JP2003059326A - Surface lighting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface lighting system allowing improvement of a luminance while suppressing increase of the system size. SOLUTION: In this lighting system, a separate first LED 15c is provided such that the separate first LED 15c can emit light to one end face 5a of a light guide body 5 facing an LED 15a through a first optical fiber 18, and a separate second LED 15d is provided such that the separate second LED 15d can emit light to the other end face 5b of the light guide body 5 facing an LED 15b through a second optical fiber 19. Because light is incident onto the light guide body 5 from the four LEDs 15, the luminance can be improved compared to conventional technology utilizing light of two LEDs (point-like light sources). By making respective volumes of first and second optical fiber light guide body side 22, 23 smaller than the volumes of the LEDs 15, the luminance can be improved without securing large spaces in areas facing one end face 5a and the other end face 5b of the light guide body 5. Accordingly, increase of the system size can be suppressed by that much.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar lighting device used for lighting means such as signboards and various display devices, and more particularly to a lighting means for liquid crystal display devices.

[0002]

2. Description of the Related Art Liquid crystal display devices that operate with low power consumption are
Because of its features such as thinness and lightness, the demand as a display device mainly for computer applications is increasing. Since the liquid crystal which is a constituent member of the liquid crystal display device does not emit light by itself, unlike a light emitting element such as a cathode ray tube, an illuminating means for observing an image is required. In particular, in response to the recent demand for thinning, a flat plate sidelight type (light guide plate type) planar illumination device is often used as the illumination means for illuminating the liquid crystal display device.

As an example of such a sidelight type planar illumination device, there is a planar illumination device configured as shown in FIG. In FIG. 6, the planar lighting device 1 includes a transparent substrate (guide plate) 2 made of a translucent material, and a rod-shaped light source 4 arranged close to one end face 3 of the transparent substrate 2.
It is composed of and. Then, in the planar lighting device 1, the light emitted from the light source 4 is made incident on the transparent substrate 2 to illuminate a liquid crystal display device (liquid crystal display panel) (not shown) arranged on the lower surface side of the transparent substrate 2 to illuminate the front light. It has a function and is used as an auxiliary light for this liquid crystal display device.

The light source 4 includes a light guide body (guide rod) 5 made of a rod-shaped transparent material, which is disposed closely along one end surface 3 of the transparent substrate 2, and one end surface 5a and the other end surface 5b of the light guide body 5.
The point light sources 6 and 7 each composed of an LED or the like arranged so as to face the above are generally configured. The outer diameters of the point light sources 6 and 7 are substantially the same as the outer diameters of the one end surface 5a and the other end surface 5b of the light guide 5. Further, a frame 8 having a reflecting member on the inner surface side is provided so as to cover the light guide 5. A light reflection pattern 9 is formed on one surface (the upper surface in FIG. 6) of the transparent substrate 2.

As another conventional example, US Pat.
There is a planar lighting device shown in Japanese Patent No. 57761. In this planar lighting device, an optical fiber having a core with a diameter equivalent to the diameter of the light guide is provided between the light guide and one point light source.

[0006]

By the way, it is desired to improve the brightness of the planar lighting device. Then, as a countermeasure against this, it is conceivable that the number of point light sources arranged facing one end surface or the other end surface of the light guide is two or more. For example, in the conventional technique shown in FIG.
It is conceivable to newly dispose a point light source in addition to the point light source 6 on one end surface 5a, or newly dispose a point light source in addition to the point light source 7 on the other end surface 5b.

However, in order to increase the number of point light sources, it is necessary to correspondingly increase the area of the end face portion of the light guide or increase the number of light guides. Will result in an increase in size.

In the planar lighting device shown in the above-mentioned US Pat. No. 5,857,761, an optical fiber having a core having a diameter equal to the diameter of the light guide is provided between the light guide and one point light source. Therefore, if it is attempted to increase the number of point light sources in order to improve the brightness, it is necessary to increase the number of light guides or increase the diameter of the light guides. This leads to an increase in size. Therefore, even in this case, it is impossible to properly meet the above demand.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a planar lighting device capable of suppressing an increase in size of the device and improving brightness.

