for developing the electrostatic latent image to form a toner image. In an image forming apparatus having a transfer means for electrostatically transferring a toner to an image support, a current value to be passed to the transfer means is set according to a charging potential of the photoreceptor, a length in the image forming width direction on the photoreceptor and a printing rate. An image forming apparatus characterized by.

[2] A toner image formed on the photoconductor, which has a latent image forming means for forming an electrostatic latent image on the photoconductor and a developing means for developing the electrostatic latent image to form a toner image. In an image forming apparatus having a transfer means for electrostatically transferring a toner to an intermediate transfer body, a current value to be flown to the transfer means is set according to a charging potential of the photoreceptor, a length in the image forming width direction on the photoreceptor and a printing rate. An image forming apparatus characterized by.

[3] The image forming apparatus according to [1] or [2], wherein the transfer means is a roller having an elastic body formed on the surface of a cored bar.

[4] A voltage is applied to the transfer means in advance,
The image forming apparatus according to [1] or [2], wherein the current value is corrected with reference to a necessary current value.

[5] The image forming apparatus as described in [1] or [2], wherein two-component reversal development is used for the developing means.

[6] The control of the charging potential of the photosensitive member is characterized in that the relationship between the back plate voltage of the charger or the value of the current flowing through the wire and the charging potential of the photosensitive member is obtained in advance. The image forming apparatus according to [1] or [2].

[7] The control of the charging potential of the photosensitive member is characterized in that the relationship between the current value or the voltage value applied to the charging roller and the charging potential of the photosensitive member is obtained in advance. 1] or the image forming apparatus described in [2].

[8] The measurement of the charging potential of the photoconductor is carried out by a surface potential sensor installed downstream of the charging device of the photoconductor and upstream of the developing device [1] or [1]. 2] The image forming apparatus described above.

[0024]

[9] Line speed of photoconductor is 200
mm / s or more [1] or [2]
The image forming apparatus described.

[10] The image forming apparatus as described in [1] or [2], wherein the relationship between the print ratio and the current value is divided and set in the lengthwise direction of image formation.

[11] A plurality of toner images formed, each having a latent image forming means for forming an electrostatic latent image on the photoconductor and a plurality of developing means for developing the electrostatic latent image to form a toner image. Are sequentially transferred to an intermediate transfer body to form a superimposed color toner image, and the transfer onto the intermediate transfer body is performed in an image forming apparatus using a transfer means to which a bias voltage is applied for the transfer to the intermediate transfer body. When a toner patch that detects the amount of toner adhered is formed, and the bias voltage is applied to the toner patch density on the intermediate transfer member when the bias voltage is not applied to the transfer unit during the transfer of the toner image that is subsequently transferred. The image forming apparatus is characterized in that the bias voltage applied to the transfer means is set so as to reduce the difference.

[12] A plurality of toner images formed, each having a latent image forming means for forming an electrostatic latent image on the photoconductor and a plurality of developing means for developing the electrostatic latent image to form a toner image. Are sequentially transferred to an intermediate transfer body to form a superimposed color toner image, and the transfer onto the intermediate transfer body is performed in an image forming apparatus using a transfer means to which a bias voltage is applied for the transfer to the intermediate transfer body. When a toner patch that detects the amount of toner adhered is formed, and the bias voltage is applied to the toner patch density on the intermediate transfer member when the bias voltage is not applied to the transfer unit during the transfer of the toner image that is subsequently transferred. And the surface potential of the photoconductor is adjusted so that the difference becomes smaller.

The above inventions [1] to [10] and [1]
In the inventions 1] to [12], the former is sometimes referred to as the first invention, and the latter is sometimes referred to as the second invention because the basic structure is slightly different.

The intermediate transfer member is a member for temporarily carrying a toner image formed by toner development, and the image support member is a member for carrying a final image. Note that these may be collectively referred to as a transfer material.

Usually, the intermediate transfer member is made of silicone rubber or a resin film which does not expand or contract, and the like, and the image support is plain paper, processed paper or the like.

First, referring to the first aspect of the present invention, in the electrophotographic image forming method, a toner image normally formed on a photoconductor is electrostatically transferred to an intermediate transfer body or an image support. There is a process. Note that electrostatically means that an attractive force based on static electricity is used.

The most basic function of the transfer means used in this transfer step is to completely transfer the toner image formed on the photosensitive member to the transfer material (intermediate transfer member or image support). There are two methods of controlling the electric charge for performing this electrostatically: constant current control and constant voltage control.
These methods have merits and demerits, and it is the substance that the current value or the voltage value is switched and controlled according to the situation based on the result obtained by the experiment in advance.

That is, in the case of constant current control, the optimum current value varies depending on the paper size in the width direction of the image and the size of the printing rate in the width direction. Therefore, the transfer conditions are different when the paper size is changed, when the printing rate is almost 100% and when the printing rate is almost 0%.

