JPH0253031A - Tft liquid crystal display element and its driving method - Google Patents

Abstract

PURPOSE:To prolong the life of liquid crystal by dividing a common electrode into many striped electrodes and connecting common electrodes facing picture electrodes in odd-numbered arrays and common electrodes facing picture element electrodes in even-numbered arrays together respectively in common. CONSTITUTION:The common electrode is divided into many striped electrodes facing picture element electrode arrays along gate lines GL and GL, and the odd-numbered common electrodes 5A and 5A corresponding to the picture element electrodes 3 and 3 in the odd arrays and the common electrodes 5B and 5B facing the picture elements 3 and 3 in the even arrays are connected in common respectively. Then mutually opposite-phase common signals A and B are applied to said the common electrodes 5A and 5A and common electrodes 5B and 5B, and a data signal which is inverted at each one-gate-line selection period DELTAh is applied to data lines DL and DL. Consequently, the DC unbalance of the applied voltage to a liquid crystal layer is eliminated, the life of the liquid crystal is prolonged, the generation of a flicker is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a TFT liquid crystal display element and a method for driving the same.

[Conventional technology]

As is well known, a TFT liquid crystal display element, which is a type of active matrix type liquid crystal display element, controls the application of a display drive voltage to a pixel electrode using a thin film transistor (TPT). A display element has a plurality of gate lines and a plurality of data lines perpendicular to the gate lines formed on the surface of one of a pair of transparent substrates facing each other with a liquid crystal layer in between. 1 along the gate line and each data line. A large number of thin film transistors each having a gate electrode connected to the gate line and a drain electrode connected to the data line, and a large number of transparent pixel electrodes each connected to the source electrode of each of the thin film transistors are arranged vertically and horizontally. In addition, a transparent common electrode facing the pixel electrode is formed.

Figure 3 shows the electrode pattern of a conventional TFT liquid crystal display element, and one substrate has a large number of gate lines GL wired on the surface of the substrate, as shown in Figure 3(a).
, GL and the data lines DL, DL, a large number of pixel electrodes 3, 3 are arranged vertically and horizontally. 4 is a pixel electrode 3 provided corresponding to each pixel electrode 3, 3, respectively.
The gate electrode of each thin film transistor 4 is connected to the gate line GL, the drain electrode is connected to the data line DL, and the source electrode is connected to the pixel electrode 3. ing. In addition, in FIG. 3(a), GLa and GLa are respective gate lines OL.

The terminals of OL, DLa, DLa are connected to each data line DL, D
This is the L terminal. On the other hand, on the second side of the other board, there is a
As shown in b), each pixel electrode 3, 3 on one surface of one substrate
A common electrode 5 is formed to face the common electrode 5, and this common electrode 5 is a full-surface electrode that covers the entire display area of the liquid crystal display element. Note that 5a is a terminal of the common electrode 5.

This TFT liquid crystal display element has each gate line GL, GL
By sequentially applying gate signals (scanning signals) to and applying data signals (video signals) to each data line DL, DL in synchronization with this, each thin film transistor 4, 4
The display is driven by applying a display drive voltage to each pixel electrode 3 through the common electrode 5 and a common signal to the common electrode 5. TFT liquid crystal display elements that display television images, etc. It is AC powered to maintain its lifespan.

[Problem to be solved by the invention]

However, in the conventional TFT liquid crystal display element, the common electrode 5 is a full-surface electrode covering the entire display area of the liquid crystal display element. Normally, the common signal is inverted every two scanning periods (from application of the gate signal to the application of the gate signal to the final gate line), and the data signal is inverted accordingly, resulting in AC drive. Conventional TFT liquid crystal display elements have the problem that the voltage applied to the liquid crystal layer becomes DC unbalanced, which not only shortens the life of the liquid crystal, but also causes flickering, which deteriorates the display image quality. had.

