JP3589391B2 - Matrix type display device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a matrix-type display device widely used in audiovisual equipment, office automation equipment, game equipment, and the like.
[0002]
[Prior art]
Generally, a matrix display device includes a display unit, a voltage generation circuit, a row electrode drive circuit, and a column electrode drive circuit. The display section has a plurality of row electrodes and column electrodes arranged in parallel with each other, and is configured to perform display with pixels formed at the intersection of both electrodes. The voltage generation circuit is a circuit that generates a row voltage for driving a row electrode and a column voltage for driving a column electrode. The row electrode drive circuit is a circuit for applying a row voltage to a row electrode, and the column electrode drive circuit is a circuit for applying a column voltage to a column electrode.
[0003]
A typical matrix type display device is a simple matrix type liquid crystal display device. The display section in this simple matrix type liquid crystal display device is a liquid crystal panel having a structure in which liquid crystal is sandwiched between a row electrode substrate having row electrodes and a column electrode substrate having column electrodes. Then, display is performed by applying a row voltage and a column voltage to the liquid crystal panel to change the optical characteristics of the liquid crystal. Here, a normally black mode in which the pixel is turned off when the effective voltage applied to the pixel is low and turned on when the effective voltage is high is considered.
[0004]
In this simple matrix type liquid crystal display device, the row electrodes and the column electrodes are usually driven by a voltage averaging method, a multiple-row simultaneous selection driving method, or the like. The voltage averaging method is described in, for example, “Latest Technology of Liquid Crystals” p. 106, published by the Industrial Research Institute. Also, the multiple row simultaneous selection driving method is described in, for example, N. Ruckmongathan, Conf. Record of 1988 International Display Research Conference, p. 80 (1988); J. Scheffer and B.S. Lifton, 1992 SID Digest of Technical Papers XXIII, p228 (1992), S Ihara et al. , 1992 SID Digest of Technical Papers XXIII, p232 (1992).
[0005]
The voltage averaging method and the multiple-row simultaneous selection driving method are based on the following basic principle. That is, the row voltage waveform is represented by an orthogonal matrix such as a unit matrix or a Walsh matrix, and the column voltage waveform is obtained by orthogonally transforming display information using the orthogonal matrix. Then, display is performed on the display panel by inversely converting the column voltage waveform into display information. According to this basic principle, a fixed effective voltage not depending on display information is applied to each pixel in a non-selected row where the matrix element of the orthogonal matrix is equal to 0, and display information is applied to pixels in the selected row other than the non-selected row. Is applied.
[0006]
However, in an actual simple matrix liquid crystal display device, the row voltage waveform and the column voltage are caused by the output impedance of the row electrode driving circuit and the column electrode driving circuit, the electrode resistance of the row electrode and the column electrode, and the load capacitance of the liquid crystal and the like. At the change point of the waveform, the row voltage waveform and the column voltage waveform are dull or distorted due to induction. Therefore, the effective voltage applied to each pixel deviates from the basic principle described above, and the deviation of the effective voltage is recognized as display unevenness.
[0007]
Among the display unevenness, the display unevenness caused by the distortion induced in the row voltage waveform due to the change in the column voltage waveform will be described here.
[0008]
The column voltage waveform applied to each column electrode changes according to the display information of the column electrode. Since each row electrode is capacitively coupled to all the column electrodes via the pixel capacitance, when the column voltage waveform changes, the induced distortion occurs in the row voltage waveform. Here, ignoring the electrode resistance of the row electrode, the amount of distortion due to induction in the row voltage waveform is formed between the sum of changes in the column voltage waveform applied to each column electrode and the row electrode and each column electrode. Is considered to be proportional to the total sum of the pixel capacitances. For example, when all the column voltage waveforms do not change, or when half of the column voltage waveforms change by a certain voltage in the positive direction and the remaining half of the column voltage waveforms change by the same voltage in the negative direction, No distortion due to induction occurs. On the other hand, when all the column voltage waveforms change in the maximum voltage width in one direction, the distortion due to induction becomes maximum.
[0009]
The row voltage level applied to each row electrode varies depending on the orthogonal function used for driving, and the column voltage level applied to each column electrode varies according to display information. For this reason, the influence of the induced distortion on the voltage applied to the pixel represented by the difference between the row voltage and the column voltage varies. Therefore, the applied voltage to each pixel varies, and display unevenness occurs.
[0010]
As a method for eliminating the display unevenness, Japanese Patent Application Laid-Open No. 5-34660 and Japanese Patent Application No. 10-40777 propose a method using a correction capacitor. These conventional methods are described below.
[0011]
In Japanese Patent Application Laid-Open No. 5-34660, the potential level applied from the column electrode driving means to the column electrode is binary, and a fixed voltage between the two column voltages, for example, a non-selection voltage is applied to the compensation electrode. Method. Then, the fluctuation of the row voltage is suppressed by the current from the compensation electrode. In this method, since a fixed voltage between binary column voltages is applied to the compensating electrode, compensation according to display information cannot be performed. In addition, in order to obtain a sufficient compensating effect, the area of the compensating electrode corresponding to the display area is reduced. I need.
[0012]
In Japanese Patent Application No. 10-40777, the potential level applied from the column electrode driving means to the column electrode is a binary value of a first potential level and a second potential level, and the potential level depends on the number of outputs of the two potential levels. And a method of applying a voltage of opposite polarity to the compensation electrode. In this method, the distortion induced by the sum of the changes in the column voltage waveform applied to each column electrode into the row voltage waveform is canceled by the distortion induced by the change in the compensation voltage waveform applied to the compensation electrode into the row voltage waveform. I have. Therefore, compensation according to display information, which is impossible with the method disclosed in Japanese Patent Application Laid-Open No. 5-34660, can be performed.
[0013]
Here, in order to cancel the distortion induced in the row voltage waveform by using the first potential level and the second potential level as the compensation voltage, the capacitance formed between the row electrode and the compensation electrode must be changed to the row electrode. And an amount corresponding to the sum of pixel capacitances formed between the column electrodes. Therefore, a compensation electrode area equivalent to the display area is required to obtain the compensation effect, which is not practical. For this reason, in the method of Japanese Patent Application No. 10-40777, the compensation electrode area is reduced by making the amplitude of the compensation voltage larger than the first voltage level or the second voltage level. Unlike the method disclosed in Japanese Patent No. 34660, a compensation electrode area equivalent to a display area is not required.
[0014]
Therefore, according to the method of Japanese Patent Application No. 10-40777, in a liquid crystal display device in which the potential level applied from the column electrode driving means to the column electrode is binary, a compensation electrode corresponding to a display area is provided according to display information. The display unevenness can be eliminated without requiring an area.
[0015]
[Problems to be solved by the invention]
In the method of Japanese Patent Application No. 10-40777, a voltage is output to the compensation electrode according to the number of the first potential level and the second potential level applied to the column electrode. Specifically, the number of lighting display data or the number of non-lighting display data is counted, and the counting result is offset, converted to a voltage, and output to the compensation electrode.
[0016]
This method limits the potential level applied to the column electrode to two values, and cannot be applied to the multiple-row simultaneous selection driving method in which the number of potential levels applied to the column electrode is three or more.
[0017]
Furthermore, the above method requires a counter for counting the number of lighting display data or the number of non-lighting display data, and a digital / analog converter for converting the counting result into a voltage, resulting in an increase in the number of circuits.
[0018]
The present invention has been made to solve such a problem of the related art, and eliminates display unevenness caused by distortion induced in a row voltage waveform due to a change in a column voltage waveform with a small circuit scale. Further, it is another object of the present invention to provide a matrix type display device to which a multiple row simultaneous selection driving method can be applied.
[0019]
[Means for Solving the Problems]
The matrix type display device of the present invention includes a row electrode substrate provided with a plurality of parallel row electrodes, and a column electrode substrate provided with a plurality of parallel column electrodes. Are disposed so as to cross each other, and between the row electrode substrate and the column electrode substrate. Display is performed using the electro-optical properties of liquid crystal materials A display medium is sandwiched, matrix-shaped pixels are formed at the intersections of both electrodes, a row voltage for selecting a row electrode for display is applied to each row electrode, and a row voltage is selected for each column electrode. In a matrix type display device, a column voltage according to display information of each pixel on the row electrode is applied, and display is performed on each pixel based on a difference between the applied row voltage and column voltage. The substrate is provided with detection electrodes that are parallel to the row electrodes and intersect with the column electrodes via the display medium. The detection electrodes are connected to the column electrodes by a change in capacitance of the display medium. It detects the waveform change of the applied column voltage, Said On the column electrode substrate, a compensation electrode is provided so as to be parallel to each of the column electrodes and intersect with each of the row electrodes via the display medium, and the compensation electrode has a column voltage detected by the detection electrode. A compensation voltage according to the amount of waveform change is applied, and the row voltage includes a selection voltage applied to a row electrode selected for display, and a non-selection voltage applied to a row electrode not selected for display. A voltage of a non-selection voltage level is applied to the detection electrode, and the amount of change in the detected column voltage waveform is shaped into a distorted waveform having a desired time constant, inverted and amplified, and superimposed on the non-selection voltage level. Then, it is applied as a non-selection voltage to the row electrode, thereby achieving the above object.
[0023]
In the matrix type display device according to the present invention, the compensation voltage is changed in a direction opposite to a detected waveform change of the column voltage, and the amount of change of the compensation voltage is increased with an increase in the amount of change of the column voltage waveform change. May be adopted.
[0024]
The matrix type display device according to the present invention may be configured such that the detected amount of change in the column voltage waveform is inverted and amplified by an operational amplifier or a transistor and applied to the compensation electrode as a compensation voltage.
[0026]
The compensation electrode is arranged such that an intersection with the row electrode is farther from the row electrode drive circuit than an intersection with the row electrode and the column electrode. Is arranged It may be configured.
[0027]
The matrix type display device of the present invention may be configured such that the compensation electrode is provided so as to surround the pixel, and blocks light from a portion other than the pixel.
[0028]
The matrix type display device according to the present invention may be configured such that, of the row electrodes, two or more row electrodes are simultaneously selected for display, and the column voltage level is three or more.
[0029]
Hereinafter, the operation of the present invention will be described.
[0030]
According to the present invention, since a compensation voltage corresponding to the amount of change in the waveform of the column voltage is applied to the compensation electrode provided on the row electrode substrate or the column electrode substrate, the change in the column voltage waveform is induced in the row voltage waveform. This can be counteracted by the distortion that the change in the compensation voltage waveform induces in the row voltage waveform via the capacitance between the compensation electrode and the row electrode.
[0031]
Further, since the change in the column voltage waveform is detected via the capacitor, the present invention can be applied to a multiple row simultaneous selection driving method in which the number of potential levels applied to the column electrodes is three or more, and the number of lighting display data and A counter for counting the number of non-lighting display data is not required, and a simple circuit configuration can be achieved.
[0032]
By providing a detection electrode on the row electrode substrate, it is possible to easily detect a change in the waveform of the column voltage via the capacitance of the display medium sandwiched between the row electrode substrate and the column electrode substrate without providing a new capacitive element. The display unevenness can be eliminated with a simple circuit configuration.
[0033]
The magnitude of the distortion induced by the change in the column voltage waveform into the row voltage waveform via the capacitance between the row electrode substrate and the column electrode substrate depends on the magnitude of the capacitance between the two substrates. For example, in a matrix type liquid crystal display device, which is a typical matrix type display device, the capacitance of liquid crystal between a row electrode substrate and a column electrode substrate changes depending on temperature or the like. Therefore, by detecting the change in the column voltage waveform via the capacitance of the liquid crystal sandwiched between the two substrates using the detection electrodes provided on the row electrode substrate, the amount of change in the detected column voltage waveform is In accordance with the amount of distortion of the row voltage waveform depending on the capacitance value of the row voltage. Therefore, it is possible to apply a compensation voltage corresponding to the liquid crystal capacitance to the compensation electrode.
[0034]
By applying a voltage of the non-selection voltage level to the detection electrodes, it is possible to avoid applying a DC voltage to the liquid crystal layer between the detection electrodes and the column electrodes. Therefore, there is no adverse effect on the display due to the decomposition of the liquid crystal molecules due to the application of the DC voltage and the lighting of the detection electrodes.
[0035]
When the compensation voltage is changed in the opposite direction to the detected column voltage waveform change, and the amount of the change is increased along with the increase in the column voltage waveform change, the row voltage waveform induced by the change in the column voltage waveform Can be canceled by applying a compensation voltage to the compensation electrode.
[0036]
Here, the amount of distortion induced in the row voltage waveform is the sum of changes in the column voltage waveform applied to each column electrode and the sum of pixel capacitances formed between the row electrode and each column electrode. Proportional. Therefore, the compensation voltage is changed in the opposite direction to the sum of the detected column voltage waveform changes, and the product of the capacitance between the row electrode and the compensation electrode and the amount of change in the compensation voltage waveform is defined as the column voltage waveform. Is equal to the product of the sum of the pixel capacitances formed between the row electrode and each column electrode, thereby compensating for the row voltage waveform distortion induced by the sum of the column voltage waveform changes. It can be canceled by applying a compensation voltage to the electrode.
[0037]
By using an operational amplifier or a transistor, it is possible to easily invert and amplify the sum of the detected changes in the column voltage waveform and apply the sum to the compensation electrode as a compensation voltage. Therefore, the compensation voltage is easily changed in the opposite direction to the sum of the detected column voltage waveform changes, and the product of the capacitance between the row electrode and the compensation electrode and the amount of change in the compensation voltage waveform is calculated as the column value. Equal to the product of the sum of the changes in the voltage waveform and the sum of the pixel capacitances formed between the row electrode and each of the column electrodes, thereby distorting the row voltage waveform induced by the sum of the changes in the column voltage waveform. It can be canceled by applying a compensation voltage to the compensation electrode.
[0038]
In this case, it is desirable to set the gain of the operational amplifier and the transistor to be large. The reason is that when the amount of change in the compensation voltage waveform is increased, the capacitance between the row electrode and the compensation electrode can be reduced accordingly, and as a result, the area of the compensation electrode can be reduced. In order to set the amplification factor to the maximum, it is desirable to set the power supply voltage of the operational amplifier or the transistor to the maximum voltage used in the matrix type display device. In the case of configuring an inverting amplifier circuit, a general-purpose operational amplifier can be configured with a smaller number of parts and inexpensive than a transistor. However, the maximum voltage width in a matrix type liquid crystal display device which is a typical matrix type display device is larger than the maximum voltage rating of a normal operational amplifier. On the other hand, a transistor having a maximum voltage rating that satisfies the maximum voltage width in a matrix-type liquid crystal display device is easily available, and the above configuration can be realized.
[0039]
As described above, by applying the compensation voltage to the compensation electrode, it is possible to cancel the distortion induced by the change in the column voltage waveform into the row voltage waveform. However, when the size of the compensation electrode is restricted, the capacitance between the compensation electrode and the row electrode is limited, so that the distortion induced in the row voltage waveform cannot be sufficiently canceled. In this case, the amount of change in the detected column voltage waveform is shaped into a distorted waveform having a desired time constant, inverted and amplified, superimposed on a non-selection voltage level, and applied to the row electrode as a non-selection voltage, thereby obtaining The distortion induced in the voltage waveform can be sufficiently canceled.
[0040]
Here, a method for superimposing a distortion component obtained by inverting and amplifying a distortion component on a non-selection voltage to cancel the distortion induced by the non-selection voltage is described in P.K. Maltese, Eurodisplay '84 Digest, p. 15 (1984).
[0041]
The detection electrode detects the sum of the column voltage waveform changes as the amount of distortion induced by the changes. Therefore, if the distortion waveform detected by the detection electrode is inverted and amplified and superimposed on the non-selection voltage level to be a non-selection voltage, the distortion induced in the row electrode can be canceled by the inversely amplified and superimposed distortion waveform. it can. However, this method alone cannot cope with the fact that the magnitude of the distortion generated in the row electrode varies depending on the distance from the row electrode drive circuit due to the row electrode resistance. Therefore, if the distortion itself generated in the row electrode is reduced by using it together with the application of the compensation voltage to the compensation electrode, the difference due to the distance from the row electrode drive circuit can be reduced, and a uniform display can be obtained. Can be.
[0042]
The strain induced in the row electrodes increases with distance from the row electrode drive circuit due to the row electrode resistance. Further, the effect of canceling the distortion due to the compensation voltage increases as the distance from the compensation electrode increases. Therefore, by arranging the intersection of the compensation electrode and the row electrode farther from the row electrode drive circuit than the intersection of the row electrode and the column electrode, the intersection is farther from the row electrode drive circuit due to the row electrode resistance. The compensation effect by the compensation electrode can be increased with respect to the distortion which becomes larger.
[0043]
In some cases, a metal film is provided around the pixel on the row electrode substrate or the column electrode substrate in order to block light from a portion other than the pixel. In this case, a capacitance layer (insulating film) is provided between the metal film and the row electrode. Therefore, if the metal film is used as a compensation electrode, a compensation effect can be obtained without newly providing a compensation electrode. Further, by using the metal film and the compensation electrode provided on the column electrode substrate as described above, the capacitance between the compensation electrode and the row electrode can be increased.
[0044]
According to the present invention, display unevenness can be eliminated with a small circuit configuration even if one row electrode is simultaneously selected for display among the row electrodes and the column voltage level is binary. Even if two or more row electrodes are simultaneously selected for display and the column voltage level is three or more, display unevenness can be solved with a small circuit configuration.
[0045]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0046]
(Embodiment 1)
FIG. 1 is a block diagram showing a simple matrix type liquid crystal display device of the present embodiment.
[0047]
This liquid crystal display device includes a liquid crystal panel 1, a row electrode driving circuit 2, a column electrode driving circuit 3, a memory 4, an arithmetic circuit 5, a function generator 6, a voltage generating circuit 7, and a compensation voltage applying means 8.
[0048]
In the liquid crystal panel 1, a row electrode substrate and a column electrode substrate (not shown) are arranged to face each other with a liquid crystal layer interposed therebetween. The row electrode substrate has a plurality of row electrodes 11 and detection electrodes 13 arranged in parallel in the row direction, and the column electrode substrate has a plurality of column electrodes 12 and compensation electrodes arranged in parallel in the column direction. 14. The row electrode 11 and the detection electrode 13 are arranged so as to be orthogonal to the column electrode 12 and the compensation electrode 14 with a liquid crystal layer (not shown) interposed therebetween. The intersections between the row electrodes 11 and the column electrodes 12 form pixels in a matrix, and display is performed at these portions. Each row electrode 11 is connected to the row electrode drive circuit 2, each column electrode 12 is connected to the column electrode drive circuit 3, and the detection electrode 13 and the compensation electrode 14 are connected to the compensation voltage applying means 8.
[0049]
The memory 4 is a storage device for temporarily storing input display information, and is, for example, a frame memory. This memory 4 can be omitted depending on the configuration.
[0050]
The arithmetic circuit 5 is a circuit for orthogonally transforming the display information from the memory 4 using the orthogonal function generated by the function generator 6.
[0051]
The function generator 6 is a circuit that generates and outputs an orthogonal function represented by a unit matrix, a Walsh matrix, or the like.
[0052]
The voltage generation circuit 7 converts a row voltage composed of a selection voltage and a non-selection voltage for driving the row electrode output to the row electrode driving circuit 2 and a column voltage for driving the column electrode output to the column electrode driving circuit 3. Generate.
[0053]
The row electrode driving circuit 2 converts a selection voltage and a non-selection voltage output from the voltage generation circuit 7 as row voltages for selecting a row electrode for display based on the orthogonal function generated by the function generator 6 into row electrodes 11. Is a circuit to be applied.
[0054]
The column electrode drive circuit 3 is a circuit that selects a column voltage output from the voltage generation circuit 7 based on the operation output of the operation circuit 5 and applies the selected column voltage to the column electrode 12.
[0055]
The detection electrode 13 is an electrode that is not used for display, and controls the amount of change in the voltage waveform applied to the column electrode 12 or the compensation electrode 14 via the liquid crystal capacitance formed at the intersection with the column electrode 12 or the compensation electrode 14. It is a means to detect. The detected change amount of the voltage waveform is supplied to the compensation voltage applying means 8.
[0056]
The compensation electrode 14 is an electrode that is not used for display, and is an electrode for canceling the distortion induced in the row electrode 11 by a change in the column voltage applied to the column electrode 12 by applying a compensation voltage. In this embodiment, the compensation electrode 14 provided on the column electrode substrate is provided only on the side far from the row electrode drive circuit 2. This is because the distortion induced in the row electrode 11 increases as the distance from the row electrode drive circuit 2 increases, and the distortion canceling effect due to the compensation voltage increases as the distance from the compensation electrode 14 increases. It is. Note that the compensation electrodes 14 may be provided on the column electrode substrate both on the side far from the row electrode drive circuit 2 and on the side close thereto. Further, the compensation electrode 14 may be provided on the row electrode substrate between the row electrode and the row electrode via a capacitor layer. Further, the compensating electrode 14 may be disposed on the row electrode substrate or the column electrode substrate so as to surround the periphery of the pixel, so as to block light from other than the pixel.
[0057]
FIG. 2 is a circuit diagram showing a configuration of the compensation voltage applying means 8 in the present embodiment. Here, an operational amplifier 20 is used to configure an inverting amplifier circuit.
[0058]
The non-inverting input terminal of the operational amplifier 20 is supplied with the non-selection potential Vc, the inverting input terminal is connected to the detection electrode 13 via the resistor 21, and the resistor 22 is connected between the inverting input terminal and the output terminal. I have. Then, the output of the operational amplifier 20 is applied to the compensation electrode 14.
[0059]
According to this circuit configuration, the potential level of the detection electrode 13 can be set to the non-selection potential Vc by using the virtual ground between the inverting input terminal and the non-inverting input terminal of the operational amplifier 20. Therefore, it is possible to prevent deterioration such as decomposition of liquid crystal due to lighting on the detection electrode 13 or application of a DC voltage.
[0060]
FIG. 3 is a timing chart for explaining the operation of the matrix type liquid crystal display device of the present embodiment. 3A shows a row voltage waveform 0 when no compensation voltage is applied, FIG. 3B shows a column voltage waveform, FIG. 3C shows a detection voltage waveform, FIG. 3D shows a compensation voltage waveform, and FIG. (E) shows the row voltage waveform 1 when the compensation voltage is applied. The row voltage waveform 0 and the row voltage waveform 1 are considered in consideration of the case where the number of column voltage waveforms as shown in FIG. 3B is dominant among the column voltage waveforms applied to each column electrode 12. Is shown.
[0061]
As shown in FIG. 3 (b), when an upward or downward change occurs in the dominant column voltage waveform, distortion occurs in the row voltage waveform due to upward or downward induction as shown in FIG. 3 (a). .
[0062]
At this time, the detection voltage waveform detected by the detection electrode 13 is not selected as shown in FIG. 3C with respect to a change in the column voltage waveform centered on the non-selection potential Vc shown in FIG. The waveform changes in the same direction around the potential Vc, and attenuates to the non-selection potential Vc with a time constant set by the resistor 21. Here, a rectangular wave is generated by increasing the resistance of the resistor 21 to increase the time constant.
[0063]
The compensation voltage waveform shown in FIG. 3D is a waveform obtained by inverting and amplifying the detection voltage waveform shown in FIG. 3C by (resistance 22 / resistance 21) times around the non-selection potential Vc. Here, since the compensation voltage also changes around the non-selection potential Vc, no DC voltage is applied between the compensation electrode 14 and the row electrode 11 even when the compensation electrode 14 is provided on the column electrode substrate. It is possible to prevent degradation such as decomposition of the liquid crystal due to application of a DC voltage.
[0064]
A row voltage waveform 1 shown in FIG. 3E shows a case where the compensation voltage waveform shown in FIG. 3D is applied to the compensation electrode 14, and is compared with the row voltage waveform 0 shown in FIG. Thus, the induced distortion is reduced. Further, when the compensation voltage is applied to the compensation electrode 14, the detection voltage level is reduced by the amount by which the distortion due to the induction is canceled out, and as a result, the inversion-amplified compensation voltage level is also reduced. Here, the case where the detection electrode 13 intersects not only the column electrode 12 but also the compensation electrode 14 has been described. It is possible. In this case, a decrease in the detection level due to the application of the compensation voltage to the compensation electrode 14 can be suppressed.
[0065]
As described above, the compensation voltage is easily generated by using the desired operational amplifier 20 and the resistors 21 and 22, and the distortion in which the change in the column voltage waveform is induced in the row voltage waveform causes the change in the compensation voltage waveform to become the row voltage waveform. Can be counteracted by induced strain.
[0066]
(Embodiment 2)
FIG. 4 is a circuit diagram showing a configuration of the compensation voltage applying means 8 in the present embodiment.
[0067]
Here, the operational amplifier 30 constitutes a voltage follower circuit for impedance conversion, and the operational amplifier 31 constitutes an inverting amplifier circuit.
[0068]
The detection electrode 13 is connected to the non-inverting input terminal of the operational amplifier 30, and the inverting input terminal and the output terminal are short-circuited. Further, a non-selection potential Vc is applied to the detection electrode 13 and the non-inverting input terminal via the resistor 32, and the potential level of the detection electrode 13 can be set to the non-selection potential Vc as in the first embodiment. Then, the total sum of changes in the column voltage waveform around the non-selection potential Vc as shown in FIG. 3B is detected by the detection electrode 13 as a detection voltage waveform as shown in FIG. The waveform changes in the same direction around the non-selection potential Vc, and attenuates to the non-selection potential Vc with a time constant set by the resistor 32. Here, if the resistance 32 is set to a sufficiently large value, the detection voltage waveform can be made a rectangular wave.
[0069]
The operational amplifier 31 and the resistors 33 and 34 are the same circuits as in the first embodiment, and invert and amplify the output of the operational amplifier 30 which has converted the detected voltage waveform into impedance to generate a compensation voltage as shown in FIG. Then, the voltage is applied to the compensation electrode 14.
[0070]
Incidentally, in order to offset the distortion generated in the row electrode 11 by the compensation voltage, it is desirable that the amount of change in the compensation voltage waveform is large. Therefore, it is desirable that the compensation voltage has a large amplitude and a small attenuation.
[0071]
In order to increase the amplitude of the compensation voltage, the operational amplifiers 20 and 31 in FIGS. 2 and 4 must have a large maximum rating of the power supply voltage. On the other hand, in order to reduce the attenuation of the compensation voltage waveform, the resistances 21 and 32 need to be increased, and the operational amplifiers 20 and 30 need to have low bias current specifications.
[0072]
Therefore, in the configuration of the compensation voltage applying means 8 of the first embodiment shown in FIG. 2, it is necessary for the operational amplifier 20 to satisfy two specifications of a low bias current and a high withstand voltage. Is difficult.
[0073]
On the other hand, according to the configuration of the compensation voltage applying means 8 of the present embodiment shown in FIG. 4, the operational amplifiers 30 and 31 only need to satisfy the specifications of the low bias current and the high withstand voltage, respectively. Therefore, according to the present embodiment, the compensation voltage is easily generated by the simpler configuration, and the distortion in which the change in the column voltage waveform induces the row voltage waveform causes the distortion in which the change in the compensation voltage waveform induces the row voltage waveform. To cancel.
[0074]
Note that the transistor configuration is more complicated since a transistor is more readily available than an operational amplifier and a high breakdown voltage product is available. However, an inverting amplifier circuit may be configured using a transistor.
[0075]
(Embodiment 3)
FIG. 5 is a circuit diagram showing a configuration of the compensation voltage applying unit 8 in the present embodiment. In this figure, the operational amplifiers 30 and 31 and the resistors 32-34 have the same functions as in FIG.
[0076]
The output of the operational amplifier 30 is also connected to an inverting input terminal of the operational amplifier 40 via a capacitor 43 and a resistor 41, and a resistor 42 is connected between the inverting input terminal and the output terminal of the operational amplifier 40. The non-selection potential Vc is applied to the input terminal.
[0077]
FIG. 6 is a timing chart for explaining the operation of the matrix type liquid crystal display device of the present embodiment. 6A shows a row voltage waveform, FIG. 6B shows a column voltage waveform, FIG. 6C shows a detection voltage waveform, and FIG. 6D shows a non-selection voltage waveform. Here, among the column voltage waveforms applied to each column electrode 12, the case where the number of column voltage waveforms as shown in FIG. 6B is dominant is taken into account, and FIG. 6B and FIG. FIG. 6C is the same as FIG. 3B and FIG. 3C, respectively.
[0078]
In the compensation voltage applying means 8, the resistor 41 and the capacitor 43 constitute a differentiating circuit, and differentiate the output of the operational amplifier 30 which has converted the detected voltage waveform shown in FIG. The operational amplifier 40 inverts and amplifies the differential waveform by a factor of (resistance 42 / resistance 41) and superimposes the differential waveform on the non-selection potential Vc to generate a non-selection voltage waveform shown in FIG.
[0079]
The row voltage waveform shown in FIG. 6A shows a case where the non-selection voltage waveform shown in FIG. 6D is applied to the row electrode 11 as a non-selection voltage, and is obtained by the induction shown in FIG. A waveform is obtained by adding the row voltage waveform 0 having distortion and the non-selection voltage waveform shown in FIG. Here, since it is assumed that the operational amplifier 40 generates a waveform having a higher frequency component than the operational amplifier 31, a differentiating circuit is provided before the operational amplifier 40.
[0080]
As described above, according to the circuit configuration shown in FIG. 5, the compensation voltage applying means 8 applies the compensation voltage to the compensation electrode 14 similarly to the second embodiment, and also sets the detection voltage waveform to a desired time constant. It is shaped into a differential waveform having the same, inverted and amplified, superimposed on the non-selection potential Vc, and output to the row electrode drive circuit 2 as a non-selection voltage.
[0081]
Therefore, even when the magnitude of the compensation voltage and the capacitance between the compensation electrode 14 and the row electrode 11 are limited, and the distortion induced in the row voltage waveform cannot be sufficiently canceled by the compensation voltage alone, the non-selection potential is also used. The distortion induced in the row voltage waveform by the superimposed distortion waveform can be canceled. Further, the distortion itself generated in the row electrode 11 by the compensation voltage can be reduced as compared with the case where only the method of inverting and amplifying the distortion component is superimposed on the non-selection potential Vc. The difference in the amount of distortion due to the distance can be reduced, and a more uniform display can be obtained.
[0082]
【The invention's effect】
As described in detail above, according to the present invention, display unevenness is eliminated by applying a compensation voltage corresponding to the waveform change amount of a column voltage to a compensation electrode provided on a row electrode substrate or a column electrode substrate, and A uniform display can be obtained by the circuit configuration. Further, even for a matrix type display device using a multiple-row simultaneous selection driving method in which the number of column voltage levels is three or more, display unevenness can be eliminated with a small circuit configuration. Further, the amount of change in the detected column voltage waveform is shaped into a distorted waveform having a desired time constant, inverted and amplified, superimposed on a non-selection voltage level, and applied to the row electrode as a non-selection voltage, thereby obtaining a compensation voltage. Even if the size and the capacitance between the compensating electrode and the row electrode are restricted, it is possible to sufficiently eliminate distortion generated in the row electrode and obtain a uniform display.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a simple matrix type liquid crystal display device according to the present invention.
FIG. 2 is a circuit diagram showing a configuration of a compensation voltage applying unit provided in the matrix type liquid crystal display device of Embodiment 1.
FIG. 3 is a timing chart for explaining the operation of the matrix type liquid crystal display device of the first embodiment.
FIG. 4 is a circuit diagram showing a configuration of a compensation voltage applying unit provided in the matrix type liquid crystal display device of Embodiment 2.
FIG. 5 is a circuit diagram showing a configuration of a compensation voltage applying unit provided in a matrix type liquid crystal display device according to a third embodiment.
FIG. 6 is a timing chart for explaining the operation of the matrix type liquid crystal display device according to the third embodiment.
[Explanation of symbols]
1 LCD panel
2 row electrode drive circuit
3 row electrode drive circuit
4 memory
5 Operation circuit
6 Function generator
7 Voltage generation circuit
8 Compensation voltage applying means
11 row electrode
12 row electrode
13 Detection electrode
14 Compensation electrode
20, 30, 31, 40 operational amplifier
21, 22, 32, 33, 34, 41, 42 resistance
43 Capacitor

Claims (6)

A row electrode substrate provided with a plurality of mutually parallel row electrodes, and a column electrode substrate provided with a plurality of mutually parallel column electrodes are disposed so as to face each other such that each row electrode and each column electrode intersect, Between the row electrode substrate and the column electrode substrate, a display medium on which display is performed using electro-optical characteristics of a liquid crystal material is sandwiched, and matrix pixels are formed at intersections of both electrodes, A row voltage for selecting a row electrode for display is applied to each row electrode, and a column voltage according to display information of each pixel on the selected row electrode is applied to each column electrode. In a matrix type display device in which a pixel performs display based on a difference between an applied row voltage and a column voltage,
The row electrode substrate is provided with detection electrodes that are parallel to the row electrodes and intersect with the column electrodes via the display medium. It detects the waveform change of the column voltage applied to the column electrode,
A compensation electrode is provided on the column electrode substrate so as to be parallel to each of the column electrodes and intersect with each of the row electrodes via the display medium.
A compensation voltage corresponding to the waveform change amount of the column voltage detected by the detection electrode is applied to the compensation electrode,
The row voltage includes a selection voltage applied to a row electrode selected for display and a non-selection voltage applied to a row electrode not selected for display, and a non-selection voltage level applied to the detection electrode. Voltage is applied,
The amount of change in the detected column voltage waveform is shaped into a distorted waveform having a desired time constant, inverted and amplified, superimposed on a non-selection voltage level, and applied to the row electrode as a non-selection voltage. Matrix type display device. 2. The matrix type according to claim 1 , wherein the compensation voltage is changed in a direction opposite to a detected change in the waveform of the column voltage, and the amount of change in the compensation voltage increases with an increase in the amount of change in the waveform change of the column voltage. Display device. 3. The matrix type display device according to claim 2 , wherein the detected change amount of the column voltage waveform is inverted and amplified by an operational amplifier or a transistor and applied to the compensation electrode as the compensation voltage. The compensation electrode, the intersections of the row electrodes, to any one of claims 1 to 3 is arranged on the far side from the row electrode driving circuit than the intersection between the column electrode and the row electrode The matrix type display device according to the above. The matrix-type display device according to claim 1 , wherein the compensation electrode is provided so as to surround a periphery of the pixel, and blocks light from a portion other than the pixel. The matrix-type display device according to claim 1, wherein two or more row electrodes are simultaneously selected for display among the row electrodes, and a column voltage level is three or more values.

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