JP2008218077A - Surface-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-emitting device capable of providing a uniform surface illumination light free from luminance unevenness by reducing high luminance regions (hot spots) of light generated in a light emission surface of a light guide plate. <P>SOLUTION: In the surface-emitting device wherein a plurality of linear prisms 3 are formed as a continuous shape in a light reflecting surface 1b of the light guide plate 1, a part corresponding to the high luminance regions (hot spots) of light generated on the light emission surface 1c of the light guide plate 1 of the linear prisms 3 is formed as a dashed-line-like prism 5, showing an intermittent shape. Of the light propagating in an inner part of the light guide plate 1, a part of the light reaching the dashed-line-like prism 5 is reflected to a light-emitting surface 1c side by a prism surface of the dashed-line-like prism 5 and other part travels to a forward direction through a clearance between adjacent singulated prisms 5a, the plurality of singulated prisms 5a structuring the dashed-line-like prism 5 without being reflected. As a result, hot spots are reduced, as the absolute quantity of the light reflected to the light-emitting surface 1c side decreases. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface light emitting device in which a point light source is disposed on a side end surface of a light guide plate, and light emitted from the light source is propagated inside the light guide plate and emitted from the light exit surface of the light guide plate to the outside. .

  Conventionally, a point light source such as an LED is disposed on the side end surface of a light guide plate made of a light-transmitting material, and light emitted from the light source is propagated through the light guide plate and emitted from the light output surface of the light guide plate to the outside. A so-called surface emitting device is known.

  In the surface light emitting device, it is desired that the light propagating inside the light guide plate is efficiently emitted from the light emitting surface. For this reason, the light reflecting surface, which is the surface facing the light emitting surface of the light guide plate, The linear prism which reflects the light which propagates toward the light-emitting surface side is formed. (For example, see Patent Documents 1, 2, and 3)

  FIG. 3 is a bottom view and a side view schematically showing a conventional surface light emitting device in which a linear prism is formed on a light reflection surface of a light guide plate. In FIG. 3, the lower surface is a light reflecting surface, and in order to make the drawing easier to understand, only the top of the linear prism is represented by a single straight line in the bottom view (hereinafter, in the drawings used in this specification). The same shall apply). In the conventional surface light emitting device shown here, one point-like light source 2 composed of LEDs is disposed on the light incident surface 1a which is one side end surface of the light guide plate 1, with the light emitting surface opposed to the light incident surface 1a. On the light reflecting surface 1b of the light guide plate 1, a plurality of linear prisms 3 extending in parallel to the light incident surface 1a are formed at equal intervals. The linear prism 3 is a so-called V-groove in which a cross section cut in the thickness direction of the light guide plate 1 forms a V shape with an apex angle of 90 °, for example.

Light emitted from the point light source 2 (indicated by a dotted arrow in the figure) enters the light guide plate inside 1 with a predetermined directivity range R and travels toward the side facing the light incident surface 1a. It propagates while diffusing inside. Of the light propagating through the light guide plate 1, the light incident on the prism surface (inclined surface) 3 a of the linear prism 3 formed on the light reflecting surface 1 b of the light guide plate 1 at a predetermined critical angle or more is the prism surface 3 a. Thus, the light is reflected toward the light exit surface 1c and is emitted from the light exit surface 1c to the outside of the light guide plate 1 as surface illumination light.
JP 2004-71413 A JP 2005-259361 A JP 2006-134634 A

  In general, since light emitted from a point light source has high directivity, a region having a relatively high luminance called a “hot spot” tends to occur on the light exit surface (particularly within the directivity range) of the light guide plate. When the hot spot is generated, it becomes uneven brightness on the entire light emitting surface, and the appearance of the light emitting surface is deteriorated, and the quality of the surface light emitting device is deteriorated.

  FIG. 4 is a diagram showing a state where a hot spot is generated on the light exit surface of the light guide plate. (A) When the linear prism is formed parallel to the light incident surface, (b) The linear prism is incident on the light. This is a case where it is formed so as to be orthogonal to the surface. The region where the hot spot is generated varies depending on the type of the point light source used, the formation pattern of the linear prism, and the like. For example, the linear prism is formed parallel to the light incident surface 1a of the light guide plate 1 As shown in FIG. 4A, the hot spots H are generated radially in a relatively wide range from the point light source 2 toward the inside of the light guide plate 1, and the linear prisms are the light of the light guide plate 1. When formed so as to be orthogonal to the incident surface 1a, the hot spot H is relatively narrow from both ends of the point light source 2 toward both side surfaces of the light guide plate 1 as shown in FIG. It occurs in two directions radially in the range.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a surface light-emitting device capable of obtaining uniform surface illumination light without luminance unevenness.

  A point light source is disposed on a light incident surface that is a side end surface of the light guide plate, and light emitted from the point light source is propagated through the inside of the light guide plate from a light emission surface that is one main surface of the light guide plate. A surface light emitting device that emits light to the outside, and a light reflecting surface that is a main surface facing the light emitting surface of the light guide plate, transmits light propagating through the light guide plate to the light emitting surface side of the light guide plate. A linear prism that forms a continuous aspect that reflects toward the light source, and a broken-line prism that is formed by an assembly of a plurality of individual prisms that are spaced apart from each other. A surface in which a formation region is adjusted in a region corresponding to a high luminance region of light emitted from the light emitting surface of the light guide plate so that the luminance of light emitted from the light emitting surface of the light guide plate is uniform. Let it be a light emitting device.

  The arrangement interval of the individual prisms in the direction orthogonal to the light output axis of the point light source is a change surface light emitting device according to the luminance distribution of light emitted from the light emission surface of the light guide plate.

  The arrangement interval of the individual prisms in the direction orthogonal to the light output axis of the point light source is changed so that the region where the luminance of the light emitted from the light exit surface of the light guide plate is high is larger than the region where the luminance is low. A surface light emitting device is used.

  In the surface light emitting device, the arrangement interval of the individual prisms in the direction along the light output axis of the point light source is changed according to the luminance distribution of the light emitted from the light emitting surface of the light guide plate.

  The arrangement interval of the individual prisms in the direction along the light output axis of the point light source is changed so that the region where the luminance of the light emitted from the light emitting surface of the light guide plate is higher than the region where the luminance is low is larger. The surface light-emitting device is used.

  The depth or height of the individual prisms is a surface light emitting device that changes according to the luminance distribution of light emitted from the light emitting surface of the light guide plate.

  In the surface light emitting device, the depth or height of the individual prism is changed so that the region where the luminance of light emitted from the light emitting surface of the light guide plate is high is smaller than the region where the luminance is low. .

  The inclination angle of the prism surface of the individual prism is a surface light emitting device that changes according to the luminance distribution of light emitted from the light emitting surface of the light guide plate.

  In the surface light emitting device, the inclination angle of the prism surface of the individual prism is changed so that the region where the luminance of the light emitted from the light emitting surface of the light guide plate is high is smaller than the region where the luminance is low. .

  The linear prism and / or the individual prism may be a surface light emitting device extending in a direction parallel to a light incident surface of the light guide plate.

  The linear prism and / or the individual prism may be a surface light emitting device that extends in a direction orthogonal to the light incident surface of the light guide plate.

  The linear prism and / or the individual prism may be a surface light emitting device extending in an arc shape around the point light source.

  The linear prism and / or the piece-like prism is a surface light emitting device that extends radially from the point light source.

  The linear prism is a surface light emitting device in which a cross section cut in the thickness direction of the light guide plate is a groove or a convex strip having a V shape, an arc shape, or a U shape.

  The individual prisms are grooves or ridges whose cross-section cut in the thickness direction of the light guide plate is V-shaped, arc-shaped, or U-shaped, or hemispherical, conical, and pyramid in outline. The surface light-emitting device is a concave portion or a convex portion that is any one of the shapes.

  The broken line prism is a surface light emitting device in which a formation region is adjusted within a directivity range of light emitted from the point light source and incident on the inside of the light guide plate.

  According to the present invention, among the linear prisms formed on the light reflecting surface of the light guide plate, the portion corresponding to the high-intensity region (hot spot) of light generated on the light exit surface of the light guide plate is formed in a broken line shape. Thus, the luminance in the region can be suitably reduced, the luminance of the entire light exit surface can be made uniform, and luminance unevenness can be eliminated.

  Further, in forming the broken-line prism, it is possible to employ substantially the same forming means (molding or cutting) as that of the linear prism, which is conventionally known as a means for eliminating luminance unevenness. It is possible to suppress an increase in man-hours and an increase in manufacturing cost as compared to separately performing sandblasting, dot printing, and the like.

  A linear prism that forms a continuous form on the light reflection surface of the light guide plate and a broken-line prism formed by an assembly of a plurality of individual prisms that are arranged at a predetermined interval from each other. The prism formation region is adjusted so that the luminance of light emitted from the light exit surface of the light guide plate is uniform.

  FIG. 1 is a bottom view, a side view, and an enlarged perspective view of a main part around a dashed prism, schematically showing an embodiment of a surface light emitting device according to the present invention. On the light incident surface 1a which is one side end surface of the rectangular light guide plate 1 made of a light transmissive material, one point light source 2 made of LED is disposed with the light emitting surface facing the light incident surface 1a. . A plurality of fine prism rows (knurls) 4 for diffusing light emitted from the point light source 2 are arranged in the thickness direction of the light guide plate 1 in a region facing at least the light emitting surface of the point light source 2 on the light incident surface 1a. Are formed in parallel with each other at regular intervals.

  For example, as shown in FIG. 1, the light emitted from the point light source 2 radially enters the light guide plate 1 from the light incident surface 1 a of the light guide plate 1 with a predetermined directivity range R around the point light source 2. It enters and propagates while diffusing inside the light guide plate 1 toward the side facing the light incident surface 1a. At this time, on the light emitting surface 1c of the light guide plate 1, the region corresponding to the directivity range R of the light emitted from the point light source 2 and entering the light guide plate 1 is shown in FIG. As shown, a portion having a relatively high luminance of light, that is, a portion having a high density of light emitted from the light emitting surface 1c (hot spot H) is generated.

  It should be noted that the hot spot generation region does not necessarily coincide completely with the directivity range R of the light emitted from the point light source 2, and is provided in various parameters such as the shape and thickness of the light guide plate and the light guide plate. It varies depending on the formation conditions of the reflecting structure (prism, rough surface, printing dots, etc.). However, in the present embodiment, the light directivity range R and the hot spot H completely coincide with each other.

  The light reflecting surface 1b that is one main surface of the light guide plate 1 includes a plurality of linear prisms 3 that reflect light propagating through the light guide plate 1 toward the light emitting surface 1c facing the light reflecting surface 1b. They are formed parallel to the light incident surface 1a and at equal intervals. In the present embodiment, the linear prism 3 is a long groove-shaped recess formed by molding or mechanical processing (cutting) of the light guide plate 1, and the cross section cut in the thickness direction of the light guide plate 1 has an apex angle of 90. It is a so-called V groove having a V shape of °.

  In addition, in the light reflecting surface 1b of the light guide plate 1, the regions corresponding to the high luminance region (hot spot H) of the light generated on the light emitting surface 1c of the light guide plate 1 are arranged at a predetermined interval from each other. A broken-line prism 5 made of an aggregate of individual prisms 5a is formed.

  The broken-line prism 5 in this embodiment is formed by intermittently dividing a part of the linear prism 3 at a predetermined interval in the extending direction, and each individual prism 5 a is more than the linear prism 3. They are substantially short and small and are arranged in alignment along the extending direction of the linear prism 3. That is, when viewed macroscopically, a part of the linear prism 3 that forms a continuous mode is configured to form an intermittent mode.

  The light emitted from the point light source 2 is first diffused to some extent by the knurl 4 formed on the light incident surface 1 a of the light guide plate 1 and then enters the light guide plate 1. The light incident on the inside of the light guide plate 1 propagates through the light guide plate 1 while repeating irregular reflection toward the side facing the light incident surface 1a, and a line formed on the light reflecting surface 1b of the light guide plate 1 in the process. A part of the light that has reached the prism 3 is reflected by the prism surface (inclined surface) 3a of the linear prism 3 toward the light exit surface 1c, and becomes surface illumination light from the light exit surface 1c to the outside of the light guide plate 1. And exit.

  In the above process, the light emitted from the point light source 2 is diffused to some extent by the knurling 4 formed on the light incident surface 1 a of the light guide plate 1, but most of the incident light is directed to the light of the point light source 2. When the linear prism 3 is uniformly formed over the entire surface of the light reflecting surface 1b because it concentrates within the range, the absolute amount of light existing in the region inevitably increases, resulting in a linear shape. The amount of light reflected by the prism 3 toward the light exit surface 1c increases, which becomes a hot spot on the light exit surface 1c, resulting in uneven brightness.

  However, in the surface light emitting device of the present invention, a part of the light (indicated by a solid arrow in the enlarged view of the main part) that reaches the region is partly the prism surface (inclined surface) of the individual prism 5a constituting the broken-line prism 5. Is reflected to the light exit surface 1c side, while the other part passes through the gap between the adjacent individual prisms 5a as it is in the traveling direction and is not reflected to the light exit surface 1c side. As a result, the absolute amount of reflected light toward the light exit surface 1c in that region is reduced, and the light emitted from the light exit surface 1c is made uniform.

  The degree to which the amount of reflected light is reduced by the broken-line prism 5 depends on the arrangement interval (pitch) in the direction perpendicular to the light output axis A of the point light source of each individual prism 5a constituting the broken-line prism 5 and this arrangement. By appropriately setting the interval according to the hot spot generation region and the luminance distribution, the light emitted from the light emitting surface 1c is adjusted to be uniform.

  However, the hot spot has a difference in luminance even in the region where the hot spot is generated. Generally, as the hot spot moves away from the light incident surface 1a of the light guide plate 1 to the side opposite to the light incident surface 1a, Since there is a tendency for the luminance to gradually decrease with increasing distance from the orthogonal side, a sufficient luminance reduction effect may not be obtained simply by forming the dashed prism 5 uniformly in the hot spot generation region. is there.

  Therefore, in such a case, for example, the arrangement interval of the individual prisms 5a constituting the broken-line prism 5 in the direction orthogonal to the light output axis A of the point light source 2 is the side facing the light incident surface 1a of the light guide plate 1 from the light incident surface 1a. The light reflectance in the entire formation area of the broken-line prism 5 is changed to the luminance distribution of the hot spot so that it gradually decreases as it moves away from the light output axis A of the point light source 2 and toward the side perpendicular thereto. Change to match. That is, in the hot spot generation region, the arrangement state of the individual prisms 5a is roughened for a portion with high luminance, and conversely, it is dense for a portion with low luminance and the luminance of the entire light exit surface 1c. Adjust.

  Further, the reflectance in the entire formation area of the broken-line prism 5 is not only changed in the arrangement interval in the direction orthogonal to the light output axis A of the point light source 2 of the individual prism 5a, but also in an individual shape. Various parameters that affect the arrangement interval of the prism 5a in the direction along the light output axis A of the point light source 2 and the light reflection characteristics of the individual prism 5a, such as the external size (vertical and horizontal width), the groove depth, and the prism It can also be changed by changing the inclination angle of the surface.

  In the above case, when the arrangement interval of the individual prisms 5a in the direction along the light output axis A of the point light source 2 is changed, the arrangement interval is reduced with respect to the high brightness portion in the hot spot generation region. When changing the outer size of the individual prism 5a, when reducing the outer size of the individual prism 5a and changing the depth of the groove with respect to the high brightness portion in the hot spot generation region, When the depth of the groove is reduced with respect to the high brightness area in the hot spot generation area and the inclination angle of the prism surface is changed, the inclination angle (light guide plate) with respect to the high brightness area in the hot spot generation area is changed. (Rise angle from 1 bottom surface) may be reduced. These configurations can be implemented in combination with each other, and by doing so, hot spots can be reduced more effectively.

  FIG. 2 is a bottom view and a side view showing another embodiment of the surface light emitting device according to the present invention. In the first embodiment, the linear prism extends in a direction parallel to the light incident surface 1a of the light guide plate 1, whereas in the second embodiment, the linear prism is orthogonal to the light incident surface 1a of the light guide plate 1. It is configured as a linear prism 6 extending in the direction.

  In this configuration, the hot spots H are generally generated in two radial directions in a relatively narrow range from the vicinity of both ends of the point light source 2 toward both side surfaces of the light guide plate 1 as shown in FIG. Then, a broken-line prism 7 is formed corresponding to the region.

  The hot spots H are reduced by the action of the broken-line prism 7 as in the first embodiment, and the luminance of the light emitted from the light emitting surface 1c of the light guide plate 1 is made uniform. Thus, even if the extending direction (formation pattern) of the linear prism is changed, it is possible to obtain the same hot spot reduction effect as in the first embodiment.

  Although the embodiments of the surface light emitting device according to the present invention have been described above, the present invention is not limited to these embodiments. For example, linear prisms and broken-line prisms extend in an arc shape or a radial shape around the light source. The shape may be a ridge protruding from the bottom surface of the light guide plate instead of a groove, and the cross-sectional shape is not limited to a V shape but is an arc shape or a U shape. May be.

  In addition, the individual prisms constituting the broken-line prism are not limited to the rectangular V-shaped outer shape as shown in the embodiment, but the outline is a hemispherical, conical or pyramidal concave or convex portion, etc. In other words, the linear prism and the dashed prism do not necessarily have the same mode.

  Further, in the above embodiment, the individual prisms are arranged in alignment along the extending direction of the linear prisms, but may be irregularly scattered in the formation area of the dashed prisms.

  There are no particular restrictions on the number, location, type, and the like of the point light sources to be used. For example, two point light sources may be used and arranged on the light guide plate side end surfaces facing each other.

  The hot spot has various occurrence positions and areas depending on the extending direction, shape, cross-sectional shape of the linear prism, and the shape and thickness of the light guide plate itself. The hot spot can be reduced or eliminated by using a dashed-line prism in the region corresponding to the hot spot.

The bottom view which shows typically one Embodiment of the surface emitting device by this invention, a side view, and the principal part expansion perspective view around a broken-line prism The bottom view and side view which show other embodiment of the surface emitting device by this invention A bottom view and a side view schematically showing a conventional surface light emitting device in which a linear prism is formed on a light reflecting surface of a light guide plate. It is a figure which shows the state which the hot spot produced on the light-projection surface of a light-guide plate, (a) When a linear prism is formed in parallel with a light-incidence surface, (b) A linear prism is orthogonal to a light-incidence surface. If formed as

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light guide plate 1a Light incident surface 1b Light reflective surface 1c Light output surface 2 Point light source (LED)
3 linear prism 3a prism surface 4 prism row (knurl)
5 Dashed prism 5a Individual prism 6 Linear prism 7 Dashed prism

Claims (16)

A point light source is disposed on a light incident surface that is a side end surface of the light guide plate, and light emitted from the point light source is propagated through the inside of the light guide plate from a light emission surface that is one main surface of the light guide plate. A surface emitting device that emits light to the outside,
The light reflecting surface, which is the main surface facing the light emitting surface of the light guide plate, has a linear shape that reflects light propagating inside the light guide plate toward the light emitting surface side of the light guide plate. A prism and a broken-line prism formed of an assembly of a plurality of individual prisms arranged at a predetermined interval from each other,
The broken line prism is formed in a region corresponding to a high luminance region of light emitted from the light emitting surface of the light guide plate so that the luminance of light emitted from the light emitting surface of the light guide plate is uniform. The surface light-emitting device characterized by being adjusted.   The arrangement interval of the individual prisms in a direction orthogonal to the light output axis of the point light source varies according to the luminance distribution of light emitted from the light exit surface of the light guide plate. 2. The surface light-emitting device according to 1.   The arrangement interval of the individual prisms in the direction orthogonal to the light output axis of the point light source is changed so that the region where the luminance of the light emitted from the light exit surface of the light guide plate is high is larger than the region where the luminance is low. The surface light-emitting device according to claim 2, wherein   The arrangement interval of the individual prisms in the direction along the light output axis of the point light source varies according to the luminance distribution of light emitted from the light exit surface of the light guide plate. The surface light-emitting device as described in any one of 1-3.   The arrangement interval of the individual prisms in the direction along the light output axis of the point light source is changed so that the region where the luminance of the light emitted from the light emitting surface of the light guide plate is higher than the region where the luminance is low is larger. The surface light-emitting device according to claim 4, wherein   The depth or height of the individual prisms changes according to the luminance distribution of light emitted from the light exit surface of the light guide plate. The surface light-emitting device described in 1.   The depth or height of the individual prisms is changed so that the higher region is smaller than the lower region of the luminance of the light emitted from the light emitting surface of the light guide plate. The surface emitting device according to claim 6.   The angle of inclination of the prism surface of the piece-like prism changes according to the luminance distribution of light emitted from the light exit surface of the light guide plate. The surface light-emitting device described in 1.   The angle of inclination of the prism surface of the individual prism is changed so that a higher region is smaller than a region where the luminance of light emitted from the light emitting surface of the light guide plate is low. The surface emitting device according to claim 8.   The surface light-emitting device according to claim 1, wherein the linear prism and / or the individual prism extends in a direction parallel to a light incident surface of the light guide plate. .   The surface light-emitting device according to claim 1, wherein the linear prism and / or the piece-like prism extends in a direction orthogonal to a light incident surface of the light guide plate. .   The surface light-emitting device according to claim 1, wherein the linear prism and / or the individual prism extends in an arc shape around the point light source.   The surface light-emitting device according to claim 1, wherein the linear prism and / or the piece-like prism extends radially around the point light source.   The said linear prism is a groove | channel or protruding item | line whose cross section cut in the thickness direction of the said light-guide plate is any one of V shape, circular arc shape, and U shape. The surface light-emitting device as described in any one.   The individual prisms are grooves or ridges whose cross-section cut in the thickness direction of the light guide plate is V-shaped, arc-shaped, or U-shaped, or hemispherical, conical, and pyramid in outline. The surface light-emitting device according to claim 1, wherein the surface light-emitting device is a concave portion or a convex portion.   The surface emitting device according to claim 10, wherein a formation region of the broken prism is adjusted within a directivity range of light emitted from the point light source and incident on the inside of the light guide plate.