That is, FIG. 4 shows the waveforms of the data signals and common signals applied to the data lines DL and DL of the TFT liquid crystal display element and the common electrode 5. When applying a common signal that is inverted every scanning period H, the data lines DL, DL have a common signal that is opposite in phase to the common signal and 1 as shown in FIG. 4(a).
A data signal that is inverted every scanning period H is applied. When the liquid crystal display element is driven by applying such a data signal and a common signal, the average value of the voltage applied to the liquid crystal layer per one scanning period H changes depending on whether the pixel electrodes 3, 3 are selected or not. Depending on the selection, it is biased towards the + side or one side, which causes a DC imbalance in the voltage applied to the liquid crystal layer.
This causes shortening of the life of the liquid crystal and generation of flicker.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to extend the life of the liquid crystal by eliminating the DC unbalance of the voltage applied to the liquid crystal layer, and to eliminate flicker. It is an object of the present invention to provide a TFT liquid crystal display element and a method for driving the same, which can improve the display image quality by preventing the occurrence of such problems.

[Means to solve the problem]

In order to achieve the above object, the TFT liquid crystal display element of the present invention divides the common electrode into a large number of strip-like electrodes facing each pixel electrode row along each gate line, and each stripe-like common electrode Among the electrodes, common electrodes facing pixel electrodes in odd-numbered columns and common electrodes facing pixel electrodes in even-numbered columns are respectively commonly connected.

Further, in the method for driving a TFT liquid crystal display element of the present invention, the TFT liquid crystal display element having the above configuration is arranged such that the common electrode facing the pixel electrodes in the odd-numbered columns and the common electrode facing the pixel electrodes in the even-numbered columns are opposite to each other. A common signal that is inverted every one scanning period or every two scanning periods is applied to each data line, and a data signal that is inverted every one gate line selection period is applied to each data line. .

[Effect]

According to the above TFT liquid crystal display element, the common electrode is divided into a large number of striped electrodes facing each pixel electrode row along each gate line, and common electrodes facing each other to pixel electrodes in odd numbered rows and common electrodes facing each other in even numbered rows. Since the common electrodes facing the pixel electrodes in the columns are connected in common, common signals with opposite phases are sent to the common electrodes facing the pixel electrodes in the odd-numbered columns and the common electrodes facing the pixel electrodes in the even-numbered columns. At the same time, by applying a data signal that is inverted every one gate line selection period to each data line, the voltage applied to the liquid crystal layer between the pixel electrodes in odd-numbered columns and the common electrode opposite thereto can be increased. The bias toward one side or one side and the bias toward one side or the + side of the voltage applied to the liquid crystal layer between the pixel electrodes of even-numbered columns and the opposing common electrode can be canceled out. therefore,
This TFT liquid crystal display element eliminates the DC unbalance of the voltage applied to the liquid crystal layer, which was a drawback of conventional TFT liquid crystal display elements, extending the life of the liquid crystal, and also prevents flickering and improves display image quality. can be improved.

In addition, in the above driving method, the TFT liquid crystal display element is arranged such that a common electrode facing the pixel electrodes in the odd numbered columns and a common electrode facing the pixel electrodes in the even numbered columns are arranged in opposite phases to each other and for one scanning period or two scanning periods. Since it is driven by applying a common signal that is inverted every period, and applying a data signal that is inverted every 1 gate line selection period to each data line, DC imbalance of the voltage applied to the liquid crystal layer is caused. It is possible to eliminate this problem, extend the life of the liquid crystal, and also prevent the occurrence of flicker, thereby allowing the TFT liquid crystal display element to display images of high quality.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

Figure 1 shows the electrode pattern of a TFT liquid crystal display element.
Similar to FT liquid crystal display elements, many gate lines GL
, GL and a large number of data lines DL, DL perpendicular to the gate lines GL, GL are formed,
Each gate line GL, GL and each data line D
L.

Along the DL, a large number of thin film transistors 5, 5 each having a gate electrode connected to the gate line GL and a drain electrode connected to the data line DL, and each thin film transistor 5.
A large number of pixel electrodes 3, each connected to a source electrode of 5,
3 are arranged vertically and horizontally. In FIG. 1(a), GLa and GLa are terminals of each gate line GL and GL, and DLa and DLa are terminals of each data line DL and DL.

On the other hand, the common electrode formed on the second surface of the other substrate is the first
As shown in Figure (b), the one substrate 1 is divided into a large number of striped electrodes 5A and 5B facing each pixel electrode row along each gate line GL and GL. Common 7 Hypolar 5A, 5B,
Common electrodes 5A, 5 facing pixel electrodes 3, 3 in odd-numbered columns
The common electrodes 5B and 5B corresponding to the pixel electrodes 3.3 in the even columns are connected at one end to the common connection lines 6A and 6B, respectively.
, 6B. The common electrodes 5A, 5B and the common connection lines 6A, 6B are formed by depositing a transparent conductive film such as ITO on two surfaces of the substrate and patterning this transparent conductive film by photo-etching. Each common connection line 6A, 6B is connected to a common signal application terminal 7a, 7B, respectively.

