JP2003297126A - Surface light source device, image display device and light guide body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique to reduce the number of parts, to efficiently take in the light from LED to a light guide plate and to uniformly illuminate a surface at high luminance. <P>SOLUTION: A light guide body 4 is installed to face one side surface of the light guide plate 2 and LED5 is installed on an end surface 10 of the light guide body 4. The light guide body 4 is provided with a reflecting surface 12 reflecting the light from LED5 to both sides facing the light guide plate 2. Furthermore, the light which is not reflected at the reflecting surface 12 but transmitted is emitted to one surface side among the light transmitted inside by the light guide body. An emitting side prism projection 13 emitting light which is reflected once by the reflecting surface 12 to one surface side of the light guide plate 2 is provided in the light guide body. On one surface side of the light guide plate 2, an incident side prism projection 16 is formed having the light from the LED5 emitted through the exiting side prism projection 13 of the light guide boy 4 made incident as light which is transmitted in the direction approximately orthogonal to one side surface. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a portable telephone,
Surface light source device used as a backlight for planarly illuminating a liquid crystal display panel (illuminated member) in a portable electronic terminal device, electronic notebook, car navigation device, digital camera, VTR device, etc. The present invention also relates to an image display device provided with the above, and also to a light guide plate used in these surface light source device and image display device.

[0002]

2. Description of the Related Art For example, portable telephones, portable electronic terminal devices, etc. have been reduced in size and weight for carrying.
The battery capacity used as a power source is also limited. Therefore, it is desired to reduce the power consumption of the surface light source device that illuminates the liquid crystal display panel (illuminated member) such as the mobile phone or the mobile electronic terminal device as much as possible.

Therefore, for example, Japanese Patent Laid-Open No. 2001-3522.
As disclosed in Japanese Patent Publication No. 5, a surface light source device using an LED (point light source) with low power consumption has been devised instead of a fluorescent lamp with high power consumption. This surface light source device 50
As shown in FIG. 13, an optical path conversion plate 53 is arranged so as to face the incident surface 52 of the light guide plate 51, and a rod-shaped light guide body 54 is arranged so as to face the optical path conversion plate 53. The light from the LED 55 arranged at the end of the light guide 54 is introduced into the inside of the light guide plate 51 from the incident surface 52 of the light guide plate 51 via the light guide 54 and the optical path conversion plate 53, and then LE
The light from D55 is emitted from the emission surface 56 of the light guide plate 51,
The emitted light illuminates an object to be illuminated such as a liquid crystal display panel in a planar manner.

[0004]

In such a surface light source device 50, a prism groove 58 is formed in a reflecting surface 57 (a surface opposite to a surface facing the optical path changing plate 53) of the light guide 54 to form an optical path. The prism array 6 is provided on the surface of the conversion plate 53 facing the light guide 54.
Although 0 is formed to control the traveling direction of the light from the LED 55, there is a problem that a light amount loss is likely to occur because there are many components interposed between the LED 55 and the light guide plate 51. Was there.

Further, as shown in FIG. 14, a surface light source device 61 in which an optical path changing plate is omitted has been developed, but a surface 64 in which light propagating in the light guide body 62 faces the light guide plate 63 of the light guide body 62. Is easily reflected by the LED 6 from the light guide 62 to the light guide plate 63.
It was difficult to take in the light of No. 5 evenly in the width direction of the light guide plate. As a result, the light stripe 66 extending in the direction orthogonal to the width direction of the light guide plate 63 is likely to be visually recognized as a difference in brightness from the exit surface 67 side of the light guide plate 63, and the illumination quality is degraded. Had.

Therefore, the present invention reduces the number of parts and reduces L
It is an object of the present invention to provide a technique that allows light from an ED to be efficiently taken into a light guide plate and enables uniform surface illumination with high brightness.

[0007]

According to a first aspect of the present invention, a substantially rod-shaped light guide is arranged so as to face at least one side surface of a light guide plate, and a point light source is arranged at at least one end of the light guide. The light from the point light source is guided to the inside of the light guide plate from the one side surface of the light guide plate through the light guide body, and the light guided to the inside of the light guide plate is emitted in a planar manner from the emission surface. The present invention relates to a surface light source device. Further, in this surface light source device, the light guide body has a reflection surface for reflecting light from the point light source propagating inside the light guide body to a surface side facing the one side surface of the light guide plate, and Among the light propagating inside the light guide, the light propagating without being reflected by the reflecting surface is emitted to the one side surface side of the light guide plate, and the light once reflected by the reflecting surface is An emission-side prism protrusion formed on a surface facing the one side surface so as to emit to the one side surface side of the light guide plate. Further, the light from the point light source, which is emitted through the emission side prism protrusion of the light guide, is incident on the one side surface of the light guide plate as light propagating in a direction substantially orthogonal to the one side surface. It is characterized in that side prism protrusions are formed. Here, the one side surface means a virtual plane in a state where the incident side prism protrusion is not formed. Further, the surface facing the one side surface means a virtual flat surface in a state where the exit side prism protrusion is not formed.

According to a second aspect of the present invention, there is provided the surface light source device according to the first aspect of the present invention, and an illuminated member that is illuminated by the planar light emitted from the surface light source device. The present invention relates to an image display device.

A third aspect of the present invention relates to a light guide body which is arranged so as to face the incident surface of the light guide plate and emits light from a point light source to the incident surface side of the light guide plate. The light guide includes a reflection surface that reflects light from the point light source toward a surface of the light guide plate that faces the incident surface, and light that is reflected once by the reflection surface is incident on the light guide plate. And an emission-side prism protrusion that emits the light, which is not reflected by the reflection surface and reaches the surface facing the incident surface, to the incident surface side of the light guide plate, while being emitted to the side. There is.

[0010]

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

[First Embodiment] (Schematic Configuration of Surface Light Source Device and Image Display Device) FIGS. 1 to 3
FIG. 1 shows a surface light source device 1 according to an embodiment of the present invention. Among these, FIG. 1 is a perspective view of the surface light source device 1, and FIG. 2 is an enlarged plan view showing a part of the surface light source device 1. 3 is a cross-sectional view taken along the line AA of FIG. As shown in these figures, in the surface light source device 1 of the present embodiment, a substantially rod-shaped light guide 4 is arranged so as to face one side surface (secondary incident surface) 3 of the light guide plate 2. L as a point light source is provided at both ends of the light guide 4.
EDs 5 and 5 are arranged. Then, the liquid crystal display panel (illuminated member) 7 is arranged so as to overlap with the secondary emission surface 6 of the light guide plate 2 which constitutes the surface light source device 1, and the image display device 8 widely used in mobile phones and the like is provided. Composed. Here, the one side surface 3 is a virtual plane when the incident side prism protrusion 16 described later is not formed, and the actual secondary incident surface is the prism surface of the incident side prism protrusion 16.

(Light Guide) The light guide 4 is made of a material having excellent light transmittance such as PMMA (polymethylmethacrylate), PC (polycarbonate), and a cycloolefin resin material. Center position CL in the width direction of the light guide plate 2
The shape is symmetrical with respect to. The light guide 4 has a side surface (primary emission surface) 11 side that opposes the secondary incidence surface 3 of the light guide plate 2 to the light H1 from the LED 5 that is incident from the opposite end surfaces (primary incidence surface) 10, 10. The reflecting surface 12 that reflects light is formed, and the light H1 that is once reflected by the reflecting surface 12 and the light H2 that directly arrives without being reflected by the reflecting surface 12 are efficiently incident on the secondary incident surface of the light guide plate 2. A large number of exit side prism protrusions 13 that exit to the 3 side are formed on the primary exit surface 11. Here, the side surface 11 facing the secondary incident surface 3
Is a virtual plane when the exit-side prism projection 13 is not formed, and the actual primary exit surface is the prism surface of the exit-side prism projection 13.

The exit-side prism projection 13 has a portion formed with a surface for efficiently emitting the light H1 that has been once reflected by the reflecting surface, and the light that has reached the primary emitting surface 11 side without being reflected by the reflecting surface. And a portion where a surface for efficiently emitting light is formed. Then, the output side prism protrusion 13 is
As shown in detail in FIG. 2, it has a substantially saw-tooth shape, and the inclination angle θ of each blade is formed so as to gradually increase as it moves away from the widthwise center position CL in the widthwise direction. ing.

As shown in FIG. 2, the planar shape of the light guide 4 is such that the width dimension (W1) of both end surfaces 10, 10 is larger than the width dimension (W2) of the center position CL in the width direction. 1
The reflecting surface 12 is formed by a smooth curved surface such that the width dimension gradually decreases from 0 to the width-direction center position CL.

Here, at the end of the light guide 4, an inclined surface 14 formed so as to increase the light H1 traveling from the LED 5 to the reflection surface 12, and the light H2 from the LED 5 are provided at the end of the light guide 4. The width direction surface 15 leading to the vicinity of the portion is formed so as to be cut out. In addition, the length of the light guide 4 is formed to have a length that slightly protrudes from both ends in the width direction of the light guide plate 2, and how much the effective use area of the secondary emission surface 6 of the light guide plate 2 is. Optimal dimensions are set as appropriate depending on whether or not to set.

(Light Guide Plate) The light guide plate 2 is made of a material having excellent light transmittance such as PMMA (polymethylmethacrylate), PC (polycarbonate), and a cycloolefin resin material, and has a planar shape. Is a substantially rectangular thin plate member. Then, the lights H1 and H2 emitted from the output side prism protrusions 13 of the light guide 4 are incident on the secondary incident surface 3 of the light guide plate 2 in a direction substantially orthogonal to the secondary incident surface 3. An incident-side prism protrusion 16 is formed. The incident-side prism protrusion 16 has a substantially triangular plan shape as shown in FIG. And
The apex angle of the incident-side prism protrusion 16 is set to an angle that allows the light emitted from the emission-side prism protrusion 13 to efficiently advance in a direction substantially orthogonal to the width direction.

Further, on the back surface 17 side of the light guide plate 2 facing the secondary emission surface 6, there is provided a projection 18 as an emission promotion means for reflecting the light so as to promote the emission of the light from the secondary emission surface 6. Many are formed. Here, as shown in FIGS. 4 to 6, the protrusion 18 as the emission promoting means has a substantially quadrangular pyramid shape, and of the light propagating through the inside of the light guide plate 2, only a small amount with respect to the back surface 17. Lights Ha and Hb propagating in an inclined state
After being reflected on the slopes 20 and 21 forming the protrusion 18,
Further, the light is reflected by the slopes 21 and 20, the traveling direction is three-dimensionally converted, and the light toward the secondary emission surface 6 is generated. Further, the light reflected by the slopes 22 and 23 may be further reflected by the slopes 21 and 20 and the slopes 20 and 21 to be converted in direction, and light may be generated toward the secondary emission surface 6.

Here, by adjusting the azimuths of the slopes 20 and 21 and the light distribution, it is possible to direct the emission direction of the light from the secondary emission surface 6 to a specific direction, for example, the secondary emission surface. The emission direction of the light from the entire 6 can be made substantially the normal line direction of the secondary emission surface 6, and a light flux having a converging property aiming at a point away from the secondary emission surface 6 can be generated. Is also possible. In the present embodiment, the slope 2
By adjusting the azimuths and orientations of 0 and 21, light is emitted almost in the normal direction of the secondary emission surface 6.
Here, the orientation of the slopes 20 and 21 refers to a three-dimensional inclination angle of the normal line of the slopes 20 and 21, and the orientation of the slopes 20 and 21 refers to the extending direction of the ridgeline 24 of the slopes 20 and 21. .

The projections 18 formed on the back surface 17 of the light guide plate 2 are minute projections and do not hinder the observation of the illuminated portion from the back surface 17. Further, the protrusion 18 shown in the present embodiment is an example of the emission promoting means, and is not limited to the shape of the present embodiment, and exhibits the same function as the protrusion 18 described above. Anything you can get.

For example, as shown in FIG. 7, a first emission promoting groove 25 in which a triangular prism-shaped space is formed, or as shown in FIG. 8, a cylinder is cut in half along the center line. The second emission promoting groove 26 having a semi-cylindrical shape may be used. The first of these
The emission promoting groove 25 and the second emission promoting groove 26 of the
Of the light H that is incident from the secondary incident surface 3 of and propagates in the light guide plate 2.
c is reflected by the inclined surface 25a and the arcuate surface 26a, and the light Hc is emitted in the direction substantially normal to the secondary emission surface 6. The first emission promoting groove 25 and the second emission promoting groove 26
The light guide plate 2 includes a protrusion 27 having a substantially triangular prism shape and a protrusion 28 having a substantially semicylindrical column formed in the cavity of the injection molding die of the light guide plate.
It is formed by transferring to the back surface 17 of the.

In the surface light source device 1 of the present embodiment configured as described above, the light emitted from the LEDs 5 and 5 is guided from the end faces (primary incident face) 10 and 10 of the light guide 4 to the light guide 2. It enters the inside and propagates inside the light guide 2. Light guide 2
Of the light propagating inside, the light H1 that is reflected once by the reflecting surface 12 and reaches the primary emitting surface 11 of the light guide 4 and the primary emitting surface of the light guide 4 without being reflected by the reflecting surface 12. 11
The light H2 that has reached directly is emitted toward the secondary incident surface 3 side of the light guide plate 2 by the action of the emission side prism protrusion 13. Light H emitted from the emission side prism protrusion 13
1 and H2 are emitted so that the light amounts thereof are substantially uniform in the width direction of the light guide plate 2.

The light emitted from the light guide 4 and reaching the secondary entrance surface 3 of the light guide plate 2 is evenly distributed inside the light guide plate 2 by the entrance side prism protrusions 16 of the secondary entrance surface 3 of the light guide plate 2. And it is adopted efficiently. The light propagating through the inside of the light guide plate 2 is reflected by the exit side prism protrusion 13 of the light guide body 2 and the light guide plate 2.
By the synergistic action of the incident side prism projections 16 of
Propagates in a direction substantially orthogonal to the width direction of. On this occasion,
Since the light propagating inside the light guide plate 2 travels almost uniformly in the width direction of the light guide plate 2, the streaks of light are less likely to appear as a difference in brightness. Of the light that propagates inside the light guide plate 2,
The light that has reached the back surface 17 of the light guide plate 2 is reflected by the projections 18 as the emission promoting means, the traveling direction is changed, and emitted from the secondary emission surface 6 of the light guide plate 2 in the substantially normal direction thereof. The liquid crystal display panel 7 arranged so as to face the light guide plate 2 is illuminated.

According to this embodiment having such a configuration,
No other optical component is arranged between the light guide 4 and the light guide plate 2, and the output side prism protrusion 13 is formed on the side surface (primary output surface) 11 side of the light guide 4 facing the light guide plate 2 while An incident side prism protrusion 16 is formed on the side surface (secondary incident surface) 3 side of the light guide plate 2 facing the light guide body 4, and the emission side prism protrusion 13 is formed.
The light from the LEDs 5 and 5 arranged at both ends of the light guide 4 can be efficiently taken into the light guide plate 2 by the incident side prism protrusions 16 and the light use loss of the light can be reduced and high brightness can be obtained. Allows surface lighting.

Further, according to the present embodiment, the light emitted from the output side prism protrusions 13 of the light guide 4 is evenly incident from the incident side prism protrusions 16 of the light guide plate 2 in the width direction of the light guide plate 2. The light propagating in the light guide plate 2 is not visually recognized as a stripe-shaped difference in brightness, and the illumination quality is improved.

Further, according to the present embodiment, as shown in FIG. 2, the light from the LEDs 5 and 5 is synergistic between the output side prism protrusion 13 of the light guide 4 and the incident side prism protrusion 16 of the light guide plate 2. By the action, it is taken in as a parallel light beam that travels in a direction substantially orthogonal to the width direction of the light guide plate 2. Therefore, according to the present embodiment, the protrusions 18 of FIG.
The first emission promoting groove 25 of FIG. 7A and the second emission promoting groove 26 of FIG. 8A are oriented according to the light propagation direction like the protrusion 18 shown in FIG. 4B. The light guide plate 2 can be easily manufactured because the light guide plate 2 does not need to be changed and can be arranged in a fixed direction.

Further, since the emission function of the emission promoting means as described above largely depends on the light propagation direction, when the LEDs are arranged directly on the incident surface of the light guide plate, the light that spreads radially from the LEDs is emitted. The direction must be changed according to the direction of propagation, and the light loss is large. However, according to the present embodiment, it is possible to ideally reflect the light emitted from the LEDs 5 and 5 as parallel light rays traveling in a direction substantially orthogonal to the width direction of the light guide plate 2 by the emission promoting means. Therefore, it is possible to reduce the use loss of light and increase the brightness of emitted light.

[Second Embodiment] FIG. 9 shows a surface light source device 1 according to a second embodiment of the present invention.
FIG. 3 is a partially enlarged plan view of the surface light source device 1. In the surface light source device 1 according to the present embodiment, the same components as those of the surface light source device 1 according to the first embodiment are designated by the same reference numerals, and a duplicate description will be omitted.

That is, the surface light source device 1 of the present embodiment
Is different from the light guide 4 of the first embodiment in the shape of the light guide 30. That is, the light guide 30 of the present embodiment
The end surface 31 is formed substantially parallel to the side surface 32 of the light guide plate 2, and the exit side prism protrusion 33 is formed along the entrance side prism protrusion 16 of the light guide plate 2. Also,
The reflection surface 34 of the light guide body 30 gradually decreases in width dimension from the end surface 31 of the light guide body 30 toward the center position CL in the width direction.
It is composed of a flat surface portion 34a and a curved surface portion 34b that is smoothly connected to the flat surface portion 34a.

The exit side prism protrusion 33 of the light guide 30 is
A portion of the reflection surface 34 that emits the light H1 once reflected toward the incident side prism projection 16 side, a light H1 that is reflected once by the reflection surface 34, and a light that directly reaches the reflection surface 34 without being reflected. A portion of the light H2 that is emitted toward the prism 16 on the incident side and the light H that has directly reached the reflecting surface 34 without being reflected.
And a portion for emitting only 2 toward the incident side prism projection 16 side.

The surface light source device 1 according to this embodiment having such a structure has the same effect as that of the surface light source device 1 according to the first embodiment.

[Third Embodiment] FIG. 10 shows a surface light source device 1 according to a third embodiment of the present invention, and is a partially enlarged plan view of the surface light source device 1. In the surface light source device 1 according to the present embodiment, the same components as those of the surface light source device 1 according to the first embodiment are designated by the same reference numerals, and a duplicate description will be omitted.

That is, the surface light source device 1 of the present embodiment
Is different from the light guides 4 and 30 of the first and second embodiments in the shape of the light guide 35. That is, in the light guide 35 of the present embodiment, the reflection surface 36 is a plane formed substantially parallel to the forming direction (width direction) of the incident side prism protrusions 16 of the light guide plate 2, and the emission side prism protrusions 37. Is the end face 38
It is formed so as to move away from the incident-side prism protrusion 16 as it goes from the center position CL in the width direction. The end surface 38 of the light guide body 35 is formed so as to be substantially orthogonal to the formation direction of the exit-side prism protrusions 37 of the light guide body 35.

The exit side prism protrusion 37 of the light guide 35 is
Similar to the light guide 30 of the second embodiment, the reflecting surface 3
6, the light H1 reflected once by 6 toward the incident side prism projection 16 side, the light H1 once reflected by the reflecting surface 36 and the light H directly reaching the reflecting surface 36 without being reflected.
2 is a portion that emits toward the incident side prism protrusion 16 side; and a portion that emits only the light H2 that has reached the incident side prism protrusion 16 side without being reflected by the reflection surface 36.
It consists of

The surface light source device 1 having such a structure is the light from the LED 5 on the one end face 38 side, and the light guide 3
5, the light emitted from the width direction central position CL side out of the light emitted from the emission side prism protrusion 37 advances to a position beyond the width direction central position CL, and enters the inside of the light guide plate 2 from the incident side prism protrusion 16. enter in.

The surface light source device 1 of this embodiment is the first
Also, the same effects as those of the surface light source device 1 according to the second embodiment are obtained.

[Fourth Embodiment] FIG. 11 shows a surface light source device 1 according to a fourth embodiment of the present invention, and is a partially enlarged plan view of the surface light source device 1. In the surface light source device 1 according to the present embodiment, the same components as those of the surface light source device 1 according to the first embodiment are designated by the same reference numerals, and a duplicate description will be omitted.

That is, the surface light source device 1 of the present embodiment
Is obtained by partially integrating the light guide body 30 and the light guide plate 2 of the second embodiment with a plurality of bridge portions 40,
The light guide 30 and the light guide plate 2 are integrally formed by injection molding. An exit-side prism protrusion 33 is formed on a portion of the light guide body 30 facing the light guide plate 2, and an incident-side prism protrusion 16 is formed on a portion of the light guide plate 2 facing the light guide body 30.

In the surface light source device 1 of the present embodiment having such a configuration, since the light guide 30 and the light guide plate 2 are not displaced in the position in the width direction, the exit side prism projection 33 and the entrance side prism projection 33. The optical path changing action by the synergistic action with 16 is more efficiently exhibited.

[Other Embodiments] The surface light source device 1 of each of the above embodiments has been exemplified as being used as a backlight for illuminating the transmissive liquid crystal display panel 7 in a planar manner from the back surface side. However, the present invention is not limited to this, and the reflection type liquid crystal display panel may be used as a front light that illuminates the surface side from the front side.

Further, the present invention is not limited to the shapes of the light guides 4, 30, 35 of the surface light source device 1 according to each of the above-mentioned embodiments, and may be constructed as shown in FIG. 12, for example. Good. That is, the light guide of the surface light source device has a structure in which the right side portion is cut off from the widthwise center position CL of the light guide 4 according to the first embodiment. A single LED 5 as a point light source may be arranged.

Further, the emission promoting means formed on the light guide plate 2 is not limited to the one described above, and the light guide plate is formed so that the cross section of the light guide plate 2 in the direction orthogonal to the secondary incident surface 3 is, for example, stepwise. 2 can also be formed.

[0042]

As described above, according to the present invention, the exit side prism protrusion is formed on the surface side of the light guide body facing the light guide plate without disposing other optical components between the light guide body and the light guide plate. On the other hand, an incident side prism protrusion is formed on the surface side of the light guide plate facing the light guide body, and the light from the point light source arranged at at least one end of the light guide body is efficiently formed by the emission side prism protrusion and the incident side prism protrusion. It can be effectively incorporated into the light guide plate, reducing the utilization loss of light and enabling high brightness surface illumination.

Further, according to the present invention, the light emitted from the exit side prism protrusions of the light guide body is uniformly incident from the entrance side prism protrusions of the light guide plate in the width direction of the light guide plate, and thus propagates in the light guide plate. The light is not visually recognized as a stripe-shaped difference in brightness, and the illumination quality is improved.

[Brief description of drawings]

FIG. 1 is an external perspective view of a surface light source device according to a first embodiment of the present invention.

FIG. 2 is an enlarged plan view showing a part of the same surface light source device.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4A is an enlarged view of a part of the back surface of the light guide plate according to the first embodiment (a view seen from the Y direction in FIG. 3), and FIG. FIG. 6 is an enlarged view showing a part of the back surface of the light guide plate when the light guide body according to the first embodiment is not used.

FIG. 5 is a partial back view of the light guide plate, and is a view for explaining the shape of protrusions on the back surface.

FIG. 6 is a diagram illustrating an operation of a protrusion on the back surface of the light guide plate.

7 (a) is a rear view of the light guide plate having a first emission promoting groove as emission promoting means, and FIG. 7 (b) is a view taken along the line BB of FIG. 7 (a). FIG. 7C is a cross-sectional view cut and shown, and FIG. 7C is a perspective view of a protrusion formed in the injection mold to form the first emission promotion groove.

8A is a rear view of a light guide plate having a second emission promoting groove as emission promoting means, and FIG. 8B is a sectional view taken along line CC of FIG. 8A. FIG. 8C is a cross-sectional view cut and shown, and FIG. 8C is a perspective view of a protrusion formed in the injection mold to form the second emission promotion groove.

FIG. 9 is a partially enlarged plan view of a surface light source device according to a second embodiment of the invention.

FIG. 10 is a partially enlarged plan view of a surface light source device according to a third embodiment of the present invention.

FIG. 11 is a partially enlarged plan view of a surface light source device according to a fourth embodiment of the present invention.

FIG. 12 is a partially enlarged plan view of a surface light source device according to another embodiment of the present invention.

FIG. 13 is a partial plan view of a surface light source device according to a first conventional example.

FIG. 14 is a partial plan view of a surface light source device according to a second conventional example.

[Explanation of symbols]

1 ... Surface light source device, 2 ... Light guide plate, 3 ... Secondary incident surface (one side surface), 4, 30, 35 ... Light guide member, 5 ... LED
(Point light source), 6 ... Secondary emission surface (emission surface), 7 ... Liquid crystal display panel (illuminated member), 8 ... Image display device, 1
2, 34, 36 ... Reflecting surface, 13, 33, 37 ... Ejection side prism protrusion, 16 ... Incident side prism protrusion

Claims (3)

[Claims] 1. A substantially rod-shaped light guide is arranged so as to face at least one side surface of a light guide plate, and a point light source is arranged at at least one end of the light guide, and the light from the point light source is guided by the light guide. A surface light source device configured to guide light from the one side surface of the light guide plate into the inside of the light guide plate through a body and to planarly emit the light guided to the inside of the light guide plate from the emission surface. The body includes a reflection surface that reflects light from the point light source that propagates inside the light guide member to a surface side that faces the one side surface of the light guide plate, and a light that propagates inside the light guide member. Thus, the light propagating without being reflected by the reflection surface is emitted to the one side surface side of the light guide plate, and the light reflected once by the reflection surface is emitted to the one side surface side of the light guide plate. And an emission-side prism protrusion formed on a surface facing the one side surface. An incident-side prism that causes the light from the point light source emitted through the emission-side prism protrusion of the light guide to enter the one side surface of the light guide plate as light propagating in a direction substantially orthogonal to the one side surface. A surface light source device having a projection formed thereon. 2. An image display device, comprising: the surface light source device according to claim 1; and a member to be illuminated which is illuminated with planar light emitted from the surface light source device. 3. A light guide body, which is arranged so as to face an incident surface of the light guide plate and emits light from the point light source toward the incident surface side of the light guide plate, wherein light from the point light source is emitted from the light guide plate. A reflecting surface that reflects toward the surface opposite to the incident surface, and light that is reflected once by the reflecting surface is emitted to the incident surface side of the light guide plate, and the incident surface is not reflected by the reflecting surface. And a light-exiting-side prism protrusion that emits light reaching a surface facing the light-incident surface side of the light guide plate.