JPH1048427A - Side light type surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively avert the occurrence of unequal luminance and to surely prevent a light guiding plate moving to the light source side by forming a stopper on the exit surface side on the front is side facing the end face of a plate member and positioning the plate member so as not to move to the primary light source side. SOLUTION: The light scattering light-guiding plate 12 which receives the illumination light emitted from a fluorescent lamp 6 from an incident surface T and emits the light from an exit surface, has the stopper 12A which projects from the incident surface side at a wedge-shaped front end and meshes with a recessed part formed on the inner side of a frame 11, thereby, the displacement to the fluorescent lamp 6 side is effectively averted. The occurrence of the unequal luminance is effectively averaged by forming the stopper 12A of this time at the edge-shaped front end. The sufficient area and strength are assured at the wedge-shaped front end, by which the failure of the fluorescent lamp 6 is effectively averaged. Since the front end is formed think, the accurate production of the light scattering light-guiding plate 12 is made possible.

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 applied to a liquid crystal display device and the like, and is applied to, for example, a sidelight type surface light source device having directivity. According to the present invention, in the sidelight type surface light source device, a stopper is formed at the end of the light guide plate, at the emission surface side or at the inclined surface side, and by preventing the light guide plate from moving toward the light source by the stopper, the emission light is reduced. Effectively avoid luminance unevenness and prevent damage to the light source.

[0002]

2. Description of the Related Art Conventionally, for example, in a liquid crystal display device,
Illuminates the liquid crystal panel with a sidelight type surface light source device,
As a result, the overall shape is reduced in thickness.

[0003] That is, in the sidelight type surface light source device, a primary light source composed of a rod-like light source such as a cold cathode tube is arranged on the side of a plate-like member (that is, composed of a light guide plate), and illumination light emitted from the primary light source is provided. From the end face of the light guide plate.
Further, the sidelight type surface light source device is formed so that the illumination light is bent and emitted from the plane of the light guide plate toward the liquid crystal 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. 9 is an exploded perspective view showing the configuration of the latter sidelight type surface light source device. The sidelight type surface light source device 1 has a primary side light scattering light guide plate 2 made of a light guide plate. After arranging the light source 3, the reflection sheet 4, the light-scattering light guide plate 2, and the prism sheet 5 as a light control member are laminated. The primary light source 3 is formed by surrounding a fluorescent lamp 6 made of a cold-cathode tube with a reflector 7 made of a reflecting member having a substantially semicircular cross section, and an end face of the light scattering light guide plate 2 from the opening side of the reflector 7. Illumination light is incident on.

The reflection sheet 4 is formed of a sheet-like regular reflection member made of a metal foil or the like, or a sheet-like irregular reflection member made of a white PET film or the like.

The light-scattering light-guiding plate 2 is a light-guiding plate having a wedge-shaped cross section. For example, in a matrix of polymethyl methacrylate (PMMA), light-transmitting fine particles having a different refractive index from the matrix are uniformly mixed and dispersed. It is formed. As a result, as shown in FIG. 10 by taking a cross section along the AA cross section, this light-scattering light-guiding plate 2 has an incident surface T
The illumination light L is incident on the illumination light L
In the case where an irregular reflection member is applied to the reflection sheet 4 while scattering the light, the reflection sheet 4 partially reflects the light, and the reflection sheet 4 side plane (hereinafter referred to as a slope) and the prism sheet 5 side plane (hereinafter an emission plane). ), And the illumination light L propagates.

During this propagation, the illumination light L gradually decreases its incident angle with respect to the exit surface every time it is reflected by the slope, and a component having a critical angle or less with respect to the exit surface is emitted from the exit surface. The illuminating light L1 emitted from the emission surface is scattered by the illuminating light L, which is scattered by the light-transmitting fine particles inside the light-scattering light guide plate 2 and diffusely reflected by the reflection sheet 4 and propagates. Is emitted. However, the illumination light L1 reflects and propagates on a slope formed to be inclined in the propagation direction with respect to the emission surface, so that the main emission direction is directed to the wedge-shaped tip direction as shown by an enlarged arrow B. It is formed inclined. That is, the outgoing light L1 from the light guide plate
Has directivity, whereby the sidelight type surface light source device 1 has directivity emission.

The prism sheet 5 is arranged to correct the directivity. That is, the prism sheet 5 is formed of a translucent sheet material such as polycarbonate, and the prism surface is formed on the side surface of the light scattering light guide plate 2. The prism surface is formed by repeatedly forming projections having a triangular cross-section extending substantially parallel to the incident surface T of the light-scattering light-guiding plate 2 from the incident surface T to the wedge-shaped tip. Thus, the prism sheet 5 corrects the main emission direction of the emission light L1 to the front direction of the emission surface on the slope of the triangular projection.
In addition, as the prism sheet 5, a prism surface in a groove direction substantially orthogonal to the groove direction of the prism surface formed on the surface on the light scattering light guide plate 2 side is further formed on the surface opposite to the light scattering light guide plate 2 side. A so-called double-sided prism sheet having a configuration may be used. Thus, 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 guide plate is formed with a substantially uniform plate thickness. I have.

The light guide plate having directivity as described above has a light guide plate formed in a wedge shape or a shape close to a wedge shape by a transparent member or a translucent member, or a light guide plate formed in a flat plate shape. In some cases, a scattering film, a matte surface, a microlens array, and the like are formed on the emission surface and / or the back surface of the light guide plate. Similarly, in the side light type surface light source device using such a light guide plate, the emitted light can be efficiently emitted in the front direction.

[0011]

By the way, in this type of sidelight type surface light source device, it is mounted on a frame or the like and integrated with a liquid crystal panel, for example, mounted on a personal computer or the like. Accordingly, in the sidelight type surface light source device, it is necessary to easily and surely position and hold the light scattering light guide plate 2 formed of the light guide plate with respect to a holding member such as a frame. In particular, in the side light type surface light source device, when the light scattering light guide plate 2 collides with the fluorescent lamp 6 due to impact or the like, the fluorescent lamp 6
Therefore, it is necessary to securely position and hold the light scattering light guide plate 2 so as not to move to the fluorescent lamp 6 side.

In this case, as shown in FIG. 11, for example, a method is conceivable in which a convex portion 9 is integrally formed on the side surface of the light-scattering light guide plate 2, and the positioning is held by the convex portion 9. However, in this type of sidelight type surface light source device, when the illumination light from the light source is propagated inside the light scattering light guide plate 2 and emitted from the emission surface, the projections 9 are integrally formed as described above. There is a problem in that uneven brightness occurs due to the influence of the projections 9.

That is, when the convex portion 9 is formed integrally, the illumination light which is originally reflected on the side surface of the light scattering light guide plate 2 and turned inward is spread more outwardly than the side surface at the convex portion 9 and the inner side. In this case, a part of the illumination light is emitted to the outside from the end face of the convex portion 9 perpendicular to the side surface of the light-scattering light-guiding plate 2 and leaks out. The amount of the emitted illumination light changes. This change in the amount of light is reflected on the prism sheet 5
Observing the exit surface from the side, the region with a low luminance level (that is, a dark band) that spreads inward from the corner on the incident surface side of the projection 9 toward the wedge-shaped tip, and the corner from the wedge-shaped tip side of the projection 9 A linear region with a high luminance level (that is, a bright line) that spreads inward toward the wedge-shaped tip is formed, whereby luminance unevenness occurs in the illumination light emitted from the emission surface.

Further, as shown in FIG.
A step may be formed near the incident surface side and both ends, and the step may be used for positioning and holding. However, in this case as well, unevenness in luminance occurs due to the influence of the step.

As one method of effectively avoiding the uneven brightness, a method of forming a convex portion 9 on the wedge-shaped tip side as shown in FIG. That is, since this type of luminance unevenness occurs in the wedge-shaped tip direction from the convex portion 9, when the convex portion 9 is formed on the wedge-shaped distal end side in this way, luminance unevenness can be effectively avoided. However, on the wedge-shaped tip side, there is a disadvantage that it is difficult to ensure a sufficient plate thickness. As a result, it is difficult to sufficiently secure the strength of the projection 9, and there is a problem that the movement of the light-scattering light guide plate toward the light source cannot be completely prevented.

The present invention has been made in view of the above points, and a sidelight type surface light source capable of effectively avoiding the occurrence of uneven brightness and reliably preventing the light guide plate from moving toward the light source. It is intended to propose a device.

[0017]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to the present invention, an illumination light is made incident from an end face of a plate-like member, and the illumination light is bent and emitted from an emission surface of the plate-like member. Applies to mold surface light source devices. In this sidelight type surface light source device, a stopper is formed on the emission surface side on the distal end side facing the end surface of the plate member, or on the surface side facing the emission surface on the distal end side, on the primary light source side,
The stopper is used to position the plate member so that the plate member does not move.

At this time, the stopper is formed by a projection projecting from the emission surface or a projection projecting from the surface facing the emission surface.

A relatively sufficient area can be ensured on the emission surface on the distal end side or on the surface side facing the emission surface on the distal end side. Therefore, if a stopper is formed in this portion, sufficient strength can be ensured. In addition, on the tip side, it is possible to effectively avoid luminance unevenness.

Preferably, the stopper is formed by a projection projecting from the emission surface or a projection projecting from the surface opposite to the emission surface, thereby effectively avoiding the occurrence of luminance unevenness. Movement to the side can be reliably prevented.

[0021]

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. The sidelight type surface light source device 10 is mounted on a personal computer together with a liquid crystal panel and the like via a frame 11 serving as a holding member. That is, the side light type surface light source device 10 arranges the primary light source 3 on the side of the light scattering light guide plate 12,
Reflection sheet 4, light scattering light guide plate 12, prism sheet 1
3. The light diffusion sheet 14 and the prism sheet 15 are stacked and held on the frame 11. In the sidelight type surface light source device 10, the same components as those in FIG. 9 are denoted by the same reference numerals, and redundant description will be omitted.

Here, the prism sheet 13 has a prism surface formed on the side surface of the light-scattering light guide plate 12 by a translucent sheet material such as polycarbonate, and a convex portion having a triangular cross section is formed on the prism surface. It is configured to be repeated from the incident surface T in the direction of the wedge-shaped tip almost in parallel with the above. As a result, the prism sheet 13 corrects the main emission direction of the emitted light to the front direction of the emission surface on the slope of each projection.

On the other hand, the prism sheet 15 is formed of the same sheet material as the prism sheet 13, and the direction in which the projections are repeated is orthogonal to the direction in which the projections in the prism sheet 13 are repeated. Thereby, the prism sheet 15 corrects the directivity of the emitted light in the direction parallel to the incident surface T.

The light diffusion sheet 14 is made of a light-transmitting sheet material that scatters light very slightly, and corrects the directivity of the emitted light by the prism sheets 13 and 15 to enlarge the viewing angle of the emitted light.

The light-scattering light-guiding plate 12, like the light-scattering light-guiding plate 2 described above with reference to FIG. 9, has a matrix of polymethyl methacrylate (PMMA) in which light-transmitting fine particles having a different refractive index from the matrix are uniformly dispersed. Into a wedge-shaped cross section. Thereby, the light scattering light guide plate 12
Emits a component having a critical angle or less with respect to the emission surface from the emission surface while repeatedly reflecting and propagating the illumination light of the fluorescent lamp 6 incident from the incidence surface 5 between the emission surface and the inclined surface.

Further, the light-scattering light-guiding plate 12 has a stopper 12A at the wedge-shaped tip portion and at the exit surface. Here, the stopper 12 </ b> A is configured by a band-shaped protrusion parallel to the incident surface T.

On the other hand, the frame 11 is formed of a frame having an opening 11B on the emission surface side of the light scattering light guide plate 12, and corresponds to the stopper 12A of the light scattering light guide plate 12.
A belt-shaped recess 11A is formed inside.

That is, FIG. 2 is a cross-sectional view taken along the line CC.
As shown in the figure, the frame 11 has a stepped periphery surrounding the opening 11B and a band-shaped recess 11A inside.
Is formed, and the stopper 12A is engaged with the concave portion 11A.

In the above configuration, the illumination light emitted from the fluorescent lamp 6 (FIG. 1) is directly or after being reflected by the reflector, enters the light scattering guide plate 12 from the entrance surface T, and The illumination light propagates inside the light-scattering light guide plate 12 while repeating reflection between the inclined surface and the emission surface. At this time, the illumination light, while being scattered inside the light-scattering light-guiding plate 12, gradually decreases the incident angle with respect to the emission surface every time it is reflected on the inclined surface, and a component equal to or less than the critical angle with respect to the emission surface is more than the emission surface. After being emitted, the directivity is corrected by the prism sheet 13, the light diffusion sheet 14, and the prism sheet 15.
Thus, the liquid crystal panel disposed on the front surface of the prism sheet 15 is illuminated.

The light-scattering light-guiding plate 12, which receives the illumination light emitted from the fluorescent lamp 6 from the incident surface T and emits the light from the emission surface, has a stopper 12A projecting from the emission surface at the wedge-shaped tip. It engages with the concave portion 11A formed inside 11, whereby the displacement toward the fluorescent lamp 6 is effectively avoided. At this time, since the stopper 12A is formed at the wedge-shaped tip, the occurrence of luminance unevenness can be effectively avoided. In addition, by being able to secure a sufficient area at this wedge-shaped tip,
Sufficient strength can be ensured, so that the fluorescent lamp 6 can be effectively prevented from being damaged. In addition, since the tip portion is partially thickened, it is possible to obtain an additional effect that the light scattering light guide plate 12 can be manufactured with high precision by molding.

According to the above configuration, the stopper 12A is formed by forming the band-shaped convex portion on the light emitting surface side of the wedge-shaped tip, thereby effectively avoiding luminance unevenness, and moving toward the light source side of the light scattering light guide plate. Can be prevented from moving.

(2) Other Embodiments In the above-described embodiment, one wedge-shaped tip is provided on the emission surface side.
Although the case where the belt-shaped protrusions are formed and the stoppers are formed by the use of the protrusions has been described, the present invention is not limited to this.
As shown in (2), a plurality of projections 22A and 22B may be formed on the wedge-shaped tip of the light-scattering light-guiding plate 22 and on the emission surface side, and a stopper may be formed by these projections 22A and 22B.
In these cases, as shown in FIG. 4, the stopper may be formed by partially projecting the side surface of the light-scattering light-guiding plate 32 and forming the projections 32A and 32B on the emission surface side. In this case, it is necessary to form the projection so as to be continuous from the portion of the emission surface concealed by the frame to the overhanging portion, so that practically sufficient strength can be secured.

In the above-described embodiment, the case where the stopper is held by the concave portion on the frame side has been described. However, the present invention is not limited to this, and the stopper is held by the groove-shaped opening as shown in FIG. You may.

Further, in the above-described embodiment, the case where the stopper is formed on the emission surface side of the light scattering light guide plate is described. However, the present invention is not limited to this, and the slope side may be changed according to the method of holding the light scattering light guide plate. May be formed with a stopper. For example, as shown in FIG. 6, a stopper may be formed on the emission surface side after the tip is bent to the slope side. Further, as shown in FIG. 7, when the light-scattering light guide plate is held by the upper frame and the lower frame, a stopper by a projection may be formed on the slope side. Further, as shown in FIG. 8, when the case is directly held on the case by a holder such as a metal plate, similarly, a stopper by a protrusion is formed on the slope side, and the stopper is held via a spacer or the like as necessary. You may.

Further, in the above-described embodiment, the case where the stopper is formed by the convex portion has been described. However, the present invention is not limited to this. A concave portion, a notch, or the like may be formed in the thick portion to form a stopper. In the present invention, since the position of the stopper is on the distal end side,
It is possible to substantially eliminate the occurrence of luminance unevenness on the emission surface due to the stopper. Therefore, the present invention can be widely applied to a surface light source device having a structure that does not use a diffusion sheet having a high diffusivity, and luminance unevenness can be effectively avoided.

Further, in the above-described embodiment, the case where the present invention is applied to a side light type surface light source device using a light scattering light guide plate made of a light guide plate in which translucent fine particles are mixed and dispersed is described. The present invention is not limited to this, and includes a sidelight-type surface using a light guide plate having directional emission, including, for example, those configured to have a directional emission by being subjected to a predetermined processing in a flat plate shape. It can be widely applied to light source devices.

Further, in the above 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.

[0039]

As described above, according to the present invention, in the sidelight type surface light source device using the light guide plate having directivity and light emission, the stopper is formed at the tip of the light guide plate, the emission surface side or the slope side. Accordingly, it is possible to effectively avoid the uneven brightness of the emitted light, and to prevent the light guide plate from moving toward the light source by the stopper, thereby preventing damage to the light source.

[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 sectional view of the sidelight type surface light source device of FIG. 1 taken along line CC.

FIG. 3 is a perspective view showing a light-scattering light guide plate of a side light type surface light source device according to another embodiment.

FIG. 4 is a perspective view showing another embodiment of FIG. 3;

FIG. 5 is a cross-sectional view showing another embodiment in which a groove-shaped convex portion is formed on an emission surface in comparison with FIG. 2, and the convex portion is held by an opening on a case side.

FIG. 6 is a cross-sectional view showing another embodiment in which the stopper is formed by bending the tip in comparison with FIG.

FIG. 7 is a cross-sectional view showing another embodiment in which a stopper is formed on a slope side of a front end in comparison with FIG.

FIG. 8 is a cross-sectional view showing another embodiment in which a stopper is formed on the slope side of the front end in comparison with FIG.

FIG. 9 is an exploded perspective view showing a conventional sidelight type surface light source device.

FIG. 10 is a cross-sectional view of the sidelight type surface light source device of FIG. 9 taken along a line AA.

FIG. 11 shows a conventional sidelight type surface light source device.
It is a perspective view which shows the case where a convex part is formed.

FIG. 12 shows a conventional sidelight type surface light source device.
FIG. 7 is a perspective view showing a case where a step is formed near both ends of an incident surface.

FIG. 13 shows a side light type surface light source device of FIG.
It is a perspective view which shows the case where a convex part is formed in the side surface of a wedge-shaped front-end | tip.

[Explanation of symbols]

1, 10 Side light type surface light source device 2, 12, 22, 32 Light scattering light guide plate 3 Primary light source 6 Fluorescent lamp 9, 12A, 22A, 22B, 32A, 32B Convex part T Incident surface

Claims (3)

[Claims] 1. A side light type surface light source device in which illumination light is incident from an end face of a plate-shaped member, and the illumination light is bent and emitted from an emission surface of the plate-shaped member. A stopper is formed on the emission surface side on the distal end side opposite to or on the surface side facing the emission surface on the distal end side, so that the plate-shaped member does not move to the primary light source side, the stopper A side light type surface light source device, wherein a plate member is positioned. 2. The side light type surface light source device according to claim 1, wherein the stopper comprises a convex portion protruding from the emission surface. 3. The side light type surface light source device according to claim 1, wherein the stopper comprises a convex portion protruding from a surface facing the emission surface.