JPH10308113A - Side light type surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce nonuniformity of luminance in the vicinity of an incident surface by forming the back surface of a plate-like member by an almost plane and a curved surface, gradually narrowing an interval between an emitting surface and the almost plane toward a surface opposed to an end surface from a tip end surface, and forming a width of the end surface in the shape of becoming narrow as an end surface of the curved surface becomes more distant from an effective light emitting area of a light source. SOLUTION: In a plate-like member, since a plate thickness becomes thin in a corner part in the vicinity of this incident surface, a large incident angle component is repeatedly reflected between the reverse 12B and an emitting surface to the emitting surface by that extent, and an incident angle to the emitting surface reduces every time when it is reflected by the reverse 12B. Therefore, a light scattering light conductive plate 12 suddenly reduces an incident angle of the illuminating light to the emitting surface in the corner part, and urges an emission of the illuminating light in the corner part by that extent, and a quantity of emitting light of the corner part increases. The illuminating light propagating on the central side of the light scattering light conductive plate 12 is distributed by scattering, and reduction in a luminance level on the wedge-shaped tip side can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sidelight type surface light source device, and more particularly to a sidelight type surface light source device formed such that the thickness of a plate-like member becomes thinner as the distance from the incident surface increases. is there. According to the present invention, the back surface of the plate-shaped member is formed by a substantially flat surface and a curved surface, and the curved surface is used to locally reduce a portion where the amount of emitted light is small, thereby reducing luminance unevenness near the entrance surface.

[0002]

2. Description of the Related Art Conventionally, for example, in a liquid crystal display device,
A liquid crystal display panel is illuminated by a sidelight type surface light source device, thereby reducing the overall shape.

That is, in the sidelight type surface light source device, a primary light source composed of a rod-shaped light source is arranged on a side of a plate-shaped member (that is, composed of a light guide plate), and illumination light emitted from the primary light source is applied to an end face of the light guide plate. More light enters the light guide plate. Further, the sidelight type surface light source device bends the illumination light and emits it from the plane of the light guide plate toward the liquid crystal display panel, whereby the overall shape can be reduced in thickness.

[0004] Such a side light type surface light source device is
A method in which the light guide plate is formed with a substantially uniform thickness,
There is a type in which the thickness of the light guide plate is gradually reduced as the distance from the primary light source increases, and the latter can emit illumination light more efficiently than the former.

FIG. 12 is an exploded perspective view showing an example of the latter sidelight type surface light source device 1, and FIG. 13 is a cross-sectional view of FIG. 12 cut along line AA. In this sidelight type surface light source device 1, a primary light source 3 is arranged on a side of a light scattering light guide plate 2 formed of a light guide plate, and a reflection sheet 4, a light scattering light guide plate 2, and a prism sheet 5 formed of a light control member are sequentially arranged. It is formed by lamination.

The primary light source 3 is formed by surrounding a fluorescent lamp 8 composed of a cold-cathode tube with a reflector 9, and from the opening side of the reflector 9 to the end surface (hereinafter, referred to as an incident surface) 2 A of the light-scattering light guide plate 2. Illumination light enters. Here the reflector 9
Is formed of, for example, a sheet material that specularly or irregularly reflects incident light.

The reflection sheet 4 is formed of a sheet-like regular reflection member made of a metal foil or the like or a sheet-shaped irregular reflection member made of a white PET film or the like, and reflects the illumination light leaking from the light scattering light guide plate 2. The light is returned into the light-scattering light guide plate 2, thereby improving the utilization efficiency of the illumination light.

The light-scattering light-guiding plate 2 is a light-guiding plate having a wedge-shaped cross section. For example, light-transmitting fine particles having a different refractive index from the matrix are uniformly dispersed and mixed in a matrix made of polymethyl methacrylate (PMMA). Formed. Thus, the light-scattering light-guiding plate 2 is formed on the incident surface 2A formed by the end surface on the primary light source 3 side.
The illumination light L is incident on the illumination light L
Sheet 4 made of a diffusely reflecting member while scattering light.
Is applied, a part of the light is reflected by the reflection sheet 4 and a flat surface (hereinafter referred to as a back surface) 2
B and the prism sheet 5 side plane (hereinafter referred to as an emission surface) 2C
And the illumination light L is propagated while repeatedly reflecting between.

At the time of this propagation, the angle of incidence of the illumination light L on the emission surface 2C becomes smaller each time the illumination light L is reflected on the back surface 2B,
A component equal to or smaller than the critical angle with respect to the emission surface 2C is emitted from the emission surface 2C. The illumination light L emitted from the emission surface 2C
Are scattered by the light-transmitting fine particles inside the light scattering light guide plate 2 and diffusely reflected by the reflection sheet 4 to propagate, for example, to be emitted by the scattered light. However, the illumination light L propagates by reflecting off the back surface 2B formed to be inclined in the propagation direction with respect to the emission surface 2C, and emits a component having a critical angle or less, so that the main emission direction has a wedge shape. It is formed to be inclined toward the tip. In other words, the light L emitted from the light scattering light guide plate 2 has directivity, whereby the sidelight type surface light source device 1 has directivity.

