JP2000067627A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device capable of improving the brightness of a light emitted from the light emission face of a light guide plate, even when the same light source as usual is used, by eliminating a portion where the light emitted from the light source arranged along the side end face of the light guide plate is not effectively used. SOLUTION: A tubular light source 12 is arranged on one side end face 11a of a light guide plate 11 having a light emission face 11b on one surface and an incident light scattering and reflecting means 11c on the other surface, a reflector 13 is arranged covering the tubular light source 12 in order to make incident a light emitted from the tubular light source 12 from one side end face 11a on the inside of the light guide plate 11 and a light source direction reflection avoiding means 15, (22 or 32) is formed on the specular portion of the reflector 13 located on a virtual axis 14 almost perpendicular to the one side end face 11a of the light guide plate 11 through the center of the tubular light source 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface light source device,
More specifically, the present invention relates to a surface light source device that can be used for various surface light sources such as a liquid crystal backlight, a lighting signboard, and a lighting body.

[0002]

2. Description of the Related Art Conventionally, a surface light source device used for various surface light sources typically includes a light-transmitting substrate, that is, a light guide plate, and one end of the light guide plate, that is, an end surface of a light incident end. A light source composed of, for example, a tubular light source installed in parallel, and a light source emitted from this light source is effectively made to enter the inside of the light guide plate from one side end surface thereof, so that a U-shaped or U-shaped cross section is provided to cover the light source. And the like.

In this type of conventional surface light source device, the direct light emitted from the light source and the reflected light reflected by the reflector enter the inside from the incident side end face of the light guide plate and exit from the light exit surface. Further, as described above, the light that has entered the inside from the light incident side end face of the light guide plate exits from one surface, which is the light exit surface. However, the incident light is controlled in order to control the amount of the emitted light and make the luminance distribution uniform. Light scattering / reflecting means is provided.

[0004]

However, in the conventional surface light source device, there is a portion where the light emitted from the tubular light source is not effectively used by the reflector, and as a result, the electric power supplied to the light source to obtain a necessary light amount is obtained. This increases the amount of battery, accelerates battery consumption, and limits the usable period of a portable personal computer or the like.

[0005] This point will be described taking a reflector having a U-shaped cross section as an example. In a conventional surface light source device, a tubular light source 2 is arranged along one side end surface 1a of a light guide plate 1 as shown in FIG. The reflector 3 is provided so as to cover the tubular light source 2 so that light emitted from the tubular light source 2 is effectively made to enter the inside from one side end surface 1a which is the incident end surface of the light guide plate 1.

[0006] However, as shown in FIG.
Is the light that is emitted toward the reflector side opposite to the one side end surface 1a, that is, the central light, and is centered on an imaginary axis 4 that passes through the center of the tubular light source 2 and is substantially perpendicular to the one side end surface 1a of the light guide plate 1. Although light emitted from within the angular range (the fan-shaped area 5 shown by oblique lines in FIG. 4) is reflected on the mirror surface of the reflector, the reflected light is blocked by the tubular light source 2 and does not go to the light guide plate 1.
That is, when the direction toward one side end surface 1a of the light guide plate 1 is the front side of the tubular light source 2, light within a certain angle range emitted from the back side of the tubular light source 2 is considered to be loss light that is not effectively used as a surface light source. Become.

SUMMARY OF THE INVENTION An object of the present invention is to solve such a conventional problem. When light emitted from a light source disposed along a side end face of a light guide plate is reflected by a reflector, the light source is provided with a light source. Provided is a surface light source device capable of improving the brightness of light emitted from the light exit surface of a light guide plate, that is, the luminance even when the same light source as in the related art is used so as to avoid a state where the light source cannot be effectively used due to being blocked. It is in.

[0008]

SUMMARY OF THE INVENTION The present invention is a surface light source device, and has the following configuration to solve the above-mentioned technical problem. That is, the surface light source device of the present invention is a light guide plate having one surface as a light exit surface and provided with incident light scattering / reflecting means, and a light source disposed at a side end of the light guide plate.
A reflector that covers the light source so that light emitted from the light source is incident on the inside of the light guide plate from the end face of the side end,
The light source direction reflection avoiding means is formed on a mirror surface portion of a reflector located on an imaginary axis substantially orthogonal to an end surface of a side end portion of the light guide plate through the center of the light source.

<Specific Configuration in the Present Invention> The surface light source device of the present invention is composed of the above-mentioned essential components, but is established even when the components are specifically as follows. Specifically, the light source comprises a tubular light source extending along the side end of the light guide plate, and the light source direction reflection avoiding means comprises at least one groove or projection extending in the longitudinal direction of the reflector. It is characterized by having.

The surface light source device according to the present invention is characterized in that the grooves and the projections constituting the light source direction reflection avoiding means are substantially triangular in cross section, wherein the diameter of the tubular light source is d.
When the length of the base of the triangular groove and the convex portion is a, d ≧ a, and the apex angle θ of the triangular groove and the convex portion in the range of 100 to 170 degrees is preferable. Is 2d / 3 ≧ a, and the apex angle θ of the groove and the protrusion having a triangular cross section is in the range of 120 to 160 degrees.

Further, in the surface light source device of the present invention, an element having a directional light emitting function is provided on the light emitting surface side of the light guide plate, and a reflecting plate is provided on the surface side facing the light emitting surface. It is also preferable to do so. In this case, foamed P
ET or a silver vapor-deposited film can be used.

According to the surface light source device of the present invention having such features, the light that is emitted toward the reflector side opposite to the one end face of the light guide plate, that is, the center light, passes through the center of the tubular light source, and Light that exits within a certain angle range centered on a virtual axis that is substantially perpendicular to the side end face is reflected in a direction that literally avoids reflection in the light source direction by light source direction reflection avoiding means formed in the reflector.

As a result, in this type of conventional surface light source device, light within a certain angle range emitted from the back side of the tubular light source hardly contributes to the brightness of the light emitted from the light exit surface of the light guide plate. (Center light within a certain angle range on the reflector side opposite to the side end face of the light guide plate) can be used effectively, so by making a slight modification to the reflector, the conventional light source can be used. Thus, a surface light source device with further increased luminance can be provided.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a surface light source device according to the present invention will be described in more detail with reference to an embodiment shown in the drawings. FIG. 1 shows a surface light source device 10 according to one embodiment of the present invention. The surface light source device 10 of this embodiment includes a substrate, that is, a light guide plate 11 made of a light-transmitting flat plate, and a tubular light source 12 on one end of the light guide plate 11 along the side end surface 11a.
Is installed.

At one end of the light guide plate 11, a reflector having a U-shaped cross section, ie, a reflector 13, is attached so as to cover the tubular light source 12, so that the direct light from the tubular light source 12 and the reflected light reflected by the reflector 13 are reflected. Are incident on the light guide plate 11 from the end face 11a of one side end which is the light incident end face.

The light guide plate 11 is, for example, a rectangular thin plate having a plate thickness of about 4 mm, and one surface, which is the upper surface in FIG. 1, is a light emission surface 11b for emitting light. The other surface on the side (the lower surface in FIG. 1) is a surface 11c facing the light emitting surface. The light guide plate 11 is provided with various incident light scattering / reflecting means as a mechanism for emitting incident light to the light exit surface side. Typical examples include a mode in which white ink or a rough surface is patterned in a dot shape, a mode in which light scattering fine particles are dispersed, and the like. However, in the present invention, this mechanism, that is, the incident light scattering / reflecting means is not particularly limited.

A reflector 13 having a U-shaped cross section, which reflects light emitted from the tubular light source 12 and enters the light guide plate 11, is used in this embodiment. There is provided a light source direction reflection avoiding means formed on a mirror portion located on a virtual axis 14 substantially orthogonal to the end face 11a. In the embodiment shown in FIG. 1, the light source direction reflection avoiding means is a groove 1 having a horizontal V-shaped cross section, that is, a triangular cross section extending along the tubular light source 12.
5.

