JPH0342680B2 - - 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 pixel. It is something.

<Prior art> Matrix-type liquid crystal display devices in which a switching transistor is added to each pixel of the display can suppress crosstalk development, which is a problem in ordinary matrix-type liquid crystal display devices, due to the switching mechanism of the transistors. Even when line multiplex driving is performed, a high contrast display equivalent to static driving can be obtained. 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. In addition, on the other substrate, red (R), green (C), and blue (B) are applied to the counter electrode and the portion facing each display pixel.
For example, the color filters are arranged as shown in the figure. Reference numeral 12 denotes a row electrode drive circuit for applying a scanning pulse to the row electrodes for sequentially selecting the switching transistors in each row. Reference numeral 13 denotes a column electrode drive circuit for applying a voltage corresponding to the display density of each picture element to the column electrodes. 14 is a display signal V containing color information by sequentially switching red, green, and blue display signals V _R , V _G , and V _B according to the color arrangement of the color filter.
This is a color changeover switch circuit for sending the color to the column electrode drive circuit 13. 15 is a control circuit for controlling the operation of the above circuits. In this liquid crystal display device, only the row selected by the scanning pulse is
The voltage of column electrode 11-b is applied to display picture element 11-c through transistor 11-d. 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. Since it is held as it is without being affected, even if multiplex driving with a small duty ratio is performed, the same voltage as in static driving is applied to the liquid crystal layer, so a good display with high contrast can be obtained. In addition, the column electrode 11
- By sequentially applying voltages corresponding to the shading of red, green, and blue display to 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 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 display content. As shown in the figure, the display contents are sent in series (V ₁₁ , V ₁₂ , . . . , V _i1 , . . . , 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 (V _i1 , V _i2 ,
..., V _ij , ..., V _iN ,) are sampled to the capacitor 23. Then, the next sampled voltage is transferred to the hold capacitor 25 and held by closing the analog switch 24 for a certain period when no sampling is performed. The held voltage is output to the column electrode through the buffer amplifier 26. Column electrode drive circuit 13 as described above
When displaying in color, the display signal V should be, for example,
A voltage representing the display content must be input into V _i1 in red, V _i2 in green, and V _i3 in blue. The circuit that does this is the color changeover switch circuit 14. This circuit consists of a switch 27 and its control circuit 28, which sequentially switches the analog switch 27 at intervals of a clock φ to output a display signal V corresponding to the color arrangement of the color filter to the column electrode drive circuit 13. Note that Hsync is a horizontal synchronization signal.

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. Furthermore, since the analog switches 27 are sequentially switched by the control circuit 28 at clock intervals, there is an inconvenience that this method can only be applied to a liquid crystal display device using a color filter having a color arrangement corresponding to the switching order.

<Object of the Invention> The present invention has been made in view of the above-mentioned problems in the drive circuit of a matrix type color liquid crystal display device, and provides a low power consumption and high display quality that does not cause color mixing due to signal deviation. The object of the present invention is to provide a new and useful driving circuit for a liquid crystal display device that can obtain a good pattern. Furthermore, the present invention has been made in view of the above-mentioned inconveniences in the drive circuit of a matrix type color liquid crystal display device, and provides a liquid crystal display device that can be applied without selecting the color arrangement of the color filter of the liquid crystal display device. The purpose of this invention is to provide a drive circuit.

<Embodiment> The feature of the drive circuit of the present invention is that a color switching 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.

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 arranged in a matrix. It has a unique 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 arranged corresponding to the opposing 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 inserted between them. 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 hue is determined by additive color mixture by combining the three picture elements corresponding to the three primary colors, and a full-color display pattern is created using a set of three picture elements as a unit. Occurs in liquid crystal display panels. 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 a display signal including a color signal to the column electrode lines in synchronization with a scanning pulse applied to the row electrode lines, and is constructed as shown in FIG. 1A. FIGS. 1A and 1B are configuration diagrams of a column electrode drive circuit 13' in a drive circuit of a liquid crystal display device used to explain an embodiment of the present invention, and timing waveforms showing voltage waveforms of main parts of the column electrode drive circuit 13'. It is a diagram. The basic structure of the column electrode drive circuit 13' is the same as the conventional one, consisting of a shift register 31 that outputs a signal corresponding to the display pattern for each column electrode line, analog switches 32, 34, capacitors 33, 35, and an output buffer amplifier 36. Three sampling analog switches 32 are connected to each sampling capacitor 33, and these are the display signals through which the red, green, and blue display signals V _R , V _G , and V _B are transmitted. It is connected to each of the three lines. The color is switched by inputting the output from the gate circuit 37 connected to the output end of the shift register 31 to the sampling analog switch 32 and selecting one of the three sampling analog switches 32. be exposed. For this purpose, three gate circuits 37 are connected in parallel to one output terminal of the shift register 31, and output signals from the shift register 31 and three types of selection signals.
Either C _R , C _G , or C _B is input. The selection signals C _R , C _G , and C _B select red, green, and blue, respectively, and by switching these according to the color arrangement, it is possible to adapt to any arrangement. The selection signal waveform shown in Figure 1B is red, green,
The case where colors are arranged in the order of blue, red, green, etc. is shown. Each of the selection signals C _R , C _G , and C _B is composed of rectangular wave pulses that are sequentially applied in synchronization with the clock signal φ input to the shift register 31 .
With the circuit configuration as described above, the initial data signal D and clock signal φ are transferred to the shift register 3.
1, and at the output end, signals necessary for display are sequentially input from the shift register to the gate circuit 37 in synchronization with the clock signal φ. In addition, selection signals C _R , C _G ,
C _B is also input to the gate circuit 37 at the same time,
Therefore, one of the selection signals V _R , V _G , and V _B corresponding to the column electrodes is sampled via the sampling analog switch 32 according to the signal output from the gate circuit 37 and stored in the sampling capacitor 33 . . This accumulated signal is transferred to the hold capacitor 3 when the analog switch 34 is closed.
5 and output to each column electrode line via the buffer amplifier 36.

According to the above circuit configuration, not only can the conventionally required color changeover switch circuit be eliminated, but also the influence of signal delay on the display signal input line can be eliminated. In addition, since color switching is performed within the column electrode drive circuit, by providing an appropriate gate circuit, it is easy to match the timing of color switching and sampling. It is possible to completely eliminate problems such as deterioration of hue freshness.

FIG. 4A is a circuit diagram showing another embodiment of the sampling circuit section in the column electrode drive circuit of the present invention. The configuration of this circuit is basically the same as the first case, but the order of connection between each sampling analog switch 42-1, 42-2, 42-3 and the red, green, and blue display signal lines. Figure 4B in each column.
They are changed according to the color arrangement pattern shown in . For example, in the analog switch 42-1, the jth column is red, and the
The +1 column is connected to the blue display signal line, the j+2 column is connected to the green display signal line, and the j+3 column is connected to the red display signal line, and the analog switch 42
Similarly, analog switch 42-2 connects green, red, blue, and green display signal lines, respectively, and analog switch 42-3 connects blue, green, and
It is connected to the red and blue display signal lines. Therefore, when sampling the display signal of the i-th row, FIG.
In the timing waveform diagram shown in , by setting only C ₁ of C ₁ to _{C 3} to high level, the j-th
Column is red, (j+1) is blue, (j+2) column is green, (j
In the +3) column, red display signals are sampled, and signals corresponding to the color array of the i-th row, red, blue, green, and red, are obtained. Similarly, by sequentially setting C ₂ to high level in the case of the (i+1)th row and C ₃ in the case of the (i+2) row, a signal corresponding to the color arrangement shown in FIG. 4B can be obtained. . As mentioned above,
If the color arrangement pattern is a repeating pattern, using a circuit like the one shown in Figure 4A, the control signals C ₁ , C ₂ , and C ₃ can be switched for each row; Compared to the example shown in FIG. 1, the frequencies of C ₁ to _{C 3} are significantly lower, eliminating the influence of signal delay and reducing power consumption. In addition, in FIG. 4, the sampling analog switch 42
By changing the order of connection with red, green, and blue display signal lines depending on the column, you can connect other parts such as control signals.
It is clear from the figure that changing the order of connection of the _C1 to _C3 lines and the gate circuits 44-1 to 44-3 depending on the column is completely equivalent.

<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 can support any color arrangement by selecting a color selection signal. Not only is it highly practical as it can be applied to liquid crystal display devices with various color arrangements, but it is also extremely useful in driving large capacity, high display quality matrix type color liquid crystal display devices.

[Brief explanation of drawings]

1A and 1B are a configuration diagram of a column electrode drive circuit in a drive circuit of a liquid crystal display device and a timing waveform diagram showing voltage waveforms of main parts of the column electrode drive circuit for explaining an embodiment of the present invention. 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. FIG. 3 is a circuit diagram and main drive waveform diagram of a conventional column electrode drive circuit and color changeover switch circuit. FIG. 4 is a configuration diagram of a sampling circuit, a color arrangement diagram of a color filter, and a voltage waveform diagram of main parts, 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, 41... Shift register, 22,
32, 42...analog switch for sampling,
23, 33, 43...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 sandwiched between these two substrates, and a color filter. In the column electrode drive circuit for the purpose of the present invention, a circuit for sampling the instantaneous voltage corresponding to the picture element to be displayed out of the input display signal is connected to a sampling capacitor, one end of which is commonly connected to the sampling capacitor, and the other end of which is connected in common to the sampling capacitor. three sampling analog switches connected to different ones of the red, green, and blue display signal lines, a shift register circuit, and a signal that selectively opens or closes one of the sampling analog switches. three gate circuits connected to different one of the sampling analog switches to output the same, and connected to the output terminal of the shift register circuit, and configured to receive a color selection signal; A driving circuit for a color liquid crystal display device, characterized in that it has the following features: