JP2003091106A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus by which a sufficient transfer coefficient is obtained by eliminating the occurrence of a defective image such as transfer void, toner scattering and image blurring likely to be caused at a transfer process and also already transferred toner is not transferred to a photoreceptor again because a toner image to be newly transferred to a transfer material is transferred at the high transfer coefficient even though a color image is formed by superposing and transferring a plurality of toner images. SOLUTION: In the image forming apparatus having a means to apply lubricant to the surface of an electrophotographic photoreceptor and a mechanism to warm the photoreceptor, the photoreceptor is provided with a mechanism to form a toner patch and the density detecting sensor of the patch, and the mechanism to warm the photoreceptor is actuated in accordance with the detected level of the sensor.

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. One is the problem of how to keep the overall transfer rate of toner from decreasing and 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 the transfer process.

In order to increase the transfer rate of the toner image from the photosensitive member to the intermediate transfer member or the image support, the voltage applied to the transfer roller or the transfer wire electrode is increased, the entire surface of the photosensitive member is exposed by pre-transfer exposure, and before transfer. A method of controlling the surface of the photoconductor or the toner to an appropriate electric charge by charging 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 image loss occurs, in the case, the toner in the image portion scatters in the peripheral portion,
However, it is difficult to properly control the charge of the photoconductor or the toner. 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 prevent 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]

As described above, in a so-called tandem type color image forming apparatus or the like, it is necessary to superimpose and transfer a plurality of toner images onto an intermediate transfer member or an image support.

In addition to preventing transfer defects, toner scattering, image blurring, and other image defects that are likely to occur in the transfer process, it is already possible to use an intermediate transfer member or an image support (both of which may be referred to as a transfer material). When the toner image has been transferred, and when the toner image is further transferred onto it, the toner image to be newly transferred to the transfer material is formed at a high transfer rate, and the toner that has already been transferred is not retransferred to the photoconductor. Must be selected.

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 gap, toner scattering, and image blur that 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.

[0014]

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

[1] In an image forming apparatus having means for applying a lubricant to the surface of an electrophotographic photoreceptor and a mechanism for heating the photoreceptor, a mechanism for forming a toner patch on the photoreceptor and a density detection sensor for the patch. And an image forming apparatus which operates a mechanism for heating the photosensitive member according to the detection level of the sensor.

[2] In an image forming apparatus having an intermediate transfer member, which has means for applying a lubricant to the surface of the electrophotographic photosensitive member and a mechanism for heating the photosensitive member, a toner patch is formed on the intermediate transfer member. An image forming apparatus, which is provided with a mechanism and a density detection sensor for the patch, and operates a mechanism for heating the photoconductor according to a detection level of the sensor.

[3] The image forming apparatus as described in [1] or [2], wherein the lubricant is solid and is in direct pressure contact with the surface of the photoreceptor.

[4] The image forming apparatus as described in [1] or [2], wherein the lubricant is solid and the lubricant is applied to the surface of the photoconductor by a brush roller installed between the lubricant and the photoconductor.

[5] The image forming apparatus as described in [1] or [2], wherein the toner patch is formed in a one-dot line pair pattern in a direction perpendicular to an image traveling direction.

[6] At least a transfer means for transferring the toner image formed by the charging means of the photoconductor, the image exposing means, and the toner developing means from the photoconductor to the image support or the intermediate transfer body is an elastic body on a core metal. [1] or [2] characterized in that a voltage is applied to an elastic roller provided with
The image forming apparatus described.

[7] A transfer unit for transferring a toner image formed by at least a charging unit of the photoconductor, an image exposing unit, and a toner developing unit from the photoconductor to an image support or an intermediate transfer body applies a voltage to a wire. The image forming apparatus according to [1] or [2] is characterized in that it is a corotron system for discharging.

[8] The image forming apparatus as described in [1] or [2], wherein the mechanism for heating the photoconductor is operated by the temperature of the photoconductor.

[0023]

[9] The image forming apparatus as described in [1] or [2], wherein the lubricant is zinc stearate or calcium stearate.

