TWI402589B - Liquid crystal display and pixel unit thereof - Google Patents

Description

Liquid crystal display and its pixel unit

The present invention relates to a liquid crystal display and a pixel unit thereof, and more particularly to a liquid crystal display having a V-T characteristic curve and a pixel unit thereof in different regions of a pixel unit.

FIG. 1 is an equivalent circuit diagram of a pixel unit of a conventional liquid crystal display. A pixel unit 110 of the liquid crystal display 101 has a first pixel unit 111 and a second pixel unit 112, and as shown in FIG. 1 , the conventional design uses two thin film transistors T1 and T2 to respectively control the first The voltage changes of the pixel unit 111 and the second pixel unit 112 enable the first pixel unit 111 and the second pixel unit 112 to obtain a better optical response through the individual gamma correction curves.

2 is a block diagram schematically showing the driving architecture for driving the liquid crystal display of the embodiment of FIG. 1. As shown in FIG. 2, the driving architecture 100 includes a thin film transistor array 102, a first image data driving circuit 104, a second image data driving circuit 106, and a scanning signal driving circuit 108. Referring to FIG. 1 and FIG. 2 simultaneously, the scan signal driving circuit 108 generates a scan signal, and couples the gates of the respective thin film transistors via the column electrodes G1A-G4A. The image data driving circuit 104 sequentially generates image signals corresponding to the respective scanning signals, and sends them to the first pixel unit 111 via the row electrodes D1A-D4A and the thin film transistors corresponding to the first pixel unit 111 (for example, the thin film transistor T1); The image data driving circuit 106 sequentially generates image signals corresponding to the respective scanning signals, and sends them to the second pixel unit 112 via the row electrodes D1B-D4B and the thin film transistors (for example, the thin film transistors T2) corresponding to the second pixel unit 112.

Although the conventional design utilizes two thin film transistors T1 and T2 to control the voltage variations of the first pixel unit 111 and the second pixel unit 112, respectively, a good optical response can be obtained under the design of a single liquid crystal structure gap, but the above design A more complex circuit architecture as shown in Figure 2 is needed to implement different gamma correction curves, such as requiring two different image data drive circuits 104, 106 and twice the Row electrodes significantly increase component cost and design complexity.

Therefore, an object of an embodiment of the present invention is to provide a liquid crystal display and a pixel unit thereof, wherein different regions of the pixel unit have respective V-T characteristic curves, thereby obtaining a good optical response with a simplified driving structure and lower manufacturing cost. Effect.

According to an embodiment of the invention, a pixel unit is electrically connected to a data line, a first scan line, and a second scan line. The pixel unit includes a first pixel unit and a second pixel unit. . The first pixel unit is formed with a first switching element electrically connected to the data line, a first liquid crystal capacitor electrically connected to one of the first switching elements, and a first storage capacitor. The second pixel unit is formed with a second switching element electrically connected to the first switching element, a coupling capacitor and a second liquid crystal capacitor electrically connected to the second switching element and a second storage capacitor. The coupling capacitor is electrically connected between the first input end and the second output end of the second switching element, and the control end of the first switching element and the control end of the second switching element are electrically connected to the first scan line and the second Two scan lines.

According to an embodiment of the invention, a liquid crystal display includes a plurality of scan lines and data lines, and a plurality of pixel units.

According to an embodiment of the present invention, in the pixel unit and the liquid crystal display, the scanning line connected to the control end of the first switching element and the scanning line connected to the control end of the second switching element are adjacent, preferably The nth (n≧1; n is a positive integer) scan line and the n-1th scan line, respectively.

