JP2005225165A - Line head and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct unevenness of a quantity of light of each light emitting element controlled by gradation data, by a simple means. <P>SOLUTION: A constant voltage is impressed by a control part 1 to each light emitting element La arranged at a light emitting element line 5, and control based on the gradation data supplied from a body controller 7 is carried out. At this time, data for correcting the unevenness of the quantity of light of each light emitting element is formed by a gradation correction setting means 3, and the correction data is added to the gradation data for each light emitting element La. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a line head configured to have no variation in the amount of light in the main scanning direction, and an image forming apparatus using the line head.

  An image forming apparatus using a line head provided with a large number of light emitting elements in one line as an exposure means has been developed. Patent Document 1 describes an image forming apparatus in which a light emitting element array composed of a plurality of light emitting elements is integrated on a single chip to form an exposure means. In this example, the single-chip light-emitting element array for each color is formed on a single substrate and then separated and placed in the developing device for each color, thereby eliminating variations in light emission characteristics.

  In a line head using a plurality of light emitting elements, there is a problem that unevenness occurs in an image because the light amount of each light emitting element varies. Therefore, Patent Document 2 relating to the LED array driving circuit describes that the variation in the light emitting elements is corrected by changing the light emitting time for each light emitting element array.

JP 11-138899 A JP 63-10293 A

  The technique described in Patent Document 1 separates a single chip light emitting element array after it is formed on a single substrate. For this reason, there is a problem that the manufacturing process becomes complicated and the light-emitting element arrays that can be used are limited. In the technique described in Patent Document 2, the light emission time adjustment amount is always the same for each light emitting element array, and variation correction for each dot cannot be performed. In the technique described in Patent Document 2, in order to perform variation correction for each dot, a current supply line must be provided for each dot. Therefore, there is a problem that the circuit configuration becomes complicated and control is difficult. there were.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a line head and an image forming apparatus that suppress variations in the amount of light in the main scanning direction with a simple configuration and prevent image quality deterioration. Is to provide a device.

  The line head of the present invention that achieves the above object is a line head that applies a constant voltage to a plurality of light emitting elements arranged in one line and controls based on gradation data, and the light quantity of each light emitting element is controlled. Correction data for correcting variation is added to the gradation data. As described above, the variation in light quantity is corrected with a simple configuration in which correction data is simply added to the original gradation data supplied to control each light emitting element. For this reason, the configuration of the line head for correcting the variation in the amount of light can be simplified.

  The correction data setting means may be provided on the same substrate as the light emitting element. As described above, since the light emitting element and the correction data setting means are provided on the same substrate of the line head, the space of the line head for correcting the variation in the amount of light can be used effectively.

  Further, the present invention is characterized in that the correction data is set for each light emitting element in accordance with a deviation amount of the light emission amount with respect to the reference light amount. Thus, since the correction data corresponding to the amount of deviation of the light emission amount with respect to the reference light amount is set for each light emitting element, the variation in the light amount can be finely corrected.

  Further, the present invention is characterized in that the correction data set for each light emitting element is stored in the setting means together with the gradation data in a table format. Thus, no special storage means for storing the correction data is required, so that the memory resources can be effectively used.

  In addition, the present invention is characterized in that the light emitting element is composed of an organic EL element. Since the organic EL element can correspond to the dot of the pixel formed on the image carrier, it is possible to correct the variation in the amount of light for each dot and to suppress the deterioration of the image quality with high accuracy.

  In the invention, it is preferable that the light emitting element is controlled by an active matrix driving circuit. For this reason, even when the switching TFT provided in the driver circuit is turned off, the operation of the light emitting element is continued and the light emission is maintained, so that the pixel can be exposed with high luminance.

  Further, the present invention is characterized in that the light amount control of each light emitting element is performed by PWM control. For this reason, control based on the gradation data of each light emitting element can be performed with high accuracy.

  Further, the present invention is characterized in that a plurality of lines in which the plurality of light emitting elements are arranged are formed in the sub-scanning direction. For this reason, when performing multiple exposure, it is possible to suppress variations in the amount of light in the main scanning direction and prevent image quality deterioration.

