JP3937644B2 - Light source, lighting device, and liquid crystal device using the lighting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light source that can be used in a lighting device or a liquid crystal device as a backlight unit used in a liquid crystal display of a portable small-sized television, a pager, a wall-mounted television, a notebook computer, or a portable game machine.
[0002]
[Prior art]
Conventionally, a cold cathode fluorescent tube (CCFL) as a light source has been placed on the side of the light guide plate in the display unit consisting of a liquid crystal panel used in small TVs, pagers, wall-mounted TVs, notebook computers and portable game machines. An edge light type (or side light type) backlight unit is used.
[0003]
However, the cold cathode fluorescent tube has various problems such as poor lighting performance, requiring a dedicated drive circuit, difficult adjustment of light quantity, large power consumption, a lot of heat generation, a lot of noise, and weakness against vibration and shock. Had.
[0004]
Therefore, an attempt has been made to use an LED (light emitting diode) as a light source as a backlight unit without the above-described drawbacks.
[0005]
However, in backlight units of liquid crystal panels such as small TVs and notebook computers, simple lighting for checking the display of wristwatches and red and green monochromatic light emitted by LEDs like pilot lamps of various electronic devices are not useful. There is a demand for white light that is close to the emission of a cold cathode fluorescent tube.
[0006]
However, LEDs that emit blue monochromatic light using InGaN-based or GaN-based compound semiconductors as a material have been put to practical use due to recent technological development, but there are still LED chips that emit white light. do not do.
[0007]
Therefore, in order to obtain white light using LEDs (red, green, and blue) that are readily available, a method of additive color mixing of red, green, and blue is generally used based on color theory. Is.
[0008]
As a conventional additive color mixing method,
(1) A method of expressing white by RGB color mixing using three types of LEDs emitting red, green and blue monochromatic light (see the spectral characteristic graph in FIG. 8).
[0009]
(2) A system in which only LEDs emitting blue monochromatic light are used, green and red are generated by wavelength conversion filters, and white is expressed by RGB color mixture (see FIG. 9).
[0010]
There is.
[0011]
[Problems to be solved by the invention]
However, in the additive color mixing method according to the above (1), the brightness of each LED emitting single-color light of red, green, and blue colors is different. Therefore, in order to generate uniform white light, three colors of RGB are used. It is necessary to strictly control the currents of the three types of LEDs so that the photostimulus values are uniform, and it takes time to design an LED array as a light source. Moreover, since it is necessary to use the same number of all three types of LEDs, the cost is increased (particularly blue LEDs have the highest unit price).
[0012]
In addition, in the additive color mixing method according to the above (2), the energy of the red (R) component generated by fluorescence conversion is blue (B), green (G ), The wavelength range is wider and the energy intensity is weaker. Therefore, when the red filter is applied, the brightness and saturation of red light are lowered.
[0013]
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 illumination device using the light source And providing a liquid crystal device.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the present invention uses a first LED that emits blue monochromatic light and a second LED that emits red monochromatic light, and the green light has a wavelength from the blue light. The white light is obtained by additive color mixing of blue light, green light generated by the first LED, and red light from the second LED.
[0015]
Thereby, high-intensity white light can be efficiently obtained by a simple method.
[0016]
That is, compared with the case of controlling three types (red, green, and blue) of LEDs as in the conventional example of (1) above, the present invention has two types of LEDs (first LED and second LED). Therefore, it is possible to reduce the time and cost for designing the light source.
[0017]
In addition, in the additive color mixing method according to the above (2), since the wavelength range of the energy of the fluorescently converted red (R) component is wide and the energy intensity is weak, the luminance and saturation of red light when a red filter is applied. However, in the present invention, the red light constituting the white light is supplied by an independent LED (second LED). It is possible to realize white light that is high and has high red luminance and saturation when combined with a red filter.
[0018]
A red filter here cuts light in a wavelength range of 560 nm to 650 nm or less used as a color filter for an LCD or the like over almost the entire area.
[0019]
In addition, the intensity of the green light generated by wavelength conversion from the blue light is measured or calculated, and in the xy chromaticity diagram showing the hue area with respect to the Munsell hue, a region to which the generated light belongs is obtained, and the generation of the region is performed. Light that is additively mixed with light is the above-mentioned xy chromaticity diagram (for example, the standard white of the standard xy chromaticity diagram showing the hue area for Munsell hue established by the CIE (Commission Internationale de l'Eclairage)) The intensity of red light from the second LED may be determined so as to belong to the region, so that white light close to standard white can be easily obtained.
