JP2000030520A - Light guide plate and surface light source device - Google Patents

Abstract

(57) [Problem] To provide a surface light source device in which a concave light incident portion is formed on a light incident surface of a light guide plate, and to reduce the influence of positional deviation of a point light source with respect to the light incident portion. SOLUTION: A concave light incident portion 24 is formed on a side surface of a light guide plate 22 opposite to a point light source 25, and fine light extending in a direction perpendicular to the light exit surface 23 is formed in the light incident portion 24 and regions on both sides thereof. The vertical stripes 30 are formed, and the light introduced into the light guide plate 22 is diffused by the vertical stripes 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a light guide plate and a surface light source device. More specifically, the present invention relates to a surface light source device used as a backlight of a liquid crystal display panel and a light guide plate used for the surface light source device.

[0002]

2. Description of the Related Art (Surface light source device using a plurality of point light sources) A conventional surface light source device 1 is shown in an exploded perspective view of FIG. 1 and a sectional view of FIG. The surface light source device 1 includes a light guide plate 2 for confining light, a light emitting unit 3 and a reflection plate 4.
The light guide plate 2 is formed of a transparent resin having a high refractive index such as a polycarbonate resin or a methacryl resin, and a diffusion pattern 5 is formed on the lower surface of the light guide plate 2 by uneven processing, dot printing of diffuse reflection ink, or the like. . Light emitting unit 3
Is a light guide plate 2 on which a so-called point light source 7 such as a plurality of light emitting diodes (LEDs) is mounted on a circuit board 6.
. The reflection plate 4 is formed of, for example, a white resin sheet having a high reflectance, and has both sides adhered to the lower surface of the light guide plate 2 by a double-sided tape 9.

[0003] As shown in FIG. 2, the light f emitted from the light emitting section 3 and guided from the side surface 8 into the light guide plate 2.
Are confined inside the light guide plate 2 by total internal reflection inside the light guide plate 2. When the light f inside the light guide plate 2 is incident on the diffusion pattern 5, the light f is diffusely reflected, and the light f reflected at an angle smaller than the critical angle of total reflection toward the light emission surface 10 is extracted to the outside from the light emission surface 10. . Further, the light f transmitted through a portion of the lower surface of the light guide plate 2 where the diffusion pattern 5 does not exist.
Is reflected by the reflection plate 4 and returns to the inside of the light guide plate 2 again, so that loss of light quantity from the lower surface of the light guide plate 2 is prevented.

On the other hand, light emitted from the point light source 7 and incident on the light guide plate 2 is reflected by the diffusion pattern 5 on the lower surface of the light guide plate 2 and spreads inside the light guide plate 2 as shown in FIG. Light is emitted from the entire light emitting surface 10.

The above-described surface light source device 1 using a plurality of point light sources is configured such that the point light source 7 is simulated to be a linear light source in order to reduce power consumption. That is, a linear light source such as a cold cathode ray tube is imitated by arranging the point light sources 7 in a line. Therefore, in order to achieve lower power consumption, it is desired to reduce the number of point light sources, and to obtain a surface light source device which is preferably high in brightness and less in luminance variation by one point light source.

(Surface light source device using one point light source) Therefore, as shown in FIG. 4, a point light source comprising one light emitting diode or a plurality of localized light emitting diodes on the side surface 8 of the light guide plate 2. A surface light source device 11 in which a light source 7 is disposed has been proposed.
In the surface light source device 11, the light f from the point light source 7 is linearly controlled by providing concentrically arranged diffusion patterns 5 on the lower surface of the light guide plate 2. Further, by increasing the pattern density of the diffusion pattern 5 as the distance from the point light source 7 increases, light is emitted almost uniformly from the entire light exit surface 10.

Therefore, according to such a surface light source device 11, a device having higher efficiency and higher uniformity of luminance distribution than the surface light source device 1 having the structure as shown in FIG. 1 can be obtained.

