JP2001215507A - Light guide plate, surface light source using the same, and backlight optical system and display using them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the weight of a surface light source and a backlight optical system by using a light guide plate, having a form which can be easily produced and which can be made light in weight, while controlling the light quantity to be uniform. SOLUTION: In the surface light source, consisting of light source devices 3, 5 and a light guide plate 2 having a light diffusing pattern 6 formed on the inclined face (or upper face 12), the inclined face of the light guide plate 2 is formed into a shaped face by constituting from a plurality of planes 13a, 13b to decrease the weight. The light-diffusing pattern rate 6 is changed discontinuously in the border 10 (or in the part of the upper surface 12 facing the border 10) of the respective flat faces 13a, 13b and the light diffusing pattern rate for making the light quantity uniform is controlled independently in each plane. The light guide plate can be produced readily, because the light guide plate has a joined form of a plurality of wedge light guide parts 11a, 11b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate which can be reduced in weight, a planar light source using the same, and a backlight optical system and a display using the same.

[0002]

2. Description of the Related Art Conventionally, a light source device such as a cold-cathode tube has been arranged on one end (light incident end) side of a light guide plate, and a light source end face has a wide surface (first wide surface) perpendicular to the light incident end surface. 2. Description of the Related Art A planar light source configured to emit light is known, and a display device (display) is known.
For the backlight optical system. In this planar light source, it is most effective to reduce the weight of the light guide plate in order to reduce the weight. Conventionally, in order to reduce the weight of the light guide plate, while the thickness of the end portion (light incident end) of the light guide plate on the cold cathode tube side is equal to or larger than the diameter of the cold cathode tube, from the light incident end to the opposite end, A method has been proposed in which a surface (a second wide surface = slope) facing the emission surface is provided with a curvature to form a curved surface.

For example, Japanese Patent Application Laid-Open No. 63-208001 discloses a light guide plate 2 in which a slope 1 is provided with a curvature as shown in FIG. In this planar light source, the light 4 from the cold cathode tube 3 enters the light guide plate 2 directly or after being reflected by the reflector 5. Then, in the light guide plate 2, light deviating from the total reflection condition on the exit surface or light irradiated on the light diffusion pattern 6 formed on the inclined surface 1 is emitted toward the observer 7, and finally all light is emitted. Is emitted to the observer 7 side. The slope 1 of the light guide plate 2 starts to become thinner rapidly near the light incident end 8 and gradually becomes thinner toward the end 9 on the opposite side. In the light guide plate 2 provided with such a curvature,
The light guide plate can be reduced in weight by going through a straight slope, and as a result, the weight of the planar light source can be reduced.

[0004]

Incidentally, the slope of the light guide plate affects the luminance distribution of the light emitted to the observer side, and the light diffusion pattern for ensuring uniform luminance on the observer side. , That is, the light diffusion pattern rate at which the light diffusion pattern is distributed per unit area is very important.

[0005] However, in the above-mentioned prior art, despite the fact that the light diffusion pattern is reconstructed,
The light diffusion pattern rate has not been optimized. In addition, since the slope is a curved surface, it is very difficult to manufacture a mold for molding a light guide plate, and a shape that can be easily manufactured has been required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and has a shape which is easy to manufacture and which can achieve a reduction in weight while equalizing the amount of light. An object is to provide a light plate, a planar light source using the same, and a backlight optical system and a display using the same.

[0007]

Means for Solving the Problems The present inventor has conducted intensive studies and researches to solve the above problems, and as a result, by appropriately setting the shape of the slope of the light guide plate and the light diffusion pattern ratio, It has been found that a light guide plate which is easy to manufacture while achieving weight reduction and a planar light source using the same can be obtained.

That is, in the light guide plate of the present invention, a light diffusion pattern is provided on a second wide surface opposite to the first wide surface, and light is incident from a light incident end surface perpendicular to the first wide surface. 1
In the light guide plate that emits light from the wide surface, the second wide surface has a shape obtained by planarly shaping a slope that forms a predetermined angle with the first wide surface, and includes a plurality of planes. Part or in the vicinity thereof, the area ratio of the light diffusion pattern changes discontinuously, and in each part on the light incident end side and the opposite end side, the area ratio of the light diffusion pattern changes continuously,
Thereby, the above object is achieved.

In the light guide plate of the present invention, a light diffusion pattern is provided on a first wide surface, and light is incident from a light incident end surface perpendicular to the first wide surface and emitted from the first wide surface. In the optical plate, the second wide surface facing the first wide surface has a shape obtained by planarly shaping a slope that forms a predetermined angle with the first wide surface, and includes a plurality of planes. The area ratio of the light diffusion pattern changes discontinuously at or near the first wide surface portion facing the boundary portion, and the area ratio of the light diffusion pattern is continuous at the light incident end side and the opposite end side. And the above-mentioned object is achieved.

A boundary portion between the planes or the vicinity thereof,
Alternatively, the area ratio of the light diffusion pattern is continuously changed so as to connect the area ratio of the discontinuous light diffusion pattern between the light incident end side and the opposite end side thereof to the first wide surface portion opposed thereto. It may have a region.

The portion where the area ratio of the light diffusion pattern varies discontinuously is closer to the light incident end side or the opposite end side than the boundary between the flat surfaces or the first wide surface portion opposed thereto. The light diffusion pattern may be provided at or near the boundary portion or a portion facing the boundary portion, or may be provided across the boundary portion or a portion facing the boundary portion.

At or near the boundary between the planes,
Additional light diffusion patterns may be further provided.

[0013] An additional light diffusion pattern may be further provided on the first wide surface portion facing the boundary between the flat surfaces or the vicinity thereof.

A planar light source device according to the present invention has at least a light guide plate according to the present invention and a light source device disposed on a light incident end face of the light guide plate, and emits light from the light source device from the light incident end face. The light enters the light guide plate and exits from the first wide surface perpendicular to the light incident end face, thereby achieving the above object.

The backlight optical system of the present invention uses the planar light source of the present invention, thereby achieving the above object.

In the display according to the present invention, the planar light source according to the present invention is disposed on the back side of the display unit with the first wide surface side disposed on the display unit side, thereby achieving the above object. .

Hereinafter, the operation of the present invention will be described.

In the present invention, since the light guide plate has a shape in which the second wide surface (slope) is flattened, the weight is reduced as compared with a conventional light guide plate having a single slope. It is possible. In addition, since the slope is formed of a plurality of flat surfaces and has a shape in which a plurality of wedge-shaped light guides are arranged, manufacture is easier than a conventional light guide plate in which the slope is a curved surface. In addition, the area ratio of the light diffusion pattern (light diffusion pattern ratio) is discontinuously changed at or near the boundary between the planes (inflection point), and the light diffusion plate is divided into a plurality of light guide plate portions capable of equalizing luminance. can do. Therefore, it is possible to independently control the light diffusion pattern ratio in each plane portion on the side opposite to the light incident end side (the end opposite to the light incident end) to optimize for uniform luminance. It is possible.

Generally, the light diffusion pattern is provided on the back (slope) side, but may be provided on the front (emission plane) side. The light diffusion pattern provided on the back side has a function of diffusing light while reflecting the light to the observer side, and the light diffusion pattern provided on the emission surface side has a function of diffusing light while transmitting the light to the observer side. , It is possible to set an optimum light diffusion pattern rate for each. Also in this case, since the second wide surface (slope) of the light guide plate is cut in a plane, the weight can be reduced as compared with a conventional light guide plate having one flat slope. . In addition, since the inclined surface is formed of a plurality of flat surfaces and has a shape in which wedge-shaped light guides are arranged, it is easier to manufacture than a conventional curved light guide plate. Further, the light diffusion pattern ratio is changed discontinuously at or near the first wide surface portion facing the boundary portion between the planes, so that the light diffusion plate portion can be divided into a plurality of light guide plate portions capable of equalizing luminance. . Therefore, it is possible to independently control the light diffusion pattern ratio in a portion opposed to each plane portion on the light incident end side and the opposite end side, and to optimize for uniform brightness.

Further, the light diffusion pattern is connected to the boundary between the planes or in the vicinity thereof, or the exit surface portion facing the boundary, so as to connect the discontinuous light diffusion pattern ratio between the light incident end side and the opposite end side. By providing a region where the rate changes continuously, it is possible to prevent luminance unevenness occurring at the boundary.

Alternatively, a portion where the area ratio of the light diffusion pattern is discontinuously changed is arranged on the light incident end side or on the opposite end side with respect to the boundary between the planes or the exit surface portion opposed thereto, The light diffusion pattern may be provided at or near the boundary or the portion facing the boundary, or may be provided over the boundary or the portion facing the boundary. Also in this case, it is possible to prevent luminance unevenness occurring at the boundary.

Alternatively, an additional light diffusion pattern may be provided at or near the boundary between the planes or at the exit surface facing the boundary, and in this case, it is also possible to prevent luminance unevenness occurring at the boundary. It is.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1A is a sectional view showing a configuration of a planar light source according to Embodiment 1. The planar light source is a side light type backlight light source, and includes a cold cathode tube 3 and a reflector 5 on the left side of the light guide plate 2 in the drawing. Light from the cold cathode tube 3 enters the light guide plate 2 directly or after being reflected by the reflector 5. And the light guide plate 2
In the inside, the light deviating from the total reflection condition on the emission surface (upper surface 12) or the light irradiated on the light diffusion pattern formed on the slopes 13a and 13b is emitted to the observer 7, and finally all the light is emitted. Is emitted to the observer 7 side.

In the present embodiment, the light guide plate 2 has, for example, two inclined planes 13a and 13b, and the inclined plane has a flat shape. The planes 13a, 1
The position on the cross section of the boundary portion 3b is referred to as an inflection point 10. Light guide plate 2 having such inflection point 10
As shown in FIG. 1B, two wedge-shaped light guide plate portions 11 a and 11 b can be integrally formed and combined with each other with the inflection point 10 at the center.

The light guide plate portion 11a and the light guide plate portion 1
Reference numeral 1b denotes a conventionally used wedge-shaped light guide plate, and it is easy to equalize the luminance distribution of light emitted to the observer 7 by a conventional method. In this case, the luminance distribution is equalized by appropriately distributing the light diffusion pattern on the upper surface 12a and the upper surface 12b or on the inclined surface 13a and the inclined surface 13b as shown in FIG.

The light diffusion pattern serves to emit light in the light guide path to the outside, and the light emission ratio is determined by the area ratio of the light diffusion pattern per unit area (light diffusion pattern ratio). . Hereinafter, the distribution of the light diffusion pattern ratio and the luminance uniformity will be described with reference to FIG. Here, the location where the light diffusion pattern 6 exists is represented by a distance X from the light incident end 8. Further, in this figure, the light diffusion pattern ratio shows a curve connecting values (area ratios) at a distance X appropriately set at a constant pitch.

First, the relationship between the thickness of the light guide plate 2 at the point X and the luminance at the point X will be described. In the light guide plate 2, light is emitted while being repeatedly reflected, so that the thinner the thickness, the more the number of reflections, the more emitted light, and the higher the brightness. Therefore, the light is more likely to be emitted as the distance from the light incident end 8 increases, and it is necessary to suppress the light emission in order to achieve uniform brightness, so that the light diffusion pattern rate needs to be reduced.

Next, the relationship between the distance X from the light incident end 8 to the point X and the luminance will be described. As the distance from the light incident end 8 increases, the amount of light in the light guide plate 2 at the point X decreases. Therefore, since it is necessary to emit a large amount of light in order to achieve uniform brightness, it is necessary to increase the light diffusion pattern ratio.

From the above, the optimum light diffusion pattern ratio is determined based on the balance between the role of suppressing light emission and the role of promoting light emission. However, at the end 9 opposite to the light incident end 8, the light diffusion pattern ratio is increased in order to emit all the light.
As a whole, as shown in FIG. 2, the light diffusion pattern ratio is designed to increase as the distance from the light incident end 8 increases.
Luminance can be equalized over the entire surface of the light guide plate.

Examples of the type of the light diffusion pattern include a stripe pattern, a satin pattern, a cone, a pyramid, and a print pattern. In addition, as a method of forming a light diffusion pattern, a method of forming the light diffusion pattern by etching on a molding die is generally used, and a method of forming the light diffusion pattern by a press, a method of using photolithography, and the like are also available. Furthermore, it is also possible to produce a light diffusion pattern simultaneously with the injection molding when forming the light guide plate, and it is also possible to produce it by printing. Due to such differences in the light diffusion pattern, the reflectance, transmittance, diffusion width, etc. of light are different, so the specific design of the light diffusion pattern is different, but the basic luminance equalization method is the same as described above. The same is true.

For these reasons, when designing the light guide plate of this embodiment, the light guide plate portion 11a and the light guide plate portion 11
Regarding b, the distribution of the light diffusion pattern ratio may be independently designed according to the thickness and the apex angle (the angle between the slope and the upper surface) of each light guide plate. However, if the light diffusion pattern rates of the light guide plate portion 11a and the light guide plate portion 11b are independently designed, the light diffusion pattern of the light guide plate portion 11a at the inflection point 10, which is the boundary between the light guide plate portion 11a and the light guide plate portion 11b. A difference occurs between the ratio and the light diffusion pattern ratio of the light guide plate portion 11b. This point will be described with reference to FIG. 1 focusing on the difference in the apex angle of the light guide plate.

As the vertex angle of the light guide plate increases, the angle of light rays incident on the upper surface increases. Therefore, when the apex angle of the light guide plate is small, the light being guided becomes difficult to emit, and it is necessary to increase the light diffusion pattern ratio of the light guide plate to promote light emission. In the present embodiment, since the apex angle of the light guide plate changes with the inflection point 10 interposed therebetween, the light diffusion pattern ratio is set to be different, and the light diffusion pattern ratio of the light guide plate portion 11a at the inflection point 10 is different from the light diffusion pattern ratio. The light diffusion pattern rates of the light plate portion 11b do not match. Then, as shown in FIG. 3, the light diffusion pattern rate changes discontinuously near the inflection point,
The size of the light diffusion pattern changes. As described above, the light guide plate of the present embodiment is characterized in that the light diffusion pattern rate changes discontinuously at the inflection point 10 portion, and has a distribution in which the light diffusion pattern rate changes continuously. This is different from a wedge-shaped light guide plate.

In this embodiment, for example, in a light guide plate of one long side type, the short side is 180 mm, the long side is 240 mm, the thickness of the light incident end is 0.6 mm to 3 mm, and the thickness of the opposite end is 0.4 mm.
If the diameter is about 2.5 mm to 2.5 mm, the diameter of the light diffusion pattern at the light incident end is about 80 μm to 250 μm, about 80 μm to 300 μm at the inflection point, and about 1 μm at the end opposite to the inflection point.
00 μm to 400 μm, about 150 μm to 1 near the opposite end
000 μm. The production of the light guide plate can be performed by injection molding.

The light guide plate of the present embodiment obtained as described above has a second wide surface (slope) of the light guide plate 2 having a plurality of flat surfaces 13.
Since it is composed of a and 13b, it can be manufactured more easily than a conventional light guide plate whose slope is a curved surface. In addition, since the slope is formed to have a planar shape, the weight can be reduced as compared with a single conventional light guide plate, and as a result, the planar light source can be reduced in weight. Further, by changing the light diffusion pattern rate discontinuously at the boundary (inflection point) 10 between the planes, each light guide plate portion 1 is changed.
In 1a and 11b, the light diffusion pattern ratio can be independently controlled and optimized, and the luminance of the entire light guide plate can be equalized.

(Embodiment 2) As described in Embodiment 1, by dividing the light guide plate having an inflection point into a plurality of wedge-shaped light guide plates, an optimum design can be independently performed. it can. However, at the inflection point 10, since the light from the light guide plate portion 11a is incident on the light guide plate portion 11b having a different slope angle, luminance unevenness may occur. The mechanism of the occurrence of the uneven brightness will be described with reference to FIG.

As shown in FIG. 4A, the light guide plate portion 11
The light which has guided the light guide a is reflected by the upper surface 12 and the light guide plate portion 1
Light guide plate portion 11b having a smaller inclination than slope 13a of 1a
To the slope 13b. Then, the light beam 14b reflected by the inclined surface 13b of the light guide plate portion 11b is closer to the end 9 opposite to the light incident end 8 as compared with the light beam 14a when the inclined surface 13a of the light guide plate portion 11a is continued. Lean. For this reason, the amount of light emitted from the upper surface of the inflection point 10 decreases, and as shown in FIG. This is the mechanism for generating luminance unevenness near the inflection point 10.

Therefore, in this embodiment, the inflection point 10
In order to prevent luminance unevenness in the vicinity, as shown in FIG. 4C, a light diffusion pattern 15 is additionally provided on the light incident end 8 of the inflection point 10 and the opposite end 9 thereof. As a result, the light incident on the light guide plate portion 11b from the light guide plate portion 11a is diffused without shifting to the opposite end 9 side as described above, and the brightness depression 17 near the inflection point 10 can be prevented. It should be noted that, as in the fourth embodiment described later, even if the light is crossed over the inflection point 10 or provided on the light incident end side, it is only necessary that the luminance drop in the luminance depression 17 can be corrected by the diffusion pattern. It depends on the diffusion characteristics of the diffusion pattern. Therefore, the distance of the additional light diffusion pattern 15 from the inflection point, the light diffusion pattern ratio, the pattern size, and the like are not uniquely determined, but can be set according to the characteristics of the light diffusion pattern.

(Embodiment 3) In the present embodiment, as shown in FIG. 4D, a light diffusion pattern 16 is formed on the upper surface portion facing the inflection point 10 in order to prevent luminance unevenness near the inflection point 10. Provide additionally.

Regarding the position of the light diffusion pattern 16,
This will be described below. In FIG. 4D, θ1 is the inflection point 1
0 is the angle when light is reflected on the inclined surface 13a on the light incident end side, and θ2 is the angle when light is reflected on the inclined surface 13b on the opposite end side of the inflection point 10. Also, the light incident end side slope 13a
Is φ1, the angle of the opposite end slope 13b is φ2 (corresponding to the above-mentioned apex angle), and the total reflection angle is α0. These relationships are expressed as θ1 = α0−2 × φ1 (1) θ2 = α0−2 × φ2 (2) Further, the total reflection angle α0 is determined by the refractive index of the light guide plate material, for example, about 42 degrees for a material having a refractive index of 1.5. From the above equation, θ for the inflection point 10
The light diffusion pattern 16 is additionally formed so as to straddle the points 1 and θ2. The distance of the additional light diffusion pattern 16 from the inflection point, the light diffusion pattern ratio, the size of the pattern, and the like are not uniquely determined, but can be set according to the characteristics of the light diffusion pattern.

(Embodiment 4) In the present embodiment, in order to prevent luminance unevenness near the inflection point 10, an additional light diffusion pattern is not provided but the entire light diffusion pattern formation position is set to the light incident end side. Or move it to the opposite end. In this case, as shown in FIG. 4 (e), it is most effective to position the light diffusion pattern on the side opposite to the light incident end of the inflection point 10, but it is formed so as to straddle the inflection point 10. Alternatively, it may be located on the light incident end side of the inflection point 10. At this time, the light diffusion pattern is such that the luminance depression 17
Is preferably formed up to the position at which the occurrence of occurs.

(Embodiment 5) In this embodiment, as shown in FIG. 5, in order to prevent luminance unevenness near the inflection point 10, the inflection point 10 which is a boundary between the light guide plate portion 11a and the light guide plate portion 11b is used. In the vicinity, the above-described discontinuous distribution of the light diffusion pattern ratio is connected.

The light diffusion pattern rate is set from the vicinity of the light incident end 8 of the light guide plate 2 in the same manner as in the first embodiment, and the light diffusion pattern rate is gradually increased near the inflection point 10. At the inflection point 10, the light diffusion pattern ratio of the light guide plate portion 11a and the light diffusion pattern ratio of the light guide plate portion 11b, which are assumed when the discontinuity is changed, are set to a value approximately in the middle. Then, the light diffusion pattern ratio is further increased toward the opposite end 9 to reach a specified value.

The length of the section (referred to as a transition section) 18 where the light diffusion pattern ratio is continuous near the inflection point 10 depends on the diffusion width of the light diffusion pattern near the inflection point 10.
The thickness is preferably about the thickness of the light guide plate at the inflection point 10.
The reason is that the diffusion width of light traveling in the light guide plate is 1 at full width at half maximum.
This is because most of the light is within 0 °, and when the light diffused on the slope reaches the upper surface, the width spread by the diffusion is smaller than the thickness of the light guide plate.

The distribution of the light diffusion pattern ratio in the transition section 18 may be changed linearly as shown in FIG. 5, or may be made a smooth shape as shown in FIG. In this case, since the light diffusion pattern ratio can be changed smoothly, the degree of light diffusion becomes smooth, and a light guide plate with a higher degree of uniformity can be realized.

(Embodiment 6) In the present invention, the position of the boundary (inflection point) between planes on the slope is not limited to the middle, and may be shifted to the light incident end side, or may be shifted to the opposite end side. May be biased to

FIG. 7A-1 shows a case where the inflection point 10 is provided so as to be offset toward the light incident end 8 side. An object of the present invention is to reduce the weight of the light guide plate. However, if the inflection point 10 is provided from the middle of the slope to the light incident end 8 side, the cross-sectional area of the light guide plate 2 can be further reduced to promote weight reduction. Can be.

However, in this case, since the slope 13a becomes large in inclination, a design in which the light diffusion pattern ratio near the light incident end 8 is reduced is performed. For example, the light diffusion pattern ratio is set as shown in FIG. In this figure, the light diffusion pattern rate at the inflection point portion is discontinuous. However, similarly to the fifth embodiment, a region connecting the discontinuous light diffusion pattern rates on both sides of the inflection point may be provided. Alternatively, Embodiment 2
As in the fourth embodiment, it is also possible to prevent luminance unevenness near the inflection point.

Further, FIG. 7 (b-1) shows a case where the inflection point 10 is provided offset to the opposite end 9 side. In this case,
The effect of reducing the weight of the light guide plate is smaller than when the inflection point is provided in the middle of the slope.

In this case, since the inclination of the slope 13a becomes gentle, the light diffusion pattern ratio is set, for example, as shown in FIG. 7 (b-2). Although the light diffusion pattern rate at the inflection point portion is discontinuous in this figure as well, a region connecting the discontinuous light diffusion pattern rates on both sides of the inflection point may be provided as in the fifth embodiment. Alternatively, it is also possible to prevent luminance unevenness near the inflection point as in the second to fourth embodiments.

The case where one inflection point is provided has been described above, but the specific size of the light diffusion pattern differs depending on the size and configuration (for example, thickness and angle) of the entire light guide plate. For example, in a light guide plate of a long side one light type, a short side 1
80mm, long side 240mm, thickness of light entrance end 0.6mm ~
In a light guide plate having a thickness of about 3 mm and a thickness of about 0.4 mm to 2.5 mm at the opposite end, the diameter of the light diffusion pattern at the light input end is about 80 μm to 250 μm, and the inflection point portion (or the light input end side portion of the transition section) About 80 μm to 300 μm, about 100 μm to 400 μm on the opposite end side (or the opposite end side from the transition section) from the inflection point, and about 150 μm near the opposite end.
Preferably it is 1000 μm. If the light diffusion pattern ratio is set as described above, the pitch of the light diffusion patterns may be equal or unequal.

In the present invention, the point of inflection is provided in order to reduce the weight of the light guide plate by shaving off the slope which was conventionally a straight line.
A plurality of the above may be provided. For example, as shown in FIG. 8A, when the slope is formed by three planes, the boundary between the planes is a first inflection point 19 and a second inflection point 20. Also, as shown in FIG.
When two planes are configured, the boundary between the planes is the first inflection point 2
There are three inflection points 1, a second inflection point 22, and a third inflection point 23. The light diffusion pattern ratio in each case is, for example, as shown in FIG.
2) and FIG. 8 (b-2). Although the light diffusion pattern rate at the inflection point portion is discontinuous, similarly to the fifth embodiment, a transition section having a continuous light diffusion pattern rate may be provided to connect the discontinuous light diffusion pattern rates. Good. Alternatively, it is possible to prevent luminance unevenness near the inflection point as in the second to fourth embodiments. Further, it goes without saying that there may be four or more inflection points as long as it is at least one or more. However, if the number of planes is increased too much, it approaches the conventional example of FIG.

(Embodiment 7) In general, the light diffusion pattern is provided on the slope side, but may be provided on the top side as shown in FIG. Also in this case, it is considered that the upper surface is separated at a position facing the inflection point 10 and is continuous at each portion,
The light diffusion pattern may be formed at a light diffusion pattern rate that is discontinuous in a portion opposed to the light diffusion pattern.

The light diffusion pattern provided on the slope has a role of reflecting and diffusing light to the observer side, but the light diffusion pattern provided on the upper surface has a role of diffusing light while transmitting the light to the observer side. The configuration of the light diffusion pattern is naturally different.

For example, in the case of a light diffusion pattern having a rough surface, the larger the inclination of the uneven surface constituting the rough surface is, the more light is emitted out of the condition of total reflection, so that it is suitable for the light diffusion pattern on the upper surface. ing. On the other hand, the smaller the inclination of the uneven surface constituting the rough surface, the less likely it is to deviate from the condition of total reflection and the more reflected light, so that it is suitable for a light diffusion pattern on an inclined surface.

The difference in the optical principle between the case where the light diffusion pattern is provided on the upper surface and the case where the light diffusion pattern is provided on the inclined surface will be described below with reference to FIG. The method of equalizing the luminance of the light guide plate portion 11a and the light guide 11b is the same as that in the case where the light diffusion pattern is provided on the slope. The difference is that the light guide plate portion 11a
When light is incident on the light guide plate portion 11b from above, since the light diffusion pattern is on the upper surface, light diffused by the light diffusion pattern near the inflection point is emitted from the upper surface after being reflected on the slope. For this reason, the unevenness in luminance caused by the existence of the inflection point can be eliminated as follows.

For example, as shown in FIG. 10A, a problem that light reaching the periphery of the inflection point 10 is directed in different directions by the inflection point 10 is caused by providing the light diffusion pattern 15 around the inflection point 10. And reduce the difference in the direction of light. Thereby, it is possible to suppress the occurrence of the depression of the brightness near the inflection point 10 as described above.

Alternatively, as shown in FIG. 10B, a light diffusion pattern 16 is provided at a position on the upper surface where light reaching the periphery of the inflection point 10 is directed in different directions by the inflection point 10 and reaches. Also in this method, light can be diffused and superimposed, and the difference in the direction of light can be reduced.

This light diffusion pattern 16 is shown in FIG.
The position can be set in the same manner as in Embodiment 3 described using (d). Further, as shown in FIG. 10C, by designing the light diffusion pattern 16 in advance at this position, an additional pattern can be unnecessary as in the fourth embodiment.

In the light guide plate of the present embodiment obtained in this way, since the second wide surface (slope) of the light guide plate 2 is composed of a plurality of planes, it is easier than a conventional light guide plate in which the slope is a curved surface. Can be manufactured. In addition, since the slope is formed to have a planar shape, the weight can be reduced as compared with a single conventional light guide plate, and as a result, the planar light source can be reduced in weight. Furthermore, by changing the light diffusion pattern rate discontinuously in the portion facing the boundary portion (inflection point) 10 between the planes, each light guide plate portion 1 is changed.
In 1a and 11b, the light diffusion pattern ratio can be independently controlled and optimized, and the luminance of the entire light guide plate can be equalized.

