JP2002229024A - Illuminator for color display liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light source having high optical efficiency and furthermore with optimal white balance, in an illuminator for a color display liquid crystal device. SOLUTION: In the illuminator for the color display liquid crystal device, the light source 12 consists of at least three pieces of light-emitting diodes, emitting light of three colors, red, green and blue, and mixing the light of the three colors to produce white light and the filter is a color filter 19 separating the white light produced by mixing the light of the three colors again into a light of the three colors, red, green and blue and transmitting it. The illuminator for the color display liquid crystal device is characterized, by having wavelengths of the light of the three colors, red, green and blue, of the light emitted by the light-emitting diode and peak wavelengths of the light of the three colors, red, green and blue, in spectral distribution transmission characteristics of the color filter which are respectively similar.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for illuminating an object to be illuminated such as a color display liquid crystal panel of a color display liquid crystal device, and more particularly to an end face facing a light source from a white light source. From the light guide plate, propagates inside while repeating total internal reflection on the upper and lower surfaces of the light guide plate, and a reflector formed on one of the upper and lower surfaces (usually the opposite surface of the illuminated body) The color display liquid crystal, which illuminates the illuminated object such as a color display liquid crystal panel with the light reflected by the, and reproduces the characters and images displayed on the color display liquid crystal panel accurately and with excellent white balance The present invention relates to a lighting device of a device.

[0002]

2. Description of the Related Art As an illuminating device for illuminating a liquid crystal display device, light from a light source is introduced into an inside of a light guide plate from an end face facing a light source, and propagated inside while repeating total reflection between upper and lower surfaces of the light guide plate. In addition, an object to be illuminated (a liquid crystal panel) is reflected by a reflector formed on one of the upper and lower surfaces (usually the surface opposite to the object to be illuminated, the lower surface in the backlight, and the upper surface in the front light). ) Is mainly used as a backlight (or front light) using a planar illumination device having a light guide plate for illuminating the light source. In this lighting device, a light emitting diode is often used as a light source.

In recent years, a color display liquid crystal device has been increasingly used as the liquid crystal display device. In the case of a color display liquid crystal device, it is necessary to illuminate with a higher brightness than a conventional monochrome liquid crystal display device in order to display in clear colors, and to adjust the white balance in order to display in a correct color. It must be illuminated with excellent light. As a light source of an illuminating device used in the color display liquid crystal device, a white light emitting diode is often used in the related art. Here, FIG. 5 schematically illustrates the structure of the white light emitting diode, and FIG. 6 is a graph illustrating a wavelength distribution of light projected from the white light emitting diode.

As shown in FIG. 5, a white light emitting diode 50 used in the prior art has a structure in which a YAG fluorescent layer 53 is formed on an upper surface of a blue light emitting diode 52 formed on a substrate 51. And the blue light emitting diode 5
A part of the blue light projected from 2 excites the YAG fluorescent layer 53 and causes the YAG fluorescent layer 53 to emit light yellow. The blue light emitted from the blue light emitting diode 52 is converted into a YAG fluorescent layer. Light yellow is emitted from the light 53 and becomes a white light by being mixed with light yellow light having a complementary color relationship. Accordingly, the distribution of wavelengths obtained by dispersing the light is shown in FIG.
As shown in (1), there are two peaks at a peak A of blue light emitted from the blue light emitting diode 52 and a peak B of pale yellow light emitted from the YAG fluorescent layer 53.

