CN112287845A - Display panel and display device - Google Patents
Display panel and display device Download PDFInfo
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- CN112287845A CN112287845A CN202011193947.0A CN202011193947A CN112287845A CN 112287845 A CN112287845 A CN 112287845A CN 202011193947 A CN202011193947 A CN 202011193947A CN 112287845 A CN112287845 A CN 112287845A
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
- G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
- G06V40/12—Fingerprints or palmprints
- G06V40/13—Sensors therefor
- G06V40/1318—Sensors therefor using electro-optical elements or layers, e.g. electroluminescent sensing
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
- H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
- H03K17/60—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being bipolar transistors
Abstract
The application discloses a display panel and a display device. The display panel comprises a fingerprint identification unit, wherein the fingerprint identification unit comprises a photosensitive module, a reset module, a signal generation module, a switch module and a storage module; the control end of the reset module is electrically connected with the reset control signal wire, the first end of the reset module is electrically connected with the first voltage end, and the second end of the reset module is electrically connected with the first node; the signal generation module comprises a first transistor, a control end of the first transistor is electrically connected with a first node, a first end of the first transistor is electrically connected with a first voltage end, and a second end of the first transistor is electrically connected with a first end of the switch module; the first end of the reset module and the first end of the first transistor receive voltage signals through a first voltage end, and the voltage signals are periodic positive voltage and periodic negative voltage. According to the embodiment of the application, the sensitivity of fingerprint identification can be ensured.
Description
Technical Field
The application relates to the technical field of display, in particular to a display panel and a display device.
Background
Fingerprints are inherent and unique biological features, and electronic devices with fingerprint identification functions are increasing. Taking a mobile phone as an example, fingerprint identification can be applied to various scenes such as unlocking, payment and the like. In the optical fingerprint recognition scheme, fingerprint recognition is generally performed by a fingerprint recognition circuit including a transistor and a photodiode, but if there is a shift in the threshold voltage of the transistor, the sensitivity of fingerprint recognition is lowered.
Disclosure of Invention
The application provides a display panel and a display device, which can ensure the sensitivity of fingerprint identification.
On one hand, the embodiment of the application provides a display panel, which comprises a fingerprint identification unit, wherein the fingerprint identification unit comprises a photosensitive module, a reset module, a signal generation module, a switch module and a storage module; the control end of the reset module is electrically connected with the reset control signal wire, the first end of the reset module is electrically connected with the first voltage end, and the second end of the reset module is electrically connected with the first node; the signal generation module comprises a first transistor, a control end of the first transistor is electrically connected with a first node, a first end of the first transistor is electrically connected with a first voltage end, and a second end of the first transistor is electrically connected with a first end of the switch module; the control end of the switch module is electrically connected with the output control signal wire, and the second end of the switch module is used as the output end of the fingerprint identification unit; a first electrode of the photosensitive module is electrically connected with the first node, and a second electrode of the photosensitive module is electrically connected with the second voltage end; the first end of the storage module is electrically connected with the first node, and the second end of the storage module is electrically connected with the second electrode of the photosensitive module; the first end of the reset module and the first end of the first transistor receive voltage signals through a first voltage end, and the voltage signals are periodic positive voltage and periodic negative voltage.
In another aspect, embodiments of the present application provide a display device including the display panel according to any one of the foregoing aspects of the present application.
According to the display panel and the display device provided by the embodiment of the application, the fingerprint identification unit comprises a photosensitive module, a reset module, a signal generation module, a switch module and a storage module, the signal generation module comprises a first transistor, a first end of the reset module is electrically connected with a first voltage end, a second end of the reset module is electrically connected with a first node, and a control end of the first transistor is electrically connected with the first node, namely, the control end of the first transistor is indirectly electrically connected with the first voltage end through the reset module. The first end of the reset module receives the positive voltage and the negative voltage of the periodic signal through the first voltage end, so that the control end of the first transistor periodically works under the positive voltage and the negative voltage, the threshold voltage of the first transistor is prevented from being positively floated when the control end of the first transistor works under the positive voltage for a long time, and the sensitivity of fingerprint identification is further ensured.
