JP2002250821A - Light guide plate and planar illuminator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily control the intensity and the directivity of the outgoing light beams emitted from the light emitting surface section of a light guide plate. SOLUTION: A planar illuminator 11 is provided with a light guide plate 12 which has an incident end face section 13a, a light emitting surface section 15, a back surface section, a light source 14a which projects illuminating light beams toward the section 13a of the plate 12 and light reflecting sheets 16 which cover the portion other than the section 13a of the plate 12 and the section 15. The plate 12 of the illuminator 11 has a plurality of light deflecting elements 19 that are arranged along the section 13a. Each of the elements 19 is provided on the back surface and projected from the surface and has a cross section which has an isosceles triangle shape and is parallel to the section 13 and has a ridgeline 20. The ridgeline 20 is extended in the direction approximately normal to the section 13a and has a length which is equal to or longer than one half of the distance from the section 13a to an end face section 13b located at the opposite side of the section 13a. The height of the ridgeline 20 with respect to the back surface section is increased or decreased as it moves toward the section 13a side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate for emitting light introduced from an incident end surface from a light exit surface crossing the incident end surface, and a flat lighting device using the light guide plate. It is possible to favorably control the diffusion state of light emitted from the emission surface.

[0002]

2. Description of the Related Art A flat lighting device used as a backlight source of a transmission type liquid crystal display or the like is configured to receive illumination light from a cold cathode tube (FCL) or an LED array as a light source at a side end surface of a transparent light guide plate. The light is guided to the end face, and the light is emitted almost uniformly from the entire light emitting surface serving as the surface of the light guide plate by utilizing total reflection of light in the light guide plate.

In such a conventional light guide plate and flat illumination device, the light emitting surface and the opposite side thereof are provided regardless of the size of the liquid crystal display device in order to make the amount of light emitted from the light emitting surface uniform. The distribution state of the light control elements such as minute concaves and convexes randomly provided on the back surface is increased as the distance from the light incident end surface increases. Also,
The size of these light control elements is partially changed to adjust the luminance distribution of the emitted light according to the requirements as a flat illumination device.

[0004]

The conventional light guide plate and the flat illuminating device have small concave portions and convex portions provided randomly on the light emitting surface portion and on the back surface opposite thereto, regardless of the size of the liquid crystal display device. The distribution state of the light control elements such as increases as the distance from the light incident end surface increases, and the amount of light emitted from the light exit surface is simply made uniform. And it is difficult to arbitrarily adjust the directional characteristics, for example, the luminance distribution of emitted light in a specific direction.

In the method of adjusting the brightness distribution of the emitted light by partially changing the size of the light control element, the brightness and the like of the light control element are not steplessly changed, but are changed stepwise. The change is also gradual, and there is a disadvantage that luminance unevenness or the like occurs, which eventually leads to a deterioration in appearance. Also in this method, the directional characteristics of the light emitted from the light emitting surface portion,
That is, it is difficult to freely adjust the light diffusion state.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a light guide plate capable of easily controlling the intensity and directivity of light emitted from an arbitrary position on a light emitting surface, and a flat lighting device using the light guide plate. It is in.

[0007]

According to a first aspect of the present invention, there is provided:
An incident end surface into which light from the light source is introduced, a light exit surface that intersects with the incident end surface and emits light introduced from the incident end surface, and a back surface located opposite to the light exit surface And a cross-sectional shape parallel to the incident end face portion protruding from the rear surface portion forms an isosceles triangle, and a ridge line extends in a direction substantially perpendicular to the incident end face portion and is opposite to the incident end face portion. A plurality of light deflecting elements, each having a length equal to or more than の of a distance to an end face portion located at a position, and a height of the ridge line from the back surface portion gradually increasing or decreasing toward the incident end face portion side, The light guide plate is characterized in that a plurality of light deflecting elements are arranged along the incident end face.

In the first embodiment of the present invention, the light from the light source entering the light guide plate from the incident end face portion travels through the light guide plate toward the end face portion located on the opposite side while repeating total reflection. I do. Part of the light is deflected along the arrangement direction by light deflecting elements protruding from the back surface, and the other part is out of the light guide plate from the light exit surface because the total reflection condition is broken. I do. Here, in the case of a light deflecting element in which the height of the ridge line from the rear surface is gradually increased toward the incident end face, light with a higher diffusion angle and a higher directivity is emitted as the light exit face closer to the incident end face, Conversely, the light exit surface closer to the end face located on the opposite side of the incident end face has a wider diffusion angle and emits light with lower directivity. The amount of light itself tends to increase as the light exit surface is closer to the end face located on the opposite side of the incident end face.

A second embodiment of the present invention is directed to an incident end face to which the illumination light is introduced, a light exit plane which intersects the incident end face and emits the illumination light introduced from the incident end face, and this light. A light guide plate having a back surface located on the opposite side of the light emission surface, a light source that projects illumination light toward the light incident surface of the light guide plate, and a light guide plate other than the light incident surface and the light emission surface. A light-reflecting sheet that covers the light-guiding plate, wherein the light guide plate projects from the back surface and has a cross-sectional shape parallel to the incident end surface that forms an isosceles triangle, and the ridge line is the incident light. It extends in a direction substantially perpendicular to the end face and has a length equal to or more than の of the distance from the incident end face to the end face located on the opposite side, and the height of the ridge line from the back face is Pluralities that gradually increase or decrease as the incident end face side Further comprising a deflecting element, in which these optical deflection element is characterized by being arranged along the incident end face.

In the second aspect of the present invention, the illumination light emitted from the light source enters the light guide plate from the incident end surface of the light guide plate and is directed to the end surface located on the opposite side while repeating total reflection. To travel in the light guide plate. Some of them are suppressed from diffusing along these arrangement directions by the light deflecting elements protruding from the rear surface, and the other part is broken from the rear surface and the light exit surface to break the light guide plate from the total reflection condition. Each is emitted outside. The light emitted from the back surface to the outside of the light guide plate is again incident on the light guide plate from the back surface by the light reflection sheet, but the light deflecting element is in a state where diffusion along these arrangement directions is suppressed, and finally, All the light exits from the light exit surface. Here, in the case of a light deflecting element in which the height of the ridge line from the rear surface is gradually increased toward the incident end face, light with a higher diffusion angle and a higher directivity is emitted as the light exit face closer to the incident end face, Conversely, the light exit surface closer to the end face located on the opposite side of the incident end face has a wider diffusion angle and emits light with lower directivity. The amount of light itself tends to increase as the light exit surface is closer to the end face located on the opposite side of the incident end face.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a light guide plate according to a first embodiment of the present invention, individual light deflecting elements may extend from an incident end face to an end face located on the opposite side of the incident end face. .

Further, the light guide plate is located at a first incident end face portion into which light from the first light source is introduced, and the light from the second light source is located opposite to the first incident end face portion. And a second incident end face to be introduced. In this case, the individual light deflecting elements may be extended from the first incident end face to the second incident end face, or may be extended from the first and second incident end faces to the central portion of the back face. You may.

When the individual light deflecting elements extend from the first incident end surface to the second incident end surface, the height of the ridge line extends from the first incident end surface to the second incident end surface. And a second set in which the height of the ridge line is gradually reduced from the second incident end face to the first incident end face, and these light deflectors are formed as the first set. And may be alternately arranged along the second incident end face.

When the individual light deflecting elements extend from the first and second incident end surfaces to the central portion of the rear surface, respectively, the ridge lines extend from the first incident end surface to the central portion of the rear surface. An optical deflecting element is constituted by a first set whose height is gradually reduced and a second set whose height of the ridge is gradually reduced from the second incident end face portion to the central portion of the back face portion, and these are straightened. May be arranged along the first and second incident end face portions in a state of being arranged in a line. Alternatively, a first set in which the height of the ridge line gradually increases from the first incident end face portion to the central portion of the back surface portion, and the ridge line height from the second incident end face portion to the central portion of the back surface portion. The light deflecting elements may be configured with the second set of which the diameter gradually increases, and may be arranged along the first and second incident end faces in a state where they are arranged in a straight line.

A number of light control elements for controlling the state of light emission from the light emitting surface may be provided on the light emitting surface. In this case, the light control element preferably has a predetermined distribution with respect to the light exit surface, and may have a spherical, columnar, or conical shape, and may have a circular, elliptical, or polygonal shape.

The ridge line of the light deflecting element may be straight or curved. In the case of a curved shape, the shape may be any of a convex shape and a concave shape.

In the planar lighting device according to the second aspect of the present invention, the light source has a first light source and a second light source, and the light guide plate has a first incidence to which illumination light from the first light source is introduced. It may further include an end face, and a second incident end face located on the opposite side of the first incident end face to which illumination light from the second light source is introduced.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the flat lighting device according to the present invention will be described in detail with reference to FIGS. 1 to 13. However, the present invention is not limited to such an embodiment, It is also applicable to other technologies that are to be encompassed by the inventive concept described in the appended claims.

FIG. 1 is an exploded view of a flat lighting device according to an embodiment of the present invention, FIG. 2 is a side view thereof, and FIG. 3 is a sectional view taken along the line III-III of FIG. 4 is shown in FIG. 4, and the schematic shape of one light deflecting element in the present embodiment is extracted and enlarged in FIG. That is, the flat lighting device 11 in this embodiment includes a transparent light guide plate 12 having a rectangular plate shape, and a pair of opposed incident end surfaces 13a and 13b of the light guide plate 12 (hereinafter collectively referred to as 13). Along with a pair of light sources 14a and 14b (hereinafter, these may be collectively described as 14), an incident end surface 13 and a light emitting surface 15 of the light guide plate 12. And a light reflection sheet 16 covering other parts. In addition, a cold cathode tube or a plurality of L
A pair of light sources 14 each composed of an ED or a semiconductor laser is a reflector 1 having a concave reflecting surface.
The light from the light source 14 and the reflected light from the reflector 17 enter the light guide plate 12 from the incident end face 13 of the light guide plate 12, respectively.

The light reflecting sheet 16 covers the pair of side end surfaces 18 and the back surface of the light guide plate 12, and the light guide sheet 12
This is for reflecting the light emitted outside to the inside of the light guide plate 12 again to be emitted from the light emitting surface portion 15 of the light guide plate 12, such as a non-conductive film or the like obtained by vapor deposition of metal such as aluminum or a metal film. Or a resin mixed with or coated with barium titanate or the like, and it is preferable that the surface of these film or resin is subjected to fine unevenness processing.

The reflector 17 is made of a sheet-like material on which a white insulating material or a metal such as aluminum is deposited, and surrounds the incident end face portion 13 of the light guide plate 12 and the light source 14, respectively.

The light guide plate 12 in this embodiment has a refractive index n
Are formed of 1.49 transparent acrylic resin (PMMA), and a pair of incident end surfaces 13a and 13b for respectively introducing light from a pair of light sources 14 and these incident end surfaces located on opposite sides of each other. A pair of side end faces 18 connected to both ends in the width direction of the section 13, and a light emitting face 15 for emitting light incident from the incident end face 13 surrounded by the incident end face 13 and the side end face 18. And a back surface on the opposite side. On this back surface, two sets of light deflecting elements 19a and 19b extending from one incident end face 13a to the other incident end face 13b (hereinafter, these may be collectively referred to as 19). ) Are protruded, and are arranged alternately along the incident end face portion 13. Each of the light deflecting elements 19 has an isosceles triangle in cross section parallel to the incident end face portion 13 and has a ridge line 20.
Extend in a direction substantially perpendicular to the incident end face portion 13, and have a pair of slopes 21 whose height from the back surface of the ridge line 20 gradually increases (gradually decreases) along the ridge line 20, and extends from the incident end face portion 13. It has a triangular pyramid shape having an isosceles triangular end surface 22. One set of individual light deflecting elements 19a has a gradual decrease in the height of the ridgeline 20 from one incident end face 13a to the other incident end face 13b, and the other set of individual light deflecting elements 19b has The height of the ridge line 20 gradually decreases from the other incident end face portion 13b to the one incident end face portion 13a, and the two sets of light deflecting elements 19a and 19b are alternately arranged on the entire back surface. ing.

FIG. 5 shows the appearance of one light deflection element 19. The oblique lines in the figure are portions that are integrally joined to the back surface portion, and light that enters the light deflecting element 19a from the oblique line region and the end surface 22 is directed to an axis perpendicular to the incident end surface portion 13a. It has a refraction angle in an arbitrary direction in the range of 0 ° to 42 °, and propagates to the top 23 side, that is, the other incident end face 13b side while repeating total reflection on the slope 21. In this case, since the pair of slopes 21 constituting the light deflecting element 19a are inclined with respect to each other and also with respect to the back surface (light emitting surface 15), the condition of total reflection is broken and one of these light rays is broken. The part exits the light guide plate 12 from the slope 21. In order to reduce the amount of light emitted from these slopes 21, it is desirable to set the apex angle α of the pair of slopes 21 of the light deflecting element 19 in a cross section parallel to the incident end face 13 as follows.

That is, the light deflecting element 1 in this embodiment
9 is shown schematically in FIG. 6, which shows points A, B, C, D, E, F
Is represented by a line segment connecting. A pair of slopes 21 are points A, B,
It is represented by a line connecting D and E and a line connecting points A, C, D and F. When the incident area of the incident light with respect to the point A of the light deflecting element 19 is represented by a plane connected by A, E, and F, and the middle point of the line segment EF is G, the incident angle γ represented by ∠DAG Maximum value,
That is, the critical angle for total reflection is about 42 ° in the case of the above-mentioned PMMA.入射 an incident angle range β expressed by EAF, and ∠
The relationship with the apex angle α of the light deflection element 19 represented by BAC is as follows: tan (β / 2) = (α / 2) / (line segment AG) (1) Here, if the height of the line segment DG is expressed by h, there is a relationship of line segment AG = h / sinγ. By substituting this into the expression (1), the expression (1) is transformed as follows. can do. ^{β = 2tan -1 (αsinγ / 2h} ) = 2tan -1 {tan (α / 2) · sinγ} ··· (2)

On the other hand, the value of β / 2 is smaller than 42 ° which is the critical angle for total reflection.
By substituting this into equation (2) together with γ = 42 assuming 90, the vertex angle α of the light deflecting element 19 becomes approximately 11
It will be appreciated that it will be 2 °. That is, the light deflection element 1
By setting the vertex angle α of 9 to be equal to or greater than 112 °, light emitted from the slope 21 to the outside of the light guide plate 12 can be reduced as much as possible.

In any case, the light leakage is smaller on the end face 22 side of the light deflecting element 19 and is larger on the opposite top 23 side.
Regardless of the light traveling direction along 0, it always has the same tendency. That is, with respect to the light incident from the other light source 14b from the top 23 side of the one light deflecting element 13a toward the end face 22 side, the leakage of the light increases toward the top 23 side of the light deflecting element 19, and the opposite side. The light leakage is reduced toward the end face 22. As a result, the light emitted from the light exit surface portion 15 located immediately above the end face 22 side of the light deflecting element 19 has a higher directivity, that is, the light diffusion angle is narrower, and the light amount tends to be smaller. The directivity is weaker as the light exits from the light exit surface 15 located immediately above the top 23 of the deflecting element 19,
That is, there is a tendency that the diffusion angle of light is wide and the amount of light is large.

However, in this embodiment, since the two sets of light deflecting elements 19a and 19b are alternately arranged in opposite directions, the amount of light emitted from the light emitting surface 15 is limited to the ridge 20 of these light deflecting elements 19. Along the ridge line 20 of the light deflecting element 19, and symmetrically arranged on the one light incident end face 13a side and the other light incident end face 13b side with respect to the center of the back surface of the light guide plate 12 as a boundary. Optical characteristics are obtained. Moreover, the light condensing effect of the pair of slopes 21 constituting the light deflecting element 19 simultaneously suppresses the diffusion of the outgoing light along the direction in which the pair of side end surfaces 18 of the light guide plate 12 face each other, and reduces the diffusion angle. Has a tendency to be narrowed.

In the above-described embodiment, the height of the ridge 20 of the light deflecting element 19 from the back surface is linearly changed. However, the height may be changed in a curved line if necessary. In this case, the shape may be either convex or concave with respect to the back surface. When changed to a convex shape, the directional characteristics of the emitted light can be changed abruptly on the top 23 side of the light deflecting element 19, and conversely, when changed to a concave shape, the light deflecting element 19 can be changed.
Can be suddenly changed on the side of the end face 22. in this way,
By adjusting the change in the height of the ridge line 20 of the light deflecting element 29 from the rear surface, the adjustment range of the diffusion angle of the light emitted from the light exit surface 15 can be adjusted to some extent according to the size of the light guide plate 12 and the purpose of use. Can be expanded. In this embodiment, an acrylic resin is used as the light guide plate 12, but other optically transparent materials, such as polycarbonate (PC) having a refractive index of 1.50, can be used.

In the embodiment described above, the individual light deflection elements 1
The nine ridge lines 20 extend from one incident end face 13a of the light guide plate 12 to the other incident end face 13b and are alternately arranged so that a flat back surface is not formed. The pair of light deflecting elements 19a and 19b are respectively extended from the respective incident end face portions 13a and 13b to the central portion of the back surface, and the light guide plates 12 are arranged such that the respective sets of light deflecting elements 19a and 19b are arranged in a straight line. A flat region may be formed on the back surface of the device.

FIG. 7 shows the appearance of another embodiment of the light guide plate according to the present invention, and FIG.
Elements having the same functions as those in the previous embodiment will be denoted by the same reference numerals, and overlapping description will be omitted. That is, two sets of light deflection elements 19a and 19b in the present embodiment are used.
Extend from each of the incident end face portions 13a, 13b to the central portion of the back surface portion 24, and each set of the light deflecting elements 19a,
The light deflecting elements 19a in one set have the height of the ridge line 20 gradually reduced from one incident end face portion 13a to the central portion of the back surface portion 24, while the other set of light deflecting elements 19a is gradually reduced. The height of the ridge line 20 gradually decreases from the other incident end face portion 13b to the center portion of the back surface portion 24, and the top portions 23 are in contact with each other. . For this reason, a flat region parallel to the light exit surface 15 is formed on the back surface 24 of the light guide plate 12.

According to the present embodiment, the light emitted from the light exit surface 15 has a large diffusion angle at the center and a large amount of light, whereas the light diffusion angle is narrower toward the light incident end surface 13. It tends to have a small amount of light. Therefore, the light guide plate 12 of the present embodiment is particularly suitable as a backlight light source for a liquid crystal monitor with a large screen, and the light diffusion angle of emitted light at the incident end face portion 13, that is, the viewing angle tends to be large. Because the light intensity distribution is widened,
There is also an effect of suppressing the occurrence of a bright line in the vicinity.

In the above-described embodiment, the two sets of light deflecting elements 19 a and 19 b are connected to the back surface 24 of the light guide plate 12 so that the end face 22 of each light deflecting element 19 extends from each incident end face 13.
, But the end face 22 of each light deflecting element 19 is
2 are integrally joined at the central portion of the back surface portion 24 so that the top portions 23 are located at the respective incident end face portions 13.
It is also possible to arrange a set of light deflecting elements 19 on the back part 24.

FIG. 9 shows the appearance of another embodiment of such a light guide plate according to the present invention, and FIG. 10 shows its planar shape. Elements having the same functions as those of the previous embodiment are denoted by the same reference numerals. It is to be noted that duplicate description will be omitted. That is, the two sets of light deflection elements 19a and 19
b, similarly to the previous embodiment, the respective incident end face portions 13a, 13b
To the central portion of the back surface portion 24, and the sets of light deflecting elements 19a and 19b are arranged so as to be aligned. One set of light deflecting elements 19a has one incident end face. The height of the ridge line 20 gradually increases from 13a to the central portion of the back surface portion 24, and the other set of light deflecting elements 19b
The height of the ridge line 20 gradually increases from the other incident end face portion 13b to the central portion of the back face portion 24, and these end faces are in a state where they abut each other.

According to this embodiment, the light emitted from the light emitting surface 15 has a small diffusion angle at the center and a small amount of light, whereas the light incident end surface 13 has a larger diffusion angle toward the light incident end 13. It tends to have a large amount of light. Therefore, the light guide plate 12 of the present embodiment is effective particularly in a large-screen liquid crystal monitor, in which two pieces of information having different screens on the left and right are simultaneously output, and the left and right observers obtain different information.

In each of the embodiments described above, it is assumed that a pair of light sources 14 is used. However, it is possible to provide only one light source 14, and another embodiment of such a flat lighting device according to the present invention. FIG. 11 shows an exploded structure of the light guide plate, FIG. 12 shows a light emitting surface portion of the light guide plate, and FIG. 13 shows a cross-sectional structure taken along the line XIII-XIII. Only the same reference numerals will be described, and duplicate description will be omitted. That is, the flat lighting device 11 in the present embodiment includes a transparent light guide plate 12 having a rectangular plate shape,
The light guide 14 includes a light source 14 disposed along the incident end face 13 of the light guide plate 12, and a light reflecting sheet 16 covering portions other than the incident end face 13 and the light emitting face 15 of the light guide plate 12. The reflecting surface is surrounded by a reflector 17 having a concave curved surface.

In this embodiment, the light guide plate 12 includes a light source 14
Incident end faces 13 for introducing light from
A pair of side end faces 1 connected to both ends in the width direction of the incident end face 13 and the reflection end face 25 located on the opposite side.
8, a light exit surface 15 for emitting light incident from the incident end 13 surrounded by the incident end 13, the side end 18, and the reflection end 25, and a back 24 opposite to the light exit 15. . A plurality of light deflecting elements 19 extending from the incident end face 13 to the reflective end face 25 are protruded from the rear face 24, and are arranged along the incident end face 13. . The light deflecting element 19 in the present embodiment has a pair of slopes 21 in which the height of the ridge line 20 gradually decreases from the incident end face 13 to the reflective end face 25, and an isosceles triangular shape extending from the incident end face 13. It has a triangular pyramid shape having an end face 22.

As described above, in this embodiment, the incident end face portion 13
The light deflecting element 19 is arranged on the back surface 24 so that the height of the ridge line 20 gradually decreases from the reflection end surface portion 25 to the reflection end surface portion 25. Conversely, the ridge line 20 extends from the incident end surface portion 13 to the reflection end surface portion 25.
Of the light deflecting element 19 so that the height of
It is also possible to arrange in.

The side end surface 1 of the light exit surface 15 of the light guide plate 12
A large number of light control elements 26 are randomly arranged in a region close to the reflection end face 8 and the reflection end face portion 25. Each light control element 26 in the present embodiment has a hemispherical convex surface having a radius of curvature of 50 μm. The projection height from the light exit surface 15 is set to 1 μm. The area of each light control element 26 on the light emitting surface section 15 needs to be 7 × 10 ⁻⁸ cm ² or more.
When the area of the light emission surface portion 15 becomes small, the light emission surface portion 15 becomes in a state of satin finish, diffused reflection by the light control element 26 increases, and it is difficult to emit high directivity light from the light emission surface portion 15 with high directivity. Become.

When the radius of curvature of the light control element 26 is set to, for example, 25 μm, its area is 7 × 10 ⁻⁸ cm ²
In order to achieve the above, the protruding height from the light emitting surface 15 needs to be about 2 μm. However, when the projection height of the light control element 26 with respect to the light exit surface 15 exceeds 2 μm, the inclination of the light control unit 21 with respect to the light exit surface 15 increases, and the diffusion angle of light emitted from the light control unit 21 tends to decrease. Therefore, it is preferable that the protruding height of the light control element 26 from the light emitting surface 15 is 2 μm or less.

These light control elements 26 are provided on the incident end face 13
With respect to the light exit surface portion 15, the density is higher at the reflection end face portion 18 side, and the density is higher at the side end face portion 18 and the reflection end surface portion 18 side with respect to the central portion of the light emission surface portion 15. By providing such a distribution of the light control elements 26 in the light emitting surface portion 15, the amount of emitted light in those regions where the amount of emitted light tends to be relatively small is increased, and the light emitting surface portion 15 is increased.
Can be emitted with a uniform amount of light over the entire region.

From the same viewpoint, the light source 14 using FCL is used.
In general, the light amount at both ends in the longitudinal direction is lower than that at the center in the longitudinal direction.
It is also effective to randomly form the light control elements 26 on the light emitting surface 15 near both ends in the longitudinal direction of the light emitting element 3. In the above-described embodiment, the light control element 26 protrudes from the light exit surface 15 of the light guide plate 12. However, the light control element 26 has a hemispherical concave surface or a columnar or conical shape, and has a circular, elliptical or polygonal shape. The light control element 26 may be formed in the flat region of the back surface 19 where the light deflecting element 19 is not formed.

[0042]

According to the light guide plate of the present invention, the cross section of the light guide plate projecting from the rear surface and being parallel to the incident end face forms an isosceles triangle, and the ridge extends in a direction substantially perpendicular to the incident end face. A plurality of light deflecting elements each having a length equal to or longer than の of a distance from the incident end face to an end face located on the opposite side, and a height of a ridge line from a back surface gradually increasing or decreasing toward the incident end face; Are arranged along the incident end face, so that the diffusion angle of the light emitted from the light exit surface is narrowed along the direction in which the light deflecting elements are arranged, and at the same time, the outgoing light The intensity and the directivity can be changed continuously.

When the individual light deflecting elements are extended from the incident end face to the end face located on the opposite side of the incident end face, the light deflecting elements extend from the incident end face of the light guide plate along the ridge line of the light deflecting element. The intensity and directivity of the emitted light can be continuously changed over the end face located on the opposite side of the incident end face.

A first incident end face to which light from the first light source is introduced, and a second incident side light opposite to the first incident end face to which light from the second light source is introduced. When having the incident end face portion, while narrowing the diffusion angle of light emitted from the light emitting surface portion along the arrangement direction of the light deflecting element, the center of the light emitting surface portion along the direction in which the ridge line of the light deflecting element extends. As a boundary, the intensity and the directivity of the emitted light can be set symmetrically between the first incident end face side and the second incident end face side.

When the individual light deflecting elements extend from the first incident end face to the second incident end face, the light guide plate extends from the first incident end face to the second incident end face. As a result, the intensity and directivity of the emitted light can be changed continuously.

A first set of light deflecting elements, wherein the height of the ridge line gradually decreases from the first incident end face to the second incident end face;
A second set in which the height of the ridge line gradually decreases from the second incident end face to the first incident end face, and these are alternately arranged along the first and second incident end face parts. If you do
Intensity and directional characteristics of outgoing light are set symmetrically between the first incident end face side and the second incident end face side with respect to the center of the light exit surface along the extending direction of the ridge line of the light deflecting element. Can be.

In the case where the light deflecting element is extended from the first and second incident end faces to the center of the rear face, the center of the light emitting face along the direction in which the ridge line of the light deflecting element extends. As a boundary, the intensity and the directivity of the emitted light can be set symmetrically between the first incident end face side and the second incident end face side.

A first set of light deflecting elements, wherein the height of the ridge line gradually decreases from the first incident end face to the center of the back face;
A second set in which the height of the ridge line gradually decreases from the second incident end face to the center of the back face, and the first and second incident end face parts are arranged in a straight line. When arranged along the direction of the ridge line of the light deflecting element, the directivity is weaker toward the center of the light emitting surface along the direction in which the ridge line of the light deflecting element extends.
The outgoing light having higher directivity can be emitted from the light emitting surface as the incident end surface portion is closer.

A first set of a light deflecting element, wherein the height of the ridge line gradually increases from the first incident end face to the center of the back face;
A second set in which the height of the ridge line gradually increases from the second incident end face portion to the central portion of the back face portion, and these are arranged in a straight line on the first and second incident face portions. When arranged along, the directivity is higher toward the center of the light exit surface along the direction in which the ridge line of the light deflecting element extends, and the directivity is lower toward the first and second incident end surfaces. The light can be emitted from the light emitting surface.

When a large number of light control elements for controlling the state of light emission from the light emitting surface are arranged on the light emitting surface, the directivity of light emitted from the light emitting surface should be more finely controlled. Can be.

When the light control elements have a predetermined distribution with respect to the light emitting surface, the directivity of light emitted from the light emitting surface can be set uniformly.

According to the flat lighting device of the present invention, the cross-sectional shape parallel to the incident end face forms an isosceles triangle, and the ridge extends in a direction substantially perpendicular to the incident end face and extends from the incident end face to the opposite side. A plurality of light deflecting elements having a length equal to or more than の of the distance to the located end face and having a height from the back face of the ridge line gradually increasing or decreasing toward the incident end face are projected to the back face of the light guide plate. Since these light deflecting elements are arranged along the incident end face, the diffusion angle of the light emitted from the light exit surface is reduced along the arrangement direction of the light deflecting elements, and at the same time, the ridge of the light deflecting elements extends The intensity and directivity of the emitted light can be continuously changed along the direction.

The light source has a first light source and a second light source, and the light guide plate is a first light source through which illumination light from the first light source is introduced.
When the light emitting device further includes an incident end surface portion of the first light emitting device and a second incident end surface portion which is located on the opposite side of the first incident end surface portion and into which illumination light from the second light source is introduced, the light exits from the light emitting surface portion. At the same time as the diffusion angle of light is narrowed along the direction in which the light deflecting elements are arranged, the first incident end face and the second incident light are separated from the center of the light exit surface along the direction in which the ridge of the light deflecting element extends. The intensity and the directivity of the emitted light can be set symmetrically with the end face side.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an embodiment of a flat lighting device according to the present invention.

FIG. 2 is a side view of the embodiment shown in FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG.

FIG. 4 is a front view of the light guide plate in the embodiment shown in FIG. 1 as viewed from the back surface side.

FIG. 5 is an enlarged perspective view of one set of one light deflection element in the embodiment shown in FIG. 1;

FIG. 6 is a schematic view geometrically showing a light propagation state with respect to a light deflection element in the embodiment shown in FIG. 1;

FIG. 7 is a perspective view illustrating an appearance of another embodiment of the light guide plate according to the present invention.

FIG. 8 is a front view of the light guide plate shown in FIG. 7 as viewed from the back surface side.

FIG. 9 is a perspective view illustrating an appearance of another embodiment of the light guide plate according to the present invention.

FIG. 10 is a front view of the light guide plate shown in FIG. 9 as viewed from a back surface side.

FIG. 11 is an exploded perspective view of another embodiment of the flat lighting device according to the present invention.

FIG. 12 is a front view of the light guide plate in the embodiment shown in FIG. 11 as viewed from a light emitting surface.

FIG. 13 is a sectional view taken along the arrow XIII-XIII in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Planar illumination device 12 Light guide plate 13, 13a, 13b Incident end face part 14, 14a, 14b Light source 15 Light emitting face part 16 Light reflection sheet 17 Reflector 18 Side end face part 19, 19a, 19b Light deflection element 20 Ridge line 21 Slope 22 End face 23 Top part 24 Back part 25 Reflection end face part 26 Light control element α Apex angle of a pair of slopes constituting light deflection element β Range of incident angle γ Incident angle of light h Height of ridge line from back part

Claims (12)

[Claims] 1. An incident end surface portion into which light from a light source is introduced, a light exit surface portion intersecting with the incident end surface portion and emitting light introduced from the incident end surface portion, and an opposite side to the light exit surface portion. A cross-sectional shape projecting from the rear surface and parallel to the incident end surface forms an isosceles triangle, and a ridge line extends in a direction substantially perpendicular to the incident end surface to extend the incident end surface. A plurality of light deflecting elements each having a length equal to or more than の of the distance from the portion to the end face located on the opposite side, and the height of the ridge line from the back surface gradually increasing or decreasing toward the incident end face. And a light guide plate, wherein the plurality of light deflection elements are arranged along the incident end face portion. 2. The light guide plate according to claim 1, wherein each of said light deflecting elements extends from said incident end surface to said end surface located on the opposite side of said incident end surface. 3. A first incident end face to which light from the first light source is introduced, and a first incident end face opposite to the first incident end face to which light from the second light source is introduced. The light guide plate according to claim 1, wherein the light guide plate has two incident end surfaces. 4. The light guide plate according to claim 3, wherein each of said light deflecting elements extends from said first incident end face to said second incident end face. 5. The light deflecting element includes: a first set in which the height of the ridge line gradually decreases from the first incident end face to the second incident end face; and the second incident end face. The height of the ridge line gradually decreases from the portion to the first incident end face portion;
5. The light guide plate according to claim 4, wherein the pairs are alternately arranged along the first and second incident end face portions. 6. 6. The light deflecting element includes the first and second light deflecting elements.
4. The light guide plate according to claim 3, wherein the light guide plate extends from a light incident end surface portion to a central portion of the back surface portion. 5. 7. The first set of light deflecting elements, wherein the height of the ridge line gradually decreases from the first incident end surface to the center of the back surface, and the second incident end surface. The height of the ridge line gradually decreases from the second portion to the center portion of the back surface portion.
7. The light guide plate according to claim 6, wherein the light guide plates are arranged along the first and second incident end face portions in a state of being aligned in a straight line. 8. 8. The first set of light deflecting elements, wherein the height of the ridge line gradually increases from the first incident end surface to the center of the back surface, and the second incident end surface. The height of the ridge line gradually increases from the second portion to the center portion of the back surface portion.
7. The light guide plate according to claim 6, wherein the light guide plates are arranged along the first and second incident end face portions in a state of being aligned in a straight line. 8. 9. The light emitting device according to claim 1, further comprising a plurality of light control elements disposed on said light emitting surface for controlling a state of light emission from said light emitting surface. The light guide plate according to any one of the above. 10. The light guide plate according to claim 9, wherein the light control element has a predetermined distribution with respect to the light emitting surface. 11. An incident end surface to which illumination light is introduced, a light exit surface that intersects with the incident end surface and emits illumination light introduced from the incident end surface, and a position opposite to the light exit surface. A light guide plate having a rear surface portion, a light source for projecting illumination light toward the incident end surface portion of the light guide plate, and a light reflecting sheet covering portions other than the incident end surface portion and the light emitting surface portion of the light guide plate. A light guide plate, wherein the light guide plate is projected from the rear surface portion, a cross-sectional shape parallel to the incident end surface portion forms an isosceles triangle, and a ridge line is substantially perpendicular to the incident end surface portion. And has a length of at least half the distance from the incident end face to the end face located on the opposite side, and the height of the ridge from the back face gradually increases toward the incident end face. Or with multiple light deflecting elements Wherein the light deflecting elements are arranged along the incident end face portion. 12. The light source has a first light source and a second light source, and the light guide plate has a first incident end face to which illumination light from the first light source is introduced, The flat illumination device according to claim 11, further comprising a second incident end surface located opposite to the incident end surface and receiving illumination light from the second light source.