JPH0349439B2 - - Google Patents

Description

Detailed Description of the Invention <Technical Field> The present invention relates to a matrix type liquid crystal display device, and more particularly to a drive circuit for a matrix type color liquid crystal display device in which a switching transistor and a color filter are added to each display picture element. It is something.

<Prior art> A matrix-type liquid crystal display device in which a switching transistor is added to each pixel in the display area has the advantage of suppressing the crosstalk phenomenon, which is a problem in ordinary matrix-type liquid crystal display devices, by the switching mechanism of the transistor. A feature of this method is that even when performing multi-line multiplex driving, it is possible to obtain a high-contrast display equivalent to static driving. Furthermore, by adding red, green, and blue color filters to each pixel of a matrix type liquid crystal display and controlling the amount of light that passes through each filter using the liquid crystal, full-color display is possible. By adding these together, a color liquid crystal display device with very good operating characteristics can be obtained.

FIG. 2 is a block diagram illustrating the general configuration of the color liquid crystal display device. In the figure, 11 indicates a liquid crystal color display panel. Row electrode 11-a and column electrode 11 provided on one substrate of panel 11
As shown in the figure, a switching transistor 11-d is incorporated in the display picture element 11-c at each intersection of -b. Further, on the other substrate, color filters of red R, green G, and blue B are arranged, for example, as shown in the figure, in a portion facing the counter electrode and each display picture element. 12
is a row electrode drive circuit that applies a scanning pulse to the row electrodes to sequentially select the switching transistors in each row. Reference numeral 13 denotes a column electrode drive circuit that applies a voltage corresponding to the display density of each picture element to the column electrodes. 14 are red, green, and blue display signals V _R , V _G , V _B
Switch sequentially according to the color array of the color filter,
The display signal V containing color information is sent to the column electrode drive circuit 13.
This is a color changeover switch circuit to send to. 1
5 is a control circuit for controlling the operation of the above circuit. In the liquid crystal display device having the above circuit configuration, the voltage of the column electrode 11-b is applied to the display picture element 11-c through the transistor 11-d only for the row selected by the scanning pulse. When the transistor 11-d is unselected, the column electrode 11-b and the display pixel 11-c are disconnected from each other, and the voltage of the display pixel 11-c is the same as that of the column electrode 11-b. It is retained as is without being affected. Therefore, even if multiplex driving with a small duty ratio is performed, a voltage equivalent to static driving is applied to the liquid crystal layer, so that a good display with high contrast can be obtained. In addition, column electrode 1
By sequentially applying voltages corresponding to the shades of red, green, and blue to 1-b according to the color arrangement of the color filter, it is possible to control the intensities of red, green, and blue completely independently, resulting in good full color. Display is obtained.

3A and 3B are a circuit diagram and a voltage waveform diagram showing the internal configuration and main drive waveforms of the column electrode drive circuit 13 and color changeover switch circuit 14 in FIG. 2. In the figure, V is a display signal indicating the display content.
Hsync is a horizontal (row direction) synchronization signal, φ is a clock signal, and qi is an output signal from the shift register 21. As shown in the figure, the display contents are sent in series (V ₁₁ , V ₁₂ , . . . , Vi ₁ , . . . , V _ij , . . ) one picture element at a time. Therefore, it is first necessary to sample only the voltage of the portion of the display signal that corresponds to the column electrode to be driven. The circuits that perform this are a shift register 21, a sampling analog switch 22,
This is a sampling capacitor 23. The shift register 21 sequentially shifts the pulses using the clock φ, and by sequentially closing the analog switches 22, voltages corresponding to each column electrode (Vi ₁ , Vi ₂ ,
..., Vij, ..., V _iN are sampled to the capacitor 23. And the next sampled voltage is
By closing the analog switch 24 during a certain period when sampling is not performed, the signal is transferred to the hold capacitor 25 and held. The held voltage is output to the column electrode through the buffer amplifier 26. When color display is performed using the column electrode drive circuit 13 as described above, the display signal V is set to, for example, Vi ₁ corresponding to the color arrangement of the color filter.
You must enter the voltage that represents the red display for Vi ₂ , green for Vi _{3, and blue for Vi 3} . The circuit that does this is the color changeover switch circuit 14. This circuit consists of a switch 27 and its control circuit 28, and switches the analog switch 2 at intervals of clock φ.
7 is sequentially switched to output a display signal V corresponding to the color arrangement of the color filter to the column electrode drive circuit 13.

When a color liquid crystal display device is driven by the above-described driving circuit, a big problem arises in that there is a difference between the sampling timing and the color switching timing. If the timings of both are shifted, the display colors of adjacent picture elements will be mixed and the color quality of the display will be degraded. Therefore, it is desirable that both timings match, but it is difficult to avoid differences in signal transmission delay times due to differences in external wiring or internal circuits of the column electrode drive circuit 13 and color changeover switch circuit 14. , the difference becomes a big problem as the frequency of the clock φ becomes higher. Furthermore, in the above drive circuit, sampling is performed through two analog switches connected in series, so the analog switch 27 of the color changeover switch circuit 14 has a larger load than the sampling analog switch 22, and has high drive capability and frequency characteristics. This results in a need for an element having the following characteristics, which poses problems both technically and in terms of power consumption. Since the control circuit 28 sequentially switches the analog switches 27 at intervals of the clock φ to obtain the display signal V corresponding to the color arrangement of the color filter, there is an inconvenience that the liquid crystal display device is limited to one with the corresponding color arrangement. There is also.

<Object of the Invention> The present invention has been made in view of the above-mentioned problems and inconveniences in the drive circuit of a matrix-type color liquid crystal display device. It is an object of the present invention to provide a new and useful driving circuit for a liquid crystal display device, which can obtain patterns with good display quality and can be applied to liquid crystal display devices with multiple types of color arrays.

<Example> A feature of the drive circuit of the present invention is that a color changeover function is provided to the sampling circuit of the column electrode drive circuit, thereby eliminating the need for a color changeover switch circuit and solving the above-mentioned problems in conventional drive circuits. It is in. In particular, it is configured to automatically switch colors in the horizontal direction through internal wiring, and 1
This is effective in the case of a color arrangement in which two colors among red, green, and blue are arranged for the column electrodes of a book. Hereinafter, it will be explained in detail according to examples.

The basic configuration of the color liquid crystal display device driven by the drive circuit of this embodiment is the same as that of the second embodiment described above.
It has almost the same configuration as the block diagram shown in the figure. In a liquid crystal color display panel, switching elements such as thin film transistors and MOS transistors are formed on the inner surface of one substrate constituting the panel, and pixel electrodes for obtaining a display pattern are connected to each switching element, and these are arranged in a matrix. It has an arranged electrode structure.
The switching elements are connected to row and column electrode lines at respective intersections of driving electrode lines, which are composed of row and column electrode lines and are arranged in directions orthogonal to each other. On the other substrate constituting the liquid crystal color display panel, three primary color filters of red, green, and blue are disposed corresponding to counter electrodes to the picture element electrodes and to each of the picture element electrodes. One color filter faces one picture element electrode between both substrates, and a field effect liquid crystal layer such as a twisted nematic liquid crystal layer is sealed between the two substrates. The amount of light transmitted through the liquid crystal layer is modulated by changes in the optical characteristics of the liquid crystal layer that respond to the electric field applied between the picture element electrode and the counter electrode in synchronization with the on/off operation of the switching element, and the display of each picture element is performed. is executed. Each picture element exhibits the hue of one of the three primary colors, and the three corresponding to the three primary colors
The picture elements are combined to determine the hue by additive color mixture, and a full-color display pattern is generated on the liquid crystal display panel, with each set of three picture elements as a unit. Row electrode lines and column electrode lines that control on/off of the switching elements are connected to a row electrode drive circuit and a column electrode drive circuit, respectively. The row electrode drive circuit has a configuration similar to that shown in FIG. 2, and applies scanning pulses to the row electrode lines. On the other hand, the column electrode drive circuit applies display signals including color signals to the column electrode lines in synchronization with the scanning pulses applied to the row electrode lines.
It is configured as shown in . FIGS. 1A, B, and C are a configuration diagram of a column electrode drive circuit 13' in a drive circuit of a liquid crystal display device, a layout diagram showing the color arrangement of color filters, and a column electrode drive circuit for explaining an embodiment of the present invention. 13' is a timing waveform diagram showing voltage waveforms of main parts of the circuit 13'. In Figure 1B, R, G, B
indicate the hues of red, green, and blue, respectively, and in each column, two types of filters having different hues among the three primary colors are arranged in combination. The basic structure of the column electrode drive circuit is the same as the conventional one, consisting of a shift register 31 that outputs a signal corresponding to a display pattern for each column electrode line, analog switches 32, 34, capacitors 33, 35, and an output buffer amplifier 36. Analog switch for sampling 32-
1 and 32-2 are connected to the sampling capacitor 33 in pairs, and these are individually connected to any two of the red, green, and blue display signal lines according to the color arrangement of each column. has been done. A set of two gate circuits 37 are arranged in parallel at each output end of the shift register 31, and the gate circuits 37
One of the sampling analog switches is sequentially and selectively brought into conduction by the output signal from the output signal, and the display signals V _R , V _G , and V _B of one of the colors are sampled. A case will be described in which an initial data signal D and a clock signal φ are input to the shift register 31, and the display signal of the i-th row of the gate circuit is sampled as an output signal sequentially in synchronization with the clock signal φ at the output terminal. Of the pair of control signals C _{1 and} C _{2 input to the gate circuit 37, if the control signal C 1 is} set to high level and the control signal C ₂ is set to low level, an output signal is obtained from one gate circuit 37-1, and the two One of the sampling analog switches 32-1 is selected. Then, due to the internal wiring, the display signals are sampled in the j-th column, green in the (j+1) column, blue in the (j+2) column, red in the (j+3) column, and green in the (j+4) column. Direction color switching is done automatically. Next, for the (i+1)th row, the control signal is switched according to the horizontal synchronization signal Hsync, and by setting the control signal _C1 to low level and _C2 to high level, an output signal is obtained from the gate circuit 37-2 and sampling is performed. analog switch 32-2 is selected and blue, red, green, blue, and red display signals are sampled as in the case of the i-th row. By repeating these steps, a display signal corresponding to the color array shown in FIG. 1B is sampled. Sampled display signal V _R ,
V _G and V _B are accumulated in a sampling capacitor 33, and the accumulated signals are transferred to a hold capacitor 35 when an analog switch 34 is closed, and outputted to each column electrode via a buffer amplifier 36. The on/off operation of the switching elements is controlled by the signals applied to each column electrode and the scanning pulse applied to the row electrodes, and full color display including halftones according to the color signals is performed.

According to the above circuit configuration, the color changeover switch circuit that was required in the past is no longer necessary, horizontal color changeover is automatically performed within the circuit, and external control is limited to changeover in the vertical (column) direction only. Become. Therefore, the switching speed is slow, the influence of signal delay is eliminated, and power consumption is also reduced.

As is clear from the above description, the drive circuit of the present invention is particularly effective in the case of a color arrangement in which two color filters are arranged in one column as shown in FIG. 1B. In addition, even in the case of a color arrangement in which three colors are arranged in one column as shown in FIG. 4A, for example, a switch at each intersection of a row electrode 41 and a column electrode 42 as shown in FIG. 4B can be used. The column electrodes 4 are connected to the column electrodes 4 every other row.
If it is incorporated into the display picture element on the right or left side of 2, focusing on one column electrode, two colors will be arranged, and the drive circuit of the present invention can also be applied to the color arrangement shown in FIG. 4A. Become. However, in this case, since the column of picture elements displayed for one column electrode differs depending on the row, it is necessary to change the timing of the pulse D input to the sampling shift register 31 by one column for each row. For example, in the example shown in Figure 4, the i-th
+1 row sampling, i row, i
It is necessary to delay the pulse D by one column compared to the case of sampling +2 rows and i+3 rows.

<Effects of the Invention> As described above, the present invention constitutes a drive circuit for a color liquid crystal display device that allows easy color switching, and moreover, by selecting a color selection signal, the same drive circuit can be used for various types of liquid crystal display devices. It is configured to be adaptable to various color arrays, and is not only extremely useful for driving large-capacity, high-quality matrix-type color liquid crystal display devices, but also for liquid crystal display devices with multiple color arrays. It is highly practical in terms of its applicability.

[Brief explanation of drawings]

FIGS. 1A, B, and C are a configuration diagram of a column electrode drive circuit in a drive circuit of a liquid crystal display device, a color arrangement diagram of a color filter, and voltages of main parts of the column electrode drive circuit in a drive circuit of a liquid crystal display device for explaining an embodiment of the present invention. FIG. 3 is a timing waveform diagram showing waveforms. FIG. 2 is a basic configuration diagram of a matrix type color liquid crystal display device to which switching transistors and color filters are added. FIGS. 3A and 3B are circuit diagrams and main drive waveform diagrams of a conventional column electrode drive circuit and color changeover switch circuit.
4A and 4B are a color arrangement diagram of a color filter and a circuit diagram showing connections within a liquid crystal panel, both of which are used to explain another embodiment of the present invention. 11...LCD color display panel, 13, 13'
... Column electrode drive circuit, 14 ... Color changeover switch circuit, 21, 31 ... Shift register, 22,
32...Sampling analog switch, 2
3, 33...Sampling capacitor.

Claims (1)

[Claims] 1. A first substrate provided with switching elements connected to picture element electrodes arranged in a matrix at each intersection of a row electrode and a column electrode, and a second substrate provided with a counter electrode.
A voltage corresponding to the color arrangement of the color filter and the density of the display is applied to the column electrode of a color liquid crystal display device comprising an electrode, a liquid crystal layer and a color filter sandwiched between these two substrates. In a column electrode drive circuit for the purpose of Two analog switches for sampling whose ends are individually connected to any two of the red, green, and blue display signal lines, a shift register circuit, and one of the analog switches for sampling are selectively connected. two gate circuits configured to be individually connected to one of the sampling analog switches for outputting open/close signals, connected to the output end of the shift register circuit, and configured to receive a color selection signal; A driving circuit for a color liquid crystal display device, comprising: