JP2000275636A - Light source and illumination device as well as liquid crystal device using the illumination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light source, capable of easily obtaining white light of high luminance and red light of high saturation by LEDs as well as to obtain a novel illumination device and liquid crystal display using this light source. SOLUTION: A first LED (LEDb) which emits a monochromatic light of blue and a second LED (LEDa) which emits a monochromatic light of red are used. Green light is formed through wavelength conversion (a fluorescent filter 2) from the blue light. The white light is obtained by additive mixture of colors, which formulate the blue light and green light formed by the first LED and the red light from the second LED.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can be used for an illumination device or a liquid crystal device as a backlight unit used for a portable small television, a pager, a wall-mounted television, a liquid crystal display of a notebook computer or a portable game machine, and the like. Light source.

[0002]

2. Description of the Related Art Conventionally, a cold cathode fluorescent tube (CCFL) as a light source is provided on a light guide plate on a display section composed of a liquid crystal panel or the like used for a small television, a pager, a wall-mounted television, a notebook computer or a portable game machine. , An edge light type (or side light type) backlight unit is used.

[0003] However, cold cathode fluorescent tubes have poor lighting characteristics, require a dedicated drive circuit, are difficult to adjust the amount of light, consume large amounts of power, generate a large amount of heat, generate a lot of noise, are susceptible to vibration and shock, and the like. It had various difficulties.

Therefore, an attempt has been made to use an LED (light emitting diode) as a light source as a backlight unit without the above-mentioned difficulties.

However, in a backlight unit of a liquid crystal panel such as a small television set or a notebook personal computer, a single light of red or green emitted from an LED such as a mere illumination for checking the display of a wristwatch or a pilot lamp of various electronic devices. There is a need for white light that is useless and is close to the light emitted from cold cathode fluorescent tubes.

[0006] However, due to the recent progress of technological development, I
An LED that emits blue monochromatic light by using a compound semiconductor such as nGaN or GaN has been put into practical use.
There is no LED chip that emits white light by itself.

Therefore, in order to obtain white light using LEDs (red, green, and blue) that are easily available at present,
Generally, a method of additively mixing red light, green light, and blue light based on color theory is used.

As a conventional additive color mixture method, there is a method of expressing white by RGB color mixture using three types of LEDs that emit red, green, and blue monochromatic light (spectral characteristic of FIG. 8). Graph).

A method of using only LEDs that emit blue-based monochromatic light, generating green and red by a wavelength conversion filter, and expressing white by mixing colors of RGB (see FIG. 9).

[0010] There is.

[0011]

However, in the above-described additive color mixture system, since the luminance of each of the LEDs that emit red, green, and blue monochromatic lights is different, uniform white light is generated. In this method, it is necessary to strictly control the current of the three types of LEDs so that the light stimulus values of the three colors RGB become uniform, and it takes time to design an LED array as a light source. In addition, there is an inconvenience that the cost increases because all three types of LEDs need to be used in the same number (especially the blue LED has the highest unit price).

In addition, in the additive color mixing method according to the above, as shown in the graph of the spectral characteristic in FIG. 9, the energy of the red (R) component generated by the fluorescence conversion is:
Since the wavelength range is wider and the energy intensity is weaker than the blue (B) and green (G) components, there is a problem that the luminance and the saturation of the red light when the red filter is applied are lowered.

An object of the present invention is to provide a light source that emits white light having high white luminance by an LED and high red luminance and saturation when combined with a red filter, and a novel light source using this light source. And a liquid crystal device.

[0014]

In order to achieve the above object, the present invention provides a first LED which emits blue monochromatic light.
And a second LED that emits red monochromatic light,
Green light is generated by wavelength conversion from the blue light, and white light is produced by additive color mixing of the blue light and green light generated by the first LED and the red light from the second LED. It is something that you get.

Thus, high-luminance white light can be efficiently obtained by a simple method.

That is, in contrast to the case of controlling three types of LEDs (red, green, and blue) as in the above-described conventional example, two types of LEDs (first LED) are used in the present invention.
And the second LED), so that the time and cost for designing the light source can be reduced.

Further, in the above-described additive color mixture method, since the wavelength range of the energy of the red (R) component subjected to the fluorescence conversion is wide and the energy intensity is weak, the luminance and the saturation of the red light when a red filter is applied. However, in the present invention, since the red light constituting the white light is supplied by an independent LED (second LED), the brightness of the white light itself is reduced by the LED. It is possible to realize white light that is high and has high red luminance and saturation when combined with a red filter.

The red filter is used to cut light in a wavelength range of 560 nm to 650 nm or less, which is used as a color filter of an LCD or the like, over almost the entire range.