[10] Prior to the actual start of image formation,
The image forming apparatus according to [1] or [2], wherein a mechanism for heating the photoconductor is activated according to the detection level of the density detection sensor, and at least the photoconductor and the developing unit are rotated once or more.

[11] At least charging means for the photosensitive member,
Image transfer means, and a transfer means for transferring the toner image formed by the toner developing means from the photoconductor to the intermediate transfer body,
An image forming apparatus comprising: a mechanism for forming a toner patch on the intermediate transfer member; and a density detection sensor for the patch, and setting conditions for a transfer unit or a pre-transfer exposure unit according to detection information from the sensor.

[12] The image forming apparatus as described in [11], wherein the transfer means is one in which a voltage is applied to an elastic roller having a cored bar provided with an elastic body.

[13] The image forming apparatus as described in [11], wherein the transfer means is an elastic roller, and the condition setting is to adjust the pressing force to the photoconductor.

[14] The image forming apparatus according to [11], wherein the transfer means is an elastic roller, and the condition setting is to adjust the voltage applied to the roller.

[15] The image forming apparatus as described in [11], characterized in that the transfer means is an elastic roller, and the condition setting is to adjust the value of current flowing through the roller.

[16] The image forming apparatus as described in [11], wherein the condition setting of the pre-transfer exposure means is to adjust a light amount condition.

[17] The image forming apparatus as described in [11], wherein the condition setting of the pre-transfer exposure means is to adjust the distance between the exposure light source and the photosensitive member surface.

[18] The image forming apparatus according to [11], wherein the patch to be formed is a 1 to 3 dot line pair pattern arranged in parallel or at right angles to the image forming direction.

[19] The image forming apparatus as described in [18], characterized in that the patch to be formed is formed by arranging circles having a diameter of 1 mm or less at center point intervals of the diameter or more.

[20] The image forming apparatus as described in [11], wherein the toner developing means adopts a reversal developing system.

The above inventions [1] to [10] and [1]
In the inventions 1] to [20], 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 is a final image carrying member. 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.

[0038]

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

In the electrophotographic transfer process, a part of the image such as characters or lines has a part where the toner forming the image is particularly dense, and a "medium clear" failure occurs in such a part. Sometimes. This is a phenomenon in which dense toner agglomerates and is separated from the photoconductor by the electric field alone and is not transferred to the intermediate transfer body or the image support. Whether the aggregated toner remains on the photoconductor or is transferred to the transfer material is determined by the releasability (adversely speaking, adhesiveness) of each other. That is, if the agglomerated toner has a greater releasability from the transfer material than the photoconductor, the agglomerated toner remains on the photoconductor, and the part is left unclear.

FIG. 1 shows the state of the middle part. In the figure, the outline of the characters is the middle missing part. This phenomenon occurs remarkably in both the intermediate transfer body and the image support in the roller transfer system. Incidentally, the roller transfer method is a method which has been widely used recently and transfers the transfer material by pressing the transfer material onto the surface of the photoconductor with an elastic roller.

As a countermeasure against the above-mentioned failure, a lubricant is applied to the surface of the photoconductor as in the constitution of the first invention to increase the releasability between the surface of the photoconductor and the toner, and the aggregated toner is transferred from the surface of the photoconductor to the transfer material. Measures have been taken to facilitate transfer. However, when the environment used is high humidity, "image blur" or "image deletion" occurs because the charge of the photoconductor moves on the surface (hence the boundary between the exposed and unexposed parts becomes unclear). A so-called failure occurs, but the lubricant application has a strong tendency to promote this.

In order to apply the lubricant to the surface of the photoconductor and prevent image blurring and image deletion, it is preferable to raise the temperature of the photoconductor and reduce the relative humidity in the vicinity. However, if the photoconductor is always heated, extra power is consumed, and the time required for the first copy after the power is turned on becomes long. Therefore, in the present invention, the toner patch is formed by the development, and it is confirmed whether or not the image blurring or the image deletion occurs, and the photoconductor is heated only when necessary.

When the image forming apparatus such as a copying machine or a printer to which the present invention is applied has an intermediate transfer body, it is better to measure the toner patch after transfer to the intermediate transfer body. This is preferable because it is easy to understand blurring and image deletion.

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.

FIG. 3 is an enlarged sectional view of the image forming portion 10Y for forming a yellow image for explaining the first aspect of the invention.

The image forming apparatus main body GH shown in FIG. 2 is called a tandem type color image forming apparatus, and includes 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 unit 1 for forming a yellow image
0Y is a charging unit 2Y, an image exposing unit 3Y, and a toner developing unit 4Y arranged around the photoconductor 1Y as an image forming body.
And a cleaning means 8Y. The image forming unit 10M that forms a magenta image has a photoreceptor 1M as an image forming body, a charging unit 2M, an image exposing unit 3M, a toner 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 image exposing unit 3C, a toner 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, a charging unit 2K, an image exposing unit 3K, a toner developing unit 4K, and a cleaning unit 8K. Charging means 2Y and image exposure means 3Y, charging means 2M and image exposure means 3M, charging means 2C and image exposure means 3C and charging means 2
The K and the image 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 is removed from the intermediate transfer body 6 separated from the image support P by the cleaning means 8A.

The toner patch density detection sensor 11 is
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 11 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 a voltage is applied to an elastic roller type in which an elastic body is mounted on a metal core such as a metal rod, or a high voltage is applied to a wire to discharge. A corotron discharger type is preferred.

Incidentally, 5Y, 5M, 5C and 5K are toner replenishing means for replenishing the toner 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 an image processing section, and then an image writing section (image exposing means) 3Y. ,
Send signals to 3M, 3C and 3K.

The automatic document feeder 201 is provided with 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 FIG. 3, reference numeral 9 is a means for applying a lubricant 9A, and a lubricant applying means is brought into contact with the photoreceptor 1Y to apply it on the surface of the photoreceptor. Further, a heater 100Y is installed inside the photoconductor as a mechanism for heating the photoconductor, and heats the photoconductor as necessary.

As shown in FIG. 2, when the density detection sensor 11 is installed not for reading the toner patch on the intermediate transfer body but for reading on the photoreceptor itself, the photoreceptor 11
On the Y surface, for example, it is installed between the toner developing means 4Y and the transfer means 7Y. Further, this is of course the same in the image forming units of other colors.

The means for applying the lubricant of the present invention is not particularly limited in its structure as long as the purpose of uniformly applying the lubricant on the surface of the photoreceptor is achieved. One of the preferred embodiments is to apply by direct pressure contact. However, in order to further enhance the uniform coating property, it is also a good method to interpose the coating brush roller 9B between the surface of the photoreceptor and the lubricant 9A as shown in FIG.

The lubricant in the present invention is used so far as to improve the sliding between the cleaning blade and the surface of the photosensitive member, and prevents the adhesion of paper powder or the like to the surface of the photosensitive member. . It is preferable that it is solid at room temperature because it is easy to handle, and typical ones are metal salts of higher fatty acids. The higher fatty acid most often used is stearic acid, and metals such as calcium and zinc are used.

The toner patch used in the present invention is
The purpose is to detect image blurring and image deletion, and surface charge leaks that cause these are also generated in the horizontal direction of image formation, but in the vertical direction, that is, the moving direction of the photoconductor (photosensitive drum Leakage in the rotation direction and the image traveling direction) is dominant. Therefore, as shown in FIG. 5, it can be said that the detection is performed with a 1-dot line pair pattern formed in the direction perpendicular to the image forming direction with high sensitivity. In FIG. 5, the left side shows the entire toner patch, and the right side shows an example of the enlarged view. As an exposure light source for making a toner patch,
An image exposure light source, that is, a semiconductor laser light source, an LED light source, or the like is used. Further, as the toner patch density detection sensor, a phototransistor or the like is used, and it is sufficient that it can detect the density pattern by scanning the line pattern at right angles.

In order to effectively operate the above system,
The mechanism for heating the photoreceptor is not particularly limited, and a sheet heater, a nichrome wire heater, a halogen lamp heater or the like is used. Further, it is preferable to operate in several stages depending on the degree of failure such as image blur, and at this time, the photosensitive member temperature is also taken into consideration. Further, it is preferable that the photoreceptor and the toner developing means are operated for at least one cycle or more before the actual image formation. Here, one cycle means one rotation for the photosensitive drum and one rotation of the developing sleeve for the toner developing means.

A specific embodiment of the first aspect of the present invention will be described later as Example 1.

Next, the second invention of the present invention will be described. It has been conventionally known that providing a pre-transfer exposure means after development is effective as a means for increasing transfer efficiency. Since the transfer means is a step of moving the toner by an electric field having a polarity opposite to that of the normal toner, the electric field with the non-exposed portion is larger, especially in the reversal development, and the applied charge easily flows to the non-exposed portion, and therefore the toner is Less charge is used to transfer. In order to compensate for this, the electric field is further increased in advance to move the toner.

However, in order to increase the electric field, the voltage applied to the image support or the intermediate transfer member which comes into contact with the photoconductor is increased, and a dielectric breakdown occurs in a minute space at the time of peeling immediately before the contact with the photoconductor and the electric field. May result in poor transfer, or may cause toner to be re-transferred to the photoconductor by charging the toner to the opposite polarity.

Therefore, after developing the toner, the potential of the non-exposed region is lowered to bring it closer to the exposed region so that there is not much difference in the magnitude of the electric field between the non-exposed region and the exposed region. This allows the toner to be efficiently transferred. For this purpose, exposing the photoreceptor after development and before transfer was an effective means. However, lowering the potential of the non-exposed area of the photosensitive member weakens the force for attaching the toner to the exposed area, so that the toner tends to scatter around, especially in places where the toner adheres closely such as lines and letters. There was a problem. This phenomenon is particularly remarkable in reversal development,
It becomes noticeable in a high humidity environment where electric charges easily leak. As described above, there was no image defect including stability in any environment, and the transfer efficiency could not be improved.

In the present invention, this problem is solved by forming a patch image on the intermediate transfer member and setting the pre-transfer exposure condition and / or the transfer condition of the toner image by the output thereof. In the case of the reversal development method in which the magnitude of the electric field in the non-exposed area was a problem,
In particular, this structure has a great effect.

At this time, the toner patch used in the present invention is intended to detect image blurring and image deletion during transfer, and the leakage of surface charges that causes these is as shown in FIG. It can be said that the detection is performed with a 1 to 3 dot line pair pattern in the traveling direction and the direction orthogonal thereto with high sensitivity (illustrated by a 2 dot line pair pattern in FIG. 6). In FIG. 6, (a) shows a dot line formed in a direction perpendicular to the traveling direction, and (b) shows a dot line formed in the traveling direction. A partially enlarged view of each is shown on the lower side. The dots forming these patches are preferably formed by arranging circles having a diameter of 1 mm or less at center point intervals of the diameter or more.

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.

FIG. 7 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.

FIG. 8 is an enlarged sectional view of the image forming portion 10Y for forming a yellow image for explaining the second invention. A pre-transfer exposure unit 12Y is installed between the toner developing unit 4Y and the transfer unit 7Y. Although the density detection sensor reads the toner patch on the intermediate transfer member and determines the condition based on the detection information, of course, the pre-transfer exposure device may not be provided if the condition is set only by the transfer device.

The image forming apparatus main body GH shown in FIG. 7 is called a tandem type color image forming apparatus, and comprises a plurality of sets of image forming sections 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 is a charging unit 2Y, an image exposing unit 3Y, and a toner developing unit 4 which are arranged around a photoconductor 1Y as an image forming body.
Y, a pre-transfer exposure unit 12Y, a transfer unit 7Y, and a cleaning unit 8Y. The image forming unit 10M that forms a magenta image has a photoreceptor 1M as an image forming body, a charging unit 2M, an image exposing unit 3M, a toner developing unit 4M, a pre-transfer exposing unit 12M, 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 image exposing unit 3C, a toner developing unit 4C, a pre-transfer exposing unit 12C, and a cleaning unit 8C. The image forming unit 10K that forms a black image includes a photoconductor 1K as an image forming body, a charging unit 2K, an image exposing unit 3K, a toner developing unit 4K, a lubricant applying unit 9, and a cleaning unit 8K. Charging means 2Y and image exposure means 3Y, charging means 2M and image exposure means 3M, charging means 2C and image exposure means 3C and charging means 2
The K and the image 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 feeding cassette 20 is fed by the paper feeding means 21 and is fed by the paper feeding 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 is
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 toner 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 (image exposing means) 3Y. ,
Send signals to 3M, 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 conditions of the pre-transfer exposure unit or the transfer unit of each color are set based on the detection level. Needless to say, the conditions of both the pre-transfer exposure unit and the transfer unit may be set.

The condition setting may be performed on any condition as long as it is a condition change that can change the transfer state of the pre-transfer exposure unit or the transfer unit. However, what can be preferably used in the present invention is the pressing force of the elastic roller against the photosensitive member, the voltage applied to the elastic roller, the value of the current flowing through the elastic roller, etc. in the transfer means. Further, in the pre-transfer exposure means, the amount of light, the distance between the light source and the surface of the photoconductor, and the like are used.

A concrete embodiment of the second aspect of the present invention will be described later as Example 2.

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, image exposing means, toner developing means, those commonly used in electrophotographic image forming apparatuses can be used in the present invention.

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

As the image exposing means, a semiconductor laser light source, an LED light source, or the like is used, and these are exposed in a beam or spot form to imagewise expose the uniformly charged surface of the photoreceptor to form a latent image.

The toner 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, the particle size of the toner preferably has a volume average particle size of 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 above-mentioned toner as it is as a non-magnetic one-component developer, but usually, the magnetic particles are made to contain 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.

Further, 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 deteriorated 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, liquid crystal shutter printers, and the like. It can be widely applied to devices such as light printing, plate making, and facsimile.

[0108]

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 performed using the color copying machine shown in FIG.

Each photosensitive drum had a diameter of 60 mm, the photosensitive layer was prepared by dispersing a phthalocyanine pigment in polycarbonate, and the photosensitive layer was applied to a total film thickness of 25 μm including the 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 having a volume average particle diameter of 6.0 μm was used. The transport speed of the intermediate transfer member is 180 mm / s, and the seamless semi-conductive resin belt (volume resistivity is 1
0 ⁸ Ω · cm) was used. As a transfer (primary transfer) means from each photoconductor to the intermediate transfer body, a foamed resin roller (10 ⁶ Ω · cm) having a diameter of 20 mm was installed on the back surface of the intermediate transfer body, and a constant current was controlled to 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.

Each color (yellow Y, magenta M, cyan C
And a black K), a 1-dot line pair pattern (16 lines / mm) toner patch is formed on the surface of the photoconductor so as to form a line in a direction perpendicular to the direction of travel of the photoconductor, and the toner patch is transferred to the intermediate transfer member. It was detected by the detection sensor.

When a phototransistor is used for detection, the output when there is no patch is 12V, the output of solid black is 3V, and when the output is 6V or less, the inside of the photoconductor of the image forming means of the corresponding color. The heater was heated to heat the photoconductor. The control flowchart at this time is shown in FIG.
It was shown to. The morning correction operation means an operation of automatically checking the state of the entire copying machine when the main switch of the copying machine is turned on. Further, the heater is a planar heater mounted inside the support of the photoconductor.

As described above, the actual copying was carried out up to 200,000 copies, but no intermediate missing, image blurring, and image deletion did not occur.

Example 2 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 toner has a volume average particle diameter of 6.0 μm. The transfer speed of the intermediate transfer member is 180 mm / s, and the seamless semi-conductive resin belt (10 ⁸ Ω · c
m) was used. Further, the transfer (primary transfer) means from each photoconductor to the intermediate transfer member has a diameter of 20 mm on the back surface of the intermediate transfer member.
Foam resin roller (10 ⁶ Ω · cm, core metal diameter 10 m
m) was installed and the constant current was controlled to 20 μA.

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 in which a heater is arranged are used.

As a control patch, a 20 × 20 mm 2-dot line pair pattern was formed by using an image exposure means.
It was formed in a direction perpendicular to the rotating direction of the photoconductor. In the actual control, when the power is turned on, the equipment is checked for a predetermined set of exposure conditions and development conditions.After that, the patch is formed, and based on the detection result, the pre-transfer exposure condition and the primary transfer condition are set. To decide. After the copying was started, a patch was formed every 500 copies thereafter, and the pre-transfer exposure condition and the transfer condition were adjusted.

A phototransistor was used for detection, and the following table was used for control based on its output.

Pre-Transfer Exposure Condition Primary Transfer Current Value Patch Output LED Applied Voltage (V) (μA) 5.1-6.0V 24 20 4.1-5.0V 20 25 3.1-4.0V 18 27 2 1 to 3.0V 16 30 2.0 or less Under the conditions of 0 35 or more, 200,000 actual copies were taken. In addition,
Room temperature / humidity (20 ℃, 55% R)
H), low temperature / low humidity up to 100,000 to 150,000 copies (10 ° C,
30% RH), 15 to 200,000 copies were performed at high temperature / high humidity (33 ° C., 80% RH).

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

[0126]

According to the present invention, it is possible to provide an image forming apparatus capable of obtaining a sufficient transfer rate without causing image defects such as transfer gap, toner scattering, and image blurring which are likely to occur in the 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 image forming apparatus that is not retransferred can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a state of blanking due to transfer.

FIG. 2 is a sectional view illustrating a configuration of a tandem type color image forming apparatus.

FIG. 3 is an enlarged cross-sectional view of an image forming unit.

FIG. 4 is an explanatory diagram of a lubricant coating method in which a coating brush roller is interposed between the surface of the photoconductor and the lubricant.

FIG. 5 is a diagram showing a toner patch of a 1-dot line pair pattern.

FIG. 6 is a diagram showing a toner patch of a 2-dot line pair pattern.

FIG. 7 is a sectional view illustrating a configuration of a tandem type color image forming apparatus.

FIG. 8 is an enlarged cross-sectional view of an image forming unit.

FIG. 9 is a flowchart of control.

FIG. 10 is a diagram showing a transfer rate of a live-copy test.

[Explanation of symbols]

1Y, 1M, 1C, 1K photoconductor 2Y, 2M, 2C, 2K charging means 3Y, 3M, 3C, 3K image exposure means 4Y, 4M, 4C, 4K toner developing means 6 Intermediate transfer body 7Y, 7M, 7C, 7K Transfer means 9 Lubricant application means 10Y, 10M, 10C, 10K Image forming unit 12Y, 12M, 12C, 12K Pre-transfer exposure means 100Y heater

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/00 G03G 21/00 372 21/14 534 21/20 15/12 (72) Inventor Hiroshi Morimoto Tokyo Konica Co., Ltd., 2970 Ishikawa-cho, Hachioji, Japan (72) Inventor Masashi Saito F-Term (Reference) 2H027 DA09 DA10 DA13 DA35 DE02 DE07 DE09 EA13 EB04 EC04 EC06 EC10 EC18 ED01 ED06 ED08 ED24 EE01 EE06 EF02 EK01 GA30 GA54 GB07 ZA07 2H134 GA01 GA06 GB02 HD01 KA16 KA31 KB13 KB15 KC01 KD05 KF02 KG03 KG04 KG08 KH01 KH04 KJ02 LA01 2 GA59 GB02 GB12 GB22 GB25 HA02 HA12 HA28 HB03 HB12 HB22 JA02 JA21 JA25 JA26 JA28 JC03 JC09 JC12 JC15 JC16 JC18 LA12 LA31 MA04 MA08 M A20 MB02 MB04 MB09 MC15 MC16 MC18 NA02 NA06 NA08 NA09 NA10 PA18 PA19 PA22 PA27 PA30 PB07 PB18 PB20 PB39

Claims (20)

[Claims] 1. An image forming apparatus having means for applying a lubricant to the surface of an electrophotographic photoreceptor and a mechanism for heating the photoreceptor, wherein a mechanism for forming a toner patch on the photoreceptor and a density detection sensor for the patch are provided. An image forming apparatus comprising: a mechanism for heating a photoconductor according to a detection level of the sensor. 2. An image forming apparatus having an intermediate transfer member, which has means for applying a lubricant to the surface of the electrophotographic photosensitive member and a mechanism for heating the photosensitive member, and forms a toner patch on the intermediate transfer member. A mechanism and a density detection sensor for the patch are provided,
An image forming apparatus characterized in that a mechanism for heating a photoconductor is operated according to a detection level of the sensor. 3. The image forming apparatus according to claim 1, wherein the lubricant is solid and is in direct pressure contact with the surface of the photoconductor. 4. The image forming apparatus according to claim 1, wherein the lubricant is solid, and the lubricant is applied to the surface of the photoconductor by a brush roller installed between the lubricant and the photoconductor. 5. The image forming apparatus according to claim 1, wherein the toner patch is formed in a 1-dot line pair pattern in a direction perpendicular to an image traveling direction. 6. A transfer means for transferring at least a toner image formed by a charging means, an image exposing means, and a toner developing means of a photoconductor from the photoconductor to an image support or an intermediate transfer body, an elastic body being provided on a core metal. The image forming apparatus according to claim 1, wherein a voltage is applied to the attached elastic roller. 7. A transfer means for transferring at least a toner image formed by a charging means, an image exposing means, and a toner developing means of a photoconductor from the photoconductor to an image support or an intermediate transfer body applies a voltage to a wire. The image forming apparatus according to claim 1, wherein the image forming apparatus is of a corotron system for discharging. 8. The image forming apparatus according to claim 1, wherein the mechanism for heating the photoconductor is operated by the temperature of the photoconductor. 9. The lubricant according to claim 1, wherein the lubricant is zinc stearate or calcium stearate.
The image forming apparatus described. 10. Prior to the actual start of image formation, a mechanism for heating the photoconductor is operated according to the detection level of the density detection sensor, and at least the photoconductor and the developing means are rotated once or more. The image forming apparatus according to claim 1. 11. A transfer unit for transferring at least a toner image formed by a charging unit of the photoconductor, an image exposing unit, and a toner developing unit from the photoconductor to an intermediate transfer body, and a toner patch on the intermediate transfer body. An image forming apparatus comprising: a forming mechanism and a density detection sensor for the patch, and setting conditions of a transfer unit or a pre-transfer exposure unit according to detection information of the sensor. 12. The image forming apparatus according to claim 11, wherein the transfer unit is an elastic roller having a cored bar provided with an elastic body, to which a voltage is applied. 13. The image forming apparatus according to claim 11, wherein the transfer unit is an elastic roller, and the condition setting is adjusting the pressing force applied to the photoconductor. 14. The image forming apparatus according to claim 11, wherein the transfer unit is an elastic roller, and the condition setting is adjusting a voltage applied to the roller. 15. The image forming apparatus according to claim 11, wherein the transfer unit is an elastic roller, and the condition setting is to adjust a value of a current supplied to the roller. 16. The condition setting of the pre-transfer exposure means includes
The image forming apparatus according to claim 11, wherein the light amount condition is adjusted. 17. The condition setting of the pre-transfer exposure means includes
The image forming apparatus according to claim 11, wherein the distance between the exposure light source and the surface of the photoconductor is adjusted. 18. The image forming apparatus according to claim 11, wherein the patch to be formed is a 1-3 dot line pair pattern arranged in parallel or at right angles to the image forming direction. 19. The image forming apparatus according to claim 18, wherein the patch to be formed is formed by arranging circles having a diameter of 1 mm or less at center point intervals of the diameter or more. 20. The image forming apparatus according to claim 11, wherein the toner developing unit adopts a reversal developing method.