KR102220733B1 - Liquid display device including fingerprinting device - Google Patents

Abstract

The present invention relates to a liquid crystal display device including a fingerprint recognition device, comprising: a display unit disposed in a plurality of pixel areas formed at intersections of a gate line and a data line; And a sensing unit disposed on a portion or all of the plurality of pixel regions, and including a sensing TFT, a Schottky photodiode, and a sensing capacitor. The Schottky photodiode may be stacked on the sensing TFT.

Description

Liquid crystal display device including a fingerprint recognition device {LIQUID DISPLAY DEVICE INCLUDING FINGERPRINTING DEVICE}

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device including a fingerprint recognition element.

In general, a liquid crystal display displays an image by adjusting the light transmittance of a liquid crystal having dielectric anisotropy using an electric field. To this end, a liquid crystal display device includes a liquid crystal panel in which display pixels are arranged in a matrix form, and a backlight unit that irradiates light to the liquid crystal panel.

Meanwhile, in the recent liquid crystal display device, in addition to the function of displaying an image, various functions have been added, and as a part of this, research on a liquid crystal display device including a fingerprint recognition element is actively progressing.

In general, a liquid crystal display device having a fingerprint recognition element recognizes a fingerprint using an optical sensing method or a capacitive method. For example, in a liquid crystal display device that recognizes a fingerprint using an optical sensing method, as shown in FIG. 1, a photo sensor 120 is provided as a fingerprint sensor in the liquid crystal panel 110. The photo sensor 120 senses light emitted from the backlight unit 100 and reflected by the finger 120 to recognize a fingerprint.

However, a conventional liquid crystal display device including a fingerprint recognition device has the following problems.

First, as shown in FIG. 2, the liquid crystal display reduces the area of each of the first to third sub-pixels SP1 to SP3 provided in a unit pixel of a general liquid crystal display, and thus the fourth sub-pixel SP4 An area is secured, and the photo sensor 120 is disposed in the fourth sub-pixel SP4. Such a liquid crystal display has a problem in that an aperture ratio decreases due to a reduction in the area of the first to third sub-pixels SP1 to SP3. In addition, when the area of the fourth sub-pixel SP4 is reduced to minimize the reduction in the aperture ratio, there is a problem in that the fingerprint recognition sensitivity is deteriorated due to the reduction in the sensing area.

Second, in the liquid crystal display, as shown in FIG. 3, the fingerprint recognition element is externally disposed in the non-display area, but the recent liquid crystal display is in a trend to reduce the area of the non-display area. There is a large space limitation to place the device.

The present invention has been conceived to solve the above-described problems, and it is an object of the present invention to provide a liquid crystal display device including a fingerprint recognition element in which an aperture ratio is improved and a fingerprint recognition sensitivity is improved.

In addition to the technical problems of the present invention mentioned above, other features and advantages of the present invention will be described below or will be clearly understood by those of ordinary skill in the art from such technology and description.

A liquid crystal display according to the present invention for achieving the above-described technical problem includes: a display unit disposed in a plurality of pixel areas formed at intersections of gate lines and data lines; And a sensing unit disposed on a portion or all of the plurality of pixel regions, and including a sensing TFT, a Schottky photodiode, and a sensing capacitor. The Schottky photodiode may be stacked on the sensing TFT.

According to the means for solving the above problems, the present invention has the following effects.

That is, the present invention is configured such that the Schottky photodiode provided in the sensing unit is stacked on the sensing TFT, thereby improving the aperture ratio and improving the fingerprint recognition sensitivity.

In addition to the effects of the present invention mentioned above, other features and advantages of the present invention will be described below or will be clearly understood by those of ordinary skill in the art from such technology and description.

1 is a diagram illustrating a general liquid crystal display device for recognizing a fingerprint using an optical sensing method.
2 is a diagram illustrating an external fingerprint recognition device.
3 is a diagram illustrating a decrease in an aperture ratio due to the provision of a photo sensor.
4 is a configuration diagram of a liquid crystal display according to an exemplary embodiment of the present invention.
5 is an equivalent circuit diagram of the pixel area P shown in FIG. 4.
6 is a driving waveform diagram of the sensing unit 14 shown in FIG. 5.
7 is a cross-sectional view of the sensing unit 14 according to the first embodiment of the present invention.
8 is a cross-sectional view illustrating a sensing unit 14 according to a second embodiment of the present invention.
9 is a diagram illustrating generation and movement of electron (-) and hole (+) pairs in the intrinsic semiconductor layer (i).
10 is a diagram illustrating an effect of increasing the work function of the upper electrode.