  The image forming apparatus according to the present invention includes at least two image forming stations in which image forming units including a charging unit, the line head described above, a developing unit, and a transfer unit are arranged around an image carrier. Two or more are provided, and the image is formed in a tandem manner by passing the transfer medium through each station. For this reason, in the tandem image forming apparatus, it is possible to suppress variations in the amount of light in the main scanning direction and prevent image quality deterioration.

  The image forming apparatus of the present invention includes an image carrier configured to carry an electrostatic latent image, a rotary development unit, and any one of the line heads described above, and the rotary development unit includes a plurality of rotary development units. The toner contained in the toner cartridge is carried on the surface thereof, and the toners of different colors are sequentially conveyed to a position facing the image carrier by rotating in a predetermined rotation direction. A developing bias is applied between the developing unit and the toner is moved from the rotary developing unit to the image carrier, whereby the electrostatic latent image is visualized to form a toner image. To do. For this reason, in the rotary image forming apparatus, it is possible to suppress variations in the amount of light in the main scanning direction and to prevent image quality deterioration.

  In addition, the image forming apparatus of the present invention includes an intermediate transfer member. For this reason, in the image forming apparatus provided with the intermediate transfer member, it is possible to suppress variations in the amount of light in the main scanning direction and prevent image quality deterioration.

The present invention will be described below with reference to the drawings. 2 to 4 are characteristic diagrams for explaining the technology underlying the present invention, and show an example in which an organic EL element is used as a light emitting element. FIG. 2 shows voltage-light quantity characteristics of the light emitting elements Ha, Hb, and Hc. As shown in FIG. 2, even when the same voltage is applied, the light amounts of the light emitting elements Ha to Hc are different. In other words, the voltage applied to obtain the same amount of light is different for each light emitting element. For example, in order to obtain a light amount of 300 (μW / cm ² ), Va (V) is applied to the light emitting element Ha, Vb (V) is applied to the light emitting element Hb, and Vc (V) is applied to the light emitting element Hc.

FIG. 3 shows current-light quantity characteristics of the light emitting elements Hd, He, and Hf. As shown in FIG. 3, even when the same current is supplied to the light emitting elements, the light amounts of the light emitting elements Hd to Hf are different. In other words, the current supplied to obtain the same amount of light is different for each light emitting element. For example, in order to obtain a light quantity of 300 (μW / cm ² ), a current of Ia (A) is supplied to the light emitting element Hd, Ib (A) is supplied to the light emitting element He, and Ic (A) is supplied to the light emitting element Hf. The

FIG. 4 shows the duty light quantity characteristics of the light emitting elements Hg, Hh, and Hi. In this example, the duty when performing pulse width modulation control (PWM control) of the light emitting element is shown. As described in FIGS. 2 and 3, even when the same voltage is applied or the same current is supplied, the light amount of each light emitting element is different. The light amounts of the light emitting elements Hg to Hi are different. For example, in order to obtain a light quantity of 300 (μW / cm ² ), the duty of the light emitting element Hg is Dx%, the duty of the light emitting element Hh is Dy%, and the duty of the light emitting element Hi is Dw%. As described above, since the light amounts of the light emitting elements corresponding to the same duty are different, image unevenness occurs.

  In a line head in which a plurality of light emitting elements are arranged in one line in the main scanning direction and constant voltage control is performed, the light emitting elements may be controlled based on gradation data by the PWM control. At this time, since each light emitting element has a duty light quantity characteristic as shown in FIG. 4, there is a problem that image unevenness occurs as described above.

  FIG. 14 is an explanatory diagram showing the basic principle of the present invention. In the embodiment of the present invention, when the light emitting element is PWM-controlled, correction data is added to the gradation data to correct the variation in the light amount. FIG. 14 shows the pulse width Wy (duty ratio Wy / Ws) when the light amount is small (−) and the light amount is large with respect to the pulse width Wx (duty ratio Wx / Ws) of the reference light amount in the gradation data Dp. The pulse width Wz (duty ratio Wz / Ws) of (+) is shown.

