JP2000098384A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device capable of improving light brightness coming out from a light emitting surface of a light guiding plate, i.e., luminance even in a case using the same light source as conventional one while removing a part being not effectively reflected by a reflector of light emitted from a light source arranged along the side end face of the light guiding plate. SOLUTION: In this device 10, a light source 12 arranged at the side end part of a light transmission plate 11, in which one surface is made a light emitting surface 11b and a light incident scattering reflection means is provided, and the light source 12 covered with a reflector 13 so that light emitted from the light source 12 is entered to inside of the light transmission plate 11 from an end face of a side end part. Where, the reflector 13 is provided with at least one parallel light reflection step 15 formed on a miller face part of the reflector 13 so as to reflect light from the light source 12, which is emitted from within a certain angle range centering a virtual axis line 14 being nearly parallel with the light emitting surface normal line 17 of the light transmission plate 11 with passing through the center of the light source 12, in a direction avoiding the 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. A light scattering / reflecting structure 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.

To explain this point in detail, in the conventional surface light source device, as shown in FIG. 7, a tubular light source 2 is arranged along one side end surface 1a of the light guide plate 1, and the tubular light source 2 emits light. A reflector 3 having a U-shaped cross section was provided so as to cover the tubular light source 2 so that light was effectively made to enter the inside from one side end surface 1a which is the incident end surface of the light guide plate 1.

However, as shown in FIG. 7, the light passes through the center of the tubular light source 2 and is within a certain angle range around the virtual axis 4 substantially parallel to the normal 17 of the light exit surface of the light guide plate 1 (FIG. 7). The light emitted from the fan-shaped area 5) indicated by hatching in FIG. 5 is reflected on the mirror surface of the reflector 3, but the reflected light is
And does not face the light guide plate 1. That is, the light guide plate 1
When the direction toward the one end surface 1a is the front side of the tubular light source 2, light within a certain angle range from the left and right sides of the tubular light source 2 is lost light that is not effectively used as the surface light source.

An object of the present invention is to solve such a conventional problem, and eliminates a portion where light emitted from a light source disposed along a side end surface of a light guide plate is not effectively reflected by a reflector. Accordingly, it is an object of the present invention to provide a surface light source device capable of improving the brightness of light emitted from the light exit surface of the light guide plate, that is, the luminance, even when the same light source as the conventional one is used.

[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 comprises a light guide plate having one surface serving as a light exit surface and provided with incident light scattering means, a light source provided at a side end of the light guide plate, and a light source emitted from the light source. A reflector for covering the light source so that the light to be incident on the inside of the light guide plate from the end face of the side end portion, wherein the reflector passes through the center of the light source and is substantially parallel to the light exit surface normal of the light guide plate. At least one parallel light reflecting means formed on a mirror surface of the reflector so as to reflect light from a light source coming out of a certain angle range centered on the light source in a direction avoiding 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. The specific component is that the light source comprises a tubular light source extending along the side end of the light guide plate, and the parallel light reflecting means comprises at least one groove or convex ridge extending in the longitudinal direction of the reflector. The groove or the ridge is formed of a two-sided mirror formed by two reflection surfaces provided at a specific inclination angle with respect to the one surface of the light guide plate.

In the surface light source device according to the present invention, the diameter of the tubular light source is d, the length of the first reflecting surface constituting the dihedral mirror portion is a, and the length of the second reflecting surface is b. And the angle formed by the second reflection surface, which mainly reflects light rays from the light source in the direction of the side end surface of the light guide plate, with one surface of the light guide plate is given by: a + b = d / 2 to 2d a: b = 1: 1.5 to 1: ∞ θ = 10 to 40 degrees.

Further, in the surface light source device of the present invention, 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 the surface side facing the light emission surface. It is also preferable to configure. In this case, foamed PET, a silver evaporated film, or the like can be used as the reflection plate.

According to the surface light source device of the present invention having such features, light that exits within a certain angle range centered on an imaginary axis substantially parallel to the side end face of the light guide plate through the center of the light source is reflected. The light is reflected in a direction avoiding the light source by the parallel light reflecting means formed in the first direction.

