JP2009300720A - Toner carrier and image forming apparatus having it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner carrier allowing accurate measurement of a toner adhesion amount regardless of a use period of the toner carrier, and also to provide an image forming apparatus using the toner carrier to perform highly precise image density control for forming a high quality image. <P>SOLUTION: An intermediate transfer belt 8 has a three-layer structure consisting of a base material layer 50, an elastic layer 51, and a coating layer 53 to be brought into contact with photoreceptor drums 1a-1d. The surface of the coating layer 53, on which minute rugged parts 53a and flat face parts 53b are formed, is a rough surface having initial glossiness of a predetermined value or less. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus using electrophotography, and more particularly to a toner carrier such as an intermediate transfer belt or a conveyor belt on which toner is carried.

  In an image forming apparatus using an electrophotographic process, generally, toner is directly transferred onto a toner carrier to form a patch image (reference image), and the toner amount and position are detected to perform density correction and color misregistration correction. Do. For example, in the case of a tandem full-color image forming apparatus, each color forming patch image is formed on the intermediate transfer belt by each of the cyan, magenta, yellow and black image forming units, and the detection means detects the image and corrects the density and color misregistration. I do.

  As the detection means, generally, an optical detection means including a light emitting element made of an LED or the like and a light receiving element made of a photodiode or the like is used. For example, when measuring the toner adhesion amount on the transfer belt, measurement light is emitted from the light emitting element to the toner image. The measurement light is incident on the light receiving element as light reflected by the toner and light reflected by the belt surface.

  When the toner adhesion amount is large, the reflected light from the belt surface is blocked by the toner, so that the light reception amount of the light receiving element is reduced. On the other hand, when the adhesion amount of toner is small, the amount of reflected light from the belt surface increases, and as a result, the amount of light received by the light receiving element increases. Therefore, the density of each color patch image is detected based on the output value of the received light signal based on the amount of reflected light received, and the charging potential, developing bias characteristic value, and exposure amount of the exposure device are adjusted in comparison with a predetermined reference density. Thus, density correction is performed for each color.

  In order to perform density correction strictly using a patch image, it is necessary to measure the exact amount of toner adhering to the intermediate transfer belt. For example, in Patent Document 1, the reference patch image formed on the toner carrier is irradiated with measurement light, and the amount of regular reflection is detected to measure the toner adhesion amount. In this case, if a toner carrier having a low surface glossiness is used, the sensor output becomes small regardless of the patch density, making it difficult to accurately detect the patch density. For this reason, in Patent Document 1, the glossiness of the surface of the toner carrying member is a predetermined value or more (50 to 98 or less at a measurement angle of 20 degrees).

  On the other hand, in Patent Document 2, the reference image is irradiated with measurement light, and the toner adhesion amount is measured by detecting the difference between the regular reflection light amount and the irregular reflection light amount. According to this method, compared to the method of Patent Document 1 in which only the amount of specular reflection is detected, the sensor output changes greatly depending on the patch density for both black toner and color toner, so that it is particularly accurate in a color image forming apparatus. It is possible to detect the amount of toner adhesion. Even in this case, in order to obtain a sufficient amount of regular reflection light, a material having a glossiness on the surface of the toner carrying member of a predetermined value or more is used as in Patent Document 1.

  By the way, in general, the surface state of the toner carrier changes depending on the usage period of the image forming apparatus and other components (for example, abrasive) other than the toner component contained in the toner. Therefore, the initial surface state cannot be maintained until the preset warranty period of the toner carrier is completed, and the light reception output of the light receiving element changes according to the change in the surface state. In this method, it is difficult to accurately measure the toner adhesion amount.

Therefore, a method for accurately measuring the toner adhesion amount regardless of the change in the surface state of the toner carrier has been proposed. Patent Document 3 discloses a transfer in which the initial glossiness of the surface is 20 or less at a measurement angle of 60 degrees. An image forming apparatus using a belt (toner carrier) is disclosed. According to this method, by suppressing the initial glossiness of the belt surface to a low level, it is possible to accurately measure the toner adhesion amount by reducing the fluctuation range of the glossiness after durable use.
JP 2002-23433 A JP 2001-194443 A JP 2006-201587 A

  However, even when the toner carrier having a low initial glossiness disclosed in Patent Document 3 is used, it is difficult to accurately measure the toner adhesion amount when the glossiness change after durable use is large. . In addition, if the glossiness of the surface is extremely low, the output signal level of the reflected light from the reference image and the output signal level (background value) of the reflected light from the belt surface are close to each other, making it difficult to control the density. There was a problem of becoming.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a toner carrier capable of accurately measuring the toner adhesion amount regardless of the usage period of the toner carrier, and high-precision image density control using the toner carrier, thereby achieving high image quality. An object of the present invention is to provide an image forming apparatus capable of forming an image.

  In order to achieve the above object, the present invention comprises at least an elastic layer and an outermost coat layer, and irradiates a reference image formed on the surface of the coat layer with light so that regular reflection from the reference image is achieved. In the toner carrier capable of detecting the toner adhesion amount of the reference image based on the light amount and the irregular reflection light amount, the initial glossiness of the surface is set to a predetermined value or less by making the surface of the coat layer rough. It is said.

  According to the present invention, in the toner carrier having the above-described configuration, the arithmetic average slope Δa of the surface of the coat layer is 0.075 or more.

  According to the present invention, in the toner carrier having the above configuration, the initial glossiness of the surface of the coat layer is 20 or less at a measurement angle of 60 degrees.

  According to the present invention, in the toner carrier having the above structure, the glossiness of the surface of the coat layer at the end of the useful life of the toner carrier is 1 or more at a measurement angle of 60 degrees, and the fluctuation range from the initial glossiness is It is characterized by being within 10 or less.

  According to the present invention, in the toner carrier having the above-described configuration, the toner carrier is an intermediate transfer belt on which toner images for transfer onto a recording medium are sequentially stacked.

  According to the present invention, in the toner carrier configured as described above, the toner carrier is a conveyance belt for conveying a recording medium.

  The present invention also provides an optical detection means capable of irradiating a reference image formed on the toner carrier having the above-described structure with light and measuring the regular reflection light quantity and the irregular reflection light quantity simultaneously, and the optical detection means. In addition, the image forming apparatus includes: a control unit that controls the image density by detecting the toner adhesion amount in the reference image based on a difference between the light reception output signals of the regular reflection light amount and the irregular reflection light amount.

  According to the first configuration of the present invention, since the surface of the coat layer is rough and the initial glossiness of the surface is not more than a predetermined value, the fluctuation range of the glossiness until the end of the useful life of the toner carrier is small. Therefore, the toner adhesion amount on the toner carrier can be accurately measured over the entire lifetime of the toner carrier.

  Further, according to the second configuration of the present invention, in the toner carrier of the first configuration, the arithmetic average slope Δa of the surface of the coat layer is 0.075 or more, so that it has a high correlation with the glossiness. The glossiness can be strictly managed using the arithmetic average inclination Δa.

  Further, according to the third configuration of the present invention, in the toner carrier of the second configuration, the initial glossiness of the surface of the coat layer is 20 or less at a measurement angle of 60 degrees, The change in the glossiness with time can be further reduced, and the toner adhesion amount can be accurately measured from the beginning of use of the toner carrier to the end of its useful life.

  According to the fourth configuration of the present invention, in the toner carrier of the second or third configuration, the glossiness of the surface of the coat layer at the end of the useful life of the toner carrier is 1 or more at a measurement angle of 60 degrees. In addition, by setting the fluctuation range from the initial glossiness to 10 or less, the output signal level of the reflected light from the reference image and the output signal level (background value) of the reflected light from the toner carrier surface approach each other. Therefore, stable concentration control is possible even at the end of the useful life.

  According to the fifth configuration of the present invention, the toner carrier of any one of the first to fourth configurations is used as an intermediate transfer belt on which toner images for transferring to a recording medium are sequentially stacked. Accordingly, when the correction patch image is formed on the intermediate transfer belt and the density correction is performed, it is possible to perform a strict correction, and it is possible to form a higher quality image.

  According to the sixth configuration of the present invention, the correction carrier patch on the transport belt is obtained by using the toner carrier of any of the first to fourth configurations as a transport belt for transporting the recording medium. When density correction is performed by forming an image, strict correction is possible, and higher-quality image formation is possible.

  According to the seventh configuration of the present invention, the reference image formed on the toner carrier having any one of the first to sixth configurations is irradiated with light, and the regular reflection light quantity and the irregular reflection light quantity are simultaneously obtained. The usage period of the toner carrier by controlling the image density by detecting the toner adhesion amount on the reference image based on the difference between the light reception output signal of the regular reflection light quantity and the irregular reflection light quantity measured by the measurable optical detection means Regardless of this, the relationship between the coverage calculated based on the difference between the regular reflection light amount and the irregular reflection light amount and the toner adhesion amount is stable, and the image forming apparatus can form a high-quality image.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing a configuration of an image forming apparatus provided with a toner carrier of the present invention. In the main body of the image forming apparatus (color printer) 100, four image forming portions Pa, Pb, Pc and Pd are sequentially arranged from the upstream side in the transport direction (the right side in FIG. 1). These image forming portions Pa to Pd are provided corresponding to images of four different colors (magenta, cyan, yellow, and black), and magenta, cyan, and yellow are respectively subjected to charging, exposure, development, and transfer processes. And a black image are sequentially formed.

  Photosensitive drums 1a, 1b, 1c, and 1d that carry visible images (toner images) of the respective colors are disposed in the image forming portions Pa to Pd, and are formed on the photosensitive drums 1a to 1d. The transferred toner image is sequentially transferred (primary transfer) onto an intermediate transfer belt (toner carrier) 8 that moves adjacent to each image forming portion while rotating clockwise in FIG. 1 by a driving means (not shown). Then, the toner image is transferred onto the paper S at the secondary transfer roller 9 (secondary transfer) at a time, and further fixed on the paper S at the fixing unit 7 and then discharged from the apparatus main body. . An image forming process for each of the photosensitive drums 1a to 1d is executed while rotating the photosensitive drums 1a to 1d counterclockwise in FIG.

  The paper S on which the toner image is transferred is accommodated in a paper cassette 16 at the lower part of the apparatus, and is conveyed to the secondary transfer roller 9 via the paper feed roller 12a and the registration roller pair 12b. A sheet made of a dielectric resin is used for the intermediate transfer belt 8, and a belt in which both ends thereof are overlapped and joined to form an endless shape, or a belt without a seam (seamless) is used. Further, a cleaning blade 19 for removing toner remaining on the surface of the intermediate transfer belt 8 is disposed on the downstream side of the secondary transfer roller 9.

  Next, the image forming units Pa to Pd will be described. There are chargers 2a, 2b, 2c, and 2d for charging the photosensitive drums 1a to 1d and image information on the photosensitive drums 1a to 1d around and below the photosensitive drums 1a to 1d that are rotatably arranged. The exposure device 4 for exposing the toner, the developing devices 3a, 3b, 3c and 3d for forming toner images on the photosensitive drums 1a to 1d, and the developer (toner) remaining on the photosensitive drums 1a to 1d are removed. Cleaning units 5a, 5b, 5c and 5d are provided.

  When the start of image formation is input by the user, first, the surfaces of the photosensitive drums 1a to 1d are uniformly charged by the chargers 2a to 2d, and then light is irradiated by the exposure device 4 to each of the photosensitive drums 1a to 1d. An electrostatic latent image corresponding to the image signal is formed on the top. Each of the developing devices 3a to 3d includes a developing roller (developer carrying member) disposed so as to face the photosensitive drums 1a to 1d, and each of magenta, cyan, yellow, and black toners is supplied by a replenishing device (not shown). A predetermined amount is filled. The toner is supplied onto the photosensitive drums 1a to 1d by the developing rollers of the developing devices 3a to 3d, and electrostatically adheres to the electrostatic latent image formed by exposure from the exposure device 4. A toner image is formed.

  After an electric field is applied to the intermediate transfer belt 8 at a predetermined transfer voltage, magenta, cyan, yellow, and black toner images on the photosensitive drums 1a to 1d are transferred to the intermediate transfer belt 8 by the primary transfer rollers 6a to 6d. Primary transferred onto. These four color images are formed with a predetermined positional relationship predetermined for forming a predetermined full-color image. Thereafter, the toner remaining on the surfaces of the photosensitive drums 1a to 1d is removed by the cleaning units 5a to 5d in preparation for the subsequent formation of a new electrostatic latent image.

  The intermediate transfer belt 8 is stretched over a driven roller 10, a drive roller 11, and a tension roller 20, and the intermediate transfer belt 8 starts to rotate clockwise as the drive roller 11 is rotated by a drive motor (not shown). Then, the sheet S is conveyed from the registration roller 12b to the secondary transfer roller 9 provided adjacent to the intermediate transfer belt 8 at a predetermined timing, and the sheet S is conveyed at a nip portion (secondary transfer nip portion) with the intermediate transfer belt 8. A full color image is secondarily transferred onto S. The sheet S on which the toner image is transferred is conveyed to the fixing unit 7.

  The sheet S conveyed to the fixing unit 7 is heated and pressurized when passing through the nip portion (fixing nip portion) of the pair of fixing rollers 13 to fix the toner image on the surface of the sheet S, and a predetermined full-color image is formed. It is formed. The sheet S on which the full-color image is formed is distributed in the transport direction by the branching section 14 that branches in a plurality of directions. When an image is formed on only one side of the sheet S, the sheet is discharged to the discharge tray 17 by the discharge roller pair 15 as it is.

  On the other hand, when images are formed on both sides of the sheet S, a part of the sheet S that has passed through the fixing unit 7 is once protruded from the discharge roller pair 15 to the outside of the apparatus. Thereafter, the sheet S is distributed to the sheet conveyance path 18 by the branching section 14 by rotating the discharge roller pair 15 in the reverse direction, and is conveyed again to the secondary transfer roller 9 with the image surface reversed. Then, after the next image formed on the intermediate transfer belt 8 is transferred to the surface of the sheet S where the image is not formed by the secondary transfer roller 9 and conveyed to the fixing unit 7 to fix the toner image, It is discharged to the discharge tray 17.

  A toner adhesion amount measuring device 21 is arranged on the downstream side of the image forming unit Pd and the upstream side of the secondary transfer roller 9. The toner adhesion amount measuring device 21 irradiates the reference image formed on the intermediate transfer belt 8 in the image forming portions Pa to Pd with measurement light, and detects the amount of reflected light from each patch image constituting the reference image. A detection result is transmitted to the control part 32 mentioned later as a light reception output signal. As the toner adhesion amount measuring device 21, an optical sensor including a light emitting element composed of an LED or the like and a light receiving element composed of a photodiode or the like is generally used. When measuring the density of the reference image, when the measurement light is sequentially irradiated from the light emitting element to each patch image on the intermediate transfer belt 8, the measurement light is received as light reflected by the toner and light reflected by the belt surface. Incident on the element. A specific configuration of the toner adhesion amount measuring device 21 will be described later.

  Since the toner adhesion amount measuring device 21 needs to strictly define the distance to the measurement object, as shown in FIG. 1, the toner adhesion amount measuring device 21 counters the driving roller 11 having a small distance variation to the surface of the intermediate transfer belt 8. The intermediate transfer belt 8 is positioned in the width direction according to the reference image formation position on the intermediate transfer belt 8.

  The toner adhesion amount measuring device 21 may be disposed at another position where the reference image on the intermediate transfer belt 8 can be detected. However, when the toner adhesion amount measuring device 21 is disposed on the downstream side of the secondary transfer roller 9, for example, the image forming unit The time from when the reference image is formed by Pa to Pd to when the density detection is performed becomes longer, and the surface state of the reference image may change due to the reference image coming into contact with the secondary transfer roller 9. Therefore, as shown in FIG. 1, it is preferable to dispose on the downstream side of the image forming unit Pd and the upstream side of the contact position of the secondary transfer roller 9.

  FIG. 2 is a block diagram illustrating a control path of the image forming apparatus. Portions common to FIG. 1 are denoted by the same reference numerals and description thereof is omitted. The image forming apparatus 100 includes an image input unit 30, an AD conversion unit 31, image forming units Pa to Pd, a control unit 32, a storage unit 33, an operation panel 34, a fixing unit 7, an intermediate transfer belt 8, a secondary transfer roller 9, And a toner adhesion amount measuring device 21 and the like.

  The toner adhesion amount measuring device 21 irradiates each patch image formed on the intermediate transfer belt 8 (see FIG. 1) with measurement light in the image forming portions Pa to Pd, and detects the amount of reflected light from the patch image. A detection result is transmitted to the control part 32 mentioned later as a light reception output signal.

  When the image forming apparatus 100 is a copying machine, the image input unit 30 is a scanning optical system equipped with a scanner lamp that illuminates an original during copying and a mirror that changes the optical path of reflected light from the original, and reflected light from the original. The image forming apparatus 100 is a printer as shown in FIG. 1, and includes a condensing lens that collects and forms an image and a CCD that converts the imaged image light into an electrical signal. In some cases, the receiving unit receives image data transmitted from a personal computer or the like. The image signal input from the image input unit 30 is converted into a digital signal by the AD conversion unit 31 and then sent to the image memory 40 in the storage unit 33 described later.

  The storage unit 33 stores print image data input from the image input unit 30 and digitally converted by the AD conversion unit 31 in units of pages, necessary data generated during control of the image forming apparatus 100, and image formation. A readable / writable RAM (Random Access Memory) 41 in which data and the like temporarily required for control of the apparatus 100 are stored, and the image forming apparatus 100 such as a control program for the image forming apparatus 100 and numerical values necessary for control. A read-only ROM (Read Only Memory) 42 that stores data that does not change during use is stored. The RAM 41 (or ROM 42) stores in advance the relationship between the measured output value of the toner adhesion amount measuring device 21 and the toner adhesion amount as toner adhesion amount data.

  The operation panel 34 displays the state of the image forming apparatus 100, the image forming status, and the number of copies, and as a touch panel, functions such as double-sided printing and black-and-white reversal, and various settings such as magnification setting and density setting, the number of copies When the image forming apparatus 100 has a FAX function, a numeric keypad for inputting the FAX number of the other party, a start button for instructing the user to start image formation, and when stopping image formation. A stop / clear button, a reset button used when setting various settings of the image forming apparatus 100 to a default state, and the like are provided. The user operates the operation panel 34 to input an instruction, whereby the image forming apparatus 100 is set. Are set to execute various functions such as image formation.

  The control unit 32 is, for example, a central processing unit (CPU), and generally controls the image input unit 30, the image forming units Pa to Pd, the fixing unit 7, and the toner adhesion amount measuring device 21 according to a set program. The image signal read by the image input unit 30 is converted into image data by scaling processing or gradation processing as necessary. The exposure device 4 irradiates laser light based on the processed image data, and forms latent images on the photosensitive drums 1a to 1d.

  Further, when a mode for appropriately setting the image density of each color (hereinafter referred to as a calibration mode) is input by the key operation on the operation panel 34, the control unit 32 is detected by the toner adhesion amount measuring device 21. A function for receiving the light reception output signal and calculating the toner adhesion amount based on the toner adhesion amount data stored in the storage unit 33, and determining the density of the patch image based on the calculated toner adhesion amount, By adjusting the charging potentials of the chargers 2a to 2d, the developing bias of the developing devices 3a to 3d, or the exposure amount of the exposure device 4 as compared with the reference density, the density correction is performed for each color. Yes. The calibration mode may be automatically set when the apparatus is turned on or when a predetermined number of image forming processes are completed.

  An example of a patch image for density correction is shown in FIG. When the calibration mode is set by the user, as shown in FIG. 3A, magenta (M), cyan (C), yellow (Y), and yellow (Y) are set at the left end in the traveling direction on the intermediate transfer belt 8. A rectangular patch image of each color of black (B) is formed in a line. The magenta (M) patch image formed by the photoconductive drum 1b is formed in order of the progression of the patch images M1 to M5 in five levels from the white solid image (M1) to the darkest image (M5). Is done.

  FIG. 3B shows an enlarged view of the portions M1 and M2 in FIG. As can be seen from the figure, the adjacent patch images M1 and M2 are each formed in a single color so that the density changes at the boundary. The patch images M3 to M5 are formed in the same manner, and the cyan (C) patch images C1 to C5, the yellow (Y) patch images Y1 to Y5, and the black (B) patch images B1 to B5 are also M1. To M5.

  In image formation by a tandem color image forming apparatus as shown in FIG. 1, toner images for patch image formation are formed on the photosensitive drums 1a to 1d by the above-described image forming process. The formed toner image is transferred to a predetermined position on the intermediate transfer belt 8 by the primary transfer rollers 6a to 6d, and patch images of magenta, cyan, yellow, and black are formed.

  FIG. 4 is a schematic diagram showing the configuration of the toner adhesion amount measuring apparatus. The toner adhesion amount measuring device 21 includes a light emitting element (for example, LED) 22 that projects measurement light onto the surface of the intermediate transfer belt 8, and first and second light receiving elements that receive reflected light reflected from the intermediate transfer belt 8. The polarizing filter 25 is disposed between the light emitting element 22 and the intermediate transfer belt 8, and the polarizing filter 25 transmits only P-polarized light. On the other hand, a polarization separation prism 26 is disposed between the second light receiving element 24 and the intermediate transfer belt 8, and this polarization separation prism 26 transmits P-polarized light to the first light receiving element 23. The S-polarized light is reflected and applied to the second light receiving element 24. The light emitting element 22 is disposed at an angle inclined by a predetermined amount with respect to the surface of the intermediate transfer belt 8.

  Assume that a sufficient amount (appropriate amount) of toner is transferred onto the intermediate transfer belt 8. When measurement light is projected from the light emitting element 22 to the intermediate transfer belt 8, as shown in FIG. 4A, P-polarized light (hereinafter referred to as regular reflection light) P1 and S-polarized light (hereinafter referred to as irregular reflection light). The measuring light including S1 is cut by the polarizing filter 25, and the light S1 is only projected onto the intermediate transfer belt 8 from the polarizing filter 25 as light P1. The light P1 passes through the toner t, does not reach the surface of the intermediate transfer belt 8, and is all reflected by the surface of the toner t.

  The reflected light is separated into specularly reflected light P3 and irregularly reflected light S3 by the polarization separation prism 26, and the light P3 is received by the first light receiving element 21 and the light S3 is received by the second light receiving element 24. The first and second light receiving elements 23 and 24 photoelectrically convert the received light and output first and second output signals. These first and second output signals are A / D converted. Then, it is given to the control unit 32 (see FIG. 2). In the control unit 32, the output levels (first and second light receiving elements) of the first and second light receiving elements are equal so that the levels of the first and second output signals are equal in a state where an appropriate amount of toner is attached to the intermediate transfer belt 8. (Gain) has been adjusted.

  On the other hand, when measurement light including regular reflection light P1 and irregular reflection light S1 is projected onto the intermediate transfer belt 8 in a state where no toner image is formed on the intermediate transfer belt 8, as shown in FIG. The light S1 is cut by the filter 25, and only the light P1 is projected onto the surface of the intermediate transfer belt 8, and includes regular reflection light and irregular reflection light corresponding to the surface shape (for example, surface roughness) of the intermediate transfer belt 8. It becomes reflected light. The reflected light is separated into specularly reflected light P2 and irregularly reflected light S2 by the polarization separation prism 26, the light P2 is received by the first light receiving element 23, and the light S2 is received by the second light receiving element 24.

  The first and second light receiving elements 23 and 24 photoelectrically convert the received light (P2, S2) and output first and second output signals. These first and second output signals are represented by A After being / D converted, it is given to the control unit 32. The control unit 32 sets the difference between the first and second output signals at this time as a reference value. As described above, after adjusting the output levels of the first and second light receiving elements and setting the reference value, the toner adhesion amount on the intermediate transfer belt 8 shown in FIG. 4C is measured. .

  In FIG. 4C, the measurement light including the P-polarized light P1 and the S-polarized light S1 is cut by the polarization filter 25 as in FIGS. 4A and 4B, and the light P1 Only the toner is projected. Now, assuming that the toner amount of the toner image formed on the intermediate transfer belt 8 is not sufficient, a part of the incident light P1 to the toner is reflected on the surface of the toner t, and the rest is transmitted through the toner t. The light transmitted through the toner t is reflected on the surface of the intermediate transfer belt 8.

  That is, the light P1 projected onto the surface of the intermediate transfer belt 8 is reflected as regular reflection light P2 and irregular reflection light S2. The regular reflection light P2 and the irregular reflection light S2 are separated by the polarization separation prism 26, the light P2 is received by the first light receiving element 23, and the light S2 is received by the second light receiving element 24. Similarly, the regular reflection light P3 and the irregular reflection light S3 reflected by the surface of the toner t are separated by the polarization separation prism 26, the light P3 is received by the first light receiving element 23, and the light S3 is received by the second light reception. Light is received by the element 24.

  As described above, the first and second light receiving elements 23 and 24 photoelectrically convert the received light and output the first and second output signals. The first and second output signals are represented by A After being / D converted, it is given to the control unit 32. In the control unit 32, a difference between the first and second output signals is obtained as a measurement output value, and the measurement output value is corrected based on the above-described reference value to obtain a corrected output value. That is, when the correction output value when the toner is not attached is 1, the correction output value is obtained by (measurement output value / reference value).

In the storage unit 33, the relationship between the measured output value and the toner adhesion amount is preset as toner adhesion amount data, and the toner adhesion amount (image density) is obtained from the toner adhesion amount data according to the corrected output value. It will be output as a measurement result. The toner coverage C is obtained by the following equation (1).
C = 1-[(P−P ₀ ) − (S−S ₀ )] / [(Pg−P ₀ ) − (Sg−S ₀ )] (1)
However,
P: Received light output voltage of the amount of regular reflection of the reference image
S: Received light output voltage of the amount of diffuse reflection of the reference image
P ₀ : Received light output voltage of the amount of specular reflection when no light is emitted
S ₀ : Received light output voltage of diffuse reflection when no light is emitted
Pg: Light reception output voltage of the amount of specular reflection on the surface of the toner carrier
Sg: light reception output voltage of the amount of irregularly reflected light on the surface of the toner carrier.

That is, when the appropriate amount of toner is attached on the belt, the output level (gain) of the light receiving element is adjusted so that P−P ₀ = S−S _0. In the state where no toner is attached, P = Pg and S = Sg, so that the coverage C is zero. When the toner adhesion amount T when the coverage C is 1 is 1 mg / cm ² , the toner adhesion amount T is directly calculated by the above equation (1).

  Here, the difference in the output signal when no toner is attached is used as a reference value, the measured output value is corrected by (measured output value / reference value), and the toner adhesion amount is measured from the corrected output value. The correction output value calculation method is not limited to this. For example, the correction output value may be calculated by further multiplying the correction output value described above by a correction coefficient considering the contamination of the light receiving element.

  In the present invention, the surface of the intermediate transfer belt 8 is made rough so that the initial glossiness of the surface is a predetermined value or less. Normally, the glossiness of the intermediate transfer belt 8 gradually decreases due to the use period of the image forming apparatus and the adhesion of external additives contained in the toner, but by using the intermediate transfer belt 8 having a sufficiently low initial glossiness, Since the change in glossiness until the end of the guarantee period (durable period) becomes small, the relationship between the calculated coverage and the toner adhesion amount can be stabilized. The initial glossiness can also be lowered by changing the color of the belt surface, but when the belt surface is roughened and the initial glossiness is lowered as in the present invention, the glossiness changes after durable use. Since the width becomes smaller, the toner adhesion amount can be accurately measured over the entire belt usage period.

  FIG. 5 is a schematic cross-sectional view showing a configuration example of the intermediate transfer belt of the present invention. The intermediate transfer belt 8 has a three-layer structure including a base material layer 50, an elastic layer 51, and a coat layer 53. The coat layer 53 is in contact with the photosensitive drums 1a to 1d (see FIG. 1). The surface of the coat layer 53 is a rough surface on which fine uneven portions 53a and flat portions 53b are formed. The base material layer 50 is a basic material constituting the intermediate transfer belt 8, imparts a predetermined rigidity, withstands the processing conditions when the elastic layer 51 and the coat layer 53 are laminated, and further manufactures the intermediate transfer belt 8. In this case, it is preferable that the material is excellent in workability, heat resistance, slipperiness, and other physical properties. As a material for such a base material layer 50, for example, a polyimide resin is preferably used.

  The elastic layer 51 imparts elasticity to the intermediate transfer belt 8 to prevent image dropout due to stress concentration. As a material of the elastic layer 51, for example, chloroprene rubber or polyurethane rubber is used. The coating layer 53 protects the elastic layer 51. As the coating agent for forming the coating layer 53, an acrylic coating agent, a fluororesin coating agent, a silicon coating agent, or the like is used, and an acrylic coating agent is preferably used. Further, a filler for making the surface of the coating layer 53 rough is added to the coating agent. As the filler, acrylic resin beads having an outer diameter of about 2 to 6 μm are used.

  As a method for manufacturing the intermediate transfer belt 8, the elastic layer 51 is laminated to a predetermined thickness on the base material layer 50 by a melt extrusion method or a laminating method, and a coating agent added with a filler is coated to coat the coating layer 53. The method of doing is mentioned. The laminated structure of the intermediate transfer belt 8 only needs to include at least the elastic layer 51 and the coat layer 53. It may be configured to include these layers.

  By the way, generally, the glossiness tends to decrease as the surface roughness increases. However, when the ten-point average roughness Rz or the centerline average roughness Ra is used as the surface roughness, the glossiness and the surface roughness are good. Correlation is not obtained. The reason for this is that, for example, in Rz, the average value of ten points with large irregularities is obtained, and therefore, in the surface shape as shown in FIG. Absent. However, since the size of the flat portion 53b contributes to the glossiness (reflectance), it is considered that the glossiness may not decrease even if the value of Rz is large.

Therefore, in the present invention, the surface roughness is measured using the arithmetic average slope Δa. The arithmetic average inclination is an average value of an inclination in an arbitrary section represented by the following formula (2), and is calculated by adding the flat portion 53b to the uneven portion 53a in FIG.
n-1
Δa = 1 / (n−1) Σ {tan ⁻¹ | (ΔYi / ΔX) |} (2)
i = 1

  FIG. 6 is a graph showing the relationship between the arithmetic average slope Δa of the surface of the intermediate transfer belt and the glossiness. A gloss meter (GLOSS CHECKER IG-330) manufactured by HORIBA was used for the measurement of gloss. Moreover, the surface roughness measuring device (SURFCOM1500DX) by Tokyo Seimitsu Co., Ltd. was used for the measurement of arithmetic mean inclination (DELTA) a. When measuring glossiness, it is common to measure with a small measurement angle for high glossiness, and with a small measurement angle for low glossiness, and this measurement angle is specified in Japanese Industrial Standards (JIS). It is defined as 20 °, 45 °, 60 °, 75 °, and 85 °. Although 20 ° is used for measuring a high glossiness, the intermediate transfer belt used in the present invention has a low surface glossiness and a wide measuring range of 60 ° is actually widely used. In the present specification, the measurement angle was set to 60 °. As shown in FIG. 6, the arithmetic average slope Δa and the glossiness are well correlated.

  FIG. 7 is a graph showing changes in glossiness of the belt surface when image output is performed using two types of intermediate transfer belts A and B having an arithmetic average inclination Δa of the surface of 0.008 and 0.1. It is. The intermediate transfer belt A had an initial glossiness of 68 and Rz of 3.0 μm, and the intermediate transfer belt B had an initial glossiness of 11.5 and Rz of 3.2 μm. As shown in FIG. 7, the intermediate transfer belt A (indicated by the broken line in the figure) having Δa of 0.008 has a glossiness reduced to 12 when outputting 20,000 sheets, and the fluctuation range of the glossiness was 56. It was. On the other hand, the intermediate transfer belt B (indicated by the solid line in the figure) having Δa of 0.1 has a glossiness reduced to 8 when outputting 20,000 sheets, and the fluctuation range of the glossiness was as small as 3.5. . That is, even if Rz is approximate, there is a large difference in the fluctuation range of the initial glossiness and the glossiness. Therefore, it is preferable to use the arithmetic average gradient Δa for glossiness management.

  Here, since it is known that if the intermediate transfer belt 8 having an initial glossiness of about 35 or less on the surface of the coat layer 53 is used, the relationship between the coverage and the toner adhesion amount is well matched. It can be seen that the arithmetic average slope Δa of the surface of 53 should be 0.075 or more. In addition, in order to reduce the change in glossiness with time of the intermediate transfer belt 8 and to enable accurate measurement of the toner adhesion amount until the end of the belt service life, the initial glossiness of the surface of the coat layer 53 is set to 20 or less. It is preferable that Moreover, it is preferable that the fluctuation range of the glossiness from the initial glossiness is 10 or less.

  Even if the initial glossiness is sufficiently low and the fluctuation range of the glossiness is small, for example, if the glossiness is less than 1, the output signal level of the reflected light from the reference image and the reflected light from the belt surface Concentration control becomes difficult because the output signal level (background value) approaches. Therefore, it is preferable to set the initial glossiness so that the glossiness is maintained at 1 or more even at the end of the belt service life.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, in the above-described embodiment, the case where a toner image is formed on the intermediate transfer belt 8 which is an example of the toner carrier and the toner adhesion amount on the intermediate transfer belt 8 is measured has been described. Not limited to this, in an image forming apparatus that sequentially transfers an image of each color onto a transfer sheet conveyed by a conveying belt, the present invention can be applied in the same manner when measuring the toner adhesion amount of a reference image formed on the conveying belt. It is.

  Further, here, as an example, a tandem color image forming apparatus having a plurality of image forming units has been described. However, the present invention is not limited to this, and a plurality of developing cartridges are provided at positions facing the photosensitive drum. It is also applied to rotary color image forming devices that rotate and move the electrostatic latent image on the photosensitive drum sequentially, digital and analog monochrome image forming devices, and other image forming devices such as facsimiles and printers. Of course it can be applied.

  An elastic layer made of chloroprene rubber having a thickness of 0.25 mm was laminated on a base layer made of polyimide having a thickness of 0.12 mm by a melt extrusion method. Next, three types of acrylic coating agent containing 11%, 10%, and 8% of acrylic resin beads having an outer diameter of 2.2 μm as a filler were coated on the elastic layer and then dried to a thickness of 0.005 mm. The coat layer was laminated to produce the intermediate transfer belt of the present invention. When the initial glossiness of the coating layer surface was measured using a gloss meter (GLOSS CHECKER IG-330, manufactured by HORIBA, Inc.), 15.3 (present invention 1), 17.8 (present invention 2), and 22 (Invention 3).

  Using the testing machine equipped with the intermediate transfer belt of the present invention 1 to 3 obtained in Example 1, the glossiness of the coating layer surface after the durability test (after printing 100,000 sheets) was measured, and the fluctuation range of the glossiness And the concentration controllability was evaluated. Further, intermediate transfer belts having an initial glossiness of 22 and 8.8 by changing the color of the belt surface were set as Comparative Examples 1 and 2, and evaluated in the same manner as in the first to third embodiments. Evaluation of density controllability requires that the reference image is formed on the belt surface, and the measurement output value measured with the toner amount measuring device in FIG. 4 can be used as it is for density control. Correction of the measurement output value is necessary. △ is the case. The results are shown in Table 1.

  As is clear from Table 1, the intermediate transfer belts of the present inventions 1 and 2 having a rough surface and an initial glossiness of 20 or less have a glossiness fluctuation range of 10 or less after the durability test, and the measured output value is The concentration could be measured with high accuracy without correction. Further, in the intermediate transfer belt of the present invention 3, although the initial glossiness is larger than 20, since the fluctuation range after the durability test is small, it is not necessary to correct the measured output value.

  On the other hand, in the intermediate transfer belt of Comparative Example 1 in which the glossiness was adjusted by the change in color, the fluctuation range of the glossiness after the durability test was as large as 27, and it was necessary to correct the measured output value. Further, the intermediate transfer belt of Comparative Example 2 had an initial glossiness as low as 8.8 and a fluctuation range of the glossiness as small as 8.1. However, the glossiness after the durability test decreased to 0.7, so that the reference The output signal level of the reflected light from the image and the output signal level (background value) of the reflected light from the belt surface approach each other, making it difficult to control the density.

  The present invention has at least an elastic layer and a coat layer that is an outermost layer, irradiates a reference image formed on the surface of the coat layer with light, and based on the regular reflection light quantity and irregular reflection light quantity from the reference image In the toner carrier capable of detecting the toner adhesion amount, the initial glossiness of the surface is set to a predetermined value or less by making the surface of the coat layer rough.

  As a result, even if the surface state of the toner carrier changes due to the use period or external additives contained in the toner, the change in glossiness until the end of the guarantee period is reduced, so the toner adhesion amount can be reduced over the entire use period. A toner carrier that can be measured with high accuracy can be provided. For the management of the surface roughness, it is preferable to use an arithmetic average gradient Δa having a high correlation with the glossiness, and a toner carrier having Δa of 0.075 or less.

  In addition, by using a toner carrier having a surface glossiness of 1 or more at a measurement angle of 60 degrees at the end of the useful life and a fluctuation range from the initial glossiness within 10 is guaranteed from the start of use of the toner carrier. Stable and accurate concentration control is possible until the end of the period. Further, it is possible to prevent a problem that the density control becomes difficult because the output signal level of the reflected light from the reference image and the output signal level (background value) of the reflected light from the belt surface approach each other.

  Further, by using the toner carrier as an intermediate transfer belt or a conveyor belt, an image forming apparatus capable of always performing highly accurate density correction regardless of a change in the usage period or surface state of the toner carrier. Can do.

FIG. 1 is a schematic diagram showing an overall configuration of an image forming apparatus of the present invention. 1 is a block diagram showing a configuration of an image forming apparatus of the present invention. FIG. 4 is a schematic diagram of a patch image for density correction. FIG. 2 is a schematic diagram showing an example of a toner adhesion amount measuring device used in the image forming apparatus of the present invention. FIG. 3 is a schematic cross-sectional view showing a configuration example of an intermediate transfer belt of the present invention. These are graphs showing the relationship between the arithmetic average inclination Δa of the intermediate transfer belt surface and the glossiness. These are graphs showing the transition of glossiness when image output is performed using two types of intermediate transfer belts having an arithmetic average inclination Δa of the surface of 0.008 and 0.1.

Explanation of symbols

Pa to Pd Image forming portion 1a to 1d Photosensitive drum 2a to 2d Charger 3a to 3d Developing device 4 Exposure device 6a to 6d Primary transfer roller 7 Fixing portion 8 Intermediate transfer belt (toner carrier)
9 Secondary transfer roller 10a to 10c Driven roller 11 Drive roller 21 Toner amount measuring device (optical detection means)
DESCRIPTION OF SYMBOLS 22 Light emitting element 23 1st light receiving element 24 2nd light receiving element 25 Polarizing filter 26 Polarization separation prism 30 Image input part 32 Control part (control means)
Reference Signs List 33 Storage Unit 34 Operation Panel 50 Base Material Layer 51 Elastic Layer 53 Coat Layer 53a Convex / Concavity 53b Plane Part 100 Image Forming Apparatus

Claims (7)

A reference layer formed on the surface of the coating layer, and irradiating light on the surface of the coating layer, and based on the amount of regular reflection and the amount of irregular reflection from the reference image In the toner carrier capable of detecting the toner adhesion amount,
A toner carrier having an initial glossiness of a predetermined value or less by making the surface of the coating layer rough.   The toner carrier according to claim 1, wherein an arithmetic average slope Δa of the surface of the coat layer is 0.075 or more.   The toner carrier according to claim 2, wherein an initial glossiness of the surface of the coat layer is 20 or less at a measurement angle of 60 degrees.   The glossiness of the surface of the coat layer at the end of the useful life of the toner carrier is 1 or more at a measurement angle of 60 degrees, and the fluctuation range from the initial glossiness is within 10 or less. The toner carrier according to claim 3.   5. The toner carrier according to claim 1, wherein the toner carrier is an intermediate transfer belt on which toner images to be transferred to a recording medium are sequentially laminated.   5. The toner carrier according to claim 1, wherein the toner carrier is a conveyance belt for conveying a recording medium.   An optical detection means capable of irradiating a reference image formed on the toner carrier according to any one of claims 1 to 6 with light and simultaneously measuring the regular reflection light amount and the irregular reflection light amount; An image forming apparatus comprising: a control unit configured to control an image density by detecting a toner adhesion amount in the reference image based on a difference between a light reception output signal of the regular reflection light amount and the irregular reflection light amount measured by a detection unit.

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