JP2004265813A - Surface light source device and display 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 guide surface having a light incident surface, on which light is incident, and an output surface, formed substantially perpendicular to the light incident surface, for emitting light from the light incident surface. A light plate 10 and a plurality of LEDs 20 provided opposite to the light incident surface 11 and having anisotropic light distribution are provided, and at least one LED 20 is arranged in a different arrangement direction from other LEDs 20. The spread of light on a plane parallel to the emission surface 12 is different from that of the other LEDs 20.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a light guide plate having a light entrance surface and an exit surface formed substantially perpendicular to the light entrance surface, and is provided to face the light entrance surface and has anisotropic light distribution. The present invention relates to a surface light source device having a plurality of light sources and a display device provided with a display plate in the surface light source device.
[0002]
[Prior art]
Conventionally, as a surface light source device, light emitted from a plurality of LEDs, which are light emitting diodes, enters 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 a dot pattern provided on the front and back surfaces of the light guide plate, the light 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 a design on the display plate. (See Patent Document 1).
[0003]
[Patent Document 1]
JP-A-8-160892 [0004]
[Problems to be solved by the invention]
In the conventional surface light source device configured as described above, since a plurality of LEDs are arranged in the same direction, the distribution of light emitted to the display panel depends on the distribution of light of the LEDs themselves, which is necessary. However, it is not always possible to cope with such a light distribution, and for that purpose, an LED having a light distribution for the light distribution is required.
[0005]
An object of the present invention is to solve the above-described problems, and an object of the present invention is to provide a surface light source device that can irradiate a display panel with light having a desired light distribution.
[0006]
Another object is to obtain a display device with high luminance and high visibility.
[0007]
[Means for Solving the Problems]
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 exit surface formed substantially perpendicular to the light incident surface and emitting light from the light incident surface; A plurality of light sources provided opposite to each other and having anisotropy in light distribution, at least one of the light sources is arranged in a different arrangement direction from the other light sources, and is parallel to the emission surface. The spread of the light on the various surfaces is different from other light sources.
[0008]
Further, in the display device according to the present invention, the display plate has a region portion divided into a plurality of regions by a boundary line parallel to a normal line of the light incident surface of the light guide plate, and the other region region is included in the region region. The light distribution of the light source corresponding to the region portion having a low transmittance compared to the portion is compared with the light distribution of the light source corresponding to the region portion having a high transmittance, with respect to the emission surface of the light guide plate. The direction in which the light sources are arranged is determined so that the spread of the parallel planes becomes large.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
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 the LEDs 20 of FIG. 1, FIG. 3 is a light distribution diagram of the LEDs 20 of FIG. FIG. 3 is a diagram for explaining one optical path.
The surface light source device 1 includes a light guide plate 10 having a light entrance surface 11, an exit surface 12, and a light exit surface 13, a light emitting diode 20 (hereinafter, abbreviated as an LED) facing the light entrance surface 11, and an LED 20. The LED board 30 on which the LED board 30 is mounted, the reflector 40 having a U-shaped cross section surrounding the LED board 30, the optical sheet 50 in contact with the emission surface 12, and the reflection sheet 60 in contact with the anti-emission surface 13 Have.
[0010]
The light guide plate 10 is made of a transparent acrylic resin, and a diffusion portion for scattering light is formed on the emission surface 12. This diffusion section is constituted by a dot pattern. The light guide plate 10 may be made of a transparent polycarbonate resin. Further, the diffusing portion may be constituted by 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 adjacent LEDs 20 in directions different from each other by approximately 90 °.
The reflector 40 is made of a silver or white material having a high reflectance in order to make the light emitted from the LED 20 efficiently enter 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 a prism array 51 in at least one direction on a surface facing the emission surface 12 of the light guide plate 10, and the ridge direction of the prism array 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 reflectance in order to efficiently re-enter the light emitted from the light exit surface 13 of the light guide plate 10 into 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.
[0011]
The LED 20 has a light distribution characteristic as shown in FIG. The light distribution of the Kamaboko LED 20 differs between the xy plane and the yz plane. As is apparent from this figure, on the xy plane, the luminous intensity becomes extremely low when the origin exceeds + 60 ° and −60 ° with respect to the origin on the y-axis. In addition, on the yz plane, the luminous intensity becomes extremely low when the origin exceeds + 30 ° and -30 ° with respect to the origin on the y-axis. As the LED 20, for example, NSSX440 series manufactured by Nichia Corporation is used.
[0012]
Next, the operation of the surface light source device 1 having the above configuration will be described with reference to FIG.
The light beam 80 emitted from the LED 20 enters 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 diffusing portion provided on the exit surface 12 exits from the exit surface 12. Note that some light is emitted from the non-emission surface 13 of the light guide plate 10, but is emitted from the emission surface 12 after being returned to the light guide plate 10 by the reflection sheet 60. The light A emitted from the light exit surface 12 of the light guide plate 10 enters from one surface of the optical sheet 50 forming the prism array 51, is totally reflected by an adjacent surface, and exits from the upper surface of the optical sheet 50.
[0013]
As described above, in the present embodiment, the optical sheet 50 is inclined with respect to the light exit surface 12 in the plane perpendicular to the light entrance surface 11 and the light exit surface 12 of the light guide plate 10 (the yz plane in FIG. 1). The light in the direction (A in FIG. 4) can be emitted by being deflected in the vertical direction with respect to the emission surface 12 by the prism array 51, and perpendicular to the light entrance surface 11 and the emission surface 12 of the light guide plate 10. A surface light source device having an arbitrary light distribution on a plane (yz plane in FIG. 1) can be obtained.
[0014]
In addition, 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 exit surface 12 of the light propagating through the light guide plate 10 (in FIG. 1). (xz plane), that is, the extent of a plane parallel to the emission surface 12 of the emitted light of the LED 20.
In this embodiment, by changing the arrangement direction by 90 ° every other general-purpose LED 20 having anisotropy with respect to the light distribution, a plane parallel to the light incident surface 11 of the light guide plate 10 (FIG. (Xy plane at), the light distribution is adjusted.
[0015]
By making the ridge direction of the prism array 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 exit surface 12 (FIG. 1 (xy plane), it is also possible to obtain a surface light source device having an arbitrary light distribution.
[0016]
Embodiment 2 FIG.
FIG. 5 is an exploded perspective view of a display device according to Embodiment 2 of the present invention, FIG. 6A is an enlarged plan view near a light incident surface of the light guide plate 15 of FIG. 5, and FIG. FIG. 8 is a diagram showing the relationship with the LED 20, and FIG. 8 is a layout diagram of the LED 20 in FIG.
The display device according to this embodiment is configured such that a display plate 70 is superimposed on the optical sheet 50 of the surface light source device 1.
A prism row 52 whose ridge direction is the thickness direction is formed on the light incident surface 16 of the light guide plate 15. The display panel 70 is made of a transparent acrylic resin, and has one of a surface facing the surface light source device 1 (hereinafter, referred to as a back surface) and a surface farther from the surface light source device 1 (hereinafter, referred to as a front surface). The pattern is provided by screen printing, a cutting sheet, or the like. In addition, you may make it provide a pattern on both surfaces. Further, the display plate may be a polycarbonate resin, transparent glass, or a diffusion transmission plate.
In this embodiment, the display panel 70 has a design used for an evacuation exit guide light, and the shaded portion is printed in green.
[0017]
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 from the light incident surface 16 of the light guide plate 15 after being reflected by the LED substrate 30 and the reflector 40. 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 exit surface 17 of the light propagating through the light guide plate 15 is increased by the light incident surface 16 shown in FIG. Is wider than that of a mirror surface.
The propagation of light through the light guide plate 15 and the operation of the optical sheet 50 are the same as those described in the first embodiment, and a description thereof will be omitted.
[0018]
In this embodiment, the light emitted from the surface light source device 1 illuminates the display panel 70 from the back, and transmits information on the display panel 70 to an observer located in front of the display panel 70.
Here, as shown in FIG. 7, when the display plate 70 is divided into three regions 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 B is reduced. It is higher than the transmittance of A and C.
As shown in FIG. 3, the LED 20 has anisotropy in which the light distribution is different in the xy plane and the yz plane, and as shown in FIG. The arrangement direction of the LEDs 20 is different in the extension, and the light distribution of the LEDs 20 located on the extension of the regions A and C is substantially equal to the distribution of light of the LEDs 20 located on the extension of the region B. The arrangement direction is such that the spread of the parallel plane (that is, the xz plane in FIG. 5) is large. For this reason, the light from the LED 20 located on the extension of the regions A and C reaches the region B having a large spread and a high transmittance, and is emitted from the display panel 70 with a wide light distribution.
On the other hand, the light from the LEDs 20 located on the extension of the region B is limited in spread, and is efficiently emitted from the region B having a high transmittance with a uniform light distribution in the front direction.
[0019]
The light distribution on a plane parallel to the light incident surface 16 of the light guide plate 15 (that is, the xz plane in FIG. 5) obtained by the display device of this embodiment is shown by a solid line in FIG.
9 is an angle from the front (that is, the y-axis in FIG. 5).
As comparative examples, the light distribution when the LEDs 20 are arranged as shown in FIG. 10A is shown by a thin line in the figure, the light distribution when the LEDs 20 are arranged as shown in FIG. 1) The luminous intensity distribution of the evacuation exit guide light defined by the Japan Lighting Fixture Manufacturers Association Standard (abbreviated as JIL Standard) is indicated by a dashed line in the figure.
