JP2003197019A - Planar lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planar lighting device capable of suppressing generation of light/dark stripes. <P>SOLUTION: A plate light guide body 2 is formed with a light reflection pattern 29 comprising a stepped prism on its upper surface 15. The plate light guide body 2 is also formed with a reflection direction dispersion surface 21 along the axial direction of a light source part 5 similar to the light reflection pattern 29 on its lower surface 16. The reflection direction dispersion surface 21 is formed into, for example, an arc shape so as to continuously change the angle of a surface for reflecting the light. The reflection direction dispersion surface 21 can make lights (31a, 31b, and 31c) reflecting in the same angle direction in a step part 27 advance in the respectively different angle directions (32a, 32b, and 32c), make them mainly reach at gentle slope parts 28 (arrows 32a and 32b), and make them bent and irradiate to the outside (arrow 33). It can also make the light direction irradiated to the outside irregular. This constitution eliminate matching of the directions not receiving lights irradiated from the light reflection pattern in a certain region, thus suppressing the generation of the light/dark stripes. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar illuminating device used for illuminating means such as signboards and various reflective display devices, and more particularly to illuminating means for liquid crystal display devices.

[0002]

2. Description of the Related Art Liquid crystal display devices, which are thin, occupy a small volume, and are lightweight, are used in many electric products such as mobile phones and personal computers, and their demand is increasing. There is. By the way, since the liquid crystal itself of the liquid crystal display device does not emit light by itself, the liquid crystal is irradiated separately from the liquid crystal display device when used in a dark place where the brightness of sunlight or room lighting cannot be sufficiently captured. Lighting means is required. Therefore, it is desired that the illuminating means for irradiating the liquid crystal is also small in size and consumes less power, and in recent years, a thin plate sidelight type (light guide plate type) planar illuminating device is often used as the means.

FIG. 12 shows one form of a conventional planar lighting device using a sidelight system. As shown in the figure,
The planar lighting device 1 ′ includes a substrate 2 made of a translucent material (hereinafter, referred to as a plate-shaped light guide 2), and a rod-shaped lighting device 1 ′ provided in proximity to one end face 8 of the plate-shaped light guide 2. The light source unit 5 is generally configured. Then, the light emitted from the light source unit 5 enters the plate-shaped light guide 2 and illuminates a liquid crystal display device (not shown) arranged below the plate-shaped light guide 2.

The light source section 5 is a rod-shaped light guide body 3 made of a rod-shaped light-transmitting material, and a point light source (for example, a light emitting diode) 4 arranged to face one end 7 of the rod-shaped light guide body 4. It consists of and. Further, the rod-shaped light guide 3 is provided with an optical path changing means 12. The optical path changing means 12 is provided with a groove having a triangular cross section on the opposite surface of the surface (one side surface) 9 facing the one end surface 8 of the plate-shaped light guide 2 so that the point light source 4 can be separated from the point light source 4. It has a function of causing the emitted light to enter the one end face 8 of the plate-shaped light guide 2 substantially uniformly. The rod-shaped light guide 3 is separated from the one end surface 8 of the plate-shaped light guide 2 by a predetermined distance, and one side surface 9 of the rod-shaped light guide 3 is provided.
Are arranged along the one end surface 8 of the plate-shaped light guide 2 (hereinafter, also referred to as a proximity arrangement).

In order to make the light emitted from the point light source 4 efficiently enter the plate-shaped light guide 2, the rod-shaped light guide 3 is provided.
A light reflecting member (frame) 13 is provided around the. The light reflection member 13 is formed in a substantially U shape, and covers the periphery of the rod-shaped light guide 3 in the longitudinal direction other than the surface 9 facing the plate-shaped light guide 2.

A plurality of light reflection patterns 39 are formed on the upper surface 15 of the plate-shaped light guide 2. Light reflection pattern 39
Is composed of a groove portion 37 having a triangular cross section and a flat portion 38 adjacent to the groove portion 37, and is formed in parallel with the rod-shaped light guide 3 at predetermined intervals. In the groove portion 37, the light incident from the rod-shaped light guide 3 is reflected almost uniformly on the entire surface of the plate-shaped light guide 2 without being influenced by the distance from the rod-shaped light guide 3 (light source unit 5), In order to uniformly illuminate a liquid crystal display device (not shown) provided on the lower side of the plate-shaped light guide 2, it is formed so as to become gradually deeper as it goes away from the rod-shaped light guide 3. In addition to the above, as the form of the light reflection pattern 39, there is also a form composed of a stepped prism.