The prism sheet 5 includes the light scattering light guide plate 2
Is arranged to correct the directivity of the image. That is, the prism sheet 5 is formed of a translucent sheet material such as polycarbonate, and has prism surfaces on both surfaces. The prism surface is formed by repeatedly forming projections having a triangular cross section extending substantially parallel to one direction, and is formed on both surfaces of the prism sheet 5 so that the repetition direction is orthogonal.

As a result, the prism sheet 5 corrects the main emission direction of the emitted light to the front direction of the emission surface 2C on the slope of the triangular projection. In some cases, a prism sheet having a structure in which a prism surface is formed on one side is used as a prism sheet. As a result, in the sidelight type surface light source device 1, the emitted light can be efficiently emitted in the front direction as compared with the sidelight type surface light source device in which the light scattering light guide plate is formed with a substantially uniform plate thickness. It has been done.

[0012]

In such a side light type surface light source device 1, the fluorescent lamp 8 is
Electrodes 8A and 8B are formed at both ends.
In the vicinity of A and 8B, a region where the phosphor is not applied is formed in the tube. Therefore, in the fluorescent lamp 8, regions where the illumination light L is not emitted are formed near both ends, and the illumination light is emitted only from the central portion (that is, the effective light emission region) excluding these regions.

Thus, in this type of side light type surface light source device, if the length of the fluorescent lamp 8 is shortened to about the same as the length of the incident surface, or if it is shorter than this,
As shown by the reference numeral B (FIG. 12), there is a problem that the amount of emitted light is partially reduced at the corner on the incident surface side, and luminance unevenness occurs near the incident surface.

In such a case, if the amount of light emitted from these corners B can be increased to the same extent as the other parts, the light emitting surface of the light-scattering light guide plate 2 can be used effectively, and The sidelight type surface light source device can be reduced in size.

The present invention has been made in view of the above points, and it is an object of the present invention to propose a side light type surface light source device capable of reducing uneven brightness near an incident surface.

[0016]

According to the present invention, an illumination light emitted from a predetermined light source is incident on an end face of a plate-like member, and the illumination light is bent to form the plate-like member. The present invention is applied to a sidelight type surface light source device that emits light from an emission surface. In this sidelight type surface light source device,
The exit surface of the plate-like member is formed substantially flat, and the back surface facing the emission surface is formed by a substantially flat surface and a curved surface smoothly connected to the substantially flat surface. Further, the gap between the emission surface and the substantially flat surface on the back surface is formed so as to gradually decrease toward the surface facing the end surface from the end surface. Then, due to the curved surface of the back surface, the width of the end face is reduced as the distance from the effective light emitting area of the light source increases.

At this time, the light source is formed by a fluorescent lamp.

Alternatively, the light source is formed by a point light source.

In addition to or instead of this,
A flat reflecting member is arranged on the back side of the plate-shaped member in parallel with the back side.

Alternatively, on the back side of the plate member,
A reflection member having a shape along this back surface is arranged.

In a similar side light type surface light source device, when a notch is formed in an end face of the plate-like member, an emission surface is formed substantially flat, and a back surface facing the emission surface is formed as an end surface. As you move toward the surface opposite to the end surface,
A substantially flat surface formed so that the distance from the emission surface is gradually reduced, and a shape which is smoothly connected to the substantially flat surface and extends from the vicinity of the notch toward the surface facing the end surface, and Preferably, the plate-shaped member is formed by a curved surface formed so as to have a region where the plate thickness is reduced.

Further, when the present invention is applied to a similar sidelight type surface light source device, when the through-hole and / or the concave portion is formed on the back surface opposite to the emission surface of the plate-like member, the emission surface is formed substantially flat. A substantially flat surface formed so that the distance between the back surface facing the light-emitting surface and the light-emitting surface is gradually reduced toward the surface facing the end surface from the end surface, and the substantially flat surface is smoothly connected to the substantially flat surface. And a curved surface formed so as to extend from the vicinity of the through hole and / or the concave portion toward the surface facing the end surface and locally to form a region where the plate-shaped member has a reduced thickness. .

In this type of sidelight type surface light source device, if the curved surface is formed on the back surface of the plate-like member so that the end face of the plate-like member becomes narrower as the distance from the effective light-emitting area of the light source increases, the plate-like member becomes flat. Out of the illuminating light propagating inside the member, the illuminating light reaching the curved surface portion is promoted, and the luminance level of this portion is increased.

At this time, if the light source is formed by a fluorescent lamp, even when the light source is formed by a fluorescent lamp having a length equal to or shorter than the entire width of the plate member, it is possible to effectively reduce the luminance level near the electrode of the fluorescent lamp. Can be avoided.

