JP2009098512A - Display and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display and its control method which can correctly detect the external illumination intensity and control a brightness level of a display image. <P>SOLUTION: This display has a display panel to display images, and an optical sensor Tr1 formed in a transistor structure on the display panel. In the period detecting the light, a first voltage stress is applied to the optical sensor Tr1 and the illumination intensity information of the external light L is detected to control the image brightness level according to the detected information. In the period not detecting the external light, a second voltage stress is applied to cancel the first voltage stress. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display device and a control method for the display device.

In general, a liquid crystal display device is used as a display device. The liquid crystal display device is used, for example, in a display unit of a mobile phone. Mobile phones and the like are used in environments where the illuminance of outside light is different. For this reason, in recent years, cellular phones, etc., measure ambient ambient light, and in conjunction with this, by changing the display brightness or performing image modulation, the power consumption of the entire set can be reduced, and the display screen It is utilized for improving visibility (see, for example, Non-Patent Document 1). In order to rationalize this and make it easy to use, a technique in which an optical sensor is built in an array substrate of a liquid crystal display device is disclosed (for example, see Patent Document 1).
P903iTV catalog, Panasonic Mobile Communication Co., Ltd. JP 2007-72243 A

  The optical sensor has a transistor structure. However, when an optical sensor having a transistor structure is used, if photometric driving is performed for a long period of time, there is a problem that the photocurrent characteristic shifts due to voltage stress applied to the optical sensor and the light receiving sensitivity changes. More specifically, since a unipolar voltage is constantly applied to the gate electrode of the transistor, a unipolar voltage stress is always applied to the transistor. If the transistor is continuously used in such a situation and in an environment where external light irradiation is also applied, the transistor causes a threshold shift, and the photocurrent characteristic shifts.

The above is particularly problematic in a low illuminance region (low illuminance environment) with a small photocurrent. Further, when a transistor is formed using an amorphous silicon thin film, it becomes a very big problem.
The present invention has been made in view of the above points, and an object thereof is to provide a display device and a display device control method capable of accurately sensing the illuminance of external light and controlling the luminance level of a display image.

In order to solve the above-described problem, a display device according to an aspect of the present invention includes:
A display panel for displaying images,
A light sensing unit provided in the display panel and having a transistor structure;
During the light detection period, a first voltage stress is applied to the light sensing unit, information on the illuminance of external light is detected, and the luminance level of the image is controlled according to the detected information. And a control mechanism for applying a second voltage stress to the light sensing unit and canceling the first voltage stress.

In addition, a display device according to another aspect of the present invention includes:
A display panel for displaying images,
A channel layer provided in the display panel, disposed opposite to the gate electrode through an insulating film, and formed of amorphous silicon; a source electrode electrically connected to one region of the channel layer; and A light sensing portion having a drain electrode electrically connected to the other region of the channel layer and changing conductivity between the source electrode and the drain electrode in accordance with a luminance level of external light received by the channel layer; ,
A light detection signal extraction line connected to the drain electrode of the light sensing unit;
A changeover switch connected to the photodetection signal extraction line, for outputting a reset voltage to the photodetection signal extraction line, and for switching whether to reset the voltage of the photodetection signal extraction line;
A storage unit connected to the light detection signal extraction line and storing a reset voltage output to the light detection signal extraction line;
An output switch connected to the photodetection signal extraction line and for switching whether to output a photodetection signal based on a reset voltage stored in the storage unit and a photodetection voltage output from the photosensor;
A control mechanism,
The control mechanism is
In the reset period, a first gate voltage is applied to the gate electrode of the light sensing unit, the changeover switch is turned on, the output switch is turned off, and the light is output from the changeover switch to the light. Applying a reset voltage to the detection signal extraction line, resetting the voltage of the light detection signal extraction line, storing the reset voltage in the storage unit, and applying a first voltage stress to the light sensing unit;
In the holding period following the reset period, the changeover switch is switched to a non-conductive state, the reset voltage is held in the storage unit, and the application of the first gate voltage to the gate electrode and the light sensing unit are performed. Maintaining the application of the first voltage stress,
In the light detection signal extraction period following the holding period, the output switch is switched to a conductive state, and the light detection signal based on the reset voltage stored in the storage unit and the light detection voltage output from the light sensing unit is output. The luminance level of the image is controlled in accordance with the photodetection signal taken out from the switch, and the application of the first gate voltage to the gate electrode and the application of the first voltage stress to the light sensing unit are maintained. ,
In a non-light detection period following a light detection period including the reset period, the holding period, and the light detection signal extraction period, the output switch is switched to a non-conductive state, and the first gate voltage is applied to the gate electrode of the light sensing unit. A second gate voltage having a relatively different polarity is applied, and a second voltage stress having a polarity different from the first voltage stress is applied to the light sensing unit to cancel the first voltage stress.

In addition, a control method for a display device according to another aspect of the present invention includes:
In a method for controlling a display device, comprising: a display panel for displaying an image; and a light sensing unit provided in the display panel and having a transistor structure.
During the light detection period, a first voltage stress is applied to the light sensing unit, information on the illuminance of external light is detected, and the luminance level of the image is controlled according to the detected information,
A second voltage stress is applied during the non-light detection period to cancel the first voltage stress.

In addition, a control method for a display device according to another aspect of the present invention includes:
A display panel for displaying an image, a channel layer provided on the display panel, disposed opposite to the gate electrode via a gate electrode and an insulating film, and electrically connected to one region of the channel layer formed of amorphous silicon And a drain electrode electrically connected to the other region of the channel layer, and conductivity between the source electrode and the drain electrode according to a luminance level of external light received by the channel layer. A photo-sensing unit that changes the nature, a photo-detection signal extraction line connected to the drain electrode of the photo-sensing unit, and a photo-detection signal extraction line connected to the photo-detection signal output line to output a reset voltage to the photo-detection signal extraction line; A selector switch for switching whether to reset the voltage of the light detection signal extraction line, and the light detection signal extraction line connected to the light detection signal extraction line A storage unit for storing the reset voltage output to the optical detection signal, and a photodetection signal connected to the photodetection signal take-out line and based on the reset voltage stored in the storage unit and the photodetection voltage output from the photodetection unit. In a control method of a display device comprising an output switch for switching whether to output,
In the reset period, a first gate voltage is applied to the gate electrode of the light sensing unit, the changeover switch is turned on, the output switch is turned off, and the light is output from the changeover switch to the light. Applying a reset voltage to the detection signal extraction line, resetting the voltage of the light detection signal extraction line, storing the reset voltage in the storage unit, and applying a first voltage stress to the light sensing unit;
In the holding period following the reset period, the changeover switch is switched to a non-conductive state, the reset voltage is held in the storage unit, and the application of the first gate voltage to the gate electrode and the light sensing unit are performed. Maintaining the application of the first voltage stress,
In the light detection signal extraction period following the holding period, the output switch is switched to a conductive state, and the light detection signal based on the reset voltage stored in the storage unit and the light detection voltage output from the light sensing unit is output. The luminance level of the image is controlled in accordance with the photodetection signal taken out from the switch, and the application of the first gate voltage to the gate electrode and the application of the first voltage stress to the light sensing unit are maintained. ,
In a non-light detection period following a light detection period including the reset period, the holding period, and the light detection signal extraction period, the output switch is switched to a non-conductive state, and the first gate voltage is applied to the gate electrode of the light sensing unit. A second gate voltage having a relatively different polarity is applied, and a second voltage stress having a polarity different from the first voltage stress is applied to the light sensing unit to cancel the first voltage stress.

