JP2008126589A - Exposure equipment and image forming system with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide exposure equipment which eliminates the crosstalk of driving signals between pixels which have a common selection signal and turn on with the same timing and an image forming system with the same. <P>SOLUTION: The exposure equipment has an exposure head board 23 having an organic EL element 34 as light-emitting element, a driving transistor 33 driving the organic EL element 34, a selection transistor 30 as a pixel selection switch, and a holding capacitor 32 holding signal charge corresponding to the display brightness of pixels and pixels (a) arranged in the main scanning direction. An optical print head puts the selective transistors of two pixels a1 and b1 having the same emission timing and connected to adjacent driving signal lines from among one array or a plurality of arrays of pixels in a selected condition through separate selection signal lines with different timing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exposure apparatus in an electrophotographic image forming apparatus and the like, and an image forming apparatus using the same.

  An electrophotographic image forming apparatus (printer apparatus) has an exposure apparatus for image formation. In recent years, various attempts have been made to use a light emitting element such as an organic EL element as a light source of the exposure apparatus. In an image display device using such a light emitting element for each pixel, a plurality of transistors for supplying a driving current corresponding to a driving voltage for selecting the pixel and driving the light emitting element to the light emitting element are applied. A holding capacitor or the like for holding the driving voltage is provided in each pixel. For example, Patent Document 1 discloses an image display device having such a configuration.

Further, Patent Document 2 has a configuration in which a plurality of light-emitting driving common electrodes are provided on a chip in which a plurality of light-emitting elements that are selectively time-division driven are formed in a line in an exposure apparatus including light-emitting elements. Disclosure.
JP 2002-156923 A JP-A-11-245440

  However, if each light emitting element of the exposure device is provided with a plurality of transistors and holding capacitors equivalent to those in the pixels of the conventional image display device, and each pixel is sequentially selected and time-division driven, it is selected at the same time. In addition, there is a problem in that crosstalk of the drive signal may occur between a plurality of pixels that are written with the drive signal and lighted at the same timing due to the parasitic capacitance between the wirings.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an exposure apparatus that eliminates crosstalk of drive signals between pixels that are lit at the same timing, and an image forming apparatus using the same. It is to provide.

    In order to achieve the above object, an invention according to claim 1 of the present invention is an exposure apparatus that includes a plurality of pixels arranged in a line and performs exposure according to image data. A plurality of pixels are divided into a plurality of pixel groups including a predetermined number of the pixels, the pixels in the pixel groups are driven in a time division manner, and the light emitting elements are driven in the pixel groups. Drive signals based on the image data to be supplied, and at least some of the drive signal lines are arranged in parallel with each other, and are provided corresponding to the pixels in each pixel group, and each pixel is selected. A plurality of selection signal lines to which a selection signal for writing the drive signal is supplied, and the plurality of selection signal lines are adjacent to each other among pixels driven at the same light emission timing in each pixel group. Drive Route separately provided to two of said pixel drive signal is supplied via, characterized in that the timing of the two pixels in a selected state is set to different timings.

  The exposure apparatus according to claim 2 is the exposure apparatus according to claim 1, wherein each of the pixel groups includes the predetermined number of pixels arranged adjacent to each other in the plurality of pixels arranged in a line. The plurality of selection signal lines are provided in common to the predetermined number of pixels in the odd-numbered pixel groups, and are common to the predetermined number of pixels in the even-numbered pixel groups. It is provided in.

  The exposure apparatus according to claim 3 is the exposure apparatus according to claim 1, wherein each of the pixels includes at least the light emitting element, a drive transistor having one end of a current path connected to the light emitting element, and a control terminal. A holding transistor connected to the selection signal line, the other end of the current path connected to the other end of the current path of the drive transistor, one end connected to the control terminal of the drive transistor, and the other end of the drive transistor A holding capacitor connected to one end of the current path, provided in common to the other end of the current path of the drive transistor of each pixel of each pixel group, and corresponding to the selection signal Is selected, a current corresponding to the drive signal is passed through the current path of the drive transistor to hold the corresponding charge in the holding capacitor and the light emitting element. Are held in a non-light-emitting state, and when the pixel is in a non-selected state, a plurality of holding signals to which a holding signal for supplying a current based on the electric charge held in the holding capacitor to the light-emitting element to make it emit light is supplied It has a line.