Therefore, the light from the white light-emitting diode 50 which looks white at first glance is not satisfactory in terms of white balance, and has a wavelength of 650n which is an orange or red wavelength.
The distribution of light having a wavelength of m or more is extremely small. Therefore, when a lighting device using the white light emitting diode 50 is used as a lighting device for a color display liquid crystal device, the display surface of the color display liquid crystal device displays strong blue and pale yellow and very weak red. Will be displayed in a bluish purple color. In order to eliminate this drawback, the blue light and the light yellow with high brightness are cut by a color filter.
This means that a considerable portion of the light emitted from the light source is cut off, which not only reduces the light efficiency and results in dark illumination as a whole, but also often does not satisfy the white balance.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, makes it possible to illuminate brightly with high light efficiency, and provides an illumination of a color liquid crystal display device excellent in white balance. An apparatus is provided.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and introduces a light source and light from the end face facing the light source into the light source. A light guide plate that illuminates the illuminated body with light that propagates inside while being reflected and is reflected by a reflector formed on one of the upper and lower surfaces, and transmits light that is reflected and projected from the illuminated body. A lighting device for a color display liquid crystal device having a filter, wherein the light source emits light of three colors, red, green, and blue, and at least three light emitting diodes that mix the lights of the three colors into white light. Wherein the filter again converts white light obtained by mixing the three colors of light into red,
A color filter that separates and transmits light of three colors of green and blue, wherein the light emitting diode emits red light,
The wavelengths of light of three colors, green and blue, and the wavelengths of red, green, and blue in the spectral distribution transmission characteristics of the color filter.
An object of the present invention is to provide a lighting device for a color display liquid crystal device, wherein peak wavelengths of light of colors are approximated to each other.

Here, the light emitting diodes which emit light of the three colors red, green and blue are selected according to the peak wavelength of the light of the three colors red, green and blue in the spectral distribution transmission characteristics of the color filter. It is desirable to be driven by the adjusted IF current. Alternatively, the light emitting diode emitting the three colors of red, green and blue light is a luminance rank selected according to the peak wavelength of the three colors of red, green and blue light in the spectral distribution transmission characteristics of the color filter. It is desirable that the light emitting diode has the following. Furthermore,
The light emitting diodes that emit light of the three colors of red, green and blue are selected from a group of light emitting diodes having a luminance rank selected according to the spectral distribution transmission characteristics of the color filter, and the light of the color filter is separated. It is desirable to use only light emitting diodes that match the range of luminance selected according to the peak wavelengths of red, green, and blue light in the distributed transmission characteristics.

Alternatively, the spectral distribution transmission characteristic of the color filter is selected in accordance with the luminance or light amount of the light emitting diode which emits light of three colors of red, green and blue, and is selected for each color of red, green and blue. It is desirable to have different transmittances for Or, the color filter is red in the spectral distribution transmission characteristics of the color filter,
For each color of green and blue, the three colors of red, green and blue
A color filter having a predetermined peak wavelength selected according to the wavelength of each color in a light emitting diode that emits light of the color, or the light emitting diode is red in the spectral distribution transmission characteristics of the color filter,
It is preferable that the light-emitting diode emits light of three colors of red, green, and blue that emits light of a predetermined wavelength selected according to the peak wavelength of each color of green and blue. Further, the light emitting diodes are selected from a group of light emitting diodes that emit light of a predetermined wavelength selected according to the peak wavelength of each color of red, green and blue in the spectral distribution transmission characteristics of the color filter, It is desirable to use only light emitting diodes that match the range of light wavelengths selected according to the peak wavelengths of red, green and blue light in the spectral distribution transmission characteristics of the color filter.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings showing embodiments. FIG. 1 is a cross-sectional view schematically showing one example of a reflective color display liquid crystal device using the illumination device of the color display liquid crystal device of the present invention, FIG. 2 is a perspective view showing details of the light source of the present invention, and FIG. FIG. 4 is a perspective view showing another embodiment of the light source according to the present invention, and FIG. 4 shows one of the spectral distribution transmission characteristics of a color filter suitable for use in the lighting device according to the present invention.
It is a graph showing an example.

The illumination device for a color display liquid crystal device of the present invention can be suitably used as a front light of a reflection type color display liquid crystal device or a backlight of a transmission type or semi-transmission type color display liquid crystal device. Since the influence of the balance appears more remarkably in the case of the front light of the reflection type color display liquid crystal device, in the following description, the front light of the reflection type color display liquid crystal device will be described as an example.

As shown in FIG. 1, a reflection type color display liquid crystal device 10 has a light source 12 and a light guide plate 13 constituting a front light disposed above a color display liquid crystal panel 11. The light guide plate 13 transmits light emitted from the light source 12 to the light guide plate 13 from an end face 13 a facing the light source 12.
And propagates inside the light guide plate 13 while being totally reflected by the upper surface 13b and the lower surface 13c.
Light reflected by a reflector (not shown) such as a prism or a dot formed on the color display liquid crystal panel 11, which is an object to be illuminated, is projected.