In the above embodiments, the light diffusion pattern may be a stripe, matte, cone, pyramid, print pattern, or the like, or the surface may be roughened. Although the material of the light guide plate is not particularly limited, for example, polymethyl methacrylate (PMMA), methyl methacrylate and other materials may be used from the viewpoint of a manufacturing method that can be manufactured by injection molding, and optical characteristics such as transparency and refractive index. A transparent resin such as a copolymer with acrylate or methacrylate or polycarbonate can be used. In addition, it is preferable to use a cycloolefin polymer having a lower specific gravity than PMMA (cycloolefin polymer 1.0 with respect to PMMA 1.2) because further weight reduction can be achieved. Further, the cycloolefin polymer has better fluidity during injection molding than PMMA, and is therefore suitable for thin molding, and has a high refractive index (PMMA 1.49).
On the other hand, since the cycloolefin polymer 1.53) has a large effect of confining light, it is suitable for reducing the thickness of the light guide plate. Furthermore, since the cycloolefin polymer has low hygroscopicity, it has the advantage that the shape is less deformed even under high humidity conditions.

The light guide plate of the present invention can be manufactured by injection molding or compression molding using the above-mentioned resin, and at the same time, the above-mentioned light diffusion pattern can be formed on the light guide plate. Further, the light diffusion pattern can be formed by printing after forming the light guide plate.

The light guide plate of the present invention can be used alone as a planar light source. However, in order to make the light diffusion pattern invisible and to increase the uniformity of the emitted light, a diffusion film is provided on the light exit surface. It is preferable to arrange them. In addition, a known prism sheet may be used in combination with the light exit surface, and in this case, higher luminance can be obtained. When a diffusion film or a prism sheet is used as described above, the light guide plate, the prism sheet, and the diffusion film may be arranged in this order, or the light guide plate, the diffusion film, and the prism sheet may be arranged in this order. , Diffusion film, prism sheet,
You may arrange | position in the order of a diffusion film. As this prism sheet, the direction of the ridge line of the prism is orthogonal to each other.
Also includes one in which two prism sheets are stacked. Further, if a reflection plate is provided along the slope, the light emitted to the slope can be guided to the observer, so that the brightness can be increased.

In the planar light source of the present invention, the light source device generally includes a combination of a cold cathode tube and a reflector.

[0065]

As described in detail above, according to the present invention,
By forming a plurality of flat surfaces as a shape obtained by shaving the slope in a planar manner, it is possible to divide the light guide plate into a plurality of light guide plate portions capable of equalizing luminance, and to independently control the light diffusion pattern ratio in each portion. Therefore, it is possible to realize a planar light source that is lightweight as a whole, easy to manufacture, and capable of equalizing luminance.

Even if the light diffusion pattern is formed on the slope side,
Even if it is formed on the emission surface side, it is possible to optimize and design any of them. However, when the light diffusion pattern is formed on the light emitting surface, the light diffusion pattern can be formed on the same plane as compared with the inclined surface side, so that the production is easier.

Further, a discontinuous light diffusion pattern ratio between the light incident end side and the opposite end side thereof may be connected through a section of about the thickness of the light guide plate at the boundary (inflection point) between the planes. . Alternatively, the position of the light diffusion pattern may be adjusted, and the light diffusion pattern may be provided at or near the inflection point or at the exit surface portion facing the inflection point. Alternatively, an additional light diffusion pattern may be provided at the inflection point, in the vicinity thereof, or at the exit surface portion facing the inflection point. In these cases, uniformity of luminance can be ensured even near the inflection point.

Further, according to the present invention, the weight of the backlight optical system and the display can be reduced by using the planar light source of the present invention whose weight is reduced.

[Brief description of the drawings]

1A is a cross-sectional view illustrating a schematic configuration of a planar light source according to a first embodiment, and FIG. 1B is a cross-sectional view illustrating that a light guide plate includes two wedge-shaped light guide plate portions; (C) is a diagram showing an example of the light diffusion pattern rate.

2A is a cross-sectional view showing a schematic configuration of a wedge-shaped light guide plate, FIG. 2B is a plan view showing an example of a light diffusion pattern distribution, and FIG. 2C is a light diffusion pattern ratio. It is a figure showing the example of.

3A is a cross-sectional view illustrating a schematic configuration of the planar light source according to the first embodiment, FIG. 3B is a plan view illustrating an example of a light diffusion pattern distribution, and FIG. It is a figure showing an example of a diffusion pattern rate.

FIGS. 4A and 4B are cross-sectional views for explaining a mechanism of generating luminance unevenness near an inflection point of a light guide plate;
(C) is an enlarged cross-sectional view of a portion near the inflection point in the second embodiment to explain a light diffusion pattern of the light guide plate for preventing luminance unevenness, and (d) is a sectional view of the light guide plate in the third embodiment. FIG. 10 is an enlarged cross-sectional view of a portion near a pole, and FIG. 10E is an enlarged cross-sectional view of a portion near a pole in the light guide plate of the fourth embodiment.

