JP2008098190A - Surface light source device - Google Patents

Abstract

A surface light source device according to the present invention can easily realize a desired light distribution.
A surface light source device according to the present invention includes a light incident surface 11 on which light is incident and a light emitting surface 12 that is formed substantially orthogonal to the light incident surface 11 and emits light from the light incident surface 11. A light plate 10 and a plurality of LEDs 20 that are provided opposite to the light incident surface 11 and have anisotropy in the light distribution are provided, and at least one LED 20 has an arrangement direction of 90 degrees with respect to the other LEDs 20. They are arranged differently, and the spread of light on a plane parallel to the emission surface 12 is different from that of the other LEDs 20.
[Selection] Figure 1

Description

  The present invention provides a light guide plate having a light incident surface and an output surface formed substantially orthogonal to the light incident surface, and is provided to face the light incident surface and has anisotropy in the light distribution. The present invention relates to a surface light source device including a plurality of light sources.

  Conventionally, as a surface light source device, light emitted from a plurality of LEDs, which are light emitting diodes, is incident from the light incident surface of the light guide plate, and the incident light propagates while totally reflecting inside the light guide plate. After being scattered by the dot pattern provided on the front and back surfaces of the light guide plate, it is emitted from the surface of the light guide plate, and the emitted light is irradiated from the back surface of the display plate to display the design on the display plate. (See Patent Document 1).

Japanese Patent Application Laid-Open No. 8-160892

  In the conventional surface light source device configured in this way, since a plurality of LEDs are arranged in the same direction, the light distribution distributed to the display panel depends on the light distribution of the LEDs themselves, which is necessary. However, it is not always possible to cope with the distribution of light distribution, and for that purpose, an LED having the distribution of light distribution for that purpose is required, and there is a problem that the price increases.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a surface light source device capable of irradiating light with a desired light distribution on a display panel.

  A surface light source device according to the present invention includes a light guide plate having a light incident surface on which light is incident and an output surface that is formed substantially orthogonal to the light incident surface and emits light from the light incident surface; A surface light source device provided with a plurality of light sources provided opposite to each other and having anisotropy in a light distribution, wherein at least one of the light sources is arranged at 90 degrees with respect to other light sources. The spread of the light in a plane parallel to the emission surface is different from that of other light sources.

  According to the surface light source device according to the present invention, the display plate can be irradiated with light having a desired light distribution.

Embodiment 1 FIG.
1 is an exploded perspective view of a surface light source device 1 according to Embodiment 1 of the present invention, FIG. 2 is a layout diagram of LEDs 20 in FIG. 1, FIG. 3 is a light distribution diagram of LEDs 20 in FIG. It is a figure for demonstrating 1 optical path.
The surface light source device 1 includes a light guide plate 10 having a light incident surface 11, an output surface 12, and a counter light exit surface 13, a light emitting diode 20 (hereinafter abbreviated as LED) facing the light incident surface 11, and the LED 20. Are mounted on the LED substrate 30, the reflector 40 having a U-shaped cross section surrounding the LED substrate 30, the optical sheet 50 in contact with the emission surface 12, and the reflection sheet 60 in contact with the non-emission surface 13. I have.

The light guide plate 10 is made of a transparent acrylic resin, and a light diffusing portion that scatters light is formed on the emission surface 12. This diffusing portion is composed of a dot pattern. The light guide plate 10 may be a transparent polycarbonate resin. Further, the diffusing portion may be composed of a random rough surface or a minute spherical surface.
As shown in FIG. 2, the LEDs 20 on the LED substrate 30 are fixed in the disposition directions that differ by approximately 90 ° between adjacent LEDs 20.
The reflector 40 is made of a silver or white material having a high reflectivity so that light emitted from the LED 20 is efficiently incident on the light guide plate 10. Specifically, it is desirable to use a material having a reflectance of 70% or more, more preferably 90% or more.
The optical sheet 50 has at least one direction of the prism row 51 on the surface facing the emission surface 12 of the light guide plate 10, and the ridge line direction of the prism row 51 is substantially parallel to the light incident surface 11 of the light guide plate 10.
The reflection sheet 60 is made of a silver or white material having a high reflectivity so that the light emitted from the non-emission surface 13 of the light guide plate 10 is efficiently re-incident on the light guide plate 10. Specifically, it is desirable to use a material having a reflectance of 70% or more, more preferably 90% or more.

  The LED 20 has a light distribution characteristic as shown in FIG. The light-emitting distribution of the bowl-shaped LED 20 differs between the xy plane and the yz plane. As is clear from this figure, on the xy plane, the light intensity becomes extremely low when it exceeds + 60 ° and −60 ° with the origin on the y-axis as the base point. On the yz plane, when the origin on the y-axis is the base point and exceeds + 30 ° and −30 °, the light intensity becomes extremely low. For example, NSSX440 series manufactured by Nichia Corporation is used as the LED 20.

Next, the operation of the surface light source device 1 configured as described above will be described with reference to FIG.
The light beam 80 emitted from the LED 20 is incident on the light guide plate 10 directly or after being reflected by the LED substrate 30 and the reflector 40 from the light incident surface 11 of the light guide plate 10. The incident light propagates while being totally reflected inside the light guide plate 10. During this propagation, the light scattered by the diffusion portion provided on the emission surface 12 is emitted from the emission surface 12. A part of the light is emitted from the opposite exit surface 13 of the light guide plate 10, but is emitted from the exit surface 12 after being returned to the light guide plate 10 by the reflection sheet 60. The light A emitted from the emission surface 12 of the light guide plate 10 is incident from one surface constituting the prism row 51 of the optical sheet 50, totally reflected by the adjacent surfaces, and emitted from the upper surface of the optical sheet 50.

  As described above, in this embodiment, the optical sheet 50 is inclined with respect to the emission surface 12 in a plane perpendicular to the light incident surface 11 and the emission surface 12 of the light guide plate 10 (the yz plane in FIG. 1). Direction light (A in FIG. 4) can be emitted by being deflected in a direction perpendicular to the emission surface 12 by the prism row 51 and is perpendicular to the light incident surface 11 and the emission surface 12 of the light guide plate 10. A surface light source device having an arbitrary light distribution in the plane (the yz plane in FIG. 1) can be obtained.

Further, the spread of the light emitted from the light guide plate 10 in a plane parallel to the light incident surface 11 (xy plane in FIG. 1) is a plane parallel to the light output surface 12 propagating through the light guide plate 10 (in FIG. 1). xz plane), that is, the spread of the plane parallel to the emission surface 12 of the emitted light of the LED 20.
In this embodiment, a plane parallel to the light incident surface 11 of the light guide plate 10 is changed by changing the direction of arrangement of every other general-purpose LED 20 having anisotropy with respect to the light distribution (90 °) (FIG. 1). The light distribution is also adjusted in the xy plane).

  In addition, by making the ridge line direction of the prism row 51 perpendicular to the light incident surface 11 of the light guide plate 10, a plane parallel to the light incident surface 11 of the light guide plate 10 and perpendicular to the light emission surface 12 (see FIG. It is also possible to obtain a surface light source device having an arbitrary light distribution in the xy plane in FIG.

Reference Example 1
5 is an exploded perspective view of the display device according to the first embodiment of the present invention, FIG. 6A is an enlarged plan view of the vicinity of the light incident surface of the light guide plate 15 in FIG. 5, and FIG. 7 is the display plate 70 and the LED 20 in FIG. FIG. 8 is a layout diagram of the LEDs 20 in FIG.
This display device is configured by superimposing a display plate 70 on the optical sheet 50 of the surface light source device 1.
On the light incident surface 16 of the light guide plate 15, a prism row 52 whose ridge line direction is the thickness direction is formed. The display board 70 is made of a transparent acrylic resin and is provided on one of a surface facing the surface light source device 1 (hereinafter referred to as a back surface) or a surface far from the surface light source device 1 (hereinafter referred to as a front surface). The pattern is provided by screen printing or cutting sheet. In addition, you may make it provide a pattern in both surfaces. Further, the display board may be a polycarbonate resin, transparent glass, or a diffuse transmission board.
In this example, the display board 70 is a symbol used for an escape exit guide light, and the hatched portion is printed in green.

Next, the operation of the display device having the above configuration will be described.
The light beam 80 emitted from the LED 20 is incident on the light guide plate 15 directly or after being reflected by the LED substrate 30 and the reflector 40 from the light incident surface 16 of the light guide plate 15. At this time, since the prism array 52 is provided on the light incident surface 16, the spread of the surface parallel to the light emission surface 17 of the light propagating through the light guide plate 15 is the light incident surface 16 shown in FIG. Is wider than that of a mirror surface.
The propagation in the light guide plate 15 and the operation of the optical sheet 50 after entering light are the same as those shown in the first embodiment, and the description thereof is omitted.

In this example, the light emitted from the surface light source device 1 illuminates the display board 70 from the back, and transmits information on the display board 70 to an observer located in front of the display board 70.
Here, as shown in FIG. 7, when the display plate 70 is divided into three region portions A, B, and C by a broken line 90 perpendicular to the light incident surface 16 of the light guide plate 15, the transmittance of the region portion B becomes the region portion. Higher than the transmittance of A and C.
As shown in FIG. 3, the LED 20 has anisotropy with different light distributions in the xy plane and the yz plane, and as shown in FIG. The arrangement direction of the LEDs 20 is different on the extension, and the light distribution distribution of the LEDs 20 positioned on the extension of the area portions A and C is almost equal to the light distribution distribution of the LED 20 positioned on the extension of the area portion B. The arrangement direction is such that the spread of parallel planes (that is, the xz plane in FIG. 5) increases. For this reason, the light from the LED 20 positioned on the extension of the area portions A and C reaches the area B having a large spread and high transmittance, and is emitted from the display panel 70 with a wide light distribution.
On the other hand, the light from the LED 20 located on the extension of the region B is limited in its spread, and is efficiently emitted from the region B having a high transmittance with a light distribution that is arranged in the front direction.