  For light emitting elements having a light amount larger than the reference light amount, correction data for reducing the gradation data is added so that the duty ratio matches the duty ratio of the reference light amount. For light emitting elements having a light amount smaller than the reference light amount, correction data for increasing the gradation data is added so that the duty ratio matches the duty ratio of the reference light amount. In the present invention, the variation in the amount of light is corrected by adjusting the duty ratio.

  FIG. 5 to FIG. 7 are explanatory diagrams showing embodiments of examples of tables for storing gradation data and correction data. FIG. 5 is an example of a table showing the increase / decrease of the gradation data in each light emitting element when the gradation data of the light emitting element having the reference light emission amount is “O” to “10”. “+” Indicates that the light emission amount is higher than that of the reference light emission element, and “1” indicates that the light emission amount is less than that of the light emission element of the reference light emission amount. Each of “+” and “1” is classified into three types “O”, “1”, and “2”.

  In the example of FIG. 5, for example, in the light emitting element having the light emission amount deviation amount “+2” with respect to the reference light emission amount, when the gradation data is “5”, the increase / decrease is “−2” from this table. . Therefore, gradation data of “3” is sent to the light emitting element. Based on the corrected gradation data, that is, the corrected duty ratio, PWM control for the light emitting element is performed, and light amount control for adjusting the light emission amount to the reference light amount is performed. As described above, in the example of FIG. 5, the variation in light amount is corrected with a simple configuration in which correction data is simply added to the original gradation data supplied to control each light emitting element. For this reason, the configuration of the line head for correcting the variation in the amount of light can be simplified.

  In the example of FIG. 5, since correction data corresponding to the amount of deviation of the light emission amount with respect to the reference light amount is set for each light emitting element, it is possible to finely correct the light amount variation. The correction data set for each light emitting element is stored together with the gradation data in a table format as shown in FIG. For this reason, no special storage means for storing the correction data is required, so that the memory resources can be effectively used.

  FIG. 6 is a table showing the light emission amount of each light emitting element when the gradation data is not corrected as described above. In FIG. 6, the light emission amount is standardized based on the light amount at the gradation “1” of the reference light emitting element. In this case, for example, if the gradation data of the reference light emission amount is “5”, the deviation of the light emission amount varies in the range of “+3” to “−2”. Such a difference in the amount of light emission appears as unevenness in the image, and the print quality deteriorates.

  FIG. 7 is a table showing the light emission amount of each element when the gradation data is corrected. In the example of FIG. 7, for example, if the gradation data of the reference light emission amount is “5”, the light emission amount of each light emitting element is not limited even if the deviation of the light emission amount varies in the range of “+2” to “−2”. Corrected to be the same. In this way, when the same gradation data is supplied to each light emitting element, even if there is a deviation in the light emitting amount of each light emitting element, the light emitting amount will be the same, so image unevenness will not occur and printing Quality degradation can be prevented.

  FIG. 1 is a block diagram illustrating a schematic configuration of the image forming apparatus. In FIG. 1, 1 is a control unit of a line head, 2 is a control circuit, 3 is a gradation correction value setting means, 4 is a drive circuit comprising TFTs, and 5 is a light emitting element in which a plurality of light emitting elements La are arranged in one line. A line, 6 is a memory, and 7 is a main body controller. The gradation correction value setting means 3 is provided on the same substrate as the light emitting element La.

  The main body controller 7 forms print data and transmits it to the control unit 1 of the line head. The memory 6 stores image data corresponding to each color light emitting element line. The gradation correction value setting means 3 stores a light emission amount for each light emitting element and a corresponding gradation data correction table. Further, correction data as described with reference to FIG. 5 is created based on the gradation data from the main body controller, and a control signal for each light emitting element is formed by the control circuit 2 based on this correction data, and the drive circuit 4 is operated. The light amount of each light emitting element is controlled.

  In the example of FIG. 1, since the light emitting element La and the gradation correction value setting means 3, that is, the correction data setting means are provided on the same substrate of the line head, the space of the line head that corrects the variation in the light amount is made effective. Can be used. In the example of FIG. 1, an organic EL element is used as the light emitting element La. Since the organic EL element can be arranged corresponding to the dot of the pixel formed on the image carrier, the deterioration of the image quality can be suppressed with high accuracy by correcting the variation in the amount of light in dot units. .

