JP3064702B2 - Active matrix type liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device, and more particularly to an active matrix type liquid crystal display device which is required to have features such as low driving power, high image quality such as high contrast and multiple gradations, and high reliability. It is about.

[0002]

2. Description of the Related Art In recent years, active matrix type liquid crystal display devices have been widely used in hand-held computers, personal word processors, portable televisions, and the like, and the range of use has been expanding. Characteristics required for an active matrix type liquid crystal display device include low power driving, high image quality, and high reliability.
Various configurations and driving methods to achieve these characteristics
It has been studied and put into practical use.

[0003] In particular, JP-A-02-000913, JP-A-02-000913
A driving method that modulates the potential of a pixel electrode by changing the potential of a scanning signal line that is capacitively coupled to the pixel electrode as proposed in Japanese Patent No. 157815 (hereinafter referred to as capacitive coupling driving). ), It is possible to remove a direct current component caused by the dielectric anisotropy of the liquid crystal, and to have characteristics such that the potential of the counter electrode is constant and the display signal amplitude is small, that is, low power consumption can be realized. , As a driving method satisfying the above requirements.

However, in the conventional capacitive coupling drive, the EWS
For an ultra-large screen and a large-capacity display, for example, a horizontal crosstalk problem has occurred. Horizontal crosstalk is a phenomenon in which areas on the screen that must originally have the same luminance have different luminances depending on the pattern of other picture elements that are turned on at the same time. Serious problem. The cause of the horizontal crosstalk is that the display signal wiring and the counter electrode are capacitively coupled, and a change in the display signal potential induces a vibration component in the counter electrode potential to obtain a desired liquid crystal applied voltage. Can not be done. According to the driving method of inverting the polarity of the display signal potential for each display signal wiring (hereinafter, referred to as V inversion driving),
It is well known that the counter electrode potential oscillation component effectively disappears because adjacent display signals cancel each other out, and no horizontal crosstalk is observed. In an active matrix type liquid crystal display device having a conventional structure, capacitively coupled V inversion driving was impossible in principle.

[0005]

SUMMARY OF THE INVENTION The present invention provides a capacitive coupling V
It is an object of the present invention to provide an active matrix type liquid crystal display device capable of inversion driving. Thereby, phenomena such as horizontal crosstalk can be eliminated, and characteristics such as low power, high image quality, and high reliability can be realized.

[0006]

In order to achieve the above object, an active matrix type liquid crystal display device according to the present invention is provided.
The scanning signal wiring and the display signal wiring are arranged in a matrix.
Formed between the scanning signal wiring and the display signal wiring.
Pixel electrodes and switching elements are formed
Active matrix type liquid crystal display device
The picture element electrode is provided every one or several display signal wires.
Forming a storage capacitor between the different scanning signal wirings;
And features . In the above active matrix liquid crystal display device, a compensation voltage is applied to the scanning signal wiring before and after the on-period of the switching element, and the compensation voltage before the on-period before the on-period is changed every one or several scanning signal wirings. It is preferable that the polarity is inverted and the polarity of the compensation voltages after the ON period is inverted every one or several scanning signal wirings.

[0007]

As described above, according to the present invention, the picture element electrode
By forming a storage capacitor between one or several display signal lines and the different scanning signal lines, the polarity of the modulation applied to the pixel electrodes during the off period of the switching element can be changed. It can be inverted every book or every few books. That is, capacitive coupling V inversion driving can be performed.

[0008]

(Embodiment 1) A first embodiment of the present invention is shown in FIG. Here, a liquid crystal display device using a thin film transistor (TFT) as a switching element was used. In FIG. 1A, reference numeral 1 denotes a scanning signal line, and 2 denotes a display signal line. A TFT 3 has a gate electrode connected to the scanning signal wiring 1 and a source electrode connected to the display signal wiring 2. Reference numeral 4 denotes a picture element electrode which is connected to the drain electrode of the TFT 3. 5 is a counter electrode, 6 is a picture element electrode 4 and a counter electrode 5
The liquid crystal capacitance (Clc) 7 formed between the pixel electrode 4 and the scanning signal is used to compensate for the lack of charge holding capacity of the liquid crystal layer and to modulate the pixel electrode by a change in the scanning signal wiring potential. A storage capacitance (Cst) formed between the wiring 1 and the wiring 1;
Each of the display signal wirings 2 is connected to a different scanning signal wiring 1 (front gate, rear gate). Reference numeral 8 denotes a gate = drain capacitance (Cgd) which is a parasitic capacitance generated between the gate electrode and the drain electrode of the TFT 3. 1v in FIG. 2B is a scanning signal, and 2v in FIG. 2C is a display signal.

The driving potential relationship will be described with reference to FIG. FIG. 2A shows modulation by the negative compensation potential immediately after the ON period, FIG. 2B shows modulation by the positive compensation potential immediately before the ON period, and FIG. 2C shows modulation by the positive compensation potential immediately after the ON period. (D) shows the modulation by the negative compensation potential immediately after the ON period. 1va is the potential applied to the scanning signal wiring 1 connected to the TFT gate electrode of the picture element of interest, 1vb
Is a potential applied to the scanning signal wiring 1 connected to the pixel electrode 4 via a storage capacitor, 1v1 is a TFT off potential level,
1v2 is a TFT ON potential level, 1v3 is a compensation potential (+) level, 1v4 is a compensation potential (-) level, 4v is a potential transmitted to the pixel electrode 4, and 5v is a counter electrode potential (constant value). The compensation voltage is applied immediately before and after the TFT ON period. The polarity of the display signal 2v is
(V inversion)
Correspondingly, the polarity of the compensation voltage is inverted before and after the TFT ON period. The display signal 2v is inverted (temporally inverted) for each of the scanning signal wirings 1 (hereinafter, referred to as the scanning signal wiring 1).
Recorded as H inversion. Correspondingly, the polarity of the compensation voltage is inverted for each scanning signal line 1.