Thus, in this type of conventional surface light source device, light within a certain angle range from the left and right sides of the light source, which hardly contributes to the brightness of the light emitted from the light exit surface of the light guide plate. (Light rays within a certain angle range that is emitted in a direction substantially parallel to the side end surface of the light guide plate) can be effectively used. A surface light source device with 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 11a of the light guide plate 11, a reflector or reflector 13 typified by a U-shaped cross section is attached so as to cover the tubular light source 12, and the direct light from the tubular light source 12 and the light reflected by the reflector 13 are reflected. The reflected light is incident on the light guide plate 11 from one side end surface 11a which is a light incident end surface. At least the inner surface of the reflector 13 is mirror-finished with a regular reflection material having a reflectance of 90% or more, for example, silver, aluminum or the like.

The light guide plate 11 is a thin plate having a square shape.
One surface, which is the upper surface in FIG. 1, is a light emitting surface 11b for emitting light, and the other surface (the lower surface in FIG. 1) on the opposite side is a surface 11c facing the light emitting surface. is there. 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.

The reflector 13 having a U-shaped cross section for reflecting the light emitted from the tubular light source 12 and entering the light guide plate 11 substantially passes through the center of the tubular light source 12 and is substantially perpendicular to the light exit surface normal 17 of the light guide plate 11. A parallel light reflecting means 15 is provided on the mirror surface in the direction of the parallel virtual axis 14.
As shown in FIG. 1, the parallel light reflecting means 15 is provided on one side of the light guide plate 11 so as to form a groove having a horizontal V-shaped cross section, that is, a triangular cross section, extending along the tubular light source 12 inside the reflector 13. 2 composed of two reflecting surfaces 16a and 16b provided at a specific inclination angle with respect to the surface 11b
It is composed of a plane mirror portion 16.

The two-sided mirror portion 16 is defined under the following conditions. That is, as shown in FIG. 1, the diameter of the tubular light source 12 is d, the length of the first reflecting surface 16a constituting the dihedral mirror portion 16 is a, and the length of the second reflecting surface 16b is b. The light from the tubular light source 12 is mainly
A + b = d / 2 to 2d, preferably 2d / 3 to d, where the angle formed by the second reflection surface 17b reflecting in the direction of the side end surface 11a of the first light guide plate 11 with the one surface 11b of the light guide plate 11 is θ. : B = 1: 1.5 to 1: ∞, preferably a: b = 1:
2-1: 5, θ = 10-40 degrees, preferably 20-35 degrees.

As described above, the virtual axis 1 substantially parallel to the one end face 11a of the light guide plate 11 through the center of the tubular light source 12
By providing parallel light reflecting means comprising a two-sided mirror part 16 so as to form a triangular groove in the mirror part of the reflector 13 in the extension direction of the light guide plate 11, the light guide plate 11 passes through the center of the tubular light source 12. Light rays exiting within a certain angle range about an imaginary axis 14 substantially parallel to the light output surface normal 17 are reflected by the first and second reflection surfaces 16a, 16b of the two-sided mirror portion 16 formed on the reflector 13. Is reflected in a direction avoiding the light source.

As a result, in the conventional surface light source device of this type, the light emitted from the light exit surface of the light guide plate hardly contributes to the brightness of the light source. Since light (light within a certain angle range that is emitted in a direction substantially parallel to one end surface 11a of the light guide plate 11) can be used effectively, the reflector 13
By slightly modifying the mirror surface portion, the brightness of the surface light source device can be further increased while maintaining the performance of the conventional tubular light source.

The surface light source device 10 according to this embodiment
In this case, the reflector 13 is constituted only by a planar shape and does not include a curved surface, so that it is easy to process, and as a result, is suitable for mass production.

FIG. 2 shows a surface light source device 20 according to another embodiment of the present invention. The surface light source device 20 according to 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 passes through the center of the tubular light source 12 and passes through the light guide plate 11.
And a parallel light reflecting means 22 formed on a mirror portion in a direction of a virtual axis 14 substantially parallel to the one side end face 11a.