  8 to 10 are diagrams illustrating an example in which the light emitting element is controlled by gradation data according to the present invention. FIG. 8 is an explanatory diagram showing an example of bit data and gradation data stored in the gradation data memory. In this example, gradation data is constituted by an 8-bit gradation data memory. In the example of FIG. 8, gradation data 0 (non-light emission) is used for bit data No1, data having the highest density is used for bit data No8, and density data for intermediate gradations are used for bit data No2 to No7.

  FIG. 9 is a block diagram illustrating an example in which PWM control is performed. In FIG. 9, the PWM control unit 70 includes gradation data memories 71a, 71b,..., Counters 72, comparators 73a, 73b,..., Light emitting units Za, Zb,. Is provided. The gradation data memory 71a, 71b,... Is supplied with a gradation data signal 74 from the main body controller 7 shown in FIG. The number of bits of the gradation data memories 71a, 71b... Is 8 bits as shown in FIG. The counter 72 counts the reference clock signal 75.

  The number of bits of the counter 72 is the same 8 bits as the gradation data memories 71a, 71b..., And the count value repeats 0 → maximum value (255) → 0 → maximum value. The comparators 73a and 73b compare the signal of the counter 72 with the gradation data stored in the gradation data memories 71a, 71b. When gradation data> counter value, the switching TFT shown in FIG. 11 is turned on. Further, when the gradation data ≦ the counter value, the switching TFT is turned off.

  FIG. 10 is a characteristic diagram showing a specific example of the PWM control shown in the block diagram of FIG. FIG. 10A shows the output value Ea of the counter 72. As described above, 0 → maximum value (255) → 0 → maximum value → 0... Is repeated. FIG. 10B shows the waveform Eb of the signal output from the comparator, that is, the operating characteristics of the switching TFT when the gradation data is bit data No. 7 (128 gradation). In this case, the switching TFT is turned on when the counter output is in the range of 0 to 127, and the switching TFT is turned off when the output of the counter is in the range of 128 to 255.

  FIG. 10C shows the waveform Ec of the signal output from the comparator, that is, the operating characteristics of the switching TFT when the gradation data is bit data No. 6 (64 gradations). In this case, the switching TFT is turned on when the counter output is in the range of 0 to 63, and the switching TFT is turned off when the output of the counter is in the range of 64 to 255.

  In the case of FIG. 10B, the pulse width of the waveform Eb is Wa, and in the case of FIG. 10C, the pulse width of the waveform Ec is Wb. That is, the length of time for which the switching TFT is turned on changes according to the magnitude of the gradation data, and the amount of light emitted from the light emitting element can be changed. As described above, since the light emitting element can be turned on and off by changing the on / off control of the switching TFT to change the exposure amount to the image carrier, the circuit configuration can be simplified. Also, the control based on the gradation data of each light emitting element can be performed with high accuracy by PWM control.

  FIG. 11 is a circuit diagram for operating the light emitting unit Z shown in FIG. 9 in an active matrix. In FIG. 11, an organic EL element is used as a light emitting element, K is a cathode terminal thereof, and A is an anode terminal thereof. The cathode terminal K is connected to a power source not shown. A scanning line 37a is connected to the gate Ga of the switching TFT (Tr1). Reference numeral 38a denotes a signal line connected to the drain Da of the switching TFT. Reference numeral 39 denotes a power supply line, and Ca denotes a storage capacitor. The source Sb of the driving TFT (Tr2) of the organic EL element is connected to the power supply line 39, and the drain Db is connected to the anode terminal A of the organic EL. Further, the gate Gb of the driving TFT is connected to the source Sa of the switching TFT.

  Next, the operation of the circuit diagram of FIG. 11 will be described. When the scanning line 37a and the signal line 38a are energized while the voltage of the power supply line 39 is applied to the source of the switching TFT, the switching TFT is turned on. For this reason, the gate voltage of the driving TFT decreases, the voltage of the power supply line 39 is supplied from the source of the driving TFT, and the driving TFT becomes conductive. As a result, the organic EL operates to emit light with a predetermined amount of light. The storage capacitor Ca is charged with the voltage of the power supply line 39.