The potential of the picture element electrode when the potential shown in FIG. 2 is applied to the configuration shown in FIG. Here, when Ctot = Clc + Cst + Cgdktg = Cgd / Ctotkzg = Cst / Ctot, ktg (V (on) -V (off)) + kzg (Vge (+) + Vge (-)) / 2 = 0 is satisfied. Each potential was set as described above. This allows
Since the display signal amplitude center, the pixel electrode potential amplitude center, and the counter electrode potential match, no DC component due to the dielectric anisotropy of the liquid crystal appears, and the liquid crystal applied voltage remains low while the display signal amplitude remains small. Since the size can be increased, low power consumption can be realized.

A potential was actually applied to a liquid crystal panel having the array structure shown in FIG. 1 to verify the effect of improving the characteristics. When the window pattern was displayed and the waveform of the counter electrode potential was observed using an oscilloscope, no counter electrode potential oscillation component was observed. Also, when visually observed, the horizontal crosstalk was completely eliminated. The same applies to (Example 2) to (Example 5).

(Embodiment 2) According to Embodiment 2 of the present invention,
(FIG. 3). In FIG. 1A, the storage capacitor 7 is connected to different scanning signal lines 1 every several display signal lines 2. The scanning signal wiring potential 1v in FIG.
The polarity of the compensation voltage is inverted for each line, and the display signal wiring potential 2v in FIG. The polarity is inverted for each book.

(Embodiment 3) The (Embodiment 3) of the present invention
(FIG. 4). In FIG. 1A, the storage capacitor 7 is connected to a different scanning signal line 1 for each display signal line 2. In the scanning signal wiring potential 1v in FIG. 3B, the polarity of the compensation voltage is inverted every few lines (the polarity of the compensation voltage is not necessarily different for a single scanning signal wiring 1 before and after the ON period). Do not have to match). The polarity of the display signal wiring potential 2v in FIG. 9C is inverted spatially every one line and temporally every several lines corresponding to the inversion of the polarity of the compensation voltage. The storage capacitor 7 is connected to the display signal wiring 2.
It is also possible to realize a case where every few lines are connected to the scanning signal wiring 1.

(Embodiment 4) According to (Example 4) of the present invention,
(FIG. 5). There are two ON periods of the switching element. It should be noted that the storage capacitor 7 may be connected to different scanning signal wirings 1 for every several display signal wirings 2 or the polarity of the compensation voltage may be inverted every several scanning signal wiring potentials 1v. realizable.

In the above-described embodiment of the present invention, the display signal is supplied by H inversion. However, the present invention can be applied to a so-called 1F inversion drive in which the voltage polarity of the display signal is inverted every frame. It can be easily analogized.

[0016]

As described above, according to the present invention, the picture element electrode forms a storage capacitor between one or several display signal wirings and the different scanning signal wirings. In addition, the polarity of the modulation applied to the picture element electrode during the off period of the switching element can be inverted every one or several display signal wirings, that is, capacitive coupling V inversion driving can be performed. As a result, the counter electrode potential oscillation component disappears,
Lateral crosstalk is eliminated. That is, in the active matrix display element, it is possible to obtain image quality superior to the conventional one while maintaining characteristics such as low power and high reliability.

[Brief description of the drawings]

FIG. 1 is an array circuit diagram and a potential relation diagram illustrating a first embodiment of the present invention.

FIG. 2 is a potential relation diagram for explaining a change in a pixel electrode potential in an embodiment of the present invention.

FIG. 3 is an array circuit diagram and a potential relation diagram illustrating a second embodiment of the present invention.

FIG. 4 is an array circuit diagram and a potential relationship diagram illustrating a third embodiment of the present invention.

FIG. 5 is an array circuit diagram and a potential relation diagram illustrating a fourth embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 scanning signal wiring 2 display signal wiring 3 TFT 4 picture element electrode 5 counter electrode 6 liquid crystal capacitance (Clc) 7 storage capacitance (Cst) 8 gate = drain capacitance (Cgd) 1v scanning signal wiring potential 1va scanning signal wiring potential (switching element ON = OFF control line) 1vb Scan signal wiring potential (pixel electrode potential modulation line) 1v1 Scan signal wiring potential (OFF potential, V (off)) 1v2 Scan signal wiring potential (ON potential, V (on)) 1v3 Scan signal Wiring potential (positive compensation voltage, Vge (+)) 1v4 Scan signal wiring potential (negative compensation voltage, Vge (-)) 2v Display signal wiring potential 4v Pixel electrode potential 5v Counter electrode potential

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-157815 (JP, A) JP-A-4-360127 (JP, A) JP-A-6-35418 (JP, A) JP-A-2- 913 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/1368 G02F 1/133 550 G09G 3/36

Claims (2)

(57) [Claims] 1. An active matrix type liquid crystal in which scanning signal lines and display signal lines are formed in a matrix, and picture element electrodes and switching elements are formed corresponding to intersections of the scanning signal lines and the display signal lines. In the display device, the picture element electrode forms a storage capacitor between the display signal wiring and the scanning signal wiring which differs every several display signal wirings. 2. A run before and after the ON period of the switching element
The compensation voltage is applied to the scanning signal wiring and the scanning signal wiring
Compensation voltages before the ON period every one or several lines
Is inverted, and one or more scanning signal wires
The polarity of the compensation voltages after the ON period is inverted for each book
Characterized in that it is an active matrix type liquid crystal display device according to claim 1.