The shape of the groove 15 is defined under the following conditions. That is, as shown in FIG.
Assuming that the length of the base of 5 is a and the diameter of the tubular light source 12 is d, d ≧ a, preferably 2d / 3 ≧ a, and the apex angle θ of the groove 15 is in the range of 100 to 170 degrees. In
Preferably it is in the range of 120 to 160 degrees.

As described above, the light source including the groove 15 having a triangular cross section is formed on the mirror surface of the reflector 13 located on the imaginary axis 14 which is substantially perpendicular to the one end face 11a of the light guide plate 11 through the center of the tubular light source 12. By providing the directional reflection avoiding means, the light emitted toward the reflector side opposite to the one end face 11a of the light guide plate 11, that is, the central light,
Through the center of the light guide plate 11, light that exits within a certain angle range about an imaginary axis 14 that is substantially orthogonal to the one end surface 11 a constitutes a groove 15 having a triangular cross section formed in the reflector 13. The light is reflected by the inclined surface 15a in a direction to avoid the light source.

As a result, in this type of conventional surface light source device, the light emitted from the light exit surface of the light guide plate hardly contributes to the brightness of the light source. Light (central light within a certain angle range that goes out on the reflector side opposite to the one end surface 11a of the light guide plate 11)
Avoids reflections that return in the direction of the tubular light source 12,
As a result, the center light described above can be used effectively, so that by slightly modifying the mirror surface of the reflector 13, the performance of the conventional tubular light source can be maintained.
Further, the brightness of the surface light source device can be increased.

In order to obtain more preferable characteristics as a surface light source device, an element having a directional light reflection function such as a micro prism array is disposed on the light emitting surface 11b side, and furthermore, a light emitting surface is provided. It is preferable to provide a reflecting plate made of foamed PET, a silver vapor-deposited film, or the like on the side of the surface 11c opposite to.

FIG. 2 shows a surface light source device 20 according to another embodiment of the present invention. The surface light source device 20 of this embodiment differs from the surface light source device 10 shown in FIG. 1 only in the structure of the reflector. That is, the reflector 21 constituting the surface light source device 20 is formed on a mirror surface portion located on an imaginary axis 14 which passes through the center of the tubular light source 12 and is substantially perpendicular to one end surface 11a of the light guide plate 11. A light source direction reflection avoiding means comprising a convex portion 22 having a V-shaped cross section, that is, a triangular cross section is provided.

In the surface light source device 20 of this embodiment, except that the reflector 31 includes the light source direction reflection avoiding means having such a configuration, the surface light source device 10 shown in FIG.
Is substantially the same as Therefore, in FIG. 2 showing the surface light source device 20, the same or corresponding components as those of the surface light source device 10 of FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted.

Also in the surface light source device 20 according to this embodiment, the shape of the convex portion 21 is defined under the following conditions. That is, as shown in FIG. 2, when the length of the base of the convex portion 21 is a and the diameter of the tubular light source 12 is d,
d ≧ a, preferably 2d / 3 ≧ a, and the vertex angle θ of the projection 21 is in the range of 100 to 170 degrees, preferably in the range of 120 to 160 degrees.

The surface light source device 20 according to such an embodiment
In the configuration of FIG. 1, the tubular light source 1 is similar to the surface light source device 10 of FIG.
Since light within a certain angle range emitted from the back surface side of the reflector 2 can be effectively used, the mirror surface of the reflector 13 is slightly modified to make the conventional tubular light source 1
With the performance of 2, the brightness of the surface light source device can be further increased.

FIG. 3 shows a surface light source device 30 according to another embodiment of the present invention. The surface light source device 30 according to this embodiment also differs from the surface light source device 10 shown in FIG. 1 only in the structure of the reflector. That is, the reflector 31 constituting the surface light source device 30 passes through the center of the tubular light source 12 and
A combination of a groove and a protrusion having a cross-sectional V-shape, that is, a triangular cross-section, formed on a mirror surface located on a virtual axis 14 substantially perpendicular to the one side end surface 11a, in other words, the cross-sectional shape is formed in a waveform. Light source direction reflection avoiding means including a zigzag portion 32 is provided.