The meaning of the terms described in this specification should be understood as follows. Singular expressions should be understood as including plural expressions unless clearly defined differently in context, and terms such as "first" and "second" are used to distinguish one element from other elements, The scope of rights should not be limited by these terms. It is to be understood that terms such as "comprise" or "have" do not preclude the presence or addition of one or more other features or numbers, steps, actions, components, parts, or combinations thereof. The term “at least one” is to be understood as including all possible combinations from one or more related items. For example, the meaning of “at least one of the first item, the second item, and the third item” means 2 among the first item, the second item, and the third item as well as each of the first item, the second item, or the third item. It means a combination of all items that can be presented from more than one. The term "on" is meant to include not only a case where a certain structure is formed directly on the upper surface of another structure, but also a case where a third structure is interposed between these elements.

Hereinafter, preferred examples of a backlight unit and a liquid crystal display device using the same according to the present invention will be described in detail with reference to the accompanying drawings.

4 is a configuration diagram of a liquid crystal display according to an exemplary embodiment of the present invention. 5 is an equivalent circuit diagram of the pixel area P shown in FIG. 4. 6 is a driving waveform diagram of the sensing unit 14 shown in FIG. 5.

Referring to FIG. 4, a liquid crystal display according to an embodiment of the present invention includes a liquid crystal panel 10, a backlight unit 70, a timing controller 50, a gate driver 30, a data driver 40, and a readout circuit. (20), and a host (60).

The present invention is configured such that the Schottky photodiode PD provided in the sensing unit 14 is stacked on the sensing TFT T2, thereby improving the aperture ratio and improving the fingerprint recognition sensitivity.

The liquid crystal panel 10 is filled between an upper substrate and a lower substrate, an upper polarizing layer disposed above the upper substrate, a lower polarizing layer disposed below the lower substrate, and the upper substrate and the lower substrate. And a liquid crystal layer. The upper substrate may include a color filter, a common electrode, and a black matrix. The common electrode may be provided on the lower substrate according to a liquid crystal driving method of the liquid crystal panel 10. In the lower substrate, a plurality of gate lines GL and a plurality of data lines DL are formed, and a pixel region P is formed at an intersection between the gate line GL and the data line DL. Further, the lower substrate further includes a plurality of reset lines RST and a plurality of read lines RW arranged parallel to the gate line GL. A display unit 12 and a sensing unit 14 are disposed in the pixel area P. Here, the sensing unit 14 may be disposed on a part or all of the plurality of pixel areas P.

As shown in FIG. 5, the display unit 12 includes a switching TFT T1, a liquid crystal cell Clc, and a storage capacitor Cst.

The switching TFT T1 is turned on according to a scan signal provided from the gate line GL to supply a data voltage provided from the data line DL to the pixel electrode of the liquid crystal cell Clc.

The liquid crystal cell Clc includes a pixel electrode connected to the switching TFT T1, a common electrode to which a common voltage is applied, and a liquid crystal layer.

The storage capacitor Cst charges a voltage difference between the data voltage applied to the pixel electrode and the common voltage applied to the common electrode to maintain a constant voltage of the liquid crystal cell Clc.

As shown in FIG. 5, the sensing unit 14 includes a sensing TFT (T2), a sensing capacitor (SC), and a Schottky photodiode (PD). The sensing unit 14 is disposed between the first and second data lines DL1 and DL2 adjacent to each other, and is connected to the reset line RST and the read line RW.