  According to the present invention, it is possible to provide a display device and a display device control method capable of accurately sensing the illuminance of external light and controlling the luminance level of a display image.

Hereinafter, embodiments in which a display device and a control method for a display device according to the present invention are applied to a liquid crystal display device and a control method for a liquid crystal display device will be described in detail with reference to the drawings.
As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4 and FIG. 5, the liquid crystal display device includes a liquid crystal display panel 1 as a display panel, an optical sensor 2, a drive circuit (LSI) 3, a backlight unit 4, and a substrate. 5, a storage unit 6 and a processing unit 7 are provided. The drive circuit 3, the storage unit 6, and the processing unit 7 form a control mechanism 8.

  The liquid crystal display panel 1 includes an array substrate 10, a counter substrate 30 having a display surface S1, and a liquid crystal layer 40. The array substrate 10 and the counter substrate 30 are each formed in a rectangular shape. The array substrate 10 is formed with a size larger than that of the counter substrate 30.

  The array substrate 10 and the counter substrate 30 are arranged so that the three sides of each of them substantially overlap. On the remaining side of the array substrate 10, the array substrate 10 extends outward from the counter substrate 30. More specifically, in the first direction d1, the array substrate 10 and the counter substrate 30 are disposed so as to substantially overlap. In a second direction d2 orthogonal to the first direction d1, the array substrate 10 extends outward from the counter substrate 30. The liquid crystal display panel 1 has a rectangular display region R1 that overlaps the array substrate 10 and the counter substrate 30.

  The array substrate 10 has a rectangular glass substrate 11 as a transparent insulating substrate. The glass substrate 11 has an extending portion 11 a that is detached from the counter substrate 30. A plurality of pixels 12 are arranged on the glass substrate 11 in the display region R1. The pixels 12 are provided in a matrix along the first direction d1 and the second direction d2 along the display surface S1. Note that the display surface S1 overlaps the display region R1.

  In the display region R1, on the glass substrate 11, a plurality of scanning lines 15 and a plurality of signal lines 22 orthogonal to these scanning lines are arranged. On the glass substrate 11, a plurality of auxiliary capacitance lower wirings 16 parallel to the scanning lines 15 are formed. In this embodiment, the pixel 12 is formed in a region surrounded by two adjacent auxiliary capacitor lower wirings 16 and two adjacent signal lines 22.

Next, one pixel 12 is taken out and described in detail.
The pixel 12 includes a pixel electrode 25, a TFT (thin film transistor) 13 as a switching element connected to the pixel electrode, and an auxiliary capacitance element 14. The TFT 13 is an N channel type. The TFT 13 is formed in the same manner as a light sensing portion Tr1 of the light sensor 2 described later.

  On the glass substrate 11, a scanning line 15, a gate electrode 15 a extending a part of the scanning line 15 and an auxiliary capacitance lower wiring 16 are formed. The scanning line 15, the gate electrode 15a, and the auxiliary capacitor lower wiring 16 are formed of the same material. A gate insulating film 17 is formed on the glass substrate 11, the scanning line 15, the gate electrode 15 a, and the auxiliary capacitance lower wiring 16. A channel layer 18 and an auxiliary capacitance electrode 19 are formed on the gate insulating film 17. In this embodiment, the channel layer 18 and the auxiliary capacitance electrode 19 are formed of an amorphous silicon (a-Si) film.

  The channel layer 18 is formed so as to overlap the gate electrode 15a. The auxiliary capacitance electrode 19 is formed so as to overlap the auxiliary capacitance lower wiring 16. The auxiliary capacitance lower wiring 16 and the auxiliary capacitance electrode 19 form an auxiliary capacitance element 14. An insulating layer 20 is formed on the channel layer 18.

  A signal line 22 and a connection wiring 23 are formed on the gate insulating film 17 on which the channel layer 18 and the auxiliary capacitance electrode 19 are formed. The signal line 22 and the connection wiring 23 are made of the same material. The source electrode 22 a of the signal line 22 is electrically connected to the source region RS of the channel layer 18. The drain electrode 23 a of the connection wiring 23 is electrically connected to the drain region RD of the channel layer 18. Further, the connection wiring 23 is electrically connected to the auxiliary capacitance electrode 19.

The channel layer 18 is connected to the source electrode 22 a and the drain electrode 23 a, but these are connected via the n ⁺ a-Si film 21. In the TFT 13 composed of the channel layer 18 made of a-Si, the n ⁺ a-Si film 21 is an essential layer.

  An interlayer insulating film 24 is formed on the glass substrate 11 on which the signal lines 22 and the connection wirings 23 are formed. A pixel electrode 25 is formed on the interlayer insulating film 24. The pixel electrode 25 is formed of a transparent conductive material such as ITO (Indium Tin Oxide). The pixel electrode 25 is electrically connected to the connection wiring 23 through a contact hole 24 h formed in the interlayer insulating film 24. The pixel electrode 25 is formed by overlapping the periphery of two adjacent auxiliary capacitor lower wirings 16 and two adjacent signal lines 22.

An alignment film 26 is formed on the interlayer insulating film 24 and the pixel electrode 25.
As described above, the array pattern 10 p is formed on the glass substrate 11 to form the array substrate 10.

The counter substrate 30 includes, for example, a glass substrate 31 as a transparent insulating substrate. A plurality of colored layers 32 of red, green and blue are formed on the glass substrate 31. On the colored layer 32, a counter electrode 33 and an alignment film 34 are sequentially formed.
As described above, the counter pattern 30 p is formed on the glass substrate 31 to form the counter substrate 30. The counter substrate 30 includes a display surface S <b> 1 on the opposite side to the array substrate 10.

  A gap between the array substrate 10 and the counter substrate 30 is held as a spacer by, for example, a columnar spacer 35 formed on the array substrate 10. The array substrate 10 and the counter substrate 30 are joined to each other by a rectangular frame-shaped sealing material 36 disposed at the peripheral portions of both substrates, which is the peripheral portion of the display region R1.

  The liquid crystal layer 40 is sandwiched between the array substrate 10 and the counter substrate 30 and is surrounded by a sealing material 36. A liquid crystal injection port 37 formed in a part of the sealing material 36 is sealed with a sealing material 38.

  The drive circuit 3 is mounted on the extension part 11a. Here, one end of each of the plurality of scanning lines 15, the plurality of auxiliary capacitance lower wirings 16, and the plurality of signal lines 22 is provided on the extending portion 11 a. That is, one end of each of the plurality of scanning lines 15, the plurality of auxiliary capacitance lower wirings 16, and the plurality of signal lines 22 exceeds the sealing material 36 and is located on the extending portion 11 a outside the sealing material 36. . The drive circuit 3 is electrically connected to the plurality of scanning lines 15, the plurality of auxiliary capacitance lower wirings 16, and the plurality of signal lines 22.

  The backlight unit 4 is disposed on the outer surface side of the array substrate 10. The backlight unit 4 includes a light guide 4a disposed to face the array substrate 10, and a light source 4b and a reflection plate 4c disposed to face one side edge of the light guide.

  As shown in FIG. 1, FIG. 3, FIG. 6 and FIG. 7, the optical sensor (photosensor) 2 is provided in the liquid crystal display panel 1, and more specifically, formed on the glass substrate 11 outside the display region R1. Yes. The photosensor (photosensor) 2 includes a photosensor Tr1 having a transistor structure, and a storage capacitor C formed of a capacitor, for example, and a changeover switch Tr2 as a storage unit. The light sensing unit Tr1 and the changeover switch Tr2 are each formed by an N-channel transistor. The light sensing portion Tr1 is formed of the same material as the TFT 13 at the same time. The storage capacitor C is formed of the same material as the auxiliary capacitor element 14 at the same time.

  The light sensing portion Tr1 is disposed to face the gate electrode through the gate electrode G and the gate insulating film 17, and is a channel layer CH made of amorphous silicon, and a source electrode S electrically connected to the source region of the channel layer, And a drain electrode D electrically connected to the drain region of the channel layer.

The gate electrode G overlaps the entire channel layer CH and prevents the backlight light from being irradiated to the channel layer CH. The light sensing unit Tr1 changes the conductivity between the source electrode S and the drain electrode D according to the luminance level of the external light L received by the channel layer CH.
The storage capacitor C is connected to the source electrode S and the drain electrode D of the light sensing unit Tr1.
The optical sensor 2 is electrically connected to the control mechanism 8, more specifically to the drive circuit 3.

  The source electrode S of the light sensing unit Tr1 is electrically connected to the input pad P1 of the drive circuit 3. A source voltage V1 is input to the source electrode S via the input pad P1. The gate electrode G of the light sensing unit Tr1 is electrically connected to the input pad P2 of the drive circuit 3. A gate voltage V2 is input to the gate electrode G via the input pad P2.

  The drain electrode D of the light sensing unit Tr1 is electrically connected to the output pad Pout of the drive circuit 3 through the light detection signal extraction line W. A light detection signal (output voltage) Vout is output to the output pad Pout via the light detection signal extraction line W.

  The gate electrode of the changeover switch Tr2 is electrically connected to the input pad P3 of the drive circuit 3. A gate voltage V3 is input to the gate electrode via the input pad P3. Therefore, the changeover switch Tr2 is turned on (conductive state) and turned off (non-conductive state) in response to the gate voltage V3.

  The source electrode of the changeover switch Tr2 is electrically connected to the input pad P4 of the drive circuit 3. The source voltage V4 is input to the source electrode via the input pad P4. The drain electrode of the changeover switch Tr2 is electrically connected to the light detection signal extraction line W and the storage capacitor C.

  The drive circuit 3 includes an output switch Tr3 and an output buffer B. The output switch Tr3 is formed by an N-channel transistor, for example. The source electrode of the output switch Tr3 is electrically connected to the light detection signal extraction line W through the output pad Pout. The drain electrode of the output switch Tr3 is electrically connected to the input terminal of the output buffer B. The output switch Tr3 is turned on (conductive state) and turned off (non-conductive state) in response to a control signal from the processing unit 7.

  The storage unit 6 and the processing unit 7 are mounted on the substrate 5. The storage unit 6 stores in advance information on the illuminance of outside light corresponding to the value of the light detection signal Vout. In this embodiment, the storage unit 6 is a ROM formed exclusively for reading.

  The processing unit 7 detects the light detection signal Vout output from the optical sensor 2 and compares it with the information in the storage unit 6. Thereby, the processing unit 7 can detect the illuminance information of the external light L. The processing unit 7 controls the luminance level of the image according to the detected illuminance information of the external light L. The brightness level of the image is controlled by controlling the amount of light emitted from the backlight unit 4, for example.

  The processing unit 7 includes a timing controller 7a. Therefore, the processing unit 7 can cause the optical sensor 2 to perform light sensing continuously or intermittently based on an instruction from the timing controller 7a. That is, the processing unit 7 can detect the light detection signal Vout continuously or intermittently.

  The substrate 5 and the liquid crystal display panel 1 are connected by a flexible cable 50. The flexible cable 50 is electrically connected to the drive circuit 3 and the processing unit 7. For this reason, the photodetection signal Vout and the like are transmitted via the flexible cable 50.

  In addition, a power supply unit 60 is mounted on the substrate 5. The substrate 5 and the backlight unit 4 are connected by a cable 70. The cable 70 is electrically connected to the power supply unit 60 and the backlight unit 4. Therefore, a direct current from the power supply unit 60 is given to the backlight unit 4 via the cable 70 under the control of the processing unit 7.

Next, a method for controlling the liquid crystal display device will be described. In particular, a method for controlling the liquid crystal display device for detecting the illuminance of the external light L will be described. As illustrated in FIGS. 12 to 15, the operation for detecting the illuminance of the external light L is divided into a light detection operation performed in the light detection period t1 and a non-light detection operation performed in the non-light detection period t2. It is done.
In this embodiment, the light detection operation and the non-light detection operation are alternately and continuously performed while the liquid crystal display panel 1 displays an image. In other words, the processing unit 7 continuously detects the light detection signal Vout.

