JPH09231822A - Surface light source device of side light type - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of uneven brightness in the longitudinal direction of a light source by installing an illumination leading part between a rod- shaped light source and the incident surface of a plate-form member from which light is emitted, and leading the light from the effective region of the light source in such a way as spreading topward the end part. SOLUTION: Among the beams of illumination light emitted from a fluorescent lamp 11, the beam L2 emitted at the end of the effective light emission region AR is put incident from the oversurfaces of parallelogramic prisms 12b, 12c of an illumination light lead-in part 12 and is emitted in such a way as distributed to both ends of a light diffusive light-guide member 2. Accordingly a sufficient illumination light L2 is cast onto the end parts even in case the light guide member 2 is longer than the region AR of the lamp 11, and the brightness of the corresponding region is heightened. The illumination beam of light L3 emitted from a part near the central part is scattered within a trapezoidal prism 12a and put incident to the light guide member 2. In the light guide member 2, therefore, sufficient illumination light L3 is cast even onto the shade zones of the slopes of the prisms 12b, 12c, and it is possible to avoid uneven brightness in the emitted light.

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, for example, to a sidelight type surface light source device using a light guide plate having directivity. . According to the present invention, in this sidelight type surface light source device, an illumination light introducing section arranged between the light source and the light guide plate spreads the illumination light emitted from the light source and guides it to the light guide plate, or a wedge shape or the like. The thickness of the light guide plate is locally reduced, and the light diffusing member is selectively arranged on the incident surface side of the light exit surface, thereby increasing the length of the light guide plate from the effective light emitting area of the light source. Therefore, it is possible to effectively avoid the uneven brightness even with a long period.

[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 as to deflect the illumination light and emit the light toward the liquid crystal panel from the plane of the light guide plate, 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. 15 is an exploded perspective view showing the structure of the latter side light type surface light source device. The side light type surface light source device 1 is provided on the side of the light scattering guide 2 made of a light guide plate. After arranging the primary light source 3, the reflection sheet 4, the light-scattering light guide 2, and the prism sheet 5 as a light control member are laminated and formed. Of these, the primary light source 3 is formed by surrounding a fluorescent lamp 7 formed of a cold cathode tube with a reflector 8 formed of a reflecting member having a substantially semicircular cross section.
Illumination light is incident on the end face of the light-scattering light guide 2 from the opening side.

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 member 2 is a light-guiding plate having a wedge-shaped cross-section. For example, a light-transmitting fine particle having a different refractive index from that of a matrix made of polymethyl methacrylate (PMMA) is uniformly mixed and dispersed. Formed. Thereby, as shown in FIG. 16 by taking a cross section along the AA cross section, this light scattering guide 2 has an incident surface T which is an end surface on the primary light source 3 side.
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 being scattered by light-transmitting fine particles inside the light-scattering light guide 2 and diffusely reflected by the reflection sheet 4 and propagated. 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 a directivity, and thus the light scattering guide 2 has a directional emission property.

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 a prism surface is formed on the side surface of the light scattering / guiding member 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 guide 2 from the incident surface T side toward 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.
The prism sheet 5 further includes a prism surface in a groove direction substantially orthogonal to the groove direction of the prism surface formed on the light scattering light guide 2 side on the surface opposite to the light scattering light guide 2 side. A so-called double-sided prism sheet having a formed 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.

As the light guide plate having such a directional emission property, a transparent member or a semi-transparent member is used to form the light guide plate in a wedge shape or a shape close to the wedge shape, or a transparent member is used to form a flat plate shape. There is also one in which a light plate is formed, and a predetermined satin surface, a microlens array, a scattering film, or the like is formed on the exit surface and / or the back surface of the light guide plate. Even in the side light type surface light source device using such a light guide plate, the prism sheet 5 is used so that the emitted light can be emitted in the front direction.

[0011]

By the way, the fluorescent lamp 7 is used.
Has electrodes 7a and 7b formed on both ends thereof, and in the vicinity of the electrodes 7a and 7b, regions where the phosphor is not applied are formed in the tube. Therefore, in the fluorescent lamp 7, a region that does not emit the illumination light is formed near both ends, and a region that emits the illumination light (hereinafter referred to as an effective light emission region).
However, there is a shortage compared to the whole length.

Therefore, in this type of sidelight type surface light source device, there is a problem that the fluorescent lamp 7 having a short length cannot be used. That is, when the length of the light guide plate is longer than the effective light emitting area of the fluorescent lamp, the brightness at both ends of the light guide plate on the incident surface side is reduced, and uneven brightness occurs in the longitudinal direction of the fluorescent lamp.

The present invention has been made in consideration of the above points, and proposes a side light type surface light source device capable of effectively avoiding uneven brightness even if the length of the light guide plate is made longer than the effective light emitting region. Is what you are trying to do.

[0014]

In order to solve such a problem, the present invention is applied to a sidelight type surface light source device in which illumination light emitted from a rod-shaped light source is incident from an incident surface of a plate-shaped member. In this sidelight type surface light source device, an illuminating light introducing section is arranged between the incident surface and the light source, and the illuminating light introducing section spreads the illuminating light of the light source to the end side of the light source to form a plate-like member. Lead.

Further, the present invention is applied to a side light type surface light source device in which a plate member is formed so that the thickness thereof becomes thinner as the distance from the incident surface increases, and the incident surface of the plate member is formed into a rectangular shape. The plate-like member is locally thinned.

Further, instead of this, a light diffusing member is selectively arranged on the incident surface side of the emitting surface or the reflecting surface facing the emitting surface.

Further, in these cases, the illumination light introducing portion and the light diffusing member are formed asymmetrically, and the plate thickness is set asymmetrically.

By these means, the illumination light introducing section disposed between the plate-shaped member and the light source spreads the illumination light of the light source to the end side of the light source and guides it to the plate-shaped member. The illumination light from the effective light emitting area is spread to an area corresponding to the outside of the effective light emitting area and guided to the plate member. As a result, even when using a light source with a short effective light emitting region, sufficient illumination light can be incident on the edge of the plate-shaped member,
It is possible to effectively avoid luminance unevenness in the longitudinal direction of the light source.

Further, in the plate-shaped member formed so that the thickness thereof becomes thinner as the distance from the incident surface increases, the illumination light incident from the incident surface is reflected between the emitting surface and the surface facing the emitting surface. Propagate while repeating. At this time, each time the illumination light is repeatedly reflected, the incident angle with respect to the emission surface gradually decreases and propagates, and the component of which the incident angle becomes equal to or less than the critical angle is emitted from the emission surface. Therefore, if the plate thickness is locally reduced, the change of the incident angle due to reflection becomes large, and the number of reflections increases, so that the amount of light emitted from the emission surface when propagating a certain distance increases. Therefore, by forming such a region on the incident surface side, the brightness at both ends can be improved, and even when a light source with a short length is used, uneven brightness in the light source longitudinal direction can be effectively avoided.

Further, when the light diffusing member is selectively arranged on the emitting surface or the reflecting surface, the illumination light is scattered by the light diffusing member, and the incident angle distribution of the illumination light on the emitting surface is arranged in the vicinity of the position where the light diffusing member is arranged. Can be changed. That is, the incident angle of the illumination light can be corrected so that the component having the critical angle or more and the component having the critical angle or less are included, and the brightness in the vicinity can be improved. Therefore, also by this, the uneven brightness in the longitudinal direction of the light source can be effectively avoided.

In these cases, if the illuminating light introducing portion and the light diffusing member are formed asymmetrically and the plate thickness is set asymmetrically, the extent to which the brightness is improved can be made different by that amount. It is possible to compensate for the difference in different light amounts.

[0022]

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

(1) First Embodiment FIG. 1 is an enlarged plan view showing a light source side of a side light type surface light source device according to an embodiment of the present invention. In addition, in FIG. 1, members such as the reflection sheet 4 are omitted, and the same components as those of the sidelight type surface light source device described above with reference to FIGS. Is omitted.

In this sidelight type surface light source device 10, a fluorescent lamp 11 made of a rod-shaped light source has electrodes 1 at both ends.
The length including 1a and 11b is shorter than the length of the incident surface of the light scattering guide 2 made of a light guide plate, which is extremely shorter than the light scattering guide 2. Has been done.

In this side light type surface light source device 10, an illumination light introducing section 12 is arranged between the incident surface of the light scattering guide 2 and the fluorescent lamp 11, and the illumination light introducing section 1 is provided.
2. The fluorescent lamp 11 and the reflector 8 form a primary light source. Here, the illumination light introducing section 1
2 spreads the illumination light of the fluorescent lamp 11 to both ends of the fluorescent lamp 11 and guides it to the incident surface of the light scattering guide 2.

Specifically, in this embodiment, the illumination light introducing section 12 is formed by a trapezoidal prism 12a and parallelogram prisms 12b and 12c. The trapezoidal prism 12a has an upper bottom side surface on the fluorescent lamp 11 side. In addition, the fluorescent lamp 11 is arranged substantially at the center of the incident surface such that both ends of the fluorescent lamp 11 are inclined. On the other hand, the parallelogram prisms 12b and 12c are arranged on the end side of the incident surface so that the slope and the slopes of the parallelogram prisms 12b and 12c are separated from each other by a minute gap on the slope of the trapezoid prism 12a. To be done.

The trapezoidal prism 12a, like the light-scattering light guide 2, is made of, for example, polymethylmethacrylate (PMM).
The matrix of A) is formed by uniformly mixing and dispersing translucent fine particles having a different refractive index from the matrix. On the other hand, the parallelogram prisms 12b and 12c are formed of a transparent material such as polycarbonate, and the angle formed between the bottom surface and the slope is equal to the angle formed between the slope of the trapezoidal prism 12a and the bottom surface. It is designed to be.

Here, this angle is the parallelogram prism 1
2b and 12c, the light incident perpendicularly from the upper surface is at an angle sufficient for total reflection on the inclined surface, whereby the parallelogram prisms 12b and 12c are illuminated by the illumination light L2.
Are incident from the upper surface, and are sequentially reflected and emitted from the opposing slopes. That is, the parallelogram prisms 12b and 12c are
The optical path of L2 of the illumination light incident from the upper surface is bent and distributed to both ends of the light scattering guide 2.

On the other hand, the trapezoidal prism 12a scatters the illumination light L3 by the fine particles inside, and divides the illumination light L2 to both sides to generate parallelogram prisms 12b and 1b.
The incident illumination light L3 is distributed and emitted to the shaded portion of the slope 2c.

Further, as shown in FIG. 2, the trapezoidal prism 1
2a, the parallelogram prisms 12a and 12c have a thickness selected so as not to generate a step with the emission surface and the slope of the light scattering guide 2, and the angles with respect to the emission surface and the slope do not suddenly change. , The surfaces corresponding to the emission surface and the slope are formed. Thereby, the trapezoidal prism 12a and the parallelogram prisms 12a and 12c prevent a space from being formed between the trapezoidal prism 12a and the parallelogram prisms 12a and 12c when the primary light source is held by the light scattering guide 2 through the reflector 8. The uneven brightness of the emitted light due to the formation of the seed space is effectively avoided.

Thus, in this embodiment, the parallelogram prisms 12a and 12c bend the optical path of the illumination light emitted from the end of the light source and distribute it to the end of the light scattering guide. The trapezoidal prism 12a constitutes a second optical block that diffuses the illumination light emitted from the light source to the first optical block side.

In the above structure, the illumination light emitted from the effective light emitting region of the fluorescent lamp 11 is incident on the light scattering guide 2 through the illumination light introducing section 12 directly or after being reflected by the reflector 8. Incident on the surface. At this time, this illumination light is spread to both ends of the incident surface in the illumination light introducing section 12 and guided to the incident surface of the light scattering guide 2.

Specifically, of this illumination light, the illumination light L2 emitted from the end of the effective light emitting area AR is mainly from the upper surfaces of the parallelogram prisms 12a and 12c constituting the illumination light introducing portion 12. The parallelogram prism 12
The light is distributed to both ends of the light scattering guide 2 by a and 12c and emitted. As a result, the length of the light scattering guide 2 is
Even if it is longer than the effective light emission area of the fluorescent lamp 11, sufficient illumination light L2 is incident on the end portion of the light scattering guide 2, and the brightness of the corresponding area on the emission surface is increased.

On the other hand, the illumination light L3 emitted from the vicinity of the central portion of the effective light emitting area AR is mainly composed of the illumination light introducing section 1.
The light enters from the upper bottom side surface of the trapezoidal prism 12a forming the second light source 2, is scattered in the trapezoidal prism 12a, and enters the incident surface of the light scattering guide 2. As a result, the light scattering guide 2
In this case, sufficient illumination light L3 can be made incident on the shaded portions of the slopes of the parallelogram prisms 12b and 12c generated by distributing the illumination light L2 to both sides. Is effectively avoided.

According to the above configuration, the illumination light introducing section 12 is arranged between the incident surface of the light scattering guide 2 and the fluorescent lamp 11, and the illumination light introducing section 12 emits the illumination light of the fluorescent lamp 11. Even if the effective light emission area AR of the fluorescent lamp 11 is shorter than that of the light scattering guide 2, the fluorescent lamp 11 can be expanded to both sides of the fluorescent lamp 11 and guided to the incident surface of the light scattering guide 2. Brightness unevenness in the longitudinal direction can be effectively avoided. Therefore, the overall shape of the sidelight type surface light source device 10 can be reduced accordingly.

Further, the trapezoidal prism 12a and the parallelogram prism 12b arranged on the slope of the trapezoidal prism 12a.
By forming this illumination light introducing portion 12 with 12 and 12c, the illumination light L2 emitted from the end of the effective light emitting area AR is distributed to both ends of the parallelogram prisms 12a and 12c light scattering guide 2. Further, the illumination light L3 emitted from the vicinity of the central portion of the effective light emitting area AR is supplied to the trapezoidal prism 1
Parallelogram prisms 12b and 12c scattered in 2a
Can be distributed to the shaded area of the slope, and thus even if the length of the fluorescent lamp 11 is extremely short, it is possible to effectively avoid uneven brightness in the longitudinal direction of the fluorescent lamp 11.

(2) Second Embodiment FIG. 3 is a plan view showing a sidelight type surface light source device according to a second embodiment. In this sidelight type surface light source device 20, the fluorescent lamp 21 has electrodes 21a at both ends.
And 21b, the length including the light-scattering light guide 22 is substantially equal to that of the light-scattering light guide 22, and the effective light emitting region AR is shorter than the light-scattering light guide 2 in length.

On the other hand, the light-scattering light guide 22 is formed so that the incident surface side projects to the fluorescent lamp 21 side, and both ends of the incident surface extend obliquely toward the inside of the fluorescent lamp 21. Has been done. As a result, in this embodiment, the extension portions 22a and 22b extending obliquely are provided.
And the incident surface side region 22c enlarged to the fluorescent lamp 21 side constitute the illumination light introducing section 23.

Here, the extension portions 22a and 22b are formed in substantially the same shape as the parallelogram prism in the above-described first embodiment, whereby the illumination light emitted from the end portion of the effective light emitting area AR is formed. The L2 is distributed to both ends of the light scattering guide 22 while being diffused.

On the other hand, in the incident surface side area 22c enlarged to the fluorescent lamp 21 side, the incident surface is formed into a matte surface (texture surface) by the matte surface treatment, and the effective light emitting area AR is formed by the matte surface and the internal fine particles. The illumination light L3 emitted from the vicinity of the center is scattered, and the illumination light L3 is distributed to the shadow portions of the extension portions 22a and 22b at the original incident surface positions.

According to the second embodiment, both ends of the light scattering guide 22 corresponding to the end of the light source are obliquely extended to the effective light emitting region side to form the illumination light introducing section 23. Also, although not to the same extent as the first embodiment, the same effect can be obtained. Moreover, since the light-scattering light guide 22 and the illumination light introducing portion 23 can be integrally formed, the entire configuration can be simplified accordingly.

(3) Third Embodiment FIG. 4 is a plan view showing a sidelight type surface light source device according to a third embodiment. Also in this sidelight type surface light source device 30, the fluorescent lamp 21 has electrodes 21 at both ends.
The length including the lengths a and 21b is substantially equal to that of the light scattering guide 32, and the length of the effective light emitting area AR is shorter than that of the light scattering guide 32.

On the other hand, in the light-scattering light guide 32, the incident surface side projects toward the fluorescent lamp 21 side to form an extension 32a, and slits 33 are radially formed in the extension 32a. . That is, the extension portion 22a has slits formed at a constant pitch from the center toward both ends, and as the slits 33 move away from the center,
The extension 32a is inclined toward both ends with respect to the incident surface and deepened toward the wedge-shaped tip. Further, the extension portion 22a is formed so that slopes are formed at both ends in correspondence with the inclination of the slit which changes as the distance from the center increases.

As a result, in this embodiment, the slits 33 form a large number of trapezoidal prisms on the incident surface of the light scattering guide 32. Further, the inclination and the depth of these slits 33 are gradually changed so that the shape and size of the trapezoidal prism are gradually changed from the center of the effective light emitting region toward the end portion. The light is bent toward the end side toward the end side.

That is, the extension 32a reflects the illumination light to the outside by the side surface of the end of the slit 33,
The central side surface of the mirror reflects the illumination light reflected at the end side surface in the original direction. In addition, the extension 32a scatters the illumination light due to the fine particles inside. This extension 32
a is a light-scattering light guide 32 for illuminating the illumination light incident from the incident surface.
It spreads toward both ends of the light scattering guide 32 and operates so as to guide it to the original incident surface of the light scattering guide 32.

As a result, in this embodiment, the extension portion 32a having the slit 33 formed therein constitutes the illumination light introducing portion 34.

According to the configuration of FIG. 4, the incident surface side of the light-scattering light guide 32 is extended to the fluorescent lamp 21 side, and the slits 33 are radially formed in the extension 32a, and the extension 32a illuminates. Even if the light introducing section 34 is configured, the same effect can be obtained, although not to the same extent as in the first embodiment. In addition, the light scattering guide 32 and the illumination light introducing section 3
Since 4 and 4 can be integrally formed, the entire configuration can be simplified accordingly.

(4) Fourth Embodiment FIG. 5 is a perspective view showing a light scattering guide applied to a sidelight type surface light source device according to a fourth embodiment. This light-scattering light guide 42 is applied to a sidelight type surface light source device in combination with a fluorescent lamp whose length including the electrodes at both ends is substantially equal to the length of the light-scattering light guide.

Here, in the light scattering guide 42, the cross sections from the wedge-shaped tip toward the incident surface side are sequentially taken along the line B-B and the line C-.
As shown in FIGS. 6 to 8 by taking the C section and the D-D section, the incident surface 42a is held in a rectangular shape and the slope side smoothly meanders at the end side near the incident surface 42a. The plate thickness is locally reduced at both ends in the vicinity of the incident surface 42a.

That is, in the side light type surface light source device using the light scattering guide, the illumination light incident from the end face propagates while being repeatedly reflected between the emission face and the inclined face. At this time, the incident angle of the illumination light with respect to the emission surface gradually decreases each time reflection is repeated, and a component of which the incidence angle becomes equal to or less than the critical angle is emitted from the emission surface. Therefore, in the region where the plate thickness is locally thin, the inclination angle of the slope locally changes and the number of reflections when propagating a certain distance increases as the plate thickness decreases. Changes, and the amount of illumination light emitted from the emission surface increases.

Accordingly, in the light scattering guide 42,
On the end side in the vicinity of the incident surface 42a, the plate thickness is such that the amount of emitted light is increased and the brightness at both ends is improved as compared with a region formed so as to be locally thin. Furthermore, the wedge-shaped tip, which is deficient by locally increasing the emitted light amount in this way,
The illumination light on both ends is compensated by the scattered light due to the fine particles inside so that uneven brightness is effectively avoided.

While keeping the incident surface in a rectangular shape,
By locally reducing the plate thickness at both ends in the vicinity of the incident surface 42a, the illumination light incident from the incident surface is efficiently incident as in the conventional case. Further, by forming the slope so as to meander smoothly, it is possible to prevent abrupt changes in the slope due to the local thinning of the plate from being observed from the emission surface, which also effectively avoids uneven brightness. .

According to the structure shown in FIG. 5, the plate thickness of the light-scattering light guide body 42 is made such that the inclined surface is smoothly meandered at the end near the incident surface 42a while keeping the incident surface 42a in a rectangular shape. Even if the thickness is locally reduced, the same effect as that of the above-described embodiment can be obtained.

(5) Fifth Embodiment FIG. 9 is a perspective view showing a sidelight type surface light source device according to a fifth embodiment. Since the other configuration according to this embodiment is the same as the conventional configuration described above with reference to FIG. 15, the description of other members will be omitted in FIG.

In this embodiment, the light scattering guide 5
No. 2 is formed so that the incident surface side projects to the fluorescent lamp 21 side, and further the end portion on the incident surface side projects to extend toward the fluorescent lamp 21. As a result, in this embodiment, the extended portions 52a and 52b having both ends extended and the incident surface side region 5 enlarged to the fluorescent lamp 21 side.
The illumination light introducing unit 53 is configured by 2c.

Here, the outer side surfaces of the extension parts 52a and 52b are formed so as to extend from the side surface of the light scattering guide 52. On the other hand, the inner side surfaces of the extension portions 52a and 52b are connected to the incident surface side region 52c by drawing a gentle curved surface, whereby the illumination light introducing portion 53 is
The incident surface side of the light-scattering light guide 52 is placed on the side of the fluorescent lamp 2 so that the region corresponding to the effective light-emitting region gradually changes into a concave shape.
It is formed so as to be enlarged on the first side, and the illumination light is made incident through this concave-shaped incident surface.

That is, the illumination light emitted from the effective light emitting region also has a component emitted so as to spread toward the end side, and such a component is compared with the illumination light emitted toward the front surface of the fluorescent lamp 21. Then, there is a feature that the amount of light per unit area is small. The illumination light introducing portion 53 bends the component emitted so as to spread toward the end side inward by the concave incident surface and collects the component, and the light scattering guide 52 at the original incident surface position of the light scattering guide 52. It is distributed to the end portions, so that uneven brightness can be effectively avoided.

According to the structure shown in FIG. 9, even if the incident surface side of the light-scattering light guide 52 is enlarged to the fluorescent lamp side so that the portion corresponding to the effective light emitting region gradually changes to the concave shape,
It is possible to obtain the same effect as that of the above-described embodiment.

(6) Sixth Embodiment FIG. 10 is a perspective view showing a sidelight type surface light source device according to a sixth embodiment. Since the other configuration according to this embodiment is the same as the conventional configuration described above with reference to FIG. 15, the description of other members will be omitted in FIG.

In this embodiment, the light scattering guide 2
The diffusing element 61 made of a light diffusing member is attached to the incident surface side and both ends of the light emitting surface. Here, as shown in FIG. 11, the diffuser 61 is formed by processing a white PET film into a right-angled triangular shape, and a predetermined adhesive is used so that the right-angled portion coincides with the corner of the light scattering guide 2. Is attached to the light scattering guide 2.

Here, the adhesive has a refractive index extremely close to that of the light-scattering light guide 2 and has a large transmittance used for bonding optical glass. As a result, the light-scattering light guide 2 scatters the illumination light at both ends on the incident surface side.

That is, in the illumination light emitted from the effective light emitting area AR, there is also a component emitted so as to spread to the end side. However, the effective issuing area A of the fluorescent lamp 11
Since R has an elongated shape almost parallel to the incident surface,
In this way, the illumination light emitted so as to spread to the end side is
First, in addition to the small amount of light itself, there are many components with a large incident angle. As a result, in the conventional light-scattering light guide 2, the illumination light that reaches the end portion from the incident surface is emitted very little from the vicinity of the incident surface, and is gradually emitted as it propagates toward the wedge-shaped tip. .

That is, in the conventional light-scattering light guide 2, although the illumination light is distributed at the end portion on the incident surface side,
The illumination light has a large incident angle with respect to the emission surface and is hardly emitted from the end portion side. Thus, as in this embodiment, if the diffuser 61 is arranged at the end and the end side illumination light is scattered, the incident angle of these illumination lights with respect to the emission surface can be converted into a wide angular distribution. Therefore, the amount of light emitted from the vicinity of the incident surface can be increased.

However, if the amount of diffused illumination light is increased too much, the brightness level on the edge side increases extremely, and uneven brightness occurs rather. As a result, in this embodiment, the shape of the diffuser 61 is set to a right triangle shape, and the degree of diffusion is increased toward both ends.

That is, the diffuser 61 is selected so that the length W on the incident surface side is substantially the same as the length of the electrodes 11a and 11b of the fluorescent lamp 11 corresponding to the region where the amount of emitted light is increased. In addition, the height H on the end side is increased according to the amount of light to be increased.
Is selected, and the shape of the side connecting the bottom and the height is selected according to the light amount distribution to be further increased. Incidentally, when it is necessary to increase the amount of light on the end side as compared with this embodiment, the height H is increased and the hypotenuse is changed to a hyperbola or arc shape to secure a desired luminance distribution. be able to.

According to the configuration shown in FIG. 10, a diffuser 61 is selectively attached to the incident surface side of the light-scattering light guide 2 corresponding to the end of the light source, and the diffuser 61 emits illumination light. By scattering, the uneven brightness can be effectively avoided with a simple configuration even if the length of the light guide plate is made longer than the effective light emitting region of the light source.

(7) Seventh Embodiment In the sidelight type surface light source device, if the uneven brightness of the end portions is reduced by the above-described first to sixth embodiments, both end portions on the incident surface side will be described. At, the difference in brightness comes to be perceived.

That is, as shown in FIG. 12, in the fluorescent lamp 11 applied to the side light type surface light source device of this type, after the driving power output from the driving circuit 62 is boosted by the boosting transformer T, It is supplied via the capacitor C. At this time, one electrode 11b of the fluorescent lamp 11 is grounded so that unnecessary radiation can be reduced.

In this way, the fluorescent lamp 11 has the ground side electrode 11b on the cold side L and the capacitor side electrode 11a.
Is set to the hot side H, and the amount of illumination light emitted from the cold side L end becomes smaller than the amount of illumination light emitted from the hot side H end. As a result, in the sidelight type surface light source device, when the brightness unevenness at the ends is reduced, the difference in light amount between the cold side L and the hot side H is perceived as a difference in brightness at the ends.

For this reason, in this embodiment, as shown in FIG. 13, the shapes of the diffusers 66a and 66b disposed on the emission surface and both ends are set to different shapes, whereby uneven brightness is effectively avoided. At the same time, it is possible to prevent a difference in brightness at the ends.

That is, the diffusers 66a and 66b are formed in the shape of a right-angled triangular shape with the tip cut off and set to the same height H. The hot side diffuser 66a is
The tip is cut off more than the diffuser 66b on the cold side, and the length W2 is equal to the length W2 of the cold diffuser 66b.
It is set to be shorter than 1. As a result, the cold-side diffuser 66b is formed so as to have a greater degree of diffusion than the hot-side diffuser 66a, and the light amount of the emitted light is increased by that amount to compensate for the decrease in the brightness on the hot side. ing.

According to the structure shown in FIG. 13, the diffusers 66a and 66b having different shapes and different degrees of diffusion are attached to the end of the light scattering guide 2 corresponding to the end of the light source.
By scattering the illumination light by the diffusers 66a and 66b, in addition to the effect of the sixth embodiment, it is possible to prevent the difference in brightness at the end portions.

(8) Eighth Embodiment FIG. 14 is a perspective view showing a sidelight type surface light source device according to the eighth embodiment. In this embodiment,
The sidelight type surface light source device 70 supplies illumination light to the large light diffusion irregular light guide 72 by the two fluorescent lamps 11. In this case, the side light type surface light source device 70
, Two fluorescent lamps 11 are linearly arranged on the incident surface. Further, when the fluorescent lamp 11 is arranged in this manner, the light scattering guide 72 corresponding to the electrodes 11a and 11b.
The diffusers 71a, 71b, and 71c are arranged on the exit surface of the device, thereby effectively avoiding the uneven brightness and further preventing the difference in brightness at the ends.

According to the structure shown in FIG. 14, the diffusers 71a, 71b, 71 are provided in the light scattering guide 2 corresponding to the ends of the light source.
By sticking c, it is possible to effectively avoid uneven brightness in the large-sized sidelight type surface light source device 70 even when the length of the light guide plate is longer than the substantial effective light emitting region of the light source.