The sensing TFT T2 connects the first and second data lines DL1 and DL2 to each other according to the voltage state of the set node N1. The sensing TFT T2 allows the voltage of the readout node N2 connected to the second data line DL2 to follow the voltage charged in the set node N1 in a source follow form in the fingerprint sensing mode. . Meanwhile, it is preferable that the threshold voltage of the sensing TFT T2 is greater than the threshold voltage of the switching TFT T1 provided in the display unit 12. This is to prevent the sensing TFT T2 from being turned on and connecting the first and second data lines DL1 and DL2 to each other in the display mode.

The sensing capacitor SC is connected to each of the read line RW and the set node N1 to form a capacitance. In the fingerprint sensing mode, the sensing capacitor SC increases the voltage charged in the set node N1 according to the read signal provided from the read line RW.

The Schottky photodiode PD is connected to each of the reset line RST and the set node N1. The Schottky photodiode PD converts light emitted from the backlight unit 70 and reflected through the user's fingerprint into a photocurrent in the reverse direction, thereby discharging the voltage of the set node N1. At this time, the amount of the photocurrent generated from the Schottky photodiode PD varies depending on whether the object reflecting the light is a ridge or valley of a fingerprint. Here, the first photocurrent due to the light reflected from the valley is greater than the second photocurrent due to the light reflected from the ridge.

The present invention is configured such that the Schottky photodiode PD provided in the sensing unit 14 is stacked on the sensing TFT T2. In the present invention, the area of the sensing unit 14 can be reduced compared to a general liquid crystal display device constituting the sensing unit by disposing a PIN-type photodiode in an area separate from the sensing TFT. That is, according to the present invention, by configuring the photodiode in the Schottky manner and stacking the Schottky photodiode on the upper part of the sensing TFT (T2), a separate area prepared for arranging the photodiode separately from the sensing TFT can be deleted. have. Accordingly, according to the present invention, the area of the sensing unit itself is reduced, the area of the display unit is relatively increased, and the aperture ratio is improved.

In addition, according to the present invention, since the photodiode is configured in a Schottky manner, it is possible to improve fingerprint recognition sensitivity compared to a general liquid crystal display device using a PIN type photodiode. This is because the reaction sensitivity of the Schottky photodiode is higher than that of the PIN type photodiode due to the characteristics of the Schottky photodiode.

A structure in which the above-mentioned Schottky photodiode PD is stacked on the sensing TFT T2 will be described later in detail with reference to FIGS. 7 and 8.

Meanwhile, a switching unit T3 is formed at an end of the second data line DL2 to switch the precharging signal PRE and supply it to the second data line DL2 in the fingerprint sensing mode. To this end, the switching unit T3 includes a pre-charging TFT T3 that supplies a pre-charging signal PRE to the second data line DL2 in response to a sensing mode signal SS provided from the host 60. It can be configured. Here, the precharging signal PRE serves to sequentially precharge the readout nodes N2 of each sensing unit 14 connected to the second data line DL2 in the fingerprint sensing mode. Further, the precharging signal PRE serves to initialize the voltage of the read-out node N2 after a read-out period in which the voltage of the read-out node N2 of each sensing unit 14 is read. To this end, the precharging signal PRE has a form of an AC signal having a width smaller than that of the scan signal.

Hereinafter, a method of driving the sensing unit 14 will be described with reference to FIGS. 5 and 6.

First, as a reset signal is applied to the reset line RST, a forward bias is applied to the Schottky photodiode PD. Accordingly, the voltage of the set node N1 is raised to the reset voltage.

Subsequently, the set node N1 raised to the reset voltage is discharged until a first scan signal is applied to the read line RW. Specifically, when the voltage of the set node N1 rises to the reset voltage, the Schottky photodiode PD enters a reverse bias state. Accordingly, the Schottky photodiode PD flows a reverse current according to the light emitted from the backlight unit 70 and reflected through the user's fingerprint, and the voltage of the set node N1 is discharged. In this case, the voltage of the set node N1 is discharged more when the object in contact with the liquid crystal panel 10 is a valley than when the object in contact with the liquid crystal panel 10 is a ridge.

