JPS60126626A - Liquid crystal display panel - Google Patents

Abstract

PURPOSE:To equalize substantially a voltage applied to a liquid crystal, and to realize a uniform display luminance by varying a pulse width of a signal voltage by depending on a distance from one end in the direction orthogonal to an arranging direction of an electrode group. CONSTITUTION:An electrode group arranged in one direction is formed on one of the opposed surface of a pair of substrates, and on the other surface, an electrode group is formed in the orthogonal direction. In this state, a liquid crystal layer is provided between the substrates, and both electrode groups are driven. In this case, a pulse width modulating circuit consisting of monostable multivibrators 1, 2 and an operating circuit 3 is provided on a circuit for driving one electrode group (Y electrode), and a pulse width of a signal voltage waveform is varied depending on a distance from one end of the direction orthogonal to the arranging direction of the Y electrode. As a result, a voltage decrease caused by an electrode resistance in an X electrode is compensated, a voltage effective value applied to each picture element is equalized substantially, and a display by a uniform luminance is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal display panel having a matrix electrode structure.

Conventional Structures and Their Problems In recent years, liquid crystal display panels have tended to have larger panel areas as the amount of display has increased. A liquid crystal display panel having a matrix electrode structure has a configuration shown in FIG. 1, in which one of a pair of substrates has a group of X electrodes aligned in the X direction, and the other has a group of Y electrodes aligned in the Y direction. A liquid crystal layer is interposed between the substrates, and its operation is as follows.
One electrode group is sequentially selected one by one, and in synchronization with this, a voltage is selectively applied to the electrodes of the other electrode group that are connected to picture elements to be lit to perform display. The display brightness of a picture element depends on the voltage applied to the picture element. An equivalent circuit for the matrix electrode structure shown in FIG. 1 is shown in FIG. If the voltage at the sending end is s1 and the voltage at a distance l from the sending end is vR, then the relationship between the two can be found by solving the equivalent circuit in Figure 2 using a distributed constant circuit method: VR/VS= [z/lω5h(z)+CO! (z) I
) ' - (1) where z=l(4πfCR) Of is the frequency of the applied voltage waveform, R is the amount of electrode resistance per unit length, and C is the unit length of the capacitance due to the liquid crystal. This is the amount of The right side of equation (1) is a simple decreasing function with respect to the variable Z. This means that the voltage applied to the transmitting end attenuates as the distance l increases. As mentioned above, as the panel area tends to increase, that is, the electrode length l tends to increase, voltage attenuation becomes more severe. This effect causes a problem in that a sufficient voltage is not applied to the picture element, and the display brightness of the picture element in the lit state is not uniform. One possible solution to this problem is to reduce the electrode resistance, but there are limits to this in terms of manufacturing process, speed, cost, etc.

OBJECTS OF THE INVENTION An object of the present invention is to provide a liquid crystal display panel that can achieve uniform display brightness.

Structure of the Invention The liquid crystal display panel of the present invention has an electrode group aligned in one direction formed on one of the opposing surfaces of a pair of substrates, and an electrode group arranged in a direction perpendicular to the said direction on the other surface. In a liquid crystal matrix display panel which has a liquid crystal layer between its substrates and is equipped with a circuit for driving both electrode groups, at least one electrode group (hereinafter referred to as Y electrode, and the opposite electrode is called an X electrode). ), the pulse width of the signal voltage waveform is Y
By providing a means that changes the voltage depending on the distance from one end in the direction perpendicular to the electrode alignment direction, the voltage reduction caused by the electrode resistance at the X electrode is compensated for, and the effective voltage applied to each picture element is increased. The values are made substantially equal, thereby realizing display with uniform brightness.

DESCRIPTION OF THE EMBODIMENTS FIG. 3 is a block diagram of a Norms width modulation circuit used as an embodiment of the present invention. When the rectangular wave generated by a normal drive circuit rises, monostable multivibrator 1 generates a positive pulse with a predetermined pulse width, and when it falls, monostable multivibrator 2 generates a negative pulse. Thereafter, the arithmetic circuit 3 performs an OR operation, and the result is pulse width modulation. The voltage applied to a certain picture element is the difference between the attenuated potential on the X side and the pulse width modulated potential on the Y side. FIG. 4 shows selection voltage waveforms applied to a picture element near the transmitting end of the X electrode (FIG. 4 (4)) and a picture element (FIG. 4 (B)) near the other end farthest from there. As shown in equation (1), voltage attenuation increases as the frequency increases, so by adjusting the pulse width, the effective effect of the voltage waveforms shown in Figures 4 (c) and (B) applied to the liquid crystal can be adjusted. It is possible to make the value voltages substantially equal. Similarly, the effective values of the selection voltages in all picture elements can be made equal. In other words, display with uniform brightness is realized.

Note that even if the voltage applied to the liquid crystal is reduced by several orders of magnitude, the effect on the display brightness that can be viewed is small, so as mentioned above,
It is not necessary to change the pulse width of all Y-side voltage waveforms, and the same effect can be obtained by dividing the Y-side electrode into several sets of blocks and changing the pulse width for each block.

Effects of the Invention In the liquid crystal display panel of the present invention, when driving the electrode group connected to the liquid crystal, the pulse width of the signal voltage can be changed depending on the distance from one end in the direction orthogonal to the alignment direction of the electrode group. This makes it possible to substantially equalize the voltages applied to the liquid crystal, thereby realizing uniform display brightness.

[Brief explanation of drawings]

Figure 1 is a plan view showing the electrode pattern of a conventional liquid crystal display panel, Figure 2 is an equivalent circuit diagram for the conventional liquid crystal panel,
Fig. 3 is a diagram showing the configuration of the pulse width modulation circuit, and Fig. 4 is a diagram showing the configuration of the pulse width modulation circuit.
In the liquid crystal display panel according to an embodiment of the present invention, it is a diagram showing voltage waveforms applied to the picture element (8) near the X electrode transmitting end and the picture element (B) near the other end. 1.2-...・Monostable multivibrator, 3...
Arithmetic circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 Figure 4

Claims (1)

[Claims] A group of electrodes aligned in one direction is formed on one of the opposing surfaces of a pair of substrates, a group of electrodes aligned in a direction perpendicular to the direction is formed on the other surface, and a liquid crystal layer is formed between the substrates. In a liquid crystal matrix display panel comprising a circuit for driving both of the electrode groups, the circuit for driving at least one of the electrode groups has a pulse width of a signal voltage waveform in a direction in which the electrode groups are aligned. A liquid crystal display panel characterized in that it is provided with means for changing the distance depending on the distance from one end in orthogonal directions.