JPS6057747B2 - liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrode structure for a liquid crystal television panel, and its purpose is to facilitate electrode structure and panel assembly, and another purpose is to improve display appearance.
Yet another objective is to make the panels more compact.

When a liquid crystal is placed between substrates on which electrodes are formed and a voltage is applied between the electrodes, the tilt of the liquid crystal molecules is controlled by the effective voltage and a display is performed.

Since the point of the present invention is the electrode structure, in order to make the explanation easier to understand, a twisted nematic (TN) type liquid crystal panel as shown in FIG. 1 will be used for explanation here.
1 is a transparent glass substrate, 2 is a transparent electrode, and 3 is a sealing member for determining the thickness of the liquid crystal layer and for sealing the liquid crystal.

4 is a so-called P-type nematic liquid crystal with positive dielectric anisotropy, and has a vertically twisted structure of approximately 90 degrees.

5 is a pair of polarizing plates whose polarization directions are almost parallel to each other. Figure 2 shows the relationship between effective voltage and light transmittance when a voltage is applied to a liquid crystal panel with such a structure. Here, the vertical axis is the light transmittance, and the horizontal axis is the effective voltage. 6 and 7 are called the threshold voltage and saturation voltage, respectively, and are 111 when the value between the minimum transmittance and the maximum transmittance is set to 1.
is the effective voltage at the 0 and 9/10 points.

When displaying television images on a liquid crystal panel with such characteristics, a matrix drive method is used to drive the liquid crystal. This is the signal applied to the scanning electrode,
The liquid crystal is in a selected state for a certain period at a certain period, and ON and OFF of the liquid crystal is determined only during that period by the signal applied to the signal electrode, and in other non-selected states, the ON and OFF of the liquid crystal is determined by the signal applied to the signal electrode.
All liquid crystals are in the OFF state regardless of the signal. The ratio of the period during which the liquid crystal in each pixel is selected to the total period is called drive utility. Therefore, in general, the drive duty is 1/N where N is the number of scanning electrodes. Also, the effective voltage applied to the liquid crystal corresponding to each pixel in the best condition is when it is in the OFF state! Nlvo, 9 early when in oN state. becomes. Here V. is a value determined by the power supply voltage. Therefore, the ratio of these becomes kimi(:α),
This value is called the operating margin, and is a factor that greatly influences display characteristics.

In order for the liquid crystal to be completely OFF in the OFF state,
The value of VO must be less than or equal to the value 6 in FIG.

Therefore, the effective voltage in the ON state is inevitably restricted. Generally, in the case of a TN type liquid crystal panel, 7 and 6 in Figure 2
The effective voltage ratio is about 1.6 to 1.9. Therefore, in order to obtain a display with good contrast, it is necessary to make the operating margin α as large as possible. However, α is determined by the number of scanning electrodes or drive duty, and increasing the operating margin results in reducing the number of scanning electrodes. This results in the inability to obtain sufficient resolution when displaying television images on a liquid crystal panel. Some conventional methods for solving this problem include dual matrix electrode structures. This is an electrode structure as shown in FIG. 3, in which signal electrodes corresponding to pixels in a vertical line are alternately coupled, and two signal electrodes constitute a -line. The horizontal lines are scanning electrodes and the vertical lines are signal electrodes.
In this figure, in order to make the relationship between the scanning electrodes and the signal electrodes easier to understand, the scanning electrodes are shown as lines, but in reality they have widths. Next, a television image display using a liquid crystal panel having such an electrode structure will be described. In the case of an ordinary television, the number of field scans is approximately 500, and in the case of a liquid crystal television, the number of pixels is approximately 100×1301i].
Therefore, it is not possible to convert all field image signals onto the liquid crystal panel, but image signals for every few fields must be converted. Here 1 and 2 fields, then 4
5 fields, then 7 and 8 fields, and so on, where adjacent fields are grouped as a set, and discrete field image signals are stored in two line memories, and these are corresponded to two adjacent lines of the liquid crystal panel. during the selection period of the scanning electrode. Apply from the signal electrode. That is, the scan electrodes corresponding to two adjacent rows of pixels on the liquid crystal panel are simultaneously selected for a certain period of time. Therefore, if the number of pixels is 80.times.100, the actual number of scanning electrodes in the double matrix method will be about 40, and the duty will be about 1140. However, in the case of a simple matrix, the number of scanning electrodes is 80, so the duty is 1180. This shows that the double matrix electrode structure greatly improves the drive duty, which is a major factor in liquid crystal display contrast. However, the biggest drawback of this double matrix electrode structure is the complexity of the electrode structure. FIG. 4 shows a partially enlarged view of the signal electrode structure shown in FIG. 3. The shaded area is the electrode. Due to the extremely narrow electrode spacing and electrode impedance, it is necessary to metalize the connecting portions, making it difficult to manufacture the electrodes and align them with the scanning electrodes. The appearance of the display is worrisome because there is a lot of waste between the electrodes and there are many joints between the electrodes corresponding to the pixels. Furthermore, if the panel is made smaller with the same number of pixels, the area of the electrode portion corresponding to the pixel and other portions will be approximately the same, making the display appearance unsightly, making it difficult to make the panel smaller. It has major drawbacks such as: The present invention is an electrode structure for solving the above-mentioned drawbacks without lowering the drive duty, and an example of its specific structure and a specific method of driving a panel using the same will be described below.

FIG. 5 shows an embodiment of the present invention, and in order to make the structure easier to understand, the number of scanning electrodes and signal electrodes is extremely small compared to the actual number. This does not impair the essence of the invention. The vertical direction is a signal electrode, and the horizontal direction is a scanning electrode. Among the scanning electrodes, those having the same number apply the same scanning signal. That is, the scanning electrodes to which the same scanning signal is applied are separated into the upper and lower parts of the display section. Further, the signal electrode corresponding to one display line in the vertical direction is divided into upper and lower halves. In this case, the number of pixels on the board is (1) ×
In the case of 100, the actual number of scanning electrodes and the number of signal electrodes are 40 and 200, as in the case of the double matrix electrode structure described above. Therefore, the duty is not lowered. Further, since the structure of the electrode pattern is simple, electrode manufacturing is easy. As a result, alignment with the scanning electrodes becomes easier. Furthermore, since there is less waste in electrode spacing or other waste than in a double matrix electrode structure, the display appearance is improved. Alternatively, since there is less waste of electrodes, further miniaturization is possible. As described above, the electrode structure according to the present invention is considered to be absolutely necessary for making liquid crystal televisions portable. Next, a specific example of a method for displaying television images using a liquid crystal panel using the electrode structure according to the present invention will be described.

FIG. 6 is its block diagram, and 8 is a television image signal;
9 is an A/D converter; 10 and 11 are an image memory device such as a RAM; hereinafter, this memory will be referred to as a frame memory. 12 and 13 are line memories, 14 and 15
1 is a signal drive circuit, 16 is a scan drive circuit, and 17 is a liquid crystal panel.

Here, the brightness modulation circuit and switch relationships are omitted. First, a field image signal that has been appropriately thinned out of the television image signal is sampled and sequentially A/D converted, and one image is stored in the frame memory 10. The data of the upper half of the image of the stored signal is sequentially transferred to the line memory 1 river 2, and the data of the lower half of the image is transferred to the line memory 13, respectively, based on the drive duty determined by the signal drive circuits 14 and 15. , are sequentially applied to the signal electrodes of the liquid crystal panel. During this time, the next image is stored in the frame memory 1, and after all the previous image signals have been sent to the liquid crystal panel, the same process is repeated. The following is a repetition. The scan drive circuit 16 sequentially selects scan electrodes based on a determined drive duty. As described above, the present invention has two frame memories that store image signals for one screen and two line memories that store the upper and lower halves of one screen. It is possible to reliably transmit and display a television video signal whose value changes to the upper and lower divided signal electrodes, and since the duty is increased, a television video screen with high contrast and high resolution can be obtained.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the liquid crystal panel. 1: Transparent glass substrate. 2: Transparent electrode. 3: Seal member. 4: Liquid crystal. 5: Polarizing plate. Figure 2 shows voltage-transmission characteristics. 6: Threshold voltage. 7: Saturation voltage. Figure 3 shows the conventional electrode structure. Figure 4 shows the conventional signal electrode structure. FIG. 5 shows the electrode structure of an embodiment of the present invention. FIG. 6 shows a specific example of a driving method for application of the present invention. 8: Image signal. 9: A/D conversion section. 10, 11: Frame memory. 12, 13: Line memorandum 14, 15: Signal drive circuit. 16: Scanning drive circuit. 17: Liquid crystal panel.

Claims (1)

[Claims] 1. In a liquid crystal display device having scanning electrodes in the row direction and signal electrodes in the column direction, and in which the signal electrodes are divided into an upper display half and a lower display half to form one screen, an image for the one screen is A first frame memory and a second frame memory that store signals, and store an upper half of an image signal output from the first or second frame memory, and display an upper half of the image signal in the upper half of the display. It is characterized by comprising a first line memory that transfers a half part of the image signal, and a second line memory that stores the lower half of the image signal and transfers the lower half of the image signal to the display lower half. LCD display device.