The light guide plate 13 and the color display liquid crystal panel 1
1 between the light guide plate 13 and the color display liquid crystal panel 1.
A polarizing plate 14 having a compensating function for polarizing and adjusting the light projected toward 1 is arranged. Further, a reflection film 16 is formed on the upper surface of the glass substrate 15 below the color display liquid crystal panel 11. The reflection film 16 reflects illumination light (including external light) projected from above, and may be provided as a reflection plate below the lower glass substrate 15.

As is well known, the color display liquid crystal panel 11 has a structure in which a liquid crystal 18 is sandwiched between an upper glass substrate 17 and a lower glass substrate 15. Therefore, light reflected or transmitted by the liquid crystal 18 and reflected by the reflection film 16 is reflected on the lower side of the upper glass substrate 17 by three colors of red, green and blue in accordance with the color components displayed on the liquid crystal 18. And a color filter 19 that transmits light separately. Then, on the upper surface of the lower glass substrate 15, a TFT surface 20 is formed together with the above-described reflective film 16.

As shown in FIG. 2, the light source 12 includes a red light emitting diode 21 for emitting red light, a green light emitting diode 22 for emitting green light, and a blue light emitting diode 23 for emitting blue light. A set of light emitting diodes of three colors is fixed to the substrate 24, and this is integrally molded with a transparent plastic to form the light source 12, or as shown in FIG. Are omitted, and the light-emitting diodes 21 of three colors are used.
22 and 23 are configured to be fixed only to the substrate 24.

The light emitted from the light emitting diodes of the three colors is mixed to form white light, which is projected on the light guide plate 13 as light projected from the white light source. Also,
The light source 12 can use two or more sets of these light emitting diodes according to a required light amount. Further, when there is a difference in the light amount (luminance) of each light emitting diode, the light amount can be balanced by using two or more light emitting diodes having a small light amount so as to obtain a required white balance.

The light source 12 is configured as described above, and the white light source composed of the light emitting diodes of these three colors may be directly disposed to face the end face 13a of the light guide plate 13.
Alternatively, the light source 12 has a well-known configuration in which a guide rod (not shown) is arranged between the light emitting diode and the light guide plate, and the light emitting diode is arranged on the end face of the guide rod, and the projection surface of the guide rod is You may comprise so that it may oppose the end surface 13a.

The light projected from the light source 12 having such a configuration is projected from the light guide plate 13 toward the color display liquid crystal panel 11, transmitted through the liquid crystal 18 and reflected by the reflection film 16, as described above. The light passes through the liquid crystal 18 again, is separated into three colors by the color filter 19 and passes through, and then passes through the light guide plate 13 and appears as characters or figures to the user's eyes. Therefore, the color balance (or white balance) of the color display liquid crystal device 10 is finally determined as the color balance after passing through the color filter 19.

For this reason, the balance of the light amount or luminance of the light emitting diode is finally determined by the color filter 19.
Must be considered as a balance of colors after transmission. When a color filter 19 having a spectral distribution transmission characteristic as shown in FIG. 4 is used, the light amount (luminance) of the red light emitting diode 21 corresponding to the red transmission characteristic R of the color filter 19 and the green light It is desirable that the light amount (luminance) of the green light emitting diode 22 corresponding to the transmission characteristic G and the light amount (luminance) of the blue light emitting diode 23 corresponding to the blue transmission characteristic B have an optimum white balance. As a method for adjusting the color balance after passing through the color filter 19 to an optimum white balance, there is the following method.

A first method is to control the brightness of the light emitting diode by an IF current that excites the light emitting diode. The amount of light (luminance) of the red light emitting diode 21, the green light emitting diode 22, and the blue light emitting diode 23 serving as light sources is adjusted so as to conform to the spectral distribution transmission characteristics R, G, and B of each color of red, green, and blue of the color filter 19. The control of the light amount (luminance) is performed by controlling the IF current of each light emitting diode. The IF current of each light emitting diode is selected according to the spectral distribution transmission characteristics of the color filter 19, By causing each light emitting diode to emit light with the selected IF current, an optimum white balance can be obtained with the highest efficiency of brightness.

The second method is to use light emitting diodes selected according to the luminance rank. It is known that even if a light emitting diode emits light of almost the same color, a difference occurs in luminance depending on a component of a light emitting element and a manufacturing method. Therefore, the red color using a device having a luminance rank that matches the peak wavelengths of the red, green, and blue light in the spectral distribution transmission characteristics R, G, and B of each color of red, green, and blue of the color filter 19 is used. , Green and blue light-emitting diodes, and adopting these light-emitting diodes as red light-emitting diodes 21, green light-emitting diodes 22, and blue light-emitting diodes 23, which are light sources of the respective colors, also provides an optimum white balance. It can be obtained with the highest efficiency brightness.

At this time, even in the case of the light emitting diode of the selected luminance rank, the luminance emitted from the actual element often varies. Therefore, as for the light emitting diodes to be actually used, all the manufactured light emitting diodes are inspected, and only the light emitting diodes having a luminance range suitable for the peak wavelength of light in the predetermined spectral distribution transmission characteristics are selected and used. It is desirable.

In the third method, on the contrary, the spectral distribution transmission characteristics R, G, and B of each color of red, green, and blue of the color filter 19 are adjusted according to the luminance (light amount) of the light emitting diode. is there. Since the spectral distribution transmission characteristics of the color filter 19 can be adjusted relatively easily,
By adjusting the spectral distribution transmission characteristics of each color of the color filter 19 so as to peak at a wavelength close to the peak wavelength of the light emitting diode, and selecting the transmission characteristic of the peak wavelength corresponding to the luminance of the light emitting diode, the optimum. White balance can be obtained. At this time, it goes without saying that the transmittance of each color of the color filter 19 is different for each of the red, green, and blue colors.

As a fourth method, focusing on the peak wavelength, the spectral distribution transmission characteristics R, G, and B of each color of red, green, and blue of the color filter 19 are changed to red, green, and blue emitted from the light emitting diode. This is a method of matching the peak wavelength of each color. In this way, a light source with the highest light efficiency can be obtained. Further, by adjusting the luminance of the light emitting diode or the transmittance of each color of the color filter 19, an appropriate white balance can be obtained.

In the fifth method, on the contrary, the red, green, and blue colors emitted from the light emitting diode are used as the red, green, and blue spectral distribution transmission characteristics R, G, and B of the color filter 19. Red, green and blue 3
Select red, green, and blue light emitting diodes using devices that have wavelengths that match the peak wavelength of the color light. In this way, a light source with the highest light efficiency can likewise be obtained. Further, by adjusting the luminance of the light emitting diode or the transmittance of each color of the color filter 19, an appropriate white balance can be obtained.

At this time, even if the light emitting diode emits light of the selected wavelength, the wavelength emitted from the actual element often varies. Therefore, the light emitting diode actually used is a light emitting diode which matches the range of the light wavelength selected according to the peak wavelength of the light in the predetermined spectral distribution transmission characteristics by inspecting all the manufactured light emitting diode groups. It is desirable to use only selected ones.

The illumination device of the color display liquid crystal device according to the present invention has been described above with reference to the front light of the reflection type color display liquid crystal device. However, the present invention is used as a backlight of a transmissive or transflective color display liquid crystal device. In use, as is well known, the same can be achieved by disposing an illuminating device below the color display liquid crystal panel and projecting light upward, so that a transmissive or semi-transmissive color display is used. Description of an example of using as a backlight of a liquid crystal device is omitted.

As described above, the illumination device of the color display liquid crystal device of the present invention is suitably used as a front light of a reflection type color display liquid crystal device or a backlight of a transmission type or semi-transmission type color display liquid crystal device. Although it is possible, it is not limited to the method described in the embodiment described above, it is also possible to use a combination of these methods, by using these methods in combination Needless to say, various changes and improvements can be made without departing from the gist of the present invention, such as achieving the highest light efficiency and the optimum white balance.

[0029]

As described above, the illuminating device for a color display liquid crystal device according to the present invention mixes three colors of light from light emitting diodes emitting three colors of red, green and blue as a light source. White light, and the spectral distribution transmission of the color filter so as to approximate the peak wavelengths of the three colors of light in the spectral distribution transmission characteristics of the color filter and the wavelengths of the three colors of red, green and blue light emitted by the light emitting diode. Since the characteristics or the wavelength of the light emitted from the light emitting diode is selected or selected so as to use only a predetermined range, a light source having high light efficiency and an optimal white balance can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of a reflection type color display liquid crystal device using the illumination device of the color display liquid crystal device of the present invention.

FIG. 2 is a perspective view showing details of a light source according to the present invention.

FIG. 3 is a perspective view showing another embodiment of the light source of the present invention.

FIG. 4 is a graph showing an example of spectral distribution transmission characteristics of a color filter suitable for use in the lighting device of the present invention.

FIG. 5 is a cross-sectional view schematically illustrating a structure of a white light emitting diode.

FIG. 6 is a graph showing a wavelength distribution of light projected from a white diode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Color display liquid crystal device 11 Color display liquid crystal panel 12 Light source 13 Light guide plate 13a End surface 13b Upper surface 13c Lower surface 14 Polarizer 15 Lower glass substrate 16 Reflective film 17 Upper glass substrate 18 Liquid crystal 19 Color filter 20 TFT surface 21 Red LED 22 Green LED 23 Blue LED 24 Board

Claims (8)

[Claims] 1. A light source and light from a light source introduced into the inside from an end face facing the light source. The light propagates inside while being reflected by upper and lower surfaces, and is reflected by a reflector formed on one of the upper and lower surfaces. A light guide plate for illuminating the object to be illuminated by the light source, and a filter for transmitting light projected from the object to be illuminated by the color display liquid crystal device. Emits colored light,
At least three light-emitting diodes that mix the three colors of light into white light, and the filter separates the mixed three-color light into red, green, and blue light again. A color filter for transmitting red, green and blue light emitted by the light emitting diode.
An illumination device for a color display liquid crystal device, wherein a wavelength of color light and a peak wavelength of light of three colors of red, green and blue in a spectral distribution transmission characteristic of the color filter are close to each other. 2. A light emitting diode which emits light of three colors of red, green and blue is selected according to peak wavelengths of light of three colors of red, green and blue in a spectral distribution transmission characteristic of the color filter. 2. The lighting device for a color display liquid crystal device according to claim 1, wherein the lighting device is driven by an IF current. 3. A light emitting diode which emits light of three colors of red, green and blue is selected according to peak wavelengths of light of three colors of red, green and blue in a spectral distribution transmission characteristic of the color filter. The lighting device for a color display liquid crystal device according to claim 1, wherein the lighting device is a light emitting diode having a different brightness rank. 4. A light emitting diode that emits light of three colors, red, green and blue, is selected from a group of light emitting diodes having a luminance rank selected according to a spectral distribution transmission characteristic of the color filter, 4. The light emitting diode according to claim 3, wherein only light emitting diodes that match a range of luminance selected according to peak wavelengths of light of three colors of red, green and blue in a spectral distribution transmission characteristic of the color filter are used. Illumination device for color display liquid crystal devices. 5. The spectral distribution transmission characteristic of the color filter is selected according to the luminance or light amount of a light emitting diode that emits light of three colors of red, green and blue, and is selected for each color of red, green and blue. 2. A lighting device for a color display liquid crystal device according to claim 1, wherein said lighting device has different transmittances. 6. The color filter according to claim 3, wherein each of the red, green, and blue colors in the spectral distribution transmission characteristics of the color filter has a wavelength of each color in a light emitting diode that emits light of the three colors red, green, and blue. 2. A lighting device for a color display liquid crystal device according to claim 1, wherein the lighting device is a color filter having a predetermined peak wavelength selected in accordance with the color filter. 7. The red, green, and blue light emitting diodes emit light of predetermined wavelengths selected according to peak wavelengths of red, green, and blue colors in the spectral distribution transmission characteristics of the color filter. 2. The lighting device for a color display liquid crystal device according to claim 1, wherein the lighting device is a light emitting diode of three colors of light. 8. The light-emitting diode is selected from a group of light-emitting diodes that emit light of a predetermined wavelength selected according to the peak wavelength of each of red, green, and blue in the spectral distribution transmission characteristics of the color filter. Then, only the light emitting diodes that match the wavelength range of the light selected according to the peak wavelength of the red, green and blue light in the spectral distribution transmission characteristics of the color filter are used. An illumination device for a color display liquid crystal device according to claim 7.