On the other hand, in the case of constant voltage control, if the impedance of the transfer means changes or the resistance value of the photoconductor or the transfer material changes, the required current value greatly changes. For this reason, it is not possible to deal with it by just making the voltage constant.

Further, there is a method in which a constant current is supplied to the transfer means in advance to obtain a voltage value and the voltage value is controlled at a constant voltage at the time of image transfer. However, in this method, the obtained voltage value may not be supported by an ordinary power source. is there.

As described above, there is a problem in both the constant current method and the constant voltage method as the charge control means of the transfer means, and a method that does not cause an image defect in any situation has not been put into practical use at present. Is.

The transfer means is generally installed in the width direction of the image, and has a mechanism for transferring all the toner passing therethrough. Therefore, what is important is the proportion of toner lined up in the width direction in image formation and the photoconductor potential in the area where toner is not attached. This is because the required transfer charge amount can be known if the charge amount of the toner and the charge amount of the area where the toner is not attached are known.

When the entire sub-scanning direction (image length direction) in the image area is viewed, the toner amount ratio changes every moment. Ideally, it is preferable that the transfer means substantially makes line contact with the transfer material in the width direction, and the amount of electric charge required for transfer in the contact area is controlled to change every moment. However, in actuality, when such a linear contact is made, discharge occurs due to dielectric breakdown at the non-contact portion, the electric field is lowered, and transfer failure or transfer failure occurs. Further, even if the toner is contacted with an extremely short surface in the image length direction, the amount of adhered toner varies in the width direction, so that the optimum charge amount cannot be calculated.

For this reason, the amount of electric charge required in a certain range of the image length is determined, and the current value is calculated from the line speed (transfer material moving speed). That is, it is a method of determining an appropriate transfer current value from the combination of the charging potential of the photoconductor at the transfer position and the printing rate for each image.

According to the study by the inventors, the photoconductor potential, the charge amount of the toner, the area ratio of the toner adhered (printing rate)
From this, it was found that an image defect does not occur by obtaining and outputting an appropriate transfer current value of the image. In addition, it is also possible to apply a voltage to the transfer unit in advance to obtain the required current value, and control the size of the transfer material, the resistance value, and the environmental conditions with reference to this value, and it is possible to widely change the situation. Accordingly, transfer without image defects is possible.

In the actual control of the transfer means, a method of calculating from the detection value of the potential sensor and the printing rate may be used, or a control table of the detection value of the potential sensor and the printing rate may be used.

In the second aspect of the present invention, the polarity of the bias voltage applied to the transfer roller in the transfer from the photosensitive member to the intermediate transfer member is positive when the toner is negatively charged. However, normally, a part of the toner transferred to the intermediate transfer member is injected with electric charges and becomes positively charged at the time of the next toner image transfer. The higher the transfer current value, the larger the amount of toner whose polarity changes. On the other hand, the transfer rate of toner from the photosensitive member to the intermediate transfer member increases until the transfer current value reaches a certain value, and thus the transfer current value (transfer voltage value) has been set in the range where retransfer does not occur so far. It was high.

However, the characteristics of the toner, the photosensitive member, the intermediate transfer member, the transfer roller, etc., change due to changes in the environment and the passage of time. As a result, the amount of toner transferred from the intermediate transfer member to the photosensitive member fluctuates, and the density of the final image is insufficient and uneven transfer occurs.

Therefore, in the second aspect of the present invention,
In advance, the toner patch density sensor should be used to form a toner patch on the intermediate transfer member under the condition that retransfer does not occur in the primary transfer process and the condition that retransfer may occur but the transfer rate is expected to be good. The measurement is performed to obtain the difference, and the transfer is performed by controlling the primary transfer conditions so that the difference becomes small. In order to reduce the difference in this case, specifically, when the output potential width of the specular reflection type densitometer of the patch detection sensor is 0.0 to 5.0 V, it is less than 0.2 V. In this case, the density difference can be suppressed to about 0.05 even in the highest density part.

Specifically, a plurality of latent image forming means for forming an electrostatic latent image on the photoconductor and a plurality of developing means for developing the electrostatic latent image to form a toner image are formed. The toner images are sequentially primary-transferred to an intermediate transfer member to form a superimposed color toner image, and an image is first formed in an image forming apparatus using a transfer means to which a bias voltage is applied for transferring to the intermediate transfer member. Place where transfer means for each color to which bias voltages of M, C, and K toner images to which the intermediate transfer body carrying the toner image (for example, Y toner image) primarily transferred onto the intermediate transfer body is sequentially applied is installed. Are sequentially passed, and then the toner patch density is measured by a sensor. This is D
When set to 1, the toner patch density is measured with a sensor in the same manner by sequentially passing through the places where the transfer means where the bias voltage is not applied is installed. This is D2
, D1 has a sufficient concentration and D2-D1 is 0.
Alternatively, the bias voltage condition of each transfer means is set in the range where it becomes as small as possible. At this time, even if the same transfer bias is applied to each photoconductor, the amount of toner retransfer is different, so the potential of the bias voltage must be adjusted according to the charge potential of the photoconductor. Further, when determining the transfer current of each photoconductor, it is necessary to perform weighting by the charging potential of the photoconductor.