Alternatively, in the case where the light source is formed by a point light source such as a light emitting diode, for example, a decrease in the brightness level between the light emitting diodes can be effectively avoided.

In addition to or instead of this,
If a flat reflecting member is arranged on the back surface side of the plate member, in addition to the illumination light incident from the end surface, the illumination light propagating in the space formed by the back surface and the reflecting member transmits through the plate member. Then, the amount of light emitted from the corner is increased.

Alternatively, on the back side of the plate member,
If a reflecting member having a shape along this back surface is arranged, only the illumination light propagating along the same path as the other portions is emitted from the corner.

Also, when applied to a similar sidelight type surface light source device, the curved surface formed on the back surface extends from the vicinity of the notch toward the surface facing the end surface, and the thickness of the plate locally increases. By forming the thinned region, the emission of the illumination light can be promoted in the shadow portion due to the cutout.

Similarly, the curved surface formed on the back surface extends from the vicinity of the through hole and / or the concave portion formed on the back surface toward the surface facing the end surface, and the plate thickness is locally reduced. By forming such a region, the emission of illumination light can be promoted at the shadowed portion due to the through hole or the concave portion.

[0030]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(1) First Embodiment FIG. 1 is an exploded perspective view showing a sidelight type surface light source device according to an embodiment of the present invention as viewed from a reflection sheet side.
The side light type surface light source device 10 is a light scattering light guide plate 1
The primary light source 3 is arranged on the side of the light source 2, and the reflection sheet 4, the light scattering light guide plate 12, and the prism sheet 5 serving as a light control member are sequentially laminated. In this side light type surface light source device 10, the side light type surface light source device 1 shown in FIG.
The same configurations as those described above are denoted by the corresponding reference numerals, and redundant description will be omitted.

Here, the side light type surface light source device 10
In the above, a sheet material made of a regular reflection member on which silver is deposited is applied to the reflection sheet 4 so as to exhibit a high reflectance to illumination light.
The leaking illumination light is efficiently returned to the inside of the light scattering light guide plate 12, and the utilization efficiency of the illumination light is improved.

The light-scattering light guide plate 12 is formed, for example, in a matrix made of polymethyl methacrylate (PMMA).
It is formed by uniformly dispersing and mixing light-transmitting fine particles having different refractive indices from this, and is formed in a wedge-shaped cross section as a whole in a direction perpendicular to the incident surface 12A. As a result, the light-scattering light-guiding plate 12 scatters the illumination light L incident from the incident surface 12A by the transparent fine particles, and
The light is repeatedly reflected and propagated between the light emitting surface 12C and the light emitting surface 12C. At this time, a part of the light is emitted from the light emitting surface 12C.

Further, the light-scattering light guide plate 12 has a flat exit surface, while the rear surface 12B has a flat surface.
It is formed by a combination of this flat surface and a smoothly connected curved surface, whereby the width of the incident surface 12A becomes narrower as the distance from the effective light emitting area of the fluorescent lamp 8 increases, and the thickness of the light scattering light guide plate 12 becomes locally narrow. It is formed so that it becomes. As a result, the light-scattering light-guiding plate 12 is formed in a wedge-shaped cross-section so that the distance between the exit surface and the plane constituting the back surface is gradually reduced.

That is, the incident surface 12A of the light scattering light guide plate 12
The portion corresponding to the effective light emitting area of the fluorescent lamp 8 is formed with a constant plate thickness. Further, the incident surface of the light-scattering light guide plate 12 has a curved surface shape on the back surface so that the electrode 8 of the fluorescent lamp 8
The portions corresponding to A and 8B are formed so that the plate thickness gradually decreases as the distance from the effective light emitting area of the fluorescent lamp 8 increases and approaches the side surfaces 12E and 12F.

On the other hand, when viewed from the side, the light-scattering light-guiding plate 12 is formed by a flat surface and a curved surface forming the back surface.
On the B side, the incident surface side corner is formed into a shape that is locally chamfered. That is, the light scattering light guide plate 12 is
Immediately near the side surfaces 12E and 12F, the incident surface side is formed to be thin, is gradually formed toward the wedge-shaped tip, and is gradually formed to be thin thereafter. The inflection point of the light-scattering light-guiding plate 12 becomes thicker toward the wedge-shaped tip as described above, and then the inflection point at which the plate thickness starts to be thinner goes inward (the X direction in FIG. 1) from the side surfaces 12E and 12F. Is formed to be close to the incident surface side according to

The light scattering light guide plate 1 thus formed
For example, the surface 2 is formed such that the curved surface constituting the back surface 12B is a free-form surface, and the curvature of the curved surface is gradually changed, so that the plane constituting the back surface 12B is smoothly connected to these curved surfaces. . Thereby, the light scattering light guide plate 12
The boundary between the plane and the curved surface is difficult to detect when viewed from the exit surface.

In the above configuration, the illuminating light emitted from the fluorescent lamp 8 (FIG. 1)
After being reflected by the light incident on the inside of the light scattering light guide plate 12 from the incident surface 12A, while being scattered by the light transmitting fine particles,
The light is repeatedly reflected between the back surface 12B and the emission surface 12C, propagates inside the light scattering light guide plate 12, and is emitted from the emission surface 12C.

At this time, in a region substantially corresponding to the effective light-emitting region of the fluorescent lamp 8, illumination light is incident on the emission surface 12C from the incident surface 12A at a predetermined angle distribution, and the illumination light is transmitted through fine particles. Back side 1 while being scattered by
Reflection is repeated between 2B and the output surface 12C, and components smaller than the critical angle are output from the output surface 12C.

On the other hand, as shown in FIG. 2, on both sides corresponding to the electrodes 8A and 8B of the fluorescent lamp 8,
When the illumination light emitted from the effective light emitting region arrives, many components of the illumination light have a large incident angle with respect to the emission surface 12C. In addition, the light amount of this portion is lower than that of the central portion as a whole. That is, at both corners near the incident surface, the amount of illumination light itself is small, and most of the illumination light has a large incident angle with respect to the emission surface 12C. As a result, in the light-scattering light-guiding plate 2 (FIG. 12) similar to the related art, the amount of emitted light decreases at the corner near the incident surface.

On the other hand, in the present embodiment, since the plate thickness is small at the corner near the incident surface, a large incident angle component with respect to the exit surface 12C is correspondingly increased.
B and the exit surface 12C are repeatedly reflected, and the back surface 12B
Each time the light is reflected, the incident angle with respect to the emission surface 12C decreases. Thereby, the light scattering light guide plate 12 sharply reduces the incident angle of the illumination light to the emission surface 12B at the corner, promotes the emission of the illumination light at the corner, and increases the amount of emitted light at the corner.

Further, with respect to the illumination light which is emitted and thus propagates through the inside of the light scattering light guide plate 12 which is insufficient, the illumination light which propagates through the center side of the light scattering light guide plate 12 is distributed by scattering, and is wedge-shaped. A decrease in the brightness level on the mold tip side is avoided.

Further, in this embodiment, as shown in FIG. 3, at the corner of the light scattering light guide plate 12 on the incident surface side, the illumination light reflected by the reflector 9 is transmitted between the reflection sheet 4 and the light scattering light guide plate 12. This illumination light propagates through the back surface 12
B passes through the light-scattering light guide plate 12 and is emitted. Thus, in this embodiment as well, a decrease in the luminance level at the corner near the incident surface is reduced.

According to the results of the experiments, the side light type surface light source device having the conventional structure can obtain a light amount of only about 70% at the corner on the incident surface side as compared with the central portion. According to this embodiment, it was possible to obtain a light amount substantially equal to that of the central portion.

According to the above configuration, in the light-scattering light-guiding plate 12 formed so that the thickness becomes gradually thinner as the distance from the incident surface as a whole is increased, the back surface 12B is constituted by a flat surface and a curved surface. Since the width of the incident surface 12A is reduced as the distance from the effective light emitting area of the fluorescent lamp 8 increases, the angle of incidence of the illumination light on the exit surface 12B at the corner near the incident surface is sharply reduced, and these illuminations are reduced. Light emission can be promoted.
As a result, the amount of emitted light at the incident surface side corner can be increased, and the luminance unevenness near the incident surface can be reduced accordingly.

(2) Second Embodiment FIG. 4 is an exploded perspective view showing a sidelight type surface light source device according to a second embodiment of the present invention in comparison with FIG. In FIG. 4, the same components as those of the sidelight type surface light source device 1 of FIG. 1 are denoted by the corresponding reference numerals, and redundant description will be omitted.

In this side light type surface light source device 20, a reflection sheet 24 is arranged on the back surface 12B side of the light scattering light guide plate 12 along the surface shape of the back surface 12B. Here, as the reflection sheet 24, a sheet material made of a silver-deposited regular reflection member is applied so as to exhibit a high reflectance with respect to the illumination light, whereby the illumination light leaking from the back surface 12B of the light-scattering light guide plate 12 is applied. To the inside of the light scattering light guide plate 12 efficiently,
Improve the utilization efficiency of illumination light.

That is, the side light type surface light source device 10 described above with reference to FIG.
Illumination light propagating inside the light scattering light guide plate 12 (FIG. 2);
The illuminating light propagating in the space between the light scattering light guide plate 12 and the reflection sheet 4 and passing through the light scattering light guide plate 12 forms an emission surface 12B.
Is emitted. On the other hand, in other parts, only the illumination light propagating inside the light scattering light guide plate 12 is emitted. Accordingly, in the above-described sidelight type surface light source device 10, the color of the light exit surface 12B may be slightly different between the corner and the other portion, and it may be applied to a liquid crystal display panel to give an uncomfortable feeling to the observer.

In this embodiment, however, only the illumination light propagating inside the light-scattering light guide plate 12 is emitted at the corners as well, so that this kind of subtle change in color is effectively avoided. Thus, the sense of incongruity of the observer can be effectively avoided.

According to the configuration shown in FIG. 4, in addition to the configuration of the first embodiment, the change in the color tone at the corner of the exit surface is achieved by disposing the reflection sheet 24 along the surface shape of the back surface 12B. Effective avoidance can reduce uneven brightness near the incident surface.

(3) Third Embodiment FIG. 5 is an enlarged front view showing a corner of an incident surface of a light-scattering light guide plate, and shows a side light type surface light source device according to a third embodiment. This light scattering light guide plate 22 is applied.

The light-scattering light guide plate 22 is, like the light-scattering light guide plate 12 applied to the sidelight type surface light source device of FIG. Due to the shape of the curved surface, the portions corresponding to the electrodes 8A and 8B are formed so that the width of the incident surface 22A gradually decreases as the distance from the effective light emitting region increases. At this time, the light scattering light guide plate 22
Is set such that after the width of the incident surface gradually narrows toward both side surfaces, the rate of narrowing increases, and thereafter the rate of narrowing again gradually decreases.

Further, the position where the width of the light incident surface of the light scattering light guide plate 22 starts to gradually decrease is determined by the above-mentioned first position.
And the light-scattering light-guiding plates 12 and 22 according to the second embodiment are formed on the effective light-emitting area side, thereby forming the incident surface 12A.
Are formed so as to protrude toward the effective light emitting area.

In this embodiment, the same reflection sheet as that applied to the first or second embodiment is applied to the reflection sheet.

According to the structure shown in FIG. 5, an area having a narrow width is formed so as to protrude toward the effective light emitting area, and light scattering is performed such that the width of the incident surface 22A is gradually reduced as the distance from the effective light emitting area increases. Even when the light guide plate is formed, the same effect as in the first or second embodiment can be obtained. Further, at this time, by forming a narrow region on the incident surface so as to protrude toward the effective light emitting region side, the amount of emitted light at the corner on the incident surface side can be increased accordingly.

(4) Fourth Embodiment FIG. 6 is an enlarged front view showing a corner of an incident surface of a light-scattering light guide plate, and shows a sidelight type surface light source device according to a fourth embodiment. In this case, the light scattering light guide plate 32 is applied.

The light-scattering light guide plate 32 has a flat emission surface, a flat back surface, and a smooth flat surface, similarly to the light-scattering light guide plate 12 applied to the sidelight type surface light source device of FIG. With the curved surfaces on the back surface, the width of the incident surface 32A is gradually reduced at portions corresponding to the electrodes 8A and 8B as the distance from the effective light emitting region increases. At this time, the light scattering light guide plate 3
2, the position where the width of the incident surface starts to narrow toward both side surfaces is formed on both side surfaces than the light scattering light guide plates 12 and 22 according to the above-described first and second embodiments. As a result, the narrower area on the incident surface 32A is allocated to a smaller area on both sides than the effective light emitting area.

In this embodiment, the same reflection sheet as that applied to the first or second embodiment is applied to the reflection sheet.

According to the structure shown in FIG. 6, the narrower area is assigned to the smaller area on both sides than the effective light emitting area, and the farther from the effective light emitting area, the larger the incidence surface 32A.
Even if the light scattering light guide plate is formed so that the width of
The same effect as in the first or second embodiment can be obtained. Furthermore, at this time, in the incident surface, the area for narrowing the width is allocated to small regions on both side surfaces outside the effective light emitting region, so that when the degree of increase in the amount of light required at the corner is small, the area near the incident surface is reduced. The generated uneven brightness can be reduced.

(5) Fifth Embodiment FIG. 7 is a perspective view showing a light-scattering light guide plate viewed from the back side. In the side light type surface light source device according to this embodiment, a light scattering light guide plate 42 is applied instead of the light scattering light guide plate 12 applied to the side light type surface light source device of FIG.

Here, similarly to the light scattering light guide plate 12 described above with reference to FIG. 1, the light scattering light guide plate 42 has a flat emission surface, a flat back surface, and a curved surface smoothly connected to this flat surface. Due to this curved surface, in the portion corresponding to the electrodes 8A and 8B, as the distance from the effective light emitting area increases,
The incident surface 42A is formed so that the width of the incident surface is gradually reduced.

On the other hand, when viewed from the side, the light-scattering light-guiding plate 42 has a flat surface and a curved surface on the rear surface 42B side so as to form an elongated shape from the corner on the incident surface side to the wedge-shaped tip. Is formed. Thus, the light scattering light guide plate 42 applies the configuration of the side light type surface light source device having the conventional configuration, and when the range of increase in the amount of light required at the corner extends to the wedge-shaped tip, the amount of light emitted from these regions is reduced. As a result, it is possible to reduce uneven brightness not only in the vicinity of the incident surface but also in the vicinity of the incident surface to the wedge-shaped tip.

According to the configuration shown in FIG. 7, the same effect as that of the first embodiment can be obtained, and the back surface 4 is formed so as to be elongated from the corner on the incident surface side to the tip of the wedge.
By forming the flat surface and the curved surface forming the 2B, it is possible to reduce the uneven brightness not only near the incident surface but also from the vicinity of the incident surface to the wedge-shaped tip.

(6) Sixth Embodiment FIG. 8 is an exploded perspective view showing a primary light source and a light-scattering light guide plate as viewed from the back side. In the side light type surface light source device according to this embodiment, the light scattering light guide plate 52 and the primary light source 53 are applied.

The primary light source 53 is a point light source.
The light emitting diodes 54 are arranged at predetermined intervals on the printed wiring board 55, and the light emitting diodes 54 and the printed wiring board 55 are surrounded by a reflector (not shown).

The light-scattering light-guiding plate 52, like the light-scattering light-guiding plate 12 described above with reference to FIG. 1, has a flat emission surface, a flat back surface 52B, and a curved surface smoothly connected to this flat surface. With this curved surface, the light emitting diode 5
The width of the incident surface 52A is formed so as to gradually decrease as the distance from the light-emitting portion (effective light-emitting region) 4 increases.

That is, in the light-scattering light-guiding plate 52, the incident surface 52 A is formed to have a constant plate thickness at a portion corresponding to the light emitting portion of the light emitting diode 54.
The width is gradually reduced as the distance from the portion corresponding to the light-emitting portion becomes smaller.

The thickness of the light scattering light guide plate 52 is
In the direction along both side surfaces 52E and 52F near 2E and 52F, the thickness is gradually increased from the incident surface 52A side, and then gradually decreased toward the wedge-shaped tip. Similarly, at the intermediate position between the light emitting diodes 54 and in the direction along both side surfaces 52E and 52F, the plate thickness gradually increases from the incident surface 52A side, and then gradually decreases toward the wedge-shaped tip. It is formed. Thus, even when the illumination light is emitted with a sharp directivity in the front direction of the light emitting diode 54, the light scattering light guide plate 52 is designed to promote the emission of the illumination light in a region shifted from the front direction.

Further, the light scattering light guide plate 52 is formed so that the curvature of the curved surface constituting the back surface 52B is gradually changed.
As a result, the flat surface constituting the back surface 52B and these curved surfaces are smoothly connected, and the boundary between the flat surface and the curved surface is difficult to detect when viewed from the emission surface.

According to the configuration shown in FIG. 8, even when a primary light source is formed by a light emitting diode that emits illumination light with sharp directivity, luminance unevenness near the incident surface can be reduced.

(7) Seventh Embodiment FIG. 9 is a perspective view showing a light-scattering light-guiding plate viewed from the back side. In the side light type surface light source device according to this embodiment, the light scattering light guide plate 62 is applied.

In the side light type surface light source device, the prism sheet, the light scattering light guide plate 62, the reflection sheet, and the primary light source 3 are held in a predetermined frame (not shown). In this frame, substantially columnar projections are formed on both sides of the incident surface 62A of the light scattering light guide plate 62, and the projections hold the light scattering light guide plate 62 so as not to be displaced toward the primary light source.

The light-scattering light guide plate 62 has arc-shaped notches 62G and 62H at the corners on the incident surface 62A side corresponding to the projections of the frame. That is, the light-scattering light-guiding plate 62 is formed by, for example, uniformly dispersing and mixing light-transmitting fine particles having a different refractive index from a matrix made of, for example, polymethyl methacrylate, and is formed in a wedge-shaped cross section as a whole. Further, in the light scattering light guide plate 62, both corners on the incident surface 62A side are cut out in an arc shape when viewed from the exit surface 62C.

The light-scattering light-guiding plate 62 has a rear surface 62B formed by a flat surface and a curved surface smoothly connected to the flat surface.
The 2H shadow portion is smoothly squared in a range from the incident surface side to a substantially central portion on the wedge-shaped tip side. That is, the cutout portions 62G and 62H of the light-scattering light guide plate 62 are formed to have a smaller thickness in the cross section in the direction parallel to the incident surface 62A than the other portions. The width is formed so as to gradually decrease and extend toward the wedge-shaped tip from the incident surface 62A.

Notches 62G, 62 are formed in the light-scattering light guide plate 62.
When H is formed, the amount of emitted light is reduced at the wedge-shaped tip side of the notches 62G and 62H, but as shown in FIG.
When a part of the back surface 62B is formed into a curved surface to locally form a thin region, the emission of illumination light is promoted in this region. Therefore, notches 62G and 62H are formed in the light scattering light guide plate 62.
Is formed, the luminance distribution of the emitted light can be made uniform.

According to the configuration shown in FIG. 9, by locally reducing the plate thickness near the notch and on the wedge-shaped tip end side, it is possible to promote the emission of illumination light at these portions. Therefore, it is possible to avoid a decrease in the luminance level on the wedge-shaped tip side of the notch, and to effectively avoid luminance unevenness. Further, since the notches 62G and 62H are formed by arcuate curved surfaces, it is possible to effectively avoid the occurrence of bright lines and the like due to the notches.

(8) Eighth Embodiment FIG. 10 is a perspective view showing a light-scattering light guide plate viewed from the back side. In the side light type surface light source device according to this embodiment, the light scattering light guide plate 72 is applied.

In this side light type surface light source device, after a prism sheet, a light scattering light guide plate 72, a reflection sheet, and a primary light source are laminated on a predetermined frame, a through hole 74 formed at a corner of the light scattering light guide plate 72 is formed. The prism sheet, the light-scattering light guide plate 72, and the reflection sheet are fixed to the frame by using.

Here, the light scattering light guide plate 72 has a through hole 74 at a corner on the incident surface side. The light scattering light guide plate 72 is formed in the same manner as the light scattering light guide plate of the conventional configuration except that the peripheral shape of the through hole 74 is different. That is, the light scattering light guide plate 7
2, the back surface 72B is formed by a flat surface and a curved surface that is smoothly connected to the flat surface, and the curved surface of the back surface is formed such that the shadow portion of the through hole 74 is locally reduced in thickness. .

That is, the light scattering light guide plate 72 is
As shown in the cross section in FIG. 11, which is cut off along the line C-C crossing the center of, the plate thickness is the thinnest near the through-hole 74 and almost in the vicinity of the incident surface 72A with respect to the through-hole 74, and the wedge-shaped tip side A region is formed such that the plate thickness gradually increases toward. In addition, when viewed in the direction along the side surface 72E, this region becomes thinnest in the vicinity of the through hole 74 at a portion corresponding to the center of the through hole 74, and then gradually becomes thicker toward both side surfaces. It is formed so that it becomes.

As a result, the light-scattering light-guiding plate 72 promotes the emission of the illuminating light in the shadow portion generated by forming the through-hole, thereby effectively avoiding luminance unevenness.

According to the configuration shown in FIGS. 10 and 11, even when a through hole is formed in the light scattering light guide plate, the plate thickness is locally thinned at the wedge-shaped tip side of the through hole, so that the luminance is reduced. Unevenness can be effectively avoided. Further, at this time, by smoothly connecting the flat surface constituting the back surface to the curved surface to locally reduce the plate thickness, it is possible to effectively avoid the occurrence of bright lines or the like due to the locally reduced plate thickness.

(9) Other Embodiments In the above-described seventh embodiment, the case where the notch is formed at the corner of the incident surface has been described. However, the present invention is not limited to this. The present invention can be widely applied to a case in which notches are formed at various places on the incident surface, such as a case where a notch is formed in a central portion of a surface.

In the above-described eighth embodiment,
Although the case where the through hole is formed at the corner of the incident surface has been described, the present invention is not limited to this. For example, a case where a concave portion is formed on the back surface of the light scattering light guide plate and the light scattering light guide plate is positioned by the concave portion, etc. Can also be widely applied.

Further, in the above-described embodiment, the case where the double-sided prism sheet is disposed on the exit surface has been described. However, the present invention is not limited to this, and a so-called single-sided prism sheet having a prism surface formed on one side may be used. When stacked and arranged toward the emission surface side or the opposite side,
Further, the present invention can be widely applied to a case where a prism surface is formed on the exit surface and the back surface of the light scattering light guide plate.

In the above embodiment, the case where the reflection sheet is formed by the regular reflection member made of the sheet material on which silver is deposited has been described. However, the present invention is not limited to this.
The present invention can be widely applied to the case of forming the lens using various regular reflection members, and further, irregular reflection members such as white PET.

Further, in the above-described embodiment, the case where the light scattering light guide plate is formed by mixing light-transmitting fine particles has been described. However, the present invention is not limited to this, and light is mixed by mixing various fine particles. It can be widely applied to the case where a scattering light guide plate is formed.

Further, in the above-described embodiment, the case where the present invention is applied to the side light type surface light source device using the light scattering light guide plate which scatters the illumination light inside has been described. The present invention is not limited to this, and can be widely applied to a sidelight type surface light source device in which a light guide plate is formed by a transparent member having a wedge-shaped cross section. In the case of using such a transparent member, a diffusion pattern is formed on the emission surface or a surface facing the emission surface by matting, printing, or the like, but can be widely applied to any case.

Further, in the above-described embodiment, the case where the illumination light is incident from one end face has been described. However, the present invention is not limited to this, and the sidelight type surface is also configured to receive the illumination light from the other end face. It can be widely applied to light source devices.

In the above-described embodiment, the case where the primary light source is constituted by the fluorescent lamp which is a rod-shaped light source or the case where the primary light source is constituted by a light-emitting diode which is a point light source has been described. However, the present invention is not limited to this. Instead, the present invention can be widely applied to a case where a primary light source is formed by various light sources.

Further, in the above-described embodiment, the case where the present invention is applied to the surface light source device of the liquid crystal display device has been described. However, the present invention is not limited to this, and the present invention is not limited to this. It can be widely applied to a surface light source device.

[0092]

As described above, according to the present invention, the back surface of the plate-like member is formed by a substantially flat surface and a curved surface, and the curved surface is used to locally form a thin portion with a small amount of outgoing light. Brightness unevenness in the vicinity can be reduced.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a sidelight type surface light source device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining the propagation of illumination light at a corner near an incident surface in the light-scattering light guide plate of FIG.

FIG. 3 is a cross-sectional view for explaining transmission of illumination light at a corner near an incident surface in the light-scattering light guide plate of FIG. 1;

FIG. 4 is an exploded perspective view showing a side light type surface light source device according to a second embodiment of the present invention.

FIG. 5 is an enlarged front view showing a light scattering light guide plate applied to a sidelight type surface light source device according to a third embodiment of the present invention.

FIG. 6 is an enlarged front view showing a light scattering light guide plate applied to a side light type surface light source device according to a fourth embodiment of the present invention.

FIG. 7 is a perspective view showing a light scattering light guide plate applied to a side light type surface light source device according to a fifth embodiment of the present invention.

FIG. 8 is an exploded perspective view showing a light scattering light guide plate applied to a side light type surface light source device according to a sixth embodiment of the present invention, together with a primary light source.

FIG. 9 is an exploded perspective view showing a light-scattering light guide plate applied to a sidelight type surface light source device according to a seventh embodiment of the present invention.

FIG. 10 is a perspective view showing a light-scattering light guide plate applied to a sidelight type surface light source device according to an eighth embodiment of the present invention.

FIG. 11 is a cross-sectional view of FIG. 10 cut along line CC.

FIG. 12 is an exploded perspective view showing a conventional sidelight type surface light source device.

FIG. 13 is a cross-sectional view of FIG. 11 taken along line AA.

[Explanation of symbols]

1, 10, 20 Sidelight type surface light source device 2, 12, 32, 42, 52, 62, 72
Light scattering light guide plate 2A, 12A, 32A, 42A, 52A, 62A, 72
A Incident surface 2B, 12B, 32B, 42B, 52B, 62B, 72
B back

Claims (7)

[Claims] 1. A sidelight type surface light source device for irradiating illumination light emitted from a predetermined light source from an end face of a plate-like member, bending the illumination light and emitting the illumination light from an emission surface of the plate-like member, The plate-like member is formed such that the emission surface is formed in a substantially flat surface, and a back surface opposed to the emission surface is formed by a substantially flat surface and a curved surface that is smoothly connected to the substantially flat surface. The distance between the emission surface and the substantially flat surface of the back surface is formed so as to gradually decrease toward the opposing surface, and the end surface is narrower as the distance from the effective light emitting region of the light source increases due to the curved surface. A side light type surface light source device characterized by being formed in such a shape. 2. The side light type surface light source device according to claim 1, wherein said light source is a fluorescent lamp. 3. The side light type surface light source device according to claim 1, wherein the light source is a point light source. 4. A sidelight type according to claim 1, wherein a flat reflecting member is arranged on a back side of said plate-shaped member in parallel with said substantially flat surface. Surface light source device. 5. The side light type surface light source according to claim 1, wherein a reflection member having a shape along the rear surface is arranged on a rear surface side of the plate-shaped member. apparatus. 6. A sidelight-type surface light source device which irradiates illumination light emitted from a predetermined light source from an end face of a plate member, bends the illumination light and emits the illumination light from an emission surface of the plate member. The plate-shaped member has a notch in the end surface, the emission surface is formed in a substantially flat surface, and a back surface facing the emission surface is directed from the end surface to a surface facing the end surface.
A substantially flat surface formed so that the distance from the emission surface is gradually narrowed; a shape which is smoothly connected to the substantially flat surface and extends from the vicinity of the notch toward a surface facing the end surface. A side light-type surface light source device characterized by being locally formed by a curved surface formed such that a region where the plate-shaped member has a reduced thickness is locally formed. 7. A sidelight-type surface light source device which irradiates illumination light emitted from a predetermined light source from an end face of a plate member, bends the illumination light and emits the illumination light from an emission surface of the plate member. In the plate-shaped member, a through hole and / or a concave portion is formed on the back surface facing the emission surface, the emission surface is formed substantially flat, and the back surface facing the emission surface faces the end surface from the end surface. As you approach the surface,
A substantially flat surface formed so that the distance from the emission surface is gradually reduced; and a smooth connection with the substantially flat surface, and extending from a vicinity of the through hole and / or the concave portion toward a surface facing the end surface. A side light type surface light source device characterized by being formed in such a shape and locally having a curved surface formed such that a region where the plate-shaped member has a small thickness is formed.