JPH05153529A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain easy to see display in a liquid crystal display panel and to prevent seisure of the display device. CONSTITUTION:A side panel section addition device 7 adds a raster signal of a black level to a video signal from an NTSC signal processing unit 6 in a prescribed timing as a side panel signal. A video signal from the side panel section addition device 7 is given to each picture element of a liquid crystal display panel 16 to display a video image in the middle to display a black level onto a side panel section. When the display is finished, a microprocessor 25 throws a switch S3 to give a signal of a white level to a side panel signal generator 8 thereby adding a raster signal of a white level to the side panel section addition device 7. Thus, a white level is displayed for a prescribed period to the side panel section of the liquid crystal display panel 16 to prevent seisure of the liquid crystal display panel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device,
In particular, the present invention relates to a liquid crystal display device suitable for making a display visible by turning on a backlight or a light source device.

[0002]

2. Description of the Related Art Currently, NTSC television broadcasting is being carried out in Japan, and high-definition television broadcasting with a large screen and high definition is about to be started. This high-definition television broadcast and wide EDTV
In broadcasting, the aspect ratio of the screen is different from that of the NTSC system, and a display device having a wider aspect ratio (16: 9) than the current NTSC television receiver is adopted. In the popularization period of these wide EDTV broadcasting and high-definition television broadcasting, it is necessary to consider compatibility with the current NTSC broadcasting, and the aspect ratio is 16:
It is necessary to develop a compatible display device capable of displaying NTSC video with an aspect ratio of 4: 3 by using a wide aspect display device of 9.

By the way, when displaying an NTSC broadcast having an aspect ratio of 4: 3 on a wide aspect display device, it is not possible to display all NTSC images without distortion on the entire screen due to the difference in aspect ratio. ..
FIG. 3 is an explanatory diagram for explaining display when a video having an aspect ratio of 4: 3 is displayed on a wide aspect display device having an aspect ratio of 16: 9.

FIG. 3A shows a central portion 2 of a screen 1 of a wide aspect display device in which the horizontal time axis of an NTSC signal is compressed.
The display mode to be displayed on is shown. In this case,
Although it is possible to display the entire image of the NTSC system, there is a part where the image is not displayed on the right and left portions (hereinafter referred to as side panel portions) 3 of the screen. Normally, a frame image of a predetermined level is displayed on the side panel section 3.

Further, as shown in FIG. 3 (b), NTSC
In some cases, a display mode in which the vertical amplitude of the image of the system is expanded and displayed on the entire screen 1 of the wide aspect display device may be adopted. In this display mode, the vertical amplitude of the image is increased and enlarged display is performed. However, in this mode, the upper and lower parts (broken line parts) of the NTSC image are not displayed, and some information is lost.

Further, as shown in FIG. 3C, an NTSC image having an aspect ratio of 4: 3 is horizontally multiplied by 4/3,
A mode in which the aspect ratio is converted to 16: 9 and the whole screen 1 is displayed may be adopted. In this case, NT
Although it is possible to display all the information of the SC image on the entire area of the screen 1 of the wide display device, the roundness is poor and the image becomes horizontally long. Further, various modes combining these three types of methods have also been proposed.

In a television receiver capable of receiving high-definition television broadcasting and NTSC broadcasting, all images can be displayed without distortion. Therefore, when receiving NTSC broadcasting, FIG. The display mode shown is often adopted. Figure 4 has this display mode, NTS
It is a block diagram which shows the conventional liquid crystal display device which can receive C broadcast, wide EDTV broadcast, high-definition television broadcast, etc.

A signal based on NTSC terrestrial broadcasting, satellite broadcasting, high-definition television broadcasting, or the like is induced in the antenna 5. The NTSC signal processing device 6 has an antenna 5
The signal based on the NTSC broadcast or the EDTV broadcast is decoded and output to the side panel unit addition device 7. On the other hand, the side panel signal generator 8 takes in a signal of a predetermined level from the variable resistor 10 connected between the power supply terminal 9 and the reference potential point, generates a raster signal of, for example, a black level, and adds the side panel section. Output to the device 7. The side panel addition device 7 adds a raster signal of a predetermined level from the side panel signal generation device 8 as a side panel signal to both sides of a signal having an aspect ratio of 4: 3 in the horizontal direction, so that the aspect ratio is 16: 9. Signal is applied to the terminal a of the switch S1. On the other hand, the signal from the antenna 5 is also input to the wide signal processing device 11, and the wide signal processing device 11 receives the wide aspect EDT from the antenna 5.
V signal or MUSE (Multiple Sub-Nyquist Sampling)
Encoding) Signal etc. is decoded and terminal b of switch S1
Output to.

