KR20160056760A - Flexible display apparatus able to image scan and driving method thereof - Google Patents

Abstract

According to one embodiment, there is provided a flexible display apparatus allowing image scan and a method of driving the same, capable of obtaining a large detection signal without an amplifier and improving an aperture ratio. According to the embodiment, provided is a flexible display apparatus including a plurality of contact sensors, a first scan line, a second scan line, and a read-out line. Each of the contact sensors includes an N type transistor, a P type transistor having a drain electrode connected with a gate electrode of the N type transistor, and a sensing capacitor having one terminal connected with a drain electrode of the N type transistor. The contact sensors are arranged without covering a unit color pixel area of a color filter layer. The first scan line is connected with a source electrode of the N type transistor and receives a selection signal periodically applied thereto. The second san line is connected with a gate electrode and a source electrode of the P type transistor to receive the selection signal after the first scan line. The read-out line is connected with the drain electrode of the N type transistor.

Description

TECHNICAL FIELD [0001] The present invention relates to a flexible display device capable of scanning an image, and a method of driving the flexible display device.

The present invention relates to a flexible display device capable of scanning an image and a driving method thereof, and more particularly, to a flexible display device capable of scanning an image with a high aperture ratio and a large detection signal without an amplifier, and a driving method thereof.

The touch screen panel is a device for inputting a command of a user by touching a character or a figure displayed on the screen of the image display device with a finger or other contact means of a person, and is attached and used on the image display device. The touch screen panel converts a contact position that is touched by a human finger or the like into an electrical signal. The electrical signal is used as an input signal.

There are various touch detection methods in the touch screen panel such as a resistive film type, an optical type, an electrostatic type, and an ultrasonic type. In the optical type, however, when the touch generating means touches the screen of a display device, And detects whether or not the touch is generated through the change. The optical system is not restricted by the nature of the touch generating means.

On the other hand, security issues have been raised recently, and security for personal mobile devices such as smart phones and tablet PCs has become a hot topic. As the frequency of users' use of mobile devices increases, security in electronic commerce or the like through mobile devices is required. Biometric information such as fingerprints, irises, facial expressions, voices, and blood vessels are used in response to these demands.

Among the various biometric information authentication technologies, the most commonly used technology is fingerprint authentication technology. In recent years, smartphone and tablet PCs have been introduced with fingerprint recognition and authentication technology.

However, in order to attach sensors for fingerprint recognition to a portable device, a device for fingerprint recognition must be mounted in addition to a video display device. This increases the volume of the portable device.

In recent years, a flexible image display device has been developed. In this case, the touch screen panel applied to the flexible image display device is also required to have a flexible characteristic.

Accordingly, it is necessary to develop a technology capable of eliminating a space for a fingerprint sensor in a portable device, and capable of imparting flexible characteristics while preventing the display area from being disturbed.

An object of the present invention is to provide a display device in which a touch sensor of a source follower type, in which an aperture ratio is improved and a circuit area is reduced, is integrated.

According to an aspect of the present invention, there is provided a method of driving an N-type transistor, the method including the steps of: forming an N-type transistor and a drain electrode on the P- A plurality of touch sensors including a capacitor and arranged so as not to cover the unit color pixel region of the color filter layer; A first scan line connected to the source electrode of the N-type transistor and to which a selection signal is periodically applied; A second scan line connected to a gate electrode and a source electrode of the P-type transistor and receiving a selection signal subsequent to the first scan line; And a lead-out line connected to the drain electrode of the N-type transistor.

When no selection signal is applied to the first scan line and the second scan line, a leak current of the N-type transistor formed by light supplied from the outside can charge the sensing capacitor.

When a selection signal is applied to the first scan line, a current proportional to the amount of charge stored in the sensing capacitor may flow from the drain electrode to the source electrode of the N-type transistor.

The display device determines whether or not the contact sensor is in contact with the top of the contact sensor based on a change in the potential value of the lead-out line connected to the drain electrode of the N-type transistor while the selection signal is applied to the first scan line Lt; / RTI >

When the application of the selection signal to the first scan line is terminated, the potential of the lead-out line may be reset.

After the reset, a selection signal may be applied to the second scan line so that the sensing capacitor may be initialized.

The plurality of touch sensors may be disposed above or below a color filter layer that extracts color on a pixel-by-pixel basis from light from a backlight source.

The plurality of contact sensors may be disposed between one of the two substrates constituting the display device and the cover window protecting the display device.

The plurality of touch sensors may be disposed on a cover window for protecting the display device, and a protective layer for protecting the touch sensors may be formed on the plurality of touch sensors.

The plurality of touch sensors may be disposed on the same layer as the thin film transistor layer in which the driving circuits for driving the display device are formed.

According to another embodiment of the present invention, there is provided an image-scanable display device comprising a plurality of touch sensors arranged such that each does not overlap with a unit color pixel area of a color filter layer, A first transistor for generating an amount of charge corresponding to the intensity of the light; A sensing capacitor for storing charges generated by the first transistor; And a second transistor through which a current proportional to the amount of charge stored in the sensing capacitor flows when a selection signal to the touch sensor is applied.

The current flowing when applying the selection signal may flow from the lead-out line to the selection line through which the selection signal is applied through the second transistor.

According to another embodiment of the present invention, there is provided a method of driving a display device, including: charging a sensing capacitor with an amount of charge generated from a first transistor by light reflected from an external object; Applying a selection signal to a source electrode of a second transistor having a gate electrode connected to the sensing capacitor; And a step of detecting a potential of a lead-out line connected to a drain electrode of the second transistor and judging whether or not to touch the top of the contact sensor and the contact state.

The image scanning method may further comprise the step of resetting the lead-out potential after the contact state and the contact state determination step.

The image scanning method may further include, after the resetting step, applying a selection signal to a source electrode of the first transistor to allow the charge stored in the sensing capacitor to pass through the first transistor .

According to still another embodiment of the present invention, there is provided a method of illuminating an object, comprising the steps of: irradiating light of different wavelength regions to cause light reflected from an external object to be received by at least a part of the plurality of touch sensors; So that the amount of charge generated by the leakage current due to the light reception is charged in the sensing capacitor of the touch sensor; Applying a selection signal to a source electrode of a transistor to which a gate electrode is connected to the sensing capacitor; And a step of detecting a potential that varies depending on light irradiation of the different wavelength region band as a potential of a lead-out line connected to the drain electrode of the transistor to determine whether or not the contact sensor is in contact with the upper portion of the contact sensor , A method of scanning an image on a display device is provided.

According to the embodiment of the present invention, by using the source-follower type contact sensor as the contact sensor attached to the display device, it is possible to obtain a large detection signal without using the amplifier.

Further, according to the embodiment of the present invention, the circuit area of the source-follower type contact sensor can be reduced, and thus the aperture ratio can be improved.

1 is a view showing an electronic device according to an embodiment of the present invention.
2A to 2D are cross-sectional views illustrating a configuration of a display device having an image scanning function according to an exemplary embodiment of the present invention.
3 is a plan view showing a configuration of a display device according to an embodiment of the present invention.
4 is a view showing the configuration of a sensor array layer implementing an image scanning function according to an embodiment of the present invention.
5 is a circuit diagram showing a first embodiment of the contact sensor shown in Fig.
Fig. 6 is a circuit diagram showing another embodiment of the touch sensor of Fig. 4; Fig.
7 is a circuit diagram showing a configuration of a touch sensor applicable to a display device according to an embodiment of the present invention.
8 is a timing chart for explaining the operation of the touch sensor SN according to an embodiment of the present invention.
9 is a plan view showing a layout of a circuit structure of a touch sensor according to an embodiment of the present invention.
10 is a view for explaining a method of performing fingerprint recognition in a display device having an image scanning function according to an embodiment of the present invention.
11 is a graph showing a characteristic difference in a touch sensor according to a wavelength region of a light source in a fingerprint recognition method according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "indirectly connected" . Also, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

In the present specification, " contact recognition " refers to a function of recognizing an object to be contacted to a surface, and includes both fingerprint or touch recognition of a human finger and touch recognition by a different touch generating means It should be understood as meaning.

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

1 is a view showing an electronic device according to an embodiment of the present invention.

Referring to FIG. 1, an electronic device 10 according to an embodiment includes a display device DP.

The electronic device 10 may be a digital device including a wired / wireless communication function or other functions. For example, as a digital device equipped with a memory means such as a mobile phone, a navigation device, a web pad, a PDA, a workstation, a personal computer (e.g., a notebook computer) Will be described assuming that a smart phone is taken as an example, but the present invention is not limited thereto.

The display device DP is formed on one surface of the electronic device 10 and is preferably implemented as a touch screen panel formed on the front surface of the electronic device 10 as shown in FIG. 1, .

According to the embodiment of the present invention, the display device DP performs not only the touching of the touch generating means (e.g., a finger or the like) and the recognition of the contact position, but also the recognition function of the fingerprint of the finger.

Specifically, when the first application is driven, the display device DP can function as a touch screen for driving a specific function or the like. When the second application is driven, the fingerprint input window FP displayed through the display device DP, Or a fingerprint recognition function can be implemented in the entire area of the display device DP.

As will be described later, the contact between the ridge and the valley of the touch or the fingerprint by the touch generating means is performed by sensors constituting a plurality of rows and columns. In order to recognize the fingerprint, Be able to distinguish contact. Therefore, the resolution of the touch sensing related to the number of sensors included in the display device DP must be formed so as to be able to distinguish the ridge of the fingerprint and the contact of the bone.