According to an embodiment of the invention, a pixel unit includes a first pixel unit, a bidirectional diode, and a second pixel unit. The first pixel unit is formed with a first switching element, a first liquid crystal capacitor electrically connected to the first switching element, and a first storage capacitor. The second pixel unit is formed with a second liquid crystal capacitor and a second storage capacitor electrically connected to each other. The bidirectional diode is electrically connected between the first liquid crystal capacitor and the second liquid crystal capacitor. Preferably, the bidirectional diode is electrically connected between a first sub-pixel electrode and a second sub-pixel electrode. In one embodiment, the bidirectional diode comprises a a first diode body and a second diode transistor, and a first parasitic capacitance is formed between the second end and the third end of the first diode transistor; and the second diode transistor is A second parasitic capacitance is formed between the second end and the third end. In one embodiment, the third end of the first diode transistor is electrically connected to the second storage capacitor of the second pixel unit and the second liquid crystal capacitor; and the third end of the second diode transistor is electrically connected to the first The first storage capacitor of the pixel unit and the first liquid crystal capacitor.

According to an embodiment of the present invention, it is possible to form an effect of making two sets of different V-T characteristic curves of the same pixel unit by using a general thin film transistor process.

3 is a schematic view showing a liquid crystal display according to an embodiment of the present invention, and FIG. 4 is an equivalent circuit diagram showing the liquid crystal display of the embodiment of FIG. 3.

3 and FIG. 4, a liquid crystal display according to an embodiment of the present invention includes a plurality of pixel units 10, a plurality of scanning lines G and data lines D, a common electrode (not shown), and a liquid crystal layer (not shown). The pixel unit 10 includes a first thin film transistor T1, a second thin film transistor T2, a first sub-pixel electrode 22, and a second sub-pixel electrode 24. Each of the pixel units 10 is, for example, a red (R) pixel, a green (G) pixel, or a blue (B) pixel.

The pixel unit 10 is divided into a first sub-pixel unit 11 and a second sub-pixel unit 12, and the first sub-pixel unit 11 A first thin film transistor T1, a storage capacitor Cs1 and a liquid crystal capacitor Clc1 are formed, and the liquid crystal capacitor Clc1 is formed by a first sub-pixel electrode 22 and a common electrode (not shown) separated by a liquid crystal layer (not shown), and The storage capacitor Cs1 and the liquid crystal capacitor Clc1 are both electrically connected to the first thin film transistor T1. The second sub-pixel unit 12 is formed with a second thin film transistor T2, a storage capacitor Cs2, a liquid crystal capacitor Clc2 and a coupling capacitor Cx. The liquid crystal capacitor Clc2 is composed of the second sub-pixel electrode 24 and the common electrode (not shown). a spacer liquid crystal layer (not shown) is formed, and the storage capacitor Cs2 and the liquid crystal capacitor Clc2 are electrically connected to the thin film transistor T2, and both ends of the coupling capacitor Cx are electrically connected to the second thin film transistor T2. Between the source and the drain, and electrically connected to the first sub-pixel electrode 22 and the second sub-pixel electrode 24. The gate of the first thin film transistor T1 is electrically connected to an nth scan line G(n) of the scan lines G, and the source thereof is electrically connected to a mth data line D(m) of the data line D, And the drain electrode is electrically connected to the source of the second thin film transistor T2, and the gate of the second thin film transistor T2 is electrically connected to an n-1th of the scan lines G of the adjacent scan lines G(n) Strip scan line G(n-1). The n-1th scanning line G(n-1) is the upper scanning line of the nth scanning line G(n). That is, the scanning signal is first input to the n-1th scanning line G(n-1) and then to the nth scanning line G(n).

Therefore, according to the design of the implementation, by adjusting the size of the second thin film transistor T2 or the magnitude of the coupling capacitance Cx, the first sub-pixel electrode 22 and the second sub-pixel electrode 24 of the same pixel unit can be The phase difference between the common electrode potentials Vcom is different, even if the same pixel unit has the effect of two different sets of V-T characteristic curves. This feature can solve the phenomenon of color shift and image-sticking, and can also be applied to different environments to obtain different effects. For example, it can be applied to a wide viewing angle liquid crystal display to provide good performance. The viewing angle compensation effect can be applied to a transflective liquid crystal display to improve optical matching between the transmissive area and the reflective area.

In one embodiment of the present invention, the coupling capacitor Cx is formed by a general thin film transistor process, so that the two thin film transistors T1 and T2 can electrically connect the same data line signal source, and the first sub-pixel electrode 22 can still be The second sub-pixel electrode 24 has two different potential differences with respect to the common electrode potential Vcom. Compared with the prior art, the embodiment of the present invention can reduce the number of data line signal sources and simplify the circuit of the pixel structure. In addition, a good optical response can be achieved with an inherent process without the need for additional manufacturing costs and a complex drive architecture.