Drawings
Other features, objects, and advantages of the present application will become apparent from the following detailed description of non-limiting embodiments thereof, when read in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof, and which are not to scale.
Fig. 1 is a schematic top view illustrating a display panel according to an embodiment of the present disclosure;
FIG. 2 is a schematic diagram of a circuit structure of a fingerprint identification unit according to an embodiment of the present application;
FIG. 3 is a schematic diagram of a circuit structure of a fingerprint identification unit according to another embodiment of the present application;
FIG. 4 is a timing diagram of the fingerprint recognition unit shown in FIG. 3;
fig. 5 is a schematic diagram illustrating a driving method of a display panel according to an embodiment of the present disclosure;
fig. 6 is a schematic diagram illustrating a driving method of a display panel according to another embodiment of the present disclosure;
FIG. 7 is a schematic top view of a display panel according to another embodiment of the present application;
FIG. 8 is a schematic diagram of a circuit structure of a fingerprint identification unit according to another embodiment of the present application;
FIG. 9 is a timing diagram of the fingerprint recognition unit shown in FIG. 8;
FIG. 10 is a schematic top view of a display panel according to another embodiment of the present application;
fig. 11 is a schematic structural diagram of a display device according to an embodiment of the present application.
Detailed Description
Features and exemplary embodiments of various aspects of the present application will be described in detail below, and in order to make objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application. It will be apparent to one skilled in the art that the present application may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present application by illustrating examples thereof.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.
It will be understood that when a layer, region or layer is referred to as being "on" or "over" another layer, region or layer in describing the structure of the component, it can be directly on the other layer, region or layer or intervening layers or regions may also be present. Also, if the component is turned over, one layer or region may be "under" or "beneath" another layer or region.
Fig. 1 is a schematic top view illustrating a display panel according to an embodiment of the present disclosure. Fig. 2 is a schematic circuit diagram of a fingerprint identification unit according to an embodiment of the present application. As shown in fig. 1 and 2, the display panel 100 according to the embodiment of the present disclosure includes a fingerprint identification unit 10, a reset control signal line 21, and an output control signal line 22. A plurality of fingerprint recognition units 10 may be distributed in an array.
The fingerprint identification unit 10 includes a signal generation module 11, a reset module 12, a switch module 13, a photosensitive module 14 and a storage module 15. The control terminal of the reset module 12 is electrically connected to the reset control signal line 21, the first terminal of the reset module 12 is electrically connected to the first voltage terminal VDD, and the second terminal of the reset module 12 is electrically connected to the first node N1. The signal generating module 11 includes a first transistor T1, a control terminal (gate) of the first transistor T1 is electrically connected to the first node N1, a first terminal of the first transistor T1 is electrically connected to the first voltage terminal VDD, and a second terminal of the first transistor T2 is electrically connected to the first terminal of the switching module 13. The control end of the switch module 13 is electrically connected to the output control signal line 22, and the second end of the switch module 13 is used as the output end of the fingerprint identification unit. The first electrode of the light sensing module 14 is electrically connected to the first node N1, and the second electrode of the light sensing module 14 is electrically connected to the second voltage terminal Vbias. A first terminal of the memory module 15 is electrically connected to the first node N1, and a second terminal of the memory module 15 is electrically connected to the second electrode of the photosensitive module 14. The first terminal of the reset module 12 and the first terminal of the first transistor T1 receive a voltage signal through the first voltage terminal VDD, and the voltage signal is a periodic positive voltage and a periodic negative voltage.
The control terminal of the reset module 12 receives a reset control signal through the reset control signal line 21, and transmits a voltage signal received from the first voltage terminal VDD to the first node N1 for resetting under the control of the reset control signal, so as to prevent the fingerprint identification unit from being interfered by a previous fingerprint identification process. The light sensing module 14 is used for sensing a light signal and changing the potential of the first node N1, and the light sensing module 14 may include a photodiode, which generates different photocurrents when receiving different light intensities. The signal generating module 11 is configured to generate a fingerprint identification signal according to the potential of the first node N1. The control end of the switch module 13 receives the output control signal through the output control signal line, and outputs the fingerprint identification signal under the control of the output control signal. The storage module 15 is used for storing the voltage signal of the first node N1.
For example, fig. 3 shows a schematic circuit structure diagram of a fingerprint identification unit according to another embodiment of the present application. As shown in fig. 3, the reset module 12 includes a second transistor T2, the switch module 13 includes a third transistor T3, the light sensing module 14 includes a photodiode D, and the memory module 15 includes a first capacitor C1.
A control terminal (gate) of the second transistor T2 is electrically connected to the reset control signal line 21, a first terminal of the second transistor T2 is electrically connected to the first voltage terminal VDD, and a second terminal of the second transistor T2 is electrically connected to the first node N1. A control terminal (gate) of the third transistor T3 is electrically connected to the output control signal line 22, and a second terminal of the third transistor T3 serves as an output terminal Vout of the fingerprint recognition unit. The cathode of the photodiode D is electrically connected to the first node N1, and the anode of the photodiode D is electrically connected to the second voltage terminal Vbias. The first capacitor C1 is connected in parallel with the photodiode D.
Illustratively, fig. 4 shows a timing diagram of the fingerprint recognition unit shown in fig. 3. The Reset control signal line 21 transmits a Reset control signal (Reset signal in fig. 4), and the output control signal line 22 transmits an output control signal (Select signal in fig. 4). The fingerprint recognition process of the index recognition unit may include: in the first period T1, the Reset signal is at a high level, the second transistor T2 is turned on, and the voltage at the first level voltage terminal (VDD in fig. 4) is transmitted to the first node N1 through the second transistor T2, so that the N1 node is Reset. In the second stage T2, the third stage T3 and the fourth stage T4, the second transistor T2 is turned off, the photodiode D generates a leakage current due to light irradiation, the first capacitor C1 discharges, the potential of the node N1 gradually decreases, the first transistor T1 operates in a linear region, the magnitude of the leakage current is proportional to the potential of the node N1, in the second stage T2, the third transistor T3 is turned on, the voltage provided by the first voltage terminal VDD flows to the output control signal line 22 through the first transistor T1 and the third transistor T3, the degree of turning on of the first transistor T1 determines the potential on the output control signal line 22, the degree of turning on of the first transistor T1 is determined by the voltage of the node N1, that is the potential of the node N1 determines the potential on the output control signal line 22, the voltage value read by the second stage T2 to the output control signal line 22 is V1, and the voltage read by the fourth stage T4 is V2, the V1-V2 is determined by the magnitude of the leakage current of the photodiode D, and the magnitude of the leakage current of the photodiode D is determined by the intensity of the light received by the photodiode D, so that the V2 is different under different light intensities, and during fingerprint detection, the light intensities reflected to the photodiode D are different in different fingerprint areas, so that fingerprint identification can be realized by detecting the V1-V2 corresponding to the light sensing units at each position in the fingerprint identification area.
An insulating layer, such as SiNx, is disposed between the gate and the active layer of the transistor, and many defects are present at the interface between the active layer and the insulating layer. The inventors of the present application have found that if a positive voltage is applied to the gate of the first transistor T1 for a long time, that is, the voltage on the first voltage terminal VDD is always a positive voltage, charges are accumulated on the interface of the active layer and the insulating layer of the first transistor T1, an electric field formed by the accumulated charges is superimposed on the gate voltage, causing the threshold voltage Vth of the first transistor T1 to be positive shifted (i.e., Vth to be increased), the voltage output from the second terminal of the first transistor T1 (e.g., the source of the first transistor T1) is limited by the voltage of the first node N1 and the threshold voltage of the first transistor T1, and in the case where the voltage of the first voltage terminal and the voltage of the first node N1 are inconvenient, the voltage Vsource output from the second terminal of the first transistor T1 is smaller, causing the voltage modulation ratio K of the fingerprint identification unit to be reduced, where K is Vsource/VDD, resulting in a decrease in fingerprint recognition sensitivity.
