JP3512133B2 - Light guide plate and side light type surface light source device - Google Patents

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 a light guide plate applied to a liquid crystal display device or the like, and more particularly to a sidelight type surface light source device using a light guide plate having a directional emission property. It is a thing. According to the present invention, in this sidelight type surface light source device, the convex portion for positioning is arranged on the light source side and the side surface of the light guide plate and the shape thereof is selected to reduce uneven brightness due to bright lines and dark bands.

[0002]

2. Description of the Related Art Conventionally, for example, in a liquid crystal display device,
Illuminate the liquid crystal panel with the side light type surface light source device,
As a result, the overall shape is made thinner.

That is, in the side light type surface light source device, a primary light source composed of a rod-shaped light source such as a cold cathode tube is arranged on the side of a plate member (that is, a light guide plate), and illumination light emitted from the primary light source is arranged. From the end surface of the light guide plate.
Further, the side light type surface light source device is formed so as to bend this illumination light and emit it toward the liquid crystal panel from the plane of the light guide plate, whereby the overall shape can be made thin.

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

FIG. 4 is an exploded perspective view showing the construction of the latter sidelight type surface light source device. The sidelight 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 6 made of a cold cathode tube with a reflector 7 made of a reflecting member having a substantially semicircular cross-section, and the light-scattering light guide 2 is provided from the opening side of the reflector 7. Illumination light is incident on the end face.

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

The light-scattering light guide 2 is a light guide plate having a wedge-shaped cross section. For example, transparent fine particles having a different refractive index are uniformly mixed and dispersed in a matrix made of polymethylmethacrylate (PMMA). Formed. As a result, as shown in FIG. 5 by taking a cross section along the line AA, the light scattering guide 2 receives the illumination light L from the incident surface T which is the end surface on the primary light source 3 side, and transmits the transparent fine particles. When the diffused reflection member is applied to the reflection sheet 4 while scattering the illumination light L by, the reflection sheet 4 partially diffuses the reflection sheet 4, and the reflection sheet 4 side plane (hereinafter referred to as a slope) and the prism sheet 5 side plane. The illumination light L is propagated by being repeatedly reflected from (to be referred to as an emission surface hereinafter).

During this propagation, the illumination light L has its incident angle with respect to the emission surface gradually reduced each time it is reflected by the slope, and a component having a critical angle or less with respect to the emission surface is emitted from the emission surface. The illumination light L1 emitted from the emission surface is scattered light because the illumination light L is scattered by the transparent fine particles inside the light-scattering light guide 2, diffused by the reflection sheet 4, and propagated. Is emitted by. However, the illumination light L1 propagates by reflecting on an inclined surface that is formed inclining in the propagation direction with respect to the emission surface and propagates, as shown in an enlarged view by an arrow B, in which the main emission direction is a wedge-shaped tip direction. It is formed with an inclination. That is, the light L1 emitted from the light guide plate
Have a directivity, and thus the sidelight type surface light source device 1 has a directional emission property.

The prism sheet 5 is arranged to correct this 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 guide 2. This prism surface is formed by repeating projections having a triangular cross-section that extend substantially parallel to the incident surface T of the light scattering guide 2 from the incident surface T side in the wedge-shaped tip direction. As a result, the prism sheet 5 corrects the main emission direction of the emission light L1 to the front direction of the emission surface by the inclined surface of the triangular protrusion.
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 guide 2 side is further provided on the surface opposite to the light scattering guide 2 side. A so-called double-sided prism sheet having a formed structure may be used in some cases. As a result, in this sidelight type surface light source device 1, compared to the sidelight type surface light source device of the type in which the light guide plate is formed with a substantially uniform plate thickness, the emitted light can be efficiently emitted in the front direction. There is.

As the light guide plate having such a directional emission property, a transparent member or a semitransparent member is used to form the light guide plate in a wedge shape or a shape close to the wedge shape, or a light guide plate is formed in a flat plate shape. However, there is one in which a scattering film, a satin surface, a minute lens array, etc. are formed on the exit surface and / or the back surface of this light guide plate. Also in the sidelight type surface light source device using such a light guide plate, similarly, emitted light can be efficiently emitted in the front direction.

[0011]

By the way, in this type of side light type surface light source device, the surface light source device is held by a frame or the like and integrally mounted with a liquid crystal panel, for example, in a personal computer or the like. Accordingly, in the sidelight type surface light source device, it is necessary to easily and reliably position and hold the light-scattering light guide body 2 formed of a light guide plate with respect to a holding member such as a frame. Particularly, in the side light type surface light source device, when the light scattering guide 2 collides with the fluorescent lamp 6 due to an impact or the like, the fluorescent lamp 6
It is necessary to securely position and hold the light-scattering light guide 2 so as not to move to the fluorescent lamp 6 side.

In this case, for example, as shown in FIG. 6, a convex portion 9 is integrally formed on the side surface of the light scattering guide 2, and the convex portion 9 is formed.
A method of positioning and holding is considered. However, in the side light type surface light source device of this type, when the illumination light from the light source is propagated inside the light scattering guide 2 and emitted from the emission surface, the convex portion 9 is integrally formed. However, there is a problem that uneven brightness occurs due to the influence of the convex portion 9.

That is, when the convex portion 9 is integrally formed, the illumination light that is originally reflected by the side surface of the light-scattering light guide 2 and returned to the inside spreads further outside the side surface at the convex portion 9. By being folded back inward, and at this time, a part of the illumination light is emitted to the outside from the end face of the convex portion 9 which is perpendicular to the side surface of the light-scattering light guide 2, and leaks out. The amount of illumination light emitted from the emission surface will change. This change in the light amount is caused by the prism sheet 5
The exit surface is observed from the side, and a region of low brightness level (that is, a dark band) that spreads inward from the entrance surface side corner of the convex portion 9 toward the wedge-shaped tip and the wedge-shaped tip side corner of the convex portion 9 A linear area (that is, a bright line) having a high brightness level that spreads inward toward the tip of the wedge is formed, and uneven brightness occurs in the illumination light emitted from the emission surface.

The present invention has been made in consideration of the above points, and it is possible to effectively avoid the occurrence of luminance unevenness due to this kind of bright lines and dark bands , and to easily hold the light guide plate. It is intended to propose a surface light source device and a light guide plate.

[0015]

In order to solve such a problem, in the invention of claim 1 or 3 , in a side light type surface light source device for emitting illumination light from an emission surface of a plate member, or a side light. In the light guide plate used for the mold surface light source device, the convex portions for positioning the plate member with respect to the holding member are arranged on the end surface side and the side surface on which the illumination light is incident. Furthermore, this convex part is tapered toward the end face side.
To achieve.

According to a second aspect of the present invention, in the side light type surface light source device that emits the illumination light from the emission surface of the plate-shaped member, the projection for positioning the plate-shaped member with respect to the holding member emits the illumination light. It is arranged on the side of the incident end face and the side face. Furthermore, the emitting surface side of this convex part is connected flat with the emitting surface.
Or a smooth curved surface is connected to the output surface,
The end face side of this convex part becomes the end face as it goes away from the emission face.
It is formed so as to be more separated .

According to a fourth aspect of the present invention, in the sidelight type surface light source device that emits the illumination light from the emission surface of the plate-shaped member, the positioning convex portion of the plate-shaped member has an end surface on which the illumination light is incident. Place on the side or side. Further, the emitting surface side of this convex portion is flatly connected to the emitting surface, or is smoothly connected to the emitting surface by a gentle curved surface, and the end surface side of this convex portion is separated from the end surface as the distance from the emitting surface increases. you formed.

In this type of side-light type surface light source device, the illumination light incident from the end face is repeatedly reflected and propagated between the emitting surface and the surface facing the emitting surface, and is critical to the emitting surface. Components below the angle are emitted from the emission surface. During this propagation, most of the illumination light incident on the side surface of the plate-shaped member is reflected by this side surface and folded back inside, and when the shape of the side surface is locally deformed by this, the tip side from this deformed portion. Brightness unevenness will occur toward. By arranging the positioning convex on the end face side where the illumination light enters, sufficient strength can be secured as the positioning convex, and various shapes of the convex can be selected to reduce uneven brightness. can do.

Further, in the convex portion, if the emitting surface side of the plate-shaped member is flatly connected to the emitting surface of the plate-shaped member or is smoothly connected to the emitting surface of the plate-shaped member by a gentle curved surface, the emitting surface side Abrupt changes in brightness level due to discontinuities will be effectively avoided. If the end face side is formed so as to be separated from the end face as it goes away from the emission face,
It is considered that the uneven brightness due to the emitting surface side of the convex portion and the uneven brightness due to the opposite side of the convex portion have a relationship of canceling each other out, whereby the overall uneven luminance is reduced.

[0020]

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings as appropriate.

FIG. 2 is a plan 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 includes a frame 11 made of a holding member.
It is mounted on a personal computer together with a liquid crystal panel or the like via. That is, the side light type surface light source device 10
After holding the primary light source 3, a reflection sheet (not shown) and a prism sheet as a light control member in the light scattering guide 12, the light scattering guide 12 is held in the frame 11.

Here, the frame 11 is a light scattering guide 12
Is formed of a frame body having an opening 13 on the exit surface side of
The opening 13 is formed such that the center line O2 of the opening 13 is displaced by a predetermined distance Δ with respect to the center line O1 of the frame 11 extending in the longitudinal direction of the frame 3. The frame 11 has the light-scattering light guide 12 centered on the center line O2 of the opening 13.
Hold.

The fluorescent lamp 6 of the primary light source 3 is a frame 1
It is arranged with the center line O1 of No. 1 as the center, so that it is arranged so as to be displaced with respect to the light scattering guide 12 in the longitudinal direction of the fluorescent lamp 6 by a distance Δ. As a result, in the fluorescent lamp 6, the effective light emitting area AR, which is a small distance inside the electrodes 6a and 6b at both ends and which effectively emits the illumination light, is displaced with respect to the incident surface of the light scattering guide 12. ing. Therefore, in the light-scattering light guide 12, the amount of illumination light of the lower incident surface side end 12a in the drawing is changed by the amount of the displacement of the fluorescent lamp 6, and the illumination light amount of the upper incident surface side end 12b in the drawing is illuminated. It is designed so that the amount of light cannot be reduced.

Thus, in the side light type surface light source device 10, the light scattering guide 12 is displaced in this way.
The drive circuit of the liquid crystal panel and the like are arranged by effectively utilizing the surrounding space that retains and retains the space, and the wasteful space is reduced by that amount, and the overall shape of the personal computer is downsized.

In the side light type surface light source device 10, the driving power output from the driving circuit 14 is boosted by the boosting transformer T1 and then the fluorescent lamp 6 is passed through the capacitor C1.
Supply to. At this time, in the fluorescent lamp 6, one electrode 6a is grounded and this electrode 6a is assigned to the cold side, and the other electrode 6b is connected to the capacitor C1 and this electrode 6b is assigned to the hot side. Further, in the side light type surface light source device 10, the hot side electrode 6b is projected from the side surface of the light scattering guide 12.
It is assigned to the electrode 6b in the displacement direction of the fluorescent lamp 6 with respect to the light-scattering light guide 12, and the drive circuit 14, the step-up transformer T1 and the like are arranged in the space on the electrode 6b side.

As a result, the side light type surface light source device 10
Then, the drive circuit 14 and the like are arranged by effectively utilizing the surrounding space which is displaced and holds the light-scattering light guide 12, and the unnecessary radiation is reduced by reducing the wiring of the hot side lead wire. It is done like this. Thus, in the fluorescent lamp 6, the amount of emitted light in the vicinity of the cold-side electrode 6a is lower than that in the vicinity of the hot-side electrode 6b. The amount of illumination light at the lower incident surface side end 12a is inevitably lower than the amount of illumination light at the upper incident surface side end 12b in the drawing.

FIG. 1 is a perspective view of the light-scattering light guide 12 as seen from the side of the slope, and like the light-scattering light guide 2 described above with reference to FIG. 4, polymethylmethacrylate (PMMA).
The translucent fine particles having a refractive index different from that of the matrix are uniformly mixed and dispersed to form a wedge-shaped cross section. As a result, the light-scattering light guide 12 becomes
The illumination light of the fluorescent lamp 6 incident from 5 is repeatedly reflected and propagated between the emission surface and the inclined surface, and a component having a critical angle or less with respect to the emission surface is emitted from the emission surface.

The light-scattering light guide 12 is uniformly formed into a matte surface (texture surface) with a predetermined roughness by matte surface treatment so that the incident surface 15 has a light diffusing function. It is formed on a rough surface to compensate for the insufficient illumination light amount on the incident surface side to reduce uneven brightness. The light-scattering light guide 12 is enlarged as shown by an arrow C,
Ink 16 as a light-shielding means is attached to the upper and lower edges E of the incident surface 15 which are parallel to the emission surface, thereby reducing bright lines generated in parallel to the incident surface and reducing uneven brightness. Here, for example, the ink 16 is made to adhere to the plate-shaped member to which the ink is adhered by pressing the edge E so as to be linearly adhered to the edge E with a very small line width, whereby the edge E becomes bright. It is designed so that it is not illuminated.

That is, in the light-scattering light guide 12, the illumination light incident from the edge E is repeatedly reflected and propagated between the emission surface and the slope similarly to the illumination light incident from the incident surface, and is below the critical angle. The component E is emitted from the emission surface, so that the brightly illuminated edge E is repeatedly observed as a bright line when viewed from the emission surface. As a result, the edge E can be shielded by the ink 16 and the bright line can be obscured.

On the other hand, in the illuminating light entering from the incident surface, a component having a critical angle or less with respect to the emitting surface is insufficient in the vicinity of the incident surface 15, and if the bright line is obscured by this, the incident surface side has The amount of illumination light will be reduced.
Therefore, by making the incident surface 15 have a light diffusion function,
The component below the critical angle, which is insufficient, can be increased to reduce the uneven brightness in the vicinity of the incident surface.

Further, the light-scattering light guide 12 is provided with convex portions 18 and 19 on the incident surface side and both side surfaces thereof.
The frame 9 positions and holds the frame 11. This prevents the light-scattering light guide 12 from being displaced by a shock or the like,
The fluorescent lamp 6 can be prevented from being damaged.

That is, since the light scattering guide 12 has a wedge-shaped cross section, the incident surface side is the thickest portion, and the convex portions 18 and 19 for positioning are provided on the side surface on the incident surface side. By arranging, the shapes of the convex portions 18 and 19 can be selected variously while ensuring sufficient strength, and thereby uneven brightness due to the formation of the convex portions 18 and 19 can be effectively avoided. be able to.

Specifically, in the convex portion 18 on the hot side, as shown by an arrow D1, the emission surface side is flatly connected to the emission surface and is formed in a triangular shape in cross section. That is, when a sharp step is provided between the convex portion of this kind and the emission surface, the step causes a sharp change in the distribution of the illumination light propagating in the light scattering guide 12, and the distribution of the illumination light is changed. It was found that a sudden change was perceived as uneven brightness. Thereby, in the light-scattering light guide 12, uneven brightness on the exit surface side of the convex portion 18 is reduced.

Further, the convex portion 18 is formed such that the surface on the incident surface 15 side is formed by the slope M1 so that the convex portion 18 is separated from the incident surface as the distance from the emission surface increases. That is, when the convex portion 18 is formed on the side surface in this way, the illumination light that is originally folded back inward by the side surface spreads further outward by the convex portion 18. Therefore, this convex portion 18
The light-scattering light guide 1 with the border between the base and the side of the
An abrupt change occurs in the distribution of the illumination light propagating in the area 2. The uneven brightness is what is observed when the illumination light near the boundary is emitted from the emission surface.

However, inside the light-scattering light guide 12, the illumination light propagates from the incident surface side toward the wedge-shaped tip, so that the boundary is divided into the emission surface side and the slope surface side. The uneven brightness caused by the boundary near the surface side occurs relatively near the boundary, whereas the uneven brightness caused by the boundary near the slope occurs at a position separated from the boundary. As a result, in this embodiment, the surface on the incident surface 15 side is formed as the slope M1 so as to be separated from the incident surface as the distance from the emission surface increases, and the uneven brightness caused by the boundary near the emission surface and the slope The uneven brightness caused by the boundary in the vicinity is canceled out, and the uneven brightness is reduced accordingly.

Further, in the convex portion 18, the surface M2 opposite to the incident surface 15 is formed by a surface parallel to the incident surface 15, and the surface on the incident surface side is an extension line extending from the slope of the light scattering guide 12. The light-scattering light guide 12 is connected to the side surface of the light-scattering light guide 12 by a curved surface.

That is, if the shapes of the surface on the outgoing surface side and the surface M1 on the incoming surface side are selected like this convex portion 18, the incoming surface 1
It was found that the surface on the side opposite to 5 had a small effect on the uneven brightness. However, when the light-scattering light guide 12 and the side surface of the light-scattering light guide 12 are connected substantially vertically, uneven brightness occurs due to a rapid change in the illumination light distribution. As a result, in this embodiment, a curved surface is connected to the side surface of the light-scattering light guide 12 to reduce abrupt changes in the illumination light distribution.
It is designed to reduce uneven brightness.

Further, as shown in FIG. 3, the light scattering guide 12
It was found that when a step was formed between the convex portion and the slope on the slope surface side, the step was observed as a streak (formed by a bright line) from the exit surface. As a result, in this embodiment, the surface M1 and the surface M2 on the incident surface side are connected by an extension line extending from the inclined surface of the light scattering guide 12 so that the uneven brightness due to this kind of bright line is effectively avoided. Has been done.

Further, in the convex portion 18, a diffuser 21 made of a light diffusing member is attached to the base portion and a triangular area remaining on the side of the incident surface, and the convex portion 18 is formed by the diffuser 21.
To correct the amount of emitted light that locally decreases.

Here, the diffuser 21 is formed by processing a white PET film into a substantially right triangle shape, has a refractive index extremely close to that of the light scattering guide 12, and is used for bonding optical glass. The light-scattering light guide body 12 is adhered to the light-scattering light guide body 12 by an adhesive having a large transmittance. As a result, the diffuser 21 scatters the illumination light incident from the incident surface 15 and increases the component having a critical angle or less with respect to the emission surface.

That is, when the convex portion 18 is formed in this manner, of the illumination light propagating toward the wedge-shaped tip, originally,
The illumination light that is folded back inward by the side surface spreads further outward by the convex portion 18, and leaks from the side surface of the convex portion 18 and the like. As a result, the amount of emitted light near the convex portion 18 decreases. Further, the illumination light that is folded back by the convex portion 18 and returns to the inside is also folded back at a position displaced in the wedge-shaped tip direction, as compared with the case where it is folded back by the side surface, and the light amount distribution of the emitted light is biased accordingly. It will be.

This deviation is shown in FIG. 6 on the incident surface side of the convex portion 18.
As described above for the
If the incident surface M1 of No. 8 is formed by a slope, the boundary of this dark band will not be perceived. On the other hand, in the fluorescent lamp 6, since the light source is a rod-shaped light source, the incident surface corresponding to the electrode 6a has a small absolute light amount of illumination light and a component having a critical angle or more with respect to the emission surface. Will occupy a lot. As a result, in the diffuser 21 arranged close to the slope M1, the illumination light occupying a large amount of the component above the critical angle is distributed so as to include a large amount of the component below the critical angle, and is reduced by the convex portion 18. It is designed to compensate for the amount of illumination light.

On the other hand, the cold-side convex portion 19 has a shape obtained by cutting out a part of the hot-side convex portion 18 shown by a dotted line, as shown in an enlarged view by an arrow D2.
8 and asymmetrical shape. That is, the cold-side convex portion 19 is configured such that the emitting surface side is connected to the emitting surface of the light scattering guide 12 by a uniform surface, and the incident surface 15 side is formed by the slope M1. On the other hand, the incident surface 15 and the opposite side surface, which have the least influence on the brightness unevenness, are formed in a shape in which the root portion of the convex portion 18 is obliquely cut from the tip of the slope M1.

That is, it has been found that when a convex portion is formed on this type of light scattering guide 12, the amount of light in the vicinity of the convex portion is reduced substantially in proportion to the volume of the convex portion. As a result, in this embodiment, the shape of the cold-side convex portion 19 is made smaller than that of the hot-side convex portion 18, and the cold-side illumination light amount that is reduced as compared with the hot side is reduced. The amount of illumination light on the cold side, which is reduced by displacing the fluorescent lamp 6, is corrected to be substantially equal to that on the hot side.

In the above-mentioned structure, the illumination light emitted from the fluorescent lamp 6 (FIGS. 2 and 4) is directly or after being reflected by the reflector and then enters the inside of the light scattering guide 12 from the incident surface 15. The incident light is propagated inside the light scattering guide 12 while being repeatedly reflected between the inclined surface and the emission surface. At this time, the illumination light is scattered inside the light-scattering light guide 12, and the incident angle with respect to the emission surface is gradually reduced each time it is reflected by the inclined surface. After being emitted further, the directivity is corrected by the prism sheet 5. As a result, this prism sheet 5
The liquid crystal panel arranged in front of the is illuminated.

Of the illumination light emitted from the fluorescent lamp 6 in this way (FIG. 1), the illumination light incident from the edge E of the incident surface 15 is shielded by the ink adhering to this edge E, and the reflector 7 side. Reflected in. As a result, the brilliance of the edge E is effectively avoided, and the generation of the bright line, which is caused when the linear brilliance of the edge E is observed from the emission surface, is effectively avoided. Further, the illumination light incident from the incident surface 15 is scattered by the incident surface 15 formed on the rough surface, whereby the distribution of the amount of light emitted from the emission surface is biased toward the incident surface side, and uneven brightness is reduced. It

On the other hand, a part of the illumination light incident from the incident surface 15 is reflected by the side surface of the light-scattering light guide 12 and is folded back inward, so that the light-scattering light guide 12 is moved in the wedge-shaped tip direction. Propagate toward. At this time, due to the positioning convex portions 18 and 19 of the light scattering guide 12 formed on the side surface, a part of the illumination light spreads outward from the original side surface position, and the convex portions 18 and 19 cause It will be folded back and returned to the inside, and a part will leak out from the convex portions 18 and 19. As a result, in the light scattering guide 12, the distribution of illumination light changes, and if left unattended, uneven brightness will occur.

Of the convex portions 18 and 19, the emission surface side is connected to the emission surface of the light scattering guide 12 by a uniform surface, so that the convex portions 18 and 1 on the emission surface side are formed.
The rapid change of the illumination light distribution in the vicinity of the connection portion 9 is effectively avoided, and the uneven brightness due to the connection portion on the emission surface side is effectively avoided.

In addition, in the convex portions 18 and 19, the incident surface side is formed by the slope M1 so as to be separated from the incident surface 15 as it goes away from the emission surface, so that the illumination light distribution is changed by the slope M1 on the emission surface side. , The change of the illumination light distribution due to the slope M1 on the slope side acts so as to cancel each other on the emission surface, whereby the convex portions 18 and 19 are formed.
The uneven brightness due to the side surface of the incident surface is reduced.

Further, on the surface opposite to this, since the connecting portion with the side surface is formed by the curved surface, the generation of the bright line due to this connecting portion is effectively avoided, whereby the uneven brightness is reduced. In addition, the surface M1 on the incident surface side and the surface M on the opposite side are formed by an extension line extending from the inclined surface of the light scattering guide 12.
By connecting the 2 and 2, it is possible to effectively avoid the generation of the bright line due to the connecting portion between the slope and the convex portion, and the uneven brightness can be effectively avoided accordingly.

Further, the diffuser 21 arranged in the triangular regions remaining on both side surfaces on the incident surface side scatters the illumination light containing a large amount of the component having the critical angle or more with respect to the emitting surface, and the diffuser 21 on the emitting surface. It is converted to include many components below the critical angle. Components below this critical angle are emitted from the vicinity of the convex portions 18 and 19, the amount of illumination light reduced by forming the convex portions 18 and 19 is compensated, and uneven brightness is effectively avoided.

Regarding the cold-side convex portion 19, the hot-side convex portion 18 is formed by obliquely cutting the incident surface side and the opposite side surface, and is formed in an asymmetrical shape with respect to the hot-side convex portion 18. The fluorescent lamp has a smaller size than that of the above, and accordingly, the reduction in the amount of illumination light due to the formation of the convex portion in comparison with the convex portion 18 on the hot side is reduced accordingly, and is reduced compared to the hot side. 6 is supplemented with the cold side illumination light quantity, and further, the end portion 12 is arranged displaced with respect to the light scattering guide 12.
The difference in light amount between a and 12b is corrected.

According to the above construction, the convex portions 18 and 19 for positioning and holding the light-scattering light guide 12 are formed on the incident surface side, so that the convex portion 18 can be secured with sufficient strength.
The shapes of Nos. 19 and 19 can be selected in various ways, whereby the uneven brightness due to the bright lines and dark bands can be effectively avoided.

That is, in the convex portions 18 and 19, the emitting surface side is formed to be flat with the emitting surface of the light scattering guide 12, and the incident surface side is formed so as to be separated from the incident surface as the distance from the emitting surface increases. By doing so, it is possible to effectively avoid abrupt changes in the light amount distribution and cancel out the abrupt changes in the light amount distribution, thereby effectively avoiding uneven brightness.

Further, since the convex portion 19 is formed in a small shape asymmetrical to the convex portion 18, the different light amount difference between the hot side and the cold side of the fluorescent lamp is corrected, and the fluorescent lamp is displaced. The difference in the amount of light at the end of the light-scattering light guide can be corrected, and the uneven brightness can be effectively avoided by these corrections.

In the above-described embodiment, the case where the convex surfaces 18 and 19 are formed with the inclined surface on the incident surface side has been described. However, the present invention is not limited to this, and as the distance from the outgoing surface is increased due to the gentle curved surface. It may be formed so as to be separated from the incident surface. Further, in these cases, the connection portion with the side surface may be formed by a curved surface.

Further, in the above-mentioned embodiment, the case where the emitting surface side of the convex portions 18 and 19 is connected flat with the emitting surface of the light scattering guide 12 has been described, but the present invention is not limited to this. , A smooth curved surface may be used for smooth connection.

Further, in the above-described embodiment, the case where the surface of the convex portion 18 opposite to the incident surface is formed by the surface parallel to the incident surface has been described, but the present invention is not limited to this.
It may be formed of a flat surface, a curved surface, or the like inclined with respect to the incident surface within a practically sufficient range. If there is no difference in the amount of light entering the incident surface at both ends of the incident surface, the convex portion 1
It goes without saying that 8 and 19 may be symmetrical.

In the above-described embodiment, the case where the diffuser 21 is arranged in the vicinity of the convex portions 18 and 19 to supplement the illumination light amount has been described, but the present invention is not limited to this, and the diffuser 2 is not limited thereto.
In place of 1, the side surface is locally formed as a light-scattering surface by a matte surface treatment, and in place of the matte surface treatment, a blasting treatment with sandpaper or a rough surface by a chemical etching treatment, and the like. Various light scattering methods can be widely applied, such as a case where a light diffusing material such as white ink is attached, or a diffusion sheet or the like is arranged to scatter illumination light.

Further, in the above-described embodiment, the case where the edge 6 of the light scattering guide is pressed against the plate member coated with ink to attach the ink to the edge E has been described. Not limited to this, various ink adhesion methods can be widely applied such as when directly printing on the edge E. Further, the edge E of the incident surface may be shielded by a reflector, a tape or the like without being limited to the case where the ink is adhered to shield the edge.

Further, in the above-mentioned embodiment, the case where the incident surface of the illumination light is formed to be a rough surface by the matte surface treatment has been described, but the present invention is not limited to this, and the blasting treatment by sandpaper and the chemical etching treatment are carried out. Therefore, various rough surface forming means can be widely applied, for example, when forming a rough surface. Further, a light diffusing 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 illumination light incident from the incident surface. Roughening treatment of the incident surface is not always required, and roughening treatment is performed on the incident surface as long as the specification allows uneven brightness occurring near the incident surface to some extent. It is also possible to apply the present invention without it.

Further, in the above-described embodiment, the case where the liquid crystal panel is integrally mounted on the personal computer through the frame has been described, but the present invention is not limited to this.
It can be widely applied to the case where the light scattering light guide 12 is positioned and held by the convex portion formed integrally with the light scattering light guide 12.

Further, in the above-mentioned embodiment, the case where the present invention is applied to the side light type surface light source device using the light-scattering light guide body formed of the light guide plate in which transparent fine particles are mixed and dispersed has been described. The present invention is not limited to this, and includes a side-light type using a light guide plate having a directional emission property, including a flat plate that is configured to have a directional emission property by performing a predetermined process. It can be widely applied to surface light source devices.

Further, in the above-mentioned 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 a constitution in which the illumination light is incident from the other end face as well. 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. However, the present invention is not limited to this, and it is a side light type such as various lighting devices and display devices. It can be widely applied to surface light source devices.

[0067]

Effects of the Invention According to the present invention as described above, in the side light type surface light source device using a light guide plate having a emitting directivity, to form a convex portion for positioning the side of the incident surface side
By selecting the shape, it is possible to secure sufficient strength as the convex portion for positioning, and select the shape of the convex portion to reduce the brightness unevenness due to the bright line and the dark band.

Particularly, in the convex portion, the emission surface side of the plate member is connected to the emission surface of the plate member flatly or smoothly with the emission surface of the plate member, and as the end face side is separated from the emission surface. By forming it away from the end surface,
It is possible to effectively avoid abrupt changes in the light amount distribution, and cancel out the abrupt changes in the light amount distribution to effectively avoid uneven brightness.

The positions of the light sources can be changed by forming the convex portions on both side surfaces in an asymmetrical shape corresponding to the positions of the light sources, and further corresponding to the hot side and the cold side of the light sources.
It is possible to reduce the difference in brightness level between the hot side and the cold side.

[Brief description of drawings]

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

FIG. 2 is a plan view showing the side light type surface light source device of FIG.

FIG. 3 is a plan view for explaining a convex portion of the light scattering guide of FIG.

FIG. 4 is an exploded perspective view showing a conventional side light type surface light source device.

5 is a cross-sectional view showing the side light type surface light source device of FIG. 4 taken along the line AA.

FIG. 6 is a perspective view showing a case where a convex portion is formed in a conventional side light type surface light source device.

[Explanation of symbols]

1, 10 Side light type surface light source device 2, 12 Light-scattering light guide 3 Primary light source 6 Fluorescent lamps 9, 18, 19 Convex portion 15 Incident surface 21 Diffuser E Edge

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-19254 (JP, A) JP-A-6-130387 (JP, A) JP-A-8-62430 (JP, A) JP-A-6- 167618 (JP, A) JP 8-271891 (JP, A) JP 9-152577 (JP, A) JP 9-15594 (JP, A) JP 4-59432 (JP, A) Unexamined Japanese Patent Publication No. 7-56170 (JP, A) Actual Development No. 5-64831 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F21V 8/00 601 G02B 6/00 331 G02F 1 / 13357 G09F 9/00-9/46 G09F 13/00-13/46

Claims (4)

(57) [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 . on the end face side, a convex portion for positioning with respect to the holding member, side light type surface light source device according to claim <br/> that are formed in a tapered shape toward the end face side. 2. 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 . On the incident surface side, for positioning with respect to the holding member
It has a convex part, and the emitting surface side of the convex part is flatly connected to the emitting surface.
, Or a smooth curved surface that connects with the exit surface smoothly
Follow the then, the end face of the convex portion, away from the exit surface
Thus, the side light type surface light source device is formed so as to be separated from the end face . 3. Illumination light incident from the incident surface is bent and output.
Side-light type surface light that is configured to emerge from the projection surface
A light guide plate used for a source device, which is for positioning with respect to a holding member on a side of the incident surface.
The convex portion is formed in a taper shape toward the incident surface side.
A light guide plate characterized by having. 4. A light guide plate used in a sidelight type surface light source device configured to bend illumination light incident from an incident surface and emit the illumination light from an emitting surface, the light guide plate being held on a side surface on the incident surface side. For positioning with respect to parts
Having a convex portion, the emitting surface side of the convex portion is flatly connected to the emitting surface or is smoothly connected to the emitting surface by a gentle curved surface, and the end face side of the convex portion is the emitting surface. A light guide plate, characterized in that it is formed so as to be separated from the end face as the distance from the surface increases.