The intensity of the green light generated by wavelength conversion from the blue light is measured or calculated, and an area to which the generated light belongs is determined in an xy chromaticity diagram showing a hue area with respect to the Munsell hue. The light obtained by additive color mixing with the above-mentioned generated light is the xy chromaticity diagram (for example, the International Commission on Illumination (CIE)).
Standard xy showing hue area for established Munsell hue
The intensity of the red light from the second LED may be determined so as to belong to the standard white area of the chromaticity diagram. Thereby, white light close to standard white can be easily obtained.

The first LED comprises an InGaN-based or GaN-based LED that emits blue light,
The second LED can be constituted by an LED that emits red light, such as a GaP-based or GaAlAs mixed-crystal-based LED.

As a result, high-luminance blue light and high-luminance red light can be obtained, and high-luminance white light is obtained by additively mixing the blue light, green light, and the red light, which have undergone fluorescence conversion from blue light. It is possible to get light.

Further, the above-mentioned fluorescence conversion method is based on a first LED.
A fluorescent filter as a wavelength conversion means to which a predetermined fluorescent material that generates at least green fluorescence by blue light of a predetermined wavelength emitted from the LED is added.

Thus, blue light and green light can be easily generated by the fluorescence conversion method. Therefore, white light can be obtained by additively mixing the red light emitted from the first LED with the blue light and the green light generated as described above.

The above-mentioned fluorescent filter can be formed by adding a predetermined rare earth element to an oxide glass matrix, or can be formed of a fluorescent substance made of a predetermined translucent organic polymer.

Further, by arranging the light source on the side of the light guide plate, it is possible to produce an illuminating device capable of supplying high brightness white light.

Further, by using the above-mentioned lighting device as a lighting means for a liquid crystal panel, for example, in a liquid crystal device such as a liquid crystal display of a notebook type personal computer which is an applied product, a high brightness white light and a high saturation red light can be obtained. An easily viewable screen can be provided by the supply.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of the configuration of an LED array as a light source according to this embodiment, FIG. 2 is a graph showing the spectral characteristics of the LED array according to this embodiment, and FIG. FIG.
(B) is a perspective view showing another configuration example of the backlight unit, FIG. 5 is a plan view and a side view of the backlight unit in FIG. 3, FIG. 6 is an xy chromaticity diagram, and FIG. 7 is a liquid crystal according to the present embodiment. FIG. 2 is an exploded perspective view illustrating a configuration of a device (pager).

In FIG. 1, reference numeral 1 denotes an LE as a light source.
Fig. 2 shows a D array main body, in which LEDa as a second LED and LEDb as a first LED are alternately mounted in the longitudinal direction.

Here, each LEDa is, for example, a GaP type, G
aAlAs mixed crystal red light (wavelength is, for example, 650 n
m).

Each LEDb is composed of an LED that emits blue light (wavelength is, for example, 470 nm) such as InGaN or GaN.

On the front surface (irradiation area) of each LED b, there is provided a fluorescent filter 2 which receives blue light and emits blue light and green light fluorescence.

The fluorescent filter 2 can be formed, for example, by adding a predetermined rare earth element to an oxide glass base, or by using a fluorescent substance made of a translucent organic polymer.

According to the LED array 1 configured as described above, the blue light emitted from each LEDb is wavelength-converted by each fluorescent filter 2 to generate blue and green fluorescent light.

The spectrum has, for example, a distribution having peaks at points B and G in FIG.

One LEDa emits red monochromatic light, and has a distribution having a peak at point R in FIG.

Then, the blue and green fluorescent lights generated by the respective fluorescent filters 2 and the red light from the LEDa are additively mixed in the irradiation area, and are mixed as shown in FIG.
mision Internationale de l'Eclairage) standard xy chromaticity diagram showing the hue area for the Munsell hue (where x is the wavelength of red light (700 nm), and y is the wavelength of green light (546 nm)). WHITE) is generated.

The white light obtained in this manner can have a sufficient luminous intensity because the red component is directly supplied by the LEDa as compared with the conventional additive color mixing system shown in FIG. High brightness white light can be obtained.

Further, in the LED array 1 according to the present embodiment, the color components obtained by wavelength conversion of the blue light from the LED b are divided into two systems of blue and green, and the inefficient red component is used as in the conventional example shown in FIG. Since fluorescence conversion of long-wavelength light is not performed, energy loss of blue light can be suppressed, and as a result, white light with high luminance can be obtained.

In the LED array 1, white light is finally obtained by combining the blue component (B), the green component (G), and the red component (R). Since the blue light and the green light are simultaneously obtained by the fluorescence conversion using, the two colors of the mixed light of the blue light and the green light and the red light are mixed.

Therefore, as shown in FIG. 8, three types of LEDs emitting monochromatic light of red, green and blue colors are used.
As compared with a case where white light is obtained by precisely controlling the degree of mixing of three colors using the method described above, the method of adjusting two colors is easier to adjust, and the manufacturing cost of the LED array 1 is reduced. can do.

Furthermore, when applied to a liquid crystal panel having a color filter, the spectral characteristics of the color filter of the liquid crystal panel are as shown in FIG.
Most of the red light component of the backlight unit is transmitted, and a highly saturated red color can be obtained.

Next, an embodiment of a backlight unit using the LED array 1 will be described with reference to FIGS.

3 and 5, reference numeral 3 denotes PMMA.
It is a light guide plate formed of a transparent resin such as (polymethyl methacrylate) resin. At one end of the light guide plate 3 is formed a mounting hole 4 into which the above-mentioned LED array 1 is engaged.

On the back surface of the light guide plate 3, a plurality of light diffusing portions 6 each having a large or small concave shape are formed. Further, a reflection plate 5 is arranged below the light guide plate 3.

Although not shown, the LED array 1
Is connected to a control circuit for controlling the amount of current and the like.

As shown in FIG. 4A, an LEDa for emitting red light and a first LED as a second LED.
A plurality of (two in the figure) LED units U each having a built-in LEDb that emits blue light and green light in one resin housing 202 are mounted on the mounting substrate 20.
The backlight unit may be arranged side by side on the light guide plate 200 so as to face the side surface 200a of the light guide plate 200.

Further, as shown in FIG. 4B, both ends of a light pipe 300 molded of a light-transmitting resin, forming a plurality of diffusion patterns 301 on side surfaces, and covering the periphery with a reflection sheet (not shown). LEDa that emits red light as the second LED and LEDb that emits blue light and green light as the first LED are arranged on the light pipe 300.
The light from the LEDa and the light from the LEDb may be mixed and the light may enter from the side surface of the light guide plate 302.

The above is the outline of one embodiment of the backlight unit as the lighting device according to the present invention. Next, the operation and action will be described.

In the present embodiment, when the LED array 1 is energized through the control circuit, the LEDs a and the LEDs b start emitting light.

The blue light emitted from the LED b is converted into blue light and green light by the fluorescent filter 2 and enters the light guide plate 3.

The red light emitted from the LED a directly enters the light guide plate 3.

The mixed color light of the blue light and the green light and the red light are radiated from each LED and are simultaneously added and mixed to become white light. This white light can have a sufficient luminous intensity because the red component is directly supplied by the LEDa, as compared with the related art, and can be white light with high luminance.

The white light generated as described above propagates in the light guide plate 3 and is emitted upward from the light guide plate 3 by reflection by the reflection plate 5 and diffusion by the light diffusion unit 6.

Therefore, according to the backlight unit according to the present embodiment, a high-luminance white light backlight can be obtained. By incorporating this backlight unit into a liquid crystal panel or the like, it is possible to obtain a brighter and higher red chroma. A good image can be provided.

Here, the embodiment shown in FIG. 7 is a pager as an example of a liquid crystal device using a backlight unit as the lighting device.

In FIG. 7, a pager 100 includes a metal frame 101 and a liquid crystal panel 10 as a liquid crystal display device.
2. Backlight unit 1 including light guide plate 3 incorporating LED array 1 as a light source according to the above embodiment
03, a first shield plate 104, a circuit board 105 on which a drive circuit and a control circuit are formed, and a second shield plate 10
6 are built in such a form that they are sequentially superimposed.

The liquid crystal panel 102 and the circuit board 105
Of the film cables 107 and 108
It is to be done by.

Although not shown, the pager 100
Is provided with a battery as a power supply, an on / off switch, and the like, and is configured so that the LED array 1 of the backlight unit 103 is energized when the pager 100 is started.

When the pager as the liquid crystal device thus configured is turned on by operating a switch, the function as the pager is activated and at the same time, the LED array 1 of the backlight unit 103 is energized. Each LEDa and each LEDb starts emitting light.

The blue light emitted from the LEDb is converted into blue light and green light by the fluorescent filter 2 and enters the light guide plate 3, and the red light emitted from the LEDa directly enters the light guide plate 3. Incident on.

The mixed color light and the red light of the blue light and the green light are radiated from each LED and are simultaneously added and mixed to become white light of high luminance.