  Even when the switching TFT is turned off, the driving TFT is in a conductive state based on the electric charge charged in the storage capacitor Ca, and the organic EL element maintains the light emitting state. Therefore, when the active matrix is applied to the driving circuit of the light emitting element, even when the switching TFT is turned off to transfer the image data by the shift register, the operation of the organic EL element continues to maintain light emission. In addition, the pixel can be exposed with high luminance.

  FIG. 15 is an explanatory diagram showing another embodiment of the present invention. In FIG. 15, the line head 10 is formed with light emitting element lines 5a in which a large number of light emitting elements La are arranged in one line in the main scanning direction (Y direction). Such light emitting element lines are provided in a plurality of rows of 5a to 5d in the sub-scanning direction (X direction). The control of the line head as shown in FIG. 15 is performed as follows in the block diagram of FIG.

  When image data from the main body controller 7 is input to the control unit 1, each light emitting element of the light emitting element line 5 a exposes a pixel on the image carrier with a predetermined light amount based on the gradation data by the operation of the drive circuit 4. To do. The image carrier is rotationally driven and moved in the direction of the arrow X, so that the pixels exposed by the light emitting elements of the first light emitting element line 5a reach the position of the light emitting elements arranged in the next light emitting element line 5b. Image data is output to the light emitting elements of the light emitting element line 5b, and each light emitting element is turned on based on the gradation data. For this reason, the pixel previously exposed by the light emitting element of the light emitting element line 5a is exposed again by the light emitting element of the light emitting element line 5b with the same amount of light.

  In this way, while moving the image carrier in the arrow X direction, the same pixel is sequentially overlapped and exposed with light emitting element lines in different columns in the sub-scanning direction. Therefore, in the example of FIG. 15, each pixel is subjected to multiple exposure with a light amount four times that when exposed by a single light emitting element, and the light amount necessary for exposure of each pixel can be acquired at high speed. it can. The image data is supplied to each light emitting element line by providing a shift register in the control circuit 2 and transferring the image data by the shift register in synchronization with the movement of the image carrier in the sub-scanning direction.

  When the intermediate density gradation control is performed with the configuration of FIG. 1, for example, when a predetermined luminance is set to 1, image data with a luminance of 0.1 is input from the main body controller 7 to the control unit 1. As described above, the process of sequentially transferring the image data to the shift register while moving the image carrier and outputting it to the light emitting element results in the luminance of one pixel being 0.1 × 4 = 0.4, and the intermediate density is can get. In this way, a gradation output when the pixel is exposed can be obtained. As described above, in the present invention, even in a line head that performs multiple exposure, it is possible to suppress variations in the amount of light and prevent deterioration in image quality.

  In the present invention, the organic EL array head configured as described above can be used as, for example, an exposure head of an image forming apparatus that forms an electrophotographic color image. FIG. 12 is a front view showing an example of an image forming apparatus using an organic EL array head. This image forming apparatus includes four organic EL array exposure heads 101K, 101C, 101M, and 101Y having the same configuration and corresponding four photosensitive drums (image carriers) 41K, 41C, and 41M having the same configuration. , 41Y, respectively, and is configured as a tandem image forming apparatus.

  As shown in FIG. 12, this image forming apparatus is provided with a driving roller 51, a driven roller 52, and a tension roller 53. The tension roller 53 applies tension to the image forming apparatus and stretches it in the direction indicated by the arrow (counterclockwise). ) Is circulated and driven. Photosensitive members 41K, 41C, 41M, and 41Y having photosensitive layers are arranged on the outer peripheral surface as four image carriers arranged at predetermined intervals with respect to the intermediate transfer belt 50.

  K, C, M, and Y added after the reference sign mean black, cyan, magenta, and yellow, respectively, and indicate that the photoconductors are black, cyan, magenta, and yellow, respectively. The same applies to other members. The photoreceptors 41K, 41C, 41M, and 41Y are rotationally driven in the direction indicated by the arrow (clockwise) in synchronization with the driving of the intermediate transfer belt 50.

  Around each photoconductor 41 (K, C, M, Y), charging means (corona charger) 42 (K) for uniformly charging the outer peripheral surface of the photoconductor 41 (K, C, M, Y), respectively. , C, M, Y) and the outer peripheral surface uniformly charged by the charging means 42 (K, C, M, Y) are synchronized with the rotation of the photoconductor 41 (K, C, M, Y). Thus, the organic EL array exposure head 1 (K, C, M, Y) as described above of the present invention for sequentially scanning the lines is provided.

  Further, a developing device 44 (K) that applies toner as a developer to the electrostatic latent image formed by the organic EL array exposure head 101 (K, C, M, Y) to form a visible image (toner image). , C, M, Y) and a primary transfer roller 45 as transfer means for sequentially transferring the toner image developed by the developing device 44 (K, C, M, Y) to the intermediate transfer belt 50 as a primary transfer target. (K, C, M, Y) and a cleaning device 46 (K, C, Y) as a cleaning unit for removing the toner remaining on the surface of the photoreceptor 41 (K, C, M, Y) after being transferred. M, Y).

  Here, in each organic EL array exposure head 1 (K, C, M, Y), the array direction of the organic EL array exposure head 1 (K, C, M, Y) is the photosensitive drum 41 (K, C, M). , Y) along the bus. The light emission energy peak wavelength of each organic EL array exposure head 1 (K, C, M, Y) and the sensitivity peak wavelength of the photoconductor 41 (K, C, M, Y) are set so as to substantially match. Yes.

  The developing device 44 (K, C, M, Y) uses, for example, a non-magnetic one-component toner as a developer, and the one-component developer is conveyed to the developing roller by a supply roller, for example, and adheres to the surface of the developing roller. The film thickness of the developed developer is regulated by a regulating blade, and the developing roller is brought into contact with or increased in thickness by the photosensitive body 41 (K, C, M, Y), whereby the photosensitive body 41 (K, C, M, Y). The toner is developed as a toner image by attaching a developer according to the potential level.

  The black, cyan, magenta, and yellow toner images formed by the four-color single-color toner image forming station are intermediated by the primary transfer bias applied to the primary transfer roller 45 (K, C, M, Y). The toner image, which is sequentially primary transferred onto the transfer belt 50 and sequentially superposed on the intermediate transfer belt 50 to become a full color, is secondarily transferred to a recording medium P such as paper by a secondary transfer roller 66, and serves as a fixing unit. The toner is fixed on the recording medium P by passing through the fixing roller pair 61, and is discharged onto a paper discharge tray 68 formed in the upper part of the apparatus by a paper discharge roller pair 62.

  In FIG. 13, reference numeral 63 denotes a paper feeding cassette in which a large number of recording media P are stacked and held, 64 denotes a pickup roller for feeding the recording media P one by one from the paper feeding cassette 63, and 65 denotes a secondary transfer roller. A pair of gate rollers for defining the supply timing of the recording medium P to the secondary transfer portion 66, a secondary transfer roller 66 as a secondary transfer means for forming a secondary transfer portion with the intermediate transfer belt 50, 67 Is a cleaning blade as a cleaning means for removing the toner remaining on the surface of the intermediate transfer belt 50 after the secondary transfer.

  As described above, since the image forming apparatus of FIG. 12 uses the organic EL array as the writing means, the apparatus can be made smaller than when the laser scanning optical system is used. In the present invention, in the tandem type image forming apparatus as shown in FIG. 12, it is possible to suppress variations in the amount of light in the main scanning direction and prevent image quality deterioration.

  Next, another embodiment of the image forming apparatus according to the present invention will be described. FIG. 13 is a vertical side view of the image forming apparatus. In FIG. 13, the image forming apparatus 160 includes, as main constituent members, a rotary developing device 161, a photosensitive drum 165 functioning as an image carrier, and an image writing means (line head) 167 provided with an organic EL array. In addition, an intermediate transfer belt 169, a paper conveyance path 174, a fixing roller heating roller 172, and a paper feed tray 178 are provided.

