JP3437029B2 - Sidelight 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 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. . According to the present invention, in this sidelight type surface light source device, a light control member having an end face shielded from the light emitting face of the light guide plate is arranged so that the tip of the light guide plate protrudes from the light source side end face of the light guide plate. Shade the edges
Also, the tip projects from the end surface of the light guide plate on the light source side.
Place the light control member on the exit surface of the light guide plate
On the side, the end surface of the reflector is used to
By blocking the light , the generation of a bright line due to the edge of the end surface of the light guide plate is effectively avoided.

[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 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 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. 13 is an exploded perspective view showing the structure 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.
Illumination light enters the end surface 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 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. Thereby, as shown in FIG. 14 by taking a section along the line AA, this light scattering guide 2 has an incident surface T which is an end surface on the primary light source 3 side.
More illumination light L is incident, and the illumination light L is emitted by the transparent fine particles.
When a diffuse reflection member is applied to the reflection sheet 4, the reflection sheet 4 is partially diffused and the reflection sheet 4 side plane (hereinafter referred to as a slope) and the prism sheet 5 side plane (hereinafter referred to as an emission surface) are scattered. (Hereinafter, referred to as)) is repeatedly reflected to propagate the illumination light L.

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 a light guide plate having a matte surface, a minute lens array, a scattering film, etc. formed on the exit surface and / or the back surface. 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, the side light type surface light source device using the light guide plate having the directional emission property as described above has a problem that uneven brightness occurs near the incident surface.
This uneven brightness is caused by a linear portion K having a high luminance level (that is, a bright line) K (FIG. 13) and a belt-shaped portion having a low luminance level (that is, a dark band) that are parallel to the incident surface at regular intervals. It is formed. As a result, in this type of sidelight type surface light source device, it is difficult to use the range of about 10 [mm] from the incident surface T, and in the end, it is difficult to effectively use the emitting surface. It was

The present invention has been made in consideration of the above points, and it is an object of the present invention to propose a sidelight type surface light source device capable of effectively avoiding the occurrence of uneven brightness near the incident surface.

[0013]

In the invention of claim 1 for solving the Means for Solving the Problems] Such problems, the side light type surface light source device for correcting the directivity by a sheet-like light control member disposed on the exit surface, the end face such that the tip protrudes more light source side, by arranging the light control member, the reflector
By sandwiching the plate-shaped member and the light control member,
A light blocking member is disposed on the light source side end surface of the light control member.

[0014]

According to the invention of claim 2 , claim 1
In the above configuration, the light shielding member is made of ink attached to the end portion on the light source side. Further, in the invention of claim 3 , in the configuration of claim 1 or 2 , the plate-shaped member adheres ink to the edge of the end face and shields the edge with the ink.

With the structure according to the first aspect, the light control member is arranged such that the tip of the plate member projects from the end face toward the light source side.
Then, by the reflector, the plate-shaped member, the light control
The member is sandwiched, and light is shielded from the light source side end surface of the light control member.
By arranging the member, it is possible to block the illumination light incident on the edge of the plate member from the light control member side. As a result, it is possible to reduce the illumination of the edge by the illumination light, effectively avoid the situation where the edge is illuminated so as to shine, and reduce the uneven brightness when the edge is observed from the emission surface .

[0017]

According to the structure of claim 2, in the structure of claim 1, if the light shielding member is made of ink adhered to the end portion on the light source side, the edge can be shielded easily and reliably. . Further, according to the structure of claim 3, in the structure of claim 1 or 2 , the plate-shaped member is
If ink is adhered to the edge of the end face and the edge is shielded by the ink, the edge can be shielded more completely, and the generation of bright lines can be effectively avoided due to manufacturing variations and the like.

[0019]

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.

(1) First Embodiment FIG. 1 is an enlarged sectional view showing a side light type surface light source device according to a first embodiment of the present invention, corresponding to FIG. In this sidelight type surface light source device 10, the frame 12 covers the primary light source 11, and the frame 12 serves as a prism sheet 1 as a light control member.
3, holding the reflection sheet 14 and the light scattering guide 15.