In the embodiment of the present application, the first terminal of the reset module 12 and the first terminal of the first transistor T1 receive the voltage signal through the first voltage terminal VDD, and the voltage signal is a periodic positive voltage and a periodic negative voltage. The gate of the first transistor T1 is indirectly electrically connected to the first voltage terminal VDD through the reset module 12, that is, the gate of the first transistor T1 receives a periodic positive voltage and a periodic negative voltage through the first voltage terminal VDD, so that the gate voltage of the first transistor T1 is periodically switched between the positive voltage and the negative voltage, and the gate voltage of the first transistor T1 is inverted between the positive voltage and the negative voltage, thereby canceling charges accumulated at an interface between an active layer and an insulating layer of the first transistor T1, avoiding positive drift of a threshold voltage caused by long-time operation of the gate of the first transistor T1 at the positive voltage, further avoiding reduction of a voltage modulation ratio of the fingerprint identification unit, and ensuring sensitivity of fingerprint identification.
In some alternative embodiments, as shown in fig. 1, the display panel 100 may include a display area AA and a non-display area NA surrounding the display area AA, and the display area AA is provided with a plurality of pixel units (not shown). The fingerprint recognition unit 10 may be disposed in the display area AA of the display panel to thereby implement the off-screen fingerprint recognition. The display panel 100 may further include a control module 20. For example, the control module 20 may be disposed in the non-display area NA of the display panel. The control module 20 may be a driver chip (IC), and may directly bond the driver chip to the non-display area NA, or may bond the driver chip to the display panel through a Flexible Printed Circuit (FPC), which is not limited in this application.
The control module 20 can be used to control a plurality of pixel units of the display panel to refresh the display screen and control the fingerprint identification unit to perform fingerprint identification. In the continuous fingerprint capturing, the gate voltage of the first transistor T1 may be periodically switched between the positive voltage and the negative voltage in a "frame interpolation" manner.
Fig. 5 is a schematic diagram illustrating a driving method of a display panel according to an embodiment of the present disclosure. For example, as shown in fig. 1 to 5, when the fingerprint identification unit performs the fingerprint identification operation, the control module 20 may control the fingerprint identification unit to perform the fingerprint identification operation in a first period of the first period, and control the plurality of pixel units to perform the display screen refresh in a second period of the first period. The first terminal of the reset module 12 and the first terminal of the first transistor T1 receive a negative voltage through the first voltage terminal VDD during at least one first period and receive a positive voltage during other first periods. The first period comprises a first time period and a second time period, and the second time period is positioned between two adjacent first time periods. The first period is the interval time between the refreshing of the pixel units when the fingerprint identification unit displays one frame of picture and the refreshing of the pixel units when the fingerprint identification unit displays the next frame of picture.
On one hand, when fingerprint identification is needed, refreshing of a display picture and fingerprint identification operation are carried out in a time-sharing mode, namely, a mode of temporarily reducing display refreshing frequency is adopted, and the influence of a display signal on fingerprint identification can be avoided.
On the other hand, the gate of the first transistor T1 is indirectly electrically connected to the first voltage terminal VDD through the Reset module 12, and taking the Reset module 12 including the second transistor T2 as an example, when the Reset signal in fig. 5 is at a high level, the voltage on the first voltage terminal VDD is transmitted to the first node N1 through the second transistor T2, the th nodeA voltage V at a node N1N1Equal to the voltage on the first voltage terminal VDD. Since the gate of the first transistor T1 receives a negative voltage from the first voltage terminal VDD through the second transistor T2 during at least one first period, and the gate of the first transistor T1 receives a positive voltage from the first voltage terminal VDD through the second transistor T2 during other first periods, the gate voltage of the first transistor T1 is switched between the positive and negative voltages, thereby canceling charges accumulated on the interface between the active layer and the insulating layer of the first transistor T1, avoiding positive drift of the threshold voltage caused by long-time operation of the gate of the first transistor T1 at the positive voltage, further avoiding reduction of the voltage modulation ratio of the fingerprint identification unit, and ensuring the sensitivity of fingerprint identification.
In some alternative embodiments, the first terminal of the reset module 12 and the first terminal of the first transistor T1 may receive a negative voltage through the first voltage terminal VDD for a plurality of first periods and receive a positive voltage for other first periods.