[0020]
The first LED is composed of an LED emitting blue light such as InGaN or GaN, and the second LED is composed of an LED emitting red light such as GaP or GaAlAs mixed crystal. can do.
[0021]
As a result, high luminance blue light and high luminance red light can be obtained, and high luminance white light can be obtained by additively mixing the blue light, green light, and red light, which are fluorescently converted from blue light. It is possible.
[0022]
Further, the fluorescence conversion method includes a fluorescent filter as a wavelength conversion unit in which a predetermined fluorescent material that generates at least green fluorescence by blue light of a predetermined wavelength emitted from the LED is added to the irradiation region of the first LED. Can be arranged.
[0023]
Thereby, 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, the blue light generated as described above, and the green light.
[0024]
The fluorescent filter can be formed by adding a predetermined rare earth element to an oxide glass matrix, or can be formed by a phosphor made of a predetermined translucent organic polymer.
[0025]
Moreover, the illuminating device which can supply white light with high brightness | luminance can be created by arrange | positioning the said light source to the side of a light-guide plate.
[0026]
Furthermore, by using the lighting device as a lighting means of a liquid crystal panel, for example, in a liquid crystal device such as a liquid crystal display of a notebook personal computer which is an applied product, it is easy to see by supplying high-intensity white light and high chroma red. A screen can be provided.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.
[0028]
Here, FIG. 1 is a schematic diagram showing a configuration example of an LED array as a light source according to the present embodiment, FIG. 2 is a graph showing spectral characteristics of the LED array according to the present embodiment, and FIG. 3 incorporates the LED array. FIG. 4A and FIG. 4B are perspective views showing other configuration examples of the backlight unit, and FIG. 5 is a plan view and a side view of the backlight unit of FIG. 6 is an xy chromaticity diagram, and FIG. 7 is an exploded perspective view showing a configuration of a liquid crystal device (pager) according to the present embodiment.
[0029]
In FIG. 1, the code | symbol 1 shows the LED array main body as a light source, and LEDa as 2nd LED and LEDb as 1st LED are attached to the longitudinal direction alternately.
[0030]
Here, each LEDa is configured by an LED that emits red light (wavelength is, for example, 650 nm) such as GaP-based, GaAlAs mixed crystal, and the like.
[0031]
Each LEDb is formed of an LED that emits blue light (wavelength is 470 nm, for example) such as InGaN or GaN.
[0032]
A fluorescent filter 2 that receives blue light and emits blue light and green light is provided on the front surface (irradiation area) of each LEDb.
[0033]
The fluorescent filter 2 can be formed, for example, by adding a predetermined rare earth element to an oxide glass matrix, or by using a phosphor made of a light-transmitting organic polymer.
[0034]
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 fluorescence.
[0035]
The spectrum has a distribution with peaks at points B and G in FIG. 2, for example.
[0036]
One LEDa emits red monochromatic light, and has a distribution having a peak at point R in FIG.
[0037]
Then, the blue and green fluorescence generated by each fluorescent filter 2 and the red light from LEDa are additively mixed in the irradiation area to establish the CIE (Commission Internationale de l'Eclairage) in FIG. In a standard xy chromaticity diagram showing a hue area with respect to the Munsell hue (where x is a wavelength of red light (700 nm) and y is a wavelength of green light (546 nm)), white light belonging to the standard white (WHITE) region is Generated.
[0038]
Compared with the case of the conventional additive color mixing method shown in FIG. 8, the white light obtained in this way can be sufficiently luminous because the red component is directly supplied by the LEDa, and has a high luminance. It can be white light.
[0039]
Further, in the LED array 1 according to the present embodiment, the color components obtained by the wavelength conversion of the blue light from the LEDs b are two systems of blue and green, and the length of the red system that is inefficient as in the conventional example shown in FIG. Since fluorescence conversion of 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.
[0040]
In the LED array 1 as well, the blue component (B), the green component (G), and the red component (R) are finally combined to obtain white light. However, the fluorescent filter 2 is used in the configuration. Since blue light and green light are simultaneously obtained by fluorescence conversion, the mixed light of blue light and green light and red light are mixed.
[0041]
Therefore, as shown in FIG. 8, compared to the case where white light is obtained by precisely controlling the mixing of the three colors using three types of LEDs emitting red, green and blue monochromatic lights. In the case of mixing two colors, the adjustment method is easier, and the manufacturing cost of the LED array 1 can be reduced.
[0042]
Furthermore, when applied to a liquid crystal panel provided with a color filter, the spectral characteristics of the color filter of the liquid crystal panel are as shown in FIG. It is possible to obtain a red color that is transmitted and has high saturation.
[0043]
Next, an embodiment of a backlight unit using the LED array 1 will be described with reference to FIGS.
[0044]
3 and 5, reference numeral 3 denotes a light guide plate formed of a transparent resin such as PMMA (polymethyl methacrylate) resin. An attachment hole 4 is formed at one end of the light guide plate 3 to engage the LED array 1 described above.
[0045]
In addition, a plurality of light diffusing portions 6 made up of large and small concave depressions are formed on the back surface of the light guide plate 3. Further, a reflector 5 is disposed below the light guide plate 3.
[0046]
Although not shown, the LED array 1 is connected to a control circuit that controls the amount of current.
[0047]
[Reference Example 1]
Further, as shown in FIG. 4A, an LEDa that emits red light as the second LED and an LEDb that emits blue light and green light as the first LED are arranged in one resin housing 202. The backlight unit may be configured by arranging a plurality of (two in the drawing) LED units U in parallel on the mounting substrate 201 and facing the side surface 200a of the light guide plate 200. .
[0048]
[Reference Example 2]
Further, as shown in FIG. 4 (b), the first and second ends of the light pipe 300 are molded with a translucent resin, a plurality of diffusion patterns 301 are formed on the side surfaces, and the periphery is covered with a reflection sheet (not shown). The LEDa that emits red light as the second LED and the LEDb that emits blue light and green light as the first LED are arranged, and the light of the LEDa and LEDb is mixed in the light pipe 300, and the side surface of the light guide plate 302 It is good also as a structure which injects from.
[0049]
The above is the outline of one embodiment of the backlight unit as the illumination device according to the present invention, and the operation and action will be described next.
[0050]
In the present embodiment, when the LED array 1 is energized via the control circuit, the LEDs a and the LEDs b start to emit light.
[0051]
The blue light emitted from the LEDb is wavelength-converted into blue light and green light by the fluorescent filter 2 and enters the light guide plate 3.
[0052]
Further, the red light emitted from the LEDa directly enters the light guide plate 3.
[0053]
These blue light and green light mixed color light and red light are emitted from each LED and additively mixed to become white light. The white light is supplied with a red component directly by the LEDa as compared with the conventional light, so that it can have a sufficient luminous intensity, and can be white light with high luminance.
[0054]
And the white light produced | generated as mentioned above propagates the inside of the light-guide plate 3, and is radiated | emitted above the light-guide plate 3 by the reflection by the reflecting plate 5, or the spreading | diffusion by the light-diffusion part 6. FIG.
[0055]
Therefore, according to the backlight unit according to the present embodiment, it is possible to obtain a high-luminance white light backlight. By incorporating this backlight unit into a liquid crystal panel or the like, a brighter and better image with high red saturation is obtained. Can be provided.
[0056]
Here, the embodiment shown in FIG. 7 is a pager as an example of a liquid crystal device using a backlight unit as the illumination device.
[0057]
In FIG. 7, a pager 100 includes a backlight unit 103 including a liquid crystal panel 102 serving as a liquid crystal display device, a light guide plate 3 incorporating the LED array 1 serving as a light source according to the above-described embodiment, and the like on a metal frame 101. The shield plate 104, the circuit board 105 on which the drive circuit and the control circuit are formed, and the second shield plate 106 are assembled in a sequentially overlapping manner.
[0058]
The liquid crystal panel 102 and the circuit board 105 are electrically connected by film cables 107 and 108.
[0059]
Although not shown, the pager 100 is provided with a battery as a power source, an on / off switch, and the like, and the LED array 1 of the backlight unit 103 is energized when the pager 100 is activated. It is configured.
[0060]
When the pager as the liquid crystal device configured as described above is turned on by the operation of the switch, the function as the pager is started up, and at the same time, the LED array 1 of the backlight unit 103 is energized, and each of the LEDs a and Each said LEDb starts light emission.
[0061]
The blue light emitted from the LEDb is wavelength-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. .
[0062]
The mixed color light and red light of these blue light and green light are radiated from each LED, and at the same time are additively mixed to become high-intensity white light.
[0063]
This high-intensity white light propagates through the light guide plate 3 and is reflected upward by the reflection plate 5 or diffused by the light diffusion unit 6 and emitted upward of the light guide plate 3. Incident light is incident from the back side.
[0064]
Therefore, it is possible to obtain a brighter and easier-to-see screen by using a white light backlight whose luminance is improved as compared with the related art.
[0065]
In this embodiment, the pager is illustrated as an example of the use of the backlight unit as a lighting device incorporating the LED array 1. However, the present invention is not limited to this, and the portable small television, wall-mounted television, and notebook personal computer are not limited thereto. It can be used for all liquid crystal devices that incorporate a backlight unit such as a liquid crystal display of a portable game machine, and in any case, the brightness of the screen is improved as compared with the conventional case, and the saturation of red constituting the screen is improved. The effect that can be obtained.
[0066]
【The invention's effect】
As described above, according to the present invention, the first LED includes a first LED that generates blue and green light by a fluorescence conversion method, and a second LED that emits red monochromatic light. Since white light is obtained by additive color mixing of the blue and green light generated by the above and the red light from the second LED, display using high brightness white light and a red filter such as LCD There is an effect that a highly saturated red color can be efficiently obtained by a simple method using the apparatus.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration example of an LED array according to the present embodiment.
FIG. 2 is a graph showing 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 showing a reference example of a backlight unit.
FIG. 5 is a plan view and a side view of the backlight unit.
[Figure 6] Standard xy chromaticity diagram showing hue area for Munsell hue established by the International Commission on Illumination (CIE), where x is the wavelength of red light (700 nm) and y is green light Wavelength (546 nm).
FIG. 7 is an exploded perspective view showing a configuration of a liquid crystal device (pager) according to the present embodiment.
FIG. 8 is a graph showing spectral characteristics of a conventional LED array.
FIG. 9 is a graph showing spectral characteristics of a conventional LED array.

Claims (8)

A light source for making light incident on the light guide plate,
The light source is
A plurality of first LEDs that emit blue monochromatic light;
A plurality of second LEDs independent of the first LED emitting red monochromatic light;
A plurality of wavelength conversion means,
Forming an LED array in which a plurality of the first LEDs and the second LEDs are alternately arranged;
The plurality of wavelength conversion means are respectively formed in an irradiation region of blue monochromatic light emitted from the plurality of first LEDs of the LED array,
Blue component light and green component light generated by wavelength-converting blue monochromatic light from the plurality of first LEDs, and red component light of red monochromatic light from the plurality of second LEDs, and The light source is characterized in that white light prepared by additive color mixing in the light guide plate is obtained by making the light incident on the light guide plate.   The intensity of the green component light generated by wavelength conversion from the blue light is measured or calculated, and in the xy chromaticity diagram showing the hue area with respect to the Munsell hue, the region to which the generated light belongs is determined, and the generation of the region is performed. The light source according to claim 1, wherein the intensity of red light from the second LED is determined so that light additively mixed with light belongs to a standard white region of the xy chromaticity diagram. The first LED is composed of an LED that emits blue light such as InGaN-based or GaN-based,
3. The light source according to claim 1, wherein the second LED is an LED that emits red light, such as a GaP-based or GaAlAs mixed crystal.   In the wavelength conversion, a fluorescent filter serving as a wavelength conversion unit is provided in the irradiation region of the first LED, to which a predetermined fluorescent material that generates at least green fluorescence by blue light having a predetermined wavelength emitted from the LED is added. The light source according to claim 1, wherein the light source is one.   The light source according to claim 4, wherein the fluorescent filter is formed by adding a predetermined rare earth element to an oxide glass matrix.   6. The light source according to claim 5, wherein the fluorescent filter is formed of a phosphor made of a predetermined translucent organic polymer.   The light source according to any one of claims 1 to 6 is disposed on a side of the light guide plate, and the light of the blue component, the light of the green component, and the light of the red component are transmitted to the light guide plate. An illuminating device that is incident and mixed into white light by additive color mixing.   A liquid crystal device comprising: the illumination device according to claim 7; and a liquid crystal panel disposed above the illumination device.

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