  According to a fourth aspect of the present invention, in the exposure apparatus according to the third aspect, the control terminal of each pixel is further connected to the selection signal line, and one end of the current path is one end of the current path of the drive transistor. And the other end of the current path is connected to the drive signal line, and when the pixel is selected according to the selection signal, the drive signal line passes through the selection transistor. The current according to the drive signal flows through the current path of the drive transistor.

  An exposure apparatus according to a fifth aspect is the exposure apparatus according to the first aspect, wherein each of the drive signal lines is commonly connected to a predetermined number of pixels in one pixel group.

  An exposure apparatus according to a sixth aspect is the exposure apparatus according to any one of the first to fifth aspects, wherein each of the light emitting elements in the light emitting element array is an organic EL element.

  According to a seventh aspect of the present invention, there is provided an image forming apparatus that includes a photosensitive drum, a charger, an exposure device, and a development device, and performs printing according to image data, and the exposure device includes a light emitting element. A plurality of pixels arranged in a main scanning direction, wherein the plurality of pixels are divided into a plurality of pixel groups including a predetermined number of the pixels, and the pixels in the pixel groups are driven in a time division manner; A drive signal based on the image data for driving the light emitting element is supplied to the pixel group, and a plurality of drive signal lines at least partially parallel to each other are provided corresponding to the pixels in the pixel group And a plurality of selection signal lines to which a selection signal for writing the drive signal is supplied with each pixel being selected, and the plurality of selection signal lines are driven at the same light emission timing in each pixel group. Of the pixel to be That is, it is provided separately for two pixels to which drive signals are supplied via adjacent drive signal lines, and the timings for selecting the two pixels are set to different timings. .

  The image forming apparatus according to claim 8, wherein each of the pixel groups is the predetermined number arranged adjacent to each other in the plurality of pixels arranged in the main scanning direction. The plurality of selection signal lines are provided in common to each of the predetermined number of pixels in each of the odd-numbered pixel groups, and each of the predetermined number of pixels in each of the even-numbered pixel groups is provided. It is characterized by being provided in common to each.

  The image forming apparatus according to claim 9 is the image forming apparatus according to claim 7, wherein each of the pixels includes at least the light emitting element, a drive transistor having one end of a current path connected to the light emitting element, and a control. A holding transistor having a terminal connected to the selection signal line, the other end of the current path connected to the other end of the current path of the drive transistor, one end connected to the control terminal of the drive transistor, and the other end of the drive A holding capacitor connected to one end of the current path of the transistor, provided in common to the other end of the current path of the drive transistor of each pixel of each pixel group, and according to the selection signal When the pixel is in a selected state, a current corresponding to the drive signal is passed through the current path of the drive transistor to hold the corresponding charge in the holding capacitor and When a light emitting element is in a non-light emitting state and the pixel is in a non-selected state, a plurality of holding signals for supplying a current based on the electric charge held in the holding capacitor to the light emitting element to make it emit light are supplied. It has a holding signal line.

  The image forming apparatus according to claim 10 is the image forming apparatus according to claim 9, wherein each of the pixels further has a control terminal connected to the selection signal line, and one end of a current path is a current path of the drive transistor. A selection transistor connected to one end of the current path and the other end of the current path connected to the drive signal line, and when the pixel is in a selected state according to the selection signal, the selection transistor is connected to the drive signal line. Thus, a current corresponding to the drive signal flows through the current path of the drive transistor.

  An image forming apparatus according to an eleventh aspect is the image forming apparatus according to the seventh aspect, wherein the drive signal lines are commonly connected to a predetermined number of pixels in one pixel group.

  The image forming apparatus according to claim 12 is the image forming apparatus according to any one of claims 7 to 11, wherein each light emitting element in the light emitting element array is an organic EL element.

