JP2003084141A - Light guide plate, illuminator, liquid crystal device and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide plate used together with a light source utilizing a white LED (light emitting diode) and with which high luminance approximately normal white light can be obtained by making up for red and green light components and an illuminator, a liquid crystal display device and an electronic apparatus using the light guide plate. SOLUTION: The light guide plate, used as the illuminator together with the light source, is constructed with a material containing pigments corresponding to wavelength components with which outputted light from the light source is supplemented. Because the light guide plate is constructed with the material containing the pigments corresponding to the wavelength so as to make up for the wavelength components which the light outputted from the light source is lacking, the outputted light with desirable spectroscopic characteristics is generated. Thereby, for example in the illuminator using the white LED, the outputted light being approximately normal white light is obtainable by including green and/or red pigments in the light guide plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination device such as a portable small television, a pager, a wall-mounted television, a backlight unit used in a liquid crystal display of a notebook personal computer or a portable game machine, and a light guide plate therefor. .

[0002]

2. Description of the Related Art Conventionally, a cold cathode fluorescent tube (CCFT) as a light source is used as a light guide plate in a display unit such as a liquid crystal panel used in a small television, a pager, a wall-mounted television, a notebook computer, a portable game machine, and the like. An edge-light type (or side-light type) backlight unit disposed laterally is used. However, the cold cathode fluorescent tube has various problems such as poor lighting performance, requiring a dedicated drive circuit, difficulty in adjusting the light amount, large power consumption, large heat generation, a lot of noise, and weakness against vibration and shock. Had a point.

As a backlight unit which does not have the above-mentioned problems, there is known one using an LED (light emitting diode) as a light source. In a backlight unit of a liquid crystal panel such as a small TV or a laptop computer, a cold cathode is not useful for a simple illumination for checking the display of a wristwatch or a red or green monochromatic light emitted from an LED like a pilot lamp of various electronic devices. White light that is close to the light emission of a fluorescent tube is required. Due to the recent progress in technological development, I
LEDs that emit blue monochromatic light using nGaN-based or GaN-based compound semiconductors as materials have been put into practical use.
No single LED chip emits white light yet.

Therefore, in order to obtain white light using currently available LEDs (red, green, blue),
A method of additively mixing red light, green light, and blue light based on the color theory is generally used. As a conventional additive color mixing method, a method is known in which three types of LEDs that emit monochromatic light of red, green, and blue are used to express white by RGB color mixing.

However, in the method of using three LEDs, the brightness of each LED that emits red, green, and blue monochromatic light is different, so that in order to generate uniform white light, RGB three colors are used. It is necessary to strictly control the currents of the three types of LEDs so that the light energy intensity becomes uniform, and it takes time to design an LED array as a light source. Further, since it is necessary to use the same number of all three types of LEDs, there is a disadvantage that the cost increases (especially, the blue LED has the highest unit price).

Therefore, as another method, a method has been proposed in which only LEDs emitting blue monochromatic light are used, green and red are generated by a wavelength conversion filter, and white is expressed by mixing RGB. As a method similar to this, there is known a method in which green and red phosphor coating materials are applied to blue LEDs to obtain white light by mixing RGB colors.

Recently, a blue LED in which green and red phosphors are used is called a white LED, and is widely used for a backlight light source of a liquid crystal display device.

[0008]

However, in the method using such a white LED, the energy of the red (R) component generated by wavelength conversion by a phosphor or a fluorescent filter is blue (B). Since the wavelength range is wider than that of the component and the energy intensity is weak, there is a problem that the brightness and saturation of the red light becomes low when the red filter is applied. Further, the energy of the green component generated by wavelength conversion is not so high as that of the red component, but the energy intensity is weaker than that of the blue component.

The present invention has been made in view of the above points, and by using it together with a light source using a white LED, a red light component and a green light component are supplemented to obtain white light with high brightness and close to standard. An object of the present invention is to provide a light guide plate capable of performing the above, and an illumination device, a liquid crystal display device, and an electronic device using the light guide plate.

[0010]

The light guide plate of the present invention is used as a lighting device together with a light source, and is made of a material containing a dye corresponding to a wavelength component to be supplemented to the output light from the light source.

According to this light guide plate, since it is made of a material containing a dye corresponding to the wavelength so as to make up for the insufficient wavelength component in the output light from the light source, the output light having a desired spectral characteristic can be obtained. It becomes possible to generate.

