JPS6243624A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To cancel the visual angle dependency of a liquid crystal panel and to display images of uniform picture quality by increasing a voltage applied between a signal electrode and a scanning electrode from an upper scanning electrode to a lower scanning electrode. CONSTITUTION:The liquid crystal layer of the liquid crystal display panel 1 of a liquid crystal display device is sandwiched between a substrate where scanning electrodes 2 are formed and a substrate where signal electrodes 3 are formed, a polarizer is arranged across those substrate, and the liquid crystal layer is twisted by the polarizer. A scanning electrode driving circuit 5 and a signal electrode driving circuit 6 are connected to their electrodes 2 and 3 and the circuits 5 and 6 are synchronized by a timing control circuit 7. A driving voltage 10 is divided by resistances R1-R5 of a voltage dividing circuit 11 and divided voltages are applied to the circuits 5 and 6. Then, the voltage applied between electrodes 2 and 3 of the panel 1 is increased from an upper electrode 2 to a lower electrode 2 to cancel the visual angle dependency of the panel 1, displaying images of uniform picture quality.

Description

[Detailed description of the invention] [Field of application to which the invention pertains] The present invention relates to a method for driving a liquid crystal display device.

[Conventional technology]

The conventional driving method for a liquid crystal display device is multiflex driving of line sequential scanning using an averaging bias method, in which the polarity of the voltage applied is reversed every time one screen is scanned using an alternating current signal. In Figure 11 / 100 denominations, 1
5 shows drive waveforms obtained by the voltage averaging method using the 5-bias method.

[Problems solved by the invention]

Due to the drive as described above, voltage is applied on average to the entire surface of the liquid crystal panel that makes up the display device, and as liquid crystal panels become larger and multi-flex, the viewing angle with respect to the liquid crystal panel surface changes. Due to the viewing angle dependence of liquid crystal panels, the larger the size, the thinner the liquid crystal panel becomes.The upper side of the liquid crystal panel has a smaller viewing angle with the liquid crystal panel, making it darker, while the lower side, on the other hand, has a larger viewing angle, making it thinner.

[Means to solve the problem]

The present invention was made in order to solve these conventional problems, and the present invention has been made in order to pass the voltage applied between the signal electrode and the scan electrode that constitute the display panel from the upper scan electrode to the lower scan electrode. Accordingly, the voltage is applied higher.

[Effect]

Since the voltages are applied as described above, a low effective voltage is applied to the upper side of the liquid crystal display panel, and a high effective voltage is applied to the lower side of the liquid crystal display panel, canceling out the viewing angle dependence of the liquid crystal display panel and obtaining uniform image quality.

[Example 1] FIG. 1 is a block diagram of a liquid crystal display device of the present invention, in which 1 is a liquid crystal display panel, in which a liquid crystal layer 4 forms a scanning electrode 2 and a substrate forms a signal electrode 3. It consists of a polarizer sandwiched between the substrates and arranged so as to sandwich these substrates, and the polarization axis of the polarizer or the absorption axis of the liquid crystal layer 4 is twisted at about 90 degrees (80 degrees to 100 degrees). It is arranged according to what is being done.

yl+yx*...ym is a row of scan electrodes 2 connected to the scan electrode drive circuit 5, and xI, X
1, . . . The scanning signal is applied to the scanning electrode 2 as a scanning signal, and in synchronization with this scanning signal, the signal electrode driving circuit 6 provides the signal electrode 3 as a data signal. 7 is a timing control circuit which synchronizes the drive circuits 5 and 6 with the data to be displayed and outputs an alternating current signal to the outside.

Reference numeral 9 denotes a drive voltage power source, which has a sawtooth waveform 22 that is reset at the rising and falling edges of the alternating current signal 8, and the waveform is shown in FIG. The oblique side of the waveform 10 may be a straight line, and the voltage difference is, for example, the resistor R1 + "1 m" 31 R4 + RI constituting the voltage dividing circuit 11 at /1°8 dea.
If is 1:1:5:1:1, then 1.8 VO'lt
The optimum value is between ~35 volts. Voltage divider circuit 1
1 is the voltage obtained by dividing the drive voltage 10 of the power supply 9 by the resistors R8 to R6, starting from the highest one: vO + vl + vl
+ vl + v4 and vs are reduced in impedance by voltage follower circuits α1 to α and supplied to the drive circuit 5.6.

FIG. 3 shows a circuit for realizing a sawtooth waveform 22. Since one end of the resistor 21 is connected to a positive voltage source, the voltage at the non-inverting input of the operational amplifier 12 is always higher by the Zener voltage of the Zener diode. Since the voltage is applied to the resistor 15 via the resistor 21, a constant current flows across the resistor 15, so the voltage increases linearly across the capacitor 16, and the same voltage is output from the output of the operational amplifier 17. be done. The rise and fall detection circuit 18 of the alternating current signal 8 detects the rise and fall of the signal 8, and as a result, the analog switch 17 is turned on, so that the voltage across the capacitor 16 becomes zero. As a result, the slope of the sawtooth waveform obtained at the output of the operational amplifier 12 is adjusted by a variable resistor 20 attached to the operational amplifier 13, and the magnitude of the drive voltage 1o is adjusted by a variable resistor 19.

Since the configuration is as described above, the scanning electrode 2, the signal electrode 3, and the voltage between the two electrodes 2 and 3 are as shown in FIG. As the voltage increases, a higher voltage is applied and offsets the viewing angle dependence of the liquid crystal panel, resulting in uniform image quality. [Example 2] Figure 5 shows that the viewing angle with the liquid crystal panel increases as the upper side of the liquid crystal panel increases. When viewing, for example, in the circuit that creates the sawtooth waveform 10 when looking down at the LCD panel vertically as shown in Figure 6, one end of the resistor 21 in Figure 5 is connected to the positive power supply, and one end of the resistor 21 in Figure 5 is connected to the negative power supply. Change the power supply and reverse the direction of the Zener diode 14. As a result, the driving voltage is changed to yl of the scanning electrode 2, as shown in FIG.
That is, since the driving voltage 10 is high on the upper side of the liquid crystal panel and lower on the lower side, the viewing angle dependence of the liquid crystal panel is canceled out by this driving voltage, and uniform image quality is obtained. [Embodiment 3] FIG. This embodiment is a liquid crystal display device using a liquid crystal display panel 1 in which the signal electrode 3 is divided into upper and lower parts, and both the upper and lower parts have independent scanning electrodes and signal electrode drive circuits. A detailed diagram of the drive voltage power supply circuit 9 is shown in FIG. 9.The structure of the drive voltage power supply circuit 9 is similar to that shown in FIG.
There are two sets corresponding to , and hereinafter they will be referred to as the upper circuit and the lower circuit. Since the non-inverting input of the operational amplifier 13 in the upper circuit is connected between the variable resistor 22 whose voltage at both ends is fixed by the constant voltage power supply circuit 23, there is no connection between the non-inverting input of the operational amplifier 13 in the upper circuit and the non-inverting input of the operational amplifier 15 in the lower circuit. Since the same voltage difference always occurs between them, even if the variable resistor 19 is moved to change the drive voltage 10, the drive voltage 10 with the same voltage difference is always output from the upper and lower circuits. FIG. 10 shows the waveform of the driving voltage.
=1%/2), the driving voltage is high and is supplied from the circuit above. The driving voltage 10 applied to the top scanning electrode 2, ym-1 of the lower half liquid crystal display panel 1 is approximately the same voltage as 3's in the above circuit.
The highest voltage is supplied to the lowest scanning electrode 2, the y-axis, from the lower circuit. At this time, the slope of the driving voltage 10 in the lower circuit is set to be the same or smaller than the slope of the driving voltage 10 in the upper circuit. As a result, uniform image quality is obtained in the same manner as in the first embodiment.

[Embodiment 4] This is an embodiment in which the liquid crystal display device having the configuration shown in FIG. 8 is viewed as shown in FIG. Uniform image quality can be obtained in the same manner as in Example 2 by reconnecting the one end of 21 connected to the power supply (2) to the power supply (e).

〔Effect of the invention〕

As described above, according to the present invention, a low effective voltage is applied to the upper side of the liquid crystal display panel, and a high effective voltage is applied to the lower side of the liquid crystal display panel, thereby canceling out the viewing angle dependence of the liquid crystal panel and achieving uniform image quality.

[Brief explanation of drawings]

FIG. 1 is a diagram of the configuration of the present invention FIG. 2 is a waveform diagram of the driving voltage 10 FIG. 3 is a circuit diagram of the driving voltage power source FIG. 4 is a diagram of driving waveforms of the present invention FIG. 5 is a driving voltage diagram of the second embodiment The circuit diagram of the power supply, Figure 6, is
FIG. 4 is an explanatory diagram showing directions in which the liquid crystal display devices of Examples 2 and 4 are viewed. FIG. 7 is a drive voltage waveform diagram of the second embodiment. FIG. 8 is a configuration diagram of the third embodiment. FIG. 9 is a circuit diagram of the drive voltage power supply of the fifth embodiment. FIG. 10 is a drive voltage waveform of the fifth embodiment. Waveform diagram Figure 11 is the drive waveform diagram of the conventional example.

Claims (1)

[Claims] In a multi-flex driven liquid crystal display device using line-sequential scanning, in which display is performed by sequentially adding a signal waveform for determining whether to turn on or off, a line of signal electrodes that add a signal waveform that determines whether to turn on or off, a line of crossed scanning electrodes, and a selection waveform, the signal electrodes and A liquid crystal display device characterized in that a voltage applied between scan electrodes is varied depending on the position of the scan electrodes.