5A is a cross-sectional view illustrating a schematic configuration of a planar light source according to a fifth embodiment, and FIG. 5B is an example in which a light diffusion pattern rate is linearly continuous at an inflection point portion of the light guide plate. FIG.

FIG. 6 is a diagram illustrating an example in which a light diffusion pattern ratio is smoothly and continuously made continuous at a point of inflection in a light guide plate according to a fifth embodiment.

FIG. 7A is a cross-sectional view illustrating a schematic configuration of a planar light source in which an inflection point of the light guide plate according to the sixth embodiment is shifted toward the light incident end, and FIG. FIG. 4 is a cross-sectional view showing a schematic configuration of a light guide plate in which the inflection point of FIG.
2) and (b-2) are diagrams illustrating examples of their light diffusion pattern rates.

8 (a-1) and (b-1) are cross-sectional views showing a schematic configuration of a light guide plate having a plurality of inflection points according to Embodiment 6, and (a-2) and (b-2) are It is a figure which shows the example of those light diffusion pattern rates.

9A is a cross-sectional view illustrating a schematic configuration of a light guide plate having a light diffusion pattern according to a seventh embodiment formed on an upper surface, and FIG.
FIG. 4 is a diagram showing an example of the light diffusion pattern ratio.

FIGS. 10A to 10C are cross-sectional views in which a portion near an inflection point of the light guide plate according to the seventh embodiment is enlarged in order to explain a light diffusion pattern of the light guide plate for preventing luminance unevenness.

11A is a cross-sectional view illustrating a schematic configuration of a conventional planar light source, FIG. 11B is a plan view illustrating an example of a light diffusion pattern distribution, and FIG. It is a figure showing an example of a rate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 13a, 13b Slope 2 Light guide plate 3 Cold cathode tube 4 Light 5 Reflector 6, 15, 16 Light diffusion pattern 7 Observer 8 Light incident end 9 Opposite end 10 Inflection point 11a, 11b Light guide plate portion 12, 12a, 12b Top surface 14a, 14b Light ray 17 Brightness depression 18 Transition section 19, 21 First inflection point 20, 22 Second inflection point 23 Third inflection point

Claims (9)

[Claims] 1. A light diffusing pattern is provided on a second wide surface opposite to the first wide surface, and light is incident from a light incident end surface perpendicular to the first wide surface and is guided out of the first wide surface. In the optical plate, the second wide surface has a shape obtained by planarly shaving a slope that forms a predetermined angle with the first wide surface, and includes a plurality of planes, and at or near a boundary between the planes, A light guide plate wherein the area ratio of the light diffusion pattern changes discontinuously, and the area ratio of the light diffusion pattern continuously changes at each of the light incident end side and the opposite end side. 2. A light guide plate, wherein a light diffusion pattern is provided on a first wide surface, and light is incident from a light incident end surface perpendicular to the first wide surface and emitted from the first wide surface. The second wide surface facing the wide surface has a shape obtained by planarly shaping a slope forming a predetermined angle with the first wide surface, and
In the first wide surface portion or the vicinity thereof, which is composed of a plurality of planes and faces the boundary between the planes, the area ratio of the light diffusion pattern changes discontinuously, and each of the light incident end side and the opposite end side has A light guide plate in which the area ratio of the light diffusion pattern changes continuously in some parts. 3. An area ratio of a discontinuous light diffusion pattern between a light incident end side and an opposite end side thereof is connected to a boundary portion between the planes or in the vicinity thereof or a first wide surface portion opposed thereto. 3. The light guide plate according to claim 1, further comprising a region in which the area ratio of the light diffusion pattern is continuously changed. 4. A portion where the area ratio of the light diffusion pattern is discontinuously changed is closer to the light incident end side or the opposite end side than the boundary between the planes or the first wide surface facing the boundary. 4. The light diffusion pattern according to claim 1, wherein the light diffusion pattern is provided at or near the boundary portion or a portion facing the boundary portion, or is provided across the boundary portion or a portion facing the boundary portion. A light guide plate as described in Crab. 5. The light guide plate according to claim 1, further comprising an additional light diffusion pattern at or near a boundary between the planes. 6. The light guide plate according to claim 1, wherein an additional light diffusion pattern is further provided on a first wide surface portion facing the boundary between the planes or the vicinity thereof. . 7. A light guide plate according to claim 1, further comprising a light source device disposed on a light incident end face of the light guide plate, and receiving light from the light source device. A planar light source which is made to enter a light guide plate from a light end face and emits light from a first wide surface perpendicular to the light incident end face. 8. A backlight optical system using the planar light source according to claim 7. 9. A display, wherein the planar light source according to claim 7 is arranged on the back side of the display unit, with the first wide surface side being arranged on the display unit side.