JP3760658B2 - Light guide, display device, and optical communication device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light guide that emits light by emitting incident light from a light emitting region. The present invention also relates to a display device and an optical communication device using the light guide.
[0002]
[Prior art]
The structure of a conventional surface light source device 1 is shown in the exploded perspective view of FIG. The surface light source device 1 includes a light guide plate 3 for confining light introduced from the light incident surface 2, a light emitting unit 4, and a reflection plate 5. The light guide plate 3 is made of a transparent resin having a large refractive index, such as polycarbonate resin or methacrylic resin. On the surface (back surface) facing the light emitting surface 6 of the light guide plate 3, unevenness processing or diffuse reflection ink dots are formed. A diffusion pattern 7 is formed by printing or the like. The light emitting unit 4 is a circuit board 8 on which a so-called point light source 9 such as a plurality of light emitting diodes (LEDs) is mounted, and faces the light incident surface (side surface) 2 of the light guide plate 3. The reflection plate 5 is formed of, for example, a white resin sheet having a high reflectance, and both side portions are attached to the back surface of the light guide plate 3 by a double-sided tape 10.
[0003]
As shown in FIG. 2, the light emitted from the light emitting unit 4 and entering the light guide plate 3 from the light incident surface 2 is diffusely reflected when entering the diffusion pattern 7, and is totally reflected toward the light emitting surface 6. Light reflected at an angle smaller than the critical angle is emitted from the light exit surface 6 to the outside. In addition, since the light that has passed through the portion where the diffusion pattern 7 on the lower surface of the light guide plate 3 does not exist is reflected by the reflecting plate 5 and returns to the inside of the light guide plate 3 again, loss of light quantity from the lower surface of the light guide plate 3 is prevented.
[0004]
[Problems to be solved by the invention]
However, if the surface light source device is used as a backlight in a display having a plurality of display locations such as an automobile console, a mobile phone, an audio device, and a video device, the same number of surface light source devices as the number of display locations is obtained. Necessary. As a result, the cost is high, and a space for storing a plurality of surface light source devices is required, which is not suitable for practical use. For this reason, a plurality of light emitting diodes and light bulbs are used in such places, and there are problems such as troublesome wiring and poor maintainability at the time of disconnection.
[0005]
Further, the surface light source device as described above is not flexible and cannot be used by being bent elastically, and thus is mainly used as a backlight of a flat panel display such as a liquid crystal display panel.
[0006]
As a flexible light source device capable of simultaneously emitting light at a plurality of locations by one light emitting unit, there is a light source device 11 using an optical fiber as shown in FIG. In this configuration, the light emitting unit 13 is disposed so as to face the end face of the optical fiber bundle 12, and the optical fiber bundle 12 is branched to guide the light from the light emitting unit 13 to a plurality of locations.
[0007]
However, in the light source device 11 using such an optical fiber, even if an optical fiber is bundled to form a surface light source by collecting a set of end faces of the optical fiber, it is expensive to bundle fine optical fibers into a surface light source. There is a problem that a very large number of optical fibers are required and the cost is extremely high. Moreover, since it consists of many optical fibers, there also existed a fault which was hard to handle. Furthermore, in such a light source device 11, it is practically difficult to increase the area of the light emitting region.
[0008]
The present invention has been made to solve the above technical problems, and an object of the present invention is to provide a flexible light guide that can constitute a surface light source device that emits surface light at a plurality of locations. There is. Moreover, it is providing the display apparatus and optical communication apparatus using this light-guide plate.
[0009]
[Means for Solving the Problems]
The light guide according to claim 1 comprises a light guide by overlapping and integrating the ends of a plurality of light guide sheets made of a flexible transparent resin material, and light incident on the light guide. Is a light guide that emits light from a light emitting region provided in the light guide sheet, and the light guide body includes a branch portion that can bend each portion of each light guide sheet that is not integrated. and, together with the branch portion has the light emitting regions of the respective one location or multiple locations, each branch portion is characterized by being separated from each other.
[0012]
The light guide according to claim 2 is a light guide according to claim 1 , wherein the light guide sheet is cut and separated to separate a plurality of branches into the light guide sheet. It is characterized by further forming a part.
[0015]
[Action]
In the light guide according to claim 1-2 constitutes the light guide by the light guide sheet, respectively emitting a plurality of curved bifurcation made from the light guide sheet provided on the light guide Since the region is provided, a plurality of light emitting regions can emit light with one light emitting unit and one light guide. Moreover, since each light guide sheet constituting the light guide is made of a flexible transparent resin material, the branch portions can be bent, and each branch portion is separated from each other, so that the light guide sheet or the branch portion is bent. Thus, the light emitting region can be arranged at a relatively arbitrary place.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 4 is a partially broken perspective view showing the surface light source device 21 using the light guide 22 according to the present invention. The surface light source device 21 includes a light guide 22 and a light emitting module 23. The light guide 22 is formed by forming a plurality of light emitting regions 25 on a bendable light guide sheet 24. The light guide sheet 24 has a high refractive index, can be bent freely, and is formed of a transparent resin material that can be easily cut with scissors, a cutter knife, or the like. Such a light guide sheet 24 is a sheet of, for example, polycarbonate, polyvinyl chloride, polyethylene terephthalate, or polypropylene. The light emitting region 25 is formed by providing a diffusion pattern 26 made of a minute uneven pattern, a diffuse reflection ink printing pattern, or the like on the back surface of the light guide sheet 24. Further, in the light emitting region 25, a specular reflection sheet 27 is attached to the back surface of the light guide sheet 24, and light leaked from the back surface of the light guide sheet 24 in the light emitting region 25 is again transmitted by the specular reflection sheet 27. Since the light is incident on the inside, light loss can be reduced.
[0022]
The light emitting module 23 is a case in which one or a plurality of light emitting elements such as light emitting diodes are sealed in a case having a front opening, and can emit light only forward. The light emitting module 23 is disposed to face the end surface (light incident surface) of the light guide 22.
[0023]
In the surface light source device 21, the light emitted from the light emitting elements in the light emitting module 23 enters the light guide sheet 24 from the end surface of the light guide sheet 24. The light that has entered the light guide sheet 24 propagates through the light guide sheet 24 while repeating total reflection between the front and back surfaces of the light guide sheet 24. The light guide sheet 24 can be bent with a curvature that does not greatly deviate from the total reflection condition at this time. For example, as shown in FIG. 5, when the thickness of the light guide sheet 24 is T, it can be bent with a curvature of up to about 1 / (50T) (the radius of curvature R is about 50T). When the light propagating through the light guide sheet 24 while being totally reflected reaches the light emitting region 25, the light reaching the light emitting region 25 is scattered by the diffusion pattern 26 on the back surface of the light guide sheet 24 and is reflected on the surface of the light guide sheet 24. The light incident at an incident angle smaller than the critical angle of total reflection is emitted from the light guide sheet 24 to the outside. As a result, the light emitting regions 25 provided on the light guide sheet 24 emit light simultaneously.
[0024]
By the way, for example, as in the case of FIG. 4, when a plurality of light emitting regions 25 are arranged along the direction connecting the light sources (light propagation direction), light is emitted from the light emitting region 25 on the side close to the light emitting module 23. As a result, the amount of light reaching the light emitting region 25 on the side far from the light emitting module 23 is smaller than that on the side near the light source. In such a case, if the emission efficiency of the light emitting area 25 on the side closer to the light emitting module 23 is made smaller than the emission efficiency of the light emitting area 25 on the side far from the light emitting module 23, the luminance of each light emitting area 25 is made uniform. can do. The emission efficiency can be adjusted by the density of the diffusion pattern 26, the shape and arrangement of the diffusion pattern 26, and the like.
[0025]
Therefore, according to such a surface light source device 21, light can be guided and emitted at a low loss to a place away from the light source (light emitting module 23) by total reflection, and light can be emitted at a plurality of locations by one light source. be able to. In addition, since only one light source is required, the maintainability is improved, and the design of heat generation and wiring of the light source is only required in one place.
[0026]
Since the light guide 22 is flexible, the light guide sheet 24 can be deformed relatively freely, and the light emitting region 25 can be disposed relatively freely. Furthermore, since the light guide 22 is in the form of a sheet, it is easier to handle than the optical fiber and is inexpensive, and a large amount of light can be propagated and emitted from the light emitting region 25. Therefore, it can be used as the surface light source device 21 capable of multi-point light emission such as backlight and display.
[0027]
Further, since the light guide 22 can be freely cut with scissors or the like, a portion including the light emitting region 25 can be cut and branched as shown in FIG. Since the light emitting regions 25 are formed in each branch portion 28, the number of the light emitting regions 25 can be increased by cutting, and moreover, the light emitting regions 25 can be arranged more freely by being separated.
[0028]
FIG. 7 shows a method of optically connecting the light guide sheet 24. If the light emitting side end surface of one light guide sheet 24 and the light incident side end surface of the other light guiding sheet 24 are arranged close to each other and face each other and connected by some means, the light guiding sheets 24 are optically connected to each other. be able to. As the connecting means, the end surfaces of both light guide sheets 24 may be bonded with a transparent resin adhesive, or the end surfaces of both light guide sheets 24 may be closely contacted with each other by tape or the like. You may connect with the white tape etc. so that the space | gap between the end surfaces of the light sheet 24 may be enclosed. When the light guide sheets 24 are connected to each other in this manner, the light emitted from the end face of one light guide sheet 24 is immediately incident from the end face of the other light guide sheet 24, so that both the light guide sheets 24 are optically coupled. In this case, in order to minimize light leakage from the connecting portion of the light guide sheets 24, it is desirable to attach a regular reflection sheet 29 between the front and back end portions of the light guide sheets 24.
[0029]
If the light guide sheet 24 is connected in this way, the light guide 22 is connected by connecting the light guide sheet 24 when the installation position of the light emitting module 23 and the installation position of the light emitting region 25 are separated. Can be lengthened. Further, as shown in FIG. 8, if the light guide sheets 24 having the light emitting regions 25 are connected to each other, the number of the light emitting regions 25 can be arbitrarily increased. Further, the direction of the light emitting region 25 can be selected at the time of connection.
[0030]
In FIG. 4, the light emitting region 25 is provided over the entire width of the belt-shaped light guide sheet 24, but the shape of the light guide sheet 24 is not particularly limited, and the shape and position of the light emitting region 25 are also particularly limited. It is not a thing. In addition, although the light emitting region 25 is formed on the surface of the light guide sheet 24 here, light is emitted from the end face of the light guide sheet 24 and substantially linear light is emitted also to the end face of the light guide sheet 24. The light emitting region 25 may be formed.
[0031]
(Second Embodiment)
FIG. 9 shows another configuration of the light emitting region 25. In this embodiment, the light emitting region 25 is formed by adhering a specular reflection sheet 27 including a diffusion material 30 such as diffusion beads to the light guide sheet 24. The diffusion material 30 may be embedded in the inner surface (adhesion surface) of the regular reflection sheet 27 or may be dispersed in an adhesive 31 applied to the regular reflection sheet 27. Here, the adhesive 31 applied to the specular reflection sheet 27 is preferably transparent and has a refractive index larger than that of the light guide sheet 24 or close to that of the light guide sheet 24.
[0032]
Therefore, if the regular reflection sheet 27 is attached to the back surface of the light guide sheet 24, the light propagating through the light guide sheet 24 enters the light emitting region 25, and then the regular reflection sheet 27 starts from the back surface of the light guide sheet 24. Leak to the side, diffusely reflected by the diffusing material 30 and reflected by the specular reflection sheet 27 to return into the light guide sheet 24. At this time, light incident on the surface of the light guide sheet 24 at an incident angle smaller than the critical angle of total reflection is emitted from the surface of the light guide sheet 24 to the outside and emitted.
[0033]
Alternatively, a concavo-convex pattern for scattering light may be formed on the inner surface of the regular reflection sheet 27 instead of the diffusing material 30.
[0034]
If the light emitting area 25 can be formed by sticking the specular reflection sheet 27 to the light guide sheet 24 in this way, the light emitting area 25 is formed at an arbitrary place when the light guide 22 or the surface light source device 21 is installed. can do. Further, the position of the light emitting area 25 can be easily changed.
[0035]
(Third embodiment)
FIG. 10 is a perspective view showing a surface light source device 32 using another light guide 22 according to the present invention. The light guide 22 is obtained by superimposing the base end portions of a plurality of light guide sheets 24 and integrating them by bonding. One light emitting module 23 is arranged on the end face of the light guide sheet 24 thus laminated and integrated so that light can be introduced into each light guide sheet 24 by one light emitting module 23. The unbonded portion of each light guide sheet 24 forms a branch portion 28, and one or a plurality of light emitting regions 25 are provided in each branch portion 28.
[0036]
Furthermore, in the light guide 22 shown in FIG. 10, the front end portion of each light guide sheet 24 is cut and branched to increase the number of branch portions 28. Therefore, according to the surface light source device 32, a large number of light emitting regions 25 can be formed by the compact light guide 22, and the light emitting regions 25 can be consolidated.
[0037]
The structure as shown in FIG. 10 is obtained by cutting the portion of the thick light guide (or the light guide sheet having a large thickness) except the base end portion into a slicing shape in the horizontal direction. Can also be obtained. In this case, it is not necessary to adhere and integrate the light guide sheet 24.
[0038]
(Automotive backlight)
FIG. 11 shows a state of a driver's seat in an automobile, and shows an automobile backlight as a field of use of the surface light source device. FIG. 12 shows the automotive backlight of FIG. 11 from the back side of the vehicle body. For example, in the surface light source device 33 having the form as shown in FIG. 10, the light emitting area 25 for display in the console 34 of the automobile, the light emitting area 25 for the speedometer 35, and the gear change lever in each branch portion 28. 36 light emitting areas 25 for display and the like are provided. Since these display portions are not all on the same plane even in the vehicle, conventionally, separate light sources are provided.
[0039]
On the other hand, according to the surface light source device 33 of the present invention, the plurality of light emitting areas 25 can be arranged relatively freely, and the light emitting areas 25 can be arranged on a curved surface or in a narrow gap. The degree of freedom is very high.
[0040]
(Optical communication device)
FIG. 13 shows an optical communication device 37 in which a light-emitting module 23 for signal output is provided at one end of a strip-shaped light guide 22 and a photodetector 38 including a light receiving element such as a photodiode is provided at the other end. According to the optical communication device 37 , the optical signal output from the light emitting module 23 propagates through the light guide 22 and is received by the photodetector 38 .
[0041]
In the optical communication device 37 of FIG. 13, only one-to-one communication can be performed. However, since the light guide sheet 24 can be branched by cutting with scissors or the like as described above, as shown in FIG. By making the photo detector 38 face the tip surface of the unit 28, a plurality of receiving stations can be provided. Further, the communication distance can be increased by connecting the light guide sheet 24 using a connecting means.
[0042]
Therefore, according to the optical communication device 37 , optical communication can be realized more easily and at a lower cost than an optical communication device using an optical fiber, and communication in a room or in an apparatus that does not perform long-distance transmission. Is suitable.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a conventional surface light source device.
FIG. 2 is an operation explanatory diagram of the surface light source device of FIG. 1;
FIG. 3 is a perspective view showing a conventional light source device using an optical fiber bundle.
FIG. 4 is a partially broken perspective view showing a surface light source device according to an embodiment of the present invention.
5 is a cross-sectional view showing a curved light guide sheet used in the surface light source device of FIG.
6 is a perspective view showing a state in which a light guide sheet is cut to form a branched portion in the surface light source device of FIG. 4;
FIG. 7 is a cross-sectional view showing a structure of a connecting portion between light guide sheets.
FIG. 8 is a perspective view showing a plurality of connected light guide sheets.
FIG. 9 is a perspective view showing another structure of the light emitting region.
FIG. 10 is a perspective view showing a structure of a surface light source device according to another embodiment of the present invention.
FIG. 11 is a schematic view showing the inside of an automobile.
12 is a diagram showing a display device that provides a light emitting unit used in the vehicle of FIG. 11. FIG.
FIG. 13 is a perspective view showing an optical communication device.
FIG. 14 is a perspective view showing an optical communication device in which a branch portion is formed.
[Explanation of symbols]
22 Light guide 23 Light emitting module 24 Light guide sheet 25 Light emitting region 26 Diffusion pattern 27 Regular reflection sheet

Claims (2)

A light guide is configured by stacking and integrating ends of a plurality of light guide sheets made of a flexible transparent resin material, and light incident on the light guide is provided in the light emitting region. A light guide designed to be emitted from
The light guide body is formed as a bendable portion that can bend each non-integrated portion of each light guide sheet ,
Each of the branch portions has one or a plurality of light emitting regions, and the branch portions are separated from each other. By separating by cutting the integrated portion not of the light guide sheet, characterized in that further form a plurality of branch portions in the light guide sheet, the light guide according to claim 1 .

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