[0008]

However, if the side surface 8 located on the light incident side of the light guide plate 2 is a flat surface, the light having a small incident angle out of the light emitted from the point light source 7 and incident on the side surface 8 is as follows. As shown by the ray f1 in FIG.
Further, the light entering the light guide plate 2 from the side surface 8 is also refracted so as to gather in a direction perpendicular to the side surface 8 as a light ray f2 shown in FIG.

As a result, in the surface light source device 11 having the structure shown in FIG. 4, light hardly reaches the corners of the light guide plate 2, and the corners of the light guide plate become dark as shown in FIG. (The shaded area is the dark area 12). FIG.
It shows a luminance distribution along the line 1-A2,
, A nonuniform brightness distribution occurs.

Similarly, in the surface light source device 1 having the structure as shown in FIG. 1, since the light emitted from the point light source 7 and incident on the light guide plate 2 does not spread sufficiently, the corners of the light guide plate 2 and the point Light hardly reaches the portion corresponding to between the light sources 7, and a dark portion 12 is generated as shown in FIG. 8 (a shaded region is the dark portion 12). FIG. 9 shows the luminance distribution along the line B1-B2 in FIG. 8. In the vicinity of the side surface 8, dark portions and light portions are alternately distributed, and the luminance distribution is non-uniform.

In view of this, there is a surface light source device 11 or 1 shown in FIG. 10 or 11 in which a concave light incident portion 13 is provided in the light guide plate 2 so as to face the point light source 7. When the concave light incident portion 13 is provided on the light guide plate 2 so as to face the point light source 7 as described above, light totally reflected by the side surface 8 of the light guide plate 2 if there is no light incident portion 13 as shown in FIG. Can also be taken into the light guide plate 2 from the light incident portion 13, and the light f <b> 3 incident from the side surface of the light incident portion 13 is refracted toward the corner of the light guide plate 2. Light can be prevented from being darkened by sending light. As a result, the luminance distribution can be made uniform near the point light source 7 as in the luminance distribution shown in FIG.

Here, when necessary light in the light guide plate is considered, the required light amount differs depending on the direction around the point light source. For example, as shown in FIG. 14, since the distance to the edge of the light guide plate is greatest in the diagonal direction, it is necessary to distribute the largest amount of light in this direction. On the other hand, the amount of light distributed in the direction parallel to the side surface 8 where the light incident portion 13 is provided may be small. More specifically, the luminance of the light exit surface 10 is as follows: luminance = k × (diffusion density of diffusion pattern) × (light quantity) However, since k is represented by a proportional constant, the luminance is uniform over the entire light exit surface 10. Thus, the pattern density of the diffusion pattern and the distribution of the amount of light are determined. Therefore, an ideal light amount distribution when the direction perpendicular to the side surface 8 where the light incident portion 13 is provided is 0 ° is shown in FIG. However, since there is actually a loss of light, a slightly larger amount of light is transmitted in each direction.

However, if the position of the point light source 7 with respect to the light incident portion shifts from the design position shown by the broken line in FIG. 16 to the position shown by the solid line due to an error in assembling the surface light source device or the light emitting section, this positional shift occurs. 16 and 17 for
The light ray f4 shown by the broken line in FIG. 16 disappears, and the light ray f5 shown by the solid line in FIGS. 16 and 17 is newly generated. Then, in the direction of the newly generated light beam f5, the light amount increases and the brightness increases, and in the direction of the disappeared light beam f4, the light amount is unexpectedly measured and the brightness decreases.
The luminance distribution along the line D2) is as shown in FIG.
The displacement of the point light source 7 causes non-uniformity of the brightness distribution, and the light guide plate 2 has uneven brightness distribution.

Here, the case where one point light source is used has been described as an example, but a similar problem occurs when a plurality of point light sources are used as in the surface light source device of FIG. However, in the surface light source device having one point light source, the light travels straight in the light guide plate in a plan view, so that the influence of the positional shift of the point light source is greater than in the case where there are a plurality of point light sources.

The present invention has been made to solve the above-mentioned technical problems, and an object of the present invention is to provide a surface light source device having a light incident portion formed on a light incident surface of a light guide plate. It is an object of the present invention to reduce the influence of a position shift of a point light source with respect to an incident portion.