As shown in FIG. 1, the parallel light reflecting means 22 are arranged inside the reflector 21 so as to form grooves having a horizontal V-shaped cross section, that is, a triangular cross section, extending along the tubular light source 12. Three two-sided mirror parts 2 provided
3, 24, and 25. Each of these dihedral mirror portions 23, 24, 25 is formed by two reflecting surfaces 23a, 23b, 24a, 24b, 25a, 25b provided at a specific inclination angle with respect to one surface 11b of the light guide plate 11. It is configured.

These two-sided mirror parts 23, 24, 25
It is defined under the following conditions. That is, as shown in FIG. 3, the diameter of the tubular light source 12 is d, and each dihedral mirror portion 2
First reflecting surface 23 constituting each of 3, 24 and 25
The lengths of a, 24a, and 25a are a1, a2, a3, and second, respectively.
The lengths of the reflecting surfaces 23b, 24b, 25b are denoted by b1, b
2, b3, and the light from the tubular light source 12 is mainly
A second reflecting surface 23b reflecting in the direction of the first side end surface 11a,
When the angles formed by 24b and 25b with one surface 11b of the light guide plate 11 are θ1, θ2 and θ3, a1: b
1, a2: b2 and a3: b3 are 1: 1.
5-1: ∞, preferably a1: b1 = 1: 2-1: 5,
Where θ1, θ2, and θ3 are each 10 to 40 degrees,
Preferably in an angle range of 20 to 35 degrees, θ1 ≦ θ
2 ≦ θ3.

The surface light source device 20 of this embodiment is substantially the same as the surface light source device 10 shown in FIG. 1 except that the reflector 21 has the parallel light reflecting means 22 having such a configuration. is there. Therefore, in FIGS. 2 and 3 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.

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 left and right sides of the light source 2 can be effectively used, by slightly modifying the reflector, the performance of the conventional tubular light source can be maintained and the surface light source device can be used. Brightness can be increased.

The surface light source device 1 according to each of the embodiments described above.
At 0 and 20, the parallel light reflecting means 15 and 22 are connected to the tubular light source 1.
Although the reflectors are provided on the reflector mirror portions located on the left and right sides of FIG. 2, they may be provided on only one side as shown in FIG.

The cross-sectional shape of the one end face 11a on which the light from the tubular light source enters does not need to be parallel to the normal 17 of the light exit surface, and is shown in FIGS. 4, 5 and 6. Such a triangular shape, a tapered surface shape, a convex curved surface shape, or the like can be used. In addition, as compared with the configuration of the surface light source device 10, the addition of the parallel light reflecting means makes it possible to suppress an increase in the amount of protrusion of the reflector portion. It also has a feature that it is possible to provide an integrated liquid crystal display device.

[0029]

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 having a + b = 3.0 mm and θ = 25 degrees was formed.

Further, a triangular prism array having a vertical angle of 63 degrees and a pitch width of 150 μm is formed on one side on the light emitting surface 11b, and the other surface has a vertex crossing 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.

The side of the double-sided prism sheet was set so that the side having a vertical angle of 63 degrees faced the light emitting surface side, and the generatrix of the prism array having a vertical angle of 63 degrees was parallel to the cold-cathode tube light source. Also, Ag is provided on the surface 11c facing the light emitting surface.
A reflective film made of a vapor-deposited film was installed to obtain a surface light source device. When arranging the light guide plate, a dot pattern made of white ink is applied to the surface 11 facing the light emitting surface.
The study was conducted such that the dot pattern formed of the rough surface was on the light emitting surface 11b side so as to be on the c side, in other words.

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 a light source direction reflection avoiding means, a ₁ + b ₁ = a ₂ + b ₂ = a ₃ + b ₃ = 1. 0mm,
The emission luminance value was measured in the same manner as in Example 1, except that the light source direction reflection avoiding means of θ ₁ = θ ₂ = θ ₃ = 25 degrees 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.

[0037]

[Table 1]

[0038]

As described above, according to the surface light source device of the present invention, the light source exiting from a certain angle range centered on a virtual axis substantially parallel to the side end face of the light guide plate through the center of the light source. In this type of conventional surface light source device, at least one parallel light reflecting means is formed on the mirror surface of the reflector so as to reflect light from the light source in a direction avoiding the light source.
Light within a certain angle range from the left and right sides of the tubular light source, which hardly contributes to the brightness of the light emitted from the light exit surface of the light guide plate (exit in a direction substantially parallel to the light exit surface normal of the light guide plate) (Light rays within a certain angle range) can be effectively used. Therefore, by slightly modifying the mirror surface of the reflector, the brightness of the surface light source device can be increased while maintaining the performance of the conventional tubular light source. Can be.

[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 cross-sectional view showing a part of the surface light source device shown in FIG. 2 in an enlarged manner.

FIG. 4 is a schematic cross-sectional view of a surface light source device according to another embodiment of the present invention, illustrating another cross-sectional shape of one end surface of a light guide plate on which light from a tubular light source is incident.

FIG. 5 is a schematic cross-sectional view of a surface light source device according to another embodiment of the present invention, illustrating another cross-sectional shape of one end surface of the light guide plate on which light from the tubular light source enters.

FIG. 6 is a schematic cross-sectional view of a surface light source device according to still another embodiment of the present invention, illustrating another cross-sectional shape of one end surface of the light guide plate on which light from the tubular light source is incident.

FIG. 7 is a schematic sectional view showing a main part of a conventional surface light source device.

[Explanation of symbols]

 10, 20 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 reflector 14 virtual axis 15 parallel light reflecting means 16 two-sided mirror Portion 16a First reflection surface 16b Second reflection surface 17 Light emission surface normal of light guide plate 22 Parallel light reflection means 23, 24, 25 Double-sided mirror portion 23a First reflection surface 23b Second reflection surface 24a 1st reflective surface 24b 2nd reflective surface 25a 1st reflective surface 25b 2nd reflective surface

Claims (5)

[Claims] 1. A light guide plate having one surface serving as a light exit surface and provided with incident light scattering means, a light source provided at a side end of the light guide plate, and a light emitted from the light source being transmitted to the side. A reflector covering the light source so as to be incident on the inside of the light guide plate from an end face of an end, wherein the reflector passes through the center of the light source and is substantially parallel to a light exit surface normal of the light guide plate. At least one parallel light reflecting means formed on a mirror portion of the reflector so as to reflect light from the light source coming out of an angle range around the light source in a direction avoiding the light source. Surface light source device. 2. A light source comprising a tubular light source extending along a side edge of the light guide plate, wherein the parallel light reflecting means forms a V-shaped groove extending along the tubular light source. 2. The light guide plate according to claim 1, further comprising at least one dihedral mirror portion formed by two reflection surfaces provided at a specific inclination angle with respect to the one surface of the light guide plate. 3. Surface light source device. 3. A light source from the light source, wherein a diameter of the tubular light source is d, a length of a first reflecting surface forming the dihedral mirror portion is a, and a length of a second reflecting surface is b. When an angle formed by a second reflection surface that mainly reflects the light guide plate toward the side end surface and one surface of the light guide plate is θ, a + b = d / 2 to 2d a: b = 1: 1 The surface light source device according to claim 2, wherein the angle is in the range of 0.5 to 1: ?? 4. The parallel light reflecting means is constituted by arranging a two-sided mirror portion formed by two reflecting surfaces provided at a specific inclination angle with respect to the one surface of the light guide plate, As the angle formed by the second reflection surface of each of the two-sided mirror portions, which mainly reflects the light rays from the light source in the direction of the side end surface of the light guide plate, with one surface of the light guide plate, increases as the distance from the light guide plate increases The surface light source device according to claim 2, wherein the surface light source device is gradually increased. 5. 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 a surface side facing the light emitting surface. The surface light source device according to claim 1, wherein: