JP2008096724A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide, in view of a drawback caused by a change in the charging characteristic of an image carrier used as a photoreceptor, an image forming apparatus having a configuration capable of forming images of high image quality that is not affected by the change in the characteristic of the image carrier for a long time. <P>SOLUTION: The image forming apparatus includes: a counting means 111 that counts the total number (R1) of rotations of the image carrier during the operation of a charging means; and a control section 110 the input side of which is connected to a counting means 112 that counts the total number (R2) of rotations of the image carrier during the non-operation of the charging means and the output side of which is connected to an exposure means 3. The control section 110 controls exposure conditions for the exposure means 3 by using the result of calculation from which the exposure conditions for the exposure means 3 are derived based on the values of the (R1) and (R2) and a target uniform charging potential. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a FAX, a printer using electrophotography, and a plotter of an electrophotographic recording apparatus. More specifically, the present invention reduces image characteristics due to deterioration of a latent image carrier used as a photoreceptor. It relates to a configuration to prevent.

As one of the image forming apparatuses, there is an apparatus using an electrophotographic method, and the image forming apparatus based on this method includes not only the creation of a black and white character document, but also a device that creates a full color image combining a plurality of colors. It has been diversified.
Color images are convenient for use in, for example, document presentation materials and pamphlets, and it has become possible to form high-quality images comparable to silver halide photographs.

  In the electrophotographic system, a photoconductor used as a latent image carrier is subjected to writing exposure for forming an electrostatic latent image according to image information after uniform charging. When performing the above, it is said that it is easy to reproduce a halftone of a natural hue. In addition, there is a strong demand for high-speed image formation, and so-called tandem image forming apparatuses that use different photoreceptors for color images created from black, cyan, magenta, and yellow toners have become common. It was.

In such a high-quality image forming apparatus, the image quality required by the user cannot be maintained unless the photosensitive member is charged and the potential of the exposed latent image pattern is always appropriate. In particular, in the case of a color image forming apparatus, if the latent image potentials of the photoconductors of the respective toners are different, they are often recognized as unnatural colors.
On the other hand, an apparatus related to image formation including a photoconductor is a process in which a part of the photoconductor and a part of the apparatus arranged around the photoconductor are collected separately from the configuration arranged independently in the image forming apparatus. A structure arranged in a cartridge is also well known.
When using a process cartridge, in order to maintain the image quality of the photoconductor as much as possible for the purpose of maintaining image quality, the photosensitivity characteristics of the photoconductor, for example, when the toner is completely consumed, are high. Even if it is in a state suitable for maintenance, it is easy to always maintain high-quality image formation by using a new photoconductor by replacing the process cartridge itself including the photoconductor. From the viewpoint of reduction and maintenance cost / time reduction, there is also a demand for image formation with high image quality while continuing to use the mounted photoconductor for as long as possible.

However, when image formation is repeated using the same photoconductor, the photoconductor gradually wears due to friction between the photoconductor and the cleaning blade.
When the photosensitive member is worn and the thickness of the photosensitive layer is reduced, the electrostatic capacity of the photosensitive member increases, so that the charge amount on the surface of the photosensitive member increases even if the charging potential is the same. As a result, even if the exposure amount is the same, the electric field strength of the latent image is different, and the image density due to development is different. In particular, when performing exposure by a multi-value method, it is difficult to reproduce the image density although the photosensitive layer is reduced.

  Therefore, conventionally, as a method of preventing changes in image density and the like in response to changes in characteristics on the photoconductor side due to long-term use, a process cartridge that collectively stores the photoconductor and an apparatus used for image forming processing for the photoconductor In the case of using, a means for storing the usage amount of the process kit is provided, and depending on the operation time of the process kit and the number of copies, the exposure amount to be exposed to the photosensitive member is changed or the charging condition is changed, A method for maintaining high-quality image formation (for example, Patent Document 1). A method for determining the degree of deterioration of the photoreceptor by classifying the total operation time per day and the total number of copies (for example, for example, changing the charging condition) Patent Document 2), or a non-volatile storage means is provided in the process cartridge, and exposure conditions are determined from the sensitivity information of the photosensitive member stored in the storage means. Set, further corrects the exposure condition by the number of prints (e.g., Patent Document 3) have.

  In addition to this, a method has been proposed in which the amount of decrease in the film thickness of the photoconductor is predicted according to the cumulative number of rotations of the photoconductor, and the exposure conditions for the photoconductor are corrected (for example, Patent Document 4). .

JP 05-257343 A Japanese Patent Laid-Open No. 05-66641 Japanese Patent Laid-Open No. 09-120245 Japanese Patent Laid-Open No. 2002-244368

  In the methods disclosed in patent documents other than the above-mentioned patent document 4, if the correlation between the number of copies and the decrease in the film thickness of the photoconductor is taken, the number of copies and the film thickness are limited as long as the copying is performed under a certain copy condition. Although there is a good correlation with the amount of decrease, the amount of decrease in film thickness varies greatly depending on various copy conditions (for example, how many copies are copied at a time, copy density, etc.) and process kit lots. Therefore, if the process kit is used for a long period of time, there will be a difference between the amount of decrease in the thickness of the photoconductor predicted from the number of copies and the actual amount of decrease in the thickness of the photoconductor. There was a problem that a preferable image could not be obtained even after correction.

  In the method disclosed in Patent Document 4, when a scorotron is used for the charging device or a DC bias is applied to the charging roller, there is an advantage that excellent image formation is possible, but the image forming device is advantageous. In order to reduce the size and improve the accuracy of the charging potential of the photosensitive member, when charging is performed by superimposing a DC bias and an AC voltage on the charging roller, the photosensitive member depends on image forming conditions (for example, the number of images to be continuously formed). In many cases, the correlation between the cumulative number of rotations and the decrease in the film thickness of the photoconductor is different, and the predicted value for the decrease in the photoconductor film thickness when the image forming apparatus is used for a long time is different from the actual value. Even if it performed, the malfunction that a preferable image was not obtained had arisen.

  An object of the present invention is to provide long-term high-quality image formation unaffected by changes in the characteristics of the image carrier in view of the problems in the above-described conventional image forming apparatuses, in particular, problems due to changes in the charging characteristics of the image carrier used as the photoreceptor. An object of the present invention is to provide an image forming apparatus having a configuration that can be realized over a wide range.

  In order to achieve this object, the present invention has the following configuration.

(1) An image bearing member, a charging unit including a charging member that performs close charging with a DC voltage and an AC voltage in proximity to or in contact with the image bearing member, and the image bearing after charging. An exposure unit that forms an electrostatic latent image on the body according to image information; a developing unit that converts the electrostatic latent image into a toner image; a transfer unit that transfers the developed toner image to a transfer body; In an image forming apparatus provided with a cleaning means for cleaning the remaining toner image with a cleaning blade,
Counting means for counting the total number of rotations (R1) that the image carrier has rotated while the charging means is operating, and the total number of rotations that the image carrier has rotated while the charging means is not operating (R1). A control unit connected to the input side, and a control unit to which the exposure unit is connected on the output side.
The control unit controls exposure conditions in the exposure unit using a calculation result obtained by calculating an exposure condition of the exposure unit based on the values of (R1) and (R2) and a target uniform charging potential. An image forming apparatus.

(2) A means for measuring the rotational torque of the image carrier is connected to the controller.
The control unit controls the exposure condition of the exposure unit using the calculation result obtained by calculating the exposure condition of the exposure unit from the values of (R1) and (R2) and the measured rotational torque of the image carrier. (1) The image forming apparatus according to (1).

(3) The image carrier, the charging unit, the developing unit, the cleaning unit, and at least the image carrier and the cleaning unit are provided in a process cartridge.
The controller measures in advance the rotational torque of the image carrier in the process cartridge, and determines the exposure means's value from the measured rotational torque of the image carrier in the process cartridge and the values of (R1) and (R2). The image forming apparatus according to (1) or (2), wherein the exposure unit is controlled using a calculation result obtained by calculating an exposure condition.

  (4) The image forming apparatus according to any one of (1) to (3), wherein the control unit controls light source output or exposure time as an exposure condition in the exposure unit.

  (5) The control unit forms a density detection reference toner image on the image carrier, detects an image density of the density detection reference toner image, and sets the image density to a target image density. And a target potential determination table that stores the target development bias and the target uniform charging potential in association with each other. The target development bias is determined based on the detection result of the image density detection means, and the target development is determined. Based on the bias, the target uniform charging potential is determined from the target potential determination table, the charging means is controlled so as to become the predetermined target uniform charging potential, and the predetermined target developing bias is obtained. The image forming apparatus according to any one of (1) to (4), wherein the developing unit is controlled.

  (6) The image forming apparatus according to any one of (1) to (5), wherein the resolution of the writing light to the image carrier is 1000 dpi or more.

  (7) The image forming apparatus according to any one of (1) to (6), wherein the initial film thickness of the photosensitive layer of the image bearing member is 28 to 45 μm.

  (8) The image forming apparatus according to (3), wherein the process cartridge is detachably attached to the apparatus main body.

According to the present invention, by predicting the decrease in mechanical strength due to the degree of film thickness reduction of the image carrier, by setting the charging condition or exposure condition according to the prediction result, the image quality in the long-term use of the image carrier can be reduced. It becomes possible to prevent.
In particular, in the first aspect of the present invention, the total number of rotations (R1) of the photosensitive member rotated while charging is performed on the total number of rotations (Rt) of the photosensitive member, and the photosensitive member is rotated while charging is not performed. Since the total number of rotations (R2) of the rotation of the body is separated and the film thickness reduction of the photoconductor is predicted from the total number of rotations, the degree of film thickness reduction due to actual operation of the image carrier can be accurately predicted, In the case of a color image as well as a monochrome image, an image having a natural color can be formed even when the image carrier is used for a long time.

  According to the second and third aspects of the invention, in addition to the parameter (total number of rotations) for predicting the film thickness reduction of the image carrier in the invention of the first aspect, the rotation of the image carrier or the process cartridge including the image carrier. By applying torque, the degree of film thickness reduction due to actual operation of the image carrier can be predicted more precisely, so that it is possible to prevent image quality degradation and abnormal image generation during long-term use of the image carrier.

  In the invention according to claim 4, in the exposure control according to the film thickness reduction of the image carrier, the configuration for assuring image quality is utilized by using the light source output or the exposure time as a control target. Can be performed.

  According to the fifth aspect of the present invention, the target uniform charging potential is set based on the target developing bias with respect to the change in the toner adhesion amount based on the density detection result from the density detection reference toner image. Unlike the case where it is constant, it is possible to prevent deterioration of the charging characteristics due to the decrease in the film thickness of the image carrier and the decrease in the toner adhesion amount in response to fluctuations in the toner charge amount. It is possible to prevent the image quality from being lowered when the carrier is used.

  In the invention described in claim 6, it is possible to obtain a high-resolution image satisfactorily even in the long-term use of the image carrier by setting the exposure condition and the charging condition corresponding to the film thickness reduction of the image carrier. It becomes.

  According to a seventh aspect of the present invention, there is provided an image forming apparatus capable of forming an image having a natural color with a long period of time during which the image carrier can be used because the initial film thickness of the photosensitive layer on the image carrier is large. Can be provided.