In some alternative embodiments, the first terminal of the reset module 12 and the first terminal of the first transistor T1 may receive a negative voltage through the first voltage terminal VDD only during one first period and receive a positive voltage during the other first periods.
For example, as shown in fig. 5, the first terminal of the reset module 12 and the first terminal of the first transistor T1 may receive a negative voltage through the first voltage terminal VDD only during the nth first period and receive a positive voltage during other first periods, where N is an integer greater than or equal to 1.
Still taking the example that the Reset module 12 includes the second transistor T2, in the first period except the nth first period, when the Reset signal in fig. 5 is at the high level, the positive voltage at the first voltage terminal VDD is transmitted to the first node N1 through the second transistor T2, and the voltage V at the first node N1 is transmitted to the first node N1N1Equal to the positive voltage on the first voltage terminal VDD. When the Reset signal in fig. 5 is low, V is applied by the photodiode D and the first capacitor C1N1Is gradually decreased and VN1Is more than or equal to 0. Wherein the gate of the first transistor T1 is electrically connected to the first node N1, and the gate voltage of the first transistor T1 is connected to the voltage V of the first node N1N1The same is true.
In the nth first period, when the Reset signal in fig. 5 is at a high level, the negative voltage at the first voltage terminal VDD is transmitted to the first node N1 through the second transistor T2, and the voltage V of the first node N1 is transmitted to the first node N1N1Equal to the negative voltage on the first voltage terminal VDD. When the Reset signal in fig. 5 is low, V is applied by the photodiode D and the first capacitor C1N1Is gradually increased and VN1Less than or equal to 0. Wherein the gate of the first transistor T1 is electrically connected to the first node N1, and the gate voltage of the first transistor T1 is connected to the voltage V of the first node N1N1The same is true.
Since the first transistor T1 is turned off when the gate voltage of the first transistor T1 is a negative voltage, the fingerprint identification unit cannot output the fingerprint identification signal. Therefore, the first terminal of the reset module 12 and the first terminal of the first transistor T1 can receive a negative voltage through the first voltage terminal VDD only during one first period, thereby ensuring fingerprint identification efficiency while avoiding positive drift of the threshold voltage of the first transistor T1.
In some alternative embodiments, N may be greater than or equal to 5. In principle, the fingerprint can be successfully identified in a first time period, the response speed of the fingerprint identification and multiple fingerprint identifications set in a special environment are comprehensively considered (namely, the fingerprint identification needs to be carried out in multiple first time periods), and under the condition that N is larger than or equal to 5, the grid of the first transistor T1 can be ensured to receive negative voltage after the sub-fingerprint identification is completed as much as possible, so that the fingerprint identification efficiency is prevented from being influenced.
In some alternative embodiments, as shown in fig. 6, when the fingerprint identification unit does not perform the fingerprint identification operation, the control module 20 is further configured to control the plurality of pixel units to perform the display screen refresh in the second period. The second period is the interval time between the refreshing of the pixel units when the fingerprint identification unit displays one frame of picture and the refreshing of the pixel units when the fingerprint identification unit displays the next frame of picture, and the second period is smaller than the first period. The first terminal of the reset module 12 and the first terminal of the first transistor T1 receive a negative voltage through the first voltage terminal during one first period adjacent to the second period and receive a positive voltage during the other first periods. That is, the gate of the first transistor T1 receives a negative voltage during the last first period and receives a positive voltage during the other first periods.
On the one hand, when fingerprint identification is not needed, the refresh rate is improved, and the display panel is switched to the normal display module, so that the display quality is improved. For example, the duration of the second period may be equal to the duration of the second period in the first period.
On the other hand, the gate of the first transistor T1 receives a negative voltage in the last first period, which can further ensure that the fingerprint is successfully recognized, and further avoid affecting fingerprint recognition efficiency.
In some alternative embodiments, as shown in fig. 6, the duration of the second period may be equal to the duration of the second period in the first period, so as to reduce the difficulty in controlling the pixel unit to perform the light emitting display.
In some alternative embodiments, the first terminal of the reset module 12 and the first terminal of the first transistor T1 receive a low voltage through the first voltage terminal for one first period after every M first periods, and receive a positive voltage for the other first periods; wherein M is an integer greater than or equal to 1. That is, the gate of the first transistor T1 regularly receives positive and negative voltages, so that charges accumulated at the interface between the active layer and the insulating layer of the first transistor T1 can be better offset, and the problem of positive drift of the threshold voltage caused by long-time operation of the gate of the first transistor T1 at a positive voltage can be better avoided.
In some alternative embodiments, the total duration of time that the first terminal of the reset module 12 and the first terminal of the first transistor T1 receive the positive voltage during the fingerprint identification operation of the fingerprint identification unit is greater than or equal to the total duration of time that the first terminal of the first transistor T1 receives the negative voltage. That is, the total duration of time that the gate of the first transistor T1 receives a positive voltage through the first voltage terminal VDD is greater than or equal to the total duration of time that the first voltage terminal VDD thereof receives a negative voltage. As described above, since the first transistor T1 is turned off when the gate voltage of the first transistor T1 is a negative voltage, the fingerprint identification unit cannot output the fingerprint identification signal. Therefore, controlling the total duration of time that the gate of the first transistor T1 receives the positive voltage to be greater than or equal to the total duration of time that it receives the negative voltage can avoid affecting fingerprint recognition efficiency.
In some alternative embodiments, in the case that the total duration of the positive voltage received by the first terminal of the reset module 12 and the first terminal of the first transistor T1 is greater than or equal to the total duration of the negative voltage, the positive voltage received by the first terminal of the reset module 12 and the first terminal of the first transistor T1 is less than or equal to the absolute value of the negative voltage received by the first terminal of the reset module 12 and the first terminal of the first transistor T1. That is, the positive voltage received by the gate of the first transistor T1 through the first voltage terminal VDD is less than or equal to the absolute value of the negative voltage received by the first voltage terminal VDD thereof. Taking the positive voltage at the first voltage terminal VDD as 5V for example, the negative voltage at the first voltage terminal VDD can be-6V, -7V, etc. Since the total duration of the positive voltage received by the first terminal of the reset module 12 and the first terminal of the first transistor T1 is greater than or equal to the total duration of the negative voltage received by the first terminal of the first transistor T1, and the duration of the positive voltage received by the gate of the first transistor T1 is greater than or equal to the duration of the negative voltage received by the gate of the first transistor T1, the release of the charges accumulated at the interface between the active layer and the insulating layer of the first transistor T1 can be accelerated by controlling the positive voltage received by the gate of the first transistor T1 through the first voltage terminal VDD to be less than or equal to the absolute value of the negative voltage received by the first voltage terminal VDD, and the problem of positive drift of the threshold voltage caused by long-time operation of the gate of the first transistor T1 at the.
Fig. 7 is a schematic top view illustrating a display panel according to an embodiment of the present application. Fig. 8 is a schematic circuit diagram of a fingerprint identification unit according to another embodiment of the present application. In some alternative embodiments, as shown in fig. 7 and 8, the display panel may further include a gate control signal line 23. The fingerprinting unit 10 may also include a gating module 16. The gating module 16 is electrically connected between the first node N1 and the first electrode of the light sensing module 14; the control terminal of the gating module 16 is electrically connected to the gating control signal line 23, the first terminal of the gating module 16 is electrically connected to the first electrode of the light sensing module 14, and the second terminal of the gating module 16 is electrically connected to the first node N1. The difference from fig. 3 is that the light sensing module 14 changes the potential of the first node N1 under the control of the gating module 16.
Illustratively, the gate module 16 includes a fourth transistor T4, a control terminal (gate) of the fourth transistor T4 is electrically connected to the gate control signal line, a first terminal of the fourth transistor T4 is electrically connected to the first electrode of the light sensing module 14, and a second terminal of the fourth transistor T4 is electrically connected to the first node N1.
Fig. 9 is a timing diagram of the fingerprint recognition unit shown in fig. 8. As shown in fig. 9, the operation process of the fingerprint identification circuit is as follows: in the first phase T11, the high level provided by the Reset control signal line (Reset signal in fig. 9) controls the second transistor T2 to be turned on, the high level provided by the gate control signal line (Tx signal in fig. 9) controls the fourth transistor T4 to be turned on, and the voltage at the first voltage terminal is transmitted to the first node N1 through the second transistor T2, so that the potential of the first node N1 is Reset; in the second stage T12, the fourth transistor T4 is turned off, the photodiode D generates a leakage current due to light irradiation, and the level of the first terminal of the fourth transistor T4 is determined by the cathode of the photodiode D; in the third stage T13, the high level provided by the output control signal line (Select signal in fig. 9) turns on the third transistor T3, and the circuit outputs the reset level; in the fourth stage T14, the low level provided by the reset control signal line controls the second transistor T2 to be turned off, the high level provided by the gate control signal line controls the fourth transistor T4 to be turned on again, the second transistor T2 is kept turned off, the level of the first terminal of the fourth transistor T4 is transferred to the first node N1, the third transistor T3 is kept turned on in the fifth stage T15, and the output signal line outputs the fingerprint identification signal. The timing chart shown in fig. 9 is merely an example, and is not intended to limit the present application.
In the embodiment of the present application, although the gating module is added, the gate of the first transistor T1 is indirectly electrically connected to the first voltage terminal VDD through the reset module 12. The first terminal of the reset module 12 and the first terminal of the first transistor T1 receive voltage signals through the first voltage terminal VDD, and the voltage signals are periodic positive voltage and negative voltage, that is, the gate of the first transistor T1 receives periodic positive voltage and negative voltage through the first voltage terminal VDD, so that the gate voltage of the first transistor T1 is periodically switched between positive voltage and negative voltage, and the gate voltage of the first transistor T1 is inverted between positive voltage and negative voltage, thereby canceling charges accumulated on the interface between the active layer and the insulating layer of the first transistor T1, avoiding positive drift of threshold voltage caused by long-time operation of the gate of the first transistor T1 at positive voltage, further avoiding reduction of voltage modulation ratio of the fingerprint identification unit, and ensuring sensitivity of fingerprint identification.
Fig. 10 is a schematic top view illustrating a display panel according to another embodiment of the present disclosure. In some optional embodiments, the display panel includes a display area AA and a non-display area NA, the display area AA is provided with a plurality of pixel units, and the fingerprint identification unit 10 is located in the non-display area NA. For example, the fingerprint identification unit 10 is located at the home key of the display panel, or the fingerprint identification unit 10 is disposed on a side of the display panel away from the light emitting surface. The fingerprint identification unit is arranged in the non-display area of the display panel, so that the light emitting area of the display panel can be avoided, and the display quality of the display panel is ensured.
The application also provides a display device which comprises the display panel provided by the application. Referring to fig. 11, fig. 11 is a schematic structural diagram of a display device according to an embodiment of the present disclosure. Fig. 11 provides a display device 1000 including the display panel 100 according to any of the above embodiments of the present application. The embodiment of fig. 11 is only an example of a mobile phone, and the display device 1000 is described, but it should be understood that the display device provided in the embodiment of the present application may be other display devices having a display function, such as a computer, a television, and a vehicle-mounted display device, and the present application is not limited thereto. The display device provided in the embodiment of the present application has the beneficial effects of the display panel provided in the embodiment of the present application, and specific reference may be specifically made to the specific description of the display panel in each of the above embodiments, which is not repeated herein.
In accordance with the embodiments of the present application as described above, these embodiments are not exhaustive and do not limit the application to the specific embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the application and its practical application, to thereby enable others skilled in the art to best utilize the application and its various modifications as are suited to the particular use contemplated. The application is limited only by the claims and their full scope and equivalents.
Claims (11)
1. A display panel is characterized by comprising a fingerprint identification unit, wherein the fingerprint identification unit comprises a photosensitive module, a reset module, a signal generation module, a switch module and a storage module;
the control end of the reset module is electrically connected with a reset control signal line, the first end of the reset module is electrically connected with a first voltage end, and the second end of the reset module is electrically connected with a first node;
the signal generation module comprises a first transistor, a control end of the first transistor is electrically connected with the first node, a first end of the first transistor is electrically connected with the first voltage end, and a second end of the first transistor is electrically connected with a first end of the switch module;
the control end of the switch module is electrically connected with the output control signal wire, and the second end of the switch module is used as the output end of the fingerprint identification unit;
a first electrode of the photosensitive module is electrically connected with the first node, and a second electrode of the photosensitive module is electrically connected with a second voltage end;
the first end of the storage module is electrically connected with the first node, and the second end of the storage module is electrically connected with the second electrode of the photosensitive module;
the first end of the reset module and the first end of the first transistor receive voltage signals through the first voltage end, and the voltage signals are periodic positive voltage and periodic negative voltage.
2. The display panel according to claim 1, wherein the display panel comprises a display area, the display area is provided with a plurality of pixel units and the fingerprint identification unit, and the display panel further comprises a control module;
the control module is used for controlling the fingerprint identification unit to perform fingerprint identification operation in a first time period in the first period and controlling the plurality of pixel units to perform display screen refreshing in a second time period in the first period when the fingerprint identification unit performs fingerprint identification operation;
the first end of the reset module and the first end of the first transistor receive negative voltage through the first voltage end in at least one first period and receive positive voltage in other first periods;
wherein the first period comprises one first time period and one second time period, and one second time period is positioned between two adjacent first time periods; the first period is the interval time between the refreshing of the pixel units when one frame of picture is displayed and the refreshing of the pixel units when the next frame of picture is displayed when the fingerprint identification unit performs fingerprint identification operation.
3. The display panel according to claim 2, wherein the first terminal of the reset module and the first terminal of the first transistor receive a negative voltage through the first voltage terminal in an nth of the first periods and receive a positive voltage in the other first periods;
wherein N is an integer greater than or equal to 1.
4. The display panel according to claim 3, wherein N is greater than or equal to 5.
5. The display panel according to claim 2, wherein the control module is further configured to control the plurality of pixel units to perform display screen refresh in a second period when the fingerprint identification unit does not perform the fingerprint identification operation;
the first terminal of the reset module and the first terminal of the first transistor receive a negative voltage through the first voltage terminal in one of the first periods adjacent to the second period and receive a positive voltage in the other first periods;
the second period is an interval time between when the plurality of pixel units start to refresh when displaying one frame of picture and when displaying the next frame of picture when the fingerprint identification unit does not perform the fingerprint identification operation, and the second period is smaller than the first period.
6. The display panel according to claim 2, wherein the first terminal of the reset module and the first terminal of the first transistor receive a low voltage through the first voltage terminal for one of the first periods after every M first periods and receive a positive voltage for the other first periods;
wherein M is an integer greater than or equal to 1.
7. The display panel of claim 1, wherein a total duration of the first terminal of the reset module and the first terminal of the first transistor receiving a positive voltage through the first voltage terminal during the fingerprint identification operation of the fingerprint identification unit is greater than or equal to a total duration of the first terminal receiving a negative voltage through the first voltage terminal.
8. The display panel according to claim 7, wherein a positive voltage received by the first terminal of the reset module and the first terminal of the first transistor through the first voltage terminal is less than or equal to an absolute value of a negative voltage received by the first terminal of the reset module and the first terminal of the first transistor through the first voltage terminal.
9. The display panel of claim 1, wherein the fingerprint recognition unit further comprises a gating module;
the gating module is electrically connected between the first node and the first electrode of the photosensitive module;
the control end of the gating module is electrically connected with a gating control signal line, the first end of the gating module is electrically connected with the first electrode of the photosensitive module, and the second end of the gating module is electrically connected with the first node.
10. The display panel according to claim 1, wherein the display panel comprises a display area and a non-display area, the display area is provided with a plurality of pixel units, and the fingerprint identification unit is located in the non-display area.
11. A display device characterized by comprising the display panel according to any one of claims 1 to 10.
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| CN112287845B (en) | 2022-09-27 |
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