JP2002150821A - Flat light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an edge light type flat light source correcting an inevitable dispersion of spectrum of an LED or the like as a light source, improving a color balance, and irradiating a white light fulfilling a prescribed standard. SOLUTION: For the flat light source 10 comprising a light source 2 and a light guide plate 1, changing the path of the light emitted from the light source by the light guide plate 1, and making a flat illumination light 5 go out from a main surface 1b of the light guide plate to an object to be lighted 7, the light source 2 emits the light with a luminous color composed of a plurality of wave length components, and the light guide plate 1 is made of a translucent material having a color of complementary spectrum against the spectrum of the light source, and the spectrum of the light of the light source is compensated into a desired spectrum by the light guide plate 1, and made to irradiate as the illumination light 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar light source for a display device having a backlight mechanism for illuminating a transmissive or transflective panel from the back.

[0002]

2. Description of the Related Art In recent years, a liquid crystal display device having a thin and easy-to-see backlight mechanism has been used as a display device of a small and thin information device such as a book-type word processor or a computer, or a portable telephone or a portable TV. I have. As such a backlight mechanism, a planar light source that irradiates the liquid crystal panel from behind to the entire surface is used. As the planar light source, a light emitting source composed of a fluorescent lamp or an LED (light emitting diode) and a light flux of the light source are used. Generally, a light guide plate that converts the light into a planar light beam to be irradiated on a liquid crystal panel is used. Among them, especially in recent years, further miniaturization,
A planar light source using an LED as a light emitting source has been increasingly used for the purpose of reducing the thickness and extending the service life.

When white light is emitted by such a planar light source and a panel or the like is to be illuminated with white light, a white fluorescent lamp is used as a light emitting source, or an LED is used.
In the case of (3), it is common to combine three types of LEDs, R, G, and B, simultaneously or in a time-division manner to synthesize white light. More recently, in the case of LEDs, white LEDs that independently emit light close to white have been developed and become available. By using such white LEDs, it is possible to form a planar light source for white illumination with a small and simple configuration. FIG. 11 is a diagram showing a main part of an edge light type planar light source having such a single LED light emitting source for the purpose of white illumination of a panel, wherein (a) is a perspective view and (b). It is AA sectional drawing in.

In FIG. 11, reference numeral 110 denotes a planar light source, which has a light guide plate 101 and an LED 102 as a light source. The light guide plate 101 is a plate made of a transparent member such as a colorless and transparent plastic material and has a substantially rectangular parallelepiped shape. One main surface of the light guide plate 101 is a light exit surface 101b.
The light from the light emitting source is placed on the surface facing the light emitting surface 10.
As a means for reflecting light toward 1b, a light diffusing surface 101a having a plurality of minute grains or a plurality of hemispherical dots is formed on the surface thereof. LED102 is L
The light guide plate 101 is supported by the ED substrate 103 and is disposed at a position facing the side surface of the light guide plate 101. A predetermined current is supplied from a drive circuit (not shown) to emit and emit light for white as described later. The light emitted from the LED 102 is the light guide plate 1
01, most of the light is emitted from the light emitting surface 101b which is the upper surface.
After performing total reflection or irregular reflection once or plural times on the light diffusion surface 101a as the lower surface, the light is emitted to the outside as illumination light 105 from the light emission surface 101b as the upper surface. The illumination light 105 emitted to the outside illuminates the liquid crystal panel 107 from behind as shown in FIG. In addition, in order to ensure the uniformity of the luminance in the surface to be illuminated, the roughness of the grain in the lower surface 101a is adjusted, and the shape and density of the hemispherical dot are changed depending on the location.

[0005]

In this manner, the liquid crystal panel is illuminated for white illumination by the small and thin planar light source. However, the above-mentioned planar light source has the following problems. FIG.
Is a diagram showing a spectrum of light emission of the LED 102,
(A) shows the spectrum H1 of a normal white light source, and (b) shows the spectrum H2 of a bluish white light source. Here, the horizontal axis indicates the wavelength, 625 nm
Is a region of R before and after, a region of G is around 560 nm, 45
The area near 0 nm is the area of B. The vertical axis indicates the relative intensity of the spectrum.