  According to the eighth aspect of the present invention, it is easy to mount and replace an image forming apparatus such as an image carrier, and it is possible to form an image with a natural color over a long period of time.

The present invention is based on the examination results described below.
In other words, the present inventors have examined in detail why the predicted value of the decrease in the film thickness of the photoreceptor differs from the actual value when charging is performed by superimposing a DC bias and an AC voltage on the charging roller. It was.

When charging is performed by superimposing a DC bias and an AC voltage on the charging roller, the number of times corresponding to the frequency of the AC voltage per unit time from the charging roller to a photosensitive member (hereinafter referred to as a photosensitive member) used as an image carrier. A discharge has occurred.
Since the energy of discharge is large enough to decompose the C—C bond of organic matter, the photoconductor is oxidized and deteriorated every time discharge occurs. The portion of the surface of the photoconductor that has been oxidized and deteriorated due to electric discharge is inferior in mechanical strength. Therefore, the rate of reduction of the photoconductor thickness due to friction with the cleaning blade is faster than when only DC voltage is applied for charging. It was found to be 2 to 10 times different.

  In the conventional image forming apparatus, in order to simplify the control system, the motor switch for rotating the photosensitive member and the ON / OFF switch for charging are often linked, but energy saving and harmful effects such as ozone. In order to reduce the amount of generated gas, image forming apparatuses that perform charging only for the time necessary for image formation have increased. In particular, in order to always enable high-resolution image formation, a refresh function that discharges old toner in the developing device and adds fresh toner in order to keep the developer characteristics constant, In an image forming apparatus having a function of performing only cleaning without performing image formation in order to remove the substance filmed on the surface, the photosensitive member is rotated many times without image formation. In that case, charging was often not performed.

  In such an image forming apparatus, even if the total number of revolutions of the photoconductor is monitored, it is not possible to accurately predict a decrease in the film thickness of the photoconductor. Therefore, it is preferable to correct the exposure amount. In an image forming apparatus that performs charging by superimposing a DC bias and an AC voltage on a charging roller, the total number of rotations (Rt) of the photosensitive member is charged. The total number of rotations (R1) in which the photosensitive member is rotated while the photosensitive member is rotated and the total number of rotations (R2) in which the photosensitive member is rotated while charging is not performed. We have found that it is necessary to predict thickness reduction.

  That is, the present invention relates to an image carrier, charging means for uniformly charging the surface of the photosensitive member by superimposing a DC voltage and an AC voltage on a charging roller, and an electrostatic latent image on the surface of the charged image carrier. An exposure unit for forming a toner image, a developing unit for converting the electrostatic latent image into a toner image, a transfer unit for transferring the developed toner image to a transfer member, and a cleaning for cleaning a residual toner image with a cleaning blade. In the image forming apparatus provided with the means, the counting means for counting the total number of rotations (R1) that the carrier rotates while the charging means is operating; and the carrier while the charging means is not operating. It has a counting means for counting the total number of rotations (R2), and uses the calculation result of calculating the exposure condition of the exposure means based on the values of (R1) and (R2) and the target uniform charging potential. Exposure means It is characterized by controlling.

  On the other hand, since the performance of the developer often changes in the process of using the image forming apparatus, a density detection reference toner image is formed on the photoreceptor, and the image density of the density detection reference toner image is increased. The target development bias is determined and determined from the image density based on the target potential determination table that stores the target development bias and the target uniform charging potential for setting the image density to the target image density in association with each other. Based on the target development bias, the target uniform charging potential is determined from the target potential determination table, the Vd (charging potential) is controlled so as to become the predetermined target uniform charging potential, and the predetermined target development is performed. In many cases, so-called process control is performed to control the developing means so as to be biased. In this case, Vd is controlled to a wide potential.

As an example, FIG. 1 shows a density curve when the power (LD power (unit: mW)) of the laser diode exposed to the photosensitive member is constant when Vd (charging potential) is 300 V, 500 V, and 700 V. There is a large density variation in the halftone with each Vd. When the LD power of this image forming apparatus is expressed as (Equation 1),
(Formula 1)
(LD power) = 0.00046 × Vd + 0.04
The density curve when corrected according to (Equation 1) is shown in FIG. It can be seen that the variation in image density due to the change in Vd is very small.
(Expression 1) is a linear expression, but is appropriately determined according to the characteristics of the photoreceptor, and may be a multidimensional expression or an expression including a plurality of curves.

As described above, the light attenuation curve of the photosensitive member also changes depending on the film thickness of the photosensitive layer of the photosensitive member. As a result, the image density also varies. As an example, FIG. 3 shows a density curve in the case where a photosensitive member having a photosensitive layer thickness (t (μm)) of 32 μm and 22 μm is used. When the LD power of the image forming apparatus of this image forming apparatus is expressed as (Equation 2),
(Formula 2)
(LD power) = 0.004 × d ² −0.0266 × d + 0.6649
The density curve when corrected according to (Equation 2) is shown in FIG.
The density curve can reduce variations due to the film thickness of the photosensitive layer of the photoreceptor.
(Equation 2) uses a quadratic polynomial, but is appropriately determined according to the characteristics of the photoconductor, and may be a one-dimensional or multi-dimensional equation or an equation composed of a plurality of curves.

  In an actual image forming apparatus, the film thickness of the photosensitive layer of the photoconductor gradually decreases. However, in order to reduce the number of times the photoconductor is replaced, the photoconductor photosensitive layer is used when used for a long period of time. The correction of the LD power based on the layer thickness is very important. By combining the correction of the LD power based on Vd, it is possible to realize an image forming apparatus with little density fluctuation.

In the image forming apparatus of the present invention, when the photosensitive member charging potential (Vd) is changed in order to correct the intermediate density, the image plane light quantity for obtaining a desired image density is calculated using the above correction formula.
Initial image plane light quantity [mW] = ξ1 × Vd + ξ2 (exposure amount correction formula)
However, ξ1: LD power correction coefficient 1
ξ2: LD power correction factor 2
It becomes. Although a linear expression is used here, it may be a polynomial as described above, or may be a combination of a plurality of linear expressions or curved expressions.

Next, a prediction formula for film thickness variation over time is set. The film thickness of the photoconductor is determined by calculating Rc from the total number of rotations (R1) that the photoconductor rotates while charging and the total number of rotations (R2) that the photoconductor rotates while charging is not performed. Calculate
Rc = n · (R1) + (R2)
(N = α / β
α: The amount of decrease in the thickness of the photoconductor (μm) when the photoconductor rotates 10,000 times when charging is performed
β: Photoreceptor film thickness reduction amount (μm) when the photoreceptor rotates 10,000 times when charging is not performed)
The value of α is 1.0 to 20.0, preferably 1.5 to 15.0, and more preferably 2.0 to 10.0.
In the case of α ≦ 1.0, there is little decrease in the thickness of the photosensitive layer when charging is performed, so the change in the characteristics of the photosensitive member is relative to the life of other members (charging roller, cleaning blade, etc.). Therefore, it is not necessary to control the exposure means according to the film thickness of the photosensitive layer as in the present invention.
In the case of α ≧ 20.0, the rate of decrease in the film thickness of the photosensitive layer is too large, so that it reaches the photosensitive layer, which is the life of the photosensitive member, and is not preferable.

The value of β is 1.00 or less, preferably 0.05 to 0.80, and more preferably 0.10 to 0.60.
In the case of β ≧ 1.0, the rate of film thickness reduction of the photosensitive layer is too large, so that it reaches the photosensitive layer, which is the life of the photosensitive member, and is not preferable.
The value of n largely depends on the system configuration of the image forming apparatus, but is usually 1.5 to 30, preferably 2 to 25, and more preferably 3 to 20.

If n <1.5, even if the film thickness of the photoconductor is estimated from only the total number of rotations of the photoconductor, which is a conventional technique, it is difficult to cause a large error.
In the case of n ≧ 30 or more, the reduction in the film thickness of the photoconductor due to charging is too large, and therefore the film of the photoconductor is caused by slight adhesion on the photoconductor or a slight error in assembly between the photoconductor and the charging roller. Thickness deviation tends to occur.
When the film thickness deviation of the photoconductor occurs, image density unevenness occurs, and the image density unevenness cannot be eliminated even by controlling the exposure control means.

The film thickness (d μm) of the photosensitive layer of the photoconductor can be estimated from the film thickness (d ₀ μm) of the photoconductive layer of the photoconductor when mounted by the following (Equation 3).
(Formula 3)
d = d ₀ −β · Rc × 10 ⁻⁴
When the image forming apparatus is always manufactured with a constant value, the values of α and β may be constant. However, the values of α and β vary depending on the lot of the cleaning blade and the manufacturing lot of the image forming apparatus. There is a case.
In this case, since there is a first-order correlation between the torque when the photosensitive member rotates and α and β, it is preferable to correct α and β based on the torque value. In this case, the torque when the photoconductor rotates can be measured either when charging is performed or not. However, in consideration of safety, the torque is measured when charging is not performed. It is preferable to do.
The torque when the photosensitive member rotates may be measured within the image forming apparatus, but when the image forming apparatus is a process cartridge, it may be measured only with the process cartridge.
Thereby, a correction formula for the LD power associated with the surface layer of the photoreceptor being scraped over time is set.
Correction LD power associated with the surface layer of the photoreceptor being scraped Pt (d) = a × d ² + b × d + c
Specifically, when the example shown in FIGS.
Pt (d) = 0.004 × d ² −0.0266 × d + 0.6649
It becomes.

Although it is a quadratic function of the photosensitive layer thickness of the photosensitive member as the photosensitive layer of the photosensitive member is scraped, a plurality of linear expressions or curved expressions may be used regardless of a linear function or a multi-order function. In combination, the thickness of the photosensitive layer of the photoconductor and the LD power at which the image density of the photoconductor is constant are obtained, and the corrected LD power is a function of the thickness of the photosensitive layer of the photoconductor. , You should ask.
Thereby, the exposure amount with time is expressed as the following (formula 4).
(Formula 4)
Time-lapse image surface light amount [mW] = initial image surface light amount × (Pt (d) / Pt (d0))
Next, the configuration of the main part related to the image forming process of the image forming apparatus according to the present invention will be described with reference to FIG.

  In other words, FIG. 5 is a cross-sectional view showing a main part related to the image forming process of the image forming apparatus. In FIG. 5, reference numeral 1 denotes a photosensitive member, 2 denotes a charging unit, 3 denotes a writing unit, 4 denotes a developing unit, and 5 denotes Transfer means 6 and image density detection means 6 respectively.

  The image forming apparatus includes a photosensitive member 1, a charging unit 2 for charging the photosensitive member 1, and a writing unit 3 for writing a latent image on the photosensitive member 1 (in FIG. And a developing means 4 for supplying toner to the latent image to generate a toner image, and a transferring means 5 for transferring the toner image from the photoreceptor, and a transfer means downstream of the developing means 4 An image density detecting means 6 for detecting the image density (or toner image adhesion amount) is provided at a position upstream of 5 and facing the photoconductor.