The shape of the zigzag portion 32 is defined under the following conditions. That is, as shown in FIG. 3, when the entire length of the zigzag portion 32 is a and the diameter of the tubular light source 12 is d, d ≧ a, preferably 2d / 3.
≧ a, and the apex angle θ of each of the triangular cross sections constituting the zigzag portion 32 is in the range of 100 to 170 degrees, preferably in the range of 120 to 160 degrees. Further, in order to further increase the utilization efficiency of the center light, it is further preferable that the vertex angle θ of the triangular portion is gradually reduced as the distance from the virtual axis 14 increases.

In the surface light source device 30 of this embodiment, except that the reflector 31 includes the light source direction reflection avoiding means having such a configuration, the surface light source device 10 shown in FIG.
Is substantially the same as Therefore, in FIG. 3 showing the surface light source device 30, the same or corresponding components as those of the surface light source device 10 of FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted.

The surface light source device 30 according to such an embodiment
In the configuration of FIG. 1, the tubular light source 1 is similar to the surface light source device 10 of FIG.
Since light within a certain angle range emitted from the back surface side of the light source 2 can be effectively used, by slightly modifying the reflector 13, the performance of the conventional tubular light source is maintained, and the surface light source device is further improved. Brightness can be increased.

[0030]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. Example 1 A light guide plate having a size of 100 × 60 mm and a thickness of 4 mm was prepared by injection molding from a commercially available acrylic resin pellet (trade name: Acrypet, manufactured by Mitsubishi Rayon Co., Ltd.). Using a mold created so that the diameter of the convex part increases as the distance from the light incident part increases on one side surface of the light guide plate molding mold, the light scattering dots composed of a rough surface are set at a distance from the light source. Therefore, it was created so that the area became large. Note that the roughness Ra of the top surface of the convex portion is 0.5 μm (JIS
The arithmetic mean roughness Ra) of B0601 is 0.18 mm, and the interval between adjacent convex portions is 0.18 mm.

Further, a dot pattern of a white ink made of TiO ₂ was printed by a screen printing method with a pitch width of 0.5 mm so that the area also increased with the distance from the light source. The surface to be printed was the surface opposite to the surface on which the rough surface was engraved.

At the side end of the light guide plate thus prepared,
A cold-cathode tube light source having a tube diameter of 3 mm and a length of 100 mm is arranged. Around the periphery, a film having a reflectivity of 94% on which Ag is deposited is affixed to the inner surface.
It was covered with a reflector having a height of 0 mm and a height of 4 mm. As the light source direction reflection avoiding means according to the present invention, as shown in FIG. 1, a light source direction reflection avoiding means in which a (length of the base of the convex portion) = 1.5 mm and θ (vertex angle of the convex portion) = 160 degrees is used. Formed.

Further, a triangular prism array with a pitch angle of 63 degrees and a pitch width of 150 μm is formed on one side on the light emitting surface 11b, and on the other surface, a generatrix crosses the prism array at 90 degrees. A double-sided prism sheet on which a triangular prism array of the same pitch having an angle of 90 degrees was formed was provided.

With respect to the orientation of the double-sided prism sheet, the side having a vertical angle of 63 degrees faces the light emitting surface, and the generatrix of the prism array having a vertical angle of 63 degrees is parallel to the cold-cathode tube light source. Also, on the surface 11c facing the light emitting surface, A
g A reflective film made of a vapor-deposited film was installed to obtain a surface light source element. When arranging the light guide plate, the dot pattern made of white ink should be placed on the surface 1 facing the light emitting surface.
The study was performed such that the dot pattern formed of the rough surface was on the light emitting surface 11b side so as to be on the 1c side, in other words, on the light emitting surface 11b side.

