JP2006234974A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide illumination light rays with color tones most suitable for the respective LCDs with a sheet of light guide plate to a double faced LCD module constructed with a main LCD and a sub-LCD with mutually different color tone characteristics. <P>SOLUTION: First LEDs to illuminate the main LCD and the sub-LCD are mounted on an edge portion of the light guide body with fine protrusions and recessions formed thereon, and second LEDs to adjust the color tones are mounted in the vicinity of the sub-LCD. It is possible to provide illumination with a color tone most suitable for the sub-LCD side, by mixing colors of light rays emitted from the first and the second LEDs. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device used in a mobile phone or the like, and relates to a backlight structure that illuminates a double-sided liquid crystal display element with a single light guide. Specifically, the present invention relates to an LED arrangement method for effectively correcting the color tone of backlight illumination light.

Conventionally, two sets of backlights have been used to illuminate each LCD in a double-sided LCD module composed of a main LCD unit and a sub LCD unit used in a folding cellular phone or the like. In order to reduce the thickness of the double-sided LCD module, the main LCD and the sub LCD are illuminated with a single light guide plate. A so-called double-sided light emission type backlight is also known (for example, see Patent Document 1).
JP 2003-279963 A

  A double-sided light-emitting backlight composed of a single light guide plate for the purpose of reducing the thickness of a double-sided LCD module is shared between the main LCD and the sub LCD in order to share the LED as the light source between the main LCD and the sub LCD. The lighting color has a common color tone. Here, when the main LCD and the sub LCD have different color transmission characteristics, the following problems occur. That is, when an LED is selected so as to obtain an optimal backlight color tone for the main LCD, an optimal color tone cannot be obtained on the sub LCD side, and the display quality must be lowered.

  Therefore, the present invention provides a sub-LCD display area with a first LED for illuminating both the main LCD and the sub LCD and a second LED for illuminating only the sub-LCD display area at the end of the light guide. It is placed at the end of the near light guide plate. When displaying the sub-LCD, the first LED and the second LED are turned on at the same time, and the light from both the LEDs is mixed to obtain the illumination with the optimum color tone.

That is, the liquid crystal display device of the present invention includes a first liquid crystal display element, a second liquid crystal display element having a smaller display area than the first liquid crystal display element, the first liquid crystal display element, and the second liquid crystal display element. A light guide for irradiating illumination light to the first liquid crystal display element and the second liquid crystal display element, and for illuminating the first liquid crystal display element and the second liquid crystal display element; The second LED is positioned in the vicinity of the second liquid crystal display element of the light guide to illuminate the first light incident part of the light guide and the display part of the second liquid crystal display element. It is provided in the second light incident portion.
Here, the second LED emits a wavelength for correcting the color tone of the second liquid crystal surface element. Specifically, the first LED is white, and the emission color of the second LED is any one of blue, red, and green. Further, one of the light emitting surfaces of the light guide plate is formed with fine irregularities for emitting light from the first LED direction to the light emitting surface, and the other surface emits light from the second LED direction to the light emitting surface. Fine irregularities are formed. At this time, the fine unevenness formed on one surface is orthogonal to the light emission axis of the first LED, and the fine unevenness formed on the other surface is orthogonal to the light emission axis of the second LED. ing.

  When illuminating the sub LCD, the first LED and the second LED are turned on at the same time, and the light of both LEDs is mixed to obtain a target color tone. Thereby, the display quality of the sub LCD can be improved. Further, since the second LED only needs to illuminate the display area of the sub-LCD, the second LED can use an LED with a small light emission output, which can greatly increase power consumption. No.

  In the liquid crystal display device of the present invention, a main LCD made of a color display liquid crystal and a sub LCD having a display area smaller than that of the main LCD are arranged back to back with their display surfaces facing outward. A light guide plate that emits light from the LEDs on both sides is installed between the main LCD and the sub LCD. The first LED is arranged at an optimal position at the end of the light guide plate in order to illuminate both the main LCD and the sub LCD from the back surface. As the first LED, a white LED having an optimum color tone is selected in accordance with the color transmission characteristics of the main LCD. A brightness enhancement film or the like is appropriately installed between each LCD and the light guide plate according to the required brightness or the like.

  The second LED is used to illuminate the sub LCD. By arranging it at the end of the light guide plate close to the display area of the sub LCD, there is little loss of light from the light guide light incident part to the sub LCD illumination area, and the illumination area is also small. Less power is consumed for driving.

  The main LCD is illuminated by turning on the first LED. When the sub LCD is made of a color liquid crystal, the first LED is turned on and the second LED is turned on, and the colors emitted from both LEDs are mixed to provide a color tone that is optimal for the color transmission characteristics of the sub LCD. It becomes possible to provide.

  Furthermore, the light guide plate used in the present invention has minute irregularities on the surface of the light guide plate in order to efficiently emit both the light from the first LED and the light from the second LED. The shape, arrangement density, and arrangement direction of the minute irregularities are determined so that the light can be efficiently emitted with respect to the light beams of the first and second LEDs.

  In addition, since the first LED and the second LED have different light incident positions on the light guide plate, the illumination characteristics on the sub-LCD side have non-uniform color tone depending on the viewing direction. An optical sheet having a light diffusion characteristic for mixing light is disposed between the light guide plate and the sub LCD.

  Further, the color LCD has three color filters of red, green, and blue, so that the amount of light passing through each filter is adjusted by the shutter effect of the liquid crystal to realize color display. Therefore, the color tone can be corrected most effectively by selecting the light emission color of the second LED from the three primary colors of red, blue and green.

  Hereinafter, an embodiment in which the second LED is provided on the double-sided light emitting light guide will be described in detail with reference to the drawings.

  The configuration of the liquid crystal display device according to this embodiment is shown in FIG. The main LCD 4 and the sub LCD 5 are arranged so that their display surfaces face each other. A light guide plate 1 is disposed between the main LCD 4 and the sub LCD 5. The light guide plate 1 is made by molding a transparent resin such as acrylic or polycarbonate, and has minute irregularities on the surface. A white LED 2 is disposed at the end of the light guide plate. The color adjustment LED 3 is disposed at the end of the light guide near the sub LCD 5. In order to increase the front brightness on the LCD, two brightness enhancement films 7 and 8 are disposed between the light guide plate and the main LCD, and two brightness enhancement films 9 and 10 are disposed between the light guide plate and the sub LCD. Is done. Further, a diffusion plate 6 is installed between the light guide plate 1 and the sub LCD 5 to soften the directional characteristics when the light from the white LED 2 and the light from the color tone adjusting LED 3 are emitted from the surface of the light guide and to mix the colors. Has been. Light generated from the white LED 2 enters from the end of the light guide 1 and proceeds while repeating total reflection in the light guide. The light hitting the minute unevenness is bent in the optical path, is emitted from the surface of the light guide plate 1, and illuminates the main LCD 4 and the sub LCD 5.

  FIG. 2 is a layout diagram of LEDs and light guide plates according to this embodiment. Three white LEDs are installed on the upper side of the light guide plate, and the illumination range is indicated by the light emitting area 24. The light emitting area 24 is set larger than the display area of the main LCD 4. In addition, two LEDs 23 for color tone correction are provided on both sides of the light guide. The illumination range is indicated by a light emitting area 25 and is set larger than the display area of the sub LCD.

  FIG. 3 shows an example of a light guide optimal for the present invention. A minute groove 31 perpendicular to the main optical axis direction is formed on the side surface of the sub-LCD of the light guide plate in order to efficiently emit light from the white LED to the surface of the light guide plate. The interval between the fine grooves 31 is wider as it is closer to the light incident portion of the white LED, and is narrower as the distance is further away. Thereby, light is emitted uniformly from the light guide plate. In addition, a fine groove 32 perpendicular to the optical axis of the color correction LED is formed on the side of the main LCD of the light guide in order to efficiently emit light from the color correction LED to the surface of the light guide. ing. When displaying the main LCD, the first LED is turned on and illuminated. When illuminating the sub LCD, the first LED and the second LED are turned on simultaneously. By changing the amount and ratio of the current flowing through the first LED and the second LED, it is possible to obtain an optimal light emission amount and color tone. Further, when the color tone correction LED is turned on, color unevenness occurs on the main LCD side. However, since both LCDs are not used at the same time, the main LCD should be displayed in black on the entire surface. Or, in the case of a folding mobile phone, there is no problem because the main LCD side is closed and cannot be seen.

  The above-described embodiment is merely an example of the present invention, and various modifications such as the number and arrangement of light emitting portions and the shape of fine irregularities on the surface of the light guide plate are possible.

  Since a single light guide plate can provide illumination light for a double-sided LCD, it can contribute to the thinning of mobile phones and the like. Furthermore, since the color tone of the sub LCD can be easily adjusted, not only the display quality can be improved, but also by controlling the current flowing in the white LED and the color tone adjustment LED, the color tone suitable for the individual user's preference can be adjusted. A display screen can also be realized.

It is a schematic diagram which shows the structure of the liquid crystal display device of this invention. It is a schematic diagram explaining arrangement | positioning of a light-guide plate and LED. It is an external view explaining the detail of a light guide.

Explanation of symbols

1 Light guide plate 2 White LED
LED for 3 color adjustment
4 Main LCD
5 Sub LCD
6 Diffusion film 7 Brightness enhancement film 1
8 Brightness enhancement film 2
9 Brightness enhancement film 3
10 Brightness increase film 4
24 Main LCD illumination area 25 Sub LCD illumination area 31 First fine groove 32 Second fine groove

Claims (6)

A first liquid crystal display element; a second liquid crystal display element having a smaller display area than the first liquid crystal display element; and provided between the first liquid crystal display element and the second liquid crystal display element, In a liquid crystal display device comprising a first liquid crystal display element and a light guide for irradiating illumination light to the second liquid crystal display element,
A first LED provided in a first light incident portion of the light guide for illuminating the first liquid crystal display element and the second liquid crystal display element, and display of the second liquid crystal display element A liquid crystal display device comprising: a second LED provided in a second light incident portion located near the second liquid crystal display element of the light guide to illuminate a portion.   The liquid crystal display device according to claim 1, wherein the second LED has an emission wavelength that corrects a color tone of the second liquid crystal surface element.   The liquid crystal display device according to claim 1, wherein the first LED is white, and the emission color of the second LED is any one of blue, red, and green.   One of the light emitting surfaces of the light guide plate has fine irregularities for emitting light from the first LED direction to the light emitting surface, and the other surface emits light from the second LED direction. The liquid crystal display device according to claim 1, wherein the liquid crystal display device has fine irregularities that are emitted to a surface.   The fine unevenness formed on the one surface is orthogonal to the light emission axis of the first LED, and the fine unevenness formed on the other surface is with respect to the light emission axis of the second LED. The liquid crystal display device according to claim 4, wherein the liquid crystal display device is orthogonal to each other.   6. The liquid crystal display device according to claim 1, wherein an optical sheet having a light diffusion property is disposed between the light guide plate and the second liquid crystal surface element.

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