That is, the frame 12 is formed in a U-shaped cross section by injection molding, and holds the edge of the reflector 18 on the emission surface side by the double-sided tape 17 attached to the inside of the emission surface. Here, the reflector 18 is made of an elastic film formed by depositing silver having a high reflectance. As a result, the frame 12 effectively utilizes the elasticity of the reflector 18 to hold the reflector 18 in a substantially arc shape along the inner side surface so as to surround the periphery of the fluorescent lamp 6 and to sequentially stack the prisms. Sheet 13, light-scattering light guide 1
5. The reflection sheet 14 is held together with the reflector 18.

Like the reflector 18, the reflection sheet 14 is composed of a film on which silver having a high reflectance is deposited,
The illumination light leaking from the slope is reflected back inside the light-scattering light guide 15 to improve the utilization efficiency of the illumination light.

On the other hand, in the light-scattering light guide 15 as a light guide plate, translucent fine particles having different refractive indexes are uniformly mixed and dispersed in a matrix made of polymethylmethacrylate (PMMA) to form a wedge-shaped cross section. It is formed in a mold shape. The light-scattering light guide 15 is uniformly formed into a matte surface (texture surface) having a predetermined roughness by matte surface treatment so that the incident surface T has a light-scattering function. Therefore, in this embodiment, The incident surface T is formed to be a rough surface to effectively avoid the occurrence of a dark band, and the uneven brightness is reduced accordingly.

That is, the basic principle of the illumination light emission of the side light type surface light source device of this type is that the illumination light incident from the incident surface T propagates through the plate member and the incident angle with respect to the emission surface gradually decreases. , Because a component having a critical angle or less is emitted from the emission surface. According to this basic principle, the illumination light incident from the incident surface T is scattered inside the light-scattering light guide 15, but a large component of the incident angle with respect to the emission surface becomes large. . As a result, as shown by symbol L3 in FIG. 2, when the incident surface T is formed as a mirror surface, the illumination light entering from the incident surface T gradually increases in amount as it goes away from the incident surface (FIG. 2).
(A) and (B)).

On the other hand, the illumination light entering from the edge E is dominated by a component having a small incident angle with respect to the exit surface. As a result, many components of the illumination light incident from the edge E are directly emitted from the emission surface or the reflection sheet side plane,
The remaining components propagate inside the light scattering guide 15, and are gradually emitted. At this time, the illumination light incident from the edge E has an incident angle range limited to upper and lower halves as compared with the illumination light incident from the incident surface T, so that the envelope connecting the peaks is incident as shown by a symbol L4. The amount of emitted light sharply decreases as the distance from the surface T increases (see FIG. 2).
(B) and (C)). Further, at this time, when the light enters from the linear edge E, the amount of emitted light sharply decreases while forming a peak. Further, in the range of the area AR defined by the incident surface T by the critical angle θ, the illumination light incident from the edge E is directly emitted, so that the brightness level rises sharply.

As a result, by forming the incident surface T to be a rough surface as in this embodiment, the illumination light incident from the incident surface T is increased so that the component having a small incident angle with respect to the emission surface increases. The distribution can be changed, and the light amount distribution of the illumination light emitted from the emission surface can be biased toward the incident surface side. That is, as shown by the symbol D, the luminance level can be increased overall in the region where the peak-to-peak luminance level is low (dark band portion), and as a result, the luminance unevenness formed by the bright line and the dark band is reduced. It can be blinded.

Observing this type of processing from the average brightness level, however, if the end face is simply formed as a rough surface to make the bright lines inconspicuous, the light quantity distribution will be too biased toward the incident surface side. A brightness gradient occurs from the T side toward the wedge-shaped tip. Preferably, it is desirable to increase the brightness level for dark bands and decrease the brightness level for bright lines. That is, it is desirable that the overall brightness level be close to the average brightness.

Therefore, in this embodiment, the edge E on the exit surface side is shielded by the prism sheet 13 which is a basic constituent member of the side light type surface light source device, and the edge E itself does not shine brightly. Thus, the generation of the bright line due to the edge E on the exit surface side is effectively avoided. For the edge E on the slope side, the frame 12
The emission surface side length W1 (about 2 [mm] from the incident surface of the light-scattering light guide 15) is sufficiently secured, so that the luminescent line due to the slope side edge E that can be recognized by the user is It should be covered by the frame 12.

That is, as shown in FIG. 3 by enlarging the fluorescent lamp 6 side of the prism sheet 13 in a sectional view, in this sidelight type surface light source device 10, the prism sheet 13 is closer to the light source side than the incident surface T and the end surface. Is about 0.2 [m
m] (indicated by symbol W2 in FIG. 1) so as to pop out, and the ink 19 is attached to the end surface on the light source side. Thereby, the prism sheet 13
As shown by the broken line, the illumination light reflected by the reflector 18 and incident on the edge is blocked, and the bright line of the edge E caused by the illumination light is effectively avoided from being observed from the emission surface.

It should be noted that it is not always necessary in the present invention to shield the end surface on the light source side with the ink 19 or the like. For example, when the prism sheet 13 having a small thickness is used, It is possible to avoid the occurrence of bright lines in a practically sufficient range without disposing a light shielding member. However, in order to make the issuing surface having a more uniform brightness, it is desirable to dispose a light shielding member for adhering the ink 19 to the light source side end surface of the prism sheet 13 as in this embodiment.

When the prism sheet 13 is arranged so as to project from the incident surface T to the light source side in this way, the illumination light incident on the prism sheet 13 from the prism surface is emitted from the prism surface as shown in FIG. To be incident on the edge. Further, in the illumination light, a component refracted by the prism surface and incident on the edge is also generated. Illumination light that enters the light scattering guide 15 through such a prism surface increases in accordance with the area of the prism surface that projects from the incident surface T, and partially illuminates the corresponding exit surface near the edge. And it will shine brightly.

As indicated by the broken line, such a component (hereinafter referred to as illumination light that circulates from the prism surface) enters the light scattering guide 15 from the exit surface, is reflected by the slope, and then near the entrance surface. It will be emitted from the emission surface. As a result, if the amount of protrusion of the prism sheet 13 is increased too much, the brightness level near the incident surface will increase, causing uneven brightness to occur.

FIG. 5 shows the result of measuring the brightness level from the incident surface side.
As shown in FIG. 7, the state in which the end surface of the prism sheet 13 is retracted by 0.2 mm from the incident surface T (indicated by symbol M1) and the state in which the incident surface T and the end surface of the prism sheet 13 are aligned (indicated by symbol M2) are shown. ) And a state in which the end surface of the prism sheet 13 is projected by 0.2 mm from the incident surface T (indicated by symbol M3), the prism sheet 13 is projected from the incident surface T to reduce uneven brightness. I understand that

On the other hand, as shown in FIG. 6, when the width of the bright line was measured by using this projection amount parameter as a parameter, even if the projection amount increased around the projection amount 0.2 [mm],
It was found that a bright line was generated even with the reduction.

Thus, in this embodiment, the edge E
The projection amount of the prism sheet 13 is set to about 0.2 [mm] so as to suppress the bright line due to the light and to effectively avoid the uneven brightness due to the illumination light that wraps around the prism surface. It is designed to be effectively avoided.

Further, in this embodiment, the ink 1
As for 9, white ink that scatters and reflects the illumination light is applied.
That is, when black ink is applied as the ink 19, the illumination light incident on the ink 19 is absorbed by the ink 19. As a result, the image of the ink 19 is observed from the emission surface via the inclined surface, and the light amount of the emitted light is observed in a band shape. As a result, in this embodiment, the end surface of the prism sheet is shielded by the white ink that scatters and reflects the illumination light to effectively avoid the uneven brightness due to the ink 19 adhering. As a method of shielding the end surface of the prism sheet from light, a method in which a white tape is attached to the end surface is used in addition to the method described above.
It is also possible to adopt a method of vapor-depositing g, Al or the like.

