JPH05289635A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display device which adjust the quantity of variation in pixel voltage and then adjust variation in hue by adjusting pixel capacity to an optimum value. CONSTITUTION:This liquid crystal display device consists of (n) channel MOS transistors nTFT1 having their gate terminals connected to scanning lines X1, X2'... connected in series between signal lines Y1, Y2... and a common power source for a common potential VCOM, liquid crystal capacitors CLC, and series circuits of (n) channel MOS transistors nTFT2 connected in parallel to the liquid crystal capacitors CLC and auxiliary capacitors CS2 for adjustment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device capable of adjusting pixel capacitance.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional active matrix T.
It is a circuit diagram which shows the display drive element matrix circuit part of an FT liquid crystal display device. That is, the n-channel MOS transistor nTFT and the liquid crystal capacitance C _LC are connected in series between the signal lines Y1, Y2 ... Connected to the signal line drive circuit section and the common power source of the common potential V _COM. An auxiliary capacitance C _S is connected in parallel to the capacitance C _LC . The n-channel MO
The gate terminals of the S-transistor nTFT are scanning lines X1 and X
2 ..., and these scanning lines X1, X2 ... Are connected to the scanning line driving circuit.

However, the gate voltage V _G from the scanning line driving circuit is supplied to the scanning lines X1, X2 ..., And the n-channel MO connected to the scanning line whose gate voltage V _G is at the high level.
The S-transistor nTFT is turned on, and the signal voltage V _D supplied from the signal line drive circuit section to the signal lines Y1, Y2, ... Is accumulated in the liquid crystal capacitance C _LC and the auxiliary capacitance C _S.

FIG. 5 is a circuit diagram showing an equivalent circuit of one pixel in FIG. In FIG. 5, C _GS is a gate-source capacitance of the n-channel MOS transistor nTFT, R _LC is a liquid crystal resistance, and the pixel voltage V _P is applied to the liquid crystal capacitance C _LC , the auxiliary capacitance C _S and the liquid crystal resistance R _LC . This pixel voltage V _P is ΔV _P = {C _GS / (C _GS + C _LC + C _S )} · V _{G with} respect to the signal voltage V _D due to the gate-source capacitance C _GS of the n-channel MOS transistor nTFT.

It fluctuates only. Therefore, a voltage shifted by a fixed voltage ΔV _P from the common potential V _COM is applied to the common electrode to which the common potential V _{COM of} the common power source is applied.

[0006]

However, depending on the display screen of the liquid crystal display device, if the entire screen is too bright or too dark, the color tone shifts to red or blue, resulting in an unnatural hue. Since the shift voltage ΔV _P is fixed, adjustment in such a case could not be performed.

The present invention has been made in view of the above circumstances, and provides a liquid crystal display device capable of adjusting a variation in pixel voltage to adjust a change in color tone by adjusting a pixel capacitance to an optimum value. The purpose is to do.

[0008]

In order to solve the above-mentioned problems, the present invention connects a first switching element having a control terminal connected to a scanning line and a liquid crystal capacitor in series between a signal line and a common power source. In the above liquid crystal display device, a series circuit including a second switching element and an adjusting auxiliary capacitance is connected in parallel with the liquid crystal capacitance.

[0009]

The present invention controls the switching element to be turned on and off in accordance with the brightness of the display screen of the liquid crystal display device, thereby connecting or not connecting the adjustment auxiliary capacitor in parallel with the liquid crystal capacitor. The pixel capacitance is adjusted to an optimum value, the variation of the pixel voltage is adjusted to adjust the change of the color tone, and the adjustment is performed so that the natural color tone of the correct color tone is obtained.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 3 is a schematic block diagram showing an active matrix liquid crystal display device according to an embodiment of the present invention. That is, the display driving element matrix circuit unit 11 is driven by the signal line driving circuit unit 12 and the scanning line driving circuit unit 13. Note that all of these circuits can be formed using thin film transistors and all the circuits can be formed over one substrate.

FIG. 1 is a circuit diagram showing an example of the display drive element matrix circuit section 11 of FIG. That is, the n-channel MOS transistor nTFT1 which is the first switching element is provided between the signal lines Y1, Y2 ... Connected to the signal line drive circuit section 12 and the common power source of the common potential V _COM.
And the liquid crystal capacitance C _LC are connected in series, the liquid crystal capacitance C _LC
A series circuit composed of an auxiliary capacitance C _S1 and an n-channel MOS transistor nTFT2 that is a second switching element and an adjustment auxiliary capacitance C _S2 is connected in parallel to the. N
The gate terminal of the channel MOS transistor nTFT1 is connected to the scanning lines X1, X2 ...
.. are connected to the scanning line drive circuit section 13. or,
The gate terminal of the n-channel MOS transistor nTFT2 is connected to the control gate signal application terminal Tg.

FIG. 2 is a sectional view showing an example of an active matrix liquid crystal display panel according to the present invention. That is, gate electrodes G1 and G2 made of, for example, Al are formed on the lower glass substrate 21, and an insulating film 22 such as SiO ₂ is formed on the gate electrodes G1 and G2 and the lower glass substrate 21.
Is formed. The gate electrode G on the insulating film 22
Silicon active layers 23 are formed at positions corresponding to 1 and G2. A pixel electrode ITO made of, for example, Al is formed on the insulating film 22, and drain electrodes D1 and D2 and source electrodes S1 and S2 are formed on the insulating film 22 and a part of the silicon active layer 23. It is formed by being connected to ITO. A protective film 24 such as SiO ₂ is formed on the insulating film 22, the pixel electrode ITO, the silicon active layer 23, the drain electrodes D1 and D2, and the source electrodes S1 and S2. On the protective film 24, for example, polyimide or the like is formed. Alignment film 25 is formed. On the other hand, a blind layer 27 such as chromium is formed on the upper glass substrate 26, and an insulating film 28 such as SiO ₂ is formed on the blind layer 27 and the upper glass substrate 26. A common electrode 29 made of, for example, Al is formed on the insulating film 28, and an alignment film 30 made of, for example, polyimide is formed on the common electrode 29. Then, the upper glass substrate 26 and the lower glass substrate 21 are arranged with a spacer (not shown) interposed so that the alignment film 30 and the alignment film 25 face each other, and between the alignment film 30 and the alignment film 25. An active matrix liquid crystal display panel is constructed by filling the liquid crystal 31. The gate electrode G1,
The drain electrode D1, the source electrode S1 and the silicon active layer 23 are the n-channel MOS which is the first switching element.
The transistor nTFT1 is formed, and the gate electrode G
2, the drain electrode D2, the source electrode S2, and the silicon active layer 23 are the n-channel M that is the second switching element.
The OS transistor nTFT2 is configured.

However, the control gate signal Gs is applied to the control gate signal application terminal Tg from the control unit in accordance with the brightness of the display screen of the liquid crystal display device or the manual operation switch, and the control gate signal Gs is, for example, When high level such as 20V, n-channel MOS transistor nTFT2
When turned on, the liquid crystal capacitance C _LC and the auxiliary capacitance C _S1 are connected in parallel with the auxiliary capacitance C _S2 for adjustment. In this state, the gate voltage V _G from the scanning line driving circuit unit 13 is applied to the scanning lines X1, X
2 ..., And an n-channel MOS transistor nTFT connected to the scanning line with a high gate voltage V _G
1 is turned on, and the signal line drive circuit unit 12 outputs the signal lines Y1,
The signal voltage V _D supplied to Y2 ...
_{Store in LC} , auxiliary capacitance C _S1 and adjustment auxiliary capacitance C _S2 .
In this case, the variation amount ΔV _P 1 of the pixel voltage V _P with respect to the signal voltage V _D is ΔV _P 1 = {C _GS / (C _GS + C _LC + C _S1 + C _S2 )} · V _G , and the variation amount ΔV _P 1 Becomes smaller. C _GS is the gate-source capacitance of the n-channel MOS transistor nTFT1.

On the other hand, the control gate signal Gs is, for example,
When it is low level such as 0V, n-channel MOS transistor
The transistor nTFT2 is turned off and the liquid crystal capacitance C_LC, Auxiliary capacity C
_S1Auxiliary capacitance C for adjustment in parallel with_S2Is not connected. This state
In the state, the gate voltage V from the scanning line drive circuit unit 13
_GTo the scanning lines X1, X2 ..._G
Is an n-channel MOS transistor connected to the high-level scanning line
The transistor nTFT1 is turned on, and the signal line drive circuit unit 1
2 the signal power supplied to the signal lines Y1, Y2 ...
Pressure V_DThe liquid crystal capacity C_LCAnd auxiliary capacity C_S1Accumulate in. This
, The signal voltage V_DAgainst the pixel voltage V_PVariation Δ
V_P2 is ΔV_P2 = {C_GS/ (C_GS+ C_LC+ C_S1)} ・ V_G  And the fluctuation amount ΔV_P2 becomes larger.

As described above, by changing the variation amount of the pixel voltage V _P to ΔV _P 1 or ΔV _P 2 in accordance with the lightness and darkness of the display screen of the liquid crystal display device, a natural hue of a correct color tone can be obtained. Can be adjusted.

The n-channel MOS transistor nTFT2, which is the second switching element, and the auxiliary capacitance C for adjustment.
Two or more sets of series circuits of _S2 may be connected in parallel with the liquid crystal capacitance C _LC , in which case the range of variation of the pixel voltage V _P can be widened.

[0018]

As described above, according to the present invention, the auxiliary storage capacitor for adjustment is connected in parallel with the liquid crystal capacitor by controlling the switching elements to be turned on and off according to the brightness of the display screen of the liquid crystal display device. Adjust the pixel capacity to the optimum value by connecting or not connecting it, and adjust the variation of the pixel voltage to adjust the change in the color tone, and adjust the color tone to obtain a natural hue. be able to.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an example of a display drive element matrix circuit section according to the present invention.

FIG. 2 is a cross-sectional view showing an example of a liquid crystal display panel according to the present invention.

FIG. 3 is a schematic block diagram showing an embodiment of the present invention.

FIG. 4 is a circuit diagram showing a conventional display drive element matrix circuit section.

FIG. 5 is an equivalent circuit diagram showing one pixel of a conventional display drive element matrix circuit section.

[Explanation of symbols]

11 ... Display drive element matrix circuit section, 12 ... Signal line drive circuit section, 13 ... Scan line drive circuit section, nTFT1 ... n
Channel MOS transistor, nTFT2 ... n-channel MOS transistors, C _LC ... liquid crystal capacitance, C _S1 ... auxiliary capacitance, C _S2 ... adjustment auxiliary capacitor, Tg ... controlling gate signal applying terminals.

Claims (1)

[Claims] 1. A first switching element and a liquid crystal capacitor having a control terminal connected to a scanning line connected in series between a signal line and a common power source, and a second switching device connected in parallel with the liquid crystal capacitor. A liquid crystal display device comprising a series circuit including a switching element and an auxiliary capacitor.