The light distribution in a plane parallel to the light incident surface 16 of the light guide plate 15 obtained by this display device (that is, the xz plane in FIG. 5) is indicated by a solid line in FIG.
9 is an angle from the front (that is, the y-axis in FIG. 5).
As a comparative example, the light distribution in the arrangement of the LED 20 shown in FIG. 10A is a thin line in the drawing, the light distribution in the arrangement of the LED 20 shown in FIG. 10B is a dotted line in the drawing, and ) The light distribution of the evacuation exit guide light determined by the Japan Lighting Equipment Manufacturers Association standard (abbreviated as JIL standard) is indicated by a one-dot chain line in the figure.
As can be seen from FIG. 9, by arranging the LEDs 20 as shown in FIG. 8, the exit guidance is high in brightness in the front (θ = 0 [degree]), wide light distribution and good visibility. A display device suitable for a lamp can be obtained.

Although the surface light source device 1 in which the LEDs 20 are arranged in a row has been described in the first embodiment and the reference example 1, the arrangement position and the number of the LEDs 20 are not limited to this, and for example, the LEDs are arranged in a plurality of rows. May be.
Moreover, although the diffusion part is formed in the output surface 12 of the light-guide plate 10, it is not limited to this, The diffusion part is formed in both surfaces of the anti-output surface 13 or the output surface 12 and the anti-output surface 13 May be.
The optical sheet 50 has a unidirectional prism row 51 on the surface facing the light emission surfaces 12 and 17 of the light guide plates 10 and 15, and the ridge line direction of the prism row 51 is the light incident surface 11 of the light guide plates 10 and 15. , 16 is used, but the optical sheet 50 is not limited to this, and a sheet or a diffusion sheet having a prism row on the surface far from the light guide plate, or a combination of a plurality of optical sheets. May be used.
Moreover, although LED which has anisotropy in light distribution as a light source was demonstrated, of course, it is not limited to this, For example, a laser diode may be sufficient.
In Reference Example 1, the display board 70 printed with the design used for the escape exit guide light is used as the display board 70. However, the display board 70 is not limited to this and is not limited to this. A changeable liquid crystal panel or the like may be used.

  As described above, according to the surface light source device of the present invention, a light guide surface having a light incident surface on which light is incident and a light exit surface that is formed substantially orthogonal to the light incident surface and emits light from the light incident surface. An optical plate and a plurality of light sources provided opposite to the light incident surface and having anisotropy in a light distribution, wherein at least one of the light sources is arranged with another light source. Are arranged 90 degrees different from each other, and the spread of the light in a plane parallel to the emission surface is different from that of other light sources, so that a desired light distribution can be easily realized.

  Further, according to this display device, the display plate has a region portion divided into a plurality of boundaries by a boundary line parallel to the normal line of the light incident surface of the light guide plate, and the other region portion among the region portions. Compared with the light distribution of the light source corresponding to the region part with high transmittance, the light distribution distribution of the light source corresponding to the region part with low transmittance is parallel to the exit surface of the light guide plate. Since the arrangement direction of the light sources is determined so that the spread of the surface becomes large, a display device with high front luminance, wide light distribution, and high visibility can be obtained.

2 is an exploded perspective view of the surface light source device in Embodiment 1. FIG. FIG. 2 is a layout diagram of LEDs in FIG. 1. It is a figure which shows the light distribution of LED of FIG. It is a figure for demonstrating the optical path of the surface light source device of FIG. 10 is an exploded perspective view of a display device in Reference Example 1. FIG. (A) is a principal part top view of FIG. 5, (b) is a top view which shows the example different from (a). It is a figure which shows the relationship between the display board of FIG. 5, and LED. FIG. 6 is a layout view of LEDs in FIG. 5. It is a figure which shows the light distribution of the display apparatus in the reference example 1. FIG. (A), (b) is the arrangement | positioning drawing of each LED in the comparative example of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Surface light source device, 10, 15 Light guide plate, 11, 16 Light-incidence surface, 12, 17 Output surface, 20 LED (light source), 30 LED board, 50 Optical sheet, 51,52 Prism row | line | column, 70 Display board.

Claims (2)

A light guide plate having a light incident surface on which light is incident and a light exit surface that is formed substantially orthogonal to the light incident surface and emits light from the light incident surface; A surface light source device comprising a plurality of light sources having anisotropy in light distribution,
The arrangement direction of at least one of the light sources is changed by 90 degrees with respect to the other light sources, and the spread of the light in a plane parallel to the emission surface is different from the other light sources. A surface light source device.   An optical sheet through which the light emitted from the emission surface is transmitted is disposed on the emission surface of the light guide plate, and a ridge line is arranged in a direction substantially parallel to the light incident surface and substantially parallel to the surface of the optical sheet. 2. The surface light source device according to claim 1, wherein a prism row extending in at least one of the vertical directions is formed.

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