2A to 2D are cross-sectional views illustrating a configuration of a display device having an image scanning function according to an exemplary embodiment of the present invention. FIGS. 2A to 2D illustrate a configuration in which an image scanning function is incorporated in a liquid crystal display (LCD) as an example.

2A to 2D, a liquid crystal display includes a first substrate 210, a thin film transistor layer 220, a liquid crystal layer 230, a color filter layer 240, a second substrate 250, And a cover window (260).

The liquid crystal display device has a structure in which light emitted from a backlight unit (BLU) located under the first substrate 210 is transmitted through the liquid crystal layer 230, And the color and the image are realized while passing through the color filter layer 240. The thin film transistor layer 220 functions to transmit or control an electrical signal and the liquid crystal present in the liquid crystal layer 230 controls the transmission of light by changing the molecular structure according to the applied electrical signal.

According to the embodiment of the present invention, the sensor array layer 300 performing the touch sensing or fingerprint recognition function of the touch generating means, that is, the image scanning function, may be disposed in a part of the liquid crystal display device.

First, as shown in FIG. 2A, the sensor array layer 300 according to an exemplary embodiment may be disposed in a layer that is in contact with the color filter layer 240. In this case, the sensor array layer 300 may be disposed in a lower region of the color filter layer 240 or in an area between the color filter layer 240 and the second substrate 250.

2B, the sensor array layer 300 according to one embodiment may be disposed between the second substrate 250 and the cover window 260, and as shown in FIG. 2C, Or may be disposed above the cover window 260 for display device protection.

2C, if the sensor array layer 300 is disposed above the cover window 260, a separate protective layer 270 for protecting the sensor array layer 300 should be further formed thereon will be.

2D, the sensor array layer 300 according to one embodiment may be formed on the same layer as the thin film transistor layer 220 in which the circuits for driving the display device are implemented.

Although the display device has been described as an example of a liquid crystal display device, the present invention can be applied to other types of display devices such as an organic light emitting diode (OLED) display device or an electrophoretic display (EPD) But may be implemented as well.

In this case, the sensor array layer 300, which performs an image scan function according to an embodiment of the present invention, may be formed on the substrate 300. The organic light emitting diode display device may include a light emitting diode Or an upper portion of the organic light emitting diode device, or the like.

3 is a plan view showing a configuration of a display device according to an embodiment of the present invention.

3, the color filter layer 240 and the sensor array layer 300 are shown. As described above, the sensor array layer 300 may be formed on the upper side or the lower side relative to the color filter layer 240.

According to one embodiment, the sensor array including a plurality of contact sensors may be formed on the front surface of the display, or may be formed on the display partial area according to another embodiment. When the touch sensor is formed in a part of the display area, the area where the touch sensor is not present can be configured not to have a step difference with the area where the touch sensor is present through passivation (not shown).

The sensor array layer 300 is provided with a plurality of contact sensors SN. The touch sensor SN may be implemented as a visible light sensor that senses light in the visible light region or an infrared sensor that senses light in the infrared region.

The color filter layer 240 may include a red pixel R for displaying a red image, a green pixel G for displaying a green image, and a blue pixel B for displaying a blue image. One red pixel R, a green pixel G and a blue pixel B constitute one unit pixel, and these unit pixels may be described as being formed in a matrix form of a plurality of rows and columns. According to this, one touch sensor SN may be provided for one unit pixel.

According to one embodiment, the touch sensor SN is formed in the sensor array layer 300 and includes a red pixel R, a green pixel G and a blue pixel R of the color filter layer 240 as viewed from the top view. (Non-overlapping) region of the pixel electrode B. In FIG. 3, the contact sensor SN is provided below the unit pixel. However, the contact sensor SN may be provided on the upper portion or the side portion of the contact sensor SN. In addition, the size of one of the red pixel R, the green pixel G, and the blue pixel B may be made relatively small to position the touch sensor SN at the corresponding position.

According to another embodiment, the contact sensor SN may include a red pixel R, a green pixel G and a blue pixel B of the color filter layer 240 in the sensor array layer 300 when the transparent electrode material is used It may be formed in an overlapping manner. According to this, since the contact sensor SN can be formed so as to cover the unit pixel, more than two contact sensors SN per unit pixel may be disposed to increase the resolution of the image scan, The sensitivity of the image scan may be improved.

4 is a diagram illustrating the configuration of a sensor array layer 300 that implements an image scan function according to an embodiment of the present invention.

Referring to FIG. 4, the sensor array layer 300 includes a plurality of scan lines SL1, SL2, ..., SLn and a plurality of lead-out lines RL1, RL2, ..., RL1. The scan signals are sequentially supplied to the plurality of scan lines SL1, SL2, ..., SLn and the plurality of lead-out lines RL1, RL2, ..., RL1 receive signals output from the contact sensor SN, To a processing circuit (not shown).