In the above-mentioned structure, the illumination light emitted from the fluorescent lamp 6 (FIG. 1) enters the inside of the light scattering guide 15 from the incident surface T directly or after being reflected by the reflector 18. The illumination light propagates inside the light scattering guide 15 while being repeatedly reflected between the inclined surface and the emission surface. At this time, this illumination light is scattered inside the light-scattering light guide 15, while the angle of incidence on the emission surface gradually decreases each time it is reflected on the slope, and a component having a critical angle or less is emitted to the emission surface. After the light is emitted from the surface, the directivity is corrected by the prism sheet 13. As a result, the liquid crystal panel or the like arranged on the front surface of the prism sheet 13 is illuminated.

Of the illumination light emitted from the fluorescent lamp 6 in this manner, the illumination light incident from the edge E of the incident surface T projects from the incident surface T toward the light source side.
3 and the ink 19 attached to the end surface of the prism sheet 13 shields the light and reflects the light toward the reflector 18 side (FIGS. 2 and 3). 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. The illumination light incident from the incident surface T is scattered by the incident surface T formed on the rough surface, whereby the distribution of the amount of light emitted from the emission surface is biased to the incident surface side (FIG. 2). As a result, the brightness level of the dark band is increased and brightness unevenness is reduced.

At this time, the protrusion amount of the prism sheet 13 is about 0.2 [m] from the incident surface side of the light scattering guide 15.
m], the prism sheet 13
The illumination light that wraps around the exit surface of the light-scattering light guide 15 from the prism surface is reduced to a practically sufficient range, so that the increase in the brightness level near the entrance surface due to the protrusion of the prism sheet 13 is effectively avoided. (Fig. 4).

Further, since the white ink 19 shields the end surface of the prism sheet 13, the illumination light is scattered and reflected by the white ink 19, and the ink 19
The uneven brightness due to the adhered particles is effectively avoided (FIG. 3). Further, the illumination light incident from the light source side is scattered and reflected to the light source side, so that the illumination light can be effectively used.

According to the above construction, the inside of the reflector
By projecting the prism sheet 13 from the incident surface of the light guide plate and shielding the end surface of this prism sheet,
The edge can be shielded by effectively utilizing the prism sheet 13 which is a basic constituent member of the side light type surface light source device. As a result, it is possible to effectively avoid the generation of the bright line in which the brilliance of the edge is observed from the emission surface, and it is possible to effectively avoid the uneven brightness due to the bright line.

Further, at this time, by shielding the end surface of the prism sheet 13 with the ink 19, it is possible to easily and surely shield the edge and effectively prevent the generation of the bright line. Further, by setting the protrusion amount of the prism sheet 13 to be about 0.2 [mm] from the incident surface of the light scattering guide 15, it is possible to effectively avoid the occurrence of uneven brightness due to the illumination light that wraps around the prism surface. it can.

(2) Second Embodiment FIG. 7 is a sectional view showing a sidelight type surface light source device according to a second embodiment in comparison with FIG. In the sidelight type surface light source device 20, the same components as those of the sidelight type surface light source device described above with reference to FIG. 1 are denoted by the same reference numerals, and the duplicated description will be omitted.

Here, in the sidelight type surface light source device 20, the light scattering guide 21 has ink 22 as a light-shielding means attached to the upper and lower edges E of the incident surface T, as shown enlarged by an arrow G. This also effectively avoids the bright line due to the upper edge E. Here, the edge E has a curvature radius R of 0.05 when viewed microscopically.
It has a curved surface of about [mm], and the ink 22 adheres to this curved surface in the state of an ink layer. The ink adhesion process is performed by applying the ink to the plate-shaped member and then pressing the edge E against the ink adhered to the plate-shaped member in a state where the light scattering guide 21 is tilted by a predetermined angle. As a result, the light-scattering light-guiding body 21 linearly adheres the ink 22 with a very small line width to the edge E, and blocks the illumination light incident from the edge E with the ink 22.

Here, as the light shielding ink 22, a white ink having a high reflectance with respect to the illumination light is applied. As a result, the sidelight type surface light source device 20 is formed so as to return the shielded illumination light of the edge E to the light source side, so that the illumination light can be efficiently utilized.

As a result, in this embodiment, the edge is shielded to effectively avoid the brilliance of the edge without reducing the area of the incident surface, and the illumination light is efficiently incident on the light scattering guide 21 accordingly. Therefore, uneven brightness can be effectively avoided. Further, since the light can be shielded with good reproducibility, it can be applied to mass production correspondingly to effectively avoid characteristic variations.

Further, regarding the bright line due to the upper edge E, even if the prism sheet 13 is not properly mounted in the replacement work of the fluorescent lamp 6 or the like, the bright line due to the upper edge E is effectively avoided by the ink 22 attached to the edge. Is made possible. On the contrary, by projecting the prism sheet 13 together, it is possible to effectively prevent the generation of the bright line even when the ink 22 on the edge E is damaged by the replacement work. There is.

On the other hand, at the lower edge, the radiance of the edge E itself can be effectively avoided, so that the emission surface side of the frame 12 is largely opened and the emission surface of the light scattering guide 21 is effectively made. It is made available.

Further, as shown in FIG. 8, in the side light type surface light source device 20, the reflector 23 has a light-shielding surface 24 formed at the edge of the incident surface side which overlaps the prism sheet 13, and thereby the light-shielding surface 24 is formed. This effectively avoids the uneven brightness when the edge of the incident surface is observed from the exit surface.

That is, in the reflector 23 of this type, the metal base film 23b and the protective layer 23c are sequentially laminated on the transparent base material 23a to form the base material 23a and the prism sheet inside the base material 23a. Illumination light is diffused at the boundary surface of 13 and the diffused illumination light enters the light scattering guide 21 from the prism sheet 13. As a result, in the sidelight type surface light source device 20, the inside of the base material 23a, the boundary surface of the base material 23a and the prism sheet 13 are illuminated so as to shine brightly, and these are observed from the emission surface, causing uneven brightness.

As a result, in this embodiment, the illumination light is shielded by the light shielding processing surface 24, and the base material 23
The uneven brightness due to the boundary surface of the inside of a, the base material 23a and the prism sheet 13 is effectively avoided. Further, at this time, this light-shielding process is performed by attaching gray ink so that the image of the light-shielding face 24 observed from the emission surface through the slope becomes inconspicuous, and the uneven brightness due to the light-shielding face 24 is caused. Avoid effectively.

Further, in this embodiment, the reflector 23 and the double-sided tape 17 are provided with the black ink at the end portion on the emission surface side to form the light shielding portion 25, and the uneven brightness due to the brightness of the end surface is effectively avoided. It is designed to do. That is, a part of the illumination light incident on the inside of the reflector 23 is diffused by the base material 23a, leaks from the end face, and is emitted. Further, at the end faces of the reflector 23 and the double-sided tape 17, illumination light coming from the outside,
Diffuse external light. As a result, the illumination light scattered and irregularly reflected is incident on the light-scattering light guide body 21, and then reflected by the slope and emitted, and reflected by the emission surface of the light-scattering light guide body 21 to obtain brightness. The unevenness will occur. As a result, in this embodiment, it is possible to effectively avoid uneven brightness by blackening the end faces of these black inks.

According to the structure shown in FIG. 7, the prism sheet 13 is projected to the light source side, ink is attached to the edge E, and the edge E is shielded by these.
Even when the assembly is not performed correctly due to the assembly work, the maintenance work, or the like, and even when the assembly accuracy is deteriorated, the uneven brightness due to the edge can be reliably prevented.

(3) Third Embodiment FIG. 9 is a sectional view showing a side light type surface light source device according to a third embodiment in comparison with FIG. In this sidelight type surface light source device 30, the same components as those of the sidelight type surface light source device described above with reference to FIG. 7 are denoted by the same reference numerals, and duplicate description will be omitted. In the sidelight type surface light source device 30, the reflection sheet 31 reflects the illumination light leaking from the slope to the inside of the light scattering guide 21.

That is, as shown in FIG. 10, the reflection sheet 31 is formed of a film, which is a sheet-like regular reflection member, on which silver having a high reflectance is deposited. Thereby, the reflection sheet 31 efficiently reflects the illumination light leaking from the slope to the inside of the light scattering guide 21, and improves the utilization efficiency of the illumination light. Further, the reflection sheet 31 has light-scattering regions 32 that diffusely reflect the illumination light on both side surfaces of the light-scattering light guide body 21 and on peripheral portions corresponding to the incident surface.

Here, the light-scattering region 32 is formed by selectively printing a light-diffusing ink so that the degree of diffusion decreases inward from the periphery. In this embodiment, a printing ink in which silica is dispersed in an acrylic ester resin is applied to this ink. As a result, in the sidelight type surface light source device 30, the uneven brightness is further reduced.

That is, both side surfaces and upper and lower edges of the light-scattering light guide 21 are illuminated by the illumination light so as to shine brightly like the edge on the incident surface side, and this brilliance is observed from the emitting surface and the emitting surface. A bright line is generated. This bright line is
In the illumination light emitted from the edge, a component having a critical angle or more is generated each time it is repeatedly reflected by the inclined surface and the emission surface, and thus is repeatedly generated at a pitch determined by the thickness of the light scattering guide 21. The reflection sheet 31 diffuses the illumination light emitted from this edge by the light scattering regions 32 corresponding to both side surfaces, and makes the brilliance of the edge inconspicuous when seen from the emission surface, whereby both side surfaces of the light scattering guide 21 are formed. The uneven brightness caused by the bright line along the line is effectively avoided.

On the other hand, even if the incident surface is roughened or the upper and lower edges of the incident surface are shielded, the pulsation of the emitted light may not be completely prevented. Illumination light is diffusely reflected by the scattering region 32, this type of pulsation is reduced, and the quality of emitted light is further improved.

Specifically, in the light scattering region 32, when the illumination light emitted from the upper edge at a critical angle with respect to the slope at the edges corresponding to both side surfaces is reflected by the slope and reaches the emission surface, It is formed with a width AR1 that is almost equal to the distance from the side surface, and as a result, in accordance with the plate thickness of the light scattering guide 21,
The width is narrowed toward the tip of the wedge shape. As a result, with respect to the edge portions corresponding to the both side surfaces, the light scattering region 32 is formed with the minimum necessary width, and the remaining specular reflection region specularly reflects the illumination light to effectively avoid the reduction of the utilization efficiency of the illumination light. To do. On the other hand, in the edge portion corresponding to the incident surface T, the light scattering region 32 is 15 degrees from the end portion of the incident surface.
It is formed with a width of about [mm], and even on the incident surface side, it is formed with a necessary minimum width to effectively avoid a decrease in utilization efficiency of illumination light.

Further, at this time, as shown by the arrow H,
The light-scattering region 32 has a coverage of 10 in the outer region of about 1/5 to 1/3 by printing a light-diffusing ink on the entire surface.
On the other hand, the coverage is sharply reduced on the inner side, and the coverage on the inner side sharply decreases due to partial printing of a circular shape having a size that is difficult to distinguish from the emission surface. Is about 10%. Thus, the area of 100% coverage is an area where the illumination light is incident from the upper edge at an angle of not more than the critical angle with respect to the slope.

As a result, in this embodiment, the light scattering region 32 is formed so that the boundary with the specular reflection region is inconspicuous, and this unevenness effectively avoids the brightness unevenness that is recognized from the emission surface. Has been done.

According to the structure shown in FIG. 9, in addition to the structure of the second embodiment, the light scattering region 32 is formed in the reflection sheet 31, so that the unevenness in brightness is further reduced and the emission light is emitted. The quality can be improved.

(4) Fourth Embodiment FIG. 11 is a sectional view showing a sidelight type surface light source device according to the fourth embodiment. In the sidelight type surface light source device 40, the same components as those of the sidelight type surface light source devices according to the first to third embodiments are designated by the same reference numerals, and the duplicated description will be omitted.

In this sidelight type surface light source device 40, the reflector 41 is made of an elastic film formed by vapor-depositing silver having a high reflectance, and is a prism sheet protruding toward the light source side from the incident surface T of the light scattering guide 15. The exit surface side end portion is adhered to and held by the prism surface of 13 with a double-sided tape 42. Further, the reflector 41 is the frame 1
It is bent along the inner side surface of 2 so as to draw a curved surface and is held by the frame 12, and the end on the slope side outside the reflection sheet 31 is sandwiched between the frame 12 and the reflection sheet 31.

As a result, the reflector 41 is held so that the end portion on the emission surface side abuts on the upper edge E of the light scattering guide 15, and shields the upper edge E. Thereby, the side light type surface light source device 40
Then, the upper edge E is shielded by the prism sheet 13 protruding from the incident surface side and the reflector 18, and even if the position of the prism sheet 13 or the like is displaced due to variations in assembly, variations in maintenance work, etc. Is surely prevented. For the lower edge E, the bright line is drawn in the frame 12
It is designed to be covered by.

On the other hand, the frame 12 is
The light-shielding surface 43 is provided in a portion overlapping with the light-scattering light guide 15.
Are formed. Here, the light-shielding surface 43 is formed by selectively attaching gray ink,
The illumination light emitted from the prism sheet 13 toward the frame 12 is blocked, and the illumination light is scattered by the light guide member 15.
It is arranged to effectively avoid the uneven brightness caused by irregular reflection on the side.

That is, the frame 12 of this type is formed by injection-molding a resin material, and diffuses incident light in order to effectively use the illumination light. As a result, the prism sheet 1 is provided at the exit surface side and the portion where the light scattering guide 15 and the frame 12 overlap each other.
Illuminated by the illumination light that has passed through 3 and is not processed at all, the illumination light diffusely reflected by the frame 12 returns to the inside of the light scattering guide 15 via the prism sheet 13 and is observed as uneven brightness. It will be.

Of the illumination light diffusely reflected by the frame 12, there are components reflected by the prism surface of the prism sheet 13 and the emission surface of the light scattering guide 15, and these components are also observed as uneven brightness. Will be. As a result, in this embodiment, the illumination light emitted from the prism sheet 13 toward the frame 12 is blocked by the light-shielding surface 43, and the illumination light is diffusely reflected toward the light-scattering light guide 15 side to generate luminance. It is designed to effectively avoid unevenness. Further, at this time, the light-shielding process is executed by using the gray ink to make the image of the light-shielding surface 43 observed from the emission surface through the inclined surface inconspicuous and effectively avoid the uneven brightness due to the light-shielding surface 43. To do.

According to the configuration shown in FIG. 11, the prism sheet 13 protruding from the incident surface side and the reflector 18 shield the upper edge E from light, so that the bright line may be generated due to variations in assembly, variations in maintenance work, and the like. It is possible to prevent the occurrence of unevenness, and thus it is possible to reliably avoid uneven brightness.

(5) Fifth Embodiment FIG. 12 is a sectional view showing a sidelight type surface light source device according to the fifth embodiment. The sidelight type surface light source device 50 is the same as the sidelight type surface light source device 40 according to the above-described fourth embodiment, except that the light scattering guide 15 is provided.
Instead, a light scattering guide 21 in which the upper and lower edges E on the incident surface side are shielded by the ink 22 is applied.

According to the structure shown in FIG. 12, the prism sheet 13 protruding from the incident surface shields the edge E of the light scattering guide 21, and at the same time, the ink 22 is attached.
Further, by abutting the reflector 41 to shield the edge E, it is possible to prevent the uneven brightness more reliably in addition to the third and fourth embodiments.

(6) Other Embodiments In the above-described embodiments, when the prism sheet is projected to shield the edges, and in addition to this, the ink adhered to the edges and the edges are shielded by the reflector, The invention is not limited to this, and may be combined with, for example, a case where a dedicated light shielding member is arranged to shield the edge.

Further, in the above-mentioned embodiment, the case where the prism sheet having the prism surface formed on one surface is applied as the light control member has been described, but the present invention is not limited to this.
The present invention can also be widely applied to a prism sheet having prism surfaces formed on both sides.

Further, in the above-mentioned embodiment, the case where the incident surface of the illumination light is formed into a rough surface by the matte surface treatment has been described, but the present invention is not limited to this, and the blasting treatment with sandpaper and the chemical etching treatment are performed. 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-mentioned embodiment, the case where the light-scattering light guide body composed of the light guide plate is formed in a wedge-shaped cross section has been described. However, the present invention is not limited to this, and a flat plate shape is subjected to a predetermined treatment. Accordingly, the present invention can be widely applied to a sidelight type surface light source device using a light guide plate having a directional emission property, including those configured to have a directional emission property.

Further, in the above-mentioned embodiments, 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 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 side light type surface light source device in which the light-scattering light guide is applied to the light guide plate has been described, but the present invention is not limited to this, and the directional emission is possible. The present invention can be widely applied to various sidelight type surface light source devices using a light guide plate having a property.

Further, in the above-mentioned embodiments, the case where the present invention is applied to the surface light source device of the liquid crystal display device has been described, but the present invention is not limited to this, and is a side light type such as various lighting devices and display devices. It can be widely applied to surface light source devices.

[0079]

As described above, according to the present invention, in the sidelight type surface light source device having the directional emission property, the light control member is arranged such that the tip of the plate member protrudes from the light source side end face of the plate member. It is possible to effectively avoid the generation of the bright line due to the edge of the end face of the plate-shaped member, and thus it is possible to effectively avoid the uneven brightness due to the bright line.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a sidelight type surface light source device according to a first embodiment of the present invention.

FIG. 2 is a characteristic curve diagram for explaining the operation of the sidelight type surface light source device of FIG.

FIG. 3 is a cross-sectional view for explaining processing of an edge of a light scattering guide in the sidelight type surface light source device of FIG.

FIG. 4 is a cross-sectional view for explaining a state in which the prism sheet 13 largely protrudes corresponding to FIG.

FIG. 5 is a characteristic curve diagram showing a brightness level when the position of the prism sheet 13 is changed.

FIG. 6 is a characteristic curve diagram corresponding to FIG. 5 and showing the degree of luminance unevenness using the protrusion amount as a parameter.

FIG. 7 is a cross-sectional view showing a sidelight type surface light source device according to a second embodiment of the invention.

FIG. 8 is a cross-sectional view for explaining the light-shielding surface of FIG.

FIG. 9 is a cross-sectional view showing a sidelight type surface light source device according to a third embodiment of the present invention.

10 is a plan view showing a reflection sheet in the sidelight type surface light source device of FIG.

FIG. 11 is a sectional view showing a sidelight type surface light source device according to a fourth embodiment of the present invention.

FIG. 12 is a sectional view showing a sidelight type surface light source device according to a fifth embodiment of the present invention.

FIG. 13 is an exploded perspective view showing a conventional side light type surface light source device.

FIG. 14 is a side view of the side light type surface light source device of FIG.
It is sectional drawing shown by taking a cross section.

[Explanation of symbols]

1, 10, 20, 30, 40, 50 Side light type surface light source device 2, 15, 21 Light scattering light guide 4, 14 Reflective sheet 5, 13 Prism sheet 6 Fluorescent lamp 7, 18, 23, 41 Reflector 19 Ink E Edge T Incident surface

Continuation of the front page (56) Reference JP-A-8-122778 (JP, A) JP-A-5-281541 (JP, A) Actually open 63-185123 (JP, U) Actually open 6-37805 (JP , U) Actual Kaihei 5-83729 (JP, U) Actual Kaihei 4-42688 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 6/00 F21V 8/00 G02F 1/1335-1/13363 G09F 9/00 G09F 13/18

Claims (3)

(57) [Claims] 1. Illumination light is incident from an end surface of a plate-shaped member, the illumination light is bent and emitted from an emission surface of the plate-shaped member, and the illumination is performed by a sheet-shaped light control member arranged on the emission surface. In a sidelight type surface light source device that corrects the directivity of light, the light control member is arranged so that the tip projects toward the light source side from the end face, and the plate member and the light control member are arranged by a reflector. A sidelight type surface light source device, characterized in that a light-shielding member is sandwiched and disposed on an end surface of the light control member on the light source side. 2. The light shielding member is made of ink attached to the end portion on the light source side .
The side light type surface light source device according to claim 1. 3. The plate-shaped member adheres ink to the edge of the end face,
Ri claim 1 or, characterized in that the shielding said edge
The sidelight type surface light source device according to claim 2 .