Since the gate of the second thin film transistor T2 is electrically connected to the scanning line G(n-1) and the source and the drain thereof are electrically connected to both ends of the coupling capacitor Cx, respectively, when the upper scanning line G(n-1) is When driving, the voltage difference between the first sub-pixel electrode 22 and the second sub-pixel electrode 24 can be neutralized by the arrangement of the second thin film transistor T2. Further, when the driving of the scanning line G(n) of the present stage is stopped, the discharge path of the second sub-pixel electrode 24 can be provided, and the problem of charge residual (DC residual) can be improved.

In addition, according to the above design, the second sub-pixel electrode 24 is also less susceptible to the influence of the feed-through issue.

FIG. 5 is an equivalent circuit diagram showing a liquid crystal display according to an embodiment of the present invention. Among the elements of the pixel unit 30, the same elements as those of the pixel unit 10 are denoted by the same reference numerals, and their description will be omitted. The difference between the two will be described below.

Referring to FIG. 5, the pixel unit 30 is divided into a first sub-pixel unit 31 and a second sub-pixel unit 32. The first pixel unit 31 is formed with a first thin film transistor T1 and a storage capacitor Cs1. A liquid crystal capacitor Clc1 is formed by a liquid crystal layer (not shown) separated from a common electrode (not shown) by a first sub-pixel electrode (not shown), and the storage capacitor Cs1 and the liquid crystal capacitor Clc1 are electrically connected. To the first thin film transistor T1. The gate of the first thin film transistor T1 is electrically connected to a scan line G(n) in the scan line G, and the source thereof is electrically connected to a data line D(m) in the data line D, and the drain is electrically connected to the liquid crystal. Capacitor Clc1. The second sub-pixel unit 32 is formed with a storage capacitor Cs2 and a liquid crystal capacitor Clc2 electrically connected to each other. The liquid crystal capacitor Clc2 is formed by a liquid crystal layer (not shown) interposed between a first sub-pixel electrode (not shown) and a common electrode (not shown). A bidirectional diode 40 is electrically connected between the liquid crystal capacitor Clc1 and the liquid crystal capacitor Clc2. Preferably, the bidirectional diode 40 is electrically connected between the first sub-pixel electrode and the second sub-pixel electrode. The bidirectional diode 40 includes a first diode transistor D1 and a second diode transistor D2, and the first end 411 of the first diode transistor D1 is electrically connected to the second diode transistor. The second end 412 of the first diode TFT D1 is electrically connected to the first end 421 of the second diode transistor D2; the third end 413 of the first diode transistor D1 Electrically connected to the first end 411 of the first diode transistor D1 and the storage capacitor Cs2 and the liquid crystal capacitor Clc2 of the second sub-pixel unit 32; the third end 423 of the second diode transistor D2 is electrically connected to the first The first end 421 of the diode body D2 and the storage capacitor Cs1 and the liquid crystal capacitor Clc1 of the first sub-pixel unit 31. Therefore, a first parasitic capacitance Cgs1 is formed between the second end 412 and the third end 413 of the first diode transistor D1 in the bidirectional diode 40; and a second end of the second diode transistor D2 is formed. A second parasitic capacitance is formed between 422 and the third terminal 423 Cgs2.

In this embodiment, the first sub-pixel electrode 22 and the second sub-pixel electrode 24 are connected by the bidirectional diode 40, and the parasitic capacitances Cgs1 and Cgs2 of the bidirectional diode 40 are coupled to the first sub-pixel electrode 22 . And the second sub-pixel electrode 24, when the scanning signal of the scanning line G(n) is driven, the image data starts to charge the first sub-pixel electrode 22 and the second sub-pixel electrode 24, and form two between the two. A different potential difference. When the scanning signal is stopped, the bidirectional diode 40 can neutralize the voltage difference between the first sub-pixel electrode 22 and the second sub-pixel electrode 24, and can provide a second sub-pixel electrode 24 with a discharge path, and thus Can improve the phenomenon of image sticking. According to the design of the embodiment, the second sub-pixel electrode 24 is also less susceptible to the influence of the feed-through issue.

In addition, according to the design of the embodiment, the sizes of the first and second diode transistors D1 and D2 and the magnitudes of the parasitic capacitances Cgs1 and Cgs2 can be adjusted to make the discharge rate of the bidirectional diode 40 follow. The off current (Ioff) of the first thin film transistor T1 is uniform, and the flicker problem can be effectively reduced.

The above is intended to be illustrative only and not limiting. Any equivalent modifications and alterations of the present invention are intended to be included in the scope of the appended claims.

10, 30‧‧‧ pixel unit

11, 31‧‧‧ first sub-pixel unit

12, 32‧‧‧ second sub-pixel unit

22‧‧‧First sub-pixel electrode

24‧‧‧Second sub-pixel electrode

40‧‧‧Two-way diode

411‧‧‧ first end of the first diode transistor

412‧‧‧ second end of the first diode transistor

413‧‧‧ Third end of the first diode transistor

421‧‧‧ the first end of the second diode transistor

422‧‧‧ second end of the second diode transistor

423‧‧‧ Third end of the second diode transistor

Cgs1, Cgs2‧‧‧ parasitic capacitance

Clc1, Clc2‧‧‧ liquid crystal capacitor

Cs1, Cs2‧‧‧ storage capacitor

Cx‧‧‧Coupling Capacitor

D, D (m) ‧ ‧ data line

D1‧‧‧First Diode Electrode

D2‧‧‧Second diode crystal

D1A, D2A, D3A, D4A, D1B, D2B, D3B, D4B‧‧‧ electrode

G, G(n)‧‧‧ scan line

G1A, G2A, G3A, G4A‧‧‧ column electrodes

T1‧‧‧ first film transistor

T2‧‧‧second film transistor

Vcom‧‧‧share electrode potential

1 is an equivalent circuit diagram of a pixel unit of a conventional liquid crystal display.

2 is a block diagram schematically showing the driving architecture for driving the liquid crystal display of the embodiment of FIG. 1.

Fig. 3 is a schematic view schematically showing a liquid crystal display according to an embodiment of the present invention.

4 is an equivalent circuit diagram showing a liquid crystal display of the embodiment of FIG. 3.

FIG. 5 is an equivalent circuit diagram showing a liquid crystal display according to an embodiment of the present invention.

10‧‧‧ pixel unit

11‧‧‧First sub-pixel unit

12‧‧‧Second sub-pixel unit

Cx‧‧‧Coupling Capacitor

Clc1, Clc2‧‧‧ liquid crystal capacitor

Cs1, Cs2‧‧‧ storage capacitor

T1, T2‧‧‧ film transistor

Vcom‧‧‧share electrode potential

D(m), D(m-1)‧‧‧ data line

G(n), G(n-1)‧‧‧ scan line

Claims (15)