[0046]

BEST MODE FOR CARRYING OUT THE INVENTION The structure of the first invention and the components used therein will be described.

The latent image forming means in the present invention usually comprises a charging means for uniformly charging the photoreceptor and an exposing means for exposing the uniformly charged photoreceptor in an imagewise manner. Of course, a so-called tandem type color image forming apparatus having a plurality of these and sequentially forming and transferring toner images may be used.

The charging means is not particularly limited, but one using an elastic roller, that is, a roller shaft (core metal)
A method in which an elastic body is wrapped around and an electric charge is applied to the elastic body is preferable. To perform the transfer, the back surface of the transfer material is pressed against the photoconductor to give a necessary electric field. It is preferable to apply a voltage to the transfer means in advance and correct the current value based on the required current value based on the following detection result.

A normal surface potential meter may be used to detect the charging potential of the photosensitive member.
In addition, it is preferable to use a surface potential sensor installed on the upstream side of the developing means. Further, the image printing rate (the ratio of the toner image area to the entire area of the image forming area such as the B4 plate) can be calculated, for example, from the writing data of the previous exposure unit.

As shown in a part of the Y image forming portion in FIG. 1, the image forming width W direction is orthogonal to the traveling direction X of the photoconductor (or the intermediate transfer member or the image support) when the image is formed. If the photoconductor is drum-shaped, it is parallel to the rotation axis.

To control the charging potential of the photoconductor, if the charging device (charging means) is of a corona discharge type, the relationship between the backplate voltage or the current value flowing through the wire and the charging potential of the photoconductor is obtained in advance. It is better to do it in advance. Further, in the case of the charging roller type, it is preferable that the relationship between the current flowing through the charging roller or the voltage value to be applied and the charging potential of the photoconductor is obtained in advance.

In controlling the transfer means of the present invention, since the printing rate often differs depending on each information original, it is preferable to set the printing rate separately in the image length direction. Here, the image length Z is the length of one page orthogonal to the width direction in the case of sheet-like data (see FIG. 1). In FIG. 1, the area defined by the image forming width W and the image length Z is the image forming area.

Further, the problem in the transfer step, which is the subject of the present invention, tends to occur when an image is formed at a high speed, and also tends to occur in reversal development in which a large amount of electric charge remains on the photoconductor. In that sense, the line speed of the photoconductor is 200 mm /
When it is s or more, the effect of the present invention is remarkably exhibited in reversal development, particularly in two-component reversal development often used for color image formation.

FIG. 2 is a sectional view for explaining the structure of a color copying machine which is an example of the image forming apparatus according to the embodiment of the present invention.

The image forming apparatus main body GH shown in FIG. 2 is called a tandem type color image forming apparatus, and comprises a plurality of sets of image forming units 10Y, 10M, 10C and 10K, a belt-shaped intermediate transfer member 6 and a sheet-shaped intermediate transfer member 6. It has a paper conveying means and a fixing device 24.

Image forming section 1 for forming a yellow image
0Y has a charging unit 2Y, an exposing unit 3Y, a developing unit 4Y, and a cleaning unit 8Y arranged around a photoconductor 1Y as an image forming body. The image forming unit 10M that forms a magenta image includes a photoconductor 1M as an image forming body,
It has a charging unit 2M, an exposing unit 3M, a developing unit 4M, and a cleaning unit 8M. The image forming unit 10C that forms a cyan image has a photoreceptor 1C as an image forming body, a charging unit 2C, an exposing unit 3C, a developing unit 4C, and a cleaning unit 8C. The image forming unit 10K that forms a black image includes a photoconductor 1K as an image forming body and a charging unit 2.
K, an exposure unit 3K, a developing unit 4K, and a cleaning unit 8K. The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure unit 3C, and the charging unit 2K and the exposure unit 3K form a latent image forming unit.

The intermediate transfer member 6 is an endless belt,
It is stretched by a plurality of rollers and is rotatably supported.

Image forming units 10Y, 10M, 10C and 1
The color image of each color formed from 0K is sequentially transferred (primary transfer) onto the rotating intermediate transfer body 6 by the transfer means 7Y, 7M, 7C and 7K to form a superimposed color image.

The image support P housed in the paper feed cassette 20 is fed by the paper feed means 21 and fed by the paper feed roller 22.
After passing through A, 22B, 22C, the registration roller 23, etc., it is conveyed to the transfer means 7A and the superimposed color image is transferred onto the image support P (secondary transfer). The image support P on which the color image has been transferred is fixed by the fixing device 24, is sandwiched by the paper ejection rollers 25, and is ejected outside the apparatus by the paper ejection tray 26.
Placed on top.

On the other hand, after the color image is transferred to the image support P by the transfer means 7A, the residual toner on the intermediate transfer body 6 from which the image support P is separated is removed by the cleaning means 8A.

Incidentally, 5Y, 5M, 5C and 5K are toner replenishing means for replenishing the developing means 4Y, 4M, 4C and 4K with new toner.

An image reading device YS including an automatic document feeding device 201 and a document image scanning exposure device 202 is installed above the image forming apparatus main body GH. The original d placed on the original table of the automatic original feeding device 201 is conveyed by the conveying means, and the image of one side or both sides of the original is scanned and exposed by the optical system of the original image scanning exposure device 202, and the line image sensor CCD is exposed. Is read.

The analog signal photoelectrically converted by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, etc. in the image processing section, and then the image writing section (exposure means) 3Y, Three
Send signals to M, 3C and 3K.

The automatic document feeder 201 is provided with an automatic double-sided document conveying means. Since the automatic document feeder 201 can continuously read the contents of a large number of documents d fed from the document table and store them in the storage means (electronic RDH function), copying is possible. It is conveniently used when copying the contents of a large number of originals by the function or when transmitting a large number of originals d by the facsimile function.

A concrete embodiment of the first aspect of the present invention will be described later as a first embodiment, and a control flow chart in that case is as shown in FIG.

Next, the second invention of the present invention will be described. The latent image forming means in the present invention, as in the first invention, is usually composed of a charging means for uniformly charging the photosensitive member and an exposing means for exposing the uniformly charged photosensitive member imagewise. . The latent image forming means is one, and a plurality of developing means are used on the same photoconductor to sequentially form yellow (Y), magenta (M), cyan (C), and black (K) color images. It may be a system of forming and sequentially transferring, or a system having a plurality of photoconductors and a plurality of developing means such as a tandem system.

FIG. 4 is a sectional view for explaining the structure of a color copying machine which is an example of the image forming apparatus according to the embodiment of the present invention.

The image forming apparatus main body GH shown in FIG. 4 is called a tandem type color image forming apparatus, and comprises a plurality of sets of image forming units 10Y, 10M, 10C and 10K, a belt-shaped intermediate transfer member 6 and a sheet feeding member. It has a paper conveying means and a fixing device 24.

Image forming section 1 for forming a yellow image
0Y has a charging unit 2Y, an exposing unit 3Y, a developing unit 4Y, a transfer unit 7Y, and a cleaning unit 8Y, which are arranged around a photoconductor 1Y as an image forming body. The image forming unit 10M that forms a magenta image has a photoreceptor 1M as an image forming body, a charging unit 2M, an exposing unit 3M, a developing unit 4M, and a cleaning unit 8M. The image forming unit 10C that forms a cyan image includes a photoconductor 1C as an image forming body, a charging unit 2C, an exposing unit 3C, and a developing unit 4.
C, and a cleaning means 8C. The image forming unit 10K that forms a black image includes a photoreceptor 1 as an image forming body.
K, charging means 2K, exposure means 3K, developing means 4K, and cleaning means 8K. The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure unit 3C, and the charging unit 2K and the exposure unit 3K form a latent image forming unit.

The intermediate transfer member 6 is an endless belt,
It is stretched by a plurality of rollers and is rotatably supported.

Image forming sections 10Y, 10M, 10C and 1
The color image of each color formed from 0K is sequentially transferred (primary transfer) onto the rotating intermediate transfer body 6 by the transfer means 7Y, 7M, 7C and 7K to form a superimposed color image.

The image support P housed in the paper feed cassette 20 is fed by the paper feed means 21 and fed by the paper feed roller 22.
After passing through A, 22B, 22C, the registration roller 23, etc., it is conveyed to the transfer means 7A and the superimposed color image is transferred onto the image support P (secondary transfer). The image support P on which the color image has been transferred is fixed by the fixing device 24, is sandwiched by the paper ejection rollers 25, and is ejected outside the apparatus by the paper ejection tray 26.
Placed on top.

On the other hand, after the color image is transferred onto the image support P by the transfer means 7A, the residual toner on the intermediate transfer body 6 from which the image support P is separated is removed by the cleaning means 8A.

The toner patch density detection sensor 13
Image forming units 10Y, 10M, 10C and 10 of the copying machine
The toner patch formed by K is detected. This patch is not formed as a final image, and when the intermediate transfer body on which these patches are formed passes through the transfer means 7A (secondary transfer means) portion, the transfer means 7A is released and the image is supported. After the toner reaches the density detection sensor 13 without being transferred to the body and the detection is completed, the cleaning unit 8A removes the residual toner.

In the above, the transfer means 7Y, 7
M, 7C and 7K are not limited by the mechanism, but it is preferable that a voltage is applied to an elastic roller type in which an elastic body is mounted on a cored bar such as a metal rod.

Incidentally, 5Y, 5M, 5C and 5K are toner replenishing means for replenishing the developing means 4Y, 4M, 4C and 4K with new toner.

An image reading device YS including an automatic document feeding device 201 and a document image scanning exposure device 202 is installed above the image forming apparatus main body GH. The original d placed on the original table of the automatic original feeding device 201 is conveyed by the conveying means, and the image of one side or both sides of the original is scanned and exposed by the optical system of the original image scanning exposure device 202, and the line image sensor CCD is exposed. Is read.

The analog signal photoelectrically converted by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, etc. in the image processing section, and then the image writing section (exposure means) 3Y, Three
Send signals to M, 3C and 3K.

The automatic document feeder 201 is provided with an automatic double-sided document conveying means. Since the automatic document feeder 201 can continuously read the contents of a large number of documents d fed from the document table and store them in the storage means (electronic RDH function), copying is possible. It is conveniently used when copying the contents of a large number of originals by the function or when transmitting a large number of originals d by the facsimile function.

In the present invention, each image forming section 10Y, 1
The toner patches of each color formed by 0M, 10C, and 10K are read by the density detection sensor 13, and the condition of the transfer unit of each color is set based on the detection level.

As the exposure light source for forming the toner patch, an image exposure light source, that is, a semiconductor laser light source, an LED light source or the like is used. Further, the toner patch density detection sensor may be one that can detect the density pattern by scanning the line at a right angle using a phototransistor, CCD, or the like.

A concrete embodiment of the second aspect of the present invention will be described later as a second embodiment, and the flow chart in that case is as shown in FIG. 5, for example.

The technology and requirements relating to the constituent features of the present invention, the toner used, the image forming apparatus and the like will be described below.

1. Photoreceptor The photoreceptor in the present invention may be either an organic or inorganic photoreceptor as long as it is a so-called electrophotographic photoreceptor, and is not particularly limited. However, the most widely used in recent years is an organic photoconductor (OPC).

In the organic photoreceptor, a phthalocyanine pigment, a perylene pigment or the like is usually used as a charge generating substance. Fine particles of these pigments are dispersed in a resin and then applied to form a charge generating layer. A laminate type is used which is used as a substance and is coated with a resin to form a charge transport layer.

2. Charging means, exposure means, developing means What is usually used in an electrophotographic image forming apparatus can be used in the present invention.

That is, the charging means is a corotron or scorotron type corona charger, a roller charger, a brush charger or the like.

As the exposure means, a semiconductor laser light source,
An LED light source or the like is used to form a beam or spot to expose the uniformly charged surface of the photoreceptor imagewise to form a latent image.

The developing means may be of any one-component or two-component developing system, and these may be any developing device capable of using the developer described later.

3. Toner Used in the Present Invention The toner used in the present invention preferably has a small particle size, a narrow particle size distribution, and a uniform shape.

Specifically, it is preferable that the volume average particle diameter of the toner is 3 to 8 μm. If the thickness is less than 3 μm, the charging may not be sufficiently performed, and the toner may be scattered to deteriorate the image quality and adversely affect the human body. If it exceeds 8 μm, the image quality may not be good. The volume average particle size can be measured by Coulter Counter TA-II or Coulter Multisizer (both manufactured by Coulter Co.).

The method for producing the toner of the present invention is not particularly limited, but it is preferable to use a so-called polymerization method in which toner particles are produced during a polymerization reaction without performing kneading and pulverization classification as in a so-called pulverization method. This is because a product having a small particle size, a narrow particle size distribution, and a uniform particle shape can be easily produced.

4. Developer and Developing Conditions Next, the developer and developing conditions used in the present invention will be described.

The toner used in the present invention may be used as a one-component developer or a two-component developer, but is preferably a two-component developer.

When used as a one-component developer, there is a method of using the toner as it is as a non-magnetic one-component developer, but normally, the magnetic particles are prepared by incorporating magnetic particles of about 0.1 to 5 μm in the toner particles. Used as a developer. As a method of containing it, it is common to incorporate it in the non-spherical particles in the same manner as the colorant.

Further, it can be used as a two-component developer by mixing with a carrier. In this case, conventionally known materials such as metals such as iron, ferrite and magnetite, alloys of these metals with metals such as aluminum and lead are used as the magnetic particles of the carrier. Ferrite particles are particularly preferable. The volume average particle diameter of the magnetic particles is 15
˜100 μm, more preferably 25 to 60 μm.

