JPH11203923A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To do way with brightness irregularity by optical and positioned displacement of a light source, in a surface light source device emitting the light introducing to a light guiding plate from a light incident end surface, from a light emitting surface. SOLUTION: A light source 23 is arranged opposed to a light incident end surface 20 of a light guiding plate 18, and plural optical patterns 32 are formed on the area of the light incident end surface 20 opposed to the light source 23. Each optical pattern 32 is formed uniformly in the thickness direction of the light guiding plate 18, and a period Λ of the plural optical patterns 32 arranged in the width direction of the light incident end surface 20 is set to be 1/n (n=1,2,...) times the width W of the light source 23. And length L of the area where the optical patterns 32 are provided is set to be larger than (W+δ+2h), that is, the sum of the width W of the light source 23, the positioned displacement δ of the light source 23 and two images the distance h from the light source 23 to the light incident end surface 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a surface light source device. More specifically, the present invention relates to a surface light source device that emits light emitted from a light source such as a so-called point light source or a linear light source almost uniformly from a light emitting surface (light emitting surface) having a larger area than the light source.

[0002]

2. Description of the Related Art A surface light source device is a device for introducing light emitted from a light source into a light guide plate, confining the light in the light guide plate, and then uniformly emitting the light from a light exit surface thereof. Widely used as such.

FIG. 1 shows a partially exploded structure of a conventional surface light source device. The surface light source device 1 includes a light guide plate 3 for confining light, a light emitting unit 2, and a reflection plate 4. The light guide plate 3 is formed of a transparent resin having a large refractive index such as a polycarbonate resin or a methacryl resin, and a diffusion pattern 8 is formed on the lower surface of the light guide plate 3 by uneven processing or dot printing of a diffuse reflection ink. I have. As shown in FIG. 2, the diffusion pattern 8 has a small pattern density in a region near the light emitting unit 2, and has a gradually increasing pattern density as the distance from the light emitting unit 2 increases. The light emitting unit 2 is arranged to face the light incident end face 5 of the light guide plate 3. The light emitting unit 2 includes a case 9 in which a plurality of small light sources (so-called point light sources) 10 such as light emitting diodes (LEDs) are arranged on a circuit board (not shown).
Each light source 10 and a circuit board are sealed in a case 9 by a transparent mold resin 11. The reflection plate 4 is formed of a material having a high reflectance, for example, a white resin sheet, and is attached to the lower surface of the light guide plate 3 by a double-sided tape 13.

[0004] As shown in FIG. 3, the light guide plate 3 is emitted from each light source 10 in the light emitting section 2,
The light f introduced into the light guide plate 3 is confined in the light guide plate 3 by repeating total reflection inside the light guide plate 3. Light guide plate 3
The light f confined in the light incident on the diffusion pattern 8 formed on the lower surface of the light guide plate 3 is diffused and reflected, and the light f reflected by the diffusion pattern 8 is smaller than the critical angle of total reflection. The light f incident on the light exit surface 6 at an angle is extracted from the light exit surface 6 to the outside, and the light exit surface 6 emits a planar light. On the other hand, the light f transmitted through a portion of the lower surface of the light guide plate 3 where the diffusion pattern 8 does not exist is reflected by the reflection plate 4,
Since the light returns to the light guide plate 3 again, loss of the light amount from the lower surface of the light guide plate 3 is prevented.

Here, in order to make the light emission luminance of the surface light source device 1 uniform over the entire light exit surface 6, as shown in FIG. 4, light f incident from the light incident end face 5 into the light guide plate 3 is guided. The light f needs to be scattered by the diffusion pattern 8 on the lower surface of the light plate 3 so that the light f is uniformly scattered over the entire light exit surface 6. Therefore, the light guide plate 3
When the diffusion pattern 8 is provided on the lower surface of the light source, as shown in FIG. 5, a part of the light f reflected by the diffusion pattern 8 is reflected toward the light emission surface 6 and emitted from the light emission surface 6 to the outside.
Further, the inclination angle, the inclination direction, and the like of each diffusion pattern 8 are varied so that a part of the light reflected by the diffusion pattern 8 changes the light traveling direction in the light guide plate 3.

The light incident on the light guide plate 3 is gradually extracted from the light emitting surface 6 as the light propagates from the light emitting portion 2 side to the opposite side in the light guide plate 3, and the light quantity gradually decreases.
For this reason, as shown in FIG. 2, the density of the diffusion pattern 8 is reduced on the light emitting unit 2 side, and is increased on the opposite side, so that the light emitting luminance is high near the light emitting unit 2 and does not decrease on the side far from the light emitting unit 2. , And the light emission luminance of the surface light source device 1 is made uniform.

Further, as shown in FIG. 1, a notch-shaped concave portion 7 is formed on the light incident end face 5 of the light guide plate 3 so as to face the light source 10. The shade 12 projects from the upper edge and the lower edge toward the recess 7. Here, the width of the concave portion 7 is sufficiently larger than the width of the light source 10 (the light source 10 is drawn larger for convenience in the drawing). The concave portion 7 of the light guide plate 3 is configured to transmit light incident on the light guide plate 3 from the light incident end face 5 to a corner of the light guide plate 3 (the light incident end face 5).
Corners of the light guide plate 3
Is to be prevented from becoming dark. The reason for this is illustrated in FIGS. As shown in FIG. 6, when the light incident end face 5 of the light guide plate 3 is flat, the light f incident into the light guide plate 3 from the light incident end face 5 is collected at the center by refraction and goes to the corner G of the light guide plate 3. The corner G of the light guide plate 3 is darkened. On the other hand, when the rectangular concave portion 7 is formed on the light incident end face 5 of the light guide plate 3 so as to face the light source 10, the light incident on the light guide plate 3 from the side surface of the concave portion 7 as shown in FIG. f
Travels toward the corner G of the light guide plate 3, the amount of light at the corner G of the light guide plate 3 increases, and the corner G of the light guide plate 3 becomes brighter. Further, the shade 12 of the light emitting unit 2 prevents light emitted from the light source 10 from leaking upward or downward from the gap between the concave portion 7 and the light emitting unit 2 without being incident on the light incident end face 5.

The shape of the concave portion 7 is not limited to a rectangle, and an appropriate amount of light can be distributed in all directions of the light guide plate 3 by selecting an appropriate shape. In particular, it is necessary to distribute a large amount of light to the diagonal corners H of the light guide plate 3 (the direction at the greatest distance from the light source 10) as viewed from the light source 10. For example, in the semicircular concave portion 7 shown in FIG. 8, the amount of the light f flying in the diagonal direction is larger than that in the rectangular concave portion 7, and the light can be distributed almost uniformly in all directions.

[0009]

In the surface light source device 1 having the above structure, the concave portion 7 is provided on the light incident end face 5 of the light guide plate 3 in order to adjust the distribution of the light that has entered the light guide plate 3. However, in such a structure, if the position of the light source 10 is shifted with respect to the concave portion 7 formed on the light incident end face 5 or if the thickness T of the mold resin 11 varies, the light emission surface 6 has uneven brightness. There was a problem that occurs. Moreover, the displacement of the light source 10 and the thickness variation of the mold resin 11 are
It is caused by repetitive errors of machines during mass production, and it is difficult to eliminate them.

For example, as shown in FIG. 9, the light source 10 is displaced from the correct position (the light source 10 at this position and its light rays are indicated by broken lines) to the right in the drawing (the light source 10 displaced and its Light rays are indicated by solid lines). When the space region where the light f is no longer emitted due to the displacement of the light source 10 is indicated by oblique lines a, the light f emitted from the light f in the direction shown in FIG. Assuming that the light f is refracted and enters the light guide plate 3 and proceeds toward the right corner G of the light guide plate 3, the light f in this angular range is emitted from the light source 1.
No longer exists due to a displacement of 0. On the other hand, the light source 10
When the spatial region in which the light f is emitted due to the positional shift is indicated by oblique lines B, the light f emitted in the same direction from here is totally reflected by the light incident end face 5 and is in the light guide plate 3. Cannot be incident. Therefore, the light f traveling toward the right corner G of the light guide plate 3 due to the displacement of the light source 10 decreases,
The right corner G of the light emitting surface 6 becomes dark. For the same reason, when the position of the light source 10 is displaced, the light emitting surface 6 becomes dark or bright in various directions as viewed from the light source 10. Become.

Also, if the thickness of the mold resin 11 varies, for example, as shown in FIG. 10, the thickness of the mold resin 11 becomes smaller than the correct thickness T (the mold resin 11 and the light beam at this time are indicated by broken lines). (The mold resin 11 and the light beam at this time are indicated by solid lines, and the thickness is t). When the mold resin 11 is thick, as shown by a broken line in FIG. 10, even if the light f incident into the light guide plate 3 from the side surface of the concave portion 7 is refracted toward the corner G of the light guide plate 3,
When the mold resin 11 becomes thinner, the light f reaching the side surface of the concave portion 7 is refracted in a direction away from the corner G of the light guide plate 3 as shown by a solid line in FIG. The amount of light f going to is reduced. As a result, the molding resin 1
The corners of the light guide plate 3 also become dark due to the thickness variation of 1,
As a result, luminance unevenness occurs on the light emitting surface 6.

The displacement of the light source can be considered as the optical displacement (lateral displacement) of the light source in a direction parallel to the light incident end face, and the thickness variation of the mold resin is caused by the light source in a direction perpendicular to the light incident end face. Therefore, in the conventional surface light source device in which one concave portion is formed facing the light source, the optical position relationship of the light source is shifted, so that There is a problem that luminance unevenness occurs.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and has as its object to eliminate luminance unevenness of a surface light source device due to optical displacement of a light source.

[0014]

DISCLOSURE OF THE INVENTION A surface light source device according to the present invention comprises a light source for emitting light forward, and a light guide plate for introducing light emitted from the light source from a light incident end face and uniformly emitting the light from a light emitting surface. In the surface light source device provided, a plurality of optical patterns uniform in a direction perpendicular to the light exit surface are periodically arranged in a region of the light incident end face facing the light source, and the period 光学 of the optical pattern is , The width W of the light source is satisfied by the following formula: Λ Λ W / n (n = 1, 2,...).

In the surface light source device of the present invention, since a regular optical pattern is formed on the light incident end face of the light guide plate so as to face the light source, the light emitted from the light source and incident on the light incident end face is formed. Direction can be controlled. Therefore, for example, the light can sufficiently reach the corners of the light guide plate, and the luminance unevenness of the surface light source device can be reduced to make the luminance distribution of the light emitting surface uniform. In addition, since the period Λ of the optical pattern is set to a value that is almost a fraction of the width W of the light source, even if a displacement of the light source or a thickness variation of the mold resin sealing the light source occurs. As a result, luminance unevenness hardly occurs, and a high-quality surface light source device can be manufactured.

The period Λ of the optical pattern is equal to the width W of the light source.
Even if it is not substantially an integral part of the light source, if the period 光学 of the optical pattern satisfies Λ ≦ 1.5 × W with respect to the width W of the light source, the displacement of the light source and the sealing of the light source can be achieved. It is possible to reduce luminance unevenness in the case where thickness variation of the molded resin or the like occurs, and to improve the quality and reliability of the surface light source device.

Further, if a plurality of light sources are installed facing the light incident end face of the light guide plate and these light sources are localized in an area smaller than the width of the light incident end face, the light amount of the light source is increased. be able to. In particular, if the period の of the optical pattern is set to be approximately 1 / integer of the width W of the light source, the brightness distribution of the light guide plate is not affected by the position of the light source. The design of the light source device becomes easy.

Further, a plurality of light sources may be provided so as to face the light incident end face of the light guide plate, and the shapes of the optical patterns corresponding to the respective light sources may be different from each other. If the shape of each optical pattern is individually different, it is possible to control the distribution of light in the light guide plate according to the position of the light source, or to superimpose light having different distributions in the light guide plate, The distribution of light in the light guide plate can be controlled by changing the shape. At this time, the length L of each optical pattern region corresponding to each light source is set to satisfy the following expression. Where W is the width of the light source, δ is the displacement of the light source,
h is the distance from the light source to the light guide plate. L ≧ W + δ + 2h In the fourth aspect, making the shapes of the optical patterns different from each other does not mean that the optical pattern regions having the same shape do not exist, but the optical patterns are provided in, for example, three regions. In this case, the optical patterns of the three regions may be different from each other, or only the shapes of the optical patterns of the two regions may be the same among the optical patterns of the three regions.

Further, when a plurality of light sources are installed facing the light incident end face of the light guide plate, means for shielding light may be provided between each light source. When the light emitted from the light source is incident on the adjacent optical pattern, the distribution of light in the light guide plate is affected, and there is a possibility that luminance unevenness may occur. As a result, light can be prevented from entering the light guide plate, and luminance unevenness can be suppressed.

In the case where a plurality of the light sources are installed so as to face the light incident end face formed on the short side of the light guide plate, an optical pattern is not provided on the light incident end face in a region facing a part of the light sources. It is desirable to make. When the optical pattern is not provided, the light of the light source is more distributed forward in the light guide plate, so it is easier to be distributed in the long side direction, and the light exit surface of the light guide plate becomes dark at the end opposite to the light source. Can be prevented.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 11 is an exploded perspective view showing a surface light source device 16 according to one embodiment of the present invention. The surface light source device 16 mainly includes a light guide plate 18, a light emitting unit 17, and a reflection plate 19. The light guide plate 18 is
The light guide plate 18 is made of a transparent resin material having a large refractive index such as polycarbonate resin and methacrylic resin.
Has a light incident end surface 20, an upper surface a light emitting surface 21, and a lower surface on which a diffusion pattern 22 is formed by uneven processing.

FIG. 12 is a plan view showing a diffusion pattern 22 provided on the lower surface of the light guide plate 18 of the above. Light guide plate 18
A large number of minute diffusion patterns 22 are recessed on the lower surface of the substrate, and each diffusion pattern 22 has a semi-cylindrical shape as shown in FIG. The diffusion pattern 22 is concentrically arranged on the entire lower surface of the light guide plate 18 around the light source 23 in the light emitting unit 17 mounted on the light incident end face 20 of the light guide plate 18. Further, the diffusion patterns 22 are arranged randomly, and the pitch between the diffusion patterns 22 decreases as the distance from the light source 23 increases, and the density of the diffusion pattern gradually increases as the distance from the light source 23 increases. Further, each of the diffusion patterns 22 having a semi-cylindrical shape is substantially perpendicular (θ) to the direction connected to the light source 23.
(≒ 90 °). Therefore, as shown in FIG. 14, the light f guided from the light source 23 into the light guide plate 18 is not diffused in the horizontal direction even when reflected by the diffusion pattern 22 and can travel straight. Further, a high light emission rate can be obtained.

FIG. 15 shows the structure of the light emitting section 17. The light-emitting unit 17 is formed by enclosing the light-emitting module 28 with an exterior member 29 made of a material having a high surface reflectance such as white resin, and only the light-emitting side of the light-emitting module 28 is exposed from the exterior member 29. . The light emitting module 28 is an LE
A minute light source 23 such as D (chip) is connected to one lead terminal 2.
4 is die-bonded to the light source and the other lead terminal 25.
After bonding with the bonding wire 26, the light source 23 and both lead terminals 24 and 25 are sealed in a transparent mold resin 27. The light emitting section 17 having such a structure is attached to the central portion of the light incident end face 20 of the light guide plate 18, and the light emitted from the light source 23 in the back direction or the side direction is formed by the transparent mold resin 27 and the exterior member 29. The light is diffusely reflected at the interface, efficiently emitted from the front surface of the light emitting module 28, and introduced into the light guide plate 18 from the light incident end face 20.

The reflection plate 19 for reflecting the light leaking from the lower surface of the light guide plate 18 and returning it to the inside of the light guide plate 18 is made of a material having a high surface reflectance, for example, hard or relatively soft white. It is formed by a plastic sheet. The reflection plate 19 is attached to the lower surface of the light guide plate 18 on both sides by a double-sided tape 31.

In the surface light source device 16 having such a structure, the light emitted from the light source 23 is efficiently reflected from the front surface of the light emitting module 28 by being reflected at the boundary between the mold resin 27 and the exterior member 29. Then, the light is introduced into the light guide plate 18 from the light incident end face 20. The light introduced into the light guide plate 18 is confined in the light guide plate 18, travels in a direction away from the light source 23 while repeating total reflection on the upper surface (light emission surface 21) and the lower surface of the light guide plate 18, and travels in the diffusion pattern 22. After being reflected, when the light reaches the light exit surface 21 at an incident angle smaller than the critical angle of total reflection, the light exits from the light exit surface 21 and emits light.

Here, as described with reference to FIG. 14, the light entering the light guide plate 18 from the light incident end face 20 is directed around the light source 23 in a circumferential direction (in a plan view, the direction connecting with the light source 23). In the direction orthogonal to the light guide plate 18).
After the incident light is evenly distributed to each direction, the luminance distribution of the light emitting surface 21 may be individually uniform in each direction. This can be achieved by appropriately changing the diffusion pattern density as the distance from the light source 23 increases in each direction. That is, this is realized by designing the diffusion pattern density in each direction as a function of the distance from the light source 23.

