JP4645580B2 - Exposure apparatus and image forming apparatus having the same - Google Patents

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. At least a light-emitting element and a holding capacitor for holding a charge for causing the light-emitting element to emit light, and the plurality of pixels are divided into a plurality of pixel groups having a predetermined number of the pixels , A drive signal connected to each of the pixel groups and having a voltage value based on the image data for driving the light emitting element of each pixel of each pixel group is supplied, and at least some of them are arranged in parallel with each other a plurality of drive signal lines provided corresponding to each pixel in each pixel group, Timing for the selected state for the write operation to hold a charge corresponding to the drive signal to the holding capacitor of the respective pixel A plurality of selection signal lines selected signal for setting the grayed are supplied at different timings that do not overlap each other temporally, each connected said common to one of said pixels in each pixel group, wherein the light emission of each pixel And a predetermined number of holding signal lines to which a holding signal for setting a light emission timing for setting the element in a light emitting state is supplied, and each of the selection signal lines includes two adjacent drive signal lines. Connected to each other, connected in common to one holding signal line , provided separately for each of the two pixels set at the same light emission timing in accordance with the holding signal, and selecting each pixel Are set at different timings that do not overlap in time .

  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 pixel includes at least the light emitting element and one end of a current path connected to the light emitting element, and the other end of the current path is the A driving transistor connected to each holding signal line, a control terminal is connected to the selection signal line, one end of a current path is connected to the control terminal of the driving transistor, and the other end of the current path is a current path of the driving transistor. and a holding transistor connected to the other end of the holding capacitor has one end connected to the control terminal of the drive transistor, the other end is connected to one end of the current path of the driving transistor, wherein the holding signal When the pixel is selected according to the selection signal, the current corresponding to the drive signal is supplied to the line through the current path of the drive transistor. The charge is held in the holding capacitor and the light emitting element is set in a non-light emitting state, and when the pixel is in a non-selected state, a current based on the charge held in the holding capacitor is supplied to the light emitting element to emit light. A signal for setting a state is supplied.

  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.

Invention of claim 7, and a developing unit and the photosensitive drum and the charger and the exposure device, an image forming apparatus that performs printing in accordance with image data, the exposure device is, at least, the light emitting element and said and a holding capacitor for holding electric charges to the light emitting element and the light-emitting state, the main scanning a plurality of pixels arranged in a direction, a plurality of pixels of the plurality of pixels having the pixel of the predetermined number A drive signal having a voltage value based on the image data for driving the light emitting element of each pixel of each pixel group, which is divided into groups and connected to each of the plurality of pixel groups, is provided; A plurality of drive signal lines arranged in parallel with each other and a write operation that is provided corresponding to each pixel in each pixel group, and holds a charge corresponding to the drive signal in a holding capacitor of each pixel selected to perform A plurality of selection signal lines selection signal for setting a timing of a state is supplied at different timings that do not overlap each other temporally, each being connected in common the one of the pixels of the pixel groups, each pixel A predetermined number of holding signal lines to which a holding signal for setting a light emission timing for setting the light emitting element to emit light is supplied, and each of the selection signal lines is disposed adjacent to the two driving signals is connected to each signal line, are connected in common to the one holding the signal line provided separately for each of the two of the pixels that are set to the same light emission time in response to the holding signal, each of said pixel The selection timing is set to different timings that do not overlap in time .

  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 and one end of a current path connected to the light emitting element, and the other end of the current path. Is connected to each holding signal line, a control terminal is connected to the selection signal line, one end of the current path is connected to the control terminal of the drive transistor, and the other end of the current path is connected to the drive transistor. A holding transistor connected to the other end of the current path, and the holding capacitor has 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. the hold signal lines, as the hold signal, when the pixel is set to the selected state in response to the selection signal electric current according to the driving signal to a current path of the driving transistor The corresponding charge is held in the holding capacitor and the light emitting element is set in a non-light emitting state, and when the pixel is in a non-selected state, a current based on the charge held in the holding capacitor is supplied to the light emitting element. Thus, a signal for turning on the light is supplied.

