JP2002042530A - Surface light-source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light-source device with an even light-emission capability by using a light source such as an LED for smooth optical flux expansion and redirection at 2-stage configuration. SOLUTION: An input light flux IF from a light supplier L equipped with an LED is guided into a first light guide part 10 from a light guide-in surface 11. It is redirected at a redirection surface 16 while advancing to an end surface 17 under scattering action, generating an intermediate output light MO heading for almost +y axis direction. The redirection surface 16 comprises many protrusion rows 18 for redirecting action and leaked light recovery. Each projection row 18 comprises a steep slope and a no-steep slope. The intermediate output light flux MO is guided into a second light guiding part 20, to provide an output light OF in almost +z axis direction under the behavior of a redirection surface 26 similar to the redirection surface 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source device using a point light source, such as a light emitting diode, as a primary light source. The present invention relates to an improved surface light source device for converting light having a small cross-sectional area from a point light source into a light beam having an enlarged cross-sectional area and outputting it to the outside.

The surface light source device of the present invention is, for example, a mobile phone,
The present invention is suitably applied to backlighting of a liquid crystal display of a mobile device such as an electronic organizer and a portable personal computer.

[0003]

2. Description of the Related Art Various surface light source devices using a light guide plate made of a scattering light guide or a transparent light guide have been proposed.
A surface light source device that supplies primary light from the side of the light guide plate is also called a sidelight type surface light source device. Since the sidelight type surface light source device has an advantage of allowing a thin structure,
It is widely applied to backlighting of liquid crystal displays and the like.

As a primary light source for supplying primary light to the light guide plate, a rod-shaped light source mainly using a cold cathode tube as a light emitting source or a point light source represented by an LED is used.
With the recent spread of mobile devices such as mobile phones, electronic organizers, and portable personal computers, and the reduction in cost of LEDs, the latter surface light source devices using point light sources are becoming mainstream.

FIG. 1 is a perspective view in which the latter is applied to backlighting of a liquid crystal display. FIG. 2 is a top view of the light guide plate in FIG. Referring to FIGS. 1 and 2, reference numeral 1 denotes a light guide plate,
It is composed of a scattered light guide having a wedge-shaped cross section. The scattering light guide is a well-known optical material having both a light guiding function and an internal scattering function, such as polymethyl methacrylate (PMM).
A matrix consisting of A) and a matrix in which the "different refractive index substance" is uniformly dispersed. By "different refractive index material" is meant a material having a refractive index substantially different from the refractive index of the matrix.

The thick end face of the light guide plate 1 is an incident end face 2, and a plurality of light sources L1 to L3 each having a small light emitting area are arranged in the vicinity thereof. Each light source L1 to L3
Each uses a single LED, LED array, light bulb, or the like as a light emitting source.

[0007] Along with a back surface 6 of the light guide plate 1, a regular or diffusely reflective reflector 3 is arranged. The illumination light is extracted from the light exit surface 5 of the light guide plate 1. Prism sheet 4
Has a prism surface on one side, and is arranged along the emission surface 5 so that the prism surface faces inward.

Referring to the broken-out portion, a smooth outer surface 4A of the prism sheet 4 is shown. Outer surface 4A
Outside the liquid crystal panel L via a polarization separation sheet LS.
P is arranged. The liquid crystal panel LP has a known configuration in which a liquid crystal cell, a transparent electrode, and the like are sandwiched between two polarizing plates arranged so that the polarization axes are orthogonal to each other.

The polarization separation sheet LS is disposed between the polarizing plate and the prism sheet 4 in the liquid crystal panel. This polarized light separating sheet LS has such a property that the transmittance is high for the polarized light component in the same direction as the polarization axis of the inner polarizing plate, and the reflectance is high for the polarized light component in the direction orthogonal to the same polarization axis. The prism surface provided by the inner surface of the prism sheet 4 has a number of prism element rows. The orientation direction of these many prism element rows is substantially parallel to the incident end face 2 of the light guide plate 1.

The light introduced into the light guide plate 1 from each of the light sources L1 to L3 is guided toward the end portion 7 while undergoing scattering and reflection in the light guide plate 1. In this process, the illumination light is gradually emitted from the emission surface 5.

Here, the main traveling direction of the light emitted from the light exit surface 5 of the light guide plate 1 is greatly inclined obliquely forward. Such a property is called directional emission. This inclined traveling direction is corrected to a substantially frontal direction by the prism sheet 4, and the liquid crystal panel LP is backlighted via the polarization separation sheet LS.

The problem here is that it is difficult to supply light uniformly over the entire length of the incident end face 2. For this reason, as shown in FIG.
Inevitably, it occurs discretely in accordance with the arrangement of L3. Such high-luminance areas S1 to S3 are also called “fireflies”.

One solution to this problem is to use a light source L
The aim is to increase the number or the entire light emitting area of 1 to L3 to achieve a light emission distribution equivalent to a rod-shaped light source. But,
Actually, it is difficult to realize an emission distribution equivalent to a rod-shaped light source using an LED or a light bulb, and it is not economically advantageous.

Another solution is to equalize the light supply by providing a strong light diffusing means between the light sources L1 to L3 and the incident end face 2 or on the incident end face 2 itself.
However, when this method is used, the traveling direction of light spreads over a very wide angle range due to back scattering or the like, and light loss is likely to occur. Further, the direction of emission from the emission surface 5 also expands, and the directivity of the emitted light decreases.

Further, as shown in FIG. 3, the light source L4
Is transmitted through a number of optical fibers F1 to F9, and light is supplied to the light guide plate 1 from the emission ends of the optical fibers F1 to F9. This method is also applicable to the optical fibers F1 to F9.
There is a problem that high-luminance areas SS1 to SS9 corresponding to the emission ends of No. 9 are generated. If the number of optical fibers is increased so that the exit end covers the entrance end face of the light guide plate 1, the luminance will be uniform, but the structure of the light supply section becomes complicated, which is economically disadvantageous.

[0016]

SUMMARY OF THE INVENTION One object of the present invention is to provide a light source provided with a light source having a small light emitting area (hereinafter referred to as a point light source) such as an LED. An object of the present invention is to provide a surface light source device in which the cross-sectional area and the necessary direction change are properly performed, and then the light is uniformly emitted from the emission surface without waste. Another object of the present invention is to provide a direction in which light emitted from an emission surface is desired,
In particular, it is an object of the present invention to provide a surface light source device that outputs light with excellent directivity substantially in the front direction.

[0017]

According to the present invention, there is provided a surface light source device using at least one point light source as a light emitting source, the first stage light beam extension including a first light guide section. -A second-stage light beam extension including a second light guide section-a direction change means including a second light guide section. Further, at least the first light guide section receives light supplied from the light supply section inside the first light guide section. By adopting the one provided with a turning surface provided with a large number of projection rows that cooperate to exhibit the reflection function and the leakage function,
Step luminous flux expansion-smoothing and efficiency of the directional change and luminous flux expansion in the directional change, so that high-efficiency and highly directional output light can be output from the output surface of the second light guide,
It is a solution to the above problem.

That is, the surface light source device according to the present invention comprises: a light supply means using at least one point light source as a light emission source; and a first-stage light beam expansion and direction change means including a first light guide. And a second-stage luminous flux expanding / redirecting means including a second light guide section.

The first light guide section has a major axis along the first direction, a thickness substantially along a second direction perpendicular to the first direction, a first direction and a second direction. A light introducing surface for receiving light supplied by the light supply means and traveling substantially along the first direction, having a width substantially along a third direction perpendicular to any of the directions; A first direction for changing the traveling direction of the light introduced into the first light guide through the introduction surface to a direction substantially along the second direction, and generating an intermediate output light flux toward the second light guide; It has a turning surface.

The first turning surface has a large number of projection rows P1,
P2, P3,... Are provided, and each projection row Pi (i = 1, 2,
...) Extend substantially along the third direction, and the first surface Si which is relatively close and steep with respect to the introduction surface and the second surface which is relatively far and inclined with respect to the introduction surface. The second surface Ti includes an internal reflection function for generating a part of the intermediate output light beam and a leakage function for generating leakage light from the projection row Pi, and includes a projection row Pj (j = 2,3 ·······························································································
They are arranged to cooperate in a chain to collect through surface Sj and internally enter second surface Tj.

The second light guide has a width substantially along the first direction, a depth substantially along the second direction, a thickness substantially along the third direction, and a first light guide. A second turning surface for changing the traveling direction of the intermediate output light beam received from the light guide to a direction substantially along the third direction to generate an output precursor light beam, and converting the output precursor light beam to a substantially third direction; And an emission surface for emitting light toward the light source.

Here, the second turning surface has the same characteristic protrusion arrangement structure as that of the first turning surface. However, the orientation of the projection arrangement in the space is different from that of the first turning surface by almost 90 degrees.

That is, a large number of projection rows Q1, Q2, Q3,... Are provided on the second direction changing surface.
(I = 1, 2, 3,...) Extend substantially along the first direction, and are relatively close to the first light guide portion and the first surface Vi is steep. The second surface Wi is relatively distant and inclined with respect to the light guide portion.

The second surface Wi has an internal reflection function for generating a part of the output precursor light beam and a leakage function for generating light leaked from the projection array Qi, and has a projection array Qj (j = 2,3 ・). ...) Are the first leakage light from the second surface Wj-1 of the preceding projection row Qj-1.
They are arranged to cooperate in a chain to collect through surface Vj and internally impinge on second surface Wj.

Here, for the second light guide section, an embodiment in which the above-described projection arrangement structure is not applied can be adopted.

In this case, the second light guide has a width substantially along the first direction, a depth substantially along the second direction, and a thickness substantially along the third direction. With
An output surface, and a back surface facing away from the output surface;
The traveling direction of the intermediate output light beam received from the light guide plate is changed to the third direction.
Is changed from the same direction to the direction inclined to the second direction side with reference to the direction, and the oblique emission light is emitted from the emission surface.

In this aspect, the direction correcting element for correcting the traveling direction of the obliquely emitted light so as to approach the third direction is arranged along the emission surface, so that the illumination directed to the front direction or the peripheral direction. Output light can be obtained.

The first light guide section has a thickness of an introduction surface in order to smoothly transfer light from the first light guide section to the second light guide section by the light beam expansion and direction change function. It is preferable to have a substantially wedge shape that decreases as the distance from the distance increases.

Similarly, the second light guide section has a light beam extension
In order to smoothly emit the light received from the first light guide portion from the emission surface by the direction changing function, the light guide portion has a substantially wedge shape such that its thickness decreases as the distance from the first light guide portion increases. Is preferred.

The first light guide and the second light guide may be formed separately, or may be formed integrally. Further, in order to improve the uniformity of the brightness of the illumination light output from the emission surface of the second light guide, at least one of the first light guide and the second light guide is provided inside the first light guide and the second light guide. Preferably has a uniform scattering power. The first light guide section may be divided into a plurality of sections, and they may be connected and arranged, and a light introduction surface may be provided for each section. In this case, a plurality of light supplies can be provided corresponding to each section. In this case, the intermediate output light beam is provided by the plurality of sections. Preferably, each section has a substantially wedge-shaped configuration such that each of the plurality of sections decreases in thickness as the distance from each corresponding light-introducing surface increases.

In some cases, the light introduction surface corresponding to a part of the plurality of sections is provided by a light supply means,
It may be provided to receive light traveling in a direction substantially opposite to the first direction. Note that in a typical embodiment, the point-like light source used in the light supplier is a light emitting diode. A plurality of point light sources such as light emitting diodes may be used.

[0032]

Embodiments of the present invention will be described below. In the drawings for describing the embodiments, dimensions of various elements are exaggerated for convenience of illustration. Further, the description will be made on the assumption that the constituent materials of the first light guide section and the second light guide section are scattering light guides having a uniform light scattering ability inside. For example, polymethyl methacrylate (PMMA) is used for the matrix of the scattering light guide, and fine particles of, for example, silicon resin are used for the different refractive index substance. The diameter of the fine particles is within a range in which sufficient forward scattering is maintained by so-called Mie scattering without inconvenience such as coloring, for example, several μm.
Preferably, it is selected in the range of about m to 60 μm.
When the diameter of the fine particles is too small, the forward scattering property is weakened, light that is scattered backward is generated, the light use efficiency is reduced, and the light emitted from the emission surface is not easily given the required directivity. Absent.

In each of the embodiments, a transparent light guide such as an acrylic resin may be adopted as a material of one or both of the first light guide and the second light guide. It is preferable to use a light-scattering light guide in order to enhance the brightness level and its uniformity.

Further, in each of the embodiments, the first light guide and the second light guide have a wedge shape, which is a preferable shape in order to smoothly perform the light beam expansion-direction change. . However, the shape is not limited to this as long as the luminous flux expanding-direction changing action of each light guide section is not impaired. For example, the thickness of each light guide may be uniform.

[First Embodiment] FIG. 4 is a perspective perspective view for explaining a main part configuration of a surface light source device according to a first embodiment of the present invention, and shows a basic form of the present invention. As shown in FIG. 4, the surface light source device SFV1 includes a first stage for a light supply unit L constituting a primary light supply unit and an input light beam IF having a small cross-sectional area supplied from the light supply unit L. Of the first light guide unit 10 that performs the direction change processing and outputs the intermediate output light beam MO, and receives the intermediate output light beam and expands the light beam of the second stage.
Direction change processing and output precursor light (the arrow is not shown)
And a second light guide section 20 for generating an output light beam OF. The output light beam OF is, for example, a surface light source device SF
A liquid crystal display panel (not shown) arranged so as to overlap with V1 is illuminated.

The first light guide section 10 has a slender and substantially wedge shape as a whole, and its thick end face is used as the light introduction face 11. It is preferable that the size of the light introducing surface 11 be approximately the same as or slightly larger than the cross-sectional area of the input light beam IF. The other end is referred to as the end 17 for convenience.

The slope connecting the wedge-shaped upper and lower side surfaces 12 and 13 provides a direction change surface (first direction change surface) 16 in which a number of projection rows 18 are formed as shown in the figure. The rows of projections 18 of the direction changing surface 16 are
Plays a crucial role in generating the intermediate output light flux MO toward The details will be described later.

On the other hand, the second light guide section 20 has a wedge plate shape as a whole, and receives the intermediate output light beam MO from its thick side. In the present embodiment, the first light guide 10 and the second light guide 20 are arranged so as to be in contact with each other at the boundary BR. Therefore, the thickness of the thickest portion of the light guide 20 (substantially along the z-axis) is substantially equal to the width of the light guide 10. The width of the light guide 20 (substantially along the x-axis) is substantially equal to the length of the light guide 10. And the depth of the light guide 20 (almost along the y-axis)
Is larger than the thickness (substantially along the y-axis) of the light guide 10.

However, the first light guide 10 and the second light guide 2
0 may be an independent block or a single block. In the case of a one-piece configuration, those manufactured in separate blocks may be bonded with a light-transmitting adhesive, or the like.
You may make it obtain the molded object of the shape which combined both the light-guide parts 10 and 20.

In the case of a separate structure, an air gap may exist between the first light guide 10 and the second light guide 20.

Here, a coordinate system is set for the description of this embodiment and other embodiments. In FIG. 4, the x-axis is taken in parallel with the main incident direction when the input light beam IF is input to the elongated first light guide unit 10. The direction orthogonal to the x-axis and on the side where the second light guide unit 20 is disposed is taken as the y-axis (+ y direction). Then, a right-handed orthogonal coordinate system is considered based on this, and the direction orthogonal to both the x-axis and the y-axis is represented by z
Axis. The symbols a and b added to the coordinate system xyz shown in FIG. 4 indicate how to set the angles related to the measurement results (graph) described later.

The angle a represents the inclination in the + x-axis direction with ± sign in the xz plane with the + z-axis direction as a reference (zero), and the angle b represents the + y-axis in the yz plane with the + z-axis direction as a reference (zero). The inclination in the direction is indicated with ± signs.

In this embodiment, the major axis direction of the first light guide 10 is “substantially parallel to the x-axis”, and the thickness direction of the first light guide 10 and the depth of the second light guide 20 The direction and the main traveling direction of the intermediate output light beam MO are "almost + y-axis direction". Further, the width direction of the first light guide section 10 and the second light guide section 2
The thickness direction of 0 and the main traveling direction of the output light beam OF are “substantially parallel to the z-axis”.

According to the above setting, the first direction changing surface 16 has a small angle (for example, several degrees to 10 degrees) with respect to the xz plane.
The second turning surface 26 is inclined at a small angle (for example, several degrees) with respect to the xy plane.

The outline of the behavior of light in this embodiment is as follows. A point-like light source (eg, one or several L
Light (primary light) emitted from the light supplier L equipped with the ED) is introduced into the first light guide unit 10 from the light introduction surface 11 as an input light beam IF having a small cross-sectional area. The light introduced into the light guide 10 travels substantially toward the end face 17 while undergoing a uniform scattering action (forward scattering). In the process, a slope connecting the upper and lower side faces 12 and 13 provides. As a result of the positive turning by the turning surface 16, intermediate output light substantially in the + y-axis direction is generated. The generation of the intermediate output light is performed over substantially the entire length (x-axis direction) and the entire width (z-axis direction) of the elongated first light guide section 10, and a substantially uniform intermediate output light beam MO is formed as a whole.

FIG. 18 conceptually shows this state. The cross-sectional area of the intermediate output light beam MO becomes larger than the input light beam IF, so that the direction change and the light beam expansion are achieved at the same time.

Here, in addition to the reference diagrams shown in FIGS.
The turning action of the turning face 16 will be described in detail.

FIG. 5 shows a cross section of the first light guide section 10 viewed from the + z direction. As shown in FIG.
The symbols P1, P2, P3,... Pi,. Generally, as shown in FIG. 4, it is represented by reference numeral 18 or Pi.

Each row of projections Pi includes a first surface Si and a second surface Ti, and extends substantially parallel to the light introduction surface 11. For each projection row Pi, the first surface Si is closer to the incident end face 11 than the second surface Ti.

The first surface Si is a steep surface. That is,
The angle is almost perpendicular to the extending surface of the light guide 10 which is substantially parallel to the x-axis direction. On the other hand, the second surface is an inclined surface that is not as steep as the first surface. The inclination angle is designed such that an intermediate output light beam MO directed substantially in the + y-axis direction is generated.

When the input light beam IF is introduced into the light guide portion 10 through the light introduction surface 11, most of the light beams enter one of the projection rows Pi. The scattering power given to the inside of the light guide section 10 has the effect of increasing the chance of entering the projection row Pi.

When light enters the projection row Pi, internal reflection occurs on the second surface Ti. The internally reflected light is the second surface T
The light is redirected in a direction determined by the internal incident angle to i and the inclination angle of the second surface Ti, and becomes intermediate output light toward the second light guide unit 20. When the light guide unit 10 is formed separately from the light guide unit 20 and an air gap exists at the boundary BR, the intermediate output light is once emitted from the emission surface of the light guide unit 10 in the air gap, and then The light is introduced into the light guide 20 from the incident end face of the second light guide 20.

Further, even when the light guide section 10 has an integrated structure, the intermediate output light is transmitted to the light guide section 10 if an adhesive layer is present at the boundary BR.
Through the adhesive layer and into the second light guide 20. Some reflection occurs at each interface. In order to prevent this reflection from becoming excessive, it is preferable that the refractive index of the adhesive layer is close to the refractive index of the light guides 10 and 20.

As described above, as the light enters the row of projections Pi, internal reflection occurs on the second surface Ti. For incident light having an internal incident angle smaller than the critical angle, a part of the internal light is internally reflected. And the rest leaks. In other words, the second surface Ti has a leakage function of generating such leakage light and an internal reflection function of generating light traveling toward the light guide 20.

What is important here is that this leakage function does not lead to waste of light, and the projection rows Pj (j = 2,
...) To provide an opportunity to be efficiently recovered and converted back into internal output light.

That is, the projection row Pj (j = 2, 3,...) Is linked to the preceding projection row Pi (i = 1, 2, 3,...) In order to collect light leakage. They are arranged to work together. Leading projection row Pj-
1 leaked from the second surface Tj-1 is collected through the first surface Sj of the succeeding projection row Pj and is internally incident on the second surface Tj. This internal incidence gives the recovered light a chance to change direction in the substantially + y axis direction. If light leakage occurs again, most of the light is recovered from the first surface Sj + 1 of the next projection row Pj + 1 into the projection row Pj + 1.

A broken line G drawn along the turning surface 16 indicates an inner surface of a frame or a housing that mounts or accommodates the illustrated elements. This inner surface has a diffuse reflection property or a regular reflection property. As described later, a reflecting member such as a silver foil may be interposed between the light guide 10 and the frame or the housing.
Such a reflecting surface means can also contribute to the collection of light leakage to some extent (see the measurement example described later).

However, what is important is that the recovery of the leaked light does not depend on the external reflection means, and the recovered light has almost the same direction (almost + y-axis direction) as the light that does not leak.
The opportunity to change direction. For example, as in the related art, in the collection using the regular reflection sheet, the collection efficiency is low, and it is not expected to change the direction substantially in the + y-axis direction. Almost +
Although some direction change in the y-axis direction can be expected, light diffusion in useless directions is inevitable.

FIG. 6 is a diagram for specifically explaining the direction change and the light leakage recovery by the projection row, and shows the cross section of two adjacent projection rows Pj-1 and Pj and the behavior of light rays.

In FIG. 6, there is a light introduction surface 11 (not shown) on the left side, so that the general light supply direction in the light guide section 10 is from left to right. Projection rows Pj, Pj-1
Has a shape including the first surfaces Sj-1 and Sj and the second surfaces Tj-1 and Tj, respectively. The first surface Sj-1 and Sj and the second surface Tj-
The intersection of 1 and Tj forms sharp tips Bj and Bj-1.

As shown in the circle, the angles formed by the first surface S and the second surface T with respect to the vertical surface M with respect to an arbitrary row of projections P (positive signs in the directions of the arrows) are α and β. The vertical surface M is defined with respect to the extension surface of the boundary BR (see FIG. 4), and in this example, the vertical surface M is parallel to the yz plane.

Α = 0 degrees and β = 48 degrees added in the figure are as follows:
This is a preferred example of the values of the angles α and β. Generally, the angle α is preferably about 0 to 10 degrees. Although α <0 degrees is acceptable, it may be inferior in terms of manufacturing difficulty, mechanical strength, and the like. The inclination angle β is designed according to a desired output direction (a main emission direction of the intermediate output light beam MO). Of course, the refractive index n of the material (for example, n = 1.49) is also taken into account. In the normal case, the tilt angle β is in the range from 30 degrees to 60 degrees.

Now, in order to consider the basic cooperative action of the projection rows Pj-1 and Pj-1, the second surface T of the projection row Pj-1 will be described.
j-1 is represented by point A. The point A is on the second surface Tj-1 and close to the base of the projection row Pj-1 (that is, the tip Bj-
(Distant from 1).

A vertical line set at the point A with respect to the second surface Tj-1 is defined as N (broken line). Symbol C represents a critical angle, which is 42 degrees in this example. Most of the internally incident rays at point A are
It can be roughly classified as follows according to the internal incident angle.

Light ray group I: a light ray group in a certain range where the internal incident angle is sufficiently smaller than the critical angle C. Many of these rays leak from the second surface Tj-1 and enter the first surface Sj of the succeeding projection row Pj. Here, since the first surface Sj is steep,
Most of the leaked light is introduced into the succeeding projection row Pj through the first surface Sj (collection of the leaked light). Then, the subsequent projection row Pj
Is internally incident on the second surface Tj.

It should be noted that, as can be seen from the illustrated passing area, the internal angle of incidence on the second surface Tj is equal to the (previously experienced) internal angle on the second surface Tj-1. That is, it is larger than the incident angle. As a result, the ray group I easily satisfies the condition of total internal reflection in the internal reflection on the second surface Tj, and as shown by I ', the light guide section 20
(See FIG. 4). In this example, the light beam group I 'is output substantially in the + y-axis direction.

Ray group II: A ray group whose internal incident angle is smaller than the critical angle C but does not belong to ray group I. A significant portion of these rays leak out of the second surface Tj-1 to form
j on the first surface Sj. Since the first surface Sj is steep, most of the leaked light is introduced into the succeeding projection row Pj through the first surface Sj (collection of light leakage).

However, as can be understood from the passing area shown in the figure, it is difficult to internally enter the second surface Tj of the succeeding projection row Pj, and it is roughly a ray group II '. Ray group II 'has not undergone any significant turning. Therefore,
If the boundary BR has an interface with the low-refractive index medium (for example, an interface with an air gap), most of the interface is totally reflected at the interface, giving a chance to be incident again on the second surface of another projection row. .

The internal incident angle at that time can be slightly larger than the internal incident angle on the second surface Tj-1 in consideration of refraction on the second surface Tj-1 and the first surface Sj. As a result, like the ray group I, a chance to be turned is provided.

Ray group III: A ray group whose internal incident angle is larger than the critical angle C. These rays are totally reflected by the second surface Tj-1 and form a ray group III 'traveling in the + y-axis direction as it is.

The above is the basic form of the direction change action with light leakage recovery, but the action may vary depending on the angles α and β and the refractive index n. For example, if the angle β (= 48 degrees) is corrected downward, total reflection on the second surface Tj becomes difficult to occur. Even in such a case, a chance of a change in direction due to total reflection is provided in the subsequent projection row Pj + 1 and the like.

FIG. 7 shows an example of such a situation. Referring to FIG. 7, three projection rows Pj-1, Pj,
The cross section of Pj + 1 and the behavior of the light beam are depicted. In FIG. 7, the angle of the first surface is α = 0 degrees, and the angle of the second surface is β = 40.
Degrees. This value is an example that gives a situation in which the collection is performed in cooperation of three parties.

The ray group IV represents a ray group in a certain range in which the internal incident angle is sufficiently smaller than the critical angle C (substantially corresponds to the ray group I described above). Many of these rays are on the second surface Tj-
1 and enters the first surface Sj of the succeeding projection row Pj. Since the first surface Sj is steep, much of the leaked light is introduced into the succeeding projection row Pj through the first surface Sj. Then, the light is internally incident on the second surface Tj of the succeeding projection row Pj.

This internal incidence has a slightly larger internal incidence angle than internal reflection on the second surface Tj-1. However, since the angle β is small, the internal reflection on the second surface Tj is not sufficient to satisfy the condition of total reflection.
As a result, most of the light rays leak out of the second surface Tj again and enter the first surface Sj + 1 of the succeeding projection row Pj + 1. Since the first surface Sj + 1 is steep, most of the leaked light is internally incident on the second surface Tj + 1 of the projection row Pj + 1 via the first surface Sj + 1.

This internal incidence has a slightly larger internal incidence angle than internal reflection at the second surface Tj. In the present example, as a result, total reflection occurs on the second surface Tj + 1. The light beam group IV 'is output by the direction change accompanying this total reflection. In this example, the light beam group IV ′ is output substantially in the + y-axis direction.

If total reflection is not possible even on the second surface Tj + 1, light leakage is relayed to the succeeding projection rows Pj + 2. By such a process, it can be expected that most of the light leakage component is turned on the second surface of any of the projection rows.

The intermediate output light beam MO (see FIG. 4) generated by the light guide section 10 is composed of the entire light traveling toward the light guide section 20 through the above-described path history.

Therefore, the angular distribution of the intermediate output light beam MO in the traveling direction generally depends largely on the blending ratio of the amount of light passing through each of the above-described path histories. However, here, since the main traveling direction of the input light beam IF is the + x-axis direction, the light beam group I plays a central role in the intermediate output light beam MO in FIG. 6, and the light beam group III or IV helps (light leakage recovery). Directivity (main traveling direction) substantially in the + y-axis direction is obtained.

In particular, as in the present embodiment, if the light guide portion 10 is formed in a substantially wedge shape and the direction changing surface 16 is inclined, it is easy to sufficiently secure the ratio of the light beam group I. In addition,
It is needless to say that the intermediate output light beam MO has some angular spread in consideration of the existence of the light beam group II and weak internal scattering (forward scattering).

The outline of the direction change operation has been described above. Various modifications (modifications) maintaining this operation are permitted. Hereinafter, these will be described as examples.

1. Modification on Shape of Projection Row (a) The angle α of the first surface of the projection row in the example shown in FIGS. 5 to 7 is α = 0. However, as shown in FIGS. 8 and 9, the angle of the first surface S of the projection row P may be α> 0 degrees or α <0 degrees. The shape as shown in FIG. 9 may be advantageous in making the angle of incidence on the first surface S close to vertical. However, as described above, it may be disadvantageous from the viewpoint of difficulty in production, mechanical stability, and the like. On the other hand, the shape as shown in FIG. 8 is generally easier to manufacture and has higher mechanical strength than the shape as shown in FIG.

(B) Tip B of the row of projections shown in FIGS.
Has a sharp shape. However, as shown in FIG. 10, the tip end of the projection row P may have a non-sharp shape B ′. By doing so, the projection row P is deformed or damaged by handling (assembly, transportation, operation, etc.) after manufacturing,
It is possible to prevent adverse effects such as characteristic deterioration. As shown by the broken line, it is more preferable to make it round.

(C) The bases of the rows of projections shown in FIGS. 5 to 7 are in contact with each other. However, as shown in FIG. 11, there may be a small interval between the adjacent projection rows Pj-1 and Pj as long as the light leakage recovery performance and the direction changing function are not impaired. Large gaps can reduce light collection performance and diversion capability.