Therefore, when the light of the light source 23 is introduced from the light incident end face 20 to the light guide plate 18, the light may be distributed in each direction by an amount corresponding to the area occupied on the light exit surface 21. It becomes important. In particular, it is necessary to largely bend the path of some light toward the corner G of the light guide plate 18. For this purpose, one method is to form a single concave portion on the light incident end face in opposition to the light source as in the conventional example. However, this involves optical displacement of the light source (position displacement of the light source, mold displacement). Corners of the light guide plate 18 due to variations in thickness of the resin).
And it is difficult for light to reach the substrate, and there is a possibility that luminance unevenness may occur.

Since such luminance unevenness is caused by the shape of the light incident end face (a concave portion larger than the width of the light source) and the optical position shift of the light source, the shape of the light incident end face can be made irrespective of the position shift of the light source. I just need. The easiest way is
The process of forming the light incident end face 20 by using a mold manufactured by a grinding process to randomly perform a rough surface process.
As a result, the light introduced into the light guide plate 18 is
Will be diffused to the corners. Moreover, even if the light source 23 is displaced as shown in FIG. 16 or the thickness of the mold resin 27 varies, if the processing rough surface a of the light incident end face 20 is applied to a sufficiently wide range, the light f There is no change in the direction in which the image is distributed, and it does not cause luminance unevenness.

However, in this method, since the roughened surface a of the light incident end face 20 is random, light passing through the roughened surface a has a Lambertian distribution as shown in FIG. There is a problem that can not be controlled.
For example, in the case of the rectangular light guide plate 18, it is necessary to distribute a relatively large amount of light in the diagonal direction. Design becomes difficult.

Therefore, in the surface light source device 16, in order to uniformly disperse the light incident on the light guide plate 18 in each direction, an optical pattern 32 as described below is formed on the light incident end face 20.
Is provided.

(First Example of Optical Pattern) FIG. 18 or FIG.
9 is a diagram showing an example of the optical pattern 32 provided on the light incident end face 20. The period Λ of the optical pattern 32 is に 対 し て = W / n (where n = 1, 2, 3, 4,...). In particular, in the optical pattern 32 shown in FIG. 18, the light source width W = pattern period パ タ ー ン, and in the optical pattern 32 shown in FIG. 19, the light source width W = pattern periodΛ × 2.

Each optical pattern (unit pattern) 32 has a bottom surface 32a of the concave portion and a tip surface 32a of the convex portion.
b are flat surfaces, and both side surfaces 32 between them are
c is an arc-shaped curved surface, and is formed in a uniform cross-sectional shape over the entire length of the light guide plate 18 in the thickness direction.

On the other hand, a fine shade 30 protrudes from the front surface of the exterior member 29 of the light emitting portion 17 in accordance with the concave portion of the optical pattern 32 of the light guide plate 18. This shade 30
Are provided above, below, or around the light emitting module 28 on the front surface of the exterior member 29, and are fitted with the concave portions of the optical pattern 32. This shade 30
When the light emitting unit 17 is attached to the light incident end face 20 of the light guide plate 18, it fits into the concave portion of the optical pattern 32. Therefore, it is preferable that the shade 30 is slightly smaller than the shape of the concave portion of the optical pattern 32 so that the shade 30 can be easily fitted into the optical pattern 32. If such a shade 30 does not exist, the light emitting unit 17 and the light guide plate 1
8, there is a risk that light emitted from the light source 23 leaks upward or downward from the gap without entering the light guide plate 18, and the light guide plate 18 appears partially shining. . Therefore, the shade 30 covers the space above and below the optical pattern 32 to prevent light from leaking.

FIGS. 20 and 21 show the optical pattern 32.
Is a diagram illustrating the operation of the optical pattern 32, where the width W of the light source 23 is equal to the period の of the optical pattern 32, and each optical pattern 32 is represented by a rectangle for convenience of explanation. As described above, even the optical pattern 23 having the same size as the width W of the light source 23 (the optical pattern 32 smaller than the width W of the light source 23) is used.
20 and FIG. 21, the light f emitted from the light source 23 is refracted toward the corner G of the light guide plate 18 at the side surface of the optical pattern 32. In addition, since the light f is incident on the light guide plate 18 depending on the shape of the optical pattern 23, the distribution in each direction can be arbitrarily designed. Moreover,
As shown in FIG. 20, when the light source 23 is displaced from the position shown by the solid line to the position shown by the broken line, the light f shown by the solid line in FIG. The indicated light f is generated, and in each direction, the disappeared light f is supplemented by the newly generated light f.
The distribution direction (or luminance distribution) of the light f does not change inside the light guide plate 18 due to the displacement of 3, and therefore, the surface light source device 16 does not have luminance unevenness.

Further, as shown in FIG. 21, the mold resin 27 which originally has reached the position indicated by the solid line has reached only the position indicated by the broken line due to insufficient filling or the like.
Is thinner, the light f emitted from the light source 23 is
Although the traveling direction changes within 8, the light source 23 as a whole shows
The distribution direction (or luminance distribution) of the light f does not change inside the light guide plate 18, so that the surface light source device 16 does not have luminance unevenness.

FIG. 22 shows the pattern period Λ and the width W of the light source 23.
FIG. 5 is a diagram illustrating a degree of luminance unevenness when the light source 23 is displaced with respect to a ratio of the luminance. As can be understood from the above description, the period (pattern period) 光学 of the optical pattern 32 is an integer fraction of the width W of the light source 23, that is, 1, 1/2, 1/3,
.., The luminance unevenness does not occur.

Next, the overall length of the optical pattern 32 will be described. The optical pattern 32 does not need to be provided on the entire light incident end face 20 of the light guide plate 18, and the maximum displacement amount δ of the light source 23 (this is usually considered to be about 200 μm) and the distance h from the light source 23 to the light guide plate 18 In consideration of the above, it is sufficient for the length L of the entire optical pattern (optical pattern region) to have a length satisfying the following expression. L ≧ W + δ + 2h... This is because, out of the light emitted from the light source 23, a small amount of light entering the light guide plate 18 at an incident angle of 45 ° or more, and 45 °
The light f incident on the light guide plate 18 at the above angle is the light incident end face 2
Since there is a high possibility that the light is reflected at 0 and returns to the light emitting unit 17, as shown in FIG.
In consideration of + δ and the moving distance h of the light traveling in the 45 ° direction in the horizontal direction, the length L of the entire optical pattern 32 only needs to be at least w + δ + 2h as in the above equation.

According to the above configuration, one light source 2
According to 3, the surface light source device 16 having a uniform luminance distribution without unevenness can be manufactured, and the surface light source device 16 can be reduced in weight and cost. In addition, since one light source 23 is used, the power consumption is low, and when it is used for a portable device such as an electronic organizer, a portable information terminal (mobile), and a mobile phone,
Battery life can be extended.

(Second Example of Optical Pattern) FIG. 23 is a sectional view showing an optical pattern 32 having another shape. Light guide plate 18
An optical pattern 32 composed of a convex portion and a flat surface is repeatedly formed on the light incident end surface 20 of the light guide plate 20, and both the convex portion and the flat surface are formed uniformly over the entire length of the light guide plate 18 in the thickness direction. Have been. The flat surface is the flat bottom surface of the concave part 3
2d, the boundary between the bottom surface 32d and the convex portion is an edge, and the base side surface 32e of the convex portion (the portion in contact with the edge) is a plane perpendicular to the bottom surface 32d and the flat base side surface 3
Between 2e, the outer peripheral surface of the convex portion is an arc-shaped curved surface 32f. The bottom surface 32d of the concave portion is for increasing the amount of light f entering in a direction perpendicular to the light incident end surface 20. Without providing this, the optical pattern 34 is formed only by a curved surface as shown in FIG. When formed, the light f that enters in the direction perpendicular to the light incident end face 20 decreases. The flat base side surface 32e of the convex portion allows the light f entering the light guide plate 18 to transmit the light f into the corner G of the light guide plate 18.
It is to turn to. The reason why the curved surface 32f is formed in the convex portion is a region where light does not reach (particularly, a region in a diagonal direction).
This is to prevent the occurrence of. Figure 2 without curved parts
If the rectangular optical pattern 35 as shown in FIG.
An area where light does not reach in a direction corresponding to the inner corner portion of the optical pattern 35 is generated. Further, as shown in FIG. 24A, when an optical pattern 33 having a flat surface at the end and a concave portion curved is formed, the light f traveling in the direction of the corner G hits the adjacent optical pattern 33 and is blocked. A flat surface (base side surface 32e) perpendicular to the bottom surface 32d is formed on the base of the convex portion as a curved surface 32f like the optical pattern 32 of this embodiment.
Is formed, the adjacent optical pattern 3 is formed as shown in FIG.
2 and the corner G of the light guide plate 18 can be prevented from becoming dark.

The light guide plate 18 having the above-described optical pattern 32 is desirably manufactured using a molding die manufactured by grinding. At this time, the forming surface of the optical pattern 32 is processed by moving the grinding wheel in the direction corresponding to the thickness direction of the light guide plate 18. If the grinding direction corresponds to the thickness direction of the light guide plate 18, as shown in FIG. 25, in the light guide plate 18 formed by using the molding die, the thickness of the light guide plate 18 Fine vertical stripes 36 are formed along the direction. Since the vertical stripes 36 are formed only in the thickness direction of the light guide plate 18, the light f entering the light guide plate 18 through the optical pattern 32 spreads and diffuses only in the horizontal direction as shown in FIG. 25 or FIG. I do.

Due to a slight error in the production of the optical pattern 32 and the undulation of the surface of the mold resin 27, fine brightness unevenness occurs in the light guide plate 18. For example, the luminance along the line A1-A2 of the light guide plate 18 in FIG. 27 usually has fine luminance unevenness as shown by a solid line in FIG. However, if fine vertical streaks 36 are formed on the optical pattern 32 by grinding, the light f is diffused by the vertical streaks f, and fine luminance unevenness is averaged. Such luminance unevenness is averaged, and as shown by a broken line in FIG. 28, the luminance unevenness is reduced.

As a method of manufacturing a molding die for molding the optical pattern 32, a stamper is duplicated from a master prepared by electroforming, an ultraviolet-curable resin is molded with the stamper, and cured by irradiation with ultraviolet light. A so-called 2P method (Photo-Polymerization method) may be used. In particular, when the ratio Λ / W between the cycle of the optical pattern 32 and the width of the light source 23 is reduced, the optical pattern 32 may be smaller than the dimension that can be ground. Method may be used.

(Second Embodiment) FIG. 29 is a partially exploded perspective view showing a surface light source device 37 according to another embodiment of the present invention. The light emitting section 17 used in the surface light source device 37 has a plurality (three in the figure) of light sources 23 localized therein. Since the plurality of light sources 23 are locally incorporated in the light emitting unit 17, the amount of light emitted from the light emitting unit 17 can be increased several times (three times in the figure). In addition, in the surface light source device 37 of the present invention, since the displacement of the light source 23 does not cause uneven brightness in principle, even if a plurality of the light sources 23 are displaced, if the light sources 23 are localized, if the light sources 23 are localized, 1 Light sources 2
The light amount can be increased without changing the luminance distribution from the case of one light source 23 as shown in FIG. 30, and the luminance of the surface light source device 37 can be increased.

When a plurality of light sources 23 are used,
As shown in FIG. 31, the above formula is applied by setting the entire width of the plurality of light sources 23 to W, and an optical pattern region having a length L larger than the lower limit given by the formula may be formed. However, in the case of a plurality of light sources 23, as shown in FIG.
It is necessary to keep an interval that is not obstructed by traffic. As is clear from FIG. 32, the weighting condition for this is g ≧ k, where g is the distance between the light sources 23 and k is the height (thickness) of the light source 23. Further, when a plurality of light sources 23 are provided, it is desirable that the entire width W of the light sources 23 be 1/5 or less of the length (lateral width) of the light incident end face 20 of the light guide plate 18.

The height difference v of the unevenness of the optical pattern 32
Is smaller than 0.1 mm, it is difficult to form or process the shade 30 of the light emitting unit 17 into the same shape as the optical pattern 32. In this case, as shown in FIG. 33, the shade 30 of the light emitting unit 17 does not match the optical pattern 32, and the tip of the shade 30 is formed in a straight line in accordance with the position closest to the light source 23 of the optical pattern 32. You may.

(Third Embodiment) FIG. 34 is a schematic view showing a part of a surface light source device according to still another embodiment of the present invention. In this embodiment, a plurality of light sources 2
3 are arranged with an interval of about L that satisfies the above equation.
The pattern shapes of the corresponding optical patterns 38 and 39 are changed every three. That is, as shown in FIG.
Assuming that the width of each light source 23 is W, each optical pattern 3 has a width L that satisfies the above equation corresponding to each light source 23.
8 and 39 are formed on the light incident end face 20, and the pattern shapes are different for each of the optical patterns 38 and 39 in each area. If the pattern shapes of the optical patterns 38 and 39 are changed, the distribution of the light f entering the light guide plate 18 in each direction changes. Therefore, for example, an optical element having a shape that distributes a large amount of the light f in a direction perpendicular to the light incident end face 20. By combining the pattern 39 (the pattern on the right in FIG. 34) and the optical pattern 38 (the pattern on the left in FIG. 34) having a shape that distributes a large amount of the light f in the direction of the corner G of the light guide plate 18, The required amount of light can be distributed to any direction.

Here, since each of the optical patterns 38 and 39 individually satisfies the above formula, the light emitted from the light source 23 passes through the adjacent optical patterns 38 and 39 and the light guide plate 18.
It does not invade the inside, the light is easily controlled, and the design of the diffusion pattern and the like is also easy.

For example, in FIG. 35, two light sources 23 are arranged so as to face the central part of the light incident end face 20, and optical patterns 38 and 39 having different shapes are formed on the light incident end face 20 so as to face both light sources 23. This shows the case where it is formed. In this case, one optical pattern 39 distributes a large amount of light f to the front, the other optical pattern 38 distributes a large amount of light f to the left and right, and passes through both optical patterns 32 in the light guide plate 18. The sum of the determined light amounts is distributed.

FIG. 36 shows a case where a plurality of light sources 23 are arranged over the entire light incident end face 20 at relatively large intervals. In this case, the optical pattern 41 facing the light source 23 at the center is a pattern that evenly distributes light to the left and right, and the optical pattern 40 facing the light source 23 near the end has a small amount of light toward the side closer to the side of the light guide plate 18. And a pattern in which a large amount of light is distributed to the far side.

(Fourth Embodiment) FIG. 37 is a sectional view showing a part of a surface light source device according to still another embodiment of the present invention. In this embodiment, a plurality of light sources 23 are provided in the light emitting section 17, and a partition wall 42 for reflecting or absorbing light is provided between the light sources 23. In addition, the pattern shape of each of the optical patterns 38 and 39 is changed at a position facing the partition wall 42.

Here, the distance D from the light source 23 to the partition wall 42 is １ ／ of the lower limit of the length L of the optical pattern area.
It is sufficient to satisfy the following equation. D ≧ L / 2 ≧ (W + δ + 2h) / 2 ...

When the partition wall 42 is provided between the light sources 23, the light f emitted from the light source 23 is reflected or absorbed by the partition wall 42 and does not enter the adjacent optical pattern 32. And the unevenness in brightness can be reduced. Such a partition wall 42 is, in particular,
This is advantageous when a plurality of light sources 23 are desired to be localized.

(Fifth Embodiment) FIG. 38 is a sectional view showing a part of a surface light source device according to still another embodiment of the present invention. In this embodiment, a plurality of light sources 23 are provided in the light emitting unit 17, and some light sources 23 have optical patterns 32.
Are made not to face each other, and the optical pattern 32 is formed on the light incident end face 20 so as to face the remaining light source 23. Since the light f of the light source 23 without the optical pattern 32 does not reach the corner side than the direction determined by the critical angle of total reflection of the light guide plate 18 and gathers forward, as shown in FIG. When it is necessary to dispose the light emitting unit 17 on the side and reach the light in the long side direction, it is effective to use the light source 23 without the optical pattern 32 as in this embodiment. Further, in the light source 23 without the optical pattern 32, there is no occurrence of uneven brightness due to a displacement of the light source 23 or a variation in the thickness of the mold resin 27.

(Sixth Embodiment) FIGS. 40A and 40B are a plan view and a sectional view showing a part of a surface light source device according to still another embodiment of the present invention. In order to prevent the light f from leaking from the gap between the light source 23 and the light guide plate 18, the shade 30 extending from the exterior member 29 of the light emitting unit 17 is attached to the light incident end face of the light guide plate 18 as in this embodiment. It is desirable to overlap the edge on the 20 side. In this case, as shown in FIG. 40B, the upper surface and the lower surface of the edge on the light incident end surface 20 side of the light guide plate 18 are partially cut out to form a step 43, and the step 43 emits light. It is preferable that the shade 30 of the part 17 fits therein. When the shade 30 is superimposed on the light guide plate 18 with such a structure, not only is no step formed between the light emitting portion 17 and the light guide plate 18 but also, as shown in FIG. The path through which the light f passes is bent, so that the light f does not easily leak.

Further, as shown in FIG. 41, as a method of overlapping the shade 30 and the light guide plate 18, a step 44 is also formed on the inner surface of the shade 30, and the step 43 of the light guide plate 18 and the step of the shade 30 are formed. If the parts 44 are combined, all of the light f of the light source 23 can be introduced into the light guide plate 18 without leakage of the light f, and the utilization efficiency of the light from the light source is extremely increased.

As shown in FIG. 42, the shade 30 on the upper surface is formed by combining a step 44 provided on the lower surface with a step 43 provided on the upper surface of the light guide plate 18, and the shade 30 on the lower surface is provided.
May be merely abutted against the light incident end face 20 of the light guide plate 18. When the light f leaks to the upper surface side, the light guide plate 1
8, the reflection plate 1 is provided on the lower surface of the light guide plate 18.
Since the light guide 9 is provided, even if the light f leaks to the lower surface side, the light f does not enter the light guide plate 18 and cause the uneven brightness, so that the lower surface side may have a simple structure.

(Seventh Embodiment) FIG. 43 is a sectional view showing a part of a surface light source device according to still another embodiment of the present invention. In this embodiment, the period Λ of the optical pattern 32 is appropriately set smaller than the width W of the light source 23.

In the conventional surface light source device, since one rectangular recess having a width sufficiently larger than the width of the light source is formed, the level of luminance unevenness is at the level of LV shown in FIG. Therefore, the pattern period Λ is not necessarily equal to the width W of the light source 23.
Even if the pattern period Λ is not more than ΛW without using W / n (n = 1, 2,...), The length of the optical pattern region When provided over the length L, luminance unevenness can be reduced as compared with the related art. In addition, slight luminance unevenness does not pose a problem in practical use. Further, as can be seen from FIG. 44, even when the period Λ of the optical pattern 32 is about several tens to about 50% of the width of the light source 23, the plurality of optical patterns 3
If 2 is provided over the length L represented by the above equation, luminance unevenness can be considerably reduced as compared with the related art.

(Liquid Crystal Display) FIG. 45 is an exploded perspective view showing a liquid crystal display 81 using the surface light source device 80 according to the present invention. In the surface light source 23 device 80, the light guide plate 2
2 on the light incident surface 26 of red (R), green (G), and blue (B).
A color point light source 30 is provided. A diffuse reflection sheet 82 is disposed on the front surface of the surface light source device 80, and a liquid crystal display panel 83 is disposed on the front surface. Liquid crystal display panel 8
Reference numeral 3 denotes two liquid crystal substrates (a glass substrate, a transparent substrate, a TFT, a color filter, a black matrix, etc.) formed thereon.
A liquid crystal material is sealed between the film substrates 84 and 85, and polarizing plates 86 are provided on both outer surfaces of the liquid crystal substrates 84 and 85. The surface light source device 80 and the liquid crystal display panel 83 are sequentially stacked and integrated by a housing 87, and the liquid crystal display panel 83 is connected to a liquid crystal driving circuit by a flat cable 88.

According to such a liquid crystal display device 81, the luminance distribution on the display screen can be made uniform and the luminance can be increased, and the image quality of the liquid crystal display device 81 can be improved.

The liquid crystal display device according to the present invention is preferably used for a wireless information transmission device such as a mobile phone or a low power radio device, a portable personal computer, and a small information terminal device such as an electronic notebook or a calculator. FIG. 46 is a perspective view showing a mobile phone 89 provided with a liquid crystal display device 81 as shown in FIG. 45 for display according to the present invention, and FIG. 47 is a functional block diagram thereof. A button switch 90 such as a numeric keypad for dial input is provided on the front of the mobile phone 89, a liquid crystal display device 81 is provided above the switch 90, and an antenna 91 is provided on the upper surface. Then, the button switch 90
When a dial or the like is input from the, the input dial information or the like is transmitted from the antenna 91 to the base station of the telephone company through the transmission circuit 92. On the other hand, the input dial information and the like are sent to the liquid crystal drive circuit 93, and the liquid crystal display device 81 is driven by the liquid crystal drive circuit 93, and the dial information and the like are displayed on the liquid crystal display device 81.

FIG. 48 is a diagram showing an example of FIG.
FIG. 5 is a perspective view showing an electronic organizer (small information terminal) 94 provided with a liquid crystal display device 81 as shown in FIG.
FIG. 49 is a functional block diagram thereof. Electronic organizer 94
When the cover 95 is opened, the key input section 96 and the liquid crystal display 8
1, a liquid crystal drive circuit 93, an arithmetic processing circuit 97, and the like are provided inside. Thus, for example, when a ten key, a kana key, or the like is input from the key input unit 96, the input information is sent to the liquid crystal drive circuit 93 and displayed on the liquid crystal display device 81. Then, when you press a control key such as a calculation key,
The arithmetic processing circuit 97 executes a predetermined process or operation, and the result is sent to the liquid crystal driving circuit 93 and displayed on the liquid crystal display device 81.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a diffusion pattern of a light guide plate constituting the surface light source device of the above.

FIG. 3 is an enlarged cross-sectional view of the surface light source device according to the first embodiment, partially broken away.

FIG. 4 is an explanatory diagram of an operation of a diffusion pattern.

FIG. 5 is a perspective view showing a part of a diffusion pattern.

FIG. 6 is a comparative diagram for explaining the function of a concave portion in a conventional example.

FIG. 7 is a view for explaining the function of a concave portion in a conventional example.

FIG. 8 is a view for explaining the function of a concave portion in a conventional example.

FIG. 9 is a diagram showing how light incident on the light guide plate changes when the light source is displaced.

FIG. 10 is a diagram illustrating a state of change of light incident on a light guide plate when the thickness of a mold resin varies.