(9) Other Embodiments In the first embodiment described above, the angle of the parallelogram prism is set so that the illumination light is totally reflected by the inclined surface. The present invention according to 2 is not limited to this, and a reflection film may be formed on the slope by attaching a reflection sheet to the slope, or by forming a metal vapor deposition film, for total reflection. In this way, the angle of the quadrilateral prism can be freely selected. It should be noted that a reflective film or the like may be similarly formed on the slopes of the extension portions in the second and third embodiments and the slits in the third embodiment.

Further, in the above-mentioned first embodiment,
The case where the parallelogram prism is used as the first optical block has been described, but the present invention according to claim 2 is not limited to this, and the trapezoid formed by deforming the parallelogram prism in which the inclination of the slope is different. A prism may be applied.

Further, in the above-described first embodiment, the case where the first optical block is formed of the transparent member has been described, but the present invention according to claim 2 is not limited to this, and the second optical block is not limited to this. Similarly to the above, fine particles having different refractive indexes may be dispersed and mixed inside. Further, the incident surfaces of the first and second optical blocks may be roughened.

In the sixth, seventh and eighth embodiments described above, the case where the white PET film is attached with the optical adhesive to dispose the diffuser has been described. The present invention is not limited to this, when attaching various diffusion sheets or the like with an optical adhesive, when attaching a silver sheet or the like made of a specular reflection member with a double-sided tape having a light scattering property, white ink or the like is used. If adhered,
Similar effects can be obtained by arranging various light diffusing members, such as when arranging the reflecting member after locally roughening the surface.

Furthermore, in the above-mentioned sixth, seventh and eighth embodiments, the case where the diffuser is arranged on the emission surface side has been described, but the present invention according to claim 8 is not limited to this.
Instead of this or in addition to this, it may be arranged on the slope side.

Further, in the above-described embodiment, the case where the incident surface of the illumination light introducing section is appropriately roughened by the matte surface treatment has been described, but the roughening method is not limited to this, and the sandpaper is not limited thereto. Various rough surface forming means can be widely applied, for example, in the case of forming a rough surface by blasting treatment or chemical etching treatment by. In addition, the illumination light is not limited to be diffused by roughening, and a light diffusion material such as white ink may be attached to the incident surface, or a diffusion sheet or the like may be arranged to diffuse the incident illumination light from the incident surface. .

Further, in the above-mentioned embodiment, the case where the light scattering guide made of the light guide plate is formed in a wedge-shaped cross section is described. However, the present invention according to claim 1 is not limited to this, and is flat. In addition to a side light type surface light source device using a light guide plate having a directional emission property, such as a device configured to have a directional emission property by performing a predetermined process in The present invention can be widely applied to a sidelight type surface light source device using a light guide plate that emits illumination light incident from the end surface of a member from an emission surface.

Further, in the above-mentioned first to fifth embodiments, the case where the illumination light introducing portion is formed in a symmetrical shape has been described, but the present invention is not limited to this, and the illumination light introducing portion is formed in an asymmetrical shape. In this case, it is possible to correct different luminances on the hot side and the cold side, as described in the seventh embodiment corresponding to the sixth embodiment. Further, even when the fluorescent lamps are shifted and arranged with respect to the light guide plate, this can be dealt with.

Further, in the above-described first to third and fifth embodiments, the illumination light introducing portion is arranged, and in the fourth embodiment, the plate thickness is locally thinned. In the sixth to eighth embodiments, the case where the uneven brightness is reduced by disposing the diffuser has been described, but the present invention is not limited to this, and these means may be combined.

In the above embodiment, the case where the illumination light is incident from one end face has been described, but the present invention is not limited to this, and the side light type surface having the constitution in which the illumination light is incident from the other end face is also described. It can be widely applied to a light source device.

Further, in the above-mentioned embodiment, the case where the present invention is applied to the surface light source device of the liquid crystal display device has been described. It can be widely applied to surface light source devices.

[0086]

As described above, according to the present invention, the illumination light introducing portion is arranged between the plate member and the light source, and the illumination light of the light source is spread to the end portion side of the end face and guided to the plate member. As a result, even when the end face is longer than the effective light emitting region, the illumination light in the effective light emitting region can be distributed to the end face outside the effective light emitting region, and uneven brightness can be effectively avoided.

Alternatively, with respect to a plate-shaped member formed so that the thickness thereof becomes thinner as the distance from the end face increases, the plate-shaped member is locally thinned to locally reduce the plate thickness. The amount of illumination light emitted from the emission surface can be increased in the region that is made thinner, and uneven brightness can be effectively avoided even when the length of the end face is longer than that in the effective light emission region.

Further, instead of this, by selectively disposing a light diffusing member on the incident surface side of the plate member, the incident angle distribution of the illumination light with respect to the emitting surface is changed by this light diffusing member, The amount of emitted light in the vicinity thereof can be increased, and even when the length of the end face is longer than that of the effective light emitting region, uneven brightness can be effectively avoided.

[Brief description of drawings]

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

FIG. 2 is a side view of FIG.

FIG. 3 is an enlarged plan view showing a light source side of a sidelight type surface light source device according to a second embodiment of the present invention.

FIG. 4 is an enlarged plan view showing a light source side of a sidelight type surface light source device according to a third embodiment of the present invention.

FIG. 5 is a perspective view showing a light scattering guide applied to a sidelight type surface light source device according to a fourth embodiment of the present invention.

FIG. 6 is a cross-sectional view showing FIG. 5 taken along the line BB.

FIG. 7 is a cross-sectional view showing FIG. 5 taken along the line CC.

FIG. 8 is a cross-sectional view showing FIG. 5 taken along the line D-D.

FIG. 9 is a perspective view showing a light source side of a sidelight type surface light source device according to a fifth embodiment of the present invention.

FIG. 10 is a perspective view showing a light source side of a sidelight type surface light source device according to a sixth embodiment of the present invention.

11 is an enlarged plan view showing the light source side of FIG.

FIG. 12 is a connection diagram for explaining a driving method of a fluorescent lamp.

FIG. 13 is an enlarged plan view showing a light source side of a sidelight type surface light source device according to a seventh embodiment of the present invention.

FIG. 14 is a perspective view showing a light source side of a sidelight type surface light source device according to an eighth embodiment of the present invention.

FIG. 15 is an exploded perspective view showing a conventional side light type surface light source device.

16 is a side view of the side light type surface light source device of FIG.
FIG. 4 is a sectional view taken along a section.

[Explanation of symbols]

1, 10, 20, 30, 50, 60, 70 Side light type surface light source device 2, 22, 32, 42, 52, 72 Light-scattering light guide 4 Reflective sheet 5 Prism sheet 7, 11, 21 Fluorescent lamp 8 Reflector 12, 23, 34, 53 Illumination light introducing part 12a Trapezoidal prism 12b, 12c Parallelogram prism 61, 66a, 66b, 71a, 71b Diffuser

Claims (10)

[Claims] 1. A sidelight type surface light source device in which illumination light emitted from a rod-shaped light source is incident from an incident surface of a plate-shaped member and emitted from an emission surface of the plate-shaped member, wherein between the incident surface and the light source. An illumination light introducing section is disposed, and the illumination light introducing section guides the illumination light emitted from the effective light emitting region of the light source to the plate-shaped member by spreading the illumination light to the end side of the light source. Side light type surface light source device. 2. The illumination light introducing section bends the optical path of the illumination light emitted from the end portion of the light source and distributes it to the end portion side of the light source, and the first optical block emitted from the light source. The sidelight type surface light source device according to claim 1, wherein the sidelight type surface light source device is formed by a second optical block that diffuses illumination light to the first optical block side. 3. The illumination light introducing portion is formed such that a part of a plate-shaped member corresponding to an end portion of the light source extends obliquely toward an effective light emitting region side of the light source. The side light type surface light source device according to claim 1. 4. The sidelight type surface light source device according to claim 1, wherein the illumination light introducing section is formed by radially forming slits on the incident surface side of the plate-shaped member. . 5. The illumination light introducing portion is formed asymmetrically with respect to a virtual line passing through the center of the effective light emitting region of the light source and orthogonal to the incident surface. The sidelight type surface light source device according to claim 2, claim 3, or claim 4. 6. A sidelight type surface in which illumination light is incident from an incident surface of a plate-shaped member formed so as to become thinner as it goes away from the incident surface, is deflected by the plate-shaped member, and is emitted from an emission surface. In the light source device, the plate-shaped member is a sidelight type surface light source device, wherein the incident surface is formed in a rectangular shape and the plate thickness is locally thin. 7. The side according to claim 6, wherein the plate thickness is set asymmetrical with respect to an imaginary line that passes through the center of the effective light emitting region of the light source and is orthogonal to the incident surface. Light type surface light source device. 8. A sidelight type surface light source device in which illumination light emitted from a rod-shaped light source is incident from an incident surface of a plate member and emitted from an emission surface of the plate member, wherein the emission surface or the emission surface is provided. A side light type surface light source device, wherein a light diffusing member is selectively arranged on the incident surface side of the reflecting surface facing to. 9. The light diffusing member is disposed so as to correspond to an end portion of the light source, and is formed such that the degree of light diffusion decreases from the end portion side of the light source toward the center side. The sidelight type surface light source device according to claim 8, wherein the surface light source device is a sidelight type surface light source device. 10. The light diffusing member is disposed corresponding to both ends of the light source, and the light diffusing members at the both ends are formed to have different degrees of light diffusion. The side light type surface light source device according to claim 8 or 9.