JP2005275204A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device whose color range can be expanded by realizing multicolor display with fewer kinds of light emitting elements than display primary colors. <P>SOLUTION: A sequential type liquid crystal display device which is equipped with a light source emitting light of a basic color and sequentially displays basic color images in synchronism with light emission of the light source is equipped with a control means of controlling the center wavelength of the light emitted by the light source according to a wavelength characteristic of the light source. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a field sequential type liquid crystal display device.

In a sequential type liquid crystal display device that divides one frame into a plurality of subframes and displays images of different colors in each subframe, the backlight that illuminates the display surface from the back also has a different color in each subframe. A light source is used. In such a liquid crystal display device, the color reproduction range using the three primary colors red, green, and blue is limited. Therefore, the color reproduction range can be increased by using a light emitting element having four or more primary colors for the backlight. A color sequential display device that can be enlarged is known (see, for example, Patent Document 1). For example, when four light emitting elements of red, green, blue green, and blue are used and these four color light emitting elements are sequentially turned on, as shown in FIG. 5, a predetermined frame is used. Sequential lighting is realized by applying current pulses for lighting the light emitting elements of the respective colors to the respective light emitting elements within four subframes corresponding to the respective light emitting elements.
JP 2002-244626 A

  However, although the color reproduction range can be expanded by using light emitting elements of four or more colors in the display device described in Patent Document 1, a light emitting element of a new primary color is added according to the color reproduction range that can be expanded. Since a space for attachment must be newly provided, there is a problem that it is difficult to increase the attachment density in the apparatus. In addition, since a primary color light emitting element necessary for expanding the color reproduction range is newly required, there is a problem that the cost of the display device is increased.

  The present invention has been made in view of such circumstances, and realizes multi-color display with the number of types of light emitting elements equal to or less than the number of display primary colors, and on the CIE chromaticity number (CIE1931 chromaticity diagram). An object of the present invention is to provide a liquid crystal display device capable of enlarging the color gamut of the displayed display device.

  The invention according to claim 1 is a sequential type liquid crystal display device that includes a light source that emits a basic color and reproduces an image by sequentially displaying a basic color image in synchronization with light emission of the light source, Control means for controlling the central wavelength of the light emitted from the light source according to the wavelength characteristics of the light source is provided.

  According to a second aspect of the present invention, the light source is a light source capable of emitting three basic colors of red, green and blue, and the control means is at least one of the three color light sources. It is characterized in that light emission of two or more colors is performed by controlling a current pulse applied to a color light source.

  According to a third aspect of the present invention, there is provided a light emission method in a sequential type liquid crystal display device that includes a light source that emits a basic color and reproduces an image by sequentially displaying a basic color image in synchronization with the light emission of the light source. And a control process for controlling a center wavelength of light emitted from the light source according to a wavelength characteristic of the light source.

  According to a fourth aspect of the present invention, there is provided a light emission control program for a sequential type liquid crystal display device that includes a light source that emits a basic color and reproduces an image by sequentially displaying a basic color image in synchronization with the light emission of the light source. According to the present invention, the computer is controlled to control the central wavelength of the light emitted from the light source according to the wavelength characteristics of the light source.

  According to the present invention, there is an effect that the number of colors of the backlight can be increased and the necessary number of LEDs can be reduced without increasing the types of colors of the light emitting elements. In addition, since the color gamut range that can be represented on the CIE chromaticity diagram is a quadrangle, a wide color gamut can be secured.

  Hereinafter, a liquid crystal display according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment. In this figure, reference numeral 1 denotes a three-color four-color conversion circuit that inputs a video signal composed of three colors of red, green, and blue and develops it into four-color signals of red, green, green blue, and blue. . Reference numeral 2 denotes a frame memory that temporarily holds display image data output from the three-color four-color conversion circuit 1 for each of red, green, green blue, and blue colors. Reference numeral 3 denotes a display unit composed of an OCB (Optically Compensated Birefringence) panel, which displays an image based on display image data held in the frame memory 2. Reference numeral 4 denotes an LED backlight (hereinafter referred to as a backlight) composed of LEDs of three colors of red, green, and blue. Reference numeral 5 denotes a backlight control circuit that controls the lighting timing of the backlight 4, the amplitude of the LED current, and the pulse width in synchronization with the rewriting timing of the frame memory 2.

Here, with reference to FIG. 3, the wavelength characteristic of the green LED used in the backlight 4 will be described. FIG. 3 is a chromaticity diagram showing color development when the forward current applied to the green LED is changed. As shown in FIG. 3, when the forward current is changed to “1 mA”, “5 mA”, “20 mA”, “50 mA”, “100 mA”, the center wavelength (main wavelength) of the light emitted from the LED is “ “536 nm”, “532 nm”, “525 nm”, “520 nm”, and “516 nm”. That is, as the current value increases, the center wavelength shifts to the shorter wavelength side, and the emission color changes. In addition, as shown in FIG. 4, the reproducible color range when using LEDs of four colors (red, green, green blue, blue) is the primary color (red, green, green blue, blue) of each LED. It is in a rectangle with the degree at the top. On the other hand, the reproducible color range when using LEDs of three colors (red, green, and blue) is within a triangle whose apex is the chromaticity of the primary colors (red, green, and blue) of each LED.
In the present invention, the characteristics shown in FIG. 3 are used to reproduce colors that can be expressed by four colors of LEDs by three colors of LEDs.

Next, the operation of the apparatus shown in FIG. 1 will be described with reference to FIG.
First, the three-color four-color conversion circuit 1 performs development from three colors to four colors for the three-color input video source, and stores display image data in the frame memory 2 for each color. Display image data stored in the frame memory is sequentially extracted in the order of red, green, green blue, and blue, and is sent to the OCB panel 3. The OCB panel 3 sequentially displays the sent display image data, thereby reproducing the image.

  On the other hand, the backlight control circuit 5 controls the current pulses applied to the LEDs constituting the backlight 4 so that the target LED is lit during the subframe corresponding to each color at the timing shown in FIG. . At this time, the backlight control circuit 5 makes the pulse height of the current pulse applied to the green LED 5 to 10 times that of the green display and the pulse width 1/5 to 1/10 during the green-blue video display period. The current pulse is controlled so that As a result, in the blue-green period, blue-green light is emitted from the green LED, and light is emitted as if four-color LEDs were used.

  In this way, by using a green LED to control the width and height of a current pulse to be applied, it is possible to emit light with the same luminance and to change the emission wavelength. It can be used as a light emission source of colors (green and blue-green).

  In addition, the pulse height of the current pulse applied to the green LED so that it has the same color reproduction range as when four-color (red, green, green-blue, and blue) LEDs are used is 5 to 10 times that of the green display (see FIG. 3), and the chromaticity of the emitted light coincides with the chromaticity of the emitted light of the blue-green LED (the chromaticity of the blue-green LED in FIG. 4). The liquid crystal display device configured using four colors can be used without changing the configuration, and the light source LED can be reduced from four colors to three colors, so that the configuration of the light source can be simplified.

  In addition, the combination of the order of display colors is not limited to the order shown in FIG. The order combination may be switched every frame or every several frames. The LED that emits two colors may be a color other than green, and any color LED may be used as long as the center wavelength of the emitted light can be changed by changing the applied current. Moreover, you may make it perform color expression of three or more colors by controlling the electric current pulse given with respect to one LED.

  In the above description, the example in which the emission color is changed by controlling the current supplied to the LED has been described. However, the light source to be used is not limited to the LED, and the emission color can be controlled by controlling the applied voltage. You may make it use the light source which can be changed. That is, it is possible to use a light source that can change the center wavelength of emitted light by applying an electrical change (current or voltage).

  Further, a program for realizing the functions of the processing units in FIG. 1 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed, thereby executing color reproduction processing. May be performed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

It is a block diagram which shows the structure of one Embodiment of this invention. It is a timing chart which shows the electric current pulse given with respect to LED of 3 colors. It is a figure which shows the wavelength characteristic of green LED. It is a chromaticity diagram showing a range of chromaticity that can be expressed by four-color LEDs. It is a timing chart which shows the electric current pulse given with respect to LED of 4 colors.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 3 color 4 color conversion circuit 2 ... Frame memory 3 ... Display part (OCB panel)
4 ... LED backlight 5 ... Backlight control circuit

Claims (4)

A sequential type liquid crystal display device that includes a light source that emits a basic color and reproduces an image by sequentially displaying a basic color image in synchronization with the light emission of the light source,
A liquid crystal display device comprising control means for controlling a center wavelength of light emitted from the light source in accordance with wavelength characteristics of the light source. The light source is a light source capable of emitting three basic colors of red, green and blue,
2. The liquid crystal display according to claim 1, wherein the control unit causes light emission of two or more colors by controlling a current pulse applied to at least one color light source among the three color light sources. apparatus. A light emitting method in a sequential type liquid crystal display device that includes a light source that emits a basic color and reproduces an image by sequentially displaying basic color images in synchronization with the light emission of the light source,
A light emitting method for a liquid crystal display device, comprising: a control process for controlling a center wavelength of light emitted from the light source according to a wavelength characteristic of the light source. A light emission control program for a sequential type liquid crystal display device that includes a light source that emits a basic color and reproduces an image by sequentially displaying a basic color image in synchronization with light emission of the light source,
An emission control program for a liquid crystal display device, which causes a computer to perform control processing for controlling a center wavelength of light emitted from the light source in accordance with wavelength characteristics of the light source.

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