[0010]

SUMMARY OF THE INVENTION According to the invention of a planar lighting device of claim 1, a rod-shaped light guide is arranged close to a side end surface of a transparent substrate made of a transparent material, and the light guide is provided. A planar illumination device having a plurality of point light sources corresponding to at least one of the two end surfaces of the light source, at least one point light source of the plurality of point light sources is separated from the light guide. It is characterized in that the point light source arranged in the predetermined portion is connected to the end face of the light guide by an optical fiber. The invention described in claim 2 is claim 1
In the configuration described in (1), the optical fiber is curved near one end connected to the light guide, and the other end extends toward the predetermined portion side, and the volume from the one end of the optical fiber to the curved portion is the point. It is characterized in that it is smaller than the volume of the linear light source.

According to a third aspect of the present invention, in the structure according to the first or second aspect, the point light sources arranged in the predetermined portion are two or more. According to a fourth aspect of the present invention, in the configuration according to the third aspect, two or more point light sources arranged in the predetermined portion are connected to an input end of an optical fiber coupler, and an output end of the optical fiber coupler is It is characterized in that it is connected to the end face of the light guide.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A planar lighting device 1A according to an embodiment of the present invention will be described with reference to FIGS. In addition,
The same parts and members as in FIG. 6 are designated by the same reference numerals,
The description will be omitted as appropriate. The planar illumination device 1A is arranged so as to cover the observation surface of the reflective liquid crystal display element 10 as shown in FIG. 3, and illuminates the reflective liquid crystal display element 10 with light (not shown) from the front side, and the reflective liquid crystal The reflected light of the display element 10 is guided to the front side (upper side in FIG. 3), that is, the front light function is exhibited, and the user can observe the image information of the reflective liquid crystal display element 10.

As shown in FIGS. 1 and 2, this planar lighting device 1A has a substantially rectangular transparent substrate 2 made of a translucent material.
And a rod-shaped light guide 5 arranged close to one end surface of the transparent substrate 2 (hereinafter referred to as the first end surface 11), one end surface 5a of the light guide 5 and one end surface 5a thereof. It is roughly composed of four LEDs (point light sources) 15a, 15b, 15c, 15d which allow light to enter from the other end surface 5b on the opposite side. The LED 15 is arranged on an electric wiring board (not shown) together with electronic components (not shown). Hereinafter, with respect to the side end surface of the transparent substrate 2, the side end surface opposite to the first side end surface 11 is referred to as a second side end surface 12 and is orthogonal to the first side end surface 11.
Of the two side end faces, the side end face (right side in FIG. 2) corresponding to the one end face 5a of the light guide 5 is referred to as a third side end face 13, and the third side end face 1
The side end surface (the left side in FIG. 2) opposite to 3 is referred to as a fourth side end surface 14. Also, the four LEDs 15a, 15b, 15c, 15
Hereinafter, d will be generically referred to as LED 15 as appropriate.

The LED 15a is provided so as to face one end surface 5a of the light guide body 5, and the LED 15b is provided so as to face the other end surface 5b of the light guide body 5. The LEDs 15c and 15d are arranged apart from the light guide body 5. Of these, the LED
15c is disposed in a portion of the transparent substrate 2 near the second side end surface 12 and facing the third side end surface 13 (hereinafter referred to as a third side end surface tip side vicinity portion, which constitutes a predetermined portion of the present invention) 16. There is. Further, the LED 15d is the second one of the transparent substrate 2.
It is arranged in a portion in the vicinity of the side end surface 12 that faces the fourth side end surface 14 (hereinafter, referred to as a portion 17 near the tip end side of the fourth side end surface, which constitutes a predetermined portion of the present invention).

The LED 15c and the one end surface 5a of the light guide 5 are arranged so that the light from the LED 15c can enter the light guide 5.
Book optical fiber (hereinafter referred to as the first optical fiber)
Connected at 18. One end 18 a of the first optical fiber 18 faces the one end face 5 a of the light guide 5 and the other end 18
b is arranged so as to face the LED 15c.

The first optical fiber 18 has one end 18a.
Is bent at a substantially right angle in the vicinity of the
The portion up to 8b is arranged along the third side end surface 13 of the transparent substrate 2. One end 18a of the first optical fiber 18
The portion 22 from the curved portion 20 to the curved portion 20 (hereinafter referred to as the first optical fiber light guide side portion) 22 is arranged side by side with the LED 15a. The volume of the first optical fiber light guide side portion 22 is smaller than the volume of the LED 15. The cross-sectional area of the first optical fiber 18 is set to a value smaller than the area of the LED 15a facing the light guide 5.

The LED 15d and the other end surface 5b of the light guide 5 are connected by one optical fiber (hereinafter referred to as the second optical fiber) 19 so that the light from the LED 15d can enter the light guide 5. There is. The second optical fiber 19 is arranged so that one end 19a thereof faces the other end surface 5b of the light guide 5 and the other end 19b thereof faces the LED 15d.

The second optical fiber 19 has one end 19a.
It bends at a substantially right angle in the vicinity, and from this bending portion 21 to the other end portion 19
The portion up to b is arranged along the fourth side end surface 14 of the transparent substrate 2. A portion 23 from one end 19a of the second optical fiber 19 to the curved portion 21 (hereinafter, referred to as a second optical fiber light guide side portion) 23 is arranged side by side with the LED 15b. The volume of the second optical fiber light guide side portion 23 is smaller than the volume of the LED 15. The cross-sectional area of the second optical fiber 19 is set to a value smaller than the area of the LED 15b facing the light guide 5.

A surface 25 of the light guide 5 which faces the transparent substrate 2.
An optical path changing means 27 is provided on the opposite side surface 26, so that the light emitted from the LED 15 is uniformly emitted on the surface 25. Further, a frame 8 is provided so as to cover the light guide body 5. The frame 8 is formed by bending a metal plate into a substantially U shape, and the inner surface of the frame 8 efficiently reflects the light emitted from the light guide body 5,
A film (not shown) on which a metal such as silver is deposited is attached. In this embodiment, the frame 8 extends to the base 2a of the transparent substrate 2, the base 2a is sandwiched, and the light guide 5 is fixed by a fixing means (not shown) such as a double-sided tape.
Also, the transparent substrate 2 is held integrally.

On one surface of the transparent substrate 2 (upper side of FIG. 1), as shown in FIG.
Further, as shown in FIG. 3, the light reflection pattern 9 (prism surface) is formed of a plurality of grooves 9a having a triangular cross section. The groove 9a extends parallel to the light guide body 5 and is formed with a large number of threads from the first side end surface 11 to the second side end surface 12.

In the light reflection pattern 9, the depth and width of the groove 9a, the inclination angle of the groove 9a, etc. are set to predetermined values, and the transparent substrate 2 of the transparent substrate 2 is not affected by the distance from the light guide 5. The brightness is made substantially uniform at any position. Light reflection pattern 9 formed on the transparent substrate 2
Since the groove 9a is extremely fine, it does not hinder the observation of the screen.

The planar lighting device 1 configured as described above.
In A, since the light guide 5 can enter the light of the four LEDs 15 and send the light to the transparent substrate 2, the two LEs are used.
It is possible to improve the brightness as compared with the conventional technique shown in FIG. 6 and the like that uses the light of D (point light source). The volume of the first optical fiber light guide side portion 22 is smaller than the volume of the LED 15, and the volume of the second optical fiber light guide side portion 23 is smaller than the volume of the LED 15. Therefore, as compared with the case where the four LEDs 15 are arranged so as to directly face the end surface of the light guide body 5, a large space should be secured in the region facing the one end surface 5a and the other end surface 5b of the light guide body 5. Therefore, the brightness can be improved without increasing the size of the device.

In the above-described embodiment, the LED 15c is arranged in the portion 16 (predetermined portion) near the tip of the third side end face. However, instead of this, as shown in FIG. Two LEDs 15 may be arranged in the side vicinity portion 16, or three or more LEDs (not shown) may be arranged. In addition, what has been described above is the LED 1
The same can be said for the fourth side end surface tip side vicinity portion 17 (predetermined portion) in which 5d is arranged. Two LEDs 15 are arranged in the fourth side end surface tip side vicinity portion 17 or three or more LEDs 15 are arranged. The LEDs may be arranged.

Further, by using the optical fiber coupler shown in FIG. 5, light from a plurality of LEDs is combined into one optical fiber, and the output side end face of the optical fiber coupler is connected to one end face of the light guide. It may be configured. By using the optical fiber coupler, it becomes easy for the light emitted from the plurality of LEDs to enter one end surface of the light guide 5.