  A toner reference pattern image for density detection (reference pattern) is formed on the surface of the photoreceptor 1 by increasing / decreasing the charging bias / development bias at a constant exposure amount, and this reference pattern is detected by the image density detection means 6. Then, a target developing bias is set from the detection result of the image density detecting means 6 so that the maximum image density is constant, and a target uniform charging potential on the surface of the photoreceptor 1 is determined from the target developing bias from the target potential determination table. Then, the charging unit 2 is controlled so as to have a predetermined target uniform charging potential, and the developing unit 4 is controlled so as to have a predetermined target developing bias. As described above, since the target development bias and the target charging potential are determined from the toner density attached to the photoreceptor 1, fluctuations in image density caused by fluctuations in the toner charge amount can be suppressed.

  The charging used in the present invention is performed by applying a voltage obtained by superimposing an AC voltage on a DC voltage to the charging roller. The DC voltage applied to the charging roller is a value of Vd (charging potential).

  The AC voltage applied to the charging roller is 1500 V to 3000 V, preferably 1600 V to 2700 V, and more preferably 1700 V to 2500 V as peak to peak.

  When the AC voltage applied to the charging roller is 1600 V or less, the charging potential unevenness of the photoconductor is likely to occur. When the voltage is 3000 V or more, the speed of oxidation deterioration of the photoconductor and the charging roller due to discharge at the closest location. Is extremely undesirably shortened and the life of the photoreceptor and the charging roller is shortened.

The frequency of the AC voltage applied to the charging roller is appropriately determined depending on the linear velocity of the photosensitive member and the resolution of the image to be formed, but is 300 Hz to 4000 Hz, preferably 500 Hz to 3000 Hz, more preferably 600 Hz to 250,000 Hz. It is.
If the frequency of the AC voltage applied to the charging roller is 300 Hz or less, the charging unevenness of the photosensitive member is likely to occur, and an abnormal image of horizontal stripes is likely to occur, which is not preferable. When the frequency of the AC voltage applied to the charging roller is 4000 Hz or more, the speed of oxidation deterioration of the photosensitive member and the charging roller is extremely high, and the life of the photosensitive member and the charging roller is shortened.

  In addition, the image density detector 6 may be positioned so as to face the transfer body 5 and detect a reference pattern on the transfer body 5.

  The control of the exposure means of the present invention can be achieved by a method for controlling the LD power and a method for controlling the exposure time.

FIG. 6 is a block diagram showing a configuration for setting the charging condition in the present invention, that is, the target uniform charging potential on the surface of the photosensitive member 1 and the exposure amount from the target developing bias as described above. In the figure, a control unit 110 is provided for setting charging conditions and exposure conditions.
The control unit 110 is configured by a microcomputer for executing an image forming sequence. As a configuration related to the present invention, the control unit 110 is sensitive to the input side while the image density detecting unit 6 and the charging unit 2 are operating. Counting means 111 for the total number of rotations (R1) that the body 1 has rotated, counting means 112 for the total number of rotations (R2) that the photoconductor 1 has rotated while the charging means 2 is not operating, and the photoconductor 1 or photoconductor 1 is connected to a rotating torque measuring means 113 for measuring the rotating torque of the photosensitive member 1 in a process cartridge in which a part of the apparatus used for image forming processing is accommodated. The means 3 and the developing means 4 are connected to each other.

  The charging means 2 is set with a charging potential, so-called charging bias potential, the exposure means 3 is set with the output of a light source corresponding to the exposure output, and the developing means 4 is used as a target for setting the developing bias.

  In the control unit 110, as described with reference to FIG. 7, processing from density control processing to exposure amount setting is performed.

  In FIG. 7, the above-described exposure condition calculation timing is immediately after the density adjustment process is finished and the setting values of the charge application bias and the development bias are determined. That is, for example, the toner adhesion amount γ is read from the toner image for density detection, and the charged potential Vd corresponding to γ is read by comparing the value with the charge potential table. Further, the exposure amount is set by calling the total number of rotations of the photoconductor in a charged state and the total number of rotations of the photoconductor in a non-charged state.

  As the resolution of the writing light to the photoconductor in the image forming apparatus of the present invention, high-quality image formation is possible for an image of any resolution. In particular, the resolution of the writing light is 1000 dpi or more, The effect is high when it is preferably 1100 or more, more preferably 1200 to 3000 dpi. When the resolution of the writing light is less than 1000 dpi, there is little problem as an image even if the exposure amount of the writing light is not corrected as the film thickness of the photosensitive layer of the photosensitive member decreases.

As the photoreceptor used in the image forming apparatus of the present invention, an organic photoreceptor is preferably used.
Although the organic photoreceptor is low in production cost, the photosensitive layer is easily worn by friction between the cleaning blade and the photoreceptor. Therefore, correcting the LD power as in the present invention is very important for maintaining high-quality image formation. The initial film thickness of the photosensitive layer of the present invention is 28 to 45 μm, preferably 30 to 43 μm, more preferably 32 to 42 μm. When the film thickness of the photosensitive layer of the photoconductor becomes more than a dozen μm, stains are likely to occur. Even without correcting the amount of light on the time-lapse image plane accompanying the decrease in the film thickness of the photosensitive layer, it is less likely to be a problem. When the initial film thickness of the photosensitive layer is 45 μm or more, it is difficult to form a high-resolution image in the initial stage, which is not preferable.

  FIG. 8 is a diagram showing an example of an image forming apparatus using a process cartridge. In the figure, reference numeral 3 denotes a writing means.

  Four image forming stages are arranged facing the transfer belt 5. The main part of each image forming stage is composed of a process cartridge. The process cartridge includes a photosensitive drum 1, a charging unit 2, and a developing unit 4. The process cartridge can be inserted into and removed from the image forming apparatus main body in the longitudinal direction of the photosensitive member 1, and can be easily replaced as necessary.