When listening to MUSE broadcasting, the switch S1 is made to select the terminal b. Then, the signal decoded by the wide signal processing device 11 is given to the LCD driving device 12. The LCD drive device 12 converts the input video signal into a predetermined level, performs AC inversion, and supplies the X driver 14 of the liquid crystal module 13. The liquid crystal display panel 16 of the liquid crystal module 13 is configured with an aspect ratio of 16: 9, and the liquid crystal module 13 drives each pixel of the liquid crystal display panel 16 by the X driver 14 and the Y driver 15 to output from the LCD drive device 12. Display an image based on the image signal. Thus, the liquid crystal display panel 16 of the liquid crystal module 13
High-definition television broadcasting is projected on.

On the other hand, when listening to NTSC broadcast,
The terminal S is selected by the switch S1 and the output of the side panel unit addition device 7 is given to the LCD drive device 12. The X driver 14 of the liquid crystal module 13 is supplied with a video signal from the LCD drive device 12, and supplies the video signal to each pixel of the liquid crystal display panel 16 via a signal line (not shown). The Y driver 15 supplies a scanning signal via a scanning line of a liquid crystal display panel 16 (not shown) to drive each pixel. The side panel addition device 7 adds a black level side panel signal to the video signal at a timing corresponding to the left and right side panel portions of the liquid crystal display panel 16, and the liquid crystal display panel 16 has an NTSC broadcast in the center. The image is displayed, and black frame images are displayed on the left and right side panel parts.

On the other hand, in a CRT (cathode ray tube), if the same pattern is continuously displayed for a long time, the fluorescent body is deteriorated in accordance with the display pattern and burn-in occurs. For example, if the display mode of FIG.
The boundary between the center part 2 and the side panel part 3 of the screen appears. This burn-in similarly occurs in the direct-view type and projection type liquid crystal display panels. 5 and 6 are for explaining the cause of image sticking in the liquid crystal display panel. Below, the document “Prior to elemental technologies in the panel multimedia era” (Kozo Yano Nikkei Microdevices 1
September 991 pp. 49-56).

The liquid crystal display panel 16 is composed of pixels arranged in a matrix. Each pixel is provided with a thin film transistor (TFT) 21 shown in FIG. Each TFT21
The scanning signal from the Y driver 15 is supplied to the gate of the X driver through the scanning line 22 and the source of the X driver is supplied through the signal line 23.
The sampling voltage VSIG of the video signal from 14 is supplied,
The drain is connected to a pixel electrode (not shown). Nematic liquid crystal (not shown) is sealed between the pixel electrode and the common electrode (not shown). The nematic liquid crystal formed between the pixel electrode and the common electrode causes a liquid crystal capacitance CLC. Further, a parasitic capacitance CGD is generated between the gate and drain of the TFT 21. An auxiliary capacitance CS is provided in parallel with the liquid crystal capacitance CLC. The TFT 21 is turned on by the scanning signal from the scanning line 22, and applies the sampling voltage VSIG of the video signal from the signal line 23 to the pixel electrode. As a result, the liquid crystal forming each pixel is driven to display an image.

By the way, as described above, the LCD drive device 12 performs the AC drive for inverting the polarity of the video signal for each pixel in order to prevent the deterioration of the liquid crystal. That is, the polarity of the voltage VSIG is inverted every field or frame. However, it is actually impossible to reduce the effective DC voltage between the electrodes to 0, and it is considered that a predetermined DC component is accumulated around the alignment film formed on the electrode surface and the TFT.

Now, as shown in FIG. 6A, it is assumed that the scanning signal Vg of 10 to 25 V is applied to the gate of the TFT 21 during a period of several tens of microseconds within the horizontal scanning period. During the ON period of the TFT 21 by the scanning signal Vg, the liquid crystal capacitance CLC
Is charged to a value near the signal voltage VSIG shown in FIG. 6 (b). Next, when the scanning signal Vg decreases and the TFT 21 turns off, the drain voltage Vd decreases by ΔV due to the influence of the parasitic capacitance CGD. In this case, ΔV can be expressed by the following equation (1).