[0016]

According to a first aspect of the present invention, there is provided a light guide plate, wherein a plurality of small holes or grooves connected to the outside are formed in a light guide plate which spreads light introduced from a light incident portion inside and emits the light in a planar manner from a light exit surface. It is provided near the light incident portion, and diffuses and reflects the introduced light inward at a boundary with the small hole or groove.

In the light guide plate according to the present invention, the small holes or grooves for diffusing and reflecting the light introduced from the light incident portion are provided near the light incident portion of the light guide plate. Light introduced into the light plate is diffusely reflected by the small holes or grooves. As a result, even if the direction of the light beam incident on the light incident portion changes, the change in the luminance distribution due to the change in the light direction is made uniform, and the occurrence of luminance unevenness is suppressed. Therefore, even if the direction of the light beam introduced into the light guide plate is different from the design value, the brightness distribution can be kept uniform.

According to a second aspect of the present invention, in the light guide plate according to the first aspect, the surface of the substantially rectangular parallelepiped transparent flat plate having a large area is a light emitting surface, and a light incident portion is provided on a surface of a small area. Drilling the small hole that does not reach the light emitting surface from the surface opposite to the light emitting surface, and fixing the reflector to almost the entire surface opposite to the light emitting surface so as to close the small hole. It is characterized by that.

The second embodiment is a case where a small hole is provided in the light guide plate. Since there is a gap between the tip of the small hole and the light emitting surface, light passes through the gap and small light is emitted. The light coming from the opening end of the small hole can reach the rear of the small hole because the light coming out of the opening end of the small hole is reflected by the reflecting plate because the reflecting plate faces the opening end of the small hole. . Therefore, even if a small hole is provided in the light guide plate, it is possible to prevent a shadow behind the small hole.

According to a third aspect of the present invention, there is provided a surface light source device comprising: a light source;
In a surface light source device having a light guide plate that spreads light introduced from a light incident portion facing the light source inside and emits the light in a planar manner from a light emission surface, a plurality of small holes or grooves connected to the outside are formed in the light guide plate. It is provided near the light incident portion, and diffuses and reflects light introduced into the light guide plate toward the inside of the light guide plate at a boundary with the small hole or groove.

In the surface light source device according to the third aspect, since small holes or grooves for diffusing and reflecting the light introduced from the light incident portion are provided near the light incident portion of the light guide plate, Light introduced into the light guide plate is diffusely reflected by the small holes or grooves. As a result, even if the position of the light source is shifted with respect to the light incident portion, the change in the luminance distribution due to the position shift of the light source is made uniform, and the occurrence of luminance unevenness is suppressed. Therefore, even if the position of the light source deviates from the design position, the luminance distribution can be kept uniform.

According to a fourth aspect of the present invention, there is provided a surface light source device comprising: a light source;
A light guide plate that spreads light introduced from a light incident portion facing the light source inside and emits the light in a planar manner from a light exit surface, wherein the light incident portion is formed by forming irregularities on the surface of the light source. And diffusing light is introduced into the light guide plate.

In the surface light source device according to the fourth aspect, since the surface of the light source is provided with irregularities, light introduced into the light guide plate is diffused when emitted from the light source. As a result, even if the position of the light source is shifted with respect to the light incident portion, the change in the luminance distribution due to the position shift of the light source is made uniform, and the occurrence of luminance unevenness is suppressed. Therefore, even if the position of the light source deviates from the design position, the luminance distribution can be kept uniform.

According to a fifth aspect of the present invention, there is provided a surface light source device comprising: a light source;
A light guide plate that spreads light introduced from a light incident portion facing the light source inside and emits the light in a planar manner from a light exit surface, wherein the light incident surface of the light guide plate is substantially A plurality of streaks extending in a vertical direction are provided, and light introduced from the light incident portion of the light guide plate is diffused by the streaks. Here, the streak is a fine streak-like unevenness, and the groove referred to in this specification includes a streak.

In the surface light source device according to the fifth aspect, since the streak for diffusing the light introduced from the light incident portion is provided in the light incident portion, the light introduced into the light guide plate from the light incident portion is provided. Is spread by the streaks. As a result, even if the position of the light source is shifted with respect to the light incident portion, the change in the luminance distribution due to the position shift of the light source is made uniform, and the occurrence of luminance unevenness is suppressed. Therefore, even if the position of the light source deviates from the design position, the luminance distribution can be kept uniform.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 19 is an exploded perspective view showing the structure of a surface light source device 21 according to one embodiment of the present invention. The light guide plate 22 is formed of a transparent resin material having a large refractive index, and an upper surface of the light guide plate 22 is a light emission surface 23. On the lower surface of the light guide plate 22, the diffusion pattern 3
3 are formed. This diffusion pattern 33 is a point light source 25 that is arranged to face the light incident portion 24 of the light guide plate 22.
And the pattern density of the diffusion pattern 33 gradually increases as the distance from the point light source 25 increases (see FIGS. 24 and 4). On the lower surface of the light guide plate 22, a reflection plate 26 made of a material having a high surface reflectance such as a white plastic sheet is adhered by a double-sided tape or the like.

At a position facing the point light source 25 on the side surface of the light guide plate 22, a light incident portion 24 slightly larger than the point light source 25 is provided. As shown in FIG. 20, fine vertical streaks (streaks) 30 extending in a direction perpendicular to the light emitting surface 23 are uniformly formed on the inner surface of the light incident portion 24 and the regions on both sides thereof. The vertical stripes 30 are provided in a molding die for molding the light guide plate 22, and the vertical stripes 30 of the molding die are transferred to the light guide plate 22 when the light guide plate 22 is molded. I just need. Alternatively, a transparent ultraviolet curable resin (UV resin) is applied to the light incident portion 24 of the molded light guide plate 22 and regions on both sides thereof, and the longitudinal grooves are transferred to the ultraviolet curable resin by a stamper and cured by irradiating ultraviolet rays. (PhotoPolymerization method).

The light emitting section 27 is provided with a point light source 25 (a light source smaller than the light guide plate 22) such as a light emitting diode or a miniature light bulb on a mounting member 28 made of a material having a high surface reflectance such as white resin.
Is attached. In addition, above and below the point light source 25, the cover portion 2 extends from the upper and lower edges of the mounting member 28.
9 has been extended. The cover portion 29 fits into the light incident portion 24 recessed in the light guide plate 22 to prevent light from leaking upward and downward from the gap between the point light source 25 and the light guide plate 22. .

As described above, when the vertical stripes 30 are provided in the light incident portion 24 and the region on both sides thereof facing the point light source 25,
Light f entering the light guide plate 22 from the light incident portion 24 or the periphery thereof is directed by the light incident portion 24 in a direction toward a corner of the light guide plate 22, and furthermore, as shown in FIG. The light is diffused in a plane parallel to the light exit surface 23. Further, the vertical streaks 30 provided on both sides of the light incident portion 24 are provided.
Is the light guide plate 2 without totally reflecting the light of the point light source 25.
2 lead inside. Therefore, according to the surface light source device 21 using such a light guide plate 22, the light use efficiency can be increased and the luminance distribution on the light exit surface 23 can be made uniform. It can prevent darkening.

FIG. 21 shows a state where the point light source 25 is shifted from the design position. The design position of the point light source 25 is indicated by a broken line, and the position of the point light source 25 shifted by an error or the like is indicated by a solid line. Further, light f6 generated by the point light source 25 being displaced is indicated by a solid line, and light f7 disappearing by the position shift is indicated by a broken line. This surface light source device 2
In FIG. 1, since the vertical streak 30 is provided in the light incident portion 24 and the vicinity thereof, the light f6 generated by the displacement of the point light source 25 is f6.
The light f7 that disappears or disappears is diffused by passing through the vertical streak 30, and compared to the case without the vertical streak 30 in FIG.
Proceed with expanse as shown in. Therefore, the point light source 2
5 are dispersed and averaged, and the light exit surface 2
The luminance distribution along the width direction 3 is shown in FIG.
(The dashed curve 32 in FIG. 23 indicates the luminance distribution when there is no vertical streak 30), and the luminance unevenness becomes inconspicuous.

On the other hand, in the cross section of the light guide plate perpendicular to the side surface provided with the light incident portion 24, the light f incident on the light guide plate 22 is not diffused by the vertical streaks 30 as shown in FIG. It is possible to prevent a large amount of light from leaking from the vicinity of the incident part 24 to cause a light loss or a local bright spot.

In the above embodiment, the case where one point light source 25 is used has been described. However, in this embodiment, as shown in FIG. 25, even when a light emitting section 27 having a plurality of point light sources 25 is used. Can be applied. Like this surface light source device 34, even if the light incident portion 24 provided on the light guide plate 22 facing the point light sources 25 and the vertical streaks 30 are provided in the regions on both sides thereof, the light use efficiency is increased and the luminance is improved. Nonuniformity of distribution can be reduced, and even if the position of the point light source 25 is shifted, luminance unevenness is less likely to occur.

(Second Embodiment) FIG. 26 is a partially broken plan view showing, in an enlarged manner, the vicinity of a light incident portion 24 of a light guide plate 22 according to another embodiment of the present invention. In this embodiment, the plane portions 35 are provided between the vertical stripes 30 by intermittently forming the vertical stripes 30 in the light incident portion 24 and the regions on both sides thereof. In the embodiment shown in FIG. 27, in the light incident portion 24 of the light guide plate 22 and the region on both sides thereof, a plurality of the vertical stripes 30 are continuously formed, and the plane portions 35 are provided between the aggregated vertical stripes 30. .

According to these embodiments, the light passing through the vertical stripes 30 diffuses, while the light passing through the plane portion 35 between the vertical stripes 30 does not spread. By changing the ratio of the plane portion 35 between the 30, it is possible to adjust the amount of diffusion of the light incident into the light guide plate 22.

(Third Embodiment) FIG. 28 is an exploded perspective view showing a structure of a surface light source device 41 according to still another embodiment of the present invention, and FIG. 29 is a structure of the light guide plate 22 in the vicinity of the light incident portion 24. FIG. 3 is an enlarged perspective view showing a partly broken view. In the surface light source device 41, a plurality of small holes 4 are formed around the light incident portion 24 of the light guide plate 22 so as to surround the light incident portion 24.
2 is provided. Each of the small holes 42 has a columnar shape, is provided perpendicular to the light exit surface 23, and penetrates the light exit surface 23 and the surface 43 on the opposite side. However, as shown in FIG. 30, each small hole 42 is a non-effective area outside the area of the diffusion pattern 33 of the light guide plate 22 (for example, an area facing a non-display surface when used as a backlight of a liquid crystal display panel). ) Is desirable.

As described above, the small hole 42 is formed around the light incident portion 24.
Is provided, the light f incident on the light guide plate 22 from the light incident portion 24 is refracted or totally reflected at the interface between the small hole 42 and the space inside the small hole 42, and as shown in FIG. The hit light f is diffused in the small holes 42. As a result, the same effect as that of the vertical stripe 30 in the first embodiment can be provided by the small holes 42. That is, the light f incident on the light guide plate 22 from the light incident portion 24 is diffused by the small holes 42, so that the light reaches the corners of the light guide plate 22, and the corners of the light guide plate 22 are darkened. Can be prevented. In addition, since the small holes 42 are oriented in a direction perpendicular to the light exit surface 23, the light f hitting the small holes 42 is not diffused in the vertical direction, and is locally bright near the small holes 42. No parts are generated. Further, by diffusing the light f incident from the light incident part 24 through the small holes 42, it is possible to prevent the occurrence of luminance unevenness due to the influence of the displacement of the point light source 25 with respect to the light incident part 24.