Subsequently, when a read signal is applied to the read line RW, the voltage of the set node N1 is increased due to the coupling phenomenon of the sensing capacitor SC. Accordingly, the sensing TFT T2 is turned on. Then, since the first data line DL1 maintains the high potential voltage VDD, the voltage of the readout node N2 connected to the second data line DL2 is the gate voltage of the sensing TFT T2, That is, the voltage charged in the set node N1 is followed in the form of a source follower. At this time, the voltage charged in the readout node N2 is output to the readout circuit 20 as fingerprint information of the user.

The period during which the sensing unit 14 outputs sensing information to the read-out circuit 20 as a read signal is applied to the read line RW is a pre-charge period P1, a read-out period P2, and a reset period ( It can be classified and defined as P3).

In the pre-charge period P1, the switching unit T3 applies a pre-charging signal PRE to the second data line DL2. Then, the readout node N2 is pre-charged to a specific voltage level.

In the read-out period P2, the voltage of the read-out node N2 is increased following the voltage of the set node N1 according to the turn-on of the sensing TFT T2, and is output to the read-out circuit 20. do.

In the reset period P3, the voltage of the read-out node N2 is initialized as the pre-charging signal PRE falls to maintain a low potential voltage.

The backlight unit 70 is disposed on the rear side of the liquid crystal panel 10. The backlight unit 70 uniformly irradiates light to the liquid crystal panel 10 including a plurality of light sources that are turned on and off by the backlight driver. The backlight unit 70 may be implemented as a direct type backlight unit 70 or an edge type backlight unit 70. The light source of the backlight unit 70 may include any one or two or more types of light sources of HCFL (Hot Cathode Fluorescent Lamp), CCFL (Cold Cathode Fluorescent Lamp), EEFL (External Electrode Fluorescent Lamp), and LED (Light Emitting Diode). have.

The timing controller 50 operates in a display mode or a fingerprint sensing mode in response to a mode signal MODE provided from the host 60.

In the display mode, the timing controller 50 receives digital video data of an input image from the host 60 through an interface such as a Low Voltage Differential Signaling (LVDS) interface and a Transition Minimized Differential Signaling (TMDS) interface, and aligns them. Then, it is transmitted to the data driver 40. In addition, the timing controller 50 receives the synchronization signal SYNC from the host 60 and outputs a gate control signal and a data control signal for controlling driving timings of the gate driver 30 and the data driver 40. Here, the synchronization signal SYNC includes a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a data enable signal (Data Enable, DE), and a main clock MCLK.

In the fingerprint sensing mode, the timing controller 50 controls the data driver 40 to apply a high potential voltage VDD to the first data lines DL1 connected to the sensing unit 14. Further, the timing controller 50 controls the gate driver 40 to sequentially apply reset signals to the plurality of reset lines RST and sequentially apply the read signals to the plurality of read lines RW.

The gate driver 30 sequentially generates a scan signal according to the gate control signal GCS provided from the timing controller 50, and shifts the swing voltage of the output into a gate-on voltage and a gate-off voltage. The scan signal output from the gate driver 30 is sequentially supplied to the gate lines GL in synchronization with the data voltage output from the data driver 40. Here, the gate-on voltage is a voltage equal to or higher than the threshold voltage of the switching TFT T1 provided in the display unit 12, and the gate-off voltage is a voltage lower than the threshold voltage of the switching TFT T1. The gate driver 30 is integrated in the form of an integrated circuit (IC), and is connected to the gate lines GL through a TAB (Tape Automated Bonding) process, or a non-display area of the lower substrate through a GIP (Gate In Panel) process. It may be formed directly on the NA and connected to the gate lines GL.

In addition, the gate driver 40 sequentially applies a reset signal to a plurality of reset lines RST and sequentially applies a read signal to a plurality of read lines RW in the fingerprint processing mode. The gate driver 40 sequentially applies the reset signal to the plurality of reset lines RST, and sequentially applies the read signal to the plurality of read lines RW. However, the gate driver 40 alternately outputs a reset signal and a read signal.

The data driver 40 samples the digital video data RGB provided from the timing controller 50 according to the data control signal provided from the timing controller 50, and then sequentially latches the digital video data RGB. Further, the data driver 40 converts the digital video data RGB into a positive or negative gamma compensation voltage to generate a data voltage. In addition, the data driver 40 supplies the converted data voltage to the data lines DL in synchronization with the scan signal output from the gate driver 30. The data driver 40 may be integrated in an IC form and connected to the data lines DL through a chip on glass (COG) process or a TAB process. Further, the data driver 40 may be integrated in the timing controller 50 and implemented as a single IC with the timing controller 50.