A pixel unit is configured to be electrically connected to a data line and a first scan line and a second scan line. The pixel unit includes: a first sub-pixel unit, and a first one of the data lines is formed a first switching element electrically connected to the first liquid crystal capacitor and a first storage capacitor of the first switching element; and a second sub-pixel unit formed with a second switching electrically connecting the first switching element An element, a coupling capacitor, and a second liquid crystal capacitor and a second storage capacitor electrically connected to the second switching element; wherein the coupling capacitor is electrically connected to the first input end and the second output of the second switching element The control end of the first switching element and the control end of the second switching element are electrically connected to the first scan line and the second scan line, respectively, and when the second scan line is driven, the first a voltage difference between the second switching element and the first sub-pixel unit and the second sub-pixel unit. The pixel unit of claim 1, wherein the first scan line and the second scan line are adjacent. The pixel unit of claim 1, wherein the first and the second switching elements are respectively formed by a first and a second thin film transistor, and the coupling capacitor is electrically connected to the second thin film transistor. The source and the bungee. The pixel unit of claim 3, wherein a source of the first thin film transistor is electrically connected to the data line; and a drain of the first thin film transistor is electrically connected to a source of the second thin film transistor. . The pixel unit of claim 4, wherein the first liquid crystal capacitor is formed by a first sub-pixel electrode and a common electrode separated by a liquid crystal layer, and the second liquid crystal capacitor is formed by a second The sub-pixel electrode and the common electrode are formed by a liquid crystal layer. A liquid crystal display comprising: a plurality of scan lines and a plurality of data lines, wherein the scan lines and the area enclosed by the data lines define a plurality of pixel units, each of the pixel units being divided into: a first sub-pixel unit Forming a first switching element electrically connected to one of the data lines, a first liquid crystal capacitor electrically connected to the first switching element, and a first storage capacitor; and a second sub-pixel unit Forming a second switching component electrically connected to the first switching component, a coupling capacitor, and a second liquid crystal capacitor and a second storage capacitor electrically connected to the second switching component; wherein the coupling capacitor is electrically connected to the second One of the switching elements is connected between the first output port and the second output port, and the control end of the first switching element is connected to the nth (n≧1; n is a positive integer) scan line, the second switching element The control terminal is connected to the n-1th scan line, and when the n-1th scan line is driven, the second switching element neutralizes the first sub-pixel unit and the second sub-pixel unit Voltage difference. The liquid crystal display of claim 6, wherein the first and the second switching elements are respectively formed by a first and a second thin film transistor, and the coupling capacitor is electrically connected to the second thin film transistor. Source and bungee. The liquid crystal display of claim 7, wherein a source of the first thin film transistor is electrically connected to the data line; and a drain of the first thin film transistor is electrically connected to a source of the second thin film transistor. pole. The liquid crystal display of claim 8, wherein the first liquid crystal capacitor is formed by a first sub-pixel electrode and a common electrode separated by a liquid crystal layer, and the second liquid crystal capacitor is formed by a second sub-pixel. The pixel electrode and a common electrode are formed by a liquid crystal layer. A pixel unit adapted to be electrically connected to a plurality of data lines and a plurality of scan lines, the pixel The unit includes: a first sub-pixel unit formed with a first switching element, a first liquid crystal capacitor electrically connected to the first switching element, and a first storage capacitor; and a second sub-pixel unit formed a second liquid crystal capacitor and a second storage capacitor electrically connected to each other; and a bidirectional diode electrically connected between the first liquid crystal capacitor and the second liquid crystal capacitor, wherein scan signals of the scan lines are When driving, the image data is charged to the first sub-pixel unit and the second sub-pixel unit to form two different potential differences between the first sub-pixel unit and the second sub-pixel unit, and when the scanning is stopped In the signal, the bipolar diode neutralizes the voltage difference between the first sub-pixel unit and the second sub-pixel unit. The pixel unit of claim 10, wherein the bidirectional diode comprises a first diode transistor and a second diode transistor, and the first diode body is One end is electrically connected to the second end of the second diode transistor; the second end of the first diode transistor is electrically connected to the first end of the second diode transistor; the first two a third end of the polar body transistor is electrically connected to the first end of the first diode transistor; a third end of the second diode transistor is electrically connected to the first end of the second diode transistor a first parasitic capacitance formed between the second end and the third end of the first diode transistor; a second portion is formed between the second end and the third end of the second diode transistor Parasitic capacitance. The pixel unit of claim 11, wherein the third end of the first diode transistor is electrically connected to the second storage capacitor and the second liquid crystal capacitor of the second sub-pixel unit; The third end of the second diode transistor is electrically connected to the first storage capacitor of the first sub-pixel unit and the first liquid crystal capacitor. The pixel unit of claim 12, wherein the first liquid crystal capacitor is formed by a first sub-pixel electrode and a common electrode separated by a liquid crystal layer, and the second liquid crystal capacitor The second sub-pixel electrode and a common electrode are formed by a liquid crystal layer. The pixel unit of claim 10, wherein the first switching element is formed by a first thin film transistor. The pixel unit of claim 14, wherein the bidirectional diode has a discharge rate equal to the off current of the first thin film transistor.