As is clear from FIG. 9, by arranging the LEDs 20 as shown in FIG. 8, an evacuation exit guide having a high luminance in front (θ = 0 [degree]), a wide light distribution, and a good visibility is provided. A display device suitable for a lamp can be obtained.
[0020]
In the first and second embodiments, the surface light source device 1 in which the LEDs 20 are arranged in a line has been described. However, the arrangement position and the number of the LEDs 20 are not limited to this. For example, the LEDs 20 may be arranged in a plurality of lines. Good.
Further, in the first and second embodiments, the diffusing portion is formed on the emission surface 12 of the light guide plate 10, but is not limited to this. The anti-emission surface 13 or the emission surface 12 and the anti-emission surface are not limited thereto. Diffusion portions may be formed on both surfaces of 13.
In the first and second embodiments, the optical sheet 50 has a one-way prism array 51 on a surface facing the emission surfaces 12 and 17 of the light guide plates 10 and 15, and the ridge line direction of the prism array 51 is the light guide plate. The optical sheet 50 is not limited thereto, but a sheet having a prism array on a surface far from the light guide plate, a diffusion sheet, Further, a plurality of optical sheets may be used in combination.
Further, in the second embodiment, the display panel 70 on which the pattern used for the evacuation exit guide light is printed is used as the display panel 70. However, the display panel 70 is not limited to this. For example, a liquid crystal panel or the like that can be changed may be used.
Further, in the above-described embodiment, an LED having anisotropic light distribution has been described as a light source. However, the light source is not limited to this, and may be, for example, a laser diode.
[0021]
【The invention's effect】
As described above, according to the surface light source device of the present invention, a light guide having a light incident surface on which light is incident and an exit surface formed substantially orthogonal to the light incident surface and emitting light from the light incident surface. A light plate and a plurality of light sources provided to face the light incident surface and having anisotropic light distribution, wherein at least one of the light sources is arranged in a direction in which the other light sources are arranged. Are arranged differently, and the spread of the light in a plane parallel to the emission surface is different from that of the other light sources, so that a desired light distribution can be easily realized.
[0022]
Further, according to the display device of the present invention, the display plate has the region portion divided into a plurality of portions by the boundary line parallel to the normal line of the light incident surface of the light guide plate, and the other portion of the region portion The light distribution of the light source corresponding to the region part having a low transmittance compared to the region part of the light source is compared with the light distribution of the light source corresponding to the region part having a high transmittance, with respect to the emission surface of the light guide plate. Since the direction in which the light sources are arranged is determined so that the spread of the parallel planes is large, a display device with high front luminance, wide light distribution and high visibility can be obtained.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a surface light source device according to a first embodiment.
FIG. 2 is a layout view of the LEDs of FIG. 1;
FIG. 3 is a diagram showing a light distribution of the LED of FIG. 1;
FIG. 4 is a diagram for explaining an optical path of the surface light source device of FIG. 1;
FIG. 5 is an exploded perspective view of a display device in Embodiment 2.
6A is a plan view of a main part of FIG. 5, and FIG. 6B is a plan view showing an example different from FIG.
FIG. 7 is a diagram showing the relationship between the display panel of FIG. 5 and LEDs.
FIG. 8 is a layout view of the LEDs of FIG. 5;
FIG. 9 is a diagram showing a light distribution of the display device according to the second embodiment.
FIGS. 10A and 10B are layout diagrams of respective LEDs in the comparative example of FIG.
[Explanation of symbols]
1 surface light source device, 10, 15 light guide plate, 11, 16 light incident surface, 12, 17 emission surface, 20 LED (light source), 30 LED substrate, 50 optical sheet, 51, 52 prism array, 70 display plate.

Claims (5)

A light guide plate having a light incident surface on which light is incident, and an exit surface formed substantially perpendicular to the light incident surface and emitting light from the light incident surface; A surface light source device including a plurality of light sources having anisotropy in light distribution,
A surface light source device wherein at least one of the light sources is arranged in a different orientation from other light sources, and the light spread on a plane parallel to the emission surface is different from the other light sources. On the light exit surface of the light guide plate, an optical sheet through which the light emitted from the light exit surface passes is provided, and on the surface of the optical sheet, a ridge line is substantially parallel to and substantially parallel to the light incident surface. The surface light source device according to claim 1, wherein a prism array extending in at least one direction in a vertical direction is formed. A display device provided with a display plate on the emission surface side of the surface light source device according to claim 1 or 2.
In the region portion divided into a plurality of portions by a boundary line parallel to a normal line of the light entrance surface of the light guide plate of the display plate, the light source corresponding to the region portion having a lower transmittance than other region portions. The arrangement direction of the light sources is such that the light distribution is larger than the light distribution of the light source corresponding to the region having a high transmittance, and the spread of a plane parallel to the emission surface of the light guide plate is large. Display device that is specified. The display device according to claim 3, wherein the light source is a light emitting diode. The display device according to claim 3, wherein the display plate is a design of a guide light.

Images