In one mode of the above light guide plate, the dye is
It is uniformly included in all parts of the light guide plate.

According to this aspect, it is possible to supplement the wavelength component corresponding to the dye with respect to all the light components diffused in the light guide plate.

In another aspect of the above light guide plate, the pigment is at least one of green pigment and red pigment.

According to this aspect, the green and / or red light components lacking in the general white LED can be supplemented to generate light close to standard white light.

In still another mode of the above-mentioned light guide plate, the pigment reduces the transmittance of blue light.

According to this aspect, the blue light having high energy intensity is slightly attenuated in the general white LED to improve the balance between the green light and the red light,
More standard white light can be obtained.

The illumination device of the present invention comprises a light source and the above light guide plate.

According to this illuminating device, it is possible to generate output light having a desired spectral characteristic by compensating for the insufficient wavelength component in the output light from the light source.

In one aspect of the above lighting device, the light source includes an LED.

According to this aspect, since the wavelength components that cannot be sufficiently emitted by the LEDs of various colors can be added to the light guide plate and supplemented by the dye, it is possible to obtain the output light having desired characteristics.

A liquid crystal device of the present invention comprises the above-mentioned lighting device,
A liquid crystal panel arranged at a position where the output light from the lighting device is irradiated.

According to this liquid crystal device, since the output light having desired spectral characteristics is emitted from the illumination device, it is possible to display an image with high fidelity.

Electronic equipment of the present invention includes the above liquid crystal device.

According to this electronic device, for example, a mobile phone,
Images with good color balance can be displayed on liquid crystal devices such as portable information processing devices.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings.

[Description of Principle] First, the principle of the present invention will be described. A backlight unit such as a liquid crystal device is generally composed of a light source and a light guide plate for irradiating the back surface of the liquid crystal panel with light from the light source. As a light source,
As described above, white LEDs are widely used.

FIG. 1 shows the spectral characteristics of the white LED. The light from the white LED is 470 nm as shown in FIG.
It has a characteristic that the blue light in the vicinity has a high energy intensity and the green light in the vicinity of 570 nm and the red light in the vicinity of 650 nm have a low energy intensity. The white LED is originally blue L
The energy of blue light is high because it is configured by applying green and red phosphors to the ED, but even if the phosphor is applied, green light and red light are not sufficiently obtained. I understand.

FIG. 2 (a) shows the light emission from the white LED and the cold cathode fluorescent lamp (CCFT) in the chromaticity diagram established by the International Commission on Illumination (CIE).
It can be seen that the components of green light and red light are insufficient as compared with the light emission from the cold cathode fluorescent tube.

On the other hand, in the backlight unit, a transmitted light characteristic of a general light guide plate used together with a light source is shown in a graph 100 of FIG. As shown in the figure, it can be seen that the light transmission characteristics of a general light guide plate are almost flat for all wavelengths (that is, for each color).

The output light of the backlight unit is the light from the light source that passes through the light guide plate and is output.
If the green light and the red light, which are deficient in the light from the light source, are supplemented when passing through the light guide plate, the output light from the backlight unit should eventually approach the standard white light.

Therefore, in the present invention, a white LED having the characteristics shown in FIG. 1 is used as the light source, and green and / or red pigments are added to the light guide plate to enhance the green and / or red component. At the same time, the blue component was attenuated to some extent so that output light close to standard white light was obtained from the backlight unit.

An example of transmitted light characteristics of the light guide plate according to the present invention is shown in graphs 110 and 120 of FIG. A graph 110 is a characteristic of the light guide plate in which a green pigment is added to supplement a green component, and a graph 120 is a characteristic of the light guide plate in which a red pigment is added to supplement a red component. In the graph 110, the light transmittance of the wavelength corresponding to the green light (near 570 nm) is high, and in the graph 120, the wavelength corresponding to the red light (650n).
The light transmittance in the vicinity of m is high.

In both graphs 110 and 120, the transmittance near the frequency of blue light (500 nm or less) is lowered. According to the backlight unit using such a light guide plate, although the blue light component is attenuated to some extent, the brightness of the entire output light is somewhat lowered, but the green light component and / or the red light component is reduced. Because RGB can be compensated for
The three colors are well balanced, and it is possible to output light close to standard white light.

The amount of the green and / or red pigments added to the light guide plate is properly determined in consideration of the original characteristics of the light source used in the backlight unit so as to make up for the lacking wavelength component. Will be. Addition of either the green pigment or the red pigment enhances the component of that color, and the addition of both enhances the components of both colors.

Basically, it is preferable to add the dye substantially uniformly to the entire light guide plate. This is because, as will be described later, the incident light from the light source is diffused in the light guide plate, further reflected by the reflection plate arranged under the light guide plate, and emitted substantially uniformly.

[Backlight Unit] Next, a backlight unit to which the light guide plate of the present invention is applied will be described. FIG. 4 is a schematic configuration diagram of a backlight unit to which the present invention is applied.

As shown in FIG. 4, the backlight unit is roughly classified into an LED array 1 which operates as a light source,
The light guide plate 3 and the reflection plate 5 are provided.

The structure of the LED array 1 is shown in FIG. Figure 5
[FIG. 3] is a front view of the LED array 1 as viewed from its light emitting surface side. As shown in FIG. 5, in the LED array 1, a plurality of LEDs 11 are arranged inside the casing 10. Each LED 11 is arranged so that its light emitting surface faces outward. A fluorescent filter 13 is attached to the casing 10 in front of the light emitting surface of each LED 11.

The LED array 1 is the above-described white LED, and each LED 11 is an LED that emits blue light (wavelength is, for example, 470 nm) such as InGaN or GaN. Further, the fluorescence filter 13 is LE
The wavelength conversion filter receives blue light from D11 and emits blue light, green light, and red light. The fluorescent filter 13 can be formed of, for example, an oxide glass matrix formed by adding a predetermined rare earth element, or a fluorescent material made of a translucent organic polymer. Although not shown, the LED array 1 is connected to a control circuit for controlling the amount of current for lighting each LED 11.

According to the LED array 1 thus constructed, the blue light emitted from each LED 11 is wavelength-converted by the fluorescent filter 13 to generate RGB three-color light. As a result, the output light from the LED array 1 becomes white light. However, the white light output from the LED array 1 is
As shown in FIG. 1, the energy intensity of green light and red light is smaller than that of blue light.

Next, the structure of the light guide plate 3 is shown in FIGS. 6 (a) and 6 (b). FIG. 6A is a plan view of the light guide plate.
(B) is a side view. As shown in FIGS. 6A and 6B, the light guide plate 3 has a mounting hole 4 at one end for mounting the LED array 1. Further, on the surface of the light guide plate 3, a plurality of light diffusing portions 6 each having a large and small concave-convex shape are formed. The light guide plate 3 is made of a transparent resin such as polymethylmethacrylate (PMMA) resin or polycarbonate resin (polycarbonate resin). As described above, the light guide plate 3 is uniformly colored with green and / or red pigments.

When each LED 11 of the LED array 1 is energized by the control circuit with the LED array 1 mounted in the mounting hole 4 of the light guide plate 3, each L in the LED array 1 is energized.
The ED 11 emits light, and white light is output from the front surface of the LED array 1 by the action of the fluorescent filter 13. As shown in FIG. 6B, the white light emitted from the LED array 1 enters the light guide plate 3 and propagates inside the light guide plate 3, and is reflected by the reflection plate 5 and diffused by the light diffusing section 6, The light is radiated above the light guide plate 3.

While being reflected and diffused in the light guide plate 3 in this way, the white light emitted from the LED array 1 is affected by the pigment added to the light guide plate 3, and the green light component and the red light component are enhanced. As a result, the energy intensity of the green light and the red light is increased, the balance of the RGB components is improved, and C
It is close to the standard white light in the IE chromaticity diagram.

Therefore, according to the backlight unit using the light guide plate of the present invention, it is possible to emit more standard white light in which the balance of blue light, green light and red light is improved.

[Modification] The light guide plate of the present invention is not limited to the one having the above-mentioned structure, and the present invention can be applied to light guide plates having various other structures.

In the above embodiment, an example in which green and / or red dyes are added to the light guide plate so as to correct the characteristics of the white LED, which generally has low energy levels of green light and red light, has been shown. In other cases, the characteristics of the light emitted from the backlight unit can be controlled by adding the dye of the required color to the light guide plate. Therefore, when it is necessary to correct the color in relation to other components used in the liquid crystal device such as a light source other than the LED and a color filter, by adding a dye of the necessary color to the light guide plate. Therefore, it becomes possible to easily obtain preferable output light.

[Liquid Crystal Device] Next, an example of a liquid crystal device using the backlight unit of the present invention will be described. Figure 7
It is a pager as an example of a liquid crystal device using the backlight unit of the present invention.

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

Incidentally, the liquid crystal panel 102 and the circuit board 105.
The electrical continuity of the film-like cables 107, 108
It is supposed to be done by.

Although not shown, the pager 100
Is provided with a battery as a power source, an on / off switch, and the like, and is configured to energize the LED array 1 of the backlight unit 103 when the pager 100 is activated.

When the pager as the liquid crystal device having such a configuration 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 also energized, The LED 11 starts emitting light.

Then, the blue light emitted from each LED 11 is wavelength-converted into blue light, green light and red light by the fluorescent filter 13 and enters the light guide plate 3 as white light. This white light propagates through the light guide plate 3 and is reflected by the reflector plate 5.
Is reflected upward by the light diffusing portion 6 and is diffused by the light diffusing portion 6 to be radiated upward from the light guide plate 3, and the liquid crystal panel 1
It is incident as uniform irradiation light from the back surface side of 02. At this time, the green and / or red pigment component contained in the light guide plate 3 diffuses and reflects the inside of the light guide plate, which is white light of green light and / or
Alternatively, since the red light component is enhanced, standard white light is output from the backlight unit 103.

[Electronic Equipment] Next, examples of electronic equipment using the backlight unit of the present invention will be described with reference to FIG.

FIG. 8A is a perspective view showing a mobile phone. 1000 indicates a mobile phone body, of which 100
Reference numeral 1 denotes a liquid crystal display section using a liquid crystal device equipped with the backlight unit of the present invention.

FIG. 8B is a perspective view showing a wrist watch type electronic device. Reference numeral 1100 denotes a watch body, and 1101 denotes a liquid crystal display unit using a liquid crystal device including the backlight unit of the present invention. Since this liquid crystal panel has high-definition pixels as compared with the conventional timepiece display section, it is possible to display a television image and realize a wristwatch television.

FIG. 8C is a diagram showing a portable information processing device such as a word processor and a personal computer. Reference numeral 1200 denotes an information processing device, and 1202 denotes an input unit such as a keyboard.
Reference numeral 06 denotes a display unit using a liquid crystal device including the backlight unit of the present invention, and 1204 denotes an information processing apparatus main body.

In addition, the backlight unit of the present invention can be used in all liquid crystal devices incorporating a backlight unit such as a portable small television, a wall-mounted television, a liquid crystal display of a notebook computer and a portable game machine. In any of these cases, it is possible to obtain the effect that an image with well-balanced RGB can be displayed.

[Brief description of drawings]

FIG. 1 shows an example of spectral characteristics of a white LED.

[Fig. 2] White LE shown by a standard chromaticity diagram by CIE.
It is a characteristic of D and a cold cathode fluorescent tube (CCFT).

FIG. 3 shows light transmission characteristics of a light guide plate.

FIG. 4 is a perspective view of an embodiment of a backlight unit using the light guide plate of the present invention.

5 is a front view of an LED array used in the backlight unit shown in FIG.

6 is a diagram showing a configuration of a light guide plate of the present invention used in the backlight unit shown in FIG.

FIG. 7 is an exploded perspective view of a liquid crystal device to which the backlight unit according to the present invention is applied.

FIG. 8 is a schematic view showing an electronic device to which the backlight unit according to the present invention is applied.

[Explanation of symbols]

1 LED array 3 Light guide plate 4 mounting holes 5 reflector 6 Light diffuser 11 LED 13 Fluorescent filter 100 LCD device 103 Backlight unit 1000, 1100, 1200 Electronic equipment

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Claims (8)

[Claims] 1. A light guide plate used as a lighting device together with a light source, wherein the light guide plate is made of a material containing a dye corresponding to a wavelength component to be supplemented to the output light from the light source. 2. The light guide plate according to claim 1, wherein the pigment is uniformly contained in all parts of the light guide plate. 3. The light guide plate according to claim 1, wherein the pigment is at least one of green pigment and red pigment. 4. The light guide plate according to claim 3, wherein the dye reduces the transmittance of blue light. 5. A lighting device comprising: a light source; and the light guide plate according to claim 1. 6. The lighting device according to claim 5, wherein the light source includes an LED. 7. A liquid crystal device comprising: the illuminating device according to claim 5 or 6, and a liquid crystal panel arranged at a position where the output light from the illuminating device is irradiated. 8. An electronic apparatus comprising the liquid crystal device according to claim 7.