However, in the case of a front light type device in which illumination using such a light reflection pattern 39 is placed in front of the reflection type liquid crystal display element, the light reflected by the reflection type liquid crystal display element passes through the light reflection pattern 39. When doing the groove 3
7 and the flat portion 38 have different transmissivities (different transmission directions due to refraction), and a mosaic pattern (cell boundary) of liquid crystal cells that are pixels of the liquid crystal display device (liquid crystal display element). The interference fringes (moiré pattern) generated by the above are conspicuous, and the image becomes difficult to observe. The moire pattern is generated by the pattern shape of the light reflection pattern 39,
That is, the groove 37 is closely related to the depth, size, pitch interval, and the like.

[0008] Further, it is a kind of bright and dark stripes different from the stripes of the moire pattern, which is a phenomenon peculiar to the front light type device, and the position and interval at which it occurs changes with the movement of the observer's viewpoint. There was a problem that streaks occurred.

[0009]

The bright and dark stripes are Fresnel reflections mainly on the lower surface of the plate-shaped light guide (the surface opposite to the surface on which the light reflection pattern is formed), that is, the plate-shaped light guide and the air. It was clarified that it was caused by the reflected light based on the difference in the refractive index of. Since it has been known that the reflected light adversely affects the contrast characteristics of the display device, it is generally a non-reflective coating applied to the lower surface of the plate-shaped light guide as a measure for improving the contrast. Has been done. By this anti-reflection coating treatment,
Although it is possible to significantly reduce the reflected light, the current non-reflective coating technology cannot completely suppress the reflected light in the entire visible range, and normally the reflection level is 0.2%. There is light. This slight reflected light causes the bright and dark stripes described above.

The present invention has been made in order to suppress the bright and dark fringes caused by the reflected light on the lower surface of the plate-shaped light guide, and does not increase the number of parts used and lowers the light utilization efficiency. It is an object of the present invention to provide a planar illumination device that can suppress the generation of bright and dark stripes different from moire stripes without causing the above.

[0011]

In order to solve the above-mentioned problems, the invention of claim 1 provides a plate-shaped light guide made of a translucent material and a proximity arrangement along the side surface of the plate-shaped light guide. On the plate-shaped light guide, a light reflection pattern including a plurality of groove portions and a flat portion adjacent to the groove portions, or a light reflection pattern formed by a step prism is provided. In the surface lighting device of the sidelight type formed in, on the surface opposite to the surface on which the light reflection pattern of the plate-shaped light guide is formed, along the same direction as the direction in which the light reflection pattern is formed. A reflective direction dispersion surface is formed.

The light that has entered the plate-shaped light guide from the light source section is
The light is reflected by the light reflection pattern formed on the upper surface of the plate-shaped light guide and travels in the direction of the lower surface of the plate-shaped light guide (the surface on which the reflection direction dispersion surface is formed), and part of the light is the lower surface. The light is reflected by and travels toward the upper surface, and is emitted from the upper surface of the plate-shaped light guide to the outside. Light is reflected by the reflection direction dispersion surface formed on the lower surface of the plate-shaped light guide in this way, so that the emission direction of the light emitted from the upper surface of the plate-shaped light guide is irregular, and the plate-shaped light guide is formed. The angle (area) where light is not emitted from the upper surface of the plate is reduced to suppress the occurrence of bright and dark portions (bright and dark stripes) that appear on the plate-shaped light guide.

In order to solve the above problems, the invention of claim 2 is characterized in that, in the invention of claim 1, the reflection direction dispersion surface is a lenticular. Here, the lenticular means a unit of a small lens group having a semi-cylindrical shape. By making the shape of the reflection direction dispersion surface into the lenticular shape of the kamaboko shape,
The reflection direction dispersion surface can be easily manufactured. Also,
By continuously disposing the arc-shaped reflection direction dispersion surface, the bright and dark fringes appearing on the plate-shaped light guide can be surely suppressed.

In order to solve the above-mentioned problems, the invention of claim 3 is the invention of claim 1, wherein the reflection direction dispersion surface is arranged between lenticular microlenses. And a flat portion.

In order to solve the above problems, the invention of claim 4 is the same as the invention of claim 2 or 3,
The lenticular microlens forming the reflecting direction dispersion surface is characterized in that the maximum angle of the tangent to the horizontal surface of the plate-shaped light guide is 3 degrees or less. By forming the reflection direction dispersion surface in a predetermined shape, bright and dark stripes on the plate-shaped light guide can be reliably suppressed without deteriorating other display performances.

In order to solve the above-mentioned problems, the invention of claim 5 relates to the invention of claim 2 or 3,
It is characterized in that each of the lenticular minute lenses constituting the reflection direction dispersion surface is composed of a plurality of flat surfaces in which the angle of the plate-shaped light guide with respect to the horizontal surface gradually changes.

In order to solve the above-mentioned problems, the invention of claim 6 is the invention of claim 1, wherein the reflection direction dispersion surface is an arcuate groove or a plurality of arcuate grooves arranged continuously. It is characterized by comprising an arcuate groove and a flat portion formed between the arcuate grooves.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a planar lighting device according to the present invention will be described below with reference to the accompanying drawings. This planar lighting device has a reflection direction dispersion surface for irregularly reflecting light formed on the lower surface of the plate-shaped light guide of the planar lighting device described as the conventional example, and its reflection direction. The dispersion surface has a characteristic shape, and the same members as those of the conventional planar lighting device are denoted by the same reference numerals and detailed description thereof will be omitted.

FIG. 1 is an exploded perspective view showing an embodiment of the planar lighting device according to the present invention. As illustrated, the planar lighting device 1 includes a plate-shaped light guide 2 and one end surface 8 of the plate-shaped light guide 2.
The light source unit 5 and the light reflecting member (also referred to as a frame) 13 that are arranged close to each other along the line are generally configured. A light reflection pattern 19 is formed on the upper surface (observation side surface) 15 of the plate-shaped light guide 2, and the light reflection pattern 19 allows light to enter from the one end surface 8 of the plate-shaped light guide 2. Light source part 5
Light is uniformly emitted to the liquid crystal display device L arranged on the lower surface 16 side of the plate-shaped light guide 2 without being affected by the distance from the light source unit 5.

The light source unit 5 is composed of a rod-shaped rod-shaped light guide 3 made of a translucent material, and point-shaped light sources 4 and 4 arranged to face the end faces 6 and 7 of the rod-shaped light guide 3. , Rod-shaped light guide 3
The optical path changing means 12 is formed on one surface. Also,
The light reflection member 13 is formed in a substantially U shape, and is arranged so as to cover the rod-shaped light guide 3 when the planar lighting device 1 is combined.

The light reflection pattern 19 comprises a groove portion 17 having a substantially triangular cross section and a flat portion 18 adjacent to the groove portion, and is arranged in the axial direction of the light source portion 5 (also referred to as the axial direction of the rod-shaped light guide 3). It is formed in parallel or at a predetermined angle (formed in parallel in FIG. 1). In addition, the intervals of the light reflection patterns 19, that is, the intervals between adjacent groove portions 17 (also referred to as groove pitches) are set to the same interval. Further, the depth of the groove 17 is shallow on the one end face 8 side (the light source 5 side) of the plate-shaped light guide 2 and deep on the one end face 10 side. That is, the groove portion 17 is formed so that the depth thereof gradually increases as the distance from the light source portion 5 increases.

A reflection direction dispersion surface 21 is provided on the lower surface 16 of the plate-shaped light guide 2, and a non-reflective coating (not shown) is applied to the surface. Like the light reflection pattern 19 formed on the upper surface 15 of the plate-shaped light guide 2, the reflection direction dispersion surface 21 is formed in parallel with the axial direction of the light source unit 5 or at a predetermined angle. There is. By providing this reflection direction dispersion surface 21, the plate-shaped light guide 2
The direction of the light reflected by the lower surface 16 without passing through the surface, that is, the reflection direction dispersion surface 21, can be made irregular, and the light and dark fringes whose positions and intervals change with the movement of the observer's viewpoint. Is suppressed (this point will be described later).

In the above embodiment, the case where the light reflection pattern 19 is composed of the groove portion 17 and the flat portion 18 has been described, but the present invention is not limited to this embodiment.
It may be configured by a stepwise prism, the groove may have a substantially trapezoidal cross section, the groove may have a plurality of steps, or the cross section may have a curve.

Further, in the above embodiment, the point light source 4
Although the case where two are arranged close to the end faces 6 and 7 of the rod-shaped light guide 3 has been described, the present invention is not limited to this form, and either one end face 6 or one end face 7 of the rod-shaped light guide 3 is described. Alternatively, one point light source 4 may be arranged only on one end face. Further, as the light source unit 5, a fluorescent lamp which is a rod-shaped light source may be used instead of a combination of the rod-shaped light guide 3 and the point light source 4. Furthermore, the light source unit 5
One is arranged close to the one end surface 8 of the plate-shaped light guide 2, but the present invention is not limited to this, and both side surfaces of the plate-shaped light guide 2, that is, one end surface 8 Alternatively, it may be arranged in close proximity to the one end face 10.

By the way, the above-mentioned bright and dark fringes are caused by the shape of the light reflection pattern and unnecessary reflected light on the lower surface of the plate-shaped light guide, and are considered to be generated by the following mechanism. Light reflection pattern 29 consisting of a stepped prism
Will be described as an example with reference to FIGS. 2 and 3. As shown in FIG. 2, the light Q, R emitted from the light source section, traveling through the plate-shaped light guide 2 and reflected by the step portion 27 of the prism, and further reflected by the lower surface 26 of the plate-shaped light guide 2 is generated. When the light passes through the light reflection pattern 29 and is emitted to the outside, the light R refracted at the prism step portion 27 and emitted to the outside and the light R refracted at the gentle slope portion 28 of the prism and emitted to the outside are Refraction direction (light Q, R
Direction of arrow) is greatly different. Therefore, as shown in FIG. 3, an angle region D in which no light is emitted from the light reflection pattern 29 is generated. When the directions in which the light is not emitted are aligned within a certain range and the viewpoint of the observer is in the direction in which the light is not emitted, the observer recognizes it as a dark portion. Although not shown in the drawing, a plurality of angular regions where light does not exit are generated due to the geometrical relationship with the adjacent step portions or other step portions other than this. Therefore, the adjacent step 27
In the structure in which the intervals are constant, a plurality of dark areas occur.

FIG. 4 is a sectional view of a plate-shaped light guide showing one form of the reflection direction dispersion surface 21 formed on the lower surface 16 of the plate-shaped light guide 2, and the arrow in the figure indicates the light reflection pattern 29. Step 27
This is a schematic representation of the light reflected by the reflection direction dispersion surface 21 after being reflected by. In addition, on the upper surface of the plate-shaped light guide 2, a light reflection pattern 29 (a step portion 27 and a gentle slope portion 28) formed of a stepped prism is formed.
Further, FIG. 5 is a cross-sectional view showing one form of a conventional plate-shaped light guide for comparison with FIG. 4, and the lower surface 26 is formed in a planar shape. The arrow in the figure indicates the light reflection pattern 29.
2 schematically shows the light reflected by the lower surface 26 after being reflected by the step portion 27 of FIG. Although the viewpoint 35 is placed near the plate-shaped light guide 2 in FIGS. 4 and 5, it is actually located far away from the plate-shaped light guide 2.
Therefore, the observer observes as uniform emission angle characteristics within a certain range of the light reflection pattern.

In FIG. 5, as the light reflected by the light reflection pattern 29, only the light emitted from the light source section and traveling through the plate-shaped light guide 2 is reflected at the same angle at each step section 27. Is indicated by an arrow (an arrow pointing diagonally to the lower left in the figure, for example, arrow 51). After these lights are reflected by the planar lower surface 26, they travel in the same angle direction (for example, the direction of the arrow 52), are refracted at the stepped portion 27 and are outside the plate-shaped light guide 2 (the same angle). Direction, for example, arrow 5
3). At this time, the observer's viewpoint is arrow 5
In the case of four directions (viewpoint 35), the light does not travel in the direction of the viewpoint 35, and this viewpoint 35 direction corresponds to the “angle region D where light does not emerge from the light reflection pattern” shown in FIG. It appears as a dark stripe on the observer.