ΔV = Vg × CGD / (CGD + CS + CLC) (1) This reduced amount ΔV is applied as a direct current component between the electrodes, which causes the image sticking to the liquid crystal. Therefore, the effective value of ΔV is applied as a DC offset to the common electrode to compensate for the decrease ΔV. However, the liquid crystal capacitance CLC changes depending on the difference in the arrangement direction of the liquid crystal molecules, that is, the signal voltage VSIG. Now, assuming that a binary image signal of a white level and a black level is given as a signal voltage, a decrease ΔV [O when the pixel is in a transmissive state is given.
N] and the decrease ΔV [OFF] when the pixel is in the non-transmissive state
By obtaining the absolute value Ω of the difference between and, and setting this Ω to 0, it is possible to suppress flicker, image sticking, and afterimage. Here, the absolute value Ω can be represented by the following formula (2).

Ω = | ΔV [ON] −ΔV [OFF] | = Vg × {CGD / (CGD + CS + CLC [ON])-CGD / (CGD + CS + CLC [OFF])} (2) However, CLC [ON] Indicates the capacitance when the pixel is in the transmissive state,
CLC [OFF] indicates the capacitance when the pixel is in the non-transmissive state.

However, when a multi-gradation video signal is input, the signal voltage VSIG takes any level within a predetermined range, and the value of the liquid crystal capacitance CLC also changes accordingly. Therefore, the decrease ΔV cannot be compensated for all pixels, and when a signal of a predetermined pattern is input for a relatively long time, a direct current component is applied to the liquid crystal, and burn-in occurs.

Therefore, in the apparatus of FIG. 4, the side panel signal generator 8 generates a gray level signal to display a gray frame image on the side panel portion. As a result, the average applied signal levels of the central image display section and the side panel section are made substantially equal to make the DC components accumulated in each pixel to be approximately the same, and the deterioration of the phosphors in the central section and the side panel section is the same. The burn-in is made inconspicuous to some extent.

However, when the side panel portion is displayed with a predetermined brightness such as a gray level, the image in the center of the screen becomes difficult to see. In particular, when a dark image such as a night portion is displayed, the left and right sides of the screen are bright and conspicuous, which makes the screen extremely difficult to see. Therefore, a method of changing the brightness of the frame image of the side panel portion according to the average brightness level of the entire screen, the ABL (automatic brightness adjustment) level, or the like may be adopted. For example, if the entire screen is dark, set the frame image of the side panel to black level,
When the whole is bright, the frame image is displayed in a gray level according to the brightness. However, with this method, the brightness of the side panel portion may change frequently, and in this case, the display is extremely difficult to see.

[0020]

As described above, in the above-mentioned conventional liquid crystal display device, there is a problem that the screen becomes extremely difficult to see in order to suppress the image sticking of the side panel portion.

It is an object of the present invention to provide a liquid crystal display device capable of displaying a side panel portion at a black level to make the screen easy to see and preventing the occurrence of burn-in.

[0022]

A liquid crystal display device according to the present invention includes a liquid crystal display panel having a first aspect ratio in which pixels are arranged in a matrix and a first liquid crystal display panel having the first aspect ratio.
Second video signal different from the first aspect ratio and the second aspect ratio
And a video signal processing device for performing a predetermined signal processing for displaying a second video signal having an aspect ratio of 1) on the liquid crystal display panel, and a second video signal from the video signal processing device having a predetermined level at a predetermined timing. By adding a raster signal, the aspect ratio of the second video signal can be adjusted to the first aspect ratio.
Raster image adding means for converting to the aspect ratio and outputting the same, and when the second image signal from the raster image adding means is given to the liquid crystal display panel for display, the raster image adding means outputs the raster signal. When a signal of black level is added as a signal to terminate the display of the second video signal, the supply of the second video signal to the raster video adding means is stopped and the raster video is added to the raster video adding means. A control means for adding a signal of a level other than the black level as a signal and supplying the signal to the liquid crystal display panel for a predetermined period is provided.

[0023]

In the present invention, when displaying the second video signal, the control means adds the raster signal of the black level to the raster video adding means and supplies it to the liquid crystal display panel.
As a result, the display based on the second video signal is performed on, for example, the central second aspect ratio portion of the liquid crystal display panel, and black is displayed on the other portions. When ending the display based on the second video signal, the control means stops the supply of the second video signal to the raster video adding means, and the raster video adding means receives the raster signal of a level other than the black level. It is added and given to the liquid crystal display panel for a predetermined period.
Then, a relatively bright display is performed on the other part of the liquid crystal display panel for a predetermined period. As a result, the execution power consumption is made substantially uniform over the entire area of the liquid crystal display panel to prevent the image sticking of the liquid crystal display panel.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a liquid crystal display device according to the present invention. In FIG. 1, the same components as those in FIG. 4 are designated by the same reference numerals.

A signal based on NTSC ground broadcasting, satellite broadcasting, high-definition television broadcasting, or the like is induced in the antenna 5. The signal induced in the antenna 5 is given to the NTSC signal processing device 6 and the wide signal processing device 11. The NTSC signal processing device 6 decodes a video signal having an aspect ratio of 4: 3 such as NTSC broadcast and EDTV broadcast. The wide signal processing device 11 decodes signals having an aspect ratio of 16: 9, such as wide EDTV broadcasting and high-definition television broadcasting. It should be noted that the NTSC signal processing device 6 and the wide signal processing device 11 are provided with a predetermined video input, not from the antenna 5.
For example, a video signal composed of a luminance signal and a color difference signal, an RGB signal, or the like may be input.

The signal decoded by the wide signal processing device 11 is given to the terminal b of the switch S1, and the signal decoded by the NTSC signal processing device 6 is given to the side panel section addition device 7 via the switch S2. The side panel unit addition device 7 is supplied with a raster signal of a predetermined level from the side panel signal generator 8 and outputs the raster signal of a predetermined level before and after the horizontal scanning period of the input signal having an aspect ratio of 4: 3. By adding it as a signal, it is converted into a signal having an aspect ratio of 16: 9 and output to the terminal a of the switch S1.

In this embodiment, two kinds of signals are selectively input to the side panel signal generator 8, and the side panel signal generator 8 outputs 2 types of signals based on the levels of these input signals. It is designed to generate raster signals of various levels. That is, the power supply terminals 21 and 22
Variable resistors 23 and 24 are respectively connected between the variable resistor 23 and the reference potential point, and the voltage generated in the variable resistors 23 and 24 is selectively applied to the side panel signal generator 8 by the switch S3. .. The variable resistor 23 is a side panel signal generator 8
Generates a voltage for generating a black level raster signal, and the variable resistor 24 generates a voltage for generating a white level raster signal from the side panel signal generator 8. By adjusting the variable resistors 23 and 24, the black level or the white level of the side panel signal added to the video signal is adjusted. The switch S3 and the switches S1 and S2 are switching-controlled by a microprocessor 25 described later.

The switch S1 is controlled by the microprocessor 25 to select the terminals a and b, and outputs the signal from the side panel unit addition device 7 or the wide signal processing device 11 to the LCD drive device 12. The LCD drive device 12 converts the input signal into a predetermined level, and performs AC inversion in which the video signal is inverted at a predetermined period in order to prevent deterioration of the liquid crystal, and supplies it to the X driver 14 of the liquid crystal module 13.

The liquid crystal module 13 has an aspect ratio of 16:
Liquid crystal display panel 16 constituted by 9, this liquid crystal display panel 16
It is composed of an X driver 14 and a Y driver 15 for driving each pixel. The Y driver 15 supplies a scanning signal to pixels of each line of the liquid crystal display panel 16 via a scanning line (not shown), and the X driver 14 supplies a video signal from the LCD driving device 12 to each pixel. This allows the liquid crystal display panel 16
The transmittance of each pixel changes according to the video signal. A backlight device 27 is provided on the back surface of the liquid crystal display panel 16. The backlight device 27 is turned on by being supplied with a power supply voltage from the power supply terminal 28 via the switch S4, and emits light from the back side of the liquid crystal display panel 16. The light from the backlight device 27 is transmitted to the front side of the panel 16 according to the transmittance of each pixel of the liquid crystal display panel 16, and a brightly displayed image can be displayed.

When the liquid crystal module 13 is used as a light valve of a projection type liquid crystal display device, a light source device is used instead of the backlight device 27.

The main power supply voltage supplied to each of the above-mentioned devices is generated by the power supply device 29. The power supply 29 is a commercial AC power supply 30.
AC voltage is applied to the respective devices other than the microprocessor 25 through the switch S5 to generate a predetermined constant voltage. The microprocessor 25 switches and controls each of the switches S1 to S5 based on a user operation. The power switch S6 provides the microprocessor 25 with a control voltage for instructing to turn on / off the power supply based on a user operation. Microprocessor
25 is a switch S based on the control voltage from the switch S6.
5 is controlled to switch the supply / stop of the main power supply voltage, and at the same time, the supply of the power supply voltage to the backlight device 27 is controlled. Further, the switch S7 supplies a control voltage for instructing switching of the video source to the microprocessor 25 based on a user operation. The microprocessor 25 switches and controls the switch S1 based on the control voltage from the switch S7. When the switch S7 is turned on, the microprocessor 25 causes the switch S1 to select the terminal a, and when the switch S7 is turned off, the microprocessor 25 causes the switch S1 to select the terminal b.

Next, the operation of the embodiment thus constructed will be described with reference to Table 1. Table 1 below describes the states of the switches S1, S3 to S7 and the control of the microprocessor 25. The-mark in Table 1 indicates indefinite.

[0033]

[Table 1] First, in the initial state, the power switch S6 is off. The column of state 1 in Table 1 shows the state in this case. Since power switch S6 is off, microprocessor 25 causes switch S4,
S5 is off. Therefore, the power supply device 29 does not generate the main power supply voltage, and the backlight device 27 is in the off state. In this case, the switches S1 and S3
, S7 may be in any state.

Next, when the user turns on the power, the NTSC
Broadcast shall be received. The state in this case is shown as state 2 in Table 1. That is, the user turns on the power switch S6 and turns on the switch S7 for switching the reception signal. This allows the microprocessor
A switch 25 turns on the switches S4 and S5 to start the supply of the main power supply voltage and turns on the backlight device 27. Further, the microprocessor 25 causes the switch S1 to select the terminal a.

Then, the NTSC signal processing device 6 decodes the NTSC broadcast induced in the antenna 5 and supplies it to the side panel section addition device 7 via the switch S2. As shown in Table 1, the microprocessor 25 causes the switch S3 to select the variable resistor 23 that generates a voltage according to the black level. The voltage of the variable resistor 23 is supplied to the side panel signal generator 8, and the side panel signal generator 8 generates a black level raster signal and supplies it to the side panel unit addition device 7. The side panel addition device 7 adds a black level signal as a side panel signal before and after the horizontal scanning period of the NTSC video signal to convert it into a signal having an aspect ratio of 16: 9, which is sent to the LCD drive device 12 via the switch S1. Output.

The LCD drive device 12 adjusts the NTSC signal to which the side panel signal is added to a predetermined level and inverts it, and then outputs it to the X driver 14 of the liquid crystal module 13. The Y driver 15 of the liquid crystal module 13 supplies the scanning signal to the pixels of each line of the liquid crystal display panel 16, and the X driver 14
Supplies a video signal to each pixel. Each pixel is turned on by the scanning signal and has a transmittance based on the video signal. As a result, the received image is displayed in the center aspect ratio of 4: 3 of the liquid crystal display panel 16, and the portions corresponding to before and after the horizontal scanning period of the NTSC broadcast, that is, the left and right side panels of the liquid crystal display panel 16. A black frame image is displayed on the part. The image displayed on the liquid crystal display panel 16 can be viewed from the front side of the panel 16 by turning on the backlight device 27.

Next, as shown in the state 3 of Table 1, the user turns off the power switch S6 to terminate the viewing of the NTSC image. The microprocessor 25 turns off the switch S2 to stop the supply of the NTSC signal to the side panel unit addition device 7, and also switches S4.
To turn off the backlight device 27. However, in this embodiment, at this point, the microprocessor 25 keeps the switch S5 in the ON state and continues the supply of the main power supply voltage from the power supply device 29. Further, the microprocessor 25 controls the switch S3 to select the variable resistor 24 which generates a voltage according to the white level. The voltage from the variable resistor 24 is supplied to the side panel signal generation device 8, and the side panel signal generation device 8 outputs a white level raster signal to the side panel part addition device 7. The side panel unit addition device 7 adds a white level raster signal to the black level signal and outputs the raster signal at a timing corresponding to the side panel unit of the liquid crystal display panel 16.

The LCD drive circuit 12 adjusts the output level of the side panel addition device 7 and supplies it to the X driver 14. X
The driver 14 supplies a signal from the LCD drive circuit 12 to each pixel. Thus, the pixels in the central portion of the liquid crystal display panel 16 having an aspect ratio of 4: 3 have a low transmittance according to the black level, and the left and right side panel portions have a high transmittance according to the white level. In this case, since the backlight device 27 is turned off, the user cannot see the image on the display panel 16. This state is continued for several minutes, for example. Then, the central part of the liquid crystal display panel 16 and the side panel part have substantially the same execution power consumption. That is, the DC component accumulated in each pixel becomes substantially uniform over the entire screen, and it is possible to prevent the image sticking. Next, in state 4 of Table 1, the microprocessor 25 turns off the switch S5 to stop the supply of the main power supply voltage.

The state 5 in Table 1 shows the case where the user turns on the power and gives an instruction to receive the MUSE signal. In this case, the microprocessor 25 uses the switch S
Let 1 select terminal b. Then, the MUSE signal induced in the antenna 5 is decoded by the wide signal processing device 11 and supplied to the LCD driving device 12 via the switch S1. In this way, a high-definition television broadcast having an aspect ratio of 16: 9 is displayed on the liquid crystal display panel 16 of the liquid crystal module 13.

Next, when the user turns off the power switch S6 and shifts to the state 6 in Table 1, the microprocessor 25 turns off the switches S4 and S5 to turn off the backlight device 27 and to turn on the main power supply voltage. Stop the outbreak.

As described above, in the present embodiment, when displaying an image having an aspect ratio of 4: 3, a black frame image is displayed on the side panel portion to make the display easier to see. Further, when the user turns off the power, the backlight device 27 is turned off to end the display of the image, and a white level signal is given to the side panel portion for a predetermined period, so that the entire area of the liquid crystal display panel 16 is covered. The execution power consumption is substantially the same. Therefore, the liquid crystal display panel 16 does not burn.

The present invention is not limited to the above embodiment, and can be applied, for example, to displaying an image having an aspect ratio of 16: 9 on a liquid crystal display panel having an aspect ratio of 4: 3. You can FIG. 2 is an explanatory diagram showing a screen display in this case. As shown in FIG. 2, an image with an aspect ratio of 16: 9 is displayed in the vertical center portion 32 of a screen 31 with an aspect ratio of 4: 3, and a black level frame image is displayed in the upper and lower portions 33. Show it. In this case, a white level signal is supplied to the upper and lower parts 33 during a predetermined period after the power is turned off.

[0043]

As described above, according to the present invention, it is possible to display the side panel portion at a black level to make it easier to see the screen and to prevent the occurrence of burn-in.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a liquid crystal display panel according to the present invention.

FIG. 2 is an explanatory diagram for explaining a modified example of the present invention.

FIG. 3 is an explanatory diagram for explaining a display when a video having an aspect ratio of 4: 3 is displayed on a wide aspect display device having an aspect ratio of 16: 9.

FIG. 4 is a block diagram showing a conventional liquid crystal display device.

FIG. 5 is an explanatory diagram illustrating pixels of a liquid crystal display panel.

FIG. 6 is a waveform diagram for explaining the problems of the conventional example.

[Explanation of symbols]

6 ... NTSC signal processing device, 7 ... side panel addition device, 8 ... side panel signal generating device, 11 ... wide signal processing device, 13 ... liquid crystal module, 16 ... liquid crystal display panel, 2
3, 24 ... Variable resistor, 25 ... Microprocessor, 29 ... Power supply device, S1 to S7 ... Switch

Claims (1)

[Claims] 1. A liquid crystal display panel having a first aspect ratio in which pixels are arranged in a matrix, a first video signal having the first aspect ratio, and the first video signal.
A video signal processing device for performing a predetermined signal processing to display a second video signal having a second aspect ratio different from the above aspect ratio on the liquid crystal display panel, and a second video signal from the video signal processing device. Raster video adding means for converting the aspect ratio of the second video signal to the first aspect ratio and outputting by adding a raster signal of a predetermined level to the signal at a predetermined timing. When the second video signal is applied to the liquid crystal display panel for display, a black level signal is added as the raster signal to the raster video adding means, and the display of the second video signal is terminated. Stops the supply of the second video signal to the raster video adding means and causes the raster video adding means to output a raster signal other than a black level as the raster signal. By adding a signal of the bell liquid crystal display device being characterized in that and a control means for supplying to said liquid crystal display panel for a predetermined time period.