  In the developing device 161, the developing rotary 161a rotates in the arrow A direction about the shaft 161b. The inside of the development rotary 161a is divided into four, and image forming units for four colors of yellow (Y), cyan (C), magenta (M), and black (K) are provided. Reference numerals 162a to 162d are arranged in the image forming units for the four colors. The developing rollers rotate in the arrow B direction, and the toner supply rollers 163a to 163d rotate in the arrow C direction. Reference numerals 164a to 164d are regulating blades that regulate the toner to a predetermined thickness.

  As described above, reference numeral 165 denotes a photosensitive drum that functions as an image carrier, 166 denotes a primary transfer member, 168 denotes a charger, and 167 denotes an image writing unit, which is provided with an organic EL array. The photosensitive drum 165 is driven in the direction of arrow D opposite to the developing roller 162a by a drive motor (not shown), for example, a step motor.

  The intermediate transfer belt 169 is stretched between the driven roller 170b and the drive roller 170a, and the drive roller 170a is connected to the drive motor of the photosensitive drum 165 to transmit power to the intermediate transfer belt. By driving the drive motor, the drive roller 170 a of the intermediate transfer belt 169 is rotated in the arrow E direction opposite to the photosensitive drum 165.

  The paper conveyance path 174 is provided with a plurality of conveyance rollers, a pair of paper discharge rollers 176, and the like, and conveys the paper. An image (toner image) on one side carried on the intermediate transfer belt 169 is transferred to one side of the paper at the position of the secondary transfer roller 171. The secondary transfer roller 171 is separated from and brought into contact with the intermediate transfer belt 169 by a clutch, and is brought into contact with the intermediate transfer belt 169 when the clutch is turned on, so that an image is transferred onto the sheet.

  The sheet on which the image has been transferred as described above is then subjected to a fixing process by a fixing device having a fixing heater H. The fixing device is provided with a heating roller 172 and a pressure roller 173. The sheet after the fixing process is drawn into the discharge roller pair 176 and proceeds in the arrow F direction. When the paper discharge roller pair 176 rotates in the opposite direction from this state, the paper reverses its direction and advances in the double-sided printing conveyance path 175 in the arrow G direction. 177 is an electrical component box, 178 is a paper feed tray for storing paper, and 179 is a pickup roller provided at the outlet of the paper feed tray 178.

  For example, a low-speed brushless motor is used as a drive motor for driving the transport roller in the paper transport path. The intermediate transfer belt 169 uses a step motor because it requires color misregistration correction. Each of these motors is controlled by a signal from a control means (not shown).

  In the state shown in the drawing, a yellow (Y) electrostatic latent image is formed on the photosensitive drum 165, and a high voltage is applied to the developing roller 62a, whereby a yellow image is formed on the photosensitive drum 165. When all of the yellow back side and front side images are carried on the intermediate transfer belt 169, the development rotary 161a rotates 90 degrees in the direction of arrow A.

  The intermediate transfer belt 169 rotates once and returns to the position of the photosensitive drum 165. Next, two images of cyan (C) are formed on the photosensitive drum 165, and this image is carried on the yellow image carried on the intermediate transfer belt 169. Thereafter, the 90-degree rotation of the development rotary 161 and the one-rotation process after the image is carried on the intermediate transfer belt 169 are repeated in the same manner.

  For carrying four color images, the intermediate transfer belt 169 rotates four times, and then the rotation position is further controlled to transfer the image onto the sheet at the position of the secondary transfer roller 171. The paper fed from the paper feed tray 178 is transported by the transport path 174, and the color image is transferred to one side of the paper at the position of the secondary transfer roller 171. The sheet on which the image is transferred on one side is reversed by the discharge roller pair 176 as described above, and stands by on the conveyance path. Thereafter, the sheet is conveyed to the position of the secondary transfer roller 171 at an appropriate timing, and the color image is transferred to the other side. The housing 180 is provided with an exhaust fan 181. In the present invention, in the rotary type image forming apparatus as shown in FIG. 13, variation in the amount of light in the main scanning direction can be suppressed and deterioration in image quality can be prevented. Further, in a tandem type and rotary type image forming apparatus provided with an intermediate transfer member, it is possible to suppress variations in the amount of light in the main scanning direction and prevent image quality deterioration.