  The timing of writing between pixels connected to adjacent driving signal lines and having the same lighting timing is set to a different timing, so that the value of the driving signal written to the pixel is caused by the parasitic capacitance between the driving signal lines. Crosstalk of drive signals between pixels can be eliminated without being affected by the value of a drive signal applied to adjacent drive signal lines.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a schematic configuration of an electrophotographic image forming apparatus (printer apparatus) to which the present invention is applied. After the photoreceptor drum 1 is uniformly charged by the charger 2, an electrostatic latent image is formed by light irradiation from a light emitting device provided in the exposure device (exposure device) 3. Next, in order to realize this electrostatic latent image, toner is adhered by the developing device 4. The toner image is transferred to the paper 5 between the transfer device 6 and the photosensitive drum 1. The paper 5 to which the toner is attached is thermally fixed by the fixing device 7 and then discharged.

  Further, a small amount of transfer leakage toner on the photosensitive drum 1 is removed by the cleaner 9, and the surface of the photosensitive drum 1 is uniformly discharged by the static eliminator 8.

  Here, the above-described light emitting device includes a light emitting element array including a plurality of light emitting elements arranged in a line in the main scanning direction of the recording scan (the width direction of the photosensitive drum, that is, the width direction of the paper). Each light emitting element consists of organic EL, for example. For example, in the case of a printer device that can print at a print density of 1200 dpi (dots / inch) to the full width using A4 size paper in the vertical direction, this light-emitting element array includes approximately 14000 light-emitting elements. I have. A pulse voltage in accordance with print information output from the host device is applied to these individual light emitting elements, and the individual light emitting elements are selectively controlled to emit light. In recent years, light-emitting devices using organic EL have been actively studied. By adopting organic EL instead of LEDs as the light source for the electrophotographic process, the number of wire bondings connected to each LED can be reduced, and the cost can be reduced.

  FIG. 2 is a view showing an outline of the configuration of the light emitting device provided in the exposure device 3 described in FIG. The light emitting device includes a system controller 20, a data driver 21, a scan driver 22, and an exposure head substrate 23. On the exposure head substrate 23, a pixel group of a to f each having, for example, four pixels is arranged.

  When exposure according to image data is performed in the light emitting device shown in FIG. 2, first, the system controller 20 performs horizontal control according to image data, paper size, and conveyance speed from a raster image processor unit of a printing device (not shown). The signal HSYNC and the vertical control signal are received. The data driver 21 generates, as output signals, a plurality of drive voltages (Vdata1 to Vdata6) having voltage values based on on / off of each pixel and a gradation signal corresponding to the pixel data in accordance with a control signal from the system controller 20. To the exposure head substrate 23. The scan driver 22 also has a plurality of selection signals (Select1 to Select4) for setting the pixels in a selected state in accordance with a control signal from the system controller 20 and a plurality of holding signals (Source1 to Source1) for setting the lighting states. A function for generating and supplying Source 4) is provided.

  FIG. 3 is an equivalent circuit as a comparison object for explaining the effect of the present invention of the exposure head substrate 23 shown in FIG. FIG. 4 is a drive timing chart thereof. 3 shows a pixel group a composed of four pixels a1 to a4 and a part of a pixel group b composed of four pixels b1 to b4 among the pixel groups a to f on the exposure head substrate 23 shown in FIG. Pixels b1, b2) are shown. Each pixel includes, for example, a thin film transistor, and includes a selection transistor 33 as a pixel selection switch, an organic EL element 34 as a light emitting element, and a thin film transistor, and includes a driving transistor 31 for driving an organic EL and a thin film transistor. The formed holding transistor 30 and a holding capacitor 32 for holding a signal charge corresponding to the display luminance of the pixel are configured.

  In the exposure head substrate 23 shown in FIG. 3, a plurality of driving signal lines to which each driving voltage is applied, a plurality of selection signal lines to which each selection signal is applied, and a plurality of holding signals to which each holding signal is applied. Drive voltage Vdata1 to Vdata6 having a voltage value based on the grayscale signal from the data driver 21 during a pixel selection period in which the selection signal applied to each selection signal line is at a high level. The charge is applied to the line, applied to the drive transistor 31 via the selection transistor 33, and the charge corresponding to the current flowing in the current path of the drive transistor 31 is accumulated in the holding capacitor 32. Then, during the holding period in which the selection signal is set to the low level and the holding signal applied to the holding signal line is set to the high level, a current corresponding to the charge accumulated in the holding capacitor 32 is supplied from the driving transistor 31 to the organic EL element 34. And the organic EL element 34 is lit with a luminance corresponding to the current value of the current.

  In addition, reset transistors 35 and 36 are provided in each drive signal line, and the reset transistors 35 and 36 are turned on at the initial stage of the selection period to discharge the charge charged in the holding capacitor 32.

  A horizontal control signal HSYNC shown in FIG. 4 is a synchronization signal in the main scanning direction of the printing apparatus, and is a dot formation processing time (one line time) in which an active to active period is allowed for one line. For example, if you use an A4 horizontal light source unit with 1 dot = 1200 dpi x 1200 dpi, 40 ppm, 50 mm between papers, one line time is ((25.4 mm / 1200 dpi) / (210 mm x 40 sheets + 50 mm x 40 sheets)) / 60 ≒ 122μsec.

  The data driver 21 drives each pixel so that light energy necessary for exposing the photosensitive drum 1 to form a latent image can be obtained during a period (one line time) when HSYNC is active to active. To emit light for a predetermined time.

  By making the light emission time sufficiently short with respect to one line time, the plurality of light emitting elements in the light emitting element array are caused to emit light in a time-sharing manner for each predetermined number of light emitting elements, thereby reducing the number of drive signal lines. The output of the data driver 21 is connected to the anodes of a plurality of pixels of one pixel group, and the pixels of the pixel group are sequentially selected and turned on by the scan driver 22 in a time-sharing manner. It is configured.

  In the configuration shown in FIG. 3, four pixels in one pixel group are driven by one drive signal of the data driver 21, and an output signal is supplied from the data driver 21 to the exposure head substrate 23. Six drive signal lines are provided corresponding to the six pixel groups a to f. The selection signal line to which the selection signal sent from the scan driver 22 to the exposure head substrate 23 and the holding signal line to which the holding signal are supplied correspond to the number of four pixels in each of the pixel groups a to f, respectively. Four are provided.

  As shown in FIG. 3, when four pixels are connected to the scan driver 22 as a unit, if 1200 dpi / 40 PPM, each selection signal is a signal shifted by 122/4 μsec = 30.5 μsec, and each holding signal The signal is set to the high level within the period when the selection signal is set to the low level. In this case, light emission can be performed up to 122-30.5 = 91.5 μsec. That is, the drive voltage corresponding to the gradation signal is output from the data driver 21 to the pixels a1, b1, c1, d1, e1, and f1 of each pixel group during the period in which the selection signal Select1 is at a high level, and the drive voltage corresponds to the drive voltage. Charge is written into the holding capacitor 32. This electric charge is held while the holding signal Source1 is at a high level, and a current corresponding to the electric charge is supplied from the driving transistor 31 to the organic EL element 34, whereby the organic EL element is held while the holding signal Source1 is at a high level. 34 lights up.

  Similarly, pixels a2, b2, c2, d2, e2, f2 of each pixel group corresponding to the selection signal Select2, and a3, b3, c3, d3, e3, f3 of each pixel group corresponding to the selection signal Select3 The driving voltage corresponding to the gradation signal is output from the data driver 21 to the pixels a4, b4, c4, d4, e4, f4 of each pixel group corresponding to the selection signal Select4, and each holding signal The corresponding pixels are lit during the high level period.

  Hereinafter, problems in the above configuration will be described. In the exposure head substrate 23, a plurality of drive signal lines to which an output signal from the data driver 21 is supplied are usually arranged close to each other and in parallel with each other in order to reduce the width of the exposure head substrate 23 as much as possible. . For this reason, a parasitic capacitance Cdata is generated between the drive signal lines as shown in FIG. That is, a parasitic capacitance Cdata is generated between adjacent drive signal lines (in the example of FIG. 3, the drive signal line to which the drive voltage Vdata1 is applied and the drive signal line to which the drive voltage Vdata2 is applied). Here, among the pixels that are connected to the same holding signal line and are lit at the same timing, there are pixels that are connected to the same selection signal line and selected at the same timing, and are connected to the adjacent drive signal lines. For example, in FIG. 3, the pixel a1 and the pixel b1, or the pixel a2 and the pixel b2 have such a relationship. Between such pixels, when the selection signal becomes high level, the pixel is in a selected state, and when the current starts to flow through the pixel, and when the selection signal becomes low level, the current is cut off from the pixel Sometimes, due to capacitive coupling between the drive signal lines, a current different from the current corresponding to the gradation signal supplied from the data driver 21 to the pixel flows in one or both pixels, and the retention capacitor of the corresponding pixel There is a problem that a charge corresponding to that is sometimes written in 32. For example, there are pixels to which a drive voltage with a high maximum gradation is applied and pixels to which a non-lighting zero voltage is applied between pixels connected to the same selection signal line and connected to adjacent drive signal lines. In this case, a minute voltage may be applied to the pixel that should not be lit due to capacitive coupling, resulting in a slight lighting.

  FIG. 5 is a schematic equivalent circuit of the exposure head substrate 23 according to the present invention for solving such a problem. FIG. 6 is a drive timing chart thereof. As an example, as in the case of FIG. 3 and FIG. 4 described above, the pixel group includes four pixels, and each pixel is sequentially selected and driven in a time-sharing manner.

  In the present embodiment, in order to solve the above-described conventional problems, the selection transistors 33 of the pixels that are supplied with the same holding signal and have the same lighting timing and connected to the adjacent drive signal lines are set to the selected state. However, the selection operation is performed at different timings using different selection signal lines. This will be described in detail below.

  In FIG. 3, the selection signal line to which the selection signal Select1 is applied is connected to the pixels a1, b1, c1, d1, e1, and f1, and the selection signal line to which the selection signal Select2 is applied is the pixels a2, b2, c2, and d2. , e2, and f2, and the selection signal line to which the selection signal Select3 is applied is connected to the pixels a3, b3, c3, d3, e3, and f3, and the selection signal line to which the selection signal Select4 is applied is the pixels a4 and b4 , c4, d4, e4, f4. On the other hand, in the configuration of the present embodiment shown in FIG. 5, two selection signals Select11 and Select12 are used instead of the selection signal Select1, and the selection signal lines to which the selection signal Select11 is applied are a1, c1, and e1 pixels. In addition to the connection, the selection signal line to which the selection signal Select12 is applied is connected to the b1, d1, and f1 pixels. Similarly, two selection signals Select21 and Select22 are used instead of the selection signal Select2, and the selection signal line to which the selection signal Select21 is applied is connected to the pixels a2, c2, and e2, and the selection signal to which the selection signal Select22 is applied. A line is connected to the b2, d2, and f2 pixels, two selection signals Select31 and Select32 are used instead of the selection signal Select3, and the selection signal line to which the selection signal Select31 is applied is connected to the a3, c3, and e3 pixels, The selection signal line to which the selection signal Select32 is applied is connected to the pixels b3, d3, and f3, the two selection signals Select41 and Select42 are used instead of the selection signal Select4, and the selection signal line to which the selection signal Select41 is applied is a4, In addition to being connected to the c4 and e4 pixels, the selection signal line to which the selection signal Select42 is applied is connected to the b4, d4 and f4 pixels. As described above, in this embodiment, the selection transistors 33 of two pixels (for example, a1 and b1) having the same light emission timing and adjacent to the drive signal lines (Vdata1 and Vdata2 in FIG. 5) connected to the selection transistor 33 are used. Are selected using separate selection signals. For example, the pixel a1 includes a holding transistor 30, a driving transistor 31, an organic EL element 34 as a pixel display element, a selection transistor 33, and a holding capacitor 32 for holding a signal charge. The pixel b1 includes a holding transistor 130, a driving transistor 131, an organic EL element 134 as a pixel display element, a selection transistor 133, and a holding capacitor 132 for holding a signal charge. Here, a parasitic capacitance Cdata is generated adjacent to the drive signal line connected to the pixel a1 and supplied with the drive voltage Vdata1 and the drive signal line connected to the pixel b1 and supplied with the drive voltage Vdata2. . Therefore, in this embodiment, the selection operation is performed for the pixel a1 by the selection signal Select11, and the selection operation is performed for the pixel b1 by the selection signal Select12.

  According to such a configuration, when the current corresponding to the drive voltages Vdata1 to Vdata6 is output from the data driver 21 to each drive signal line, the a1, c1, and e1 pixels are output according to the selection signal Select11. Writing is performed, and writing to the b1, d1, and f1 pixels is performed according to the selection signal Select12. Then, the pixels a1, b1, c1, d1, e1, and f1 are turned on during the period when the holding signal Source1 is set to the high level. Similarly, writing is performed on the a2, c2, and e2 pixels according to the selection signal Select21, and writing is performed on the b2, d2, and f2 pixels according to the selection signal Select22. Then, a2, b2, c2, d2, e2, and f2 are lit during a period when Source2 is at a high level. Similarly, in the pixels a3 to f3, writing with the selection signal Select31 and the selection signal Select32 and lighting with the holding signal Source3 are performed, and in pixels a4 to f4, writing with the selection signals Select41 and Select42 and lighting with the holding signal Source4 are performed. Is called. In this way, all pixels are written and lit for one line time.

  According to the above-described procedure, the writing period is shifted between pixels connected to adjacent drive signal lines and having the same lighting timing. Therefore, even when the parasitic capacitance Cdata exists between the drive signal lines, the data driver is used at the time of writing. In accordance with the voltage value of the drive voltage from 21, the correct signal charge is written into the holding capacitor 32 and is not affected by the voltage value of the drive voltage applied to the adjacent drive signal line. In this way, it is possible to eliminate the influence of the drive voltage between pixels having the same lighting timing and connected to adjacent drive signal lines.

FIG. 1 is a diagram showing a schematic configuration of an electrophotographic system to which the present invention is applied. FIG. 2 is a view showing a configuration of a conventional organic EL head unit provided in the exposure device 3 described in FIG. FIG. 3 is a schematic equivalent circuit of the exposure head substrate 23 shown in FIG. FIG. 4 is a drive timing chart of the schematic equivalent circuit shown in FIG. FIG. 5 is a schematic equivalent circuit of the exposure head substrate 23 according to the present invention. FIG. 6 is a drive timing chart of the schematic equivalent circuit shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging device 3 Exposure device 4 Developing device 5 Paper 6 Transfer device 7 Fixing device 8 Electric discharge device 9 Cleaner 20 System controller 21, 211-1 Data driver 22, 22-1 Scan driver 23 Exposure head substrate

Claims (12)