On the other hand, the arrow 5 in FIG. 5 shown in FIG.
Light corresponding to 1 (for example, arrows 31a, 31b, 31
After being reflected by the reflection direction dispersion surface 21 formed on the lower surface 16 of the plate-shaped light guide 2, c) travels in directions of different angles (for example, arrows 32 a, 32 b, 32 c), and the light reflection pattern 29. The light is refracted by and is emitted to the outside of the plate-shaped light guide 2 (in the figure, only the light emitted in the direction of arrow 33 is shown).

The reflection direction dispersion surface 21 formed on the lower surface 16 of the plate-shaped light guide 2 has a semi-circular shape with its outer peripheral surface facing the liquid crystal display device L side (downward in the figure), that is, a lenticular shape. , Are arranged in the direction in which the light reflection pattern 29 is arranged (the left-right direction in the drawing). Here, the lenticular reflection direction dispersion surface 21 will be described with reference to FIG. 6. As for the depth of the reflection direction dispersion surface 21, the tangential line S of the lenticular is 3 with respect to the horizontal surface T of the plate-shaped light guide. It is desirable to form it so that it is not more than a degree. That is, FIG.
Then, the maximum angle θma formed by the tangent line S and the horizontal plane T
It is desirable that x is 3 degrees or less.

By forming the lenticular reflection direction dispersion surface 21 in which the angle θi formed with respect to the horizontal surface T continuously changes in this way, the light reflected in the same angular direction at each step 27 ( 31a, 31b, 31c)
In different angular directions (32a, 32b, 32
It is possible to proceed to c). Therefore, as shown in FIG. 5, after reflecting on the step portion 27 (arrow 51), after reflecting on the lower surface 26, it proceeds uniformly in the direction of the step portion 27 (arrow 52 direction), both of which are on the step portion 27. Light refracted and emitted to the outside (arrow 53) is reflected by the step portion 27 as shown in FIG. 4 (arrows 31a, 31b, 31 corresponding to the arrow 51 in FIG. 5).
light of c), and after being reflected by the reflection direction dispersion surface 21, they travel in different directions (32a, 32b, 32c) respectively, and mainly reach the gentle slope portion 28 (arrows 32a, 32).
b), the light can be refracted at the gentle slope portion 28 and emitted to the outside (for example, the arrow 33).

As a result, the viewpoint of the observer is changed to the arrow 54.
Even in the direction of the arrow 34 (viewpoint 35) which is the same direction as (FIG. 5), the light is emitted in the direction of the arrow 33, so that the light travels in the direction of the viewpoint 35 and extends over a certain region. The "angle regions D where light does not emerge from the light reflection pattern" shown in FIG. 3 are not aligned, and it is possible to prevent the occurrence of stripes in the dark part. Further, not only the light (arrows 31a, 31b, 31c) shown in FIG. 4, but also all the light reflected by the reflection direction dispersion surface 21 is reflected in an irregular direction by the lenticular surface whose angle changes continuously. As a result, as a result, the light emitted from the light reflection pattern 29 to the outside is also irregularly emitted, and the occurrence of bright and dark fringes can be suppressed.

Further, it is desirable that the pitch P (FIG. 4) of the reflection direction dispersion surface 21 is formed differently from the pitch of the light reflection patterns 19 and 29, so that the generation of bright and dark fringes can be suppressed more effectively. it can. Further, an enlarged view of the dotted line portion B of FIG. 6 is shown in FIG. As shown in the drawing, by processing the edge portion 61 of the reflection direction dispersion surface 21 into a round shape, the presence of the reflection direction dispersion surface 21 can be made inconspicuous when viewed from the observation surface side, and the visibility can be improved.

The reflection direction dispersion surface 21 is the same as that shown in FIG.
The present invention is not limited to the lenticular form as shown in FIG. 2, but may be the form as shown in FIG. 8 or FIG. Reflection direction dispersion surface 2 shown in FIG.
1'has an arcuate shape with the inner peripheral surface thereof facing the liquid crystal display device L side (downward in the figure). In the case of this shape,
Since the angle of the reflection direction dispersion surface of light can be continuously changed, the same effect as that of the reflection direction dispersion surface 21 (FIG. 4) described above can be obtained.

The reflection direction dispersion surface 21 "shown in FIG. 9 has a shape constituted by a number of flat surfaces 61 to 68. Even in this case, the surfaces 61 to 68 for dispersing the reflection direction of light. Of the angle θA, θB with respect to the horizontal plane T of
θC can be changed stepwise (note that plane 6
4 and 68 are formed in parallel with the horizontal plane T), it is possible to obtain the same effect as in the case of the reflection direction dispersion plane 21 (FIG. 4) described above. Note that the angles θA, θB, θC
It is desirable that the maximum angle θA be 3 degrees or less. Further, the structure without the plane 68 may be used.

The reflection direction dispersion surface 21 '''shown in FIG.
It is composed of lenticular minute lenses 71 and 72 and a flat portion 73 of a reflection direction dispersion surface disposed between the reflection portions. Also in the case of this shape, the angle of the light reflection direction dispersion surface can be continuously changed, so that the same effect as the case of the reflection direction dispersion surface 21 (FIG. 4) described above can be obtained. Further, in this case, since the flat portion 73 of the reflection direction dispersion surface is provided between the minute lenses 71 and 72, it is more manufactured than the reflection direction dispersion surface in which only the minute lenses are continuously arranged. Has the advantage of being easy. Further, the same effect can be obtained by providing a flat portion on the reflection direction dispersion surface 21 'of the form shown in FIG.

As another means for suppressing the generation of bright and dark stripes, there is a means for irregularly changing the pitch of the light reflection pattern 19 formed on the upper surface 15 of the plate-shaped light guide 2, as shown in FIG. . Although the drawing shows the light reflection pattern 19 formed by the groove portion 17 and the flat portion 18, FIG.
0, etc., the light reflection pattern 29 (the step 27 and the gentle slope 28
In the case of the light reflection pattern 29, the step portion 27 corresponds to the groove portion 17.

The light reflection pattern 19 is composed of a groove portion 17 having a substantially triangular cross section and a flat portion 18 adjacent to the groove portion, and is arranged in the axial direction of the light source portion 5 (also referred to as the axial direction of the rod-shaped light guide 3). It is formed in parallel or with a predetermined angle. The intervals of the light reflection patterns 19, that is, the intervals between adjacent groove portions 17 (also referred to as groove pitches) are set with irregular variations (variations). By setting the intervals of the grooves 17 irregularly, the relationship between the intervals of the grooves 17 and the intervals of the mosaic pattern of the liquid crystal cell is not constant, so that the generation of moire patterns can be suppressed and the emission of light can be suppressed. It is possible to make the directions (the angular regions where the light does not come out from the light reflection pattern shown in FIG. 2 and FIG. 3) not adjacent to each other be uneven (dispersed) between adjacent steps, and to move the observer's viewpoint. It is possible to prevent the generation of bright and dark fringes of a different type from the fringes of the moire pattern, the positions and intervals of which are changed due to the change. In order to suppress the occurrence of bright and dark stripes more effectively,
Fluctuation width of groove pitch that fluctuates irregularly (maximum fluctuation) is 25
It is necessary to set it in the range of not less than% and less than 85%.

Therefore, as shown in FIG. 1, the plate-shaped light guide 2
Is formed on the upper surface 15 of the plate-shaped light guide 2, and the reflection direction dispersion surface 21, 21 ', 21 ", or 21"' is formed on the lower surface 16 of the plate-shaped light guide 2. By forming the structure, it is possible to more effectively suppress the generation of bright and dark fringes of a different type from the fringes of the moire pattern, in which the positions and intervals at which they occur change as the observer's viewpoint moves. .

[0039]

According to the surface illumination device of the present invention, a plurality of reflection direction dispersion surfaces are formed on the surface of the plate-shaped light guide opposite to the surface on which the light reflection pattern is formed. After the light is reflected by the reflection pattern and further reflected by the reflection direction dispersion surface, the light traveling to the light reflection pattern can be made to travel again in a predetermined direction.

Further, by forming the reflection direction dispersion surface into a lenticular shape in which the angle of the light reflection surface changes continuously, the light reflection direction can be made irregular, and as a result, Since the emission direction of the light emitted to the outside via the light reflection pattern can also be irregular,
The angle areas where light does not emerge from the light reflection pattern are not aligned and the bright and dark fringes are no longer recognized. In addition, by setting the angle of the reflection direction dispersion surface to 3 degrees or less with respect to the horizontal surface of the plate-shaped light guide, bright and dark fringes can be efficiently generated without degrading other display performance. Can be suppressed.