The high-brightness white light propagates in the light guide plate 3 and is reflected upward by the reflection plate 5 or diffused by the light diffusion unit 6 to be radiated upward of the light guide plate 3 to be illuminated with the liquid crystal. Light is incident as uniform irradiation light from the back side of the panel 102.

Therefore, a brighter and easier-to-view screen can be provided by the backlight of white light whose luminance is improved as compared with the related art.

In the present embodiment, a pager is exemplified as an example of using a backlight unit as a lighting device incorporating the LED array 1. However, the present invention is not limited to this, and a portable small television, a wall-mounted television, It can be used for all liquid crystal devices incorporating a backlight unit, such as a liquid crystal display of a notebook computer or a portable game machine. In each case, the brightness of the screen is improved and the saturation of red which constitutes the screen is improved. Can be obtained.

[0066]

As described above, according to the present invention,
A first LED that generates blue and green light by a fluorescence conversion method, and a second LED that emits red monochromatic light, and the blue and green light generated by the first LED; Since the white light is obtained by additive color mixing that mixes the red light from the second LED, a high luminance white light and a high saturation red light can be obtained by a simple method using a display device using a red filter such as an LCD. There is an effect that it can be obtained efficiently.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration example of an LED array according to an embodiment.

FIG. 2 is a graph showing the spectral characteristics of the LED array according to the embodiment.

FIG. 3 is an exploded perspective view showing a configuration example of a backlight unit incorporating the LED array according to the embodiment.

FIG. 4 is a perspective view illustrating another configuration example of the backlight unit according to the embodiment.

FIG. 5 is a plan view and a side view of the backlight unit.

[Figure 6] International Commission on Illumination (CIE: Commision International)
xy chromaticity diagram showing the hue area with respect to the Munsell hue established by ale de l'Eclairage (where x is the wavelength of red light (700 nm) and y is the wavelength of green light (546 nm)).

FIG. 7 is an exploded perspective view illustrating a configuration of a liquid crystal device (pager) according to the embodiment.

FIG. 8 is a graph showing the spectral characteristics of a conventional LED array.

FIG. 9 is a graph showing the spectral characteristics of a conventional LED array.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 LED array (light source) LEDa 2nd LED (red LED) LEDb 1st LED (blue LED) 2 Fluorescent filter 3 Light guide plate 4 LED array mounting hole 5 Reflector 6 Light diffuser 100 Pager (liquid crystal device) REFERENCE SIGNS LIST 101 metal frame 102 liquid crystal panel 103 backlight unit (illumination device) 104 first shield plate 105 circuit board 106 second shield plate 107, 108 film-like cable 200 light guide plate 201 mounting substrate 202 housing U LED unit 300 light pipe 301 Diffusion pattern 302 Light guide plate

 ──────────────────────────────────────────────────続 き Continued from the front page F-term (reference) 2H091 FA16Z FA23Z FA31Z FA45Z FB09 LA11 LA13 LA16 5C094 AA08 AA10 AA22 BA23 BA43 EB02 ED01 ED02 ED11 ED13 ED20 FB01 FB02 FB03 5F041 AA42 AA37 CB23

Claims (8)

[Claims] 1. A first LED that emits blue monochromatic light and a second LED that emits red monochromatic light, wherein green light is generated by converting the wavelength of the blue light. A light source, wherein white light is obtained by additive color mixing of blue light and green light generated by a first LED and red light from the second LED. 2. The apparatus according to claim 1, wherein the intensity of the green light generated by wavelength conversion from the blue light is measured or calculated, and a region to which the generated light belongs is determined in an xy chromaticity diagram showing a hue area with respect to the Munsell hue. The intensity of the red light from the second LED is determined so that the light obtained by adding the generated light to the xy chromaticity diagram belongs to the standard white region of the xy chromaticity diagram. light source. 3. The first LED comprises an LED emitting blue light such as InGaN or GaN, and the second LED emits red light such as GaP or GaAlAs mixed crystal. The light source according to claim 1, wherein the light source is configured by an LED. 4. The wavelength conversion means according to claim 1, wherein a predetermined fluorescent material that generates at least green fluorescence by blue light of a predetermined wavelength emitted from said LED is added to an irradiation area of said first LED. The light source according to any one of claims 1 to 3, wherein the fluorescent filter is disposed. 5. The light source according to claim 4, wherein said fluorescent filter is formed by adding a predetermined rare earth element to an oxide glass base. 6. The light source according to claim 5, wherein said fluorescent filter is formed of a fluorescent substance made of a predetermined organic polymer having translucency. 7. A lighting device, wherein the light source according to claim 1 is arranged on a side of a light guide plate. 8. A liquid crystal device comprising: the lighting device according to claim 7; and a liquid crystal panel disposed above the lighting device.