  By adopting such a configuration, the user can easily perform the replacement work and the maintainability is improved. In addition, the image forming apparatus can obtain a good image only by replacing the process cartridge.

  In the photoreceptor used in the image forming apparatus of the present invention, a photosensitive layer is provided on a conductive support. The photosensitive layer is composed of a single layer type in which a charge generation material and a charge transport material are mixed, a forward layer type in which a charge transport layer is provided on the charge generation layer, or a charge generation layer provided on the charge transport layer. There is a reverse layer type. A protective layer can also be provided on the photosensitive layer. An undercoat layer may be provided between the photosensitive layer and the conductive support. In addition, an appropriate amount of a plasticizer, an antioxidant, a leveling agent and the like can be added to each layer as necessary.

As the conductive support of the photoreceptor, a material having a volume resistance of 10 ¹⁰ Ω · cm or less, for example, a metal such as aluminum, nickel, chromium, nichrome, copper, gold, silver, platinum, tin oxide, oxidation A metal oxide such as indium is deposited or sputtered on a film or cylindrical plastic or paper, or a plate of aluminum, aluminum alloy, nickel, stainless steel, etc. After forming the tube into a drum shape, it is possible to use a tube that has been surface-treated by cutting, superfinishing, polishing, or the like. A drum-shaped support having a diameter of 20 to 150 mm, preferably 24 to 100 mm, and more preferably 28 to 70 mm can be used. If the diameter of the drum-shaped support is 20 mm or less, it is physically difficult to arrange the charging, exposure, development, transfer, and cleaning steps around the drum. If the diameter of the drum-shaped support is 150 mm or more, image formation is performed. The apparatus becomes undesirably large. In particular, when the image forming apparatus is a tandem type, it is necessary to mount a plurality of photoconductors, and thus the diameter is preferably 70 mm or less, and preferably 60 mm or less. Further, endless nickel belts and endless stainless steel belts disclosed in JP-A-52-36016 can also be used as the conductive support.

  As the undercoat layer of the photosensitive member used in the image forming apparatus of the present invention, a resin or a material mainly composed of a white pigment and a resin, a metal oxide film obtained by chemically or electrochemically oxidizing the surface of a conductive substrate, etc. However, those containing a white pigment and a resin as main components are preferable. Examples of the white pigment include metal oxides such as titanium oxide, aluminum oxide, zirconium oxide, and zinc oxide. Among them, it is most preferable to contain titanium oxide that is excellent in preventing charge injection from the conductive substrate. As the resin used for the undercoat layer, thermoplastic resins such as polyamide, polyvinyl alcohol, casein, and methyl cellulose, thermosetting resins such as acrylic, phenol, melamine, alkyd, unsaturated polyester, and epoxy, one or various kinds of these Mixtures can be exemplified.

  Examples of the charge generating substance for the photoreceptor used in the image forming apparatus of the present invention include azo pigments such as monoazo pigments, bisazo pigments, trisazo pigments, and tetrakisazo pigments, triarylmethane dyes, thiazine dyes, and oxazines. Dyes, xanthene dyes, cyanine dyes, styryl dyes, pyrylium dyes, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, bisbenzimidazole pigments, indanthrone pigments, squarylium pigments Inorganic materials such as pigments, organic pigments and dyes such as phthalocyanine pigments, selenium, selenium-arsenic, selenium-tellurium, cadmium sulfide, zinc oxide, titanium oxide, and amorphous silicon can be used. It can be used alone or in combination.

  Examples of the charge transport material for the photoreceptor used in the image forming apparatus of the present invention include anthracene derivatives, pyrene derivatives, carbazole derivatives, tetrazole derivatives, metallocene derivatives, phenothiazine derivatives, pyrazoline compounds, hydrazone compounds, styryl compounds, styryl hydrazone compounds, Enamine compounds, butadiene compounds, distyryl compounds, oxazole compounds, oxadiazole compounds, thiazole compounds, imidazole compounds, triphenylamine derivatives, phenylenediamine derivatives, aminostilbene derivatives, triphenylmethane derivatives, etc. can do.

  The binder resin used to form the photosensitive layer of the charge generation layer and the charge transport layer is electrically insulating and is a known thermoplastic resin, thermosetting resin, photocurable resin, and photoconductive material. Suitable binder resins include, for example, polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, Ethylene-vinyl acetate copolymer, polyvinyl butyral, polyvinyl acetal, polyester, phenoxy resin, (meth) acrylic resin, polystyrene, polycarbonate, polyarylate, thermoplastic resin such as polysulfone, polyethersulfone, ABS resin, phenol resin , Epoxy resin, urethane resin, melamine resin, isocyanate resin, alkyd resin, Examples thereof include a thermosetting resin such as a ricone resin, a thermosetting acrylic resin, a type of binder resin such as a photoconductive resin such as polyvinyl carbazole, polyvinyl anthracene, and polyvinyl pyrene, or a mixture of various types of binder resins. In particular, it is not limited to these.