  The light detection operation is divided into a reset operation performed in the reset period t1a, a holding operation performed in the holding period t1b, and a light detection signal extraction operation performed in the light detection signal extraction period t1c.

First, the reset operation will be described.
As shown in FIGS. 8 and 1, 6, 7, 12-15, in the reset period t <b> 1 a, the drive circuit 3 supplies the first source voltage V <b> 1 to the source electrode S and the gate electrode G to the first gate. A voltage V2 is applied.

At the same time, the drive circuit 3 applies a first gate voltage V3 at a level (ON potential) that makes the changeover switch Tr2 conductive (ON state) to the gate electrode of the changeover switch Tr2, and applies a high level to the source electrode of the changeover switch Tr2. The reset voltage V4, which is the first source voltage, is applied. The reset voltage V4 is sufficiently larger than the first source voltage V1.
The output switch Tr3 is supplied with a control signal at a level (off potential) for turning off the driving circuit 3 from the driving circuit 3.

  Thereby, the reset voltage V4 is applied to the light detection signal extraction line W from the changeover switch Tr2, and the voltage of the light detection signal extraction line W is reset. At the same time, the reset voltage V4 is held in the holding capacitor C. In other words, the reset voltage V4 is stored in the storage capacitor C.

In the above-described reset operation, the first voltage stress α is applied to the light sensing unit Tr1. As described above, in the light sensing unit Tr1, a potential difference (Vout (V4) −V2) is generated between the drain electrode D and the gate electrode G, and a potential difference (V1−V2) is generated between the source electrode S and the gate electrode G. Because.
Hereinafter, in the present embodiment, the first voltage stress α refers to the potential difference (α1) between the drain electrode D and the gate electrode G with reference to the potential V2 of the gate electrode G, and the source electrode S and the gate electrode G. Potential difference (α2).

  This completes the reset operation.

Next, the holding operation will be described.
As shown in FIGS. 9, 1, 6, 7, and 12-15, in the holding period t <b> 1 b subsequent to the reset period t <b> 1 a, the changeover switch Tr <b> 2 is switched to the off state while the output switch Tr <b> 3 is maintained in the off state. That is, the second gate voltage V3 at a level (off potential) that turns off the changeover switch Tr2 is applied to the gate electrode of the changeover switch Tr2.
Thereby, the holding capacitor C holds the written reset voltage V4. At the time described above, the application of the first gate voltage V2 to the gate electrode G of the light sensing unit Tr1 is maintained.

In the holding operation described above, application of the first voltage stress α to the light sensing unit Tr1 is maintained. The above is caused by the holding of the reset voltage V4 by the holding capacitor C. In the light sensing unit Tr1, the potential difference (Vout−v2) between the drain electrode D and the gate electrode G is between the source electrode S and the gate electrode G. This is because a potential difference (V1-V2) occurs.
This completes the holding operation.

Next, the light detection signal extraction operation will be described.
As shown in FIGS. 10 and 1, 6, 7, 12-15, in the light detection signal extraction period t 1 c following the holding period t 1 b, the output switch Tr 3 is switched to the on state while the changeover switch Tr 2 is maintained in the off state. . That is, a control signal for turning on the output switch Tr3 is applied to the output switch Tr3.

  Thereby, the reset voltage V4 stored in the storage capacitor C and the photodetection signal Vout based on the photodetection voltage output from the photosensor Tr1 are transmitted to the output switch Tr3 via the photodetection signal extraction line W. Needless to say, the value of the photodetection voltage changes according to the illuminance of the external light L applied to the channel layer CH.

  The processing unit 7 extracts the light detection signal Vout from the output switch Tr3 via the output buffer B. The processing unit 7 detects the light detection signal Vout, compares it with the information in the storage unit 6, and detects the illuminance information of the external light L. Then, the processing unit 7 controls the luminance level of the image according to the extracted light detection signal Vout. The brightness level of the image is controlled by controlling the amount of light emitted from the backlight unit 4.

Further, in the above case, the application of the first gate voltage V2 to the gate electrode G of the light sensing unit Tr1 is maintained.
In the above-described light detection signal extraction operation, the application of the first voltage stress α to the light sensing unit Tr1 is maintained. The above is caused by the holding of the reset voltage V4 by the holding capacitor C. In the light sensing unit Tr1, the potential difference (Vout−v2) between the drain electrode D and the gate electrode G is between the source electrode S and the gate electrode G. This is because a potential difference (V1-V2) occurs.

  Thus, the light detection signal extraction operation is completed.

Next, the non-light detection operation will be described.
As shown in FIGS. 11 and 1, 6, 7, and 12-15, in the non-light detection period t2 following the light detection signal extraction period t1c, the output switch Tr3 is turned off while the changeover switch Tr2 is kept off. Switch to. That is, a control signal for turning off the output switch Tr3 is applied to the output switch Tr3.

  Then, a non-reset voltage V4 having a polarity relatively different from the reset voltage V4 is applied to the source electrode of the changeover switch Tr2. At the same time, the second source voltage V1 having a polarity relatively different from that of the first source voltage V1 is applied to the source electrode S of the light sensing unit Tr1. At the same time, a second gate voltage V2 having a polarity relatively different from that of the first gate voltage V2 is applied to the gate electrode G of the light sensing unit Tr1.

  Thereby, in the above-described non-light detection operation, the second voltage stress β having a polarity relatively different from the first voltage stress α can be applied to the light sensing unit Tr1 to cancel the first voltage stress α. As described above, the potential difference (Vout (V1) −V2) between the drain electrode D and the gate electrode G and the potential difference (V1−V2) between the source electrode S and the gate electrode G in the light sensing unit Tr1 are This is because the polarity is opposite to that of the light detection period t1.

  The second voltage stress β refers to a potential difference (β1) between the drain electrode D and the gate electrode G and a potential difference (β2) between the source electrode S and the gate electrode G with reference to the potential V2 of the gate electrode G. .

  In order to cancel the first voltage stress α, in the light detection period t1 and the non-light detection period t2, the control mechanism 8 causes the time average value of the voltages to be applied to the gate electrode G, the source electrode S, and the drain electrode D of the light sensing unit Tr1. Are almost the same.

  Note that, as in this embodiment, it is not necessary to apply the second voltage stress β to the light sensing unit Tr1 in the entire non-light detection period t2, and the application of the second voltage stress β is equal to the first voltage stress α. It is only necessary to perform the period necessary for cancellation.

  Alternatively, the length of the non-light detection period t2 itself may be adjusted to a length necessary for canceling the first voltage stress α. The length of the non-light detection period t2 itself is preferably set to an optimum value according to voltage setting and transistor characteristics.

This completes the non-light detection operation.
The above-described light detection operation and non-light detection operation are alternately and continuously performed while the liquid crystal display panel 1 displays an image.

  According to the liquid crystal display device configured as described above and the method for controlling the liquid crystal display device, the first voltage stress α is applied to the light sensing unit Tr1 and the illuminance information of the external light L is detected during the light detection period t1. Then, the luminance level of the image is controlled according to the detected information, and the second voltage stress β is applied to the light sensing unit Tr1 in the non-light detection period t2 to cancel the first voltage stress α.

  As described above, by switching the polarity of the voltage stress one after another, the injection of carriers into the gate insulating film 17 and the movement of fixed charges in the light sensing portion Tr1 are suppressed. For this reason, the threshold shift of the light sensing unit Tr1 can be suppressed and the photocurrent characteristic shift can be greatly improved. In the case where the channel layer CH of the light sensing portion Tr1 is formed of amorphous silicon, it is particularly effective because charge injection easily occurs in the gate insulating film due to dangling bonds of amorphous silicon.

When the pixel 12 is formed, the photosensor 2 can be formed simultaneously with the same material. For this reason, it is possible to suppress the manufacturing cost, and consequently the increase in the product price.
As described above, it is possible to obtain a liquid crystal display device and a control method for the liquid crystal display device that can accurately sense the illuminance of the external light L and can control the luminance level of the display image.

  Next, another embodiment in which the display device and the control method of the display device of the present invention are applied to the liquid crystal display device and the control method of the liquid crystal display device will be described in detail. In this embodiment, the drive circuit 3 of the liquid crystal display device has a change-over switch Tr4. Other configurations of the liquid crystal display device are the same as those of the above-described embodiment, and the same portions are denoted by the same reference numerals and detailed description thereof is omitted.

  As shown in FIG. 16, the changeover switch Tr4 is formed of, for example, an N-channel transistor. The source electrode of the changeover switch Tr4 is grounded via the pad GND. The drain electrode of the changeover switch Tr4 is electrically connected between the output pad Pout and the output switch Tr3. The changeover switch Tr4 is turned on (conductive state) and turned off (non-conductive state) in response to a control signal from the processing unit 7.

Next, a method for controlling the liquid crystal display device will be described. In particular, a method for controlling the liquid crystal display device for detecting the illuminance of the external light L will be described. As shown in FIGS. 22 to 25, the operation for detecting the illuminance of the external light L includes a light detection operation performed during the light detection period t1, a non-light detection operation performed during the non-light detection period t2, and a standby period. It is divided into a standby operation performed at t3.
In this embodiment, while the liquid crystal display panel 1 displays an image, the light detection operation and the non-light detection operation are alternately and intermittently performed. In other words, the processing unit 7 detects the light detection signal Vout intermittently.

First, the reset operation will be described.
As shown in FIGS. 17 and 1, 7, 16, 22-25, in the reset period t 1 a, the driving circuit 3 supplies the first source voltage V 1 to the source electrode S of the light sensing unit Tr 1 and the first gate to the gate electrode G. A voltage V2 is applied.

At the same time, the drive circuit 3 applies a first gate voltage V3 at a level (ON potential) that makes the changeover switch Tr2 conductive (ON state) to the gate electrode of the changeover switch Tr2, and applies a high level to the source electrode of the changeover switch Tr2. The reset voltage V4, which is the first source voltage, is applied. The reset voltage V4 is sufficiently larger than the first source voltage V1.
The output switch Tr3 and the changeover switch Tr4 are supplied with a control signal of a level (off potential) for making the nonconductive state (off state) from the drive circuit 3.

  Thereby, the reset voltage V4 is applied to the light detection signal extraction line W from the changeover switch Tr2, and the voltage of the light detection signal extraction line W is reset. At the same time, the reset voltage V4 is stored in the storage capacitor C.

  In the above-described reset operation, the first voltage stress α is applied to the light sensing unit Tr1.

The first voltage stress α refers to a potential difference (α1) between the drain electrode D and the gate electrode G and a potential difference (α2) between the source electrode S and the gate electrode G with reference to the potential V2 of the gate electrode G. .
This completes the reset operation.

Next, the holding operation will be described.
As shown in FIG. 18 and FIGS. 1, 7, 16, and 22-25, in the holding period t1b following the reset period t1a, the changeover switch Tr2 is turned off while the output switch Tr3 and the changeover switch Tr4 are maintained in the off state. Switch. That is, the second gate voltage V3 at a level (off potential) that turns off the changeover switch Tr2 is applied to the gate electrode of the changeover switch Tr2.
Thereby, the holding capacitor C holds the written reset voltage V4. At the time described above, the application of the first gate voltage V2 to the gate electrode G of the light sensing unit Tr1 is maintained.

In the holding operation described above, application of the first voltage stress α to the light sensing unit Tr1 is maintained.
This completes the holding operation.

Next, the light detection signal extraction operation will be described.
As shown in FIGS. 19 and 1, 7, 16, 22-25, in the light detection signal extraction period t 1 c following the holding period t 1 b, the output switch Tr 3 is turned on while the change-over switch Tr 2 and change-over switch Tr 4 are maintained in the off state. Switch to the on state. That is, a control signal for turning on the output switch Tr3 is applied to the output switch Tr3.

  Thereby, the reset voltage V4 stored in the storage capacitor C and the photodetection signal Vout based on the photodetection voltage output from the photosensor Tr1 are transmitted to the output switch Tr3 via the photodetection signal extraction line W.

  The processing unit 7 extracts the light detection signal Vout from the output switch Tr3 via the output buffer B. The processing unit 7 detects the light detection signal Vout, compares it with the information in the storage unit 6, and detects the illuminance information of the external light L. Then, the processing unit 7 controls the luminance level of the image according to the extracted light detection signal Vout. The brightness level of the image is controlled by controlling the amount of light emitted from the backlight unit 4.

Further, in the above case, the application of the first gate voltage V2 to the gate electrode G of the light sensing unit Tr1 is maintained.
In the above-described light detection signal extraction operation, the application of the first voltage stress α to the light sensing unit Tr1 is maintained.
Thus, the light detection signal extraction operation is completed.

Next, the non-light detection operation will be described.
As shown in FIGS. 20 and 1, 7, 16, and 22-25, in the non-light detection period t <b> 2 that follows the light detection signal extraction period t <b> 1 c, the output switch Tr <b> 2 and the change-over switch Tr <b> 4 are maintained in the OFF state. Tr3 is switched off. That is, a control signal for turning off the output switch Tr3 is applied to the output switch Tr3.

  Then, a non-reset voltage V4 having a polarity relatively different from the reset voltage V4 is applied to the source electrode of the changeover switch Tr2. At the same time, the second source voltage V1 having a polarity relatively different from that of the first source voltage V1 is applied to the source electrode S of the light sensing unit Tr1. At the same time, a second gate voltage V2 having a polarity relatively different from that of the first gate voltage V2 is applied to the gate electrode G of the light sensing unit Tr1.

  Thereby, in the above-described non-light detection operation, the second voltage stress β having a polarity relatively different from the first voltage stress α can be applied to the light sensing unit Tr1 to cancel the first voltage stress α. As described above, the potential difference (Vout (V1) −V2) between the drain electrode D and the gate electrode G and the potential difference (V1−V2) between the source electrode S and the gate electrode G in the light sensing unit Tr1 are This is because the polarity is opposite to that of the light detection period t1.

  The second voltage stress β refers to a potential difference (β1) between the drain electrode D and the gate electrode G and a potential difference (β2) between the source electrode S and the gate electrode G with reference to the potential V2 of the gate electrode G. .

In order to cancel the first voltage stress α, in the light detection period t1 and the non-light detection period t2, the control mechanism 8 causes the time average value of the voltages to be applied to the gate electrode G, the source electrode S, and the drain electrode D of the light sensing unit Tr1. Are almost the same. The length of the non-light detection period t2 itself is adjusted to a length necessary for canceling the first voltage stress α. The length of the non-light detection period t2 is about several milliseconds to several tens of milliseconds.
This completes the non-light detection operation.

Next, the standby operation will be described. The standby period t3 has the same potential period t3a following the non-light detection period t2.
As shown in FIGS. 21 and 1, 7, 16, 22-27, in the same potential period t 3 a of the standby period t 3, the changeover switch Tr 4 is switched to the on state while the output switch Tr 3 is maintained in the off state. That is, a control signal for turning on the changeover switch Tr4 is applied to the changeover switch Tr4.

  Then, the same voltage is applied to the gate electrode G and the source electrode S of the light sensing unit Tr1 and the gate electrode and the source electrode of the changeover switch Tr2. In this embodiment, since the pad GND is grounded (voltage V5 = 0V), a voltage of 0V is applied to the gate electrode G and source electrode S of the light sensing unit Tr1 and the gate electrode and source electrode of the changeover switch Tr2, respectively. Apply. That is, the source voltage V1, the gate voltage V2, the gate voltage V3, and the source voltage V4 are set to 0V.

  For this reason, the gate electrode G, the source electrode S, and the drain electrode D of the light sensing unit Tr1 and the gate electrode, the source electrode, and the drain electrode of the changeover switch Tr2 have the same potential.

Subsequently, in the standby period t3 after the end of the equipotential period t3a, the changeover switch Tr4 is switched to the on state. As described above, voltage stress is not applied to the light sensing unit Tr1 during the standby period t3. In this embodiment, voltage stress is not applied to the changeover switch Tr2, the output switch Tr3, and the changeover switch Tr4 during the standby period t3. The length of the waiting period t3 is about 1 second to several seconds.
Thus, the standby operation ends.
In the above-described waiting period t3, the control mechanism 8 matches the time average values of the voltages applied to the gate electrode G, the source electrode S, and the drain electrode D of the light sensing unit Tr1. Further, in the light detection period t1, the non-light detection period t2, and the standby period t3, the control mechanism 8 substantially matches the time average values of the voltages applied to the gate electrode G, the source electrode S, and the drain electrode D of the light sensing unit Tr1. I am letting.

  The above-described light detection operation, non-light detection operation, and standby operation are repeatedly performed in order while the liquid crystal display panel 1 displays an image.

  According to the liquid crystal display device configured as described above and the method for controlling the liquid crystal display device, the first voltage stress α is applied to the light sensing unit Tr1 and the illuminance information of the external light L is detected during the light detection period t1. Then, the luminance level of the image is controlled according to the detected information, and the second voltage stress β is applied to the light sensing unit Tr1 in the non-light detection period t2 to cancel the first voltage stress α.

  As described above, driving by changing the polarity of the voltage stress suppresses the injection of carriers into the gate insulating film 17 and the movement of fixed charges in the light sensing portion Tr1. For this reason, the photocurrent characteristic shift of the light sensing unit Tr1 can be greatly improved.

In the standby period t3, the control mechanism 8 matches the time average values of the voltages applied to the gate electrode G, the source electrode S, and the drain electrode D of the light sensing unit Tr1. For this reason, the photocurrent characteristic shift of the light sensing part Tr1 can be further improved.
As described above, it is possible to obtain a liquid crystal display device and a control method for the liquid crystal display device that can accurately sense the illuminance of the external light L and can control the luminance level of the display image.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  For example, as shown in FIG. 28, the control mechanism 8 may alternately apply voltage stresses having different polarities to the light sensing unit Tr1 during the standby period t3. Thereby, in the standby period t3, the time average values of the voltages applied to the gate electrode G, the source electrode S, and the drain electrode D of the light sensing unit Tr1 may be substantially matched.

  The light sensing unit Tr1, the changeover switch Tr2, the output switch Tr3, the changeover switch Tr4, and the TFT 13 may be P-channel transistors. In this case, the above-described effects can be obtained by adjusting the voltage applied to the gate electrode of each transistor.

  Further, even if the amorphous silicon used in the thin film transistor is replaced with polysilicon, the same effect as described above can be obtained.

  The changeover switch Tr2, the output switch Tr3, the changeover switch Tr4, and the TFT 13 have a transistor structure, but are not limited to this and may have a switching function.

The change-over switch Tr2 is provided in the optical sensor 2, but is not limited to this, and may be provided in the drive circuit 3 (control mechanism 8).
The present invention is not limited to the liquid crystal display device and the control method of the liquid crystal display device, and can be applied to the display device and the control method of the display device.

1 is a schematic diagram showing a liquid crystal display device according to an embodiment of the present invention. Sectional drawing which shows the said liquid crystal display device. FIG. 2 is a plan view showing the liquid crystal display panel shown in FIG. 1. FIG. 4 is an enlarged plan view showing a part of the array substrate shown in FIGS. 1 to 3. FIG. 5 is a cross-sectional view taken along line AA of the liquid crystal display device illustrated in FIG. 4. The circuit block diagram which shows the optical sensor and control mechanism of the said liquid crystal display device. Sectional drawing which shows the light detection part of the said optical sensor. The equivalent circuit which shows the optical sensor and control mechanism in reset operation | movement of the optical detection operation | movement of the said liquid crystal display device. The equivalent circuit which shows the optical sensor and control mechanism in the holding | maintenance operation | movement of the optical detection operation | movement of the said liquid crystal display device. The equivalent circuit which shows the optical sensor and control mechanism in the optical detection signal extraction operation | movement of the optical detection operation of the said liquid crystal display device. The equivalent circuit which shows the optical sensor and control mechanism in the non-light detection operation | movement of the said liquid crystal display device. 4 is a timing chart showing changes in a source voltage, a gate voltage, and a light detection signal (output voltage) during a light detection period and a non-light detection period according to an embodiment of the present invention. 13 is a timing chart individually showing changes in a source voltage, a gate voltage, and a light detection signal (output voltage) in the light detection period and the non-light detection period shown in FIG. 12. 6 is a timing chart showing a change in potential difference between a light detection signal (output voltage) and a gate voltage and a difference between a source voltage and a gate voltage in the light detection period and the non-light detection period. FIG. 15 is a timing chart individually showing changes in the potential difference between the light detection signal (output voltage) and the gate voltage and the source voltage and the gate voltage in the light detection period and the non-light detection period shown in FIG. 14. The circuit block diagram which shows the optical sensor and control mechanism of the liquid crystal display device which concern on other embodiment of this invention. FIG. 17 is an equivalent circuit showing a light sensor and a control mechanism in a reset operation of the light detection operation of the liquid crystal display device shown in FIG. 16. 17 is an equivalent circuit showing a photosensor and a control mechanism in the holding operation of the light detection operation of the liquid crystal display device shown in FIG. 17 is an equivalent circuit showing a photosensor and a control mechanism in a photodetection signal extraction operation of the photodetection operation of the liquid crystal display device shown in FIG. The equivalent circuit which shows the optical sensor and control mechanism in the non-light detection operation | movement of the liquid crystal display device shown in FIG. 17 is an equivalent circuit showing an optical sensor and a control mechanism in a standby operation of the liquid crystal display device shown in FIG. The timing chart which shows the change of the source voltage in the light detection period of another embodiment of this invention, a non-light detection period, and a standby period, a gate voltage, and a photon detection signal (output voltage). The timing chart which shows separately the change of the source voltage in the light detection period shown in FIG. 22, a non-light detection period, and a standby period, a gate voltage, and a light detection signal (output voltage). 24 is a timing chart showing changes in the potential difference between the light detection signal (output voltage) and the gate voltage and the difference between the source voltage and the gate voltage in the light detection period, the non-light detection period, and the standby period shown in FIGS. FIG. 25 is a timing chart individually showing changes in the potential difference between the light detection signal (output voltage) and the gate voltage and the potential difference between the source voltage and the gate voltage in the light detection period, the non-light detection period, and the standby period shown in FIG. 24. 25 is a timing chart shown in FIG. 24, and particularly shows a state in which the potential difference between the light detection signal (output voltage) and the gate voltage and the potential difference between the source voltage and the gate voltage are constant during the standby period. FIG. 26 is a timing chart shown in FIG. 25, specifically showing a state in which the potential difference between the light detection signal (output voltage) and the gate voltage and the potential difference between the source voltage and the gate voltage are constant in the standby period. Timings indicating changes in the potential difference between the light detection signal (output voltage) and the gate voltage, and the potential difference between the source voltage and the gate voltage in the light detection period, the non-light detection period, and the standby period according to the modification of the other embodiment of the present invention 9 is a timing chart showing a state in which a potential difference between a light detection signal (output voltage) and a gate voltage, and a potential difference between a source voltage and a gate voltage are changed, particularly in a standby period.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display panel, 2 ... Optical sensor, 3 ... Drive circuit, 4 ... Backlight unit, 6 ... Memory | storage part, 7 ... Processing part, 7a ... Timing controller, 8 ... Control mechanism, 10 ... Array substrate, 12 ... Pixel , 13 ... TFT, 14 ... auxiliary capacitance element, 25 ... pixel electrode, 30 ... counter substrate, 40 ... liquid crystal layer, 50 ... flexible cable, 60 ... power source, 70 ... cable, d1 ... first direction, d2 ... second Direction, R1... Display area, Tr1... Photosensitive part, G... Gate electrode, S... Source electrode, D... Drain electrode, CH ... Channel layer, C ... Retention capacitor, Tr2. Changeover switch, W ... light detection signal extraction line, B ... output buffer, V1, V2, V3, V4 ... voltage, L ... external light, t1 ... light detection period, t1a ... reset period, t1b ... holding period t1c ... light detection signal extraction period, t2 ... non-light detection period, t3 ... waiting period, t3a ... same potential period, alpha ... first voltage stress, beta ... second voltage stress.

Claims (15)

A display panel for displaying images,
A light sensing unit provided in the display panel and having a transistor structure;
During the light detection period, a first voltage stress is applied to the light sensing unit, information on the illuminance of external light is detected, and the luminance level of the image is controlled according to the detected information. And a control mechanism that applies a second voltage stress to the light sensing unit to cancel the first voltage stress.   The display device according to claim 1, wherein the control mechanism substantially matches time average values of voltages applied to the gate electrode, the source electrode, and the drain electrode of the light sensing unit.   The control mechanism alternately applies the first voltage stress in the light detection period and the second voltage stress in the non-light detection period, and waits between the non-light detection period and the light detection period. The display device according to claim 1, wherein time average values of voltages applied to the gate electrode, the source electrode, and the drain electrode of the light sensing unit are substantially matched during the period.   The display device according to claim 3, wherein the control mechanism applies the same voltage to the gate electrode, the source electrode, and the drain electrode of the light sensing unit during the standby period.   The display device according to claim 3, wherein the control mechanism alternately applies voltage stresses having different polarities to the light sensing unit alternately during the standby period.   The control mechanism alternately applies the first voltage stress in the light detection period and the second voltage stress in the non-light detection period, and the light detection period, the non-light detection period, and the non-light detection 2. The display device according to claim 1, wherein time average values of voltages applied to the gate electrode, the source electrode, and the drain electrode of the light sensing unit are substantially matched in a standby period between the period and the light detection period.   The light sensing unit is disposed opposite to the gate electrode through a gate electrode, an insulating film, a channel layer formed of amorphous silicon, a source electrode electrically connected to one region of the channel layer, and the The display device according to claim 1, further comprising a drain electrode electrically connected to the other region of the channel layer. A display panel for displaying images,
A channel layer provided in the display panel, disposed opposite to the gate electrode through an insulating film, and formed of amorphous silicon; a source electrode electrically connected to one region of the channel layer; and A light sensing portion having a drain electrode electrically connected to the other region of the channel layer and changing conductivity between the source electrode and the drain electrode in accordance with a luminance level of external light received by the channel layer; ,
A light detection signal extraction line connected to the drain electrode of the light sensing unit;
A changeover switch connected to the photodetection signal extraction line, for outputting a reset voltage to the photodetection signal extraction line, and for switching whether to reset the voltage of the photodetection signal extraction line;
A storage unit connected to the light detection signal extraction line and storing a reset voltage output to the light detection signal extraction line;
An output switch connected to the photodetection signal extraction line and for switching whether to output a photodetection signal based on a reset voltage stored in the storage unit and a photodetection voltage output from the photosensor;
A control mechanism,
The control mechanism is
In the reset period, a first gate voltage is applied to the gate electrode of the light sensing unit, the changeover switch is turned on, the output switch is turned off, and the light is output from the changeover switch to the light. Applying a reset voltage to the detection signal extraction line, resetting the voltage of the light detection signal extraction line, storing the reset voltage in the storage unit, and applying a first voltage stress to the light sensing unit;
In the holding period following the reset period, the changeover switch is switched to a non-conductive state, the reset voltage is held in the storage unit, and the application of the first gate voltage to the gate electrode and the light sensing unit are performed. Maintaining the application of the first voltage stress,
In the light detection signal extraction period following the holding period, the output switch is switched to a conductive state, and the light detection signal based on the reset voltage stored in the storage unit and the light detection voltage output from the light sensing unit is output. The luminance level of the image is controlled in accordance with the photodetection signal taken out from the switch, and the application of the first gate voltage to the gate electrode and the application of the first voltage stress to the light sensing unit are maintained. ,
In a non-light detection period following a light detection period including the reset period, the holding period, and the light detection signal extraction period, the output switch is switched to a non-conductive state, and the first gate voltage is applied to the gate electrode of the light sensing unit. A display device that applies a second gate voltage having a relatively different polarity, and applies a second voltage stress having a polarity that is relatively different from a first voltage stress to the light sensing unit to cancel the first voltage stress. In a method for controlling a display device, comprising: a display panel for displaying an image; and a light sensing unit provided in the display panel and having a transistor structure.
During the light detection period, a first voltage stress is applied to the light sensing unit, information on the illuminance of external light is detected, and the luminance level of the image is controlled according to the detected information,
A control method for a display device, wherein a second voltage stress is applied during a non-light detection period to cancel the first voltage stress.   The method of controlling a display device according to claim 9, wherein time average values of voltages applied to the gate electrode, the source electrode, and the drain electrode of the light sensing unit are substantially matched. Alternately applying the first voltage stress in the light detection period and the second voltage stress in the non-light detection period;
The display according to claim 9, wherein time average values of voltages applied to the gate electrode, the source electrode, and the drain electrode of the light sensing unit are substantially matched in a standby period between the non-light detection period and the light detection period. Control method of the device.   The method of claim 11, wherein the same voltage is applied to the gate electrode, the source electrode, and the drain electrode of the light sensing unit during the standby period.   The method of controlling a display device according to claim 11, wherein voltage stresses having different polarities are applied alternately to the light sensing unit during the standby period. Alternately applying the first voltage stress in the light detection period and the second voltage stress in the non-light detection period;
Time average values of voltages to be applied to the gate electrode, the source electrode, and the drain electrode of the light sensing unit in the light detection period, the non-light detection period, and the standby period between the non-light detection period and the light detection period. The display device control method according to claim 9, wherein the display devices are substantially matched. A display panel for displaying an image, a channel layer provided on the display panel, arranged opposite to the gate electrode via a gate electrode and an insulating film, and electrically connected to one region of the channel layer formed of amorphous silicon And a drain electrode electrically connected to the other region of the channel layer, and conductivity between the source electrode and the drain electrode according to a luminance level of external light received by the channel layer. A photo-sensing unit that changes the nature, a photo-detection signal extraction line connected to the drain electrode of the photo-sensing unit, and a photo-detection signal extraction line connected to the photo-detection signal output line to output a reset voltage to the photo-detection signal extraction line; A selector switch for switching whether to reset the voltage of the light detection signal extraction line, and the light detection signal extraction line connected to the light detection signal extraction line A storage unit for storing the reset voltage output to the optical detection signal, and a photodetection signal connected to the photodetection signal take-out line and based on the reset voltage stored in the storage unit and the photodetection voltage output from the photodetection unit. In a control method of a display device comprising an output switch for switching whether to output,
In the reset period, a first gate voltage is applied to the gate electrode of the light sensing unit, the changeover switch is turned on, the output switch is turned off, and the light is output from the changeover switch to the light. Applying a reset voltage to the detection signal extraction line, resetting the voltage of the light detection signal extraction line, storing the reset voltage in the storage unit, and applying a first voltage stress to the light sensing unit;
In the holding period following the reset period, the changeover switch is switched to a non-conductive state, the reset voltage is held in the storage unit, and the application of the first gate voltage to the gate electrode and the light sensing unit are performed. Maintaining the application of the first voltage stress,
In the light detection signal extraction period following the holding period, the output switch is switched to a conductive state, and the light detection signal based on the reset voltage stored in the storage unit and the light detection voltage output from the light sensing unit is output. The luminance level of the image is controlled in accordance with the photodetection signal taken out from the switch, and the application of the first gate voltage to the gate electrode and the application of the first voltage stress to the light sensing unit are maintained. ,
In a non-light detection period following a light detection period including the reset period, the holding period, and the light detection signal extraction period, the output switch is switched to a non-conductive state, and the first gate voltage is applied to the gate electrode of the light sensing unit. Control of a display device that applies a second gate voltage having a relatively different polarity, and applies a second voltage stress having a polarity different from that of the first voltage stress to the light sensing unit to cancel the first voltage stress. Method.

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