The volume average particle diameter of the carrier is typically measured by a laser diffraction type particle size distribution measuring apparatus "HELOS" equipped with a wet disperser (SYMPATIC (SYMP).
(Made by ATEC)).

The carrier is preferably one in which magnetic particles are further coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin. The resin composition for coating is not particularly limited, but, for example, an olefin resin, a styrene resin, a styrene-acrylic resin, a silicone resin, an ester resin, a fluorine-containing polymer resin, or the like is used. The resin for forming the resin-dispersed carrier is not particularly limited, and known ones can be used. For example, styrene acrylic resin, polyester resin, fluorine resin, phenol resin, etc. can be used. it can.

The developing method can be used either in contact or in non-contact. The direct current developing electric field at that time is 1 × 10 ³ to 1 × 10 ⁵ V / cm in absolute value, preferably 5 × 10 ³
Is a ^{~1 × 10 4 V / cm,} 10 3 and development is less than V / cm is insufficient, no sufficient image density is obtained, 10 ⁵ V / c
If it exceeds m, the image quality is poor and fogging occurs.

AC bias is 0.5 to 4 kV (p-
p), preferably 1 to 3 kV (pp), and the frequency is 0.1 to 10 kHz, preferably 2 to 8 kHz. When the AC bias is less than 0.5 kV (pp), the toner adhering to the carrier does not separate, the non-contact development becomes insufficient, and the image density becomes insufficient. When the AC bias exceeds 4 kV (pp), the carrier in the developer flies and carrier adheres to the photoconductor. Further, if the frequency of the AC bias is less than 0.1 kHz, the toner is not sufficiently detached from the carrier, resulting in insufficient development and lowering of image density. Further, when the frequency of the AC bias exceeds 10 kHz, the toner cannot follow the fluctuation of the electric field, resulting in defective development and a decrease in image density.

5. Other Configurations A so-called contact heating method can be cited as a suitable fixing method used in the present invention. In particular, as the contact heating method, a heat pressure fixing method, a heat roller fixing method, and a pressure contact heating fixing method in which fixing is performed by a rotating pressure member containing a fixedly arranged heating body can be mentioned.

The image forming apparatus of the present invention can be applied to general electrophotographic apparatuses such as copying machines, laser printers, LED printers and liquid crystal shutter type printers. It can be widely applied to devices such as light printing, plate making, and facsimile.

[0103]

EXAMPLES Next, the concrete aspects of the present invention will be shown to further explain the constitution and effects of the present invention, but the constitution of the present invention is not limited thereto.

Example 1 The following evaluation was carried out using an image forming apparatus similar to the image forming apparatus shown in FIG.

Each photosensitive drum had a diameter of 60 mm, a photosensitive layer in which a phthalocyanine pigment was dispersed in polycarbonate was used, and a photosensitive layer coated to a total film thickness of 25 μm including a charge transporting layer was used. All the photoconductors have a potential of -600 in the non-exposed area.
V, the exposed portion potential was adjusted to −50 V or less, image exposure was performed using a semiconductor laser light source (300 μW), and development was performed by a two-component developing method.

The volume average particle diameter of the toner was 6.0 μm, and the toner manufactured by the polymerization method was used. The transport speed of the intermediate transfer member was 180 mm / s, and a seamless semiconductive resin belt (10 ⁸ Ω · cm) was used. Further, the transfer (primary transfer) means from each photoconductor to the intermediate transfer body includes a foamed resin roller (10 ⁶ Ω.
m, diameter of core metal 10 mm) was installed, and constant current control was performed at 20 μA.

As a transfer (secondary transfer) means from the intermediate transfer member to the image support (plain paper), a semiconductor roller was pressed against the intermediate transfer member from the back surface of the plain paper, and a constant current was controlled to 80 μA.

As the fixing means (apparatus), a heat roller and a pressure roller in which a heater is arranged are used.

The control was performed as shown in FIG. 3, but in the actual control, the control tables shown in Tables 1 and 2 below were prepared and used.

[0110]

[Table 1]

[0111]

[Table 2]

The transfer rate was maintained at 95% or more, and image defects such as image dust did not occur up to 200,000 copies.

Example 2 The following evaluations were performed using the color copying machine shown in FIG.

Each photosensitive drum had a diameter of 60 mm, and a photosensitive layer was prepared by dispersing a phthalocyanine pigment in polycarbonate, and was coated to a total film thickness of 25 μm including a charge transport layer. All the photoconductors have a potential of -600 in the non-exposed area.
V, the exposed portion potential was adjusted to −50 V or less, image exposure was performed using a semiconductor laser light source (300 μW), and development was performed by a two-component developing method.