  The line head and the image forming apparatus of the present invention have been described based on the embodiments. The line head and the image forming apparatus of the present invention are not limited to these embodiments, and various modifications are possible.

  As described above, according to the present invention, when a plurality of light emitting elements are arranged in one line and operated for lighting, a line head having a configuration in which there is no variation in the amount of light in the main scanning direction and image formation using the line head An apparatus can be provided.

It is a block diagram which shows the control part of the line head of this invention. It is a characteristic view which shows the characteristic of a light emitting element. It is a characteristic view which shows the characteristic of a light emitting element. It is a characteristic view which shows the characteristic of a light emitting element. It is explanatory drawing which shows the example of gradation data. It is explanatory drawing which shows the example of gradation data. It is explanatory drawing which shows the example of gradation data. It is explanatory drawing which shows the relationship between bit data and gradation data. It is a block diagram of the example which carries out PWM control of the light emitting element. It is explanatory drawing of the example which carries out PWM control of the light emitting element. It is a circuit diagram of an active matrix system. 1 is a side view showing a tandem image forming apparatus. 1 is a side view showing a rotary type image forming apparatus. It is explanatory drawing of this invention. It is explanatory drawing which shows the example of a line head.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Control part, 2 ... Control circuit, 3 ... Tone correction value setting means, 4 ... Drive circuit, 5 ... Light emitting element line, 6 ... Memory, 7 ... Main body controller, 10... Line head, 41 (K, C, M, Y)... Photosensitive drum (image carrier), 44 (K, C, M, Y). ..Intermediate transfer belt, 66... Secondary transfer roller, 70... PWM control unit, 71a, 71b... Gradation data memory, 72... Counter, 73a, 73b. ..Gradation data signal, 75... Reference clock signal, 76... Select signal, 101K, 101C, 101M, 101Y... Organic EL array exposure head (line head), 161. ... Photosensitive drum, 167 ... Exposure head Line head), 169 ... intermediate transfer belt, 171 ... secondary transfer roller, P ... recording medium, La ... organic EL element, Z, Za, Zb ... light emitting portion

Claims (11)

A line head that applies a constant voltage to a plurality of light emitting elements arranged in one line and controls each light emitting element based on gradation data, wherein correction data for correcting variations in the amount of light of each light emitting element A line head characterized by being added to gradation data. The line head according to claim 1, wherein the correction data setting unit is provided on the same substrate as the light emitting element. The line head according to claim 1, wherein the correction data is set for each light emitting element according to a deviation amount of the light emission amount with respect to a reference light amount. 4. The line head according to claim 3, wherein the correction data set for each light emitting element is stored in the setting unit together with the gradation data in a table format. The line head according to claim 1, wherein the light emitting element is an organic EL element. 6. The line head according to claim 1, wherein the light emitting element is controlled by an active matrix driving circuit. The line head according to any one of claims 1 to 6, wherein light amount control of each light emitting element is performed by PWM control. The line head according to any one of claims 1 to 7, wherein a plurality of lines in which the plurality of light emitting elements are arranged are formed in a sub-scanning direction. At least two image forming stations in which image forming units including a charging unit, a line head according to any one of claims 1 to 8, a developing unit, and a transfer unit are arranged around an image carrier. An image forming apparatus provided as described above, wherein a transfer medium passes through each station and forms an image by a tandem method. An image carrier configured to carry an electrostatic latent image, a rotary developing unit, and the line head according to claim 1, wherein the rotary developing unit includes a plurality of toner cartridges. The toner stored in the toner is carried on the surface, and toners of different colors are sequentially conveyed to a position facing the image carrier by rotating in a predetermined rotation direction, and the image carrier, the rotary developing unit, An image forming method characterized in that a developing bias is applied between the toner and the toner is moved from the rotary developing unit to the image carrier to visualize the electrostatic latent image to form a toner image. apparatus. The image forming apparatus according to claim 9, further comprising an intermediate transfer member.

Images