In an exposure apparatus that includes a plurality of pixels arranged in a line and performs exposure according to image data,
Each pixel has a light emitting element,
The plurality of pixels are divided into a plurality of pixel groups including a predetermined number of the pixels, and the pixels in the pixel groups are driven in a time division manner.
A drive signal based on the image data for driving the light emitting element is supplied to each pixel group, and a plurality of drive signal lines at least partially parallel to each other;
A plurality of selection signal lines provided corresponding to the respective pixels in each of the pixel groups, and supplied with a selection signal for writing the drive signal with each of the pixels in a selected state;
With
The plurality of selection signal lines are separately provided for two pixels to which a drive signal is supplied via adjacent drive signal lines among pixels driven at the same light emission timing in each pixel group, An exposure apparatus characterized in that timings for selecting the two pixels are set to different timings. Each pixel group includes the predetermined number of pixels arranged adjacent to each other in the plurality of pixels arranged in a line,
The plurality of selection signal lines are provided in common to the predetermined number of pixels in the odd-numbered pixel groups, and are common to the predetermined number of pixels in the even-numbered pixel groups. The exposure apparatus according to claim 1, wherein the exposure apparatus is provided. Each pixel includes at least the light emitting element, a drive transistor having one end of a current path connected to the light emitting element, a control terminal connected to the selection signal line, and the other end of the current path being a current of the drive transistor. A holding transistor connected to the other end of the path, and a holding capacitor having one end connected to the control terminal of the driving transistor and the other end connected to one end of the current path of the driving transistor,
Provided in common to the other end of the current path of the drive transistor of each pixel of each pixel group, and when the pixel is selected according to the selection signal, the current path of the drive transistor A current corresponding to the drive signal is supplied to hold the corresponding charge in the holding capacitor, and the light emitting element is set in a non-light emitting state, and the charge held in the holding capacitor when the pixel is not selected. The exposure apparatus according to claim 1, further comprising a plurality of holding signal lines to which a holding signal for supplying a current based on the light emitting element to the light emitting element to make it emit light is supplied. Each pixel further has a control terminal connected to the selection signal line, one end of the current path connected to one end of the current path of the drive transistor, and the other end connected to the drive signal line. With transistors,
The current according to the drive signal flows from the drive signal line to the current path of the drive transistor through the selection transistor when the pixel is selected according to the selection signal. Item 4. The exposure apparatus according to Item 3. 2. The exposure apparatus according to claim 1, wherein each of the drive signal lines is commonly connected to a predetermined number of pixels in one pixel group. 6. The exposure apparatus according to claim 1, wherein each light emitting element in the light emitting element array is an organic EL element. In an image forming apparatus that includes a photosensitive drum, a charger, an exposure device, and a developing device, and performs printing according to image data.
The exposure device has a plurality of pixels having light emitting elements and arranged in the main scanning direction,
The plurality of pixels are divided into a plurality of pixel groups including a predetermined number of the pixels, and the pixels in the pixel groups are driven in a time division manner.
A drive signal based on the image data for driving the light emitting element is supplied to each pixel group, and a plurality of drive signal lines at least partially parallel to each other;
A plurality of selection signal lines provided corresponding to the respective pixels in each of the pixel groups, and supplied with a selection signal for writing the drive signal with each of the pixels in a selected state;
With
The plurality of selection signal lines are separately provided for two pixels to which a drive signal is supplied via adjacent drive signal lines among pixels driven at the same light emission timing in each pixel group, An image forming apparatus, wherein the timing for selecting the two pixels is set to a different timing. Each of the pixel groups includes the predetermined number of pixels arranged adjacent to each other in the plurality of pixels arranged in the main scanning direction,
The plurality of selection signal lines are provided in common to the predetermined number of pixels in the odd-numbered pixel groups, and are common to the predetermined number of pixels in the even-numbered pixel groups. The image forming apparatus according to claim 7, wherein the image forming apparatus is provided. Each pixel includes at least the light emitting element, a drive transistor having one end of a current path connected to the light emitting element, a control terminal connected to the selection signal line, and the other end of the current path being a current of the drive transistor. A holding transistor connected to the other end of the path, and a holding capacitor having one end connected to the control terminal of the driving transistor and the other end connected to one end of the current path of the driving transistor,
Provided in common to the other end of the current path of the drive transistor of each pixel of each pixel group, and when the pixel is selected according to the selection signal, the current path of the drive transistor A current corresponding to the drive signal is supplied to hold the corresponding charge in the holding capacitor, and the light emitting element is set in a non-light emitting state, and the charge held in the holding capacitor when the pixel is not selected. The image forming apparatus according to claim 7, further comprising: a plurality of holding signal lines to which a holding signal for supplying a current based on the light emitting element to the light emitting element to make it emit light is supplied. Each pixel further has a control terminal connected to the selection signal line, one end of the current path connected to one end of the current path of the drive transistor, and the other end connected to the drive signal line. With transistors,
The current according to the drive signal flows from the drive signal line to the current path of the drive transistor through the selection transistor when the pixel is selected according to the selection signal. Item 10. The image forming apparatus according to Item 9. 8. The image forming apparatus according to claim 7, wherein each of the drive signal lines is commonly connected to a predetermined number of pixels in one pixel group. The image forming apparatus according to claim 7, wherein each light emitting element in the light emitting element array is an organic EL element.

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