2. Modification on Forming Form of Projection Row (a) In the example shown in FIGS.
And are integrally formed of the same material. But,
As shown in FIG. 12A, the substrate part 101 and the projection row 1
02 is a different material, for example, polymethyl methacrylate (PM
The light guide element 100 made of MA) and polycarbonate (PC) may be employed as the first-stage light beam extension / direction changing means.

(B) Further, as shown in FIG. 12 (b), a light guide element 110 may be employed by coupling a prism sheet 112 provided with a row of projections 113 to a substrate section 111. For bonding, an optical adhesive may be used.
In that case, the material of each part is as follows, for example.

The substrate 111 of the light guide element 110 = polymethyl methacrylate (PMMA / refractive index n = 1.49) The substrate of the prism sheet 112 = polyethylene terephthalate (PET film / refractive index n = 1.52) Protrusion row of prism sheet 112 = polymethyl methacrylate (PMMA / refractive index n = 1.49) Adhesive layer between substrate portion 111 and substrate portion of prism sheet 112 = epoxy adhesive / refractive index n = 1. 55) Thus, some refraction and reflection occur at the interface of each layer. Therefore, it is generally preferable that the difference in the refractive index is small as in the above-described material examples. Even if some refraction and reflection occur, the basic operation described with reference to FIGS. 6 and 7 (light leakage recovery and direction change)
Needless to say that is not lost.

3. Modification on Internal Scattering Ability of Light Guide Portion One or both of the substrate portion and the projection row of the light guide portion 10 may have an internal scattering capability. For example, a well-known light scattering light guide may be used as the material of the base.
However, a material (for example, Equation 1) that causes significant backscattering
Use of a scatterer of 00 nm) is not preferable because it weakens the directivity of the intermediate output light and lowers the light use efficiency. In general, it is preferable to provide a weak internal scattering power with little backscattering.

Now, the intermediate output light beam MO generated by the light beam extension and redirection function of the light guide unit 10 described above.
Is introduced into the light guide unit 20. The features of this embodiment are as follows.
As shown in FIG. 4, this light guide section 20 is also provided with a light beam extension / direction change function based on the same principle as that of the light guide section 10. With this function, the intermediate output light beam MO is converted into an output light beam OF having a cross-sectional area corresponding to the area of the emission surface 25 of the light guide unit 20.

The second light guide section 20 also has a substantially wedge shape as a whole, and the intermediate output light beam MO is introduced from the thick side.
The thinner end is referred to as the end 27 for convenience.

Back surface (second turning surface) 2 of light guide 20
Reference numeral 6 denotes an inclined surface extending at an angle of about several degrees with respect to the light exit surface 25, and a large number of projection rows 28 are formed thereon. The row of projections 28 of the turning surface 26 plays a decisive role in generating an output light beam IF in a substantially frontal direction (+ z-axis direction).

The light (intermediate output light beam MO) introduced into the light guide section 20 travels substantially toward the end face 27 while undergoing uniform scattering action (forward scattering). Positive turning by surface 26, almost + z
An output precursor light directed toward the axial direction is generated. The generation of the output precursor light is performed over the entire light guide unit 20 (depth and width), and a substantially uniform output precursor light beam is formed as a whole. The output precursor light beam is emitted from the emission surface 25 and becomes an output light beam OF.

Therefore, the cross-sectional area of the output light beam OF becomes larger than the intermediate output light beam MO, so that the change of direction and the expansion of the light beam can be achieved simultaneously. The turning action of the turning face 26 is in principle the same as the turning face 16 described above. Therefore, in addition to FIGS.
The turning action of No. 6 will be briefly described.

FIG. 13 shows a cross section of the second light guide section 20 as viewed from the + x-axis direction. As shown in the figure, the number of protrusions 28 provided on the direction changing surface 26 is Q1, Q2, Q3,... Qi in order from the side closer to the first light guide unit 10.
・ ・ ・ ・ ・

Each projection row Qi includes a first surface Vi and a second surface Wi, and extends substantially parallel to the x-axis. For each projection row Qi, the first surface Vi is closer to the first light guide 10 than the second surface Ti.
Close to.

The first surface Vi is a steep surface. That is,
The angle is almost perpendicular to the emission surface 25 that is substantially parallel to the y-axis direction. On the other hand, the second surface is an inclined surface that is not as steep as the first surface. The output light flux OF emitted from the emission surface 25 and output substantially in the + z-axis direction has the inclination angle.
(That is, an output precursor beam that is directed substantially in the + z-axis direction).

When the intermediate output light flux MO is introduced into the light guide section 20, most of the light flux MO enters one of the projection rows Qi. The scattering power given to the inside of the light guide section 20 depends on the projection row Q
It has the effect of increasing the chance of entry into i.

When light enters the projection row Qi, internal reflection occurs on the second surface Wi. The internally reflected light is the second surface W
The light is redirected in a direction determined according to the internal angle of incidence on i and the inclination angle of the second surface Wi, and becomes output precursor light heading to the emission surface 25. The output precursor light is emitted from the emission surface 25 and becomes a part of the output light beam OF.

As described above, when light enters the projection row Qi, internal reflection occurs on the second surface Wi. However, part of the incident light whose internal incident angle is smaller than the critical angle is internally reflected,
The rest leaks. In other words, the second surface Wi has a leakage function of generating such leakage light and an internal reflection function of generating light traveling toward the light guide unit 20.

As in the case of the direction changing surface 16 of the first light guide section 10, this leaking function does not lead to waste of light, and is achieved by successively adjacent projection rows Qj (j = 2, 3,...). An opportunity is provided to efficiently collect and convert again into output precursor light directed to the exit surface 25.

That is, the projection row Qj (j = 2, 3,...) Is linked to the preceding projection row Qi (i = 1, 2, 3,...) They are arranged to work together. Leading projection row Qj-
1 leaked from the second surface Wj-1 is collected through the first surface Vj of the succeeding projection row Qj and is internally incident on the second surface Wj. This internal incidence gives the recovered light a chance to change direction in the substantially + z-axis direction. If light leakage occurs again, most of the light is recovered from the first surface Vj + 1 of the next projection row Qj + 1 into the projection row Qj + 1.

A broken line H drawn along the direction changing surface 26 indicates an inner surface of a frame or a housing for mounting or housing the illustrated elements. This inner surface has a diffuse reflection property or a regular reflection property. As described later, a reflective member such as a silver foil may be interposed between the light guide 20 and the frame or the housing.
Such reflecting surface means may also contribute somewhat to light leakage recovery.

However, the recovery of the leaked light does not depend on the external reflection means, and the recovered light is given a chance to change its direction in almost the same direction (almost + z axis direction) as the light that does not leak. It should be noted that Due to this feature, for example, the collection efficiency can be easily increased and the light diffusion in a useless direction can be easily avoided as compared with the collection using a regular reflection sheet or a diffuse reflection sheet.

FIG. 14 is a diagram for specifically explaining the direction change and light leakage recovery by the projection array provided on the direction changing surface 26. The cross section of two adjacent projection arrays Qj-1 and Qj and the light beam The behavior is depicted in a format similar to FIG.

In FIG. 14, there is a first light guide 10 (not shown), so that the general light supply direction in the light guide 20 is from left to right. The projection rows Qj and Qj-1 have shapes including the first surfaces Vj-1 and Vj, and the second surfaces Wj-1 and Wj, respectively. First surface Vj-1, Vj and second surface Wj-1
, Wj form sharp tip portions Ej, Ej-1.

As described in the circle, the angles formed by the first surface V and the second surface W with respect to the vertical surface M (the direction of the arrow is a plus sign) with respect to an arbitrary row of projections Q are α and β ( Application of the definition in FIG. 6). The vertical surface MM is defined with respect to the extension surface of the emission surface 25 (see FIGS. 4 and 13), and in this example, the vertical surface MM is parallel to the xz plane.

Α = 0 degrees and β = 48 degrees added in FIG.
This is a preferred example of the values of the angles α and β. Generally, the angle α is preferably about 0 to 10 degrees. Although α <0 degrees is acceptable, it may be inferior in terms of manufacturing difficulty, mechanical strength, and the like. The inclination angle β is designed according to a desired output direction (a main traveling direction of the output precursor light beam). Of course,
The refractive index n of the material (eg, n = 1.49) is also considered. In the normal case, the tilt angle β is in the range from 30 degrees to 60 degrees.

The basic cooperation of the projection rows Qj-1 and Qj-1 is the same as in the case of FIG. That is, the second surface Wj-1 of the projection row Qj-1 is represented by the point AA. Point AA is the second surface W
j-1 and at a position close to the base of the projection row Qj-1 (that is, far from the tip Bj-1).

[0108] A perpendicular line to the second surface Wj-1 at the point AA is defined as NN (broken line). Symbol C represents a critical angle, which is 42 degrees in this example. Most of the internally incident light rays to the point AA can be roughly classified as follows according to the internal incident angle (the sign of the light ray group is shared) as in the case of FIG.

Light group I: a light group in a certain range where the internal incident angle is sufficiently smaller than the critical angle C. Many of these light rays leak from the second surface Wj-1 and enter the first surface Vj of the succeeding projection row Qj. Here, since the first surface Vj is steep,
Most of the leaked light is introduced into the succeeding projection row Qj through the first surface Vj (collection of the leaked light). Then, the subsequent projection row Qj
At the second surface Wj.

The internal angle of incidence on the second surface Wj is given by
It is larger than the internal incidence angle to 1 (previously experienced). As a result, the ray group I easily satisfies the condition of total internal reflection in the internal reflection on the second surface Wj, and is turned into a ray group toward the exit surface 25 (see FIGS. 4 and 13) as shown by I '. Is done. In this example, the ray group I ′ is output substantially in the + z-axis direction.

Ray group II: A ray group whose internal incident angle is smaller than the critical angle C but does not belong to ray group I. A significant portion of these rays escape from the second surface Wj-1 and form
j on the first surface Vj. Since the first surface Vj is steep, much of the leaked light is introduced into the succeeding projection row Qj through the first surface Vj (collection of light leakage).

However, it is difficult to internally enter the second surface Wj of the succeeding projection row Qj, and it is roughly a light group II '. Ray group II 'has not undergone any significant turning.
Therefore, most of the light is totally reflected when the light is internally incident on the light exit surface 25, and a chance to be incident again on the second surface of another projection row is given.

The internal incident angle at that time may be slightly larger than the internal incident angle on the second surface Wj-1 in consideration of refraction on the second surface Wj-1 and the first surface Vj. As a result, like the ray group I, a chance to be turned is provided.

Ray group III: A ray group whose internal incident angle is larger than the critical angle C. These rays are totally reflected by the second surface Wj-1 and form a ray group III 'traveling in the + z-axis direction.

The above is the basic form of the direction change action with light leakage recovery, but the action may vary depending on the angles α and β and the refractive index n. For example, if the angle β (= 48 degrees) is corrected downward, total reflection on the second surface Wj becomes difficult to occur. Even in this case, a chance of a change in direction due to total reflection is provided in the subsequent projection row Qj + 1 and the like.

FIG. 15 shows an example of such a situation in the same format as in FIG. Referring to FIG. 15, the cross section of three adjacent projection rows Qj-1, Qj, Qj + 1 and the behavior of light rays are depicted. In FIG. 15, the angle of the first surface is α = 0.
The angle of the second surface is β = 40 degrees. This value is an example that gives a situation in which the collection is performed in cooperation of three parties.

The ray group IV represents a ray group in a certain range where the internal incident angle is sufficiently smaller than the critical angle C (substantially corresponds to the ray group I described above). Many of these rays are on the second surface Wj-
1 and enters the first surface Vj of the succeeding projection row Qj. Since the first surface Vj is steep, much of the leaked light is introduced into the succeeding projection row Qj through the first surface Vj. Then, the light is internally incident on the second surface Wj of the succeeding projection row Qj.

This internal incidence has a slightly larger internal incidence angle than internal reflection at the second surface Wj-1. However, since the angle β is small, the internal reflection on the second surface Wj is not sufficient to satisfy the condition of total reflection.
As a result, most of the light rays leak again from the second surface Wj and enter the first surface Vj + 1 of the succeeding projection row Qj + 1. Since the first surface Vj + 1 is steep, most of the leaked light is internally incident on the second surface Wj + 1 of the projection row Qj + 1 via the first surface Vj + 1.

This internal incidence has a slightly larger internal incidence angle than internal reflection at the second surface Wj. In this example, as a result, total reflection occurs on the second surface Wj + 1. The light beam group IV 'is output by the direction change accompanying this total reflection. In this example, the light beam group IV 'is output substantially in the + z-axis direction.

If total reflection is not possible even on the second surface Wj + 1, light leakage is relayed to the succeeding projection row Qj + 2. By such a process, it can be expected that most of the light leakage component is turned on the second surface of any of the projection rows.

The output precursor light beam (output light beam MO before emission) generated by the light guide section 20 is composed of the entire light traveling toward the emission surface 25 via the above-described path history.

Accordingly, the angular distribution of the output precursor light beam in the traveling direction generally depends largely on the blending ratio of the amount of light passing through each of the above-described path histories. Here, the intermediate output light beam MO
13 is a + y-axis direction.
, The beam group I plays a central role in the output precursor beam, which is assisted by the beam group III or IV (light leakage recovery), and
Directivity (main traveling direction) in the z-axis direction is obtained. However, if the existence of the light beam group II and the weak internal scattering (forward scattering) are taken into consideration, it is needless to say that the output precursor light beam is slightly angularly spread.

The above is an outline of the turning action of the turning face 26, but various deformations (modifications) maintaining this action are permitted as in the case of the turning face 16 described above. is there. That is, the “modification on the shape of the projection row”, the “modification on the form of the projection row”, and the “modification on the internal scattering power of the light guide section” described with reference to FIGS. The light guide 20 to the direction changing surface 26 can be applied mutatis mutandis.

[Second Embodiment] FIG. 16 shows a second embodiment of the present invention.
It is a perspective see-through view explaining the principal section composition of the surface light source device concerning an embodiment. As shown in the drawing, the surface light source device SFV2 of the present embodiment also has a light supplier L constituting a primary light supply unit and a first-stage light beam extension, similarly to the surface light source device SFV1 of the first embodiment. -Direction changing means and second stage luminous flux expansion-
Direction changing means. However, the same configuration as that of the first embodiment is adopted for the light supply unit L and the first-stage light beam extension / direction changing means, while the second-stage light beam expansion / direction changing device is provided with a light guide unit. 20 (see FIG. 4), a light guide section 30 is employed, and a prism sheet PS is further arranged along an emission surface 35 of the light guide section 30 to form a rear surface 36.
The reflection sheet RF2 is arranged along the line.

The details of the operation of the light supplier L and the first light guide 10 are as described in the first embodiment, and will not be repeated here. As shown in FIG. 18, the input light beam IF having a small cross-sectional area supplied from the light supply unit L is subjected to the first-stage light beam expansion-direction changing process to become an intermediate output light beam MO. The intermediate output light beam MO is efficiently used by the large number of protrusion rows (combination of the steep first surface S and the non-steep second surface T) 18 formed on the direction changing surface 16 of the light guide unit 10 without waste. Generation with high directivity (almost in the + y-axis direction) is as described in the first embodiment.

The first light guide 1 described in the first embodiment is used.
It goes without saying that various modifications (modifications) regarding 0 are also applicable in the present embodiment. That is, “modification related to the shape of the projection row”, “modification related to the form of formation of the projection row”, “modification related to the internal scattering power of the light guide section” described with reference to FIGS. Is similarly applicable to the first light guide unit 10 in the present embodiment.

The intermediate output light flux MO generated by the first light guide 10 is input to the second light guide 30. The second light guide unit 30 in the present embodiment has a wedge plate shape as a whole, and receives the intermediate output light flux MO from the thick side thereof, and the second light guide unit 30 and the light guide unit 30 Are arranged so that they contact each other at the boundary BR without any step.
This is the same as in the embodiment.

The light guide 30 differs from the light guide 20 employed in the first embodiment in that the rear surface 36 has a flat slope.

That is, the back surface 36 of the light guide section 30 is
5 is a flat inclined surface extending at an angle of about several degrees. Further, a reflection sheet RF2 is arranged along the back surface 36. The reflection sheet RF2 is a member having a specular or diffuse reflection surface, and may be omitted in some cases. However, unlike the first embodiment in which the light guide unit 20 including the projection row 28 having the cooperative light collection function is used, the light guide unit 30 has a function of collecting the light leaked from the back surface 26 once. Since there is no such sheet, it is preferable that the reflection sheet RF2 be disposed.

Also in the present embodiment, the thickness of the thickest part of the second light guide 30 (substantially along the z-axis) is substantially equal to the width of the first light guide 10. Also, the width of the light guide 30 (almost x
(The size along the axis) is approximately equal to the length of the light guide 10. The depth (the size substantially along the y-axis) of the light guide 30 is larger than the thickness (the size substantially along the y-axis) of the light guide 10.

The light guide section 10 and the light guide section 30 may be independent blocks or one block. In the case of a one-body structure, the two light guide portions 1 may be bonded by using a light-transmitting adhesive to those manufactured in separate blocks, but by applying an injection molding technique or the like.
A molded body having a shape obtained by combining 0 and 20 may be obtained.

In the case of a separate structure, an air gap may exist between the light guide 10 and the light guide 30.

The behavior when light is supplied to the light guide section 30 from the thick side is basically the same as that of a known wedge-shaped scattering light guide plate. That is, the light (intermediate output light beam MO) introduced into the light guide unit 30 has a uniform scattering action (forward scattering).
While traveling, the vehicle substantially advances toward the end surface 37. In the process, the internal light is repeatedly incident on the output surface 35 and the rear surface 36,
Many are reflected. The light leaked from the back surface 36 is
The light is reflected by the reflection sheet RF2 and returned into the light guide unit 30.

As is well known, at the time of internal incidence on the exit surface 35, components whose incident angle is equal to or larger than the critical angle are totally reflected.
Is emitted from. As is well known, the main traveling direction of the emitted light OB is greatly inclined toward the end 37 (+ y-axis direction).

It is possible to use this emitted light OB as it is or after weakly diffusing it with a light diffusing sheet, and then use it for illumination light for a liquid crystal display panel or the like. However, as in this embodiment, a prism sheet PS is arranged. It is preferable that the main traveling direction of the outgoing light OB is corrected substantially in the front direction (+ z direction) to obtain the output light beam OF.

As shown in FIG. 16 on an enlarged scale, the prism sheet PS corrects the traveling direction of the obliquely emitted light OB substantially in the front direction (+ z-axis direction) by the well-known action of a large number of prism cuts PR. . The output light beam OF illuminates, for example, a liquid crystal display panel (not shown) arranged so as to overlap the surface light source device SFV2. Various arrangements and types of the prism sheet PS are known, and these can be applied as appropriate.

For example, contrary to the case of FIG. 16, the prism cut formation surface may be arranged outward (+ z side) in some cases. Further, a so-called asymmetric prism sheet having an asymmetric prism cut or a double-sided prism sheet having prism cut forming surfaces (orthogonal on both sides) may be employed.

Also in the present embodiment, the first-stage light beam expansion-direction change for the input light beam IF having a small cross-sectional area from the light supply unit L using a small light emitting source such as an LED is performed as described above. Due to the direction change of the row of protrusions and the light leakage collecting action described in the first embodiment), the light guide is efficiently performed, and the second light guide section 30 is formed.
Output light MO with high directivity matched to the depth direction
Is generated.

Therefore, the second light guide section 30 to which this is input is provided.
Can provide bright illumination light. In particular, by arranging the direction correcting element along the emission surface, it is possible to obtain a bright output light beam OF (an output light beam having characteristics similar to those of the first embodiment) directed substantially in the front direction.

[Third Embodiment] FIG. 17 shows a third embodiment of the present invention.
It is a perspective see-through view explaining the principal section composition of the surface light source device concerning an embodiment. As shown in the figure, the surface light source device SFV3 of the present embodiment also has the same light supply device L as primary light supply means, as in the surface light source devices SFV1 and SFV2 of the first or second embodiment, It has a first-stage light beam extension / direction changing device and a second-stage light beam expansion / direction changing device.
However, the same configuration as that of the first and second embodiments is adopted for the light supply unit L and the first-stage light beam expansion-direction changing means, whereas the second-stage light beam expansion-direction changing device is used. , Light guide 10 (see FIG. 4), light guide 30 (FIG. 1)
6) is employed instead. Also, the second
As in the case of the embodiment, the prism sheet PS is arranged along the emission surface 45 of the light guide 40, and the reflection sheet RF2 is arranged along the back surface 46.

The details of the operations of the light supplier L and the first light guide 50 are the same as those described in the first embodiment, and will not be repeated here. However, in the present embodiment, since the first light guide unit 50 is clearly specified as being separate from the second light guide unit 40, the intermediate output light beam MO is incident via the air gap AR. The light is introduced into the light guide 40 from the surface 41.

As for the second light guide section 40, a large number of projection rows 48 are formed on the back surface 46 so as to extend in the depth direction of the light guide section 40. An outline of the behavior of light, including the operation of the projection array 48, will be described.

As shown in FIG. 18, the input light beam IF having a small sectional area supplied from the light supply device L is supplied to the first light guide section 5.
At 0, the first stage light beam expansion-direction change processing is performed, and an intermediate output light beam MO is obtained. The light guide 50 has the same structure and operation as the light guide 10 except that the light guide 50 is clearly separate from the second light guide 40.

Therefore, the intermediate output light beam MO is formed by a large number of projection rows (combination of the first surface S which is not sharp and the second surface T which is not notched) formed on the direction changing surface 56 of the light guide 50.
As in the first embodiment, it is generated with high directivity (almost in the + y-axis direction) by use of the function 58 without waste.

The first light guide 1 described in the first embodiment is used.
It goes without saying that various modifications (modifications) regarding 0 are also applicable in the present embodiment. Intermediate output light flux M generated by first light guide unit 50
O is input from the incident surface 41 to the second light guide 40 through the air gap AR. The second light guide section 40 in the present embodiment has a wedge plate shape as a whole, and receives the intermediate output light flux MO from the thick side thereof.

The rear surface 46 of the light guide 40 is provided on a general surface extending at an angle of about several degrees with respect to the exit surface 45.
In a depth direction (substantially parallel to the y-axis).

It is known that the row of projections 48 formed in such an orientation has a direction correcting function of narrowing the spread of the traveling direction of light in the left-right direction when viewed from the incident surface 41.
In the present embodiment, the directivity (substantially + y-axis direction) of the intermediate output light MO is further enhanced after the light is introduced into the light guide unit 40 by this action.

That is, as described with reference to FIG.
The intermediate output light beam MO includes one derived from the light beam group indicated by the symbol II ′ in FIG. Such a ray group is considered to be internally propagated light having a direction component largely deviated from the + y-axis direction in the light guide unit 40. Many parts of such internally propagated light are given a chance to enter the back surface 46 directly or after being reflected by the exit surface 45 or scattered by internal scattering power.

Here, since the projection row 48 is formed on the rear surface 46, any of the projection rows 48 is formed at the time of internal incidence.
Incident on one of the slopes, and a considerable portion is internally reflected. Accordingly, a part of the direction component largely deviating from the + y-axis direction is corrected to a direction component approaching the + y-axis direction. Through this correction operation wp, when the light is emitted from the emission surface 45, the light output corrected in the front direction with respect to the xz plane as compared with the case where the back surface of the second light guide is flat as in the second embodiment. Light emission is obtained. As a result, the directivity of the output bundle OF is improved both in the xz plane. If the prism sheet PS is arranged in the same manner as in the second embodiment, an output bundle OF having excellent directivity in both the yz plane and the xz plane can be obtained. The reflection sheet RF2 arranged along the back surface 46 includes:
A member having a specular or diffuse reflection surface, which may be omitted in some cases. However, in this embodiment, since the light leakage collecting function is poor, the reflection sheet RF2 is preferably disposed.

Note that, also in the present embodiment, the second light guide 40
Has a thickness (substantially along the z-axis) that is approximately equal to the width of the first light guide 50. Further, the width (the size substantially along the x-axis) of the light guide 40 is substantially equal to the length of the light guide 50. The depth (the size substantially along the y-axis) of the light guide 40 is larger than the thickness (the size substantially along the y-axis) of the light guide 50.

The output light beam OF illuminates, for example, a liquid crystal display panel (not shown) arranged so as to overlap the surface light source device SFV3. As in the case of the second embodiment, various arrangements and types of prism sheets PS are known, and these can be applied as appropriate.

As described above, also in this embodiment, L
First-stage luminous flux expansion for an input luminous flux IF having a small cross-section from a light supplier L using a small light-emitting source such as an ED
The direction change is efficiently performed by the direction change of the projection row and the light leakage collecting action described above (described in the first embodiment),
Intermediate output light MO that is rich in directivity and is aligned in the depth direction of the second light guide unit 40 is generated.

Therefore, the second light guide section 40 to which this is input is provided.
Can provide bright illumination light. In particular, the output bundle OF having excellent directivity (almost in the front direction) in the xz plane can be obtained by the above-described operation of the rear surface 46 provided with the projection rows 48. If the prism sheet PS is further combined, yz is obtained. Excellent directivity (almost in the front direction) can also be achieved in a plane.

[Measurement Example] In order to confirm the performance of the first stage light beam expansion-direction change, which is a basic feature of the present invention,
For some examples, the angular distribution of the intensity (luminance) of the emitted light was measured.

(Example 1 = see FIGS. 16, 19, 20, etc.);
This measurement is based on the function of the light guide section with the projection row, which is used for the first stage luminous flux expansion-direction change (excellent directivity in almost + y direction).
Was carried out to confirm how is reflected on the output light flux OF.

Prototypes of the light guide section 50 and the light guide section 30 (adopting a separate structure) used in the arrangement of FIG. 16 (third embodiment) were manufactured. These are referred to as “prototype 1” and “prototype 2” for convenience. Further, a reference product having the same material and size as the prototype 1, but having no projection rows on the back surface and flat was manufactured. First, the angular distribution of the emitted light intensity was measured using the prototype 1 and the prototype 2 in the arrangement of FIG. 16 (third embodiment).

The prototypes 1 and 2 and the reference product are light-scattering light guides of the same material composition, and the matrix is PMMA (polymethyl methacrylate; refractive index = about 1.49), and 0.05 wt% is contained therein. (% By weight), a molded article in which silicon resin fine particles (diameter: 7 μm) were uniformly dispersed was prepared.
The design angles of the slopes of the projection rows on the rear surface of the prototype 1 (see slopes S and T in FIG. 6) were set to α = 0 degrees and β = 48 degrees.

The sizes of the prototype 1 and the reference product were as follows: length (x-axis direction) = 43 mm / width (z-axis direction) = 2.5
mm / thickness (y-axis direction) = 2.5 mm for the thickest part and 0.4 mm for the thinnest part. The size of the prototype 2 is: depth (y-axis direction) = 43 mm / width (x-axis direction) = 43 mm
/ Thickness (z-axis direction) = 2.5 mm thickest part, 0.4 thinnest part
mm.

The measurement was performed on the light emitted from each central part of the emission surface 35 of the light guide 30. As the light supplier L, a commercially available LED light source was used alone. The results are shown in FIGS.
0 are shown by curves CV1 to CV4 in each graph. here,
The specific measurement contents represented by the curves CV1 to CV4 are as follows.

CV1 / CV3: Prototype 1 was converted to light guide section 10,
Prototypes 2 are each regarded as light guide sections 30 and arranged in the posture shown in FIG. 16, and light supply devices L (LE
Light was supplied from D), and an output light beam OF was output through the prism sheet PS. Then, this output light beam OF
, The angle dependence of the luminance (emission intensity) in the zx plane and in the zy plane was measured. The former result is CV1 and the latter result is CV3.

CV2 / CV4: The reference product was assumed to be the light guide section 10 instead of the prototype 1, while the prototype 2 was assumed to be the light guide section 30, and was arranged in the posture shown in FIG. Further, the output surface of the prototype 1 (the output surface of the intermediate output light beam MO is z
x plane) and the entrance surface of the light guide 30 (intermediate output light flux MO
Of the intermediate output light beam M
A prism sheet (not shown) for correcting the main traveling direction of O in the + y-axis direction was arranged, and the same measurement as that for obtaining CV2 / CV4 was performed. That is, light was supplied from the light supplier L (LED) in the same manner as in FIG. 16, and the output light beam MO was output through the prism sheet PS.

With respect to the output light beam OF, the angle dependence of luminance (emission intensity) in the zx plane and the zy plane was measured. The former result is CV2, and the latter result is CV4.

Here, the horizontal axis of the graph of FIG.
(See coordinate systems in FIGS. 4, 16 and 17),
The luminance is plotted on the vertical axis. 0 degrees corresponds to the + z-axis direction. The horizontal axis of the graph in FIG. 20 represents the angle b (see the coordinate system in FIGS. 4, 16, and 17), and the luminance is plotted on the vertical axis. 0 degrees corresponds to the zy-axis direction.

The following can be understood from these results. (1) Comparing the curves CV1 and CV2, the former peak is higher and sharper than the latter peak.
From this, regarding the first stage luminous flux expansion-direction change,
According to the invention of the present application, if a light guide section having a projection row (a combination of a steep slope S and a non-steep slope T) formed on the back surface is employed, an output light beam OF having better directivity in the zx plane can be obtained. It is understood that.

Such a characteristic is obtained when the intermediate output light flux MO is x
This is considered to be due to having excellent directivity in the y-plane. Note that the peak position of the curve CV1 is shifted from 0 degree to about 15 degrees, which is considered to be mainly due to a manufacturing error of the prototype 1. This shift can be reduced by fine adjustment of the angles α and β (particularly, fine adjustment of the angle β).

(2) Comparing the curves CV3 and CV4, there is no significant difference between the former and the latter, including the peak height, position and sharpness. From this, the first stage luminous flux extension-
Regarding the direction change, according to the present invention, even if a light guide section having a projection row (combination of slopes S and T) formed on the rear surface is employed, the directivity of the output light beam OF in the yz plane is hardly affected. Understood.

(Example 2 = See FIGS. 21 and 4);
The operation of the first embodiment which is the basic form of the present invention (almost + z
(The generation of an output light beam OF rich in directivity in the direction).

In the first embodiment shown in FIG. 4, the prototype 1 is adopted as the light guide 10 while the light guide 20 is used.
With respect to, a prototype 3 was prepared using the same material and the same size as the prototype 2 (excluding the protrusion on the back surface). The design angles of the slopes of the row of projections on the rear surface of the prototype 3 (see slopes S and T in FIG. 6) were set to α = 0 degrees and β = 48 degrees, as in the prototype 1.

The size of the prototype 3 is width (x-axis direction) = 4.
3 mm / thickness (z-axis direction) = thickest part 2.5 mm, thinnest part 0.4 mm / depth (y-axis direction) = 43 mm.

The measurement was performed on the light emitted from the central portion of the emission surface of the prototype 3 (see the emission surface 25 in FIG. 4). As the light supplier L, a commercially available LED light source was used alone. The results are shown by curves CV5 and CV6 in the graph of FIG. Here, the specific measurement contents represented by the curves CV5 and CV6 are as follows.

CV5: Prototype 1 is light guide unit 10, Prototype 3
4 was arranged in the posture shown in FIG. 4, light was supplied from the light supplier L (LED) in the same manner as in FIG. 4, and the output light beam OF was output.

Then, the angle dependence of the luminance (emission intensity) of the output light beam OF in the zx plane and the zy plane was measured. The former result is CV5, the latter result is CV
6.

Here, the horizontal axis of the graph of FIG.
Represents an angle a, and CV6 represents an angle b (see the coordinate system in FIGS. 4, 16, and 17). CV
For both 5 and CV6, 0 degrees corresponds to the + z-axis direction. The luminance is plotted on the vertical axis (CV5, CV common).

The following is understood from the results. (1) It can be seen from the curves CV5 and CV6 that in the arrangement of the first embodiment, an excellent output light beam OF can be obtained both in the zy plane and in the zy plane. In particular, it is noted that most of the outgoing light is collected around the front side without the prism sheet in the zy plane.

(2) The peak position of the curve CV5 deviates from 0 degrees by about 15 degrees. This is considered to be mainly due to a manufacturing error of the prototype 1. Angles α and β of prototype 1
(Particularly, fine adjustment of the angle β) can reduce this deviation.

(Example 3 = See FIG. 16, FIG. 22, FIG. 23, etc.): This measurement is used for the first-stage light beam expansion-turning to confirm the light leakage collecting effect of the light guide with projections. It went to.

In the above (Example 1), as shown in FIG. 23, the reflection sheet RF1 was additionally arranged in the arrangement where the curve CV1 was obtained, and the same measurement was performed under the same conditions as when the curve CV1 was obtained. CV8 was obtained. Regular reflection silver foil was used for the reflection sheet RF1. The specific measurement contents represented by the curves CV7 and CV8 are as follows.

CV7 (= same as CV1); above (Example 1)
As described above, the prototype 1 is regarded as the light guide unit 50, and FIG.
And the light supply device L in the same manner as in FIG.
Light was supplied from the (LED), and the angle dependence of the luminance (emission intensity) of the output light beam OF in the zx plane was measured. CV8; In the arrangement where CV7 (= same as CV1) is obtained,
The reflection sheet RF1 is additionally arranged, and the output light flux OF under the same conditions.
The angle dependence of the brightness (emission intensity) in the zx plane was measured. Here, the horizontal axis of the graph of FIG. 22 represents the angle a, and the luminance is plotted on the vertical axis. 0 degrees corresponds to the + y-axis direction.

The following can be understood from the results. (1) Comparing the curves CV7 and CV8, the former and the latter have no significant difference including the peak height, position and sharpness. From this, according to the present invention, when the light guide section having the projection rows (combinations of the slopes S and T) formed on the back face is adopted as the first-stage light beam extension / direction changing section, the reflection sheet is formed along the back face. It can be seen that light loss due to light leakage hardly occurs even without disposing. This confirms that the light guide portion with the row of protrusions has a sufficient light leakage collecting action.

Even if the light guide section having the projection rows (combinations of the slopes S and T) formed on the back surface is employed in the second-stage light flux extension / direction change section, the same light leakage recovery action can be expected. it is obvious.

[Other Modified Arrangement Examples] In the embodiment described above, the light guide section (first light guide section) in the first-stage light beam expansion / direction changing means is constituted by one wedge-shaped section. Correspondingly, the input light beam is supplied from one light supply device. However, this is not intended to limit the present invention.

For example, as shown in FIGS. 24 and 25,
The light guide section in the first stage light beam extension / direction changing means may be divided and connected to a plurality of sections. in this case,
A light introduction surface is provided for each section, and a plurality of light supply devices are provided for supplying light thereto. The intermediate output beam will be provided as the combined output of these sections.

In the example shown in FIG. 24, the one used in any of the first to third embodiments (the size may be different) is adopted as the second-stage light guide, and along the one side thereof, 3
The first section of the light guide section 60 is configured by connecting and connecting the three sections. Each section includes one wedge-shaped light guide block 61, 62, 63 and a light supply L10, L20,
L30.

Each light supplier L10, L20, L30
Light guide blocks 61, 6
2, 63 are stuck to the end surface (light introduction surface) on the thickest side. Each of the light supply units L10, L20, and L30 is provided with input light fluxes IF1 and IF parallel to each other (almost in the + x-axis direction).
2. Supply IF3 in each section.

On the back of each light guide block 61, 62, 63, the first light guide 10 used in the first to third embodiments,
Protrusion rows are formed in the same manner as 50. Accordingly, the intermediate output light is efficiently formed by the same operation as in the first to third embodiments, and the whole of the intermediate output light has directivity (almost + y-axis direction).
To provide an intermediate output light flux MO that is excellent.

In the example shown in FIG. 25 as well, the one used in any of the first to third embodiments (the size may be different) is adopted as the second stage light guide. The two sections are connected and arranged along one side to constitute the first-stage light guide section 70. These sections are composed of a pair of wedge-shaped light guide blocks 71 and 72 that are opposite to each other and light supplies L40 and L50. Each light supply L4
Reference numerals 0 and L50 each include one to several LEDs, and are attached to the end surfaces (light introduction surfaces) of the light guide blocks 71 and 72 on the thickest side.

[0187] The light supply units L40 and L50 supply the input light beams IF4 and IF5 in the respective sections. However, the supply direction of the input light beam IF4 is substantially in the + x-axis direction, whereas the supply direction of the input light beam IF5 is substantially in the -x-axis direction.

On the back surface of each of the light guide blocks 71 and 72, a projection row is formed in the same manner as the first light guide portions 10 and 50 used in the first to third embodiments. Therefore, the intermediate output light is efficiently formed by the same operation as the first to third embodiments, and the entire intermediate output light MO having the excellent directivity as a whole is obtained.
I will provide a.

As illustrated in FIGS. 24 and 25, the configuration in which a plurality of sections and a plurality of light supply units are combined uses a relatively large-sized light guide section as the second-stage light beam extension / direction changing means. Therefore, a surface light source device having a relatively large size can be provided under the condition that a point light source such as an LED is used as a primary light source. In addition, application to a liquid crystal display device of a size corresponding to that is also possible.

[0190]

According to the present invention, even if a light source having a small light-emitting area, such as an LED, is adopted as the light supply means, the light beam can be expanded and turned in a two-stage configuration, and the first-stage light beam can be obtained. For example, LE can be extended and turned by using a light guide with a row of projections having both a light leakage recovery function and a direction changing function.
By using a light source having a small light emitting area such as D as the light supply means, a surface light source device that can obtain a uniform and efficient output is provided.

Also, in the second stage light beam expansion and direction change,
By using a light guide unit with a row of projections that has both a light leakage recovery function and a direction change function, or by using a direction correcting element such as a prism sheet in the desired direction of the light emitted from the emission surface, A surface light source device that outputs light with excellent directivity in the front direction can be provided.

Further, through these advantages, a liquid crystal display device of a surface light source device employing a light source having a small light emitting area such as an LED as a light supply means, particularly, a mobile device such as a mobile phone, an electronic organizer, and a portable personal computer. The applicability of the attached liquid crystal display to backlighting or front lighting can be remarkably improved.

[Brief description of the drawings]

FIG. 1 is a schematic view of a conventional example in which a surface light source device using a point light source is applied to backlighting of a liquid crystal display.

FIG. 2 is a top view of the light exit surface of the light guide plate viewed from the direction of arrow A in FIG.

FIG. 3 is a diagram illustrating a conventional example in which light from a point light source is transmitted through a number of optical fibers and supplied to a light guide plate.

FIG. 4 is a perspective perspective view illustrating a main part configuration of the surface light source device according to the first embodiment of the present invention.

FIG. 5 shows a cross section of the first light guide section 10 viewed from the + z direction.

FIG. 6 is a view for specifically explaining a direction change and light leakage recovery by a projection row, and two adjacent projection rows Pj-
1, the cross section of Pj and the behavior of light rays are depicted.

FIG. 7 is a diagram illustrating the cross section of three adjacent projection rows Pj-1, Pj, and Pj + 1 and the behavior of light rays.

FIG. 8 is a diagram illustrating an example in which the angle of the first surface S of the projection row P is set to α> 0 degrees.

FIG. 9 is a diagram illustrating an example in which the angle of the first surface S of the projection row P is set to α <0 degrees.

FIG. 10 is a diagram illustrating an example in which a tip end of a projection row P is not sharp.

FIG. 11 is a diagram illustrating an example in which a small interval is provided between adjacent projection rows Pj-1 and Pj.

FIG. 12A is a diagram illustrating an example in which a light guide element 100 in which a substrate unit 101 and a row of protrusions 102 are formed of different materials is used as a first-stage light beam expanding / direction changing unit. (B) shows a prism sheet 1 having a projection row 113.
FIG. 12 is a diagram for explaining that a light guide element 110 is adopted by combining the light guide element 12 with a substrate part 111.

FIG. 13 is a diagram illustrating a cross section of the second light guide unit 20 viewed from the + x-axis direction.

FIG. 14 is a view for specifically explaining a direction change and light leakage recovery by a row of projections provided on a direction change surface 26. FIG. 14 shows a cross section of two adjacent row of projections Qj-1 and Qj and behavior of light rays. It is drawn in the same format as 6.

FIG. 15 shows three adjacent projection rows Qj-1, Qj, and Qj + 1.
FIG. 3 is a diagram depicting the cross section of the light beam and the behavior of light rays.

FIG. 16 is a perspective perspective view illustrating a main configuration of a surface light source device according to a second embodiment of the present invention.

FIG. 17 is a perspective perspective view illustrating a main part configuration of a surface light source device according to a third embodiment of the present invention.

FIG. 18 is a diagram conceptually showing how a substantially uniform intermediate output light beam MO is formed.

FIG. 19 is a graph showing measurement results of Measurement Example 1.

FIG. 20 is another graph showing the measurement results of Measurement Example 1.

FIG. 21 is a graph showing measurement results of Measurement Example 2.

FIG. 22 is a graph showing measurement results of Measurement Example 3.

FIG. 23 is a diagram illustrating a case where a reflection sheet RF1 is additionally disposed on the back side of the first-stage light guide unit in connection with Measurement Example 3.

FIG. 24 is a view for explaining an example in which the light guide section in the first stage light beam extension / direction changing means is divided and connected to a plurality of sections.

FIG. 25 is a view for explaining another example in which the light guide section in the first stage light beam extension / direction changing means is divided and connected to a plurality of sections.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 light guide plate 2 light guide plate incident end face 3 reflector 4, PS prism sheet 4A smooth outer surface of prism sheet 5 light guide plate output surface 6 back surface of light guide plate 10, 50, 60, 70 light guide section (first light guide section) Light part) 11, 51 Light introduction surface 20, 30, 40 Light guide part (second light guide part) 16, 26, 36 Back face of light guide part 17, 27, 37 Numerous projection rows (Pi) 18, 58 Numerous projection rows (Pi) 25, 35, 45 Outgoing surface of second light guide section 28 Numerous projection rows (Qi) 48 Projection rows 61 to 63, 71, 72 Light guide blocks F1 to F9 Optical fiber IF Input light flux L , L1 to L3, L10, L20, L30, L40, L
50 Small size light source LP Liquid crystal panel LS Polarization separation sheet MO Intermediate output light flux OF Output light flux RF1, RF2 Reflection sheet S1-S3, SS1-SS9 Local high brightness area SFV1-SFV1 Surface light source device

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G02F 1/13357 F21Y 101: 02 // F21Y 101: 02 G02F 1/1335 530 (72) Inventor Eisaburo Higuchi Tokyo 2-9-9 Hiratsuka, Shinagawa-ku, Tokyo F-term (reference) in Nitto Jushi Kogyo Co., Ltd. 2H038 AA52 AA55 BA01 2H091 FA23Z FA31Z FA45Z FD03 LA16 LA18

Claims (14)

[Claims] 1. A light supply means using at least one point light source as a light emitting source, a first-stage light beam expanding / redirecting means including a first light guide section, and a second light guide section. A surface light source device comprising: a second-stage light beam expanding / redirecting means: the first light guide portion has a major axis along a first direction and a second axis perpendicular to the first direction. And a third direction perpendicular to both the first direction and the second direction.
And a light introduction surface for receiving light supplied by the light supply means and traveling substantially along the first direction, and the first through the light introduction surface. A first turning surface for changing the traveling direction of the light introduced into the light guide portion of the second light guide portion to a direction substantially along the second direction, and generating an intermediate output light beam toward the second light guide portion. A plurality of projection rows P1, P2, P3.
.. Are provided, and each projection row Pi (i = 1, 2, 3,...) Extends substantially along the third direction and is relative to the introduction surface. A first surface Si that is close and steep, and a second surface Ti that is relatively far and inclined with respect to the introduction surface. The second surface Ti has an internal reflection function for generating a part of the intermediate output light beam; The projection line Pj (j = 2, 3,...) Has a leakage function of generating leakage light from the projection line Pi, and the leakage line Pj (j = 2, 3,...) Leaks from the second surface Tj-1 of the preceding projection line Pj-1. Light is collected through the first surface Sj and cooperatively arranged for internal incidence on the second surface Tj; the second light guide portion is substantially along the first direction. And has a depth substantially along the second direction and a thickness substantially along the third direction, and is provided from the first light guide portion. A second turning surface that changes the traveling direction of the inserted intermediate output light beam to a direction substantially along the third direction to generate an output precursor light beam, and converts the output precursor light beam to approximately the third direction. And an emission surface for emitting light toward the second direction-changing surface. A large number of projection rows Q1, Q2, Q3.
Are provided, and each of the projection rows Qi (i = 1, 2, 3,...) Extends substantially along the first direction and the first light guide. A first surface Vi that is relatively close and steep with respect to the portion, and a second surface Wi that is relatively far and inclined with respect to the first light guide portion, wherein the second surface Wi forms a part of the output precursor light flux. Has a function of generating internal reflection and a function of generating leakage light from the projection row Qi. The projection row Qj (j = 2, 3,...) The above-mentioned surface light source device, wherein the surface light source device is arranged so as to cooperate in a chain manner so as to collect light leaked from the two surfaces Wj-1 through the first surface Vj and make the light internally enter the second surface Wj. 2. The surface light source device according to claim 1, wherein the first light guide has a substantially wedge-like shape whose thickness decreases as the distance from the light introduction surface increases. 3. The first light guide section has a substantially wedge-like shape whose thickness decreases as the distance from the light introduction surface increases, and the second light guide section has a thickness. The surface light source device according to claim 1, wherein the surface light source device has a substantially wedge shape that decreases as the distance from the first light guide unit increases. 4. A light supply means using at least one point light source as a light emitting source, a first-stage light beam expanding / redirecting means including a first light guide section, and a second light guide section. A surface light source device comprising: a second-stage light beam expanding / redirecting means: the first light guide portion has a major axis along a first direction and a second axis perpendicular to the first direction. And a third direction perpendicular to both the first direction and the second direction.
And a light introduction surface for receiving light supplied by the light supply means and traveling substantially along the first direction, and the first through the light introduction surface. A direction change surface for changing the traveling direction of the light introduced into the light guide portion to a direction substantially along the second direction, and generating an intermediate output light flux toward the second light guide portion. , A plurality of projection rows P1, P2, P3,... Are provided on the direction changing surface, and each projection row Pi (i = 1, 2, 3,...) And a second surface Ti that is relatively close and steep with respect to the introduction surface and a second surface Ti that is relatively far and inclined with respect to the introduction surface. Is an internal reflection function for generating a part of the intermediate output light beam, and a leakage from the projection row Pi. , And the projection row Pj (j = 2, 3,...) Transmits the leaked light from the second face Tj-1 of the preceding projection row Pj-1 through the first face Sj. And a second light guide portion having a width substantially along the first direction and a second width extending along the second direction. And a thickness substantially along the third direction, a light-emitting surface, and a back surface facing the light-emitting surface, the light-receiving surface being received from the first light guide plate. The traveling direction of the intermediate output light beam is changed from the same direction with respect to the third direction to a direction inclined toward the second direction side to emit oblique emission light from the emission surface, Surface light source device. 5. The surface light source device according to claim 4, wherein the first light guide has a substantially wedge shape such that its thickness decreases as the distance from the light introduction surface increases. 6. The first light guide section has a substantially wedge shape such that its thickness decreases as the distance from the light introduction surface increases, and the second light guide section has a thickness thereof. 5. The surface light source device according to claim 4, wherein the surface light source device has a substantially wedge shape that decreases as the distance from the first light guide unit increases. 6. 7. The surface light source device according to claim 4, wherein a direction correcting element for correcting the traveling direction of the obliquely emitted light so as to approach the third direction is arranged along the emission surface. . 8. The surface light source device according to claim 1, wherein the first light guide and the second light guide are formed separately. . 9. The surface light source device according to claim 1, wherein the first light guide and the second light guide are integrally formed. 10. The apparatus according to claim 1, wherein at least one of the first light guide and the second light guide has a uniform scattering power. Item 2. The surface light source device according to item 1. 11. The first light guide section is divided and connected to a plurality of sections, the light introduction surface is provided for each section, and a plurality of light supply devices corresponding to the plurality of sections are provided. The surface light source device according to any one of claims 1 to 10, wherein the intermediate output light flux is provided by the plurality of sections. 12. The first light guide section is divided and connected to a plurality of sections, the light introduction surface is provided for each section, and a plurality of light supply sections corresponding to the plurality of sections are provided. A vessel is provided, wherein the intermediate output light flux is provided by the plurality of sections, and each of the plurality of sections decreases in thickness as the distance from each corresponding light introduction surface increases 11. The surface light source according to claim 1, which has a substantially wedge shape as described above. apparatus. 13. A light introduction surface corresponding to a part of the plurality of sections is provided to receive light supplied by the light supply means and traveling in a direction substantially opposite to the first direction. The surface light source device according to claim 11. 14. The surface light source device according to claim 1, wherein the light supply means uses one or a plurality of light emitting diodes as a light emitting source.