  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 according to the 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, is applied to the drive transistor 31 via the selection transistor 33, and charges corresponding to the current flowing in the current path of the drive transistor 31 are 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 the connection to the scan driver 22 is performed in units of four pixels, 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 occurs 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 such a 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 the present embodiment, the selection operation is performed on the pixel a1 by the selection signal Select11, and the selection operation is performed on 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 pixels a3 to f3, writing with selection signal Select31 and selection signal Select32 and lighting with holding signal Source3 are performed, and in pixels a4 to f4, writing with selection signals Select41 and Select42 and lighting with 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 of the pixels includes at least a light emitting element and a holding capacitor that holds a charge for making the light emitting element emit light.
The plurality of pixels are divided into a plurality of pixel groups having a predetermined number of the pixels,
A drive signal connected to each of the plurality of pixel groups and having a voltage value based on the image data for driving the light emitting element of each pixel of each pixel group is supplied, and at least some of them are parallel to each other A plurality of drive signal lines arranged;
A selection signal that is provided corresponding to each pixel in each pixel group and sets a timing for selecting a write operation that holds a charge corresponding to the drive signal in a holding capacitor of each pixel is temporally related to each other. A plurality of selection signal lines supplied at different timings that do not overlap each other,
A predetermined number of holding signal lines, each of which is connected in common to one of the pixels of each of the pixel groups and is supplied with a holding signal for setting a light emission timing at which the light emitting element of each pixel is in a light emitting state; ,
With
Each selection signal line is connected to each of the two drive signal lines arranged adjacent to each other, is commonly connected to one holding signal line, and is set to the same light emission timing according to the holding signal. An exposure apparatus provided separately for each of the two pixels, wherein the timing for selecting each pixel is set to a different timing that does not overlap in time. 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 driving transistor in which one end of a current path is connected to the light emitting element, and the other end of the current path is connected to each holding signal line, and a control terminal is the selection signal line. A holding transistor in which one end of the current path is connected to the control terminal of the drive transistor, and the other end of the current path is connected to the other end of the current path of the drive transistor,
The holding capacitor has one end connected to the control terminal of the drive transistor and the other end connected to one end of the current path of the drive transistor.
Wherein each holding signal line, as the holding signal, the time in which the pixel is the selected state in response to the selection signal, by flowing a current corresponding to the drive signal to a current path of the driving transistor, the corresponding charge Is held in the holding capacitor and the light emitting element is set in a non-light emitting state, and when the pixel is in a non-selected state, a current based on the electric charge held in the holding capacitor is supplied to the light emitting element and the light emitting state is set. 2. An exposure apparatus according to claim 1, wherein a signal to be supplied 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 includes at least a light emitting element and a holding capacitor that holds charges for making the light emitting element emit light, and includes a plurality of pixels arranged in the main scanning direction,
The plurality of pixels are divided into a plurality of pixel groups having a predetermined number of the pixels,
A drive signal connected to each of the plurality of pixel groups and having a voltage value based on the image data for driving the light emitting element of each pixel of each pixel group is supplied, and at least some of them are parallel to each other A plurality of drive signal lines arranged;
A selection signal that is provided corresponding to each pixel in each pixel group and sets a timing for selecting a write operation that holds a charge corresponding to the drive signal in a holding capacitor of each pixel is temporally related to each other. A plurality of selection signal lines supplied at different timings that do not overlap each other,
A predetermined number of holding signal lines, each of which is connected in common to one of the pixels of each of the pixel groups and is supplied with a holding signal for setting a light emission timing at which the light emitting element of each pixel is in a light emitting state; ,
With
Each selection signal line is connected to each of the two drive signal lines arranged adjacent to each other, is commonly connected to one holding signal line, and is set to the same light emission timing according to the holding signal. An image forming apparatus, wherein the image forming apparatus is provided separately for each of the two pixels, and the timing for selecting each pixel is set to a different timing that does not overlap in time. 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 driving transistor in which one end of a current path is connected to the light emitting element, and the other end of the current path is connected to each holding signal line, and a control terminal is the selection signal line. A holding transistor in which one end of the current path is connected to the control terminal of the drive transistor, and the other end of the current path is connected to the other end of the current path of the drive transistor,
The holding capacitor has one end connected to the control terminal of the drive transistor and the other end connected to one end of the current path of the drive transistor.
Wherein each holding signal line, as the holding signal, the time in which the pixel is the selected state in response to the selection signal, by flowing a current corresponding to the drive signal to a current path of the driving transistor, the corresponding charge Is held in the holding capacitor and the light emitting element is set in a non-light emitting state, and when the pixel is in a non-selected state, a current based on the electric charge held in the holding capacitor is supplied to the light emitting element and the light emitting state is set. The image forming apparatus according to claim 7, wherein a signal 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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