As antioxidant, the following are used, for example.
Monophenol compounds 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearyl-β- (3,5-di-t -Butyl-4-hydroxyphenyl) propionate, 3-t-butyl-4-hydroxynisol and the like.
Bisphenol compounds 2,2′-methylene-bis- (4-methyl-6-tert-butylphenol), 2,2′-methylene-bis- (4-ethyl-6-tert-butylphenol), 4,4′- Thiobis- (3-methyl-6-tert-butylphenol), 4,4′-butylidenebis- (3-methyl-6-tert-butylphenol) and the like.
High molecular phenolic compound 1,1,3-tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5 -Di-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, bis [3,3' -Bis (4'-hydroxy-3'-t-butylphenyl) butyric acid] glycol ester, tocophenols and the like.
Paraphenylenediamines N-phenyl-N′-isopropyl-p-phenylenediamine, N, N′-di-sec-butyl-p-phenylenediamine, N-phenyl-N-sec-butyl-p-phenylenediamine, N , N′-di-isopropyl-p-phenylenediamine, N, N′-dimethyl-N, N′-di-t-butyl-p-phenylenediamine, and the like.
Hydroquinones 2,5-di-t-octylhydroquinone, 2,6-didodecylhydroquinone, 2-dodecylhydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t-octyl-5-methylhydroquinone, 2- (2 -Octadecenyl) -5-methylhydroquinone and the like.
Organic sulfur compounds Dilauryl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, ditetradecyl-3,3′-thiodipropionate, and the like.
Organophosphorus compounds triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine, and the like.

  As the plasticizer, those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the amount used is about 0 to 30 parts by weight with respect to 100 parts by weight of the binder resin. Is appropriate.

  A leveling agent may be added to the charge transport layer. As the leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, polymers or oligomers having a perfluoroalkyl group in the chain are used, and the amount used is 100 parts by weight of binder resin. 0 to 1 part by weight is suitable.

(Example 1)
15 parts by weight of acrylic resin (Acridic A-460-60 (Dainippon Ink Chemical Co., Ltd.)), 10 parts by weight of melamine resin (Super Becamine L-121-60 (Dainippon Ink Chemical Co., Ltd.)), 80 parts by weight of methyl ethyl ketone 90 parts by weight of titanium oxide powder (TM-1 (manufactured by Fuji Titanium Industry Co., Ltd.)) was added thereto and dispersed for 12 hours with a ball mill to prepare an undercoat layer coating solution. An aluminum drum having an outer diameter of 30 mm and an inner diameter of 28.5 mm was dipped in the undercoat layer coating solution, and then applied by pulling it up vertically at a constant speed. While maintaining the direction of the aluminum drum, it was moved to a drying chamber and dried at 140 ° C. for 23 minutes to form a subbing layer having a thickness of 3.4 μm on the aluminum drum.

  Next, 15 parts by weight of a butyral resin (ESREC BLS (manufactured by Sekisui Chemical Co., Ltd.)) was dissolved in 150 parts by weight of cyclohexanone, and 10 parts by weight of a trisazo pigment having the structural formula shown in FIG. 9 was added thereto and dispersed in a ball mill for 48 hours.

  The aluminum drum having the undercoat layer was immersed in the coating solution for charge generation layer thus obtained, and the coating was performed by pulling it up vertically at a constant speed. Drying was performed in the same manner as the undercoat layer at 120 ° C. for 20 minutes to form a charge generation layer of about 0.2 μm. Furthermore, 6 parts by weight of the charge transport material represented by the structural formula shown in FIG. 10, 10 parts by weight of Z-type polycarbonate resin, 0.7 parts by weight of 1,4-bis (2,5-dimethylbenzyl) benzene, silicon oil ( KF-50, manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved in 90 parts by weight of methylene chloride.

  In the charge transport layer coating solution thus obtained, an aluminum drum on which an undercoat layer / charge generation layer is formed is dipped, applied at a constant speed and pulled vertically, dried at 120 ° C. for 20 minutes, and a thickness of about 32 μm. The charge transport layer was formed.

Four manufactured photoconductors are used in a color laser printer CX400 remodeling machine (manufactured by Ricoh, tandem type, AC charging is applied only when image formation is performed, and charging is not applied when the photoconductor is rotating otherwise). equipped. This laser printer is designed to perform AC charging only during image formation. The rotation speed of the photosensitive member when AC charging is applied and the photosensitive member when AC charging is not applied. The number of rotations can be stored separately. A field test was conducted in which 12 employees were connected to the printer and allowed to form images freely.
When α and β were measured before the field test, α was 1.9, β was 0.23, and n was 8.26.
The function of controlling the LD power was given by the above-mentioned formula 1, formula 2, formula 3, and formula 4.

After the field test, the film thickness of the photoconductor is different for each color. The photoconductor for black is 18.0 μm, the photoconductor for cyan is 22.1 μm, the photoconductor for yellow is 22.4 μm, and the photoconductor for magenta is used. It was 22.2 μm. During the field test, there were no complaints from the 12 employees regarding the images formed. When an image obtained by copying a female face with a digital still camera was printed at a resolution of 600 dpi, 1200 dpi, or 1600 dpi, there was no problem in the color tone of any of the images.
(Comparative Example 1)
In Example 1, four photoconductors were produced in the same manner as in Example except that the thickness of the charge transport layer was 31 μm.

The same field test as in Example 1 was performed without correcting the LD power written on the magenta photoconductor. Since complaints about unnatural color began to appear in 1/4 of the test period of Example 1, the test was stopped in 1/3 of the test period of Example 1. As in Example 1, when the above-mentioned 12 employees evaluated an image obtained by printing a woman's face with a digital still camera at a resolution of 600 dpi, 1200 dpi, and 1600 dpi, 5 people at 600 dpi and 1200 dpi were used. Then, 10 people and all 12 people at 1600 dpi answered that the color was unnatural.
(Example 2)
In Example 1, 5 parts by weight of Z-type polycarbonate resin and 5 parts by weight of bisphenol A-type polycarbonate resin were used instead of 10 parts by weight of Z-type polycarbonate resin of the charge transport layer of the photoreceptor, and the thickness of the charge transport layer was 35 μm. Except that, four photosensitive members were produced in the same manner as in Example 1.

  When α and β were measured, α = 2.9, β = 0.54, and n = 5.37.

  The function of controlling the LD power was given by the above-mentioned formula 1, formula 2, formula 3, and formula 4.

  When the same field test as in Example 1 was performed, there was no claim regarding the hue in the testing machine.

When an image obtained by copying a female face with a digital still camera was printed at a resolution of 600 dpi, 1200 dpi, or 1600 dpi, there was no problem in the color tone of any of the images.
(Comparative Example 2)
In the image forming apparatus of the second embodiment, when the LD power was not corrected, a complaint began to appear when the image density was low in 1/3 of the field test of the second embodiment. In the period of / 2, the bad impression result that the image density was light was given from nine employees.
(Comparative Example 3)
In the image forming apparatus of Example 2,
Equation (3)
d = 35-2.7 ((R1) + (R2)) × 10 ⁻⁴
Except for the above, an image forming apparatus was produced in the same manner as in Example 2, and a field test was performed.
After the same test period as in Example 2, an image obtained by copying a female face with a digital still camera was printed at a resolution of 600 dpi, 1200 dpi, and 1800 dpi. Three people at 600 dpi, 9 at 1200 dpi, and all 12 at 1800 dpi were shades. Answered unnatural.
(Example 3)
In Example 1, an image forming apparatus was produced in the same manner as in Example 1 except that the rotational torque of each color photoconductor was measured in advance and α, β, and n were as shown in Table 1 below.

When the same field test as in Example 1 was conducted over a period of 1.2 times, there was no claim regarding the hue in the test machine.
When an image obtained by copying a female face with a digital still camera was printed at a resolution of 600 dpi, 1200 dpi, or 1600 dpi, there was no problem in the color tone of any of the images.

It is a diagram showing a density curve when the power (LD power (unit: mW)) of the laser diode exposed to the photosensitive member is constant when the charging potential is 300V, 500V, and 700V. FIG. 2 is a diagram showing a density curve in a state where an exposure amount is corrected based on the charging potential shown in FIG. 1. FIG. 5 is a diagram showing a density curve when a photosensitive member having a photosensitive layer thickness (t (μm)) of 32 μm and 22 μm is used. FIG. 4 is a diagram showing a density curve in a state where an exposure amount is corrected based on the film thickness of the photosensitive layer shown in FIG. 3. FIG. 2 is a diagram for explaining a main configuration of an image forming unit in an embodiment of the present invention. It is a block diagram for demonstrating the structure of the control part in embodiment of this invention. It is a flowchart for demonstrating the process procedure implemented in the control part shown in FIG. 1 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention. 3 is a structural formula showing one of the components of the photoreceptor in the embodiment of the present invention. 4 is a structural formula showing another one of the components of the photoreceptor in the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging means 3 Exposure means 4 Development means 6 Image density detection means 100 Image forming apparatus 110 Control part 111 Counting means of total rotation speed (R1) 112 Counting means of total rotation speed (R2) 113 Rotation torque measurement means

Claims (8)

An image carrier, a charging unit including a charging member that is charged in proximity to or in contact with the image carrier to superimpose a DC voltage and an AC voltage, and uniformly charged, and the image carrier after charging Exposure means for forming an electrostatic latent image according to image information, developing means for converting the electrostatic latent image into a toner image, transfer means for transferring the developed toner image to a transfer member, and residual toner after transfer In an image forming apparatus provided with a cleaning means for cleaning an image with a cleaning blade,
Counting means for counting the total number of rotations (R1) that the image carrier has rotated while the charging means is operating, and the total number of rotations that the image carrier has rotated while the charging means is not operating (R1). A control unit connected to the input side, and a control unit to which the exposure unit is connected on the output side.
The control unit controls exposure conditions in the exposure unit using a calculation result obtained by calculating an exposure condition of the exposure unit based on the values of (R1) and (R2) and a target uniform charging potential. An image forming apparatus. The image forming apparatus according to claim 1.
The controller is connected to a means for measuring the rotational torque of the image carrier,
The control unit controls the exposure condition of the exposure unit using the calculation result obtained by calculating the exposure condition of the exposure unit from the values of (R1) and (R2) and the measured rotational torque of the image carrier. An image forming apparatus. The image forming apparatus according to claim 1.
In the image carrier, charging means, developing means, cleaning means farmland, at least the image carrier and cleaning means are equipped in a process cartridge,
The controller measures in advance the rotational torque of the image carrier in the process cartridge, and determines the exposure means's value from the measured rotational torque of the image carrier in the process cartridge and the values of (R1) and (R2). An image forming apparatus, wherein the exposure unit is controlled using a calculation result obtained by calculating an exposure condition. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the control unit controls a light source output or an exposure time as an exposure condition in the exposure unit. The image forming apparatus according to claim 1,
The control unit forms a density detection reference toner image on the image carrier, detects an image density of the density detection reference toner image, and sets the image density to a target image density. A target potential determination table that stores the target development bias and the target uniform charging potential in association with each other, determines the target development bias based on the detection result of the image density detection means, and based on the determined target development bias Then, the target uniform charging potential is determined from the target potential determination table, the charging means is controlled so as to be the predetermined target uniform charging potential, and the development is performed so as to be the predetermined target developing bias. An image forming apparatus that controls the means. The image forming apparatus according to claim 1,
An image forming apparatus, wherein the resolution of the writing light to the image carrier is 1000 dpi or more. The image forming apparatus according to claim 1,
An image forming apparatus, wherein an initial film thickness of a photosensitive layer of an image carrier is 28 to 45 μm. The image forming apparatus according to claim 3.
The image forming apparatus, wherein the process cartridge is detachably attached to the apparatus main body.

Images