If the cross-sectional shape of the small hole 42 is made longer in the direction in which the light from the point light source 25 comes and becomes shorter in the direction orthogonal thereto, the light diffusion effect of the small hole 42 can be increased. . For example, as shown in FIG. 31, the cross-sectional shape of the small hole 42 may be an ellipse, and the major axis direction of the ellipse may be parallel to the direction in which the light f from the point light source 25 comes. In this way, the entrance of light into the small hole 42 can be suppressed, the angle of the side surface of the small hole 42 with respect to the light coming from the point light source 25 increases, and the probability that the light is reflected by the small hole 42 is increased. Will be higher. Therefore, the diffusion effect of the small holes 42 can be enhanced.

Further, as shown in FIG.
Is formed in a wedge shape, and the tip of the wedge shape is directed in the direction of light f coming from the point light source 25.
It is possible to suppress the entry of light into the inside, increase the reflectance by the small holes 42, and further enhance the diffusion effect by the small holes 42.

In this embodiment, one point light source 2
5 has been described, but in this embodiment, FIG.
As shown in (1), the present invention can also be applied to a surface light source device 44 using a light emitting unit 27 provided with a plurality of point light sources 25.

(Fourth Embodiment) FIGS. 34 and 35 are enlarged sectional views showing the structure of a small hole 42 according to still another embodiment of the present invention, in which the light guide plate 22 is partially cut away. In this embodiment, the plurality of small holes 42 provided around the light incident portion 24 of the light guide plate 22 are all open at the surface 43 opposite to the light exit surface 23. Has not reached.

In the small hole 42 penetrating up and down as described in the third embodiment, a shadow may be formed behind the small hole 42 (on the side opposite to the point light source 25) to become a dark portion. As shown in FIG. 34, when the small hole 42 does not reach the light exit surface 23 and there is a gap between the upper end of the small hole 42 and the light exit surface 23, the light enters the light guide plate 22 as shown in FIG. The light f reaches behind the small hole 42 through this gap. Further, a small hole 42
Is open at the surface 43 opposite to the light exit surface 23,
As shown in FIG. 35, the light f
Is reflected by the reflection plate 26 fixed to the lower surface of the light guide plate 22 and returns to the inside of the light guide plate 22 behind the small hole 42. Therefore, according to this embodiment, it is possible to prevent the shadow behind the small hole 42 from becoming dark.

In this embodiment, the amount of light diffusion can also be adjusted by adjusting the height of the small holes 42 and the interval between the small holes 42.

However, if the cross-sectional shape of the small hole 42 is substantially the same from top to bottom, even if the small hole 42 is opened on the surface opposite to the light exit surface 23, as shown in FIG. The light f leaks slightly from the upper surface of the small hole 42 and escapes to the light emitting surface 23 by being refracted at the interface of the small hole 42 or reflected by the reflection plate 26 at the lower surface opening of the small hole 42. In order to prevent this, as shown in FIG. 37, the cross section of the small hole 42 is made smaller as approaching the light exit surface 23,
For example, if the small hole 42 is formed in a conical shape and the upper surface of the small hole 42 is eliminated, all the light f passing through the small hole 42 can be confined in the light guide plate 22, and the light f is emitted from the light exit surface above the small hole 42. 2
3 can be prevented from causing luminance unevenness.

(Fifth Embodiment) FIG. 38 is an exploded perspective view of a surface light source device 51 according to still another embodiment of the present invention. In the surface light source device 51, a plurality of grooves 52 are formed on the upper surface, the lower surface, or both upper and lower surfaces of the light guide plate 22 around the light incident portion 24. As shown in FIG. 39, the grooves 52 are formed in a substantially radial shape so that their respective longitudinal directions are parallel to the direction of the light f coming from the light source in plan view. Further, as shown in FIG. 40, each groove 52 is formed in a semi-cylindrical shape. Thus, when the light f emitted from the point light source 25 enters the light guide plate 22 from the light incident portion 24 and hits the groove 52, the light f is diffused and reflected in various directions by being reflected by the groove 52. As a result, the light f is transmitted to the light guide plate 2.
2 can be uniformly dispersed, and the luminance unevenness of the surface light source device 51 can be reduced. In particular, even if the point light source 25 is misaligned with respect to the light incident part 24 due to an error, luminance unevenness hardly occurs. The grooves 52 are parallel to the direction in which the light travels, and each light f is diffused only in a direction perpendicular to the traveling direction, so that the diffusion pattern can be easily designed. Further, by adjusting the size, depth, length, density, and the like of the groove 52, the degree of light diffusion by the groove 52 can be adjusted. The grooves 52 may be fine linear irregularities as shown as vertical stripes.

This embodiment can also be applied to a surface light source device 53 provided with a plurality of point light sources 25 and a plurality of light incident portions 24, as shown in FIG.

(Sixth Embodiment) FIG. 42 is an exploded perspective view showing a part of a surface light source device 61 according to still another embodiment of the present invention. In the surface light source device 51, irregularities are formed on the surface of the point light source 25. That is, as shown in FIG. 43, the point light source 25 is formed by molding a light emitting chip 63 such as an LED chip with a transparent molding resin 64, and the surface of the molding resin 64 has
A diffusion pattern 62 is formed. As the diffusion pattern 62, in the illustrated example, the concave and convex stripes 62 extending in a direction perpendicular to the cover portion 29 are shown. However, the diffusion pattern 62 does not need to be linear, and it is sufficient that light can be simply diffused. Since the cover portions 29 are provided above and below the point light source 25, the light does not leak upward or downward to cause a loss, and therefore, the diffusion pattern 62 may have a satin finish.

FIG. 43 shows a state where the light emitting chip 63 is shifted from the designed position. The design position of the light emitting chip 63 is indicated by a broken line, and the point light source 20 which is shifted due to an error or the like.
Is indicated by a solid line. Further, light f6 generated by the point light source 25 being displaced is indicated by a solid line, and light f7 disappearing by the position shift is indicated by a broken line. In the surface light source device 61, since the point light source 25 is provided with the diffusion pattern 62, the light f6 generated by the displacement of the light emitting chip 63 and the light f7 that disappears are diffused by passing through the diffusion pattern 62, and the light is incident. The light enters the unit 24. For this reason, the influence of the displacement of the light emitting chip 63 is dispersed and averaged, so that the uneven brightness is not noticeable.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a conventional surface light source device.

FIG. 2 is a sectional view showing a behavior of light in the light guide plate of the above.

FIG. 3 is a plan view showing the behavior of light in the light guide plate of the above.

FIG. 4 is a plan view showing another conventional surface light source device.

FIG. 5 is a diagram showing a behavior of light in a light incident part.

FIG. 6 is a diagram showing a dark part of the surface light source device of the above.

FIG. 7 is a diagram showing a luminance distribution of the above light guide plate along the line A1-A2.

FIG. 8 is a diagram showing a dark portion of still another conventional surface light source device provided with a plurality of point light sources.

FIG. 9 is a diagram showing a luminance distribution of the above surface light source device along a line B1-B2.

FIG. 10 is a diagram showing still another conventional surface light source device.

FIG. 11 is a diagram showing still another conventional surface light source device.

FIG. 12 is an enlarged plan view of a light incident portion of the surface light source device of FIG. 10 or FIG.

13 is a diagram showing a luminance distribution of the surface light source device of FIG. 10 along line C1-C2.

FIG. 14 is a diagram illustrating a method of distributing light in a light guide plate provided with a concave light incident portion.

FIG. 15 is a diagram showing the relationship between the direction of light and the amount of light.

FIG. 16 is a diagram showing a change in behavior of a light beam when the position of a point light source is shifted.

FIG. 17 is a diagram illustrating a change in behavior of a light beam when the position of a point light source is shifted.

18 is a diagram showing a luminance distribution along a line D1-D2 in FIG.

FIG. 19 is an exploded perspective view showing a surface light source device according to an embodiment of the present invention.

FIG. 20 is an enlarged perspective view showing a vertical streak provided in the light incident portion.

FIG. 21 is a diagram showing a change in the behavior of light when the position of the point light source is shifted in the surface light source device of the above.

FIG. 22 is a diagram showing a change in behavior of light when the position of the point light source is shifted in the surface light source device of the above.

FIG. 23 is a diagram showing a luminance distribution along the width direction of the surface light source device of the above.

FIG. 24 is a cross-sectional view showing a behavior of light in the light guide plate.

FIG. 25 is an exploded perspective view showing a surface light source device according to another embodiment of the present invention.

FIG. 26 is a partially broken plan view showing a vertical streak provided on a light incident portion and a plane portion in still another embodiment of the present invention.

FIG. 27 is a partially broken plan view showing a vertical streak and a plane portion provided in a light incident portion in still another embodiment of the present invention.

FIG. 28 is an exploded perspective view showing a surface light source device according to still another embodiment of the present invention.

FIG. 29 is an enlarged perspective view showing a small hole provided in the vicinity of a light incident part.

FIG. 30 is a plan view of a light guide plate in the embodiment.

FIG. 31 is a partially broken plan view showing a small hole of another shape provided in the vicinity of a light incident portion in still another embodiment of the present invention.

FIG. 32 is a partially cutaway plan view showing a small hole of another shape provided in the vicinity of a light incident portion in still another embodiment of the present invention.

FIG. 33 is an exploded perspective view showing a surface light source device according to still another embodiment of the present invention.

FIG. 34 is a cross-sectional view showing the shape of a small hole in still another embodiment of the present invention.

FIG. 35 is an operation explanatory view of the embodiment.

FIG. 36 is a view for explaining a problem of the small hole in the above.

FIG. 37 is a cross-sectional view showing the shape of a small hole in still another embodiment of the present invention.

FIG. 38 is an exploded perspective view showing a surface light source device according to still another embodiment of the present invention.

FIG. 39 is an enlarged plan view showing a groove provided near a light incident portion.

FIG. 40 is an enlarged perspective view showing a groove provided near a light incident portion.

FIG. 41 is an exploded perspective view showing a surface light source device according to still another embodiment of the present invention.

FIG. 42 is an exploded perspective view showing a surface light source device according to still another embodiment of the present invention, with a part cut away.

FIG. 43 is a diagram showing a change in light behavior when the position of the point light source is shifted in the surface light source device of the above.

[Explanation of symbols]

 Reference Signs List 22 light guide plate 23 light emitting surface 24 light incident part 25 point light source 26 reflector 27 light emitting part 30 vertical stripe 35 plane part 42 small hole 52 groove 62 diffusion pattern

Claims (5)

[Claims] 1. A light guide plate which spreads light introduced from a light incident portion inside and emits the light in a planar manner from a light exit surface, wherein a plurality of small holes or grooves connected to the outside are provided in the vicinity of the light incident portion. A light guide plate for diffusing the reflected light inward at a boundary with the small hole or groove. 2. A substantially rectangular parallelepiped transparent flat plate having a large area as a light exit surface, a light entrance portion being provided on a small surface, and not reaching the light exit surface from a surface opposite to the light exit surface. The light guide plate according to claim 1, wherein the small hole is formed, and a reflecting plate is fixed to substantially the entire surface opposite to the light emitting surface so as to close the small hole. 3. A surface light source device comprising: a light source; and a light guide plate that spreads light introduced from a light incident portion facing the light source and emits the light in a planar manner from a light exit surface. A surface provided with a hole or a groove near the light incident portion of the light guide plate, and diffusing and reflecting light introduced into the light guide plate toward the inside of the light guide plate at a boundary with the small hole or groove. Light source device. 4. A surface light source device comprising: a light source; and a light guide plate which internally spreads light introduced from a light incident portion facing the light source and emits the light in a planar manner from a light exit surface. Wherein the diffused light is introduced into the light guide plate from the light incident portion. 5. A surface light source device comprising: a light source; and a light guide plate which spreads light introduced from a light incident portion facing the light source and emits the light in a planar manner from a light exit surface, wherein the light of the light guide plate is provided. A surface light source device, wherein a plurality of streaks extending in a direction substantially perpendicular to a light exit surface are provided in an incident portion, and light introduced from the light incident portion of the light guide plate is diffused by the streaks.