Further, when the reflection direction dispersion surface is composed of a lenticular minute lens and a flat portion arranged adjacent to the minute lens, or the angle of the plate-shaped light guide with respect to the horizontal direction is stepwise. The same effect as described above can be obtained even when it is composed of a plurality of changing planes. Also,
Since the reflection direction dispersion surface is formed on the plate-shaped light guide, an additional component is not required and an increase in cost can be prevented.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a planar lighting device according to the present invention.

FIG. 2 is a diagram showing a refraction direction of light which causes light and dark stripes.

FIG. 3 is a diagram showing an emission angle region of light which causes bright and dark stripes.

FIG. 4 is a diagram showing one form of a reflection direction dispersion surface of the planar lighting device according to the present invention.

FIG. 5 is a cross-sectional view showing one form of a plate-shaped light guide of a conventional planar lighting device.

FIG. 6 is a schematic view showing another mode of the reflection direction dispersion surface of the planar lighting device according to the present invention.

FIG. 7 is a partially enlarged view of FIG.

FIG. 8 is a diagram showing another mode of the reflection direction dispersion surface of the planar lighting device according to the present invention.

FIG. 9 is a diagram showing another mode of the reflection direction dispersion surface of the planar lighting device according to the present invention.

FIG. 10 is a diagram showing another mode of the reflection direction dispersion surface of the planar lighting device according to the present invention.

FIG. 11 is an exploded perspective view showing another form of the planar lighting device according to the present invention.

FIG. 12 is an exploded perspective view showing one form of a conventional planar lighting device.

[Explanation of symbols]

1 planar lighting device 2 Plate-shaped light guide 3 Bar-shaped light guide 4 point light sources 5 Light source 6, 7 end face 8, 10 One end face 15 Upper surface 16, 26 lower surface 17 Groove 18 Flat part 19, 29 Light reflection pattern 21 Reflection direction dispersion surface 27 steps 28 Slope area 61-68 plane 71, 72 Micro lens 73 Flat part of reflection direction dispersion surface L liquid crystal display

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI theme code (reference) G02F 1/13357 G02F 1/13357 // F21Y 101: 02 F21Y 101: 02 (72) Inventor Genji Egawa Shizuoka 1743-1 Asana-cho, Iwata-gun, Ibaraki Prefecture F-term in Hamamatsu Plant, Minebea Co., Ltd. (reference) 2H038 AA52 AA55 BA06 2H091 FA14Z FA23Z FA28Z FA42Z LA16 LA18 LA30

Claims (6)

[Claims] 1. A plate-shaped light guide body made of a translucent material, and a rod-shaped light source section arranged in proximity along a side surface of the plate-shaped light guide section, the plurality of groove sections being adjacent to the groove sections. A planar lighting device of a side light system, wherein a light reflection pattern composed of a flat portion or a light reflection pattern composed of a stepped prism is formed on the plate light guide. 2. A planar illumination device, wherein a reflection direction dispersion surface is formed on the surface opposite to the surface on which the light reflection pattern is formed, along the same direction as the direction on which the light reflection pattern is formed. 2. The planar lighting device according to claim 1, wherein the reflection direction dispersion surface is a lenticular. 3. The planar lighting device according to claim 1, wherein the reflection direction dispersion surface is composed of lenticular microlenses and a flat portion disposed between the microlenses. 4. The lenticular microlens forming the reflection direction dispersion surface is formed such that the maximum angle of its tangent to the horizontal surface of the plate-shaped light guide is 3 degrees or less. Item 2. The planar lighting device according to item 2 or 3. 5. The lenticular microlenses forming the reflection direction dispersion surface are each composed of a plurality of flat surfaces whose angles with respect to the horizontal surface of the plate-shaped light guide gradually change. Item 2. The planar lighting device according to item 2 or 3. 6. The reflection direction dispersion surface comprises an arcuate groove or a plurality of arcuate grooves continuously arranged, and a flat portion formed between the arcuate grooves. The planar lighting device according to claim 1.