FIG. 13 is a CIE chromaticity diagram showing the chromaticity of light emission of an LED for white light such as the LED 102.
Here, x indicates the ratio of R, and y indicates the ratio of G. Then, although not shown in the figure, when z is a ratio of B,
It is assumed that there is always a relationship of x + y + z = 1 (1). C0 indicates a chromaticity point at which the R, G, B component ratio is 1: 1: 1. In this case, the coordinates are approximately x = 0.33, y = 0.33, (z = 0.33). It has become. The range of the region S inside the broken line surrounding the vicinity of C0 has chromaticity recognized as normal white, and the chromaticity in the case of the spectrum distribution H1 of FIG. 11A is included in this region. . The LED for white color is manufactured with the aim that the chromaticity of light emission falls within the above-mentioned region R. However, the characteristics of actual products vary, and the chromaticity of light emission deviates considerably from the region S. Not a few.

This is an example of the case of an LED that produces the spectrum H2 shown in FIG. 12B. In this case, the B component is considerably larger than the R and G components. , X, and y decrease, and the point indicating the chromaticity is shifted from the area S to the lower left side in the figure, and is located at the point C2. The chromaticity at this position is not recognized as normal white, but is recognized as bluish white. By the way, as shown in FIG.
Is generated through the colorless and transparent light guide plate 101, so that the spectrum of the illumination light 105 is the same as the spectrum of the light emitted by the LED 102. Therefore, the spectrum H2
In the case of the LED that produces the above, the spectrum of the illumination light is also the same as H2, and the illumination light does not become normal white light but becomes bluish white light. Therefore, in this case, the purpose of the planar light source 110 for normal white illumination cannot be achieved, and the display quality expected for the panel 107 cannot be satisfied.

As described above, in an edge light type planar light source having a simple configuration including a light emitting source such as an LED and a light guide plate, the spectrum of the wavelength component of the illumination light emitted from the light guide plate depends on the spectrum of the light source. It will be decided. When an LED or the like for white light is used as a light source,
Due to the unavoidable variation in the characteristics, the light emission of the light emitting source often loses the color balance of R, G, and B, and has a spectrum shifted from desired normal white light, and the spectrum is illuminated as it is. Since the light spectrum is used, colors other than white are slightly mixed in the illumination light, and it is not often the case that desired white light illumination cannot be obtained. Therefore, an object of the present invention is to improve the color balance of the illumination light of the planar light source for white illumination. The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0009]

The present invention as a first means for solving the above-mentioned problems has a light-emitting light source and a light guide plate, and converts the light from the light-emitting light source into an optical path by the light guide plate. In a planar light source that emits planar illumination light from a main surface to an object to be illuminated, the light-emitting light source emits light of a color that includes a plurality of wavelength components, and the planar light source is a color that corrects the spectrum of light. The color correction component corrects the emission spectrum of the light emitting light source to a desired spectrum and emits the light as the planar illumination light.

According to a second aspect of the present invention, in the first aspect, the color tone of the color correction component is substantially equal to the color tone of the light emission color of the light emitting light source. It has a complementary color relationship.

According to a third aspect of the present invention, there is provided the light emitting device according to the first or second aspect, wherein the color correction component is a light guide plate made of a colored translucent material. There is a feature.

According to a fourth aspect of the present invention, there is provided the light emitting device according to the first or second aspect, wherein the color correction component is a light guide plate made of a colored translucent material. There is a feature.

According to a fifth aspect of the present invention, in order to solve the above-mentioned problems, in the first or the second means, the color correction component may be a light guide plate made of a transparent material and the illumination object. And a color filter disposed between the two.

According to a sixth aspect of the present invention, in order to solve the above-mentioned problem, the present invention is characterized in that in any one of the first to fifth means, the light emitting light source is a white light source or a light source close to white. It is characterized by.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a planar light source according to a first embodiment of the present invention will be described with reference to the drawings. 1A and 1B are diagrams showing a configuration of an edge light type planar light source according to the present embodiment, wherein FIG. 1A is a perspective view, and FIG.
It is AA sectional drawing of. In FIG. 1, reference numeral 10 denotes a planar light source, which includes a light guide plate 1 and an LED 2 as a light source. The light guide plate 1 is made of a translucent plastic material or the like colored in a color described later, has a plate-like shape, and has a substantially rectangular parallelepiped shape.
One of the main surfaces is a light emitting surface 1b, and a surface facing the light emitting surface 1b is provided with a means for reflecting light from a light emitting source toward the light emitting surface 1b. A light diffusing surface 1a having a plurality of minute grain or a plurality of hemispherical dots is formed.

The LED 2 is supported by the LED board 3 and is disposed at a position facing the side surface of the light guide plate 1. A predetermined current is supplied from a drive circuit (not shown) to emit light for white as described later. Emit and emit. The light emitted from the LED 2 enters the light guide plate 1, and most of the light is totally reflected on the light emitting surface 1b, which is the upper surface, and once or more than once, on the light diffusing surface 1a, which is the lower surface. From the light exit surface 1b. Light emitted to the outside is illumination light 5
The liquid crystal panel 7 is illuminated from behind. In addition, in order to ensure the uniformity of the luminance in the surface to be illuminated, the roughness of the grain in the lower surface is adjusted, and the shape and density of the hemispherical dot are changed depending on the location.

FIG. 2 is a diagram showing a coloring spectrum H11 of the light guide plate 1, and FIG. 3 is a diagram showing a spectrum H2 of the light emission of the LED 2 and a spectrum H21 of the illumination light 5.
FIG. 4 is a CIE chromaticity showing the chromaticity of the light emission of the LED 2 and the illumination light 5 and the like. As shown by the solid line in FIG. 3, the light emission spectrum distribution of the LED 2 of the present embodiment is H2 in FIG.
H2 has the same spectrum as the emission spectrum of the LED 102 shown in H2. Then, the position C2 of the coordinates of the light emission of the LED 2 in the CIE chromaticity diagram of FIG. 4 is the same as the position C2 shown in FIG. As shown in H2 in FIG. 3 and C2 in FIG.
The balance of R, G, and B of the light emission of the ED2 is not sufficient, and the ED2 emits bluish white light. However, in the present embodiment, instead of the colorless and transparent light guide plate (101) as in the conventional example shown in FIG. 10, the light guide plate 1 is a translucent colored yellowish white as shown by H11 in FIG. A member (such as plastic) is used.

The spectrum H11 of the light guide plate 1 is 450
The Y (yellow) component around 600 nm (or the R component around 625 nm and 560n) than the B component around nm.
G component near m) is high. Therefore, the light B
The transmittance of the component is lower than the transmittance of the Y component, and the emission spectrum of the LED 2 indicated by H2 in FIG.
The illumination light 5 is emitted as the illumination light 5 whose B component has been reduced and corrected to the spectrum indicated by H21. Generally speaking, such a filter action is such that the ratio of R, G, B is r1: g1:
The ratio of R, G, and B in which the incident light b1 is colored is r2: g.
When the light passes through the filter of 2: b2b, the ratio of R, G, and B in the emitted light is calculated according to the principle of subtractive color mixing: R: G: B = r1 × r2: g1 × g2: b1 × b2 (2) ). In the case of this example, r2: g2: b2 of the filter
Is approximately 1: 1: 0.8 as shown by H11 in FIG. 2, the ratio of R, G, and B in the emitted light (corresponding to H21 in FIG. 3) is obtained from the equation (2) as follows: G = r1: g1: 0.8 × b1, and as shown at H21, the R and G components remain unchanged and only the B component decreases as compared to the incident light (corresponding to H2).

Thus, the spectrum H2 of the illumination light 5 is obtained.
In 1, the balance of R, G, and B is improved, and the position on the chromaticity diagram moves from C2 to point C21 in the area S recognized as normal white. C21 is in the upper right direction as viewed from C2 in the figure, but has moved in the upper right direction due to the decrease of the B component. On the other hand, the above-mentioned component ratio of R, G, and B of the color of the light guide plate 1 (1: 1: 0.8)
Therefore, the position on the chromaticity diagram obtained by Expression (1) is C11 in FIG. This point is a position further moved to the upper right from the point C21 having a good color balance. That is, L
The component ratio of the light emission color of the ED 2 and the component ratio of the coloring color of the light guide plate 1 as a filter are substantially opposite, and it can be said that they have a complementary color relationship with each other. In particular, the component ratio of B is completely opposite. As described above, in the present embodiment, the color of the translucent light guide plate 1 serving as a filter is used for the light emission of the bluish-white LED 2, which has a complementary color relationship with the color of the light emission. By making the color yellow, the color balance is corrected and improved, and the illumination light 5 recognized as normal white light can be emitted.

A planar light source according to a second embodiment of the present invention will be described below with reference to the drawings. This embodiment is different from the first embodiment shown in FIG.
The emission spectrum of D2 is the same, and only the coloring spectrum of the light guide plate 1 is different. Here, FIG. 5 is a diagram illustrating a coloring spectrum H12 of the light guide plate 1 according to the present embodiment, and FIG. 6 is a diagram illustrating a spectrum characteristic H2 of light emission of the LED 2 and a spectrum H22 of the illumination light 5. As shown in FIG. 6, the emission spectrum H2 of LED2 is the same as the emission spectrum H2 of LED2 shown in FIG.
2 shows the coloring spectrum H12 of the light guide plate in the first embodiment shown in FIG.
Compared to 1, the component of R is larger than the component of G, and the color is reddish yellow.

That is, in the present embodiment, the ratios r2, g2, and b2 of R, G, and B in the light guide plate 1 have a relationship of r2>g2> b2. And LE
The component ratios r1, g1, and b1 of the light emission of D2 have a relationship of r1 <g1 <b1 as shown by H2 in FIG.
In other words, the nature of the color balance shift is opposite between the spectrum H12 of the light guide plate and the spectrum H2 of the LED for all of R, G, and B, and has a substantially perfect complementary color relationship. The light emission of the LED 2 is transmitted through the light guide plate 1,
Corrected according to the principle of subtractive color mixture shown in equation (2), R,
The illumination light 5 has a ratio of G and B of approximately 1: 1: 1. Here, the illumination light 5 is almost completely white, and its chromaticity substantially matches C0 in the chromaticity diagram of FIG. As described above, in the present embodiment, a substantially perfect white illumination light can be obtained by using a light guide plate having a spectral characteristic that is substantially completely complementary to the emission of the LED.

Hereinafter, a planar light source according to a third embodiment of the present invention will be described with reference to the drawings. This embodiment has the same shape and configuration as the first embodiment shown in FIG. 1, but differs in the emission spectrum of the LED 2 and the coloring spectrum of the light guide plate 1. Here, FIG. 7 is a diagram showing a spectral characteristic H13 of coloring of the light guide plate 1 according to the present embodiment, and FIG. 8 is a diagram showing a spectral characteristic H3 of light emission of the LED 2 and a spectral characteristic H23 of the illumination light 5. .
As shown by H3 in FIG. 8, the light source L of the present embodiment is
The emission of ED2 has a G component and a B component,
Color tone. Here, the present embodiment aims to obtain the illumination light 5 of G color from the light emission of the light emission source 2. Therefore, as shown in FIG. 7, the coloring spectrum H13 of the light guide plate 1 of the present embodiment is higher in the range of R and G, and the light guide plate 1 is in a state of being colored Y (yellow). . Thereby, the light emission of the color tone of C is transmitted through the light guide plate of the color tone of Y, which is a complementary color relationship with the light emission of C,
According to the principle of subtractive color mixing already described, color correction is performed, and as shown in the spectrum of H23 in FIG. 8, the illumination light 5 of the desired color G can be obtained. As described above, according to the present invention, by using a colored light guide plate, it is possible to obtain illumination light of a desired color contained in a component of a light emitting source as well as white from a light emitting source having a plurality of wavelength components. it can.

Hereinafter, a planar light source according to a fourth embodiment and a fifth embodiment of the present invention will be described with reference to the drawings. FIG. 9 is a sectional view showing a fourth embodiment of the present invention. In FIG. 9, reference numeral 4 denotes a thin plate or film color filter, which is made of a translucent material colored in a spectrum having a color complementary to the spectrum of the LED 2 serving as a light emitting source. The light guide plate 1 is similar in shape to that shown in FIG. 1, but is not colored and is made of a colorless and transparent material. The color filter 4 is disposed between the light guide plate 1 and a liquid crystal panel 7 which is an object to be illuminated. In this example, the color filter 4 is closely attached to the light guide plate 1 for convenience, but it is not always necessary to closely adhere. In the present embodiment, the light emission of the LED 2 incident on the light guide plate 1 is converted into an optical path according to the principle described above, but no color correction is performed during this time. The light whose path has been changed enters the color filter 4, where the color correction is performed according to the same principle as already described in the first, second and third embodiments. The illumination light 5 of a desired color is emitted.