The scan lines SL1, SL2, ..., SLn and the lead out lines RL1, RL2, ..., RL1 are arranged so as to cross each other. At least one contact sensor SN may be formed for each of the intersections.

5 is a circuit diagram showing a first comparative example of the contact sensor SN shown in Fig. Referring to FIG. 5, the touch sensor SN includes a photodiode PD, a transistor T1, and a sensing capacitor C0.

The photodiode PD is an element that converts light energy into electric energy, and when the light touches the photodiode PD, current flows. The cathode of the photodiode PD is connected to the source of the switch transistor T1, and the anode is connected to the ground potential. Such a photodiode PD may be implemented by an organic light emitting diode (OLED), a quantum dot (QD), a transistor, or the like.

One end of the sensing capacitor C0 is connected to the source of the switch transistor T1 and the other end of the sensing capacitor C0 is connected to the ground potential. Responses to the change of the potential at one end of the sensing capacitor C0 are transmitted to the lead out lines RL1 and RL2 and the signals transmitted to the lead out lines RL1 and RL2 are transmitted to a predetermined IC chip. The gate electrode of the switch transistor T1 is connected to the scan lines SL1 to SLn, the drain electrode thereof is connected to the lead-out lines RL1 and RL2, and the source electrode thereof is connected to the cathode of the photodiode PD. The switch transistor T1 may be formed of a transistor such as a hydrogenated amorphous silicon (a-Si: H), a poly silicon (Poly-Si), or an oxide transistor. However, the present invention is not limited to this, and it may be implemented by an organic thin film transistor (Organic TFT) or the like.

A method of sensing the light incident from the outside, that is, the light reflected by the contact means and incident on the contact sensor SN, and transmitting a signal corresponding to the size of the sensed light will be described. Respectively.

A predetermined voltage is applied to the lead-out lines RL1 and RL2. A separate circuit (not shown) for voltage application may be further included. When the selection signal for turning on the switch transistor T1 is applied to the scan lines SL1 to SLn, the potential V1 is once set to the sensing capacitor C0 with the voltage applied to the lead-out lines RL1 and RL2. That is, due to the turn-on of the switch transistor T1, the sensing capacitor C0 is set to the voltage applied to the lead-out lines RL1 and RL2.

If light reflected from an external object is not incident, a current does not flow through the photodiode PD, so that the one end potential V1 of the sensing capacitor C0 is maintained at the set voltage.

The lead-out lines RL1 and RL2 are reset to a predetermined period. After the lead-out lines RL1 and RL2 are reset to, for example, 0 V, the next selection signal is input to the scan lines SL1 to SLn When the switch transistor T1 is turned on, the charge stored in the sensing capacitor C0 is shared with the parasitic capacitance (not shown) of the lead-out lines RL1 and RL2.

Assuming that the voltage applied to the lead-out lines RL1 and RL2 is Vdc, the parasitic capacitance of the lead-out lines RL1 and RL2 is Cpl and the potential at one end of the sensing capacitor C0 is V1, the following equation is established.

However,

However, when light reflected from an external object is incident, a current flows through the photodiode PD. Accordingly, a difference occurs in the total amount of charges shared by the parasitic capacitance of the sensing capacitor C0 and the lead-out lines RL1 and RL2. In the equation (1), the potential V1 at one end of the sensing capacitor Will be different.

The magnitude of the current flowing through the photodiode PD is increased as the intensity of the incident light is increased so that the amount of change of the potential V1 at the one end of the sensing capacitor C0 is also increased and the sensing capacitor C0 and the lead out lines RL1 and RL2 The total amount of charge shared between the parasitic capacitances of the first and second transistors is also increased. Therefore, output signals of different levels are obtained from the lead-out lines RL1 and RL2 according to the intensity of light incident on the photodiode PD.

The above-described method utilizes charge sharing phenomenon between the sensing capacitor C0 and the parasitic capacitance of the lead-out lines RL1 and RL2. Therefore, the level difference of the output signal obtained from the actual lead-out lines RL1 and RL2 is a difference between the result of the charge sharing with the sensing capacitor C0, and accordingly, the level of the output signal The level difference may not be large enough. Therefore, a separate circuit for amplifying the output signals of the lead-out lines RL1 and RL2 is required.

Fig. 6 is a circuit diagram showing a source-follower type contact sensor SN as another comparative example to the contact sensor SN of Fig.

Referring to FIG. 6, the source follower type contact sensor SN includes one photodiode PD, three transistors T1, T2, and T3, and one sensing capacitor C1.

The first transistor T1 is a transistor T1 for resetting the first electrode potential V1 of the sensing capacitor C1 according to a reset control signal Reset and is hereinafter referred to as a reset transistor T1. The source electrode of the reset transistor T1 is connected to the cathode of the photodiode PD and the drain electrode is connected to the input voltage line VDD.

The gate electrode of the second transistor T2 is connected to the cathode of the photodiode PD and the first electrode of the two electrodes of the sensing capacitor C1. Also, the drain electrode of the second transistor T2 is connected to the input voltage line VDD. The second transistor T2 converts the first electrode potential V1 of the sensing capacitor C1 into a current signal and amplifies the current signal. Therefore, the second transistor T2 can be referred to as an amplifying transistor T2.

The gate electrode of the third transistor T3 is connected to the scan line SL, the drain electrode thereof is connected to the source electrode of the amplification transistor T2 and the source electrode thereof is connected to the lead-out line RL. When the selection signal is applied to the scan line SL, the third transistor T3 is turned on and the first electrode potential V1 of the sensing capacitor C1 amplified by the amplifying transistor T2 is applied to the current signal To the lead-out line RL. The third transistor T3 may be referred to as a selection transistor T3.

The cathode and the anode of the photodiode PD are respectively connected to the first electrode and the ground potential of the sensing capacitor C1 and the first and second electrodes of the sensing capacitor C1 are connected to the gate electrode of the amplifying transistor T2 Respectively.

The operation of the source follower type contact sensor will be described below.

First, when the reset transistor T1 is turned on by the reset control signal Reset, the potential of the first electrode potential V1 of the sensing capacitor C1 and the potential of the input voltage line VDD are reset.

When light reflected by an external object (e.g., a fingerprint of a person's finger) is supplied to the photodiode PD, a leakage current is generated, and the leakage current can charge the sensing capacitor C1 .

When the sensing capacitor C1 is charged, the gate electrode potential of the amplifying transistor T2 connected to the first electrode of the sensing capacitor C1 is increased. When the potential exceeds the threshold voltage, the amplifying transistor T2 The transistor T2 is turned on, and thus the current flows through the amplifying transistor T2.

When the selection transistor T3 is turned on by applying the selection signal to the scan line SL, the first electrode potential V1 of the sensing capacitor C1 through the amplifying transistor T2 and the selection transistor T3 Is amplified and transmitted as a current signal to the lead-out line RL. The lead-out line RL potential R1 rises due to the current transfer to the lead-out line RL, and the change in the value of the lead-out potential R1 when the selection signal is applied to the scan line SL And is converted into a digital signal through an analog-to-digital converter (ADC).

The potential R1 of the lead-out line RL is proportional to the first electrode potential V1 of the sensing capacitor C1, that is, the amount of charge charged in the sensing capacitor C1 and is stored in the sensing capacitor C1 Since the amount of charge is proportional to the amount of light supplied to the photodiode PD, it is possible to grasp how much light is supplied to the contact sensor SN through the lead-out line RL potential R1. As a result, it is possible to grasp the contact state and the contact state (contact distance and contact area, etc.) of the object by the contact sensor SN.

6, since the signal amplified by the amplifying transistor T2 is output, a separate amplifier is unnecessary, the analog signal can be directly converted into a digital signal to detect the signal, Signal processing is possible. However, since the number of transistors is large, there is a limit of the space that can be integrated in the pixels of the display device, and the aperture ratio is narrow.

7 is a circuit diagram showing a configuration of a touch sensor applicable to a display device according to an embodiment of the present invention. 7 (a) and 7 (b) are circuit diagrams equivalent to each other. The contact sensor according to the embodiment of the present invention is basically a source follower type contact sensor.

Referring to FIG. 7, the contact sensor SN according to an embodiment of the present invention may be disposed at the same position as the contact sensor SN described with reference to FIG. 5 and FIG. According to one embodiment, the touch sensor SN includes a red pixel R, a green pixel G and a blue pixel B of the color filter layer 240 (see Figs. 2A to 2D) when viewed from the top view, Non-overlapping regions.

According to another embodiment, the contact sensor SN may include a red pixel R, a green pixel G, and a red pixel R of the color filter layer 240 in the sensor array layer 300 (see Figs. 2A to 2D) And the blue pixel B may overlap with each other. According to this, since the contact sensor SN can be formed so as to cover the unit pixel, more than two contact sensors SN per unit pixel may be disposed to increase the resolution of the image scan, The sensitivity of the image scan may be improved.

Referring to FIG. 7A, each touch sensor SN includes one P-type transistor PT1, an N-type transistor T1, and a sensing capacitor C1.

Each of the transistors PT1 and T1 may be implemented with a silicon-based transistor such as a hydrogenated amorphous silicon (a-Si: H), a polysilicon (Poly-Si) However, the present invention is not limited to this, and it may be implemented by an organic thin film transistor (Organic TFT) or the like.

The gate electrode and the source electrode of the P-type transistor PT1 are connected to each other and equalized to the photodiode PT1 as shown in Fig. 7 (b). The gate electrode and the source electrode of the P-type transistor PT1 are connected to each other to serve as a cathode of the photodiode PT1, and the drain electrode serves as an anode. The source electrode of the P-type transistor PT1 is connected to the scan line SLn + 1. On the other hand, the drain electrode of the P-type transistor PT1 is connected to the first one of the two electrodes of the sensing capacitor C1 and the gate electrode of the N-type transistor T1.

The gate electrode of the N-type transistor T1 is connected to the first electrode of the sensing capacitor C1 and the drain electrode of the P-type transistor PT1, and the drain electrode thereof is connected to the lead-out line RL. A source electrode of the N-type transistor T1 is connected to the scan line SLn.

The scan line SLn connected to the source electrode of the N-type transistor T1 and the scan line SLn + 1 connected to the source electrode of the P-type transistor PT1 are different adjacent scan lines. The application of the selection signal to the specific touch sensor SN among the plurality of touch sensors SN is performed through the scan line. The first scan line SLn connected to the source electrode of the N-type transistor T1, A selection signal may be sequentially applied to the second scan line SLn + 1 to which the source electrode of the first transistor PT1 is connected.

On the other hand, the sensing capacitor C1 functions to charge the charge corresponding to the leakage current formed by the P-type transistor PT1. The first electrode of the sensing capacitor C1 is connected to the gate electrode of the N-type transistor T1 and the drain electrode of the P-type transistor PT1, and the second electrode of the sensing capacitor C1 is connected to the ground potential.

8 is a timing chart for explaining the operation of the touch sensor according to an embodiment of the present invention.

8, RL Reset is a signal that periodically resets the potential of the lead-out line RL. The potential of the lead-out line RL can be reset when the RL Reset signal is at a high level.

SCANn is a signal applied to the first scan line SLn and SCANn + 1 is a signal applied to the second scan line SLn. When the signals SCANn and SCANn + 1 supplied to the scan lines SLn and SLn + 1 are low level, the corresponding touch sensor SN is selected. For example, when a signal applied to the first scan line SLn is switched to a low level (when a selection signal is applied), a drain electrode is connected to the lead-out line RL and the first scan line SLn, The touch sensor SN including the N-type transistor T1 to which the source electrode is connected is selected and the sensed value from the touch sensor SN is output to the lead-out line RL. The period from when the signals SCANn and SCANn + 1 supplied to the scan lines SLn and SLn + 1 are switched from the high level to the low level and then again becomes the low level can be regarded as one frame.

V1 represents the first electrode potential V1 of the sensing capacitor C1 and R1 represents the potential R1 of the lead-out line RL. In the timing chart of V1 and R1, a solid line is a state when light reflected by an external object is supplied to the contact sensor SN (Light), and a broken line is a state when light is not supplied (Dark).

Hereinafter, the operation of the contact sensor SN will be described with reference to FIGS. 7 and 8. FIG.

Since no selection signal is applied to the first scan line SLn and the second scan line SLn + 1 during the T1 period, the current flows through the N-type transistor N and the second current flows from the P- No current flows to the scan line SLn + 1.

The T1 period may be a period after a low level signal is applied to the second scan line SLn + 1 and a low level signal is applied to the second scan line SLn. That is, the T1 period is a period after T4 when the low level signal is applied to the second scan line SLn + 1. When a low level signal is applied to the second scan line SLn + 1 in the period T4, the charges charged in the sensing capacitor C1 are discharged through the P-type transistor PT1 serving as a photodiode, The capacitor C1 is reset. Therefore, the first electrode potential V1 of the sensing capacitor C1 becomes 0 V in the period T4.

Since no selection signal is applied to the first scan line SLn and the second scan line SLn + 1 during the T1 period, if a leakage current is generated in the P-type transistor PT1 serving as a photodiode, the corresponding leakage current So that the sensing capacitors C1 are charged.

If light reflected from the outside is not supplied, leakage current is not formed in the P-type transistor PT1. Therefore, no charge is stored in the sensing capacitor C1 connected to the drain electrode of the P-type transistor PT1 , The first electrode potential V1 of the sensing capacitor C1 is maintained at a low level (Dark).

On the other hand, when light reflected from the outside is supplied during the T1 period, a leakage current is formed in the P-type transistor PT1 as described above. This leakage current charges the sensing capacitor C1 and the charging is continued until the low level signal is applied to the second scan line SLn + 1, that is, during one frame. Accordingly, the first electrode potential V1 of the sensing capacitor C1 gradually increases (Light).

At this time, when the signal SCANn supplied to the first scan line SLn is switched from the high level to the low level (T2 period), the source electrode potential of the N-type transistor T1 becomes lower than the drain electrode potential.

If the light reflected from the outside is not supplied, charge is not charged in the sensing capacitor C1 in the T1 section and the gate electrode potential of the N-type transistor T1 is less than the threshold voltage, Will not turn on. Therefore, a minute current flows or no current flows through the N-type transistor T1 and the potential R1 of the lead-out line RL is kept equal to the T1 period or can be lowered to a certain degree with a fine current flow (Dark).

However, when light reflected from the outside is supplied, since the gate electrode potential V1 of the N-type transistor T1 will exceed the threshold voltage, a current flows from the drain electrode of the N-type transistor T1 to the source electrode . That is, a current flows from the lead-out line RL to the first scan line SLn. The magnitude of the current flowing is proportional to the gate electrode potential of the N-type transistor T1, that is, the magnitude of the first electrode potential V1 of the sensing capacitor C1. The larger the intensity of the light reflected from the outside is, the larger the leakage current formed by the P-type transistor PT1 becomes. Accordingly, the first electrode potential V1 of the sensing capacitor C1 becomes larger, The width of the potential R1 of the lead-out line RL lowered by the current flowing through the transistor T1 becomes proportional to the intensity of the supplied light. That is, as the intensity of the light reflected from the outside increases, the potential R1 of the lead-out line RL is greatly reduced in the period T2. The potential R1 of the lead-out line RL is transferred to the IC chip separately when the low level signal is applied to the first scan line SLn. The contact state and the contact state can be determined.

Since the touch sensor is provided for each pixel of the display device, it is possible to check the contact state and the contact state of each pixel, and when not only the touch by the touch generating means and the touch generation point but also the user's finger, It is possible to recognize the fingerprint by judging whether or not the ridge or valley of the fingerprint has been touched.

The reset signal RL Reset for resetting the potential R1 of the lead-out line RL is applied after the T2 period so that the potential R1 of the lead-out line RL is applied to the first scan line SLn ) Is initialized to the same level as before the low level signal is applied.

When the signal SCANn + 1 supplied to the second scan line SLn + 1 is lowered from the high level to the low level (T4 section) after the lead-out line RL potential R1 is reset, All of the charges stored in the sensing capacitor C1 are discharged to the second scan line SLn + 1 through the P-type transistor PT1, whereby the first electrode potential V1 of the sensing capacitor C1 is initialized. When the low level signal is applied to the second scan line SLn + 1, the operations of T1, T2, and T3 are repeated again.

When the photodiode PD of the general source follower type sensor described with reference to FIG. 6 is equivalent to a transistor and is compared with the source follower type contact sensor of the present invention described with reference to FIG. 7, It can be seen that the two transistors are reduced. Therefore, the contact sensor SN is formed on the substrate having the display area. As the elements constituting the contact sensor SN are reduced for the above reasons, the aperture ratio in the entire display panel can be improved.

9 is a plan view showing the circuit structure of the contact sensor as a layout. Fig. 9 (a) shows the structure of a general contact sensor described with reference to Fig. 6, and Fig. 9 (b) Fig. 2 shows the structure of a contact sensor according to the invention.

9 (a), four transistors and one capacitor are required for a general source follower type contact sensor. Referring to FIG. 9 (b), the source follower type contact sensor according to the embodiment of the present invention The sensor requires only two transistors and one capacitor.

Therefore, according to the embodiment of the present invention, it is possible to reduce the area of the circuit configuration (about 27% reduction) compared with a general source follower type contact sensor, and when the contact sensor is integrated in the display device, .

In addition, the advantage of the source follower method that can obtain a large detection signal without an amplifier can be taken as it is.

FIG. 10 is a view for explaining a method of performing fingerprint recognition in a display device having an image scanning function according to an embodiment of the present invention. FIG. 11 is a flowchart illustrating a fingerprint recognition method according to an embodiment of the present invention. FIG. 5 is a graph showing a characteristic difference in a touch sensor according to a wavelength range of a light source. FIG.

Referring to FIG. 10, in the display device described with reference to FIG. 2A, a backlight unit is disposed under the first substrate 210, and a light source 900 for a sensor may be further included in addition to the backlight unit.

The light source 900 for a sensor may be composed of a plurality of light sources having different wavelength ranges, for example, a red light source, a green light source, a blue light source, and a white light source. The sensor light source 900 may be a light source that provides light in the infrared region instead of the visible light region, for example.

When the fingerprint recognition function is activated by the application installed in the electronic device 10 (see Fig. 1), the user touches the finger in a specific area. The sensor light source 900 sequentially activates the light sources in the wavelength region one by one . The light irradiated from the sensor light source 900 is reflected by the ridge or fingerprint of the finger and is incident on the contact sensor described above. Even if the light is reflected at the same point, The characteristics of the light incident on the light guide plate 10 are different. If the characteristics of the light incident on the touch sensor are changed, the electrical value formed in the sensing transistor included in the touch sensor also changes.

Referring to FIG. 11, it can be seen that the change characteristics of the drain-source current I _DS depend on the gate-source voltage V _GS of the sensing transistor depending on the wavelength region of the used light source.