A toner of polymerization method having a volume average particle diameter of 6.5 μm was used. The transfer speed of the intermediate transfer body is 180 mm
/ S and a seamless semi-conductive resin belt (10 ⁸ Ω
* Cm) was used. In addition, the transfer (primary transfer) means from each photosensitive member to the intermediate transfer member has a diameter of 20 on the back surface of the intermediate transfer member.
mm foam resin roller (10 ⁶ Ω · cm) is installed,
Constant current control was performed.

As a transfer (secondary transfer) means from the intermediate transfer body to the image support (plain paper), a semiconductor roller was pressed against the intermediate transfer body from the back surface of the plain paper, and a constant current was controlled to 80 μA.

As the fixing means (apparatus), a heat roller and a pressure roller, each having a heater therein, were used.

The environmental conditions for actual copying are normal temperature and normal humidity (NN;
50,000 copies at 25 ℃, 55RH%, low temperature and low humidity (L
L; 50,000 copies at 10 ° C, 20RH%), 50,000 copies at high temperature and high humidity (HH; 33 ° C, 80RH%), 50,000 copies at room temperature and normal humidity (NN; 25 ° C, 55RH%) Total 2
100,000 copies were continuously made.

As for the used original, the printing rate is 5 for the B4 size.
%, Y, M, C, K four-color, continuous copying under each environmental condition, the density difference was measured.

The control procedure was basically performed as shown in FIG. 5, but specifically, the final control procedure was changed slightly as follows.

A feedback method using a patch detection sensor (regular reflection type: density is output in the potential range of 0 to 5 V) was performed as follows. PWM 50% halftone patch (200 lpi: 1 inch, 20 per 2.54 cm)
(0 line) was formed on the photosensitive member, and the patch was transferred onto the intermediate transfer member with a primary transfer current of 25 μA for each color at the start. The patch density of each color was measured with a patch detection sensor, and when the output difference was 0.2 V or more, the transfer current was reduced by 3 μA and remeasurement was performed. For example, when a color image is formed in the order of Y, M, C, and K, and primary transfer is performed, if the Y image density is reduced, the transfer currents of M, C, and K are reduced by 3 μA, and the M image is reduced. At that time, the transfer currents of C and K were lowered by 3 μA. If the output difference is still 0.2V or more, it is further reduced by 2μA.
Further, when the output difference was less than 0.2 V in the first measurement, it was increased by 2 μA once, and the measurement was performed under the increased condition except when the output difference was 0.2 V or more.

The results are shown in Table 3. In the second embodiment of the present invention, the output difference of the patch detection sensor does not become so large even after the actual copying of 200,000 copies. On the other hand, it can be seen that in Comparative Example 2 in which the control as in the present invention is not performed, the output difference is large depending on the conditions, and retransfer to the photoreceptor occurs.

[0123]

[Table 3]

Example 3 In Example 2, the charging potential Vh of the photoconductor was constant, but in Example 3, Vh of each color photoconductor was measured with a surface electrometer to measure the halftone patch on the intermediate transfer member. Output is 2 ±
Vh was controlled to be 0.1V.

This is because the Vh of each color photoconductor is different,
A table of Vh and the amount of current decrease was created in advance by experiments (see Table 4 below), and the current value corresponding to the measured Vh was decreased.

[0126]

[Table 4]

The results are shown in Table 5. In the third embodiment of the present invention, the output difference of the patch detection sensor does not become so large even after the actual copying of 200,000 copies. On the other hand, in Comparative Example 3 in which the control as in the present invention is not performed, the output difference is large depending on the conditions and retransfer to the photosensitive member occurs.

[0128]

[Table 5]

[0129]

According to the first aspect of the present invention, it is possible to provide the image forming apparatus to which the transfer control method is applied regardless of the use environment, the characteristics / type of the transfer material, the printing rate and the like.

According to the second aspect of the present invention, the characteristics of the toner, the photosensitive member, the intermediate transfer member, the transfer roller, etc. vary due to changes in the environment and the passage of time. It is possible to provide an image forming apparatus that eliminates the amount of toner transferred to the photoconductor and prevents the density of the final image from becoming insufficient and transfer unevenness from occurring.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an image formation width and an image length.

FIG. 2 is a cross-sectional view illustrating the configuration of a color copying machine that is an example of an image forming apparatus.

FIG. 3 is a control flow chart in the first invention.

FIG. 4 is a cross-sectional view illustrating the configuration of a color copying machine that is an example of an image forming apparatus.

FIG. 5 is a control flow chart in the second invention.

