JPS6377276A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To display a character and a graphic brightly and easily by lowering forcibly at least one side of the luminance of a TV picture and a contrast while the character and the graphic are displayed at a liquid crystal panel. CONSTITUTION:A color bar displaying period pulse generating circuit 18 generates a displaying period pulse DP to continue the pulse period and the constant period after completing it by using an operating pulse TP generated from a station selecting voltage generating circuit 3, controls a pulse moulding circuit 17 and displays a color bar only for the pulse DP period. Further, the pulse DP is supplied to a contrast control circuit 7 and a luminance control circuit 8 and a color bar displaying period lowers forcibly the contrast and luminance of a TV image projected to a liquid crystal displaying panel 10. Thus, when the character and graphic are displayed, the character and graphic are brightly overlapped and displayed on a dark TV picture with the panel 10 and the easy displaying is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal display bag for displaying color television images using a liquid crystal display panel such as a liquid crystal color television receiver.

2. Description of the Related Art In recent years, liquid crystal color television receivers using a liquid crystal display panel have been put into practical use as portable color television receivers that are easy to carry.

In these LCD color television receivers, a large number of liquid crystal cells are arranged in a matrix on the liquid crystal display panel, and the light transmittance of each liquid crystal cell is controlled according to the television signal C.
1 to display the television image.

Also, red to display color TV images.

A blue and green filter is provided for each pixel, and a liquid crystal cell is formed in correspondence with each filter, and each liquid crystal cell is controlled according to a color signal corresponding to each color1. If you try to display channels such as i, TV channels using light emitting diodes or large knobs, the size will be too large, so if you try to display channel letters or color par figures of a specific color on the TV screen. It is designed so that the image on the TV screen is displayed brightly with heavy, :!?, l,.

Problems to be Solved by the Invention However, in display panels using liquid crystals, the liquid crystal itself does not emit light, but rather displays television images by controlling its transmittance or reflectance. In order to display images with as high brightness and contrast as possible, each liquid crystal cell is driven to its maximum operating limit. There was a problem in that the characters and figures could not be displayed in an easy-to-understand manner.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve these conventional problems and provide a device that can display characters, figures, etc. brightly and easily in an easy-to-understand manner in a device that displays color television images using a liquid crystal display panel. shall be.

Means for Solving the Problems In the liquid crystal display device of the present invention, the liquid crystal display panel ((
At least one of the brightness and contrast of the color television image projected on the liquid crystal display panel is forcibly reduced during the period when characters and graphics are displayed by applying a pulse signal for displaying characters and graphics. It is characterized by

According to this configuration, in order to reduce the brightness and contrast of a color television image during 100 seconds when characters or figures are displayed, when a pulse signal for displaying one character or figure is supplied, the characters or figures are displayed in a dark color. It can be displayed brightly and superimposed on a television image, and can be displayed in an easy-to-understand manner.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to all the drawings. This example was implemented in a liquid crystal color television receiver.

Figure 1 shows its overall configuration, in which 1 is an antenna, 2
is an electronic tuning type tuner which selects a television broadcast signal of a desired channel in accordance with the magnitude of a tuning voltage BT supplied from a tuning voltage generating circuit 3. The intermediate frequency signal output from the tuner 2 is amplified by a VIP circuit 4 and detected by a detection circuit 6 to obtain a composite video signal. Furthermore, the video circuit 6 separates the luminance signal and chroma signal, adjusts all the color difference signals, and further synthesizes the brightness signal and color difference signal to produce red (R) and green (G).
), ? Each primary color signal of r (B) is output. The contrast control circuit 7 controls the contrast of the displayed color television image by controlling the amplification factor of the composite video signal or the amplification factor of each primary color signal in the video circuit 6. On the other hand, the brightness control circuit 8 controls the brightness of the displayed color television image by controlling the DC level of each primary color signal. The panel and drive recess 9 receives these primary color signals, divides each color into the number of picture elements in the horizontal direction of the liquid crystal panel 10, samples them, and supplies them to Y' and the pixels of the liquid crystal display panel 10, respectively. The Y electrode is a vertical electrode among the matrix electrodes. The above circuit constitutes an image display circuit that supplies an image display signal for displaying a color television image on the liquid crystal display panel 10.

On the other hand, a synchronization separation circuit 11 separates horizontal and vertical synchronization signals from the composite video signal, and a controller 12 uses the synchronization signals to generate sampling pulses for primary color signal sampling to control the panel drive circuit 9. The controller 12 also generates line scan pulses and supplies the panel to a scan drive circuit 13. In the Bonnell scanning drive circuit 13, the upper line (horizontal scanning line) is sequentially moved every horizontal scanning period.
A line scanning pulse is applied to the X electrode (horizontal direction electrode) of the liquid crystal display panel 10 so as to change the display line from the lower line to the lower line.

The above parts have the same configuration as a normal liquid crystal color television receiver.

Next, a configuration for displaying image receiving channels using color bars will be described. First, the color/<- generation circuit 14 generates a color bar display pulse signal for displaying a color bar consisting of a vertical line whose position changes from left to right on the screen depending on the reception. create. A specific example of this color par generating circuit 14 is shown in FIG. 2, and waveforms of each part thereof are shown in FIG. 3, respectively. In this circuit 14, first, the horizontal pulse H which is also supplied to the same 19'' separation circuit 11 is
In synchronization with P, a sawtooth wave generation circuit 15 generates a horizontally synchronized sawtooth wave voltage ST. Next, the comparison circuit 16 compares this sawtooth wave voltage ST with the channel selection voltage BT for controlling the image receiving channel from the channel selection voltage generation circuit 3 and generates a comparison output pulse CP1. This comparison output pulse CP is differentiated, and only the differential output of the falling edge is taken out and shaped into a waveform to create a color pulse display pulse signal CB.Then, this display pulse signal C
By applying B to the R, G, and H primary color signal lines on the input side of the panel drive circuit 90, a color pattern consisting of vertical lines is displayed brightly on both sides of the liquid crystal display panel 1°. At this time, if only the R primary color signal line t is applied, the color par can be displayed in red, and if it is applied to the R and G primary color lines, it can be displayed in yellow.

If applied to all B primary color lines, white can be displayed.

The voltage can be applied depending on the color desired to be displayed.

When the magnitude of the channel selection voltage BT changes as shown by the arrow in accordance with the receiving channel, the position of the display signal CB changes as shown by the arrow, and the position of the displayed carano ζ- changes from side to side. The reception channel can be displayed from the display position iK.

On the other hand, in the color par display period pulse generation country -] - Raku 18, the operation pulse TP generated from the circuit 3 during the period when the channel selection voltage generation circuit 3 is operated for switching (adjustment) of the reception channel. Using a monostable multivibrator or an integrating circuit, a display period pulse DP that continues for the period of the operation pulse TP and a certain period (for example, about 3 seconds) after the end of the operation pulse TP is generated. Pulse shaping circuit 1 only during pulse DP period
7 is controlled so that the above-mentioned color par is displayed only during this period.

Furthermore, as a feature of this device, this display period pulse DP
It is also supplied to the total contrast control circuit 7 and the brightness control circuit 8 to forcibly reduce the contrast and brightness of the color television screen image projected on the liquid crystal display panel 10 during the 1υ period during which the color par is displayed. ing. However, if these frequencies are lowered too much, the television image becomes extremely difficult to view and it becomes difficult to operate the channel selection operation, so it is important to lower the intensity to a level that allows the user to select the receiving channel while viewing the television image.

In this way, by reducing the core trust and brightness of the color TV screen image during the color par display period,
During this period, the liquid crystal display panel 1° is not driven to the maximum level by the color TV signal, and is driven to a higher level by the color bar display signal CB, thereby changing the color for channel display. It is possible to display a bright and easy-to-understand display that stands out from the parlor television image.In other words, when using a liquid crystal display panel 1of, which is usually driven to its maximum limit as a display element and has no margin for brightness, etc. It is possible to obtain a practically effective effect of being able to display a bright and easy-to-understand image.In addition, the contrast and brightness are strongly reduced by the contrast control circuit T and the brightness control circuit 8. To do this, the levels of the contrast control voltage and brightness control voltage that are normally used for control in those circuits may be erroneously lowered using the display period pulse DP.

Furthermore, in the above embodiment, both the contrast and brightness of the color TV image are reduced during the color par display period, but only one of them may be reduced. .

In addition, although the above embodiment describes a case where a color par is displayed on a liquid crystal color television receiver screen, there are other methods as well.
In fact, it is possible to display channel characters and characters received from teletext broadcasts brightly ('7).
It goes without saying that the present invention can also be implemented in liquid crystal display devices other than television receivers.

Effects of the Invention As described above, according to the present invention, an apparatus for displaying characters and figures superimposed on a color television image using various channels, (2) During the display period; the LCD panel was used to reduce at least one of the contrast and brightness of the color television image, and the normal limit was 1. Even in the case of Vζ, it is possible to obtain the practical effect of being able to display characters and figures in a clear and easy-to-understand manner.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a block diagram of its main parts, and FIG. 3 is a waveform diagram of each part thereof. 2...Tuner, 3...Tuning voltage generation circuit,
6... Video circuit, 7... Contrast control circuit, 8... Brightness control circuit, 9... Panel, elemental circuit, 10... Liquid crystal display panel, 11...・・・・・・
- Synchronization separation circuit, 14... Color bar generation circuit, 18... Color bar display period pulse generation circuit.

Claims (1)

[Claims] a liquid crystal display panel; an image display circuit that supplies an image display signal for displaying a color television image on the liquid crystal display panel; a display pulse generation circuit that generates a pulse signal for bright display and supplies it to the image display circuit, and at least one of the brightness and contrast of the color television image during the period when the characters or figures are displayed. A liquid crystal display device comprising means for controlling the image display signal so as to reduce the image display signal.