Next, a display driving method of the above TFT liquid crystal display element will be explained. This driving method includes odd-numbered common electrodes 5A facing the odd-numbered rows of pixel electrodes 3, 3 of the TFT liquid crystal display element;
5A and the even-numbered common electrodes 5B, 5B facing the even-numbered pixel electrodes 3.3, gate signals are applied in opposite phases to each other and for one scanning period, that is, from the gate signal application to the first gate line to the final gate line. A common signal that is inverted every period until the signal is applied is applied to each data line DL.

A data signal that is inverted every selection period Δh of one gate line GL is applied to DL, and the common signal applied to the odd-numbered common electrodes 5A, 5A is different from the one common signal applied. Common connection line 6 from terminal 7a
The common signals applied to all the odd-numbered common electrodes 5A, 5A simultaneously through A, and the common signals applied to the even-numbered common electrodes 5B, 5B are all applied from the other common signal application terminal 7b to the common connection line 6B. even-numbered common electrode 5B,
5B at the same time.

FIG. 2 shows the data line DL of the TFT liquid crystal display element,
This shows the waveforms of the data signal and common signal applied to the DL and the common electrodes 5A, 5B. The common signal A is applied to the odd-numbered common electrodes 5A, 5A, and the common signal A is applied to the even-numbered common electrodes 5B, 5B. The applied common signal B is m2
As shown in FIGS. (b) and (c), the signals are mutually opposite in phase and inverted every scanning period H, and the data line DL
.

As shown in FIG. 2(a), the data signal applied to the DL is a signal that has an opposite phase to the common signal and is inverted every scanning period H.

Therefore, in the above TFT liquid crystal display element, the common electrode is divided into a large number of striped electrodes facing each pixel electrode row along each gate line GL, GL, and pixel electrodes 3, 3 in odd rows are divided into a plurality of striped electrodes. Since the common electrodes 5A, 5A in odd numbers facing each other and the common electrodes 5B, 5B facing each other in pixel electrodes 3, 3 in even rows are connected in common, the pixel electrodes 3.3 in odd rows are connected in common. Common signals A and B having mutually opposite phases are applied to the common electrodes 5A and 5A opposite to the pixel electrodes 3 and 3 in even-numbered columns, and one gate line selection period is applied to each data line DL. By applying a data signal that is inverted every Δh, the pixel electrodes 3, 3 in odd-numbered columns and the common electrode 5A opposite thereto.

5A to the liquid crystal layer between the pixel electrodes 3.3 and the common electrodes 5B and 5B facing each other. Therefore, according to this TFT liquid crystal display element, the DC voltage applied to the liquid crystal layer, which was a drawback of conventional TFT liquid crystal display elements, can be canceled out. It is possible to eliminate unbalance and extend the life of the liquid crystal, and also to prevent flickering and improve display image quality.

Further, in the driving method, the TFT liquid crystal display element is driven by common electrodes 5A, 5A opposite to the pixel electrodes 3, 3 in odd columns.
and a common flit facing the pixel electrodes 3, 3 in even-numbered columns.
5B and 513, a common signal AB which is used inversely to each other and is inverted every scanning period H is applied to each data line D.
Since L and DL are driven by applying a data signal that is inverted every 1 gate line selection period Δh, the DC imbalance of the voltage applied to the liquid crystal layer can be eliminated and the life of the liquid crystal can be extended. This allows the TFT liquid crystal display element to display images of good quality by extending the time and preventing the occurrence of flicker.

In addition, in the above embodiment, the odd numbered common electrodes 5A, 5A
One common signal application terminal 7a, 7B is provided for each common connection line 6A that commonly connects the common electrodes 5B, 5B, and the common connection line 6B that commonly connects the even numbered common electrodes 5B, 5B.
are connected, but these common signal application terminals 7a and 7B
may be connected to each of the common connection lines 6A, 6B at intervals in the length direction, and odd-numbered common electrodes 5A, 5A and even-numbered common electrodes 5B,
5B may be divided into blocks each having a predetermined number of lines, and each block may be commonly connected by a common connection line. Furthermore, in the above embodiment, the common signal A is applied to the odd numbered common electrodes 5A, 5A, and the even numbered common electrode 5B.