In the above embodiment, the LED 15c is arranged in the portion 16 (predetermined portion) near the tip end side of the third side end surface, and
LED 15d on the part 17 (predetermined part) near the tip of the side end face
Although the case where the LED 15c and the LED 15d are arranged is described as an example, both the LED 15c and the LED 15d may be arranged in either one of the third side end face tip side near portion 16 and the fourth side end face tip side near side portion 17. . Further, the predetermined portion described in claim 1 is not limited to the above-described third side end surface tip side near side portion 16 and fourth side end surface tip side near side portion 17, and other portions may be used.

In the above embodiment, the one end surface 5 of the light guide 5 is
LED 15a, 15c is made to correspond to a, and the other end surface 5
b is provided with LEDs 15b and 15d in association with each other, and the light guide 5
On the other hand, the case where light is incident through both end surfaces of the one end surface 5a and the other end surface 5b is taken as an example, but instead of this, only one end surface of the one end surface 5a and the other end surface 5b of the light guide 5 is provided. You may comprise so that LED may be provided correspondingly.
Further, in the above-mentioned embodiment, the so-called front light arranged on the front surface of the liquid crystal display element (reflection type liquid crystal display element) is taken as an example, but the present invention is not limited to this, and the liquid crystal display element (transmissive type or semi-transmissive type) It is also applicable to a so-called backlight arranged on the back surface of the liquid crystal device).

[0027]

According to the invention described in any one of claims 1 to 4, there is provided a plurality of point light sources corresponding to at least one of the end faces of the light guide. Therefore, it is possible to improve the brightness as compared with the related art in which one point light source is provided on the end surface of the light guide. At least one point light source of the plurality of point light sources is disposed in a predetermined portion separated from the light guide, and the point light source and the end surface of the light guide are disposed in the predetermined portion. Is connected by an optical fiber, and it is possible to reduce the volume of the part of the optical fiber on the light guide side by bending the optical fiber, etc., so that a large space is provided in the area facing the one end surface and the other end surface of the light guide. It is possible to improve the brightness without ensuring the above, and it is possible to suppress the increase in size of the device.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a planar lighting device according to an embodiment of the present invention.

FIG. 2 is a plan view schematically showing the planar lighting device of FIG.

FIG. 3 is a side view schematically showing the planar lighting device of FIG.

FIG. 4 is a diagram schematically showing an example in which a plurality of LEDs are provided in a predetermined portion.

FIG. 5 is a diagram schematically showing an optical fiber coupler in which a plurality of LEDs are connected to the input side.

FIG. 6 is an exploded perspective view showing an example of a conventional planar lighting device.

[Explanation of symbols]

1A planar lighting device 2 transparent substrate 5 Light guide 15a, 15b, 15c, 15d LED (point light source) 16 Part near the tip side of the third side end face (predetermined part) 17 Part near the tip side of the fourth side end face (predetermined part) 18 1st optical fiber (optical fiber) 19 Second optical fiber (optical fiber)

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) // F21Y 101: 02 F21Y 101: 02 F term (reference) 2H091 FA23Z FA24Z FA45Z LA11 LA16 LA17 5G435 AA03

Claims (4)

[Claims] 1. A rod-shaped light guide is arranged close to a side end surface of a transparent substrate made of a light-transmissive material, and a plurality of dot-shaped light guides corresponding to at least one of the end surfaces of the light guide. In a planar lighting device having a light source, at least one point light source among the plurality of point light sources is arranged in a predetermined portion separated from the light guide, and the point light source is arranged in the predetermined portion. A planar lighting device characterized in that the end face of the light guide is connected by an optical fiber. 2. The structure according to claim 1, wherein the optical fiber is curved in the vicinity of one end connected to the light guide, and the other end extends toward the predetermined portion side, and the optical fiber extends from one end of the optical fiber. A planar illumination device, wherein the volume up to the curved portion is smaller than the volume of the point light source. 3. The planar illumination device according to claim 1 or 2, wherein the point light sources arranged in the predetermined portion are two or more. 4. The structure according to claim 3, wherein two or more point light sources arranged in the predetermined portion are connected to an input end of an optical fiber coupler, and an output end of the optical fiber coupler is connected to the light guide body. A planar lighting device characterized by being connected to an end face.