According to one embodiment, a touch sensor may be constructed by setting a wavelength region of light incident on the touch sensor in the designing stage of the electronic device 10 and utilizing a sensing transistor made of a material that receives the wavelength region more efficiently have.

According to another embodiment, the fingerprint recognition is performed a plurality of times by utilizing the light source 900 for sensors having various wavelength regions. Whenever a light source having a different wavelength region is used, the scan is sequentially performed from the top to the bottom of the fingerprint. More specifically, as shown in FIG. 1, a light source is irradiated from the upper end to the lower end of the fingerprint, thereby detecting light reflected by ridges or ridges of the fingerprint through the touch sensor and outputting the electric signal. According to this, a short-range fingerprint image parallel to the lateral direction of the finger is obtained from the upper end to the lower end of the finger, and the completed fingerprint image is obtained by combining these. When a fingerprint image having different characteristics is obtained by using light sources of different wavelength ranges, a final fingerprint image can be obtained by comparing and synthesizing the fingerprint images.

As a result, since a plurality of fingerprint images are obtained by using light sources having different wavelength regions, and a final fingerprint image is obtained by comparing the images, a more accurate fingerprint image acquisition becomes possible.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims (16)

Type transistor, a P-type transistor having a drain electrode connected to the gate electrode of the N-type transistor, and a sensing capacitor having one end connected to the drain electrode of the N-type transistor, and arranged so as not to cover the unit color pixel region of the color filter layer A plurality of contact sensors;
A first scan line connected to the source electrode of the N-type transistor and to which a selection signal is periodically applied;
A second scan line connected to a gate electrode and a source electrode of the P-type transistor and receiving a selection signal subsequent to the first scan line; And
And a lead-out line connected to the drain electrode of the N-type transistor. The method according to claim 1,
Type transistor formed by light supplied from the outside charges the sensing capacitor when no selection signal is applied to the first scan line and the second scan line. 3. The method of claim 2,
And a current proportional to the amount of charge stored in the sensing capacitor flows from the drain electrode of the N-type transistor toward the source electrode when the selection signal is applied to the first scan line. The method of claim 3,
Type transistor and the drain electrode of the N-type transistor while the selection signal is applied to the first scan line, the contact state and the contact state of the contact sensor are determined based on the potential value change of the lead- Possible flexible display. The method of claim 3,
And the potential of the lead-out line is reset when the application of the selection signal to the first scan line is terminated. 6. The method of claim 5,
And after the reset, a selection signal is applied to the second scan line to initialize the sensing capacitor. The method according to claim 1,
Wherein the plurality of touch sensors are disposed above or below a color filter layer that extracts color on a pixel-by-pixel basis from light from a backlight source. The method according to claim 1,
Wherein the plurality of contact sensors are disposed between one of the two substrates constituting the display device and the cover window protecting the display device. The method according to claim 1,
Wherein the plurality of contact sensors are disposed on a cover window for protecting the display device,
And a protective layer for protecting the contact sensors is formed on the plurality of touch sensors. The method according to claim 1,
Wherein the plurality of touch sensors are disposed on the same layer as the thin film transistor layer in which the driving circuits for driving the display device are formed. A plurality of touch sensors arranged such that each of the plurality of touch sensors is not overlapped with the unit color pixel area of the color filter layer,
The contact sensor includes:
A first transistor for generating a charge amount corresponding to the intensity of light reflected from an external object;
A sensing capacitor for storing charges generated by the first transistor; And
And a second transistor having a current proportional to the amount of charge stored in the sensing capacitor when applying a selection signal to the touch sensor. 12. The method of claim 11,
Wherein the current flowing when applying the selection signal flows from the lead-out line to the selection line through which the selection signal is applied through the second transistor. Causing the sensing capacitor to charge an amount of charge generated from the first transistor by light reflected from an external object;
Applying a selection signal to a source electrode of a second transistor having a gate electrode connected to the sensing capacitor; And
Detecting a potential of a lead-out line connected to a drain electrode of the second transistor, and judging whether or not to touch the upper portion of the contact sensor and the contact state. 14. The method of claim 13,
After the contact state and the contact state determination step,
Further comprising the step of resetting the lead-out potential. 15. The method of claim 14,
After the reset step,
And applying a selection signal to a source electrode of the first transistor to cause the charge stored in the sensing capacitor to pass through the first transistor. Irradiating light of different wavelength regions to cause light reflected from an external object to be received by at least a portion of the plurality of touch sensors;
So that the amount of charge generated by the leakage current due to the light reception is charged in the sensing capacitor of the touch sensor;
Applying a selection signal to a source electrode of a transistor to which a gate electrode is connected to the sensing capacitor; And
And a step of detecting a potential varying depending on light irradiation of the different wavelength region band as a potential of a lead-out line connected to a drain electrode of the transistor, A method of scanning an image on a display device.

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