FIG. 10 is a sectional view showing a fifth embodiment of the present invention. In FIG. 10, reference numeral 4 denotes a thin-plate or film-like color filter, which is made of a translucent material colored in a spectrum having a color complementary to the spectrum of the LED 2 as a light emitting source. The light guide plate 1 is similar in shape to that shown in FIG. 1, but is not colored and is made of a colorless and transparent material. The color filter 4 is disposed between the light guide plate 1 and the LED 2. In this example, the color filter 4 is closely attached to the light guide plate 1 for convenience, but it is not always necessary to closely adhere. In the present embodiment, the LED
The light emission of 2 first enters the color filter 4, where
According to the same principle as described in the first, second, and third embodiments, color correction is performed, light of a desired color is incident on the light guide plate 1, the light path is changed, and the light guide plate 1 is changed. Emits illumination light of a desired color. Thus, the fourth
In the fifth embodiment and the fifth embodiment, a color filter separate from the light guide plate is used as a color filter member. However, when the emission spectrum of the LED as the light emission source varies, Since it is necessary to prepare various colors for the filter member for correcting the color difference, the use of a dedicated color filter increases the number of components, but has an advantage that it can be easily handled.

[0025]

As described above, according to the present invention, a filter means such as a colored light guide plate is used in a simple configuration of an edge light type planar light source having a light source such as an LED and a light guide plate. Thereby, the illumination light of a desired color such as white can be emitted by correcting the spectrum of the light emitting source. Accordingly, even when the desired white light emission or the like cannot be obtained due to inevitable variations in the spectral characteristics of products such as LEDs, the color balance of the light emission source is corrected by the filter means to obtain illumination light of a desired color. It became possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a planar light source according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a spectrum of coloring of a light guide plate in the planar light source shown in FIG.

FIG. 3 is a diagram showing a spectrum of a light emitting source and a spectrum of illumination light in the planar light source shown in FIG.

FIG. 4 is a diagram showing chromaticity of a light emitting source, chromaticity of illumination light, and the like in the planar light source shown in FIG.

FIG. 5 is a diagram showing a spectrum of coloring of a light guide plate in a planar light source according to a second embodiment of the present invention.

FIG. 6 is a diagram showing a spectrum of a light source and a spectrum of illumination light in a planar light source according to a second embodiment of the present invention.

FIG. 7 is a diagram showing a coloring spectrum of a light guide plate in a planar light source according to a third embodiment of the present invention.

FIG. 8 is a diagram showing a spectrum of a light-emitting source and a spectrum of illumination light in a planar light source according to a third embodiment of the present invention.

FIG. 9 is a diagram illustrating a configuration of a planar light source according to a fourth embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of a planar light source according to a fifth embodiment of the present invention.

FIG. 11 is a diagram showing a configuration of a conventional planar light source.

12 is a diagram showing a spectrum distribution of a light emitting source in the planar light source shown in FIG.

13 is a diagram showing chromaticity of a light emitting source in the planar light source shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light guide plate 2 LED 3 LED board 4 color filter 5 illumination light 7 liquid crystal panel 10 planar light source

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 6/00 331 G02B 6/00 331 H01L 33/00 H01L 33/00 M

Claims (6)

[Claims] 1. A planar light source having a light-emitting light source and a light guide plate, wherein light from the light-emitting light source is converted into an optical path by a light guide plate, and planar light is emitted from a main surface of the light source to an object to be illuminated. The light-emitting light source emits light of an emission color composed of a plurality of wavelength components, the planar light source includes a color correction component for correcting a spectrum of light, and the color correction component changes the emission spectrum of the light-emitting light source to a desired spectrum. A planar light source which corrects and emits the planar illumination light. 2. The planar light source according to claim 1, wherein the color tone of the light transmission characteristic of the color correction component is substantially complementary to the color tone of the emission color of the emission light source. 3. The planar light source according to claim 1, wherein the color correction component is the light guide plate made of a colored translucent material. 4. The planar light source according to claim 1, wherein the color correction component is a color filter disposed between the light emitting light source and the light guide plate made of a transparent material. 5. The surface according to claim 1, wherein the color correction component is a color filter disposed between the light guide plate made of a transparent material and the illumination object. light source. 6. The planar light source according to claim 1, wherein the light emitting light source is a white light source or a light source close to white.