The cold-cathode tube is turned on through an inverter as usual, and is 10 m from the incident light end face 11a of the surface light source element.
The emission light luminance values at m, 30 mm, and 50 mm were measured using a luminance meter (BM-7, manufactured by Topcom). Table 1 shows the results.

(Embodiment 2) As shown in FIG. 3, as a light source direction reflection avoiding means, a (base length of the convex portion) = 1.5 mm, θ (convex portion) composed of three triangular convex portions. The apex angle of the portion) = 160 degrees, and the emitted light luminance value was measured in the same manner as in Example 1 except that the light source direction reflection avoiding means was formed. Table 1 shows the results.

Comparative Example A measurement was performed in the same manner as in Example 1 except that the light source direction reflection avoiding means was not provided. Table 1 shows the results.

[0038]

[Table 1]

[0039]

As described above, according to the surface light source device of the present invention, the light source is provided on a part of the reflector located on a virtual axis passing through the center of the light source and substantially perpendicular to one end face of the light guide plate. With the provision of the directional reflection avoiding means, the conventional surface light source device of this type hardly contributes to the brightness of light emitted from the light exit surface of the light guide plate. Since the light within the range (center light within a certain angle range on the reflector side opposite to one end face of the light guide plate) can be used effectively, a slight modification to the mirror surface of the reflector is required. By doing so, the brightness of the surface light source device can be increased while maintaining the performance of the conventional tubular light source.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a main part of a surface light source device according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a main part of a surface light source device according to another embodiment of the present invention.

FIG. 3 is a schematic sectional view showing a main part of a surface light source device according to still another embodiment of the present invention.

FIG. 4 is a schematic sectional view showing a main part of a conventional surface light source device.

[Explanation of symbols]

 10, 20, 30 surface light source device 11 light guide plate 11a one side end surface (incident light side surface) 11b light emitting surface 11c surface facing light emitting surface 12 tubular light source 13, 21, 31 reflector 15 triangular groove (light source direction reflection) Avoidance means) 22 Triangular cross-section convex part (light source direction reflection avoidance means) 32 Zigzag section (light source direction reflection avoidance means)

Claims (7)

[Claims] 1. A light guide plate having one surface as a light emitting surface and provided with incident light scattering / reflecting means, a light source disposed at a side end of the light guide plate, and a light emitted from the light source being transmitted to the side. A reflector that covers the light source so as to be incident on the inside of the light guide plate from an end surface of the end portion, and is located on an imaginary axis that is substantially perpendicular to the end surface of the side end portion of the light guide plate through the center of the light source. A light source direction reflection avoiding means is formed on a mirror portion of the reflector. 2. The light source comprises a tubular light source extending along a side end of the light guide plate, and the light source direction reflection avoiding means includes at least one light source extending in a longitudinal direction of the reflector.
2. A structure comprising two grooves.
A surface light source device according to claim 1. 3. The light source comprises a tubular light source extending along a side end of the light guide plate, and the light source direction reflection avoiding means includes at least one light source extending in a longitudinal direction of the reflector.
2. The method according to claim 1, wherein the projection is formed of two projections.
A surface light source device according to claim 1. 4. The surface light source device according to claim 2, wherein the groove and the convex constituting the light source direction reflection avoiding means have a substantially triangular cross section. 5. When the diameter of the tubular light source is d and the length of the base of the groove and the protrusion having a triangular cross section is a, d ≧ a, and the groove and the protrusion having a triangular cross section are provided. The surface light source device according to claim 4, wherein the apex angle θ of the portion is in a range of 100 to 170 degrees. 6. When the diameter of the tubular light source is d, and the length of the base of the groove and the protrusion having a triangular cross section is a, 2d / 3 ≧ a, and the groove and the triangular cross section are provided. The surface light source device according to claim 4, wherein the apex angle θ of the convex portion is in a range of 120 to 160 degrees. 7. An element having a directional light emission function is provided on the light emission surface side of the light guide plate, and a reflection plate is provided on a surface side facing the light emission surface. The surface light source device according to claim 1, wherein: