JP2506796B2 - Liquid crystal display - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device effective for use in video and information equipment.

2. Description of the Related Art In recent years, there has been an increasing demand for large-screen, thin display devices in the field of information equipment centering on computers and in the field of video equipment centering on televisions and video tape recorders (VTRs). As a display device of this type, a device using liquid crystal is easily attracting attention because of its thinness, light weight, and large screen.

A conventional method of driving a liquid crystal display device will be described below with reference to the drawings.

FIG. 4 (a) shows an ideal drive voltage waveform of the voltage averaging method which is a general drive method of the conventional liquid crystal display device,
A window pattern as shown in FIG. 6 is displayed on a dot matrix type liquid crystal panel, and a drive voltage waveform in the pixel 1 when AC is made in a cycle of one scanning selection period is shown. 4 (b) and 4 (c) are a scanning voltage waveform and a signal voltage waveform for realizing the drive voltage waveform shown in FIG. 4 (a). In Fig. 4, V0, V5
Is a selection voltage, V1 and V4 are scanning-side non-selection voltages, and V2 and V3 are signal-side non-selection voltages.

In Fig. 4 (a), ± Vs, ± Vn and ± Vb are ON.
Indicates voltage, OFF voltage, bias voltage, and is set so that Vs = V0-V5 Vn = V2-V5 = V0-V3 Vb = V0-V1 = V4-V5 Vb = V1-V2 = V3-V4 .

In the case of a matrix panel using twisted nematic (TN) liquid crystal, the liquid crystal responds to the effective value of the applied voltage, so the effective value voltage, which is the sum of the OFF voltage and the bias voltage, is set equal to the threshold voltage, and the ON voltage is turned on. By setting the effective value voltage, which is the sum of the voltage and the bias voltage, higher than the above threshold voltage, it is possible to realize the state of lighting and non-lighting between the ON pixel and the OFF pixel, and display the desired pattern. (For example, “Basics and Applications of Liquid Crystal Electronics”, Ohmsha).

However, when the scanning voltage and the signal voltage shown in FIGS. 4B and 4C are applied to an actual liquid crystal panel, the voltage waveform applied to the liquid crystal layer is as shown in FIG. ) Not the ideal voltage waveform shown in FIG. 5B, but the distorted waveform shown in FIG.

This is because the liquid crystal layer is equivalently a capacitive load when viewed from the scan driver and the signal driver, and the output resistance of the driver and the electrode resistance of the liquid crystal panel are added to this, which causes a transient phenomenon due to a change in the signal voltage. This is because the voltage applied to the liquid crystal layer is distorted.

5 (a) and 5 (b) show voltage waveforms applied to the liquid crystal layers of the pixels 1 and 2 on the display pattern shown in FIG.

As is apparent from FIG. 5, the applied voltage waveforms in the above-mentioned pixels, which should have the same display brightness, are different.

Problems to be Solved by the Invention Therefore, when the liquid crystal panel is driven by the scanning voltage and the signal voltage shown in FIGS. 4 (b) and 4 (c), originally the same display brightness should be obtained. In the pixels 1 and 2, the effective value voltage applied to each liquid crystal layer is different due to the difference in applied voltage waveform, which causes a problem that display unevenness depending on the display pattern occurs.

In particular, when the liquid crystal panel is a simple matrix panel, the signal voltage of other display pixels is applied as a bias voltage even in a pixel other than the display selection period, so that the problem of display unevenness described above is to obtain a uniform display. Will be an important issue.

Therefore, the present invention provides a liquid crystal display device which solves the above problems and can obtain a uniform display.

Means for Solving the Problems And, the technical means of the present invention for solving the above problems is to provide a predetermined signal detecting means on the scanning electrode side of a liquid crystal panel, and to detect a voltage detected by the signal detecting means. To
The correction voltage obtained by performing a predetermined process is applied to the scan electrodes.

More specifically, at least one scan electrode of the liquid crystal panel is added, this scan electrode is used as a detection electrode, and a voltage obtained by reversing the polarity of the voltage waveform detected by this detection electrode is used as a correction voltage. It is configured so that it can be applied to the scanning electrodes.

Further, the scanning electrodes of the liquid crystal panel are used as the detection electrodes of the detection means.

Action The action of this technical means is as follows.

That is, in the present invention, the waveform distortion that the voltage applied to the liquid crystal layer undergoes due to the transient phenomenon accompanying the change of the signal voltage,
Detected by a predetermined signal detection means, extract the distortion component of the above waveform from the detected voltage, apply it as a correction voltage to the scan electrodes of the liquid crystal panel, and set the effective value voltage of ON or the effective value voltage of OFF to the correct value. The correction is intended to reduce the cause of display unevenness.

By adding one scanning electrode of the liquid crystal panel and applying a non-selective voltage to this electrode as a detection electrode, the waveform generated on the scanning electrode for display is capacitively coupled to the signal electrode. The same distorted waveform is generated. Since this distorted waveform becomes the detection voltage, a voltage obtained by reversing the polarity of this voltage is used as a correction voltage and is added to the non-selection voltage of the scanning electrode for display, thereby distorting the waveform generated on the scanning electrode for display. Can be offset.

Further, since the scanning electrodes of the liquid crystal panel are used as the detection electrodes used in the detection means, all the non-selection voltages are applied to one scanning electrode except one selection voltage application. If the voltage detection is stopped only when the voltage is applied, it can be handled in the same manner as the above-mentioned detection electrode, and the distorted waveform can be easily detected without providing a special detection electrode.

Examples Hereinafter, one example of the liquid crystal display device of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a liquid crystal display device according to an embodiment of the present invention. In FIG. 1, 10 is a liquid crystal panel, 11 and 12 are scanning electrodes and signal electrodes of the liquid crystal panel, 13 and
Reference numeral 14 denotes a scan driver and a signal driver that drive the scan electrode 11 and the signal electrode 12, respectively. Reference numeral 15 denotes a detection electrode provided on the scan electrode 11 side, and one of the scan electrodes 11 may be used.
Reference numeral 16 is a detection circuit that controls the detection electrode 15 to detect waveform distortion. Reference numeral 17 denotes a correction voltage generation circuit, which generates a correction voltage based on the signal extracted by the detection circuit 16. Reference numerals 18 and 19 denote a control circuit and a drive voltage generation circuit, respectively, which are a scan driver 13,
It supplies necessary timing signals, display data, and drive voltage to the signal driver 14, the detection circuit 16, and the correction voltage generation circuit 17.

The operation of the liquid crystal display device of one embodiment of the present invention configured as above will be described below.

The scan driver 13 and the signal driver 14 are used to drive each scan electrode of the liquid crystal panel 10 by a driving method based on a normal voltage averaging method.
11 and the signal electrode 12 are driven. The detection circuit 16 is a scanning electrode.
The same voltage as the non-selection voltage applied to the scan electrode 11 is applied to the detection electrode 15 configured similarly to 11 via a predetermined resistance component. As a result, the detection electrode 15 intersects with the signal electrode 12 via the liquid crystal similarly to the scanning electrode 11, so that the signal electrode 12
A non-selective voltage that is capacitively coupled to the detection electrode 15 and that includes a transient distortion waveform similar to the waveform generated on the scan electrode 11 with respect to the voltage change of the signal electrode 12 is generated on the detection electrode 15. This detection electrode
By subtracting the non-selection voltage from the voltage of 15, only the distortion component can be detected. The correction voltage generation circuit 17 outputs a voltage obtained by adding a voltage obtained by inverting the polarity of the waveform of the distortion component detected by the detection circuit 16 to a non-selection voltage to be applied to the scan electrode 11 as a correction voltage. This correction voltage generator 17
By inputting the above-mentioned correction voltage output from the scanning driver 13 into the scanning driver 13 as a driving voltage, the scanning driver 13 can output a non-selected scanning voltage corrected in the opposite direction to the distortion waveform in advance. As a result, the waveform distortion generated in the scan electrode 11 due to the capacitive coupling with the signal electrode 12 can be canceled.

FIG. 2A is a scanning voltage waveform diagram after the above correction. FIG. 2B shows the signal voltage applied to the signal electrode, which is the drive voltage when the pattern of the window as shown in FIG. 6 is displayed and AC is made in a cycle of one scanning period. . In FIG. 2, V0 and V5 are selection voltages, and V1 and
V4 indicates the non-selection voltage on the scanning side, and V2 and V3 indicate the non-selection voltage on the signal side. In FIG. 2A, the detection circuit is used when the signal voltage becomes the selected voltage and when it becomes the non-selected voltage.
Since the waveforms detected in 16 are different, the waveforms at the rising and falling edges of the scanning voltage are corrected differently at the corresponding timings.

FIG. 3 shows a driving voltage waveform applied to the pixel 1 of FIG. 6 when the actual liquid crystal panel is driven by the voltages on the scanning side and the signal side shown in FIGS. 2 (a) and 2 (b). Since the pre-corrected scanning voltage shown in FIG. 2 (a) is applied, there is almost no distortion of the liquid crystal applied voltage waveform shown in FIG. 5, and the distortion is shown in FIG. 4 (a). It can be seen that the drive is performed in a state close to the ideal drive waveform.

Note that the drive voltage waveforms shown in FIGS. 2A and 2B are merely examples, and the present invention is not limited to this. For example, the AC cycle may be one display selection period (one frame period).
The correction voltage applied to the scan driver is not limited to the inverted waveform of the detected distortion waveform, but may be a waveform of an effective value voltage equal to the inverted waveform. It suffices that the effective value voltages of OFF and OFF are correct values and can be corrected so as to be applied to the liquid crystal layer.

Further, the driving waveform may be such that the pulse width of the signal voltage in one scanning selection period can be changed so that gradation display can be performed.

As shown in FIG. 2B, the signal voltage type is not corrected, but the reason is that the scanning voltage as an addition seen from the signal electrode is the selection voltage on the scanning side. Is only sequentially shifted and is always constant regardless of the displayed data, so correcting the signal voltage waveform is not very effective.

EFFECTS OF THE INVENTION The present invention has an effect that display unevenness depending on a display pattern is reduced by a method of correcting a voltage on a scanning side in a liquid crystal panel, and as a result, a liquid crystal panel having good display uniformity can be realized. be able to.

Furthermore, since the above-mentioned ON and OFF effective value voltages can be corrected to correct values, the ripple effect that the display contrast can be improved can also be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a liquid crystal display device according to an embodiment of the present invention, and FIG. 2 (a) is a driving voltage waveform diagram on the scanning side of the liquid crystal display device according to the embodiment of the present invention. (B) is a drive voltage waveform diagram on the signal side in one embodiment of the present invention, FIG. 3 is a drive voltage waveform diagram applied to the liquid crystal panel of the liquid crystal display device in one embodiment of the present invention, FIG. ) Is an ideal drive voltage waveform diagram of the liquid crystal panel, FIG. 4 (b) is a drive voltage waveform diagram of the scanning side of the conventional liquid crystal display device, and FIG. 4 (c) is a signal side of the conventional liquid crystal display device. Drive voltage waveform diagram, FIGS. 5 (a) and 5 (b) are drive voltage waveform diagrams applied to the liquid crystal layer when an actual liquid crystal panel is driven by the conventional drive voltage waveform, and FIG. 6 is an example of a display pattern. FIG. V0, V5 …… Selection voltage, V1, V4 …… Scanning side non-selection voltage, V
2, V3 …… Signal side non-selection voltage, Vs …… ON voltage, Vn …… OF
F voltage, Vb ... Bias voltage, 11 ... Scan electrode, 12 ...
Signal electrode, 13 ... Scan driver, 14 ... Signal driver,
15 ... Detection electrode, 16 ... Detection circuit, 17 ... Correction voltage generation circuit.

Claims (3)

(57) [Claims] 1. A predetermined signal detection means provided on the scan electrode side of a liquid crystal panel having scan electrodes and signal electrodes arranged in a matrix, and a predetermined voltage applied to a detection voltage detected by the signal detection means. And a correction voltage generating means for generating a predetermined correction voltage, and the correction voltage generated by the correction voltage generating means corrects the drive voltage applied to the scan electrodes of the liquid crystal panel. A liquid crystal display device comprising: 2. A liquid crystal display device according to claim 1, wherein at least one of the scanning electrodes of the liquid crystal panel is used as a detection electrode of the signal detecting means. 3. The correction voltage generating means is configured to extract a distortion component of a waveform from the detection voltage detected by the signal detecting means, and to apply a voltage having the polarity opposite to that of the distortion component to the scanning electrode as a correction voltage. The liquid crystal display device according to claim (1), characterized in that