5B and the common signal B applied to
Although the signals are inverted every scanning period H, the common signals A and B are in opposite phases to each other and are inverted for 2 scanning periods (2H).
It may also be a signal that is inverted every time.

〔Effect of the invention〕

In the TFT if & product list non-display element of the present invention, the common electrode is divided into a large number of striped electrodes facing each pixel electrode row along each gate line, and the common electrode is divided into a plurality of striped electrodes facing the pixel electrodes in odd numbered rows. Since the common electrodes and the common electrodes facing the pixel electrodes in the even-numbered columns are connected in common, the common electrodes facing the pixel electrodes in the odd-numbered columns and the common electrodes facing the pixel electrodes in the even-numbered columns are connected to each other. At the same time as applying a common signal of opposite phase, one signal is applied to each data line.
By applying a data signal that is inverted every gate line selection period, the voltage applied to the liquid crystal layer between the pixel electrodes in odd-numbered columns and the opposing common electrode is biased to the + side or to one side. The voltage applied to the liquid crystal layer between the even-numbered pixel electrodes and the opposing common electrode can be canceled out to one side or to the + side, and therefore, this TFT liquid crystal display element According to , it is possible to eliminate the DC unbalance of the voltage applied to the liquid crystal layer, which was a drawback of conventional TFT liquid crystal display elements, to extend the life of the liquid crystal, and to improve the display image quality by preventing the occurrence of flicker. can.

Further, in the method for driving a TFT liquid crystal display element of the present invention, the TFT liquid crystal display element is arranged such that a common electrode facing the pixel electrodes in the odd-numbered columns and a common electrode facing the pixel electrodes in the even-numbered columns have opposite phases to each other. A common signal that is inverted every one or two scanning periods is applied to each data line.
Since it is driven by applying a data signal that is inverted every one gate line selection period, it eliminates the DC unbalance of the voltage applied to the liquid crystal layer, extending the life of the liquid crystal and also preventing the occurrence of flicker. The above TFT
The liquid crystal display element can display images of good quality.

[Brief explanation of the drawing]

1 and 2 are electrode pattern diagrams and driving waveform diagrams of a TFT liquid crystal display element showing an embodiment of the present invention, and FIGS. 3 and 4 are electrode pattern diagrams and driving waveform diagrams of a conventional TFT liquid crystal display element. FIG. 1.2... Substrate, 3... Pixel electrode, 4... Thin film transistor, GL... Gate line, DL... Data line, 5A, 5B... Common electrode, 6A, 6B.
...Common connection line, 7A, 7B...Common signal application terminal, H...1 scanning period, Δh...1 gate line selection period. Applicant's agent Patent attorney Takehiko Suzue

Claims (2)

[Claims] (1) A large number of gate lines and a large number of data lines perpendicular to the gate lines are formed on the surface of one of a pair of transparent substrates facing each other with a liquid crystal layer in between, and each gate along each data line, a large number of thin film transistors each having a gate electrode connected to the gate line and a drain electrode connected to the data line, and a large number of transparent pixel electrodes each connected to the source electrode of each thin film transistor. In a TFT liquid crystal display element in which a transparent common electrode is formed in arrays in the vertical and horizontal directions and faces the pixel electrode on the other substrate surface, the common electrode is formed in a plurality of electrodes facing each pixel electrode row along each gate line. It is divided into two striped common electrodes, and among these striped common electrodes, the common electrodes facing the pixel electrodes in odd-numbered columns and the common electrodes facing the pixel electrodes in even-numbered columns are respectively connected in common. Characteristic TFT liquid crystal display element. (2) Applying common signals opposite to the pixel electrodes in the odd-numbered columns and the common electrodes facing the pixel electrodes in the even-numbered columns that have mutually opposite phases and are inverted every one scan period or every two scan periods; 2. The method of driving a TFT liquid crystal display element according to claim 1, wherein a data signal that is inverted every one gate line selection period is applied to each data line.