[Explanation of symbols]

1Y, 1M, 1C, 1K photoconductor 2Y, 2M, 2C, 2K charging means 3Y, 3M, 3C, 3K exposure means 4Y, 4M, 4C, 4K developing means 6 Intermediate transfer body 7Y, 7M, 7C, 7K Transfer means 10Y, 10M, 10C, 10K Image forming unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/00 350 G03G 21/00 350 (72) Inventor Masashi Saito 2970 Ishikawacho, Hachioji, Tokyo Konica Stocks In-house (72) Inventor Hiroshi Morimoto 2970 Ishikawa-cho, Hachioji, Tokyo Konica Stock Company F-term (reference) 2H027 DA02 DA06 DA09 DB01 DB09 DE02 DE05 DE07 DE09 DE10 EA01 EA03 EB04 EC04 EC06 EC07 EC09 ED03 ED06 ED24 EE07 EF08 ZA07 2H030 AA04 AB02 AD02 BB02 BB42 BB54 2H035 CA07 CG00 2H200 FA05 FA18 FA19 GA12 GA14 GA16 GA23 GA28 GA29 GA30 GA34 GA45 GA47 GA53 GA54 GA57 GA59 GB12 GB22 GB25 GB41 HA02 HA12 HA29 HA15 J02 J02C15 J02 J15 JA18 JA29 J29 JA18 JA29 J29 JA18 JA29 J02 JA28 JA29 J29 JA18 JA29 J02 JA28 JA29 J29 JA18 JA29 J29 JA18 JA29 J02 JA28 JA29 JA15 JA18 JA29 J15 JA18 JA29 JA15 JA15 NA08 NA09 PA04 PA05 PA15 PA19 PA23 PB04 PB20 PB28 PB29

Claims (12)

[Claims] 1. A latent image forming means for forming an electrostatic latent image on a photoconductor, and a developing means for developing the electrostatic latent image to form a toner image. In an image forming apparatus having a transfer unit for electrostatically transferring to an image support, it is possible to set a current value to be flown to the transfer unit according to the charging potential of the photosensitive member, the length in the image forming width direction on the photosensitive member and the printing rate. A characteristic image forming apparatus. 2. A latent image forming means for forming an electrostatic latent image on a photoconductor, and a developing means for developing the electrostatic latent image to form a toner image. In an image forming apparatus having a transfer means for electrostatically transferring to an intermediate transfer body, it is possible to set a current value to be flown to the transfer means according to a charging potential of the photosensitive body, a length in the image forming width direction on the photosensitive body and a printing rate. A characteristic image forming apparatus. 3. The image forming apparatus according to claim 1, wherein the transfer means is a roller having an elastic body formed on the surface of a cored bar. 4. The image forming apparatus according to claim 1, wherein a voltage is applied to the transfer means in advance, and the current value is corrected based on a required current value. 5. The image forming apparatus according to claim 1, wherein the developing means uses two-component reversal development. 6. The control of the charging potential of the photoconductor is performed by previously obtaining the relationship between the backplate voltage of the charger or the value of current flowing through the wire and the charging potential of the photoconductor. The image forming apparatus according to item 1 or 2. 7. The control of the charging potential of the photosensitive member is performed by previously determining the relationship between the current value or the voltage value applied to the charging roller and the charging potential of the photosensitive member. The image forming apparatus according to 1 or 2. 8. The charging potential of the photoconductor is measured by a surface potential sensor installed downstream of the charger of the photoconductor and upstream of the developing device.
Or the image forming apparatus according to 2. 9. The line speed of the photoconductor is 200 mm /
The image forming apparatus according to claim 1, wherein the image forming apparatus is s or more. 10. The image forming apparatus according to claim 1, wherein the relationship between the print ratio and the current value is divided and set in the lengthwise direction of image formation. 11. A latent image forming means for forming an electrostatic latent image on a photoconductor, and a plurality of developing means for developing the electrostatic latent image to form a toner image. In the image forming apparatus that uses the transfer means to which a bias voltage is applied for primary transfer to the intermediate transfer member to form a superimposed color toner image, the transferred color toner image is transferred onto the intermediate transfer member. When a toner patch for detecting the toner adhesion amount is formed and the bias voltage is not applied to the transfer unit during the transfer of the toner image to be transferred thereafter, the toner patch density on the intermediate transfer member and the case where the bias voltage is applied An image forming apparatus, characterized in that the bias voltage applied to the transfer means is set so as to compare with the density and reduce the difference. 12. A latent image forming means for forming an electrostatic latent image on a photoconductor, and a plurality of developing means for developing the electrostatic latent image to form a toner image. In the image forming apparatus that uses the transfer means to which a bias voltage is applied for primary transfer to the intermediate transfer member to form a superimposed color toner image, the transferred color toner image is transferred onto the intermediate transfer member. When a toner patch for detecting the toner adhesion amount is formed and the bias voltage is not applied to the transfer unit during the transfer of the toner image to be transferred thereafter, the toner patch density on the intermediate transfer member and the case where the bias voltage is applied An image forming apparatus characterized in that the surface potential of a photoconductor is adjusted so that the difference between the density and the density is reduced.