JPH03294822A - Liquid crystal panel display device - Google Patents

Abstract

PURPOSE:To correct picture quality over the entire display image plane by controlling a liquid crystal panel driving voltage with a signal which has a saw-tooth waveform synchronized with vertical scanning, a parabolic waveform synchronized with horizontal scanning, or their combined waveform. CONSTITUTION:A signal generating circuit 9 generates the vertical synchronizing saw-tooth signal 11 to adjust the amplification degrees of amplifying circuits 6 - 8, and the saw-tooth signal 11 is adjusted in amplitude and added by adders 3 - 5 to driving voltages of R, G, and B which are output signals of a brightness/chroma processing circuit 1 to control the liquid crystal panel driving voltage. Thus, the liquid crystal panel driving voltage is controlled with the saw-tooth control signal 11 synchronized with the vertical scanning and then variance in voltage-brightness characteristics which is generated by vertical variation in view angle among respective positions on a liquid crystal panel, thereby correcting the picture quality over the entire display image plane.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-quality liquid crystal panel display device, and particularly to a correcting means suitable for contrast deterioration caused by differences in viewing angles of various parts of a liquid crystal panel.

[Conventional technology]

BACKGROUND ART Conventionally, in liquid crystal panel display devices, when the surface of the liquid crystal panel is viewed from a vertical position, contrast deterioration phenomena such as the display screen becoming whitish or inverted occur.

JP-A-63-142387 solves the above problem in a passenger transport in-flight system using a liquid crystal panel display device. In a display system in a passenger transport aircraft, a liquid crystal panel display device is attached to the back of the seat back of an airplane, passenger train, etc., so that passengers in the rear seats can enjoy TV images or obtain necessary information. Since the seats are usually reclining, the viewing angle for rear seat passengers changes depending on the reclining angle of the front seats, resulting in a deterioration in image quality.

Therefore, Japanese Patent Application Laid-Open No. 63-142387 discloses a method of attaching a variable resistor to the reclining rotating shaft of the backrest, detecting the reclining angle, and thereby controlling the liquid crystal panel running voltage.

Even if the viewing angle changes depending on the reclining angle, image brightness is automatically controlled to prevent image quality deterioration.

[Problem to be solved by the invention]

The above-mentioned prior art is a correction means only for the visual angle that changes depending on the reclining angle of the backrest. In other words, it is a means for correcting only the viewing angle with respect to, for example, the center of the screen. However, when viewing a liquid crystal panel from a certain perspective, the viewing angle given by the angle between the line of sight and the normal to the liquid crystal panel differs depending on the location within the liquid crystal panel. For example, even if you adjust the LCD panel drive voltage to obtain the best image when looking at the center of the screen from a certain viewpoint,
Contrast deterioration occurs in the periphery because the viewing angle is different.

Figure 2 shows the top of the LCD panel when viewed from the front.

The viewing angle at the lower end portion is shown, and FIG. 3 shows the liquid crystal panel driving voltage-luminance characteristics of the viewing angle in FIG. 2.

Figure 2 shows a normally black liquid crystal panel 2 in which two polarizing plates sandwiching a liquid crystal layer are arranged so that their polarization axes are parallel to each other, and the brightness decreases when the driving voltage is decreased.
, human eye 10, center point A of liquid crystal panel 2, upper end B
point, lower end point C, visual angle θA when looking at point A from eye 10 (
O') with respect to the perpendicular line on the second surface of the panel, viewing angle θ when looking at point B, and screen viewing angle θ when looking at point C. shows. FIG. 3 shows the voltage-brightness characteristic A' at θ6, the rise voltage VA' of brightness at that time, the voltage-brightness characteristic B' at θ, and the rise voltage VB'θ of brightness at that time. Voltage-luminance characteristic C' when , brightness rise voltage V. ′, the voltage at A′ ■ the brightness at that time BRA, the voltage v at B′
Brightness B R at time A.

The brightness BRc when the voltage is 6 at C′, the brightness B
The voltage VB at B' and the voltage v0 at C' at the time of RA are shown.

As shown in FIG. 2, the viewing angle at point A at the center of the liquid crystal panel is 06=0°, while at point B at the top end the viewing angle is θ1, looking up at the panel 2 from below, and at point C at the bottom end the viewing angle is θ. This will give you a view of panel 2 from above.

In other words, even when viewing the same screen, the viewing angle changes depending on the location on the panel.

As shown in Figure 3, the voltage-luminance characteristics of the liquid crystal panel are as follows:
It changes depending on the viewing angle, and the viewing angle θ6 in FIG.
θ8. θ. When , it becomes A', B'C'. For example, when the brightness at point A is BRA, the brightness at point B is BR,
The brightness at point 0 is BR, and when looking at the screen, the upper side of the screen becomes whitish, the lower side does not have sufficient brightness, and the image quality deteriorates in the periphery of the panel. Furthermore, as the screen size of the liquid crystal panel becomes larger, the viewing angle of each location on the panel changes more greatly, and the voltage-luminance characteristics also change more greatly, making the above problem more pronounced.

As described above, the conventional technology is an image quality correction means for one viewing angle, for example, at the center of the screen, and cannot be said to be a sufficient correction means for the entire screen.

An object of the present invention is to provide a correction means for the entire display screen of a liquid crystal panel, and an image quality correction means particularly effective for a large-screen liquid crystal panel.

[Means to solve the problem]

The above object is achieved by controlling the liquid crystal panel running voltage with a signal having a sawtooth waveform synchronized with vertical scanning, a parabolic waveform synchronized with horizontal scanning, or a combination thereof.

[Effect]

As mentioned above, by changing the LCD panel drive voltage according to the viewing angle dependence at the location where the LCD panel is installed,
It is possible to reduce variations in voltage-luminance characteristics depending on the viewing angle of the screen at a location within the liquid crystal panel, and it is possible to correct the image quality over the entire display screen and display with uniform contrast.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure shows a block diagram of a liquid crystal panel driving voltage control circuit according to a first embodiment of the present invention. FIG. 1 shows a luminance/chroma processing circuit 1, adders 3, 4, 5° amplification circuits 6, 7, 8, and a sawtooth waveform or parabolic waveform signal generation circuit 9.

FIG. 6 shows the signal waveform generated by the signal generating circuit 9 in FIG. 1, where 11 shows a sawtooth signal synchronized with vertical scanning, and 12 shows a parabolic signal synchronized with horizontal scanning. .

As shown in FIGS. 2 and 3, the voltage-brightness characteristic B' at point B at the upper end of the liquid crystal panel 2 is higher than the voltage-brightness characteristic A' at point A at the center of the panel 2, since the brightness rise voltage ■ゎ′
is smaller than vA', and when the driving voltage is increased from ○■, the brightness rises at a low voltage. Further, the voltage-luminance characteristic C' at point C at the lower end of the panel 2 is compared with the voltage-luminance characteristic A', and the luminance rising voltage Vc' is VA'
It is larger, and its brightness rises at a relatively high voltage.

Therefore, in order to eliminate variations in voltage-luminance characteristics depending on the viewing angle, a voltage component of VA'=■,' is added to the drive voltage part at point B, and V . The vertical synchronization sawtooth signal 11 shown in FIG. 6 from which the voltage component of /VAL is subtracted is used as a control signal. In FIG. , the amplification degree of each of the amplifier circuits 6°7.8, the amplitude of the sawtooth signal 11 is adjusted, and the output signals of the brightness/chroma processing circuit 1, R, G,
The adders 3 and 4.5 add the driving voltages of each of the signals H to control the driving voltage of the liquid crystal panel.

In this way, if the liquid crystal panel drive voltage is controlled using a sawtooth control signal that is synchronized with vertical scanning, the voltage generated by the vertical viewing angle change at each location on the liquid crystal panel -
Variations in brightness characteristics can be reduced, and image quality can be corrected over the entire display screen.

The above is a means for correcting the deterioration in image quality due to changes in the viewing angle in the vertical direction, but the voltage-luminance characteristics also vary depending on changes in the viewing angle in the left and right directions at each location on the liquid crystal panel.

Figure 4 is the left side of the LCD panel when viewed from the front.

Figure 5 shows the change in visual angle at the right end.

FIG. 4 shows changes in liquid crystal panel drive voltage-luminance characteristics depending on the viewing angle in FIG. 4. FIG. FIG. 4 shows point A at the center of the liquid crystal panel 2 and point 1 at the left end. Right end point E, screen viewing angle θ^ when looking at point A from eye 10, screen viewing angle θゎ when looking at point D, E
Shows the screen viewing angle θ when looking at a point.

Figure 5 shows the voltage-brightness characteristic A' at that time of θ, the brightness rise voltage at that time ■6', the voltage-brightness characteristic D' at that time θ0, the brightness rise voltage VD' at that time, and the voltage at θ□. - Brightness characteristic E', brightness rise voltage at that time■
. ', brightness BRA when the voltage is 9 at A', D
' Voltage ■ Brightness at that time BRD, E ' Voltage ■ Brightness at that time B R! , voltage (2) at D' and voltage (6) at E' when the brightness is BRA are shown.

Here, the control signal is determined from the voltage-luminance characteristic in the same way as when the sawtooth signal 11 for correcting the vertical viewing angle was determined.

4 and 5, the left end point of the liquid crystal panel 2,
The voltage-brightness characteristics D' and E' at point E at the right end are in proportion to the voltage-brightness characteristic A' at point A at the center, and the brightness rise voltage y,
',y,' is thicker than ■6'.

Therefore, the drive voltage part at points D and E is V9VA'+V
A parabolic signal 12 synchronized with horizontal scanning in FIG. 6 from which a voltage component of %VA' is subtracted is used as a control signal.

In FIG. 1, if the signal generating circuit 9 generates the parabolic signal 12, the liquid crystal panel running voltage is controlled by the parabolic control signal. Variations in voltage-luminance characteristics caused by changes in viewing angle can be reduced, and image quality can be corrected over the entire display screen.

FIG. 7 is a block diagram of a liquid crystal panel drive voltage control circuit according to a second embodiment of the present invention. FIG. 7 shows the sawtooth signal generating circuit 9-1. Parabolic signal generation circuit 9-2
．． Adder 13 is shown. The second example is the top and bottom at each location on the liquid crystal panel.

This is a means for correcting image quality deterioration caused by changes in screen viewing angle in both left and right directions.The signal generating circuit 9-1 forms a sawtooth signal synchronized with vertical scanning, and the signal generating circuit 9-2 forms a parabolic signal synchronized with horizontal scanning. adder 1
3 and used as a control signal to control the liquid crystal panel running voltage.

In this manner, the second embodiment can provide a display screen with higher image quality that is more corrected in viewing angle in both the horizontal and vertical directions than in the first embodiment.

FIG. 8 is a block diagram of a liquid crystal panel dynamic voltage control circuit according to a third embodiment of the present invention. In the third embodiment, the present invention is applied to the seatback television for a reclining seat described in the prior art, and the signal generating circuit 9 generates a vertical synchronization sawtooth signal, a horizontal synchronization parabolic signal, or a combination thereof. A signal is formed by combining the signals, and is added to the output voltage of the conventional seat reclining angle detection circuit 14 in an adder 13 to obtain a control signal to control the liquid crystal panel drive voltage. As described above, according to the third embodiment, the effects of the present invention can be sufficiently enhanced even when a liquid crystal panel display device is attached to the backrest of a seat.

FIG. 9 is a block diagram of a liquid crystal panel drive voltage control circuit according to a fourth embodiment of the present invention. In the fourth embodiment, the liquid crystal panel drive voltage is controlled at the input stage of the luminance/chroma processing circuit 1, and the signal generation circuit 9 generates a sawtooth signal for vertical synchronization, a parabolic signal for horizontal synchronization, or both. The amplifier circuit 16 forms a signal combining the signals of
The voltage is adjusted by the adder 15 and added to the video signal, which is the input signal of the brightness/chroma processing circuit 1, to control the liquid crystal panel bias voltage. If the voltages required for viewing angle correction are the same between each red, green, and blue pixel, the use of this embodiment has the advantage that only one adder is required.

FIG. 10 is a block diagram of a liquid crystal panel drive voltage control circuit according to a fifth embodiment of the present invention.6 In the fifth embodiment, the liquid crystal panel drive voltage is controlled in the brightness/chroma processing circuit 1. The slope of the voltage-luminance characteristic curve is controlled according to the viewing angle of the screen.

In FIG. 10, a signal generating circuit 9 generates a sawtooth signal for vertical synchronization, a parabolic signal for horizontal synchronization, or a combination thereof, which is input to amplifier #ti circuits 21 and 22, and is then input to each amplifier circuit. Adjust the amplification degree and adjust the amplitude of the control signal. and.

In the brightness control system, an adder 17 adds the amplitude-adjusted control signal and the output voltage of the brightness adjustment voltage source 19, and inputs the result to the brightness control terminal T1 of the brightness/chroma processing circuit 1. In the color signal control system, the control signal and the output voltage of the color signal adjustment voltage source 20 are added together by an adder 18 and input to one color signal control terminal T2. In this way, it is also possible to correct the viewing angle.

〔Effect of the invention〕

According to the present invention, image quality deterioration caused by changes in viewing angle at various locations on the liquid crystal panel can be corrected, so there is an effect of correcting image quality over the entire display screen.
It is especially effective for large LCD panels.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a liquid crystal panel running voltage control circuit according to a first embodiment of the present invention, and FIGS. 2 and 4 are model diagrams showing vertical and horizontal viewing angles of a location above the liquid crystal panel. FIGS. 3 and 5 are the above-mentioned FIG. 2. FIG. 4 is a corresponding voltage-luminance characteristic diagram, FIG. 6 is a waveform diagram of the liquid crystal panel suspicious voltage control signal, and FIG. 7 is a block diagram of the liquid crystal panel negative voltage control circuit according to the second embodiment of the present invention. 8 is a block diagram of a liquid crystal panel active voltage control circuit according to a third embodiment of the present invention, and FIG. 9 is a block diagram of a liquid crystal panel active voltage control circuit according to a fourth embodiment of the present invention. ,
FIG. 10 is a block diagram of a liquid crystal panel dynamic voltage control circuit according to a fifth embodiment of the present invention. 1... Brightness/chroma processing circuit, 2... Liquid crystal panel, 3.4, 5, 13, 15, 17.18... Adder, 6
．． 7, 8, 15, 21. 22... Amplification circuit, 9... Signal generation circuit, 11... Sawtooth signal, 12... Parabolic signal.

Claims (1)

[Claims] 1. In a liquid crystal panel display device using a liquid crystal panel as a display panel, the liquid crystal panel driving voltage is synchronized with vertical scanning.
A liquid crystal panel display device characterized in that it is controlled by a signal having a substantially sawtooth waveform, a substantially parabolic waveform synchronized with horizontal scanning, or a combination thereof.