FIG. 11 is a partially exploded perspective view showing a surface light source device according to an embodiment of the present invention.

FIG. 12 is a view showing a diffusion pattern provided on the lower surface of the light guide plate of the above.

FIG. 13 is a diagram showing one diffusion pattern.

FIG. 14 is a diagram showing a path of light that has entered a light guide plate from a light source.

FIG. 15 is an enlarged cross-sectional view showing the structure of the light emitting unit of the above.

FIG. 16 is an explanatory diagram for comparison with an optical pattern provided in the surface light source device of the above.

FIG. 17 is an explanatory diagram for comparison with an optical pattern provided in the surface light source device of the above.

FIG. 18 is a diagram illustrating an example of an optical pattern.

FIG. 19 is a diagram showing different optical patterns.

FIG. 20 is an explanatory diagram of an operation of the above optical pattern.

FIG. 21 is an explanatory diagram of the operation of the above optical pattern.

FIG. 22 is a diagram showing a relationship between a ratio Λ / W between a pattern cycle and a light source width and luminance unevenness.

FIG. 23 is a schematic view showing an optical pattern having a different structure.

FIGS. 24 (a), (b) and (c) are comparison diagrams for explaining the function of the above optical pattern.

FIG. 25 is a partially broken perspective view of a light guide plate having an optical pattern with vertical stripes.

FIG. 26 is an explanatory diagram of the operation of the above optical pattern.

FIG. 27 is a schematic view of a surface light source device provided with the above optical pattern.

FIG. 28 is a diagram showing a change in luminance along the width direction of the light guide plate.

FIG. 29 is an exploded perspective view showing a surface light source device according to another embodiment of the present invention.

FIG. 30 is a diagram showing a light path in the surface light source device of the above.

FIG. 31 is an enlarged partially sectional view showing a surface light source device in which a plurality of light sources are provided in a light emitting unit.

FIG. 32 is a diagram for explaining a minimum required interval between the light sources.

FIG. 33 is a diagram illustrating a shape of a shade when a difference in height of an optical pattern is small.

FIG. 34 is a schematic sectional view showing an embodiment in which optical patterns of different shapes are opposed to each other for each light source.

FIG. 35 is an explanatory diagram of the operation of the above.

FIG. 36 is a schematic view showing another embodiment in which optical patterns having different shapes are opposed to each other for each light source.

FIG. 37 is a partially broken schematic sectional view showing a surface light source device according to still another embodiment of the present invention.

FIG. 38 is a partially broken schematic sectional view showing an embodiment in which an optical pattern is not provided in a region facing some light sources.

FIG. 39 is an operation explanatory view of the above.

FIGS. 40 (a) and (b) are a partially broken plan view and a partially broken enlarged sectional view showing a surface light source device according to still another embodiment of the present invention.

FIG. 41 is an enlarged cross-sectional view of a surface light source device according to still another embodiment of the present invention, with a part cut away.

FIG. 42 is an enlarged cross-sectional view of a surface light source device according to still another embodiment of the present invention, with a part cut away.

FIG. 43 is an enlarged partially sectional view showing a surface light source device according to still another embodiment of the present invention.

FIG. 44 is a diagram showing a relationship between a ratio Λ / W between a pattern cycle and a light source width and luminance unevenness, and a conventional level of luminance unevenness.

FIG. 45 is an exploded perspective view showing a liquid crystal display device using the surface light source device according to the present invention.

FIG. 46 is a perspective view showing a mobile phone provided with a liquid crystal display device for a display.

FIG. 47 is a functional block diagram of the mobile phone of the above.

FIG. 48 is a perspective view showing an electronic organizer (small information terminal) including a liquid crystal display device for a display.

FIG. 49 is a functional block diagram of the above electronic notebook (small information terminal).

[Explanation of symbols]

 Reference Signs List 18 light guide plate 20 incidence end face 21 light emission face 23 light source 32, 38 to 41 optical pattern 42 partition wall

Claims (6)

[Claims] 1. A surface light source device comprising: a light source that emits light forward; and a light guide plate that introduces light emitted from the light source from a light incident end surface and uniformly emits the light from a light emission surface. A plurality of optical patterns uniform in a direction perpendicular to the emission surface are periodically arranged in a region of the light incident end face opposed to the light source, and the period Λ of the optical pattern is relative to the width W of the light source. A surface light source device characterized by satisfying Λ ≦ 1.5 × W. 2. A surface light source device comprising: a light source that emits light forward; and a light guide plate that introduces light emitted from the light source from a light incident end surface and uniformly emits the light from a light emission surface. A plurality of optical patterns uniform in a direction perpendicular to the emission surface are periodically arranged in a region of the light incident end face opposed to the light source, and the period Λ of the optical pattern is relative to the width W of the light source. A surface light source device characterized by satisfying Λ W / n (n = 1, 2,...). 3. The light source according to claim 1, wherein a plurality of the light sources are provided so as to face the light incident end face of the light guide plate, and these light sources are localized in a small area compared to the width of the light incident end face. Item 3. The surface light source device according to item 1 or 2. 4. A plurality of said light sources are provided in opposition to the light incident end face of said light guide plate, and the shape of optical pattern regions corresponding to each light source is different from each other, and each optical pattern region corresponding to each light source is provided. 3. The surface light source device according to claim 1, wherein the length L is L ≧ W + δ + 2h, where W: width of the light source δ: displacement amount of the light source h: distance from the light source to the light guide plate. . 5. The light guide plate according to claim 1, wherein a plurality of the light sources are provided so as to face the light incident end face of the light guide plate, and a means for shielding light is provided between the light sources. Surface light source device. 6. A plurality of the light sources are provided so as to face a light incident end face formed on a short side of the light guide plate, and at least one of the areas of the light incident end face facing each light source includes:
The surface light source device according to claim 1, wherein the surface light source device does not include the optical pattern.