In addition, in the fingerprint sensing mode, the data driver 40 applies a high potential voltage VDD to the first data lines DL1 connected to the sensing unit 14.

The read-out circuit 20 is activated in the fingerprint sensing mode, reads signals output from the sensing unit 14 of the liquid crystal panel 10 to generate sensing data (SDATA), and supplies it to the host 60 do. To this end, the readout circuit 20 is electrically connected to each of the second data lines DL2 connected to the sensing unit 14, and digitally converts the current or voltage value output from the second data line DL2. The signal is converted into sensing data SDATA and supplied to the host 60.

The host 60 transmits digital video data RGB of an input image and synchronization signals SYNCs SYNC to the timing controller 50 through an interface such as an LVDS interface or a TMDS interface. In addition, the host 60 transmits a mode signal MODE indicating a display mode and a fingerprint sensing mode to the timing controller 50. In addition, the host 60 analyzes the sensing data SDATA provided from the readout circuit 20 according to a preset fingerprint sensing algorithm to calculate fingerprint information.

7 is a cross-sectional view of the sensing unit 14 according to the first embodiment of the present invention. 8 is a cross-sectional view illustrating a sensing unit 14 according to a second embodiment of the present invention.

Referring to FIGS. 5 and 7, a cross-sectional view of the sensing unit 14 according to the first embodiment is as follows.

The sensing TFT T2 includes a gate electrode 82, a source electrode 84, a drain electrode 85, a semiconductor layer 83, and an ohmic contact layer 79.

The gate electrode 82 is formed on the lower substrate 80, and one or two or more of aluminum (Al), aluminum neodium (AlNd), molybdenum (Mo), chromium (Cr), and copper (Cu) It is formed of metal or alloy material.

The source electrode 84 and the drain electrode 85 are disposed on the gate electrode 82 with the gate insulating layer 95 interposed therebetween, and are spaced apart from each other. Here, the source electrode 84 is connected to a first data line DL1, and the drain electrode 85 is connected to a second data line DL2. The source electrode 84 and the drain electrode 85 are formed of a metal selected from molybdenum (Mo), chromium (Cr), copper (Cu), or a laminate or alloy thereof.

The semiconductor layer 83 forms a channel between the source electrode 84 and the drain electrode 85. To this end, the semiconductor layer 83 is formed of pure amorphous silicon.

The ohmic contact layer 79 is disposed between the source electrode 84 and the drain electrode 85 and the semiconductor layer 83. The ohmic contact layer 79 is formed of impurity amorphous silicon.

The Schottky photodiode PD is disposed in a region overlapping the gate electrode 82 of the sensing TFT T2, and is connected to the gate electrode 82 and the upper electrode 89, respectively. Such a Schottky photodiode PD is sequentially stacked between the gate electrode 82 as a cathode electrode, the upper electrode 89 as an anode electrode, the gate electrode 82, and the upper electrode 89. An intrinsic semiconductor layer 87 and an impurity semiconductor layer 88 are included.

The intrinsic semiconductor layer 87 penetrates the interlayer insulating layer 96 and the gate insulating layer 95 to cover the first contact hole exposing the gate electrode 82 of the sensing TFT T2, thereby covering the sensing TFT T2. Is connected to the gate electrode 82 of the.

The impurity semiconductor layer 88 is stacked on the intrinsic semiconductor layer 87 and is connected to the upper electrode 89. The impurity semiconductor layer 88 may be doped with n+ type impurities.

The upper electrode 89 is stacked on the impurity semiconductor layer 88 and penetrates the interlayer insulating layer 96 and the gate insulating layer 95 to cover a second contact hole exposing the reset line RST. As a result, it is connected to the reset line RST. The upper electrode 89 is formed on the same layer as the pixel electrode provided in the display unit 12, and indium tin oxide (ITO), tin oxide (TO), indium tin zinc oxide (Indium tin oxide) Tin Zinc Oxide: ITZO), Indium Zinc Oxide (Indium Zinc Oxide: IZO) may be formed of a light-transparent electrode material such as.

The sensing capacitor SC is formed by overlapping the gate electrode 82 and the auxiliary electrode 91 of the sensing TFT T2 with each other with a gate insulating layer 95 interposed therebetween. The auxiliary electrode 91 is formed on the same layer as the source electrode 84 and the drain electrode 85 and penetrates the gate insulating layer 95 to cover a third contact hole exposing the read line RW. Is connected to the read line RW.

Referring to FIGS. 5 and 8, a cross-sectional view of the sensing unit 14 according to the second embodiment is as follows.

The sensing TFT (T2) includes a semiconductor layer 83, a gate electrode 82, a source electrode 84, and a drain electrode 85.

The semiconductor layer 83 includes an active region 83b formed of polysilicon, and a source region 83a and a drain region 83c doped with impurities positioned on both sides of the active region 83b. do.

The gate electrode 82 is formed on the first insulating layer 95 covering the semiconductor layer 83.

The source electrode 84 is formed on the second insulating layer 96 covering the gate electrode 82 and penetrates the second insulating layer 96 to expose the source region 83a. By covering the hole, it is connected to the source region 83a.

The source electrode 85 is formed on the second insulating layer 96 covering the gate electrode 82 and penetrates the second insulating layer 96 to expose the drain region 83c. By covering the hole, it is connected to the drain region 83c.

The Schottky photodiode PD is disposed in a region overlapping with the gate electrode 82 of the sensing TFT T2, and the gate electrode 82 and the upper electrode 89 are respectively Is connected to. The Schottky photodiode (PD) is an intrinsic layer sequentially stacked between the gate electrode 82 as a cathode electrode, the upper electrode 89 as an anode electrode, the gate electrode 82, and the upper electrode 89 A semiconductor layer 87 and an impurity semiconductor layer 88 are included.

The intrinsic semiconductor layer 87 is connected to the gate electrode 82 of the sensing TFT T2 through the first auxiliary electrode 98. The first auxiliary electrode 98 penetrates the second insulating layer 96 and covers the third contact hole exposing the gate electrode 82 of the sensing TFT (T2). Connected.

The impurity semiconductor layer 88 is stacked on the intrinsic semiconductor layer 87 and is connected to the upper electrode 89. The impurity semiconductor layer 88 may be doped with n+ type impurities.

The upper electrode 89 is stacked on the impurity semiconductor layer 88 and passes through the third insulating layer 97 and the second insulating layer 96 to expose the reset line RST. It is connected to the reset line RST by covering the hole.

The sensing capacitor SC is formed by overlapping the read line RW and the second auxiliary electrode 92 with the second insulating layer 96 therebetween. The second auxiliary electrode 92 is formed on the second insulating layer 96 and is connected to the first auxiliary electrode through a connection line (not shown).

In the first and second embodiments, it has been described that the semiconductor layers of the sensing TFT T2 are made of an amorphous semiconductor and a polycrystalline semiconductor, respectively, but the present invention is not limited thereto. That is, in the sensing TFT (T2) of the present invention, the semiconductor layer may be formed of any one material selected from an amorphous semiconductor, a polycrystalline semiconductor, an oxide semiconductor, and an organic semiconductor.

On the other hand, in the present invention, the upper electrode 89 is treated with O2 plasma so that the work function of the upper electrode 89 becomes larger than the work function of the pixel electrode provided in the display unit 12, or the upper electrode 89 The electrode 89 is formed of indium zinc oxide (IZO). This is to improve fingerprint sensing sensitivity by increasing a difference in reverse current according to a case where an object in contact with the liquid crystal panel 10 for fingerprint sensing is a ridge of a fingerprint and a valley of a fingerprint. Unlike the above, in the present invention, the upper electrode 89 and the pixel electrode may be formed of the same material on the same layer. Unlike the above, in the present invention, the upper electrode 89 and the pixel electrode may be formed of the same material on the same layer. In this case, it is preferable that the upper electrode 89 is formed of a metal (at least 4.9 eV or more) of a material having a work function greater than 4.7 eV.

Specifically, as shown in FIG. 9, when external light flows into the Schottky photodiode PD, an electron (-) and a hole (+) pair are generated in the intrinsic semiconductor layer (i), and the generated electrons (- ) And hole (+) pairs move to the anode electrode ITO and the cathode electrode Al, respectively. If, as shown in Fig. 10, the object in contact with the liquid crystal panel 10 is a ridge of a fingerprint (aka, in a dark state), the anode electrode ITO of the Schottky photodiode PD has a large work function. Relatively, the movement of holes (+) from the impurity semiconductor layer 88 to the anode electrode ITO is blocked. On the other hand, when the object in contact with the liquid crystal panel 10 is the valley of the fingerprint (aka photo illuminated state), the anode electrode (ITO) and the cathode electrode (ITO) and the cathode electrode (in the band gap) increase due to an increase in the ionized acceptor density. The work function difference (Built-In Potential) between Al) is reduced. Accordingly, the movement of holes (+) from the impurity semiconductor layer 88 to the anode electrode ITO is facilitated according to the tunneling effect, so that a reverse current flows well.

As described above, the present invention is configured such that the Schottky photodiode (PD) provided in the sensing unit 14 is stacked on the sensing TFT (T2). In the present invention, the area of the sensing unit 14 can be reduced compared to a general liquid crystal display device constituting the sensing unit by disposing a PIN-type photodiode in an area separate from the sensing TFT. That is, according to the present invention, by configuring the photodiode in the Schottky manner and stacking the Schottky photodiode on the upper part of the sensing TFT (T2), a separate area prepared for arranging the photodiode separately from the sensing TFT can be deleted. have. Accordingly, according to the present invention, the area of the sensing unit itself is reduced, the area of the display unit is relatively increased, and the aperture ratio is improved.

In addition, according to the present invention, since the photodiode is configured in a Schottky manner, it is possible to improve fingerprint recognition sensitivity compared to a general liquid crystal display device using a PIN type photodiode. This is because the reaction speed of the Schottky photodiode is faster than that of the PIN type photodiode due to the characteristics of the Schottky photodiode.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications and changes are possible within the scope of the technical matters of the present invention. It will be obvious to those who have the knowledge of. Therefore, the scope of the present invention is indicated by the claims to be described later, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

12: display unit 14: sensing unit
T2: sensing TFT PD: Schottky photodiode
SC: sensing capacitor RST: reset line
RW: read line PRE: pre-charging signal

Claims (6)

A plurality of gate lines and a plurality of data lines crossing each other; And
A display unit disposed in a plurality of pixel areas formed at an intersection between the gate line and the data line; And
A sensing unit disposed on some or all of the plurality of pixel regions, and including a sensing TFT, a Schottky photodiode, and a sensing capacitor;
The Schottky photodiode is
Disposed in a region overlapping with the gate electrode of the sensing TFT and connected to each of the gate electrode and the upper electrode of the sensing TFT,
A liquid crystal display device comprising an intrinsic semiconductor layer and an impurity semiconductor layer sequentially stacked between the gate electrode and the upper electrode of the sensing TFT. The method of claim 1,
The sensing TFT connects adjacent first and second data lines to each other according to the voltage state of the set node,
The Schottky photodiode is connected to each of the reset line and the set node,
The sensing capacitor is connected to each of the read line and the set node. delete The method of claim 1,
The display unit
A switching TFT for supplying a data voltage provided from the data line to a pixel electrode in response to a scan signal provided from the gate line;
A liquid crystal cell comprising a common electrode to which a common voltage is applied, a liquid crystal layer, and the pixel electrode; And
A storage capacitor connected to the pixel electrode;
The upper electrode and the pixel electrode are formed on the same layer, and a work function of the upper electrode is greater than a work function of the pixel electrode. The method of claim 1,
The semiconductor layer of the sensing TFT
A liquid crystal display made of any one material selected from an amorphous semiconductor, a polycrystalline semiconductor, an oxide semiconductor, and an organic semiconductor. The method of claim 1,
The work function of the upper electrode is greater than 4.7 eV.

Images